Tutorial 6 Compression Members PDF

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CIVE1179SteelStructures1

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Tutorial#6 Designofcolumns  Steelmembersundercompressionbehavesverydifferentlyfromthoseundertension.Compression causesbuckling.Bucklingisaninstabilityphenomenon.Bucklingmaybeconsideredas“catastrophic typefailure”wherenowarningisseenpriortofailure.Manystructuralcollapsesinthepastweredue tobuckling.Formembersundercompression,twotypesofbucklingwilloccur,namely(1)local bucklingand(2)Eulerbuckling.  Forlocalbuckling,AS4100usestheconceptofformfactorkftoreducethecrosssectionalarea.When kfissmallerthan1.0,aportionofcrosssectionalareaisdeductedtoaccountforreduceinstrength  duetolocalbuckling.Ifkfequalsto1.0,thesectionisfullyeffectiveanddoesnotexhibitlocal buckling.Forstandardhotrolledsections(UB,UC,etc),thevalueskfofaregiveninsectiontables.It shouldbenotedthatkf ofallUC’sare1.0.  ForEulerbuckling,AS4100usesafactorαctoreducethenominalsectioncapacity Ns. N   s isinfactthe squashloadofthemember(crossareaxyieldstress).  Example a. ComparethecompressioncapacityNcforthefollowingtwosectionsofsimilarweight: 610UB113and310UC118(Grade300Plus).Specification:Actuallength:6.0m,bracedand fixended. b. Repeatpart(a)ifabeamisconnectedtotheweakaxisofcolumnatmidheightwhichmaybe oftwoaxes) consideredasalateralrestraint.(hint:youneedtocompareλn   Answer 2 For610UB113 ,kf=0.926,Ag=14500mm .  3 =3759.6kN (Cl.6.2.1) A f N s=k  f  ny=0.926x14500x280x10   6000mm l= le= (Cl.6.3.2.andCl.4.6.3)  k el  =0.7x6000=4200mm (Table6.3.3(2),thickness...