shear wall shear design

ANALYSISANDDESIGNOF
SHEARWALL
 Introduction
 Shearwall
 Placementof shearwall
 Architecturalaspect
 Applications
 Functions
 Design
 Forcesacting
 Comparison
 AdvantagesandDisadvantages
 Pictorialview
 Conclusion

 Reference
INTRODUCTION:
 Increasein theconstructionof tallbuildingsboth
residential,commercial andthemoderntrendis
towardsmoretallstructures.
 Theeffectsof lateralloads
 Likewindloads,earthquakeloadsandblast
forcesare attainingincreasingimportance.
 Almosteverydesignerisfacedwiththeproblemsof
 Providingadequatestrengthandstability
against
 Lateralloads.

SHEARWALL:
 Shearwallsare especiallyimportantin high-rise
buildings.
 In residentialbuildings,shearwallsare externalforma
boxwhichprovidesallof thelateralsupportforthe
building.
 Resist: Lateralloads,Seismicloads,VerticalForces
(gravity).
 Reduceslateralswayof thebuilding.
 Providelargestrengthandstiffnessto buildingsin the
directionoftheirorientation.
 Excellentstructuralsystemto resistearthquake
 Providedthroughouttheentireheightof wall

 Practicingfrom1960sformediumandhighrise
buildings(4to 35 storieshigh)
 Rigidverticaldiaphragmtransferstheloadsinto
Foundations.
 Shearwallsbehaviordependsuponmaterialused,wall
thickness,walllength,wallpositioningin building
framealso.
PLACEMENTOFSHEARSHEARWALL:

 Locatedsymmetricallyto reduceilleffectsof twist
 Symmetrycanbe alongoneorboththedirections
 Can be locatedat exteriororinterior
 Moreeffectivewhenlocatedalongexteriorperimeterof
building

ARCHITECTURALASPECT:
 Shearwallsprovideslargestrengthandstiffnesswhich
reduceslateralsway,reduces damageto structureand
itscontents.
 Overturningeffectsare large.
 Designof foundationsrequiresspecialattention.
 Moment-resistantframemustbe providedalongthe
otherdirectionto resiststrongearthquakeeffects.
 Specialdesignchecksarerequiredin orderto carrythe
horizontalearthquakeforce.
APPLICATION:
 Shearwallsare notonlydesignedto resistgravity/
verticalloads butdesignedforlateralloadsof
earthquakes/ wind.

 wallsare structurallyintegratedwithroofs/ floors
(diaphragms)
 Otherlateralwallsrunningacrossat rightangles,
therebygivingthethreedimensionalstabilityforthe
buildingstructures.
 Wallshaveto resisttheupliftforces causedby thepull
of thewind.
 Wallshaveto resisttheshearforcesthattryto push
thewallsover.
 Wallshaveto resistthelateralforceofthewindthat
pushthewallsin and awayfromthebuilding.
 Shearwallstructuralsystemsaremorestable.
 Supportingareawithtotalplansareaofbuilding,is
comparativelymore,unlikein thecaseof RCCframed
structures.

FUNCTIONS:
 StrengthandStiffness
 Strength-Shearwallsmustprovidethenecessary
lateralstrengthto resisthorizontalearthquakeforces.
 Whenshearwallsare strongenough,theywilltransfer
thesehorizontalforcesto thenextelementin theload
pathbelowthem,suchasothershearwalls,floors,
foundationwalls,slabsorfootings.
 Stiffness-Shearwallsalsoprovidelateralstiffnessto
preventtherooforfloorabovefromexcessiveside-
sway.
 Whenshearwallsare stiffenough,theywillprevent
floorandroofframingmembersfrommovingofftheir
supports.

 Also,buildingsthatare sufficientlystiffwillusually
sufferlessnonstructuraldamage.
Classificationof ShearWallsAccordingTo TheirHeight-
to-LengthRatios:
 Shearwallsare classifiedasshortorlongaccordingto
theiraspectratios(theratioof itsheighthwto length
in theplaneofloadinglw),asfollows:

 Forhw / lw < 2,theyarecalledshortorsquatshear
walls.
 Theirdesignisdominatedby shear,ratherthan
flexure.Aspectratiosbelow2 markthetransitionfrom
slenderto shortbehavior,andwallswithsuch
dimensionsrequireconsiderablecarein designif a
ductilefailuremodeisrequired.Withoutthisattention,
shearwallsarelikelyto failin brittlefailuremodes
suchasdiagonaltensionorslidingshearratherthan
undergoingthemoreductileflexuralfailurepossiblein
slenderwalls.Shortshearwallsmayneedincreased
strengthorspecialdetailing,includingdiagonalsteelto
overcometheseproblems.
 Forhw/lw ≥ 2, theyarecalledlongorslendershear
walls.

 Theirdesignisdominatedby flexure.Aspectratiosare
normallyrestrictedto 7, higher ratiosmayresultin
inadequatestiffness,problemsin anchoringthetension
sideof theshearwallandpossiblysignificant
amplificationsdueto P − ∆ effects.Theabove
classificationisnotexplicitlystatedin ACI318-08
Code.
DESIGN:
 Theshearwallisdesignedasa cantileverbeamfixedat
thebase,to transferloadto thefoundation.Shear
force,bendingmoment,andaxialloadare maximum
at the baseof thewall.
 Accordingto ACI11.1.1,designofcrosssections
subjectto sheararebasedon

𝑽𝒖 ≤ ∅𝑽𝒏 (1)
 whereVu isthefactoredforceat thesectionconsidered
andVn is thenominalshearstrengthcomputedby
 Vn = Vc+Vs (2)
 WhereVn is nominalshearstrengthprovidedby
concreteandVsis nominalshearstrengthprovidedby
shearreinforcement.
 Basedon ACI11.9.3,Vn,maxat any horizontal
sectionforshearin planeof thewallisnotto be taken
greaterthan
𝑽𝒏 ≤ 𝟏𝟎𝝀√𝒇𝒄′
𝒉𝒅 (3)
 Where 𝝀 isthelightweightconcrete strength
modificationfactor
 𝒅 istakenequalto 𝟎. 𝟖𝒍𝒘

 A largervalueof 𝒅 = distancefromextreme
compressionfaceto thecenterofforceof all
reinforcementin tension.
 Accordingto ACI code11.9.5forwallsubjectedto
verticalcompression
𝑽𝒄 = 𝟐𝝀√𝒇𝒄′
𝒉𝒅 (4)
 Andforwallssubjectedto VerticalTensionNu,
𝑽𝒄 = 𝟐(𝟏 +
𝑵𝒖
𝟓𝟎𝟎𝑨𝒈
) 𝝀√𝒇𝒄′
𝒉𝒅
(5)
 WhereNu isthefactoredloadin poundstaken
negativefortension
 Ag is thegrossareaof horizontalconcretesectionin
squareinches.

 Thevalueof Vc basedon othercalculationsin details,
Vc is thelesserof thetwovaluesshownin eq (6) &
(7).
𝑽𝒄 = 𝟑. 𝟑 𝝀√ 𝒇𝒄′ 𝒉𝒅 +
𝑵𝒖𝒅
𝟒𝒍𝒘
(6)
Or
 WhereNu ispositiveforcompressionandnegativefor
tension.
oIf (Mu/Vu– lw / 2) is negative,Eqn.(7)isnot
applicable

 WhenfactoredshearforceVu doesnotexceed∅
𝑽𝒄
𝟐
a
wallmaybe reinforcedto minimumrequirement,
whenVu exceeds∅
𝑽𝒄
𝟐
Reinforcementforshear
providedaccordingto followingrequirement
𝑽𝒔 =
𝑨𝒗𝒇𝒚𝒅
𝒔
(8)
 WhereAv =areaofhorizontalshearreinforcement
withinverticaldistancess ,in2
 S=verticaldistanceb/whorizontalreinforcement,in
 fy=yieldstrengthof reinforcement,psi
 Substitutingeq (8) intoeq (2) andthencombining
witheq (1),we get
Av =
(Vu − фVc) s
ф𝒇𝒚 𝒅
(9)

 Minimumpermittedratioof horizontalshearsteelto
grossconcreteareaof verticalsection is
 𝝆𝒕 = 𝟎. 𝟎𝟎𝟐𝟓 (10)
 Maxspacingnotexceedsto
oLw/5
o3h
o18in
 Forlowshearwallsverticaldistributed reinforcementis
neededaswellas horizontalreinforcement.Vertical
steelof areaAh withina spacings1,suchthattheratio
of verticalsteeltogrossconcreteareaof horizontal
sectionwillbe notlessthan
 𝝆1 = 0.0025+0.5 [2.5 −
𝒉𝒘
𝒍𝒘
] (ρt−0.0025) (11)
oNorlessthan0.0025

 Spacingnotexceedsforverticalbar
oLw/3
o3h
o18in
DesignProvisions:
 Minimumratioofverticalreinforcementareato gross
concretearea,rl , shallbe
 · 0.0012fordeformedbarsupto #5Bars,with
f y not lessthan 60 ksi.
 0.0015forotherdeformedbars.
 Minimumratioofhorizontalreinforcementareato
grossconcretearea,rt , shallbe
 · 0.0020fordeformedbarsupto #5Bars,with
f y not lessthan 60ksi.

 0.0025forotherdeformedbars.
 Thethicknessof theshearwallshouldnotbe lessthan
6 inchesto avoidunusuallythinsections.
 If thewallthicknessexceeds8 inches,the
reinforcementshouldbe providein twolayers.
 Eachbarsrunningin boththelongitudinaland
transversedirectionsin theplaneof thewall.
 Wallthicknessshouldnotexceedsfrom16inches.
 Thediametershouldnotexceed1/10thofthicknessof
wallweb.
oThecriticalsectionforshearistakenat a distance
equalto halfthewalllengthlw/ 2,or halfthe
wallheighthw / 2, whicheverisless.Sections
betweenthebaseof thewallandthecritical

sectionareto be designedfortheshearat the
criticalsection,as specifiedin ACI 11.9.7.
o

o
 SHEARWALLREINFORCEMENT
DesignForFlexure:
 Thewallmustbe designedto resistthebending
momentat thebaseandtheaxialforceproducedby

thewallweightortheverticalloadsit carries.Thus,it
isconsideredasa beam-column.
 Forrectangularshearwallscontaininguniformly
distributedverticalreinforcementandsubjectedtoan
axialloadsmallerthanthatproducingbalancedfailure,
thefollowingequation,developedby Cardenasand
Magurain ACISP-36in 1973,canbe usedto
determinetheapproximatemomentcapacityofthe
wall.
 𝑴𝒖 = 𝝋 [𝟎. 𝟓𝑨𝒔 𝒇𝒚 𝒍𝒘(𝟏 +
𝑷𝒖
𝑨𝒔 𝒇𝒚
) (𝟏 −
𝑪
𝒍𝒘
)]
(12)
 Where
 𝑪
𝒍𝒘
=
𝝎+𝜶
𝟐𝝎+𝟎.𝟖𝟏𝜷𝟏

o 𝝎 =
𝑨𝒔 𝒇𝒚
𝒍𝒘 𝒉 𝒇𝒄′ and 𝜶 =
𝑷𝒖
𝒍𝒘 𝒉 𝒇𝒄′
 C= distancefromtheextremecompressionfiberto the
neutral
 axis
 As = totalareaof verticalreinforcement
 lw = horizontallengthof wall
 Pu = factoredaxialcompressiveload
 f y = yieldstrengthof reinforcement
 F = strengthreductionfactorforbending
DesignLoadCombinations:
 TheDesignLoadCombinationsforconcreteShear
wallaregivenby thefollowingequations.

 1.4D (ACI9-1)
 1.2D+ 1.6+ 0.5Lr (ACI9-2)
 1.2D+ 1.0L+ 1.6Lr (ACI9-3)
 1.2D+ 1.6(0.75PL)+ 0.5Lr (ACI9-2,13.7.6.3)
 1.2D± 1.6L+ 0.5S (ACI9-2)
 1.2D+ 1.0L+ 1.6S (ACI9-3)
 0.9D± 1.6W (ACI9-6)
 1.2D+ 1.0L+ 0.5Lr± 1.6W (ACI9-4)
 1.2D+ 1.6Lr ± 0.8W (ACI9-3)
 1.2D+1.6S± 0.8W (ACI9-3)
 1.2D+ 1.0L+ 0.5S± 1.6W (ACI9-4)
 0.9D± 1.0E (ACI9-7)
 1.2D+ 1.0L+ 0.2S± 1.0E (ACI9-5)
oIn theprecedingEquations,

oD = the sumofalldeadloadcasesdefinedforthe
model.
oL = Thesumof allliveloadcasesdefinedforthe
model.Notethatthisincludesroofliveloadsas
wellas floorliveloads.
oLr = the sumof allroofliveloadcasesdefinedfor
themodel.
oS = Thesumofallsnowload casesdefinedforthe
model
oW = Any singlewindloadloadcasedefinedfor
themodel.
oE = Any singleearthquakeloadloadcasedefined
forthemodel.
FORCESACTING:
 Shearwallsresisttwotypesofforces:

 Shearforcesandupliftforces.
 Shearforces are generatedin stationarybuildings:
 By externalforceslikeWindandWaves.
 Upliftforcesgreateron tallshortwallsand
 Lesson lowlongwalls.
 Bearingwallshavelessupliftthannon-bearingwalls.
 Equallengthshearwallsshouldbe placed
symmetrically.
 It canalsoprovidein interior, if exteriorwallcan’t
provide
 sufficientstrengthandstiffness.
COMPARISON:
 Loadbearingmasonryisverybrittlematerial.

 Duestressessuchasshear,tension,torsion,etc.,
causedby theearthquakes,theconventional
unreinforcedbrickmasonryinstantlycollapsesduring
theunpredictableandsuddenearthquakes.
 TheRCCframedstructuresare slender,when
comparedto shearwallconceptofboxlikethree
dimensionalstructures.
 It ispossibleto designtheearthquakeresistantRCC
frame,it requiresextraordinaryskillsat design,
detailingandconstructionlevels,whichcannotbe
anticipatedin alltypesof constructionprojects.
 Evenmoderatelydesignedshearwallstructuresnot
onlymorestable,butalsocomparativelyquiteductile.
oDuringverysevereearthquakestheywillnot
suddenlycollapsecausingdeathof people.

oTheygiveenoughindicativewarningssuchas
wideningstructuralcracks,yieldingrods,etc.,
offeringmostpreciousmomentsforpeopleto run
outof structures.
oForstructuralpurposeswe considertheexterior
wallsasthe shear-resistingwalls.
oForcesfromtheceilingandroofdiaphragmsmake
theirwayto theoutsidealongassumedpaths,
enterthewalls,andexitat the foundation.
ADVANTAGES& DISADVANTAGES:
 Advantages:
oThinnerwalls.
oLightweight.
oFast constructiontime.
oFast performance.

oEnoughwelldistributedreinforcements.
oCosteffectiveness.
oMinimizeddamagesto structuraland
nonstructuralelements.
oProvidesgreaterstiffness.
 Disadvantages:
oLessenergydissipation.
oCauseshigherlossesto non-structural
components.
PICTORIALVIEW:

o
CONCLUSION:
 Thusshearwallsare oneofthemosteffectivebuilding
elementsin resistinglateralforcesduringearthquake.
 By constructingshearwallsdamagesdueto effectof
lateralforcesdueto earthquakeandhighwindscanbe
minimized.
 Shearwallsconstructionwillprovidelargerstiffnessto
thebuildingsthereby reducingthedamageto
structureanditscontents.

 Not onlyhasitsstrength,in orderto accommodate
hugenumberofpopulationin a smallareatall
structuredwithshearwallsareconsideredto be most
useful.
 Hencea developingcountrylikePakistan,shearwall
willbe a backboneto ourconstruction industry.
REFRENCE:
 Designof ConcreteStructuresBy AuthorH. Nelson,
DavidDarwinandCharlesW.Dolan14thEdition.
 Definitionof ShearwallanddetailingusingSlide
Share.
 StructuralwallforresistingearthquakeengineeringBy
S.K.Duggal.

 ACI,2008.BuildingCodeRequirementsforStructural
Concrete(ACI318-08)andCommentary(ACI318R-
08),AmericanConcreteInstitute,P.O.Box9094,
FarmingtonHills,Michigan

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