PERFORMANCE BASED DESIGN structural analysis and design

performance

1. PERFORMANCE BASEDSEISMIC
ANALYSISOFRCBUILDINGS
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2. Contents
1.Introduction
2.Methodsofanalysis
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3. Introduction
Performance-basedDesign
➢Thebasicconceptofperformancebasedseismicdesignisto
provideengineerswiththecapabilitytodesignbuildingsthathave
apredictableandreliableperformanceinearthquakes.
➢ThusthePerformance-basedseismicdesignisaprocessthat
permitsdesignofnewbuildingsorupgradeofexistingbuildings
witharealisticunderstandingoftheriskoflife,occupancyand
economiclossthatmayoccurasaresultoffutureearthquakes.
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4. Introduction
Performance-basedDesign
➢Performance-baseddesignbeginswiththeselectionofdesign
criteriastatedintheformofoneormoreperformance
objectives.Eachperformanceobjectiveisastatementofthe
acceptableriskofincurringspecificlevelsofdamage,andthe
consequentiallossesthatoccurasaresultofthisdamage,ata
specifiedlevelofseismichazard.
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5. PerformanceObjectives
➢FullyOperational,
➢Operational
➢Immediate-occupancy,
➢life-safetyand
➢collapse-prevention
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6. SelectingPerformancePresentGeneration
Beer!
Food!
Operational
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BBe
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!Foood!
!
Beer!
Food!
Joe’s
Immediate
Occupancy
BBe
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!FFoood!!
BBe
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!FoFo
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Beer!
Food!
Life
Safety
C ol l apse
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P reventi on
Operational–negligibleimpacton building.
Immediate Occupancy–buildingissafetooccupybut
possibly notusefuluntil cleanupandrepair hasoccurred.
Life Safe–buildingissafeduringeventbutpossiblynot
afterward
CollapsePre ve ntion–buildingisonvergeof
collapse,probabletotalloss

7. Performancebaseddesign
Immediate
occupancy
Life
safety
Collapse
prevention
Displacement
parameter
BuildingDamageStates
Force
parameter
PerformanceLevels
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8. flow chartfor“Performancebaseddesign”
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9. Determination of Performance Point
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10. AdvantagesofPerformanceBased
SeismicDesign
➢Systematicmethodology forassessingtheperformancecapability of
abuilding
➢Designindividual buildingswitha higherlevelofconfidence
➢Designindividual buildingstoachievehigherperformance and lower
potential losses.
➢Designindividualbuildingsthatfalloutsideofcode-prescribedlimits
with regardtoconfiguration,materials,and systemstomeetthe
performance intended bypresentbuilding codes
➢Assessthepotentialseismicperformanceofexistingstructuresand
estimate potentiallosses in theeventofa seismic event.
➢Performance-based seismic design offers society the potential to be
both more efficientandeffectivein theinvestmentoffinancial
resourcestoavoidfutureearthquakelosses
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11. 11
Differencesbetweentraditionalapproach
and performancebasedapproach
1)Conventionallimit-statesdesignistypicallyatwo-leveldesign
approachhavingconcernfortheserviceoperationalandultimate-
strengthlimitstatesforabuilding,performance-baseddesigncan
beviewedasamulti-leveldesignapproachthatadditionallyhas
explicitconcernfortheperformanceofabuildingatintermediate
limitstatesrelatedtosuchissuesasoccupancyandlife-safety
standards.
2)Theperformancebasedanalysisisbasedonquantifyingthe
deformationofthemembersandthebuildingasawhole,underthe
lateralforcesofanearthquakeofacertainlevelofseismichazard.
TraditionalApproach-ForcebasedDesignhasnomeasureofthe
deformationcapabilityofmembersorofbuilding
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12. 3)Thedeformationorstrainsarebetterquantitiestoassessdamage
thanstressorforces.Sincethedeformationareexpectedtogo
beyondtheelasticvalues.
4)Theperformancebasedanalysisgivestheanalystmorechoice
of‘performance’ofthebuildingascomparedtothelimitstates
ofcollapseandserviceabilityinadesignbasedonlimitstate
method.
5)TraditionalbaseddesignusesElasticbehaviorwhereas
Performancebaseddesignusesinelasticbehavior
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13. Methodsofanalysis
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14. Methodsofanalysis
Generallyforanalyzingthestructurethefollowing analysis
methodsareuseddependingupontherequirements.
1)Linear staticprocedure
2)Lineardynamicprocedure
3)Nonlinearstaticprocedure
1.Pushoveranalysis
2.Capacityspectrummethod
4)Nonlineardynamicprocedure
1.TimehistoryAnalysis
Push-overandTimeHistoryanalysestoolstoperformnon-linear analysis
areconsidered.
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15. ➢pushoveranalysisistheonewhichissuitableforthe
performancebasedseismicdesign,becauseelasticanalysesare
insufficient,thereforetheycannotrealisticallypredicttheforce
anddeformationdistributionsaftertheinitiationofdamagein
thebuilding.
➢Inelasticanalyticalproceduresbecomenecessaryto
identifythemodesoffailureandthepotentialfor
progressivecollapse.
➢Inelastictime-historyanalysisaremostrealisticanalytical
approachforevaluatingtheperformanceofabuilding.
However,theinelastictime-historyanalysisisusuallytoo
complexandtime-consuminginthedesignofmost
buildings.
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16. WhatisPush-OverAnalysis?
➢Push-overanalysisisatechniquebywhichacomputermodelofthebuildingis
subjectedtoalateralloadofacertainshape(i.e.,parabolic,invertedtriangularor
uniform).
➢Buildingispushedinonehorizontaldirection.Theintensityofthelateralloadis
slowlyincreasedandthesequenceofcracks,yielding,plastichinge
formations,andfailureofvariousstructuralcomponentsisrecorded.
➢Proportionofappliedforceoneachfloorisconstant,onlyitsmagnitudeis
increasedgradually(i.e.,Loadpatternmaybe1stmodeshape,parabolic,
uniform,invertedtriangularetc.).
➢Materialnonlinearityismodeledbyinsertingplastichingeatpotentiallocation.
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17. Continued…
➢Aseriesofiterationsareusuallyrequiredduringwhich,thestructuraldeficiencies
observedinoneiteration,arerectifiedandfollowedbyanother.
➢Thisiterativeanalysisanddesignprocesscontinuesuntilthedesignsatisfiesa
pre-establishedperformancecriteria.
➢Theperformancecriteriaforpush-overanalysisisgenerallyestablishedasthe
desiredstateofthebuildinggivenaroof-toporspectraldisplacementamplitude.
➢Pushoveranalysisrequiresalargenumberofassumptionsand
memberresponsecurvesaretobeprovidedtotheprogrambeforeitcan
analyze.
.
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18. V
B
Δ
roof
Δ
roof
V
B
Continued…
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19. WhyPush-OverAnalysis?
➢StaticNonlinearAnalysistechnique,alsoknownassequentialyield
analysis,orsimply"push-over"analysis.
➢Togettheperformancelevelofstructureincaseofseismicload.
➢Elasticanalysiscannotpredictfailuremechanismandaccountfor
redistributionofforcesduringprogressiveyielding.
➢Theuseofinelasticprocedurefordesignandevolutionisanattempttohelp
engineerbetterunderstandhowstructureswillbehavewhensubjectedtomajor
EQ,whereitisassumedthattheelasticcapacityofthestructurewillbe
exceeded.
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20. WhatisTimeHistoryAnalysis?
➢TimeHistoryanalysisisastepbystepanalysisofthedynamicalresponseofa
structuretoaspecifiedloadingthatmayvarywithtime.
➢Theperformanceanalysismaybe
1.Linear
2.Non-linear
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21. WhyLinearTimeHistoryAnalysis?
➢Togetthevariationofforcesateachtimestepandtogetthemaximumresponse
underthetheparticulartimehistory.
➢Toverifythedesignofstructure.Ifforcesinthememberarewithinthedesign
forces,thennoneedtodoNon-Lineartimehistoryanalysis.
➢Iftheforcesareexceedingthedesignforces,thenNon-Linear
timehistoryanalysisisrequiredtounderstandtheperformanceofstructure.
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22. WhyNon-LinearTimeHistoryAnalysis?
➢Elasticanalysiscannotpredictfailuremechanismandaccountforredistribution
offorcesduringprogressiveyielding.
➢Certainpartmayyieldwhensubjecttomajorearthquake.
➢Togettheperformancelevelofstructureincaseofseismicload.
➢Theuseofinelasticprocedurefordesignandevolutionisanattempttohelp
engineertobetterunderstandhowthestructureswillbehavewhensubjectedto
majorEQ.
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23. PushoverAnalysisProcedure
Create2D/3DModel
Assignendoffsets
DesignStructure
AssignHingeproperties
Beams–M3,V2
Columns–PMM,V2
DefineStaticPushover
Cases
Gravity Pushover
(Forcecontrolled)
Lateral Pushover
(Displacement controlled)
DefineLoadcase
(LateralLoadat centreofmass)
Analyze
Runanalysis,RunNow
EstablishPerformancepointBase
shear Vs Roof Displacement
SequentialHingeFormation
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24. 26
PerformanceAnalysis
CreateModelasDesigned
DefineTimeHistoryFunction
DefineLinearTimeHistorycases
Analyze
Check
MemberForces≤DesignForce
Define Non linear Time
HistoryCase
Assign Plastic Hinges
(MaterialNonlinearity)
DefineGeometricNonlinearity
Analyze
Results
Checktheperformanceof the
structureandifrequired,redesign
YES
No
●Material nonlinearityismodeledbyinserting
plastichingeatpotentiallocation.
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25. Thank you