Seismic Response of Typical Highway Bridges in...
Transcript of Seismic Response of Typical Highway Bridges in...
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SeismicResponseofTypicalHighwayBridgesinCaliforniato
ComponentModelingandCharacteristics
Bahareh Mobasher1, Roshanak Omrani2,Ertugrul Taciroglu2,FarzinZareian1
1UniversityofCalifornia,Irvine2UniversityofCalifornia,LosAngeles
The42ndRisk,Hazard&UncertaintyWorkshop; Hydra,2016
Outline
ü Introductionü Problemstatement&Objectivesü BridgeModeling
• Shearkeys• Backfillpassive resistance
ü Analysis/Discussion• EDP:ColumnDriftRatio,Deckrotation,longitudinalandtransverse
deckmovement
ü ConcludingRemarks
Historyofbridgeseismicdesign
ü Caltrans(CaliforniaDepartment ofTransportation)formulatedthefirstcoderequirements intheUnitedStatesforseismic designofbridges in1940.
TheNewhallPassinterchange
Ø Insufficient seatwidth
FoothillFreewayInterchange
ü Hingerestrainersü Increasetheamountofsteelspiralsandties incolumnsü Increaseearthquake designforce
Historyofbridgeseismicdesign
ü LomaPrieta earthquake,1989
Ø Collapse ofupperdeckandsupportcolumns.Ø Localsoileffect(Amplified groundmotion)Ø Insufficient hoopreinforcement
ü Northridgeearthquake, 1994.
Lessons fromprevious earthquakes:
ü Understand seismicbehaviorofbridges.
ü Specifyimportantcomponents inbridges.
ü Updatecodesandguidelinebasedonthecurrent state-of-the-art.
PreviousWork
q Outcomes:§ Recommendations foradoption ofappropriatemodeldimension (2Dor3D)§ Assessment ofvariousplastichingemodeling optionsforcapturingnonlinear
response ofbentcolumns§ Criteriaforselection ofanalysismethods
q Shortcomings:§ Linearanalysisofsoil-structure interaction§ Simplified (orlackof)modelsforabutments, foundation,columns,expansion joints,
andshearkeys§ Groundmotionselection andscaling
PEER2008/03- Guidelines forNonlinear AnalysisofBridgeStructures inCaliforniaAdy Aviram,KevinR.Mackie,Bozidar Stojadinovic
ProblemStatement
θ
ü Current-state-of-research inperformanceassessment ofbridgestructures ismostlyconfined intothetwoStructural andGeotechnicaldomains.
GeotechnicalStructural
ProblemStatementü Current-state-of-research inperformanceassessment ofbridgestructures ismostly
confined intothetwoStructural andGeotechnicaldomains.
GeotechnicalStructural
θ
Beam with hinges
Rigid link
Elastic beam column element
Exterior Shear Key
CIDH and H Pile
ProblemStatementü There isagapbetween therecommendedmodeling approachesbyseismic design
guidelines andthecurrentstate-of-the-art inbridgecomponentmodeling
Quantifytheadvantages(anddisadvantages)ofutilizingadvancedcomponentmodels, comparedwithsimpleones
ProblemStatementü Currentperformancebaseassessment
• Neglects time-dependent effects(i.e.,combination ofcorrosion,andpreviousseismic damages)conditioned onhazardlevels.
Developenhanceddemandmodel(EDP|IM)
HazardCurve
IM
λ EDP
DemandCurve
ExteriorShearkeyü What is a shear key?
• Shear keys are used at bridge abutments to provide transverse support to bridge superstructure.
ü There are two types of shear keys• Exterior shear key. • Interior shear key (Interior shear keys are not recommended by Caltrans
because of maintenance problems).
Exterior shear key
Stem wall
Back wall
Footing
Wing wall
interior shear keyBearings
Schematic of typical seat-type abutment
ExteriorShearkey
ü The are two kinds of failure mechanism for exterior shear key joints (Bozorgzadeh et al. 2004, Megally et al. 2001).
• A single horizontal crack that develops at the Interface (sliding shear failure).
• Multiple diagonal cracks along the direction of predominant principal compressive stresses (Strut-and-Tie failure)
(Bozorgzadeh et al. 2004)
Shearkey Model
Concrete02
ENT
EPPG
Bilinear
ENT
Hysteretic
Back Wall
Stem Wall
Shear Key
(a) (b)
db
Area=a x d
h Force
Deformation
A
B
Ck1
k2
k3
K1=(h/AG+h3/3EI)-1
K2=f.k1f=(0.5%- %2.5)
h :Heightofshearkeyd :DepthofshearkeyG:ShearmodulusE:ModulusofelasticityI:Momentofinertia
k3 =%2.5.K1
Shear key Failure
Force
Deformation
A’B’
C’ D’Vn
Vs
Shear key Failure
Forc
e
Deformation
Forc
e
Deformation
EPPG material Concrete 02 materialFo
rce
Deformation
Bilinear hysteretic material
Forc
e
Deformation
Forc
e
ENT material
Vs
Vc
Validatedmacroelement modelsforabutmentshearkeysandseismic responsesensitivityofordinarybridgestoshearkeybehavior.(EngineeringStructures)Bahareh Mobasher ,Roshanak Omrani ,Ertugrul Taciroglu ,FarzinZareian
Based on Test Results:ü Bozorgzadeh et al. 2004 ü Megally et al. 2001.
BackfillPassivePressure
ExternalShearKeyWingWall
Deck
Force&
Deflec)on&
Pbw&
Gap&between&deck&and&back&wall&
Kabut&
!! !≈ !50!!"#/!"
!" !
!!!"#$ != !! .!.ℎ!"5.5!" !!!!!!!!!!. !.!"#$!
!!" != !! . 5.0!!"#. !!"!.! !!!!!!!!!!. !.!"#$ !!! != ℎ!" .!!" !!!!!!!!!!!!
UCDavis(1995);UCLA(2007)
BackfillPassivePressureü Abutment backfill soil type classification in California Highway Bridges (Earth
Mechanics, Inc. , 2005):I. DensetoverydensesandwithgravelII.Mediumdense silty sands,somewithgravelIII.MediumClayeysands,somewithgravelIV.Stiff-hardclayswithfinetocoarse-grained sands,somewithsilts
v Singleforce-deformationcannotcapturedifferent
typesofsoil
Variability inthePredictedSeismicPerformanceofaTypicalSeat-typeBridgeDuetoEpistemicUncertainties initsAbutmentBackfillandShear-keyModels.(Engineering Structures)Roshanak Omrani ,Bahareh Mobasher ,FarzinZareian,Ertugrul Taciroglu
BackfillPassivePressure
LSHmodel(Shamsabadietal.,2007)Log-Spiralfailuresurface+
Hyperbolicstress-strainmodel
GHFDmodel(Khalili-Tehranietal.,2011)GeneralizedHyperbolicForce-Displacementmodel
( )r
n
r
rHHHH
ybHyafyF ≡
+= ˆ,ˆˆδ
CalibratedforgranularandcohesivebackfillsutilizingextensivesimulationsgeneratedbytheLSHmodel.
δfba rr ,, γφ,,c
SkewedAbutment1. Linearpassivereduction,
α
SkewedModel
ACUT
OBTfromGHFDmodel
Skewedabutmentmodel(Kavianietal.,2012).
3. Non-uniformpassive reduction
(Kaviani etal.,2012)
!60tantan3.0 αβ ×=
Stiffness/StrengthVariationFactor
SkewedAbutment1. Linearpassivereduction,
α
SkewedModel
ACUT
OBTfromGHFDmodel
Skewedabutmentmodel(Kavianietal.,2012).
3. Non-uniformpassive reduction
2. Uniformpassivereduction(RollinsandJesse(2012),andMarshetal.(2013))
(Kaviani etal.,2012)
!60tantan3.0 αβ ×=
Stiffness/StrengthVariationFactor
Stiffness/StrengthVariationFactor
5 28 10 0.0181 1R α α−= × − +
SelectedBridgeü Jack Tone Road Overcrossing (Type A), a bridge with two spans supported on a
single-column bent
ü La Veta Avenue Overcrossing (Type B), a bridge with two spans and a two-column bent
Bridge Type Bridge No. Structure Name
Bridge Length
(m)
Width (m)
Year Built
2 Span Single Column 29 0315K JACKTONE-SB 99 ON-RAMP SEPARAT 67.2 8.3 20012 Span Multiple Column 55 0938 LA VETA AVENUE OC 91.4 23 20013 Span Single Column 29 0318 JACK TONE ROAD OH 127.5 23.5 2001
SelectedBridge
θ
θ
Beam with hinges
Rigid link
Elastic beam column element
Elastic beam column element
Elastic beam column element
γ
Χ
Ζ
Bearings + abutment stiffnessSpring element
(Hyperbolic Gap Material)
BridgeB
Exterior Shear Key
BridgeA
CIDH and H Pile CIDH and H Pile
GroundMotion
10-110-1
100
100
Sa(g)
Periods(s)
Medianresponsespectrum
ü Selected bridgeissubjectedtoasetof40pulse-like groundmotions withtwohorizontalcomponents,and21differentincident angles (Baker2007)
Geometricmeanresponsespectra(FN/FPcomponents)forselected pulse-likerecords(ShahiandBaker,2011)
Collapsecriteria
ü Collapse is defined as either the column drift ratio larger than 8% (Hutchinson et al., 2004)
ü The deck displacement relative to the abutment and in longitudinal direction is larger than the seat width (i.e., 30").
d
H≥ 8%100)./( Hδ
ü Deck rotation, column drift ratio, and deck movement considered as three engineering demand parameters (EDP) in this research
α
Wing%wall%
Back%wall%
Deck%C.L%
C.L%C.L%
Columndriftratio% Abutment unseating
ShearKeys&DeckRotation
1.5$ 1.5$ 1.5$ 1.5$
Uniform(backfill(Bridge(B)(
Linear(backfill(Bridge(B)(
Deck$Rota-on$(Rad)$
IM$(g)$
IM$(g)$
Brittle Shearkey
DuctileShearkey
CompoundEffectofShearkeyandBackfill
b)
uniform backfill resistance
Column
Resultant Force
Non-uniform backfill resistance
Column
Resultant Force
a)
CompoundEffectofShearkeyandBackfill
(a)
(b)
ColumnCollapse
AbutmentCollapse
ü 0-15o:ColumnCollapse
ü 30-60o:Unseating
Ø Non-uniformpassivereduction,Brittle Shearkey
(a)
(b)
(a)
(b)
CompoundEffectofShearkeyandBackfill
ColumnCollapse
AbutmentCollapse
ColumnCollapse
AbutmentCollapse
UniformBF
Non-uniformBF
ConcludingRemarks1. NewGuidelines forNonlinearAnalysisofBridgeStructures inCalifornia.2. Inastraightabutmentconfiguration,
a. Columnfailureisfoundtobethemajorcollapsemechanism (atmost10%).
b. Columndriftratioissignificantlyaffected bythelevelofpassiveresistance.
2. Atlargerskewangles (30o andabove)a. Abutmentunseatingbecomesnoticeable.b. Thebackfillandshear-key responses areshowntobecoupled.c. Thedynamicequilibriumamongthereaction forcesdefine the
directionandextentofbridgerotation,anddominanceofeitherofthetwofailuremechanisms (columnfailureorabutmentunseating).
ConcludingRemarks3. Theactualforce-deformation capacityofshear-keys predominantly
controlsthecouplingbetween longitudinalandtransverse seismicresponse ofthebridge.
4. Themethodologyemployedforreducing thepassive resistance ofbackfillinskewedconfiguration isshowntosignificantlyaffect thecollapsemechanism
ConcludingRemarksBridgeDesignFrameworkforTargetSeismicLoss(Zakeri &Zareian,2016)
IM EDP DM DV
GroundMotionBridgeResponse Component
DamagesPERFORMANCE
ConcludingRemarksBridgeDesignFrameworkforTargetSeismicLoss(Zakeri &Zareian,2016)
1000yearReturnperiod
AcknowledgmentsThis study is based on work supported by the CaliforniaDepartment of Transportation (Caltrans) under Award No.65A0454. This financial support is gratefully acknowledged. Anyopinions, findings, and conclusions or recommendationsexpressed in this paper are those of the authors and do notnecessarily reflect the viewsof sponsors.