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PDHonline Course S184 (2 PDH)
Flexible Metal Deck Roof Diaphragms
Instructor: D. Matthew Stuart, P.E., S.E., F.ASCE, F.SEI , SECB, MgtEng
2013
PDH Online | PDH Center
5272 Meadow Estates DriveFairfax, VA 22030-6658
Phone & Fax: 703-988-0088www.PDHonline.orgwww.PDHcenter.com
An Approved Continuing Education Provider
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D.MatthewStuart 1
Sheardiaphragmsareessentiallyplanarstructuralsystemsfoundinroofs,floors,andwallsof
buildings. Theyarecomprisedofinterconnectedunits,attachedtosupportingmembers,such
thattheentireassemblypossessesbothinplaneshearstrengthandstiffness.Themajor
components
of
a
diaphragm
include
the
individual
deck
panels,
the
structural
members
to
which
theyareconnectedandtheconnectingdevicesorfasteners. Fastenertypesincludewelds,
screws,powerdrivenpins,orothermechanicaldevicesthathaveapredictablecapacity. The
strengthandstiffnessofadiaphragmdependsonthepanelproperties,thespanarrangements,
andthequalityoftheconnections.
Figure1illustratesthebasicconceptforaroofandwalldiaphragm.InFigure1windpressureon
thewallsparalleltolengthLactonthebuilding. Alineloadreactionofthispressureis
distributedto
the
top
of
the
wall
at
the
roof
plane
via
the
vertical
spanning
capacity
of
the
claddingoverheightH. Theroof,actingasasimplespanhorizontalgirderofdepthB,distributes
thewindlineloadasashearreactionalongthetopoftheendwallsperpendiculartoL. Theend
wallsinturnactasdiaphragmsbetweentheroofandfoundationlevels.
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D.MatthewStuart 2
Fortheroofinthisexample,thetotaluniformloadonthediaphragmequalsthecombined
effectsofthewindwardandleewardcladdingreactions(ww +wL). The maximumendreaction(R)
oftheroofdiaphragmthereforeis((ww +wL)xL)/2. RdividedbylengthBequalsthecollector
load
or
maximum
uniform
shear
force
in
the
diaphragm.
The
maximum
roof
diaphragm
moment
(M)equals((ww +wL)xL2)/8. Thecorrespondingdiaphragmchordforcesarethereforeequalto
MdividedbythediaphragmdepthB. Themaximumunitshearonthewalldiaphragmisalso
equaltotheroofreaction,R,dividedbyB. However,thewalldiaphragmmomentequalsRxH.
Itshouldalsobenotedthat:
a. Adiaphragmactslikeashortdeepbeam.
b. Themaximumaverageshear(R/B)occursattheendsoftheroofdiaphragm.
c. Zonesnearthemidspanoftheroofaresubjectedtolessunitshearthereforeless
diaphragmstrengthisrequired.
d. Thelargerdesignshearsmayberesistedbyusingbothheaviergagepanelsandfewer
connectionsorbymorefrequentlyconnectedlightergagepanels.Thereforethemost
efficientuseofmaterialsmaynotbemetbyusingasinglediaphragmdesignforthe
entireroofarea. However,fromapracticalconstructabilitystandpointitismore
commonto
use
asingle
deck
and
connector
type
over
an
entire
roof
and
increase
the
frequencyoftheconnectorsinordertoresistgreaterinplaneshearforces.
Roofdiaphragmsmaybeassembledfrom
awidevarietyofpanelprofilesincluding
NarrowRib
(NR),
Intermediate
Rib
(IR)
and
WideRib(WR). Eachofthesedifferent
decktypesaredescribedintheSteelDeck
Institute(SDI)PublicationNo.31,Design
ManualforCompositeDecks,FormDecks
andRoofDecks. Roofdiaphragmpanels
typicallyvaryfrom0.0295inchesto0.064
inchesinthicknessandcomeinwidthsof
18inchesto36inchesormore.
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D.MatthewStuart 3
Adiaphragmshouldbedesignedandassembledtocoveraspecifiedareainsuchawaythatin
planeshearstrengthandstiffnessispredictable. Theprincipalelementsdeterminingthese
factorsincludespacingofthesupportframing,thesizeandthicknessoftheindividualdeck
panels
and
the
interconnecting
fasteners.
A
metal
roof
deck
diaphragm
is
a
fairly
flexible
system
somewhatanalogoustoatrussasshowninFigure2. Priortoinstallingthetrussdiagonalor
attachingthediaphragmtothesupports(andeachadjacentsheetviasidelapconnectors),
neitheroftheframespossessmuchstrengthorstiffness.Theshearstrengthofadiaphragm
systemislimitedbythestrengthofconnections,localpanelbucklingandthegeneralplatelike
bucklingcharacteristicsoftheentirediaphragmarea.
Inadditiontoneedingtoresistplanarshearforces,inorderforadiaphragmtofunctionproperly
itisalsonecessarytoprovidemembersalongtheextremeedgesofthedeckasrequiredtoresist
theflexural
tension
and
compression
components
of
the
deep
beam
member.
This
is
analogous
tothetopandbottomchordsofatrussresistingthecompressionandtensionforcesofthe
member.
Source: CSI
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D.MatthewStuart 4
Thestrengthofadiaphragmcanalsobelimitedbyproperattentiontotheedgeandend
terminationconditions.Inaddition,atinteriorpositions,panelsmustbesufficientlyoverlapped
toprovideadequateenddistancesfortheconnectorused.Ifpanelsarebuttedattheirends
rather
than
end
lapped,
as
is
common
with
floor
decks,
then
each
panel
must
be
individually
connectedatitsendswiththespecifiedpattern.
Theoverlappingedgesofpanelsshouldbeinclosecontactinordertominimizetheeccentricity
. . ,
usedattheoverlapconditionshouldalsobeinstalledontheedgepanelatthediaphragm
perimeterwherethesidelapconnectorwouldnormallyoccuriftherewereanotheradjacent
panel. Otherwisetheshearstrengthalongthefirstinteriorsidelapmayexceedthatalongthe
perimetermemberthusdiminishingthecontributionofthedeckendconnectionatthe
supportingshearwallorverticalXbracedframe.
Source: TataSteel
Establishingwhat
type
of
fastener
is
to
be
used
is
acritical
component
of
designing
and
detailing
adiaphragm.Fastenerscommonlyincludewelds,screwsandpowderdrivennaillikepins.
Structuralconnectionsincludefastenersthatconnectoneormoresheetstoheavierorthicker
frameorstructuralmembers. Sidelapconnectionsincludefastenersthatconnectadjacentpanels
toeachotherandnottothesupportingframemembers. Stitchconnectionsareanothername
forsidelapconnections.
Fasteners
Source: Hilti;MetalDeckSupply;HobartBrothers
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D.MatthewStuart 5
Arcspotwelds,orpuddlewelds,areproducedbystrikinganarcontheuppersheet,thereby
causingaholetoform,whilethelowersheetisbeingraisedtofusiontemperature. Withthe
attainmentof
the
proper
temperature,
the
electrode
is
moved
in
acircular
pattern
until
the
hole
isfilledandfusionattainedonthearcpuddleperimeter. Therelativestrengthinaseriesofwelds
canvarysignificantlybymodestchangesinweldingtimes.
WeldedConnections:
rcspotwe stostructura mem ers .e.we ngo t nners eetstot c erstructura
members)requiredirectcontactbetweentheunitsforproperheattransfer. Inaddition,aproper
balancebetweentheweldingtimeandtheelectrodeburnoffrateisessentialtogoodquality
welding.Weldingmachinepowersettingsrequiredusuallyarewellbelowthoseneededfor
weldinginhotrolledsteels. Thetimerequiredperweldmayvarybetween3and6secondsor
moredependingofthepropertiesofpartsbeingconnected.
Source: PalmBeachCountySchools
Weldwashersfunctionasaheatsinkallowingholeformationinthinnerpanelswithoutexcessive
growthofthehole,asthetemperatureoftheunderlyingpanelisincreased. Thewasheris
subsequentlyfilled
with
the
weld
stem
growing
into
the
lower
panel
which
becomes
anchored
on
thewashersholeperimeter. Uponcooling,thewasherisclampeddownontheattachedsheet.
Weldwashersarerecommendedforpanelsthinnerthan0.0280inches.
Source: MetalDeckSupply
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D.MatthewStuart 6
AllweldsshouldbemadebyqualifiedoperatorsfollowingAWSD1.3Specifications.Asindicated
previously,weldingthinmaterialusuallyrequiresamuchlowerpowersettingandlowerburnoff
ratethanwithheavysteelunits. Particularcareisalsorequiredwhenweldingdecktojoistsin
ordertoavoiddamagetothejoistchords.Preliminaryfieldqualitycontrolcheckscanbemadeby
placingapair
of
welds
in
adjacent
valleys
at
one
end
of
apanel.
A
visual
inspection
will
show
if
theweldmaterialisfusedproperlyandincontactwiththeunderlyingpanel. Intermittent
contactmayindicateexcessivepowersettings. Separationbetweenthepanelsmayindicate
insufficientweldingtimeandpoorfusion. Theterminationoftheweldingoperationmaynot
.
thanthreequartersoftheweldperimeter.
Inadjacentdiaphragmpanelswithnestableorflatoverlappingedges,sheettosheetorstitch
connectionsaretypicallyrequiredawayfromthesupportingmembers. Theplacementofarc
spotweldsatsuchsidelapsisdifficult. Inaddition,thethinnerthematerial,themoredifficultthe
weldingoperationbecomes. Weldingofsidelapsisnotrecommendedformaterialof0.0295inch
orthinner. Theamountofslipormovementexperiencedasweldsareloadedinshearinthin
steelelementsisverysmallrelativetothatformostothermechanicalconnectors. The
movementisessentiallylimitedtopaneldistortionaroundtheweld.
SidelapScrewConnector
Source: Bondek
Screwsmust
be
installed
using
properly
calibrated
tools
in
order
to
avoid
overdriving
which
can
stripthethreadsatsidelapsorseverthescrewwhenitisplacedintoathickersupporting
member. Thequalityofscrewconnectorsingeneralistypicallynotamajorproblemalthough
thesetypesofconnectorscansometimesfracturewhenbeingdrivenintoathickersupporting
material. Themostcommonproblemwithscrewconnectorsinvolvesallowingthescrewto
threadupontheuppersheetbeforebecomingengagedinthelowersheetthusleavingmajor
ScrewConnections:
gapsbetweentheseparatepanels. Suchscrewsshouldberemovedandredrivennearbywhile
forcingsheetlayerstoremainindirectcontact.
Source: Simpson
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D.MatthewStuart 7
Powderdrivenfastenersmustbeinstalledfollowingthemanufacturersrecommendations. Care
mustbeexercisedinsettingthedrivingforcetoobtaintheproperdepthofpenetration. Once
drivenproperly,thesenaillikefastenersareveryresistanttoextractionbyupliftforces. Inuplifttestsonsheetmaterial,theusualmodeoffailureinvolvestearingthesheetaroundtheheador
washerleavingthefastenerinplace.
PowderDrivenFasteners:
Source: Hilti
Thequality
of
button
punching
is
difficult
to
maintain
because
the
attachment
depends
on
the
careandtheenergyusedbytheinstallerandthetoolthatisused.
ButtonPunchedSidelaps:
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D.MatthewStuart 8
1. Strengthvs.Cost:Itistypicallybettertoachievetherequireddiaphragmstrengthwitha
greaternumberofweakerbutlessexpensivefasteners. Howeveritisrecommendedthatthe
designershouldcheckthedeflectionofthediaphragm.
2. Theinsurancefireratingorwindupliftrequirementsofabuildingmaynotallowa
Miscellaneous:
.
3. Thecommonavailabilityofanygivendeckattachmenttool,equipmentorpowersourcemay
dictatethechoiceoffastenerforanygivenproject.
4. Theexposedundersideappearanceofthedeckmaybeimportant. Ifappearanceiscritical
sidelapscrewsorevenveryweakbuttonpunchesmayberequiredeventhoughanincreased
numberoftheseconnectorswouldbeneededoverthatprovidedbywelding.
5. Atthistimetherearenostandardtestsforupliftloadingsonfasteners. However,uplift
failureofadeckpanelunderserviceloadingisveryuncommon. Thisisbecausethespacing
offasteners
as
dictated
by
diaphragm
design
or
insurance
requirements
(Factory
Mutual
or
UnderwritersLaboratories)typicallyexceedsanynetupliftforces.
Fasteningof
metal
deck
to
the
supports
at
one
time
was
only
done
by
welding
until
self
drilling
screwsbecameavailable. Inaddition,weldingofdeckhasalsobeenreplacedtosomedegreeby
fastenersthatareshotin(eitherairorpowderactuated). Allthreeofthesemethodsof
attachmentperformthesamefunctionofholdingthedeckinplaceandthusallowingshear
strengthandstiffness(thatcanbepredicted)tobedeveloped.
HowtoFastenSteelDeck
Becausetheconnectionofthedeck(bothsidelapsandtothesupports)isaveryimportant
componentofthediaphragmcapacity,forbothstructuralstabilityandinsuranceandfirerating
approvals,itisuptothedesignertochoosethecorrectfastenerstobespecifiedandbeableto
judgethemeritsofsubstitutionsrequestedbythecontractor.
Source: BarsinProducts
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D.MatthewStuart 9
Welding,whenproperlyexecuted,providesthestrongestandstiffestdeckconnections. Welding
alsorequires
the
most
skill
and
therefore
should
be
inspected
thoroughly.
Because
most
visible
welddiametersusedwithsteeldeckarebetweeninchesandinchesneitherAISInorAWS
capacityformulasshouldbeused. However,testingperformedbytheSDIhasestablished
strengthsforwelddiametersbetweeninchandinches. Theultimatestrengthformulawas
determined to be that shown on this slide. The corres ondin AISI formula indicates that reater
WeldedConnections:
.
weldstrengthscanresultwithmultiplemetalthickness(suchasatoverlaps),howevertheSDI
testssuggeststhatformetaldeckthiseffectshouldbeignored. TheSDIalsorecommends,based
onthedistributionofthetestresults,thatasafetyfactorof2.75beusedfortheseweldsrather
thanasafetyfactorof2.56assuggestedbytheAISISpecifications.
Qf =2.2*t*Fu *(dt)[inkips]
Where: d=averagevisiblediameter[inches]
Fu =steelstrength[ksi]
t=basemetalthickness[inches]
Itisgoodpracticetouseweldwashersfordeckswithametalthicknesslessthan0.0280inches.It
isalsorecommendedtouse5/8inchpuddleweldswithoutwashersformaterialthicknesses
greaterthan
0.0280
inches.
In
no
case
should
washers
be
used
on
interior
sidelaps.
Inadjacentdeckpanelswithnestableorflatoverlappingedges,sheettosheet(stitch)
connectionsarerequired. Theinstallationofarcspotweldsatsidelapscanbeproblematic. In
addition,thethinnerthematerial,themoredifficulttheweldingoperation. Weldingofsidelaps
. .
Source: Cordeck
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D.MatthewStuart 10
Screwconnections,suchasBuildexTEKSscrews,maybeeitherselfdrillingortheselftapping
typethat
requires
apredrilled
hole
prior
to
installation.
The
most
commonly
used
screw
size
to
attachdecktobarjoistsorstructuralsteelareNo.12andNo.14. SmallerNo.8andNo.10
screwsaremorecommonlyusedforsidelapconnections.
ScrewConnections:
enconnec ng nme a ec o c ers ruc ura mem erssuc as ar o s sor eam
flanges,littledifferenceexistsintheshearstrengthforNo.12andNo.14screws. Thisisbecause
thefailuremodeofthedecktendstoinvolvearolluporcrushingofthedeckonthebearing
sideofthescrewwithfracturelinessubsequentlydevelopinginthedecking.
Forstitchconnectionsbetweensheets(atthesidelaps)adifferenttypeoffailureoccurs. The
screw,whennotanchoredintoathickermorerigidelement,tipsovermoreeasilyandismore
flexible. Althoughtheresultingstrengthmaybelimitedbybearingandtearinginthemetaldeck,
withsufficientrotationofthesidelap,acombinedtearingandpulloutfailuremayalsooccur.
TheSDIscrewstudiesindicatethatstitchscrewshearcapacityisindependentoftheyield
strengthof
steel
deck
that
is
commonly
used
for
flexible
diaphragms.
The
most
common
prematurefailureproblemwithsidelapattachmentsoccurswhenthescrewisallowedtothread
upontheuppersheetbeforebecomingfullyengagedinthelower,thuscreatingmajorgaps
betweentheadjacentunits. Suchimproperlyinstalledscrewsshouldberemovedandredriven
whileforcingtheoverlappingsheetstoremainincontact.
Metaldeck
to
structural
support
connections
can
also
be
made
by
using
nail
like
fasteners,
driven
eitherpneumaticallyorwithpowderactuatedtools. Suchfastenersaremadefromhardened
steelandusuallyhaveaheattreatedshafttoenhanceanchorage. Theshaft,whichmayhavea
slighttaper,canbefittedwithwashers,concavetothedrivingdirectiontoabsorbthefinaldriving
energyandclampthesheetinposition.
PowderDrivenFasteners:
Sincetherearenopredrilledholesrequiredwiththesetypesofconnectors,theinstallation
processdisplacesmaterialandleavesitlockedunderthewasher,resultinginverystiff
connections. Thedrivingdepthiscontrolledbythepowerselectionforthetoolused. Fastener
strengthisinfluencedbythedrivingdepth.TestsconductedbyWestVirginiaUniversityalso
indicatethatthethicknessoftheunderlyingmaterialhasnoeffectonshearstrengthsincethe
thinnersheetmaterialwillcontrolperformance.
Adrivenfastenershouldbeinstalledsotheheadprojectsoutward,fromtheattachedpart,to
m sse y emanu ac urer. eax so e as enermus eperpen cu ar o es ee pr or
todriving,
usually
within
plus
or
minus
10
degrees
of
vertical.
In
addition,
it
is
recommended
that
edgeandendfastenershaveaminimumsidelapedgedistanceof3/8inchandaminimumend
andendlapdistanceof1inch.
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D.MatthewStuart 11
Incertainpanels,oneedgehasanupstandingsingleelement,whiletheoppositesidehasa
foldedover
double
element.
As
panels
are
placed,
the
single
element
is
inserted
into
the
double
element,producinganupstandingsidelapthatcanbebuttonpunchedtoprovideinterlockingof
thetwoadjacentsheets.
ButtonPunchedSidelaps:
an opera e punc ng oo ormsa ree ayernes o sma cones a s e nas g y
loosestate,becauseofelasticrebound,astheformingforceisremoved.Manualbuttonpunched
sidelapsdostabilizepaneledgesbutcontributelittlediaphragmstrengthastheycanvarygreatly
inshapeandeffectiveness. Thequalityofhandinstalledbuttonpunchesisdifficulttomaintain.
Theattachmentdependsonthecareandtheenergyusedbytheinstallerandthetoolused. A
safetyfactorofthreeisrecommended.
Atconditionswherejoistsspanperpendiculartoandterminateatashearwall,theedge
mostdiaphragm
panel
may
not
be
in
direct
contact
with
the
wall.
At
these
conditions
the
requiredperimeterdiaphragmconnectionscanbeaccomplishedbyinstallingablockspacer
orcollectoralongthetopofthewallbetweenthejoiststhatmatchesthedepthofthe
bearingassembly. Acontinuousangleattacheddirectlytothetopofandperpendicularto
thejoistmayalsobeusedaslongasthebearingassemblyofthejoistsiscapableof
Miscellaneous:
.
AllowableloadtablesareavailablefromtheSDIandanumberofdifferentdeck
manufacturers. Loadtablesaretypicallycategorizedbythemeansofconnection,thepanel
widthandthickness,spanlengths,thefasteningpatternandthetypeoffastenerandsidelab
connector.
Thestiffnessofadiaphragmisadirectindicationofhowsusceptiblethedeckistodistortions
undertheinfluenceofinplaneshearforces. Theneedtoknowthemagnitudeofmovement
isparticularlyimportantwhenassessingthetransferofforces,throughadiaphragm,
betweenadjacentframesorshearwalls. Inaddition,thehorizontaldeflectionofthe
diaphragmcanhaveanimpactontheswayofexteriorcladdingmembers,suchasprecastor
tiltuppanels,inadditionaltothelocalizedflexuraldeflectionofthesameasaresultofwind
loadsperpendicular
to
the
span
of
the
diaphragm.
Steeldeckdiaphragmsmaybereinforcedwithoverlaymentssuchas insulatingconcrete,
structuralconcrete,orbydirectlyattachingflatpanelssuchasplywoodtoproduceaflat
surface. Thesupplementalmaterialprovidesadditionalpathsthroughwhichshearforces
maytraversethediaphragm.
Itisalsopossibletoinstallhorizontaldiagonalsteelbracingorstrapsbeneaththedeckin
ordertosupplementorsupplanttheshearcapacityofthedeck.
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D.MatthewStuart 12
Thefollowingdesignexampleisforasimpleonestoryrectangularbuildingexposedtoatotalwindwardandleewardpressureof35PSF. Itshouldbenotedthatinthisexamplethewindwardandleeward
pressurereactions
at
the
top
of
the
cladding
and
along
the
edge
of
the
diaphragm
are
shown
as
acombinedlineloadof245PLF.
Asindicatedintheexample,thediaphragmreactionof16.54kipsisdividedbythelengthoftheendwalltoarriveattheunitcollectordiaphragmshearforceof367.5PLF. Atthesametimeashear
DesignExample
fastenerzonesasrequiredtosatisfythevaryingmagnitudesofplanarshearresistance resultingfromtheimposedloads.
AnAllowableDiaphragmShearStrengthTable(availablefrommostoftheroofdeckmanufacturesaswellastheSDI)isthenreferredtoinordertoassessthemostappropriatefastenerspacingfortheappliedloads.Inthisexample,36inchwide,1inch,TypeB,22Gagemetalroofdeckusing5/8inchpuddleweldsand#10TEKscrewsidelapfastenershavebeenpreselectedasthetypeofdeckandfastenerstobeused.ItshouldbenotedthatthecapacitiesintheShearStrengthTablealreadyincludea1/3increaseforwind.
Forajoistspacingof6feetandapreselectedweldpatternof4uniformlyspacedpuddleweldsacrossthe36inchwidepanel,ashearcapacityof374PLFcanbeobtainedusing8uniformlyspacedsidelapscrewsalongthe6feetspanofthedeck.Thisvalueisgreaterthanthe367.5PLFendshearreactioncalculatedintheexample.
Nextatanarbitrarylocationapproximatelyofthediaphragmspanfromtheendsupportwallisanalyzedinordertoallowforareductioninthenumberoffastenersoverthemiddlehalfoftheroof.Theequivalentuniformshearloadatthislocationonthediaphragmis193PLF.ReferringagaintotheAllowableShearStrengthTableindicatesthatusingaweldpatternof3uniformlyspacedpuddleweldsacrossthe36inchwidepanel,ashearcapacityof193PLFcanbeobtainedusing2uniformlyspacedsidelapscrewsalongthe6feetspanofthedeck.
Detailingoftheconnectionofthemetalroofdecktotheendshearwallsisnotcoveredinthisexample,howevertypicallyacontinuousembeddedsteelplateinthetopofthewallwouldbeprovidedinorderforthedecktobesecuredtothetopofthewall.
Shearinthedeckdiaphragmisalsocheckedforwindloadsagainsttheshortsideofthebuildinginwhichthediaphragmonlyhastospan45feetbetweenthe135feetlongCMUshearwalls.Thecalculatedmaximumunitcollectordiaphragmshearforceof41PLFislessthantheminimum193PLFshearcapacityofthedeckintheotherorthogonaldirection,thereforethefastenerpatterndevelopedinthefirstpartoftheexampleisadequateforwindloadsintheoppositedirection.However,asthe
joistbearingassemblyseparatesthetopedgeofthedeckfromtheCMUshearwallitisnecessaryforthecollectorforcetobetransmittedfromthediaphragmtothetopofthewallthroughthejoistbearingassemblies.Amaximumrolloverforceof246poundsiscalculated ateachjoist,whichislessthanthetypicalindustrystandardjoistbearingassemblycapacityof1,650pounds,thereforenocollectorblockisrequiredbetweeneachjoisttotransfertheshearforcestothetopofthewall.
Inorderforthediaphragmtofunctionproperly,inadditiontoananalysisoftheplanarshearforces,itisnecessarytoprovidechordmembersalongtheextremeedgesofthedecktoprovideresistancetotheextremeflexuraltensionandcompressioncomponentsofthedeepbeamdiaphragmanalogy. Forthisexamplethemaximumchordforceiscalculatedasfollows:
Mmax=((245PLF)*(135FT)2)/8=558.14KipFeet;ChordForce=558.14KF/45FT=12.4Kips
Assumingthat
compression
controls,
the
maximum
allowable
compressive
stress
of
10.14
ksi
is
calculatedfora36ksi,continuousL3x3xbracedat6feetoncenterwereitisconnectedtothetopofthejoistbearingassemblies.Theactualcalculated compressivestressof8.61ksiintheL3x3islessthantheallowable.Itisimportanttounderstandthatthischordmembermustbeprovidedalongboth135feetlongedgesofthedeckwithbuttweldsprovidedatalljointsoftheL3x3.Thechordmemberforwindforcesintheoppositedirectionisprovidedbythecontinuousembeddedsteelplatelocatedinthetopofthe45feetlongendshearwallsasdescribedinthepreviousslide.
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D.MatthewStuart 13
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D.MatthewStuart 14
Source:SDI
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D.MatthewStuart 15
Thefollowingareillustrationsofroofdeckattachmentdiagramsandschedulesfromanexample
project.Thisinformationshouldbeprovidedonallprojectsinordertoprovideclearinstructions
tothedeckinstallerconcerningtherequiredfastenertype,spacingandextent.
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