1、,4C2 + .z-8910u?u141415161718191920212224252627282930.3132. . . - .- - -z .- C? . , . . _ . .-Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-t !.STIFFENED-PANELBOXCONSTRUCTK)N.StabilizationofCompressionCuVer.GeneralInstability.Rotational+tiffnessCon
2、siderationsiiLateral-PressureEffects.Efluenceofspars OptimumConstruction.AH?ENDIXA -AEPLICATJDNSECTK)Ncrippling StragthAngle-typeelementsT-typeelementsShortrivetedpels. .ColumuStrengthofPsnelsI?oxconstructionREFmmmsTABLESFIGURES.a71a71a15a71a15a15. .*.*a71 a11a71a71a71a159a71a71.9.a71.a71a71a71.9a71
3、a719a719a71.9.a719.a71a71a71a71.a71.a71.a71a15a71a15a719a71a71.a71a71a71.9a71a71a71a7199999.a7199a71a71a71a71a71a71a71a71a71a71a71a15a71a719a71a71a71a7198a71a71a71a719a71a71a719a719a71a71a71a71a71.a71G9a71a719a71a71a71a71.a71a71sa71a71a71a719*a71 9a71 99*a71 *a71 *a71 99999a71 ma71 ma71 *a71 .a71 ma
4、71 ma71 9a71 9a719a71.a71a71a71a71a719a71a719a71a71a718a71a719a71a71a71a71a71a71.a719a71a71a718a718w89a71a7199a71b8a71898Ga71333436373839404141414142E434753. . . -. .-. Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-.NATIONALADVISORYCOMMITTEEFORAERO
5、NAUTICS.TECHNICALNWE 3785HANDEOOKOFSTRUCTURALSTABILITYPARTV -coMl?REssrvEmSTRENGTHOFlforstiffenedpanel,areaofstiffenerplusareaof .sheetcorrespondingtostiffenerspac,ing,sqin.flexuralrigidityperunitwidth,in-lb.-. - -.-.-. ._ _. - ._. _ _-. -. .-. Provided by IHSNot for ResaleNo reproduction or network
6、ing permitted without license from IHS-,-,-.a71 bbebeiccddeEEEs%efgK.kJ%LLIm.NPqRspacing,h.effectivewidth,h.effectivewidthofskincorrespondingto Ui fromequation(10)shearrigidityperunitwidth,in-lbnuniberofcornersrivetdismeter,in.effectiverivetdismeter,in.mdulusofelasticity,psi .effectivemodulus,psisec
7、antmodulus,psitangentmodulus,psi -ena-fixitycoefficienteffectiverivetoffset,in.nmberofcutsplusflsngesdeflectionalspringconstant,lb/in.bucklingcoefficientcoefficientinwrinklingmcdecolumnlengthorribspacing,in.effectivecolumnlength,Li=L/elp,mslope10SdiIlgper unitwidth,lb/in.rivetpitch,in.a71lateralpres
8、sure,psiradius,in.3. . . _ _ .-. _ .-.Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-. .NACATN3785rivetstrength,ksithiclmess,in.effectivethiclmess,in.panelwidthorsparspacing,in.cripplingcoefficientpanelefficiencycoefficientcripplingcoefficientbasedo
9、ncornerscripplingcoefficientbasedonctisplusflangesplasticity-reductionfactorforplatescladdingreductionfactmrotationalspringconstant,torqueperunitrotationPoissonssratioradiusofation,in.bucklingstress,ksicompressiveyieldstrength,ksiEulercolumnstress,ksititerrivetbuckHngstress,ksiproportional-limitstre
10、ngth,ksipanelstrengthat L/p=20,ksi .effectivestrength,psieffectivepanelstrength,ksicompressiveyieldstrengthh cornerofformedsection,ksicripplhgstrength,ksistrengthofashortrivetedpanel,ksi. .). . . .- - - - - -Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IH
11、S-,-,-NACA 3785 . 5c%panelstrengthunderlateralpressure,ksi.% strengthofrivetedpanelinwrhkl?mcde,ksiT plasticity-reductionfactor7 pl.astici-reductionfactorforoptimumstiffenedpanelsSubscripts:o optimumr rivetorribs skinorsheetSt Stiffenerw stiffenerwebav averageCRIPF!GINGSTRENGTHOFPANE.GSWITHIUIMEDSTE
12、FENERS4. .Considerationsofthecompressivestrengthofstiffenedpanelscanbeconvenientlydividedintoaroximatelythreeregions:Longpanelswhichbehsveessentiallyascolumns,shortpanelswhicharesubjecttocrippling,andpanelsofintermediatelength.Thelattergenerallyfailasaresultofccmbinedcripplingandcolumnbehaviorwithto
13、rsionaleffectsoftenevideut.b thepresentsection,thecripplingstrengthofstiffenedpanelswithformelstiffenersistreated.Theskinandstiffenerse assumedtobefastenedtogetherinsuchamannerthatthepanelcanbeconsideredtobemonolithicfrcmthestandpointofcripplingstrength.Rivetingrequirementstoobtainmonolithicbehavior
14、areconsideredinscmedetailinthesectionentitled“StrengthofShortRivetedPanels.”ThemethodofcripplinganalysisusedforfomedstiffenedpanelsisanextensionofthegeneralizedcripplinganalysispresentedinPartIVofthisHandbook(ref.1). Panelsutilizingextrudedstringersofcomplexcrosssection,suchasY-shapes,me consideredi
15、nthesection“CripplingStrengthofPanelsWithExtrudedStringers.4. . .- .- - - . - -.-.Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-6 NACATN3785GeneralizedCrippling-AnalysisReview . .Inreference1,thecrippltngstrengthofavarietyoffed sec-tionswiththreeor
16、morecornerswasanalyzed.Itwasshownthatexcel-lentcorrelationwasobtatiedwiththefollowingfamula:Gf +(71/20.85ct2=fic Ucycy (1)Thecoefficientf3=dependedscxnewhatintheccmnersoftheformedsection.minumallqyfonn isheightofsidewebs)betweenO.6and1.2andarangeofWPS valuesof1.25,1.00,0.63,and0.39.Foratypicalhat-st
17、iffened-.panelareaelement,thefacta c=6 inequation(1),.consistingof4 cornersfcmthehatplus2 rivetlines._ - -. _Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-WCA m 37/35 9The test dataforeachvalueof /ts are,- arebasedonthencmdnalvaluesofthegecmetricsh
18、owninfigure5andparametersandthecompressiveyieldstragthofU ksi.mfildatac-8 beplacedone&tion(1)that&autionbeexercisedinusingthisforhat-stiffenedpanelsandequationforpanelswith%/% =0.39.C!RIEPLINGSTRENGTHOFPANELSWITHEXTRUDEDSTIFFENERS. M attemptingtoextendthegeneralizecrippling-strengthanalysistopanelsw
19、ithextrudedstiffeners,inthemamnerdemonstratedinthesection“CripplingStrengthofPanelsWithFarmedStiffeners,”snessen-tialdifficultyIS encountered.ThisdtificulcentersaroundtheselectionofthenumberofcornersforanextrudedsectioninwhichseveralfI.angesorwebsmaymeetata ccmmmijuncttie.Also,asshowninreference1,th
20、ebehaviorofthejunctionofadjacentweborflsngeelementshasasignificantinfluenceonthecripplingstrength.Forexample,thejunctionoftheflangeelenentsofansngleissubjecttodistortionafterbuckling.Ontheoerhand,theflangeelementsofacruciformsectionarehorizontallyopposedsothatthejunctionoftheflangeelementsremainsess
21、entiallystraight.Forthisreaaon,itwasfoundthatthecripplingstrengthperflangeofthecruciformwhichisessentiallyccmposedoftwoanglesisgreaterthanthecrippklngstrengthperflangeoftheanglealone.h ordertocharacterizethisclifferenceinbehaviorthefollpwingnomenclaturehasbeenadupted:“Angle-type”isusedtorefertotwoad
22、jacentelematswhichmeetata junction,whereas“T-type”refersto. . . . . . -. . .Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-10threetheseposedNACATN3785“.ormoreadjacentelementsmeetingatacommonjuncture.withdefinitionsitcanbeobservedthatallformedsection
23、sarecom-ofangle-typeelements,whereasextrudedsectionsmsybecmposed .ofsngle-and/orT-me elem&nts. Thus,forextrudedsectionscomposedofonlysngle+ypeelements,thegen=elized-crippling-analysisprocedureoftheprecedingsectionmaybeused.Insuchcases,thereisnomajorclifferencebetweencom-parableextrudedandformedsecti
24、ons.Theminordifferencesincludefilletradiuseffectsfortheextrusionandraisedyieldcornereffectsfortheformedsection.Anydifferencesinyieldsti-h exeaccountedfordirectlyinthecripplhg-strmgthformula.Forextrudedsectionscmposedwhollyor partiallyofT-typeelements,thecornerconceptinequation(1)isnowreplacedbyanewc
25、onceptwhichinvolvescuttingthesectionintoaseriesofflanges.Ihorderto$urMfythis.methodofsnalysis,testdataonV-grooveplates,extrudedengles,. squaretubes,T-,H.,andcruciformsectionsarereviewed.TheanalysisoisthenextendedtostiffenedpanelswithextrudedY stiffeners.Finally,intheinterestofasinglemethodofanalysis
26、foralltypesofmulti-cornersectionssmds,tiffen,panels,thedataoftheprecedhgsectiononZ-andhat-stiffenedpsnelsarereviewedintermsoftheanalysisofthissection.Angleand T+pe ElementsIhref=ence1,equation(1)wasusedtocorrelatetestdataonsqyaresadrectsnguhrtubes.Itwasfouudthatavalueof Pc=1.42for c=4 gaveexcellentc
27、orrelationwiththeavailabletestdataonfourdifferentaluninumOyS .I$ycuttingthetubeintoaseriesoffouranglesasshowninfig-ure6andcorrelatingthetestdataaccordhgtotheparameterg whichisthetotalnmhr ofcutsplusflanges,thefollowingrelationfaangle-typeelementsisobtained:. 011/20.85%=pg$#-=Cy CyByuseofequation(1),
28、itisevidentthatg = Pc(c/g)o”85(2)(3). - . _ _Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-NACATN3785Thus,forthe11extrudedtubesBg=1.42(4/Q0”85=0.558 (4)Thecorrelationaccordingtoequations(2)and.(4)fortheextruded-tubetestdataofreference1isshowninfigu
29、reT(a)bythelinedesignatedangletype.Alsoshownwiththislinearesometestdatafromrefer-ence1onextrudedaugesfm whichg=2 andonV-grouveplatesforwhichg=3. Goodcorrelationisobtainedwiththesedataalthoughtheextruded-angledataaretoofewinnumbertop-t definiteconclusiaustobedrawn.TheanalysisforT-typeextrusionsisbase
30、donthefollowingrela-tionestablishedinreference1frcmtestdataoncruciformextrusions:af ()2 1/20.40=Pgacy (5)ForthecrucifomnPg=0.670and-g=4 asshowninfigure6. TMRrelationshipalsocorrelateswell.withsanelimitedtestdataonT-extrusionsasshowninfigurey(a).RatherextensivetestdataonH-extrusionsoffouralminumalloy
31、sandonemagnesiumalloyareavailabletotestfurthertheg-correlationscheme.h reference1,theH-adzrusionwastreatedasaspecialtype.oftwo-cornerelementandthegeneralizedcripplinganalysiswasnotappliedtothissection.ASshowninfigure6, g=7 foranH-extrusion.ThetestdatacorrelatedaccordtigtotheparsmeterA/gt2axeillustra
32、tedinfig-urey(b).Itcanbeobservedthatsatisfactorycorrelationwitheqya-tion(5)isobtainedbyutilizingthe g valueforthecruciformfor5tJ 3/4.(6).- - . . _ - . _ -. Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,- . .-12 NACATN3785FYomtheresultspresentedinfig
33、ure7,itappearsthattheg-correlationschemeforangle-sndT-typeextrusionspermitsaninte-gratedapprosch“tothecrippling-strengthanalysisofextmudedelements. -Y-stiffenedPsnelsInanslyzingthecripplingstrengthofmonolithicstiffenedpanelsutilizingextrudedY-stringers,certainadditionalconsiderationsareencounteredwh
34、ichhavenotarismpreviously.Theseinclude:.(1)Themethodofdeterminhgg forastiffenedpanel.(2) Thethicknessesofthevariousflangesoftheextrusionmaynotbeconstant.(3)Thecompressiveyieldstrengthoftheextrudedstiffenermaybesignificautilydiffentfromthatofthesheet.Themethodofdeterminingg fm aY-stiffenedpanelisillu
35、stratedinfigure8. Sincethetestdataareforpanelstestedwithsixstiff-eners,itisdesirabletodetemnheanaveragevalueof g foratypicalareaelementeqpaltothestiffenerspacing.Itcanbenotedfrcmfig-ure8thatthecutsmidwaybetweenstiffenersarecreditedtotheelementtotheleftofthecut.Thusthelastelementontherighthasavalue .
36、of g ofoneunitlessthantheotherelements.Thus,theaveragevalueof g=18.83fortheY-sttifenedpanelaccouutsforthisfact.FortheparticularY-extrusimusedinreference7,thethicknessofthehorizontallyopposedflsngesatthetopofthesectionisgreaterthanthatoftheotherelementsinthecrosssection,asshowninfig-ure8. Conequently
37、,indeterminingtheeffectivethicknessofthea71stiffenert+ foruseinthegeneralizcripplingrelation,thefollowlngmethodofweightingwasused:(7)b equation(7),bi and ti refertothelengthendthickness,respec-tively,ofthecross-sectimalelements.Similarly,forthe7075-T6alunhum-alloypanels,thecompressiveyieldstrengthof
38、thestiffener(Ucyw=78ki) was Signific=tl.yhigher .thanthatofthesheet(ucys=67ksi). Thefollowingweightingprocedurewasused: ,. . -. . . -. . . .Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-NACATN3785where istheeffectivethiclmessofthestiffenedAsaconseq
39、uenceoftheseweight”&procedures,cripplingrelationfortheY-stiffenedpanelhastheu(8)panel.thegeneralizedform(9)Thetestdataofreference7 for2024+3and7075-%aluminum-alloypanelswerecorrelatedaccordingtotheparametersofequation(9)forthreedifferent/ts ratios.Ihallcasesncminaldimensionswereused.SincetheYextrusi
40、onisccmposedofbothsngle-andT-typeelements,thevalueof m ineqyation(9)isnotevidentapriori.Asshowninfigure9,satisfactorycorrelationisobtainedbyconsideringtheY-extrusiontobeanangle-meelementsothatm =0.85.The gvaluesvarysomewhatwiththeparameter/tsasgivenintable3.!Ihisvariationwaspreviouslyobservedfortheh
41、at-stiffenedpsnels.PanelsWithFormedStiffenersInviewofthedestiabiliofhavingonemethalofanalysisforbothformedandextrudedsections,ifpossible,theresultsofthesection“CripplingStrengthofPanelsWithFormedStiffeaers”onpanelswithfomedZandhatstiffenersarereviewed.Thesepqnelswere-z accOIdingtoequation(1)fOrmulti
42、cornerelementsasdemon-stratedinreference1. useofeqyation(3),thec-correlationmethodcanbeconvertedtotheg-correlationmethod.Theresultsarelistedintable4.Similarly,byuseoffigure8,thevaluesof g canbeobtainedforthestiffenedpanelsandthe PC valuesconvertedto g valuesbyuseofequation(3).Suchresultsaregivmintab
43、le4.All pg valuesaresmmarizedasafunctionof %Jts infigure10.Itcanbeobservedthatat /ts=1,all Pg valuesareh gocdagree-ment.Furthermore,thevariationof g with/ts forthehat-andY-s”tiffenedpanelsissubstantiallythesame.-. - .z . .Provided by IHSNot for ResaleNo reproduction or networking permitted without l
44、icense from IHS-,-,-14 MAOATM3785STRENGTHOFSHORTRIVETEDP-Illtheprecedingsections,thecripplingstrengthofmonolithicpanelswasconsidered.Suchpanelsincludeintegralformsofconstruc-tionsuchasmachined,extruded,fygedorrolled,andgenerallybondedorsesmwel,dedp=els. lhrivetorspotweldedpanels,thediscretelocations
45、oftheattachmentscanpermittheoccurrenceofadditionalbucklingandfailuremodeswhichreducethecripplingorcolumnstrengthofthepanelbelowthatofthecorrespondingmonolithicpanelSpotWeldsgenerallycanbeplacedsufficientlyclosetogethersothatthemonolithicstrengthcanbereadilyachievedinspotweldedpenels.Forpanelswithriv
46、etedattachments,however,carefuldesignisoftenreqxlredtoachievemonolithicstrengthlevels,particularlyinshortpanelsofheavy-sheetandlight-strerconstruction.Insuchcases,closelyspacedlarge-diemetrivetsareoftenreq.ed.Theadditionalbucldingorfailuremodesthatcamdestroythemono-lithicbehaviorofrivetedpanelsaxeti
47、terrivetbuckling,wrinklhgorforcedcrippling,andrivetfailure.Inthepresentsection,thebehaviorofstiffenedpanelssubjettedtotheseadditionalbucklingandfailmemodesisreviewedandavailabletheoriesarepresented.Designcriteriaaregiventhatpresentarationalapproachtotheachievementofmono-lithicstrengthlevelsforrivetedpanels.AdditimalFailureModes.Theinterrivetmodehml.vesbuckl oftheskinofthesttffenedpanelasawidecolwnnuponessentiddyundistort$istringerssothatseparationoccursbetweentheskinendstringers.Thewidthofthewidecolumnisgenerallyequaltothatofthepanelendthelengthcorrespondsto
