FEMA 306

EVALUATION OF EARTHQUAKE DAMAGED

CONCRETE AND MASONRY WALL BUILDINGS

Basic Procedures Manual

Prepared by:

Applied Technology Council (ATC-43 Project)

555 Twin Dolphin Drive, Suite 550

Redwood City, California 94065

Prepared for:

The Partnership for Response and Recovery

Washington, D.C.

Funded by:

Federal Emergency Management Agency

1998
Applied Technology Council

The Applied Technology Council (ATC) is a nonprofit, tax-exempt corporation established in 1971 through the efforts of the Structural Engineers Association of California. 

ATC is guided by a Board of Directors consisting of representatives appointed by the 

American Society of Civil Engineers, the Structural Engineers Association of California, the Western States Council of Structural Engineers Associations, and four at-large 

representatives concerned with the practice of structural engineering. Each director 

serves a three-year term.

The purpose of ATC is to assist the design practitioner in structural engineering (and 

related design specialty fields such as soils, wind, and earthquake) in the task of keeping abreast of and effectively using technological developments. ATC also identifies 

and encourages needed research and develops consensus opinions on structural engineering issues in a nonproprietary format. ATC thereby fulfills a unique role in funded 

information transfer.

Project management and administration are carried out by a full-time Executive Director and support staff. Project work is conducted by a wide range of highly qualified consulting professionals, thus incorporating the experience of many individuals from 

academia, research, and professional practice who would not be available from any single organization. Funding for ATC projects is obtained from government agencies and 

from the private sector in the form of tax-deductible contributions.

1998-1999 Board of Directors

Charles H. Thornton, President

Edwin T. Dean, Vice President

Andrew T. Merovich, Secretary/

Treasurer

C. Mark Saunders, Past President

James R. Cagley

Arthur N. L. Chiu

Robert G. Dean

Edwin H. Johnson

Kenneth A. Luttrell

Newland J. Malmquist

Stephen H. Pelham

Richard J. Phillips

Charles W. Roeder

Jonathan G. Shipp

Notice

This report was prepared under Contract EMW-95-C-4685 between the Federal Emergency Management Agency and the Partnership for Response and Recovery.

Any opinions, findings, conclusions, or recommendations expressed in this publication 

do not necessarily reflect the views of the Applied Technology Council (ATC), the 

Partnership for Response and Recovery (PaRR), or the Federal Emergency Management Agency (FEMA). Additionally, neither ATC, PaRR, FEMA, nor any of their employees makes any warranty, expressed or implied, nor assumes any legal liability or 

responsibility for the accuracy, completeness, or usefulness of any information, product, or process included in this publication. Users of information from this publication 

assume all liability arising from such use.

For further information concerning this document or the activities of the ATC, contact 

the Executive Director, Applied Technolgy Council, 555 Twin Dolphin Drive, Suite 

550, Redwood City, California 94065; phone 650-595-1542; fax 650-593-2320; e-mail 

atc@atcouncil.org.
FEMA 306 Basic Procedures Manual iii

Preface

Following the two damaging California earthquakes in 

1989 (Loma Prieta) and 1994 (Northridge), many 

concrete wall and masonry wall buildings were repaired 

using federal disaster assistance funding. The repairs 

were based on inconsistent criteria, giving rise to 

controversy regarding criteria for the repair of cracked 

concrete and masonry wall buildings. To help resolve 

this controversy, the Federal Emergency Management 

Agency (FEMA) initiated a project on evaluation and 

repair of earthquake damaged concrete and masonry 

wall buildings in 1996. The project was conducted 

through the Partnership for Response and Recovery 

(PaRR), a joint venture of Dewberry & Davis of 

Fairfax, Virginia, and Woodward-Clyde Federal 

Services of Gaithersburg, Maryland. The Applied 

Technology Council (ATC), under subcontract to PaRR, 

was responsible for developing technical criteria and 

procedures (the ATC-43 project).

The ATC-43 project addresses the investigation and 

evaluation of earthquake damage and discusses policy 

issues related to the repair and upgrade of earthquakedamaged buildings. The project deals with buildings 

whose primary lateral-force-resisting systems consist of 

concrete or masonry bearing walls with flexible or rigid 

diaphragms, or whose vertical-load-bearing systems 

consist of concrete or steel frames with concrete or 

masonry infill panels. The intended audience is design 

engineers, building owners, building regulatory 

officials, and government agencies.

The project results are reported in three documents. The 

FEMA 306 report, Evaluation of Earthquake Damaged 

Concrete and Masonry Wall Buildings, Basic 

Procedures Manual, provides guidance on evaluating 

damage and analyzing future performance. Included in 

the document are component damage classification 

guides, and test and inspection guides. FEMA 307, 

Evaluation of Earthquake Damaged Concrete and 

Masonry Wall Buildings, Technical Resources, contains 

supplemental information including results from a 

theoretical analysis of the effects of prior damage on 

single-degree-of-freedom mathematical models, 

additional background information on the component 

guides, and an example of the application of the basic 

procedures. FEMA 308, The Repair of Earthquake 

Damaged Concrete and Masonry Wall Buildings, 

discusses the policy issues pertaining to the repair of 

earthquake damaged buildings and illustrates how the 

procedures developed for the project can be used to 

provide a technically sound basis for policy decisions. It 

also provides guidance for the repair of damaged 

components.

The project also involved a workshop to provide an 

opportunity for the user community to review and 

comment on the proposed evaluation and repair criteria. 

The workshop, open to the profession at large, was held 

in Los Angeles on June 13, 1997 and was attended by 

75 participants.

The project was conducted under the direction of ATC 

Senior Consultant Craig Comartin, who served as CoPrincipal Investigator and Project Director. Technical 

and management direction were provided by a 

Technical Management Committee consisting of 

Christopher Rojahn (Chair), Craig Comartin (CoChair), Daniel Abrams, Mark Doroudian, James Hill, 

Jack Moehle, Andrew Merovich (ATC Board 

Representative), and Tim McCormick. The Technical 

Management Committee created two Issue Working 

Groups to pursue directed research to document the 

state of the knowledge in selected key areas: (1) an 

Analysis Working Group, consisting of Mark Aschheim 

(Group Leader) and Mete Sozen (Senior Consultant) 

and (2) a Materials Working Group, consisting of Joe 

Maffei (Group Leader and Reinforced Concrete 

Consultant), Greg Kingsley (Reinforced Masonry 

Consultant), Bret Lizundia (Unreinforced Masonry 

Consultant), John Mander (Infilled Frame Consultant), 

Brian Kehoe and other consultants from Wiss, Janney, 

Elstner and Associates (Tests, Investigations, and 

Repairs Consultant). A Project Review Panel provided 

technical overview and guidance. The Panel members 

were Gregg Borchelt, Gene Corley, Edwin Huston, 

Richard Klingner, Vilas Mujumdar, Hassan Sassi, Carl 

Schulze, Daniel Shapiro, James Wight, and Eugene 

Zeller. Nancy Sauer and Peter Mork provided technical 

editing and report production services, respectively. 

Affiliations are provided in the list of project 

participants. 

The Applied Technology Council and the Partnership 

for Response and Recovery gratefully acknowledge the 

cooperation and insight provided by the FEMA 

Technical Monitor, Robert D. Hanson.

Tim McCormick 

PaRR Task Manager 

Christopher Rojahn

ATC-43 Principal Investigator

ATC Executive Director
iv Basic Procedures Manual FEMA 306
FEMA 306 Basic Procedures Manual v

Table of Contents

Preface . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .iii

List of Figures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ix

List of Tables . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . xi

List of Test and Inspection Guides . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .xiii

List of Component Damage Classification Guides . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . xv

Prologue . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . xvii

What have we learned? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . xvii

What does it mean? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .xviii

1. Introduction and Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1

1.1 Purpose . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1

1.2 Scope . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1

1.3 Basis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2

1.4 Overview of the Damage Investigation and Evaluation Procedures . . . . . . . . . . . . . . . . . . . . 4

1.4.1 Introduction and Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4

1.4.2 Characteristics of Concrete and Masonry Wall Buildings . . . . . . . . . . . . . . . . . . . 4

1.4.3 Investigation of Earthquake Damage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4

1.4.4 Evaluation of Earthquake Damage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6

1.4.5 Component Information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7

1.4.6 Terms and Symbols . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7

1.4.7 Related Documents . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7

1.5 Limitations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8

2. Characteristics of Concrete And Masonry Wall Buildings . . . . . . . . . . . . . . . . . . . . . 9

2.1 Typical Vertical Elements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9

2.1.1 Bearing Walls and Infilled Frames . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9

2.1.2 Wall Elevations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10

2.1.3 Foundation Effects . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10

2.2 Horizontal Elements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10

2.3 Three-Dimensional Considerations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14

2.4 Identification of Components . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14

3. Investigation of Earthquake Damage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17

3.1 Characteristics of the Damaging Earthquake . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17

3.2 Review of Existing Building Data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17

3.3 Assessing the Consequences of the Damaging Earthquake . . . . . . . . . . . . . . . . . . . . . . . . . . 18

3.4 Pre-existing Conditions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22

3.5 Component Damage Classification . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23
vi Basic Procedures Manual FEMA 306

3.6 Verification . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .24

3.7 Documentation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .26

3.8 Test and Inspection Guides . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .29

4. Evaluation of Earthquake Damage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .61

4.1 Basis of Evaluation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .61

4.2 Seismic Performance Objectives . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .61

4.3 Seismic Performance Parameters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .61

4.4 Relative Performance Analysis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .62

4.4.1 Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .62

4.4.2 Global Displacement Performance Limits . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .64

4.4.3 Component Modeling and Acceptability Criteria . . . . . . . . . . . . . . . . . . . . . . . . . .65

4.4.4 Global Displacement Demand . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .70

4.5 Performance Restoration Measures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .74

4.6 An Alternative—The Direct Method . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .75

5: Reinforced Concrete . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .77

5.1 Introduction and Background . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .77

5.2 Reinforced Concrete Component Types and Behavior Modes . . . . . . . . . . . . . . . . . . . . . . . .77

5.2.1 Component Types . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .77

5.2.2 Behavior Modes and Damage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .77

5.2.3 Behavior Modes with High Ductility Capacity (Flexural Response) . . . . . . . . . . .78

5.2.4 Behavior Modes with Intermediate Ductility Capacity . . . . . . . . . . . . . . . . . . . . .78

5.2.5 Behavior Modes with Little or No Ductility Capacity . . . . . . . . . . . . . . . . . . . . . .82

5.2.6 Foundation Rocking Response . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .83

5.3 Reinforced Concrete Evaluation Procedures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .83

5.3.1 Cracking . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .83

5.3.2 Expected Strength and Material Properties . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .84

5.3.3 Plastic-Hinge Location and Length . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .85

5.3.4 Ductility Classifications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .86

5.3.5 Moment Strength . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .87

5.3.6 Shear Strength . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .88

5.3.7 Wall Boundary Confinement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .90

5.3.8 Lap Splice Strength . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .91

5.3.9 Wall Buckling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .92

5.4 Symbols for Reinforced Concrete . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .93

5.5 Reinforced Concrete Component Guides . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .95

6: Reinforced Masonry . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .107

6.1 Introduction and Background . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .107

6.2 Reinforced Masonry Component Types and Behavior Modes . . . . . . . . . . . . . . . . . . . . . . .108

6.2.1 Component Types . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .108

6.2.2 Behavior Modes with High Ductility . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .109

6.2.3 Behavior Modes with Moderate Ductility . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .113

6.2.4 Behavior Modes with Low Ductility . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .113
FEMA 306 Basic Procedures Manual vii

6.3 Reinforced Masonry Evaluation Procedures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 114

6.3.1 Material Properties . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 114

6.3.2 Flexure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 114

6.3.3 Shear . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 116

6.3.4 Sliding . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 117

6.3.5 Wall Instability . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 117

6.3.6 Lap-Splice Slip . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 118

6.3.7 Masonry Beams . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 118

6.4 Symbols for Reinforced Masonry . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 120

6.5 Reinforced Masonry Component Guides . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 121

7: Unreinforced Masonry . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 137

7.1 Introduction and Background . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 137

7.1.1 Section Organization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 137

7.1.2 Material Types and Structural Framing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 137

7.1.3 Seismically Rehabilitated URM Buildings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 138

7.2 Unreinforced Masonry Component Types and Behavior Modes . . . . . . . . . . . . . . . . . . . . 139

7.2.1 Non-Wall Components . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 139

7.2.2 Wall Components . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 142

7.2.3 Foundation Rocking . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 144

7.2.4 Wall-Pier Rocking . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 144

7.2.5 Bed-Joint Sliding . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 146

7.2.6 Bed-Joint Sliding at Wall Base . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 149

7.2.7 Spandrel-Joint Sliding . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 150

7.2.8 Rocking/Toe Crushing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 150

7.2.9 Flexural Cracking/Toe Crushing/Bed Joint Sliding . . . . . . . . . . . . . . . . . . . . . . 151

7.2.10 Flexural Cracking/Diagonal Tension . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 151

7.2.11 Flexural Cracking/Toe Crushing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 151

7.2.12 Spandrel-Unit Cracking . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 152

7.2.13 Corner Damage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 152

7.2.14 Preemptive Diagonal Tension . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 152

7.2.15 Preemptive Toe Crushing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 152

7.2.16 Out-of-Plane Flexural Response . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 153

7.2.17 Other Modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 154

7.3 Unreinforced Masonry Evaluation procedures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 154

7.3.1 Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 154

7.3.2 Evaluation Procedures for In-Plane Behavior of Piers in Walls with 

Weak Pier - Strong Spandrel Mechanisms . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 155

7.3.3 Evaluation Procedures for In-Plane Behavior of Solid Wall Components . . . . . 157

7.3.4 Evaluation Procedures for In-Plane Behavior of Perforated Walls with 

Spandrel Damage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 157

7.3.5 Evaluation Procedures for Out-of-Plane Behavior of Wall and Pier Components 162

7.4 Symbols for Unreinforced Masonry . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 163

7.5 Unreinforced Masonry Component Guides . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 165
viii Basic Procedures Manual FEMA 306

8: Infilled Frames . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .183

8.1 Introduction and Background . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .183

8.2 Infilled Frame Masonry Component Types and Behavior Modes . . . . . . . . . . . . . . . . . . . .184

8.2.1 Component Types . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .184

8.2.2 Panel and Frame Modeling and Interaction . . . . . . . . . . . . . . . . . . . . . . . . . . . . .187

8.2.3 Behavior Modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .187

8.3 Infilled Frame Evaluation Procedures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .197

8.3.1 Solid Infilled-Panel Components . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .197

8.3.2 Infilled-Panel Components with Openings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .199

8.3.3 Out-of-Plane Behavior of Infilled-Panel Components . . . . . . . . . . . . . . . . . . . . .199

8.3.4 Steel-Frame Components . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .200

8.3.5 Concrete-Frame Components . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .200

8.4 Infilled Frame Component Guides . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .205

Glossary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .215

List of General Symbols . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .217

References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .219

ATC-43 Project Participants . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .233

Applied Technology Council Projects And Report Information . . . . . . . . . . . . . . . . . . . . .237
FEMA 306 Basic Procedures Manual ix

List of Figures

Figure 1-1 Global Displacement Capacities for Various Performance Levels. Capacities will 

vary, depending on damage level and restoration measure. . . . . . . . . . . . . . . . . . . . . . . . . . . 2

Figure 1-2 Global Displacement Demands for Restored and Unrestored Damaged Buildings. . . . . . . . . 3

Figure 1-3 Flowchart for the Investigation and Evaluation of Earthquake Damage to Concrete 

and Masonry Wall Buildings. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5

Figure 2-1 Global Structure, Lateral-Force-Resisting Elements, and Components. . . . . . . . . . . . . . . . . . 9

Figure 2-2 Characteristics of Bearing Walls and Infilled Frames . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11

Figure 2-3 Three General Categories of Concrete and Masonry Wall Configurations . . . . . . . . . . . . . . 12

Figure 2-4 Example Wall Mechanisms and Components . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13

Figure 3-1 Parameters Needed and Form of Approximate Site Response Spectrum . . . . . . . . . . . . . . . 18

Figure 3-2 Peak Ground Acceleration Contours for 1994 Northridge, California, Earthquake. . . . . . . . 19

Figure 3-3 Spectral Acceleration Contours for T=0.3 sec., 1994 Northridge, California, Earthquake . . 21

Figure 3-4 Spectral Acceleration Contours for T=1.0 sec., 1994 Northridge, California, Earthquake . . 22

Figure 3-5 Different Inelastic Lateral Mechanisms and Components for Same Wall Element . . . . . . . 25

Figure 3-6 Relationship between design strength and expected strength . . . . . . . . . . . . . . . . . . . . . . . . 26

Figure 3-7 Component force-deformation behavior, ductility, and severity of damage . . . . . . . . . . . . . 27

Figure 3-8 Example Component Damage Record . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28

Figure 4-1 Displacement Parameters for Damage Evaluation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 63

Figure 4-2 Idealized Component Force-Deformation Relationship . . . . . . . . . . . . . . . . . . . . . . . . . . . . 64

Figure 4-3 Global Displacement Limits and Component Acceptability used in FEMA 273/274 . . . . . . 65

Figure 4-4 Component Modeling Criteria . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 66

Figure 4-5 Component Acceptability Criteria . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 67

Figure 4-6 Component Modification Factors and Damage Severity . . . . . . . . . . . . . . . . . . . . . . . . . . . . 68

Figure 4-7 Determining λ values from structural testing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 69

Figure 4-8 Maximum Displacement Dependency on Damaging Earthquake . . . . . . . . . . . . . . . . . . . . . 71

Figure 4-9 Global Capacity Dependency on Initial and Effective Stiffness . . . . . . . . . . . . . . . . . . . . . . 71

Figure 4-10 Pre- and Post-Event Capacity Curves with Associated Stiffnesses . . . . . . . . . . . . . . . . . . . . 72

Figure 7-1 Diagram of Parapet Failure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 140

Figure 7-2 Photo of Parapet Failure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 141

Figure 7-3 Diagram of an Appendage Failure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 144

Figure 7-4 Photos of Appendage Failures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 145

Figure 7-5 Diagram of Wall-Diaphragm Tension Tie Failure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 146

Figure 7-6 Photo of Wall-Diaphragm Tension Tie Failure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 147

Figure 7-7 Diagram of Wall-Diaphragm Shear Tie Failure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 148

Figure 7-8 Examples of Various Masonry Diaphragms . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 149

Figure 7-9 URM Wall Components . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 150

Figure 7-10 Photo of Bed Joint Sliding . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 151

Figure 7-11 Diagram of Corner Damage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 153

Figure 7-12 Photo of Corner Damage. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 154
x Basic Procedures Manual FEMA 306

Figure 7-13 Spandrel Joint Sliding . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .158

Figure 7-14 Implications of Spandrel Cracking . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .161

Figure 8-1 Ductile reinforced concrete frames with concrete masonry infills tested by 

Mehrabi et al. (1996) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .189

Figure 8-2 Bed-joint sliding of a two-bay steel frame-block infill. Model study by Gergely 

et al. (1994). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .190

Figure 8-3 Specimen tested by Mander et al. (1993a). Steel frame-clay brick masonry infill. 

Top and seat angles semi-rigid connections used to connect beams to columns. . . . . . . . . .191

Figure 8-4 Effect of openings on the monotonic lateral-load performance of steel framemasonry infill tested by Dawe and Seah (1988). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .192

Figure 8-5 Out-of-plane behavior of infilled masonry walls showing crack patterns and outof-plane lateral load vs. lateral displacement of an air bag test. . . . . . . . . . . . . . . . . . . . . . .193

Figure 8-6 Experiments conducted by Aycardi et al. (1994), showing the performance of 

nonductile frame members with lap splices at the base of the column. . . . . . . . . . . . . . . . . .194
FEMA 306 Basic Procedures Manual xi

List of Tables

Table 2-1 Component Types for Reinforced Concrete Walls . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15

Table 3-1 Summary of Inspection and Test Procedures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20

Table 5-1 Component Types and Descriptions for Reinforced Concrete Walls. . . . . . . . . . . . . . . . . . . 78

Table 5-2 Behavior Modes for Reinforced Concrete Wall Components. . . . . . . . . . . . . . . . . . . . . . . . 79

Table 5-3 Likelihood of Earthquake Damage to Reinforced Concrete Walls According to 

Wall Component and Behavior Mode. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 80

Table 6-1 Component Types for Reinforced Masonry . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 109

Table 6-2 Likelihood of Earthquake Damage to Reinforced Masonry Components 

According to Component and Behavior Mode. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 110

Table 6-3 Behavior Modes for Reinforced Masonry Components . . . . . . . . . . . . . . . . . . . . . . . . . . . 111

Table 6-4 Initial Clay or Concrete Masonry Properties . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 114

Table 7-1 Behavior Modes for Non-Wall URM Elements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 142

Table 7-2 Behavior Modes for URM Walls . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 143

Table 8-1 Component Types for Infilled Frames . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 185

Table 8-2 Behavior Modes For Solid Infilled Panel Components . . . . . . . . . . . . . . . . . . . . . . . . . . . . 188

Table 8-3 Behavior Modes For Infilled Steel-Frame Components . . . . . . . . . . . . . . . . . . . . . . . . . . . 196

Table 8-4 Behavior Modes For Infilled Concrete-Frame Components . . . . . . . . . . . . . . . . . . . . . . . . 197

Table 8-5 Out-of-plane infill strength parameters. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 201
xii Basic Procedures Manual FEMA 306
FEMA 306 Basic Procedures Manual xiii 

List of Test and Inspection Guides

(See Section 3.8)

ID Title Page No.

NDE1 Visual Inspection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30

NDE2 Sounding . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34

NDE3 Rebound Hammer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36

NDE4 Rebar Detector. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38

NDE5 Ultrasonic Pulse Velocity. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40

NDE6 Impact Echo. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 42

NDE7 Spectral Analysis of Surface Waves (SASW) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 44

NDE8 Radiography. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 46

NDE9 Penetrating Radar . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 48

IT1 Selective Removal . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50

IT2 Petrography . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 52

IT3 Material Extraction and Testing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 54

IT4 In Situ Testing - In-Place Shear. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 56

IT5 In Situ Testing - Flat Jack . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 58
 List of Test and Inspection Guides

xiv Basic Procedures Manual FEMA 306
FEMA 306 Basic Procedures Manual xv 

List of Component Damage Classification Guides

Concrete (See Chapter 5)

ID Component Type Behavior Mode Page No.

RC1A Isolated Wall or Stronger Pier Ductile Flexural . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 96

RC1B Isolated Wall or Stronger Pier Flexure/Diagonal Tension. . . . . . . . . . . . . . . . . . . . . . . . . . . . 98

RC1C Isolated Wall or Stronger Pier Flexure/Web Crushing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 100

RC1D Isolated Wall or Stronger Pier Flexure/Sliding Shear . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 101

RC1E Isolated Wall or Stronger Pier Flexure/Boundary Compression . . . . . . . . . . . . . . . . . . . . . . 102

RC2A Weaker Pier Ductile Flexural . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 103

RC2H Weaker Pier Preemptive Diagonal Tension. . . . . . . . . . . . . . . . . . . . . . . . 104

RC3B Coupling Beam Flexure/Diagonal Tension. . . . . . . . . . . . . . . . . . . . . . . . . . . 105

RC3D Coupling Beam Flexure/Sliding Shear . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 106

Reinforced Masonry (See Chapter 6)

ID Component Type Behavior Mode Page No.

RM1A Stronger Pier Ductile Flexural . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 122

RM1B Stronger Pier Flexure/Shear . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 124

RM1C Stronger Pier Flexure/Sliding Shear . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 126

RM1D Stronger Pier Flexure/Out-of-Plane Instability. . . . . . . . . . . . . . . . . . . . . . 127

RM1E Stronger Pier Flexure/Lap Splice Slip . . . . . . . . . . . . . . . . . . . . . . . . . . . . 128

RM2B Weaker Pier Flexure/Shear . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 130

RM2G Weaker Pier Preemptive Shear . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 132

RM3A Weaker Spandrel Flexure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 134

RM3G Weaker Spandrel Preemptive Shear . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 135

Unreinforced Masonry (See Chapter 7)

ID Component Type Behavior Mode Page No.

URM2A Weaker Pier Wall-Pier Rocking . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 166

URM2B Weaker Pier Bed Joint Sliding . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 168

URM3D Weaker Spandrel Spandrel Joint Sliding. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 170

URM1F Solid Wall Flexural Cracking/Toe Crushing/Bed Joint Sliding . . . . . . . 172
 List of Component Damage Classification Guides

xvi Basic Procedures Manual FEMA 306

URM2K Weaker Pier Diagonal Tension . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 174

URM1H Solid Wall Flexural Cracking/Toe Crushing . . . . . . . . . . . . . . . . . . . . . 176

URM3I Weak Spandrel Spandrel Unit Cracking . . . . . . . . . . . . . . . . . . . . . . . . . . . . 178

URM1M Solid Wall Out-of-Plane Flexural Response . . . . . . . . . . . . . . . . . . . . . 180

Infilled Frames (See Chapter 8)

ID Component Type Behavior Mode Page No.

INPS1 Infill Panel Corner Crushing. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 206

INPS2 Infill Panel Diagonal Tension . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 207

INPS3 Infill Panel Bed Joint Sliding . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 208

INPS4 Infill Panel Corner Crushing and Diagonal Cracking. . . . . . . . . . . . . . . 209

INPS5 Infill Panel Out-of-Plane. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 210

INF1C1 Concrete Column Column Snap through Shear Failure . . . . . . . . . . . . . . . . . . 211

INF1C2 Concrete Column Lap Splice Failure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 212

INF3C Concrete Frame Connection Damage. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 213

INF3S Framed Connection Simple Connection Damage . . . . . . . . . . . . . . . . . . . . . . . . 214
FEMA 306 Basic Procedures Manual xvii 

Prologue

This document is one of three to result from the ATC-43 

project funded by the Federal Emergency Management 

Agency (FEMA). The goal of the project is to develop 

technically sound procedures to evaluate the effects of 

earthquake damage on buildings with primary lateralforce-resisting systems consisting of concrete or 

masonry bearing walls or infilled frames. The 

procedures are based on the knowledge derived from 

research and experience in engineering practice 

regarding the performance of these types of buildings 

and their components. The procedures require 

thoughtful examination and review prior to 

implementation. The ATC-43 project team strongly 

urges individual users to read all of the documents 

carefully to form an overall understanding of the 

damage evaluation procedures and repair techniques.

Before this project, formalized procedures for the 

investigation and evaluation of earthquake-damaged 

buildings were limited to those intended for immediate 

use in the field to identify potentially hazardous 

conditions. ATC-20, Procedures for Postearthquake 

Safety Evaluation of Buildings, and its addendum, ATC20-2 (ATC, 1989 and 1995) are the definitive 

documents for this purpose. Both have proven to be 

extremely useful in practical applications. ATC-20 

recognizes and states that in many cases, detailed 

structural engineering evaluations are required to 

investigate the implications of earthquake damage and 

the need for repairs. This project provides a framework 

and guidance for those engineering evaluations.

What have we learned?

The project team for ATC-43 began its work with a 

thorough review of available analysis techniques, field 

observations, test data, and emerging evaluation and 

design methodologies. The first objective was to 

understand the effects of damage on future building 

performance. The main points are summarized below.

• Component behavior controls global 

performance.

Recently developed guidelines for structural 

engineering seismic analysis and design techniques 

focus on building displacement, rather than forces as 

the primary parameter for the characterization of 

seismic performance. This approach models the 

building as an assembly of its individual 

components. Force-deformation properties (e.g., 

elastic stiffness, yield point, ductility) control the 

behavior of wall panels, beams, columns, and other 

components. The component behavior, in turn, 

governs the overall displacement of the building and 

its seismic performance. Thus, the evaluation of the 

effects of damage on building performance must 

concentrate on how component properties change as 

a result of damage. 

• Indicators of damage (e.g., cracking, 

spalling) are meaningful only in light of the 

mode of component behavior.

Damage affects the behavior of individual 

components differently. Some exhibit ductile modes 

of post-elastic behavior, maintaining strength even 

with large displacements. Others are brittle and lose 

strength abruptly after small inelastic 

displacements. The post-elastic behavior of a 

structural component is a function of material 

properties, geometric proportions, details of 

construction, and the combination of demand 

actions (axial, flexural, shearing, torsional) imposed 

upon it. As earthquake shaking imposes these 

actions on components, the components tend to 

exhibit predominant modes of behavior as damage 

occurs. For example, if earthquake shaking and its 

associated inertial forces and frame distortions 

cause a reinforced concrete wall panel to rotate at 

each end, statics defines the relationship between 

the associated bending moments and shear force. 

The behavior of the panel depends on its strength in 

flexure relative to that in shear. Cracks and other 

signs of damage must be interpreted in the context 

of the mode of component behavior. A one-eighthinch crack in a wall panel on the verge of brittle 

shear failure is a very serious condition. The same 

size crack in a flexurally-controlled panel may be 

insignificant with regard to future seismic 

performance. This is, perhaps, the most important 

finding of the ATC-43 project: the significance of 

cracks and other signs of damage, with respect to 

the future performance of a building, depends on the 

mode of behavior of the components in which the 

damage is observed. 
 Prologue

xviii Basic Procedures Manual FEMA 306

• Damage may reveal component behavior 

that differs from that predicted by evaluation 

and design methodologies.

When designing a building or evaluating an 

undamaged building, engineers rely on theory and 

their own experience to visualize how earthquakes 

will affect the structure. The same is true when they 

evaluate the effects of actual damage after an 

earthquake, with one important difference. If 

engineers carefully observe the nature and extent of 

the signs of the damage, they can greatly enhance 

their insight into the way the building actually 

responded to earthquake shaking. Sometimes the 

actual behavior differs from that predicted using 

design equations or procedures. This is not really 

surprising, since design procedures must account 

conservatively for a wide range of uncertainty in 

material properties, behavior parameters, and 

ground shaking characteristics. Ironically, actual 

damage during an earthquake has the potential for 

improving the engineer’s knowledge of the behavior 

of the building. When considering the effects of 

damage on future performance, this knowledge is 

important. 

• Damage may not significantly affect 

displacement demand in future larger 

earthquakes.

One of the findings of the ATC-43 project is that 

prior earthquake damage does not affect maximum 

displacement response in future, larger earthquakes 

in many instances. At first, this may seem illogical. 

Observing a building with cracks in its walls after an 

earthquake and visualizing its future performance in 

an even larger event, it is natural to assume that it is 

worse off than if the damage had not occurred. It 

seems likely that the maximum displacement in the 

future, larger earthquake would be greater than if it 

had not been damaged. Extensive nonlinear timehistory analyses performed for the project indicated 

otherwise for many structures. This was particularly 

true in cases in which significant strength 

degradation did not occur during the prior, smaller 

earthquake. Careful examination of the results 

revealed that maximum displacements in time 

histories of relatively large earthquakes tended to 

occur after the loss of stiffness and strength would 

have taken place even in an undamaged structure. In 

other words, the damage that occurs in a prior, 

smaller event would have occurred early in the 

subsequent, larger event anyway. 

What does it mean?

The ATC-43 project team has formulated performancebased procedures for evaluating the effects of damage. 

These can be used to quantify losses and to develop 

repair strategies. The application of these procedures 

has broad implications.

• Performance-based damage evaluation uses 

the actual behavior of a building, as 

evidenced by the observed damage, to 

identify specific deficiencies.

The procedures focus on the connection between 

damage and component behavior and the 

implications for estimating actual behavior in future 

earthquakes. This approach has several important 

benefits. First, it provides a meaningful engineering 

basis for measuring the effects of damage. It also 

identifies performance characteristics of the 

building in its pre-event and damaged states. The 

observed damage itself is used to calibrate the 

analysis and to improve the building model. For 

buildings found to have unacceptable damage, the 

procedures identify specific deficiencies at a 

component level, thereby facilitating the 

development of restoration or upgrade repairs. 

• Performance-based damage evaluation 

provides an opportunity for better allocation 

of resources.

The procedures themselves are technical 

engineering tools. They do not establish policy or 

prescribe rules for the investigation and repair of 

damage. They may enable improvements in both 

private and public policy, however. In past 

earthquakes, decisions on what to do about damaged 

buildings have been hampered by a lack of technical 

procedures to evaluate the effects of damage and 

repairs. It has also been difficult to investigate the 

risks associated with various repair alternatives. The 

framework provided by performance-based damage 

evaluation procedures can help to remove some of 

these roadblocks. In the long run, the procedures 

may tend to reduce the prevailing focus on the loss 

caused by damage from its pre-event conditions and 

to increase the focus on what the damage reveals 

about future building performance. It makes little 
 Prologue

FEMA 306 Basic Procedures Manual xix

sense to implement unnecessary repairs to buildings 

that would perform relatively well even in a 

damaged condition. Nor is it wise to neglect 

buildings in which the component behavior reveals 

serious hazards regardless of the extent of damage.

• Engineering judgment and experience are 

essential to the successful application of 

the procedures.

ATC-20 and its addendum, ATC-20-2, were 

developed to be used by individuals who might be 

somewhat less knowledgeable about earthquake 

building performance than practicing structural 

engineers. In contrast, the detailed investigation of 

damage using the performance-based procedures of 

this document and the companion FEMA 307 report 

(ATC, 1998a) and FEMA 308 report (ATC, 1998b) 

must be implemented by an experienced engineer. 

Although the documents include information in 

concise formats to facilitate field operations, they 

must not be interpreted as a “match the pictures” 

exercise for unqualified observers. Use of these 

guideline materials requires a thorough 

understanding of the underlying theory and 

empirical justifications contained in the documents. 

Similarly, the use of the simplified direct method to 

estimate losses has limitations. The decision to use 

this method and the interpretation of the results must 

be made by an experienced engineer.

• The new procedures are different from past 

damage evaluation techniques and will 

continue to evolve in the future.

The technical basis of the evaluation procedures is 

essentially that of the emerging performance-based 

seismic and structural design procedures. These will 

take some time to be assimilated in the engineering 

community. The same is true for building officials. 

Seminars, workshops, and training sessions are 

required not only to introduce and explain the 

procedures but also to gather feedback and to 

improve the overall process. Additionally, future 

materials-testing and analytical research will 

enhance the basic framework developed for this 

project. Current project documents are initial 

editions to be revised and improved over the years.

In addition to the project team, a Project Review Panel 

has reviewed the damage evaluation and repair 

procedures and each of the three project documents. 

This group of experienced practitioners, researchers, 

regulators, and materials industry representatives 

reached a unanimous consensus that the products are 

technically sound and that they represent the state of 

knowledge on the evaluation and repair of earthquakedamaged concrete and masonry wall buildings. At the 

same time, all who contributed to this project 

acknowledge that the recommendations depart from 

traditional practices. Owners, design professionals, 

building officials, researchers, and all others with an 

interest in the performance of buildings during 

earthquakes are encouraged to review these documents 

and to contribute to their continued improvement and 

enhancement. Use of the documents should provide 

realistic assessments of the effects of damage and 

valuable insight into the behavior of structures during 

earthquakes. In the long run, they hopefully will 

contribute to sensible private and public policy 

regarding earthquake-damaged buildings.
 Prologue

xx Basic Procedures Manual FEMA 306
FEMA 306 Basic Procedures Manual 1 

1. Introduction and Overview

1.1 Purpose

The purpose of this document is to provide practical 

criteria and guidance for evaluating earthquake damage

to buildings with primary lateral-force-resisting systems 

consisting of concrete or masonry walls or infilled 

frames. The procedures in this manual are intended to 

characterize the observed damage caused by the 

earthquake in terms of the loss in building performance 

capability. This information may be used to facilitate 

the settlement of insurance claims, the development of 

strategies for repair, or other purposes. The intended 

users of this document are primarily practicing 

engineers with experience in concrete and masonry 

design in seismic regions. Information in this document 

also may be useful to building owners, building officials 

insurance adjusters, and government agencies; however 

these users should consult with a qualified engineer for 

interpretation or specific application of the document.

1.2 Scope

Concrete and masonry wall buildings include those with 

vertical-load bearing wall panels, with and without 

openings. This document also applies to buildings with 

vertical-load-bearing frames of concrete or steel that 

incorporate masonry or concrete infill panels to resist 

horizontal forces. For both types of buildings, the 

procedures and criteria in this document address:

a. The investigation and documentation of damage 

caused by earthquakes

b. The classification of the damage for building 

components according to mode of structural 

behavior and severity of damage

c. The evaluation of the effects of the damage on 

the performance of the building during future 

earthquakes

d. The development of hypothetical measures that 

would restore the performance of the building to 

that of its condition immediately before the 

damaging earthquake

Evaluating of the effects of earthquake damage on 

future seismic performance entails the relative 

performance analysis of the building in its damaged and 

pre-event states for one or more seismic performance 

objectives. If the expected performance of the damaged 

building is significantly worse than that anticipated for 

the building in its pre-event condition, conceptual 

performance restoration measures are developed on a 

component level to generate global performance nearly 

equivalent to the pre-event condition. Performance 

restoration measures rely on the technical analysis of 

potential component actions. The document also 

includes a simplified direct method for generating an 

approximate scope for performance restoration 

measures for some cases. Although performance 

restoration measures specified by either method are 

essentially hypothetical physical repairs, they are not 

recommended for actual implementation solely on the 

basis of these damage evaluation procedures. The 

selection of appropriate repairs for an earthquakedamaged building typically requires consideration of a 

wider range of technical and policy issues. This process 

is summarized in a companion document, FEMA 308:

The Repair of Earthquake Damaged Concrete and 

Masonry Wall Buildings (ATC, 1998b). 

The procedures for damage evaluation in this document 

are technical; however, their use requires policy 

considerations including the selection of performance 

objectives as benchmarks for measuring changes in 

seismic performance. This document does not specify 

or limit the use of the damage evaluations, nor does it 

impose damage repair scope or procedures. Users 

should not infer otherwise.

Earthquakes can cause damage to the structural and 

nonstructural components of buildings. This document 

addresses structural damage. The direct evaluation of 

nonstructural damage is not included. The effects of 

structural damage on potential future nonstructural 

damage can be addressed indirectly by the selection of 

appropriate seismic performance objectives for the 

evaluation procedure.

The term damage, when used in this document, refers to 

damage to the building caused by the earthquake. It is 

important to note that prior effects of environmental 

deterioration, service conditions, and previous 

earthquakes are considered to be pre-existing conditions 

and not part of the damage to be evaluated. This 

distinction is covered further in the presentation of the 

evaluation procedures.
 Chapter 1: Introduction and Overview

2 Basic Procedures Manual FEMA 306

1.3 Basis

The evaluation procedure assumes that when an 

earthquake causes damage to a building, a competent 

engineer can assess the effects, at least partially, through 

visual inspection augmented by investigative tests, 

structural analysis, and knowledge of the building 

construction. By determining how the structural damage 

has changed structural properties, it is feasible to 

develop potential actions (performance restoration 

measures) that, if implemented, would restore the 

damaged building to a condition such that its future 

earthquake performance would be essentially equivalent 

to that of the building in its pre-event condition. The 

costs associated with these conceptual performance 

restoration measures quantify the loss associated with 

the earthquake damage.

The damage evaluation procedure measures the effects 

of damage by comparing the relative capability of preevent, damaged, and restored models of a building to 

meet seismic performance objectives for future 

earthquakes. The analysis technique is to compare a 

global displacement capacity limit, dc, to a global 

displacement demand, dd, for the building model (see 

Figures 1-1 and 1-2). Both of these global displacement 

parameters are controlled by the force-deformation 

properties of all the individual structural components of 

the building model. The procedure includes techniques 

for modifying these component force-deformation 

properties to account for the effects of both the observed 

damage and potential restoration measures.

The damage evaluation criteria build, to the extent 

possible, on existing performance-based procedures in 

the FEMA 273 and FEMA 274 reports, NEHRP 

Guidelines for the Seismic Rehabilitation of Buildings

(ATC, 1997a) and companion Commentary (ATC, 

1997b), and the ATC-40 Report, Seismic Evaluation 

and Retrofit of Concrete Buildings (ATC, 1996). This 

document adapts the existing state of knowledge rather 

than developing completely new techniques. This 

approach contributes to consistency of language, 

nomenclature, and technical concepts among emerging 

procedures intended for use by structural engineering 

practitioners. The intent is to improve the application of 

the existing knowledge and techniques by using 

observations of earthquake damage to calibrate 

analytical models of component behavior.

Two principal research efforts augment the basic 

procedures:

• An Analysis Working Group has investigated the 

theoretical effects of prior damage on the 

displacement response of single-degree-of-freedom 

models subjected to earthquakes in an effort to 

verify and/or modify current methods of predicting 

displacement demand. The implications of the 

results from this investigation for damage evaluation 

are reflected in Section 4.4.4 of this volume. A 

summary report on the results is included in FEMA 

307: Evaluation of Earthquake Damaged Concrete 

and Masonry Wall Buildings, Technical Resources

(ATC, 1998a).

Figure 1-1 Global Displacement Capacities for Various Performance Levels. Capacities will vary, depending on 

damage level and restoration measure.

dc(Pre-event)

'

c d (Damaged)

dc

* (Restored)

Immediate Occupancy (I.O.) Life Safety (L.S.) Collapse Prevention (C.P.)

Notes:

1. Displacement capacity varies depending on performance level and the condition of the building at the

time of the earthquake.

2. See Chapter 4 for discussion of performance levels.

3. Pre-event ( ), Damaged ('), and Restored (*) designate the condition of the building at the time of the

earthquake.

dc (Pre-event)

'

c d (Damaged)

dc

* (Restored)

dc (Pre-event)

'

c d (Damaged)

dc

* (Restored)
 Chapter 1: Introduction and Overview

FEMA 306 Basic Procedures Manual 3

• A Materials Working Group has assembled tests and 

investigative techniques to document the effects of 

earthquake damage. This effort produced the Test 

and Inspection Guides included in Chapter 3 of this 

volume. This group also used existing research 

results to develop recommended modifications to 

component force-deformation relationships for 

nonlinear structural analysis to include the effects of 

damage. The results are the Component Damage 

Classification Guides included in Chapters 5 through 

8. Additional background information including that 

forming the basis of the Component Guides is in

FEMA 307 (ATC, 1998a). Finally this group 

assembled information on repair techniques 

commonly applied to earthquake damage in concrete 

and masonry wall buildings. These are documented 

in a companion document, FEMA 308: The Repair 

of Earthquake Damaged Concrete and Masonry 

Wall Buildings (ATC, 1998b).

In the past, there has been a tendency to gauge the effect 

of earthquake damage by estimating the loss of lateralFigure 1-2 Global Displacement Demands for Restored and Unrestored Damaged Buildings.

Time Pre-event

State

Original

Performance

Damage State

Performance

Earthquake dd

a) Building without prior earthquake damage

Restoration Time

Measures

Performance

Damage State ( * )

dd*

Intermediate Time

Damage State

Damaging

Earthquake

Performance

Damage State ( ' )

dd d ' e

b) Building with prior earthquake damage

c) Building restored after prior earthquake damage

Notes:

1. Displacement demand varies depending on the condition of the

building at the time of the performance earthquake.

2. Pre-event ( ), Damaged ('), and Restored (*) designate the condition

of the building at the time of the performance earthquake.
 Chapter 1: Introduction and Overview

4 Basic Procedures Manual FEMA 306

force-resisting capacity of the structure (Hanson, 1996). 

It has been suggested by some that this loss can be 

related to the observed width and extent of concrete and 

masonry cracks in the damaged structure. There has 

been widespread disagreement on the significance of 

cracking on capacity and skepticism on the suitability of 

force capacity as a parameter for measuring damage. 

The procedure in this document is based on global 

displacement and component deformation capacities 

rather than force capacities. This approach facilitates a 

more meaningful engineering assessment of the effects 

of damage on future performance.

1.4 Overview of the Damage 

Investigation and 

Evaluation Procedures

This section briefly summarizes the damage 

investigation and evaluation procedures, referring as 

necessary to specific chapters. One objective is to 

provide the practicing engineer with a road map for the 

use of the document in real-life applications. Another 

equally important objective is to provide a basic 

exposure to the process for owners, building officials, 

disaster assistance personnel, and others with an interest 

in the results who may not be familiar with the technical 

details.

1.4.1 Introduction and Overview

Chapter 1 summarizes the purpose, basis, and scope of 

the document. The technical basis of the damage 

investigation and evaluation procedures are reviewed. A 

step-by-step outline presents these basic procedures. 

Brief synopses are included for subsequent chapters.

1.4.2 Characteristics of Concrete and 

Masonry Wall Buildings 

Chapter 2 presents a summary of the characteristic 

features of concrete and masonry wall buildings. The 

chapter introduces the concept of structural systems, 

elements and components that is used throughout the 

evaluation process. The discussion includes the 

distinction between bearing walls and infilled frames. 

The effect of the dimensional and material 

characteristics of the wall components and the 

importance of this concept for the investigation of the 

damage caused by an earthquake are discussed. This 

chapter also illustrates the formulation of an inelastic 

lateral mechanism for a building based on the properties 

of its individual components. Additionally, the chapter 

discusses how observed damage can be used to enhance 

and augment the model used for the investigation 

process.

1.4.3 Investigation of Earthquake 

Damage

The initial effort in the evaluation of damage to a 

specific building concentrates on investigating and 

documenting the damage that has occurred to a building 

during the earthquake (see Figure 1-3). Investigation 

procedures are given in Chapter 3. The objective is to 

assemble the basic information in a format that 

facilitates its use in evaluating the effects of the damage 

on future seismic performance. The primary steps in the 

investigation are summarized below.

1.4.3.1 Assemble Information

The first step in the investigation is a compilation of 

basic information on the damaging earthquake and the 

building. 

A. Damaging Earthquake

Performance-based evaluations rely on a comparison 

between the capacity of a building to sustain lateral 

movement and the demand for lateral movement 

imposed by the performance ground motion. 

Information about the performance characteristics of a 

building can be derived from estimating the 

displacement demand that the damaging earthquake 

placed on it. For example, the decision regarding repair 

or upgrading of a building with moderate damage is 

affected by the magnitude of shaking that caused the 

damage. Section 3.1 provides a summary of suggestions 

for characterizing the damaging ground motion at the 

site for subsequent analysis. 

B. Building Data

A discussion of the common configuration 

characteristics and components of concrete and 

masonry wall buildings is given in Chapter 2. The focus 

of the damage investigation is on the structural 

components that make up the vertical- and lateral-forceresisting system for the specific building under 

investigation. The construction drawings for the 

building, soils reports, prior building inspections, and 

other relevant reports and documents are the primary 

sources of the pertinent information (see Section 3.2). 

Basic information about the building includes its age, 

size, and use. If it was inspected after the damaging 

earthquake for posting purposes, these data can be 
 Chapter 1: Introduction and Overview

FEMA 306 Basic Procedures Manual 5

Figure 1-3 Flowchart for the Investigation and Evaluation of Earthquake Damage to Concrete and Masonry Wall 

Buildings. (Section numbers are indicated.)

Document Damage:

•Inspections and Tests (3.3, 3.8)

•Pre-existing conditions (3.4)

Investigation

Assemble Information:

•Damaging Earthquake (3.1)

•Building (3.2)

Classify Component Damage: (3.5)

•Behavior Mode (5,6,7,8)

•Severity (5,6,7,8)

Verification (3.6)

Gather more information and revise

assumptions to obtain consistency

between damage classification

and observations.

Identify Components: (2.4, 5,6,7,8)

•Materials

•Configuration

•Behavior

Evaluation

Select Performance Objective(s): (4.2)

•Performance Level

•Seismic Hazard

Analyze Relative Performance: (4.4)

•Pre-event State

•Damaged

•Restored

Alternative Direct Method (4.6)

•Simple approximation

•Unsuitable for repair/upgrade design

Performance Restoration Measures (4.5)

•Construction costs

•Project costs

•Loss of revenue

Component Damage

Records (3.7)
 Chapter 1: Introduction and Overview

6 Basic Procedures Manual FEMA 306

useful. If records of the operation and maintenance are 

available, they can be useful in distinguishing between 

pre-existing conditions and damage caused by the 

earthquake.

C. Performance Objectives

The evaluation procedures are based on the 

performance objective for the building (see 

Section 4.2). Although it is possible to investigate and 

document damage without choosing a performance 

objective, it is worthwhile to consider this issue early in 

the evaluation process.

1.4.3.2 Identify Components

The engineer identifies basic structural components by 

anticipating the governing mechanism of inelastic 

behavior for each element in the structural system. This 

process normally requires some basic calculations to 

compare the relative strength and stiffness of the 

individual components of the structure . For each type 

of wall material (reinforced concrete, reinforced 

masonry, and unreinforced masonry) and for infilled 

frames, there are a number of basic component types. 

These are compiled in Chapters 5, 6, 7, and 8. 

1.4.3.3 Document Damage

After assembling and reviewing available data, the 

engineer documents the actual damage based on field 

inspections and tests. Section 3.8 provides a 

compilation of outline specifications for different types 

of tests and investigative procedures. It includes 

guidance on the selection of appropriate procedures, 

equipment and personnel requirements, report format, 

and interpretation of results.

1.4.3.4 Classify Component Damage

For each component of the structural system, the 

engineer classifies the damage according to behavior 

mode and severity. The various behavior modes for each 

material and framing type are tabulated in Component 

Damage Classification Guides in Chapters 5, 6, 7, and 

8. The engineer also categorizes the severity of damage 

for each type of damage encountered within any 

component. 

1.4.3.5 Verification

The investigation of damage is a cyclic process. 

Information from the field can help the engineer 

determine component type based on actual behavior. 

Calculations and analyses can also help with the 

interpretation of field data. In some cases, the engineer 

may decide to conduct further tests to resolve 

conflicting data. Properly implemented, the process 

concludes with a reasonable representation of the actual 

damage and a basic understanding of the response of the 

structure to the earthquake shaking. 

1.4.4 Evaluation of Earthquake 

Damage

Chapter 4 provides guidance on how to evaluate the 

significance of the observed damage. A seismic 

performance objective (see Section 4.2) consists of a 

specific performance level (e.g., collapse prevention,

life safety, or immediate occupancy) for a specific 

seismic hazard (probability of shaking of a given 

intensity, or a deterministic event). The damage 

evaluation procedure uses a specified performance 

objective as a benchmark to gauge the effects of 

damage. The selection of applicable performance 

objectives for a building is a policy decision that 

depends on its age, size, use, and other considerations. 

For some cases, consideration of multiple performance 

objectives is appropriate. 

Once the effects of the damaging ground motion on all 

of the components are tabulated, the engineer quantifies 

these effects for the entire building by determining the 

scope of actions that, if implemented, would restore the 

future seismic performance of the building to that of its 

pre-event state. These are performance restoration 

measures and they are the subject of Chapter 4. These 

measures are formulated by detailed analysis of the 

building in its pre-event, damaged, and restored 

conditions (i.e., relative performance analysis). In some 

cases a simplified approach (i.e., direct method) may be 

applicable to generate an estimate of loss. The selection 

of the appropriate method for a building depends on a 

number of considerations, including the severity of the 

earthquake, the extent and type of damage, and the 

likely course of action for repair or upgrade of the 

building.

The performance restoration measures determined by 

either the relative performance analysis or the direct 

method represent the conceptual physical changes to the 

damaged structure that would be required to restore the 

performance to the level that existed before the 

damaging earthquake. The loss in future seismic 

performance caused by the damaging earthquake is 

measured by the hypothetical costs to implement these 

measures. The total loss includes indirect costs, such as 
 Chapter 1: Introduction and Overview

FEMA 306 Basic Procedures Manual 7

design and management fees and loss of use of the 

facility, in addition to direct construction costs that 

would be associated with the performance restoration 

measures if they were to be implemented. 

Section 4.4 addresses the technical aspects of seismic 

performance analysis of concrete and masonry wall 

buildings. This quantitative procedure uses nonlinear 

analysis techniques to estimate the performance of the 

building in future earthquakes in its pre-event, damaged 

and restored states. The force-deformation 

characteristics of components are modified to account 

for damage according to recommendations in the 

Component Damage Classification Guides in Chapters 

5 through 8. In order to determine the scope of the 

performance restoration measures, the engineer 

analyzes selective component restoration measures as 

well as the possible addition of supplemental 

components with the objective of restoring the seismic 

performance to that of the pre-event building.

1.4.5 Component Information

1.4.5.1 Component Damage Classification 

Guides

Chapters 5, 6, 7, and 8 provide a compilation of 

Component Guides for use in the damage evaluation 

process. These assist the engineer in identifying the 

structural components, determining behavior modes, 

and gauging damage severity. The guides also provide 

information on how damage affects the forcedeformation characteristics of the components. This 

information is for use in the performance analysis. 

Recommendations for measures to restore structural 

properties are also tabulated. The component guides are 

classified according to structural system. The four 

classifications are:

• Concrete (Chapter 5)

• Reinforced masonry (Chapter 6)

• Unreinforced masonry (Chapter 7)

• Infilled frames (Chapter 8)

1.4.6 Terms and Symbols

A conscientious effort has been made to utilize concepts 

and language that are familiar to practicing engineers. 

This document, however, introduces terms whose 

definitions are not necessarily in common use. Such 

items, italicized at their first occurrence, are defined in 

the Glossary.

To the extent possible this document uses common 

symbols and notation that are familiar to practicing 

engineers. New symbols are required in some instances. 

These are listed at the end of this document. Symbols 

related primarily to specific materials are listed at the 

end of Chapter 5 for concrete, Chapter 6 for reinforced 

masonry, Chapter 7 for unreinforced masonry, and 

Chapter 8 for infilled frames.

1.4.6.1 Test and Inspection Guides

Section 3.8 presents information on common tests and 

inspection methods for investigation of earthquake 

damage to concrete, masonry wall, and infill frame 

buildings. It includes summaries of the required 

equipment and personnel, and the objectives and 

limitations of the procedures are reviewed. Reference 

and resource materials are listed.

1.4.7 Related Documents 

FEMA 307: Evaluation of Earthquake Damaged 

Concrete and Masonry Wall Buildings, Technical 

Resources (ATC, 1998a)

FEMA 307 provides additional detailed information on 

the basis and use of the damage-evaluation procedures 

of FEMA 306. Background information on the 

development of the Component Guides is included for 

each material type and for infilled frames. It is essential 

that the engineer understand this information both for 

the general application of the procedures and for special 

cases when the typical component data must be 

modified to suit actual conditions. A summary of the 

analytical studies on the effects of damage on the global 

response of buildings is provided. This information is 

the basis for the recommendations on determining 

seismic displacement demand contained in FEMA 306. 

Finally, damage evaluation of a specific building is 

presented as a practical illustration of the application of 

the procedures.

FEMA 308: The Repair of Earthquake Damaged 

Concrete and Masonry Wall Buildings (ATC, 1998b)

This document supplements the evaluation procedures 

with a summary of policy considerations on the repair 

of earthquake-damaged concrete and masonry wall 

buildings. A model framework for repair policy is 

developed from past experience with damaging 

earthquakes. The use of the information from the 

evaluation process within this framework is illustrated 

for both the private and public sectors. The alternatives 
 Chapter 1: Introduction and Overview

8 Basic Procedures Manual FEMA 306

for repairing and upgrading earthquake-damaged 

buildings are reviewed along with potentially applicable 

standards and methodologies. Outline specifications for 

typical repair techniques are provided. Information on 

the objectives and limitations of the procedures is 

summarized. Reference standards and quality 

assurance measures are tabulated. These Repair Guides 

are also intended for use in the damage evaluation 

process to assist in the development of performance 

restoration measures.

ATC-20: Procedures for the Post Earthquake Safety 

Evaluation of Buildings (ATC, 1989)

ATC-20 is the standard for the safety investigation of 

buildings immediately following an earthquake. The 

intent of the document is to determine by visual 

observation of damage whether buildings are safe to 

occupy shortly after the earthquake. There are three 

levels of possible evaluation implied in ATC 20. The 

first level, Rapid Evaluation, is an inspection of the 

damage, which is intended to be implemented by 

building officials, engineers, architects, inspectors, or 

other individuals with a general familiarity with 

building construction. Questionable structures may be 

then subject to Detailed Evaluation by a structural 

engineer. If a structure cannot be appraised effectively 

by visual techniques alone, an Engineering Evaluation 

is required. At the time that ATC-20 was published, 

guidelines for Engineering Evaluations were not 

available. The procedures in FEMA 306 may be 

effectively utilized by qualified structural engineers to 

fill this gap. Consequently, FEMA 306 supplements the 

provisions of ATC-20.

1.5 Limitations

The procedures and criteria for the evaluation of 

damage in this document have been developed based on 

the current state of the knowledge on nonlinear inelastic 

behavior of structures and structural components. The 

state of knowledge varies by material, component type, 

and mode of behavior as discussed in Chapters 5, 6, 7, 

and 8 and FEMA 307. This knowledge will expand over 

time. The evaluation procedures and the information on 

component behavior must be adapted appropriately to 

reflect new information.

The interpretation of damage and the performance of 

buildings subject to earthquakes benefits from 

considerable experience and expert judgment. These 

procedures and criteria provide a framework for an 

engineer to apply experience and to formulate 

judgments on the effects of earthquake damage on 

future performance. The limitations of the procedures 

notwithstanding, the relative validity of results for a 

given situation are predominantly dependent on the 

capabilities of the engineer or engineers. The 

procedures should not be applied by non-engineering 

personnel (e.g., inspectors, insurance adjusters, claims 

managers).

In the past, other methodologies have been used to 

evaluate buildings damaged in earthquakes and to 

design repairs. If the procedures and criteria of this 

document are applied retroactively to such buildings, 

the results may be different. Any difference is not 

necessarily a reflection on the competency of the 

individual or firm responsible for the original work. 

Prior repairs should be judged on the basis of the 

procedures and criteria that were available at the time of 

the work. 
FEMA 306 Basic Procedures Manual 9 

2. Characteristics of Concrete And Masonry Wall 

Buildings

This chapter describes the basic design and construction 

features of concrete and masonry wall buildings. 

Descriptions of typically encountered structural 

components for various material types serve as a guide 

for the user when investigating actual buildings.

The evaluation of damage to a building requires an 

understanding on the part of the engineer of the way in 

which it supports gravity loads, resists earthquake 

forces, and accommodates related displacements. It is 

helpful to imagine the global building structure as an 

assembly of elements (see Figure 2-1). An element is a 

vertical or a horizontal portion of a building that acts to 

resist lateral and/or vertical loads. Common vertical 

elements in concrete and masonry wall buildings 

include structural walls and combined frame-wall 

(infilled) elements. Common floor or roof horizontal 

elements are reinforced concrete or wood diaphragms. 

For evaluation and analysis purposes, each element acts 

in its own plane to transmit seismic actions through the 

building in a three-dimensional global assembly of twodimensional elements. Although out-of-plane seismic 

actions can act on elements at the same time, these 

actions are conventionally considered separately.

Elements are themselves assemblies of individual 

components such as beams, slabs, columns, joints, and 

others. The global performance of the structural system 

is an aggregation of the performance of its components. 

For seismic performance analysis, structural properties 

(force-deformation relationships) and acceptability 

criteria (deformation limits) are specified for 

components. The global behavior of the building 

depends on these component properties. Evaluation 

procedures tabulate damage type and severity for 

components. The identification of components (see 

Section 2.4) of the lateral-force-resisting elements 

normally requires some basic engineering analysis and 

consideration of the type of damage that may have 

occurred. 

2.1 Typical Vertical Elements

Concrete and masonry wall buildings rely primarily on 

the walls as vertical elements for lateral seismic 

resistance. The construction of these elements varies by 

material and the basic system for vertical load transfer. 

Behavior and damage characteristics of the walls during 

earthquakes depend on the physical dimensions and 

configuration of the wall elements including openings 

and penetrations.

2.1.1 Bearing Walls and Infilled 

Frames

In concrete and masonry wall buildings, there are two 

basic systems through which vertical loads are 

transmitted from the roofs and floors to the foundations: 

Figure 2-1 Global Structure, Lateral-Force-Resisting Elements, and Components.

A2

A3

A1 A5

A4

Global Structure Wall Element A

Wall

Element A

(vertical)

Wall

Element B

(vertical)

Components

Diaphragm

Element C

(horizontal)

Returns included in

properties of components

A1 and A5
Chapter 2: Characteristics of Concrete And Masonry Wall 

Buildings

10 Basic Procedures Manual FEMA 306

bearing walls and infilled frames (see Figure 2-2). 

Bearing walls may support a portion of adjacent vertical 

load, as well as their own weight. In some areas of a 

bearing wall building, supplemental frames, columns, 

and/or flat slabs might support a portion of the vertical 

load. The walls themselves can be made of reinforced or 

unreinforced concrete or masonry.

Infilled frames differ from bearing walls in that they 

always include a vertical load carrying frame of 

concrete or steel beams and columns. Wall panels are 

placed within the frame. The infill can be reinforced or 

unreinforced concrete or masonry. To be effective at 

resisting in-plane lateral loads, the infill must be in 

contact with the surrounding frame. In basic 

configuration (e.g., distribution of elements within a 

building, extent of openings in walls), bearing wall and 

infilled frame buildings often appear similar. 

Reinforced concrete or masonry bearing walls can have 

boundary elements that are wider than the wall itself 

that resemble beams or columns of a frame. Their 

details of construction and behavior of bearing walls 

and infilled frames under lateral loads, however, can be 

quite different. The basic components of bearing wall 

and infilled frame buildings also differ from one 

another, as detailed further in Chapters 5, 6, 7, and 8.

2.1.2 Wall Elevations

The elevations of Figure 2-3 illustrate three general 

categories of concrete and masonry wall element 

configurations. Each of these configurations may be 

built of bearing wall or infilled frame construction.

Cantilevered walls are those that act predominantly as 

vertical beams restrained at their foundation level. This 

is not to imply fixity at the base. In fact, many wall 

elements are sensitive to foundation movements caused 

by uplift, soil displacements, or deformations of 

foundation components, as discussed in Section 2.1.3. 

Coupled walls or wall elements are those with a 

generally regular pattern of openings that form a 

configuration of vertical (piers) and horizontal 

(spandrels or coupling beams) components similar to a 

frame element. The inelastic action of a coupled wall 

element consequently depends on the relative strength 

and stiffness of the pier and spandrel components. 

Perforated walls or wall elements may also exhibit an 

irregular pattern of openings in contrast to coupled 

walls. If the total area of opening relative to wall area is 

small, their behavior tends toward that of cantilevered 

walls. This behavior is illustrated by the strongly 

coupled perforated wall in Figure 2-4. When there is a 

relatively large proportion of wall openings, behavior 

tends toward that of coupled walls with irregular (semivertical and semi-horizontal) components. This 

behavior is illustrated by the weakly coupled perforated 

wall in Figure 2-4. The modeling of perforated walls 

requires judgment and experience. Strut and tie models 

can be used to analyze walls with an irregular pattern of 

penetrations (Pauley and Priestley, 1992). Observations 

of damage after an earthquake can provide valuable 

evidence to assist the engineer in formulating a model 

to reflect actual behavior.

When walls intersect to form L-shaped, T-shaped, Cshaped, or similar sections, typically the entire section 

is considered as an integral unit and a single 

component. The contribution of flanges and wall returns 

should be considered in evaluating the strength of the 

component, based on the guidelines given in Chapters 5 

through 8.

2.1.3 Foundation Effects

Foundation flexibility and deformation affect the 

earthquake response of many concrete and masonry 

wall buildings. Foundation effects tend to reduce the 

force demand on the primary lateral-force-resisting 

elements such as shear walls. At the same time, 

however, the rotational flexibility of the base of the 

shear walls often results in larger lateral displacements 

of the entire structure. The larger drifts can lead to 

damage in the beams, columns, or slabs. There is 

evidence of this type of damage from past earthquakes. 

Fixed-base analysis techniques do not adequately model 

these effects. FEMA 273/274 (ATC, 1997a,b) and ATC40 (ATC, 1996) contain recommendations for modeling 

foundation elements and components similarly to other 

structural components.

2.2 Horizontal Elements

Horizontal elements (diaphragms) typically 

interconnect vertical elements at floor and roof levels in 

concrete and masonry wall buildings. Reinforced 

concrete slabs and the associated framing comprise 

relatively rigid diaphragms. These rigid diaphragms are 

characteristic of many concrete and masonry wall 

buildings. For analysis purposes, the flexibility of these 

diaphragms is often neglected, and the vertical elements 

are assumed to be rigidly linked at floor and roof levels. 

While this assumption is tolerable for most buildings, 

concrete diaphragms are not always rigid and can be 
Chapter 2: Characteristics of Concrete And Masonry Wall 

Buildings

FEMA 306 Basic Procedures Manual 11

Figure 2-2 Characteristics of Bearing Walls and Infilled Frames

Section

Elevation

a) Bearing Wall

Floor and roof loads 

supported on wall

Concrete or masonry 

bearing wall

Portion of vertical load may be 

carried by beam/slab/column 

framing

Section

Elevation

Floor and roof loads 

supported by steel or 

concrete frame

Concrete or masonry 

infill panels

Essentially all vertical 

load carried by frame

b) Infilled Frame

Note: 

Reinforced concrete panels 

well-anchored to boundary members 

behave similar to bearing walls
Chapter 2: Characteristics of Concrete And Masonry Wall 

Buildings

12 Basic Procedures Manual FEMA 306

Figure 2-3 Three General Categories of Concrete and Masonry Wall Configurations

Cantilever Wall Elements

Coupled Wall Elements

Perforated Wall Elements

Beam and column

components

Slender wall Squat wall

Stong pier/weak spandrel Weak pier/strong spandrel
Chapter 2: Characteristics of Concrete And Masonry Wall 

Buildings

FEMA 306 Basic Procedures Manual 13

Figure 2-4 Example Wall Mechanisms and Components

Cantilever Wall Mechanisms

Pier/Spandrel Mechanisms

Mixed Mechanisms

RC1

RC1

RC1

RC1

RC2

RC3 RC1

RC2

RC3 RC5

RC5 RC4

Squat wall

Stong pier/weak spandrel Weak pier/strong spandrel

Wall component types

(see Table 2-1) Beam and column

components

Slender wall Strongly coupled

perforated wall

RC1

RC1

Weakly coupled

perforated wall

RC1

RC1

RC3

RC2

RC1

RC3

RC3

RC3

RC4

RC4
Chapter 2: Characteristics of Concrete And Masonry Wall 

Buildings

14 Basic Procedures Manual FEMA 306

damaged in earthquakes. Such damage has been 

observed, and repair may be required in some cases.

Many unreinforced masonry and precast (tilt-up) 

reinforced concrete bearing wall buildings have flexible 

diaphragms of wood sheathing. Walls resist the in-plane 

lateral loads that are distributed based on the tributary 

area. Connections between flexible diaphragms and 

walls are frequently the weak links in the lateral load 

path of the building, for forces both parallel and 

perpendicular to the wall. These connections are not 

addressed specifically in this document, but damage 

evaluations should consider the potential at these 

locations. Guidance may be found in FEMA 273/274.

2.3 Three-Dimensional 

Considerations 

The interpretation of earthquake damage in concrete 

and masonry wall buildings can be complicated by the 

three-dimensional response of the buildings.

• Global horizontal torsion of the building can affect 

the distribution of damage to vertical elements. 

Analysis techniques contained in FEMA 273/274 

and ATC-40 that can account for this effect are 

helpful for damage evaluation. However, the 

magnitude of the actual torsional response may 

differ from the estimates (actual plus accidental 

torsion) conventionally used for design. Careful 

interpretation of the distribution of damage in the 

field is required to interpret the torsional behavior.

• Damage to individual elements and components can 

be due to actions from either, or both, orthogonal 

directions. For example, a shear wall element acting 

parallel to one orthogonal direction may include a 

perpendicular return at either or both ends. Damage 

to the perpendicular return can be due to forces in 

either direction and must be carefully interpreted.

• Wall elements and components are subject to both 

in-plane and out-of-plane earthquake forces. 

Cracking or other damage due to out-of-plane forces 

can be misinterpreted as an in-plane effect. If cracks 

are evident on only one side of a wall element, they 

may be due to out-of-plane forces.

As a separate issue, parapets and other building 

appendages can pose serious risks, particularly in 

unreinforced masonry buildings. 

2.4 Identification of 

Components 

The procedures for damage evaluation focus on the 

components of the building that resist earthquake 

shaking. The identification of these components is 

central to the overall evaluation process. The ultimate 

identification of components for an earthquakedamaged building entails a combination of theoretical 

analysis and observation of the damage itself. 

At the beginning of the evaluation process, the engineer 

identifies basic components by anticipating the 

governing inelastic lateral mechanism for each element 

in the lateral-force-resisting system. This analysis 

consists of determining the relevant stiffness and 

ultimate strength (flexure, shear, axial) of each 

component to anticipate the behavior and geometry of 

the mechanism that would form as the element is 

displaced laterally by a monotonically increasing lateral 

load pattern. Reinforced concrete wall component types 

are summarized in Table 2-1 and Figure 2-4. The 

component strength and load patterns are initially 

assumed using conventional sources including FEMA 

273/274, ATC-40, and consensus design standards. 

FEMA 273/274 and ATC-40 also provide guidance on 

foundation components. 

For each basic material, there are a number of 

component types. Chapters 5, 6, 7, and 8 provide a 

compilation of component data by material and framing 

type. The data in these chapters are supplemented in 

FEMA 307 by expanded information on component 

behavior that is based on available test data and 

theoretical techniques that go beyond conventional 

design standards. This resource material is useful when 

the effects of damage are introduced into the evaluation 

process, as discussed in Section 3.5.
Chapter 2: Characteristics of Concrete And Masonry Wall 

Buildings

FEMA 306 Basic Procedures Manual 15

Table 2-1 Component Types for Reinforced Concrete Walls

Component Type Description

RC1 Cantilever wall 

or stronger wall 

pier

This type of component is stronger than beam or spandrel components that may frame 

into it, so that nonlinear behavior (and damage) is generally concentrated at the base, 

with a flexural plastic hinge or shear failure. This category includes isolated (cantilever) walls. If the component has a major setback or reduction of reinforcement above 

the base, this location should be also checked for nonlinear behavior.

RC2 Weaker wall 

pier

This type of component is weaker than the spandrels to which it connects. Damage is 

characterized by flexural hinging at the top and bottomof the pier, or by shear failure.

RC3 Weaker spandrel or coupling beam

This type of component is weaker than the wall piers to which it connects. Damage is 

characterized by hinging at each end, shear failure, or sliding shear failure.

RC4 Stronger spandrel

This type of component should not suffer damage because it is stronger than attached 

piers. If such a component is damaged, it should be re-classified as RC3.

RC5 Pier-spandrel 

panel zone

This component is a pier-spandrel connection zone. High shear forces in this zone can 

cause cracking. Severe damage is uncommon in reinforced concrete and masonry.
Chapter 2: Characteristics of Concrete And Masonry Wall 

Buildings

16 Basic Procedures Manual FEMA 306
FEMA 306 Basic Procedures Manual 17 

3. Investigation of Earthquake Damage

This chapter describes the investigation and 

documentation of earthquake damage to concrete and 

masonry wall or infill frame buildings. The objectives 

of the investigation are listed below.

• To gather information on the characteristics of the 

damaging ground motion at the building site

• To verify the general physical characteristics of the 

building, including its geometry and mass

• To identify structural components and elements of 

the lateral-force-resisting system

• To determine structural properties of the components 

in sufficient detail for structural analysis purposes

• To observe and record damage to the components

• To distinguish, to the extent possible, between 

damage caused by the earthquake and damage that 

may have existed before

The process includes the assembly and review of 

available existing information relating to the 

characteristics of the earthquake, assembly and review 

of information on the structural condition of the 

building both immediately before and after the 

earthquake, inspections and tests to characterize the 

nature and extent of damage, and the documentation 

and interpretation of the results of the investigation. 

3.1 Characteristics of the 

Damaging Earthquake

During the evaluation of damage to concrete or masonry 

wall buildings, information on the characteristics of the 

damaging earthquake can lead to valuable insight on the 

performance characteristics of the structure. For 

example, if the ground motion caused by the earthquake 

can be estimated quantitatively, the analysis techniques 

summarized in Chapter 4 can provide an estimate of the 

resulting maximum displacement of the structure. This 

displacement, in conjunction with the theoretical 

capacity curve, indicates an expected level of 

component damage. If the observed component damage 

is similar to that predicted, the validity of the theoretical 

model is verified in an approximate manner. If the 

damage differs, informed adjustments can be made to 

the model.

A general process for gathering information and 

evaluating the effects of a damaging earthquake is 

outlined below:

1. Collect information on the damaging earthquake. If 

strong motion data is available, it is preferable to 

use data

a. from a record taken at or very near to the site, or

b. from contour maps of ground motions 

parameters, such as those shown in Figures 3-2, 

3-3, and 3-4, created from a spatial interpolation 

of all nearby strong-motion data.

If strong-motion data is not available, contours of 

intensity (e.g., Modified Mercalli Intensity) could 

be used to estimate spectral accelerations.

Attenuation relationships can also be used to 

estimate ground-motion parameters. However, the 

scatter inherent in such relationships can lead to a 

large uncertainty in the prediction of ground motion 

for an individual site.

In all cases, site soil conditions should be 

considered in the estimate of ground motion.

2. Formulate an approximate response spectrum for 

the site (see Figures 3-1 through 3-4). The example 

in the figures uses the acceleration at a period of 0.3 

second to define the acceleration response regime. 

The 1997 NEHRP Recommended Provisions for 

New Buildings (BSSC, 1997) uses 0.2 second. 

Either approach may be used depending on the 

available data.

3. Generate a capacity curve for the structure at the 

time of the damaging earthquake (see Chapter 4)

4. Use nonlinear static procedures to estimate the 

maximum global displacement, de, that the damaging earthquake should have generated for the structure.

5. Estimate the expected component damage for the 

maximum global displacement of de and compare 

to the observed damage.

3.2 Review of Existing Building 

Data

The data collection process begins with the acquisition 

of documents describing the pertinent conditions of the 

building. Review of construction drawings simplifies 
 Chapter 3: Investigation of Earthquake Damage

18 Basic Procedures Manual FEMA 306

field work and leads to a more complete understanding 

of the building. Original architectural and structural 

construction drawings are central to an effective and 

efficient evaluation of damage. Potential sources of 

these and other documents include the current and 

previous building owners, building departments, and the 

original architects or engineers. Drawings may also be 

available from architects or engineers who have 

performed prior evaluations for the building. In addition 

to construction drawings, it is helpful to assemble the 

following documents if possible:

• Site seismicity/geotechnical reports

• Structural calculations

• Construction specifications

• Contractors' shop drawings and other construction 

records

• Foundation reports

• Prior building assessments

Review of the existing building information serves 

several purposes. If reviewed before field investigations, 

the information facilitates the analytical identification 

of structural components, as discussed in Section 2.4. 

This preliminary analysis also helps to guide the field 

investigation to components that are likely to be 

damaged. Existing information can also help to 

distinguish between damage caused by the earthquake 

and pre-existing damage. Finally, the scope of the field 

inspection and testing program depends on the accuracy 

and availability of existing structural information. For 

example, if structural drawings reliably detail the size 

and placement of reinforcing, expensive and intrusive 

tests to verify conditions in critical locations may be 

unnecessary.

3.3 Assessing the 

Consequences of the 

Damaging Earthquake

Methods for inspecting and testing concrete and 

masonry wall buildings for earthquake damage fall into 

two general categories, nondestructive and intrusive. 

Nondestructive techniques do not require any removal 

of the integral portions of the components. In some 

cases, however, it may be necessary to remove finishes 

in order to conduct the procedure. In contrast, intrusive 

techniques involve extraction of structural materials for 

the purpose of testing or for access to allow inspection 

of portions of a component. Table 3-1 summarizes the 

types of inspections and tests that apply to concrete and 

masonry wall buildings. 

Figure 3-1 Parameters Needed and Form of Approximate Site Response Spectrum

Period, T

(sec.)

Spectral Acceleration,

Sa

0.5 1.0 1.5

Sa at T=0.3 sec from Figure 3-3

Sa

 at T=1.0 sec from Figure 3-4

Peak ground acceleration at T=0 sec from Figure 3-2

Sa = (Sa at T=1.0)/ T
 Chapter 3: Investigation of Earthquake Damage

FEMA 306 Basic Procedures Manual 19

Section 3.8 provides guides for each procedure. Each 

guide includes a basic background for the practicing 

engineer on selecting and implementing appropriate 

procedures based on the actual conditions encountered 

in the field. Each guide consists of the following 

information:

Test Name and ID For reference and identification

Test Type Nondestructive (NDE) or 

Intrusive (IT)

Materials Applicability to reinforced 

concrete, reinforced masonry, 

and/or unreinforced masonry

Description Basic overview of the objectives 

and scope of the procedure

Equipment A summary of the tools, 

instrumentation, or devices 

required

Execution General sequence of operations 

Reporting Format for reporting of results

Requirements

Personnel Skill level and specialized

Qualifications training that may be required

Limitations Restrictions on the type of 

information that can be gained 

and advice on the interpretation 

of results

References Applicable standards, detailed 

specifications, or sources of 

additional information

Figure 3-2 Peak Ground Acceleration Contours for 1994 Northridge, California, Earthquake (from NIST, 1997, 

“dots” indicate locations of a particular building type)
 Chapter 3: Investigation of Earthquake Damage

20 Basic Procedures Manual FEMA 306

Table 3-1 Summary of Inspection and Test Procedures

Structural Or Material 

Property Material Test ID Test Type

Reinf.

Conc.

Reinf. 

Mas. URM (Section 3.8)

Crack Location and Size ✓✓✓ NDE 1 Visual observation

Spall Location and Size ✓✓✓ NDE 1 Visual observation

✓✓✓ NDE 2 Sounding

Location of Interior Cracks or ✓✓✓ NDE 6 Impact echo

Delaminations ✓ NDE 7 Spectral Analysis of Surface Waves

✓✓✓ IT 1 Selective removal

Reinforcing Bar Buckling or ✓ ✓ NDE 1 Visual observation

Fracturing ✓ ✓ IT 1 Selective removal

Relative Age of Cracks ✓✓✓ IT 2 Petrography

Relative Compressive Strength ✓✓✓ NDE 3 Rebound hammer

Compressive Strength ✓✓✓ IT 3 Material extraction and testing

Reinforcing Bar Location and ✓ ✓ NDE 4 Rebar detector

Size ✓ ✓ NDE 8 Radiography

✓ ✓ NDE 9 Penetrating radar

✓ ✓ IT 1 Selective removal

Strength of Reinforcing Bar ✓ ✓ IT 3 Material extraction and testing

Wall Thickness ✓✓✓ NDE 1 Visual observation

✓✓✓ NDE 6 Impact echo

✓✓✓ IT 1 Selective removal

Presence of Grout in Masonry ✓ ✓ NDE 2 Sounding

Cells ✓ ✓ NDE 6 Impact echo

✓ ✓ NDE 7 Spectral Analysis of Surface Waves

✓ ✓ IT 1 Selective removal

Strength of Masonry ✓ ✓ IT 3 Material extraction and testing

✓ IT 4, 5 In situ testing

Mortar Properties ✓ ✓ IT 2 Petrography

✓ IT 4, 5 In situ testing

NDE: Nondestructive

IT: Intrusive
 Chapter 3: Investigation of Earthquake Damage

FEMA 306 Basic Procedures Manual 21

The procedures included in Section 3.8 are those that 

are generally accessible to the practicing engineering 

community and that have been used successfully on 

projects that required evaluation of existing concrete 

and masonry structures. They are not, however, an 

exhaustive list. Other more sophisticated or specialized 

techniques may be useful in specific instances.

The overall scope of the type and number of tests and 

inspections depends on a number of factors including:

• The completeness of existing documentation. If 

accurate and complete documentation of the 

structural conditions is available, the scope of the 

investigation may be relatively small.

• The nature and extent of the damage. Pervasive or 

diverse damage trigger more extensive 

investigations. Buildings with damage that may have 

occurred prior to the earthquake may require a 

greater degree of attention to distinguish between 

pre-existing conditions and earthquake damage. 

• The quality of construction. If the field conditions 

differ routinely from construction documents, more 

investigative work will be required. If in-place 

material quality is inconsistent, more tests of 

individual components will be necessary.

• The correlation between analytical information and 

field observation. If calculations to identify critical 

components and expected damage give results that 

are corroborated by the actual damage, then fewer 

tests and inspections are warranted. 

Figure 3-3 Spectral Acceleration Contours for T=0.3 sec., 1994 Northridge, California, Earthquake (from NIST, 1997, 

“dots” indicate locations of a particular building type)
 Chapter 3: Investigation of Earthquake Damage

22 Basic Procedures Manual FEMA 306

• The degree of accessibility to critical areas for visual 

examination. 

In general, the scope of the investigation can vary 

considerably among individual buildings. A plan for the 

investigation should begin with relatively simple and 

inexpensive procedures. The goal should be to visually 

inspect all the elements and components of the lateralload-resisting system. In some cases, finishes may 

prevent the examination of certain elements and 

components. If analysis suggests that damage is likely 

to have occurred in hidden areas, finishes should be 

removed for inspection at critical locations. As the 

investigation proceeds, the scope can be expanded, if 

necessary, based on the results of visual inspections and 

comparison with analytical predictions of behavior. 

When testing is needed to obtain material properties for 

a relative performance analysis, the number of tests 

required to quantify the in-place properties of the 

materials may be based on the guidelines provided in 

FEMA 273/274 and ATC-40.

3.4 Pre-existing Conditions

Interpretation of the findings of damage observations 

requires care and diligence. When evaluating damage to 

a concrete or masonry wall, an engineer should consider 

all possible causes in an effort to distinguish between 

that attributable to the damaging earthquake and that 

which occurred earlier (pre-existing conditions). ACI 

Figure 3-4 Spectral Acceleration Contours for T=1.0 sec., 1994 Northridge, California, Earthquake (from NIST, 1997, 

“dots” indicate locations of a particular building type)
 Chapter 3: Investigation of Earthquake Damage

FEMA 306 Basic Procedures Manual 23

224.1R (ACI Committee 224, 1994) discusses possible 

causes of cracking in reinforced concrete. Some of the 

causes described are also applicable to reinforced and 

unreinforced masonry construction. Since the 

evaluation of earthquake damaged buildings is typically 

conducted within weeks or months of the event, 

cracking and spalling caused by earthquakes is 

normally relatively recent damage. cracks associated 

with drying shrinkage or a previous earthquake, on the 

other hand, would be relatively old. General guidance 

for assessing the relative age of cracks based on visual 

observations is as follows.

Recent cracks typically have the following 

characteristics:

• Small, loose edge spalls

• Light, uniform color of concrete or mortar within 

crack

• Sharp, uneroded edges

• Little or no evidence of carbonation

Older cracks typically have the following 

characteristics:

• Paint or soot inside crack

• Water, corrosion, or other stains seeping from crack

• Previous, undisturbed patches over crack

• Rounded, eroded edges

• Deep carbonation

Evaluating the significance of damage requires an 

understanding of the structural behavior of the wall 

during the earthquake. The evaluating engineer must 

consider the implications of the observations with 

respect to the overall behavior of the building and the 

results of analytical calculations. The behavior must be 

correlated with the damage. If the observed damage is 

not reasonably consistent with the overall seismic 

behavior of the structure, the crack may have been 

caused by an action other than the earthquake. 

3.5 Component Damage 

Classification

For each component of the structural system, the 

engineer classifies the damage according to behavior 

mode. Behavior mode indicates the predominant type of 

damage that a component sustains, or has the potential 

to sustain, in response to earthquake forces and 

displacements. The behavior mode depends on the 

relative strength of the component part for various 

actions (e.g., shear or moment). For each component, 

the engineer also classifies the severity of damage as 

follows:

Chapters 5, 6, 7, and 8 address the classification of 

damage for components of reinforced concrete, 

reinforced masonry, unreinforced masonry, and infilled 

frames, respectively. Guidance is tabulated according to 

component type and behavior mode, to assist the 

engineer in identifying and for assessing the severity of 

Insignificant: Damage does not significantly affect 

structural properties in spite of a minor 

loss of stiffness. Restoration measures 

are cosmetic unless the performance 

objective requires strict limits on 

nonstructural component damage in 

future events.

Slight: Damage has a small effect on structural 

properties. Relatively minor structural 

restoration measures are required for 

restoration for most components and 

behavior modes.

Moderate: Damage has an intermediate effect on 

structural properties. The scope of 

restoration measures depends on the 

component type and behavior mode. 

Measures may be relatively major in 

some cases.

Heavy: Damage has a major effect on 

structural properties. The scope of 

restoration measures is generally 

extensive. Replacement or 

enhancement of some components may 

be required.

Extreme: Damage has reduced structural 

performance to unreliable levels. The 

scope of restoration measures 

generally requires replacement or 

enhancement of components.
 Chapter 3: Investigation of Earthquake Damage

24 Basic Procedures Manual FEMA 306

the damage based on the observed conditions and 

calculations of component properties.

The information and guidance for each typical 

component type are summarized in tabular form in the 

Component Damage Classification Guides (Component 

Guides) at the end of each chapter. The intention is to 

provide practical assistance in a concise format for use 

by an engineer in applying the evaluation procedures. 

Component Guides are not intended to be used by 

inexperienced or unqualified observers of damage. The 

identification of components and the determination of 

modes of behavior requires a thorough understanding of 

the technical basis of the damage evaluation 

procedures. 

The format of the Component Guides is similar for all 

components. 

Behavior Mode

A brief summary of how to distinguish the particular 

behavior mode both by observation of the damage and 

by analysis is provided. These relate to damage 

inspection procedures (Sections 3.3 and 3.8) and the 

component evaluation techniques (Chapters 5, 6, 7, and 

8).

Description of Damage

The central column in the tabular layout of the 

Component Guides contains descriptive information on 

the typical damage for the particular component. These 

data consist of sketches and verbal criteria relating the 

observed damage to the various damage severity 

classifications.

Severity 

The left hand column of the Component Guides 

designates the severity of damage for the five categories 

described above in this Section. This column also 

contains the recommended component modification 

factors (λ - factors) for damaged components. These are 

used to change the basic properties of the components 

to reflect the effects of damage in a relative 

performance analysis (Section 4.4.3).

Performance Restoration Measures

The right hand column in the Component Guides 

tabulates performance restoration measures intended to 

restore, as much as possible, the structural properties of 

the component. In cases where complete restoration is 

not possible, component modification factors for the 

restored component (λ*) are tabulated. The use of the 

performance restoration measures for damage 

evaluation is discussed in Section 4.5. The specific 

repair techniques are summarized in FEMA 308: The 

Repair of Earthquake Damaged Concrete and Masonry 

Wall Buildings.

It is important to recognize that the Component Guides 

in Chapters 5, 6, 7, and 8 are representative of typically 

encountered conditions. Judgment is required to adapt 

and apply this information to specific conditions. The 

Component Guides were developed from a review of 

available empirical and theoretical data. Included with 

the Component Guides for each material is guidance on 

their use and the evaluation of component behavior. 

FEMA 307 provides additional technical background 

information and identifies resources for component 

identification and damage classification.

3.6 Verification

In practice, the investigation of damage and 

identification of components may be an iterative 

process. As presented in Chapter 2, the initial 

identification of components is based on relative 

strength and stiffness, and the anticipated inelastic 

lateral mechanism. Information from the field helps the 

engineer verify the component type based on actual 

behavior. For example, Figure 3-5 illustrates two 

possible inelastic lateral mechanisms for the same 

element. Theoretical calculations may predict one 

mechanism and therefore certain types of component 

damage. Observations of damage in the field, however, 

may lead to a different conclusion regarding the basic 

mechanism and component identification. There are 

several sources of discrepancies between analysis and 

observation, described below.

1. The distribution of the lateral forces from the damaging earthquake might have differed from that 

used in the analysis to generate the inelastic lateral 

mechanism. In such a case, the component behavior 

modes observed in the field might differ from those 

predicted analytically because of the relative magnitudes of component actions. For example, the use 

of a conventional upper triangular distribution of 

lateral load for a cantilevered shear wall might predict a flexural behavior mode in which the ultimate 

moment capacity at the base of the wall is attained 

before reaching the shear capacity. If a shearing 

behavior mode is encountered in the field, it may 

indicate a more rectangular or trapezoidal lateral 
 Chapter 3: Investigation of Earthquake Damage

FEMA 306 Basic Procedures Manual 25

load distribution, which would tend to lower the 

shear span (M/V) for the component. Also, a uniform distribution of seismic forces is more likely to 

cause a story mechanism than an inverted triangular 

distribution

2. The strength of components for various actions may 

differ from that predicted analytically. This could 

lead to different component types and/or behavior 

modes being a better representation of actual behavior. Many of the conventional theoretical formulations for component strength are intended for use as 

design equations. As such, they reflect an appropriate degree of conservatism and are suitable for a 

wide range of applications. The damage evaluation 

process differs fundamentally from design. The 

objective is to use theory and observation to assess 

the actual strength and behavior of the structural 

components. Figure 3-6 illustrates the difference 

between design strength and expected strength for a 

flexural component. The component data in FEMA 

307 provide resources for alternative formulations 

based on available empirical and theoretical 

research on actual behavior and material properties. 

If an alternative strength estimate correlates more 

closely with observed behavior and specific conditions, it is appropriate to use that estimate for evaluation purposes. This is not to imply that the estimate 

is then applicable for general design purposes. 

3. The severity and significance of damage depends 

heavily on ductility and behavior mode (see 

Figure 3-7). Some components exhibit mixed 

behavior modes, as shown in the moderate-ductility 

example in Figure 3-7(b). The component initially 

exhibits flexural behavior, but there is a transition to 

shear-controlled behavior at higher deformations. 

This type of behavior is not unusual, and it can be 

difficult to identify. Chapters 5 through 8 and 

FEMA 307 provide additional information and 

guidance on this point.

4. The overall intensity of the damaging ground 

motion might differ from that assumed in the analysis. The maximum global displacement that actually 

occurred during the earthquake, de, could be larger 

or smaller than that predicted. This would tend to 

produce a correspondingly greater or lesser overall 

severity of component damage. Component type 

and behavior mode would not be affected in the 

absence of other differences.

Resolution of these discrepancies entails adjustments to 

the analysis and the structural model so that the 

resulting component types, behavior modes, and 

severity of damage match the observed conditions. In 

some cases, the engineer may decide to conduct further 

tests or investigations to resolve conflicting data. 

Properly implemented, the process concludes with a 

reasonable and consistent representation of the 

governing behavior modes and the actual damage, as is 

necessary for an accurate understanding of the response 

of the structure to the damaging ground motion. 

Figure 3-5 Different Inelastic Lateral Mechanisms and Components for Same Wall Element

RC1

RC3 RC1

RC2 RC4

Mechanism A Mechanism B

Wall component types

(see Table 2-1)

RC5
 Chapter 3: Investigation of Earthquake Damage

26 Basic Procedures Manual FEMA 306

3.7 Documentation

Documentation of the results of the investigation should 

be complete and unambiguous. Plan drawings should 

show the location of elements and components and the 

locations and dates of tests. Elevations of critical 

elements and components should also be included 

where appropriate. Test results should be tabulated in 

accordance with the recommendations in the guides. 

Crack maps, sketches, and photographs, keyed to the 

plan drawings, should record all visual observations. 

Results of the investigation should be organized to 

focus on structural components and behavior modes. 

This organization facilitates the generation of 

Component Damage Record forms, shown in 

Figure 3-8. 

Figure 3-6 Relationship between design strength and expected strength

Expected strength ME

Nominal strength MN

Design strength φ MN

Moment

Strain hardening

Uncertainty

Envelope of response

Rotation
 Chapter 3: Investigation of Earthquake Damage

FEMA 306 Basic Procedures Manual 27

Figure 3-7 Component force-deformation behavior, ductility, and severity of damage

Force

Deformation

Severity of Damage

a) High ductility behavior

Force

Deformation

Severity of Damage

b) Moderate ductility behavior (mixed mode)

Force

Deformation

I

N

S

I

G

N.

S

L

I

G

H

T

M

O

D

E

R

A

T

E

H

E

A

V

Y

E

X

T

R

E

M

E

Severity of Damage

I

N

S

I

G

N.

S

L

I

G

H

T

M

O

D

E

R

A

T

E

H

E

A

V

Y

E

X

T

R

E

M

E

Degrading shear strength

Flexural strength

I

N

S

I

G

N.

S

L

I

G

H

T

M

O

D

E

R

A

T

E

H

E

A

V

Y

E

X

T

R

E

M

E

c) Low ductility behavior
 Chapter 3: Investigation of Earthquake Damage

28 Basic Procedures Manual FEMA 306

Figure 3-8 Example Component Damage Record

Component Damage Record

Component ID: Component Type: Location:

Sketch and description of damage types and severities (attach supplemental data if necessary):

Test results summary (attach detail):

Building: Engineer: Inspection date:

FEMA 306: Evaluation and Repair of Earthquake

Damaged Concrete and Masonry Wall Buildings
 Chapter 3: Investigation of Earthquake Damage

FEMA 306 Basic Procedures Manual 29

3.8 Test and Inspection Guides

This section provides guidelines for the use of typical 

tests and inspections to assess the consequences of 

earthquake damage to concrete and masonry wall 

buildings as discussed in Section 3.3.
 Chapter 3: Investigation of Earthquake Damage

30 Basic Procedures Manual FEMA 306

Description

Visual inspection is perhaps the most useful test 

available in the assessment of earthquake damage to 

concrete and masonry walls. Generally, earthquake 

damage to concrete and masonry walls is visible on the 

exposed surface. Observable types of damage include 

cracks, spalls and delaminations, permanent lateral 

displacement, and buckling or fracture of 

reinforcement. Visual inspection can also be useful for 

estimating the drift experienced by the building.

Visual inspection should always accompany other 

testing methods that are used. Findings from the visual 

inspections should be used as a basis for determining 

locations for conducting further testing. The observed 

damage should be documented on sketches. The 

patterns of damage can then be interpreted to assess the 

behavior of the wall during the earthquake.

Equipment

The materials and equipment typically required for a 

visual inspection are a tape measure, a flashlight, a 

crack comparator, a pencil, and a sketchpad.

A tape measure is used to measure the dimensions of 

the wall and, if necessary, to measure the lengths of the 

cracks. Tape measures that are readily available from a 

hardware store, with lengths of 20 to 50 feet, are 

sufficiently accurate for damage evaluation.

Flashlights are used to aid in lighting the areas to be 

inspected. In postearthquake evaluations, electric 

power may not be completely available, so 

supplemental lighting should be supplied.

In a visual inspection, the engineer uses a crack 

comparator or a tape measure to measure the width of 

cracks at representative locations. Two types of crack 

comparators are generally available: thin clear plastic 

cards, which have specified widths denoted on the card 

and small, hand-held magnifying lenses with a scale 

marked on the surface. Plastic card comparators have 

gradated lines to a minimum width of about 0.002 

inches. Magnifying lens comparators are accurate to 

about 0.001 inch (ACI Committee 201, 1994a).

The engineer uses a sketchpad to prepare a 

representation of the wall elevation, indicating the 

locations of the cracks, spalling, or other damage. All 

significant features of the wall should be recorded, 

including the dimensions of openings, the finishes on 

the wall, and the presence of nonstructural elements that 

may affect the repairs. The sketch should be 

supplemented with photographs or video tape.

Detailed examination of the surface of a crack can be 

accomplished with a portable microscope, which allows 

for magnified viewing of the surface of the cracks. 

Portable microscopes are available with magnifications 

of 18- to 36-fold. An external light source is needed for 

viewing. A camera adapter may be available for 

photographic documentation.

TEST AND INVESTIGATION GUIDE Test Type: Nondestructive

VISUAL INSPECTION Materials: Concrete, 

Reinforced Masonry, 

Unreinforced Masonry

NDE 1
 Chapter 3: Investigation of Earthquake Damage

FEMA 306 Basic Procedures Manual 31

Execution

The initial steps in the visual observation of earthquake 

damage are to identify the location of the wall in the 

building and to determine the dimensions of the wall 

(height, length, and thickness). A tape measure is used 

for quantifying the overall dimensions of the wall. A 

sketch of the wall elevation should then be prepared. 

The sketch should include sufficient detail to depict the 

dimensions of the wall, it should be roughly to scale, 

and it should be marked with the wall location (See 

example on page 33).

Observable damage such as cracks, spalling, and 

exposed reinforcing bars should be indicated on the 

sketch. Sketches should be made in sufficient detail to 

indicate the approximate orientation and width of 

cracks. Crack width is measured using the crack 

comparator or tape measure at representative locations 

along significant cracks. Avoid holes and edge spalls 

when measuring crack widths. Crack widths typically 

do not change abruptly over the length of a crack. If the 

wall is accessible from both sides, the opposite side of 

the wall should be checked to evaluate whether the 

cracks extend through the thickness of the wall and to 

verify that the crack widths are consistent.

Photographs can be used to supplement the sketches. If 

the cracks are small, they may not show up in the 

photographs, except in extreme close-up shots. Paint, 

markers, or chalk can be used to highlight the location 

of cracks in photographs. However, photographs with 

highlighted crack should always be presented with a 

written disclaimer that the cracks have been highlighted 

and that the size of the cracks cannot be inferred from 

the photograph.

During a visual inspection, the engineer should 

carefully examine the wall for the type of damage and 

possible causes. ACI 201 is a guide that describes 

conditions that might be observed when surveying 

concrete walls. Indications that the cracks or spalls may 

be recent or that the damage may have occurred prior to 

the earthquake should be noted. The guidelines in 

Section 3.4 can be helpful for assessing the relative age 

of the cracks.

Visual observation of the nonstructural elements in the 

building can also be very useful in assessing the overall 

severity of the earthquake, the interstory displacements 

experienced by the building, and the story accelerations. 

Full-height nonstructural items such as partitions and 

facades should be inspected for evidence of interstory 

movement such as recent scrapes, cracked windows, or 

crushed wallboard.

Personnel Qualifications

Visual inspection of concrete and masonry walls should 

be performed by an engineer or trained technician. 

Engineers and technicians should have previous 

experience in identifying damage to concrete and 

masonry structures and should be familiar with the use 

of a tape measure and crack comparator. Engineers and 

technicians should also have sufficient training to be 

able to distinguish between recent damage and damage 

that may have been pre-existing. For this type of 

assessment, the person conducting the inspection 

should understand how the structure is designed and 

how earthquake, gravity, and other forces may have 

acted on the wall.

TEST AND INVESTIGATION GUIDE

continued NDE 1
 Chapter 3: Investigation of Earthquake Damage

32 Basic Procedures Manual FEMA 306

Limitations

The width of a crack can vary substantially along its 

length. Both the plastic card and the magnifying crack 

comparators can produce a reasonable estimate of the 

width of a crack. The magnifying comparators are 

generally more accurate when measuring small (<0.001 

inches) crack widths. The plastic cards can sometimes 

overestimate the crack width due to the lighting 

conditions. With either type of comparator, the crack 

width is only measured at representative locations to 

determine repair thresholds. The measurements should 

be used primarily to compare damage levels among 

walls. The crack comparators may not be necessary 

when the crack widths are to be measured in 1/16-inch 

increments. For wider cracks, a tape measure will 

provide sufficiently accurate values.

Visual observation of concrete and masonry walls can 

generally identify most of the earthquake damage to 

those elements. In some cases, the presence of finishes 

on the walls can prevent an accurate assessment of the 

damage. Brittle finishes such as plaster can indicate 

damage that may not be present in the underlying 

substrate. Soft finishes such as partitions isolated from 

the structural walls can obscure minor amounts of 

damage.

References

ACI Committee 201, 1994a, “Guide for Making a Condition Survey of Concrete in Service”, ACI 201.1R92, Manual of Concrete Practice, American Concrete Institute, Detroit, Michigan.

ACI Committee 224, 1994b, Causes, Evaluation and 

Repair of Cracks in Concrete Structures”, ACI 

Committee 224.1R-93, Manual of Concrete Practice, American Concrete Institute, Detroit, Michigan.

ACI Committee 364, 1994c, “Evaluation of Structures 

Prior to Rehabilitation”, ACI 364.1R, ACI Manual 

of Concrete Practice, American Concrete Institute, 

Detroit, Michigan.

TEST AND INVESTIGATION GUIDE

continued NDE 1
 Chapter 3: Investigation of Earthquake Damage

FEMA 306 Basic Procedures Manual 33

Component Damage Record (Example)

Building Name:

Concrete Shear Wall Building

Project ID:

ATC 43 Example

Prepared by:

ATC

Location Within Building:

Floor: 1st/2nd Column Line: B Component Type: 

Date:

24-Sep-97

Sketch and Description of Damage:

Legend:

Crack 

Crack Width in Mils (0.001 Inch)

Crack Previously Filled with Epoxy

Crack at Pre-existing Surface Patch

Spall

Not Accessible

Partition
 Chapter 3: Investigation of Earthquake Damage

34 Basic Procedures Manual FEMA 306

Description

Tapping on a wall with a dense object, such as a 

hammer, and listening to the vibrations emitted from the 

wall can be useful for identifying voids or 

delaminations in concrete walls. The sound produced 

from a solid wall will be different from that from a wall 

with voids or delaminations close to the surface. In 

concrete block masonry walls, sounding can be used to 

verify that the cells in the blocks have been grouted.

Equipment

The typical equipment required for sounding is a 

hammer. However, any hard, dense object can be used.

Execution

In areas where the visual observations indicate that the 

wall may have delaminations, the wall can be sounded 

by tapping with a hammer. Delaminations and spalls 

will generally produce a hollow sound (ACI, 1994) 

when compared with solid material. The wall should be 

tapped several times in the suspect area and away from 

the suspect area, and the sounds compared. It is 

important to test an area that is undamaged, and of the 

same material and thickness to use as a baseline 

comparison. For a valid comparison, the force exerted 

by the tapping should be similar for both the suspect 

and baseline areas.

In reinforced masonry construction, sounding can be 

used to assess whether the cells in the wall have been 

grouted. Near the ends of a block, the unit is solid for 

the full thickness of the wall. For most of the length of 

the block, it is relatively thin at the faces. If the sound 

near the end of the block is substantially different than 

at the middle of the cell, the cell is probably not 

grouted.

Personnel Qualifications

Sounding of concrete and masonry walls should be 

performed by an engineer or trained technician. 

Engineers and technicians should have previous 

experience in identifying damage to concrete and 

masonry structures. Engineers and technicians should 

also be able to distinguish between sounds emitted from 

a hammer strike. Prior experience is necessary for 

proper interpretation of results.

Reporting Requirements

The personnel conducting the tests should provide

sketches of the wall indicating the location of the tests

and the findings. The sketch should include the

following information:

• Mark the location of the test on either a floor plan or 

wall elevation.

• Report the results of the test, indicating the extent of 

delamination.

• Report the date of the test.

• List the responsible engineer overseeing the test and 

the name of the company conducting the test.

TEST AND INVESTIGATION GUIDE Test Type: Nondestructive

SOUNDING Materials: Concrete, NDE 2 Reinforced Masonry
 Chapter 3: Investigation of Earthquake Damage

FEMA 306 Basic Procedures Manual 35

Limitations

The properties of the wall can influence the usefulness 

of sounding. The geometry of the wall and the 

thickness of the wall will affect the results (ASCE, 

1990). Sounding is best used away from the perimeter 

of the wall and on a wall of uniform thickness.

The accuracy of information from sounding with a 

hammer also depends on the skill of the engineer or 

technician performing the test and on the depth of 

damage within the thickness of the wall. Delaminations 

up to the depth of the cover for the reinforcing bars 

(usually about 1 to 2 inches) can usually be detected. 

Detection of deeper spalls or delamination requires the 

use of other NDE techniques. Sounding cannot 

determine the depth of the spall or delamination (Poston 

et al., 1995).

Tapping on a loose section of material can cause the 

piece to become dislodged and fall. Avoid sounding 

overhead. A ladder, scaffold, or other lift device should 

be used to reach higher elevations of a wall.

References

ACI Committee 224, 1994, Causes, Evaluation and 

Repair of Cracks in Concrete Structures”, ACI 

Committee 224.1R-93, Manual of Concrete Practice, American Concrete Institute, Detroit, Michigan.

ASCE, 1990, Guideline for Structural Condition 

Assessment of Existing Buildings, ASCE 11-90, 

American Society of Civil Engineers, New York, 

New York.

Poston, R.W, A.R. Whitlock, and K.E. Kesner, 1995, 

“Condition Assessment Using Nondestructive 

Evaluation” Concrete International, July, 1995, 

American Concrete Institute, Detroit, Michigan, pp 

36-42.

TEST AND INVESTIGATION GUIDE

continued NDE 2
 Chapter 3: Investigation of Earthquake Damage

36 Basic Procedures Manual FEMA 306

Description

A rebound hammer provides a method for assessing the 

in-situ compressive strength of concrete. In this test, a 

calibrated hammer impact is applied to the surface of 

the concrete. The amount of rebound of the hammer is 

measured and correlated with the manufacturer's data to 

estimate the strength of the concrete. The method has 

also been used to evaluate the strength of masonry. 

Equipment

A calibrated rebound hammer is a single piece of 

equipment that is hand operated

Execution

ASTM C805 (ASTM, 1995) provides a standard on the 

use of a rebound hammer. The person operating the 

equipment places the impact plunger of the hammer 

against the concrete and then presses the hammer until 

the hammer releases. The operator then records the 

value on the scale of the hammer. Typically three or 

more tests are conducted at a location. If the values 

from the tests are consistent, record the average value. 

If the values vary significantly, additional readings 

should be taken until a consistent pattern of results is 

obtained.

Since the test is relatively rapid, a number of test 

locations can be chosen for each wall. The values from 

the tests are converted into compressive strength using 

tables prepared by the manufacturer of the rebound 

hammer.

Personnel Qualifications

A technician with minimal training can operate the 

rebound hammer. An engineer experienced with 

trebound hammer data should be available to supervise 

to verify that any anomalous values can be explained.

Reporting Requirements

The personnel conducting the tests should provide 

sketches of the wall, indicating the location of the tests 

and the findings. The sketch should include the 

following information:

• Mark the location of the test marked on either a floor 

plan or wall elevation.

• Record the number of tests conducted at a given 

location.

• Report either the average of actual readings or the 

average values converted into compressive strength 

along with the method used to convert the values 

into compressive strength.

• Report the type of rebound hammer used along with 

the date of last calibration.

• Record the date of the test.

• List the responsible engineer overseeing the test and 

the name of the company conducting the test.

TEST AND INVESTIGATION GUIDE Test Type: Nondestructive

REBOUND HAMMER Materials: Concrete, NDE 3 Unreinforced Masonry
 Chapter 3: Investigation of Earthquake Damage

FEMA 306 Basic Procedures Manual 37

Limitations

The rebound hammer does not give a precise value of 

compressive strength, but rather an estimate of strength 

that can be used for comparison. Frequent calibration 

of the unit is required (ACI, 1994). Although 

manufacturers’ tables can be used to estimate the 

concrete strength, better estimates can be obtained by 

removing core samples at selected locations where the 

rebound testing has been performed. The core samples 

are then subjected to compression tests. The rebound 

values from other areas can be compared with the 

rebound balues that correspond to the measured core 

compressive strength.

The results of the rebound hammer tests are sensitive to 

the quality of the concrete on the outer several inches of 

the wall (Krauss, 1994). More reproducible results can 

be obtained from formed surfaces rather than from 

finished surfaces.

Surface moisture and roughness can also affect the 

readings. The impact from the rebound hammer can 

produce a slight dimple in the surface of the wall. Do 

not take more than one reading at the same spot, since 

the first impact can affect the surface, and thus affect the 

results of a subsequent test.

When using the rebound hammer on masonry, the 

hammer should be placed at the center of the masonry 

unit. The values of the tests on masonry reflect the 

strength of the masonry unit and the mortar (Noland et 

al., 1982). This method is only useful in assessing the 

strength of the outer wythe of a multi-wythe wall.

References

ACI Committee 364, 1994, “Evaluation of Structures 

Prior to Rehabilitation”, ACI 364.1R, ACI Manual 

of Concrete Practice, American Concrete Institute, 

Detroit, Michigan

ASTM, 1995, Test for Rebound Number of Hardened 

Concrete, ASTM C805, American Society for Testing and Materials, Washington, DC

Krauss, P.D., 1994, Repair Materials and Techniques 

for Concrete Structures in Nuclear Power Plants, 

NRC JNC No. B8045, US Nuclear Regulatory 

Commission, Washington, DC.

Noland, J.L. et al., 1982, An Investigation into Methods 

of Nondestructive Evaluation of Masonry Structures, Report to the National Science Foundation, 

Atkinson-Noland & Associates, Boulder, Colorado

TEST AND INVESTIGATION GUIDE

continued NDE 3
 Chapter 3: Investigation of Earthquake Damage

38 Basic Procedures Manual FEMA 306

Description

Covermeter is the general term for a rebar detector used 

to determine the location and size of reinforcing steel in 

a concrete or masonry wall. The basic principle of most 

rebar detectors is the interaction between the 

reinforcing bar and a low frequency magnetic field. If 

used properly, many types of rebar detectors can also 

identify the amount of cover for the bar and/or the size 

of the bar. Rebar detection is useful for verifying the 

construction of the wall, if drawings are available, and 

in preparing as-built data if no previous construction 

information is available.

Equipment

Several types and brands of rebar detectors are 

commercially available. The two general classes are 

those based on the principle of magnetic reluctance and 

those based on the principle of eddy (Carino, 1992). 

The various models can have a variety of features 

including analog or digital readout, audible signal, onehanded operation, and readings for reinforcing bars and 

prestressing tendons. Some models can store the data on 

floppy disks to be imported into computer programs for 

plotting results.

Execution

The unit is held away from metallic objects and 

calibrated to zero reading. After calibration, the unit is 

placed against the surface of the wall. The orientation 

of the probe should be in the direction of the rebar that 

is being detected. The probe is slid slowly along the 

wall, perpendicular to the orientation of the probe, until 

an audible or visual spike in the readout is encountered. 

The probe is passed back and forth over the region of 

the spike to find the location of the maximum reading, 

which should correspond to the location of the rebar. 

This location is then marked on the wall. The procedure 

is repeated for the perpendicular direction of 

reinforcing.

If size of the bar is known, the covermeter readout can 

be used to determine the depth of the reinforcing bar. If 

the depth of the bar is known, the readout can be used to 

determine the size of the bar. If neither quantity is 

known, most rebar detectors can be used to determine 

both the size and the depth using a spacer technique. 

The process involves recording the peak reading at a bar 

and then introducing a spacer of known thickness 

between the probe and the surface of the wall. A second 

reading is then taken. The two readings are compared 

to estimate the bar size and depth.

Intrusive testing can be used to help interpret the data 

from the detector readings. Selective removal of 

portions of the wall can be performed to expose the 

reinforcing bars. The rebar detector can be used 

adjacent to the area of removal to verify the accuracy of 

the readings.

Personnel Qualifications

The personnel operating the equipment should be 

trained and experienced with the use of the particular 

model of covermeter being used and should understand 

the limitations of the unit.

TEST AND INVESTIGATION GUIDE Test Type: Nondestructive

REBAR DETECTOR Materials: Concrete, NDE 4 Reinforced Masonry
 Chapter 3: Investigation of Earthquake Damage

FEMA 306 Basic Procedures Manual 39

Reporting Requirements

The personnel conducting the tests should provide a

sketch of the wall indicating the location of the testing

and the findings. The sketch should include the

following information:

• Mark the locations of the test on either a floor plan 

or wall elevation.

• Report the results of the test, including bar size and 

spacing and whether the size was verified.

• List the type of rebar detector used.

• Report the date of the test.

• List the responsible engineer overseeing the test and 

the name of the company conducting the test.

Limitations

The readings can be difficult to interpret if the depth of 

the reinforcement is too great or if there is heavy 

congestion of reinforcement, such as at splices or 

boundaries (ACI, 1994). The accuracy will vary 

between units and manufacturers. Except at the 

boundaries of the wall, the spacing of bars is generally 

wide enough that the influence of adjacent bars should 

not affect the readings. Other embedded metals, such as 

metallic conduits or pipes will be detected and may give 

false readings.

For walls with two layers of reinforcing steel, the rebar 

detector can only be used to detect the reinforcing bars 

closest to the face on which the probe is used. The unit 

should be used on both faces to detect bars in a wall 

with two layers of reinforcement. When two layers are 

present, the second layer of reinforcement can affect the 

readings by producing a stronger signal for a bar of 

given size and depth than the bar would produce in the 

absence of a second layer (ACI, 1997).

Some rebar detectors require recalibration at regular 

intervals during use. Therefore, the user should 

frequently check the readings to verify that the readings 

are still reproducible. The spacer technique to 

determine the size and depth of reinforcement is only 

accurate to within 1 or 2 bar diameters (Krauss, 1994 

and Bungey, 1989).

When measuring the cover depth, many units actually 

measure the distance to the center of the reinforcing 

steel. The manufacturer’s literature should be reviewed 

to determine the meaning of the depth reading.

References

ACI Committee 228, 1997, Nondestructive Tests Methods for Evaluation of Concrete in Structures, ACI 

228.2R - Draft, American Concrete Institute, 

Detroit, Michigan.

ACI Committee 364, 1994, Guide for Evaluation of 

Concrete Structures Prior to Rehabilitation, ACI 

364.1R, ACI Manual of Concrete Practice, American Concrete Institute, Detroit, Michigan.

Bungey, J.H., 1989, Testing Concrete in Structures, 2nd

Edition, Chapman and Hall, New York, New York.

Carino, N.J, 1992, Performance of Electromagnetic 

Covermeters for Nondestructive Assessment of 

Steel Reinforcement, NISTR 4988, National Institute of Standards and Technology, Gaithersburg, 

Maryland.

Krauss, P.D., 1994, Repair Materials and Techniques 

for Concrete Structures in Nuclear Power Plants, 

NRC JNC No. B8045, US Nuclear Regulatory 

Commission, Washington, DC.

TEST AND INVESTIGATION GUIDE

Continued NDE 4
 Chapter 3: Investigation of Earthquake Damage

40 Basic Procedures Manual FEMA 306

Description

The ultrasonic pulse velocity method measures the 

travel time of an ultrasonic pulse through the thickness 

of the wall. The velocity at which the pulse travels 

through the wall is affected by the quality of the 

material, including the presence of cracking or damage. 

By comparing the relative travel time at various sections 

of known thickness, the ultrasonic pulse velocity can be 

used to assess relative strength of concrete or masonry 

and to indicate the presence of cracking or 

delamination.

Equipment

The equipment and calibration procedures are described 

in ASTM C 597, Standard Test Method for Pulse 

Velocity Through Concrete. Portable equipment is 

available from several manufacturers. Transmitting and 

receiving transducers are required. 

The frequency of the transducers is typically about 50 

kHz, which is adequate for walls that are at least four 

inches thick, corresponding to the wave length of the 

pulse (Krauss, 1994).

A time-measuring meter with either a digital time 

display or a digital storage oscilloscope is also required.

Execution

The area of the wall to be examined should be laid out 

with a grid. The location of the grid should be 

coordinated so that the intersection of the grid lines will 

be at the same location on both sides of the wall. The 

spacing of the grid will vary, depending on the size of 

the wall and the extent of the expected damage. A grid 

spacing of one-foot centers should provide a reasonably 

fine spacing to capture potential damage.

The transmitting and receiving transducers are mounted 

on opposite sides of the wall, using a couplant between 

the transducer and the surface of the wall. For masonry 

walls, the transducer should be mounted to the masonry 

units, not to the mortar joints. The meter sends a series 

of pulses through the wall and measures the 

transmission time, which is recorded. The transducers 

are moved to the next location, and the test is repeated. 

If high readings are encountered, indicating possible 

discontinuities, a finer grid should be laid out in the 

vicinity of the possible damage to eastablish the extent 

of the discontinuity.

The results are displayed as travel time. The travel time 

needs to be converted into velocity using the thickness 

of the wall. The pulse velocity, not the travel time, 

should be used to compare results at various locations.

To establish the relative strength of the wall, samples 

should be taken at representative test locations. 

Correlate the strength of the extracted material samples 

and the pulse velocity readings at those locations, then 

use this correlation to estimate the strength at other 

sections of the wall.

Personnel Qualifications

A technician with training in the use of the equipment 

can carry out the test. An engineer or technician with 

extensive experience in the use and limitations of the 

equipment should be responsible for overseeing the 

tests and interpreting the results.

TEST AND INVESTIGATION GUIDE Test Type: Nondestructive

ULTRASONIC PULSE VELOCITY Materials: Concrete,

Reinforced Masonry,

Unreinforced Masonry

NDE 5
 Chapter 3: Investigation of Earthquake Damage

FEMA 306 Basic Procedures Manual 41

Reporting Requirements

The personnel conducting the tests should provide a 

sketch of the wall indicating the location of the testing 

and the findings. The sketch should include the 

following information:

• Mark the location of the test on either a floor plan or 

wall elevation.

• Report the test results as either actual velocity 

measurements or interpreted results.

• List the type of pulse-velocity equipment used, 

including the date of last calibration.

• Record the date of the test.

• List the responsible engineer overseeing the test and 

the name of the company conducting the test.

Limitations

Pulse-velocity measurements require access to both 

sides of the wall. The wall surfaces need to be relatively 

smooth. Rough areas can be ground smooth to improve 

the acoustic coupling. Couplant must be used to fill the 

air space between the transducer and the surface of the 

wall. If air voids exist between the transducer and the 

surface, the travel time of the pulse will increase, 

causing incorrect readings.

Some couplant materials can stain the wall surface. 

Non-staining gels are available, but should be checked 

in an inconspicuous area to verify that it will not disturb 

the appearance.

Embedded reinforcing bars, oriented in the direction of 

travel of the pulse, can affect the results, since the 

ultrasonic pulses travel through steel at a faster rate than 

through concrete. Bars larger than 3/8-inch diameter 

will significantly affect the results (Chung and Law, 

1983). The moisture content of the concrete also has a 

slight effect (up to about 2 percent) on the pulse 

velocity.

Pulse-velocity measurements can detect the presence of 

voids or discontinuities within a wall; however, these 

measurements cannot determine the depth of the voids 

(ACI, 1997).

References

ACI Committee 228, 1997, Nondestructive Tests Methods for Evaluation of Concrete in Structures, ACI 

228.2R - Draft, American Concrete Institute, 

Detroit, Michigan.

ACI Committee 364, 1994, Guide for Evaluation of 

Concrete Structures Prior to Rehabilitation, ACI 

364.1R, ACI Manual of Concrete Practice, American Concrete Institute, Detroit, Michigan.

Berra, M., L. Binda, G. Baronio, and A. Fatticcioni, 

1987, “Ultrasonic Pulse Transmission: A Proposal 

to Evaluate the Efficiency of Masonry Strengthened 

by Grouting”, Evaluation and Retrofit of Masonry 

Structures, Proceedings of the Second Joint USAItaly Workshop on Evaluation and Retrofit of 

Masonry Structures, pp 93-110.

Chung, H.W. and K.S. Law, 1983, “Diagnosing In Situ 

Concrete by Ultrasonic Pulse Technique”, Concrete 

International, October 1983, American Concrete 

Institute, Detroit, Michigan, pp 42-49.

Krauss, P.D., 1994, Repair Materials and Techniques 

for Concrete Structures in Nuclear Power Plants, 

NRC JNC No. B8045, US Nuclear Regulatory 

Commission, Washington, DC.

TEST AND INVESTIGATION GUIDE

Continued NDE 5
 Chapter 3: Investigation of Earthquake Damage

42 Basic Procedures Manual FEMA 306

Description

Impact echo is a method for detecting discontinuities 

within the thickness of a concrete or masonry wall. The 

surface of the material is struck with an impactor, a 

small hammer, which introduces an energy pulse into 

the material. The energy pulse is reflected off of wavespeed discontinuities within the material. The 

discontinuities can be cracks, the back surface of the 

material, side surfaces, delaminations, or voids. A 

transducer mounted to the striking surface records the 

reflection of the energy. The transducer is connected to 

a Fast Fourier Transform (FFT) analyzer, which 

converts the time history signal from the transducer into 

the frequency domain. The frequency results and the 

raw time history can be interpreted to assess the 

thickness of the material and the size and location of 

discontinuities within the wall, such as voids, cracks, 

and delaminations.

Equipment

The typical impact echo equipment consists of a small 

impactor (hammer) to strike the surface of the material, 

a transducer to measure the surface response of the 

material, and an FFT analyzer to analyze the 

measurements made by the transducer. Some FFT 

analyzers are extremely sophisticated portable 

computers that allow for extensive manipulation of the 

output, while others simply provide a graph showing the 

frequency content of the output.

The equipment can be assembled from available 

components. Complete systems are also commercially 

available (ACI, 1997).

Execution

The transducer is placed on the surface of the material. 

Good contact must be developed between the transducer 

and the material, or the transducer will not be able to get 

a clean signal from the energy pulse. Strike the material 

with the impactor to introduce an energy pulse into the 

material. The FFT analyzer produces a frequency 

content analysis of the transducer's signal, but the final 

analysis of the data rests with the operator. If the 

impactor and transducer are in the middle of a solid 

wall, the energy pulse bounces back and forth between 

the front and back surfaces, typically giving an FFT 

frequency content with one major frequency peak. This 

peak corresponds to how quickly the energy pulse 

bounces between the front and back surfaces of the 

material. If the impactor and transducer are in the 

middle of a wall with a delamination, the first peak 

should be at a higher frequency, since the energy pulse 

will tend to bounce between the front surface of the wall 

and the surface of the delamination, a shorter distance 

requiring less travel time. The presence of side 

boundaries, voids, large concentrated amounts of 

reinforcement, and cracks will complicate the signal.

Personnel Qualifications

Impact echo testing should be performed by an engineer 

or technician well-trained and experienced in using this 

technique.

TEST AND INVESTIGATION GUIDE Test Type: Nondestructive

IMPACT ECHO Materials: Concrete,

Reinforced Masonry,

Unreinforced Masonry

NDE 6
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FEMA 306 Basic Procedures Manual 43

Reporting Requirements

The personnel conducting the tests should provide 

sketches of the wall indicating the location of the tests 

and the findings. The sketch should include the 

following information:

• Mark location of the test on either a floor plan or 

wall elevation.

• Record the number of tests conducted at a given 

location.

• Report the results of the test using either the actual 

readings or the interpreted results, including the 

peak frequency values.

• Describe the type of impact echo equipment used, 

along with the date of last calibration.

• Report the date of the test.

• List the responsible engineer overseeing the test and 

the name of the company conducting the test.

Limitations

The accuracy of impact echo testing is typically highly 

dependent on the skill of the engineer or technician in 

understanding the testing method and interpreting the 

results. Incompletely trained or untrained persons using 

impact echo methods have a high probability of 

interpreting the results incorrectly. The physical 

limitations and accuracy of impact echo are governed in 

part by the size of the impactor, the type, sensitivity, and 

natural frequency of the transducer, the uniformity of 

the concrete, and the ability of the FFT analyzer to 

manipulate the data into useful information.

The impact echo technique has been applied extensively 

to concrete structures. However, there is little 

experience with applying the technique to reinforced or 

unreinforced masonry components.

References

ACI Committee 228, 1997, Nondestructive Test Methods for Evaluations of Concrete in Structures, ACI 

228.2R - Draft, American Concrete Institute, 

Detroit, Michigan.

Poston, R.W, et al., 1995, “Condition Assessment Using 

Nondestructive Evaluation” Concrete International, July, 1995, American Concrete Institute, 

Detroit, Michigan, pp 36-42.

TEST AND INVESTIGATION GUIDE

continued NDE 6
 Chapter 3: Investigation of Earthquake Damage

44 Basic Procedures Manual FEMA 306

Description

Spectral analysis of surface waves (SASW) is a method 

of measuring the propagation of surface waves over a 

wide range of wavelengths. The propagation velocities 

are measured using accelerometers and a Fast Fourier 

Transform (FFT) analyzer. The results can be 

interpreted to assess the thickness of the material and 

the size and location of discontinuities within the wall, 

such as voids, large cracks, and delaminations.

Equipment

The SASW tests require the following equipment:

• An impactor, which is usually a hammer

• Two or more receivers, which could be 

accelerometers or velocity transducers

• An FFT spectrum analyzer for recording and 

analyzing the input signal from each receiver

Execution

Mount the receivers on the surface of the wall using a 

removable adhesive. The spacing between the receivers 

will depend on the thickness of the wall. Strike the 

surface of the wall with the hammer away from the 

receivers, producing a surface R-wave that propagates 

along the surface (ACI, 1997). The surface velocity or 

acceleration is recorded by the receivers and processed. 

The processed results can then be interpreted to assess 

the condition of the concrete.

Personnel Qualifications

Use of the SASW equipment should be limited to those 

with extensive training in the use of the equipment. 

Specialized experience is required to interpret the 

results.

Reporting Requirements

The personnel conducting the tests should provide 

sketches of the wall indicating the location of the tests 

and the findings. The sketch should include the 

following information:

• Mark the location of the test on either a floor plan or 

wall elevation.

• Record the number of tests conducted at a given 

location.

• Report the results of the test using either the actual 

readings or the interpreted results.

• Describe the type of equipment used.

• Report the date of the test.

• List the responsible engineer overseeing the test and 

the name of the company conducting the test.

TEST AND INVESTIGATION GUIDE Test Type: Nondestructive

SPECTRAL ANALYSIS OF SURFACE

WAVES (SASW)

Materials: Concrete NDE 7
 Chapter 3: Investigation of Earthquake Damage

FEMA 306 Basic Procedures Manual 45

Limitations

The signal processing equipment used for the 

interpretation of the results is very complex and not 

readily available. The SASW process has been used 

mainly on pavement, slabs, and other horizontal 

surfaces. Its use on walls has not been documented 

extensively.

References

ACI Committee 228, 1997, Nondestructive Tests Methods for Evaluation of Concrete in Structures, ACI 

228.2R - Draft, American Concrete Institute, 

Detroit, Michigan.

TEST AND INVESTIGATION GUIDE 

continued NDE 7
 Chapter 3: Investigation of Earthquake Damage

46 Basic Procedures Manual FEMA 306

Description

Radiography can be used to determine the location of 

reinforcing steel within a concrete or masonry wall. 

The process involves transmitting x-rays through the 

concrete. A radiographic film on the opposite side from 

the x-ray source records the intensity of the x-rays that 

exit the wall. The processed film presents an image of 

the locations of reinforcing bars and other 

discontinuities.

Equipment

A portable X-ray tube with a radioactive isotope is 

required. For wall thickness less than six inches, 

iridium-192 or cesium-137 can be used (see, for 

example, Mitchell et al., 1979). For thicker materials, 

more intense isotopes are needed. Special photographic 

film is used to capture the X-rays.

Execution

An x-ray technician mounts the photographic film on 

the surface of the wall. The location of the film is 

marked on the wall for future reference. The X-ray tube 

is mounted or placed on the opposite side of the wall 

from the film. The x-ray technician exposes the wall to 

the radioactive isotope. The length of time for the 

exposure will depend on the thickness of the wall, the 

size of the film, and the amount of reinforcement in the 

wall. Thicker walls and areas with a high concentration 

of reinforcing bars require longer exposure times.

The film is then processed. The processed image is 

interpreted to assess the locations of reinforcing bars 

and discontinuities. Reinforcing bars, which are denser 

than concrete, show up on the image as light areas. 

Voids are seen on the film as relatively darker areas 

(ACI, 1997).

Personnel Qualifications

The personnel operating the x-ray equipment require 

highly specialized training on the handling of 

radioactive material. The technicians who interpret the 

images should be experienced in viewing x-rays from 

concrete or masonry structures.

Reporting Requirements

The personnel conducting the tests should provide 

sketches of the wall indicating the location of the tests 

and the findings. The sketch should include the 

following information:

• Mark the location of the test on either a floor plan or 

wall elevation.

• Report the results of the test along with a sketch of 

the findings.

• Describe the type of X-ray equipment used, along 

with the date of last calibration.

• Report the date of the test.

• List the responsible engineer overseeing the test and 

the name of the company conducting the test.

TEST AND INVESTIGATION GUIDE Test Type: Nondestructive

RADIOGRAPHY Materials: Concrete, NDE 8 Reinforced Masonry
 Chapter 3: Investigation of Earthquake Damage

FEMA 306 Basic Procedures Manual 47

Limitations

Because radiography involves the release of radiation, 

the vicinity of the testing needs to be evacuated, except 

for the personnel conducting the tests. The size of the 

area to be evacuated depends on the type of radioactive 

isotope used and the thickness of the wall. Thicker 

walls require longer exposure times, and therefore more 

radiation is released. The time, expense, and logistics 

of the evacuation must be considered in planning the 

tests. Most commercially available x-ray equipment is 

capable of penetrating walls up to 12 inches thick. For 

thicker walls, the expense of the highly specialized 

equipment needed is generally not cost-effective for 

commercial buildings.

The presence of steel within the concrete will produce a 

shadow on the film to indicate its location. Since the 

radiation emits from a point source onto the 

photographic film, the amount of shadow will depend 

on the depth of the reinforcing bar from the face where 

the x-ray source is placed. Therefore, it is usually not 

possible to determine the size of the reinforcing bars 

based on the photographic image.

References

ACI Committee 228, 1997, Nondestructive Test Methods for Evaluation of Concrete Structures, ACI 

228.2R - Draft, American Concrete Institute, 

Detroit, Michigan.

Mitchell, T.M., P.L. Lee, and G.J. Eggert, 1979, “The 

CMD: A Device for the Continuous Monitoring of 

the Consolidation of Plastic Concrete, Public 

Roads, Vol. 42, No. 148.

TEST AND INVESTIGATION GUIDE

continued NDE 8
 Chapter 3: Investigation of Earthquake Damage

48 Basic Procedures Manual FEMA 306

Description

Penetrating radar transmits electromagnetic waves, 

which are received by an antenna. The propagation of 

the waves through the material is influenced by the 

dielectric constant and the conductivity of the material. 

The signal received can be interpreted to discover 

discontinuities and variations in the material properties. 

The interpreted data can be used to detect the location 

of reinforcing bars, cracks, voids, or other material 

discontinuities.

Equipment

The penetrating radar instrumentation consists of several components including:

• An antenna that emits an electromagnetic pulse of 

various frequencies

• A receiving antenna

• A control unit that provides power to the 

transmitting antenna and acquires the signal from 

the receiving antenna

• A data recording device such as a printed display or 

digital storage device

Execution

Place the antenna of the radar unit on the surface of the 

wall and move along the surface while data are being 

recorded. The antenna produces an electromagnetic 

pulse that passes through the wall. Some of the pulse is 

reflected back to the receiving antenna. The received 

signal is printed on a strip-recording chart or stored for 

later analysis (Mellett, 1992). The recorded data 

represent the condition along the length of the wall for 

the width of the antenna. Multiple passes are required 

to obtain data for widths greater than the width of the 

antenna.

The data can then be interpreted to evaluate the location 

and depth of reinforcing steel, the thickness of the wall, 

and the location of delaminations or voids.

Personnel Qualifications

Use of the penetrating radar equipment should be 

limited to those with the extensive training required to 

correctly interpret the results (ACI, 1994).

Reporting Requirements

The personnel conducting the tests should provide 

sketches of the wall indicating the location of the tests 

and the findings. The sketch should include the 

following information:

• Mark the location of the test on either a floor plan or 

wall elevation.

• Report the results of the test using either the actual 

recorded data with the interpretations marked on the 

printed data or the interpreted results only.

• List the type of radar equipment used, including the 

type of antenna.

• Report the date of the test.

• List the engineer responsible for interpreting the test 

results and the name of the company conducting the 

test.

TEST AND INVESTIGATION GUIDE Test Type: Nondestructive

PENETRATING RADAR Materials: Concrete,

Reinforced Masonry,

Unreinforced Masonry

NDE 9
 Chapter 3: Investigation of Earthquake Damage

FEMA 306 Basic Procedures Manual 49

Limitations

Although penetrating radar units are commercially 

available, very few units are in service for use with 

concrete and masonry structures. For example, less 

than five units are in use in California. Penetrating 

radar has been used primarily on slabs-on-grade for 

detecting subsurface conditions. Some work has been 

done to apply the method to concrete columns (Delgado 

and Heald, 1996) and to unreinforced masonry 

buildings.

A high-frequency antenna provides high resolution, but 

has shallow penetration, whereas deeper penetration 

with reduced resolution can be achieved with lowerfrequency antennae (Krauss, 1994). Radar cannot 

effectively detect small differences in materials because 

the effective resolution is typically one-half of the 

wavelength (Candor, 1984).

Although penetrating radar is useful for locating the 

spacing and depth of reinforcing bars, it is not possible 

to determine the size of the bars. Closely-spaced bars 

can make it difficult to discern bar locations and depths. 

Close spacing make it difficult to detect features below 

the layer of reinforcing steel (ACI, 1997). Large 

metallic objects, such as embedded steel members 

cannot be clearly identified because of the scattering of 

the electromagnetic pulse.

References

ACI Committee 228, 1997, Nondestructive Tests Methods for Evaluation of Concrete in Structures, ACI 

228.2R - Draft, American Concrete Institute, 

Detroit, Michigan.

ACI Committee 364, 1994, Guide for Evaluation of 

Concrete Structures Prior to Rehabilitation, ACI 

364.1R, ACI Manual of Concrete Practice, American Concrete Institute, Detroit, Michigan.

Candor, T. R., 1984, “Review of Penetrating Radar as 

Applied to Nondestructive Evaluation of Concrete”, 

In Situ/Nondestructive Testing of Concrete, ACI 

SP-82, American Concrete Institute, Detroit, Michigan, pp 581-601.

Delgado, M., and S.R. Heald, 1996, “Post-Earthquake 

Damage Assessed Nondestructively”, Materials 

Evaluation, pp 378-382.

Krauss, P.D., 1994, Repair Materials and Techniques 

for Concrete Structures in Nuclear Power Plants, 

NRC JNC No. B8045, US Nuclear Regulatory 

Commission, Washington, DC.

Mellet, J, 1992, “Seeing Through Solid Materials”, 

Building Renovation, Penton Publishing.

TEST AND INVESTIGATION GUIDE

Continued NDE 9
 Chapter 3: Investigation of Earthquake Damage

50 Basic Procedures Manual FEMA 306

Description

When information regarding the construction of 

portions of the concrete or masonry cannot be obtained 

using nondestructive techniques, selective removal of 

portions of the wall is sometimes required to allow 

direct observation of the condition of the reinforcing 

bars or interior portion of the concrete or masonry. 

Removal is suggested only when visual observations of 

the surface indicate that the wall may have hidden 

damage such as buckled rebar, or when it is necessary to 

determine the construction of the wall.

Equipment

Light chipping tools, small diameter core drills, or 

masonry saws are used for creating openings in the 

wall.

A fiber-optic borescope can be used to view interior 

spaces through small openings.

Execution

Portions of the wall are removed by chipping, drilling, 

or sawing to a specified depth of the wall. The inner 

construction and condition of the wall are then observed 

visually. A small mirror and flashlight can be used to 

better view spaces that are difficult to examine, 

eliminating the need to remove extensive portions of the 

wall.

When small holes are used, a fiber-optic borescope can 

be used to view the interior construction and to look for 

evidence of damage or deterioration (ACI, 1994). Some 

borescopes can be fitted with a camera to produce 

photographic documentation of the observations. Some 

models also have flexible shafts and pivoting viewing 

heads to allow for multidirectional viewing.

Following the observations, the intrusive openings 

should be patched with appropriate material.

Personnel Qualifications

Engineers performing selective removal should be 

experienced with the equipment being used. The 

engineer should also be familiar with the drawings or 

other available documentation on the building to 

understand the expected results of the intrusive 

observation.

Reporting Requirements

The personnel conducting the tests should provide 

sketches of the wall indicating the location of the 

intrusive openings and the findings. The sketch should 

include the following information:

• Mark the location of the test on either a floor plan or 

wall elevation.

• Describe the size and type of opening.

• Specify the maximum strength of the core obtained 

during the test, in terms of force and in pressure.

• Describe the results of the test by a written 

description and a sketch or photograph.

• Report the date of the test.

• List the responsible engineer overseeing the test and 

the name of the company conducting the test.

TEST AND INVESTIGATION GUIDE Test Type: Intrusive

SELECTIVE REMOVAL Materials: Concrete,

Reinforced Masonry,

Unreinforced Masonry

IT 1
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FEMA 306 Basic Procedures Manual 51

Limitations

If the findings of the intrusive opening are substantially 

different from what was expected, the engineer should 

review all of the available information before 

proceeding.

The use of selected intrusive openings is often 

performed in conjunction with nondestructive testing 

procedures. For example, a rebar detector can be used 

to establish the location of reinforcing bars 

nonintrusively. Selected locations of reinforcement can 

then be chipped out to determine the size of the bar and/

or depth of the cover. These data are then used to 

calibrate the rebar detector.

The information gained from observations at selected 

locations is only applicable to the surveyed areas. 

Construction with similar appearance and condition 

may be different. The amount of variability will depend 

on several factors, including the era of construction, the 

amount of gravity and lateral load on the wall, and 

normal variations in construction quality. The locations 

of the intrusive openings should be carefully chosen to 

include sufficient typical and atypical areas so that the 

engineer has confidence that the data gathered represent 

most of the walls in the building.

Conversely, it is seldom cost effective or necessary to 

intrusively test every wall in a building. Intrusive 

openings may damage reinforcing bars or other hidden 

structural elements. Large intrusive openings can 

weaken the wall.

References

ACI Committee 364, 1994, “Evaluation of Structures 

Prior to Rehabilitation”, ACI 364.1R, ACI Manual 

of Concrete Practice, American Concrete Institute, 

Detroit, Michigan.

TEST AND INVESTIGATION GUIDE

continued IT 1
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52 Basic Procedures Manual FEMA 306

Description

A petrographic evaluation is a microscopic evaluation 

of the concrete or masonry material. A sample of the 

material is removed and sent to a laboratory where the 

sample is prepared and studied using a high-powered 

microscope. Petrographic examination can also be used 

to determine the cause of cracking and the approximate 

mix design of the concrete or mortar.

Equipment

• Typical equipment includes:

• Core drill or other tools for removing concrete or 

masonry

• Laboratory equipment including concrete saws for 

sectioning, grinding wheels for polishing, and stereo 

microscopes

Execution

Remove samples of the concrete or masonry material 

from the building using core drilling equipment or other 

concrete removal tools. The samples are then sent to a 

laboratory where they are cut, polished and examined 

under a microscope in accordance with ASTM C 856 

(ASTM, 1991) procedures.

The condition of the concrete or masonry located along 

the edge or within a crack can often be used to 

determine if the crack formed recently and thus may be 

earthquake related. Some of the methods used to assess 

the age of cracks are:

• Weathering along cracks. Since the edges of the 

material on either side of the crack tend to become 

rounded over time due to normal weathering, it may 

be possible to estimate whether a crack is “relatively 

young” or “relatively old” by estimating the amount 

of weathering. 

• Secondary deposits. Secondary deposits within a 

crack such as mortar, paint, epoxy, or spackling 

compound indicate that the crack formed before the 

installation of the material contained within it.

• Interpretation of carbonation patterns. Carbonation 

of calcium hydroxide contained in hydrated cement 

paste is inevitable and typically begins along formed 

or cracked surfaces. Carbonation penetrates into the 

cementitous material in a direction perpendicular to 

the plane of the formed or cracked surface. If an 

estimate of the carbonation rate can be made, then 

studies of the pattern of cementitious matrix 

carbonation adjacent to a crack can be used to 

estimate the age of the crack.

Petrographic studies can also establish the approximate 

composition of concrete and mortar. This information 

can be used to establish an approximate material 

strength. The material composition is needed to 

formulate or specify compatible materials that will be 

used for repairs and modifications.

Personnel Qualifications

Much of the results of a petrographic examination are 

subject to the personal judgment of the petrographer 

(Krauss, 1994). Therefore, the petrographer must have 

extensive experience in the evaluation of the materials 

being tested.

TEST AND INVESTIGATION GUIDE Test Type: Intrusive

PETROGRAPHY Materials: Concrete,

Reinforced Masonry,

Unreinforced Masonry

IT 2
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FEMA 306 Basic Procedures Manual 53

Reporting Requirements

A variety of information is available through 

petrography. The personnel conducting the tests on the 

material samples should provide a written report of the 

findings to the evaluating engineer. The results should 

contain, at a minimum, the following information for 

each sample:

• Identify the sample using the description of location 

or sample number provided by the engineer.

• Specify the length and diameter of the core and the 

cross-sectional area.

• Describe the tests performed on the sample, along 

with the appropriate references.

• Describe the results of the examination.

• Report the date the sample was taken and the date of 

the test.

• List the responsible engineer overseeing the test and 

the name of the company conducting the test.

Limitations

Although petrographic analysis can reveal considerable 

information regarding the composition of materials and 

the cause of damage, the results are subjective.

The exact cause and age of cracks may not be 

discernable. Cracks can have several causes (ACI, 

1994). Walls that have been protected with finishes are 

not subject to the typical surface deterioration that 

would allow comparison of crack faces for assessing 

relative age.

References

ACI Committee 201, 1994, “Guide for Making a Condition Survey of Concrete in Service”, ACI 201.1R92, ACI Manual of Concrete Practice, American 

Concrete Institute, Detroit, Michigan.

ASTM, 1991, Standard Practice for Petrographic 

Examination of Hardened Concrete, ASTM C 856-

83, 1991 ASTM Annual Book of Standards, American Society for Testing and Materials, Philadelphia, 

PA, pp 416-428.

Krauss, P.D., 1994, Repair Materials and Techniques 

for Concrete Structures in Nuclear Power Plants, 

NRC JNC No. B8045, US Nuclear Regulatory 

Commission, Washington, DC.

TEST AND INVESTIGATION GUIDE

continued IT 2
 Chapter 3: Investigation of Earthquake Damage

54 Basic Procedures Manual FEMA 306

Description

Material testing requires removal of a sample of the 

material, which can be either the reinforcing steel, 

concrete, or concrete masonry. The removed samples 

are then tested to determine the tensile or compressive 

strength for the steel or concrete, respectively.

Equipment

Concrete cores should be taken with diamond-studded 

core bits.

Reinforcing steel should be extracted with a 

reciprocating saw or torch.

Execution

Concrete testing requires removal of core samples with 

a diamond-tipped drill bit. Typical cores are three to six 

inches in diameter. For compression testing of the 

concrete, the length of the cores should be at least two 

times the diameter (ACI, 1994a). The cores should be 

taken through sections of walls that have no significant 

cracking. The core should be taken through the 

thickness of the wall and should avoid reinforcing steel. 

The cores should then be prepared and tested in 

accordance with ASTM C42 procedures (ASTM, 

1991a).

Rebar testing requires removal of concrete surrounding 

a length of reinforcing bar. The length of the sample 

required is dependent of the size of the bar. The rebar is 

removed. The removed sample is then subjected to 

tensile testing. It can also be subjected to metallurgical 

examination to assess the weldability of the steel. The 

reinforcing steel sample should be prepared and tested 

in accordance with ASTM A 370 (ASTM, 1991b).

Following removal of either concrete or rebar samples, 

the openings should be patched.

Personnel Qualifications

Material samples should be obtained by an experienced 

contractor. Most areas have contractors that specialize 

in concrete coring and sawing. The contractor should 

be familiar with the use of the equipment. An engineer 

should be responsible for specifying the locations of the 

sampling. Testing of the samples should be 

accomplished by a qualified laboratory under the 

direction of a licensed engineer.

Reporting Requirements

The personnel conducting the tests on the material 

samples should provide a written report of the findings 

to the evaluating engineer. The results for the concrete 

core tests should contain, at a minimum, the following 

information for each sample:

• Identify the sample using the description of location 

or sample number provided by the engineer.

• Specify the length and diameter of the core, and 

cross-sectional area.

• Report the maximum strength of the core obtained 

during the test, in terms of force and stress.

• Specify the correction factor applied to the results 

due to the ratio of the length to the diameter, and 

report the corrected results.

• Report the date the sample was taken and the date of 

the test.

• List the responsible engineer overseeing the test and 

the name of the company conducting the test.

TEST AND INVESTIGATION GUIDE Test Type: Intrusive

MATERIAL EXTRACTION

AND TESTING

Materials: Concrete,

Reinforced Masonry,

Unreinforced Masonry

IT 3
 Chapter 3: Investigation of Earthquake Damage

FEMA 306 Basic Procedures Manual 55

Testing of reinforcing steel should include the following 

information:

• Identify the sample using the description of location 

or sample number provided by the engineer.

• Report the length and diameter (or size) of the bar.

• Report the yield and ultimate strength of the core or 

reinforcing bar obtained during the test, in terms of 

force and stress.

• Plot the force-elongation data in stress-versus-strain 

units.

• Report the date the sample was taken and the date of 

the test.

• List the responsible engineer overseeing the test and 

the name of the company conducting the test.

Limitations

Extraction of samples causes damage to the wall, and 

repairs to those areas may be required (ACI, 1994b). 

Therefore, samples should be removed from areas of 

low expected demands. 

The values obtained from the concrete core tests should 

not be expected to exactly equal the anticipated design 

strength values. Core test values can have an average 

value of 85 percent of the specified strength (ACI, 

1995). The core strength values should be adjusted 

using the procedure described in FEMA 274 (ATC, 

1997b) to obtain the in-place strength of the concrete. 

If the results indicate high variability in values, 

additional samples should be taken and tested to reduce 

the coefficient of variation. However, the cost of the 

additional tests should be considered against the benefit 

of the increased precision of the results.

References

American Concrete Institute, 1994a, Strength Evaluation of Existing Concrete Buildings, ACI 437R-91, 

ACI Manual of Concrete Practice, Part 3, Detroit, 

Michigan.

American Concrete Institute, 1994b, Evaluation of 

Structures Prior to Rehabilitation, ACI 364.1R, ACI 

Manual of Concrete Practice, Part 3, Detroit, Michigan.

American Concrete Institute, 1995, Building Code 

Requirements for Structural Concrete (ACI 318-95) 

and Commentary (ACI 318R-95), Detroit, Michigan, pg 52.

American Society for Testing and Materials, 1991a, 

Standard Test Method of Obtaining and Testing 

Drilled Cores and Sawed Beams of Concrete, 

ASTM C 42-90, 1991 ASTM Standards in Building 

Codes, Philadelphia, Pennsylvania, pp 27-30.

American Society for Testing and Materials, 1991b,

Standard Test Methods for Mechanical Testing of 

Steel Products, ASTM A 370-92, 1991 ASTM 

Standards in Building Codes, Volume 1, Philadelphia, Pennsylvania, pp 484-529.

ATC, 1997a, NEHRP Guidelines for the Seismic Rehabilitation of Buildings, FEMA 273, prepared by the 

Applied Technology Council for the Building Seismic Safety Council, published by the Federal Emergency Management Agency, Washington, DC.

ATC, 1997b, NEHRP Commentary on the Guidelines 

for the Seismic Rehabilitation of Buildings, FEMA 

274, prepared by the Applied Technology Council 

for the Building Seismic Safety Council, published 

by the Federal Emergency Management Agency, 

Washington, DC.

TEST AND INVESTIGATION GUIDE

continued IT 3
 Chapter 3: Investigation of Earthquake Damage

56 Basic Procedures Manual FEMA 306

Description

The shear strength of unreinforced masonry 

construction depends largely on the strength of the 

mortar used in the wall. An in-place shear test is the 

preferred method for determining the strength of 

existing mortar. The results of these tests are used to 

determine the shear strength of the wall.

Equipment

• Chisels and grinders are needed to remove the bricks 

and mortar adjacent to the test area.

• A hydraulic ram, calibrated and capable of 

displaying the applied load.

• A dial gauge, calibrated to 0.001 inch.

Execution

Prepare the test location by removing the brick, 

including the mortar, on one side of the brick to be 

tested. The head joint on the opposite side of the brick 

to be tested is also removed. Care must be exercised so 

that the mortar joint above or below the brick to be 

tested is not damaged.

The hydraulic ram is inserted in the space where the 

brick was removed. A steel loading block is placed 

between the ram and the brick to be tested so that the 

ram will distribute its load over the end face of the 

brick. The dial gauge can also be inserted in the space.

The brick is then loaded with the ram until the first 

indication of cracking or movement of the brick. The 

ram force and associated deflection on the dial gage are 

recorded to develop a force-deflection plot on which the 

first cracking or movement should be indicated. A dial 

gauge can be used to calculate a rough estimate of shear 

stiffness (Eilbeck et al., 1996).

Inspect the collar joint and estimate the percentage of 

the collar joint that was effective in resisting the force 

from the ram. The brick that was removed should then 

be replaced and the joints repointed.

Personnel Qualifications

The technician conducting this test should have 

previous experience with the technique and should be 

familiar with the operation of the equipment. Having a 

second technician at the site is useful for recording the 

data and watching for the first indication of cracking or 

movement. The structural engineer or designee should 

choose test locations that provide a representative 

sampling of conditions.

TEST AND INVESTIGATION GUIDE Test Type: Intrusive

IN SITU TESTING -

IN PLACE SHEAR

Materials: Unreinforced Masonry IT 4
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FEMA 306 Basic Procedures Manual 57

Reporting Results

The personnel conducting the tests should provide a 

written report of the findings to the evaluating engineer. 

The results for the in-place shear tests should contain, at 

a minimum, the following information for each test 

location:

• Describe test location or give the identification 

number provided by the engineer.

• Specify the length and width of the brick that was 

tested, and its cross-sectional area.

• Give the maximum mortar strength value measured 

during the test, in terms of force and stress.

• Estimate the effective area of the bond between the 

brick and the grout at the collar joint.

• Record the deflection of the brick at the point of 

peak applied force.

• Record the date of the test.

• List the responsible engineer overseeing the test and 

the name of the company conducting the test.

Limitations

This test procedure is only capable of measuring the 

shear strength of the mortar in the outer wythe of a 

multi-wythe wall. The engineer should verify that the 

exterior wythe being tested is a part of the structural 

wall, by checking for the presence of header courses. 

This test should not be conducted on veneer wythes.

Test values from exterior wythes may produce lower 

values when compared with tests conducted on inner 

wythes. The difference can be due to weathering of the 

mortar on the exterior wythes. The exterior brick may 

also have a reduced depth of mortar for aesthetic 

purposes.

The test results can only be qualitatively adjusted to 

account for the presence of mortar in the collar joints. 

If mortar is present in the collar joint, the engineer or 

technician conducting the test is not able to discern how 

much of that mortar actually resisted the force from the 

ram.

The personnel conducting the tests must carefully watch 

the brick during the test to accurately determine the ram 

force at which first cracking or movement occurs. First 

cracking or movement indicates the maximum force, 

and thus the maximum shear strength. If this peak is 

missed, the values obtained will be based only on the 

sliding friction contribution of the mortar, which will be 

less than the bond strength contribution.

References

Eilbeck, D.E, J.D. Lesak, and J.N. Chiropolos, 1996, 

“Seismic Considerations for Repair of Terra Cotta 

Cladding”, Proceedings, Seventh North American 

Masonry Conference, June, pp 847-858.

ICBO, 1994, In-Place Masonry Shear Tests, UBC Standard 21-6, International Conference of Building 

Officials, Whittier, California, pg 3-614.

TEST AND INVESTIGATION GUIDE

continued IT 4
 Chapter 3: Investigation of Earthquake Damage

58 Basic Procedures Manual FEMA 306

Description

Flat jacks are thin hydraulic jacks that are inserted into 

the mortar joints of masonry walls. Flat jacks can be 

used to measure the state of stress of a masonry wall, 

the modulus of elasticity of the masonry, and the 

compressive strength of the masonry.

Equipment

• One or two flat jacks, 1/4- to 3/8-inch thick, with a 

hydraulic pump and pressure gauge

• Measuring points that are secured to the masonry 

wall

• Dial calipers or other instruments for measuring the 

distance between points to within 0.001 inch

• Chipping tools or masonry saws to remove mortar

Execution

A single flat jack is used to determine the state of stress 

in the masonry. A set of measuring points are attached 

with epoxy above and below the section of masonry to 

be tested. The distance between the points is measured 

and then one horizontal mortar joint is removed with 

chipping tools or saws. A flat jack is inserted in the 

mortar joint and pressurized to fill the void. The 

pressure is increased incrementally while measuring the 

distance between the measuring points. When the 

distance between the points returns to the original value, 

the pressure is recorded and then converted into 

compressive stress (σ) using the following equation 

(Rossi, 1987):

σ = p Km Ka

Where:

p is the gauge pressure

Km is a jack constant determined by laboratory 

calibration

Ka is the ratio of the surface area of the jack to 

the surface area of mortar removed

A “double flat jack test” is used to evaluate the 

compressive modulus of elasticity and the compressive 

strength. A section of the masonry construction to be 

tested is isolated by cutting two parallel sections of 

mortar joint. The joints should be separated by 

approximately the length of the flat jack, typically about 

14 inches. Prior to cutting, install measuring points 

within the section of masonry to be tested. Once the 

test section has been prepared, insert the flat jacks into 

the mortar joints and pressurize them to fill the voids. 

Apply loads to both jacks equally in increments, and 

measure the distance between the points. If the 

compressive strength is to be determined, the pressure 

should be increased until cracking is observed 

(Kingsley and Noland, 1987a). The pressure and 

deflection values are then converted into a stress-strain 

plot for the masonry.

Following the tests, the mortar should be replaced.

Personnel Qualifications

The engineers or technicians conducting the tests 

should be thoroughly familiar with the use of the 

equipment and should have experience conducting 

similar tests.

TEST AND INVESTIGATION GUIDE Test Type: Intrusive

IN SITU TESTING -

FLAT JACK

Materials: Unreinforced Masonry IT 5
 Chapter 3: Investigation of Earthquake Damage

FEMA 306 Basic Procedures Manual 59

Reporting Requirements

The personnel conducting the tests should provide a 

written report of the findings to the evaluating engineer. 

The report for the flat jack tests should contain, at a 

minimum, the following information for each test 

location:

• Describe the test location or use the sample number 

provided by the engineer.

• For a single flat jack test, report the stress state. For a 

double flat jack test, report the maximum value for 

masonry strength, that was measured in the test, in 

terms of force and pressure.

• Provide the load-deflection curve obtained during 

the test.

• Report the value of Km determined by calibration 

tests.

• Report the date of the test.

• List the responsible licensed engineer overseeing the 

test and the name of the company conducting the 

test.

Flat jack tests can be expensive and are prone to several 

problems.

Limitations

Flat jack tests should be performed in areas that are 

undamaged. Care should be exercised when removing 

the mortar for the tests to avoid damaging the mortar or 

masonry in the test area.

The measuring points must be securely fastened to the 

masonry units to avoid being dislodged during the 

testing. The gauge length between the measuring points 

should be as large as possible so that small changes in 

movement are easier to detect. The measuring points 

should be located at the midpoint of the joint and the 

jack so that the maximum deflections are measured.

If the wall is composed of masonry wythes of differing 

stiffness (for example, a terra-cotta veneer with brick 

backup), applying a uniform compressive load using the 

flat jack may cause out-of-plane bending of the wall. If 

a flat jack test of the entire wall thickness is performed, 

measuring points can be attached to both faces of the 

wall.

Often a flat jack test is performed only on the outer 

wythe. However, header bricks and mortar in the collar 

joints may prevent accurate results by restraining the 

outer wythe. If the masonry units have uneven surfaces, 

the flat jack will deform into the voids. This causes the 

pressure to be nonuniformly distributed. An uneven 

surface also makes it difficult to remove the flat jack 

from the mortar joint. Also, flat jacks may not have the 

capacity to fail the masonry in all cases.

References

Kingsley, G.R. and J.L. Noland, 1987a, A Note on 

Obtaining In-Situ Load-Deformation Properties of 

Unreinforced Brick Masonry in the United States 

Using Flatjacks, Evaluation and Retrofit of 

Masonry Structures, Proceedings of the Second 

Joint USA-Italy Workshop on Evaluation and Retrofit of Masonry Structures, pp 215-223.

Kingsley, G.R. and J.L. Noland 1987b, An Overview of 

Nondestructive Techniques For Structural Properties of Brick Masonry, Evaluation and Retrofit of 

Masonry Structures, Proceedings of the Second 

Joint USA-Italy Workshop on Evaluation and Retrofit of Masonry Structures, pp 225-237.

Rossi, P.P., 1987, Recent Developments of the Flat-Jack 

Test on Masonry Structures, Evaluation and Retrofit of Masonry Structures, Proceedings of the Second Joint USA-Italy Workshop on Evaluation and 

Retrofit of Masonry Structures, pp 257-285.

TEST AND INVESTIGATION GUIDE

continued IT 5
 Chapter 3: Investigation of Earthquake Damage

60 Basic Procedures Manual FEMA 306
FEMA 306 Basic Procedures Manual 61 

4. Evaluation of Earthquake Damage

4.1 Basis of Evaluation

The quantitative evaluation of the effects of earthquake 

damage on structures requires the selection of a 

measurement parameter. Procedures in this document 

use change in the anticipated performance of the 

building during future earthquakes as the measurement 

parameter. This is the change due directly to effects of 

earthquake damage on the basic structural properties 

that control seismic performance. If the structural 

property changes are estimated, the corresponding 

change in future performance can also be estimated. 

The total cost to restore the anticipated performance to 

approximately that of the building before the damaging 

earthquake quantifies the effects of the observed 

damage. These hypothetical “repairs” to structural 

components are referred to as performance restoration 

measures.

4.2 Seismic Performance 

Objectives

The damage evaluation procedures in this document are 

performance-based; that is, they assess the acceptability 

of the structural system (and the significance of changes 

in the structural system) on the basis of the degree to 

which the structure achieves one or more performance 

levels for the hazard posed by one or more hypothetical 

future earthquakes. A performance level typically is 

defined by a particular damage state for a building. The 

performance levels defined in FEMA 273, in order of 

decreasing amounts of damage, are collapse prevention, 

life safety, and immediate occupancy. Hazards 

associated with future hypothetical earthquakes are 

usually defined in terms of ground shaking intensity 

with a certain likelihood of being exceeded over a 

defined time period or in terms of a characteristic 

earthquake likely to occur on a given fault. The 

combination of a performance level and a hazard 

defines a performance objective. For example, a 

common performance objective for a building is that it 

maintain life safety when subjected to ground motion 

with a ten-percent chance of exceedance in fifty years.

The damage evaluation begins with the selection of an 

appropriate performance objective. The performance 

objective serves as a benchmark for measuring the 

difference between the anticipated performance of the 

building in its damaged and pre-event states, that is, 

relative performance analysis. The absolute 

performance acceptability of the damaged or pre-event 

building does not affect the quantification of loss. The 

quantification of performance loss is affected by the 

choice of performance objective, as illustrated in the 

following paragraph. Consequently, the selection of 

objectives is a matter of policy that depends on the 

occupancy and use of the facility. Guidance may be 

found in ATC-40, FEMA 273/274, and FEMA 308. 

It is important to note that the damage evaluation 

procedure can be used to investigate changes in 

performance characteristics for either single or multiple 

performance objectives. For example, a hospital might 

be expected to remain functional (immediate 

occupancy) after a rare event. For a very rare event, the 

life safety performance level might be acceptable. The 

damage evaluation procedure may be used with either 

or both performance objectives, and the loss associated 

with the damage may be different for the two objectives. 

The example hospital might have suffered a $1,000,000 

loss, based on the cost of restoration measures, with 

respect to its ability to remain functional after a rare 

event. The same level of damage might not have 

resulted in any loss in its ability to preserve life safety in 

the very rare event. In summary, the effects of damage 

can depend greatly on the chosen performance 

objective. 

4.3 Seismic Performance 

Parameters

Recent research and development activities have 

resulted in the introduction of structural analysis 

methodologies based on the inelastic behavior of 

structures (FEMA 273/274, ATC-40). These techniques 

generate a plot, called a capacity curve, that relates a 

global displacement parameter (at the roof level, for 

example) to the lateral force imposed on the structure. 

The magnitude of the maximum global displacement to 

occur during an earthquake depends on elastic and 

inelastic deformations of the individual components of 

the structure and their combination into the system 

response. 

For a given global displacement of a structure subject to 

a given lateral load pattern, there is an associated 

deformation of each structural component of the 

building. Since inelastic deformation indicates 

component damage, the maximum global displacement 
 Chapter 4: Evaluation of Earthquake Damage

62 Basic Procedures Manual FEMA 306

to occur during an earthquake defines a structural 

damage state for the building in terms of inelastic 

deformations for each of its components. The capacity 

of the structure is represented by the maximum global 

displacement, dc, at which the component damage is on 

the verge of exceeding the tolerable limit for a specific 

performance level. For example, the collapse prevention 

capacity of a building might be the roof displacement 

just short of that at which the associated damage would 

result in collapse of one or more of the column 

components. Displacement limits for components are 

tabulated in FEMA 273 and ATC-40.

The analysis methodologies also include techniques to 

estimate the maximum global displacement demand, dd,

for a specific earthquake ground motion. The ratio of 

the displacement capacity, dc, of the building for a 

specific performance level to the displacement demand, 

dd, for a specific hazard is a measure of the degree to 

which the building meets the performance objective. If 

the ratio is less than 1.0 the performance objective is not 

met. If it is equal to one the objective is just met. If it is 

greater than 1.0, performance exceeds the objective.

4.4 Relative Performance 

Analysis

The results of the damage investigation include two 

related categories of information on the structural 

damage consequences of the earthquake on the 

building. First, they comprise a compilation of the 

physical effects on all of the structural components. 

These typically consist of cracks in concrete or 

masonry, spalling or crushing of concrete or masonry, 

and fracture or buckling of reinforcement. Second, the 

damage is classified according to component type, 

behavior mode, and severity. Using these data it is 

possible for the engineer to quantify the changes 

attributable to the damage with respect to basic 

structural properties of the components of the building. 

These properties include stiffness, strength, and 

deformation limits.

Damage caused by an earthquake can affect the ability 

of a structure to meet performance objectives for future 

earthquakes in two fundamental ways. First, the damage 

may cause the displacement demand for the future, , 

event to differ from that for the pre-event structure, . 

This is due to changes in the global stiffness, strength, 

and damping of the structure, which in turn affect the 

maximum dynamic response of the structure by 

changing its global stiffness, strength, and damping. 

Also, the displacement capacity of the damaged 

structure, , may differ from that of the pre-event 

structure, . Damage to the structural components can 

change the magnitude of acceptable deformation for a 

component in future earthquakes. 

The analysis procedure described in the following 

sections uses the change in the ability of the damaged 

building to meet performance objectives in future 

earthquakes to measure the effects of the damage. The 

same basic analysis procedure is also used to formulate 

performance restoration measures that quantify the loss 

of seismic performance.

4.4.1 Overview

This section summarizes the basic steps of a seismic 

relative performance analysis for concrete and masonry 

wall buildings. This is a quantitative procedure that 

uses nonlinear static techniques to estimate the 

performance of the building in future events in both its 

pre-event and damaged states. The procedure is also 

used to investigate the effectiveness of potential 

performance restoration measures. This procedure 

requires the selection of one or more performance 

objectives for the building as discussed in Section 4.2. 

The analysis compares the degree to which the preevent and damaged buildings meet the specified 

objective. Figure 4-1 illustrates a generalized 

relationship between lateral seismic forces (base shear 

or spectral acceleration) and global structural 

displacements (roof or spectral displacement). 

This plot of structural capacity is characteristic of 

nonlinear static procedures (FEMA 273/274, ATC-40). 

A point on the curve defines a specific damage state for 

the structure, since the deformation of all of its 

components can be related to the global displacement of 

the structure. Figure 4-2 illustrates the basic 

idealization of force-deformation characteristics for 

individual components. 

The nonlinear static procedures estimate the maximum 

global displacement of a stucture to shaking at its base. 

These procedures are easier to implement and interpret 

than nonlinear dynamic time history analyses, but they 

are relatively new and subject to further development. 

In their present form, they have limitations (Krawinkler, 

1996), particularly for buildings that tend to respond in 

their higher modes of vibration. This limitation, 

d′

d

dd

d′

c

dc
 Chapter 4: Evaluation of Earthquake Damage

FEMA 306 Basic Procedures Manual 63

however, is relatively less restrictive for concrete and 

masonry wall buildings because of their tendency to 

repond in the fundamental mode. Future development 

of the procedures may also allow improved treatment 

for higher modes (Paret et al., 1996). Nonlinear static 

procedures must be carefully applied to buildings with 

flexible diaphragms.

The basic steps for using the procedure to measure the 

effect of damage caused by the damaging ground 

motion on future performance during the performance 

ground motion is outlined as follows:

1. Using the properties (strength, stiffness, energy dissipation) of all of the lateral-force-resisting components and elements of the pre-event structure, 

formulate a capacity curve relating global lateral 

force to global displacement. 

2. Determine the global displacement limit, dc , at 

which the pre-event structure would just reach the 

performance level specified for the performance 

objective under consideration.

3. For the specified performance ground motion, 

determine the hypothetical maximum displacement 

for the pre-event structure, dd .The ratio of dc to dd

indicates the degree to which the pre-event structure 

satisfies the specified performance objective.

4. Using the results of the investigation of the effects 

of the damaging ground motion, modify the component force-deformation relationships using the 

Figure 4-1 Displacement Parameters for Damage Evaluation

Global

Displacement

Parameter

de

de = Estimate of maximum global displacement caused by damaging earthquake

dc = Global displacement capacity for pre-event structure for specified performance level

dc' = Global displacement capacity for damaged structure for specified performance level

dd = Global displacement demand for pre-event structure for specified seismic hazard

dd' = Global displacement demand for damaged structure for specified seismic hazard

Post-event

(damaged)

capacity

curve

Global

Force

Parameter

Pre-event

capacity

curve

dc dd dc' dd'
 Chapter 4: Evaluation of Earthquake Damage

64 Basic Procedures Manual FEMA 306

Component Damage Classification Guides in Chapters 5 through 8. Using the revised component 

properties, reformulate the capacity curve for the 

damaged building and repeat steps 2 and 3 to determine and . The ratio of to indicates the 

degree to which the damaged structure satisfies the 

specified performance objective.

5. If the ratio of to is the same, or nearly the 

same, as the ratio of dc to dd , the damage caused by 

the damaging ground motion has not significantly 

degraded future performance for the performance 

objective under consideration. 

6. If the ratio of to is less than the ratio of dc to

dd , the effects of the damage caused by the damaging ground motion has diminished the future performance characteristics of the structure. Develop 

hypothetical actions in accordance with Section 4.5, 

to restore or augment element and component properties so that the ratio of to (where the * designates the restored condition) is the same, or nearly 

the same, as the ratio of dc to dd .

4.4.2 Global Displacement 

Performance Limits

The global displacement performance limits 

are a function of the acceptability of the 

deformation of the individual components of the 

structure as it is subjected to appropriate vertical loads 

and to a monotonically increasing static lateral load 

distributed to each floor and roof level in an assumed 

pattern. The deformation of the components depends on 

both their geometric configuration in the model and 

their individual force-deformation chacteristics (see 

Section 2.4) compared to those of other components. 

The plot of the total lateral load parameter versus global 

displacement parameter represents the capacity curve 

for the building for the assumed load pattern. Thus, the 

capacity curve is characteristic of the global assembly 

of individual components and the assumed load pattern. 

The current provisions of FEMA 273 limit global 

displacements for the performance level under 

consideration (e.g., Immediate Occupancy, Life Safety, 

Collapse Prevention) to that at which any single 

component reaches its acceptability limit (see 

Figure 4-2 Idealized Component Force-Deformation Relationship

Force, F

Deformation, D

F

Backbone curve

Actual hysteretic

behavior

D

Ductile 

(deformation controlled)

Backbone curve

Idealized

component

behavior

A

B C

D E

D

Semi- ductile 

A

B

C, D

E D

Brittle 

(force contolled)

A

B, C, D

E

(a) Backbone curve from actual hysteretic behavior

(b) Idealized component behavior from backbone curves

F F

d′

c d′d d′

c d′

d

d′

c d′

d

d′

c d′

d

dc

∗ dd

∗

(, , ) ddd c c c ′ ∗
 Chapter 4: Evaluation of Earthquake Damage

FEMA 306 Basic Procedures Manual 65

Figure 4-3). The provisions of FEMA 273/274 allow 

for the re-designation of such components as 

"secondary". Secondary components have higher 

deformation acceptability limits but the remaining 

primary lateral load resisting system components must 

be capable of meeting acceptability criteria without 

them. The same allowance may be made for relative 

performance analysis of earthquake damaged buildings 

as long as it is applied appropriately to both the preevent and damaged models.

The acceptability limits were developed for FEMA 273 

to identify and mitigate specific seismic deficiencies in 

buildings to improve anticipated performance. As such, 

they are intended to be conservative. In a relative 

performance analysis, the degree of conservatism 

should be same for both the pre-event and damaged 

models to give reliable results to estimate the scope of 

restoration repairs. In an actual earthquake, some 

"unacceptable" component behavior may not result 

necessarily in unacceptable global performance. In the 

future, it is possible that alternative procedures for 

better estimating global displacement limits will 

emerge. These also may be suitable for relative 

performance analyses provided that they are applied 

consistently and appropriately to both the pre-event and 

the damaged models.

4.4.3 Component Modeling and 

Acceptability Criteria

4.4.3.1 Pre-Event Building

In determining the capacity curve for the pre-event 

building, component properties are generated using the 

procedures of FEMA 273/274 or ATC-40, modified, if 

necessary, to reflect the results of the damage 

Figure 4-3 Global Displacement Limits and Component Acceptability used in FEMA 273/274

Global

Displacement

Limits, dc

Global

capacity

curve

Global

Force

Parameter

Collapse

 prevention

(CP)

Life safety

(LS)

Immediate

occupancy

(IO) Performance Levels

F

o

r

c

e

Deformation

A

B C

D E

F

o

r

c

e

Deformation

A

B C

D E

F

o

r

c

e

Deformation

A

B C

D E

First component reaches

IO acceptability limit

First component reaches LS

acceptability limit

First component reaches

CP acceptability limit

Component Force-Deformation Relationships
 Chapter 4: Evaluation of Earthquake Damage

66 Basic Procedures Manual FEMA 306

investigation. Modifications may be warranted for two 

reasons:

1. The procedures assume a normal, relatively minor, 

degree of deterioration of the building due to service conditions. If the investigation reveals preexisting conditions (see Section 3.4) that affect 

component properties beyond these normal conditions, then the "pre-event" component properties 

must be modified to reflect the condition of the 

structure just before the earthquake. 

2. If the verification process (see Section 3.6) indicates component types or behavior modes inconsistent with the FEMA 273/274 or ATC-40 predicted 

properties, then the pre-event component properties 

are modified to reflect the observed conditions.

4.4.3.2 Damaged Building

The effects of damage on component behavior are 

modeled as shown generically in Figure 4-4. 

Acceptability criteria for components are illustrated in 

Figure 4-5. The factors used to modify component 

properties are defined as follows:

λK = modification factor for idealized component 

force-deformation curve accounting for 

change in effective initial stiffness resulting 

from earthquake damage.

λQ = modification factor for idealized component 

force-deformation curve accounting for 

change in expected strength resulting from 

earthquake damage.

λD = modification factor applied to component 

deformation acceptability limits accounting 

for earthquake damage.

RD = absolute value of the residual deformation in 

a structural component, resulting from 

earthquake damage.

The values of the modification factors depend on the 

behavior mode and the severity of damage to the 

individual component. They are tabulated in the 

Component Guides in Chapters 5 through 8. The 

notation λ* is used to denote modifications to pre-event 

properties for restored components. These also vary by 

behavior mode, damage severity, and type of restoration 

measure, in accordance with the recommendations of 

Chapters 5 through 8. Figure 4-6 illustrates the general 

relationship between damage severity and the 

modification factors. Component stiffness is most 

sensitive to damage, so this parameter must be modified 

even when damage is slight. Reduction in strength 

implies more significant damage. After relatively severe 

damage, the magnitudes of acceptable displacements 

are reduced.

4.4.3.3 Establishing λ Factors by Structural 

Testing

The component modification factors (λ factors) for an 

earthquake damaged building can be established by 

Figure 4-4 Component Modeling Criteria

Force

parameter

Deformation

parameter

A

B C

D E

D' E'

B' C'

Damaged component

Undamaged component

QCE

Q' CE

K

K'

A'

Residual deformation,

RD

Stiffness Strength

Undamaged K QCE

Damaged K' = λK

 K Q'CE = λ QQCE
 Chapter 4: Evaluation of Earthquake Damage

FEMA 306 Basic Procedures Manual 67

laboratory structural testing of critical components, 

rather than using the values given in the Component 

Guides of Chapters 5, 6, 7, and 8. The testing must be 

directly applicable to the specific structural details of 

the building, and to the damaging and performance 

earthquakes considered. Typically this would mean that 

a project-specific test program must be carried out. In 

certain circumstances, the expense of such a test 

program may be justified. 

If testing is carried out to establish λ values, the test 

program should conform to the following guidelines:

A. Test Procedure

Two identical test specimens are required for each 

structural component of interest. One specimen is 

tested to represent the component in its post-event

condition subjected to the performance earthquake; the 

second specimen is tested to represent the component in 

its pre-event condition subjected to the performance 

earthquake. The λ values are derived from the 

differences in the force-displacement response between 

the two specimens.

Figure 4-7 schematically illustrates the required testing. 

Specimen A is tested first by a load-displacement 

sequence representative of the damaging earthquake. 

After this testing, the damage in the specimen should be 

similar in type and severity to that observed in the 

actual building after the damaging earthquake.. 

Specimen A is then tested by a load-displacement 

sequence representative of the performance level 

earthquake. From the resulting force-displacement 

hysteresis data, a backbone curve is drawn, according to 

Section 2.13.3 of FEMA 273.

A similar testing process is carried out on Specimen B, 

except that the initial test sequence representing the 

damaging earthquake is not applied. The λ values are 

derived from a direct comparison of the backbone curve 

of Specimen B with the backbone curve of Specimen A. 

B. Test Specimens

Each pair of test specimens are to be identical in all 

details of construction, and in material strengths.

Scale. The scale of the components should be as near to 

full-scale as is practical. Generally, reinforced concrete 

specimens should not be tested below 1/4 to 1/3 scale.

Materials. Material strengths for the actual building 

should be established by testing, and test specimen 

materials shall be used that match the actual strengths as 

closely as possible. Material strengths should be 

identical between Specimen A and Specimen B.

Figure 4-5 Component Acceptability Criteria

LS = Life Safety

CP = Collapse Prevention

Force

parameter

A

B C

D E

Deformation

parameter

D' E'

B' C'

A'

Residual deformation,

RD

IO = Immediate Occupancy

a) Undamaged Component b) Damaged Component

IO' = IO - RD

LS' = λD LS - RD

CP' = λD CP - RD

designates primary components

designates secondary components

P

S

S

S

P P P

S

S

P P P
 Chapter 4: Evaluation of Earthquake Damage

68 Basic Procedures Manual FEMA 306

For reinforced concrete structures, it may be preferable 

to cast Specimens A and B at the same time from the 

same batch of concrete. Cylinders should be tested to 

establish the concrete strength at the time each 

specimen is tested.

Reinforcing steel used in the test specimens should be 

tested, and the yield strength should be close to that for 

the actual building. If it is not possible to match yield 

strength, the area of reinforcement can be adjusted to 

compensate for the difference in yield strength. 

Pre-existing Damage. If the component of the actual 

building contains damage that is identified as preexisting (e.g. cracks from shrinkage or a previous 

earthquake) then, to the extent possible, this damage 

should be induced in both Specimen A and Specimen B.

Number of Specimens. For simplicity of presentation, 

these guidelines refer to testing only one pair of 

specimens. For behavior modes or seismic response 

that shows substantial variability, more specimens 

would need to be tested so that results are based on a 

statistically significant sample.

C. Loading

Cyclic-static loading would typically be used for the 

testing. The test set-up and applied loading should be 

designed so that moment and shear diagrams and axial 

stress levels are representative of those occurring in the 

actual structure. Established test protocols, e.g. ATC 

(1992), should be followed to the extent applicable. A 

pseudo-dynamic loading sequence may be used, with 

consideration of the issues identified below. 

Representing the Damaging Earthquake. To represent 

the damaging earthquake, the load sequence should 

recreate the displacement amplitudes and number of 

cycles undergone by the actual component in the 

damaging earthquake. Ground motion parameters for 

the damaging earthquake, from contour maps and 

recording stations near to the building site, should be 

reviewed for preliminary estimates of these parameters. 

The final determination of appropriate displacement 

amplitudes should be made during testing, so that the 

loading produces damage that is similar in type and 

severity to that observed in the actual building.

If a pseudo-dynamic loading sequence is used, it must 

be designed to allow adjustments during testing to 

better represent the actual input level of the damaging 

earthquake.

Representing the Performance Earthquake. To 

represent the performance earthquake, the load 

sequence should reflect the demands associated with the 

selected seismic hazard level. The load sequence 

should also contain enough cycles at different 

displacement levels to allow the construction of the 

backbone curve per Section 2.13.3 of FEMA 273. 

Figure 4-6 Component Modification Factors and Damage Severity

Insignificant Slight Moderate Heavy Extreme

Component modification factors, λ

1.0

Severity of damage

λ D (deformation acceptability)

λ K (stiffness)

λ Q(strength)

Shading reflects uncertainty
 Chapter 4: Evaluation of Earthquake Damage

FEMA 306 Basic Procedures Manual 69

Figure 4-7 Determining λ values from structural testing
 Chapter 4: Evaluation of Earthquake Damage

70 Basic Procedures Manual FEMA 306

Pseudo-dynamic test sequences may need to be 

carefully selected to produce enough cycles in each 

direction.

4.4.4 Global Displacement Demand

Prior earthquake damage may alter the future seismic 

response of a building by affecting the displacement 

demand and the displacement capacity. Effects of prior 

damage on the future displacement demands may be 

evaluated according to methods described in this 

section. Effects of prior damage on displacement 

capacity are described in Section 4.4.3. 

FEMA 307 describes analytical and experimental 

studies of effects of prior damage on future earthquake 

response demands. A primary conclusion is that prior 

earthquake damage often does not cause a statistically 

significant change in maximum displacement demand 

for the overall structural system in future earthquakes 

under the following circumstances: 

a. there is not rapid degradation of resistance with 

repeated cycles. 

b. the performance ground motion associated with 

the future event produces a maximum 

displacement, , larger than that produced by 

the damaging ground motion, de. 

c. the residual drift of the damaged or repaired 

structure is small relative to de. 

If the performance ground motion produces a maximum 

displacement, less than that produced by the 

damaging ground motion, de. the response of the 

damaged structure is more likely to differ from that of 

the pre-event structure, dd (see Figure 4-8). 

There are several alternatives for estimating the 

displacement demand for a given earthquake motion. 

FEMA 273 relies primarily on the displacement 

coefficient method. This approach uses a series of 

coefficients to modify the hypothetical linear-elastic 

response of a building to estimate its nonlinear-inelastic 

displacement demand. The capacity spectrum method 

(ATC 40) characterizes seismic demand initially using a 

5% damped linear-elastic response spectrum and 

reduces the spectrum to reflect the effects of energy 

dissipation in an iterative process to estimate the 

inelastic displacement demand. The secant stiffness 

method (Kariotis et al., 1994), although formatted 

differently, is fundamentally similar to the capacity 

spectrum method. Both these latter two methods can be 

related to the substitute structure method (Shibata and 

Sozen, 1976). The use of each of these approaches to 

generate estimates of global displacement demand (dd, 

dd'

, and dd*) is summarized in the following sections. 

Generally, any of the methods may be used for the 

evaluation of the effects of damage; however, the same 

method should be used to calculate each of the global 

displacement demands (dd, dd'

, and dd*) when making 

relative comparisons using these parameters.

4.4.4.1 Displacement Coefficient Method

The displacement coefficient method refers to the 

nonlinear static procedure described in Chapter 3 of 

FEMA 273. The method also is described in Section 

8.2.2.2 of ATC 40. The reader is referred to those 

documents for details in application of the procedure. 

A general overview and a description of the application 

of the method to damaged buildings are presented 

below.

The displacement coefficient method estimates the 

earthquake displacement demand for the building using 

a linear-elastic response spectrum. The response 

spectrum is plotted for a fixed value of equivalent 

damping, and the spectral response acceleration, Sa, is 

read from the spectrum for a period equal to the 

effective period, Te. The effective period is defined by 

the following:

 (4-1)

where Ti is the elastic fundamental period (in seconds) 

in the direction under consideration calculated by 

elastic dynamic analysis, Ki

 is the elastic lateral 

stiffness of the building in the direction under 

consideration (refer to Figure 4-9), and Ke is the 

effective lateral stiffness of the building in the direction 

under consideration (refer to Figure 4-9). As described 

in FEMA 273, the effective lateral stiffness is taken as a 

secant to the capacity curve at base shear equal to 0.6Vy. 

For a concrete or masonry wall building that has not 

been damaged previously by an earthquake, the 

effective damping is taken equal to 5% of critical 

damping. 

The target displacement, δt

, is calculated as: 

dd

d′

d T T K

K e i

i

e

=
 Chapter 4: Evaluation of Earthquake Damage

FEMA 306 Basic Procedures Manual 71

(4-2)

where C0, C1, C2, C3 are modification factors defined in 

FEMA 273, and all other terms are as defined 

previously.

The maximum displacement, dd, of the building in its 

pre-event condition for a performance ground motion is 

estimated by applying the displacement coefficient 

method using component properties representative of 

the pre-event conditions. To use the displacement 

coefficient method to estimate the maximum 

displacement demand, , during a performance 

Figure 4-8 Maximum Displacement Dependency on Damaging Earthquake

Figure 4-9 Global Capacity Dependency on Initial and Effective Stiffness

Global

displacement

parameter

de

Post-event

(damaged)

capacity

curve

Global

force

parameter

Pre-event

capacity

curve

dd d ' d dd dd'

For reponse greater than the damaging

earthquake, the maximum displacement of the

damaged structure,dd

', may not differ significantly

from the pre-event structure,dd.

For reponse less than the

damaging earthquake, the

maximum displacement of the

damaged structure, d d¢, may

differ from the pre-event

structure,dd.

Global force

parameter

Global

displacement

parameter

Vy

Ki

0.6Vy

Ke

Global capacity

curve

δ

π t a

e CCCCS

T = 0123

2

2 4

d′

d
 Chapter 4: Evaluation of Earthquake Damage

72 Basic Procedures Manual FEMA 306

ground motion for a building damaged by a previous 

earthquake use the following steps: (See Figure 4-10.)

1. Construct the relation between lateral seismic force 

(base shear) and global structural displacement 

(roof displacement) for the pre-event structure. 

Refer to this curve as the pre-event capacity curve. 

Pre-event force-displacement relations should 

reflect response characteristics observed in the 

damaging earthquake, as discussed in Section 3.6.

2. Construct a similar relationship between lateral 

seismic force and global structural displacement for 

the structure based on the damaged condition of the 

structure, using component modeling parameters 

defined in Section 4.4.3. Refer to this curve as the 

post-event capacity curve. 

3. Define effective stiffnesses K1, K2, and K3 as shown 

in Figure 4-10. K1 is Ke (see Figure 4-9) calculated 

from the pre-event capacity curve. K2 is Ke (see 

Figure 4-9) calculated from the post-event capacity 

curve. K3 is the effective post-yield stiffness from 

the post-event capacity curve. 

4. Apply the displacement coefficient method as 

defined in FEMA 273 with the effective stiffness 

taken as Ke = K1, effective damping equal to 5% of 

critical damping, post-yield stiffness defined by 

stiffness K3 , and effective yield strength defined by 

the intersection of the lines having slopes K1 and K3 

to calculate δt

 using Equation 4-2. Assign the displacement parameter the value calculated for δt

.

5. Apply the displacement coefficient method as 

defined in FEMA 273 with the effective stiffness 

taken as Ke = K2, effective damping as defined by 

Equation 4-3, post-yield stiffness defined by stiffness K3 , and effective yield strength defined by the 

intersection of the lines having slopes K2 and K3 to 

calculate the displacement parameter . 

6. Using the displacement parameters and , 

estimate the displacement demand, , for the 

structure in its damaged condition as follows:

a. If is greater than de, then 

b. If is less than de, then 

The effective damping as defined by Equation 4-3 is 

consistent with experimental results obtained by Gulkan 

and Sozen (1974), 

 (4-3)

For a restored or upgraded structure, the displacement 

demand, , for a performance ground motion may be 

Figure 4-10 Pre- and Post-Event Capacity Curves with Associated Stiffnesses

Global force

parameter

Global

displacement

parameter

K1

K2

Post-event capacity

curve

K3

Pre-event capacity

curve

d′

d1

d′

d2

d′

d1 d′d2

d ′

d

d′

d1 d d ′ = ′ d d1

d′

d1 d d ′ = ′ d d2

β =+ − F

H

G I

K

J

L

N

M

M

O

Q

P

P

0 05 0 2 1 2

1

0 5

. .

.

K

K

dd

*
 Chapter 4: Evaluation of Earthquake Damage

FEMA 306 Basic Procedures Manual 73

calculated using the displacement coefficient method 

with 5% damping using a capacity curve generated 

using applicable properties for existing components, 

whether repaired or not, and any supplemental 

components added to restore or upgrade the structure.

4.4.4.2 Capacity Spectrum Method

The capacity spectrum method is described in Section 

8.2.2.1 of ATC 40. The reader is referred to that 

document for details in application of the procedure. A 

general overview and a description of the application of 

the method to damaged buildings are presented below.

The capacity spectrum method estimates the earthquake 

displacement demand for the building using a linearelastic response spectrum. The response spectrum is 

plotted for a value of equivalent damping based on the 

degree of nonlinear response, and the spectral 

displacement response is read from the intersection of 

the capacity curve and the demand curve. In some 

instances of relatively large ground motion, the curves 

may not intersect, indicating potential collapse. In these 

cases the displacement coefficient method could be 

used as an alternate method for damage evaluation.

The maximum displacement of the building in its preevent condition, dd, for a performance ground motion is 

estimated by applying the capacity spectrum method 

using component properties representative of the preevent conditions. To use the capacity spectrum method 

to estimate the maximum displacement demand, , 

during a performance ground motion for a building 

damaged by a previous earthquake, use the following 

steps: 

1. Construct the relation between lateral seismic force 

(spectral acceleration) and global structural displacement (spectral displacement) for the structure 

assuming the damaging ground motion and its 

resultant damage had not occurred. Pre-event component force-deformation relationships should 

reflect response characteristics observed in the 

damaging earthquake as discussed in Section 3.6. 

Refer to this curve as the pre-event capacity curve.

2. Construct a similar relation between lateral seismic 

force and global structural displacement for the 

structure based on the damaged condition of the 

structure, using component modeling parameters 

defined in Section 4.4.3. Refer to this curve as the 

post-event capacity curve. 

3. Apply the capacity spectrum method using the preevent capacity curve to calculate the displacement 

parameter .

4. Apply the capacity spectrum method using the postevent capacity curve to calculate the displacement 

parameter . For determining the effective damping, the yield strength and displacement for the 

post-event capacity curve should be taken identically equal to the yield strength and displacement 

determined for the pre-event capacity curve. (See 

Equation 4-3.)

5. Using the displacement parameters and , 

estimate the displacement demand, , for the 

structure in its damaged condition as follows:

a. If is greater than de, then 

b. If is less than de, then 

For a restored or upgraded structure the displacement 

demand for a performance ground motion, dd*, may be 

calculated using the capacity spectrum method based on 

a capacity curve using applicable properties for existing 

components, whether repaired or not, and any 

supplemental components added to restore or upgrade 

the structure.

4.4.4.3 Secant Stiffness Method

The secant stiffness method is described in Section 

8.4.2.1 of ATC-40, Seismic Evaluation and Retrofit of 

Concrete Buildings (ATC, 1996). The reader is referred 

to that document for details in application of the 

procedure. To use the method for damaged buildings, 

the general procedure should be applied based on the 

properties of the damaged building. 

4.4.4.4 Nonlinear Dynamic Procedure

As an alternative to the nonlinear static procedures 

described above, nonlinear dynamic response histories 

may be computed to estimate the displacement demand 

for the building. This dynamic analysis approach 

requires that suitable ground motion records be selected 

for both the damaging event and the performance 

ground motion. It also requires that representative 

structural models be prepared for the building in its preevent (no superscript), damaged ('), and restored or 

upgraded (*) conditions. Detailed procedures have not 

been developed for the use of nonlinear dynamic 

response histories in relative performance analyses. 

The following sections offer general guidance on 

d ′

d

d′

d1

d′

d2

d′

d1 d′d2

d ′

d

d′

d1 d d ′ = ′ d d1

d′

d1 d d ′= ′ d d2
 Chapter 4: Evaluation of Earthquake Damage

74 Basic Procedures Manual FEMA 306

nonlinear dynamic procedures consistent with the 

nonlinear static procedures.

A. Ground Motions

Damaging Event. If available, ground motion time 

histories at, or near, the site may be used to represent 

the damaging ground motion. Alternatively, an estimate 

of spectral response can be generated using the 

procedures of Section 3.1. Time histories consistent 

with the estimated spectral response may then be 

generated to represent the damaging ground motion. 

The average maximum displacement response, dd, of 

the pre-event structural model to the time histories 

should be near that which is estimated to have actually 

occurred in the structure under evaluation. This effort 

may involve some adjustments to both the structural 

model and the ground motion in a verification process, 

similar to that outlined in Section 3.6, to calibrate the 

analysis with the observed damage. 

Performance Ground Motions. Three to five ground 

motion accelerograms might be used to represent 

potential motions at the site for each performance level 

considered. Each of the records should be consistent 

with the response spectra that would be used with the 

nonlinear static procedures for the performance level 

under consideration as presented in FEMA 273/274 

(ATC, 1997a,b) and ATC-40 (ATC, 1996). The 

maximum global displacement responses of the 

structural models can be averaged to generate a best 

estimate of the response.

B. Structural Modeling 

The analysis procedure will vary, depending on the type 

of model used for the individual structural components. 

Non-degrading Component Models. If the components 

are modeled using force-deformation relations that do 

not include strength degradation (non-degrading 

model), a procedure to estimate displacement demands 

is as follows:

1. Determine the maximum displacement response of 

the pre-event building, dd, to the performance 

ground motion using a structural model with component properties representative of pre-event conditions. This pre-event model should be calibrated, as 

discussed above, to the damaging ground motion.

2. Modify the component properties to reflect the 

effects of the observed damage in accordance with 

the recommendations of Section 4.4.3. Determine 

the maximum displacement response of the building in its damaged condition, dd', to the performance ground motion using the damaged structural 

model.

3. Modify the model to reflect the effects of restoration or upgrade measures. These may include the 

modification of existing components or the addition 

of new components as discussed in Section 4.5. 

Determine the maximum displacement response of 

the building in its restored or upgraded condition, 

dd*, to the performance ground motion using the 

restored or upgraded structural model.

Degrading Component Models. If the components are 

modeled using force-deformation relations that allow 

strength degradation during the response history 

(degrading model), a procedure to estimate 

displacement demands is as follows:

1. Determine the maximum displacement response of 

the pre-event building, dd, to the performance 

ground motion using a structural model with component properties representative of pre-event conditions. This pre-event model should be calibrated, as 

discussed in Section 3.6, to the damaging ground 

motion.

2. Subject the pre-event model to a composite ground 

motion comprised of the damaging ground motion, 

followed by a quiescent period in which the structure comes to rest, followed by the performance 

ground motion. Estimate the maximum displacement response, dd', of the building in its damaged 

condition as the maximum displacement to occur in 

the time period after the quiescent period in the 

record.

3. Modify the model to reflect the effects of both the 

damage and restoration or upgrade measures. 

These may include the modification of existing 

components or the addition of new components as 

discussed in Section 4.5. Determine the maximum 

displacement response, dd*, of the building in its 

restored or upgraded condition to the performance 

ground motion using the modified structural model.

4.5 Performance Restoration 

Measures

If the performance capability of the structure is 

diminished by the effects of earthquake damage 

, the magnitude of the loss is 

quantified by the costs of performance restoration 

measures. These are hypothetical actions that, if 

(/ /) dd dd cd cd ′ ′ <
 Chapter 4: Evaluation of Earthquake Damage

FEMA 306 Basic Procedures Manual 75

implemented, would result in future performance 

approximately equivalent to the undamaged building 

. Performance restoration measures 

may take several different forms:

• Component restoration entails the repair of 

individual components to restore structural 

properties that were diminished as a result of the 

earthquake damage. The Component Guides in 

Chapters 5 through 8 provide guidance based on 

component type, behavior mode, and severity of 

damage. They refer to outline specifications for 

individual restoration techniques that are compiled 

in FEMA 308: The Repair of Earthquake Damaged 

Concrete and Masonry Wall Buildings.

• An extreme case of component repair is complete 

replacement. In some cases, this is the only 

alternative indicated in the Component Guides. In 

other cases, it may be a more economical alternative 

than component repair.

• Performance can also be restored by the addition of 

new supplemental lateral-force-resisting elements or 

components.

Performance restoration measures are specified at the 

component level using one or more of the above 

alternatives. The measures are then tested by analyzing 

the performance of the modified structure, as outlined in 

Section 4.4. If necessary, the scope of the measures 

should be adjusted until the performance is 

approximately the same as that of the undamaged 

building. It should be noted that all components need 

not necessarily be restored individually to restore 

overall performance. It is advisable to explore several 

strategies to reach an economical solution.

Once the scope has been determined, the loss associated 

with the earthquake damage can be calculated as the 

cost of the performance restoration measures if they 

were to be actually implemented. The cost should 

include estimates of direct construction costs, as well as 

the associated indirect costs. Indirect costs include 

project costs such as design and management fees. In 

some cases, the costs of hypothetical temporary 

relocation of building occupants, loss of revenue, and 

other indirect costs, should be included. Detailed 

guidelines on determining both direct and indirect costs 

are not included in this document.

4.6 An AlternativeThe Direct 

Method 

A direct method of determining performance restoration 

measures may be used to estimate the loss caused by the 

earthquake. This method assumes that the scope of 

performance restoration measures is equivalent to 

restoring the significant structural properties of all of 

the components of the structure. The method uses 

individual repair actions for each component addressing 

the observed damage directly without explicitly 

considering its effect on seismic performance. These 

repair actions are summarized in the Component Guides 

of Chapters 5 through 8. The fundamental assumption is 

that the restored structure would have equivalent 

performance capability to the undamaged building for 

performance ground motions greater than that of the 

damaging ground motion ( ). For this case the 

direct method will tend to overestimate losses, because 

some of the damage will have no effect on seismic 

performance. If the anticipated performance ground 

motion is less than that of the damaging ground motion 

( ), the direct method may underestimate losses 

in some cases, depending on individual building 

characteristics. This is because it neglects some loss of 

stiffness in components that theoretically could increase 

displacement response for smaller events. In these 

cases, relative performance analysis may be necessary 

to evaluate losses more accurately.

The direct method should be used only if the sole 

objective is to estimate the loss from the damaging 

earthquake based on the cost of the performance 

restoration measures. The direct method provides no 

information on the actual performance of the building in 

its damaged or undamaged states and cannot be used for 

design purposes. 

Relative performance analysis is preferred because it 

determines the seismic performance of the building in 

its damaged and undamaged states.The scope of 

performance restoration measures is determined by 

analyzing their effect on the predicted performance. 

Since the effect on global performance of damage to 

individual components is considered, this technique 

generally provides a more accurate evaluation of the 

actual loss due to the damaging earthquake. The 

analysis also provides information that may be used for 

design purposes to restore or upgrade the building. 

(/ /) dd dd cd cd

∗ ∗ ≈

d d d e

* >

d d d e

* <
 Chapter 4: Evaluation of Earthquake Damage

76 Basic Procedures Manual FEMA 306
FEMA 306 Basic Procedures Manual 77 

5: Reinforced Concrete

5.1 Introduction and 

Background

This section provides information on reinforced 

concrete wall components including the Component 

Damage Classification Guides (Component Guides) for 

reinforced concrete (RC). Section 5.2 defines and 

describes the component types and behavior modes that 

may be encountered in reinforced concrete wall 

structures. Section 5.3 gives evaluation procedures for 

assessing component strength and determining likely 

behavior modes. Section 5.4 defines symbols for 

studies on reinforced concrete walls.

The Component Guides and evaluation procedures in 

Section 5.5 are based on a review of the applicable 

research. Extensive structural testing has been done on 

reinforced concrete walls and wall components. Inplane tests on concrete walls in the 1950s and early 

1960s generally applied monotonic loading and focused 

on ultimate strength without considering displacement 

or ductility capacity. Two major programs during this 

time period were carried out at Stanford University 

(Benjamin and Williams, 1957 and 1958) and at MIT 

(Antebi et al., 1960).

From the late 1960s to early 1980s, the Portland 

Cement Association conducted a comprehensive and 

pioneering test program on the earthquake resistance of 

reinforced concrete walls (Cardenas, 1973; Oesterle et 

al., 1976, 1979, 1983; Shiu et al., 1981; Corley et al., 

1981). The tests principally used cyclic-static loading 

and identified several possible behavior modes in 

reinforced concrete walls, including flexural behavior, 

diagonal tension, diagonal compression (web crushing), 

boundary compression and bar buckling, sliding shear, 

and out-of-plane wall buckling.

Research on the behavior of coupling beams of walls 

was begun in the late 1960s at the University of 

Canterbury in New Zealand (Paulay, 1971a, b; Paulay 

& Binney, 1974; Paulay and Santhakumar, 1976). 

Research on numerous aspects of reinforced concrete 

wall behavior continued at Canterbury through the 

1990s, covering ductile flexural behavior, diagonal 

tension, boundary confinement and bar buckling, 

sliding shear, out-of-plane stability, and walls with 

irregular openings (Paulay, 1980, 1986; Paulay et al., 

1982; Paulay & Priestley, 1992, 1993). The research 

findings have contributed to code provisions for 

reinforced concrete walls in the United States and 

elsewhere.

As part of a U.S.- Japan cooperative research program, 

a seven-story full-scale, shear-wall structure was tested 

(Wight, 1985). This test demonstrated the contribution 

made by beams and slabs that framed into the wall to 

the capacity of wall structures.

Wall testing has also been carried out at the University 

of California, Berkeley (Wang et al., 1975; Vallenas et 

al., 1979; Iliya & Bertero, 1980) and on small shaketable specimens at the University of Illinois (Aristisabal 

and Sozen, 1976; Lybas and Sozen, 1977). More recent 

tests have been done by Wallace and Thomsen (1995). 

A number of tests have been carried out in Japan, 

including those by Ogata and Kabeyasawa (1984).

5.2 Reinforced Concrete 

Component Types and 

Behavior Modes

5.2.1 Component Types

Five possible component types are defined for 

reinforced concrete wall structures. The component 

types are listed and described in Table 5-1. Typically 

only component types RC1, RC2, and RC3 will suffer 

earthquake damage. Component types RC4 and RC5 

are mentioned for completeness, but since they are not 

expected to suffer earthquake damage, they are not 

discussed in detail.

Wall Component types are assigned based on 

identifying the governing mechanism for nonlinear 

lateral deformation for the structure, as described in 

Section 2.4.

5.2.2 Behavior Modes and Damage

The possible modes of nonlinear behavior and damage 

for reinforced concrete wall components are outlined in 

Table 5-2, along with their response characteristics. 

Section 2.2 of FEMA 307 presents typical forcedisplacement hysteresis loop shapes for the behavior 

modes. The likelihood of such behavior modes 

occurring in each of the prevalent component types is 

shown in Table 5-3.
 Chapter 5: Reinforced Concrete

78 Basic Procedures Manual FEMA 306

The behavior modes are described in the following 

sections according to the ductility categories given in 

Table 5-2. 

This document focuses on structures for which 

earthquake damage occurs primarily in wall 

components. Engineers should be aware that damage 

can also occur in other structural elements such as 

foundations, columns, beams, and slabs.

5.2.3 Behavior Modes with High 

Ductility Capacity (Flexural 

Response)

Adequately designed reinforced concrete walls of 

various configurations can respond to earthquake 

shaking in a ductile manner. Ductile wall response 

usually results from flexural behavior, which requires 

that the wall components be designed to avoid the 

following less desirable behavior effects:

• Failures in shear corresponding to diagonal tension, 

web crushing, or sliding shear

• Buckling of longitudinal bars in boundary regions of 

plastic hinge zones

• Loss of concrete strength due to high compressive 

strains in unconfined boundary regions of plastic 

hinge zones

• Slip of lap splices

• Out-of-plane buckling of thin wall sections

The strength of wall components in flexure is calculated 

using conventional procedures given in Section 5.3.5. 

Wall components responding in flexure generally have 

good displacement capacity, typically in-plane rotations 

exceeding two percent (or 0.02 radians), or 

displacements at least eight times yield.

5.2.4 Behavior Modes with 

Intermediate Ductility Capacity

The following behavior modes can be defined as having 

intermediate ductility capacity:

• Flexure/Diagonal tension

• Flexure/Web crushing

• Flexure/Sliding shear

• Flexure/Boundary-zone compression

• Flexure/Lap-splice slip

• Flexure/Out-of-plane wall buckling

The earthquake response in these behavior modes is 

initially governed by flexure, but after some number of 

cycles, reaching some level of earthquake 

displacements, a response mode other than flexure 

predominates. At this point, the component suffers 

strength degradation.

Table 5-1 Component Types and Descriptions for Reinforced Concrete Walls.

Component Type Description

RC1 Isolated Wall or 

Stronger Wall Pier

Stronger than beam or spandrel elements that may frame into it, so that nonlinear behavior (and

damage) is generally concentrated at the base, with, for example, a flexural plastic hinge or shear

failure. Includes isolated (cantilever) walls. If the component has a major setback or cutoff of

reinforcement above the base, this section should be also checked for nonlinear behavior.

RC2 Weaker Wall Pier Weaker than the spandrels to which it connects, characterized, for example, by flexural hinging at 

top and bottom, or shear failure.

RC3 Weaker Spandrel 

or Coupling Beam

Weaker than the wall piers to which it connects, characterized, for example, by hinging at each 

end, shear failure, or sliding shear failure.

RC4 Stronger Spandrel Should not suffer damage because it is stronger than attached piers. If this component is damaged, it should probably be re-classified as RC3.

RC5 Pier-Spandrel 

Panel Zone

Typically not a critical area in RC walls.
 Chapter 5: Reinforced Concrete

FEMA 306 Basic Procedures Manual 79

Table 5-2 Behavior Modes for Reinforced Concrete Wall Components.

Behavior Mode Approach to calculate strength 

(use expected material values)

Approach to estimate displacement 

capacity

Ductility Category

A. Ductile flexural 

response

Conventional calculations per 

Section 5.3.5.

Good displacement capacity (e.g. 2% drift, or 

8x yield displacement).

High ductility 

capacity

B. Flexure/ Diagonal 

tension

Based on shear strength as a function of ductility. See Section 5.3.6.b.

C. Flexure/ Diagonal 

compression (web 

crushing)

Moment strength per Section 5.3.5 initially 

governs strength.

Based on relationship of web crushing 

strength to drift per Oesterle et al (1983). See 

Section 5.3.6.c.

Ductility capacity 

varies

D. Flexure/ Sliding shear Shear friction approach per ACI 318, or recommendations of Paulay and Priestley 

(1992). See Section 5.3.6.d.

(Failure only occurs 

after some degree of 

flexural yielding 

and concrete degradation.)

E. Flexure/ Boundaryzone compressionBased on amount of ties required for moderate and high ductility levels, per Paulay and 

Priestley (1992). See Section 5.3.7.

F. Flexure/Lap-splice 

slip

Based on lap strength as a function of ductility. See Section 5.3.8 

G. Flexure/Out-of-plane 

wall buckling

Based on wall thickness requirements for 

moderate and high ductility levels. See 

Section 5.3.9.

H. Preemptive diagonal 

tension

Shear strength governs at low ductility levels, per Section 5.3.6.b.

I. Preemptive web 

crushing

May occur at shear stresses of 12√f’ce –

15√f’ce. See Section 5.3.6.c.

J. Preemptive sliding 

shear

Shear friction approach per ACI 318. See 

Section 5.3.6.d.

No inelastic displacement capacity. Little or no ductility 

capacity 

(Flexural reinforcement does not 

yield.)

K. Preemptive boundary 

zone compression

Applies only to unusually high axial loads, 

above the balance point. Moment strength 

calculation still governs.

L. Preemptive lap-splice 

slip

Lap strength, per FEMA 273 and ATC-40, 

or approach of Priestly et al. (1996) governs. See Section 5.3.8.

M. Global foundation 

rocking of wall

See FEMA 273 or ATC-40 Moderate to high 

ductility capacity

N. Foundation rocking of 

individual piers
 Chapter 5: Reinforced Concrete

80 Basic Procedures Manual FEMA 306

Table 5-3 Likelihood of Earthquake Damage to Reinforced Concrete Walls According to Wall 

Component and Behavior Mode.

Behavior Mode Wall Component Type

Isolated Wall or Stronger Wall 

Pier (RC1)

Weaker Wall Pier

(RC2)

Weaker Spandrel or Coupling Beam (RC3)

A. Ductile flexural response Common in well-designed walls

See Guide RC1A

May occur

See Guide RC2A

May occur, particularly if 

diagonally reinforced

Similar to Guide RC2A

B. Flexure/Diagonal tension Common 

See Guide RC1B

Common

Similar to Guide RC1B

Common

See Guide RC3B

C. Flexure/Diagonal compression (web crushing)

Common (frequently observed in 

laboratory tests) 

See Guide RC1C

May occur May occur

D. Flexure/Sliding shear May occur, particularly for squat 

walls 

See Guide RC1D

May occur Common 

See Guide RC3D

E. Flexure/ Boundary-zone 

compression

Common

See Guide RC1E

May occur Unlikely

F. Flexure/Lap-splice slip May occur May occur May occur

G. Flexure/Out-of-plane 

wall buckling

May occur (observed in laboratory 

tests)

Unlikely Unlikely

H. Preemptive diagonal 

tension

Common

Similar to Guide RC2H

Common 

See Guide RC2H

Common 

Similar to Guide RC2H

I. Preemptive web crushing May occur in squat walls 

(observed in laboratory tests)

May occur May occur

J. Preemptive sliding shear May occur in very squat walls or 

at poor construction joints.

May occur in very squat 

walls or at poor construction joints.

Unlikely

K. Preemptive boundary 

zone compression

May occur in walls with unsymmetric sections and high axial 

loads

May occur in walls with 

unusually high axial load

Unlikely

L. Preemptive lap-splice 

slip

May occur May occur May occur

M. Global foundation 

rocking of wall

Common n/a n/a

N. Foundation rocking of 

individual piers

May occur May occur n/a

Notes: • Shaded areas of table indicate behavior modes for which a specific Component Damage Classification Guide is

provided in Section 5.5. The notation Similar to Guide... indicates that the behavior mode can be assessed by

using the guide for a different, but similar, component type or behavior mode.

• Common indicates that the behavior mode has been evident in postearthquake field observations and/or that experimental evidence supports a high likelihood of occurrence. 

• May occur indicates that the behavior mode has a theoretical or experimental basis, but that it has not been frequently reported in postearthquake field observations.

• Unlikely indicates that the behavior mode has not been observed in either the field or the laboratory.
 Chapter 5: Reinforced Concrete

FEMA 306 Basic Procedures Manual 81

a. Strength and Displacement Capacity

Flexural behavior governs the maximum strength 

achieved in behavior modes with intermediate ductility 

capacity. For these behavior modes, the full flexural 

strength will not be sustained at high levels of cyclic 

deformation. Section 5.3.5 gives guidelines for 

calculating flexural strength.

Displacement capacity may be difficult to assess for 

behavior modes with intermediate ductility capacity. 

One approach for estimating displacement capacity is to 

consider the intersection of the force-displacement 

curve for flexural response with a degrading strength 

envelope for the governing failure mechanism. The 

degrading strength envelope may represent, for 

example, lap-splice strength or shear strength. Useful 

research has been carried out using this approach. For 

example, Priestley et al. (1996) have developed specific 

recommendations on the degradation of strength as a 

function of ductility for lap-splice failure and shear 

failure.

b. Flexure/Diagonal Tension

The flexure/diagonal tension behavior mode occurs in a 

wall component when the shear strength in diagonal 

tension initially exceeds the flexural strength, allowing 

flexural yielding to occur. However, after the cracks 

open and the concrete in the plastic hinge zone 

degrades, the shear strength is reduced below the 

flexural strength, and shear behavior predominates.

At low levels of response, this behavior mode may 

appear similar to a ductile flexural response, although 

diagonal cracks due to shear stress may be more 

prominent. At higher levels of response, diagonal 

cracking tends to concentrate in one or two wide cracks. 

Eventually horizontal reinforcement can be strained to 

the point of fracture, signaling a diagonal tension 

failure.

c. Flexure/Diagonal Compression (Web Crushing)

For heavily reinforced walls subject to high shear 

forces, shear-related compression failures may occur 

rather than diagonal tension failures. This mode of 

behavior has been commonly observed in laboratory 

testing, and it may be prevalent in low-rise walls or 

when shear reinforcement is sufficient to prevent a 

diagonal tension failure. Higher axial loads also 

increase the likelihood of web-crushing behavior. 

Web crushing generally occurs after some degree of 

cyclic flexural behavior and degradation. The 

vulnerability to web crushing can be considered to be 

proportional to the story drift ratio to which the 

component is subjected. This behavior mode is 

characterized by diagonal cracking and spalling in the 

web region of the wall. Localized web crushing can be 

initiated by the uneven closing of diagonal cracks under 

cyclic earthquake forces.

d. Flexure/Sliding Shear

Coupling beams and low-rise walls are particularly 

vulnerable to failure by sliding shear. Low axial loads 

and poor construction joint details increase the 

probability of sliding shear.

In this behavior mode, flexural yielding initially 

governs the response. Flexural cracks at the critical 

section tend to join up to form a single crack across the 

section which becomes a potential sliding plane. Under 

cyclic forces and displacements, this crack opens more 

widely so that the aggregate interlock and shear friction 

resistance on the sliding plane degrade. When the 

sliding shear strength drops below the shear 

corresponding to the moment strength, lateral sliding 

offsets begin to occur.

For many low-rise walls, lateral strength may be 

governed by the strength of the foundation to resist 

overturning. Sliding shear behavior is likely to occur 

only in low-rise walls where the foundations have the 

capacity to force flexural yielding.

e. Flexure/Boundary-Zone Compression

Taller walls with adequate shear strength but inadequate 

boundary tie reinforcement tend to be vulnerable to this 

behavior mode. Under inelastic flexural response, the 

boundary regions of plastic hinge zones may be 

subjected to high compression strains, which cause 

spalling of the cover concrete. If sufficient tie 

reinforcement is not placed around the longitudinal bars 

in the wall boundaries, the longitudinal bars are prone 

to buckling. Additionally, in walls where concrete 

compressive strains exceed 0.004 or 0.005, the concrete 

in the boundary regions can rapidly lose compressive 

strength if it is not confined by adequate boundary ties. 

In addition to bar-buckling restraint and confinement, 

ties around the lap splices of boundary longitudinal bars 

significantly increase lap-splice strength.
 Chapter 5: Reinforced Concrete

82 Basic Procedures Manual FEMA 306

f. Flexure/Lap-Splice Slip

Lap splices in the critical plastic hinge regions of walls 

are commonly encountered in existing buildings. Even 

when relatively good lap-splice length is provided, lap 

splices in plastic hinge zones tend to slip when the 

concrete compressive strain exceeds 0.002, unless ties 

are provided around the lap splices. 

Slipping of lap splices is accompanied by splitting 

cracks in the concrete, oriented parallel to the spliced 

reinforcement. The use of tie reinforcement around lap 

splices, which restrains the opening of the splitting 

cracks, can prevent or delay the onset of lap-splice slip.

Once lap splices slip, the component strength falls 

below the full moment strength of the section and the 

strength is governed by the residual strength of the 

splices plus the moment capacity due to axial load.

g. Flexure/Out-of-Plane Wall Buckling

Several experimental studies have shown that thin wall 

sections can experience out-of-plane buckling when 

subjected to cyclic flexural forces and displacements. 

For typical wall sections the buckling occurs only at 

high ductility levels.

Single curtain walls and walls with higher amounts of 

longitudinal reinforcement tend to be more vulnerable 

to out-of-plane buckling. Walls with large story heights 

between floors that brace the wall in the out-of-plane 

direction are more vulnerable to buckling. T- or Lshaped wall sections with thin stems may also be more 

vulnerable. Walls with flanges or other enlarged 

boundary elements are less susceptible.

5.2.5 Behavior Modes with Little or 

No Ductility Capacity

The following five behavior modes can be considered to 

have little or no inelastic deformation capacity:

• Preemptive diagonal tension

• Preemptive diagonal compression (web crushing)

• Preemptive sliding shear

• Preemptive boundary-zone compression

• Preemptive lap-splice slip

The term preemptive is used to indicate that a brittle 

failure mode preempts any flexural yielding of the wall 

component. These are force-controlled rather than 

displacement-controlled behavior modes, as defined in 

FEMA 273.

a. Strength and Displacement Capacity

During preemptive boundary-zone compression, peak 

strength is equal to the component flexural strength. For 

the other four behavior modes of this category, strength 

will be less than the component flexural strength. 

Displacement capacity of these force-controlled 

behavior modes is limited to the elastic displacement 

corresponding to peak strength. These behavior modes 

cannot be considered to have any dependable inelastic 

displacement capacity.

b. Preemptive Diagonal Tension

Preemptive shear failure of wall components in 

diagonal tension has been commonly observed after 

earthquakes. This type of failure typically occurs in 

components with high flexural strength and inadequate 

shear reinforcement. The failure is characterized by one 

or more wide diagonal cracks, which can occur 

suddenly, with little or no early indication of incipient 

failure.

c. Preemptive Diagonal Compression (Web 

Crushing)

Preemptive web crushing is a compression failure 

caused by high shear forces in the web of a wall section. 

This behavior mode has been observed in laboratory 

tests of low-rise flanged walls. Walls with flanges or 

heavy boundary elements are more prone to this type of 

failure because larger shear stresses are typically 

generated in the webs of such sections, as compared to 

rectangular sections. The web crushing begins at small 

displacement values, preempting any flexural yielding 

of the wall.

This failure mode has not been reported in actual 

structures. Typical buildings do not have foundations 

with enough overturning capacity to sustain the high 

forces associated with preemptive diagonal 

compression failures.

d. Preemptive Sliding Shear

Preemptive sliding shear is most likely to occur in lowrise wall piers that have poor construction joints. Before 

flexural strength can be reached in such walls, sliding 

occurs along the surfaces of the construction joint.
 Chapter 5: Reinforced Concrete

FEMA 306 Basic Procedures Manual 83

e. Preemptive Boundary Zone Compression

This behavior mode only occurs in walls with unusually 

high axial load — above the balance point considering a 

maximum concrete strain of 0.004 or 0.005. Such 

conditions typically occur only in T- or L-shaped 

sections where the stem of the section is in compression 

and has inadequate boundary confinement.

f. Preemptive Lap-Splice Slip

Wall behavior governed by preemptive lap-splice slip 

has not been widely reported. Lap-splice lengths may 

need to be unusually short for splice failures to occur 

without prior flexural cyclic behavior. Damage in this 

behavior mode would be characterized by splitting 

cracks at lap splices and eventual rocking of the wall 

component on a crack across the lap-spliced section.

5.2.6 Foundation Rocking Response

Foundation rocking of walls and wall piers is usually a 

ductile mode of behavior. Capacities depend on the 

foundation type and geometry and the properties of the 

soil material. Displacement capacity is normally very 

high, but the effects of large foundation movements on 

the superstructure must be considered. FEMA 273 and 

ATC-40 provide detailed recommendations for 

foundation components.

5.3 Reinforced Concrete 

Evaluation Procedures

5.3.1 Cracking

The Component Damage Classification Guides require 

the user to distinguish between flexural cracks and 

shear cracks, to identify vertical cracking in the 

compression zone of wall piers, and to identify 

horizontal cracking in the compression zone of wall 

spandrels. The guides also require the user to identify 

cracks that may indicate lap-splice slipping.

The guides require the user to determine crack widths, 

which is a factor in assessing the severity of earthquake 

damage in reinforced concrete wall components.

a. Flexural and Shear Cracks

Flexural cracks are those that develop perpendicular to 

flexural tension stresses. In wall piers, flexural cracks 

run horizontally; in wall spandrels, the cracks run 

vertically. Flexural cracks typically initiate at the 

extreme fiber of a section and propagate towards the 

section’s neutral axis. For components that have 

undergone cyclic earthquake displacements in both 

directions, opposing flexural cracks often join with each 

other to form a relatively straight crack through the 

entire section.

Shear cracks are those that result from diagonal tension 

stresses corresponding to applied shear forces. The 

cracks run diagonally, typically at an angle of 35o to 70o 

from the horizontal. The angle of cracking depends on 

normal forces (e.g., axial load) and on the geometry of 

the component. For components that have undergone 

cyclic earthquake displacements of similar magnitude 

in both directions, the cracks cross each other, forming 

X patterns.

Flexural cracks often join up with diagonal shear 

cracks. A typical case is in a wall pier where a 

horizontal crack at the wall boundary curves downward 

to become a diagonal shear crack as it approaches the 

pier centerline. When shear cracks connect to flexural 

cracks, determine the widths of the flexural portion of 

the crack and the shear portion of the crack separately.

Cracks initially form perpendicular to the direction of 

the principal tension stresses in a section. At any point 

of a component, it is possible to relate the orientation of 

initial cracking to the applied stresses by considering 

the stress relationships represented by Mohr’s Circle. 

However, after initial cracking, the orientation of 

principal stresses will change and crack patterns and 

stress orientations are affected by the reinforcement.

b. Full-Thickness versus Partial-Thickness Cracking

In investigating reinforced concrete wall components, 

the engineer should establish whether critical flexural 

and shear cracks extend through the thickness of the 

wall. The Component Damage Classification Guides 

are written under the assumption that the most 

significant flexural and shear cracks are full-thickness 

cracks having a similar crack width on each side of the 

wall.

Laboratory tests on walls have invariably used in-plane 

loading. Therefore, significant cracks observed in these 

studies are typically full-thickness. In actual buildings, 

out-of plane forces and wall deformations may cause 

cracks to be partial-thickness, or they may result in 

cracks that remain open to a measurable width on one 

wall face, but are completely closed on the opposite 

wall face. In such cases, the engineer should use 

judgment in assessing the consequences of the critical 

cracks. It may be justified to use the average of the 

measured crack width on each face of the wall. More 
 Chapter 5: Reinforced Concrete

84 Basic Procedures Manual FEMA 306

conservatively, the maximum crack width on either face 

of the wall can be used in the Component Damage 

Classification Guides.

c. Cracking as a Precursor to Spalling

In the compression region of wall components, cracks 

occur as a precursor to concrete spalling. Such cracks 

form parallel to the principal compression stresses, and 

they may develop when compressive strains in the 

concrete exceed 0.003 to 0.005. Such cracking typically 

signals an increased damage severity in the Component 

Damage Classification Guides. This type of cracking 

occurs (1) at the boundary regions of component 

plastic-hinge zones for flexural behavior, and (2) under 

a diagonal-compression (web-crushing) type of shear 

failure.

For wall piers in flexure, this type of cracking is 

vertical. For wall spandrels in flexure, the cracks are 

horizontal. In both cases, the cracks occur near the 

extreme fibers of the section in the plastic hinge 

zone(s). Such cracking is less likely in spandrels 

because of the absence of axial load.

The cracking in compression regions of flexural 

members could appear similar to splitting cracks 

resulting from lap-splice or bond slip of the 

reinforcement. Both types of cracking tend to occur in 

the boundary regions of plastic-hinge zones. Some 

distinguishing features of the two different types of 

cracks are described below:

Diagonal cracking in the web of the wall can be a 

precursor to a diagonal-compression (web-crushing) 

shear behavior. Unlike diagonal tension cracks, these 

cracks may not open widely, but under increasing 

damage, the cracks will be followed by spalling of the 

web concrete. This occurs because the compressive 

strength of concrete reduces in the presence of 

transverse tensile strains.

d. Splitting Cracks at Lap Splices

If lap splices are insufficient to develop the required 

tension forces in the reinforcement, slip occurs at the 

splices. The visible evidence of lap-splice slip is 

typically longitudinal cracks (parallel to the splice) that 

originate at the lap splice and propagate to the concrete 

surface. Thus, the crack locations reflect the locations 

of the lap-spliced reinforcement.

e. Crack Widths

Crack widths are to be measured according to the 

investigation procedures outlined in this document. In 

the Component Damage Classification Guides, the 

maximum crack width defines the damage severity. 

When multiple cracks are present, the widest crack of 

the type being considered (e.g., shear or flexure) 

governs the damage severity classification.

The maximum crack width may be significantly larger 

than the average width of a series of parallel cracks. 

Although average crack width may be a better indicator 

of average strain in the reinforcement, maximum crack 

width is judged to be more indicative of maximum 

reinforcement strain, and, in general, damage severity. 

A concentration of strain at one or two wide cracks 

typically indicates an undesirable behavior mode and 

more serious damage, whereas an even distribution of 

strain and crack width among numerous parallel cracks 

indicates better seismic performance.

The crack width criteria in the Component Damage 

Classification Guides are based on a comparison to 

research results, rather than on detailed analyses of 

crack width versus strain relationships. The criteria 

recognize that the residual crack width observed after 

an earthquake may be less than the maximum crack 

widths occuring during the earthquake.

5.3.2 Expected Strength and 

Material Properties 

a. Expected Strength

The capacity of reinforced concrete components is 

calculated initially using expected strength values. 

Expected strength is defined in Section 6.4.2.2 of 

FEMA 273 and Section 9.5.4.1 of ATC-40 as “the mean 

Cracks as a precursor to 

spalling in the compression 

region:

Bond or lap-splice splitting 

cracks:

• Occur under conditions 

of high compressive 

strain.

• Cracks may be 

relatively short. 

Sounding with a 

hammer (See 

Section 3.8) may reveal 

incipient spalling.

• Cracks occur at the 

extreme fibers of the 

section, typically 

within the cover of the 

concrete. 

• Occur at the locations of 

longitudinal 

reinforcement that is 

susceptible to bond or 

lap-splice slip. (Large 

bar diameters or 

inadequate lap-splice 

length.) 

• Cracks tend to be 

relatively long and 

straight, mirroring rebar 

locations. The cracks 

originate at the 

reinforcement and 

propagate to the concrete 

surface.
 Chapter 5: Reinforced Concrete

FEMA 306 Basic Procedures Manual 85

maximum resistance expected over the range of 

deformations to which the component is likely to be 

subjected.”

Expected component strength may be calculated 

according to the procedures of ACI 318 — or other 

procedures specified in this document — with a 

strength-reduction factor, φ, taken equal to 1.0. 

Expected material strength rather than specified 

minimum material strength is used in the calculations. 

Material strength values are discussed below.

b. Reinforcing Steel Strength

Tables 6-1 and 6-2 of FEMA 273 gives the specified 

yield and tensile strength of reinforcing steel that has 

been used in buildings since the turn of the century. 

ASTM A432 reinforcing steel, with a specified yield 

strength of 60 ksi, was introduced in 1959 (CRSI Data 

Report 11). Prior to this date, reinforcing steel typically 

had a specified yield strength of 40 ksi or less.

The actual yield strength of reinforcing steel typically 

exceeds the specified value, as discussed in Section 

9.5.4.1 of ATC-40. Tests by Wiss, Janney, Elstner 

Associates (1970) on ASTM A432 Grade-60 bars 

showed an average tensile stress of 67 ksi for bars at a 

strain of 0.005 and an average tensile stress of 70 ksi for 

bars at a strain of 0.008. Stresses were based on actual 

rather than nominal bar areas, and the standard 

deviation was about 7 ksi. Similarly, data cited by Park 

(1996) indicate that actual bar yield strength averages 

about 1.15 times the specified value. At moderate-tohigh ductilities, strain hardening will further increase 

the stress in yielding reinforcement. 

FEMA 273 (Section 6.4.2.2) and ATC-40 prescribe that 

expected strength values be calculated assuming a 

strength of yielding reinforcement equal to “at least 

1.25 times the nominal yield strength.” For this 

document, in the absence of applicable test data, the 

initial expected strength of yielding reinforcement, fye, 

is assumed equal to 1.25 times the nominal yield 

strength. A range of reinforcement strength, between 

1.1 and 1.4 times the nominal yield strength, can also be 

considered in the evaluation procedures, should field 

observation warrant.

Section 6.3.2 of FEMA 273 gives recommendations for 

establishing reinforcing steel strength by testing. 

c. Concrete Strength

Table 6-3 of FEMA 273 gives typical concrete 

compressive strength values that may be assumed in 

buildings according to year of construction and 

structural member type. These values can be considered 

as specified or nominal values, , rather than expected 

values, . If structural drawings are available that 

indicate specified concrete strengths, use the values 

from the drawings instead of the assumed values from 

the table. 

The actual concrete strength in existing structures can 

significantly exceed the specified minimum concrete 

strength, by factors of up to 2.3 (Park, 1996). For this 

document, in the absence of applicable test data, the 

initial expected concrete compressive strength is 

assumed to be equal to 1.5 times the specified strength. 

A range of concrete strength, between 1.0 and 2.0 times 

the specified strength, can also be considered in the 

evaluation procedures, when based on field 

observations. FEMA 273 and ATC-40 do not 

specifically address the relationship between expected 

and specified concrete strengths.

In the case that concrete compressive strength test 

results from the existing construction are available, use 

these results to establish the expected concrete strength. 

The expected concrete strength considers the likely 

strength increase of the concrete over time, as is 

discussed in Section 9.5.2.2 of ATC-40. In the absence 

of more specific data, the initial expected strength can 

be taken equal to 1.2 times the tested strength at 28 days 

after construction.

Section 6.3.2 of FEMA 273 gives recommendations for 

establishing concrete compressive strength by testing.

Concrete strength seldom has a significant effect on 

wall flexural strength. It will have a more significant 

effect on shear strength, one component of which is 

taken proportional to .

d. Concrete Modulus of Elasticity

The modulus of elasticity for concrete is calculated 

according to ACI-318, using the expected concrete 

strength as defined above.

5.3.3 Plastic-Hinge Location and 

Length

Plastic hinges occur at the critical flexural regions of 

wall members where moment demand reaches moment 

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86 Basic Procedures Manual FEMA 306

strength. For earthquake-induced forces, plastic hinges 

typically occur at the face of a supporting member or 

foundation. Lap splices may force plastic hinges to 

develop or concentrate at the ends of the lap-splice 

length.

Potential plastic-hinge locations are to be identified for 

all wall elements subjected to earthquake forces and 

displacements. The locations are established as part of 

identifying the governing mechanism for nonlinear 

lateral deformation of the structure, as described in 

Section 2.4.

Isolated walls or stronger wall piers (component type 

RC1) typically have a single plastic hinge region at the 

base of the wall. A plastic hinge could also occur above 

the base of a wall at a location of reduced strength such 

as (1) a setback of the wall, (2) a level where a 

substantial amount of the vertical reinforcement is 

curtailed, or (3) a level above which the number of 

walls resisting seismic forces is reduced.

The curtailment of reinforcement may need to be 

investigated in some detail. Plastic hinging may occur 

at an area of reinforcement curtailment because (1) 

higher mode effects cause a moment at that level which 

exceeds the moment diagram assumed in design, and 

(2) designers may not have extended reinforcement 

“beyond the point at which it is no longer required to 

resist flexure for a distance equal to the flexural depth 

of the member” as is required by ACI 318 (1995).

Weaker wall piers (component type RC2) under flexural 

behavior develop plastic hinges at the top and bottom 

regions of the component, typically at the face of the 

connecting spandrel or foundation component. 

Similarly, weak spandrels (component type RC3) under 

flexural behavior develop plastic hinges at each end of 

the component, typically at the face of the connecting 

wall piers.

Plastic hinges are developed only for the ductile 

flexural behavior mode or for behavior modes with 

intermediate ductility capacity in which flexure initially 

governs response. Wall components governed by 

preemptive shear failures or foundation rocking do not 

exhibit plastic hinging (although, for foundation 

rocking, the soil beneath the foundation could be treated 

conceptually as the plastic-hinge region). 

Plastic-hinge lengths define the equivalent zones over 

which nonlinear flexural strain can occur. The length of 

plastic hinging generally depends on the depth of the 

member and on the moment-to-shear ratio (M/V). Bond 

conditions of the reinforcement also affect the length 

over which yielding occurs and the penetration of 

reinforcement yielding into the supporting member.

For reinforced concrete, equivalent plastic-hinge length 

can be roughly estimated as equal to one-half the 

member depth (Park and Paulay, 1975). A similar 

estimate is applied to walls in Section 6.8.2.2 of FEMA 

273, where lp is “set equal to one half the flexural depth, 

but less than one story height.” The 1997 UBC (ICBO, 

1997) states that lp “shall be established on the basis of 

substantiated test data or may be alternatively taken as 

0.5lw.” 

Based on research specifically applicable to walls, the 

equivalent plastic-hinge length, lp, can be set at 0.2 

times the wall length, lw, plus 0.07 times the momentto-shear ratio, M/V (Paulay and Priestley, 1993).

Equivalent plastic-hinge length, as calculated above, is 

used to relate plastic curvature to plastic rotation and 

displacement. The actual zone of nonlinear behavior 

may extend beyond the equivalent plastic-hinge zone.

The Component Damage Classification Guides refer to 

the plastic hinge length to identify the zone over which 

nonlinear flexural behavior and damage may be 

observed. The expected zone of inelastic flexural 

behavior and damage in the Component Damage 

Classification Guides can be taken as two times lp.

In short spandrel beams, the plastic zones at the ends of 

the beam may merge. In diagonally reinforced coupling 

beams, the entire length of the spandrel will yield.

5.3.4 Ductility Classifications

In these evaluation procedures, ductility capacity and 

demand are classified as either low, moderate, or high. 

The following approximate relationship can be 

assumed:

Classification Displacement Ductility

Low Ductility μ∆ < 2

Moderate Ductility 2 ≤ μ∆ ≤ 5

High Ductility μ∆> 5
 Chapter 5: Reinforced Concrete

FEMA 306 Basic Procedures Manual 87

This is similar to the classification in Table 6-5 of 

FEMA-273, except that μ∆ = 5 is used as the threshold 

for high ductility, rather than μ∆ = 4. The less 

conservative value of five is considered more 

appropriate for damage evaluation, as opposed to 

retrofit design. The value of five also correlates best 

with the data for the shear strength recommendations of 

Section 5.3.6.b.

5.3.5 Moment Strength

The moment strength of a reinforced concrete 

component under flexure and possible axial loads is 

calculated according to conventional procedures, as 

defined in ACI-318, Section 10.2 (ACI, 1995), except 

that expected material strengths are used as discussed in 

Section 5.3.2 of this document. The moment strength 

accounts for all reinforcement that contributes to 

flexural strength. For example, the moment strength for 

a wall pier (component type RC1 or RC2) includes all 

well-anchored vertical bars at the section of interest, not 

just those in the wall boundaries. The axial load present 

on the wall component is taken into account in the 

calculation of moment strength. 

For wall components that experience significant 

earthquake axial loads, such as the piers in a coupled 

wall system, the moment strength in each direction 

must consider the axial load combination corresponding 

to moments in that direction.

For sections with an overall reinforcement ratio, ρg, less 

than 0.008 x (60ksi/fy) the expected cracking moment 

strength, Mcr, may exceed the expected moment 

strength Me. In such a case, both Me and Mcr are 

considered in determining the governing mechanism 

and behavior mode.

a. Uncertainties or discrepancies in strength

Typically, there should be little uncertainty in the 

calculation of moment strength for a reinforced 

concrete component if reinforcement sizes, layout, and 

the steel and concrete material strengths have been 

established. The possible range of axial load on the 

component must also be considered.

b. Effective Flange Width

When wall sections have flanges or returns, the moment 

strength includes the effective width of flanges that 

contribute to flexural strength. C-shaped, I-shaped, Lshaped, T-shaped, and box-shaped wall sections fall in 

this category. The effective flange width is a function of 

the moment-to-shear ratio (M/V) for the wall 

component. Moment strength is relatively insensitive to 

the assumed flange width in compression, but can be 

quite sensitive to the assumed flange width in tension. 

Underestimating the effective flange width could lead 

to a conclusion that a wall is flexure-critical when in 

reality it is shear-critical. Typically, as displacement (or 

ductility level) increases, more of the vertical 

reinforcement in the flange is mobilized to resist 

flexure, and the effective flange width increases.

For isolated (cantilever) walls, effective flange width 

can be related to wall height, hw, as described and 

illustrated in Section 5.22 of Paulay and Priestley 

(1992). For wider applicability to different loading 

patterns, the moment-to-shear ratio (M/V) can be used 

in place of the wall height.

FEMA 273 and ATC-40 prescribe an effective flange 

width of one-quarter of the wall height on each side of 

the wall web, with engineering judgment to be 

exercised if significant reinforcement is located outside 

this width. The 1997 UBC prescribes an effective flange 

width on each side of the wall web of 0.15 times the 

wall height. The proposed NEHRP Provisions for New 

Buildings (BSSC, 1997) prescribe a maximum effective 

width on each side of the wall web of 0.15 times the 

wall height for compression flanges and 0.30 times the 

wall height for tension flanges.

A more specific estimate of effective flange width is 

supported by research (Paulay and Preistley, 1992; 

Wallace and Thomsen, 1995) and is recommended in 

this document as defined below: 

The effective flange width in compression, on each side 

of the wall web, may be taken as 0.15 times the 

moment-to-shear ratio (M/V). The effective flange 

width in tension, on each side of the wall web, may be 

taken as 0.5 to 1.0 times the moment-to-shear ratio (M/

V). The effective width of the flange does not exceed 

the actual width of the flange, and the assumed flange 

widths of adjacent parallel walls do not overlap. 

The foundation structure should be checked to ensure 

that the uplift forces in tension flanges can be 

developed.
 Chapter 5: Reinforced Concrete

88 Basic Procedures Manual FEMA 306

c. Contribution of Frame and Slab Coupling to Wall 

Capacity

Beams and slabs that frame into a wall may contribute 

to the lateral capacity of the structural system. This was 

demonstrated in the testing of a full-scale seven-story 

wall structure in Japan (Wight, 1985). Beams transverse 

to the wall and in-line with the wall helped resist the 

lateral displacement of the wall, resulting in a total 

strength significantly greater than that of the wall alone.

5.3.6 Shear Strength

a. Shear Demand and Capacity

Consistent with the requirement in Section 2.4 to 

identify the mechanism of inelastic lateral response for 

the structure, shear demand is based on the expected 

strength developed at the locations of nonlinear action 

(e.g., plastic hinge zones). This is also addressed in 

Section 6.4.1.1 of FEMA 273.

For behavior modes with intermediate ductility capacity 

such as flexure/diagonal tension, flexure/diagonal 

compression, and flexure/sliding shear, the shear 

demand is based on the expected moment strength 

developed in the plastic hinge regions. The shear 

demand so derived can be magnified because of 

inelastic dynamic effects which change the pattern of 

inertial force in the building from the inverted triangular 

distribution typically assumed in analysis and design.

For the example of a cantilever wall with a plastic hinge 

at the base, the shear demand will equal the expected 

moment strength at the base divided by 2/3 the wall 

height for an inverted triangular distribution of lateral 

forces. However, if inelastic dynamic effects cause the 

pattern of lateral forces to approach a uniform 

distribution, then the shear demand will increase to a 

value equal to the expected moment strength at the base 

(which will still be developed) divided by 1/2 the wall 

height.

Inelastic dynamic effects have been studied by 

researchers, and a shear magnification factor, ωv, taken 

as a function of the number of stories, is recommended 

by Paulay and Priestley (1992). The dynamic 

amplification of shear demand can be considered by use 

of such a factor or by considering different vertical 

distributions of lateral forces in the nonlinear static 

analysis.

Traditional design equations for shear strength tend to 

reflect the lower bound of test results, but the overall 

correlation of the equations with the data is not good. 

While some wall specimens show strength values close 

to the prediction of design equations, others show 

strength values five times higher than the predicted 

values (Cardenas, 1973).

b. Diagonal Tension

FEMA 273 specifies that the shear strength of 

reinforced concrete walls be calculated according to 

Section 21.6 of ACI 318-95. The applicable ACI 

equations are:

Vn = Acv (2 + ρn fye) for walls with a ratio of

hw / lw greater than 2.0, and 

Vn = Acv (3 + ρn fye) for walls with a ratio of

hw / lw less than 1.5

FEMA 273 allows the use of these equations for walls 

with reinforcement ratios, ρn, as low as 0.0015 — 

below the 1995 ACI-specified minimum of 0.0025. For 

walls with reinforcement ratios below 0.0015, FEMA 

273 specifies that the strength calculated at ρn = 0.0015 

can still be used.

ATC-40 modifies the provisions of FEMA 273 and ACI 

318-95 for wall shear strength. The principal 

modifications are that Vn need not be taken lower than 

4 Acv, and that 2 is assumed for the concrete 

contribution to shear strength, regardless of the ratio of 

hw / lw. Reinforcement ratios less than 0.0025 are also 

addressed differently in the ATC-40 document, but in 

typical cases of light reinforcement, the 4 Acv lower 

limit governs the calculations.

The FEMA 273 and ATC-40 wall shear strength 

recommendations are design equations that do not 

explicitly consider:

• The effect of axial load on shear strength 

• The distinction between shear strength at plastichinge zones versus that away from plastic-hinge 

zones

• The potential degradation of shear strength at plastic 

hinge zones

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 Chapter 5: Reinforced Concrete

FEMA 306 Basic Procedures Manual 89

Equations for wall shear strength given in Paulay and 

Priestley (1992) recognize a significant increase in 

shear strength due to axial load level. The equations 

also recommend a much lower shear strength at plastichinge zones, accounting for potential degradation, than 

away from plastic-hinge zones. 

If warranted by the specific conditions under 

evaluation, an approach similar to that used by Priestley 

et al. (1996) and Kowalsky et al. (1997) for columns 

can be used. The following shear strength equation:

Vn = Vc + Vs + Vp (5-1)

expresses the shear strength as the sum of three 

components: the contributions of the concrete, steel, 

and axial load. Each of these components is defined as 

follows:

Vc = αβkrc bw(0.8lw) (5-2)

where krc is a function of ductility, as shown below:

krc = 3.5 for low ductility (μ∆ ≤ 2) and away from 

plastic hinge regions.

krc = 0.6 for high ductility (μ∆ ≥ 5)

For values of ductility between the above limits, krc is 

calculated by linear interpolation.

The coefficient α accounts for wall aspect ratio, as 

considered in the ACI-318 equations:

α = 3 – M/(0.8lwV) (5-3)

1.0 ≤ α ≤ 1.5

The coefficient β accounts for longitudinal 

reinforcement ratio, as recognized by ASCE/ACI Task 

Committee 426 (1973):

β = 0.5 + 20ρg (5-4)

β ≤ 1.0

where ρg is the ratio of total longitudinal reinforcement 

over gross cross-sectional area for the wall component.

Vs = ρnfye bwhd (5-5)

where hd equals the height over which horizontal 

reinforcement contributes to shear strength, taken as (lw

– c)cot θ, where θ equals the angle, from the vertical, of 

the critical inclined shear crack. θ is taken as 35 degrees 

unless limited to larger angles by the potential cornerto-corner crack. Thus hd does not exceed the clear 

height of a wall pier.

Vp = ((lw – c)Nu)/(2M/V) (5-6)

M/V is taken as the larger of the values at the top and 

bottom of the wall pier. Thus 2M/V should not be less 

than the clear height of the wall pier.

These shear strength equations might also apply to 

coupling beams, for which lw is the overall depth 

(measured vertically) of the coupling beam, and hd is 

the horizontal length over which vertical stirrups 

contribute to shear strength.

c. Diagonal Compression (Web Crushing)

Walls and wall piers that have sufficient horizontal 

reinforcement to prevent a shear failure in diagonal 

tension may still suffer a shear failure associated with 

diagonal compression or web crushing. Web crushing 

behavior becomes more likely at higher levels of lateral 

deformation, and for walls with higher axial loads, Nu.

The web-crushing shear strength of a wall can be 

estimated according to the following equation (Oesterle 

et al., 1983):

(5-7)

where δ is the story drift ratio to which the wall 

component is subjected. The above equation applies to 

a typical range of axial loads for walls: 0 < Nu / Ag < 

0.09. For walls with higher axial loads, Vwc is held 

constant at the value calculated for Nu / Ag = 0.09. 

Thus, Vwc does not exceed:

(5-8)

f ′

ce

V f

N

A f

b l wc

ce

u

g ce

= w w

′

+ − ′

F

H

G I

K

J

1 8

1 600 2000

0 8 . (. )

f ′

ce

f ′

ce

V f b l wc

ce

w w = ′

+

1 8

1 420

0 8 . (. )

δ
 Chapter 5: Reinforced Concrete

90 Basic Procedures Manual FEMA 306

The above expressions give a lower bound to the test 

data. Multiplying Vwc by 1.5 would give a reasonable 

upper bound to the web-crushing shear strength.

An alternative expression for the web-crushing shear 

strength is given in Section 5.44 of Paulay and Priestley 

(1992). This expression is based on displacement 

ductility rather than story drift and does not consider the 

effect of axial load.

The above procedures apply to the flexure/webcrushing behavior mode, and they indicate a 

degradation of web-crushing strength with increasing 

drift or ductility. Tests (Barda et al., 1976) have also 

shown preemptive web-crushing behavior; that is, web 

crushing that occurs at small displacement levels, 

before the wall has attained its flexural strength. The 

test results show that walls may suffer preemptive web 

crushing when shear stress levels exceed 12 to 

15 .

d. Sliding Shear

Sliding shear strength is assessed at construction joints 

and plastic hinge zones using the shear friction 

provisions of Section 11.7.4 of ACI 318-95. All 

reinforcement that crosses the potential sliding plane 

and is located within the wall section that resists shear is 

assumed to contribute to the sliding-shear strength.

Isolated Walls and Wall Piers. For isolated walls and 

wall piers, the potential sliding plane is a horizontal 

plane. Vertical reinforcement that crosses this plane and 

contributes to flexural strength also contributes to 

sliding-shear strength. 

Shear transfer occurs primarily in the web of a wall 

section rather than in wall flanges. All vertical bars 

located in the web of the wall section, or within a 

distance bw from the web, are considered effective as 

shear-friction reinforcement. For wall sections that have 

typical columns as boundary elements, the vertical bars 

in the wall web plus those in the boundary elements can 

be used for shear friction. For wall sections that have 

wide flanges as boundary elements, the vertical bars 

placed in the flanges, at a distance of more than bw from 

the web, are not considered effective for shear friction 

(Paulay and Priestley, 1992).

It may be argued that only the reinforcement on the 

tension side of the neutral axis should be effective in 

contributing to shear friction strength, but such a 

recommendation has not been well established or 

tested.

Sliding-shear strength is investigated at construction 

joints and at plastic-hinge zones. The quality of the 

construction joint should be considered in establishing 

the appropriate coefficient of friction, μ, as specified in 

ACI 318. At plastic-hinge regions, increasing cyclic 

deformations cause horizontal flexural cracks at the 

potential sliding plane to open more widely, which 

results in a degradation of sliding-shear strength. In 

such a case, the effective coefficient of friction, μ, can 

be considered to be reduced.

A more detailed assessment of the sliding-shear 

strength of squat walls can be carried out according to 

the recommendations in Section 5.7 of Paulay and 

Priestley (1992).

Coupling Beams. If diagonal tension failures are 

prevented by sufficient stirrup reinforcement, and if 

diagonal bars are not used, sliding shear is likely to 

occur in short coupling beams at moderate-to-high 

ductilities. According to Paulay and Priestley (1992), 

there is a danger of sliding shear occurring in coupling 

beams whenever Vu exceeds 1.2 (ln / h) bw d, 

(assuming diagonal bars are not present and stirrups 

prevent a diagonal tension failure). The provisions of 

the 1997 UBC require diagonal bars in coupling beams 

when Vu exceeds 4 bwd and ln/d is less than four.

For this document, in the absence of more detailed 

analyses, the sliding-shear strength of coupling beams 

may be assumed to be equal to 1.2 (ln / h) bw d at 

high ductility levels and may be assumed equal to 3(ln/

h) bwd at moderate ductility levels. Alternatively, a 

shear-friction approach could be considered for 

coupling beams. 

5.3.7 Wall Boundary Confinement

For walls responding in flexure, boundary-tie 

reinforcement is usually needed in the plastic hinge 

regions to allow high ductility values to be achieved. 

Table 6-18 of FEMA 273 and Table 9-10 of ATC-40 

reference the boundary confinement requirements of 

ACI 318-95, and both FEMA 273 and ATC-40 

reference the 1994 Uniform Building Code (ICBO, 

1994) and Wallace (1994, 1995). These references give 

substantially different recommendations for boundary 

tie requirements. 

f ′

ce

f ′

ce

f ′

ce

f ′

ce

f ′

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f ′

ce
 Chapter 5: Reinforced Concrete

FEMA 306 Basic Procedures Manual 91

Paulay and Priestley (1992) and the New Zealand 

concrete code (SANZ, 1995) present more widely 

applicable recommendations for wall boundary ties. An 

adaptation of these recommendations is given below.

For walls to achieve high ductility capacities, boundary 

ties must meet the following criteria:

a. Walls with :

Boundary ties are not required.

b. Walls with :

Boundary ties are necessary, as specified below, to 

prevent buckling of longitudinal bars:

• Boundary ties extend over a length of the wall 

section at the compression boundary greater than 

or equal to c', taken as the larger of c – 0.1lw or 

0.5c, where c is the distance from the 

compression face to the neutral axis.

• Boundary ties extend over a height of the wall at 

the plastic hinge region greater than or equal to 

2lp.

• Ties are spaced at no more than 6db, where db is 

the diameter of the longitudinal bar being tied.

• Each longitudinal bar is restrained against bar 

buckling by either a crosstie or a 90-degree bend 

of a hoop with dbt greater than or equal to 

0.25db; or is restrained by a hoop leg parallel to 

the wall surface which spans not more than 14 in. 

between 90-degree bends of the hoop, with dbt

greater than or equal to 0.4db. (dbt is the diameter 

of the crosstie or hoop.)

c. Walls with c > 0.15lw:

Boundary ties are necessary to prevent buckling of 

longitudinal bars and to confine the concrete to 

achieve higher compressive strains. In addition to 

meeting the requirements of item (b) above, ties are 

provided so that:

(5-9)

The term ρl

 is the local reinforcement ratio for flexural 

reinforcement, as defined below:

ρl = As/bsl

where As is the area of vertical wall reinforcement in a 

layer spaced at s1 along the length of the wall, and 

where b is the width of the wall at the compression 

boundary. 

Walls that do not meet the criteria for high ductility 

capacities, but which have some boundary ties in the 

plastic hinge region, spaced at no more that 10 db, and 

that have dimensions , can be assumed to 

achieve moderate ductility capacities .

5.3.8 Lap Splice Strength

As specified in Section 6.4.5 of FEMA 273 and Section 

9.5.4.5 of ATC-40, the strength of existing lap splices 

may be estimated according to the ratio of lap-length 

provided to the tension development length required by 

ACI 318-95. 

Thus, the strength of lap splices can be taken as:

fs = (lb/ld)fye (5-10)

Note that the tension development length, ld,

 is used in 

the above equations without the 1.3 splice factor of 

ACI-318, because the specified lap-splice lengths 

prescribed for new design are conservative (ATC 1996). 

For splices in plastic-hinge regions, the evaluation 

should consider that lap-splice slip may still be possible 

even if splice lengths are adequate according to the 

above criteria.

A method of assessing lap-splice strength and the 

ductility capacity of flexural plastic hinges that contain 

lap splices is given in Sections 5.5.4, 7.4.5, and 7.4.6 of 

Priestley et al. (1996). The method allows the 

calculation of strength based on a fundamental 

consideration of the mechanics of lap-splice slip. 

cl f ≤ ≤ w l ye 015 400 . / and ρ

cl f ≤ > w l ye 015 400 . / and ρ

A sh f

f

A

A

c

l sh c

ce

yhe

g

ch w

≥ ′ − F

H

G I

K

J

F

H

G I

K

J

F

H

G I

K 0 2 0 10J . .

where: fs = stress capacity of the lap splice

lb = provided lap-splice length

ld = tension development length for

straight bars, taken according to

ACI 318, Chapter 12

c l ≤ w 0 20 .

( ) 2 5 ≤ ≤ μ ∆
 Chapter 5: Reinforced Concrete

92 Basic Procedures Manual FEMA 306

When the lap-splice strength is less than that required to 

yield the reinforcement, the full moment strength of the 

section will not develop. Even when lap splices have 

sufficient capacity to yield the reinforcement, they may 

still slip when moderate ductility levels are reached. As 

developed for columns, the Priestley et al. (1996) 

method indicates that all lap splices may become prone 

to slipping when the concrete compressive strain 

reaches 0.002. The method gives an estimate of the 

degradation of lap splice strength with increasing 

ductility, which results in a loss of moment capacity 

down to a residual value based on axial force alone. 

5.3.9 Wall Buckling

Thin wall sections responding in flexure may be prone 

to out-of-plane buckling, typically at higher ductility 

levels. The 1997 UBC prescribes a minimum wall 

thickness of 1/16 the clear story height for walls that 

require boundary confinement. Out-of-plane buckling is 

possible in plastic-hinge regions of walls even if they do 

not require confinement. Paulay and Priestley (1992, 

1993) address the wall buckling phenomenon in detail, 

and the New Zealand concrete code (SANZ, 1995) 

provides design recommendations for minimum wall 

thickness based on the research. 

Flanged or barbell-shaped wall sections are typically 

not vulnerable to buckling, unless the flange is 

unusually narrow, having a width, b, less than that 

specified below.

Based on the research, the following simplified criteria 

are recommended: Walls with width, b, equal to or 

greater than lu/16 can be assumed to achieve high 

ductility capacity without buckling. Walls with b equal 

to lu/24 can be assumed to be vulnerable to buckling at 

moderate-to-high ductility levels.

The length, lu, is taken as the smaller of:

• The clear story height between floors bracing the 

wall in the out-of-plane direction, and

• 2.5lp for single-curtain walls and walls with ρl

greater than , or 2.0lp for two-curtain walls 

with ρl

 less than or equal to .

The term b is the width of the wall at the compression 

boundary. The term ρl

 is the local reinforcement ratio 

for flexural reinforcement, as defined in Section 5.3.7.

FEMA 273 and ATC-40 do not address overall wall 

buckling.

200 / fye

200 / fye
 Chapter 5: Reinforced Concrete

FEMA 306 Basic Procedures Manual 93

5.4 Symbols for Reinforced 

Concrete

Symbols that are used in this chapter are defined below. 

Further information on some of the variables used 

(particularly those noted “per ACI”) may be found by 

looking up the symbol in Appendix D of ACI 318-95.

Ach = Cross sectional area of confined core of wall 

boundary region, measured out-to-out of confining reinforcement and contained within a 

length c’ from the end of the wall, Section 5.3.7 

Acv = Net area of concrete section bounded by web 

thickness and length of section in the direction 

of shear force considered, in2 (per ACI)

Ag = Gross cross sectional area of wall boundary 

region, taken over a length c’ from the end of 

the wall, Section 5.3.7 

Ash = Total cross-sectional area of transverse reinforcement (including crossties) within spacing s

and perpendicular to dimension hc. (per ACI)

b = Width of compression face of member, in (per 

ACI)

bw = Web width, in (per ACI)

c = Distance from extreme compressive fiber to 

neutral axis (per ACI)

c’ = Length of wall section over which boundary 

ties are required, per Section 5.3.7 

db = Bar diameter (per ACI)

dbt = Bar diameter of tie or loop

= Specified compressive strength of concrete, psi 

(per ACI)

= Expected compressive strength of concrete, psi 

fy = Specified yield strength of nonprestressed reinforcement, psi. (per ACI)

fye = Expected yield strength of nonprestressed reinforcement, psi.

fyh = Specified yield strength of transverse reinforcement, psi (per ACI)

fyhe = Expected yield strength of transverse reinforcement, psi 

hc = Cross sectional dimension of confined core of 

wall boundary region, measured out-to-out of 

confining reinforcement

hd = Height over which horizontal reinforcement 

contributes to Vs per Section 5.3.6.b

hw = Height of wall or segment of wall considered 

(per ACI)

krc = Coefficient accounting the effect of ductility 

demand on Vc per Section 5.3.6.b

lp = Equivalent plastic hinge length, determined 

according to Section 5.3.3.

lu = Unsupported length considered for wall buckling, determined according to 5.3.9

ln = Beam clear span (per ACI)

lw = Length of entire wall or segment of wall considered in direction of shear force (per ACI). 

(For isolated walls and wall piers equals horizontal length, for spandrels and coupling beams 

equals vertical dimension i.e., overall depth)

Mcr = Cracking moment (per ACI)

Me = Expected moment strength at section, equal to 

nominal moment strength considering expected 

material strengths.

Mn = Nominal moment strength at section (per ACI)

Mu = Factored moment at section (per ACI)

M/V = Ratio of moment to shear at a section. When 

moment or shear results from gravity loads in 

addition to seismic forces, can be taken as 

Mu /Vu

Nu = Factored axial load normal to cross section 

occurring simultaneously with Vu; to be taken 

as positive for compression, negative for tension (per ACI)

s = Spacing of transverse reinforcement measured 

along the longitudinal axis of the structural 

member (per ACI)

s1 = spacing of vertical reinforcement in wall (per 

ACI)

Vc = Nominal shear strength provided by concrete 

(per ACI)

f ¢

c

f ′

ce
 Chapter 5: Reinforced Concrete

94 Basic Procedures Manual FEMA 306

Vn = Nominal shear strength (per ACI)

Vp = Nominal shear strength related to axial load per 

Section 5.3.6 

Vs = Nominal shear strength provided by shear reinforcement (per ACI)

Vu = Factored shear force at section (per ACI)

Vwc = Web crushing shear strength per Section 5.3.6.c

α = Coefficient accounting for wall aspect ratio 

effect on Vc per Section 5.3.6.b

β = Coefficient accounting for longitudinal reinforcement effect on Vc per Section 5.3.6.b

δ = Story drift ratio for a component, corresponding to the global target displacement, used in 

the computation of Vwc, Section 5.3.6.c

μ = Coefficient of friction (per ACI)

μ∆ = Displacement ductility demand for a component, used in Section 5.3.4, as discussed in Section 6.4.2.4 of FEMA-273. Equal to the 

component deformation corresponding to the 

global target displacement, divided by the 

effective yield displacement of the component 

(which is defined in Section 6.4.1.2B of 

FEMA-273). 

ρg = Ratio of total reinforcement area to cross-sectional area of wall.

ρl = Local reinforcement ratio in boundary region of 

wall according to Section 5.3.7

ρn = Ratio of distributed shear reinforcement on a 

plane perpendicular to plane of Acv (per ACI). 

(For typical wall piers and isolated walls indicates amount of horizontal reinforcement.) 
 Chapter 5: Reinforced Concrete

FEMA 306 Basic Procedures Manual 95

5.5 Reinforced Concrete Component Guides

The following Component Damage Classification 

Guides contain details of the behavior modes for 

reinforced concrete components. Included are the 

distinguishing characteristics of the specific behavior 

mode, the description of damage at various levels of 

severity, and performance restoration measures. 

Information may not be included in the Component 

Damage Classification Guides for certain damage 

severity levels; in these instances, for the behavior 

mode under consideration, it is not possible to make 

refined distinctions with regard to severity of damage. 

See also Section 3.5 for general discussion of the use of 

the Component Guides and Section 4.4.3 for 

information on the modeling and acceptability criteria 

for components.
 Chapter 5: Reinforced Concrete

96 Basic Procedures Manual FEMA 306

COMPONENT DAMAGE

CLASSIFICATION GUIDE

System: Reinforced Concrete

Component Type: Isolated Wall or Stronger Pier

Behavior Mode: Ductile Flexural

How to distinguish behavior mode:

By observation:

Wide flexural cracking and spalling should be concentrated in the 

plastic hinge zone, although minor flexural cracking (width not 

exceeding 1/8 in.) may extend beyond the plastic hinge zone. Shear 

cracks may occur but widths should not exceed 1/8 in. If cracks 

exceed this width, see RC1B. Vertical cracks and spalling may occur 

at the extreme fibers of the plastic hinge region (toe region). If there 

is spalling or crushing of concrete within the web or center area of 

the section, see RC1C. If reinforcing bars in the toe region buckle, 

see RC1E.

Ductile flexural behavior typically occurs in well-designed walls that 

have sufficient horizontal reinforcement and do not have heavy vertical (flexural) reinforcement.

Note: At low damage levels, damage observations will be similar to 

those for other behavior modes.

By analysis:

Strength in all other behavior modes, even after 

possible degradation, is sufficient to ensure that 

flexural behavior controls. Strength associated with 

shear, web crushing, sliding shear, and lap splices 

— taken for conditions of high ductility — exceeds 

moment strength. Foundation rocking strength 

exceeds moment strength. Boundary ties are sufficient to prevent bar buckling or loss of confinement, 

and wall thickness is sufficient to prevent overall 

buckling.

Refer to Evaluation Procedures for:

• Identifying plastic hinge locations and extent.

• Identifying flexural versus shear cracks.

• Calculation of moment, diagonal tension, webcrushing, sliding-shear, lap splice, and foundation 

rocking strength.

• Required boundary ties and wall thicknesses.

Severity Description of Damage Performance Restoration Measures

Insignificant Criteria: • No crack widths exceed 3/16 in., and

• No shear cracks exceed 1/8 in., and

• No significant spalling or vertical cracking

(Repairs may be necessary for restoration of 

nonstructural characteristics.)

λK = 0.8

λQ = 1.0

λD = 1.0

Typical Appearance:

Note:

lp is length of 

plastic hinge. 

See 

Section 5.3.3

RC1A

2lp
 Chapter 5: Reinforced Concrete

FEMA 306 Basic Procedures Manual 97

COMPONENT DAMAGE CLASSIFICATION GUIDE 

continued

Severity Description of Damage Performance Restoration Measures

Slight

λK = 0.6

λQ = 1.0

λD = 1.0

Criteria: • Crack widths do not exceed 1/4 in., and

• No shear cracks exceed 1/8 in., and

• No significant spalling or vertical cracking, and

• No buckled or fractured reinforcement, and

• No significant residual displacement.

• Inject cracks 

λK* = 0.9

λQ* = 1.0

λD* = 1.0

Typical 

Appearance:

Similar to insignificant damage, except wider 

flexural cracks and typically more extensive 

cracking.

Moderate

λK = 0.5

λQ = 0.8

λD = 0.9

Criteria: • Spalling or vertical cracking (or incipient spalling 

as identified by sounding) occurs at toe regions in 

plastic hinge zone, typically limited to the cover 

concrete, and

• No buckled or fractured reinforcement, and

• No significant residual displacement.

• Remove and patch spalled and loose 

concrete. Inject cracks.

λK* = 0.8

λQ* = 1.0

λD* = 1.0

Typical Appearance:

Crack widths typically do not exceed 1/4 in.

Note:

lp is length of plastic hinge. See Section 5.3.3

Heavy Not Used

Extreme Criteria: • Reinforcement has fractured. • Replacement or enhancement 

required.

Typical Indications

• Wide flexural cracking typically concentrated in 

a single crack.

• Large residual displacement.

RC1A

2lp

vertical cracking

and/or spalling
 Chapter 5: Reinforced Concrete

98 Basic Procedures Manual FEMA 306

COMPONENT DAMAGE

CLASSIFICATION GUIDE

System: Reinforced Concrete

Component Type: Isolated Wall or Stronger Pier

Behavior Mode: Flexure/Diagonal Tension

How to distinguish behavior mode:

By observation:

For insignificant to moderate levels of damage, indications will 

be similar to those for RC1A, although shear cracking may 

begin at lower ductility levels. At higher levels of damage, one 

or more wide shear cracks begin to form. 

Typically occurs in walls that have a low-to-moderate amount 

of horizontal reinforcement, and which may have heavy vertical (flexural) reinforcement. May be most prevalent in walls 

with intermediate aspect ratios, M/Vlw ≈ 2, but depending on 

the reinforcement, can occur over a wide range of aspect ratios.

By analysis:

Shear strength calculated for conditions of low ductility 

exceeds flexural capacity, but shear strength calculated for 

conditions of high ductility is less than the flexural capacity. 

Foundation rocking strength exceeds moment strength. 

Boundary ties are sufficient to prevent buckling of longitudinal bars and loss of confinement prior to shear failure. 

Wall thickness is sufficient to prevent overall buckling prior 

to shear failure. Sliding shear strength is not exceeded.

Refer to Evaluation Procedures for:

• Identifying plastic hinge locations and extent.

• Identifying flexural versus shear cracks.

• Calculation of moment, diagonal tension, web-crushing, 

sliding-shear, lap splice, and foundation rocking strength.

• Required boundary ties and wall thickness.

Severity Description of Damage Performance Restoration Measures

Insignificant Criteria: • Shear crack widths do not exceed 1/16 in., and

• Flexural crack widths do not exceed 3/16 in., and

• No significant spalling or vertical cracking.

(Repairs may be necessary for restoration of 

nonstructural characteristics.)

λK = 0.8

λQ = 1.0

λD = 1.0

Typical Appearance:

Note:

lp is length of 

plastic hinge. 

See 

Section 5.3.3

RC1B

2lp
 Chapter 5: Reinforced Concrete

FEMA 306 Basic Procedures Manual 99

COMPONENT DAMAGE CLASSIFICATION GUIDE 

continued

Severity Description of Damage Performance Restoration Measures

Slight Not Used

Moderate

λK = 0.5

λQ = 0.8

λD = 0.9

Criteria: • Shear crack widths do not exceed 1/8 in., and

• Flexural crack widths do not exceed 1/4 in., and

• Shear cracks exceed 1/16 in., or limited spalling (or 

incipient spalling as identified by sounding) occurs 

at web or toe regions, and

• No buckled or fractured reinforcement, and

• No significant residual displacement.

• Remove and patch spalled and loose 

concrete. Inject cracks.

Typical 

Appearance:

Similar to insignificant damage except wider 

cracks, possible spalling, and typically more extensive cracking.

λK* = 0.8

λQ* = 1.0

λD* = 1.0

Heavy Criteria: • Shear crack widths may exceed 1/8 in., but do not 

exceed 3/8 in. Higher cracking width is concentrated 

at one or more cracks.

• Replacement or enhancement is 

required for full restoration of seismic 

performance.

λK = 0.2

λQ = 0.3

λD = 0.7

Note: λQ can 

be calculated 

based on shear 

strength at 

high ductility. 

See 

Section 5.3.6. 

Typical Appearance:

Note:

lp is length of 

plastic hinge. 

See Section 5.3.3

• For partial restoration of performance, 

inject cracks

λK* = 0.5

λQ* = 0.8

λD* = 0.8

Extreme Criteria: • Reinforcement has fractured. • Replacement or enhancement required.

Typical 

Indications

• Wide shear cracking typically concentrated in a 

single crack.

RC1B

2lp
 Chapter 5: Reinforced Concrete

100 Basic Procedures Manual FEMA 306

COMPONENT DAMAGE

CLASSIFICATION GUIDE

System: Reinforced Concrete

Component Type: Isolated Wall or Stronger Pier

Behavior Mode: Flexure/Web Crushing

How to distinguish behavior mode:

By observation:

For insignificant-to-moderate levels of damage, indications 

will be similar to those for RC1A and RC1B. At higher levels of damage, extensive diagonal cracking and spalling of 

web regions begins to occur.

Typically occurs in walls that have sufficient horizontal 

reinforcement, and that may have heavy vertical (flexural) 

reinforcement. May be more prevalent in low-rise walls, 

walls with higher axial loads, and in walls with flanges or 

heavy boundary elements.

By analysis:

Web crushing strength, calculated for high levels of story drift 

or ductility, is less than flexural strength.

Foundation rocking strength exceeds moment strength. Boundary ties are sufficient to prevent buckling of longitudinal bars 

and loss of confinement prior to web-crushing failure. Wall 

thickness is sufficient to prevent overall buckling prior to web 

crushing failure. Sliding shear strength is not exceeded.

Refer to Evaluation Procedures for:

• Identifying plastic hinge locations and extent.

• Identifying flexural versus shear cracks.

• Calculation of moment, diagonal tension, web-crushing, 

sliding-shear, lap splice, and foundation rocking strength.

• Required boundary ties and wall thickness.

Severity Description of Damage Performance Restoration Measures

Insignificant μ∆ ≤ 3 See RC1B See RC1B

Slight Not Used

Moderate

λK = 0.5

λQ = 0.8

λD = 0.9

Criteria: • Shear crack widths do not exceed 1/8 in., and

• Flexural crack widths do not exceed 1/4 in., and

• Limited spalling (or incipient spalling as identified 

by sounding) occurs at web or toe regions, or shear 

cracks exceed 1/16 in., and

• No buckled or fractured reinforcement, and

• No significant residual displacement.

• Remove and patch spalled and loose 

concrete. Inject cracks.

λK* = 0.8

λQ* = 1.0

λD* = 1.0

Heavy Criteria: • Significant spalling of concrete in web, and

• No fractured reinforcement.

• Remove and patch all spalled and loose 

concrete. Inject cracks.

λK = 0.2

λQ = 0.3

λD = 0.7

Typical Appearance:

Note:

lp is length 

of plastic 

hinge. See 

Section 5.3.3

λK* = 0.8

λQ* = 1.0

λD* = 1.0

Extreme Criteria: • Heavy spalling and voids in web concrete, or

significant residual displacement.

• Replacement or enhancement required.

RC1C

2lp
 Chapter 5: Reinforced Concrete

FEMA 306 Basic Procedures Manual 101

COMPONENT DAMAGE

CLASSIFICATION GUIDE

System: Reinforced Concrete

Component Type: Isolated Wall or Stronger Pier

Behavior Mode: Flexure/Sliding Shear

How to distinguish behavior mode:

By observation:

For insignificant-to-moderate levels of damage, indications 

will be similar to those for RC1A. In the plastic hinge zone, 

flexural cracks join up across the section, which becomes a 

potential sliding plane. At higher levels of damage, degradation 

of the concrete and sliding along this crack begin to occur.

Typically occurs in low-rise walls that have sufficient horizontal reinforcement. Sliding may occur at horizontal construction 

joints. May be more prevalent in walls with lower axial loads, 

and in walls with flanges or heavy boundary elements. 

Unlikely to occur if diagonal reinforcement crosses the potential sliding plane.

By analysis:

Sliding shear strength is less than shear corresponding to 

moment strength. 

Strength associated with diagonal tension, web crushing, 

and lap splices — taken for conditions of high ductility — 

exceeds moment strength. Foundation rocking strength 

exceeds moment strength. Boundary ties are sufficient to 

prevent buckling of longitudinal bars and loss of confinement prior to sliding. Wall thickness is sufficient to prevent overall buckling.

Boundary ties are insufficient to prevent bar buckling or 

provide adequate confinement.

Refer to Evaluation Procedures for:

• Identifying plastic hinge locations and extent.

• Identifying flexural versus shear cracks.

• Calculation of moment, diagonal tension, web-crushing, 

sliding-shear, lap splice, and foundation rocking 

strength. 

• Required boundary ties and wall thickness.

Severity Description of Damage Performance Restoration Measures

Insignificant See RC1A See RC1A

Slight See RC1A See RC1A

Moderate Not Used

Heavy

λK = 0.4

λQ = 0.5

λD = 0.8

Criteria: • Development of a major horizontal flexural crack 

along the entire wall length, with some degradation of concrete along the crack, indicating that 

sliding has occurred. Possible small lateral offset 

at crack.

• Remove and patch all spalled or loose 

concrete. Inject cracks.

λK* = 0.8

λQ* = 1.0

λD* = 1.0

Typical Appearance:

Crack widths typically do not exceed 3/8 in.

Note:

lp is length 

of plastic 

hinge. See 

Section 5.3.3

Extreme Criteria: • Significant lateral offset at sliding plane • Replacement or enhancement required.

RC1D

2lp
 Chapter 5: Reinforced Concrete

102 Basic Procedures Manual FEMA 306

COMPONENT DAMAGE

CLASSIFICATION GUIDE

System: Reinforced Concrete

Component Type: Isolated Wall or Stronger Pier

Behavior Mode: Flexure/Boundary Compression

How to distinguish behavior mode:

By observation:

For insignificant-to-moderate levels of damage, indications will be 

similar to those for RC1A (although spalling may occur at lower ductility levels). At higher levels of damage, boundary regions in plastic 

hinge zone begin to sustain spalling and crushing.

Flexure/boundary compression typically occurs in walls that have 

sufficient horizontal reinforcement and do not have well confined 

boundary regions. May be more prevalent in walls with a higher 

M/Vlw ratio.

Caution: When vertical cracks or spalling at boundary regions is 

observed, boundary reinforcement should be exposed and inspected 

for buckling or cracking.

By analysis:

Strength in all other behavior modes, even after 

possible degradation, is sufficient to ensure that 

flexural behavior controls. Strength associated 

with shear, web crushing, sliding shear, and lap 

splices — taken for conditions of high ductility 

— exceeds moment strength. Foundation rocking 

strength exceeds moment strength. Wall thickness is sufficient to prevent overall buckling.

Boundary ties are insufficient to prevent bar 

buckling or provide adequate confinement.

Refer to Evaluation Procedures for:

• Identifying plastic hinge locations and extent.

• Identifying flexural versus shear cracks.

• Required boundary ties and wall thickness.

• Calculation of moment, diagonal tension, webcrushing, sliding-shear, lap splice, and foundation rocking strength.

Severity Description of Damage Performance Restoration Measures

Insignificant See RC1A See RC1A

Slight See RC1A See RC1A

Moderate See RC1A See RC1A

Heavy

λK = 0.4

λQ = 0.6

λD = 0.7

Criteria: • Spalling or vertical cracking occurs at toe regions 

in plastic hinge zone, and

• Boundary longitudinal reinforcement is buckled 

or concrete within core of boundary regions (not 

just cover concrete) is heavily damaged.

• Remove spalled and loose concrete. 

Remove and replace buckled reinforcement. Provide additional ties 

around longitudinal bars of the critical 

boundary region, at the location of the 

replaced bars.

Typical Appearance:

Crack widths typically do not exceed 3/8 in.

Note: lp is length of plastic hinge. See Section 5.3.3

Patch concrete. Inject cracks.

λK* = 0.8

λQ* = 1.0

λD* = 1.0

Extreme See RC1A See RC1A

RC1E

buckled reinforcement and/or

heavily damaged concrete

2lp
 Chapter 5: Reinforced Concrete

FEMA 306 Basic Procedures Manual 103

COMPONENT DAMAGE

CLASSIFICATION GUIDE

System: Reinforced Concrete

Component Type: Weaker Pier

Behavior Mode: Ductile Flexural

How to distinguish behavior mode:

By observation:

Wide flexural cracking and spalling should be concentrated in the 

plastic hinge zone, although minor flexural cracking (width not 

exceeding 1/8 in.) may extend beyond the plastic hinge zone. 

Shear cracks may occur but widths should not exceed 1/8 in. Vertical cracks and spalling may occur at the extreme fibers of the 

plastic hinge region.

Ductile flexural behavior typically occurs in well-designed, slender wall piers that have sufficient horizontal reinforcement and do 

not have heavy vertical (flexural) reinforcement.

Note: At low damage levels, damage observations will be similar 

to those for other behavior modes.

By analysis:

Strength in all other behavior modes, even after possible degradation, is sufficient to ensure that flexural 

behavior controls. Strength associated with shear, 

web crushing, sliding shear, and lap splices — taken 

for conditions of high ductility — exceeds moment 

strength. Foundation rocking strength exceeds 

moment strength. Boundary ties are sufficient to prevent bar buckling or loss of confinement, and wall 

thickness is sufficient to prevent overall buckling.

Refer to Evaluation Procedures for:

• Identifying plastic hinge locations and extent.

• Identifying flexural versus shear cracks.

• Calculation of moment, diagonal tension, webcrushing, sliding-shear, lap splice, and foundation 

rocking strength.

• Required boundary ties and wall thickness.

Severity Description of Damage Performance Restoration Measures

Insignificant See RC1A See RC1A

Slight See RC1A See RC1A

Moderate

λK = 0.5

λQ = 0.8

λD = 0.9

Criteria: • Spalling or vertical cracking (or incipient spalling 

as identified by sounding) occurs at toe regions in 

plastic hinge zone, typically limited to the cover 

concrete, and

• No buckled or fractured reinforcement, and

• No significant residual displacement.

• Remove and patch spalled and loose 

concrete. Inject cracks.

λK* = 0.8

λQ* = 1.0

λD* = 1.0

Typical Appearance:

Crack widths typically do not exceed 1/4 in.

Note:

lp is length of 

plastic hinge. 

See 

Section 5.3.3

Heavy Not Used

Extreme See RC1A See RC1A

RC2A

2lp

2lp
 Chapter 5: Reinforced Concrete

104 Basic Procedures Manual FEMA 306

COMPONENT DAMAGE

CLASSIFICATION GUIDE

System: Reinforced Concrete

Component Type: Weaker Pier

Behavior Mode: Preemptive Diagonal Tension

How to distinguish behavior mode:

By observation:

For lower levels of damage, indications will be similar to those for 

other behavior modes, although flexural cracks may not be apparent. Damage quickly becomes heavy when diagonal cracks open 

up. Because flexural reinforcement never yields, flexural cracks 

should not have a width greater than 1/8 in.

Preemptive diagonal shear typically occurs in wall piers that have 

inadequate (or no) horizontal reinforcement, and that may have 

heavy vertical reinforcement. May be more prevalent in wall piers 

with low M/Vlw ratio.

By analysis:

Strength in shear at low ductility is less than the 

capacity corresponding to moment strength, foundation rocking strength, or lap-splice strength (at low 

ductility).

Refer to Evaluation Procedures for:

• Identifying flexural versus shear cracks. • Calculation of moment, shear, lap-splice, and foundation rocking strength.

Severity Description of Damage Performance Restoration Measures

Insignificant

λK = 0.9

λQ = 1.0

λD = 1.0

Criteria:

Typical

Appearance:

• No shear cracking and

• Flexural crack widths do not exceed 1/8 in.

Similar to RC2A except no shear cracking and 

smaller crack widths.

See RC1A

Slight Not Used

Moderate

λK = 0.5

λQ = 0.8

λD = 0.9

Criteria:

Typical

Appearance:

• No crack widths exceed 1/8 in. and

• No vertical cracking or spalling

Similar to insignificant damage except thin 

shear cracks may be present.

• Inject cracks 

λK* = 0.8

λQ* = 1.0

λD* = 1.0

Heavy Criteria: • Shear crack widths exceed 1/8 in., but do not 

exceed 3/8 in. Cracking becomes concentrated 

at one or more cracks.

• Replacement or enhancement is 

required for full restoration of seismic 

performance.

λK = 0.2

λQ = 0.3

λD = 0.7

Note: λQ can 

be calculated 

based on 

shear strength 

at high ductility See 

Section 5.3.6

Typical Appearance:

• For partial restoration of performance, 

Inject cracks.

λK* = 0.5

λQ* = 0.8

λD* = 0.8

Extreme Criteria:

Typical 

Indications

• Reinforcement has fractured.

• Wide shear cracking typically concentrated in a 

single crack.

• Replacement or enhancement required

RC2H
 Chapter 5: Reinforced Concrete

FEMA 306 Basic Procedures Manual 105

COMPONENT DAMAGE

CLASSIFICATION GUIDE

System: Reinforced Concrete

Component Type: Coupling Beam

Behavior Mode: Flexure/Diagonal Tension

How to distinguish behavior mode:

By observation:

For insignificant-to-moderate levels of damage, indications will be 

similar to those for RC1A, although shear cracking may begin at 

lower ductility levels. At higher levels of damage, one or more 

wide shear cracks begin to form. 

Flexure/Diagonal tension typically occurs in coupling beams that 

have inadequate stirrup reinforcement and that may have heavy 

horizontal (flexural) reinforcement. More prevalent in deeper 

beams than in shallower beams, but depending on the reinforcement, can occur over a wide range of aspect ratios.

By analysis:

Shear strength calculated for conditions of low ductility exceeds flexural capacity, but shear strength 

calculated for conditions of high ductility is less than 

the flexural capacity. 

Web crushing strength and sliding shear strength are 

not exceeded.

Refer to Evaluation Procedures for:

• Identifying plastic hinge locations and extent.

• Identifying flexural versus shear cracks.

• Calculation of moment, diagonal tension, webcrushing, sliding-shear, and lap splice strength.

• Required boundary ties and wall thicknesses.

Severity Description of Damage Performance Restoration Measures

Insignificant See RC1B See RC1B

Slight Not Used

Moderate See RC1B See RC1B

Heavy Criteria: • Shear crack widths may exceed 1/8 in., but do not 

exceed 3/8 in. Higher width cracking is concentrated at one or more cracks.

• Replacement or enhancement is 

required for full restoration of seismic 

performance.

λK = 0.2

λQ = 0.3

λD = 0.7

Note: λQ can 

be calculated 

based on 

shear 

strength at 

high ductility See 

Section 5.3.6

Typical Appearance: • For partial restoration of performance, 

Inject cracks.

λK* = 0.5

λQ* = 0.8

λD* = 0.8

Extreme See RC1B See RC1B

RC3B
 Chapter 5: Reinforced Concrete

106 Basic Procedures Manual FEMA 306

COMPONENT DAMAGE

CLASSIFICATION GUIDE

System: Reinforced Concrete

Component Type: Coupling Beam

Behavior Mode: Flexure/Sliding Shear

How to distinguish behavior mode:

By observation:

For insignificant-to-moderate levels of damage, indications will 

be similar to those for RC1A. Vertical flexural cracks join up 

across one or both ends of the section, which become a potential 

sliding plane. At higher levels of damage, degradation of the concrete and sliding along the critical crack begin to occur.

This behavior typically occurs in coupling beams that do not have 

diagonal reinforcement, but have sufficient stirrups to prevent 

diagonal tension failures.

By analysis:

Sliding shear strength is less than shear corresponding to moment strength. 

Strength associated with diagonal tension, web 

crushing, and lap splices for conditions of high ductility exceeds moment strength.

Refer to Evaluation Procedures for:

• Identifying plastic hinge locations and extent.

• Identifying flexural versus shear cracks.

• Calculation of moment, diagonal tension, webcrushing, sliding-shear, and lap splice strength. 

• Required boundary ties and wall thickness.

Severity Description of Damage Performance Restoration Measures

Insignificant See RC1D See RC1D

Slight See RC1D See RC1D

Moderate Not Used

Heavy

λK = 0.2

λQ = 0.3

λD = 0.7

Criteria: • Development of a major vertical flexural crack 

along the entire beam depth, with some degradation of concrete along the crack, indicating that 

sliding has occurred. Possible small lateral offset 

at crack.

• Remove and patch all spalled or loose 

concrete. Inject cracks.

λK* = 0.8

λQ* = 1.0

λD* = 1.0

Typical Appearance:

Crack widths typically do not exceed 3/8 in.

Extreme See RC1D See RC1D

RC3D
FEMA 306 Basic Procedures Manual 107 

6: Reinforced Masonry

6.1 Introduction and 

Background

This section provides material relating to reinforced 

masonry (RM) construction and includes the 

Component Damage Classification Guides (Component 

Guides) in Section 6.5. Reinforced masonry component 

types and behavior modes are defined and discussed in 

Section 6.2. The overall damage evaluation procedure 

uses conventional material properties as a starting point. 

Section 6.3 provides supplemental information on 

strength and deformation properties for evaluating 

reinforced masonry components. Typical hysteretic 

behavior for reinforced masonry components and the 

interpretation of cracking are discussed in FEMA 307. 

The information presented on reinforced masonry 

components has been generated from a review of 

available empirical and theoretical data listed in the 

reference section and the annotated tabular bibliography 

in FEMA 307. These provide the user with further 

detailed resources on reinforced masonry component 

behavior.

Unreinforced masonry components (URM) are covered 

in Chapter 7 of this document. The distinction between 

reinforced and unreinforced masonry can sometimes be 

an issue. In those cases, masonry with less that 25 

percent of the recommended minimum reinforcement 

specified in FEMA 273 should be considered 

unreinforced.

The most effective first step in identifying reinforced 

masonry components and their likely behavior modes is 

to place the structure in the context of the history of 

local construction practices, and to determine the type 

and amount, if any, of reinforcement used. There are 

examples of the use of iron to reinforce brick masonry 

construction in the 19th century; however, the 

widespread use of modern reinforced masonry did not 

begin until the 1930s. The use of reinforced masonry 

building systems was accelerated on the west coast 

following the 1933 Long Beach earthquake when the 

use of unreinforced masonry for new buildings in 

California was prohibited, so there is a distinct 

difference in building types in California before and 

after 1933. Reinforced masonry construction 

technology also developed in the east, although 

unreinforced masonry structures may still be built in 

some areas. The use of Portland cement mortars 

increased steadily from the beginning of the 20th 

century, as did the strength and quality of fired clay 

masonry. FEMA 274, Chapter 7, includes additional 

information on the history of masonry construction in 

the United States, as does the Brick Institute of America 

“Technical Notes on Brick Construction, No. 17.” (BIA, 

1988)

A wide variety of construction systems may be 

classified as reinforced masonry. The most common 

are:

• Fully-grouted hollow concrete block

• Partially-grouted hollow concrete block

• Fully-grouted hollow clay brick

• Partially-grouted hollow clay brick

• Grouted-cavity wall masonry (two wythes of clay 

brick or hollow units with a reinforced, grouted 

cavity)

Most of these are addressed in this section; however, the 

quantity and quality of experimental data available for 

each type varies considerably. 

The last twenty-five years have seen a dramatic increase 

in masonry research over that in prior years, as 

evidenced by the proceedings of the International Brick/

Block Masonry Conferences (1969 - present), The 

North American Masonry Conferences (1976 - present), 

and the Canadian Masonry Symposia (1976 - present). 

Much of this work has been directed toward measuring 

strength and serviceability characteristics under gravity 

or wind loading or toward development of workingstress design methods. Since the early eighties, a 

growing number of studies have addressed the strength 

and deformation characteristics of reinforced masonry 

components under cyclic (simulated seismic) loading. 

Notable early studies include those at the University of 

California, San Diego (e.g., Hegemier et al., 1978), 

University of California, Berkeley (e.g., Hidalgo et al., 

1978 and 1979), and the University of Canterbury at 

Christchurch, New Zealand (e.g., Priestley and Elder, 

1982). In 1985, the Technical Coordinating Committee 

for Masonry Research (TCCMAR) organized the U.S.-

Japan Coordinated Program for Masonry Building 

Research. The majority of experimental data available 

today for the complete load-displacement response of 

reinforced masonry under fully-reversed cyclic loads 

(static and dynamic) were generated in this program 

(Noland, 1990). The U.S.-Japan Coordinated Program 

for Masonry Building Research (often referred to as the 
 Chapter 6: Reinforced Masonry

108 Basic Procedures Manual FEMA 306

“TCCMAR program”) included experimental and 

analytical studies on the seismic response of reinforced 

masonry materials, components, seismic structural 

elements, and complete building systems. 

Documentation of the data was thorough, and 

coordination of materials and methods between 

different research institutions was carefully controlled. 

Noland (1990) provides a complete list of experimental 

studies and associated publications.

Despite the variety of reinforced masonry systems in 

use, most of the TCCMAR research and earlier cyclicloading studies were conducted with fully-grouted, 

hollow concrete block masonry. Most of the 

Component Damage Classification Guides for 

reinforced masonry in this document therefore apply 

most directly to fully-grouted concrete block masonry. 

A series of coordinated studies (Atkinson and Kingsley, 

1985; Young and Brown, 1988; Hamid et al., 1989; 

Shing et al., 1991; Blondet and Mayes, 1991; Agbabian 

et al., 1989) have shown that the behavior characteristics of hollow concrete and hollow clay masonry in 

compression, in-plane flexure, and out-of-plane flexure 

are quite similar in terms of ductility and energydissipation characteristics, although clay masonry is 

generally of significantly higher strength. Clay masonry 

is also more likely to exhibit brittle characteristics and 

separation of faceshells from grout, whereas concrete 

masonry with well-designed grout can behave more 

homogeneously. For the purposes of this document, the 

behavior of fully-grouted hollow clay and hollow 

concrete masonry is assumed to be identical.

Relatively little work has been conducted on the seismic 

response of partially-grouted masonry. An extensive 

study of partially-grouted shear walls was conducted by 

NIST (Fattal, 1993), but the emphasis in reported 

results was on shear strength only. Schultz (1996) 

reports that in-plane response of partially-grouted walls 

with light horizontal reinforcement is characterized by 

vertical cracking at the junction of grouted and 

ungrouted vertical cells, propagating between 

horizontally grouted cells. Load degradation is 

associated with widening of the vertical cracks to 0.25”

and greater. Masonry pier tests conducted at the 

University of California, Berkeley (Hidalgo et al., 1978; 

Chen et al., 1978; and Hidalgo et al., 1979) included 

several partially-grouted specimens. Damage patterns 

for these specimens were not so different from fullygrouted specimens, and strength was only mildly 

affected by partial grouting. However, deformation 

capacity was dramatically decreased relative to 

identical walls with full grouting.

Seismic response of grouted brick-cavity wall masonry 

has also received relatively little attention. The masonry 

pier tests conducted at UC Berkeley (Hidalgo et al., 

1978; Chen et al., 1978; and Hidalgo et al., 1979) 

included 18 tests on two-wythe, grouted clay brick 

masonry. Failure modes were similar to those for 

hollow clay masonry, but tended to be more brittle, 

involving the development of vertical splitting cracks 

between the brick wythes and the grout. Horizontal 

reinforcement had little or no effect on the behavior of 

grouted brick-cavity walls failing in shear. This can be 

attributed to the rapid failure and delamination of the 

brick wythes, leaving a narrow and unstable groutreinforced core that was incapable of developing a 

stable flexural compression zone.

Component Damage Classification guides for 

reinforced masonry reflect the availability of 

experimental data for each of the reinforced masonry 

systems. Reinforced masonry systems that are not well 

represented by experimental tests are not included in the 

guides.

6.2 Reinforced Masonry 

Component Types and 

Behavior Modes

6.2.1 Component Types

Component types for reinforced masonry are 

conceptually very similar to those for reinforced 

concrete (see Chapter 5). Table 6-1 lists four common 

reinforced masonry component types. Note that 

components are distinguished in terms of both 

geometric characteristics and behavior modes.

Each component defined in Table 6-1 may suffer from 

different types of damage, acting either in a pure 

behavior mode such as flexure, or, more likely, in a 

mixed mode such as flexure degrading to shear or 

sliding-shear failure. Table 6-2 outlines the likelihood 

of different behavior modes occurring in components 

RM1 through RM4, and references the relevant 

Component Guides in Section 6.5. 

Table 6-3 outlines the manner in which the strength and 

deformation capacity of each behavior mode may be 

evaluated. A detailed description of each entry in Table 

6-3 is given in Section 6.3. Additional example 

hysteresis curves are provided in FEMA 307, Section 3.
 Chapter 6: Reinforced Masonry

FEMA 306 Basic Procedures Manual 109

6.2.2 Behavior Modes with High 

Ductility 

Reinforced masonry structural components with 

relatively high ductility exhibit some of the following 

common attributes:

• Wall piers with aspect ratios (height / length) of two 

or greater or spandrels with span to depth ratios of 

four or greater.

• Moderate levels of axial load (P/Ag < 0.10fme). High 

axial loads decrease ductility by increasing the strain 

in the flexural compression zone, resulting in 

crushing at lower curvatures than in lightly-loaded 

walls. Walls with very low levels of axial load may 

be limited by sliding shear capacity.

• Relatively large flexural demand compared to 

corresponding shear. An example is a wall with 

flexible or weak spandrels. The lack of significant 

intermediate rotational restraint on the wall leads to 

cantilever behavior with relatively high M/V ratios 

as compared to frame behavior.

• Very small, or no, tension flange. Development of 

reinforcement in tension flanges can result in overreinforced sections, dramatically limiting ductility. 

• Uniformly distributed reinforcement.

• Sufficient shear reinforcement to ensure flexural 

response

The initial expected strength of a ductile reinforced 

masonry component in flexure is given by the in-plane 

moment strength as defined in Section 7.4.4 of FEMA 

273. Flanges, particularly on the tension side, should be 

included as part of the critical section according to the 

limits set in FEMA 273. It is also important to consider 

the effects of axial load, and to consider all 

reinforcement in the wall as effective. The theoretical 

basis for calculating flexural strength of reinforced 

masonry walls follows the well-established principles 

of ultimate strength design for reinforced concrete, and 

there is sufficient experimental data to support its use 

for masonry. For additional discussion, see Priestley 

and Elder (1982), Shing et al. (1991), Kingsley et al. 

(1994), and Seible et al. (1994b). 

The displacement capacity of a ductile flexural wall can 

be determined with reasonable accuracy by idealizing it 

as a cantilever beam and calculating the flexural and 

shear deformations. Displacements following cracking, 

but prior to significant yielding, may be approximated 

using an effective cracked stiffness (Priestley and Hart, 

1989). After yielding, the wall can be idealized as 

having an equivalent plastic-hinge zone at the base, and 

displacement can be calculated using the methods 

presented in Paulay and Priestley (1992). 

With increasing distance from the plastic-hinge zone, 

the contribution of shear deformations to displacements 

is less significant, and a pure flexural model is 

sufficient. Seible et al. (1995) showed that at the 

maximum displacement in a five-story, full-scale 

reinforced masonry building, the shear deformation 

component of lateral displacement was as high as 50 

percent at the first story, and less than 10 percent at the 

fifth floor. Priestley and Elder (1982), Leiva and 

Klingner (1991), Shing et al. (1990a, b), and Kingsley 

et al. (1994) provide additional experimental evidence 

to support the calculation of displacements in ductile 

flexural walls. The probable displacement capacity of 

ductile flexural walls should be at least four times the 

yield displacement, or one percent of building drift. 

Table 6-1 Component Types for Reinforced Masonry

Component Type Description

RM1 Stronger pier Examples are cantilever walls that ultimately are controlled by capacity at their base (e.g., 

flexural plastic hinge, shear failure, rocking) and story-height wall piers that are stronger 

than spandrels that frame into them. Wall components may be rectangular (planar) or may 

include out-of-plane components (flanges) that can have a significant effect on the response. 

RM2 Weaker pier Wall piers controlled by shear failure (more likely) or flexural hinging at the top and bottom 

(less likely). Wall components may be rectangular (and planar) or may include out-of-plane 

components (flanges) that can have a significant effect on the response. 

RM3 Weaker spandrel or 

coupling beam

Masonry beams that are weaker than the wall piers into which they frame. These are often 

controlled by shear capacity and less frequently by flexure.

RM4 Stronger spandrel or 

coupling beam

Masonry beams that are stronger than the wall piers into which they frame. 
 Chapter 6: Reinforced Masonry

110 Basic Procedures Manual FEMA 306

Table 6-2 Likelihood of Earthquake Damage to Reinforced Masonry Components According to 

Component and Behavior Mode.

Ductility Behavior 

Mode

Wall Component Type

RM1

Stronger Pier

RM2

Weaker Pier

RM3

Weaker Spandrel

RM4

Stronger

Spandrel

High ductility

A Flexure Common

See Guide RM1A

Unlikely Common

See Guide RM3A

N/A

Foundation 

rocking

May occur, but not 

considered

See FEMA 273 or 

ATC-40

May occur, but not 

considered

See FEMA 273 or 

ATC-40

N/A N/A

Moderate 

ductility

B Flexure / 

Diagonal 

shear

Common

See Guide RM1B

Common

See Guide RM2B

May occur

Similar to Guide 

RM3A

N/A

C Flexure / 

Sliding shear

May occur 

See Guide RM1C

May occur

Similar to Guide 

RM1C

Unlikely N/A

D Flexure / Outof-plane 

instability

May occur following large displacement cycles 

See Guide RM1D

Unlikely Unlikely N/A

E Flexure / Lap 

splice slip

May occur

See Guide RM1E

Unlikely May occur N/A

F Pier rocking May occur

Similar to Guide 

RM1E

May occur

Similar to Guide 

RM1E

N/A N/A

Little or no 

ductility

G Preemptive 

diagonal 

shear

Common

Similar to Guide 

RM2G

Common

See Guide RM2G

Common

See Guide RM3G

N/A

H Preemptive 

sliding shear

May occur in poorly 

detailed wall

Similar to Guide 

RM1C

May occur in 

poorly detailed wall

Similar to Guide 

RM1C

N/A N/A

Notes: • Shaded areas of the table with notation “See Guide...” indicate behavior modes for which a specific Component 

Guide is provided in Section 6.5. The notation “Similar to Guide...” indicates that the behavior mode can be 

assessed by using the guide for a different, but similar component type or behavior mode.

• Common indicates that the behavior mode has been evident in postearthquake field observations and/or that 

experimental evidence supports a high likelihood of occurrence. 

• May occur indicates that a behavior mode has a theoretical or experimental basis, but that it has not been frequently reported in postearthquake field observations. 

• Unlikely indicates that the behavior mode has not been observed in either the field or the laboratory.

• N/A indicates that the failure mode cannot occur for that component.
FEMA 306 Basic Procedures Manual 111

Table 6-3 Behavior Modes for Reinforced Masonry Components (Note: Hysteresis Curves from Shing et al., 1

Behavior Mode Approach to calculate strength (use expected material values) Approach to estimate dis- placement capacity Ductility Category Example hysteresA.Ductile Flexure The expected strength under in-plane forces is limited by the development of the expected moment strength, 

Me. 

This is calculated considering all distributed steel, axial loads, and the development of tension flanges, if present. Note that the maximum possible strength is greater than the expected strength, which may influence the governing mode.See Section 6.3.2a

The displacement capacity is limited by the maximum curvature attained within the effective plastic-hinge zone. Classical moment-curvature analysis may be used and related to displacement with some empirical calibration. See Sections 6.3.2b and 6.3.2c

High ductility capacitySee Section 6.2.2

B. Flexure / 

Shear

The initial expected strength is governed by 

Me, as calculated for the ductile flexural mode. Strength degrades 

as the masonry component of the shear strength, 

Vm, degrades, with residual 

strength governed by the reinforcement component 

Vs. 

See Sections 6.3.2a and 6.3.3a

Displacement capacity at the initial expected strength may be estimated as the intersection of the flexural load-displacement curve with the degrading shearstrength envelope.See Section 6.3.3b

Moderate ductility capacitySee Section 6.2.3

C. Flexure / 

Sliding shear

The initial expected strength is governed by 

Me, as calculated for the ductile flexural mode. Stiffness and 

strength degrade as sliding-shear mode develops, and hysteresis becomes pinched. The initial strength may be maintained, but only at large displacements.See Sections 6.3.2a and 6.3.4

Displacements due to sliding may be large. Displacement capacity for ductile flexural behavior may provide reasonable estimate. See Section 6.3.4b

Moderate-to-high ductility capacitySee Section 6.2.2 and 6.2.3
112 Basic Procedures Manual FEMA 306

D. Flexure / Out-of- plane stabil- ity The initial expected strength is gov- erned by 

Me, as calculated for the ductile flexural mode. Following 

instability failure, strength drops rapidly.See Sections 6.3.2a and 6.3.5

Displacement capacity is limited by the slenderness of the wall with respect to the height and/or the length.See Section 6.3.5

Moderate-to-high ductility capacitySee Section 6.2.2 and 6.2.3

E. Flexure / 

Lap splice slip

The initial expected strength is governed by 

Me, as calculated for the ductile flexural mode. With failure of lap 

splices, strength degrades to rocking mode, limited by crushing of wall toes.See Sections 6.3.2a and 6.3.6

Displacement capacity at expected strength limited by lap-splice slip.See Section 6.3.6

Moderate ductility capacitySee Section 6.2.3

G. Preemptive

diagonal shear

The expected strength is reached before the development of the expected moment capacity and is governed by shear strength, 

Ve. 

See Section 6.3.3

No inelastic capacity. No ductility capacity

See Section 6.2.4

H. Preemptive sliding 

shear

The expected strength is reached prior to the development of the expected moment capacity, and is governed by the sliding shear strength, 

Vse. 

See Section 6.3.4

Little displacement capacity, limited by crushing of bottom course of masonry and/or buckling of vertical reinforcement.

Little ductility capacitySee Section 6.2.4

Table 6-3 Behavior Modes for Reinforced Masonry Components (Note: Hysteresis Curves from Shing et al., 1
 Chapter 6: Reinforced Masonry

FEMA 306 Basic Procedures Manual 113

Damage in flexural walls is likely to include both 

horizontal and diagonal cracks of small size 

concentrated in the plastic-hinge region. Diagonal 

cracks typically propagate from horizontal, flexural 

cracks, and therefore have similar, regular spacing. At 

the large displacements, crushing may occur at the wall 

toes. 

Another relatively ductile behavior mode is foundation 

rocking. This can occur if the rocking capacity of the 

foundation is less than the strength of the wall 

component it supports. Foundation components are 

covered in FEMA 273 and ATC-40.

6.2.3 Behavior Modes with Moderate 

Ductility 

Moderately-ductile components initially behave 

similarly to highly-ductile components, but their 

ultimate displacement capacity is limited by the 

influence of less-ductile modes such as sliding or 

diagonal shear. The response of moderately-ductile 

components is difficult to predict analytically due to the 

complex interaction of moment, shear, and axial load, 

and less difficult to recognize in a damaged component. 

The majority of experimental data for reinforced 

masonry components falls into this moderately ductile 

category, For some examples, refer to Shing et al. 

(1991).

The initial strength is governed by the flexural capacity; 

however, the initial strength cannot be maintained at 

high ductility levels. Displacement capacity for 

moderate-ductility modes is difficult to calculate. 

Research is currently underway to improve the ability to 

predict displacements associated with diagonal shear 

modes of behavior, but there are currently no 

established guidelines, with the exception of the semiempirical recommendations in FEMA 273.

At low levels of response, damage in moderately ductile 

components resembles that for ductile components, 

consisting primarily of horizontal flexural and diagonal 

shear cracks. The component response at larger 

displacements depends on the governing behavior 

mode, as described in the following paragraphs.

a. Flexure / Diagonal shear

Diagonal shear response is characterized by the growth 

of diagonal cracks accompanied by degrading strength. 

Eventually, cracks cross the entire length of the wall, 

and the residual strength of the wall is that provided by 

the horizontal reinforcement alone. Extensive 

experimental evidence is available to document this 

behavior mode, including Shing et al. (1991), Hidalgo 

et al. (1978), and Chen et al.(1978).

b. Flexure / Sliding shear

Walls may be susceptible to sliding-shear mechanisms 

when axial load levels are low, vertical reinforcement 

ratios are low, or when very large ductilities are 

achieved and the shear friction mechanism degrades. At 

low displacements, sliding may be observed as a simple 

lateral offset in a wall. At very large displacements, 

localized crushing of the bottom course of masonry can 

result, and vertical reinforcement can experience large 

lateral offsets.

c. Flexure / Out-of-plane instability

At high ductility levels, the flexural compression zone 

of slender walls may be susceptible to instability after 

the development of large tensile strains during previous 

cycles. This type of failure has been observed in 

laboratory tests of well-detailed, highly-ductile flexural 

walls, (see Paulay and Priestley, 1993) but it has not 

been noted in the field. Out-of-plane instability would 

not be expected in walls with flanges at the end of the 

wall, or in very thick walls.

d. Flexure / Lap splice slip

If starter bars with insufficient development length are 

located at the base of structural walls, overturning 

forces can result in bond degradation and eventual 

rocking of the wall on the foundation. Local damage 

may appear first as vertical cracks at the location of the 

lap splices, and eventually crushing at the wall toes. 

(Priestley et al., 1978).

6.2.4 Behavior Modes with Low 

Ductility

General characteristics of reinforced masonry 

components exhibiting low-ductility behavior include:

• Wall piers with aspect ratios (height / length) of less 

than 0.8 and spandrels with span-to-depth ratios of 

less than two

• High levels of axial load (Pu/fme Ag > 0.15)

• Large tension flanges connected continuously to the 

component
 Chapter 6: Reinforced Masonry

114 Basic Procedures Manual FEMA 306

• Large amounts of flexural reinforcement at 

component edges

• Light shear reinforcement relative to flexural 

reinforcement

Experimental research on non-ductile walls under 

cyclic load histories includes Shing et al. (1991), 

Hidalgo et al. (1978), Chen et al. (1978), and Hidalgo et 

al. (1979).

Flexural capacity does not govern the nonductile modes 

of failure. Strength is defined by the diagonal shear 

strength or the horizontal sliding strength. In the first 

case, diagonal shear failure causes the lateral capacity 

of the wall to be immediately reduced to the capacity of 

the horizontal reinforcement alone. In the latter case, 

preemptive sliding of the wall does not allow the 

development of the full flexural capacity, resulting in 

large displacements with little capacity to dissipate 

hysteretic energy. It should be noted that bed-joint 

sliding in URM components may be considered as 

relatively ductile behavior. Calculation of the shear 

strength of masonry structural walls is addressed by 

Leiva and Klingner (1991), Shing et al. (1991), and 

Anderson and Priestley (1992).

Components that experience preemptive, forcecontrolled failures cannot be considered to have 

dependable inelastic displacement capacity.

Diagonal shear failure can occur with little or no early 

indication of incipient failure. Damage is characterized 

by one or two dominant diagonal cracks of large width. 

Damage may ultimately include crushing and spalling 

in the central portion of the wall. Walls that fail in 

sliding shear may have very little cracking or damage 

outside the sliding joint. Ultimately, crushing and 

spalling of the base course of masonry units can occur. 

6.3 Reinforced Masonry 

Evaluation Procedures

This section provides the basis for calculating the 

strength and deformation capacities of reinforced 

masonry components both before and after a damaging 

earthquake. Subsections are organized according to 

behavior modes. 

6.3.1 Material Properties 

The procedures for evaluating strength and deformation 

capacities presuppose the knowledge of component 

characteristics, including dimensions, amounts and 

location of reinforcement and the material properties. 

Methodologies for structural investigation and the 

evaluation of these parameters are given in Chapter 3. 

Additional guidelines for estimating masonry material 

properties are given in FEMA 273, Section 7.3.2.

If no information from testing is available, initial 

assumptions for expected material properties as given in 

FEMA 273 and summarized in Table 6-4 may be 

assumed.

a. Masonry

If observed failure modes are not consistent with the 

initial material strength values given above, actual 

expected values may be substantially greater (more than 

three times the table values).

b. Reinforcing steel

Recommendations in FEMA 273 Section 6.4.2.2. are 

adopted here for yield strength of reinforcement. In the 

absence of applicable test data, the expected strength of 

yielding reinforcement, fye, is assumed to be equal to 

1.25 times the nominal yield stress. A range of 

reinforcement strength values between 1.1 and 1.4 

times the nominal yield strength can also be considered 

in the evaluation procedures. 

6.3.2 Flexure 

a. Strength

The in-plane flexural capacity of a reinforced masonry 

wall with distributed reinforcement may be calculated 

based on the well-established principles of ultimate 

strength design, as stated in FEMA 273, Section 

Table 6-4 Initial Expected Clay or Concrete 

Masonry Properties

Condition Expected 

Strength fme

(psi)

Elastic 

Modulus

(psi)

Friction 

Coefficient

Good 900 550 fme 0.7

Fair 600 550 fme 0.7

Poor 300 550 fme 0.7
 Chapter 6: Reinforced Masonry

FEMA 306 Basic Procedures Manual 115

7.4.4.2.A. It is convenient to express this moment 

strength in terms of contributions from the masonry, the 

reinforcement, and the axial load independently, 

including all distributed reinforcement (Paulay and 

Priestley, 1992), as shown in Equation 6-1.

(6-1)

Where:

Me = expected moment capacity of a masonry 

section

Cm = compression force in the masonry

fye = expected reinforcement yield strength

Asi = area of reinforcing bar i

xi = location of reinforcing bar i

c = depth to the neutral axis

a = depth of the equivalent stress block

Pu = wall axial load

lw = length of the wall

Note that all bars are considered to participate, and it is 

assumed for the purpose of calculating the moment that 

all bars are yielding. This expression arbitrarily sums 

moments about the neutral axis of the section. In some 

cases, it may be more convenient to use a different 

location. For example, the axial component often passes 

through the centroid of the section and can be 

eliminated from the summation of moments at the 

centroid; however, its effect on moment capacity must 

be included by proper calculation of Cm.

The expression for moment strength is valid for 

masonry walls with reinforcement concentrated in the 

wall boundaries. Walls with concentrated 

reinforcement, particularly when larger bar sizes are 

used, are vulnerable to grout flaws in the wall toes. 

These walls are more likely to develop lap-splice slip or 

sliding-shear behavior modes.

b. Deformation

A ductile flexural component can be idealized as a 

cantilever element with a zone of concentrated plastic 

rotation at the base (the equivalent plastic hinge). 

Paulay and Priestley (1992) provide a simple model for 

calculating displacements. At first yield, the 

displacement at the level of the horizontal force 

resultant (i.e., the effective height), is

(6-2)

Where:

φy = yield curvature of a masonry section

he = effective height of the wall

The maximum displacement capacity at the effective 

height is:

(6-3)

Where:

φm = maximum plastic curvature of a masonry 

section

lp = effective plastic-hinge length (see 

Section 6.3.2c)

The displacement ductility is:

(6-4)

c. Plastic-Hinge Length

The concept of a plastic hinge in masonry is adopted as 

a computational convenience to describe in simple 

terms the complex distribution of cracks and the 

localized inelastic deformations in reinforcement. 

While there is no plastic hinge at a point per se, there is 

a zone over which the curvature may be expected to 

exceed the yield curvature at large displacements. The 

following expression for plastic-hinge length has been 

shown to agree reasonably well with experimental 

results for reinforced masonry walls (Paulay and 

Priestley, 1993), and is given in FEMA 274 Section 

C7.4.4.3A:

(6-5)

Where:

lw = length of the wall

he = height to the resultant of the lateral

force

= M/V

See also Shing et al. (1990a, b).

M Cc a fAcx P l c e m ye si i

i

n

u w = - F

H

G I

K

J + -+ - F

H

G I

K

J = 2 2 Â

1

b g

D y

y e h = f 2

3

D p m y p e p =- - d id i f f l h 0.5l

μ ∆

∆ ∆

∆

∆

∆ = +

= + y p

y

p

y

1

ll h pw e = + 0 2 0 04 . .
 Chapter 6: Reinforced Masonry

116 Basic Procedures Manual FEMA 306

For the purposes of this document, the plastic-hinge 

length is useful for calculating ultimate displacements 

in flexural walls, and for identifying the zone over 

which to expect degradation in shear strength with 

increasing ductility.

d. Flanges

When a flexural wall includes flanges, there is a 

potential to develop the flange reinforcement in flexural 

tension, thus increasing the flexural strength, and 

potentially decreasing the ductility capacity. In 

reinforced masonry, a flange can only be engaged when 

reinforcement and grout are continuous around the wall 

intersections. When calculating the flexural capacity of 

a flanged wall, FEMA 273, Section 7.4.4.2.C 

recommends that an effective flange width equal to 3/4 

of the effective wall height (he = M/V) should be 

assumed, (He and Priestley, 1992; Seible et al., 1994b).

Damage patterns in fully-engaged flanges appear as 

horizontal cracks, and possibly as the continuation of 

diagonal cracks from the in-plane wall. 

e. Coupling

Coupling between wall pier and spandrel components 

causes cyclic axial loads in the piers generated by shear 

in the spandrels. When the cyclic axial force is 

compressive, the pier strength is increased, and the 

ductility decreased. Similarly, when the axial force is 

tensile, the strength is decreased and the ductility is 

increased. For walls with relatively little gravity load, 

the tension force due to coupling can be sufficient to 

place the wall in a state of net tension. For the purposes 

of damage classification, the coupling-induced axial 

loads are to be considered when identifying the 

governing behavior mode.

Experimental data for reinforced masonry coupled 

walls is given in Seible et al. (1991), Paulay and 

Priestley (1992), and Merryman et al. (1990).

6.3.3 Shear

a. Strength

The in-plane shear capacity of an undamaged structural 

wall may be calculated using the recommended 

procedure in FEMA 273, Section 7.4.4.2.B, which may 

be expressed as the sum of three components 

corresponding to the contributions of masonry, 

reinforcement, and axial load, respectively:

(6-6)

where:

(6-7)

(6-8)

Vp = 0.25Pu (6-9)

In FEMA 273, the Vp component is included as a part of 

the Vm component; they are expressed separately here 

to facilitate the following discussion of degrading shear 

strength. Note that in FEMA 273, the total shear 

strength Ve is limited to:

for walls with M/Vd < 0.25 (6-10)

for walls with M/Vd 1.00 (6-11)

Equations 6-10 and 6-11 describe the maximum shear 

strength of an initially undamaged wall. As a flexural 

wall undergoes cyclic displacements, horizontal cracks 

initiate on the tension side of the wall and propagate 

towards the neutral axis, and diagonal cracks initiate 

near the center of the wall and propagate outward. As 

cracks open, horizontal reinforcement is engaged, and 

the mechanism of shear resistance in the masonry 

changes. The bulk of the masonry shear is transferred 

through the flexural compression zone – where the local 

shear strength is enhanced by the increasing 

compression stresses – and the remainder is transferred 

through aggregate interlock across the cracks. This 

mechanism degrades as both flexural and shear cracks 

open wider, until the capacity of the wall is reduced to 

nearly that of the horizontal reinforcement alone. 

Priestley, et al. (1994) have developed a model that 

captures this response for concrete columns, but such a 

relationship has not yet been developed and verified for 

masonry walls. Because it is nonconservative to ignore 

the degrading strength, however, the following 

relationship may serve for masonry in the area of the 

plastic-hinge zone until an improved model can be 

developed:

V V VV e msp = ++

V A m

M

Vl f

w

g me = − F

H

G I

K

J L

N

M O

Q

P 4 0 1 75 . .

V

A

s f d s v = ye vs

F

H

G I

K 0.5 J

V A e g me = 6 f

V A e g me = 4 f ≥
 Chapter 6: Reinforced Masonry

FEMA 306 Basic Procedures Manual 117

(6-12)

where k=1 for displacement ductility values less than 

1.5, and reduces linearly to a value of 0.1 at a 

displacement ductility of 4, and further to 0.0 at a 

displacement ductility of 8.

b. Deformation

Deformation mechanisms of walls with a predominant 

shear mode behavior cannot be quantified as simply as 

those of walls with flexural behavior modes, 

particularly after significant diagonal cracking and after 

yielding of reinforcement. As an approximation, the 

flexural force-displacement relationship can be 

developed, as described in Section 6.3.2, and the 

degrading shear strength relationship in Equation 6-12 

above may be used to identify the displacement at 

which shear modes of behavior begin to dominate the 

response.

6.3.4 Sliding

a. Strength

The ability of a structural masonry wall to resist sliding 

shear may be described in terms of shear friction across 

a crack or construction joint, as described in ACI 318-

95, Chapter 11. This friction may be visualized as 

having two components, (Paulay and Priestley 1992), 

the first due to the friction associated with the axial load 

on the wall, and the second due to the friction 

associated with the clamping force provided by the 

vertical reinforcement across the sliding plane, thus:

(6-13)

Where:

Pu = wall axial load

Avf = area of reinforcement crossing perpendicular to the sliding plane

fye = expected yield strength of reinforcement

μ = coefficient of friction at the sliding plane

Values for the coefficient of friction may be determined 

using the recommendations of ACI 318-95, Section 

11.7.4.3. Atkinson et al. (1988) determined that for 

mortared brick masonry joints, a value of 0.7 represents 

an average expected value. 

Uniformly distributed reinforcement is more effective 

in resisting sliding shear than is reinforcement 

concentrated at the ends of the wall. Distributed 

reinforcement leads to a larger flexural compression 

zone than does concentrated reinforcement, thus 

enhancing shear transfer across the plane. Distributed 

reinforcement is also located closer to the rough 

surfaces that generate the shear friction forces. 

Wall components that are classified as RM1 may be 

particularly vulnerable to sliding-shear behavior, or, 

more specifically, flexural response that degrades to 

sliding-shear response. The reason for this vulnerability 

is that, at the large curvature ductilities developed in the 

plastic-hinge zones of flexural walls, horizontal cracks 

open wide and cause the reinforcement across the 

sliding plane to yield. As the cracks open, the potential 

to develop the shear friction mechanism degrades, 

leaving only the comparatively flexible dowel-action 

mechanism of the reinforcing bars (Paulay and 

Priestley, 1992). Under cyclic reversals at large 

curvature ductility, it is possible to open a horizontal 

crack across the entire length of a wall. Sliding behavior 

is well documented for reinforced masonry walls (Shing 

et al., 1991), particularly those with light axial loads 

and light vertical reinforcement (Seible et al., 1994a, b).

b. Deformation

The deformation limit for sliding-shear behavior modes 

may be governed by the fracture of bars (dowels) 

crossing the sliding plane, crushing of the base course 

of masonry, or degradation of the shear and flexure 

transfer mechanisms in the flexural compression zone 

of the wall as the wall slides beyond its support.

6.3.5 Wall Instability

Out-of-plane buckling in the compression zone of 

flexural walls has been observed in experiments (Paulay 

and Priestley, 1992), but has not been reported for 

actual masonry structures subjected to earthquakes. The 

phenomenon is associated with compression stresses in 

flexural reinforcement that has achieved large inelastic 

tensile strains in previous cycles. Until the 

reinforcement yields in compression and the flexural 

cracks close, the reinforcement must carry the entire 

flexural compression force alone, thus leaving the wall 

in the compression zone vulnerable to buckling. 

Masonry walls, where the reinforcement is typically 

centered, are particularly vulnerable. Paulay and 

Priestley (1993) have suggested a simplified design 

relationship to calculate the critical wall width for 

Vk A m

M

Vl f

w

g me = − F

H

G I

K

J L

N

M O

Q

P 4 0 1 75 . .

V P Af se u vf ye = + m m
 Chapter 6: Reinforced Masonry

118 Basic Procedures Manual FEMA 306

which instability may limit ductility. For building 

evaluation, it is useful to determine the maximum 

ductility that may be expected for a given wall 

thickness. The following relationships, where the 

thickness, length, and height of the wall are given by t, 

l, and h, may be used to identify walls for which 

stability may be a limiting factor:

For or 

the displacement ductility may 

be no greater than μ∆ = 4 (6-14)

For and 

the displacement ductility will not be 

limited by stability (6-15)

Experimental tests on slender masonry walls at large 

ductilities suggest that this relationship may be 

conservative (Seible et al., 1994a, b). 

The lack of evidence for this type of failure in existing 

structures may be due to the large number of cycles at 

high ductility that must be achieved – most 

conventionally-designed masonry walls are likely to 

experience other behavior modes such as diagonal shear 

before instability becomes a problem.

6.3.6 Lap-Splice Slip

Relatively little research has been conducted 

specifically to investigate aspects of lap-splice slip that 

are unique to reinforced masonry as opposed to 

reinforced concrete (Hammons et al., 1994; Soric and 

Tulin, 1987). Experimental evidence of strength and/or 

deformation capacity of reinforced masonry 

components being limited by lap-splice slip failure has 

been noted in shear walls (Igarashi et al., 1993; Shing et 

al., 1991; Kubota and Murakami, 1988) and masonry 

beams (Okada and Kumazawa, 1987). Experimental 

studies in which lap splices were specifically avoided in 

plastic-hinge regions (Kingsley et al., 1994; Seible et 

al., 1994b; Shing et al., 1991) have shown superior 

performance over similar component tests including lap 

splices. In particular, the specimens without lap-splices 

in the plastic-hinge zones showed development of large 

curvature ductilities and well-distributed cracking in 

plastic hinge zones.

Research in Japan (for example, Seible et al., 1987; 

Okada and Kumazawa, 1987) has included the use of 

special spiral reinforcement for lap-splice confinement. 

Such reinforcement has been shown to limit 

successfully lap-splice slip, and to extend the effective 

plastic-hinge zone from one or two cracks to numerous 

cracks in the ends of masonry coupling beams or at the 

base of shear walls.

Studies to date indicate that lap splices in masonry are 

more susceptible to slip than are splices in concrete, 

because lap-splice regions in masonry are unlikely to 

include significant lateral confinement reinforcement. 

Hammons et al. (1994) found that splitting failure of 

masonry units in lap-splice regions was likely, 

regardless of lap-splice length, for bars #4 and greater 

in four-inch hollow units, #6 and greater in six-inch 

units, and #8 and greater in eight-inch units. While there 

are no experimental data on laps with more than two 

bars in a single grouted cell, it may be supposed that 

such bar configurations are susceptible to lap-splice 

failure.

For evaluation of lap-splice development length, ld, 

refer to FEMA 222A, NEHRP Recommended 

Provisions for Seismic Regulations for New Buildings, 

Section 8.4.5. The lap-splice equation in FEMA 222A 

should be modified to include the expected yield 

strength rather than the characteristic yield strength, and 

to use a strength-reduction factor of 1.0. 

Rocking in reinforced masonry walls may develop as a 

consequence of lap-splice failure at the base of shear 

walls. While the strength of the wall can be 

compromised dramatically, there is evidence to suggest 

that rocking can be a stable mechanism of energy 

dissipation (Priestley et al.,1978; Igarashi et al.,1993). 

The validity of such a mechanism depends on the 

deformation capacity of connected components relative 

to the increased displacement demand that results from 

rocking.

6.3.7 Masonry Beams

Because of the physical restrictions of typical hollow 

clay or concrete masonry units, it is difficult to provide 

satisfactory confinement reinforcement, and impossible 

to provide diagonal reinforcement of masonry spandrels 

or coupling beams. It is therefore difficult to avoid 

preemptive shear or, at best, flexure/shear behavior 

modes in masonry beams. Masonry beams which are 

t

lw

≤

1

24

t

he

≤

1

18

t

lw

≥ 1

12

t

he

≥ 1

8
 Chapter 6: Reinforced Masonry

FEMA 306 Basic Procedures Manual 119

detailed to allow ductile flexural response are likely to 

fall under the category of RM3 components.

Bending and shear capacity of reinforced masonry 

beams may be evaluated using the principles set forth in 

FEMA 222A (BSSC, 1994), incorporating expected 

material strengths rather than characteristic strengths, 

and setting strength reduction factors equal to 1.0.

Many tests have been conducted on masonry beams 

under gravity loading, but few have been conducted 

under reversed cyclic loading with boundary conditions 

representative of typical coupled wall systems (i.e. 

incorporating slabs). A number of studies have been 

conducted in Japan as a part of the JTCCMAR research 

program, including Matsuno et al. (1987), Okada and 

Kumazawa (1987), and Yamazaki et al. (1988a and 

1988b).
 Chapter 6: Reinforced Masonry

120 Basic Procedures Manual FEMA 306

6.4 Symbols for Reinforced 

Masonry

Ag = Gross crossectional area of wall

Asi = Area of reinforcing bar i 

Av = Area of shear reinforcing bar

Avf = Area of reinforcement crossing perpendicular 

to the sliding plane

a = Depth of the equivalent stress block

c = Depth to the neutral axis

Cm = Compression force in the masonry

fme = Expected compressive strength of masonry

fye = Expected yield strength of reinforcement

he = Effective height of the wall (height to the 

resultant of the lateral force) = M/V

ld = Lap splice development length

lp = Effective plastic hinge length

lw = Length of the wall

M/V = Ratio of moment to shear (shear span) at a 

section 

Me = Expected moment capacity of a masonry section

Pu = Wall axial load 

s = Spacing of reinforcement

t = Wall thickness

Ve = Expected shear strength of a reinforced 

masonry wall

Vm = Portion of the expected shear strength of a 

wall attributed to masonry

Vs = Portion of the expected shear strength of a 

wall attributed to steel

Vp = Portion of the expected shear strength of a 

wall attributed to axial compression effects

Vse = Expected sliding shear strength of a masonry 

wall

xi = Location of reinforcing bar i

∆p = Maximum inelastic displacement capacity

∆y = Displacement at first yield

φm = Maximum inelastic curvature of a masonry 

section

φy = Yield curvature of a masonry section

μ∆ = Displacement ductility

μ = Coefficient of friction at the sliding plane
 Chapter 6: Reinforced Masonry

FEMA 306 Basic Procedures Manual 121

6.5 Reinforced Masonry Component Guides

The following Component Damage Classification 

Guides contain details of the behavior modes for 

reinforced masonry components. Included are the 

distinguishing characteristics of the specific behavior 

mode, the description of damage at various levels of 

severity, and performance restoration measures. 

Information may not be included in the Component 

Damage Classification Guides for certain damage 

severity levels; in these instances, for the behavior 

mode under consideration, it is not possible to make 

refined distinctions with regard to severity of damage. 

See also Section 3.5 for general discussion of the use of 

the Component Guides and Section 4.4.3 for 

information on the modeling and acceptability criteria 

for components.
 Chapter 6: Reinforced Masonry

122 Basic Procedures Manual FEMA 306

RM1A COMPONENT DAMAGE

CLASSIFICATION GUIDE

System: Reinforced Masonry

Component Type: Stronger Pier

Behavior Mode: Ductile Flexural

Applicable

Materials:

Fully grouted hollow 

concrete or clay units

How to distinguish behavior mode:

By observation: 

Damage in an RM1 component with a flexural response is 

likely to be localized in a zone with a vertical extent equal to 

approximately twice the length of the wall. Both horizontal and 

diagonal cracks of small size (< 0.05 in.) and uniform distribution may be present. Diagonal cracks typically propagate from 

horizontal, flexural cracks, and therefore have similar, regular 

spacing. If shear deformations are localized to one or two diagonal cracks of large width, the behavior mode is likely to be 

Flexure/Shear or Preemptive Shear. If a permanent horizontal 

offset is visible, the behavior mode may be Flexure/Sliding 

Shear

Caution: At low damage levels, damage observations will be 

similar to those for other behavior modes.

By analysis:

A wall detailed to ensure ductile flexural response will have 

sufficient horizontal reinforcement to allow development of 

a flexural plastic hinge mechanism through stable and distributed yielding of the vertical bars at the base of the wall. 

The ultimate capacity of the horizontal reinforcement alone 

in the hinge zone should be greater than the shear developed 

at the moment capacity of the wall. Wall vertical loads are 

likely to be small. 

Refer to Evaluation Procedures for:

• Evaluation of flexural response.

• Identifying flexural versus shear cracks.

• Crack evaluation.

Severity Description of Damage Performance Restoration Measures

Insignificant Criteria: • No crack widths exceed 1/16”, and

• No significant spalling

Not necessary for restoration of structural 

performance. 

λK = 0.8

λQ = 1.0

λD = 1.0

Typical Appearance: (Cosmetic measures may be necessary 

for restoration of nonstructural 

characteristics.)
 Chapter 6: Reinforced Masonry

FEMA 306 Basic Procedures Manual 123

COMPONENT DAMAGE 

CLASSIFICATION GUIDE continued

Severity Description of Damage Performance Restoration Measures

Slight

λK = 0.6

λQ = 1.0

λD = 1.0

Criteria: • No crack widths exceed 1/8"

• No significant spalling or vertical cracking

• Inject cracks 

λK* = 0.9

λQ* = 1.0

λD* = 1.0

Typical 

Appearance:

Similar to insignificant damage except cracks are 

wider and more extensive.

Moderate

λK = 0.4

λQ = 0.9

λD = 1.0

Criteria: • Crack widths do not exceed 1/8"

• Moderate spalling of masonry unit faceshells or 

vertical cracking at toe regions

• No buckled or fractured reinforcement

• No significant residual displacement.

• Remove and patch spalled masonry and 

loose concrete. Inject cracks.

λK* = 0.8

λQ* = 1.0

λD* = 1.0

Typical 

Appearance: 

Similar to slight damage except cracks are wider 

and more extensive.

Extreme Criteria: • Reinforcement has fractured. • Replacement or enhancement required.

Typical Indications

• Wide flexural cracking (>1/8" residual) 

• Large residual displacement

• Extensive crushing or spalling

• Visibly fractured or buckled reinforcing

RM1A
 Chapter 6: Reinforced Masonry

124 Basic Procedures Manual FEMA 306

COMPONENT DAMAGE

CLASSIFICATION GUIDE

System: Reinforced Masonry

Component Type: Stronger Pier

Behavior Mode: Flexure / Shear

Applicable

Materials:

Fully grouted hollow 

concrete or clay units

How to distinguish behavior mode:

By observation:

Damage in an RM1 component with a flexural /shear response 

is typically localized to the base of the wall, within the plastic 

hinge region. Both horizontal and diagonal cracks will be 

present, with diagonal cracks predominant. Diagonal cracks 

may appear to be independent from horizontal, flexural cracks, 

and may propagate across the major diagonal dimensions. At 

heavy damage levels, shear deformations are likely to be localized to one or two diagonal cracks of large width. If a permanent horizontal offset is visible, the behavior mode may be 

Flexure/Sliding Shear

By analysis:

Analysis of a wall with a Flexure / Shear behavior mode 

may be difficult, with no clear distinction between the controlling mechanism of flexure (deformation-controlled) or 

shear (force-controlled). Calculated capacities should be in 

the same range. Wall axial loads may be moderate-to-high.

Refer to Evaluation Procedures for:

• Evaluation of flexural response.

• Evaluation of shear response

• Evaluation of plastic hinge length

• Identifying flexural versus shear cracks.

• Crack evaluation.

Severity Description of Damage Performance Restoration Measures

Insignificant Criteria: • No crack widths exceed 1/16”, and

• No significant spalling

Not necessary for restoration of structural 

performance. 

λK = 0.8

λQ = 1.0

λD = 1.0

Typical Appearance: (Cosmetic measures may be necessary 

for restoration of nonstructural characteristics.)

Slight

λK = 0.6

λQ = 1.0

λD = 1.0

Criteria: • No crack widths exceed 1/8”, and

• No significant spalling or vertical cracking

• Inject cracks

λK* = 0.9

λQ* = 1.0

λD* = 1.0

Typical 

Appearance:

Similar to insignificant damage except cracks are 

wider with more extensive cracking.

RM1B
 Chapter 6: Reinforced Masonry

FEMA 306 Basic Procedures Manual 125

COMPONENT DAMAGE 

CLASSIFICATION GUIDE continued

Severity Description of Damage Performance Restoration Measures

Moderate

λK = 0.4

λQ = 0.8

λD = 0.9

Criteria: • Crack widths do not exceed 3/16”

• Moderate spalling of masonry unit faceshells or 

vertical cracking at toe regions

• No buckled or fractured reinforcement

• No significant residual displacement

• Remove and patch spalled masonry 

and loose concrete. 

• Inject cracks.

λK* = 0.8

λQ* = 1.0

λD* = 1.0

Typical 

Appearance: 

Extreme Criteria: • Reinforcement has fractured • Replacement or enhancement required.

Typical 

Indications

• Wide flexural cracking (> 1⁄4”), typically concentrated in a single crack

• Wide diagonal cracking, typically concentrated 

in one or two cracks

• Crushing or spalling at wall toes of more than 

one-half unit height or width, delamination of 

faceshells from grout

• Visibly fractured or buckled reinforcing

Typical 

Appearance

RM1B
 Chapter 6: Reinforced Masonry

126 Basic Procedures Manual FEMA 306

COMPONENT DAMAGE

CLASSIFICATION GUIDE

System: Reinforced Masonry

Component Type: Stronger Pier

Behavior Mode: Flexure / Sliding Shear

Applicable

Materials:

Fully or partially 

grouted hollow concrete 

or clay units

How to distinguish behavior mode:

By observation:

Evidence of movement will appear first in the form of pulverized mortar across a bed joint or construction joint. If grout 

cores include shear keys into the slab below, short diagonal 

cracks initiating at the keys may be visible in the course above 

the sliding joint. After severe sliding, crushing of the bottom 

course of masonry may occur.

By analysis:

Walls with very light axial loads (P/f’m Ag ≤ 0.05) may be 

susceptible to sliding, as are walls with very light flexural 

reinforcement, or large ductility demands.

Refer to Evaluation Procedures for:

• Evaluation of sliding response.

Severity Description of Damage Performance Restoration Measures

Insignificant See RM1A See RM1A

Slight

λK = 0.5

λQ = 0.9

λD = 1.0

Typical 

Appearance

As for RM1A or RM1B and: Not necessary for restoration of structural 

performance. 

(Cosmetic measures may be necessary 

for restoration of nonstructural characteristics.)

Moderate

λK = 0.2

λQ = 0.8

λD = 0.9

Typical 

Appearance

Similar to slight with more extensive cracking 

and movement

• Remove and patch spalled masonry 

and loose concrete. 

• Inject cracks.

λK* = 0.8

λQ* = 1.0

λD* = 1.0

Extreme Criteria • Permanent wall offset

• Spalling and crushing at base

• Replacement or enhancement required.

Typical 

Appearance

As for 

RM1A or 

RM1B and:

RM1C
 Chapter 6: Reinforced Masonry

FEMA 306 Basic Procedures Manual 127

COMPONENT DAMAGE

CLASSIFICATION GUIDE

System: Reinforced Masonry

Component Type: Stronger Pier

Behavior Mode: Flexure / Out-of-Plane 

Instability

Applicable

Materials:

Fully or partially 

grouted hollow concrete 

or clay units

How to distinguish behavior mode:

By observation:

As for any unstable behavior mode, there will be little evidence 

of impending failure. Instability of the compression toe is preceded by large horizontal flexural cracks with significant plastic strains in the reinforcement crossing the crack. Evidence of 

such cracks, particularly when distributed across the plastic 

hinge zone rather than localized, may indicate incipient failure. 

Following failure, the wall will have visible out-of-plane displacements and localized crushing.

Caution: At low damage levels, damage observations will be 

identical to those for the RM1A behavior mode.

By analysis:

Walls with a tendency for compression toe instability will 

have large flexural displacement capacity, and little possibility for shear failure, even at large ductilities. Wall thickness will be less than or equal to the critical wall thickness 

for instability.

Refer to Evaluation Procedures for:

• Evaluation of flexural response.

• Evaluation of wall instability

• Identification of the plastic hinge zone.

Severity Description of Damage Performance Restoration Measures

Insignificant See RM1A See RM1A

Slight See RM1A See RM1A

Moderate See RM1A See RM1A

Heavy

λK = 0.4

λQ = 0.5

λD = 0.5

Typical 

Appearance

• Complete or partial replacement or 

enhancement required.

Extreme Criteria: • Compression toe of wall buckled.

• Reinforcement has fractured.

• Replacement or enhancement required.

• Wide flexural cracking.

• Laterally displaced units.

• Localized crushing or spalling.

RM1D
 Chapter 6: Reinforced Masonry

128 Basic Procedures Manual FEMA 306

COMPONENT DAMAGE

CLASSIFICATION GUIDE

System: Reinforced Masonry

Component Type: Stronger Pier

Behavior Mode: Flexure / lap splice slip

Applicable

Materials:

Fully or partially 

grouted hollow concrete 

or clay units

How to distinguish behavior mode:

By observation:

Walls that are vulnerable to lap splice slip will exhibit flexural 

response, and possible flexure/shear response, until the lap 

splice capacity is exceeded. Observed damage will therefore be 

very similar to RM1A and RM1B until lap splice slip occurs. 

Lap splice slip failure is characterized by splitting of the 

masonry units parallel to the reinforcing bars.

Caution: At low damage levels, damage observations will be 

identical to those for the RM1A behavior modes.

By analysis:

Walls that are vulnerable to lap splice slip may have:

• Bar size greater than:

#4 in 4 inch units

#6 in 6 inch units

#8 in 8 inch units

• Lap splice less than ld

Refer to Evaluation Procedures for:

• Evaluation of flexural response. • Evaluation of lap splice slip response.

• Evaluation of development length ld.

Severity Description of Damage Performance Restoration Measures

Insignificant See RM1A or RM1B See RM1A or RM1B

Slight See RM1A or RM1B See RM1A or RM1B

Moderate Criteria: • Vertical cracks at toe of wall, particularly in 

narrow dimension of wall.

See RM1A or RM1B

λK = 0.4

λQ = 0.5

λD = 0.8

Typical 

Appearance

RM1E
 Chapter 6: Reinforced Masonry

FEMA 306 Basic Procedures Manual 129

COMPONENT DAMAGE 

CLASSIFICATION GUIDE continued

Severity Description of Damage Performance Restoration Measures

Extreme Criteria: • Splitting of face shells at toe of wall

• Crushing and delamination of faceshells from 

grout cores

• Replacement or enhancement required.

Typical 

Appearance

• Wide flexural cracking and/or crushed units at 

base of wall

• Pulverized mortar at base – evidence of 

rocking.

RM1E
 Chapter 6: Reinforced Masonry

130 Basic Procedures Manual FEMA 306

COMPONENT DAMAGE

CLASSIFICATION GUIDE

System: Reinforced Masonry

Component Type: Weaker Pier

Behavior Mode: Flexure / Shear

Applicable

Materials:

Fully grouted hollow 

concrete or clay units

How to distinguish behavior mode:

By observation:

Damage in an RM2 component with a flexural/shear response 

may be localized to the first story, or it may be evident at a 

number of levels in story-height piers. Both horizontal and 

diagonal cracks may be present, with diagonal cracks predominant. Diagonal cracks may appear to be independent from horizontal flexural cracks, and propagate across the major diagonal 

dimensions. When severely damaged, shear deformations will 

be localized to one or two diagonal cracks of large width. If 

diagonal cracks are uniformly distributed and of small width, 

the behavior mode may be ductile flexure. If a permanent horizontal offset is visible, the behavior mode may include Flexure/

Sliding Shear.

By analysis:

Analysis of a wall with a Flexure / Shear behavior mode 

may not indicate a clear distinction between the controlling 

mechanism of flexure (deformation controlled) or shear 

(force controlled). Calculated capacities should be in the 

same range. Wall axial loads may be moderate to high.

Refer to Evaluation Procedures for:

• Evaluation of flexural response.

• Evaluation of shear response.

• Identifying flexural versus shear cracks.

• Crack width discussion.

Severity Description of Damage Performance Restoration Measures

Insignificant Criteria: • No crack widths exceed 1/16.”

• No significant spalling.

Not necessary for restoration of structural 

performance. 

λK = 0.8

λQ = 1.0

λD = 1.0

Typical Appearance:

May appear similar to flexure following small displacement 

cycles. Diagonal cracks often propagate from horizontal cracks.

(Cosmetic measures may be necessary 

for restoration of nonstructural characteristics.)

RM2B
 Chapter 6: Reinforced Masonry

FEMA 306 Basic Procedures Manual 131

COMPONENT DAMAGE 

CLASSIFICATION GUIDE continued

Severity Description of Damage Performance Restoration Measures

Slight

λK = 0.6

λQ = 1.0

λD = 1.0

Criteria: • No crack widths exceed 1/8”.

• No significant spalling or vertical cracking.

• Inject cracks. 

λK* = 0.9

λQ* = 1.0

λD* = 1.0

Typical 

Appearance:

Similar to insignificant damage, except cracks 

are wider and cracking is more extensive.

Moderate

λK = 0.4

λQ = 0.8

λD = 0.9

Criteria: • Crack widths do not exceed 3/16”.

• Moderate spalling of masonry unit faceshells or 

vertical cracking at toe regions.

• No buckled or fractured reinforcement.

• No significant residual displacement.

• Remove and patch spalled masonry and 

loose concrete. Inject cracks.

• Consider horizontal fiber composite 

overlay.

Typical 

Appearance: 

λK* = 0.8

λQ* = 1.0

λD* = 1.0

Extreme Criteria: • Reinforcement has fractured • Replacement or extensive enhancement 

required.

Typical 

Indications

• Wide flexural cracking typically > 1⁄4” concentrated in a single crack.

• Wide diagonal cracking, typically concentrated 

in one or two cracks

• Extensive crushing or spalling at wall toes, 

visible delamination of faceshells from grout

Typical 

Appearance

RM2B
 Chapter 6: Reinforced Masonry

132 Basic Procedures Manual FEMA 306

COMPONENT DAMAGE

CLASSIFICATION GUIDE

System: Reinforced Masonry

Component Type: Weaker Pier

Behavior Mode: Preemptive Shear

Applicable

Materials:

Fully grouted hollow 

concrete or clay units

How to distinguish behavior mode:

By observation:

At low levels of damage, wall may appear similar to RM2B. 

Diagonal cracks may be visible before flexural cracks. Damage 

occurs quickly in the form of one or two dominant diagonal 

cracks. Subsequent cycles may cause crushing or face shell 

debonding at the center of the wall and/or at the wall toes.

By analysis:

Calculated shear load capacity, including both masonry and 

steel components, will be less than or equal to shear associated with flexural load capacity

Refer to Evaluation Procedures for:

• Evaluation of flexural response.

• Evaluation of shear response.

• Evaluation of crack patterns.

• Crack evaluation.

Severity Description of Damage Performance Restoration Measures

Insignificant

λK = 0.9

λQ = 1.0

λD = 1.0

Criteria: • No diagonal cracks.

• Flexural crack <1/16”.

• No significant spalling.

Not necessary for restoration of structural 

performance. 

(Cosmetic measures may be necessary 

for restoration of nonstructural characteristics.)

Typical 

Appearance:

No visible damage.

Slight

λK = 0.8

λQ = 1.0

λD = 1.0

Criteria: • No crack widths exceed 1/16”.

• No significant spalling or vertical cracking.

• Inject cracks.

λK* = 0.9

λQ* = 1.0

λD* = 1.0

Typical 

Appearance:

Similar to insignificant damage, except that 

small diagonal cracks may be present.

RM2G
 Chapter 6: Reinforced Masonry

FEMA 306 Basic Procedures Manual 133

COMPONENT DAMAGE 

CLASSIFICATION GUIDE continued

Severity Description of Damage Performance Restoration Measures

Moderate

λK = 0.5

λQ = 0.8

λD = 0.9

Criteria: • Crack widths do not exceed 1/16”.

• No spalling of masonry unit faceshells or vertical 

cracking at toe regions.

• Inject cracks.

• Consider horizontally oriented fiber 

composite overlay.

λK* = 0.8

λQ* = 1.0

λD* = 1.0

Typical 

Appearance: 

May be several diagonal cracks, typically with 

one dominant crack.

Heavy Criteria: • Single dominant crack, may be > 3/8”. • Inject cracks.

• Provide horizontally oriented fiber 

composite overlay.

• Consider replacement.

λK = 0.3

λQ = 0.4

λD = 0.5

See FEMA 

307 for calculation of 

λQ

Typical

Appearance: 

Extreme Criteria: • Reinforcement has fractured. • Replacement or enhancement required.

Typical Indications

• Wide diagonal cracking, typically concentrated in one or two cracks.

• Crushing or spalling at center of wall or at 

wall toes.

RM2G
 Chapter 6: Reinforced Masonry

134 Basic Procedures Manual FEMA 306

COMPONENT DAMAGE

CLASSIFICATION GUIDE

System: Reinforced Masonry

Component Type: Weaker Spandrel

Behavior Mode: Flexure

Applicable

Materials:

Fully grouted hollow 

concrete or clay units

How to distinguish behavior mode:

By observation:

Masonry wall frames will develop numerous flexural cracks 

within the beam plastic hinge zones, with very little damage in 

the pier or joint regions. If significant damage develops in 

piers, component should be reclassified as RM2.

By analysis:

Wall frame dimensions and reinforcement satisfy the 

requirements of Section 2108.2.6 of the 1994 or 1997 UBC, 

or

the component can be shown by the principles of capacity 

design to develop flexural plastic hinges in the beams without developing the strength of the piers.

Refer to Evaluation Procedures for:

• Evaluation of flexural response. • Identification of the plastic hinge zone.

Severity Description of Damage Performance Restoration Measures

Insignificant

λK = 0.9

λQ = 1.0

λD = 1.0

Criteria: • No crack widths exceed 1/16”.

• No significant spalling.

Not necessary for restoration of structural 

performance. 

(Cosmetic measures may be necessary 

for restoration of nonstructural characteristics.)

Slight Criteria: • No crack widths exceed 1/8”.

• No significant spalling.

λK = 0.8

λQ = 0.9

λD = 1.0

Typical 

Appearance:

• Inject cracks.

λK* = 0.8

λQ* = 1.0

λD* = 1.0

Moderate Criteria: • No crack widths exceed 1⁄4”.

• Minor spalling (less than one unit depth) in 

beam ends.

• Replace spalled material.

λK = 0.6

λQ = 0.8

λD = 1.0

Typical 

Appearance:

• Inject cracks.

λK* = 0.8

λQ* = 1.0

λD* = 1.0

Extreme Criteria: • Reinforcement has fractured. • Replacement or enhancement required.

Typical 

Appearance

• Wide flexural cracking (> 3/8”).

• Significant crushing or spalling at junction of 

pier and beams.

RM3A
 Chapter 6: Reinforced Masonry

FEMA 306 Basic Procedures Manual 135

COMPONENT DAMAGE

CLASSIFICATION GUIDE

System: Reinforced Masonry

Component Type: Weaker Spandrel

Behavior Mode: Preemptive Shear

Applicable

Materials:

Fully or partially 

grouted hollow concrete 

or clay units

How to distinguish behavior mode:

By observation:

Cracking in reinforced masonry beams may be concentrated at 

the beam ends or distributed over the beam. Development of a 

plastic hinge zone is unlikely because of the difficulty of providing sufficient confinement reinforcement. Visible cracking 

is often a continuation of cracks in slabs or other adjacent elements, so beam damage should be evaluated in the context of 

the system behavior. If damage patterns appear to be associated 

with ductile flexural response, component may be reclassified 

as RM3.

By analysis:

Expected shear strength will typically be less than shear 

associated with the development of a flexural yielding 

mechanism at each end of the beam. If a stable plastic hinge 

can develop, component may be reclassified as RM3.

Refer to Evaluation Procedures for:

• Evaluation of flexural response.

Severity Description of Damage Performance Restoration Measures

Insignificant

λK = 0.9

λQ = 1.0

λD = 1.0

Criteria • Hairline cracks only. Not necessary for restoration of structural 

performance. 

(Cosmetic measures may be necessary 

for restoration of nonstructural characteristics.)

Moderate Criteria • Cracks < 1/8”.

λK = 0.8

λQ = 0.8

λD = 1.0

Typical 

Appearance

• Inject cracks.

λK* = 0.8

λQ* = 1.0

λD* = 1.0

Heavy Criteria • Cracks > 1/8”.

λK = 0.3

λQ = 0.5

λD = 0.9

Typical 

Appearance

• Inject cracks.

• Repair spalled areas

λK* = 0.8

λQ* = 1.0

λD* = 1.0

Extreme Criteria: • Reinforcement has fractured. • Replacement or enhancement required.

Typical 

Appearance

• Crushing or spalling at beam ends.

• Large diagonal cracks and / or spalling at center portion of beam.

RM3G
 Chapter 6: Reinforced Masonry

136 Basic Procedures Manual FEMA 306
FEMA 306 Basic Procedures Manual 137 

7: Unreinforced Masonry

7.1 Introduction and 

Background

7.1.1 Section Organization

This section summarizes evaluation methodologies and 

repair recommendations for earthquake-damaged 

unreinforced masonry (URM) bearing-wall buildings. 

Reinforced masonry is covered in Chapter 6. Masonry 

with less than 25 percent of the minimum reinforcement 

required by FEMA 273 (ATC, 1997a) should be 

considered unreinforced. This material supports and 

supplements the Component Damage Classification 

Guides (Component Guides) for URM components 

contained in Section 7.5. The section is organized as 

follows:

Section 7.1 discusses the various materials and 

structural systems used in URM buildings, evaluation 

of rehabilitated buildings, and the limitations of the 

URM guidelines.

Section 7.2 identifies typical URM elements, 

components, and behavior modes, as well as 

characteristics of the types of earthquake damage these 

components can experience. Behavior modes discussed 

include those resulting from in-plane and out-of-plane 

demands on walls and those occurring in other elements 

or due to the interrelationships between building 

elements. Information on the relative likelihood of 

occurrence of each damage type is included, where 

information is available. For in-plane behavior modes, 

the strength and displacement capacity of each mode is 

discussed along with uncertainties in capacity 

calculations.

Section 7.3 presents evaluation procedures for URM 

walls subjected to in-plane and out-of-plane demands. 

This section also identifies the testing that may be 

needed to provide information on required material 

properties. Symbols are listed in Section 7.4 and 

references are listed in the Reference section.

FEMA 307 provides a summary of the hysteretic 

behavior observed in experimental tests of URM 

specimens and commentary on the FEMA 273 forcedisplacement relationships. It describes the 

development of the λ-factors in the component guides 

of FEMA 306. FEMA 307 also provides a tabular 

summary of important experimental research and a list 

of other references on URM elements.

7.1.2 Material Types and Structural 

Framing

Unreinforced masonry is one of the oldest and most 

diverse building materials. Important material variables 

include masonry unit type, construction, and the 

material properties of various constituents. 

Solid clay-brick unit masonry is the most common type 

of masonry unit, but there are a number of other 

common types, such as hollow clay brick, structural 

clay tile, concrete masonry, stone masonry, and adobe. 

There are additional subgroupings within each of these 

larger categories. For example, as shown in FEMA 274, 

structural clay tile has been classified into structural 

clay load-bearing wall tile, structural clay non-loadbearing tile (used for partitions, furring, and 

fireproofing), structural clay floor tile, structural clay 

facing tile, and structural glazed facing tile. Hollow clay 

tile (HCT) is a more common term for some types of 

structural clay tile. Concrete masonry units (CMU) can 

be ungrouted, partially grouted, or fully grouted. Stone 

masonry can be made from any type of stone, but 

sandstone, limestone, and granite are common. Other 

stones common in a local area are used as well. 

Sometimes materials are combined, such as brick facing 

over CMU backing, or stone facing over a brick 

backing.

Wall construction patterns also vary widely, with bond 

patterns ranging from common running bond in brick to 

random ashlar patterns in stone masonry to stacked 

bond in CMU buildings. The variety of solid brick bond 

patterns is extensive. Key differences include the extent 

of header courses, whether collar joints are filled, 

whether cavity-wall construction was used, and the 

nature of ties between facing and backing wythes. In the 

United States, for example, typical running-bond brick 

masonry includes header courses interspersed by about 

five to six stretcher courses. Header courses help tie the 

wall together and allow it to behave in a more 

monolithic fashion for both in-plane and out-of-plane 

demands. The UCBC (ICBO, 1994) has specific 

prescriptive requirements on the percentage, spacing, 

and depth of headers. Facing wythes not meeting these 

requirements must be considered as veneer and are 

therefore not used to determine the effective thickness 

of the wall. Veneer wythes must be tied to the backing 

to help prevent out-of-plane separation and falling 

hazards. Although bed and head joints are routinely 

filled with mortar, the extent of collar-joint fill varies 

widely. Completely filled collar joints with metal ties 
 Chapter 7: Unreinforced Masonry

138 Basic Procedures Manual FEMA 306

between wythes help the wall to behave in a more 

monolithic fashion for out-of-plane demands. One form 

of construction where interior vertical joints are 

deliberately not filled is cavity-wall construction. Used 

in many northeastern United States buildings, the cavity 

helps provide an insulating layer and a means of 

dissipating moisture. The cavity also reduces the out-ofplane capacity of the wall.

Material properties—such as compressive, tensile, and 

shear strengths and compressive and shear moduli—

vary widely among masonry units, brick, and mortar. 

An important issue for in-plane capacity is the relative 

strength of masonry and mortar. Older mortars typically 

used a lime/sand mix and are usually weaker than the 

masonry units. With time, cement was added to the mix 

and mortars became stronger. When mortars are 

stronger than the masonry, strength may be enhanced, 

but brittle cracking through the masonry units may be 

more likely to occur, resulting in lower deformation 

capacity.

Given the wide range of masonry units, construction, 

and material properties, developing a comprehensive 

methodology for the evaluation of earthquake damage 

is difficult. The methodology in this document is most 

directly relevant to solid clay masonry laid in running 

bond with a typical spacing of header courses. 

Additional issues that should be considered for different 

conditions are identified in some cases.

For additional general background on URM materials, 

see ABK (1981a), FEMA 274, and Rutherford and 

Chekene (1997).

There is significant diversity in the characteristics of the 

structural systems used in URM bearing wall buildings. 

A primary issue is the rigidity of floor and roof 

diaphragms. While the 1994 UCBC includes provisions 

for both flexible and rigid diaphragms, the original 

ABK research, upon which it was based, primarily 

addressed flexible wood diaphragms (ABK, 1984). 

While such wood-diaphragm buildings are the most 

common, there are a substantial number of buildings 

with more rigid diaphragms, particularly in areas 

outside California. These include concrete slabs 

spanning between steel beams, hollow concrete planks, 

and brick and HCT arches spanning between steel 

beams.

Buildings with rigid floor and roof diaphragms will 

respond to earthquake shaking in a substantially 

different manner from those with flexible diaphragms. 

When rigid diaphragms are used, the traditional model 

of building behavior used in the building code is that of 

a lumped-mass system. In this model, the diaphragms 

represent the mass, and the vertical elements (such as 

walls) are flexible and are the primary source of the 

dynamic response experienced by the building. In 

contrast, in URM buildings with flexible diaphragms, 

the ABK model assumption is that the ground motion is 

applied to the ends of the flexible diaphragms without 

significant amplification. Any amplification that occurs 

is caused by the dynamic response of the diaphragm and 

the coupled out-of-plane walls. In some cases, the 

diaphragm may yield, limiting the forces that can be 

transmitted to the in-plane walls. In rigid-diaphragm 

URM buildings, diaphragm yielding is unlikely, and the 

frequency of response of the wall and diaphragms is 

likely to be much closer.

The methodology in this document is most directly 

relevant to URM bearing-wall buildings with flexible 

diaphragms. While FEMA 273 generally separates 

diaphragm issues from wall issues, there can be 

interrelationships between the two. Such issues are 

pointed out where appropriate.

7.1.3 Seismically Rehabilitated URM 

Buildings

When evaluating earthquake damage to unreinforced 

masonry buildings, it is important to determine the 

extent of seismic rehabilitation work that may have 

been performed, because this can affect the 

interpretation and significance of the damage. For 

example, if the building has not been seismically 

rehabilitated, horizontal cracking near the floor lines 

may be related to buckling of a slender wall. However, 

if wall-to-diaphragm ties have been installed in a 

rehabilitation effort, then the cracking may be related to 

an out-of-plane bed-joint sliding-shear failure in the 

mortar below the wall ties. If the wall is backed by 

shotcrete as is commonly done in a seismic 

rehabilitation, then the masonry wall cracking may be 

less significant than if there were no concrete present. 

URM buildings have been the focus of seismic-hazard 

mitigation policies, evaluation and rehabilitation 

standards, and seismic-strengthening efforts. On the 

west coast, in California in particular, a substantial 

number of URM buildings have been rehabilitated. 

Seismic strengthening practices and standards have 

evolved over the years, and the scope of work and 
 Chapter 7: Unreinforced Masonry

FEMA 306 Basic Procedures Manual 139

expected performance of the rehabilitated buildings 

varies significantly. It is important to appreciate the 

variety of potential rehabilitation work that may be 

encountered in the field. Using FEMA 273 terminology, 

performance objectives used in URM rehabilitation 

include:

• Limited Partial Rehabilitation efforts, such as those 

that address only certain specific elements such as 

parapets (e.g., San Francisco Parapet Safety 

Program).

• More substantial Partial Rehabilitation efforts such 

as the San Francisco “Bolts-plus” provisions that 

address parapets, wall-diaphragm ties, and wall 

bracing.

• Reduced risk rehabilitation programs such as the 

City of Los Angeles Division 88 and RGA 

requirements (Division 88, 1985 and SEAOSC, 

1986), the Uniform Code for Building Conservation, 

and FEMA 178 (BSSC, 1992)—all of which address 

the complete lateral-load-resisting system, but which 

require only a single-level check of the life safety 

performance level instead of the two-level check 

required by FEMA 273. Retrofit approaches using 

these methodologies may be capable of meeting the 

Basic Safety Objective if it can be shown that the 

building can meet the collapse prevention 

performance level for the BSE-2 earthquake as 

defined in FEMA 273.

• Basic Safety Objectives, such as the Field Act 

strengthening requirements for California 

elementary and secondary public schools.

• Enhanced Rehabilitation Objectives to limit damage 

and increase functionality have been implemented 

for a few select buildings.

While many voluntary and mandatory strengthening 

programs are in place in the west, and the number of 

rehabilitated URM buildings continues to grow 

nationwide, the vast majority of the rehabilitated URM 

buildings are those in Southern California strengthened 

to Division 88 (City of Los Angeles, 1985), RGA 

(SEAOSC, 1986) and similar standards and those in 

San Francisco that have complied with an earlier 

parapet safety program, but have not yet completed 

more stringent current requirements.

In general, this document is intended to be used with 

unrehabilitated buildings. The guidelines for in-plane 

and out-of-plane wall behavior assume, for example, 

that the wall has not been strengthened with other 

materials such as concrete, adhered fabric, or 

ferrocement overlays. If the URM wall has been 

strengthened with shotcrete or cast-in-place concrete, 

then the evaluating engineer will have to exercise 

judgment about the significance of the damage using 

both the provisions of Chapter 5 for reinforced concrete 

and those of Section 7. Generally, greater attention 

should be given to the damage in the concrete elements 

because they are usually the primary or intended lateralforce-resisting element. Fabrics and overlays have been 

the subject of experimental testing, but very limited 

rehabilitation has actually been performed using these 

techniques; as a result, they are not addressed in these 

provisions.

Even though the focus is on unrehabilitated buildings, 

the guidelines contain descriptions of damage and 

commentary on its interpretation for certain selected 

elements in rehabilitated buildings. Such commentary is 

based on observations from the 1987 Whittier, 1989 

Loma Prieta, and 1994 Northridge, California, 

earthquakes.

7.2 Unreinforced Masonry 

Component Types and 

Behavior Modes

7.2.1 Non-Wall Components

For the procedures in this document, structural systems 

are subdivided into elements, which are further 

subdivided into components that can be related to 

specific modes of behavior during seismic shaking. 

Components within URM bearing wall buildings 

include parapets, appendages, wall-diaphragm ties, 

diaphragms, and walls. The focus of this document is 

in-plane wall behavior modes. For other building types, 

such as concrete wall buildings, earthquake damage is 

primarily related to the in-plane behavior of the wall or 

displacement incompatibility between the walls and 

other elements. For URM bearing wall buildings, 

however, other elements and components figure 

prominently in observations of actual damage. In many 

cases, non-wall component damage may occur before 

in-plane damage to the wall becomes significant. These 

other features and their common behavior modes are 

discussed briefly below. The remainder of the document 

focuses on wall elements and components.
 Chapter 7: Unreinforced Masonry

140 Basic Procedures Manual FEMA 306

Parapets: These short extensions of walls above the 

roof typically occur at the perimeter of the buildings 

and are primarily present for fire safety or aesthetic 

reasons. As originally constructed, they are not braced 

back to the roof and are thus susceptible to brittle 

flexural out-of-plane failure (see Figures 7-1 and 7-2). 

Braced parapets typically fail at the connections 

between the parapet and the brace (see wall-diaphragm 

tie failures for similar examples).

Appendages: This category includes veneer, cornices, 

friezes, pediments, dentils, brackets, statuary, and 

finials—in short, any minor masonry feature that is 

susceptible to falling. Damage may result from 

excessive accelerations of appendages and 

deformations that cause connection failures between the 

appendage and the structure; delamination of veneer 

can result from missing or inadequate ties; deformation 

incompatibility between the appendage and structure 

can cause cracking and spalling; and pounding against 

adjacent buildings can lead to localized falling hazards 

(see Figures 7-3 and 7-4).

Wall-Diaphragm Ties: In the United States, wall-todiaphragm ties in existing URM buildings are generally 

limited to low-strength tension connections called 

“government anchors” or “dog anchors,” in which one 

end of a steel bar is embedded one wythe in from the 

outer face of the wall and the other end is hammered 

into the side of a wood joist. These ties typically occur 

where joists bear on the walls, not where they are 

parallel to the walls. Wall-diaphragm separation due to 

inadequate or missing tension ties can lead to out-ofplane failures of walls; missing shear ties can lead to the 

Figure 7-1 Diagram of Parapet Failure (from Rutherford and Chekene, 1990)
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FEMA 306 Basic Procedures Manual 141

diaphragm sliding along the in-plane walls and then 

pushing against the walls perpendicular to the 

movement, resulting in corner damage to the walls (see 

Figures 7-5, 7-6 and 7-7). In rehabilitated buildings, a 

variety of tie failures have been observed, including 

bond failures between the masonry and the cementitious 

grout used in older drilled dowel connections, cone 

failures due to shallow embedment and/or weak 

masonry, pullthrough of through-plated anchors, and 

bed-joint sliding near ties. Wall-diaphragm failures are 

often associated with thin walls (such as two-wythe 

walls at upper stories), poor mortar conditions, and lack 

of sufficient overburden pressure. 

Floor and Roof Diaphragms: Three categories of 

diaphragms can be identified: rigid concrete slab 

diaphragms, flexible wood and metal diaphragms, and 

intermediate systems such as hollow concrete planks 

and brick and HCT arches spanning between steel 

beams. In flexible diaphragms, excessive deflections 

can lead to out-of-plane wall damage. Hollow concrete 

plank systems may lack adequate interconnections to 

function as a continuous load path. Brick and HCT arch 

systems may be susceptible to vertical failure if beams 

separate locally. See Figure 7-8 for diagrams of some of 

the diaphragm types. Rigid concrete diaphragms are 

generally not significantly damaged or the source of 

damage to other elements in URM bearing wall 

buildings, but they do affect the dynamic behavior of 

the building.

Table 7-1 summarizes behavior modes for non-wall 

URM elements, providing the source of the deficiency, 

type of damage, and intensity of ground shaking usually 

required to produce the damage. The intensity of 

ground shaking is a qualitative judgment based on 

actual earthquake reconnaissance and damage 

collection efforts. Individual buildings may respond in a 

different manner. Even though some types of damage 

do not generally lead to collapse, they can nonetheless 

endanger life safety either within the building or around 

the perimeter due to localized falling hazards. A simple 

example is an exterior parapet failure, which rarely 

leads to building collapse, but still poses a risk to 

pedestrians adjacent to the wall. Damage to non-URM 

wall elements is typically brittle or force-controlled, 

and it often does not affect the overall forcedisplacement relationship for the building. The 

component guides in this volume focus on wall damage. 

For non-URM wall elements that can affect the overall 

force-displacement relationship, such as wallFigure 7-2 Photo of Parapet Failure (from Rutherford and Chekene, 1990).
 Chapter 7: Unreinforced Masonry

142 Basic Procedures Manual FEMA 306

diaphragm ties, it is important to include their behavior 

and characteristics in modeling efforts.

7.2.2 Wall Components

URM wall elements can be subdivided into five 

Component Types as shown in Figure 7-9, based on the 

mode of inelastic behavior. Figure 7-9 also shows some 

of the common behavior modes. The majority of modes 

relate to in-plane damage, but out-of-plane damage can 

occur as well in each of the systems, often in 

combination with in-plane damage. The five component 

types are described below.

URM1: Solid cantilever walls. Such walls are typically 

found adjacent to other buildings or on alleys, and they 

act as cantilevers up from the foundation.

URM2: This component is a weak pier in a perforated 

wall. In this system, inelastic deformation occurs in the 

piers.

URM3: This component is a weak spandrel in a 

perforated wall. Inelastic deformation occurs first in the 

spandrels, which may create multistory piers similar to 

URM1 or URM2 and then lead to inelastic deformation 

and damage in the piers.

URM4: This component is a strong spandrel in a weak 

pier-strong spandrel mechanism. By definition, it 

should not suffer damage, and it is not discussed further 

in the report.

URM5: Perforated wall with panel zone weak joints. 

Inelastic deformation occurs in the region where the 

pier and spandrel intersect. Such damage is not 

observed generally in experimental tests, nor is it seen 

in actual earthquakes, except at outer piers of upper 

stories. In this document, such damage is considered a 

case of corner damage and, when caused by in-plane 

demands, is addressed as part of the URM3 spandrel 

provisions.

Table 7-2 summarizes behavior types for URM wall 

components identified above. The table provides an 

Table 7-1 Behavior Modes for Non-Wall URM Elements

Element Source of Deficiency Behavior Mode Intensity of Ground 

Shaking Usually 

Required to Produce 

Behavior Mode

Parapet Out-of-plane flexural tension Parapet falls Low-to-moderate

Appendages Connection failure Falling hazard Low-to-moderate

Missing headers or veneer 

ties

Veneer delamination Moderate

Stiffness incompatibility Cracking and spalling Low-to-moderate

Pounding Local spalling Moderate

Wall-Diaphragm Ties

Tension Ties Inadequate or missing ties Wall-diaphragm separation Moderate

Shear Ties Diaphragm slides Perpendicular walls 

punched out

Moderate

Diaphragms

Rigid Concrete Slab Not typically damaged NA NA

Hollow Concrete Plank Lack of interconnection Incomplete load path, 

excessive deflection

Moderate-to-high

HCT/Brick Arch on 

Steel Beams

Lack of tie rods between 

steel beams

Localized falling hazard as 

beams separate

Moderate-to-high

Flexible Inadequate strength/stiffness Excessive deflection can 

cause wall damage

Moderate-to-high
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FEMA 306 Basic Procedures Manual 143

Table 7-2 Behavior Modes for URM Walls

Likelihood of Occurrence and Damage Guide Reference

Ductility 

Category

Behavior Mode Solid Wall

(URM1)

Weak Piers

(URM2)

Weak Spandrels

(URM3)

Higher 

Ductility 

Foundation Rocking Common in field; no 

experiments; see text

NA NA

Wall-Pier Rocking Possible; similar to 

URM2A Guide

Common in field;

experiments done;

see URM2A Guide

NA

Bed Joint Sliding Common in field; has 

experiments; similar to 

URM2B

Common in field; 

experiments done; 

see URM2B Guide

Unlikely; no guide

Bed Joint Sliding at Wall Base Possible; similar to 

URM2B Guide

NA NA

Spandrel Joint Sliding NA NA Common in field; no 

experiments; 

see URM3D Guide

Moderate 

Ductility

Rocking/Toe Crushing Seen in experiments; 

similar to URM2A 

Guide

Possible; similar to 

URM2A Guide

NA

Flexural Cracking/Toe 

Crushing/Bed Joint Sliding

Seen in experiments; see 

URM1F Guide

Possible; similar to 

URM1F Guide

Unlikely; no guide

Flexural Cracking/Diagonal 

Tension

Possible Seen in experiments; 

similar to URM2K 

Guide

Unlikely

Flexural Cracking/Toe Crushing Seen in experiments; see 

URM1H Guide

Possible; similar to 

URM1H guide

Possible; no guide

Spandrel Unit Cracking NA NA Common in field; see 

URM3I guide

Little or No 

Ductility

Corner Damage Common in field; no 

experiments; no specific 

guide; see text

NA Common in outer pier 

of upper stories; no 

specific guide; see text

Preemptive Diagonal Tension Possible; similar to 

URM2K guide

May be common in 

field; seen in 

experiments; 

see URM2K Guide

May be common in 

field; no experiments; 

similar to URM2K 

Guide

Preemptive Toe Crushing Theoretical; similar to 

URM1H Guide

Theoretical; similar to 

URM1H Guide

Unlikely; no guide

Out-of-Plane Flexural Response Common in field; see 

URM1M Guide

Possible; similar to 

URM1M Guide

Unlikely; no guide

Notes: • Shaded areas of the table with notation “See ...Guide” indicate behavior modes for which a specific Component 

Guide is provided in Section 7.5. The notation “Similar to ...Guide” indicates that the behavior mode can be 

assessed by using the guide for a different, but similar component type or behavior mode.

• Common in field: Frequently observed in earthquakes, even those of moderate size. 

• Possible: May not be explicitly documented but is assumed to have occurred or to occur in future. 

• Seen in experiments: Reported in experiments and may have occurred in earthquakes.

• Theoretical: Theoretically possible but not widely reported, if at all. 

• Unlikely: Although reported for another component, it is unlikely for this one.

• NA indicates that the failure mode cannot occur for this component.
 Chapter 7: Unreinforced Masonry

144 Basic Procedures Manual FEMA 306

indication of the ductility associated with a behavior 

mode, and the frequency with which such modes are 

observed. There are several categories for frequency of 

occurrence: “common in field” means that the mode has 

been frequently observed in earthquakes, even those of 

moderate size; “possible” means that the mode may not 

be explicitly documented in the literature, but it seems 

reasonable to assume it has occurred or will occur in 

earthquakes; “seen in experiments” means that such 

modes have been reported in experiments and may have 

occurred in some earthquakes; “theoretical” means that 

the mode, while theoretically possible, has not been 

widely reported in the literature, if at all. “Unlikely” 

means that, even though a mode has been reported for 

another component, it is unlikely to occur in the 

component under consideration. The modes listed in 

Table 7-2 are described in greater detail in the following 

sections. Component Guides have been developed for 

the damage resulting from the common modes and are 

shaded in Table 7-2; the designations such as 

“URM2A” refer to a specific guide. 

7.2.3 Foundation Rocking

Rocking of a wall and its foundation on the supporting 

soil has been observed in the field. Though recognized 

as a potentially favorable mode of nonlinear response 

and a source of damping rather than significant damage, 

excessive rocking could theoretically lead to some 

instability and nonstructural damage in the 

superstructure, particularly if various walls rock out-ofphase or elements attached to the walls cannot tolerate 

the wall drift. See FEMA 273 and ATC-40 for an 

evaluation methodology for foundation rocking.

7.2.4 Wall-Pier Rocking 

In the wall-pier rocking behavior mode, after flexural 

cracking develops at the heel, the wall or pier acts as a 

rigid body rotating about the toe. The rocking mode 

typically occurs when material shear capacity is high, 

piers are slender, and compressive stress is low. Postcracking deformations can be large and relatively stable 

for many cycles. The ultimate limit state and the 

deflection at which it occurs are not well defined by the 

research, but three possible damage types can occur: inFigure 7-3 Diagram of an Appendage Failure (from Rutherford and Chekene, 1990)
 Chapter 7: Unreinforced Masonry

FEMA 306 Basic Procedures Manual 145

1994 Northridge 

Earthquake:

Santa Monica.

1989 Loma Prieta 

Earthquake:

Watsonville.

Figure 7-4 Photos of Appendage Failures (from Rutherford &Chekene, 1990)
 Chapter 7: Unreinforced Masonry

146 Basic Procedures Manual FEMA 306

plane overturning, gradual degradation and softening of 

the pier, and excessive out-of-plane residual 

displacements (“walking”) of the pier, leading to 

instability.

The strength and displacement capacities of an element 

in rocking are based on FEMA 273, where the “d” drift 

value of 0.4he /L was established. Currently available 

experimental results are insufficient to determine the 

relative influence of number of cycles, drift, and 

ductility on rocking degradation. In the field, it is often 

difficult to find evidence of rocking, because the cracks 

close at the completion of shaking. However, horizontal 

cracks at the top and bottom of piers have been 

observed, particularly as pointing mortar spalls.

7.2.5 Bed-Joint Sliding

In this type of behavior, sliding occurs on bed joints. 

Commonly observed both in the field and in 

experimental tests, there are two basic forms: sliding on 

a horizontal plane, and a stair-stepped diagonal crack 

where the head joints open and close to allow for 

movement on the bed joint. See Figure 7-10 for an 

example of typical stair-stepped bed-joint sliding 

observed in the field. Pure bed-joint sliding is a ductile 

mode with significant hysteretic energy dissipation 

capability. If sliding continues in the absence of one of 

the less-ductile modes noted in the sections that follow, 

then gradual degradation of the cracking region occurs 

until instability is reached. Theoretically possible, but 

not widely reported, is the case of stair-stepped 

cracking in which sliding goes so far that an upper brick 

slides off a lower brick.

The strength and displacement capacities (in shear) for 

bed-joint sliding are based on FEMA 273, which uses a 

Mohr-Coulomb model originally developed as part of 

the ABK research. A Mohr-Coulomb model includes a 

bond and friction component. There are many 

uncertainties in this model, in relating the in-situ testing 

to the model, and in the in-situ testing itself. The FEMA 

273 equation for shear capacity is:

Vbjs= vme An = An[0.75(0.75vte+PCE/An)]/1.5 (7-1)

Figure 7-5 Diagram of Wall-Diaphragm Tension Tie Failure (from Rutherford and Chekene, 1990)
 Chapter 7: Unreinforced Masonry

FEMA 306 Basic Procedures Manual 147

where:

vte = the average test value from in-place testing

PCE = the expected gravity compressive force

An = the area of net mortared/grouted section.

The model was calibrated with limited empirical tests 

using brick units, which resulted in the first 0.75 

coefficient. Calibrations for other types of masonry 

such as ungrouted CMU or HCT have not been done. 

The model is most appropriate for estimating strength 

before cracking; after cracking the bond capacity will 

be eroded, and the strength is likely to be based on only 

the friction portion of the equation. Significant strength 

degradation has been observed in experiments at drifts 

of 0.3-0.4% which are likely to correspond to complete 

erosion of bond capacity. See Sections 7.3 and FEMA 

307 for the implications of strength degradation due to 

sliding. 

The vte value representing bond strength is derived from 

the average of the individual push test values, vto , 

adjusted for dead load by the equation:

vto = Vtest /Ab - pD+L, (7-2)

Figure 7-6 Photo of Wall-Diaphragm Tension Tie Failure (from Rutherford and Chekene, 1990)
 Chapter 7: Unreinforced Masonry

148 Basic Procedures Manual FEMA 306

where:

Vtest = the test value

Ab = the net mortared area of the bed joints 

above and below the test 

pD+L= the estimated gravity stress at the test location.

Ab does not include the potential resistance of the collar 

joint; the influence of collar-joint fill is applied later to 

the vme equation with the second 0.75 factor. This factor 

is waived if collar-joint fill is not present. While this 

simplifies the data reduction, it is less accurate than 

addressing the effect of fill in the collar joint at the test 

location itself. In many instances, it is difficult to 

determine the extent of the collar-joint fill. It can also 

be difficult to determine the actual gravity stress at a 

test location in walls with irregular openings. In some 

cases, flat-jack testing can be used to estimate gravity 

stresses. In FEMA 273, a 100 psi limit is set on vte; 

although such a limit may be appropriate for design 

purposes, it is inappropriate for evaluating actual 

damage. The 1.5 factor in the vte equation is to relate the 

average shear of V/An to the critical shear value of 1.5

V/An, as derived from a parabolic distribution of shear 

Figure 7-7 Diagram of Wall-Diaphragm Shear Tie Failure (from City of Los Angeles, 1991)
 Chapter 7: Unreinforced Masonry

FEMA 306 Basic Procedures Manual 149

in a rectangular section. ABK (1984) indicates that the 

1.5 factor may overestimate the critical shear in long 

walls without openings.

Finally, the in-place push test has a number of 

uncertainties. Experience has shown that test results can 

vary substantially within the same masonry class, with 

coefficients of variation of 0.30 or more when the 

required number of tests are performed. This may be 

due to actual material variations, but it is also probably 

due in part to the uncertainty in determining when 

“either a crack can be seen or slip occurs”—the 

governing criteria in UBC Standard 21-6 (ICBO, 1994) 

for determining the test load, Vtest. Alternatives have 

been proposed to define Vtest as the load occurring when 

the load-deflection curve stiffness is reduced to a 

certain percentage of the initial stiffness, or more 

simply, when a certain threshold deflection is reached.

7.2.6 Bed-Joint Sliding at Wall Base

Observed in experiments, this mode is a variation of 

bed-joint sliding in which the sliding occurs on the 

Figure 7-8 Examples of Various Masonry Diaphragms (from Rutherford and Chekene, 1997)
 Chapter 7: Unreinforced Masonry

150 Basic Procedures Manual FEMA 306

surface where the URM wall meets the foundation. 

Strength and displacement capacities are assumed to be 

similar to bed-joint sliding as described in 

Section 7.2.5.

7.2.7 Spandrel-Joint Sliding

Commonly observed in the field in running bond 

masonry, this form of bed-joint sliding in the ends of the 

spandrel resembles interlocked fingers pulling apart, 

and it occurs when the in-plane moment capacity of the 

spandrel is reached, but before the shear capacity of the 

spandrel is reached. This mode can be relatively ductile 

and can allow for significant drift, provided a reliable 

lintel is present. As the spandrel displaces, the nonlinear 

mechanism of response may move to other portions of 

the wall such as the piers.

The strength and displacement capacity are based on a 

modified version of the bed-joint sliding equation in 

FEMA 273. See Section 7.3 for details.

7.2.8 Rocking/Toe Crushing

This sequence of damage occurs when rocking (see 

Section 7.2.4) continues for several cycles, followed by 

an abrupt loss of capacity occurs as the toe crushes. 

Specimen W3 of Abrams and Shah (1992) is an 

example of such a phenomenon.

There is insufficient testing to determine parameters 

that would allow for an analytical determination of 

when rocking will degenerate into toe crushing. 

Intuitively, piers with higher axial stress and those 

subjected to higher drift levels and repeated cycles 

would be more likely to experience toe crushing. 

Because of the lack of data, this behavior is combined 

Figure 7-9 URM Wall Components

Solid Wall (URM1)

Weak "Joints" (URM5)

Weak Spandrels (URM3)

Weak Piers (URM2 and URM4)

Wall

Rocking,

Toe Crushing,

Bed Joint

Sliding, and

Diagonal

Tension

Wall/Foundation

Sliding

Foundation

Rocking

Pier

Rocking

Pier Toe

Crushing

Bed Joint

Sliding

Diagonal

Tension

Spandrel

Joint

Sliding

Spandrel

Unit

Cracking

Spandrel

Diagonal

Tension

Joint

Diagonal

Tension
 Chapter 7: Unreinforced Masonry

FEMA 306 Basic Procedures Manual 151

in this document with typical rocking behavior, and 

rocking capacity is set conservatively in FEMA 273.

7.2.9 Flexural Cracking/Toe 

Crushing/Bed Joint Sliding

In this sequence of behavior, flexural cracking occurs at 

the heel, but rocking does not begin. Instead, shear is 

redistributed to the toe, seismic forces increase, and a 

compression failure occurs in the toe. Diagonal cracks 

form, oriented toward the corners. Initial toe crushing is 

followed immediately by the ultimate limit state of bedjoint sliding.

This sequence was observed in Specimens W1, W2, and 

W3 of Manzouri et al. (1995). Initial capacity appears to 

be close to the FEMA 273 equation for toe crushing 

with a final capacity close to the frictional strength of 

the mortar. Under repeated cyclic loading, the toes may 

eventually deteriorate to the point of vertical instability. 

See FEMA 307 for commentary on this mode. 

7.2.10 Flexural Cracking/Diagonal 

Tension

In this mode of behavior, flexural racking occurs at the 

heel, but not rocking. Shear is redistributed to the toe, 

seismic forces increase, a diagonal tension crack 

develops, and capacity can be rapidly lost. Cracking 

typically occurs in the units as well as the joints. See 

Section 7.2.14 for more details.

Strength capacity is assumed to be the same as the 

FEMA 273 equation for diagonal tension capacity; 

displacements of approximately 0.5% have been 

observed in tests. 

7.2.11 Flexural Cracking/Toe Crushing

In this sequence of behavior, flexural cracking occurs at 

the heel, but not rocking. Shear is redistributed to the 

toe, the seismic load increases, and a compression 

failure occurs in the toe. This type of behavior typically 

occurs in stockier walls with L/heff > 1.25. Based on 

laboratory testing of cantilever specimens, four steps 

can usually be identified. First, flexural cracking 

happens at the base of the wall, but it does not 

propagate all the way across the wall. This can also 

cause a series of horizontal cracks to form above the 

heel. Second, sliding occurs on bed joints in the central 

portion of the pier. Third, diagonal cracks form at the 

toe of the wall. Finally, large cracks form at the upper 

corners of the wall. Failure occurs when the triangular 

portion of wall above the crack rotates off the crack or 

Figure 7-10 Photo of Bed Joint Sliding
 Chapter 7: Unreinforced Masonry

152 Basic Procedures Manual FEMA 306

the toe crushes so significantly that vertical load 

carrying capability is compromised.

Testing is limited to five monotonic specimens in 

Epperson and Abrams (1989), which all exhibited 

similar behavior, and Specimen W2 in Abrams and 

Shah (1992), which was tested with quasistatic 

reversed-cyclic loading. The strength is well-predicted 

by the FEMA 273 toe crushing equation. Toe crushing 

is considered in FEMA 273 to be a force-controlled 

mode, but moderate ductility was observed in Epperson 

and Abrams (1989), with drift values at conclusion of 

the test equal to 0.2-0.4%. In the Abrams and Shah 

(1992) test, even higher drift appears to have been 

achieved. Thus, some moderate degree of nonlinear 

capacity is possible. As noted above, behavior is similar 

to the Manzouri et al. (1995) tests, except that bed-joint 

sliding at the base did not occur at higher drifts.

7.2.12 Spandrel-Unit Cracking

In this type of damage, the moment at the end of the 

spandrel is not relieved by sliding, but instead causes 

brittle vertical cracking though the masonry units. 

Depending on the lintel construction, this can lead to a 

local falling hazard. It also can alter the height of the 

piers.

The cracked portion of the spandrel is assumed to lack 

both shear and tensile capacity. As a result, only the 

uncracked section is assumed to contribute to the 

strength and displacement capacity. See Section 7.3 for 

details.

7.2.13 Corner Damage

This form of damage is commonly observed at the 

intersection of the roof and walls subjected to in-plane 

and out-of-plane demands in moderate earthquakes. See 

Figures 7-11 and 7-12 for a diagram and photo of this 

damage type. Although not studied in experiments, it is 

likely to result from a combination of any of three 

possible causes: 

• When a roof diaphragm without shear anchorage 

moves parallel to the walls subjected to in-plane 

demands, the walls subjected to out-of-plane 

demands may be punched outward. The tensile 

capacity of the wall (from the strength of the bed 

joints) is exceeded locally, and the wall corner falls.

• Damage may be exacerbated by cracking resulting 

from the horizontal spanning of the wall. In a 

horizontal span, there is bending restraint at the ends 

of the wall due to the returns around the corner. If 

the resulting moment at the wall ends exceeds the 

capacity, a vertical crack occurs at the corner.

• For walls with openings near the corner, in-plane 

demands force moments into the joint between the 

outer pier at the top story and the adjacent spandrel. 

The moment places tensile demands on the head and 

bed joints at the pier/spandrel intersection, causing a 

diagonal crack to form.

Capacities are difficult to identify for the first two 

causes; the third is covered in a methodology developed 

in Section 7.3.

7.2.14 Preemptive Diagonal Tension

In this behavior mode, a diagonal tension crack forms 

without significant ductile response. Typical diagonal 

tension cracking—resulting from strong mortar, weak 

units, and high compressive stress—can be identified 

by diagonal cracks (“X” cracks) that propagate through 

the units. In many cases, the cracking is sudden and 

brittle, and vertical load capacity drops quickly. The 

cracks may then extend to the toe, and the triangles 

above and below the crack separate. In a few cases, the 

load drop may be more gradual with cracks increasing 

in size and extent with each cycle. 

A second form of diagonal tension cracking exists with 

weak mortar, strong units, and low compressive stress, 

when the cracks propagate in a stair-stepped manner in 

head and bed joints. In Specimen MA of Calvi and 

Magenes (1994), this behavior was observed (Magenes, 

1997).

Capacity is based on the FEMA 273 equation for 

diagonal tension. This equation requires calculation of 

masonry tensile strength, but there is no direct test for 

this value. As a substitute, the bed-joint mortar strength 

is used. This strength value only applies to the mortar, 

not the masonry units. Thus, there is a great deal of 

uncertainty in diagonal tension-strength calculations.

7.2.15 Preemptive Toe Crushing

In this form of damage, compression at the toe causes 

crushing without significant ductile response, such as 

rocking. There are no reported experimental 

observations of such behavior.
 Chapter 7: Unreinforced Masonry

FEMA 306 Basic Procedures Manual 153

The FEMA 273 equation for toe crushing is used. Postcrack displacement capacity is assumed to be negligible.

7.2.16 Out-of-Plane Flexural Response

Out-of-plane failures are common in URM buildings. 

Usually they occur due to the lack of adequate wall ties 

as discussed in Table 7-1. When floor and roof ties are 

adequate, the wall may fail due to out-of-plane bending 

between floor levels. One mode of failure observed in 

experiments is rigid-body out-of-plane rocking 

occurring on three cracks: one at the top of the wall, one 

at the bottom, and one at midheight. The ultimate limit 

state is that the walls rock too far and overturn. 

Important variables identified by ABK (1984) and 

Adham (1985) were the vertical stress on the wall, the 

height-to-thickness ratio of the wall, and the input 

velocity provided to the wall by the diaphragms. As 

rocking increases, the mortar and masonry units at the 

crack locations can degrade, and residual offsets can 

occur at the crack planes.

ABK (1984) and Adham (1985) provide a graph, based 

on ABK (1981c), showing the relationship between the 

velocity at the top and bottom of the piers, the 

overburden ratio of superimposed load over wall load, 

Figure 7-11 Diagram of Corner Damage (from City of Los Angeles, 1991)
 Chapter 7: Unreinforced Masonry

154 Basic Procedures Manual FEMA 306

and the height-to-thickness ratio. The graph indicates 

that walls meeting the requirements have a “98% 

probability of survival.” The authors did not provide 

relationships between damage and spectral acceleration 

or peak ground acceleration because input velocities 

were found to be a better predictor of wall performance. 

Therefore, it is difficult to relate damage to the spectral 

accelerations and nonlinear static procedures used in 

documents such as FEMA 273 for in-plane motions. As 

a result, the prescriptive h/t ratio concept is retained in 

this document.

7.2.17 Other Modes

A review of the literature provides a substantial number 

of specimens that cannot be easily placed in the above 

set of categories. Most common are tests that report 

“diagonal cracking” but do not specify stair-stepping 

bed-joint sliding, diagonal tension cracking, or 

diagonally-oriented compressive splitting cracks.

In addition, given the geometric complexity and 

material variation inherent in unreinforced masonry 

walls, localized stress concentrations can develop that 

are difficult to predict.

7.3 Unreinforced Masonry 

Evaluation procedures

7.3.1 Overview

This section contains evaluation procedures for 

analytical determination of expected behavior mode 

strengths and capacities. It is to be used in concert with 

the component guides contained in Section 7.5. Only 

in-plane and out-of-plane behavior of walls are 

addressed; for information on non-URM wall element 

behavior modes, see Section 7.2.

The analytical procedures described below help 

establish or confirm the expected inelastic mechanism 

of response so that component types and behavior 

modes are correctly identified. See previous portions of 

the document for details on how these capacity curves 

are to be used. The sophistication of the forcedeformation relationship of a multi-story URM wall can 

vary widely, primarily depending on whether spandrel 

effects and global overturning effects are taken into 

consideration. Existing standards--such as ABK (1984), 

Division 88 (City of Los Angeles, 1985), RGA 

(SEAOSC, 1986), UCBC (ICBO, 1994) and FEMA 178 

Figure 7-12 Photo of Corner Damage (from Rutherford and Chekene, 1990)
 Chapter 7: Unreinforced Masonry

FEMA 306 Basic Procedures Manual 155

(BSSC, 1992)--do not have specific provisions for 

modeling of spandrels, and, in provisions for weak pier 

systems, these standards also do not provide provisions 

for the impact of global overturning on individual piers. 

FEMA 273 (ATC, 1997a) also does not provide explicit 

guidance for these issues.

For this document, it is considered acceptable to ignore 

potential spandrel and global overturning effects in a 

perforated wall element if spandrel damage is not 

observed in the field. In such a case, the spandrels are 

assumed to have sufficient capacity and the inelastic 

mechanism of response is assumed to be a weak pier 

system. Consequently, the nonlinear static analysis need 

only consider the force-displacement relationships of 

the piers in the wall element. See Section 7.3.2 for 

specific evaluation procedures.

See Section 7.3.3 for specific evaluation procedures for 

solid wall components.

If spandrel damage is observed, then the model of the 

wall should include spandrel components. In many 

cases, inelastic behavior in spandrels will transform an 

initial system of strong piers and weak spandrels into a 

system of weak piers and strong spandrels, as the 

strength of the spandrel diminishes. See Section 7.3.4 

for an example and specific evaluation procedures.

In this document, out-of-plane wall and pier behavior 

are separated from in-plane behavior. Out-of-plane 

capacity and its potential reduction due to observed 

damage is to be evaluated and reported separately. See 

Section 7.3.5 for specific evaluation procedures. When 

significant out-of-plane damage is observed, it may 

have an effect on the wall for the force-deformation 

curve oriented parallel or in-plane to the wall. For such 

cases, the component guides in Section 7.5 contain λfactors to apply for in-plane loading.

The analytical procedures require the determination of 

material properties which can be obtained through 

testing or by assumption and verification. FEMA 273 

(ATC, 1997a) provides the scope and details of testing 

for determining vme (in-place push tests), f’me (extracted 

or mockup prism tests or in-situ flatjack tests), and 

modulus of elasticity E (extracted prisms or flatjack 

testing). Conservative default values are also given to 

be used in lieu of testing. To determine the value of 

average flat-wise compressive strength of the brick, use 

ASTM C-67.

7.3.2 Evaluation Procedures for InPlane Behavior of Piers in Walls 

with Weak Pier - Strong 

Spandrel Mechanisms

Evaluation of pier capacity is a three-step process:

a. Step 1: Calculate Capacities for Individual 

Behavior Modes

Determine capacities for each of the following five

values:

• Rocking (Vr):

Vr = 0.9αPCE(L/heff) (7-3)

where:

α = factor equal to 0.5 for fixed-free cantilever 

wall, or equal to 1.0 for a fixed-fixed pier

PCE = expected vertical axial compressive force 

per load combinations in FEMA 273 

(ATC, 1997a)

L = length of the wall

heff = height to resultant of lateral force. For 

piers with regular opening, heff is the clear 

height of pier; for irregular openings, see 

Kingsley (1995). The parameter heff may 

be varied to reflect observed crack patterns. See Figure 7-14 for an example.

• Bed joint sliding with bond plus friction (Vbjs1) 

and with friction only (Vbjs2):

Vbjs1= vmeAn (7-4)

where:

vme = bond plus friction strength of mortar, as 

defined in FEMA 273 (1997a)

An = area of net mortared/grouted section

and:

Vbjs2= vfrictionAn 

= [0.75(PCE /An )/1.5][An] = 0.5PCE (7-5)
 Chapter 7: Unreinforced Masonry

156 Basic Procedures Manual FEMA 306

• Diagonal tension (Vdt):

Vdt= f’dt An(β)(1 + fae/f 'dt)

1/2 (7-6)

where:

f’dt = diagonal tension strength, assumed as vme, 

per FEMA 273 (1997a)

β = 0.67 for L/heff <0.67, L/heff when 0.67 ≥

L/heff ≤ 1.0, and 1.0 when L/heff >1

• Toe crushing (Vtc):

Vtc = αPCE(L/heff)(1 - fae/0.7f’me) (7-7)

where:

fae = expected vertical axial compressive stress 

as defined in FEMA 273 (ATC, 1997a)

f’me = expected masonry compressive strength

b. Step 2: Determine Predicted Behavior Mode and 

Capacity:

Differentiate piers by aspect ratio and applied 

vertical stress to determine which behavior mode is 

predicted as follows. Unless otherwise noted, forcedisplacement relationships are per FEMA 273 (ATC, 

1997a).

Piers with aspect ratios of L/heff >1.25

• If Vbjs1 is the lowest value and less than 0.75 of 

Vtc or Vr, then URM2B (bed joint sliding) is the 

predicted mode, with an initial capacity of Vbjs1.

• If Vtc or Vr are the lowest values and are less than 

0.75 of Vbjs1, then URM1H (flexural cracking/toe 

crushing) is the predicted mode, and Vtc is the 

predicted capacity. Assume this mode is forcecontrolled.

• If Vtc , Vr , and Vbjs1 are lower than Vdt, 0.75 Vbjs1 

≤ Vtc ≤ Vbjs1 and 0.75 Vbjs1 ≤ Vr ≤ Vbjs1 , then a 

sequence of URM1F (flexural cracking/toe 

crushing/bed joint sliding) is the predicted mode. 

Use Vtc for the initial capacity up to a “d” drift of 

0.4% and Vbjs2 for the final capacity from “d” to 

an “e” of 0.8%.

• If one of the categories above is not met, then the 

predicted capacity is the lowest of Vr , Vbjs1 , Vdt , 

and Vtc and the associated behavior mode is as 

follows:

- Vr : Mode URM2A (wall-pier rocking)

- Vbjs1: Mode URM2B (bed joint sliding)

- Vdt : Mode URM2K (preemptive diagonal 

tension)

- Vtc : Mode URM2L (preemptive toe crushing)

Piers with aspect ratios of L/heff ≤ 1.25

• If Vr or Vtc are the lowest values and fae< 100 psi, 

then URM2A is the predicted mode with Vr as the 

initial capacity.

• If Vr or Vtc are the lowest values and fae ≥ 150 psi, 

then diagonal cracking with limited ductility, such 

as URM2G (flexural cracking/diagonal tension) is 

the predicted mode with Vtc as the capacity.

• If one of the categories above is not met, then the 

predicted capacity is the lowest of Vr, Vbjs1, Vdt

and Vtc and the associated behavior mode is as 

follows:

- Vr : Mode URM2A (wall-pier rocking)

- Vbjs1: Mode URM2B (bed joint sliding)

- Vdt : Mode URM2K (preemptive diagonal 

tension)

- Vtc : Mode URM2L (preemptive toe crushing)

c. Step 3: Compare Predicted Mode with Observed 

Field Damage:

If field damage is consistent with predicted damage 

shown in the damage guide, then assume the 

component and damage classification and the 

capacity are correct.
 Chapter 7: Unreinforced Masonry

FEMA 306 Basic Procedures Manual 157

If field damage is inconsistent with predicted 

damage shown in the damage guide, return to 

analysis at Step 1 and vary assumptions as to 

material properties and possible alternative modes. 

Consider, for example, for f’dt, using 1/30 of the 

value of average flat-wise compressive strength of 

the brick in lieu of vme. This test is standardized in 

ASTM C-67.

7.3.3 Evaluation Procedures for InPlane Behavior of Solid Wall 

Components

Evaluation procedures for solid walls are similar to 

those for piers in walls with weaker pier-stronger 

spandrel mechanisms. Equations in Section 7.3.2 may 

be used, with the appropriate use of α=0.5. For the 

rocking equation in Section 7.3.2, the weight of the pier 

is ignored for simplicity, since it is assumed to be only a 

small fraction of the superimposed vertical load. When 

the weight of the wall represents a significant fraction 

of the vertical load, then the rocking equation may be 

modified as follows. 

Vr = 0.9α(PCE +WW)L/heff (7-8)

where:

α = factor equal to 0.5 for fixed-free cantilever 

wall

PCE = expected vertical axial compressive force 

per load combinations in FEMA 273 

(ATC, 1997a). This superimposed load is 

assumed to act at the center of the wall 

coincident with the location of the weight 

of the wall.

WW = expected weight of the wall

L = length of the wall

heff = height to resultant of lateral force

7.3.4 Evaluation Procedures for InPlane Behavior of Perforated 

Walls with Spandrel Damage

There is no methodology to analyze spandrels in the 

literature. As a placeholder until research is carried out, 

the following procedures have been developed. 

Procedures are given for estimating the moment and 

shear capacity of an uncracked spandrel, and for 

damaged walls that have experienced spandrel joint 

sliding or spandrel unit cracking. Examples are given of 

how to address the implications of spandrel cracking on 

in-plane behavior of perforated walls.

a. Capacities of an Uncracked Spandrel

Moment Capacity. The moment capacity of the 

uncracked spandrel is assumed to be derived from the 

interlock between the bed joints and collar joint at the 

interface between the pier and the spandrel. See Figure 

7-13. An elastic stress distribution is assumed across the 

end of the spandrel with the neutral axis located at the 

centerline of the spandrel height. It is assumed that the 

bed joint and collar joint capacities can be linearly 

superimposed to produce a resultant force. Both tension 

and compressive resultants are assumed to be derived 

from the mortar shear strength. (Note that alternative 

formulations are possible that use the compressive 

strength of the masonry to develop the compressive 

force.) Irregularities due to header courses are ignored. 

The uncracked moment capacity Mspun is then the 

product of the resultant force and the effective distance 

between the resultant.

• Uncracked bed joint shear stress, (vbjun):

vbjun= 0.75(0.75 vte +γPCE/ An)/1.5 (7-9)

where:

vte = the average test value from in-place testing

PCE = the expected vertical axial compressive 

force per load combinations in FEMA 273 

(ATC, 1997a) at the adjacent pier

An = the area of net mortared/grouted section of 

the adjacent pier

γ = 0.5. This arbitrary value indicates that the 

vertical axial stress on the spandrel bed 

joints at the end of the spandrel is assumed 

to be approximately half of the axial stress 

within the pier above the pier/spandrel 

joint.

• Uncracked collar joint shear stress, (vcun):

vcun= 0.75(0.75 vte +γ PCE / An) / 1.5

= 0.375vte (7-10)

where:

vte = the average test value from in-place testing
 Chapter 7: Unreinforced Masonry

158 Basic Procedures Manual FEMA 306

PCE = the expected vertical axial compressive 

force per load combinations in FEMA 273 

(ATC, 1997a) at the adjacent pier

An = the area of net mortared/grouted section of 

the adjacent pier

γ = 0. This arbitrary value indicates that the 

axial stress on the spandrel collar joints at 

the end of the spandrel is assumed to be 

negligible.

• Effective length of interface for an uncracked 

spandrel, (beffun):

beffun= bl /2 (7-11)

where:

bl /2 = half the length of the masonry unit

• Number of rows of bed joints, (NR):

NR= 0.5(dsp / bh) (7-12)

Round NR down to the nearest whole number

where:

bh = height of the brick unit plus the bed joint 

thickness

dsp = depth of the spandrel

• Resultant tensile and compressive result forces, 

(T=C):

T= [(vbjun ) (bw) ( beffun) + 

(vcun ) (bh) ( beffun) (NB-1)] (η) (7-13)

where:

bw = width of the brick unit

Figure 7-13 Spandrel Joint Sliding

beff

bw

dsp

deff

bsp

vbj

vbjun vcun vbjcr

bh

bl

vc

T

C

Pier Spandrel
 Chapter 7: Unreinforced Masonry

FEMA 306 Basic Procedures Manual 159

bh = height of the brick unit

NB = number of brick wythes

η = NR/2 or for more sophistication:

= Σi=1,NR [(dsp / 2 - bh(i)) / ( dsp / 2 - bh)]

• Uncracked moment of spandrel, (Mspun):

Mspun= (deffun ) (T) (7-14)

where:

deffun = distance between T and C

= (2/3) (dsp)

Shear Capacity. The shear capacity of the spandrel is 

derived here from the equation for diagonal tensile 

capacity for the pier as follows. 

• Diagonal tension (Vspun):

Vspun= f’dt dsp bsp(β) (1+fae / f’dt)

1/2 (7-15)

where:

f’dt = diagonal tension strength, assumed as vme, 

per FEMA 273 (ATC, 1997a)

β = 0.67 for Lsp/dsp <0.67, Lsp/dsp when 0.67≥

Lsp / dsp ≤1.0, and 1.0 when Lsp / dsp >1

Lsp = length of spandrel

fae = expected horizontal axial stress in the pier

= 0, unless known.

bsp = width of spandrel

With fae=0, this equation then reduces to:

Vspun= f’dt dsp bsp(β) (7-16)

b. Capacities of a Cracked Spandrel with Spandrel 

Joint Sliding

Moment Capacity. The moment capacity of the cracked 

spandrel with spandrel joint sliding is derived similar to 

the procedure given for an uncracked spandrel. Again 

see Figure 7-13. 

• Cracked bed joint shear stress, (vbjcr):

vbjcr= 0.75(εvte +γPCE / An) /1.5 

=0.25 PCE / An (7-17)

where:

vte = the average test value from in-place testing

ε = 0. The bond strength of the mortar is 

assumed to be lost.

PCE = the expected vertical axial compressive 

force per load combinations in FEMA 273 

(ATC, 1997a) at the adjacent pier

An = the area of net mortared/grouted section of 

the adjacent pier

γ = 0.5. This arbitrary value indicates that the 

vertical axial stress on the spandrel bed 

joints at the end of the spandrel is assumed 

to be approximately half of the axial stress 

within the pier above the pier/spandrel 

joint.

• Cracked collar joint shear stress, (vccr): 

vccr= 0.75 (ε vte +γPCE / An) / 1.5 = 0 (7-18)

where:

ε = 0. The bond strength of the mortar is 

assumed to be lost.

γ = 0. This arbitrary value indicates that the 

axial stress on the spandrel collar joints at 

the end of the spandrel is assumed to be 

negligible.

• Effective length of interface for a cracked spandrel, 

(beffcr):

beffcr= bl /2 - ∆s (7-19)

where:

bl /2 = half the length of the masonry unit

∆s = average slip (can be estimated as average 

opening width of open head joint)

• Number of rows of bed joints, (NR):

NR= 0.5(dsp / bh) (7-20)

Round NR down to the nearest whole number

where:

bh = height of the brick unit plus the bed joint 

thickness

dsp = depth of the spandrel
 Chapter 7: Unreinforced Masonry

160 Basic Procedures Manual FEMA 306

• Resultant tensile and compressive result forces, 

(T=C):

T= (vbjcr ) (bw) ( beffcr) (NR) (7-21)

where:

bw = width of the brick unit

• Cracked moment of spandrel, (Mspcr):

Mspcr= (deffcr) (T) (7-22)

where:

deffcr= distance between T and C

= (1/2)(dsp)

Shear Capacity. The shear capacity of a cracked 

spandrel with spandrel joint sliding is assumed to be the 

same as that of an uncracked spandrel provided keying 

action between bricks remains present at the end of the 

spandrel. Shear is resisted by bearing on the bed joints 

of the interlocked units.

c. Capacities of a Cracked Spandrel with Spandrel 

Unit Cracking

The moment and shear capacity of an cracked spandrel 

with spandrel unit cracking is derived similar to the 

procedure given above for an uncracked spandrel. The 

only modification is that the effective depth of the 

spandrel is reduced to only the amount of uncracked 

masonry remaining.

d. Examples of the Implications of Spandrel Cracking

Figure 7-14 shows a wall line with some cracking at the 

ends of spandrels. This section qualitatively discusses 

corner damage and gives quantitative procedures for 

assessing the impact of spandrel cracking on adjacent 

piers.

Corner Damage. One of the potential causes of corner 

damage is shown at the top of Figure 7-14 where the 

moment and shear at the end of the spandrel are resisted 

only by the weight of the masonry near the joint, direct 

tension on the head joints and bed joints, and shear in 

the collar joints. When these fairly weak capacities are 

exceeded, a diagonally-oriented crack propagates from 

the upper corner of the opening across the last pier. 

Since the crack is inclined, the effective height of the 

last pier is increased. For loading to the right, it may be 

appropriate to move the superimposed dead load closer 

to the center of the pier in the evaluation of the pier 

rocking capacity of the last pier.

Multistory Pier Rocking. As noted above, it is assumed in 

this document that if there is no spandrel damage, then a 

weak pier-strong spandrel model should be used. On the 

other hand, if the spandrels are fully cracked, then there 

will be no bending rigidity provided by the spandrel, 

and the pier rocking should be assessed using a 

multistory pier. When the spandrels have a reduced 

capacity, it is necessary to determine the capacity of 

both the typical single story pier rocking and the 

multistory case. Figure 7-14 shows an example. To 

assess the multistory rocking capacity of Mechanism 1 

in the figure the following procedure may be used:

• Assume that the shear imparted by the spandrel on 

the pier (Vsp) is 

Vsp=2Msp / Lsp (7-23)

where:

Msp = the bending capacity of the spandrel as 

determined from previous sections

Lsp = the length of the spandrel

• Assume a distribution of acceleration within the wall 

line. Using ABK (1984) assumptions, the 

acceleration is uniform up the wall. Further assume 

for this example that loads tributary to each level are 

the same so that VrR = Vr2

• Sum the moments around the pier toe at the first 

story so that:

ΣM=0

=(VrR)(h1 +h2+dsp) +(Vr2) (h1+dsp/2) - 

(PDLR) (0.9L) - (Vsp + (1/2) ( PDL2))(0.9L)

- 2Msp (7-24)

Substituting for Vr2 and Vsp gives:

VrR=[0.9 (PDLR+ PDL2 /2 + 2Msp / Lsp) + 2Msp] /

[2h1 + h1+ 3dsp/2] (7-25)

where:

VrR = the shear at the second story

h1 = height of the first story pier

h2 = height of the second story pier

dsp = depth of the spandrel
 Chapter 7: Unreinforced Masonry

FEMA 306 Basic Procedures Manual 161

PDLR= the expected gravity load at the roof

PDL2= the expected gravity load at the second 

story, assumed here to be split equally on 

both sides of pier. Note that the pier weight 

is ignored for simplicity.

Single Story Pier Rocking. The rocking capacity of the 

piers in Mechanism 2 is given here. For the second 

story:

VrR=0.9L (PDLR) / h2 (7-26)

For the first story:

(VrR + Vr2)( h1) = (PDLR+ PDL2) (0.9L) (7-27)

Substituting for Vr2 gives:

VrR=0.9L [(PDLR + PDL2) / 2h1 (7-28)

Governing Mode. To determine the governing mode of 

behavior, compare the values for VrR for multi-story 

and single-story rocking. The lowest rocking capacity 

will govern for determining the pier rocking strength. 

Figure 7-14 Implications of Spandrel Cracking

Vp

Mp

Msp Msp

Msp

Vsp Vsp

Vsp

Vsp

VrR

dsp

VrR + Vr2 VrR + Vr2

PDLR + PDL2

PDLR PDLR

PDLR + PDL2

VrR

Vsp

Msp

Lsp

dsp

Psp

Fp

CORNER DAMAGE SPANDREL

heff

Revise pier 

height to reflect

crack locations

Vr2

h1 h1 + h2 +dsp

h2

PIER ROCKING

MECHANISM 2

PIER ROCKING

MECHANISM 1

0.9L 0.9L

PDL2 1

2

PDL2 1

2

Vr2
 Chapter 7: Unreinforced Masonry

162 Basic Procedures Manual FEMA 306

Shear capacities for bed joint sliding, toe crushing and 

diagonal tension should then be compared. Use the 

equations in Section 7.3.2.

7.3.5 Evaluation Procedures for Out-ofPlane Behavior of Wall and Pier 

Components

Prescriptive strength and deformation acceptance 

criteria for out-of-plane wall demands are contained in 

FEMA 273 (ATC, 1997a). For the immediate 

occupancy performance level, flexural stresses should 

not exceed the tensile capacity of the wall. Thus, for any 

level of damage above Insignificant, where by 

definition some flexural cracking has occurred, the 

damaged wall should be considered as not meeting the 

immediate occupancy performance level.

For the collapse prevention and life safety performance 

levels, Table 7-4 of FEMA 273 tabulates permissible h/t 

ratios for walls without prior damage. For damaged 

walls, the Component Guides in this volume specify 

λh/t-factors which, when multiplied by the ratios in 

Table 7-4 (FEMA 273), give permissible h/t ratios for 

damaged walls.

The Component Guide also gives λ-factors for use 

when the damaged wall is a component in a force 

deformation curve oriented parallel to the length of the 

wall.
 Chapter 7: Unreinforced Masonry

FEMA 306 Basic Procedures Manual 163

7.4 Symbols for Unreinforced 

Masonry

Symbols used in the unreinforced masonry sections of 

FEMA 306 and 307 are the same as those given in 

Section 7.9 of FEMA 273, except for the following 

additions and modifications.

C Resultant compressive force in a spandrel, lb

Lsp Length of spandrel, in.

Mspcr Expected moment capacity of a cracked spandrel, lb-in.

Mspun Expected moment capacity of an uncracked 

spandrel, lb-in.

Vspcr Expected diagonal tension capacity of a 

cracked spandrel, lb

Vspun Expected diagonal tension capacity of an 

uncracked spandrel, lb

NB Number of brick wythes in a spandrel

NR Number of rows of bed joints in a spandrel

T Resultant tensile force in a spandrel, lb

Vbjs1 Expected shear strength of wall or pier based on 

bed joint shear stress, including both the bond 

and friction components, lb

Vbjs2 Expected shear strength of wall or pier based on 

bed joint shear stress, including only the friction component, lb

Vsp Shear imparted on the spandrel by the pier, lb

Vdt Expected shear strength of wall or pier based on 

diagonal tension using vme for f’dt, lb

Vtc Expected shear strength of wall or pier based on 

toe crushing using vme for f’dt, lb

Ww Expected weight of a wall, lb

beffcr Effective length of interface for a cracked spandrel, in.

beffun Effective length of interface for an uncracked 

spandrel, in.

bh Height of masonry unit plus bed joint thickness, 

in.

bl Length of masonry unit, in.

bw Width of brick unit, in.

dsp Depth of spandrel, in.

deffcr Distance between resultant tensile and compressive forces in a cracked spandrel, in.

deffun Distance between resultant tensile and compressive forces in an uncracked spandrel, in.

f’dt Masonry diagonal tension strength, psi

vbjcr Cracked bed joint shear stress, psi

vbjun Uncracked bed joint shear stress in a spandrel, 

psi

vccr Cracked collar joint shear stress in a spandrel, 

psi

vcun Uncracked collar joint shear stress in a spandrel, psi

β =0.67 when L/heff <0.67, =L/heff when 

0.67≤L/heff ≤1.0, and =1.0 when L/heff >1

∆s Average slip at cracked spandrel (can be estimated as average opening width of open head 

joint), in.

ε Factor for estimating the bond strength of the 

mortar in spandrels

γ Factor for coefficient of friction in bed joint 

sliding equation for spandrels

η Factor to estimate average stress in uncracked 

spandrel. Equal to NR/2 or, for more sophistication, use Σi=1,NR [(dsp /2 - bh (i))/( dsp /2 - bh)]

λh/t Factor used to estimate the loss of out-of-plane 

wall capacity to damaged URM walls
 Chapter 7: Unreinforced Masonry

164 Basic Procedures Manual FEMA 306

μ∆ Displacement ductility demand for a component, used in Section 5.3.4, and discussed in 

Section 6.4.2.4 of FEMA 273. Equal to the 

component deformation corresponding to the 

global target displacement, divided by the 

effective yield displacement of the component 

(which is defined in Section 6.4.1.2B of 

FEMA 273). 
 Chapter 7: Unreinforced Masonry

FEMA 306 Basic Procedures Manual 165

7.5 Unreinforced Masonry Component Guides

The following Component Damage Classification 

Guides contain details of the behavior modes for 

unreinforced masonry components. Included are the 

distinguishing characteristics of the specific behavior 

mode, the description of damage at various levels of 

severity, and performance restoration measures. 

Information may not be included in the Component 

Damage Classification Guides for certain damage 

severity levels; in these instances, for the behavior 

mode under consideration, it is not possible to make 

refined distinctions with regard to severity of damage. 

See also Section 3.5 for general discussion of the use of 

the Component Guides and Section 4.4.3 for 

information on the modeling and acceptability criteria 

for components.
 Chapter 7: Unreinforced Masonry

166 Basic Procedures Manual FEMA 306

COMPONENT DAMAGE

CLASSIFICATION GUIDE

System: URM

Component Type: Weaker Pier

Behavior Mode: Wall-Pier Rocking

How to distinguish behavior mode:

By observation:

Rocking-critical piers form horizontal flexural cracks at the top 

and bottom of piers. Because the cracks typically close as the 

pier comes back to rest at the end of ground shaking, these 

cracks can be quite subtle when only a few cycles of rocking 

have occurred and when pier drift ratios during shaking were 

small. As damage increases, softening of the pier can occur due 

to cracking, and the pier may begin to “walk” out-of-plane at 

the top and bottom. At the highest damage levels, crushing of 

units at the corners can occur.

By analysis:

As damage increases to the Moderate level and beyond, 

some small cracking within the pier may occur. Confirm by 

analysis that rocking governs over diagonal tension and bed 

joint sliding.

Caution: If horizontal cracks are located directly 

below wall-diaphragm ties, damage may be due to bed 

joint sliding associated with tie damage. If a horizontal 

crack is observed at midheight of the pier, see 

URM1M.

Refer to Evaluation Procedures for:

• In-plane wall behavior: See Section 7.3.2.

Level Description of Damage Typical Performance Restoration Measures

Insignificant Criteria: • Hairline cracks/spalled mortar in bed joints at top 

and bottom of pier.

Not necessary for restoration of structural 

performance. 

λΚ = 0.8

λQ = 1.0

λD = 1.0

μ∆ ≤ 1.5

Typical Appearance: (Measures may be necessary for restoration of nonstructural characteristics.)

URM2A
 Chapter 7: Unreinforced Masonry

FEMA 306 Basic Procedures Manual 167

COMPONENT DAMAGE 

CLASSIFICATION GUIDE continued

Level Description of Damage Typical Performance Restoration 

Measures

Slight Not used.

Moderate

λΚ = 0.6

λQ = 0.9

Criteria: 1. Hairline cracks/spalled mortar in bed joints at top 

and bottom of pier.

2. Possible hairline cracking/spalled mortar in bed 

joints within piers.

Replacement or enhancement is required 

for full restoration of seismic performance.

λD = 1.0

∆/heff≤

heff/Leff*

0.4%

Typical Appearance: For partial restoration of performance:

• Repoint spalled mortar.

λΚ* = 0.8

λQ* = 0.9

λD* = 1.0

Heavy

λΚ = 0.4

λQ = 0.8

λD = 0.7

∆/heff≤

heff/Leff*

0.8%

Criteria: 1. Hairline cracks/spalled mortar in bed joints at top 

and bottom of pier, plus one or more of:

2. Hairline cracking/spalled mortar in bed joints 

within piers, but bed joints typically do not open.

3. Possible out-of-plane or in-plane movement at 

top and bottom of piers (“walking”).

4. Crushed/spalled bricks at corners of piers.

Replacement or enhancement is required 

for full restoration of seismic performance.

For partial restoration of performance:

• Replace/drypack damaged units

• Repoint spalled mortar

• Inject cracks

λΚ* = 0.8

λQ* = 0.9

λD* = 1.0

Typical Appearance:

Extreme Criteria: • Vertical load-carrying ability is threatened. • Replacement or enhancement required.

Typical Indications

• Significant out-of-plane or in-plane movement 

at top and bottom of piers (“walking”).

• Significant crushing/spalling of bricks at corners of piers.

URM2A
 Chapter 7: Unreinforced Masonry

168 Basic Procedures Manual FEMA 306

COMPONENT DAMAGE

CLASSIFICATION GUIDE

System: URM

Component Type: Weaker Pier

Behavior Mode: Bed Joint Sliding

How to distinguish behavior mode:

By observation:

In this type of behavior, sliding occurs on bed joints. Commonly observed both in the field and in experimental tests, 

there are two basic forms: sliding on a horizontal plane, and a 

stair-stepped diagonal crack where the head joints open and 

close to allow for movement on the bed joint. Note that, for 

simplicity, the figures below only show a single crack, but 

under cyclic loading, multiple cracks stepping in each direction 

are possible. Pure bed joint sliding is a ductile mode with significant hysteretic energy absorption capability. If sliding continues without leading to a more brittle mode such as toe 

crushing, then gradual degradation of the cracking region 

occurs until instability is reached. Theoretically possible, but 

not widely reported, is the case of stair-stepped cracking when 

sliding goes so far that an upper brick slides off a lower unit.

By analysis:

Stair-stepped cracking may resemble a form of diagonal 

tension cracking; confirm by analysis that bed joint sliding 

governs over diagonal tension.

Refer to Evaluation Procedures for:

• In-plane wall behavior: See Section 7.3.2.

Level Description of Damage Typical Performance Restoration Measures

Insignificant Criteria: 1. Hairline cracks/spalled mortar in head and bed 

joints either on a horizontal plane or in a stairstepped fashion have been initiated, but no offset along the crack has occurred and the crack 

plane or stair-stepping is not continuous across 

the pier.

2. No cracks in masonry units.

Not necessary for restoration of structural 

performance. (Measures may be necessary for restoration of nonstructural characteristics.)

λΚ = 0.9

λQ = 0.9

λD = 1.0

μ∆ ≤ 1.5

Typical Appearance:

URM2B
 Chapter 7: Unreinforced Masonry

FEMA 306 Basic Procedures Manual 169

COMPONENT DAMAGE 

CLASSIFICATION GUIDE continued

Level Description of Damage Typical Performance Restoration 

Measures

Slight Not used.

Moderate

λΚ = 0.8

λQ = 0.6*

λD = 1.0

Criteria: 1. Horizontal cracks/spalled mortar at bed joints 

indicating that in-plane offset along the crack has 

occurred and/or opening of the head joints up to 

approximately 1/4”, creating a stair-stepped 

crack pattern.

2. 5% of courses or fewer have cracks in masonry 

units.

Replacement or enhancement is required 

for full restoration of seismic performance.

For partial restoration of performance:

• Repoint spalled mortar and open head 

joints.

• Inject cracks and open head joints

*As an alternative, calculate as Vbjs2/

Vbjs1

∆/heff≤0.4%

Typical Appearance: λΚ* = 0.8 

λQ* = 0.8*

λD* = 1.0*

*In some cases, grout injection may 

actually increase strength, but decrease 

deformation capacity, by changing 

behavior from bed joint sliding to a less 

ductile behavior mode (see FEMA 307, 

Section 4.1.3).

Heavy

λΚ = 0.6

λQ = 0.6*

λD = 0.9

Criteria: 1. Horizontal cracks/spalled mortar on bed joints 

indicating that in-plane offset along the crack has 

occurred and/or opening of the head joints up to 

approximately 1/2”, creating a stair-stepped 

crack pattern.

2. 5% of courses or fewer have cracks in masonry 

units.

Replacement or enhancement is required 

for full restoration of seismic performance.

For partial restoration of performance:

• Repoint spalled mortar and open head 

joints.

• Inject cracks and open head joints.

*As an alternative, calculate as Vbjs2/

Vbjs1

∆/heff≤0.8%

Typical Appearance: λΚ* = 0.8 

λQ* = 0.8*

λD* = 1.0*

*In some cases, grout injection may 

actually increase strength, but decrease 

deformation capacity, by changing 

behavior from bed joint sliding to a less 

ductile behavior mode (see FEMA 307, 

Section 4.1.3).

Extreme Criteria: • Vertical load-carrying ability is threatened. • Replacement or enhancement required.

Typical Indications

• Stair-stepped movement is so significant that 

upper bricks have slid off their supporting 

brick.

• Cracks have propagated into a significant number of courses of units.

• Residual set is so significant that portions of 

masonry at the edges of the pier have begun or 

are about to fall.

URM2B
 Chapter 7: Unreinforced Masonry

170 Basic Procedures Manual FEMA 306

COMPONENT DAMAGE

CLASSIFICATION GUIDE

System: URM

Component Type: Weaker Spandrel

Behavior Mode: Spandrel Joint Sliding

How to distinguish behavior mode:

By observation:

Commonly observed in the field in running bond masonry, this 

form of bed joint sliding is characterized by predominantly 

vertical cracks at the ends of the spandrel, which look like 

interlocked fingers being pulling apart. This mode can be relatively ductile and allow for significant drift, provided a reliable 

lintel is present. As the spandrel displaces, the nonlinear mechanism of response may move to other portions of the wall such 

as the piers.

By analysis:

No analysis is typically necessary to distinguish this mode. 

Analytical procedures are provided to estimate the reduction 

in capacity due to damage.

Refer to Evaluation Procedures for:

• In-plane wall behavior: See Section 7.3.4.

Level Description of Damage Typical Performance Restoration 

Measures

Insignificant Criteria: 1. Staggered hairline cracks/spalled mortar in head 

and bed joints in up to 3 courses at the ends of 

the spandrel. No cracks in units.

Not necessary for restoration of structural performance. (Measures may be 

necessary for restoration of nonstructural 

characteristics.)

λΚ =0.9

λQ = 0.9

λD = 1.0

μ∆ ≤ 1.5

Typical Appearance:

Slight Not used

URM3D
 Chapter 7: Unreinforced Masonry

FEMA 306 Basic Procedures Manual 171

COMPONENT DAMAGE 

CLASSIFICATION GUIDE continued

Level Description of Damage Typical Performance Restoration 

Measures

Moderate

λΚ =0.8

λQ = 0.41

λD = 0.9

Criteria: 1. Staggered hairline cracks/spalled mortar at the 

ends of the spandrel in head and bed joints indicating that in-plane offset along the crack has 

occurred and opening of the head joints up to 

approximately 1/4”. No cracks in units.

2. No vertical slip of the spandrel.

Replacement or enhancement is required 

for full restoration of seismic performance.

For partial restoration of performance:

• Repoint spalled mortar and open head 

joints.

• Inject cracks and open head joints.

1. As an 

alternative, 

calculate per 

Section 7.3.4

Typical Appearance: λΚ* = 0.8 

λQ* = 0.81

λD* = 1.01

1. In some cases, grout injection may 

actually increase strength, but decrease 

deformation capacity, by changing 

behavior from bed joint sliding to a less 

ductile behavior mode (see FEMA 307, 

Section 4.1.3).

Heavy

λΚ = 0.6

λQ = 0.41

λD = 0.9

Criteria: 1. Staggered hairline cracks/spalled mortar at the 

ends of the spandrel in head and bed joints, indicating that in-plane offset along the crack has 

occurred and opening of the head joints up to 

approximately 1/2”. No cracks in units.

2. Possibly some deterioration of units at bottom 

ends of spandrel, but no vertical slip of the spandrel.

3. Possibly spandrel rotation with respect to the 

pier.

Replacement or enhancement is required 

for full restoration of seismic performance.

For partial restoration of performance:

• Repoint spalled mortar and open head 

joints

• Inject cracks and open head joints

λΚ*= 0.8 

λQ* = 0.81

λD* = 1.01

1. As an 

alternative, 

calculate per 

Section 7.3.4

Typical Appearance:

1. In some cases, grout injection may 

actually increase strength, but decrease 

deformation capacity, by changing 

behavior from bed joint sliding to a less 

ductile behavior mode (see FEMA 307, 

Section 4.1.3).

Extreme Criteria: • Vertical load-carrying ability is threatened. • Replacement or enhancement required.

Typical Indications

• Sliding and/or deterioration of the units is so 

significant that keying action between bricks is 

lost.

• Lintel support has separated from the pier.

URM3D
 Chapter 7: Unreinforced Masonry

172 Basic Procedures Manual FEMA 306

COMPONENT DAMAGE System: URM

CLASSIFICATION GUIDE Component Type: Solid Wall

Behavior Mode: Flexural Cracking/

Toe Crushing/Bed 

Joint Sliding

How to distinguish behavior mode:

By observation:

This type of moderately ductile behavior has been experimentally observed in walls with L/heff 1.7 in which bed joint 

sliding and toe crushing strength capacities are similar. Damage occurs in the following sequence. First, flexural cracking 

occurs at the heel of the wall. Then diagonally-oriented cracks 

appear at the toe of the wall, typically accompanied by spalling 

and crushing of the units. In some cases, toe crushing is immediately followed by a steep inclined crack propagating upward 

from the toe. Next, sliding occurs along a horizontal bed joint 

near the base of the wall, accompanied in some cases by stairstepped bed joint sliding at upper portions of the wall. With 

repeated cycles of loading, diagonal cracks increase. Eventually, crushing of the toes or excessive sliding leads to failure.

By analysis:

At higher damage levels, cracking may be similar to 

URM1H; however, in URM1F, the bed joint sliding will 

occur at the base of the wall, in addition to the center of the 

wall. Confirm by analysis that bed joint sliding capacities 

are sufficiently low to trigger URM1F.

Caution: At low damage levels, flexural cracking may be 

similar to cracking that occurs in other modes.

Refer to Evaluation Procedures for:

• In-plane wall behavior: See Section 7.3.2

Level Description of Damage Typical Performance Restoration 

Measures

Insignificant Criteria: 1. Horizontal hairline cracks in bed joints at the 

heel of the wall.

2. Possibly diagonally-oriented cracks and minor 

spalling at the toe of the wall.

Not necessary for restoration of structural performance. (Measures may be 

necessary for restoration of nonstructural 

characteristics.)

λΚ = 1.0

λQ = 1.0

λD = 1.0

μ∆ ≤ 1.5

Typical Appearance:

Slight Not used

URM1F

≈
 Chapter 7: Unreinforced Masonry

FEMA 306 Basic Procedures Manual 173

COMPONENT DAMAGE 

 CLASSIFICATION GUIDE continued

Level Description of Damage Typical Performance Restoration 

Measures

Moderate

λΚ = 0.9

λQ = 0.61

λD = 0.9

Criteria: 1. Horizontal cracks/spalled mortar at bed joints at 

or near the base of the wall indicating that inplane offset along the crack has occurred up to 

approximately 1/4”.

2. Possibly diagonally-oriented cracks and spalling 

at the toe of the wall. Cracks extend upward several courses.

3. Possibly diagonally-oriented cracks at upper portions of the wall which may be in the units.

• Replace/drypack damaged units.

• Repoint spalled mortar and open head 

joints.

• Inject cracks and open head joints.

• Install pins and drilled dowels in toe 

regions.

1. As an 

alternative, 

calculate as 

Vbjs2/Vtc

∆/heff≤0.8%

Typical Appearance: λΚ* = 1.01

λQ* = 1.01

λD* = 1.01

1. In some cases, grout injection may 

actually increase strength, but decrease 

deformation capacity, by changing 

behavior from bed joint sliding to a less 

ductile behavior mode (see FEMA 307, 

Section 4.1.3).

Heavy

λΚ = 0.8

λQ = 0.61

λD = 0.9

Criteria: 1. Horizontal bed joint cracks near the base of the 

wall similar to Moderate, except width is up to 

approximately 1/2”.

2 Possibly extensive diagonally-oriented cracks 

and spalling at the toe of the wall. Cracks extend 

upward several courses.

3 Possibly diagonally-oriented cracks up to 1/2” at 

upper portions of the wall.

• Replace/drypack damaged units.

• Repoint spalled mortar and open head 

joints.

• Inject cracks and open head joints.

• Install pins and drilled dowels in toe 

regions.

1. As an 

alternative, 

calculate as 

Vbjs2/Vtc

∆/heff≤1.2%

Typical Appearance: λΚ* = 1.01

λQ* = 1.01

λD* = 1.01

1. In some cases, grout injection may 

actually increase strength, but decrease 

deformation capacity, by changing 

behavior from bed joint sliding to a less 

ductile behavior mode (see FEMA 307, 

Section 4.1.3).

Extreme Criteria: • Vertical load-carrying ability is threatened • Replacement or enhancement

required.

Typical 

Indications

• Stair-stepped movement is so significant that 

upper bricks have slid off their supporting 

brick.

• Toes have begun to disintegrate.

• Residual set is so significant that portions of 

masonry at the edges of the pier have begun or 

are about to fall.

URM1F
 Chapter 7: Unreinforced Masonry

174 Basic Procedures Manual FEMA 306

COMPONENT DAMAGE

CLASSIFICATION GUIDE

System: URM

Component Type: Weaker Pier

Behavior Mode: Diagonal Tension

How to distinguish behavior mode:

By observation:

Typical diagonal tension cracking—resulting from strong mortar, weak units, and high compressive stress—can be identified 

by diagonal cracks (“X” cracks) that propagate through the 

units. In many cases, the cracking is sudden, brittle, and vertical load capacity drops quickly. The cracks may then extend to 

the toe and the triangles above and below the crack separate. In 

a few cases, the load drop may be more gradual with cracks 

increasing in size and extent with each cycle. A second form of 

diagonal tension cracking also has been experimentally 

observed with weak mortar, strong units and low compressive 

stress where the cracks propagate in a stair-stepped manner in 

head and bed joints. The first (typical) case is shown below.

By analysis:

Since the stair-stepping form of cracking would appear similar to the early levels of stair-stepped bed joint sliding, confirm by analysis that diagonal tension governs over bed joint 

sliding. Since deterioration at the corners in the Heavy damage level may resemble toe crushing, also confirm that diagonal tension governs over toe crushing.

Refer to Evaluation Procedures for:

• In-plane wall behavior: See Section 7.3.2.

Level Description of Damage Typical Performance Restoration 

Measures

Insignificant Criteria: 1. Hairline diagonal cracks in masonry units in 

fewer than 5% of courses.

Not necessary for restoration of structural performance. 

λΚ =1.0

λQ = 1.0

λD = 1.0

μ∆ ≤1

Typical Appearance: (Measures may be necessary for

restoration of nonstructural characteristics.)

URM2K
 Chapter 7: Unreinforced Masonry

FEMA 306 Basic Procedures Manual 175

COMPONENT DAMAGE 

CLASSIFICATION GUIDE continued

Level Description of Damage Typical Performance Restoration 

Measures

Slight Not used.

Moderate

λΚ =0.8

λQ = 0.9

λD = 1.0

μ∆ ≈1-1.5

Criteria: 1. Diagonal cracks in pier, many of which go 

through masonry units, with crack widths below 

1/4”.

2. Diagonal cracks reach or nearly reach corners.

3. No crushing/spalling of pier corners.

• Repoint spalled mortar.

• Inject cracks.

λΚ* = 0.8

λQ* = 1.0

Typical Appearance: λD* = 1.0

Heavy

λΚ = 0.4

λQ = 0.8

λD = 0.7

μ∆ >1.5

Criteria: 1. Diagonal cracks in pier, many of which go 

through masonry units, with crack widths over 

1/4”. Damage may also include:

2. Some minor crushing/spalling of pier corners 

and/or

3. Minor movement along or across crack plane.

Replacement or enhancement is required 

for full restoration of seismic performance.

For partial restoration of performance:

• Replace/drypack damaged units.

• Repoint spalled mortar.

• Inject cracks.

λΚ* = 0.8

λQ* = 0.8

λD* = 1.0

Typical Appearance:

Extreme Criteria: • Vertical load-carrying ability is threatened • Replacement or enhancement required.

Typical Indications

• Significant movement or rotation along crack 

plane.

• Residual set is so significant that portions of 

masonry at the edges of the pier have begun or 

are about to fall.

URM2K
 Chapter 7: Unreinforced Masonry

176 Basic Procedures Manual FEMA 306

DAMAGE CLASSIFICATION

AND REPAIR GUIDE

System: URM

Component Type: Solid Wall

Behavior Mode: Flexural Cracking/

Toe Crushing

How to distinguish behavior mode:

By observation:

This type of behavior typically occurs in stockier walls with 

L/heff > 1.25. Based on laboratory testing, four steps can usually be identified. First, flexural cracking happens at the base 

of the wall, but it does not propagate all the way across the 

wall. This can also cause a series of horizontal cracks to form 

above the heel. Second, sliding occurs on bed joints in the central portion of the pier. Third, diagonal cracks form at the toe of 

the wall. Finally, large cracks form at the upper corners of the 

wall. Failure occurs when the triangular portion of wall above 

the crack rotates off the crack or the toe crushes so significantly that vertical load is compromised. Note that, for simplicity, the figures below only show a single crack, but under 

cyclic loading, multiple cracks stepping in each direction are 

possible.

By analysis:

Stair-stepped cracking may resemble a form of bed joint 

sliding; confirm by analysis that toe crushing governs over 

bed joint sliding.

Refer to Evaluation Procedures for:

• In-plane wall behavior: See Section 7.3.2

Level Description of Damage Typical Performance Restoration 

Measures

Insignificant

λΚ = 0.9

λQ = 1.0

λD = 1.0

Criteria: 1. Horizontal hairline cracks in bed joints at the 

heel of the wall. 

2. Horizontal cracking on 1-3 cracks in the central 

portion of the wall. No offset along the crack has 

occurred and the crack plane is not continuous 

across the pier.

3 No cracks in masonry units.

Not necessary for restoration of structural performance. (Measures may be 

necessary for restoration of nonstructural 

characteristics.)

μ∆ ≤ 1.5 Typical Appearance:

Slight Not used

Moderate Not used

URM1H
 Chapter 7: Unreinforced Masonry

FEMA 306 Basic Procedures Manual 177

COMPONENT DAMAGE 

 CLASSIFICATION GUIDE continued

Level Description of Damage Typical Performance Restoration Measures

Heavy

λΚ = 0.8

λQ = 0.8

λD = 1.0

∆/heff≤0.3%

Criteria: 1. Horizontal hairline cracks in bed joints at the 

heel of the wall.

2. Horizontal cracking on 1-3 cracks in the central 

portion of the wall. Some offset along the crack 

may have occurred.

3. Diagonal cracking at the toe of the wall, likely 

to be through the units, and some of units may 

be spalled.

Replacement or enhancement is required 

for full restoration of seismic performance.

For partial restoration of performance:

• Repoint spalled mortar.

• Inject cracks.

λΚ* = 0.9

λQ* = 0.9

λD* = 1.0

Typical Appearance:

Extreme

λΚ = 0.6

λQ = 0.6

λD = 0.9

∆/heff≤0.9%

Criteria: 1. Horizontal hairline cracks in bed joints at the 

heel of the wall.

2 Horizontal cracking on 1 or more cracks in the 

central portion of the wall. Offset along the 

crack will have occurred.

3 Diagonal cracking at the toe of the wall, likely 

to be through the units, and some of units may 

be spalled.

4 Large cracks have formed at upper portions of 

the wall. In walls with aspect ratios of

L/heff >1.5, these cracks will be diagonally oriented; for more slender piers, cracks will be 

more vertical and will go through units.

Replacement or enhancement is required 

for full restoration of seismic performance.

For partial restoration of performance:

• Replace/drypack damaged units.

• Repoint spalled mortar.

• Inject cracks.

• Install pins and drilled dowels in toe 

regions.

λΚ* = 0.9

λQ* = 0.8

λD* = 1.0

Typical Appearance:

URM1H
 Chapter 7: Unreinforced Masonry

178 Basic Procedures Manual FEMA 306

COMPONENT DAMAGE

CLASSIFICATION GUIDE

System: URM

Component Type: Weak Spandrel

Behavior Mode: Spandrel Unit 

Cracking

How to distinguish behavior mode:

By observation:

In this type of behavior, the moment at the end of the spandrel is 

not relieved by sliding, but instead causes brittle vertical cracking though the masonry units. Cracking propagates rapidly as 

displacement increases and cycles continue. Depending on the 

lintel construction, this can lead to a local falling hazard. It also 

increases the effective height of the piers. As the spandrel displaces, the nonlinear mechanism of response may move to other 

portions of the wall such as the piers.

By analysis:

No analysis is typically necessary to distinguish this mode.

Refer to Evaluation Procedures for:

• In-plane wall behavior: See Section 7.3.4.

Level Description of Damage Typical Performance Restoration Measures

Insignificant Criteria: 1. Predominantly vertical cracks/spalled mortar 

through no more than one unit at the ends of the 

spandrel.

Not necessary for restoration of structural 

performance. (Measures may be necessary for restoration of nonstructural characteristics.)

λΚ = 0.9

λQ = 0.9

λD = 1.0

μ∆ ≤ 1.5

Typical Appearance:

Slight Not used.

URM3I
 Chapter 7: Unreinforced Masonry

FEMA 306 Basic Procedures Manual 179

COMPONENT DAMAGE 

CLASSIFICATION GUIDE continued

Level Description of Damage Typical Performance Restoration 

Measures

Moderate Not Used 

Heavy

λΚ = 0.2

λQ = 0.41

λD = 0.6

Criteria: 1. Predominantly vertical cracks/spalled mortar 

across the full depth of each end of the spandrel. 

In over 1/3 of the courses, cracks go through the 

masonry units.

2. Possibly some deterioration of units at bottom 

ends of spandrel, but no vertical slip of the spandrel.

Replacement or enhancement is 

required for full restoration of seismic 

performance.

For partial restoration of performance:

• Stitch across crack with pins and 

drilled dowels.

• Repoint spalled mortar.

• Inject cracks.

λΚ* = 0.8

λQ* = 0.8

λD* = 1.0

1. As an 

alternative, 

calculate per 

Section 7.3.4

Typical Appearance:

Extreme Criteria: • Vertical load-carrying ability is threatened. • Replacement or enhancement 

required.

Typical Indications

One or more of the following:

• Lintel support has separated from the pier.

• Out-of-plane movement of the spandrel.

• Spandrel has slipped vertically.

URM3I
 Chapter 7: Unreinforced Masonry

180 Basic Procedures Manual FEMA 306

COMPONENT DAMAGE

CLASSIFICATION GUIDE

System: URM

Component Type: Solid Wall

Behavior Mode: Out-of-Plane Flexural Response

How to distinguish behavior mode:

By observation:

Out-of-plane failures are common in URM buildings. Usually 

they occur due to the lack of adequate wall ties, as discussed in 

Table 7-1. When ties are adequate, the wall may fail due to outof-plane bending between floor levels. One mode of failure 

observed in experiments is rigid-body rocking motion occurring 

on three cracks: one at the top of the wall, one at the bottom, 

and one at midheight. As rocking increases, the mortar and 

masonry units at the crack locations can be degraded, and residual offsets can occur at the crack planes. The ultimate limit state 

is that the walls rock too far and overturn. Important variables 

are the vertical stress on the wall and the height-to-thickness 

ratio of the wall. Thus, walls at the top of buildings and slender 

walls are more likely to suffer damage.

By analysis:

None required.

Caution: 

If horizontal cracks are located directly below wall-diaphragm ties, damage may be due to bed joint sliding associated with tie damage. For piers, if horizontal cracks are 

observed at the top and bottom of the pier but not at midheight, see URM2A. Confirm whether the face brick is 

unbonded to the backing brick. If so, the thickness in the h/t

requirement is reduced to the thickness of the backing 

wythes.

Refer to Evaluation Procedures for: Out-of-plane wall behavior: See Section 7.3.5.

Level Description of Damage Typical Performance Restoration Measures

Insignificant

For out-ofplane loads: 

Criteria: 1. Hairline cracks at floor/roof lines and midheight 

of stories.

2. No out-of-plane offset or spalling of mortar 

along cracks.

Not necessary for restoration of structural 

performance. 

λh/t= 1.0

For in-plane 

modes given 

previously, 

assume outof-plane 

damage leads 

to Moderate 

damage for 

URM2B and 

Insignificant 

damage for 

all other 

modes.

Typical Appearance: (Measures may be necessary for restoration of nonstructural characteristics.)

URM1M
 Chapter 7: Unreinforced Masonry

FEMA 306 Basic Procedures Manual 181

COMPONENT DAMAGE 

CLASSIFICATION GUIDE continued

Level Description of Damage Typical Performance Restoration 

Measures

Slight Not used.

Moderate

For out-ofplane loads:

λh/t= 0.9

Criteria: 1. Cracks at floor/roof lines and midheight of stories may have mortar spalls up to full depth of 

joint and possibly:

2. Out-of-plane offsets along cracks of up to 1/8”.

• Repoint spalled mortar:

• For out-of-plane loads:

λh/t= 1.0

• For in-plane loads: use Moderate for 

URM2B and Insignificant for all other 

For in-plane modes.

modes, see 

Insignificant 

damage

Typical Appearance: See Insignificant damage 

above.

Heavy

For out-ofplane loads:

λh/t= 0.6

Criteria: 1 Cracks at floor/roof lines and midheight of stories may have mortar spalls up to full depth of 

joint.

2 Spalling and rounding at edges of units along 

crack plane.

3 Out-of-plane offsets along cracks of up to 1/2”.

Replacement or enhancement is required 

for full restoration of seismic performance.

For partial restoration of out-of-plane 

performance:

• Replace/drypack damaged units

For in-plane 

modes given 

previously, 

assume outof-plane 

damage leads 

to Heavy for 

all other 

modes.

Typical Appearance: • Repoint spalled mortar

λh/t= 0.8

Extreme Criteria: • Vertical-load-carrying ability is threatened • Replacement or enhancement required.

Typical Indications

• Significant out-of-plane or in-plane movement 

at top and bottom of piers (“walking”).

• Significant crushing/spalling of bricks at crack 

locations.

URM1M
 Chapter 7: Unreinforced Masonry

182 Basic Procedures Manual FEMA 306
FEMA 306 Basic Procedures Manual 183 

8: Infilled Frames

8.1 Introduction and 

Background

This section provides material relating to infilled frame 

(INF) construction that supports and supplements the 

Damage Classification Guides (or Component Guides) 

in Chapters 5 through 7. Following this introductory 

material, infilled frame component types are defined 

and discussed in Section 8.2. Inelastic behavior modes 

are also summarized in Section 8.2. The overall damage 

evaluation procedure uses conventional material 

properties as a starting point. Section 8.3 provides 

information on strength and deformation properties of 

infilled frame components. The information on infilled 

frame components has been generated from a review of 

available empirical and theoretical data listed in the 

Tabular Bibliography (Section 5.2 of FEMA 307) and 

References section of this document, or Section 5.3 of 

FEMA 307). These provide the user with further 

detailed resources on infilled frame component 

behavior.

Infilled frame construction has been in use for more 

than 200 years. The infilling of frames, in contrast with 

URM structures, is associated primarily with the 

construction of high-rise buildings—the frames being a 

means of carrying gravity loads, the infills a means of 

providing a building envelope and/or internal 

partitioning. In high-rise structures, the frames have 

been generally well-engineered in accordance with the 

state-of-knowledge of the day, whereas the infill panels 

were invariably considered to be “nonstructural”. It was 

not until the 1950s that investigations began on the 

interaction between infill panels and the frames of 

buildings (Polyakov, 1956). This pioneering work 

undertaken in the former Soviet Union was strictly a 

reflection of Russian building practice. However, many 

of the theoretical techniques and other findings are still 

of relevance. The first study in the United States that 

investigated the lateral-load behavior of infilled frames, 

using specimens typical of U.S. construction practice 

(steel frames with brick infills), was reported by 

Benjamin and Williams (1958). These and other early 

studies were mostly concerned with the monotonic 

lateral-strength capacity of infilled frame systems.

Immediately following the advent of experimental 

investigations, analytical research began on the 

performance of infilled-frame systems. Over the years, 

several different methods of analysis were proposed for 

determining the composite strength of an infilled-frame 

system. These methods included elasticity solutions 

based on the Airy stress function, the finite-difference 

method, the finite-element method, and plastic methods 

of analysis. For a summary, see Maghaddam and 

Dowling (1987).

Although these methods of analysis have been shown to 

be reasonably successful in predicting the strength 

capacity of infilled-frame systems, each method has its 

roots in elasticity or rigid plasticity, making it either 

difficult or impossible to extend the findings to inelastic 

(elasto-plastic) behavior, especially if cyclic loading is 

to be considered. Therefore, it is not surprising that the 

equivalent-strut method of analysis has become the 

most popular approach for analyzing infilled frame 

systems. Early equivalent-strut methods, starting with 

Stafford-Smith (1966), used an equivalent single strut to 

represent infill behavior. It was later realized that such a 

simplification did not accurately capture all facets of 

frame/panel interaction. Therefore, several multiplestrut methods of analysis have been proposed (see for 

example Chrysostomou et al., 1988; Thiruvengadam, 

1985; Mander et al., 1994). In spite of these attempts to 

enhance infilled frame analysis using a multiple-strut 

approach, there are still drawbacks—principally the 

inability to model force transfer-slip at the frame-panel 

interfaces (Gergely et al., 1994). Nonlinear finite 

element analysis, however, can be used if such a 

refinement is required (Shing et al., 1994; Mosalan et 

al., 1994), but difficulties remain, mostly due to 

computational limitations, on analyzing more than one 

panel at a time.

The general consensus is that a single equivalent-strut 

approach (two struts per panel for reversed cyclic 

loading analysis, one across each diagonal) may be 

successfully used for design and evaluation studies of 

infilled frame systems. Such an approach has been 

recently adopted by FEMA 273.

In spite of the general success of modeling infilled 

frames with solid panels, major difficulties still remain 

unresolved regarding the modeling approach for infilled 

frames with openings. Such frames, in practice, are 

commonplace and are perhaps the norm rather than the 

exception. However, only a limited amount of research 

has been undertaken on infilled frames with openings 

(e.g., Benjamin and Williams, 1958; Durrani and Luo, 

1994; Coul, 1966; Dawe et al., 1985a,b; Holmes, 1961; 

Liauw, 1977; Mallick and Garg, 1971). Other strength 

analysis recommendations have been made for infills 
 Chapter 8: Infilled Frames

184 Basic Procedures Manual FEMA 306

with wide openings, but these have not been 

substantiated by experimental studies (Hamburger and 

Chakradeo, 1993; Freeman, 1994). For this reason, it is 

suggested that infilled frames with openings exceeding 

50 percent of the panel area be treated either using other 

sections of this document (namely URM for infills with 

brick piers or reinforced concrete for cases in which 

infills surround steel columns) or by nonlinear finite 

element procedures such as discussed by Kariotis et al. 

(1996).

It is important to recognize that many behavior 

problems with infilled frames arise from discontinuities 

of infill, resulting from soft stories or checkered 

patterns, leading to a high concentration of forces to be 

transferred among components.

Other impediments to reliable modeling generalizations 

of infilled-frame systems are the large variation in 

construction practice over different geographic regions 

and changes of materials over time. Early infilled-frame 

construction generally consisted of clay brick (or 

sometimes stone masonry) and iron/steel frames. With 

time, concrete frames became popular and concrete 

masonry units or solid (poured) concrete were used for 

the infill panels. Concrete masonry or concrete infill 

panels may be either unreinforced or reinforced (and 

grouted or not in the case of concrete blocks).

Early research that investigated the seismic 

performance of infilled-frame specimens using reversed 

cyclic loading mostly focused on developing improved 

seismically-resistant design, analysis, and construction 

techniques for new structures (e.g., Axely and Bertero, 

1979; Bertero and Brokken, 1983; Klingner and 

Bertero, 1976, 1978; Zarnic and Tomazevic, 1984, 

1985a,b). Little research was done to investigate the 

seismic performance of existing structures with 

nonductile detailing. Although some studies have been 

conducted on infilled frames with deficient detailing 

(e.g., Gergely et al., 1993, 1994; Flannagan and 

Bennett, 1994; Mander et al., 1993a,b; Reinhorn et al., 

1995), much work, especially experimental 

investigations, remains to be done.

8.2 Infilled Frame Masonry 

Component Types and 

Behavior Modes

8.2.1 Component Types

Infilled-frame elements are made up of infilled-panel 

and frame components, as summarized in Table 8-1. 

The general characteristics of these basic components 

are summarized as follows:

a. Infilled Panels

Infilled panels are primarily categorized according to 

material and geometric configuration.

Materials. Clay brick masonry is perhaps the most 

commonly encountered type of infill material. The use 

of this traditional building material for infill 

construction dates back to the 1800s, when steel or iron 

frames were first used for high-rise construction. 

Generally twin or multi-wythe bricks are used, but other 

forms exist, such as cavity walls for exterior facades. 

Most often, brick masonry is unreinforced (see 

Section 7.1). In more modern buildings, reinforced, 

grouted-cavity wall construction may be found.

Hollow clay tile (HCT) is a relatively modern form of 

unreinforced masonry infill construction (see 

Section 7.1). The infills are often offset with respect to 

the centerlines of columns. HCT is often found on 

building facades. With steel frames, the clay tiles can be 

placed around the frames for aesthetic and fire 

protection purposes. HCT is very commonly used for 

interior partitions in framed buildings. As a material, 

HCT is generally very brittle and prone to forcecontrolled behavior.

Concrete masonry unit (CMU) construction is a form of 

infill using hollow concrete blocks laid up with mortar. 

CMU may be left hollow or filled with grout, either 

partially or completely. If grouted, steel reinforcement 

may or may not be present. The strength and ductility of 

the infill is highly dependent on the degree of grouting 

and reinforcement. Ungrouted infills are comparatively 

weak. This is because when the in-plane forces become 

large, compressive splitting of the face shells occurs 

with a complete loss of strength in masonry. Moreover, 

sliding-shear resistance relies entirely on the mortar in 

the bed joints. Grouted concrete masonry infills can be 

quite strong for normal bay sizes. Although early 

spalling of face shells may occur due to high in-plane 

lateral compression stresses, the grouted core has 

considerable ability in resisting additional loads, 

particularly if reinforced. Chapter 6 has additional 

information for reinforced CMU and Chapter 7 is 

applicable to unreinforced CMU.

Concrete infills are typically reinforced, though often 

minimally. In older buildings, the reinforcement is 

generally only for temperature and shrinkage control 

and is rarely provided to resist structural loads. In 
 Chapter 8: Infilled Frames

FEMA 306 Basic Procedures Manual 185

Table 8-1 Component Types for Infilled Frames

Component Type Description/Examples Materials/Details

INPS Solid infill panel Space within frame components completely filled Concrete

Reinforced

Unreinforced

Masonry (clay brick, hollow clay tile, 

concrete block)

Reinforced

Unreinforced

INPO Infill panel with 

openings

Doors and windows

Horizontal or vertical gaps

Partial-height infill

Partial-width infill

Same as solid infill panel

Sub-components similar to:

INP1

Strong pier

RC1 

RM1 

URM1 

Concrete

Reinforced masonry

URM

INP2

Weak pier

RC2 

RM2 

URM2 

Concrete

Reinforced masonry

URM

INP3

Weak spandrel 

(lintel)

RC3 

RM3 

URM3 

Concrete

Reinforced masonry

URM

INP4

Strong spandrel 

(lintel)

RC4 

RM4 

URM4

Concrete

Reinforced masonry

URM

INF1 Frame column Vertical, gravity-load-carrying Concrete

Steel

INF2 Frame beam Horizontal, gravity-load-carrying Concrete

Steel

INF3 Frame joint Connection between column and beam components

Rigid moment-resisting 

Partially-rigid

Simple shear

Monolithic concrete

Precast concrete

Bolted steel

Riveted steel

Welded steel
 Chapter 8: Infilled Frames

186 Basic Procedures Manual FEMA 306

modern buildings, however, the reinforced concrete 

infill may be well reinforced and act compositely with 

the surrounding frame. See Chapter 5 for additional 

information applicable to concrete infill.

Geometry. Infill may have a wide variety of geometric 

configurations. Aspect ratios (length/height of the 

planar space defined by the surrounding frame 

components) for infilled panels varies from 

approximately 1:1 to 3:1 with most ranging from 1.5:1 

to 2.5:1. Infills may be configured in many forms to suit 

partitioning and/or facade requirements. It is not 

uncommon to find infills placed eccentrically to the axis 

of the frame components. For wider multi-wythe infills, 

entire rows of bricks may not engage with the frame at 

all. This leads to differential behavior and movements. 

For the purposes of evaluating infilled frame 

performance, only those bricks/blocks bounded by 

frames should be considered as part of the load infilled 

panel component.

For the purposes of damage evaluation, Table 8-1 

identifies two categories for infilled panel components 

based on geometric configuration. Solid infilled panel 

components (INPS) are those that completely fill the 

planar space tightly within the surrounding frame 

components. Those with openings (INPO) may exhibit 

fundamentally different behavior. 

Initial gaps at the top or sides of an infill affect 

performance of the solid panel configurations. These 

gaps can arise from the construction process not 

providing a tight infill, or in the case of concrete 

masonry units, from shrinkage. Until gaps are closed, 

normal frame behavior can be expected. When the gaps 

suddenly close, impacting forces on the infill can 

dramatically change the behavior patterns of the frame. 

Seismic gaps can be built into infill wall panels, 

although this practice is not common in the United 

States.

Perforations within the infill panels are the most 

significant parameter affecting seismic behavior of 

infilled systems. Doors and windows are the two most 

prevalent opening types. Openings located in the center 

portion of the infill can lead to weak infill behavior. On 

the other hand, partial-height infills (with windows 

spanning the entire top half of the bay) can be relatively 

strong. The frames are often relatively weak in column 

shear and when partial-height infill is present, this 

potentially leads to a short-column soft-story collapse 

mechanism. Partial-width infills are also relatively 

common: in this case, window openings extend the full 

height between floors. Partial-width infill often has 

been placed on each side of a column component.

b. Frames

The frame components of infilled-frame seismic 

elements are categorized primarily by material.

Steel. Steel frames are common, especially for older 

structures. Steel frames are also popular for modern 

high-rise buildings and low-rise, light-weight, 

commercial, building construction. Column and beam 

components are most often I-sections (older) or wideflange sections (newer). Built-up columns and doublechannel beams are much less common. In older steel 

frames, the beam and column components are typically 

joined by semi-rigid riveted connections. More modern 

steel frames often use bolted or welded, or both, semirigid connections. Many of the frame systems are 

enclosed by concrete, the beams enclosed as a part of 

the floor system and the columns encased for fire 

protection. In these circumstances semi-rigid (or 

partially restrained) riveted connections will behave as 

fully restrained until the confining concrete cracks. 

Because of the relatively high shear capacity of steel 

columns, the fully restrained mode of behavior may be 

dominant.

Concrete. Concrete frames are also a common form of 

construction. Reinforced concrete frames may be 

classified as either ductile or nonductile for seismic 

performance, based primarily on the details of 

reinforcement. Contemporary structural design requires 

ductile detailing of the members. Ductile detailing 

requires closely-spaced transverse hoops in the beams, 

columns, and connections. If such members surround 

weak infill panels, they will suffer relatively less serious 

damage under lateral loads. Fully-ductile frames are 

relatively rare and, in the United States, are found only 

in the west, and seldom in infilled frame buildings. 

Typically, beams do not have adequate confinement and 

rarely is the bottom reinforcement continued through 

the joint. Concrete columns can, however, be designed 

with ductility, particularly in the western United States, 

where it is not uncommon for the better-built buildings 

to have spiral reinforcing. Under these circumstances 

the columns possess a relatively high shear capacity and 

displacement ductility, and the beam or the infill will be 

the deformation-limiting component.

Non-ductile frames are very common, particularly in 

regions of low-to-medium seismic risk. These frames 

are not detailed for ductility and may have one or more 

deficiencies: columns weaker than beams, lap splices in 
 Chapter 8: Infilled Frames

FEMA 306 Basic Procedures Manual 187

column hinge zones, and insufficient transverse 

reinforcement for confinement, for shear strength, and 

for longitudinal reinforcement stability. The beam/

column joints in concrete frames need to transmit high 

shear forces. When infills are present, shear force 

demands are considerably higher, leaving the beam or 

column vulnerable to shear failure.

Precast, prestressed, concrete frames are also 

commonly encountered with infilled panels. Although 

in many respects similar to reinforced concrete, the 

connections between columns and beams in precast 

construction are distinctly different. When nonengineered infills are placed between columns, 

premature failure may occur at the beam/column 

connections, leading to unseating of the beams.

8.2.2 Panel and Frame Modeling and 

Interaction

Because of the highly nonlinear nature of the infill/

frame interaction, proper modeling of the behavioral 

characteristics is best accomplished by a thorough 

analysis, material testing, and nonlinear, finite-element, 

modeling. Lacking the resources for that approach, an 

estimate of the behavior may be made by using a 

procedure similar to the identification of the appropriate 

inelastic lateral mechanism, as discussed in Section 2.4 

of this volume. The frame is modeled conventionally as 

an assembly of column (indicated by INF1) and beam 

(INF2) components, and connection components 

(INF3). The solid infilled components (INPS) can be 

modeled as equivalent struts in accordance with the 

recommendations of FEMA 273. Infilled components 

with openings (INPO) can sometimes also be modeled 

as struts depending on the size and location of the 

openings. Alternatively, sub-component “piers” (INP1, 

INP2) and “spandrels” (INP3, INP4) can be used to 

represent the infilled component with openings. 

Appropriate force-deformation characteristics for the 

sub-components can be generated using the information 

in Chapter 5 for concrete, Chapter 6 for reinforced 

masonry, and Chapter 7 for unreinforced masonry.

To establish the inelastic force-deformation behavior of 

the frame and infill using the component method, the 

engineer must manually determine the bifurcation 

points defining the mode of behavior. Broadly speaking, 

the behavior can be separated into two conditions which 

depend primarily on the degree of the infill interaction 

with the frame. In the case where the openings are 

extensive, the components can be assembled as frame 

elements and piers, with the frame performance 

modified by a potential for beam shear failure for cases 

with the infill primarily around the column, or by shortcolumn effects where the infill is primarily around the 

beam. Small piers within the frame contribute little to 

the overall stiffness, but must be checked to ensure 

displacement compatibility with the frame-limited 

deformations. 

For conditions where the infill is the controlling 

element, the degree of interaction is more complex. 

Initially, the defining characteristic is an uncracked 

panel. As the loading increases, the panel will 

experience bed-joint sliding or diagonal tension failure 

and transform the infill into an equivalent strut. Beam 

and column shears need to be investigated at this 

loading to ensure they are not the load-limiting 

condition. Following strut formation, corner crushing is 

often the next and final limiting condition. When 

checking corner crushing, the beam and column need to 

be checked for shear, and the column needs to be 

checked to verify that it has sufficient tension capacity 

to support the corner crushing. The tensile capacity is 

usually adequate for steel columns, but may be the 

limiting factor for lightly reinforced concrete columns, 

or columns having lap-splice problems.

8.2.3 Behavior Modes

a. Solid Panels

In cases where the infill component controls the 

stiffness, the events that define the shape of the forcedeformation curve are bed-joint sliding, diagonal 

tension, corner crushing, general shear failure, and outof-plane failure. Under small deformations the stiffness 

and behavior are dominated by the panel stiffness 

characteristics. As the deformation increases the panel 

characteristics will be a function of its element 

properties. When the masonry units are strong relative 

to the mortar, diagonal tension will result in a stairstepped pattern of cracks through head and bed joints. 

When the mortar is stronger than the units (rare), cracks 

will develop through the units as well as the mortar and 

follow a line normal to the direction of the principal 

stress. With the stair-stepped cracks, shear can continue 

to be resisted after cracking by the development of a 

compressive stress normal to the bed joints, 

characterized as a compression strut. If the mortar is 

weak relative to the units, an infill panel may crack 

along the bed joints instead of along the diagonal. In 

this case, horizontal cracks may occur across several 

bed joints as an assembly of units slides to 

accommodate the deflected shape of the frame. 

Although this cracking mode may occur at lower shear 
 Chapter 8: Infilled Frames

188 Basic Procedures Manual FEMA 306

forces, the overall frame-infill will possess greater 

inelastic deformation capacity because frame action 

will dominate. When the infill panel is sufficiently 

strong in shear, the compressive stress at the corners 

will fail in crushing. This mode will be the strongest 

and stiffest, but has limited deformation capacity 

because the crushing will be abrupt. Furthermore, the 

large forces generated in this mode will be distributed to 

the beam and column members, and may result in either 

column or beam shear failures. Table 8-2 presents four 

principal behavior modes for solid-infill panel 

components. Further explanation on the expected 

damage characteristics and likelihood of occurrence are 

given below.

i. Bed-Joint Sliding: This behavior mode commonly 

occurs in conjunction with other modes of failure. 

Bed-joint sliding is likely to occur when the bounding frame is strong and flexible (such as steel 

frames). If the mortar beds are relatively weak compared to the adjacent masonry units (especially 

bricks), a plane of weakness forms, usually near the 

mid-height level of the infill panel. Damage takes 

the form of minor crushing. There is really no limit 

to the displacement capacity of this behavior mode. 

Therefore, energy is continuously dissipated via 

Coulomb friction.

ii. Diagonal Cracking: Under lateral in-plane loading 

of an infill frame system, high compression stresses 

form across the diagonal of an infill. Transverse to 

these principal compression stresses and strains are 

tension strains. When the tensile strains exceed the 

cracking strain of the infill panel material, diagonal 

cracking occurs. These cracks commence in the 

center of the infill and run parallel to the compression diagonal. As interstory drifts increase, the 

diagonal cracks tend to propagate until they extend 

from one corner to the diagonally opposite corner. 

This common form of cracking is evident in most 

infill panels that have been subjected to high lateral 

loads and sometimes occur with bed-joint sliding. 

Diagonal cracking behavior usually signals the formation of a new diagonal strut behavior mode. 

iii. Corner Compression: Under lateral loading of 

infilled frames, some form of corner compression 

inevitably occurs. This is because of the high stress 

concentrations at each corner of the compression 

diagonal. For strong/stiff columns and beams, corner crushing is located over a relatively small 

region; whereas for weaker frames, especially concrete frames, corner crushing is more extensive and 

the damage extends into the concrete frame itself. 

In spite of the crushing damage that occurs, this is a 

relatively ductile failure mode. As interstory drifts 

increase, corner crushing becomes more pronounced to the extent that masonry units in the corner may fall out entirely. When this happens, 

crushing propagates towards the center of the beam 

and/or column.

iv. Out-of-Plane Failure: Ground shaking transverse to 

the plane of a wall may lead to an out-of-plane 

behavior mode. Experiments using air bags 

(Abrams, 1994), as well as shaking-table studies 

(Mander et al., 1994), show that for normal, infill 

panel, height-to-thickness ratios, considerable shaking is necessary to cause failure of the infill. However, out-of-plane failure may occur in the upper 

stories of high-rise buildings, where the floor accelerations are basically resonance amplifications of 

prominent sinusoidal ground motion input. In lower 

stories, when combined with high in-plane story 

shears, infill panels tend to progressively “walkout” of the frame enclosure on each cycle of loading. Although complete out-of-plane failure is not 

common, there is some evidence that this behavior 

mode has occurred. 

Table 8-2 Behavior Modes For Solid Infilled Panel Components 

Behavior Mode Description/Likelihood of Occurrence Ductility Figure Paragraph 

(Section 

8.2.3a)

Bed-joint sliding Occurs in brick masonry, particularly when 

length of panel is large relative to height 

aspect ratio is large and the mortar strength is 

low.

High 8-2 i

Diagonal cracking Likely to occur in some form Moderate 8-1, 8-4, 8-5 ii

Corner compression Crushing generally occurs with stiff columns. Moderate 8-1 iii

Out-of-plane failure More likely to occur in upper stories of buildings. However, out-of-plane “walking” is 

likely to occur in the bottom stories, due to 

concurrent in-plane loading.

Low 8-5 iv
 Chapter 8: Infilled Frames

FEMA 306 Basic Procedures Manual 189

Figure 8-1 Ductile reinforced concrete frames with concrete masonry infills tested by Mehrabi et al. (1996). (The 

weak and strong infills were ungrouted and grouted, respectively). (a) Specimen 4, (b) Specimen 5, (c) 

Specimen 7; h/L aspect ratio = 0.67. Note 1 in. = 1.65% interstory drift
 Chapter 8: Infilled Frames

190 Basic Procedures Manual FEMA 306

Figure 8-2 Bed-joint sliding of a two-bay steel frame-block infill. Model study by Gergely et al. (1994).
 Chapter 8: Infilled Frames

FEMA 306 Basic Procedures Manual 191

Figure 8-3 Specimen tested by Mander et al. (1993a). Steel frame-clay brick masonry infill. Top and seat angles 

semi-rigid connections used to connect beams to columns.

(a) Original specimen.

(b) Specimen repaired with 1/2-inch ferrocement overlay and retested.
 Chapter 8: Infilled Frames

192 Basic Procedures Manual FEMA 306

Figure 8-4 Effect of openings on the monotonic lateral-load performance of steel frame-masonry infill tested by 

Dawe and Seah (1988).
 Chapter 8: Infilled Frames

FEMA 306 Basic Procedures Manual 193

Figure 8-5 Out-of-plane behavior of infilled masonry walls showing crack patterns and out-of-plane lateral load vs. 

lateral displacement of an air bag test. (From Angel and Abrams, 1994).
 Chapter 8: Infilled Frames

194 Basic Procedures Manual FEMA 306

Figure 8-6 Experiments conducted by Aycardi et al. (1994), showing the performance of nonductile frame members 

with lap splices at the base of the column.

Specimen 1: Column with a moderately high level of axial load.

Specimen 3: Column with a lower level, variable, axial load.

Slab-beam-column subassemblage: Tested with variable axial load.

(Note: Deterioration was due to cyclic loading action, the weak zone being the beam rather than the 

column).
 Chapter 8: Infilled Frames

FEMA 306 Basic Procedures Manual 195

b. Panels With Openings

Infilled panels with openings are best viewed as 

assemblies of subcomponents of the appropriate 

material. The behavior modes for the subcomponents 

are discussed in the other material sections (Chapter 5 

for concrete, Chapter 6 for reinforced masonry, and 

Chapter 7 for URM). These subcomponents interact 

with the surrounding frame and can alter the frame 

response. Principal types of interaction can that can 

occur are strong columns and strong piers inducing 

shear failure in the beams, strong spandrel components 

reducing the ductility by causing short-column effects, 

and by the infill inducing tension yielding or bar splice 

failures in the column. A discussion of the frame 

component behavior modes is given below in 

Section 8.2.3c.

c. Frame components

Table 8-3 and Table 8-4 present the principal behavior 

modes for steel and concrete frames, respectively, 

possessing infills. An explanation of these behavior 

modes follows.

i. Flexural Yielding in Steel: Flexural yielding of the 

frame is primarily associated with steel frames. 

When large lateral loads are imposed on moment 

frames, flexural yielding that leads to plastic hinging is to be expected adjacent to rigid connection. 

For infilled frames, this generally occurs at the base 

of fixed-base columns. This is generally evidenced 

by cracking of paint (if any) and buckling of compression flanges. As the rotational capacity of flexural plastic hinges in steel members is high, and 

unlikely to be attained in infilled-frame systems 

because the infills limit the interstory drifts, damage 

from this behavior mode is mostly cosmetic and 

generally not serious.

ii. Shear Yielding in Steel: When corner crushing 

occurs in a strong infill, the diagonal compression 

strut moves downward into the column providing a 

large shear force at the end-region of the column. 

For thin webbed steel members (non-compact sections) that are not confined by concrete, this may 

lead to web buckling and large localized shear 

deformations in the frame members. However, 

shear yielding in steel is ductile, and damage arising 

from this behavior mode is not serious.

iii. Bolted or Riveted Connection Failure: Steel-frame 

systems with infill panels generally have bolted or 

riveted semi-rigid, beam-to-column connections, 

and the connection is usually encased in concrete. 

Under these conditions the joint will behave as a 

rigid joint until the concrete breaks. Under large lateral loads the concrete can fail, or, when there is no 

confinement, yielding of the connection may occur. 

Such behavior is not serious, because the ductility 

capacity of semi-rigid connections is considerable 

(Mander et al., 1994 and 1995). However, in the 

presence of infill panels, the large diagonal strut 

force puts the connection under considerable axial 

tension. This may cause prying in the connection 

angles, giving the appearance of serious damage. 

Nevertheless, the ductility capability of these connections is still considerable and they are capable of 

sustaining many cycles of loading before a lowcycle fatigue failure, by which time the infill panel 

itself will have inevitably failed (Mander et al., 

1993a). 

iv. Flexural Yielding in Reinforced Concrete Frame 

Components: This behavior mode is expected to 

occur in reinforced concrete frames with infill when 

the interstory drift ratios exceed about 0.005. Flexural yielding behavior occurs where moments are 

greatest—that is, at the ends of beam and column 

members. In order for a complete side-sway mechanism to form in a structural concrete frame, flexural 

yielding and plastic hinging must also occur at the 

base of the columns (ground-floor level). Flexural 

yielding behavior in reinforced concrete beam and 

column components is characterized by tensile 

cracking in the cover concrete (transverse to the 

axis of the member), coupled with some compression crushing in the cover concrete on the opposite 

face. High bending moments in frames are also generally associated with high shear forces. Shear 

demand, when coupled with bending moment, produces diagonal cracking. When flexural plastichinge rotations become substantial (note that this is 

unlikely for infilled frames as the infills substantially limit the amplitudes of interstory drifts), considerable crushing and loss of cover concrete is 

evident, often leaving the longitudinal and transverse reinforcement exposed. If such severe damage is evident in an infilled-frame system, it is 

likely to occur in the lowest story, where high story 

shear demand has caused the infill panel to fail, 

leading to subsequent, high, interstory drifts (see, 

for example, Klingner and Bertero, 1978).

v. Lap-Splice Slip in Concrete: Most older infilledframe structures have not been specifically 

designed for earthquake resistance, and the frames 

possess nonductile details. This can lead to column 

lap splices occurring in potential plastic-hinge 
 Chapter 8: Infilled Frames

196 Basic Procedures Manual FEMA 306

zones. For the lap-splice detail deficiency, the connection will undergo flexural yielding at large lateral drifts. Cracking associated with incipient 

hinging tends to show a combination of transverse 

(flexure) cracks along with longitudinal (splitting) 

cracks that run parallel to the longitudinal column 

reinforcement. These longitudinal cracks signal that 

the bars in the lap-splice zone have begun to slip. If 

the interstory drifts are substantial and the cyclic 

loading pronounced, then the bond within the lapsplice zone is destroyed. Moment transfer in the 

lap-splice zone becomes limited when spalling of 

the cover concrete is apparent. It should be noted, 

however, that this behavior mode does not necessarily lead to an unsafe situation, for the lack of 

moment capacity finally leads to a pinned connection, capable of transferring axial load and shear. 

For some experimental results on nonductile concrete columns with lap splices at the base of columns, see Aycardi et al. (1992, 1994). 

vi. Column Tension Yielding: When the effect of the 

infill is substantial, the frame will behave more like 

a braced frame than moment frame, resulting in the 

columns resisting the lateral forces and overturning 

forces in tension and compression. For many older 

buildings the columns are lightly reinforced and 

may have more compression capacity than tension 

capacity, resulting in a tension yielding condition. 

This is a ductile mode, allowing larger displacements without causing an abrupt failure. The limiting deformation in this mode is the deformation 

capacity of the infill.

vii. Concrete Shear Failure: Infilled frames that possess 

strong infill panels generate large shear forces in the 

infill panels when under lateral side-sway. These 

shear forces must be transferred from the panel into 

the frame. If the infill panel is damaged in the corners as a result of corner crushing, then the diagonal 

strut tends to move away from the panel corner. The 

high transverse forces from the diagonal strut then 

enter the frame some distance (typically about one 

member depth) away from the beam/column connection. This provides a very high shear demand 

over a short column (or sometimes beam) length. 

Damage to the frame members is indicated by large 

diagonal X-cracks and spalling of the cover concrete. Under very severe cases of damage (weak 

frame / strong infill), complete loss of cover concrete and bulging of the core may be expected. If 

this occurs in a column, it is a serious form of damage, because the ability of the column to transfer 

axial loads may be seriously impaired. Therefore, it 

is not surprising that the ductility capability of such 

shear-critical elements is low.

viii.Concrete Joint Failure: Beam/column joints are 

subjected to high shear forces when under lateral 

loading. These shear forces can be amplified when 

infills are present. For concrete frames with nonductile reinforcing steel details, there is generally a 

deficiency or complete absence of transverse reinforcement within the beam/column joint core. 

Therefore, the shear-strength capacity is inevitably 

less than the demand imposed, even at moderate 

interstory drifts. Consequently, this highly likely 

behavior mode leads to large X-cracks in the beamcolumn joint region. Under cyclic loading, the 

cover concrete spalls, the joint concrete bulges, and 

the longitudinal column reinforcement tends to 

buckle. Such behavior tends to keep the adjacent 

beam and column plastic-hinge regions from being 

severely damaged. However, the ability of the 

frame system to carry axial loads through the damaged joints is suspect, especially if the behavior 

mode is associated with an adjacent infill panel that 

is also near failure. 

Table 8-3 Behavior Modes For Infilled Steel-Frame Components

Behavior Mode Description, and Likelihood of Occurrence Ductility Figure Paragraph 

(see Section 

8.2.3c):

Flexural yielding Hinges form at base of columns, and can 

occur adjacent to the beam/column joint if the 

members are weaker than the connection.

High Similar to 

8-1(a)

i

Shear yielding Unlikely, except when infill causes short-column effect.ii

Bolted or riveted connection failureLikely. High 8-3 iii
 Chapter 8: Infilled Frames

FEMA 306 Basic Procedures Manual 197

8.3 Infilled Frame Evaluation 

Procedures

8.3.1 Solid Infilled-Panel 

Components

This subsection gives equations for quantifying the 

stiffness, strength and deformation capacity of infilled 

panels. Note that Young's modulus and strength values 

for the infill panel are given in terms of masonry 

materials. For reinforced concrete infills, make the 

following substitutions: for Em and 

for .

a. Stiffness

The effective width(s) of a diagonal compression strut 

that can be used to assess the stiffness and strength of an 

infill panel is initially calculated using the 

recommendations given in FEMA 273. The provisions 

are based on the early work of Mainstone (1971) and 

Mainstone and Weeks (1970) and are restated below for 

the convenience of the user.

The equivalent strut is represented by the actual infill 

thickness that is in contact with the frame (tinf) and the 

diagonal length (rinf) and an equivalent width, a, given 

by:

(8-1)

where

(8-2)

and

column height between centerlines of 

beams, in. 

height of infill panel, in. 

expected modulus of elasticity of frame 

material, psi.

expected modulus of elasticity of infill 

material, psi. 

moment of inertial of column, in4

. 

diagonal length of infill panel, in.

thickness of infill panel and equivalent 

strut, in.

angle whose tangent is the infill height-tolength aspect ratio, radians

(8-3)

where

length of infill panel, in.

Only the masonry wythes in full contact with the frame 

elements need to be considered when computing inplane stiffness, unless positive anchorage capable of 

transmitting in-plane forces from frame members to all 

masonry wythes is provided on all sides of the walls.

Table 8-4 Behavior Modes For Infilled Concrete-Frame Components

Behavior Mode Description, and Likelihood of Occurrence Ductility Figure Paragraph 

(see Section 

8.2.3c):

Flexural yielding Should always occur at ground-floor level. 

Probably will also occur adjacent to beam/

column joint.

High 8-1c iv

Lap-splice slip Probable, will normally occur at ground-floor 

level.

Moderate-tolow8-6 v

Column tension yielding Lightly reinforced columns with strong infill Moderate-tohighvi

Shear failure Probable in nonductile frames. Likely at partial-height infills.Low 8-1b vii

Joint failure Probable with nonductile detailing. Low 8-1a viii

Ec f = 57000 ce′ f ′

ce

fme′

a hr = col inf

- 0175 1

0 4 .( ) . l

l

q

1

1

2 4

4 =

L

N

M

M

O

Q

P

P

E t

E I h

me inf

fe col inf

sin

hcol =

hinf =

E fe =

Eme =

I col =

rinf =

tinf =

q =

q = F

H

G I

K

J - tan 1 h

L

inf

inf

Linf =
 Chapter 8: Infilled Frames

198 Basic Procedures Manual FEMA 306

b. Strength

The strength capacity of an infill panel is a complex 

phenomenon. It is important to analyze several potential 

failure modes, as these will give an indication of 

potential crack and damage patterns. Four failure modes 

are possible, as described below.

i. Sliding-Shear Failure. The Mohr-Coulomb failure 

criteria can be used to assess the initial sliding-shear 

capacity of the infill:

(8-4)

where cohesive capacity of the mortar beds, 

which, in the absence of data may be taken as

(8-5)

where φ = the angle of sliding friction of the 

masonry along a bed joint. Note that μ = tan φ, 

where coefficient of sliding friction along the 

bed joint. After the infill's cohesive bond strength is 

destroyed as a result of cyclic loading, the infill still 

has some ability to resist sliding through shear 

friction in the bed joints. As a result, the final MohrCoulomb failure criteria reduce to:

(8-6)

where vertical load in the panel. If 

deformations are small, then because 

may only result from the self-weight of the panel. 

However, if these interstory drifts become large, 

then the bounding columns impose a vertical load 

due to shortening of the height of the panel. The 

vertical shortening strain in the panel is given by

(8-7)

where

downward movement of the upper beam as 

a result of the panel drift angle, θ

h = interstory height (center-to-center of 

beams)

interstory drift (displacement)

θ = interstory drift angle

The axial load on the infill is

(8-8)

where Young's modulus of the masonry, which 

in the absence of tests may be set at .

Substituting equations (8-7) and (8-8) into (8-6) 

gives

(8-9)

ii. Compression Failure. For compression failure of the 

equivalent diagonal strut, a modified version of the 

method suggested by Stafford-Smith and Carter 

(1969) can be adopted. The shear force (horizontal 

component of the diagonal strut capacity) is calculated as

(8-10)

where

equivalent strut width, defined above

infill thickness

expected strength of masonry in the horizontal direction, which may be set at 50% 

of the expected stacked prism strength 

.

iii. Diagonal Tension Failure of Panel. Using the recommendation of Saneinejad and Hobbs (1995), the 

cracking shear in the infill is given by

(8-11)

The cracking capacity of masonry, , is somewhat 

dependent on the orientation of the principal stresses 

with respect to the bed joints.

In the absence of tests results, the cracking strength 

may be taken as 

(8-12)

V Lt N slide

i

y inf inf = = τσ φ + μ 0 c tan h

t 0 =

τ 0

90

20 = f ′

me

m =

V Lt N slide

i

y inf inf = = c h σ φ tan μ

N =

Vslide a 0 s y

e

d == = q q

h h

D 2

d =

D =

N LtE = inf inf m ε

Em =

550 f ′

me

V LtE slide

i = μ θ inf inf m

2

V at f c = ¢ inf m90 cosq

a =

tinf =

f ′ = me90

f ′

me

V

t

cr

inf cr

inf

inf

inf

inf

L

h

h

L

=

+ F

H

G I

K

J

2 2 σ

s cr

δ cr

fme = ′ 90

20
 Chapter 8: Infilled Frames

FEMA 306 Basic Procedures Manual 199

or

(8-13)

where cohesive strength of the masonry bed 

joint, which is given by

(8-14)

where = expected comprehensive strength of a 

masonry prism.

iv. General Shear Failure of Panel. Based on the recommendations of FEMA 273, as well as Paulay and 

Priestley (1992), the initial and final contributions 

of shear carried by the infill panel may be defined 

as:

(8-15)

(8-16)

where

available initial shear capacity that is consumed during the first half-cyclic (monotonic) loading

final shear capacity as a result of cyclicloading effects

net horizontal shear area of the infill panel. 

Note for a complete infill with no openings

(8-17)

The above values give upper and lower bounds to 

the cyclic-loading resistance of the infill.

v. The Effect of Infill Panel Reinforcement. If either a 

masonry or concrete infill panel is reinforced, then 

the reinforcement should improve the shear 

strength of the panel. The shear demand carried by 

the reinforcement is given by the well known ACI 

318-95 (ACI, 1995) provisions.

(8-18)

where volumetric ratio of the reinforcement in 

the infill panel, fye = expected yield strength of the 

web reinforcement within the infill panel, and is 

defined above.

c. Deformation Capacity of Solid Infilled-Panel 

Components

There are no clear experimental results for the 

deformation capacities for each of the four behavior 

modes for infilled panel components, nor are there 

suitable analytical models available. Experiments show 

that diagonal cracking begins with the onset of 

nonlinear behavior at interstory drifts of 0.25% and is 

essentially complete (from corner to corner) in a panel 

by about 0.5%. Corner crushing begins at the same 

stage, but its extent depends on the amount of cyclic 

loading sustained. There is essentially no limit to the 

ability of an infill panel to deform in sliding shear—

other behavior modes usually govern. Thus, limits 

imposed by the general shear behavior mode determine 

the displacement capacity of infill panels. Experimental evidence supports the following interstory drift 

limit states for different masonry infill panels:

Brick masonry 1.5%

Grouted concrete block masonry 2.0%

Ungrouted concrete block masonry 2.5%

8.3.2 Infilled-Panel Components with 

Openings

The strength of infill panels with openings is best 

assessed using rational models composed of 

subcomponents of the relevant materials. See Chapter 5 

for concrete, Chapter 6 for reinforced masonry, and 

Chapter 7 for unreinforced masonry.

8.3.3 Out-of-Plane Behavior of 

Infilled-Panel Components 

FEMA 273 as well as Angel and Abrams (1994) 

describe methods for assessing infill capacity to resist 

out-of-plane demands. Based on these 

recommendations, the following formulae can be used 

to assess the infill strength. In these expressions, w is 

the uniform pressure that causes out-of-plane failure of 

the wall.

s cr me a v

vme =

vme me = 20 f ′

f ′

me

v A mi vh me = 2 f ′

V V mf mi = 0 3.

Vmi =

Vmf =

Avh =

A Lt vh inf inf =

v fA s w ye vh = ρ

r w =

Avh
 Chapter 8: Infilled Frames

200 Basic Procedures Manual FEMA 306

(8-19)

where

expected masonry strength

slenderness parameter defined in Table 8-5

out-of-plane reduction factors, set at 

for no damage (See Table 8-5 for moderate 

and severe damage)

Stiffness-reduction factor for bending 

frame members, given by

(8-20)

where

flexural rigidity of the weakest frame on 

the non-continuous side of the infill panel 

(units: k-in)

8.3.4 Steel-Frame Components

a. Flexure

The flexural strength of steel frames, based on conventional plastic concepts is given as

(8-21)

where

plastic-section modulus

Fye= expected yield strength

In the absence of specific data, Fye is set initially at 48 

ksi (330 MPa) and 55 ksi (380 MPa) for Grades A36 

and 50, respectively.

b. Shear

Steel-frame shear-strength capacity of beams and 

columns is based on the relationship

(8-22)

where

expected yield strength, with default values defined above

web area of the member

The 0.6 coefficient is based on the Von Mises yield 

criteria.

The critical section in a steel frame component with 

respect to shear is assumed to occur at an equivalent 

short beam or column formed between a frame joint and 

the compression strut associated with the infill panel. It 

may conservatively be assumed that the centroid of the 

diagonal strut force moves downward by an amount 

equal to

(8-23)

where 

effective width of a longitudinal compression struct. This is defined in Section 

Section 8.3.1a.

effective length of a “short” fixed-fixed 

column.

(8-24)

The shear demand is at a maximum when flexural 

plastic hinges form at each end of this so-called “short 

column”, thus

(8-25)

c. Joints

The strength and deformation capacity of riveted, 

bolted and welded connections along the panel zones 

are largely geometry-dependent. Due to wide variations 

in construction practice, the reader is referred to FEMA 

273.

8.3.5 Concrete-Frame Components

a. Flexure

Flexural strength of reinforced concrete frames should 

be based on the nominal strength provisions of the ACI 

318-95 code. However, expected strength values should 

be used for the material properties. Flexural 

deformation capacity depends on the amount of 

transverse reinforcement. If ductile detailing is used, then 

dependable plastic-hinge rotations of 0.035 radians can 

easily be attained. For nonductile detailing, experimental 

w RR f

h t

me = 2 ′ 1 2 a f /

λ

f ′ = me

l =

R1 = R1 = 1

R2 =

R EI 2

9 =+× 0 35 71 4 ( ) 10 − . . not to exceed 1 

EI =

M FZ p ye x =

Zx =

V AF p w ye = 0 6.

Fye =

Aw =

l a ceff

c

= cosq

a =

lceff =

tan

cos

q

q c

inf

c

inf

h a

L =

- F

H

G I

K

J

V

M

l col

p

col

ceff

= 2
 Chapter 8: Infilled Frames

FEMA 306 Basic Procedures Manual 201

research by Aycardi et al. (1992, 1994) has shown that 

interstory drifts of 0.03 radians are possible. Because the 

drift demands on infilled-frame systems are generally not 

as great as for bare frames, it is likely that the rotational 

demands will be less than the rotational capacity.

b. Shear

The critical section for shear strength is similar to that 

for steel frames, as discussed in Section 8.3.4. If the 

“short column” member is shear-critical, then the 

corner-to-corner crack angle forms. This angle can be 

calculated from

(8-26)

where

internal lever arm within the column member. In lieu of a precise analysis, this may 

be set at 80% of the overall member width.

Similarly, the beam should also be checked so that the 

effective length of the beam is given by

(8-27)

(8-28)

(8-29)

The corner-to-corner crack angle forming in a 

reinforced concrete beam is:

(8-30)

in which

= “short-beam” length

distance between centroids of top and bottom reinforcement

maximum positive moment generated by 

tensile yielding of the bottom reinforcement

maximum negative moment generated by 

tensile yielding of the top beam steel, 

including the effects of slab steel, if any.

(8-31)

(8-32)

where

Table 8-5 Out-of-plane infill strength parameters.

Height-to-thickness ratio Slenderness parameter Strength-reduction factor

Moderate Damage Severe Damage

5 0.130 1.0 1.0

10 0.060 0.9 0.9

15 0.035 0.9 0.8

20 0.020 0.8 0.7

25 0.015 0.8 0.6

30 0.008 0.7 0.5

35 0.005 0.7 0.5

40 0.003 0.7 0.5

h 

t 

λ R 1 

a c

ceff

jd

l = - tan 1

jd =

l a ceff

b

= sinq

V

M M

l b

p p

ceff

= + + - e j

tan

sin

q

q

b

inf

inf

b

L

L a =

-

ab

ceff

d d

l = - - ¢ tan 1

l

ceff

d - ¢= d

M p

+ =

M p

- =

M A p s ye f dd + = c1 25 . h( ) − ′

M A p s ye f dd − = ′c1 25 . h( ) − ′
 Chapter 8: Infilled Frames

202 Basic Procedures Manual FEMA 306

area of bottom steel. If this steel is not 

fully anchored and only extends a short 

distance into the joint, the value of used 

in Equation 8-31 should be prorated 

by where embedment length 

and development length, as given by 

ACI 318.

area of top steel, including slab steel

1.25fye= expected overstrength of the tension reinforcement, the 1.25 factor allowing for 

strain-hardening effects, and probable/measured yield strength of the longitudinal beam reinforcement

Concrete-frame shear-strength capacity is initially 

based on the recommendations of ATC-40 and FEMA 

273. This recommended design procedure generally 

provides a lower bound to the shear-strength capacity. 

The ultimate shear capacity is given by

(8-33)

where is the shear carried by the steel

(8-34)

and is the shear carried by concrete:

(8-35)

where

k = 1.0 in regions of low ductility demand 

and 0 in regions of moderate or high ductility demand,

λ = 0.75 for lightweight aggregate concrete 

and 1.0 for normal-weight aggregate concrete

Nu = axial compression force in pounds 

(equals 0 for tension force)

The approach recommended by Priestley et al. (1996) is 

less conservative and may provide an estimate of shear 

capacity that is more compatible with observations in 

the field, particularly in the presence of large diagonal 

cracks. In this approach, the shear capacity is given by:

(8-36)

where , and are the shear demand carried by 

steel, compressive axial-strut force, and concrete 

mechanism, respectively. These are defined below. 

, the shear carried by the transverse reinforcement, is 

given by: 

(8-37)

where

area of steel in one transverse hoop set

expected strength of the transverse reinforcement

internal lever arm, which in lieu of a more 

precise analysis may be set at 0.8D

member depth

center to center spacing of the hoop sets

corner-to-corner crack angle measured to 

the axis of the column

, the shear demand carried by axial load (strut 

action) in a column, is given by

(8-38)

where

axial load in the frame member

as defined above.

, the shear demand carried by the concrete is given 

by

(8-39)

in which 

web width

effective member depth, and

coefficient depending on the displacement 

ductility of the member and may be 

defined as follows:

k = 3.5 for (8-40)

k = 1.2 for (8-41)

k = 0.6 for (8-42)

As =

As

l

l em

d

lem =

ld =

As

¢ =

f y =

V VV u sc = +

Vs

V Af d

s s sh yh =

Vc

V k

N

A

fbd c

u

g

c w = + ′ F

H

G I

K

J 3 5

2000

. λ

Vn =++ Vs Vp Vc

V Vs p , Vc

Vs

V Af s sh yhe

jd

s = cot θ

Ash =

fyhe =

jd =

D =

s =

q =

Vp

V P p = tanq

P =

q =

Vc

V k bd c ce w = f ′

bw =

d =

k =

m £ 2

m = 4

m ≥ 8
 Chapter 8: Infilled Frames

FEMA 306 Basic Procedures Manual 203

To find for and , use linear 

interpolation between the above-specified ductility 

limits. For equations containing , use psi units. Note 

that upper- and lower-bound values of should be 

computed, representing the initial and the final 

(residual) shear capacity values using Equations 8-40 

and 8-42, respectively.

c. Joints

FEMA 273 presents guidelines for assessing beamcolumn joint strength using the formula given below:

(8-43)

where

nominal gross-section area

0.75 or 1.0 for light weight and normal 

weight aggregate concrete, respectively

strength coefficient ranging from 4 to 12 

and 8 to 20 for joints without and with 

appreciable transverse reinforcement, 

respectively.

Specific values of may be found in Table 6-8 of 

FEMA 273.

As an alternative to the FEMA 273 approach, the 

following procedure used in bridge-joint evaluation 

(Priestley, 1996) may be helpful for correlating 

behavior modes and observed damage patterns.

The nominal principal stresses on a joint are used to 

assess whether the joint will crack. A stress analysis 

that employs Mohr's circle is used to determine the 

major principal tension stress

(8-44)

where and are the average bounding actions on 

the joint, as defined below.

 is the average normal stress on the column 

given by: 

(8-45)

where

column axial load (tension positive)

column depth

column width

σx is the average normal stress on the beam, given by:

(8-46)

in which

overall beam depth

beam width

Pb = axial force in the beam (if any)

, the average joint shear stress is given by: 

(8-47)

in which

horizontal joint shear force assuming column and beam

smaller of or 

If: (8-48)

then the joint may be assumed to remain elastic and 

uncracked.

If: (8-49)

or (8-50)

then full diagonal cracking may be expected for exterior 

joints or corner joints, respectively, under biaxial 

response.

If is between the above limits, then some partial 

cracking may be expected. Moreover, if hinging occurs 

in the beam adjacent to the connection, then yield 

penetration of the longitudinal bars into the joint occurs. 

With sequential cycling, this eventually leads to joint 

failure.

Similarly, the principal compression stress, , should 

be checked such that

k 2 4 < < m 4 8 < < m

f ′

ce

Vc

V A n ce j = λγ f ′

Aj =

l =

g =

g

σ

σσ σσ

t

x y

j

x y

= v

+

+ +

+ F

H I

2 2 K 2

2

s sx y , v j

s y

s y col

c c

P

b h =

Pcol =

bc =

hc =

s x b

b b

P

d b =

db =

bb =

v j

vj

jh

j c

V

b h =

Vjh =

bj = bc bb

σ t ce < 3 5. f ′

σ t ce > 5 f ′

σ t ce > 7 f ′

s t

s c
 Chapter 8: Infilled Frames

204 Basic Procedures Manual FEMA 306

(8-51)

If, for one-way frames

(8-52)

or, if for two-way joints where biaxial loading may 

occur

(8-53)

then joint failure may be expected due to compression 

crushing of the diagonal struts within the joints.

Degradation of joint strength after crack formation may 

be expected. For assessing the degraded strength, the 

following rules may be used:

< 0.005 no change in (8-54)

< 0.02 (8-55)

< 0.04 (8-56)

where

joint rotation angle (in radians)

For intermediate values of linear interpolation may 

be used to determine . With this value for , the 

joint shear strength may be determined from 

Equations 8-44 and 8-47 as follows:

(8-57)

d. Bond Slip of Lap-Splice Connections

Lap-splice connections often occur at the base of a 

column, particularly in older nonductile concrete 

frames. Provided that the lap length is sufficient to 

develop yield (i.e., ), the nominal ultimate strength 

capacity can be attained. However, postelastic 

deformations quickly degrade the bond-strength 

capacity, and within one inelastic cycle of loading, the 

lap splice may be assumed to have failed. This failure is 

evident if longitudinal (tensile) splitting cracks are 

noticed at the base of the column.

When the lap splice fails in bond, it does not generally 

lead to a catastrophic failure, as the column is still able 

to transfer moment due to the presence of the eccentric 

compression stress block that arises as a result of the 

axial load in the column. Thus, the following initial and 

final failure model may be assumed:

 for (8-58)

and

 for (8-59)

where

θp = plastic rotation of the connection in radians

P = axial load that takes into account the variation in force due to the truss action of 

infilled frames. Note that axial load will 

increase for a compression side column, 

whereas for a tension side column the axial 

load will decrease to a point that tension 

could be induced. For the latter case 

assume P = 0.

distance between the outer layers of reinforcement in the column. 

For intermediate values of plastic hinge rotation 

( ) the following interpolation may be used

(8-60)

At large rotations the concrete crushes and may be 

severely damaged.

σ

σσ σσ

c

x y

j

x y = − v

+

+ F +

H

G I

K

J 2 2

2

2

σ c f

ce > 0 5. ′

σ c f

ce > 0 45 . ′

g j s t

g j σ t fce = 1 2. ′

g j s t = 0

g j =

g j

s t s t

V bh jh

x y

jc t

x y = − F +

H

G I

K

J F

H IK − +

σ

σ σ σ σ

2 2

2

20db

M M i n = q p = 0

M P d d

f = F - ¢

H

G I

K

J 2

q p > 0 025 .

b g d d - ¢ =

q p > 0 025 .

MM MM l n

p =- -n f

q

0 025 . d i
 Chapter 8: Infilled Frames

FEMA 306 Basic Procedures Manual 205

8.4 Infilled Frame Component Guides

The following Component Damage Classification 

Guides contain details of the behavior modes for 

infilled-frame components. Included are the 

distinguishing characteristics of the specific behavior 

mode, the description of damage at various levels of 

severity, and performance restoration measures. 

Information may not be included in the Component 

Damage Classification Guides for certain damage 

severity levels; in these instances, for the behavior 

mode under consideration, it is not possible to make 

refined distinctions with regard to severity of damage. 

See also Section 3.5 for general discussion of the use of 

the Component Guides and Section 4.4.3 for 

information on the modeling and acceptability criteria 

for components.
 Chapter 8: Infilled Frames

206 Basic Procedures Manual FEMA 306

COMPONENT DAMAGE

CLASSIFICATION GUIDE

System: Infilled Frame

Component Type: Infill Panel

Behavior Mode: Corner crushing

Applicable Materials: Concrete FrameBlock Infill

How to Distinguish Damage Type:

By Observation:

This type of damage occurs because ungrouted concrete block infills are inherently weak compared to adjacent concrete columns. Lateral movements create 

high corner strains leading to early failure of the corner concrete blocks. Some 

diagonal cracking and/or concrete bed joint sliding is also evident.

By Analysis (See Section 8.3):

The plastic limit methods of Liauw and Kwan 

(1983) or the simplified truss method of 

Stafford-Smith (1966) can be used to analyze 

the hierarchy of strength mechanisms. 

Severity Description of Damage Performance Restoration Measures

Insignificant

λK = 0.9

λQ = 0.9

λD = 1.0

Criteria:Separation of mortar around perimeter of panel and 

some crushing or mortar near corners of infill panel

Typical Appearance:.

• Repoint spalled mortar. 

• Inject cracks.

Moderate

λK = 0.6

λQ = 0.8

λD = 0.8

Criteria: Crushing of mortar, cracking of blocks including lateral movement of face shells.

Typical Appearance:

• Remove and replace damaged units. 

• Inject cracks around perimeter of infill. 

• Apply composite overlay at damaged corners.

Heavy

λK = 0.5

λQ = 0.7

λD = 0.7

Criteria: Loss of corner blocks through complete spalling of 

face shells. Diagonal (stairstep) cracking and/or bed 

joint sliding may also be evident.

Typical Appearance:

• Remove and replace infill or apply composite overlay on infill.

INPS1
 Chapter 8: Infilled Frames

FEMA 306 Basic Procedures Manual 207

COMPONENT DAMAGE

CLASSIFICATION GUIDE

System: Infilled Frame

Component Type: Infill Panel

Behavior Mode: Diagonal Tension

Applicable Materials: Masonry Units

How to distinguish damage type:

By Observation:

In this type of damage, cracking occurs across the diagonals of the infill panel. If 

drifts are large, secondary cracking may also be expected at an angle of about 45 

degrees to 65 degrees to the horizontal. For large drifts the corner strains are intense 

and crushing may also be observed.

By Analysis (See Section 8.3):

It is possible to determine the diagonal 

cracking strength by rational mechanics, or 

by simplified strut methods such as that 

proposed by Stafford-Smith et al. (1969).

Severity Description of Damage Performance Restoration Measures

Insignificant

λK = 0.7

λQ = 0.9

λD = 1.0

Criteria:Initial hairline cracking occur on diagonals in masonry. 

This is mostly associated with breaking of the bond 

between mortar and bricks. Cracking mostly concentrated within center region of panel

Typical appearance:. 

Measures not necessary for structural performance restoration. (Certain measures 

may be necessary for the restoration of 

nonstructural characteristics).

Moderate

λK = 0.4

λQ = 0.8

λD = 0.9

Criteria:Hairline cracks fully extend along diagonals following 

the mortar courses in a stairstep fashion, but sometimes 

propagate through bricks. Some crushing and/or “walking-out” of the mortar may be observed. Cracks mostly 

closed due to confinement provided by frames.

Typical appearance

Repoint spalled mortar. Remove and 

replace damaged masonry units.

Heavy

λK = 0.2

λQ = 0.5

λD = 0.8

Criteria:Cracks widen to about 1/8”, and are usually associated 

with corner crushing. Much loss of mortar is evident. 

More than one diagonal crack is generally evident. 

Crushing/cracking of the bricks is also evident. Portions 

of the entire infill may “walk” out-of-plane under cyclic 

loading.

Typical appearance:

Remove and replace damaged infill, or 

patch spalls. Apply shotcrete, ferrocement 

or composite overlay.

INPS2
 Chapter 8: Infilled Frames

208 Basic Procedures Manual FEMA 306

COMPONENT DAMAGE

CLASSIFICATION GUIDE

 System: Infilled Frame

 Component Type: Infill Panel

 Behavior Mode: Bed joint sliding.

 Applicable Materials: Steel-Frame 

Brick Infill

How to Distinguish Damage Type:

By Observation:

In this type of damage, crushing may initially occur at the corner of the infill. As the 

displacements become large to accommodate racking movements in the panel, 

movements occur along bed joints in the form of diagonal (stairstep) cracking or 

horizontal bed joint sliding. Such movements are a secondary outcome to corner 

crushing. 

By Analysis (See Section 8.3):

The effective strut method of analysis suggested by Stafford-Smith (1966) and/or 

plastic limit methods suggested by Liauw 

and Kwan (1983) should be used to check 

the hierarchy of failure mechanisms. 

Severity Description of Damage Performance Restoration Measures

Insignificant

λK = 0.8

λQ = 0.9

λD = 0.9

Criteria:Crushing of mortar around perimeter of frame. This is 

particularly noticeable adjacent to the columns near the 

corners of the infill panels.

Typical appearance:

Repoint spalled mortar. Inject cracks.

Moderate

λK = 0.5

λQ = 0.8

λD = 0.8

Criteria:Crushing of mortar and cracking of bricks extend over 

larger zones adjacent to beam and column

Typical appearance:.

Remove damaged bricks and replace. 

Heavy

λK = 0.4

λQ = 0.7

λD = 0.7

Criteria:Significant crushing of mortar and bricks extends around 

most of the perimeter frame, particularly along the 

height of the column.

Typical appearance:

Remove and replace infill, or patch spalls. 

Apply shotcrete, ferrocement or composite overlay on infill.

INPS3
 Chapter 8: Infilled Frames

FEMA 306 Basic Procedures Manual 209

COMPONENT DAMAGE

CLASSIFICATION GUIDE

 System: Infilled Frame

 Component Type: Infill Panel

 Behavior Mode: Corner crushing and

diagonal cracking

 Applicable Materials: Concrete FrameBlock Infill

How to Distinguish Damage Type:

By Observation:

Damage is equally distributed between both the frame and the infill. Crushing 

of the blocks and severe flexural cracking of infill occurs. Distributed diagonal 

cracks also occur.

By Analysis (See Section 8.3):

Limit-strength analysis methods are necessary 

to determine strength distribution well into the 

inelastic range.

Severity Description of Damage Performance Restoration Measures

Insignificant

λK = 0.9

λQ = 1.0

λD = 1.0

Criteria:Separation of mortar around frame occurs first in 

beam-to-infill interface. Some hairline cracks may 

be evident along mortar courses.

Repoint spalled mortar. Inject cracks.

Moderate

λK = 0.6

λQ = 0.8

λD = 0.8

Criteria:For a ductile (strong column-weak beam) frame 

design, yielding of longitudinal reinforcement 

occurs first in beam, with minor cracking in columns. Compression splitting occurs in corner 

blocks. Some hairline X cracks may be expected in 

beam-column joint

Typical appearance:.

Remove and replace damaged masonry units. 

Inject cracks.

Heavy

λK = 0.5

λQ = 0.6

λD = 0.6

Criteria:Extensive cracking in beam and column hinge 

zones, leading to spalling of cover concrete in 

frame. Diagonal cracking passes through blocks. 

Faceshells spall off in corners, and also across a critical shear plane at mid-height of infill

Typical appearance:.

Remove and replace infill. Remove and patch 

spalled and loose concrete in frame. Inject 

cracks.

INPS4
 Chapter 8: Infilled Frames

210 Basic Procedures Manual FEMA 306

COMPONENT DAMAGE

CLASSIFICATION GUIDE

 System: Infilled Frame

 Component Type: Infill Panel

 Behavior Mode: Out-of-Plane

 Applicable Materials: Masonry Infill

How to Distinguish Damage Type:

By Inspection:

This type of damage occurs with strong out-of-plane shaking. When coupled 

with in-plane shaking, the panel could potentially fall out. This behavior makes 

it difficult to distinguish which of the two types of shaking caused the damage.

By Analysis (See Section 8.3):

Arching action analysis is necessary.

Severity Description of Damage Performance Restoration Measures

Insignificant

λK = 0.9

λQ = 1.0

λD = 1.0

Criteria:Flexural cracking in the mortar beds around the 

perimeter, with hairline cracking in mortar bed at 

mid-height of panel.

Repoint spalled mortar.

Moderate

λK = 0.9

λQ = 0.8

λD = 1.0

Criteria:Crushing and loss of mortar along top, mid-height, 

bottom and side mortar beds. Possibly some in-plane 

damage, as evidenced by hair-line X-cracks in the 

central panel area.

Typical appearance:

Apply shotcrete, ferrocement, or composite 

overlay to the infill.

Heavy

λK = 0.5

λQ = 0.6

λD = 0.9

Criteria:Severe corner-to-corner cracking with some out-ofplane dislodgment of masonry. Top, bottom and midheight mortar bed is completely crushed and/or missing. There is some out-of-plane dislodgment of 

masonry. Concurrent in-plane damage should also be 

expected, as evidenced by extensive X-cracking.

Typical appearance:

Remove and replace infill.

INPS5
 Chapter 8: Infilled Frames

FEMA 306 Basic Procedures Manual 211

COMPONENT DAMAGE

CLASSIFICATION GUIDE

 System: Infilled Frame

 Component Type: Concrete Column

Behavior Mode: Column Snap 

through Shear Failure

 Applicable Materials: Concrete Frame 

Masonry Infill 

How to Distinguish Damage Type:

By Observation:

If infills are stiff and/or strong, then the frame is the weaker component. Cracking is not across a corner-to-corner diagonal, but on a flatter angle. Column 

cracking over a length equal to two member widths is severe and a sign of low 

frame shear capacity. 

By Analysis (See Section 8.3):

Column shear capacity should be checked. 

Shear failure is generally associated with inadequate transverse (shear/confinement) reinforcement. 

Severity Description of Damage Performance Restoration Measures

Insignificant

λK = 0.9

λQ = 0.9

λD = 1.0

Criteria:Several flexural cracks form in columns near top 

corner of infill.

Typical appearance:

Remove and patch spalled and loose concrete. 

Inject cracks.

Moderate

λK = 0.7

λQ = 0.7

λD = 0.4

Criteria:Flexure cracks change into shear X-cracks over a 

short length near column end. (Generally over about 

two column widths). Column cover in this vicinity 

will be loose. Some associated crushing may appear 

in the infill.

Typical appearance:

Remove and patch spalled and loose concrete. 

Apply composite overlay to damaged region of 

column.

Heavy

λK = 0.4

λQ = 0.2

λD = 0.4

Criteria: Cracking in column may be so severe that transverse 

hoops have fractured about one member width away 

from column end (at middle of X-cracks). Cover 

concrete in this vicinity will be mostly spalled away.

Typical appearance:

Remove spalled and loose concrete. Remove 

and replace buckled or fractured reinforcing. 

Provide additional ties over length of replaced 

bars. Patch concrete. Inject cracks. Apply composite overlay to damaged region of column.

INF1C1
 Chapter 8: Infilled Frames

212 Basic Procedures Manual FEMA 306

COMPONENT DAMAGE

CLASSIFICATION GUIDE

 System: Infilled Frame

 Component Type: Concrete Column

 Behavior Mode: Lap Splice Failure

 Applicable Materials: Reinforced Concrete

How to Distinguish Damage Type:

By Inspection:

Lack of sufficient lap length in hinge zone leads to eventual slippage. The 

cover spalls off due to high compression stresses, exposing the core concrete 

and damaged lap splice zone.

By Analysis (See Section 8.3):

Refer to FEMA 307.

Severity Description of Damage Performance Restoration Measures

Insignificant

λK = 0.9

λQ = 1.0

λD = 1.0

Criteria:Flexural cracks at floor level. Slight hairline vertical 

cracks.

Typical appearance

Inject cracks in frame.

Moderate

λK = 0.8

λQ = 0.5

λD = 1.0

Criteria:Tensile flexural cracks at floor slab level with some 

evidence of toe crushing over the bottom 1/2”. Longitudinal splitting cracks loosen the cover concrete.

Typical appearance:

Inject cracks in frame.

Heavy

λK = 0.5

λQ = 0.5

λD = 1.0

Criteria:Significant spalling of the cover concrete over the 

length of the lap splice, exposing the core and reinforcing steel

Typical appearance:.

Remove spalled and loose concrete. Provide 

additional ties over the length of the exposed 

bars. Patch concrete. Apply composite overlay 

to damaged region of column.

INF1C2

FLEXURAL

CRACK

LONGITUDINAL

SPLITTING

TOE

CRUSHING

COVER SPALLS

OFF
 Chapter 8: Infilled Frames

FEMA 306 Basic Procedures Manual 213

COMPONENT DAMAGE

CLASSIFICATION GUIDE

 System: Infilled Frame

 Component Type: Concrete Frame

 Behavior Mode: Connection Damage

 Applicable Materials: Reinforced Concrete

How to Distinguish Damage Type:

By Inspection:

Distress is caused by overstrength of members framing into the connection, 

leading to very high principal tension stresses.

By Analysis (See Section 8.3):

Refer to FEMA 307.

Severity Description of Damage Performance Restoration Measures

Insignificant

λK = 0.9

λQ = 1.0

λD = 1.0

Criteria:Slight X hairline cracks in joint

Typical appearance:.

Inject cracks.

Moderate

λK = 0.8

λQ = 0.5

λD = 0.9

Criteria:X-cracks in joint become more extensive and widen 

to about 1/8”.

Typical appearance:

Inject cracks.

Heavy

λK = 0.5

λQ = 0.5

λD = 0.5

Criteria:Extensive X-cracks in joint widen to about 1/4”. 

Exterior joints show cover concrete spalling off from 

back of joint. Some side cover may also spall off.

Typical appearance:

Remove spalled and loose concrete. Remove 

and replace buckled or fractured reinforcing. 

Provide additional ties over the length of the 

replaced bars. Patch concrete. Inject cracks. 

INF3C

SPALLED

COVER
 Chapter 8: Infilled Frames

214 Basic Procedures Manual FEMA 306

COMPONENT DAMAGE

CLASSIFICATION GUIDE

 System: Infilled Frame

Component Type: Framed Connection

Behavior Type: Simple Connection 

Damage

Applicable Materials: Steel FrameMasonry Infill

How to Distinguish Damage Type:

By Observation:

Damage to simple (semi-rigid) steel connections occur due to the high shears 

that must be transferred in the inelastic range.

By Analysis (See Section 8.3):

Plastic limit analysis of connections (see 

Mander et al. (1994)) is necessary. Fatigue failure is unlikely, but should be checked. 

Severity Description of Damage Performance Restoration Measures

Insignificant

λK = 0.9

λQ = 1.0

λD = 1.0

Criteria:As the frame racks, the connection yields and paint 

may flake off.

Unnecessary for restoration of structural performance. (Certain measures may be necessary 

for restoration of nonstructural characteristics).

Moderate

λK = 0.9

λQ = 1.0

λD = 1.0

Criteria:As drifts increase, both prying and slip may be evident. Angles pull away from column face, leaving 

infill frame bay with a larger overall opening. Gaps 

may be apparent around the perimeter of the infill.

Repaint and retorque bolts if loosened.

Heavy

λK = 0.5

λQ = 1.0

λD = 0.9

Criteria:Angles may show fatigue cracks or failure. If this is 

the case, the infill will also be showing signs of significant distress.

Remove angles and replace both bolts and 

angles. Remove infill and replace.

INF3S

STEEL BEAM

GAP

STEEL

COLUMN

SPLITTING

POTENTIAL CRACKS
FEMA 306 Basic Procedures Manual 215 

Glossary

Bearing wall A concrete or masonry wall that 

supports a portion of the building 

weight, in addition to its own 

weight, without a surrounding 

frame.

Behavior mode The predominant type of damage 

observed for a particular 

component. This is dependent on 

the relative magnitudes of the 

ratios of applied loads to 

component strength for axial, 

flexural and shearing actions.

Collapse 

Prevention

A performance level whereby a 

building is extensively damaged, 

has little residual stiffness and 

strength, but remains standing; 

any other damage is acceptable.

Component A structural member such as a 

beam, column, or wall, that is an 

individual part of a structural 

element.

Coupled wall A wall element in which vertical 

pier components are joined at one 

or more levels by horizontal 

spandrel components.

Damage Physical evidence of inelastic 

deformation of a structural 

component caused by a damaging 

earthquake.

Damaging 

ground motion

The ground motion that shook the 

building under consideration and 

caused resulting damage. This 

ground motion may or may not 

have been recorded at the site of 

the building. In some cases, it may 

be an estimate of the actual 

ground motion that occurred. It 

might consist of estimated timehistory records or corresponding 

response spectra.

Direct method The determination of performance 

restoration measures from the 

observed damage without relative 

performance analysis.

Element An assembly of structural 

components (e.g., coupled shear 

walls, frames).

Global 

displacement 

capacity

The maximum global 

displacement tolerable for a 

specific performance level. This 

global displacement limit is 

normally controlled by the 

acceptability of distortion of 

individual components or a group 

of components within the 

structure.

Global 

performance 

displacement 

demand

The overall displacement of a 

representative point on a building 

subject to a performance ground 

motion. The representative point 

is normally at the roof level or at 

the effective center of mass for a 

given mode of vibration.

Global structure The assembly representing all of 

the structural elements of a 

building.

Immediate 

Occupancy

A performance level whereby a 

building sustains minimal or no 

damage to its structural elements 

and only minor damage to its 

nonstructural components.

Inelastic lateral 

mechanism

The plastic mechanism formed in 

an element, or assembly of 

elements, under the combined 

action of vertical and lateral loads. 

This is a unique mechanism for a 

specified pattern of lateral loads.

Infilled frame A concrete or steel frame with 

concrete or masonry panels 

installed between the beams and 

columns.

Life Safety A performance level whereby a 

building may experience extensive 

damage to structural and 

nonstructural components, but 

remains stable and has significant 

reserve capacity.
 Glossary

216 Basic Procedures Manual FEMA 306

Nonlinear static 

procedure

A structural analysis technique in 

which the structure is modeled as 

an assembly of components 

capable of nonlinear forcedeformation behavior, then 

subjected to a monotonically 

increasing lateral load in a specific 

pattern to generate a global forcedisplacement capacity curve. The 

displacement demand is 

determined with a spectral 

representation of ground motion 

using one of several alternative 

methods.

Performance 

ground motion

Hypothetical ground motion 

consistent with the specified 

seismic hazard level associated 

with a specific performance 

objective. This is characterized by 

time history record(s) or 

corresponding response spectra.

Performance 

objective

A goal consisting of a specific 

performance level for a building 

subject to a specific seismic 

hazard.

Performance 

level

A hypothetical damage state for a 

building used to establish design 

seismic performance objectives. 

The most common performance 

levels, in order of decreasing 

amounts of damage, are Collapse 

Prevention, Life Safety, and 

Immediate Occupancy.

Performance 

restoration 

measures

Actions that might be 

implemented for a damaged 

building that result in future 

performance equivalent to that of 

the building in its pre-event state 

for a specific performance 

objective. These hypothetical 

repairs would result in a restored 

performance index equal to the 

performance index of the preevent building.

Pier A vertical wall component.

Pre-existing 

condition

Physical evidence of inelastic 

deformation or deterioration of a 

structural component that existed 

before the damaging earthquake

Relative 

performance 

analysis

An analysis of a building in its 

damaged and pre-event condition 

to determine the effects of the 

damage on the capability of the 

building to meet specific seismic 

performance objectives.

Repair An action taken to address a 

damaged component of a building. 

Severity of 

damage

The relative intensity of damage to 

a particular component classified 

as insignificant, slight, moderate, 

heavy, or extreme.

Shear wall A concrete or masonry panel, 

connected to the adjacent floor 

system, that resists in-plane lateral 

loads.

Spandrel A wall component that spans 

horizontally.

Structural 

repairs

Repairs that address damage to 

components to restore structural 

properties. 
 List of General Symbols

FEMA 306 Basic Procedures Manual 217

List of General Symbols

Global displacement capacity for pre-event 

structure for specified performance level. 

Global displacement capacity for damaged 

structure for specified performance level.

Global displacement capacity for repaired 

structure for specified performance level.

Global displacement demand for pre-event 

structure for specified seismic hazard.

Global displacement demand for damaged 

structure for specified seismic hazard.

Global displacement demand for repaired 

structure for specified seismic hazard.

Maximum global displacement caused by 

the damaging ground motion.

Modification factor applied to component 

deformation acceptability limits to account 

for earthquake damage.

dc

d′

c

dc

*

dd

d′

d

dd

*

de

λ D

Modification factor for idealized 

component force-deformation curve to 

account for change in effective initial 

stiffness resulting from earthquake 

damage.

Modification factor for idealized 

component force-deformation curve to 

account for change in expected strength 

resulting from earthquake damage.

RD Absolute value of the residual deformation 

in a structural component resulting from 

earthquake damage.

QCE Expected strength of a component or 

element at the deformation level under 

consideration in a deformation-controlled 

element.

λ K

λ Q
 List of General Symbols

218 Basic Procedures Manual FEMA 306
FEMA 306 Basic Procedures Manual 219 

References

ABK, 1981a, Methodology for Mitigation of Seismic 

Hazards in Existing Unreinforced Masonry Buildings: Categorization of Buildings, A Joint Venture 

of Agbabian Associates, S.B. Barnes and Associates, and Kariotis and Associates (ABK), Topical 

Report 01, c/o Agbabian Associates, El Segundo, 

California.

ABK, 1981b, Methodology for Mitigation of Seismic 

Hazards in Existing Unreinforced Masonry Buildings: Diaphragm Testing, A Joint Venture of Agbabian Associates, S.B. Barnes and Associates, and 

Kariotis and Associates (ABK), Topical Report 03, 

c/o Agbabian Associates, El Segundo, California.

ABK, 1981c, Methodology for Mitigation of Seismic 

Hazards in Existing Unreinforced Masonry Buildings: Wall Testing, Out-of-Plane, A Joint Venture of 

Agbabian Associates, S.B. Barnes and Associates, 

and Kariotis and Associates (ABK), Topical Report 

04, c/o Agbabian Associates, El Segundo, California

ABK, 1984, Methodology for Mitigation of Seismic 

Hazards in Existing Unreinforced Masonry Buildings: The Methodology, A Joint Venture of Agbabian Associates, S.B. Barnes and Associates, and 

Kariotis and Associates (ABK), Topical Report 08, 

c/o Agbabian Associates, El Segundo, California.

Abrams, D.P., 1992, “Strength and Behavior of Unreinforced Masonry Elements,” Proceedings of Tenth 

World Conference on Earthquake Engineering, 

Balkema Publishers, Rotterdam, The Netherlands, 

pp. 3475-3480.

Abrams, D.P. (Ed.), 1994, Proceedings of the NCEER 

Workshop on Seismic Response of Masonry Infills, 

National Center for Earthquake Engineering 

Research, Technical Report NCEER-94-0004.

Abrams, D.P., 1997, personal communication, May.

Abrams, D.P., and Epperson, G.S, 1989, “Evaluation of 

Shear Strength of Unreinforced Brick Walls Based 

on Nondestructive Measurements,” 5th Canadian 

Masonry Symposium, Department of Civil Engineering, University of British Columbia, Vancouver, British Columbia., Volume 2.

Abrams, D.P., and Epperson, G.S, 1989, “Testing of 

Brick Masonry Piers at Seventy Years”, The Life of 

Structures: Physical Testing, Butterworths, London.

Abrams, D.P., and Paulson, T.J., 1989, “Measured Nonlinear Dynamic Response of Reinforced Concrete 

Masonry Building Systems,” Proceedings of the 

Fifth Canadian Masonry Symposium, University of 

British Columbia, Vancouver, B.C., Canada.

Abrams, D.P., and Paulson, T.J., 1990, “Perceptions and 

Observations of Seismic Response for Reinforced 

Masonry Building Structures,” Proceedings of the 

Fifth North American Masonry Conference, University of Illinois at Urbana-Champaign.

Abrams, D.P., and Shah, N., 1992, Cyclic Load Testing 

of Unreinforced Masonry Walls, College of Engineering, University of Illinois at Urbana, Advanced 

Construction Technology Center Report #92-26-10.

ACI, 1995, Building Code Requirements for Reinforced 

Concrete, American Concrete Institute, Report ACI 

318-95, Detroit, Michigan.

ACI Committee 224, 1994, “Causes, Evaluation and 

Repair of Cracks in Concrete Structures”, Manual 

of Concrete Practice, American Concrete Institute, 

Detroit, Michigan.

Adham, S.A., 1985, “Static and Dynamic Out-of-Plane 

Response of Brick Masonry Walls,” Proceedings of 

the 7th International Brick Masonry Conference, 

Melbourne, Australia.

Agbabian, M., Adham, S, Masri, S.,and Avanessian, V., 

1989, Out-of-Plane Dynamic Testing of Concrete 

Masonry Walls, U.S. Coordinated Program for 

Masonry Building Research, Report Nos. 3.2b-1 

and 3.2b-2.

Al-Chaar, G., Angel, R. and Abrams, D., 1994, 

“Dynamic testing of unreinforced brick masonry 

infills,” Proc. of the Structures Congress ‘94, 

Atlanta, Georgia., ASCE, 1: 791-796.

Alexander, C.M., Heidebrecht, A.C., and Tso, W.K., 

1973, Cyclic Load Tests on Shear Wall Panels, Proceedings, Fifth World Conference on Earthquake 

Engineering, Rome, pp. 1116–1119.

Ali, Aejaz and Wight, J.K., 1991, R/C Structural Walls 

with Staggered Door Openings, Journal of Structural Engineering, ASCE, Vol. 117, No. 5, 

pp. 1514-1531.

Anderson, D.L., and Priestley, M.J.N., 1992, “In Plane 

Shear Strength of Masonry Walls,” Proceedings of 
 References

220 Basic Procedures Manual FEMA 306

the 6th Canadian Masonry Symposium, Saskatoon, 

Saskatchewan.

Angel R., and Abrams, D.P., 1994, "Out-Of-Plane 

Strength evaluation of URM infill Panels," Proceedings of the NCEER Workshop on Seismic 

Response of Masonry Infills, D.P. Abrams editor, 

NCEER Technical Report NCEER-94-0004.

Antebi, J., Utku, S., and Hansen, R.J., 1960, The 

Response of Shear Walls to Dynamic Loads, MIT 

Department of Civil and Sanitary Engineering, 

Report DASA-1160, Cambridge, Massachusetts.

Anthoine, A., Magonette, G., and Magenes, G., 1995, 

“Shear-Compression Testing and Analysis of Brick 

Masonry Walls,” Proceedings of the 10th European 

Conference on Earthquake Engineering, Duma, 

editor, Balkema: Rotterdam, The Netherlands.

Aristizabal-Ochoa, D., J., and Sozen, M.A., 1976, 

Behavior of Ten-Story Reinforced Concrete Walls 

Subjected to Earthquake Motions, Civil Engineering Studies Structural Research Series No. 431, 

Report UILU-ENG-76-2017, University of Illinois, 

Urbana, Illinois.

ASCE/ACI Task Committee 426, 1973, The Shear 

Strength of Reinforced Concrete Members, ASCE 

Journal of Structural Engineering, Vol. 99, No. ST6, 

pp 1091-1187.

ASTM, latest editions, Standard having the number C67, American Society for Testing Materials Philadelphia, Pennsylvania.

ATC, 1983, Seismic Resistance of Reinforced Concrete 

Shear Walls and Frame Joints: Implication of 

Recent Research for Design Engineers, Applied 

Technology Council, ATC-11 Report, Redwood 

City, California.

ATC, 1989, Procedures for the Post Earthquake Safety 

Evaluation of Buildings, Applied Technology 

Council, ATC-20 Report, Redwood City, California.

ATC, 1992, Guidelines for Cyclic Seismic Testing of 

Components of Steel Structures, Applied Technology Council, ATC-24 Report, Redwood City, California.

ATC, 1995, Addendum to the ATC-20 Post Earthquake 

Building Safety Evaluation Procedures, Applied 

Technology Council, ATC-20-2 Report, Redwood 

City, California.

ATC, 1996, The Seismic Evaluation and Retrofit of 

Concrete Buildings, Applied Technology Council, 

ATC-40 Report, Redwood City, California.

ATC, 1997a, NEHRP Guidelines for the Seismic Rehabilitation of Buildings, prepared by the Applied 

Technology Council (ATC-33 project) for the 

Building Seismic Safety Council, published by the 

Federal Emergency Management Agency, Report 

No. FEMA 273, Washington, D.C.

ATC, 1997b, NEHRP Commentary on the Guidelines 

for the Seismic Rehabilitation of Buildings, prepared by the Applied Technology Council (ATC-33 

project) for the Building Seismic Safety Council, 

published by the Federal Emergency Management 

Agency, Report No. FEMA 274, Washington, D.C.

ATC, 1998a, Evaluation of Earthquake Damaged Concrete and Masonry Wall Buildings, Technical 

Resources, prepared by the Applied Technology 

Council (ATC-43 project) for the Partnership for 

Response and Recovery, published by the Federal 

Emergency Management Agency, Report No. 

FEMA 307, Washington D.C.

ATC, 1998b, Repair of Earthquake Damaged Concrete 

and Masonry Wall Buildings, prepared by the 

Applied Technology Council (ATC-43 project) for 

the Partnership for Response and Recovery, published by the Federal Emergency Management 

Agency, Report No. FEMA 308, Washington D.C.

Atkinson, R.H.,Amadei, B.P.,Saeb, S., and Sture, S., 

1989, “Response of Masonry Bed Joints in Direct 

Shear,” American Society of Civil Engineers Journal of the Structural Division, Vol. 115, No. 9.

Atkinson, R.H., and Kingsley, G.R., 1985, A Comparison of the Behavior of Clay and Concrete Masonry 

in Compression, U.S. Coordinated Program for 

Masonry Building Research, Report No. 1.1-1.

Atkinson, R.H., Kingsley, G.R., Saeb, S., B. Amadei, 

B., and Sture, S., 1988, “A Laboratory and In-situ 

Study of the Shear Strength of Masonry Bed 

Joints,” Proceedings of the 8th International Brick/

Block Masonry Conference, Dublin.

Axely, J.W. and Bertero, V.V., 1979, “Infill panels: their 

influence on seismic response of buildings,” Earthquake Eng. Research Center, University of California at Berkeley, Report No. EERC 79-28.

Aycardi, L.E., Mander, J.B., and Reinhorn, A.M., 1992, 

Seismic Resistance of RC Frame Structures 
 References

FEMA 306 Basic Procedures Manual 221

Designed only for Gravity Loads, Part II: Experimental Performance of Subassemblages, National 

Center for Earthquake Engineering Research, Technical Report NCEER-92-0028.

Aycardi, L.E., Mander, J.B., and Reinhorn, A.M., 1994, 

"Seismic resistance of reinforced concrete frame 

structures designed only for gravity loads: Experimental performance of subassemblages", ACI 

Structural Journal, (91)5: 552-563.

Azizinamini, Atorod, Glikin, J.D., and Oesterle, R.G., 

1994, Tilt-up Wall Test Results, Portland Cement 

Association, RP322D, Skokie, Illinois.

Barda, Felix, 1972, Shear Strength of Low-Rise Walls 

with Boundary Elements, Ph.D. University, Lehigh 

University, Bethlehem, Pennsylvania.

Barda, Felix, Hanson, J.W., and Corley, W.G., 1976, 

Shear Strength of Low-Rise Walls with Boundary 

Elements, Research and Development Bulletin 

RD043.01D, preprinted with permission from ACI 

Symposium Reinforced Concrete Structures in 

Seismic Zones, American Concrete Institute.

Benjamin, J.R., and Williams, H.A., 1958, “The behavior of one-story shear walls,” Proc. ASCE, ST. 4, 

Paper 1723: 30. 

Benjamin, J.R., and Williams, H.A., 1958a, “The 

Behavior of One-Story Reinforced Concrete Shear 

Walls,” Journal of the Structural Division, ASCE, 

Vol. 83, No. ST3.

Benjamin, J.R., and Williams, H.A., 1958b, Behavior of 

One-Story Reinforced Concrete Shear Walls Containing Openings, ACI Journal, Vol. 55, pp. 605-

618.

Bertero, V.V. and Brokken, S.T., 1983, “Infills in seismic resistant building,” Proc. ASCE, 109(6).

BIA, 1988, Technical Notes on Brick Construction, No. 

17, Brick Institute of America, Reston, Virginia.

Blakeley, R.W.G., Cooney, R.C., and Megget, L.M., 

1975, “Seismic Shear Loading at Flexural Capacity 

in Cantilever Wall Structures,” Bulletin of the New 

Zealand National Society for Earthquake Engineering, Vol. 8, No. 4.

Blondet, M., and Mays, R.L., 1991, The Transverse 

Response of Clay Masonry Walls Subjected to 

Strong Motion Earthquakes, Vols. 1 through 4, U.S. 

Coordinated Program for Masonry Building 

Research, Report No. 3.2(b)-2.

Bracci, J.M., Reinhorn, A.M., and Mander, J.B., 1995, 

"Seismic resistance of reinforced concrete frame 

structures designed for gravity loads: Performance 

of structural system", ACI Structural Journal, 

(92)5: 597-609.

Brokken, S.T., and Bertero, V.V., 1981, “Studies on 

effects of infills in seismic resistance R/C construction,”Earthquake Engineering Research Centre, 

University of California at Berkeley, Report No. 

EERC 81-12.

BSSC, 1992, NEHRP Handbook for the Seismic Evaluation of Existing Buildings , prepared by the Building Seismic Safety Council for the Federal 

Emergency Management Agency, Report No. 

FEMA 178, Washington, D.C.

BSSC, 1994, NEHRP Recommended Provisions for 

Seismic Regulations for New Buildings, prepared by 

the Building Seismic Safety Council for the Federal 

Emergency Management Agency, Report No. 

FEMA 222A, Washington, D.C.

BSSC, 1997, NEHRP Recommended Provisions for 

Seismic Regulations for New Buildings and Other 

Structures, prepared by the Building Seismic Safety 

Council for the Federal Emergency Management 

Agency, Report No. FEMA 302, Composite Draft 

Copy, Washington, D.C.

Calvi, G.M., Kingsley, G.R., and Magenes, G., 1996, 

“Testing of Masonry Structures for Seismic Assessment,” Earthquake Spectra, Earthquake Engineering Research Institute, Oakland, California, Vol. 12, 

No. 1, pp. 145-162.

Calvi, G.M., Macchi, G., and Zanon, P., 1985, “Random 

Cyclic Behavior of Reinforced Masonry Under 

Shear Action,” Proceedings of the Seventh International Brick Masonry Conference, Melbourne, Australia.

Calvi, G.M, and Magenes, G., 1994, “Experimental 

Results on Unreinforced Masonry Shear Walls 

Damaged and Repaired,” Proceedings of the 10th 

International Brick Masonry Conference, Vol. 2, 

pp. 509-518.

Calvi, G.M., Magenes, G., Pavese, A., and Abrams, 

D.P., 1994, “Large Scale Seismic Testing of an 

Unreinforced Brick Masonry Building,” Proceedings of Fifth U.S. National Conference on Earthquake Engineering, Chicago, Illinois, July 1994, 

pp.127-136.
 References

222 Basic Procedures Manual FEMA 306

Cardenas, Alex E., 1973, “Shear Walls -- Research and 

Design Practice,” Proceedings, Fifth World Conference on Earthquake Engineering, Rome, Italy.

Chang, G. A., and Mander, J.B.,1994, Seismic Energy 

Based Fatigue Damage Analysis of Bridge Columns: Part I - Evaluation of Seismic Capacity, 

Technical Report NCEER-94-0006, and Part II -

Evaluation of Seismic Demand, Technical Report 

NCEER-94-0013, National Center for Earthquake 

Engineering Research, State University of New 

York at Buffalo.

Chen, S.J., Hidalgo, P.A., Mayes, R.L., and Clough, 

R.W., 1978, Cyclic Loading Tests of Masonry Single Piers, Volume 2 – Height to Width Ratio of 1, 

Earthquake Engineering Research Center Report 

No. UCB/EERC-78/28, University of California, 

Berkeley, California.

Chrysostomou, C.Z., Gergely, P, and Abel, J.F., 1988, 

Preliminary Studies of the Effect of Degrading Infill 

Walls on the Nonlinear Seismic Response of Steel 

Frames, National Center for Earthquake Engineering Research, Technical Report NCEER-88-0046.

City of Los Angeles, 1985, “Division 88: Earthquake 

Hazard Reduction in Unreinforced Masonry Buildings,” City of Los Angeles Building Code, Los 

Angeles, California.

City of Los Angeles, 1991, Seismic Reinforcement Seminar Notes, Los Angeles Department of Building 

and Safety.

Corley, W.G., Fiorato, A.E., and Oesterle, R.G., 1981, 

Structural Walls, American Concrete Institute, Publication SP-72, Detroit, Michigan, pp. 77-131.

Costley, A.C., Abrams, D.P., and Calvi, G.M., 1994, 

“Shaking Table Testing of an Unreinforced Brick 

Masonry Building,” Proceedings of Fifth U.S. 

National Conference on Earthquake Engineering, 

Chicago, Illinois, July 1994, pp.127-136.

Costley, A.C., and Abrams, D.P, 1996a, “Response of 

Building Systems with Rocking Piers and Flexible 

Diaphragms,” Worldwide Advances in Structural 

Concrete and Masonry, Proceedings of the Committee on Concrete and Masonry Symposium, ASCE 

Structures Congress XIV, Chicago, Illinois.

Costley, A.C., and Abrams, D.P., 1996b, Dynamic 

Response of Unreinforced Masonry Buildings with 

Flexible Diaphragms, National Center for Earthquake Engineering Research, Technical Report 

NCEER-96-0001, Buffalo, New York.

Coul, A., 1966, “The influence of concrete infilling on 

the strength and stiffness of steel frames,” Indian 

Concrete Journal.

Crisafulli, F.J., Carr, A.J., and Park, R., 1995, “Shear 

Strength of Unreinforced Masonry Panels,” Proceedings of the Pacific Conference on Earthquake 

Engineering; Melbourne, Australia, Parkville, Victoria, 3: 77-86.

CRSI, No publication date given, Evaluation of Reinforcing Steel in Old Reinforced Concrete Structures, Concrete Reinforcing Steel Institute, 

Engineering Data Report No. 11, Chicago, Illinois.

Dawe, J.L. and McBride, R.T., 1985a, “Experimental 

investigation of the shear resistance of masonry 

panels in steel frames,” Proceedings of the 7th 

Brick Masonry Conf., Melbourne, Australia.

Dawe, J.L. and Young, T.C., 1985b, “An investigation 

of factors influencing the behavior of masonry infill 

in steel frames subjected to in-plane shear,” Proceedings of the 7th International. Brick Masonry 

Conference, Melbourne, Australia.

Dawe, J.L., and Seah, C.K., 1988, “Lateral Load Resistance of Masonry Panels in Flexible Steel Frames,” 

Proceedings of the Eighth International Brick and 

Block Masonry Conference, Trinity College, Dublin, Republic of Ireland.

Dhanasekar, K., Page, A.W., and Kleeman, P.W., 1985, 

“The behavior of brick masonry under biaxial stress 

with particular reference to infilled frames,” Proceedings of the 7th International. Brick Masonry 

Conference, Melbourne, Australia.

Drysdale, R.G., Hamid, A.A., and Baker, L.R., 1994, 

Masonry Structures, Behavior and Design, Prentice 

Hall, New Jersey.

Durrani, A.J., and Luo, Y.H., 1994, "Seismic Retrofit of 

Flat-Slab Buildings with Masonry Infills," in Proceedings of the NCEER Workshop on Seismic 

Response of Masonry Infills, D.P. Abrams editor, 

National Center for Earthquake Engineering 

Research, Technical Report NCEER-94-0004.

El-Bahy, A., Kunath, S.K., Taylor, A.W., and Stone, 

W.C., 1997, Cumulative Seismic Damage of Reinforced Concrete Bridge Piers, Building and Fire 

Research Laboratory, National Institute of Standards and Technology (NIST), Draft Report, Gaithersburg, Maryland.

Epperson, G.S., and Abrams, D.P., 1989, Nondestructive Evaluation of Masonry Buildings, College of 
 References

FEMA 306 Basic Procedures Manual 223

Engineering, University of Illinois at Urbana, 

Advanced Construction Technology Center Report 

No. 89-26-03, Illinois.

Epperson, G.S., and Abrams, D.P., 1992, “Evaluating 

Lateral Strength of Existing Unreinforced Brick 

Masonry Piers in the Laboratory,” Journal of The 

Masonry Society, Boulder, Colorado, Vol. 10, No. 2, 

pp. 86-93.

Fattal, S.G., 1993, Strength of Partially-Grouted 

Masonry Shear Walls Under Lateral Loads, 

National Institute of Standards and Technology, 

NISTIR 5147, Gaithersburg, Maryland.

Feng, Jianguo, 1986, “The Seismic Shear Strength of 

Masonry Wall,” Proceedings of the US-PRC Joint 

Workshop on Seismic Resistance of Masonry Structures, State Seismological Bureau, PRC and 

National Science Foundation, USA, Harbin, China.

Flanagan, R.D. and Bennett, R.M., 1994, “Uniform Lateral Load Capacity of Infilled Frames,” Proceedings of the Structures Congress ‘94, Atlanta, 

Georgia, ASCE, 1: 785-790.

Focardi, F. and Manzini, E., 1984, “Diagonal tension 

tests on reinforced and non-reinforced brick panels,” Proceedings of the 8th World Conference on 

Earthquake Engineering, San Francisco, California, 

VI: 839-846.

Foltz, S., and Yancy, C.W.C., 1993, “The Influence of 

Horizontal Reinforcement on the Shear Performance of Concrete Masonry Walls”, Masonry: 

Design and Construction, Problems and Repair, 

ASTM STP 1180, American Society for Testing 

and Materials, Philadelphia, Pennsylvania.

Freeman S. A., 1994 "The Oakland Experience During 

Loma Prieta - Case Histories," Proceedings of the 

NCEER Workshop on Seismic Response of Masonry 

Infills, D.P. Abrams editor, National Center for 

Earthquake Engineering Research, Technical 

Report NCEER-94-0004.

Gambarotta, L. and Lagomarsino, S., 1996, “A Finite 

Element Model for the Evaluation and Rehabilitation of Brick Masonry Shear Walls,” Worldwide 

Advances in Structural Concrete and Masonry, Proceedings of the Committee on Concrete and 

Masonry Symposium, ASCE Structures Congress 

XIV, Chicago, Illinois.

Gergely, P., White, R.N., and Mosalam, K.M., 1994, 

“Evaluation and Modeling of Infilled Frames,” Proceedings of the NCEER Workshop on Seismic 

Response of Masonry Infills, D.P. Abrams editor, 

National Center for Earthquake Engineering 

Research, Technical Report NCEER-94-0004, pp. 

1-51 to 1-56.

Gergely, P., White, R.N., Zawilinski, D., and Mosalam, 

K., 1993, “The Interaction of Masonry Infill and 

Steel or Concrete Frames,” Proceedings of the 1993 

National Earthquake Conference, Earthquake Hazard Reduction in the Central and Eastern United 

States: A Time for Examination and Action; Memphis, Tennessee, II: 183-191.

Ghanem, G.M., Elmagd, S.A., Salama, A.E., and 

Hamid, A.A., 1993, “Effect of Axial Compression 

on the Behavior of Partially Reinforced Masonry 

Shear Walls,” Proceedings of the Sixth North American Masonry Conference, Philadelphia, Pennsylvania.

Gulkan, P., and Sozen, M.A., 1974, “Inelastic Response 

of Reinforced Concrete Structures to Earthquake 

Motions,” Journal of the American Concrete Institute, Detroit, Michigan, pp. 604-610.

Hamburger, R.O. and Chakradeo, A.S., 1993, “Methodology for seismic capacity evaluation of steel-frame 

buildings with infill unreinforced masonry,” Proceedings of the 1993 National Earthquake Conference, Earthquake Hazard Reduction in the Central 

and Eastern United States: A Time for Examination 

and Action; Memphis, Tennessee, II: 173-182.

Hamid, A., Assis, G., and Harris, H., 1988, Material 

Models for Grouted Block Masonry, U.S. Coordinated Program for Masonry Building Research, 

Report No. 1.2a-1.

Hamid, A., Abboud, B., Farah, M., Hatem, K., and Harris, H., 1989, Response of Reinforced Block 

Masonry Walls to Out-of-Plane Static Loads, U.S. 

Coordinated Program for Masonry Building 

Research, Report No. 3.2a-1.

Hammons, M.I., Atkinson, R.H., Schuller, M.P.,and 

Tikalsky, P.J., 1994, Masonry Research for LimitStates Design, Construction Productivity Advancement Research (CPAR)U.S. Army Corps of Engineers Waterways Experiment Station, Program 

Report CPAR-SL-94-1, Vicksburg Mississippi.

Hanson, R.D., 1996, "The Evaluation of Reinforced 

Concrete Members Damaged by Earthquakes", 

Spectra, Vol. 12, No. 3, Earthquake Engineering 

Research Institute.
 References

224 Basic Procedures Manual FEMA 306

Hart, G.C., and Priestley, M.J.N., 1989, Design Recommendations for Masonry Moment-Resisting Wall 

Frames, UC San Diego Structural Systems 

Research Project Report No. 89/02.

Hart, G.C., Priestley, M.J.N., and Seible, F., 1992, 

“Masonry Wall Frame Design and Performance,” 

The Structural Design of Tall Buildings, John Wile 

& Sons, New York.

He, L., and Priestley, M.J.N., 1992, Seismic Behavior of 

Flanged Masonry Walls, University of California, 

San Diego, Department of Applied Mechanics and 

Engineering Sciences, Report No. SSRP-92/09.

Hegemier, G.A., Arya, S.K., Nunn, R.O., Miller, M.E., 

Anvar, A., and Krishnamoorthy, G., 1978, A Major 

Study of Concrete Masonry Under Seismic-Type 

Loading, University of California, San Diego 

Report No. AMES-NSF TR-77-002.

Hidalgo, P.A., Mayes, R.L., McNiven, H.D., and 

Clough, R.W., 1978, Cyclic Loading Tests of 

Masonry Single Piers, Volume 1 – Height to Width 

Ratio of 2, University of California, Berkeley, 

Earthquake Engineering Research Center Report 

No. UCB/EERC-78/27.

Hidalgo, P.A., Mayes, R.L., McNiven, H.D., and 

Clough, R.W., 1979, Cyclic Loading Tests of 

Masonry Single Piers, Volume 3 – Height to Width 

Ratio of 0.5, University of California, Berkeley, 

Earthquake Engineering Research Center Report 

No. UCB/EERC-79/12.

Hill, James A., 1994, “Lateral Response of Unreinforced Masonry Infill Frame,” Proceedings of the 

Eleventh Conference (formerly Electronic Computation Conference) held in conjunction with ASCE 

Structures Congress ‘94 and International Symposium ‘94, Atlanta, Georgia, pp. 77-83.

Hill, James A, 1997, oral communicaton.

Holmes, M., 1961, “Steel frames with brickwork and 

concrete infilling,” Proceedings of the Institute of 

Civil Engineers, 19: 473.

Hon, C.Y., and Priestley, M.J.N., 1984, Masonry Walls 

and Wall Frames Under Seismic Loading, Department of Civil Engineering, University of Canterbury, Research Report 84-15, New Zealand. 

ICBO, 1994, Uniform Code for Building Conservation, 

International Conference of Building Officials, 

Whittier, California.

ICBO, 1994, UBC Standard 21-6, International Conference of Building Officials, Whittier, California.

ICBO, 1994, 1997, Uniform Building Code, International Conference of Building Officials, Whittier, 

California.

Igarashi, A., F. Seible, and Hegemier, G.A., 1993, 

Development of the Generated Sequential Displacement Procedure and the Simulated Seismic 

Testing of the TCCMAR 3-Story In-plane Walls, 

U.S. Coordinated Program for Masonry Building 

Research Report No. 3.1(b)-2.

Iliya, R., and Bertero, V.V., 1980, Effects of Amount and 

Arrangement of Wall-Panel Reinforcement on 

Behavior of Reinforced Concrete Walls, Earthquake 

Engineering Research Center, University of California at Berkeley, Report UCB-EERC-82-04.

Innamorato, D. , 1994, The Repair of Reinforced Structural Masonry Walls using a Carbon Fiber, Polymeric Matrix Composite Overlay, M.Sc. Thesis in 

Structural Engineering, University of California, 

San Diego.

Kadir, M.R.A., 1974, The structural behavior of 

masonry infill panels in framed structures, Ph.D. 

thesis, University of Edinburgh.

Kahn, L.F. and Hanson, R.D., 1977, “Reinforced concrete shear walls for a seismic strengthening,” Proceedings of the 6th World Conf. on Earthquake 

Engineering, New Delhi, India, III: 2499-2504.

Kariotis, J.C., 1986, “Rule of General Application - 

Basic Theory,” Earthquake Hazard Mitigation of 

Unreinforced Pre-1933 Masonry Buildings, Structural Engineers Association of Southern California, 

Los Angeles, California.

Kariotis, J.C., Ewing, R.D., and Hill, J.,1996, Lecture 

Notes, Retrofit of Existing Tilt-Up Buildings and 

In-fill Frame Seminar, Structural Engineers Association of Southern California, Los Angeles, California.

Kariotis, J.C., Ewing, R.D., and Johnson, A.W., 1985a, 

“Predictions of Stability for Unreinforced Brick 

Masonry Walls Shaken by Earthquakes,” Proceedings of the 7th International Brick Masonry Conference, Melbourne, Australia.

Kariotis, J.C., Ewing, R.D., and Johnson, A.W., 1985b, 

“Strength Determination and Shear Failure Modes 

of Unreinforced Brick Masonry with Low Strength 
 References

FEMA 306 Basic Procedures Manual 225

Mortar,” Proceedings of the 7th International Brick 

Masonry Conference, Melbourne, Australia.

Kariotis, J.C., Ewing, R.D., and Johnson, A.W., 1985c, 

“Methodology for Mitigation of Earthquake Hazards in Unreinforced Brick Masonry Buildings,” 

Proceedings of the 7th International Brick Masonry 

Conference, Melbourne, Australia.

Kariotis, J.C., Rahman, M.A., and El-mustapha, A.M., 

1993, “Investigation of Current Seismic Design 

Provisions for Reinforced Masonry Shear Walls,” 

The Structural Design of Tall Buildings, Vol. 2, 

163-191.

Kariotis, J.C., Hart, G., Youssef, N., Goo, J., Hill, J., 

and Ngelm, D., 1994, Simulation of Recorded 

Response of Unreinforced Masonry (URM) Infill 

Frame Building, California Division of Mines and 

Geology, SMIP 94-05, Sacramento, California.

Kawashima, K., and Koyama, T., 1988, “Effect of 

Number of Loading Cycles on Dynamic Characteristics of Reinforced Concrete Bridge Pier Columns,” Proceedings of the Japan Society of Civil 

Engineers, Structural Eng./Earthquake Eng., Vol. 

5, No. 1. 

Kingsley, G.R., 1994, Seismic Design and Response of 

a Full-scale Five-Story Reinforced Masonry 

Research Building, Doctoral Dissertation, University of California, San Diego, School of Structural 

Engineering.

Kingsley, G.R., 1995, “Evaluation and Retrofit of Unreinforced Masonry Buildings,” Proceedings of the 

Third National Concrete and Masonry Engineering 

Conference, San Francisco, California, pp. 709-728.

Kingsley, G.R., Magenes, G., and Calvi, G.M., 1996, 

“Measured Seismic Behavior of a Two-Story 

Masonry Building,” Worldwide Advances in Structural Concrete and Masonry, Proceedings of the 

Committee on Concrete and Masonry Symposium, 

ASCE Structures Congress XIV, Chicago, Illinois.

Kingsley, G.R., Noland, J.L., and Atkinson, R.H., 1987, 

“Nondestructive Evaluation of Masonry Structures 

Using Sonic and Ultrasonic Pulse Velocity Techniques,” Proceedings of the Fourth North American 

Masonry Conference, Univ. of Calif. Los Angeles.

Kingsley, G.R., Seible, F., Priestley, M.J.N., and Hegemier, G.A., 1994, The U.S.-TCCMAR Full-scale 

Five-Story Masonry Research Building Test, Part 

II: Design, Construction, and Test Results, Structural Systems Research Project, Report No. SSRP94/02, University of California at San Diego. 

Klingner, R.E. and Bertero, V.V., 1976, Infilled frames 

in earthquake resistant construction, Earthquake 

Engineering Research Centre, University of California at Berkeley, Report No. EERC 76-32.

Klingner, R.E. and Bertero, V.V., 1978, “Earthquake 

resistance of infilled frames,” Journal of the Structural Division, Proc. ASCE, (104)6. 

Kodur, V.K.R., Erki, M.A., and Quenneville, J.H.P., 

1995, “Seismic design and analysis of masonryinfilled frames,” Journal of Civil Engineering, 22: 

576-587.

Krawinkler, H., 1996, "Pushover Analysis: Why, How, 

When, and When not to Use It", Proceedings of the 

65th Annual Convention of the Structural Engineers Association of California, Maui.

Kubota, T., and Murakami, M., 1988, “Flexural Failure 

Test of Reinforced Concrete Masonry Walls -- 

Effect of Lap Joint of Reinforcement,” Proceedings 

of the Fourth Meeting of the U.S.-Japan Joint Technical Coordinating Committee on Masonry 

Research, San Diego, California.

Kubota, T., Okamoto, S., Nishitani, Y., and Kato, S., 

1985, “A Study on Structural Behavior of Brick 

Panel Walls,” Proceedings of the Seventh International Brick Masonry Conference, Melbourne, Australia.

Kürkchübasche, A.G., Seible, F., and Kingsley, G.R., 

1994, The U.S.-TCCMAR Five-story Full-scale 

Reinforced Masonry Research Building Test: Part 

IV, Analytical Models, Structural Systems Research 

Project, Report No. TR - 94/04, University of California at San Diego.

Laursen, P. T., Seible, F., and Hegemier, G. A. , 1995, 

Seismic Retrofit and Repair of Reinforced Concrete 

with Carbon Overlays, Structural Systems Research 

Project, Report No. TR - 95/01, University of California at San Diego.

Leiva, G., and Klingner, R.E., 1991, In-Plane Seismic 

Resistance of Two-story Concrete Masonry Shear 

Walls with Openings, U.S. Coordinated Program for 

Masonry Building Research, Report No. 3.1(c)-2.

Leiva, G., and Klingner, R.E., 1994, “Behavior and 

Design of Multi-Story Masonry Walls under Inplane Seismic Loading,” The Masonry Society 

Journal, Vol. 13, No. 1.
 References

226 Basic Procedures Manual FEMA 306

Liauw, T.C. and Lee, S.W., 1977, “On the behavior and 

the analysis of multi-story infilled frames subjected 

to lateral loading,” Proceedings of the Institute of 

Civil Engineers, 63: 641-656.

Liauw, T.C., 1979, “Tests on multi-storey infilled 

frames subject to dynamic lateral loading,” ACI 

Journal, (76)4: 551-563.

Liauw, T.C. and Kwan, K.H., 1983a, “Plastic theory of 

infilled frames with finite interface shear strength,” 

Proceedings of the Institute of Civil Engineers, 

(2)75: 707-723.

Liauw, T.C. and Kwan, K.H., 1983b, “Plastic theory of 

non-integral infilled frames,” Proceedings of the 

Institute of Civil Engineers, (2)75: 379-396.

Lybas, J.M. and Sozen, M.A., 1977, Effect of Beam 

Strength and Stiffness on Dynamic Behavior of 

Reinforce Concrete Coupled Walls, University of 

Illinois Civil Engineering Studies, Structural 

Research Series No. 444, Report UILU-ENG-77-

2016 (two volumes), Urbana, Illinois.

Magenes, G., 1997, oral communication, May.

Magenes, G., and Calvi, G.M., 1992, “Cyclic Behavior 

of Brick Masonry Walls,” Proceedings of the Tenth 

World Conference, Balkema: Rotterdam, The Netherlands.

Magenes, G. and Calvi, G.M., 1995, “Shaking Table 

Tests on Brick Masonry Walls,” 10th European 

Conference on Earthquake Engineering, Duma, 

editor, Balkema: Rotterdam, The Netherlands.

Maghaddam, H.A. and Dowling, P.J., 1987, The State of 

the Art in Infilled Frames, Civil Engineering 

Department, Imperial College, ESEE Research 

Report No. 87-2, London.

Maier, Johannes, 1991, “Shear Wall Tests,” Preliminary 

Proceedings, International Workshop on Concrete 

Shear in Earthquake, Houston Texas.

Mainstone, R.J. and Weeks, G.A., 1970, “The influence 

of bounding frame on the racking stiffness and 

strength of brick walls,” 2nd International Brick 

Masonry Conference.

Mainstone, R.J., 1971, “On the stiffness and strength of 

infilled frames,” Proceedings of the Institute of 

Civil Engineers Sup., pp. 57-90.

Mallick, D.V. and Garg, R.P., 1971, “Effect of openings 

on the lateral stiffness of infilled frames,” Proceedings of the Institute of Civil Engineers, 49: 193-209.

Mander J. B., Aycardi, L.E., and Kim, D-K, 1994, 

"Physical and Analytical Modeling of Brick Infilled 

Steel Frames," Proceedings of the NCEER Workshop on Seismic Response of Masonry Infills, D.P. 

Abrams editor, National Center for Earthquake 

Engineering Research, Technical Report NCEER94-0004.

Mander, J.B., Chen, S.S., and Pekcan, G., 1994, "Lowcycle fatigue behavior of semi-rigid top-and-seat 

angle connections", AISC Engineering Journal, 

(31)3: 111-122.

Mander, J.B., and Dutta, A., 1997, "How Can Energy 

Based Seismic Design Be Accommodated In Seismic Mapping," Proceedings of the FHWA/NCEER 

Workshop on the National Representation of Seismic Ground Motion for New and Existing Highway 

Facilities, Technical Report, National Center for 

Earthquake Engineering Research, NCEER-97-

0010, pp 95-114.

Mander, J.B., Mahmoodzadegan, B., Bhadra, S., and 

Chen, S.S.,1996, Seismic Evaluation of a 30-YearOld Highway Bridge Pier and Its Retrofit, Department of Civil Engineering, State University of New 

York, Technical Report NCEER-96-0008, Buffalo 

NY.

Mander, J.B., and Nair, B., 1993a, "Seismic Resistance 

of Brick-Infilled Steel Frames With and Without 

Retrofit," The Masonry Society Journal, 12(2): 24-

37.

Mander, J.B., Nair, B., Wojtkowski, K., and Ma, J., 

1993b, An Experimental Study on the Seismic Performance of Brick Infilled Steel Frames, National 

Center for Earthquake Engineering Research, Technical Report NCEER-93-0001.

Mander, J.B., Pekcan, G., and Chen, S.S., 1995, "Lowcycle variable amplitude fatigue modeling of topand-seat angle connections," AISC Engineering 

Journal, American Institute of Steel Construction, 

(32)2: 54-62.

Mansur, M.A., Balendra, T., and H’Ng, S.C., 1991, 

“Tests on Reinforced Concrete Low-Rise Shear 

Walls Under Cyclic Loading,” Preliminary Proceedings, International Workshop on Concrete 

Shear in Earthquake, Houston Texas.

Manzouri, T., Shing, P.B., Amadei, B., Schuller, M., 

and Atkinson, R., 1995, Repair and Retrofit of 

Unreinforced Masonry Walls: Experimental Evaluation and Finite Element Analysis, Department of 

Civil, Environmental and Architectural Engineer-
 References

FEMA 306 Basic Procedures Manual 227

ing, University of Colorado: Boulder, Colorado, 

Report CU/SR-95/2.

Manzouri, T., Shing, P.B., Amadei, B., 1996, “Analysis 

of Masonry Structures with Elastic/Viscoplastic 

Models, 1996,” Worldwide Advances in Structural 

Concrete and Masonry, Proceedings of the Committee on Concrete and Masonry Symposium, ASCE 

Structures Congress XIV, Chicago, Illinois.

Matsumura, A., 1988, “Effectiveness of Shear Reinforcement in Fully Grouted Hollow Clay Masonry 

Walls,” Proceedings of the Fourth Meeting of the 

U.S.-Japan Joint Technical Coordinating Committee on Masonry Research, San Diego, California.

Matsuno, M., Yamazaki, Y., Kaminosono, T., Teshigawara, M., 1987, “Experimental and Analytical 

Study of the Three Story Reinforced Clay Block 

Specimen,” Proceedings of the Third Meeting of the 

U.S.-Japan Joint Technical Coordinating Committee on Masonry Research, Tomamu, Hokkaido, 

Japan.

Mayes, R.L., 1993, Unpublished study in support of the 

U.S. Coordinated Program for Masonry Building 

Research Design and Criteria Recommendations 

for Reinforced Masonry.

Mehrabi, A.B., Shing, P.B., Schuller, M.P., and Noland, 

J.L., 1996, “Experimental evaluation of masonryinfilled RC frames,” Journal of Structural Engineering.

Merryman, K.M., Leiva, G., Antrobus, N., and Klingner, 1990, In-plane Seismic Resistance of Two-story 

Concrete Masonry Coupled Shear Walls, U.S. 

Coordinated Program for Masonry Building 

Research, Report No. 3.1(c)-1.

Modena, C., 1989, “Italian Practice in Evaluating, 

Strengthening, and Retrofitting Masonry Buildings,” Proceedings of the International Seminar on 

Evaluating, Strengthening, and Retrofitting 

Masonry Buildings, University of Texas, Arlington, 

Texas.

Mosalam, K.M., Gergely, P., and White, R., 1994 “Performance and Analysis of Frames with “URM” 

Infills,” Proceedings of the Eleventh Conference

(formerly Electronic Computation Conference) 

held in conjunction with ASCE Structures Congress 

‘94 and International Symposium ‘94, Atlanta, 

Georgia, pp. 57-66.

NIST, 1997, Development of Procedures to Enhance the 

Performance of Rehabilitated URM Buildings, 

National Institute of Standards and Technology, 

GCR 97-724-1, Gaithersburg, Maryland.

Noakowski, Piotr, 1985, Continuous Theory for the 

Determination of Crack Width under the Consideration of Bond, Beton-Und Stahlbetonbau, 7 u..

Noland, J.L., 1990, "1990 Status Report: U.S. Coordinated Program for Masonry Building Research," 

Proceedings of the Fifth North American Masonry 

Conference, Urbana-Champaign, Illinois.

Oesterle, R.G., Fiorato, A.E., Johal, L.S., Carpenter, 

J.E., Russell, H.G., and Corley, W.G., 1976, Earthquake Resistant Structural Walls -- Tests of Isolated 

Walls, Report to National Science Foundation, Portland Cement Association, Skokie, Illinois, 315 pp.

Oesterle, R.G., Aristizabal-Ochoa, J.D., Fiorato, A.E., 

Russsell, H.G., and Corley, W.G., 1979, Earthquake 

Resistant Structural Walls -- Tests of Isolated Walls 

-- Phase II, Report to National Science Foundation, 

Portland Cement Association, Skokie, Illinois.

Oesterle, R.G., Aristizabal, J.D., Shiu, K.N., and Corley, W.G., 1983, Web Crushing of Reinforced Concrete Structural Walls, Portland Cement 

Association, Project HR3250, PCA R&D Ser. No. 

1714, Draft Copy, Skokie, Illinois.

Ogata, K., and Kabeyasawa, T., 1984, “Experimental 

Study on the Hysteretic Behavior of Reinforced 

Concrete Shear Walls Under the Loading of Different Moment-to-Shear Ratios,” Transactions, Japan 

Concrete Institute, Vol. 6, pp. 274-283.

Ohkubo, M., 1991, Current Japanese System on Seismic Capacity and Retrofit Techniques for Existing 

Reinforced Concrete Buildings and Post-Earthquake Damage Inspection and Restoration Techniques, University of California, San Diego 

Structural Systems Research Project Report No. 

SSRP-91/02.

Okada, T., and Kumazawa, F., 1987, “Flexural Behavior 

of Reinforced Concrete Block Beams with SpirallyReinforced Lap Splices,” Proceedings of the Third 

Meeting of the U.S.-Japan Joint Technical Coordinating Committee on Masonry Research, Tomamu, 

Hokkaido, Japan.

Parducci, A. and Mezzi, M., 1980, "Repeated horizontal 

displacement of infilled frames having different 

stiffness and connection systems--Experimental 

analysis", Proceedings of the 7th World Conference 

on Earthquake Engineering, Istanbul, Turkey, 7: 

193-196.
 References

228 Basic Procedures Manual FEMA 306

Paret, T.F., Sasaki, K.K., Eilbeck, D.H., and Freeman, 

S.A., 1996, “Approximate Inelastic Procedures to 

Identify Failure Mechanisms from Higher Mode 

Effects,” Proceedings of the Eleventh World Conference on Earthquake Engineering, Paper 966.

Park, R., 1996, “A Static Force-Based Procedure for the 

Seismic Assessment of Existing R/C Moment 

Resisting Frames,” Proceedings of the Annual 

Technical Conference, New Zealand National Society for Earthquake Engineering.

Park, R. and Paulay, T., 1975, Reinforced Concrete 

Structures, John Wiley & Sons, New York.

Paulay, T., 1971a, “Coupling Beams of ReinforcedConcrete Shear Walls,” Journal of the Structural 

Division, ASCE, Vol. 97, No. ST3, pp. 843–862.

Paulay, T., 1971b, “Simulated Seismic Loading of 

Spandrel Beams,” Journal of the Structural Division, ASCE, Vol. 97, No. ST9, pp. 2407-2419.

Paulay, T., 1977, “Ductility of Reinforced Cocnrete 

Shearwalls for Seismic Areas,” Reinforced Concrete Structures in Seismic Zones, American Concrete Institute, ACI Publication SP-52, Detroit, 

Michigan, pp. 127-147.

Paulay, T., 1980, “Earthquake-Resisting Shearwalls -- 

New Zealand Design Trends,” ACI Journal, pp. 

144-152.

Paulay, T., 1986, “A Critique of the Special Provisions 

for Seismic Design of the Bulding Code Requirements for Reinforced Concrete,” ACI Journal, pp. 

274-283.

Paulay, T., and Binney, J.R., 1974, “Diagonally Reinforced Coupling Beams of Shear Walls,” Shear in 

Reinforced Concrete, ACI Publication SP-42, 

American Concrete Institute, Detroit, Michigan, pp. 

579-598.

Paulay, T. and Priestley, M.J.N., 1992, Seismic Design 

of Reinforced Concrete and Masonry Buildings, 

John Wiley & Sons, New York.

Paulay, T., and Priestley, M.J.N., 1993, “Stability of 

Ductile Structural Walls,” ACI Structural Journal,

Vol. 90, No. 4.

Paulay, T., Priestley, M.J.N., and Synge, A.J., 1982, 

“Ductility in Earthquake Resisting Squat Shearwalls,” ACI Journal, Vol. 79, No. 4, pp.257-269.

Paulay, T., and Santhakumar, A.R., 1976, “Ductile 

Behavior of Coupled Shear Walls,” Journal of the 

Structural Division, ASCE, Vol. 102, No. ST1, pp. 

93-108.

Polyakov, S.V., 1956, Masonry in framed buildings, 

pub. by Gosudarstvennoe Izdatelstvo po Stroitelstvu I Arkhitekture (Translation into English by 

G.L.Cairns).

Prawel, S.P. and Lee, H.H., 1994, “Research on the 

Seismic Performance of Repaired URM Walls,” 

Proc. of the US-Italy Workshop on Guidelines for 

Seismic Evaluation and Rehabilitation of Unreinforced Masonry Buildings, Department of Structural Mechanics, University of Pavia, Italy, June 22-

24, Abrams, D.P. et al. (eds.) National Center for 

Earthquake Engineering Research, SUNY at Buffalo, pp. 3-17 - 3-25.

Priestley, M.J.N., 1977, “Seismic Resistance of Reinforced Concrete Masonry Shear Walls with High 

Steel Percentages,” Bulletin of the New Zealand 

National Society for Earthquake Engineering, Vol. 

10, No. 1, pp.1-16.

Priestley, M.J.N, 1985, “Seismic Behavior of Unreinforced Masonry Walls,” Bulletin of the New 

Zealand National Society for Earthquake Engineering, Vol. 18, No. 2.

Priestley, M.J.N., 1986, “Flexural Strength of Rectangular Unconfined Shear Walls with Distributed 

Reinforcement,” The Masonry Society Journal, Vol. 

5, No. 2.

Priestley, M.J.N., 1990, Masonry Wall-Frame Joint 

Test, Report No. 90-5, Sequad Consulting Engineers, Solana Beach, California.

Priestley, M.J.N., 1996, "Displacement-based seismic 

assessment of existing reinforced concrete buildings," Bulletin of the New Zealand National Soc. for 

Earthquake Eng., (29)4: 256-271.

Priestley, M.J.N. and Elder, D.M., 1982, Seismic Behavior of Slender Concrete Masonry Shear Walls, Dept. 

of Civil Engineering, University of Canterbury, 

Christchurch, Research Report ISSN 0110-3326, 

New Zealand.

Priestley M.J.N., Evison, R.J., and Carr, A.J., 1978, 

“Seismic Response of Structures Free to Rock on 

their Foundations,” Bulletin of the New Zealand 

National Society for Earthquake Engineering, Vol. 

11, No. 3, pp. 141–150.

Priestley, M.J.N., and Hart, G.C., 1989, Design Recommendations for the Period of Vibration of Masonry 

Wall Buildings, Structural Systems Research 
 References

FEMA 306 Basic Procedures Manual 229

Project, Report No. SSRP 89/05, University of California at San Diego.

Priestley, M.J.N., and Hon, C.Y., 1985, “Seismic 

Design of Reinforced Concrete Masonry Moment - 

Resisting Frames,” The Masonry Society Journal, 

Vol. 4., No. 1.

Priestley, M.J.N., and Limin, He, 1990, “Seismic 

Response of T-Section Masonry Shear Walls,” The 

Masonry Society Journal, Vol. 9, No. 1.

Priestley, M.J.N., Seible, F., and Calvi, G.M., 1996, 

Seismic Design and Retrofit of Bridges, John Wiley 

& Sons, New York, 686 pp.

Priestley, M.J.N., Verma, R., and Xiao, Y., 1994, “Seismic Shear Strength of Reinforced Concrete Columns,” ASCE Journal of Structural Engineering, 

Vol. 120, No. 8.

Reinhorn, A.M., Madan, A., Valles, R.E., Reichmann, 

Y., and Mander, J.B., 1995, Modeling of Masonry 

Infill Panels for Structural Analysis, National Center for Earthquake Engineering Research, Technical 

Report NCEER-95-0018.

Riddington, J. and Stafford-Smith, B., 1977, “Analysis 

of infilled frames subject to racking with design 

recommendations,” Structural Engineers, (52)6: 

263-268.

Riddington, J.R., 1984, “The influence of initial gaps on 

infilled frame behavior,” Proceedings of the Institute of Civil Engineers, (2)77: 259-310.

Rutherford & Chekene, 1990, Seismic Retrofitting 

Alternatives for San Francisco’s Unreinforced 

Masonry Buildings: Estimates of Construction Cost 

and Seismic Damage for the San Francisco Department of City Planning, Rutherford and Chekene 

Consulting Engineers: San Francisco, California.

Rutherford & Chekene, 1997, Development of Procedures to Enhance the Performance of Rehabilitated 

Buildings, prepared by Rutherford & Chekene Consulting Engineers, published by the National Institute of Standards and Technology as Reports NIST 

GCR 97-724-1 and 97-724-2.

Saatcioglu, Murat, 1991, “Hysteretic Shear Response of 

Low-rise Walls,” Preliminary Proceedings, International Workshop on Concrete Shear in Earthquake, Houston Texas.

Sachanski, S., 1960, “Analysis of earthquake resistance 

of frame buildings taking into consideration the carring capacity of the filling masonry,” Proceedings 

of the 2nd World Conference on Earthquake Engineering, Japan, 138: 1-15.

Saneinejad, A and Hobbs, B., 1995, “Inelastic design of 

infilled frames,” Journal of Structural Engineering, 

(121)4: 634-650.

SANZ, Standards Association of New Zealand, 1995, 

Code of Practice for the Design of Concrete Structures, NZS3101.

Sassi, H., and Ranous, R., 1996, “Shear Failure in Reinforced Concrete Walls,” From Experience, Structural Engineers Association of Southern California, 

Whittier, California.

Schuller, M.P., Atkinson, R.H., and Borgsmiller, J.T. , 

1994, “Injection Grouting for Repair and Retrofit of 

Unreinforced Masonry,” Proceedings of the 10th 

International Brick and Block Masonry Conference, 

Calgary, Alberta, Canada.

Schultz, A.E., 1996 “Seismic Resistance of PartiallyGrouted Masonry Shear Walls,” Worldwide 

Advances in Structural Concrete and Masonry,

A.E. Schultz and S.L. McCabe, Eds., American 

Society of Civil Engineers, New York.

SEAOC, 1996, Recommended Lateral Force Requirements and Commentary (“Blue Book”), 6th Edition, 

Seismology Committee, Structural Engineers Association of California, Sacramento, California.

SEAOC/CALBO, 1990, “Commentary on the SEAOCCALBO Unreinforced Masonry Building Seismic 

Strengthening Provisions,” Evaluation and 

Strengthening of Unreinforced Masonry Buildings, 

1990 Fall Seminar, Structural Engineers Association of Northern California, San Francisco, California.

SEAOSC, 1986, “RGA (Rule of General Application) 

Unreinforced Masonry Bearing Wall Buildings 

(Alternate Design to Division 88),” Earthquake 

Hazard Mitigation of Unreinforced Pre-1933 

Masonry Buildings, Structural Engineers Association of Southern California: Los Angeles, California.

Seible, F., Hegemier, G.A., Igarashi, A., and Kingsley, 

G.R., 1994a, “Simulated Seismic-Load Tests on 

Full- Scale Five-Story Masonry Building,” ASCE 

Journal of Structural Engineering, Vol. 120, No. 3.

Seible, F., Kingsley, G.R., and Kürkchübasche, A.G., 

1995, “Deformation and Force Capacity Assessment Issues in Structural Wall Buildings,” Recent 
 References

230 Basic Procedures Manual FEMA 306

Developments in Lateral Force Transfer in Buildings – Thomas Paulay Symposium, ACI SP-157.

Seible, F., Okada, T., Yamazaki, Y., and Teshigawara, 

M., 1987, "The Japanese 5-story Full Scale Reinforced Concrete Masonry Test — Design and Construction of the Test Specimen," The Masonry 

Society Journal, Vol. 6, No. 2.

Seible, F., Priestley, M.J.N., Kingsley, G.R., and 

Kürkchübasche, A.G., 1991, Flexural coupling of 

Topped Hollow Core Plank Floor Systems in Shear 

Wall Structures, Structural Systems Research 

Project, Report No. SSRP-91/10, University of California at San Diego.

Seible, F., Priestley, M.J.N., Kingsley, G.R., and 

Kürkchübasche, A.G., 1994b, “Seismic Response 

of a Five-story Full-scale RM Research Building”, 

ASCE Journal of Structural Engineering, Vol. 120, 

No. 3.

Seible, F., Yamazaki, Y., Kaminosono, T., and Teshigawara, M., 1987, "The Japanese 5-story Full Scale 

Reinforced Concrete Masonry Test -- Loading and 

Instrumentation of the Test Building," The Masonry 

Society Journal, Vol. 6, No. 2.

Shapiro, D., Uzarski, J., and Webster, M., 1994, Estimating Out-of-Plane Strength of Cracked Masonry 

Infills, University of Illinois at Urbana-Champaign, 

Report SRS-588, 16 pp.

Shen, J. and Zhu, R., 1994, “Earthquake response simulation of reinforced concrete frames with infilled 

brick walls by pseudo-dynamic test,” Proc. of the 

Second International Conference on Earthquake 

Resistant Construction and Design, Berlin, A. 

Balkema, Rotterdam, pp. 955-962.

Sheppard, P.F. and Tercelj, S., 1985, “Determination of 

the Seismic Resistance of an Historical Brick 

Masonry Building by Laboratory Tests of Cut-Out 

Wall Elements,” Proceedings of the 7th International Brick Masonry Conference, Melbourne, Australia.

Shibata, A., and Sozen, M.A., 1976, “Substitute-Structure Method for Seismic Design in R/C,” Journal of 

the Structural Division, ASCE, vol. 102, no. 1, pp. 

1-18.

Shiga, Shibata, and Takahashi, 1973, “Experimental 

Study on Dynamic Properties of Reinforced Concrete Shear Walls,” Proceedings, Fifth World Conference on Earthquake Engineering, Rome, pp. 

107–117

Shiga, Shibata, and Takahashi, 1975, “Hysteretic 

Behavior of Reinforced Concrete Shear Walls,” 

Proceedings of the Review Meeting, US-Japan 

Cooperative Research Program in Earthquake Engineering with Emphasis on the Safety of School 

Buildings, Honolulu Hawaii, pp. 1157–1166

Shing, P.B., Brunner, J., and Lofti, H.R., 1993, “Analysis of Shear Strength of Reinforced Masonry 

Walls,” Proceedings of the Sixth North American 

Masonry Conference, Philadelphia, Pennsylvania.

Shing, P.B., Mehrabi, A.B., Schuller, M., and Noland, 

J.D., 1994, “Experimental evaluation and finite element analysis of masonry-infilled R/C frames,” 

Proc. of the Eleventh Conference (formerly Electronic Computation Conference) held in conjunction with ASCE Structures Congress ‘94 and 

International Symposium ‘94, Atlanta, Georgia., 

pp. 84-93.

Shing, P.B., Noland, J.L., Spaeh, H.P., Klamerus, E.W., 

and Schuller, M.P., 1991, Response of Single Story 

Reinforced Masonry Shear Walls to In-plane Lateral Loads, TCCMAR Report No. 3.1(a)-2.

Shing, P., Schuller, M., Hoskere, V., and Carter, E., 

1990a, “Flexural and Shear Response of Reinforced 

Masonry Walls,” ACI Structural Journal, Vol. 87, 

No. 6.

Shing, P., Schuller, M., and Hoskere, V., 1990b, “Inplane Resistance of Reinforced Masonry Shear 

Walls,” Proceedings of ASCE Journal of the Structural Division, Vol 116, No. 3.

Shiu, K.N., Daniel, J.I., Aristizabal-Ochoa, J.D., A.E. 

Fiorato, and W.G. Corley, 1981, Earthquake Resistant Structural Walls -- Tests of Wall With and Without Openings, Report to National Science 

Foundation, Portland Cement Association, Skokie, 

Illinois.

Soric, Z. and Tulin, L.E., 1987, “Bond in Reinforced 

Concrete Masonry,” Proceedings Fourth North 

American Masonry Conference, Los Angeles, California.

Sozen, M.A., and Moehle, J.P., 1993, Stiffness of Reinforced Concrete Walls Resisting In-Plane Shear, 

Electric Power Research Institute, EPRI TR102731, Palo Alto, California.
 References

FEMA 306 Basic Procedures Manual 231

Stafford-Smith, B.S., 1966, “Behavior of square infilled 

frames,” ASCE (92)1: 381-403.

Stafford-Smith, B. and Carter, C., 1969, “A method of 

analysis for infilled frames,” Proceedings of the 

Institute of Civil Engineers, 44: 31-48.

Tena-Colunga, A., and Abrams, D.P., 1992, Response of 

an Unreinforced Masonry Building During the 

Loma Prieta Earthquake, Department of Civil 

Engineering, University of Illinois at UrbanaChampaign, Structural Research Series No. 576.

Thiruvengadam, V., 1985, "On the natural frequencies 

of infilled frames," Earthquake Engineering and 

Structural Dynamics, 13: 401-419.

Thomas, F.G., 1953, “The strength of brickwork,” J. 

Instnt. Struct. Engrs., (31)2: 35-46.

Thurston, S., and Hutchinson, D., 1982, “Reinforced 

Masonry Shear Walls Cyclic Load Tests in Contraflexure, “ Bulletin of the New Zealand Society for 

Earthquake Engineering, Vol. 15, No. 1.

TMS, 1994, Performance of Masonry Structures in the 

Northridge, California Earthquake of January 17, 

1994, Richard E. Klingner, ed., The Masonry Society.

Tomazevic, M., and Anicic, 1989, “Research, Technology and Practice in Evaluating, Strengthening, and 

Retrofitting Masonry Buildings: Some Yugoslavian Experiences,” Proceedings of the International 

Seminar on Evaluating, Strengthening and Retrofitting Masonry Buildings, The Masonry Society: 

Boulder, Colorado.

Tomazevic, M., and Lutman, M., 1988, “Design of 

Reinforced Masonry Walls for Seismic Actions,” 

Brick and Block Masonry, J.W. DeCourcy, Ed., 

Elsevier Applied Science, London.

Tomazevic, M., Lutman, M., and Velechovsky, T., 1993, 

“The Influence of Lateral Load Time-history on the 

Behavior of Reinforced-Masonry Walls Failing in 

Shear,” Proceedings of the Sixth North American 

Masonry Conference, Philadelphia, Pennsylvania.

Tomazevic, M., Lutman, M., and Weiss, P., 1996, “Seismic Upgrading of Old Brick-Masonry Urban 

Houses: Tying of Walls with Steel Ties,” Earthquake Spectra, EERI: Oakland, California, Volume 

12, No. 3.

Tomazevic, M., and Modena, C., 1988, “Seismic 

Behavior of Mixed, Reinforced Concrete, Reinforced Masonry Structural Systems,” Brick and 

Block Masonry, J.W. DeCourcy, Ed., Elsevier 

Applied Science, London.

Tomazevic, M., and Weiss, P., 1990, “A Rational, 

Experimentally Based Method for the Verification 

of Earthquake Resistance of Masonry Buildings,” 

Proceedings of the Fourth U.S. National Conference on Earthquake Engineering, EERI: Oakland, 

California.

Tomazevic, M., and Zarnic, R., 1985, “The Effect of 

Horizontal Reinforcement on the Strength and Ductility of Masonry Walls at Shear Failure,” Proceedings of the Seventh International Brick Masonry 

Conference, Melbourne, Australia.

Turnsek, V., and Sheppard, P., 1980, “The Shear and 

Flexural Resistance of Masonry Walls,” Proceedings of the International Research Conference on 

Earthquake Engineering, Skopje, Yugoslavia.

Vallenas, J.M., Bertero, V.V., Popov, E.P., 1979, Hysteretic Behavior of Reinforced Concrete Structural 

Walls, Earthquake Engineering Research Center, 

University of California, Report No. UCB/EERC79/20, Berkeley, California, 234 pp.

Vulcano A., and Bertero, V.V., 1987, Analytical Models 

for Predicting the Lateral Response of RC Shear 

Walls, University of California, UCB/EERC Report 

No. 87-19, Berkeley, California.

Wallace, J. W., 1994, “New Methodology for Seismic 

Design of RC Shear Walls,” Journal of the Structural Engineering Division, American Society of 

Civil Engineers, New York, New York, Vol. 120, 

No. 3, pp. 863-884.

Wallace, J. W., 1995, “Seismic Design of RC Structural 

Walls, Part I: New Code Fromat,” Journal of the 

Structural Engineering Division, American Society 

of Civil Engineers, New York, New York, Vol. 121, 

No. 1, pp. 75-87.

Wallace, J. W., 1996, “Evaluation of UBC-94 Provisions for Seismic Design of RC Structural Walls,” 

Earthquake Spectra, EERI, Oakland, California.

Wallace, J. W. and Moehle, J.P., 1992, “Ductility and 

Detailing Requirements for Bearing Wall Buildings,” Journal of Structural Engineering, ASCE, 

Vol. 118, No. 6, pp. 1625–1644.

Wallace, J. W. and Thomsen IV, J.H., 1995, “Seismic 

Design of RC Shear Walls (Parts I and II),” Journal 

of Structural Engineering, -ASCE, pp. 75-101.
 References

232 Basic Procedures Manual FEMA 306

Wang, T.Y., Bertero, V.V.,Popov, E.P., 1975, Hysteretic 

Behavior of Reinforced Concrete Framed Walls, 

Earthquake Engineering Research Center, University of California at Berkeley, Report No. UCB/

EERC-75/23, Berkeley, California, 367 pp.

Weeks, J., Seible, F., Hegemier, G., and Priestley, 

M.J.N., 1994, The U.S.-TCCMAR Full-scale Fivestory Masonry Research Building Test, Part V - 

Repair and Retest, University of California Structural Systems Research Project Report No. SSRP94/05.

Wight, James K. (editor), 1985, Earthquake Effects on 

Reinforced Concrete Structures, US-Japan 

Research, ACI Special Publication SP-84, American Concrete Institute, Detroit Michigan.

Willsea, F.J., 1990, ”SEAOC/CALBO Recommended 

Provisions”, Evaluation and Strengthening of Unreinforced Masonry Buildings, 1990 Fall Seminar, 

Structural Engineers Association of Northern California, San Francisco, California.

Wiss, Janney, Elstner and Associates, 1970, Final 

Report on Bar Tests, for the Committee of Concrete 

Reinforcing Bar Producers, American Iron and 

Steel Institute (Job #70189), Northbrook, Illinois.

Wood, R.H., 1978, “Plasticity, composite action and 

collapse design of unreinforced shear wall panels in 

frames,” Proceedings of the Institute of Civil Engineers, 2: 381-411.

Wood, S. L, 1990, “Shear Strength of Low-Rise Reinforced Concrete Walls,” ACI Structural Journal, 

Vol. 87, No. 1, pp 99-107. 

Wood, S. L., 1991, “Observed Behavior of Slender 

Reinforced Concrete Walls Subjected to Cyclic 

Loading,” Earthquake-Resistant Concrete Structures, Inelastic Response and Design, ACI Special 

Publication SP-127, S.K. Ghosh, Editor, American 

Concrete Institute, Detroit Michigan, pp. 453–478

Xu, W., and Abrams, D.P., 1992, Evaluation of Lateral 

Strength and Deflection for Cracked Unreinforced 

Masonry Walls, U.S. Army Research Office: Triangle Park, North Carolina, Report ADA 264-160.

Yamamoto, M., and Kaminosono, T., 1986, “Behavior 

of Reinforced Masonry Walls with Boundary 

Beams,” Proceedings of the Second Meeting of the 

Joint Technical Coordinating Committee on 

Masonry Research, Keystone, Colorado. 

Yamazaki, Y., F. Seible, H., Mizuno, H., Kaminosono, 

T., Teshigawara, M., 1988b, "The Japanese 5-story 

Full Scale Reinforced Concrete Masonry Test -- 

Forced Vibration and Cyclic Load Test Results," 

The Masonry Society Journal, Vol. 7, No. 1.

Yamazaki, Y., Kaminosono, T., Teshigawara, M., and 

Seible, F., 1988a, "The Japanese 5-story Full Scale 

Reinforced Concrete Masonry Test -- Pseudo 

Dynamic and Ultimate Load Test Results," The 

Masonry Society Journal, Vol. 7, No. 2.

Yoshimura, K. and Kikuchi, K., 1995, “Experimental 

study on seismic behavior of masonry walls confined by R/C frames,” Proceedings of the Pacific 

Conference on Earthquake Engineering, Melbourne, Australia, Parkville, Victoria, 3: 97-106.

Young, J.M., and Brown, R.H., 1988, Compressive 

Stress Distribution of Grouted Hollow Clay 

Masonry Under Stain Gradient, U.S. Coordinated 

Program for Masonry Building Research, Report 

No. 1.2b-1.

Zarnic, R. and Tomazevic, M., 1984, “The behavior of 

masonry infilled reinforced concrete frames subjected to seismic loading,” Proceedings of the 8th 

World Conference on Earthquake Engineering, California, VI: 863-870.

Zarnic, R. and Tomazevic, M., 1985a, “Study of the 

behavior of masonry infilled reinforced concrete 

frames subjected to seismic loading,” Proc. 7th Intl. 

Brick Masonry Conf., Melbourne, Australia.

Zarnic, R. and Tomazevic, M., 1985b, Study of the 

behavior of masonry infilled reinforced concrete 

frames subjected to seismic loading, Part 2. A 

report to the research community of Slovenia, 

ZRMK/IKPI - 8502, Ljubljana.

Zsutty, T.C., 1990, “Applying Special Procedures”, 

Evaluation and Strengthening of Unreinforced 

Masonry Buildings, 1990 Fall Seminar, Structural 

Engineers Association of Northern California, San 

Francisco, California.
FEMA 306 Basic Procedures Manual 233 

ATC-43 Project Participants

Atc Management

Mr. Christopher Rojahn,

Principal Investigator

Applied Technology Council

555 Twin Dolphin Drive, Suite 550

Redwood City, CA 94065

Mr. Craig Comartin,

Co-PI and Project Director

7683 Andrea Avenue

Stockton, CA 95207

Technical Management Committee

Prof. Dan Abrams

University of Illinois

1245 Newmark Civil Eng’g. Lab., MC 250

205 North Mathews Avenue

Urbana, IL 61801-2397

Mr. James Hill

James A. Hill & Associates, Inc.

1349 East 28th Street

Signal Hill, CA 90806

Mr. Andrew T. Merovich

A.T. Merovich & Associates, Inc.

1163 Francisco Blvd., Second Floor

San Rafael, CA 94901

Prof. Jack Moehle

Earthquake Engineering Research Center

University of California at Berkeley

1301 South 46th Street

Richmond, CA 94804

FEMA/PARR Representatives

Mr. Timothy McCormick

PaRR Task Manager

Dewberry & Davis

8401 Arlington Boulevard

Fairfax, VA 22031-4666

Mr. Mark Doroudian

PaRR Representative

42 Silkwood

Aliso Viejo, CA 92656

Prof. Robert D. Hanson

FEMA Technical Monitor

74 North Pasadena Avenue, CA-1009-DR

Parsons Bldg., West Annex, Room 308

Pasadena, CA 91103
 ATC-43 Project Participants

234 Basic Procedures Manual FEMA 306

Materials Working Group

Dr. Joe Maffei, Group Leader

Consulting Structural Engineer

148 Hermosa Avenue

Oakland California

Mr. Brian Kehoe, Lead Consultant

Wiss, Janney, Elstner Associates, Inc.

2200 Powell Street, Suite 925

Emeryville, CA 94608

Dr. Greg Kingsley

KL&A of Colorado

805 14th Street

Golden, CO 80401

Mr. Bret Lizundia

Rutherford & Chekene

303 Second Street, Suite 800 North

San Francisco, CA 94107

Prof. John Mander

SUNY at Buffalo

Department of Civil Engineering

212 Ketter Hall

Buffalo, NY 14260

Analysis Working Group

Prof. Mark Aschheim, Group Leader

University of Illinois at Urbana

2118 Newmark CE Lab

205 North Mathews, MC 250

Urbana, IL 61801

Prof. Mete Sozen, Senior Consultant

Purdue University, School of Engineering

1284 Civil Engineering Building

West Lafayette, IN 47907-1284

Project Review Panel

Mr. Gregg J. Borchelt

Brick Institute of America

11490 Commerce Park Drive, #300

Reston, VA 20191

Dr. Gene Corley

Construction Technology Labs

5420 Old Orchard Road

Skokie, IL 60077-1030

Mr. Edwin Huston

Smith & Huston

Plaza 600 Building, 6th & Stewart, #620

Seattle, WA 98101

Prof. Richard E. Klingner

University of Texas

Civil Engineering Department

Cockbell Building, Room 4-2

Austin, TX 78705

Mr. Vilas Mujumdar

Office of Regulation Services

Division of State Architect

General Services

1300 I Street, Suite 800

Sacramento, CA 95814

Dr. Hassan A. Sassi

Governors Office of Emergency Services

74 North Pasadena Avenue

Pasadena, CA 91103

Mr. Carl Schulze

Libby Engineers

4452 Glacier Avenue

San Diego, CA 92120

Mr. Daniel Shapiro

SOH & Associates

550 Kearny Street, Suite 200

San Francisco, CA 94108
 ATC-43 Project Participants

FEMA 306 Basic Procedures Manual 235

Prof. James K. Wight

University of Michigan

Department of Civil Engineering

2368 G G Brown

Ann Arbor, MI 48109-2125

Mr. Eugene Zeller

Long Beach Department of Building & Safety

333 W. Ocean Boulevard, Fourth Floor

Long Beach, CA 90802
 ATC-43 Project Participants

236 Basic Procedures Manual FEMA 306
FEMA 306 Basic Procedures Manual 237 

Applied Technology Council Projects And Report 

Information

One of the primary purposes of Applied Technology 

Council is to develop resource documents that translate 

and summarize useful information to practicing engineers. This includes the development of guidelines and 

manuals, as well as the development of research recommendations for specific areas determined by the profession. ATC is not a code development organization, 

although several of the ATC project reports serve as 

resource documents for the development of codes, standards and specifications.

Applied Technology Council conducts projects that 

meet the following criteria:

1. The primary audience or benefactor is the design 

practitioner in structural engineering. 

2. A cross section or consensus of engineering opinion 

is required to be obtained and presented by a neutral 

source.

3. The project fosters the advancement of structural 

engineering practice. 

A brief description of several major completed projects 

and reports is given in the following section. Funding 

for projects is obtained from government agencies and 

tax-deductible contributions from the private sector.

ATC-1: This project resulted in five papers that were 

published as part of Building Practices for Disaster 

Mitigation, Building Science Series 46, proceedings of a 

workshop sponsored by the National Science Foundation (NSF) and the National Bureau of Standards 

(NBS). Available through the National Technical Information Service (NTIS), 5285 Port Royal Road, Springfield, VA 22151, as NTIS report No. COM-73-50188.

ATC-2: The report, An Evaluation of a Response Spectrum Approach to Seismic Design of Buildings, was 

funded by NSF and NBS and was conducted as part of 

the Cooperative Federal Program in Building Practices 

for Disaster Mitigation. Available through the ATC 

office. (Published 1974, 270 Pages)

ABSTRACT: This study evaluated the applicability 

and cost of the response spectrum approach to seismic analysis and design that was proposed by various segments of the engineering profession. 

Specific building designs, design procedures and 

parameter values were evaluated for future application. Eleven existing buildings of varying dimensions were redesigned according to the procedures.

ATC-3: The report, Tentative Provisions for the Development of Seismic Regulations for Buildings (ATC-3-

06), was funded by NSF and NBS. The second printing 

of this report, which includes proposed amendments, is 

available through the ATC office. (Published 1978, 

amended 1982, 505 pages plus proposed amendments)

ABSTRACT: The tentative provisions in this document represent the results of a concerted effort by a 

multi-disciplinary team of 85 nationally recognized 

experts in earthquake engineering. The provisions 

serve as the basis for the seismic provisions of the 

1988 Uniform Building Code and the 1988 and subsequent issues of the NEHRP Recommended Provisions for the Development of Seismic Regulation for 

New Buildings. The second printing of this document contains proposed amendments prepared by a 

joint committee of the Building Seismic Safety 

Council (BSSC) and the NBS.

ATC-3-2: The project, Comparative Test Designs of 

Buildings Using ATC-3-06 Tentative Provisions, was 

funded by NSF. The project consisted of a study to 

develop and plan a program for making comparative 

test designs of the ATC-3-06 Tentative Provisions. The 

project report was written to be used by the Building 

Seismic Safety Council in its refinement of the ATC-3-

06 Tentative Provisions.

ATC-3-4: The report, Redesign of Three Multistory 

Buildings: A Comparison Using ATC-3-06 and 1982 

Uniform Building Code Design Provisions, was published under a grant from NSF. Available through the 

ATC office. (Published 1984, 112 pages)

ABSTRACT: This report evaluates the cost and technical impact of using the 1978 ATC-3-06 report, 

Tentative Provisions for the Development of Seismic 

Regulations for Buildings, as amended by a joint 
 Applied Technology Council Projects And Report Information

238 Basic Procedures Manual FEMA 306

committee of the Building Seismic Safety Council 

and the National Bureau of Standards in 1982. The 

evaluations are based on studies of three existing 

California buildings redesigned in accordance with 

the ATC-3-06 Tentative Provisions and the 1982 

Uniform Building Code. Included in the report are 

recommendations to code implementing bodies. 

ATC-3-5: This project, Assistance for First Phase of 

ATC-3-06 Trial Design Program Being Conducted by 

the Building Seismic Safety Council, was funded by the 

Building Seismic Safety Council to provide the services 

of the ATC Senior Consultant and other ATC personnel 

to assist the BSSC in the conduct of the first phase of its 

Trial Design Program. The first phase provided for trial 

designs conducted for buildings in Los Angeles, Seattle, 

Phoenix, and Memphis.

ATC-3-6: This project, Assistance for Second Phase of 

ATC-3-06 Trial Design Program Being Conducted by 

the Building Seismic Safety Council, was funded by the 

Building Seismic Safety Council to provide the services 

of the ATC Senior Consultant and other ATC personnel 

to assist the BSSC in the conduct of the second phase of 

its Trial Design Program. The second phase provided 

for trial designs conducted for buildings in New York, 

Chicago, St. Louis, Charleston, and Fort Worth.

ATC-4: The report, A Methodology for Seismic Design 

and Construction of Single-Family Dwellings, was published under a contract with the Department of Housing 

and Urban Development (HUD). Available through the 

ATC office. (Published 1976, 576 pages)

ABSTRACT: This report presents the results of an 

in-depth effort to develop design and construction 

details for single-family residences that minimize 

the potential economic loss and life-loss risk associated with earthquakes. The report: (1) discusses 

the ways structures behave when subjected to seismic forces, (2) sets forth suggested design criteria 

for conventional layouts of dwellings constructed 

with conventional materials, (3) presents construction details that do not require the designer to perform analytical calculations, (4) suggests 

procedures for efficient plan-checking, and (5) presents recommendations including details and schedules for use in the field by construction personnel 

and building inspectors. 

ATC-4-1: The report, The Home Builders Guide for 

Earthquake Design, was published under a contract 

with HUD. Available through the ATC office. (Published 1980, 57 pages) 

ABSTRACT: This report is an abridged version of 

the ATC-4 report. The concise, easily understood 

text of the Guide is supplemented with illustrations 

and 46 construction details. The details are provided to ensure that houses contain structural features that are properly positioned, dimensioned and 

constructed to resist earthquake forces. A brief 

description is included on how earthquake forces 

impact on houses and some precautionary constraints are given with respect to site selection and 

architectural designs.

ATC-5: The report, Guidelines for Seismic Design and 

Construction of Single-Story Masonry Dwellings in 

Seismic Zone 2, was developed under a contract with 

HUD. Available through the ATC office. (Published 

1986, 38 pages) 

ABSTRACT: The report offers a concise methodology for the earthquake design and construction of 

single-story masonry dwellings in Seismic Zone 2 

of the United States, as defined by the 1973 Uniform Building Code. The Guidelines are based in 

part on shaking table tests of masonry construction 

conducted at the University of California at Berkeley Earthquake Engineering Research Center. The 

report is written in simple language and includes 

basic house plans, wall evaluations, detail drawings, and material specifications. 

ATC-6: The report, Seismic Design Guidelines for 

Highway Bridges, was published under a contract with 

the Federal Highway Administration (FHWA). Available through the ATC office. (Published 1981, 210 

pages)

ABSTRACT: The Guidelines are the recommendations of a team of sixteen nationally recognized 

experts that included consulting engineers, academics, state and federal agency representatives from 

throughout the United States. The Guidelines 

embody several new concepts that were significant 

departures from then existing design provisions. 

Included in the Guidelines are an extensive commentary, an example demonstrating the use of the 
 Applied Technology Council Projects And Report Information

FEMA 306 Basic Procedures Manual 239

Guidelines, and summary reports on 21 bridges 

redesigned in accordance with the Guidelines. 

The guidelines have been adopted by the American Association of Highway and Transportation 

Officials as a guide specification. 

ATC-6-1: The report, Proceedings of a Workshop 

on Earthquake Resistance of Highway Bridges, was 

published under a grant from NSF. Available 

through the ATC office. (Published 1979, 625 pages)

ABSTRACT: The report includes 23 state-of-theart and state-of-practice papers on earthquake 

resistance of highway bridges. Seven of the 

twenty-three papers were authored by participants from Japan, New Zealand and Portugal. 

The Proceedings also contain recommendations 

for future research that were developed by the 45 

workshop participants. 

ATC-6-2: The report, Seismic Retrofitting Guidelines for Highway Bridges, was published under a 

contract with FHWA. Available through the ATC 

office. (Published 1983, 220 pages) 

ABSTRACT: The Guidelines are the recommendations of a team of thirteen nationally recognized experts that included consulting engineers, 

academics, state highway engineers, and federal 

agency representatives. The Guidelines, applicable for use in all parts of the United States, 

include a preliminary screening procedure, 

methods for evaluating an existing bridge in 

detail, and potential retrofitting measures for the 

most common seismic deficiencies. Also 

included are special design requirements for various retrofitting measures.

ATC-7: The report, Guidelines for the Design of 

Horizontal Wood Diaphragms, was published under 

a grant from NSF. Available through the ATC 

office. (Published 1981, 190 pages)

ABSTRACT: Guidelines are presented for designing roof and floor systems so these can function 

as horizontal diaphragms in a lateral force resisting system. Analytical procedures, connection 

details and design examples are included in the 

Guidelines.

ATC-7-1: The report, Proceedings of a Workshop 

of Design of Horizontal Wood Diaphragms, was 

published under a grant from NSF. Available 

through the ATC office. (Published 1980, 302 pages)

ABSTRACT: The report includes seven papers on 

state-of-the-practice and two papers on recent 

research. Also included are recommendations 

for future research that were developed by the 35 

workshop participants.

ATC-8: This report, Proceedings of a Workshop on 

the Design of Prefabricated Concrete Buildings for 

Earthquake Loads, was funded by NSF. Available 

through the ATC office. (Published 1981, 400 pages)

ABSTRACT: The report includes eighteen stateof-the-art papers and six summary papers. Also 

included are recommendations for future 

research that were developed by the 43 workshop participants.

ATC-9: The report, An Evaluation of the Imperial 

County Services Building Earthquake Response and 

Associated Damage, was published under a grant 

from NSF. Available through the ATC office. (Published 1984, 231 pages)

ABSTRACT: The report presents the results of an 

in-depth evaluation of the Imperial County Services Building, a 6-story reinforced concrete 

frame and shear wall building severely damaged 

by the October 15, 1979 Imperial Valley, California, earthquake. The report contains a review 

and evaluation of earthquake damage to the 

building; a review and evaluation of the seismic 

design; a comparison of the requirements of various building codes as they relate to the building; 

and conclusions and recommendations pertaining to future building code provisions and future 

research needs. 

ATC-10: This report, An Investigation of the Correlation Between Earthquake Ground Motion and 

Building Performance, was funded by the U.S. Geological Survey (USGS). Available through the ATC 

office. (Published 1982, 114 pages)

ABSTRACT: The report contains an in-depth analytical evaluation of the ultimate or limit capacity of selected representative building framing 

types, a discussion of the factors affecting the 

seismic performance of buildings, and a sum-
 Applied Technology Council Projects And Report Information

240 Basic Procedures Manual FEMA 306

mary and comparison of seismic design and seismic 

risk parameters currently in widespread use. 

ATC-10-1: This report, Critical Aspects of Earthquake 

Ground Motion and Building Damage Potential, was 

co-funded by the USGS and the NSF. Available 

through the ATC office. (Published 1984, 259 pages)

ABSTRACT: This document contains 19 state-ofthe-art papers on ground motion, structural 

response, and structural design issues presented by 

prominent engineers and earth scientists in an ATC 

seminar. The main theme of the papers is to identify the critical aspects of ground motion and building performance that currently are not being 

considered in building design. The report also contains conclusions and recommendations of working 

groups convened after the Seminar. 

ATC-11: The report, Seismic Resistance of Reinforced 

Concrete Shear Walls and Frame Joints: Implications 

of Recent Research for Design Engineers, was published under a grant from NSF. Available through the 

ATC office. (Published 1983, 184 pages)

ABSTRACT: This document presents the results of 

an in-depth review and synthesis of research reports 

pertaining to cyclic loading of reinforced concrete 

shear walls and cyclic loading of joint reinforced 

concrete frames. More than 125 research reports 

published since 1971 are reviewed and evaluated in 

this report. The preparation of the report included a 

consensus process involving numerous experienced 

design professionals from throughout the United 

States. The report contains reviews of current and 

past design practices, summaries of research developments, and in-depth discussions of design implications of recent research results. 

ATC-12: This report, Comparison of United States and 

New Zealand Seismic Design Practices for Highway 

Bridges, was published under a grant from NSF. Available through the ATC office. (Published 1982, 270 

pages)

ABSTRACT: The report contains summaries of all 

aspects and innovative design procedures used in 

New Zealand as well as comparison of United 

States and New Zealand design practice. Also 

included are research recommendations developed 

at a 3-day workshop in New Zealand attended by 16 

U.S. and 35 New Zealand bridge design engineers 

and researchers.

ATC-12-1: This report, Proceedings of Second Joint 

U.S.-New Zealand Workshop on Seismic Resistance of 

Highway Bridges, was published under a grant from 

NSF. Available through the ATC office. (Published 

1986, 272 pages)

ABSTRACT: This report contains written versions of 

the papers presented at this 1985 Workshop as well 

as a list and prioritization of workshop recommendations. Included are summaries of research 

projects being conducted in both countries as well 

as state-of-the-practice papers on various aspects of 

design practice. Topics discussed include bridge 

design philosophy and loadings; design of columns, 

footings, piles, abutments and retaining structures; 

geotechnical aspects of foundation design; seismic 

analysis techniques; seismic retrofitting; case studies using base isolation; strong-motion data acquisition and interpretation; and testing of bridge 

components and bridge systems.

ATC-13: The report, Earthquake Damage Evaluation 

Data for California, was developed under a contract 

with the Federal Emergency Management Agency 

(FEMA). Available through the ATC office. (Published 

1985, 492 pages)

ABSTRACT: This report presents expert-opinion 

earthquake damage and loss estimates for industrial, commercial, residential, utility and transportation facilities in California. Included are damage 

probability matrices for 78 classes of structures and 

estimates of time required to restore damaged facilities to pre-earthquake usability. The report also 

describes the inventory information essential for 

estimating economic losses and the methodology 

used to develop loss estimates on a regional basis.

ATC-14: The report, Evaluating the Seismic Resistance 

of Existing Buildings, was developed under a grant from 

the NSF. Available through the ATC office. (Published 

1987, 370 pages)

ABSTRACT: This report, written for practicing 

structural engineers, describes a methodology for 

performing preliminary and detailed building seis-
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FEMA 306 Basic Procedures Manual 241

mic evaluations. The report contains a state-ofpractice review; seismic loading criteria; data collection procedures; a detailed description of the 

building classification system; preliminary and 

detailed analysis procedures; and example case 

studies, including nonstructural considerations. 

ATC-15: The report, Comparison of Seismic Design 

Practices in the United States and Japan, was published 

under a grant from NSF. Available through the ATC 

office. (Published 1984, 317 pages)

ABSTRACT: The report contains detailed technical 

papers describing design practices in the United 

States and Japan as well as recommendations emanating from a joint U.S.-Japan workshop held in 

Hawaii in March, 1984. Included are detailed 

descriptions of new seismic design methods for 

buildings in Japan and case studies of the design of 

specific buildings (in both countries). The report 

also contains an overview of the history and objectives of the Japan Structural Consultants Association. 

ATC-15-1: The report, Proceedings of Second U.S.-

Japan Workshop on Improvement of Building Seismic 

Design and Construction Practices, was published 

under a grant from NSF. Available through the ATC 

office. (Published 1987, 412 pages)

ABSTRACT: This report contains 23 technical 

papers presented at this San Francisco workshop in 

August, 1986, by practitioners and researchers from 

the U.S. and Japan. Included are state-of-the-practice papers and case studies of actual building 

designs and information on regulatory, contractual, 

and licensing issues.

ATC-15-2: The report, Proceedings of Third U.S.-

Japan Workshop on Improvement of Building Structural 

Design and Construction Practices, was published 

jointly by ATC and the Japan Structural Consultants 

Association. Available through the ATC office. (Published 1989, 358 pages)

ABSTRACT: This report contains 21 technical 

papers presented at this Tokyo, Japan, workshop in 

July, 1988, by practitioners and researchers from 

the U.S., Japan, China, and New Zealand. Included 

are state-of-the-practice papers on various topics, 

including braced steel frame buildings, beam-column joints in reinforced concrete buildings, summaries of comparative U. S. and Japanese design, 

and base isolation and passive energy dissipation 

devices. 

ATC-15-3: The report, Proceedings of Fourth U.S.-

Japan Workshop on Improvement of Building Structural 

Design and Construction Practices, was published 

jointly by ATC and the Japan Structural Consultants 

Association. Available through the ATC office. (Published 1992, 484 pages)

ABSTRACT: This report contains 22 technical 

papers presented at this Kailua-Kona, Hawaii, 

workshop in August, 1990, by practitioners and 

researchers from the United States, Japan, and Peru. 

Included are papers on postearthquake building 

damage assessment; acceptable earth-quake damage; repair and retrofit of earthquake damaged 

buildings; base-isolated buildings, including Architectural Institute of Japan recommendations for 

design; active damping systems; wind-resistant 

design; and summaries of working group conclusions and recommendations.

ATC-15-4: The report, Proceedings of Fifth U.S.-

Japan Workshop on Improvement of Building Structural 

Design and Construction Practices, was published 

jointly by ATC and the Japan Structural Consultants 

Association. Available through the ATC office. (Published 1994, 360 pages)

ABSTRACT: This report contains 20 technical 

papers presented at this San Diego, California 

workshop in September, 1992. Included are papers 

on performance goals/acceptable damage in seismic 

design; seismic design procedures and case studies; 

construction influences on design; seismic isolation 

and passive energy dissipation; design of irregular 

structures; seismic evaluation, repair and upgrading; quality control for design and construction; and 

summaries of working group discussions and recommendations.

ATC-16: This project, Development of a 5-Year Plan 

for Reducing the Earthquake Hazards Posed by Existing 

Nonfederal Buildings, was funded by FEMA and was 

conducted by a joint venture of ATC, the Building Seismic Safety Council and the Earthquake Engineering 
 Applied Technology Council Projects And Report Information

242 Basic Procedures Manual FEMA 306

Research Institute. The project involved a workshop in 

Phoenix, Arizona, where approximately 50 earthquake 

specialists met to identify the major tasks and goals for 

reducing the earthquake hazards posed by existing nonfederal buildings nationwide. The plan was developed 

on the basis of nine issue papers presented at the workshop and workshop working group discussions. The 

Workshop Proceedings and Five-Year Plan are available 

through the Federal Emergency Management Agency, 

500 “C” Street, S.W., Washington, DC 20472.

ATC-17: This report, Proceedings of a Seminar and 

Workshop on Base Isolation and Passive Energy Dissipation, was published under a grant from NSF. Available through the ATC office. (Published 1986, 478 

pages)

ABSTRACT: The report contains 42 papers describing the state-of-the-art and state-of-the-practice in 

base-isolation and passive energy-dissipation technology. Included are papers describing case studies 

in the United States, applications and developments 

worldwide, recent innovations in technology development, and structural and ground motion issues. 

Also included is a proposed 5-year research agenda 

that addresses the following specific issues: (1) 

strong ground motion; (2) design criteria; (3) materials, quality control, and long-term reliability; (4) 

life cycle cost methodology; and (5) system 

response. 

ATC-17-1: This report, Proceedings of a Seminar on 

Seismic Isolation, Passive Energy Dissipation and 

Active Control, was published under a grant from NSF. 

Available through the ATC office. (Published 1993, 841 

pages)

ABSTRACT: The 2-volume report documents 70 

technical papers presented during a two-day seminar in San Francisco in early 1993. Included are 

invited theme papers and competitively selected 

papers on issues related to seismic isolation systems, passive energy dissipation systems, active 

control systems and hybrid systems. 

ATC-18: The report, Seismic Design Criteria for 

Bridges and Other Highway Structures: Current and 

Future, was published under a contract from the Multidisciplinary Center for Earthquake Engineering 

Research (formerly NCEER), with funding from the 

Federal Highway Administration. Available through the 

ATC office. (Published 1997, 152 pages)

ABSTRACT: This report documents the findings of a 

4-year project to review and assess current seismic 

design criteria for new highway construction. The 

report addresses performance criteria, importance 

classification, definitions of seismic hazard for 

areas where damaging earthquakes have longer 

return periods, design ground motion, duration 

effects, site effects, structural response modification 

factors, ductility demand, design procedures, foundation and abutment modeling, soil-structure interaction, seat widths, joint details and detailing 

reinforced concrete for limited ductility in areas 

with low-to-moderate seismic activity. The report 

also provides lengthy discussion on future directions for code development and recommended 

research and development topics.

ATC-19: The report, Structural Response Modification 

Factors was funded by NSF and NCEER. Available 

through the ATC office. (Published 1995, 70 pages)

ABSTRACT: This report addresses structural 

response modification factors (R factors), which are 

used to reduce the seismic forces associated with 

elastic response to obtain design forces. The report 

documents the basis for current R values, how R 

factors are used for seismic design in other countries, a rational means for decomposing R into key 

components, a framework (and methods) for evaluating the key components of R, and the research 

necessary to improve the reliability of engineered 

construction designed using R factors.

ATC-20: The report, Procedures for Postearthquake 

Safety Evaluation of Buildings, was developed under a 

contract from the California Office of Emergency Services (OES), California Office of Statewide Health 

Planning and Development (OSHPD) and FEMA. 

Available through the ATC office (Published 1989, 152 

pages)

ABSTRACT: This report provides procedures and 

guidelines for making on-the-spot evaluations and 

decisions regarding continued use and occupancy 

of earthquake damaged buildings. Written specifically for volunteer structural engineers and building 

inspectors, the report includes rapid and detailed 
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FEMA 306 Basic Procedures Manual 243

evaluation procedures for inspecting buildings and 

posting them as “inspected” (apparently safe), “limited entry” or “unsafe”. Also included are special 

procedures for evaluation of essential buildings 

(e.g., hospitals), and evaluation procedures for nonstructural elements, and geotechnical hazards.

ATC-20-1: The report, Field Manual: Postearthquake 

Safety Evaluation of Buildings, was developed under a 

contract from OES and OSHPD. Available through the 

ATC office (Published 1989, 114 pages)

ABSTRACT: This report, a companion Field Manual 

for the ATC-20 report, summarizes the 

postearthquake safety evaluation procedures in 

brief concise format designed for ease of use in the 

field. 

ATC-20-2: The report, Addendum to the ATC-20 

Postearthquake Building Safety Procedures was published under a grant from the NSF and funded by the 

USGS. Available through the ATC office. (Published 

1995, 94 pages)

ABSTRACT: This report provides updated assessment forms, placards, and procedures that are based 

on an in-depth review and evaluation of the widespread application of the ATC-20 procedures following five earthquakes occurring since the initial 

release of the ATC-20 report in 1989. 

ATC-20-3: The report, Case Studies in Rapid 

Postearthquake Safety Evaluation of Buildings, was 

funded by ATC and R. P. Gallagher Associates. Available through the ATC office. (Published 1996, 295 

pages)

ABSTRACT: This report contains 53 case studies 

using the ATC-20 Rapid Evaluation procedure. 

Each case study is illustrated with photos and 

describes how a building was inspected and evaluated for life safety, and includes a completed safety 

assessment form and placard. The report is intended 

to be used as a training and reference manual for 

building officials, building inspectors, civil and 

structural engineers, architects, disaster workers, 

and others who may be asked to perform safety 

evaluations after an earthquake.

ATC-20-T: The report, Postearthquake Safety Evaluation of Buildings Training Manual was developed under 

a contract with FEMA. Available through the ATC 

office. (Published 1993, 177 pages; 160 slides)

ABSTRACT: This training manual is intended to 

facilitate the presentation of the contents of the 

ATC-20 and ATC-20-1. The training materials consist of 160 slides of photographs, schematic drawings and textual information and a companion 

training presentation narrative coordinated with the 

slides. Topics covered include: posting system; 

evaluation procedures; structural basics; wood 

frame, masonry, concrete, and steel frame structures; nonstructural elements; geotechnical hazards; 

hazardous materials; and field safety.

ATC-21: The report, Rapid Visual Screening of Buildings for Potential Seismic Hazards: A Handbook, was 

developed under a contract from FEMA. Available 

through the ATC office. (Published 1988, 185 pages)

ABSTRACT: This report describes a rapid visual 

screening procedure for identifying those buildings 

that might pose serious risk of loss of life and 

injury, or of severe curtailment of community services, in case of a damaging earthquake. The 

screening procedure utilizes a methodology based 

on a "sidewalk survey" approach that involves identification of the primary structural load resisting 

system and building materials, and assignment of a 

basic structural hazards score and performance 

modification factors based on observed building 

characteristics. Application of the methodology 

identifies those buildings that are potentially hazardous and should be analyzed in more detail by a 

professional engineer experienced in seismic 

design.

ATC-21-1: The report, Rapid Visual Screening of 

Buildings for Potential Seismic Hazards: Supporting 

Documentation, was developed under a contract from 

FEMA. Available through the ATC office. (Published 

1988, 137 pages)

ABSTRACT: Included in this report are (1) a review 

and evaluation of existing procedures; (2) a listing 

of attributes considered ideal for a rapid visual 

screening procedure; and (3) a technical discussion 

of the recommended rapid visual screening procedure that is documented in the ATC-21 report. 
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244 Basic Procedures Manual FEMA 306

ATC-21-2: The report, Earthquake Damaged Buildings: An Overview of Heavy Debris and Victim Extrication, was developed under a contract from FEMA. 

(Published 1988, 95 pages)

ABSTRACT: Included in this report, a companion 

volume to the ATC-21 and ATC-21-1 reports, is 

state-of-the-art information on (1) the identification 

of those buildings that might collapse and trap victims in debris or generate debris of such a size that 

its handling would require special or heavy lifting 

equipment; (2) guidance in identifying these types 

of buildings, on the basis of their major exterior features, and (3) the types and life capacities of equipment required to remove the heavy portion of the 

debris that might result from the collapse of such 

buildings. 

ATC-21-T: The report, Rapid Visual Screening of 

Buildings for Potential Seismic Hazards Training Manual was developed under a contract with FEMA. Available through the ATC office. (Published 1996, 135 

pages; 120 slides)

ABSTRACT: This training manual is intended to 

facilitate the presentation of the contents of the 

ATC-21 report. The training materials consist of 

120 slides and a companion training presentation 

narrative coordinated with the slides. Topics covered include: description of procedure, building 

behavior, building types, building scores, occupancy and falling hazards, and implementation. 

ATC-22: The report, A Handbook for Seismic Evaluation of Existing Buildings (Preliminary), was developed 

under a contract from FEMA. Available through the 

ATC office. (Originally published in 1989; revised by 

BSSC and published as the NEHRP Handbook for Seismic Evaluation of Existing Buildings in 1992, 211 

pages)

ABSTRACT: This handbook provides a methodology for seismic evaluation of existing buildings of 

different types and occupancies in areas of different 

seismicity throughout the United States. The methodology, which has been field tested in several programs nationwide, utilizes the information and 

procedures developed for and documented in the 

ATC-14 report. The handbook includes checklists, 

diagrams, and sketches designed to assist the user.

ATC-22-1: The report, Seismic Evaluation of Existing 

Buildings: Supporting Documentation, was developed 

under a contract from FEMA. (Published 1989, 160 

pages)

ABSTRACT: Included in this report, a companion 

volume to the ATC-22 report, are (1) a review and 

evaluation of existing buildings seismic evaluation 

methodologies; (2) results from field tests of the 

ATC-14 methodology; and (3) summaries of evaluations of ATC-14 conducted by the National Center 

for Earthquake Engineering Research (State University of New York at Buffalo) and the City of San 

Francisco.

ATC-23A: The report, General Acute Care Hospital 

Earthquake Survivability Inventory for California, Part 

A: Survey Description, Summary of Results, Data Analysis and Interpretation, was developed under a contract 

from the Office of Statewide Health Planning and 

Development (OSHPD), State of California. Available 

through the ATC office. (Published 1991, 58 pages)

ABSTRACT: This report summarizes results from a 

seismic survey of 490 California acute care hospitals. Included are a description of the survey procedures and data collected, a summary of the data, 

and an illustrative discussion of data analysis and 

interpretation that has been provided to demonstrate 

potential applications of the ATC-23 database. 

ATC-23B: The report, General Acute Care Hospital 

Earthquake Survivability Inventory for California, Part 

B: Raw Data, is a companion document to the ATC23A Report and was developed under the above-mentioned contract from OSHPD. Available through the 

ATC office. (Published 1991, 377 pages)

ABSTRACT: Included in this report are tabulations 

of raw general site and building data for 490 acute 

care hospitals in California.

ATC-24: The report, Guidelines for Seismic Testing of 

Components of Steel Structures, was jointly funded by 

the American Iron and Steel Institute (AISI), American 

Institute of Steel Construction (AISC), National Center 

for Earthquake Engineering Research (NCEER), and 

NSF. Available through the ATC office. (Published 

1992, 57 pages)
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FEMA 306 Basic Procedures Manual 245

ABSTRACT: This report provides guidance for most 

cyclic experiments on components of steel structures for the purpose of consistency in experimental 

procedures. The report contains recommendations 

and companion commentary pertaining to loading 

histories, presentation of test results, and other 

aspects of experimentation. The recommendations 

are written specifically for experiments with slow 

cyclic load application. 

ATC-25: The report, Seismic Vulnerability and Impact 

of Disruption of Lifelines in the Conterminous United 

States, was developed under a contract from FEMA. 

Available through the ATC office. (Published 1991, 440 

pages)

ABSTRACT: Documented in this report is a national 

overview of lifeline seismic vulnerability and 

impact of disruption. Lifelines considered include 

electric systems, water systems, transportation systems, gas and liquid fuel supply systems, and emergency service facilities (hospitals, fire and police 

stations). Vulnerability estimates and impacts 

developed are presented in terms of estimated first 

approximation direct damage losses and indirect 

economic losses.

ATC-25-1: The report, A Model Methodology for 

Assessment of Seismic Vulnerability and Impact of Disruption of Water Supply Systems, was developed under 

a contract from FEMA. Available through the ATC 

office. (Published 1992, 147 pages)

ABSTRACT: This report contains a practical methodology for the detailed assessment of seismic vulnerability and impact of disruption of water supply 

systems. The methodology has been designed for 

use by water system operators. Application of the 

methodology enables the user to develop estimates 

of direct damage to system components and the 

time required to restore damaged facilities to preearthquake usability. Suggested measures for mitigation of seismic hazards are also provided. 

ATC-28: The report, Development of Recommended 

Guidelines for Seismic Strengthening of Existing Buildings, Phase I: Issues Identification and Resolution, was 

developed under a contract with FEMA. Available 

through the ATC office. (Published 1992, 150 pages)

ABSTRACT: This report identifies and provides resolutions for issues that will affect the development of 

guidelines for the seismic strengthening of existing 

buildings. Issues addressed include: implementation and format, coordination with other efforts, 

legal and political, social, economic, historic buildings, research and technology, seismicity and mapping, engineering philosophy and goals, issues 

related to the development of specific provisions, 

and nonstructural element issues.

ATC-29: The report, Proceedings of a Seminar and 

Workshop on Seismic Design and Performance of 

Equipment and Nonstructural Elements in Buildings 

and Industrial Structures, was developed under a grant 

from NCEER and NSF. Available through the ATC 

office. (Published 1992, 470 pages)

ABSTRACT: These Proceedings contain 35 papers 

describing state-of-the-art technical information 

pertaining to the seismic design and performance of 

equipment and nonstructural elements in buildings 

and industrial structures. The papers were presented 

at a seminar in Irvine, California in 1990. Included 

are papers describing current practice, codes and 

regulations; earthquake performance; analytical and 

experimental investigations; development of new 

seismic qualification methods; and research, practice, and code development needs for specific elements and systems. The report also includes a 

summary of a proposed 5-year research agenda for 

NCEER. 

ATC-29-1: The report, Proceedings Of Seminar On 

Seismic Design, Retrofit, And Performance Of Nonstructural Components, was developed under a grant 

from NCEER and NSF. Available through the ATC 

office. (Published 1998, 518 pages)

ABSTRACT: These Proceedings contain 38 papers 

presenting current research, practice, and informed 

thinking pertinent to seismic design, retrofit, and 

performance of nonstructural components. The 

papers were presented at a seminar in San Francisco, California, in 1998. Included are papers 

describing observed performance in recent earthquakes; seismic design codes, standards, and procedures for commercial and institutional buildings; 

seismic design issues relating to industrial and hazardous material facilities; design, analysis, and test-
 Applied Technology Council Projects And Report Information

246 Basic Procedures Manual FEMA 306

ing; and seismic evaluation and rehabilitation of 

conventional and essential facilities, including hospitals. 

ATC-30: The report, Proceedings of Workshop for Utilization of Research on Engineering and Socioeconomic 

Aspects of 1985 Chile and Mexico Earthquakes, was 

developed under a grant from the NSF. Available 

through the ATC office. (Published 1991, 113 pages)

ABSTRACT: This report documents the findings of a 

1990 technology transfer workshop in San Diego, 

California, co-sponsored by ATC and the Earthquake Engineering Research Institute. Included in 

the report are invited papers and working group recommendations on geotechnical issues, structural 

response issues, architectural and urban design considerations, emergency response planning, search 

and rescue, and reconstruction policy issues. 

ATC-31: The report, Evaluation of the Performance of 

Seismically Retrofitted Buildings, was developed under 

a contract from the National Institute of Standards and 

Technology (NIST, formerly NBS) and funded by the 

USGS. Available through the ATC office. (Published 

1992, 75 pages)

ABSTRACT: This report summarizes the results from 

an investigation of the effectiveness of 229 seismically retrofitted buildings, primarily unreinforced 

masonry and concrete tilt-up buildings. All buildings were located in the areas affected by the 1987 

Whittier Narrows, California, and 1989 Loma Prieta, California, earthquakes.

ATC-32: The report, Improved Seismic Design Criteria 

for California Bridges: Provisional Recommendations,

was funded by the California Department of Transportation (Caltrans). Available through the ATC office. 

(Published 1996, 215 Pages)

ABSTRACT: This report provides recommended 

revisions to the current Caltrans Bridge Design 

Specifications (BDS) pertaining to seismic loading, 

structural response analysis, and component design. 

Special attention is given to design issues related to 

reinforced concrete components, steel components, 

foundations, and conventional bearings. The recommendations are based on recent research in the 

field of bridge seismic design and the performance 

of Caltrans-designed bridges in the 1989 Loma Prieta and other recent California earthquakes.

ATC-34: The report, A Critical Review of Current 

Approaches to Earthquake Resistant Design, was developed under a grant from NCEER and NSF. Available 

through the ATC office. (Published, 1995, 94 pages)

ABSTRACT. This report documents the history of U. 

S. codes and standards of practice, focusing primarily on the strengths and deficiencies of current 

code approaches. Issues addressed include: seismic 

hazard analysis, earthquake collateral hazards, performance objectives, redundancy and configuration, response modification factors (R factors), 

simplified analysis procedures, modeling of structural components, foundation design, nonstructural 

component design, and risk and reliability. The 

report also identifies goals that a new seismic code 

should achieve.

ATC-35: This report, Enhancing the Transfer of U.S. 

Geological Survey Research Results into Engineering 

Practice was developed under a contract with the 

USGS. Available through the ATC office. (Published 

1996, 120 pages)

ABSTRACT: The report provides a program of recommended “technology transfer” activities for the 

USGS; included are recommendations pertaining to 

management actions, communications with practicing engineers, and research activities to enhance 

development and transfer of information that is 

vital to engineering practice.

ATC-35-1: The report, Proceedings of Seminar on New 

Developments in Earthquake Ground Motion Estimation and Implications for Engineering Design Practice, 

was developed under a cooperative agreement with 

USGS. Available through the ATC office. (Published 

1994, 478 pages)

ABSTRACT: These Proceedings contain 22 technical 

papers describing state-of-the-art information on 

regional earthquake risk (focused on five specific 

regions--California, Pacific Northwest, Central 

United States, and northeastern North America); 

new techniques for estimating strong ground 

motions as a function of earthquake source, travel 

path, and site parameters; and new developments 
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FEMA 306 Basic Procedures Manual 247

specifically applicable to geotechnical engineering and the seismic design of buildings and 

bridges.

ATC-37: The report, Review of Seismic Research 

Results on Existing Buildings, was developed in conjunction with the Structural Engineers Association of 

California and California Universities for Research 

in Earthquake Engineering under a contract from the 

California Seismic Safety Commission (SSC). Available through the Seismic Safety Commission as 

Report SSC 94-03. (Published, 1994, 492 pages)

ABSTRACT. This report describes the state of 

knowledge of the earthquake performance of 

nonductile concrete frame, shear wall, and 

infilled buildings. Included are summaries of 90 

recent research efforts with key results and conclusions in a simple, easy-to-access format written for practicing design professionals. 

ATC-40: The report, Seismic Evaluation and Retrofit of Concrete Buildings, was developed under a contract from the California Seismic Safety 

Commission. Available through the ATC office. 

(Published, 1996, 612 pages)

ABSTRACT. This 2-volume report provides a 

state-of-the-art methodology for the seismic 

evaluation and retrofit of concrete buildings. 

Specific guidance is provided on the following 

topics: performance objectives; seismic hazard; 

determination of deficiencies; retrofit strategies; 

quality assurance procedures; nonlinear static 

analysis procedures; modeling rules; foundation 

effects; response limits; and nonstructural components. In 1997 this report received the Western States Seismic Policy Council “Overall 

Excellence and New Technology Award.” 

ATC-44: The report, Hurricane Fran, South Carolina, September 5, 1996: Reconnaissance Report, is 

available through the ATC office. (Published 1997, 

36 pages.) 

ABSTRACT: This report represents ATC’s 

expanded mandate into structural engineering 

problems arising from wind storms and coastal 

flooding. It contains information on the causative 

hurricane; coastal impacts, including storm 

surge, waves, structural forces and erosion; 

building codes; observations and interpretations 

of damage; and lifeline performance. Conclusions address man-made beach nourishment, the 

effects of missile-like debris, breaches in the 

sandy barrier islands, and the timing and duration 

of such investigations. 

ATC-R-1: The report, Cyclic Testing of Narrow Plywood Shear Walls, was developed with funding from 

the Henry J. Degenkolb Memorial Endowment Fund 

of the Applied Technology Council. Available 

through the ATC office (Published 1995, 64 pages)

ABSTRACT: This report documents ATC's first 

self-directed research program: a series of static 

and dynamic tests of narrow plywood wall panels having the standard 3.5-to-1 height-to-width 

ratio and anchored to the sill plate using typical 

bolted, 9-inch, 5000-lb. capacity hold-down 

devices. The report provides a description of the 

testing program and a summary of results, 

including comparisons of drift ratios found during testing with those specified in the seismic 

provisions of the 1991 Uniform Building Code. 
248 Basic Procedures Manual FEMA 306

ATC BOARD OF DIRECTORS (1973-Present)

Milton A. Abel (1979-85)

James C. Anderson (1978-81)

Thomas G. Atkinson* (1988-94)

Albert J. Blaylock (1976-77)

Robert K. Burkett (1984-88)

James R. Cagley (1998-2001)

H. Patrick Campbell (1989-90)

Arthur N. L. Chiu (1996-99)

Anil Chopra (1973-74)

Richard Christopherson* (1976-80)

Lee H. Cliff (1973)

John M. Coil* (1986-87, 1991-97)

Eugene E. Cole (1985-86)

Edwin T. Dean (1996-99)

Robert G. Dean (1996-2001)

Edward F. Diekmann (1978-81)

Burke A. Draheim (1973-74)

John E. Droeger (1973)

Nicholas F. Forell* (1989-96)

Douglas A. Foutch (1993-97)

Paul Fratessa (1991-92)

Sigmund A. Freeman (1986-89)

Barry J. Goodno (1986-89)

Mark R. Gorman (1984-87)

Gerald H. Haines (1981-82, 1984-85)

William J. Hall (1985-86)

Gary C. Hart (1975-78)

Lyman Henry (1973)

James A. Hill (1992-95)

Ernest C. Hillman, Jr. (1973-74)

Ephraim G. Hirsch (1983-84)

William T. Holmes* (1983-87)

Warner Howe (1977-80)

Edwin T. Huston* (1990-97)

Paul C. Jennings (1973-75)

Carl B. Johnson (1974-76)

Edwin H. Johnson (1988-89, 1998-2001)

Stephen E. Johnston* (1973-75, 1979-80)

Joseph Kallaby* (1973-75)

Donald R. Kay (1989-92)

T. Robert Kealey* (1984-88)

H. S. (Pete) Kellam (1975-76)

Helmut Krawinkler (1979-82)

James S. Lai (1982-85)

Gerald D. Lehmer (1973-74)

James R. Libby (1992-98)

Charles Lindbergh (1989-92)

R. Bruce Lindermann (1983-86)

L. W. Lu (1987-90)

Walter B. Lum (1975-78)

Kenneth A. Luttrell (1991-98)

Newland J. Malmquist (1997-2000)

Melvyn H. Mark (1979-82)

John A. Martin (1978-82)

John F. Meehan* (1973-78) 

Andrew T. Merovich (1996-99)

David L. Messinger (1980-83)

Stephen McReavy (1973)

Bijan Mohraz (1991-97)

William W. Moore* (1973-76)

Gary Morrison (1973)

Robert Morrison (1981-84)

Ronald F. Nelson (1994-95)

Joseph P. Nicoletti* (1975-79)

Bruce C. Olsen* (1978-82)

Gerard Pardoen (1987-91)

Stephen H. Pelham (1998-2001)

Norman D. Perkins (1973-76)

Richard J. Phillips (1997-2000)

Maryann T. Phipps (1995-96)

Sherrill Pitkin (1984-87)

Edward V. Podlack (1973)

Chris D. Poland (1984-87)

Egor P. Popov (1976-79)

Robert F. Preece* (1987-93)

Lawrence D. Reaveley* (1985-91)

Philip J. Richter* (1986-89)

John M. Roberts (1973)

Charles W. Roeder (1997-2000)

Arthur E. Ross* (1985-91, 1993-94)

C. Mark Saunders* (1993-2000)

Walter D. Saunders* (1975-79)

Lawrence G. Selna (1981-84)

Wilbur C. Schoeller (1990-91)

Samuel Schultz* (1980-84)

Daniel Shapiro* (1977-81)

Jonathan G. Shipp (1996-99)

Howard Simpson* (1980-84)

Mete Sozen (1990-93)

Donald R. Strand (1982-83)

James L. Stratta (1975-79)

Scott Stedman (1996-97)

Edward J. Teal (1976-79)

W. Martin Tellegen (1973)

John C. Theiss* (1991-98)

Charles H. Thornton* (1992-99)

James L. Tipton (1973)

Ivan Viest (1975-77)

Ajit S. Virdee* (1977-80, 1981-85)

J. John Walsh (1987-90)

Robert S. White (1990-91)

James A. Willis* (1980-81, 1982-86)

Thomas D. Wosser (1974-77)

Loring A. Wyllie (1987-88)

Edwin G. Zacher (1981-84)

Theodore C. Zsutty (1982-85)

* President

ATC EXECUTIVE DIRECTORS (1973-Present)

Ronald Mayes (1979-81)

Christopher Rojahn (1981-present)

Roland L. Sharpe (1973-79)
FEMA 306 Basic Procedures Manual 249 

Applied Technology Council 

Sponsors, Supporters, and Contributors

Sponsors

Structural Engineers Association of California

James R. & Sharon K. Cagley

John M. Coil

Burkett & Wong

Supporters

Charles H. Thornton

Degenkolb Engineers

Japan Structural Consultants Association

Contributors

Lawrence D. Reaveley

Omar Dario Cardona Arboleda

Edwin T. Huston

John C. Theiss

Reaveley Engineers

Rutherford & Chekene

E. W. Blanch Co.
 Applied Technology Council Projects And Report Information

250 Basic Procedures Manual FEMA 306