introduction to wood: structural design – gravity & lateral...structural wood design:...

IntroductiontoWood:StructuralDesign–Gravity&Lateral

SpecialThankstoWEI

WoodWorks wouldliketorecognizeandthanktheWoodEducationInstitutefortheuseofsomeofthegraphicsdisplayedinthispresentation.Inparticular,wewouldliketothank:

MikhailGershfeldCharlesChadwellRakesh GuptaKennyMartin

woodeducationinstitute.org

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

Credit(s)earnedoncompletionofthiscoursewillbereportedtoAIACESforAIAmembers.CertificatesofCompletionforbothAIAmembersandnon-AIAmembersareavailableuponrequest.

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

CourseDescription

Thispresentationwillprovideanintroductoryreviewofallowableusesandbestdesignpracticesassociatedwithwood-frameconstruction.Woodscienceincludingwood’scellstructureandmoistureinteractionpropertieswillbediscussed.Woodspeciesandgradeswillbecoveredalongwithanoverviewoftheirstructuralpropertiesanddurability.Structuralwooddesignforvertical(gravity)loadsincludingbending,shear,deflection,vibration,tension,compression,andconnectionswillbeintroduced.Commonwood-framedlateralforce-resistingsystemswillbediscussedaswillthecomponentsincludedinwoodshearwalls.Architecturalconsiderationsassociatedwithwoodframingwillbeexamined,includingfireprotectionandsprinklers,constructiontypes,acoustics,andbuildingenvelopes.Designanddetailingbestpracticesforwood-framebuildingswillbeexplainedinanefforttohighlighttheitemsthatplayanimportantroleintheconstructionprocessandultimatebuildingperformance.

LearningObjectives

1. Reviewwood’sroleandallowableusesundercurrentbuildingcodes.

2. Discussdesignconsiderationsspecifictowoodframinginnon-residentialandmulti-familybuildings.

3. Inthecontextofwoodasabiologicalmaterial,identifybestpracticesforitsuseinnon-residentialandmulti-familybuildings.

4. Explorethevarietyofavailablewoodbuildingproductsanddiscusshowtoefficientlyutilizeeach.

StructuralWoodDesign:GravityLoads

Forstructuralbuildingdesign,twomainloadingdirectionsexist:gravity(vertical)andlateral(horizontal)• Thispresentationwillfocusonstructuralwooddesignforgravityloads• Gravityloadsincludedead,live,snow,andrain

Lateral Loads

WindUpliftLoads

GravityLoads

Outline

• DesignBasis&Notation• AllowableStresses• WoodMemberDesign• Connections:Design&Options

GravityLoadDemand

IBC:BaseCode– ReferencesASCE7fordeterminationof

gravityloads

ASCE7:ReferencedStandard.Providesinformationrequiredtodeterminegravityloadsona

structure

StructuralWoodDesign:Codes

IBC:ReferencesNationalDesignSpecification(NDS)

fordesignofwoodconstruction

NationalDesignSpecification(NDS):Providesdesignproceduresandreferencedesignvaluesusedinthestructuraldesignofwoodframing

membersandconnections

ASD• AllowableStressDesign

• Traditionalforwooddesign

• Basedonallowablestrengthsandnominal (unfactored) loads

StructuralWoodDesign:ASDvs.LRFD

LRFD• LoadandResistanceFactorDesign

• NDS2005– 1st timewasincluded

• Basedonnominal strengthsandfactoredloads

DualformathasbeeninNDSsincethe2005edition

StructuralWoodDesign:Nomenclature

WoodDesignNomenclature

Demand Theexternalloadorstimuliapplied toastructure

Capacity Theamountof resistancethatamember, connection,orsystemiscapableofresistingbeforealimitstateisreached

LimitState Adefinedpoint inasystemorstructuralresponse(i.e.deflection limitstate,bending limitstate)

ASD AllowableStressDesign.Utilizesunfactored serviceloadestimates(demands) andcomparesthosewithscaleddowncapacitiesadjustedbysafetyfactors(checksaretypicallymadeatthestresslevel).

LRFD LoadResistanceFactorDesign.Usesscaledup(factored)demands (basedonprobabilities) tocompare withscaleddownmorerealisticcapacities(basedonprobabilitiesandprotectionofnon-ductile (catastrophic)failuremechanisms).

WoodEducation Institute

StructuralWoodDesign:ASDNotation

Demand– indicatedbytheLOWERCASEletter“f”representingastress

Capacity– indicatedbytheUPPERCASEletter“F”representingareferenceallowablestress

Memberstress

ftStresstype

Memberstressesaredeterminedfromloadsandmemberssizes

ReferenceDesignValue

FtStresstype

ReferencedesignvaluesarefoundintheNDSSupplement


StructuralWoodDesign:LRFDNotation

Load(Demand)- indicatedanUPPERCASEletter representingatypeofFORCE

Resistance(Capacity)- indicatedbyanUPPERCASEletterrepresentinganominalreferencedesignvalue(FORCE)

MemberFORCE

TuIndicatesforceduetofactoredloads

MemberFORCESaredeterminedfromloadsandmemberssizes

NominalResistance Tn = (F’t xKF)x A=F’tn x A

Adjusted referencedesignvalue

ReferencedesignvaluesarefoundintheNDSSupplementandadjustedforNominalDesignValues

Indicatesnominal

Formatconversionfactor

Crosssectionalarea

NominaladjustedreferencevalueWoodEducation Institute

Woodmemberdesign(ASDorLRFD)comparesdemandtocapacity.Anadequatedesignisonewherecapacityisequaltoorgreaterthandemand.

Mostwoodmemberdesign isa3stepprocess:1. Determineloads&resulting forces2. Determinemembercross-sectionalproperties&resultingstresses3. Compareactualtoallowablestresses(or forces)

Notethat3designstepprocesscanbere-arrangedasneeded:• Ifallowablestressesandactualloadsareknown, candetermine

requiredmembersize• Ifactualloadsandmembersizeareknown,candeterminerequired

allowablestresses

WoodDesign:Demandvs.Capacity

ASD

LRFD

WoodDesign:ReferenceDesignValues

ReferenceDesignValues:Thequantifiablemechanicalpropertiesthatareassociatedwitheachidentifiablecommercialgradeofwood


WoodDesign:ReferenceDesignValues

ReferenceDesignValuesinNDSaregivenbasedonfourmainvariables:• GradingMethod• SpeciesGroup• CommercialGrade• SizeClassification


WoodDesign:AdjustmentFactors

AdjustmentFactors:adjustreferencedesignvalues(ASD)or nominaldesignvalues(LRFD)toadjusteddesignvalues• Account fortheuniquepropertiesandbehaviorofwoodunderavariety

ofconditions

F’t =Ft x(AdjustmentFactors)ASD

LRFDF’tn =Ftn x(AdjustmentFactors)

• Mostadjustmentfactorsapplytobothdesignmethodologies

• Differentadjustmentfactorsareappliedtodifferenttypesofstressandindifferentcombinations

• Adjustmentfactors>1.0maybeneglected,those<1.0mustbeused

WoodDesign:AdjustmentFactors

WoodDesign:SectionProperties

Sectionproperties:geometricpropertiesforagivencross-sectionwhichareusedindeterminingtheresultingstressesofappliedforcesB=widthofmember, paralleltoaxisofbendingD=depthofmember, perpendicular toaxisofbending

b

d

ElasticSectionModulusBending

AreaShear,Compression,

Tension

MomentofInertiaBending, Deflection,

Vibration

d

b

Bendingaxis

Bendingaxis

WoodDesign:Multi-PlyMembers

P

Multi-plymemberdesign:• Wheninterfaceplanesareparalleltodirectionofload,

canassumeallpliestoactasonememberifadequatelyconnectedtogethertodistributeloadsamongallplies.

• Wheninterfaceplanesareperpendiculartodirectionofload,alsoneedtoconsider“shearflow”

P

Fastenersdistributeloadsuniformly toall

plies

Fastenersdesignedforshearflowtoavoidslipatinterface

ShearFlowEquation

WoodDesign:Bending

Bending(ormoment)designanalyzesamember’sabilitytoresistforceswhichcauseittobend.Theseforcestypicallyareverticalloadsappliedtothestrongaxis.


WoodDesign:Bending

• Forsimplysupportedmembers,useequationsofstatics

WoodEducation InstituteSimply supported,

concentratedloadatmid-span

Simply supported,uniformly loaded

WoodDesign:Bending

NDS3.3.2


• Calculateactualdesignbendingstress(ASD)

• Bendingcapacityisdependentonbracingofcompressionedgeofmember.Commonoverlookedapplicationsofthisincludewallheaders(especiallygaragedoorheaders)andmemberssupportingconcentratedloadsonly.TheBeamStabilityFactorCLaccountsforthis(NDS3.3.3.8):

WoodDesign:Bending

• Compareactualdesignstresstoallowabledesignstress

Sheardesignanalyzesamember’sabilitytoresistforceswhichcauseittoshear,orbreakoff,perpendiculartograininthedirectionoftheappliedload.Theseforcestypicallyareverticalloadsappliedtothemember’sstrongaxis.

WoodDesign:Shear

• Uniformloadswithindofsupportmaybeneglected;concentratedloadswithindofsupportedmaybereducedforshearcheckincertainconditions(NDS3.4.3.1)

WoodDesign:Shear

Simplysupported,concentratedload

atmid-span

Simplysupported,uniformlyloaded


• Calculateactualdesignshearstress,fv

• Compareactualstress,fv,toallowableF’v

WoodDesign:Shear

NDS3.4.2


Notchingaffectsamember’sshearcapacity• Forrectangularmembersnotchedontheirtensionface,

adjustedshearcapacityis(NDS3.4.3.2(a)):

WoodDesign:Shear&Notching

Where:• Vr’=Adjusteddesignshear• Fv’=Adjustedsheardesignvalue• d=depthofunnotchedmember• dn =depthofmemberremainingatnotch

• Forendsofmembersnotchedontheircompressionface(NDS3.4.3.2(e)):

WoodDesign:Shear&Notching

Where:• Vr’=Adjusteddesignshear• Fv’=Adjustedsheardesignvalue• d=depthofunnotchedmember• dn =depthofmemberremainingatnotch• e=notchextensionbeyondinnerfaceofsupport

WoodDesign:Deflection

Deflectionisameasurementofawoodmember’sdisplacementwhensubjectedtodesignloads(comparedtoanunloadedcondition).Displacementistypicallycheckedformemberssupportingverticalloadsappliedtothestrongaxis.



WoodDesign:Deflection

• Calculateactualdeflection&comparetocriteria(IBCTable1604.3)forgeneral,somecanexceedminimumlimitsbasedonfinishes,surroundingfeatures

BeamDesignExample

12’-0”

12’-0”8’-0”

OfficeBuildingFloorFramingPlanAssumeLiveLoad=50psf,DeadLoad=30psfAllframingisDouglas-FirLarch#2

TypicalFloorFraming:2x10@16”o.c.

FloorBeamtoDesign

BeamDesignExample

LoadingConditions:• TributaryWidth=12/2+12/2=12ft• UniformLiveLoad=12ft x50psf =600lb/ft• UniformDeadLoad=12ft x30psf =360lb/ft• UniformTotalLoad=600+360=960lb/ft• Span=8ft

• Douglas-FirLarch#2:Fb =900psi,Fv =180psi,E=1,600,000psiperNDS2012Supplement

BeamDesignExample

Try3-2x12Beam;BendingCheck:

BeamDesignExample

Check3-2x12BeamforShear:

BeamDesignExample

Whatifwenotchthe3-2x12beamdownto9-1/4”depthatbearinglocationstomaintainuniformwallplateelevations?

2x10FloorJoists

2x12FloorBeamNotchedto9-1/4”atBearing

3-2x12FloorBeam

PostinWallUnderBeamEnd

BearingWallStuds

BeamDesignExample

CheckNotched3-2x12beamforShear:

BeamDesignExample

Check3-2x12beamforDeflection:

BeamDesignExample

Whathappensifweintroduceaconcentratedloadtothefloorbeam:

WLL =600lb/ft WDL =360lb/ft

PLL =1,000lb PDL =600lb@beammid-span

BeamDesignExample

Check3-2x12beamforconcentratedanduniformloads:

BeamDesignExample

Try4-2x12beamforconcentratedanduniformloads:

BeamDesignExample

Try4-2x12beamforconcentratedanduniformloads;notchedshear:

BeamDesignExample

Try4-2x12beamforconcentratedanduniformloads;deflection:

BeamDesignAids

AmericanWoodCouncilSpanCalculator:http://www.awc.org/calculators/index.php

AmericanWoodCouncilSpanTables:http://www.awc.org/technical/spantables/index.php

Compressionperpendiculartograin,orbearingdesignanalyzesamember’sabilitytoresistforcesappliedtooneofit’sfaces,orsurfaces,withoutcrushing.• Considerpointsofsupport

andconcentratedloads• Considerloadingdirectionto

grain

WoodDesign:Compression(Bearing)


• Calculateactualbearingstress

• Compareactualbearingstresstoallowable

WoodDesign:Compression(Bearing)

Where:• P=Supportreactionor

appliedload• Abrg =BearingArea


BearingDesignExample

2x12FloorBeamNotchedto9-1/4”atBearing

4-2x12FloorBeam

BearingWallTopPlates

WLL =600lb/ft WDL =360lb/ft

PLL =1,000lb PDL =600lb@beammid-span


ReactionatBeamEnd:

NeedtoLookatBearingArea• OfBottomofBeam• OfWallTopPlates

4-2x12FloorBeam:Width=6”,Species=DFL#2,Fcperp =625psi2x6BearingWall:Width=5-1/2”,Species=SPF#2,Fcperp =425psi


Beamwidthexceedswalltopplatewidth;canonlyusewalltopplatewidth.Determinerequiredbearinglength:

Bearingwidthwillbesameforbothbeamandwalltopplates(5-1/2”).Wallplateswillcontrolasallowablebearingstressislower.

Beamneedstoextend2”minimumontowalltopplate

Compressionparalleltograindesignanalyzesamember’sabilitytoresistcompressiveforcesappliedtoitslongitudinalaxiswithoutbucklingorfailing.Commonapplicationsarecolumnsandtrussmembers.

WoodDesign:Compression


• Calculateactualcompressionstress&comparetoallowable

• Unbraced lengthinbothaxesneedtobeconsidered• NDSColumnStabilityFactorCp accountsforunbraced

lengths(NDS3.7.1)

WoodDesign:Compression

ColumnDesignExample

12’-0”

12’-0”4’-0”

TypicalFloorFraming:2x10@16”o.c.Columnto

Design

4’-0”

Usingsameofficebuildingfloorframingplanandloadingconditionsfrompreviousexample,addcolumnatbeammid-span

ColumnDesignExample

LoadingConditions:• TributaryArea=(12/2+12/2)+(4/2+4/2)=48ft2• UniformLiveLoad=48ft2 x50psf =2,400lb• UniformDeadLoad=48ft2 x30psf =1,440lb• ConcentratedLiveLoad=1,000lb• ConcentratedDeadLoad=600lb• TotalLoad=2,400+1,440+1,000+600=5,440lb• Height=10ft

• Try6x6column(useTimber5x5orlargerreferencedesignvalues):Douglas-FirLarch#2:Fb =750psi,Fc =700psi,E=

1,300,000psi,Emin =470,000psiperNDS2012Supplement

ColumnDesignExample

• Assumeendconnectionsaremodeledaspins,columnbucklingcoefficientK=1.0

• Le/d=[(10ft)(12in/ft)]/5.5in=21.8<50,OK

Tensionparalleltograindesignanalyzesamember’sabilitytoresisttension(pulling)forcesappliedtoitslongitudinalaxiswithoutfailing.• Unbraced lengthfortensiondesigndoesnotneedtobe

considered• Avoidtensionperpendiculartograin

• Calculateactualtensionstress&comparetoallowable

WoodDesign:Tension



Memberssubjecttobothbendingandaxialloads(tensionorcompression)shallbeadequatelydesignedtomeetaseriesofinteractionequationsperNDS3.9.1(bending&tension)&NDS3.9.2(bending&compression):

WoodDesign:CombinedLoads

Tension+Bending

Compression+Bending

Axial+BiaxialBending




fb/Fb +ft/Ft <1.0

CombinedLoadsDesignAids:

WesternWoodProductsAssociation(WWPA)DesignSuite:http://www.wwpa.org/TECHGUIDE/DesignSoftware/tabid/859/Default.aspx

WoodConnections:Design

Woodconnectionsgenerallyresist2typesofforces:shear(lateral)andwithdrawal.Connectionstypicallyconsistofoneormoreofthefollowing:• Fastener(nail,screw,bolt,etc.)• Connector(steelsideplate,lightgaugesteelangle,wood

spliceplate,etc.)

MichaelStenstrom,Strenstrom-Schneider, Inc.

WoodConnections:Design

Connectiondesignisafunctionofanumberoffactorsincluding:• Wooddowelbearingstrength• Woodmember(s)thickness• Angletograin• Fastener(diameter,penetration,

bendingcapacity)• Edge/EndDistance• Spacing

NDSprovidesreferencesdesignvaluesandadjustmentfactors

WoodConnections:Options

Woodconnectioncategories:• Doweltypefasteners(bolts,lagscrews,woodscrews,nails,spikes,driftbolts,driftpins)

• Splitrings&shearplates• Timberrivets• Spikegrids

WoodConnections:DowelTypeFasteners

• Doweltypefasteners,particularlynails,aremostcommonfastenerinwoodconstruction

• Otherdoweltypefastenersincludebolts,lagscrews,woodscrews,spikes,driftbolts,anddriftpins

• Usedassoleconnectorsorinconjunctionwithconnectingmember(steelsideplate,prefabricatedhardware,etc.)

• IBCSection2304.9providesfastenerschedulesforstandardconnections

DowelTypeFasteners:WithdrawalDesign

Withdrawalconnectiondesign:• Connectionsinwithdrawalresistforceswhichwould

attempttopullafasteneroutofthewood• Withdrawalnotpermittedfornails&spikesinendgrainof

wood• NDSChapter11providesreferencewithdrawaldesign

valuesfornails,woodscrews,lagscrews,andringshanknails

DowelTypeFasteners:WithdrawalDesign

Withdrawalconnectiondesign:• Capacityisafunctionof:

• Fastenerdiameter• Fastenerpenetration• Woodproperties(SG)

DowelTypeFasteners:ShearDesign

Shear(Lateral)connectiondesign:• Shearconnectionsresistforceswhichwouldattemptto

move(ordisplace)onememberrelativetoitsconnectedmember

• Usedtoresistgravity(vertical)loadsandlateral(horizontal)loads

• NDSChapter11providesreferencelateraldesignvaluesforbolts,nails,woodscrews,rinkshanknails,andlagscrews

• Edgedistance,enddistance,spacingrequirements


Shear(Lateral)connectiondesign:• Capacityisafunctionof:

• Fastenerdiameter,penetration,mechanicalstrength• Woodproperties(SG)• Woodmember(s)angletograin


Shear(Lateral)capacity:• NDSChapter11TablesProvideShearCapacityTables


Shear(Lateral)capacity:• Connectionsconsistofonesidememberandonemain

member(singleshear)ortwosidemembersandonemainmember(doubleshear)

• Shearcapacityiscalculatedbasedonleastof6failuremodes(NDS11.3.1)

• Sidemember(s),mainmember,orfastenercanfail

Source:WoodHandbook,USDAForestService


Doubleshearconnectiondesign:

Source:WoodHandbook,USDAForestService

DoubleShearConnection

ConnectionDesignAids

AmericanWoodCouncilConnectionCalculatorforsheardesignofbolts,lagscrews,woodscrews,andnails:http://www.awc.org/calculators/connections/ccstyle.asp

WoodConnections:SplitRings&ShearPlates

• Actaslargediameterbolts(bearingarea)• Splitinringallowsforshrinkage• Note-malleableironwasherforbolttowoodconnection• SplitRing:woodtowood;ShearPlate:woodtosteel• Commonlyusedinsteelplatedglulamtrusses• NDSChapter12providesdesignequations&referencedesignvalues

SplitRingShearplates

WoodConnections:TimberRivets

• Ovalshapednailswithnarrowsideparalleltograin• Allowscloserspacingofrivets- reducessplitting• NDSChapter13limitsuse:onlyforsteelsideplatesconnectingtoglulammembers

WoodConnections:SpikeGrids

• Malleableirongridswithbluntteethorspikesprotrudingoutwardfrombothsides

• Squareorcircular,flatorcurved(oneonesideorboth)• Teeth~1-1/4”long,in~4”squaregridpattern

WoodConnections:Other

• Adhesives:typicallynotincludedinstructuralcapacity• Staples:nocapacitiesinNDS,IBCprovidesshearwall&diaphragmcapacitiesforstaples

Commonadhesivelocations

WoodConnections:Other

• MetalPlateConnectors:usedintrusses,joiningmembersinsameplane

• Traditionaltimberpegs

WoodConnections:PrefabricatedHardware

Manufacturersprovidecapacitiesbasedontesting&fastenerlimits

StructuralWoodDesign:LateralLoads

Forstructuralbuildingdesign,twomainloadingdirectionsexist:gravity(vertical)andlateral(horizontal)• Thispresentationwillfocusonstructuralwooddesignforlateralloads• Lateralloadsincludewindandseismic

Lateral Loads

WindUpliftLoads

GravityLoads

Outline

• LateralLoads:Demand&Capacity• WSPSystems:Diaphragms&ShearWalls• WSPShearWallComponents• OtherWoodFramedLFRS

LateralLoadDemand

IBC:BaseCode– ReferencesASCE7fordeterminationofwindandseismicForces

ASCE7:ReferencedStandard.Providesinformationrequiredtodeterminewindandseismic

forcesonastructure

LateralLoadCapacity

IBC:ReferencesSpecialDesignProvisionsfor

Wind&Seismic(SDPWS)forcapacitiesofmost woodframedlateralsystems.IBCprovidescapacityofstapledWSPandgypsumshearwalls

SDPWS:Providescapacitiesofmostwood-framedverticalandhorizontallateralforceresisting

systems

ProprietaryProductswhichhave3rd party

testingreportsmayalsobesubmitted

• Wallframingdistributessurfaceloadstodiaphragms(floors&roof)

WSPShearWall&DiaphragmDesign

ElevationView

• Lateralloadsonabuildingaremodeledasuniformsurfaceloads

WSPShearWall&DiaphragmDesign

Diaphragm-PlanView

• Uniformdiaphragmloadsaredistributedtoshearwalls

ShearWall–ElevationView

• Shearwallresistsappliedloadthroughshearpanel&boundarychords

DiaphragmDesign• Diaphragm:Roof,floor,orothermembraneorbracing

systemactingtotransferlateralforcestotheverticalresistingelements

• Diaphragmloadsaregenerallyuniformloads,resistedbythediaphragminbending,similartoahorizontaldeepbeam

• Diaphragmbendingresultsintension/compressioninchordsperpendiculartoload


DiaphragmDesign• Reactionsatdiaphragmendstransferloadtoshearwall

throughshearinpanels• Principlesofshearresistance,panelattachment,

boundaryelementssimilartoshearwalldesign• Dragstrutscarryor“drag”diaphragmloadsintoshear

walls


DiaphragmDesign:Capacity• CapacitieslistedinAWC’sSpecialDesign

ProvisionsforWindandSeismic• Sheatheddiaphragmmostcommon.Can

alsousehorizontalanddiagonaldecking• Unblockeddiaphragmsmostcommon.

Addingblockingatpaneledgesincreasesdiaphragmcapacity

DiaphragmDesign:Flexibility• Diaphragmscanbeidealizedasflexible,semi-rigid,or

rigid• Lightwoodframediaphragmstraditionallyidealizedas

flexible,afunctionofdiaphragmconstructionanddeflection

• Trendsinmid-rise,multi-familybuildingstowardfewerexteriorshearwallsmoveintosemi-rigid&rigidmodeling

• ASCE7Section12.3.1ProvidesDiaphragmFlexibilitydefinitions

DiaphragmDesign:Flexibility


AdditionalDiaphragmConsiderations

• Typicalfloorplanresultsindiaphragmoffsets,re-entrantcorners,discontinuities,openings

• Diaphragmopenings,discontinuities=higherconcentrated,localizedloads

• Coderequirementsfordiaphragmlengthtowidthratiosmustbemet

AdditionalDiaphragmConsiderations

• Higherconcentratedloads=closerpaneledgefastenerspacing,largerchord&strutloads,mayrequireblockeddiaphragm

• Diaphragmdeflectionsmayneedtobecalculated

WSPShearWallDesign• Shearwall:verticalcomponentsofabuilding’slateralforce

resistingsystem• Shearwalltransferslateralloadsfromdiaphragmaboveto

wall/foundationbelow


WSPShearWallDesign• Diaphragmtransferslateralconcentratedloadtotopof

wall• Wallresistsloadthroughunitshear(panel)&resisting

moment(endposts/holddowns)• 3shearwalldesigncomponents:

• Sheathingpaneledgefasteners(unitshear)• Baseofwallanchorage(unitshear)• Endpost&holddownsizes(resistingmoment)

Unitshear Resistingmoment

WSPShearWallDesign:Capacity• CapacitieslistedinAWC’sSpecialDesign

ProvisionsforWindandSeismic(SDPWS)• Blockedshearwallsmostcommon.SDPWShas

reductionfactorsforunblockedshearwalls• Notethatcapacitiesaregivenasnominal:must

beadjustedbyareductionorresistancefactortodetermineallowableunitshearcapacity(ASD)orfactoredunitshearresistance(LRFD)

EngineeredShearWallSystemsw/WSP

SolidorSegmentedWalls

PerforatedWallsForceTransferAround

OpeningsWalls

ShearWalls:AdditionalConsiderations

• AspectRatio:HeighttoWidthLimitations(SDPWS)• SomesystemsmayonlybeusedinlowerSeismicDesignCategories(SDPWS)

• Strengthlimitationswithsomesystems(horizontalboardsheathing,gypsum)

• ShearWalldeflectionshouldbeconsidered

WSPShearWallComponents

Source:NationalResource Council ofCanada

Sheathing&Fasteners

WallFraming

Endholddown&

post

BaseAnchorage

Source:Norbord

ShearWallComponents:WallFraming

Strut/collector

WallFraming(Studs)

BlockingBetweenStudsatAllPanelEdges

WallTopPlates

WallSolePlate

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

ShearWallComponents:WSP&Fasteners

Strut/collector

FieldorIntermediateNailing– Typ.10”– 12”o.c.

PanelEdgeNailing– Typ.

2”– 6”o.c.

BoundaryNailing:Attachesall4edgesofeverypaneltowallframing(studs,blocking,top&soleplates)FieldorIntermediateNailing:Attachespaneltointermediatewallframing(studs)notalongpaneledges

SheathingPanelsOSBorPlywood

ShearWallComponents:BaseAnchorage,EndPosts&HoldDowns

Strut/collector

SolePlateUniformAnchorage:Transfersshearfromwallsoleplatetofloor/wallorfoundationbelow.

SolePlateUniform

Anchorage(Nails,Screws,AnchorBolts)

WallEndPost&HoldDown:Transfersverticaltension&compressionforcestofloor/wallorfoundationbelow.

WallEndPost&HoldDown

WallEndPosts(Sized

forTension&Compression)

ShearWallComponents:HoldDowns

StandardHoldDownInstallation(BucketStyle)

StrapHoldDownInstallation

…………

………

ContinuousRod- AutomaticTensioningSystems


Source:DartDesignInc.com

Source:strongtie.com

BucketStyle


Straps



ContinuousRodTieDownswithShrinkageCompensation

Devices Source:hardyframe.com


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

WhereWoodisaviableoption,it’slikelythemostappropriatechoice.

IBC2308.3,9,11,12:PrescriptiveBracedWallLines• ProvidesBracedWallSpacings,Components,Fasteners• Limitations:

• BuildingHeight:• 3StoriesmaxforSDCAandB• 2StoriesmaxforSDCC• 1StorymaxforSDCDandE• FloortoFloormax=11’-7”• BearingWallStudLengthmax=10’-0”

• Loads• MaxDL=15psf,MaxLL=40psf• MaxGroundSnow=50psf,MaxWindVasd =

100mph• Others:seeIBC2308.2

PrescriptiveShearWallSystems– IBC2308

PrescriptiveShearWallSystems– IBC2308



PrescriptivePortalFrameSystems



PrescriptiveCodePortalFramesIBC2308.9.3.2

ProprietaryPortalFrames


EngineeredShearWallSystemsw/WSP

StapledShearWalls

Source:nees.orgSource:Journal ofStructural Engineering, 2007

• CapacitiesinIBC2306

Mid-PlyShearWalls

Non-WSPEngineeredShearWallSystems

GypsumShearWalls

ProprietaryTrussedShearWalls

Source:smartcomponents.us

Non-WSPEngineeredShearWallSystems

Horizontal&DiagonalBoardSheathing

Source:firstdayonpei

Source:johnotvos

CapacitiesinAWC’sSDPWSTable4.3D

PostFrameBuildings– LateralOptions

Source:newenglandbarn.comEmbedded/CantileverColumns

• Kickers/KneeBraces• SheathedWalls/Roof• SteelRodX-Bracing• Others

HeavyTimberBracedFrames(HTBF)

Source:naturallywood.comSource:niji-architects.com

HybridWood/SteelBracedFramesTheBullitt Center

Architect: TheMillerHull PartnershipPhoto:JohnStamets

HybridWood/SteelProprietarySystems

Source:hardyframe.com

Questions?

ThisconcludesTheAmericanInstituteofArchitectsContinuingEducationSystemsCourse

Visitwww.woodworks.org formoreeducationalmaterials,casestudies,designexamples,aprojectgallery,andmore

ThispresentationisprotectedbyUSandInternationalCopyrightlaws.

Reproduction,distribution,displayanduseofthepresentationwithoutwrittenpermission

ofthespeakerisprohibited.

©TheWoodProductsCouncil2015

CopyrightMaterials

introduction to wood: structural design – gravity & lateral...structural wood design:...

Documents