ATC 110 - California Earthquake Authority

Transcription

ATC 110
Plan for development of a
prestandard for evaluation
and retrofit of wood
light-frame dwellings
Applied Technology Council
Funded by
California Earthquake Authority
In cooperation with
Federal Emergency Management Agency
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's
mission is to develop state-of-the-art, user-friendly engineering resources and applications
for use in mitigating the effects of natural and other hazards on the built environment. 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.
ATC is guided by a Board of Directors consisting of representatives appointed by the
American Society of Civil Engineers, the National Council of Structural Engineers
Associations, the Structural Engineers Association of California, the Western Council of
Structural Engineers Associations, and four at-large representatives concerned with the
practice of structural engineering. Each director serves a three-year term.
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.
2014 Board of Directors
Roberto Leon, President
James A. Amundson, Vice President
Victoria Arbitrio, Secretary/Treasurer
Nancy Gavlin, Past President
Leighton Cochran
Michael D. Engelhardt
Kurtis R. Gurley
Erleen Hatfield
Andrew B. Kennedy
Bret Lizundia
Robert Paullus Jr.
Donald R. Scott
William Staehlin
Williston (Bill) L. Warren, IV
ATC Disclaimer
While the information presented in this report is believed to be correct, ATC assumes
no responsibility for its accuracy or for the opinions expressed herein. The material
presented in this publication should not be used or relied upon for any specific
application without competent examination and verification of its accuracy, suitability,
and applicability by qualified professionals. Users of information from this publication
assume all liability arising from such use.
Copyright 2014 Applied Technology Council
Cover Photo: Single-family dwelling exhibiting many features common to wood light-frame
residential construction (from ATC-50-1, Seismic Rehabilitation Guidelines for Detached SingleFamily Wood-Frame Dwellings)
ATC-110
Plan for Development of a Prestandard for
Evaluation and Retrofit of Wood Light-Frame
Dwellings
by
APPLIED TECHNOLOGY COUNCIL
201 Redwood Shores Parkway, Suite 240
Redwood City, California 94065
www.ATCouncil.org
Funded by
CALIFORNIA EARTHQUAKE AUTHORITY
Janiele Maffei, Chief Mitigation Officer
Marianne Knoy, Mitigation Program Manager
Sacramento, California
In cooperation with
FEDERAL EMERGENCY MANAGEMENT AGENCY
Michael Mahoney, Project Officer
J. Daniel Dolan, Technical Monitor
Washington, D.C.
ATC MANAGEMENT AND OVERSIGHT
Christopher Rojahn (Project Executive)
Jon A. Heintz (Project Manager)
PROJECT STEERING COMMITTEE
David Bonowitz (Chair)
Vikki Bourcier
David Khorram
Philip Line
Thor Matteson
Steve Pryor
PROJECT TECHNICAL COMMITTEE
Colin Blaney (co-Project Tech. Director)
Kelly Cobeen (co-Project Tech. Director)
Thomas Anderson
Andre Filiatrault
Ramin Golesorkhi
John Osteraas
Frank Rollo
PROJECT WORKING GROUP
David Welch
2014
Preface
In 2013, the California Earthquake Authority (CEA) and the Federal
Emergency Management Agency (FEMA) jointly funded a project with the
Applied Technology Council (ATC) to initiate a multi-year project to
develop a prestandard for the evaluation and retrofit of one- and two-family
wood light-frame residential buildings (ATC-110 Project). This class of
structure represents the most common type of dwelling in the United States.
Although this type of construction has generally provided good performance
in past earthquakes, there are well-known vulnerabilities that have led to
large numbers of homes being rendered uninhabitable or even unrepairable
following an earthquake.
Improved seismic design, and seismic retrofitting of vulnerable
configurations, will increase the probability that homes are available to
provide shelter immediately following moderate to large seismic events. A
number of technical guidance documents exist in the area of seismic
evaluation and retrofit; however, current model building codes and available
seismic retrofit standards do not adequately address the specifics of existing
light frame one- and two-family residential wood structures, and there is no
single resource document that covers all aspects of design and construction
associated with wood light-frame construction.
The purpose of this initial phase of work was to determine the recommended
scope and preliminary outline for a prestandard addressing the evaluation and
retrofit of residential structures, and to identify the technical development
work necessary in future years to make the goal of a comprehensive
prestandard on wood light-frame construction a reality. This document
represents the product of this first year of work, outlining the tasks, teams,
budget, and approximate schedule for a program to develop the eventual
prestandard document.
ATC is indebted to the members of the ATC-110 Project Team who prepared
this report, including Colin Blaney and Kelly Cobeen (co-Project Technical
Directors), and the members of the Project Technical Committee consisting
of Tom Anderson, Andre Filiatrault, Ramin Golesorkhi, John Osteraas, and
Frank Rollo. ATC gratefully acknowledges the members of the Project
Steering Committee consisting of David Bonowitz, Vikki Bourcier, David
ATC-110
Preface
iii
Khorram, Phil Line, Thor Matteson, and Steve Pryor, who provided advice
and assistance at key stages of the work.
ATC also gratefully acknowledges funding provided by the California
Earthquake Authority and the Federal Emergency Management Agency, the
guidance and support provided by Janiele Maffei (CEA Chief Mitigation
Officer), Michael Mahoney (FEMA Project Officer) and Dan Dolan (FEMA
Technical Monitor), and report production services provided by Amber
Houchen (ATC).
Jon A. Heintz
ATC Director of Projects
iv
Preface
Christopher Rojahn
ATC Executive Director
ATC-110
Table of Contents
Preface.......................................................................................................... iii
List of Figures............................................................................................. vii
List of Tables ................................................................................................ix
1.1
Introduction ..........................................................................................2
1.2
General Requirements .........................................................................3
1.2.1 Decide on Initial Assessment and Retrofit Design
Methodologies ...........................................................................4
1.2.2 Development of Performance Measures and Criteria ...............5
1.2.3 Prestandard Development .........................................................5
1.2.4 Development of Engineered Approach .....................................6
1.2.5 Pilot Study – Short Cripple Walls and Anchorage to
Foundation ................................................................................6
1.2.6 Pilot Study – Chimneys.............................................................7
1.3
Cripple Walls and Anchorage to Foundation ....................................8
1.3.1 Analytical Investigations .........................................................10
1.3.2 Investigation of Load Path and Development of Assessment
Procedures ...............................................................................13
1.3.3 Development of Retrofit Methods ..........................................15
1.3.4 Development of Draft Prestandard Provisions ........................16
1.4
House or Room over Garage .............................................................16
Procedures ..............................................................................20
1.4.4 Development of Prestandard Provisions .................................22
1.5
Hillside Dwellings ...............................................................................23
Procedures ...............................................................................27
1.6
Split-Level Dwellings .........................................................................29
1.6.2 & 1.6.3 Investigation of Load Path and Development of
Assessment and Retrofit Procedures .......................................31
ATC-110
Table of Contents
v
1.7
Inadequate Wall Bracing – Occupied Spaces ................................. 32
1.7.1 Analytical Investigations ........................................................ 34
Procedures .............................................................................. 37
1.7.3 Development of Retrofit Methods .......................................... 39
1.7.4 Development of Prestandard Provisions................................. 40
1.8
Anchorage of Slab on Grade Dwellings ........................................... 40
1.8.1 Analytical Investigations ........................................................ 41
Procedures .............................................................................. 43
1.8.3 Development of Retrofit Methods .......................................... 44
1.9
Parts and Portions of Dwellings ....................................................... 45
1.9.1 Compilation of Resources ...................................................... 46
Assessment and Retrofit Procedures ...................................... 46
1.10 Recommendations and Priorities ..................................................... 47
1.10.1 Summary of Program ............................................................. 47
1.10.2 Estimated Budget Requirements ............................................ 48
1.10.3 Budget Assumptions............................................................... 50
1.10.4 Priority and Schedule Recommendations ............................... 50
1.10.5 Priority Level 1 ....................................................................... 51
1.10.6 Priority Level 2 ....................................................................... 51
1.10.7 Priority Level 3 ....................................................................... 52
1.10.8 Schedule ................................................................................. 52
1.10.9 Adoption into Codes and Standards ....................................... 52
Appendix A: Prestandard Outline and Recommended Scope .............. A-1
Appendix B: Testing Needs ...................................................................... B-1
Project Participants................................................................................... C-1
ATC Directors ........................................................................................... D-1
vi
Table of Contents
ATC-110
List of Figures
Figure 1-1
Hillside dwelling terminology .............................................23
Figure 1-2
Front elevation of common split-level dwelling
configuration ........................................................................29
Figure 1-3
Detailed schedule of Priority Level 1 and Priority Level 2
studies ..................................................................................53
Figure 1-4
Detailed schedule of Priority Level 3 studies ......................54
ATC-110
List of Figures
vii
List of Tables
Table 1.2-1
Tasks Related to General Requirements ................................3
Table 1.3-1
Tasks Related to Cripple Walls and Anchorage to
Foundation ...........................................................................10
Table 1.4-1
Tasks Related to Assessment and Retrofit ...........................17
Table 1.5-1
Tasks Related to Hillside Dwellings ....................................24
Table 1.6-1
Tasks Related to Split-Level Dwellings ..............................30
Table 1.7-1
Tasks Related to Assessment and Retrofit of homes with
inadequate Wall Bracing within the Occupied Space ..........34
Table 1.8-1
Tasks Related to Anchorage of Slab on Grade Dwellings ...37
Table 1.9-1
Tasks Related to Parts and Portions of Dwellings ...............46
Table 1.10-1
Summary of Proposed Tasks and Engineering Studies .......48
Table 1.10-2
Estimated Budget by Study Area or Dwelling Type............49
Table 1.10-3
Recommendations for Prioritization of Tasks .....................51
Table 1.10-4
Priority Level 1 Studies .......................................................51
Table 1.10-5
Table 1.10-6
Table B-1
Testing Needs for the Prestandard Development Plan.......B-2
ATC-110
List of Tables
ix
Chapter 1
Prestandard Development Plan
This document outlines a detailed plan for the development of a prestandard
for the practical seismic assessment and retrofit of wood light-frame
dwellings (ATC-110 Project). The scope of the prestandard is intended to
address one- and two-family dwellings, and buildings with three or more
dwelling units (such as townhouses), to the extent that vulnerabilities and
retrofits are similar to those for one- and two-family dwellings.
A draft outline and recommended scope for the eventual prestandard is
provided in Appendix A. The tasks, teams, and approximate timelines for
development activities in each major area of the prestandard are described in
the sections that follow, organized in accordance with specific dwelling
configurations that are known to be vulnerable to earthquake-related damage:
Section 1.1 describes overarching guiding principles used in formulating the
concept for the eventual prestandard document.
Section 1.2 addresses the development of general methodology and
performance criteria, as well as overarching coordination of the resulting
prestandard and engineering requirements developed under other sections.
Section 1.3 addresses cripple wall configurations and anchorage to the
foundation (prestandard Chapters 3 and 4).
Section 1.4 addresses house or room over garage configurations (prestandard
Chapter 6).
Section 1.5 addresses hillside dwelling configurations (prestandard
Chapter 5).
Section 1.6 addresses split-level dwelling configurations (prestandard
Chapter 7).
Section 1.7 addresses inadequate wall bracing in occupied spaces
(prestandard Chapter 8).
Section 1.8 addresses anchorage of slab-on-grade dwellings (prestandard
Chapter 9).
ATC-110
1: Prestandard Development Plan
1
Section 1.9 addresses parts and portions of dwellings, including decks,
porches, porch roofs, stairs, landings, patio covers, carports, and masonry
veneer (prestandard Chapters 10, 11, and 12).
Section 1.10 summarizes estimated budget requirements, and provides
recommendations for prioritization and phasing of the overall developmental
effort.
Appendix A presents a draft outline and scope for the recommended
prestandard document.
Appendix B outlines recommendations for testing of wood light-frame
components, sub-systems and systems that would serve to improve
understanding of behavior and reduce potential uncertainty in analytical
studies.
1.1
Introduction
The following overarching guiding principles for the eventual prestandard
document were derived from discussions between the Project Technical
Committee and the Project Steering Committee:
2

The prestandard will address practical assessment and retrofit of seismic
vulnerabilities. As a prestandard, it will be subjected to further
development in an ANSI-approved consensus standard process.

The prestandard will provide a single stand-alone source for addressing
structural and a limited scope of nonstructural assessment and retrofit
needs.

The prestandard will build from available technical resource documents
to develop a stand-alone prestandard.

The prestandard will develop prescriptive procedures for retrofitting
wherever appropriate.

The approach will be vulnerability-based with the objective of risk
reduction, rather than based on overall building performance derived
from systematic evaluation and retrofit. Guidance for systematic
engineered evaluation will be developed, to the extent possible, based on
work during the course of this prestandard development.

The prestandard is intended to permit addressing an individual
vulnerability, multiple vulnerabilities or all identified vulnerabilities.
Retrofit to the prestandard will require that all work associated with the
selected vulnerability be retrofit (no picking and choosing of work within
a vulnerability).
ATC-110

The prestandard will not include triggers for use. It is anticipated that
policy directing voluntary, mandatory, or code-triggered use will be in
other documents.

Recommendations for prioritization of vulnerabilities for retrofit will be
provided.

The scope is wood light-frame dwellings.

The scope is one- and two-family dwellings, and buildings with three or
more dwelling units (such as townhouses), to the extent that
vulnerabilities and retrofits are similar to those for one- and two-family
dwellings. This scope is intended to match the scope of the International
Residential Code (IRC) to the extent possible, and with limited
exceptions.

The scope is dwellings located in moderate to high seismic hazard areas,
including IRC Seismic Design Categories C and higher.

Focus will be on more commonly occurring and more readily addressed
vulnerabilities. However all known potential vulnerabilities will be
identified in discussion (possibly in an appendix), even if assessment and
retrofit measures are not developed.

Collaboration will be sought with other research and/or development
projects occurring in parallel with this project. Future research and
development needs identified during the course of the project will be
documented to provide guidance to researchers.
1.2
General Requirements
Section 1.2 addresses overarching tasks affecting the prestandard project.
Development plan tasks are summarized in Table 1.2-1.
Table 1.2-1
Tasks Related to General Requirements
Research or Study
Estimated Timeline
1.2.1 Decide on Initial Assessment and Retrofit Design
Methodologies
Mos. 1-12
1.2.2 Development of Performance Measures and Criteria
1.2.3 Prestandard Development
1.2.4 Development of Engineered Approach
Mos. 1-12
Mos. 1-36
Mos. 24-36
1.2.5 Pilot Study - Short Cripple Wall Assessment and
Retrofit Provisions
Mos. 3-21
1.2.6 Pilot Study - Chimney Assessment and Retrofit
Provisions
Mos. 3-15
ATC-110
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1.2.1
Decide on Initial Assessment and Retrofit Design
Methodologies
This task will set initial direction for use of the information obtained from the
analytical studies of each section. The intent is that overarching
commonalities and objectives be set, but that the development team for each
section revisit and revise the overall direction. Information envisioned to
come from analytical studies includes:

Base shear associated with selected performance criteria (component and
global).

Displacements associated with selected performance criteria (component
and global).

Required retrofit strength and stiffness (summary of how different
retrofits affect performance).

Back calculation of effective R factor.

Distribution of forces and deformations.
Considerations regarding potential assessment and retrofit methodologies
include:



4
Force-based methodology considerations (including method for
comparing demands and capacities):
o
Develop equivalent Code level procedure.
o
How we use forces (reduced or unreduced forces; allowable or
strength-based capacities, capacity based design methods).
o
Stiffness characteristics associated with forces.
o
Calculation of new R factor.
Probabilistic-based methodology considerations:
o
FEMA P-807 style of nonlinear response-history analysis results
database.
o
FEMA P-695 style collapse assessment on an individual basis.
ASCE 41 linear static procedures or force-/displacement-based
methodology considerations:
o
Determine equivalent component demand modification factors (mfactors) for components and connections.
o
Development of non-linear deformation limits for components and
connections.
ATC-110
Team:
Project technical committee, working groups consisting of engineers and
researchers to apply the different retrofit design methodologies to a few
building types.
1.2.2
Development of Performance Measures and Criteria
Develop the criteria for investigating behavior and measuring acceptance of
existing or retrofitted conditions (intended to be instructions to researcher
running the analysis and overall guidance).

Determine probability of collapse percent (%) in the maximum
considered earthquake (MCE.).

Determine probability of exceeding drift levels at MCE

Study to determine if retrofitting should be in line with existing codes
(IEBC A3 etc.), new codes, or other standards.

Review possible damage-control (limiting damage) performance
measures.

If MCE is to be used, address whether or not risk-adjustment will be
included.

Review possible use of hazard levels other than MCE (e.g. performance
criteria such as reduced damage in moderate earthquakes)

Determine acceptance criteria for load path consistent with performance
measures

Determine performance expectations for foundations consistent with
performance measures

Develop screens or criteria whereas site factors should be considered
prior to implementation of specific retrofitting.
Team:
Project technical committee, working groups consisting of engineers and
researchers to take a few building types through the different methodologies.
1.2.3
Prestandard Development
Overarching synthesis of prestandard provisions developed under various
tasks; includes development of appendices; workshops/review. The
following major work areas are addressed.

Overall synthesis.
ATC-110
5

Appendix A (site factors)

Appendix B (Engineering Design Aids)

Appendix C (Not Used)

Appendix D (other vulnerabilities).

Appendix E (recommendations for implementation).

Commentary C0 (commentary for standards committee).

Commentary C1-C11 (commentary standard for users).

Development of criteria or guidance within each section which would
address the evaluation of existing “retrofitted” conditions.
Team:
Appendix A will be developed by two geotechnical engineers and one
structural engineer. The balance of this work will primarily be delegated to
members of the project technical committee, possibly with small working
groups.
1.2.4
Development of Engineered Approach
Overarching synthesis of engineered concepts developed under various tasks;
includes development of design aids (Appendix B); workshops/review.
Team:
Two lead structural engineers working with two staff engineers and one
geotechnical engineer.
1.2.5
Pilot Study - Short Cripple Walls and Anchorage to
Foundation
Section 1.2.5 will use the results of initial analytical studies to develop
assessment and retrofit methodologies for wood light-frame dwellings with a
crawlspace below the lowest framed floor, enclosed by wood light-frame
cripple walls. This section moves forward in the schedule work that would
otherwise occur under Section 1.3 with the intent that initial development of
assessment and retrofit methodologies will inform the work to follow. See
Section 1.3 for details of this study.
Section 1.2.5 addresses the assessment and retrofit of cripple walls, including
sheathing, the connection of the cripple wall to the structure above, and
anchorage of the cripple wall to the foundation. Also included is retrofit or
replacement of foundation systems where existing foundations are not
continuous.
6
ATC-110
Under Section 1.2.5 short cripple walls are thought to respond primarily as
shear elements and as such do not require consideration of uplift due to
cripple wall overturning. Foundation and supporting soils deformations are
not thought to contribute significantly to overall displacement of the cripple
wall system for short cripple walls. Zero height cripple walls (framed floor
sitting directly on foundation or foundation wall) will be analytically
investigated under Section 1.5.1 and included in assessment and retrofit
solutions developed under Section 1.3.
Investigation of load path and development of assessment procedures will
include:

Establishment of a method by which cripple wall bracing and its load
path can be compared to the demands identified,

Quantification of existing cripple wall components and load path
connections from existing test and design information. This will be used
for development of prescriptive assessment and retrofit methodologies
and will be provided to the standard user for engineered methodologies.

Identification of methodologies for assessing the acceptability of existing
construction and identifying dwellings that require retrofit.
Development of retrofit methods will provide prescriptive design solutions
and engineering design methods and tools for use where engineered design is
required or chosen. Development of draft prestandard provisions will
transform retrofit procedures into technical provisions of the prestandard,
including development of standard language and appropriate documentation
format.
Team:
A group of two lead structural engineers, one researcher, two staff structural
engineer, one geotechnical engineer, one construction practitioner, and one
CAD drafter.
1.2.6
Pilot Study - Chimneys
Section 1.2.6 will develop assessment and retrofit methodologies for
masonry and light-frame chimneys. This task moves forward work that
would otherwise occur under Section 1.9 with the intent of informing work
that follows.
The focus of this section will be the compilation of existing research and
design information and synthesis into practical prescriptive details and
engineering guidance. Chimney retrofit methods will take into account the
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7
inherent deformation compatibility issues posed by stiff chimneys and
flexible wood dwellings. Available retrofit design and detailing guidance and
available post-earthquake repair guidance (City of Napa, City of Los
Angeles, etc.) will be complied as a starting point.
Investigation of Load Path and Development of Assessment and Retrofit Procedures
will include:

Identify configurations that need to be addressed.

Identify appropriate strategies for mitigating seismic damage.

Identify approach for quantifying mitigation criteria (force, deformation,
etc.).

Develop methodologies for assessment of existing conditions.

Develop prescriptive details

Develop engineering strategies
Retrofit procedures will be developed into prestandard provisions, including
development of standard language and appropriate documentation format.
Team:
A group of one lead structural engineer, one researcher, one staff engineer,
one construction practitioner, and one CAD drafter.
1.3
Cripple Walls and Anchorage to Foundation
Section 1.3 addresses wood light-frame dwellings with a crawlspace or
basement below the lowest framed floor, including the following dwelling
configurations:

Crawlspaces enclosed by wood-frame cripple walls, concrete or masonry
stem walls, basement walls, or combinations thereof on flat to
moderately sloped sites.

Unenclosed crawl spaces having post and pier systems below the exterior
walls (when retrofitted with cripple wall systems).

Continuous and partial perimeter foundations.

Foundation, stem wall and basement wall materials include concrete,
brick masonry and stone masonry.
Section 1.3 addresses the assessment and retrofit of:

8
Cripple walls, including sheathing, the connection of the cripple wall to
the structure above, and anchorage of the cripple wall to the foundation.
ATC-110

Anchorage of wood framed dwellings to stem wall and basement wall
foundation systems (based on Section 1.5.1 investigations).

Retrofit or replacement of foundation systems where existing
foundations are not continuous.

Assessment and retrofit of foundations as required to support overturning
in medium height (estimated to be four feet and taller) cripple walls.

Assessment considerations will include condition of existing components
where required.
Under Section 1.3 for dwellings with short cripple walls (estimated to be up
to four ft. in height) (Prestandard Chapter 3):

Short cripple walls are thought to respond primarily as shear elements
and as such do not require consideration of uplift due to cripple wall
overturning. Section 1.3.1 includes a limited study to identify where this
assumption can be made.

Foundation and supporting soils deformations are not thought to
contribute significantly to overall displacement of the cripple wall
system for short cripple walls, and are therefore neglected in analytical
modeling. A limited illustrative study will demonstrate this assumption.
Under Section 1.3 for dwellings with short to medium cripple walls
(estimated to be up to eight feet in height) (Prestandard Chapter 4):

Overturning and shear behavior of medium height cripple walls are
thought to both be significant contributors to seismic performance and
will be specifically addressed in analytical modeling, assessment and
retrofit.

Diaphragm deflection and torsional response are thought to potentially
influence seismic force distribution and will be investigated in analytical
work.

Foundation and supporting soils deformations are thought to be possible
contributors to overall displacement of the cripple wall system. A limited
analytical study will evaluate potential influence and, if required,
develop recommendations for inclusion in modeling.
Not addressed under Section 1.3 are tall cripple walls (estimated to be above
eight feet in height), which are being addressed in Section 1.5.
Zero height cripple walls (framed floor sitting directly on foundation or
foundation wall) will be analytically investigated under Section 1.5.1, but are
ATC-110
9
also included in assessment and retrofit solutions developed under
Section 1.3.
Conditions involving dwelling with cripple wall relative heights that vary
considerably will be studied for response. Criterial will be determined where
such conditions warrant compliance with Section 1.5 Hillside Homes in lieu
of Section 3.
Inadequate fastening of stucco to foundation sill plates (either due to as-built
conditions or deterioration) will be addressed in Sec. 1.3, as will other
common condition issues.
Development plan tasks related to assessment and retrofit are summarized in
Table 1.3-1.
Table 1.3-1 Tasks Related to Cripple Walls and Anchorage to Foundation
Research or Study
Estimated Timeline
1.3.1 Analytical Investigations
Short cripple walls
Mos. 1-12
Medium height cripple walls
Mos. 1-18
1.3.2 Investigation of load path and development of
assessment procedures
Short cripple walls
Mos. 9-27
Mos. 9-27
1.3.3 Development of retrofit procedures
Short cripple walls
Mos. 18-30
Mos. 18-30
1.3.4 Development of prestandard provisions
1.3.1
Short cripple walls
Mos. 24-36
Mos. 24-36
Analytical Investigations
Analytical investigations will study seismic demand in cripple wall structures
associated with the targeted seismic performance measures and criteria. The
purpose of the study is to determine the seismic demand and variation in the
distribution of seismic demand in cripple walls and their load path, based on
differing cripple wall and foundation configurations (type, size, etc.) and
differing bracing materials in the superstructure and cripple walls. This
study is intended to provide analytical results that will serve as a basis for the
Section 1.3 tasks that follow. It is also intended that this study provide
information to confirm or adjust the use of a four foot upper limit on cripple
10
ATC-110
wall height as the dividing line between short and medium height cripple
walls for purposes of assessment and retrofit design.
Details of Study:

Example dwellings will be designed as necessary to facilitate the
analytical studies.

Available test data describing in-plane load deflection behavior of
bracing wall components and available full-building test data will be
collected, evaluated, and appropriate analytical characterization of
bracing systems established.

Limited studies will be conducted of the influence of the deformation of
foundations and supporting soils. For short cripple walls, this will
include an anecdotal study of deformation contributions. For medium
height cripple walls, this will include a limited two-dimensional study of
deformation effects, methods to limit the effects (e.g. aspect ratios), and
methods to include the effects in analysis models if necessary (e.g.
rotational soil springs at the base of cripple wall components).

Non-linear response history analyses will be conducted on threedimensional building models to determine probabilities of exceedance of
acceptance criteria under pre-determined seismic hazard levels.

Validation comparisons of analytical modeling will be conducted as
possible, with limited comparisons to component, assembly, or fullbuilding test results, or comparisons to other accepted analysis results as
available. These test results will be found in technical journals,
academic theses, proprietary test reports (if permission for access can be
obtained), etc. In this context, validation means the use of test results
other than those used to develop or calibrate the models or analytical
equations (tests with specimens of different configurations, strengths,
etc.).

Pancake modeling is acceptable. No investigation of vertical ground
motion is intended. P-delta effects are to be included in modeling.
Elements will be modeled at the global component level (i.e., cripple
wall force-displacement hysteretic behavior per unit length).

Analytical studies will determine sensitivity to variants, and variants of
greater importance will be studied in greater detail. Assume 60 building
plus variant combinations combined for short and medium height cripple
walls, including existing conditions and retrofit schemes.

From these analytical studies, recommendations will be made regarding
characterizing the demand and distribution of demand for subsequent
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11
assessment and retrofit tasks, performance summary of variants will be
developed identifying what existing configurations and retrofit solutions
meet the performance objective.
Short cripple wall analysis example buildings and variants will be established
to describe the range of:

Cripple wall heights (e.g., 1, 2, 4 feet) (zero height cripple walls will be
analytically investigated under Section 1.5.1).

Combinations of heights (e.g., assume three combinations of cripple
walls and stem walls).

Existing cripple wall sheathing materials. Four variants will be selected
to capture a range of materials and material conditions. Possible
materials include stucco, horizontal wood siding, T1-11 siding, diagonal
sheathing with stucco, exterior gypsum board under stucco. Selection of
materials will include consideration of how common they are, how much
they affect behavior, and availability of data from which to develop
modeling.

Cripple walls with retrofit sheathing materials (e.g., wood structural
panels in combination with the above).

Detailing variants thought to impact cripple wall component behavior
(e.g. cripple wall sheathing attached top and bottom versus able to slip
past the framing, fastening of sheathing to the foundation sill plate versus
blocking between studs, staple fastening of blocks rather than nailing,
etc.).

Superstructure size, strength, and bracing materials (e.g., assume three
combinations varying number of stories with strength and stiffness; note:
propagation of yielding is currently being investigated in the pilot study).

Complex plan geometries (e.g., L-shaped and T-shaped).

Level of seismicity (e.g., IRC SDC C/D0, D1, D2,max).
Short to medium cripple wall height example buildings and variants will be
established to describe the range of:
12

Cripple wall heights (e.g.,6 and 8 feet) ( 1, 2 & 4 feet information will
come from Section 1.3.1, 0 foot information will be developed in Section
1.5.1).

Combinations of heights (e.g., assume three combinations of cripple
walls and stem walls).
ATC-110

Variables in resistance to overturning (i.e. number of stories, bearing and
non-bearing walls, overturning anchorage variables, etc.).

Existing cripple wall sheathing materials (see short cripple wall
discussion).

Cripple walls with retrofit sheathing materials (see short cripple wall
discussion).

Superstructure size, strength, and bracing materials (e.g., assume three
combinations varying number of stories with strength and stiffness).

Complex plan geometries (e.g., L-shaped and T-shaped).

Team:
Working group consisting of:

Two researchers assisted by two graduate students (one graduate student
per researcher)

An independent analysis peer reviewer, either researcher or practitioner

A resource group of two structural engineers, one geotechnical engineer,
and one construction practitioners to identify building parameters and
variations, develop example building and retrofit designs, and provide
other required input to the researchers and graduate students.
1.3.2
Investigation of Load Path and Development of
Assessment Procedures
There are three primary portions of this task:

Establishment of a method by which cripple wall bracing and its load
path can be compared to the demands identified in Item 1.3.1,

Quantification of existing cripple wall components and load path
connections from existing test and design information. This will be used
for development of prescriptive assessment and retrofit methodologies
and will be provided to the standard user for engineered methodologies.

Identify methodologies for assessing the acceptability of existing
construction and identifying dwellings that require retrofit.
Details of Study:
General activities required at the start are:
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13

Collection of available test data and engineering design tools, establish
component and load path connection capacities and identify method for
comparison of capacities with demands identified in Task 1.3.1. To the
extent possible this should address capacities of both original
construction and common retrofit approaches.

Collection of available assessment criteria and establish assessment
methodologies for both prescriptive and engineered assessment methods.
For the first portion of the task, a methodology for comparison of demand
and capacity will be established, building on the direction set in Task 1.2.2. It
will be decided whether this comparison is made at code level forces, by
capacity methodologies, or other methods, considering phi factors and other
modifiers. Assessment methods and load path checks will be derived from
the results of analytical studies conducted under Task 1.3.1. Stiffness and
displacement characteristics will be included as appropriate to set
performance criteria.
For the second portion of the task, available test data describing in-plane load
deflection behavior of bracing wall components and load path connections
will be collected, and supplemented by engineering calculations where
necessary. Capacities of commonly occurring bracing materials and
connections will be developed where possible. Capacities of load path details
commonly used in retrofit will be developed where possible. Example
components and connections include:

Cripple wall components with various bracing materials.

Anchor bolts and hold-downs at foundations, including foundation
material and configuration variations.

Load path connections from top of cripple wall or foundation sill plates
to floor systems above (including variants that occur commonly in
retrofit).

Foundations resisting primarily shear loads.

Foundations resisting overturning loads from retrofit.

For medium height cripple walls, hold-downs at foundations, including
foundation material and configuration variations.
For the third portion of the task, based on information previously developed
and available assessment tools, components and load path connections that
require assessment will be identified, and methodologies for both
prescriptive and engineered assessments will be developed considering the
following:
14
ATC-110

Intended scope of assessment.

Available assessment tools (e.g., FEMA P-50, ASCE 41).

Full-building versus deficiency-only assessments.

Prescriptive versus engineered assessment concepts.
Assessment tools will be developed to the point where they are ready for
implementation.
Team:
A group consisting of two lead structural engineers, two staff structural
engineers, one geotechnical engineer, and one construction practitioner.
The researchers involved in Task 1.3.1.
1.3.3
Development of Retrofit Methods
This task will provide prescriptive design solutions for retrofit of as many
commonly occurring field conditions as possible (variations in existing asbuilt conditions, etc.) and provide engineering design methods and tools for
use where engineered design is required or chosen. Tasks include:

Identification of components and connections requiring retrofit.

Development of engineering methodology for design of retrofit.

Development of prescriptive details for retrofit of commonly occurring
configurations.
Details of Study:
It is anticipated that the development of prescriptive and engineered retrofit
procedures will occur in parallel, and that the engineering methodology will
guide the design of prescriptive retrofit methods.
Steps in the development of prescriptive retrofit procedures will include:

Defining the scope of dwellings to which the procedures can be applied.

Developing example buildings to use as a basis for proportioning of
retrofit.

Development of typical details.

Development of plan sets based on the previous information.
Steps in development of the engineered retrofit procedures include:

Development of the minimum engineering considerations.
ATC-110
15

Development of tools to assist the designer, possibly including analysis
shortcuts, and tabulated engineering properties for use in analysis.
Team:
A group of three lead structural engineers, three staff structural engineers,
one geotechnical engineer, one construction practitioner, and one CAD
drafter.
1.3.4
Development of Draft Prestandard Provisions
This task will transform retrofit procedures developed in Task 1.3.3 into
technical provisions of the prestandard, including development of standard
language and appropriate documentation format.
Team:
A group of two lead structural engineers, one staff structural engineer, one
construction practitioner, and one CAD drafter.
1.4
House or Room over Garage
Section 1.4 addresses wood light-frame dwellings with a living space over
open front garages which are either unbraced or have minimal lateral bracing
and an apparent weak first story at the lowest occupied story, including:

Single or multi-level residential units over a first story consisting of a
garage or a combination of a garage and living spaces.

Two story ranch-style configurations which include bedrooms or other
occupancies directly above or partially above a garage.

Related conditions such as horizontal offsets within the vertical (gravity)
force-resisting systems, with or without a discontinuous floor diaphragm.
Typical damage modes would include excessive drift in the lower weak story
relative to the upper story resulting in significant damage and possibly a
partial or complete weak story collapse.
16

Weak stories relative to the structure above.

First story wall panel elements, including the attachments to the
superstructure above and the existing or new foundation system.

Second floor diaphragm and collector elements – specifically their ability
to transfer superstructure inertial loads to first level lateral force-resisting
elements.
ATC-110

Existing or new foundation systems supporting existing weak story
elements.
Anticipated retrofitting schemes which will be developed under Section 1.4
include:

Sheathing of existing wall systems adjacent to garage openings or other
weak wall lines, in conjunction with hold-downs and new or retrofitted
foundation systems.

Addition of steel moment frame systems.

Addition of cantilevered columns adjacent to garage openings.

Sheathing of interior transverse walls at the rear of garage spaces,
including new foundation systems.

Addition of diaphragm retrofit (sheathing) and collector and /or chord
elements to the underside of the first occupied level.
Table 1.4-1.
Table 1.4-1 Tasks Related to Assessment and Retrofit
Research or Study
Estimated Timeline
1.4.1 Analytical investigations
Mos. 1-18
1.4.2 Detailed investigation of load path and
development of assessment procedures
1.4.3 Development of retrofit methods
Mos. 9-27
1.4.1
Mos. 18-36
Mos. 24-36
Analytical investigations will study seismic demand at the lower level of
multi-level residential dwellings associated with the targeted seismic
performance measures and criteria developed under Section 1.2. The
purpose of the study will be to determine the seismic demand and the
distribution of this demand at the first level as it correlates to varying
horizontal geometries, vertical geometries, and bracing materials in the
superstructure and lower level wall systems. This study is intended to
provide analytical results that will serve as a basis for tasks in Section 1.4
that follow.
Details of Study:

Example dwellings will be surveyed and designed as necessary to
facilitate the analytical studies. Sample building types may include:
ATC-110
17
18
o
Single level house or room over garage (two-stories).
o
Single family and multi-family flats (multi-level above garage- three
stories maximum).
o
Ranch-style houses with second floor systems at the same elevation
above the ground floor.
o
Structures with first story heights ranging from seven to ten feet.
o
Structures with non-rectangular plan geometries (e.g., L-shaped and
T-shaped).

Building upon Section 1.3.1, available test data will be collected which
describes in-plane load deflection behavior of bracing wall components
and available full-building test data. Appropriate analytical
characterizations of bracing systems will be established.

Four existing wall sheathing materials will be selected to capture a range
of materials and material conditions. Possible exterior materials include
stucco, horizontal wood siding, T1-11 siding, diagonal sheathing with
stucco, with either gypsum board or plaster on the inside. The selection
of materials will include consideration of how common they are, how
much they affect behavior, and availability of data from which to
develop modeling.

Three variations in percent open along the garage front with variations in
the existing pier width to aid in development of assessment
methodology.

Retrofit schemes will be developed by considering the addition of
sheathing materials (e.g., wood structural wall panels in combination
with the above listed existing wall sheathings), steel portal frames and
cantilevered columns. Additional retrofitting systems may also be
developed.

Consideration will be given to superstructure size, strength, and bracing
materials (e.g., assume three combinations varying number of stories
with strength and stiffness; note: propagation of yielding is currently
being investigated in the pilot study).

Available test data will be collected for in-plane load deflection behavior
of proprietary slender bracing wall systems which are publically
available (e.g., Simpson Strong Wall, Hardy Frame, etc.).

ATC-110
acceptance criteria under pre-determined seismic hazard levels. P-
effects will be included however vertical excitation will be ignored.

Limited studies will be conducted to determine the effects of foundation
flexibility on seismic demand and variation in the distribution of seismic
demand at the first level as well as on targeted seismic performance
measures.

Level of seismicity may include IRC SDC C/D0, D1, D2,max.

Analytical studies will determine sensitivity to variants; variants of
greater importance will be studied in greater detail. Assume a minimum
of 60 building combinations including existing and retrofitted conditions.
General goals of the analytical investigations are assumed to include the
following:
o
Determination of seismic demands (force and displacements) and the
distribution of seismic demands at the first story.
o
Determination of the relative seismic demands (force and
displacement) of the lower story relative to the upper stories as a
base line for the development of retrofitting schemes.
o
Sensitivity or degree to which increasingly narrower pier widths of
various construction materials lead to excessive drift and increased
probability of collapse. Compare to acceptance requirements
developed under Section 1.2.2 (Development of Performance
Measures and Criteria).

Diaphragm flexibility, deflection and torsional response are thought to
potentially influence seismic force distribution and will be investigated
in analytical work.

assessment and retrofit tasks. A performance summary of variants will be
developed that identifies what existing configurations and retrofit
solutions meet the performance objectives.

Validation comparisons of analytical modeling will be conducted when
possible, with limited comparisons to component, assembly, or fullbuilding test results, or comparisons to other accepted analysis results
equations.
ATC-110
19

Based upon the global retrofitting schemes developed, appropriate
determination of code-based design parameters (R, Cd, Ώo) will be
performed using FEMA P695 methodologies, which can be used for
subsequent prescriptive and engineered design solutions.
Team:
Two researchers assisted by two graduate students (one graduate student per
researcher).
An independent analysis peer reviewer, either researcher or practitioner.
A resource group of two structural engineers, one construction practitioners
to identify building parameters and variations and provide other required
input to researcher.
1.4.2
There are three primary purposes of this task:

Establish a method by which first story wall bracing and its load path can
be compared to the demands identified in Section 1.4.1.

Quantify the capacities of wall components and load path connections
from existing test and design information in order to gage acceptability.

construction and identifying houses that require retrofit.
Details of Study:

Establish component and load path connection capacities and identify
method for comparison of capacities with demands identified in Section
1.4.1. To the extent possible, this should address capacities of both
original construction and common retrofit approaches.

Collect available assessment criteria and establish assessment
For the first activity, a methodology for comparison of demand and capacity
will be established. It will be decided whether this comparison is made at
code level forces, by capacity methodologies, or other methods, considering
 factors and/or other modifiers. Assessment methods and load path checks
will be derived from the results of analytical studies conducted under Section
1.4.1.
20
ATC-110
For the second activity, available test data describing in-plane load deflection
behavior of bracing wall components and load path connections will be
collected and supplemented by engineering calculations where necessary.
Capacities of commonly occurring bracing materials and connections will be
developed where possible for comparison of demands. Capacities of load
path details commonly used in retrofits will be developed where possible.
Example components and connections include:

Lower level wall components with various bracing materials.

Anchor bolts to foundations, including foundation material and
configuration variations.

Load path connections from the foundation sill plate to the underside of
the upper story including non-typical variants that occur commonly in
retrofits.


For the third activity, based on information previously developed and
available assessment tools, components and load path connections that
following:




Assessment tools will be developed to the point where they are ready for
implementation.
Team:
A group consisting of two structural engineers, two staff engineers and one
construction practitioner, and one geotechnical engineer.
The researcher(s) involved in Section 1.4.1.
1.4.3
The purpose of this task is to provide prescriptive design solutions for the
retrofit of as many commonly occurring conditions as possible, and provide
engineering design methods and tools for use where engineered design is
ATC-110
21
required or chosen. Triggers will also be established for those conditions
where engineered solutions will be required.
Details of Study:
It is anticipated that the development of prescriptive and engineered retrofit


retrofits.

Developing typical details.

Developing plan sets which incorporate the items above.
Steps in development of the engineered retrofit procedures include:

Development of the engineering methodology.

shortcuts and tabulated engineering properties for use in analysis.
Team:
A group of two lead engineers, two staff structural engineers, one
construction practitioner, one geotechnical engineer and one CAD drafter
1.4.4
Development of Prestandard Provisions
The purpose of this task is to transform retrofitting procedures developed in
Section 1.4.3 into prestandard provisions, including development of standard
Team:
construction practitioner and one CAD drafter.
22
ATC-110
1.5
Hillside Dwellings
Section 1.5 addresses wood light-frame dwellings with a crawlspace below
the lowest framed floor, including the following dwelling configurations:

Dwellings with cripple wall systems sited on slight to steep sloped
hillsides with a crawlspace below all or a portion of the framed floors.

Dwellings on moderate to steep sloped hillsides with wood light-frame
post and beam systems that have no bracing, have wood or steel diagonal
bracing, or have skirt walls, when retrofit using cripple wall or base level
diaphragm solutions.

Side cripple walls on stepped continuous foundations. Cripple walls on
sloped continuous foundations (i.e. foundation top and bottom faces cast
at same slope as the hillside without steps; this is common in California
hillside homes).

Foundation systems may include shallow continuous foundations,
shallow isolated foundations, or deep foundations (such as drilled piers)
with or without connecting grade beams.
Figure 1-1 illustrates hillside dwelling terminology used in this section.
Figure 1-1
Hillside dwelling terminology.

Anchorage to the uphill foundation for dwellings on sloped sites. In
coordination with Section 1.3, this will consider a zero height cripple
wall on the uphill foundation side in combination with side walls and
with downhill cripple walls that are short, medium and tall, in order to
establish distribution of demand, anchorage requirements at the uphill
foundation, and deformation limitations at the side and downhill cripple
walls. This will consider both conventional anchorage approaches and
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23
the anchorage of the base level diaphragm approached developed by the
City of Los Angeles for hillside dwellings.

Tall downhill and sloped or stepped side cripple walls on steeply sloped
sites.

Diagonal bracing systems for post and pier dwellings on steeply sloped
sites.
Under Section 1.5:

Tall cripple walls are thought to have significant contributions to
displacement due to overturning, and possibly due to foundation and soil
deformations. Analytical modeling will consider these effects.
Table 1.5-1.
Table 1.5-1 Tasks Related to Hillside Dwellings
Research or Study
Estimated Timeline
Side cripple wall 2-D detailed study
Mos. 1-6
Cripple wall dwelling study
Mos. 6-18
Base level diaphragm study
Mos. 12-24
1.5.1
Mos. 9-27
Mos. 18-30
Mos. 24-36
These analytical investigations build on results of investigations from
Sections 1.3 and 1.4. The purposes of this study are to

Identify seismic demands for anchorage to uphill foundations.

Identify seismic bracing systems that will provide adequate performance.

Determine the seismic demand appropriate for design of retrofits.
The study will look at two primary types of structural systems between the
occupied floor and grade (cripple wall and post and beam) and determine
bracing systems and retrofit methods.

24
Cripple wall two-dimensional detailed study: The effectiveness and
performance issues for stepped and sloped side walls will be
investigated. The purpose is to follow up on the cripple wall testing
ATC-110
conducted by Chai et al. (CUREE W-17, 2002) and identify whether
there are systematic issues with the seismic performance of stepped or
sloped cripple walls. A combination of non-linear static (push-over)
analysis will be conducted. Planar models of cripple wall components are
intended. Elements will be modeled on a detailed level (i.e. sheathing,
framing members and fasteners will be modeled). Vertical loads will be
investigated for cripple walls on sloped foundations to the extent that
vertical loads affect seismic load path. In addition, this analysis effort
will provide guidance to the following analytical efforts regarding best
modeling of stepped and sloped cripple walls at the component level.

Cripple wall dwelling analytical study: It is perceived that tall side walls
and downhill walls may not adequately brace hillside dwellings. The
stiffness requirements for effective tall downhill walls and stepped or
sloped side walls will be evaluated to determine where such walls can be
effective. Consideration of all possible sources of deformation, including
foundation and soils deformation are seen to be potentially important to
performance, and intended to be specifically evaluated to determine
order of influence. Diaphragm flexibility will also be investigated to
determine modeling approach required. Where downhill walls and side
walls are effective, the magnitude and distribution of cripple wall and
anchorage forces will be identified for assessment and retrofit. Nonlinear response history analysis will be conducted on three-dimensional
building models to determine probabilities of exceedance of acceptance
criteria. P-delta behavior will be included however vertical excitation
will be ignored. Modeling will be at the component level (i.e. cripple
wall).

Base level diaphragm analytical study: Develop solutions that involve
anchorage of the base level diaphragm to the uphill foundation (City of
Los Angeles approach) as an alternative approach for either cripple wall
dwellings or post and beam dwellings. Non-linear response history
analysis will be conducted on three-dimensional building models to
determine probabilities of exceedance of acceptance criteria. Analysis
will develop force demands and deformation limits for design of
retrofits.
These studies are intended to provide analytical results that will serve as a
basis for the tasks that follow in Sections 1.5.2, 1.5.3 and 1.5.4.
No investigation of vertical ground motion is intended. P-delta effects are to
be included in modeling, except as noted above. Elements will be modeled
at the global component level (i.e., wall force-displacement hysteretic
ATC-110
25
behavior per unit length). For the latter two analyses, pancake modeling is
acceptable.
Details of Study:
Existing hillside dwelling configurations will be surveyed to establish
example buildings and define any required scope limits.
Example dwellings will be designed as necessary to facilitate the analytical
studies.
Available test data for bracing components will be collected, evaluated, and
appropriate analytical characterization of bracing systems established.
Limited validation comparisons of analytical modeling will be conducted as
possible. See Section 1.3.1 discussion.
For the cripple wall two-dimensional detailed study the following variants
will be evaluated:

Variations in site slope leading to variations in number and height of
steps (1:4, 1:3, 1:2, 1:1) (large step, small step).

Variation in cripple wall sheathing material (stucco, wood structural
panel, stucco and wood structural panel combined, T1-11).

Cripple walls with wood structural panel retrofit.

Sloped cripple walls (two variants to identify differences from stepped).
For the cripple wall dwelling, the following variants will be evaluated (3-D
model):

Variations in site slope (1:4, 1:3, 1:2, 1:1).

Variations in foundation system.

Variations in site soil conditions.

Variation in cripple wall sheathing material (stucco, wood structural
panel, stucco and wood structural panel combined, T1-11).

Cripple walls with wood structural panel retrofit.

Variation in dwelling configuration (with and without partial occupied
lower floors in downhill section, simple and more complex building
plans).

Level of seismicity (e.g., IRC SDC C/D0, D1, D2,max)
For the base level diaphragm anchorage the following variants will be
evaluated:
26
ATC-110

Variations in site slope (1:4, 1:3, 1:2, 1:1).

Variation in dwelling configuration (with and without partial occupied
lower floors in downhill section, simple and more complex building
plans).

effectiveness of the systems, scoping required to assure effectiveness,
characterization of the demand and distribution of demand for subsequent
assessment and retrofit tasks.
Team:
Three researchers assisted by three graduate students (one graduate student
per researcher).
A group consisting of two lead structural engineers, two staff structural
engineers, one geotechnical engineer, and one construction practitioner. They
will identify building parameters and variations and provide other required
input to researcher. They will also perform building designs as required.
1.5.2
There are three primary portions of this task:

Establishment of a method by which bracing systems and their load path
can be compared to the demands identified in Section 1.5.1.

Quantification of the strength and stiffness of existing bracing systems
and load path connections.

Identification of methodologies for assessing the acceptability of existing
construction and identifying houses that require retrofit.
Details of Study:
For the first portion, a methodology for comparison of demand and capacity
will be established, building on the directions set in Tasks 1.2.2 and 1.3.2. It
will be decided whether this comparison is made at a code level forces, by
capacity methodologies, or other method.
For the second portion, available test data describing in-plane load-deflection
behavior of bracing systems and connections and fasteners in the seismic
load path will be collected, and supplemented extensively by engineering
ATC-110
27
calculations. Strength and stiffness characteristics of commonly occurring
bracing systems and connections will be developed where possible. Strength
and stiffness of load path details used in retrofit will be developed where
possible. Example systems and connections include:

Tall downhill cripple walls.

Stepped side cripple walls.

Sloped side cripple walls.

Anchorage to the uphill foundation for loads in both directions.
For the third portion, based on information previously developed and
available assessment tools, components and load path connections that
prescriptive and engineered assessments will be developed. Assessment tools
will be developed to the point where they are ready for implementation.
Team:
A group of two lead structural engineers, two staff structural engineers, one
geotechnical engineer, and one construction practitioner.
1.5.3
The retrofit methods will first address engineered design methodologies.
Where possible prescriptive bracing methodologies will be developed.
Details of Study:
It is anticipated that development of engineered retrofit procedures will occur
first, and that the engineering methodology will guide the design of
prescriptive retrofit methods.
Steps in development of the engineered retrofit procedures include
development of the engineering methodology and development of tools to
assist the designer, possibly including analysis shortcuts and tabulated
engineering properties for use in analysis.
Steps in the development of prescriptive retrofit procedures will include
defining the scope of dwellings to which the procedures can be applied,
developing example buildings to use as a basis for proportioning of retrofit,
development of typical details, and development of plan sets based on the
previous information.
28
ATC-110
Team:
A group of two lead structural engineers, two staff structural engineers, one
geotechnical engineer, one construction practitioner, and one CAD drafter.
1.5.4
Transform retrofit procedures developed in Task 1.5.3 into prestandard
provisions, including development of standard language and appropriate
documentation format.
Team:
1.6
Split-Level Dwellings
Section 1.6 addresses wood light-frame dwellings with split-level
configurations. The term split level refers to dwelling configurations which
include vertical offsets greater than the depth of the floor framing members.
Such offsets are commonly approximately one-half story tall. Figure 1-2
shows a commonly occurring split-level configuration occurring in
combination with a room-over-garage condition.
Figure 1-2
Front elevation of common split-level dwelling configuration.
Table 1.6-1.
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29
Table 1.6-1 Tasks Related to Split-level Dwellings
Research or Study
Estimated Timeline
Mos. 1-12
Mos. 6-18
Mos. 6-18
Mos. 18-24
1.6.1
The purposes of this study are:

Identification of the behavior of concern leading to significant damage to
and partial collapses of split-level dwellings.

Determination of the seismic force and deformation demands appropriate
for design of retrofits.

Non-linear response-history analysis will be conducted. Elements will be
modeled on a component level (i.e. wall components), except that special
attention will be paid to linking of the structures at the vertical offset to
identify force and deformation demands.

No investigation of vertical ground motion is intended. P-delta effects
are to be included in modeling. Elements will be modeled at the global
component level (i.e., cripple wall force-displacement hysteretic
behavior per unit length).
The analytical studies are intended to provide big-picture guidance regarding
vulnerabilities and general directions for mitigation. Once general direction
is developed, it is anticipated that standard engineering calculations will be
primarily relied upon for design guidance.
Details of Study:
The performance of split-level dwellings is believed to be primarily related to
deformation compatibility issues at the split-level interface. Damage is
believed to be primarily related to the deformation capacity being exceeded.
Available retrofit details provide positive ties between the two sides, but the
force and deformation capacities required for adequate performance are not
known.
Surveying of existing split-level dwellings to capture the range of commonly
occurring configurations and construction will be necessary at the start of the
analytical investigations.
30
ATC-110
Example dwellings will be designed as necessary to facilitate the analytical
studies.
Available test data for bracing components (including the work of Tasks 1.3,
1.4 and 1.5) will be collected, evaluated, and appropriate analytical
characterization of bracing systems established. Limited validation
comparisons of analytical modeling will be conducted as possible, as
described in Section 1.3.1. The following variants will be evaluated:

Four variants of dwelling configuration including two cripple wall
dwellings and two slab-on-grade dwellings.

Three variants of change in floor elevation at the split level.

Two variants in number of stories.

Two variants of cripple wall bracing.

Two variants of garage front bracing.

Four variants of retrofit approaches including two with direct connection
to the common wall and two with collectors.
Team:
Two researchers assisted by two graduate students (one graduate student per
researcher).
An independent analysis peer reviewer, either researcher or practitioner
A resource group of two engineering and one construction practitioners to
identify building parameters and variations and provide other required input
to researcher
1.6.2 & 1.6.3
Assessment and Retrofit Procedures
The primary objectives of these tasks are:

Identify split-level configurations and detailing that are of concern.

Identify appropriate strategies for mitigating life-safety issues related to
split-level behavior.

Identify approaches to either force or deformation capacity needed for
performance.

Develop methodologies for assessment of existing conditions

Develop retrofit details.
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31
Details of Study:
It is anticipated that development of prescriptive and engineered assessment
and retrofit procedures will be occur in parallel, and that the engineering
methodology will guide the design of prescriptive retrofit methods.
Steps in the development of prescriptive retrofit procedures will include
defining the scope of dwellings to which the procedures can be applied,
developing example buildings to use as a basis for proportioning of retrofit,
development of typical details, and development of plan sets based on the
previous information.
Steps in development of the engineered retrofit procedures include
development of the engineering methodology and development of tools to
assist the designer, possibly including analysis shortcuts and tabulated
engineering properties for use in analysis.
Team:
A group of two lead structural engineers, 2 staff structural engineers, and one
construction practitioner.
A CAD drafter.
1.6.4
Team:
A group of two lead structural engineers, 2 staff structural engineers, one
construction practitioner, and a CAD drafter.
1.7
Inadequate Wall Bracing – Occupied Spaces
This section addresses wood light-frame dwellings with inadequate wall
bracing within the occupied spaces, including:

32
One story buildings or the first story of a multi-level building excluding
garage areas, which have inadequate wall bracing in any of the principal
directions.
ATC-110

The assessment of cripple walls and any foundation systems either on
related flat sites or hillside conditions (addressed in Sections 1.3 and 1.5
respectively).
Typical damage modes would include:

Large permanent drifts in the first story leading to significant cracking of
the vertical interior and exterior wall systems,

Partial or complete weak story collapse,

Compromised function of both interior and exterior doors and windows
due to racking,

Damage to exterior glazing systems, gypsum board or plaster ceilings,

Damage to non-ductile mechanical, electrical and plumbing systems.

Existing perimeter and interior bearing and non-bearing wall elements
that comprise the key elements of the vertical force-resisting system.

Attachment of exterior and interior bearing and non-bearing wall
elements to the superstructure above and to the existing or new
foundation system.

Second level diaphragm and collector elements – specifically their ability
to transfer superstructure inertial loads to first level lateral-force resisting
elements.

Existing or new foundation required for the support of those wall
systems participating as lateral-force-resisting elements.
Anticipated retrofit schemes which will be developed under Section 1.7
include:

Sheathing of existing perimeter and interior bearing wall elements that
comprise the key elements of the gravity force-resisting system.

Sheathing of existing interior non-bearing wall elements at strategic
locations to increase lateral strength of the overall lateral force-resisting
system.

Introduction of new exterior or interior sheathed wall systems to increase
lateral strength.

Addition of new concrete foundation systems as required to properly
support the new or existing elements of the first story lateral forceresisting system.
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33

Addition of new perimeter or interior steel moment frames, including
new foundation systems and attachments to increase lateral strength.
This is assumed to be an engineering approach and non-prescriptive

New attachments at the top and base of new or existing wall elements.

Proper attachment for existing exterior wood panel systems such as T111 siding.
Table 1.7-1.
Table 1.7-1 Tasks Related to Assessment and Retrofit of homes with
inadequate Wall Bracing within the Occupied Space
Research or Study
Estimated Timeline
Mos. 1-18
Mos. 12-24
1.7.1
Mos. 18-30
Mos. 30-36
Analytical investigations will study the seismic demand at the lower level of
single or multi-level residential dwellings associated with the targeted
seismic performance measures and criteria developed under Section 1.2.
The purpose of the study will be to determine the seismic demand and the
distribution of this demand at the first level as it correlates to varying
horizontal geometries, vertical geometries, and bracing materials in the
superstructure and lower level wall systems. Specifically, this study
addresses wall systems that appear to have excessive glazing on one or more
exterior walls lines and /or inadequate sheathing to laterally support lateral
loads. This study will also investigate the effectiveness of interior bearing
and non-bearing walls on the distribution of forces and overall building
drifts. This study is intended to provide analytical results that will serve as a
basis for tasks in Section 1.7 that follow. FEMA P-807 will be studied to
determine whether it will have direct applicability to this effort.
Details of Study:

o
34
Single or multi-level residential buildings with rectangular or nonrectangular plan geometries (e.g., L-shaped and T-shaped).
ATC-110
o
Plan configurations with limited solid wall panel systems at the
perimeter.
o
Plan configurations with large open spaces which may result in
disproportionately higher loads to both perimeter and interior wall
panel systems.
o
Structures with first story heights ranging from eight to ten feet.

Collect available data pertaining to the seismic response of wood lightframe buildings with inadequate wall bracing within the occupied space.

Collect available data pertaining to excessive building drifts within light
wood frame buildings and associated damage to critical non-structural
components such as gas, heating, plumbing and typical exterior glazing.

The survey of existing analytical studies on inadequate wood buildings

characterizations of bracing systems will be established.

of materials and material conditions. Possible materials include stucco,
horizontal wood siding, T1-11 siding, exterior gypsum board with
stucco, interior gypsum board, and plaster. Selection of materials will
include consideration of how common they are, how much they affect
behavior, and availability of data from which to develop modeling.

Retrofit schemes will be developed by considering the addition of
sheathing materials (e.g., wood structural wall panels in combination
with the above listed existing wall sheathings), steel portal frames and
cantilevered columns. Additional retrofitting systems may also be
developed.

materials.

acceptance criteria under pre-determined seismic hazard levels.

Elements will be modeled at the global component level.

ATC-110
35

36
following:
o
Determination of seismic demands (force and displacements) and the
distribution of seismic demands at the first story.
o
Determination of the relative seismic demands (force and
displacement) of the lower story relative to the upper stories as a
base line for the development of retrofitting schemes.
o
Sensitivity or degree to which increasingly narrow pier widths of
various construction materials lead to excessive drift and increased
probability of collapse. Compare to acceptance requirements
developed under Section 1.2.2 (Development of Performance
Measures and Criteria).
o
Sensitivity or degree to which interior bearing and non-bearing wall
partitions may decrease excessive drift and decrease probability of
collapse.
o
Overturning study of wall panels of varying aspect ratios (with the
goal of determining a prescriptive methodology for higher aspect
ratio walls or hold-downs).

Diaphragm flexibility, deflection and torsional response are thought to
potentially influence seismic force distribution and will be investigated
in analytical work.


equations.
ATC-110

determination of code-based design parameters (R, Cd, Ώo) will be
Team:

Two researchers assisted by two graduate students (one graduate student
per researcher).


A resource group of two engineering and one construction practitioners
to identify building parameters and variations and provide other required
input to researcher.
1.7.2

Establish a method by which first story wall bracing and its load path can
be compared to the demands identified in Section 1.7.1.

Quantify the capacities of wall components and load path connections, as
well as identify excessive drifts, from existing test and design
information in order to gage acceptability.

construction.
Details of Study:

method for comparison of capacities with demands identified in Task

For the first purpose, a methodology for comparison of demand and capacity
will be established. A methodology for comparison of deformations which
would result in permanent residual drifts thus causing extensive structural
and non-structural damage will also be established. It will be decided
whether this comparison is made at code level forces, by capacity
methodologies, or other method.
ATC-110
37
For the second purpose, available test data describing in-plane load
deflection behavior of bracing wall components and load path connections
will be collected and supplemented by engineering calculations where
necessary. Capacities of commonly occurring bracing materials and
connections will be developed where possible. Capacities of load path details
commonly used in retrofits will be developed where possible. Associated
first-level drifts which might lead to extensive non-structural damage will
also be determined and may be used as secondary acceptance criteria.
Example assemblies and building conditions may include the following:

Lower level exterior wall components with various bracing materials.

Interior wall components with various bracing materials.

Connections of roof or second floor members to areas of first level
bracing.

Anchor bolts to foundations of limited wall sections, including
foundation material and configuration variations.

Load path connections from the foundation sill plate (where occurs) to
the underside of the upper story including non-typical variants that occur
commonly in retrofits.


For the third purpose, based on information previously developed and
available assessment tools, components and load path connections such as
anchor bolt to foundations and roof or floor diaphragm vertical wall elements
that require assessment will be identified, and methodologies for both
following:




Team:

A group consisting of two lead engineers, two staff engineers and one

The researcher involved in Section 1.7.1.
Timeline:
38
ATC-110
This study will take approximately 12 months, thought to occur in months 12
to 24 of the overall timeline.
1.7.3
retrofit of as many commonly occurring conditions as possible, and provide
where engineered solutions will be required. Based upon the wider range of
possible plan and geometric configurations, which now may include interior
partition walls and greater consideration of full wall opening versus punched
wall opening, it is anticipated that fewer prescriptive solutions may be
available as compared to the development of engineering guidelines.
Details of Study:
It is anticipated that development of prescriptive and engineered retrofit


retrofits.


Steps in development of the engineered retrofitting procedures include:


While unknown at this time, it is currently assumed that fewer prescriptive
solutions may be developed and that a great emphasis may need to be put on
engineering and engineering-assisted solutions.
Team:
A group of three lead engineers and three staff engineers, one construction
practitioner, and one drafter.
ATC-110
39
1.7.4
The purpose of this task is to transform retrofit procedures developed in Task
1.7.3 into prestandard provisions, including development of standard
Team:
A group of two lead engineers, one staff engineer, one construction
practitioner, and one drafter.
1.8
Anchorage of Slab on Grade Dwellings
Section 1.8 addresses the anchorage one or two story light-frame dwellings
to slab-on-grade foundation systems including:

Single and possibly multi-level residential units supported completely by
a slab-on-grade foundation system with various plan configurations.

Note that the performance of the interior and wall systems will be
evaluated under Section 1.3 and 1.7.

Attachment of exterior stucco to the sill plate including conditions with
the weep screed will be evaluated in section 1.3.
Typical damage modes would include failure of the mudsill to concrete slab
on grade foundation elements resulting in displacement of the superstructure
relative to the slab-on-grade/foundation system and localized damage.

Anchorage of ground-level wall panel systems, including perimeter and
interior bearing and non-bearing walls of various material compositions.

Attachment of ground-level interior and exterior walls to the diaphragm
above.
Anticipated retrofitting schemes, which will be developed under Section 1.8,
include:

Installation of additional wall to foundation slab anchorage for interior
and exterior wall systems utilizing expansion or adhesive anchors.

New attachments at the top of interior non-bearing partitions to the floor
or roof diaphragm where they can be utilized as new braced wall panels.
Table 1.8-1.
40
ATC-110
Table 1.8-1 Tasks Related to Anchorage of Slab on Grade Dwellings
Research or Study
Estimated Timeline
Mos. 1-6
Mos. 6-12
1.8.1
Mos. 12-18
Mos. 18-24
Analytical investigations will study the seismic demand and variation in
seismic demand distribution at the interface of the first floor wall systems to
the slab on grade foundation system with the targeted seismic performance
measures and criteria developed under Section 1.2. This study will also
investigate the effectiveness of interior bearing and non-bearing walls on the
distribution of forces and overall building anchorage. This study is intended
to provide analytical results that will serve as a basis for tasks in Section 1.8
that follow.
Details of Study:

o
Single or multi-level residential units with rectangular or more
complex plan geometries (e.g., L-shaped and T-shaped).
o
Plan configurations with limited exterior solid wall panel systems at
the perimeter.
o
Plan configurations with large open spaces which may result in
disproportionately higher loads to both perimeter and interior wall
panel systems.
o
Structures with first floor heights ranging from eight to ten feet.

characterization of bracing systems will be established.

of materials and material conditions. Possible materials include stucco,
horizontal wood siding, T1-11 siding, exterior gypsum board with
stucco, interior gypsum board and plaster. Selection of materials will
ATC-110
41
include consideration of how common they are, how much they affect
behavior, and availability of data from which to develop modeling.
42

Retrofit schemes will be developed by considering accurately
proportioned lateral loads to both exterior and interior wall elements and
supplementing existing anchorage where appropriate.

materials.

Limited non-linear response history analyses may be conducted on threedimensional building models to determine the distribution of forces and
probabilities of exceedance of acceptance criteria under pre-determined
seismic hazard levels.

Elements will be modeled at the global component level


following:
o
Determination of seismic demands (forces) and the distribution of
seismic demands at the first story.
o
Sensitivity or degree to which interior bearing and non-bearing wall
partitions may decrease component anchorage damage and the
probability of local collapse.


ATC-110
equations.

determination of code-based design parameters (R, Cd, ΏoΏo) will be
Team:

One researcher with one graduate student.


One engineering and one construction practitioner to identify building
parameters and variations and provide other required input to researcher.
1.8.2

Establish a method by which the first story wall to foundation load path
can be compared to the demands identified in Section 1.8.1.

Quantify the capacities of existing wall to slab connections both for
existing and retrofitted conditions in order to gage acceptability.

construction and identifying conditions that require retrofit.
Details of Study:

method for comparison of capacities with demands identified in Section

For the first purpose, a methodology for comparison of demand and capacity
will be established. It will be decided whether this comparison is made at
code level forces, by capacity methodologies, or other methods.
For the second purpose, available test data describing in-plane, and possibly
out-of-plane, wall components anchorage will be collected and supplemented
by engineering calculations where necessary. Capacities of commonly
ATC-110
43
occurring connections will be developed. Capacities of load path details
commonly used in retrofits will be developed. Example assemblies and
building conditions may include the following:

Connections of anchor bolts to foundations of longer as well as shorter
wall sections, including various mudsill dimensions and variations in
slab on grade systems.

Foundation connections resisting primarily shear loads.

Foundation connections resisting overturning loads from existing or
retrofitted load paths.
For the third purpose, based on information previously developed and
available assessment tools, load path connections that require assessment will
be identified, and methodologies for both prescriptive and engineered
assessments will be developed considering the following:



Team:

A group consisting of one lead engineer, one staff engineer and one

The researcher involved in Section 1.8.1.
1.8.3
retrofit of as many commonly occurring conditions as possible and provide
where engineered solutions will be required.
Details of Study:
It is anticipated that development of retrofit methodologies will be largely
prescriptive but will guide engineering methodologies.
44


retrofitting.
ATC-110


Steps in development of the engineered retrofitting procedures include:


Team:
One lead engineer and one staff engineer, one construction practitioner, and
one drafter.
1.8.4
The purpose of this task is to transform retrofitting procedures developed in
Section 1.8.3 into prestandard provisions, including development of standard
Team:
A group of lead engineering, one staff engineer, one construction
practitioners, and one drafter.
1.9
Parts and Portions of Dwellings
This section addresses:

Parts and portions of dwellings, attached to and supported off of the
dwelling, including decks, porches, porch roofs, stairs, landings, patio
covers, carports.

Masonry veneer.
The focus of this section will be the compilation of existing research and
design information and synthesis into practical prescriptive details and
engineering guidance. Development of prescriptive details addressing
commonly occurring configurations will be prioritized.
Table 1.9-1.
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45
Table 1.9-1 Tasks Related to Parts and Portions of Dwellings
Research or Study
Estimated Timeline
1.9.1 Compilation of resources
Mos. 0-6
Mos. 6-18
Mos. 6-18
Mos. 18-24
1.9.1
Compilation of Resources
The purposes of this task are to compile and prioritize available information
to guide tasks 1.9.2, 1.9.3 and 1.9.4.
Available resources of interest are:

Deck testing: Understanding the Lateral strength, Load Path and
Occupant Loads of Exterior Decks, Brian Parsons, MS Thesis,
Washington State University, 2012.

Testing of structures with masonry veneer: Seismic Performance Tests of
Masonry and Masonry Veneer, Klingner et al., 2010.
Team:
A group of one research, two lead structural engineers, and one construction
practitioner.
Assessment and Retrofit Procedures
The primary portions of this task are:

Identify configurations that need to be addressed.

Identify appropriate strategies for mitigating seismic damage.

Identify approach for quantifying mitigation criteria (force, deformation,
etc.).

Develop methodologies for assessment of existing conditions.

Develop retrofit details.
Team:
The researcher involved in Task 1.9.1.
46
ATC-110
1.9.4
Team:
A group of one lead structural engineer, one construction practitioner, and
one CAD drafter.
1.10
Recommendations and Priorities
This section summarizes estimated budget requirements, recommended
priorities and phasing, and approximate schedule for the development of the
prestandard.
1.10.1 Summary of Program
The overall program outlines a series of tasks and engineering studies to
address key gaps in the current state-of-knowledge related to seismic
assessment and retrofit of one- and two-family dwellings. The recommended
tasks and engineering studies are intended to: (1) investigate the behavior of
existing configurations and construction details associated with typical
dwellings; (2) evaluate the expected seismic performance; (3) develop a
simplified assessment methodology for identifying deficiencies without the
need for engineering calculations; and (4) develop prescriptive retrofitting
techniques that can be applied by non-engineers to eliminate deficiencies.
The tasks are summarized in Table 1.10-1. Together, the recommended tasks
and engineering studies cover the most common types of residential
construction, and key deficiencies that have been known to perform poorly in
past earthquakes. Nonlinear response history analyses are proposed to
statistically investigate expected behavior and parametrically evaluate
variable conditions. Extensive engineering calculations are anticipated to
“pre-engineer” solutions for identified deficiencies. To cover a wide variety
of existing conditions, reliably evaluate the expected seismic performance of
multiple dwelling configurations, and perform the engineering studies
required to develop solutions for many uncertain conditions, the overall
program is necessarily comprehensive.
Detailed information on the purpose of each task, the scope of the
recommended analytical investigations, engineering studies, and the
development of assessment and retrofit techniques was provided in the
preceding sections.
ATC-110
47
1.10.2 Estimated Budget Requirements
The total estimated budget for the tasks outlined in this development plan is
summarized in Table 1.10-1.
Table 1.10-1
Reference
Section
1.2
Task or Engineering Study
Estimated
Budget
1.2.1
Determine Initial Assessment and Retrofit Design
Methodologies
$110,000
1.2.2
Development of Performance Measures and Criteria
$110,000
1.2.3
Prestandard Development
$260,000
1.2.4
Development of Engineered Approach
$160,000
1.2.5
Pilot Study - Cripple Walls
$320,000
1.2.4
Pilot Study - Chimneys
$180,000
1.3
1.3.1
$300,000
1.3.2
$160,000
1.3.3
Development of Retrofit Procedures
$200,000
1.3.4
$110,000
1.4
1.4.1
$280,000
1.4.2
$210,000
1.4.3
$310,000
1.4.4
$170,000
1.5
Hillside Dwellings
1.5.1
$450,000
1.5.2
$190,000
1.5.3
$310,000
1.5.4
$220,000
1.6
48
Summary of Proposed Tasks and Engineering Studies
1.6.1
$230,000
1.6.2
$170,000
1.6.3
$180,000
1.6.4
$180,000
ATC-110
Table 1.10-1 Summary of Proposed Tasks and Engineering Studies
(continued)
Reference
Section
1.7
Estimated
Budget
1.7.1
$170,000
1.7.2
$190,000
1.7.3
$230,000
1.7.4
$180,000
1.8
Anchorage of Slab-on-Grade Dwellings
1.8.1
$70,000
1.8.2
$80,000
1.8.3
$110,000
1.8.4
$120,000
1.9
1.9.1
Compilation of resources
$110,000
1.9.2
$130,000
1.9.3
$150,000
1.9.4
$130,000
Total Estimated Budget
$6,480,000
Estimated budget requirements by study area or dwelling type are
summarized in Table 1.10-2.
Table 1.10-2
Reference
Section
1.2
Estimated Budget by Study Area or Dwelling Type
Study Area or Dwelling Type
Estimated Budget
$1,140,000
1.3
$770,000
1.4
House or Room over Garage or Deck
$970,000
1.5
Hillside Dwellings
1.6
$760,000
1.7
$770,000
1.8
$380,000
1.9
$520,000
$1,170,000
Total Estimated Budget
$6,480,000
In order to comprehensively investigate all parameters of interest, the number
of permutations quickly rises to levels that are impractical to implement. As
a result, the recommendations are a compromise between the need to cover
ATC-110
49
variation in important controlling parameters, and what can reasonably be
accomplished in a limited time frame.
In preparing budget estimates, individual tasks and engineering studies have
been priced individually. Some consideration has been given to combining
studies where feasible. It is anticipated that recommendations will evolve as
implementation progresses, and that additional efficiencies will be realized as
results become available, lessons are learned, and the state of knowledge
improves on which parameters are most important.
1.10.3 Budget Assumptions
Budgeting assumptions have been based on the traditional ATC project
model, which consists of a Project Technical Director as technical lead,
assisted by a group of researchers and practitioners on a Project Technical
Committee responsible for managing and implementing the work, and one or
more working groups responsible for performing the work. Working groups
can consist of members of the Project Technical Committee assisted by
graduate students or staff engineers.
The following basic budget categories were included in the estimates for total
project costs:

Consultant services (lead practitioners, researchers, staff engineers and
graduate students).

Management, oversight, and review activities.

Direct expenses (e.g., travel).

Allowance for overhead.
1.10.4 Priority and Schedule Recommendations
The list of tasks and engineering studies is comprehensive and ambitious,
and practical implementation will require prioritization. Considerations for
prioritization include: (1) the most common types of dwellings; (2) the most
commonly observed deficiencies; (3) the severity of the consequences
associated with each deficiency; (4) the likelihood of success in the
development of prescriptive retrofit procedures; and (5) where retrofit would
provide the most advantageous result. Based on the above considerations,
Table 1.10-3 summarizes recommended prioritization of the tasks.
50
ATC-110
Table 1.10-3
Recommendations for Prioritization of Tasks
Priority
Level
Approximate
Timeline
1
1.2 General Requirements
1 year
2
1.3 Cripple Walls and Anchorage to Foundation
1.4 House or Room over Garage
1.5 Hillside Dwellings
3 years
3 years
3 years
3
1.6
1.7
1.8
1.9
6 years
6 years
6 years
6 years
Inadequate Wall Bracing- Occupied Spaces
Individual research or engineering studies contributing to each priority level
are summarized in the sections that follow.
1.10.5 Priority Level 1
Completing studies on General Requirements is considered Priority Level 1
because these studies for the basis of the work that will be done on the other
studies. Studies related to Priority Level 1 objectives are summarized in
Table 1.10-4.
Table 1.10-4
Reference
Section
1.2
Priority Level 1 Studies
Research or Engineering Study
Estimated
Budget
$1,140,000
Total Estimated Budget – Priority Level 1
$1,140,000
Studies related to Priority Level 2 objectives are summarized in Table 1.10-5.
Table 1.10-5
Reference
Section
Estimated
Budget
1.3
$770,000
1.4
$970,000
1.5
Hillside Dwellings
$1,170,000
ATC-110
$2,910,000
51
Studies related to Priority Level 3 objectives are summarized in Table 1.10-6.
Table 1.10-6
Reference
Section
Estimated
Budget
1.6
$760,000
1.7
$770,000
1.8
$380,000
1.9
$520,000
$2,430,000
1.10.8 Schedule
The anticipated overall schedule to complete Priority Level 1, 2, and 3
studies is 6 years. A detailed schedule of Priority Level 1 and Priority Level
2 studies is shown in Figure 1-3. A detailed schedule of Priority Level 3
studies is shown in Figure 1-4.
1.10.9 Adoption into Codes and Standards
As a prestandard, the eventual product of this work will need to pass through
an ANSI-approved consensus process to become a standard. As a standard,
it can be referenced in the building code and other relevant standards.
Potential targets for adoption include future editions of the International
Building Code (ICC, 2015), International Existing Building Code (ICC,
2015), International Residential Code (ICC, 2015), and ASCE 41-13 Seismic
Assessment and Retrofit of Existing Buildings (ASCE, 2014).
52
ATC-110
ATC-110
53
Figure 1-3
Detailed schedule of Priority Level 1 and Priority Level 2 studies.
54
ATC-110
Figure 1-4
Detailed schedule of Priority Level 3 studies.
Appendix A
Prestandard Outline and
Recommended Scope
PRESTANDARD
SCOPE: The prestandard will comprehensively address assessment and seismic
retrofit of one- and two-family detached dwellings. Townhouses, as defined in
the IRC, will be included to the extent that evaluation and retrofit measures for
one- and two-family dwellings also apply to townhouses (new vulnerabilities
specific to townhouses will not be added); houses divided into multiple living
units will be treated in a similar fashion. Scoping limits will be used as
necessary to limit the size of townhouse to which the prestandard applies. Use
of engineered retrofit solutions is generally anticipated for townhouses.
NOTE: Items in italics are discussion of intent.
Preface
List of Figures
List of Tables
1. Introduction
1.1. Background
1.2. Project objectives
1.3. Project scope
2. General Requirements
2.1. Overview - what the prestandard contains, how it is to be used
2.2. Performance expectations - will target specified performance (i.e.
collapse prevention) for retrofitted item. Prestandard will not able
to speak to full building performance since the primary provisions
only address vulnerability-based retrofits. A systematic evaluation
in accordance with Section 13 might allow target for full building
performance.
2.3. Voluntary versus code triggered use - the intent is to permit the
provisions of this standard to be triggered and used for assessment
and retrofit of vulnerabilities for voluntary work or as triggered by
a code or ordinance provision outside of this standard: a) one
vulnerability at a time, b) for multiple vulnerabilities, or c) for all
vulnerabilities addressed.
ATC-110
A: Prestandard Outline and Recommended Scope
A-1
2.4. Assessment/Evaluation - discuss assessment methods incorporated,
including based on FEMA P-50 checklist items
2.5. Site Factor Issues
2.5.1. Overview of site soil hazards - Briefly introduce potential site
soil hazards and note that occasionally the potential hazard
from site soil conditions can be so significant that the benefit
gained from retrofit of other vulnerabilities should be
carefully considered. Include reference to new Appendix A
2.5.2. Site hazards in combination with other vulnerabilities
2.6. Site seismicity - effects on assessment and retrofit
2.7. Submittal documents - minimum requirements for prescriptive
retrofits
2.8. Testing and inspections
2.9. Other conditions
2.9.1. Dwellings with combinations of vulnerabilities
2.9.2. Unusual configurations
2.9.3. Retrofit of engineered dwellings
2.9.4. Phased construction - do no harm
3. Cripple Walls Less Than or Equal to Four Feet in Height and
Anchorage to Foundation
3.1. Overview
3.2. Typical damage modes - due to anchorage or cripple wall in-plane
failure, dwelling shifts off of foundation
3.3. Assessment/evaluation
3.3.1. Simplified assessment - screening checklist document starting
from FEMA P-50 form with points removed (ASCE 31 Tier 1
concept)
3.3.2. Detailed prescriptive assessment- Similar to a ASCE 31 Tier
II evaluation
3.3.3. Detailed engineering assessment- Guidance for best practices
3.4. Prescriptive retrofit scope check - checklist
3.5. Prescriptive retrofit procedures
3.5.1. Building documentation prior to retrofit design
3.5.2. Floor to cripple wall connections
3.5.3. Floor to mudsill connections
3.5.4. Mudsill connections to foundations - include discussion of
splitting of sills
3.5.5. Cripple wall sheathing requirements and distribution
3.5.6. Stepped cripple walls - detailing issues, what would you do
differently, different mode of response
3.5.7. Foundation systems - as they impact bolting and cripple wall
bracing: no foundation, post & pier, partial perimeter,
unreinforced masonry
3.5.8. Prescriptive retrofit documentation
A-2
ATC-110
3.6. Engineered retrofit procedures
3.6.1. Engineered design assumptions
3.6.2. Retrofit design
3.6.3. Retrofit detailing
3.7. Related Design and construction issues
3.7.1. Foundation ventilation
4. Cripple Walls Over Four Feet in Height and Anchorage to
Foundation
4.1. Overview
4.2. Typical Damage Modes - due to anchorage or cripple wall in-plane
failure, dwelling shifts off of foundation. Cripple wall overturning
failures may also occur for taller cripple walls, do you get to
collapse?
concept)
4.3.2. Detailed prescriptive assessment
4.3.3. Detailed engineering assessment
4.4. Prescriptive Retrofit Scope Check
4.5. Prescriptive Retrofit Procedures
4.5.1. Building Documentation Prior to Retrofit Design
4.5.2. Floor to Cripple Wall Connections
4.5.3. Floor to Mudsill Connections
4.5.4. Mudsill Connections to Foundations
4.5.5. Cripple Wall Sheathing Requirements and Distribution
4.5.6. Stepped cripple walls
4.5.7. Hold-down Requirements
4.5.8. Foundation Evaluation for Hold-downs
4.5.9. Foundation Systems (as they impact bolting and cripple wall
unreinforced masonry)
4.5.10. Detailed Retrofit Documentation
4.6. Engineered Retrofit Procedures
4.6.1. Engineered Design Assumptions
4.6.2. Retrofit Design
4.6.3. Retrofit Detailing
4.7.1. Foundation Ventilation
5. Hillside Condition
5.1. Overview - if yes to conditions listed in Section 3, consider
retaining geotech before structure retrofit
5.2. Typical Damage Modes - lack of bracing between lowest floor and
grade causes partial or full collapse, lack of detailing or stiffness of
ATC-110
A-3
non-detailed wood or rod bracing system, skirt wall is not detailed
at top or bottom for load path (list of conditions, prioritization
would be of assistance to user)
concept)
5.3.3. Detailed engineering assessment - geotech related also?
When does hillside become of concern based on slope?
Analytical parametric studies would be good
5.4. Prescriptive Retrofit Scope Check - size, weight, irregularity, site
slope, site slope + geotech hazard, etc.
5.5.1. Cripple Wall Retrofit
5.5.1.1. Floor to Cripple Wall Connections
5.5.1.2. Floor to Mudsill Connections
5.5.1.3. Mudsill Connections to Foundations
5.5.1.4. Cripple Wall Sheathing Requirements and Distribution
5.5.1.5. Stepped Cripple Walls
5.5.1.6. Hold-down Requirements
5.5.1.7. Foundation Evaluation for Hold-downs- no foundation,
post & pier, partial perimeter, unreinforced masonry
What are we asking the foundation to do? Care with
new foundations on steep hillsides.
5.5.1.8. Foundation Systems
5.5.2. Retrofit of Hillside Post and Beam Structures (to the extent
that retrofit involves addition of cripple walls or anchorage to
the uphill foundation)
5.5.3. Anchorage to Uphill Foundation (Horizontal tension ties)
5.5.4. Split Level Floor Retrofit - to the extent that it occurs in
combination with hillside configuration.
5.6.1.1. Engineered Design Assumptions
5.6.1.2. Retrofit Design
5.6.1.3. Retrofit Detailing
5.7. Related Design and Construction Issues
6. House or Room Over Garage
6.1. Overview
6.2. Typical Damage Modes - excessive drift at garage front, partial or
complete weak story collapse - offset walls = incomplete floor
diaphragm
A-4
ATC-110
concept)
6.5.1. Open Front Wall Line Retrofit (at narrow wall piers)
6.5.1.1. Plywood Shear Walls
6.5.1.2. Steel Moment Frames
6.5.1.3. Proprietary Bracing Systems
6.5.2. Bracing Walls Not at Open Front
6.5.3. Collector From Open Front to Other Portions of Dwelling
7. Split-Level Condition
7.1. Overview
7.2. Typical Damage Modes - framing ledgered off of common wall
separates from wall allowing partial collapse
concept)
8. Inadequate Wall Bracing - Occupied Spaces
8.1. Overview
8.2. Typical Damage Modes - inadequate bracing wall capacity,
distribution causes significant damage, possibly local, global
collapse (more glazing hazard)
8.3. Relevant FEMA P-50 Assessment Items (Simplified Assessment)
concept)
ATC-110
A-5
8.5.1. Wall Line Retrofit (Exterior and Interior Walls)
8.5.1.1. Plywood Shear Walls
8.5.1.2. Proprietary Bracing Systems
8.5.2. Load Path Connections
8.5.3. Hold-down Requirements
8.5.4. Foundation Evaluation for Hold-downs
8.5.5. Foundation Systems (as they impact bolting and cripple wall
unreinforced masonry)
9. Anchorage of Slab on Grade Dwellings
9.1. Overview
9.2. Typical Damage Modes - inadequate anchorage of bracing walls to
foundations permits walls to shift, slide off foundation
concept)
10. Decks, Porches, Stairs, Landings. Patio Covers And Carports
10.1. Overview
10.2. Typical Damage Modes - porch, deck, exit stair and landing
detachment from supporting residence and collapse, patio cover
and carport collapse can be life-safety hazard
10.3.1. Simplified assessment - screening checklist document
starting from FEMA P-50 form with points removed (ASCE
31 Tier 1 concept)
10.4. Prioritization (Life Safety Focus)
A-6
ATC-110
11. Masonry Chimneys
11.1. Overview
11.2. Typical Damage Modes - falling hazard from fractured chimneys,
veneer, can cause life-safety concern, fractured chimney can
damage, fall through adjacent roof,
11.3.1. Simplified assessment - screening checklist document
starting from FEMA P-50 form with points removed (ASCE
31 Tier 1 concept)
11.5.1. Unreinforced Masonry Chimneys
11.5.2. Lightly Reinforced Masonry Chimneys
12. Masonry Veneer
12.1. Overview
12.2. Typical Damage Modes - falling hazard
12.3.1. Simplified assessment
13. Engineered Approach to Evaluation and Retrofit - this will take
knowledge gained from development of engineered retrofit procedures
and communicate it to designers for more general application to
residential retrofit
13.1. Overview
13.2. Site Investigations
13.3. Unusual configurations
13.4. Prioritizing the Elements of the Primary Force Resisting System
13.5. Performance Objectives
13.6. Simplified Evaluation Procedures
13.7. Determining Seismic Mass and Forces
13.8. Distribution of Seismic Forces
13.9. Evaluation of Sheathing Materials Not Permitted for New
Construction
13.10. Evaluation of Existing Connections
13.10.1. Roof to Walls
ATC-110
A-7
13.10.2. Second Floor
13.10.3. Ground Floor
13.10.4. Anchorage to Existing Footings
13.11. Evolution of Existing Foundation Systems
13.12. Suggested Details
NON-MANDATORY APPENDICES
Appendix A: Site Factors
A.1. Overview
A.2. Site hazards in combination with other vulnerabilities
A.3. Simplified assessment/screening
A.3.1. Site Topography - Flat to 4:1 (horizontal to vertical) – Slope not
a factor, Steeper than 4:1
A.3.2. Fault rupture – Refer to Fault-Rupture Hazard Zones in
California and consult with local jurisdictions to assess the
hazard
A.3.3. Liquefaction – Refer to hazard maps in California and if in a
hazard zone, consult with a geotechnical engineer to further
evaluate consequences of liquefaction and potential mitigation
measures which could include: grouting, drain piers, tying
foundations together, mat foundation, grid foundation can we
refine guidance to homeowner, when geotech required? - discuss
more appropriate foundation retrofits where liquefaction hazard
exists (tie beams, grid foundation), better performance rather
than fully mitigate?
A.3.4. Densification – screen by referring to geologic maps published
by appropriate agencies. If extensive, loose near-surface
unsaturated sand deposits are present, densification-induced
settlement may be a factor. However, amount of vertical
settlement is generally small – less than 2-inches. Not that
worried about this one, but discuss for completeness
A.3.5. Stability - suggestions for foundation for hillside home? If
steeper than 4:1, assess geologic conditions. Drilled deep
foundation with adequate penetration to provide fixity, tie
foundation together by grade beams perpendicular to slope
contours (relates to 3.1)
A.3.6. Foundation performance – evaluation by geotechnical engineer
to assess consequences of shaking and ground deformation on
foundation performance. (if geotech involved due to other issues,
ask them to look at this globally, could be triggered by P-50
section A, etc.) Where does this belong?
A.4. Detailed assessment
A-8
ATC-110
Appendix B: Engineering Design Aids
B.1. Load Table
B.2. Seismic Design Tables
B.3. Spreadsheets
B.4. Standard Details
Appendix C: Not Used
Appendix D: Other Vulnerabilities and Reference Documents
D.1. Non-structural Elements
D.1.1. Roof tiles
D.1.2. Water Heaters
D.1.3. Overhead Glazing
D.1.4. Residence Contents
D.2. Roof diaphragms
Appendix E: Recommendations for Implementation
E.1. Required Submittal Documents
E.1.1. Plans
E.1.2. Specifications/ General Notes
E.1.3. Checklist of Items to Submit
E.2. Guidance for Conditions Outside of Prescriptive Details
E.3. Installation Procedures
E.4. Safety
E.5. Assessor, Contractor and Inspector Training
E.6. Authority Having Jurisdiction
E.7. Verification of Retrofit
E.8. Testing and Inspection
COMMENTARY
SCOPE: It is intended that commentary will be provided for most prestandard
sections. Commentary language will be directed to the builder or designer that
is implementing the prestandard provisions only. Background information and
assumptions and justification relating to the development of the provisions will
be located in C#.0 sections in each vulnerability chapter. This information will
primarily be provided for those involved in the standard development process,
and might be removed from the final published standard.
C1.
C2.
C3.
C4.
Introduction
Site Factors
Cripple Walls Less Than or Equal to Four Feet in Height
C4.1. Background and Justification
C4.2. Overview
C4.3. Typical Damage Modes
C4.4. Assessment/Evaluation
C4.5. Prescriptive Retrofit Scope Check
ATC-110
A-9
C4.6. Prescriptive Retrofit Procedures
C4.7. Engineered Retrofit Procedures
C4.8. Related Design and Construction Issues
C5. Cripple Walls Over Four Feet in Height
NOTE: The pattern above will be repeated for each prestandard section
needing commentary.
A-10
ATC-110
Appendix B
Testing Needs
Development of a prestandard for assessment and retrofit of wood lightframe dwellings will use analytical investigations to generate information on
the seismic demand and performance of various components, sub-systems
and systems. These analytical investigations will use available test data to
build a large number of numerical models. Although testing is available
from various sources to inform the analytical modeling, uncertainty will
occur due to the need for the modelers to make numerous judgment-based
modeling assumptions. This appendix identifies focused testing that would
serve to reduce these uncertainties. It is understood that results of the testing
described herein is not likely to be available for use in analytical studies
conducted in the near term; however, results of testing could possibly be used
in later years of the developmental program, and in subsequent analytical
studies.
Most of the testing needs are for full-scale wood light-frame components.
In-plane reverse cyclic testing of these components is recommended up to
failure, or at least up to a deformation level causing a degradation of 20%
past the observe peak strength of a component. The CUREE test protocol for
ordinary ground motions1 should be used for conducting reverse cyclic
testing. In order to determine the median hysteretic properties of a
component, a minimum of three specimens should be tested for each
parameter variant. Most testing standards (e.g. ASTM E2126) permit the
testing of only two specimens if their strength values are within 15% of the
lower value. However, because the prestandard will be developing full
hysteretic response quantities, it is difficult to achieve a 15% variation
requirement in stiffness values.
Table B-1 describes testing needs related to the various sections of the
prestandard development plan.
1
H. Krawinkler, F. Parisi, L. Ibarra, A. Ayoub, and R. Medina. Development of a
testing protocol for wood frame structures. Technical Report No. W-02, CUREE,
2001.
ATC-110
B: Testing Needs
B-1
Table B-1
Testing Needs for the Prestandard Development Plan
Development Plan
Section
1.3 Cripple Walls and
Anchorage to
Foundation.
Testing Needs
Comments
2 ft., 4ft. & 6ft. high x 12
ft. long level cripple walls
sheathed with wood
structural panels and
with sill plates of various
widths.
Foundation sill plates are often
wider that the studs they
support Fastening of sheathing
to the foundation sill plate or to
blocking between the
foundation sill plates changes
behavior as nailing directly to
foundation sill means that
foundation sill is damaged
earlier on. Also, nailing the
sheathing on top of a wider sill
plate causes and interference in
rotation of the panels resulting
in higher stiffness and strength.
Staples on blocks rather than
nails are another variant of
interest. This is primarily a
durability issue, not a strength
issue because of the current
use of electroplated galvanized
staples.
2 ft., 4ft. & 6ft. high x 12
ft. long level cripple walls
sheathed with stucco,
horizontal wood siding,
T1-11 siding, diagonal
sheathing with stucco,
and exterior gypsum
board under stucco.
To extend the testing
conducted by Chai et al.2
2 ft., 4ft. & 6ft. high x 12
ft. long retrofitted level
cripple walls sheathed
with wood structural
panels in combination
with stucco, horizontal
wood siding, T1-11
siding, diagonal
sheathing with stucco, or
exterior gypsum board
under stucco.
To extend the testing
conducted by Chai et
al.2Based on the performance
observed from the testing of
individual sheathing materials,
testing of some of the retrofit
combinations may not be
required.
2
Chai, Y.H., Hutchinson, T.C. and Vukazich, S.M. Seismic Behavior of Level and
Stepped Cripple Walls Technical Report No. W-17, CUREE, 2002.
B-2
B: Testing Needs
ATC-110
Table B-1
Testing Needs for the Prestandard Development Plan (continued)
Development Plan
Section
1.5 Hillside Dwellings
Testing Needs
Comments
12 ft. long stepped cripple
walls with various numbers
and heights of steps (1:4,
1:3, 1:2, 1:1) sheathed with
wood structural panels
stucco, horizontal wood
siding, and T1-11 siding.
Some limiting testing on
To extend the testing conducted
by Chai et al.2. The testing
should be focused on the effect
of the steps on performance
rather than a comprehensive
testing of all sheathing materials.
Results obtained from level
cripple wall tests above could be
extrapolated to stepped cripple
walls.
12 ft. long sloped cripple
walls with various slopes
(1:4, 1:3, 1:2, 1:1) sheathed
with wood structural panels
stucco, horizontal wood
siding, and T1-11 siding.
This would be a low priority due
to the perceived small building
stock volume with sloped cripple
walls.
Bracing systems of various
slopes made of steel tie-rods
designed under UBC, wood
diagonal bracing under
UBC, generic detailed highand low-ductility bracing
systems.
1.4 House or Room
over Garage
ATC-110
Portal frame test results should be
obtained from APA if possible.
B: Testing Needs
B-3
Project Participants
Christopher Rojahn (Project Executive)
Jon A. Heintz (Project Manager)
Janiele Maffei (Chief Mitigation Officer)
801 K Street, Suite 1000
Sacramento, California 95814
Marianne Knoy (Mitigation Program Manager)
801 K Street, Suite 1000
Sacramento, California 95814
J. Daniel Dolan (Program Manager)
Dept. of Civil and Environ. Engineering
Washington State University
Pullman, Washington 99164
Michael Mahoney (Project Officer)
500 C Street, SW, Room 416
Washington, D.C. 20472
Project Technical Committee
Colin Blaney (co-Project Technical Director)
ZFA Structural Engineers
1390 El Camino Real, Suite 100
San Carlos, California 94070
Ramin Golesorkhi
Langan Treadwell Rollo
555 Montgomery Street, Suite 1300
San Francisco, California 94111
Kelly Cobeen (co-Project Technical Director)
Wiss, Janney, Elstner Associates, Inc.
2000 Powell Street, Suite 1650
Emeryville, California 94608
John Osteraas
Exponent
149 Commonwealth Drive
Menlo Park, California 94025
Thomas Anderson
Anderson-Niswander Construction, Inc.
3500 Portola Heights Road
La Honda, California 94020
Frank Rollo
Consulting Geotechnical Engineer
1977 Sixteenth Avenue
Andre Filiatrault
University at Buffalo
9100 Michael Douglas Drive
Clarence Center, New York 14032
ATC-110
C-1
Project Steering Committee
David Bonowitz (Chair)
605A Baker Street
Vikki Bourcier
Hohbach-Lewin
296 East Fifth Avenue, Suite 302
Eugene, Oregon 97401
David Khorram
City of Long Beach
333 West Ocean Boulevard, Third Floor
Long Beach, California 90802
Philip Line
American Wood Council
803 Sycolin Road, Suite 201
Leesburg, Virginia 20175
Thor Matteson
Shearwalls.com
P.O. Box 2143
Berkeley, California 94710
Steve Pryor
Simpson Strong-Tie
11263 Rothschild Court
Dublin, California 94568
Project Working Group
David Welch
304 West Main Street
P.O. Box 202
Elbridge, New York 13060
C-2
ATC-110
Directors
ATC Board of Directors (1973-Present)
Milton A. Abel
(1979-1985)
James C. Anderson
(1978-1981)
Thomas G. Atkinson*
(1988-1994)
Steven M. Baldridge
(2000-2003)
Albert J. Blaylock
(1976-1977)
Robert K. Burkett
(1984-1988)
Patrick Buscovich
(2000-2003)
James R. Cagley*
(1998-2004)
H. Patrick Campbell
(1989-1990)
Arthur N. L. Chiu*
(1996-2002)
Anil Chopra
(1973-1974)
Richard Christopherson*
(1976-1980)
Lee H. Cliff
(1973)
John M. Coil*
(1986-1987; 1991-1997)
Eugene E. Cole
(1985-1986)
Anthony B. Court
(2001-2004)
Edwin T. Dean*
(1996-2002)
Robert G. Dean
(1996-2001)
James M. Delahay
(1999-2005)
Edward F. Diekmann
(1978-1981)
Burke A. Draheim
(1973-1974)
John E. Droeger
(1973)
Nicholas F. Forell*
(1989-1996)
Douglas A. Foutch
(1993-1997)
Paul Fratessa
(1991-1992)
Sigmund A. Freeman
(1986-1989)
Barry J. Goodno
(1986-1989)
Mark R. Gorman
(1984-1987)
Melvyn Green
(2001-2002)
Lawrence G. Griffis
(2002-2005)
Gerald H. Haines
(1981-1982; 1984-1985)
William J. Hall
(1985-1986)
Ronald O. Hamburger
(1999-2000)
Robert W. Hamilton
(2002-2005)
Gary C. Hart
(1975-1978)
Robert H. Hendershot
(2000-2001)
Lyman Henry
(1973)
Richard L. Hess
(2000-2003)
James A. Hill
(1992-1995)
Ernest C. Hillman, Jr.
(1973-1974)
Eve Hinman
(2002-2005)
Ephraim G. Hirsch
(1983-1984)
William T. Holmes*
(1983-1987)
Warner Howe
(1977-1980)
ATC-110
Edwin T. Huston*
(1990-1997)
Jeremy Isenberg
(2002-2005)
Paul C. Jennings
(1973-1975)
Carl B. Johnson
(1974-1976)
Edwin H. Johnson
(1988-1989; 1998-2001)
Stephen E. Johnston* (1973-1975; 1979-1980)
Christopher P. Jones
(2001-2004)
Joseph Kallaby*
(1973-1975)
Donald R. Kay
(1989-1992)
T. Robert Kealey*
(1984-1988)
H. S. (Pete) Kellam
(1975-1976)
Helmut Krawinkler
(1979-1982)
James S. Lai
(1982-1985)
Gerald D. Lehmer
(1973-1974)
James R. Libby
(1992-1998)
Charles Lindbergh
(1989-1992)
R. Bruce Lindermann
(1983-1986)
L. W. Lu
(1987-1990)
Walter B. Lum
(1975-1978)
Kenneth A. Luttrell
(1991-1999)
Newland J. Malmquist
(1997-2001)
Melvyn H. Mark
(1979-1982)
John A. Martin
(1978-1982)
Stephen McReavy
(1973)
John F. Meehan*
(1973-1978)
Andrew T. Merovich*
(1996-2002)
David L. Messinger
(1980-1983)
Bijan Mohraz
(1991-1997)
William W. Moore*
(1973-1976)
Gary Morrison
(1973)
Robert Morrison
(1981-1984)
Ronald F. Nelson
(1994-1995)
Joseph P. Nicoletti*
(1975-1979)
Bruce C. Olsen*
(1978-1982)
Gerard Pardoen
(1987-1991)
Stephen H. Pelham
(1998-2004)
Norman D. Perkins
(1973-1976)
Richard J. Phillips
(1997-2000)
Maryann T. Phipps
(1995-1996; 1999-2002)
Sherrill Pitkin
(1984-1987)
Edward V. Podlack
(1973)
Chris D. Poland
(1984-1987)
Egor P. Popov
(1976-1979)
Robert F. Preece*
(1987-1993)
ATC Directors
D-1
Lawrence D. Reaveley* (1985-1991; 2000-2003)
Philip J. Richter*
(1986-1989)
John M. Roberts
(1973)
Charles Roeder
(1997-2000)
Arthur E. Ross*
(1985-1991; 1993-1994)
C. Mark Saunders*
(1993-2000)
Walter D. Saunders*
(1975-1979)
Lawrence G. Selna
(1981-1984)
Wilbur C. Schoeller
(1990-1991)
Samuel Schultz*
(1980-1984)
Daniel Shapiro*
(1977-1981)
Jonathan G. Shipp
(1996-1999)
Howard Simpson*
(1980-1984)
Mete Sozen
(1990-1993)
Scott Stedman
(1996-1997)
Donald R. Strand
(1982-1983)
James L. Stratta
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
*President
(1975-1979)
(1976-1979)
(1973)
(1991-1998)
(1992-2000)
(1973)
(1975-1977)
(1977-1980; 1981-1985)
(1987-1990)
(1990-1991)
(1980-1981; 1982-1986)
(1974-1977)
(1987-1988)
(1981-1984)
(1982-1985)
ATC Executive Directors (1973-Present)
Ronald Mayes
Christopher Rojahn
D-2
(1979-1981)
(1981-present)
Roland L. Sharpe
ATC Directors
(1973-1979)
ATC-110
Sponsors, Supporters, and Contributors
Sponsors
Contributors
Structural Engineers Association of California
Charles H. Thornton
John M. Coil
James R. & Sharon K. Cagley
Degenkolb Engineers
Walter P. Moore & Associates
Nabih Youssef & Associates
Burkett & Wong
Sang Whan Han
Omar D. Cardona
Computers & Structures, Inc.
Lawrence D. Reaveley
Edwin T. Huston
Edwin & Jonelle Dean
Barrish, Pelham & Partners
Bliss & Nyitray, Inc.
Shapiro, Daniel and Lois R.
John C. Theiss
E. W. Blanch Co.
Kenneth B. Bondy
Buehler & Buehler Associates
Patrick Buscovich & Associates
DPIC Companies
DeSimone Consulting Engineers
John A. Martin & Associates
Lane Bishop York Delahay, Inc.
LeMessurier Consultants, Inc.
Marr Shaffer & Miyamoto, Inc
Master Builders
Reaveley Engineers
Rutherford & Chekene
Severud Associates
Tokyo Engineering Power Company
William Bevier Structural Engineer, Inc.
Supporters
Baker Concrete Company
Cagley & Associates
Cagley, Harman & Associates
CBI Consulting, Inc.
Japan Structural Consultants Association
Nishkian Menninger
Structon

ATC 110 - California Earthquake Authority

Transcription

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