土木工程英文翻译外文翻译毕业论文

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1、TheFireResistanceofSteelStructuresE.GEHRIFederalInstituteofTechnology,Zurich,SwitzerlandINTRODUCTIONSTEELISanoncombustiblematerial,butthemechanicalpropertiesofstructuralsteelareaffectedbyheat.Thefireresistanceormoreexactly,thefireenduranceofasteelelementvarie

2、sgreatlyand,therefore,weneedabetterunderstandingoftheconditionswhichaffectfireresistance.Fireresistanceisunderstoodasthetimeduringwhichthestructuralelementcanwithstandthestandardprovisionsofafiretest.Forstructuralelementstheonlycriteriontobeconsideredisthestr

3、ucturalcollapseoftheelement.Othercriterialiketemperaturetransmissionmaybedisregarded.ForasteelcolumnthestandardprovisionsforafiretestaregiveninFigure1.Wemustnotethatthestandardtestprescribestheuseofaconstantloadcorrespondingtothemaximumdesignvalue.Thethermall

4、ongitudinaloraxialexpansionofthecolumnwillbecompensatedduringthetest,i.e.thereisnorestraint,thecolumncanmovefreelyintheaxialdirection.Bytestswecanfindtheultimatestrengthofthecolumnfordifferentfireendurances.Usingthesametypeofcolumnandsamedimensionsweobtainani

5、nteractiondiagram(Figure2).Thereductioninstrengthwiththepassingoftimedependsonthetemperatureincreaseinthespecimentested.Thetemperatureincreaseisafunctionoftheso-calledsectionfactorandoftheinsulationapplied.Thescatteroftestresultsisquitenormal,sincethecolumnst

6、estedarenotidenticalduetothedimensionaltolerancesandthevariationinstrengthofthesteel.Moreorlessthesamescatterisfoundwhentestingsteelcolumnsatroomtemperature.NowintroducingthedesignvalueintoFigure2,wecandirectlyfindthefireresistance.Generally,themeanvalueofthe

7、testresultswillbehigherthanthefireresistancebasedonthenominalguaranteedstrengthofthesteel.FromFigure2itcanalsoeasilybeseen,thatacolumnwhichissubjectedtoalowerstresslevel--i.e.,toaneffectiveloadlowerthanthedesignload--willhavehigherfireresistance.Finally,wemus

8、tnotethattheconditionsduringthefiretestdonotcorrespondtothoseinpractice.Besidesdifferentheatingratesinanaturalfire,wehavetoconsidertherealboundaryconditions.Supportconditionsandthelongitu