Designing for Wind Loads in High Seismic Regions€¦ · Designing for Wind Loads in High Seismic...

transcript

DesigningforWindLoadsinHighSeismicRegions

PresentedbyRickyMcLain,MS,PE,SEOaklandWoodSolu:onsFairMay17,2016

“TheWoodProductsCouncil”isaRegisteredProviderwithTheAmericanIns:tuteofArchitectsCon:nuingEduca:onSystems(AIA/CES),Provider#G516.Credit(s)earnedoncomple:onofthiscoursewillbereportedtoAIACESforAIAmembers.Cer:ficatesofComple:onforbothAIAmembersandnon-AIAmembersareavailableuponrequest.

ThiscourseisregisteredwithAIACESforcon:nuingprofessionaleduca:on.Assuch,itdoesnotincludecontentthatmaybedeemedorconstruedtobeanapprovalorendorsementbytheAIAofanymaterialofconstruc:onoranymethodormannerofhandling,using,distribu:ng,ordealinginanymaterialorproduct.________________________________ Ques:onsrelatedtospecificmaterials,methods,andserviceswillbeaddressedattheconclusionofthispresenta:on.

CourseDescrip8on

Inregionsofthecountrywherehighseismicitytendstocontrollateralbuildingdesign,windloadsandtheireffectsonastructurecaneasilybeoverlooked.Intendedforstructuralengineerswhoarewellversedinseismicdesign,thispresenta:onwilladdressthedesignofwood-framebuildingsforwindloadsinhighseismicregions,withafocuson:mesavingdesign:psandbestprac:cesassociatedwiththeeffectsofout-of-planewindforcesonwalldesignandroofupliZ.Differencesbetweenseismicandwindloadswillbehighlighted,alongwithseveralrulesofthumbthatcanbeappliedwhenconsideringwhichforceshouldcontrol.Walldesignforout-of-planewindloadswillbepresentedasastraigh\orwardthree-stepprocesswithuniqueconsidera:onsandop:onsforwood-frametallwalls.Calcula:onsformagnitudeofroofupliZwindloadswillbereviewed,aswill:psforminimizingtheireffectsonthestructurebelowwhilemaintainingloadpathcon:nuity.

LearningObjec8ves

1.  Explorewindloadcalcula:onsandprovisionsspecifictowood-framestructurespertheInterna:onalBuildingCodeandreferencedstandards.

2.  Highlightthekeydifferencesbetweenseismicandwindforcesandreviewtheuniquedesignconsidera:onsassociatedwiththeeffectsofwindloadsonwoodstructures.

3.  Reviewwallframingdesignstepsforout-of-planewindloadsandcombinedaxialandout-of-planewindloads.

4.  Discusscalcula:onsanddetailingbestprac:cesfordesigningwood-frameroofstoresistupliZwindforces.

Overview

•  Calcula:ngWindLoads•  UpliZ•  WallDesign•  Seismic/WindComparisons

WindLoadDemand

CBC:BaseCode–ReferencesASCE7fordetermina8onofwindforceson

structuresoruseCBC1609.6

ASCE7:ReferencedStandard.Providesinforma8onrequiredtodeterminewindforcesona

structure

Calcula8ngWindLoads

• ASCE7-05:ASDWindLoads§  Chpt.6:ContainedAllProvisions

• ASCE7-10:Ul8mateWindLoads§  Chpt.26:GeneralRequirements§  Chpt.27:MWFRS–Direc8onal§  Chpt.28:MWFRS–Enveloped§  Chpt.29:OtherStructures§  Chpt.30:Components&Cladding§  Appendices

• ASCE7-16:(mostlikelyref.inCBC2019)§  LowerWindSpeedsinCA

WindSpeedByLoca8onSoYware

windspeed.atcouncil.org

WindLoadsTypes

2TypesofWindLoads• MWFRS–MainWindForceResis8ngSystem

Anassemblageofstructuralelementsassignedtoprovidesupportandstabilityfortheoverallstructure.Thesystemgenerallyreceiveswindloadingfrommorethanonesurface.Eg.Shearwalls,diaphragms

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

MWFRSMethodOp8ons

TwoMethodsofCalcula8ngMWFRSloads:• Envelope:Pressurecoefficientsrepresent“pseudo”loadingthatenvelopethedesiredmoment,shear...Limitedtolow-rise

• Direc8onal:Pressurecoefficientsreflectwindloadingoneachsurfaceasafunc:onofwinddirec:on

Example–Direc8onalLoads

10’6’ 8’5’

6’4’

29’24’

3’3’

P=(11.3psf*(5’+3’)+(30.2)*3’)*(84’/2)=7,602lb

νdiaphragm=7,602lb/34’νdiaphragm=224plf

Example–EnvelopeLoads

10’6’ 8’5’

6’4’

29’24’

3’3’

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

(Direc:onalmethodgaveus7,602lb~10%reduc8on)

CBC’sAlternateAll-HeightsMethod

CBCSec:on1609.6providesanalterna:vetotheDirec:onalWindLoadProcedureinASCE7AlternateAll-HeightsMethodLimita:onssuchas:•  BuildingHeight≤75Z•  BuildingHeight/Width≤4•  Buildinghassimplediaphragm•  Others(CBC1609.6.1)

Pnet=0.00256V2KzCnetKzt

Pnet=0.00256V2KzCnetKzt•  V=Basicwindspeed(ASCE7)•  Kz=Exposurecoefficient(ASCE7)•  Kzt=Topographicfactor(ASCE7)•  Cnet=Net-pressurecoefficient(CBCTable1609.6.2)

CBCTable1609.6.2

Overview

UpliY:MWFRSorC&C?

ConsidermemberpartofMWFRSif:• TributaryArea>700Y2perASCE7-1030.2.3• LoadcomingfrommorethanonesurfaceperASCE7-1026.2

UpliY:MWFRSorC&C?

ASCE7-1026.2commentaryprovidessomediscussiononupliZ&MWFRSvs.C&C.

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

UpliY:MWFRSorC&C?

AWC’sWFCMcommentaryC1.1.2statesthatMWFRSisusedforallupliZcondi:ons:

TheraConaleforusingMWFRSloadsforcompuCngtheupliDofroofassembliesrecognizesthatthespaCalandtemporalpressurefluctuaConsthatcausethehighercoefficientsforcomponentsandcladdingareeffecCvelyaveragedbywindeffectsondifferentroofsurfaces.

RoofUpliY&Effec8veWindArea

Forwinddesign,tributaryareadoesnotnecessarily=effec:vewindareaEffec:veWindArea(EWA)-Twocases:•  Areaofbuildingsurfacecontribu:ngtoforcebeing

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

ofeffec:veareamaybetakenas1/3length;increaseseffec:vearea,decreasesload(perASCE7-10sec:on26.2commentary);EWA=L2/3

Effec8veWindAreaExample

44’-0”

Trusses@2’o.c.

44’-0”

Trusses@2’o.c.

Trib.A=(44)(2)=88Y2 EWA=442/3=645Y2

MethodstoResistUpliYLoads

•  Mechanicalconnectors(straps,hurricane:es,screws,threadedrods)

•  Sheathing

•  DeadLoads

Source:strong:e.com

UpliYWindLoads

Truss/RaZertoTopPlateConnec:on

WhathappenstotheupliDloadaDerthis?

UpliYResistance:MechanicalConnectors

Source:IIBHS

UpliYResistance:DirectLoadPath

ImportanttodetailupliZrestraintconnectorstoprovidedirectloadpath

UpliYWindLoads

UpliYResistance:WallSheathing

•  Whenjoints,fastenersareconsidered,canusesheathingtoresistupliZonlyorupliZ&shear

•  SDPWSSec:on4.4

SDPWSFigure4J

UsingDeadLoadtoResistUpliY

Source:Strong:e

Deadloadfromabove(Wall,Floor,Roof)canbeusedtoresistsomeorallupliZforces,dependingonmagnitude

LoadCombina:onsofASCE7-10:06.D-0.6W

UpliYExampleCalcula8on

• RoofFramingRaYer•  20’Span•  2’Spacing•  2’Overhang•  115mphExposureB• RoofH=80Y•  65’x220’

Photocredit:MawTodd&PB

Architects

MWFRS-ExternalPressureCoefficient

Lookatwindac8ngonbuilding’slongside:L=65Y,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-RoofOverhangpersec8on27.4.4•  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•  pohnet=18.2+29.6=47.8psf

PerASCE7-10sec:on27.4.4

MWRFS-DeterminingtheUpliYLoad

• p=(34.4psf)(2Y)=68.8plf• poh=(47.8psf)(2Y)=95.6plf

68.8plf

UpliZ=0.6(95.6plf(2Z.)+68.8plf*20Z/2)=528lbsDeadLoad=0.6((2+20/2)*10psf*2Z)=144lbsNetUpliYatLeYSupport=528lbs-144lbs=384lbsNote:Itiscommonprac:cetouse2setsofdeadloads:highestpoten:aldeadloadsforgravity,lowestpoten:aldeadloadsforupliZ

95.6plf

C&C-ExternalPressureCoefficient3zoneswithdifferingwindloads:1:Field2:Perimeter3:Salientcornersa=smallerof10%ofleasthorizontaldimensionor0.4h,butnotlessthaneither4%ofleasthorizontaldimensionof3Z

ASCE7-10Fig.30.4-2A

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

EWA=H2/3=222/3=161Z2

GCP=-1.4FOROVERHANGGCP=-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-RoofOverhangpersec8on30.10•  ForOverhangsFigures30.4-2A&30.10-1areu8lized•  poh=26.8psf(1.7+0.18)=50.4psf•  ps=pw=34.3psf•  pohnet=50.4+34.3=84.7psf

ASCE7-10Fig.30.4-2A

PerASCE7-10Fig.30.10-1

C&C-DeterminingtheUpliYLoad

• p=(34.3psf)(2Y)=68.6plf• poh=(84.7psf)(2Y)=169.4plf

68.6plf

UpliZ=0.6(169.4plf(2Z.)+68.6plf*20Z/2)=615lbsDeadLoad=0.6((2+20/2)*10psf*2Z)=144lbsNetUpliYatLeYSupport=615lbs-144lbs=471lbsNote:Itiscommonprac:cetouse2setsofdeadloads:highestpoten:aldeadloadsforgravity,lowestpoten:aldeadloadsforupliZ

169.4plf

DeterminingtheUpliYLoad

384lbsMWFRSOR471lbsC&C@ea.raZer

Uplift Resistance Shear Wall Overturning Resistance

KeyDifferences:•  Rodloca:on•  Loaddirec:on•  Framing

Requirements•  Loadpath•  Shrinkage/

compressionloca:on

GraphicsSource:Strong:e

OverturningResistancevs.UpliYResistance

RoofFraming:CompressionEdgeBracing

•  Bendingcausescompressioninoneedgeofmember•  Roofsheathingbracescompressionflangeofroofjoists

Compressionedge

Tensionedge

Loadingdirec:on

RoofFraming:CompressionEdgeBracing

•  WhataboutUpliZ?Needfulldepthblocking/bridgingorbowomchordbracing

BowomChordBracing

Someinsurancecompaniesrequireabuilding’srooftoberatedforwindupliZresistance

WindUpliYRequirements:Insurance

Somedesignersandownersaren’tawarethattherearewoodassemblieswhichmeetFMupliZrequirementsULandFactoryMutual(FM)havedonetes:ng&researchonroofupliZassemblies.ULassignsra:ngsbasedonmax.upliZresistanceallowedforanassemblyinpsf,suchasClass30,60,90FMrequiresafactorofsafetyof2,i.e.FMUpliZRa:ngof90requiredforroofswith45psfupliZforces

WindUpliYRequirements:Insurance

Source:APAFormG310

WindUpliY:SolarPanels

Resources:DSAFormIR16-8SEAOCPV2

Overview

PanelsL/dRa:oUnbracedLengthWallVeneerWindonlyloadingC&CDesignProper:esHinges

WallDesignConsidera8ons

3StepProcess:ExteriorWallDesign

•  StrengthCheck1:Gravity(axial)+MainWindForceLoads

•  StrengthCheck2:FullComponentsandCladdingWindLoads,NoAxial(orminimalaxial)

•  DeflecAonCheck:ReducedComponentsandCladdingWindLoads

WallDesignConsidera8ons

BasisforMWFRSvs.C&CWindLoadsforWallDesign:

•  Considera:onsinWindDesignofWoodStructures•  FreedownloadfromAWCavailableat:

hwp://www.awc.org/pdf/codes-standards/publica:ons/archives/AWC-Considera:ons-0310.pdf

StrengthCheck1forStudDesign

StrengthCheckasaVer8calLoadSuppor8ngelement:•  ApplyVer:calDead,Live,Roofand/orSnowLoads•  Applyout-of-planelateralloads

•  MWFRSwindloads(ASCE7-10Chapter27or28)•  Seismicwallforces(ASCE7-1012.11.1)

•  CombinedBending&AxialLoadCheckperAWCNDS3.9•  Usestandardloadcombina:ons

•  CBCSec:on1605or•  ASCE7-10Chapter2

DesignTip:BoFomplatecrushingmaygovernoverStudCapacity

DeterminingUnbracedLength

Whatistheunbracedlength,lu?Strong&weakaxis

WallSheathingProvidesWeakAxisBracing

NDSCommentary:“Experiencehasshownthatanycodeallowedthicknessofgypsumboard,hardwoodplywood,orotherinteriorfinishadequatelyfasteneddirectlytostudswillprovideadequatelateralsupportofthestudacrossitsthicknessirrespec:veofthetypeorthicknessofexteriorsheathingand/orfinishused.”

DesignConsidera8ons

SlendernessLimits(NDS20153.7.1.4)MaxEffec:veUnbracedLength=50d,d=depthininches

Maxof75dduringconstruc:on

1½” depth 6’-3” max unbraced length. 9’-4” during construction.

3½” (2x4) Max Height: 14’-7” 5½” (2x6) Max Height: 22’-11” 7¼” (2x8) Max Height: 30’-2”

Studorcolumncanbebracedagainstbucklinginthisdirec:onbysheathing.

Studorcolumnisnotbracedagainstbucklinginthisdirec:onbysheathing.

StrengthCheckforComponents&CladdingWindLoads•  Noaxialloading•  C&CWindloadsonly•  Checkstudforbendingandshear

DesignTip:BeawareofASCE7DefiniAonofEffecAveWindAreatodecreasetherequiredC&Cwindload

StrengthCheckforComponents&CladdingWinds•  Noaxialloading•  C&CtransverseWindloadsonly•  Checkstudbendingandshear.

DesignTip:Forbendingstresscheck,beawareofRepeAAveUsefactorCrofNDSandWallStudRepeAAveMemberFactorofSDPWS3.1.1.ChangeinSDPWS2015referencedfromIBC2015(CBC2016)allowsapplicaAonofWallStudRepeAAveFactortoStud

STIFFNESS.SeeSDPWS3.1.1

Deflec8onCheckforStudDesignDeflec8onCheckforComponentsandCladdingWinds

•  Checkout-of-planedeflec:ontoCBCTable1604.3orothermorestringentrequirements.

Note:Thischecko]engovernstallwalls

DesignTip:Readallthefootnotes!CBCTable1604.3footnotefallowsthefollowingC&CWindloadreducAon:

MulAplycalculatedC&CWindLoadsby0.42whenusingVULT(ASCE7-10)OR0.70whenusingVASD(ASCE7-05andearlier)fordeflecAon

WallStudDesignAidWesternWoodProductsAssocia:on(WWPA)DesignSuite:hwp://www.wwpa.org/TECHGUIDE/DesignSoZware/tabid/859/Default.aspx

Example:OfficeBuildingWallStuds

2StoryBuilding

13’tallwoodframedwalls.

Assumestuds16”o.c.

110mphExposureC

LeastHorizontalDim.=90Z

WallStudDesign:StrengthCheck1

GravityLoads:

RoofDeadLoad=20psf; FloorDeadLoad=30psf

RoofLiveLoad=20psf; FloorLiveLoad=65psf

WallDeadLoad=18psf; WallDeflec:on=L/360

Roof&FloorTributaryWidth=(22Z)(0.5)=11Z

WallTributaryWidth=13Z+13Z=26Z

WDL=(11Z)(20psf+30psf)+(26Z)(18psf)=1018plf

WRL=(11Z)(20psf)=220plf

WLL=(11Z)(65psf)=715plf

ControllingLoadCombo:D+L=1018+715=1733plf

GravityLoads:

AxialLoadPerStud=(1733plf)(1.333Z)=2310lb

Bowomplatecrushing:2310/(1.5”*5.5”)=280psi<625psi:OK

MWFRSWindLoads:

ULT.=28.5psf;ASD=(28.5psf)(0.6)=17.1psfASCETable27.6-1

2x6DF#2Studs@16”o.c.OKforStrengthCheck1

Member #

Location :

Sits on Sill Plate ? Yes

** Dimension Lumber ** ** Dimension Lumber **

Yes Nominal Size : ( 1 ) 2 x 6 Sill Plate Nominal Size : 2 x 6

DochDN.2 Species = Species or Symbol = DochDN.2

No.226 Grade = Grade = No.226

2400f-2.0E 1500f-1.4E

Bearing at < 3" of Sill End? No

Height ( H ) = 13 ft - 0 in P = 2310 lb =

Unbraced Length ( l 1 ) = 13 ft - 0 in w = 22.8 plf = Wind

Unbraced Length ( l 2 ) = 2 ft - 0 in lu = 13 ft - 0 in 13

(pressed-down buttons are selected)

Yes Repetitive Use ?

No 1.00 Incised for PT ?

No Flat Use :

< 19% 1.60 Moisture Content : for P only, fc (psi) = 280 < 533 = Fc //

< 100 Temperature (° F) : for P + w, fc (psi) = 280 < 558 = Fc //

1.00 C D = 1.00 (P) & 1.60 (P+w) (1.3/2) fb (psi) = 497 < 1346 = Fb

1.60 K = 1.00 (fc / F'c)2 + fb / [F'b (1 - fc / Fce)] = 0.95 < 1.00 OK

∆ / H = 120 Mid-H Deflection due to w, ∆ (inch) = 0.85 < H / 120 OK

Section Properties

Post/Stud Sill PL

breadth (b) = 1.5 in 1.5 Sill PL

depth (d) = 5.5 in 5.5 Bending Comp // E Comp -|

Area (A) = 8.3 in^2 8.3 Wet Service CM = 1.00 1.00 1.00 1.00

Section Modulus (S) = 7.6 in^3 Temperature Ct = 1.00 1.00 1.00 1.00

Moment of Inertial (I) = 20.8 in^4 Beam Stability CL = 1.00 N/A N/A N/A

Size CF = 1.30 1.10 N/A N/A

Flat Use Cfu = 1.00 N/A N/A N/A

Sill PL Incising Ci = 1.00 1.00 1.00 1.00

Fb Fc // E Fc -| Emin Repetitive Member Cr = 1.15 N/A N/A N/A

Reference 900 1350 1600000 625 580000 Column Stability (P) CP = N/A 0.36 N/A N/A

Adjusted (P) 533 1600000 781 580000 Column Stability (P+w) CPw = N/A 0.23 N/A N/A

Adjusted (P+w) 1346 558 1600000 781 580000 Bearing Area Cb = N/A N/A N/A 1.25

2152.8 2376

Adjustment Factors

How to

Enter Data

Designed on: April 12, 2016

DL + FL

Douglas Fir-Larch

Design Values (psi)

Douglas Fir-Larch

Strength Check 1

PrintOrder Pro VersionDeveloped by:

Forum Engineers

ASD Method

<19% >19%

<100 100~125 125~150

No Yes

Set Duration Factors

Set Ef f ectiv e-Length Factor

Version: 3.1

Set Def lection Limit

C&CWindLoads:ASCE7Fig.30.4-1

a=Lesserof:

•  10%leasthorizontaldimension(LHD)90’*0.1=9’•  0.4h=0.4*26=10.4’.

Butnotlessthan:

•  0.04LHD=3.6’or3’

Usea=9’forzone5

StrengthCheck2:C&CWindLoads

Wallstudsare13’long

EWA=h2/3=56Z2

Zone4:

GCpf=-0.97

GCpi=-0.18(Table26.11-1)

Zone5:

GCpf=-1.1

ASCE7-10Figure30.4-1

Runningthenumbers–Zone4

• GCpf:0.97(Figure30.4-1)• GCpi:0.18(Table26.11-1)• qh=0.00256KzKztKdV2

§  Kh:0.98-Table30.3-1

§  Kzt:1.00-Figure26.8-1§  Kd:0.85-Table26.6-1§  V:110mph

• qh=25.8psf• p=25.8psf(0.97+0.18)=29.7psf• 0.6W=0.6(29.7)=17.8psf

StrengthCheck2&Deflec8onCheck(Zone4)

2x6DF#2Studs@16”o.c.OKforStrengthCheck2&Deflec:onCheck

Member #

Location :

2400f-2.0E 1500f-1.4E

Height ( H ) = 13 ft - 0 in P = 1357 lb =

No Flat Use :

1.00 C D = 1.00 (P) & 1.60 (P+w) (1.3/2) fb (psi) = 516 < 1346 = Fb

Section Properties

Post/Stud Sill PL

Size CF = 1.30 1.10 N/A N/A

2152.8 2376

Adjustment Factors

How to

Enter Data

DL + FL

Douglas Fir-Larch

Design Values (psi)

Douglas Fir-Larch

Strength Check 1

Forum Engineers

ASD Method

<19% >19%

<100 100~125 125~150

No Yes

Version: 3.1

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

§  Kh:0.98-Table30.3-1

§  Kzt:1.00-Figure26.8-1§  Kd:0.85-Table26.6-1§  V:110mph

• qh=25.8psf• p=25.8psf(1.1+0.18)=33psf• 0.6W=0.6(33)=19.8psf

Runningthenumbers–Zone5

StrengthCheck2&Deflec8onCheck(Zone5)

2x6DF#2Studs@16”o.c.OKforStrengthCheck2&Deflec:onCheck

Member #

Location :

2400f-2.0E 1500f-1.4E

Height ( H ) = 13 ft - 0 in P = 1357 lb =

No Flat Use :

1.00 C D = 1.00 (P) & 1.60 (P+w) (1.3/2) fb (psi) = 575 < 1346 = Fb

Section Properties

Post/Stud Sill PL

Size CF = 1.30 1.10 N/A N/A

2152.8 2376

Adjustment Factors

How to

Enter Data

DL + FL

Douglas Fir-Larch

Design Values (psi)

Douglas Fir-Larch

Strength Check 1

Forum Engineers

ASD Method

<19% >19%

<100 100~125 125~150

No Yes

Version: 3.1

TallWallsinCommercialDesign

ExampleTallWoodWall§  CorteMadera,CA§  25’WallHeight§  ASDWind:C&C:30psf;MWFRS:21.7psf§  NonLoad-BearingStuds§  L/240Deflec:onCriteriaStudOp8on MaterialCost

2x12DF-L#1@19.2”o.c. $2.40/sf

1.75”x11.875”LSL@19.2”o.c. $2.90/sf

2x10DF-L#1@12”o.c. $3.20/sf

1.75”x9.5”LSL@12”o.c. $3.80/sf

1.625”x10.5”DFGlulam@19.2”o.c. N/A

OutofPlaneForces:TietoDiaphragm

WoodFramedStair/ElevatorShaYWalls

StairwayShaYEnclosures&Framing

StairFraming(Landing&Stringers)

ShaYwall

Consider“Hinge”atwallplatesforout-of-planewind&seismicloadsduetolackofadjacentfloor:•  SpanPlates

Horizontally(nojoints)•  Installaddi8onal

member(rim)tospanhorizontally

StairExteriorWallDetail

IntermediateStairLanding

WhenStairShaYWallisExteriorWall

WallPlatesatTypicalFloorEleva8on–CreatesPoten8al“Hinge”

WallFramingatShaYs

8’TallWalls 10’TallWalls 12’TallWalls

2-2x4 7’-10”B/6’-4”D 7’-0”B/5’-10”D 6’-4”B/5’-6”D

3-2x4 10’-3”B/7’-3”D 9’-2”B/6’-8”D 8’-4”B/6’-4”D

2-2x6 11’-5”B/9’-11”D 10’-3”B/9’-2”D 9’-4”B/8’-8”D

3-2x6 15’-0”B/11’-4”D 13’-5”B/10’-6”D 12’-3”B/9’-11”D

HowfarcanjustwallplatesspanatshaYstudbreaks?Requiresnojointsintheseplates:

Assump8ons:DF#2L/360Deflec8onCriteria18psfC&C(bending)12.6psfC&C(deflec8on)

B–spancontrolledbybendingD–spancontrolledbydeflec:on

WallFramingatShaYs

Framing

ShaYwall

StairExteriorWallDetail

StairSha]Side

ExteriorSideConsider“Hinge”atwallplatesforout-of-planewind&seismicloadsduetolackofadjacentfloor:•  Installaddi8onal

member(rim)tospanhorizontally

•  Op8onsincludesolidsawnlumber(4xor6x),glulam,PSL

•  Ifmul8-plymember,uniquedesignconsidera8ons

WallFramingatShaYs

FloorPlan

WallFramingatShaYs

ConnecAonsareKey

WallFramingatShaYsFramingPlan 1 2

WallFramingatShaYsStraponoutsideofbeam/clipangleoninsideofbeamAwachestorim/blockingonadjacentwall

ExteriorWall SpanningRim

StairTopLandingFraming

CorridorFloorFraming

Interio

WallFramingatShaYsMiterbeamsatcornerStraponoutsideofbeams/clipangleoninsideofbeamsAwachperpendicularbeamstogether

SpanningRim

StairIntermediateLandingFraming

WallFramingatShaYsClipanglesoninside/outsideofbeamAwachestorim/blockingonadjacentwall

SpanningRim

ExteriorWallInteriorWall

Exterio

StairIntermediateLandingFraming

ExteriorWallPlateEleva8onsShiYedDowntoIntermediate

LandingEleva8on

•  EliminatesHingeEffect•  AvoidsInterferencewith

LandingWindows

WhenStairShaYWallisExteriorWall

DroppedHeaders:OutofPlaneBraced?

OutofPlaneBracing

SmallRetailBuilding–NorthernCA

CanthisExteriorWallPassDeflec8onCheck?

“HingePoint”createsastructuralweaknessinthewall

GableEndwithslopedceiling

2StoryExteriorWall

Overview

DifferencesBetweenWind&Seismic

Wind Seismic

Shearwall&DiaphragmCapacity

40%Increase BaseValue

ShearwallA/R 3.5/1* 2/1*

DiaphragmA/R 3/1unblocked 3/1unblocked

OverstrengthFactoronCollectors

None 3(insomecondi8ons)

Re-distribu8onofforcestoupperstories

NotRequired Required

GypsumShearwalls Permiued OnlypermiuedinSDCA-D

DissimilarMaterialShearwalls

Permiuedtocombinecapaci8esofWSP&gypsum

Can’tcombinecapaci8es.Use2xsmallercap.orlargersinglesidedcapacity,whicheverisgreater

DriYCheck UsesServiceorLowerLoads UsesStrengthLoads

GypsumShearwalls•  Lowercapaci:esthanWSPShearwalls(about1/3capacity)•  SDPWSTable4.3C,Sec:on4.3.7.5providescapaci:es&

requirements•  NotpermiwedinSDCEorF

DifferencesBetweenWind&Seismic

Wind Seismic

LateralForceVariables

SurroundingTopographyAreaSpecificWindGustsDegreeofBuilding“Openness”

StructureMassLateralForceResis8ngSystemSiteSpecificSoilCondi8ons

Occupancy/ImportanceRisk

10%IncreaseIItoIII&IV 25%IncreaseIItoIII50%IncreaseIItoIV

SurroundingTopography

ExposureBtoC:Increasevaries,usually~25%

Nochange

Massofstructure

Noimpactonwindforces Directly8edtoseismicforces

TypeofLFRS Noimpactonwindforces Directly8edtoseismicforces

ExampleBuildings:Wind

ExampleBuildings:Seismic

ExampleBuilding:Seismicvs.Wind

1StoryCommercialRetailBuilding84’-0”x34’-0”13’WallHeight+3’ParapetR=6.5I=1.0Sdsrequiredtomakebaseshearsequal:ExposureB:1.08longbldgdim.0.52shortbldgdim.ExposureC:1.64longbldgdim.0.8shortbldgdim.

2StorySchool,ClassroomWing210’-0”x80’-0”13’WallHeightR=6.5I=1.25(seismic)Sdsrequiredtomakebaseshearsequal:ExposureB:0.39longbldgdim.0.32shortbldgdim.ExposureC:0.58longbldgdim.0.47shortbldgdim.

3StoryOfficeBuilding142’-0”x66’-0”14’WallHeightR=6.5I=1.0Sdsrequiredtomakebaseshearsequal:ExposureB:0.65longbldgdim.0.3shortbldgdim.ExposureC:0.93longbldgdim.0.43shortbldgdim.

4StoryMul:-FamilyBuilding75’-0”x75’-0”10’WallHeightR=6.5I=1.0Sdsrequiredtomakebaseshearsequal:ExposureB:0.4short&longbldgdim.ExposureC:0.56short&longbldgdim.

ExampleBuildings:Seismicvs.Wind

Bldg LongDimSds ShortDimSds

1Story,84’x34’ 1.64 0.8

2Story,210’x80’ 0.58 0.47

3Story,142’x66’ 0.93 0.43

4Story,75’x75’ 0.56 0.56

Buildingassump:ons:LightFramewoodconstruc:onincludingshearwallsExteriorfinish:StuccoWindExposureC

Shearwall&DiaphragmDeflec8on

Whencalcula:ngshearwallanddiaphragmdeflec:ons,valuesofapparentshears:ffness,Ga,arerequired,butarenotprovidedforwinddesigninSDPWS

Shearwall&DiaphragmDeflec8onAWCFAQ:Cantheeffec8veshears8ffnessvalues,Ga,inSDPWSbeusedforcalcula8onofdiaphragmandshearwalldeflec8onsduetowindloads?Valuesofapparentshears:ffness,Ga,aretabulatedinseismiccolumnsoftheSDPWStofacilitatecalcula:onofseismicstorydriZinaccordancewithASCE7MinimumDesignLoadsforBuildingsandOtherStructures.ValuesofGaareequallyapplicableforcalcula:onofthesheardeforma:oncomponentoftotaldeflec:onduetowindloadsuptotheASDwindunitshearvaluecalculatedasvw/2.0.Thislevelofunitshearforwindisiden:calto1.4:mestheASDseismicunitshearcapacityforwhichapparentshears:ffnessvalueswereoriginallydeveloped.hwp://awc.org/faqs/general/can-the-effec:ve-shear-s:ffness-values-ga-in-special-design-provisions-for-wind-and-seismic-%28sdpws%29-be-used-for-calcula:on-of-diaphragm-and-shear-wall-deflec:ons-due-to-wind-loads

ShearwallDeflec8onCriteriaforWind

Unlikeseismic,nocodeinforma:onexistsondeflec:on/driZcriteriaofstructuresduetowindloads

Serviceabilitychecktominimizedamagetocladdingandnonstructuralwalls

ASCE7-10:C.2.2DriDofWallsandFrames.LateraldeflecConordriDofstructuresanddeformaConofhorizontaldiaphragmsandbracingsystemsduetowindeffectsshallnotimpairtheserviceabilityofthestructure.Whatwindforceshouldbeused?Whatdri]criteriashouldbeapplied?

Allowable=?

ShearwallDeflec8onCriteriaforWindWindForcesConsensusisthatASDdesignlevelforcesaretooconserva:veforbuilding/framedriZcheckduetowind•  CommentarytoASCE7-10AppendixCsuggeststhatsome

recommendusing10yearreturnperiodwindforces:•  ~70%of700returnperiodwind(ul:matewindspeed

forriskcategoryIIbuildings)•  Others(AISCDesignGuide3)recommendusing75%of50

yearreturnperiodforcesDri]CriteriaCanvarywidelywithbriwlenessoffinishesbutgenerallyrecommenda:onsareintherangeofH/240toH/600

Ques8ons?

ThisconcludesTheAmericanIns:tuteofArchitectsCon:nuingEduca:onSystemsCourse RickyMcLain,MS,PE,SE

TechnicalDirector–ArchitecturalandEngineeringSolu:onsWoodWorksRicky.McLain@WoodWorks.org(802)498-3310

Visitwww.woodworks.orgformoreeduca8onalmaterials,casestudies,designexamples,aprojectgallery,andmore

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