15LS03 Designing Wood-Frame Structures For High Winds V2 · ASCE 7-10 26.2 commentary provides some discussion on uplift & MWFRS vs. C&C. Components receive wind loads directly or

DesigningWoodFrameStructuresForHighWinds

“TheWoodProductsCouncil”isaRegisteredProviderwithTheAmericanInstituteofArchitectsContinuingEducationSystems(AIA/CES),Provider#G516.

Credit(s)earnedoncompletionofthiscoursewillbereportedtoAIACESforAIAmembers.CertificatesofCompletionforbothAIAmembersandnon-AIAmembersareavailableuponrequest.

ThiscourseisregisteredwithAIACESforcontinuingprofessionaleducation.Assuch,itdoesnotincludecontentthatmaybedeemedorconstruedtobeanapprovalorendorsementbytheAIAofanymaterialofconstructionoranymethodormannerofhandling,using,distributing,ordealinginanymaterialorproduct.________________________________Questionsrelatedtospecificmaterials,methods,andserviceswillbeaddressedattheconclusionofthispresentation.

CourseDescription

Woodframingisconducivetomeetingthechallengesofwind-resistivedesign.Amongitscharacteristics,woodcancarrysubstantiallygreatermaximumloadsforshortdurationsoftimeasisthecaseinhigh-windevents.Woodbuildingsalsotendtoincludemultipleandoftenredundantloadpathsforresistancetowindforces.Thispresentationwillcoverthedesignofabuilding’swind-resistingsystem,includingwindloadcalculations,diaphragms,shearwallsandcollectors.Loadpathcontinuitywillbediscussed,aswilluniquedesignconsiderationsfordesigningwood-framestructurestoresistuplift,in-plane,andout-of-planewindloads.Designexampleswillbepresentedtoillustraterelevantdesignproceduresanddetailingbestpractices.

LearningObjectives

1. ReviewtheparametersforbuildingwindloadcalculationsperASCE7andtheInternationalBuildingCode.

2. Examinethethreemaintypesofbuildingwindloads(uplift,in-plane,andout-of-plane)anddesignconsiderationsassociatedwitheach.

3. Discusscommonwood-frameshearwall,diaphragm,andtie-downsystems.

4. Recognizethebenefitsofredundancyinwind-resistingwood-framesystems.

Overview

• Wind• CalculatingWindLoads• Uplift• WallDesign• Diaphragms• Shearwalls

MakingourBuildingsSafe- WindHighwindloadsactingonabuildingarearesultofavarietyoftypesofwindstormswhichhavedifferingnaturesandoccurrences.Buildingdesignshouldincludewindloadresistanceandaccountforthecharacteristicsofthetypeofstormsthatcanimpactthebuilding.

MakingourBuildingsSafe- Hurricanes

ImageSource:WholeBuildingDesignGuide


MakingourBuildingsSafe- Tornadoes

“Experiencehasshownthatcode-compliantwoodbuildingsperformexceedinglywellduringhighwindeventssuchashurricanes.Woodisstrongandmostwood-framebuildingsoffertheadvantageofrepetitivemembersandmultipleconnections,whichtogethercreateredundantloadpathstoeffectivelytransferwindforcesfromthebuildingenvelopetothefoundationandsoilbelow”.

UsingWoodtoResistWind:Benefits

QuoteSource:Wind-ResistiveDesignofWoodBuildings,AWC

Photo:NewGenesisApartments,Killefer Flammang Architects,KCKim,GBConstruction

WhyWood?

UsingWoodHelpsReduceYourEnvironmentalImpact

WoodProductsPlayaSignificantRoleinModernEconomy

WoodCostsLess

WoodisVersatile

WoodMeetsCode

WoodisDurable

WoodisRenewable

WindLoadsWindloadsactingonbuildingsaremodeledasuniformsurfaceloads.Windloadscancreatebothpositiveandnegativeloads(inwardsandoutwardsloads)onbuildingsurfacesandcreatethreedifferentloadingconditions:

• Uplift

• Racking/overturning

• Sliding/shear

WindForceDistribution


WindLoadDemand

IBC:BaseCode– ReferencesASCE7fordeterminationofwindforcesonstructures

ASCE7:ReferencedStandard.Providesinformationrequiredtodeterminewindforcesona

structure

CalculatingWindLoads

• ASCE7-05§ Chpt.6:ContainedAllProvisions

• ASCE7-10§ Chpt.26:GeneralRequirements§ Chpt.27:MWFRS– Directional§ Chpt.28:MWFRS– Enveloped§ Chpt.29:OtherStructures§ Chpt.30:Components&Cladding§ Appendices

DetermineBasicWindSpeed,Vmph

PerASCE7-10Fig.26.5-1A

115

DetermineBasicWindSpeed,V

• ASCE7-05§ ASDLoads§ 90mphperfig.6-1

• ASCE7-10 (figuresincorporateimportancefactor)§ UltimateLoads§ 115mphperfigure26.5-1AforRKII

§ 120mphperfigure26.5-1BforRKIII&IV

§ 105mphperfigure26.5-1CforRKI

Note:RK=RiskCategoryImageSource:SKGhosh Associates

WindSpeedByLocationSoftware

windspeed.atcouncil.org

RunningtheNumbers:VelocityPressure

• qz =0.00256KzKztKdV2

§ qz =velocitypressure(psf)§ Kz – Exposurecoefficient,Table30.3-1(7-05Table6-3)

§ Kzt – Topographicfactor,Figure26.8-1(7-05Figure6-4)

§ Kd – Directionalityfactor,Table26.6-1(7-05Table6-4)

WindLoadsTypes

2TypesofWindLoads

• MWFRS– MainWindForceResistingSystemAnassemblageofstructuralelementsassignedtoprovidesupportandstabilityfortheoverallstructure.Thesystemgenerallyreceiveswindloadingfrommorethanonesurface.Eg.Shearwalls,diaphragms

• C&C– Components&CladdingElementsofthebuildingenvelopethatdonotqualifyaspartoftheMWFRS.Eg.Wallstuds

MWFRSMethodOptions

TwoMethodsofCalculatingMWFRSloads:• Envelope:Pressurecoefficientsrepresent“pseudo”loadingthatenvelopethedesired

moment,shear...Limitedtolow-rise

• Directional:Pressurecoefficientsreflectwindloadingoneachsurfaceasafunctionofwind

direction

MWFRSMethodOptions

Howtodecidewhichmethodtouse:Envelope:ASCE7-10Chapter28• Part1:Canbeusedforallregular-shapedenclosed&partiallyenclosedbuildingswithmeanroofheight≤60ft

• Part2(Simplified):Canbeusedforallregular-shaped,enclosed,simplediaphragmbuildingswithmeanroofheight≤60ft

MWFRSMethodOptions

Howtodecidewhichmethodtouse:Directional:ASCE7-10Chapter27• Part1:Canbeusedforallregular-shapedbuildings

• Part2(Simplified):Canbeusedforallregular-shaped,enclosed,simplediaphragmbuildingswithmeanroofheight≤160ft

MWFRSMethodOptions

ASCE7-10MWFRSOptions

Part1:Enclosed,PartiallyEnclosed,Open

BuildingsAllHeights

DirectionalMethod,CH27 EnvelopeMethodCH28

Part2:Enclosed,Simple

DiaphragmBuildingswithh≤160ft

Part1:Enclosed&PartiallyEnclosed Buildingswithh≤60ft

Part2:Enclosed,Simple

DiaphragmBuildingswithh≤60ft

Note:WindTunnelProcedure(ASCE7-10Chpt31)canalsobeused

Simplified,Directio

nal

Simplified,Envelope

SimpleDiaphragmBuildings

Abuildinginwhichbothwindwardandleewardwindloadsaretransmittedbyroofandverticallyspanningwallassemblies,throughcontinuousfloorandroofdiaphragms,totheMWFRS.

SimpleDiaphragmBuilding Non-SimpleDiaphragmBuilding

Example:FlatRoof,30’x60’Building:

Ch.27Directional

• WindwardWall(0.8)• LeewardWalls(-0.3)

• DetermineGustEffect(G)=0.85

• ForMWFRSGCpf =(1.1)(0.85)=0.935

Ch.28Enveloped

§ LimitedtoLow-Rise(h≤60’)§ WindwardWall(0.4)

§ LeewardWall(-0.29)

§ ForMWFRSGCpf =0.69

35%differenceinloadingnotaccountingforendzones.

ComparisonofmethodstocalculateMWFRS(GCpf)

ASCE7-10Figure28.4-1


MWFRSMethodOptions

Beneficialtousetheenvelopemethodwhenitslimitationsaremet

ASCE7-10Fig.C28.4-1

MinimumWindLoads

ForboththeDirectional&EnvelopeMethods,considerminimumwindloads:ASCE7-10Sections27.1.5&28.4.4:

WindLoadsforMWFRSinanenclosedorpartiallyenclosedbuildingshallnotbelessthan:§ 16psf (ultimateor~10psf ASD)forwalls§ 8psf (ultimateor~5psf ASD)forroofs

Wallandroofloadsshallbeappliedsimultaneously.Thedesignwindforceforopenbuildingsshallbenotlessthan16psf ultimate(openbuildingprovisionsapplyonlytoDirectionalMethod).

BuildingEnclosure

Accountsfordegreetowhichwindforcescanenterandexitastructure,creatingvaryingamountsofinternalwindpressure

3buildingenclosureclassifications:Open,PartiallyEnclosed,andEnclosed

RunningtheNumbers:DesignWindPressure

• p=qh[(GCp)– (GCpi)]§ p=Designwindpressure(psf)§ qh =velocitypressure(psf)§ GCp:Externalpressurecoefficient

Figures27.4-1,28.4-1,30.4-1Note:Figure27.4-1alsorequiresGusteffectfactor(G)persection26.9

§ GCpi:Internalpressurecoefficient,Table26.11-1(7-05Figure6-5)

InternalPressureCoefficient– Table26.11-1

+/- 0.18- Enclosed+/- 0.55– PartiallyEnclosed

ActualWindLoads

ComparingASCE7-05toASCE7-10:LoadCombinations:

7.0.6D+W(ASCE7-05)7.0.6D+0.6W(ASCE7-10)

3SecondWindSpeed:90mph (ASCE7-05)115mph*√0.6=89mph(ASCE7-10)

Finalloadonbuildingisverysimilar

IBC’sAlternateAll-HeightsMethodIBCSection1609.6providesanalternativetotheDirectionalWindLoadProcedureinASCE7

AlternateAll-HeightsMethod

Limitationssuchas:• BuildingHeight≤75ft• BuildingHeight/Width≤4• Buildinghassimplediaphragm• Others(IBC1609.6.1)

Pnet =0.00256V2KzCnetKzt

IBC’sAlternateAll-HeightsMethod

Pnet =0.00256V2KzCnetKzt

• V=Basicwindspeed(ASCE7)

• Kz =Exposurecoefficient(ASCE7)

• Kzt =Topographicfactor(ASCE7)

• Cnet =Net-pressurecoefficient(IBCTable1609.6.2)

IBC’sAlternateAll-HeightsMethod

IBCTable1609.6.2

WindBorneDebrisRegions

PerASCE7-10,section26.2,WindBorneDebrisregionsareAreaswithinhurricane-proneregionswhereimpactprotectionisrequiredforglazedopenings(buildingsinRiskCategoryIareexempt– ASCE26.10.3&IBC1609.1.2)

Protectionofglazedopeningsisrequired(ASCE726.10.3):

• Within1mileofthecoastalmeanhighwaterlinewherethebasicwindspeedisequaltoorgreaterthan130mph,or

• Inareaswherethebasicwindspeedisequaltoorgreaterthan140mph

• Otherexemptions,testingrequirementsgiveninASCE7-10,section26.10.3


Image:greenheck.com


Failedopeningscanchangeastructurefromenclosedtopartiallyenclosed,significantlyincreasingwindforces

Let’sTalkAboutWood

1.Uplift– LoadPathContinuity2.Wall– StudDesign3.Diaphragms4.Shearwalls

UpliftWindLoads

Uplift– Outward(suction)forceactingonroof

Loadpath- rooftofoundationrequiredunlessdeadloadisgreaterthanuplift

UpliftLoads

Source:strongtie.com

MethodstoResistUpliftLoads

• Mechanicalconnectors(straps,hurricaneties,screws,threadedrods)

• Sheathing

• DeadLoads


UpliftResistance:MechanicalConnectors

Source:IIBHS

UpliftResistance:WallSheathing

• Whenjoints,fastenersareconsidered,canusesheathingtoresistuplift

• SDPWSSection4.4

SDPWSFigure4I

UpliftResistance:DirectLoadPath

Importanttodetailupliftrestraintconnectorstoprovidedirectloadpath

RoofGeometry&Uplift


Uplift:MWFRSorC&C?

ConsidermemberpartofMWFRSif:• TributaryArea>700ft2 perASCE7-1030.2.3• LoadcomingfrommorethanonesurfaceperASCE7-1026.2

Uplift:MWFRSorC&C?

AWC’sWFCMcommentaryC1.1.2statesthatMWFRSisusedforallupliftconditions:

TherationaleforusingMWFRSloadsforcomputingtheupliftofroofassembliesrecognizesthatthespatialandtemporalpressurefluctuationsthatcausethehighercoefficientsforcomponentsandcladdingareeffectivelyaveragedbywindeffectsondifferentroofsurfaces.

Uplift:MWFRSorC&C?

ASCE7-1026.2commentaryprovidessomediscussiononuplift&MWFRSvs.C&C.

ComponentsreceivewindloadsdirectlyorfromcladdingandtransfertheloadtotheMWFRS.Examplesofcomponentsincludefasteners,purlins,girts,studs,roofdecking,androoftrusses.ComponentscanbepartoftheMWFRSwhentheyactasshearwallsorroofdiaphragms,buttheymayalsobeloadedasindividualcomponents.

EffectiveWindArea

Forwinddesign,tributaryareadoesnotnecessarily=effectivewindarea

EffectiveWindArea(EWA)- Twocases:• Areaofbuildingsurfacecontributingtoforcebeing

considered(tributaryarea)• Longandnarrowarea(wallstuds,rooftrusses):width

ofeffectiveareamaybetakenas1/3length;increaseseffectivearea,decreasesload(perASCE7-10section26.2commentary);EWA=L2/3

EffectiveWindAreaExample

44’-0”

Trusses@2’o.c.

44’-0”

Trusses@2’o.c.

Trib.A=(44)(2)=88ft2 EWA=442/3=645ft2

UpliftExampleCalculation

• RoofFramingRafter• 20’Span• 2’Spacing• 2’Overhang• 115mphExposureB• RoofH=80ft• 65’x220’

Photocredit:MattTodd&PBArchitects

MWFRS- ExternalPressureCoefficient

Lookatwindactingonbuilding’slongside:L=65ft,h/L=80/65=1.23Cp =1.3,-0.18

ASCE7-10Fig.27.4-1

• GCp:(0.85)(-1.3)=1.105(26.9.4&Fig.27.4-1)• GCpi:±0.18(Table26.11-1)• qh =0.00256KzKztKdV2

§ Kz :0.93– Table27.3-1§ Kzt :1.00- Figure26.8-1§ Kd :0.85- Table26.6-1§ Vu:115mph

• qh =26.8psf• p=(26.8psf)(-1.105+(-0.18))=34.4psf

MWFRS- Runningthenumbers

MWFRS- RoofOverhangpersection27.4.4• ForOverhangs:ASCE727.4.4– useCp =0.8onundersideofoverhang,usesametoppressurescalculatedfortyp.roof

• poh =(26.8psf)(-0.8)(0.85)=18.2psf• pext =(26.8psf)(-1.105)=29.6psf• poh net=18.2+29.6=47.8psf

Poh

pext

PerASCE7-10section27.4.4

pint

MWRFS- DeterminingtheUpliftLoad• p=(34.4psf)(2ft)=68.8plf• poh =(47.8psf)(2ft)=95.6plf

68.8plf

Uplift=0.6(95.6plf(2ft.)+68.8plf*20ft/2)=528lbsDeadLoad=0.6((2+20/2)*10psf*2ft)=144lbsNetUpliftatLeftSupport=528lbs -144lbs =384lbsNote: Itiscommonpracticetouse2sets ofdead loads:highestpotential dead loadsforgravity,lowestpotential deadloadsforuplift

95.6plf

C&C- ExternalPressureCoefficient3zoneswithdifferingwindloads:

1:Field2:Perimeter3:Salientcorners

a=smallerof10%ofleasthorizontaldimensionor0.4h,butnotlessthaneither4%ofleasthorizontaldimensionof3ft

ASCE7-10Fig.30.4-2A

C&C- ExternalPressureCoefficient– Fig.30.4-2A

EWA=H2/3=222/3=161ft2

GCP =-1.1FORINTERIOR

ASCE7-10Fig.30.4-2A

• GCp:-1.1(Figure30.4-2A)• GCpi:±0.18(Table26.11-1)• qh =0.00256KzKztKdV2

§ Kz :0.93- Table30.3-1§ Kzt :1.00- Figure26.8-1§ Kd :0.85- Table26.6-1§ Vu:115mph

• qh =26.8psf• p=(26.8psf)(-1.1+(-0.18))=34.3psf

C&C- Runningthenumbers– Zone2

C&C- RoofOverhangpersection30.10• ForOverhangsFigures30.4-2A&30.10-1areutilized• poh =26.8psf(1.7+0.18)=50.4psf• ps =pw =34.3psf• poh net=50.4+34.3=84.7psf

ps

pW

pOH

EWA=2*2=4sf

GCp =-1.7

PerASCE7-10Fig.30.10-1ASCE7-10Fig.30.4-2A

C&C- DeterminingtheUpliftLoad• p=(34.3psf)(2ft)=68.6plf• poh =(84.7psf)(2ft)=169.4plf

68.6plf

Uplift=0.6(169.4plf(2ft.)+68.6plf*20ft/2)=615lbsDeadLoad=0.6((2+20/2)*10psf*2ft)=144lbsNetUpliftatLeftSupport=615lbs -144lbs =471lbsNote: Itiscommonpracticetouse2sets ofdead loads:highestpotential dead loadsforgravity,lowestpotential deadloadsforuplift

169.4plf

DeterminingtheUpliftLoad

384lbs MWFRSOR471lbs C&[email protected]

Overview


DesigningWoodWalls

WindLoadsUniformsurfacewindloadsgenerallyincreasewithbuildingheight

ASCE7-10Fig.27-6.1

Ifwindloadsvarywithbuildingheight,commontousehigherwindloadoverasinglestoryorbuilding

Panels

Hinges

L/dRatio

Unbraced Length

WallVeneer

WindonlyloadingC&C

DesignProperties

WallDesignConsiderations

LoadsintoWSPWindloadsaretransferredtowallframingstudsthroughwoodstructuralpanels(sheathing)

SDPWSTable3.2.1

ForASDCapacity:DivideNominalCapacityby1.6

ForLRFDCapacity:MultiplyNominalCapacityby0.85

TOPPLATE

L/D<502x6:22’-11”2x4:14’-7”

Whichwallisgoingtowithstandhighwinds?

GableEndWallHinge

GableEndBracingDetails• AWC’sWoodFrameConstructionManual

GableEndBracingDetails

• Gableendwallandroofframingmayrequirecrossbracing

FullHeightStudsatGableEndWalls

• Ifnoopeningsingableendwallexist,candesignstudstospanfromfloor/foundationtoroof(varyingstudheights).Mayrequirecloserstudspacings attallerportionsofwall

GableEndWallswithOpenings

GableEndWallswithOpenings

GableEndWallGirts&Jambs

• Oftengableendwallsarelocations oflargewindows

• Horizontallyspanningmember inplaneofwallbreaksstud length,providesallowableopening

Verticallyspanningjambs

Horizontallyspanning

girts

DeterminingUnbraced Length

Whatistheunbracedlength,lu ?Strong&weakaxis

Gypsum&WeakAxisBuckling

NDSCommentary:“Experiencehasshownthatanycodeallowedthicknessofgypsumboard,hardwoodplywood,orotherinteriorfinishadequatelyfasteneddirectlytostudswillprovideadequatelateralsupportofthestudacrossitsthicknessirrespectiveofthetypeorthicknessofexteriorsheathingand/orfinishused.”

IntermediateWallStudBlocking

CalculatingDeflection– IBCTable1604.3

ForΔ ofmostbrittlefinishesusel/240

ForC&Cpressuresa30%loadreductionisallowedforΔ only(IBCTable1604.3footnotef)

f.Thewindload ispermitted tobetakenas0.42times the"component andcladding” loadsforthepurposeofdetermining deflection limits herein.

WoodStudswithBrickVeneer- Deflection

IBCTable1604.3:min.walldeflectionwithbrittlefinishes=L/240

BrickIndustryAssociationrecommendsmuchstricterlimits

StructureMagazineMay2008article,HaroldSprague

BIATechNote28

Example:LargeDiamondRetailer22’tallwoodframedwalls.

Assumestuds16”o.c.

130mphExposureB

LeastHorizontalDim.=64ft.

ExternalPressureCoefficients– WallZones4&5

a=Lesserof:

• 10%leasthorizontaldimension(LHD)64’*0.1=6.4’

• 0.4h=0.4*22=8.8’.Butnotlessthan:

• 0.04LHD=2.6’or3’

Usea=6.4’forzone5

ExternalPressureCoefficients- Walls

Assumewallstudsare22’long

EWA=h2/3=161ft2

Zone4:

GCpf =-0.89

GCpi =-0.18(Table26.11-1)

Zone5:

GCpf=-1.0


Runningthenumbers– Zone4

• GCpf:0.89(Figure30.4-1)• GCpi:0.18(Table26.11-1)• qh =0.00256KzKztKdV2

§ Kh :0.70- Table30.3-1§ Kzt :1.00- Figure26.8-1§ Kd :0.85- Table26.6-1§ V:130mph

• qh =25.74psf• p=25.74psf(0.89+0.18)=27.54psf• 0.6W=0.6(27.54)=16.52psf

LumberDesignProperties

DesignPropertiesfromNDSSupplement.

Assume2x8DouglasFir-Larch#2Studs,16”o.c.

RepetitiveMemberadjustment=1.25

SizeFactor=1.2

DurationofLoad=1.6

StudRepetitiveMemberFactorNoteonstudrepetitivememberfactor:

NDSsection4.3.9:CR =1.15

SDPWSTable3.1.1.1largerCR factorsforstudsinbending,16”spacingmaxincreasedto24”in2015SDPWS),interiorcoveredwithmin.½”gypsum,exteriorcoveredwithmin.3/8”WSP,otherfastenerrequirements

DESIGNPROPERTIES

Fb (psi) 900 NDSSupp.Table 4A

CD 1.6 NDSTable2.3.2

CR 1.25 SDPWS Table 3.1.1

CF 1.2 NDSSupp.Table 4A

E(psi) 1600000 NDSSupp.Table 4A

Sx (in3) 13.1 CalculatedNDS3.3-4

I(in4) 47.6 CalculatedNDS3.3-3

Soisourstudgoingtowork?

Twoofthemostcriticaldesignparametersarebendinganddeflection.

Studswork!

IBCTable1604.3footnotef

• GCp:1.00(Figure30.4-1)• GCpi:0.18(Table26.11-1)• qh =0.00256KzKztKdV2

§ Kh :0.70- Table30.3-1§ Kzt :1.00- Figure26.8-1§ Kd :0.85- Table26.6-1§ V:130mph

• qh =25.74psf• p=25.74psf(1.0+0.18)=30.37psf• 0.6W=0.6(30.37)=18.22psf

Runningthenumbers– Zone5

Whataboutcornerzones?

Deflectionchecknogood– solution:reduceloadsoneachstud


12”StudSpacing

Sincestuddepthcannotbeincreasedconsiderreducingstudspacingto12”inallZone5areas:

Studswork!– Use2x8@16”o.c.typical,use2x8@12”o.c.incorners(Zone5areas)



Fortallwallswhileitislesslikelyforcombinedbendingandaxialtocontrol

• MainWindForceLoadsmaybe

utilized

• Loadcombinations(ASCE7Chpt 2)

for:

§ wind+deador

§ dead+0.75live+0.75rooflive

(orsnow)

D,L,S

W


Forotherdesignissuesseethearticle:

• ConsiderationsinWindDesignofWoodStructures

• FreedownloadfromAWCavailableat:http://www.awc.org/pdf/codes-standards/publications/archives/AWC-

Considerations-0310.pdf

WallStudDesignAidWesternWoodProductsAssociation(WWPA)DesignSuite:

http://www.wwpa.org/TECHGUIDE/DesignSoftware/tabid/859/Default.aspx

Overview


DiaphragmDesign

WindLoadDistributiontoDiaphragm

WINDINTODIAPHRAGMS

WINDSURFACELOADSONWALLS

WindLoadPaths

WINDINTODIAPHRAGMSASUNIFORMLINEARLOADS

WindLoadPaths

DIAPHRAGMSSPANBETWEEN

SHEARWALLS

WINDINTOSHEARWALLSASCONCENTRATEDLOADS

StudtoDiaphragm

WINDLOAD

DIAPHRAGMSHEATHING

Floor/Roofframingperpendiculartowalls

FLOORJOIST

StudtoDiaphragm

WINDLOAD

DIAPHRAGMSHEATHING

Floor/Roofframingparalleltowalls(addblocking)

FLOORJOIST

BLOCKING

VisualCue

VisualCue:FloorBeaminPlan=DiaphragminElevation

FloorBeam

FloorBeam

FloorBeam

FloorJoists

FloorFramingPlan

FloorJoists

VisualCue

VisualCue:FloorBeaminPlan=DiaphragminElevation

Diaphragm

Diaphragm

Foundation

WallStuds

WallFramingElevation

WallStuds

Floor- BendingMember

• SimplySupportedMember:loadingcausescompressioninoneedgeofmember,tensioninotheredge

Compressionedge

Tensionedge

Loadingdirection

ReactionReaction

Diaphragm– BendingMember

Tensionedge

Compressionedge

WindLoadPath- Lateral

•Diaphragmactslikeadeepbeam.• Sheathingcarriesshearforces• ChordshaveT&Cforces• Rimboardtransfersshear

DIAPHRAGM

UnblockedDiaphragm

BlockedDiaphragm

ChordForces

SPLICEINRIMBOARD

LAPINTOPPLATEPROVIDESCONT.TENSILERESISTANCE

TENSILEFORCE

AssumeBasicWindSpeed=115mphUltimate

ExposureB

DiaphragmDesign

• Capacity

Shearwall Design

• Conventional

• ForceTransferAroundOpening

• PerforatedShearwall

Example:RetailRestaurant

RetailRestaurant– DiaphragmDesign

84’

34’

10’6’ 8’5’

6’

6’

6’

6’

6’

3’3’

4’

29’24’

CriticalShearwall atfrontofbuilding

CheckDiaphragmforwindloadson84’wall


CriticalShearwall atfrontofbuilding

CheckDiaphragmforwindloadson84’wall

84’

34’

10’6’ 8’5’

6’

6’

6’

6’

6’

3’3’

4’

29’24’

DiaphragmAspectRatios

SDPWSTABLE4.2.4

TYPE- MAXIMUMLENGTH/WIDTHRATIO

Foran84x34diaphragmtheaspectratiois2.5<3.

DiaphragmaspectratioisOK.

Woodstructural panel,unblocked 3:1

Woodstructural panel,blocked 4:1

Single-layerstraightlumbersheathing 2:1

Single-layerdiagonallumbersheathing 3:1

Double-layerdiagonallumbersheathing 4:1

CalculatingMWFRSWindLoadsCalculatewindpressureusingDirectionalMethod(ASCE7Chpt 27)

p=qh[(GCpf)-(GCpi)]

qh =0.00256*0.57*1.0*0.85*1152*1=16.4psf

GCpf =0.85*[0.8– (-0.3)]=0.935

GCpi =0.18- 0.18=0

p=(16.4psf)(0.935)=15.34psf

0.6*W=0.6*15.34=9.2 psf onwalls

Usemin9.6psf perASCE27.1.5


ParapetDesign– Figure27.6-2

Atparapetswindwardandleewardpressuresoccuroneachparapet.

Section27.4.5:Pp =q(GCpn)GCpn =1.5Windwardparapet,-1.0LeewardparapetWindwardParapetGCpf is1.5:16.4*1.5*0.6=14.76psfLeewardParapetGCpf is1.0:16.4*1.0*0.6=9.84psfNetParapet=14.76+9.84=24.6psf


84’

34’

10’6’ 8’5’

6’

6’

6’

6’

6’4’

29’24’

10’

3’

3’

P=(9.6psf*(5’+3’)+(24.6)*3’)*(84’/2)=6,325lb

νdiaphragm=6,325lb/34’νdiaphragm=186plf

P

DiaphragmTypes

CASE1DIAPHRAGM•HigherShearValues•Panelsperpendiculartofloorframingforimprovedperformance

CASES2-6Maybepreferredforlowsheardemandwherechangingframingdirectionhelps•HVACruns•FireBlocking/DraftStopping

RoofTrusses4x8sheathingN-S

DiaphragmTypes

SDPWSTables4.2A&B

DiaphragmCapacity- SDPWSChpt 4

• CapacitiesareNominal:ModifybyASDreductionfactorof2,ModifybyLRFDmultiplicationfactorof0.8

• CapacityisreducedforspecieswithSpecificGravity<0.5• ForSprucePineFirmultiplyby0.92

DiaphragmCapacity:SDPWSTable4.2C

PANELGRADE

COMMONNAILSIZEORSTAPLEf

LENGTHANDGAGE

MINIMUMFASTENERPENETRATIONINFRAMING

MINIMUMPANELTHIICKNESS

MINIMUMNOMINALWIDTHOFFRAMINGMEMBERSATADJOININGPANELEDGESANDBOUNDARIESg

NAILSPACINGATALLPANELEDGES

Case1(Nounblockededgesorcontinuousjointsparalleltoload)

Allotherconfigurations(Cases2,3,4,5and6)

Sheathing&singlefloor

8d(2½“x0.131”)

13/8”

7/16”

2IN. 6IN. 460(Seismic)645(Wind)

340(Seismic)475(Wind)

3IN. 6IN. 510(Seismic)715(Wind)

380(Seismic)530(Wind)

CapacityisreducedforspecieswithSpecificGravity<0.5.ForSprucePineFirmultiplyby0.92

Capacity =(645plf)(0.92)/2=297plf297plf >186plf,diaphragmisadequatewithsheathing&fasteningasshownabove

TransferringDiaphragmShearForces

BLOCKTOTRANSFERFORCES

UPPERWALL


BLOCKTOTRANSFERFORCES

PARAPET

NOTE:PARAPETKICKERSMAYBEREQUIREDFORTALLTRUSSPARAPETS


SHEARWALLBELOW

SHEARFORCEFROMDIAPHRAGM

RIMJOISTPROVIDESDIAPHRAGMLOAD

TRANSFER

DiaphragmtoShearwall Fastener

RIMBOARD

FLOORJOIST

TOPPLATE

TOENAIL150plf (ASD)LIMITINSDCD,E,F(SDPWS4.1.7)

METALCLIPSFORADD’LSTRENGTH

RoofDiaphragmtoShearwall

BLOCKINGTRANSFERSSHEARFORCESFROMROOFDIAPHRAGMTO

TRUSS

DIAPHRAGM

SHEARWALL

TRUSSTOWALLCONNECTION

COMPLETESLOADPATH

RoofDiaphragmtoShearwall

BLOCKINGTOTRANSFERSHEAR

FORCES

DIAPHRAGM

SHEARWALL

• Diaphragmscanbeidealizedasflexible,semi-rigid,orrigid

• ASCE7-10Section26.2statesthatdiaphragmsconstructedofwoodstructuralpanelsarepermittedtobeidealizedasflexible

WoodEducationInstitute

DiaphragmFlexibility

DiaphragmFlexibilitySomebuildinglayoutsmayrequirediaphragmdesigntoaccountforcantilevers,oropenfrontstructures.• Trendsinmid-rise,multi-familybuildingstowardfewer

exteriorshearwallsmoveintosemi-rigid&rigidmodeling

Cant.

SWSWSWSW

SWSWSWSWSW

SW

NoexteriorShearwalls

Cor

ridor

onl

y sh

ear w

alls

Offs

et s

hear

wal

ls

DiaphragmsofOpenFrontStructures

ExamplesofOpenFrontStructuresper2015SDPWSFigure4A

OpenFrontStructures(SDPWS4.2.5)

• Canidealizediaphragmasrigidifmax.in-planediaphragm

deflectionis≤2xavg.storydriftofverticalelements

• Ifnotidealizingasflexibleorrigid,mayusesemi-rigidanalysis,

distributesshearbasedonrelativestiffnessofbothdiaphragm

andverticalresistingelements

• Commontouseenvelopeanalysisinlieuofsemi-rigidanalysis• 2015SDPWS:DiaphragmCantilever≤35feet

AdditionalConsiderations:

• L/WRatio

• Irregularities&TorsionalEffects

• Diaphragmdeflections,especiallyatcorners

Shearwall &DiaphragmDeflection

Whencalculatingshearwall anddiaphragmdeflections,valuesofapparentshearstiffness,Ga,arerequired,butarenotprovidedforwinddesigninSDPWS

Shearwall &DiaphragmDeflectionAWCFAQ:Cantheeffectiveshearstiffnessvalues,Ga,inSDPWSbeusedforcalculationofdiaphragmandshearwalldeflectionsduetowindloads?

Valuesofapparentshearstiffness,Ga,aretabulatedinseismiccolumnsofthe SDPWS tofacilitatecalculationofseismicstorydriftinaccordancewithASCE7MinimumDesignLoadsforBuildingsandOtherStructures.ValuesofGa areequallyapplicableforcalculation ofthesheardeformationcomponentoftotaldeflectionduetowindloadsuptotheASDwindunitshearvaluecalculatedasvw/2.0.Thislevelofunitshearforwindisidenticalto1.4timestheASDseismicunitshearcapacityforwhichapparentshearstiffnessvalueswereoriginallydeveloped.

http://awc.org/faqs/general/can-the-effective-shear-stiffness-values-ga-in-special-design-provisions-for-wind-and-seismic-%28sdpws%29-be-used-for-calculation-of-diaphragm-and-shear-wall-deflections-due-to-wind-loads

Overview


WindLoadDistributiontoShearwalls

WINDINTODIAPHRAGMSWINDINTOSHEARWALLS

WINDSURFACELOADSONWALLS

Shearwalls

HOLD-DOWN

WSPSHEATHING

ANCHORBOLTS

WOODSTUDS

WSPShearwall Capacity• CapacitieslistedinAWC’sSpecialDesign

ProvisionsforWindandSeismic(SDPWS)• Sheathedshearwallsmostcommon.Canalso

usehorizontalanddiagonalboardsheathing,gypsumpanels,fiberboard,lathandplaster,andothers

• Blockedshearwallsmostcommon.SDPWShasreductionfactorsforunblockedshearwalls

• Notethatcapacitiesaregivenasnominal:mustbeadjustedbyareductionorresistancefactortodetermineallowableunitshearcapacity(ASD)orfactoredunitshearresistance(LRFD)

Shearwall Capacity- SDPWSChpt 4

WindLoadscreateshear(sliding)andrackingforcesonastructure

Slidingresistedbyshearwall baseanchorageRackingresistedbyshearpanel&fasteners

Shearwall Functions

ShearWallComponents:WallFraming

Strut/collector

WallFraming(Studs)

BlockingBetweenStudsatAllPanelEdges

WallTopPlates

WallSolePlate

Note:Canuse“un-blocked”wallbutcapacitiescanbesignificantlylower:SDPWS4.3.3

RackedShearwall

EDGENAILINGPROVIDESRACKINGRESISTANCE

ShearWallComponents:WSP&Fasteners

Strut/collector

FieldorIntermediateNailing– Typ.12”o.c.

BoundaryNailing–Typ.2”– 6”o.c.

BoundaryNailing:Attachesall4edgesofeverypaneltowallframing(studs,blocking,top&soleplates)

FieldorIntermediateNailing:Attachespaneltointermediatewallframing(studs)notalongpaneledges

SheathingPanelsOSBorPlywood

PanelFasteners

Shearwalls

ANCHORBOLTSTOFOUNDATION

PREVENTSLIDING!

Duetocantilevernatureofshearwalls,overturningforcesarealsogenerated

Overturningforcesareresistedbytension/compressioncouple–tensionportionresistedbydeadloadsandholddownanchors

Shearwalls - Overturning

Floor- CantileverMember

Tensionedge

Compressionedge

Shearwall - CantileverMember

Tensionedge

Compressionedge

Hold-DownsResistEndUplift

HOLD-DOWNS

ShearWallComponents:BaseAnchorage,EndPosts&HoldDowns

Strut/collector

SolePlateUniformAnchorage:Transfersshearfromwallsoleplatetofloor/wallorfoundationbelow.

SolePlateUniformAnchorage(Nails,Screws,Anchor

Bolts)

WallEndPost&HoldDown:Transfersverticaltension&compressionforcestofloor/wallorfoundationbelow.

WallEndPost&HoldDown

WallEndPosts(SizedforTension&Compression)

Shearwall HoldDowns

Source:DartDesignInc.com


BucketStyle

Shearwall HoldDowns

Straps


Shearwall HoldDowns

ContinuousRodTieDownswithShrinkageCompensation

Devices Source:hardyframe.com

Source:cteg.com

Shearwall Placement- Symmetrical

INTHISCASEDRAGSTRUTSCARRYLITTLE LOAD

TOPPLATE– NTSDRAGSTRUT

SHEARWALLS

WINDWARD

LEEWARD

Shearwall Placement– LargeDragStruts

INTHISCASEDRAGSTRUTSTRANSFERLEEWARDLOAD

TOPPLATE– NTSDRAGSTRUTSHEARWALLS

WINDWARD

LEEWARD

DragStruts&IsolatedWalls

INSOMECASESDOUBLETOPPLATEISINADEQUATE

WHATTOWATCHFOR:

• ISOLATEDSWWITHHEAVYNAILING• NOSHEARWALLSWITHIN10’OFWALLCORNER

LateralForceResistingSystem

Shearwalls inaLine- Stiffness• Windloadstomultipleshearwalls inthesamelinearedistributed

basedonshearwall stiffness• Ifwallshavethesameframing&sheathing,assumedtohavethe

sameper-footstiffness&loadsaredistributedbasedonwalllength• Eg.5’longwallreceives5/(5+12)=29%oftotalload

12’longwallreceives12/(5+12)=71%oftotalload

SHEARWALLLENGTHSDETERMINESTIFFNESS&LOADSHARING5’12’

Shearwall AspectRatio

NDSSDPWSTABLE4.3.4

MAXIMUMSHEARWALLDIMENSIONRATIOS

SeeSDPWSTable4.3.4forfootnotes

Woodstructural panels,blocked Forotherthanseismic:3½:11

Forseismic: 2:11

Woodstructural panels,unblocked 2:1

Diagonalsheathing, single 2:1

StructuralFiberboard 3½:13

Gypsumboard,portland cement plaster 2:12

L

H

AR=H/L

EngineeredShearWallSystemsw/WSP

SolidorSegmentedWalls

PerforatedWallsForceTransferAround

OpeningsWalls

RetailRestaurant– Shearwall Design

84’

34’

10’6’ 8’5’

6’

6’

6’

6’

6’4’

29’24’

10’

3’

3’

P =7,602lb – fromdiaphragmcalcs usingDirectionalMethod

Let’sseewhathappenswhenweuseEnvelopeMethodtocalculateMWFRSloadstofrontshearwall

P

CalculatingMWFRSWindLoadsCalculatewindpressureusingEnvelopeMethod(ASCE7Chpt28)

p=qh[(GCpf)-(GCpi)]

qh =0.00256*0.70*1.0*0.85*1152*1=20.14psf

GCpf (Zones1&4) =0.4– (-0.29)=0.69(ASCE7Fig.28.4-1)

GCpf (Zones1E&4E) =0.61– (-0.43)=1.04(ASCE7Fig.28.4-1)

GCpi =0.18- 0.18=0

P1&4=(20.14psf)(0.69)=13.9psf;0.6*W=0.6*13.9=8.3psfwallstyp.

P1E&4E=(20.14psf)(1.04)=20.9psf;0.6*W=0.6*20.9=12.5psf wallscrnr


CalculatingMWFRSWindLoads


a=Lesserof:

• 10%leasthorizontaldimension(LHD)34’*0.1=3.4’

• 0.4h=0.4*13’=5.2’.Butnotlessthan:

• 0.04LHD=1.4’or3’

Usea=3.4’forzones1E&4E

2a=3.4’*2=6.8’

ParapetDesign– Section28.4.2

Atparapetswindwardandleewardpressuresoccuroneachparapet.

Section28.4.2:Pp =q(GCpn)GCpn =1.5Windwardparapet,-1.0LeewardparapetWindwardParapetGCpf is1.5:20.14*1.5*0.6=18.12psfLeewardParapetGCpf is1.0:20.14*1.0*0.6=12.08psfNetParapet=18.12+12.08=30.2psf

RetailRestaurant– Shearwall Design

84’

34’

10’6’ 8’5’

6’

6’

6’

6’

6’4’

29’24’

10’

3’

3’

P

6.8’12.5psf8.3psf

77.2’

P=(8.3psf*(5’+3’)+(30.2)*3’)*(84’/2)+((12.5psf-8.3psf)*(5’+3’))*6.8’*(77.2’/84’)=6,804lb(forcomparison:Directionalmethodgaveus6,325lb)

Shearwall AspectRatios

10’

3’

3’34’

6’ 6’ 6’ 6’ 6’2’ 2’

10’

• CheckAspectRatios:AssumeblockedWSPShearwall• 10’/2’=5>3.5;Inadequate• 10’/6’=1.67<3.5;OK

FrontWallElevation

• CheckAspectRatios:AssumeblockedWSPShearwall• 10’/2’=5>3.5;Inadequate• 10’/6’=1.67<3.5;OK

Shearwall AspectRatios

10’

3’

3’34’

6’ 6’ 6’ 6’ 6’2’ 2’

10’

νshearwall =6,804lb/12’=567plf

ConventionalShearwall Capacities

νshearwall =567plf

Assume15/32”,StructuralIsheathingattachedwith8dnails

NominalTabulatedCapacity=1540plfAdjustedASDCapacity =(1370plf)(0.92)/2=630plf630plf >567plf,OK8dnailsat3”o.c.acceptable

PANELGRADE FASTENERTYPE&SIZE



NAIL SPACINGATALLPANELEDGES

PANEL EDGEFASTENERSPACING

WoodStructuralPanels–Sheathing

8d(2½“x0.131”)

15/32” 13/8” 3IN. 980(Seismic)1370(Wind)

SDPWSTable4.3A

DesignTableDetails– 16”o.c.Studs

• Spacefasteners12inchesoncenteronintermediatesupports(SDPWS4.3.7.1.3)

• Ifnailspacingis2”o.c.use3inchnominalframing (SDPWS4.3.7.1.4)

• If10dnailsareutilizedalongwith3incho.c.edgenailingusenominal3xframing(SDPWS4.3.7.1.4)

• Ifnominalunitshearoneithersideofwallexceeds700plf inSDCD,E,orF,usenominal3xframing(SDPWS4.3.7.1.4)

ConventionalShearwall Overturning

νshearwall =567plfHolddownsrequiredatshearwallsT=νhT=567plf*10’=5,670lb

Holddowncapacity=7,045lbManyavailableprefabricatedholddownswithcapacitieslistedbymanufacturers

34’

6’ 6’ 6’ 6’ 6’2’ 2’

10’

Hold-DownAnchor

ConventionalShearwall Overturningνshearwall =567plfPostsarealsorequiredatendsofthewalltoresistcompressionforcesC=T=νhC=567plf*10’=5,670lb

6’ 6’ 6’ 6’ 6’2’ 2’

10’

SizepostforbearingonwallsoleplateAssume2x6wall,Requiredpostwidth=5,670lb/(565psi)(5.5in)=1.8in;Use2-2x6postmin.

ConventionalShearwall BaseAnchorage• νshearwall =567plf• ½”AnchorBoltcapacityforwoodbearing=680lb*1.6=1,088lb

perNDSTable11E• Spacing=1088lb/567plf =1’-11”o.c.max.

Hold-Downs:Segmentedv.PerforatedSegmentedShearwall

PerforatedShearwall

PerforatedShearWallMethod

HOLDDOWNSATENDOFWALL

WSPSHEATHING

Fewerholddownsrequired,shearcapacityisreduced

Uniformupliftatbaseofwallrequired– magnitude=shearforce– SDPWS4.3.6.4.2.1

• CheckAspectRatios:AssumeblockedWSPShearwall• 10’/2’=5>3.5;Inadequate• 10’/6’=1.67<3.5;OKUseonlyfullheightsheathedsectionstoresistshear

PerforatedShearwall Design

10’

3’

3’34’

6’ 6’ 6’ 6’ 6’2’ 2’

10’

νshearwall =6,804lb/12’=567plf

TotalPerforatedShearwall

PerforatedShearwall CapacityWallhas12’/18’=67%fullheightsheathing,max.openingH=6’-8”

Multiplycapacityby0.75foropening2H/3

Reducedcapacityis630plf*0.75=473plf <567plf,Inadequate

SDPWSTable4.3.3.5

PerforatedShearwall Capacity

νshearwall =567plf

Tryreducingnailspacingto2”with8dnails– willrequire3xframing

NominalTabulatedCapacity=1790plfAdjustedASDCapacity=(1790plf)(0.92)(0.75)/2=618plf618plf >567plf,OK8dnailsat2”o.c.acceptableforperforatedwall

PANELGRADE FASTENERTYPE&SIZE



NAIL SPACINGATALLPANELEDGES

PANEL EDGEFASTENERSPACING

WoodStructuralPanels–Sheathing

8d(2½“x0.131”)

15/32” 13/8” 2IN. 1280(Seismic)1790(Wind)

SDPWSTable4.3A

PerforatedShearwall Overturning

34’

6’ 6’ 6’ 6’ 6’2’ 2’

10’

νshearwall =567plfHolddownsrequiredatendsofperforatedwallT=νh/CoT=567plf*10’/0.75=7,560lb

Holddowncapacityfromsegmentedwalloption=7,045lb,Inadequate– needtoselecthighercapacityholddown

PerforatedShearwall Uplift

34’

6’ 6’ 6’ 6’ 6’2’ 2’

10’

νshearwall =567plf/0.75=756plf,usesamemagnitudeforuniformupliftatfullheightsegmentsOneoptionistouseanchorboltswithlargewasherstoresistupliftinbearingIfnetwasherarea=8in2,canresist(565psi)(8in2)=4,520lb inuplift• Max.anchorboltspacing=4,520lb/756plf =5’-11”o.c.• Willalsoneedtocheckshearloadsonanchorboltsforcontrolling

case

ForceTransferAroundOpening(FTAO)

HOLDDOWNSATENDSOFWHOLEWALL

WSPSHEATHING

ForceTransferAroundOpening(FTAO)

FTAOShearwallsMethodologies• Shearwall designmethodologywhichaccountsforsheathed

portionsofwallaboveandbelowopenings(perforatedneglects)• Openingsaccountedforbyreinforcingedgesusingstrappingor

framing• SDPWS4.3.5.2providesspecificrequirements

• H/Lratiodefinedbywallpier• Min.wallpierwidth=2’-0”

• Reducednumberofholddowns(onlyatendsoftotalwall)

• Thereare3mainmethodsofFTAOanalysis;SDPWSdoesnotrequireoneparticularmethodbeused,onlythatdesignis“basedonarationalanalysis”• DragStrut,CantileverBeam,&DiekmannDesignOptions

FTAOShearwallsDragStrutDesignMethodology• Forcesarecollectedandconcentratedintotheareasaboveand

belowtheopenings• Strapforcesareafunctionofopeningandpierwidths

APAFormM410

FTAOShearwallsCantileverBeamDesignMethodology• Forcesaretreatedasmomentcouples• Segmentedpanelsarepiersatsidesofopenings• Strapforcesareafunctionofwallheightaboveandbelow

openingsandpierwidths

APAFormM410

FTAOShearwallsDiekmann DesignMethodology• Assumeswallbehavesasmonlithic trussorframe• Internalforcesresolvedviaprinciplesofstatics• Wallsectionsonallsidesofopeningareassumedtohaveapoint

ofinflectionatmidlength,producingnoforceintheinnerchordsofthesections

APAFormM410

FTAOShearwall DesignAid

ImagesSource:RISATechnologies

RISATechnologiesdesignsoftwareincludesanoptiontodesignFTAOwoodsheathedshearwalllsusingfiniteelementanalysis(FEM)

Double-SidedShearwalls

High-strengthwoodshearwallscanbedouble-sidedwithWSPsheathingoneachside:SDPWS4.3.3.3SummingShearCapacities:Forshearwallssheathedwiththesameconstructionandmaterialsonoppositesidesofthesamewall,thecombinednominalunitshearcapacity shallbepermittedtobetakenastwicethenominalunitshearcapacityforanequivalentshearwallsheathedononeside(4.3.5.3hasmaxcapacitiesfordouble-sidedperforatedwalls)

Double-SidedShearwalls

Thereisalsoanoptiontohaveasinglesided,doublesheathedshearwall.

TestingandreportbyAPAconcludethatitispermissibletousethecapacityofthewallthesameasiftherewasonelayerofWSPoneachsideofthewallprovidedthatanumberofcriteriaaremetincluding:• Framingmembersatpanel

jointsare3xor2-2x• Minimumnailspacingis4”• Others

OpenFront&NarrowWalls

UsingPrefabShearwalls

Considerations:EngineeredNarrowWallSection

Proprietary

LargeHold-downforces

Deflections

HybridWood/SteelPrefabShearwalls

Source:hardyframe.com

PrefabWallAspectRatios

10’

3’

3’34’

30’2’ 2’

10’

• AspectRatioInadequate• 10’/2’=5>3.5• V=6,804lb• Let’stryaprefabshearwall

PrefabShearwall CapacitiesLOADIS=6,804lb

3,660lb *2panels=7,320lb

PrefabShearwall Anchorage

PrefabShearwall Anchorage

PrescriptivePortalFrameSystems

• SeniorLiving• Apartments/Condos• MixedUse• StudentHousing• AffordableHousing• Hotels

WhereWoodisaviableoption,it’slikelythemostappropriatechoice.

PrescriptiveCodePortalFramesIBC2308.9.3.2

ProprietaryPortalFrames


PrescriptivePortalFrameSystems

• SeniorLiving• Apartments/Condos• MixedUse• StudentHousing• AffordableHousing• Hotels

WhereWoodisaviableoption,it’slikelythemostappropriatechoice.

APAReportTT-100F

Allowable DesignShearValues

Min.Width(in.)

Max.Height(ft.)

Shear(lb)

168 850

10 625

248 1,675

10 1,125

GypsumShearwalls• LowercapacitiesthanWSPShearwalls (about1/3capacity)• SDPWSTable4.3C,Section4.3.7.5providescapacities&

requirements• NotpermittedinSDCEorF

WSPShearwalls OverGypsum• Fireresistanceratedwallsmayrequiregypsumboardon

eachside• SDPWSTable4.3Bprovidesshearwall capacitiesforwalls

withWSPinstalledover½“or5/8”gypsumboard• Ruleofthumb:samecapacitiesaswithoutgypsumcan

beobtainediffastenerlengthincreased(gouponenailsize;i.e.if8dwithoutgypsum,use10dwithgypsum).

WallFraming

Gypsumboardeachsideofwall

WSPinstalledovergypsum

board

WallSection

Recap

• Wind• CalculatingWindspeeds• Uplift• WallDesign• Diaphragms• Shearwalls

Questions?

ThisconcludesTheAmericanInstituteofArchitectsContinuingEducationSystemsCourse

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15LS03 Designing Wood-Frame Structures For High Winds V2 · ASCE 7-10 26.2 commentary provides some discussion on uplift & MWFRS vs. C&C. Components receive wind loads directly or