ATC 83 Presentation

1TRAININGWEBINARSoilStructureInteractionforBuilding

Structures(ATC83)

ATC83ImprovedProceduresforCharacterizing&ModelingSoilStructureInteractionforPerformanceBasedEngineering

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JonathanP.StewartProfessorandChairofCivilEngineering,UCLA

NISTGCR1291721REPORTOctober30,2013


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ProjectTechnicalCommitteeJonathanPStewart(Chair)

CBCrouseTaraHutchinsonBretLizundiaFarzadNaeim

FarhangOstadanWorkingGroupMembers

CurtHaseltonFortunatoEnriquezMichaelGivensSilviaMazzoniErikOlstad

AndreasSchellenberg

ReviewPanelCraigComartinYousefHashashAnnieKammererGyimahKasali

GeorgeMylonakisGrahamPowell

2ProjectScope Literatureassimilationandreportpreparation

Exampleapplications(problemfocusedstudies)

Practitionerinterviewsandinput


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Outline SSImodelingstrategies[Chaps1,4,7] Inertialinteraction[Chaps2,5] Kinematicinteraction[Chap3] ExampleapplicationsandRHArecommendations[Chap7,8]

Recommendationsforgeotechnicalstructuralengineerinteractions[Chap6].


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3Somemajorissuesaddressedbyproject: WhatfieldandlaboratoryinvestigationsarerequiredtodevelopsoilspringsanddashpotsforSSIanalysis?

Underwhatconditionsistheuseofsoilsprings/dashpotsimportant(andwhatstructuralresponseparametersareaffected)?

Forwhatconditionsisconsiderationofthedifferencesbetweenfoundationandfreefieldgroundmotionsimportant?


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SSIModelingStrategiesSubStructureAnalysis: FIM Foundationflexibility&damping

Responseanalysis

4SSIModelingStrategiesDirectAnalysis: Soil,structural,andinterfaceelements

Amenabletofullynonlinearanalysis

ModelingwithSVGMispossible

SomeSimplifications BathtubModel

Includesfoundationsprings

Nospatialvariabilityofinputmotions

FixedBaseModels Fixedatgroundlevel Fixedatbase

Welllookattherelativeperformanceofthesemodelingapproaches

5InertialInteraction SSIsystembehavior Foundationstiffnessanddamping(shallow) Additionalissuescoveredinreport:

Pilefoundationstiffnessanddamping[2.3] Nonlinearbehaviorofshallowfoundations[2.4]


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SystemBehavior Comparefixed andflexiblebaseoscillator

Deriveexpressionforperiodlengthening

yyx kkh

kk

TT 21~

kx =FoundationhorizontalstiffnessATC83ImprovedProceduresforCharacterizing&ModelingSoil

StructureInteractionforPerformanceBasedEngineering10

6SystemBehavior Comparefixed andflexiblebaseoscillator

Deriveexpressionforperiodlengthening

yyx kkh

kk

TT 21~

kyy =FoundationrockingstiffnessATC83ImprovedProceduresforCharacterizing&ModelingSoil

StructureInteractionforPerformanceBasedEngineering11

Mostcriticalcontrollingparameters:

andBLhm

LB

Bh

TVh

ss

,4

,,,

Velocityratio:structuretosoilstiffness


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7Mostcriticalcontrollingparameters:

Aspectratio:heightofstructure/widthoffoundation

andBLhm

LB

Bh

TVh

ss

,4

,,,


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PeriodLengtheningTrends


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InertialSSIsignificantifh/(VsT) >0.1orT

8 inf TT ~ 10

Flexiblebasesystemdamping

SSISystemDamping


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inf TT ~ 10

Fixedbasedamping

SSISystemDamping


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9 inf TT ~ 10

Foundationdamping

SSISystemDamping


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FoundationDampingTrends:


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EffectsofPeriodLengthening&DampingonBaseShear


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FoundationStiffnessandDamping

Requiredsoilproperties Modelelements


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RequiredSoilProperties GeotechnicalandVsprofiles.


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RequiredSoilProperties GeotechnicalandVsprofile.

Soilshearstrength(undrained belowgwt)


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SoilPoissonsratio,(canbeevaluatedfromVp/Vs abovegwt)


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SoilPoissonsratio,(canbeevaluatedfromVp/Vs abovegwt)

Soilhystereticdamping,D


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Seed&Idriss,1970

Vucetic&Dobry,1991

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ModelElements Staticstiffness,surfacefoundation:

Translation:Kj =GBfn(,B/L)Rotation:Kjj =GB3fn(,B/L)


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Embedmentmodifiers,j orjj:fn(D/B,B/L)


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Embedmentmodifiers,j orjj:fn(D/B,B/L) Dynamicmodifiers,j or jj:fn(B/L,a0=B/Vs)


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Embedmentmodifiers,j orjj:fn(D/B,B/L) Dynamicmodifiers,j or jj:fn(B/L,a0=B/Vs) Radiationdamping,j:fn(B/L,j,a0,Kj/GB);

jj:fn(B/L,jj,a0,Kjj/GB3)ATC83ImprovedProceduresforCharacterizing&ModelingSoilStructure

InteractionforPerformanceBasedEngineering28

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FiguresfromTileyliogluetal.(2011)

GarnerValleyTestStructure

Keyfeatures: Frequencydependentstiffnessforrotation(nottranslation) Moredampingintranslationthanrocking


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Outline SSImodelingstrategies Inertialinteraction Kinematicinteraction ExampleapplicationsandRHArecommendations

Recommendationsforgeotechnicalstructuralengineerinteractions


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KinematicInteraction Baseslabaveraging Foundationembedment

Expressedastransferfunctions 2L

g

FIM

g

FIMu u

LHuuH

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PhysicalBasisforBaseSlabAveraging

Katoetal.,1998Variabilityexpressedintermsof: Phasechange Amplitudechange

PhysicalBasisforBaseSlabAveraging

Spatialvariabilityisstronglyfrequencydependent

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PhysicalBasisforBaseSlabAveragingPlanview

PhysicalBasisforBaseSlabAveragingPlanview

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PhysicalBasisforBaseSlabAveragingLowfrequencycomponents

uFIM () ug ()2003OffMiyagiEqkFF,swavewindow

PhysicalBasisforBaseSlabAveragingHighfrequencycomponents

uFIM ()< ug ()2003OffMiyagiEqkFF,pwavewindow

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PhysicalBasisforEmbedmentEffect

LowfrequencyLongwavelength =Vs/fuFIM ugFIM 0

PhysicalBasisforEmbedmentEffect

HighfrequencyShortwavelength =Vs/fuFIM 0

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Numerousmodelsforwavepassageonly(e.g.,Mylonakisetal.,2006)

ModelsforBaseSlabAveraging

Numerousmodelsforwavepassageonly FEanalysiswithincoherentinput(SASSI)


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Numerousmodelsforwavepassageonly FEanalysiswithincoherentinput Semiempiricalmodel smVV ssa /500200,00065.0

Closedformequations.Sec3.1


Modelsforrigidembeddedcylinders

Coherent,verticallypropagatingswaves

ModelsforEmbedment

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ImplementationinDesignStandards

Implementedasratiosofresponsespectra(RRS) Lua

FIMa fffHfSfS ),()()(

LLua

FIMa fffHfSfS ),()()(

fL affectedbyfrequencycontentofgroundmotion

Implementedasratiosofresponsespectra(RRS)

FirstappearedinASCE41:Seismicrehabilitationofexistingbuildings,2006UpdatedinNIST91721:Soilstructureinteractionforbuildingstructures,2012

ImplementationinDesignStandards

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Exampleoffoundation/freefieldgroundmotionvariations:

RanchoCucamongaLaw&JusticeCenter1987WhittierEarthquake

Exampleoffoundation/freefieldgroundmotionvariations:

RanchoCucamongaLaw&JusticeCenter1987WhittierEarthquake

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RanchCucamongasiteresponsespectra:

Outline

SSImodelingstrategies Inertialinteraction Kinematicinteraction ExampleapplicationsandRHArecommendations

Recommendationsforgeotechnicalstructuralengineerinteractions


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ObjectivesofPFS ExampleapplicationsofSSIguidelinesforrealisticconditions

UsingstructuralmodelsinOpenSees,investigatewhereSSIsignificant: WhatconditionsgiverisetoimportantSSIeffects?

WhatEDPsaremostaffected?


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ScopeofPFS Identifyappropriatebuildingswithrecordings Develop3DmodelsincludingSSIcomponents Tunestructuralparameterstomatchrecordings(baselinemodel MB)

StripoutSSIelementstoevaluateeffects.Considercommonconfigurationsfrompractice.


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IdealCaseStudyBuilding Regularstructure SignificantSSIeffects Instrumentation:

Horiz bldg array Vert sensorsonfndn Groundstation

Strongandweakmotionrecordings

Structure#1:ShermanOaks Attributes:

RCframe 2levelsofembedment Alluvialsoils,pile

foundations Good:

Embeddedfoundation Strongshaking,multiple

events Regularstructure

Bad: NoFForrocking

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Structure#2:WalnutCreek Attributes:

Shearwallcore&RCframe Noembedment Shallowsoils,mat

foundation Good:

Baserocking Stiffstructure

Bad: Lackofembedment NoFFmotionorstrong

motion

GeneralFindings RecordedresponseswellmatchedbyMB

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Modelfixedatgroundsurfaceperformspoorly

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Bathtubmodelperformsreasonablywell

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Bathtubmodelperformsreasonablywell

RHARecommendations Modelsubterraneanlevels,

fixatbase(Model2)


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fixatbase(Model2) Modelsubterranean,include

foundationsprings,bathtubsupportsforsprings(Model4)


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fixatbase(Model2) Modelsubterranean,include

foundationsprings,bathtubsupportsforsprings(Model4)

ConsiderkinematiceffectsforbelowgroundEDPs


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Outline Inertialinteraction Kinematicinteraction RecommendationsforRHA&otherkeytakeaways

Recommendationsforgeotechnicalstructuralengineerinteractions(CourtesyBretLizundia)


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IncreaseSEGEDialogue RequiredraftGEreportswithSEreview IncludejointmeetingsinGEandSEscopes,perhapsincludingfoundationcontractor,asappropriate

CoordinatetimingofGEandSEwork(donthaveGEreportfinishedbeforeSEhired)

Owners:RequireGESEmeetings

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SEtoGEChecklist Projectlocation,buildinglocationonsite Buildingcode,performanceobjective Descriptionofbuildingandstructuralsystemwithdrawingswhenpossible

Differentialsettlementtolerance Approximatefundamentalperiod Loadstofoundation IntendeduseofSSI Requiredgroundmotionformat[Sa orug(t)]

GERecommendationsshouldinclude

Typicalreportingofdata(siteplan,boring&CPTlogs,fieldandlaboratorytestresults)

Seismichazardanalysisresults(spectra,accelerationhistories)

Foundationstiffness&capacitywithrationaluncertainties

RRS,transferfunctions,ormodifiedaccelerationhistories

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SummaryofKeyPoints

WhatfieldandlaboratoryinvestigationsarerequiredtodevelopsoilspringsanddashpotsforSSIanalysis?

CharacterizationofsiteprofileShearstrengthparameters(undrained belowwatertable)Seismicvelocities


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Underwhatconditionsistheuseofsoilsprings/dashpotsimportantandwhatstructuralresponseparametersareaffected?


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Stiffstructures(shearwalls,bracedframes,etc.)h/(VsT) >0.1Dualsystems(esp.ifoneisstiff)


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StructuralperiodSystemdampingVerticaldistributionofstorydriftsandshearsLateraldistributionofelementforces(esp.indualsystems)Subterraneandemands


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Forwhatconditionsisconsiderationofthedifferencesbetweenfoundationandfreefieldgroundmotionsimportant?

BuildingswithmultilevelbasementsLargeplanareasStructureswithshortfundamentalmodeperiodsorsignificantcontributionsfromhighermodes


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Donot:UseconventionalcoefficientsofsubgradereactionfordynamicspringstiffnessesUselimitingfoundationpressuresderivedfromsettlementconsiderationsorfactoredbearingcapacitytodeveloplimitingspringforcesReserveconsiderationofSSIonlyforimportant(oftentall)buildingsAssumethatignoringSSIisalwaysconservative


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ATC 83 Presentation

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