ement of

tative Seismic Provisions

e on Review and Refinement I i

oordinating Committee

I

Technical Committee

1: Seismic Risk Maps

2: Structural Design

Committee 4: Concrete

mmittee 5: Masonry

mmittee 6: Steel

ommittee 7: Wood

Committee 3: Architectural, Mechanical and

Electrical

Committee 9: Regulatory Use

Report of Technical Committee 3:

Foundations

Th.s report documents the deliberations cf a group of professionals jointly

selected by the Building Seismic Safety Councii and the National Bureau

cf Standards and is for use in modifying the Tentative Provisions for trial designs.

•QC

100

U56

80-2111-31

1980

lent of Commerce

of Standards

iring Laboratory

g Technology

October 1980

NBSIR 80-2111-3

ATiOj»AL

OF STANDARDS

Lihmary

MAY 1 8 1981

/)/>/ dCC ~~

REVIEW AND REFINEMENT OF ATC 3-06

TENTATIVE SEISMIC PROVISIONS

Report of Technical Committee 3: Foundations

Richard Simon, Chairman, Association of Soil and Foundation Engineers

Lawrence Salomone, Secretary, National Bureau of Standards

James G. LaBastie, American Society of Civil Engineers

William Travis, Structural Enginners Association of California

Joseph V. Tyrrell, Interagency Committee on Seismic Safety in Construction

Henry Degenkolb, Applied Technology Council

Leroy Crandall, Building Seismic Safety Council

Prepared for use by the:

Building Seismic Sa'fety Council

Sponsored by:

Federal Emergency Management Agency

Center for Building Technology

National Bureau of Standards

Washington, D.C. 20234

October 1980

U.S. DEPARTMENT OF COMMERCE, Phillip M. Klutznick, Secretary

Luther H. Hodges, Jr., Deputy Secretary

Jordan J. Baruch, Assistant Secretary for Productivity,

Technology and Innovation

NATIONAL BUREAU OF STANDARDS, Ernest Ambler, Director
A * *

i Yv
ABSTRACT

The Tentative Provisions for the Development of Seismic Regulations for Buildings

were developed by the Applied Technology Council to present, in one comprehensive

document, current state-of-knowledge pertaining to seismic engineering of

buildings. The Tentative Provisions are in the process of being assessed by

the building community. This report is one of a series of reports that documents

the deliberations of a group of professionals jointly selected by the Building

Seismic Safety Council and the National Bureau of Standards and charged with

reviewing the Tentative Provisions prior to conducting trial designs.

This report documents the activities of Technical Committee 3: Foundations.

Other committee reports are similarly available. The task of Technical

Committee 3 was to review and refine Chapter 6, Soil-Structure Interaction

and Chapter 7, Foundation Design Requirements in the ATC report (NBS SP-510)

entitled, "Tentative Provisions for the Development of Seismic Regulations for

Buildings." Two meetings were held. The opening meeting of the group was on December 11, 1979, and the concluding meeting was on February 5, 1980. The

minutes of these meetings and the findings /recommendations of Technical

Committee 3 are presented in this report. These recommendations were made

to the parent group, the Joint Committee on Review and Refinement, and their

action on these recommendations is documented in a companion report.

Keywords: Buildings; design; earthquakes; engineering; foundations; professional

practice; provisions; soil-structure interaction; standards

iii
TABLE OF CONTENTS

Page

1.0 INTRODUCTION 1

1.1 General 1 1.2 Committee Summary 1 1.3 Chairman's Statement 3

2.0 COMMITTEE ACTIONS 5

2.1 Recommendations for Change 5 2.2 Recommendations for Trial Design NONE

2.3 Recommendations for Commentary NONE

2.4 Other Recommendations NONE

3.0 COMMITTEE RECORDS 12

3.1 Minutes of Meetings 12

3.2 Roster 49

3.3 Selected Committee Correspondence and Applied

Technology Council Comments NONE

IV
1.0

INTRODUCTION

1.1 General

The Tentative Provisions for the Development of Seismic Regulations were

developed by the Applied Technology Council (ATC) in an effort that included

a wide range of experts in the actual drafting of the provisions. Two

external review drafts were circulated to a large portion of the interested

and informed community of eventual users. However, because the Tentative

Provisions were innovative, doubts about them existed. Consequently, an attempt was made to investigate these doubts and to improve the Tentative

Provisions where possible before an expensive assessment of the Tentative

Provisions was undertaken by conducting trial designs.

This review and refinement project was planned and conducted by the National

Bureau of Standards with the advice and approval of the Building Seismic

Safety Council, a private sector organization formed in 1979 for the

purpose of enhancing public safety by providing a national forum to foster

improved seismic safety provisions for use by the building community.

The assessment of the Tentative Provisions was performed using the committee

structure shown in figure 1. Nine Technical Committees were formed with

interests that collectively cover the Tentative Provisions . The Joint

Committee on Review and Refinement consists of all voting members of the

Technical Committees. The chairmen of the Technical Committees form a Coordinating Committee.

Membership of each Technical Committee is made up of representatives of

organizations that have particular interest in the Tentative Provisions ; the participants are listed in the committee membership section of this

report

In addition to the voting members, each Technical Committee includes a non-voting member from each of the following organizations: The Applied

Technology Council (ATC), the Building Seismic Safety Council (BSSC)

and the National Bureau of Standards (NBS). The ATC representative served

as a technical resource to the committee since he was closely involved with

the development of the provisions of interest to the committee. The NBS

representative was the technical secretary throughout the effort. The

BSSC representative provided a link with the Building Seismic Safety

Council, which will be involved in trial designs and evaluations.

1 .2 Committee Summary

This report documents the activities of Technical Committee 3: Foundations.

Other committee reports are similarly available.

The task of Technical Committee 3 was to review and refine Chapter 6, SoilStructure Interaction and Chapter 7, Foundation Design Requirement, in the

ATC report (NBS SP-510) entitled "Tentative Provisions for the Development

of Seismic Regulations for Buildings.” Two meetings were held. The opening

meeting of the group was on December 11, 1979 at the National Bureau of

Standards in Building 226, Room B— 113. The topics discussed included:

1
JOINT COMMITTEE ON

REVIEW AND REFINEMENT

COORDINATING

COMMITTEE

TECHNICAL COMMITTEES

Committee 1: Seismic Risk Maps

Committee 2: Structural Design

Committee 3 : Foundations

Committee 4: Concrete

Committee 5: Masonry

Committee 6: Steel

Committee 7: Wood

Committee 8: Architectural,

Mechanical, and Electrical

Committee 9: Regulatory Use

Figure 1: Committee Structure

2
1) Introduction and Orientation by NBS Secretary

2) Selection of Chairman

3) Selection of Representative to Committee 2

4) Selection of Date and Location for Next Meeting

5) Establishment of Work Plan and Preliminary Discussion

of Chapters 6 and 7

The minutes of the opening meeting are provided in Section 3 of this report.

The second meeting of the group was held on February 15, 1980 at Law Engineering Testing Company, 109 Inverness Drive East, Englewood, Colorado. The

meeting served as a workshop to discuss comments received by February 15,

1980 on Chapters 6 and 7 and to develop recommendations for revising these

chapters. Comments were provided to the members of the committee in letters

from Lawrence Salomone to members of Technical Committee 3 dated January 16

and January 31, 1980. Also, late comments received prior to February 15, 1980

meeting were distributed to committee members at the opening of the second

meeting

The second meeting was conducted in the following manner:

1) Each of the comments received were discussed and a final position

of the committee developed. The final position consisted of a recommendation

for change for the section in question or a recommendation that the section

not be modified.

2) Following development of the final position of the committee a vote

was taken.

The results of this meeting and the items voted on are presented in detail in

the minutes of the second meeting provided in Section 3. With the completion

of Meeting 2 the review of Chapters 6 and 7 by Technical Committee 3 was

completed. The recommendations of Technical Committee 3 are presented in

Section 2.

1.3 Chairman’s Statement

In adopting positions concerning the various sections covered in Chapters

6 and 7 of the tentative provisions, the Committee tried to improve clarity

and specificity of the clauses (e.g.: Section 7.2.2, Paragraph #1 - changing

"at the elastic limit" to "at acceptable strains" to describe allowable

stress on soil). Where analytical developments or concepts permit a better

description of the desired structural performance, refined definitions have

been recommended (e.g.: require piles to sustain soil-determined displacements rather than specify that the piles resist flexure induced by lateral

soil pressures).

With respect to design of piles for earthquake, the Committee adopted a position based primarily on the experiences gained following the San

Fernando and Anchorage earthquakes. For this reason, the Committee recommended phrases that stress the importance of providing a ductile connection

and a ductile pile section in the vicinity of the pile cap. Since precast

concrete piles exhibited unsatisfactory performance in some instances in

the past, extra conservatism was judged to be appropriate for their use.

3
Finally, the Committee considered the Chapter on soil-structure interaction.

The discussion was wide ranging, but a strong consensus was reached. The

provisions of Chapter 6 are so complex that they are not effective in implementing a new concept. The equations could not be applied by practicing

engineers in general without an extraordinary risk of error. The practicing

engineer would have little "feel" for what he was calculating. Finally,

there are few or no prototype observations that would justify the use of

this sophisticated procedure. The Committee recommended that Chapter 6

be deleted from the Provisions at this stage. A compromise position stressing

the optional nature of the Chapter was developed by the coordinating committee

(Committee 10) as contained on the full committee ballot. Committee 10

accepted that the deletion of the Chapter 6 provisions should be reconsidered following a specific evaluation of their effect during the trail design

phase.

4
2.0 COMMITTEE ACTIONS

2.1 Recommendations for Change

In this section the changes to Chapters 6 and 7 proposed by Technical

Committee #3 are presented. These changes have been unanimously adopted

by the committee members, i.e. there were four affirmative votes. It should

also be pointed out that Joseph V. Tyrrell of the Interagency Committee

on Seismic Safety in Construction voted affirmative with reservations for

Ballot Item 8e. This item involved Section 7.4.4(A) on page 74 of the

ATC report, which the committee decided not to modify. Mr. Tyrrell

indicated that he did not want this reservation to be voted on by the

committee but merely wanted to state for the record that he recommends

that "for caissons greater than 30" diameter, minimum reinforcement

(steel ratio) should be .0020." Because the committee decided not to

modify this item in Section 7.4.4(A) in their ballot for no change,

the item in question does not appear in the following pages.

5
REVIEW AND REFINEMENT OF TENTATIVE SEISMIC PROVISIONS

PROPOSED CHANGE

TECHNICAL COMMITTEE: #3, FOUNDATIONS COMMITTEE ITEM NUMBER: le

ATC-3-06 SECTION REFERENCE: 3.2.1

The last paragraph in Section 3.2.1 should be changed to read "In

locations where the soil properties are not known in sufficient detail to

determine the soil profile type or where the profile does not fit any of

the three types, Soil Profile S£ or Soil Profile S-^ shall be used depending

on whichever soil profile type results in the higher value of seismic

coefficient, C e> as determined in Section 4.2.1 .

FINAL BALLOT : 4 YES

NO

ABSTAIN

DID NOT VOTE

COMMENT ON PROPOSED CHANGE:

Soil Profile Type S 2 is much better than Type S

3

. Section 3.2.1

suggests soil profile type S 2 when the soil properties are not known.

This did not seem logical. Hence the proposed change was recommended.

6
REVIEW AND REFINEMENT OF TENTATIVE SEISMIC PROVISIONS

PROPOSED CHANGE

TECHNICAL COMMITTEE: #3, FOUNDATIONS COMMITTEE ITEM NUMBER: 4e

ATC-3-06 SECTION REFERENCE: 7.2.2

The last sentence in Section 7.2.2 should read "For the load combination

including earthquake as specified in Section 3.7, the soil capacities must

be sufficient to resist loads at acceptable strains considering both the

short time of loading and the dynamic properties of the soil.

FINAL BALLOT : 4 YES

NO

ABSTAIN

DID NOT VOTE

COMMENT ON PROPOSED CHANGE:

Soils are inherently inelastic materials. To specify stressing below

the elastic limit is practically without meaning. Hence, the term "elastic

limit" should be replaced with the phrase, "to resist loads at acceptable

strains"

7
REVIEW AND REFINEMENT OF TENTATIVE SEISMIC PROVISIONS

PROPOSED CHANGE

TECHNICAL COMMITTEE: #3, FOUNDATIONS COMMITTEE ITEM NUMBER: 7e

ATC-3-06 SECTION REFERENCE: 7.5.2

The first sentence in Section 7.5.2 should be changed to read "Individual

spread footings unless founded directly on rock, as defined in Section 3.2. 1(1) , shall be interconnected by ties".

FINAL BALLOT: 4 YES

NO

ABSTAIN

DID NOT VOTE

COMMENT ON PROPOSED CHANGE:

The comment was made that it is overly conservative to require structural

ties between pile caps equal to 25% of the maximum vertical load for a Category B structure. This conservatism is amplified in the commentary of this

paragraph where it states, "Lateral soil pressure on pile caps is not a re- commended method; and if the soil is soft enough to require ties, little

reliance can be placed on soft-soil passive pressure to restrain relative

displacement under dynamic conditions." There are many cases in which the use of piles is dictated by deep soil deposits and the near surface materials

are relatively stiff and strong (such as compact or dense gravels and sands

overlying soft clays or controlled, compacted fill over clays or organic

soils. In these cases, it would seem reasonable to permit at least a portion

of the lateral tie resistance between the pile caps to be provided by lateral

soil resistance with some guidance provided. In light of these considerations

and after discussing the terminology that would be appropriate, the committee

agreed to recommend the change shown above.

8
REVIEW AND REFINEMENT OF TENTATIVE SEISMIC PROVISIONS

PROPOSED CHANGE

TECHNICAL COMMITTEE: #3, FOUNDATIONS COMMITTEE ITEM NUMBER: 9e

ATC-3-06 SECTION REFERENCE: 7.4.4

At the end of paragraph 2 of Section 7.4.4 (before Item A) the following

sentence should be added, "Where special reinforcement at the top of the pile

is required alternative measures for containing concrete and maintaining

ductility will be permitted provided due consideration is given to forcing

the hinge to occur in the contained section.

FINAL BALLOT: 4 YES

NO

ABSTAIN

DID NOT VOTE

COMMENT ON PROPOSED CHANGE:

The committee discussed possible designs for the connection at the top

of the pile. It was agreed that the intent was to put the ductile section

where the hinge would form. Considering this fact and the comments received,

the proposed change was recommended. The minority view as expressed in a comment from Committee 4 to use an exposed strand was rejected by the

committee because it was judged that one could not manufacturer a ductile

connection between the pile and the pile cap using steel strand. Furthermore, it is at the point where the pile is connected to the pile cap that

the greatest damage was observed during the San Fernando and Alaskan earthquakes .

9
REVIEW AND REFINEMENT OF TENTATIVE SEISMIC PROVISIONS

PROPOSED CHANGE

TECHNICAL COMMITTEE: #3, FOUNDATIONS COMMITTEE ITEM NUMBER: lOe

ATC-3-06 SECTION REFERENCE: 7.5.3(c)

The last sentence in Section 7.5.3(c) should be revised to read, "Precast

concrete and prestressed concrete piling shall be designed to withstand maximum imposed curvatures resulting from a dynamic analysis of the soil profile.

FINAL BALLOT: 4 YES

NO

ABSTAIN

DID NOT VOTE

COMMENT ON PROPOSED CHANGE:

The basis for the proposed change was that prestressed precast concrete

piling can withstand considerable curvature and through proper detailing

confinement and ductility can be provided.

10
REVIEW AND REFINEMENT OF TENTATIVE SEISMIC PROVISIONS

PROPOSED CHANGE

TECHNICAL COMMITTEE: #3, FOUNDATIONS COMMITTEE ITEM NUMBER: 12e

ATC-3-06 SECTION REFERENCE: Chapter 6

Chapter 6 should be deleted.

FINAL BALLOT: 4 YES

NO

ABSTAIN

DID NOT VOTE

COMMENT ON PROPOSED CHANGE:

After reviewing Chapter 6 and thoroughly examining the procedures therein,

the committee felt strongly that the provisions were not effective in implementing a new concept. Chapter 6 is too complicated for the practicing engineer and it is not justified based on field observations. The sophistication

of the analysis is inconsistent with the accuracy of the results and the com- plexity masks the understanding of the performance of the soil structure

system. Further documentation for deletion of Chapter 6 is provided in the

minutes for the February 15, 1980 meeting (attachments).

11
3.0 COMMITTEE RECORDS

3.1 Minutes of Meetings

Committee 3 held two meetings. The opening meeting was on December 11,

1979 at the National Bureau of Standards in Building 226, Room B113. The

second and final meeting was on February 15, 1980 at Law Engineering Testing

Company, 109 Inverness Drive East, Englewood, Colorado. The minutes for

these meetings are provided in this section. Included in the minutes for the

February 15, 1980 meeting are the items which were voted on by Committee 3

and the ballot which was used to document the votes of each member.

12
Minutes of 1st Meeting

of

Technical Committee No. 3 on Foundations

for

Review and Refinement of

Tentative Seismic Provisions (ATC-3-06)

at

National Bureau of Standards

December 11, 1979

Introduction

On December 11, 1979 a meeting was held at the National Bureau of Standards

in Building 226, Room 3113 with the members of ATC Review and Refinement

Committee No. 3, Foundations. This was the opening meeting of the group

assembled for reviewing and refining Chapter 6, Soil-Structure Interaction,

and Chapter 7, Foundation Design Requirements, in the ATC report (NBS SP-510)

entitled "Tentative Provisions for the Development of Seismic Regulations

for Buildings". The topics discussed included:

1) Introduction and Orientation by NBS Secretary

2) Selection of Chairman

3) Selection of Representative to Committee 2

4) Selection of Date and Location for Next Meeting

5) Establishment of Work Plan and Preliminary Discussion

of Chapters 6 and 7

The participants in the meeting are listed in Table 1, List of Participants.

With the exception of the ATC representative, Henry Degenkolb, and the

Building Seismic Safety Council representative who had not been selected

as of December 11, 1979, all members of Committee 3 attended the opening

meeting. To aid in the review of Chapters 6 and 7, the following handouts

were provided:

13
1) List, of Members of ATC Review and Refinement Committee

No. 3 (Table. 2)

2) ATC report (NBS SP-510) entitled "Tentative Provisions for

the Development of Seismic Regulations for Buildings"

3) NBS Technical Note 1100 entitled "Analysis of Tentative

Seismic Design Provisions for Buildings"

4) Work Plan for Review and Refinement of Tentative Seismic

Provisions dated 11/27/79

5) Edward 0. Pfrang's letter to the Participants on the

Review and Refinement of Tentative Seismic Provisions dated

November 30, 1979

A summary of the meeting highlights follows.

Proceedings

General

The proceedings of the meeting will be summarized using the following

categories

:

Item A - Background Information

Item B - Work Plan

Item C - Preliminary Comments on Chapters 6 and 7

Item A: Background Information

1) Lawrence Salomone called the meeting to order, presented the agenda

for the meeting, summarized some of the milestones in the schedule, informed the members of the source documents which are available (Handouts

2 and 3), circulated the List of Committee 3 Members for review and com- ment and answered any questions.

2) Richard Simon was elected Chairman.

3) Joseph V. Tyrrell was selected to represent Committee 3 in Committee

4) The next meeting will be held in the offices of Law Engineering

Testing Company, 109 Inverness Drive East, Suite West 3, Englewood,

Colorado 80110 on February 15, 1980 at 9:00 A.M. Arrangements for the

14
meeting' will be made by James LaBastie.

5) In response to the question raised at the meeting why no BSSC representative has been selected, the writer has learned that an individual

will be selected. However, similar to other committees, circumstances

did not permit selection of a BSSC representative before the December 11,

1979 meeting.

6) Lawrence Salomone informed the members that Chapter 3 of T2T1100

(pages 20-29) summarizes the findings of the study of the ATC - 3 provisions and that Committee 3 may find Section 3.3.5, and Sections 3.1.4,

3.1.5 and 3.5 helpful.

Item B: Work Plan

1) It was agreed that Chapters 6 and 7 were difficult to read and that

not enough background information was provided. It was hoped that the

ATC representative will be able to attend the next meeting in order to

provide the necessary background information. Richard Simon will call

Henry Degenkolb, the ATC representative, to inform him of the time and

location of the next meeting.

2) The schedule will require that the equations presented in Chapter 6 be accepted. _ However, the committee will use the review time available

to see if the equations can be used.

3) Richard Simon suggested that the members read some of the other

sections in the ATC report (e.g. Chapters 1 and 2) before the next meeting to aid in their understanding of the contents of Chapters 6 and 7.

4) Richard Simon encouraged the committee to solicit comments from

their colleagues.

Item C: Preliminary Comments on Chapters 6 and 7

1) The committee discussed the need for spread footings to be interconnected by ties in Section 7.5.2. William Travis questioned the need

and thought that the economic impact of this requirement would be great.

J. LaBastie indicated that some conservatism may be necessary considering

the different levels of background and experience of the users of a standard. William Travis said the problem is that this section does not

allow the designer to demonstrate that ties between spread footings are

not necessary. William Travis will call Henry Degenkolb to ask him why

this requirement is in the ATC provisions.

2) Richard Simon pointed out the relative absence of the need to evaluate

liquefaction potential of foundation soils in the report. Liquefaction

15
does not seem to be extensively discussed. The committee agreed that

some provision may be necessary. R. Simon will draft a recommendation

regarding- the evaluation of the liquefaction potential of foundation

soils.

3) Joseph Tyrrell said that it may be necessary to add something about

site investigations.

4) The committee agreed that reference to the elastic limit in Section

7.2.2 should be changed.

5) William Travis discussed the need for requiring ties in pole-type

structures. It was concluded that it may not be necessary because of the

relative importance of the structures covered by Section 7.4.2.

Respectfully submitted.

Larry Salomone, Secretary

16
Table 1

List of Participants

Partic ipant Organization

James G. LaBastie American Society of Civil Engineers

Richard Simon Association of Soil and Foundation

Engineers

Joseph V. Tyrrell Interagency Committee on Seismic

Safety in Construction

William Travis Structural Engineers Association

of California

Lawrence A. Salomone

(Secretariat)

National Bureau of Standards

Riley Chung National Bureau of Standards

Visitor

Felix Y. Yokel

Chairman, ASCE

Committee on Foundation

and Excavation Standards

National Bureau of Standards
TABLE 2

COMMITTEE 3: Foundations

American Society of Civil Engineers

Mr. James G. LaBastie

6252 Powell Road

Parker, Colorado 80134

Phone: 303-771-8641

Association of Soil and Foundation Engineers

Mr. Richard Simon (Chairman)

Goldberg, Zoino, Dunnicliff & Assoc. , Inc.

30 Tower Road

Newton Upper Falls, Massachusetts 02164

Phone: 617-969-0050

Interagency Committee on Seismic Safety in Construction

Mr. Joseph V. Tyrrell

Director, Civil/ St rue. Div.

Naval Facilities Engineering Comnd.

200 Stovall Street

Alexandria, VA 22332

Phone: 202-325-0064

Structural Engineers Association of California

Mr. William Travis

7851 Mission Center Court

Suite 250

San Diego, California 92108

Phone: 714-291-2800

Applied Technology Council

Mr. Henry Degenkolb

H. J. Degenkolb & Associates

350 Sansome Street

San Francisco, CA 94104

Building Seismic Safety Council

18
Committee 3 (continued)

National Bureau of Standards

Mr. Larry Salomone

Secretariat

Committee 3, Foundations

National Bureau of Standards

Rm. B168, Bldg. 226

Washington, D. C. 20234

Phone: 301-921-3128

(Dr. Riley Chung)

Phone: 301-921-2137

(Dr. Felix Yokel)

Phone: 301-921-2648

301-921-2647

19
Minutes of 2nd Meeting

of

Technical Committee No. 3 on Foundations

for

Review and Refinement

of Tentative Seismic

Provisions (ATC-3-06)

at

Law Engineering Testing

Company

February 15, 1980

Introduction

On February 15, 1980, a meeting was held at Law Engineering Testing

Company, 109 Inverness Drive East, Englewood, Colorado. This was the

second meeting of the group assembled for reviewing and refining Chapter 6,

Soil-Structure Interaction, and Chapter 7, Foundation Design Requirements,

in the ATC Report (NBS SP-510) entitled "Tentative Provisions for the

Development of Seismic Regulations for Buildings." The meeting served as

a workshop to discuss comments received by February 15, 1980 on Chapter 6

and 7 and to develop recommendations for revising these chapters. The

participants in the meeting are listed in Table 1, List of Participants.

A numerical listing of the sections in which comments were received was prepared by Richard Simon, Chairman of Technical Committee No. 3 and

provided to the committee members (Table 2) . At the beginning of the

workshop the secretary of Technical Committee 3, Lawrence Salomone,

distributed comments from the Concrete Reinforcing Steel Institute and

Professor V. V. Bertero of the University of California, Berkeley. These

comments were sent to Committee 4 and were not received by Committee 3 until just prior to the workshop. Joseph V. Tyrrell, representative of

Committee 3 in Committee 2, distributed the comments sent to Committee 2.

Proceedings

The workshop was conducted in the following manner:

1) Each of the comments received (Table 2) were discussed and a final position of the committee developed. The final position consisted

of a recommendation for change for the Section in question or a recommendation that the Section not be modified.

2) Following development of the final position of the committee a vote was taken.

20
The meeting highlights were:

la Section 3.2.1 Paragraph 4

Author of Comment - Joseph V. Tyrrell, Interagency Committee on Seismic Safety in Construction.

lb Excerpt from ATC 3-06

"In location where the soil properties are not known in sufficient

detail to determine the soil profile type or where the profile does

not fit any of the three types. Soil Profile S^ should be used."

lc Comment

Soil Profile Type S is much better than Type S^. This section

suggests soil profile Type S^ when the soil properties are not

known. This does not seem logical.

Id Discussion

The discussion centered around Figure Cl-13 , Normalized Lateral

Design Force Coefficients (A =A =1.0) and the effect of soil type

on the normalized design coefficient.

le Recommendation

The last paragraph in Section 3.2.1 should be changed to read

"In locations where the soil properties are not known in sufficient

detail to determine the soil profile type or where the profile does

not fit any of the three types. Soil Profile S^ or Soil Profile S,, shall be used depending on whichever soil profile type results in

the higher value of seismic coefficient C , as determined in

Section 4.2.1.

If Ballot - The recommendation for change was voted on and

unanimously accepted by the members of Committee 3.

2a Section 3.2.1 Paragraph 1 "...stable deposits of sands, gravels

or stiff clays."

Author of Comment - Richard M. Simon, Association of Soil and

Foundation Engineers

2b Excerpt from ATC 3-06

"Stiff soil conditions where the soil depth is less than 200 feet

and the soil types overlying rock are stable deposits of sands,

gravels, or stiff clays."

2c Comment

The use of the word "stable" was questioned.
2d Discussion - The group discussed the appropriateness of the use

of the word "stable". J. LaBastie, American Society of Civil

Engineers, stated that he had no problem with the term stable.

The committee agreed and no change was recommended.

3a Section 7.1 , Paragraph 1

Author of Comment - Joseph V. Tyrrell, Interagency Committee

on Seismic Safety in Construction.

3b Excerpt from ATC 3-06

"These include, but are not limited to provisions for the extent

of investigation, fills, slope stability, bearing and lateral

soil pressures, reports, drainage, settlement control, and pile

requirements and capacities."

3c Comment :

The word "reports" here does not read right. Suggest the last

sentence be changed to: "... These include ... fills, slope

stability, bearing capacity, lateral soil pressure and support,

drainage and settlement control, and pile requirement and

capacities .

3d Discussion

The committee referred to the commentary on page 403 of the

ATC 3-06 document in which Section 7.1 is discussed. The

committee felt that this section is discussed in the commentary

and the proposed change would not add anything.

3e Recommendation

J. Tyrrell suggested dropping the comment and the committee

agreed to J. Tyrrell's recommendation.

4a Section 7.22 , Paragraph 1

Authors of Comments - Joseph V. Tyrrell and Richard M. Simon

4b Excerpt from ATC 3-06

"... the soil capacities must be. sufficient to provide

resistance at the elastic limit or less ...."

22
4c Comment (Joseph V. Tyrrell)

This section is not clear as the elastic limit of the soil is

generally difficult to define. Furthermore, the soil bearing

capacity is developed from the plastic equilibrium concept.

Thus, to use the elastic limit to restrain the capacities of

the soil resistance is not reasonable. This needs clarification.

Comment (Richard M. Simon)

The last sentence of this paragraph states ...Soil capacities

must be sufficient to provide resistance at the elastic limit or less considering both the short time of loading and the dynamic

properties of the soil." Soils are inherently inelastic materials

and to specify stressing below the elastic limit is practically

without meaning. The term "elastic limit" should be replaced

with a term such as peak shear strength, yield limit, or other

which has a more significant meaning for soils. Because elastic

has so little meaning for soils, it is not possible to know what

the author of this section had in mind when writing this sentence.

4d Discussion

The committee discussed the fact that "elastic limit" was not

the correct term to use and discussed alternate terminology for

elastic limit.

4e Recommendation

The last sentence in Section 7.2.2 should read "For the load

combination including earthquake as specified in Sec. 3.7, the

soil capacities must be sufficient to resist loads at acceptable

strains considering both the short time of loading and the

dynamic properties of the soil.

4f Ballot

The recommendation for change was voted on and unanimously

accepted by the members of Committee 3.

5a Section 7.4.2

Author of Comment - Wm. Travis, Structural Engineers Association

of California.

5b Excerpt from ATC 3-06

Construction employing posts or poles as columns embedded in

earth or embedded in concrete footings in the earth may be used

to resist both axial and lateral loads. The depth of embedment

required for posts or poles to resist seismic loads shall be

determined by means of the design criteria established in the

foundation investigation report.

23
5c Comment

No formal comment was proposed.

5d Discussion

William Travis discussed the need for requiring ties in pole-type

structures. Henry Degenkolb mentioned that in San Francisco

ties are required in Class C and D structures. However, it was

also stated that pole-type structures were used only for

agriculture purposes.

5e Recommendation

William Travis suggested dropping the comment and the committee

agreed to his recommendation.

6a Section 7.4.3 , Paragraph 1

Author of Comment Richard M. Simon

6b Excerpt from ATC 3-06

Individual pile caps, drilled piers, or caissons shall be interconnected by ties. All ties shall be capable of carrying, in

tension or compression, a force equal to A / 4 of the larger pile

cap or column load unless it can be demonstrated equivalent

restraint can be provided by other approved means.

6c Comment

In my opinion, it is overly conservative to require structural

ties between pile caps equal to 25% of the maximum vertical load

for a Category B structure. This conservatism is amplified in

the commentary of this paragraph where it states, "Lateral soil

pressure on pile caps is not a recommended method; and if the

soil is soft enough to require ties, little reliance can be

placed on soft-soil passive pressure to restrain relative displacement under dynamic conditions." There are many cases in

which the use of piles is dictated by deep soil deposits and the near surface materials are relatively stiff and strong (such as compact or dense gravels and sands overlying soft clays or con- trolled, compacted fill over clays or organic soils. In these

cases, it would seem reasonable to permit at least a portion of

the lateral tie resistance between the pile caps to be provided

by lateral soil resistance with some guidance provided. In

light of these considerations, the following changes in the

tentative provisions and commentary are suggested:

a) Section 7.4.3 — Sentence 2

A /4 should be changed to A /6. v ° v

24
b) Section 7.5.2

"Individual pile caps, drilled piers, caissons or spread

footings shall be interconnected by ties. All ties shall

be capable of carrying by tension or compression A^/4 of the

larger footing or column load unless it can be demonstrated

that equivalent restraint can be provided by other approved

means

.

c) Commentary — Section 7.4.3 Paragraph 3

In my opinion it is overly conservative to preclude the use

of lateral soil pressure on pile caps and spread footings from

consideration in tying of foundation elements in all cases. The

alternative paragraph below is a suggested replacement for the

paragraph provided in the Commentary:

1. Alternative methods of tying foundation together are permitted,

such as use of properly reinforced floor slab that can take

both tension and compression. Lateral soil pressure on pile

caps is not a recommended method if the pile caps are embedded

in soft soil because the motion is transmitted from soil to

structure (not inversely, as is commonly assumed) ; if the soil

is soft enough to require ties, little reliance can be placed

on soft-soil passive pressure to restrain relative displacement

under dynamic conditions. However, if pile caps or caissons

are embedded in stiff soil such as medium dense to dense sand or sand and gravel or stiff to hard clay, and backfill sur- rounding the pile caps or caissons is systematically compacted

to a minimum of 95% of the modified Procter density, lateral

soil pressure may be used to provide 100% of the required

lateral force for category B structures. No contribution to

the lateral force on the pile cap may be provided by shear

stresses on the base of the pile cap because underlying soils

may settle the soil from beneath this pile cap leaving a gap.

For category C or D structures, lateral soil pressure may be

used to provide up to 50% of the lateral force required for

foundation ties. For category C or D structures on spread

footings, the lateral forces may be used to provide up to 50%

of the total required tie force and both lateral pressure on sides of footings as well as shear stresses on the base of

footings may be considered to provide the necessary force.

6d Discussion

Richard Simon said that one should be able to take advantage of

the compacted backfill. William Travis said that piles should be

tied together. The committee discussed using the term "rock" in

Section 7.4.3 (material with a shear wave velocity of 2500 fps)

6e Recommendation

The committee decided not to modify Section 7.4.3.

25
7a Section 7.5.2 , Paragraph 1

Author of Comment Richard M. Simon

7b Excerpt from ATC 3-06

Individual spread footings shall be interconnected by ties. All

ties shall be capable of carrying, in tension or compression, a force equal to A /4 of the larger footing or column load unless

it can be demonstrated that equivalent restraint can be provided

by other means.

7c Comment

See Item 6c.

7d Discussion

The committee discussed terminology that would be appropriate.

7e Recommendation

The first sentence in Section 7.5.2 should be changed to read

"Individual spread footings unless founded directly on rock , as defined in Section 3.2.1 (1)

,

shall be interconnected by ties."

7f Ballot

The recommendation for change was voted on and unanimously

accepted by the members of Committee 3.

8a Section 7.4.4, Item A, Uncased Concrete Piles

Author of Comment Joseph V. Tyrrell

8b Excerpt from ATC 3-06

(A) UNCASED CONCRETE PILES

Reinforcing steel shall be provided in the top portion of

uncased cast- in-place concrete piles or caissons for a distance of ten pile diameters, with a minimum steel ratio of

0.0025 with a minimum of four No. 5 bars. Ties (or equivalent spirals) shall be provided at 16-bar diameter spacing

(maximum spacing) with a maximum spacing of 4 inches in the

top 2 feet.

8c Comment

The pile diameters generally range from 12 inch to 16 inch, but

caisson shaft diameters are generally 24 inch to 30 inch minimum.

The ten pile diameter reinforcement requirement for caisson would

26
be excessive. I believe the word 'fcaisson" here means drilled

piers or drilled caissons.

8d Discussion

J. Tyrrell thought a minimum steel ratio of .0025 was too high.

The committee then discussed the need for steel and the amount

of steel required in caissons. J. LaBastie said he never saw

caissons without steel. William Travis pointed out that steel

may be needed since stresses due to concrete shrinkage and tests

have shown the steel is necessary. J. Tyrrell concluded the

discussion by saying that he did not have strong feelings about

his comment.

8e Recommendation

The committee decided not to modify Section 7.4.4, Item A.

9a Section 7.4.4 , Item E, Paragraph 1

Author of Comment - David A. Sheppard, Prestressed Concrete Institute

9b Excerpt from ATC 3-06

(E) PRECAST-PRESTRESSED PILES.

The upper 2 feet of the pile shall have No. 3 ties minimum at

not over 4-inch spacing, or equivalent spirals. The pile cap

connection may be by means of dowels as required in Sec. 7.4.4(C).

9c Comment

Revise Section 7.4.4(E) to read as follows: The upper 2 feet . .

. . or equivalent spirals. The pile cap connection may be made

by developing exposed strand or by the use of field placed anchor

dowels grouted into sleeves cast in the pile top as outlined in

Section 11.9.

BASIS: Present accepted practice in UBC-79 and CAL-TRANS

specifications

9d Discussion

H. Degenkolb showed pictures of how piles shattered at the top

during the 1971 San Fernando Earthquake. Precast prestressed

piles performed poorly.

The committee discussed possible designs for the connection at

the top of the pile. It was agreed that the intent was to put

the ductile section where the hinge would form. Considering

this fact and the comment from David Sheppard, PCI, a recommendation for changes was prepared. When addressing Sheppard's

comment the committee did not accept the use of an exposed strand.

27
9e Recommendation

At the end of paragraph 2 of Section 7.4.4 (before Item A) the

following sentence should be added, "Where special reinforcement at

the top of the pile is required alternative measures for containing

concrete and maintaining ductility will be permitted provided

due consideration is given to forcing the hinge to occur in the

contained section."

9f Ballot

The committee unanimously rejected the comment made by the

Prestressed Concrete Institute. The recommendation for change was voted on and unanimously accepted by the members of Committee 3.

10a Section 7.5.3 (C) Paragraph 1

Authors of Comments - David A. Sheppard, PCI and Joseph G. Manning,

Concrete Reinforcing Steel Institute

10b Excerpt from ATC 3-06

(C) PRECAST CONCRETE PILES.

Ties in precast concrete piles shall conform to the requirements of Sec. 11.6.2 for the top half of the pile. Precast

concrete piles shall not be used to resist flexure caused by

earthquake motions unless it can be shown that they will be

stressed to below the elastic limit under the maximum soil

deformations that would occur during an earthquake.

10c Comment (D. Sheppard, PCI)

Revise the last sentence of Section 7.5.3(c) to read as follows:

"Precast concrete and prestressed concrete piling shall be designed

to withstand maximum imposed curvatures resulting from a dynamic

analysis of the soil profile present, with detailing as specified

in Section 11.9."

BASIS: See my letter and accompanying documentation from

Gerwick, et al presented at the BSSC meeting on November 8, 1979.

Comment (Joseph G. Manning, CRSI)

Revise second sentence to read as follows:

Precast concrete and prestressed precast concrete piling

shall be designed to withstand maximum imposed curvatures

resulting from the maximum soil deformations that would

occur during an earthquake.

Reason: Prestressed precast concrete piling can withstand con- siderable curvature and through proper detailing confinement and

ductility can be provided.

28
lOd Discussion

The committee discussed the validity of D. Sheppard’s comment

and agreed that it should be accepted. The committee also con- sidered the comment from Joseph G. Manning, Concrete Reinforcing

Steel Institute, and decided the comment was similar to

D. Sheppard's comment.

lOe Re commendat ion

The last sentence in Section 7.5.3(c) should be revised to read,

"Precast concrete and prestressed concrete piling shall be

designed to withstand maximum imposed curvatures resulting from

a dynamic analysis of the soil profile.

lOf Ballot

The recommendation for change was voted on and unanimously accepted

by the members of Committee 3.

11a Section 7.6.1, Paragraph 1

Authors of Comments - David A. Sheppard, PCI, and Joseph G. Manning,

CRSI

lib Excerpt from ATC 3-06

Sec. 7.6.1 SPECIAL PILE LIMITATIONS

Precast-prestressed piles shall not be used to resist flexure

caused by earthquake motions.

11c Comment (David A. Sheppard)

Sec. 7.6.1

Revise this section to read as follows: "All piling types in

Category D shall be designed to withstand maximum imposed curvatures resulting from a dynamic response analysis of the soil

profile present."

BASIS: Same as 7.5.3 above. Foundation requirements should be

performance oriented, and not arbitrarily penalize certain

materials (prestressed concrete) because of local bias, in spite

of recent tests and successful design applications developing

large curvatures resulting from layered soil movements in maximum

credible seismic conditions.

Comment (Joseph G. Manning)

Section 7.6.1 Special Pile Limitations

Delete this section.

Reason: See comments on Section 7.5.3.

29
lid Discussion

The committee considered the comments that were received, but decided

that additional conservatism was required for Category D structures.

Therefore, Section 7.6.1 should not be modified.

lie Recommendation

The committee recommended not to change or delete Section 7.6.1

12a Chapter 6

Author of Comment - Richard M. Simon and William M. Travis

12b Excerpt from ATC 3-06

Refer to pages 65-71 in ATC 3-06 report.

12c Comment (Richard M. Simon)

1. Chapter 6 —SOIL- STRUCTURE INTERACTION

Chapter 6 contains some relatively complex equations for

adjustment of the equivalent lateral force and modal analysis

procedures for evaluation of earthquake induced forces.

It may be inappropriate to include these soil structure

interaction (SSI) equations in the tentative provisions

document at this time for the following reasons:

a) Both the equivalent lateral force and modal analysis

procedures are approximate in themselves. There have

been few prototype observations to explore the accuracy

of either procedure. The equations contained in

Chapter 6 are based solely on analytical studies with

almost no prototype or even laboratory verification.

Because of the approximate nature of the entire analysis

procedures it is, in my opinion, inappropriate to add an additional level of sophistication to the equations. The

SSI equations are so complex as to make me question

whether they could be properly applied by the average

structural/civil engineer. There are no guidelines

provided in the provisions or commentary as to the approximate magnitude of the effect produced by these equations

other than the reduced base shear shall in no case be

taken less than 0.7 times the rigid support base shear.

Little guidance is provided in the readily available

published literature. Although failure to incorporate

the effects of SSI is in almost all cases a conservative

assumption, it is not clear that applying the equations

without complete understanding and with potential errors will lead to conservative design forces and displacements.

30
b) The Tentative Provisions have emphasized the inelastic

behavior of structures in response to earthquake loading.

The analytical procedures used as the basis of the

Chapter 6 provisions assume a linear response for the

superstructure which is inconsistent with the general

philosophy of the Tentative Provisions.

c) It may be inconsistent with the charges of this committee

to expurgate the entire chapter of the provisions at this

review stage, however, as a minimum, it is recommended

that the trial designs be carried through both with and

without use of the SSI equations so that an evaluation of

the effect of these equations on the final design may be

determined. If the effect of the SSI equations is shown

by trial designs to be of little significance, it may be

proper to omit the entire section at that time.

2 . Section 6.1 — General

Inasmuch as the SSI equations require the expenditures significant additional design effort with questionable return in terms

of design savings, Section 6.1 does not contain a clear enough

statement that they may be conservatively ignored. To clarify

this idea, it is recommended that the following sentence be

impended to the end of paragraph 1 of the section: It is

acceptable to evaluate the design earthquake forces and corresponding displacement of the building using only the equations

contained in chapters 4 and 5.

Comment (William L. Travis)

See letter from William L. Travis to Lawrence A. Salomone

dated 2/20/80 (attached).

12d Discussion

R. Simon opened the discussion by outlining three approaches with

respect to Chapter 6:

1) Do not change Chapter 6

2) Omit Chapter 6

3) Do trial designs both ways

I In addition, H. Degenkolb presented the background on Chapter 6. He

said the section is theoretical.

! Simon then said that this section lowers coefficient and hardware

to resist earthquakes. William Travis followed by presenting the

need for having a practical feel for what the structure is doing.

He showed the complexity of the procedure in Section 6.0 (see

Travis's letter dated February 20, 1980). The theoretical approach

results in losing sight of what actually is happening. William Travis

31
said he thought Chapter 6 should be cleaned up and it should be

modeled after UBC. He thought that an error could be made using

Chapter 6 and the designer would not know it. Chapter 6 is too

complicated for the practicing engineer and it is not justified.

J. Tyrrell said his people ran through the Chapter 6 procedure and

he supported William Travis’s comments. It was pointed out that

John Christian of Stone & Webster said that the procedure was

sound. However, William Travis said he did not agree. J. La Bastie

explained that John Christian's experience is mainly in soils and

nuclear power plants.

After these comments were expressed the committee discussed what

course of action could be taken. It was pointed out that in the

beginning of the ATC 3-06 report it was said that Chapter 6 could

be ignored (it stands alone). Therefore, the impact of eliminating

or modifying Chapter 6 would be minimal. Furthermore, page 4 of

the guidelines given to committee members states that the effectiveness of a section can be questioned. The committee felt that soil

conditions were considered by S factors. Consequently, they

formulated and agreed to the position stated below.

12e Recommendation

After reviewing Chapter 6 and thoroughly examining the procedures

therein, the committee feels strongly that the provisions are not

effective in implementing a new concept. Chapter 6 is too complicated

for the practicing engineer and it is not justified based on field

observations. The sophistication of the analysis is inconsistent

with the accuracy of the results and the complexity masks the understanding of the performance of the soil structure system. Consequently,

the committee recommends deleting Chapter 6 from the tentative

provisions

.

With the completion of the discussion of Chapter 6 the meeting was

adjourned. It was agreed that:

1) A draft of the minutes will be distributed for review and

comment by the committee members.

2) William Travis will send the required backup for elimination

of Chapter 6 within 3 weeks of the date of the meeting.

3) Committee members will send letters documenting their vote

regarding the items discussed. (Please use the enclosed form

for this documentation)

.

4) There is no need to send out a ballot for the items discussed

except for Chapter 6.

5) Any future discussions that were required would be performed by

a telephone conference call.
TABLE 1

Meeting 2/15/80

List of Attendees

Participant

Lawrence Salomone

William L. Travis

Henry J. Degenkolb

J. G. LaBastie

J. V. Tyrrell (IACSSC)

Richard M. Simon

Affiliation

NBS

SEAOC

ATC 3-06

ASCE

Naval Fac. , Eng. Com.

ASFE

33
TABLE 2

Numerical List of Sections

Prepared by Richard Simon

Prior to February 15, 1980 Meeting

1 § 3.2.1 a. Default S^ Tyrrell

b. "Stable" deposits

of S & G

Simon

2 Cpt 6 a. As is Simon

b. Omit

c. Trial designs

both ways

3 § 7.1 "reports" Tyrrell

4 § 7.2.2 "elastic limit" Tyrrell

5 § 7.4.2 Pole structures Travis

6 § 7.4.3 Foundation ties Simon

7 § 7.44 Exposed strand PCI

8 § 7.53 "withstand curvature"

elastic limit

PCI

9 § 7.6.1 PCC piles

Simon

34
REVIEW AND REFINEMENT OF TENTATIVE SEISMIC PROVISIONS (ATC 3-06)

COMMITTEE 3 BALLOT

Pg 1 of 2

Committee 3 on Foundations Issue Date 3/10/80

Deadline for Receipt 4/1/80

Information and Instructions

1. The return of this ballot is required from voting members of Committee 3.

2. When voting affirmative with reservations (Column 4) or negative (Column 3) the member can provide an explanation in the remarks column (Column 5).

3. The member should refer to the minutes for the February 15, 1980 meeting

for a detailed description of the item listed in Column 1.

Signature Date

Return ballot to Lawrence A. Salomone

Technical Committee No. 3 Tentative Seismic Provisions Project

B168, Bldg. 226

National Bureau of Standards

Washington, D. C. 20234

Section No. - Item No. (see minutes from

2/15/80 mtg.)

Affirmative Negative Affirmative

with

Reservations

Remarks

(Check box and

use Pg 2)

Section 3.2.1 - Item le

Section 3.2.1 - Item 2d

Section 7.1 - Item 3e

Section 7.2.2 - Item 4e

Section 7.4.2 - Item 5e

Section 7.4.3 - Item 6e

• j Section 7.5.2 - Item 7e [ Section 7.4.4(A) - Item 8e

Section 7.4.4(E) - Item 9e

Section 7.5.3(C) - Item lOe

Section 7.6.1 - Item lie i

1 Chapter 6 - Item 12e

«

35
Review and Refinement

of Tentative Seismic Provisions (ATC 3-06)

Committee 3 Ballot

Pg 2 of 2

Section No. - Item No. Remarks

36
TRAVIS, VERDUGO & ASSOCIATES

February 20, 1980

Mr. Lawrence A. Salomone

Secretary Committee 3

National Bureau of Standards

Room B168, Bldg. 226

Washington, D.C. 20234

Subject: Comments on Chapter 6, ATC-3

Dear Larry:

As agreed, I have put together some background material for our position

as formulated in Denver, February 15, 1980.

Hopefully this will reach you soon enough to distribute with the minutes.

Let me know if I can do anything else at this time.

Very truly yours,

TRAVIS, VERDUGO & ASSOCIATES

William L. Travis

President

WLT : cdp

Enclosures

STRUCTURAL CONSULTANTS

7851 MISSION CENTER COURT, SUITE 250

SAN DIEGO. CALIFORNIA 92108

PHONE (714) 291-2800 37
COMMENTS ON CHAPTER 6, ATC-3

A. While trying to find out how a young practicing engineer might apply

Chapter 6, I tried to analyse the steps he would go through. By the

32nd step I was so confused that I forgot what I was trying to find out!

Also gone was any feel that I might have had for the effect of the various

formulae. (Refer to handwritten notes.)

3. A comparision seemed in order to the relatively simple UBC Chapter 23.

The same material is adequately covered on what amounts to less than

4 pages (copies of pages 132-136 from 1976 UBC) .

C. A recent publication by Mr. Roy Becker refers to work by Mr. Edward

Teal who, while noting that the formula for building period, T=0.10N

is inadequate for buildings less than say 40 stories in height and that

the Rayleigh Formula should be used suggests that the Rayleigh Formula

is impractical to use. Instead, he proposes a simplified version and notes

that the SEAOC recommends only two-thirds of the completely arbitrary

0.5% drift limitation for initial building period calculations. A few of these

pages are attached. Note that after these simplifications and approximations

with assumed S-values and so on, the SEAOC recommends a further limita- ; tion of T.

D. As stated by Mr. Richard Simon, Chairman of the technical committee,

the "additional level of sophistication" added to the equations is inappropriate when considering the approximate nature of the .entire analysis

procedure, at least at this time. Those portions of his comments are attached, with an "AMEN" from Mr. Henry Degenkolb.

I 38
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SSSf^/JiSSSSKSiWSSsSS®?*
o

SECTION II: DUCTILE MOMENT FRAME DESIGN*

A.) EAST-WEST SEISMIC FORCES:

V = ZIKCSW 1976 UBC Formula (12-1)

Z = 1.00 for Zone No. 4

I = 1.00 per UBC Table No. 23-K

K = 0.67 per UBC Table No. 23-1

V = (1.00) (1.00) (0.67) (CSW) = 0.67CSW

In order to determine C, the period T may be taken as:

(T = 0.10N = 0.10(7) = 0.70 sec\ (12-3B)

However, use of this formula often results in a poor estimate of the

period for a moment-resisting frame building. As stated by Mr. Eduard

Teal in the AISC Engineering Journal, Fourth Quarter, 1975, "this

formula yields reasonable period estimates for buildings in the 40-

story range, but very poor estimates for short buildings." Therefore,

Formula (12-3), sometimes known as Rayleigh's Formula, should be used

rather than Formula (12-3B) for determining the period.

T = 2m

n-f

X> + Fn

)S n

jL- I (12-3)

For an initial approximation of the building period. Formula (12-3) is impractical to use. However, there is a convenient formula which can bi utilized for a good initial approximation without having to do any tria! and error design. It is known as Teal's Method or Formula which is givi

by Edward Teal in the AISC Engineering Journals, Second and Fourth Quart

1975. This formula very closely approximates the actual building perioi

and is really a simplified version of Formula (12-3)

i ^ T = 0.25 /A /Ci

where

T = Period of building, sec.

A = Lateral deflection at top of building, in.

C ]_ = Lateral force coefficient by which the total weight of the

building is multiplied in order to obtain the seismic lateral

force due to the building's response to a given base motion.

Drift limitations usually control the design of a moment frame and UBC

Sect. 2312(h) limits the drift to 0.5%.

* In lieu of a ductile moment frame, this building could utilize a momen frame not meeting the special ductility requirements. See Section IU

for design of this type of framing system, especially Section III A, "Comparison of Moment Frame with Ductile Moment Frame."
The SEAOC Commentary recommends that for an initial approximation for

this building period, that two-thirds of the allowable drift be used.

This factor of two-thirds is used to account for the fact that the

maximum drift limits are seldom met over the building's height. (In

general, this recommended factor of two-thirds is too small for a steel

moment frame unless wind loading criteria governs the design.)

Therefore,

a = (0.67)(.005)H = (0.67) (.005) (83.0 x 12) = 3.34 in.

Use 4 = 3.4 in.

As related to the UBC:

Ci = ZICS = (1.0) (1.0) (CS) * CS

Note that the factor K is omitted from the above equation, since it is

a factor assigned to a type of construction in recognition of its inherent

resistance to earthquakes and, therefore, is not directly related to stiffness and drift.

Substituting, T = 0.25 /3.4/CS

Since both C and S are rather complex functions of T, the solution to this

equation might be by trial and error. However, a more direct solution can

be achieved by assuming a value for S, which has a rather narrow range of

values: 1.0 < S < 1.5. Assume S = 1.30.

%

C = 1 -

15

( 12- 2 )

Substituting into Teal’s formula.

T = 0.2 = 0.25 V T1/2 = 1.57T1/4

45
o o

Checking the assumed value of S:

T_ = 1.82 =1.82 > 1.0

Ts 1.00

S = 1.2 +

= 1.2 +

Therefore, T =

0.6 (1.82) - 0.3 (1.82)

1.82 sec. is valid.

(12-4A)

1.30 = assumed S

However, as stated in the SEAOC Commentary, "the Committee feels that the

period determination of frame structures should be thoroughly examined if a final period greater than T = 0.5 N

2//3 is calculated." "Thoroughly

examined" probably implies that the following be taken into account: P-A effects, participation of non-moment frames, composite action between

girders and floor slab, etc. In order to avoid taking these difficult to determine items into account, the period of the building will be limited

by this recommendation.

T = 0.5 N

2 / 3

= (0.5) (7.0) 2/3 = 1.83 sec.

This is approximately the same period obtained by using two- thirds of the

allowable drift.

Hence, for design purposes,

T ,

. = 1 . 8 sec

design

C = 15 /T 15/178

= 0.050

S = 1.2 + 0 . 6f X_\ - 0.3%)

1 - 2 + 0 - 6

( iif )- 0 - 3

(r!)

2 - 1 - 31

Substituting into Formula (12-1)

,

( 12 - 2 )

(12-4A)

V = ZIKCSW

= (1.0) (1.0) (0.67) (.050) (1.31)W

V = .044 W

46
u Q

W

fl = (122.5 x 77.5) (.085) + (400 x 11.5) (.015) = 874 kips

W . = (122.5 x 77.5) (.067) + (400 x 8.75) (.015) = 687 kips n•

W = 6(874) + 687 = 5930 kips (total dead load)

V = 0.044W = (.044) (5930) = 260 kips (total lateral force)

The total lateral force is distributed over the height of the building in

accordance with UBC Formulas (12-5) , (12-6) and (12-7). See Fig. 4.2.

R

-f F t

EARTHQUAKE

FORCES F x AT

EACH LEVEL

Figure 4.2 Distribution of earthquake

forces over height of building .

n v = h + SF

i

i-l

F

t = 0.07TV = .07(1.8) (260) = 33 kips

(V - F t )vx

hx

227 vx

hx

(12-5)

( 12-6 )

(12-7)

Vw.h . V* w .h

Z 1Z 1

The distribution of lateral forces over the height of the building is shown

in Table 4-1.

\

47
FROM: Richard M. Simon, Go! dberg-Zoi no & Associates, Inc.

a) Both the equivalent lateral force and modal analysis procedures are approximate in themselves. There have been few prototype observations

to explore the accuracy of either procedure. The equations contained

in Chapter 6 are based solely on analytical studies with almost no prototype or even laboratory verification. Because of the approximate

nature of the entire analysis procedures it is, in my opinion, inappropriate to add an additional level of sophistication to the equations.

The SSI equations are so complex as to make me question whether they

could be properly applied by the average s tructura 1 /c i vi 1 engineer.

There are no guidelines provided in the provisions or commentary

as to the approximate magnitude of the effect produced by these

equations other than the reduced base shear shall in no case be taken

less than 0.7 times the rigid support base shear. Little guidance is

provided in the readily available published literature. Although

failure to incorporate the effects of SSI is in almost all cases a conservative assumption, it is not clear that applying the equations

without complete understanding and with potential errors will lead to

conservative design forces and displacements.

b) The Tentative Provisions have emphasized the inelastic behavior of

structures in response to earthquake loading. The analytical procedures

used as the basis of the Chapter 6 provisions assume a linear response

for the superstructure which is inconsistent with the general philosophy

of the Tentative Provisions.

From: Henry J. Degenkolb

1 . Chapter 6 - Soil-Structure Interaction

First, it must be understood that I was in the minority on this when it was decided to include the soil-structure interaction provisions in ATC 3-06.

However, I’m also in the spot of defending them. I do believe that in some

(many?), structures the soil-structure relationship is very important. It

is so complex, however, that little is known about it and almost everything we do know about it is from theory and not from measurements or observations - especially at the level of strains associated with earthquake motions. Even

the theory has only been advanced for certain unique cases such as mat

foundations, etc. Therefore, I cannot honestly argue with the reasons that

Simon presents under (a) or (b)

48 D
3 . 2 ROSTER

COMMITTEE 3: Foundations

American Society of Civil Engineers

Mr. James G. LaBastie

6252 Powell Road

Parker, Colorado 80134

Phone: 303-771-8641

Association of Soil and Foundation Engineers

Mr. Richard Simon (Chairman)

Goldberg, Zoino, Dunnicliff & Assoc., Inc.

30 Tower Road

Newton Upper Falls, Massachusetts 02164

Phone: 617-969-0050

Interagency Committee on Seismic Safety in Construction

Mr. Joseph V. Tyrrell

Director, Civil/Struc. Div.

Naval Facilities Engineering Comnd.

200 Stovall Street

Alexandria, VA 22332

Phone: 202-325-0064

Structural Engineers Association of California

Mr. William Travis

7851 Mission Center Court

Suite 250

San Diego, California 92108

Phone: 714-291-2800

Applied Technology Council

Mr. Henry Degenkolb

H. J. Degenkolb St Associates

350 Sansome Street

San Francisco, CA 94104

49
Committee 3 (continued)

Building Seismic Safety Council

Mr. Leroy Crandall, President

L. Leroy Crandall and Associates

711 North Alvarado Street

Los Angeles, California 90026

Phone: 213-413-3550

National Bureau of Standards

Mr. Lawrence Salomone

Secretariat

Committee 3, Foundations

National Bureau of Standards

Rm. B162 , Bldg. 226

Washington, D.C. 20234

Phone: 301-921-3128

50
NBS-1 14A (Rev. 9- 78 )

4. TITLE AND SUBTITLE

Review and Refinement of ATC 3-06 Tentative Seismic

Report of Technical Committee 3: Foundations

Provisions October 1980

SvPerformingiQrgamzatiorc Code

7. AUTHOR! S) Lawrence A. Salomone

8. Performing Organ. Report No.

9. PERFORMING ORGANIZATION NAME AND ADDRESS

NATIONAL BUREAU OF STANDARDS

DEPARTMENT OF COMMERCE

WASHINGTON, DC 20234

10. Project/Task/Work Unit No.

11. Contract/Grant No.

12. SPONSORING ORGANIZATION NAME AND COMPLETE ADDRESS (Street, City, state. ZIP)

Federal Emergency Management Agency

Washington, DC 20472

13. Type of Report & Period Covered Final

14. Sponsonng Agency Code

15. SUPPLEMENTARY NOTES

|

I Document describes a computer program; SF-185, FIPS Software Summary, is attached.

16. ABSTRACT (A 200-word or leas tactual summary of most significant information . If document includes a significant bibliography or

literature survey, mention it here.) The Tentative Provisions for the Development of Seismic Regulations for Buildings were

developed by the Applied Technology Council to present, in one comprehensive document,

current state-of-knowledge pertaining to seismic engineering of buildings. The Tentative Provisions are in the process of being assessed by the building community.

This report is one of a series of reports that documents the deliberations of a group

of professionals jointly selected by the Building Seismic Safety Council and the

National Bureau of Standards and charged with reviewing the Tentative Provisions prior

to conducting trial designs.

This report documents the activities of Technical Committee 3: Foundations. Other com- mittee reports are similarly available. The task of Technical Committee 3 was to review

and refine Chapter 6, Soil-Structure Interaction and Chapter 7, Foundation Design Requirements in the ATC report (NBS SP-510) entitled, "Tentative Provisions for the

Development of Seismic Regulations for Buildings." Two meetings were held. The opening

meeting of the group was on December 11, 1979, and the concluding meeting was on February 5, 1980. The minutes of these meetings and the findings /recommendations of

Technical Committee 3 are presented in this report. These recommendations were made to

the parent group, the Joint Committee on Review and Refinement, and their action on these recommendations is documented in a companion report.

17. KEY WORDS (s ix to twelve entries; alphabetical order; capitalize only the first letter of the first key word unless a proper name;

separated by semicolons)

Buildings; design; earthquakes; engineering; foundations; professional practice;

provisions; soil-structure interaction; standards

18. AVAILABILITY XXXUn limited

I | For Official Distribution. Do Not Release to NTIS

! Order From Sup. of Doc., U.S. Government Printing Office, Washington, DC

20402, SD Stock No. SN003-003-

j~xi Order From National Technical Information Service (NTIS), Springfield,

VA. 22161

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(THIS REPORT)

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