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FEDERAL EMERGENCY MdANAGEVENT AGENCYFEDERAL EMERGENCY MANAGEMENT
AGENCY
g ll lIACTION PLAN
FOR
PERFORMANCE BASEDSEISMIC DESIGN
1k
Prepared for theFederal Emergency Management AgencyBy
theEarthquake Engineering Research Institute
_FEM~A-349IAorilFEMA-349!Anril 2000000
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FORWARDOne of the primary goals of the Federal Emergency
Management Agency (FEMA) is theprevention, or mitigation, of this
country's losses from natural hazards. To achieve thisgoal, we as a
nation need to ask what level of performance do we expect from
ourbuildings during an event such as an earthquake. Inorder to
answer this question, FEMAis exploring the possible development of
"performance-based seismic design" criteria.Such criteria could be
voluntarily used by this nation's engineers and designers to
improvethe performance of critical classes of buildings that are
currently only designed to a"lifesafety" level to avoid collapse,
but would infact probably still suffer significant damagein a
design event.FEMA contracted with the Earthquake Engineering
Research Institute (EERI) (contractnumber EMW-92-K-3955, Task 13)
to solicit the input of the nation's leading seismicprofessionals
in developing an action plan that could be used to develop
performance-based seismic design criteria. This project and the
resulting action plan have gone a longway in identifying key issues
that will need to be addressed in this process.This action plan
builds upon a similar effort that FEMA funded in 1993 with the
EarthquakeEngineering Research Center, now the Pacific Earthquake
Engineering Research Center(PEER). The end product of that study
was a similar plan, "Performance Based SeismicDesign of Buildings"
(FEMA-283), published by FEMA in September 1996. The material
inthat plan had an emphasis on the research that would be required,
and has in fact beenused by PEER inthe last several years as the
basis for their research work inthis arena.While this action plan
does an excellent job of describing the requirements that would
beneeded to successfully develop performance based seismic design
criteria, FEMA doeshas some concerns, such as the proposed budget,
which exceeds what FEMA is capableof devoting within the recomended
time frame. FEMA is planning to identify some of thekey elements of
the plan and to begin to address them through a series of projects
underits Problem Focused Studies program. However, without
additional specific funding forthis plan, it will be very difficult
to accomplish the entire plan. To avoid further delay,FEMA has
decided to publish this document as a "final draft for
informational purposesonly. Publication of this document in no way
obligates this or any other Federal agency toany portion of plan
contained herein. The information and opinions contained
inthisdocument are solely those of EERI and the project
participants and do not necessarilyrepresent the views of FEMA.In
closing, FEMA sincerely wishes to express its,gratitude to all who
were involved in thisproject. The results of their hard work will
play an important role as this country movesforward towards
performance-based seismic design and reducing the losses suffered
bythis nation's citizens after the next earthquake.Cover Art: Part
of a presentation developed by Ronald 0. Hamburger, EE
International
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I ACTION PLAN
FORPERFORMANCE BASED SEISMIC DESIGN
Executive Summary
PrepareFederalBy theEarthqu
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Action Plan for Performance Based Seismic Design
Table of Contents
The Need for Changes in Current Seismic Design Practice
...................What is Performance Based Seismic Design?
....................................... v
Products Necessary to ImplementPerformance Based Seismic Design
................................i
Schedule and Budget ................... VIConclusion
.......................................................................
EE..E...ixReferences
...........................................................................................
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Action Plan for Performance B ased Seismic Design
The Need for Changes inCurrent Seism ic Design-IR ecent decades
have seen a dramaticrise in insured and uninsuredearthquake related
losses. In the past tenyears estimated losses were twenty
timeslarger than in the previous 30 yearscombined. F E MAs
expenditures related toearthquake losses have become anincreasing
percentage of its disasterassistance budget.' Predictions are
thatfuture single earthquakes, which willinevitably occur, may
result in losses of
$50-100 billion each.'Losses are rising due to several
factors.These include: a denser population ofbuildings being
located in seismicallyactive regions. an aging building stock
andthe increasing cost of business FEMA Disaster
Assistanceinterruption. Nonstructural and contents 1988-1997damage
are also large contributors to loss,especially in regions with
high-technologymanufacturing and health-care industries.It is this
increase in losses from all hazardsthat has led FEMA to support
actions to re-duce future losses. One of these is P rojectImpact,
an initiative to encourage loss re-duction activities through
partnerships atthe local community level. One of the keycomponents
of Project Impact is the com-munity's adoption and enforcement of
anadequate building codeHistorically, building codes have required
I * 4that buildings be built to a minimum level of I**
I,OEarthquakessafety. Specifically, structures designed to mother I
Ithe Uniform Building Code are expected to"resist a minor level of
earthquake ...without damage,...a moderate level.. with
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Action Plan for Performance Based Seismic Designsome
nonstructural damage, [and] a majorlevel of earthquake.. without
collapse."3Deaths in recent California earthquakeshave been few,
showing that the intent ofthe code has been met. However, there isa
major misperception on the part of manyowners, insurers, lending
institutions andgovernment agencies about the expectedperformance
of a code conformingbuilding. This has led to losses that
wereunexpected and in many cases financiallyruinous. Building
stakeholders--those witha financial or social interest in the
builtenvironment--who expect that theirbuildings are "earthquake
proof" becausethey meet the code, have often been verydisappointed.
It must be said, too, thatnone of these recent events has been ofan
intensity that would typically beconsidered catastrophic.
Catastrophictemblors with a magnitude similar to the1812 New Madrid
or 1906 San Franciscoearthquakes will now likely result in
lossesseveral times larger than anythingpreviously experienced if
they occur in adensely populated area.Many building owners are
unaware of thetradeoffs they face when using the currentstate of
design practice. Interestingly,people make similar tradeoffs with
moreeveryday choices. For example, thenumber of highway fatalities
could bedramatically reduced if everyone drovetanks. Yet most
people are unwilling orcannot afford to do so, and instead
acceptthe increased risk of driving a car.Consciously or not, car
buyers performcost-benefit analyses when weighing therisk of an
accident against a car's cost. Acareful consumer may decide to
spendmore to buy a safer car or he may opt tospend the same amount
of money, butresearch much more closely the safetyrecords of
similarly priced cars. Thisconsumer is reducing risk either
byincreasing his investment or by reducinghis uncertainty.
Current codes clearly serve an essentialand effective role in
protecting buildingoccupants. The design basis of the code
isintended to provide a basic level of safetyand a relatively
economical means bywhich to construct buildings. However,using
current code methods to design andbuild to a higher level of
performance mayadd significantly to a project's cost.Stakeholders,
however, have becomepainfully aware of the financial and
socialconsequences of earthquakes and aredemanding that practical
and cost-effectivemeans be developed to address the issuesof damage
control and loss reduction.
The community of designprofessionals needs to be able torespond
to this demand with thedevelopment of design andevaluation
methodologies thatlook at a broad range of buildingperformance and
constructiontechniques.Current codes represent an evolution
ofprescriptive rules that have changed everythree years as more is
learned aboutbuilding behavior. The expectedperformance of new code
designedbuildings is poorly understood, andprobably inconsistent
among buildingtypes. It is currently difficult for rationaladvanced
design techniques andinnovative systems to be fit into the
codeframework. It is also difficult to applybuilding codes for new
buildings toevaluation and retrofit of existing buildings.Special
guidelines have been developedfor these purposes, potentially
creating adouble standard.Performance Based Seismic Design(PBSD) is
a methodology that provides ameans to more reliably predict seismic
riskinall buildings in terms more useful tobuilding users. It
permits owners to:
ii
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Action Plan for Performance Based Seismic Design
> Make an efficient use of their designand construction
budgets, resulting inmore reliable performance for themoney
spent.> Consider spending more money toachieve quantifiably
higherperformance than provided for in thecode, thereby reducing
risk andpotential losses.PBSD will benefit nearly all building
users.The PBSD methodology will be used bycode writers to develop
building codes thatmore accurately and consistently reflectthe
minimum standards desired by thecommunity. A performance based
designoption in the code will facilitate design ofbuildings to
higher standards and will allowrapid implementation of
innovativetechnology. When performance levels aretied to probable
losses in a reliabilityframework, the building design processcan be
tied into owner's long-term capitalplanning strategies, as well as
numericallife cycle cost models.PBSD is not limited to the design
of newbuildings. With it, existing facilities can beevaluated
and/or retrofitted to reliableperformance objectives. Sharing
thecommon framework of PBSD, existingbuildings and new buildings
can becompared equitably. It is expected that arating system will
develop to replace thecurrently used ProbableMaximum Loss(PML)
system. Such a system is highlydesirable to owners, tenants,
insurers,lenders, an d others involved with buildingfinancial
transactions. Despite itsinconsistency and lack of transparency,
thePML system is widely used and a poorrating often creates the
financial incentiveneeded for retrofit decisions.PBSD will provide
a common base fordesign of new buildings, evaluation of
existing buildings, and prediction of futuredamages. This will
enable the results ofregional loss estimates to be
directlyinterpreted in terms of building code an dretrofit
strategies. PSD will thus supportand encourage efficient mitigation
on bothan individual and a regional scale, resultingin safer and
economically strongercommunities.The availability and use of PBSD
will alsoallow building owners and a local community to determine
the performance level ofbuildings within their jurisdiction. This
isespecially true for structures that are critical to the continued
function and livabilityof a community. For this reason, PBSDcan
play a significant role in meeting theintent and goals of FEMVIA's
Project Impactinitiative to reduce future losses.This Action
Planpresents a rational an dcost effective approach by which
buildingstakeholders: owners, financial institutions,engineers,
architects, contractors,researchers, the public and
governingagencies, will be able to move to aperformance based
design and evaluationsystem.The Plan recognizes that there is a
strongdemand from stakeholder groups for morereliable, quantifiable
and practical meansto control building damage. It alsorecognizes
that there is not a focusedunderstanding among these groups as
tohow these goals can be obtained. ThisPlan describes how
performance basedseismic design guidelines can bedeveloped and used
to achieve thesegoals. Itwill be a vehicle to bring togetherthe
diverse sets of demands from withinthe stakeholder groups and
distill them intocohesive and practical guidelines. Itengages each
of the groups in thedevelopment these guidelines, by whichfuture
building design will become moreefficient and reliable.
iii
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Action Plan for Perfo rmance Based Seismic Design
What i s PerformanceBased Seismic Design(PBSD)?
T based seismic design ishe basic concept of performanceto
provideengineers with the capability to designbuildings that have a
predictable andreliable performance in earthquake^^Further, it
permits owners and otherstakeholders to quantify financially
orotherwise the expected risks to theirbuildings and to select a
level ofperformance that meets their needs whilemaintaining a basic
level of safety.PBSD employs the concept of performanceobjectives.
A performance objective is thespecification of an acceptable level
ofdamage to a building if it experiences anearthquake of a given
~everity.~hiscreates a sliding scale whereby a buildingcan be
designed to perform in a mannerthat meets the owners economic
andsafety goals. A single performanceobjective that requires
buildings remainoperational even in the largest events, willresult
in extraordinarily high costs.Conversely, a design where life
safety isthe only consideration may not adequatelyprotect the
economic interests of buildingstakeholders.A key to knowing how a
building willperform in a given earthquake is having theability to
estimate the damage it will sustainand the consequences of that
damage.Current codes do notevaluate a buildingsperformance after
the onset of damage.Instead, they obtain compliance with aminimum
safety standard by specifying adesign which historically has
protected life
safety in earthquakes. In some cases, thecode may actually be
unconservative. if abuildings irregularities are very
substantial,or if a higher performance level such asdamage control
is the desired.
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Action Plan for Perform ance Based Seismic DesignP BS D differs
from current codes in that itfocuses on a building's
individuaipedormance. I t provides a road map thatpermits design
professionals, owners andother stakeholders to learn more about
abuilding's performance in differentearthquakes, and implement a
design thatoptimizes design and construction costswith respect to
life-cycle performance. Inits broadest sense, P BS D creates
globalplanning opportunities for reducingeconomic and social losses
to wholecommunities, regions and states.To implement PBS D several
issues mustbe resolved. P BS D will change the waystakeholders look
at the built environment.It will require a comprehensive effort
tobring the various interested parties to aconsensus. Six
challenges to adoptionexist. They are:i ncreasing the current
knowledge baseof building behavior. This fundamentalissue will
require that broader and moreaccurate information be developed
andcollected on structural andnonstructural performance.i aising
awareness amongstakeholders about how PBS D canaddress many of the
problems theyalready perceive with current designpractice.i
Developing PBS D to be compatible thestakeholders' economic
interests.i Communicating the complex conceptsand information in a
way that ISunderstandabie to all stakeholders.i Reducing
uncertainty about how PBS D
will effect stakeholders, in terms of costand possible changes
in liabilityexposures.i Implementing incremental changes inthe
current standards, to create acontinuum of design improvementrather
than a perceived radical change.This Action Plan identifies the
specifictasks required to develop a cohesive set ofproducts and
guidelines that will meetthese challenges. These products will
be
more than just technical documents. TheP lan calls for going
beyond earlier andmore purely analytical performance basedefforts
by creating education andimplementation programs to bring
allstakeholders on boardThis Plan is to be used by the
teamsdeveloping the guidelines. It will provide amechanism to
ensure that the goals ofPBSD are being tracked.
Itencouragescreativity while capturing the requiredelements of a
successful program. Foreach of the products, a proposed budgetand
schedule are presented. A priority isassigned to individual tasks
so that theprogram can be tailored to an overallfunding level.
A Successful Useof
er, were unac
ethodologybThe re$
ner'sminimum eq ufdingrepresenteda
1 to thenextmostneedy facilities. .", . _ A
