FeDERALEMERGENCY MANAGEMENTAGENCY FEMA --- / "Myl'-i

Repair of

Earthquake Damaged

Concreteaand, Masonry Wall

Biuildings

FEDERALEMERGENCY MANA.GEMENTAGENCY FFMA30n8/MaV199
FEMA 308

REPAIR OF EARTHQUAKE DAMAGED

CONCRETE AND MASONRY WALL BUILDINGS

Prepared by:

L\TC

The Applied Technology Council

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

I .. - I ~"2 I 
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 H. Johnson

Edwin T. Dean, Vice President Kenneth A. Luttrell

Andrew T. Merovich, Secretary/ Newland J. Malmquist

Treasurer Stephen H. Pelham

C. Mark Saunders, Past President Richard J. Phillips

James R. Cagley Charles W. Roeder

Arthur N. L. Chiu Jonathan G. Shipp

Robert G. Dean

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, orrecommendations 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.
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

FEMA306report,Evaluationof EarthquakeDamaged

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,

Evaluationof EarthquakeDamagedConcreteand

Masonry Wall Buildings, TechnicalResources, 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 WallBuildings,

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

FEMA 308 Repair of Earthquake Damaged Concrete and Masonry Wall Buildings Hii
Table of Contents

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

List of Figures ..... .. ....... .......... .. . . vii

List of Tables ................. vii

List of Repair Guides ................. ix

Prologue.................................. o .. ... ....... ... ... ... .. xi

1. Introduction .

1.1 Purpose .

1.2 Scope ...............................

1.3 Basis.

1.4 Document Overview .

1.5 Limitations.

2. Background.

2.1 Introduction .........................

2.2 Experience in Recent Past Earthquakes

2.3 Basic Policy Considerations .............

2.4 Technical Impediments ................

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3. Performance-Based Policy Framework.

3.1 Introduction ...........................

3.2 Basic Alternatives ......................

3.3 Damage Evaluation Procedure .

3.3.1 Performance Objectives.

3.3.2 Global Displacement Parameters

3.3.3 Structural Components.

3.4 Performance Capacity and Loss .

3.5 Restoration or Upgrade Procedure .

3.6 Relative Seismic Demand .

3.7 Relative Risk .

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3.8 Thresholds for Restoration and Upgrade.

3.9 Policy Implications and Limitations of Component Acceptability and

Displacement Demand .

3.10 Public Sector Policy Planning Recommendations.

3.11 Private Policy Planning Recommendations.

3.12 Summary ...............................................

4. Implementation....................................

4.1 Introduction .....................................

4.2 Performance-Based Repair Design ...................

4.3 Repair Technologies .

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Repair of Earthquake Damaged Concrete and Masonry Wall Buildings

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FEMA 308 v
4.3.1 Categories of Repairs .......................... 21

4.3.2 Nonstructural Considerations .......................... 22

4.3.3 Repair Guides .......................... 23

Glossary .......................... 43

Symbols .......................... 45

References .......................... 47

ATC-43Project Participants . . . 49

Applied Technology Council Projects And Report Information . . . 53.

vi Repair of Earthquake Damaged Concrete and Masonry Wall Buildings FEMA 308
List of Figures

Figure 2-1 Sensitivity of displacement to changes in force ............... ..................... 8

Figure 3-1 Capacity curves from nonlinear static procedures. ............ .................... 10

Figure 3-2 Global displacement capacities, dc, for various performance levels ....... ............ 10

Figure 3-3 Global displacement demand for undamaged, damaged, and restored/upgraded

conditions................................................................ 11

Figure 3-4 Structural component force-deformation characteristics ............. ............... 11

Figure 3-5 Global displacement demands and capacities .................................... 13

Figure 3-6 Risk associated with damage acceptance, restoration, and upgrade for a specific

performance objective .13

Figure 3-7 Thresholds and performance limits for restoration and upgrade of earthquakedamaged buildings ........................................... 16

List of Tables

Table 3-1 Parameters governing whether damage is acceptable .................... . 15........

Table 3-2 Parameters governing whether restoration is acceptable ... ........... 15

Table 4-1 Summary of repair procedures ....................................... .... 22

FEMA 308 Repair of Earthquake Damaged Concrete and MasonryWall Buildings vi!
List of Repair Guides

(See Section 4.3.3)

Title Page No.

Cosmetic Patching.......................... 24

Repointing Mortar .......................... 26

Crack Injection - Epoxy.......................... 28

Crack Injection - Grout .......................... 30

Spall Repair .......................... 32

Rebar Replacement .......................... 34

Wall Replacement .......................... 36

Structural Overlay - Concrete .......................... 38

Structural Overlay - Composite Fibers .......................... 40

Crack Stitching .......................... 42

Repair of Earthquake Damaged Concrete and Masony Wall Buildings

ID

CR1

CR2

CR3/SRl

SR2

SR3

SR4

SR5

SEl

SE2

SE3

FEMA 308
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. They 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, with in-plane distortion, 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-eighth-inch crack in a wall panel on

the verge of brittle shear failure is a very serious

condition. The same size crack in a flexurallycontrolled 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.

FEMA 308 Repair of Earthquake Damaged Concrete and Masonry Wall Buildings
Prologue

* 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.

o 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

Repair of Earthquake Damaged Concrete and Masonry Wall Buildings FEMA 308
Prologue

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 306 report

(ATC, 1998a) and FEMA 307 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.

FEMA 308 Repair of Earthquake Damaged Concrete and Masonry Wall Buildings ; ~~~~~x
Introduction

1.1 Purpose

The purpose of this document is to present practical

guidance for the repair and upgrading of earthquakedamaged buildings with primary lateral-force-resisting

systems consisting of concrete bearing walls, masonry

bearing walls, or infilled frames. The guidance consists

of a policy framework for facilitating the determination

of the appropriate scope of repair or upgrading

measures. This document also includes outlines of

specific repair techniques that can address the

component damage common to these buildings. The

criteria and procedures are based on the evaluation of

the anticipated seismic performance of a subject

building at three different times: in its condition

immediately before the damaging earthquake (preevent), in its damaged condition, and in its repaired or

upgraded condition. This document may be used as a

technical resource to facilitate the settlement of

insurance claims, the development of policy and

strategy for repair, or other appropriate purposes. The

intended users of the document are design engineers,

building owners, building officials, insurance adjusters,

and government agencies.

1.2 Scope

This document is one of several to result from a

research project on the evaluation and repair of

earthquake-damaged concrete and masonry wall

buildings. Concrete and masonry wall buildings include

those with vertical-load-bearing wall panels, with and

without intermediate openings. In this document,

concrete and masonry wall buildings also include those

with vertical-load-bearing frames of concrete or steel

that incorporate masonry or concrete infill panels to

resist horizontal forces. The specific recommendations

for repair technologies developed for this project

primarily address the type of damage normally

encountered in concrete and masonry wall buildings;

however, the policy framework developed in this

document applies to buildings in general without regard

to structural system.

The guidance on policies and techniques for repair of

earthquake damage in this document addresses:

1. The parameters normally considered in decisions

on the scope of repair or upgrading for buildings

damaged by earthquakes

2. The formulation of these parameters in terms of the

anticipated seismic performance of buildings in

their pre-event, restored, and upgraded conditions

3. The process of evaluating anticipated seismic performance to decide whether to accept, restore, or

upgrade earthquake-damaged buildings

4. The development of repair strategies to meet performance goals

5. Specific repair techniques to address damaged

structural components in concrete and masonry wall

buildings

1.3 Basis

The policy framework and repair techniques in this

document are based on the evaluation of the effects of

earthquake damage on the anticipated future

performance of buildings. FEMA 306: The Evaluation

of Earthquake-DamagedConcreteand MasonryWall

Buildings- Basic ProceduresManual(ATC,1998a)

documents the performance-based evaluation

procedures. The procedures and criteria in FEMA 306

address:

1. The investigation and documentation of damage

caused by earthquakes

2. The classification of the damage for building components according to mode of structural behavior

and severity

3. The evaluation of the effects of the damage on the

performance of the building during future earthquakes

4. The development of hypothetical measures that

would restore the performance to that of the undamaged building

FEMA 307: The Evaluation of Earthquake-Damaged

Concreteand Masonry WallBuildings- Technical

Resources (ATC, 1998b) provides supplemental data

that facilitates use of the FEMA 306 procedures. The

evaluation procedures build, to the extent possible, on

existing performance-based procedures in the FEMA

273 and FEMA 274 reports, NEHRP Guidelinesfor 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). The intention is to document

Repair of Earthquake Damaged Concrete and Masonry Wall Buildings

1.

FEMA 308 1
Chapter 1: Introduction

and adapt the existing state of knowledge rather than to

develop completely new techniques. This approach also

contributes to consistency of language, nomenclature,

and technical concepts among emerging procedures

intended for use by structural engineers.

As a part of the research program for FEMA 306, 307

and this document (FEMA 308), two issues working

groups focused on the key aspects of adapting and

enhancing the existing technology to the evaluation and

repair of earthquake-damaged buildings. The general

scope of work for each group is outlined in FEMA 307.

The scope of work for the Materials Working Group

included the review and summary of repair techniques

for concrete and masonry wall buildings. The group

reviewed experimental and analytical research reports,

technical papers, standards, manufacturers'

specifications, and practical example applications

relating to the repair of damage in concrete and

masonry walls and infill panels. The primary interest

was the repair of earthquake damage to structural

components. The review focused on materials and

methods of installation and tests for assessing the

effectiveness of repair techniques for cracking,

crushing, and deterioration of concrete or masonry; and

yielding, fracture, and deterioration of reinforcing steel.

Based on the review, practical guidelines for damage

repair were developed and are contained in this

document (FEMA 308). These guidelines consist of

outline specifications for equipment, materials, and

procedures required to execute the repairs as well as

criteria for quality control and verification of field

installations. The efficacy and advisability of various

techniques are discussed in relation to the objective of

restoring and supplementing the force-deformation

behavior of individual components.

1.4 Document Overview

This document comprises three major parts. First,

background material on repair of earthquake-damaged

buildings is summarized in Chapter 2. This consists of

some discussion of experiences of communities after

recent past earthquakes. The result is the identification

of some common issues and parameters for earthquake

repair policies and procedures, as well as some

technical impediments to the overall process.

Chapter 3 briefly reviews the performance-based

damage evaluation procedures of FEMA 306. It also

introduces a policy framework based on building

performance parameters. Recommendations are offered

to both public policy agencies and private-sector

building owners to facilitate the use of the performancebased framework.

Finally, Chapter 4 discusses the implementation of

repairs. Although conventional prescriptive approaches

are acceptable alternatives in many simple cases, the

use of performance-based standards is recommended

for general application. Typical repairs are categorized

according to their intended objective. Outline

specifications for repairs typically applied to concrete

and masonry wall buildings are tabulated.

1.5 Limitations

The policy framework for repair presented in this

document incorporates parameters related to the

performance characteristics of individual buildings, the

shaking severity of the damaging event, performance

objectives for future events, thresholds for restoration

and upgrading, and others. Policy decisions include the

selection of specific limits or values for some of these

parameters. This document is not intended to

recommend policy for the repair or upgrading of

buildings beyond the use of the generic framework.

Specific limits or values for controlling parameters are

not recommended in this document. In some cases,

examples are used for illustration. These should not be

construed by the user as policy recommendations.

Earthquakes can cause damage to both the structural

and the 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

the damage suffered during the damaging earthquakeby

the building in its existing condition immediately before

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.

The procedures and criteria for evaluating and repairing

damage in this document have been based on the

current state of the knowledge on nonlinear inelastic

behavior of structures and structural components. This

knowledge will expand over time. The evaluation

FEMA 3Ut�

Repair of Earthquake Damaged Concrete and Masonry Wall Buildings FEMA 308

2
Chapter 1: Introduction

procedures and the information on component behavior

must be adapted appropriately to reflect new

information as it becomes available.

The interpretation of damage as it relates to the

performance of buildings subject to earthquakes is

complex and requires experience and 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 validity of the results primarily

depend.on the capability of the engineer, or engineers,

as opposed to the procedures and criteria themselves.

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 competence of the

individual or firm responsible for the original work.

This should be judged on the basis of the procedures

and criteria that were available at the time of the work.

FEMA 308 Repair of Earthquake Damaged Concrete and Masonry Wall Buildings 3
Background

2.1 Introduction

The effort to improve policy regarding the repair of

earthquake-damaged buildings benefits from

observations on the recovery of communities after past

earthquakes. Recent experience in California and Japan

reflect recent recovery efforts in urban and suburban

settings and a range of local damage intensities. These

observations lead to a synthesis of key policy

considerations. They also reveal major technical

challenges that must be met before policy can be

improved.

2.2 Experience in Recent Past

Earthquakes

In 1975, an earthquake in northern California severely

affected the small town of Oroville. Many buildings in

its downtown central business district were closed due

to damage. The situation also raised concern for the

safety of other buildings, particularly unreinforced

masonry (URM) buildings. With the assistance of

several engineers, the city council quickly passed an

ordinance allowing the reopening of buildings provided

that repairs designed by a civil or structural engineer

reduced risk to an acceptable level (Olson and Olson,

1992). These repairs did not need to comply with

current code requirements. The city also began to

develop criteria for evaluation and retrofit of all

buildings for seismic safety. Significant opposition from

the local business community soon materialized,

however, because of economic concerns over the costs

of repairs and mitigative actions. After a period of

intense political wrangling, the city council

significantly weakened the repair ordinance and

defeated the proposal for evaluation and retrofit.

After the Loma Prieta earthquake of 1989, the city of

San Francisco relied primarily on the San Francisco

Building Code (City and County of San Francisco,

1989) as a standard for repair and upgrading of

damaged buildings. The San Francisco code is based on

the Uniform Building Code (UBC), which is prepared

by the International Conference of Building Officials

(ICBO). The UBC allows repairs or alterations to

existing structures so long as the repairs themselves

conform to the provisions of the code. Absent a change

in occupancy or other major change for the building,

there is no UBC requirement to upgrade the entire

building to the current provisions of the UBC. San

Francisco modified this section of the code to require

that the building be upgraded to full compliance (at the

75% force level) when the repairs reach a certain

threshold. The existing trigger in the San Francisco

code at the time of Loma Prieta required full

compliance (at the 75% force level) when 30% of the

structure was affected by the work. In practice, this

provision has been extremely difficult to interpret and

apply (Holmes, 1994).

Other cities implemented requirements for seismic

upgrading based on a loss of lateral-load-carrying

capacity as a result of the damaging earthquake. In

Oakland, California, buildings damaged by the 1989

Loma Prieta earthquake were required to be upgraded to

full compliance with the UBC if they lost a certain

percentage of their capacity. Buildings were divided

into two risk categories, relatively high and normal.

Those determined to have a high risk, based on type of

construction, size, and occupancy were required to be

brought into full compliance if they had lost more than

10% of their lateral-load-resisting capacity. Those in the

lower-risk group could lose 20% before full upgrade

was required. Exceptions to full compliance could be

issued by the building official for buildings of historical

significance and for those where the cost was

considered economically unfeasible. Nonetheless, these

exceptions still were required to conform to the 1973

UBC and the California State Historic Building Code,

where applicable.

The town of Los Gatos, a small community located

relatively near the epicenter of the 1989 Loma Prieta

earthquake, suffered extensive damage, particularly to

its historic area. Rather than adopt standards that would

be applied to all types of buildings and observed

damaged conditions, Los Gatos developed policies

based on five categories of damaged buildings. These

included historic buildings, unreinforced masonry

buildings, older wood-frame dwellings, older

commercial buildings of various types, and damaged

masonry chimneys (Russell, 1994). The URM buildings

were required to be brought into compliance with a

standard essentially equivalent to Division 88 of the Los

Angeles Building Code (City of Los Angeles, 1985).

This is a prescriptive model building ordinance directed

at risk reduction performance for unreinforced masonry

buildings. Damaged buildings other than the URM

structures were required to have repairs designed to

meet 75% of the lateral-force requirements of the 1985

Repair of Earthquake Damaged Concrete and Masonry Wall Buildings

2.

FEMA 308 5
Chapter 2: Background

edition of the UBC. This was the current code in effect

in Los Gatos at the time of the earthquake. Further, the

owner's engineer was allowed to prescribe repair or

strengthening only for those structural elements found

to have suffered damage. In effect, this policy was

consistent with the requirements for alterations and

repairs in the Uniform Building Code.

The city of Santa Cruz, located very close to the

epicenter of the 1989 Loma Prieta earthquake, also

suffered severe damage to its downtown area. The city

passed an ordinance requiring all damaged buildings to

meet the lateral-force requirements of the 1970 UBC.

Santa Clara County near San Jose allowed damaged

URM buildings to be repaired by upgrading to the

requirements of their URM ordinance, which was

passed immediately after the 1989 Loma Prieta

Earthquake. Their requirements are similar to Division

88 in Los Angeles.

Damage caused by the Northridge earthquake in 1994

in southern California was greater overall and more

widespread than damage caused by the Loma Prieta

earthquake. Repair requirements varied by local

jurisdiction (CSSC, 1994). In the City of Los Angeles,

when the damage at a floor resulted in less than a ten

percent loss of capacity along any single line of

resistance, the damaged sections could be replaced with

the same construction. If the damage in any single line

of resistance exceeded 10% of capacity, all components

in the line were required to be brought into full code

compliance. If the total loss of capacity at any floor

exceeded 50%, the entire lateral-force-resisting system

of the entire floor had to be brought into full

compliance. Because of the technical difficulty in

interpreting these requirements, the recommendations

of individual engineers were accepted in most cases.

In 1991, the Japan Building Disaster Prevention

Association issued guidelines for the inspection and

restoration of earthquake-damaged buildings (Sugano,

1996). These guidelines were generally used in the

Kobe area following the earthquake in 1995. The

options for dealing with damaged buildings in these

guidelines include acceptance of the building in its

damaged condition, repair to its pre-event condition,

strengthening to a level greater than its pre-event

condition, or demolition. The recommended action

depends on two factors. The first is the level of damage

that was sustained during the damaging event. There are

five classifications for the degree of damage ranging

from "slight" to "collapse". Procedures are provided to

categorize the degree of damage based on the damage

observed in the field. The second factor determining the

degree of repair or upgrade required for the building is

the intensity of shaking in the vicinity of the building.

This is designated in accordance with the Japanese

Meteorological Agency intensity scale, which has five

levels of shaking intensity. This scale is qualitative and

similar to the Modified Mercalli Intensity scale used in

the United States. These guidelines recognize that the

level of repair or upgrade depends both on the amount

of damage and on the intensity of shaking to which the

building was subjected. It differs from the approach of

the City of Oakland and others who established a lossof-capacity criterion that apparently applies regardless

of the intensity of shaking.

2.3 Basic Policy Considerations

All communities in past earthquakes addressed the

challenge of recovery and reconstruction their own

ways. In spite of this, observations on these experiences

lead to several general conclusions and key

considerations for future policy:

1. The economic impact of earthquakes is a major factor in the implementation of policies for repair and

upgrading after an event. A damaging earthquake

presents particularly difficult and complex problems for individual building owners and the general

community. Owners may be confronted with large

repair costs along with a business downturn, both

caused by the earthquake. It is in the community's

long-term interest to require restoration or upgrading of damaged buildings to avoid similar or greater

losses in future earthquakes. In the short term, however, restrictive policies for repair can restrain vital

economic recovery. Effective policy to deal with

this situation is a balance of often-competing

imperatives including, for example, public safety,

private property rights, historic preservation, urban

planning, economic development, and ethical and

legal considerations.

2. There is a virtually complete lack of standards

directed toward the postearthquake repair of damaged buildings. Most jurisdictions rely upon some

adaptation of an existing code or model building

ordinance for these guidelines. These adaptations

are developed after the event in a reactive manner

by city governments and engineers.

Repair of Earthquake Damaged Concrete and Masonry Wall Buildings FEMA 308 6
Chapter 2: Background

3. The policies for specific buildings are related to

their occupancy and function. It seems reasonable

to hold important buildings to a somewhat higher

standard than others. The risk of failure associated

with damage in a hospital is greater than that for

single-family residences.

4. The vulnerability associated with different building

types is a factor. Older buildings or those with

structural systems known to pose greater risks during earthquakes (e.g., URM) are often held to more

stringent requirements.

5. Insurance companies and agencies tend to measure

losses by comparing the damaged condition of

buildings to their pre-event condition. While this

policy limits the liability of the insurer, it does little

to reduce future losses, particularly for larger

events.

6. There is a tolerance for some amount of damage

during an earthquake. This seems logically to be

related to the intensity of shaking of the damaging

earthquake. If a building suffers a small amount of

damage in a small or moderate event, most communities are willing to accept this damage, or, at the

most, require that the building be brought back to

its previous condition. On the other hand, when

buildings suffer a large amount of damage in a

small or moderate event, the tolerance for acceptance of the restoration to the previous condition is

less. This attitude is related to the economic considerations discussed above.

2.4 Technical Impediments

Experience from recent past earthquakes demonstrates

that technical improvement in engineering standards for

the evaluation and repair of buildings would enhance

and facilitate the recovery. Holmes (1994) summarized

the primary impediments to effective standards for the

evaluation and repair of earthquake damage. These are

consolidated and summarized as follows:

1. Lack offormalized methods for analyzing the realisticeffectsof earthquakeshakingand resulting

damageon theperformanceof buildingsand their

components. Traditionally, the focus of structural

analysis and design has been on forces. This is due

to the fact that the most obvious structural demand

that most buildings face are their own weight and

the imposed vertical load. These are easily and

acceptably treated as static forces. Over the years, it

has become increasingly clear that the dynamic

loads imparted to buildings by earthquakes are fundamentally different from static loads. The magnitude of the demand depends on the weight and

stiffness of the building. Inevitably, the structure

yields to dissipate energy during an earthquake.

When it does, ductility, the ability to deform inelastically without abrupt loss of strength, is a critical

capacity parameter. Stiffness, energy dissipation,

and ductility are all dependent on displacements, as

is damage.

Traditional analyses of forces assume linearlyelastic structural response. Therefore, the global

demand is reduced and the allowable component

force capacities are increased to account indirectly

for inelastic behavior. The actual global

displacement of the structure and the distortion of

its components remain obscure, at best. Since

damage depends on the actual displacements, the

condition of the structure for a specific level of

force is very difficult to characterize. This can be

visualized by examining a typical inelastic capacity

curve for a building (see Figure 2-1). As the

structure begins to yield, the curve generally

flattens with respect to the displacement axis. In the

inelastic region, a small change in force can result

in a large change in displacement. This is a

fundamental improvement in analysis that is

currently emerging in engineering practice (ATC,

1996; 1997a,b).

The key to realistic evaluation of the effects of

earthquake damage on performance is a

methodology that focuses on displacements rather

than forces.

2. Limited information on the behavior of structural

components particularly on the effectiveness of

repairs, the relationship between repair techniques

anddamageintensity,andthe effectsof local repair

on global behavior Traditional codes and structural

analysis techniques address structural component

behavior in the linear range. Little data on inelastic

behavior have been formally compiled from available research and test results. Observations of damage (e.g., crack size and extent) to components have

not been related to changes in structural properties.

There are few standards for design and construction

related to the repairs normally used for damaged

structural components, nor are there readily availFEMA 308 Repair of Earthquake Damaged Concrete and Masonry Wall Buildings 7
Chapter 2: Background

Figure 2-1 Sensitivity of displacement to changesin force

able data on the effect of repairs on structural properties.

The state of knowledge on component behavior

needs to be documented and augmented as

necessary to relate damage (and repair) to structural

performance.

3. Inadequate methods of measuring the significance

of damage with respect tofuture risks. When considering what to do with a building damaged by an

earthquake, a logical question is: "How does the

damage affect what will happen in a future earthquake?" Design codes and conventional engineering methodologies are prescriptive, and they do not

provide specific insight into seismic performance of

new or damaged existing buildings. The costs to

upgrade a damaged building to current code provisions are rarely trivial. The implication of a community building department requirement for such

upgrade work is that the future consequences of

earthquakes to the community are worth the price.

Similarly, the decision by a building owner to

accept a damaged building without repair is tacit

acceptance of the future costs.

Effective earthquake repair policy and individual

decisions require better estimates of future seismic

performance.

Repair of Earthquake Damaged Concrete and Masonry Wall Buildings

Force

Parameter,F

Small ___ change i

in force T I I

Capacity curve

_4 _0-i Displacement

Large change in Parameter, d

displacement

8 FEMA 308
Performance-Based PolicyFramework

3.1 Introduction

In practice, successful recovery after a damaging

earthquake depends on effective policies and a

cooperative effort between the private and public

sectors. The action to be taken on a damaged building is

ultimately the responsibility of the owner. Normally,

however, the owner's options are constrained through

building regulations intended to protect public safety

and to reduce future economic losses. The experience in

past earthquakes outlined in Chapter 2 suggests that

policy planning for recovery in advance of earthquakes

might greatly improve the process. Such planning could

address key considerations encountered after past

earthquakes. The performance-based procedures for the

evaluation of earthquake-damaged buildings presented

in FEMA 306 and FEMA 307 can provide improved

technical information to facilitate both the planning and

recovery efforts. These procedures allow policies and

decisions to be fundamentally based on estimates of the

performance of damaged, restored, or upgraded

buildings.

3.2 Basic Alternatives

There are a number of alternatives for dealing with a

building that has been damaged by an earthquake. For

the purposes of developing a policy framework to

facilitate the decision-making process, three alternatives

are considered:

* Accept the building for continued use in its damaged

condition. Sometimes the damage is obviously

slight, implying that the building is only marginally

worse off than before the damaging earthquake. If

the damage is greater and the building seems more

prone to future damage, perhaps the occupancy can

be changed to reduce the risk and, at the same time,

avoid repairs.

* Restore the building to its pre-event condition. It

seems logical to fix the damage that was done. In

fact, this is the traditional approach in the insurance

industry. The restored building would behave in

future earthquakes as it would have in its pre-event

condition. The risks would be no greater than before

the damaging event.

* Upgrade the building to a condition of improved

seismic performance compared to its pre-event

condition. Earthquake damage can reveal significant

deficiencies in buildings. The risks associated with

the building in future earthquakes, even in a restored

condition, might be too large. In this case, the repairs

are designed to improve the future performance and

to reduce risks.

Selecting among these basic alternatives for a damaged

building requires consideration of all of the policy

issues outlined in Chapter 2. The decision process and

the alternatives themselves imply a capability to answer

a fundamental technical question: How can the

acceptability of a building's anticipated earthquake

performance be measured? A benchmark is needed to

compare the performance of the building in damaged,

restored, and upgraded states.

3.3 Damage Evaluation

Procedure

There has been a tendency to attempt to gauge the effect

of earthquake damage by estimating the loss of lateralforce-resisting capacity of the structure (Hanson, 1996).

It has been assumed that this loss can be related to the

observed width and extent of concrete and masonry

cracks in damaged shear-wall buildings, for example. In

reality, there is widespread disagreement on the effect

of cracking on capacity and skepticism on the suitability

of force capacity itself as a parameter for measuring

damage.

Recent progress in the development of performancebased evaluation techniques allows a more meaningful

measurement of the effect of damage on concrete and

masonry wall buildings (FEMA 273/274, and ATC-40).

Performance-based procedures characterize the effects

of earthquake shaking on structures in terms of

displacement limit states. The adaptation of these

procedures to the evaluation of earthquake-damaged

buildings is presented in FEMA 306. 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 possible to compare

analytically the future performance of the damaged

building with that of the building in its undamaged

condition. It is also feasible to investigate the

Repair of Earthquake Damaged Concrete and Masonry Wall Buildings

3.

FEMA 308
Chapter 3: Performance-Based Policy Framework

effectivenessof potential measures to restore or upgrade

the damaged building.

3.3.1 Performance Objectives

The proposed evaluation procedure is performancebased; that is, it measures acceptability (and changes in

acceptability caused by previous damage) 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. Commonly-used performance levels, in

order of decreasing amounts of damage, are collapse

prevention, life safety, and immediate occupancy.

Hazards associated with future hypothetical

earthquakes commonly are defined in terms of ground

shaking amplitudes 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 (ATC, 1996;

1997a, b).

3.3.2 Global Displacement Parameters

The performance-based procedures use structural

analysis methods that focus on realistic estimates of the

displacements of a building subjected to seismic ground

motions. These nonlinear static procedures (NSPs)

generate a plot, called a capacity curve (see Figure 3-1),

that relates a global displacement parameter (at the roof

level, for example) to the lateral force imposed on the

structure. There are several available NSPs, and they

differ from one another in the technique used to

estimate the maximum global displacement, dd, for a

given ground motion. The damage evaluation procedure

provided in FEMA 306 uses NSPs to compare a global

displacement capacity limit for a specific performance

level, d, (Figure 3-2), with a maximum global

displacement demand for a particular ground shaking

hazard, dd (Figure 3-3). The ratio of the displacement

capacity, dc, of the building for the specific performance

level to the displacement demand, dd, for a specific

hazard is a measure of the degree to which the building

meets the associated performance objective.

3.3.3 Structural Components

The FEMA 306 evaluation method uses a model of the

building composed of its structural components. The

Figure 3-1 Capacity curves from nonlinear static

procedures.

Building Damar e

Global

Force

Parameter

Global Global

capacity Displacement ^ curyeLimits, d,

Immediate Life Collapse

occupancy safety prevention

Performance Levels

Figure 3-2 Global displacement capacities, dc, for

various performance levels

behavior of the structure in its undamaged, damaged,

and restored conditions is controlled by associated

inelastic force-deformation relationships for each

component. The model for analysis of the building

comprises an assembly of individual structural

components. The force-deformation characteristics for

individual components are idealizations of

representative hysteretic behavior under cyclic loading

Repair of Earthquake Damaged Concrete and Masonry Wall Buildings

Global Damaged Pre-event(undamaged)

Force capacity / capacitycurve

Parameter cure.

//| g g l ~~~Global

Displacement

Parameter

do' o d, d .

d= Estimateof maximumglobaldisplacement causedby damagingearthquake

d= Globaldisplacementcapacityfor pre-event structurefor specifiedperformancelevel

d' = Global displacementcapacityfor damaged structurefor specifiedperformancelevel

dd = Global displacementdemandfor pre-event structurefor specifiedseismichazard

dd'= Globaldisplacementdemandfor damaged

structure for specifiedseismic hazard

FEMA 308
Chapter 3: Performance-Based Policy Framework

Figure 3-3 Global displacement demand for

undamaged, damaged, and restored!

upgraded conditions

conditions (Figure 3-4). For a given global

displacement of a structure subjected to a given lateral

load pattern, there is an associated deformation for each

of the structural components of the building. Since

inelastic deformation indicates component damage,

then the maximum global displacement, dd, to occur

during an earthquake represents a structural damage

state for the building in terms of inelastic deformations

for each of its components. The capacity of a given

structure for a given performance level is represented by

the maximum global displacement, dc, at which the

damage is on the verge of exceeding the limit for the

specific performance level. For example, the collapseprevention capacity of a building might be the roof

displacement at which the associated damage would

result in one or more of the column components being

in danger of imminent collapse.

At the beginning of the evaluation process, the engineer

identifies basic components and documents the damage

to each. The global displacement parameters for the

Figure 3-4 Structural component force-deformation

characteristics

building are calculated using component properties for

the pre-event conditions (dc and dd).The structural

properties of the components then are modified to

reflect the effects of the observed damage using factors

contained in FEMA 306 supplemented by additional

information contained in FEMA 307. This allows the

evaluation of the global displacement parameters for the

building in its damaged condition (,d' and dd).

Information also is provided to modify component

properties to reflect the effects of repairs to restore or

upgrade on global displacement parameters (dc and

d; ) for the building.

3.4 Performance Capacity and

Loss

The ratios of global displacement limits or capacities

(dr, d', d2 ) for a specific performance level to the C 

corresponding displacement demands (dd,d', d; ) for a

specific seismic hazard define indices of measurement

(PEP, P*) of the ability of an undamaged ( ), damaged

('), or restored or upgraded (*) building to meet a

specific performance objective (see Figure 3-1). These

indices are:

Repair of Earthquake Damaged Concrete and Masonry Wall Buildings

Pre-event Building

I7:~~~21 ~Performance 4 de

LA ~~~~~~~~~~Time

Prgven t E ace tate Nmg ate

Damaaed Buildina

d

F]Damacang Eatquake WA.~M

event ~ ntermetate' Perortrrr Sr97tate Damagetate Damage tate(')

Restored or UDaradedBuilding

Time

Prg-event '" Restoration Perfrac State q2t pgrade Damage ae(

For.e F* Backbone

Actualhysteretic behavior

(a) Backbonecurvefromactualhysteretic behavior

F Backbone F

I,Cvdealized l C, D B.C, D

14 \behvior 1(1

E 

Ductile Semi-ductile Brittle

(deformationcontrolled) (forcecontolled)

(b) Idealizedcomponentbehaviorfrom

backbonecurves

FEMA 308 11
Chapter 3: Performance-Based Policy Framework

P = d /dd Pre-event performance index,

P = dc I dd Damaged performance index,

P = d* I dd* Restored or upgraded performance

index.

If a performance index is less than one, the implication

is that the building in its undamaged ( ), damaged ('), or

repaired (*) state is not able to meet the specific

performance objective. If a performance index is 1.0 or

greater, the implication is that it can meet the objective.

Note that these indices are always associated with a

specific performance objective. The same building may

have different performance indices for different

performance objectives.

The ratio of the damaged performance index, P', to the

undamaged, P, for a building for a specific performance

objective is a measure of the anticipated performance

capacity of the damaged building relative to that for the

building in its pre-event state. The loss in performance

capacity caused by damaging ground motion is:

L = 1 - (P'IP)

3.5 Restoration or Upgrade

Procedure

The procedures of FEMA 306 include guidelines for

formulating repair measures to restore the damaged

building to its pre-event performance capability. If the

performance capability of the structure for a selected

performance objective is diminished by the effects of

earthquake damage (P' < P) the magnitude of the

economic loss is quantified by the costs of performance

restoration measures. These are hypothetical actions

that, if implemented, would result in future performance

approximately equivalent to that of the undamaged

building (P* =P). Performance,restoration measures

may take several different forms:

a. Component restoration entails the repair of

individual components to restore structural

properties that were diminished as a result of the

earthquake damage. For example, cracks in a

shear wall might be injected with grout to restore

component strength and stiffness. Outline

specifications for typical repairs for concrete and

masonry wall buildings are included in this

document in Chapter 4.

b. An extreme case of component repair is

complete replacement. A severely damage wall

section might be completely removed and

replaced with a similar or improved component.

In some cases, this is the only alternative. In

other cases, it may be an economic alternative.

c. Performance can also be restored by the addition

of supplemental lateral-resisting elements or

components. Instead of repairing or replacing a

damaged section of wall, a new wall element

might be installed in another location.

The process of formulating performance restoration

measures involves developing a component-level

strategy that includes one, or a combination, of the three

alternatives. The measures are then tested by analyzing

the performance of the modified structure and adjusting

the scope of the measures until the performance is

approximately the same as that of the pre-event building

(P* =P)

The same basic strategy can be used to formulate

performance upgrade measures to provide the capacity

to meet the selected performance objective (P* 1.0).

3.6 Relative Seismic Demand

Decisions regarding an appropriate policy for the

acceptance, restoration, or upgrade of earthquakedamaged buildings, depend in part on the severity of the

damaging event (Section 3.8). The severity of shaking is

a function of the magnitude of the damaging event as

well as the epicentral distance and the amplification

caused by site soils. The Modified Mercalli Intensity

scale or other intensity scales can be useful in

formulating a qualitative perspective of shaking severity

for a specific building relative to others in the vicinity.

Quantitative parameters include site peak ground

acceleration and spectral acceleration at the period of

the building.

Displacement-based analysis procedures also can be

used to gauge the relative severity of ground motion

demand on specific buildings. FEMA 306 provides

guidance on estimating the maximum displacement, de,

caused by the damaging ground motion using the

capacity curve and the damage observations for a

specificbuilding. The capacity curve can also be used to

estimate the maximum displacement demand, dd, for a

performance ground motion. The ratio, S, of the real

global displacement, de, caused by the damaging

Repair of Earthquake Damaged Concrete and Masonry Wall Buildings FEMIA 308
Chapter 3: Performance-Based Policy Framework

ground motion to the hypothetical displacement

demand, dd, for the performance ground motion is an

index of relative displacement demand and is

represented as:

S = de Idd

The relative displacement demand provides an

improved and unambiguous measure of the demand on

the building associated with the damaging earthquake

for several reasons. First, it is a measure that applies

directly to the specific building and site. Secondly, the

basis of measurement, displacement, is a better index of

damage for buildings than acceleration. Finally, the

index is normalized relative to a defined performance

objective.

3.7 Relative Risk

The capacity curve for a pre-event ( ), damaged ('), or

repaired (*) building allows one to estimate

Figure3-5 Global displacement demandsand

capacities

displacement demands for various levels of seismic

hazard as shown in Figure 3-5. These may be generated

using nonlinear static procedures according to the

recommendations in FEMA 306, in conjunction with

the appropriate capacity curve. In Figure 3-5 these are

plotted on the upper horizontal axis noting their chance

of exceedance in 50 years. Component acceptability

criteria in conjunction with capacity curves also can be

used to define global displacement limits for various

performance levels (e.g., immediate occupancy, life

safety, collapse prevention). These are shown in

Figure 3-5 along the lower horizontal axis. The

combined plot provides a complete picture of the risks

associated with the particular repair alternative.

Global displacement demand for various repair

alternatives can also be plotted versus a risk parameter

as shown in Figure 3-6. The intersection of a global

displacement capacity value, for a selected performance

level, with the corresponding displacement demand

curve allows an estimate of the risk that the

performance level would be exceeded for a given repair

alternative. Doing this for several repair alternatives, as

Figure 3-6 Risk associated with damage

acceptance,restoration, and upgradefor

a specific performance objective

shown in Figure 3-6, provides a comparison of the risks

associated with each alternative for the selected

performance level. For example, suppose that the

performance level of interest is life safety. Figure 3-6

illustrates that the chance that the global displacement

demand would exceed the life safety capacity of the

damaged structure is slightly higher than 20% in fifty

years. Restoration of the structure to its pre-event

condition would reduce the life safety risk to less than

10%. The upgrade could reduce risk to just above 2% or

approximately ten times less than the damaged structure

in this illustration.

Repair of Earthquake Damaged Concrete and Masonry Wall Buildings

Seismic Hazard Levels

Global (chanceof exceedance in 50 yrs.) Global

Force Displacement Parameter 0o% 10% 2% sl Demand

undamaged ()

damaged ('), or

repaired (*)

city curve

-| >-.GIobal

Immediate Life Collapse Displacement

occupancy safety prevention Capacity

Performance Levels d

_Displacementdemand curves

Damaged,dd

Restored,dd

Upgraded,d*

Global

Displacement, d

Upgraded,d.'

Displacementcapacities

FEMA 308 13
Chapter 3: Performance-Based Policy Framework

3.8 Thresholds for Restoration

and Upgrade

The decision on an appropriate course of action (accept

damage, restore, or upgrade) for a specific building

damaged during an earthquake depends on a number of

interrelated factors discussed below:

a. Relative Severity of Damaging GroundMotion.

The tolerance for damage caused by relatively

large earthquake ground motions is logically

greater than if the same damage were caused by

small ground motions. It makes sense that a

building significantly damaged by small ground

motions is a good candidate for upgrading. After

earthquake ground motions at about the design

level for which damage is expected, a less

restrictive policy on upgrading will facilitate the

economic recovery of the community.

b. Theacceptabilityof performancecharacteristics

of the building after the damaging earthquake.

If the damaged building is capable of meeting

reasonable performance objectives in its

damaged state, repair or upgrading may be

unnecessary. It is also possible that short-term

performance objectives, lower than those

appropriate for the longer term, may be

reasonable to use in some circumstances,

eliminating the need for immediate action.

c. The acceptabilityof performancecharacteristics

of the building before the damaging earthquake.

The decision between restoration and upgrading

is largely controlled by the acceptability of the

restored performance, which would be equivalent

to that before the earthquake. It is not logical to

restore a building to a poor level of expected

performance.

d. The change in performance characteristics of the

building caused by the damaging earthquake.

If the damaging earthquake causes a large

decrease in the performance characteristics of a

building, restoration or upgrading are obviously

more advisable than if the loss were small. Small

losses, particularly for large earthquakes, are

often acceptable.

e. Nonseismic issues related to the condition and

use of the building. Nonseismic deficiencies

(e.g., disabled access, fire and life safety,

programmatic, maintenance) are important

considerations. So is the anticipated future use of

a building and any change in appropriate seismic

performance objectives. It makes little sense to

extend the life of a building significantly without

addressing seismic deficiencies.

Some of these factors governing decisions on

acceptance, restoration, or upgrading have no

fundamental technical basis. The rationale for allowing

some leeway in these decisions to account for

nontechnical considerations is based on the precedent

established in past earthquakes and common sense. It is

helpful, however, to establish quantifiable parameters to

represent the results of judgement and experience.

The performance indices for the building in its preevent (P) and damaged (P) condition can be determined

using the relative performance analysis procedures of

FEMA 306. Component acceptability and global

displacement demand control the thresholds for

restoration and repair because the performance index

for both the pre-event structure (P) and the damaged

structure (P') are defined as the ratio of global

displacement capacity (d, or d,') to the global

displacement demand (dd or ddt

). The behavior of

individual components, as discussed in Section 3.3.3

and FEMA 306, governs global displacement

capacities. Performance loss, L, is a function of the

performance indices.

Boundaries between acceptance and restoration, and

between acceptance or restoration and upgrading can be

defined as in Tables 3-1 and 3-2. The parameters

introduced in these tables can be plotted, for a given

damaging earthquake with relative displacement

demand, S. as illustrated in Figure 3-7a and b and used

as a guide for the need for restoration or upgrading of a

damaged building.

The performance loss (L) for the selected objective is

determined and plotted as a horizontal line as in

Figure 3-7a and b. Figure 3-7a illustrates the boundary

between restoration or upgrade and acceptance of the

damage. Figure 3-7b illustrates the boundary between

damage acceptance (or restoration) and upgrade.

Turning first to Figure 3-7a, the point (P', L) is used to

determine if the damage can be accepted. If the

damaged building is capable of meeting reasonable

performance objectives, repair or upgrading is

unnecessary. The restoration boundary between

acceptance of the damage and the need for restoration;

or upgrade is defined by the parameters in Table 3-1. If

the performance loss (L) is small, then restoration or

14 Repair of Earthquake Damaged Concrete and Masonry Wall Buildings FEMA 308
I Chapter 3: Performance-Based Policy Framework

Table3-1 Parameters governing whether

damage is acceptable (see

Figure 3-7a)

Lr(min) = Performance loss threshold below which restoration is not required regardless of the

Damaged Performance Index, P'.

(Avoids requiring restoration when the effects

of damage on performance are small. This

threshold would be comparatively lower for

damaging earthquakes with small relative displacement demand (S) and higher for large

ones.)

P 'in = Damaged Performance Index limit below

which restoration is required unless the Performance Loss is less than Lr(min).

(Limits how far the Damaged Performance

Index (P') can fall and still be acceptable

without restoration. This limit would be comparatively lower for damaging earthquakes

with large relative displacement demand (S)

and higher for smaller ones.)

Lr(n,.) = Performance Loss threshold above which restoration is required unless the Damaged Performance Index exceeds P mar

(Requires restoration for relatively large

losses unless the Damaged Performance

Index (P') is high. The threshold would be

comparatively lower for damaging earthquakes with small relative displacement

demand (S) and higher for larger ones.)

PImax = Damaged Performance Index limit above

which restoration is not required regardless of

the Performance Loss.

(Establishes when the Damaged Performance

Index (P') is acceptable without restoration.

This limit would be comparatively lower for

damaging earthquakes with large relative displacement demand (S) and higher for smaller

ones.)

upgrading might not be required since the change in

performance is negligible. This concept is represented

by the horizontal line at L,,minj. If the loss exceeds the

minimum, then the decision on Whether to accept the

damage is controlled by how close the damaged

performance index is to P'm and P',. The lower end

of the sloping portion of the restoration boundary

represents the limit (P'min). As the loss increases there is

logically less tolerance for a lower damaged

performance index (Pt

). As the loss increases further,

there comes a point Lr(ma), at which the damaged

Table 3-2 Parameters governing whether

restoration is acceptable (see

Figure 3-7b)

Luamin) = Performance Loss threshold below which

upgrading is not required regardless of the

Pre-event (Undamaged) Performance Index.

(Avoids requiring upgrading when the

effects of damage on performance are small.

The threshold would be relatively lower for

damaging earthquakes with small relative

displacement demand (S) and higher for

larger ones.)

Pmin = Pre-event Performance Index limit below

which upgrading is required unless the Performance Loss is less than Lu (min)-

(Establishes when the Pre-event Performance Index (P) is acceptable without

upgrading. This limit would be relatively

lower for damaging earthquakes with high

relative displacement demand (S) and higher

for smaller ones.)

Lufma,:) = Performance Loss threshold above which

upgrading is required unless the Pre-event

Performance Index exceeds Pmx.

(Requires upgrading for relatively large

losses unless the Pre-event Performance

Index (P) is high. The threshold would be

comparatively lower for damaging earthquakes with small relative displacement

demand (S) and higher for larger ones.)

Pmax = Pre-event Performance Index limit above

which upgrading is not required regardless

of Performance Loss.

(Establishes when the Pre-event Performance Index (P) is acceptable without

upgrading. This limit would be comparatively lower for damaging earthquakes with

large relative displacement demand (S) and

higher for smaller ones.)

performance index must be greater than P'maX(P'>

P'ma,,)if damage is to be acceptable regardless of the

loss. If the damaged performance index (P', L) is within

the restoration boundary, then either restoration or

upgrading is required.

The parameters affecting the decision between upgrade

or restoration are illustrated in Figure 3-7b. The

decision between upgrade or restoration is controlled by

the loss (L) and the pre-event performance index (P).

The upgrade boundary is delineated similarly to the

restoration boundary using the parameters in Table 3-2.

FEMA 308 Repair of Earthquake Damaged Concrete and Masonry Wall Buildings
Chapter 3: Performance-Based Policy Framework

Restoration boundary for damaging

earthquake

Performance

Loss

L=1-P'/P

1.0 -

Lr(max) -

L

L - remin)

Restore or upgrade

performance if (PL) is

within restoration

boundary % /

Different restoration

boundaryfor a smaller

damaging earthquake

Accept damage if (PL)

falls outside restoration

/ boundary

Damaged _ Performance

Index, P'

a) Relationship between acceptance of damage versus repair or upgrade

Upgrade boundary for damaging earthquake

Performance Upgrade performance

Loss if (PL) is within

L=1-PVP upgrade boundary

1.0 -

u(max)

Lumn)

L

P

Different upgrade

boundary for a smaller

damaging earthquake

Pre-event

Performance

IP Index, P max

b) Relationship between acceptance of damage or restoration versus upgrade

Thresholds and performance limits for restoration and upgrade of earthquake-damagedbuildings

Repair of Earthquake Damaged Concrete and Masonry Wall Buildings

Figure 3-7

FEMA 308 16
Chapter 3: Performance-Based Policy Framework

It is important to recognize that the parameters affecting

decisions between acceptance, restoration, and upgrade

may vary with the size of the damaging earthquake as

defined by the relative displacement demand, S, for a

given building. This reflects the logic that greater losses

and lower performance indices are tolerable for larger

earthquakes. The effects of this variable on the

restoration and upgrade boundaries are illustrated in

Figure 3-7a and b with the lighter boundaries for

smaller earthquakes.The intersection of the pre-event

performance index with the loss line in Figure 3-7b falls

outside the upgrade boundary indicating that restoration

is sufficient. However if this same loss had occurred in

the smaller earthquake, the intersection of P and L

would fall within the boundary indicating that upgrade

is necessary.

3.9 Policy Implications and

Limitations of Component Acceptabilityand

Displacement Demand

If component acceptability and global displacement

demand criteria are applied to both the pre-event and

damaged structures consistently, the effects of damage,

as gauged by the scope and cost of measures to restore

performance, are not sensitive to variations in the

criteria. In the evaluation of the effects of damage, the

numerical value of the performance indices and loss are

not meaningful in themselves. The same is not the case

when these parameters are used to facilitate policy

decisions for acceptance, repair, or upgrade.

Component acceptability and displacement demand

affect these decisions directly.

I

The current provisions of FEMA 273 (ATC, 1997a) and

ATC-40 (ATC, 1996) 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. There is not universal agreement among

researchers and practitioners regarding the accuracy of

these acceptability provisions for several reasons:

1. The amount of available research data on the force!

deformation characteristics of various components

for different behavior modes is not sufficient. The

interpretation of test data is also difficult since standard protocols have not been available.

2. The acceptability limits for deformation of individual components are difficult to generalize. Twoof

the key findings of the research effort for this

project are that the mode of component behavior

controls acceptability and that the mode of behavior

is not always what might be predicted using analysis procedures, similar to those of FEMA 273 and

ATC-40, intended primarily for design. This concern is obviated to some degree by the use of

FEMA 306, which requires that component force/

deformation relationships match the mode of

behavior observed in the field from the effects of

damage.

3. In many structures, the failure of a single component to meet acceptability criteria is not an accurate

indicator of global acceptability. For example, the

lack of acceptability for life safety of a highly

shear-critical, vertical-load-bearing, wall pier might

indeed limit global acceptability. By contrast, the

unacceptability of a single coupling beam carrying

only a small local gravity load in addition to earthquake forces may not alone be sufficientjustification for a global life safety limit. In reality, global

displacement limits are a complex function of component behavior and acceptability. Important considerations include the number and location of

critical components, vertical load transfer, and

interactions among components, particularly with

respect to the development of collapse mechanisms.

There is also controversy with regard to the

determination of maximum displacement demand for

use with nonlinear static procedures. FEMA 273

emphasizes the use of the displacement coefficient

method while ATC-40 documents the capacity spectrum

method. In some circumstances these two alternatives

can lead to different estimates of displacements.

The lack of complete consensus on component

acceptability and displacement demand is

understandable, since nonlinear static procedures have

not been used extensively to date. They still require a

great deal of engineering judgment, and common sense,

to produce reliable results. Over the years acceptability

limits and displacement demand are likely to become

more accurate and less controversial.

Use of the performance-based framework introduced in

this document requires the understanding of the

controlling influence of the component acceptability

and displacement demand criteria. The absolute

numerical values for Performance Indices and Loss

parameters have no significance in and of themselves.

They are only as reliable and meaningful as the

FEMA 308 Repair of Earthquake Damaged Concrete and Masonry Wall Buildings 17
Chapter 3: Performance-Based Policy Framework

component acceptability and displacement demand

criteria used to generate them. If the acceptability

criteria are overly conservative or liberal, the

Performance Indices will directly reflect this with a

relatively low or high value. The use of the framework

and associated parameters must include a definitive and

consistent specification for the component acceptability

and displacement demand criteria. The parameters

themselves then provide a convenient way to measure

performance and loss within the limitations of the

specified criteria.

3.10 Public Sector Policy Planning

Recommendations

Public agencies, particularly building authorities, can

prepare for a future earthquake by taking action

beforehand. The following are some suggestions related

specifically to the procedures developed in this

document:

1. Establish seismic performance objectives for buildings within the community. These can be modeled

on existing standards including FEMA 273 and

ATC 40. Selection of appropriate objectives should

be based on the size, age, occupancy, and function

of the individual building.

2. Adopt a seismic hazard demand standard. These

also can be generated using FEMA 273 or ATC 40.

Communities may wish to develop more detailed

specific earthquake ground motion or other seismic

hazard specifications based on regional or local

conditions.

3. Adopt loss thresholds for repair and upgrading

based on the intensity of future seismic events.

Guidance on the actual value for these thresholds

can only be qualitative at this point. In the future, it

is possible that research on loss and economic

recovery after earthquakes can shed some light on

the appropriate levels of tolerable damage. Similarly, tolerable levels of performance deficiencies

can be developed for damaged buildings.

4. Review and document the extent to which non-seismic compliance requirements are imposed on the

repair and upgrading process. Issues for prior consideration include disabled access, fire and life

safety, and historic buildings.

5. Establish programs for encouraging building owners to document the anticipated performance characteristics for their building. In some cases,

mandatory investigations or retrofit may be appropriate. Even if this cannot be implemented, building

owners should be allowed to investigate performance deficiencies without the requirement to

address them immediately.

6. Establish a repository of public information on

earthquake hazards and the vulnerabilities of buildings. Building database technologies such as those

specified in HAZUS (NIBS, 1997) and ATC-36

(ATC, in preparation) can facilitate this effort. Such

databases are useful both before, immediately after,

and during the recovery process of an earthquake.

3.11 Private Policy Planning

Recommendations

In the private sector, building owners and occupants can

benefit greatly by planning an investigation before an

earthquake. Some useful efforts are listed below:

1. Assemble design and construction information on

the specific building or group of buildings of concern. Structural information is particularly important to the investigation of damage. This might

consist of drawings, calculations, and previous

reports.

2. Engage a qualified engineer to document the existing condition of each building. This entails mapping existing cracks and other damage that may be

due to previous earthquakes or other causes. This

information serves to establish a baseline for any

future damage that may occur in an earthquake.

Additionally, it gives the engineer a chance to

become familiar with the basic structural characteristics of the building.

3. Evaluate the need for and implement, if necessary,

further investigations to determine the component

characteristics of the building in its current state.

The scope of these investigations can range from

rather straightforward and inexpensive to very

sophisticated analyses. The knowledge about the

future performance of the building is important to

the building owner or occupant even if immediate

upgrading or repair is not possible.

4. Consider the effects that earthquakes may have on

the business enterprise carried out in the building.

FEMA 308 Repair of Earthquake Damaged Concrete and Masonry Wall Buildings 18
Chapter 3: Performance-Based Policy Framework

This knowledge, coupled with the performance

analysis of the building helps the owner and occupants to make informed decisions on performance

goals for future earthquakes. These may differ from

those that have been established as the minimum

through public policy. If repairs or upgrades to meet

the objectives are not possible immediately, owners

or occupants can develop contingency plans to

respond and recover more effectively from future

earthquakes.

5. Incorporate seismic performance objectives, and

related required repairs and modifications to meet

them, into the long-term facility planning and

replacement process. Buildings and their systems

and furnishings deteriorate over time. Additionally,

the programmatic needs of the owner or occupant

also evolve. Modifications to improve seismic performance should fall into essentially the same category, unless extraordinary life safety problems are

found.

3.12 Summary

The performance-based procedures for the evaluation of

damage presented in FEMA 306 (ATC, 1998a) and the

repair issues and procedures discussed in this document

offer several technical improvements that support

effective engineering standards and policy for repair

and upgrading.

First, these methods provide a technically sound

framework for earthquake damage evaluation and

repair. The distortions and damage of the individual

components relate directly to the global displacement of

the structure. For a given movement at the roof level, for

example, there is an associated damage state for each

building component. This damage state implies a level

of performance capacity as a function of the global

displacement. Consequently, the displacement demand

associated with a specific intensity of earthquake

shaking defines a corresponding specific level of

damage for the building.

Second, the global analysis procedure relies on a

theoretical model built from the individual components

of the structure. In the past, there has been a concern on

the part of engineers that the repair, strengthening, or

replacement of individual components and/or the

addition of new components or elements might impose

critical future damage on other parts of the structure.

The proposed analytical technique allows the engineer

to evaluate directly these potential adverse effects. A

compilation of available information in FEMA 307

(ATC, 1998b) and this document summarizes the state

of knowledge on the behavior of individual components

of concrete and masonry wall buildings, including the

effects of damage and repair. Although the available

component data are by no means complete, the

proposed procedures and criteria provide a conceptual

protocol for compiling and using data that become

available in the future.

Finally, the performance-based formulation provides

relevant measurement devices to assess the effects of

damage and other parameters that are useful in

developing and implementing private and public policy

for evaluation, repair, and upgrading of buildings. These

devices are flexible enough to accommodate the

tolerance of the individual community for risk, the

selection of building-specific performance objectives,

coordination of seismic performance with other public

and private goals, and other important considerations.

When selecting performance objectives, consideration

should be made of the possibility that damage may

affect future performance in events of a smaller

magnitude than the event that caused the damage.

Specifically,some damage may decrease the stiffness of

the building without significantly affecting its

performance in larger events; however, the loss of

stiffness may result in larger displacements and greater

damage in smaller events than would have occurred in

the pre-event structure.

FEMUA 308 Repair of Earthquake Damaged Concrete and Masonry Wall Buildings 19
Implementation

4.1 Introduction

Once a policy decision has been made on the

appropriate action to take with an earthquake-damaged

building (accept, restore, or upgrade), a design

professional may need to develop a repair design. As

noted previously, repair design has been hampered by a

lack of truly applicable standards. Furthermore, the

effectiveness of specific repair technologies has been

poorly documented. This section summarizes a

performance-based approach that uses emerging

technologies. Additionally, some practical information

on the specification of repairs for concrete and masonry

wall buildings is tabulated.

4.2 Performance-Based Repair Design

Performance-based procedures for the evaluation and

retrofit of existing buildings, FEMA 273/274 (ATC,

1997a, b) and ATC-40 (ATC, 1996), are technically

similar. The FEMA 273 Guidelines, which are written

in a style similar to a building code, and its companion

FEMA 274 Commentary apply to any building type.

The scope of ATC-40 emphasizes concrete buildings,

but also includes extensive discussion of the evaluation

and retrofit process that can be applied to all building

types. It is written in textbook style.

The FEMA 273 and ATC-40 documents provide

procedures to evaluate the anticipated performance of

an existing building and to develop design measures to

improve performance. These procedures can be readily

adapted to the repair of earthquake-damaged buildings

using this document and FEMA 306 and FEMA 307.

The evaluation process for damaged concrete and

masonry wall buildings is covered extensivelyin FEMA

306.

The use of performance-based procedures for repair

design for a damaged building is actually just a special

case of a retrofit of an existing building. The process is

briefly reviewed here:

1. Select an appropriate performance objective for the

building. For an upgrade, the goal would be to

repair the building in such a way that its repaired

performance index, P*, for the specific objective is

equal to or greater than 1.0. In the case of a restoration, the goal would be to implement repairs to

return the building to its pre-event performance

index for that specific objective (P* =P).

2. Develop a repair strategy at the component level.

Actions might include repairing individual components to restore their structural properties, removing

and replacing damaged components, or adding new

components in other locations. In some cases, damaged components might be left unrepaired.

3. Generate a global capacity curve representative of

the building in its repaired condition. This requires

the selection of appropriate component properties

for damaged, repaired, or new components. For

concrete and masonry wall buildings, FEMA 306

and FEMA 307 provide extensive guidance.

4. Using the procedures of FEMA 306, determine

whether the repair strategy allows the repaired

building to meet the performance objective. If not,

revise or modify the strategy and repeat Steps 3

and 4.

5. Develop design drawings and specifications for the

repair strategy. Section 4.3 summarizes repair technologies for concrete and masonry wall buildings.

For the design of new components, the recommendations of FEMA 273/274, ATC 40, and conventional design standards are appropriate.

4.3 Repair Technologies

This section provides guidance on the specification of

individual repair techniques applicable to the

components of earthquake-damaged concrete and

masonry wall buildings. The scope of repairs for an

individual element or for an entire building depends on

the objectives of the repair program.

4.3.1 Categories of Repairs

Repairs for earthquake-damaged concrete and masonry

wall buildings fall into three generic categories:

1. Cosmetic Repairs are those repairs that improve the

visual appearance of component damage. These

repairs may also restore the nonstructural properties

of the component, such as weather protection. Any

structural benefit is negligible. An example is the

routing, sealing, and painting of cracks in concrete

or masonry.

F 0Repairof Earthquake Damaged Concreteand MasonryWall Buildings

4-.

FIRMA 308 21
Chapter 4: Implementation

2. Structural Repairs address component damage

directly, with the intent to restore structural properties. Examples include injection of cracks or the

replacement of fractured reinforcing bars.

3. Structural Enhancements are repairs that comprise

supplemental additions, or removal and replacement of existing damaged components. They also

include the addition of new components in the

structure not necessarily at the site of existing damaged components. In this case, the intent is to

replace structural properties of damaged components rather than to restore them. Examples include

the application of concrete overlays to damaged

walls or the addition of shear walls or steel bracing

to the building where these elements and components were not present before the earthquake.

Table 4-1 is a list of repairs by category identifying the

applicability of the repair to individual components,

according to material and framing type.

4.3.2 Nonstructural Considerations

This document focuses on the structural performance of

individual components. In practice, the restoration or

upgrading of a damaged building is a program of repairs

applied globally. The broader program perspective gives

rise to a number of other critical issues.

• The efficiency associated with the structural repairs

must be considered at the global level. For example,

a given component might be most effectively

repaired using a particular procedure; however, an

alternative procedure might lead to overall lower

costs when architectural or other constraints are

considered.

* The historic status of the building must be

considered when developing the repair program.

Some repair procedures may not satisfy preservation

goals for the building.

* Local building departments may have restrictions or

requirements for certain repair procedures.

Table 4-1 Summary of repair procedures

Material Repair ID

Repair Category Repair Type

Reinf. Reinf. URM

Concrete Masonry

Cosmetic Repair i V CR 1 Surface coating

V CR 2 Repointing

a/ * CR 3 Crack injection with epoxy

Structural Repair R*1 Crack injection with epoxy

I/ V SR 2 Crack injection with grout

V 9 SR 3 Spall repair

V SR 4 Rebar replacement

V VV/ SR 5 Wall replacement

Structural Enhancement 9 iSE 1 Concrete overlay

9 / / V ISE 2 Composite Fibers

9 SE 3 Crack Stitching

Notes: Repairs for concrete walls can also be used for concrete frames in infilled frame systems.

Repairs for steel frames of infill systems are described in the component repair guides.

* Epoxy injection not recommended for partially-grouted reinforced masonry.

FEMA 308 Repair of Earthquake Damaged Concrete and Masonry Wall Buildings 22
Chapter 4: Implementation

4.3.3 Repair Guides

The Repair Guides at the end of this section provide

outline specifications for typical repair procedures for

earthquake-damaged concrete and masonry wall

buildings. These have been developed in conjunction

with procedures for evaluating earthquake damage

specifically for these building types. The Repair Guides

themselves may be applicable, in whole or in part, to

other building types, depending on specific

circumstances. Many other repair techniques-useful for

other building types are not documented here.

The Repair Guides describe procedures that have been

used routinely in the past for concrete and masonry

components. There are undoubtedly other repair*

techniques that may also be applicable in general or in

specific instances. Often, repair procedures need to be

adapted to actual field conditions. The Repair Guides

convey the basic information for repair selection on a

conceptual level. They are not complete specifications

and should not be used directly as construction

documents. The design engineer must adapt these

general repairs to meet the requirements of each

building and component.

Each guide includes the following information:

Repair Name an.

Repair Category

Materials

Description

Repair Material!

Equipment

Execution

Quality Assuran

Limitations

Standards and

References

d ID For reference and

identification

*Cosmetic repair, structural

repair, or structural

enhancement

Applicability to reinforced

concrete, reinforced masonry,

or unreinforced masonry

Basic overview of the

objectives and scope of the

repair procedure

Is Typical products used for the

repair

A summary of the tools,

instrumentation, or devices

required

General sequence of

operations

Ice Measures required to achieve

satisfactory installation

Restrictions on the

effectiveness of the repair

Applicable sources of further

information

FEMA 308 Repair of Earthquake Damaged Concrete and Masonry Wall Buildings
Chapter 4: Implementation

REPAIR GUIDE Repair Type: Cosmetic Repair

COSMETIC PATCHING Materials: Concrete,

CR1 elReinforced Masonry,

Unreinforced Masonry

Description

A cosmetic patch consists of applying a surface coating

on the surface of the concrete or masonry wall to conceal the surface projection of cracks. The purpose of

patching is to improve the aesthetic appearance of the

wall or to provide an additional barrier against water

infiltration into the wall. Restoration of the fire resistance of a wall may also be required. Alternately, repair

or installation of architectural finishes covering the wall

is another method of cosmetic patching. Surface coatings in such repairs are not intended to provide any

increase in strength or stiffness to the wall.

RepairMaterials

Various materials can be used for surface coatings. The

choice of repair material will depend on the functional

and architectural requirements. Some examples of

materials are:

c Paint can be used to conceal fine cracks on the surfaces of concrete and reinforced masonry walls

* Wall coverings such as wallpaper can be used on

smooth interior concrete surfaces

* Dry-wall taping compound can be used to fill cracks

on interior surfaces before paint or wall coverings

are are applied

o Organic polymer materials can be used to fill cracks

on interior and exterior concrete or reinforced

masonry surfaces

e Coatings or sealers can be used on cracks on exterior

surfaces to reduce water penetration for concrete,

reinforced masonry, and unreinforced masonry walls

* Portland cement plaster can be applied to the surface

to cover the appearance of cracks in concrete, reinforced masonry, or unreinforced masonry walls

o Cracks that need to be sealed only to prevent water

intrusion can be injected with urethane

Equipment

The equipment required to apply the various repair

materials are generally available tools such as mixing

equipment and sprayers.

Execution

The owner or responsible party should choose a proper

material for the surface coating. The choice of material

should be based on the functional requirements of the

wall, architectural considerations, and considerations of

the historic nature of the building, if applicable.

Prior to implementing the repair, a test area should be

prepared using the contractor, equipment, procedures,

and materials to be used for the project. The completed

mock-up should be allowed to cure and then carefully

reviewed to verify that the appearance will match that

of the surrounding walls.

The surfaces to receive the coatings should be properly

prepared to ensure adequate bonding between the new

and existing materials. For paint or wall-covering application, the surface of the wall should be clean and free

of loose materials. Surface coatings such as plaster or

water-resistant coatings should typically receive a light

sand blasting to remove the existing coating and to provide a rougher surface for improved bonding.

24 Repair of Earthquake Damaged Concrete and Masonry Wall Buildings FEMA 308
Chapter 4: Implementation

uublVl. IrA1i tIlNt

continued

Oualitv Assurance

Paint or film-forming surface coatings or membranes

exposed to moisture should be checked for adhesion to

the existing surface.

Limitations

Paint can be used to bridge small cracks, with some

paints capable of bridging cracks up to 0.06 inch. The

manufacturer of the paint should be consulted for determining the capabilities and required preparation for the

specific application.

The surface coatings listed can be effective at preventing water intrusion through cracks in exterior walls.

However, these materials are only appropriate if the

crack is dormant. Cracks caused by earthquake loading

are typically dormant since they will not change in

width over time. If the crack was caused by shrinkage,

temperature movements, or other reasons, these treatments will not be effective at bridging the cracks.

Therefore, the engineer must be confident that the

earthquake caused the crack. Active or moving cracks

that are to be watertight must be routed out and sealed

with a flexible sealant.

Portland cement stucco plaster can be applied directly

to a concrete or masonry surface. Since the existing

wall is rigid and the new stucco coating will tend to

exhibit drying shrinkage, shrinkage cracks may develop

in the stucco. If the surface of the wall is not expected to

produce adequate bond to the stucco, mechanical

anchorage of the stucco to the wall should be specified

(PCA, 1988).

Walls that had a designated fire rating may have the fire

resistance compromised by cracks that extend through

the thickness of the wall, since the cracks will allow hot

combustion gases to pass through the wall. Epoxy injection will fill the cracks, but the heat from a fire will

cause epoxy to melt. Testing has shown that unprotected concrete walls with epoxy-filled cracks up to 1/4-

inch wide could have about 3 inches of the epoxy

burned out during a standard fire (Plecnick and Pham,

1980). The burned-out epoxy can be cleaned out and the

crack re-injected. A final plaster coating on the wall can

significantly reduce epoxy burnout.

References

PCA, 1988, Portland Cement Plaster (Stucco) Manual,

Portland Cement Association, Skokie, Illinois.

Plecnick, J.M. and M.G. Pham, 1980, Final Report on

Fire Testing of Epoxy Repaired Shear Walls, Structures Laboratory Report # SL80-7-11, California

State University, Long Beach, Long Beach, California.

Repair of Earthquake Damaged Concrete and Masonry Wall Buildings

1.......-

FEIVA 308 25
Chapter 4: Implementation

REPAIR GUIDE Repair Type: Cosmetic Repair

REPOINTING MORTAR Materials: Reinforced Masonry,

Unreinforced Masonry

Purpose

Repointing is the process of removing deteriorated mortar from the joints of a masonry wall and replacing it

with new mortar. Repointing may be required to repair

earthquake-damaged mortar joints or to repair deterioration of mortar joints caused by weathering. Properly

installed repointing restores the visual and physical

integrity of the masonry. Improperly installed repointing can detract from the appearance of the building and

can cause physical damage to the masonry.

A method known variously as "grouting," "scrub

coats," "slurry coats," or "slur coats" is sometimes sold

as a substitute for repainting. The process involves

brushing a thin coat of mortar over all masonry units

and joints, and when the mortar is dry, brushing it off

the masonry units. This technique has a life expectancy

of only a few years, it masks the joint detailing or tooling, and the residue is difficult to remove from the

masonry. This technique is not a substitute for repointing, and should never be used on historic buildings.

RepairMaterials

The new (repointing) mortar should:

* match the existing mortar in color, texture, and

detailing. The best way to match the color is by

using sand similar in color, size and shape of grains

as the original mortar. As the mortar weathers, the

sand gives the mortar its characteristic color and texture. Pigments should not be used to match mortar

color, unless matching cannot be achieved with

sand, since pigments will fade over time.

* be softer, in terms of compressive stiffness, than the

adjacent masonry units. A new mortar that is too

hard will cause stresses in the wall (from thermal

and moisture expansion and contraction, and settlement) to be accommodated by the masonry units

rather than the mortar, causing cracking and spalling

of the masonry.

* be as soft as or softer than the original mortar, in

terms of compressive stiffness.

Many older historic buildings used a lime mortar. If a

lime mortar was originally used, the building should be

repointed with a lime mortar. New cement mortar

should not be used, as it can cause deterioration of the

wall by not allowing moisture out of the wall and by

introducing salts. If a cement or cement-lime mortar

*wasoriginally used, the building should be repointed

with a similar mortar.

Masonry cement should not be used for repainting mortar. Appropriate mortar materials are as follows:

e Lime should conform to ASTM C207, Type S,

Hydrated Lime for Masonry Purposes.

* Cement should conform to ASTM C150, Type I or

II, low alkali, nonstaining Portland cement.

* Sand should conform to ASTM C144 to ensure

proper gradation and freedom from impurities. Sand

color, size, and texture should match the original as

closely as possible.

* Water should be clean and free from significant

amounts of acids, alkalis, or organic material.

The mortar mix for historic buildings should be specified by the preservation consultant. Generally,it should

comply with the UBC Standard No. 24-9 (ICBO, 1994)

and ASTM C270, Standard Specificationfor Mortarfor

Unit Masonry. Material proportions should be given

by volume.

Mortar samples should be made before starting work on

the building. Samples of the proposed mortar should be

made, allowed to cure, then broken open. The broken

surface of the new mortar should be compared with a

broken surface of the original mortar to determine

whether they match.

Equipment

In general, the old mortar should be removed using a

hammer and cold chisel. Power saws should not be used

as they can damage the adjacent masonry units. A dallett-style pneumatic carving tool can be used successfully by experienced masons to remove old mortar.

Repair of Earthquake Damaged Concrete and Masonry Wall Buildings

:CR

FEMA 308 26
Chapter 4: Implementation

X1(I'AILKItUluk,

continued

Execution

The contractor should demonstrate repointing on a test

panel in an inconspicuous area of the building that

includes all types of masonry, joint types, and problems

to be encountered on the job. Usually a 3-foot by 6-foot

test panel is sufficient. Once the test panel is approved,

work can begin.

Thejoint is prepared by removing the mortar to a depth

of 2 l/2times the width of the joints. For most masonry,

this depth is l/2to 1 inch. Any loose or disintegrated

mortar beyond this minimum depth should be removed.

Care should be taken not to damage the existing adjacent masonry units. Loose material in the joints should

be removed with a brush, and the joint flushed with a

water stream.

The mortar is prepared by measuring all dry ingredients

and mixing them together. When ready to use the mortar, add water to bring it to a consistency that is somewhat drier than conventional masonry mortar.

The joints should be damp, but with no standing water.

Install new mortar only when temperature is between 40

and 950 F During hot weather, repoint on the shady side

of the building, or install netting over the scaffolding to

provide shade. Mortar is packed into the joint in 1/4-

inch-thick layers, leaving no voids, until the joint is

filled. Tool the joint to match the original mortar. If

desired, after mortar has initially hardened, stipple with

a brush to give a weathered appearance. Remove excess

mortar from adjacent masonry using a bristle brush.

Keep the pointing mortar damp for 2 to 3 days, using a

fine-mist hand sprayer.

Quality Assurance

e Make sure that only damaged or deteriorated joints

requiring it are repointed.

* Require samples of the repointing mortar to verify

the mortar matches the original.

* Require test panels to verify the quality of workmanship and retain them throughout the job for comparison.

* Inspect joints after preparation to verify that enough

old mortar has been removed.

* Make surejoints are dampened before application of

- new mortar.

* Make sure that joints are being tooled to match original appearance. Often, the corners of the masonry

units are worn back and if the joints are completely

filled to the surface, the joints will be considerably

wider than original, ruining the appearance. If the

corners of the masonry units are spalled or worn, the

mortar will have to be slightly recessed in the joint

to achieve the original appearance.

Limitations

The owner, consultant, and contractor should realize

that repainting can be a time-consuming and expensive

repair. (However, proper repainting is the only longlasting repair for cracked or deteriorated mortarjoints.

A good repointing job can last up to 50 years.)

References

ASTM, 1997, Standard Specification for Aggregatefor

Masonry Mortar, C144-97, American Society for

Testing and Materials, West Conshohocken, Pennsylvania.

ASTM,1997,StandardSpecificationforPortland

Cement, C150-97a, American Society for Testing

and Materials, West Conshohocken, Pennsylvania.

ASTM,1997,StandardSpecificationfor Hydrated

Lime for Masonry Purposes,,C207-97, American

Society for Testing and Materials, West Conshohocken, Pennsylvania.

ASTM,1997,StandardSpecificationfor Mortarfor

Unit Masonry, C270-97, American Society for

Testing and Materials, West Conshohocken, Pennsylvania.

ICBO, 1994, Pointing of Unreinforced Masonry Walls,

Uniform Building Code Standard No. 24-9, International Conference of Building Officials, Whittier, California.

Mack, R.C., T.P Tiller, & J.S. Askins., 1980, Preservations Briefs: 2 Repointing Mortar Joints in Historic

Brick Buildings, U. S. Depart of the Interior, Heritage Conservation and Recreation Service, Technical Preservation Services Division, U. S.

Government Printing Office, Washington, D.C.

Repair of Earthquake Damaged Concrete and. Masonry Wall Buildings

.. R. 2

TX TX - -TT-T -

FEMA 308 27
Chapter 4: Implementation

REPAIR GUIDE ERepairType: Cosmetic Repair

Structural Repair

CRACK INJECTION - EPOXY Materials: Concrete

(ZR3/SR I Reinforced Masonry

Purpose

Crack injection consists of applying a structural binding

agent into a crack for the purpose of filling the crack

and adhering to the substrate material. Various types of

materials and methods can be used for crack injection

depending on the required performance. For concrete

and fully-grouted, reinforced masonry walls, epoxy is

typically injected into cracks under pressure.

RepairMaterials

* ASTM Standard C881, Type I, low-viscosity grade

epoxy.

e Other materials such as fine cementitious grout and

urethanes can also be used for structural bonding.

Equipment

* Pressure injection machine with mixing nozzle at the

tip capable of injecting with pressures of 300 psi.

o Porting devices installed with specialized drill bits.

* Equipment to monitor pressure and mixing.

Execution

Prior to injection, loose material should be removed

from the cracks. Cracks can be injected through surface-mounted ports or into drilled entry ports, although

surface-mounted ports are used by most contractors

(Krauss et al., 1995). The injection ports are located

along the length of the crack and should be spaced at a

distance roughly equal to the thickness of the wall,

depending on the viscosity of the material and the manufacturer's recommendations. Ports should be drilled

with drills that prevent fines from remaining in the

crack. When full-thickness repairs are required, it is

beneficial to seal both surfaces of the wall along the

crack, except for the entry ports. When epoxy injection

is for cosmetic purposes or when less than full-thickness repairs are acceptable, the crack is sealed only on

the injection side.

Before injecting, the epoxy should be pumped into a

paper cup until the material appears to be completely

mixed. Cracks are injected starting at the bottom of vertical and diagonal cracks, changing to the next port as

the epoxy appears there. Splitting tubes can be used so

that the epoxy can be pumped into multiple ports simultaneously. Previously injected ports should be sealed. If

necessary, the surface is ground smooth to remove the

surface seal and leakage after the epoxy has set. Grinding should not be started until the epoxy has cured.

Quality Assurance

Personnel experienced in epoxy injection should be

used for the work. The mixing equipment should be

evaluated before beginning the work to verify proper

operation. Samples should be prepared and tested for

consistency of the epoxy and bond strength. Twice daily

during the epoxy work, the mix ratio should be tested to

ensure it is within the manufacturer's tolerances. The

mix test should be conducted at the pressures at which

the work is being done.

The effectiveness of crack injection can be confirmed

by alternative methods. These methods, however, only

test the penetration of the epoxy into the cracks; they do

not check the adequacy of the bond of the epoxy to the

substrate.

Core holes can be drilled through the cracks after injection and visually examined to verify that the epoxy has

penetrated the cracks. Typically, 2-inch diameter core

holes are specified. The spacing of the core holes

should be between 50 feet and 100 feet (Trout, 1991)

Nondestructive evaluation methods can be used to verify the effectiveness of the epoxy penetration (Guedelhoefer and Krauklis,1986).

28 Repair of EarthquakeDamaged Concrete and Masonry Wall Buildings IFEMA 308
Chapter 4: Implementation

REPAIR GUIDE

continued CR 3SR 

Limitations

Moisture on the crack surface can reduce the bond of

the epoxy to the crack faces. If the crack contains contaminants, it should be cleaned to remove both the contaminants and any moisture that will reduce the bond.

Crack widths as small as 0.002 inch in width can be

injected with epoxy. Crack widths up to 0.012 inch can

be tolerated in reinforced concrete in humid or moist air

conditions (ACI, 1994a). A low-viscosity epoxy will

not be effective for crack widths greater than 1/8 inch.

For widths greater than 1/8 inch a medium-viscosity

epoxy should be used. For surface crack widths greater

than 1/4 inch, epoxy pastes or gels should be used. For

cracks that are wider at the surface, an epoxy paste can

be applied at the surface and a low-viscosity epoxy

injected through the cured paste to the smaller, interior

cracks.

Epoxy injection can also restore the bond of reinforcing

bars (French et al., 1990). For the epoxy to restore the

bond, there needs to be a sufficient amount of surface

cracking that intersects the debonded reinforcing for the

epoxy to penetrate along the surface of the reinforcing

bar.

The operator must be attentive to the amount of epoxy

being injected relative to the spacing of the ports. A theoretical quantity of epoxy to be used can be calculated.

Injection should stop if the amount required exceeds 50

percent more than the calculated amount (ACI, 1994b).

This is particularly important when injecting reinforced

masonry walls that may contain large voids. Excessive

amounts of epoxy may also indicate that epoxy is leaking out through a crack or joint.

If the ports are spaced too far apart for the viscosity of

the epoxy, the epoxy may harden before reaching the

adjacent port. Conversely, if the ports are too closely

spaced, the epoxy may not reach the full thickness of

the wall before bleeding out of the adjacent port.

After finding satisfactory penetration from a number of

cores, the spacing of subsequent cores can by increased,

provided the same operator, epoxy, and equipment are

used and the environmental and structural conditions

remain the same.

Nondestructive evaluation (NDE) methods should be

used on the cracked wall prior to repairs and should be

calibrated for the repaired condition using undamaged

sections of wall. However, NDE methods may not be

effective in evaluating the penetration into small cracks.

References

ACI Committee 224R, 1994a, "Control of Cracking in

ConcreteStructures" ACI Manualof Concrete

Practice, Detroit, Michigan.

ACI Committee 503R, 1994b, Use of Epoxy Compounds with Concrete ", A CI Manual of Concrete

Practice, Detroit, Michigan.

ASTM, 1990, Standard Specification for Epoxy-ResinBase Bonding Systems for Concrete, C881-90,

American Society for Testing and Materials, West

Conshohocken, Pennsylvania.

French, C.W.et al, 1990, "Epoxy Repair Techniques for

Moderate Earthquake Damage", ACI Structural

Journal, July-August 1990, American Concrete

Institute, Detroit, Michigan, pp 416-424.

Guedelhoefer, O.C. and A.T. Krauklis, 1986, "To Bond

Or Not To Bond", Concrete International, August

1986, Detroit, Michigan, pp. 10- 15.

Krauss, P.D, et al, 1995, Evaluation of Injection Materialsfor the Repairof Deep Cracksin Concrete

Structures, Technical Report REMR-CS-48, US

Army Corps of Engineers, Washington, DC.

Trout, J.F., 1991, "Quality Control on the Injection

Project", Concrete International, December 1991,

American Concrete Institute, Detroit, Michigan,

pp 50-52.

FEM\IA308 Repair of Earthquake Damaged Concrete and Masonry Wall Buildings 29
Chapter 4: Implementation

REPAIR GUIDE Repair Type: Structural Repair

CRACK INJECTION - GROUT Materials: Concrete,

SR2 >EzraAas V> Reinforced Masonry,

Unreinforced Masonry

Description Equipment

Where cracks along the mortar joints in unreinforced The following equipment is typically required to permasonry walls produce horizontal offsets in the plane of form this work: mixing equipment and pump, pressurethe wall, the cracks can be repaired by injection of fine monitoring system. Additional equipment may be necgrout into the cracks. The grout fills the cracks with essary, depending on the local conditions.A rotary drill

material that bonds to the masonry. The grout can also with masonry bits with vacuum chucks is useful in prefill voids within the wall, such as in the collar joint. If venting dust from accumulating in the hole.

the bond of the grout is at least equal to the bond of the

original mortar, the repaired wall will have at least the Execution

same strength and stiffness as the pre-earthquake condi- The walls are prepared by removing loose mortar from

tion. Since the grout can also fill pre-existing voids open joints. The cracks are flushed with water and then

within the wall, some improvement may be realized, but filled with pre-hydrated mortar, which is tooled to

should not be expected. match the existing joints. Loose bricks should be

removed and reset with mortar.

RepairMaterials

The material used for injection is grout. Removable Injection holes are drilled at head joints or cracked

loose bricks will require mortar. The grout is typically brick, through to the inner wythe in each course,

composed of sand, portland cement, lime, and fly ash. although not entering any air space. Verification ports

Recommended proportions are presented by the City of are drilled 8 to 12 inches to each side of the injection

Los Angeles Rule of General Application (RGA) holes. The holes are flushed with water.

No. 1-91 (City of LA, 1991). Variations may be

required based on local material availability and other Grout is mixed and then pumped into the holes. Typical

requirements. pressures are 10 to 30 psi. Injection should start at the

bottom and work upwards. Grout is injected at a port

Other proportions and materials can be used. It is rec- until grout flows from the adjacent holes. All of the

ommended that the materials and proportions be veri- holes along a horizontal joint are filled before moving

fied for use in the subject application by testing before to the next higher mortar joint.

implementation.

When the grout has set, the holes are pointed with mortar.

30 Repair of Earthquake Damaged Concrete and Masonry Wall Buildings FEM.A 308
Chapter 4: Implementation

1nTntA Twi r'TrTnT narAjlt %xUIlLz

continued

Oualitv Assurance

For work within the City of Los Angeles, contractors

performing grout injection must be certified by the

department of Building and Safety. The certification

process is described in the RGA and generally involves

a meeting with an Earthquake Repair Inspector and a

demonstration of the procedure (City of Los Angeles,

1991).

To perform the grouting properly, the work requires a

minimum crew of two certified persons;.one as a foreman, and one as a nozzleman. The foreman is responsible for coordination, verifying the pressure of the grout,

and batching the grout. The nozzleman is responsible

for operating the injection nozzle at the wall.

Before injecting grout, all of the injection and verification holes should be inspected to verify the depth of the

holes. During the injection, the grout mixture and injection pressure should be continuously monitored for conformance with the specifications. The verification holes

should be watched to verify that the grout is filling the

voids. After injecting, core holes should be drilled and

visually inspected to verify that the grout filled the

voids.

Limitations

This procedure has been demonstrated to be effective

for cracks ranging from 0.007 inch wide up to 3/4inch

wide. Epoxy resins are not recommended for injection

into masonry since the properties of the epoxy will not.

be compatible with those of the masonry. Admixtures

such as superplasticizers can aid in the fluidity of the

grout so that the grout fills more of the voids.

Existing grout in the collar joints will prevent some dispersion of the injected grout. Crack injection with grout

may not restore all of the compressive strength of the

masonry, since the grout may not penetrate all of the

micro-cracks (Manzouri et al., 1996).

Increasing the pump pressure is not effective at increasing the distance of dispersion of the grout from the

injection port (Kariotis and Roselund, 1987). The dispersion can be increased by increasing the fluidity of

the grout mixture.

References

City of Los Angeles, 1991, "Crack Repair Of Unreinforced Masonry Walls With Grout Injection," Rule

of GeneralApplication- RGANo. 1-91.

Kariotis, J.C and N.A Roselund, 1987, "Repair of

Earthquake Damage to Unreinforced Masonry

Buildings,"Evaluationand Retrofitof Masonry

Structures, Proceedings of the Second USA-Italy

Workshop on Evaluation and Retrofit of Masonry

Structures, pp 201-214.

Manzouri, T., M.P. Schuller, P.B. Shing, and B Amadei,

1996, Repair and Retrofit of Unreinforced

Masonry Structures, Earthquake Spectra, Vol. 12,

No. 4, Earthquake Engineering Research Institute,

Oakland, California, pp 903-922.

Repair of Earthquake Damaged Concrete and Masonry Wall Buildings

SR: 2-:-

FEMA 308 31
Chapter 4: Implementation

REPAIR GUIDE Repair Type: Structural Repair

SPALL REPAIR Materials: Concrete

: 2 ::i3 5 1 ~~~~~~~~~~~~Reinforced Masonry,

Unreinforced Masonry

Description Execution

Spalls are small sections of wall that become loose or The concrete or reinforced masonry wall should have

dislodged. Spalls can occur in both concrete and all loose material removed with chipping hammers to

masonry walls. The missing material is replaced with a expose sound substrate. If reinforcing bars are signifisuitable patch. The material used for the patch must cantly exposed, the concrete or grout should be

have structural and thermal properties similar to the removed to provide sufficient clearance around the bar

existing material. The materials and procedures for the for the patch to bond to the full diameter. The perimeter

patch will also depend on the size and location of the of the spall should be cut with a saw or grinder to create

spall and the wall material. These spall repair procedure an edge perpendicular to the original surface.

can be used for concrete, reinforced masonry, infill

materials, and unreinforced masonry walls. Shallow spall repairs are those that are less than about

3/4 inch deep (Krauss, 1994). Deep spalls require correRepair Materials spondingly course aggregate to be added to the repair

For concrete and reinforced masonry walls, the repair mortar. For large patches, new steel dowels should be

material is typically a repair mortar mix, which can be set into the substrate with epoxy and placed so that they

based on inorganic materials, such as Portland cement extend into the patch.

and latex-modified concrete, or organic materials, such

as epoxy and polyester. The mortar mix will include The substrate should be prepared in accordance with the

sand and may also include pea gravel. For thick repairs, recommendations of the manufacturer. Separate bonda mechanical anchorage, using epoxy-embedded dow- ing agents do not generally have to be applied to the

els, may need to be added to secure the patch. surface. The mortar is first scrubbed onto the surface

with a stiff broom or brush and then applied with a

Equipment trowel in lifts. The surface is finished to match the

The following equipment is typically required: appearance of the original wall surface. The patch is

3 Chipping hammer and grinders or concrete saws then cured in accordance with manufacturer's recom-

* Mixing and placing tools mendations.

32 Repair of Earthquake Damaged Concrete and Masonry Wall Buildings FERMA308
Chapter 4: Implementation

REPAIR GUIDE

continued FSRf3.

Oualitv Assurance

Contractors conducting the repairs should be familiar

with the repair materials and procedures. If proprietary

mortars are specified, the contractor performing the

repairs should be certified by the manufacturer of the

mortar.

The most critical aspect of the performance of a patch is

the bond of the repair material to the substrate (Holl and

O'Connor, 1997). The bond strength can be evaluated

by a pull-off test, as described in ACI 503R (AC1,

1994). The quality of the bond can also be assessed

using nondestructive testing techniques such as Impact Echo or SASW.

Limitations

When patching spalls in unreinforced masonry walls

and infill frame walls, it may be difficult to obtain

repair materials that have properties similar to the

masonry. The repairs may also need to consider the

changes to the appearance of the wall due to the patch. Mock-up tests should be conducted to verify the appli- cability of the repairs prior to wide-spread use throughout a building.

These spall repair procedures are suitable for most

spalls in concrete or reinforced masonry that are up to %/2

cubic foot in volume. Larger spalls in concrete walls

may require using formwork and portland cement concrete as the patch material or by the use of shotcrete.

Large spalls in reinforced and unreinforced masonry walls may require removing damaged masonry units

and replacing them with new, similar units.

Most repair mortars will experience some shrinkage after curing. Therefore, a visible crack may develop around the patch. If the appearance of this crack will be

unacceptable, a nonshrink grout mixture should be used

or provisions made to conduct cosmetic repairs several

days or weeks later.

References

ACI Committee 503, 1994, "Use of Epoxy Compounds with Concrete", ACI 503R-93, ACI Manual of

Concrete Practice, American Concrete Institute,

Detroit, Michigan.

Holl, C.H and Scott O'Connor, 1997, "Cleaning and

Preparing Concrete before Repair", Concrete

International, March 1997, American Concrete

Institute, Detroit, Michigan, pp 60-63.

Krauss, P.D. 1994, Repair Materials and Techniquesfor ConcreteStructuresin NuclearPowerPlants,

NRC JNC No. B8045, US Nuclear Regulatory

Commission, Washington, DC.

FEMA 308 Repair of Earthquake Damaged Concrete and Masonry Wall Buildings 33
Chapter 4: Implementation

REPAIR GUIDE

REBAR REPLACEMENT

'S R 4 ..

Descrilption

Mechanical connections can be used in lieu of conventional lapped bar splices to connect or splice two pieces

of reinforcing bar. Mechanical connections are particularly useful for connecting new bars to existing bars

already embedded in a masonry or concrete structure.

They are also useful for repairing damaged structures.

Where fractures have occurred in reinforcing bars, or

where conventional lapped bar splices have failed, it

may be possible to repair the discontinuity by means of

a mechanical connection. When repairing certain types

of damage, it is necessary to cut out the damaged length

of reinforcing bar and to replace it with new bar. In this

instance, two mechanical connections are required,

where one connection is installed at each end of the

replacement bar.

RepairMaterials

The materials used to make a mechanical connection

include the mechanical connection device itself,

obtained from the splice manufacturer, and the reinforcing bar being connected. Some mechanical connections

use a filler material, such as cementitious grout or a

molten metal, typically provided by the splice manufacturer. Most mechanical devices can be used with either

ASTM A615 or ASTM A706 reinforcing bar. Certain

devices require use of reinforcing bar provided by the

splice manufacturer.

Numerous types and configurations of proprietary

mechanical connections are available from several difRepair Type: Structural Repair

Materials: Concrete

Reinforced Masonry

ferent manufacturers. Mechanical connection configurations include:

* Cold-swaged sleeves

* Grout-filled sleeves

* Steel-filled sleeves

e Upset-and-threaded couplers

* Tapered-threaded couplers

• Sleeve with wedge

e Sleeve with lock screws

These and other devices are further described in ACI

439.3R-9, Mechanical Connections of Reinforcing

Bars, by Committee 439 of the American Concrete

Institute (ACI) and also in Reinforcement Anchorages

and Splices, by the Concrete Reinforcing Steel Institute

(CRSI). Detailed technical information is obtained from

the proprietary manufacturers.

Equipment

Many proprietary connections can be assembled using

readily-available hand or power tools, such as ordinary

wrenches, calibrated wrenches, or non-impact torque

wrenches. Assembly of some connector devices

requires special equipment such as an hydraulic press.

Tools required vary with the type of connection. The

splice manufacturer should be consulted for specific

equipment requirements.

Repair of Earthquake Damaged Concrete and Masonry Wall Buildings

___ _ _ _

FEIIA 308 34
Chapter 4: Implementation

Execution

Unless threaded, the reinforcing bars to be connected

need no special preparation beyond a clean-cut end.

Connections to bars embedded in masonry require limited removal of some surrounding masonry in order to

provide room for insertion of the splice device (but the

volume of masonry removed to make a mechanical connection is generally less than that required to make a

conventional lapped bar splice). Generally, bars can be

set loosely into place, with final alignment made just

before completing the splice assembly. The final completion of the connection is carried out in accordance

with the instructions provided by the manufacturer.

Quality Assurance

Prior to completing final assembly of the connection, it

should be verified that the proper length of reinforcing

bar has been inserted into the splice device and that the

bars are correctly aligned. There are also other quality

assurance checks that will vary depending upon the particular type of connection being used. For example,

with grout-filled sleeve splices, the slump of the grout

mixture should be measured. Again, the manufacturer

should be consulted for detailed instruction regarding

quality assurance.

For work within the City of Los Angeles, mechanical

connection devices must have a General Approval

issued by the Department of Building and Safety. As

part of the approval process, a series of cyclic tests and

tensile strength tests are carried out on sample mechanical connections. The application for General Approval

is typically undertaken by the manufacturer of the

mechanical connection in advance of any use of the

product within the City of Los Angeles. However, the

use of non-preapproved devices may be permitted on a

case-by-case basis, upon submission of acceptable test

data to the Department of Building and Safety.

to inelastic cyclic loading, such as bars in or adjacent to

a potential or actual plastic-hinge zone, it is also recommended that inelastic cyclic test data be provided by the

device manufacturer. The test data should graphically

illustrate the load-deflection behavior of the connectorand-bar system under repeated inelastic load cycles, and

the post-cycling residual tensile strength of the system

should approach or exceed the specified tensile strength

of the unspliced reinforcing bar. The proposed ACI

Standard includes such testing and strength criteria.

Limitations

There are some limitations on the use of mechanical

splices, but a limitation for one device may not apply to

a different device. Threaded devices are generally not

suitable for connections involving existing bars embedded in concrete because the embedded bar cannot be

threaded. The physical size of some devices may prevent their use in the occasional application with tight

size constraints.

References

ACI Committee 439, In Progress, Standard Specificationfor MechanicalReinforcementSplicesfor

Seismic Designs using Energy Dissipation Criteria, ACI 439, American Concrete Institute, Detroit,

Michigan.

ASTM, 1996, Standard Specificationfor Deformed and

PlainBillet-SteelBarsfor ConcreteReinforcement,

A615/A615M-96a, American Society for Testing

and Materials, West Conshohocken, Pennsylvania.

ASTM, 1996, Standard Specificationfor Low-Alloy

SteelDeformedand Plain Barsfor ConcreteReinforcement, A706/A706M-96b, American Society

for Testing and Materials, West Conshohocken,

Pennsylvania.

For mechanical connection of reinforcing bars subject

Repair of Earthquake Damaged Concrete and Masonry Wall Buildings

REPAIR GUIDE

continued SR1', T4'. ::. 1 .0 0 10t' I ..I..S 1. 

FEMA 308 35
Chapter 4: Implementation

REPAIR GUIDE Repair Type: Structural Repair

WALL REPLACEMENT Materials: Concrete

Reinforced Masonry,

Unreinforced Masonry

Description

Wall replacement requires the removal of an existing

wall and replacement with a new wall. The removal of

the existing wall should be performed carefully so that

the existing reinforcing bars, if present, can be spliced

to new reinforcing. The construction of the new wall

should match, as closely as possible, the construction of

the existing wall.

RepairMaterials

For concrete replacement walls, the strength of the concrete should be specified to be at least 3000 psi.

For reinforced masonry walls, open-ended units should

be specified. These will allow easier installation within

the existing structure. The masonry units, mortar, and

grout used should conform to the requirements of ACI

530/ASCE 6.

Eguipment

The equipment used will depend on the construction of

the existing wall and the methods used to install the new

wall. The following are general equipment items that

might be needed for removal and replacement of walls:

o Chipping tools for removal of the wall

* Light chipping tools for preparing the surface of the

remaining structure

* Equipment for mixing and placing the concrete,

grout, or mortar

Execution

If the existing wall is a load-bearing wall, shoring must

be installed adjacent to the wall to support the gravity

loads while the wall is missing.

The existing wall is carefully removed using saws and

chipping tools. Around the perimeter of the opening,

care should be exercised to avoid damaging the remaining portions of the structure and to avoid damaging the

reinforcing bars, if present.

The surface of the surrounding structure should be prepared for the new material. For concrete and reinforced

masonry, the surface of the structure should be roughened to an amplitude of 1/4inch (ACI, 1995).

New reinforcing bars should be spliced to existing bars.

If new reinforcing bars are required to be attached to the

existing structure, these bars should be anchored to the

existing structure by setting them into holes with epoxy.

The depth of the hole should be sufficient to develop the

strength of the bar. The manufacturer of the epoxy

should be consulted for the proper depth of the bar and

for the instructions for installing the epoxy.

The new concrete can be placed by forming the wall or

by applying shotcrete. Shotcrete application should follow the guidelines for shotcrete overlays (SEl). For

cast-in-place walls, concrete is placed through an access

hole near the top of the formwork. Additional holes are

required for inserting vibrators.

Cast-in-place concrete walls should be wet cured following placement. A curing compound should be used

following the wet cure.

The cementitious materials in the new wall will experience drying shrinkage. Since the existing structure will

not shrink, the shrinkage will cause a crack to form, typically along the top of the wall. After a significant

amount of the drying shrinkage has occurred, typically

after two to four months, the crack should be filled with

epoxy.

Repair of Earthquake Damaged Concrete and Masonry Wall Buildings

SR5~ 

36 FlEMlA308
Chapter 4: Implementation

REPAIR GUIDE

continued SR -

Following rebar installation, open-ended masonry units

can be installed around the reinforcing bars. When the

height of the lift of grout is more than 5 feet, holes are

left at the top and bottom for installation of grout. If

open-ended units are used, access holes are needed

every 2 to 3 feet. If closed-end units are used, cleanouts

are needed for each cavity. Grout is pumped in through

a hole in the top of the wall. The hole at the base is used

to verify that the grout has flowed down to the base.

After grout is observed at the bottom hole, the hole is

sealed to prevent the grout from flowing out of the wall.

OualitUAssurance

The mix design for the concrete, grout, or mortar should

be submitted by the contractor and reviewed prior to

use. Concrete core samples should be required from

each batch of concrete used. The cores should be tested

in accordance with ASTM C39 (ACI, 1995). Masonry

units should be tested in accordance with the appropriate standards referenced in ACI 530/ASCE 6-92 (ACT,

1992). Concrete masonry units should be tested using

ASTM C140. Brick should be tested using ASTM C 67.

The layout and anchorage of the reinforcing steel

should be inspected before forming the concrete or

installing the masonry units. A special inspector familiar with epoxy installation should observe installation of

the epoxy. A percentage of the epoxy-anchored dowels

should be load-tested to at least 50 percent of the yield

strength of the bar.

Limitations

If the wall to be replaced was constructed with unreinforced masonry, the local building department may not

allow replacement with a new unreinforced masonry

wall. If the construction of the new wall is substantially

different from the previous wall, the strength and stiffness behavior could adversely affect the performance of

the building. It may be possible either to negotiate a

compromise with the local building department or to

introduce a weak link in the wall to prevent its increased

stiffness or strength from affecting the behavior of the

remainder of the building.

The shrinkage cracks that develop at the top of the wall,

if not filled with epoxy or grout, will produce a weakened joint. This weakened joint may cause the behavior

mode of the wall to be different from that of the original

wall.

References

ACI Committee 530/ ASCE Committee 6,1992, Specifications for Masonry Structures, American Society of Civil Engineers, New York, New York.

ACI Committee 318, 1995, Building Code Requirements for Structural Concrete and Commentary,

American Concrete Institute, Detroit, Michigan.

ASTM, 1997, Standard Test Methods for Sampling and

Testing Brick and Structural Clay Tile, C67-97,

American Society for Testing and Materials, West

Conshohocken, Pennsylvania.

ASTM, 1997, Standard Test Methods of Sampling and

Testing Concrete Masonry Units, C140-97, American Society for Testing and Materials, West Conshohocken, Pennsylvania.

FEIVIA 308 Repair of Earthquake Damaged Concrete and Masonry Wall Buildings 37
Chapter 4: Implementation

REPAIR GUIDE Repair Type: Structural Enhancement

STRUCTURAL OVERLAY - Materials: Concrete

SE ACONCRETE Reinforced Masonry,

Unreinforced Masonry

Description

Overlay concrete is applied pneumatically (shotcrete) or

as a cast-in-place layer onto one or both surfaces of the

wall. The concrete is reinforced and attached to the

existing structure to enable the concrete to provide supplemental strength to the wall. Two different processes

for shotcrete are used in practice: wet mix and dry mix.

In the wet-mix process, all ingredients are premixed and

the wet mixture delivered to the nozzle where it is shot

toward the surface. In the dry-mix process, the dry

cement and aggregate are delivered to the nozzle where

they are mixed with water while being shot out of the

nozzle to the surface (Warner, 1995a).

RepairMaterials

Portland cement, aggregate, and water are needed. The

mixing and proportions will depend on a number of factors, including the process (wet-mix process or dry-mix

process)

Equipment

The basic equipment includes a mixer, pump or gun,

compressor, hoses, and nozzles. (ACI, 1994a, b)

Execution

The surface of the existing wall should be prepared by

removing loose or damaged material. The surface

should be chipped or scarified to avoid abrupt changes

in dimension (ACI, 1994b). Reinforcing steel is

installed and securely anchored into the existing slabs

above and below using dowels set in epoxy.

Before applying the shotcrete, the surface of the existing wall should be prewetted so that specified shotcrete

moisture content will not be absorbed into the existing

wall (Warner, 1995b). Forms or guide wires are

installed to provide alignment control for the application, finishing, and verification of sufficient cover for

the reinforcing steel. The nozzleman should direct the

shotcrete from the nozzle to the surface with a steady,

uninterrupted flow. The angle of the nozzle should be

kept as close as possible to perpendicular to the surface

of the wall to reduce rebound. A slight angle is required

when directing the shotcrete around reinforcing steel to

avoid shadowing behind the bars. The shotcrete is

applied in several passes starting at the base of the wall,

building up the thickness slightly beyond the guide

wires.

The shotcrete surface should be finished as required

using the guide wires. The shotcrete should then be wet

cured for at least one day and preferably seven days

(Warner, 1995c). Following the wet cure, a final cure

using liquid curing membranes, or other moistureretaining coverings should be provided.

Quality Assurance

The quality of the shotcrete operation is highly dependent on the skill of the nozzleman. Each nozzleman

used on a project should be certified and have sufficient

experience in similar applications. The nozzlemen can

be qualified by completing a large or full-scale mock-up

test representing the thickness and congestion conditions that will be encountered.

The mix design for the shotcrete should be submitted by

the contractor for review. Small test panels should be

prepared in accordance with ASTM C1140, Standard

Practicefor Preparingand TestingSpecimensfrom

Shotcrete Test Panels (ASTM, 1997), by each nozzleman at the beginning of each day and at the start of each

batch of shotcrete. The sample panels should be cured

in the same manner as the walls. Core or cube samples

should be removed from each panel and tested to verify

the compressive strength .and quality.

A qualified inspector should continuously inspect the

shotcrete application. The inspector should verify that

the materials, placement, finishing, and curing are conducted in accordance with the specifications.

Repair FEMA 308 of Earthquake Damaged Concrete and Masonry Wall Buildings 38
Chapter 4: Implementation

Limitations

The amount of reinforcing steel in the shotcrete wall

should be kept to a minimum. This can be accomplished

by using small bars, staggering bars when more than

one layer of reinforcing is required (Warner, 1994), and

using mechanical splices rather than lap splices. Excessive reinforcing prevents the shotcrete from being

placed completely behind the reinforcing steel and also

traps the rebound.

Shotcrete bonds well to clean concrete and masonry

surfaces. The use of bonding agents is not recommended.

The wet-mix and dry-mix processes have different production requirements and require different skills of the

operators. However, both can produce satisfactory

results. The dry-mix process is capable of producing

higher compressive strength, can be transported longer

distances, and produces a material that generally has

less shrinkage. The wet-mix process requires less skill

of the nozzleman in order to mix uniformly the water

with the cement and aggregate and is capable of greater

production. The choice of which process to use depends

on the capabilities and experience of the contractor.

An apprentice or blow man is recommended to be

present to remove rebound, which is the aggregate and

cement paste that bounces off the surface during shotcreting. The blowman should prevent the rebound from

being mixed in with the shotcrete.

Reinforcing bars should generally not be larger than # 5

bars (ICBO, 1994). However, if larger bar sizes are

required, the contractor should be required to perform

mockup tests to demonstrate that the shotcrete can

effectively be placed around the reinforcing bars. The

mock-ups should be tested by core drilling or saw cutting samples at the reinforcing bars. The samples should

then be visually analyzed to verify complete coverage

of shotcrete around the bars. Full-time inspection of the

shotcrete operation in the vicinity of the large bars is

also recommended.

References

ACI, 1994a, "Guide to Shotcrete" ACI 506-90, ACI

Manual of Concrete Practice, American Concrete

Institute, Detroit, Michigan.

ACI, 1994b, "Specification for Shotcrete" ACI 506.2-

90,ACI Manualof ConcretePractice,American

Concrete Institute, Detroit, Michigan.

ASTM,1997,StandardPracticefor Preparingand

TestingSpecimens from Shotcrete TestPanels,

C1140-97, American Society for Testing and Materials, West Conshohocken, Pennsylvania.

ICBO, 1994, Uniform Building Code, International

Conference of Building Officials, Whittier, California.

Warner, James, 1994, "Shotcrete in Seismic Repair and

Retrofit", Seismic Rehabilitation of Concrete

Structures, ACI SP-160, American Concrete Institute, Detroit, Michigan.

Warner, James, 1995a, "Understanding Shotcrete - The

Fundamentals", Concrete International, May 1995,

American Concrete Institute, Detroit, Michigan, pp

59-64.

Warner, James, 1995b, "Understanding Shotcrete - Its

Application", Concrete International, June 1995,

American Concrete Institute, Detroit, Michigan, pp

37-41.

Warner, James, 1995, "Understanding Shotcrete - Finishing, Curing and Quality Control", Concrete

International, August 1995, American Concrete

Institute, Detroit, Michigan, pp 72-75.

Repair of Earthquake Damaged Concrete and Masonry Wall Buildings

REPAIR GUIDE

continued S... -.1

[L.i-4 ... ..1 -:LX`- IC

FEMA 308 39
Chapter 4: Implementation

REPAIR GUIDE Repair Type: Structural Enhancement

STRUCTURAL OVERLAY - Materials: Concrete

;R; <<<<SAE 2 u1 COMPOSITE FIBERS Reinforced Masonry,

Unreinforced Masonry

Description surface to the finish required by the manufacturer of the

Thin glass or carbon fibers woven into a fabric sheet composite fiber.

can be applied to the surface of the wall to enhance the

stiffness and strength of the wall. The fibers are gener- A thin epoxy binding coat is applied to the surface using

ally applied to the surface using an epoxy resin binder rollers. The composite fibers are saturated in epoxy and

and can be oriented in one direction or two directions. are pressed into the binder epoxy with a roller. The

The composite fibers are used as tension reinforcing for number of layers and the orientation of the layers

the wall and can therefore increase the in-plane and out- depends on the design requirements. Additional epoxy

of-plane strength of the wall. may be applied to fully coat the fibers.

Repair Materials The fabric layers should wrap around the edges of the

The typical repair methods use: wall for a distance as recommended by the manufac-

* Carbon-fiber or glass-fiber sheets turer. If a physical interference prevents wrapping the

fabric, anchors should be installed through the fabric

3 Epoxy for bonding the sheets to the wall along the perimeter of the wall and secured to the sub-

@ Anchors for attaching composite fiber sheets to sub- strate. The epoxy is then allowed to cure for at least 24

strate hours, or as recommended by the manufacturer.

* Surface coatings After the epoxy has cured, the wall should be covered

with a nonstructural coating such as paint, plaster, or Eguipment wallboard. Special fire-resistant coatings are also avail-

* Surface preparation equipment such as light chip- able, if needed

ping hammers or sandblasting equipment

* Brushes or rollers are used to apply the epoxy to the Quality Assurance

wall and to the fabric The behavior of the wall following application of the

fiber reinforcement is strongly influenced by the proceExecution dures used to apply the composite fibers to the wall.

Cracks in the walls should be repaired using epoxy or The installation should be carefully monitored to verify

grout injection. Spalls should also be repaired. The wall that the work is being done in accordance with the mansurfaces are then prepared by lightly sandblasting the ufacturer's recommendations.

40 Repair of Earthquake Damaged Concrete and Masonry Wall Buildings FEMA 308
Chapter 4: Implementation

REPAIR GUIDE

continued SE2

The following items should be checked: by debonding of the coating from the wall. Following

* The surface preparation of the wall to verify that all the debonding, the composite fibers fail in a brittle manfinishes and loose materials have been removed ner (Reinhorn and Madan, 1995).

* The mixing of the epoxy to verify that the two com- When composite fibers are installed in an area that

ponents have been ponents~ ~ ~ ~ ~ ~ mixed with mixewithletheprpe the proper havesibeer ~~~~~We propor- requires a fire rating, a supplemental coating will areaptha need

tions to be applied to prevent the epoxy from releasing dan-

* The installed composite fabric to verify that the fab- gerous fumes when heated.

ric has been completely embedded in the epoxy resin

* The overlapping of the fabric sheets and the wrap- References

ping of the sheets around corners, to verify that the Ehsani, M.R. and H Saadatmanesh, 1997, "Fiber Comsheets are anchored as required by the manufacturer posites: An Economical Alternative for Retrofitting Earthquake-Damaged Precast-Concrete

* The curing of the epoxy to ensure conformance with Walls", Earthquake Spectra, Vol. 13, No. 2, Earththe manufacturer's recommendations quake Engineering Research Institute, Oakland,

California, pp 225-241.

Limitations

There are no standards for the design of composite Laursen, P.T., F. Seible, G.A. Hegemier, and D. Innamfibers used for the repair of shear walls. Manufacturers orato, 1995, "Seismic Retrofit and Repair of

of the material can supply references and recommenda- Masonry Walls with Carbon Overlays", Nontions for application. Metallic (FRP) Reinforcement for Concrete Structures, RILEM, E & FN Spon, London, pp 619-623.

Carbon fibers have a modulus of elasticity and tensile

strength that are greater than those of steel. Glass fibers Reinhorn, A. M. and A. Madan, 1995, Evaluation of

have a lower modulus of elasticity and tensile strength. Tyfo-S Fiber Wrap System For Out of Plane

Both the glass and the carbon fibers exhibit brittle Strengthening of Masonry Walls, Preliminary Test

behavior in tension. The failure of the composite fiber Report, Report No. AMR 95-0001, State Universystem for out-of-plane loading is generally precipitated sity of New York at Buffalo.

FEMA 308 Repair of Earthquake Damaged Concrete and Masonry Wall Buildings 41
Chapter 4: Implementation

REPAIR GUIDE Repair Type: Structural Enhancement

CRACK STITCHING Materials: Concrete | SE3 s | Reinforced Masonry

Description

When a crack occurs in a lightly-reinforced concrete or

reinforced masonry wall, the shear capacity along the

crack can be restored and improved by local repair

along the crack. This type of repair is most useful for

sliding-shear behavior modes when reinforcing bars

may be bent or the condition of the crack prevents

epoxy from producing an adequate bond. For this

repair, new reinforcing bars are inserted across the

crack for improved shear resistance.

RepairMaterials

* Reinforcing bars

* Epoxy for binding the reinforcing bars to the concrete or masonry

Equipment

The following equipment is needed:

e Rotary drill to create the holes (Core drills are not

recommended)

* Air compressor and brushes

* Mixing and placing equipment for epoxy resin

Execution

Holes are drilled across the crack. The holes should be

deep enough to develop the strength of the reinforcing

bars in the wall and in the substrate above or below.

Typically No. 4 or 5 bars are used with a hole depth

equal to 18 inches on each side of the crack (ACI,

1994). The holes should intersect the crack at approximately a 45 degree angle. The spacing of the holes and

the size of the reinforcing bars should be chosen to provide shear resistance using shear-friction theory for

reinforcement inclined to the shear plane, in accordance

with ACI 318.

The holes should be thoroughly cleaned by alternate use

of compressed air and a brush. Epoxy is placed in the

hole and then the reinforcing bar is inserted into the

hole. Enough epoxy should be placed in the hole so that

some epoxy is forced out of the hole when the reinforcing bar is placed.

Oualitv Assurance

The bond of the epoxy to the reinforcing bars and the

substrate are critical to the effectiveness of the repair.

For the bond to the substrate to be adequate, the hole.

must be thoroughly cleaned. This usually involves several cycles of brushing and blowing out the hole. The

compressor used for blowing out the hole should be fitted with a filter to prevent oil from mixing with the air.

The compressor oil will reduce the bond, if present.

Water in the hole can also prevent proper bonding.

The reinforcing bar should not be rotated while it is

inserted into the hole. Rotating the bar will break some

of the initial bond of the epoxy, which can prevent further bonding.

An inspector should check each hole to verify that it has

been adequately cleaned and of the required depth

before inserting the reinforcing bar. Each hole should

also be inspected following insertion of the bar to verify

that the epoxy completely fills the annular space around

the bar.

Limitations

Inserting dowels across the cracks is only effective if

there is sufficient thickness of material above or below

the wall to develop the bars. Using bars larger than No.

5 is not usually feasible, since drill bits may not be

readily available to achieve the depth of the hole

required to develop these larger bars.

Care must be taken to avoid damaging the existing reinforcing bars when drilling the holes for the new reinforcing bars. Rebar detectors should be used to lay out

the existing bar placement.

Angle drilling with a rotary bit may be difficult to

accomplish precisely by hand. A rig or guide may be

needed to confirm that the hole is drilled at the proper

angle.

References

ACI Committee 224, 1994, "Causes, Evaluation, and

Repair of Cracks in Concrete Structures," ACI

224.1R-93,ACIManualof ConcretePractice,

American Concrete Institute, Detroit Michigan

Repair of EarthquakeDamaged Concrete and MasonryWall Buildings .FEMIA308 42
Chapter 4: Implementation

Glossary

Component A structural member such as a beam,

column, or wall that is an individual

part of a structural element

Cosmetic Repairs that improve the visual

repairs appearance of damage to a component. These repairs may also restore

the nonstructural properties of the

component, such as weather protection. Any structural benefit is negligible.

Damaging The ground motion that shook the

ground building under consideration and

motion 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 time-history records or corresponding response spectra.

Direct The determination of performance

method restoration measures from the

observed damage without relative

performance analysis.

Element An assembly of structural components (e.g., coupled shear walls,

frames)

Globi

displh

dema

Globs

strucl

Infifl4

frame

Nonlii

static

procef

Perfo

groun

motio

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.

11 The overall displacement of a repreacement sentative point on a building subject

nd to a performance ground motion. The

representative point is normally taken

at the roof level or at the effective

center of mass for a given mode of

vibration.

al The assembly representing all of the

ture structural elements of a building.

d A concrete or steel frame with concrete or masonry panels installed

between the beams and columns

tear A structural analysis technique in

which the structure is modeled as an

lure assembly of components capable of

nonlinear force-displacement behavior and subjected to a monotonically

increasing lateral load in a specific

pattern to generate a global force-displacement capacity curve. The displacement demand is determined with

a spectral representation of ground

motion, using one of several alternative methods

rmance Hypothetical ground motion consis-

.d tent with the specified seismic hazard

n level associated with a specific performance objective. This is characterized by time-history record(s) or

corresponding response spectra.

Repair of Earthquake Damaged Concrete and Masonry Wall Buildings

Global

displacement

capacity

FEIVA 308

,I
Chapter 4: Implementation

The ratio of the global displacement

performance limit to the global displacement demand for a specific seismic performance objective. If this

ratio is greater than 1.0, the seismic

performance objective is satisfied.

This index represents the degree to

which the performance meets or falls

short of the specific performance

objective.

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.

1.0 minus the ratio of the performance index for a damaged building

to the performance index in its

undamaged state for a specific performance objective. Performance loss

ranges from 0 to 1.0 and represents

the fraction of seismic performance

that was lost during a damaging earthquake.

A goal consisting of a specific performance level for a building subject to

specific seismic hazard.

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

undamaged building.

Physical evidence of inelastic deformation, damage, or deterioration of a

structural component that existed

before a damaging earthquake

Relative

performance

analysis

Repair

Restoration

Severity of

damage

An analysis of a building in its damaged and pre-event condition to determine the effects of the damage on the

ability of the building to meet specific

performance objectives

An action taken to address a damaged

building component.

The repair of structural components

intended to restore the seismic performance of a damaged building to a

level equivalent to the pre-event condition of the building.

The relative intensity of damage to a

particular component, classified as

insignificant, slight, moderate, heavy,

or extreme.

Shear wall A concrete or masonry panel that is

connected to the adjacent floor system or a surrounding frame (infilled

frame) and that resists in-plane lateral

loads.

Structural

enhancements

Structural

repairs

Upgrade

Repairs that comprise supplemental

additions to, or removal and replacement of existing damaged components. They also include the addition

of new components in the structure

not necessarily at the site of existing

damaged components. The intention

is to replace rather than restore structural properties of damaged components.

Repairs that address damage to components to directly restore structural

properties

The repair of structural components

intended to improve the seismic performance of a damaged building to a

level better than that of the pre-event

building.

Repair of Earthquake Damaged Concrete and Masonry Wall Buildings

Performance

index

Performance

level

Performance

loss

Performance

objective

Performance

restoration

measures

Pre-existing

condition

44 FEMA 308
Chapter 4: Implementation

Symbols

dt Global displacement capacity for pre-event

structure for specified performance level

td' Global displacement capacity for damaged

structure for specified performance level

d* Global displacement capacity for repaired

structure for specified performance level

d' Global displacement demand for damaged

structure for specified seismic hazard

dd* Global displacement demand for repaired structure for specified seismic hazard

de Maximum global displacement caused by a

damaging ground motion

dd Global displacement demand for pre-event

structure for specified seismic hazard

FEIVA 308 Repair of Earthquake Damaged Concrete and'Masonry Wall Buildings
Chapter 4: Implementation

References

ATC, 1989, Procedures for the Post Earthquake Safety

Evaluation of Buildings, Applied Technology

Council, ATC-20 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, Seismic Evaluation and Retrofit of Concrete

Buildings, prepared for the California Seismic

Safety Commission by the 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,Evaluationof EarthquakeDamagedConcreteandMasonryWallBuildings- Basic Procedures Manual, prepared by the Applied Technology

Council (ATC-43project) for the Partnership for

Response and Recovery, publisned by the Federal

Emergency Management Agency, Report No.

FEMA 306, Washington, D.C.

ATC,1998b,Evaluationof EarthquakeDamagedConcreteandMasonryWallBuildings- Technical

Resources, prepared by the Applied Technology

Council (ATC-43project) for the Partnership for

Response and Recovery, publisned by the Federal

Emergency Management Agency, Report No.

FEMA 307, Washington, D.C.

ATC, in preparation, Earthquake Loss Evaluation Methodology and Databasesfor Utah, Applied Technology Council, ATC-36 report, Redwood City,

California.

City of Los Angeles, 1985, City ofLos Angeles Building

Code,Division88 - EarthquakeHazardReduction

in Existing Buildings, Los Angeles, California.

City and County of San Francisco, 1989, City and

County of San Francisco Municipal Code: Building

Code, Book Publishing Company, Seattle, Washington.

CSSC, 1994, Compendium of Background Reports on

the NorthridgeEarthquakefor ExecutiveOrderW78-94, California Seismic Safety Commission

(Report No. SSC 94-08).

Hanson, R.D., 1996, "The Evaluation of Reinforced

Concrete Members Damaged by Earthquakes,"

Spectra, Vol. 12, No. 3, Earthquake Engineering

Research Institute, Oakland, California.

Holmes, W.T., 1994, "Policies and Standards for Reoccupancy Repair of Earthquake Damaged Buildings," Spectra, Vol. 10, No. 1, Earthquake

Engineering Research Institute, Oakland, California.

ICBO, 1997 and other years, Uniform Building Code,

International Conference of Building Officials,

Whittier, California.

NIBS, 1997,Earthquake Loss Estimation Methodology:

HAZUS 97, prepared by National Institute of Building Standards, NIBS Document Number 5200, for

the Federal Emergency Management Agency,

Washington, D.C.

Olson, R.S., and Olson, R.A., 1992, "But the Rubble's

Standing Up": The Politics of Building Safety in

Oroville, California 1975-1976, VSP Associates,

Sacramento, California.

Russell, J.E., 1994, "Post Earthquake Reconstruction

Regulation by Local Government," Spectra, Vol.

10, No. 1, Earthquake Engineering Research Institute, Oakland, California.

Sugano, S., 1996, "State-of-the-Art in Techniques for

Rehabilitation of Buildings," Proceedings of the

Eleventh World Conference on Earthquake Engineering, Acapulco, Mexico.

FEIVIA 308 Repair of Earthquake Damaged Concrete and Masonry Wall Buildings 47
ATC-43Project 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

FEMAIPARRRepresentatives

Mr. Timothy McCormick

PaRR Representative

Dewberry & Davis

8401 Arlington Boulevard

Fairfax, VA 22031-4666

Prof. Robert D. Hanson

FEMA Technical Monitor

74 North Pasadena Avenue, CA-1009-DR

Parsons Bldg., West Annex, Room 308

Pasadena, CA 91103

Mr. Mark Doroudian

PaRR Representative

42 Silkwood

Aliso Viejo, CA 92656

FEMAA 308 Repair of Earthquake Damaged Concrete and Masonry Wall Buildings 49
ATC-43 Project Participants

Materials Working Group

Dr. Joe Maffei, Group Leader

c/o Rutherford & Chekene

303 Second Street, Suite 800 North

San Francisco, CA 94107

Mr. Brian Kehoe, Lead Consultant

Wiss, Janney, Elstner Associates, Inc.

2200 Powell Street, Suite 925

Emeryville, CA 94608

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

Dr. Greg Kingsley

KL&A of Colorado

805 14th Street

Golden, CO 80401

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

Mr. 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

FEMA308 50 Repair of Earthquake Damaged Concrete and Masonry Wall Buildings
ATC-43 Project Participants

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

FEMA 308 Repair of Earthquake Damaged Concrete and Masonry Wall Buildings 51
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 Provisionsfor 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 Provisionsfor the Development of Seismic Regulationfor

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 UsingATC-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 Provisionsfor the Development of Seismic

Regulations for Buildings, as amended by a joint

FEMA 308 Repair of Earthquake Damaged Concrete and Masonry Wall Buildings 53
Applied Technology Council Projects And Report Information

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 Guidefor

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, Guidelinesfor 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 Guidelinesfor

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

Repair of Earthquake Damaged Concrete and Masonry Wall Buildings FEIVA 308 54
Applied Technology Council Projects And Report Information

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 Guidelinesfor 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, Guidelinesfor 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 Designof HorizontalWoodDiaphragms,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 Workshopon

the Designof PrefabricatedConcreteBuildingsfor

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 CorrelationBetweenEarthquakeGroundMotionand

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 sumFEMA 308 Repair of Earthquake Damaged Concrete and Masonry Wall Buildings 55
Applied Technology Council Projects And Report Information

mary and comparison of seismic design and seismic

risk parameters currently in widespread use.

ATC-10-1: This report, CriticalAspects of Earthquake

GroundMotion 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

ConcreteShearWallsand FrameJoints: Implications

of Recent Researchfor 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 Practicesfor 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

Datafor 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 seis56 Repair of Earthquake Damaged Concrete and Masonry Wall Buildings FEMA 308
Applied Technology Council Projects And Report Information

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 Workshopon Improvement of Building Structural

Designand ConstructionPractices,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 Workshopon Improvement of Building Structural

Designand ConstructionPractices,waspublished

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

Designand ConstructionPractices,waspublished

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

FEMA 308 Repair of Earthquake Damaged Concrete and Masonry Wall Buildings
Applied Technology Council Projects And Report Information

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

WorkshopProceedings and Five-Year Plan are available

through the Federal Emergency Management Agency,

500 "C" Street, S.W., Washington, DC 20472.

ATC-17:Thisreport,Proceedingsof a Seminarand

Workshopon BaseIsolationand PassiveEnergyDissipation, 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

SeismicIsolation,PassiveEnergyDissipationand

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 Criteriafor

Bridgesand OtherHighwayStructures: Currentand

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, Proceduresfor 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

Repair of EarthquakeDamaged Concrete and MasonryWall Buildings FEMA 308 58
Applied Technology Council Projects And Report Information

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

Postearth quake 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 TrainingManual 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 Buildingsfor 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 VisualScreening of

Buildingsfor PotentialSeismicHazards: 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.

FEMA 308 Repair of Earthquake Damaged Concrete and Masonry Wall Buildings
Applied Technology Council Projects And Report Information

ATC-21-2: The report, Earthquake Damaged Buildings: An Overview of Heavy Debris and VictimExtrication, 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 VisualScreening 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-14report. 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 Inventoryfor 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 Testingof

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)

60 Repair of Earthquake Damaged Concrete and Masonry Wall Buildings FEMA 308
Applied Technology Council Projects And Report Information

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

Assessmentof Seismic VulnerabilityandImpactof 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

Guidelinesfor 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,Proceedingsof a Seminarand

Workshopon SeismicDesignand Performanceof

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 testFEMA 308 3Repair of Earthquake Damaged Concrete and Masonry Wall Buildings
Applied Technology Council Projects And Report Information

ing; and seismic evaluation and rehabilitation of

conventional and essential facilities, including hospitals.

ATC-30: The report, Proceedings of Workshopfor 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 CaliforniaBridges:ProvisionalRecommendations,

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 ImplicationsforEngineeringDesignPractice,

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

Repairof EarthquakeDamaged Concrete and MasonryWall Buildings FEMA 308 62
Applied Technology Council Projects And Report Information

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.

FEMA 308 Repair of Earthquake Damaged Concrete and Masonry Wall Buildings 63
Milton A. Abel

James C. Anderson

Thomas G. Atkinson*

Albert J. Blaylock

Robert K. Burkett

James R. Cagley

H. Patrick Campbell

Arthur N. L. Chiu

Anil Chopra

Richard Christopherson*

Lee H. Cliff

John M. Coil*

Eugene E. Cole

Edwin T. Dean

Robert G. Dean

Edward F. Diekmann

Burke A. Draheim

John E. Droeger

Nicholas F. Forell*

Douglas A. Foutch

Paul Fratessa

Sigmund A. Freeman

Barry J. Goodno

Mark R. Gorman

Gerald H. Haines

William J. Hall

Gary C. Hart

Lyman Henry

James A. Hill

Ernest C. Hillman, Jr.

Ephraim G. Hirsch

William T. Holmes*

Warner Howe

Edwin T. Huston*

Paul C. Jennings

Carl B. Johnson

Edwin H. Johnson

Stephen E. Johnston*

Joseph Kallaby*

Donald R. Kay

T. Robert Kealey*

H. S. (Pete) Kellam

Helmut Krawinkler

James S. Lai

Gerald D. Lehmer

James R. Libby

Charles Lindbergh

R. Bruce Lindermann

L. W. Lu

Walter B. Lum

Kenneth A. Luttrell

Newland J. Malmquist

Melvyn H. Mark

John A. Martin

ATC BOARD

(1979-85)

(1978-81)

(1988-94)

(1976-77)

(1984-88)

(1998-2001)

(1989-90)

(1996-99)

(1973-74)

(1976-80)

(1973)

(1986-87, 1991-97)

(1985-86)

(1996-99)

(1996-2001)

(1978-81)

(1973-74)

(1973)

(1989-96)

(1993-97)

(1991-92)

(1986-89)

(1986-89)

(1984-87)

(1981-82, 1984-85)

(1985-86)

(1975-78)

(1973)

(1992-95)

(1973-74)

(1983-84)

(1983-87)

(1977-80)

(1990-97)

(1973-75)

(1974-76)

(1988-89, 1998-2001)

(1973-75, 1979-80)

(1973-75)

(1989-92)

(1984-88)

(1975-76)

(1979-82)

(1982-85)

(1973-74)

(1992-98)

(1989-92)

(1983-86)

(1987-90)

(1975-78)

(1991-98)

(1997-2000)

(1979-82)

(1978-82)

OF DIRECTORS(1973-Present)

John F. Meehan*

Andrew T. Merovich

David L. Messinger

Stephen McReavy

Bijan Mohraz

William W. Moore*

Gary Morrison

Robert Morrison

Ronald F. Nelson

Joseph P. Nicoletti*

Bruce C. Olsen*

Gerard Pardoen

Stephen H. Pelham

Norman D. Perkins

Richard J. Phillips

Maryann T. Phipps

Sherrill Pitkin

Edward V. Podlack

Chris D. Poland

Egor P. Popov

Robert F. Preece*

Lawrence D. Reaveley*

Philip J. Richter*

John M. Roberts

Charles W. Roeder

Arthur E. Ross*

C. Mark Saunders*

Walter D. Saunders*

Lawrence G. Selna

Wilbur C. Schoeller

Samuel Schultz*

Daniel Shapiro*

Jonathan G. Shipp

Howard Simpson*

Mete Sozen

Donald R. Strand

James L. Stratta

Scott Stedman

Edward J. Teal

W. Martin Tellegen

John C. Theiss*

Charles H. Thornton*

James L. Tipton

Ivan Viest

Ajit S. Virdee*

J. John Walsh

Robert S. White

James A. Willis*

Thomas D. Wosser

Loring A. Wyllie

Edwin G. Zacher

Theodore C. Zsutty

(1973-78)

(1996-99)

(1980-83)

(1973)

(1991-97)

(1973-76)

(1973)

(1981-84)

(1994-95)

(1975-79)

(1978-82)

(1987-91)

(1998-2001)

(1973-76)

(1997-2000)

(1995-96)

(1984-87)

(1973)

(1984-87)

(1976-79)

(1987-93)

(1985-91)

(1986-89)

(1973)

(1997-2000)

(1985-91, 1993-94)

(1993-2000)

(1975-79)

(1981-84)

(1990-91)

(1980-84)

(1977-81)

(1996-99)

(1980-84)

(1990-93)

(1982-83)

(1975-79)

(1996-97)

(1976-79)

(1973)

(1991-98)

(1992-99)

(1973)

(1975-77)

(1977-80, 1981-85)

(1987-90)

(1990-91)

(1980-81, 1982-86)

(1974-77)

(1987-88)

(1981-84)

(1982-85)

* President

ATC EXECUTIVE DIRECTORS (1973-Present)

Ronald Mayes

Christopher Rojahn

(1979-81)

(1981-present)

Roland L. Sharpe

Repair of Earthquake Damaged Concrete and Masonry Wall Buildings

(1973-79)

64 IFEMA 308
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.

FEMA 308 Repair of Earthquake Damaged Concrete and Masonry Wall Buildings 65