atc 83 presentation
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Soil Structure Interaction PresentationTRANSCRIPT
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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
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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
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4SSIModelingStrategiesDirectAnalysis: Soil,structural,andinterfaceelements
Amenabletofullynonlinearanalysis
ModelingwithSVGMispossible
SomeSimplifications BathtubModel
Includesfoundationsprings
Nospatialvariabilityofinputmotions
FixedBaseModels Fixedatgroundlevel Fixedatbase
Welllookattherelativeperformanceofthesemodelingapproaches
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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
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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
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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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RequiredSoilProperties GeotechnicalandVsprofile.
Soilshearstrength(undrained belowgwt)
SoilPoissonsratio,(canbeevaluatedfromVp/Vs abovegwt)
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RequiredSoilProperties GeotechnicalandVsprofile.
Soilshearstrength(undrained belowgwt)
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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ModelElements Staticstiffness,surfacefoundation:
Translation:Kj =GBfn(,B/L)Rotation:Kjj =GB3fn(,B/L)
Embedmentmodifiers,j orjj:fn(D/B,B/L)
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ModelElements Staticstiffness,surfacefoundation:
Translation:Kj =GBfn(,B/L)Rotation:Kjj =GB3fn(,B/L)
Embedmentmodifiers,j orjj:fn(D/B,B/L) Dynamicmodifiers,j or jj:fn(B/L,a0=B/Vs)
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ModelElements Staticstiffness,surfacefoundation:
Translation:Kj =GBfn(,B/L)Rotation:Kjj =GB3fn(,B/L)
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
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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)
ModelsforBaseSlabAveraging
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Numerousmodelsforwavepassageonly FEanalysiswithincoherentinput Semiempiricalmodel smVV ssa /500200,00065.0
Closedformequations.Sec3.1
ModelsforBaseSlabAveraging
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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GeneralFindings RecordedresponseswellmatchedbyMB
GeneralFindings RecordedresponseswellmatchedbyMB
Modelfixedatgroundsurfaceperformspoorly
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GeneralFindings RecordedresponseswellmatchedbyMB
Modelfixedatgroundsurfaceperformspoorly
GeneralFindings RecordedresponseswellmatchedbyMB
Modelfixedatgroundsurfaceperformspoorly
Bathtubmodelperformsreasonablywell
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GeneralFindings RecordedresponseswellmatchedbyMB
Modelfixedatgroundsurfaceperformspoorly
Bathtubmodelperformsreasonablywell
RHARecommendations Modelsubterraneanlevels,
fixatbase(Model2)
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RHARecommendations Modelsubterraneanlevels,
fixatbase(Model2) Modelsubterranean,include
foundationsprings,bathtubsupportsforsprings(Model4)
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RHARecommendations Modelsubterraneanlevels,
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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Underwhatconditionsistheuseofsoilsprings/dashpotsimportantandwhatstructuralresponseparametersareaffected?
Stiffstructures(shearwalls,bracedframes,etc.)h/(VsT) >0.1Dualsystems(esp.ifoneisstiff)
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Underwhatconditionsistheuseofsoilsprings/dashpotsimportantandwhatstructuralresponseparametersareaffected?
StructuralperiodSystemdampingVerticaldistributionofstorydriftsandshearsLateraldistributionofelementforces(esp.indualsystems)Subterraneandemands
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Forwhatconditionsisconsiderationofthedifferencesbetweenfoundationandfreefieldgroundmotionsimportant?
BuildingswithmultilevelbasementsLargeplanareasStructureswithshortfundamentalmodeperiodsorsignificantcontributionsfromhighermodes
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Donot:UseconventionalcoefficientsofsubgradereactionfordynamicspringstiffnessesUselimitingfoundationpressuresderivedfromsettlementconsiderationsorfactoredbearingcapacitytodeveloplimitingspringforcesReserveconsiderationofSSIonlyforimportant(oftentall)buildingsAssumethatignoringSSIisalwaysconservative
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