considerations for out-of-plane wall and uplift design

ConsiderationsforOut-of-PlaneWallandUpliftDesign

WoodWorksTexasWorkshops–December,2016

Overview

• Uplift• WallDesign

WindLoads

Windloadsactingonbuildingsaremodeledasuniformsurfaceloads.Windloadscancreatebothpositiveandnegativeloads(inwardsandoutwardsloads)onbuildingsurfacesandcreatethreedifferent loadingconditions:• Uplift• Racking/overturning• Sliding/shear

UpliftWindLoads

Uplift– Outward(suction)forceactingonroof

Loadpath- rooftofoundationrequiredunlessdeadloadisgreaterthanuplift

UpliftLoads

Source:strongtie.com

MethodstoResistUpliftLoads

• Mechanicalconnectors(straps,hurricaneties,screws,threadedrods)

• Sheathing

• DeadLoads

Source:strongtie.com

UpliftResistance:MechanicalConnectors

Source:IIBHS

UpliftResistance:WallSheathing

• Whenjoints,fastenersareconsidered,canusesheathingtoresistuplift

• SDPWSSection4.4

SDPWSFigure4I

UpliftResistance:WallSheathing

SDPWSFigure4J

UpliftResistance:DirectLoadPath

Importanttodetailupliftrestraintconnectorstoprovidedirectloadpath

UpliftWindLoads

Truss/RaftertoTopPlateConnection

Whathappenstotheupliftloadafterthis?

UpliftWindLoads

WindLoadsTypes

2TypesofWindLoads•MWFRS– MainWindForceResistingSystem

Anassemblageofstructuralelementsassignedtoprovidesupportandstabilityfortheoverallstructure.Thesystemgenerallyreceiveswindloadingfrommorethanonesurface.Eg.Shearwalls,diaphragms

• C&C– Components&CladdingElementsofthebuildingenvelopethatdonotqualifyaspartoftheMWFRS

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:Itiscommonpracticetouse2setsofdeadloads:highestpotentialdeadloadsforgravity,lowestpotentialdeadloadsforuplift

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.30.10-1 ASCE7-10Fig.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:Itiscommonpracticetouse2setsofdeadloads:highestpotentialdeadloadsforgravity,lowestpotentialdeadloadsforuplift

169.4plf

DeterminingtheUpliftLoad

384lbs MWFRSOR471lbs C&[email protected]

RoofFraming:CompressionEdgeBracing

• Bendingcausescompressioninoneedgeofmember• Roofsheathingbracescompressionflangeofroofjoists

Compressionedge

Tensionedge

Loadingdirection

RoofFraming:CompressionEdgeBracing

• WhataboutUplift?Needfulldepthblocking/bridgingorbottomchordbracing

BottomChordBracing

Someinsurancecompaniesrequireabuilding’srooftoberatedforwindupliftresistance

WindUpliftRequirements:Insurance

Somedesignersandownersaren’tawarethattherearewoodassemblieswhichmeetFMupliftrequirements

ULandFactoryMutual(FM)havedonetesting&researchonroofupliftassemblies.

ULassignsratingsbasedonmax.upliftresistanceallowedforanassemblyinpsf,suchasClass30,60,90

FMrequiresafactorofsafetyof2,i.e.FMUpliftRatingof90requiredforroofswith45psf upliftforces

WindUpliftRequirements:Insurance

Source:APAFormG310

WindUplift:SolarPanels

Resources:

DSAFormIR16-8SEAOCPV2

Overview

• Uplift• WallDesign

DesigningWoodWalls

WindLoads

Uniformsurfacewindloadsgenerallyincreasewithbuildingheight

ASCE7-10Fig.27-6.1

Ifwindloadsvarywithbuildingheight,commontousehigherwindloadoverasinglestoryorbuilding

PanelsL/dRatioUnbraced LengthWallVeneerWindonlyloadingC&CDesignPropertiesHinges

WallDesignConsiderations

LoadsintoWSP

Windloadsaretransferredtowallframingstudsthroughwoodstructuralpanels(sheathing)

SDPWSTable3.2.1

ForASDCapacity:DivideNominalCapacityby1.6ForLRFDCapacity:MultiplyNominalCapacityby0.85

DeterminingUnbraced Length

Whatistheunbracedlength,lu ?Strong&weakaxis

Gypsum&WeakAxisBuckling

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

IntermediateWallStudBlocking

3StepProcess:ExteriorWallDesign

• StrengthCheck1:

Gravity(axial)+MainWindForceLoads

• StrengthCheck2:

FullComponentsandCladdingWindLoads,NoAxial(orminimalaxial)

• DeflectionCheck:

ReducedComponentsandCladdingWindLoads

WallDesignConsiderations

Forotherdesignissuesseethearticle:

• ConsiderationsinWindDesignofWoodStructures• FreedownloadfromAWCavailableat:

http://www.awc.org/pdf/codes-standards/publications/archives/AWC-Considerations-0310.pdf

StrengthCheck1forStudDesign

StrengthCheckasaVerticalLoadSupportingelement:• ApplyVerticalDead,Live,Roofand/orSnowLoads• Applyout-of-planelateralloads

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

• CombinedBending&AxialLoadCheckperAWCNDS3.9• Usestandardloadcombinations

• IBCSection1605or• ASCE7-10Chapter2

DesignTip:Bottomplatecrushingmaygovern

overStudCapacity

DesignConsiderations

SlendernessLimits(NDS20153.7.1.4)MaxEffectiveUnbracedLength=50d,d=depthininches

Maxof75dduringconstruction

1½” depth6’-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”

Studorcolumncanbebracedagainstbucklinginthisdirectionbysheathing.

Studorcolumnisnot bracedagainstbucklinginthisdirectionbysheathing.

StrengthCheck2forStudDesign

StrengthCheckforComponents&CladdingWindLoads• Noaxialloading• C&CWindloadsonly• Checkstudforbendingandshear

DesignTip:BeawareofASCE7DefinitionofEffectiveWind

AreatodecreasetherequiredC&Cwindload

StrengthCheck2forStudDesignStrengthCheckforComponents&CladdingWinds• Noaxialloading• C&CtransverseWindloadsonly• Checkstudbendingandshear.

DesignTip:Forbendingstresscheck,beawareofRepetitiveUsefactor

Cr ofNDSandWallStudRepetitiveMemberFactorofSDPWS3.1.1.

ChangeinSDPWS2015referencedfromIBC2015allows

applicationofWallStudRepetitiveFactortoStudSTIFFNESS.See

SDPWS3.1.1

DeflectionCheckforStudDesignDeflectionCheckforComponentsandCladdingWinds• Checkout-of-planedeflectiontoIBCTable1604.3or

othermorestringentrequirements.

Note:Thischeckoftengovernstallwalls

DesignTip:Readallthefootnotes!IBCTable1604.3footnotef

allowsthefollowingC&CWindloadreduction:

MultiplycalculatedC&CWindLoadsby0.42whenusingVULT (ASCE

7-10)OR0.70whenusingVASD (ASCE7-05andearlier)fordeflection

CalculatingDeflection– IBCTable1604.3

ForΔ ofmostbrittlefinishesusel/240

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

f.Thewindloadispermittedtobetakenas0.42timesthe"componentandcladding”loadsforthepurposeofdeterminingdeflectionlimitsherein.

WoodStudswithBrickVeneer- Deflection

IBCTable1604.3:min.walldeflectionwithbrittlefinishes=L/240

BrickIndustryAssociationrecommendsmuchstricterlimits

StructureMagazineMay2008article,HaroldSprague

BIATechNote28

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

Example:OfficeBuildingWallStuds

2StoryBuilding

13’tallwoodframedwalls.

Assumestuds16”o.c.

110mphExposureC

LeastHorizontalDim.=90ft

WallStudDesign:StrengthCheck1

GravityLoads:

RoofDeadLoad=20psf; FloorDeadLoad=30psf

RoofLiveLoad=20psf; FloorLiveLoad=65psf

WallDeadLoad=18psf; WallDeflection=L/360

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

WallTributaryWidth=13ft +13ft =26ft

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

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

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

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


GravityLoads:

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

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

MWFRSWindLoads:

ULT.=28.5psf;ASD=(28.5psf)(0.6)=17.1psf ASCETable27.6-1


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

1485

2152.8 2376

Adjustment Factors

How to

Enter Data

Designed on: April 12, 2016

DL + FL

Douglas Fir-Larch

No.2

Design Values (psi)

Douglas Fir-Larch

No.2

Studs

Strength Check 1

PrintOrder Pro VersionDeveloped by:

Forum Engineers

P

H

w

Setup

ASD Method

YesNo

YesNo

<19% >19%

<100 100~125 125~150

YesNo

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=56ft2

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&DeflectionCheck(Zone4)

2x6DF#2Studs@16”o.c.OKforStrengthCheck2&DeflectionCheck

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







1485

2152.8 2376

Adjustment Factors

How to

Enter Data


DL + FL

Douglas Fir-Larch

No.2

Design Values (psi)

Douglas Fir-Larch

No.2

Studs

Strength Check 1


Forum Engineers

P

H

w

Setup

ASD Method

YesNo

YesNo

<19% >19%

<100 100~125 125~150

YesNo

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&DeflectionCheck(Zone5)

2x6DF#2Studs@16”o.c.OKforStrengthCheck2&DeflectionCheck

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







1485

2152.8 2376

Adjustment Factors

How to

Enter Data


DL + FL

Douglas Fir-Larch

No.2

Design Values (psi)

Douglas Fir-Larch

No.2

Studs

Strength Check 1


Forum Engineers

P

H

w

Setup

ASD Method

YesNo

YesNo

<19% >19%

<100 100~125 125~150

YesNo

No Yes



Version: 3.1


GableEndWallHinge

GableEndBracingDetails

• Gableendwallandroofframingmayrequirecrossbracing

FullHeightStudsatGableEndWalls

• Ifnoopeningsingableendwallexist,candesignstudstospanfromfloor/foundation toroof(varyingstudheights).Mayrequirecloserstudspacings attallerportionsofwall

GableEndWallswithOpenings

GableEndWallGirts&Jambs

• Oftengableendwallsarelocationsoflargewindows• Horizontallyspanningmemberinplaneofwallbreaksstudlength,providesallowable

opening

Verticallyspanningjambs

Horizontallyspanning

girts

DroppedHeaders:OutofPlaneBraced?

OutofPlaneBracing

SmallRetailBuilding– NorthernCA

WoodFramedStair/ElevatorShaftWalls

StairwayShaftEnclosures&Framing

IntermediateStairLanding

WhenStairShaftWallisExteriorWall

WallPlatesatTypicalFloorElevation– CreatesPotential“Hinge”

WallFramingatShafts

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

Howfarcanjustwallplatesspanatshaftstudbreaks?Requiresnojointsintheseplates:

Assumptions:DF#2L/360DeflectionCriteria18psf C&C(bending)12.6psf C&C(deflection)

B– spancontrolledbybendingD– spancontrolledbydeflection

WallFramingatShafts


Framing

Shaftwall

StairExteriorWallDetail

StairShaftSide

ExteriorSide

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

member(rim)tospanhorizontally

• Optionsincludesolidsawnlumber(4xor6x),glulam,PSL

• Ifmulti-plymember,uniquedesignconsiderations

WallFramingatShafts

FloorPlan

WallFramingatShafts

ConnectionsareKey



ExteriorWallPlateElevationsShiftedDowntoIntermediate

LandingElevation

• EliminatesHingeEffect• AvoidsInterferencewith

LandingWindows

WhenStairShaftWallisExteriorWall

Questions?

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considerations for out-of-plane wall and uplift design

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