2013 nees webinar lowes lehman slides
TRANSCRIPT
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Performance,Analysisand
Design
of
Flexural
Concrete
Walls
Reducing Earthquake Losses:
From Research To Practice
Reducing Earthquake Losses:
From Research To Practice
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Performance,Analysisand
DesignofFlexuralConcreteWalls
DawnLehmanandLauraLowes
UniversityofWashington,Seattle
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Acknowledgements UWResearchers
Dr.AnnaBirely,TexasA&MUniversity
Dr.JoshuaPugh,EDG,Inc.
JacobTurgeon,Hammel,GreenandAbrahamson,Inc.
UIUCResearchers
Dr.DanielKuchma,UniversityofIllinois AnahidBehrouzi,UniversityofIllinois
Dr.ChrisHart,ThorntonTomasetti
KenMarley,WJE
AndrewMock,UniversityofIllinois
ProfessionalEngineers
RonKlemencicandJohnHooper,MKA
AndyTaylor,KPFF
NeilHawkins,UWandUIUC
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Acknowledgements
Fundedbythe
National
Science
Foundation
throughtheNEESRprogram
SupplementalfundingprovidedbytheCharles
Pankow Foundation
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ResearchObjectives
1. Establish the seismicperformance of modern
reinforced concrete walls.
2. Develop response anddamage-prediction
models for these systems.
3. Advance seismic design
of walled buildings.PhotocourtesyofMKASeattle
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CurrentDesign
Process
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DefinitionofShearWallTerms
Boundary
Zone:Heavy Vertical
And TransverseSteel
Web:Light Vertical
And TransverseSteel
hw
lw
twlb
(http://www.jacobsschool.ucsd.edu)
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AvoidingDamageinWalls:HighShear
shear force V
diagonal compression strut
crushed web concrete
From: Seismic Design of Cast-in-Place Concrete Special Structural Walls Moehle et al. 2011
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AvoidingDamageinWalls:InadequateConfinement
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WallDesigntoAchieveDuctileFlexureControlledResponse
1. Proportionwall
soshear
stress
demand
islow
forelasticforce (typicallywithsystemtorsion
includedincalculation)
2. Designflexuralreinforcementtoachievebasemomentcapacity(similartoacolumn)
3. Designforsheardemandcorrespondingto
flexuralyieldingofwall(capacitydesign)
4. Detailboundaryelementwithrequired
confinement
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AchievingFlexuralYielding
Vu,CS oVu,CS
(b) Wall elevation
Vu,CSM
u,CS
Mu,CS Mn,CS
(c) Shear (d) Moment
capacity-amplified
code forces
code forces
(a) Lateral forces
Idealized Response: Flexural Yielding at Base of Wall
From: Seismic Design of Cast-in-Place Concrete Special Structural Walls Moehle et al. 2011
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SpecialRCShearWalls(ACI21.7)1. Finddemands(ELForMRSA)
2. Provideminimum
reinforcement
(21.7.2).
3. Capacitydesign?
No,designforPu,Mu andVu,basedonprescribedlateralloadsandshear (21.7.3).
Yes,higherforshear4. Designanddetailforshear(21.7.4).
5. Designanddetailforflexure(Pu andMu)
LengthofBoundary
Element
ConfinementofBoundaryElement ifendcompressionhigh(21.7.6).
6. Couplingbeamsoftenused (21.7.7).Diagonallyor
conventionallyreinforced.
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DesignIssues/Uncertainties Demand
Overstrength,torsion,nonlineardynamicamplificationeffects.
Sheardemand/capacity
Demanddependsonaccuracyofanalysis.
ACI3812011givesmaximumshearstressof8fc (psi).
Sometargetshearstresslevelsof46fc (psi)underelasticdemands(withtorsionincluded).
Confinement Constructability
Splices
Typicallyeveryotherfloorandbase.
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Experimental Program
UNIVERSITY of ILLINOIS
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TestProgram
Rangeofconfigurations
SimulatesACI31811
Actualdetails(confinement/splices)
Realisticdemands(shear/axial)(Courtesy of MKA, Seattle)
CShaped
Wall
CoupledWalls
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PlanarWallTestSpecimens
1/3scalemodelof
bottom3storiesofa10storywall
FullScale:
12ft.storyheight18in.thick
30ft.long
Lab:4ft.storyheight
6in.thick
10ft.long
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A B
A
B
LVL 3
LVL 2
LVL 1
LVL 0
1'-8" 1'-8"6'-8"
A
10'-0"
MARK REINFORCEMENTEMBED
LENGTH
LAP
LENGTHA (3) #4 @ 3" 1' - 8" 2' - 0"
B (2) #2 @ 6" 7" 9"
REINFORCEMENT SCHEDULE
Section A
B
NOTES:
Scale: Not to Scale
#2 TIES @ 2" o.c. (TYP.)
Detail B
Scale: Not to Scale
HOOKS OVERLAP TIE3" (TYP.)
2(TYP
.)
PlanarWallTestSpecimens
BoundaryElements(3.5%)
SpliceatBaseofWall
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PlanarWallTestMatrix
Moment-to
Shear RatioDistribution of
ReinforcementSplices?
STUDY
PARAMETERS
Wall 1
Wall 2
Wall 3
Wall 4
Mb = 0.71hVbVb = 2.8f c = 0.7Vn
UNIFORM
NO
YESBE at EDGE
BE at EDGE
BE at EDGE
YES
YES
Mb = 0.50hVbV
b
= 4.0f c = 0.9Vn
Mb = 0.50hVbVb = 4.0f c = 0.9Vn
Mb = 0.50hVbVb = 4.0f c = 0.9Vn
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NEESandPriorTestsNEES Tests
ACICompliant
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PlanarWallTestatMUSTSIM@UIUC
Lowerstoriesofmid
risebuildingstoriessimulatedinlab.
Shearandmoment
applied to
varysheardemand Axialloadof0.1Agfc.
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PW2: heff =0.5h,concentratedBE,splice
-300
-200
-100
0
100
200
300
-2.0 -1.5 -1.0 -0.5 0.0 0.5 1.0 1.5 2.0
Ba
seShear(kips)
Top Drift (%)
W
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PW1: heff =0.7h, concentratedBE,splice
-300
-200
-100
0
100
200
300
-2.0 -1.5 -1.0 -0.5 0.0 0.5 1.0 1.5 2.0
Ba
seShear(kips)
Top Drift (%)
W
Spalling above splice
Spalling towards baseSteel fracture at base
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-300
-200
-100
0
100
200
300
-2.0 -1.5 -1.0 -0.5 0.0 0.5 1.0 1.5 2.0
Ba
seShear(
kips)
Top Drift (%)
W
PW3: heff =0.5h;uniformreinf.;splice
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PW4: heff =0.5h, concentratedBE, nosplice
BaseShear(
kips)
Top Drift (%)
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SummaryofTestResults
Force-displacement envelopes
for all specimens
PW1: Low shear
PW2: Splice
PW3: Uniform
reinforcement
PW4: No splice
TexasA&MSeminar 32
PW 1 PW 2
PW 3 PW 4
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VerticalStrain:+1.0%Drift
PW11.5% drift
PW21.1% drift
PW31.25% drift
PW41.0% drift
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ShearStrain:+1.0%Drift
PW1 PW2 PW3 PW4
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2nd (Compressive)PrincipalStrain
PW1 PW2 PW3 PW4
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CoupledWallTestSpecimen Geometrytakenfrombuildinginventory
Couplingbeams(AR=2)and
diagonalreinforcement. Codebaseddesign(IBC,ACI)
Pierwallsarecapacity
protectedforshear(IBC
SeismicDesignManual). Seismicloadingresultsin
yieldingincouplingbeams
andwallpiers.
Additionaldesignparameters Nonlinearanalysesofthe
designwereusedtoassess
behavior(Mohr,2007)Coupling beams:
aspect ratio = 2.0
diag = 1.3%
Vn = gcAf2.6
Boundary Element
long = 3.7% trans = 1.6%
Web
long = 0.27% horz = 0.27%
0.54%
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WallPiersYield
0.50%
CB3
-2.5 -2 -1.5 -1 -0.5 0 0.5 1 1.5 2 2.5-200
-150
-100
-50
0
50
100
150
200
3rd
Story Drift [ % ]
Base
Shear[kips
]
0.50%
-2.5 -2 -1.5 -1 -0.5 0 0.5 1 1.5 2 2.5-200
-150
-100
-50
0
50
100
150
200
3rd
Story Drift [ % ]
Base
Shear[kips
]
CBYield
Walls Yield
CB1Yields
0.75%
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InitialSpalling
1.00%
Initial Spalling
CBYield
Walls Yield
1.50%
C
B3
ModerateSpalling
ModerateSpalling
CB2
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ProgressionofDamage to2.25%
2.20% 2.27%
-2.5 -2 -1.5 -1 -0.5 0 0.5 1 1.5 2 2.5-200
-150
-100
-50
0
50
100
150
200
3rd
Story Drift [ % ]
Base
Shear[kips
]
1.80%
2.00%
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2.0% drift (Moderate
Spalling near failure)
0.50% drift
(TWP Yields)
ShearStrains1.00% drift
(Initial Spalling)
0 m 6 m
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PrincipalCompressiveStrains
-6 m 0 m
2.0% drift (Moderate
Spalling near failure)0.50% drift
(TWP Yields)1.00% drift
(Initial Spalling)
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CouplingBeamRotation
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AxialForceinCompressionPier
L
CWP
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CshapedWallCrossSection
4 x 6 Flanges (Coupled wall)
10 x 6 Web (planar wall)
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1.44in(1.0%drift)
-2 -1 0 1 2 3 4
-6000
-4000
-2000
0
2000
4000
6000
% Drift
Moment(kip-ft)
Base Moment vs. 3rd Story Drift
WestFlangeEastFlange3rd Story Shear and Base Moment:
Fx = 217 kip
My = 6,075 kip-ft
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2.16in(1.5%drift)
-2 -1 0 1 2 3 4
-6000
-4000
-2000
0
2000
4000
6000
% Drift
Moment(kip-ft)
Base Moment vs. 3rd Story Drift
3rd Story Shear and Base Moment:Fx = 201 kip
My = 5,765 k-ft
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3rd Story Shear and Base Moment:Fx = 198 kip
My = 5,612 k-ft
3.24in(2.25%drift)
-2 -1 0 1 2 3 4
-6000
-4000
-2000
0
2000
4000
6000
% Drift
Moment(kip-ft)
Base Moment vs. 3rd Story Drift
WestFlangeEastFlange
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+5.1in(3.512%drift)
-2 -1 0 1 2 3 4
-6000
-4000
-2000
0
2000
4000
6000
% Drift
Mome
nt(kip-ft)
Base Moment vs. 3rd Story Drift
Pushed to 3.5% to
evaluate post-lateral
failure response. Retained almost 50% of
strength
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EvaluationforPerformanceandDesign:
ComparisonwithPriorTestData
Wallace 2011
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SlenderWallExperimentalDataSet
Assembledtoprovideinsightintothefactorsthat
affectdamageanddriftcapacity
Includes
Datafrom49testsfrom15testprograms
Dataforwallswithshearspanratio>2
DataforrectangularandflangedRCwalls
Doesnotinclude
Wallslessthan2in.thick
Wallswithopenings
Wallssubjectedtomonotonicordynamicloading
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OverviewofSlenderWallDatabase(Birely2012)
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DamageModesforThisDiscussion
Compression Failure Bar Rupture Failure
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TensileStrainatMn
Compression
Failure
Bar RuptureFailure
Wall that are tension controlled still fail
in compression damage mode
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Confinement
Resultssuggestyouneedalottomakea
differenceindriftcapacity
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ShearDemandCapacityRatio
Compression
Failure
Bar Rupture
Failure
Mixed
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Modelingthe
NonlinearResponse
ofWallsResponse
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NonlinearModelsTypicallyEmployedforSimulationofWalledBuildings
Fiber Model (M,P) = function(,)
Uniform Shear
Model
(V) = function()
Lumped PlasticityModel (e.g., SAP2000)
Distributed PlasticityModel (e.g., OpenSees)
Planar Element(e.g., Perform)
fiberandshear
sections(typ.)
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ForceBasedFiberTypeBeamColumnElement(OpenSees) Assume:linearmomentdistribution,constantaxialload >
solveforsectionstrainandcurvaturetosatisfycompatibilityreqts.
Flexural section
Shear section
Elastic section w/ reduced shear stiffness,
per Oyen (2006)
Fiber-type section
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FiberSection:ConcreteModel
CyclicmodelperYassin (1994)
Compression:
ModifiedKentPark(Scottetal.1982)
Unconfinedfibers:
Confinedfibers:
K,0,20 perSaatcioglu andRazvi (1992)
Tension: Elasticstiffness:
StrengthperWongandVecchio (2006):
PostpeakstiffnessperYassin (1994):
4
57000
0.05
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FiberSection:Steel Model
MenegottoPintoFilippou
model(1983)
4
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ModelEvaluation Datasetof21walls
Slenderwalls
(M/hlw >
1.5)
Exhibitingflexuralfailure
modes:
Modelevaluatedonthe
basisofsimulatedstiffness,
strengthanddriftcapacity
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No.of
I.P.
No. of
SpecsMean COV Mean COV Mean COV
3 21 0.97 0.09 0.98 0.10
Mesh
Dependent5 21 1.00 0.08 0.99 0.10
7 21 1.00 0.09 0.99 0.10
ModelEvaluationforFlexuralFailure
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LocalizationofDamage/Deformation
Specimen WSH4
(Dazio et al. 2009)
0.63%
Inelastic Localization
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ToAchieveMeshObjectiveResults
Regularizematerialresponse
Thisistypicallydoneincontinuumanalysis.
Useamaterialenergyandameshdependentlengthtodefine
thepostpeak(softening)portionofthestressstraincurve.
ColemanandSpacone (2001)proposedthisapproachforbeamcolumnelements,butprovidedlimited
recommendationsforthematerialenergytobeused.
Todetermine
material
energy
Useexperimentaldatafromwalltests(concrete)andcoupon
tests(steel)
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MaterialRegularization:PlainConcrete
3-I.P. Element
LIP,1
LIP,1
LIP,2
Constant material energy
Mesh dependent length
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MaterialRegularizationRecommendations
Bare Bar Regularized
ConcreteCrushingEnergy Unconfined:Gfc =2fc (N/mm)
Calibratedusingdatafrom2planarwallspecimensconstructedentirelyofunconfinedconcrete.
Confined:Gfcc =1.70Gfc Calibratedusingdatafor12planarwallspecimens
constructed
of
unconfined
and
confined
concrete.
SteelPostYieldHardening ComputedusingASTMgagelengthformaterialtesting
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ImpactofRegularizationWSH4 Specimen (Dazio et al., 2009)
No regularization of
material response
Regularization of
material response
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SimulationUsingRegularizedModel Forcebasedbeam
columnelement
Fibertypeflexural
section Concreteandsteel
modelsareregularized
Steelassumedtobuckle
whenconcrete
compressivestrength
is
lost
Elasticshearsection
(0.1GcAcv)
3elementsusedtomodeleachwall
specimen
3to7sections/I.P.sper
element
WSH4 (Dazio et al. 2009):
Crushing/Buckling Failure
WSH1 (Dazio et al. 2009):
Rupture Failure
RW1 (Thompson and Wallace 2004):
Buckling/Rupture FailureSW6 (Vallenas et al. 1979): High
Shear and Crushing/Buckling Failure
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FailureMode
(3EL/7IP)Mean COV Mean COV Mean COV
Crushing
(12Specimen)0.94 0.04 0.98 0.10 1.02 0.17
BucklingorRupture
(9Specimens)0.99 0.06 0.99 0.10 1.12 0.25
AllFlexure 0.96 0.04 0.98 0.06 1.06 0.17
RegularizedLineElementModelResults
CShapedWalls
(6Specimen)0.97 0.07 1.07 0.11 0.99 0.17
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EvaluationofCurrent
DesignProcedures
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EvaluationProcess
Design8idealizedcorewallbuildingsranginginheight
from16to30stories
DesignusingcurrentCodesandstandardpractice:
DemandsdefinedperASCE7(2010)
WallssizedforshearperSeismicDesign
of
Cast
in
Place
ConcreteSpecialStructuralWallsandCouplingBeams(NIST
2011)
Wallcapacities
and
detailing
determined
per
ACI
318
(2011)
EvaluatewallsusingtheFEMAP695Methodology(ATC
2009)
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BuildingDesigns
loading direction
considered
Seismic weight = 170 psf
Gravity weight = 190 psf
Wall axial load at base = 0.1fcAg
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NumericalModelUsedforEvaluation
ag(t)
CoreWall
P-Column(Leaning)
Regularizedfibertypeforce
basedbeamcolumnelement
1elementwith5integration
pointsperstory
Elastic,grosssectionshearstiffnessemployed(shear
stiffness=GAcv)
Impactoflargedisplacementson
walldemands(i.e.pdeltaeffects)
wasincluded
2%Rayleighdampingemployed
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FEMAP695UsedforEvaluation
SMT
ST1
T1= Cu Ta Determines
1. Probability of collapse in
the MCE, and
2. If the design procedure (R-factor, etc.) is acceptable.
CollapseMargin Ratio=
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Nonlinear
Analysis
Results(ELFProcedureDesigns)
MCE
DBEVn,pr
Ground Motion Intensity Ratio = ST1/SMT
flexural failure
shear failure
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Developmentof
ImprovedDesign
ProceduresforWalls
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ConsiderationsforWallDesign
Sheardesign
Capacitydesignforshearisrequired
Designforincreasedsheardemandtoensurethat
shearcapacitynotexceededpriortoflexuralyielding
Flexuraldesign
Designenvelopetoensurethatflexuralyielding
occursinexpectedlocations
Rfactorcalibratedtoachievedesiredcollapse
probability
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CapacityDesignforShear
Sheardemandincreasedtoaccountfor
FlexuralOverstrength
DynamicAmplification
Currentdesign
method
(ASCE
7and
ACI
318)
Vn Vuwith =0.6
Capacitydesignforshear
Vn VuwithVu
= voVu
Flex. Overstrength
Dyn. Amplification
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FlexuralOverstrength
ag(t)
Shear, V Moment, M
VE MEVu Mu
RR
Mu
Mn
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FlexuralOverstrength
ag(t)
Shear, V Moment, M
VE MEVu Mu
RR
Mu Mn
Mpr= oMu
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FlexuralOverstrength
ag(t)
Shear, V Moment, M
VE MEVu Mu MprVpr
R/
o
Mpr= oMu
Dynamic Amplification
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DynamicAmplification
heff
1
stmode
2
nd
mode
total
Base Moment Demand
Base Shear Demand
+ + =elastic
model
DynamicAmplification
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y p
h
eff
Mu
Vu
1
stmode
2
nd
mode
totalu
nreduced
tota
lreduced
Assume all
modes are
reduced
equally
+ + =
DynamicAmplification
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y p
Mu
heff
Vu
1st
mode
2nd
mode
totalr
educed
Only 1st
mode
demands
limited due
to inelasticaction in 1st
mode
heff
Mu
Vu
1stmode
2nd
mode
totalunreduced
totalreduced
Assume all
modes are
reduced
equally
+ + =
+ + =
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Designandanalyzeasetofprototypewalled
buildings CompareshearfromITHAwithdesignshear
Buildingdesigns
64Buildings
Buildingheights:N=6 24stories
Fundamentalbuildingperiods:T1= 0.08N 0.20N Forcereductionfactors:R=2,3,4
To
Determine
a
Capacity
Design
MethodforShear
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IdealizedBuildings
N = 16, 20, 24 storiesN = 6, 8, 12 stories
loading
direction
Seismicweight=170psf
Gravityweight=190psf
Wallaxialloadatbase=0.1fc
Ag
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SeismicDemandforITHA
7syntheticgroundmotionrecords
Providedconsistencyindemandbetweendesignspectrumusedfordesignandearthquakemotions
usedforevaluation
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ShearDemandComparison
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ShearDemand
Components:overstrength,o,anddynamicamplification,v
o 1.4
Dynamic Amplification, v
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DynamicAmplification,v Mostexistingmodelsresultinimpreciseprediction
ofv
andhighconservatismfortallerbuildings
SEAOC(2008)
NZ3101(2004)
Priestleyetal.(2007)
MRSAmethodbyEibl etal.(1998)isbestmodel
1st modecontributiontoshearisreducedbyRandelastic/
unreducedcontributionsfromallothermodesareused
(Eibl etal.1988)
Providesminimaldispersionandslightlyconservative
estimatefor6 12storybuildingsbutlargerdispersion
andinaccuracy
for
16+
story
buildings
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ModifiedMRSAMethod
Eibl Method: Reduce 1st mode elastic shear contribution
Proposed Modified MRSA Method: Reduce largest elastic shear
contribution
Eibl et al. (1988): MRSA Method
Proposed Modified MRSA Method
Building Height (Stories)
RecommendedCapacityDesign
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ProcedureforShear
Vn VuwithVu= voVu o=1.4toaccountforflexuraloverstrength
v determinedusingModifiedMRSAmethod
Sheardemandissummationofmodelcontributions
withonlythemodethatcontributesthemosttothe
baseshear(1st or2nd typically)reducedbyR
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ValidationofCapacityDesignProcedure
Designnewsuiteofwalledbuildingsusingtwo
proceduresforshear CapacitydesignforshearwithR=2,3,4
CodebaseddesignforshearwithRASCE =5,6
ConsiderDesignandMCEleveleventsusing
syntheticgroundmotions
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ClarificationofRvs.RASCE
R = 5Stories
l f f
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ClarificationofRvs.RASCE
R = 5
RASCE = 5; R 3.3
Scaling MRSA demands upso that Vbase,MRSA= Vbase,ELFRASCE = 5; R 3-3.5
RASCE = 6; R 4-4.5
Stories
DesignLevelShearDemandCapacityRatio(10% probabilit of e ceedance in 50 ears)
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6-story
(10% probability of exceedance in 50 years)
8-story 12-story
16-story 20-story 24-story
MCELevelShearDemandCapacityRatio(2% probability of exceedance in 50 years)
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6-story
(2% probability of exceedance in 50 years)
8-story 12-story
16-story 20-story 24-story
Fl lD i
fW ll
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Flexural Design ofWalls Goals:
Determinepreferredenvelope(s)forflexuraldesign
EstimateanRfactorforslenderwallsthatprovidesacceptableprobabilityoflossoflateralcapacity
Method:
Investigatedesignenvelopes(i.e.barcurtailments)forflexure
Redesign64buildingsusingmultipledesignenvelopes ConsiderdistributionofcurvatureductilitydemandsatMCE
Note:designwithR=3andemploysyntheticgroundmotionsuite
Rfactor
Designnewsetofbuildingsusingpreferreddesignmethod EmployP695Methodology
EstimateRfactorrequiredtoachieve20%probabilityoflossoflateral
loadcarryingcapacityunderMCE
Fl l D i E l
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FlexuralDesignEnvelopes
MRSA Moment Envelope
Mu Mu
Mu Mu
Fl l D i E l
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FlexuralDesignEnvelopes
MRSA Moment Envelope
Mu Mn
Constant
Mu Mn
MRSA/ELF
Mu Mu
Paulay/Priestley (1992)
Mn Mn
Dual Hinge
(Panagiotou and
Restrepo, 2009)
0.5H
I t f Fl l D i E l
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ImpactofFlexuralDesignEnvelopes DesignsemployR=3
Analysesaredonefor
MCEintensitylevel
Analysesaredone
usingsynthetic
groundmotionsuite
P695 Methodology for Estimation of R
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P695MethodologyforEstimationofR Evaluate6,12 and20storysimplifiedbuildingdesigns
6 and12storybuildingshaveplanarwalls
20storybuildinghascshapedwalls
Sheardesign:
Capacitydesignforshear
Overstrength:0 =1.4
Dynamicamplification:ModifiedMRSAMethod
Flexuraldesign:
R=3
BothPaulay/Priestely andDualHingeenvelopesemployed
EstimationofrequiredRusingP695Methodology
UseP695 groundmotionstoincluderecordtorecordvariability
EstimateRfactorrequiredtoachieve20%probabilityoffailureatMCE
P695 Evaluation Results
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P695Evaluation Results
Prob. of
Failure
P695 Evaluation: Capacity Designed Walls
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P695Evaluation:CapacityDesignedWalls
Slender planar
walls: R 2.5
Slender core
walls: R 3.5
Prob. of
Failure
= R
required to
achieve 20%
probability of
failure
SummaryofRecommendedDesign
A h
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Approach
ShearDesign
CapacityDesignforShear
Overstrength:0 =1.4
Dynamicamplification:ModifiedMRSAMethod FlexuralDesign
DesignEnvelope:Paulay/PriestleyorDualHinge
Planarwalls:R 2.5
Corewalls:R 3.5 } ASCE 7-10:RASCE = 5,6(RASCE 4.0)
(RASCE 5.0)
Conclusions about Wall Performance
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ConclusionsaboutWallPerformance Wallsmayexhibitcompressioncontrolledfailureevenif
tensilestrainsatnominalstrength,Mn,arelarge(
t>0.02
reqd fortensioncontrolledresponse)
Highaxialloadsmaydevelopinacoupledwallsystem
Presence
of
a
splice
affects
the
location
of
inelastic
action
and
damagepattern
Ahighsheardemandcapacityratioincreasesthelikelihoodof
acompressioncontrolledfailure
Cshapedwallsandsymmetricflangedwallsingeneralexhibit
higherdriftcapacitiesandretainmoreflexuralstrength(post
failure)thanplanarwalls.
Conclusions about Wall Analysis
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ConclusionsaboutWallAnalysis Regularizationofmaterialresponseisrequired
forpredictionofdriftcapacitybecauseresponseiscompressioncontrolledwith
localizedsoftening
Regularizedlineelementmodelsprovide
accurateandprecisesimulationofstiffness,
strength
and
drift
capacity
Conclusions about Wall Design
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ConclusionsaboutWallDesign CurrentUScodedesignunderestimatesshear
demandinwalls Anoverstrengthfactor,0 =1.4andthe
ModifiedMRSAmethodcanbeusedto
estimatesheardemandinwalls
Smallerforcereductionfactors,Rfactors,are
requiredtolimitflexuraldamageatMCE
CrossSectional Shape
Please enter your questions in
Questions?Questions?
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Cross SectionalShape
Symmetric Flanged
Asymmetric Flanged
Rectangular
Pleaseenteryourquestionsin
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