Of the National Institute of Building Sciences

Program

on

Improved

Seismic

Safety

Provisions

 2000 Edition

NEHRP RECOMMENDED PROVISIONS

FOR SEISMIC REGULATIONS

FOR NEW BUILDINGS

AND OTHER STRUCTURES

Part 1: Provisions (FEMA 368)
The Building Seismic Safety Council (BSSC) was established in 1979 under the auspices of the National Institute of Building Sciences as an entirely new type of instrument for dealing with the complex

regulatory, technical, social, and economic issues involved in developing and promulgating building

earthquake hazard mitigation regulatory provisions that are national in scope. By bringing together in

the BSSC all of the needed expertise and all relevant public and private interests, it was believed that

issues related to the seismic safety of the built environment could be resolved and jurisdictional problems overcome through authoritative guidance and assistance backed by a broad consensus.

The BSSC is an independent, voluntary membership body representing a wide variety of building

community interests. Its fundamental purpose is to enhance public safety by providing a national forum that fosters improved seismic safety provisions for use by the building community in the planning,

design, construction, regulation, and utilization of buildings.

To fulfill its purpose, the BSSC: (1) promotes the development of seismic safety provisions suitable

for use throughout the United States; (2) recommends, encourages, and promotes the adoption of

appropriate seismic safety provisions in voluntary standards and model codes; (3) assesses progress in

the implementation of such provisions by federal, state, and local regulatory and construction agencies;

(4) identifies opportunities for improving seismic safety regulations and practices and encourages

public and private organizations to effect such improvements; (5) promotes the development of

training and educational courses and materials for use by design professionals, builders, building regulatory officials, elected officials, industry representatives, other members of the building community,

and the public; (6) advises government bodies on their programs of research, development, and implementation; and (7) periodically reviews and evaluates research findings, practices, and experience

and makes recommendations for incorporation into seismic design practices.

See the back of the Commentary volume for a full description of BSSC activities.

BOARD OF DIRECTION: 2000

Chairman William W. Stewart, Stewart-Schaberg Architects, Clayton, Missouri

Vice Chairman Charles Thornton, Ph.D., PE, The Thornton P Tomasetti Group, Inc., New York, New

York (representing the Applied Technology Council)

Secretary Jack Prosek, PE, Turner Construction Company, San Francisco, California (representing

the Associated General Contractors of America)

Ex-Officio Eugene Zeller, PE, City of Long Beach, California

Members J. Gregg Borchelt, PE, Brick Institute of America, Reston, Virginia; Charles Carter, PE,

American Institute of Steel Construction, Chicago, Illinois; Bradford K. Douglas, PE,

American Forest and Paper Association, Washington, D.C.; S. K. Ghosh, Ph.D., S. K.

Ghosh Associates, Inc., Northbrook, Illinois (representing the Portland Cement Association); Gerald H. Jones, PE, Kansas City, Missouri (representing the National Institute of

Building Sciences); Do Y. Kim, PE, Institute for Business and Home Safety, Tampa,

Florida (through October 2000); H. S. Lew, Ph.D., PE, National Institute of Standards and

Technology, Gaithersburg, Maryland (representing the Interagency Committee for Seismic

Safety in Construction); Joseph Nicoletti, PE, URS/John A. Blume and Associates, San

Francisco, California (representing the Earthquake Engineering Research Institute); W. Lee

Shoemaker, Ph.D., Metal Building Manufacturers Association, Cleveland, Ohio; Howard

Simpson, Sc.D., P.E., Simpson, Gumpertz and Heger, Arlington, Massachusetts (representing the National Council of Structural Engineers Associations); Charles Spitz, NCARB,

AIA, CSI, Architect/Planner Code Consultant, Wall, New Jersey (representing the

American Institute of Architects); John C. Theiss, PE, Theiss Engineers, Inc., St. Louis,

Missouri (representing the American Society of Civil Engineers); David Wismer, PE,

CBO, Department of Licenses and Inspections, Philadelphia, Pennsylvania (representing

the Building Officials and Code Administrators International)

BSSC Staff Claret M. Heider, Acting Executive Director; Bernard Murphy, PE, Director, Special

Projects; Patricia Blasi, Administrative Assistant; Carita Tanner, Administrative Assistant;

Kelly Harris, Summer Intern
BSSC Program on Improved Seismic Safety Provisions

NEHRP RECOMMENDED PROVISIONS

(National Earthquake Hazards Reduction Program)

FOR SEISMIC REGULATIONS

FOR NEW BUILDINGS AND

OTHER STRUCTURES

2000 EDITION

Part 1: PROVISIONS

(FEMA 368)

Prepared by the

Building Seismic Safety Council

for the

Federal Emergency Management Agency

BUILDING SEISMIC SAFETY COUNCIL

Washington, D.C.

2001
ii

This report was prepared under Contract EMW-97-CO-0481 between the

Federal Emergency Management Agency and the National Institute of Building

Sciences.

Building Seismic Safety Council activities and products are described at the end

of this report. For further information, contact the Building Seismic Safety

Council, 1090 Vermont, Avenue, N.W., Suite 700, Washington, D.C. 20005;

phone 202-289-7800; fax 202-289-1092; e-mail bssc@nibs.org. 

Copies of this report may be obtained by contacting the FEMA Publication

Distribution Facility at 1-800-480-2520.

The National Institute of Building Sciences and its Building Seismic Safety

Council caution users of these Provisions documents to be alert to patent and

copyright concerns especially when applying prescriptive requirements.

NOTICE: Any opinions, findings, conclusions, or recommendations expressed in this publication do

not necessarily reflect the views of the Federal Emergency Management Agency. Additionally, neither

FEMA nor any of its employees make any warranty, expressed or implied, nor assume any legal

liability or responsibility for the accuracy, completeness, or usefulness of any information, product, or

process included in this publication.
iii

 PREFACE

One of the primary goals of the Federal Emergency Management Agency (FEMA) and the

National Earthquake Hazards Reduction Program (NEHRP) is to encourage design and building

practices that address the earthquake hazard and minimize the resulting damage. Publication of

the 2000 NEHRP Recommended Provisions for Seismic Regulation of New Buildings and Other

Structures reaffirms the continuing FEMA-sponsored effort to improve the seismic safety of new

structures in this country. Its publication marks the fifth in a planned updating of both the

Provisions documents and several complementary publications. As in the case of the earlier

editions of the Provisions (1985, 1988, 1991, 1994, and 1997), FEMA is proud to sponsor this

Building Seismic Safety Council project and encourages widespread dissemination and voluntary

use of this state-of-the-art consensus resource document.

In contrast with the 1997 Provisions update, this update does not make significant changes to the

hazard maps or design procedures. Rather, the 2000 Provisions contains new material in select

areas that keep the document at the cutting edge of seismic design practices. An example of this

new material is the addition of a comprehensive procedure for the design of structures with

energy dissipating devices. As this new technology gains further acceptance in practice, the

design guidance within the Provisions will enjoy widespread use. Another example is the

inclusion of material on anchorage to concrete. A special anchorage subcommittee was

assembled to integrate this much-needed new material into the Provisions. A third example is

the comprehensive treatment of design of steel moment frame structures based on the research

results of a FEMA-funded project started after the 1994 Northridge earthquake. Finally, some

new material in the areas of ‘pushover’ design and simplified design procedures was developed. 

Further refinement of these two areas is expected during the next update cycle.

The above changes are but a few of the nearly 170 that were balloted by the BSSC member

organizations. The number of changes continues to grow over the numbers of earlier update

efforts and is testament to the increased attention being paid to the Provisions. This is due in

large part to the decision to use the NEHRP Provisions as the basis for the seismic requirements

in both the International Building Code and NFPA 5000 Code. FEMA welcomes this increased

scrutiny and the chance to work with these code organizations.

Looking ahead, FEMA has already contracted with BSSC for and work already has begun on the

update process that will lead to the 2003 Provisions. The update effort will continue to capture

the state of the art, continue work on simplified methods, and seek to improve the treatment of

non-building structures within the Provisions.

Finally, FEMA wishes to express its deepest gratitude for the yeoman efforts of a large number

of volunteer experts and the BSSC Board of Directors and staff who made possible the 2000

Provisions documents. It is truly their efforts that make the Provisions a reality. Americans

unfortunate enough to experience the earthquakes that will inevitably occur in this country in the

future will owe much, perhaps even their very lives, to the contributions and dedication of these

individuals to the seismic safety of buildings. Without the dedication and hard work of these

men and women, this document and all it represents with respect to earthquake risk mitigation

would not have been possible. 

Federal Emergency Management Agency
iv

INTRODUCTION and ACKNOWLEDGEMENTS

The 2000 Edition of the NEHRP Recommended Provisions for Seismic Regulations for New Buildings

and Other Structures is the sixth edition of the document and, like the 1985, 1988, 1991, 1994, and

1997 Editions that preceded it, has the consensus approval of the Building Seismic Safety Council

membership. It represents a major product of the Council's multiyear, multitask Program on Improved

Seismic Safety Provisions and is intended to continue to serve as a source document for use by any

interested members of the building community. (For readers unfamiliar with the program, a detailed

description of the BSSC’s purpose and activities concludes the Commentary volume.)

In September 1997, NIBS entered into a contract with FEMA for initiation of the BSSC 2000 Provisions update effort. Late in 1997, the BSSC member organization representatives and alternate

representatives and the BSSC Board of Direction were asked to identify individuals to serve on the

2000 Provisions Update Committee (PUC) and its Technical Subcommittees (TSs).

The 2000 PUC was constituted early in 1998, and 12 PUC Technical Subcommittees were established

to address design criteria and analysis, foundations and geotechnical considerations, cast-inplace/precast concrete structures, masonry structures, steel structures, wood structures, mechanicalelectrical systems and building equipment and architectural elements, quality assurance, composite

steel and concrete structures, energy dissipation and base isolation, and nonbuilding structures.

More than 200 individuals have participated in the 2000 update effort, and 169 substantive proposals

for change were developed. A series of editorial/organizational changes also have been made. All

draft TS and PUC proposals for change were finalized in late January 2000. The PUC Chairman

presented to the BSSC Board of Direction the PUC’s recommendations concerning proposals for

change to be submitted to the BSSC member organizations for balloting, and the Board accepted these

recommendations.

The first round of balloting concluded in early June 2000. There were 147 items on the official ballot,

and a large majority passed; however, many comments were submitted with “no” and “yes with

reservations” votes. These comments were compiled for distribution to the PUC, which met in midJuly to review the comments, receive TS responses to the comments and recommendations for change,

and formulate its recommendations concerning what items should be submitted to the BSSC member

organizations for a second ballot. The PUC directed several of the proposals from the first ballot to be

revised requiring them to be reballoted. The PUC deliberations resulted in the decision to recommend

to the BSSC Board that 17 items be included in the second ballot. The PUC Chairman subsequently

presented the PUC’s recommendations to the Board, which accepted those recommendations. 

The second round of balloting was completed in early October 2000. Of the 17 proposals, all passed

except for one. This had to be revised because of a duplication error. There were also three other

proposals developed by the PUC to clarify last minute concerns. The PUC met on the last two days of

October to formulate its recommendations to the Board, and the Board subsequently accepted those

recommendations. 

During the review of the first ballot, there was a request to table the proposals from TS 6 regarding 

Chapter 8 on Steel. The American Institute of Steel Construction (AISC) was in the process of

updating their supplement to AISC Seismic and the PUC expected publication of Supplement No. 2
v

during the second ballot voting period. If the supplement was published in time for the TS and PUC to

review the changes and incorporate the most current information available, it would be beneficial to

all. AISC Seismic Supplement No. 2 was published in November 2000. Since the second ballot was

already on the street, this drove the necessity to have a third ballot. A fifth proposal for the third ballot

was prepared to allow AISC Seismic Supplement No. 2 to be incorporated.

The third ballot was developed to include 5 proposals and all ballots were received by early February

2001. The comments and responses were prepared in time for the PUC Executive Committee to

review and accept all proposals in early March 2001. One of the proposals accepted AISC Seismic

Supplement No. 2 as a reference document that overrode the necessity for several proposals initially

balloted for the Chapter 8 on Steel. The PUC Chair once again presented the recommendations to the

BSSC Board of Direction and they were approved. The final versions of the Provisions and

Commentary volumes were developed and the Provisions includes, as Appendix A, a summary of the

differences between the 1997 and 2000 Editions. Once the documents were edited and supporting

information was prepared they were transmitted to FEMA for publication.

In presenting this 2000 Edition of the Provisions, the BSSC wishes to acknowledge the accomplishments of the many individuals and organizations involved over the years. The BSSC program resulting

in the first four editions of the Provisions, the 2000 update effort, and the information

development/dissemination activities conducted to stimulate use of the Provisions has benefitted from

the expertise of hundreds of specialists, many of whom have given freely of their time over many

years.

With so many volunteers participating, it is difficult to single out a given number or group for special

recognition without inadvertently omitting others without whose assistance the BSSC program could

not have succeeded; nevertheless, the 2000 Edition of the Provisions would not be complete without at

least recognizing the following individuals to whom I, acting on behalf of the BSSC Board of

Direction, heartily express sincerest appreciation:

C The members of the BSSC Provisions Update Committee, especially Chairman William Holmes;

C The members of the 12 PUC Technical Subcommittees, the Simplified Design Task Group, and the

Anchorage Task Group; and

C Timothy Sheckler, the FEMA Project Officer.

Appreciation also is due to the BSSC staff members, all of whose talents and experience were crucial

to conduct of the program. 

At this point I, as Chairman, would like to express my personal gratitude to the members of the BSSC

Board of Direction and to all those who provided advice, counsel, and encouragement during conduct

of the update effort or who otherwise participated in the BSSC program that resulted in the 2000

NEHRP Recommended Provisions.

William Stewart, Chairman, BSSC Board of Direction
vi

CONTENTS

Chapter 1 GENERAL PROVISIONS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1

1.1 PURPOSE ..........................................................1

1.2 SCOPE AND APPLICATION ...........................................1

1.2.1 Scope ..........................................................1

1.2.2 Additions .......................................................2

1.2.3 Change of Use ...................................................2

1.2.4 Alterations ......................................................2

1.2.5 Alternate Materials and Alternate Means and Methods of Construction ......3

1.3 SEISMIC USE GROUPS ...............................................3

1.3.1 Seismic Use Group III .............................................3

1.3.2 Seismic Use Group II .............................................3

1.3.3 Seismic Use Group I ..............................................4

1.3.4 Multiple Use ....................................................4

1.3.5 Seismic Use Group III Structure Access Protection . . . . . . . . . . . . . . . . . . . . . . 4

1.4 OCCUPANCY IMPORTANCE FACTOR .................................4

Chapter 2 GLOSSARY AND NOTATIONS ........................................5

2.1 GLOSSARY .........................................................5

2.2 NOTATIONS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14

Chapter 3 QUALITY ASSURANCE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33

3.1 SCOPE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33

3.2 QUALITY ASSURANCE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33

3.2.1 Details of Quality Assurance Plan . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34

3.2.2 Contractor Responsibility . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34

3.3 SPECIAL INSPECTION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34

3.3.1 Piers, Piles, Caissons . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34

3.3.2 Reinforcing Steel . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34

3.3.3 Structural Concrete . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35

3.3.4 Prestressed Concrete . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35

3.3.5 Structural Masonry . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35

3.3.6 Structural Steel . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35

3.3.7 Structural Wood . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35

3.3.8 Cold–Formed Steel Framing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36

3.4 TESTING . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37

3.4.1 Reinforcing and Prestressing Steel . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37

3.4.2 Structural Concrete . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37

3.4.3 Structural Masonry . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37

3.4.4 Structural Steel . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37

3.4.5 Mechanical and Electrical Equipment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37

3.4.6 Seismically Isolated Structures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38

3.5 STRUCTURAL OBSERVATIONS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38

3.6 REPORTING AND COMPLIANCE PROCEDURES . . . . . . . . . . . . . . . . . . . . . . . 38

Chapter 4 GROUND MOTION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39
vii

4.1 PROCEDURES FOR DETERMINING MAXIMUM CONSIDERED EARTHQUAKE

AND DESIGN EARTHQUAKE GROUND MOTION ACCELERATIONS AND

RESPONSE SPECTRA . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39

4.1.1 Maximum Considered Earthquake Ground Motions . . . . . . . . . . . . . . . . . . . . 39

4.1.2 General Procedure for Determining Maximum Considered Earthquake and

Design Spectral Response Accelerations: . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39

4.1.3 Site-Specific Procedure for Determining Ground Motion Accelerations . . . . . 45

4.2 SEISMIC DESIGN CATEGORY . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 47

4.2.1 Determination of Seismic Design Category . . . . . . . . . . . . . . . . . . . . . . . . . . . 47

4.2.2 Site Limitation for Seismic Design Categories E and F . . . . . . . . . . . . . . . . . . 48

Chapter 5 STRUCTURAL DESIGN CRITERIA . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 49

5.1 REFERENCE DOCUMENT: . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 49

5.2 DESIGN BASIS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 49

5.2.1 General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 49

5.2.2 Basic Seismic-Force-Resisting Systems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 49

5.2.3 Structure Configuration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 58

5.2.4 Redundancy . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 61

5.2.5 Structural Analysis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 62

5.2.6 Design and Detailing Requirements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 64

5.2.7 Combination of Load Effects . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 69

5.2.8 Deflection and Drift Limits . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 70

5.3 INDEX FORCE ANALYSIS PROCEDURE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 71

5.4 EQUIVALENT LATERAL FORCE PROCEDURE . . . . . . . . . . . . . . . . . . . . . . . . . 71

5.4.1 Seismic Base Shear . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 71

5.4.2 Period Determination . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 73

5.4.3 Vertical Distribution of Seismic Forces . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 75

5.4.4 Horizontal Shear Distribution . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 75

5.4.5 Overturning . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 76

5.4.6 Drift Determination and P-Delta Effects . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 77

5.5 MODAL RESPONSE SPECTRUM ANALYSIS PROCEDURE . . . . . . . . . . . . . . . 78

5.5.1 Modeling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 79

5.5.2 Modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 79

5.5.3 Modal Properties . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 79

5.5.4 Modal Base Shear . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 79

5.5.5 Modal Forces, Deflections, and Drifts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 81

5.5.6 Modal Story Shears and Moments . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 82

5.5.7 Design Values . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 82

5.5.8 Horizontal Shear Distribution . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 83

5.5.9 Foundation Overturning . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 83

5.5.10 P-Delta Effects . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 83

5.6 LINEAR RESPONSE HISTORY ANALYSIS PROCEDURE . . . . . . . . . . . . . . . . . 83

5.6.1 Modeling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 83

5.6.2 Ground Motion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 83

5.6.3 Response Parameters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 84

5.7 NONLINEAR RESPONSE HISTORY ANALYSIS . . . . . . . . . . . . . . . . . . . . . . . . . 84

5.7.1 Modeling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 84

5.7.2 Ground Motion and Other Loading . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 85
viii

5.7.3 Response Parameters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 85

5.7.4 Design Review . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 85

5.8 SOIL-STRUCTURE INTERACTION EFFECTS . . . . . . . . . . . . . . . . . . . . . . . . . . . 86

5.8.1 General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 86

5.8.2 Equivalent Lateral Force Procedure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 86

Appendix to Chapter 5

NONLINEAR STATIC ANALYSIS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 94

Chapter 6 ARCHITECTURAL, MECHANICAL, AND ELECTRICAL COMPONENTS 

DESIGN REQUIREMENTS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 99

6.1 GENERAL . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 99

6.1.1 References and Standards . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 100

6.1.2 Component Force Transfer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 102

6.1.3 Seismic Forces . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 102

6.1.4 Seismic Relative Displacements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 103

6.1.5 Component Importance Factor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 104

6.1.6 Component Anchorage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 105

6.1.7 Construction Documents . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 105

6.2 ARCHITECTURAL COMPONENT DESIGN . . . . . . . . . . . . . . . . . . . . . . . . . . . 106

6.2.1 General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 106

6.2.2 Architectural Component Forces and Displacements . . . . . . . . . . . . . . . . . 106

6.2.3 Architectural Component . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 108

6.2.4 Exterior Nonstructural Wall Elements and Connections . . . . . . . . . . . . . . . 108

6.2.5 Out-of-Plane-Bending . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 109

6.2.6 Suspended Ceilings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 109

6.2.7 Access Floors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 110

6.2.8 Partitions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 111

6.2.9 Steel Storage Racks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 111

6.2.10 Glass in Glazed Curtain Walls, Glazed Storefronts, and Glazed

 Partitions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 111

6.3 MECHANICAL AND ELECTRICAL COMPONENT DESIGN . . . . . . . . . . . . . 113

6.3.1 General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 113

6.3.2 Mechanical and Electrical Component Forces and Displacements . . . . . . . 113

6.3.3 Mechanical and Electrical Component Period . . . . . . . . . . . . . . . . . . . . . . . 114

6.3.4 Mechanical and Electrical Component Attachments . . . . . . . . . . . . . . . . . . 115

6.3.5 Component Supports . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 115

6.3.6 Component Certification . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 115

6.3.7 Utility and Service Lines at Structure Interfaces . . . . . . . . . . . . . . . . . . . . . 115

6.3.8 Site-Specific Considerations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 115

6.3.9 Storage Tanks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 116

6.3.10 HVAC Ductwork . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 116

6.3.11 Piping Systems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 116

6.3.12 Boilers and Pressure Vessels . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 118

6.3.13 Mechanical Equipment Attachments and Supports . . . . . . . . . . . . . . . . . . 119

6.3.14 Electrical Equipment Attachments and Supports . . . . . . . . . . . . . . . . . . . . 120

6.3.15 Alternate Seismic Qualification Methods . . . . . . . . . . . . . . . . . . . . . . . . . 122

6.3.16 Elevator Design Requirements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 122
ix

Chapter 7 FOUNDATION DESIGN REQUIREMENTS . . . . . . . . . . . . . . . . . . . . . . . . . . . . 125

7.1 GENERAL . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 125

7.2 STRENGTH OF COMPONENTS AND FOUNDATIONS . . . . . . . . . . . . . . . . . . 125

7.2.1 Structural Materials . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 125

7.2.2 Soil Capacities . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 125

7.3 SEISMIC DESIGN CATEGORIES A AND B . . . . . . . . . . . . . . . . . . . . . . . . . . . 125

7.4 SEISMIC DESIGN CATEGORY C . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 125

7.4.1 Investigation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 125

7.4.2 Pole-Type Structures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 126

7.4.3 Foundation Ties . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 126

7.4.4 Special Pile Requirements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 126

7.5 SEISMIC DESIGN CATEGORIES D, E, AND F . . . . . . . . . . . . . . . . . . . . . . . . . 127

7.5.1 Investigation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 128

7.5.2 Foundation Ties . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 128

7.5.3 Liquefaction Potential and Soil Strength Loss . . . . . . . . . . . . . . . . . . . . . . . 128

7.5.4 Special Pile and Grade Beam Requirements . . . . . . . . . . . . . . . . . . . . . . . . 128

Chapter 8 STEEL STRUCTURE DESIGN REQUIREMENTS . . . . . . . . . . . . . . . . . . . . . . . 133

8.1 REFERENCE DOCUMENTS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 133

8.2 SEISMIC REQUIREMENTS FOR STEEL STRUCTURES . . . . . . . . . . . . . . . . . 133

8.3 SEISMIC DESIGN CATEGORIES A, B, and C . . . . . . . . . . . . . . . . . . . . . . . . . . 133

8.4 SEISMIC DESIGN CATEGORIES D, E, AND F . . . . . . . . . . . . . . . . . . . . . . . . . 133

8.4.1 Modifications to AISC Seismic . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 134

8.5 COLD-FORMED STEEL SEISMIC REQUIREMENTS . . . . . . . . . . . . . . . . . . . 135

8.5.1 Modifications to AISI . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 135

8.5.2 Modifications to ANSI/ASCE 8-90 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 135

8.6 LIGHT-FRAMED WALLS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 136

8.6.1 Boundary Members . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 136

8.6.2 Connections . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 136

8.6.3 Braced Bay Members . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 136

8.6.4 Diagonal Braces . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 136

8.6.5 Shear Walls . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 136

8.7 SEISMIC REQUIREMENTS FOR STEEL DECK DIAPHRAGMS . . . . . . . . . . 137

8.8 STEEL CABLES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 137

Chapter 9 CONCRETE STRUCTURE DESIGN REQUIREMENTS . . . . . . . . . . . . . . . . . . . 139

9.1 REFERENCE DOCUMENTS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 139

9.1.1 Modifications to ACI 318 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 139

9.2 ANCHORING TO CONCRETE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 148

9.2.1 Scope . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 148

9.2.2 Notations and Definitions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 149

9.2.3 General Requirements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 154

9.2.4 General Requirements for Strength of Structural Anchors . . . . . . . . . . . . . 155

9.2.5 Design Requirements for Tensile Loading . . . . . . . . . . . . . . . . . . . . . . . . . . 157

9.2.6 Design Requirements for Shear Loading . . . . . . . . . . . . . . . . . . . . . . . . . . . 161

9.2.7 Interaction of Tensile and Shear Forces . . . . . . . . . . . . . . . . . . . . . . . . . . . . 164

9.2.8 Required Edge Distances, Spacings, and Thicknesses to Preclude 
x

Splitting Failure

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 164

9.2.9 Installation of Anchors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 165

9.3 CLASSIFICATION OF SHEAR WALLS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 165

9.3.1 Ordinary Plain Concrete Shear Walls . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 165

9.3.2 Detailed Plain Concrete Shear Walls . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 165

9.4 SEISMIC DESIGN CATEGORY A . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 165

9.5 SEISMIC DESIGN CATEGORY B . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 165

9.5.1 Ordinary Moment Frames . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 166

9.6 SEISMIC DESIGN CATEGORY C . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 166

9.6.1 Seismic-Force-Resisting Systems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 166

9.6.2 Discontinuous Members . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 166

9.6.3 Plain Concrete . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 166

9.6.4 Anchor Bolts in the Tops of Columns . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 167

9.7 SEISMIC DESIGN CATEGORIES D, E, OR F . . . . . . . . . . . . . . . . . . . . . . . . . . 167

9.7.1 Seismic-Force-Resisting Systems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 167

9.7.2 Frame Members Not Proportioned to Resist Forces Induced by Earthquake

Motions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 167

Appendix to Chapter 9

REINFORCED CONCRETE DIAPHRAGMS CONSTRUCTED USING

UNTOPPED PRECAST CONCRETE ELEMENTS . . . . . . . . . . . . . . . . . . . . . . . 168

Chapter 10 COMPOSITE STEEL AND CONCRETE STRUCTURE DESIGN REQUIRE 

MENTS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 173

10.1 REFERENCE DOCUMENTS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 173

10.2 REQUIREMENTS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 173

Chapter 11 MASONRY STRUCTURE DESIGN REQUIREMENTS . . . . . . . . . . . . . . . . . . 175

11.1 GENERAL . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 175

11.1.1 Scope . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 175

11.1.2 Reference Documents . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 175

11.1.3 Definitions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 175

11.1.4 Notations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 178

11.2 CONSTRUCTION REQUIREMENTS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 180

11.2.1 General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 180

11.2.2 Quality Assurance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 180

11.3 GENERAL REQUIREMENTS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 180

11.3.1 Scope . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 180

11.3.2 Empirical Masonry Design . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 180

11.3.3 Plain (Unreinforced) Masonry Design . . . . . . . . . . . . . . . . . . . . . . . . . . . . 180

11.3.4 Reinforced Masonry Design . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 181

11.3.5 Seismic Design Category A . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 181

11.3.6 Seismic Design Category B . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 181

11.3.7 Seismic Design Category C . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 181

11.3.8 Seismic Design Category D . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 182

11.3.9 Seismic Design Categories E and F . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 183

11.3.10 Properties of Materials . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 183
xi

11.3.11 Section Properties . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 185

11.3.12 Headed and Bent-Bar Anchor Bolts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 185

11.4 DETAILS OF REINFORCEMENT . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 190

11.4.1 General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 190

11.4.2 Size of Reinforcement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 190

11.4.3 Placement Limits for Reinforcement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 190

11.4.4 Cover for Reinforcement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 190

11.4.5 Development of Reinforcement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 191

11.5 STRENGTH AND DEFORMATION REQUIREMENTS . . . . . . . . . . . . . . . . . 193

11.5.1 General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 193

11.5.2 Required Strength . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 193

11.5.3 Design Strength . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 193

11.5.4 Deformation Requirements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 194

11.6 FLEXURE AND AXIAL LOADS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 194

11.6.1 Scope . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 194

11.6.2 Design Requirements of Reinforced Masonry Members . . . . . . . . . . . . . . 194

11.6.3 Design of Plain (Unreinforced) Masonry Members . . . . . . . . . . . . . . . . . . 196

11.7 SHEAR . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 197

11.7.1 Scope . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 197

11.7.2 Shear Strength . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 197

11.7.3 Design of Reinforced Masonry Members . . . . . . . . . . . . . . . . . . . . . . . . . . 197

11.7.4 Design of Plain (Unreinforced) Masonry Members . . . . . . . . . . . . . . . . . . 199

11.8 SPECIAL REQUIREMENTS FOR BEAMS . . . . . . . . . . . . . . . . . . . . . . . . . . . . 200

11.9 SPECIAL REQUIREMENTS FOR COLUMNS . . . . . . . . . . . . . . . . . . . . . . . . . 200

11.10 SPECIAL REQUIREMENTS FOR SHEAR WALLS . . . . . . . . . . . . . . . . . . . . 201

 11.10.1 Ordinary Plain Masonry Shear Walls . . . . . . . . . . . . . . . . . . . . . . . . . . . 201

 11.10.2 Detailed Plain Masonry Shear Walls . . . . . . . . . . . . . . . . . . . . . . . . . . . . 201

 11.10.3 Ordinary Reinforced Masonry Shear Walls . . . . . . . . . . . . . . . . . . . . . . . 201

 11.10.4 Intermediate Reinforced Masonry Shear Walls . . . . . . . . . . . . . . . . . . . . 201

 11.10.5 Special Reinforced Masonry Shear Walls . . . . . . . . . . . . . . . . . . . . . . . . 201

 11.10.6: Flanged Shear Walls . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 202

 11.10.7 Coupled Shear Walls . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 202

 11.11 SPECIAL MOMENT FRAMES OF MASONRY . . . . . . . . . . . . . . . . . . . . . . . 203

 11.11.1 Calculation of Required Strength . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 203

 11.11.2 Flexural Yielding . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 203

 11.11.3 Reinforcement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 203

 11.11.4 Wall Frame Beams . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 203

 11.11.5 Wall Frame Columns . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 204

 11.11.6 Wall Frame Beam-Column Intersection . . . . . . . . . . . . . . . . . . . . . . . . . 205

 11.12 GLASS-UNIT MASONRY AND MASONRY VENEER . . . . . . . . . . . . . . . . 207

 11.12.1 Design Lateral Forces and Displacements . . . . . . . . . . . . . . . . . . . . . . . . 207

 11.12.2 Glass-Unit Masonry Design . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 207

 11.12.3 Masonry Veneer Design . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 207

Chapter 12 WOOD STRUCTURE DESIGN REQUIREMENTS . . . . . . . . . . . . . . . . . . . . . . 209

12.1 GENERAL . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 209

12.1.1 Scope . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 209

12.1.2 Reference Documents . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 209
xii

12.1.3 Notations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 210

12.2 DESIGN METHODS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 210

12.2.1 Engineered Wood Design . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 210

12.2.2 Conventional Light-Frame Construction . . . . . . . . . . . . . . . . . . . . . . . . . . 211

12.3 GENERAL DESIGN REQUIREMENTS FOR ENGINEERED WOOD CONSTRUCTION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 211

12.3.1 General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 211

12.3.2 Shear Resistance Based on Principles of Mechanics . . . . . . . . . . . . . . . . . 211

12.3.3 Deformation Compatibility Requirements . . . . . . . . . . . . . . . . . . . . . . . . . 211

12.3.4 Framing Requirements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 211

12.3.5 Sheathing Requirements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 211

12.3.6 Wood Members Resisting Horizontal Seismic Forces Contributed by Masonry and Concrete . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 212

12.4 DIAPHRAGMS AND SHEAR WALLS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 212

12.4.1 Diaphragms . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 212

12.4.2 Shear Walls . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 215

12.4.3 Perforated Shear Walls . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 217

12.5 CONVENTIONAL LIGHT-FRAME CONSTRUCTION . . . . . . . . . . . . . . . . . . 220

12.5.1 Scope . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 220

12.5.2 Braced Walls . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 225

12.5.3 Detailing Requirements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 225

12.6 SEISMIC DESIGN CATEGORY A . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 228

12.7 SEISMIC DESIGN CATEGORIES B, C, AND D . . . . . . . . . . . . . . . . . . . . . . . . 228

12.7.1 Conventional Light-Frame Construction . . . . . . . . . . . . . . . . . . . . . . . . . . 229

12.7.2 Engineered Construction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 229

12.8 SEISMIC DESIGN CATEGORIES E AND F . . . . . . . . . . . . . . . . . . . . . . . . . . . 229

12.8.1 Limitations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 229

Chapter 13 SEISMICALLY ISOLATED STRUCTURES DESIGN REQUIREMENTS . . . . 241

13.1 GENERAL . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 241

13.2 CRITERIA SELECTION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 241

13.2.1 Basis for Design . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 241

13.2.2 Stability of the Isolation System . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 241

13.2.3 Seismic Use Group . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 241

13.2.4 Configuration Requirements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 241

13.2.5 Selection of Lateral Response Procedure . . . . . . . . . . . . . . . . . . . . . . . . . . 241

13.3 EQUIVALENT LATERAL FORCE PROCEDURE . . . . . . . . . . . . . . . . . . . . . . 243

13.3.1 General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 243

13.3.2 Deformation Characteristics of the Isolation System . . . . . . . . . . . . . . . . . 243

13.3.3 Minimum Lateral Displacements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 243

13.3.4 Minimum Lateral Forces . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 246

13.3.5 Vertical Distribution of Force . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 247

13.3.6 Drift Limits . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 248

13.4 DYNAMIC LATERAL RESPONSE PROCEDURE . . . . . . . . . . . . . . . . . . . . . . 248

13.4.1 General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 248

13.4.2 Isolation System and Structural Elements Below the Isolation System . . . 248

13.4.3 Structural Elements Above the Isolation System . . . . . . . . . . . . . . . . . . . . 249

13.4.4 Ground Motion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 249
xiii

13.4.5 Mathematical Model . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 250

13.4.6 Description of Analysis Procedures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 251

13.4.7 Design Lateral Force . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 251

13.5 LATERAL LOAD ON ELEMENTS OF STRUCTURES AND

NONSTRUCTURAL COMPONENTS SUPPORTED BY BUILDINGS . . . . . . 252

13.5.1 General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 252

13.5.2 Forces and Displacements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 252

13.6 DETAILED SYSTEM REQUIREMENTS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 253

13.6.1 General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 253

13.6.2 Isolation System . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 253

13.6.3 Structural System . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 255

13.7 FOUNDATIONS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 255

13.8 DESIGN AND CONSTRUCTION REVIEW . . . . . . . . . . . . . . . . . . . . . . . . . . . 255

13.8.1 General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 255

13.8.2 Isolation System . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 255

13.9 REQUIRED TESTS OF THE ISOLATION SYSTEM . . . . . . . . . . . . . . . . . . . . 255

13.9.1 General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 255

13.9.2 Prototype Tests . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 256

13.9.3 Determination of Force-Deflection Characteristics . . . . . . . . . . . . . . . . . . 257

13.9.4 Test Specimen Adequacy . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 258

13.9.5 Design Properties of the Isolation System . . . . . . . . . . . . . . . . . . . . . . . . . 258

Appendix to Chapter 13

STRUCTURES WITH DAMPING SYSTEMS . . . . . . . . . . . . . . . . . . . . . . . . . . 261

Chapter 14 NONBUILDING STRUCTURE DESIGN REQUIREMENTS . . . . . . . . . . . . . . . 291

14.1 GENERAL . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 291

14.1.1 Scope . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 291

14.2 REFERENCES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 291

14.3 INDUSTRY DESIGN STANDARDS AND RECOMMENDED PRACTICE . . 293

14.4 NONBUILDING STRUCTURES SUPPORTED BY OTHER STRUCTURES . 294

14.4.1 Architectural, Mechanical, and Electrical Components . . . . . . . . . . . . . . . 294

14.5 STRUCTURAL DESIGN REQUIREMENTS . . . . . . . . . . . . . . . . . . . . . . . . . . . 294

14.5.1 Design Basis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 294

14.5.2 Rigid Nonbuilding Structures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 298

14.5.3 Loads . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 298

14.5.4 Fundamental Period . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 299

14.5.5 Drift Limitations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 299

14.5.6 Materials Requirements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 299

14.5.7 Deflection Limits and Structure Separation . . . . . . . . . . . . . . . . . . . . . . . . 299

14.5.8 Site-Specific Response Spectra . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 299

14.6 NONBUILDING STRUCTURES SIMILAR TO BUILDINGS . . . . . . . . . . . . . . 299

14.6.1 General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 299

14.6.2 Pipe Racks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 299

14.6.3 Steel Storage Racks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 300

14.6.4 Electrical Power Generating Facilities . . . . . . . . . . . . . . . . . . . . . . . . . . . . 301

14.6.5 Structural Towers for Tanks and Vessels . . . . . . . . . . . . . . . . . . . . . . . . . . 301

14.6.6 Piers and Wharves . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 301
xiv

14.7 NONBUILDING STRUCTURES NOT SIMILAR TO BUILDINGS . . . . . . . . . 301

14.7.1 General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 302

14.7.2 Earth Retaining Structures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 302

14.7.3 Tanks and Vessels . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 302

14.7.4 Stacks and Chimneys . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 320

14.7.5 Amusement Structures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 320

14.7.6 Special Hydraulic Structures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 320

14.7.7 Secondary Containment Systems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 321

Appendix to Chapter 14

ELECTRICAL TRANSMISSION, SUBSTATION, AND DISTRIBUTION STRUCTURES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 322

Appendix A DIFFERENCES BETWEEN THE 1997 AND THE 2000 EDITIONS OF THE 

NEHRP RECOMMENDED PROVISIONS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 327

Appendix B PARTICIPANTS IN THE BSSC 2000 PROVISIONS UPDATE PROGRAM

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 345
Errata 

2000 Edition 

NEHRP RECOMMENDED PROVISIONS 

FOR SEISMIC REGULATIONS 

FOR NEW BUILDINGS 

AND OTHER STRUCTURES 

Part 1: Provisions (FEMA 368)

March 1, 2002 

Section Page Correction

5.8.2.1.1 88/89 Add the following to the legend at the top of page 89 after I0: 

"2 = dynamic foundation stiffness modifier for rocking (see 

Commentary) 

5.8.2.1.2 90 Change legend for SDS in Figure 5.8.2.1.2 as shown below: 

FIGURE 5.8.2.1.2 Foundation damping factor.

5.8.3.1 91 Change “ K ” to “ k ” in very last sentence. 
6.2.10.1 112 Under Exception 1, delete the following: 

“or 0.5 inch (13mm); whichever is greater,” 

6.2.10.2 112 In the last sentence on the page replace the reference “SMACNA 

Restraint” with “AAMA 501.4” 

6.3.8 115 In the last sentence replace “...Ca is equal to or greater than 0.15.” with 

“...SDS is equal to or greater than 0.33.” 

6.3.15 122 In the last sentence, delete “CISCA Recs for Zones 3-4” and replace 

with “IEE344”. 

7.5.4.4 131 In equation 7.5.4.4-3, replace “0.12 shc” with “0.3 shc” . 

8.4.1.1 134 Replace the entire existing Section 8.4.1.1 with the following: 

8.4.1.1: Revise Sec. 7.3b of AISC Seismic to read as follows: 

“All welds used in primary members and connections of the seismicforce-resisting system shall be made with filler metal capable of 

producing welds that conform to the following: 

1. For structures in which the steel frame is normally enclosed and 

maintained at a temperature of 500

 F or higher, minimum Charpy 

V-notch toughness of 20 ft-lb at 00

 F, using AWS A5 

classification methods, and minimum Charpy V-notch toughness 

of 40 ft-lb at 700

 F, under a range of welding conditions in 

accordance with FEMA 353, Recommended Specifications and 

Quality Assurance Guidelines for Moment Resisting Steel Frames 

for Seismic Applications. 

2. For structures with service temperatures lower than 500 F, 

minimum Charpy V-notch toughness of 20 ft-lb at 00 F, using 

AWS A5 classification methods, and minimum Charpy V-notch 

toughness of 40 ft-lb at 200 F above the lowest anticipated service 

temperature, under a range of welding conditions in accordance 

with FEMA 353, Recommended Specifications and Quality 

Assurance Guidelines for Moment Resisting Steel Frames for 

Seismic Applications.” 

9.2.5.2.6 159 Replace “R3 = 0.4 for post installed anchors.” with “R3 = 1.4 for post 

installed anchors.” 

9.6.3.2 166 The first exception should read: 

Exception: “In detached one- and two- family dwellings three stories 

or less in height, the projection of the footing beyond the face of the 

supported member shall be permitted to exceed the footing thickness.” 

9.7.1.2 167 In the second line, change “spacial” to “special.” 
11.1.2 175 Replace Sec. 11.1.2 to include the expanded reference titles of ACI 

530 and 530.1 as follows: 

“11.1.2 Reference Documents: The designation and title of

documents cited in this chapter are listed in this section. 

ACI 318 American Concrete Institute (ACI), Building Code 

Requirements for Structural Concrete, excluding 

Appendix A, 1999 

ACI 530/ASCE 5/ American Concrete Institute (ACI), Building 

TMS 402 Code Requirements for Masonry Structures, 1999 

ACI 530.1/ASCE 6/American Concrete Institute (ACI), Specifications

TMS 602 for Masonry Structures, 1999 

Compliance with specific provisions of ACI 530/ASCE 5/TMS 402 is 

mandatory where required by this chapter.” 

11.2.1 180 Expand the reference titles in two places for ACI 530.1 to read: 

“ACI 530.1/ASCE 6/TMS 602” 

11.3.2 180 Expand the reference title for ACI 530.1 to read: 

“ACI 530.1/ASCE 6/TMS 602” 

11.3.7.5 182 Expand the reference title for ACI 530 in the last sentence to read: 

“ACI 530/ASCE 5/TMS 402” 

11.3.10.5.2 185 Replace the second sentence, “For grouted stack bond masonry, 

tension parallel to the bed joints for in-plane bending shall be assumed 

to be resisted only by the continuous grout core section.” with “For 

grouted stack bond masonry, in-plane flexural tension parallel to the 

bed joints for in-plane bending shall be assumed to be resisted only by 

the continuous horizontally grout cross section.” 

11.6.3.5 196 Replace Equation (11.6.3.5-1) with the following: 

2

1 9

1 4 0 n n n

h h fo r

r r

P A f     = −           Φ Φ ′ < 9

11.7.31 197 Replace “M/Vdv < 0.25:” with M/Vdv # 0.25:” and place it before 

equation (11.7.3.1-2). 

11.7.31 198 At the top of the page replace “M/Vdv < 1.00:” with M/Vdv $1.00:” 

11.7.31 198 In the last sentence of the section replace “Vm (max) =” with “Vn (max)

=”. 

11.9.3 200 In the last sentence of paragraph “c” replace “84 tie diameters.” with 

“48 tie diameters.” 

11.12.2.1 207 Expand the reference titles in two places for ACI 530 to read: 

“ACI 530/ASCE 5/TMS 402” 
11.12.3.1 207 Expand the reference title for ACI 530 to read: 

“ACI 530/ASCE 5/TMS 402” 

12.1.2.3 209-

210 

Change “Natioanal” to “National” in the titles of PS 20 and PS2. 

12.3.4 211 After the sentence reading, “Shear wall and diaphragm boundary 

elements.... tension and compression forces,” add the following 

sentences: “Continuity of wall top plates or provision for transfer of 

induced axial load forces is required. When offsets occur in the wall 

line, portions of the shear wall on each side of the offset shall be 

considered as separate shear walls.” 

12.4.1.1 213 In the first Exception replace the reference “12.4.3.5” with “12.4.1.5” 

12.4.1.3 214 In the second paragraph add a period at the end of the second line. 

12.4.1.5 215 In the second paragraph add a period after the last sentence. 

12.4.2.4 216 Under Bolt size replace the “2” with “1⁄2” in the first row. 

12.4.2.6 216 At the end of the first paragraph replace “ Tables 12.4.2-6a and 12.4.2-

6b” with “Tables 12.4.3-2a and 12.4.3-2b”. 

12.4.2.6 216 At the end of the second paragraph replace “ Tables 12.4.2-6a and b.” 

with “Tables 12.4.3-2a and b.” 

12.4.3.1 217 At the paragraph titled Unadjusted factored shear resistance replace 

“Tables 12.4.2-6a and b” with “Tables 12.4.3-2a and b” in both the 

first line and the last line. 

12.4.3.2 217 In the first line replace “Sec. 12.4.4." with “Sec. 12.4.3.” 

12.4.3.2 217 In paragraph b replace “ set fort in Tables 12.4.2-6a and 12.4.2-6b” 

with “set forth in Tables 12.4.3-2a and 12.4.3-2b”. 

12.4.3.3.3 218 Replace “Table 12.4.4-1” with “Table 12.4.3-1” in two locations. 

12.4.3.4.1 218 At the end of the paragraph replace “ Tables 12.4.2-6a and 12.4.2-6b” 

with “Tables 12.4.3-2a and 12.4.3-2b”. 

12.4.3.4.2 218 In the legend below the equation delete “h = shear wall height (ft, 

mm/1000),”. 

12.4.3.4.2 219 In the legend for Co below the equation on page 218 replace “Table 

12.4.4-1” with “Table 12.4.3-1”. 

12.4.3.4.3 219 Replace “Sec. 12.4.4.4.1” with “Sec. 12.4.3.4.1”. 

12.4.3.4.3 219 Replace “Sec. 12.4.4.4.2” with “Sec. 12.4.3.4.2”. 

12.4.3.4.4 219 In the legend for Co below the equation replace “Table 12.4.4-1" with 

“Table 12.4.3-1”. 
12.4.3.4.4 219 In the legend for GLi below the equation add “perforated” before 

“shear wall segments”. 

Notes for 

Table 

12.4.3-2a 

235 Replace footnote b with the following: 

All panel edges backed with 2-inch nominal or wider framing. Panels 

installed either horizontally or vertically. Space nails at 6 in. on center 

along intermediate framing members for 3/8-in. panels installed with 

strong axis parallel to studs spaced 24 in. on center and 12 in. on 

center for other conditions and panel thicknesses. For framing 

members of other species set forth in Ref. 12-1, Table 12A, with the 

range of specific gravity (SG) noted, allowable shear values shall be 

calculated for all panel grades by multiplying the values from the table 

above for nail size and actual panel grade by the following factor: 

Specific Gravity Adjustment Factor = (1-(0.5 - SG)), Where SG = 

Specific Gravity of the framing lumber. This adjustment factor shall 

not be greater than 1. 

Notes for 

Table 

12.4.3-2b 

237 Replace footnote b with the following: 

All panel edges backed with 38 mm nominal or wider framing. Panels 

installed either horizontally or vertically. Space nails at 150 mm on 

center along intermediate framing members for 9 mm panels installed 

with strong axis parallel to studs spaced 610 mm on center and 305 

mm on center for other conditions and panel thicknesses. For framing 

members of other species set forth in Ref. 12-1, Table 12A, with the 

range of specific gravity (SG) noted, allowable shear values shall be 

calculated for all panel grades by multiplying the values from the table 

above for nail size and actual panel grade by the following factor: 

Specific Gravity Adjustment Factor = (1-(0.5 - SG)), Where SG = 

Specific Gravity of the framing lumber. This adjustment factor shall 

not be greater than 1. 

13.9.2.3 256 At the beginning of item 4., replace “30SDIBD/SDS” with 

“30SDI/BDSDS”. 

13.9.4 258 In item 2. and 3. replace “30SDIBD/SDS” with “30SDI/BDSDS”. 
14.5.1 294 Replace item 2 with the following: 

2. For nonbuilding systems that have an R value provided in Table 

14.5.2.1, the minimum specified value in Eq. 5.4.1.1-3 shall be 

replaced by: 

 CS = 0.14 SDS I (14.5.1-1) 

and the minimum value specified in Eq. 5.4.1.1-4 shall be 

replaced by: 

 CS = 0.8 S1 I/R (14.5.1-2) 

14.5.3 298 In the first sentence, replace the first reference to “Sec. 5.4.3" with 

“Sec. 5.3.” 

 

14.7.3.2 302 Paragraph c. replace the sentence, “For tanks and vessels not covered 

by an approved national standard, the vertical seismic force shall be 

defined as 67 percent of the equivalent lateral force.” with “For tanks 

and vessels not covered by an approved national standard, the vertical 

seismic force shall be based on a vertical ground acceleration defined 

as 67 percent of the design horizontal ground acceleration.” 

14.7.3.6.1.5 308 In the last sentence of the first paragraph under a., replace “base 

shear” with “base friction”. 

14.7.3.6.1.5 308 In the first sentence of the second paragraph under a.., replace “V” 

with “W”. 
14.7.3.7.1 310 Replace the series of equations under Eq. 14.7.3.7.1 with the 

following: 

For Ti < Ts 

1 . 4

D S

i i

S I

V W R = (14.7.3.7.1) 

For Ts < Ti < 4.0 sec. 

1.4

DS s

i i

i

S I T V W R T =

For Ts < Tc < < 4.0 sec. 

1.5

1.4

DS s

c c

c

S I T V W R T =

For Tc of 4.0 sec. or greater, 

2

6

1.4

DS s

c c

c

S I T V W R T = 

14A.2.2 323 In the definition of CS , replace the reference to “Sec. 1.4.2.2" with 

“Sec. 4.1.2.5.” 

14A2.2 324 In the first paragraph of the last sentence, replace “Sec. 14.2.1" with 

“Sec.5.4.3". 

14A.2.2 324 In the second paragraph, delete the last phrase, “ and recommended 

practices specified in Sec. 14.1.9". 

14A.3.2 324 In the definition of CS , replace the reference to “Sec. 4.2.2" with “Sec. 

4.1.2.5.” 

14A.3.2 324 In the fist paragraph of the section, replace “....and analysis shall be 

performed per Sec. 14.2.1 of the Provisions.” with “....and analysis 

shall be performed per Sec. 5.4.3 of the Provisions.” 

14A.3.2 324 In the last paragraph of the page, replace “(see Sec. 14.1.2 of the 

Provisions)” with “(see Sec. 14.4 of the Provisions)” 
14A.3.2 325 At the top of the page delete the last phrase of the first paragraph, 

“recommended practices specified in Sec. 14.1.9.” and replace with 

“the appropriate section of the recommended practices specified in 

Chapter 3. 

Appendix B 354 Under Technical Subcommittee 5, MASONRY STRUCTURES, add 

“Vilas Mujumdar, Concrete Masonry Association of California and 

Nevada, Citrus Heights, California” 

Appendix B 358 Under Technical Subcommittee 9, QUALITY ASSURANCE Chair, 

add “ Charles Spitz, Architect/Planner/Code Consultant, Wall, New 

Jersey (January 1998 to January 1999)” 
1

Chapter 1

GENERAL PROVISIONS

1.1 PURPOSE: The NEHRP Recommended Provisions for Seismic Regulations for New

Buildings and Other Structures (referred to hereinafter as the Provisions) present criteria for the

design and construction of structures to resist earthquake ground motions. The purposes of the

Provisions are as follows:

1. To provide minimum design criteria for structures appropriate to their primary function and

use considering the need to protect the health, safety, and welfare of the general public by

minimizing the earthquake-related risk to life and

2. To improve the capability of essential facilities and structures containing substantial

quantities of hazardous materials to function during and after design earthquakes. 

The design earthquake ground motion levels specified herein could result in both structural and

nonstructural damage. For most structures designed and constructed according to the Provisions,

structural damage from the design earthquake ground motion would be repairable although

perhaps not economically so. For essential facilities, it is expected that the damage from the

design earthquake ground motion would not be so severe as to preclude continued occupancy

and function of the facility. The actual ability to accomplish these goals depends upon a number

of factors including the structural framing type, configuration, materials, and as-built details of

construction. For ground motions larger than the design levels, the intent of the Provisions is

that there be a low likelihood of structural collapse.

1.2 SCOPE AND APPLICATION: 

1.2.1 Scope: The Provisions shall apply to the design and construction of structures including

additions, change of use, and alterations to resist the effects of earthquake motions. Every

structure, and portion thereof, shall be designed and constructed to resist the effects of earthquake motions as prescribed by the Provisions.

Exceptions:

1. Detached one- and two-family dwellings in Seismic Design Categories A, B, and C

are exempt from all requirements of the Provisions.

2. Detached one- and two-family wood frame dwellings that are designed and constructed in accordance with the conventional light frame construction requirements

in Sec. 12.5 are exempt from all other requirements of the Provisions.

3. Agricultural storage structures intended only for incidental human occupancy are

exempt from all requirements of the Provisions.

4. Structures located where S1 is less than or equal to 0.04 and Ss is less than or equal to

0.15 shall only be required to comply with Sec. 5.2.5 and Sec. 5.2.6.1 and tanks in
2000 Provisions, Chapter 1

2

Seismic Use Group III according to Table 14.5.1.2 also shall comply with the

freeboard requirements of Sec. 14.7.3.6.1.2. 

1.2.2 Additions: Additions shall be designed and constructed in accordance with Sec. 1.2.2.1

and 1.2.2.2:

1.2.2.1: An addition that is structurally independent from an existing structure shall be designed

and constructed as required for a new structure in accordance with Sec. 1.2.1.

1.2.2.2: An addition that is not structurally independent from an existing structure shall be

designed and constructed such that the entire structure conforms to the seismic-force-resistance

requirements for new structures unless all of the following conditions are satisfied:

1. The addition conforms with the requirements for new structures, and

2. The addition does not increase the seismic forces in any structural element of the existing

structure by more than 5 percent, unless the capacity of the element subject to the increased

forces is still in compliance with the Provisions, and

3. The addition does not decrease the seismic resistance of any structural element of the

existing structure to less than that required for a new structure.

1.2.3 Change of Use: When a change of use results in a structure being reclassified to a higher

Seismic Use Group, the structure shall conform to the requirements of Section 1.2.1 for a new

structure.

Exception: When a change of use results in a structure being reclassified from Seismic

Use Group I to Seismic Use Group II, compliance with the Provisions is not required if

the structure is located where SDS is less than 0.3.

1.2.4 Alterations: Alterations are permitted to be made to any structure without requiring the 

structure to comply with the Provisions provided the alterations conform to the requirements for

a new structure. Alterations that increase the seismic force in any existing structural element by

more then 5 percent or decrease the design strength of any existing structural element to resist

seismic forces by more than 5 percent shall not be permitted unless the entire seismic-forceresisting system is determined to conform to the Provisions for a new structure. All alterations

shall conform to the Provisions for a new structure.

Exception: Alterations to existing structural elements or additions of new structural

elements that are not required by these Provisions and are initiated for the purpose of

increasing the strength or stiffness of the seismic-force-resisting system of an existing

structure need not be designed for forces conforming to these Provisions provided that

an engineering analysis is submitted indicating the following:

1. The design strengths of existing structural elements required to resist seismic forces

is not reduced,

2. The seismic force on existing structural elements is not increased beyond their

design strength,
General Provisions

3

3. New structural elements are detailed and connected to the existing structural

elements as required by the Provisions, and

4. New or relocated nonstructural elements are detailed and connected to existing or

new structural elements as required by the Provisions.

1.2.5 Alternate Materials and Alternate Means and Methods of Construction: Alternate

materials and alternate means and methods of construction to those prescribed in the Provisions

are permitted if approved by the authority having jurisdiction. Substantiating evidence shall be

submitted demonstrating that the proposed alternate, for the purpose intended, will be at least

equal in strength, durability, and seismic resistance.

1.3 SEISMIC USE GROUPS: All structures shall be assigned to one of the Seismic Use

Groups described in Sec 1.3.1 through 1.3.3.

1.3.1 Seismic Use Group III: Seismic Use Group III structures are those having essential

facilities that are required for post-earthquake recovery and those containing substantial

quantities of hazardous substances including:

1. Fire, rescue, and police stations

2. Hospitals

3. Designated medical facilities having emergency treatment facilities

4. Designated emergency preparedness centers

5. Designated emergency operation centers

6. Designated emergency shelters

7. Power generating stations or other utilities required as emergency back-up facilities for

Seismic Use Group III facilities

8. Emergency vehicle garages and emergency aircraft hangars

9. Designated communication centers

10. Aviation control towers and air traffic control centers

11. Structures containing sufficient quantities of toxic or explosive substances deemed to be

hazardous to the public

12. Water treatment facilities required to maintain water pressure for fire suppression.

1.3.2 Seismic Use Group II: Seismic Use Group II structures are those that have a substantial

public hazard due to occupancy or use including:

1. Covered structures whose primary occupancy is public assembly with a capacity greater than

300 persons

2. Educational structures through the 12th grade with a capacity greater than 250 persons

3. Day care centers with a capacity greater than 150 persons
2000 Provisions, Chapter 1

4

4. Medical facilities with greater than 50 resident incapacitated patients not otherwise designated a Seismic Use Group III structure

5. Jails and detention facilities

6. All structures with a capacity greater than 5,000 persons

7. Power generating stations and other public utility facilities not included in Seismic Use

Group III and required for continued operation

8. Water treatment facilities required for primary treatment and disinfection for potable water

9. Waste water treatment facilities required for primary treatment

1.3.3 Seismic Use Group I: Seismic Use Group I structures are those not assigned to Seismic

Use Groups III or II.

1.3.4 Multiple Use: Structures having multiple uses shall be assigned the classification of the

use having the highest Seismic Use Group except in structures having two or more portions that

are structurally separated in accordance with Sec. 5.2.8, each portion shall be separately

classified. Where a structurally separated portion of a structure provides access to, egress from,

or shares life safety components with another portion having a higher Seismic Use Group, the

lower portion shall be assigned the same rating as the higher.

1.3.5 Seismic Use Group III Structure Access Protection: Where operational access to a

Seismic Use Group III structure is required through an adjacent structure, the adjacent structure

shall conform to the requirements for Seismic Use Group III structures. Where operational

access is less than 10 ft (3 m) from an interior lot line or less than 10 ft (3 m) from another

structure, access protection from potential falling debris shall be provided by the owner of the

Seismic Use Group III structure. 

1.4 OCCUPANCY IMPORTANCE FACTOR: An occupancy importance factor, I, shall be

assigned to each structure in accordance with Table 1.4.

TABLE 1.4 Occupancy Importance Factors

Seismic Use Group I

I 1.0

II 1.25

III 1.5
5

Chapter 2

GLOSSARY AND NOTATIONS

2.1 GLOSSARY:

Active Fault: A fault for which there is an average historic slip rate of 1mm per year or more

and geographic evidence of seismic activity within Holocene times (past 11,000 years).

Addition: An increase in the building area, aggregate floor area, height, or number of stories of

a structure.

Adjusted Resistance (D’): The reference resistance adjusted to include the effects of all

applicable adjustment factors resulting from end use and other modifying factors. Time effect

factor (8) adjustments are not included.

Alteration: Any construction or renovation to an existing structure other than an addition.

Appendage: An architectural component such as a canopy, marquee, ornamental balcony, or

statuary.

Approval: The written acceptance by the authority having jurisdiction of documentation that

establishes the qualification of a material, system, component, procedure, or person to fulfill the

requirements of the Provisions for the intended use.

Architectural Component Support: Those structural members or assemblies of members,

including braces, frames, struts and attachments, that transmit all loads and forces between

architectural systems, components, or elements and the structure.

Attachments: Means by which components and their supports are secured and connected to the

seismic-force-resisting system of the structure. Such attachments include anchor bolts, welded

connections, and mechanical fasteners.

Base: The level at which the horizontal seismic ground motions are considered to be imparted to

the structure.

Base Shear: Total design lateral force or shear at the base.

Basement: A basement is any story below the lowest story above grade.

Boundary Elements: Diaphragm and shear wall boundary members to which sheathing

transfers forces. Boundary members include chords and drag struts at diaphragm and shear wall

perimeters, interior openings, discontinuities, and re-entrant corners.

Braced Wall Line: A series of braced wall panels in a single story that meets the requirements

of Sec. 12.5.2.

Braced Wall Panel: A section of wall braced in accordance with Sec. 12.5.2.
2000 Provisions, Chapter 2

6

Building: Any structure whose use could include shelter of human occupants.

Boundary Members: Portions along wall and diaphragm edges strengthened by longitudinal

and transverse reinforcement and/or structural steel members.

Cantilevered Column System: A seismic-force-resisting system in which lateral forces are

resisted entirely by columns acting as cantilevers from the foundation.

Component: A part or element of an architectural, electrical, mechanical, or structural system.

Component, Equipment: A mechanical or electrical component or element that is part

of a mechanical and/or electrical system within or without a building system.

Component, Flexible: Component, including its attachments, having a fundamental

period greater than 0.06 sec.

Component, Rigid: Component, including its attachments, having a fundamental period

less than or equal to 0.06 sec.

Concrete: 

Plain Concrete: Concrete that is either unreinforced or contains less reinforcement than

the minimum amount specified in ACI 318 for reinforced concrete.

Reinforced Concrete: Concrete reinforced with no less than the minimum amount

required by ACI 318, prestressed or non-prestressed, and designed on the assumption that

the two materials act together in resisting forces.

Confined Region: The portion of reinforced concrete component in which the concrete is

confined by closely spaced special transverse reinforcement restraining the concrete in directions

perpendicular to the applied stress.

Construction Documents: The written, graphic, electronic, and pictorial documents describing

the design, locations, and physical characteristics of the project required to verify compliance

with the Provisions.

Container: A large-scale independent component used as a receptacle or a vessel to

accommodate plants, refuse, or similar uses. 

Coupling Beam: A beam that is used to connect adjacent concrete wall piers to make them act

together as a unit to resist lateral loads.

Damping Device: A flexible structural element of the damping system that dissipates energy

due to relative motion of each end of the device. Damping devices include all pins, bolts gusset

plates, brace extensions, and other components required to connect damping devices to the other

elements of the structure. Damping devices may be classified as either displacement-dependent

or velocity-dependent, or a combination thereof, and may be configured to act in either a linear or

nonlinear manner.

Damping System: The collection of structural elements that includes all the individual damping

devices, all structural elements or bracing required to transfer forces from damping devices to the
Glossary and Notations

7

base of the structure, and the structural elements required to transfer forces from damping

devices to the seismic-force-resisting system.

Deformability: The ratio of the ultimate deformation to the limit deformation.

High Deformability Element: An element whose deformability is not less than 3.5

when subjected to four fully reversed cycles at the limit deformation.

Limited Deformability Element: An element that is neither a low deformability nor a

high deformability element.

Low Deformability Element: An element whose deformability is 1.5 or less.

Deformation: 

Limit Deformation: Two times the initial deformation that occurs at a load equal to 40

percent of the maximum strength. 

Ultimate Deformation: The deformation at which failure occurs and which shall be

deemed to occur if sustainable load reduces to 80 percent or less of the maximum

strength.

Design Earthquake Ground Motion: The earthquake effects that buildings and structures are

specifically proportioned to resist as defined in Sec. 4.1.

Design Earthquake: Earthquake effects that are two-thirds of the corresponding maximum

considered earthquake. 

Designated Seismic System: Those architectural, electrical, and mechanical systems and their

components that require design in accordance with Sec. 6.1 and that have a component

importance factor (Ip) greater than 1.

Diaphragm: A roof, floor, or other membrane system acting to transfer lateral forces to the

vertical resisting elements. Diaphragms are classified as either flexible or rigid according to the

requirements of Sec. 5.2.3.1 and 12.4.1.1.

Diaphragm, Blocked: A diaphragm in which all sheathing edges not occurring on a framing

member are supported on and fastened to blocking.

Diaphragm Boundary: A location where shear is transferred into or out of the diaphragm

sheathing. Transfer is either to a boundary element or to another free-resisting element.

Diaphragm Cord: A diaphragm boundary element perpendicular to the applied load that is

assumed to take axial stresses due to the diaphragm moment in a manner analogous to the

flanges of a beam. Also applies to shear walls.

Displacement:

Design Displacement: The design earthquake lateral displacement, excluding additional

displacement due to actual and accidental torsion, required for design of the isolation

system.
2000 Provisions, Chapter 2

8

Total Design Displacement: The design earthquake lateral displacement, including

additional displacement due to actual and accidental torsion, required for design of the

isolation system or an element thereof.

Total Maximum Displacement: The maximum considered earthquake lateral

displacement, including additional displacement due to actual and accidental torsion,

required for verification of the stability of the isolation system or elements thereof, design

of structure separations, and vertical load testing of isolator unit prototypes.

Displacement-Dependent Damping Device: The force response of a displacement-dependent

damping device is primarily a function of the relative displacement between each end of the

device. The response is substantially independent of the relative velocity between each end of

the device and/or the excitation frequency.

Displacement Restraint System: A collection of structural elements that limits lateral

displacement of seismically isolated structures due to maximum considered earthquake ground

shaking.

Drag Strut (Collector, Tie, Diaphragm Strut): A diaphragm or shear wall boundary element

parallel to the applied load that collects the transfered diaphragm shear forces to the verticalforce-resisting elements or distributes forces within the diaphragm or shear wall. A drag strut

often is an extension of a boundary element that transfers forces into the diaphragm or shear

wall.

Effective Damping: The value of equivalent viscous damping corresponding to energy

dissipated during cyclic response of the isolation system.

Effective Stiffness: The value of lateral force in the isolation system, or an element thereof,

divided by the corresponding lateral displacement.

Enclosure: An interior space surrounded by walls.

Equipment Support: Those structural members or assemblies of members or manufactured

elements, including braces, frames, legs, lugs, snuggers, hangers or saddles, that transmit gravity

load and operating load between the equipment and the structure.

Essential Facility: A facility or structure required for post-earthquake recovery.

Factored Resistance (8N D): Reference resistance multiplied by the time effect and resistance

factors. This value must be adjusted for other factors such as size effects, moisture conditions,

and other end-use factors.

Flexible Equipment Connections: Those connections between equipment components that

permit rotational and/or transitional movement without degradation of performance. Examples

included universal joints, bellows expansion joints, and flexible metal hose.

Frame:

Braced Frame: An essentially vertical truss, or its equivalent, of the concentric or

eccentric type that is provided in a building frame system or dual frame system to resist

shear.
Glossary and Notations

9

Concentrically Braced Frame (CBF): A braced frame in which the members

are subjected primarily to axial forces.

Eccentrically Braced Frame (EBF): A diagonally braced frame in which at

least one end of each brace frames into a beam a short distance from a beamcolumn joint or from another diagonal brace.

Ordinary Concentrically Braced Frame (OCBF): A steel concentrically

braced frame in which members and connections are designed in accordance with

the provisions of AISC Seismic without modification.

Special Concentrically Braced Frame (SCBF): A steel or composite steel and

concrete concentrically braced frame in which members and connections are

designed for ductile behavior

Moment Frame: A frame provided with restrained connections between the beams and

columns to permit the frame to resist lateral forces through the flexural rigidity and

strength of its members.

Intermediate Moment Frame: A moment frame of reinforced concrete meeting

the detailing requirements of ACI 318, of structural steel meeting the detailing

requirements of AISC Seismic, or of composite construction meeting the

requirements of AISC Seismic.

Ordinary Moment Frame: A moment frame or reinforced concrete conforming

to the requirements of ACI 318 exclusive of Chapter 21, of structural steel

meeting the detailing requirements of AISC Seismic or of composite construction

meeting the requirements of AISC Seismic

Special Moment Frame: A moment frame of reinforced concrete meeting the

detailing requirements of ACI 318, of structural steel meeting the detailing

requirements of AISC Seismic, or of composite construction meeting the

requirements of AISC Seismic.

Frame System:

Building Frame System: A structural system with an essentially complete space frame

system providing support for vertical loads. Seismic-force resistance is provided by shear

walls or braced frames.

Dual Frame System: A structural system with an essentially complete space frame

system providing support for vertical loads. Seismic force resistance is provided by a

moment resisting frame and shear walls or braced frames as prescribed in Sec. 5.2.2.1

Space Frame System: A structural system composed of interconnected members, other

than bearing walls, that is capable of supporting vertical loads and that also may provide

resistance to shear.

Glazed Curtain Wall: A nonbearing wall that extends beyond the edges of the building floor

slabs and includes a glazing material installed in the curtain wall framing.
2000 Provisions, Chapter 2

10

Glazed Storefront: A nonbearing wall that is installed between floor slabs typically including

entrances and includes a glazing material installed in the storefront framing.

Grade Plane: A reference plane representing the average of the finished ground level adjoining

the structure at the exterior walls. Where the finished ground level slopes away from the exterior

walls, the reference plane shall be established by the lowest points within the area between the

buildings and the lot line or, where the lot line is more than 6 ft (1829 mm) from the structure,

between the structure and a point 6 ft (1829 mm) from the structure.

Hazardous Contents: A material that is highly toxic or potentially explosive and in sufficient

quantity to pose a significant life-safety threat to the general public if an uncontrolled release

were to occur.

High Temperature Energy Source: A fluid, gas, or vapor whose temperature exceeds 220

degrees F (378 K).

Inspection, Special: The observation of the work by the special inspector to determine

compliance with the approved construction documents and the Provisions. 

Continuous Special Inspection: A full-time observation of the work by an approved

special inspector who is present in the area where work is being performed.

Periodic Special Inspection: The part-time or intermittent observation of the work by

an approved special inspector who is present in the area where work has been or is being

performed. 

Inspector, Special (who shall be identified as the Owner’s Inspector): A person approved by

the authority having jurisdiction as being qualified to perform special inspection required by the

approved quality assurance plan. The quality assurance personnel of a fabricator is permitted to

be approved by the authority having jurisdiction as a special inspector.

Inverted Pendulum Type Structures: Structures that have a large portion of their mass

concentrated near the top and, thus, have essentially one degree of freedom in horizontal

translation. The structures are usually T-shaped with a single column supporting the beams or

framing at the top.

Isolation Interface: The boundary between the upper portion of the structure, which is isolated,

and the lower portion of the structure, which moves rigidly with the ground.

Isolation System: The collection of structural elements that includes all individual isolator

units, all structural elements that transfer force between elements of the isolation system, and all

connections to other structural elements. The isolation system also includes the wind-restraint

system, energy-dissipation devices, and/or the displacement restraint system if such systems and

devices are used to meet the design the requirements of Chapter 13.

Isolator Unit: A horizontally flexible and vertically stiff structural element of the isolation

system that permits large lateral deformations under design seismic load. An isolator unit is

permitted to be used either as part of or in addition to the weight-supporting system of the

structure.
Glossary and Notations

11

Joint: The portion of a column bounded by the highest and lowest surfaces of the other members

framing into it.

Load: 

Dead Load: The gravity load due to the weight of all permanent structural and

nonstructural components of a building such as walls, floors, roofs, and the operating

weight of fixed service equipment.

Gravity Load (W): The total dead load and applicable portions of other loads as defined

in Sec. 5.3.2.

Live Load: The load superimposed by the use and occupancy of the building not

including the wind load, earthquake load, or dead load; see Sec. 5.3.

Maximum Considered Earthquake Ground Motion: The most severe earthquake effects

considered by the Provisions as defined in Sec. 4.1.

Nonbuilding Structure: A structure, other than a building, constructed of a type included in

Chapter 14 and within the limits of Sec. 14.1.1.

Occupancy Importance Factor: A factor assigned to each structure according to its Seismic

Use Group as prescribed in Sec. 1.4.

Owner: Any person, agent, firm, or corporation having a legal or equitable interest in the

property.

Partition: A nonstructural interior wall that spans from floor to ceiling, to the floor or roof

structure immediately above, or to subsidiary structural members attached to the structure above.

P-Delta Effect: The secondary effect on shears and moments of structural members induced due

to displacement of the structure.

Quality Assurance Plan: A detailed written procedure that establishes the systems and

components subject to special inspection and testing.

Reference Resistence: The resistence (force or moment as appropriate) of a member or

connection computed at the reference end use conditions.

Registered Design Professional: An architect or engineer registered or licensed to practice

professional architecture or engineering as defined by statuary requirements of the professional

registrations laws of the state in which the project is to be constructed.

Roofing Unit: A unit of roofing material weighing more than 1 pound (0.5 kg).

Seismic Design Category: A classification assigned to a structure based on its Seismic Use

Group and the severity of the design earthquake ground motion at the site.

Seismic-Force-Resisting System: That part of the structural system that has been considered in

the design to provide the required resistence to the shear wall prescribed herein.

Seismic Forces: The assumed forces prescribed herein, related to the response of the structure

to earthquake motions, to be used in the design of the structure and its components.
2000 Provisions, Chapter 2

12

FIGURE 2.1 Definition of story above grade.

Seismic Response Coefficient: Coefficient Cs as determined from Sec. 5.4.1.

Seismic Use Group: A classification assigned to the structure based on its use as defined in

Sec. 1.3.

Shallow Anchors: Anchors with embedment length-to-diameter ratios of less than 8.

Shear Panel: A floor, roof, or wall component sheathed to act as a shear wall or diaphragm.

Site Class: A classification assigned to a site based on the types of soils present and their

engineering as defined in Sec. 4.1.2.

Site Coefficients: The values of Fa and Fv indicated in Tables 4.1.2.4a and 4.1.2.4b,

respectively.

Special Transverse Reinforcement: Reinforcement composed of spirals, closed stirrups, or

hoops and supplementary cross-ties provided to restrain the concrete and qualify the portion of

the component, where used, as a confined region. 

Storage Racks: Include industrial pallet racks, moveable shelf racks, and stacker racks made of

cold-formed and hot-rolled structural members. Does not include other types of racks such as

drive-in and drive-through racks, cantilever racks, portable racks, or racks made of materials

other than steel.

Story: The portion of a structure between the top to top of two successive finished floor

surfaces and, for the topmost story. From the top of the floor finish to the top of the roof

structural element.

Story Above Grade: Any story having its finished floor surface entirely above grade, except

that a story shall be considered as the story above grade where the finished floor surface of the

story immediately above is more

than 6 ft (1829 mm) above the

grade plane, more than 6 ft (1829

mm) above the finished ground

level for more than 40 percent of

the total structure perimeter, or

more than 12 ft (3658 mm) above

the finished ground level at any

point. This definition is

illustrated in Figure 2.1.

Story Drift Ratio: The story

drift, as determined in Sec. 5.4.6,

divided by the story height. 

Story Shear: The summation of design lateral forces at levels above the story under

consideration.
Glossary and Notations

13

Strength: 

Design Strength: Nominal strength multiplied by the strength reduction factor, N.

Nominal Strength: Strength of a member or cross section calculated in accordance with

the requirements and assumptions of the strength design methods of the Provisions (or

the reference standards) before application of any strength reduction factors.

Required Strength: Strength of a member, cross section, or connection required to

resist factored loads or related internal moments and forces in such combinations as

stipulated by the Provisions.

Structure: That which is built or constructed and limited to buildings and nonbuilding

structures as defined herein.

Structural Observations: The visual observations performed by the registered design

professional in responsible charge (or another registered design professional) to determine that

the seismic-force-resisting system is constructed in general conformance with the construction

documents. 

Wood Structural Panel: A wood-based panel product that meets the requirements of PS 1 or

PS 2 and is bonded with a waterproof adhesive. Included under this designation is plywood,

oriented strand board, and composite panels.

Subdiaphragm: A portion of a diaphragm used to transfer wall anchorage forces to the

diaphragm cross ties.

Testing Agency: A company or corporation that provides testing and/or inspection services. 

The person in responsible charge of the special inspector(s) and the testing services shall be a

registered design professional.

Tie-Down (Hold-Down): A device used to resist uplift of the chords of shear walls. These

devices are intended to resist load without significant slip between the device and the shear wall

chord or be shown with cyclic testing to not reduce the wall capacity and ductility.

Time Effect Factor: A factor applied to the adjusted resistence to account for effects of duration

load.

Torsional Force Distribution: The distribution of horizontal shear wall through the rigid

diaphragm when the center of the mass of the structure at the level under consideration does not

coincide with the center of the rigidity (sometimes referred to as diaphragm rotation).

Toughness: The ability of a material to absorb energy without losing significant strength.

Utility or Service Interface: The connection of the structure’s mechanical and electrical

distribution systems to the utility or service company’s distribution system.

Velocity-Dependent Damping Device: The force-displacement relation for a velocitydependent damping device is primarily a function of the relative velocity between each end of the

device and also may be a function of the relative displacement between each end of the device.
2000 Provisions, Chapter 2

14

Veneers: Facings or ornamentations of brick, concrete, stone, tile, or similar materials attached

to a backing.

Wall: A component that has a slope of 60 degrees or greater with the horizontal plane used to

enclose or divide space.

Bearing Wall: An exterior or interior wall providing support for vertical loads.

Cripple Wall: A framed stud wall, less than 8 ft (2400 mm) in height, extending from

the top of the foundation to the underside of the lowest floor framing. Cripple walls can

occur in both engineered structures and conventional construction.

Light-Framed Wall: A wall with wood or steel studs.

Light-Framed Wood Shear Wall: A wall constructed with wood studs and sheathed

with material rated for shear resistance.

Nonbearing Wall: An exterior or interior wall that does not provide support for vertical

loads other than its own weight or as permitted by the building code administered by the

authority having jurisdiction.

Nonstructural Wall: All walls other than bearing walls or shear walls.

Shear Wall (Vertical Diaphragm): A wall designed to resist lateral forces parallel to

the plane of the wall (sometimes referred to as a vertical diaphragm).

Wall System, Bearing: A structural system with bearing walls providing support for all or

major portions of the vertical loads. Shear walls or braced frames provide seismic-force

resistance.

Wind-Restraint System: The collection of structural elements that provides restraint of the

seismic-isolated structure for wind loads. The wind-restraint system may be either an integral

part of isolator units or a separate device.

2.2 NOTATIONS:

A, B, C, D, E, F Site classes as defined in Sec. 4.1.2.

Ab Area (in.2

 or mm2) of anchor bolt or stud in Chapters 6 and 11.

Ach Cross sectional-area (in.2 or mm2) of a component measured to the outside

of the special lateral reinforcement.

An Net-cross sectional area of masonry (in.2

 or mm2) in Chapter 11.

Ao The area of the load-carrying foundation (ft2 or m2).

Ap Projected area on the masonry surface of a right circular cone for anchor

bolt allowable shear and tension calculations (in.2

 or mm2) in Chapter 11.

As The area of an assumed failure surface taken as a pyramid in Eq. 2.4.1-3 or

in Chapter 9.

As Cross-sectional area of reinforcement (in.2 or mm2) in Chapters 6 and 11.
Glossary and Notations

15

Ash Total cross-sectional area of hoop reinforcement (in.2

 or mm2), including

supplementary cross-ties, having spacing of sh and crossing a section with

a core dimension of hc.

Avd Required area of leg (in.2

 or mm2) of diagonal reinforcement.

Ax The torsional amplification factor.

ab Length of compressive stress block (in. or mm) in Chapter 11.

ad The incremental factor related to P-delta effects in Sec. 5.4.5.

ap The component amplification factor as defined in Sec. 6.1.3.

Ba Nominal axial strength of an anchor bolt (lb or N) in Chapter 11.

BD Numerical coefficient as set forth in Table 13.3.3.1 for effective damping

equal to $D.

BID Numerical coefficient as set forth in Table A13.3.1 for effective damping

equal to $ml (m=1) and period of structure equal to T11.

Bm Numerical coefficient as set forth in Table 13.3.3.1 for effective damping

equal $M

BIM Numerical coefficient as set forth in Table A13.3.1 for effective damping

equal to $mM (m=1) and period of structure equal to TIM.

BmD Numerical coefficient as set forth in Table A13.3.1 for effective damping

equal to $ml and period of structure equal to Tm.

BmM Numerical coefficient as set forth in Table A13.3.1 for effective damping

equal to $mM and period of structure equal to Tm.

BR Numerical coefficient as set forth in Table A13.3.1 for effective damping

equal to $R and the period of structure equal to TR.

Bv Nominal shear strength of an anchor bolt (lb or N) in Chapter 11.

BV-1 Numerical coefficient as set forth in Table A13.3.1 for effective damping

equal to the sum of viscous damping in the fundamental mode of vibration

of the structure in the direction of interest, $Vm (m = 1), plus inherent

damping, $l

, and period of structure equal to T1.

b The shortest plan dimension of the structure, in ft (mm), measured

perpendicular to d.

ba Factored axial force on an anchor bolt (lb or N) in Chapter 11.

bv Factored shear force on an anchor bolt (lb or N) in Chapter 11.

bw Web width (in.or mm) in Chapter 11.
2000 Provisions, Chapter 2

16

Cu Coefficient for upper limit on calculated period; see Table 5.4.2.

Cd The deflection amplification factor as given in Table 5.2.2.

CmFD Force coefficient as set forth in Table A13.7.3.2.1.

CmFV Force coefficient as set forth in Table A13.7.3.2.2.

Cs The seismic response coefficient (dimension-less) determined in Sec.

5.4.1.1.

CS1 Seismic response coefficient (dimension-less) of the fundamental mode of

vibration of the structure in the direction of interest. Sec. A13.4.3.4 or

Sec. A13.5.3.4 (m = 1).

Csm The modal seismic response coefficient (dimension-less) determined in

Sec. 5.5.4..

CSm Seismic response coefficient (dimension-less) of the mth mode of vibration

of the structure in the direction of interest, Sec. A13.5.3.4 (m = 1) or Sec.

A13.5.3.6 (m > 1).

CSR Seismic response coefficient (dimension-less) of the residual mode of

vibration of the structure in the direction of interest, Sec. A13.4.3.8.

Cvx The vertical distribution factor as determined in Sec. 5.4.3.

c Distance from the neutral axis of a flexural member to the fiber of

maximum compressive strain (in. or mm).

ceq Effective energy dissipation device damping coefficient (Eq. 13.3.2.1).

D Reference resistance in Chapter 12.

D The effect of dead load in Sec. 5.2.7 and Chapter 13.

D Adjusted resistance in Chapter 12.

DD Design displacement (in. or mm) at the center of rigidity of the isolation

system in the direction under consideration as prescribed by Eq. 13.3.3.1.

DD! Design displacement (in. or mm), at the center of rigidity of the isolation

system in the direction under consideration, as prescribed by Eq. 13.4.2-1.

D1D Fundamental mode design displacement at the center rigidity of the roof

level of structure in the direction under consideration, Sec. A13.4.4.3 (in.

or mm).

D1M Fundamental mode maximum displacement at the center of rigidity of the

roof level of the structure in the direction under consideration, Sec.

A13.4.4.6 (in. or mm).
Glossary and Notations

17

DmD Design displacement at the center of rigidity of the roof level of the

structure due to the mth mode of vibration in the direction under

consideration, Sec. A13.5.4.3 (in. or mm).

DmM Maximum displacement at the center of rigidity of the roof level of the

structure due to the mth mode of vibration in the direction under

consideration, Sec. A13.5.4.6 (in. or mm).

DM Maximum displacement (in. or mm), at the center of rigidity of the

isolation system in the direction under consideration as prescribed by Eq.

13.3.3.3.

DM Maximum displacement (in. or mm), at the center of rigidity of the

isolation system in the direction under consideration as prescribed by Eq.

13.4.2-2.

Dp Relative seismic displacement that the component must be designed to

accommodate as defined in Sec. 6.1.4.

DRD Residual mode design displacement at the center of rigidity of the roof

level of the structure in the direction under consideration, Sec. A13.4.4.3

(in. or mm).

DRM Residual mode maximum displacement at the center of rigidity of the roof

level of the structure in the direction under consideration, Sec. A13.4.4.6

(in. or mm).

Ds The total depth of the stratum in Eq. 5.8.2.1.2-4 (ft or m).

DY Displacement at the center of rigidity of the roof level of the structure at

the effective yield point of the seismic-force-resisting system, Sec. A13.3.4

(in. or mm).

DTD Total design displacement (in. or mm), of an element of the isolation

system including both translational displacement at the center of rigidity

and the component of torsional displacement in the direction under

consideration as prescribed by Eq. 13.3.3.5-1.

DTM Total maximum displacement (in. or mm), of an element of the isolation

system including both translational displacement at the center of rigidity

and the component of torsional displacement in the direction under

consideration as prescribed by Eq. 13.3.3.5-2.

d Overall depth of member (in.or mm) in Chapters 5 and 11.

d The longest plan dimension of the structure (ft.or mm) in Chapter 13.

db Diameter of reinforcement (in.or mm) in Chapter 11.

de Distance from the anchor axis to the free edge (in.or mm) in Chapter 9.

dp The longest plan dimension of the structure (ft or mm).
2000 Provisions, Chapter 2

18

E The effect of horizontal and vertical earthquake-induced forces (Sec. 5.2.7

and Chapter 13).

Eloop Energy dissipated (kip-inches or kN-mm), in an isolator unit during a full

cycle of reversible load over a test displacement range from )+ to )- as

measured by the area enclosed by the loop of the loop of the forcedeflation curve.

Em Chord modulus of elasticity of masonry (psi or MPa) in Chapter 11.

Es Modulus of elasticity of reinforcement (psi or MPa) in Chapter 11.

Ev Modulus of rigidity of masonry (psi or Mpa) in Chapter 11.

e The actual eccentricity ( ft or mm), measured in plan between the center of

mass of the structure above the isolation interface and the center of

rigidity of the isolation system, plus accidental eccentricity (ft or mm),

taken as 5 percent the maximum building dimension perpendicular to the

direction of the force under consideration.

Fa Acceleration-based site coefficient (at 0.3 sec period).

F- Maximum negative force in an isolator unit during a single cycle of

prototype testing a displacement amplitude of )-.

F- Positive force in kips (kN) in an isolator unit during a single cycle of

prototype testing at a displacement amplitude of )-.

Fi, Fn, Fx The portion of the seismic base shear, V, induced at level i, n, or x,

respectively, as determined in Sec. 5.3.4 (kip or kN).

Fi1 Inertial force at Level i (or mass point i) in the fundamental mode of

vibration of the structure in the direction of interest, Sec. A13.4.3.9.

Fim Inertial force at Level i (or mass point i) in the mth mode of vibration of the

structure in the direction of interest, Sec. A13.5.3.7.

FiR Inertial force at Level i (or mass point i) in the residual mode of vibration

of the structure in the direction of interest, Sec. A13.4.3.9.

Fp The seismic design force center of gravity and distributed relative to the

component’s weight distribution as determined in Sec. 6.1.3.

Fp The induced seismic force on connections of anchorages as determined in

Sec. 5.2.6.1.2

Fu Specified ultimate tensile strength (psi or MPa) of an anchor (Sec. 9.2.4). 

Fv Velocity-based site coefficient (at 1.0 sec period).

Fx Total force distributed over the height of the structure above the isolation

interface as prescribed by Eq. 13.3.5.
Glossary and Notations

19

Fxm The portion of the seismic base shear, Vm, induced at a Level x as

determined in Sec. 5.5.5 (kip or kN).

fc! Specified compressive strength of concrete used in design

fi Lateral force at Level i of the structure distributed approximately in

accordance with Equation 5.3.4-2, Sec. A13.4.3.3.

fm! Specified compressive strength of masonry (psi or MPa) at the age of 28

days unless a different age is specified, Chapter 11.

fr Modulus of rupture of masonry (psi or MPa) in Chapter 11.

fs! Ultimate tensile strength (psi or MPa) of the bolt, stud or insert leg wires. 

For A307 bolts or A108 studs, is permitted to be assumed to be 60,000 psi

(415 Mpa).

fy Specified yield strength of reinforcement (psi or kPa).

fyh Specified yield stress of the special lateral reinforcement (psi or kPa).

G yvs

2

/g = the average shear modulus for the soils beneath the foundation at

large strain levels (psf of Pa).

Go yvso

2

/g = the average shear modulus for the soils beneath the foundation at

small strain levels (psf of Pa).

g Acceleration of gravity in in./sec2 (mm/s2).

H Thickness of soil.

h The height of a shear wall measured as the maximum clear height from

the foundation to the bottom of the floor or roof framing above or the

maximum clear height from the top of the floor or roof framing to the

bottom of the floor or roof framing above.

h The effective height of the building as determined in Sec. 5.8.2.1.1 (ft or

m). 

h Height of a wood shear panel or diaphragm (ft or mm) in Chapter 12.

h The roof elevation of a structure in Chapter 6.

h Height of the member between points of support (in. or mm) on Chapter

11.

hc The core dimension of a component measured to outside of the special

lateral reinforcement (in. or mm).

hi

, hn, hx The height above the base Level I, n, or x, respectively (ft or m).

hr Height of the structure above the base to the roof level (ft or m), Sec.

A13.4.3.3.
2000 Provisions, Chapter 2

20

hsx The story height below Level x = hx - hx-1 (ft. Or m).

I The occupancy importance factor in Sec. 1.4.

Icr Moment of inertia of the cracked section (in.4 or mm) in Chapter 11.

In Moment of inertia of the net cross-sectional area of a member (in.4 or

mm4

) in Chapter 11.

Io The static moment of inertia of the load-carrying foundation , see Sec.

5.5.2.1 (in.4 or mm4).

Ip The component importance factor as prescribed in Sec. 6.1.5.

I The building level referred to by the subscript I; I = 1 designates the first

level above the base.

Kp The stiffness of component or attachment as defined in Sec. 6.3.3.

Ky The lateral stiffness of the foundation as defined in Sec. 5.8.2.1.1 (lb/in. or

N/m).

K2 The rocking stiffness of the foundation as defined in Sec. 5.8.2.1.1

(ft.lb/degree or N m/rad).

KL/r The lateral slenderness of a compression member measured in terms of its

effective buckling length, KL, and the least radius of gyration of the

member cross section, r.

k The distribution exponent given in Sec. 5.4.3.

Kdmax Maximum effective stiffness, in kips/inch (kN/mm) of the isolation system

at the design displacement in the horizontal direction under consideration

as prescribed by Eq. 13.9.5.1-1.

KDmin Minimum effective stiffness (kips/inch or kN/mm) of the isolation system

at the design displacement in the horizontal direction under consideration

as prescribed by Eq. 13.9.5.1-2.

Kmax Maximum effective stiffness (kips/inch or kN/mm) of the isolation system

at the maximum displacement in the horizontal direction under

consideration as prescribed by Eq 13.9.5.1-3.

KMin Minimum effective stiffness (kips/inch or kN/mm) of the isolation system

at the maximum displacement in the horizontal direction under

consideration, as prescribed by Eq. 13.9.5.1-4.

keff Effective stiffness of an isolator unit as prescribed by Eq. 13.9.3-1.

k The stiffness of the building as determined in Sec. 5.8.2.1.1 (lb/ft or N/m).

L The overall length of the building (ft or m) at the base in the direction

being analyzed.
Glossary and Notations

21

L Length of bracing member (in. or mm) in Chapter 8.

L Length of coupling beam between coupled shear walls in Chapter 11 (in.

or mm).

L The effect of live load in Chapter 13.

Lo The overall length of the side of the foundation in the direction being

analyzed, Sec. 5.8.2.1.2 (ft or m).

l The dimension of a diaphragm perpendicular to the direction of

application of force. For open-front structures, l is the length from the

edge of the diaphragm at the open front to the vertical resisting elements

parallel to the direction of the applied force. For a cantilevered

diaphragm, l is the length from the edge of the diaphragm at the open

front to the vertical resisting elements parallel to the direction of the

applied force. 

Rb Effective embedment length of anchor bolt (in. or mm) in Chapter 11.

Rbc Anchor bolt edge distance (in. or mm) in Chapter 11.

Rd Development length (in. or mm) in Chapter 11.

Rdh Equivalent development length for a standard hook (in. or mm) in Chapter

11.

R1d Minimum lap splice length (in. or mm) in Chapter 11.

M Moment on a masonry section due to un-factored loads (in. lb or N @ mm)

in Chapter 11.

Ma Maximum moment in a member at deflation is computed (in. @lb or N @

mm) in Chapter 11.

Mcr Cracking moment strength of the masonry (in. @lb or N @mm) in Chapter

11.

Md Design moment strength (in. @lb or N @mm) in Chapter 11.

Mf The foundation overturning design moment as defined in Sec. 5.4.5 (ft @kip

or kN @m).

Mo, Mo1 The overturning moment at the foundation-soil interface as determined in

Sec. 5.5.6 and 5.8.3 (ft @lb or N @m)

Mnb Un-factored ultimate moment capacity at balanced strain conditions.

Mt The torsional moment resulting from the location of the building masses

(ft @kip or kN @m).

Mta The accidental torsional moment as determined in Sec. 5.4.4.2 (ft @kip or

kN @m).
2000 Provisions, Chapter 2

22

Mu Required flexural strength due to factored loads (in.@lb or N @mm) in

Chapter 11.

M1, M2 Nominal moment strength at the ends of the coupling beam (in @lb or N

@mm) in Chapter 11.

Mx The building overturning design moment at Level x as defined in Sec.

5.3.6 or Sec. 5.4.10 (ft @kip or kN @m).

m A subscript denoting the mode of vibration under consideration; i.e., m=1

for the fundamental mode.

N Number of stories, Sec. 5.4.2.1.

N Standard penetration resistance, ASTM D1536-84.

N Average field standard penetration test for the top 100 ft (30 m); see Sec.

4.1.

Nch Average standard penetration of cohesion-less soil layers for the top 100 ft

(30 m); see Sec. 4.1.

Nv Force acting normal to shear surface (lb or N) in Chapter 11.

n Designates the level that is uppermost in the main portion of the building.

n Number of anchors in Chapter 9.

P Axial load on a masonry section due to unfactored loads (lb or N) in

Chapter 11.

Pc Design tensile strength governed by concrete failure of anchor bolts in

Chapter 9.

PD Required axial strength on a column resulting from the application of dead

load, D, in Chapter 5 (kip or kN).

PE Required axial strength on a column resulting from the application of the

amplified earthquake load, E!, in Chapter 5 (kip or kN).

PL Required axial strength on a column resulting from application of live

load, L, in Chapter 5(kip or kN).

Pn Nominal axial load strength (lb or N) in Chapter 8.

Pn The algebraic sum of the shear wall and the minimum gravity loads on the

joint surface acting simultaneously with the shear (lb or N).

Pn Nominal axial load strength (lb or N) in Chapter 11.

Ps Design tensile strength governed by steel of anchor bolts in Chapter 9.

Pu Required axial load (lb or N) in Chapter 11.

Pu Tensile strength required due to factored loads (lb or N) in Chapter 9.
Glossary and Notations

23

Pu

’ Required axial strength on a brace (kip or kN) in Chapter 8.

Px The total unfactored vertical design load at and above level x (kip or kN).

PI Plasticity index, ASTM D4318-93.

QDSD Force in an element of the damping system required to resist design

seismic forces of displacement-dependent damping devices, Sec.

A13.7.3.2.

QE The effect of horizontal seismic forces (kip or kN) in Chapters 5 and 13.

QmDSV Forces in an element of the damping system required to resist design

seismic forces of velocity-dependent damping devices due to the mth mode

of vibration of structure in the direction of interest, Sec. A13.7.3.2.

QmSFRS Force in a element of the damping system equal to the design seismic force

of the mth mode of vibration of the seismic force resisting system in the

direction of interest, A13.7.3.2.

Qv The load equivalent to the effect of the horizontal and vertical shear

strength of the vertical segment in the Appendix to Chapter 8.

qH Hysteresis loop adjustment factor as determined in Sec. A13.3.3.

R The response modification coefficient as given in Table 5.2.2.

R1 Numerical coefficient related to the type of lateral-force-resisting system

above the isolation system as set forth in Table 13.3.4.2 for seismically

isolated structures.

Rp The component response modification system factor as defined in Chapter

6.

r The characteristic length of the foundation as defined in Chapter 5 (ft or

m)

r Radius of gyration (in. or mm) in Chapter 11.

ra, rm The characteristic foundation length defined in Sec. 5.8.2.1.1 (ft or m).

rx The ratio of the design story shear resisted by the most heavily loaded

single element in the story, in direction x, to the total story shear.

S Section modules based on net cross sectional area of a wall (in.3

 or mm3)

in Chapter 11.

S1 The maximum considered earthquake, 5 percent damped, spectral response

acceleration at a period of 1 second as defined in Chapter 4.

SD1 The design, 5 percent damped, spectral response acceleration at a period of

1 second as defined in Chapter 4..
2000 Provisions, Chapter 2

24

SDS The design, 5 percent damped, spectral response acceleration at short

periods as defined in Chapter 4.

SM1 The maximum considered earthquake, 5 percent damped, spectral response

acceleration at a period of one second adjusted for site class effects as

defined in Chapter 4.

SMS The maximum considered earthquake, 5 percent damped, spectral response

acceleration at short periods adjusted for site class effects as defined in

Chapter 4.

Ss The mapped maximum considered earthquake, 5 percent damped, spectral

response acceleration at short periods as defined in Chapter 4.

Spr Probable strength of precast element connectors (Sec. 9.1.1.12).

s Average undrained shear strength in top 100 ft (30.5 m); see Sec. 4.1.2.3, u

ASTM D2166-91 or ASTM D2850-87.

sh Spacing of special lateral reinforcement (in. or mm). .

T The period (sec) of the fundamental mode of vibration of the structure in

the direction of interest as determined in Chapter 5.

T, T1 The effective fundamental period (sec) of the building as determined in

Chapter 5.

T1 Period, in seconds, of the fundamental mode of vibration of the structure

in the direction of interest, Sec. A13.4.3.3.

Ta The approximate fundamental period (sec) of the building as determined

in Chapter 5.

TD Effective period, in seconds (sec), of the seismically isolated structure at

the design displacement in the direction under consideration as prescribed

by Eq. 13.3.3.2.

T1D Effective period, in seconds, of the fundamental mode of vibration of the

structure at the design displacement in the direction under consideration,

as prescribed by Sec. A13.4.3.5 or Sec. A13.5.3.5.

T1M Effective period, in seconds, of the fundamental mode of vibration of the

structure at the maximum displacement in the direction under

consideration, as prescribed by Sec. A13.4.3.5 or Sec. A13.5.3.5.

TM Effective period, in seconds (sec), of the seismically isolated structure at

the maximum displacement in the direction under consideration as

prescribed by Eq. 13.3.3.4.

Tm The period (sec) of the mth mode of vibration of the structure in the

direction of interest determined in Chapter 5.
Glossary and Notations

25

Tm Period, in seconds, of the mth mode of vibration of the structure in the

direction under consideration, Sec. A13.5.3.6.

T0 0.2SD1/SDS

Tp The fundamental period (sec) of the component and its attachment(s) as

defined in Sec. 6.3.3.

TR Period, in seconds, of the residual mode of vibration of the structure in the

direction under consideration, Sec. A13.4.3.7.

TS SDI/SDS.

T4 Net tension in steel cable due to dead load, prestress, live load, and

seismic load.

t Specified wall thickness dimension or least lateral dimension of a column

(in. or mm) in Chapter 11.

tc Thickness of masonry cover over reinforcing bars measured from the

surface of the masonry to the surface of the reinforcing bars (in. or mm) in

Chapter 11.

V The total design shear at the base of the structure in the direction of

interest, as determined using the procedure of Sec. 5.3, including Sec.

5.4.1 (kip or kN).

V Shear on a masonry section due to un-factored loads (lb or N) in Chapter

11.

Vb The total lateral seismic design force or shear on elements of the isolation

system or elements below the isolation system as prescribed by Eq.

13.3.4.1.

Vm Shear strength provided by masonry (lb or N) in Chapter 11.

Vm Design value of the seismic base shear of the mth mode of vibration of the

structure in the direction of interest, Sec. 5.4.5 or Sec. A13.5.3.2 (kip or

kN).

Vmm Minimum allowable value of base shear permitted for design of the

seismic-force-resisting system of the structure in the direction of interest,

Sec. A13.2.4.1 (kip or kN).

Vn Nominal shear strength (lb or N) in Chapter 11.

VR Design value of the seismic base shear of the residual mode of vibration

of the structure in a given direction, as determined in Sec. A13.4.3.6 (kip

or kN).

Vs The total lateral seismic design factor or shear on elements above the

isolation system as prescribed by Eq. 13.3.4.2.
2000 Provisions, Chapter 2

26

Vs Shear strength provided by shear reinforcement (lb or N) in Chapters 6 and

11.

Vt The design value of the seismic base shear as determined in Chapter 5

(kip or N).

Vu Required shear strength (lb or N) due to factored loads in Chapters 6 and

11.

Vx The seismic design shear in Story x as determined in Chapter 5 (kip or

kN).

V1 The portion of seismic base shear, V, contributed by the fundamental

mode as determined in Chapter 5 (kip or kN).

Vl The design value of the seismic base shear of the fundamental mode in a

given direction as determined in Chapter 5 (kip or kN).

)V The reduction in V as determined in Chapter 5 (kip or kN).

)V1 The reduction of V1 as determined in Chapter 5 (kp or kN).

vs The average shear wave velocity for the soils beneath the foundation at

large strain levels as determined in chapter 5 (ft/s or m/s).

v Average shear wave velocity in top one 100 ft (30 m); see Chapter 4. s

vso The average shear wave velocity for the soils beneath the foundation at

small strain levels as determined in chapter 5 (ft/s or m/s).

W The total gravity load of the structure defined in Chapter 5 (kip or kN). 

For calculation of a seismically isolated building structure, the period, W,

is the total seismic dead load weight of the structure above the isolation

system (kip or kN).

W The effective gravity load of the structure as defined in Chapter 5 and

5.5.3 (kip or kN).

W 1 Effective fundamental mode gravity load of structure including portions

of the live load determined in accordance with Eq. 5.4.5-2 for m = 1 (kip

or kN).

WR Effective residual mode gravity load of the structure determined in

accordance with Eq. A13.4.3.7-3 (kip or kN).

WD The energy dissipated per cycle at the story displacement for the design

earthquake.
Glossary and Notations

27

The effective gravity load of mth W mode of vibration of the structure m

determined in Chapter 5 (kip or kN).

Wp Component operating weight (lb or N).

w Width of wood shear panel or diaphragm in Chapter 9 (ft or mm).

w Moisture content (in percent), ASTM D2216-92.

w The dimension of a diaphragm or shear wall in the direction of application

of force.

wi, wx The portion of the total gravity load, W, located or assigned to Level I or x

(kip or kN).

z The level under consideration; x = 1 designates the first level above the

base.

x Elevation in structure of a component addressed by Chapter 6.

y Elevation difference between points of attachment in Chapter 6.

y The distance, in ft (mm), between the center of rigidity of the isolation

system rigidity and the element of interest measured perpendicular to the

direction of seismic loading under consideration.

" The relative weight density of the structure and the soil as determined in

Chapter 5.

" Angle between diagonal reinforcement and longitudinal axis of the

member (degree or rad).

" Velocity power term relating damping device force to damping device

velocity.

$ Ratio of shear demand to shear capacity for the story between Level x and

x-1.

$ The fraction of critical damping for the coupled structure-foundation

system determined in Chapter 5.

$D Effective damping of the isolation system at the design displacement as

prescribed by Eq. 13.9.5.2-1.

$eff Effective damping of the isolation system as prescribed by Eq. 13.9.3-2.

$HD Component of effective damping of the structure in the direction of

interest due to post-yield hysteric behavior of the seismic-force-resisting

system and elements of the damping system at effective ductility demand

μD, Sec. A13.3.2.2.

$HM Component of effective damping of the structure in the direction of

interest due to post-yield hysteric behavior of the seismic-force-resisting
2000 Provisions, Chapter 2

28

system and elements of the damping system at effective ductility demand,

μM, Sec. A13.3.2.2.

$I Component of effective damping of the structure due to the inherent

dissipation of energy by elements of the structure, at or just below the

effective yield displacement of the seismic-force-resisting system, Sec.

A13.3.2.1.

$M Effective damping of the isolation system at the maximum displacement as

prescribed by Eq. 13.9.5.2-2.

$mD Total effective damping of the mth mode of vibration of the structure in the

direction of interest at the design displacement, Sec. A13.3.2.

$mM Total effective damping of the mth mode of vibration of the structure in the

direction of interest at the maximum displacement , Sec. A13.3.2.

$o The foundation damping factor as specified in Chapter 5.

$R Total effective damping in the residual mode of vibration of the structure

in the direction of interest, calculated in accordance with Sec. A13.3.2 

(μD =1.0 and μM = 1.0).

$Vm Component of effective damping of the mth mode of vibration of the

structure in the direction of interest due to viscous dissipation of energy by

the damping system, at or just below the effective yield displacement of

the seismic-force-resisting system, Sec. A13.3.2.3.

( Lightweight concrete factor

( The average unit weight of soil (lb/ft3 or kg/m3).

) The design story drift as determined in Chapter 5 (in. or mm).

) The displacement of the dissipation device and device supports across the

story.

) Suspended ceiling lateral deflection (calculated) in Chapter 6 (in. or mm).

)a The allowable story drift as specified in Chapter 5 (in. or mm).

)D Total design earthquake story drift of the structure in the direction of

interest, Sec. A13.4.4.4 (in. or mm).

)ID Design earthquake story drift due to the fundamental mode of vibration of

the structure in the direction of interest, Sec. A13.4.4.4 (in. or mm).

)M Total maximum earthquake story drift of the structure in the direction of

interest, Sec. A13.4.4.6 (in. or mm).

)m The design modal story drift determined in Chapter 5 (in. or mm).

)mD Design earthquake story drift due to the mth mode of vibration of the

structure in the direction of interest, Sec. A13.4.4.4 (in. or mm).
Glossary and Notations

29

)p Relative displacement that the component must be designed to

accommodate as defined in Chapter 6.

)RD Design earthquake story drift due to the residual mode of vibration of the

structure in the direction of interest, Sec. A13.4.4.4 (in. or mm).

)- Maximum positive displacement of an isolator unit during each cycle of

prototype testing.

)- Maximum negative displacement of an isolator unit during each cycle of

prototype testing.

*avg The average of the displacements at the extreme points of the structure at

Level x (in. or mm).

*cr Deflation based on cracked section properties (in. or mm) in Chapter 11.

*i Elastic deflection of Level i of the structure due to applied lateral force, fi,

Sec. A13.4.3.3 (in. or mm).

*iID Fundamental mode design earthquake deflection of Level i at the center of

rigidity of the structure in the direction under consideration, Sec.

A13.4.4.2 (in. or mm).

*iD Total design earthquake deflection of Level i at the center of rigidity of the

structure in the direction under consideration, Sec. A13.4.4.2 (in. or mm).

*iM Total maximum earthquake deflection of Level i at the center of rigidity of

the structure in the direction under consideration, Sec. A13.4.4.2 (in. or

mm).

*iRD Residual mode design earthquake deflection of Level i at the center of

rigidity of the structure in the direction under consideration, Sec.

A13.4.4.2 (in. or mm).

*im Deflection of Level i in the mth mode of vibration at the center of rigidity

of the structure in the direction under consideration, Sec. A13.5 (in. or

mm).

*max The maximum displacement at Level x (in. or mm).

*x The deflection of Level x at the center of the mass at and above Level x as

determined in Chapter 5 (in. or mm).

*xe The deflection of Level x at the center of the mass at and above Level x

determined by an elastic analysis as specified in Chapter 5 (in. or mm).

*xem The modal deflection of Level x at the center of the mass at and above

Level x determined by an elastic analysis as specified in Chapter 5 (in. or

mm).
2000 Provisions, Chapter 2

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*xmv *xm The modal deflection of Level x at the center of the mass at and above

Level x as determined in Chapter 5 (in. or mm).

*x, *xl The deflection of Level x at the center of the mass at and above Level x as

determined in Chapter 5 (in. or mm).

,mu Maximum useable compressive strain of masonry (in./in. or mm/mm) in

Chapter 11.

μ Effective ductility demand on the seismic-force-resisting system in the

direction of interest.

μD Effective ductility demand on the seismic-force-resisting system in the

direction of interest due to the design earthquake, Sec. A13.4.

μM Effective ductility demand on the seismic-force-resisting system in the

direction of interest due to the maximum considered earthquake, Sec.

A13.4.

μmax Maximum allowable effective ductility demand on the seismic-forceresisting system due to design earthquake, Sec. A13.3.5.

2 The stability coefficient for P-delta effects as determined in Chapter 5.

J The overturning moment reduction factor.

D A reliability coefficient based on the extent of structural redundancy

present in a building as defined in Chapter 5.

D Ratio of the area of reinforcement to the net cross-sectional area of

masonry in a plane perpendicular to the reinforcement in Chapter 11.

Db Reinforcement ratio producing balanced strain conditions in Chapter 11.

Dh Ratio of the area of shear reinforcement to the cross sectional area of

masonry in a plane perpendicular to the reinforcement in Chapter 11.

Ds Spiral reinforcement ratio for precast prestressed piles in Chapter 7.

Dv Ratio of vertical or horizontal reinforcement in walls.

Dx A reliability coefficient based on the extent of structural redundancy

present in the seismic-force-resisting system of a building in the x

direction.

8 Time effect factor.

N The capacity reduction factor.

N Strength reduction factor in Chapters 6 and 11.

N Resistance factor for steel in Chapter 8 and wood in Chapter 12.
Glossary and Notations

31

Nil Displacement amplitude at Level i of the fundamental mode of vibration

of the structure in the direction of interest, normalized to unity at the roof

level, Sec. A13.4.3.3.

Nim The displacement amplitude at the i

th level of the structure for the fixed

base condition in the mth mode of vibration in the direction of interest

normalized to unity at the roof level as determined in Chapter 5.

NiR Displacement amplitude at Level i of the residual mode of vibration of the

structure in the direction of interest normalized to unity at the roof level,

Sec. A13.4.3.7.

'1 Participation factor of fundamental mode of vibration of the structure in

the direction of interest, Sec. A13.4.3.3 or Sec. A13.5.3.3 (m = 1).

'm Participation factor on the mth mode of vibration of the structure in the

direction of interest, Sec. A13.5.3.3.

'R Participation factor of the residual mode of vibration of the structure in the

direction of interest, Sec. A13.4.3.7.

LlD Design earthquake story velocity due to the fundamental mode of

vibration of the structure in the direction of interest, Sec. A13.4.4.5 (in/sec

or mm/sec).

LD Total design earthquake story velocity of the structure in the direction of

interest, Sec. A13.4.4.5 (in/sec or mm/sec).

LM Total maximum earthquake story velocity of the structure in the direction

of interest, Sec. A13.4.4.6 (in/sec or mm/sec).

LmD Design earthquake story velocity due to the mth mode of vibration of the

structure in the direction of interest, Sec. A13.4.4.5 (in/sec or mm/sec).

S0 Overstrength factor as defined in Table 5.2.2.

S Factor of safety in Chapter 8.

3ED Total energy dissipated, in kip-inches (kN-mm), in the isolation system

during a full cycle of response at the design displacement, DD.

3EM Total energy dissipated, in kip-inches (kN-mm), on the isolation system

during a full cycle of response at the maximum displacement , DM.

3 *FD

+*max Sum, for all isolator units, of the maximum absolute value of force, in kips

(kN), at a positive displacement equal to DD.

3 *FD

+*min Sum, for all isolator units, of the minimum absolute value of force, in kips

(kN), at a positive displacement equal to DD.

3 *FD

-

*max Sum, for all isolator units, of the maximum absolute value of force, in kips

(kN), at a negative displacement equal to DD.
2000 Provisions, Chapter 2

32

3 *FD

-

*min Sum, for all isolator units, of the minimum absolute value force , in kips

(kN), at a negative displacement equal to DD.

3 *FM

 – *max Sum, for all isolator units, of the maximum absolute value of force, in kips

(kN), at a positive displacement equal to DM.

3 *FM

 – *min Sum, for all isolator units, of the minimum absolute value of force, in kips

(kN), at a positive displacement equal to DM.

3 *FM

 – *max Sum, for all isolator units, of the minimum absolute value of force, in kips

(kN), at a negative displacement equal to DM.

3 *FM

 – *min Sum, for all isolator units, of the minimum absolute value of force, in kips

(kN), at a negative displacement equal to DM.
33

Chapter 3 

QUALITY ASSURANCE

3.1 SCOPE: This chapter provides minimum requirements for quality assurance for seismicforce-resisting systems and designated seismic systems. These requirements supplement the

testing and inspection requirements contained in the reference standards given in Chapters 8

through 14. 

3.2 QUALITY ASSURANCE: A quality assurance plan shall be submitted to the authority

having jurisdiction. A quality assurance plan, special inspection(s), and testing as set forth in

this chapter shall be provided for the following:

1. The seismic-force-resisting systems in structures assigned to Seismic Design Categories C,

D, E, and F.

2. Designated seismic systems in structures assigned to Seismic Design Categories D, E, and F

that are required in Table 6.1.7.

Exception: Structures that comply with the following criteria are exempt from the

preparation of a quality assurance plan but those structures are not exempt from special

inspection(s) or testing requirements:

1. The structure is constructed of light wood framing or light gauge cold-formed steel

framing, SDS does not exceed 0.50, the height of the structure does not exceed 35 ft

above grade, and the structure meets the requirements in Items 3 and 4 below

or

2. The structure is constructed using a reinforced masonry structural system or

reinforced concrete structural system, SDS does not exceed 0.50, the height of the

structure does not exceed 25 ft above grade, and the structure meets the requirements in Items 3 and 4 below.

3. The structure is classified as Seismic Use Group I.

4. The structure does not have any of the following plan irregularities as defined in

Table 5.2.3.2 or any of the following vertical irregularities as defined in Table

5.2.3.3:

a. Torsional irregularity,

b. Extreme torsional irregularity,

c. Nonparallel systems,

d. Stiffness irregularity -- soft story,

e. Stiffness irregularity -- extreme soft story,

f. Discontinuity in capacity -- weak story.
2000 Provisions, Chapter 3

34

3.2.1 Details of Quality Assurance Plan: The registered design professional in responsible

charge of the design of a seismic-force-resisting system and a designated seismic system shall be

responsible for the portion of the quality assurance plan applicable to that system. The quality

assurance plan shall include: 

1. The seismic-force-resisting systems and designated seismic systems in accordance with this

chapter that are subject to quality assurance,

2. The special inspections and testing to be provided as required by the Provisions and the

reference standards in Chapters 4 through 14,

3. The type and frequency of testing,

4. The type and frequency of special inspections,

5. The frequency and distribution of testing and special inspection reports,

6. The structural observations to be performed, and

7. The frequency and distribution of structural observation reports.

3.2.2 Contractor Responsibility: Each contractor responsible for the construction of a seismicforce-resisting system, designated seismic system, or component listed in the quality assurance

plan shall submit a written contractor's statement of responsibility to the authority having

jurisdiction and to the owner prior to the commencement of work on the system or component. 

The contractor's statement of responsibility shall contain the following:

1. Acknowledgment of awareness of the special requirements contained in the quality assurance plan;

2. Acknowledgment that control will be exercised to obtain conformance with the construction

documents approved by the authority having jurisdiction;

3. Procedures for exercising control within the contractor's organization, the method and

frequency of reporting, and the distribution of the reports; and

4. Identification and qualifications of the person(s) exercising such control and their position(s)

in the organization.

3.3 SPECIAL INSPECTION: The owner shall employ a special inspector(s) to observe the

construction for compliance with the requirements presented below. 

3.3.1 Piers, Piles, Caissons: Continuous special inspection during driving of piles and

placement of concrete in piers, piles, and caissons. Periodic special inspection during construction of drilled piles, piers, and caissons including the placement of reinforcing steel.

3.3.2 Reinforcing Steel: 

3.3.2.1: Periodic special inspection during and upon completion of the placement of reinforcing

steel in intermediate moment frames, in special moment frames, and in shear walls.
Quality Assurance

35

3.3.2.2: Continuous special inspection during the welding of reinforcing steel resisting flexural

and axial forces in intermediate moment frames and special moment frames, in boundary

members of concrete shear walls, and during welding of shear reinforcement.

3.3.3 Structural Concrete: Periodic special inspection during and upon completion of the

placement of concrete in intermediate moment frames, in special moment frames, and in

boundary members of shear walls.

3.3.4 Prestressed Concrete: Periodic special inspection during the placement and after

completion of placement of prestressing steel and continuous special inspection is required

during all stressing and grouting operations and during the placement of concrete.

3.3.5 Structural Masonry:

3.3.5.1: Periodic special inspection during the preparation of mortar, the laying of masonry

units, and the placement of reinforcement and prior to the placement of grout

3.3.5.2: Continuous special inspection during the welding of reinforcement, grouting, consolidation, reconsolidation, and placement of bent-bar anchors as required by Sec. 11.3.12.2.

3.3.6 Structural Steel:

3.3.6.1: Continuous special inspection for all structural welding.

Exception: Periodic special inspection is permitted for single-pass fillet or resistance

welds and welds loaded to less than 50 percent of their design strength provided the

qualifications of the welder and the welding electrodes are inspected at the beginning of

the work and all welds are inspected for compliance with the approved construction

documents at the completion of welding.

3.3.6.2: Periodic special inspection in accordance with AISC LRFD or AISC ASD for installation and tightening of fully tensioned high-strength bolts in slip-critical connections and in

connections subject to direct tension. Bolts in connections identified as not being slip-critical or

subject to direct tension need not be inspected for bolt tension other than to ensure that the plies

of the connected elements have been brought into snug contact.

3.3.7 Structural Wood: 

3.3.7.1: Continuous special inspection during all field gluing operations of elements of the

seismic-force-resisting system. 

3.3.7.2: Periodic special inspection for nailing, bolting, anchoring, and other fastening of

components within the seismic-force-resisting system including drag struts, braces, and tiedowns.

3.3.7.3: Periodic Special Inspections for wood shear walls, shear panels, and diaphragms, that

are included in the seismic force resisting system when the Provisions require the spacing of

nails, screws, or fasteners for wood sheathing to be 4 inches or less on center.
2000 Provisions, Chapter 3

36

3.3.8 Cold–Formed Steel Framing:

3.3.8.1: Periodic special inspection during all welding operations of elements of the seismicforce-resisting system.

3.3.8.2: Periodic special inspection for screw attachment, bolting, anchoring, and other

fastening of components within the seismic-force-resisting system, including struts, braces, and

hold-downs.

3.3.9 Architectural Components: Special inspection for architectural components shall be as

follows:

1. Periodic special inspection during the erection and fastening of exterior cladding, interior

and exterior nonbearing walls, and interior and exterior veneer in Seismic Design Categories

D, E, and F.

Exceptions:

a. Architectural components less than 30 ft (9 m) above grade or walking surface,

b. Cladding and veneer weighing 5 lb/ft2 (24.5 N/m2) or less, and

c. Interior nonbearing walls weighing 15 lb/ft2 (73.5 N/m2) or less.

2. Periodic special inspection during erection of glass 30 ft (9m) or more above an adjacent

grade or walking surface in glazed curtain walls, glazed storefronts, and interior glazed

partitions in Seismic Design Categories D, E, and F.

3. Periodic special inspection during the anchorage of access floors, suspended ceilings, and

storage racks 8 ft (2.4 m) or greater in height in Seismic Design Categories D, E, and F.

3.3.10 Mechanical and Electrical Components: Special inspection for mechanical and

electrical components shall be as follows:

1. Periodic special inspection during the anchorage of electrical equipment for emergency or

standby power systems in Seismic Design Categories C, D, E, and F;

2. Periodic special inspection during the installation of anchorage of all other electrical

equipment in Seismic Design Categories E and F;

3. Periodic special inspection during installation of flammable, combustible, or highly toxic

piping systems and their associated mechanical units in Seismic Design Categories C, D, E,

and F;

4. Periodic special inspection during the installation of HVAC ductwork that will contain

hazardous materials in Seismic Design Categories C, D, E, and F; and

5. Periodic special inspection during the installation of vibration isolation systems when the

construction documents indicate a maximum clearance (air gap) between the equipment

support frame and restraint of less than or equal to 1/4 inch.

3.3.11 Seismic Isolation System: Periodic special inspection during the fabrication and

installation of isolator units and energy dissipation devices if used as part of the seismic isolation

system.
Quality Assurance

37

3.4 TESTING: The special inspector(s) shall be responsible for verifying that the testing

requirements are performed by an approved testing agency for compliance with the requirements

below.

3.4.1 Reinforcing and Prestressing Steel: Special testing of reinforcing and prestressing steel

shall be as indicated in the requirements below.

3.4.1.1: Examine certified mill test reports for each shipment of reinforcing steel used to resist

flexural and axial forces in reinforced concrete intermediate frames, special moment frames, and

boundary members of reinforced concrete shear walls or reinforced masonry shear walls and

determine conformance with the construction documents. 

3.4.1.2: Where ASTM A615 reinforcing steel is used to resist earthquake-induced flexural and

axial forces in special moment frames and in wall boundary elements of shear walls in structures

of Seismic Design Categories D, E, and F, verify that the requirements of Sec. 21.2.5.1 of ACI

318 have been satisfied.

3.4.1.3: Where ASTM A615 reinforcing steel is to be welded, verify that chemical tests have

been performed to determine weldability in accordance with Sec. 3.5.2 of ACI 318.

3.4.2 Structural Concrete: Samples of structural concrete shall be obtained at the project site

and tested in accordance with requirements of ACI 318.

3.4.3 Structural Masonry: Quality assurance testing of structural masonry shall be in

accordance with the requirements of ACI 350.

3.4.4 Structural Steel: The testing needed to establish that the construction is in conformance

with these Provisions shall be included in a quality assurance plan. The minimum testing

contained in the quality assurance plan shall be as required in AISC Seismic and the following

requirements:

3.4.4.1 Base Metal Testing: Base metal thicker than 1.5 in. (38 mm), when subject to throughthickness weld shrinkage strains, shall be ultrasonically tested for discontinuities behind and

adjacent to such welds after joint completion. Any material discontinuities shall be accepted or

rejected on the basis of ASTM A435, Specification for Straight Beam Ultrasound Examination

of Steel Plates, or ASTM A898, Specification for Straight Beam Ultrasound Examination for

Rolled Steel Shapes, (Level 1 Criteria), and criteria as established by the registered design

professional(s) in responsible charge and the construction documents.

3.4.5 Mechanical and Electrical Equipment: As required to ensure compliance with the

seismic design requirements herein, the registered design professional in responsible charge

shall clearly state the applicable requirements on the construction documents. Each manufacturer

of designated seismic system components shall test or analyze the component and its mounting

system or anchorage as required and shall submit evidence of compliance for review and

acceptance by the registered design professional in responsible charge of the designated seismic

system and for approval by the authority having jurisdiction. The evidence of compliance shall

be by actual test on a shake table, by three-dimensional shock tests, by an analytical method

using dynamic characteristics and forces, by the use of experience data (i.e., historical data

demonstrating acceptable seismic performance), or by more rigorous analysis providing for
2000 Provisions, Chapter 3

38

equivalent safety. The special inspector shall examine the designated seismic system and shall

determine whether the anchorages and label conform with the evidence of compliance.

3.4.6 Seismically Isolated Structures: For required system tests, see Sec. 13.9.

3.5 STRUCTURAL OBSERVATIONS: Structural observations shall be provided for those

structures included in Seismic Design Categories D, E, and F when one or more of the following

conditions exist:

1. The structure is included in Seismic Use Group II or Seismic Use Group III or

2. The height of the structure is greater than 75 ft above the base or

3. The structure is in Seismic Design Category E or F and Seismic Use Group I and is greater

than two stories in height.

Observed deficiencies shall be reported in writing to the owner and the authority having

jurisdiction.

3.6 REPORTING AND COMPLIANCE PROCEDURES: Each special inspector shall

furnish copies of inspection reports, noting any work not in compliance with the approved

construction documents and corrections made to previously reported work to the authority having

jurisdiction, registered design professional in responsible charge, the owner, the registered

design professional preparing the quality assurance plan, and the contractor. All deficiencies

shall be brought to the immediate attention of the contractor for correction.

At completion of construction, each special inspector shall submit a report certifying that all

inspected work was completed substantially in compliance with the approved construction

documents. Work not in compliance with the approved construction documents shall be

described in the report.

At completion of construction, the contractor shall submit a final report to the authority having

jurisdiction certifying that all construction work incorporated into the seismic-force-resisting

system and other designated seismic systems was constructed substantially in compliance with

the approved construction documents.
39

Chapter 4

GROUND MOTION

4.1 PROCEDURES FOR DETERMINING MAXIMUM CONSIDERED EARTHQUAKE

AND DESIGN EARTHQUAKE GROUND MOTION ACCELERATIONS AND

RESPONSE SPECTRA: Ground motion accelerations, represented by response spectra and

coefficients derived from these spectra, shall be determined in accordance with the general

procedure of Sec. 4.1.2 or the site-specific procedure of Sec. 4.1.3. The general procedure in

which spectral response acceleration parameters for the maximum considered earthquake ground

motions are derived using Maps 1 through 24, modified by site coefficients to include local site

effects and scaled to design values, are permitted to be used for any structure except as

specifically indicated in the Provisions. The site-specific procedure also is permitted to be used

for any structure and shall be used where specifically required by the Provisions.

4.1.1 Maximum Considered Earthquake Ground Motions: The maximum considered

earthquake ground motions shall be as represented by the mapped spectral response acceleration

at short periods, SS, and at 1 second, S1, obtained from Maps 1 through 24 of the Provisions,

respectively, and adjusted for Site Class effects using the site coefficients of Sec. 4.1.2.4. When

a site-specific procedure is used, maximum considered earthquake ground motion shall be

determined in accordance with Sec. 4.1.3.

4.1.2 General Procedure for Determining Maximum Considered Earthquake and Design

Spectral Response Accelerations: The mapped maximum considered earthquake spectral

response acceleration at short periods, SS ,and at 1 second ,S1, shall be determined from Maps 1

through 24.

For structures located within those regions of the maps having values of the short period spectral

response acceleration, SS, less than or equal to 0.15 and values of the 1 second period spectral

response acceleration, S1, less than or equal to 0.04, accelerations need not be determined. Such

structures are permitted to be directly categorized as Seismic Design Category A in accordance

with Sec. 4.2.1.

For all other structures, the Site Class shall be determined in accordance with Sec. 4.1.2.1. The

maximum considered earthquake spectral response accelerations adjusted for Site Class effects,

SMS and SM1, shall be determined in accordance with Sec. 4.1.2.4 and the design spectral response

accelerations, SDS and SD1, shall be determined in accordance with Sec. 4.1.2.5. The general

response spectrum, when required by the Provisions, shall be determined in accordance with Sec.

4.1.2.6.

4.1.2.1 Site Class Definitions: For all structures located within those regions of the maps

having values of the short period spectral response acceleration, SS, greater than 0.15 or values of

the 1 second period spectral response acceleration, S1, greater than 0.04, the site shall be

classified as one of the following classes:
2000 Provisions, Chapter 4

40

A Hard rock with measured shear wave velocity,  ̄vs > 5,000 ft/sec (1500 m/s)

B Rock with 2,500 ft/sec <  ̄vs # 5,000 ft/sec (760 m/s <  ̄vs # 1500 m/s)

C Very dense soil and soft rock with 1,200 ft/sec <  ̄vs # 2,500 ft/sec (360 m/s <  ̄vs # 760 m/s) or

with either N ̄ > 50 or  ̄su > 2,000 psf (100 kPa)

D Stiff soil with 600 ft/sec #  ̄vs # 1,200 ft/sec (180 m/s #  ̄vs # 360 m/s) or with either 15 # N ̄ #

50 or 1,000 psf #  ̄su # 2,000 psf (50 kPa #  ̄su # 100 kPa)

E A soil profile with  ̄vs < 600 ft/sec (180 m/s) or with either

N ̄ < 15  ̄su < 1,000 psf or any profile with more than 10 ft (3 m) of soft clay defined as soil

with PI > 20, w $ 40 percent, and su < 500 psf (25 kPa)

F Soils requiring site-specific evaluations:

1. Soils vulnerable to potential failure or collapse under seismic loading such as liquefiable

soils, quick and highly sensitive clays, and collapsible weakly cemented soils.

Exception: For structures having fundamental periods of vibration equal to or

less than 0.5 second, site-specific evaluations are not required to determine

spectral accelerations for liquefiable soils. Rather, the Site Class may be

determined in accordance with Sec. 4.1.2.2 and the corresponding values of Fa

and Fv determined from Tables 4.1.2.4a and 4.1.2.4b.

2. Peats and/or highly organic clays (H > 10 ft [3 m] of peat and/or highly organic clay

where H = thickness of soil)

3. Very high plasticity clays (H > 25 ft [8 m] with PI > 75)

4. Very thick soft/medium stiff clays (H > 120 ft [36 m])

When the soil properties are not known in sufficient detail to determine the Site Class, Site Class

D shall be used. Site Classes E or F need not be assumed unless the authority having jurisdiction

determines that Site Classes E or F could be present at the site or in the event that Site Classes E

or F are established by geotechnical data.

4.1.2.2 Steps for Classifying a Site (also see Table 4.1.2.2 below):

Step 1: Check for the four categories of Site Class F requiring site-specific evaluation. If the

site corresponds to any of these categories, classify the site as Site Class F and

conduct a site-specific evaluation.

Step 2: Check for the existence of a total thickness of soft clay > 10 ft (3 m) where a soft clay

layer is defined by: su < 500 psf (25 kPa), w $ 40 percent, and PI > 20. If these

criteria are satisfied, classify the site as Site Class E.

Step 3: Categorize the site using one of the following three methods with  ̄vs, N ̄, and  ̄su

computed in all cases as specified by the definitions in Sec. 4.1.2.2:

a.  ̄vs for the top 100 ft (30 m) ( ̄vs method)

b. N ̄ for the top 100 ft (30 m) (N ̄ method)
Ground Motion

41

c. N ̄ch for cohesionless soil layers (PI < 20) in the top 100 ft (30 m) and average  ̄su

for cohesive soil layers (PI > 20) in the top 100 ft (30 m) ( ̄su method).

TABLE 4.1.2.2 Site Classification

Site Class

 ̄vs N ̄ or N ̄ ch  ̄su

E < 600 fps

( < 180 m/s)

< 15 < 1,000 psf

( < 50 kPa)

D 600 to 1,200 fps

(180 to 360 m/s)

15 to 50 1,000 to 2,000 psf

(50 to 100 kPa)

C > 1,200 to 2,500 fps

(360 to 760 m/s)

> 50 > 2,000

( > 100 kPa)

NOTE: If the  ̄su method is used and the N ̄ch and  ̄su criteria differ, select the category with the softer soils

(e.g., use Site Class E instead of D).

The shear wave velocity for rock, Site Class B, shall be either measured on site or estimated for

competent rock with moderate fracturing and weathering. Softer and more highly fractured and

weathered rock shall either be measured on site for shear wave velocity or classified as Site Class

C.

The hard rock category, Site Class A, shall be supported by shear wave velocity measurements

either on site or on profiles of the same rock type in the same formation with an equal or greater

degree of weathering and fracturing. Where hard rock conditions are known to be continuous to

a depth of 100 ft (30 m), surficial shear wave velocity measurements may be extrapolated to

assess  ̄vs.

The rock categories, Site Classes A and B, shall not be used if there is more than 10 ft (3 m) of

soil between the rock surface and the bottom of the spread footing or mat foundation.

4.1.2.3 Definitions of Site Class Parameters: The definitions presented below apply to the

upper 100 ft (30 m) of the site profile. Profiles containing distinctly different soil layers shall be

subdivided into those layers designated by a number that ranges from 1 to n at the bottom where

there are a total of n distinct layers in the upper 100 ft (30 m). The symbol i then refers to any

one of the layers between 1 and n.

vsi is the shear wave velocity in ft/sec (m/s).

di

 is the thickness of any layer between 0 and 100 ft (30 m),

 ̄vs is:

s

i

i

n

i

si i

n v

d

d

v

=

∑

∑

=

=

1

1

(4.1.2.3-1)
2000 Provisions, Chapter 4

42

where is equal to 100 ft (30 m) i

i

n

d =

∑

1

Ni is the Standard Penetration Resistance (ASTM D1586-84) not to exceed 100 blows/ft as

directly measured in the field without corrections.

N ̄ is:

N

d

d

N

i

i

n

i

i i

n =

∑

∑

=

=

1

1

(4.1.2.3-2)

N ̄ch is:

ch

s

i

i i

N m

d

d

N

=

∑

=1

(4.1.2.3-3)

where . i

i

m

d ds =

∑ = 1

(Use only di and Ni for cohesionless soils.)

ds is the total thickness of cohesionless soil layers in the top 100 ft (30 m).

sui is the undrained shear strength in psf (kPa), not to exceed 5,000 psf (250 kPa), ASTM D2166-

91 or D2850-87.
Ground Motion

43

 ̄su is:

u

c

i

ui i

k s

d

d

s

=

∑

=1

(4.1.2.3-4)

where . i

i

k

d dc =

∑ = 1

dc is the total thickness (100 - ds) of cohesive soil layers in the top 100 ft (30 m).

PI is the plasticity index, ASTM D4318-93.

w is the moisture content in percent, ASTM D2216-92.

4.1.2.4 Site Coefficients and Adjusted Maximum Considered Earthquake Spectral

Response Acceleration Parameters: The maximum considered earthquake spectral response

acceleration for short periods, SMS, and at 1 second, SM1, adjusted for site class effects, shall be

determined by Eq. 4.1.2.4-1 and 4.1.2.4-2, respectively:

S FS MS a s = (4.1.2.4-1)

and

S FS M v 1 1 = (4.1.2.4-2) 

where site coefficients Fa and Fv are defined in Tables 4.1.2.4a and b, respectively.

TABLE 4.1.2.4a Values of Fa as a Function of Site Class and 

Mapped Short-Period Maximum Considered Earthquake Spectral Acceleration

Site Class Mapped Maximum Considered Earthquake Spectral Response

Acceleration at Short Periods

SS # 0.25 SS = 0.50 SS = 0.75 SS = 1.00 SS $ 1.25

A 0.8 0.8 0.8 0.8 0.8

B 1.0 1.0 1.0 1.0 1.0

C 1.2 1.2 1.1 1.0 1.0

D 1.6 1.4 1.2 1.1 1.0

E 2.5 1.7 1.2 0.9 0.9
2000 Provisions, Chapter 4

Site Class Mapped Maximum Considered Earthquake Spectral Response

Acceleration at Short Periods

SS # 0.25 SS = 0.50 SS = 0.75 SS = 1.00 SS $ 1.25

44

F aaa a a

NOTE: Use straight line interpolation for intermediate values of SS.

 a

 Site-specific geotechnical investigation and dynamic site response analyses shall be performed. Exception: For structures with periods of vibration equal to or less than 0.5 second,

values of Fa for liquefiable soils may be assumed equal to the values for the Site Class

determined without regard to liquefaction in Step 3 of Sec. 4.1.2.2.

TABLE 4.1.2.4b Values of Fv as a Function of Site Class and 

Mapped 1 Second Period Maximum Considered Earthquake Spectral Acceleration

Site Class Mapped Maximum Considered Earthquake Spectral Response

Acceleration at 1 Second Periods

S1 # 0.1 S1 = 0.2 S1 = 0.3 S1 = 0.4 S1 $ 0.5

A 0.8 0.8 0.8 0.8 0.8

B 1.0 1.0 1.0 1.0 1.0

C 1.7 1.6 1.5 1.4 1.3

D 2.4 2.0 1.8 1.6 1.5

E 3.5 3.2 2.8 2.4 2.4

F aaa a a

NOTE: Use straight line interpolation for intermediate values of S1.

 a

 Site-specific geotechnical investigation and dynamic site response analyses shall be performed.

Exception: For structures with periods of vibration equal to or less than 0.5 second, values of Fv

for liquefiable soils may be assumed equal to the values for the Site Class determined without

regard to liquefaction in Step 3 of Sec. 4.1.2.2. 

4.1.2.5 Design Spectral Response Acceleration Parameters: Design earthquake spectral

response acceleration at short periods, SDS , and at 1 second period, SD1, shall be determined from

Eq. 4.1.2.5-1 and 4.1.2.5-2, respectively:

S S DS MS = 2

3 (4.1.2.5-1)

and

S S D M 1 1

2

3 = (4.1.2.5-2)

4.1.2.6 General Procedure Response Spectrum: Where a design response spectrum is required

by the Provisions and site-specific procedures are not used, the design response spectrum curve

shall be developed as indicated in Figure 4.1.2.6 and as follows:
Ground Motion

45

FIGURE 4.1.2.6 Design response spectrum.

1. For periods less than or equal to T0, the design spectral response acceleration, Sa, shall be taken

as given by Eq. 4.1.2.6-1:

a

DS

o

S DS

S

T

= + 06 04 . . T S (4.1.2.6-1)

2. For periods greater than or equal to T0 and less than or equal to TS, the design spectral response

acceleration, Sa, shall be taken as equal to SDS.

3. For periods greater than TS, the design spectral response acceleration, Sa, shall be taken as given

by Eq. 4.1.2.6-3:

a

D

S

S

T = 1 (4.1.2.6-3)

where:

SDS = the design spectral response acceleration at short periods,

SD1 = the design spectral response acceleration at 1 second period,

T = the fundamental period of the structure (sec),

T0 = 0.2SD1/SDS, and

TS = SD1/SDS.

4.1.3 Site-Specific Procedure for Determining Ground Motion Accelerations: A site-specific

study shall account for the regional seismicity and geology, the expected recurrence rates and

maximum magnitudes of events on known faults and source zones, the location of the site with

respect to these, near source effects if any, and the characteristics of subsurface site conditions.
2000 Provisions, Chapter 4

46

FIGURE 4.1.3.2 Deterministic limit on maximum considered earthquake

response spectrum.

4.1.3.1 Probabilistic Maximum Considered Earthquake: When site-specific procedures are

utilized, the maximum considered earthquake ground motion shall be taken as that motion

represented by a 5 percent damped acceleration response spectrum having a 2 percent probability of

exceedance within a 50 year period. The maximum considered earthquake spectral response

acceleration, SaM, at any period, T, shall be taken from that spectrum.

Exception: Where the spectral response ordinates for a 5 percent damped spectrum

having a 2 percent probability of exceedance within a 50 year period at periods of 0.2

second or 1 second exceed the corresponding ordinate of the deterministic limit of Sec.

4.1.3.2, the maximum considered earthquake ground motion shall be taken as the lesser of

the probabilistic maximum considered earthquake ground motion or the deterministic

maximum considered earthquake ground motion of Sec. 4.1.3.3 but shall not be taken less

than the deterministic limit ground motion of Sec. 4.1.3.2.

4.1.3.2 Deterministic Limit on Maximum Considered Earthquake Ground Motion: The

deterministic limit on maximum considered earthquake ground motion shall be taken as the

response spectrum determined in accordance with Figure 4.1.3.2, where Fa and Fv are determined in

accordance with Sec. 4.1.2.4 with the value of SS taken as 1.5 and the value of S1 taken as 0.6.

4.1.3.3 Deterministic Maximum Considered Earthquake Ground Motion: The deterministic

maximum considered earthquake ground motion response spectrum shall be calculated as 150

percent of the median 5 percent damped spectral response accelerations, SaM, at all periods resulting

from a characteristic earthquake on any known active fault within the region.
Ground Motion

47

4.1.3.5 Site-Specific Design Ground Motion: Where site-specific procedures are used to

determine the maximum considered earthquake ground motion response spectrum, the design

spectral response acceleration at any period shall be determined from Eq. 4.1.3.5:

S S a aM = 2

3 (4.1.3.5)

and shall be greater than or equal to 80 percent of the Sa determined by the general response

spectrum in Sec. 4.1.2.6.

4.2 SEISMIC DESIGN CATEGORY: Each structure shall be assigned a Seismic Design

Category in accordance with Sec. 4.2.1. Seismic Design Categories are used in the Provisions to

determine permissible structural systems, limitations on height and irregularity, those components

of the structure that must be designed for seismic resistance, and the types of lateral force analysis

that must be performed.

4.2.1 Determination of Seismic Design Category: All structures shall be assigned to a Seismic

Design Category based on their Seismic Use Group and the design spectral response acceleration

coefficients, SDS and SD1, determined in accordance with Sec. 4.1.2.5. Each building and structure

shall be assigned to the most severe Seismic Design Category in accordance with Table 4.2.1a or

4.2.1b, irrespective of the fundamental period of vibration of the structure, T.

TABLE 4.2.1a Seismic Design Category Based on Short Period Response Accelerations

Value of SDS Seismic Use Group

I II III

 SDS < 0.167 A A A

0.167 # SDS < 0.33 B B C

0.33 # SDS < 0.50 C C D

0.50 # SDS D a D a D a

 a Seismic Use Group I and II structures located on sites with mapped maximum considered earthquake spectral

response acceleration at 1 second period, S1, equal to or greater than 0.75 shall be assigned to Seismic Design

Category E and Seismic Use Group III structures located on such sites shall be assigned to Seismic Design

Category F.
2000 Provisions, Chapter 4

48

TABLE 4.2.1b Seismic Design Category Based on 1 Second Period Response Accelerations

Value of SD1

Seismic Use Group

I II III

SD1 < 0.067 A A A

0.067 # SD1 < 0.133 B B C

0.133 # SD1 < 0.20 C C D

0.20 # SD1 D a D a D a

 a Seismic Use Group I and II structures located on sites with mapped maximum considered earthquake spectral

response acceleration at 1 second period, S1, equal to or greater than 0.75 shall be assigned to Seismic Design

Category E and Seismic Use Group III structures located on such sites shall be assigned to Seismic Design

Category F.

4.2.2 Site Limitation for Seismic Design Categories E and F: A structure assigned to Seismic

Design Category E or F shall not be sited where there is the potential for an active fault to cause

rupture of the ground surface at the structure. 

Exception: Detached one- and two-family dwellings of light-frame construction.
49

Chapter 5

STRUCTURAL DESIGN CRITERIA

5.1 REFERENCE DOCUMENT:

The following reference document shall be used for loads other than earthquake and for

combinations of loads as indicated in this chapter:

ASCE 7 Minimum Design Loads for Buildings and Other Structures, ASCE 7, 1998

5.2 DESIGN BASIS: 

5.2.1 General: The seismic analysis and design procedures to be used in the design of buildings

and other structures and their components shall be as prescribed in this chapter.

The structure shall include complete lateral- and vertical-force-resisting systems capable of

providing adequate strength, stiffness, and energy dissipation capacity to withstand the design

ground motions within the prescribed limits of deformation and strength demand. The design

ground motions shall be assumed to occur along any direction of the structure. The adequacy of

the structural systems shall be demonstrated through construction of a mathematical model and

evaluation of this model for the effects of the design ground motions. Unless otherwise required,

this evaluation shall consist of a linear elastic analysis in which design seismic forces are

distributed and applied throughout the height of the structure in accordance with the procedures

in Sec. 5.3 or Sec. 5.4. The corresponding structural deformations and internal forces in all

members of the structure shall be determined and evaluated against acceptance criteria contained

in the Provisions. Approved alternative procedure based on general principles of engineering

mechanics and dynamics are permitted to be used to establish the seismic forces and their

distribution. If an alternative procedure is used, the corresponding internal forces and deformations in the members shall be determined using a model consistent with the procedure

adopted.

Individual members shall be provided with adequate strength to resist the shears, axial forces,

and moments determined in accordance with the Provisions, and connections shall develop the

strength of the connected members or the forces indicated above. The deformation of the

structure shall not exceed the prescribed limits.

A continuous load path, or paths, with adequate strength and stiffness shall be provided to

transfer all forces from the point of application to the final point of resistance. The foundation

shall be designed to accommodate the forces developed or the movements imparted to the

structure by the design ground motions. In the determination of the foundation design criteria,

special recognition shall be given to the dynamic nature of the forces, the expected ground

motions, and the design basis for strength and energy dissipation capacity of the structure.

5.2.2 Basic Seismic-Force-Resisting Systems: The basic lateral and vertical seismic-forceresisting system shall conform to one of the types indicated in Table 5.2.2 subject to the
2000 Provisions, Chapter 5

50

limitations on height based on Seismic Design Category indicated in the table. Each type is

subdivided by the types of vertical element used to resist lateral seismic forces. The appropriate

response modification coefficient, R, system overstrength factor, S0, and deflection amplification

factor, Cd, indicated in Table 5.2.2 shall be used in determining the base shear, element design

forces, and design story drift as indicated in the Provisions.

Seismic-force-resisting systems that are not contained in Table 5.2.2 shall be permitted if

analytical and test data are submitted that establish the dynamic characteristics and demonstrate

the lateral force resistance and energy dissipation capacity to be equivalent to the structural

systems listed in Table 5.2.2 for equivalent response modification coefficient, R, system overstrength coefficient, S0, and deflection amplification factor, Cd, values. 

Special framing requirements are indicated in Sec. 5.2.6 and in Chapters 8, 9, 10, 11, and 12 for

structures assigned to the various Seismic Design Categories.

5.2.2.1 Dual System: For a dual system, the moment frame shall be capable of resisting at least

25 percent of the design forces. The total seismic force resistance is to be provided by the

combination of the moment frame and the shear walls or braced frames in proportion to their

rigidities.

5.2.2.2 Combinations of Framing Systems: Different seismic-force-resisting systems are

permitted along the two orthogonal axes of the structure. Combinations of seismic-forceresisting systems shall comply with the requirements of this section.

5.2.2.2.1 R and S0 Factors: The response modification coefficient, R, in the direction under

consideration at any story shall not exceed the lowest response modification factor, R, for the

seismic-force-resisting system in the same direction considered above that story excluding

penthouses. For other than dual systems where a combination of different structural systems is

utilized to resist lateral forces in the same direction, the value of R used in that direction shall not

be greater than the least value of any of the systems utilized in the same direction. If a system

other than a dual system with a response modification coefficient, R, with a value of less than 5 is

used as part of the seismic-force-resisting system in any direction of the structure, the lowest

such value shall be used for the entire structure. The system overstrength factor, S0, in the

direction under consideration at any story shall not be less than the largest value of this factor for

the seismic-force-resisting system in the same direction considered above that story. 

Exceptions:

1. Supported structural systems with a weight equal to or less than 10 percent of the

weight of the structure.

2. Detached one- and two-family dwellings of light-frame construction.

5.2.2.2.2 Combination Framing Detailing Requirements: The detailing requirements of Sec. 

5.2.6 required by the higher response modification coefficient, R, shall be used for structural

components common to systems having different response modification coefficients.

5.2.2.3 Seismic Design Categories B and C: The structural framing system for structures

assigned to Seismic Design Categories B and C shall comply with the structure height and

structural limitations in Table 5.2.2.
51

Table 5.2.2 Design Coefficients and Factors for Basic Seismic-Force-Resisting Systems 

Basic Seismic-Force-Resisting System Detailing

ReferenceSection

ResponseModification Coefficient, Ra

System Overstrength Factor, S0 g Deflection Ampli- fication

Factor, Cdb

System Limitations aations (ft) by Seismic B C D 

Bearing Wall SystemsOrdinary steel concentrically braced frames -- Lightframed wall

8.6 4 2 31⁄2 NL NL 6

Special reinforced concrete shear walls 9.3.2.4 5 21⁄2 5 NL NL 1Ordinary reinforced concrete shear walls 9.3.2.3 4 21⁄2 4 NL NL NDetailed plain concrete shear walls 9.3.2.2 21⁄2 21⁄2 2 NL NL NOrdinary plain concrete shear walls 9.3.2.1 11⁄2 21⁄2 11⁄2 NL NP NSpecial reinforced masonry shear walls 11.11.5 31⁄2 21⁄2 31⁄2 NL NL 1Intermediate reinforced masonry shear walls 11.11.4 21⁄2 21⁄2 21⁄4 NL NL NOrdinary reinforced masonry shear walls 11.11.3 2 21⁄2 13⁄4 NL NP NDetailed plain masonry shear walls 11.11.2 2 21⁄2 13⁄4 NL 160 NOrdinary plain masonry shear walls 11.11.1 11⁄2 21⁄2 11⁄4 NL NP NLight frame walls with shear panels 8.6, 12.3.4,

12.4

61⁄2 3 4 NL NL 6

Building Frame SystemsSteel eccentrically braced frames, moment resisting,

connections at columns away from links

AISC Seismic,  Part I, Sec. 15

8 2 4 NL NL 1

Steel eccentrically braced frames, nonmoment resisting, connections at columns away from links AISC Seismic, Part I, Sec. 15 7 2 4 NL NL 1
Basic Seismic-Force-Resisting System Detailing

ReferenceSection

ResponseModification Coefficient, Ra

System Overstrength Factor, S0 g Deflection Ampli- fication

Factor, Cdb

System Limitations aations (ft) by Seismic B C D 

52

Special steel concentrically braced frames AISC Seismic,

Part I, Sec. 13

6 2 5 NL NL 1

Ordinary steel concentrically braced frames 8.4.4; AISC

Seismic

5 2 41⁄2 NL NL 3

Special reinforced concrete shear walls 9.3.2.4 6 21⁄2 5 NL NL 1Ordinary reinforced concrete shear walls 9.3.2.3 5 21⁄2 41⁄2 NL NL NDetailed plain concrete shear walls 9.3.2.2 3 21⁄2 21⁄2 NL NL NOrdinary plain concrete shear walls 9.3.2.1 2 21⁄2 2 NL NP NComposite eccentrically braced frames AISC Seismic,

Part II, Sec. 14

8 2 4 NL NL 1

Composite concentrically braced frames AISC Seismic,

Part II, Sec. 13 

5 2 41⁄2 NL NL 1

Ordinary composite braced frames AISC Seismic,

Part II, Sec. 12 

3 2 3 NL NL N

Composite steel plate shear walls AISC Seismic,

Part II, Sec. 17 

61⁄2 21⁄2 51⁄2 NL NL 1

Special composite reinforced concrete shear wallswith steel elements

AISC Seismic,Part II, Sec. 16 

6 21⁄2 5 NL NL 1

Ordinary composite reinforced concrete shear walls

with steel elements

AISC Seismic.Part II, Sec. 15 

5 21⁄2 41⁄2 NL NL N

Special reinforced masonry shear walls 11.11.5 41⁄2 21⁄2 4 NL NL 1Intermediate reinforced masonry shear walls 11.11.4 3 21⁄2 21⁄2 NL NL NOrdinary reinforced masonry shear walls 11.11.3 21⁄2 21⁄2 21⁄4 NL NP N
Basic Seismic-Force-Resisting System Detailing

ReferenceSection

ResponseModification Coefficient, Ra

System Overstrength Factor, S0 g Deflection Ampli- fication

Factor, Cdb

System Limitations aations (ft) by Seismic B C D 

53

Detailed plain masonry shear walls 11.11.2 21⁄2 21⁄2 21⁄4 NL 160 NOrdinary plain masonry shear walls 11.11.1 11⁄2 21⁄2 11⁄4 NL NP NLight frame walls with shear panels 8.6, 12.3.4,

12.4

7 21⁄2 41⁄2 NL NL 1

Moment Resisting Frame SystemsSpecial steel moment frames AISC Seismic,

Part I, Sec. 9

8 3 51⁄2 NL NL N

Special steel truss moment frames AISC Seismic,

Part I, Sec. 12

7 3 51⁄2 NL NL 1

Intermediate steel moment frames AISC Seismic, 

Part I, Sec. 10

41⁄2. 3 4 NL NL 3

Ordinary steel moment frames AISC Seismic,

Part I, Sec. 11

31⁄2 3 3 NL NL N

Special reinforced concrete moment frames 9.3.1.3 8 3 51⁄2 NL NL NIntermediate reinforced concrete moment frames 9.3.1.2 5 3 41⁄2 NL NL NOrdinary reinforced concrete moment frames 9.3.1.1 3 3 21⁄2 NL NP NSpecial composite moment frames AISC Seismic,

Part II, Sec. 9 

8 3 51⁄2 NL NL N

Intermediate composite moment frames AISC Seismic,

Part II, Sec. 10 

5 3 41⁄2 NL NL N

Composite partially restrained moment frames AISC Seismic,

Part II, Sec. 8 

6 3 51⁄2 160 160 10

Ordinary composite moment frames AISC Seismic,

Part II, Sec. 11 

3 3 21⁄2 NL NP N
Basic Seismic-Force-Resisting System Detailing

ReferenceSection

ResponseModification Coefficient, Ra

System Overstrength Factor, S0 g Deflection Ampli- fication

Factor, Cdb

System Limitations aations (ft) by Seismic B C D 

54

Special masonry moment frames 11.2 51⁄2 3 5 NL NL 1Dual Systems with Special Moment Frames Capable of Resisting at Least 25% of Prescribed Seismic ForcesSteel eccentrically braced frames, moment resisting

connections, at columns away from links

AISCSeismic,Part I,Sec. 15

8 21⁄2 4 NL NL N

Steel eccentrically braced frames, non-moment

resisting connections, at columns away from links

AISC Seismic,Part I, Sec. 15

7 21⁄2 4 NL NL N

Special steel concentrically braced frames AISC Seismic,

Part I, Sec. 13

8 21⁄2 61⁄2 NL NL N

Special reinforced concrete shear walls 9.3.2.4 8 21⁄2 61⁄2 NL NL NOrdinary reinforced concrete shear walls 9.3.2.3 7 21⁄2 6 NL NL NComposite eccentrically braced frames AISC Seismic,

Part II, Sec. 14 

8 21⁄2 4 NL NL N

Composite concentrically braced frames AISC Seismic,

Part II, Sec. 13 

6 21⁄2 5 NL NL N

Composite steel plate shear walls AISC Seismic,

Part II, Sec. 17 

8 21⁄2 61⁄2 NL NL N

Special composite reinforced concrete shear wallswith steel elements

AISC Seismic,Part II, Sec. 16 

8 21⁄2 61⁄2 NL NL N

Ordinary composite reinforced concrete shear walls

with steel elements

AISC Seismic,Part II, Sec. 15 

7 21⁄2 6 NL NL N

Special reinforced masonry shear walls 11.11.5 7 3 61⁄2 NL NL NIntermediate reinforced masonry shear walls 11.11.4 61⁄2 3 51⁄2 NL NL NDual Systems with Intermediate Moment Frames Capable of Resisting at Least 25% of Prescribed Seismic Forces
Basic Seismic-Force-Resisting System Detailing

ReferenceSection

ResponseModification Coefficient, Ra

System Overstrength Factor, S0 g Deflection Ampli- fication

Factor, Cdb

System Limitations aations (ft) by Seismic B C D 

55

Special steel concentrically braced frames f AISC Seismic,

Part I, Sec. 13

41⁄2 21⁄2 4 NL NL 3

Special reinforced concrete shear walls 9.3.2.4 6 21⁄2 5 NL NL 1Ordinary reinforced concrete shear walls 9.3.2.3 51⁄2 21⁄2 41⁄2 NL NL NOrdinary reinforced masonry shear walls 11.11.3 3 3 21⁄2 NL 160 NIntermediate reinforced masonry shear walls 11.11.4 5 3 41⁄2 NL NL 1Composite concentrically braced frames AISC Seismic,

Part II, Sec. 13 

5 21⁄2 41⁄2 NL NL 1

Ordinary composite braced frames AISC Seismic,

Part II, Sec. 12 

4 21⁄2 3 NL NL N

Ordinary composite reinforced concrete shear walls

with steel elements

AISC Seismic,Part II, Sec. 15 

51⁄2 21⁄2 41⁄2 NL NL N

Inverted Pendulum Systems and Cantilevered Column SystemsSpecial steel moment frames AISC Seismic,

Part I, Sec. 9

21⁄2 2 21⁄2 NL NL N

Ordinary steel moment frames AISC Seismic,

Part I, Sec. 11

11⁄4 2 21⁄2 NL NL N

Special reinforced concrete moment frames 9.3.1.3 21⁄2 2 11⁄4 NL NL NStructural Steel Systems Not Specifically Detailedfor Seismic Resistance

AISC-ASD,AISC-LRFD,AISI

3 3 3 NL NL N
56

NOTES FOR TABLE 5.2.2

a

 Response modification coefficient, R, for use throughout the Provisions.

b

 Deflection amplification factor, Cd, for use in Sec. 5.4.6.1 and 5.4.6.2.

c

 NL = not limited and NP = not permitted. If using metric units, 100 ft approximately equals 30

m and 160 ft approximately equals 50 m. Heights are measured from the base of the structure as

defined in Sec. 2.1.

d

 See Sec. 5.2.2.4.1 for a description of building systems limited to buildings with a height of 240

ft (70 m) or less.

e

 See Sec. 5.2.2.5 for building systems limited to buildings with a height of 160 ft (50 m) or less.

f

 An ordinary moment frame is permitted to be used in lieu of an Intermediate moment frame in

Seismic Design Categories B and C.

g

 The tabulated value of the overstrength factor, S0, may be reduced by subtracting 1⁄2 for

structures with flexible diaphragms but shall not be taken as less than 2 for any structure.

i

 Steel ordinary moment frames and intermediate moment frames are permitted in single-story

buildings up to a height of 60 ft when the moment joints of field connections are constructed of

bolted end plates and the dead load of the roof does not exceed 15 psf.

j

 Steel ordinary moment frames are permitted in buildings up to a height of 35 ft where the dead

load of the walls, floors, and roofs does not exceed 15 psf.

k

 Steel ordinary braced frames are permitted in single-story buildings up to a height of 60 ft when

the dead load of the roof does not exceed 15 psf and in penthouse structures.
Structural Design Criteria

57

5.2.2.4 Seismic Design Categories D and E: The structural framing system for a structure

assigned to Seismic Design Categories D and E shall comply with Sec. 5.2.2.3 and the additional

requirements of this section.

5.2.2.4.1 Limited Building Height: The height limit in Table 5.2.2 is permitted to be increased

to 240 ft (70 m) in buildings that have steel braced frames or concrete cast-in-place shear walls. 

Such buildings shall be configured such that the braced frames or shear walls arranged in any

one plane conform to the following:

1. The braced frames or cast-in-place special reinforced concrete shear walls in any one plane

shall resist no more than 60 percent of the total seismic forces in each direction, neglecting

torsional effects, and

2. The seismic force in any braced frame or shear wall resulting from torsional effects shall not

exceed 20 percent of the total seismic force in that braced frame or shear wall.

5.2.2.4.2 Interaction Effects: Moment frames that are enclosed or adjoined by more rigid

elements not considered to be part of the seismic-force-resisting system shall be designed so that

the action or failure of those elements will not impair the vertical load and seismic-force-resisting

capability of the frame. The design shall consider and provide for the effect of these rigid

elements on the structural system at structure deformations corresponding to the design story

drift, ), as determined in Sec. 5.4.6. In addition, the effects of these elements shall be considered

when determining whether a structure has one or more of the irregularities defined in Sec. 5.2.3.

5.2.2.4.3 Deformational Compatibility: Every structural component not included in the

seismic-force-resisting system in the direction under consideration shall be designed to be

adequate for the vertical load-carrying capacity and the induced moments and shears resulting

from the design story drift, ), as determined in accordance with Sec. 5.4.6 (also see Sec. 5.2.7).

Exception: Beams and columns and their connections not designed as part of the lateralforce-resisting system but meeting the detailing requirements for either intermediate

moment frames or special moment frames are permitted to be designed to be adequate for

the vertical load-carrying capacity and the induced moments and shears resulting from the

deformation of the building under the application of the design seismic forces.

When determining the moments and shears induced in components that are not included in the

seismic-force-resisting system in the direction under consideration, the stiffening effects of

adjoining rigid structural and nonstructural elements shall be considered and a rational value of

member and restraint stiffness shall be used.

5.2.2.4.4 Special Moment Frames: A special moment frame that is used but not required by

Table 5.2.2 is permitted to be discontinued and supported by a more rigid system with a lower

response modification coefficient, R, provided the requirements of Sec. 5.2.6.2.3 and 5.2.6.4.2

are met. Where a special moment frame is required by Table 5.2.2, the frame shall be continuous

to the foundation.
2000 Provisions, Chapter 5

58

5.2.2.5 Seismic Design Category F: The framing systems of buildings assigned to Seismic

Design Category F shall conform to the requirements of Sec. 5.2.2.4 for Seismic Design

Categories D and E and to the additional requirements and limitations of this section. The height

limitation of Sec. 5.2.2.4.1 shall be reduced from 240 ft to 160 ft (70 to 50 m).

5.2.3 Structure Configuration: Structures shall be classified as regular or irregular based upon

the criteria in this section. Such classification shall be based on the plan and vertical configuration.

5.2.3.1 Diaphragm Flexibility: Diaphragms constructed of untopped steel decking, wood

structural panels, or similar panelized construction shall be considered flexible in structures

having concrete or masonry shear walls. Diaphragms constructed of wood structural panels

shall be considered rigid in light-frame structures using structural panels for lateral load

resistance. Diaphragms of other types shall be considered flexible when the maximum lateral

deformation of the diaphragm is more than two times the average story drift of the associated

story. The loadings used for this calculation shall be those prescribed by Sec. 5.4

5.2.3.2 Plan Irregularity: Structures having one or more of the features listed in Table 5.2.3.2

shall be designated as having plan structural irregularity and shall comply with the requirements

in the sections referenced in Table 5.2.3.2.

5.2.3.3 Vertical Irregularity: Structures having one or more of the features listed in Table

5.2.3.3 shall be designated as having vertical irregularity and shall comply with the requirements

in the sections referenced in Table 5.2.3.3.

Exceptions: 

1. Structural irregularities of Types 1a, 1b, or 2 in Table 5.2.3.3 do not apply where no

story drift ratio under design lateral load is greater than 130 percent of the story drift

ratio of the story immediately above. Torsional effects need not be considered in the

calculation of story drifts for the purpose of this determination. The story drift ratio

relationship for the top two stories of the structure are not required to be evaluated.

2. Irregularities Types 1a, 1b, and 2 of Table 5.2.3.3 are not required to be considered

for one-story structures or for two-story structures in Seismic Design Categories A,

B, C, or D.
Structural Design Criteria

59

TABLE 5.2.3.2 Plan Structural Irregularities

Irregularity Type and Description Reference

Section

Seismic 

Design 

Category 

Application

1a Torsional Irregularity – to be considered when diaphragms are not flexible

Torsional irregularity shall be considered to exist when

the maximum story drift, computed including accidental

torsion, at one end of the structure transverse to an axis is

more than 1.2 times the average of the story drifts at the

two ends of the structure.

5.2.6.4.2

5.4.4

D, E, and F

C, D, E, and F

1b Extreme Torsional Irregularity -- to be considered

when diaphragms are not flexible

Extreme torsional irregularity shall be considered to exist

when the maximum story drift, computed including

accidental torsion, at one end of the structure transverse

to an axis is more than 1.4 times the average of the story

drifts at the two ends of the structure.

5.2.6.4.2

5.4.4

5.2.6.5.1

D, E, and F

C, D, E, and F

E and F

2 Re-entrant Corners 

Plan configurations of a structure and its lateral-force-resisting system contain re-entrant corners where both

projections of the structure beyond a re-entrant corner are

greater than 15 percent of the plan dimension of the

structure in the given direction.

5.2.6.4.2 D, E, and F 

3 Diaphragm Discontinuity 

Diaphragms with abrupt discontinuities or variations in

stiffness including those having cutout or open areas

greater than 50 percent of the gross enclosed diaphragm

area or changes in effective diaphragm stiffness of more

than 50 percent from one story to the next.

5.2.6.4.2 D, E, and F 

4 Out-of-Plane Offsets

Discontinuities in a lateral force resistance path such as

out-of-plane offsets of the vertical elements.

5.2.6.4.2

5.2.6.2.10

D, E, and F 

B, C, D, E, and

F

5 Nonparallel Systems 

The vertical lateral-force-resisting elements are not

parallel to or symmetric about the major orthogonal axes

of the lateral-force-resisting system.

5.2.5.2 C, D, E, and F
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TABLE 5.2.3.3 Vertical Structural Irregularities

Irregularity Type and Description Reference

Section

Seismic

 Design

Category 

Application

1a Stiffness Irregularity – Soft Story 

A soft story is one in which the lateral stiffness is less

than 70 percent of that in the story above or less than

80 percent of the average stiffness of the three stories

above.

5.2.5.1 D, E, and F 

1b Stiffness Irregularity--Extreme Soft Story

An extreme soft story is one in which the lateral

stiffness is less than 60 percent of that in the story

above or less than 70 percent of the average stiffness

of the three stories above.

5.2.5.1

5.2.6.5.1

D, E, and F

E and F

2 Weight (Mass) Irregularity 

Mass irregularity shall be considered to exist where the

effective mass of any story is more than 150 percent of

the effective mass of an adjacent story. A roof that is

lighter than the floor below need not be considered.

5.2.5.1 D, E, and F 

3 Vertical Geometric Irregularity 

Vertical geometric irregularity shall be considered to

exist where the horizontal dimension of the lateralforce-resisting system in any story is more than 130

percent of that in an adjacent story.

5.2.5.1 D, E, and F 

4 In-Plane Discontinuity in Vertical Lateral-Force

Resisting Elements

An in-plane offset of the lateral-force-resisting elements greater than the length of those elements or a

reduction in stiffness of the resisting element in the

story below.

5.2.5.1 

5.2.6.2.10

5.2.6.4.2

D, E, and F 

B, C, D, E, and

F

D, E, and F

5 Discontinuity in Capacity – Weak Story

A weak story is one in which the story lateral strength

is less than 80 percent of that in the story above. The

story strength is the total strength of all seismic-resisting elements sharing the story shear for the direction

under consideration.

5.2.6.2.3

5.2.5.1

5.2.6.5.1

B, C, D, E, and

F

D, E, and F

E and F
Structural Design Criteria

61

Dx ' 2 & 20

rmaxxAx

(5.2.4.2)

5.2.4 Redundancy: A reliability factor, D, shall be assigned to all structures based on the extent

of structural redundancy inherent in the lateral-force-resisting system. 

5.2.4.1 Seismic Design Categories A, B, and C: For structures in Seismic Design Categories

A, B and C, the value of D may be taken as 1.0. 

5.2.4.2 Seismic Design Category D: For structures in Seismic Design Category D, D shall be

taken as the largest of the values of Dx calculated at each story of the structure “x” in accordance

with Eq. 5.2.4.2:

where:

rmaxx = the ratio of the design story shear resisted by the single element carrying the most

shear force in the story to the total story shear for a given direction of loading. 

For braced frames, the value of rmaxx is equal to the lateral force component in the

most heavily loaded brace element divided by the story shear. For moment

frames, rmaxx

 shall be taken as the maximum of the sum of the shears in any two

adjacent columns in the plane of a moment frame divided by the story shear. For

columns common to two bays with moment resisting connections on opposite

sides at the level under consideration, 70 percent of the shear in that column may

be used in the column shear summation. For shear walls, rmaxx shall be taken

equal to the maximum ratio, rix, calculated as the shear in each wall or wall pier

multiplied by 10/lw (the metric coefficient is 3.3/lw), where lw is the wall or wall

pier length in feet (m) divided by the story shear and where the ratio 10/lw need

not be taken greater than 1.0 for buildings of light frame construction. For dual

systems, rmaxx

 shall be taken as the maximum value as defined above considering

all lateral-load-resisting elements in the story. The lateral loads shall be distributed to elements based on relative rigidities considering the interaction of the

dual system. For dual systems, the value of D need not exceed 80 percent of the

value calculated above.

Ax = the floor area in square feet of the diaphragm level immediately above the story.

The value of D need not exceed 1.5, which is permitted to be used for any structure. The value of

D shall not be taken as less than 1.0.

Exception: For structures with lateral-force-resisting systems in any direction comprised

solely of special moment frames, the lateral-force-resisting system shall be configured

such that the value of D calculated in accordance with this section does not exceed 1.25.

The metric equivalent of Eq. 5.2.4.2 is:
2000 Provisions, Chapter 5

62

Dx ' 2 & 6.1

rmaxxAx

where Ax is in square meters.

5.2.4.3 Seismic Design Categories E and F: For structures in Seismic Design Categories E

and F, the value of D shall be calculated as indicated in Section 5.2.4.2, above.

Exception: For structures with lateral-force-resisting systems in any direction comprised

solely of special moment frames, the lateral-force-resisting system shall be configured

such that the value of D calculated in accordance with Sec. 5.2.4.2 does not exceed 1.1.

5.2.5 Structural Analysis: A structural analysis conforming to one of the types permitted in

Section 5.2.5.1 shall be made for all structures. Application of loading shall be as indicated in

Sec. 5.2.5.2 and as required by the selected analysis procedure. All members of the structure’s

seismic-force-resisting system and their connections shall have adequate strength to resist the

forces, QE, predicted by the analysis in combination with other loads as required by Sec. 5.2.7. 

Drifts predicted by the analysis shall be within the limits specified by Sec. 5.2.8. If a nonlinear

analysis is performed, component deformation demands shall not exceed limiting values as

indicated in Sec. 5.7.3.2.

Exception: For structures in Seismic Design Category A, drift need not be evaluated.

5.2.5.1 Analysis Procedures: The structural analysis required by Sec. 5.2.5 shall consist of one

of the types permitted in Table 5.2.5.1 based on the structure’s Seismic Design Category,

structural system, dynamic properties, and regularity or, with the approval of the authority having

jurisdiction, an alternative generally accepted procedure shall be permitted to be used.

5.2.5.2 Application of Loading: The directions of application of seismic forces used in the

design shall be those that will produce the most critical load effects. It shall be permitted to

satisfy this requirement using the procedures of Sec. 5.2.5.2.1 for Seismic Design Category A or

B, Sec. 5.2.5.2.2 for Seismic Design Category C, and Sec. 5.2.5.2.3 for Seismic Design Category

D, E, or F.

5.2.5.2.1 Seismic Design Category A or B: For structures assigned to Seismic Design

Category A or B, the design seismic forces are permitted to be applied separately in each of two

orthogonal directions and orthogonal interaction effects may be neglected.
63

TABLE 5.2.5.1 Permitted Analytical Procedures

SeismicDesignCategory Structural Characteristics

Index ForceAnalysis,Sec. 5.3

EquivalentLateralForce Analysis, Sec.5.4

Modal ResponseSpectrumAnalysis,Sec. 5.5

LinearResponseHistoryAnalysis,Sec. 5.6

A Regular or irregular P P P P B, C Regular or irregular NP P P P D, E, F Regular structures with T < 3.5Ts

and all structures of light frame

construction

NP P P P 

Irregular structures with T < 3.5Ts

and having only plan irregularitiesType 2, 3, 4, or 5 Table 5.2.3.2 orvertical irregularities Type 4 or 5 ofTable 5.2.3.3.

NP P P P 

Irregular structures with T < 3.5Tsand having either plan irregularitiesType 1a or 1b of Table 5.2.3.2 orvertical irregularities Type 1a or1b, 2, or 3 of Table 5.2.3.3.

NP NP P P 

All other structures NP NP P P 

Notes: P indicates permitted; NP indicates not permitted.
2000 Provisions, Chapter 5

64

5.2.5.2.2 Seismic Design Category C: Loading applied to structures assigned to Seismic

Design Category C shall, as a minimum, conform to the requirements of Sec. 5.2.5.2.1 for

Seismic Design Categories A and B and the requirements of this section. Structures that have

plan structural irregularity Type 5 in Table 5.2.3.2 shall be analyzed for seismic forces using a

three-dimensional representation and either of the following procedures:

a. The structure shall be analyzed using the equivalent lateral force analysis procedure of Sec.

5.4, the modal response spectrum analysis procedure of Sec. 5.5, or the linear response

history analysis procedure of Sec. 5.6 as permitted under Sec. 5.2.5.1 with the loading

applied independently in any two orthogonal directions. The most critical load effect due to

direction of application of seismic forces on the structure may be assumed to be satisfied if

components and their foundations are designed for the following combination of prescribed

loads: 100 percent of the forces for one direction plus 30 percent of the forces for the

perpendicular direction; the combination requiring the maximum component strength shall be

used.

b. The structure shall be analyzed using the linear response history analysis procedure of Sec.

5.6 or the nonlinear response history analysis procedure of Sec. 5.7 as permitted by Sec.

5.2.5.1 with simultaneous application of ground motion in each of two orthogonal directions.

5.2.5.2.3 Seismic Design Category D, E, or F: Structures assigned to Seismic Design Category

D, E, or F shall be designed for the most critical load effect due to application of seismic forces

in any direction. Either of the procedures of Sec. 5.2.5.2.2 shall be permitted to be used to satisfy

this requirement. Two-dimensional analysis shall be permitted to be used where diaphragms are

flexible and the structure does not have plan structural irregularity Type 5 of Table 5.2.3.2.

5.2.6 Design and Detailing Requirements: The design and detailing of the components of the

seismic-force-resisting system shall comply with the requirements of this section. Foundation

design shall conform to the applicable requirements of Chapter 7. The materials and the systems

composed of those materials shall conform to the requirements and limitations of Chapters 8

through 12 for the applicable category.

5.2.6.1 Seismic Design Category A: The design and detailing of structures assigned to Seismic

Design Category A shall comply with the requirements of this section.

5.2.6.1.1 Connections: All parts of the structure between separation joints shall be interconnected, and the connections shall be capable of transmitting the seismic force, Fp, induced by

the parts being connected. Any smaller portion of the structure shall be tied to the remainder of

the structure with elements having a strength of 0.133 times the short period design spectral

response acceleration coefficient, SDS, times the weight of the smaller portion or 5 percent of the

portion's weight, whichever is greater.

A positive connection for resisting a horizontal force acting parallel to the member shall be

provided for each beam, girder, or truss to its support. The connection shall have a minimum

strength of 5 percent of the dead load and live load reaction.

5.2.6.1.2 Anchorage of Concrete or Masonry Walls: Concrete and masonry walls shall be

anchored to the roof and all floors and to members that provide lateral support for the wall or

which are supported by the wall. The anchorage shall provide a direct connection between the
Structural Design Criteria

65

walls and the roof or floor construction. The connections shall be capable of resisting a seismic

lateral force, Fp, induced by the wall of 400 times the short period design spectral response

acceleration coefficient, SDS, in pounds per lineal ft (5840 times SDS in N/m ) of wall multiplied

by the occupancy importance factor, I. Walls shall be designed to resist bending between

anchors where the anchor spacing exceeds 4 ft (1.2 m).

5.2.6.2 Seismic Design Category B: Structures assigned to Seismic Design Category B shall

conform to the requirements of Sec. 5.2.6.1 for Seismic Design Category A and the requirements

of this section.

5.2.6.2.1 P-Delta Effects: P-delta effects shall be included as required by Sec. 5.4.6.2

5.2.6.2.2 Openings: Where openings occur in shear walls, diaphragms or other plate-type

elements, reinforcement at the edges of the openings shall be designed to transfer the stresses

into the structure. The edge reinforcement shall extend into the body of the wall or diaphragm a

distance sufficient to develop the force in the reinforcement.

5.2.6.2.3 Discontinuities in Vertical System: Structures with a discontinuity in lateral

capacity, vertical irregularity Type 5 as defined in Table 5.2.3.3, shall not be over 2 stories or 30

ft (9 m) in height where the "weak" story has a calculated strength of less than 65 percent of the

strength of the story above.

Exception: The height limitation shall not apply when the "weak" story is capable of

resisting a total seismic force equal to 75 percent of the deflection amplification factor,

Cd, times the design force prescribed in Sec. 5.3.

5.2.6.2.4 Nonredundant Systems: The design of a structure shall consider the potentially

adverse effect that the failure of a single member, connection, or component of the seismic-forceresisting system would have on the stability of the structure.

5.2.6.2.5 Collector Elements: Collector elements shall be provided that are capable of transferring the seismic forces originating in other portions of the structure to the element providing the

resistance to those forces.

5.2.6.2.6 Diaphragms: The deflection in the plane of the diaphragm, as determined by engineering analysis, shall not exceed the permissible deflection of the attached elements. 

Permissible deflection shall be a deflection that permits the attached element to maintain its

structural integrity under the individual loading and to continue to support the prescribed loads.

Floor and roof diaphragms shall be designed to resist the following seismic forces: A minimum

force equal to 20 percent of the short period design spectral response acceleration, SDS, times the

weight of the diaphragm and other elements of the structure attached thereto plus the portion of

the seismic shear force at that level, Vx, required to be transferred to the components of the vertical seismic-force-resisting system because of offsets or changes in stiffness of the vertical

components above and below the diaphragm.

Diaphragms shall provide for both the shear and bending stresses resulting from these forces. 

Diaphragms shall have ties or struts to distribute the wall anchorage forces into the diaphragm. 

Diaphragm connections shall be positive, mechanical, or welded type connections.
2000 Provisions, Chapter 5

66

F

p ' 1.2SDS IWp (5.2.6.3.2)

5.2.6.2.7 Bearing Walls: Exterior and interior bearing walls and their anchorage shall be designed for a force equal to 40 percent of the short period design spectral response acceleration,

SDS, times the weight of wall, Wc, normal to the surface, with a minimum force of 10 percent of

the weight of the wall. Interconnection of wall elements and connections to supporting framing

systems shall have sufficient ductility, rotational capacity, or strength to resist shrinkage, thermal

changes, and differential foundation settlement when combined with seismic forces.

5.2.6.2.8 Inverted Pendulum-Type Structures: Supporting columns or piers of inverted

pendulum-type structures shall be designed for the bending moment calculated at the base determined using the procedures given in Sec. 5.3 and varying uniformly to a moment at the top equal

to one-half the calculated bending moment at the base.

5.2.6.2.9 Anchorage of Nonstructural Systems: When required by Chapter 6, all portions or

components of the structure shall be anchored for the seismic force, Fp, prescribed therein.

5.2.6.2.10 Columns Supporting Discontinuous Walls or Frames: Columns supporting

discontinuous walls or frames of structures having plan irregularity Type 4 of Table 5.2.3.2 or

vertical irregularity Type 4 of Table 5.2.3.3 shall have the design strength to resist the maximum

axial force that can develop in accordance with the special combination of loads of Sec. 5.2.7.1.

5.2.6.3 Seismic Design Category C: Structures assigned to Seismic Design Category C shall

conform to the requirements of Sec. 5.2.6.2 for Seismic Design Category B and to the requirements of this section.

5.2.6.3.1 Collector Elements: Collector elements shall be provided that are capable of

transferring the seismic forces originating in other portions of the structure to the element

providing the resistance to those forces. Collector elements, splices, and their connections to

resisting elements shall resist the of Sec. 5.2.7.1.

Exception: In structures or portions thereof braced entirely by light frame shear walls,

collector elements, splices, and connections to resisting elements are permitted to be

designed to resist forces in accordance with Eq. 5.2.6.4.4.

The quantity S0E in Eq. 5.2.7.1-1 need not exceed the maximum force that can be transferred to

the collector by the diaphragm and other elements of the lateral-force-resisting system.

5.2.6.3.2 Anchorage of Concrete or Masonry Walls: Concrete or masonry walls shall be

anchored to all floors, roofs, and members that provide out-of-plane lateral support for the wall

or that are supported by the wall. The anchorage shall provide a positive direct connection

between the wall and the floor, roof, or supporting member capable of resisting the horizontal

forces specified in this section for structures with flexible diaphragms or of Sec. 6.1.3 for

structures with diaphragms that are not flexible.

Anchorage of walls to flexible diaphragms shall have the strength to develop the out-of-plane

force given by Eq. 5.2.6.3.2:
Structural Design Criteria

67

where:

Fp = the design force in the individual anchors,

SDS = the design spectral response acceleration at short periods in accordance with Sec.

4.1.2.5,

I = the occupancy importance factor in accordance with Sec. 1.4, and

Wp = the weight of the wall tributary to the anchor.

Diaphragms shall be provided with continuous ties or struts between diaphragm chords to

distribute these anchorage forces into the diaphragms. Added chords are permitted to be used to

form subdiaphragms to transmit the anchorage forces to the main continuous cross-ties. The

maximum length to width ratio of the structural subdiaphragm shall be 2-1/2 to 1. Connections

and anchorages capable of resisting the prescribed forces shall be provided between the diaphragm and the attached components. Connections shall extend into the diaphragm a sufficient

distance to develop the force transferred into the diaphragm.

In wood diaphragms, the continuous ties shall be in addition to the diaphragm sheathing. 

Anchorage shall not be accomplished by use of toe nails or nails subject to withdrawal nor shall

wood ledgers of framing be used in cross-grain bending or cross-grain tension. The diaphragm

sheathing shall not be considered as effectively providing the ties or struts required by this

section.

In metal deck diaphragms, the metal deck shall not be used as the continuous ties required by

this section in the direction perpendicular to the deck span.

Diaphragm-to-wall anchorage using embedded straps shall be attached to or hooked around the

reinforcing steel or otherwise terminated so as to effectively transfer forces to the reinforcing

steel.

5.2.6.4 Seismic Design Category D: Structures assigned to Seismic Design Category D shall

conform to the requirements of Sec. 5.2.6.3 for Seismic Design Category C and to the requirements of this section.

5.2.6.4.1 Collector Elements: Collector elements shall be provided that are capable of

transferring the seismic forces originating in other portions of the structure to the element

providing the resistance to those forces. Collector elements, splices, and their connections to

resisting elements shall resist the forces determined in accordance with Eq. 5.2.6.4.4. In

addition, collector elements, splices, and their connections to resisting elements shall have the

design strength to resist the earthquake loads defined in the special load combination of Sec.

5.2.7.1.

Exception: In structures or portions thereof braced entirely by light shear walls,

collector elements, splices, and connections to resisting elements are permitted to be

designed to resist forces in accordance with Eq. 5.2.5.4.

The quantity S0E in Eq. 5.2.7.1-1 need not exceed the maximum force that can be transferred to

the collector by the diaphragm and other elements of the lateral-force-resisting system.
2000 Provisions, Chapter 5

68

F

px '

3

n

i ' x

Fi

3

n

i ' x

wi

w

px (5.2.6.4.4)

5.2.6.4.2 Plan or Vertical Irregularities: The design shall consider the potential for adverse

effects when the ratio of the strength provided in any story to the strength required is significantly less than that ratio for the story immediately above and the strengths shall be adjusted

to compensate for this effect.

For structures having a plan structural irregularity of Type 1a, 1b, 2, 3, or 4 in Table 5.2.3.2 or a

vertical structural irregularity of Type 4 in Table 5.2.3.3, the design forces determined from Sec.

5.4.1 shall be increased 25 percent for connections of diaphragms to vertical elements and to

collectors and for connections of collectors to the vertical elements. Collectors also shall be

designed for these increased forces unless subject to the requirements of Sec. 5.2.6.4.1 or Sec.

8.6.2.

5.2.6.4.3 Vertical Seismic Forces: The vertical component of earthquake ground motion shall

be considered in the design of horizontal cantilever and horizontal prestressed components. The

load combinations used in evaluating such components shall include E as defined by Eq. 5.2.7-1

and 5.2.7-2. Horizontal cantilever structural components shall be designed for a minimum net

upward force of 0.2 times the dead load in addition to the applicable load combinations of Sec.

5.2.7.

5.2.6.4.4 Diaphragms: Diaphragms shall be designed to resist design seismic forces determined in accordance with Eq. 5.2.6.4.4 as follows:

where:

Fpx = the diaphragm design force,

Fi = the design force applied to Level i,

wi = the weight tributary to Level I, and

wpx = the weight tributary to the diaphragm at Level x.

The force determined from Eq. 5.2.6.4.4 need not exceed 0.4SDSIwpx but shall not be less than

0.2SDSIwpx. When the diaphragm is required to transfer design seismic forces from the verticalresisting elements above the diaphragm to other vertical-resisting elements below the diaphragm

due to offsets in the placement of the elements or to changes in relative lateral stiffness in the

vertical elements, these forces shall be added to those determined from Eq. 5.2.6.4.4. 

5.2.6.5 Seismic Design Categories E and F: Structures assigned to Seismic Design Categories

E and F shall conform to the requirements of Sec. 5.2.6.4 for Seismic Design Category D and to

the requirements of this section.
Structural Design Criteria

69

E ' DQE % 0.2SDSD (5.2.7-1)

E ' DQE & 0.2SDS D (5.2.7-2)

E ' S0QE & 0.2SDS D (5.2.7.1-2)

E ' S0QE % 0.2SDS D (5.2.7.1-1)

5.2.6.5.1 Plan or Vertical Irregularities: Structures having plan irregularity Type 1b of Table

5.2.3.2 or vertical irregularities Type 1b or 5 of Table 5.2.3.3 shall not be permitted.

5.2.7 Combination of Load Effects: The effects on the structure and its components due to

gravity loads and seismic forces shall be combined in accordance with the factored load

combinations as presented in ASCE7- 98 except that the effect of seismic loads, E, shall be as

defined herein.

The effect of seismic load E shall be defined by Eq. 5.2.7-1 as follows for load combinations in

which the effects of gravity loads and seismic loads are additive:

where:

E = the effect of horizontal and vertical earthquake-induced forces,

SDS = the design spectral response acceleration at short periods obtained from Sec.

4.1.2.5.

D = the effect of dead load, 

D = the reliability factor, and

QE = the effect of horizontal seismic forces.

The effect of seismic load E shall be defined by Eq. 5.2.7-2 as follows for load combinations in

which the effects of gravity counteract seismic load:

where E, D, QE, SDS, and D are as defined above.

5.2.7.1 Special Combination of Loads: When specifically required by the Provisions, the

design seismic force on components sensitive to the effects of structural overstrength shall be as

defined by Eq. 5.2.7.1-1 and 5.2.7.1-2 when seismic load is, respectively, additive or

counteractive to the gravity forces as follows:
2000 Provisions, Chapter 5

70

where E, QE, SDS, and D are as defined above and S0 is the system overstrength factor as given in

Table 5.2.2. The term S0QE calculated in accordance with Eq. 5.2.7.1-1 and 5.2.7.1-2 need not

exceed the maximum force that can develop in the element as determined by a rational plastic

mechanism analysis or nonlinear response analysis utilizing realistic expected values of material

strengths.

Exception: The special load combination of Eq. 5.2.7.1-1 need not apply to the design of

components in structures in Seismic Design Category A.

5.2.8 Deflection and Drift Limits: The design story drift, ), as determined in Sec. 5.3.7 or

5.4.6 shall not exceed the allowable story drift, )a, as obtained from Table 5.2.8 for any story. 

For structures with significant torsional deflections, the maximum drift shall include torsional

effects. All portions of the structure shall be designed and constructed to act as an integral unit

in resisting seismic forces unless separated structurally by a distance sufficient to avoid damaging

contact under total deflection, *x , as determined in Sec. 5.3.7.1.

TABLE 5.2.8 Allowable Story Drift, )a

a

 (in. or mm)

Structure 

Seismic Use Group

I II III

Structures, other than masonry shear wall or

masonry wall frame structures, four stories or

less in height with interior walls, partitions, ceilings, and exterior wall systems that have been

designed to accommodate the story drifts

0.025 hsx

b 0.020 hsx 0.015 hsx

Masonry cantilever shear wall structures c 0.010 hsx 0.010 hsx 0.010 hsx

Other masonry shear wall structures 0.007 hsx 0.007 hsx 0.007 hsx

Masonry wall frame structures 0.013 hsx 0.013 hsx 0.010 hsx

All other structures 0.020 hsx 0.015 hsx 0.010 hsx

 a hsx is the story height below Level x. 

 b

 There shall be no drift limit for single-story structures with interior walls, partitions, ceilings, and exterior

wall systems that have been designed to accommodate the story drifts.

 c Structures in which the basic structural system consists of masonry shear walls designed as vertical

elements cantilevered from their base or foundation support which are so constructed that moment transfer

between shear walls (coupling) is negligible.
Structural Design Criteria

71

Fx ' 0.01wx (5.3)

V ' CsW (5.4.1)

5.3 INDEX FORCE ANALYSIS PROCEDURE: An index force analysis shall consist of the

application of static lateral index forces to a linear mathematical model of the structure independently in each of two orthogonal directions. For purposes of analysis, the structure shall be

considered to be fixed at the base. The lateral index forces shall be as given by Eq. 5.3 and shall

be applied simultaneously at each floor level:

where:

Fx = the design lateral force applied at Story x,

wx = the portion of the total gravity load of the structure, W, located or assigned to Level x,

and

W = the total dead load and applicable portions of other loads listed below:

1. In areas used for storage, a minimum of 25 percent of the floor live load shall be

applicable. Floor live load in public garages and open parking structures is not

applicable. 

2. Where an allowance for partition load is included in the floor load design, the

actual partition weight or a minimum weight of 10 psf (500 Pa/m2

) of floor area,

whichever is greater, shall be applicable.

3. Total operating weight of permanent equipment.

4. In areas where the design flat roof snow load does not exceed 30 pounds per

square ft, the effective snow load is permitted to be taken as zero. In areas where

the design snow load is greater than 30 pounds per square ft and where siting and

load duration conditions warrant and when approved by the authority having

jurisdiction, the effective snow load is permitted to be reduced to not less than 20

percent of the design snow load.

5.4 EQUIVALENT LATERAL FORCE PROCEDURE: An equivalent lateral force analysis

shall consist of the application of equivalent static lateral forces to a linear mathematical model

of the structure. The directions of application of lateral forces shall be as indicated in Sec.

5.2.5.2. The lateral forces applied in each direction shall sum to a total seismic base shear given

by Sec. 5.4.1 and shall be distributed vertically in accordance with Sec. 5.4.3. For purposes of

analysis, the structure shall be considered fixed at the base.

5.4.1 Seismic Base Shear: The seismic base shear, V, in a given direction shall be determined

in accordance with the following equation:

where:

Cs = the seismic response coefficient determined in accordance with Sec. 5.4.1.1 and
2000 Provisions, Chapter 5

72

Cs ' SDS

R/I (5.4.1.1-1)

Cs ' SD1

T(R/I) (5.4.1.1-2)

Cs ' 0.044ISDS (5.4.1.1-3)

Cs ' 0.5S1

R/I (5.4.1.1-4)

W = the total dead load and applicable portions of other loads as defined in Sec. 5.3.

5.4.1.1 Calculation of Seismic Response Coefficient: The seismic response coefficient, Cs,

shall be determined in accordance with the following equation:

where:

SDS = the design spectral response acceleration in the short period range as determined

from Sec. 4.1.2.5,

R = the response modification factor from Table 5.2.2, and

I = the occupancy importance factor determined in accordance with Sec. 1.4.

The value of the seismic response coefficient computed in accordance with Eq. 5.4.1.1-1 need not

exceed the following:

where I and R are as defined above and

SD1 = the design spectral response acceleration at a period of 1.0 second as determined

from Sec. 4.1.2.5,

T = the fundamental period of the structure (sec) determined in Sec. 5.4.2, and

S1 = the mapped maximum considered earthquake spectral response acceleration

determined in accordance with Sec. 4.1.

Cs shall not be taken less than:

For structures in Seismic Design Categories E and F, the value of the seismic response coefficient, Cs, shall not be taken less than:

For regular structures 5 stories or less in height and having a period, T, of 0.5 seconds or less, the

seismic response coefficient, Cs, shall be permitted to be calculated using values of 1.5 and 0.6,
Structural Design Criteria

73

Ta ' Crh x

n (5.4.2.1-1)

respectively, for the mapped maximum considered earthquake spectral response accelerations, SS

and S1.

A soil-structure interaction reduction is permitted when determined using Sec. 5.8 or other

generally accepted procedures approved by the authority having jurisdiction.

5.4.2 Period Determination: The fundamental period of the building, T, in the direction under

consideration shall be established using the structural properties and deformational characteristics of the resisting elements in a properly substantiated analysis. The fundamental period, T, so

calculated, shall not exceed the product of the coefficient for the upper limit on calculated period,

Cu, from Table 5.4.2 and the approximate fundamental period, Ta, calculated in accordance with

Sec. 5.4.2.1. The approximate period formulae of Sec. 5.4.2.1 is permitted to be used directly as

an alternative to performing an analysis to determine the fundamental period of the building, T. 

TABLE 5.4.2 Coefficient for Upper Limit on Calculated Period

Design Spectral

Response Acceleration at 1 Second, SD1 Coefficient Cu

Greater than or equal to 0.4 1.4

0.3 1.4

0.2 1.5 

0.15 1.6

0.1 1.7

Less than or equal to 0.05 1.7

5.4.2.1 Approximate Fundamental Period: The approximate fundamental period, Ta, in

seconds, shall be determined from the following equation:

where hn is the height (ft or m) above the base to the highest level of the structure and the values

of Cr and x shall be determined from Table 5.4.2.1.
2000 Provisions, Chapter 5

74

Ta ' 0.1N (5.4.2.1-2)

Ta ' 0.0019

Cw

hn Ta ' 0.0062

CW

hn (5.4.2.1-3)

Cw ' 100

AB

j

n

i ' 1

hn

hi

Ai

1 % 0.83

hn

D

2 (5.4.2.1-4)

TABLE 5.4.2.1 Values of Approximate Period Parameters Cr and x

Structure Type COT x

Moment resisting frame systems of steel in which the

frames resist 100 percent of the required seismic force

and are not enclosed or adjoined by more rigid components that will prevent the frames from deflecting when

subjected to seismic forces.

0.028

(metric 0.0724)

0.8

Moment resisting frame systems of reinforced concrete in

which the frames resist 100 percent of the required seismic force and are not enclosed or adjoined by more rigid

components that will prevent the frames from deflecting

when subjected to seismic forces.

0.016

(metric 0.0466)

0.9

Eccentrically braced steel frames 0.03

(metric 0.0731)

0.75

All other structural systems 0.02

(metric 0.0488)

0.75

Alternatively, the approximate fundamental period, Ta, in seconds, is permitted to be determined

from the following equation for concrete and steel moment resisting frame structures not

exceeding 12 stories in height and having a minimum story height of 10 ft (3 m):

where N = number of stories.

The approximate fundamental period, Ta, in seconds, for masonry or concrete shear wall

structures is permitted to be determined from the following equation:

where Cw is a coefficient related to the effective shear wall area and hn is as defined above. The 

coefficient Cw shall be calculated from the following equation:
Structural Design Criteria

75

Fx ' CvxV (5.4.3-1)

Cvx ' wxh k

x

3

n

i'1

wih k

i

(5.4.3-2)

Vx ' 3

n

i'x

Fi (5.4.4)

where:

AB = the base area of the structure (ft2. or m2),

Ai = the area of shear wall i (ft2. or m2),

Di = the length of shear wall i (ft or m),

hi = the height of shear wall i (ft or m), and

n = the number of shear walls in the building effective in resisting lateral forces in the

direction under consideration.

5.4.3 Vertical Distribution of Seismic Forces: The lateral force, Fx (kip or kN), induced at any

level shall be determined from the following equations:

and

where:

Cvx = vertical distribution factor,

V = total design lateral force or shear at the base of the structure (kip or kN),

wi and wx = the portion of the total gravity load of the structure, W, located or assigned to

Level i or x,

hi and hx = the height (ft or m) from the base to Level i or x, and

k = an exponent related to the structure period as follows:

For structures having a period of 0.5 seconds or less, k = 1

For structures having a period of 2.5 seconds or more, k = 2

For structures having a period between 0.5 and 2.5 seconds, k shall be 2 or

shall be determined by linear interpolation between 1 and 2

5.4.4 Horizontal Shear Distribution: The seismic design story shear in any story, Vx (kip or

kN), shall be determined from the following equation:
2000 Provisions, Chapter 5

76

Ax ' *max

1.2*

avg

2

(5.4.4.3-1)

Mx ' 3

n

i & x

Fi(hi & hx ) (5.4.5)

where Fi

 = the portion of the seismic base shear, V (kip or kN), induced at Level i.

The seismic design story shear, Vx (kip or kN), shall be distributed to the various vertical

elements of the seismic-force-resisting system in the story under consideration based on the

relative lateral stiffnesses of the vertical-resisting elements and the diaphragm.

5.4.4.1 Inherent Torsion: The distribution of lateral forces at each level shall consider the

effect of the inherent torsional moment, Mt (kip"ft or kN"m), resulting from eccentric location of

the masses.

5.4.4.2. Accidental Torsion: In addition to the inherent torsional moment, the distribution of

lateral forces also shall include accidental torsional moments, Mta (kip"ft or kN"m), caused by an

assumed displacement of the mass each way from its actual location by a distance equal to 5

percent of the dimension of the structure perpendicular to the direction of the applied forces.

5.4.4.3 Dynamic Amplification of Torsion: For structures of Seismic Design Categories C, D,

E and F where Type 1a or 1b torsional irregularity exists as defined in Table 5.2.3.1, the effects

of torsional irregularity shall be accounted for by multiplying the sum of Mt plus Mta at each level

by a torsional amplification factor, Ax, determined from the following equation:

where:

*max = the maximum displacement at Level x (in. or mm) and

*avg = the average of the displacements at the extreme points of the structure at Level x

(in. or mm).

The torsional amplification factor, Ax, is not required to exceed 3.0. The more severe loading for

each element shall be considered for design.

5.4.5 Overturning: The structure shall be designed to resist overturning effects caused by the

seismic forces determined in Sec. 5.3.4. At any story, the increment of overturning moment in

the story under consideration shall be distributed to the various vertica- force-resisting elements

in the same proportion as the distribution of the horizontal shears to those elements.

The overturning moments at Level x, Mx (kip"ft or kN"m), shall be determined from the following

equation:

where:
Structural Design Criteria

77

*x ' Cd*xe

I (5.4.6.1)

Fi = the portion of the seismic base shear, V, induced at Level i and

hi and hx = the height (ft or m) from the base to Level i or x,

The foundations of structures, except inverted pendulum-type structures, shall be permitted to be

designed for three-fourths of the foundation overturning design moment, Mf

 (kip"ft or kN"m),

determined using Eq. 5.4.5 at the foundation-soil interface.

5.4.6 Drift Determination and P-Delta Effects: Story drifts and, where required, member

forces and moments due to P-delta effects shall be determined in accordance with this section. 

Determination of story drifts shall be based on the application of the design seismic forces to a

mathematical model of the physical structure. The model shall include the stiffness and strength

of all elements that are significant to the distribution of forces and deformations in the structure

and shall represent the spatial distribution of the mass and stiffness of the structure. In addition,

the model shall comply with the following:

1. Stiffness properties of reinforced concrete and masonry elements shall consider the effects of

cracked sections and

2. For steel moment resisting frame systems, the contribution of panel zone deformations to

overall story drift shall be included.

5.4.6.1 Story Drift Determination: The design story drift, ), shall be computed as the

difference of the deflections at the center of mass at the top and bottom of the story under

consideration.

Exception: For structures of Seismic Design Categories C, D, E and F having plan

irregularity Type 1a or 1b of Table 5.4.3.2-2, the design story drift, ), shall be computed

as the largest difference of the deflections along any of the edges of the structure at the

top and bottom of the story under consideration.

The deflections of Level x, *x (in. or mm), shall be determined in accordance with following

equation:

where:

Cd = the deflection amplification factor in Table 5.2.2,

*xe = the deflections determined by an elastic analysis (in. or mm), and

I = the occupancy importance factor determined in accordance with Sec. 1.4.

The elastic analysis of the seismic-force-resisting system shall be made using the prescribed

seismic design forces of Sec. 5.4.3. For the purpose of this section, the value of the base shear,

V, used in Eq. 5.3.2 need not be limited by the value obtained from Eq. 5.3.2.1-3.
2000 Provisions, Chapter 5

78

2 ' Px)

VxhsxCd

(5.4.6.2-1)

2max ' 0.5

$Cd

# 0.25 (5.4.6.2-2)

For determining compliance with the story drift limitation of Sec. 5.2.8, the deflections of Level

x, *x (in. or mm), shall be calculated as required in this section. For purposes of this drift

analysis only, it is permissible to use the computed fundamental period, T (secs), of the structure

without the upper bound limitation specified in Sec. 5.4.2 when determining drift level seismic

design forces.

Where applicable, the design story drift, ) (in. or mm), shall be increased by the incremental

factor relating to the P-delta effects as determined in Sec. 5.4.6.2.

5.4.6.2 P-Delta Effects: P-delta effects on story shears and moments, the resulting member

forces and moments, and the story drifts induced by these effects are not required to be considered when the stability coefficient, 2, as determined by the following equation is equal to or

less than 0.10:

where:

Px = the total vertical design load at and above Level x (kip or kN). When calculating

the vertical design load for purposes of determining P-delta, the individual load

factors need not exceed 1.0.

) = the design story drift occurring simultaneously with Vx (in. or mm).

Vx = the seismic shear force acting between Level x and x - 1 (kip or kN).

hsx = the story height below Level x (in. or mm). 

Cd = the deflection amplification factor in Table 5.2.2.

The stability coefficient, 2, shall not exceed 2max determined as follows:

where $ is the ratio of shear demand to shear capacity for the story between Levels x and x - 1. 

This ratio is permitted to be conservatively taken as 1.0.

When the stability coefficient, 2, is greater than 0.10 but less than or equal to 2max, the incremental factor related to P-delta effects, ad, shall be determined by rational analysis (see Part 2,

Commentary). To obtain the story drift for including the P-delta effects, the design story drift

determined in Sec. 5.4.6.1 shall be permitted to be multiplied by 1.0/(1 - 2).

When 2 is greater than 2max, the structure is potentially unstable and shall be redesigned.

5.5 MODAL RESPONSE SPECTRUM ANALYSIS PROCEDURE: A modal response

spectrum analysis shall consist of the analysis of a linear mathematical model of the structure to
Structural Design Criteria

79

Vm ' CsmWm (5.5.4-1)

Wm '

3

n

i'1

wiNim

2

3

n

i'1

wiN2

im

(5.5.4-2)

determine the maximum accelerations, forces, and displacements resulting from the dynamic

response to ground shaking represented by the design response spectrum. The analysis shall be

performed in accordance with the requirements of this section. For purposes of analysis, the

structure shall be permitted to be considered to be fixed at the base or, alternatively, it shall be

permitted to use realistic assumptions with regard to the stiffness of foundations. The symbols

used in this section have the same meaning as those for similar terms used in Sec. 5.4 but with

the subscript m denoting quantities relating to the mth mode.

5.5.1 Modeling: A mathematical model of the structure shall be constructed that represents the

spatial distribution of mass and stiffness throughout the structure. For regular structures with

independent orthogonal seismic-force-resisting systems, independent two-dimensional models

are permitted to be constructed to represent each system. For irregular structures or structures

without independent orthogonal systems, a three-dimensional model incorporating a minimum of

three dynamic degrees of freedom consisting of translation in two orthogonal plan directions and

torsional rotation about the vertical axis shall be included at each level of the structure. Where

the diaphragms are not rigid compared to the vertical elements of the lateral-force-resisting

system, the model should include representation of the diaphragm’s flexibility and such

additional dynamic degrees of freedom as are required to account for the participation of the

diaphragm in the structure’s dynamic response. In addition, the model shall comply with the

following:

1. Stiffness properties of concrete and masonry elements shall consider the effects of cracked

sections and

2. The contribution of panel zone deformations to overall story drift shall be included for steel

moment frame resisting systems.

5.5.2 Modes: An analysis shall be conducted to determine the natural modes of vibration for the

structure including the period of each mode, the modal shape vector N, the modal participation

factor, and modal mass. The analysis shall include a sufficient number of modes to obtain a

combined modal mass participation of at least 90 percent of the actual mass in each of two

orthogonal directions. 

5.5.3 Modal Properties: The required periods, mode shapes, and participation factors of the

structure shall be calculated by established methods of structural analysis for the fixed-base

condition using the masses and elastic stiffnesses of the seismic-force-resisting system.

5.5.4 Modal Base Shear: The portion of the base shear contributed by the mth mode, Vm, shall

be determined from the following equations:
2000 Provisions, Chapter 5

80

Csm ' Sam

R/I (5.5.4-3)

Csm ' 0.4SDS

(R/I) (1.0 % 5.0Tm) (5.5.4-4)

where:

Csm = the modal seismic response coefficient as determined by Eq. 5.5.4-3,

W = the effective modal gravity load including portions of the live load as defined in m

Sec. 5.3,

wi = the portion of the total gravity load of the structure at Level i, and

Nim = the displacement amplitude at the i

th level of the structure when vibrating in its

mth mode.

The modal seismic response coefficient, Csm, shall be determined in accordance with the

following equation:

where:

Sam = The design spectral response acceleration at period Tm determined from either the

general design response spectrum of Sec. 4.1.2.5 or a site-specific response

spectrum determined in accordance with Sec. 4.1.3,

R = the response modification factor determined from Table 5.2.2, 

I = the occupancy importance factor determined in accordance with Sec. 1.4, and

Tm = the modal period of vibration (in seconds) of the mth mode of the structure.

Exceptions: 

1. When the general design response spectrum of Sec. 4.1.2.6 is used for structures on

Site Class D, E or F soils, the modal seismic design coefficient, Csm, for modes other

than the fundamental mode that have periods less than 0.3 seconds is permitted to be

determined by the following equation:

where SDS is as defined in Sec. 4.1.2.5 and R, I, and Tm are as defined above.

2. When the general design response spectrum of Sec. 4.1.2.6 is used for structures

where any modal period of vibration, Tm, exceeds 4.0 seconds, the modal seismic

design coefficient, Csm, for that mode is permitted to be determined by the following

equation: 
Structural Design Criteria

81

Csm ' 4SD1

(R/I)T 2

m

(5.5.4-5)

Fxm ' Cvxm Vm (5.5.5-1)

Cvxm ' wxNxm

3

n

i'1

wiNim

(5.5.5-2)

*xm ' Cd*xem

I (5.5.5-3)

where R, I, and Tm are as defined above and and SD1 is the design spectral response

acceleration at a period of 1 second as determined in Sec. 4.1.2.5.

The reduction due to soil-structure interaction as determined in Sec. 5.8.3 shall be permitted to

be used.

5.5.5 Modal Forces, Deflections, and Drifts: The modal force, Fxm, at each level shall be

determined by the following equations:

and

where:

Cvxm = the vertical distribution factor in the mth mode,

Vm = the total design lateral force or shear at the base in the mth mode,

wi, wx = the portion of the total gravity load, W, located or assigned to Level i or x,

Nxm = the displacement amplitude at the xth level of the structure when vibrating in

its mth mode, and

Nim = the displacement amplitude at the i

th level of the structure when vibrating in

its mth mode.

The modal deflection at each level, *xm, shall be determined by the following equations:

and
2000 Provisions, Chapter 5

82

*xem ' g

4B2

T 2

m Fxm

wx

(5.5.5-4)

0.85 V

Vt

(5.5.7.1)

where:

Cd = the deflection amplification factor determined from Table 5.2.2,

*xem = the deflection of Level x in the mth mode at the center of the mass at Level x

determined by an elastic analysis,

g = the acceleration due to gravity (ft/s2

 or m/s2),

I = the occupancy importance factor determined in accordance with Sec. 1.4,

Tm = the modal period of vibration, in seconds, of the mth mode of the structure,

Fxm = the portion of the seismic base shear in the mth mode, induced at Level x, and

wx = the portion of the total gravity load of the structure, W, located or assigned to

Level x.

The modal drift in a story, )m, shall be computed as the difference of the deflections, *xm, at the

top and bottom of the story under consideration.

5.5.6 Modal Story Shears and Moments: The story shears, story overturning moments, and

the shear forces and overturning moments in vertical elements of the structural system at each

level due to the seismic forces determined from the appropriate equation in Sec. 5.5.5 shall be

computed for each mode by linear static methods.

5.5.7 Design Values: The design value for the modal base shear, Vt; each of the story shear,

moment, and drift quantities; and the deflection at each level shall be determined by combining

their modal values as obtained from Sec. 5.5.5 and 5.5.6. The combination shall be carried out

by taking the square root of the sum of the squares of each of the modal values or by the

complete quadratic combination technique. The complete quadratic combination shall be used

where closely spaced periods in the translational and torsional modes will result in crosscorrelation of the modes.

A base shear, V, shall be calculated using the equivalent lateral force procedure in Sec. 5.4. For

the purpose of this calculation, the fundamental period of the structure, T (sec), shall not exceed

the coefficient for upper limit on the calculated period, Cu, times the approximate fundamental

period of the structure, Ta. Where the design value for the modal base shear, Vt

, is less than 85

percent of the calculated base shear, V, using the equivalent lateral force procedure, the design

story shears, moments, drifts, and floor deflections shall be multiplied by the following

modification factor:
Structural Design Criteria

83

where:

V = the equivalent lateral force procedure base shear calculated in accordance with Sec.

5.4 and

Vt = the modal base shear calculated in accordance with this section.

Where soil-structure interaction in accordance with Sec. 5.8 is considered, the reduced value of V

calculated in accordance with that section may be used for V in Eq. 5.5.7.1.

5.5.8 Horizontal Shear Distribution: The horizontal distribution of shear shall be in accordance with the requirements of Sec. 5.4.4 except that amplification of torsion per Sec.

5.4.4.1.3 is not required for that portion of the torsion included in the dynamic analysis model.

5.5.9 Foundation Overturning: The foundation overturning moment at the foundation-soil

interface shall be permitted to be reduced by 10 percent.

5.5.10 P-Delta Effects: The P-delta effects shall be determined in accordance with Sec. 5.4.6. 

The story drifts and story shears shall be determined in accordance with Sec. 5.4.6.1.

5.6 LINEAR RESPONSE HISTORY ANALYSIS PROCEDURE: A linear response history

analysis shall consist of an analysis of a linear mathematical model of the structure to determine

its response, through methods of numerical integration, to suites of ground motion acceleration

histories compatible with the design response spectrum for the site. The analysis shall be

performed in accordance with the provisions of this section. For the purposes of analysis, the

structure shall be permitted to be considered to be fixed at the base or, alternatively, it shall be

permitted to use realistic assumptions with regard to the stiffness of foundations.

5.6.1 Modeling: Mathematical models shall conform to the requirements of Sec. 5.5.1.

5.6.2 Ground Motion: A suite of not less than three appropriate ground motions shall be used

in the analysis. Ground motion shall conform to the requirements of this section.

5.6.2.1 Two-Dimensional Analysis: When two-dimensional analyses are performed, each

ground motion shall consist of a horizontal acceleration history selected from an actual recorded

event. Appropriate acceleration histories shall be obtained from records of events having

magnitudes, fault distances, and source mechanisms that are consistent with those that control the

maximum considered earthquake. Where the required number of appropriate recorded ground

motion records are not available, appropriate simulated ground motion records shall be used to

make up the total number required. The ground motions shall be scaled such that the average

value of the 5 percent damped response spectra for the suite of motions is not less than the design

response spectrum for the site determined in accordance with Sec. 4.1.3 for periods ranging from

0.2T to 1.5T seconds where T is the natural period of the structure in the fundamental mode for

the direction of response being analyzed.

5.6.2.2 Three-Dimensional Analysis: When three-dimensional analysis is performed, ground

motions shall consist of pairs of appropriate horizontal ground motion acceleration components

that shall be selected and scaled from individual recorded events. Appropriate ground motions

shall be selected from events having magnitudes, fault distances, and source mechanisms that are

consistent with those that control the maximum considered earthquake. Where the required
2000 Provisions, Chapter 5

84

number of recorded ground motion pairs are not available, appropriate simulated ground motion

pairs shall be used to make up the total number required. For each pair of horizontal ground

motion components, the square root of the sum of the squares (SRSS) of the 5 percent damped

response spectrum of the scaled horizontal components shall be constructed. Each pair of

motions shall be scaled such that the average value of the SRSS spectra from all horizontal

component pairs is not less than 1.3 times the 5 percent damped design response spectrum

determined in accordance with Sec. 4.1.3 for periods ranging from 0.2T to 1.5T seconds where T

is the natural period of the fundamental mode of the structure.

5.6.3 Response Parameters: For each ground motion analyzed, the individual response

parameters shall be scaled by the quantity I/R where I is the occupancy importance factor

determined in accordance with Sec. 1.4 and R is the response modification coefficient selected in

accordance with Sec. 5.2.2. The maximum value of the base shear, Vj

, member forces, QEj, and

the interstory drifts, *ij, at each story scaled as indicated above shall be determined. When the

maximum scaled base shear predicted by the analysis, Vj

, is less than given by Eq. 5.4.1.1-3 or, in

Seismic Design Categories E and F, Eq. 5.4.1.1-4, the scaled member forces, QEj, shall be

additionally scaled by the factor V/Vj where V is the minimum base shear determined in accordance with Eq. 5.4.1.1-3 or, for structures in Seismic Design Category E or F, Eq. 5.4.1.1-4.

If at least seven ground motions are analyzed, the design member forces, QE, used in the load

combinations of Sec. 5.2.7 and the design interstory drift, ), used in the evaluation of drift in

accordance with Sec. 5.2.8 shall be permitted to be taken, respectively, as the average of the

scaled QEj and *ij values determined from the analyses and scaled as indicated above. If less than

seven ground motions are analyzed, the design member forces, QE, and the design interstory drift,

), shall be taken as the maximum value of the scaled QEj and *ij values determined from the

analyses.

Where the Provisions require the consideration of the special load combinations of Sec. 5.2.7.1,

the value of S0QE need not be taken larger than the maximum of the unscaled value, QEj,

obtained from the suite of analyses.

5.7 NONLINEAR RESPONSE HISTORY ANALYSIS PROCEDURE : A nonlinear

response history analysis shall consist of an analysis of a mathematical model of the structure

that directly accounts for the nonlinear hysteretic behavior of the structure's components to

determine its response, through methods of numerical integration, to suites of ground motion

acceleration histories compatible with the design response spectrum for the site. The analysis

shall be performed in accordance with the requirements of this section.

5.7.1 Modeling: A mathematical model of the structure shall be constructed that represents the

spatial distribution of mass throughout the structure. The hysteretic behavior of elements shall

be modeled consistent with suitable laboratory test data and shall account for all significant

yielding, strength degradation, stiffness degradation, and hysteretic pinching indicated by such

test data. Strength of elements shall be based on expected values considering material overstrength, strain hardening, and hysteretic strength degradation. Linear properties consistent with

the provisions of Sec. 5.5.1 shall be permitted to be used for those elements demonstrated by the

analysis to remain within their linear range of response. The structure shall be assumed to have a

fixed base or, alternatively, it shall be permitted to use realistic assumptions with regard to the
Structural Design Criteria

85

stiffness and load carrying characteristics of the foundations consistent with site-specific soils

data and rational principles of engineering mechanics.

For regular structures with independent orthogonal seismic-force-resisting systems, independent

two-dimensional models shall be permitted to be constructed to represent each system. For

structures having plan irregularity Type 1a, 1b, 4, or 5 of Table 5.2.3.2 or structures without

independent orthogonal systems, a three-dimensional model incorporating a minimum of three

dynamic degrees of freedom consisting of translation in two orthogonal plan directions and

torsional rotation about the vertical axis at each level of the structure shall be used. Where the

diaphragms are not rigid compared to the vertical elements of the lateral-force-resisting system,

the model shall include representation of the diaphragm's flexibility and such additional dynamic

degrees of freedom as are required to account for the participation of the diaphragm in the

structure's dynamic response.

5.7.2 Ground Motion and Other Loading: Ground motion shall conform to the requirements

of Sec. 5.6.2. The structure shall be analyzed for the effects of these ground motions simultaneously with the effects of dead load in combination with not less than 25 percent of the

required live loads.

5.7.3 Response Parameters: For each ground motion analyzed, individual response parameters

consisting of the maximum value of the individual member forces, QEj, member inelastic

deformations, (j, and interstory drifts, *ij, at each story shall be determined. 

If at least seven ground motions are analyzed, the design values of member forces, QE, member

inelastic deformations, (i, and interstory drift, ) , shall be taken, respectively, as the average of

the scaled QEj, (i, and *i values determined from the analyses. If less than seven ground motions

are analyzed, the design member forces, QE, design member inelastic deformations, (i

 and the

design interstory drift, ), shall be taken as the maximum value of the scaled QEj, (j

, and *ij values

determined from the analyses.

5.7.3.1 Member Strength: The adequacy of members to resist the load combinations of Sec

5.2.7 need not be evaluated.

Exception: Where the Provisions requires the consideration of the special load combinations of Sec. 5.2.7.1, the maximum value of QEj obtained from the suite of analyses

shall be taken in place of the quantity S0QE.

5.7.3.2 Member Deformation:. The adequacy of individual members and their connections to

withstand the design deformation values, (i, predicted by the analyses shall be evaluated based

on laboratory test data for similar components. The effects of gravity and other loads on member

deformation capacity shall be considered in these evaluations. Member deformation shall not

exceed two thirds of the value that results in loss of ability to carry gravity loads or that results in

deterioration of member strength to less than the 67 percent of the peak value.

5.7.3.3 Interstory Drift: The design interstory drift obtained from the analyses shall not exceed

125 percent of the drift limit specified in Sec. 5.2.8. 

5.7.4 Design Review: A design review of the seismic-force-resisting system and the structural

analysis shall be performed by an independent team of registered design professionals in the
2000 Provisions, Chapter 5

86

V ̃ ' V & )V (5.8.2.1-1)

)V ' Cs & C ̃

s

0.05

$ ̃

0.4

W (5.8.2.1-2)

appropriate disciplines and others experienced in seismic analysis methods and the theory and

application of nonlinear seismic analysis and structural behavior under extreme cyclic loads. The

design review shall include, but not be limited to, the following:

1. Review of any site-specific seismic criteria employed in the analysis including the development of site-specific spectra and ground motion time histories,

2. Review of acceptance criteria used to demonstrate the adequacy of structural elements and

systems to withstand the calculated force and deformation demands, together with that

laboratory and other data used to substantiate these criteria,

3. Review of the preliminary design including the determination of the target displacement of

the structure and the margins remaining beyond these displacements, and

4. Review of the final design of the entire structural system and all supporting analyses.

5.8 SOIL-STRUCTURE INTERACTION EFFECTS:

5.8.1 General: The requirements set forth in this section are permitted to be used to incorporate

the effects of soil-structure interaction in the determination of the design earthquake forces and

the corresponding displacements of the structure. The use of these requirements will decrease

the design values of the base shear, lateral forces, and overturning moments but may increase the

computed values of the lateral displacements and the secondary forces associated with the

P-delta effects.

The requirements for use with the equivalent lateral force procedure are given in Sec. 5.8.2 and

those for use with the modal analysis procedure are given in Sec. 5.8.3.

5.8.2 Equivalent Lateral Force Procedure: The following requirements are supplementary to

those presented in Sec. 5.4.

5.8.2.1 Base Shear: To account for the effects of soil-structure interaction, the base shear, V,

determined from Eq. 5.4.1-1 may be reduced to:

The reduction, )V, shall be computed as follows:

where:

Cs = the seismic response coefficient computed from Eq. 5.4.1.1-1 using the fundamental

natural period of the fixed-base structure (T or Ta) as specified in Sec.5.4.2,

= the seismic response coefficient computed from Eq. 5.4.1.1-1 using the fundamental C ̃

s

natural period of the flexibly supported structure ( ) defined in Sec. 5.8.2.1.1, T ̃
Structural Design Criteria

87

T ̃'T 1 % k

K

y

1 % K

y

h 2

K2

(5.8.2.1.1-1)

k ' 4B2 W

gT 2 (5.8.2.1.1-2)

B ̃ = the fraction of critical damping for the structure-foundation system determined in

Sec. 5.8.2.1.2, and

W = the effective gravity load of the structure, which shall be taken as 0.7W, except that

for structures where the gravity load is concentrated at a single level, it shall be taken

equal to W.

The reduced base shear, , shall in no case be taken less than 0.7V. V ̃

5.8.2.1.1 Effective Building Period: The effective period, , shall be determined as follows: T ̃

where:

T = the fundamental period of the structure as determined in Sec. 5.4.2;

k = the stiffness of the structure when fixed at the base, defined by the following:

h = the effective height of the structure, which shall be taken as 0.7 times the total

height, hn, except that for structures where the gravity load is effectively concentrated at a single level, it shall be taken as the height to that level;

Ky = the lateral stiffness of the foundation defined as the horizontal force at the level of

the foundation necessary to produce a unit deflection at that level, the force and

the deflection being measured in the direction in which the structure is analyzed;

K2 = the rocking stiffness of the foundation defined as the moment necessary to

produce a unit average rotation of the foundation, the moment and rotation being

measured in the direction in which the structure is analyzed; and 

g = the acceleration of gravity.

The foundation stiffnesses, Ky and K2, shall be computed by established principles of foundation

mechanics (see the Commentary) using soil properties that are compatible with the soil strain

levels associated with the design earthquake motion. The average shear modulus, G, for the soils

beneath the foundation at large strain levels and the associated shear wave velocity, vs, needed in

these computations shall be determined from Table 5.8.2.1.1 where:

vso = the average shear wave velocity for the soils beneath the foundation at small strain

levels (10-3 percent or less),

Go = (v2

so/g = the average shear modulus for the soils beneath the foundation at small

strain levels, and
2000 Provisions, Chapter 5

88

T ̃ ' T 1 % 25"ra h

v

2

s T 2

1 % 1.12rah 2

"2r

3

m

(5.8.2.1.1-3)

" ' W

(Ao h (5 8.2.1.1-4)

ra ' Ao

B

(5.8.2.1.1-5)

rm '

4 4Io

B

(5.8.2.1.1-6)

( = the average unit weight of the soils.

TABLE 5.8.2.1.1 Values of G/Go and vs/vso

Peak Ground 

Acceleration, (g)

# 0.10 # 0.15 0.20 $ 0.30

Value of G/Go 0.81 0.64 0.49 0.42

Value of vs/vso 0.90 0.80 0.70 0.65

Alternatively, for structures supported on mat foundations that rest at or near the ground surface

or that are embedded in such a way that the side wall contact with the soil cannot be considered

to remain effective during the design ground motion, the effective period of the structure may be

determined from:

where:

" = the relative weight density of the structure and the soil defined by:

ra and rm = characteristic foundation lengths defined by:

and

where:

Ao = the area of the foundation,
Structural Design Criteria

89

$ ̃ ' $o % 0.05

T ̃

T

3 (5.8.2.1.2-1)

r ' ra ' Ao

B

(5.8.2.1.2-2)

r ' rm '

4 4Io

B

(5.8.2.1.2-3)

Io = the static moment of the foundation about a horizontal centroidal axis normal to the

direction in which the structure is analyzed, and

5.8.2.1.2 Effective Damping: The effective damping factor for the structure-foundation system,

, shall be computed as follows: $ ̃

where $o = the foundation damping factor as specified in Figure 5.8.2.1.2.

The values of $o corresponding to SDS = 0.375 in Figure 5.8.2.1.2 shall be determined by

averaging the results obtained from the solid lines and the dashed lines.

The quantity r in Figure 5.8.2.1.2 is a characteristic foundation length that shall be determined as

follows:

For / h Lo # 0.5,

For / h Lo $ 1,

where:

Lo = the overall length of the side of the foundation in the direction being analyzed,

Ao = the area of the load-carrying foundation, and

Io = the static moment of inertia of the load-carrying foundation.
2000 Provisions, Chapter 5

90

FIGURE 5.8.2.1.2 Foundation damping factor.

$)

o ' 4Ds

VsT ̃

2

$o (5.8.2.1.2-4)

For intermediate values of , the value of h/L r shall be determined by linear interpolation. 0

Exception: For structures supported on point bearing piles and in all other cases where

the foundation soil consists of a soft stratum of reasonably uniform properties underlain

by a much stiffer, rock-like deposit with an abrupt increase in stiffness, the factor $o in

Eq. 5.8.2.1.2-1 shall be replaced by:

if < 1 where Ds 4D is the total depth of the stratum. s/vsT ̃

The value of computed from Eq. 5.8.2.1.2-1, both with or without the adjustment represented ~

β

by Eq. 5.8.2.1.2-4, shall in no case be taken as less than = 0.05 or greater than = 0.20. ~

β ~β
Structural Design Criteria

91

* ̃

x ' V ̃

V

Mo hx

K2

% *x (5.8.2.3)

V ̃

1 ' V1 & )V1 (5.8.3.1-1)

5.8.2.2 Vertical Distribution of Seismic Forces: The distribution over the height of the

structure of the reduced total seismic force, , shall be considered to be the same as for the V ̃

structure without interaction.

5.8.2.3 Other Effects: The modified story shears, overturning moments, and torsional effects

about a vertical axis shall be determined as for structures without interaction using the reduced

lateral forces.

The modified deflections, , shall be determined as follows: * ̃

x

where:

Mo = the overturning moment at the base determined in accordance with Sec. 5.4.5 using

the unmodified seismic forces and not including the reduction permitted in the design

of the foundation,

hx = the height above the base to the level under consideration, and

*x = the deflections of the fixed-base structure as determined in Sec. 5.4.6.1 using the unmodified seismic forces.

The modified story drifts and P-delta effects shall be evaluated in accordance with the requirements of Sec. 5.4.6.2 using the modified story shears and deflections determined in this

section.

5.8.3 Modal Analysis Procedure: The following requirements are supplementary to those

presented in Sec. 5.5.

5.8.3.1 Modal Base Shears: To account for the effects of soil-structure interaction, the base

shear corresponding to the fundamental mode of vibration, V1, is permitted to be reduced to:

The reduction, )V1, shall be computed in accordance with Eq. 5.8.2.1-2 with taken as equal W 1

to the gravity load defined by Eq. 5.5.4-2, Cs W 1 computed from Eq. 5.5.4-3 using the

fundamental period of the fixed-base structure, T1, and computed from Eq. 5.5.4-3 using the C ̃

s

fundamental period of the elastically supported structure, . T ̃

1

The period shall be determined from Eq. 5.8.2.1.1-1, or from Eq. 5.8.2.1.1-3 when applicable, T ̃

1

taking T = , evaluating from Eq. 5.8.2.1.1-2 with , and computing as T ̃

1 K W = W 1 h

follows:
2000 Provisions, Chapter 5

92

h '

3

n

i'1

wiNi1 hi

3

n

i'1

wiNi1

(5.8.3.1-2)

The above designated values of , W h, T, and also shall be used to evaluate the factor T ̃ " from

Eq. 5.8.2.1.1-4 and the factor $o from Figure 5.8.2.1.2. No reduction shall be made in the shear

components contributed by the higher modes of vibration. The reduced base shear, , shall in 1

~

V

no case be taken less than 0.7V1.

5.8.3.2 Other Modal Effects: The modified modal seismic forces, story shears, and overturning moments shall be determined as for structures without interaction using the modified

base shear, , instead of V1. The modified modal deflections, , shall be determined as 1

~

V * ̃

xm

follows:

xm

o x

xl

V

V

M h

K

~ ~

δ δ

θ

= +





 



 1

1

1 (5.8.3.2-1)

and

for m = 2, 3, ...... (5.8.3.2-2) xm x

~

δ = δ

where:

Mo1 = the overturning base moment for the fundamental mode of the fixed-base structure, as determined in Sec. 5.5.6 using the unmodified modal base shear V1, and

*xm = the modal deflections at Level x of the fixed-base structure as determined in

Sec. 5.5.5 using the unmodified modal shears, Vm.

The modified modal drift in a story, , shall be computed as the difference of the deflections, ) ̃

m

, at the top and bottom of the story under consideration. * ̃

xm

5.8.3.3 Design Values: The design values of the modified shears, moments, deflections, and

story drifts shall be determined as for structures without interaction by taking the square root of

the sum of the squares of the respective modal contributions. In the design of the foundation, the

overturning moment at the foundation-soil interface determined in this manner may be reduced

by 10 percent as for structures without interaction.
Structural Design Criteria

93

The effects of torsion about a vertical axis shall be evaluated in accordance with the requirements

of Sec. 5.5.8 and the P-delta effects shall be evaluated in accordance with the requirements of

Sec. 5.4.6.2, using the story shears and drifts determined in Sec. 5.8.3.2.
94

Appendix to Chapter 5

NONLINEAR STATIC ANALYSIS

PREFACE: This appendix introduces nonlinear static analysis, a new seismic

analysis procedure sometimes known as pushover analysis, for review and

comment and for later adoption into the body of the NEHRP Recommended Provisions.

Although nonlinear static analysis has not previously been included in design

provisions for new building construction, the procedure itself is not new and has

been used for many years in both research and design applications. For example,

nonlinear static analysis has been used for many years as a standard methodology in

the design of offshore platform structures. It also has been adopted in several

standard methodologies for the seismic evaluation and retrofit of building

structures, including the NEHRP Guidelines for the Seismic Rehabilitation of

Buildings (FEMA 273) and Methodolgies for Post-earthquake Evaluation and Repair

of Concrete and Masonry Buildings (ATC 40). Nonlinear static analysis also forms

the basis for earthquake loss estimation procedures contained in HAZUS, FEMA’s

nationally applicable earthquake loss estimation model. Finally, although it does

not explicitly appear in the NEHRP Recommended Provisions, the nonlinear static

analysis methodology forms the basis for the equivalent lateral force procedures

contained in the Provisions for base-isolated structures and proposed for inclusion

for energy-dissipated structures.

One of the key controversies surrounding the introduction of this methodology into

the Provisions relates to the determination of the limit deformation, sometimes also

called a target displacement. Several methodologies for estimating the amount of

deformation induced in a structure by the design earthquake have been proposed and

are included in various adoptions of the procedure. The approach presented in this

appendix is based on statistical correlations of the displacements predicted by linear

and nonlinear dynamic analyses of structures similar, but not identical, to the

approach contained in FEMA 273.

A second controversy relates to the lack of consensus-backed acceptance criteria to

be used to determine the adequacy of a design once the forces and deformations

produced by design earthquake ground shaking are estimated. It should be noted

that this same lack of acceptance criteria applies equally to the nonlinear response

history approach, which already has been adopted into building codes.

Nonlinear static analysis provides a simplified method of directly evaluating

nonlinear response of structures to strong earthquake ground shaking that can be

an attractive alternative to the more complex procedures of nonlinear response

history analysis. It is hoped that exposure of this approach through inclusion in this
Structural Design Criteria

95

appendix will allow the necessary consensus to be developed to permit later integration into the Provisions as such.

Users of this appendix also should consult the Commentary for guidance. Please

direct all feedback on this appendix and its commentary to the BSSC.

5A.1 NONLINEAR STATIC ANALYSIS: A nonlinear static analysis shall consist of an

analysis of a mathematical model of the structure that directly accounts for the nonlinear

behavior of the structure’s components under an incrementally increased pattern of lateral forces. 

In this procedure, a mathematical model of the structure is incrementally displaced to a target

displacement through application of a series of lateral forces or until the structure collapses and

the resulting internal forces, QEj, and member deformations, (I

, at each increment of loading are

determined. At the target displacement for the structure, the resulting internal forces and

deflections should be less than the capacity of each element calculated according to the applicable acceptance criteria in Sec. 5A.1.3. The analysis shall be performed in accordance with 

this section.

5A.1.1 Modeling: A mathematical model of the structure shall be constructed to represent the

spatial distribution of mass and stiffness of the structural system considering the effects of

component nonlinearity at deformation levels that exceed their elastic limit.

The nonlinear force-deformation characteristics of components shall be represented by suitable

multilinear models. Unless analysis indicates that a component remains elastic, as a minimum a

bilinear model shall be used for each component. The multilinear force-deformation characteristics for each component, termed a backbone, should include representation of the linear

stiffness of the component before onset of yield, the yield strength, and the stiffness properties of

the component after yield at various levels of deformation. These properties shall be consistent

with principles of mechanics or laboratory data. Linear properties representing component

behavior before yield shall be consistent with the provisions of Sec. 5.5.1. Strength of elements

shall be based on expected values considering material overstrength and strain hardening. The

properties of elements and components after yielding should account for strength and stiffness

degradation due to softening or fracture as indicated by principles of mechanics or test data. The

model for columns should reflect the influence of axial load when axial loads exceed 15 percent

of the buckling load. The structure shall be assumed to have a fixed base or, alternatively, it

shall be permitted to use realistic assumptions with regard to the stiffness and load-carrying characteristics of the foundations, consistent with site-specific soil data and rational principles of

engineering mechanics.

For regular structures with independent orthogonal seismic-force-resisting systems, independent

two-dimensional models shall be permitted to be constructed to represent each system. For

structures having plan irregularities Types 4 and 5 of Table 5.2.3.2 or structures without

independent orthogonal systems, a three-dimensional model incorporating a minimum of three

degrees of freedom, consisting of translation in two orthogonal plan directions and torsional

rotation about the vertical axis to each level of the structure, shall be used. Where the diaphragms are not rigid compared to the vertical elements of the lateral-force-resisting system, the

model should include representation of the diaphragm’s flexibility. A control point shall be

selected for each model. This control point normally shall be taken as the center of mass of the
2000 Provisions, Chapter 5

96

Ci ' (1 & Ts/T1)

Rd

% (Ts/T1) (5A.1.3-1)

Rd ' 1.5R

S0

(5A.1.3-2)

highest level of the structure. For structures with penthouses, the control point shall be taken as

the center of mass of the level at the base of the penthouse. This level shall be termed the control

level.

5A.1.2 Lateral Loads: A pattern of lateral loads shall be applied incrementally at the mass

centroid of each level I. The pattern of lateral loads applied in each direction should follow the

distribution obtained from a modal analysis for the fundamental mode of response in the

direction under consideration as given by Sec. 5.5.5.

At each increment of lateral loading, k, the total force applied to the model shall be characterized

by the base shear, Vk. The base shear at the initial increment of load, V1, shall be taken as the

design base shear calculated in accordance with Sec. 5.4.1. The base shear, V, should be

incremented in steps that are sufficiently small to permit significant changes in individual

component behavior, such as yielding, buckling or failure, to be detected. The structure shall be

analyzed for these lateral forces simultaneously with the effects of dead load in combination with

not less than 25 percent of the required live loads, reduced as permitted for the area of a single

floor.

Loading shall be applied independently in each of two directions. At each load step, the total

applied force, Vk, the lateral displacement of the control point, )k, and the forces and deformations in each component shall be recorded.

5A.1.3 Limit Deformation: The incremental nonlinear analysis should be continued by

increasing the base shear until the deflection at the control point exceeds 150 percent of the

inelastic deflection. The expected inelastic deformation of the control panel shall be taken as the

deflection predicted for the control point from a modal response spectrum analysis using a 5

percent damped design level response spectrum, considering only the fundamental mode of

response in the direction under consideration, and factored by the coefficient Ci

. When the ratio

for the period, Ts, as defined in Sec. 4.1.2.6, to the fundamental period of the structure in the

direction under consideration, T1, is less than or equal to a value of 1.0, the coefficient Ci

 shall be

taken as having a value of 1.0. Otherwise, the value of the coefficient Ci shall be calculated from

the following equation:

where Ts and Ti

 are as defined above and Rd is given by the following equation:

where R and S0 are, respectively, the response modification and overstrength coefficients from

Table 5.2.2.
Structural Design Criteria

97

5A.1.4 Design Response Parameters: For each lateral force analyzed, the design response

parameters including interstory drift and member force and deformation shall be taken as the

value obtained from the analysis at the expected inelastic displacement.

5A.1.4.1 Member Strength: The adequacy of members to resist the load combinations of Sec.

5.2.7 need not be evaluated.

Exception: Where the Provisions require the consideration of the special load combinations of Sec. 5.2.7.1, the value of SEi obtained from the analysis at the expected

inelastic deformation, as calculated from Sec. 5A.1.3, shall be taken in place of the

quantity S0QE.

5A.1.4.2 Member Deformation: The adequacy of individual members and their connections to

withstand the design deformation values, (i, predicted by the analyses shall be evaluated based

on laboratory test data for similar components. The effects of gravity and other loads on member

deformation capacity shall be considered in these evaluations. Member deformation shall not

exceed two thirds of a value that results in loss of ability to carry gravity loads or that results in

deterioration of member strength to less than 67 percent of the peak value.

5A.1.4.3 Interstory Drift: The design interstory drift obtained from the analysis shall not

exceed 125 percent of the drift limit specified in Sec. 5.2.8.

5A.1.5 Design Review: When the nonlinear static analysis method is used to design the

structure, a design review of the seismic-force-resisting system and the structural analysis shall

be performed by an independent team of registered design professionals in the appropriate

disciplines and others experienced in seismic analysis methods and the theory and application of

nonlinear seismic analysis and structural behavior under extreme cyclic loads. The design review

shall include, but not be limited to, the following:

1. Review of any site-specific seismic criteria employed in the analysis including the development of site-specific spectra.,

2. Review of acceptance criteria used to demonstrate the adequacy of structural elements and

systems to withstand the calculated force and deformation demands togther with that

laboratory and other data used to substantiate these criteria,

3. Review the preliminary design including the determination of the expected inelastic displacement of the structure and the margins remaining beyond these displacements, and

4. Review of the final design of the entire structural system and all supporting analyses.

99

Chapter 6

ARCHITECTURAL, MECHANICAL, AND

ELECTRICAL COMPONENTS DESIGN REQUIREMENTS

6.1 GENERAL: This chapter establishes minimum design criteria for architectural,

mechanical, electrical, and nonstructural systems, components, and elements permanently

attached to structures, including supporting structures and attachments (hereinafter referred to as

"components"). The design criteria establish minimum equivalent static force levels and relative

displacement demands for the design of components and their attachments to the structure,

recognizing ground motion and structural amplification, component toughness and weight, and

performance expectations.

This chapter also establishes minimum seismic design force requirements for nonbuilding

structures that are supported by other structures. Seismic design requirements for nonbuilding

structures that are supported at grade are prescribed in Chapter 14. However, the minimum

seismic design forces for nonbuilding structures that are supported by another structure shall be

determined in accordance with the requirements of Sec. 6.1.3 with Rp equal to the value of R

specified in Chapter 14 and ap = 2.5 for nonbuilding structures with flexible dynamic

characteristics and ap = 1.0 for nonbuilding structures with rigid dynamic characteristics. The

distribution of lateral forces for the supported nonbuilding structure and all nonforce

requirements specified in Chapter 14 shall apply to supported nonbuilding structures.

Exception: For structures in Seismic Design Categories D, E and F if the combined

weight of the supported components and nonbuilding structures with flexible dynamic

characteristics exceeds 25 percent of the weight of the structure, the structure shall be

designed considering interaction effects between the structure and the supported items.

Seismic Design Categories for structures are defined in Sec. 4.2. For the purposes of this

chapter, components shall be considered to have the same Seismic Design Category as that of the 

structure that they occupy or to which they are attached unless otherwise noted.

In addition, all components are assigned a component importance factor (Ip) in this chapter. The

default value for Ip is 1.00 for typical components in normal service. Higher values for Ip are

assigned for components that contain hazardous substances, must have a higher level of

assurance of function, or otherwise require additional attention because of their life-safety

characteristics. Component importance factors are prescribed in Sec. 6.1.5.

All architectural, mechanical, electrical, and other nonstructural components in structures shall

be designed and constructed to resist the equivalent static forces and displacements determined in

accordance with this chapter. The design and evaluation of support structures and architectural

components and equipment shall consider their flexibility as well as their strength.

Exception: The following components are exempt from the requirements of this chapter:
2000 Provisions, Chapter 6

100

1. All components in Seismic Design Category A,

2. Architectural components in Seismic Design Category B other than parapets

supported by bearing walls or shear walls when the importance factor (Ip) is equal to

1.00,

3. Mechanical and electrical components in Seismic Design Category B,

4. Mechanical and electrical components in Seismic Design Category C when the

importance factor (Ip) is equal to 1.00,

5. Mechanical and electrical components in Seismic Design Categories D, E, and F

where Ip= 1.0 and flexible connections between the components and associated

ductwork, piping, and conduit are provided or that are mounted at 4 ft (1.22 m) or less

above a floor level and weigh 400 lb (1780 N) or less, or

6. Mechanical and electrical components in Seismic Design Categories C, D, E, and F

where Ip= 1.0 and flexible connections between the components and associated

ductwork, piping, and conduit are provided that weigh 20 lb (95 N) or less or, for

distribution systems, weight 5 lb/ft (7 N/m) or less.

The functional and physical interrelationship of components and their effect on each other shall

be considered so that the failure of an essential or nonessential architectural, mechanical, or

electrical component shall not cause the failure of an essential architectural, mechanical, or

electrical component.

6.1.1 References and Standards:

6.1.1.1 Consensus Standards: The following references are consensus standards and are to be

considered part of these provisions to the extent referred to in this chapter:

ASME A17.1 American Society of Mechanical Engineers (ASME), ASME

A17.1, Safety Code For Elevators And Escalators, 1996.

ASTM C635 American Society For Testing And Materials (ASTM), ASTM

C635, Standard Specification for the Manufacture,

Performance, and Testing of Metal Suspension Systems for

Acoustical Tile and Lay-in Panel Ceilings, 1997.

ASME/BPV American Society of Mechanical Engineers (ASME/BPV), Boiler and

Pressure Vessel Code, including addendums through 2000.

ASTM C636 American Society for Testing and Materials (ASTM), ASTM

C636, Standard Practice for Installation of Metal Ceiling

Suspension Systems for Acoustical Tile and Lay-in Panels,

1996.
Architectural, Mechanical, and Electrical Components Design Requirements

101

ANSI/ASME B31.1 American National Standards Institute/American Society of

Mechanical Engineers, ANSI/ASME B31.1-98, Power Piping

ANSI/ASME B31.3 American National Standards Institute/American Society of

Mechanical Engineers, ANSI/ASME B31.3-96, Process Piping

ANSI/ASME B31.4 American National Standards Institute/American Society of

Mechanical Engineers, ANSI/ASME B31.4-92, Liquid Transportation

Systems for Hydrocarbons, Liquid Petroleum Gas, Anhydrous

Ammonia, and Alcohols

ANSI/ASME B31.5 American National Standards Institute/American Society of

Mechanical Engineers, ANSI/ASME B31.5-92, Refrigeration Piping

ANSI/ASME B31.8 American National Standards Institute/American Society of

Mechanical Engineers, ANSI/ASME B31.8-95, Gas Transmission and

Distribution Piping Systems

ANSI/ASME B31.9 American National Standards Institute/American Society of

Mechanical Engineers, ANSI/ASME B31.9-96, Building Services

Piping

ANSI/ASME B.31.11 American National Standards Institute/American Society of

Mechanical Engineers, ANSI/ASME B31.11-89 (Reaffirmed, 1998),

Slurry Transportation Piping Systems

NFPA-13 National Fire Protection Association (NFPA), NFPA-13, Standard for

the Installation of Sprinkler Systems, 1999.

IEEE- 344 Institute of Electrical and Electronic Engineers (IEEE). Standard 344,

Recommended Practice for Seismic Qualification of Class I E

Equipment for Nuclear Power Generating Stations, 1987.

6.1.1.2 Accepted Standards: The following references are standards developed within the

industry and represent acceptable procedures for design and construction:

ASHRAE SRD American Society of Heating, Ventilating, and Air Conditioning

(ASHRAE), Handbook, “Seismic Restraint Design,”1999.

CISCA Recs./Zones 0-2 Ceilings and Interior Systems Construction Association (CISCA),

Recommendations for Direct-Hung Acoustical Tile and Lay-in Panel

Ceilings, Seismic Zones 0-2, 1991.

CISCA Recs/ Zones 3-4 Ceilings and Interior Systems Construction Association (CISCA),

Recommendations for Direct-Hung Acoustical Tile and Lay-in Panel

Ceilings, Seismic Zones 3-4, 1991.

SMACNA HVAC Sheet Metal and Air Conditioning Contractors National Association

(SMACNA), HVAC Duct Construction Standards, Metal and Flexible,

1995.
2000 Provisions, Chapter 6

102

F

p ' 0.4a

p

SDSW

p

R

p

I

p

1 % 2 z

h (6.1.3-1)

F

p ' 1.6SDS Ip

W

p (6.1.3-2)

F

p ' 0.3SDS Ip

W

p (6.1.3-3)

SMACNA Rectangular Sheet Metal and Air Conditioning Contractors National Association

(SMACNA), Rectangular Industrial Duct Construction Standards,

1980.

SMACNA Restraint Sheet Metal and Air Conditioning Contractors National Association

(SMACNA), Seismic Restraint Manual Guidelines for Mechanical

Systems, 1991, including Appendix B, 1998.

AAMA 501.4 American Architectural Manufacturers Association (AAMA),

Recommended Static Test Method for Evaluating Curtain Wall and

Storefront Systems Subjected to Seismic and Wind Induced Interstory

Drifts. Publication No. AAMA 501.4-2000.

6.1.2 Component Force Transfer: Components shall be attached such that the component

forces are transferred to the structure. Component seismic attachments shall be bolted, welded,

or otherwise positively fastened without consideration of frictional resistance produced by the

effects of gravity. A continuous load path of sufficient strength and stiffness between the

component and the supporting structure shall be verified. Local elements of the supporting

structure shall be verified for the component forces where they control the design of the elements

or their connections. The component forces shall be those determined in Section 6.1.3, except

that modifications to Fp and Rp due to anchorage conditions need not be considered. The design

documents shall include sufficient information relating to the attachments to verify compliance

with the requirements of these provisions.

6.1.3 Seismic Forces: Seismic forces (Fp) shall be determined in accordance with Eq. 6.1.3-1:

Fp is not required to be taken as greater than:

and Fp shall not be taken as less than:
Architectural, Mechanical, and Electrical Components Design Requirements

103

where:

Fp = Seismic design force centered at the component's center of gravity and distributed relative

to component's mass distribution.

SDS = Spectral acceleration, short period, as determined from Sec. 4.1.2.5.

ap = Component amplification factor that varies from 1.00 to 2.50 (select appropriate value

from Table 6.2.2 or Table 6.3.2).

Ip = Component importance factor that is either 1.00 or 1.50 (see Sec. ).

Wp = Component operating weight.

Rp = Component response modification factor that varies from 1.0 to 5.0 (select appropriate

value from Table 6.2.2 or Table 6.3.2).

z = Height in structure of point of attachment of component. For items at or below the base,

z shall be taken as 0. The value of z/h need not exceed 1.0.

h = Average roof height of structure relative to grade elevation.

The force, Fp, shall be applied independently longitudinally and laterally in combination with

service loads associated with the component. Combine horizontal and vertical load effects as

indicated in Sec. 5.2.7 substituting Fp for the term QE. The reliability/redundancy factor, D, is

permitted to be taken equal to 1.

When positive and negative wind loads exceed Fp for nonstructural exterior walls, these wind

loads shall govern the design. Similarly, when the building code horizontal loads exceed Fp for

interior partitions, these building code loads shall govern the design.

In lieu of the forces determined in accordance with Eq. 6.1.3-1, accelerations at any level may be

determined by the modal analysis procedures of Sec. 5.5 with R = 1.0. Seismic forces shall be in

accordance with Eq. 6.1.3-4:

F (6.1.3-4)

aaW

R

I

p A ip p

p

p

= x

Where ai is the acceleration at level I obtained from the modal analysis.

The upper and lower limits of Fp determined by Eq. 6.1.3-2 and 3 apply.

6.1.4 Seismic Relative Displacements: Seismic relative displacements (Dp) shall be determined

in accordance with the following equations:

D (6.1.4-1) p xA yA = − δ δ
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104

Dp is not required to be taken as greater than:

D XY ( ) (6.1.4-2) h p

aA

sx

= − ∆

For two connection points on separate Structures A and B or separate structural systems, one at

level x and the other at level y, Dp shall be determined as:

D (6.1.4-3) p xA yB = + δ δ

Dp is not required to be taken as greater than:

D (6.1.4-4)

X

h

Y

h p

aA

sx

aB

sx

= +

∆ ∆

where:

Dp = Relative seismic displacement to the component must be designed to accommodate.

*xA = Deflection at building level x of Structure A, determined by an elastic analysis as

defined in Sec. 5.2.8 and multiplied by the Cd factor.

*yA = Deflection at building level y of Structure A, determined by an elastic analysis as

defined in Sec. 52.8 and multiplied by the Cd factor.

*yB = Deflection at building level y of Structure B, determined by an elastic analysis as

defined in Sec. 5.2.8 and multiplied by the Cd factor.

X = Height of upper support attachment at level x as measured from the base.

Y = Height of lower support attachment at level y as measured from the base. 

)aA = Allowable story drift for Structure A as defined in Table 5.2.8.

)aB = Allowable story drift for Structure B as defined in Table 5.2.8.

hsx = Story height used in the definition of the allowable drift, )a, in Table 5.2.8. Note that

)a/hsx = the allowable drift index.

The effects of seismic relative displacements shall be considered in combination with

displacement caused by other loads as appropriate.

6.1.5 Component Importance Factor: The component importance factor, Ip, shall be selected

as follows:

Ip = 1.5 Life safety component is required to function after an earthquake.
Architectural, Mechanical, and Electrical Components Design Requirements

105

Ip = 1.5 Component contains hazardous contents.

Ip = 1.5 Storage racks in occupancies open to the general public (e.g., warehouse retails

stores).

Ip = 1.0 All other components.

In addition, for structures in Seismic Use Group III:

Ip = 1.5 All components needed for continued operation of the facility or whose failure could

impair the continued operation of the facility.

6.1.6 Component Anchorage: Components shall be anchored in accordance with the following

provisions.

6.1.6.1: The force in the connected part shall be determined based on the prescribed forces for

the component specified in Sec. 6.1.3. Where component anchorage is provided by shallow

expansion anchors, shallow chemical anchors or shallow (low deformability) cast-in-place

anchors, a value of Rp = 1.5 shall be used in Sec. 6.1.3 to determine the forces in the connected

part.

6.1.6.2: Anchors embedded in concrete or masonry shall be proportioned to carry the least of the

following:

a. The design strength of the connected part,

b. 1.3 times the force in the connected part due to the prescribed forces, and

c. The maximum force that can be transferred to the connected part by the component structural

system.

6.1.6.3: Determination of forces in anchors shall take into account the expected conditions of

installation including eccentricities and prying effects.

6.1.6.4: Determination of force distribution of multiple anchors at one location shall take into

account the stiffness of the connected system and its ability to redistribute loads to other anchors

in the group beyond yield.

6.1.6.5: Power driven fasteners shall not be used for tension load applications in Seismic Design

Categories D, E, and F unless approved for such loading.

6.1.6.6: The design strength of the anchors shall be determined in accordance with the

provisions in Chapter 9.

6.1.6.7: For additional requirements for anchors to steel, see Chapter 10.

6.1.6.8: For additional requirements for anchors in masonry, see Chapter 11.

6.1.6.9: For additional requirements for anchors in wood, see Chapter 12.

6.1.7 Construction Documents: Construction documents shall be prepared by a registered

design professional in a manner consistent with the requirements of the Provisions, as indicated
2000 Provisions, Chapter 6

106

in Table 6.1.7, in sufficient detail for use by the owner, building officials, contractors, and

inspectors.

TABLE 6.1.7 Construction Documents

Component Description

Provisions Reference Required Seismic 

Design 

Categories

Quality

Assurance

Design

Exterior nonstructural wall elements,

including anchorage

3.2.8 No. 1 6.2.4 D, E, F

Suspended ceiling system, including

anchorage

3.2.8 No. 3 6.2.6 D, E, F

Access Floors, including anchorage 3.8 No. 2 6.2.7 D, E, F

Steel storage racks, including anchorage 3.2.8 No. 2 6.2.9 D, E, F

Glass in glazed curtain walls, glazed

storefronts and interior glazed partitions,

including anchorage.

3.3.9 No. 3 6.2.10 D, E, F

HVAC ductwork containing hazardous

materials, including anchorage.

3.2.9 No. 4 6.3.10 C, D, E, F

Piping systems and mechanical units

containing flammable, combustible, or

highly toxic materials. 

3.2.9 No. 3 6.3.11

6.3.12

6.3.13

C, D, E, F

Anchorage of electrical equipment for

emergency standby power systems

3.2.9 No. 1 6.3.14 C, D, E, F

Anchorage for all other electrical

equipment

3.2.9 No. 2 6.3.14 E, F

Project-specific requirements for

mechanical and electrical components and

their anchorage

3.3.5 6.30 C, D, E, F

6.2 ARCHITECTURAL COMPONENT DESIGN:

6.2.1 General: Architectural systems, components, or elements (hereinafter referred to as

“components”) listed in Table 6.2.2 and their attachments shall meet the requirements of Sec.

6.2.2 through Sec. 6.2.9.

6.2.2 Architectural Component Forces and Displacements: Architectural components shall

meet the force requirements of Sec. 6.1.3 and 6.4 and Table 6.2.2.
Architectural, Mechanical, and Electrical Components Design Requirements

107

Exception: Components supported by chains or otherwise suspended from the structural

system above are not required to meet the lateral seismic force requirements and seismic

relative displacement requirements of this section provided that they cannot be damaged or

cannot damage any other component when subject to seismic motion and they have ductile or

articulating connections to the structure at the point of attachment. The gravity design load

for these items shall be three times their operating load.

TABLE 6.2.2 Architectural Components Coefficients 

Architectural Component or Element ap

a Rp

b

Interior Nonstructural Walls and Partitions (See also Sec. 6.8)

 Plain (unreinforced) masonry walls

 All other walls and partitions 

1.0

1.0

1.5

2.5

Cantilever Elements (Unbraced or braced to structural frame below its center of mass)

 Parapets and cantilever interior nonstructural walls

 Chimneys and stacks where laterally supported by structures.

2.5

2.5

2.5

2.5

Cantilever elements (Braced to structural fame above its center of mass)

 Parapets 

 Chimneys and Stacks

 Exterior Nonstructural Walls

1.0

1.0

1.0b

2.5

2.5

2.5

Exterior Nonstructural Wall Elements and Connections (see also Sec. 6.2.4)

 Wall Element

 Body of wall panel connections

 Fasteners of the connecting system

1.0

1.0

1.25

2.5

2.5

1

Veneer

 High deformabiliy elements and attachments

 Low deformability and attachments

1.0

1.0

2.5

1.5

Penthouses (except when framed by an extension of the building frame) 2.5 3.5

Ceilings (see also Sec. 6.2.6)

 All 1.0 2.5

Cabinets 

 Storage cabinets and laboratory equipment 1.0 2.5

Access floors (see also Sec. 6.2.7)

 Special access floors (designed in accordance with Sec. 6.2.7.2)

 All other

1

1

2.5

1.5
2000 Provisions, Chapter 6

108

Appendages and Ornamentations 2.5 2.5

Signs and Billboards 2.5 2.5

Other Rigid Components

 High deformability elements and attachments

 Limited deformability elements and attachments

 Low deformability elements and attachments

1.0

1.0

1.0

3.5

2.5

1.5

Other flexible components

 High deformability elements and attachments

 Limited deformability elements and attachments

 Low deformability elements and attachments

2.5

2.5

2.5

3.5

2.5

1.5

a

 A lower value for ap may be justified by detailed dynamic analysis. The value for ap shall not be

less than 1.00. The value of ap = 1 is for equipment generally regarded as rigid and rigidly attached. 

The value of ap = 2.5 is for flexible components or flexibility attached components. See Chapter 2

for definitions of rigid flexible components including attachments.

b

 Where flexible diaphragms provide lateral support for walls and partitions, the design forces for

anchorage to the diaphragm shall be specified in Sec. 5.2.5.

6.2.3 Architectural Component: Architectural components that could pose a life-safety hazard

shall be designed for the seismic relative displacement requirements of Sec. 6.1.4. Architectural

components shall be designed for vertical deflection due to joint rotation of cantilever structural

members.

6.2.4 Exterior Nonstructural Wall Elements and Connections:

6.2.4.1 General: Exterior nonstructural wall panels or elements that are attached to or enclose

the structure shall be designed to resist the forces in accordance with Eq. 6.1.3-1 or 6.1.3-2 and

shall accommodate movements of the structure resulting from response to the design basis

ground motion, Dp, or temperature changes. Such elements shall be supported by means of

positive and direct structural supports or by mechanical connections and fasteners in accordance

with the following requirements:

a. Connections and panel joints shall allow for a relative movement between stories for not less

than the calculated story drift Dp or 1⁄2 in. (13 mm), whichever is greater..

b. Connections to permit movement in the plane of the panel for story drift shall be sliding

connections using slotted or oversize holes, connections that permit movements by bending

of steel, or other connections that provide equivalent sliding or ductile capacity.

c. Bodies of connectors shall have sufficient deformability and rotation capacity to preclude

fracture of the concrete of low deformation failures at or near welds.
Architectural, Mechanical, and Electrical Components Design Requirements

109

d. All fasteners in the connecting system such as bolts, inserts, welds, and dowels and the body

of the connectors shall be designed for the force, Fp, determined in by Eq. 6.1.3-2 with

vallues of Rp and ap taken from Table 6.2.2 applied at the center of mass of the panel.

e. Anchorage using flat straps embedded in concrete or masonry shall be attached to or hooked

around reinforcing steel or otherwise terminated so as to effectively transfer forces to the

reinforcing steel.

6.2.4.2 Glass: Glass is a glazed curtain walls and storefronts shall be designed and installed in

accordance with sec. 6.2.10.

6.2.5 Out-of-Plane-Bending: Transverse or out-of-plane bending or deformation of a

component or system that is subjected to forces as determined in Sec. 6.1.3 shall not exceed the

deflection capacity of the component or system.

6.2.6 Suspended Ceilings: Suspended ceilings shall be designed to meet the seismic force

requirements of Sec. 6.2.6.1. In addition, suspended ceilings shall meet the requirements of

either Industry Standard Construction as modified in Sec. 6.2.6.2 or integral construction as

specified in Sec. 6.2.6.3.

6.2.6.1 Seismic Forces: Suspended ceilings shall be designed to meet the force requirements of

Sec. 6.1.3.

The weight of the ceiling, Wp, shall include the ceiling grid and panels; light fixtures if attached

to, clipped to, or laterally supported by the ceiling grid; and other components that are laterally

supported by the ceiling. Wp shall be taken as not less than 4 psf (19 N/m2).

The seismic force, Fp, shall be transmitted through the ceiling attachments to the building

structural elements or the ceiling-structure boundary.

Design of anchorage and connections shall be in accordance with these provisions.

6.2.6.2 Industry Standard Construction: Unless designed in accordance with Sec. 6.2.6.3,

suspended ceilings shall be designed and constructed in accordance with this section.

6.2.6.2.1 Seismic Design Category C: Suspended ceilings in Seismic Design Category C shall

be designed and installed in accordance with CISCA Rec for Zones 0-2, except that seismic

forces shall be determined in accordance with Sec. 6.1.3 and 6.2.6.1.

Sprinkler heads and other penetrations in Seismic Design Category C shall have a minimum of

1/4 inch (6 mm) clearance on all sides.

6.2.6.2.2 Seismic Design Categories D, E, and F: Suspended ceilings in Seismic Design

Categories D, E, and F be designed and installed in accordance with CISCA Rec for Zones 3-4

and the additional requirements listed in this subsection.

a. A heavy duty T-bar grid system shall be used.

b. The width of the perimeter supporting closure angle shall be not less than 2 in. (50 mm). In

each orthogonal horizontal direction, one end of the ceiling grid shall be attached to the
2000 Provisions, Chapter 6

110

closure angle. The other end in each horizontal direction shall have a 3/4 in. (19 mm)

clearance from the wall and shall rest upon and be free to slide on a closure angle.

c. For ceiling areas exceeding 1000 ft2 (92.9 m2), horizontal restraint of the ceiling to the

structural system shall be provided. The tributary areas of the horizontal restraints shall be

approximately equal.

Exception: Rigid braces are permitted to be used instead of diagonal splay

wires. Braces the attachments to the structural system above shall be adequate

to limit relative lateral deflections at point of attachment of ceiling grid to less

than 1/4 in. (6 mm) for the loads prescribed in Sec. 6.1.3.

d. For ceiling areas exceeding 2500 ft2 (232 m2

), a seismic separation joint or full height

partition that breaks the ceiling up into areas not exceeding 2500 ft2

 shall be provided unless

structural analyses are performed of the ceiling bracing system for the prescribed seismic

forces which demonstrate ceiling system penetrations and closure angles provide sufficient

clearance to accommodate the additional movement. Each areas shall be provided with

closure angles in accordance with Item b and horizontal restraints or bracing in accordance

with Item c.

e. Except where rigid braces are used to limit lateral deflections, sprinkler heads and other

penetrations shall have a 2 in. (50 mm) oversize ring, sleeve, or adapter through the ceiling

tile to allow for free movement of at least 1 in. (25 mm) in all horizontal directions. 

Alternatively, a swing joint can accommodate 1 in. (25 mm) of ceiling movements in all

horizontal directions are permitted to be provided at the top of the sprinkler head extension.

f. Changes in ceiling plan elevation shall be provided with positive bracing.

g. Cable trays and electrical conduits shall be supported independently of the ceiling.

h. Suspended ceilings shall be subject to the special inspection requirements of Sec. 3.3.9 of the

Provisions.

6.2.6.3 Integral Ceiling/Sprinkler Construction: As a alternative to providing large

clearances around sprinkler system penetrations through ceiling systems, the sprinkler system and

ceiling grid are permitted to be designed and tied together as an integral unit. Such a design shall

consider the mass and flexibility of all elements involved, including: ceiling system, sprinkler

system, light fixtures, and mechanical (HVAC) appurtenances. The design shall be performed by

a registered design professional. 

6.2.7 Access Floors:

6.2.7.1 General: Access floors shall be designed to meet the force provisions of Sec. 6.1.3 and

the additional provisions of this section. The weight of the access floor, Wp, shall include the

weight of the floor system, 100 percent of the weight of all equipment fastened to the floor, and

25 percent of the weight of all equipment supported by but not fastened to the floor. The seismic

force, Fp, shall be transmitted from the top surface of the access floor to the supporting structure.
Architectural, Mechanical, and Electrical Components Design Requirements

111

Overturning effects of equipment fastened to the access floor panels also shall be considered. 

The ability of “slip on” heads for pedestals shall be evaluated for suitability to transfer

overturning effects of equipment.

When checking individual pedestals for overturning effects, the maximum concurrent axial load

shall not exceed the portion of Wp assigned to the pedestal under construction.

6.2.7.2 Special Access Floors: Access floors shall be considered to be “special access floors” if

they are designed to comply with the following considerations:

1. Connections transmitting seismic loads consist of mechanical fasteners, concrete anchors,

welding, or bearing. Design load capacities comply with recognized design codes and/or

certified test results.

2. Seismic loads are not transmitted by friction produced solely by the effects of gravity,

powder-actuated fasteners (shot pins), or adhesives.

3. The bracing system shall be designed considering the destabilizing effects of individual

members buckling in compression.

4. Bracing and pedestals are of structural or mechanical shape produced to ASTM specifications

that specify minimum mechanical properties. Electrical tubing shall be used.

5. Floor stingers that are designed to carry axial seismic loads that are mechanically fastened to

the supporting pedestals are used.

6.2.8 Partitions:

6.2.8.1 General: Partitions that are tied to the ceiling and all partitions greater than 6 ft (1.8 m)

in height shall be laterally braced to the building structure. Such bracing shall be independent o f

any ceiling splay bracing. Bracing shall be spaced to limit horizontal deflection at the partition

head to comparable with ceiling deflection requirements as determined in Sec. 6.2.6 for

suspended ceilings and Sec. 6.2.2 for other systems.

6.2.8.2 Glass: Glass in glazed partitions shall be designed and installed in accordance with Sec.

6.2.10.

6.2.9 Steel Storage Racks: Steel storage racks shall be designed to meet the force requirements

of Chapter 14.

6.2.10 Glass in Glazed Curtain Walls, Glazed Storefronts, and Glazed Partitions: 

6.2.10.1 General: Glass in glazed curtain walls, glazed storefronts and glazed partitions shall

meet the relative displacement requirement of Eq. 6.2.10.1-1:

∆ fallout p ≥ 125 . ID (6.2.10.1-1)

or 0.5 inch (13 mm), whichever is greater, where:

)fallout = the relative seismic displacement (drift) causing glass fallout from the

curtain wall, storefront wall or partition (Section 6.2.10.2).
2000 Provisions, Chapter 6

112

Dp = the relative seismic displacement that the component must be designed

to accommodate (Eq. 6.1.4-1). Dp shall be determined over the height

of the glass component under consideration.

I = the occupancy importance factor (Table 1.4).

Exceptions:

1. Glass with sufficient clearances from its frame such that physical

contact between the glass and frame will not occur at the design

drift, as demonstrated by Eq. 6.2.10.1-2, shall be exempt from the

provisions of Eq. 6.2.10.1-1:

D D (6.2.10.1-2) clear p ≥ 125 .

or 0.5 inch (13 mm); whichever is greater, where:

Dclear = 2 1 1

2

1

c

h c

b c

p

p

+

















hp = the height of the rectangular glass,

bp = the width of the rectangular glass,

c1 = the clearance (gap) between the vertical glass edges

and the frame, and

c2 = the clearance (gap) between the horizontal glass

edges and the frame.

2. Fully tempered monolithic glass in Seismic Use Groups I and II located no

more than 10 ft (3 m) above a walking surface shall be exempt from the

provisions of Eq. 6.2.10.1-1.

3. Annealed or heat-strengthened laminated glass in single thickness with

interlayer no less than 0.030 in. (0.76 mm) that is captured mechanically in a

wall system glazing pocket, and whose perimeter is secured to the frame by a

wet glazed gunable curing elastomeric sealant perimeter bead of 1⁄2 in. (13

mm) minimum glass contact width, or other approved anchorage system, shall

be exempt from the provisions of Eq. 6.2.10.1-1.

6.2.10.2 Seismic Drift Limits for Glass Components: )fallout, the drift causing glass fallout

from the curtain wall, storefront or partition, shall be determined in accordance with SMACNA

Restraint, or by engineering analysis.
Architectural, Mechanical, and Electrical Components Design Requirements

113

6.3 MECHANICAL AND ELECTRICAL COMPONENT DESIGN:

6.3.1 General: Attachments and equipment supports for the mechanical and electrical systems,

components, or elements (hereinafter referred to as “components”) shall meet the requirements of

Sec. 6.3.2 through Sec. 6.3.16.

6.3.2 Mechanical and Electrical Component Forces and Displacements: Mechanical and

electrical components shall meet the force and seismic relative displacement requirements of Sec.

6.1.3, Sec. 6.1.4, and Table 6.3.2.

Some complex equipment such as valve operators, turbines and generators, and pumps and

motors are permitted to be functionally connected by mechanical links not capable of transferring

the seismic loads or accommodating seismic relative displacements and may require special

design considerations such as a common rigid support or skid.

Exception: Components supported by chains or similarly suspended from the structure

above or not required to meet the lateral seismic force requirements and seismic relative

displacement requirements of this section provided that they cannot be damaged or

cannot damage any other component when subject to seismic motion and they have high

deformation or articulating connections to the building at the point of attachment. The

gravity design load for these items shall be three times their operating load.

TABLE 6.3.2 Mechanical and Electrical Components Coefficients

Mechanical and Electrical Component or Elementb ap

a Rp

General Mechanical

 Boilers and Furnaces

 Pressure vessels on skirts and free-standing

 Stacks

 Cantilevered chimneys

 Other

1.0

2.5

2.5

2.5

1.0

2.5

2.5

2.5

2.5

2.5

Manufacturing and Process Machinery

 General

 Conveyors (nonpersonnel)

1.0

2.5

2.5

2.5

Piping Systems

 High deformability elements and attachments

 Limited deformability elements and attachments

 Low deformability elements and attachments

1.0

1.0

1.0

3.5

2.5

1.5
2000 Provisions, Chapter 6

Mechanical and Electrical Component or Elementb ap

a Rp

114

HVAC System Equipment 

 Vibration isolated 

 Non-vibration isolated

 Mounted in-line with ductwork

 Other

2.5

1.0

1.0

1.0

2.5

2.5

2.5

2.5

Elevator Components 1.0 2.5

Escalator Components 1.0 2.5

Trussed Towers (free-standing or guyed) 2.5 2.5

General Electrical 

 Distributed systems (bus ducts, conduit, cable tray)

 Equipment 

2.5

1.0

5

2.5

Lighting Fixtures 1.0 1.5

a

 A lower value for ap is permitted provided a detailed dynamic analysis is performed which

justifies a lower limit. The value for ap shall not be less than 1.00. The value of ap = 1 is for

equipment generally regarded as rigid or rigidly attached. The value of ap = 2.5 is for flexible

components or flexibly attached components. See Chapter 2 for definitions of rigid and flexible

components including attachments.

b Components mounted on vibration isolation systems shall have a bumper restraint or snubber in

each horizontal direction. The design force shall be taken as 2Fp if the maximum clearance (air

gap) between the equipment support frame and restraint is greater than 1/4 inch. If the maximum

clearance is specified on the construction documents to be not greater than 1/4 inch, the design

force may be taken as Fp.

6.3.3 Mechanical and Electrical Component Period: The fundamental period of the

mechanical and electrical component (and its attachment to the building), Tp, may be determined

by the following equation provided that the component and attachment can be reasonably

represented analytically by a simple spring and mass single-degree-of-freedom system:

T (6.3.3)

W

K g p

p

p

= 2π

where:

Tp = Component fundamental period,

Wp = Component operating weight,
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115

g = Gravitational acceleration, and

Kp = Stiffness of resilient support system of the component and attachment, determined

in terms of load per unit deflection at the center of gravity of the component.

Note that consistent units must be used.

Alternatively, determine the fundamental period of the component in seconds, Tp, from

experimental test data or by a properly substantiated analysis.

6.3.4 Mechanical and Electrical Component Attachments: The stiffness of mechanical and

electrical component attachments shall be designed such that the load path for the component

performs its intended function.

6.3.5 Component Supports: Mechanical and electrical component supports and the means by

which they are attached to the component shall be designed for the forces determined in Sec.

6.1.3 and in conformance with Chapters 5 though 9, as appropriate, for the materials comprising

the means of attachment. Such supports include structural members, braces, frames, skirts, legs,

saddles, pedestals, cables, guys, stays, snubbers, ans tethers. Component supports may be forged

or cast as a part of the mechanical or electrical component. If standard or proprietary supports are

used, they shall be designed by either load rating (i.e., testing) or for the calculated seismic

forces. In addition, the stiffness of the support, when appropriate, shall be designed such that the

seismic load path for the component performs its intended function.

Component supports shall be designed to accommodate the seismic relative displacements

between points of support determined in accordance with Sec. 6.1.4.

In addition, the means by which supports are attached to the component, except when integral

(i.e., cast or forged), shall be designed to accommodate both the forces and displacements

determined in accordance with Sec. 6.1.3 and 6.1.4. If the value of Ip = 1.5 for the component,

the local region of the support attachment point to the component shall be evaluated for the effect

of the load transfer on the component wall.

6.3.6 Component Certification: The manufacturer’s certificate of compliance with the force

requirements of the Provisions shall be submitted to the regulatory agency when required by the

contract documents or when required by the regulatory agency.

6.3.7 Utility and Service Lines at Structure Interfaces: At the interface of adjacent structures

or portions of the same structure that may move independently, utility lines shall be provided

with adequate flexibility to accommodate the anticipated differential movement between the

ground and the structure. Differential displacement calculations shall be determined in

accordance with Sec. 6.1.4.

6.3.8 Site-Specific Considerations: The possible interruption of utility service shall be

considered in relation to designated seismic systems in Seismic Use Group III as defined in Sec.

1.3.1. Specific attention shall be given to the vulnerability of underground utilities and utility

interfaces between the structure and the ground in all situations where Site Class E and F soil is

present and where the seismic coefficient Ca is equal to or greater than 0.15.
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116

6.3.9 Storage Tanks:

6.3.9.1 Above-Grade Storage Tanks: For storage tanks mounted above grade in structures,

attachments, supports, and the tank shall be designed to meet the force requirements of Chapter

14.

6.3.10 HVAC Ductwork: Attachments and supports for HVAC ductwork systems shall be

designed to meet the force and displacement requirements of Sec. 6.1.3 and 6.1.4 and the

additional requirements of this section. In addition to their attachments and supports, ductwork

systems designated as having Ip greater than 1.0 shall be designed to meet the force and

displacement requirements of Sec. 6.1.3 and 6.1.4 and the additional requirements of this section. 

Where HVAC ductwork runs between structures that could displace relative to one another and

for isolated structures where the HVAC ductwork crosses the isolation interface, the HVAC

ductwork shall be designed to accommodate the seismic relative displacements specified in Sec.

6.1.4.

Seismic restraints are not required for HVAC ducts with Ip = 1.0 if either of the following

conditions are met for the full length of each duct run:

a. HVAC ducts are suspended from hangers, and all hangers are 12 in. (305 mm) or less in

length from the top of the duct to the supporting structure and the hangers are detailed to

avoid significant bending of the hangers and their attachments.

or

b. HVAC ducts have a cross-sectional area of less than 6 ft2

 (0.557 m2).

HVAC duct systems fabricated and installed in accordance with the SMACNA HVAC,

SMACNA Rectangular, and SMACNA Restraint shall be deemed to meet the lateral bracing

requirements of this section.

Equipment items installed in-line with the duct system (e.g., fans, heat exchangers, and

humidifiers) with an operating weight greater than 75 lb (334 N) shall be supported and laterally

braced independently of the duct system and shall meet the force requirements of Sec. 6.1.3. 

Appurtenances such as dampers, louvers, and diffusers shall be positively attached with

mechanical fasteners. Unbraced piping attached to in-line equipment shall be provided with

adequate flexibility to accommodate differential displacements.

6.3.11 Piping Systems: Attachments and supports for piping systems shall be designed to meet

the force and displacement requirements of Sec. 6.1.3 and 6.1.4 and the additional requirements

of this section. In addition to their attachments and supports, piping systems designated as

having Ip greater than 1.0 shall be designed to meet the force and displacement provisions of Sec.

6.1.3 and 6.1.4 and the additional requirements of this section. When piping systems are

attached to structures that could displace relative to one another and for isolated structures,

including foundations, where the piping system crosses the isolation interface, the piping system

shall be designed to accommodate the seismic relative displacements specified in Sec. 6.1.4.
Architectural, Mechanical, and Electrical Components Design Requirements

117

Seismic effects that shall be considered in the design of a piping system include the dynamic

effects of the piping system, its contents, and, when appropriate, its supports. The interaction

between the piping system and the supporting structures, including other mechanical and

electrical equipment, also shall be considered.

See Sec. 6.3.16 for elevator system piping requirements.

6.3.11.1 Fire Protection Sprinkler Systems: Fire protection sprinkler systems designed and

constructed in accordance with NFPA 13 shall be deemed to meet the force, displacement, and

other requirements of this section provided that the seismic design force and displacement

calculated in accordance with NFPA 13, multiplied by a factor of 1.4, is not less than that

determined using the Provisions.

6.3.11.2 Other Piping Systems. The following documents have been adopted as national

standards by the American National Standards Institute (ANSI) and are appropriate for use in the

seismic design of piping systems provided that the seismic design forces and displacements used

are comparable to those determined using the Provisions: ANSI/ASME B31.1, ANSI/ASME

B31.3, ANSI/ASME B31.4, ANSI/ASME B31.5, ANSI/ASME B31.9, ANSI/ASME B31.11, and

ANSI/ASME 31.8.

Exception: Piping systems designated as having an Ip greater than 1.0 shall not be

designed using the simplified analysis procedures of ANSI/ASME B31.9, Sec. 919.4.1

(a).

The following requirements shall also be met for piping systems designated as having an Ip

greater than 1.0.

a. Under design loads and displacements, piping shall not be permitted to impact other 

components.

b. Piping shall accommodate the effects of relative displacements that may occur between

piping support points on the structure on the ground, other mechanical and/or electrical

equipment, and other piping

6.3.11.2.1 Supports and Attachments for Other Piping: In addition to meeting the force,

displacement, and other requirements of this section, attachments and supports for piping shall be

subject to the following other requirements and limitations.

a. Attachments shall be designed in accordance with Sec. 6.1.6.

b. Seismic supports are not required for:

1. Piping supported by rod hangers provided that all hangers in the pipe run are 12 in.

(305 mm) or less in length from the top of the pipe to the supporting structure and the

pipe can accommodate the expected deflections. Rod hangers shall not be

constructed in a manner that would subject the rod to bending moments.

2. High deformability piping in Seismic Design Categories D, E, and F designated as

having Ip greater than 1.0 and a nominal pipe size of 1 in. (25 mm) or less when
2000 Provisions, Chapter 6

118

provisions are made to protect the piping from impact or to avoid the impact of larger

piping or other mechanical equipment.

3. High deformability piping in Seismic Design Category C designated as having an Ip

greater than 1.0 and a nominal pipe size of 2 in. (51 mm) or less when provisions are

made to protect the piping from impact or to avoid the impact of larger piping or other

mechanical equipment.

4. High deformability piping in Seismic Design Categories D, E, and F designated as

having an Ip equal to 1.0 and a nominal pipe size of 3 in. (76 mm) or less.

c. Seismic supports shall be constructed so that support engagement is maintained.

6.3.12 Boilers and Pressure Vessels: Attachments and supports for boilers and pressure

vessels shall be designed to meet the force and displacement provisions of Sec. 6.1.3 and 6.1.4

and the additional provisions of this section. In addition to their attachments and supports,

boilers and pressure vessels designated as having an Ip = 1.5 themselves shall be designed to

meet the force and displacement provisions of Sec. 6.1.3 and 6.1.4.

Seismic effects that shall be considered in the design of a boiler or pressure vessel include the

dynamic effects of the boiler or pressure vessel and it supports, sloshing of liquid contents, loads

from attached components such as piping, and the interaction between the boiler or pressure

vessel and its support.

6.3.12.1 ASME Boilers and Pressure Vessels: Boilers or pressure vessels designed in

accordance with ANSI/ASME B31.9 shall be deemed to meet the force, displacement, and other

requirements of this section. In lieu of the specific force and displacement provisions provided

in the ASME code, the force and displacement provisions of Sec. 6.1.3 and 6.1.4 shall be used.

6.3.12.2 Other Boilers and Pressure Vessels: Boilers and pressure vessels designated as

having an Ip = 1.5 but not constructed in accordance with the provisions of ANSI/ASME B31.9

shall meet the following provisions:

a. The design strength for seismic loads of combination with other service loads and appropriate

environmental effects shall not exceed the following:

(1) For boilers and pressure vessels constructed with ductile materials (e.g., steel

aluminum or copper), 90 percent of the material minimum specified yield strength .

(2) For threaded connections in boilers or pressure vessels or their supports constructed

with ductile materials, 70 percent of the material minimum specified yield strength.

(3) For boilers and pressure vessels constructed with nonductile materials (e.g., plastic,

cast iron, or ceramics), 25 percent of the material minimum specified tensile strength.

(4) For threaded connections in boilers or pressures vessels or their supports constructed

with nonductile materials, 20 percent of the material minimum specified tensile

strength.
Architectural, Mechanical, and Electrical Components Design Requirements

119

b. Provisions shall be made to mitigate seismic impact for boiler and pressure vessel

components constructed of nonductile materials or in cases where material ductility is

reduced (e.g., low temperature applications).

c. Boilers and pressure vessels shall be investigated to ensure that the interaction effects

between them and other constructions are acceptable.

6.3.12.3 Supports and Attachments for Boilers and Pressure Vessels: Attachments and

supports for boilers and pressure vessels shall meet the following provisions:

a. Attachments and supports transferring seismic loads shall be constructed of materials suitable

for the application and designed and constructed in accordance with nationally recognized

structural code such as, when constructed of steel, AISC LRFD and AISC ASD (see Chapter

8 for full references).

b. Attachments embedded in concrete shall be suitable for cyclic loads.

c. Seismic supports shall be constructed so that support engagement is maintained.

6.3.13 Mechanical Equipment Attachments and Supports: Attachments and supports for

mechanical equipment not covered in Sec. 6.3.8 through 6.3.12 or 6.3.16 shall be designed to

meet the force and displacement requirements of Sec. 6.1.3 and 6.1.4 and the additional

requirements of this section. In addition, mechanical equipment designated as having an Ip

greater than 1.0 shall be designed to meet the force and displacement requirements of Sec. 6.1.3

and 6.1.4 and the additional requirements of this section.

When required, seismic effects that shall be considered in the design of mechanical equipment,

attachments and their supports include dynamic effects of the equipment, its contents, and when

appropriate its supports. The interaction between the equipment and the supporting structures,

including other mechanical and electrical equipment, also shall be considered.

6.3.13.1 Mechanical Equipment: Mechanical equipment having an Ip greater than 1.0 shall

meet the following requirements:

a. Provisions shall be made to eliminate seismic impact for equipment components vulnerable

to impact, equipment components constructed of nonductile materials, and in cases where

material ductility is reduced (e.g., low temperature applications).

b. The possibility for loadings imposed on the equipment by attached utility or service lines due

to differential motions of points of support from separate structures shall be evaluated.

In addition, components of mechanical equipment designated as having an Ip greater than 1.0 and

containing sufficient material that would be hazardous if released shall be designed for seismic

loads. The design strength for seismic loads in combination with other service loads and

appropriate environmental effects such as corrosion shall be based on the following:

a. For mechanical equipment constructed with ductile materials (e.g., steel, aluminum, or

copper), 90 percent of the equipment material minimum specified yield strength.
2000 Provisions, Chapter 6

120

b. For threaded connections in equipment constructed with ductile materials, 70 percent of the

material minimum specified yield strength.

c. For mechanical equipment constructed with nonductile materials (e.g., plastic, cast iron, or

ceramics), 25 percent of the equipment material minimum tensile strength.

d. For threaded connections in equipment constructed with nonductile, 20 percent of the

material minimum specified yield strength.

6.3.13.2 Attachments and Supports for Mechanical Equipment: Attachments and supports

for mechanical equipment shall meet the following requirements:

a. Attachments and supports transferring seismic loads shall be constructed of materials suitable

for the application and designated and constructed in accordance with a nationally recognized

standard specification such as, when constructed of steel, AISC LRFD and AISC ASD.

b. Friction clips shall not be used for anchorage attachment.

c. Expansion anchors shall not be used for non-vibration isolated mechanical equipment rated

over 10 hp (7.45 kW).

Exception: Undercut expansion anchors are permitted.

d. Supports shall be specifically evaluated if weak-axis bending of cold-formed support steel is

relied on for the seismic load path.

e. Components mounted on vibration isolation systems shall have a bumper restraint or snubber

in each horizontal direction, and vertical restraints shall be provided where required to resist

overturning. Isolator housings and restraints shall be constructed of ductile materials. (See

additional design force requirements in Table 6.3.2.) A viscoelastic pad or similar material

of appropriate thickness shall be used between the bumper and equipment item to limit the

impact load.

f. Seismic supports shall be constructed so that support engagement is maintained.

6.3.14 Electrical Equipment Attachments and Supports: Attachments and supports for

electrical equipment shall be designed to meet the force and displacement requirements of Sec.

6.1.3 and 6.1.4 and the additional requirements of this section. In addition, electrical equipment

designated as having IP greater than 1.0 shall be designed to meet the force displacement

requirements of Sec. 6.1.3 and 6.1.4 and the additional requirements of this section.

Seismic effects that shall be considered in the design of other electrical equipment include the

dynamic effects of the equipment, its contents, and, when appropriate, its supports. The

interaction between the equipment and the supporting structures, including other mechanical and

electrical equipment, also shall be considered. When conduit, cable trays, or similar electrical

distribution components are attached to structures that could displace relative to one another and

for isolated structures where the conduit or cable trays cross the isolation interface, the conduit
Architectural, Mechanical, and Electrical Components Design Requirements

121

or cable trays shall be designed to accommodate the seismic relative displacements specified in

Sec. 6.1.4.

6.3.14.1 Electrical Equipment: Electrical equipment designed as having an Ip greater than 1.0

shall meet the following requirements:

a. Provisions shall be made to eliminate seismic impact between the equipment and other

components.

b. The loading on the equipment imposed by attached utility or service lines that also are

attached to separate structures shall be evaluated. 

c. Batteries on racks shall have wrap-around restraints to ensure that the batteries will not fall

off the rack. Spacers shall be used between restraints and cells to prevent damage to cases. 

Racks shall be evaluated for sufficient lateral load capacity.

d. Internal coils of dry type transformers shall be positively attached to their supporting

substructure within the transformer enclosure

e. Slide out components in electrical control panels, computer equipment, etc., shall have a

latching mechanism to hold contents in place.

f. Electrical cabinet design shall conform to the applicable National Electrical Manufacturers

Association (NEMA) standards. Cut-outs in the lower shear panel that do not appear to have

been made by the manufacturer and are judged to significantly reduce the strength of the

cabinet shall be specifically evaluated.

g. The attachment of additional external items weighing more than 100 pounds (445 N) shall be

specifically evaluated if not provided by the manufacturer.

6.3.14.2 Attachments and Supports for Electrical Equipment: Attachments and supports for

electrical equipment shall meet the following requirements:

a. Attachments and supports transferring seismic loads shall be constructed of materials suitable

for the application and designed and constructed in accordance with a nationally recognized

structural standard specification such as, when constructed of steel, AISC LRFD and AISC

and ASD.

b. Friction clips shall not be used for anchorage attachment.

c. Oversized plate washers extending to the equipment wall shall be used at bolted connections

through the base sheet metal if the base is not reinforced with stiffeners or not judged capable

of transferring the required loads.

d. Supports shall be specifically evaluated if weak-axis bending of light gage support steel is

relied on for the seismic load path.

e. The supports for linear electrical equipment such as cable trays, conduit, and bus ducts shall

be designed to meet the force and displacement requirements of Sec. 6.1.3 and 6.1.4 if any of

the following situations apply:
2000 Provisions, Chapter 6

122

(1) Supports are cantilevered up from the floor;

(2) Supports include bracing to limit deflection;

(3) Supports are constructed as rigid welded frames;

(4) Attachments into concrete utilize non-expanding insets, shot pins, or cast iron

embedments;

(5) Attachments utilize spot welds, plug welds, or minimum size welds as defined by

AISC.

f. Components mounted on vibration isolation systems shall have a bumper restraint or snubber

in each horizontal direction, and vertical restraints shall be provided where required to resist

overturning. Isolator housings and restraints shall not be constructed of cast iron or other

materials with limited ductility. (See additional design force requirements in Table 6.3.2.) A

viscoelastic pad or similar material or appropriate thickness shall be used between the

bumper and equipment item to limit the impact load.

6.3.15 Alternate Seismic Qualification Methods: As an alternative to the analysis methods

implicit in the design methodology described above, equipment testing is an acceptable method

to determine seismic capacity. Thus, adaptation of a nationally recognized standard, such as

CISCA Recs for Zones 3-4, is acceptable so long as the equipment seismic capacity equals or

exceeds the demand expressed in Sec. 6.1.3 and 6.1.4.

6.3.16 Elevator Design Requirements: Elevators shall meet the force and displacement

provisions of Sec. 6.3.2 unless exempted by either Sec. 1.2 or Sec. 6.1. Elevators designed in

accordance with the seismic provisions of ASME A17.1 shall be deemed to meet the seismic

force requirements of this section, except they also shall meet the additional requirements

provided in Sec. 6.3.16.1 through 6.3.16.4.

6.3.16.1 Elevators and Hoistway Structural System: Elevators and hoistway structural

systems shall be designed to meet the force and displacement provisions of Sec. 6.3.2.

6.3.16.2 Elevator Machinery and Controller Supports and Attachments: Elevator

machinery and controller supports and attachments shall be designed to meet the force and

displacement provisions of Sec. 6.3.2.

6.3.16.3 Seismic Controls: Seismic switches shall be provided for all elevators addressed by

Sec. 6.3.16.1, including those meeting the requirements of ASME A17.1, provided they operate

with a speed of 150 ft/min (46 m/min) or greater. Seismic switched shall provide an electrical

signal indicating that structural motions are of such a magnitude that the operation of elevators

may be impaired. Upon activism of the seismic switch, elevator operations shall conform the

provisions of ASME A17.1 except as noted below. The seismic switch shall be located at or

above the highest floor serviced by the elevator. The seismic switch shall have two horizontal

perpendicular axes of sensitivity. Its trigger level shall be set to 30 percent of the acceleration of
Architectural, Mechanical, and Electrical Components Design Requirements

123

gravity in facilities where the loss of the use of an elevator is a life-safety issue, the elevator may

be used after the seismic switch has triggered provided that:

1. The elevator shall operate no faster than the service speed,

2. The elevator shall be operated remotely from top to bottom and back to top to verify that it is

operable, and

3. The individual putting the elevator back in service should ride the elevator from top to

bottom and back to top to verify acceptable performance.

6.3.16.4 Retainer Plates: Retainer plates are required at the top and bottom of the car and

counterweight.
125

 

Chapter 7

FOUNDATION DESIGN REQUIREMENTS

7.1 GENERAL: This chapter includes only those foundation requirements that are specifically

related to seismic resistant construction. It assumes compliance with all other basic

requirements. These requirements include, but are not limited to, requirements for the extent of

the foundation investigation, fills to be present or to be placed in the area of the structure, slope

stability, subsurface drainage, and settlement control. Also included are pile requirements and

capacities and bearing and lateral soil pressure recommendations. Except as specifically noted,

where the term “pile” is used in Sec. 7.4.4 and 7.5.4, it shall include all foundation piers,

caissons, and piles. The term “pile cap” shall include all elements to which piles are connected,

including grade beams and mats.

7.2 STRENGTH OF COMPONENTS AND FOUNDATIONS: The resisting capacities of

the foundations, subjected to the prescribed seismic forces of Chapters 1, 4 and 5, shall meet the

requirements of this chapter.

7.2.1 Structural Materials: The strength of foundation components subjected to seismic forces

alone or in combination with other prescribed loads and their detailing requirements shall

conform to the requirements of Chapter 8, 9, 10, 11, or 12. The strength of foundation components shall not be less than that required for forces acting without seismic forces.

7.2.2 Soil Capacities: The capacity of the foundation soil in bearing or the capacity of the soil

interface between pile, pier, or caisson and the soil shall be sufficient to support the structure

with all prescribed loads, without seismic forces, taking due account of the settlement that the

structure can withstand. For the load combination including earthquake as specified in Sec. 

5.2.7, the soil capacities must be sufficient to resist loads at acceptable strains considering both

the short duration of loading and the dynamic properties of the soil.

7.3 SEISMIC DESIGN CATEGORIES A AND B: Any construction meeting the requirements of Sec. 7.1 and 7.2 is permitted to be be used for structures assigned to Seismic Design

Category A or B.

7.4 SEISMIC DESIGN CATEGORY C: Foundations for structures assigned to Seismic

Design Category C shall conform to all of the requirements for Seismic Design Categories A and

B and to the additional requirements of this section.

7.4.1 Investigation: The authority having jurisdiction may require the submission of a written

report that shall include, in addition to the requirements of Sec. 7.1 and the evaluations required

in Sec. 7.2.2, the results of an investigation to determine the potential hazards due to slope

instability, liquefaction, and surface rupture due to faulting or lateral spreading, all as a result of

earthquake motions.
2000 Provisions, Chapter 7

126

7.4.2 Pole-Type Structures: Construction employing posts or poles as columns embedded in

earth or embedded in concrete footings in the earth are permitted to be used to resist both axial

and lateral loads. The depth of embedment required for posts or poles to resist seismic forces

shall be determined by means of the design criteria established in the foundation investigation

report.

7.4.3 Foundation Ties: Individual pile caps, drilled piers, or caissons shall be interconnected

by ties. All ties shall be capable of carrying, in tension or compression, a force equal to the

product of the larger pile cap or column load times SDS divided by 10 unless it can be

demonstrated that equivalent restraint can be provided by reinforced concrete beams within slabs

on grade or reinforced concrete slabs on grade or confinement by competent rock, hard cohesive

soils, very dense granular soils, or other approved means.

7.4.4 Special Pile Requirements: The following special requirements for piles, piers, or

caissons are in addition to all other requirements in the code administered by the authority having

jurisdiction.

All concrete piles and concrete filled pipe piles shall be connected to the pile cap by embedding

the pile reinforcement in the pile cap for a distance equal to the development length as specified

in ACI 318 as modified by Chapter 9 of the Provisions. The pile cap connection can be made by

the use of field-placed dowel(s) anchored in the concrete pile. For deformed bars, the

development length is the full development length for compression or tension, in the case of

uplift, without reduction in length for excess area. 

Ends of rectangular hoops, spirals, and ties in piles shall be terminated with seismic hooks as

defined in Sec. 21.1 of ACI 318 turned into the confined concrete core. The ends of circular

spirals and hoops shall be terminated with 90-degree hooks turned into the confined concrete

core.

For resistance to uplift forces, anchorage of steel pipe (round HSS sections), concrete filled steel

pipe or H piles to the pile cap shall be made by means other than concrete bond to the bare steel

section. 

Exception: Anchorage of concrete filled steel pipe piles is permitted to be accomplished

using deformed bars developed into the concrete portion of the pile. 

Where a minimum length for reinforcement or the extent of closely spaced confinement

reinforcement is specified at the top of the pile, provisions shall be made so that those specified

lengths or extents are maintained after pile cut-off.

7.4.4.1 Uncased Concrete Piles: A minimum reinforcement ratio of 0.0025 shall be provided

for uncased cast-in-place concrete drilled or augured piles, piers, or caissons in the top one-third

of the pile length, a minimum length of 10 ft (3 m) below the ground, or throughout the flexural

length of the pile, whichever length is greatest. There shall be a minimum of four bars with

closed ties (or equivalent spirals) of a minimum of a 3/8 in. (9 mm) diameter provided at 16

longitudinal-bar-diameter maximum spacing. A maximum spacing of 6 in. (152mm) or eight

longitudinal-bar-diameters, whichever is less, shall be provided in the pile within three pile

diameters of the bottom of the pile cap.
Foundation Design Requirements

127

7.4.4.2 Metal-Cased Concrete Piles: Reinforcement requirements are the same as for uncased

concrete piles.

Exception: Spiral welded metal-casing of a thickness not less than No. 14 gauge can be

considered as providing concrete confinement equivalent to the closed ties or equivalent

spirals required in an uncased concrete pile, provided that the metal casing is adequately

protected against possible deleterious action due to soil constituents, changing water

levels, or other factors indicated by boring records of site conditions.

7.4.4.3 Concrete-Filled Pipe: Minimum reinforcement 0.01 times the cross-sectional area of

the pile concrete shall be provided in the top of the pile with a length equal to two times the

required cap embedment anchorage into the pile cap.

7.4.4.4 Precast (non-prestressed) Concrete Piles: Longitudinal reinforcement shall be provided for precast concrete piles with a minimum steel ratio of 0.01. The longitudinal reinforcing

shall be confined with closed ties or equivalent spirals of a minimum 3/8 in. (10mm) diameter. 

Transverse confinement reinforcing shall be provided at a maximum spacing of eight times the

diameter of the smallest longitudinal bar, but not to exceed 6 inches (152 mm), within three pile

diameters of the bottom of the pile cap. Outside of the confinement region, closed ties or

equivalent spirals shall be provided at a 16 longitudinal-bar-diameter maximum spacing, but not

greater than 8 in. (200 mm). Longitudinal reinforcement shall be full length. 

7.4.4.5 Precast-Prestressed Piles: The minimum volumetric ratio of spiral reinforcement shall

not be less than 0.007 or the amount required by the following formula for the upper 20 ft (6 

m)of the pile:

(7.4.4.5-1) s

c

yh

f

f ρ = 012 . ′

where:

Ds = spiral reinforcement index (vol. spiral/ vol. core)

fc

! = specified compressive strength of concrete, psi (Mpa), and

fyh = yield strength of spiral reinforcement, which shall not be taken greater than 85,000 psi

(586 MPa).

Below the 20 ft (6 m) length, provide at least one-half the volumetric ratio provided by Eq,

7.4.4.5-1.

7.5 SEISMIC DESIGN CATEGORIES D, E, AND F: Foundations for structures assigned to 

Seismic Design Categories D, E, and F shall conform to all of the requirements for Seismic

Design Category C construction and to the additional requirements of this section. Design and

construction of concrete foundation components shall conform with the requirements of ACI 318,

Sec. 21.8, except as modified by the requirements of this section.
2000 Provisions, Chapter 7

128

Exception: Detached one and two family dwellings of light frame construction not

exceeding two stories in height above grade need only comply with the requirements of

Sec.7.4 and Sec. 7.5.3. 

7.5.1 Investigation: The owner shall submit to the authority having jurisdiction a written report

that includes an evaluation of potential site hazards such as slope instability, liquefaction, and

surface rupture due to faulting or lateral spreading and the determination of lateral pressures on

basement and retaining walls due to earthquake motions.

7.5.2 Foundation Ties: Individual spread footings founded on soil defined in Sec. 4.1.2 as Site

Class E or F shall be interconnected by ties. Ties shall conform to Sec. 7.4.3.

7.5.3 Liquefaction Potential and Soil Strength Loss: The geotechnical report shall assess

potential consequences of any liquefaction and soil strength loss, including estimation of

differential settlement, lateral movement or reduction in foundation soil-bearing capacity, and

shall discuss mitigation measures. Such measures shall be given consideration in the design of

the structure and can include, but are not limited to, ground stabilization, selection of appropriate

foundation type and depths, selection of appropriate structural systems to accommodate

anticipated displacements, or any combination of these measures.

The potential for liquefaction and soil strength loss shall be evaluated for site peak ground

accelerations, magnitudes, and source characteristics consistent with the design earthquake

ground motions. Peak ground acceleration is permitted to be determined based on a site-specific

study taking into account soil amplification effects or, in the absence of such a study, peak

ground accelerations shall be assumed equal to SDS/2.5.

7.5.4 Special Pile and Grade Beam Requirements: Piling shall be designed and constructed

to withstand maximum imposed curvatures from earthquake ground motions and structure

response. Curvatures shall include free-field soil strains (without the structure) modified for

soil-pile interaction coupled with pile deformations induced by lateral pile resistance to structure

seismic forces. Concrete piles in Site Class E or F shall be designed and detailed in accordance

with Sec. 21.4.4.1, 21.4.4.2, and 21.4.4.3 of ACI 318 within seven pile diameters of the pile cap

and the interfaces of soft to medium stiff clay or liquefiable strata. For precast prestressed

concrete piles, detailing provisions as given in Sec. 7.5.4.4 shall apply.

Section 21.8.3.3 of ACI 318 need not apply when grade beams have the required strength to

resist the forces from the load combinations of Section 5.2.7.1. Section 21.8.4.4(a) of ACI 318

need not apply to concrete piles. Section 21.8.4.4(b) of ACI 318 need not apply to precast

prestressed concrete piles. 

Design of anchorage of piles into the pile cap shall consider the combined effect of axial forces

due to uplift and bending moments due to fixity to the pile cap. For piles required to resist uplift

forces or provide rotational restraint, anchorage into the pile cap shall be capable of developing

the following:

1. In the case of uplift, the lesser of the nominal tensile strength of the longitudinal

reinforcement in a concrete pile, or the nominal tensile strength of a steel pile, or the pile

uplift soil nominal strength factored by 1.3, or the axial tension force resulting from the load

combinations of Sec. 5.2.7.1.
Foundation Design Requirements

129

2. In the case of rotational restraint, the lesser of the axial and shear forces, and moments

resulting from the load combinations of Section 5.2.7.1 or development of the full axial,

bending, and shear nominal strength of the pile.

Splices of pile segments shall develop the nominal strength of the pile section, but the splice

need not develop the nominal strength of the pile in tension, shear, and bending when it has been

designed to resist axial and shear forces, and moments from the load combinations of Sec.

5.2.7.1. 

Pile moments, shears, and lateral deflections used for design shall be established considering the

interaction of the shaft and soil. Where the ratio of the depth of embedment of the pile-to-thepile diameter or width is less than or equal to 6, the pile may be assumed to be rigid with respect

to the soil.

Pile group effects from soil on lateral pile nominal strength shall be included where pile centerto-center spacing in the direction of the lateral force is less than eight pile diameters. Pile group

effects on vertical nominal strength shall be included where pile center-to-center spacing is less

than three pile diameters. The pile uplift soil nominal strength shall be taken as the pile uplift

strength as limited by the frictional force developed between the soil and the pile.

The connection between batter piles and grade beams or pile caps shall be designed to resist the

full strength of the pile acting as a short column. Batter piles shall be capable of resisting forces

and moments from the load combinations of Sec. 5.2.7.1.

7.5.4.1 Uncased Concrete Piles: A minimum longitudinal reinforcement ratio of 0.005 shall be

provided for uncased cast-in-place drilled or augured concrete piles, piers, or caissons in the top

one-half of the pile length, a minimum length of 10 ft (3 m) below ground, or throughout the

flexural length of the pile, whichever length is greatest. The flexural length shall be taken as the

length of pile to a point where the concrete section cracking moment multiplied by the resistance

factor 0.4 exceeds the required factored moment at that point. There shall be a minimum of four

longitudinal bars with transverse confinement reinforcing provided in the pile in accordance with

Sec. 21.4.4.1, 21.4.4.2, and 21.4.4.3 of ACI 318 within three pile diameters of the bottom of the

pile cap.

 It shall be permitted to use a transverse spiral reinforcing ratio of not less than one-half of that

required in Sec. 21.4.4.1(a) of ACI 318 for other than Class E, F, or liquefiable sites. Tie spacing

of longitudinal bars throughout the remainder of the pile length shall not exceed 12 longitudinal

bar diameters, one-half the diameter of the section, or 12 inches (305 mm). Ties shall be a

minimum of No. 3 bars for up to 20-in.-diameter (500 mm) piles and No. 4 bars for piles of

larger diameter.

7.5.4.2 Metal-Cased Concrete Piles: Reinforcement requirements are the same as for uncased

concrete piles.

Exception: Spiral welded metal-casing of a thickness not less than No. 14 gauge can be

considered as providing concrete confinement equivalent to the closed ties or equivalent

spirals required in an uncased concrete pile, provided that the metal casing is adequately

protected against possible deleterious action due to soil constituents, changing water

levels, or other factors indicated by boring records of site conditions.
2000 Provisions, Chapter 7

130

7.5.4.3 Precast (non-prestressed) Concrete Piles: Transverse confinement reinforcing of

closed ties or equivalent spirals shall be provided in accordance with Sec. 21.4.4.1, 21.4.4.2, and

21.4.4.3 of ACI 318 within three pile diameters of the bottom of the pile cap. It shall be

permitted to use a transverse spiral reinforcing ratio of not less than one-half of that required in

Sec. 21.4.4.1(a) of ACI 318 for other than Class E, F, or liquefiable sites.

7.5.4.4 Precast-Prestressed Piles: The requirements of ACI 318 need not apply unless

specifically referenced.

Where the total pile length in the soil is 35 ft (10.7 m) or less, transverse confinement

reinforcement shall be provided throughout the length of the pile. Where the pile length exceeds

35 ft (10.7 m), transverse confinement reinforcement shall be provided for the greater of 35 ft

(10.7 m) or the distance from the underside of the pile cap to the point of zero curvature plus

three times the least pile dimension.

The transverse confinement reinforcement shall be spiral or hoop reinforcement with a center-tocenter spacing not greater than one-fifth of the least pile dimension, six times the diameter of the

longitudinal tendons, or 8 in. (203mm), whichever is smaller. 

Circular spiral reinforcement shall be spliced by lapping one full turn and bending the end of the

spiral to a 90-degree hook or by use of a mechanical or welded splice complying with Sec.

12.14.3 of ACI 318. Where the transverse confinement reinforcement consists of circular spirals,

the volumetric ratio of spiral transverse reinforcement shall comply with:

s

c

yh

g

ch c g

f

f

A

A

P

f A

ρ =

 ′













 − 



 



 + ′















 0 25 10 05

14 . .. . (7.5.4.4-1)

but not less than

s

c

yh c g

f

f

P

f A ρ =  ′













 + ′





 

 012 05  14 . . . (7.5.4.4-2)

and need not exceed Ds = 0.021 where:

Ds = spiral reinforcement index (vol. spiral/ vol. core),

fc

! = specified compressive strength of concrete, psi (MPa),

fyh = yield strength of spiral reinforcement, which shall not be taken as greater than 85,000

psi (586 MPa),

Ag = pile cross-sectional area,

Ach = core area defined by spiral outside diameter, and

P = axial load on pile resulting from the load combinations of Sec. 5.2.7
Foundation Design Requirements

131

The required amount of spiral reinforcement shall be permitted to be obtained by providing an

inner and outer spiral.

When transverse confinement reinforcement consists of rectangular hoops and cross ties, the total

cross-sectional area of lateral transverse reinforcement in the ductile region with spacing s and

perpendicular to dimension hc shall conform to:

sh c

c

yh

g

ch c g

A sh f

f

A

A

P

f A =  ′



 



 − 



 



 + ′





 

 012 1 05  14 . . . (7.5.4.4-3)

but not less than

sh c

c

yh c g

A sh f

f

P

f A =  ′













 + ′





 

 012 05  14 . . . (7.5.4.4-4)

where 

s = spacing of transverse reinforcement measured along length of pile,

hc = cross-sectional dimension of pile core measured center to center of hoop

reinforcement,

fc

! = specified compressive strength of concrete, psi (Mpa), and

fyh = yield strength of transverse confinement reinforcement which shall not be taken as

greater than 70,000 psi (483 MPa).

The hoops and cross ties shall be equivalent to deformed bars not less than No.3 in size. 

Rectangular hoop ends shall terminate at a corner with seismic hooks.

Outside of the length of the pile requiring transverse confinement reinforcing, the spiral or hoop

reinforcing with a volumetric ratio not less than one-half of that required for transverse

confinement reinforcing shall be provided.

7.5.4.5 Steel Piles: The connection between the pile cap and steel piles or unfilled steel pipe

piles shall be designed for a tensile force no less than 10 percent of the pile compression

capacity. 

Exception: The pile connection need not meet this requirement where it can be

demonstrated that the pile connection has the strength to resist the axial forces and

moments resulting from the load combinations of Sec. 5.2.7.1.
133 133

Chapter 8

STEEL STRUCTURE DESIGN REQUIREMENTS

8.1 REFERENCE DOCUMENTS: The design, construction, and quality of steel components

that resist seismic forces shall conform to the requirements of the references listed in this section

except as modified by the requirements of this chapter.

AISC LRFD American Institute of Steel Construction (AISC), Load and Resistance

Factor Design Specification for Structural Steel Buildings (LRFD),

December 1993.

AISC ASD American Institute of Steel Construction (AISC), Allowable Stress Design

and Plastic Design Specification for Structural Steel Buildings (ASD), June

1, 1989.

AISC Seismic American Institute of Steel Construction (AISC)., Seismic Provisions for

Structural Steel Buildings (1997), Part I, including Supplement No. 2

(November 2000).

AISI American Iron and Steel Institute (AISI), Specification for the Design of

Cold-Formed Steel Structural Members, 1996.

ANSI/ASCE 8-90 American Society of Civil Engineers, Specification for the Design of Cold-

-formed Stainless Steel Structural Members, ANSI/ASCE 8-90, 1990.

SJI Steel Joist Institute, Standard Specification, Load Tables and Weight Tables

for Steel Joists and Joist Girders, 1994.

ASCE 19 American Society of Civil Engineers (ASCE), Structural Applications for

Steel Cables for Buildings, ASCE 19, 1995.

8.2 SEISMIC REQUIREMENTS FOR STEEL STRUCTURES: The design of steel

structures to resist seismic forces shall be in accordance with Sec. 8.3 or 8.4 for the appropriate

Seismic Design Category.

8.3 SEISMIC DESIGN CATEGORIES A, B, and C: Steel structures assigned to Seismic

Design Categories A, B, and C shall be of any construction permitted by the references in Sec.

8.1. An R factor as set forth in Table 5.2.2 for the appropriate steel system is permitted when the

structure is designed and detailed in accordance with the requirements of AISC Seismic, Part I,

or Sec. 8.6 for light framed cold-formed steel wall systems. Systems not detailed in accordance

with the above shall use the R factor in Table 5.2.2 designated for “steel systems not detailed for

seismic.”

8.4 SEISMIC DESIGN CATEGORIES D, E, AND F: Steel structures assigned to Seismic

Design Categories D, E, and F shall be designed and detailed in accordance with AISC Seismic,
2000 Provisions, Chapter 8

134 134

except as modified by other provisions in this section. Light framed cold-formed steel wall

systems shall be designed and detailed in accordance with Sec. 8.6.

8.4.1 Modifications to AISC Seismic:

8.4.1.1: Revise Sec. 7.3b as follows: After the words “Charpy V-Notch toughness of 20 ft-lbs at

0o

 F, as determined by AWS classification or manufacturer certification” add the following: “For

structures in which the steel frame is normally enclosed and maintained at a temperature of 50o

F

or higher, critical welded joints in seismic-force-resisting systems, including CJP welds of beam

flanges to column flanges, CJP welds of shear tabs and beam webs to column flanges, column

splices, and similar joints shall be made with weld filler metal capable of producing welds with

minimum Charpy V-Notch toughness of 40 ft-lbs at 70o

F and 20 ft-lbs at -20oF, under a range of

welding conditions in accordance with FEMA 353, Recommended Specifications and Quality

Assurance Guidelines for Moment Resisting Steel Frames for Seismic Applications. For

structures with service temperatures lower than 50o

F, the Charpy V-notch toughness shall be a

minimum of 40 ft-lbs at 20o F above the lowest anticipated service temperature.”

8.4.1.2: Revise Sec. 9.2c and 10.2b.3 as follows: After the words “in the opposite sense on each

end of the beam” add the words “segment between the plastic hinge points.” Delete the words

“The required shear strength need not exceed the shear resulting from load combination 4-1.”

8.4.1.3: Revise Sec. 11.2a1 by adding the following exception:

Exception: Where weld access holes are provided, they shall conform to Figure X.
Steel Structure Design Requirements

135 135

FIGURE X Legend: (1) bevel as required by AWS

D1.1for selected groove weld procedure; (2) larger tbf or 1/2

inch; (3) tbf to tbf with a 3/4 inch minimum; (4) 3/8 inch

minimum radius; (5) 3 tbf , (6) surfaces to 500 microinches

roughness.

8.5 COLD-FORMED STEEL SEISMIC REQUIREMENTS: The design of cold-formed

carbon or low-alloy steel members to resist seismic loads shall be in accordance with the

requirements of AISI and the design of cold-formed stainless steel structural l to resist seismic

loads shall be in accordance with the requirements of ANSI/ASCE 8-90, except as modified by

this section. The reference to section and paragraph numbers are to those of the particular

specification modified.

8.5.1 Modifications to AISI: Revise Sec. A5.1.3 of AISI as follows:

"A4.4 Wind or Earthquake Loads Where load combinations specified by the

applicable code include wind loads, the resulting forces are permitted to be

multiplied by 0.75. Seismic load combinations shall be as determined by these

provisions."

8.5.2 Modifications to ANSI/ASCE 8-90: Modify Sec. 1.5.2 of ANSI/ASCE 8-90 by

substituting a load factor of 1.0 in place of 1.5 for nominal earthquake load.
2000 Provisions, Chapter 8

136 136

8.6 LIGHT-FRAMED WALLS: When required by the requirements in Sec. 8.3 or 8.4, coldformed steel stud walls designed in accordance with AISI and ANSI/ASCE 8-90 shall also

comply with the requirements of this section.

8.6.1 Boundary Members: All boundary members, chords, and collectors shall be designed to

transmit the specified induced axial forces.

8.6.2 Connections: Connections for diagonal bracing members, top chord splices, boundary

members, and collectors shall have a design strength equal to or greater than the nominal tensile

strength of the members being connected or S0 times the design seismic force. The pull-out

resistance of screws shall not be used to resist seismic forces.

8.6.3 Braced Bay Members: In stud systems where the lateral forces are resisted by braced

frames, the vertical and diagonal members in braced bays shall be anchored such that the bottom

tracks are not required to resist uplift forces by bending of the track or track web. Both flanges

of studs shall be braced to prevent lateral torsional buckling. In vertical diaphragm systems, the

vertical boundary members shall be anchored so the bottom track is not required to resist uplift

forces by bending of the track web.

8.6.4 Diagonal Braces: Provision shall be made for pretensioning or other methods of

installation of tension-only bracing to guard against loose diagonal straps.

8.6.5 Shear Walls: Nominal shear values for wall sheathing materials are given in Table 8.6.5. 

Design shear values shall be determined by multiplying the nominal values therein by a N factor

of 0.55. In structures over one story in height, the assemblies in Table 8.6.5 shall not be used to

resist horizontal loads contributed by forces imposed by masonry or concrete construction.

Panel thicknesses shown in Table 8.6.5 shall be considered to be minimums. No panels less than

24 inches wide shall be used. Plywood or oriented strand board (OSB) structural panels shall be

of a type that is manufactured using exterior glue. Framing members, blocking, or strapping

shall be provided at the edges of all sheets. Fasteners along the edges in shear panels shall be

placed not less than 3/8 in. (9.5 mm) in from panel edges. Screws shall be of sufficient length to

ensure penetration into the steel stud by at least two full diameter threads.

The height to length ratio of wall systems listed in Table 8.6.5 shall not exceed 2:1.

Perimeter members at openings shall be provided and shall be detailed to distribute the shearing

stresses. Wood sheathing shall not be used to splice these members.

Wall studs and track shall have a minimum uncoated base thickness of not less than 0.033 in.

(0.84 mm) and shall not have an uncoated base metal thickness greater than 0.048 in. (1.22 mm). 

Panel end studs and their uplift anchorage shall have the design strength to resist the forces

determined by the seismic loads determined by Eq. 2.2.6-3 and Eq. 2.2.6-4.

TABLE 8.6.5 Nominal Shear Values for Seismic Forces for Shear Walls

Framed with Cold-Formed Steel Studs (in pounds per foot)a, b

Assembly

Description

Fastener Spacing at Panel

Edges c

 (inches)

Framing

Spacing

(inches o.c.)
Steel Structure Design Requirements

137 137

64 3 2

15/32 rated Structural I sheathing

(4-ply) plywood one side d

780 990 1465 1625 24

7/16 in. oriented strand board one

side d

700 915 1275 1700 24

NOTE: For fastener and framing spacing, multiply inches by 25.4 to obtain metric mm.

 a

 Nominal shear values shall be multiplied by the appropriate strength reduction factor N to

determine design strength as set forth in Sec. 8.6.5.

 b

 Studs shall be a minimum 1-5/8 in. by 3-1/2 in. with a 3/8-in. return lip. Track shall be a

minimum 1-1/4 in. by 3-1/2 in. Both studs and track shall have a minimum uncoated base metal

thickness of 0.033 in. and shall be ASTM A446 Grade A (or ASTM A653 SQ Grade 33 [new

designation]). Framing screws shall be No. 8 x 5/8 in. wafer head self-drilling. Plywood and OSB

screws shall be a minimum No. 8 x 1 in. bugle head. Where horizontal straps are used to provide

blocking, they shall be a minimum 1-1/2 in. wide and of the same material and thickness as the stud

and track.

 c

 Screws in the field of the panel shall be installed 12 in. o.c. unless otherwise shown.

 d

 Both flanges of the studs shall be braced in accordance with Sec. 8.6.3.

8.7 SEISMIC REQUIREMENTS FOR STEEL DECK DIAPHRAGMS: Steel deck

diaphragms shall be made from materials conforming to the requirements of AISI and

ANSI/ASCE 8-90. Nominal strengths shall be determined in accordance with approved

analytical procedures or with test procedures prepared by a registered design professional

experienced in testing of cold-formed steel assemblies and approved by the authority having

jurisdiction. Design strengths shall be determined by multiplying the nominal strength by a

resistance factor, N, equal to 0.60 for mechanically connected diaphragms and equal to 0.50 for

welded diaphragms. The steel deck installation for the structure, including fasteners, shall

comply with the test assembly arrangement. Quality standards established for the nominal

strength test shall be the minimum standards required for the steel deck installation, including

fasteners.

8.8 STEEL CABLES: The design strength of steel cables shall be determined by the

requirements of ASCE 19 except as modified by the Provisions. Sec. 5d of ASCE 19 shall be

modified by substituting 1.5(T4) where T4 is the net tension in cable due to dead load, prestress,

live load, and seismic load. A load factor of 1.1 shall be applied to the prestress force to be

added to the load combination of Sec. 3.1.2 of ASCE 19.
139

Chapter 9

CONCRETE STRUCTURE DESIGN REQUIREMENTS

9.1 REFERENCE DOCUMENTS: The quality and testing of concrete and steel materials and

the design and construction of concrete components that resist seismic forces shall conform to the

requirements of the reference listed in this section except as modified by the requirements of this

chapter.

ACI 318 American Concrete Institute (ACI), Building Code Requirements for Structural Concrete, excluding Appendix A, ACI 318, 1999.

ACI ITG/T1.1 American Concrete Institute (ACI), Acceptance Criteria for Moment

Frames Based on Structural Testing (An ACI Provisional Standard), 1999.

ASME B1.1 American Society of Mechanical Engineers (ASME), Unified Inch Screw

Threads UN and UNR Thread Form, ASME B1.13, 1989.

ASME B18.2.1 American Society of Mechanical Engineers (ASME), Square and Hex Bolts

and Screws, Inch Series, ASME B18.2.1, 1996

ASME B18.2.6.9 American Society of Mechanical Engineers (ASME),

ATC-24 Applied Technology Council (ATC), Guidelines for Seismic Testing of

Components of Steel Structures, ATC-24, 1992

9.1.1 Modifications to ACI 318:

9.1.1.1: Insert the following notations in Sec. 21.0:

Ab = the area of the shank of the bolt or stud (in.2

 or mm2)

bd = diaphragm width (ft)

cu

! = neutral axis depth at Pu!

 and Mn

!

.

Rp = height of the plastic hinge above critical section; shall be established on the

basis of substantiated test data or may be alternatively taken at 0.5Rw.

Pu

! = 1.2D + 0.5L + E.

h = overall dimension of member in the direction of action considered.

hs = story height (ft)

Leff = length of diaphragm between inflection points (ft)

Sc Connection = nominal strength of connection cross section in flexural, shear, or axial load

per Sec. 21.2.7.3.
2000 Provisions Chapter 9

140

Se Connection = moment, shear, or axial force at strong connection cross section corresponding to probable strength at the nonlinear action location, taking gravity load

effects into consideration per Sec. 21.2.8.3.

Sn Connection = nominal strength of connection cross section in flexural, shear, or axial load

per Sec. 21.2.7.3.

Spr = probable strength of connection cross section in flexural, shear, or axial

load. See Sec. 21.11.5.

Sy = yield strength of connection cross section in flexural, shear, or axial load

action as determined from physical experiments on the connection or the use

of analytical models for the response of the connection that are based on the

results of physical experiments on connections with characteristics similar

to those being modeled. See Sec. 21.11.5.

)E = elastic design displacement at the top of the wall using gross section properties and code-specified seismic forces.

)i = inelastic deflection at top of wall = )t - )y.

)m = Cd)s.

)s = design level response displacement, which is the total drift or total story

drift that occurs when the structure is subjected to the design seismic forces.

)t = total deflection at the top of the wall equal to Cd times the elastic design

displacement using cracked section properties or may be taken as

(Ig/Ieff)Cd)E. Ig is the gross moment of inertia of the wall and Ieff is the

effective moment of inertia in the wall. Ieff may be taken as 0.5Ig.

)y = displacement at the top of the wall corresponding to yielding of the tension

reinforcement at critical section or may be taken as (Mn

!

/ME))E where ME

equals moment at critical section when top of wall is displaced )E. Mn

!

 is

nominal flexural strength of critical section at Pu

!

.

Ny = yield curvature which may be estimated as 0.003/Rw.

R = dynamic amplification factor from Sec. 21.2.8.3 and 21.2.8.4.

9.1.1.2: Insert the following definitions in Sec. 21.1:

Anchorage – The means by which, for precast construction, the force in the connection is

transferred into the precast or cast-in-place member.

Connection – An element that joins two precast members or a precast member and a cast-inplace member.

Connection Region – The portion of the precast or cast-in-place member through which the

concentrated forces from the connection and anchorage are transferred to the concrete. Its extent

from the connection is the distance for the forces to be distributed over the cross section and shall

be permitted to not exceed the largest dimension of that cross section.
Concrete Structure Design Requirements

141

Design Displacement – Design story drift as specified in Sec. 5.2.2.4.3 of the 2000 NEHRP

Recommended Provisions.

Design Load Combinations – Combinations of factored loads and forces specified in Sec. 5.2.7

of the the 2000 NEHRP Recommended Provisions.

Dry Connection – Connection used between precast members which does not qualify as a wet

connection.

Joint – The geometric volume common to intersecting members.

Moment Frame

Special moment frame – A cast-in-place frame complying with the requirements of Sec.

21.2 through 21.5 in addition to the requirements for ordinary moment frames or a precast

concrete frame complying with the requirements for a cast-in-place frame and Sec. 21.11.

Nonlinear Action Location – Center of the region of yielding in flexure, shear, or axial

action.

Nonlinear Action Region – The member length over which nonlinear action takes place. It shall

be taken as extending a distance of no less than h/2 on either side of the nonlinear action

location.

Strong Connection – A connection that remains elastic while the designated nonlinear action

regions undergo inelastic response under the design basis ground motion.

Structural Walls

Ordinary precast concrete structural wall – A wall incorporating precast concrete

elements and complying with the requirements of Chapters 1 through 18 with the requirements of Chapter 16 superseding those of Chapter 14. Where connections between wall

panels are required or anchorage of wall panels to foundations is required for resistance to

overturning, Type Y or Type Z connections shall be provided as required by Sec. 21.11.6.

Special precast concrete structural wall – A wall complying with the requirements of Sec.

21.11 in addition to the requirements for ordinary reinforced concrete structural walls.

Wall Pier – A wall segment with a horizontal length-to-thickness ratio of at least 2.5, but not

exceeding 6, whose clear height is at least two times its horizontal length.

Wet Connection – A connection that uses any of the splicing methods permitted by Sec. 21.3.2.3

or 21.3.2.4 to connect precast members and uses cast-in-place concrete or grout to fill the

splicing closure.

Wet Connection – A connection in precast construction that uses any of the splicing methods

permitted by Sec. 21.2.6, 21.2.7, or 21.3.2.3 to connect precast members and uses cast-in-place

concrete or grout to fill the splicing closure.

9.1.1.3: Revise Sec. 21.2.1.2, 21.2.1.3, and 21.2.1.4 as follows:

“21.2.1.2 For structures assigned to Seismic Design Categories A and B, provisions of

Chapters 1 through 18 and 22 shall apply except as modified by the requirements of
2000 Provisions Chapter 9

142

Chapter 9 of the 2000 NEHRP Recommended Provisions. Where the seismic design

loads are computed using provisions for intermediate or special concrete systems, the

requirements of Chapter 21 for intermediate or special systems, as applicable, shall be

satisfied.

“21.2.1.3 For structures assigned to Seismic Design Category C, intermediate or special

moment frames or ordinary or special reinforced concrete structural walls shall be used

to resist seismic forces induced by earthquake motions. Where the design seismic loads

are computed using the provisions for special concrete systems, the requirements of

Chapter 21 for special systems, as applicable, shall be satisfied.

“21.2.1.4 For structures assigned to Seismic Design Categories D, E and F, special

moment frames, special reinforced concrete structural walls, diaphragms and trusses, and

foundations complying with Sec. 21.2 through 21.8 and 21.11 shall be used to resist

forces induced by earthquake motions. Frame members not proportioned to resist

earthquake forces shall comply with Sec. 21.9.”

9.1.1.4: Insert the following new Sec. 21.2.1.6 and 21.2.1.7:

21.2.1.6 Precast concrete seismic-force-resisting systems used in regions of high seismic

risk or for structures assigned to high seismic performance or design categories shall

satisfy the requirements of Sec. 21.11 in addition to the requirements of Sec. 21.2

through 21.9.

“21.2.1.7 In structures having precast gravity load-carrying systems, the seismic-forceresisting system shall be one of the systems listed in Table 5.2.2 of the 2000 NEHRP

Recommended Provisions and shall be well distributed using one of the following

methods:

“1. The diaphragm or diaphragm segment between seismic-force-resisting systems shall

be designed to resist a force not less than S0 times the force determined in accordance with Sec. 5.2.5.4 of the 2000 NEHRP Recommended Provisions. The chord

force determined in accordance with Sec. 21.7.8.1 of ACI 318 shall be increased by

a factor equal to:

d

eff

d

s

b

L

b

h

1 04

12

2

+ 



 



 



 



. 

but not less than unity where:

Leff = length of diaphragm between inflection points, ft,

hs = story height, ft, and

bd = diaphragm width, ft
Concrete Structure Design Requirements

143

“Where the seismic-force-resisting system consists of moment resisting frames, at

least (Nb/4) + 1 of the bays (rounded up to the nearest integer) along any frame line

at any story shall be part of the seismic-force-resisting system where Nb is the total

number of bays along that line at that story. This requirement applies to only the

lower two thirds of the stories of buildings three stories or taller.

“2. All beam-to-column connections that are not part of the seismic-force-resisting

system shall be designed in accordance with the following:

“Connection Design Force. The connection shall be designed to develop

strength M. M is the moment developed at the connection when the frame is

displaced by )s assuming fixity at the connection and a beam flexural stiffness

of no less than one half of the gross section of stiffness. M shall be sustained

through a deformation of )m.

“Connection Characteristics. The connection shall be permitted to resist moment in

one direction only, positive or negative. The connection at the opposite end of the

member shall resist moment with the same positive or negative sign. The connection

shall be permitted to have zero flexural stiffness up to a frame displacement of )m.

“In addition, complete calculations for the deformation compatibility of the gravity load

carrying system shall be made in accordance with Sec. 5.2.2.4.3 of the 2000 NEHRP

Recommended Provisions using cracked section stiffness in the seismic-force-resisting

system and the diaphragm. 

“Where gravity columns are not provided with lateral support on all sides, a positive

connection shall be provided along each unsupported direction parallel to a principal

plan axis of the structure. The connection shall be designed for a horizontal force equal

to 4 percent of the axial load strength, Po, of the column.

“The bearing length shall be calculated to include end rotation, sliding, and other

movements of precast ends at supports due to earthquake motions in addition to other

movements and shall be at least 2 inches more than that required for bearing strength.”

9.1.1.5: Change Sec. 21.2.5.1 as follows and insert the following new Sec. 21.2.5.2 and 21.2.5.3.

“21.2.5.1 Except as permitted in 21.2.5.2 and 21.2.5.3, reinforcement resisting earthquakeinduced flexural and axial forces in the frame members and in wall boundary elements shall

comply with a ASTM A 706. ASTM A 615 Grades 40 and 60 reinforcement shall be

permitted if (a) the actual yield strength based on mill tests does not exceed the specified

yield strength by more than 18,000 psi (retests shall not exceed this value by more than an

additional 3000 psi) and (b) the ratio of the actual ultimate tensile strength to the actual

tensile yield strength is not less than 1.25.

“21.2.5.2 Prestressing tendons shall be permitted in the flexural members of frames

provided the average prestress, fpc, calculated for an area equal to the member’s shortest

cross-sectional dimension multiplied by the perpendicular dimension shall not exceed the

lesser of 700 psi or at locations of nonlinear action where prestressing tendons are f c

′ 6

used in members of frames.
2000 Provisions Chapter 9

144

“21.2.5.3 Unless the seismic-force-resisting frame is qualified for use through structural

testing as required by 21.8.3.1, for members in which prestressing tendons are used together

with mild steel reinforcement to resist earthquake-induced forces, prestressing tendons shall

not provide more than one quarter of the strength for either positive or negative moment at

the nonlinear action and be anchored at the exterior face of the joint or beyond.

“21.2.5.4 Anchorages for tendons shall be demonstrated to perform satisfactorily for seismic

loadings. Anchorage assemblies shall withstand, without failure, a minimum of 50 cycles of

loading between 40 and 85 percent of the minimum tensile strength of the prestressing steel.

9.1.1.6: Add the following new Sec. 21.4.5.3:

“21.4.5.3 At any section where the design strength, NPn, of the column is less than the sum

of the shear Ve computed in accordance with 21.4.5.1 for all the beams framing into the

column above the level under consideration, special transverse reinforcement shall be

provided. For beams framing into opposite sides of the column, the moment components

may be assumed to be of opposite sign. For determination of the nominal strength, Pn, of the

column, these moments may be assumed to result from the deformation of the frame in any

one principal axis.” 

9.1.1.7: In Sec. 21.6.3, change “factored load combinations” to “design load combinations.” 

9.1.1.8: Modify Sec. 21.6 by adding a new Sec. 21.6.10 to read as follows:

“21.6.10 Wall Piers and Wall Segments

“21.6.10.1 Wall piers not designed as part of a special moment frame shall have transverse

reinforcement designed to satisfy the requirements of Sec. 21.6.10.2

“Exceptions:

“1. Wall piers that satisfy Sec. 21.9.

“2. Wall piers along a wall line within a story where other shear wall segments provide

lateral support to the wall piers and such segments have a total stiffness of at least

six times the sum of the stiffness of all the wall piers.

“21.6.10.2 Transverse reinforcement shall be designed to resist the shear forces determined

from Sec. 21.4.5.1 and 21.3.4.2. Where the axial compressive force, including earthquake

effects , is less than As fc! /20, transverse reinforcement in wall piers is permitted to have

standard hooks at each free end and in lieu of hoops. Spacing of transverse reinforcement

shall not exceed 6 inches (152 mm). Transverse reinforcement shall be extended beyond the

pier clear height for at least the development length of the largest longitudinal reinforcement

in the wall pier.”

9.1.1.9: Change Sec. 21.8.1.1 to read as follows:

“21.8.1.1 Foundations resisting earthquake-induced forces or transferring earthquakeinduced forces between structure and ground shall comply with requirements of Sec. 21.8

and other applicable code provisions unless modified by Chapter 7 of the 2000 NEHRP

Recommended Provisions.
Concrete Structure Design Requirements

145

9.1.1.10: Revise Sec. 21.9.3.3 to read as follows:

“21.9.23.3 Members with factored gravity axial force exceeding Ag fc!/10 shall satisfy Sec.

21.4.3.1, 21.4.4, 21.4.5, and 21.5.2.1. The maximum longitudinal spacing of ties shall be so

for the full column height. The spacing, so, shall not be more than six diameters of the

smallest longitudinal bar enclosed or 6 in. (152 mm), whichever is smaller. Lap splices of

longitudinal reinforcement in such members need not satisfy Sec. 21.4.3.2 in structures

where the seismic-force-resisting system does not include special moment frames.”

9.1.1.11: Insert in Sec. 21.10 the following new Sec. 21.10.7:

“21.10.7 Precast concrete moment frames. For structure assigned to Seismic Design

Category C, precast concrete seismic-force-resisting frames shall be permitted provided the

frame conforms to 21.10.1 through 21.10.5 and Type Y or Type Z connections as defined in

21.11.5 are used.”

9.1.1.12: Insert new Sec. 21.11 as follows:

“21.11 Precast concrete special moment frames and special structural walls.

“21.11.1 Scope.

Requirements of 21.11 apply to special moment frames, and to special reinforced concrete

structural walls, resisting the earthquake induced forces and utilizing precast concrete

elements.”

“21.11.2 Seismic-force-resisting system requirements.

“21.11.2.1 A precast seismic-force-resisting system shall be permitted providing it satisfies

either of the following criteria:

“1. The behavior of the system for forces up to and including those at the design

displacement emulates the behavior of monolithic reinforced concrete construction and

the system satisfies 21.11.3 or 

“2. The system relies on its unique properties as a structure composed of interconnected

precast elements and is demonstrated by experimental evidence and analysis to satisfy

Sec. 21.2 through 21.7 of Chapter 21. Substantiating experimental evidence of acceptable performance of those elements required to sustain inelastic deformations shall be

based upon cyclic testing of specimens representing those elements and shall satisfy

21.11.4.1 for special precast concrete moment frames and 21.11.4.2 for special precast

concrete structural walls.

“21.11.3 Emulation Design. Precast structural systems emulating the behavior of monolithic reinforced concrete construction shall satisfy 21.11.3.1 where ductile connections are

used and 21.11.3.2 where strong connections are used.

“21.11.3.1 Precast structural systems utilizing either wet or dry ductile connections at

nonlinear action locations shall comply with all the applicable requirements of monolithic

concrete construction for resisting seismic forces and satisfy the following:
2000 Provisions Chapter 9

146

“1. Where the moment acting on the connection is assumed equal to Mpr, the co-existing

shear on the connection shall be no greater than 0.5Sn Connection and

“2. The nominal shear strength for the connection shall not be less than the shear strengths

of the members immediately adjacent to that connection.

“21.11.3.2 Precast structural systems not meeting the requirements of 21.11.2 shall utilize

strong connections resulting in nonlinear response away from connections. Design shall

satisfy the requirements of 21.11.5 in addition to the applicable requirements of monolithic 

concrete construction for resisting seismic forces except that the provisions of 21.3.1.2 shall

apply to segments between nonlinear action locations.

“21.11.4 Interconnected element design.

“21.11.4.1 For special moment frames composed of interconnected precast elements,

substantiating experimental evidence and analysis shall satisfy the requirements of ACI 

ITG/T1.1. It shall also be demonstrated by experimental evidence that the modules used for

the validation testing of ACI ITG/T1.1 have the ability to carry, at 5 percent or greater drift

ratios, the gravity loads that act on them in the generic frame.

“21.11.4.2 For special structural wall systems composed of precast elements substantiating

experimental evidence and analysis shall meet the requirements of Sec. 4.1, 4.2, 5.2, 5.3, 6.0,

7.0 and 8.0 of ACI ITG/T1.1 and: 

 2. The minimum stack module shall be a stack of wall panels at least two panels high.

2. For the third cycle at drift ratios equal to or exceeding the limiting drift ratio, the criteria

for acceptance shall be that:

a. Lateral load resisting capacity of the module shall be at least 80 percent of the peak

lateral load;

b. The relative energy dissipation ratio, as defined in ACI ITG/T1.1-99, shall equal or

exceed 15 percent for that third cycle; and 

c. The stiffness at zero drift shall equal or exceed that required by ACI ITG/T1.1-99.

“3. The limiting drift ratio in percent shall satisfy the following criterion:

10 0 67 0 5 30 . . .. ≤ +≤ [ ] h l w w

“21.11.4.3 Unless there is substantial experimental evidence obtained during a prior

development program, the validation tests required in Sec. 21.11.4.1 and 21.11.4.2 shall:

1. Be conducted at full scale and

2. Be at least two in number for each characteristic configuration of intersecting beams and

columns or structural walls.

“21.11.4.4 The nonlinear response history analysis of Sec. 5.7 of the 2000 NEHRP Recommended Provisions shall be used to design the special precast concrete moment frame and
Concrete Structure Design Requirements

147

structural wall systems using the force-deformation characteristics from the subassemblage

tests required by Sec. 21.11.4.1 or Sec. 21.11.4.2.

“21.11.5 Emulation design of frames using strong connections.

“21.11.5.1 Location. Nonlinear action location shall be selected so that there is a strong

column/weak beam deformation mechanism under seismic effects. The nonlinear action

location shall be no closer to the near face of strong connection than h/2. For column-tofooting connections where nonlinear action may occur at the column base to complete the

mechanism, the nonlinear action location shall be no closer to the near face of the connection

than h/2.

“21.11.5.2 Anchorage and splices. Reinforcement in nonlinear action region shall be fully

developed outside both the strong connection region and the nonlinear action region. 

Noncontinuous anchorage reinforcement of strong connection shall be fully developed

between the connection and the beginning of nonlinear action region. Lap splices are

prohibited within connections adjacent to a joint.

“21.11.5.3 Design forces. Design strength of strong connections shall be based on :

φ ψ S S nConnection eConnection ≥

“ The dynamic amplification factor, R, shall be taken as 1.0.

“21.11.5.4 Column-to-column connection. The strength of such connection shall comply

with 21.2.7.3 with the R taken as 1.4. Where the column-to-column connections occur, the

columns shall be provided with transverse reinforcement as specified in 21.4.4.1 through

21.4.4.3 over their full height in the factorial axial compressive force in these members,

including seismic effects, exceeds Agfc

!

/10.

“Exception: Where column-to-column connection is located within the middle third of

the column clear height, the following shall apply: (a) the design moment strength, NMn, 

the connection shall not be less than 0.4 times the maximum Mpr for the column within

the story height and (b) the design shear strength, NVn, of the connection shall not be less

than that determined per 21.4.5.1.

“21.11.5.5 Column-face connection. Any strong connection located outside the middle

half of a beam span shall be a wet connection unless a dry connection can be substantiated by

approved cyclic test results. Any mechanical connector located within such a column-face

strong connection shall develop in tension or compression, as required, at least 40 percent of

the specified yield strength, fy, of the bar.

“21.11.6 Connections.

“21.11.6.1 At dry connections that are nonlinear action locations, displacements both in the

direction of the action of the connection and the transverse to it shall be controlled.

“21.11.6.2 Dry connections shall be mechanical splices that are Type 2 at nonlinear action

locations. Type 1 mechanical splices and welded splices shall be permitted elsewhere.
2000 Provisions Chapter 9

148

“21.11.6.3 Based on the results of physical experiments and analytical modeling of connections, their anchorage and their connection regions, both dry and wet connections at nonlinear action locations shall be classified as either Type Y or Type Z connections, as follows:

1. Type Y connections shall conform to 21.11.6.4 and develop, for the specified loading,

ductility ratios greater than 4.0.

2. Type Z connections shall conform to 21.11.6.5 and develop, for the specified loading

ductility ratios greater than 8.0.

“Testing of connections and evaluation of results shall be made in accordance with the

principles specified in ACI ITG/T1.1 and ATC-24.

“21.11.6.4 Type Y connections shall develop under flexural, shear, and axial load actions, as

required, a probable strength, Spr, determined using a N value of unity, that is not less than

125 percent or more of the yield strength, Sy, of the connection. The anchorage on either side 

of the connection shall be designed to develop 1.3Spr in tension and shall be connected

directly by mechanical splice, welded splice, or tension lap splice to the principal

reinforcement of the precast or cast-in-place element.

“21.11.6.5 Type Z connections shall develop under flexural, shear and axial load actions, as

required, a probable strength, Spr, determined using a N value of unity, that is not less than

140 percent of the yield strength, Sy of the connection. The anchorage on either side of the

connection shall be designed to satisfy the requirements for Type Y connections in tension

and in compression, and the connection region shall be able to develop 1.3Spr. Equilibriumbased plasticity models (strut-and-tie models) shall be permitted to be used for design of the

connection region. Confinement reinforcement in the form of closed hoops or spirals with a

yield force equal to not less than 5 percent of the compressive force and having a spacing not

greater than 3 in. shall be provided where the local compressive stress exceeds 0.7fc

!

.

“Exception: Connections in nonlinear action regions in test modules used to qualify

seismic-force resisting systems for use based on structural testing in accordance with

21.11.3 shall be deemed to satisfy the requirements of this provision.

“21.11.6.6 Connections at nonlinear action locations shall be Type Z connections. Type Y

connections shall be permitted at cross sections other than nonlinear action locations. 

“21.11.6.7 Connections and the structural components of which they are part shall have a

quality assurance plan satisfying the requirements of the 2000 NEHRP Recommended

Provisions Sec. 3.2.1 and 3.2.2.”

9.2 ANCHORING TO CONCRETE:

9.2.1 Scope:

9.2.1.1: These provisions provide design requirements for structural anchors in concrete used to

transmit structural loads from attachments into concrete members or from one connected member

to another by means of tension, shear, or a combination of tension and shear. Safety levels

specified are intended for in-service conditions rather than for short-term handling and

construction conditions.
Concrete Structure Design Requirements

149

9.2.1.2: These provisions apply to both cast-in concrete anchors such as headed studs, headed

bolts or hooked bolts, and post-installed anchors, such as expansion anchors and undercut

anchors. Specialty inserts, through bolts, bolts anchored to embedded large steel plates, adhesive

or grouted bounded anchors, and direct anchors, such as powder or pneumatic actuated nails or

bolts are not included. Reinforcement used as a part of the embedment shall be designed in

accordance with ACI 318.

9.2.1.3: Headed studs and headed bolts that have a geometry consistent with ASME B1.1,

B18.2.1, and B18.2.6.9 shall be designed by Sec. 9.2.4. Hooked bolts that have a geometry that

has been demonstrated to result in pullout strength without the benefit of friction in uncracked

concrete equal to or exceeding 1.4 Np (where Np is given by Eq. 9.2.5.3.5) are included. 

9.2.1.4: Post-installed anchors shall be tested before use to determine their nominal strength in

uncracked concrete, cracked concrete, or both and also to verify their compliance with the

requirements of these design provisions for reliability and performance under anticipated

conditions of service. Such tests shall be conducted by an independent testing agency and shall

be verified by a registered design professional with full description and details of the testing

program, procedures, results, and conclusions. The test program shall be comprehensive and

shall include tests, results, and analysis for the requirements of Sec. 9.2.1.4.1 and 9.2.1.4.3.

9.2.1.4.1 Reference Tests: Reference tests shall establish failure modes, technical data, and k

factors to use with these design provisions for uncracked or cracked concrete or both.

9.2.1.4.2 Reliability Tests: Reliability tests shall establish the appropriate category for the

fastener using tests of sensitivity to reduced installation effort, sensitivity to low strength

concrete with larger tolerance drill bit in cracked or uncracked concrete, and sensitivity to high

strength concrete with a lower tolerance drill bit in cracked or uncracked concrete. Tests shall

also be performed in uncracked concrete with repeated loading and in cracked concrete with an

opening and closing crack of at least 1,000 cycles to establish the fastener suitability.

9.2.1.4.3 Service-condition Tests: Service-condition tests shall establish requirements for edge

distance, spacing between fasteners, splitting near an edge, shear capacity and pryout. For

cracked concrete, simulated seismic qualification tests shall establish the ability of the fastener to

perform in tension and shear under seismic conditions.

9.2.1.5: Load applications that are predominantly high cycle fatigue or impact are not covered by

these provisions.

9.2.2 Notations and Definitions:

9.2.2.1 Notations:

Ab = bearing area of the head of the stud or anchor bolt (in2

).

ANo = projected concrete failure area of one anchor, for calculation of strength in tension, when

not limited by edge distance or spacing, as defined in Sec. 9.2.5.2.1 (in2). (see Figure

C9.2.5.2.2-1). 
2000 Provisions Chapter 9

150

AN = projected concrete failure area of an anchor or group of anchors for calculation of

strength in tension as defined in Sec. 9.2.5.2.1, in2. AN shall not be taken greater than

nANo (see Figure C9.2.5.2.1-2).

Ase = effective cross-sectional area of anchor (in2).

Asl = effective cross-sectional area of expansion or undercut anchor sleeve, if sleeve is within

shear plane (in2

).

AVo = projected concrete failure area of one anchor, for calculation of strength in shear, when

not limited by corner influences, spacing, or member thickness, as defined in Sec.

9.2.6.2.1 ( in2) (See Figure C9.2.6.2.1-1). 

AV = projected concrete failure area of an anchor or group of anchors, for calculation of

strength in shear, as defined in Sec. 9.2.6.2.1 ( in2

). AV shall not be taken greater than

nAVo. (see Figure C9.2.6.2.1-2).

c = distance from center of an anchor shaft to the edge of concrete (in.).

c1 = distance from the center of an anchor shaft to the edge of the concrete in one direction

(in). Where shear force is applied to an anchor, c1 is in the direction of the shear force

(see Figure C9.2.6.2.1-2).

c2 = distance from center of an anchor shaft to the edge of the concrete in the direction

orthogonal to c1 ( in.).

cmax = the largest of the edge distances that are less than or equal to 1.5 hef (in.) used only for

the case of 3 or 4 edges.

cmin = the smallest of the edge distances that are less than or equal to 1.5 hef (in.)

do = outside diameter of anchor or shaft diameter of headed stud, headed anchor bolt, or

hooked anchor (in.) (see also Sec. 9.2.8.4).

du = diameter of head of stud or anchor bolt or equivalent diameter of effective perimeter of

an added plate or washer at the head of the anchor (in.).

eh = distance from the inner surface of the shaft of a J-bolt to the outer tip of the J- or L-bolt

(in.).

eN

! = eccentricity of normal force on a group of anchors; the distance between the resultant

tension load on a group of anchors in tension and the centroid of the group of anchors

loaded in tension (in.) (see Figures C9.2.5.2.4-1 and -2).

ev

! = eccentricity of shear force on a group of anchors; the distance between the point of shear

force application and the centroid of the group of anchors resisting shear in the direction

of the applied shear (in.).

fc

! = specified compressive strength of concrete (psi).

fct = specified tensile strength of concrete (psi).

fr = modules of rapture of concrete (psi).
Concrete Structure Design Requirements

151

ft = calculated tensile stress in a region of a member (psi).

fy = specified yield strength of anchor steel (psi).

fut = specified tensile strength of anchor steel (psi).

futsl = specified tensile strength of anchor sleeve (psi).

h = thickness of member in which an anchor is anchored measured parallel to the anchor axis

(in.).

hef = effective anchor embedment depth (in.) (see Sec. 9.2.8.5 and Figure C9.2.2.2).

k = coefficient for basic concrete breakout strength in tension.

kcp = coefficient for pryout strength.

l = load bearing length of anchor for shear, not to exceed 8do (in.).

l = hef for anchors with a constant stiffness over the full length of the embedded section,

such as headed studs or post-installed anchors with one tubular shell over the full length

of the embedment depth.

l = 2do for torque-controlled expansion anchors with a distance sleeve separated from the

expansion sleeve. 

n = number of anchors in a group.

Nb = basic concrete breakout strength in tension of a single anchor in cracked concrete, as

defined in Sec. 9.2.5.2.2 (lb).

Ncb = nominal concrete breakout strength in tension of a single anchor, as defined in Sec.

9.2.5.2.1 (lb).

Ncbg = nominal concrete breakout strength in tension of a group of anchors, as defined in Sec. 

9.2.5.2.1 (lb).

Nn = nominal strength in tension (lb).

Np = pullout strength in tension of a single anchor in cracked concrete, as defined in Sec.

9.2.5.3.4 or 9.2.5.3.5 (lb).

Npn = nominal pullout strength in tension of a single anchor, as defined in Sec. 9.2.5.3.1 (lb).

Nsb = side-face blowout strength of a single anchor (lb).

Nsbg = side-face blowout strength of a group of anchors (lb).

Ns = nominal strength of a single anchor in tension as governed by the steel strength, as

defined in Sec. 9.2.5.1.2 (lb).

Nu = factored tensile load (lb).

s = anchor center-to center spacing (in).

so = spacing of the outer anchors along the edge in a group (in).
2000 Provisions Chapter 9

152

t = thickness of washer or plate (in).

Vb = basic concrete breakout strength in shear of a single anchor in cracked concrete, as

defined in Sec. 9.2.6.2.2 or 9.2.6.2.3 (lb).

Vcb = nominal concrete breakout strength in shear of a single anchor as defined in Sec.

9.2.6.2.1 (lb).

Vcbg = nominal concrete breakout strength in a shear group of anchors as defined in Sec.

9.2.6.2.1 (lb).

Vcp = nominal concrete pryout strength, as defined in Sec. 9.2.6.3 (lb).

Vn = nominal shear strength (lb).

Vs = nominal strength in shear of a single anchor as governed by the steel strength as defined

in Sec. 9.2.6.1.1 (lb).

Vu = factored shear load (lb).

N = strength reduction factor (see Sec. 9.2.4.4 and 9.2.4.5).

Q1 = modification factor, for strength in tension, to account for anchor groups loaded

eccentrically as defined in Sec. 9.2.5.2.4.

Q2 = modification factor, for strength in tension, to account for edge distances smaller than

1.5hef as defined in Sec. 9.2.5.2.5

Q3 = modification factor, for strength in tension, to account for cracking as defined in Sec.

9.2.5.2.6 and 9.2.5.2.7.

Q4 = modification factor, for pullout strength, to account for cracking as defined in Sec. 

9.2.5.3.1 and Sec. 9.2.5.3.6.

Q5 = modification factor, for strength in shear, to account for the anchor groups loaded

eccentrically as defined in Sec. 9.2.6.2.5.

Q6 = modification factor, for strength in shear, to account for edge distances smaller than 1.5c1

as defined in Sec. 9.2.6.2.6.

Q- = modification factor, for strength in shear, to account for cracking, as defined in Sec.

9.2.6.2.7

9.2.2.2 Definitions:

Anchor: A metallic element either cast into concrete or post-installed into a hardened concrete

member and used to transmit applied loads including straight bolts, hooked bolts (J-or L-bolt),

headed studs, expansion anchors, undercut anchors, or inserts.

Anchor Group: A number of anchors of approximately equal effective embedment depth with

each anchor spaced as less than three times its embedment depth from one or more adjacent

anchors.
Concrete Structure Design Requirements

153

Anchor Pullout Strength: The strength corresponding to the anchoring device or a major

component of the device sliding out from concrete without breaking out a substantial portion of

the surrounding concrete.

Attachment: The structural assemble, external to the surface of the concrete, that transmits

loads to the anchor.

Brittle Steel Element: An element with a tensile test elongation of less than 14 percent over a 2

in. gage length reduction in area of less than 40 percent, or both.

Concrete Breakout Strength: The strength corresponding to a volume of concrete surrounding

the anchor or group of anchors separating from the memeber.

Concrete Pryout Strength: The strength corresponding to formation of a concrete spall behind

a short, stiff anchor with an embedded base that is displaced in the direction opposite to the

applied shear force.

Distance Sleeve: A sleeve that encases the center part of an undercut anchor, a torque-controlled

expansion anchor, or a displacement-controlled expansion anchor but does not expand.

Ductile Steel Element: An element with a tensile test elongation of at least 14 percent over a 2

in. gage length and reduction in area of at least 40 percent.

Edge Distance: The distance from the edge of the concrete surface to the center of the nearest

anchor.

Effective Embedment Depth: The overall depth through which the anchor transfers force to the

surrounding concrete. The effective embedment depth normally will be the depth of the failure

surface in tension applications. For cast-in headed anchor bolts and headed studs, the effective

embedment depth is measured from the bearing contact surface of the head. (See Figure

C9.2.2.1.)

Expansion Anchor: A post-installed anchor inserted into hardened concrete that transfers loads

into the concrete by direct bearing and/or friction. Expansion anchors may be torque-controlled,

where the expansion is achieved by a torque acting on the screw or bolt, or displacementcontrolled, where the expansion is achieved by impact forces acting on a sleeve or a plug and the

anchorage is controlled by the length of travel of the sleeve or plug.

Expansion Sleeve: The outer part of an expansion anchor that is forced outward by the center

part, either by applied torque or impact, to bear against the sides of the pre-drilled hole.

5 Percent Fractile: A statistical term meaning 90 percent confidence that 95 percent of the

actual strengths will exceed the nominal strength. Determination shall include the number of

tests when evaluating data.

Hooked Bolt: A cast-in anchor anchored mainly by mechanical interlock from the 90-degree

bend (L-bolt) or 180-degree bend (J-bolt) at its lower end.

Insert (specialty insert): Predesigned and pre-fabricated cast-in anchors specifically designed

for attachment of bolted or slotted connections. Inserts often are used for handling,

transportation, and erection but are used also for anchoring structural elements.
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154

Post-Installed Anchor: An anchor installed in hardened concrete. Expansion anchors and

undercut anchors are examples of post-installed anchors.

Projected Area: The area on the free surface of the concrete member that is used to represent

the larger base of the assumed rectilinear failure surface.

Side-Face Blowout Strength: The strength of the anchors with deeper embedment but thinner

side cover corresponding to concrete spalling on the side face around the embedded head while

no major breakout occurs at the top concrete surface.

Undercut Anchor: A post-installed anchor anchored mainly by mechanical interlock provided

by an undercutting in the anchoring concrete. The undercutting is achieved with a special drill

before installing the anchor or, alternatively, by the anchor itself during its installation.

9.2.3 General Requirements:

9.2.3.1: Anchors and anchor groups shall be designed for critical effects of factored loads as

determined by elastic analysis. Plastic analysis approaches are permitted where nominal strength

is controlled by ductile steel elements provided that deformational compatibility is taken into

account.

9.2.3.2: Except for load combinations that include earthquake forces or effects, anchors shall be

designed for all load combinations outlined in Sec. 9.2 of ACI 318. Where resistance to

specified earthquake loads or forces, E, are included in the design, the load combinations Sec.

5.2.7 of this document shall apply.

9.2.3.3: When anchor design includes seismic loads, the following additional requirements shall

apply.

9.2.3.3.1: In structures assigned to Seismic Design Categories C, D, E, or F post-installed

structural anchors for use under Sec. 9.2.3.2 shall have passed the simulated seismic tests in

accordance with Sec. 9.2.1.4.

9.2.3.3.2: In structures assigned to Seismic Design Categories C, D, E or F, the design strength

of anchors shall be taken as 0.75 N Vn, where N is given in Sec. 9.2.4.4 or 9.2.4.5 and Nn and Vn

are determined in accordance with Sec. 9.2.4.1.

9.2.3.3.3: In structures assigned to Seismic Design Categories C, D, E or F, anchors shall be

designed to be governed by tensile or sheer strength of a ductile steel element unless Sec.

9.2.3.3.4 is satisfied.

9.2.3.3.4: In lieu of Sec. 9.2.3.3.3, the attachment that the anchor is connecting to the structure

shall be designed so that the member being attached will undergo ductile yielding at a load level

no greater than 75 percent of the minimum anchor design strength or the minimum anchor design

strength is at least S0 times the attachment force determined from design loads of the attached

structure or 2.5 times the attachment force determined from the design loads of the attached

nonstructural component.

9.2.3.4: All provisions for anchor axial tension and shear strength apply to normal-weight

concrete. When lightweight aggregate concrete is used, provisions for Nn and Vn shall be
Concrete Structure Design Requirements

155

modified by multiplying all values of affecting Nn and Vn f ′ by 0.75 for “all lightweight” c

concrete and 0.85 for “sand-lightweight” concrete. Linear interpolation shall be permitted when

partial sand replacement is used.

9.2.3.5: The values of fc

!

 used for calculations in these provisions shall not exceed 10,000 psi for

cast-in anchors and 8000 psi for post-installed anchors.

9.2.4 General Requirements for Strength of Structural Anchors:

9.2.4.1: Strength design of structural anchors shall be based on the computation or test evaluation of the following:

a. Steel strength of anchor in tension Sec. 9.2.5.1,

b. Steel strength of anchor is shear Sec. 9.2.6.1,

c. Concrete breakout strength of anchor in tension Sec. 9.2.4.2 and 9.2.5.2

d. Concrete breakout strength of anchor in shear Sec. 9.2.4.2 and 9.2.6.2,

e. Pullout strength of anchor in tension Sec. 9.2.4.2 and 9.2.5.3,

f. Concrete side-face blowout strength of anchor in tension Sec. 9.2.4.2 and 9.2.5.4, 

g. Concrete pryout strength of anchor in shear Sec. 9.2.4.2 and 9.2.6.3,

h. Required edge distances, spacings and thickness to preclude splitting failure Sec. 9.2.4.2 and

9.2.8.

9.2.4.1.1: For the design of anchors, except as required in Sec. 9.2.3.3:

φN N (9.2.4.1.1-1) n u ≥

φV V n u ≥ (9.2.4.1.1-2) 

9.2.4.1.2: When both Nu and Vu are present, interaction effects shall be considered in accordance

with 9.2.4.3.

9.2.4.1.3: In Eq. 9.2.4.1.1-1 and 9.2.4.1.1-2, NNn and NVn are the lowest design strengths

determined from all appropriate failure modes. NNn is the lowest design strength in tension of an

anchor or group of anchors as determined from consideration of NNs, NNpn, either NNsb or NNsbg,

and either NNcb or NNcbg. NVn is the lowest design strength in shear of an anchor or a group of

anchors as determined from consideration of NVs , either NVcb or NVcbg, and NVcp.

9.2.4.2: The nominal strength for any anchor and group of anchors shall be based on design

models that result in predictions of strength in substantial agreement with results of

comprehensive tests. The materials used in the tests shall be compatible with the materials used

in the structure. The nominal strength shall be based on the 5 percent fractile of the basic

individual anchor strength with the modifications made for the number of anchors, the effects of
2000 Provisions Chapter 9

156

close spacing of anchors, proximity to edges, depth of the concrete member, eccentric loadings of

anchor groups, and presence or absence of cracking. Limits on edge distances and anchor

spacing in the design models shall be consistent with the tests that verified the model.

9.2.4.2.1: The effect of supplementary reinforcement provided to confine or restrain the concrete

breakout, or both, shall be permitted to be included in the design models of Sec. 9.2.4.2.

9.2.4.2.2: For anchors with diameters not exceeding 2 in. and with tensile embedment not

exceeding 25 in. in depth, the concrete breakout strength requirements of Sec. 9.2.4.2 shall be

considered satisfied by the design procedure of Sec. 9.2.5.2 and 9.2.6.2.

9.2.4.3: Resistance to combined tensile and shear loads shall be considered in design using an

interaction expression that results in computation of strength in substantial agreement with

results of comprehensive tests. This requirement shall be considered satisfied by Sec. 9.2.7.

9.2.4.4: Strength reduction factor N for anchoring to concrete shall be as follows when the load

combinations of Sec. 9.2 of ACI 318 and Sec. 5.2.7 of this document are used:

Anchor governed by tensile or shear strength of a ductile steel element 0.90

Anchor governed by tensile or shear strength of a brittle steel element 0.75

Anchor governed by concrete breakout, blowout, pullout, or pryout

Condition A Condition B

i. Shear loads 0.85 0.75

ii. Tension loads

Cast-in headed studs, headed bolts, or hooked bolts 0.85 0.75

Post-installed anchors with category as determined

from anchor pre-qualification tests of Sec. 9.2.1.4

Category 1 (low sensitivity to 0.85 0.75

installation and high reliability)

Category 2 (medium sensitivity to 0.75 0.65

installation and medium reliability)

Category 3 (high sensitivity to 0.65 0.55

installation and lower reliability)

Condition A applies where the potential concrete failure surfaces are crossed by supplementary

reinforcement proportional to tie the potential concrete failure prism into the structural member. 

Condition B applies where such supplementary reinforcement is not provided to where pullout or

pryout strength governs.

9.2.4.5: Strength reduction factor N for fastening to concrete shall be as follows when the load

combinations referenced in ASCE 7 are used:

Anchor governed by tensile or shear strength of a ductile steel element 0.80 
Concrete Structure Design Requirements

157

Anchor governed by tensile or shear strength of a brittle steel element 0.70

Anchor governed by concrete breakout, blowout, pullout, or pryout

Condition A Condition B

i. Shear loads 0.75 0.70

ii. Tension loads

Cast-in headed studs, headed bolts 0.75 0.70

or hooked bolts 

Post-installed anchors with category as determined

from anchor prequalification tests of Sec. 9.2.1.4

Category 1 (low sensitivity to 0.75 0.65

installation and high reliability)

Category 2 (medium sensitivity to 0.65 0.55

installation and medium reliability) 

Category 3 (high sensitivity to 0.55 0.45

installation and lower reliability)

Condition A applies where the potential concrete failure surfaces are crossed by supplementary

reinforcement proportioned to tie the potential concrete failure prism into the structural member. 

Condition B applies where such supplementary reinforcement is not provided where pullout or

pryout strength governs.

9.2.5 Design Requirements for Tensile Loading:

9.2.5.1 Steel Strength of Anchor in Tension:

9.2.5.1.1: The nominal strength of an anchor in tension as governed by the steel, Ns, shall be

evaluated by calculations based on the properties of the anchor material and the physical

dimensions of the anchor. Alternatively, it shall be permitted to use values based on the 5

percent fractile of the test results to establish values of Ns

9.2.5.1.2: Unless determined by the 5 percent fractile of test results, nominal strength of an

anchor or group of anchors in tension shall not exceed the following:

For anchor material with a well-defined yield point

N nA f s se y =

For anchor material without a well-defined yield point where fut shall not be taken greater than

125,000 psi

N nA f ( ) s se ut = 08.

9.2.5.2 Concrete Breakout Strength of Anchor in Tension:
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158

9.2.5.2.1: Unless determined in accordance with Sec. 9.2.4.2, nominal concrete breakout

strength of an anchor or group of anchors in tension shall not exceed the following:

For a single anchor

N (9.2.5.2.1-1)

A

A cb N N

No

= ψ ψ2 3 b

For a group of anchors

N (9.2.5.2.1-2)

A

A cbg N n

No

= ψψψ 123 b

Nb is the basic concrete breakout strength value for a single anchor in tension in cracked concrete. 

An is the projected area of the failure surface for the anchor or group of anchors that shall be

approximated as the base of the rectilinear geometrical figure that results from projecting the

failure surface outward 1.5hef from the center lines of the anchor or, in the case of a group of

anchors, from a line through a row of adjacent anchors. An shall not exceed nANo, where n is the

number of tensioned anchors in the group. ANo is the projected area of the failure surface of the

single anchor in remote from edges:

A h No ef = 9 2

9.2.5.2.2: Unless determined in accordance with Sec. 9.2.4.2, the basic concrete breakout

strength of a single anchor in tension in cracked concrete shall not exceed:

N fh (9.2.5.2.2-1) b c

k = ef ′ 1 5.

where

k = 24 for cast-in headed studs, headed bolts and hooked bolts and

k = 17 for post-installed anchors.

Alternatively, for cast-in headed studs and headed bolts with 11 in. < hef < 25 in., the basic

concrete breakout strength of a single anchor in tension in cracked concrete shall not exceed:

N fh (9.2.5.2.2-2) b c

k = ef

′ 5 3/

where k = 16.

9.2.5.2.3: For the special case of anchors in an application with three or four edges and the

largest edg e distance cmax < 1.5 hef, the embedment depth hef used in Eq. 9.2.5.2.1-3, 9.2.5.2.2-1,

9.2.5.2.4 and 9.2.5.2.5-1 and -2 shall be limited to cmax/1.5.

9.2.5.2.4: The modification factor for eccentrically loaded anchor groups is:
Concrete Structure Design Requirements

159

ψ (9.2.5.2.4) 1

1

1

2

3

= 1

+

 ′















≤

e

h

N

ef

Eq. 9.2.5.2.4 is valid for en

!

# s/2.

If the loading of an anchor group is such that only some anchors are in tension, only those

anchors that are in tension shall be considered when determining the eccentricity, en

!

, for use in

Eq. 9.2.5.2.4.

Where eccentric loading exists about two axes, the modification factor, yl

, shall be computed for

each axis individually and the product of these factors used as yl in Eq. 9.2.5.2.4

9.2.5.2.5: The modification factor for edge effects is:

ψ (9.2.5.2.5-1) 2 = ≥ 1 15 if h cmin ef .

ψ (9.2.5.2.5-1) 2 07 03

15

=+ < . . 15 . . min

min

c

c h if h

ef

ef

9.2.5.2.6: When an anchor is located in a region of a concrete member where analysis indicates

no cracking (ft < fr) at service load levels, the following modification factor shall be permitted:

R3 = 1.25 for cast-in headed studs, headed bolts, and hooked bolts and

R3 = 0.4 for post-installed anchors.

9.2.5.2.7: When analysis indicates cracking at service load levels, y3 shall be taken as 1.0 for

both cast-in anchors and post-installed anchors. Post-installed anchors shall be qualified for use

in cracked concrete in accordance with Sec. 9.2.1.4. The cracking in the concrete shall be

controlled by flexural reinforcement distributed in accordance with Sec. 10.6.4 of ACI 318 or

equivalent crack control shall be provided by confining reinforcement.

9.2.5.2.8: When an additional plate or washer is added at the head of the anchor, it shall be

permitted to calculate the projected area of the failure surface by projecting the failure surface

outward 1.5hef from the effective perimeter of the plate or washer. The effective perimeter shall

not exceed the value at a section projected outward more than t from the outer edge of the head

of the anchor where t is the thickness of the washer or plate.

9.2.5.3 Pullout Strength of Anchor in Tension:

9.2.5.3.1: Unless determined in accordance with Sec. 9.2.4.2 the nominal pullout strength of an

anchor in tension shall not exceed:

 (9.2.5.3.1) N N pn p =ψ 4
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160

9.2.5.3.2: For post-installed expansion and undercut anchors, it is not permissible to calculate

the pullout strength of tension. Values of Np shall be based on 5 percent fractile of tests

performed and evaluated according to Sec. 9.2.1.4.

9.2.5.3.3: For single cast-in headed studs and headed bolts, it shall be permitted to evaluate the

pullout strength in tension using Sec. 9.2.5.3.4. For single J-bolts and L-bolts, it shall be

permitted to evaluate the pullout strength in tension using Sec. 9.2.5.3.5. Alternatively, it shall

be permitted to use values of Np based on the 5 percent fractile of tests performed and evaluated

in the same manner as the test procedures of Sec. 9.2.1.4 but without the benefit of friction.

9.2.5.3.4: Unless determined in accordance with Sec. 9.2.4.2, the pullout strength in tension of a

single headed stud or headed bolt, Np for use in Eq. 9.2.5.3.1 shall not exceed:

N A (9.2.5.3.4) p b c = f ′ 8

9.2.5.3.5: Unless determined in accordance with Sec. 9.2.4.2 the pullout strength in tension of a

single J-bolt or L-bolt, Np for use in Eq. 9.2.5.3.1 shall not exceed:

N ed (9.2.5.3.5) p c = f h o

′ 0 9.

where 3do < eh < 4.5do.

9.2.5.3.6: For an anchor located in a region of concrete member where analysis indicates no

cracking (ft

 < fr) at service load levels, the following modification factor shall be permitted:

ψ 4 = 14.

Otherwise, Q, shall be taken as 1.0.

9.2.5.4 Concrete Side-Face Blowout Strength of a Headed Anchor in Tension:

9.2.5.4.1: For a single headed anchor with deep embedment close to an edge c < 0.4hef), unless

determined in accordance with Sec. 9.2.4.2, the nominal side-face blowout strength Nsb shall not

exceed:

Nsb c b A c = f ′ 160

If the single anchor is located at a perpendicular distance, c2, less than 3c from an edge, the value

of Nsb shall be modified by multiplying it by the factor (1 + c2/c)/4 where 1 < c2/c < 3.

9.2.5.4.2: For multiple headed anchors with deep embedment close to an edge c < 0.4 hef) and

spacing between anchors less than 6c, unless determined in accordance with Sec. 9.2.4.2, the

nominal strength of the group of anchors for a side-face blowout failure, Nsbg, shall not exceed:

N (9.2.5.4.2) S

c sbg N o = + sb





 

 1  6
Concrete Structure Design Requirements

161

where so is the spacing of the outer anchors along the edge in the group and Nsb is obtained from

Eq. 9.2.5.4.1 without the modification for a perpendicular edge distance.

9.2.6 Design Requirements for Shear Loading:

9.2.6.1 Steel Strength of Anchor in Shear:

9.2.6.1.1: The nominal strength of anchor in shear as governed by steel, Vs, shall be evaluated by

calculations based on the properties of the anchor material and the physical dimensions of the

anchor. Alternatively, it shall be permitted to use values based on the 5 percent fractile of test

results to establish values of Vs. 

9.2.6.1.2: Unless determined by the 5 percent fractile of test results, nominal strength of an

anchor or group of anchors in shear shall not exceed the following:

a. For anchor material with a well-defined yield point:

V nA f (9.2.6.1.2-1) s se y =

b. For cast-in anchors without a well defined yield point:

V n Af (9.2.6.1.2-2) s se ut = 0 6.

where fut shall not be taken greater than 125,000 psi.

c. For post-installed anchors without a well-defined yield point:

V n Af Af ( ) (9.2.6.1.2-3) s se ut sl utsl = + 06 04 . .

where fut shall be taken greater than 125,000 psi.

9.2.6.1.3: Where anchors are used with built-up grout pads, the nominal strengths of Sec.

9.2.6.1.2 shall be reduced by 20 percent.

9.2.6.2: Concrete Breakout Strength of Anchors in Shear:

 9.2.6.2.1: Unless determined in accordance with Sec. 9.2.4.2, nominal concrete breakout

strength in shear of an anchor or group of anchors shall not exceed the following:

For shear force perpendicular to the edge on a single anchor:

V (9.2.6.2.1-1) A

A b V V

Vo

= ψ ψ6 7 b

For shear force perpendicular to the edge on a group of anchors:

V (9.2.6.2.1-2)

A

A cbg V v

vo

= ψψψ 567 b

For shear force parallel to an edge, Vch or Vcbg shall be permitted to be twice the value for the

force determined from Eq. 9.2.6.2.1-1 or 9.2.6.2.1-2- respectively, with R6 taken equal to 1. 
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162

For anchors located at a corner, the limiting nominal concrete breakout strength shall be

determined for each edge and the minimum value shall be used.

Vb is the basic concrete breakout strength value for a single anchor. Av is the projected area of the

failure surface on the side of the concrete member at its edge for a single anchor or a group of

anchors. It shall be permitted to evaluate this area as the base of a truncated half pyramid

projected on the side face of the member where the top of the half pyramid is given by the axis of

the anchor row selected as critical. The value of c1 shall be taken as the distance from the edge to

this axis, Ay, and shall not exceed nAvo where n is the number of anchors in the group

Avo is the projected area for a single anchor in a deep member and remote from edges in the

direction perpendicular to the shear force. It shall be permitted to evaluate this area as the base

of a half pyramid with a side length parallel to the edge of 3c1 and the depth of 1.5 c1.

A c (9.2.6.2.1-3) vo = 4 5 1

2 .

Where anchors are located at varying distances from the edge and the anchors are welded to the

attachment so as to distribute the force to all anchors, it shall be permitted to evaluate the

strength based on the distance to the farthest row of anchors from the edge. In this case, it shall

be permitted to base the value of c1 on the distance from the edge to the axis of the farthest

anchor row that is selected as critical, and all of the shear shall be assumed to be carried by this

critical anchor row alone.

9.2.6.2.2: Unless determined in accordance with Sec. 9.2.4.2, the basic concrete breakout

strength in shear of a single anchor in cracked concrete shall not exceed:

V (9.2.6.2.2) l

d d c b

o

o c = f 



 



 ′ 7

0 2

1

1 5

.

.

9.2.6.2.3: For cast-in headed studs, headed bolts, or hooked bolts that are rigidly welded to steel

attachments having a minimum thickness equal to the greater of 3/8 in. or half of the anchor

diameter, unless determined in accordance with Sec. 9.2.4.2, the basic concrete breakout strength

in shear of a single anchor in cracked concrete shall not exceed:

V (9.2.6.2.3) d d c b

o

o c = f 



 



 ′ 8

1 0 2

1

1 5

.

.

provided that:

a. For groups of anchors, the strength is determined based on the strength of the row of anchors

farthest from the edge,

b. The center-to-center spacing of the anchors is not less than 2.5 in., and

c. Supplementary reinforcement is provided at the corners if c2 # 1.5hef. 
Concrete Structure Design Requirements

163

9.2.6.2.4: For the special case of anchors in a thin member influenced by three or more edges,

the edge distance c1 used in Eq. 9.2.6.2.1-3, 9.2.6.2.2, 9.2.6.2.3, 9.2.6.2.5, 9.2.6.2.6-1 or -2 shall

be limited to h/1.5.

9.2.6.2.5: The modification factor for eccentrically loaded anchor groups is:

(9.2.6.2.5) 5

1

1

1

2

3

ψ = 1

+

′ ≤

ev

c

Eq. 9.2.6.2.5 is valid for ev

! # s/2.

9.2.6.2.6: The modification factor edge effects is:

(9.2.6.2.6-1) 6 2 1 ψ = ≥ 1 15 if c c.

(9.2.6.2.6-2) 6

2

1

2 1 07 0315 ψ =+ < . . 15 . . c

c

if c c

9.2.6.2.7: For anchors located in a region of a concrete member where analysis indicates no

cracking (ft < fr) at the service loads, the following modification factor shall be permitted:

7 ψ = 14.

For anchors located in a region of a concrete member where analysis indicates cracking at service

load levels, the following modification factors shall be permitted. In order to be considered as

edge reinforcement, the reinforcement shall be designed to resist the concrete breakout:

R = 1.0 for anchors in cracked concrete with no edge reinforcement or edge reinforcement

smaller that a No. 4 bar

R = 1.2 for anchors in cracked concrete with edge reinforcement of a No. 4 bar or greater

between the anchor and the edge

R = 1.4 for anchors in cracked concrete with edge reinforcement of a No. 4 bar or greater

between the anchor and the edge and with the edge reinforcement enclosed within

stirrups spaced at not more than 4 in.

9.2.6.3 Concrete Pryout Strength of Anchor in Shear:

9.2.6.3.1: Unless determined in accordance with Sec. 9.2.4.2, the nominal pryout strength, Vcp,

shall not exceed:

V kN (9.2.6.3.1) cp cp cb =

where

kcp = 1.0 for hef < 2.5 in.,

kcp = 2.0 for hef > 2.5 in., and Ncb shall be determined from Eq. 9.2.5.2-1 (lb).
2000 Provisions Chapter 9

164

9.2.7 Interaction of Tensile and Shear Forces: Unless determined in accordance with Sec.

9.2.4.3, anchors or groups of anchors that are subjugated to both shear and axial loads shall be

designed to satisfy the requirements of Sec. 9.2.7.1 through 9.2.7.3. The value of NNn shall be

the smallest of shear strength of the anchor in tension, concrete breakout strength of anchor in

tension, pullout strength of anchor in tension, and side-face blowout strength. The value of NVn

shall be the smallest of the steel strength of an anchor and shear, the concrete breakout strength

of anchor in shear, and the pryout strength.

9.2.7.1: If Vu # 0.2 NVn, then full strength in tension shall be permitted: NNn > Nu

9.2.7.2: If Nu # 0.2 NNn, then full strength in shear shall be permitted: NVn > Vu

9.2.7.3: If Vu > 0.2 NVn and Nu > 0.2 NNn, then:

(9.2.7.3) u

n

u

n

N

N

V

φ φV + ≤ 12.

9.2.8 Required Edge Distances, Spacings, and Thicknesses to Preclude Splitting Failure:

Minimum spacings and edge distances for anchors and minimum thickness of members shall

conform to Sec. 9.2.8.1 through Sec. 9.2.8.5, unless reinforcement is provided to control

splitting. Lesser values from product-specific tests performed in accordance with 

prequalification test in accordance with Sec. 9.2.1.4 shall be permitted.

9.2.8.1: Unless determined in accordance with Sec. 9.2.8.4, minimum center-to-center spacing

of anchors will be 4do for untorqued cast-in anchors that will not be torqued or otherwise

pretensioned and 6do for torqued or otherwise pretensioned cast-in anchors and all post-installed

anchors. 

9.2.8.2: Unless determined in accordance with Sec. 9.2.8.4, minimum edge distances for cast-in

headed anchors that will not be torqued or otherwise pre-tensioned shall be based on minimum

cover requirements for reinforcement in Sec. 7.7 of ACI 318. For cast-in headed anchors that

will be torqued or otherwise pretensioned, the minimum edge distances shall be 6do.

9.2.8.3: Unless determined in accordance with Sec. 9.2.8.4, minimum edge distances for postinstalled anchors shall be based on the greater of the minimum cover requirements for

reinforcement in Sec. 7.7 of ACI 318 or the minimum edge distance requirements for the

products as determined by tests in accordance with Sec. 9.2.1.4 and shall not be less than 2.0

times the maximum aggregate size. In the absence of such product-specific test information, the

minimum edge distance shall be taken as not less than:

 6do for undercut anchors 

8do for torque-controlled anchors 

10do for displacement-controlled anchors

9.2.8.4: For anchors where installation does not produce a splitting force and the anchors will

remain untorqued, if the edge distance or spacing is less than that specified in Sec. 9.2.8.1 to

9.2.8.3, calculations shall be performed using a fictitious value of do that meets the requirements
Concrete Structure Design Requirements

165

of Sec.9.2.8.1 to 9.2.8.3. Calculated forces applied to the anchor shall be limited to values

corresponding to an anchor having the fictitious diameter.

9.2.8.5: The value of hef for an expansion or undercut post-installed anchor shall not exceed the

greater of either two thirds of the member thickness or the member thickness less than 4 in.

9.2.8.6: Project drawings and project specifications shall specify use of anchors with a minimum

edge distance as assumed in design.

9.2.9 Installation of Anchors: Anchors shall be installed in accordance with the project

drawings and specifications.

9.3 CLASSIFICATION OF SHEAR WALLS: Structural concrete shear walls that resist

seismic forces shall be classified in accordance with Sec. 9.3.1 through 9.3.4. 

9.3.1 Ordinary Plain Concrete Shear Walls: Ordinary plain concrete shear walls are walls

conforming to the requirements of Chapter 22 of ACI 318.

9.3.2 Detailed Plain Concrete Shear Walls: Detailed plain concrete shear walls are walls

above the base conforming to the requirements of Chapter 22 of ACI 318 and containing

reinforcement as follows:

Vertical reinforcement of at least 0.20 in.2

 (129 mm2) in cross-sectional area shall be provided

continuously from support to support at each corner, at each side of each opening, and at the ends

of walls. The continuous vertical bar required by Sec. 22.6.6.5 of ACI 318 shall be provided.

Horizontal reinforcement at least 0.20 in.2 (129 mm2) in cross-sectional area shall be provided:

a. Continuously at structurally connected roof and floor levels and at the top of walls, 

b. At the bottom of load-bearing walls or in the top of foundations when doweled to the wall,

and

c. At a maximum spacing of 120 inches (3050 mm).

Reinforcement at the top and bottom of openings, when used in determining the maximum

spacing specified in Item c above, shall be continuous in the wall.

Basement, foundation, or other walls below the base shall be reinforced as required by Sec.

22.6.6.5 of ACI 318.

9.3.2.1 Ordinary Reinforced Concrete Shear Walls: Ordinary reinforced concrete shear

walls are walls conforming to the requirements of ACI 318 exclusive of Chapters 21 and 22.

9.3.2.2 Special Reinforced Concrete Shear Walls: Special reinforced concrete shear walls

are walls conforming to the requirements of ACI 318 in addition to the requirements for ordinary

reinforced concrete shear walls.

9.4 SEISMIC DESIGN CATEGORY A: Structures assigned to Seismic Design Category A

may be of any construction permitted in ACI 318 and the Provisions. 

9.5 SEISMIC DESIGN CATEGORY B: Structures assigned to Seismic Design Category B

shall conform to all the requirements for Seismic Design Category A and the additional
2000 Provisions Chapter 9

166

requirements for Seismic Design Category B of this section and in other chapters of the Provisions.

9.5.1 Ordinary Moment Frames: Flexural members of ordinary moment frames forming part

of the seismic-force-resisting system shall be designed in accordance with Sec. 7.13.2 of ACI 318

and at least two main flexural reinforcing bars shall be provided continuously top and bottom

throughout the beams, through or developed within exterior columns or boundary elements. 

Columns of ordinary moment frames having a clear height to maximum plan dimension ratio of

5 or less shall be designed for shear in accordance with Sec. 21.10.3 of ACI 318.

9.6 SEISMIC DESIGN CATEGORY C: Buildings assigned to Seismic Design Category C

shall conform to all requirements for Seismic Design Category B and to the additional

requirements for Seismic Design Category C of this section an in other chapters of the Provisions.

9.6.1 Seismic-Force-Resisting Systems: Seismic-force-resisting systems shall conform to Sec.

9.6.1.1 and Sec. 9.6.1.2.

9.6.1.1 Moment Frames: All moment frames that are part of the seismic-force-resisting system

shall be intermediate moment frames or special moment frames.

9.6.1.2 Shear Walls: All shear walls that are part of the seismic-force-resisting system shall be

ordinary reinforced concrete shear walls conforming to Sec. 9.3.3 or special reinforced concrete

shear walls conforming to Sec. 9.3.4.

9.6.2 Discontinuous Members: Columns supporting reactions from discontinuous stiff

members such as walls shall be designed for special load combinations in Sec. 5.2.7.1 and shall

be provided with transverse reinforcement at the spacing so as defined in Sec. 21.10.5.1 of ACI

318 over their full height beneath the level at which the discontinuity occurs. This transverse

reinforcement shall be extended above and below the column as required in Sec. 21.4.4.5 of ACI

318. 

9.6.3 Plain Concrete: Structural plain concrete members in buildings assigned to Seismic

Design Category C shall conform to ACI 318 and the additional requirements and limitations of

this section.

9.6.3.1 Walls: Structural plain concrete walls are not permitted in structures assigned to Seismic

Design Category C.

Exception: Structural plain concrete basement, foundation, or other walls below the

base are permitted in detached one- and two-family dwellings three stories or less in

height constructed with stud bearing walls. Such walls shall have reinforcement in

accordance with Sec. 22.6.6.5 of ACI 318.

9.6.3.2 Footings: Isolated footings of plain concrete supporting pedestals or columns are

permitted provided the projection of the footing beyond the face of the supported member does

not exceed the footing thickness.

Exception: In detached one- and two-family dwellings three stories or less in height of

light-frame construction, structural plain concrete basement walls, foundation, or other
Concrete Structure Design Requirements

167

walls below the basement shall be permitted. Such concrete walls shall have reinforcement in accordance with Sec. 22.6.6.5 of ACI 318.

Plain concrete footings supporting walls shall be provided with no less than two continuous

longitudinal reinforcing bars. Bars shall not be smaller than No. 4 (#13) and shall have a total

area of not less than 0.002 times the gross cross-sectional area of the footing. For footings that

exceed 8 in. in thickness, a minimum of one bar shall be provided at the top and bottom of the

footing. For foundation systems consisting of plain concrete footing and plain concrete

stemwall, a minimum of one bar shall be provided at the top of the stemwall and at the bottom

the footing. Continuity of reinforcement shall be provided at corners and intersections.

Exceptions: 

1. In detached one- and two-family dwellings three stories or less in height and

constructed with stud bearing walls, plain concrete footings supporting walls shall

be permitted without longitudinal reinforcement.

2. Where a slab-on-ground is cast monolithically with the footing, one No. 5 (#16) bar

is permitted to be located at either the top or bottom of the footing.

9.6.3.3 Pedestals: Plain concrete pedestals shall not be used to resist lateral seismic forces.

9.6.4 Anchor Bolts in the Tops of Columns: Anchor bolts that are set in the top of a column

shall be provided with ties that completely enclose at least four longitudinal column bars. There

shall be at least two No. 4 (#13) or three No. 3 (#10) ties within 5 inches of the top of the

column. The ties shall have hooks on each free end that comply with Sec. 7.1.3 of ACI 318.

9.7 SEISMIC DESIGN CATEGORIES D, E, OR F: Structures assigned to Seismic Design

Category D, E, or F shall conform to all of the requirements for Seismic Design Category C and

to the additional requirements in this section.

9.7.1 Seismic-Force-Resisting Systems: Seismic-force-resisting systems shall conform to Sec.

9.7.1.1 and Sec. 9.7.1.2.

9.7.1.1 Moment Frames: All moment frames that are part of the seismic-force-resisting system,

regardless of height, shall be special moment frames.

9.7.1.2 Shear Walls: All shear walls that are part of the seismic-force-resisting system shall be

spacial reinforced concrete shear walls conforming to Sec. 9.3.4.

9.7.2 Frame Members Not Proportioned to Resist Forces Induced by Earthquake Motions:

All frame members assumed not to contribute to lateral forces resistance shall conform to Sec.

21.9 of ACI 318 is modified by Sec. 9.1.1.11 of this chapter.
168

Appendix to Chapter 9

REINFORCED CONCRETE DIAPHRAGMS CONSTRUCTED USING

UNTOPPED PRECAST CONCRETE ELEMENTS

Preface: Reinforced concrete diaphragms constructed using untopped precast concrete

elements are permitted in the body of the 2000 NEHRP Recommended Provisions for

Seismic Design Categories A, B, and C but not for Categories D, E, and F. For the

latter the precast elements must be topped and the topping designed as the diaphragm. 

For resisting seismic forces, a composite-topping slab cast in place on precast concrete

elements must have a thickness no less than 2 in. and a topping slab not relying on

composite action with the precast elements must have a thickness not less than 2-1/2 in.

There are two principal reasons why a framework for the design of untopped diaphragms for Seismic Design Categories D, E, and F may be desirable. One relates to

the performance of topping slab diaphragms in recent earthquakes and the other to

durability considerations. The 1997 Provisions incorporated ACI 318-95 for which the

provisions for topping slab diaphragms on precast elements were essentially the same

as those in ACI 318-89. In the 1994 Northridge earthquake, performance was poor for

structures where demands on the topping slab diaphragms on precast elements were

maximized and the structures had been designed using ACI 318-89. The topping

cracked along the edges of the precast elements and the welded wire reinforcement

crossing those cracks fractured. The diaphragms became the equivalent of an

untopped diaphragm with the connections between precast concrete elements, the

connectors, and the chords not detailed for that condition. Another problem found

with topping slab diaphragms was that the chords often took the large diameter bars,

grouped closely together at the topping slab edge. Under severe loading, these unconfined chord bars lost bond with the concrete and with it, ability to transfer seismic

forces.

The 2000 NEHRP incorporates ACI 318-99 which recognizes that for topping slab

diaphragms a controlling condition is the in-plane shear in concrete along the edges of

the precast elements. Ductility is provided by requiring that the topping slab reinforcement crossing the edges be spaced at not less than 10 in. on center. While those

requirements are based on best available engineering judgement and evidence, they

have not yet been proven to provide adequate safety either by laboratory testing or

field performance. Due to the dimensions of the precast element relative to the

thickness of the topping slab, it may well be prudent to have seismic provisions for

diaphragms incorporating precast elements controlled by untopped diaphragm

considerations and to have those provisions modified for topped diaphragms. Further,

in geographic areas where corrosive environments are a significant concern, the

construction of un-topped diaphragms using “pretopped” precast elements rather than

topped elements is desirable.
Concrete Structure Design Requirements

169

This appendix provides a compilation of current engineering judgment on a framework

for seismic provisions for untopped diaphragms. That framework does not, however,

adequately address all the concerns needed for its incorporation into the body of the

Provisions. This appendix proposes that a diaphragm composed of untopped elements

be designed to remain elastic, and that the connectors be designed for limited ductility

in the event that design forces are exceeded during earthquake response and some

inelastic action occurs when the demands on the diaphragm are maximized. By

contrast, for all other systems for Seismic Design Categories D, E and F, the philosophy

of the 2000 NEHRP is to require significant ductility. For the approach of this appendix, critical issues are how best to define:

1. The design forces for the diaphragm so that they are large enough to result in

essentially elastic behavior when the demands on the diaphragm are maximized or

whether that criterion is even achievable;

2. The relation between the response of the diaphragm, its dimensions, and the

ductility demands on the connectors;

3. The ductility changes that occur for connectors under various combinations of inplane and out-of-plane shear forces and tensile and compressive forces;

4. The boundary conditions necessary for testing and for application of the loading

for the validation testing of connectors; and

5. The constraints on connector performance imposed by their size relative to the size

of the diaphragm elements.

The use of this appendix as a framework for laboratory testing, analyses of the

performance of diaphragms in past earthquakes, analytical studies, and trial designs, is

encouraged. Users should also consult the Commentary for guidance and references. 

Please direct all feedback on this appendix and its commentary to the BSSC.

9A.1 Background: ACI 318-99 was significantly revised for structural diaphragms to add new

detailing provisions in response to the poor performance of some cast-in-place composite topping

slab diaphragms during the 1994 Northridge earthquake. New code and commentary Sec. 21.7

and R21.7 were inserted into Chapter 21. In those provisions, cast-in-place composite topping

slabs and cast-in-place topping slab diaphragms are permitted but no mention is made of

untopped precast diaphragms. The evidence from the recently completed PRESS 5-story

building test (PCI Journal, November-December 1999), from Italian and English tests (M. J.

NM. Priestley, D. Sritharan, J. R. Connley, and S. Pampanin, “Preliminary Results and Conclusions from the PRESSS Five-Story Precast Concrete Test Building,” PCI Journal, Vol. 44, No.

6, November-December 1999; K. S. Elliott, G. Davies, and W. Omar, “Experimental Hollowcored Slabs Used as Horizontal Floor Diaphragms,” The Structural Engineer, Vol. 70, No. 10,

May 1922, pp. 175-187; M. Menegotto, Seismic Diaphragm Behavior of Untopped Hollow-Core

Floors, Proceedings, FIP Congress, Washington, D. C., May 1994), and from the 1999 Turkey

earthquake is that such diaphragms can perform satisfactorily if they are properly detailed and if

they and their connections remain elastic under the force levels the diaphragms experience. 

However, further additions are needed to the ACI 318 requirements to make that possible both in
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170

terms of the forces for which diaphragms should be designed and the ductilities that should be

inherent in connections as a second line of defense.

In this appendix, the untopped precast diaphragm is designed to remain elastic by requiring that

its design forces be based on Eq. 5.2.5.4 and be not less than a minimum value dependent upon

the seismic response coefficient, with both values multiplied by the overstrength and redundancy

factors associated with the seismic-force-resisting system. In addition, the connections are

required to be able to perform in a ductile manner in the unlikely event that the diaphragm is

forced to deform inelastically.

9A.2 References: The following references are to be considered part of this appendix to the

extent referred to in this document:

ACI 318-99/ American Concrete Institute (ACI), Building Code Requirements for Structural 

ACI 318-99R Concrete, 1999

ACI ITG/T1.1 American Concrete Institute (ACI), Acceptance Criteria For Moment

Frames, Based on Structural Testing ( An ACI Provisional Standard),

ITG/T1.1, 1999

ATC-24 Applied Technology Council (ATC), Guidelines for Seismic Testing of

Components of Steel Structures, ATC-24, 1992.

9A.3 Untopped Precast Diaphragms:

9A.3.1: An untopped precast floor or roof shall be permitted as a structural diaphragm provided

Sec. 9A.3.2 through 9A.3.3 are satisfied. Untopped diaphragms shall not be permitted in

structures having plan irregularity Type 4 as defined in Provisions Table 5.2.3.2.

9A.3.2: Rational elastic models shall be used to determine the in-plane shear and

tension/compression forces acting on connections that cross joints. For any given joint, the

connections shall resist the total shear and total moment acting on the joint according to an

elastic distribution of stresses

9A.3.3: The diaphragm design force shall be not less than the force calculated from either of the

following two criteria:

1. Deo times the Fpx value calculated from Eq. 5.2.5.4 but not less than DeoCswpx. 

2. A shear force corresponding to 1.25 times that for yielding of the seismic-force-resisting

system calculated using a M value of unity.

The overstrength factor, eo, shall be that for the seismic-force-resisting system specified in 

Provisions Table 5.2.2 unless derived by analysis of the probable strength of the seismic-forceresisting system and shall not be taken as less than 1.25 times the yield strength of that system. 

The redundancy factor, D, shall be as specified in Sec. 5.2.4 and the seismic response coefficient

,Cs, shall be that determined in accordance with Provisions Sec. 5.3.2.1.
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171

9A.3.4: For diaphragms in buildings having plan irregularities Type 1a, 1b, 2 or 5 as defined in

Provisions Table 5.2.3.2, the analysis required by Sec. 9A.3.3 shall explicitly include the effect

of such irregularities as required by Provisions Sec. 5.2.6.

9A.3.5: Mechanical connections shall have design strength for the body of the connector greater

than the factored forces determined in accordance with Sec. 9A.3.3 and 9A.3.4.

9A.3.6: Mechanical connections used at joints shall be shown by analysis and test results to

develop, under reversed cyclic loading, the capacity in shear, tension, compression, or a 

combination as required by the analysis specified in Sec. 9A.3.2. Testing of connections and

evaluation of results shall be made in accordance with the principles specified in ACI ITG/T1.1

and ATC-24. Connections shall develop for the specified loading ductility ratios equal to or

grater than 2.0. Embedments for connections shall be governed by steel yielding and not by

fracture of concrete or welds.

9A.3.7: Connections shall be designed using the strength reduction factors N specified in ACI

318-99 and ACI 318-99R. When the N factor is modified by Sec. 9.3.4 of ACI 318-99 and ACI

318-99R, the modified value shall be used for the diaphragm connections.

9A.3.8: Where the design relies on friction in grouted joints for shear transfer across the joints,

shear friction resistance shall be provided by mechanical connectors or reinforcement.

9A.3.9: Cast-in place strips shall be permitted in the end or edge regions of precast components

as chords or collectors. These strips shall meet the requirements for topping slab diaphragms. 

The reinforcement in the strips shall conform to 21.7.8.2 and 21.7.8.3 of ACI 318-99 and ACI 

318-99R.

9A.3.10: In satisfying the compatibility requirement of Provisions Sec. 5.2.2.4.3, the additional

deformation that results from the diaphragm flexibility shall be considered. The assumed

flexural and shear stiffness properties of the elements that are part of the seismic-force-resisting

system shall not exceed one-half of the gross-section properties, unless a rational cracked-section

analysis is performed.

9A.3.11: Diaphragms shall have a quality assurance plan satisfying the requirements of 

Provisions Sec. 3.2.1.

9A.3.12: Ties to supporting members and bearing lengths shall satisfy the requirements for

design force and geometry characteristics specified for the connections in ACI 318, Sec. 21.2.1.7

as modified by Provisions Sec. 9.1.1.4.
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Chapter 10

COMPOSITE STEEL AND CONCRETE

STRUCTURE DESIGN REQUIREMENTS

10.1 REFERENCE DOCUMENTS: The design, construction, and quality of composite steel and

concrete components that resist seismic forces shall conform to the relevant requirements of the

following references except as modified by the provisions of this chapter.

ACI 318 American Concrete Institute (ACI), Building Code Requirements for Structural

Concrete, 1999, excluding Appendix A (Alternate Design Method) and Chapter

22 (Structural Plain Concrete) and making Appendix C (Alternative Load and

Strength Reduction Factors) mandatory

AISC/LRFD American Institute of Steel Construction (AISC), Load and Resistance Factor

Design Specification for Structural Steel Buildings (LRFD), 1999

AISC Seismic American Institute of Steel Construction (AISC), Seismic Provisions for

Structural Steel Buildings, including Supplement No. 1, July 1997, Parts I and II

AISI American Iron and Steel Institute (AISI), Specification for the Design of ColdFormed Steel Structural Members, 1996, including Supplement 2000, excluding

ASD provisions

10.1.1: When using ACI 318, Appendix A and Chapter 22 are excluded and Appendix C is

mandatory.

10.2 REQUIREMENTS: An R factor as set forth in Table 5.2.2 for the appropriate composite steel

and concrete system is permitted when the structure is designed and detailed in accordance with the

provisions of AISC Seismic, Part II.

In Seismic Design Categories B and above, the design of such systems shall conform to the

requirements of AISC Seismic, Part II. Composite structures are permitted in Seismic Design

Categories D and above, subject to the limitations in Table 5.2.2, when substantiating evidence is

provided to demonstrate that the proposed system will perform as intended by AISC Seismic Part II.. 

The substantiating evidence shall be subject to the approval of the authority having jurisdiction. Where

composite elements or connections are required to sustain inelastic deformations, the substantiating

evidence shall be based upon cyclic testing.
175

Chapter 11

MASONRY STRUCTURE DESIGN REQUIREMENTS

11.1 GENERAL:

11.1.1 Scope: The design and construction of reinforced and plain (unreinforced) masonry

components and systems and the materials used therein shall comply with the requirements of this

chapter.

11.1.2 Reference Documents: The designation and title of documents cited in this chapter are listed

in this section.

ACI 318 American Concrete Institute (ACI), Building Code Requirements for Structural

Concrete, excluding Appendix A, 1999

ACI 530 American Concrete Institute (ACI), Building Code Requirements for Masonry Structures,

ACI 530/ASCE 5/TMS 402, 1999

ACI 530.1 American Concrete Institute (ACI), Specifications for Masonry Structures, ACI

530.1/ASCE 6/TMS 602, 1999

Compliance with specific provisions of ACI 530 is mandatory where required by this chapter.

11.1.3 Definitions:

Anchor: Metal rod, wire, bolt, or strap that secures masonry to its structural support.

Area:

Gross Cross-Sectional Area: The area delineated by the out-to-out specified dimensions of

masonry in the plane under consideration.

Net Cross-Sectional Area: The area of masonry units, grout, and mortar crossed by the plane

under consideration based on out-to-out specified dimensions.

Bed Joint: The horizontal layer of mortar on which a masonry unit is laid.

Backing: The wall surface to which veneer is secured. The backing can be concrete, masonry, steel

framing, or wood framing.

Cleanout: An opening to the bottom of a grout space of sufficient size and spacing to allow removal of

debris.

Collar Joint: Vertical longitudinal joint between wythes of masonry or between masonry wythe and

back-up construction which is permitted to be filled with mortar or grout.
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176

Column: An isolated vertical member whose horizontal dimension measured at right angles to the

thickness does not exceed three times its thickness and whose height is at least three times its thickness.

Composite Masonry: Multiwythe masonry members acting with composite action.

Connector: A mechanical device (including anchors, wall ties, and fasteners) for joining two or more

pieces, parts, or members.

Cover: Distance between surface of reinforcing bar and edge of member.

Detailed Plain Masonry Shear Wall: A masonry shear wall designed to resist lateral forces

neglecting stresses in reinforcement and designed in accordance with Sec. 11.10.2.

Dimension:

Actual Dimension: The measured dimension of a designated item (e.g., a designated masonry unit

or wall).

Nominal Dimension: The specified dimension plus an allowance for the joints with which the units

are to be laid. Nominal dimensions are usually given in whole numbers. Thickness is given first,

followed by height and then length.

Specified Dimension: The dimension specified for the manufacture or construction of masonry,

masonry units, joints, or any other component of a structure. 

Effective Height: For braced members, the effective height is the clear height between lateral

supports and is used for calculating the slenderness ratio. The effective height for unbraced members is

calculated in accordance with engineering mechanics. 

Effective Period: Fundamental period of the structure based on cracked stiffness.

Glass Unit Masonry: Nonload-bearing masonry composed of glass units bonded by mortar.

Head Joint: Vertical mortar joint between masonry units within the wythe at the time the masonry

units are laid.

Intermediate Reinforced Masonry Shear Wall: A masonry shear wall designed to resist lateral

forces considering stresses in reinforcement and designed in accordance with Sec. 11.10.4.

Masonry Unit:

Hollow Masonry Unit: A masonry unit whose net cross-sectional area in every plane parallel to

the bearing surface is less than 75 percent of the gross cross-sectional area in the same plane.

Solid Masonry Unit: A masonry unit whose net cross-sectional area in every plane parallel to the

bearing surface is 75 percent or more of the gross cross-sectional area in the same plane.

Ordinary Plain Masonry Shear Wall: A masonry shear wall designed to resist lateral forces

neglecting stresses in reinforcement and designed in accordance with Sec. 11.10.1.
Masonry Structure Design Requirements

177

Ordinary Reinforced Masonry Shear Wall: A masonry shear wall designed to resist lateral forces

considering stresses in reinforcement and designed in accordance with Sec. 11.10.3.

Plain Masonry: Masonry in which the tensile resistance of the masonry is taken into consideration

and the effects of stresses in reinforcement are neglected.

Plastic Hinge: The zone in a structural member in which the yield moment is anticipated to be

exceeded under loading combinations that include earthquake.

Reinforced Masonry: Masonry construction in which reinforcement acts in conjunction with the

masonry to resist forces.

Running Bond: The placement of masonry units such that head joints in successive courses are

horizontally offset at least one-quarter the unit length.

Special Reinforced Masonry Shear Wall: A masonry shear wall designed to resist lateral forces

considering stresses in reinforcement and designed in accordance with Sec. 11.10.5.

Specified: Required by construction documents.

Specified Compressive Strength of Masonry, f : Required compressive strength (expressed as )

m

force per unit of net cross-sectional area) of the masonry. Whenever the quantity f is under the )

m

radical sign, the square root of numerical value only is intended and the result has units of pounds per

square inch (MPa).

Stack Bond: Stack bond is other than running bond. Usually, the placement of units is such that the

head joints in successive courses are aligned vertically.

Stirrup: Shear reinforcement in a beam or flexural member.

Strength:

Design Strength: Nominal strength multiplied by a strength reduction factor.

Nominal Strength: Strength of a member or cross section calculated in accordance with these

provisions before application of any strength reduction factors.

Required Strength: Strength of a member or cross section required to resist factored loads.

Tie:

Lateral Tie: Loop of reinforcing bar or wire enclosing longitudinal reinforcement.

Wall Tie: A connector that joins wythes of masonry walls together. 

Veneer:

Masonry Veneer: A masonry wythe that provides the exterior finish of a wall system and

transfers out-of-plane load directly to a backing but that is not considered to add load-resisting

capacity to the wall system.
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178

Anchored Veneer: Masonry veneer secured to and supported laterally by the backing through

anchors and supported vertically by the foundation or other structural support.

Adhered Veneer: Masonry veneer secured to and supported by the backing through adhesion. 

Wall: A vertical element with a horizontal length at least three times its thickness. 

Wall Frame: A moment resisting frame of masonry beams and masonry columns within a plane with

special reinforcement details and connections that provides resistance to lateral and gravity loads. 

Wythe: A continuous vertical section of a wall, one masonry unit in thickness. 

11.1.4 Notations:

Ab = cross-sectional area of an anchor bolt, in.2

 (mm2).

An = net cross-sectional area of masonry, in.2

 (mm2).

Ap = projected area on the masonry surface of a right circular cone for anchor bolt allowable

shear and tension calculations, in.2 (mm2).

As = cross-sectional area of reinforcement, in.2

 (mm2).

Av = cross-sectional area of shear reinforcement, in.2

 (mm)2

a = length of compressive stress block, in. (mm).

Ba = design axial strength of an anchor bolt, lb (N).

Bv = design shear strength of an anchor bolt, lb (N).

ba = factored axial force on an anchor bolt, lb (N).

bv = factored shear force on an anchor bolt, lb (N).

bw = web width, in. (mm).

Cd = deflection amplification factor as given in Table 5.2.2.

c = distance from the fiber of maximum compressive strain to the neutral axis, in. (mm).

db = diameter of reinforcement, in. (mm).

dbb = diameter of the largest beam longitudinal reinforcing bar passing through, or anchored in,

the wall frame beam-column intersection, in. (mm).

dbp = diameter of the largest column (pier) longitudinal reinforcing bar passing through, or

anchored in, the wall frame beam-column intersection, in. (mm).

dv = length of member in direction of shear force, in. (mm).

Em = modulus of elasticity of masonry, psi (MPa).

Es = modulus of elasticity of reinforcement, psi (MPa).
Masonry Structure Design Requirements

179

Ev = modulus of rigidity of masonry, psi (MPa).

fg = specified compressive strength of grout, psi (MPa).

f = specified compressive strength of masonry at the age of 28 days, unless a different age is )

m

specified, psi (MPa).

fr = modulus of rupture of masonry, psi (MPa).

fy = specified yield strength of the reinforcement or the anchor bolt as applicable, psi (MPa).

h = effective height of a column, pilaster or wall, in. (mm).

hn = height of structure above the base level to level n, ft. (m).

hb = beam depth in the plane of the wall frame, in. (mm).

hc = cross-sectional dimension of grouted core of wall frame member measured center to center

of confining reinforcement, in. (mm).

hp = pier depth in the plane of the wall frame, in. (mm).

Icr = moment of inertia of the cracked section, in.4

 (mm4).

Ieff = effective moment of inertia, in.4

 (mm4).

In = moment of inertia of the net cross-sectional area of a member, in.4

 (mm4).

Lc = length of coupling beam between coupled shear walls, in. (mm). 

lb = effective embedment length of anchor bolt, in. (mm).

lbe = anchor bolt edge distance, in. (mm).

ld = development length, in. (mm).

ldh = equivalent development length for a standard hook, in. (mm).

lld = minimum lap splice length, in. (mm).

M = moment on a masonry section due to unfactored load, in.-lb (N-mm).

Ma = maximum moment in member due to the applied loading for which deflection is computed,

in.-lb (N-mm).

Mcr = cracking moment strength of the masonry, in.-lb (N-mm).

Md = design moment strength, in.-lb (N-mm).

Mu = required flexural strength due to factored loads, in.-lb (N-mm).

M1,M2 = nominal moment strength at the ends of the coupling beam, in.-lb (N-mm).

Nv = force acting normal to shear surface, lb (N).
2000 Provisions Chapter 11

180

P = axial force on a masonry section due to unfactored loads, lb (N).

Pn = nominal axial load strength, lb (N).

Pu = required axial strength due to factored loads, lb (N).

r = radius of gyration, in. (mm).

S = section modulus based on net cross-sectional area of a wall, in.3

 (mm3).

s = spacing of lateral reinforcement in wall frame members, in. (mm).

t = specified wall thickness dimension or least lateral dimension of a column, in. (mm).

V = shear on a masonry section due to unfactored loads, lb (N).

Vg = unfactored shear force due to gravity loads, lb (N).

Vm = shear strength provided by masonry, lb (N).

Vn = nominal shear strength, lb (N).

Vs = shear strength provided by shear reinforcement, lb (N).

Vu = required shear strength due to factored loads, lb (N).

) = design story drift as determined in Sec. 5.3.7.1, in. (mm).

)a = allowable story drift as specified in Sec. 5.2.8, in. (mm).

*max = the maximum displacement at level x, in. (mm).

D = ratio of the area of reinforcement to the net cross-sectional area of masonry in a plane

perpendicular to the reinforcement.

Db = reinforcement ratio producing balanced strain conditions.

,mu = maximum usable compressive strain of masonry, in./in. (mm/mm).

N = strength reduction factor.

11.2 CONSTRUCTION REQUIREMENTS:

11.2.1 General: Masonry shall be constructed in accordance with the requirements of ACI 530.1.

Materials shall conform to the requirements of the standards referenced in ACI 530.1.

11.2.2 Quality Assurance: Inspection and testing of masonry materials and construction shall

comply with the requirements of Chapter 3.

11.3 GENERAL REQUIREMENTS:

11.3.1 Scope: Masonry structures and components of masonry structures shall be designed in

accordance with the requirements of reinforced masonry design, plain (unreinforced) masonry design,

empirical design or design for architectural components of masonry subject to the limitations of this
Masonry Structure Design Requirements

181

section. All masonry walls, unless isolated on three sides from in-plane motion from the basic structural

system, shall be designed as shear walls. For design of glass-unit masonry and masonry veneer, see

Sec. 11.12

11.3.2 Empirical Masonry Design: The requirements of Chapter 5 of ACI 530.1 shall apply to the

empirical design of masonry.

11.3.3 Plain (Unreinforced) Masonry Design:

11.3.3.1: In the design of plain (unreinforced) masonry members, the flexural tensile strength of

masonry units, mortar and grout in resisting design loads shall be permitted.

11.3.3.2: In the design of plain masonry members, stresses in reinforcement shall not be considered

effective in resisting design loads.

11.3.3.3: Plain masonry members shall be designed to remain uncracked.

11.3.4 Reinforced Masonry Design: In the design of reinforced masonry members, stresses in

reinforcement shall be considered effective in resisting design loads.

11.3.5 Seismic Design Category A: Structures assigned to Seismic Design Category A shall

comply with either the requirements of Sec. 11.3.2 (empirical masonry design), Sec. 11.3.3 (plain

masonry design), or Sec. 11.3.4 (reinforced masonry design).

11.3.6 Seismic Design Category B: Structures assigned to Seismic Design Category B shall

conform to all the requirements for Seismic Design Category A and the lateral-force-resisting system

shall be designed in accordance with Sec. 11.3.3 or Sec. 11.3.4.

11.3.7 Seismic Design Category C: Structures assigned to Seismic Design Category C shall

conform to the requirements for Seismic Design Category B and to the additional requirements of this

section.

11.3.7.1 Material Requirements: Structural clay load-bearing wall tile shall not be used as part of

the basic structural system.

11.3.7.2 Masonry Shear Walls: Masonry shear walls shall comply with the requirements for

detailed plain masonry shear walls (Sec. 11.10.2), intermediate reinforced masonry shear walls

(Sec. 11.10.4), or special reinforced masonry shear walls (Sec. 11.10.5).

11.3.7.3 Minimum Wall Reinforcement: Vertical reinforcement of at least 0.20 in.2 (129 mm2) in

cross-sectional area shall be provided continuously from support to support at each corner, at each

side of each opening, at the ends of walls, and at a maximum spacing of 4 feet (1219 mm) apart

horizontally throughout the walls. Horizontal reinforcement not less than 0.20 in.2 (129 mm2) in cross

section shall be provided as follows:

a. At the bottom and top of wall openings extending not less than 24 in. (610 mm) nor less than 40

bar diameters past the opening,

b. Continuously at structurally connected roof and floor levels and at the top of walls,
2000 Provisions Chapter 11

182

c. At the bottom of load-bearing walls or in the top of foundations when doweled to the wall, and

d. At maximum spacing of 120 in. (3048 mm) unless uniformly distributed joint reinforcement is

provided.

Reinforcement at the top and bottom of openings, when used in determining the maximum spacing

specified in Item d above, shall be continuous in the wall.

11.3.7.4 Stack Bond Construction: Where stack bond is used, the minimum horizontal

reinforcement shall be 0.0007 times the gross cross-sectional area of the wall. This requirement shall

be satisfied with uniformly distributed joint reinforcement or with horizontal reinforcement spaced not

over 48 in. (1219 mm) and fully embedded in grout or mortar.

11.3.7.5 Multiple Wythe Walls Not Acting Compositely: At least one wythe of a cavity wall shall

be reinforced masonry designed in accordance with Sec. 11.3.4. The other wythe shall be reinforced

with a minimum of one W1.7 wire per 4-in. (102 mm) nominal wythe thickness and spaced at intervals

not exceeding 16 in. (406 mm). The wythes shall be tied in accordance with ACI 530, Sec. 5.8.3.2.

11.3.7.6 Walls Separated from the Basic Structural System: Masonry walls, laterally supported

perpendicular to their own plane but otherwise structurally isolated on three sides from the basic

structural system, shall have minimum horizontal reinforcement of 0.0007 times the gross crosssectional area of the wall. This requirement shall be satisfied with uniformly distributed joint

reinforcement or with horizontal reinforcement spaced not over 48 in. (1219 mm) and fully embedded

in grout or mortar. Architectural components of masonry shall be exempt from this reinforcement

requirement.

11.3.7.7 Connections to Masonry Columns: Structural members framing into or supported by

masonry columns shall be anchored thereto. Anchor bolts located in the tops of columns shall be set

entirely within the reinforcing cage composed of column bars and lateral ties. A minimum of two No. 4

(13 mm) lateral ties shall be provided in the top 5 inches (127 mm) of the column.

11.3.8 Seismic Design Category D: Structures assigned to Seismic Design Category D shall

conform to all of the requirements for Seismic Design Category C and the additional requirements of

this section.

11.3.8.1 Material Requirements: Neither Type N mortar nor masonry cement shall be used as part

of the basic structural system.

11.3.8.2 Masonry Shear Walls: Masonry shear walls shall comply with the requirements for

special reinforced masonry shear walls (Sec. 11.10.5) 

11.3.8.3 Minimum Wall Reinforcement: All walls shall be reinforced with both vertical and

horizontal reinforcement. The sum of the areas of horizontal and vertical reinforcement shall be at least

0.002 times the gross cross-sectional area of the wall and the minimum area of reinforcement in each

direction shall not be less than 0.0007 times the gross cross-sectional area of the wall. The spacing of

reinforcement shall not exceed 48 in. (1219 mm). Except for joint reinforcement, the bar size shall not

be less than a No. 3 (10-mm diameter). Reinforcement shall be continuous around wall corners and
Masonry Structure Design Requirements

183

through intersections, unless the intersecting walls are separated. Only horizontal reinforcement that is

continuous in the wall or element shall be included in computing the area of horizontal reinforcement. 

Reinforcement spliced in accordance with Sec. 11.4.5.6 shall be considered as continuous reinforcement. Architectural components of masonry shall be exempt from this reinforcement requirement.

11.3.8.4 Stack Bond Construction: Where masonry is laid in stack bond, the minimum amount of

horizontal reinforcement shall be 0.0015 times the gross cross-sectional area of the wall. If open-end

units are used and grouted solid, the minimum amount of horizontal reinforcement shall be 0.0007 times

the gross cross-sectional area of the wall. The maximum spacing of horizontal reinforcement shall not

exceed 24 in. (610 mm). Architectural components of masonry shall be exempt from these

requirements.

11.3.8.5 Minimum Wall Thickness: The nominal thickness of masonry bearing walls shall not be

less than 6 in. (152 mm). Nominal 4-in. (102 mm) thick load-bearing reinforced hollow clay unit

masonry walls with a maximum unsupported height or length to thickness ratio of 27 are permitted to

be used provided the net area unit strength exceeds 8,000 psi (55 MPa), units are laid in running

bond, bar sizes do not exceed No. 4 (13 mm) with not more than two bars or one splice in a cell, and

joints are not raked.

11.3.8.6 Minimum Column Reinforcement: Lateral ties in columns shall be spaced not more than

8 in. (203 mm) on center for the full height of the column. Lateral ties shall be embedded in grout and

shall be No. 3 (10 mm) or larger.

11.3.8.7 Minimum Column Dimension: The nominal dimensions of a masonry column shall not be

less than 12 in. (305 mm).

11.3.8.8: Separation Joints: Where concrete abuts structural masonry and the joint between the

materials is not designed as a separation joint, the concrete shall be roughened so that the average

height of aggregate exposure is 1/8 in. (3 mm) and shall be bonded to the masonry in accordance with

these requirements as if it were masonry. Vertical joints not intended to act as separation joints shall be

crossed by horizontal reinforcement as required by Sec. 11.3.8.3.

11.3.9 Seismic Design Categories E and F: Structures assigned to Seismic Design Categories E

and F shall conform to the requirements of Seismic Design Category D and to the additional

requirements and limitations of this section.

11.3.9.1 Material Requirements: Construction procedures or admixtures shall be used to minimize

shrinkage of grout and to maximize bond between reinforcement, grout, and units.

11.3.9.2 Masonry Shear Walls: Masonry shear walls shall comply with the requirements for special

reinforced masonry shear walls (Sec. 11.10.5).

11.3.9.3 Stack Bond Construction: Masonry laid in stack bond shall conform to the following

requirements:

11.3.9.3.1: For masonry that is not part of the basic structural system, the minimum ratio of horizontal

reinforcement shall be 0.0015 and the maximum spacing of horizontal reinforcement shall be 24 in. (610
2000 Provisions Chapter 11

184

Em' 750f

)

m

(11.3.10.2)

mm). For masonry that is part of the basic structural system, the minimum ratio of horizontal

reinforcement shall be 0.0025 and the maximum spacing of horizontal reinforcement shall be 16 in. (406

mm). For the purpose of calculating this ratio, joint reinforcement shall not be considered.

11.3.9.3.2: Reinforced hollow unit construction shall be grouted solid and all head joints shall be

made solid by the use of open end units.

11.3.10 Properties of Materials:

11.3.10.1 Steel Reinforcement Modulus of Elasticity: Unless otherwise determined by test, steel

reinforcement modulus of elasticity, Es, shall be taken to be 29,000,000 psi (200,000 MPa).

11.3.10.2 Masonry Modulus of Elasticity: The modulus of elasticity of masonry. Em, shall be

determined in accordance with Eq. 11.3.10.2 or shall be based on the modulus of elasticity determined

by prism test and taken between 0.05 and 0.33 times the masonry prism strength:

where Em = modulus of elasticity of masonry (psi) and f = specified compressive strength of )

m

masonry, psi. The metric equivalent of Eq. 11.3.10.2 is the same except that Em and f are in MPa. )

m

11.3.10.3: The modulus of rigidity of masonry, Ev, shall be taken equal to 0.4 times the modulus of

elasticity of masonry, Em.

11.3.10.4 Masonry Compressive Strength:

11.3.10.4.1: The specified compressive strength of masonry, f , shall equal or exceed 1,500 psi (10 )

m

MPa).

11.3.10.4.2: The value of f used to determine nominal strength values in this chapter shall not )

m

exceed 4,000 psi (28 MPa) for concrete masonry and shall not exceed 6,000 psi (41 MPa) for clay

masonry.

11.3.10.5 Modulus of Rupture:

11.3.10.5.1 Out-of-Plane Bending: The modulus of rupture, fr, for masonry elements subjected to

out-of-plane bending shall be taken from Table 11.3.10.5.1.

TABLE 11.3.10.5.1 Modulus of Rupture for Out-of-Plane Bending (fr)
Masonry Structure Design Requirements

185

Masonry type

Mortar types, psi (MPa)

Portland cement/lime

Masonry cement and

air-entrained Portland

cement/lime

M or S N M or S N

Normal to bed joints

 Solid units

 Hollow unitsa

Ungrouted

Fully grouted

80 (0.55)

50 (0.34)

136 (0.94)

60 (0.41)

38 (0.26)

116 (0.80)

48 (0.33)

30 (0.21)

82 (0.57)

30 (0.21)

18 (0.12)

52 (0.36)

Parallel to bed joints in running bond

 Solid units

 Hollow units

Ungrouted and partially grouted

Fully grouted (running bond masonry)

Parallel to bed joints in stack bond:

160 (1.10)

100 (0.69)

160 (1.10)

0

120 (0.83)

76 (0.52)

120 (0.83)

0

96 (0.66)

60 (0.41)

96 (0.66)

0

60 (0.41)

38 (0.26)

60 (0.41)

0

 a For partially grouted masonry, modulus of rupture values shall be determined on the basis of linear interpolation between

hollow units that are fully grouted and hollow units that are ungrouted based on amount (percentage) of grouting.

11.3.10.5.2 In-Plane Bending: The modulus of rupture, fr, for masonry elements subjected to inplane forces shall be taken as 250 psi (1.7MPa). For grouted stack bond masonry, tension parallel to

the bed joints for in-plane bending shall be assumed to be resisted only by the continuous grout core

section.

11.3.10.6 Reinforcement Strength: Masonry design shall be based on a reinforcement strength

equal to the specified yield strength of reinforcement, fy, that shall not exceed 60,000 psi (400 MPa).

11.3.11 Section Properties:

11.3.11.1: Member strength shall be computed using section properties based on the minimum net

bedded and grouted cores cross-sectional area of the member under consideration.

11.3.11.2: Section properties shall be based on specified dimensions.

11.3.12 Headed and Bent-Bar Anchor Bolts: All bolts shall be grouted in place with at least 1 in.

(25 mm) grout between the bolt and masonry, except that 1/4-inch (6.4 mm) bolts may be placed in

bed joints that are at least 1/2 in. (12.7 mm) in thickness.
2000 Provisions Chapter 11

186

Ba' 4 A

p

f

)

m

(11.3.12.1-1)

Ba' Abf

y

(11.3.12.1-2)

A

p

' R

2

be (11.3.12.1.1-2)

A

p

' R

2

b

(11.3.12.1.1-1)

11.3.12.1: The design axial strength, Ba, for headed anchor bolts embedded in masonry shall be the

lesser of Eq. 11.3.12.1-1 (strength governed by masonry breakout) or Eq. 11.3.12.1-2 (strength

governed by steel):

where:

Ba = design axial strength of the headed anchor bolt, lb;

N = strength reduction factor where N = 0.5 for Eq. 11.3.12.1-1 and N = 0.9 for Eq.

11.3.12.1-2;

Ap = projected area on the masonry surface of a right circular cone, in.2;

Ab = effective tensile stress area of the headed anchor bolt, in.2;

f = specified compressive strength of the masonry, psi; and )

m

fy = specified yield strength of the headed anchor bolt, psi.

The metric equivalent of Eq. 11.3.12.1-1 is where Ba is in N, Ap is in mm2 B ,

a

' (0.33A

p

f

)

m

)

and is in MPa. The metric equivalent of Eq. 11.3.12.1-2 is the same except that Ba is in N, Abf is in )

m

mm2, and fy is in MPa.

11.3.12.1.1: The area Ap in Eq. 11.3.12.1-1 shall be the lesser of Eq. 11.3.12.1.1-1 or Eq.

11.3.12.1.1-2:

where:

Ap = projected area on the masonry surface of a right circular cone, in.2;
Masonry Structure Design Requirements

187

Ba' 4 A

p

f

)

m

(11.3.12.2-1)

Ba' 1.5 f

)

m

edb% 200 l

b

% e % dbdb

(11.3.12.2-3)

Ba' Abf

y (11.3.12.2-2)

lb = effective embedment length of the headed anchor bolt, in.; and 

lbe = anchor bolt edge distance, in..

The metric equivalents of Eq. 11.3.12.1.1-1 and Eq. 11.3.12.1.1-2 are the same except that Ap is in

mm2 and lb and lbe are in mm.

Where the projected areas, Ap, of adjacent headed anchor bolts overlap, the projected area, Ap, of

each bolt shall be reduced by one-half of the overlapping area. That portion of the projected area

falling in an open cell or core shall be deducted from the value of Ap calculated using Eq. 11.3.12.1.1-1

or Eq. 11.3.12.1.1-2, whichever is less.

11.3.12.1.2: The effective embedment length of a headed bolt, lb, shall be the length of embedment

measured perpendicular from the surface of the masonry to the head of the anchor bolt.

11.3.12.1.3: The minimum effective embedment length of headed anchor bolts resisting axial forces

shall be 4 bolt diameters or 2 in. (51 mm), whichever is greater.

11.3.12.2: The design axial strength, Ba,,for bent-bar anchor bolts (J- or L-bolts) embedded in

masonry shall be the least of Eq. 11.3.12.2-1 (strength governed by masonry breakout), Eq.

11.3.12.2-2 (strength governed by steel), or Eq. 11.3.12.2-3 (strength governed by anchor pullout):

where:

Ba = design axial strength of the bent-bar anchor bolt, lb;

N = strength reduction factor where N = 0.5 for Eq. 11.3.12.2-1, N = 0.9 for Eq. 11.3.12.2-2,

and N = 0.65 for Eq. 11.3.12.2-3;

Ap = projected area on the masonry surface of a right circular cone, in.2;

Ab = effective tensile stress area of the bent-bar anchor bolt, in.2;

e = projected leg extension of bent-bar anchor bolt, measured from inside edge of anchor at

bend to farthest point of anchor in the plane of the hook, in.; shall not be taken larger than

2db for use in Eq. 11.3.12.2-3.
2000 Provisions Chapter 11

188

Ba' 0.33 A

p

f

)

m

Ba' 1.5 f

)

m

edb% 2.05 (l

b

% e % db)db

A

p

' l

2

b

(11.3.12.2.1-1)

A

p

' l

2

be (11.3.12.2.1-2)

db = nominal diameter of bent-bar anchor bolt, in.

lb = effective embedment length of bent-bar anchor bolt, in.

f = specified compressive strength of the masonry, psi; )

m

fy = specified yield strength of the bent-bar anchor bolt, psi.

The metric equivalent of Eq. 11.3.12.2-1 is:

where Ba is in N, Ap is in mm2, and f is in MPa. The metric equivalent of Eq. 11.3.12.2-2 is the same )

m

except that Ba is in N, Ab is in mm2, and fy is in MPa. The metric equivalent of Eq. 11.3.12.2-3 is:

where Ba is in N, e and db are in mm, and f is in MPa. )

m

The second term in Eq. 11.3.12.2-3 shall be included only if continuous special inspection is provided

during placement per Sec. 11.3.5.2.

11.3.12.2.1: The area Ap in Eq. 11.3.12.2-1 shall be the lesser of Eq.11.3.12.2.1-1 or Eq.

11.3.12.2.1-2:

where:

Ap = projected area on the masonry surface of a right circular cone, in.2;

lb = effective embedment length of the bent-bar anchor bolt, in.; and 

lbe = anchor bolt edge distance, in..
Masonry Structure Design Requirements

189

Bv' 1750

4

f

)

m

Ab

(11.3.12.3-1)

Bv' 0.6 Abf

y (11.3.12.3-2)

The metric equivalents of Eq. 11.3.12.2.1-1 and Eq. 11.3.12.2.1-2 are the same except that Ap is in

mm2 and lb and lbe are in mm.

Where the projected areas, Ap, of adjacent bent-bar anchor bolts overlap, the projected area, Ap, of

each bolt shall be reduced by one-half of the overlapping area. That portion of the projected area

falling in an open cell or core shall be deducted from the value of Ap calculated using Eq. 11.3.12.2.1-1

or Eq. 11.3.12.2.1-2, whichever is less.

11.3.12.2.2: The effective embedment of a bent-bar anchor bolt, lb , shall be the length of embedment

measured perpendicular from the surface of the masonry to the bearing surface of the bent end, minus

one anchor bolt diameter.

11.3.12.2.3: The minimum effective embedment length of bent-bar anchor bolts resisting axial forces

shall be 4 bolt diameters or 2 in. (51 mm), whichever is greater.

11.3.12.3: Where the anchor bolt edge distance, lbe, equals or exceeds 12 bolt diameters, the design

shear strength, Bv, shall be the lesser of the values given by Eq. 11.3.12.3-1 (strength governed by

masonry) or Eq. 11.3.12.3-2 (strength governed by steel):

where:

N = strength reduction factor where N = 0.5 for Eq. 11.3.12.3-1 and N = 0.9 for Eq.

11.3.12.3-2;

Ab = effective tensile stress area of the anchor bolt, in.2;

f = specified compressive strength of the masonry, psi, and )

m

fy = specified yield strength of anchor bolt as applicable, psi.

The metric equivalent of Eq. 11.3.12.3-1 is where Ab is in mm2 and and f B y

v

' 5350

4

f

)

m

Ab

f

)

m

are in MPa. The metric equivalent of Eq. 11.3.12.3-2 is the same as that above except that Ab is in

mm2 and fy is in MPa.

Where the anchor bolt edge distance, lbe, is less than 12 bolt diameters, the value of Bv in Eq.

11.3.12.3-1 shall be reduced by linear interpolation to zero at an lbe distance of 1 in. (25 mm).
2000 Provisions Chapter 11

190

ba

Ba

%

bv

Bv

# 1 (11.3.12.4)

11.3.12.4: Anchor bolts subjected to combined shear and tension shall be designed to satisfy Eq.

11.3.12.4:

where:

ba = design axial force on the anchor bolt, lb (N);

Ba = design axial strength of the anchor bolt, lb (N); 

bv = design shear force on the anchor bolt, lb (N); and 

Bv = design shear strength of the anchor bolt, lb (N).

11.4 DETAILS OF REINFORCEMENT: 

11.4.1 General:

11.4.1.1: Details of reinforcement shall be shown on the contract documents.

11.4.1.2: Reinforcing bars shall be embedded in grout. 

11.4.2 Size of Reinforcement:

11.4.2.1: Reinforcing bars used in masonry shall not be larger than a No. 9 bar (29 mm diameter).

The bar diameter shall not exceed one-eighth of the nominal wall thickness and shall not exceed onequarter of the least clear dimension of the cell, course, or collar joint in which it is placed. The area of

reinforcing bars placed in a cell, or in a course, of hollow unit construction shall not exceed 4 percent

of the cell area.

11.4.2.2: Longitudinal and cross wire joint reinforcement shall be a minimum W1.1 (0.011 mm2) and

shall not exceed one-half the joint thickness.

11.4.3 Placement Limits for Reinforcement:

11.4.3.1: The clear distance between parallel reinforcing bars shall not be less than the nominal

diameter of the bars nor less than 1 in. (25 mm).

11.4.3.2: In columns and pilasters, the clear distance between vertical reinforcing bars shall not be less

than one and one-half times the nominal bar diameter, nor less than 1-1/2 in. (38 mm).

11.4.3.3: The clear distance limitations between reinforcing bars also shall apply to the clear distance

between a contact lap splice and adjacent splices or bars.

11.4.3.4: Reinforcing bars shall not be bundled.

11.4.4 Cover for Reinforcement:
Masonry Structure Design Requirements

191

11.4.4.1: Reinforcing bars shall have a minimum thickness of masonry and grout cover not less than 2-

1/2 db nor less than the following:

a. Where the masonry face is exposed to earth or weather, 2 in. (51 mm) for bars larger than No. 5

(16 mm) and 1-1/2 in. (38 mm) for No. 5 (16 mm) bar or smaller.

b. Where the masonry is not exposed to earth or weather, 1-1/2 in. (38 mm).

11.4.4.2: The minimum grout thickness between reinforcing bars and masonry units shall be 1/4 in. (6

mm) for fine grout or 1/2 in. (12 mm) for coarse grout.

11.4.4.3: Longitudinal wires of joint reinforcement shall be fully embedded in mortar or grout with a

minimum cover of 1/2 in. (13 mm) when exposed to earth or weather and 3/8 in. (10 mm) when not

exposed to earth or weather. Joint reinforcement in masonry exposed to earth or weather shall be

corrosion resistant or protected from corrosion by coating. 

11.4.4.4: Wall ties, anchors, and inserts, except anchor bolts not exposed to the weather or moisture,

shall be protected from corrosion.

11.4.5 Development of Reinforcement:

11.4.5.1 General: The calculated tension or compression in the reinforcement where masonry

reinforcement is anchored in concrete shall be developed in the concrete by embedment length, hook or

mechanical device, or a combination thereof. Hooks shall be used only to develop bars in tension.

11.4.5.2 Development of Reinforcing Bars and Wires in Tension: The development length, ld, of

reinforcing bars and wire shall be determined by Eq. 11.4.5.2 but shall not be less than 12 in. (305 mm)

for bars and 6 in. (152 mm) for wire:

(11.4.5.2) d

b y

m

l

d f

K f

=





























1 013 2

f

. g

'

where:

ld = development length, in.;

f = strength reduction factor as given in Table 11.5.3;

db = diameter of the reinforcement, in.;

K = the least of the clear spacing between adjacent reinforcement, the cover of masonry and

grout to the reinforcement, or 5 times db, in.;

 = specified compressive strength of masonry, psi;

m

f ′

fy = specified yield strength of the reinforcement, psi; and
2000 Provisions Chapter 11

192

l

dh ' 13db (11.4.5.3.2)

= 1.0 for No. 3 through No. 5 reinforcing bars,

1.4 for No. 6 through No. 7 reinforcing bars, or

1.5 for No. 8 through No. 9 reinforcing bars.

The metric equivalent of Eq. 11.4.5.2 is

(11.4.5.2-1) d

b y

m

l

d f

K f

=





























1 157 2

f

. g

'

where ld, K, and db are in mm and fy and f’m are in MPa.

11.4.5.3 Standard Hooks:

11.4.5.3.1: The term standard hook as used in the Provisions shall mean one of the following:

11.4.5.3.1.1: A 180-degree turn plus extension of at least 4 bar diameters but not less than 2-1/2 in.

(64 mm) at free end of bar.

11.4.5.3.1.2: A 90-degree turn plus extension of at least 12 bar diameters at free end of bar.

11.4.5.3.1.3: For stirrup and tie anchorage only, either a 135-degree or a 180-degree turn plus an

extension of at least 6 bar diameters at the free end of the bar.

11.4.5.3.2: The equivalent embedment length for standard hooks in tension, ldh, shall be as follows:

where db = diameter of the reinforcement, in. The metric equivalent of Eq. 11.4.5.3.2 is the same

except that db is in mm.

11.4.5.3.3: The effect of hooks for bars in compression shall be neglected in design computations.

11.4.5.4 Minimum Bend Diameter for Reinforcing Bars:

11.4.5.4.1: The diameter of bend measured on the inside of the bar, other than for stirrups and ties,

shall not be less than values specified in Table 11.4.5.4.1.

TABLE 11.4.5.4.1 Minimum Diameters of Bend

Bar Size Grade Minimum Bend

No. 3 (10 mm) through No. 7 (22 mm)

No. 3 (10 mm) through No. 8 (25 mm)

No. 9 (29 mm)

40

50 or 60

50 or 60

 5 bar diameters

 6 bar diameters

 8 bar diameters
Masonry Structure Design Requirements

193

11.4.5.5 Development of Shear Reinforcement:

11.4.5.5.1: Shear reinforcement shall extend the depth of the member less cover distances. 

11.4.5.5.2: The ends of single leg or U-stirrups shall be anchored by one of the following means:

a. A standard hook plus an effective embedment of 0.5 times the development length, ld

. The

effective embedment of a stirrup leg shall be taken as the distance between the mid-depth of the

member and the start of the hook (point of tangency).

b. For No. 5 (16 mm) bar and D31 wire and smaller, bending around longitudinal reinforcement

through at least 135 degrees plus an embedment of ld/3 . The ld/3 embedment of a stirrup leg shall

be taken as the distance between mid-depth of the member and the start of the hook (point of

tangency).

c. Between the anchored ends, each bend in the continuous portion of a transverse U-stirrup shall

enclose a longitudinal bar.

11.4.5.5.3: Except at wall intersections, the end of a reinforcing bar needed to satisfy shear strength

requirements in accordance with Sec. 11.7.3.3 shall be bent around the edge vertical reinforcing bar

with a 180-degree hook. At wall intersections, reinforcing bars used as shear reinforcement shall be

bent around the edge vertical bar with a 90-degree standard hook and shall extend horizontally into the

intersecting wall.

11.4.5.6 Splices of Reinforcement: Lap splices, welded splices, or mechanical connections shall be

in accordance with the provisions of this section. 

11.4.5.6.1 Lap Splices: Lap splices shall not be used in plastic hinge zones. The length of the plastic

hinge zone shall be taken as at least 0.15 times the distance between the point of zero moment and the

point of maximum moment.

11.4.5.6.1.1: The minimum length of lap, lld, for bars in tension or compression shall be equal to the

development length, ld, as determined by Eq. 11.4.5.2 but shall not be less than 12 in. (305 mm) for

bars and 6 in (152 mm) for wire.

11.4.5.6.1.2: Bars spliced by non-contact lap splices shall not be spaced transversely farther apart

than one-fifth the required length of lap or more than 8 in. (203 mm).

11.4.5.6.2 Welded Splices: A welded splice shall be capable of developing in tension 125 percent of

the specified yield strength, fy, of the bar. Welded splices shall only be permitted for ASTM A706 steel

reinforcement. Welded splices shall not be permitted in plastic hinge zones of intermediate or special

reinforced walls or special moment frames of masonry.

11.4.5.6.3 Mechanical Splices: Mechanical splices shall be classified as Type 1 or Type 2 according

to Sec. 21.2.6.1 of ACI 318.
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194

Type 1 mechanical splices shall not be used within a plastic hinge zone or within a beam-column joint of

intermediate or special reinforced masonry shear walls or special moment frames. Type 2 mechanical

splices shall be permitted in any location within a member.

11.5 STRENGTH AND DEFORMATION REQUIREMENTS:

11.5.1 General: Masonry structures and masonry members shall be designed to have strength at all

sections at least equal to the required strength calculated for the factored loads in such combinations

as are stipulated in these provisions.

11.5.2 Required Strength: The required strength shall be determined in accordance with Chapters 

5 and 6.

11.5.3 Design Strength: Design strength provided by a member and its connections to other

members and its cross sections in terms of flexure, axial load, and shear shall be taken as the nominal

strength multiplied by a strength reduction factor, N, as specified in Table 11.5.3.

TABLE 11.5.3 Strength Reduction Factor N

Axial load, flexure, and

combinations of axial load

and flexure 

Reinforced masonry

Plain masonry 

N = 0.85

N = 0.60

Shear Reinforced masonry N = 0.80

Shear Plain masonry N = 0.80

Reinforcement development length and splices N = 0.80

Anchor bolt strength as governed by steel N = 0.90

Anchor bolt strength as governed by masonry N = 0.50

Bearing N = 0.60

11.5.4 Deformation Requirements:

11.5.4.1: Masonry structures shall be designed so the design story drift, ), does not exceed the

allowable story drift, )a, obtained from Table 5.2.8.

11.5.4.1.1: Cantilever shear walls shall be proportioned such that the maximum displacement, *max, at

Level n does not exceed 0.01hn.

11.5.4.2: Deflection calculations for plain masonry members shall be based on uncracked section

properties.

11.5.4.3: Deflection calculations for reinforced masonry members shall be based on an effective

moment of inertia in accordance with the following:
Masonry Structure Design Requirements

195

I

eff ' In

Mcr

Ma

3

% I

cr

1&

Mcr

Ma

3

< I

n

(11.5.4.3)

where:

Mcr = Sfr ,

Mcr = cracking moment strength of the masonry, in.-lb;

Ma = maximum moment in the member at the stage deflection is computed, in.-lb;

Icr = moment of inertia of the cracked section, in.4;

In = moment of inertia of the net cross-sectional area of the member, in.4;

S = uncracked section modulus of the wall, in.3; and

fr = modulus of rupture of masonry, psi.

The metric equivalent of Eq. 11.5.4.3 is the same except that Mcr and Ma are in (N-mm), Icr and In are

in mm4, S is in mm3, and fr is in MPa.

11.5.4.4: The calculated deflection shall be multiplied by Cd for determining drift.

11.6 FLEXURE AND AXIAL LOADS:

11.6.1 Scope: This section shall apply to the design of masonry members subject to flexure or axial

loads or to combined flexure and axial loads.

11.6.2 Design Requirements of Reinforced Masonry Members:

11.6.2.1: Strength design of members for flexure and axial loads shall be in accordance with principles

of engineering mechanics and in accordance with the following design assumptions:

a. Strain in reinforcement and masonry shall be assumed directly proportional to the distance from the

neutral axis, except for deep flexural members with overall depth to clear span ratio greater than

2/5 for continuous span members and 4/5 for simple span members where a nonlinear distribution

of strain shall be considered.

b. Maximum usable strain, ,mu, at the extreme masonry compression fiber shall be assumed equal to

0.0025 in./in. for concrete masonry and 0.0035 in./in. for clay-unit masonry.

c. Stress in reinforcement below the specified yield strength, fy

, shall be taken as the modulus of

elasticity, Es, times the steel strain. For strains greater than those corresponding to the specified

yield strength, fy, the stress in the reinforcement shall be considered independent of strain and equal

to the specified yield strength, fy,
2000 Provisions Chapter 11

196

d. Tensile strength of masonry shall be neglected in calculating the flexural strength of a reinforced

masonry cross section.

e. Flexural compression in masonry shall be assumed to be an equivalent rectangular stress block. 

Masonry stress of 0.80 times the specified compressive strength, f shall be assumed to be )

m

uniformly distributed over an equivalent compression zone bounded by edges of the cross section

and a straight line located parallel to the neutral axis at a distance a = 0.80c from the fiber of

maximum compressive strain. For out of plane bending, the width of the equivalent stress block

shall not be taken greater than 6 times the nominal thickness of the masonry wall or the spacing

between reinforcement, whichever is less. For in-plane bending of flanged walls, the same

dimension shall apply.

11.6.2.2: For structures designed using an R value greater than 1.5, the ratio of reinforcement, D, shall

not exceed the lesser ratio as calculated with either of the following two critical strain conditions:

a. For walls subjected to in-plane forces, for columns, and for beams, the critical strain

condition corresponds to a strain in the extreme tension reinforcement equal to 5 times the

strain associated with the reinforcement yield stress, fy.

b. For walls subjected to out-of-plane forces, the critical strain condition corresponds to a

strain in the extreme tension reinforcement equal to 1.3 times the strain associated with the

reinforcement yield stress, fy.

For both cases, the strain in the extreme compression fiber shall be assumed to be either 0.0035 for

clay masonry or 0.0025 for concrete masonry.

The calculation of the maximum reinforcement ratio shall include unfactored gravity axial loads. The

stress in the tension reinforcement shall be assumed to be 1.25 fy. Tension in the masonry shall be

neglected. The strength of the compressive zone shall be calculated as 80 percent of f!m times 80

percent of the area of the compressive zone. Stress in reinforcement in the compression zone shall be

based on a linear strain distribution.

For structures designed using an R value less than or equal to 1.5, the ratio of reinforcement, D, shall

not exceed the ratio as calculated with the following critical strain condition:

The critical strain condition corresponds to a strain in the extreme tension reinforcement equal to 2

times the strain associated with the reinforcement yield stress, fy. The strain in the extreme compression

fiber shall be assumed to be either 0.0035 for clay masonry or 0.0025 for concrete masonry.

The calculation of the maximum reinforcement ratio shall include unfactored gravity axial loads. The

stress in the tension reinforcement shall be calculated by multiplying the strain by the modulus of

elasticity of the reinforcement, but need not be taken greater than 1.25 fy. Tension in the masonry shall

be neglected. The strength of the compressive zone shall be calculated using an triangular stress block

whose maximum value is the strain in the extreme compression fiber of the masonry, times the modulus

of elasticity of the masonry. Stress in reinforcement in the compression zone shall be based on a linear

strain distribution.
Masonry Structure Design Requirements

197

Pn' Anf

)

m

1 &

h

140r

2

for h/r < (11.6.3.5-1)

Pn' Anf

)

m

70r

h

2

for h/r $ 99 (11.6.3.5-2)

11.6.2.3: Members subject to compressive axial load shall be designed for the maximum moment that

can accompany the axial load. The required moment, Mu, shall include the moment induced by relative

lateral displacements.

11.6.3 Design of Plain (Unreinforced) Masonry Members:

11.6.3.1: Strength design of members for flexure and axial load shall be in accordance with principles

of engineering mechanics .

11.6.3.2: Strain in masonry shall be assumed directly proportional to the distance from the neutral axis.

11.6.3.3: Flexural tension in masonry shall be assumed directly proportional to strain.

11.6.3.4: Flexural compressive stress in combination with axial compressive stress in masonry shall be

assumed directly proportional to strain. Maximum compressive stress shall not exceed 0.85f .

)

m

11.6.3.5: Design axial load strength shall be in accordance with Eq. 11.6.3.5-1 or Eq. 11.6.3.5-2:

where:

N = strength reduction factor per Table 11.5.3; 

An = net cross-sectional area of the masonry, in.2;

f = specified compressive strength of the masonry, psi; )

m

h = effective height of the wall between points of support, in. and

r = radius of gyration, inches.

The metric equivalents for Eq. 11.6.3.5-1 and Eq. 11.6.3.5-2 are the same except that An is in mm2,

f is in MPa, and h and r are in mm.. )

m

11.7 SHEAR:

11.7.1 Scope: Provisions of this section shall apply for design of members subject to shear.
2000 Provisions Chapter 11

198

Vu# Vn

(11.7.2.1)

Vn' Vm% Vs (11.7.3.1-1)

Vn(max) ' 6 f

)

m

An

(11.7.3.1-2)

Vn(max) ' 4 f

)

m

An

(11.7.3.1-3)

11.7.2 Shear Strength:

11.7.2.1: Design of cross sections subjected to shear shall be based on:

where:

Vu = required shear strength due to factored loads, lb;

N = strength reduction factor per Table 11.5.3; and

Vn = nominal shear strength, lb.

The metric equivalent of Eq. 11.7.2.1 is the same except that Vu and Vn are in N.

11.7.2.2: The design shear strength, NVn , shall exceed the shear corresponding to the development of

1.25 times the nominal flexural strength of the member, except that the nominal shear strength need not

exceed 2.5 times Vu.

11.7.3 Design of Reinforced Masonry Members:

11.7.3.1: Nominal shear strength, Vn, shall be computed as follows:

where:

Vn = nominal shear strength, lb;

Vm = nominal shear strength provided by masonry, lb; and 

Vs = shear strength provided by reinforcement, lb.

The metric equivalent for Eq. 11.7.3.1-1 is the same except that Vn, Vm, and Vs are in N.

For M/Vdv < 0.25:

For M/Vdv < 1.00:
Masonry Structure Design Requirements

199

Vm' 4.0 & 1.75 M

Vd

Anf

)

m

% 0.25P (11.7.3.2)

where:

Vn(max) = maximum nominal shear strength, lb;

An = net cross-sectional area of the masonry, in.2;

f!m = specified compressive strength of the masonry, psi;

M = moment on the masonry section due to unfactored design loads, in.-lb;

V = shear on the masonry section due to unfactored loads, lb; and

dv = length of member in direction of shear force, inches.

Values of M/Vdv between 0.25 and 1.0 may be interpolated.

The metric equivalent of Eq. 11.7.3.1-2 is V and the metric equivalent of Eq.

m(max)

' 0.5 f

)

m

An

11.7.3.1-3 is where Vn (max) is in N, An is in mm2 V , fmN is in MPa, M is in N- m

(max) ' 0.33 f

)

m

An

mm, and d is in mm.

11.7.3.2: Shear strength, Vm, provided by masonry shall be as follows:

where M/Vdv need not be taken greater than 1.0 and

Vm = shear strength provided by masonry, lb;

M = moment on the masonry section due to unfactored design loads, in.-lb;

V = shear on the masonry section due to unfactored loads, psi;

dv = length of member in direction of shear force , in.;

An = net cross-sectional area of the masonry, in.2;

f = specified compressive strength of the masonry, psi; and )

m

P = axial load on the masonry section due to unfactored design loads, lb.

The metric equivalent of Eq. 11.7.3.2 is V where

m

' 0.083 4.0 & 1.75 M

Vd

Anf

)

m

% 0.25P

Vm and P are in N, M is in N-mm, fNm is in MPa, d is in mm, and An is in mm2.
2000 Provisions Chapter 11

200

Vs' 0.5

Av

s

f

y

dv

(11.7.3.3)

11.7.3.3: Nominal shear strength, Vs, provided by reinforcement shall be as follows:

where:

Av = area of shear reinforcement, in.2 (mm2

);

dv = length of member in direction of shear force, in. (mm);

s = spacing of shear reinforcement, in. (mm); and

fy = specified yield strength of the reinforcement or the anchor bolt as applicable, psi

(MPa).

The metric equivalent of Eq. 11.7.3.3 is the same. 

11.7.4 Design of Plain (Unreinforced) Masonry Members:

11.7.4.1: Nominal shear strength, Vn, shall be the least of the following:

a. 1.50 An

, lb (the metric equivalent is 0.375 An, where is in MPa and An is in mm2

f ); )

m

f

)

m

f

)

m

b. 120An

, lb (the metric equivalent is 0.83An, N, where An is in mm2);

c. 37 An

 + 0.3 Nv for running bond masonry not grouted solid, lb (the metric equivalent is 0.26An

+ 0.3Nv where An is in mm2 and Nv is in N);

37 An + 0.3 Nv for stack bond masonry with open end units grouted solid, lb (the metric

equivalent is 0.26An + 0.3Nv when An is in mm2 and Nv is in N);

60 An + 0.3 Nv for running bond masonry grouted solid, lb (the metric equivalent is 0.414An +

0.3Nv when An is in mm2 and Nv is in N); and

15 An for stack bond masonry with other than open end units grouted solid, lb (the metric

equivalent is 0.103An when An is in mm2

where:

f = specified compressive strength of the masonry, psi; )

m

An = net cross-sectional area of the masonry, in.2; and

Nv = force acting normal to shear surface, lb.

11.8 SPECIAL REQUIREMENTS FOR BEAMS:
Masonry Structure Design Requirements

201

11.8.1: The spacing between lateral supports shall be determined by the requirements for out of-plane

loading but shall not exceed 32 times the least width of beam.

11.8.2: The effects of lateral eccentricity of load shall be taken into account in determining spacing of

lateral supports.

11.8.3: The minimum positive reinforcement ratio r in a beam shall not be less than 120/fy (the metric

equivalent is 0.83/fy where fy is in MPa) except that this minimum positive steel reinforcement ratio need

not be satisfied if the area of reinforcement provided is one third greater than that required by analysis

for gravity loads and the Seismic Design Category is A, B, or C.

Where a concrete floor provides a flange and where the beam web is in tension, the ratio, D, shall be

computed using the web width.

11.8.4 Deep Flexural Members:

11.8.4.1: Flexural members with overall depth to clear span ratios greater than 2/5 for continuous

spans or 4/5 for simple spans shall be designed as deep flexural members taking into account nonlinear

distribution of strain and lateral buckling.

11.8.4.2: Minimum flexural tension reinforcement shall conform to Sec. 11.8.3.

11.8.4.3: Uniformly distributed horizontal and vertical reinforcement shall be provided throughout the

length and depth of deep flexural members such that the reinforcement ratios in both directions are at

least 0.001. Distributed flexural reinforcement is to be included in the determination of the actual

reinforcement ratios.

11.9 SPECIAL REQUIREMENTS FOR COLUMNS:

11.9.1: Area of longitudinal reinforcement for columns shall be not less than 0.005 or more than 0.04

times cross-sectional area of the column.

11.9.2: There shall be a minimum of four longitudinal bars in columns.

11.9.3: Lateral ties shall be provided to resist shear and shall comply with the following:

a. Lateral ties shall be at least 1/4 in. (6 mm) in diameter.

b. Vertical spacing of lateral ties shall not exceed 16 longitudinal bar diameters, 48 lateral tie

diameters, nor the least cross sectional dimension of the column.

c. Lateral ties shall be arranged such that every corner and alternate longitudinal bar shall have lateral

support provided by the corner of a lateral tie with an included angle of not more than 135 degrees

and no bar shall be farther than 6 in. (152 mm) clear on each side along the lateral tie from such a

laterally supported bar. Lateral ties shall be placed in either a mortar joint or grout. Where

longitudinal bars are located around the perimeter of a circle, a complete circular lateral tie is

permitted. Minimum lap length for circular ties shall be 84 tie diameters.
2000 Provisions Chapter 11

202

d. Lateral ties shall be located vertically not more than one-half lateral tie spacing above the top of

footing or slab in any story and shall be spaced as provided herein to not more than one-half a

lateral tie spacing below the lowest horizontal reinforcement in beam, girder, slab or drop panel

above.

e. Where beams or brackets frame into a column from four directions, lateral ties may be terminated

not more than 3 in. (76 mm) below lowest reinforcement in the shallowest of such beams or

brackets.

 11.10 SPECIAL REQUIREMENTS FOR SHEAR WALLS:

 11.10.1 Ordinary Plain Masonry Shear Walls: The design of ordinary plain masonry shear

walls shall be in accordance with Sec. 11.3.2 or Sec. 11.3.3. No reinforcement is required to resist

seismic forces.

 11.10.2 Detailed Plain Masonry Shear Walls: The design of detailed plain masonry shear

walls shall be in accordance with Sec. 11.3.3. Detailed plain masonry shear walls shall have

minimum amounts of reinforcement as prescribed in Sec. 11.3.7.3 and 11.3.7.4.

 11.10.3 Ordinary Reinforced Masonry Shear Walls: The design of ordinary reinforced

masonry shear walls shall be in accordance with Sec. 11.3.4. No prescriptive seismic reinforcement

is required for ordinary reinforced masonry shear walls

11.10.4 Intermediate Reinforced Masonry Shear Walls: The design of intermediate reinforced

masonry shear walls shall be in accordance with Sec. 11.3.4. Intermediate reinforced masonry

shear walls shall have minimum amounts of reinforcement as prescribed in Sec. 11.3.7.3 and 11.3.7.4.

 11.10.5 Special Reinforced Masonry Shear Walls: Special reinforced masonry shear walls

shall meet the requirements for intermediate reinforced masonry shear walls (Sec. 11.10.4) in

addition to the requirements of this section.

The design of special reinforced masonry shear walls shall be in accordance with Sec. 11.3.4. 

Special reinforced masonry shear walls shall comply with material requirements of Sec. 11.3.8,

minimum reinforcement requirements of Sec. 11.3.8.3 and 11.3.8.4, and minimum thickness

requirements of Sec. 11.3.8.5. In addition, special reinforced masonry shear walls shall be

reinforced and constructed as required in this section.

 11.10.5.1 Vertical Reinforcement: The maximum spacing of vertical reinforcement in an special

reinforced masonry shear wall shall be the smaller of::

a. One-third the length of the wall,

b. One-third the height of the wall, or

c. 48 in. (1219 mm). 
Masonry Structure Design Requirements

203

 11.10.5.2 Horizontal Reinforcement: Reinforcement required to resist in-plane shear in a special

reinforced masonry shear wall shall be placed horizontally, shall be uniformly distributed, and shall be

embedded in grout. The maximum spacing of horizontal reinforcement shall be the smaller of:

a. One-third the length of the wall,

b. One-third the height of the wall,

c. 48 in. (1219 mm), or

d. 24 in. (610 mm) for stack bond masonry.

 11.10.5.3 Shear Keys: The surface of concrete upon which a special reinforced masonry shear

wall is constructed shall have a minimum surface roughness of 1/8 in. (3.0 mm). Keys with the

following minimum requirements shall be placed at the base of special reinforced masonry shear

walls when the calculated strain in vertical reinforcement exceeds the yield strain under load

combinations that include seismic forces based on a R factor equal to 1.5: 

a. The width of the keys shall be at least equal to the width of the grout space

b. The depth of the keys shall be at least 1.5 in. (40 mm),

c. The length of the key shall be at least 6 in. (152 mm),

d. The spacing between keys shall be at least equal to the length of the key,

e. The cumulative length of all keys shall be at least 20 percent of the length of the shear wall,

f. A minimum of one key shall be placed within 16 in. (406 mm) of each end of a shear wall, and

g. Each key and the grout space above each key in the first course of masonry shall be grouted solid.

 11.10.6: Flanged Shear Walls:

 11.10.6.1: Wall intersections shall be considered effective in transferring shear when either

conditions (a) or (b) and condition (c) as noted below are met:

a. The face shells of hollow masonry units are removed and the intersection is fully grouted.

b. Solid units are laid in running bond and 50 percent of the masonry units at the intersection are

interlocked.

c. Reinforcement from one intersecting wall continues past the intersection a distance not less than 40

bar diameters or 24 in. (600 mm). 

 11.10.6.2: The width of flange considered effective in compression on each side of the web shall be

taken equal to 6 times the thickness of the web or shall be equal to the actual flange on either side of the

web wall, whichever is less.
2000 Provisions Chapter 11

204

 11.10.6.3: The width of flange considered effective in tension on each side of the web shall be taken

equal to 3/4 of the wall height or shall be equal to the actual flange on either side of the web wall,

whichever is less.

 11.10.7 Coupled Shear Walls:

 11.10.7.1 Design of Coupled Shear Walls: Structural members that provide coupling between

shear walls shall be designed to reach their moment or shear nominal strength before either shear

wall reaches its moment or shear nominal strength. Analysis of coupled shear walls shall conform to

accepted principles of mechanics.

 11.10.7.2 Shear Strength of Coupling Beams: The design shear strength,N Vn, of the coupling

beams shall exceed the shear calculated as follows:

(

( )

n

c

V g

M M

L

f ≥ V

+

+

1 25

14

. 1 2

.

11.10.7.2)

where:

NVn = shear strength, lb (N);

M1 and M2 = nominal moment strength at the ends of the beam, lb-in. (N-mm); 

Lc = length of the beam between the shear walls, in. (mm); and 

Vg = unfactored shear force due to gravity loads, lb (N).

The metric equivalent of Eq. 11.10.7.2 is the same except that Vn and Vg are in N, M1 and M2 are in

N-mm, and L is in mm.

The calculation of the nominal flexural moment shall include the reinforcement in reinforced concrete

roof and floor system. The width of the reinforced concrete used for calculations of reinforcement shall

be six times the floor or roof slab thickness.

 11.11 SPECIAL MOMENT FRAMES OF MASONRY:

 11.11.1 Calculation of Required Strength: The calculation of required strength of the members

shall be in accordance with principles of engineering mechanics and shall consider the effects of the

relative stiffness degradation of the beams and columns.

 11.11.2 Flexural Yielding: Flexural yielding shall be limited to the beams at the face of the columns

and to the bottom of the columns at the base of the structure.

 11.11.3 Reinforcement:
Masonry Structure Design Requirements

205

 11.11.3.1: The nominal moment strength at any section along a member shall not be less than one-half

of the higher moment strength provided at the two ends of the member.

 11.11.3.2: Lap splices are permitted only within the center half of the member length.

 11.11.3.3: Welded splices and mechanical connections may be used for splicing the reinforcement at

any section provided not more than alternate longitudinal bars are spliced at a section and the distance

between splices on alternate bars is at least 24 in. (610 mm) along the longitudinal axis.

 11.11.3.4: Reinforcement shall have a specified yield strength of 60,000 psi (414 MPa). The actual

yield strength shall not exceed 1.5 times the specified yield strength.

 11.11.4 Wall Frame Beams:

 11.11.4.1: Factored axial compression force on the beam shall not exceed 0.10 times the net crosssectional area of the beam, An , times the specified compressive strength, f .

)

m

 11.11.4.2: Beams interconnecting vertical elements of the lateral-load-resisting system shall be limited

to a reinforcement ratio of 0.15f!m/fy or that determined in accordance with Sec. 11.6.2.2. All

reinforcement in the beam and adjacent to the beam in a reinforced concrete roof or floor system shall

be used to calculate the reinforcement ratio.

 11.11.4.3: Clear span for the beam shall not be less than 4 times its depth.

 11.11.4.4: Nominal depth of the beam shall not be less than 4 units or 32 in. (813 mm), whichever is

greater. The nominal depth to nominal width ratio shall not exceed 4.

 11.11.4.5: Nominal width of the beams shall equal or exceed all of the following criteria:

a. 8 in. (203 mm),

b. Width required by Sec. 11.8.1, and

c. 1/26 of the clear span between column faces.

 11.11.4.6: Longitudinal Reinforcement:

 11.11.4.6.1: Longitudinal reinforcement shall not be spaced more than 8 in. (203 mm) on center.

 11.11.4.6.2: Longitudinal reinforcement shall be uniformly distributed along the depth of the beam.

 11.11.4.6.3: In lieu of the limitations of Sec. 11.8.3, the minimum reinforcement ratio shall be 130/fy

(the metric equivalent is 0.90/fy where fy is in MPa).

 11.11.4.6.4: At any section of a beam, each masonry unit through the beam depth shall contain

longitudinal reinforcement.
2000 Provisions Chapter 11

206

 11.11.4.7 Transverse Reinforcement:

 11.11.4.7.1: Transverse reinforcement shall be hooked around top and bottom longitudinal bars and

shall be terminated with a standard 180-degree hook.

 11.11.4.7.2: Within an end region extending one beam depth from wall frame column faces and at

any region at which beam plastic hinges may form during seismic or wind loading, maximum spacing of

transverse reinforcement shall not exceed one-fourth the nominal depth of the beam.

 11.11.4.7.3: The maximum spacing of transverse reinforcement shall not exceed one-half the nominal

depth of the beam or that required for shear strength.

 11.11.4.7.4: Minimum transverse reinforcement ratio shall be 0.0015.

 11.11.4.7.5: The first transverse bar shall not be more than 4 in. (102 mm) from the face of the pier.

 11.11.5 Wall Frame Columns:

 11.11.5.1: Factored axial compression force on the wall frame column shall not exceed 0.15 times

the net cross-sectional area of the column, An, times the specified compressive strength, f . The )

m

compressive stress shall also be limited by the maximum reinforcement ratio.

 11.11.5.2: Nominal dimension of the column parallel to the plane of the wall frame shall not be less

than two full units or 32 in. (810 mm), whichever is greater.

 11.11.5.3: Nominal dimension of the column perpendicular to the plane of the wall frame shall not

be less than 8 in. (203 mm) or 1/14 of the clear height between beam faces.

 11.11.5.4: The clear height-to-depth ratio of column members shall not exceed 5.

 11.11.5.5 Longitudinal Reinforcement:

 11.11.5.5.1: A minimum of 4 longitudinal bars shall be provided at all sections of every wall frame

column member.

 11.11.5.5.2: The flexural reinforcement shall be uniformly distributed across the member depth.

 11.11.5.5.3: The nominal moment strength at any section along a member shall be not less than 1.6

times the cracking moment strength and the minimum reinforcement ratio shall be 130/fy (the metric

equivalent is 0.90/fy where fy is in MPa).

 11.11.5.5.4: Vertical reinforcement in wall-frame columns shall be limited to a maximum

reinforcement ratio equal to the lesser of 0.15f!m / fy or that determined in accordance with Sec.

11.6.2.2.

 11.11.5.6 Transverse Reinforcement:

 11.11.5.6.1: Transverse reinforcement shall be hooked around the extreme longitudinal bars and shall

be terminated with a standard 180-degree hook.
Masonry Structure Design Requirements

207

hp>

4,800dbb

f

)

g

(11.12.6.1-1)

hb>

1800dbp

f

)

g

(11.11.6.1-2)

 11.11.5.6.2: The spacing of transverse reinforcement shall not exceed one-fourth the nominal

dimension of the column parallel to the plane of the wall frame.

 11.11.5.6.3: Minimum transverse reinforcement ratio shall be 0.0015.

 11.11.6 Wall Frame Beam-Column Intersection:

 11.11.6.1: Beam-column intersection dimensions in masonry wall frames shall be proportioned such

that the wall frame column depth in the plane of the frame satisfies Eq. 11.11.6.1-1:

where:

hp = pier depth in the plane of the wall frame, in.;

dbb = diameter of the largest beam longitudinal reinforcing bar passing through, or anchored in,

the wall frame beam-column intersection, in.; and 

f!g = specified compressive strength of grout, psi (shall not exceed 5,000 psi (34.5 MPa) for use

in Eq. 11.11.7.1-1).

The metric equivalent of Eq. 11.11.6.1-1 is where hp and dbb h are in mm and is in p>

400dbb

f

)

g

f

)

g

MPa.

Beam depth in the plane of the frame shall satisfy Eq. 11.11.6.1-2:

where:

hb = beam depth in the plane of the wall frame, in.;

dbp = diameter of the largest column (pier) longitudinal reinforcing bar passing through, or

anchored in, the wall frame beam-column intersection, in.; and

f!g = specified compressive strength of grout, psi (shall not exceed 5,000 psi (34.2MPa) for use

in Eq. 11.11.6.1-1).
2000 Provisions Chapter 11

208

As$

0.5Vn

f

y

(11.11.6.2)

The metric equivalent of Eq. 11.11.6.1-2 is where hb and dbp h are in mm and is in b>

150dbp

f

)

g

f

)

g

MPa.

Nominal shear strength of beam-column intersections shall exceed the shear occurring when wall frame

beams develop their nominal flexural strength.

 11.11.6.2: Beam longitudinal reinforcement terminating in a wall frame column shall be extended to

the far face of the column and shall be anchored by a standard hook bent back into the wall frame

column.

Special horizontal shear reinforcement crossing a potential diagonal beam column shear crack shall be

provided such that:

where:

As = cross-sectional area of reinforcement in.2;

Vn = nominal shear strength, lb; and

fy = specified yield strength of the reinforcement or the anchor bolt as applicable, psi.

The metric equivalent of Eq. 11.11.6.2 is the same except that As is in mm2, Vn is in N, and fy is in

MPa.

Special horizontal shear reinforcement shall be anchored by a standard hook around the extreme wall

frame column reinforcing bars.

Vertical shear forces may be considered to be carried by a combination of masonry shear-resisting

mechanisms and truss mechanisms involving intermediate column reinforcing bars.

The nominal horizontal shear stress at the beam-column intersection shall not exceed the lesser of 350

psi (2.5 MPa) or 7 f (the metric equivalent is MPa). )

m

0.58 f

)

m

 11.12 GLASS-UNIT MASONRY AND MASONRY VENEER:

 11.12.1 Design Lateral Forces and Displacements: Glass-unit masonry and masonry veneer shall

be designed and detailed to resist the design lateral forces as described in Sec. 6.1 and 6.2.

 11.12.2 Glass-Unit Masonry Design:

 11.12.2.1: The requirements of Chapter 7 of ACI 530 shall apply to the design of glass unit

masonry. The out-of-plane seismic strength shall be considered as the same as the strength to resist

wind pressure as specified in Sec. 7.3 of ACI 530 . 
Masonry Structure Design Requirements

209

 11.12.3 Masonry Veneer Design:

 11.12.3.1: The requirements of Chapter 6 of ACI 530 shall apply to the design of masonry veneer.

 11.12.3.2: For structures in Seismic Design Category E, corrugated sheet metal anchors shall not

be used.
209

 

Chapter 12

WOOD STRUCTURE DESIGN REQUIREMENTS

12.1 GENERAL:

12.1.1 Scope: The design and construction of wood structures to resist seismic forces and the

material used therein shall comply with the requirements of this chapter.

12.1.2 Reference Documents: The quality, testing, design, and construction of members and

their fastenings in wood systems that resist seismic forces shall conform to the requirements of

the reference documents listed in this section except as modified by the provisions of this chapter.

12.1.2.1 Engineered Wood Construction:

ASCE 16 American Society of Civil Engineers (ASCE), Load and Resistance

Factor Standard for Engineered Wood Construction, including

supplements, ASCE 16, 1995.

APA Y510T American Plywood Association (APA), Plywood Design

Specifications 1998

APA N375B American Plywood Association (APA), Design Capacities of APA

Performance-Rated Structural-Use Panels, N375B, 1995

APA E315H American Plywood Association (APA), Diaphragms, Research Report

138, 1991

12.1.2.2 Conventional Light-Frame Construction:

CABO Code Council of American Building Officials (CABO), One- and TwoFamily Dwelling Code, 1995

NFoPA T903 National Forest and Paper Association (NFoPA), Span Tables for

Joists and Rafters, T903, 1992

12.1.2.3 Materials Standards:

PS 20 U.S. Department of Commerce, Natioanal Institute of Standards and

Technology, American Softwood Lumber Standard, PS 20, 1999

ANSI/AITC A190.1 American National Standards Institute/American Institute of Timber

Construction (ANSI/AITC), American National Standard for Wood

Products Structural Glues Laminated Timber, A190.1, 1992

ASTM D5055-95A American Society of Testing and Materials (ASTM), Standard

Specification for Establishing and Monitoring Structural Capacities of

Prefabricated Wood I-Joists, D5055-95A, 1995
2000 Provisions Chapter 12

210

PS 1 U.S. Department of Commerce, National Institute of Standards and

Technology, Construction and Industrial Plywood American, PS 1,

1995

PS 2 U.S. Department of Commerce, Natioanal Institute of Standards and

Technology, Performance Standard for Wood-Based Structural-use

Panels, PS 2, 1992

ANSI 05.1 American National Standards Institute (ANSI), Wood Poles, ANSI

05.1, 1992

ANSI A208.1 American National Standards Institute (ANSI), Wood Particleboard,

ANSI A208.1, 1992

AWPA C1, 2, 3, 9, 28 American Wood Preservers Association (AWPA), Preservative

Treatment by Pressure Process, AWPA C1, 1991; C2 and C3, 1991;

C9, 1990; and C28, 1991

12.1.3 Notations:

D = Reference resistance.

D’ = Adjusted resistance.

h = The height of a shear wall measured as:

1. The maximum clear height from top of foundation to bottom of diaphragm

framing above or

2. The maximum clear height from top of diaphragm to bottom of diaphragm

framing above.

l = The dimension of a diaphragm perpendicular to the direction of application of force. 

For open-front structures, l is the length from the edge of the diaphragm at the open

front to the vertical resisting elements parallel to the direction of the applied force. 

For a cantilevered diaphragm, l is the length of the cantilever.

w = The width of a diaphragm or shear wall in the direction of application of force

measured as the sheathed dimension of the shear wall or diaphragm.

8 = Time effect factor.

N = Resistance factor.

8ND = Factored resistance.

12.2 DESIGN METHODS: Design of wood structures to resist seismic forces shall be by one

of the methods described in Sec. 12.2.1 and 12.2.2.

12.2.1 Engineered Wood Design: Engineered design of wood structures shall use load and

resistance factor design (LRFD) and shall be in accordance with this chapter and the reference

documents specified in Sec. 12.1.2.1. 
Wood Structure Design Requirements

211

12.2.2 Conventional Light-Frame Construction: Where permitted by Sec.12.7 and 12.8,

wood structures shall be permitted to be constructed in accordance with the provisions of Sec.

12.5. 

12.2.2.1 When a structure of otherwise conventional construction contains structural elements

not conforming to Sec.12.5, those elements shall be designed in accordance with Sec. 12.2.1 and

force resistance and stiffness shall be maintained.

12.3 GENERAL DESIGN REQUIREMENTS FOR ENGINEERED WOOD CONSTRUCTION: 

12.3.1 General: The proportioning, design, and detailing of engineered wood systems,

members, and connections shall be in accordance with the reference documents except as

modified by this section.

12.3.2 Shear Resistance Based on Principles of Mechanics: Shear resistance of diaphragms

and shear walls shall be permitted to be calculated by principles of mechanics using values of

fastener strength and sheathing shear resistance provided consideration is given to the combined

fastener and sheathing performance under cyclic loading. 

12.3.3 Deformation Compatibility Requirements: Deformation compatibility of connections

within and between structural elements shall be considered in design such that the deformation of

each element and connection comprising the seismic-force-resisting system is compatible with

the deformations of the other seismic-force-resisting elements and connections and with the

overall system. See Sec. 5.2.8 for story drift limitations.

12.3.4 Framing Requirements: All wood columns and posts shall be framed to provide full

end bearing. Alternatively, column and post end connections shall be designed to resist the full

compressive loads, neglecting all end bearing capacity. Column and post end connections shall

be fastened to resist lateral and net induced uplift forces.

Shear wall and diaphragm boundary elements shall be provided to transmit the design tension

and compression forces. Diaphragm and shear wall sheathing shall not be used to splice

boundary elements. Diaphragm chords and drag struts shall be placed in, or tangent to, the

plane of the diaphragm framing unless it can be demonstrated that the moments, shears, and

deflections and deformations, considering eccentricities resulting from other configurations, can

be tolerated without exceeding the adjusted resistance and drift limits.

12.3.5 Sheathing Requirements: Wood structural panel sheathing shall have nominal sheet

sizes of 4 ft by 8 ft (1200 mm by 2400 mm) or larger except where reduced widths are permitted

per Sec. 12.4.1.3 and 12.4.2.6. Sheathing fasteners shall be placed at least 3/8 in. (10 mm) from

ends and edges of boards and sheets. It is advised that the edge distance be increased where

possible to reduce the potential for splitting of the framing and nail pull through in the sheathing. 

Sheathing nails or other approved sheathing connectors shall be driven flush with the surface of

the sheathing.

Where wood structural panel sheathing is used as the exposed finish on the exterior of outside

walls, it shall have an exterior exposure durability classification. Where wood structural panel

sheathing is used on the exterior of outside walls but not as the exposed finish, it shall be of a
2000 Provisions Chapter 12

212

type manufactured with exterior glue. Where wood structural panel sheathing is used elsewhere,

it shall be of a type manufactured with intermediate or exterior glue.

Panel materials other than wood structural panel sheathing have no recognized capacity for

seismic-force resistance and are not permitted as part of the seismic-force-resisting system except

in conventional light-frame construction, Sec.12.5.

12.3.6 Wood Members Resisting Horizontal Seismic Forces Contributed by Masonry and

Concrete: Wood shear walls, diaphragms, horizontal trusses, and other members shall not be

used to resist horizontal seismic forces contributed by masonry or concrete construction in

structures over one story in height.

Exceptions:

1. Wood floor and roof members shall be permitted to be used in horizontal trusses and

diaphragms to resist horizontal seismic forces (including those due to masonry

veneer, fireplaces, and chimneys) provided such forces do not result in torsional force

distribution through the truss or diaphragm.

2. Vertical wood structural panel sheathed shear walls shall be permitted to be used to

provide resistance to seismic forces in two-story structures of masonry or concrete

construction provided the following requirements are met:

a. Story-to-story wall heights shall not exceed 12 ft (3660 mm).

b. Diaphragms shall not be considered to transmit lateral forces by torsional force

distribution or cantilever past the outermost supporting shear wall.

c. Combined deflections of diaphragms and shear walls shall not permit per story

drift of supported masonry or concrete walls to exceed the limits of Table 5.2.8.

d. Wood structural panel sheathing in diaphragms shall have all unsupported edges

blocked. Wood structural panel sheathing for both stories of shear walls shall

have all unsupported edges blocked and, for the lower story, shall have a

minimum thickness of 15/32 inch (12 mm).

e. There shall be no out-of-plane horizontal offsets between the first and second

stories of wood structural panel shear walls.

12.4 DIAPHRAGMS AND SHEAR WALLS:

12.4.1 Diaphragms:

12.4.1.1 Horizontal Distribution of Shear: Diaphragms shall be defined as flexible for the

purposes of distribution of story shear and torsional moment when the maximum lateral

deformation of the diaphragm is more than two times the average story drift of the associated

story determined by comparing the computed maximum in-plane deflection of the diaphragm

itself under lateral load with the story drift of adjoining vertical-resisting elements under

equivalent tributary lateral load. Other diaphragms shall be defined as rigid. Design of

structures with rigid diaphragms shall include the structure configuration requirements of Sec.

5.2.3.1 and the horizontal shear distribution requirements of Sec. 5.4.4. 
Wood Structure Design Requirements

213

FIGURE 12.4.1.1-1 Diaphragm length and width for plan view of open front building.

Open-front structures with rigid wood diaphragms resulting in torsional force distribution shall

be permitted provided the length, l, of the diaphragm normal to the open side does not exceed 25

ft (7620 mm), the diaphragm sheathing conforms to Sec.12.4.1.3 through 12.4.1.5, and the l/w

ratio (as shown in Figure 12.4.1.1-1) is less than 1/1 for one-story structures or 1/1.5 for

structures over one story in height.

Exception: Where calculations show that diaphragm deflections can be tolerated, the

length, l, normal to the open end shall be permitted to be increased to a l/w ratio not

greater than 1.5/1 when sheathed in conformance with Sec. 12.4.1.3 or 12.4.3.5 or to 1/1

when sheathed in conformance with Sec. 12.4.1.4.

Rigid wood diaphragms shall be permitted to cantilever past the outermost supporting shear wall

(or other vertical resisting element) a length, l, of not more than 25 ft (7620 mm) or two thirds of

the diaphragm width, w, whichever is the smaller. Figure 12.4.1.1-2 illustrates the dimensions of

l and w for a cantilevered diaphragm.

Structures with rigid wood diaphragms having a torsional irregularity in accordance with Table

5.2.3.2, Item 1, shall meet the following requirements: The l/w ratio shall not exceed 1/1 for onestory structures or 1/1.5 for structures greater than one story in height where l is the dimension

parallel to the load direction for which the irregularity exists.

Exception: Where calculations demonstrate that the diaphragm deflections can be tolerated,

the width is permitted to be increased and the l/w ratio may be increased to 1.5/1 when

sheathed in conformance with Sec. 12.4.1.3 or to 1/1 when sheathed in conformance with Sec

12.4.1.4 or 12.4.1.5.
2000 Provisions Chapter 12

214

FIGURE 12.4.1.1-2 Diaphragm length and width for plan view of cantilevered diaphragm.

12.4.1.2 Aspect Ratio: The aspect ratio l/w of a diaphragm shall not be more than 4/1 for

blocked wood structural panel diaphragms or 3/1 for unblocked wood structural panel

diaphragms, single diagonally sheathed lumber diaphragms, and double diagonally sheathed

lumber diaphragms.

12.4.1.3 Wood Structural Panel Sheathing: Diaphragms and shear walls sheathed with wood

structural panel sheathing shall be permitted to be used to resist seismic forces based on the 

factored shear resistance, 8ND, set forth in Tables 12.4.3-1a and b. Where diaphragms are

designated as blocked in Tables 12.4.3-1a and b, all joints in sheathing shall occur over framing

members of the width prescribed in the tables.

The size and spacing of fasteners at wood structure panel sheathing boundaries, wood structural

panel sheet edges, and intermediate supports shall be as given in Tables 12.4.3-1a and b

Sheathing shall be arranged so that the width shall not be less than 2 ft (600 mm). 

12.4.1.4 Single Diagonally Sheathed Lumber Diaphragms: The factored shear resistance,

8ND, of 0.22 Klf (3.2 kN/m) is permitted for single diagonally sheathed lumber diaphragms.

Single diagonally sheathed lumber diaphragms shall consist of 1-by (actual 3⁄4 in., 19 mm)

sheathing boards laid at an angle of approximately 45 degrees (0.8 rad) to supports. Common

nails at each intermediate support shall be two 8d (0.131 x 21⁄2 in., 3 x 64 mm) for 1 by 6 (actual

3⁄4 in by 51⁄2 in., 19 mm by 140 mm) and three 8d (0.131 x 21⁄2 in., 3 x 64 mm) for 1 by 8 (actual 3⁄4

in. by 71⁄2 in., 19 mm by 190 mm) boards. One additional nail shall be provided in each board at

diaphragm boundaries. For box nails of the same penny weight, one additional nail shall be

provided in each board at each intermediate support and two additional nails shall be provided in

each board at diaphragm wall boundaries. End joints in adjacent boards shall be separated by at

least one framing space between supports. Single diagonally sheathed lumber diaphragms shall

be permitted to consist of 2-by (actual 11⁄2 in., 38 mm) sheathing boards where 16d (0.131 by 21⁄2

in., 3 by 64 mm) nails are substituted for 8d (0.131 by 21⁄2 in., 3 x 64 mm) nails, end joints are
Wood Structure Design Requirements

215

located as above, and the support is not less than 3 in. (actual 21⁄2 in., 64 mm) width or 4 in.

(actual 31⁄2 in., 89 mm) depth.

12.4.1.5 Double Diagonally Sheathed Lumber Diaphragms: Double diagonally sheathed

lumber diaphragms conform to the requirements for single diagonally sheathed lumber

diaphragms in Sec. 12.4.1.4 and the requirements of this section, and shall be permitted to be

used to resist seismic forces based on the factored shear resistance, 8ND, of 0.66 Klf (9.6 kN/m).

Double diagonally sheathed lumber diaphragms shall be sheathed with two layers of diagonal

boards placed perpendicular to each other on the same face of the supports. Each chord shall be

designed for the axial force induced and for flexure between supports due to a uniform load equal

to 50 percent of the shear per foot in the diaphragm

12.4.2 Shear Walls:

12.4.2.1 Summing Shear Capacities: The shear values for shear panels of different capacities

applied to the same side of the wall are not cumulative except as allowed in Tables 12.4.3-2a and

12.4.3.2b. The shear values for material of the same capacity applied to both faces of the same

wall are cumulative. Where the material capacities are not equal, the allowable shear shall be

either two times the smaller shear capacity or the capacity of the stronger side, whichever is

greater. Summing shear capacities of dissimilar materials applied to opposite faces or to the

same wall line is not allowed. 

12.4.2.2 Adhesives: Adhesive attachment of shear wall sheathing is not permitted.

Exception: Approved adhesive attachment systems shall be permitted in Seismic Design

Category B where R = 1.5 and S0 = 2.5 unless other values are approved.

12.4.2.3 Aspect Ratio: The shear wall aspect ratio, h/w, shall not exceed 2/1. See Sec. 12.1.3

for definitions of w and h.

Exception: Shear wall aspect ratios greater than 2/1, but not exceeding 3.5/1, shall be

permitted provided the factored shear resistance values in Tables 12.4.3-2a and 12.4.3-2b are

multiplied by 2w/h.

12.4.2.4 Shear Wall Anchorage: Where net uplift is induced, tie-down (hold-down) devices

shall be used. Tie-down (hold-down) devices shall be attached to the end posts with nails,

screws, or other fasteners. All tie-down devices shall be used only where the uplift resistance

values are based on cyclic testing of wall assemblies and the test results indicate that the tiedown device does not reduce the stiffness, ductility, or capacity of the shear wall when compared

to nailed-on devices. Nominal strength of the tie-down assemblies shall be equal to or greater

than the forces resulting from factored resistance values of Tables 12.4.3-2a and 12.4.3-2b times

So/1.3. The nominal strength of the tie-down device shall be defined as the average maximum

test load the device can resist under cyclic testing without connection failure by either metal or

wood failure. The stiffness of the tie-down assemblies shall be such as to prevent premature

failure of the sheathing fasteners, and the effect of the tie-down displacement shall be included in

drift calculations. End posts shall be selected such that failure across the net section of the post

is not a limit state for the connection of the tie-down.
2000 Provisions Chapter 12

216

Foundation anchor bolts shall have a plate washer under each nut. The minimum plate washer

sizes are as follows: 

Plate washer size

Bolt size for shear walls

2 and 5/8 in. 1/4x3x3 in.

 (13 and 16 mm) (6x75x75 mm)

3/4, 7/8, and 1 in. 3/8x3x3 in.

(19, 22, and 25 mm) (10x75x75 mm)

Hole diameters in the plate washer 3/16 in. (5 mm) larger than the bolt diameter are permitted

provided that a standard cut washer is placed between the plate washer and the nut. Foundation

anchor bolt embedment shall conform to the requirements of Chapters 6 and 8.

Bolts shall be placed a maximum of 2 in. (50 mm) from the sheathed side of wall sheathed on

one face. Walls sheathed on both faces shall have the bolts staggered with the bolt a maximum

of 2 in. (50 mm) from either side of the wall. Alternatively, for wall sheathed on both faces, the

bolts shall be placed at the center of the foundation sill with the edge of the plate washer within 2

in. (13 mm) of each face of the wall. The plate washer width shall be a minimum of 3 in. (75

mm) and the plate thickness shall be determined by analysis using the upward force on the plate

equal to the tension capacity of the bolt.

Anchor bolt and tie-down nuts shall be tightened without crushing the wood, and provision for

preventing nuts from loosening shall be made just prior to covering the framing.

12.4.2.5 Framing: All framing used for shear wall construction shall conform to PS 20 for 2-by

(1.5 in., 38 mm) or larger members.

12.4.2.6 Wood Structural Panel Sheathing: Shear walls sheathed with wood structural panel

sheathing shall be permitted to be used to resist seismic forces based on the factored shear

resistance, 8ND, set forth in Tables 12.4.2-6a and 12.4.2-6b.

The size and spacing of fasteners at wood structural panel sheathing boundaries, wood structural

panel sheet edges, and intermediate supports shall be as given in Tables 12.4.2-6a and b.

All panel sheathing joints shall occur over studs or blocking. Sheathing shall be arranged so that

the width shall not be less than 2 ft (600mm). 

Exception: For sheathing attached with the long direction of the panels perpendicular to

the studs, a single sheathing panel with a minimum vertical dimension of 1 ft (300 mm)

and a minimum horizontal dimension of 4 ft (1200 mm) is permitted to be used if it is

located at mid-height of the wall, and is fully blocked and nailed.

12.4.2.7 Single Diagonally Sheathed Lumber Shear Walls: Single diagonally sheathed

lumber diaphragms are permitted using the construction and resistance provisions of Sec.

12.4.1.4.
Wood Structure Design Requirements

217

12.4.2.8 Double Diagonally Sheathed Lumber Shear Walls: Double diagonally sheathed

lumber diaphragms are permitted using the construction and resistance provisions of Sec.

12.4.1.5.

12.4.2.9 Shear Walls With Openings Designed for Force Transfer Around Openings: 

Where structural-use panel shear walls with openings are designed for force transfer around the

openings, the aspect ratio, h/w, limitations of Sec. 12.4.2.3 shall apply to the overall shear wall

including openings and to each wall pier at the side of an opening. The height of a wall pier shall

be defined as the clear height of the pier at the side of an opening. The width of a wall pier shall

be defined as the sheathed width of the pier. Design and detailing of boundary elements around

the opening shall be provided in accordance with Sec. 12.2.1 or ASCE 16. The width of a wall

pier shall not be less than 2 ft (610mm).

12.4.3 Perforated Shear Walls: The provisions of Sec. 12.4.3 shall be permitted to be used for

the design of perforated shear walls.

12.4.3.1 Definitions:

Adjusted shear resistance: The unadjusted factored shear resistance multiplied by the shear

resistance adjustment factors of Table 12.4.3-1.

Perforated shear wall: A wood structural panel sheathed wall with openings but not

specifically designed and detailed for force transfer around wall openings.

Perforated shear wall segment: A section of shear wall with full height sheathing that meets

the aspect ratio limits of Sec. 12.4.2.3. 

Unadjusted factored shear resistance: The factored shear resistance set forth in Tables 12.4.2-

6a and 12.4.2-6b when the aspect ratio of any perforated shear wall segment used in calculation

of perforated shear wall resistance does not exceed 2/1. When the aspect ratio of any perforated

shear wall segment used in calculation of perforated shear wall resistance is greater than 2/1, but

not exceeding 3.5/1, the unadjusted factored shear resistance shall be the factored shear

resistance set forth in Tables 12.4.2-6a and 12.4.2-6b multiplied by 2w/h. 

12.4.3.2 Limitations: The following limitations shall apply to the use of Sec. 12.4.4:

a. A perforated shear wall segment shall be located at each end of a perforated shear wall.

Openings shall be permitted to occur beyond the ends of the perforated shear wall, however

the width of such openings shall not be included in the width of the perforated shear wall.

b. The factored shear resistance set fort in Tables 12.4.2-6a and 12.4.2-6b shall not exceed 0.64

klf (9.4 kN/m).

c. A perforated shear wall shall not have out of plane (horizontal) offsets. Where out of plane

offsets occur, portions of the wall on each side of the offset shall be considered as separate

perforated shear walls.

d. Collectors for shear transfer shall be provided through the full length of the perforated shear

wall. 
2000 Provisions Chapter 12

218

e. A perforated shear wall shall have uniform top of wall and bottom of wall elevations. 

Perforated shear walls not having uniform elevations shall be designed by other methods.

f. Perforated shear wall height, h, shall not exceed 20 ft.

12.4.3.3 Perforated Shear Wall Resistance: The resistance of a perforated shear wall shall be

calculated in accordance with the following:

12.4.3.3.1 Percent full height sheathing: The percent of full height sheathing shall be

calculated as the sum of widths of perforated shear wall segments divided by the total width of

the perforated shear wall including openings.

12.4.3.3.2 Maximum opening height ratio: The maximum opening height ratio shall be

calculated by dividing the maximum opening clear height by the shear wall height, h.

12.4.3.3.3 Adjusted shear resistance: The adjusted shear resistance shall be calculated by

multiplying the unadjusted factored shear resistance by the shear resistance adjustment factors of

Table 12.4.4-1. For intermediate percentages of full height sheathing the values in Table 12.4.4-

1 are permitted to be interpolated.

12.4.3.3.4 Perforated shear wall resistance: The perforated shear wall resistance shall be

equal to the adjusted shear resistance times the sum of the widths of the perforated shear wall

segments.

12.4.3.4 Anchorage and Load Path: Design of perforated shear wall anchorage and load path

shall conform to the requirements of this section or shall be calculated using principles of

mechanics. Except as modified by this section, wall framing, sheathing, sheathing attachment,

and fastener schedules shall conform to the requirements of 12.4.2.6 and Tables 12.4.3-2a and

12.4.3-2b.

12.4.3.4.1 Uplift anchorage at perforated shear wall ends: Anchorage for uplift forces due to

overturning shall be provided at each end of the perforated shear wall. The uplift anchorage shall

conform to the requirements of Sec. 12.4.2.4 using the factored resistance values set forth in

Tables 12.4.2-6a and 12.4.2-6b times S0/1.3.

12.4.3.4.2 Anchorage for in-plane shear: The unit shear force ,v, transmitted into the top of a

perforated shear wall, out of the base of the perforated shear wall at full height sheathing, and

into collectors (drag struts) connecting shear wall segments, shall be calculated in accordance

with the following:

v

V

C L o i

= ∑

where:

v = unit shear force (klf, kN/m),

V = shear force in perforated shear wall (kips, kN),

h = shear wall height (ft, mm/1000),
Wood Structure Design Requirements

219

Co = shear resistance adjustment factor from Table 12.4.4-1, and

ELi = sum of widths of perforated shear wall segments (ft, mm/1000).

12.4.3.4.3 Uplift anchorage between perforated shear wall ends: In addition to the

requirements of Sec. 12.4.4.4.1, perforated shear wall bottom plates at full height sheathing shall

be anchored for a uniform uplift force, t, equal to the unit shear force, v, determined in Sec.

12.4.4.4.2.

12.4.3.4.4. Compression chords: Each end of each perforated shear wall segment shall be

designed for a compression force, C, from each story calculated in accordance with the

following:

C = V h / (Co 3 Li

)

where:

C = compression chord force (kips, kN),

V = shear force in perforated shear wall (kips, kN),

h = shear wall height (ft, mm/1000),

Co = shear resistance adjustment factor from Table 12.4.4-1, and

3Li = sum of widths of shear wall segments (ft, mm/1000).

12.4.3.4.5. Load path: A load path to the foundation shall be provided for each uplift force, T

and t, for each shear force, v, and for each compression force, C. Elements resisting shear wall

forces contributed by multiple stories shall be designed for the sum of forces contributed by each

story.
2000 Provisions Chapter 12

220

TABLE 12.4.3-1 Shear Resistance Adjustment Factor, Co

Maximum Opening Height Ratioa and Height

Wall Height (h) h/3 h/2 2h/3 5h/6 h

8'-0” 

(2440 mm)

2'-8" 

(810 mm)

4'-0"

(1220 mm)

5'-4"

(1630 mm)

6'-8"

(2030 mm)

8'-0"

(2440 mm)

10'-0” 

(3050 mm)

3'-4"

(1020 mm)

5'-0"

(1530 mm)

6'-8"

(2030 mm)

8'-4"

(2540 mm)

10'-0"

(3050 mm)

Percent Full-Height Sheathing b Shear Resistance Adjustment Factor

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

1.00

1.00

1.00

1.00

1.00

1.00

1.00

1.00

1.00

1.00

0.69

0.71

0.74

0.77

0.80

0.83

0.87

0.91

0.95

1.00

0.53

0.56

0.59

0.63

0.67

0.71

0.77

0.83

0.91

1.00

0.43

0.45

0.49

0.53

0.57

0.63

0.69

0.77

0.87

1.00

0.36

0.38

0.42

0.45

0.50

0.56

0.63

0.71

0.83

1.00 a

 See Sec. 12.4.3.3.2.

b

 See Sec. 12.4.3.3.1.

12.5 CONVENTIONAL LIGHT-FRAME CONSTRUCTION:

12.5.1 Scope: Conventional light-frame construction is a system constructed entirely of

repetitive horizontal and vertical wood light-framing members selected from tables in NFoPA

T903 and conforming to the framing and bracing requirements of the CABO Code except as

modified by the provisions in this section. Structures with concrete or masonry walls above the

basement story shall not be considered to be conventional light-frame construction. Construction

with concrete and masonry basement walls shall be in accordance with the CABO Code or

equivalent. Conventional light-frame construction is limited to structures with bearing wall

heights not exceeding 10 ft (3 m) and the number of stories prescribed in Table 12.5.1-1. The

gravity dead load of the construction is limited to 15 psf (720 Pa) for roofs and exterior walls and

10 psf (480 Pa) for floors and partitions and the gravity live load is limited to 40 psf (1915 Pa).

Exceptions: Masonry veneer is acceptable for:

1. The first story above grade or the first two stories above grade when the lowest story

has concrete or masonry walls of Seismic Design Category B and C structures.

2. The first two stories above grade or the first three stories above grade when the lowest

story has concrete or masonry walls of Seismic Design Category B structures,

provided structural use panel wall bracing is used and the length of bracing provided

is 1.5 times the length required by Table 12.5.2-1.
Wood Structure Design Requirements

221

FIGURE 12.5.1.1.1-1 Out-of-plane exterior walls irregularity.

The requirements of this section are based on platform construction. Other framing systems must

have equivalent detailing to ensure force transfer, continuity, and compatible deformation.

When a structure of otherwise conventional light-frame construction contains structural elements

not conforming to Sec. 12.5, those elements shall have an engineered design to resist the forces

specified in Chapter 5 in accordance with Sec. 12.2.2.1.

12.5.1.1 Irregular Structures: Irregular structures in Seismic Design Categories C and D of

conventional light-frame construction shall have an engineered lateral-force-resisting system

designed to resist the forces specified in Chapter 5 in accordance with Sec. 12.2.1. A structure

shall be considered to have an irregularity when one or more of the conditions described in Sec.

12.5.1.1.1 to 12.5.1.1.7 are present.

12.5.1.1.1: A structure shall be considered to have an irregularity when exterior braced wall

panels are not in one plane vertically from the foundation to the uppermost story in which they

are required. See Figure 12.5.1.1.1-1.

Exceptions: Floors with cantilevers or setbacks not exceeding four times the nominal

depth of the floor joists (see Figure 12.5.1.1.1-2) are permitted to support braced wall

panels provided:

1. Floor joists are 2 in. by 10 in. (actual 11⁄2 by 91⁄4 in., 38 by 235 mm) or larger and

spaced not more than 16 inches (405 mm) on center.

2. The ratio of the back span to the cantilever is at least 2 to 1.

3. Floor joists at ends of braced wall panels are doubled.

4. A continuous rim joist is connected to the ends of all cantilevered joists. The rim

joist shall be permitted to be spliced using a metal tie not less than 0.058 in. (2 mm)

(16 galvanized gage) and 11⁄2 in. (38 mm) wide fastened with six 16d (0.162 by 31⁄2 in,

4 by 89 mm) common nails on each side. Steel used shall have a minimum yield of

33,000 psi (228 MPa) such as ASTM 653 Grade 330 structural quality or ASTM

A446 Grade A galvanized steel.

5. Gravity loads carried by joists at setbacks or the end of cantilevered joists are limited

to single story uniform wall and roof loads and the reactions from headers having a

span of 8 ft (2440 mm) or less.
2000 Provisions Chapter 12

222

FIGURE 12.5.1.1.1-2 Cantilever/setback irregularity for exterior walls.

FIGURE 12.5.1.1.2-1 Unsupported diaphragm irregularity.

12.5.1.1.2: A structure shall be considered to have an irregularity when a section of floor or

roof is not laterally supported by braced wall lines on all edges. See Figure 12.5.1.1.2-1.

Exception: Portions of roofs or floors that do not support braced wall panels above shall

be permitted to extend up to 6 ft (1830 mm) beyond a braced wall line. See Figure

12.5.1.1.2-2.
Wood Structure Design Requirements

223

FIGURE 12.5.1.1.2-2 Allowable cantilevered diaphragm.

FIGURE 12.5.1.1.3 Opening in wall below irregularity.

12.5.1.1.3: A structure shall be considered to have an irregularity when the end of a required

braced wall panel extends more than 1 ft (305 mm) over an opening in the wall below. This

requirement is applicable to braced wall panels offset in plane and to braced wall panels offset

out of plane as permitted by the exception to Sec. 12.5.1.1.1. See Figure 12.5.1.1.3.

Exception: Braced wall panels shall be permitted to extend over an opening not more

than 8 ft (2440 mm) in width when the header is a 4-in. by 12-in. (actual 31⁄2 by 111⁄4 in.,

89 by 286 mm) or larger member.

12.5.1.1.4: A structure shall be considered to have an irregularity when portions of a floor level

are vertically offset such that the framing members on either side of the offset cannot be lapped

or tied together in an approved manner. See Figure 12.5.1.1.4.

Exception: Framing supported directly by foundations.
2000 Provisions Chapter 12

224

FIGURE 12.5.1.1.4 Vertical offset irregularity.

FIGURE 12.5.1.1.5 Nonperpendicular wall irregularity.

FIGURE 12.5.1.1.6 Diaphragm opening irregularity.

12.5.1.1.5: A structure shall be considered to have an irregularity when braced wall lines are not

perpendicular to each other. See Figure 12.5.1.1.5

12.5.1.1.6 Diaphragm Openings: A structure shall be considered to have an irregularity when

openings in floor and roof diaphragms having a maximum dimension greater than 50 percent of

the distance between lines of bracing or an area greater than 25 percent of the area between

orthogonal pairs of braced wall lines are present. See Figure 12.5.1.1.6.
Wood Structure Design Requirements

225

12.5.1.1.7 Stepped Foundation: A structure shall be considered to have an irregularity when

the shear walls of a single story vary in height more than 6 ft (1800 mm).

12.5.2 Braced Walls: The following are the minimum braced wall requirements.

12.5.2.1 Spacing Between Braced Wall Lines: Interior and exterior braced wall lines shall be

located at the spacing indicated in Table 12.5.1-1.

12.5.2.2 Braced Wall Line Sheathing Requirements: All braced wall lines shall be braced by

one of the types of sheathing prescribed in Table 12.5.2-1. The required sum of lengths of braced wall panels at each braced wall line is prescribed in Table 12.5.2-1. Braced wall panels

shall be distributed along the length of the braced wall line with sheathing placed at each end of

the wall or partition or as near thereto as possible. To be considered effective as bracing, each

braced wall panel shall conform to Sec. 602.9 of the CABO Code. All panel sheathing joints

shall occur over studs or blocking. Sheathing shall be fastened to all studs and top and bottom

plates and at panel edges occurring over blocking. All wall framing to which sheathing used for

bracing is applied shall be 2-by (actual 11⁄2 in., 38 mm) or larger members.

Cripple walls shall be braced as required for braced wall lines and shall be considered an

additional story. Where interior post and girder framing is used, the capacity of the braced wall

panels at exterior cripple walls shall be increased to compensate for length of interior braced

wall eliminated by increasing the length of the sheathing or increasing the number of fasteners.

12.5.2.3 Attachment:

12.5.2.3.1: Nailing of braced wall panel sheathing shall be not less than the minimum included

in Tables 12.4.2-6a and 12.4.2-6b or as prescribed in Table 12.5.2-1.

12.5.2.3.2: Nailing for diagonal boards shall be as prescribed in Sec. 12.4.3.3 and 12.4.3.4.

12.5.2.3.3 : Adhesive attachment of wall sheathing is not permitted.

12.5.3 Detailing Requirements: The following requirements for framing and connection

details shall apply as a minimum.

12.5.3.1 Wall Anchorage: Anchorage of braced wall line sills to concrete or masonry

foundations shall be provided. Such anchorage shall conform to the requirements in Figure

403.1a of Sec. 403 of the CABO code except that such anchors shall be spaced at not more than

4 ft (1220 mm) on center for structures over two stories in height. For Seismic Design

Categories C, D and E, plate washers, a minimum of 1⁄4 in. by 3 in. by 3 in. in size, shall be

provided between the foundation sill plate and the nut. Other anchorage devices having

equivalent capacity shall be permitted.

12.5.3.2 Top Plates: Stud walls shall be capped with double-top plates installed to provide

overlapping at corners and intersections. End joints in double-top plates shall be offset at least 4

ft (1220 mm). Single top plates shall be permitted to be used when they are spliced by framing

devices providing capacity equivalent to the lapped splice prescribed for double top plates.

12.5.3.3 Bottom Plates: Studs shall have full bearing on a 2-by (actual 11⁄2 in., 38 mm) or larger

plate or sill having a width at least equal to the width of the studs.
2000 Provisions Chapter 12

226

12.5.3.4 Braced Wall Panel Connections: Accommodations shall be made to transfer forces

from roofs and floors to braced wall panels and from the braced wall panels in upper stories to

the braced wall panels in the story below. Where platform framing is used, such transfer at

braced wall panels shall be accomplished in accordance with the following:

1. All braced wall panel top and bottom plates shall be fastened to joists, rafters, or full

depth blocking. Braced wall panels shall be extended and fastened to roof framing at

intervals not to exceed 50 ft (15.2 m).

Exception: Where roof trusses are used, provisions shall be made to transfer

lateral forces from the roof diaphragm to the braced wall

2. Bottom plate fastening to joist or blocking below shall be with not less than 3-16d (0.162

by 31⁄2 in., 4 by 89 mm) nails at sixteen inches on center.

3. Blocking shall be nailed to the top plate below with not less than 3-8d (0.131 by 21⁄2 in., 3

by 64 mm) toenails per block.

4. Joists parallel to the top plates shall be nailed to the top plate with not less than 8d (0.131

by 21⁄2 in., 3 by 64 mm) toenails at 6 in. (150 mm) on center.

In addition, top plate laps shall be nailed with not less than 8-16d (0.162 by 31⁄2 in., 4 by 89 mm)

face nails on each side.

12.5.3.5 Foundations Supporting Braced Wall Panels: For structures with maximum plan

dimensions not over 50 ft (15250 mm) foundations supporting braced wall panels are required at

exterior walls only. Structures with plan dimensions greater than 50 ft (15250 mm) shall, in

addition, have foundations supporting all required interior braced wall panels. Foundation to

braced wall connections shall be made at every foundation supporting a braced wall panel. The

connections shall be distributed along the length of the braced wall line. Where all-wood

foundations are used, the force transfer shall be determined based on calculation and shall have

capacity greater than or equal to the connections required by Sec. 12.5.3.1.

12.5.3.6 Stepped Footings: Where the height of a required braced wall panel extending from

foundation to floor above varies more than 4 ft. (1220 mm) (see Figure 12.5.3.6), the following

construction shall be used:

a. Where only the bottom of the footing is stepped and the lowest floor framing rests

directly on a sill bolted to the footings, the requirements of Sec. 12.5.3.1 shall apply.

b. Where the lowest floor framing rests directly on a sill bolted to a footing not less than 8 ft

(2440 mm) in length along a line of bracing, the line shall be considered to be braced. 

The double plate of the cripple stud wall beyond the segment of footing extending to the

lowest framed floor shall be spliced to the sill plate with metal ties, one on each side of

the sill and plate not less than 0.058 in. (16 gage, 2mm) by 1.5 in. (38 mm) wide by 4.8

in. (122 mm) with eight 16d (0.162 by 3.5 in., 4 by 89 mm) common nails on each side of

the splice location (see Figure 12.5.3.6). Steel used shall have a minimum yield of

33,000 psi (228 MPa) such as ASTM 653 Grade 330 structural quality or ASTM A446

Grade A galvanized steel.
Wood Structure Design Requirements

227

FIGURE 12.5.3.6 Stepped footing detail.

c. Where cripple walls occur between the top of the footing and the lowest floor framing,

the bracing requirements for a story shall apply.

12.5.3.7 Detailing for Openings in Diaphragms: For openings with a dimension greater than

4 ft (1220 mm) or openings in structures in Seismic Design Categories D and E, the following

minimum detail shall be provided. Blocking shall be provided beyond headers and metal ties not

less than 0.058 in. (16 gage, 2 mm) by 1.5 in. (38 mm) wide by 4.8 in. (122 mm) with eight 16d

(0.162 by 3.5 in., 4 by 89 mm) common nails on each side of the header-joist intersection (see

Figure 12.5.3.7). Steel used shall have a minimum yield of 33,000 psi (228 MPa) such as ASTM

653 Grade 330 structural quality or ASTM A446 Grade A galvanized steel.
2000 Provisions Chapter 12

228

FIGURE 12.5.3.7 Detail for diaphragm opening.

12.6 SEISMIC DESIGN CATEGORY A: Structures assigned to Seismic Design Category A

are permitted to be designed and constructed using any applicable materials and procedures

permitted in the reference documents and, in addition, shall conform to the requirements of Sec.

5.2.6.1.2. Structures constructed in compliance with Sec. 12.5 are deemed to comply with

Sec. 5.2.6.1.2.

Exceptions: 

1. Where Sec. 1.2.1, Exception 1, is applicable, one- and two-family detached dwellings

are exempt from the requirements of the Provisions.

2. Where Sec. 1.2.1, Exception 2, is applicable, one- and two-family dwellings that are

designed and constructed in accordance with the conventional construction

requirements of Sec. 12.5 are exempt from other requirements of the Provisions.

12.7 SEISMIC DESIGN CATEGORIES B, C, AND D: Structures assigned to Seismic

Design Categories B, C, and D shall conform to the requirements of this section, and Sec.

5.2.6.1.2.

Exceptions: 

1. Where Sec. 1.2.1, Exception 1, is applicable, one- and two-family detached dwellings

are exempt from the requirements of the Provisions.

2. Where Sec. 1.2.1, Exception 2, is applicable, one- and two-family dwellings that are

designed and constructed in accordance with the conventional construction

requirements of Sec. 12.5 are exempt from other requirements of the Provisions.
Wood Structure Design Requirements

229

12.7.1 Conventional Light-Frame Construction: Conventional light-frame construction shall

meet the requirements of Sec. 12.5. Alternatively, such structures shall meet the requirements of

Sec. 12.7.2. See Sec. 12.2.2.1 for design of nonconventional elements.

12.7.2 Engineered Construction: All engineered wood construction shall meet the

requirements of Sec. 12.3 and 12.4.

12.8 SEISMIC DESIGN CATEGORIES E AND F: Structures assigned to Seismic Design

Categories E and F shall conform to all of the requirements for engineered construction in

accordance with Sec. 12.3 and 12.4 and to the additional requirements of this section.

Exception: Structures assigned to Seismic Use Group I that are designed and constructed

in accordance with the requirements of Sec. 12.5 are permitted.

12.8.1 Limitations: Structures shall comply with the requirements given below.

12.8.1.1 Unblocked structural-use panel sheathing diaphragms shall not be considered to be

part of the seismic-force-resisting system. Structural-use panel sheathing used for diaphragms

and shear walls that are part of the seismic-force-resisting system shall be applied directly to the

framing members.

Exception: Structural-use panel sheathing may be used as a diaphragm when fastened

over solid lumber planking or laminated decking provided the panel joints and lumber

planking or laminated decking joints do not coincide.

12.8.1.2 In addition to the requirements of Sec. 12.3.4.1, the factored shear resistance, 8ND, for

structural-use panel sheathed shear walls used to resist seismic forces in structures with concrete

or masonry walls shall be one-half the values set forth in Tables 12.4.3-2a and 12.4.3-2b.
TABLE 12.4.3-1a Factored Shear Resistance in Kips per Foot for Horizontal Wood Diaphragm

with Framing Members of Douglas Fir-Larch or Southern Pine for Seismic Loadinga,b

Fastenerc Blocked Diaphragms 

Panel Grade Type Minimum

penetration

Minimum

nominal

Minimum

nominal

Lines of

Fastener spacing at diaphragm boundaries (all cases), at co

edges parallel to load (Cases 3 and 4) and at all panel edges 

in framing

(in.)

panel thickness (in.) width of framing fasteners 6 4 2-1/2f 

(in.) Spacing per line at other panel edges (in.)

6 6443

Structural I

6d

common

1-1/4 3/8 2

3

11

0.240.27

0.330.36

------

0.490.55

------

8d

common

1-3/8 3/8 2

3

11

0.350.39

0.470.52

------

0.690.78

------

10dg

common

1-1/2 15/32 2

3

11

0.420.47

0.550.62

------

0.830.94

------

10dg

common

1-1/2 23/32 3

44

223

---------

0.850.981.22

1.131.271.70

1.221.401.79

1.601.832.35

14 gauge

staples

2 23/32 3

4

23

------

0.781.09

0.781.17

1.091.48

1.171.76

Sheathing,

6d common 1-1/4 3/8 2

3

11

0.240.27

0.330.36

------

0.490.55

------

single floor

8d common 1-3/8 3/8 2

3

11

0.310.35

0.420.47

------

0.620.70

------

and other

7/16 2

3

11

0.330.37

0.440.49

------

0.660.74

------

grades

15/32 2

3

11

0.350.39

0.470.52

------

0.690.78

------

covered

10dg

common

1-1/2 15/32 2

3

11

0.380.42

0.500.56

------

0.750.85

------

in Ref.

19/32 2

3

11

.0420.47

0.550.62

------

0.830.94

------

9-10 and 9-11

23/32 3

44

223

---------

0.840.981.22

1.131.271.70

1.221.401.78

1.591.811.96

14 gauge

staples

2 23/32 3

4

23

------

0.781.07

0.781.17

1.071.46

1.171.76
Wood Structure Design Requirements

231

NOTES for TABLE 12.4.3-1a 

a 8 = 1.0 n = 0.65

b

 l/w shall not be more than 4/1 for blocked diaphragms or more than 3/1 for unblocked diaphragms. For framing

members of other species set forth in Ref. 12-1, Table 12A, with the range of specific gravity (SG) noted, allowable

shear values shall be calculated for all panel grades by multiplying the values from the table above for nail size and

actual panel grade by the following factor: Specific Gravity Adjustment Factor = (1-(0.5 - SG)), Where SG =

Specific Gravity of the framing lumber. This adjustment factor shall not be greater than 1.

c

 Space nails along intermediate framing members at 12 in. centers except where spans are

greater than 32 in..; space nails at 6 in. centers.

d Blocked values are permitted to be used for 1-1/8 in. panels with tongue-and-groove edges where 1 in. by 3/8 in..

crown by No. 16 gauge staples are driven through the tongue-and-groove edges 3/8 in. from the panel edge so as to

penetrate the tongue. Staples shall be spaced at one half the boundary nail spacing for Cases 1 and 2 and at one

third the boundary nail spacing for Cases 3 through 6.

e Maximum shear for Cases 3 through 6 is limited to 1500 pounds per foot.

f For values listed for 2 in. nominal framing member width, the framing members at adjoining panel edges shall be 3

in. nominal width. Nails at panel edges shall be placed in two lines at these locations.

g Framing at adjoining panel edges shall be 3 in. nominal or wider and nails shall be staggered where 10d nails

having penetration into framing of more than 1-5/8 in. are spaced 3 in. or less on center.
TABLE 12.4.3-1b Factored Shear Resistance in kiloNewtons per Meter for Horizontal Wood D

with Framing Members of Douglas Fir-Larch or Southern Pine for Seismic Loadinga,b

Fastenerc Blocked Diaphragms 

Panel Grade Type Minimum

penetration

Minimum

nominal

Minimum

nominal

Lines of

Fastener spacing at diaphragm boundaries (all cases), at con

edges parallel to load (Cases 3 and 4) and at all panel edges (

(mm)e

in framing

(mm.)

panel thickness (mm.) width of framing fasteners 150 100 65f 

(mm.) Spacing per line at other panel edges (mm.)

150 150 100 100 75 7

Structural I

6d

common

32 9.5 50

75

11

3.54.0

4.75.3

------

7.18.0

------

89

8d

common

35 9.5 50

75

11

5.15.7

6.87.6

------

10.111.4

------

112

10dg

common

38 12 50

75

11

6.16.8

8.19.1

------

12.113.7

------

1315

10dg

common

38 18 75

100100

223

---------

12.314.317.8

16.518.624.8

17.820.526.1

23.326.834.1

---

14 gauge

staples

50 18 75

100

23

------

11.415.9

11.417.1

15.921.6

17.125.6

1927

Sheathing,

6d common 32 9.5 50

75

11

3.54.0

4.75.3

------

7.18.0

------

89

single floor

8d common 35 9.5 50

75

11

4.65.1

6.16.8

------

9.1

10.2

------

101

and other

11 50

75

11

4.85.4

6.57.2

------

10.912.2

------

1012

grades

12 50

75

11

5.15.7

6.97.6

------

10.111.4

------

112

covered

10dg

common

38 12 50

75

11

5.56.2

7.38.2

------

10.912.3

------

1213

in Ref.

15 50

75

11

6.16.8

8.19.1

------

12.113.7

------

1315

9-10 and 9-11

18 75

100100

223

---------

12.214.217.7

16.518.624.8

17.720.426.4

23.226.528.6

---

14 gauge

staples

50 18 75

100

23

------

11.415.6

11.417.1

15.621.2

17.125.6

1926
Wood Structure Design Requirements

233

NOTES for TABLE 12.4.3-1b

a 8 = 1.0 n = 0.65

b

 l/w shall not be more than 4/1 for blocked diaphragms or more than 3/1 for unblocked diaphragms. For framing

members of other species set forth in ASCE 16, Table 12A, with the range of specific gravity (SG) noted, allowable

shear values shall be calculated for all panel grades by multiplying the values from the table above for nail size and

actual panel grade by the following factor:

 

Specific Gravity Adjustment Factor = (1-(0.5 - SG)), Where SG = Specific Gravity of the framing lumber. This

adjustment factor shall not be greater than 1.

c

 Space nails along intermediate framing members at 300 mm centers except where spans are greater than 810 mm;

space nails at 150 mm centers.

d Blocked values are permitted to be used for 28.5 mm panels with tongue-and-groove edges where 25 mm by 9 mm

crown by No. 16 gauge staples are driven through the tongue-and-groove edges 9 mm. from the panel edge so as to

penetrate the tongue. Staples shall be spaced at one half the boundary nail spacing for Cases 1 and 2 and at one

third the boundary nail spacing for Cases 3 through 6.

e Maximum shear for Cases 3 through 6 is limited to 22.8 kiloNewtons per meter.

f For values listed for 50 mm nominal framing member width, the framing members at adjoining panel edges shall

be 75 mm nominal width. Nails at panel edges shall be placed in two lines at these locations.

g Framing at adjoining panel edges shall be 75 mm nominal or wider and nails shall be staggered where 10d nails

having penetration into framing of more than 41 mm are spaced 75 mm or less on center.
TABLE 12.4.3-2a Factored Shear Resistance in Kips per Foot (KLF) for Seismic Forces on Structural Use 

Shear Walls with Framing Members of Douglas Fir-Larch or Southern Pinea,b,c

Panel Grade Nail Size

(Common or

Hot-Dipped

Galvanized

Box)

Minimum

Penetration

in Framing

(in.)

Panel

Thickne

ss

(in.)

Panel Applied Direct to Framing Nail Spacing

at Panel Edges (in.)

Nail Size

(Common or

Hot-Dipped

Galvanized

Box)

Panel Applied Over 1/2 

Nail Spacing 

643 2d 6 4 

Structural I 6d 1-1/4 3/8 0.26 0.39 0.51 0.66 8d 0.26 0.39 

8d 1-3/8 3/8 0.30f 0.47f 0.60f 0.79f 10de 0.30f 0.47f 

8d 1-3/8 7/16 0.33f 0.51f 0.66f 0.87f 10de 0.33f 0.51f 8d 1-3/8 15/32 0.36 0.56 0.72 0.95 10de 0.36f 0.56f 

10de 1-1/2 15/32 0.44 0.66 0.86 1.13 - - 

14 ga staple 2 3/8 0.19 0.29 0.39 0.58 - - 14 ga staple 2 7/16 0.27 0.40 0.53 0.80 - - 

Sheathing,

Panel Siding

and

Other

Grades

Covered inReferences

9.10

and

9.11

6d 1-1/4 3/8 0.26 0.39 0.51 0.66 8d 0.26 0.39 8d 1-3/8 3/8 0.29f 0.42f 0.53f 0.69f 10de 0.29f 0.42f 

8d 1-3/8 7/16 0.31f 0.46f 0.59f 0.76f 10de 0.31f 0.46f 8d 1-3/8 15/32 0.34 0.49 0.64 0.83 10de 0.34f 0.49f 

10de 1-1/2 15/32 0.40 0.60 0.78 1.00 - - 

10de 1-1/2 19/32 0.44 0.66 0.86 1.13 - - 

14 ga staple 2 3/8 0.17 0.25 0.33 0.50 - - 14 ga staple 2 7/16 0.23 0.36 0.47 0.70 - - 14 ga staple 2 15/32 0.27 0.40 0.53 0.80 - - 

(Hot- Dipped

Galvanized

Casing Nail)

(Hot-Dipped

Galvanized

Casing Nail)

Panel Siding

as Covered in

Reference 9.10

6d 1-1/4 3/8 0.18 0.27 0.36 0.47 8d 0.18 0.27 8d 1-3/8 3/8 0.21 0.31 0.40 0.53 10de 0.21 0.31 
Wood Structure Design Requirements

235

NOTES for TABLE 12.4.3-2a

a 8 = 1.0 N = 0.65

b

 All panel edges backed with 2-inch nominal or wider framing. Panels installed either

horizontally or vertically. Space nails at 6 in. on center along intermediate framing members for

3/8-in. panels installed with strong axis parallel to studs spaced 24 in. on center and 12 in. on

center for other conditions and panel thicknesses. Allowable shear values for fasteners in

framing members of other species set forth in Table 12A of ASCE 16 shall be calculated for all

grades by multiplying the values by the following factors: 0.82 for species with a specific gravity

greater than or equal to 0.42 but less than 0.49 (0.42 # G < 0.49) and 0.65 for species with a

specific gravity less than 0.42 (G < 0.42). For panel siding using hot-dipped galvanized casing

nails, the shear values shall be the values in the table multiplied by the same factors.

c

 Where panels are applied on both faces of a wall and nail spacing is less than 6 inches on center

on either side, panel joints shall be offset to fall on different framing members or framing shall

be 3-inch nominal or wider and nails on each side of joint shall be staggered.

d

 Framing at adjoining panel edges shall be 3-in. nominal or wider and nails shall be staggered

where nails are spaced 2 in. on center.

e

 Framing at adjoining panel edges shall be 3-in. nominal or wider and nails shall be staggered

where 10d nails having penetration into framing of more than 1-5/8 in. are spaced 3 in. or less on

center.

f

 The values for 3/8-in. and 7/16-in. panels applied directly to framing are permitted to be

increased to the values shown for 15/32-in. panels provided studs are spaced a maximum of 16

in. on center or panel is applied with strong axis across studs.
TABLE 12.4.3-2b Factored Shear Resistance in kiloNewtons per Meter (kN/m) for Seismic Forces on Stru

Shear Walls with Framing Members of Douglas Fir-Larch or Southern Pinea,b,c

Panel Grade Nail Size

(Common or

Hot-Dipped

Galvanized

Box)

Minimum

Penetration

in Framing

(mm)

Panel

Thickness

(mm)

Panel Applied Direct

to Framing 

Nail Spacing at Panel Edges (mm)

Nail Size

(Hot-Dipped

Common or

Galvanized Box)

Panel Applie

 G

Nail Spa

150 100 75 50 150 

Structural I 6d 32 9.5 3.8 5.7 7.4 9.7 8d 3.8 

8d 35 9.5 4.4f 6.8f 8.7f 11.6f 10de 4.4 

8d 35 11 4.8f 7.5f 9.6f 12.7f 10de 4.8 8d 35 12 5.3 8.2 10.4 13.8 10de 5.3 

10de 38 12 6.5 9.7 12.6 16.5 - 

14 ga staple 50 9.5 2.8 4.3 5.7 8.4 - 14 ga staple 50 11 3.9 5.8 7.8 11.7 - 

Sheathing,

Panel Siding

and

Other

Grades

Covered inReferences

9.10

and

9.11

6d 32 10 3.8 5.7 7.4 9.7 8d 3.8 8d 35 10 4.2f 6.1f 7.8f 10.1f 10de 4.2 

8d 35 11 4.6f 6.6f 8.5f 11.1f 10de 4.6 8d 35 12 4.9 7.2 9.3 12.1 10de 4.9 

10de 38 12 5.9 8.7 11.4 14.6 - 

10de 38 15 6.5 9.7 12.6 16.5 - 

14 ga staple 50 9.5 2.5 3.7 4.8 7.3 - 14 ga staple 50 11 3.4 5.2 6.8 10.2 - 14 ga staple 50 12 3.9 5.8 7.8 11.7 - 

Panel Siding

as Covered in

Reference 9.10

(Hot-Dipped

Galvanized

Casing Nail)

(Hot-Dipped

Galvanized

Casing Nail)

6d 32 9.5 2.7 4.0 5.2 6.8 8d 2.7 8d 35 9.5 3.0 4.6 5.9 7.8 10de 3.0 
Wood Structure Design Requirements

237

NOTES for TABLE 12.4.3-2b

a 8 = 1.0 n = 0.65

b

 All panel edges backed with 38 mm nominal or wider framing. Panels installed either

horizontally or vertically. Space nails at 150 mm on center along intermediate framing members

for 9 mm panels installed with strong axis parallel to studs spaced 610 mm on center and 305

mm on center for other conditions and panel thicknesses. Allowable shear values for fasteners in

framing members of other species set forth in Table 12A of ASCE 16 shall be calculated for all

grades by multiplying the values by the following factors: 0.82 for species with a specific gravity

greater than or equal to 0.42 but less than 0.49 (0.42 # G < 0.49) and 0.65 for species with a

specific gravity less than 0.42 (G < 0.42). For panel siding using hot-dipped galvanized casing

nails, the shear values shall be the values in the table multiplied by the same factors.

c

 Where panels are applied on both faces of a wall and nail spacing is less than 610 mm on center

on either side, panel joints shall be offset to fall on different framing members or framing shall

be 64 mm or wider and nails on each side of joint shall be staggered.

d

 Framing at adjoining panel edges shall be 64 mm or wider and nails shall be staggered where

nails are spaced 50 mm on center.

e

 Framing at adjoining panel edges shall be 64 mm or wider and nails shall be staggered where

10d nails having penetration into framing of more than 41 mm are spaced 76 mm or less on

center.

f

 The values for 9 mm and 11 mm panels applied directly to framing are permitted to be

increased to the values shown for 12 mm panels provided studs are spaced a maximum of 406

mm on center or panel is applied with strong axis across studs.
2000 Provisions Chapter 12

238

TABLE 12.5.1-1 Conventional Light-Frame Construction Braced Wall Requirements

Seismic Performance

Category

Maximum Distance

Between Braced Walls

Maximum Number of Stories

Above Grade Permitted a

Ab 35 ft (10675 mm) 3

B 35 ft (10675 mm) 3

C 25 ft (7625 mm) 2

D and 

E (Seismic Use Group I) 25 ft (7625 mm) 1 c

E (Seismic Use Group

II) and F

Conventional construction not permitted; conformance

with Sec. 12.3 required.

 a A cripple stud wall is considered to be a story above grade. Maximum bearing wall height shall not exceed

 10 ft (3050 mm)

 b See exceptions to Sec. 1.2.1.

 c Detached one- and two-family dwellings are permitted to be two stories above grade.
Wood Structure Design Requirements

239

TABLE 12.5.2-1 Conventional Light-Frame Construction Braced Wall Requirements

in Minimum Length of Wall Bracing per Each 25 Lineal Feet (7625 mm) of Braced Wall

Linea

Story

Location

Sheathing

Typeb

0.125 #

SDS < 0.25

0.25 # SDS 

< 0.375 

0.375 # SDS

< 0.50

0.50 # SDS

< 0.75

0.75 # SDS

< 1.0e

Top or

only

story

above

grade

G-Pd 8 ft 0 in.

(2440 mm)

 8 ft 0 in.

(2440 mm)

10 ft 8 in.

(3250 mm)

14 ft 8 in.

(4470 mm)

18 ft 8 in.c

(5690 mm)

S-W 4 ft 0 in.

(1220 mm)

 4 ft 0 in.

(1220 mm)

 5 ft 4 in.

(1625 mm)

 8 ft 0 in.

(2440 mm)

 9 ft 4 in.c

(2845 mm)

Story below top

story

above

grade

G-Pd 10 ft 8 in

(3250 mm)

14 ft 8 in.

(4470 mm)

18 ft 8 in.c

(6590 mm)

NP NP

S-W 5 ft 4 in.

(1625 mm)

 6 ft 8 in.

(2030 mm)

10 ft 8 in.c

(3250 mm)

13 ft 4 in.c

(4065 mm)

17 ft 4 in.c

(5280 mm)

Bottom

story of

3 stories

above

grade

G-Pd 14 ft 8 in.

(4470 mm)

Conventional construction not permitted;

conformance with Sec. 12.3 required.

S-W 8 ft 0 in.

(2440 mm)

 a Minimum length of panel bracing of one face of wall for S-W sheathing or both faces of wall for G-P

sheathing; h/w ratio shall not exceed 2/1, except structures in Seismic Design Category B need only meet the

requirements of Sec. 602.9 of the CABO Code. For S-W panel bracing of the same material on two faces of the

wall, the minimum length is permitted to be one half the tabulated value but the h/w ratio shall not exceed 2/1 and

design for uplift is required.

 b

 G-P = gypsumboard, fiberboard, particleboard, lath and plaster, or gypsum sheathing boards; S-W =

structural-use panels and diagonal wood sheathing. NP = not permitted.

 c

 Applies to one- and two-family detached dwellings only.

 d

 Nailing shall be as follows:

For 1⁄2 in. (13 mm) gypsum board, 5d ( 0.086 in., 2.2 mm diameter) coolers at 7 in. (178 mm) centers;

For e in. (16mm) gypsum board, 6d ( 0.092 in. ( 2.3 mm) diameter) at 7 in (178 mm) centers;

For gypsum sheathing board, 13⁄4 in. long by 7/16 in. (44 by 11 mm) head, diamond point galvanized at 4 in.

(100mm) centers;

For gypsum lath, No. 13 gauge (0.092 in., 2.3 mm) by 1c in. long, 19/64 in. (29 by 7.5 mm) head, plasterboard

at 5 in. (125 mm) centers;

For Portland cement plaster, No. 11 gauge (0.120 in., 3 mm) by 11⁄2 in. long, 7/16 in. head (89 by 11 mm) at 6 in.

(150 mm) centers; 

For fiberboard and particleboard, No. 11 gauge (0.120 in., 3 mm) by 11⁄2 in. (38 mm) long, 7/16 in. ( 11 mm)

head, galvanized at 3 in. (76 mm) centers. 

For structural wood sheathing, the minimum nail size and maximum spacing shall be in accordance with the

minimum nails size and maximum spacing allowed for each thickness sheathing in Tables 12.4.3-2a and b.

 Nailing as specified above shall occur at all panel edges at studs, at top and bottom plates, and, where

occurring, at blocking.

 e

 Where SDS > 1.0, conventional construction is not permitted.

241

Chapter 13

SEISMICALLY ISOLATED STRUCTURES DESIGN REQUIREMENTS

13.1 GENERAL: Every seismically isolated structure and every portion thereof shall be

designed and constructed in accordance with the requirements of this section and the applicable

requirements of Chapter 1. The lateral-force-resisting system and the isolation system shall be

designed to resist the deformations and stresses produced by the effects of seismic ground

motions as provided in this section.

13.2 CRITERIA SELECTION:

13.2.1 Basis for Design: The procedures and limitations for the design of seismically isolated

structures shall be determined considering zoning, site characteristics, vertical acceleration,

cracked section properties of concrete and masonry members, Seismic Use Group, configuration,

structural system, and height in accordance with Sec. 5.2 except as noted below.

13.2.2 Stability of the Isolation System: The stability of the vertical load-carrying elements of

the isolation system shall be verified by analysis and test, as required, for lateral seismic

displacement equal to the total maximum displacement.

13.2.3 Seismic Use Group: All portions of the structure, including the structure above the

isolation system, shall be assigned a Seismic Use Group in accordance with the requirements of

Sec. 1.3. The Occupancy Importance Factor shall be taken as 1.0 for a seismically isolated

structure, regardless of its Seismic Use Group categorization. The Component Importance Factor

shall be selected in accordance with Sec. 6.1.5.

13.2.4 Configuration Requirements: Each structure shall be designated as being regular or

irregular on the basis of the structural configuration above the isolation system in accordance

with the requirements of Sec. 5.2. 

13.2.5 Selection of Lateral Response Procedure:

13.2.5.1 General: Any seismically isolated structure is permitted to be and certain seismically

isolated structures defined below shall be designed using the dynamic lateral response procedure

of Sec. 13.4.

13.2.5.2 Equivalent Lateral Force Procedure: The equivalent-lateral-response procedure of

Sec. 13.3 is permitted to be used for design of a seismically isolated structure provided that:

1. The structure is located at a site with S1 less than or equal to 0.60 ;

2. The structure is located on a Class A, B, C, or D site;

3. The structure above the isolation interface is not more than four stories or 65 ft (20 m) in

height;

4. The effective period of the isolated structure, TM, is less than or equal to 3.0 sec.
2000 Provisions Chapter 13

242

5. The effective period of the isolated structure, TD, is greater than three times the elastic, fixedbase period of the structure above the isolation system as determined by Eq. 5.4.2.1-1 or

5.4.2.1-2;

6. The structure above the isolation system is of regular configuration; and

7. The isolation system meets all of the following criteria:

a. The effective stiffness of the isolation system at the design displacement is greater than

one third of the effective stiffness at 20 percent of the design displacement,

b. The isolation system is capable of producing a restoring force as specified in Sec.

13.6.2.4,

c. The isolation system has force-deflection properties that are independent of the rate of

loading,

d. The isolation system has force-deflection properties that are independent of vertical load

and bilateral load, and

e. The isolation system does not limit maximum capable earthquake displacement to less

than SM1/SD1 times the total design displacement.

13.2.5.3 Dynamic Analysis: A dynamic analysis is permitted to be used for the design of any

structure but shall be used for the design of all isolated structures not satisfying Sec. 13.2.5.2.

The dynamic lateral response procedure of Sec. 13.4 shall be used for design of seismically

isolated structures as specified below.

13.2.5.3.1 Response-Spectrum Analysis: Response-spectrum analysis is permitted to be used

for design of a seismically isolated structure provided that:

1. The structure is located on a Class A, B, C, or D site and

2. The isolation system meets the criteria of Item 7 of Sec. 13.2.5.2.

13.2.5.3.2 Time-History Analysis: Time-history analysis is permitted to be used for design of

any seismically isolated structure and shall be used for design of all seismically isolated

structures not meeting the criteria of Sec. 13.2.5.3.1.

13.2.5.3.3 Site-Specific Design Spectra: Site-specific ground-motion spectra of the design

earthquake and the maximum considered earthquake developed in accordance with Sec. 13.4.4.1

shall be used for design and analysis of all seismically isolated structures if any one of the

following conditions apply:

1. The structure is located on a Class F site or

2. The structure is located at a site with S1 greater than 0.60 .
Base Isolation and Energy Dissipation

243

DD ' g

4B2

SD1TD

BD

(13.3.3.1)

13.3 EQUIVALENT LATERAL FORCE PROCEDURE:

13.3.1 General: Except as provided in Sec. 13.4, every seismically isolated structure or portion

thereof shall be designed and constructed to resist minimum earthquake displacements and forces

as specified by this section and the applicable requirements of Sec. 5.4.

13.3.2 Deformation Characteristics of the Isolation System: Minimum lateral earthquake

design displacement and forces on seismically isolated structures shall be based on the

deformation characteristics of the isolation system. The deformation characteristics of the

isolation system shall explicitly include the effects of the wind-restraint system if such a system

is used to meet the design requirements of these Provisions. The deformation characteristics of

the isolation system shall be based on properly substantiated tests performed in accordance with

Sec. 13.9.

13.3.3 Minimum Lateral Displacements:

13.3.3.1 Design Displacement: The isolation system shall be designed and constructed to

withstand minimum lateral earthquake displacements that act in the direction of each of the main

horizontal axes of the structure in accordance with the following:

where:

g = acceleration of gravity. The units of the acceleration of gravity, g, are in./sec2

(mm/sec2) if the units of the design displacement, DD, are inches (mm);

SD1 = design 5 percent damped spectral acceleration at 1 sec period as determined in Sec.

4.1.1;

TD = effective period, in seconds (sec), of seismically isolated structure at the design

displacement in the direction under consideration, as prescribed by Eq. 13.3.3.2; and

BD = numerical coefficient related to the effective damping of the isolation system at the

design displacement, $D, as set forth in Table 13.3.3.1.

TABLE 13.3.3.1 Damping Coefficient, BD or BM

Effective Damping, $D or $M

 (Percentage of Critical)a,b

BD or BM

 Factor

# 2% 0.8

5% 1.0

10% 1.2

20% 1.5

30% 1.7

40% 1.9

$ 50% 2.0
2000 Provisions Chapter 13

244

TD ' 2B

W

kDmin g

(13.3.3.2)

DM '

g

4B2

SM1TM

B

(13.3.3.3)

NOTES for Table 13.3.3.1

 a The damping coefficient shall be based on the effective damping of the

isolation system determined in accordance with the requirements of Sec.

13.9.5.2.

 b The damping coefficient shall be based on linear interpolation for effective

damping values other than those given.

13.3.3.2 Effective Period: The effective period of the isolated structure, TD, shall be determined

using the deformational characteristics of the isolation system in accordance with the following

equation:

where:

W = total seismic dead load weight of the structure above the isolation interface as

defined in Sec. 5.4.1 and 5.5.3 (kip or kN);

kDmin = minimum effective stiffness, in kips/inch (kN/mm), of the isolation system at the

design displacement in the horizontal direction under consideration as

prescribed by Eq. 13.9.5.1-2; and

g = acceleration of gravity. The units of the acceleration of gravity, g, are in./sec2

(mm/sec2) if the units of the design displacement, DD, are inches (mm).

13.3.3.3 Maximum Displacement: The maximum displacement of the isolation system, DM, in

the most critical direction of horizontal response shall be calculated in accordance with the

formula:

where:

g = acceleration of gravity. The units of the acceleration of gravity, g, are in./sec2

(mm/sec2) if the units of the design displacement, DD, are inches (mm);

SM1 = maximum considered 5 percent damped spectral acceleration at 1 sec period as

determined in Sec. 4.1.1;
Base Isolation and Energy Dissipation

245

TM ' 2B

W

kMming

(13.3.3.4)

DTM ' DM 1 % y

12e

b 2 % d 2 (13.3.3.5-2)

DTD ' DD 1 % y

12e

b 2 % d 2 (13.3.3.5-1)

TM = effective period, in seconds (sec), of seismic-isolated structure at the maximum

displacement in the direction under consideration as prescribed by Eq. 13.3.3.4;

and

BM = numerical coefficient related to the effective damping of the isolation system at

the maximum displacement, $D, as set forth in Table 13.3.3.1.

13.3.3.4 Effective Period at Maximum Displacement: The effective period of the isolated

structure at maximum displacement, TM, shall be determined using the deformational

characteristics of the isolation system in accordance with the equation:

where:

W = total seismic dead load weight of the structure above the isolation interface as

defined in Sec. 5.3.2 and 5.5.3 (kip or kN);

kMmin = minimum effective stiffness, in kips/inch (kN/mm), of the isolation system at the

maximum displacement in the horizontal direction under consideration as

prescribed by Eq. 13.9.5.1-4; and

g = the acceleration due to gravity. The units of the acceleration of gravity, g, are

in./sec2 (mm/sec2) if the units of the design displacement, DD, are inches (mm).

 13.3.3.5 Total Displacement: The total design displacement, DTD, and the total maximum

displacement, DTM, of elements of the isolation system shall include additional displacement due

to actual and accidental torsion calculated considering the spatial distribution of the lateral

stiffness of the isolation system and the most disadvantageous location of mass eccentricity.

The total design displacement, DTD, and the total maximum displacement, DTM, of elements of an

isolation system with uniform spatial distribution of lateral stiffness shall not be taken as less

than that prescribed by the following equations:

where:

DD = design displacement, in inches (mm), at the center of rigidity of the isolation system

in the direction under consideration as prescribed by Eq. 13.3.3.1;
2000 Provisions Chapter 13

246

Vb ' kDmaxDD (13.3.4.1)

DM = maximum displacement, in inches (mm), at the center of rigidity of the isolation

system in the direction under consideration as prescribed in Eq. 13.3.3.3;

y = the distance, in feet (mm), between the center of rigidity of the isolation system

rigidity and the element of interest measured perpendicular to the direction of

seismic loading under consideration;

e = the actual eccentricity, in feet (mm), measured in plan between the center of mass of

the structure above the isolation interface and the center of rigidity of the isolation

system, plus accidental eccentricity, in feet (mm), taken as 5 percent of the longest

plan dimension of the structure perpendicular to the direction of force under

consideration,

b = the shortest plan dimension of the structure, in feet (mm), measured perpendicular to

d, and

d = the longest plan dimension of the structure, in feet (mm).

The total design displacement, DTD, and the total maximum displacement, DTM, is permitted to be

taken as less than the value prescribed by Eq. 13.3.3.5-1 and Eq. 13.3.3.5-2, respectively, but not

less than 1.1 times DD and DM, respectively, provided the isolation system is shown by

calculation to be configured to resist torsion accordingly.

13.3.4 Minimum Lateral Forces:

13.3.4.1 Isolation System and Structural Elements At or Below the Isolation System: The

isolation system, the foundation, and all structural elements below the isolation system shall be

designed and constructed to withstand a minimum lateral seismic force, Vb, using all of the

appropriate provisions for a nonisolated structure where:

where:

kDmax = maximum effective stiffness, in kips/inch (kN/mm), of the isolation system at

the design displacement in the horizontal direction under consideration as

prescribed by Eq. 13.9.5.1-1, and

DD = design displacement, in inches (mm), at the center of rigidity of the isolation

system in the direction under consideration as prescribed by Eq. 13.3.3.1.

In all cases, Vb shall not be taken as less than the maximum force in the isolation system at any

displacement up to and including the design displacement.
Base Isolation and Energy Dissipation

247

Vs ' kDmax DD

RI

(13.3.4.2)

Fx ' Vswxhx

j

n

i'1

wihi

(13.3.5)

13.3.4.2 Structural Elements Above the Isolation System: The structure above the isolation

system shall be designed and constructed to withstand a minimum shear force, Vs, using all of the

appropriate provisions for a nonisolated structure where:

where:

kDmax = maximum effective stiffness, in kips/inch (kN/mm), of the isolation system at

the design displacement in the horizontal direction under consideration as

prescribed by Eq. 13.9.5.1-1;

DD = design displacement, in inches (mm), at the center of rigidity of the isolation

system in the direction under consideration as prescribed by Eq. 13.3.3.1; and

RI = numerical coefficient related to the type of lateral-force-resisting system above

the isolation system.

The RI factor shall be based on the type of lateral-force-resisting system used for the structure

above the isolation system and shall be 3/8 of the R value given in Table 5.2.2 with an upper

bound value not to exceed 2.0 and a lower bound value not to be less than 1.0. 

13.3.4.3 Limits on Vs: The value of Vs shall be taken as not less than the following:

1. The lateral seismic force required by Sec. 5.3 for a fixed-base structure of the same weight,

W, and a period equal to the isolated period, TD;

2. The base shear corresponding to the factored design wind load; and

3. The lateral seismic force required to fully activate the isolation system (e.g., the yield level of

a softening system, the ultimate capacity of a sacrificial wind-restraint system, or the breakaway friction level of a sliding system) factored by 1.5.

13.3.5 Vertical Distribution of Force: The total force shall be distributed over the height of

the structure above the isolation interface in accordance with the following equation:

where:

Vs = total lateral seismic design force or shear on elements above the isolation system

as prescribed by Eq. 13.3.4.2;

Wx = portion of W that is located at or assigned to Level x;.
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D )

D ' DD

1 % T

TD

2 (13.4.2-1)

D )

M ' DM

1 % T

TM

2 (13.4.2-2)

hx = height above the base Level x;

wi = portion of W that is located at or assigned to Level I , respectively; and

hi = height above the base Level I .

At each level designated as x, the force, Fx, shall be applied over the area of the structure in

accordance with the mass distribution at the level. Stresses in each structural element shall be

calculated as the effect of force, Fx, applied at the appropriate levels above the base.

13.3.6 Drift Limits: The maximum interstory drift of the structure above the isolation system

shall not exceed 0.015hsx. The drift shall be calculated by Eq. 5.4.6-1 with the Cd factor of the

isolated structure equal to the RI factor defined in Sec. 13.3.4.2.

13.4 DYNAMIC LATERAL RESPONSE PROCEDURE:

13.4.1 General: As required by Sec. 13.2, every seismically isolated structure or portion

thereof shall be designed and constructed to resist earthquake displacements and forces as

specified in this section and the applicable requirements of Sec. 5.5.

13.4.2 Isolation System and Structural Elements Below the Isolation System: The total

design displacement of the isolation system shall be taken as not less than 90 percent of DTD as

specified by Sec. 13.3.3.5.

The total maximum displacement of the isolation system shall be taken as not less than 80

percent of DTM as specified by Sec. 13.3.3.5 . 

The design lateral shear force on the isolation system and structural elements below the isolation

system shall be taken as not less than 90 percent of Vb as prescribed by Eq. 13.3.4.1.

The limits of the first and second paragraphs of Sec. 13.4.2 shall be evaluated using values of

DTD and DTM determined in accordance with Sec. 13.3.3 except that is permitted to be used in D )

D

lieu of DD and is permitted to be used in lieu of D DM where and D!M are prescribed by the )

M D )D

following equations:
Base Isolation and Energy Dissipation

249

where:

DD = design displacement, in inches (mm), at the center of rigidity of the isolation system

in the direction under consideration as prescribed by Eq. 13.3.3.1;

DM = maximum displacement in inches (mm), at the center of rigidity of the isolation

system in the direction under consideration as prescribed by Eq. 13.3.3.3;

T = elastic, fixed-base period of the structure above the isolation system as determined

by Sec. 5.3.3;

TD = effective period, in seconds (sec), of the seismically isolated structure at the design

displacement in the direction under consideration as prescribed by Eq. 13.3.3.2; and

TM = effective period, in seconds (sec), of the seismically isolated structure at the

maximum displacement in the direction under consideration as prescribed by Eq.

13.3.3.4. 

13.4.3 Structural Elements Above the Isolation System: The design lateral shear force on the

structure above the isolation system, if regular in configuration, shall be taken as not less than 80

percent of Vs, as prescribed by Eq. 13.3.4.2 and the limits specified by Sec. 13.3.4.3.

Exception: The design lateral shear force on the structure above the isolation system, if

regular in configuration, is permitted to be taken as less than 80 percent, but not less than

60 percent of Vs, provided time-history analysis is used for design of the structure.

The design lateral shear force on the structure above the isolation system, if irregular in

configuration, shall be taken as not less than Vs, as prescribed by Eq. 13.3.4.2 and the limits

specified by Sec. 13.3.4.3.

Exception: The design lateral shear force on the structure above the isolation system, if

irregular in configuration, is permitted to be taken as less than 100 percent, but not less

than 80 percent of Vs, provided time-history analysis is used for design of the structure.

13.4.4 Ground Motion:

13.4.4.1 Design Spectra: Properly substantiated site-specific spectra are required for the design

of all structures located on a Class F site or located at a site with S1 greater than 0.60 . Structures

that do not require site-specific spectra and for which site specific spectra have not been

calculated shall be designed using the response spectrum shape given in Figure 4.1.2.6.

A design spectrum shall be constructed for the design earthquake. This design spectrum shall be

taken as not less than the design earthquake response spectrum given in Figure 4.1.2.6.

Exception: If a site-specific spectrum is calculated for the design earthquake, the design

spectrum is permitted to be taken as less than 100 percent but not less than 80 percent of the

design earthquake response spectrum given in Figure 4.1.2.6.

A design spectrum shall be constructed for the maximum considered earthquake. This design

spectrum shall be taken as not less than 1.5 times the design earthquake response spectrum given

in Figure 4.1.2.6. This design spectrum shall be used to determine the total maximum

displacement and overturning forces for design and testing of the isolation system.
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Exception: If a site-specific spectrum is calculated for the maximum considered

earthquake, the design spectrum is permitted to be taken as less than 100 percent but not

less than 80 percent of 1.5 times the design earthquake response spectrum given in

Figure 4.1.2.6.

13.4.4.2 Time Histories: Pairs of appropriate horizontal ground motion time history

components shall be selected and scaled from not less than three recorded events. Appropriate

time histories shall be based on recorded events with magnitudes, fault distances and source

mechanisms that are consistent with those that control the design earthquake (or maximum

considered earthquake). Where three appropriate recorded ground motion time history pairs are

not available, appropriate simulated ground motion time history pairs are permitted to be used to

make up the total number required. For each pair of horizontal ground-motion components, the

square root sum of the squares of the 5 percent damped spectrum of the scaled, horizontal

components shall be constructed. The motions shall be scaled such that the average value of the

square-root-sum-of-the-squares spectra does not fall below 1.3 times the 5 percent damped

spectrum of the design earthquake (or maximum considered earthquake) by more than 10 percent

for periods from 0.5TD seconds to 1.25TM seconds.

13.4.5 Mathematical Model:

13.4.5.1 General: The mathematical models of the isolated structure including the isolation

system, the lateral-force-resisting system, and other structural elements shall conform to Sec.

5.5.2 and to the requirements of Sec. 13.4.5.2 and 13.4.5.3, below.

13.4.5.2 Isolation System: The isolation system shall be modeled using deformational

characteristics developed and verified by test in accordance with the requirements of Sec. 13.3.2.

The isolation system shall be modeled with sufficient detail to:

1. Account for the spatial distribution of isolator units;

2. Calculate translation, in both horizontal directions, and torsion of the structure above the

isolation interface considering the most disadvantageous location of mass eccentricity;

3. Assess overturning/uplift forces on individual isolator units; and

4. Account for the effects of vertical load, bilateral load, and/or the rate of loading if the force

deflection properties of the isolation system are dependent on one or more of these attributes.

13.4.5.3 Isolated Building:

13.4.5.3.1 Displacement: The maximum displacement of each floor and the total design

displacement and total maximum displacement across the isolation system shall be calculated

using a model of the isolated structure that incorporates the force-deflection characteristics of

nonlinear elements of the isolation system and the lateral-force-resisting system.

Lateral-force-resisting systems with nonlinear elements include, but are not limited to, irregular

structural systems designed for a lateral force less than 100 percent and regular structural systems

designed for a lateral force less than 80 percent of Vs as prescribed by Eq. 13.3.4.2 and the limits

specified by Sec. 13.3.4.3.
Base Isolation and Energy Dissipation

251

13.4.5.3.2 Forces and Displacements in Elements of the Lateral-Force-Resisting System:

Design forces and displacements in elements of the lateral-force-resisting system are permitted

to be calculated using a linear elastic model of the isolated structure provided that:

1. Stiffness properties assumed for nonlinear isolation-system components are based on the

maximum effective stiffness of the isolation system and

2. No elements of the lateral-force-resisting system of the structure above the isolation system

are nonlinear.

13.4.6 Description of Analysis Procedures:

13.4.6.1 General: Response-spectrum and time-history analyses shall be performed in

accordance with Sec. 5.4 and the requirements of this section.

13.4.6.2 Input Earthquake: The design earthquake shall be used to calculate the total design

displacement of the isolation system and the lateral forces and displacements of the isolated

structure. The maximum considered earthquake shall be used to calculate the total maximum

displacement of the isolation system.

13.4.6.3 Response-Spectrum Analysis: Response-spectrum analysis shall be performed using

a modal damping value for the fundamental mode in the direction of interest not greater than the

effective damping of the isolation system or 30 percent of critical, whichever is less. Modal

damping values for higher modes shall be selected consistent with those appropriate for response

spectrum analysis of the structure above the isolation system with a fixed base.

Response-spectrum analysis used to determine the total design displacement and the total

maximum displacement shall include simultaneous excitation of the model by 100 percent of the

most critical direction of ground motion and 30 percent of the ground motion on the orthogonal

axis. The maximum displacement of the isolation system shall be calculated as the vectorial sum

of the two orthogonal displacements.

The design shear at any story shall not be less than the story shear obtained using Eq. 13.3.5 and

a value of Vs taken as that equal to the base shear obtained from the response-spectrum analysis

in the direction of interest.

13.4.6.4 Time-History Analysis: Time-history analysis shall be performed with at least three

appropriate pairs of horizontal time-history components as defined in Sec. 13.4.4.2.

Each pair of time histories shall be applied simultaneously to the model considering the most

disadvantageous location of mass eccentricity. The maximum displacement of the isolation

system shall be calculated from the vectorial sum of the two orthogonal components at each time

step.

The parameter of interest shall be calculated for each time-history analysis. If three time-history

analyses are performed, the maximum response of the parameter of interest shall be used for

design. If seven or more time-history analyses are performed, the average value of the response

parameter of interest shall be used for design.

13.4.7 Design Lateral Force:
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13.4.7.1 Isolation System and Structural Elements At or Below the Isolation System: The

isolation system, foundation, and all structural elements below the isolation system shall be

designed using all of the appropriate requirements for a nonisolated structure and the forces

obtained from the dynamic analysis without reduction.

13.4.7.2 Structural Elements Above the Isolation System: Structural elements above the

isolation system shall be designed using the appropriate provisions for a nonisolated structure

and the forces obtained from the dynamic analysis divided by a factor of RI. The RI factor shall be

based on the type of lateral-force-resisting system used for the structure above the isolation

system.

13.4.7.3 Scaling of Results: When the factored lateral shear force on structural elements,

determined using either response spectrum or time-history analysis, is less than the minimum

level prescribed by Sec. 13.4.2 and 13.4.3, all response parameters, including member forces and

moments, shall be adjusted proportionally upward.

13.4.7.4 Drift Limits: Maximum interstory drift corresponding to the design lateral force

including displacement due to vertical deformation of the isolation system shall not exceed the

following limits:

1. The maximum interstory drift of the structure above the isolation system calculated by

response spectrum analysis shall not exceed 0.015hsx and

2. The maximum interstory drift of the structure above the isolation system calculated by timehistory analysis considering the force-deflection characteristics of nonlinear elements of the

lateral-force-resisting system shall not exceed 0.020hsx.

Drift shall be calculated using Eq. 5.3.8.1 with the Cd factor of the isolated structure equal to the

RI factor defined in Sec. 13.3.4.2.

The secondary effects of the maximum considered earthquake lateral displacement ) of the

structure above the isolation system combined with gravity forces shall be investigated if the

inter story drift ratio exceeds 0.010/RI

.

13.5 LATERAL LOAD ON ELEMENTS OF STRUCTURES AND NONSTRUCTURAL

COMPONENTS SUPPORTED BY BUILDINGS:

13.5.1 General: Parts or portions of an isolated structure, permanent nonstructural components

and the attachments to them, and the attachments for permanent equipment supported by a

structure shall be designed to resist seismic forces and displacements as prescribed by this

section and the applicable requirements of Chapter 6.

13.5.2 Forces and Displacements:

13.5.2.1 Components At or Above the Isolation Interface: Elements of seismically isolated

structures and nonstructural components, or portions thereof, that are at or above the isolation

interface shall be designed to resist a total lateral seismic force equal to the maximum dynamic

response of the element or component under consideration.
Base Isolation and Energy Dissipation

253

Exception: Elements of seismically isolated structures and nonstructural components or

portions thereof are permitted to be designed to resist total lateral seismic force as

prescribed in Sec. 5.2.6 and 6.1.3 as appropriate.

13.5.2.2 Components Crossing the Isolation Interface: Elements of seismically isolated

structures and nonstructural components, or portions thereof, that cross the isolation interface

shall be designed to withstand the total maximum displacement.

13.5.2.3 Components Below the Isolation Interface: Elements of seismically isolated

structures and nonstructural components, or portions thereof, that are below the isolation

interface shall be designed and constructed in accordance with the requirements of Sec. 5.2.

13.6 DETAILED SYSTEM REQUIREMENTS:

13.6.1 General: The isolation system and the structural system shall comply with the material

requirements of these Provisions. In addition, the isolation system shall comply with the detailed

system requirements of this section and the structural system shall comply with the detailed

system requirements of this section and the applicable portions of Sec. 5.2.

13.6.2 Isolation System:

13.6.2.1 Environmental Conditions: In addition to the requirements for vertical and lateral

loads induced by wind and earthquake, the isolation system shall be designed with consideration

given to other environmental conditions including aging effects, creep, fatigue, operating

temperature, and exposure to moisture or damaging substances.

13.6.2.2 Wind Forces: Isolated structures shall resist design wind loads at all levels above the

isolation interface. At the isolation interface, a wind restraint system shall be provided to limit

lateral displacement in the isolation system to a value equal to that required between floors of the

structure above the isolation interface.

13.6.2.3 Fire Resistance: Fire resistance rating for the isolation system shall be consistent with

the requirements of columns, walls, or other such elements in the same area of the structure.

13.6.2.4 Lateral-Restoring Force: The isolation system shall be configured to produce a

restoring force such that the lateral force at the total design displacement is at least 0.025W

greater than the lateral force at 50 percent of the total design displacement.

Exception: The isolation system need not be configured to produce a restoring force, as

required above, provided the isolation system is capable of remaining stable under full

vertical load and accommodating a total maximum displacement equal to the greater of

either 3.0 times the total design displacement or 36SM1 in. (or 915 SM1 mm).

13.6.2.5 Displacement Restraint: The isolation system is permitted to be configured to include

a displacement restraint that limits lateral displacement due to the maximum considered

earthquake to less than SM1/SD1 times the total design displacement provided that the seismically

isolated structure is designed in accordance with the following criteria when more stringent than

the requirements of Sec. 13.2:
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1. Maximum considered earthquake response is calculated in accordance with the dynamic

analysis requirements of Sec. 13.4 explicitly considering the nonlinear characteristics of the

isolation system and the structure above the isolation system.

2. The ultimate capacity of the isolation system and structural elements below the isolation

system shall exceed the strength and displacement demands of the maximum considered

earthquake.

3. The structure above the isolation system is checked for stability and ductility demand of the

maximum considered earthquake, and

4. The displacement restraint does not become effective at a displacement less than 0.75 times

the total design displacement unless it is demonstrated by analysis that earlier engagement

does not result in unsatisfactory performance.

13.6.2.6 Vertical-Load Stability: Each element of the isolation system shall be designed to be

stable under the maximum vertical load (1.2D + 1.0L + *E*) and the minimum vertical load

(0.8D - *E*) at a horizontal displacement equal to the total maximum displacement. The dead

load, D, and the live load, L, are specified in Sec. 5.2.7. The seismic load, E, is given by Eq.

5.2.7-1 and 5.2.7-2 where SDS in these equations is replaced by SMS and the vertical load due to

earthquake, QE, shall be based on peak response due to the maximum considered earthquake.

13.6.2.7 Overturning: The factor of safety against global structural overturning at the isolation

interface shall not be less than 1.0 for required load combinations. All gravity and seismic

loading conditions shall be investigated. Seismic forces for overturning calculations shall be

based on the maximum considered earthquake and W shall be used for the vertical restoring

force.

Local uplift of individual elements is permitted provided the resulting deflections do not cause

overstress or instability of the isolator units or other structure elements.

13.6.2.8 Inspection and Replacement:

1. Access for inspection and replacement of all components of the isolation system shall be

provided.

2. A registered design professional shall complete a final series of inspections or observations

of structure separation areas and components that cross the isolation interface prior to the

issuance of the certificate of occupancy for the seismically isolated structure. Such

inspections and observations shall indicate that the conditions allow free and unhindered

displacement of the structure to maximum design levels and that all components that cross

the isolation interface as installed are able to accommodate the stipulated displacements.

3. Seismically isolated structures shall have a periodic monitoring, inspection and maintenance

program for the isolation system established by the registered design professional

responsible for the design of the system.

4. Remodeling, repair or retrofitting at the isolation system interface, including that of

components that cross the isolation interface, shall be performed under the direction of a

registered design professional.
Base Isolation and Energy Dissipation

255

13.6.2.9 Quality Control: A quality control testing program for isolator units shall be

established by the registered design professional responsible for the structural design in

accordance with Sec. 3.2.1.

13.6.3 Structural System:

13.6.3.1 Horizontal Distribution of Force: A horizontal diaphragm or other structural

elements shall provide continuity above the isolation interface and shall have adequate strength

and ductility to transmit forces (due to nonuniform ground motion) from one part of the structure

to another.

13.6.3.2 Building Separations: Minimum separations between the isolated structure and

surrounding retaining walls or other fixed obstructions shall not be less than the total maximum

displacement.

13.6.3.3 Nonbuilding Structures: These shall be designed and constructed in accordance with

the requirements of Chapter 14 using design displacements and forces calculated in accordance

with Sec. 13.3 or 13.4.

13.7 FOUNDATIONS: Foundations shall be designed and constructed in accordance with the

requirements of Chapter 7 using design forces calculated in accordance with Sec. 13.3 or 13.4, as

appropriate.

13.8 DESIGN AND CONSTRUCTION REVIEW:

13.8.1 General: A design review of the isolation system and related test programs shall be

performed by an independent team of registered design professionals in the appropriate

disciplines and others experienced in seismic analysis methods and the theory and application of

seismic isolation.

13.8.2 Isolation System: Isolation system design review shall include, but not be limited to, the

following:

1. Review of site-specific seismic criteria including the development of site-specific spectra

and ground motion time histories and all other design criteria developed specifically for the

project;

2. Review of the preliminary design including the determination of the total design

displacement of the isolation system design displacement and the lateral force design level;

3. Overview and observation of prototype testing (Sec. 13.9);

4. Review of the final design of the entire structural system and all supporting analyses; and

5. Review of the isolation system quality control testing program (Sec. 13.6.2.9).

13.9 REQUIRED TESTS OF THE ISOLATION SYSTEM:

13.9.1 General: The deformation characteristics and damping values of the isolation system

used in the design and analysis of seismically isolated structures shall be based on tests of a

selected sample of the components prior to construction as described in this section.
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The isolation system components to be tested shall include the wind-restraint system if such a

system is used in the design.

The tests specified in this section are for establishing and validating the design properties of the

isolation system and shall not be considered as satisfying the manufacturing quality control tests

of Sec. 13.6.2.9.

13.9.2 Prototype Tests:

13.9.2.1 General: Prototype tests shall be performed separately on two full-size specimens (or

sets of specimens, as appropriate) of each predominant type and size of isolator unit of the

isolation system. The test specimens shall include the wind restraint system as well as individual

isolator units if such systems are used in the design. Specimens tested shall not be used for

construction unless accepted by the registered design professional.

13.9.2.2 Record: For each cycle of tests, the force-deflection behavior of the test specimen shall

be recorded.

13.9.2.3 Sequence and Cycles: The following sequence of tests shall be performed for the

prescribed number of cycles at a vertical load equal to the average dead load plus one-half the

effects due to live load on all isolator units of a common type and size:

1. Twenty fully reversed cycles of loading at a lateral force corresponding to the wind design

force;

2. Three fully reversed cycles of loading at each of the following increments of the total design

displacement -- 0.25DD, 0.5DD, 1.0DD, and 1.0DM;

3. Three fully reversed cycles of loading at the total maximum displacement, 1.0DTM; and

4. 30SD1BD/SDS, but not less than ten, fully reversed cycles of loading at 1 total design

displacement, 1.0DTD.

If an isolator unit is also a vertical-load-carrying element, then Item 2 of the sequence of cyclic

tests specified above shall be performed for two additional vertical load cases: 1.1.2D + 0.5L +

|E| and 2.0.8D - |E| where dead load, D, and live load, L, are specified in Sec. 5.2.7. The seismic

load, E, is given by Eq. 5.2.7-1 and 5.2.7-2 and the load increment due to earthquake overturning,

QE, shall be equal to or greater than the peak earthquake vertical force response corresponding to

the test displacement being evaluated. In these tests, the combined vertical load shall be taken as

the typical or average downward force on all isolator units of a common type and size.

13.9.2.4 Units Dependent on Loading Rates: If the force-deflection properties of the isolator

units are dependent on the rate of loading, then each set of tests specified in Sec. 13.9.2.3 shall be

performed dynamically at a frequency equal to the inverse of the effective period, TD. 

If reduced-scale prototype specimens are used to quantify rate-dependent properties of isolators,

the reduced-scale prototype specimens shall be of the same type and material and be

manufactured with the same processes and quality as full-scale prototypes and shall be tested at a

frequency that represents full-scale prototype loading rates.
Base Isolation and Energy Dissipation

257

keff ' *F %* % *F &*

*)%* % *)&* (13.9.3-1)

The force-deflection properties of an isolator unit shall be considered to be dependent on the rate

of loading if there is greater than a plus or minus 15 percent difference in the effective stiffness

and the effective damping at the design displacement when tested at a frequency equal to the

inverse of the effective period, TD, of the isolated structure and when tested at any frequency in

the range of 0.1 to 2.0 times the inverse of the effective period, TD, of the isolated structure.

13.9.2.5 Units Dependent on Bilateral Load: If the force-deflection properties of the isolator

units are dependent on bilateral load, the tests specified in Sec. 13.9.2.3 and 13.9.2.4 shall be

augmented to include bilateral load at the following increments of the total design displacement:

0.25 and 1.0, 0.50 and 1.0, 0.75 and 1.0, and 1.0 and 1.0.

Exception: If reduced-scale prototype specimens are used to quantify bilateral-loaddependent properties, then such specimens shall be of the same type and material and

manufactured with the same processes and quality as full-scale prototypes.

The force-deflection properties of an isolator unit shall be considered to be dependent on

bilateral load if the bilateral and unilateral force-deflection properties have greater than a plus or

minus 15 percent difference in effective stiffness at the design displacement.

13.9.2.6 Maximum and Minimum Vertical Load: Isolator units that carry vertical load shall

be statically tested for the maximum and minimum vertical load at the total maximum

displacement. In these tests, the combined vertical load, 1.2D + 1.0L + |E|, shall be taken as the

maximum vertical force, and the combined vertical load, 0.8D - |E|, shall be taken as the

minimum vertical force, on any one isolator of a common type and size. The dead load, D, and

live load, L, are specified in Sec. 5.2.7. The seismic load, E, is given by Eq. 5.2.7-1 and 5.2.7-2,

where SDS in these equations is replaced by SMS, and the load increment due to earthquake

overturning, QE, shall be equal to or greater than the peak earthquake vertical force response

corresponding to the maximum considered earthquake.

13.9.2.7 Sacrificial-Wind-Restraint Systems: If a sacrificial-wind-restraint system is to be

utilized, the ultimate capacity shall be established by test.

13.9.2.8 Testing Similar Units: The prototype tests are not required if an isolator unit is of

similar dimensional characteristics and of the same type and material as a prototype isolator unit

that has been previously tested using the specified sequence of tests.

13.9.3 Determination of Force-Deflection Characteristics: The force-deflection

characteristics of the isolation system shall be based on the cyclic load tests of isolator prototypes

specified in Sec. 13.9.2. 

As required, the effective stiffness of an isolator unit, keff, shall be calculated for each cycle of

loading by the equation:
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$eff ' 2

B

Eloop

keff *)%* % *)&* 2 (13.9.3-2)

where F+ and F- are the positive and negative forces at )+ and )-, respectively. 

As required, the effective damping, $eff, of an isolator unit shall be calculated for each cycle of

loading by the equation:

where the energy dissipated per cycle of loading, Eloop, and the effective stiffness, keff, shall be

based on peak test displacements of )+

 and )-.

13.9.4 Test Specimen Adequacy: The performance of the test specimens shall be assessed as

adequate if the following conditions are satisfied:

1. The force-deflection plots of all tests specified in Sec. 13.9.2 have a positive incremental

force carrying capacity.

1.1. For each increment of test displacement specified in Item 2 of Sec. 13.9.2.3 and for

each vertical load case specified in Sec. 13.9.2.3: 

There is no greater than a plus or minus 15 percent difference between the effective

stiffness at each of the three cycles of test and the average value of effective stiffness

for each test specimen;

1.2. For each increment of test displacement specified in Item 2 of Sec. 13.9.2.3 and for

each vertical load case specified in Sec. 13.9.2.3; 

There is no greater than a 15 percent difference in the average value of effective

stiffness of the two test specimens of a common type and size of the isolator unit over

the required three cycles of test;

2. For each specimen there is no greater than a plus or minus 20 percent change in the initial

effective stiffness of each test specimen over the 30SD1BD/SDS, but not less than 10, cycles of

test specified in Item 3 of Sec. 13.9.2.3;

3. For each specimen there is no greater than a 20 percent decrease in the initial effective

damping over for the 30SD1BD/SDS, but not less than 10, cycles of test specified in Item 3 of

Sec. 13.9.2.3; and

4. All specimens of vertical-load-carrying elements of the isolation system remain stable up to

the total maximum displacement for static load as prescribed in Sec. 13.9.2.6 .

13.9.5 Design Properties of the Isolation System:

13.9.5.1 Maximum and Minimum Effective Stiffness: At the design displacement, the

maximum and minimum effective stiffness of the isolated system, kDmax and kDmin, shall be based

on the cyclic tests of Item 2 of Sec. 13.9.2.3 and calculated by the equations:
Base Isolation and Energy Dissipation

259

kDmax ' '*F %

D*max % '*F &D *max

2DD

(13.9.5.1-1)

kDmin ' '*F %

D*min % '*F &D *min

2DD

(13.9.5.1-2)

kMmax ' '*F %

M*max % '*F &M *max

2DM

(13.9.5.1-3)

kMmin ' '*F %

M*min % '*F &M *min

2DM

(13.9.5.1-4)

At the maximum displacement, the maximum and minimum effective stiffness of the isolation

system, kMmax and kMmin, shall be based on the cyclic tests of Item 2 of Sec. 13.9.3 and calculated

by the equations:

The maximum effective stiffness of the isolation system, kDmax (or kMmax), shall be based on forces

from the cycle of prototype testing at a test displacement equal to DD (or DM) that produces the

largest value of effective stiffness. Minimum effective stiffness of the isolation system, kDmin (or

kMmin), shall be based on forces from the cycle of prototype testing at a test displacement equal to

DD (or DM) that produces the smallest value of effective stiffness.

For isolator units that are found by the tests of Sec. 13.9.3, 13.9.4 and 13.9.5 to have forcedeflection characteristics that vary with vertical load, rate of loading or bilateral load,

respectively, the values of kDmax and kMmax shall be increased and the values of kDmin and kMmin shall

be decreased, as necessary, to bound the effects of measured variation in effective stiffness.

13.9.5.2 Effective Damping: At the design displacement, the effective damping of the isolation

system, $D, shall be based on the cyclic tests of Item 2 of Sec. 13.9.3 and calculated by the

equation:
2000 Provisions Chapter 13

260

$D ' 1

2B

'ED

kDmaxD 2

D

(13.9.5.2-1)

$M ' 1

2B

'EM

kMmaxD 2

M

(13.9.5.2-2)

In Eq. 13.9.5.2-1, the total energy dissipated per cycle of design displacement response, GED,

shall be taken as the sum of the energy dissipated per cycle in all isolator units measured at a test

displacement equal to DD. The total energy dissipated per cycle of design displacement response,

GED, shall be based on forces and deflections from the cycle of prototype testing at test

displacement DD that produces the smallest value of effective damping.

At the maximum displacement, the effective damping of the isolation system, $M, shall be based

on the cyclic tests of Item 2 of Sec. 13.9.3 and calculated by the equation:

In Eq. 13.9.5.2-2, the total energy dissipated per cycle of design displacement response, GEM,

shall be taken as the sum of the energy dissipated per cycle in all isolator units measured at a test

displacement equal to DM. The total energy dissipated per cycle of maximum displacement

response, GEM, shall be based on forces and deflections from the cycle of prototype testing at test

displacement DM that produces the smallest value of effective damping.
261

Appendix to Chapter 13

STRUCTURES WITH DAMPING SYSTEMS

PREFACE: Appendix A13 is an entirely new addition to the 2000 Provisions and

contains design criteria, analysis methods, and testing recommendations that have

no or only limited history of use.

The appendix is intended for the trial use by design professionals, code groups, and

regulatory agencies. Design (peer) review is recommended for all structures with a

damping system and should be considered essential when this appendix is used as a

basis for regulating or approving the design of actual construction.

13A.1 GENERAL: Every structure with a damping system and every portion thereof shall be

designed and constructed in accordance with the requirements of this appendix and the applicable

requirements of Chapter 1. 

Exception: Motion and accelerations of seismically isolated structures which contain

damping devices across the plane of isolation shall be determined in accordance with the

provisions of Chapter 13. Testing and strength requirements of damping devices and

other elements of the damping system shall be determined in accordance with the

applicable provisions of this Appendix.

13A.2 CRITERIA SELECTION:

13A.2.1 Basis for Design: The procedure and limitations for the design of structures with a

damping system shall be determined considering zoning, site characteristics, vertical acceleration,

cracked section properties of concrete and masonry members, Seismic Use Group, configuration,

structural system, and height in accordance with Sec. 5.2, except as noted below.

13A.2.2 Seismic Use Group: All portions of the structure shall be assigned a Seismic Use

Group in accordance with the requirements of Sec. 1.3.

13A.2.3 Seismic Design Category: Each structure shall be assigned to a Seismic Design

Category based on the Seismic Use Group and the design spectral response acceleration in

accordance with Sec. 4.2.

Exception: Seismic Design Category A structures with a damping system shall be

designed using the design spectral response acceleration determined in accordance with

Sec. 4.1.2.5 and the analysis methods and design provisions required for Seismic Design

Category B structures.

13A.2.4 Configuration Requirements: Structure design shall consider the combination of

forces that occur in the basic seismic-force-resisting system and the damping system, as defined

in the following sections.
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262

13A.2.4.1 Seismic-Force-Resisting System: Structures that contain a damping system are

required to have a basic seismic-force-resisting system that, in each lateral direction, shall

conform to one of the types indicated in Table 5.2.2. 

The design of the seismic-force-resisting system in each direction shall comply with the

requirements of Sec.13A.7.1 and the following:

1. The materials, detailing, construction and inspection of the seismic-force-resisting system

shall meet all applicable requirements defined by the Seismic Design Category. 

2. The lateral stiffness of the seismic-force-resisting system used to determine elastic periods

and displacements shall include the modeling requirements of Sec. 5.3.7 and 5.4.2.

3. The seismic base shear used for design of the seismic-force-resisting system shall not be less

than Vmin, where Vmin is determined as the greater of the following values: 

 V min (13A.2.4.1-1)

V

BV

= +1

V V (13A.2.4.1-2) min = 0 75 .

where:

V = total design shear at the base of the structure in the direction of interest, as

determined using the procedure of Sec. 5.4, including Sec.5.4.2 (kip or kN), and

BV+I = numerical coefficient as set forth in Table 13A.3.1 for effective damping equal to

the sum of viscous damping in the fundamental mode of vibration of the structure

in the direction of interest, $Vm (m = 1), plus inherent damping, $I, and period of

structure equal to T1.

Exception: Seismic base shear used for design of the seismic-force-resisting system

shall not be taken as less than 1.0V, if either of the following conditions apply:

1. In the direction of interest, the damping system has less than two damping devices on

each floor level, configured to resist torsion.

2. The seismic-force-resisting system has a vertical irregularity of Type 1b (Table 5.2.3.3)

or a plan irregularity of Type 1b (Table 5.2.3.2). 

4. Minimum strength requirements for elements of the seismic-force-resisting-system that are

also elements of the damping system or are otherwise required to resist forces from damping

devices shall meet the additional requirements of Sec. 13A.7.3.

13A.2.4.2 Damping System: Elements of the damping system shall be designed to remain

elastic for design loads including unreduced seismic forces of damping devices as required in

Sec. 13A.7.3, unless it is shown by analysis or test that inelastic response of elements would not
Base Isolation and Energy Dissipation

263

adversely affect damping system function and inelastic response is limited in accordance with the

requirements of Sec. 13A.7.3.4.

13A.2.5 Seismic Criteria:

13A.2.5.1 Design Spectra: Spectra of the design earthquake and the maximum considered

earthquake developed in accordance with Sec. 13.4.4.1 shall be used for the design and analysis

of all structures with a damping system. Site-specific design spectra shall be developed and used

for design of structures with a damping system if any one of the following conditions apply:

1. The structure is located on a Class F site or

2. The structure is located at a site with S1 greater than 0.60.

13A.2.5.2 Time Histories: Ground-motion time histories of the design earthquake and the

maximum considered earthquake developed in accordance with Sec. 13.4.4.2 shall be used for

design and analysis of all structures with a damping system if either of the following conditions

apply:

1. The structure is located at a site with S1 greater than 0.60.

2. The damping system is explicitly modeled and analyzed using the time history analysis

method.

13A.2.6 Selection of Analysis Procedure:

13A.2.6.1 General: A structural analysis shall be made for all structures with a damping system

in accordance with the requirements of this section. The structural analysis shall use linear

procedures, nonlinear procedures, or a combination of linear and nonlinear procedures as

described below.

The seismic-force-resisting system shall be designed using the procedures of either Sec.

13A.2.6.2 or Sec. 13A.2.6.3.

The damping system may be designed using the procedures of either Sec. 13A.2.6.2 or 13A.2.6.3,

subject to the limitations set forth in these sections. Damping systems not meeting these

limitations shall be designed using the nonlinear analysis methods as required in Sec. 13A.6.

13A.2.6.2 Equivalent Lateral Force Analysis Procedure: Structures with a damping system

designed using the equivalent lateral force analysis procedure of Sec. 13A.4 shall be subject to

the following limitations:

1. In the direction of interest, the damping system has at least two damping devices in each

story, configured to resist torsion.

2. The total effective damping of the fundamental mode, βmD (m = 1), of the structure in the

direction of interest is not greater than 35 percent of critical.

3. The seismic-force-resisting system does not have a vertical irregularity of Type 1a, 1b, 2, or 3

(Table 5.2.3.3) or a plan irregularity of Type 1a or 1b (Table 5.2.3.2).

4. Floor diaphragms are rigid (Sec. 5.2.31).
2000 Provisions Chapter 13

264

5. The height of the structure above the base does not exceed 100 ft (30 m).

6. Peak dynamic response of the structure and elements of the damping system are confirmed

by nonlinear time history analysis, when required by Sec. 13A.2.6.4.3.

13A.2.6.3 Response Spectrum Analysis: Structures with a damping system meeting the

limitations of Sec. 13A.2.6.2 may be designed using the response spectrum analysis procedure of

Sec. 13A.5 and structures not meeting the limitations of Sec. 13A.2.6.2 shall be designed using

the response spectrum analysis procedure of Sec. 13A.5, subject to the following limitations:

1. In the direction of interest, the damping system has at least two damping devices in each

story, configured to resist torsion,

2. The total effective damping of the fundamental mode, βmD (m = 1), of the structure in the

direction of interest is not greater than 35 percent of critical, and

3. Peak dynamic response of the structure and elements of the damping system are confirmed

by nonlinear time history analysis, when required by Sec. 13A.2.6.4.3.

13A.2.6.4 Nonlinear Analysis:

13A.2.6.4.1 General: Nonlinear analysis procedures of Sec.13A.6 are permitted for design of

all structures with damping systems and shall be used for design of structures with damping

systems not meeting linear analysis criteria of Sec. 13A.2.6.3.

Nonlinear time history analysis shall be used to confirm peak dynamic response of the structure

and elements of the damping system if the structure is located at a site with S1 greater than 0.60g.

The nonlinear force-deflection characteristics of elements of the seismic-force-resisting system

shall be modeled as required by Sec. 5.7.1 and 5.8.1. The nonlinear force-deflection

characteristics of damping devices shall be modeled, as required, to explicitly account for device

dependence on frequency, amplitude and duration of seismic loading.

13A.2.6.4.2 Nonlinear Static Analysis: Structures with a damping system designed using the

nonlinear static analysis procedure of Sec. 13A.6 shall be subject to the following limitations:

1. Peak dynamic response of the structure and elements of the damping system is confirmed by

nonlinear time history analysis, when required by Sec. 13A.2.6.4.3.

13A.2.6.4.3 Nonlinear Time History Analysis: Structures with a damping system may be

designed using the nonlinear time history analysis procedure of Sec. 13A.6 without limitation. 

Nonlinear time history analysis shall be used to confirm peak dynamic response of the structure

and elements of the damping system for structures with a damping system if the following

conditions applies: 

1. The structure is located at site with S1 greater than 0.60.

13A.3 DAMPED RESPONSE MODIFICATION:

13A.3.1 General: As required in Sec. 13A.4 and 13A.5, response of the structure shall be

modified for the effects of the damping system using coefficients prescribed in Table 13A.3.1.
Base Isolation and Energy Dissipation

265

Table 13A.3.1 Damping Coefficient, BV+I, B1D, BR, B1M, BmD or BmM

Effective Damping, β Period of the Structure

$TS/5

# 2% 0.8

5% 1.0

10% 1.2

20% 1.5

30% 1.8

40% 2.1

50% 2.4

60% 2.7

70% 3.0

80% 3.3

90% 3.6

$ 100% 4.0

1The damping coefficient is equal to 1.0 at a period of the structure

equal to 0 second for all values of effective damping. Interpolation

may be used for intermediate values of effective damping at periods of

the structure between 0 second and TS/5 seconds.

13A.3.2 Effective Damping: The effective damping at the design displacement, $mD, and at the

maximum displacement, $mM, of the mth mode of vibration of the structure in the direction under

consideration shall be calculated as follows:

β ββ μ β (13A.3.2-1) mD I Vm D HD =+ +

β ββ μ β (13A.3.2-2) mM I Vm M HM =+ +

where:

$HD = component of effective damping of the structure in the direction of interest due to

post-yield hysteretic behavior of the seismic-force-resisting system and elements of

the damping system at effective ductility demand, μD;

$HM = component of effective damping of the structure in the direction of interest due to

post-yield hysteretic behavior of the seismic-force-resisting system and elements of

the damping system at effective ductility demand, μM;

$I = component of effective damping of the structure due to the inherent dissipation of

energy by elements of the structure, at or just below the effective yield displacement

of the seismic-force-resisting system;
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266

$Vm = component of effective damping of the mth mode of vibration of the structure in the

direction of interest due to viscous dissipation of energy by the damping system, at

or just below the effective yield displacement of the seismic-force-resisting system; 

μD = effective ductility demand on the seismic-force-resisting system in the direction of

interest due to the design earthquake; and

μM = effective ductility demand on the seismic-force-resisting system in the direction of

interest due to the maximum considered earthquake.

Unless analysis or test data supports other values, the effective ductility demand of higher modes

of vibration in the direction of interest shall be taken as 1.0. 

13A.3.2.1 Inherent Damping: Inherent damping, $I, shall be based on the material type,

configuration and behavior of the structure and nonstructural components responding

dynamically at or just below yield of the seismic-force-resisting system. Unless analysis or test

data supports other values, inherent damping shall be taken as not greater than 5 percent of

critical for all modes of vibration.

13A.3.2.2 Hysteretic Damping: Hysteretic damping of the seismic-force-resisting system and

elements of the damping system shall be based either on test or analysis, or in accordance with

the following equations:

β β ( ) (13A.3.2.2-1)

μ

HD H I

D

= −− q 



 

 0 64 1  1 .

β β ( ) (13A.3.2.2-2)

μ

HM H I

M

= −− q 



 

 0 64 1  1 .

where:

qH = hysteresis loop adjustment factor, as defined in Sec. 13A.3.3;

μD = effective ductility demand on the seismic-force-resisting system in the direction of

interest due to the design earthquake, as defined in Sec. A.13.3.4; and

μM = effective ductility demand on the seismic-force-resisting system in the direction of

interest due to the maximum considered earthquake, as defined in Sec. 13A.3.4.

Unless analysis or test data supports other values, the hysteretic damping of higher modes of

vibration in the direction of interest shall be taken as zero.

13A.3.2.3 Viscous Damping: Viscous damping of the mth mode of vibration of the structure,

$Vm, shall be calculated as follows: 
Base Isolation and Energy Dissipation

267

β (13A.3.2.3-1)

π

Vm

mj

j

m

W

W =

∑

4

W F (13A.3.2.3-2) m im im

i

= ∑

1

2

δ

where:

Wmj = work done by j

th damping device in one complete cycle of dynamic response

corresponding to the mth mode of vibration of the structure in the direction of

interest at modal displacements, *im; 

Wm = maximum strain energy in the mth mode of vibration of the structure in the direction

of interest at modal displacements, *im;

Fim = mth mode inertial force at Level i (or mass point); and

*im = deflection of Level i (or mass point) in the mth mode of vibration at the center of

rigidity of the structure in the direction under consideration.

Viscous modal damping of displacement-dependent damping devices shall be based on a

response amplitude equal to the effective yield displacement of the structure.

The calculation of the work done by individual damping devices shall consider orientation and

participation of each device with respect to the mode of vibration of interest. The work done by

individual damping devices shall be reduced as required to account for the flexibility of elements,

including pins, bolts, gusset plates, brace extensions, and other components that connect

damping devices to other elements of the structure. 

13A.3.3 Hysteresis Loop Adjustment Factor: Hysteretic damping of the seismic-forceresisting system and elements of the damping system shall consider pinching and other effects

that reduce the area of the hysteresis loop during repeated cycles of earthquake demand. Unless

analysis or test data support other values, the fraction of full hysteretic loop area of the seismicforce-resisting system used for design shall be taken as equal to the factor, qH, as defined below:

q (13A.3.3-1)

T

T H

S = 0 67 .

1

where:

Ts = period, in seconds, defined by the ratio, SD1/SDS, and

T1 = period, in seconds of the fundamental mode of vibration of the structure in the

direction of the interest.

The value of qH shall not be taken as greater than 1.0, and need not be taken as less than 0.5.
2000 Provisions Chapter 13

268

13A.3.4 Effective Ductility Demand: The effective ductility demand of seismic-force-resisting

system due to the design earthquake, μD, and due to the maximum considered earthquake, μM,

shall be calculated as the ratio of the fundamental mode displacement, D1D or D1M, to effective

yield displacement, DY:

μ (13A.3.4-1) D

D

Y

D

D

= ≥ 1 10.

μ (13A.3.4-2) M

D M = ≥ 1

DY

10.

D (13A.3.4-3) g C

R Y C T o d = S





 









 



 4 2

2

π

Ω Γ1 11

where:

D1D = fundamental mode design displacement at the center of rigidity of the roof level of

the structure in the direction under consideration, Sec. 13A.4.4.3 (in. or mm),

D1M = fundamental mode maximum displacement at the center of rigidity of the roof level

of structure in the direction under consideration, Sec. 13A.4.4.6 (in. or mm),

DY = displacement at the center of rigidity of the roof level of the structure at the

effective yield point of the seismic-force-resisting system, Sec. 13A.3.4 (in. or mm),

R = response modification factor from Table 5.2.2,

Cd = deflection amplification factor from Table 5.2.2,

So = system overstrength factor from Table 5.2.2,

'1 = participation factor of the fundamental mode of vibration of the structure in the

direction of interest, Sec. 13A.4.3.3 or Sec. 13A.5.3.3 (m =1), 

CS1 = seismic response coefficient (dimensionless) of the fundamental mode of vibration

of the structure in the direction of interest, Sec. 13A.4.3.4 or Sec. 13A.5.3.4 (m =1),

and

T1 = period, in seconds, of the fundamental mode of vibration of the structure in the

direction of interest. 

Design earthquake ductility demand, μD, shall not exceed the maximum value of effective

ductility demand, μmax, given in Sec. 13A.3.5. 
Base Isolation and Energy Dissipation

269

13A.3.5 Maximum Effective Ductility Demand: For determination of the hysteresis loop

adjustment factor, hysteretic damping and other parameters, ductility demand used for design of

the structure shall not exceed the maximum value of effective ductility demand, μmax, as defined

below:

For T1D < TS : (13A.3.5-1) μmax = 



 



 +

















1

2

1

2

R

I Ωo

For T1 $ TS : (13A.3.5-2) μ max = R

I Ωo

where:

I = the occupancy importance factor determined in accordance with Sec. 1.4.

T1D = effective period, in seconds, of the fundamental mode of vibration of the structure

at the design displacement in the direction under consideration.

For periods: T1 # TS # T1D, interpolation shall be used to determine μmax.

13A.4 EQUIVALENT LATERAL FORCE ANALYSIS PROCEDURE:

13A.4.1 General: This section provides required minimum standards for equivalent lateral

force analysis of structures with a damping system. For purposes of analysis, the structure is

considered to be fixed at the base. See Sec. 13A.2.6 for limitations on the use of this procedure.

Seismic base shear and lateral forces at floors used for design of the seismic-force-resisting

system shall be based on the procedures of Sec. 13A.4.3. Seismic forces, displacements and

velocities used for design of the damping system shall be based on the procedures of Sec.

13A.4.4. 

The load combinations and acceptance criteria of Sec. 13A.7 shall be used to check design

responses of seismic-force-resisting and damping systems, respectively.

13A.4.2 Modeling Requirements: Elements of the seismic-force-resisting system shall be

modeled in a manner consistent with the requirements of Sec. 5.4.

Elements of the damping system shall be modeled as required to determine design forces

transferred from damping devices to both the ground and the seismic-force-resisting system. The

effective stiffness of velocity-dependent damping devices shall be modeled.

Damping devices need not be explicitly modeled provided effective damping is calculated in

accordance with the procedures of Sec. 13A.3 and used to modify response as required in Sec.

13A.4.3 and 13A.4.4.

The stiffness and damping properties of the damping devices used in the models shall be based

on or verified by testing of the damping devices as specified in Sec. 13A.10.
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270

13A.4.3 Seismic-Force-Resisting-System Design Response:

13A.4.3.1 Seismic Base Shear: The seismic base shear, V, of the seismic-force-resisting

system in a given direction shall be determined as the combination of the two modal components,

V1 and VR, in accordance with the following equation:

V VV V (13A.4.3.1-1) = +≥ 1 R

2 2

min

where:

V1 = design value of the seismic base shear of the fundamental mode in a given direction

of response (kip or kN),

VR = design value of the seismic base shear of the residual mode in a given direction (kip

or kN), and

Vmin = minimum allowable value of base shear permitted for design of the seismic-forceresisting-system of the structure in direction of the interest (kip or kN).

13A.4.3.2 Fundamental Mode Base Shear: Fundamental mode base shear, V1, shall be

determined in accordance with the following equation:

V CW (13A.4.3.2-1) 1 11 = S

where:

W1 = the effective fundamental mode gravity load including portions of the live load as

defined by Eq. 5.5.5-2 for m = 1 (kip or kN).

13A.4.3.3 Fundamental Mode Properties: Fundamental mode shape, Ni1, and participation

factor, '1, shall be determined by either dynamic analysis of elastic structural properties and

deformational characteristics of the resisting elements or in accordance with the following

equations:

φ (13A.4.3.3-1) i

i

r

h

h 1 =

Γ (13A.4.3.3-2) 1

1

1

i=

=

∑

W

wi i

n

φ

1

where:

hi = the height of the structure above the base to Level i (ft or m),
Base Isolation and Energy Dissipation

271

hr = the height of the structure above the base to the roof level (ft or m), and

wi = the portion of the total gravity load, W, located or assigned to Level i.

The fundamental period, T1, shall be determined either by dynamic analysis of elastic structural

properties and deformational characteristics of the resisting elements, or in accordance with the

following equation:

T (13A.4.3.3-3)

w

g f

i i

i

n

i i

i

1 n = =

=

∑

∑

2

2

1

1

π

δ

δ

where:

fi = lateral force at Level i of the structure distributed in accordance with Eq. 5.4.3-2,

and

*i = elastic deflection at Level i of the structure due to applied lateral forces fi.

13A.4.3.4 Fundamental Mode Seismic Response Coefficient: The fundamental mode seismic

response coefficient, CS1, shall be determined in accordance with the following equations:

For T1D < TS:

C (13A.4.3.4-1)

R

C

S

B S

d

DS

o D

1

1

= 



 





Ω

For T1D $ TS :

(13A.4.3.4-2) ( ) C R

C

S

B S

d

D

o D

1

1

T1D 1

= 



 



 Ω

where:

SDS = the design spectral response acceleration in the short period range as determined

from Sec. 4.1.2.5,

SD1 = the design spectral response acceleration at a period of 1 second as determined from

Sec. 4.1.2.5,

B1D = numerical coefficient as set forth in Table 13A.3.1 for effective damping equal to

$mD (m = 1) and period of the structure equal to T1D,
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272

13A.4.3.5 Effective Fundamental Mode Period Determination: The effective fundamental

mode period at the design earthquake, T1D, and at the maximum considered earthquake, T1M, shall

be based either on explicit consideration of the post-yield force deflection characteristics of the

structure or in accordance with the following equations:

T T (13A.4.3.5-1) 1 1 D D = μ

T T M M (13A.4.3.5-2) 1 1 = μ

where:

T1M = effective period, in seconds, of the fundamental mode of vibration of the structure

at the maximum displacement in the direction under consideration.

13A.4.3.6 Residual Mode Base Shear: Residual mode base shear, VR, shall be determined in

accordance with the following equation:

V CW (13A.4.3.6-1) R SR R =

where:

CSR = the residual mode seismic response coefficient as determined in Sec. 13A.4.3.8, and

W = the effective residual mode gravity load of the structure determined in accordance R

with Eq. 13A.4.3.7-3 (kip or kN).

13A.4.3.7 Residual Mode Properties: Residual mode shape, NiR, participation factor, ΓR,

effective gravity load of the structure, , and effective period, TR W , shall be determined in R

accordance with the following equations:

φ (13A.4.3.7-1) φ

iR

i = −

−

1

1

Γ

Γ

1 1

1

Γ Γ (13A.4.3.7-2) R = −1 1

W WW (13A.4.3.7-3) R = − 1

T T (13A.4.3.7-4) R = 0 4. 1

13A.4.3.8 Residual Mode Seismic Response Coefficient: The residual mode seismic response

coefficient, CSR, shall be determined in accordance with the following equation:
Base Isolation and Energy Dissipation

273

C (A13.4.3.8-1)

R

C

S

B SR

d

DS

o R

= 



 





Ω

where:

BR = Numerical coefficient as set forth in Table 13A.3.1 for effective damping equal to

$R, and period of the structure equal to TR. 

13A.4.3.9 Design Lateral Force: Design lateral force in elements of the seismic-forceresisting system at Level i due to fundamental mode response, Fi1, and residual mode response,

FiR, of the structure in the direction of interest shall be determined in accordance with the

following equations:

F w V (13A.4.3.9-1) il i i = φ 1

1

W1

Γ

1

F w (13A.4.3.9-2)

W iR i iR VR

R

= φ R

Γ

Design forces in elements of the seismic-force-resisting system shall be determined as the squareroot-sum-of-squares of the forces due to fundamental and residual modes.

13A.4.4 Damping System Design Response:

13A.4.4.1 General: Design forces in damping devices and other elements of the damping

system shall be determined on the basis of the floor deflection, story drift and story velocity

response parameters described in the following sections.

Displacements and velocities used to determine maximum forces in damping devices at each

story shall account for the angle of orientation from horizontal and consider the effects of

increased response due to torsion required for design of the seismic-force-resisting system.

Floor deflections at Level i, *iD and *iM, design story drifts, )D and )M, and design story

velocities, «D and «M, shall be calculated for both the design earthquake and the maximum

considered earthquake, respectively, in accordance with the following sections. 

13A.4.4.2 Design Earthquake Floor Deflection: Fundamental and residual mode deflections

due to the design earthquake, *i1D and *iRD (in. or mm), at the center of rigidity of Level i of the

structure in the direction of interest shall be determined in accordance with the following

equations:

δ φ (13A.4.4.2-1) iD D i 1 11 = D

δ φ (13A.4.4.2-2) iRD RD iR = D
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274

where:

DRD = Residual mode design displacement at the center of rigidity of the roof level of the

structure in the direction under consideration, Sec. 13A.4.4.3 (in. or mm).

The total design earthquake deflection at each floor of the structure in the direction of interest

shall be calculated as the square-root-sum-of-squares of fundamental and residual mode floor

deflections.

13A.4.4.3 Design Earthquake Roof Displacement: Fundamental and residual mode

displacements due to the design earthquake, D1D and D1R (in.or mm) at the center of rigidity of

the roof level of the structure in the direction of interest shall be determined in accordance with

the following equations:

D (13A.4.4.3-1) g S T g S T

B D

D D DS D

D

1 1

1 1

1D

1

B 1

= 



 



 ≤ 



 



 4 4 2 2 1

2

π π

Γ Γ

D (13A.4.4.3-2) g S T g S T

B RD R

D R

R

DS R

R

= 



 



 ≤ 



 



 4 4 2 2

2

π π

Γ Γ 1

BR

13A.4.4.4 Design Earthquake Story Drift: Design earthquake story drift, )D, of the structure

in the direction of interest shall be calculated in accordance with the following equation:

∆ ∆∆ (13A.4.4.4-1) D D = + 1 RD

2 2

where:

)1D = design earthquake story drift due to the fundamental mode of vibration of the

structure in the direction of interest (in. or mm) and

)RD = design earthquake story drift due to the residual mode of vibration of the structure

in the direction of interest (in. or mm).

Modal design earthquake story drifts, ∆1D and ∆1R, shall be determined in accordance with Sec.

5.3.7.1 using the floor deflections of Sec. 13A.4.4.2.

13A.4.4.5 Design Earthquake Story Velocity: Design earthquake story velocity, VD, of the

structure in the direction of interest shall be calculated in accordance with the following

equations:

∇ ∇∇ (13A.4.4.5-1) D D RD = + 1

2 2

∇ (13A.4.4.5-2) 1

1

1

D

D

T D

= 2π

∆
Base Isolation and Energy Dissipation

275

∇ (13A.4.4.5-3) RD

RD

TR

= 2π

∆

where:

∇ = design earthquake story velocity due to the fundamental mode of vibration of the 1D

structure in the direction of interest (in./sec or mm/sec), and 

∇ = design earthquake story velocity due to the residual mode of vibration of the RD

structure in the direction of interest (in./sec or mm/sec).

13A.4.4.6 Maximum Earthquake Response: Total and modal maximum earthquake floor

deflections at Level i, design story drift values and design story velocity values shall be based on

the formulas of Sec. 13A.4.2, 13A.4.4 and 13A.4.5, respectively, except design earthquake roof

displacements shall be replaced by maximum earthquake roof displacements. Maximum

earthquake roof displacements shall be calculated in accordance with the following equations:

D (13A.4.4.6-1) g S T g S T

M

M M MS M

1

1 1

1M

1

1

2

B B1M

= 



 



 ≤ 



 



 4 4 2 1 2 π π

Γ Γ

D (13A.4.4.6-2) g S T

B

g S T

B RM R

M R

R

R

MS R

R

= 



 



 ≤ 



 



 4 4 2 2

2

π π

Γ Γ 1

where:

SM1 = the maximum considered earthquake, 5 percent damped, spectral response

acceleration at a period of 1 second adjusted for site class effects as defined in

Sec.4.1.2.

SMS = the maximum considered earthquake, 5 percent damped, spectral response

acceleration at short periods adjusted for site class effects as defined in Sec. 4.1.2.

B1M = Numerical coefficient as set forth in Table 13A.3.1 for effective damping equal to

$mM (m = 1) and period of structure equal to T1M.

13A.5 RESPONSE SPECTRUM ANALYSIS PROCEDURE

13A.5.1 General: This section provides required standards for response spectrum analysis of

structures with a damping system. See Sec. 13A.2.6 for limitations on the use of this procedure.

Seismic base shear and lateral forces at floors used for design of the seismic-force-resisting

system shall be based on the procedures of Sec. 13A.3.2. Seismic forces, displacements and

velocities used for design of the damping system shall be based on the procedures of Sec. 13A.3. 

The load combinations and acceptance criteria of Sec. 13A.7 shall be used to check design

responses of seismic-force-resisting system and the damping system.
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276

13A.5.2 Modeling and Analysis Requirements:

13A.5.2.1 General: A mathematical model of the seismic-force-resisting system and damping

system shall be constructed that represents the spatial distribution of mass, stiffness and damping

throughout the structure. The model and analysis shall conform to the requirements of Sec.

5.5.1, 5.5.2, and 5.5.3 for the seismic-force-resisting system and to the requirements of Sec.

13A.5.2.2 for the damping system. The stiffness and damping properties of the damping devices

used in the models shall be based on or verified by testing of the damping devices as specified in

Sec. 13A.10.

13A.5.2.2 Damping System: The elastic stiffness of elements of the damping system other than

damping devices shall be explicitly modeled. Stiffness of damping devices shall be modeled

depending on damping device type:

1. Displacement-Dependent Damping Devices: Displacement-dependent damping devices

shall be modeled with an effective stiffness that represents damping device force at the

response displacement of interest (e.g., design story drift). Alternatively, the stiffness of

hysteretic and friction damping devices may be excluded from response spectrum analysis

provided design forces in displacement-dependent damping devices, QDSD, are applied to the

model as external loads (Sec. 13A.7.3.2).

2. Velocity-Dependent Damping Devices: Velocity-dependent damping devices that have a

stiffness component (e.g., visco-elastic damping devices) shall be modeled with an effective

stiffness corresponding to the amplitude and frequency of interest.

13A.5.3 Seismic-Force-Resisting-System Design Response:

13A.5.3.1 Seismic Base Shear: The seismic base shear, V, of the structure in a given direction

shall be determined as the combination of modal components, Vm, subject to the limits of the

following equation:

V V≥ (13A.5.3.1-1) min

The seismic base shear, V, of the structure shall be determined by the square root sum of the

squares or complete quadratic combination of modal base shear components, Vm. 

13A.5.3.2 Modal Base Shear: Modal base shear of the mth mode of vibration, Vm, of the

structure in the direction of interest shall be determined in accordance with the following

equation:

V CW (13A.5.3.2-1) m Sm m =

where:

CSm = seismic response coefficient (dimensionless) of the mth mode of vibration of the

structure in the direction of interest, Sec. 13A.5.3.4 (m = 1) or Sec. 13A.5.3.6 (m >

1) and
Base Isolation and Energy Dissipation

277

= the effective gravity load of the mth W mode of vibration of the structure determined in m

accordance with Eq. 5.4.4-2 (kip or kN).

13A.5.3.3 Modal Participation Factor: The modal participation factor of the mth mode of

vibration, 'm, of the structure in the direction of interest shall be determined in accordance with

the following equation:

Γ (13A.5.3.3-1) m

m

i im

i

n

W

w

=

=

∑ φ

1

where:

= displacement amplitude at the i

th φ level of the structure for the fixed base condition im

in the mth mode of vibration in the direction of interest, normalized to unity at the

roof level.

13A.5.3.4 Fundamental Mode Seismic Response Coefficient: The fundamental mode (m = 1)

seismic response coefficient, CS1, in the direction of interest shall be determined in accordance

with the following equations:

For T1D < TS : (13A.5.3.4-1) C R

C

S

B S

d

DS

o D

1

1

= 



 





Ω

For T1D $ TS : (13A.5.3.4-2) ( ) C R

C

S

B S

d

D

o D

1

1

T1D 1

= 



 



 Ω

13A.5.3.5 Effective Fundamental Mode Period Determination: The effective fundamental

mode (m = 1) period at the design earthquake, T1D, and at the maximum considered earthquake,

T1M, shall be based either on explicit consideration of the post-yield nonlinear force deflection

characteristics of the structure or determined in accordance with the following equations:

T T (13A.4.3.5-1) 1 1 D D = μ

T T M M (13A.4.3.5-2) 1 1 = μ

13A.5.3.6 Higher Mode Seismic Response Coefficient: Higher mode (m > 1) seismic

response coefficient, CSm, of the mth mode of vibration (m > 1) of the structure in the direction of

interest shall be determined in accordance with the following equations:
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278

For Tm < TS : (13A.5.3.6-1) C R

C

S

B Sm

d

DS

o mD

= 



 





Ω

For Tm $ TS : (13A.5.3.6-2) ( ) C R

C

S

B Sm

d

D

o mD

= 



 



 1

Tm Ω

where:

Tm = period, in seconds, of the mth mode of vibration of the structure in the direction

under consideration and

BmD = numerical coefficient as set forth in Table 13A.3.1 for effective damping equal to

$mD and period of the structure equal to Tm.

13A.5.3.7 Design Lateral Force: Design lateral force at Level i due to mth mode of vibration,

Fim, of the structure in the direction of interest shall be determined in accordance with the

following equation:

F w (13A.5.3.7-1)

W im i im V m

m

= φ m

Γ

Design forces in elements of the seismic-force-resisting system shall be determined by the square

root sum of squares or complete quadratic combination of modal design forces.

13A.5.4 Damping System Design Response:

13A.5.4.1 General: Design forces in damping devices and other elements of the damping

system shall be determined on the basis of the floor deflection, story drift and story velocity

response parameters described in the following sections.

Displacements and velocities used to determine maximum forces in damping devices at each

story shall account for the angle of orientation from horizontal and consider the effects of

increased response due to torsion required for design of the seismic-force-resisting system.

Floor deflections at Level i, *iD and *iM, design story drifts, )D and )M, and design story

velocities, LD and LM, shall be calculated for both the design earthquake and the maximum

considered earthquake, respectively, in accordance with the following sections. 

13A.5.4.2 Design Earthquake Floor Deflection: The deflection of structure due to the design

earthquake at Level i in the mth mode of vibration, *imD (in. or mm), of the structure in the

direction of interest shall be determined in accordance with the following equation:

δ φ (13A.5.4.2-1) imD mD im = D
Base Isolation and Energy Dissipation

279

The total design earthquake deflection at each floor of the structure shall be calculated by the

square root sum of squares or complete quadratic combination of modal design earthquake

deflections.

13A.5.4.3 Design Earthquake Roof Displacement: Fundamental (m = 1) and higher mode (m

> 1) roof displacements due to the design earthquake, D1D and DmD (in. or mm), of the structure

in the direction of interest shall be determined in accordance with the following equations:

For m = 1: (13A.5.4.3-1) D g S T g S T

B D

D D DS D

D

1

1 1

B1D 1

= 



 



 ≤ 



 



 4 4 2 1 2 1

1

2

π π

Γ Γ

For m > 1: (13A.5.4.3-2) D g S T

B

g S T

B mD m

D m

mD

m

DS m

mD

= 



 



 ≤ 



 



 4 4 2 2

2

π π

Γ Γ 1

13A.5.4.4 Design Earthquake Story Drift: Design earthquake story drift of the fundamental

mode, )1D, and higher modes, )mD (m > 1), of the structure in the direction of interest shall be

calculated in accordance with Sec. 5.3.7.1 using modal roof displacements of Sec. 13A.5.4.3.

Total design earthquake story drift, )D (in. or mm), shall be determined by the square root of the

sum of squares or complete quadratic combination of modal design earthquake drifts.

13A.5.4.5 Design Earthquake Story Velocity: Design earthquake story velocity of the

fundamental mode, L1D, and higher modes, LmD (m > 1), of the structure in the direction of

interest shall be calculated in accordance with the following equations:

For m = 1: (13A.5.4.5-1) ∇1

1

1

D

D

T D

= 2π

∆

For m > 1: (13A.5.4.5-1) ∇ mD = 2π

∆mD

Tm

Total design earthquake story velocity, LD (in/sec or mm/sec), shall be determined by the square

root of the sum of squares or complete quadratic combination of modal design earthquake

velocities.

13A.5.4.6 Maximum Earthquake Response: Total modal floor deflection at Level i, design

story drift values and design story velocity values shall be based on the formulas of Sec.

13A.5.4.2, 13A.5.4.4 and 13A.5.4.5, respectively, except design earthquake roof displacement

shall be replaced by maximum earthquake roof displacement. Maximum earthquake roof

displacement of the structure in the direction of interest shall be calculated in accordance with

the following equations:
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280

For m = 1: (13A.5.4.6-1) D g S T g S T

M

M M MS M

1

1 1

1M

1

2

B B1M

= 



 



 ≤ 



 



 4 4 2 1 2 1

π π

Γ Γ

For m > 1: (13A.5.4.6-2) D g S T

B

g S T

B

M m

mM

m

MS m

mM

mM m

1 = 



 



 ≤ 



 



 4 4 2 2

2

π π

Γ Γ

where:

BmM = numerical coefficient as set forth in Table 13A.3.1 for effective damping equal to

$mM and period of the structure equal to Tm.

13A.6 NONLINEAR ANALYSIS PROCEDURES:

13A.6.1 General: The nonlinear procedures provided in Sec. 13A.6 supplement the nonlinear

procedures of Sec. 5.7 and 5.8 to accommodate the use of damping systems.

The stiffness and damping properties of the damping devices used in the models shall be based

on or verified by testing of the damping devices as specified in Sec. 13A.10.

13A.6.2. Nonlinear Static Analysis: The nonlinear modeling described in Sec. 5.7.1 and the

lateral loads described in Sec. 5.7.2 shall be applied to the seismic-force-resisting system. The

resulting force-displacement curve shall be used in lieu of the assumed effective yield

displacement, DY, of Equation 13A.3.4-3 to calculate the effective ductility demand due to the

design earthquake, μD, and due to the maximum considered earthquake, μM, in Eq. 13A.3.4-1 and

13A.3.4-2. The value of (R/Cd) shall be taken as 1.0 in Equations 13A.4.3.4-1, 13A.4.3.4-2 and

13A.4.3.8-1 for the equivalent lateral force analysis procedure, and in Eq. 13A.5.3.4-1,

13A.5.3.4-2, 13A.5.3.6-1, and 13A.5.3.6-2 of the response spectrum analysis procedure.

13A.6.3 Nonlinear Response History Analysis: A nonlinear response history (time history)

analysis shall utilize a mathematical model of the structure and the damping system as provided

in Sec. 5.8 and this section. The model shall directly account for the nonlinear hysteretic

behavior of elements of the structure and the damping devices to determine its response, through

methods of numerical integration, to suites of ground motions compatible with the design

response spectrum for the site. 

The analysis shall be performed in accordance with Sec. 5.8 together with the requirements of

this section.

13A.6.3.1 Damping Device Modeling: Mathematical models of displacement-dependent

damping devices shall include the hysteretic behavior of the devices consistent with test data and

accounting for all significant changes in strength, stiffness, and hysteretic loop shape. 

Mathematical models of velocity-dependent damping devices shall include the velocity

coefficient consistent with test data. If this coefficient changes with time and/or temperature,

such behavior shall be modeled explicitly. The elements of damping devices connecting damper

units to the structure shall be included in the model.
Base Isolation and Energy Dissipation

281

Exception: If the properties of the damping devices are expected to change during the

duration of the time history analysis, the dynamic response may be enveloped by the

upper and lower limits of device properties. All these limit cases for variable device

properties must satisfy the same conditions as if the time dependent behavior of the

devices were explicitly modeled.

13A.6.3.2 Response Parameters: In addition to the response parameters given in Sec. 5.8.3,

the design earthquake and maximum considered earthquake displacements, velocities, and forces

of the damping devices shall be determined.

13A.7 SEISMIC LOAD CONDITIONS AND ACCEPTANCE CRITERIA:

13A.7.1 General: Design forces and displacements determined in accordance with the

equivalent lateral force analysis procedures of Sec. 13A.4 or the response spectrum analysis

procedure of Sec. 13.5 shall be checked using the strength design criteria of these Provisions and

the seismic loading conditions of the following sections.

13A.7.2 Seismic-Force-Resisting System: The seismic-force-resisting system shall meet the

design provisions of Sec. 5.2.2 using seismic base shear and design forces determined in

accordance with Sec. 13A.4.3 or Sec 13A.5.3.

The design earthquake story drift, ∆D, as determined in either Sec. 13A.4.4.4 or 13A.5.4.4 shall

not exceed (R/Cd) times the allowable story drift, as obtained from Table 5.2.8, considering the

effects of torsion as required in Sec. 5.2.8.

13A.7.3 Damping System: The damping system shall meet the provisions of Sec. 5.2.2 for

seismic design forces determined in accordance with Sec. 13A.7.3.1 and the seismic loading

conditions of Sec. 13A.7.3.2 and Sec. 13A.5.4.

13A.7.3.1 Modal Damping System Design Forces: Modal damping system design forces shall

be calculated on the basis of the type of damping devices, and the modal design story

displacements and modal design story velocities determined in accordance with either Sec.

13A.4.4 or Sec. 13A.5.4.

Exception: Modal design story displacements and velocities determined in accordance

with either Sec. 13A.4.4 or Sec. 13A.5.4 shall be increased as required to envelop total

design story displacements and velocities determined in accordance with Sec. 13A.6,

when Sec. 13A.2.6.4.3 requires peak response to be confirmed by time history analysis.

1. Displacement-Dependent Damping Devices: Design seismic force in displacementdependent damping devices shall be based on the maximum force in the device at

displacements up to and including the design earthquake story drift, )D. 

2. Velocity-Dependent Damping Devices: Design seismic force in each mode of vibration

of velocity-dependent damping devices shall be based on the maximum force in the

device at velocities up to and including the design earthquake story velocity of the mode

of interest.
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282

Displacements and velocities used to determine design forces in damping devices at each story

shall account for the angle of orientation from horizontal and consider the effects of increased

floor response due to torsional motions.

13A.7.3.2 Seismic Load Conditions and Combination of Modal Responses: Seismic design

force, QE, in each element of the damping system due to horizontal earthquake load shall be taken

as the maximum force of the following three loading conditions:

1. Stage of Maximum Displacement: Seismic design force at the stage of maximum

displacement shall be calculated in accordance with the following equation:

Q QQ ( ) (13A.7.3.2-1) E o mSFRS

m

= ± Ω ∑ DSD

2

where:

QmSFRS = Force in an element of the damping system equal to the design seismic force

of the mth mode of vibration of the seismic-force-resisting system in the

direction of interest.

QDSD = Force in an element of the damping system required to resist design seismic

forces of displacement-dependent damping devices.

Seismic forces in elements of the damping system, QDSD, shall be calculated by imposing

design forces of displacement-dependent damping devices on the damping system as pseudostatic forces. Design seismic forces of displacement-dependent damping devices shall be

applied in both positive and negative directions at peak displacement of the structure.

2. Stage of Maximum Velocity: Seismic design force at the stage of maximum velocity shall

be calculated in accordance with the following equation:

Q Q( ) (13A.7.3.2-2) E mDSV

m

= ∑ 2

where:

QmDSV = Force in an element of the damping system required to resist design seismic

forces of velocity-dependent damping devices due to the mth mode of

vibration of structure in the direction of interest.

Modal seismic design forces in elements of the damping system, QmDSV, shall be calculated by

imposing modal design forces of velocity-dependent devices on the non-deformed damping

system as pseudo-static forces. Modal seismic design forces shall be applied in directions

consistent with the deformed shape of the mode of interest. Horizontal restraint forces shall

be applied at each floor Level i of the non-deformed damping system concurrent with the

design forces in velocity-dependent damping devices such that the horizontal displacement at

each level of the structure is zero. At each floor Level i, restraint forces shall be proportional

to and applied at the location of each mass point.
Base Isolation and Energy Dissipation

283

 

3. Stage of Maximum Acceleration: Seismic design force at the stage of maximum

acceleration shall be calculated in accordance with the following equation:

Q C Q CQ Q ( ) (13A.7.3.2-3) E mFD o mSFRS mFV mDSV

m

= +± ∑ Ω DSD

2

The force coefficients, CmFD and CmFV, shall be determined from Tables 13A.7.3.2.1 and

13A.7.3.2.2, respectively, using values of effective damping determined in accordance with

the following requirements:

a. For fundamental-mode response (m = 1) in the direction of interest, the coefficients, C1FD

and C1FV, shall be based on the velocity power term, ", that relates device force to

damping device velocity. The effective fundamental-mode damping, shall be taken as

equal to the total effective damping of the fundamental mode less the hysteretic

component of damping (e.g., $1D - $HD) at the response level of interest (i.e., μ = μD or μ

= μM).

b. For higher-mode (m > 1) or residual-mode response in the direction of interest, the

coefficients, CmFD and CmFV, shall be based on a value of " equal to 1.0. The effective

modal damping shall be taken as equal to the total effective damping of the mode of

interest (e.g., $mD). For determination of the coefficient CmFD, the ductility demand shall

be taken as equal to that of the fundamental mode (e.g., μ = μD).

Table 13A.7.3.2.1 Force Coefficient, CmFD

a, b

Effective

Damping

μ # 1.0

CmFD =1.0c

" # 0.25 " = 0.5 " = 0.75 " $ 1.0

# 0.05 1.00 1.00 1.00 1.00 μ $1.0

0.1 1.00 1.00 1.00 1.00 μ $1.0

0.2 1.00 0.95 0.94 0.93 μ $1.1

0.3 1.00 0.92 0.88 0.86 μ $1.2

0.4 1.00 0.88 0.81 0.78 μ $1.3

0.5 1.00 0.84 0.73 0.71 μ $1.4

0.6 1.00 0.79 0.64 0.64 μ $1.6

0.7 1.00 0.75 0.55 0.58 μ $1.7

0.8 1.00 0.70 0.50 0.53 μ $1.9

0.9 1.00 0.66 0.50 0.50 μ $2.1

$ 1.0 1.00 0.62 0.50 0.50 μ $2.2
2000 Provisions Chapter 13

Effective

Damping

μ # 1.0

CmFD =1.0c

" # 0.25 " = 0.5 " = 0.75 " $ 1.0

284

a

 Unless analysis or test data support other values, the force coefficient CmFD for visco-elastic

systems shall be taken as 1.0.

b

 Interpolation shall be used for intermediate values of effective damping, ", and μ. c CmFD shall be taken as equal to 1.0 for values of μ greater than or equal to the values shown.

Table 13A.7.3.2.2 Force Coefficient, CmFV

a, b

Effective

Damping

" # 0.25 " = 0.5 " = 0.75 " $ 1.0

# 0.05 1.00 0.35 0.20 0.10

0.1 1.00 0.44 0.31 0.20

0.2 1.00 0.56 0.46 0.37

0.3 1.00 0.64 0.58 0.51

0.4 1.00 0.70 0.69 0.62

0.5 1.00 0.75 0.77 0.71

0.6 1.00 0.80 0.84 0.77

 0.7 1.00 0.83 0.90 0.81

0.8 1.00 0.90 0.94 0.90

0.9 1.00 1.00 1.00 1.00

$ 1.0 1.00 1.00 1.00 1.00

a

 Unless analysis or test data support other values, the force coefficient CmFD for visco-elastic 

systems shall be taken as 1.0.

b

 Interpolation shall be used for intermediate values of effective damping, ", and μ.

13A.7.3.3 Combination of Load Effects: The effects on the damping system and its

components due to gravity loads and seismic forces shall be combined in accordance with Sec.

5.2.7 using the effect of horizontal seismic forces, QE, determined in accordance with Sec.

13A.7.3.2.

Exception: The reliability factor, D, shall be taken as equal to 1.0 in all cases and the

special load combinations of Sec. 5.2.7.1 need not apply to the design of the damping

system.

13A.7.3.4 Inelastic Response Limits: Elements of the damping system may exceed strength

limits for design loads provided it is shown by analysis or test that:
Base Isolation and Energy Dissipation

285

1. Inelastic response does not adversely affect damping system function.

2. Element forces calculated in accordance with Sec. 13A.7.3.2, using a value of So, taken as

equal to 1.0, do not exceed the strength required to meet the load combinations of Sec. 5.2.7. 

13A.8 DETAILED SYSTEM REQUIREMENTS:

13A.8.1 Damping Device Design: The design, construction and installation of damping devices

shall be based on maximum earthquake response and the following load conditions: 

1. Low-cycle, large displacement degradation due to seismic loads;

2. High-cycle, small-displacement degradation due to wind, thermal or other cyclic loads;

3. Forces or displacements due to gravity loads;

4. Adhesion of device parts due to corrosion or abrasion, biodegradation, moisture or chemical

exposure; and 

5. Exposure to environmental conditions, including but not limited to temperature, humidity,

moisture, radiation (e.g., ultraviolet light) and reactive or corrosive substances (e.g., salt

water).

Damping devices subject to failure by low-cycle fatigue shall resist wind forces without slip,

movement, or inelastic cycling.

The design of damping device shall incorporate the range of thermal conditions, device wear,

manufacturing tolerances, and other effects that cause device properties to vary during the

lifetime of the device.

13A.8.2 Multi-Axis Movement: Connection points of damping devices shall provide sufficient

articulation to accommodate simultaneous longitudinal, lateral, and vertical displacements of the

damping system.

13A.8.3 Inspection and Periodic Testing: Means of access for inspection and removal of all

damping devices shall be provided. 

The registered design professional responsible for design of the structure shall establish an

appropriate inspection and testing schedule for each type of damping device to ensure that the

devices respond in a dependable manner throughout device design life. The degree of inspection

and testing shall reflect the established in-service history of the damping devices, and the

likelihood of change in properties over the design life of devices.

13A.8.4 Manufacturing Quality Control: The registered design professional responsible for

design of the structure shall establish a quality control plan for the manufacture of damping

devices. As a minimum, this plan shall include the testing requirements of Sec. 13A.10.3. 

13A.9 DESIGN REVIEW:

13A.9.1 General: Review of the design of the damping system and related test programs shall

be performed by an independent engineering panel including persons licensed in the appropriate

disciplines and experienced in seismic analysis including the theory and application of energy

dissipation methods.
2000 Provisions Chapter 13

286

13A.9.2 Review Scope: The design review shall include the following:

1. Review of the earthquake ground motions used for design.

2. Review of design parameters of damping devices, including device test requirements, device

manufacturing quality control and assurance, and scheduled maintenance and inspection

requirements.

3. Review of nonlinear analysis methods incorporating the requirements of Sec. 5.8.4. 

4. Review of the preliminary design of the seismic-force-resisting system and the damping

system.

5. Review of the final design of the seismic-force-resisting system and the damping system and

all supporting analyses. 

13A.10 REQUIRED TESTS OF DAMPING DEVICES:

13A.10.1 General: The force-velocity-displacement and damping properties used for the design

of the damping system shall be based on the prototype tests of a selected number of damping

devices, as specified in Sec. 13A.10.2.1.

The fabrication and quality control procedures used for all prototype and production damping

devices shall be identical.

13A.10.2 Prototype Tests:

13A.10.2.1 General: The following tests shall be performed separately on two full-size

damping devices of each type and size used in the design, in the order listed below.

Representative sizes of each type of device may be used for prototype testing, provided both of

the following conditions are met:

(1) Fabrication and quality control procedures are identical for each type and size of devices

used in the structure.

(2) Prototype testing of representative sizes is accepted by the registered design professional

responsible for design of the structure.

Test specimens shall not be used for construction, unless they are accepted by the registered

design professional responsible for design of the structure and meet the requirements of Sec.

13A.10.2 and Sec. 13A.10.3.

13A.10.2.2 Data Recording: The force-deflection relationship for each cycle of each test shall

be recorded.

13A.10.2.3 Sequence and Cycles of Testing: For the following test sequences, each damping

device shall be subjected to gravity load effects and thermal environments representative of the

installed condition. For seismic testing, the displacement in the devices calculated for the
Base Isolation and Energy Dissipation

287

maximum considered earthquake, termed herein as the maximum earthquake device

displacement, shall be used.

1. Each damping device shall be subjected to the number of cycles expected in the design

windstorm, but not less than 2000 continuous fully reversed cycles of wind load. Wind load

shall be at amplitudes expected in the design wind storm, and applied at a frequency equal to

the inverse of the fundamental period of the building (f1 = 1/T1).

Exception: Damping devices need not be subjected to these tests if they are not

subject to wind-induced forces or displacements, or if the design wind force is less

than the device yield or slip force.

2. Each damping device shall be loaded with 5 fully reversed, sinusoidal cycles at the maximum

earthquake device displacement at a frequency equal to 1/T1M as calculated in Sec. 13A.4.3.5. 

Where the damping device characteristics vary with operating temperature, these tests shall

be conducted at a minimum of 3 temperatures (minimum, ambient, and maximum) that

bracket the range of operating temperatures.

Exceptions: Damping devices may be tested by alternative methods provided each

of the following conditions is met:

a. Alternative methods of testing are equivalent to the cyclic testing requirements of

this section.

b. Alternative methods capture the dependence of the damping device response on

ambient temperature, frequency of loading, and temperature rise during testing.

c. Alternative methods are accepted by the registered design professional

responsible for the design of the structure.

3. If the force-deformation properties of the damping device at any displacement less than or

equal the maximum earthquake device displacement change by more than 15 percent for

changes in testing frequency from 1/T1M to 2.5/T1, then the preceding tests shall also be

performed at frequencies equal to 1/T1 and 2.5/T1.

If reduced-scale prototypes are used to qualify the rate dependent properties of damping

devices, the reduced-scale prototypes should be of the same type and materials, and

manufactured with the same processes and quality control procedures, as full-scale

prototypes, and tested at a similitude-scaled frequency that represents the full-scale loading

rates.

13A.10.2.4 Testing Similar Devices: Damping devices need not be prototype tested provided

that both of the following conditions are met:

1. The damping device manufacturer substantiates the similarity of previously tested devices.

2. All pertinent testing and other damping device data are made available to, and accepted by

the registered design professional responsible for the design of the structure.
2000 Provisions Chapter 13

288

13A.10.2.5 Determination of Force-Velocity-Displacement Characteristics: The forcevelocity displacement characteristics of a damping device shall be based on the cyclic load and

displacement tests of prototype devices specified above. Effective stiffness of a damping device

shall be calculated for each cycle of deformation using Eq. 13.9.3-1.

13A.10.2.6 Device Adequacy: The performance of a prototype damping device shall be

assessed as adequate if all of the conditions listed below are satisfied. The 15-percent limits

specified below may be increased by the registered design professional responsible for the

design of the structure provided that the increased limit has been demonstrated by analysis to not

have a deleterious effect on the response of the structure.

13A.10.2.6.1 Displacement-Dependent Devices:

1. For Sec. 13A.10.2.3 Test 1, no signs of damage including leakage, yielding, or breakage.

2. For Sec. 13A.10.2.3 Tests 2 and 3, the maximum force and minimum force at zero

displacement for a damping device for any one cycle does not differ by more than plus or

minus 15 percent from the average maximum and minimum forces at zero displacement as

calculated from all cycles in that test at a specific frequency and temperature.

3. For Sec. 13A.10.2.3 Tests 2 and 3, the maximum force and minimum force at maximum

earthquake device displacement for a damping device for any one cycle does not differ by

more than plus or minus 15 percent from the average maximum and minimum forces at the

maximum earthquake device displacement as calculated from all cycles in that test at a

specific frequency and temperature.

4. For Sec. 13A.10.2.3 Tests 2 and 3, the area of hysteresis loop (Eloop) of a damping device for

any one cycle does not differ by more than plus or minus 15 percent from the average area of

the hysteresis loop as calculated from all cycles in that test at a specific frequency and

temperature.

5. The average maximum and minimum forces at zero displacement and maximum earthquake

displacement, and the average area of the hysteresis loop (Eloop), calculated for each test in

the sequence of Sec. 13A.10.2.3 Tests 2 and 3, shall not differ by more than plus or minus 15

percent from the target values specified by the registered design professional responsible for

the design of the structure.

13A.10.2.6.2 Velocity-Dependent Devices:

1. For Sec. 13A.10.2.3 Test 1, no signs of damage including leakage, yielding, or breakage.

2. For velocity-dependent damping devices with stiffness, the effective stiffness of a damping

device in any one cycle of Tests 2 and 3 of Sec. 13A.10.2.3 does not differ by more than plus

or minus 15 percent from the average effective stiffness as calculated from all cycles in that

test at a specific frequency and temperature.
Base Isolation and Energy Dissipation

289

3. For Sec. 13A.10.2.3 Tests 2 and 3, the maximum force and minimum force at zero

displacement for a damping device for any one cycle does not differ by more than plus or

minus 15 percent from the average maximum and minimum forces at zero displacement as

calculated from all cycles in that test at a specific frequency and temperature.

4. For Sec. 13A.10.2.3 Tests 2 and 3, the area of hysteresis loop (Eloop) of a damping device for

any one cycle does not differ by more than plus or minus 15 percent from the average area of

the hysteresis loop as calculated from all cycles in that test at a specific frequency and

temperature.

5. The average maximum and minimum forces at zero displacement, effective stiffness (for

damping devices with stiffness only), and average area of the hysteresis loop (Eloop)

calculated for each test in the sequence of Sec. 13A.10.2.3 Tests 2 and 3, shall not differ by

more than plus or minus 15 percent from the target values specified by the registered design

professional responsible for the design of the structure.

13A.10.3 Production Testing: Prior to installation in a building, damping devices shall be

tested to ensure that their force-velocity-displacement characteristics fall within the limits set by

the registered design professional responsible for the design of the structure. The scope and

frequency of the production-testing program shall be determined by the registered design

professional responsible for the design of the structure.
291

 

Chapter 14

NONBUILDING STRUCTURE DESIGN REQUIREMENTS

14.1 GENERAL:

14.1.1 Scope: Nonbuilding structures considered by the Provisions include all self-supporting

structures which carry gravity loads, with the exception of: buildings, vehicular and railroad

bridges, nuclear power generation plants, offshore platforms, and dams. Nonbuilding structures

are supported by the earth or supported by other structures, and shall be designed and detailed

to resist the minimum lateral forces specified in this chapter . Design shall conform to the

applicable requirements of the Provisions as modified by this chapter. Nonbuilding structures

that are beyond the scope of this section shall be designed in accordance with approved

standards. Approved standards as referenced herein shall consist of standards approved by the

authority having jurisdiction and shall be applicable to the specific type of nonbuilding structure.

The design of nonbuilding structures shall provide sufficient stiffness, strength, and ductility,

consistent with the requirements specified herein for buildings, to resist the effects of seismic

ground motions as represented by the following:

a. Applicable strength and other design criteria shall be obtained from other sections of the

Provisions or its referenced codes and standards.

b. When applicable strength and other design criteria are not contained in or referenced by the

Provisions, such criteria shall be obtained from approved standards. Where approved 

standards define acceptance criteria in terms of allowable stresses as opposed to strength, the

design seismic forces shall be obtained from the Provisions and reduced by a factor of 1.4 for

use with allowable stresses. Allowable stress increases used in approved standards are

permitted. Detailing shall be in accordance with the approved standards.

14.2 REFERENCES:

ACI 313 American Concrete Institute (ACI), Standard Practice for the Design and

Construction of Concrete Silos and Stacking Tubes for Storing Granular

Materials, ACI 313, 1997

ACI 350.3 American Concrete Institute (ACI), Standard Practice for the Seismic

Design of Liquid-Containing Concrete Structures, ACI 350.3/350.3R,

2001

ACI 371R-98 American Concrete Institute (ACI), Guide to the Analysis, Design, and

Construction of Concrete-Pedestal Water Towers, ACI 371R, 1995

ANSI K61.1 American National Standards Institute (ANSI), Safety Requirements for

the Storage and Handling of Anhydrous Ammonia, ANSI K61.1
2000 Provisions Chapter 14

292

ANSI/API 620 American Petroleum Institute (API), Design and Construction of Large,

Welded, Low Pressure Storage Tanks, API 620, 1992

ANSI/API 650 American Petroleum Institute (API), Welded Steel Tanks For Oil Storage,

API 650, 10th Edition, November 1998.

ANSI/API 653 American Petroleum Institute (API), Tank Inspection, Repair, Alteration,

and Reconstruction, API 653, 2nd edition, December 1995

ANSI/API 2510 American Petroleum Institute (API), Design and Construction of Liquefied

Petroleum Gas Installation, ANSI/API 2510, 7th Edition, May 1995

API Spec 12B American Petroleum Institute (API), Bolted Tanks for Storage of

Production Liquids, Specification 12B, 14th edition, February 1995

ASCE Task Rpt American Society of Civil Engineers (ASCE) Petrochemical Energy

Committee Task Report, Design of Secondary Containment in

Petrochemical Facilities, 1997

ASCE 7 American Society of Civil Engineers (ASCE), Minimum Design Loads for

Buildings and Other Structures, ASCE 7, 1998

ASME BVP American Society of Mechanical Engineers (ASME), Boiler And Pressure

Vessel Code, including addenda through 1998

ANSI/ASME American Society of Mechanical Engineers (ASME), STS-1Steel Stacks,

ASME STS, 1992

ASME B31.8 American Society of Mechanical Engineers (ASME), Gas Transmission

and Distribution Piping Systems, ASTM B31.8, 1995

ASME B96.1 American Society of Mechanical Engineers (ASME), Welded AluminumAlloy Storage Tanks, ASME B96.1, 1993

ASTM F1159 American Society for Testing and Materials (ASTM), Standard Practice

for the Design and Manufacture of Amusement Rides and Devices, ASTM

F1159, 1992

ASTM C 1298 American Society of Testing and Materials (ASTM), Standard Guide for

Design and Construction of Brick Liners for Industrial Chimneys. (ASTM

C1298)

ANSI/AWWA D100 American Water Works Association (AWWA), Welded Steel Tanks AWS

D5.2 forWater Storage, 1996

ANSI/AWWA D103 American Water Works Association (AWWA), Factory-Coated Bolted

Steel Tanks for Water Storage, 1997

ANSI/AWWA D110 American Water Works Association AWWA), Wire- and Strand-Wound

Circular for Water Storage, 1995

ANSI/AWWA D115 American Water Works Association (AWWA), Circular Prestressed

Concrete Tanks with Circumferential Tendons, 1995
Nonbuilding Structures

293

ANSI/NFPA 30 National Fire Protection Association (NFPA), Flammable and Combustible Liquids Code, 1996

ANSI/NFPA 58 National Fire Protection Association (NFPA), Storage and Handling of

Liquefied Petroleum Gas, 1995

ANSI/NFPA 59 National Fire Protection Association (NFPA), Storage and Handling of

Liquefied Petroleum Gases at Utility Gas Plants, 1998

ANSI/NFPA 59A National Fire Protection Association (NFPA), Production, Storage and

Handling of Liquefied Natural Gas (LNG), 1996

RMI Specification Rack Manufacturers Institute (RMI), Specification for the Design, Testing,

and Utilization of Industrial Steel Storage Racks, 1997

Troitsky 1990 Troitsky, M. S., Tubular Steel Structures, 1990 

49CFR, Part 193 U.S. Department of Transportation (DOT), Pipeline Safety Regulations,

Title 49 CFR Part 193

NAVFAC R-939 U.S. Naval Facilities Command (NAVFAC), The Seismic Design of

Waterfront Retaining Structures, NAVFAC R-939

NAVFAC DM-25.1 U.S. Naval Facilities Engineering Command (NAVFAC), Piers and

Wharves. NAVFAC DM-25.1

Army TM 5-809-10/ U.S. Army Corps of Engineers (USACE), Seismic Design for Buildings

NAVFAC P-355/ Chapter 13, 1992

Air Force AFM 88-3

14.3 INDUSTRY DESIGN STANDARDS AND RECOMMENDED PRACTICE: The

following standards and references form a part of the Provisions as referenced herein.

TABLE 14.3 Standards, Industry Standards, and References

Application Standard or Reference

Steel Storage Racks RMI Specification

Piers and Wharves NAVFAC R-939, NAVFAC DM-25.1

Welded Steel Tanks for Water Storage AWWA D100

Welded Steel Tanks for Petroleum and Petrochemical

Storage

API 650, API 620

Bolted Steel Tanks for Water Storage AWWA D103

Concrete Tanks for Water Storage AWWA D115, AWWA D110, ACI 350.3

Pressure Vessels ASME

Refrigerated Liquids Storage:

 Liquid Oxygen, Nitrogen and Argon NFPA 50

 Liquefied Natural Gas (LNG) NFPA 59A, DOT 49CFR

 LPG (Propane, Butane, etc.) NFPA 59, API 2510

 Ammonia ANSI K61.1

Concrete silos and stacking tubes ACI 313

Petrochemical structures ASCE Design of Secondary Containment
2000 Provisions Chapter 14

Application Standard or Reference

294

in Petrochemical Facilities

Impoundment dikes and walls:

 Hazardous Materials ANSI K61.1

 Flammable Materials NFPA 30

 Liquefied Natural Gas NFPA 59A, DOT 49CFR

Cast-in-place concrete stacks and chimneys ACI 307

Steel stacks and chimneys ASME STS

Guyed steel stacks and chimneys ASME STS, Troitsky 1990

Brick masonry liners for stacks and chimneys ASTM C1298

Amusement structures ASTM F1159

14.4 NONBUILDING STRUCTURES SUPPORTED BY OTHER STRUCTURES: If a

nonbuilding structure is supported above the base by another structure and the weight of the

nonbuilding structure is less than 25 percent of the combined weight of the nonbuilding structure

and the supporting structure, the design seismic forces of the supported nonbuilding structure

shall be determined in accordance with the requirements of Sec. 6.1.3.

If the weight of a nonbuilding structure is 25 percent or more of the combined weight of the

nonbuilding structure and the supporting structure, the design seismic forces of the nonbuilding

structure shall be determined based on the combined nonbuilding structure and supporting

structural system. For supported nonbuilding structures that have non-rigid component dynamic

characteristics, the combined system R factor shall be a maximum of 3. For supported

nonbuilding structures that have rigid component dynamic characteristics (as defined in Sec.

14.2.2), the combined system R factor shall be the value of the supporting structural system. The

supported nonbuilding structure and attachments shall be designed for the forces determined for

the nonbuilding structure in a combined systems analysis.

14.4.1 Architectural, Mechanical, and Electrical Components: Architectural, mechanical,

and electrical components supported by nonbuilding structures shall be designed in accordance

with Chapter 6 of the Provisions.

14.5 STRUCTURAL DESIGN REQUIREMENTS:

14.5.1 Design Basis: Nonbuilding structures having specific seismic design criteria established

in approved standards shall be designed using the standards as amended herein. In addition,

nonbuilding structures shall be designed in compliance with Sec. 14.3 and 14.4 to resist

minimum seismic lateral forces that are not less than the requirements of Sec. 5.4.1 with the

following additions and exceptions:

1. The response modification coefficient, R, shall be the lesser of the values given in Table

14.5.1.1 or the values in Table 5.2.2.

2. For nonbuilding systems that have an R value provided in Table 14.5.2.1, the minimum

specified value in Eq. 5.4.1.1-1 shall be replaced by:
Nonbuilding Structures

295

Cs = 0.14SDSI (14.2.1-1)

and the minimum value specified in Eq. 5.3.2.1-4 shall be replaced by:

Cs = 0.8S1I/R (14.2.1-2)

3. The overstrength factor, S0, shall be as given in Table 14.5.1.1 or Table 5.2.2..

4. The importance factor, I, shall be as given in Table 14.5.1.2 .

5. The height limitations shall be as given in Table 14.5.1.1 or Table 5.2.2.

6. The vertical distribution of the lateral seismic forces in nonbuilding structures covered by

this section shall be determined:

a. In accordance with the requirements of Sec. 5.4.3 or

b. In accordance with the procedures of Sec. 5.5 or

c. In accordance with an approved standard applicable to the specific nonbuilding

structure.

7. For nonbuilding structural systems containing liquids, gases, and granular solids supported at

the base as defined in Sec. 14.7.3.1, the minimum seismic design force shall not be less than

that required by the approved standard for the specific system.

8. Irregular structures per Sec. 5.2.3 at sites where the seismic coefficient SDS is greater than or

equal to 0.50 that cannot be modeled as a single mass shall use the procedures of Sec. 5.5.

9. Where an approved standard provides a basis for the earthquake resistant design of a

particular type of nonbuilding structure such a standard may be used subject to the following

limitations:

a. The seismic ground acceleration and seismic coefficient shall be in conformance with

the requirements of Sec. 4.1 and 4.2, respectively.

b. The values for total lateral force and total base overturning moment used in design

shall not be less than 80 percent of the base shear value and overturning moment,

each adjusted for the effects of soil-structure interaction that would be obtained using

the Provisions.

10. The base shear is permitted to be reduced in accordance with Sec. 5.5.7 to account for the

effects of soil-structure interaction. In no case shall the reduced base shear, V ̃, be less than

0.7V.
2000 Provisions Chapter 14

296

14.5.1.1 Seismic Factors:

TABLE 14.5.1.1 Seismic Coefficients for Nonbuilding Structures

Nonbuilding Structure Type R S0 Cd Structural System and Height

Limits (ft)c

Seismic Design Category

A & B C D E & F

Nonbuilding frame systems:

Concentric Braced Frames of Steel

Special Concentric Braced Frames of Steel

See Table 

5.2.2 NL

NL

NL

NL

NL

NL

NL

NL

Moment Resisting Frame Systems:

Special Moment Frames of Steel

Ordinary Moment Frames of Steel

Special Moment Frames of Concrete

Intermediate Moment Frames of Concrete

Ordinary Moment Frames of Concrete

See Table 

5.2.2 NL

NL

NL

NL

NL

NL

NL

NL

NL

50

NL

50

NL

50

NP

NL

50

NL

50

NP

Steel Storage Racks 4 2 3-1/2 NL NL NL NL

Elevated tanks, vessels, bins, or hoppersa

:

On braced legs

On unbraced legs

Irregular braced legs single pedestal or skirt supported

Welded steel

Concrete

3

3

2

2

2

2

2

2

2

2

2-1/2

2-1/2

2

2

2

NL

NL

NL

NL

NL

NL

NL

NL

NL

NL

NL

NL

NL

NL

NL

NL

NL

NL

NL

NL

Horizontal, saddle supported welded steel vessels 3 2 2-1/2 NL NL NL NL

Tanks or vessels supported on structural towers

similar to buildings

3 2 2 NL NL NL NL

Flat bottom, ground supported tanks, or vessels:

Anchored (welded or bolted steel)

Unanchored (welded or bolted steel)

Reinforced or prestressed concrete:

Tanks with reinforced nonsliding base

Tanks with anchored flexible base

Tanks with unanchored and unconstrained:

Flexible base

Other material

3

2-1/2

2

3

1-1/2

1 -/2

2

2

2

2

1-1/2

1-1/2

2-1/2

2

2

2

1-1/2

1-1/2

NL

NL

NL

NL

NL

NL

NL

NL

NL

NL

NL

NL

NL

NL

NL

NL

NL

NL

NL

NL

NL

NL

NL

NL

Cast-in-place concrete silos, stacks, and chimneys

having walls continuous to the foundation

3 1-3/4 3 NL NL NL NL
Nonbuilding Structures

Nonbuilding Structure Type R S0 Cd Structural System and Height

Limits (ft)c

Seismic Design Category

A & B C D E & F

297

Reinforced masonry structuresnot similar to

buildings

3 2 2-1/2 NL NL 50 50

Nonreinforced masonry structures not similar to

buildings

1-1/4 2 1-1/2 NL 50 50 50

Steel and reinforced concrete distributed mass

cantilever structures not covered herein including

stacks, chimneys, silos, and skirt-supported vertical

vessels that are not similar to buildings

3 2 2-1/2 NL NL NL NL

Trussed towers (freestanding or guyed), guyed stacks

and chimneys

3 2 2-1/2 NL NL NL NL

Cooling towers:

Concrete or steel

Wood frame

3-1/2

3-1/2

1-3/4

3

3

3

NL

NL

NL

NL

NL

50

NL

50

Amusement structures and monuments 2 2 2 NL NL NL NL

Inverted pendulum type structures (except elevated

tanks, vessels, bins and hoppers)b

2 2 2 NL NL NL NL

Signs and billboards 3-1/2 1-3/4 3 NL NL NL NL

Self-supporting structures, tanks or vessels not

covered above or by approved standards that are not

similar to buildings

1-1/4 2 2-1/2 NL 50 50 50

 a Support towers similar to building type structures, including those with irregularities (see Sec. 5.2.3 of the

Provisions for definition of irregular structures) shall comply with the requirements of Sec. 5.2.6.

 b

 Height shall be measured from the base.

NL = No limit.

14.5.1.2 Importance Factors and Seismic Use Group Classifications: The importance factor

(I) and seismic use group for nonbuilding structures are based on the relative hazard of the

contents, and the function. The value of I shall be the largest value determined by the approved

standards, or the largest value as selected from Table 14.5.1.2 or as specified elsewhere in

Chapter 14.
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298

V ' 0.30SDSWI (14.2.2)

TABLE 14.5.1.2

Importance Factor (I) and Seismic Use Group Classification for Nonbuilding Structures

Importance Factor I = 1.0 I = 1.25 I = 1.5

Seismic Use Group I II III

Hazard H - I H - II H - III

Function F - I F - II F - III

H - I The nonbuilding structures that are not assigned to H-II or H-III.

H - II The nonbuilding structures that have a substantial public hazard due to contents or use as

determined by the authority having jurisdiction. 

H - III The nonbuilding structures containing sufficient quantities of toxic or explosive substance

deemed to be hazardous to the public as determined by the authority having jurisdiction. 

F - I Nonbuilding structures not classified as F - III.

F - II Not applicable for nonbuilding structures.

F - III The nonbuilding structures or designated ancillary nonbuilding structures that are required

for post-earthquake recovery or as emergency back-up facilities for Seismic Use Group III

structures.

14.5.2 Rigid Nonbuilding Structures: Nonbuilding structures that have a fundamental period,

T, less than 0.06 sec, including their anchorages, shall be designed for the lateral force obtained

from the following:

where:

V = the total design lateral seismic base shear force applied to a nonbuilding

structure,

SDS = the site design response acceleration as determined from Sec. 4.2.2,

W = nonbuilding structure operating weight.

I = the importance factor as determined from Table 14.2.1.2.

The force shall be distributed with height in accordance with Sec. 5.4.3.

14.5.3 Loads: The weight, W, for nonbuilding structures shall include all dead loads as defined

for structures in Sec. 5.4.3. For purposes of calculating design seismic forces in nonbuilding

structures, W also shall include all normal operating contents for items such as tanks, vessels,

bins, and hoppers and the contents of piping. W shall include snow and ice loads when these

loads constitute 25 percent or more of W or when required by the authority having jurisdiction

based on local environmental characteristics.
Nonbuilding Structures

299

*x'

Cd*xe

I (14.6.2.1)

14.5.4 Fundamental Period: The fundamental period of the nonbuilding structure shall be

determined by methods as prescribed in Sec. 5.4.2 or by other rational methods. 

14.5.5 Drift Limitations: The drift limitations of Sec. 5.2.8 need not apply to nonbuilding

structures if a rational analysis indicates they can be exceeded without adversely effecting

structural stability or attached or interconnected components and elements such as walkways and

piping. P-delta effects shall be considered when critical to the function or stability of the

structure.

14.5.6 Materials Requirements: The requirements regarding specific materials in Chapters 8,

9, 10, 11, and 12 shall be applicable unless specifically exempted in this chapter.

14.5.7 Deflection Limits and Structure Separation: Deflection limits and structure separation

shall be determined in accordance with the Provisions unless specifically amended in this

chapter.

14.5.8 Site-Specific Response Spectra: Where required by an approved standard or the

authority having jurisdiction, specific types of nonbuilding structures shall be designed for sitespecific criteria that accounts for local seismicity and geology, expected recurrence intervals and

magnitudes of events from known seismic hazards as provided for in Sec. 4.1.3 of the

Provisions. If a longer recurrence interval is defined in the approval standard for the nonbuilding

structure such as LNG tanks, the recurrence interval required in the standard shall be used

14.6 NONBUILDING STRUCTURES SIMILAR TO BUILDINGS:

14.6.1 General: Nonbuilding structures that have structural systems that are designed and

constructed in a manner similar to buildings and have a dynamic response similar to building

structures shall be designed similar to building structures and in compliance with the Provisions

with exceptions as contained in this section.

This general category of nonbuilding structures shall be designed in accordance with Sec. 14.5.

The lateral force design procedure for nonbuilding structures with structural systems similar to

building structures (those with structural systems listed in Table 5.2.2) shall be selected in

accordance with the force and detailing requirements of Sec. 5.2.1.

The combination of load effects, E, shall be determined in accordance with Sec. 5.2.7.

14.6.2 Pipe Racks:

14.6.2.1 Design Basis: Pipe racks supported at the base shall be designed to meet the force

requirements of Sec. 5.4 or 5.5.

Displacements of the pipe rack and potential for interaction effects (pounding of the piping

system) shall be considered using the amplified deflections obtained from the following formula:

where:
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Cd = the deflection amplification factor in Table 14.5.1.1,

*xe = the deflections determined using the prescribed seismic design forces of the

Provisions, and

I = the importance factor determined from Table 14.5.1.2.

Exception: The importance factor, I, shall be determined from Table 14.5.1.2 for the

calculation of *xe.

See Sec. 3.3.11 for the design of piping systems and their attachments. Friction resulting from

gravity loads shall not be considered to provide resistance to seismic forces.

14.6.3 Steel Storage Racks: Steel storage racks supported at or below grade shall be designed

in accordance with Sec. 14.6.3 and the following or, alternatively, with the method detailed in

Section 2.7 of the RMI Specification provided that when determining the value of Ca in Sec.

2.7.3 of the RMI Specification, the value of Cs is taken as equal to SDS/2.5, the value of Cv is

taken as equal to SD1, and the value of Ip shall not be taken as less than that required in Sec. 6.1.5

of the Provisions. In addition, the value of Cs in the RMI Specification shall not be less than

0.14SDS. For storage racks supported above grade, the value of Cs in the RMI Specification shall

not be less than the value determined for Fp in accordance with Sec. 6.2 of the Provisions with Rp

taken as equal to R and ap taken as equal to 2.5.

14.6.3.1 General Requirements: Steel storage racks shall satisfy the force requirements of 

this section. 

Exception: Steel storage racks supported at the base are permitted to be designed as

structures with an R of 4 provided that the requirements of Chapter 2 are met. Higher

values of R are permitted to be used when justified by test data approved in accordance

with Sec. 1.2.6 or when the detailing requirements of Chapter 5 and 10 are met. The

importance factor I shall be taken equal to the Ip values in accordance with Sec. 6.1.5 

14.6.3.2 Operating Weight: Steel storage racks shall be designed for each of the following

conditions of operating weight, W or Wp. 

a. Weight of the rack plus every storage level loaded to 67 percent of its rated load capacity.

b. Weight of the rack plus the highest storage level only loaded to 100 percent of its rated load

capacity.

The design shall consider the actual height of the center of mass of each storage load component.

14.6.3.3 Vertical Distribution of Seismic Forces: For all steel storage racks, the vertical

distribution of seismic forces shall be as specified in Sec. 5.4.3 and in accordance with the

following:

a. The base shear, V, of the typical structure shall be the base shear of the steel storage rack

when loaded in accordance with Sec. 14.6.3.2.

b. The base of the structure shall be the floor supporting the steel storage rack. Each steel

storage level of the rack shall be treated as a level of the structure, with heights hi

, and hx

measured from the base of the structure.
Nonbuilding Structures

301

c. The factor k may be taken as 1.0.

d. The factor I shall be in accordance with Sec. 6.1.5.

14.6.3.4 Seismic Displacements: Steel storage rack installations shall accommodate the

seismic displacement of the storage racks and their contents relative to all adjacent or attached

components and elements. The assumed total relative displacement for storage racks shall be 

not less than 5 percent of the height above the base unless a smaller value is justified by test data

or analysis approved in accordance with Sec. 1.5.

14.6.4 Electrical Power Generating Facilities:

14.6.4.1 General: Electrical power generating facilities are power plants that generate

electricity by steam turbines, combustion turbines, diesel generators or similar turbo machinery.

14.6.4.2 Design Basis: Electrical power generating facilities shall be designed using the

Provisions and the appropriate factors contained in Sec. 14.5.

14.6.5 Structural Towers for Tanks and Vessels:

14.6.5.1 General: Structural towers which support tanks and vessels shall be designed to meet

the provisions of Sec 14.4. In addition, the following special considerations shall be included:

a. The distribution of the lateral base shear from the tank or vessel onto the supporting

structure shall consider the relative stiffness of the tank and resisting structural elements.

b. The distribution of the vertical reactions from the tank or vessel onto the supporting structure

shall consider the relative stiffness of the tank and resisting structural elements. When the

tank or vessel is supported on grillage beams, the calculated vertical reaction due to weight

and overturning shall be increased at least 20 percent to account for nonuniform support. The

grillage beam and vessel attachment shall be designed for this increased design value.

c. Seismic displacements of the tank and vessel shall consider the deformation of the support

structure when determining P-delta effects or evaluating required clearances to prevent

pounding of the tank on the structure.

14.6.6 Piers and Wharves:

14.6.6.1 General: Piers and wharves are structures located in waterfront areas that project into

a body of water or parallel the shore line.

14.6.6.2 Design Basis: Piers and wharves shall be designed to comply with the Provisions and

approved standards. Seismic forces on elements below the water level shall include the inertial

force of the mass of the displaced water. The additional seismic mass equal to the mass of the

displaced water shall be included as a lumped mass on the submerged element, and shall be

added to the calculated seismic forces of the pier or wharf structure. Seismic dynamic forces

from the soil shall be determined by the registered design professional.

The design shall account for the effects of liquefaction on piers and wharfs as required.

14.7 NONBUILDING STRUCTURES NOT SIMILAR TO BUILDINGS:
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302

14.7.1 General: Nonbuilding structures that have structural systems that are designed and

constructed in a manner such that the dynamic response is not similar to buildings shall be

designed in compliance with the Provisions with exceptions as contained in this section. 

This general category of nonbuilding structures shall be designed in accordance with the

Provisions and the specific applicable approved standards. Loads and load distributions shall not

be less than those determined in the Provisions.

The combination of load effects, E, shall be determined in accordance with Sec. 5.2.6.2.

Exception: The redundancy/reliability factor, D, per Sec. 5.2.4 shall be taken as 1.

14.7.2 Earth Retaining Structures:

14.7.2.1 General: This section applies to all earth retaining walls. The applied seismic forces

shall be determined in accordance with Sec. 7.5.1 with a geotechnical analysis prepared by a

registered design professional.

14.7.3 Tanks and Vessels:

14.7.3.1 General: This section applies to all tanks, vessels, bins, and silos and similar

containers storing liquids, gases, and granular solids supported at the base (hereafter referred to

generically as tanks and vessels). Tanks and vessels covered herein include reinforced concrete,

prestressed concrete, steel, and fiber-reinforced plastic materials. 

14.7.3.2 Design Basis: Tanks and vessels storing liquids, gases, and granular solids shall be

designed in accordance with the Provisions and shall be designed to meet the requirements of the

applicable approved standards shown in Table 14.3 and Chapter 4 of the Provisions as defined in

this section. Resistance to seismic forces shall be determined from a substantiated analysis based

on the approved standards shown in Table 14.3. 

h. Damping for the convective (sloshing) force component shall be taken as 0.5 percent

i. Impulsive and convective components may be combined by the direct sum or the square root

of the sum of the square (SRSS) method when the modal periods are separated. If modal

coupling may occur, the complete quadratic combination (CQC) method shall be used.

j. Vertical component of ground acceleration shall be considered in accordance with the

appropriate national standard. If the approved national standard permits the user the option

of including or excluding the vertical component of ground acceleration to comply with the

Provisions, it shall be included. For tanks and vessels not covered by an approved national

standard, the vertical seismic force shall be defined as 67 percent of the equivalent lateral

force.

14.7.3.3 Strength and Ductility: Structural components and members that are part of the lateral

support system shall be designed to provide the following:

a. Connections and attachments for anchorage and other lateral force resisting components shall

be designed to develop the strength of the anchor (e.g., minimum published yield strength, Fy

in direct tension, plastic bending moment) or So times the calculated element design load.
Nonbuilding Structures

303

b. Penetrations, manholes, and openings in shell components shall be designed to maintain the

strength and stability of the shell to carry tensile and compressive membrane shell forces.

c. Support towers for tanks and vessels with irregular bracing, unbraced panels, asymmetric

bracing, or concentrated masses shall be designed using the provisions of Sec. 5.2.3 for

irregular structures. Support towers using chevron or eccentric braced framing shall comply

with the requirements of Sec. 5. Support towers using tension only bracing shall be designed

such that the full cross section of the tension element can yield during overload conditions.

d. Compression struts that resist the reaction forces from tension braces shall be designed to

resist the lesser of the yield strength of the brace (Ag Fy), or So times the calculated tension

load in the brace.

e. The vessel stiffness relative to the support system (e.g., foundation, support tower, skirt) shall

be considered in determining forces in the vessel, the resisting components and the

connections. 

f. For concrete liquid-containing structures, system ductility and energy dissipation under

unfactored loads shall not be allowed to be achieved by inelastic deformations to such a

degree as to jeopardize the serviceability of the structure. Stiffness degradation and energy

dissipation shall be allowed to be obtained either through limited microcracking, or by means

of lateral-force resistance mechanisms that dissipate energy without damaging the structure.

14.7.3.4 Flexibility of Piping Attachments: Piping systems connected to tanks and vessels

shall consider the potential movement of the connection points during earthquakes and provide

sufficient flexibility to avoid release of the product by failure of the piping system. The piping

system and supports shall be designed so as to not impart significant mechanical loading on the

attachment to the tank or vessel shell. Local loads at piping connections shall be considered in

the design of the tank or vessel shell. Mechanical devices which add flexibility such as bellows,

expansion joints, and other flexible apparatus may be used when they are designed for seismic

loads and displacements.

Unless otherwise calculated, the minimum displacements in Table 14.7.3.4 shall be assumed. 

For attachment points located above the support or foundation elevation, the displacements in

Table 14.7.3.4 shall be increased to account for drift of the tank or vessel.
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TABLE 14.7.3.4 Minimum Displacements for Piping Attachments

Anchored Tanks or Vessels Displacements

 (inches)

Vertical displacement relative to support or foundation 2

Horizontal ( radial and tangential ) relative to support or foundation 0.5

Unanchored Tanks or Vessels (at grade)

Vertical displacement relative to support or foundation

If designed to meet approved standard.

If designed for seismic loads per the provisions but not covered by an approved standard

For tanks and vessels with a diameter <40 ft, horizontal (radial and tangential) relative to

support or foundation

6

12

8

When the elastic deformations are calculated, the minimum design displacements for piping

attachments shall be the calculated displacements at the point of attachment increased by the

amplification factor Cd.

The values given in Table 14.7.3.4 do not include the influence of relative movements of the

foundation and piping anchorage points due to foundation movements (e.g., settlement, seismic

displacements). The effects of the foundation movements shall be included in the piping system

design including the determination of the mechanical loading on the tank or vessel, and the total

displacement capacity of the mechanical devices intended to add flexibility.

14.7.3.5 Anchorage: Tanks and vessels at grade are permitted to be designed without

anchorage when they meet the requirements for unanchored tanks in approved standards. Tanks

and vessels supported above grade on structural towers or building structures shall be anchored

to the supporting structure.

The following special detailing requirements shall apply to steel tank anchor bolts in seismic

regions where SDS > 0.5 or where the structure is classified as Seismic Use Group III.

a. Hooked anchor bolts (L or J shaped embedded bolts) or other anchorage systems based solely

on bond or mechanical friction shall not be used when SDS $ 0.33. Post-installed anchors may

be used provided that testing validates their ability to develop yield load in the anchor under

cyclic loads in cracked concrete.

b. When anchorage is required, the anchor embedment into the foundation shall be designed to

develop the minimum specified yield strength of the anchor.

14.7.3.6 Ground-Supported Storage Tanks for Liquids:

14.7.3.6.1 General: Ground-supported, flat bottom tanks storing liquids shall be designed to

resist the seismic forces calculated using one of the following procedures:

a. The base shear and overturning moment calculated as if tank and the entire contents are a

rigid mass system per Sec. 14.5.2 of the Provisions or
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305

b. Tanks or vessels storing liquids in Seismic Use Group III or with a diameter greater than 20 

ft shall be designed to consider the hydrodynamic pressures of the liquid in determining the

equivalent lateral forces and lateral force distribution per the approved standards listed in

Table 14.3 and Sec. 14.7.3 of the Provisions.

c. The force and displacement provisions of Sec. 14.5.4 of the Provisions.

The design of tanks storing liquids shall consider the impulsive and convective (sloshing) effects

and consequences on the tank, foundation, and attached elements. The impulsive component

corresponds to the high frequency amplified response to the lateral ground motion of the tank

roof, shell and portion of the contents that moves in unison with the shell. The convective

component corresponds to the low frequency amplified response of the contents in the

fundamental sloshing mode. Damping for the convective component shall be 0.5 percent for the

sloshing liquid unless otherwise defined by the approved national standard. The following

definitions shall apply: 

Tc = natural period of the first (convective) mode of sloshing,

Ti

 = fundamental period of the tank structure and impulsive component of the content,

Tv = natural period of vertical vibration of the liquid and tank structural system,

Vi = base shear due to impulsive component from weight of tank and contents,

Vc = base shear due to the convective component of the effective sloshing mass,

The seismic base shear is the combination of the impulsive and convective components: 

V = + V V i c ( 14.7.3.6.1)

where:

i

ai i V

S W

R =

c

ac c V

S W

R =

Sai = the spectral acceleration as a multiplier of gravity including the site impulsive

components at period Ti

 and 5 percent damping.

For Ti < Ts, Sai = SDS.

For Ti > Ts, . ai

D

i

S

S

T = 1
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306

Note: When an approved national standard is used in which the spectral acceleration

for the tank shell, and the impulsive component of the liquid is independent of Ti, then

Sai = SDS for all cases.

Sac = the spectral acceleration of the sloshing liquid based on the sloshing period Tc and 0.5

percent damping.

For Tc < 4.0 sec, ac

D

c

S

S

T = 15. 1

For Tc of 4.0 sec or greater, ac

D

c

S

S

T = 1

2

6

and Tc

D

g

H

D

= 



 





2

368

368 π

. tanh .

where D = the tank diameter in feet, H = liquid height (feet or meters) and g =

acceleration due to gravity in consistent units. 

Wi = impulsive weight (impulsive component of liquid, roof and equipment, shell, bottom, and

internal components,

Wc = the portion of the liquid weight sloshing.

The general design response spectra for ground-supported liquid storage tanks is shown in Figure

14.7.3.6-1.
Nonbuilding Structures

307

*s ' 0.5DISac (14.7.3.6.1.2)

Design Response Spectra for Ground-Supported Liquid Storage Tanks

Period, T

Spectral Response Acceleration, Sa

SDS

SD1

T0 TS

T

=1 sec

T=4 sec 

( ) 5% 1= β = T

S Sai D

( ) 0.5% 1.5 1

= β = T

S Sac D

( ) 0.5% 6

2

1

= β= T

S Sac D

Figure 14.7.3.6-1

14.7.3.6.1.1 Distribution of Hydrodynamic and Inertia Forces: Unless otherwise required by

the appropriate approved standard in Table 14.3, the method given in ACI 350.3 may be used to

determine the vertical and horizontal distribution of the hydrodynamic and inertia forces on the

walls of circular and rectangular tanks. 

14.7.3.6.1.2 Freeboard: Sloshing of the liquid within the tank or vessel shall be considered in

determining the freeboard required above the top capacity liquid level. A minimum freeboard

shall be provided per Table 14.7.3.6.1.2. The height of the sloshing wave can be estimated by: 

TABLE 14.7.3.6.1.2 Minimum Required Freeboard

Value of SDS Seismic Use Group

I II III

SDS < 0.167g a a *s

c

0.167g # SDS < 0.33g a a *s

c

0.33g # SDS < 0.50g a 0.7*s

b *sc

0.50g # SDS a 0.7*s

b *sc
2000 Provisions Chapter 14

308

a

 No minimum freeboard is required.

b

 A freeboard equal to 0.7*s is required unless one of the following alternatives is provided:

1. Secondary containment is provided to control the product spill.

2. The roof and supporting structure are designed to contain the sloshing liquid. c

 Freeboard equal to the calculated wave height, *s, is required unless one of the following alternatives is

provided:

1. Secondary containment is provided to control the product spill.

2. The roof and supporting structure are designed to contain the sloshing liquid.

14.7.3.6.1.3 Equipment and Attached Piping: Equipment, piping, and walkways or other

appurtenances attached to the structure shall be designed to accommodate the displacements

imposed by seismic forces. For piping attachments, see Sec. 14.7.3.4. 

14.7.3.6.1.4 Internal Components: The attachments of internal equipment and accessories

which are attached to the primary liquid or pressure retaining shell or bottom, or provide

structural support for major components (e.g., a column supporting the roof rafters) shall be

designed for the lateral loads due to the sloshing liquid in addition to the inertial forces. (See

Wozniak and Mitchell, 1978).

14.7.3.6.1.5 Sliding Resistance: The transfer of the total lateral shear force between the tank or

vessel and the subgrade shall be considered as follows:

a. For unanchored flat bottom steel tanks, the overall horizontal seismic shear force shall be

resisted by friction, Vs, between the tank bottom and the foundation or subgrade. Unanchored

storage tanks must be designed such that sliding will not occur when the tank is full of stored

product. The maximum calculated seismic base shear, Vs, shall not exceed W tan 30o (Vs < W

tan 30o

).

V shall be determined using the effective weight of the tank, roof and contents after reduction

for coincident vertical earthquake. Lower values of the friction factor should be used if the

design of bottom to supporting foundation does not justify the friction value above (e.g., leak

detection membrane beneath the bottom with a lower friction factor, smooth bottoms, etc).

b. No additional lateral anchorage is required for anchored steel tanks designed in accordance

with approved standards.

c. The lateral shear transfer behavior for special tank configurations (e.g., shovel bottoms,

highly crowned tank bottoms, tanks on grillage) can be unique and are beyond the scope of

the provisions.

14.7.3.6.1.6 Local Shear Transfer: Local transfer of the shear from the roof to the wall and the

wall of the tank into the base shall be considered. For cylindrical tanks and vessels, the peak

local tangential shear per unit length shall be calculated by: 

V max

V

D = 2

π

(14.7.3.6.1.6)
Nonbuilding Structures

309

a. Tangential shear in flat bottom steel tanks shall be transferred through the welded connection

to the steel bottom. This transfer mechanism is deemed acceptable for steel tanks designed in

accordance with the approved standards and Sas < 1.0.

b. For concrete tanks with a sliding base where the lateral shear is resisted by friction between

the tank wall and the base, the friction coefficient shall not exceed tan 30o.

c. In fixed-base or hinged-base concrete tanks, the total horizontal seismic base shear is shared

by membrane (tangential) shear and radial shear into the foundation. For anchored flexiblebase concrete tanks, the majority of the base shear is resisted by membrane (tangential) shear

through the anchoring system with only insignificant vertical bending in the wall. The

connection between the wall and floor shall be designed to resist the maximum tangential

shear.

14.7.3.6.1.7 Pressure Stability: For steel tanks, the internal pressure from the stored product

stiffens thin cylindrical shell structural elements subjected to membrane compression forces. 

This stiffening effect may be considered in resisting seismically induced compressive forces if

permitted by the approved standard or the building official having jurisdiction.

14.7.3.6.1.8 Shell Support: Steel tanks resting on concrete ring walls or slabs shall have a

uniformly supported annulus under the shell. Uniform support shall be provided by one of the

following methods:

a. Shimming and grouting the annulus,

b. Using fiberboard or other suitable padding

c. Using butt-welded bottom or annular plates resting directly on the foundation,

d. Using closely spaced shims (without structural grout) provided that the localized bearing

loads are considered in the tank wall and foundation to prevent local crippling and spalling.

Anchored tanks shall be shimmed and grouted. Local buckling of the steel shell for the peak

compressive force due to operating loads and seismic overturning shall be considered.

14.7.3.6.1.9 Repair, Alteration ,or Reconstruction: Repairs, modifications or reconstruction

(i.e., cut down and re-erect) of a tank or vessel shall conform to industry standard practice and

the Provisions. For welded steel tanks storing liquids, see API 653 and the approved national

standard in Table 14.3. Tanks that are relocated shall be re-evaluated for the seismic loads for

the new site and the requirements of new construction in accordance with the appropriate

approved national standard and the Provisions. 

14.7.3.7 Water and Water Treatment Tanks and Vessels:

14.7.3.7.1 Welded Steel: Welded steel water storage tanks and vessels shall be designed in

accordance with the seismic requirements of AWWA D100 except that the design input forces

shall be modified as follows: 

The impulsive and convective components of the base shear are defined by the following

equations for allowable stress design procedures:
2000 Provisions Chapter 14

310

i

DS V i

S I

R = W 14. (14.7.3.7.1)

For Ts < Tc < 4.0 sec., . c

DS

c

V c

S I

RT = W 14.

For Tc of 4.0 sec or greater, . c

DS s

c

V c

S I

R

T

T = W

6

14 2 .

a. Substitute the above parameters into AWWA D100Eq. 13-4 and 13-8. Substitute the

expression and substitute the term “B” for the term “S” in these ( )

DS

w

S I

R for

ZI

2514 . . R ... ...

equations in AWWA D100, where SDS and TS, are defined in Sec. 4.1.2.5, R is defined in

Table 14.2.1.1, B = 1.25Ts when Tc is in the range Ts < Tc # 4.0 sec, B = 1.11TS when Tc is >

4.0 sec.

Thus, AWWA D100 Eq. 13-4 for base shear at the bottom of the tank shell becomes: 

( ) ACT [ ] ( ) DS V sr f

S I

R

= ++ + + W W W W BC W

18

25 14

014 1 12

. . .

Alternatively, 

For Ts < Tc < 4.0 sec, . ACT ( ) DS

sr f

s

c

V

S I

R WWW W

T

T

= ++ + + W 



 



 14 1 2 15 . .

For Tc > 4.0 sec, . ACT ( ) DS

sr f

s

c

V

S I

R WWW W

T

T

= ++ + + W 



 



 14 1 6 2 2 .

Similarly, AWWA D100 Eq. 13-8 for overturning moment applied to the bottom of the tank

shell in AWWA D100 becomes:

( ) M [ ] ( ) S I

R W X W H W X BC W X DS

= ss rt





 



 ++ +

18

2514 014 11 12 2 . . .
Nonbuilding Structures

311

b. The hydrodynamic seismic hoop tensile stress is defined in AWWA D100 Eq. 13-20 through

13-25. When using these equations, make the following substitution directly into the

equations: 

c. Sloshing height shall be calculated per Sec 14.7.3.7.1.2 instead of (Eq 13-26) of AWWA

D100.

14.7.3.7.2 Bolted Steel: Bolted steel water storage structures shall be designed in accordance

with the seismic requirements of AWWA D103 except that the design input forces shall be

modified in the same manner shown in Sec 14.7.3.8.1 of the Provisions.

14.7.3.7.3 Reinforced and Prestressed Concrete: Reinforced and prestressed concrete tanks

shall be designed in accordance with the seismic requirements of ACI 350.3 except that the

design input forces shall be modified as follows:

a. For TI

 < To, and TI > Ts, substitute the term where Sa is defined in Sec. 4.1.2.6,

Sa I

14. R

Subsections 1, 2, or 3 or Eq. 4.1.2.6-3, for the terms in the appropriate equations as shown

below: 

For shear and overturning moment equations of AWWA D110 and AWWA D115. 1

1

ZIC

R

For in the base shear and overturning moment equations of ACI 350.3. 

ZISC1

Ri

b. For To # TI # Ts, substitute the term for terms and . S DS I

14. R

ZICi

R1

i

i

ZISC

R

c. For all values of Tc (or Tw), and are replaced by c

c

ZIC

R

c

c

ZISC

R

D

c

DS

c

S

S I

T

or

S I

T

T 1

2 2

6 6 .. ..



 









 





w

DS

R

ZI for R

S I ..... ..... 2.5(1.4 )
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Thus, for To # TI # Ts, AWWA D110 Eq. 4-1 becomes and Eq. I ( ) DS V sRI

S I

R

= ++ WW W 14.

4-2 becomes where Sa, SD1, SDS, T0, and Ts c are defined in Sec. 4.1.2.6 DS s

c

V C

S I

R

T

T = W 



 



 6

14 2 .

of the Provisions.

14.7.3.8 Petrochemical and Industrial Tanks and Vessels Storing Liquids:

14.7.3.8.1 Welded Steel: Welded steel petrochemical and industrial tanks and vessels storing

liquids shall be designed in accordance with the seismic requirements of API 650 and API 620

except that the design input forces shall be modified as follows: 

a. When using the equations in API 650 Sec. E.3, substitute the following into the equation for

overturning moment M (where SDS and Ts are defined in Sec. 4.1.2.5 of the Provisions). 

Thus,

In the range Ts < Tc # 4.0 sec, 2

0 75

C 10

S

T

and S c

= = . ... ... .

M = ++ + S DS s s t t I[ ] 0 24 080 . . ( ) W X WH WX CTW X 1 1 22 2 2

In the range Tw > 4.0 sec,

 and M = ++ + S DS s s t t s I[ ] 0 24 0 71 . . ( ) W X WH W X CTW X 11 2 2 2

2 2

3375

C 10

S

T

and S c

= = . ... ... .

14.7.3.8.2 Bolted Steel: For bolted steel tanks used for storage of production liquids, API 12B

covers the material, design, and erection requirements for vertical, cylindrical, and aboveground

bolted tanks in nominal capacities of 100 to 10,000 barrels for production service. Unless

required by the authority having jurisdiction, these temporary structures need not be designed for

seismic loads. If design for seismic load is required, the loads may be adjusted for the temporary

nature of the anticipated service life.

14.7.3.8.3 Reinforced and Prestressed Concrete: Reinforced concrete tanks for the storage

of petrochemical and industrial liquids shall be designed in accordance with the force

requirements of Sec. 14.7.3.8.3.

14.7.3.9 Ground-Supported Storage Tanks for Granular Materials

14.7.3.9.1 General: The intergranular behavior of the material shall be considered in

determining effective mass and load paths, including the following behaviors:

a. Increased lateral pressure (and the resulting hoop stress) due to loss of the intergranular

friction of the material during the seismic shaking.
Nonbuilding Structures

313

b. Increased hoop stresses generated from temperature changes in the shell after the material

has been compacted.

c. Intergranular friction which can transfer seismic shear directly to the foundation.

14.7.3.9.2 Lateral Force Determination: The lateral forces for tanks and vessels storing

granular materials at grade shall be determined by the requirements and accelerations for short

period structures (i.e., Sas).

14.7.3.9.3 Force Distribution to Shell and Foundation:

14.7.3.9.3.1 Increased Lateral Pressure: The increase in lateral pressure on the tank wall shall

be added to the static design lateral pressure but shall not be used in the determination of

pressure stability effects on the axial buckling strength of the tank shell.

14.7.3.9.3.2 Effective Mass: A portion of a stored granular mass will acts with the shell (the

effective mass). The effective mass is related to the physical characteristics of the product, the

height-to-diameter (H/D) ratio of the tank and the intensity of the seismic event. The effective

mass shall be used to determine the shear and overturning loads resisted by the tank.

14.7.3.9.3.3 Effective Density: The effective density factor (that part of the total stored mass

of product which is accelerated by the seismic event) shall be determined in accordance ACI 313.

14.7.3.9.3.4 Lateral Sliding: For granular storage tanks that have a steel bottom and are

supported such that friction at the bottom to foundation interface can resist lateral shear loads, no

additional anchorage to prevent sliding is required. For tanks without steel bottoms (i.e., the

material rests directly on the foundation), shear anchorage shall be provided to prevent sliding.

14.7.3.9.3.5 Combined Anchorage Systems: If separate anchorage systems are used to prevent

overturning and sliding, the relative stiffness of the systems shall be considered in determining

the load distribution.

14.7.3.9.4 Welded Steel Structures: Welded steel granular storage structures shall be designed

for Chapter 4 of the Provisions. Component allowable stresses and materials shall be per

AWWA D100 except the allowable circumferential membrane stresses and material

requirements in API 650 shall apply.

14.7.3.9.5 Bolted Steel Structures: Bolted steel granular storage structures shall be designed in

compliance with Chapter 4 of the Provisions. Component allowable stresses and materials shall

be per AWWA D103.

14.7.3.9.6 Reinforced Concrete Structures: Reinforced concrete structures for the storage of

granular materials shall be designed in accordance with the force requirements of Chapter 4 of

the Provisions and the requirements of ACI 313.

14.7.3.9.7 Prestressed Concrete Structures: Prestressed concrete structures for the storage of

granular materials shall be designed in accordance with the force provisions of Chapter 4 of the

Provisions and the requirements of ACI 313.

14.7.3.10 Elevated Tanks and Vessels for Liquids and Granular Materials:
2000 Provisions Chapter 14

314

14.7.3.10.1 General: This section applies to tanks, vessels, bins, and hoppers that are elevated

above grade where the supporting tower is an integral part of the structure or where the primary

function of the tower is to support the tank or vessel. Tanks and vessels that are supported within

buildings, or are incidental to the primary function of the tower are considered mechanical

equipment and shall be designed in accordance with Chapter 6 of the Provisions.

Elevated tanks shall be designed for the force and displacement requirements of the applicable

approved standard, or Sec 14.5.

14.7.3.10.2 Effective mass: The design of the supporting tower or pedestal, anchorage, and

foundation for seismic overturning shall assume the material stored is a rigid mass acting at the

volumetric center of gravity. The effects of fluid-structure interaction may be considered in

determining the forces, effective period, and mass centroids of the system if the following

requirements are met:

a. The sloshing period, Tc is greater than 3T where T = natural period of the tank with confined

liquid (rigid mass) and supporting structure. 

b. The sloshing mechanism (i.e., the percentage of convective mass and centroid) is determined

for the specific configuration of the container by detailed fluid structure interaction analysis

or testing.

Soil-structure interaction may be included in determining T providing the provisions of Sec 2.5

are met. 

14.7.3.10.3 P-Delta effects: The lateral drift of the elevated tank shall be considered as follows:

a. The design drift, the elastic lateral displacement of the stored mass center of gravity shall be

increased by the factor Cd for evaluating the additional load in the support structure.

b. The base of the tank shall be assumed to be fixed rotationally and laterally

c. Deflections due to bending, axial tension or compression shall be considered. For pedestal

tanks with a height to diameter ratio less than 5, shear deformations of the pedestal shall be

considered.

d. The dead load effects of roof mounted equipment or platforms shall be included in the

analysis.

e. If constructed within the plumbness tolerances specified by the approved standard, initial tilt

need not be considered in the P-delta analysis.

14.7.3.10.4 Transfer of Lateral Forces into Support Tower: For post supported tanks and

vessels that are cross braced:

a. The bracing shall be installed in such a manner as to provide uniform resistance to the lateral

load (e.g., pretensioning or tuning to attain equal sag).

b. The additional load in the brace due to the eccentricity between the post to tank attachment

and the line of action of the bracing shall be included.
Nonbuilding Structures

315

c. Eccentricity of compression strut line of action (elements that resist the tensile pull from the

bracing rods in the lateral force resisting systems) with their attachment points shall be

considered.

d. The connection of the post or leg with the foundation shall be designed to resist both the

vertical and lateral resultant from the yield load in the bracing assuming the direction of the

lateral load is oriented to produce the maximum lateral shear at the post to foundation

interface. Where multiple rods are connected to the same location, the anchorage shall be

designed to resist the concurrent tensile loads in the braces.

14.7.3.10.5 Evaluation of Structures Sensitive to Buckling Failure: Shell structures that

support substantial loads may exhibit a primary mode of failure from localized or general

buckling of the support pedestal or skirt during seismic loads. Such structures may include

single pedestal water towers, skirt supported process vessels, and similar single member towers. 

Where the structural assessment concludes that buckling of the support is the governing primary

mode of failure, structures and components in Seismic Use Group III shall be designed to resist

the seismic forces as follows:

a. The seismic response coefficient for this evaluation shall be per Sec 5.3.2.1 of the Provisions

with I/R set equal to 1.0. Soil-structure and fluid-structure interaction may be utilized in

determining the structural response. Vertical or orthogonal combinations need not be

considered.

b. The resistance of the structure or component shall be defined as the critical buckling

resistance of the element (i.e. a factor of safety set equal to 1.0).

c. The anchorage and foundation shall be designed to resist the load determined in item a. The

foundation shall be proportioned to provide a stability ratio of 1.2 for the overturning

moment. The maximum toe pressure under the foundation shall not exceed the ultimate

bearing capacity or the lesser of 3 times the allowable bearing capacity. All structural

components and elements of the foundation shall be designed to resist the combined loads

with a load factor of 1.0 on all loads, including dead load, live load and earthquake load.

Anchors shall be permitted to yield. 

14.7.3.10.6 Welded Steel Water Storage Structures: Welded steel elevated water storage

structures shall be designed and detailed in accordance with the seismic requirements of AWWA

D100 and the Provisions except that the design input forces shall be modified by substituting the

following terms for in AWWA D100 Eq.13-1 and 13-3 of and set the value for S = 1.0. ZIC

Rw

For T < Ts, substitute the term .

S DS I

14. R

For Ts < T < 4.0 sec, substitute the term . ( )

S D I

T R

1

14.
2000 Provisions Chapter 14

316

For T > 4.0 sec, substitute the term . ( )

S D I

T R

1

2 14.

14.7.3.10.6.1 Analysis Procedures: The equivalent lateral force procedure may be used. A

more rigorous analysis shall be permitted. Analysis of single pedestal structures shall be based

on a fixed-base, single-degree-of-freedom model. All mass, including the liquid, shall be

considered rigid unless the sloshing mechanism (i.e., the percentage of convective mass and

centroid) is determined for the specific configuration of the container by detailed fluid structure

interaction analysis or testing. Soil-structure interaction may be included.

14.7.3.10.6.2 Structure Period: The fundamental period of vibration of the structure shall be

established using the structural properties and deformational characteristics of the resisting

elements in a substantiated analysis. The period used to calculate the seismic response

coefficient shall not exceed 4.0 sec. See AWWA D100 for guidance on computing the

fundamental period of cross braced structures.

14.7.3.10.7 Concrete Pedestal (Composite) Tanks: Concrete pedestal (composite) elevated

water storage structures shall be designed in accordance with the requirements of ACI 371 

except that the design input forces shall be modified as follows:

In ACI 371 Eq. 4-8a:

For Ts < T < 4.0 sec, substitute the term for

S D I

TR

1 Cv

RT

12

2 3

.

For T > 4.0 sec, substitute the term for 

S D I

T R

1

2

4 Cv

RT

12

2 3

.

In ACI 371 Eq. 4-8b, substitute the term for S DS I

R

Ca

R

2 5.

In ACI 371 Eq. 4-9, substitute the term 0.2SDS for 0.5Ca.

14.7.3.10.7.1 Analysis Procedures: The equivalent lateral force procedure may be used for all

structures and shall be based on a fixed-base, single-degree-of-freedom model. All mass,

including the liquid, shall be considered rigid unless the sloshing mechanism (i.e., the percentage

of convective mass and centroid) is determined for the specific configuration of the container by

detailed fluid structure interaction analysis or testing. Soil-structure interaction may be included.

A more rigorous analysis is permitted.

14.7.3.10.7.2 Structure Period: The fundamental period of vibration of the structure shall be

established using the uncracked structural properties and deformational characteristics of the

resisting elements in a properly substantiated analysis. The period used to calculate the seismic

response coefficient shall not exceed 2.5 sec.

14.7.3.11 Boilers and Pressure Vessels:
Nonbuilding Structures

317

14.7.3.11.1 General: Attachments to the pressure boundary, supports, and lateral force resisting

anchorage systems for boilers and pressure vessels shall be designed to meet the force and

displacement requirements of Sec 3.1.3 and 3.1.4 and the additional requirements of this section. 

Boilers and pressure vessels categorized as Seismic Use Group II or III shall be designed to meet

the force and displacement requirements of Sec 3.1.3 and 3.1.4.

14.7.3.11.2 ASME Boilers and Pressure Vessels: Boilers or pressure vessels designed and

constructed in accordance with ASME shall be deemed to meet the requirements of this section

provided that the displacement requirements of Sec 3.1.3 and 3.1.4 are used with appropriate

scaling of the force and displacement requirements to the working stress design basis.

14.7.3.11.3 Attachments of Internal Equipment and Refractory: Attachments to the pressure

boundary for internal and external ancillary components (e.g., refractory, cyclones, trays) shall be

designed to resist the seismic forces in the Provisions to safeguard against rupture of the pressure

boundary. Alternatively, the element attached may be designed to fail prior to damaging the

pressure boundary provided that the consequences of the failure does not place the pressure

boundary in jeopardy. For boilers or vessels containing liquids, the effect of sloshing on the

internal equipment shall be considered if the equipment can damage the integrity of the pressure

boundary.

14.7.3.11.4 Coupling of Vessel and Support Structure: Where the mass of the operating

vessel or vessels supported is greater than 25 percent of the total mass of the combined structure,

the coupling of the masses shall be considered. Coupling with adjacent, connected structures

such as multiple towers shall be considered if the structures are interconnected with elements

that will transfer loads from one structure to the other.

14.7.3.11.5 Effective Mass: Fluid-structure interaction (sloshing) shall be considered in

determining the effective mass of the stored material providing sufficient liquid surface exists for

sloshing to occur and the Tc is greater than 3T. Changes to or variations in material density with

pressure and temperature shall be considered.

14.7.3.11.6 Other Boilers and Pressure Vessels: Boilers and pressure vessels that are

designated Seismic Use Group III but are not designed and constructed in accordance with the

requirements of ASME shall meet the following requirements:

The seismic loads in combination with other service loads and appropriate environmental effects

shall not exceed the material strength shown in Table 14.7.3.11.6.

TABLE 14.7.3.11.6 Maximum Material Strength

Material

Minimum

Ratio

Fu/Fy

Max Material

Strength

Vessel Material

Max Material

Strength

Threaded Materiala

Ductile (e.g., steel, aluminum,

copper) 1.33 b 90% 70%

Semi-ductile 1.2 c 70% 50%

Nonductile (e.g., cast iron, ceramics,

fiberglass) NA 25% 20%

a

 Threaded connection to vessel or support system.

b

 Minimum 20% elongation per the ASTM material specification.
2000 Provisions Chapter 14

318

c

 Minimum 15% elongation per the ASTM material specification.

Consideration shall be made to mitigate seismic impact loads for boiler or vessel components

constructed of nonductile materials or vessels operated in such a way that material ductility is

reduced (e.g., low temperature applications).

14.7.3.11.7 Supports and Attachments for Boilers and Pressure Vessels: Attachments to the

pressure boundary and support for boilers and pressure vessels shall meet the following

requirements: 

a. Attachments and supports transferring seismic loads shall be constructed of ductile materials

suitable for the intended application and environmental conditions.

b. Seismic anchorages embedded in concrete shall be ductile and detailed for cyclic loads.

c. Seismic supports and attachments to structures shall be designed and constructed so that the

support or attachment remains ductile throughout the range of reversing seismic lateral loads

and displacements.

d. Vessel attachments shall consider the potential effect on the vessel and the support for

uneven vertical reactions based on variations in relative stiffness of the support members,

dissimilar details, non-uniform shimming or irregular supports. Uneven distribution of

lateral forces shall consider the relative distribution of the resisting elements, the behavior of

the connection details, and vessel shear distribution.

The requirements of Sec.14.5 and 14.7.3.10.5 shall also be applicable to this section.

14.7.3.12 Liquid and Gas Spheres:

14.7.3.12.1 General: Attachments to the pressure or liquid boundary, supports, and lateral force

resisting anchorage systems for liquid and gas spheres shall be designed to meet the force and

displacement requirements of Sec 3.1.3 and 3.1.4 and the additional requirements of this section.

Spheres categorized as Seismic Use Group II or III shall themselves be designed to meet the force

and displacement requirements of Sec 3.1.3 and 3.1.4.

14.7.3.12.2 ASME Spheres: Spheres designed and constructed in accordance with Division

VIII of ASME shall be deemed to meet the requirements of this section providing the

displacement requirements of Sec 3.1.3 and 3.1.4 are used with appropriate scaling of the force

and displacement requirements to the working stress design basis.

14.7.3.12.3 Attachments of Internal Equipment and Refractory: Attachments to the pressure

or liquid boundary for internal and external ancillary components (e.g., refractory, cyclones,

trays) shall be designed to resist the seismic forces in the Provisions to safeguard against rupture

of the pressure boundary. Alternatively, the element attached to the sphere could be designed to

fail prior to damaging the pressure or liquid boundary providing the consequences of the failure

do not place the pressure boundary in jeopardy. For spheres containing liquids, the effect of

sloshing on the internal equipment shall be considered if the equipment can damage the pressure

boundary.
Nonbuilding Structures

319

14.7.3.12.4 Effective Mass: Fluid-structure interaction (sloshing) shall be considered in

determining the effective mass of the stored material providing sufficient liquid surface exists for

sloshing to occur and the Tc is greater than 3T. Changes to or variations in fluid density shall be

considered.

14.7.3.12.5 Post- and Rod- Supported: For post-supported spheres that are cross braced:

a. The requirements of Sec. 14.7.3.10.4 shall also be applicable to this section.

b. The stiffening effect of (reduction in lateral drift) from pretensioning of the bracing shall be

considered in determining the natural period.

c. The slenderness and local buckling of the posts shall be considered.

d. Local buckling of the sphere shell at the post attachment shall be considered.

e. For spheres storing liquids, bracing connections shall be designed and constructed to develop

the minimum published yield strength of the brace. For spheres storing gas vapors only,

bracing connection shall be designed for Wo times the maximum design load in the brace.

Lateral bracing connections directly attached to the pressure or liquid boundary are

prohibited.

14.7.3.12.6 Skirt Supported: For skirt-supported spheres, the following requirements shall

apply:

a. The provisions of Sec. 14.7.3.10.5 also shall apply. 

b. The local buckling of the skirt under compressive membrane forces due to axial load and

bending moments shall be considered.

c. Penetration of the skirt support (e.g., manholes, piping) shall be designed and constructed to

maintain the strength of the skirt without penetrations.

14.7.3.13 Refrigerated Gas Liquid Storage Tanks and Vessels:

14.7.3.13.1 General: The seismic design of the tanks and facilities for the storage of liquefied

hydrocarbons and refrigerated liquids is beyond the scope of this section. The design of such

tanks is addressed in part by various approved standards as listed in Table 14.3.

Exception: Low pressure, welded steel storage tanks for liquefied hydrocarbon gas

(e.g., LPG, butane) and refrigerated liquids (e.g., ammonia) could be designed in

accordance with the requirements of Sec. 14.7.3.8 and API 620.

14.7.3.14 Horizontal, Saddle-Supported Vessels for Liquid or Vapor Storage:

14.7.3.14.1 General: Horizontal vessels supported on saddles (sometimes referred to as

blimps) shall be designed to meet the force and displacement requirements of Sec 3.1.3 and

3.1.4.

14.7.3.14.2 Effective mass: Changes to or variations in material density shall be considered. 

The design of the supports, saddles, anchorage, and foundation for seismic overturning shall

assume the material stored is a rigid mass acting at the volumetric center of gravity.
2000 Provisions Chapter 14

320

14.7.3.14.3 Vessel Design: Unless a more rigorous analysis is performed, vessels shall be

designed as follows:

a. Horizontal vessels with a length to diameter ratio of 6 or more may be assumed to be a

simply supported beam spanning between the saddles for determining the natural period of

vibration and global bending moment. 

b. Horizontal vessels with a length to diameter ratio of less than 6, the effects of “deep beam

shear” shall be considered when determining the fundamental period and stress

distribution.

c. Local bending and buckling of the vessel shell at the saddle supports due to seismic load

shall be considered. The stabilizing effects of internal pressure shall not be considered to

increase the buckling resistance of the vessel shell.

d. If the vessel is a combination of liquid and gas storage, the vessel and supports shall be

designed both with and without gas pressure acting (assume piping has ruptured and

pressure does not exist).

14.7.4 Stacks and Chimneys:

14.7.4.1 General: Stacks and chimneys are permitted to be either lined or unlined, and shall

constructed from concrete, steel, or masonry. 

14.7.4.2 Design Basis: Steel stacks, concrete stacks, steel chimneys, concrete chimneys, and

liners shall be designed to resist seismic lateral forces determined from a substantiated

analysis using approved standards. Interaction of the stack or chimney with the liners shall be

considered. A minimum separation shall be provided between the liner and chimney equal to

Cd times the calculated differential lateral drift. 

14.7.5 Amusement Structures: 

14.7.5.1 General: Amusement structures are permanently fixed structures constructed

primarily for the conveyance and entertainment of people.

14.7.5.2 Design Basis: Amusement structures shall be designed to resist seismic lateral

forces determined from a substantiated analysis using approved standards.

14.7.6 Special Hydraulic Structures:

14.7.6.1 General: Special hydraulic structures are structures that are contained inside liquid

containing structures. These structures are exposed to liquids on both wall surfaces at the

same head elevation under normal operating conditions. Special hydraulic structures are

subjected to out of plane forces only during an earthquake when the structure is subjected to

differential hydrodynamic fluid forces. Examples of special hydraulic structures include 

separation walls, baffle walls, weirs, and other similar structures.

14.7.6.2 Design Basis: Special hydraulic structures shall be designed for out-of-phase

movement of the fluid. Unbalanced forces from the motion of the liquid must be applied

simultaneously "in front of" and "behind" these elements.
Nonbuilding Structures

321

Structures subject to hydrodynamic pressures induced by earthquakes shall be designed for

rigid body and sloshing liquid forces and their own inertia force. The height of sloshing shall

be determined and compared to the freeboard height of the structure. 

Interior elements, such as baffles or roof supports, also shall be designed for the effects of

unbalanced forces and sloshing.

14.7.7 Secondary Containment Systems:

14.7.7.1 General: Secondary containment systems such as impoundment dikes and walls

shall meet the requirements of the applicable standards for tanks and vessels and the authority

having jurisdiction. 

Secondary containment systems shall be designed to withstand the effects of a maximum

considered earthquake when empty and a maximum considered earthquake when full

including all hydrodynamic forces.

14.7.7.2 Freeboard: Sloshing of the liquid within the secondary containment area shall be

considered in determining the height of the impound. A minimum freeboard Sec 14.7.3.6.1.2,

*s, shall be provided when: 

δ s ac = 050 . DS (14.7.7.2)

where Sac is determined per Sec. 14.7.3.6.1. For circular impoundment dikes, D shall be the

diameter of the impoundment. For rectangular impoundment dikes, D shall be the longer

longitudinal plan dimension.
322

Appendix to Chapter 14

ELECTRICAL TRANSMISSION, SUBSTATION, AND

DISTRIBUTION STRUCTURES

PREFACE: This appendix is a resource document for future voluntary

standards and model code development. The BSSC’s Technical Subcommittee

13, Nonbuilding Structures has determined that this appendix material

represents the current industry design practice for these types of nonbuilding

structures.

These sections are included here so that the design community can gain

familiarity with the concepts, update standards, and send comments on this

appendix to the BSSC. It is hoped that the various consensus design standards

will be updated to include the design and construction methodology presented in

this appendix.

14A.1 REFERENCES:

IEEE 693 Institute of Electrical and Electronics Engineers (IEEE), Recommended

Practices for Seismic Design of Substations, Power Engineering Society,

Piscataway, New Jersey, 1997

14A.2 ELECTRICAL TRANSMISSION, SUBSTATION, AND DISTRIBUTION

STRUCTURES:

14A.2.1 General: This section applies to electrical transmission, substation, and distribution

structures.

Table 14A.2.1 Seismic Coefficients for Nonbuilding Structures

Nonbuilding Structure Type R S0 Cd Structural System and Height

Limits (ft)c

Seismic Design Category

A &

B

C D E & F

Electrical transmission towers,

substation wire support

structures, distribution

structures

Truss: Steel and aluminum 3 1-1/2 3 NL NL NL NL
Nonbuilding Structures

Nonbuilding Structure Type R S0 Cd Structural System and Height

Limits (ft)c

Seismic Design Category

A &

B

C D E & F

323

Pole: Steel

Wood

Concrete

Frame: Steel

Wood

Concrete

1-1/2

1-1/2

1-1/2

3

2-1/2

2

1-1/2

1-1/2

1-1/2

1-1/2

1-1/2

1-1/2

1-1/2

1-1/2

1-1/2

1-1/2

1-1/2

1-1/2

NL

NL

NL

NL

NL

NL

NL

NL

NL

NL

NL

NL

NL

NL

NL

NL

NL

NL

NL

NL

NL

NL

NL

NL

Telecommunication towers

Truss: Steel 

Pole: Steel

Wood

Concrete

Frame: Steel

Wood

Concrete

3

1-1/2

1-1/2

1-1/2

3

2-1/2

2

1-1/2

1-1/2

1-1/2

1-1/2

1-1/2

1-1/2

1-1/2

3

1-1/2

1-1/2

1-1/2

1-1/2

1-1/2

1-1/2

NL

NL

NL

NL

NL

NL

NL

NL

NL

NL

NL

NL

NL

NL

NL

NL

NL

NL

NL

NL

NL

NL

NL

NL

NL

NL

NL

NL

14A.2.2 Design Basis: Electrical transmission, substation, wire support, and distribution

structures shall be designed to resist a minimum seismic lateral load determined from the

following formula:

V' Cs

R

I

W

where:

V = seismic base shear;

I = importance factor, I = 1.0;

W = total dead load (does not include the supported wire or ice and snow loads applied

to the tower);

R = response modification factor, Table 14A.2.1.1;

Cs = seismic response coefficient – SDS but not greater then SD1/T where SDS and SD1 are

as defined in Sec.1.4.2.2; and 

T = The fundamental period of the tower.
1997 Provision Appendix to Chapter 14

324

A simplified static analysis and applying the seismic base shear (times a load factor of 1.0) at

the center of mass of the structure can be used to determine if seismic load controls the

design. The lateral force shall be evaluated in both the longitudinal and transverse directions

to the support wire. When it is determined that seismic loads are significant (control the

design of main load carrying members), a more detailed lateral force distribution shall be

performed per Sec. 14.2.1 (with k = 1) of the Provisions and/or a modal analysis as specified

by Sec. A.1.5 of IEEE 693.

Seismic lateral loads and design criteria for substation equipment support structures shall be

in accordance with the requirements of IEEE 693. The design, manufacture, and inspection

shall be in accordance with the quality control and quality assurance requirements of the

industry design standards and recommended practices specified in Sec. 14.1.9.

14A.3 TELECOMMUNICATION TOWERS:

14A.3.1 General: This section applies to telecommunication towers.

14A.3.2 Design Basis: Self-supporting telecommunication towers shall be designed to resist

a minimum seismic lateral force determined from the following formula:

V

C

R

I

Ws

= 



 



 (14A.5.2)

where:

V = seismic base shear;

I = importance factor, Table 14.2.1.2;

W = total dead load (including all attachments);

R = response modification factor, Table 14A.2.1.1; and

Cs = seismic response coefficient – SDS but not greater then SD1/T where SD1 and SDS, are

as defined in Sec. 4.2.2 and T is the fundamental period of the tower

A simplified static analysis applying the lateral load (times a load factor of 1.0) at the center of

mass of the tower can be used to determine if seismic load controls the design of selfsupporting towers. When it is determined that seismic loads are significant (control the design

of main load carrying members), a more detailed lateral force distribution (with k = 1) and

analysis shall be performed per Sec. 14.2.1 of the Provisions.

The lateral force applied to a telecommunication tower supported on a structure should

account for the base motion input amplification as a result of the building earthquake response

(see Sec. 14.1.2 of the Provisions). Guyed towers require a more detailed computer analysis

including nonlinear analysis and guy-tower interaction effects. An industry accepted modal

analysis procedure should be used for guyed towers.
Nonbuilding Structures

325

The design, manufacture, and inspection shall be in accordance with the quality control and

quality assurance requirements of the industry design standards and recommended practices

specified in Sec. 14.1.9.

14A.4 BURIED STRUCTURES:

14A.4.1 General: Buried structures are subgrade structures such as tanks, tunnels, and

pipes. Buried structures that are designated as Seismic Use Group II or III or are of such a

size or length to warrant special seismic design as determined by the registered design

professional shall be identified in the geotechnical report.

14A.4.2 Design Basis: Buried structures shall be designed to resist minimum seismic lateral

forces determined from a substantiated analysis using approved procedures. Flexible

couplings shall be provided for buried structures requiring special seismic considerations

where changes in the support system, configuration, or soil condition occur.

14A.5 PERFORMANCE CRITERIA FOR TANKS AND VESSELS: Tanks and vessels

shall be designed to meet the following minimum post-earthquake performance criteria. 

These criteria depend on the Seismic Use Group (category) classification and content-related

hazards of the tanks and vessels being considered:

TABLE 14A.5 Performance Criteria for Tanks and Vessels

Performance

Categorya

Minimum Post-Earthquake Performance

I

b The structure shall be permitted to fail provided the resulting spill does not

pose a threat to the public or to adjoining Category I, II or III structures.

II The structure shall be permitted to sustain localized damage, including

minor leaks, provided (a) such damage remains localized and does not

propagate; and (b) the resulting leakage does not pose a threat to the

public or to adjoining Category I, II or III structures.

III The structure shall be permitted to sustain minor damage, and its

operational systems or components (valves and controls) shall be permitted

to become inoperative, provided that (a) the structure retains its ability to

contain 100% of its contents; and (b) the structure’s minor damage, and the

failure of its operational systems or components, are not accompanied by,

or lead to, leakage.

IV The structure shall be permitted to sustain minor damage provided that (a)

it shall retain its ability to contain 100% of its contents without leakage;

and (b) its operational systems or components shall remain fully

operational.

a

 Performance Categories I, II, and III correspond to the Seismic Use Groups defined in Sec.

1.3 and tabulated in Tables 14.2.1.2 and 14.7.3.7.1.2.

b

 For tanks and vessels in Performance Category IV, an Importance Factor I = 1.0 shall be

used.
327

Appendix A

DIFFERENCES BETWEEN THE 1997 AND THE 2000 EDITIONS OF

THE NEHRP RECOMMENDED PROVISIONS

EDITORIAL AND ORGANIZATIONAL CHANGES

For the 2000 Provisions, an editorial change has been made to the format used to cite reference

documents. In the past, reference documents generally were listed at the beginning of a chapter

and identified as Ref. X-1, Ref. X-2, etc., with the “X” being the chapter number. The references 

then were cited in the chapter using the “Ref. X-1” format. In the 2000 Provisions, the reference

documents continue to be listed at the beginning of a chapter with an indication of the edition to

be used but are presented with an abbreviated designation that is used to cite the reference in the

text of the chapter (e.g., ACI 318).

2000 CHAPTER 1, GENERAL PROVISIONS

In the 1997 Provisions, one-and two-story wood frame dwellings were exempted from the

seismic requirements if the design spectral response acceleration at short periods was less than

0.4g. For the 2000 Provisions, these dwellings are exempted from all Provisions requirements if

they are in Seismic Design Categories A, B, or C. They also are exempted from the remaining

requirements in the Provisions if they are designed and constructed in accordance with the

conventional light frame construction requirements in Sec. 12.5. 

In Sec.1.2.4, alterations that increase the seismic force in any existing structural element by more

then 5 percent or decrease the design strength of any existing structural element to resist seismic

forces by more than 5 percent are not permitted unless the entire seismic-force-resisting system is

determined to conform to the Provisions for a new structure. All alterations are required to

conform to the Provisions for a new structure. Excepted from these requirements are alterations

to existing structural elements or additions of new structural elements that are not required by the

Provisions but are initiated to increase the strength or stiffness of the seismic-force-resisting

system of an existing structure provided an engineering analysis meeting several specifically

stated requirements is submitted.

2000 CHAPTER 2, GLOSSARY AND NOTATIONS

Additions and deletions have been made to reflect changes made in the text of the Provisions.

2000 CHAPTER 3, QUALITY ASSURANCE

For the 2000 Provisions, several inspection-related changes have been made. One is a

requirement for periodic inspection of shear walls with structural wood and the second requires
2000 Provisions, Appendix A

328

periodic special inspection of architectural components (glass). The special inspection

requirements also have been modified to exempt nonbearing metal stud and gypsum board

partitions from periodic special inspection; however, interior and exterior veneers are now

covered with exceptions pertaining to lightweight partitions.

Sec. 3.6, Reporting and Compliance Procedures, also has been modified to more clearly state

who is to receive reports.

2000 CHAPTER 4, GROUND MOTION

The only substantive changes made for the 2000 Provisions relate to the exception in Sec. 4.1.2.1

indicating that, under certain conditions, no site-specific evaluation is required for structures

having a fundamental period of less than 0.5 second. This is further clarified in exceptions

presented in the footnotes to Tables 4.1.2.4a and 4.1.2b.

2000 CHAPTER 5, STRUCTURAL DESIGN CRITERIA

For the 2000 Provisions, the requirements regulating the types of analysis that may be used in

determining design seismic forces and drifts have been reformatted so that they all appear in a

single table. In addition, two new analysis methods – linear time history analysis and nonlinear

time history analysis – are introduced into the text of Chapter 5 and a third analysis method –

nonlinear static analysis (pushover analysis) – is introduced as an appendix.

The approximate period formulae used to obtain Ta has been revised to reflect the expanded data

base of the measured period of buildings obtained from strong ground motion recordings. 

Equation 5.2.1-3 for determining the equivalent lateral force base shear also has been revised to

change the equation’s dependence on SD1 to dependence on SDS. This was done to maintain

consistency with parallel provisions in the 2000 International Building Code, 1997 Uniform

Building Code, and ASCE 7-98. The requirements also were modified to clarify that the base

shear need not be limited by Eq. 5.2.1-3 when used to evaluate drift. This was the intent when

Eq. 5.2.1-3 was originally introduced in the 1997 Provisions but was not properly specified.

A change has been made to clarify that collectors in certain irregular buildings need not be

designed for 125 percent of the forces otherwise required if other provisions require design of

these elements for the special load combinations of Sec. 5.2.7.1.

Another change clarifies that when calculating the redundancy coefficient, D, for structures of

light frame construction, the quantity 10/lw need not be taken as having a value greater than 1. 

This was the original intent of the requirement when it was introduced in the 1997 Provisions but

was not adequately presented in the text.
Differences Between the 1997 and 2000 Editions of the Provisions

329

2000 CHAPTER 6, ARCHITECTURAL, MECHANICAL, AND ELECTRICAL

COMPONENTS

For the 2000 Provisions, it was determined that additional conservatism was needed and a

number of the component modification factor values in Tables 6.2.2 and 6.3.2 have been

modified.

Simplified formulae are provided for use with the equivalent lateral force procedure of Sec. 5.4

and exceptions concerning mechanical and electrical components in Seismic Design Categories

D, E, and F are clarified.

The relationship between the component transfer of forces and the basic design of the structure

also has been clarified so that the design engineer must take into account the forces on the

structure generated by the components fixed to the structure. 

One of the most significant changes for the 2000 edition of the Provisions is the addition of a

new section on glass in glazed curtain walls, glazed storefronts, and glazed partitions. The

Provisions text provides basic requirements concerning drift limits and the Commentary contains

a detailed study and review of research performed on racking tests. 

Commentary Sec. 6.1.6 has been revised to ensure that the user understands what is required

concerning chemical anchors.

2000 CHAPTER 7, FOUNDATION DESIGN REQUIREMENTS

Several changes to the sections on soil-structure interaction (SSI) have been made for the 2000

Provisions. Recent studies dictated that these changes be made because they significantly affect

the period lengthening and foundation damping for a given structure and, hence, a change in base

shear.

Both Sec. 7.4 and 7.5 have been modified either to meet the requirements of ACI 318-99 or to

highlight exceptions to ACI 318-99.

The steel pile cap tensile force requirement has been adjusted with an exception, and widththickness ratios have been added to ensure that the formation of plastic hinges in the piles will

result without premature local buckling and fracture.

The Commentary has been expanded to provide additional guidance on the subject of seismic

earth pressures on retaining walls including the addition of more formulations for estimating the

seismic earth pressure for dry (nonsubmerged) backfills behind yielding and nonyielding

retaining walls. The approach of designing yielding walls based on tolerable displacements also

is discussed and key references are provided. Soil-structure interaction implications for seismic

earth pressures on nonyielding retaining walls also are discussed and references given for

detailed analysis methods. Further, the effects of backfill submergence on seismic earth

pressures are discussed and key references cited.
2000 Provisions, Appendix A

330

2000 CHAPTER 8, STEEL STRUCTURE DESIGN REQUIREMENTS

The most significant change for the 2000 Provisions is the reference to AISC Seismic including

Supplement No. 2. Completion of the 2000 Provisions update was deliberately delayed so that

the results of the SAC Joint Venture program could be integrated via reference to this document. 

However, some modifications to AISC Seismic are included to, among other things, modify the

Charpy V-notch toughness at two temperatures in order to ensure adequate toughness over the

range of expected use and to reflect the SAC results indicating that, in reducing seismic hazards

in moment resisting steel frames, the shape and size of the weld access hole are critical to the

performance moment connections with direct welds of beam flanges to columns. The access

hole configuration provided in the 2000 Provisions was developed to minimize strain

concentrations and has been successfully tested. It is anticipated that this configuration will be

adopted into later editions of the AISC specifications. 

2000 CHAPTER 9, CONCRETE STRUCTURE DESIGN REQUIREMENTS

The primary modifications for the 2000 Provisions reflect the changes made in the 1999 edition

of the ACI 318 reference document.

The seismic strength design load combination of the International Building Code (adopted from

ASCE 7-95) in which the gravity and earthquake effects are counteractive – the load combination

that governs the seismic design of reinforced concrete columns and shear walls – is essentially

identical to the corresponding design load combination of ACI 318. Thus, there is no basis for

the use of N factors with this load combination and this requirement has been eliminated.

ACI 318-99 has revised its terminology for moment frames to be consistent with the Provisions;

therefore, the provisions describing types of moment frames have been eliminated and references

to these requirements have been deleted as well. 

A new section on anchoring to concrete is included to reflect work done by ACI on the design of

anchoring with cast-in-place headed bolts, J- and L- bolts headed studs, hooked bolts, and postinstalled mechanical anchors. Although these requirements are not included in ACI-318-99

because the anchor prequalification standard, ACI 355.2, was not completed in time, the

inclusion of comprehensive anchoring design methods in the 2000 Provisions was deemed

important and it is anticipated that these requirements will eventually be included in ACI 318.

The requirements concerning foundations, gravity columns, and transverse reinforcement have

all been modified to comply with ACI 318-99.

Finally, there has been a major expansion of the requirements found in Sec.9.1.1. Recent

advances in understanding of the seismic behavior of precast/prestressed concrete frame and wall

structures resulting from various research programs and the codification of test procedures have

made possible the elimination of 1997 Provisions appendix and the inclusion in the 2000

Provisions of precast/prestressed concrete requirements based entirely on amendments to ACI

318-99. These are now sequentially listed to conform with Chapter 21 of ACI 318-99. 
Differences Between the 1997 and 2000 Editions of the Provisions

331

A new appendix to the Provisions and Commentary presenting requirements for untopped

diaphragms is included. 

2000 CHAPTER 10, STEEL AND CONCRETE STRUCTURE

DESIGN REQUIREMENTS

The only change for the 2000 Provisions is the updating of the reference list to reflect the most

current documents. 

2000 CHAPTER 11, MASONRY STRUCTURE DESIGN REQUIREMENTS

The 2000 Provisions reflects several editorial changes. The scope section now requires that

masonry walls be designed as shear walls with one exception. New requirements regarding

reinforcing bars are included: lab splices are detailed to reflect new research that eliminates the

confusion between splices found in masonry versus concrete, more rational and reliable design

requirements for large and small reinforcement diameters are presented, the requirement for 135

degree hooks have been eliminated in masonry construction, and the requirement for end bearing

splices has been eliminated since they are seldom used. 

The translation from stress design to strength design found in the 1997 Provisions for plain

(unreinforced) masonry members was not correct and modifications have been made. In

addition, the 1997 Appendix to Chapter 11 has been eliminated to achieve parity with other

material chapters that base their design on strength versus stress design. 

A limitation on the width of the stress block in out-of-plane and in-plane bending has been

included. Welded splices are specified to use ASTM A706 reinforcement to ensure the proper

chemistry in the weld (i.e., the amount of carbon, sulfur, phosphorus, and other elements must be

controlled).

The requirements for mechanical connections have been modified to reflect in fact that their

specified yield strength is usually higher than the 125 percent specified in the 1997 Provisions. 

Consequently, the 125 percent requirement has been eliminated and Type 1 or 2 mechanical

splices are required.

2000 CHAPTER 12, WOOD STRUCTURE DESIGN REQUIREMENTS

A major change for the 2000 Provisions is the elimination in Tables 12.4.3-2a and 12.4.3-2b of

the 10 percent reduction of design values imposed on shear walls in the 1997 Provisions. This

essentially brings these values back to the levels found in the 1994 Provisions. These tables also

feature changes regarding minimum penetration of nailing. Earlier, thinner side panel members

required the same penetration as thicker members, but testing has shown that less penetration is

necessary for the conventional siding thickness used in construction. The footnote regarding the

specific gravity adjustment factor also now requires that it not be greater than 1.0. 
2000 Provisions, Appendix A

332

The definition of diaphragm has been changed to include sloping roofs; therefore, they now are

considered to be diaphragms rather than shear walls and the requirement for edge blocking is

eliminated.

A major reformatting of Sec. 12.3 and 12.4 clarifies the requirements for engineered wood

construction and diaphragms and shear walls. Once this was completed, it permitted additional

changes to be incorporated to improve clarity.

Another major change is the inclusion of new requirements for perforated shear walls. The

perforated shear wall design presented in the 2000 Provisions is a recently developed empirical

method that recognizes the strength and stiffness provided to framed walls by sheathing above

and below wall openings. The Chapter 12 Commentary provides background on development

and verification.

2000 CHAPTER 13, SEISMICALLY ISOLATED STRUCTURES DESIGN

REQUIREMENTS

Sec. 13.2.3 has been revised for the 2000 Provisions to correct an oversight concerning the

importance factor, which is intended to reduce ductility demand for conventional structures but

does not apply in the case of seismically isolated structures that are designed to remain

“essentially elastic.”

Sec. 13.4.4.1 has been revised to reflect that Site Class E is now covered by the seismic maps and

appropriate changes are included in the Commentary as well. Sec. 13.6.2.3 has been revised to

provide additional wording to clarify the intent of the Provisions. Further, Sec.13.9.2.1 has been

revised to allow the prototype bearings used for testing to be used in the construction of the

structure if the registered design professional will permit their use; this may have a significant

impact on smaller projects where the number of test isolators represents a significant number of

the total to be used.

The most significant change is the replacement of the brief 1997 Appendix to Chapter 13 with an 

extensive appendix with a complete set of design provisions for structures with damping systems. 

Since this information contains design criteria, analysis methods, and testing recommendations

that have limited history of use, considerable information on this evolving technology is included

to guide the building professional.

2000 CHAPTER 14, NONBUILDING STRUCTURE DESIGN REQUIREMENTS

Since Chapter 14 is intended to provide a bridge from the basic seismic design methodologies

contained in the Provisions to nonbuilding structure design practices, the reference documents

have been updated.

Given the evolving nature of Chapter 14, the 2000 Provisions requirements for tanks and vessels

have been moved from the Appendix to Chapter 14 into the chapter itself as a result of changes

in voluntary standards and other research.
Differences Between the 1997 and 2000 Editions of the Provisions

333

Sections on electrical transmission, substation, and distribution structures that were included in

the 1997 Provisions text have been moved to the appendix since these lifelines systems generally

do not fall under the jurisdiction of the code official. Other sections on telecommunication

towers and buried structures also have been moved to the appendix because additional time is

needed by the respective industries to evaluate the requirements presented. The Commentary

sections on buried structures, pipe racks, earth retaining structures, and steel storage racks have

been expanded as has the Provisions section on steel storage racks.

The importance factors and Seismic Use Group classifications in Chapter 14 have been revised to

be consistent with Provisions Sec. 1.3; consequently, there are similar changes in the

Commentary where the four examples in Table 14.2.1.2 have been modified to clarify the use of

these factors.

CHANGES IN SECTION NUMBERS BETWEEN THE

1997 AND 2000 EDITIONS PROVISIONS

Chapter 1, GENERAL PROVISIONS

1.1 PURPOSE

1.2 SCOPE AND APPLICATION

1.2.1 Scope

1.2.2 Additions

1.2.3 Change of Use

1.2.4 Alterations

1.2.5 Alternate Materials and Alternate Means and Methods of Construction

1.3 SEISMIC USE GROUPS

1.3.1 Seismic Use Group III

1.3.2 Seismic Use Group II

1.3.3 Seismic Use Group I

1.3.4 Multiple Use

1.3.5 Seismic Use Group III Structure Access Protection

1.4 OCCUPANCY IMPORTANCE FACTOR

Chapter 2, GLOSSARY AND NOTATIONS

2.1 GLOSSARY

2.2 NOTATIONS

Chapter 3 , QUALITY ASSURANCE

3.1 SCOPE

3.2 QUALITY ASSURANCE

3.2.1 Details of Quality Assurance Plan

3.2.2 Contractor Responsibility
2000 Provisions, Appendix A

334

3.3 SPECIAL INSPECTION

3.3.1 Piers, Piles, Caissons

3.3.2 Reinforcing Steel

3.3.3 Structural Concrete

3.3.4 Prestressed Concrete

3.3.5 Structural Masonry

3.3.6 Structural Steel

3.3.7 Structural Wood

3.3.8 Cold–Formed Steel Framing

3.3.9 Architectural Components

3.3.10 Mechanical and Electrical Components

3.3.11 Seismic Isolation System

3.4 TESTING

3.4.1 Reinforcing and Prestressing Steel

3.4.2 Structural Concrete

3.4.3 Structural Masonry

3.4.4 Structural Steel

3.4.5 Mechanical and Electrical Equipment

3.4.6 Seismically Isolated Structures

3.5 STRUCTURAL OBSERVATIONS

3.6 REPORTING AND COMPLIANCE PROCEDURES

Chapter 4, GROUND MOTION

4.1 PROCEDURES FOR DETERMINING MAXIMUM CONSIDERED EARTHQUAKE

AND DESIGN EARTHQUAKE GROUND MOTION ACCELERATIONS AND RESPONSE

SPECTRA

4.1.1 Maximum Considered Earthquake Ground Motions

4.1.2 General Procedure for Determining Maximum Considered Earthquake and Design Spectral

Response Accelerations

4.1.3 Site-Specific Procedure for Determining Ground Motion Accelerations

4.2 SEISMIC DESIGN CATEGORY

4.2.1 Determination of Seismic Design Category

4.2.2 Site Limitation for Seismic Design Categories E and F

Chapter 5, STRUCTURAL DESIGN CRITERIA

5.1 REFERENCE DOCUMENT

ASCE 7

5.2 DESIGN BASIS

5.2.1 General

5.2.2 Basic Seismic-Force-Resisting Systems

5.2.3 Structure Configuration

5.2.4 Redundancy

5.2.5 Analysis Procedures
Differences Between the 1997 and 2000 Editions of the Provisions

335

5.2.6 Design and Detailing Requirements, and Structural Component Load Effects

5.2.7 Combination of Load Effects

5.2.8 Deflection and Drift Limits

5.3 INDEX FORCE ANALYSIS PROCEDURE

5.3 4 EQUIVALENT LATERAL FORCE PROCEDURE64

5.3.1 General

5.4.1 5.3.2 Seismic Base Shear

5.4.2 5.3.3 Period Determination

5.4.3 5.3.4 Vertical Distribution of Seismic Forces

5.4.4 5.3.5 Horizontal Shear Distribution

5.4.5 5.3.6 Overturning

5.4.6 5.3.7 Drift Determination and P-Delta Effects

5.5 5.4 MODAL ANALYSIS PROCEDURE

5.4.1 General

5.5.1 5.4.2 Modeling

5.5.2 5.4.3 Modes

5.5.3 5.4.4 Modal Properties

5.5.4 5.4.5 Modal Base Shear

5.5.5 5.4.6 Modal Forces, Deflections, and Drifts

5.5.6 5.4.7 Modal Story Shears and Moments

5.5.7 5.4.8 Design Values 

5.5.8 5.4.9 Horizontal Shear Distribution 

5.5.9 5.4.10 Foundation Overturning 

5.5.10 5.4.11 P-Delta Effects

5.6 LINEAR RESPONSE HISTORY ANALYSIS PROCEDURE

5.6.1 Modeling

5.6.2 Ground Motion

5.6.3 Response Parameters

5.7 NONLINEAR RESPONSE HISTORY ANALYSIS PROCEDURE

5.7.1 Modeling

5.7.2 Ground Motion and Other Loading

5.7.3 Response Parameters

5.7.4 Design Review

5.8 5.4 SOIL-STRUCTURE INTERACTION EFFECTS 

5.8 5.4.1 General 

5.8 5.4.2 Equivalent Lateral Force Procedure 

5.8 5.4.3 Modal Analysis Procedure

Appendix to Chapter 5, NONLINEAR STATIC ANALYSIS

Chapter 6, ARCHITECTURAL, MECHANICAL, AND ELECTRICAL COMPONENTS

DESIGN REQUIREMENTS 

6.1 GENERAL 

6.1.1 References and Standards 
2000 Provisions, Appendix A

336

ASME A17.1

ASTM C635

ASME/BPV

ASTM C636

ANSI/ASME B31.1

ANSI/ASME B31.3

ANSI/ASME B31.4

ANSI/ASME B31.5

ANSI/ASME B31.9

ANSI/ASME B31.11

ANSI/ASME B31.8

NFPA 13

IEEE 344

ASHRAE SRD

CISCA Recs for Zones 0-2

CISCA Recs for Zones 3-4

SMACNA HVAC

SMACNA Rectangular

SMACNA Restraint

AAMA 501.4

6.1.2 Component Force Transfer

6.1.3 Seismic Forces 

6.1.4 Seismic Relative Displacements 

6.1.5 Component Importance Factor

6.1.6 Component Anchorage 

6.1.7 Construction Documents 

6.2 ARCHITECTURAL COMPONENT DESIGN 

6.2.1 General 

6.2.2 Architectural Component Forces and Displacements 

6.2.3 Architectural Component Deformation 

6.2.4 Exterior Nonstructural Wall Elements and Connections 

6.2.5 Out-of-Plane Bending 

6.2.6 Suspended Ceilings 

6.2.7 Access Floors 

6.2.8 Partitions 

6.2.9 Steel Storage Racks 

6.2.10 Glass in Glazed Curtain Walls, Glazed Storefronts, and Glazed Partitions

6.3 MECHANICAL AND ELECTRICAL COMPONENT DESIGN 

6.3.1 General 

6.3.2 Mechanical and Electrical Component Forces and Displacements 

6.3.3 Mechanical and Electrical Component Period 

6.3.4 Mechanical and Electrical Component Attachments 

6.3.5 Component Supports 

6.3.6 Component Certification 

6.3.7 Utility and Service Lines at Structure Interfaces 
Differences Between the 1997 and 2000 Editions of the Provisions

337

6.3.8 Site-Specific Considerations 

6.3.9 Storage Tanks 

6.3.10 HVAC Ductwork 

6.3.11 Piping Systems 

6.3.12 Boilers and Pressure Vessels 

6.3.13 Mechanical Equipment Attachments, and Supports 

6.3.14 Electrical Equipment Attachments, and Supports

6.3.15 Alternative Seismic Qualification Methods

6.3.16 Elevator Design Requirements

Chapter 7, FOUNDATION DESIGN REQUIREMENTS 

7.1 GENERAL 

7.2 STRENGTH OF COMPONENTS AND FOUNDATIONS 

7.2.1 Structural Materials 

7.2.2 Soil Capacities 

7.3 SEISMIC DESIGN CATEGORIES A AND B 

7.4 SEISMIC DESIGN CATEGORY C 

7.4.1 Investigation 

7.4.2 Pole-Type Structures 

7.4.3 Foundation Ties 

7.4.4 Special Pile Requirements 

7.5 SEISMIC DESIGN CATEGORIES D, E, AND F 

7.5.1 Investigation 

7.5.2 Foundation Ties 

7.5.3 Liquefaction Potential and Soil Strength Loss 

7.5.4 Special Pile and Grade Beam Requirements 

Chapter 8, STEEL STRUCTURE DESIGN REQUIREMENTS 

8.1 REFERENCE DOCUMENTS 

AISC LRFD

AISC ASD

AISC Seismic

AISI

ANSI/ASCE 8-90

SJI

ASCE 19

8.2 SEISMIC REQUIREMENTS FOR STEEL STRUCTURES 

8.3 SEISMIC DESIGN CATEGORIES A, B, AND C 

8.4 SEISMIC DESIGN CATEGORIES D, E, AND F 

8.4.1 Modifications to AISC Seismic

8.5 COLD-FORMED STEEL SEISMIC REQUIREMENTS 

8.5.1 Modifications to AISI Ref. 8.4 

8.5.2 Modifications to ANSI/ASCE 8-90 Ref. 8.5 
2000 Provisions, Appendix A

338

8.6 LIGHT-FRAMED WALLS 

8.6.1 Boundary Members 

8.6.2 Connections 

8.6.3 Braced Bay Members 

8.6.4 Diagonal Braces 

8.6.5 Shear Walls

8.7 SEISMIC REQUIREMENTS FOR STEEL DECK DIAPHRAGMS 

8.8 STEEL CABLES 

Chapter 9, CONCRETE STRUCTURE DESIGN REQUIREMENTS 

9.1 REFERENCE DOCUMENTS 

ACI 318

ACI ITG/T1.1

ASME B1.1

ASME B18.2.1

ASME B18.2.6.9

ATC 24

9.1.1 Modifications to ACI 318 Ref. 9-1

9.2 ANCHORING TO CONCRETE

9.2.1 Scope

9.2.2 Notations and Definitions

9.2.3 General Requirements

9.2.4 General Requirements for Strength of Structural Anchors

9.2.5 Design Requirements for Tensile Loading

9.2.6 Design Requirements for Shear Loading

9.2.7 Interaction of Tensile and Shear Forces

9.2.8 Required Edge Distances, Spacings, and Thicknesses to Preclude Splitting Failure

9.2.9 Installation of Anchors

9.2 BOLTS AND HEADED STUD ANCHORS IN CONCRETE 

9.2.1 Load Factor Multipliers 

9.2.2 Strength of Anchors 

9.2.3 Strength Based on Tests 

9.2.4 Strength Based on Calculations 

9.3 CLASSIFICATION OF SEISMIC-FORCE-RESISTING SYSTEMS 

9.3.1 Classification of Moment Frames 

9.3.2 Classification of Shear Walls

9.3 CLASSIFICATION OF SHEAR WALLS

9.3.1 Ordinary Plain Concrete Shear Walls

9.3.2 Detailed Plain Concrete Shear Walls

9.4 SEISMIC DESIGN CATEGORY A 

9.5 SEISMIC DESIGN CATEGORY B 

9.5.1 Ordinary Moment Frames 

9.6 SEISMIC DESIGN CATEGORY C 

9.6.1 Seismic-Force-Resisting Systems
Differences Between the 1997 and 2000 Editions of the Provisions

339

9.6.2 Discontinuous Members 

9.6.3 Plain Concrete

9.6.4 Anchor Bolts in the Tops of Columns

9.7 SEISMIC DESIGN CATEGORIES D, E, OR F 

9.7.1 Seismic-Force-Resisting Systems 

9.7.2 Frame Members Not Proportioned to Resist Forces Induced by Earthquake Motions 

9.7.3 Plain Concrete 

Appendix to Chapter 9, REINFORCED CONCRETE DIAPHRAGMS CONSTRUCTED

USING UNTOPPED PRECAST CONCRETE ELEMENTS REINFORCED CONCRETE

STRUCTURAL SYSTEMS COMPOSED FROM INTERCONNECTED PRECAST

ELEMENTS 

Chapter 10, STEEL AND CONCRETE STRUCTURE DESIGN REQUIREMENTS 

10.1 REFERENCE DOCUMENTS 

ACI 318

AISC/LRFD

AISC Seismic

AISI

10.2 REQUIREMENTS

Chapter 11, MASONRY STRUCTURE DESIGN REQUIREMENTS 

11.1 GENERAL 

11.1.1 Scope 

11.1.2 Reference Documents 

ACI 318

ACI 530

ACI 530.1

11.1.3 Definitions 

11.1.4 Notations 

11.2 CONSTRUCTION REQUIREMENTS 

11.2.1 General 

11.2.2 Quality Assurance 

11.3 GENERAL REQUIREMENTS 

11.3.1 Scope 

11.3.2 Empirical Masonry Design 

11.3.3 Plain (Unreinforced) Masonry Design 

11.3.4 Reinforced Masonry Design 

11.3.5 Seismic Design Category A 

11.3.6 Seismic Design Category B 

11.3.7 Seismic Design Category C 

11.3.8 Seismic Design Category D 

11.3.9 Seismic Design Categories E and F 
2000 Provisions, Appendix A

340

11.3.10 Properties of Materials 

11.3.11 Section Properties 

11.3.12 Headed and Bent-Bar Anchor Bolts

11.4 DETAILS OF REINFORCEMENT 

11.4.1 General 

11.4.2 Size of Reinforcement 

11.4.3 Placement Limits for Reinforcement 

11.4.4 Cover for Reinforcement 

11.4.5 Development of Reinforcement 

11.5 STRENGTH AND DEFORMATION REQUIREMENTS 

11.5.1 General 

11.5.2 Required Strength 

11.5.3 Design Strength 

11.5.4 Deformation Requirements 

11.6 FLEXURE AND AXIAL LOADS 

11.6.1 Scope 

11.6.2 Design Requirements of Reinforced Masonry Members 

11.6.3 Design of Plain (Unreinforced) Masonry Members 

11.7 SHEAR 

11.7.1 Scope 

11.7.2 Shear Strength 

11.7.3 Design of Reinforced Masonry Members 

11.7.4 Design of Plain (Unreinforced) Masonry Members 

11.8 SPECIAL REQUIREMENTS FOR BEAMS 

11.9 SPECIAL REQUIREMENTS FOR COLUMNS 

11.10 SPECIAL REQUIREMENTS FOR WALLS 

11.11 SPECIAL REQUIREMENTS FOR SHEAR WALLS 

11.10 11.1 Ordinary Plain Masonry Shear Walls 

11.10 11.2 Detailed Plain Masonry Shear Walls 

11.10 11.3 Ordinary Reinforced Masonry Shear Walls 

11.10 11.4 Intermediate Reinforced Masonry Shear Walls 

11.10 11.5 Special Reinforced Masonry Shear Walls 

11.10 11.6 Flanged Shear Walls 

11.10 11.7 Coupled Shear Walls 

11.11 12 SPECIAL MOMENT FRAMES OF MASONRY 

11.11 12.1 Calculation of Required Strength 

11.11 12.2 Flexural Yielding 

11.11 12.3 Reinforcement 

11.11 12.4 Wall Frame Beams 

11.11 12.5 Wall Frame Columns 

11.11 12.6 Wall Frame Beam-Column Intersection 

11.12 13 GLASS-UNIT MASONRY AND MASONRY VENEER 

11.12 13.1 Design Lateral Forces and Displacements 

11.12 13.2 Glass-Unit Masonry Design 

11.12 13.3 Masonry Veneer Design 
Differences Between the 1997 and 2000 Editions of the Provisions

341

Appendix to Chapter 11, ALTERNATIVE PROVISIONS FOR THE DESIGN

OF MASONRY STRUCTURES 

Chapter 12, WOOD STRUCTURE DESIGN REQUIREMENTS 

12.1 GENERAL 

12.1.1 Scope 

12.1.2 Reference Documents 

ASCE 16

APA Y510T

APA N375B

APA E315H

CABO Code

NFoPA T903

PS20

ANSI/AITC A190.1

ASTM D5055-95A

PS 1

PS 2

ANSI 05.1

ANSI A208.1

AWPA C1, 2, 2, 3, 9, 28

12.1.3 Notations 

12.2 DESIGN METHODS 

12.2.1 Engineered Wood Design 

12.2.2 Conventional Light-Frame Construction 

12.3 GENERAL DESIGN REQUIREMENTS FOR ENGINEERED WOOD CONSTRUCTION 

12.3.1 General 

12.3.2 Shear Resistance Based on Principles of Mechanics Framing Requirements 

12.3.3 Deformation Compatibility Requirements 

12.3.4 Framing Requirements

12.3.5 Sheathing Requirements

12.3.6 Wood Members Resisting Horizontal Seismic Forces Contributed by Masonry and

Concrete

12.3.4 Design Limitations 

12.4 DIAPHRAGMS AND SHEAR WALLS 

12.4.1 Diaphragms and Shear Wall Aspect Ratios

12.4.2 Shear Walls

12.4.3 Perforated Shear Walls

12.4.2 Shear Resistance Based on Principles of Mechanics 

12.4.3 Sheathing Requirements 

12.5 CONVENTIONAL LIGHT-FRAME CONSTRUCTION 

12.5.1 Scope 

12.5.2 Braced Walls 
2000 Provisions, Appendix A

342

12.5.3 Detailing Requirements 

12.6 SEISMIC DESIGN CATEGORY A 

12.7 SEISMIC DESIGN CATEGORIES B, C, AND D 

12.7.1 Conventional Light-Frame Construction 

12.7.2 Engineered Construction 

12.8 SEISMIC DESIGN CATEGORIES E AND F 

12.8.1 Limitations 

Chapter 13, SEISMICALLY ISOLATED STRUCTURES DESIGN 

REQUIREMENTS 

13.1 GENERAL 

13.2 CRITERIA SELECTION 

13.2.1 Basis for Design 

13.2.2 Stability of the Isolation System 

13.2.3 Seismic Use Group 

13.2.4 Configuration Requirements 

13.2.5 Selection of Lateral Response Procedure 

13.3 EQUIVALENT LATERAL FORCE PROCEDURE 

13.3.1 General 

13.3.2 Deformation Characteristics of the Isolation System 

13.3.3 Minimum Lateral Displacements 

13.3.4 Minimum Lateral Forces 

13.3.5 Vertical Distribution of Force 

13.3.6 Drift Limits 

13.4 DYNAMIC LATERAL RESPONSE PROCEDURE 

13.4.1 General 

13.4.2 Isolation System and Structural Elements Below the Isolation System 

13.4.3 Structural Elements Above the Isolation System 

13.4.4 Ground Motion 

13.4.5 Mathematical Model 

13.4.6 Description of Analysis Procedures 

13.4.7 Design Lateral Force 

13.5 LATERAL LOAD ON ELEMENTS OF STRUCTURES AND NONSTRUCTURAL

COMPONENTS SUPPORTED BY BUILDINGS 

13.5.1 General 

13.5.2 Forces and Displacements 

13.6 DETAILED SYSTEM REQUIREMENTS 

13.6.1 General 

13.6.2 Isolation System 

13.6.3 Structural System 

13.7 FOUNDATIONS 

13.8 DESIGN AND CONSTRUCTION REVIEW 

13.8.1 General 

13.8.2 Isolation System 
Differences Between the 1997 and 2000 Editions of the Provisions

343

13.9 REQUIRED TESTS OF THE ISOLATION SYSTEM 

13.9.1 General 

13.9.2 Prototype Tests 

13.9.3 Determination of Force-Deflection Characteristics 

13.9.4 Test Specimen Adequacy 

13.9.5 Design Properties of the Isolation System 

Appendix to Chapter 13, STRUCTURES WITH DAMPING SYSTEMS PASSIVE ENERGY

DISSIPATION 

Chapter 14, NONBUILDING STRUCTURE DESIGN REQUIREMENTS 

14.1 GENERAL 

14.1.1 Scope 

14.2 REFERENCES

14.3 INDUSTRY DESIGN STANDARDS AND RECOMMENDED PRACTICE

14.4 14.1.2 Nonbuilding Structures Supported by Other Structures 

14.4.1 14.1.3 Architectural, Mechanical, and Electrical Components 

14.1.4 Loads 

14.1.5 Fundamental Period 

14.1.6 Drift Limitations 

14.1.7 Materials Requirements 

14.5 14.2 STRUCTURAL DESIGN REQUIREMENTS 

14.5.1 14.2.1 Design Basis 

14.5.2 14.2.2 Rigid Nonbuilding Structures 

14.5.3 Loads

14.5.4 Fundamental Period

14.5.5 Drift Limitations

14.5.6 Materials Requirements

14.5.7 14.2.3 Deflection Limits and Structure Separation 

14.5.8 Site-Specific Response Spectra

14.6 14.3 NONBUILDING STRUCTURES SIMILAR TO BUILDINGS 

14.6 14.3.1 General 

14.6 14.3.2 Pipe Racks 

14.6 14.3.3 Steel Storage Racks 

14.6 14.3.4 Electrical Power Generating Facilities 

14.6 14.3.5 Structural Towers for Tanks and Vessels 

14.6 14.3.6 Piers and Wharves 

14.7 14.4 NONBUILDING STRUCTURES NOT SIMILAR TO BUILDINGS 

14.7 14.4.1 General 

14.7 14.4.2 Earth Retaining Structures 

14.7 14.4.3 Tanks and Vessels 

14.4.4 Electrical Transmission, Substation, and Distribution Structures 

14.4.5 Telecommunication Towers 

14.7.4 14.4.6 Stacks and Chimneys 
2000 Provisions, Appendix A

344

14.7.5 14.4.7 Amusement Structures 

14.7.6 14.4.8 Special Hydraulic Structures 

14.7.7 Secondary Containment Systems

14.4.9 Buried Structures 

14.4.10 Inverted Pendulums 

 
345

Appendix B

PARTICIPANTS IN THE BSSC 2000 PROVISIONS UPDATE PROGRAM

1998 BSSC BOARD OF DIRECTION

Chairman

Eugene Zeller, City of Long Beach, California

Vice Chairman

William W. Stewart, Stewart-Schaberg Architects, Clayton, Missouri (representing the American

Institute of Architects)

Secretary

David P. Tyree, American Forest and Paper Association, Colorado Springs, Colorado

Ex-Officio

James E. Beavers, Beavers and Associates, Oak Ridge, Tennessee

Members

J. Gregg Borchelt, Brick Industry Association, Reston, Virginia

Eugene Cole, Carmichael, California (representing the Structural Engineers Association of

California)

S. K. Ghosh, S.K. Ghosh Associates, Skokie, Illinois (representing the Portland Cement

Association)

Nestor Iwankiw, American Institute of Steel Construction, Chicago, Illinois

Gerald H. Jones, Kansas City, Missouri (representing the National Institute of Building Sciences)

Joseph Nicoletti, URS/John A. Blume and Associates, San Francisco, California (representing

the Earthquake Engineering Research Institute)

Jack Prosek, Turner Construction Company, San Francisco, California, (representing the

Associated General Contractors of America)

W. Lee Shoemaker, Metal Building Manufacturers Association, Cleveland, Ohio

John C. Theiss, Theiss Engineers, Inc., St. Louis, Missouri (representing the American Society of

Civil Engineers)

Charles Thornton, Thornton-Tomasetti Engineers, New York, New York (representing the

Applied Technology Council)
2000 Provisions, Appendix B

346

David Wismer, Department of Licenses and Inspections, Philadelphia, Pennsylvania

(representing the Building Officials and Code Administrators International)

Richard Wright, National Institute of Standards and Technology, Gaithersburg, Maryland 

(representing the Interagency Committee for Seismic Safety in Construction)

1999 BSSC BOARD OF DIRECTION

Chairman

William W. Stewart, Stewart-Schaberg Architects, Clayton, Missouri

Vice Chairman

David P. Tyree, American Forest and Paper Association, Colorado Springs, Colorado 

Secretary

Jack Prosek, Turner Construction Company, San Francisco, California (representing the

Associated Contractors of America)

Ex-Officio

Eugene Zeller, City of Long Beach, California

Members

J. Gregg Borchelt, Brick Industry Association, Reston, Virginia

Bradford K. Douglas, American Forest and Paper Association, Washington, D.C.

Do Y. Kim, Institute for Business and Home Safety, Boston, Massachusetts

Howard Simpson, Simpson Gumpertz & Heger, Arlington, Massachusetts (representing National

Council of Structural Engineers Associations)

Charles Carter, American Institute of Steel Construction, Chicago, Illinois 

S. K. Ghosh, Portland Cement Association, Skokie, Illinois

Gerald H. Jones, Kansas City, Missouri (representing the National Institute of Building Sciences)

H. S. Lew, National Institute of Standards and Technology, Gaithersburg, Maryland (representing

the Interagency Committee on Seismic Safety in Construction)

Joseph Nicoletti, URS Consultants, San Francisco, California (representing the Earthquake

Engineering Research Institute)

Lee Shoemaker, Metal Building Manufacturers Association, Cleveland, Ohio

Charles Spitz, Architect/Planner/Code Consultant, Wall, New Jersey (representing the American

Institute of Architects)

John Theiss, St, Albans, Missouri (representing the American Society of Civil Engineers)
Participants in the BSSC 2000 Provisions Update Program

347

Charles Thornton, Thornton-Tomasetti Group, New York, New York (representing the Applied

Technology Council)

David Wismer, Department of Licenses and Inspections, Philadelphia, Pennsylvania

(representing Building Officials and Code Administrators International)

2000 BSSC BOARD OF DIRECTION

Chairman

William W. Stewart, Stewart-Schaberg Architects, Clayton, Missouri (representing the American

Institute of Architects)

Vice Chairman

Charles Thornton, Chairman/Principal, Thornton-Tomasetti Group, Inc., New York, New York

Secretary

John “Jack” Prosek, Jr., Project Manager, Turner Construction Company, Oakland, California

(representing Associated General Contractors of America) 

Ex-Officio

Eugene Zeller, Director of Planning and Building, City of Long Beach, California

Members

J. Gregg Borchelt, Vice President, Brick Industry Association, Reston, Virginia

Charles J. Carter, Director of Manuals, American Institute of Steel Construction, Chicago,

Illinois

Bradford K. Douglas, Director of Engineering, American Forest and Paper Association,

Washington, D.C.

S. K. Ghosh, S.K. Ghosh Associates, Skokie, Illinois (representing the Portland Cement

Association)

Gerald H. Jones, Kansas City, Missouri (representing the National Institute of Building Sciences)

H.S. Lew, Senior Research Engineer, National Institute of Standards and Technology,

Gaithersburg, Maryland (representing Interagency Committee on Seismic Safety in Construction)

Joseph Nicoletti, Senior Consultant, URS/John A. Blume and Associates, San Francisco,

California (representing the Earthquake Engineering Research Institute)

W. Lee Shoemaker, Director, Engineering and Research, Metal Building Manufacturers

Association, Cleveland, Ohio

Howard Simpson, Simpson Gumpertz and Heger, Arlington, Massachusetts (representing

National Council of Structural Engineers Associations)
2000 Provisions, Appendix B

348

Charles A. Spitz, Architect/Planner/Code Consultant, Wall New Jersey (representing the

American Institute of Architects)

John C. Theiss, Consultant, St. Albans, Missouri (representing the American Society of Civil

Engineers)

David Wismer, Department of Licenses and Inspections, Philadelphia, Pennsylvania

(representing the Building Officials and Code Administrators International)

BSSC STAFF

Thomas R. Hollenbach, Executive Director (through April 2000)

Claret M. Heider, Vice President, BSSC

Bernard F. Murphy, Director, Special Projects

Carita Tanner, Communications/Public Relations Manager

Patricia Blasi, Administrative Assistant

Kelly Harris, Summer Intern
Participants in the BSSC 2000 Provisions Update Program

349

2000 PROVISIONS UPDATE COMMITTEE

Chair

William T. Holmes, Rutherford and Chekene, San Francisco, California

Representing Technical Subcommittee 1, Design Mapping 

R. Joe Hunt, BWXT Y-12, LLC, Oak Ridge, Tennessee

C. B. Crouse, URS Corporation, Seattle, Washington

E. V. Leyendecker, U.S. Geological Survey, Denver, Colorado

Representing Technical Subcommittee 2, Design Criteria and Analysis

Ronald O. Hamburger, EQE International, San Francisco, California 

James R. Harris, J. R. Harris and Company, Denver, Colorado

Richard J. Phillips, Hillman, Biddison and Loevenguth, Los Angeles, California

Representing Technical Subcommittee 3, Foundations and Geotechnical Considerations

Maurice S. Power, Geomatrix Consultants, Oakland, California

Cetin Soydemir, Haley and Aldrich, Boston, Massachusetts

Representing Technical Subcommittee 4, Concrete Structures

W. Gene Corley, Construction Technology Laboratories, Skokie, Illinois

Joseph J. Messersmith, Regional Code Services, Portland Cement Association, Rockville,

Virginia (since February 1997)

Neil Hawkins, Newmark CE Laboratory, University of Illinois, Urbana, Illinois

Representing Technical Subcommittee 5, Masonry Structures

Daniel Shapiro, SOHA Engineers, San Francisco, California

Daniel P. Abrams, MAE Center, University of Illinois, Urbana

Jason J. Thompson, National Concrete Masonry Association, Herndon, Virginia

Representing Technical Subcommittee 6, Steel Structures

C. Mark Saunders, Rutherford and Chekene, San Francisco, California

Harry W. Martin, American Iron and Steel Institute, Auburn, California

Subhash C. Goel, University of Michigan, Ann Arbor, Michigan

Representing Technical Subcommittee 7, Wood Structures

J. Daniel Dolan, Virginia Polytechnic Institute and State University, Blacksburg

Kelly Cobeen, GFDS Engineers, San Francisco, California
2000 Provisions, Appendix B

350

Philip Line, American Forest and Paper Association, Washington, D.C.

Representing Technical Subcommittee 8, Mechanical/Electrical Systems and Building

Equipment and Architectural Elements

John D. Gillengerten, Office of Statewide Health and Planning and Development, Sacramento,

California 

Robert E. Bachman, Consulting Structural Engineer, Westlake Village, California

Pat Lama, Mason Industries, Hauppage, New York 

Representing Technical Subcommittee 9, Quality Assurance

Douglas M. Smits, Division of Building Inspections, City of Charleston, South Carolina 

Jim W. Sealy, Jim W. Sealy/Architect/Consultant, Dallas, Texas

Representing Technical Subcommittee 11, Composite Steel and Concrete Structures

Roberto T. Leon, Georgia Institute of Technology, Atlanta, Georgia

Clarkson W. Pinkham, S. B. Barnes Associates, Los Angeles, California

Representing Technical Subcommittee 12, Base Isolation and Energy Dissipation

Charles Kircher, Charles Kircher and Associates, Consulting Engineers, Palo Alto, California

Michael Constantinou, State University of New York, Buffalo

Representing Technical Subcommittee 13, Nonbuilding Structures

Harold Sprague, Structural Engineer, Black and Veatch, Overland Park, Kansas

Stephen W. Meier, Tank Industry Consultants, Indianapolis, Indiana

At-Large Member

Ed Sutton, National Association of Home Builders, Washington, D.C. (since June 1997)

Robert McCluer, Building Officials and Code Administrators International, Country Club Hills,

Illinois

Alan Carr, International Council of Building Officials, Bellevue, Washington

Ex-officio Voting Member

Loring Wyllie, Degenkolb Engineers, San Francisco, California
Participants in the BSSC 2000 Provisions Update Program

351

PUC TECHNICAL SUBCOMMITTEES

Technical Subcommittee 1, DESIGN MAPPING

Chair

R. Joe Hunt, BWXT Y-12, LLC, Oak Ridge, Tennessee

Members

C.B. Crouse, Dames and Moore, Inc., Seattle, Washington

John D. Hooper, Skilling Ward Magnusson Barkshire, Seattle, Washington

William B. Joyner, U.S. Geological Survey, Menlo Park, California

Jeffrey K. Kimball, Engineering and Operations Support, U.S. Department of Energy,

Germantown, Maryland

E.V. Leyendecker, U.S. Geological Survey, Denver, Colorado

Guy J. P. Nordenson, Nordenson & Associates, New York, New York

Chris D. Poland, Degenkolb Engineers, San Francisco, California

Paul G. Somerville, Woodward-Clyde Federal Services, Pasadena, California

Corresponding Members

Roger D. Borcherdt, U.S. Geological Survey, Menlo Park, California

S.K. Ghosh, S.K. Ghosh Associates, Inc., Northbrook, Illinois

Rene W. Luft, Simpson, Gumpertz & Heger, San Francisco, California 

Perry M. McKimmey, City of Fayetteville, Arkansas

Jeffrey Munsey, Tennessee Valley Authority, Knoxville, Tennessee

R. Hayne Palmer, Jr., United Consulting Group, Ltd., Norcross, Georgia

John C. Theiss, St. Albans, Missouri

Eugene L. Trahern, Coughlin Porter Lundeen, Seattle, Washington

Technical Subcommittee 2, DESIGN CRITERIA AND ANALYSIS

Chair

Ronald O. Hamburger, EQE International, Inc., Oakland, California
2000 Provisions, Appendix B

352

Members

Anil K. Chopra, Civil and Environmental Engineering, University of California, Berkeley

Anthony Brooks Court, Travis, Verdugo, Curry and Associates, San Diego, California

Mohammed M. Ettourney, Weidlinger Associates, Inc., New York, New York

S.K. Ghosh, S.K. Ghosh Associates, Inc., Northbrook, Illinois

James R. Harris, J. R. Harris and Company, Denver, Colorado

John D. Hooper, Skilling Ward Magnusson, Seattle, Washington

Richard J. Phillips, Hillman, Biddison and Loevenguth, Los Angeles, California

Andrei M. Reinhorn, State University of New York, Buffalo

Corresponding Members

David R. Bonneville, Degenkolb Engineers, San Francisco, California

Antonio Braga, Factory Mutual, Orange, California

Walter B. Grossman, Department of Advanced Technology, Brookhaven National Laboratory,

Upton, New York

Husein Hasan, Tennessee Valley Authority, Knoxville, Tennessee

Leonard Joseph, Thornton-Tomasetti Group, New York, New York

John P. Kiland, DASSE Design, Inc., San Francisco, California

Uno Kula, Uno Kula, P.E., Phoenix, Arizona

Colin Kumabe, Department of Building and Safety, Los Angeles, California

Mark Pierepiekarz, EQE International, Seattle, Washington

Steven E. Pryor, Simpson Strong-Tie, Dublin, California

John G. Shipp, EQE International, Irvine, California

Richard Silva, National Park Service, Lakewood, Colorado

Chia-Ming Uang, University of California, San Diego

Howard Zee, Monte Stott and Associates, San Fracisco, California

Technical Subcommittee 3, FOUNDATIONS AND GEOTECHNICAL

CONSIDERATIONS

Chair

Maurice S. Power, Geomatrix Consultants, San Francisco, California
Participants in the BSSC 2000 Provisions Update Program

353

Members

C. B. Crouse, URS Corporation, Seattle, Washington

Ricardo Dobry, Renssalaer Polytechnic Institute, Troy, New York 

Tom H. Hale, California Office of Statewide Health Planning and Development, Sacramento,

California

Edward E. Rinne, Kleinfelder, Inc., Oakland, California

Cetin Soydemir, Haley and Aldrich, Inc., Boston, Massachusetts

Corresponding Members

Roger D. Borcherdt, U.S. Geological Survey, Menlo Park, California

Paul L. Cloke, Science Applications International Corporation, Las Vegas, Nevada 

Richard B. Fallgren, Myers, Nelson, Houghton & Partners, Inc., Lawndale, California

Husein Hasan, Tennessee Valley Authority, Knoxville, Tennessee

Neil M. Hawkins, University of Illinois, Urbana

Klaus H. Jacob, Lamont Doherty Earth Observatory of Columbia University, Palisades, New

York

William B. Joyner, U.S. Geological Survey, Menlo Park, California

Farhang Ostadan, Bechtel Corporation, San Francisco, California

Jonathan P. Stewart, University of California, Los Angeles

Steven A. Wendland, GeoSystems Engineering, Inc., Lenexa, Kansas

T. Leslie Youd, Brigham Young University, Provo, Utah

Technical Subcommittee 4, CONCRETE STRUCTURES

Chair

W. Gene Corley, Construction Technology Laboratories, Skokie, Illinois

Members:

David E. Arndt, KPFF Consulting Engineers, Seattle, Washington

Ned M. Cleland, Blue Ridge Design, Inc., Winchester, Virginia

S. K. Ghosh, S.K. Ghosh Associates, Northbrook, Illinois
2000 Provisions, Appendix B

354

David P. Gustafson, Concrete Reinforcing Steel Institute, Schaumburg, Illinois

Neil M. Hawkins, University of Illinois, Urbana

H. S. Lew, National Institute of Standards and Technology, Gaithersburg, Maryland

Rene W. Luft, Simpson Gumpertz & Heger, San Francisco, California

Joe Maffei, Rutherford & Chekene Consulting Engineers, Oakland, California

Joseph J. Messersmith, Jr., Portland Cement Association, Rockville, Virginia

James K. Wight, Department of Civil and Environmental Engineering, University of Michigan,

Ann Arbor

Richard Wollmershauser, Hilti, Inc., Tulsa, Oklahoma

Corresponding Members:

Max A. Gregersen, Centry Inc., Salt Lake City, Utah

Jacob S. Grossman, Rosenwasser-Grossman and Associates, New York, New York 

Jack P. Moehle, Pacific Earthquake Engineering Research Center, Richmond, California

Antonio Nanni, Pennsylvania State University, University Park

Michael G. Oliva, University of Wisconsin, Madison 

Frank K.H. Park, Guilford County Planning and Development, Greensboro, North Carolina

Paul C. Perrin, Black and Veatch Special Projects Corporation, Overland Park, Kansas

David A. Sheppard, Consulting Structural Engineer, Inc., Sonora, California

Itzhak Tepper, American Structural Engineers, Falls Church, Virginia

Jack Walker, Jack Walker, Inc., Calabasas, California

Technical Subcommittee 5, MASONRY STRUCTURES

Chair

Daniel Shapiro, SOH and Associates, Structural Engineers, San Francisco, California

Members

Daniel P. Abrams, University of Illinois MAE Center, Urbana

J. Gregg Borchelt, Brick Institute of America, Reston, Virginia 

John C. Kariotis, Kariotis and Associates, Structural Engineers, Inc., South Pasadena, California

H. Kit Miyamoto, Structural Engineers Association of Central California, Fair Oaks, California

Max L. Porter, Department of Civil Engineering, Iowa State University, Ames
Participants in the BSSC 2000 Provisions Update Program

355

Jason J. Thompson, National Concrete Masonry Association, Herndon, Virginia

Terence A. Weigel, Department of Civil Engineering, University of Louisville, Kentucky

Corresponding Members

David T. Biggs, Ryan-Biggs Associates, P.C., Troy, New York 

Thomas A. Gangel, Wallace Engineering Structural Consultants, Inc., Tulsa, Oklahoma

Ramon Gilsanz, Gilsanz Murray Steficek, LLP, New York, New York 

Jon P. Kiland, DASSE Design, Inc., San Francisco, California

Richard E. Kligner, University of Texas, Austin

Antonio Nanni, University of Missouri, Rolla

Frank K. H. Park, Guilford County Planning and Development, Greensboro, North Carolina

Arturo E. Schultz, Civil Engineering, University of Minnesota, Minneapolis

Richard Silva, National Park Service, Lakewood, Colorado

John Tawresey, KPFF Consulting Engineers, Seattle, Washington

Diane Throop, International Masonry Institute, Ann Arbor, Michigan

Technical Subcommittee 6, STEEL STRUCTURES

Chair

C. Mark Saunders, Rutherford and Chekene, San Francisco, California

Members

Subhash C. Goel, University of Michigan, Ann Arbor

Larry G. Griffis, Walter P. Moore and Associates, Houston, Texas

John L. Gross, National Institute of Standards and Technology, Gaithersburg, Maryland 

Nestor R. Iwankiw, Technology and Research, American Institute of Steel Construction,

Chicago, Illinois

Helmut Krawinkler, Stanford University, Stanford, California

James O. Malley, Degenkolb Engineers, San Francisco, California
2000 Provisions, Appendix B

356

Harry W. Martin, Construction Codes and Standards, American Iron and Steel Institute, Auburn,

California

Clarkson W. Pinkham, S. B. Barnes Associates, Los Angeles, California

W. Lee Shoemaker, Metal Building Manufacturers Association, Cleveland, Ohio

Kurt D. Swensson, Stanley D. Lindsey and Associates, Ltd., Atlanta, Georgia

Corresponding Members:

Michel Bruneau, Multidisciplinary Center for Earthquake Engineering Research, Buffalo, New

York

Richard M. Drake, Fluor Daniel, Inc., Irvine, California

Maury Golovin, Ceco Building Systems, Columbus, Mississippi

Max A. Gregersen, Centry, Inc., Salt Lake City, Utah

Y. Henry Huang, Los Angeles County Department of Public Works, Alhambra, California

Terry R. Lundeen, Coughlin Porter Lundeen, Inc., Seattle, Washington

Paul C. Perrin, Black and Veatch Special Projects Corporation, Overland Park, Kansas

Walter Schultz, Nucor Research and Development, Norfolk, Nebraska

Steven Thomas, Butler Manufacturing Company, Kansas City, Missouri

Chia-Ming Uang, University of California, San Diego

Howard Zee, Monte Stott and Associates, San Francisco, California

Technical Subcommittee 7, WOOD STRUCTURES

Chair

J. Daniel Dolan, Virginia Polytechnic Institute and State University, Blacksburg, Virginia

Members

Joseph G. Burns, Thornton-Tomasetti Group, Chicago, Illinois

Kelly Cobeen, GFDS Engineers, San Francisco, California

Jay Crandell, National Association of Home Builders Research Center, Upper Marlboro,

Maryland

Larry D. Franks, Southern Building Code Congress International, Birmingham, Alabama

Robert S. George, Robert S. George Architect, San Bruno, California

Cynthia A. Hoover, City of Seattle, Washington
Participants in the BSSC 2000 Provisions Update Program

357

Philip Line, American Forest and Paper Association, Washington, D.C.

Frank K. H. Park, Guilford County Planning and Development, Greensboro, North Carolina

Thomas D. Skaggs, APA - The Engineered Wood Association, Tacoma, Washington

Edwin Zacher, H. J. Brunnier Associates, San Francisco, California

Corresponding Members

Kevin C. K. Cheung, Engineering Support, Western Wood Products Association, Portland,

Oregon

Ted Christensen, Wheeler and Gray Inc., Los Angeles, California

Andre Filiatrault, University of California, San Diego

C. Robert Fuller, National Association of Home Builders Research Division

Erol Karacabeyl, Forintek Canada Corporation, Vancouver, British Columbia, Canada

Edward L. Keith, APA - The Engineered Wood Association, Tacoma, Washington

Mark Oakford, RSE Consulting, Federal Way, Washington

Steven E. Pryor, Simpson Strong-Tie, Dublin California

Victor L. Taugher, Taugher and Associates, Castro Valley, California

David P. Tyree, American Forest and Paper Association, Colorado Springs, Colorado

Technical Subcommittee 8, MECHANICAL/ELECTRICAL SYSTEMS AND BUILDING

EQUIPMENT AND ARCHITECTURAL ELEMENTS

Chair

John D. Gillengerten, Office of Statewide Health Planning and Development, Sacramento,

California

Members 

Leo Argiris, Ove Arup and Partners, New York, New York

Christopher Arnold, Building Systems Development, Inc., Palo Alto, California

Victor Azzi, Rack Manufacturers Institute, Rye, New Hampshire

Robert E. Bachman, Consulting Structural Engineer, Westlake Village, California

Leo Bragagnolo, Port of San Francisco, California

Russell Fleming, National Fire Sprinkler Association, Patterson, New York

Husein Hasan, Tennessee Valley Authority, Knoxville, Tennessee

David B. Hattis, Building Technology, Inc., Silver Spring, Maryland
2000 Provisions, Appendix B

358

Pat Lama, Mason Industries, Hauppage, New York

John V. Loscheider, Loscheider Engineering Company, Renton, Washington

Richard J. Phillips, Hillman, Biddison and Loevenguth, Los Angeles, California

Harold Sprague, Black and Veatch Special Projects Corporation, Overland Park, Kansas

William Staehlin, Office of Statewide Health Planning and Development, Sacramento, California

William W. Stewart, Stewart–Schaberg/Architects, Clayton, Missouri

Richard Wollmershauser, Hilti, Inc., Tulsa, Oklahoma

Corresponding Members

Richard A. Behr, Department of Architectural Engineering, Pennsylvania State University,

University Park

Antonio Braga, Factory Mutual, Orange, California

Philip Caldwell, Square D Company, Seneca, South Carolina

Paul Meisel, Kinetics Noise Control, Dublin, Ohio

Antonio Nanni, University of Missouri, Rolla

Todd Noce, Mason Industries, Anaheim, California

John “Jack” Prosek, Turner Construction Company, Oakland, California

John F. Silva, Hilti, Inc., San Rafael, California

Tsu T. Soong, Department of Civil Engineering, State University of New York, Buffalo

Jack Walker, Jack Walker, Inc., Calabasas, California

Technical Subcommittee 9, QUALITY ASSURANCE

Chair

Douglas M. Smits, City of Charleston, South Carolina

Members

Warner Howe, Consulting Structural Engineer, Germantown, Tennessee

Robert C. Jacobson, City of Bartlett, Tennessee

Mark Kluver, Regional Code Services, San Ramon, California

Raymond W. McNealy, McNealy Bumberry, Des Peres, Missouri

Tom Schlafly, American Institute of Steel Construction, Chicago, Illinois
Participants in the BSSC 2000 Provisions Update Program

359

Jim W. Sealy, Jim W. Sealy/Architect/Consultant, Dallas, Texas

Charles A. Spitz, Architect/Planner/Code Consultant, Wall, New Jersey

Scott Stedman, Professional Engineers, Arroyo Grande, California

Ed Sutton, Construction, National Association of Home Builders, Washington, D.C. (since June

1997)

Corresponding Members

John V. Loscheider, Loscheider Engineering Company, Renton, Washington 

Richard J. Phillips, Hillman, Biddison and Loevenguth, Los Angeles, California

William A. Stewart, Stewart-Schaberg Architects, Clayton, Missouri

James R. Thomas, Delich, Roth and Goodwillie, P.A., Kansas City, Missouri

Technical Subcommittee 11, COMPOSITE STEEL AND CONCRETE STRUCTURES

Chair

Roberto T. Leon, School of Civil and Environmental Engineering, Georgia Institute of

Technology, Atlanta

Members

Gregory Deierlein, School of Civil and Environmental Engineering, Cornell University, Ithaca,

New York

Subhash C. Goel, University of Michigan, Ann Arbor

Lawrence G. Griffis, Walter P. Moore and Associates, Houston, Texas

Jerome F. Hajjar, University of Minnesota, Minneapolis

Neil M. Hawkins, University of Illinois, Urbana

Kevin LeSmith, Skilling Ward Magnusson Barkshire, Inc., Seattle, Washington

Clarkson W. Pinkham, S. B. Barnes Associates, Los Angeles, California

Bahram M. Sharooz, University of Cincinnati, Ohio

Corresponding Members

Scott A. Civjan, University of Massachusetts, Amherst

Nestor R. Inwankiw, Technology and Research, American Institute of Steel Construction,

Chicago, Illinois

James O. Malley, Degenkolb Engineers, San Francisco, California

Ivan M. Viest, Hellertown, Pennsylvania
2000 Provisions, Appendix B

360

James K. Wight, University of Michigan, Ann Arbor

Technical Subcommittee 12, BASE ISOLATION AND ENERGY DISSIPATION

Chair

Charles Kircher, Charles Kircher and Associates, Consulting Engineers, Palo Alto, California

Members

Ian Aiken, Seismic Isolation Engineering, Inc., Oakland, California

Michael Constantinou, Department of Civil Engineering, State University of New York, Buffalo

Robert D. Hanson, Federal Emergency Management Agency, Pasadena, California

Douglas Hochbach, Hochbach-Lewin, Inc., Palo Alto, California

Andrew W. Taylor, KPFF Consulting Engineers, Seattle, Washington

Andrew Whittaker, Earthquake Engineering Research Center, University of California,

Richmond

Corresponding Members

Finley A. Charney, Schnabel Engineering Associates, Denver Colorado 

Husein Hasan, Tennessee Valley Authority, Knoxville, Tennessee

Ronald L. Mayes, Dynamic Isolation Systems, Lafayette, California

Tsu T. Soong, State University of New York, Buffalo

Technical Subcommittee 13, NONBUILDING STRUCTURES

Chair

Harold Sprague, Black and Veatch Special Projects Corporation, Overland Park, Kansas

Members

Victor Azzi, Rack Manufacturers Institute, Rye, New Hampshire

Clayton L. Clem, Structural and Foundation Engineering Department, Tennessee Valley

Authority, Chattanooga, Tennessee

Ralph T. Eberts, Black and Veatch, Los Angeles, California

John D. Gillengerten, Office of Statewide Health Planning and Development, Sacramento,

California

Frank J. Hsiu, Chevron Research and Technology Company, Richmond, California

Leon Kempner, Jr., Bonneville Power Administration, Portland, Oregon
Participants in the BSSC 2000 Provisions Update Program

361

Nicholas A. Legatos, Vice President, Preload Inc., Hauppage, New York

Stephen W. Meier, Engineering and Technology, Tank Industry Consultants, Inc., Indianapolis,

Indiana

Corresponding Members

Mark Anderson, Consulting Engineer, Anchorage, Alaska 

Douglas G. Honegger, Consultant, Arroyo Grande, California

Praveen K. Malhotra, Factory Mutual Research, Norwood, Massachusetts

Dennis Niehoff, Bechtel Savannah River, Inc., Grovetown, Georgia

Michael R. Simac, Earth Improvement Technologies, Cramerton, North Carolina

BSSC SIMPLIFIED PROCEDURES TASK GROUP

Chair

Glenn Bell, Simpson Gumpertz & Heger, Inc., Arlington, Massachusetts

Members

Gary Y.K. Chock, Martin and Chock, Inc., Honolulu, Hawaii

William T. Holmes, Rutherford & Chekene, Oakland, California

Edwin T. Huston, Smith and Huston, Inc., Seattle, Washington

Paul A. Murray, Structural Design Group, Inc., Nashville, Tennessee

Richard J. Phillips, Hillman Biddison and Loevenguth, Los Angeles, California

Douglas, M. Smits, City of Charleston, South Carolina

Corresponding Members

Ramon Gilsanz, Gilsanz Murray Steficek, LLP, New York, New York

Robert I. Johnson, R.I. Johnson & Associates Consulting Engineers, Wheaton, Illinois

Jacob M. Kramer, Sargent & Lundy, LLP, Chicago, Illinois

Philip Line, American Forest and Paper Association, Washington, D.C.

Robert McCluer, Codes, Building Officials and Code Administrators International, Country Club

Hills, Illinois

Guy J.P. Nordenson, Nordenson & Associates, LLP, New York, New York

Michael G. Oliva, College of Engineering, University of Wisconsin, Madison

Cetin Soydemir, Haley and Aldrich, Inc., Boston, Massachusetts

Philip C. Terry, Burns & McDowell, Kansas City, Missouri
2000 Provisions, Appendix B

362

John C. Theiss, St. Albans, Missouri

BSSC ANCHORAGE TASK GROUP

Chair

Daniel Shapiro, SOHA Engineers, San Francisco, California

Members

Robert E. Bachman, Consulting Structural Engineer, Westlake Village, California

David E. Bonneville, Degenkolb Engineers, San Francisco, California

J. Gregg Borchelt, Brick Industry Association, Reston, Virginia

W. Gene Corley, Construction Technology Laboratories, Skokie, Illinois

J. Daniel Dolan, Virginia Polytechnic and State University, Blacksburg, Virginia

John D. Gillengerten, Office of Statewide Health Planning and Development, Sacramento

,California

James R. Harris, J. R. Harris & Company, Denver, Colorado

Philip J. Iverson, Precast/Prestressed Concrete Institute, Chicago, Illinois

Richard E. Klingner, University of Texas, Austin

Stephen W. Meier, Tank Industry Consultants, Inc., Indianapolis, Indiana

A. Fattah Shaikh, University of Wisconsin, Milwaukee

Douglas M. Smits, City of Charleston, South Carolina

James R. Tauby, Mason Industries, Hauppage, New York

Jason J. Thompson, National Concrete Masonry Association, Herndon, Virginia

David L. Wismer, City of Philadelphia, Pennsylvania

Richard Wollmershauser, Technical Services, Hilti, Inc., Tulsa, Oklahoma

Roger Becker, Computerized Structural Design, Inc., Milwaukee, Wisconsin

William T. Holmes, Rutherford and Chekene, Oakland, California
Participants in the BSSC 2000 Provisions Update Program

363

REPRESENTATIVES OF BSSC MEMBER ORGANIZATIONS 

AND THEIR ALTERNATES

AFL-CIO Building and Construction Trades Department

Representative Pete Stafford, Center to Protect Workers’ Rights, Washington, D.C.

American Concrete Institute

Representative Shuaib H. Ahmed, American Concrete Institute, Farmington Hills, Michigan

Alternate Daniel W. Falconer, American Concrete Institute, Farmington Hills, Michigan

American Consulting Engineers Council

Representative Roy G. Johnston, Brandow and Johnston Associates, Los Angeles, California

Alternate Edward Bajer, American Consulting Engineers Council, Washington, D.C.

American Forest and Paper Association

Representative David P. Tyree, American Forest and Paper Association, Colorado Springs,

Colorado

Alternate Bradford K. Douglas, American Forest and Paper Association, Washington,

D.C.

American Institute of Architects

Representative Charles A. Spitz, Architect/Planner/Code Consultant, Wall, New Jersey

Alternate Gabor Lorant, Lorant Group, Inc., Phoenix, Arizona

American Institute of Steel Construction

Representative Charles J. Carter, American Institute of Steel Construction, Chicago, Illinois

Alternate Nestor R. Iwankiw, American Institute of Steel Construction, Chicago, Illinois
2000 Provisions, Appendix B

364

American Insurance Services Group, Inc. 

Representative John A. Mineo, American Insurance Services Group, Inc., New York, New

York

Alternate James G. Borchardt, Bituminous Insurance Company, Rock Island, Illinois

American Iron and Steel Institute

Representative Harry W. Martin, American Iron and Steel Institute, Auburn, California

American Society of Civil Engineers

Representative James A. Rossberg, American Society of Civil Engineers, Reston, Virginia

Alternate Douglas E. Honegger, Consultant, Arroyo Grande, California

American Society of Civil Engineers – Kansas City Chapter

Representative F. Alan Wiley, Black and Veatch, Overland Park, Kansas

Alternate Thomas Heausler, Heausler Structural Engineers, Foster City, California

American Society of Heating, Refrigeration, and Air-Conditioning Engineers

Representative William Staehlin, Office of State Health Planning and Development,

Sacramento, California

Alternate Bruce D. Hunn, American Society of Heating, Refrigeration, and AirConditioning Engineers

American Society of Mechanical Engineers

Representative Ronald W. Haupt, Pressure Piping Engineering Associates, Inc., Foster City,

California

American Welding Society

Representative Hardy H. Campbell III, American Welding Society, Miami, Florida 

Alternate William R. Oates, American Welding Society, Miami, Florida
Participants in the BSSC 2000 Provisions Update Program

365

APA - The Engineered Wood Association

Representative Thomas D. Skaggs, APA - The Engineered Wood Association, Tacoma,

Washington

Alternate Edward L. Keith, APA - The Engineered Wood Association, Tacoma,

Washington

Applied Technology Council

Representative Christopher Rojahn, Applied Technology Council, Redwood City, California

Alternate Charles Thornton, Thornton-Tomasetti Group, Inc., New York, New York

Associated General Contractors of America

Representative John “Jack” Prosek, Turner Construction Company, Oakland, California

Alternate Dirk Haire, Associated General Contractors of America, Alexandria, Virginia

Association of Engineering Geologists

Representative Ellis Krinitzsky, U.S. Army Corps of Engineers, Vicksburg, Mississippi

Alternate Patrick J. Barosh, Patrick J. Barosh and Associates, Bristol, Rhode Island

Association of Major City Building Officials

Representative Andrew A. Adelman, City of Los Angeles, California

Alternate Walter R. Krukow, City of Los Angeles, California

Brick Industry Association

Representative J. Gregg Borchelt, Brick Industry Association, Reston, Virginia

Alternate Charles Clark, Jr., Brick Industry Association, Reston, Virginia

Building Officials and Code Administrators International

Representative David L .Wismer, City of Philadelphia, Pennsylvania

Alternate Paul K. Heilstedt, Building Officials and Code Administrators International,

Country Club Hills, Illinois
2000 Provisions, Appendix B

366

Building Owners and Managers Association International

Representative Michael Jawer, Building Owners and Managers Association International,

Washington, D.C.

California Geotechnical Engineers Association

Representative Alan Kropp, Alan Kropp and Associates, Berkeley, California

Alternate John A. Baker, Kleinfelder, Inc., Sacramento, California

California Seismic Safety Commission

Representative Fred Turner, Seismic Safety Commission, Sacramento, California

Canadian National Committee on Earthquake Engineering

Representative R.H. Devall, Canadian National Committee on Earthquake Engineering,

Vancouver, British Columbia, Canada

Alternate Cathleen Taraschuk, National Research Council of Canada, Ottawa, Ontario,

Canada

Concrete Masonry Association of California and Nevada

Representative Vilas Mujumdar, Concrete Masonry Association of California and Nevada,

Citrus Heights, California

Alternate Daniel Shapiro, SOHA Engineers, San Francisco, California

Concrete Reinforcing Steel Institute

Representative David P. Gustafson, Concrete Reinforcing Steel Institute, Schaumburg,

Illinois

Alternate Anthony Felder, Concrete Reinforcing Steel Institute, Schaumburg, Illinois

California Division of the State Architect

Representative Dennis Bellet, Division of State Architect, Sacramento, California

Alternate Richard T. Conrad, Division of State Architect, Sacramento, California
Participants in the BSSC 2000 Provisions Update Program

367

Earthquake Engineering Research Institute

Representative Joseph Nicoletti, URS Consultants, San Francisco, California

Alternate F. Robert Preece, San Francisco, California

General Services Administration (9PCT)

Representative Bela I. Palfalvi, General Services Administration 9PCT, San Francisco,

California

Alternate Catherine K. Lee, General Services Administration 9 PCT, San Francisco,

California

Hawaii State Earthquake Advisory Board

Representative Gary Y. K. Chock, Martin and Chock, Inc., Honolulu, Hawaii

Alternate Paul Okubo, Hawaii State Earthquake Advisory Board, Honolulu, Hawaii

Institute for Business and Home Safety

Representative Jeffrey Sciaudone, Institute for Business and Home Safety, Tampa Florida

Interagency Committee on Seismic Safety in Construction

Representative H. S. Lew, National Institute of Standards and Technology, Gaithersburg,

Maryland

Alternate Shyam Sunder, National Institute of Standards and Technology, Gaithersburg,

Maryland

International Conference of Building Officials

Representative Paul Armstrong, International Conference of Building Officials, Whittier,

California

Alternate Alan Carr, International Conference of Building Officials, Bellevue,

Washington

International Masonry Institute

Representative Diane Throop, International Masonry Institute, Ann Arbor, Michigan

Alternate Richard Filloramo, International Masonry Institute, Glastonbury, Connecticut 
2000 Provisions, Appendix B

368

Masonry Institute of America

Representative John Chrysler, Masonry Institute of America, Los Angeles, California

Metal Building Manufacturers Association

Representative W. Lee Shoemaker, Metal Building Manufacturers Association, Cleveland,

Ohio

Alternate Joe N. Nunnery, VP Buildings, Memphis, Tennessee

Mid-America Earthquake Center

Representative Daniel P. Abrams, Mid-America Earthquake Center, University of Illinois,

Urbana

Alternate James E. Beavers, Mid-America Earthquake Center, University of Illinois,

Urbana

National Association of Home Builders

Representative Ed Sutton, National Association of Home Builders, Washington, D.C.

National Concrete Masonry Association

Representative Jason J. Thompson, National Concrete Masonry Association, Herndon,

Virginia

Alternate Robert Zobel, National Concrete Masonry Association, Herndon, Virginia

National Conference of States on Building Codes and Standards

Representative Richard T. Conrad, Division of State Architect, Sacramento, California

Alternate Robert C. Wible, National Conference of States on Building Codes and

Standards, Herndon, Virginia

National Council of Structural Engineers Associations

Representative Howard Simpson, Simpson, Gumpertz and Heger, Arlington, Massachusetts

Alternate W. Gene Corley, Construction Technology Laboratories, Skokie, Illinois
Participants in the BSSC 2000 Provisions Update Program

369

National Elevator Industry, Inc.

Representative George A. Kappenhagen, Schindler Elevator Company, Morristown, New

Jersey

National Fire Sprinkler Association

Representative Russell P. Fleming, National Fire Sprinkler Association, Patterson, New York

Alternate Victoria Valentine, National Fire Sprinkler Association, Patterson, New York

National Institute of Building Sciences

Representative Henry L. Green, State of Michigan Department of Consumer and Industry

Services, Okemos, Michigan

Alternate Gerald H. Jones, Kansas City, Missouri

National Ready Mixed Concrete Association

Representative George Muste, National Ready Mixed Concrete Association, Silver Spring,

Maryland

Alternate Colin L. Lobo, National Ready Mixed Concrete Association, Silver Spring,

Maryland

Portland Cement Association

Representative Joseph J. Messersmith, Jr., Portland Cement Association, Rockville, Virginia

Alternate S. K. Ghosh, S. K. Ghosh Associates, Inc., Skokie, Illinois

Precast/Prestressed Concrete Institute

Representative Philip J. Iverson, Precast/Prestressed Concrete Institute, Chicago, Illinois

Alternate David A, Sheppard, Consulting Structural Engineer, Sonora, California

Rack Manufacturers Institute

Representative Victor Azzi, Rack Manufacturers Institute, Rye, New Hampshire

Alternate John Nofsinger, Rack Manufacturers Institute, Charlotte, North Carolina
2000 Provisions, Appendix B

370

Southern Building Code Congress International

Representative John Battles, Souther Building Code Congress International, Birmingham,

Alabama

Alternate T. Eric Stafford, Southern Building Code Congress International,

Birmingham, Alabama

Steel Deck Institute, Inc.

Representative Steven A. Roehrig, Steel Deck Institute, Fox River Grove, Illinois

Alternate Donald W. Ball, Consolidated Systems, Inc., Columbia, South Carolina

Structural Engineers Association of California

Representative Bob Hendershot, Structural Engineers Association of California, San Diego,

California

Alternate Dough Hochbach, Hochbach-Lewin, Inc., Palo Alto, California

Structural Engineers Association of Central California

Representative H. Kit Miyamoto, Structural Engineers Association of Central California, Fair

Oaks, California

Alternate Tom H. Hale, Office of Statewide Health Planning and Development,

Sacramento, California

Structural Engineers Association of Colorado

Representative James R. Harris, J. R. Harris and Company, Denver, Colorado

Alternate Robert B. Hunnes, JVA, Inc., Boulder, Colorado

Structural Engineers Association of Illinois

Representative W. Gene Corley, Construction Technology Laboratories, Skokie, Illinois

Structural Engineers Association of Northern California

Representative James O. Malley, Degenkolb Engineers, San Francisco, California

Alternate Edwin G. Zacher, H. J. Brunnier Associates, San Francisco, California
Participants in the BSSC 2000 Provisions Update Program

371

Structural Engineers Association of Oregon

Representative Joseph P. Gehlen, Kramer Gehlen Associates, Vancouver, Washington

Alternate Grant L. Davis, SE Consulting, Cornelius, Oregon

Structural Engineers Association of San Diego

Representative H. John Khadivi, Precision Structural Engineering, San Diego, California

Structural Engineers Association of Southern California

Representative Brian L. Cochran, Brian L. Cochran Associates, Inc. Los Angeles, California

Alternate Saiful Islam, Saiful/Bouquet, Inc., Pasadena, California

Structural Engineers Association of Texas

Representative Joseph Kallaby, OSI, Houston, Texas

Alternate Michael D. Engelhardt, University of Texas – Austin

Structural Engineers Association of Utah

Representative A. Parry Brown, Reaveley Engineers and Associates, Salt Lake City, Utah

Alternate David L. Pierson, ARW Engineers, Ogden, Utah

Structural Engineers Association of Washington

Representative James Carpenter, Structural Engineers Association of Washington,

Southworth, Washington

Alternate Michael Valley, Skilling Ward Magnusson Barkshire, Seattle, Washington

The Masonry Society

Representative Arturo E. Schultz, University of Minnesota, Minneapolis

Western States Clay Products Association

Representative Jeff I. Elder, Western State Clay Products Association, West Jordan, Utah
2000 Provisions, Appendix B

372

Western States Structural Engineers Association

Representative Greg Shea, Moffat, Nichol and Bonney, Inc., Portland, Oregon

Alternate William T. Rafferty, Structural Design North, Spokane, Washington

Wire Reinforcement Institute, Inc.

Representative Roy H. Reiterman, Wire Reinforcement Institute, Findlay, Ohio

Alternate Robert C. Richardson, Consultant, Sun Lakes, Arizona
Participants in the BSSC 2000 Provisions Update Program

373

REPRESENTATIVES OF BSSC AFFILIATE MEMBERS 

AND THEIR ALTERNATES

Bay Area Structural, Inc.

Representative David Benaroya Helfant, Bay Area Structural, Inc., Oakland, California

Building Technology, Incorporated

Representative David B. Hattis, Building Technology, Inc., Silver Spring, Maryland

Eagle Point Software

Representative Ed Graham, Eagle Point Software, Dubuque, Iowa

Alternate Joe Deppe, Eagle Point Software, Dubuque, Iowa

H & H Group, Inc.

Representative Les. L. Hegyi, H&H Group, Inc., McLean, Virginia

LaPay Consulting, Inc.

Representative William S. LaPay, LaPay Consulting, Inc., Export, Pennsylvania

Northroad Builders

Representative Paul O. Johnson, Northroad Builders, Brisbane, California

Alternate Clara A. Johnson, Northroad Builders, Brisbane, California

Southern California Gas Company

Representative Don Dockray, Southern California Gas Company, Los Angeles, California

Square D Company

Representative Philip J. Caldwell, Square D Company, Seneca, South Carolina

Alternate Jeffrey Gatscher, Square D Company, Nashville, Tennessee
2000 Provisions, Appendix B

374

Steel Joist Institute

Representative R. Donald Murphy, Steel Joist Institute, Myrtle Beach, South Carolina

Vibration Mountings and Controls

Representative John P. Giuliano, Vibration Mountings and Controls, Bloomingdale, New

Jersey

Alternate Rajendra Prasad, Vibration Mountings and Controls, Bloomingdale, New

Jersey