《欧规3 钢结构设计》基础教程 教程25计算案例参考文件.docx

《欧规3 钢结构设计》基础教程 教程25计算案例参考文件.docx

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《欧规3钢结构设计》基础教程教程25计算案例参考文件

StructuralSteelworkEurocodesDevelopmentof

ATrans-nationalApproach

Course:

Eurocode3

Module7:

WorkedExamples

Lecture25:

PlasticDesignofPortalframes

ReferencesfortheWorkedExample

Ref1

17.2Plasticdesign-ultimatelimitstate

Thefollowingprocedureissuggested:

1）Defineframegeometry,determineloads,loadcombinations,factorsandfactors（seeSection11）.

2）Choosetrialsectionsandtrialhaunchlengthsbyselectingbeamsectionsthathaveresistancesatleastequaltothefollowing:

WherewisthemaximumULSgravityload/unitlengthalongthespanandListhespanoftheportal.

Thehaunchlengthshouldbechosentooptimisetheoverallportalstructure.AlengthofL/10fromthecolumnfaceisareasonableinitialchoice,buttheproportionsofthehaunchgenerallydependofthecharacteristicsofeachindividualbuilding,especiallythesizeoftherafter（seeSection6.3）.AhaunchlengthofL/10willnormallyplacethefirsthingeinthetopofthecolumn.Aratherlongerhaunchwillplacethefirsthingeatthesharpendofthehaunch.

3）Calculateframeimperfectionequivalentforces,referringtoENV 1993-1-1Section 5.2.4.3andSection15ofthispublication.Thiscanbebyapreliminaryframeanalysis（whichisnecessaryforallbutthesimplestbuildings）orbyasuitableapproximation.

4）Performplasticanalysisoftheframe（seeSection12.4）assuming:

（a）noreductioninplasticmomentofresistancefromcoexistentaxialandshearforces.Thisapproachmayneedmodifying,whereaxialloadsarehigh,e.g.intiedportals,inportalswithsteepslopesandinportalswithheavyroofingloads.

（b）TrialVSd/Vcr 0,12unlessabetterestimateispossible.

Notethatinupliftcases,themembersmightbesubjecttoaxialtension.Inthiscase,therewillbenodestabilisationoftheframeandVSd/Vcrcanbetakenaszero.

5）CalculateanaccuratevalueofVSd/Vcr.（SeeSection12andAppendixB）.

6）If[accurateVSd/Vcr] > [trialVSd/Vcr]orifamorerefineddesignisrequired,returntoStep4.

Note:

Forrelativelyslenderframes,itisoftenwisetocheckthedeflectionsattheServiceabilityLimitState,asexplainedinSection 17.4,beforecheckingthebucklingresistance.

7）Forthecolumnscheckthat:

（a）TheclassificationisClass1orClass2asappropriate,asexplainedinSection 13andAppendix C;Sections13.1,13.2,13.3andAppendix C.2areparticularlyrelevant.

（b）Thecrosssectionalresistanceisadequate,asexplainedinSection 13andAppendix C;Sections 13.4andAppendix C.4andC.6areparticularlyrelevant.

（c）Theresistanceofthemembertominoraxisbucklingbetweenlateralrestraintsisadequate,asexplainedinSection 13andAppendix D,togetherwiththeappropriatepartsofAppendix F;Section 13.5isparticularlyrelevant.

Forelementswithaplastichingewithinthelengthorateitherend,Appendix D.4shouldbeused（whichcontainsthesamecheckasAppendix F.4）.

Forelementsresistingmomentsandforcesclosetotheplasticresistance,Appendix D.4mightneedtobeused,becauseAppendix D.3.4.2cannotbesatisfied.

Forelementswithoutplastichingesandnotveryhighlystressed,Appendix D.3.4.2shouldbeused,togetherwithAppendix F.2,withLtakenasthedistancebetweenlateralrestraints,e.g.betweenpurlins.

（d）Resistanceofmembertominoraxisbucklingbetweentorsionalrestraintsisadequate,asexplainedinSection 13andAppendix D,togetherwiththeappropriatepartsofAppendix F.

Themethodofcheckingissimilarto（c）above,butAppendix F.3shouldbeusedinsteadofAppendix F.2.

8）Fortherafterscheckthat:

（a）TheclassificationisClass1orClass2asappropriate,asstep7（a）above.

（b）Thecrosssectionalresistanceisadequate,asstep 7（b）above,butwithoutAppendix C.6.

（c）Theresistanceofthemembertominoraxisbucklingbetweenlateralrestraintsisadequate,asstep 7（c）above.

（d）Theresistanceofthemembertominoraxisbucklingbetweentorsionalrestraintsisadequate,asstep 7（d）above.

9）Forthehaunchescheckthat:

（a）TheclassificationisClass1orClass2asappropriate,asstep 7（a）above,butusingAppendix EwherethewebslendernessisClass 3.

（b）Thecrosssectionalresistanceisadequate,asstep 7（b）above,butcheckingatseveralcrosssectionswithinthelengthofthehaunch（bothends,quarter,mid-spanandthreequarterpointsarerecommended）.Appendix E.2orAppendix E.3shouldbeusedwherethewebslendernessisClass 3.

（c）Theresistanceofthemembertominoraxisbucklingbetweenlateralrestraintsisadequate,asStep 7（c）above,butgivingspecialattentiontotheeffectofthetaper.TheseeffectsaredescribedinSection13.5.4,Appendix D.3.4.2,Appendix D.5andAppendix E.4.

（d）Theresistanceofthemembertominoraxisbucklingbetweentorsionalrestraintsisadeq