Joseph1 , Amalu Grace Lal2
1) SingleWeb
2) MultiWeb
Neethu
Coldformedsteelismorepopularthanhotrolledsteel duetoitsfasterconstruction,lightweightetc.Useofthese CFSsteelcanleadtomaterialsavingsbecauseofhavinghigh strengthtoweightratio.NowadaystheseCFSsectioncanbe used in purlins, floor joists, prefabrication floor and wall panels, trusses and in steel racks. The CFS sections are usuallydesignedasslendermembersbecauseofhavinghigh widthtothicknessratio.Whilesubjectingtoreactionforces or loading forces the section may get failed due to their limitedthickness.Thefailuresincludewebcripplingfailure and bending of the sections. Among these web crippling failuresarecommoninwhichalocalizedfailureoccurswhen thesectionissubjectedtoconcentratedloads.
Abstract Cold formed steel constructions are common in nowadays due to its benefits including light weight, faster construction and high strength. Major cold formed steel sections used construction activities include channel sections, perforated channel sections, SupaCee sections, Lite steel beam sections etc. However due to the limited thickness of CFS section, they are vulnerable to web crippling. Web crippling is a localized failure occurs when concentrated loads are acting on the section. This paper aims to provide a review in detail about the web crippling capacity analysis for different CFS channel sections along with experimental and FEM modeling of the sections and also describes the major parameters which affect the web crippling capacity of sections.
1. INTRODUCTION
4) IOF(InteriorTwoFlangeLoading).
Fig -2:WebCripplingFailure
Dept. of
DependingSectionsonthe load cases and failure locations web cripplingfailureofcoldformedsectionswithasinglewebis classifiedintofourtypes
Review on Web Crippling Capacity of Cold Formed Steel Sections
1) ETF(EndTwoFlange),
2) ITF(InteriorTwoFlangeLoading), 3) EOF(EndOneFlange)and
Janarthananetal.[8] statedthatiffailureoccurswithin1.5 d1( where d1 is the depth of flat portion of web element) fromthespecimenedgethentheloadcaseistermedasend loadingandiffailureoccursatadistancemorethan1.5d1 then it is termed as interior loading case Web crippling strengthforasectionwithlowerthicknessislowerforETF loadcasesthanotherthreecases.Webcripplingcapacityof section mainly depends on factors including shear area underbearingplate,interlaminarshearstrengthandshear stressdistribution.
3) I
Engineering, St.Joseph’s College of Engineering& Technology, Kerala, India 2Student, Dept. of Civil Engineering, St.Joseph’s College of Engineering& Technology, Kerala, India ***
Key Words ColdFormedSteel,WebCripplingCapacity
Fig -1:ColdFormedSteelStructures
1Assistant Professor, Civil
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Gatheeshkaretal.[5]fromhisstudydefinewebcrippling isalocalizedbearingfailureoccurswhencoldformedsteel beams are subjected to concentrated loads. Three main classificationofcoldformedsteelsectionincludes:
:
2. WEB CRIPPLING
4.2 Perforated Channel Sections
4. SECTIONS CONSIDERED
Perforated channel sections are provided with the web opening. Usually these openings are important in CFS sectionstoprovideservicelinesforwatersupplysystems and air conditioning ducts etc Usually two types of web holesareprovidedinthechannelsection
4.1 Channel Sections
The effect of holes in the web crippling capacity were initiatedbyYuandDavisbystudyingwebcripplingbehavior of lipped channel sections with square and circular holes under IOF case In order to know the influence of web openingswithdifferentshapes,Sivakumaran andSielonka
Fig -4:ChannelSections
2)offsetwebholes
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1)centredbeneathwebholes
Various investigations on web crippling capacity of channel sections were conducted by scholars. Channel sectionsarecommonlyusedinvariousconstructionactivities today. Channel sections are further classified to lipped capacity.influenceexpressionflangefastenedcripplingthickness,1.5mmtestCFSJanarthananexperimentbeamswebHeigentuduwachannelsectionandunlippedchannelsection.Macdonaldand[15]conductedseveralinvestigationsonthecripplingcapacityofcoldformedsteellippedchannelunderallfourcasesandcametotheconclusionthatresultsshowsgoodagreementwithFEAresults.etal.[8]investigatethewebcripplingfailuresinunlippedchannelsectionsbyconductingwebcripplingontheunlippedchannelsectionswiththicknessvaryingto6mmandABACUSwasusedforFEMmodeling.Healsostudiedtheeffectofparameterslikesectioninsidebentradiusadbearinglengthinwebcapacity.Alsanataetal[4]studiedthebehaviorofaluminiumlippedchannelsectionssubjectedtooneloadingconditionsandintroducemodifieddesigngiveninAS/NSSbytakenintoaccounttheofheightandthicknessofwebinthewebcrippling
min =3(d1 +bearinglength)
Theyarenewinnovationsinthechannelsections.Theweb partofthesectionsareusuallystiffenedandprovidedwith lipscurvedandribbedweb.Thisribbedwebelementmake the SupaCee sections more economical than traditional channelsectionswhicharebothlippedandunlipped.Usually stiffenersareprovidedalongwiththeribbedweb.SupaCee sectionswhencomparedwithlippedandunlipped sections, haveenhancedflexuralcapacities.Thischannelsectionsare mainly provided with four web stiffeners which are longitudinallyarranged.
foraccuratetakentheoflengthFor1.3channelplateabplate,dynamicnonlinearstaticprocedureiscomplicatedbutquasistaticexplicitanalysisismoreeasyandaccurate.Ellilarasietal.[7]statedthatforthedesignofbearingnormallyusehighstrengthsteelwiththethicknessout25mm.Twotypesoflengthareadoptedforbearing1)fullflangewidthofchannelsection2)Halfwidthofsection.Thenominalthicknessshouldbevariedfromto2.0mm.ITFloadcase,bearingplateswereprovidedinthemidofspecimenandforETFtheywereprovidedintheendspecimen.Lengthofthespecimenhasagreatinfluenceinwebcripplingbehaviorofsections.Usuallythelengthisastwicetheheightofthechannelsection.Butforresults,minimumspecimenlengthcanbeprovideddifferentloadcasesbasedontheequationsbelow:ForEOFandIOFloadcaseL
Keerthan et al. [13] developed direct strength method equations for Lite Steel beams after conducting 28 web cripplingstrengthtestsundertwoflangeloadcases.Steauet al.[12]then extend theaboveanalysisbyinvestigaterivet fastened rectangular hollow flange channel beams web cripplingbehaviorundertwoflangeloadbyconducting52 webcrippling
ForETFloadcaseLmin =3d1
sizes play an important role in determining accuracy of results. Fine meshes are usually adopted in cornerregionsofthesectionduetotransferofstressfrom
From the studies conducted by Uzzaman et al. [14] on lipped channel sections under both EOF and IOF cases, provided equation for minimum specimen length for perforatedsection3d+lbforITFand1.5d+lbforETFloadcase wheredistheoveralldepthofsectionandlb isthebearing length.Mesh
Whered1=clearwebheight
4.3 Hollow Flange Section or Lite Steel Beam
5. FEM MODELLING AND ANALYSIS
[16] conducted experiment of lipped channel with unfastenedsupport.
4.4 SupaCee Sections
Fig 6:SupaCeeSections
Fig 5:HollowFlangeSections[3]
et al.[3] conducted both experimental andnumericalanalysistoknowtheeffectofcircularholeson thewebcripplingcapacityofcoldformedLitesteelbeams underITFloadcaseandhestudiedtheeffectofparameters including bearing length, yield strength and web opening diameter.
ForITFloadcaseLmin =5d1
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Wheredisthedepthofthesection,bfistheflangewidth, df is the flange depth, d1 is the clear web height ,t is the thicknessandriistheinsidebentradius
Due to complexities in plate imperfection, inelastic behaviorofwebelement,non uniformstressdistributionit is not advisable to develop the web crippling capacity equation theoretically. As an alternative, finite element proceduresareusedbyscholarsnowadaysinordertofind the web crippling capacity. Nonlinear static, quasi static dynamic implicit and quasi static dynamic explicit are the FEM analysiscommonlyused nowadays. From the studies conductedbyNatarioetal.[10,11]cametotheconclusion that
Hareindirasarmatests.
theflangetowebportionofchannelsections.Inperforated channelsections,finermeshesareprovidedaroundtheweb openingareas.Displacementcontrolmethodisusedtoapply verticalloadtothesections.Atthenodesofthebearingplate, imposeddisplacementisapplied.
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Fig 10:ETFloadCase
Fig 11:WebCripplingTestUp[15]
Uzzamanetal.[14]conductedexperimentalstudiesfor CFSchannelsectionunderETFloadingcase.Hingesupports areoftenprovidedbyusing2halfrounds.Bearingplateis provided for applying load which is act across full flange width. In order to facilitate fastened condition flanges are boltedtothebearingplate.Janarthananetal.[9]conducted web crippling test in CFS unlipped channel sections for comparingthetestresultswithnumericalresults.Boxbeam arrangementisprovidedfortestspecimensandtheflanges are connected at quarter points by angles. Displacement controlmethodisusedforapplyingmidspanloadatarateof 1mm/min.
6. EXPERIMENTAL STUDIES
Fig -9:ITFloadCase
Fig 7:FEMModelingofChannelSectionofETFloadcase [3]
Fig 8:SchematicViewofTestSetUp
Hareindirisarmaetal.[3]fortheirmodelingoflitesteel beamsectiontheyusuallyusedmeshsize of3x3mm2 inthe topoftheflangesand5x5mm2 meshsizeisappliedonthe bearingplateortheloadingplate.Forassigningthesupport conditionstothebearingplateunderITFloadcases,hemake X axis rotation is free and the translations and rotations aboutalltheotheraxisasfixed.Forsupportingplatehekept Xaxisrotationisfreeandallmovementsabouttheotheraxis isfixed Janarthananetal.[8]fromthe modelingofunlipped channelsection assignedgeometricimperfectionmagnitude asd/150, butgenerallytakes0.5twtotwastheimperfection magnitudewheretw isthesectionthickness.Healsotested thedevelopedFEmodelswithdifferentcoefficientsincluding 0.1,0.2,0.4and0.8andconcludedthatfrictioncoefficientof 0.8isusedforsteel steelinterfacesandfrictioncoefficientof 0.1forzinccoating.Theeffectofgeometricimperfectionon webcripplingcapacityisverylessi.e2%forEOFcaseand 1.23%forIOFcase
withincreaseinwebslendernessratiowebcripplingcapacity decrease.
Graph 3:EffectofSlendernessratioinWebCrippling Capacity[8]
Graph 1:EffectofInsideBentRadiusonWebCrippling Capacity[8]
Graph 2:EffectofBearingLengthinWebCrippling Capacity[8]
7. FACTORS AFFECTINGWEB CRIPPLING CAPACITY
Case1:Flangesareunfastenedtosupport Rp=0.95 0.49(a/h)+0.17(x/h)<1
Janarthanan etal. [8] introduce the effect of inside bent radiusonwebcripplingcapacitybyconductingexperimentin unlippedchannelsectionunderbothEOFandIOFcase.Inhis studytheinsidebentradiusoftheunlippedchannelsectionis varied from 2 to 10 mm and stated that with inside bent radiusincreasethereisadecreaseinwebcripplingcapacity reductionrateandconcludedthatthereisareductioninweb cripplingcapacitylinearlywiththeincreasingratioofinside bentradiustothicknessoftheweb Hestudiedthesections bearing230x75x6mm,250x90x6mmand300x90x6mmwithdifferentlengthincluding50,100,150mmandconcludedthat
Whereaisthedepthofhole,histheflatportionoftheweb andxisthedistanceofholefromthebearingedge.
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After the analysis of model and compared it with the experimentalresultsheintroduceastrengthreductionfactor for accounting the webcripplingcapacityafterconducting study on the offset web holes effect in the CFS sections. Strengthreductionfactorisusedtodeterminethereduction inwebcripplingstrengthundertheinfluenceofwebholes andtheymodifiedtheequationforstrengthreductionfactor forbothfastenedandunfastenedcase.
Case2 :Flangesarefastenedtosupport Rp=0.96 0.36(a/h)+0.14(x/h)<1
Uzzamanetal.[14]studiedtheeffectofoffsetwebholes intheCFSsectionwebcripplingbehavior.Inhisstudy the size of circular holes kept varying from 40 to 240mm.He conductedparametricstudybyvaryingtheratioofdiameter ofholestodepthofflatportionofwebfrom0.2to0.8and varyingtheratioofdistanceofholefromtheedgeofbearing platetodepthofflatportionofwebfrom0.2to0.6
Fig 12:UnfastenedandFastenedflange
Graph 4:Effectofx/h ratioinWebCripplingCapacity[3]
Gatheeshgar et al. [5] stated that web crippling capacity decreaseswithincreaseinthewebdepthofthesectionwhile conductastudytoknowthecombined bending,shearand web crippling capacity of CFS section. In this study lipped channelsectionisdesignedforcombined bendingshearand web crippling and stated that effective width is used to determine the beam bending capacity and the ultimate bendingcapacityforlaterallybracedbeamsistheminimum ofbendingcapacitysubjectedtotwotypesoffailureincluding localanddistortionalbucklingfailures.
The web buckling plays an important role in the determination of shear resistance capacity. Design shear resistance of a channel section is the sum of web shear resistance and flange shear resistance. Web portion of the section contribute a major proportion in the total shear resistance capacity. Four point bending arrangement is provided for conducting bending tests and three point bendingarrangementisconductedforanalyzingtheshear capacityofthesection.
Fig 15:ChannelSectionWithUnstiffenedWebHole[2]
Hareindirasarma et al. [3] from their studies on web cripplingcapacityundertheeffectofcircularholesconcluded thatwebcripplingcapacityincreaseswiththeincreaseinthe horizontaldistancefrombearingplatetowebopeningand duetosuddendecreaseinareawithwebholes,webcrippling capacity decreases, web crippling capacity depends on bearing length to clear web height ratio and web opening diameter to clear web height ratio. Keerthan et al. [13] in theirstudyonwebcripplingcapacityofhollow steelflange theyieldstrengththatheonlydealtwithis450Mpaandhe concludedthatwebcripplingcapacitylinearlyvarywiththe material yield strength. However the study conducted by Hareindirasarmaetal.[3] onconsideringwebholeeffectin webcripplingcapacitybyvaryingtheyieldstrength250and 450 Mpa and stated that web crippling capacity increases withbearinglengthandmaterialyieldstrength.Howeverthe relation with web crippling capacity and material yield strength is not in a linear manner and the yield strength factoris
flanges have better web crippling capacity compared with unfastenedflange.Fromthestudytheyconcludedthatthere isanincreaseofwebcripplingcapacityabout71%forETF load cases and an increase of 30% for ITF load case for fastened flangecondition.There is resistance to rotate the flangeswhenitisfastenedtosupportwhichwillincreasethe webcripplingcapacityofthechannelsection.
YieldproposedStrengthFactor=1+Cs(250/fy)
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Chenetal[2]fromthestudyofCFSchannelsectionwith edgestiffened,unstiffenedwebholesandplainwebsunder twoflangeloadingrecognizedthatedgestiffenedwebholes havemorewebcripplingcapacitywhencomparedwiththe sectionshavingunstiffenedwebholes.Sectionswithfastened
Fig 14:EdgeStiffenedWebHole[2]
Fig 13:LocalandDistortionalBuckling
8. CONCLUSION
[1] A. McIntosh, P. Gatheeshgar, K. Poologanathan, S. Gunalan, S. Navaratnam, C. Higgins, Web crippling of cold formedcarbonsteel,stainlesssteel,andaluminium channels:Investigationanddesign,J.Constr.SteelRes. 179(2021)106538
EOF EndOneFlange
Graph
[11] Natario P, Silvestre N, Camotim D. Direct strength predictionofwebcripplingfailureofbeamsunderETF loading.Thin WallStruct2016;98:360 74.
[14] A. Uzzaman, J.B.P. Lim, D. Nash, J. Rhodes, B. Young, Effectofoffsetwebholesonwebcripplingstrength of
5:EffectofyieldstrengthinWebCripplingCapacity [3]
This paper presents a review on web crippling capacity analysis of different cold formed channel section. It addresses the numerical as well as the experimental web crippling investigations on the Lite steel beam section, channel sections and perforated channel sections consideringallfourloadcasesincludingITF,ETF,IOF,EOF and the effect of various parameters including bearing length, inside bent radius, web hole diameter and slenderness ratio on the web crippling capacity of the channelsconsideredandcametotheconclusionthatwith theincreaseinthebearinglength,webcripplingcapacityofa section increase, with the increase in web hole diameter ratio and slenderness ratio, the web crippling capacity decreases.
[4] 1754conditions,channelcripplingH.Alsanata,S.Gunalan,K.PoologanathanH.Guan,WebcapacitiesoffastenedaluminiumlippedsectionssubjectedtooneflangeloadingStructures,Volume33,October2021,Pages1763
[8] Janarthanan B, Mahendran M, Gunalan S. Numerical modellingofwebcripplingfailuresincold formedsteel unlipped channel sections. J Constr Steel Res 2019; 158:486 501.
[3] S.Hareindirasarma ,K.Elilarasi B.Janarthanan,Effect of circular holes on the web crippling capacity of cold formedLiteSteelbeamsunderInterior Two Flangeload case,Thin Walled Structures Volume 166, September 2021,108135
[6] Wu.C, Zhang.L.,Tam,L., Yan,L., and He, L., “Effect of bearinglengthonwebcripplingbehaviorofpultruded GFRPchannel section”,Composite Structures,Volume 253,1December2020,112810
IOF InteriorOneFlange
[13] KeerthanP,MahendranM,SteauE.Experimentalstudy of web crippling behaviour of hollow flange channel beams under two flange load cases. Thin Wall Struct 2014;85:207 19.
[2] B.Chen,K.Roy,Z.Fang,A.Uzzaman,Y.Chi,J.B.P.Lim, Web crippling capacity of fastened cold formed steel channels with edge stiffened web holes, un stiffened web holes and plain webs under two flange loading, Thin WalledStruct.163(2021)107666.
ABBREVATIONS
International Research Journal of Engineering and Technology (IRJET) e ISSN: 2395 0056 Volume: 09 Issue: 03 | Mar 2022 www.irjet.net p ISSN: 2395 0072 © 2022, IRJET | Impact Factor value: 7.529 | ISO 9001:2008 Certified Journal | Page1736 Wherefyistheyieldstrengthofthesteel
[7] K. Elilarasi, B. Janarthanan, Effect of web holes on the web crippling capacity of cold formed litesteel beams under end two flangeload case,Structures25 (2020) 411 425,
[9] B. Janarthanan, L. Sundararajah, M. Mahendran, P. Keerthan, S. Gunalan, Web crippling behaviour and designofcold formedsteelsections,Thin WalledStruct. 140(2019)387 403[25]
[10] 2 NatarioP,SilvestreN,CamotimD. ebcripplingof beams under itf loading: Anovel DSM based design approach.JConstrSteelRes2017;128:812 24.
ITF InteriorTwoFlange
[12] E.Steau,M.Mahendran,P.Keerthan,Webcripplingtests of rivet fastened rectangular hollow flange channel beamsundertwoflangeloadcases,Thin WalledStruct. 95(2015)262 275
Mcintosh et al.[1] by comparing the web crippling capacity of carbon steel, stainless steel and aluminium channels madea conclusionthat webcripplingcapacityof stainless steel is more compared to carbon steel and aluminiumchannelsectionsandhestatedthatmodulusof elasticityplaysanimportantroleinwebcripplingbehaviorof the sections. Aluminium has less web crippling capacity becauseithaslowmodulusofelasticityvalueandduetothe strainhardeningbehaviorofstainlesssteelwhensubjectedto large strain there is an enhancement in web crippling capacityofsection
[5] Gatheeshgar.P,Poologanathan,K.Gunalan,S.,Shyha,I., Daniel,K.T.,andCorradia,M.,“Optimaldesignofcold formedsteellippedchannelbeams:Combinedbending, shear, and web crippling”, Structures , Volume 28, December2020,Pages825 836.
ETF EndTwoFlange
CFS ColdFormedSteel
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[16] K.S.Sivakumaran,K.M.Zielonka,Webcripplingstrength ofthin walledsteelmemberswithwebopening,Thin Walled Struct. 8 (1989) 295 319, http://dx. doi.org/10.1016/0263 8231(89)90035 9.
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