钢结构英语PPT课件

精品课件,1,Summary：,4.1Theapplicationandsectiontypesofaxiallyloadedcompressionmembers4.2Thestrengthandstiffnessofaxiallyloadedcompressionmembers4.3Theoverallstabilityofaxiallyloadedcompressionmembers4.4Thelocalstabilityofsolid-webaxiallyloadedcompressionmembers4.5Thedesignofsolid-webaxiallyloadedcompressionmembers4.6Thedesignoflatticeformaxiallyloadedcompressionmembers4.7Thestructureandcalculationofaxiallyloadedcompressioncolumnheadandheel,精品课件,2,Theaxiallyloadedcompressionmemberscanclassifyintotwocategories:tensionandcompression.Bothofthemmustmeettherequirementsofsupportingcapacitylimitstateandserviceabilitylimitstate.Serviceabilitylimitstateisdecidedbyslendernessratio.Supportingcapacitylimitstaterequiresforstrength,Overallstability,localstability.,4.1Theapplicationandsectiontypesofaxiallyloadedcompressionmembers,4.1.1Theapplicationofaxiallyloadedcompressionmembers,Theapplicationofaxiallyloadedcompressionmembers,精品课件,3,4.1.2Sectiontypes,Axiallyloadedcompressionmembershasmanykindsofsectiontypes，itcanbedividedintothestructuresteelsectionsandbuilt-upsections，andthebuilt-upsectionscontainssolid-webandlatticeform.,(a)structuresteelsections(b)solid-web(c)latticeform,精品课件,4,精品课件,5,4.2Thestrengthandstiffnessofaxiallyloadedcompressionmembers,4.2.1Thestrengthofaxiallyloadedcompressionmembers,Toundamagedsectionmembers，wemustcontrolthegrosssectionsmeanstressunderthematerialsyieldstrength：,Buttoweakensectionmembers,wemustcontrolthenetsectionsunderthematerialstensilestrength.AccordingtoCodefordesignofsteelstructures（500172003），partialsafetyfactorforresistance:,精品课件,6,Astomakethecalculationmoresimpleandconvenient,Codefordesignofsteelstructures（500172003）choosestheyieldratioas0.8.Sototheaxiallyloadedmembers,wecancalculatethestrengthas:,designvaluenetsectionareatensilestrengthorcompressivestrength,back,精品课件,7,4.2.2Thestiffnessofaxiallyloadedcompressionmembers,Asnottomakeexcessivedeformability,theaxiallyloadedcompressionmembersmusthaveenoughstiffness,sowecanthroughcontrollingtheslendernessratiotoassurancemembersstiffness,thatis:,themaximalslendernessratiomemberseffectivelengthradiusofgyrationallowableslendernessratio,back,精品课件,8,4.3Theoverallstabilityofaxiallyloadedcompressionmembers,4.3.1IntroductionofStabilitiesproblem,Indealingwithcompressionmembers,theproblemofstabilityisofgreatimportance.Unliketensionmembers,whiletheloadtendstoholdthemembersinalignment,compressionmembersareverysensitivetofactorsthatmaytendtocauselateraldisplacementsorbuckling.Thesituationissimilarinwaystothelateralbucklingofbeams.Thebuckingproblemisintensifiedandtheload-carryingcapacityisaffectedbysuchfactorsaseccentricload,imperfectionofmaterial,andinitialcrookednessofthemember.Also,residualstressesplayarole.Therearethevariablestressesthatare“lockedup”inthememberasaresultofthemethodofmanufacture,whichinvolvesunequalcoolingrateswithinthecrosssection.Thepartsthatcoolfirstwillhaveresidualcompressionstresses,whilepartsthatcoolthatcoollastwillhaveresidualtensionstresses.Residualstressesmayalsobeinducedbynon-uniformplasticdeformationcausedbycoldworking,suchasinthestraighteningprocess.,精品课件,9,4.3.2Idealaxiallyloadedcompressionmembersandbucklingforms,Idealaxiallyloadedcompressionmembersbasicassumption：1）thememberbarmustbeprismaticidealmember2）theloadsarecoincidentwiththelongitudinalcentroidalaxisofthemembers3）withouttheinitialstressinfluence4）thematerialmustbehomogeneous、isotropicandinfiniteelastic，correspondwithhookeslaw.,精品课件,10,Bucklingmodesofstrut:,bending-bucklingtorsional-bucklingbendingandtorsional-buckling,精品课件,11,4.3.3Cripplingloadofaxiallyloadedcompressionmembers,(1)Criticalforceofbending-bucklingelasticbending-bucklingEulersformula,criticalstateofhinged-hingedaxiallyloadedcompressionbar,精品课件,12,Criticalforce：,Criticalstress：,derivationprocessofcriticalforce,精品课件,13,Elasticbendingassumptionofaxiallyloadedcompressionmembersrequires:criticalstressmustbelessthanmaterialsproportionallimit,thatis:,solve：,iscriticalslenderness,精品课件,14,theelastoplasticitycriticalforceandstressofidealaxiallyloadedcompressionmembers,Astoaxiallyloadedcompressionmembers(slendernessrationp)takeplacetobending-bucking，theformulaofcriticalforceandstressis：,精品课件,15,（2）criticalforceoftorsional-buckling,thetorsional-bucklingcriticalforcecomputationalformulaoftheaxiallyloadedcompressionmembersis:,thefirstpartoftheformulaiswarpingtorsion,itisrelatedtothelengthofthemembers,thesecondpartisfreetorsion.,精品课件,16,Inordertofacilitatetheapplication,wecanconventthetorsional-bucklingcalculationofthecriticalforceintobending-bucklingintheformofEulersformula,thatis：Themeaningoftheformulaisthatwecanwrittenthetorsional-bucklingcalculationformulaintheformofEulersformula,butweshouldchangetheintoequivalentslendernessratioz。,精品课件,17,（3）criticalforceofbendingandtorsional-buckling,Thecriticalforceofbendingandtorsional-bucklingcalculationformulais：Astofacilitatetheapplication，wecanwritetheformulaintheformofEulersformula,thatis:,精品课件,18,Equivalentslendernessratiois：,distancefromsectioncentroidtoshearcenterradiusofgyrationtoshearcenterslendernessratioofbending-bucklingtosymmetryaxisequivalentslendernessratiooftorsional-buckling,精品课件,19,4.3.4theeffectofinitialdefecttotheaxiallyloadedcompressionmembers,Thebuckingproblemisintensifiedandtheload-carryingcapacityisaffectedbysuchfactorsaseccentricload,imperfectionofmaterial,andinitialcrookednessofthemember.Also,residualstressesplayarole.Therearethevariablestressesthatare“lockedup”inthememberasaresultofthemethodofmanufacture,whichinvolvesunequalcoolingrateswithinthecrosssection.Thepartsthatcoolfirstwillhaveresidualcompressionstresses,whilepartsthatcoolthatcoollastwillhaveresidualtensionstresses.Residualstressesmayalsobeinducedbynon-uniformplasticdeformationcausedbycoldworking,suchasinthestraighteningprocess.,精品课件,20,4.3.5Overallstabilitycalculationofactualaxiallyloadedcompressionmembers,（1）Calculationanalysisofstabilitybearingcapacity,Eulersformulaisthebasicformulaofcalculatingthestability,butastheinfluenceofdefects,wehavetousethecolumncurveswhichiscomefromtheorycalculationandexperimenttodothestabilitycalculation.,（2）Columncurvesofaxiallyloadedcompressionmembers,精品课件,21,Columncurves,精品课件,22,(3)Calculationformulaofoverallstability,Accordingtothepricipleofthecriticalforceofoverallstabilityshouldbelessthanaxialforce,atthesametimeconsideratethesubentrycoefficient,thatis:,or,designvalueofaxialforcegrosssectionareadesignvalueofcompressionstrength,overallstabilitycoefficient,back,精品课件,23,Weshouldputattentiontotheslendernessratio,whenwecalculatetheslendernessration,wecanconsiderateintheseaspects.（1）Sectionisbisymmetryorpolarsymmetry（bending-buckling）,、effectivelength,精品课件,24,（2）sectionismonosymmetric（bendingandtorsion-buckling）,Formonosymmetricsection，weshouldconsideratetorsion,sointhesamecondition,thecriticalforceofbendingandtorsion-bucklingislessthanbending-buckling,soweneedusetheequivalentslendernessratioinstead.,Practicalapplicationoftenusesimplifiedcalculationformula（sheet4.5.3),精品课件,25,4.4Thelocalstabilityofsolid-webaxiallyloadedcompressionmembers,Thesolid-webaxiallyloadedcompressionmembersdependonwebplateandflangetobearthecompressiveforce.Whenwebplateandflangearethinner,undertheaxiscompressiveforce,boththewebplateandflangesprobablyattaincriticalbearingcapacityandthendestabilizate.Thiskindofdestabilizationusuallytakeplacepartially,sobecalledcrippling.,Cripplingofaxiallyloadedmembers,web-buckling,flange-buckling,精品课件,26,4.4.1Stabilityofrectangularflat-plateinone-wayuniformcompression,（1）Rectangularflat-plateofsimplysupportedonfoursides,simplysupportedrectangularflat-plateinone-wayuniformcompression,精品课件,27,theformulaofcalculatethecriticalforceofthesimplesupportedonfoursidesrectangularplate:,（2）Rectangularflat-plateofthesimplesupportedonthreesidesandtheothersideisfreeAccordingtotheoryanalysis,forlongerplate,thebucklingcoefficientcanbecalculatedbythebottomformular：,精品课件,28,Forlongplate，,Whenplateisonelasto-plasticityprocess,wecanusethisformualtocalculatethecriticalforce:,Intheformula：,精品课件,29,4.4.2theflakinessratiolimitvalueofflange,theflakinessratiolimitvalueofflangeshouldmeettheformulasdemand：,themaximumslendernessratio，when100，take100,4.4.3theratioofheighttothicknesslimitvalueofweb,、widthandthicknessofweb,themaximumslendernessratio，when100，take100,精品课件,30,4.4.3sectionaldimensionlimitvalueofaxiallyloadedcompressionsteeltube,Douterdiameterofsteeltubetwallthicknessofsteeltube,精品课件,31,4.5Thedesignofsolid-webaxiallyloadedcompressionmembers,4.5.1Designprinciples,1）Equistabilityprinciple,2）Widthlimbandthinwall,3）Manufacturesavingoflabor,4）Connectconvenient,4.5.2designsection,(1)Calculatetheparameter,1)Assumetheslendernessratio,2)Accordingtothesectiontypeselectand,calculatethearea,3)Calculatetheradiusofgyrationand,精品课件,32,(2)Selectprofilesteelorinitialdeterminethedimensionofcompoundsection,ifweuseprofilesteel,wecanselectitaccordingto、.butifweusecompoundsection,weshouldaccordingtotheappendix4todetermine、,andthesametimeweshouldaccordwiththedesignprinciple.,(3)Checkingcalculation,1)Checkingcalculationofthestrength:,2)Checkingcalculationofthestiffness:,精品课件,33,3)Checkingcalculationofoverallstability:,4)Checkingcalculationoflocalstability:,(4)Therelevantstructurerequest,Program4.1,精品课件,34,Forlargeloadsitiscommontousealatticeformbuilt-upcrosssection.Inadditiontoprovideingincreasedcross-sectionalarea,thebulit-upsectionsallowadesignertotailortoprovidingincreasedcross-sectionalarea,thebuilt-upsectionsallowadesignertotailortospecificneedstheradiusofgyrationvaluesaboutthex-xandy-yaxes.Thedashedlinesshownonthecrosssectionsoffigurebulit-uosectionsandrepresenttieplates,lacingbars,orperforatedcoverplatesanddonotcontributetothecross-sectionalproperties.Thefunctionsaretoholdthemainlongitudinalcomponentsofthecross-sectioninproperties.Theirfunctionsaretoholdthemainlongitudinalcomponentsofthecrosssectioninproperrelativepositionandtomakethebuilt-upsectionactasasingleunit.,4.6Thedesignoflatticeformaxiallyloadedcompressionmembers,4.6.1Theoverviewoflatticeformaxiallyloadedcompressionmembers,Bulit-upsections,精品课件,35,4.6.2Overallstabilityoflatticeformbuilt-upsections,(1)Checkingcalculationofrealaxisoverallstability,Wecanuseformula(4.31)tocheckcalculatetheoverallstability,(2)Checkingcalculationofvirtualaxisoverallstability,Consideratedtheeffectofshearingdeformation,wecanusethisformulacalculatetheoverallstability.,精品课件,36,equivalentslendernessratioofvirtualaxisangleofshear,assume：,then：,精品课件,37,becauseofdifferentcolumnshasdifferent,theequivalentslendernessratioisdifferent.,1）Doublelacingbarcolumn,As：,Derivationofdoublelacingbarcolumnsequivalentslendernessratio,精品课件,38,2)Thecalculationformulaofbattenedplatecolumnsequivalentslenderness,3)Thecalculationformulaofpolymeliacolumnsequivalentslendernesssheet4.7,精品课件,39,4.6.3Overallstabilityoflimbs,Lacingbar：,Battenplate：,andequalorlesserthan40,Intheformula：themaximumslendernessratio,when，take；,4.6.4thecalculationoflacingandbattenelements(1)Transverseshearingforce,back,精品课件,40,shearingforcescattergram,精品课件,41,Weoftenusesingularsetlacingbar，inordertoreducethelimbscalculationlength,wecanaddtransverselacingbar.Andwhenthelimbsspaceortheloadarebigger,wecanusecrosslacingbar.,(2)Designoflacingbar,精品课件,42,Underthetransverseshearingforce,theaxiallycompressionofonelacingbarbeared：,shearingforceofonelacingbardistributedsingularsetlacingbar=1;crosslacingbar=2angleofinclination,精品课件,43,(3)Designofbattenedplate,Calculationdiagramofbattenedplate,精品课件,44,Shearingforce：,moment：,精品课件,45,(4)Connectingnodesandstructurerequest,Thesplicinglengthofthebattenplateandlimbusualtake2mm30mm，inordertocutdowntgesplicinglength,wecanuseweldallaroundofthreesides,andthesametimeaddgussetplate.Andthelacingbarshouldnotbesmallerthan454or56364.Thethicknessshouldbethickerthan6mm.Inordertoaddthetorsionalstiffness,weshouldsetthetabulaplate.,Tabulaplateofbulit-upcolunmn,精品课件,46,4.6.5Designoflatticeformaxillyloadedmembers,Accordingtotherequestforutilization、thesizeofaxistowingforce、andthecalculationlengthtodeterminetheshapeandthetypeofsteels.,（1）Primaryselectsections,1)Assumeslendernessratiosearch,calculate。Accordingtoprimaryselectradiusofgrration,andsoon,2）calculate,精品课件,47,（2）DeterminethelimbsspaceAccordingtoequistabilityprincple,assume：,Forlacingbarcolunmn：,Forbattenplatecolumn：,Calculate:,精品课件,48,Checkingcalculationofprimarysections：CheckingcalculationofstrengthCheckingcalculationofstiffness,forvirtualaxisuseequivalentslendernessratioCheckingcalculationofoverallstability；forvirtualaxisuseequivalentslendernessratiocheckingcalculationoflimbsstability,(3)Checkingcalculationofsections,Program4.2,(4)Designofnodesandstructure,精品课件,49,4.7Thestructureandcalculationofaxiallyloadedcompressioncolumnheadandheel,4.7.1Columnhead,(1)Designprincple,1)Spreadthetowingforceaccurate2)Convenienttocreationandinstallation3)Economicandreasonable,(2)Connectionofthebeamsandcolumns,精品课件,50,1)Hingedjointofbeamsupportedbycol