Principles Of Limit State Design

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1、1PrinciplesofLimitStateDesign1.1DesignPhilosophiesforSteelStructuresSteel-platedstructuresarelikelytobesubjectedtovarioustypesofloadsanddeformationsarisingfromservicerequirementsthatmayrangefromtheroutinetotheextremeoraccidental.Themissionofthestructuraldesigneristodesignastructurethatcanw

2、ithstandsuchdemandsthroughoutitsexpectedlifetime.Indesign,thestructureishencerequiredtohaveanadequatemarginofsafetyagainstsuchdemands,thesafetyfactorbeingnecessarytoaccountforvariousuncertaintiesduetonaturalvariability,inaccuracyinproceduresusedfortheevaluationandcontrolofloadsorloadeffect

3、s(e.g.,stress,deformation),similaruncertaintiesinstructuralresistance(capacity)anditsdetermination,andalsovariationsinbuildingprocedures.Ademandisanalogoustoload,andacapacityisanalogoustostrengthnecessarytoresistthatload,bothmeasuredconsistently(e.g.,asstress,deformation,resistiveorapplied

4、loadormoment,orenergyeitherlostorabsorbed,andsoon).Thepartialsafety-factor-baseddesigncriterionforastructureundermultipletypesofloadsappliedatthesametimeisexpressibleasfollows:Dd1(1.1)
whereDd=γ0iDki(Fki,γfi)=designdemand,Cd=Ck/γM=designcapacity,Dki(Fki,γfi)=charac

5、teristicmeasureofdemandforloadtypei,calculatedfromthecharacteristicmeasuresofloads,Fk,andmagnifiedbythepartialsafetyfactor,γf,takingaccountoftheuncertaintiesrelatedtoloads,γ0=partialsafetyfactortakingintoaccountthedegreeofseriousnessoftheparticularlimitstateinregardtosafetyandserviceability

6、accountingofeconomicalandsocialconsequencesaswellasanyspecialcircumstance(e.g.,themissionoftheship,typeofcargo,interactionofthelimitstateconsideredwiththeothers,etc.),Ck=characteristicmeasureofcapacity,γM=γmγc=capacity-relatedsafetyfactor,γm=partialsafetyfactortakingaccountoftheuncertainti

7、esduetomaterialproperties,γc=partialsafetyfactortakingaccountoftheuncertaintiesonthecapacityofthestructure,suchasqualityoftheconstruction,corrosion,methodconsideredfordeterminationofthecapacity.MorediscussionaboutthedesignformatmaybefoundinSection1.10.2ULSDESI