2013 nees webinar lowes lehman slides

7/30/2019 2013 NEES Webinar Lowes Lehman Slides

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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


2/102

Performance,Analysisand

DesignofFlexuralConcreteWalls

DawnLehmanandLauraLowes

UniversityofWashington,Seattle


3/102

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


4/102

Acknowledgements

Fundedbythe

National

Science

Foundation

throughtheNEESRprogram

SupplementalfundingprovidedbytheCharles

Pankow Foundation


5/102

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


6/102

CurrentDesign

Process


7/102

DefinitionofShearWallTerms

Boundary

Zone:Heavy Vertical

And TransverseSteel

Web:Light Vertical

And TransverseSteel

hw

lw

twlb

(http://www.jacobsschool.ucsd.edu)


8/102

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


9/102

AvoidingDamageinWalls:InadequateConfinement


10/102

WallDesigntoAchieveDuctileFlexureControlledResponse

1. Proportionwall

soshear

stress

demand

islow

forelasticforce (typicallywithsystemtorsion

includedincalculation)

2. Designflexuralreinforcementtoachievebasemomentcapacity(similartoacolumn)

3. Designforsheardemandcorrespondingto

flexuralyieldingofwall(capacitydesign)

4. Detailboundaryelementwithrequired

confinement


11/102

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


12/102

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.


13/102

DesignIssues/Uncertainties Demand

Overstrength,torsion,nonlineardynamicamplificationeffects.

Sheardemand/capacity

Demanddependsonaccuracyofanalysis.

ACI3812011givesmaximumshearstressof8fc (psi).

Sometargetshearstresslevelsof46fc (psi)underelasticdemands(withtorsionincluded).

Confinement Constructability

Splices

Typicallyeveryotherfloorandbase.


14/102

Experimental Program

UNIVERSITY of ILLINOIS


15/102

TestProgram

Rangeofconfigurations

SimulatesACI31811

Actualdetails(confinement/splices)

Realisticdemands(shear/axial)(Courtesy of MKA, Seattle)

CShaped

Wall

CoupledWalls


16/102

PlanarWallTestSpecimens

1/3scalemodelof

bottom3storiesofa10storywall

FullScale:

12ft.storyheight18in.thick

30ft.long

Lab:4ft.storyheight

6in.thick

10ft.long


17/102

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


18/102

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


19/102

NEESandPriorTestsNEES Tests

ACICompliant


20/102

PlanarWallTestatMUSTSIM@UIUC

Lowerstoriesofmid

risebuildingstoriessimulatedinlab.

Shearandmoment

applied to

varysheardemand Axialloadof0.1Agfc.


21/102

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


22/102

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


23/102

-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


24/102

PW4: heff =0.5h, concentratedBE, nosplice

BaseShear(

kips)

Top Drift (%)


25/102

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


26/102

VerticalStrain:+1.0%Drift

PW11.5% drift

PW21.1% drift

PW31.25% drift

PW41.0% drift


27/102

ShearStrain:+1.0%Drift

PW1 PW2 PW3 PW4


28/102

2nd (Compressive)PrincipalStrain

PW1 PW2 PW3 PW4


29/102

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%


30/102

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%


31/102

InitialSpalling

1.00%

Initial Spalling

CBYield

Walls Yield

1.50%

C

B3

ModerateSpalling

ModerateSpalling

CB2


32/102

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%


33/102

2.0% drift (Moderate

Spalling near failure)

0.50% drift

(TWP Yields)

ShearStrains1.00% drift

(Initial Spalling)

0 m 6 m


34/102

PrincipalCompressiveStrains

-6 m 0 m

2.0% drift (Moderate

Spalling near failure)0.50% drift

(TWP Yields)1.00% drift

(Initial Spalling)


35/102

CouplingBeamRotation


36/102

AxialForceinCompressionPier

L

CWP


37/102

CshapedWallCrossSection

4 x 6 Flanges (Coupled wall)

10 x 6 Web (planar wall)


38/102

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


39/102

2.16in(1.5%drift)

-2 -1 0 1 2 3 4

-6000

-4000

-2000

0

2000

4000

6000

% Drift

Moment(kip-ft)


3rd Story Shear and Base Moment:Fx = 201 kip

My = 5,765 k-ft


40/102

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)


WestFlangeEastFlange


41/102

+5.1in(3.512%drift)

-2 -1 0 1 2 3 4

-6000

-4000

-2000

0

2000

4000

6000

% Drift

Mome

nt(kip-ft)


Pushed to 3.5% to

evaluate post-lateral

failure response. Retained almost 50% of

strength


42/102

EvaluationforPerformanceandDesign:

ComparisonwithPriorTestData

Wallace 2011


43/102

SlenderWallExperimentalDataSet

Assembledtoprovideinsightintothefactorsthat

affectdamageanddriftcapacity

Includes

Datafrom49testsfrom15testprograms

Dataforwallswithshearspanratio>2

DataforrectangularandflangedRCwalls

Doesnotinclude

Wallslessthan2in.thick

Wallswithopenings

Wallssubjectedtomonotonicordynamicloading


44/102

OverviewofSlenderWallDatabase(Birely2012)


45/102

DamageModesforThisDiscussion

Compression Failure Bar Rupture Failure


46/102

TensileStrainatMn

Compression

Failure

Bar RuptureFailure

Wall that are tension controlled still fail

in compression damage mode


47/102

Confinement

Resultssuggestyouneedalottomakea

differenceindriftcapacity


48/102

ShearDemandCapacityRatio

Compression

Failure

Bar Rupture

Failure

Mixed


49/102

Modelingthe

NonlinearResponse

ofWallsResponse


50/102

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.)


51/102

ForceBasedFiberTypeBeamColumnElement(OpenSees) Assume:linearmomentdistribution,constantaxialload >

solveforsectionstrainandcurvaturetosatisfycompatibilityreqts.

Flexural section

Shear section

Elastic section w/ reduced shear stiffness,

per Oyen (2006)

Fiber-type section


52/102

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


53/102

FiberSection:Steel Model

MenegottoPintoFilippou

model(1983)

4


54/102

ModelEvaluation Datasetof21walls

Slenderwalls

(M/hlw >

1.5)

Exhibitingflexuralfailure

modes:

Modelevaluatedonthe

basisofsimulatedstiffness,

strengthanddriftcapacity


55/102

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


56/102

LocalizationofDamage/Deformation

Specimen WSH4

(Dazio et al. 2009)

0.63%

Inelastic Localization


57/102

ToAchieveMeshObjectiveResults

Regularizematerialresponse

Thisistypicallydoneincontinuumanalysis.

Useamaterialenergyandameshdependentlengthtodefine

thepostpeak(softening)portionofthestressstraincurve.

ColemanandSpacone (2001)proposedthisapproachforbeamcolumnelements,butprovidedlimited

recommendationsforthematerialenergytobeused.

Todetermine

material

energy

Useexperimentaldatafromwalltests(concrete)andcoupon

tests(steel)


58/102

MaterialRegularization:PlainConcrete

3-I.P. Element

LIP,1

LIP,1

LIP,2

Constant material energy

Mesh dependent length


59/102

MaterialRegularizationRecommendations

Bare Bar Regularized

ConcreteCrushingEnergy Unconfined:Gfc =2fc (N/mm)

Calibratedusingdatafrom2planarwallspecimensconstructedentirelyofunconfinedconcrete.

Confined:Gfcc =1.70Gfc Calibratedusingdatafor12planarwallspecimens

constructed

of

unconfined

and

confined

concrete.

SteelPostYieldHardening ComputedusingASTMgagelengthformaterialtesting


60/102

ImpactofRegularizationWSH4 Specimen (Dazio et al., 2009)

No regularization of

material response

Regularization of

material response


61/102

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


62/102

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


63/102

EvaluationofCurrent

DesignProcedures


64/102

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)


65/102

BuildingDesigns

loading direction

considered

Seismic weight = 170 psf

Gravity weight = 190 psf

Wall axial load at base = 0.1fcAg


66/102

NumericalModelUsedforEvaluation

ag(t)

CoreWall

P-Column(Leaning)

Regularizedfibertypeforce

basedbeamcolumnelement

1elementwith5integration

pointsperstory

Elastic,grosssectionshearstiffnessemployed(shear

stiffness=GAcv)

Impactoflargedisplacementson

walldemands(i.e.pdeltaeffects)

wasincluded

2%Rayleighdampingemployed


67/102

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=


68/102

Nonlinear

Analysis

Results(ELFProcedureDesigns)

MCE

DBEVn,pr

Ground Motion Intensity Ratio = ST1/SMT

flexural failure

shear failure


69/102

Developmentof

ImprovedDesign

ProceduresforWalls


70/102

ConsiderationsforWallDesign

Sheardesign

Capacitydesignforshearisrequired

Designforincreasedsheardemandtoensurethat

shearcapacitynotexceededpriortoflexuralyielding

Flexuraldesign

Designenvelopetoensurethatflexuralyielding

occursinexpectedlocations

Rfactorcalibratedtoachievedesiredcollapse

probability


71/102

CapacityDesignforShear

Sheardemandincreasedtoaccountfor

FlexuralOverstrength

DynamicAmplification

Currentdesign

method

(ASCE

7and

ACI

318)

Vn Vuwith =0.6

Capacitydesignforshear

Vn VuwithVu

= voVu

Flex. Overstrength

Dyn. Amplification


72/102


ag(t)

Shear, V Moment, M

VE MEVu Mu

RR

Mu

Mn


73/102


ag(t)

Shear, V Moment, M

VE MEVu Mu

RR

Mu Mn

Mpr= oMu


74/102


ag(t)

Shear, V Moment, M

VE MEVu Mu MprVpr

R/

o

Mpr= oMu

Dynamic Amplification


75/102


heff

1

stmode

2

nd

mode

total

Base Moment Demand

Base Shear Demand

+ + =elastic

model



76/102

y p

h

eff

Mu

Vu

1

stmode

2

nd

mode

totalu

nreduced

tota

lreduced

Assume all

modes are

reduced

equally

+ + =



77/102

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

+ + =

+ + =


78/102

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


79/102

IdealizedBuildings

N = 16, 20, 24 storiesN = 6, 8, 12 stories

loading

direction

Seismicweight=170psf

Gravityweight=190psf

Wallaxialloadatbase=0.1fc

Ag


80/102

SeismicDemandforITHA

7syntheticgroundmotionrecords

Providedconsistencyindemandbetweendesignspectrumusedfordesignandearthquakemotions

usedforevaluation


81/102

ShearDemandComparison


82/102

ShearDemand

Components:overstrength,o,anddynamicamplification,v

o 1.4

Dynamic Amplification, v


83/102

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


84/102

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


85/102

ProcedureforShear

Vn VuwithVu= voVu o=1.4toaccountforflexuraloverstrength

v determinedusingModifiedMRSAmethod

Sheardemandissummationofmodelcontributions

withonlythemodethatcontributesthemosttothe

baseshear(1st or2nd typically)reducedbyR


86/102

ValidationofCapacityDesignProcedure

Designnewsuiteofwalledbuildingsusingtwo

proceduresforshear CapacitydesignforshearwithR=2,3,4

CodebaseddesignforshearwithRASCE =5,6

ConsiderDesignandMCEleveleventsusing

syntheticgroundmotions


87/102

ClarificationofRvs.RASCE

R = 5Stories

l f f


88/102

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)


89/102

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)


90/102

6-story

(2% probability of exceedance in 50 years)

8-story 12-story

16-story 20-story 24-story

Fl lD i

fW ll


91/102

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


92/102

FlexuralDesignEnvelopes

MRSA Moment Envelope

Mu Mu

Mu Mu

Fl l D i E l


93/102

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


94/102

ImpactofFlexuralDesignEnvelopes DesignsemployR=3

Analysesaredonefor

MCEintensitylevel

Analysesaredone

usingsynthetic

groundmotionsuite

P695 Methodology for Estimation of R


95/102

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


96/102

P695Evaluation Results

Prob. of

Failure

P695 Evaluation: Capacity Designed Walls


97/102

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


98/102

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


99/102

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


100/102

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

thechatwindowaddressed

toAllPanelists

2013 nees webinar lowes lehman slides

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