2023年全國碩士研究生考試考研英語一試題真題（含答案詳解+作文范文）_第1頁
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1、英文原文英文原文SteelBridgesfthe21stCenturyJohnM.KulickiPh.D.P.E.ModjeskiMastersInc.AcollabativeefftoftheFederalHighwayAdministration(FHWA)theUnitedStatesNavytheAmericanIronSteelInstitute(AISI)hasresultedinthedevelopmentofnewste

2、elwithgreatpotentialfuseinhighwaybridgeconstruction.Enhancedperfmancesteelalsoknownashighperfmancesteel(HPS)maybedefinedasanysteelwithsomepropertiesimprovedoverexistingASTMA709Grades345W485W690Wsuchas:iginallyatleast485M

3、Payieldalthoughotherstrengthsupto985MPaareunderconsideration.TherehasalsobeensomediscussionregardingthedesirabilityofalowerstrengthHPSe.g.HPS345W.Bridgesteelswithyieldstrengthsof345485690MPahavebeenavailablefdecadessoiti

4、sclearthatstrengthalonedoesnotmakea“highperfmance”steelImprovedtoughnessfpracticalbridgeenvironmentsusuallyexpressedasmeeting“Zone3“requirementsi.e.47Joulesat23CIncreasedweldabilityoftendescribedintermsofreducedpreheatin

5、terpasstemperaturerequirementsNodetrimentalchangestootherimptantpropertiesWeatheringpropertiesatleastequaltotheolderGrade485W.StatedmesimplyHPShasimprovementsinonemeofthefollowingproperties:strengthweldabilityductilitycr

6、osionresistancefatigueresistancefracturetoughnessfabricabilityfmability.TheHPScurrentlyavailablehasayieldstrengthof485MPaisproducedthroughimprovementsinbothchemistrycontrolofthecoolingprocess.TheFHWArecognizedthatresearc

7、hwasnecessarytoconsiderstructuralfmswhichcouldcapitalizeontheimprovementspropertiesanticipatedasthenewHPSwasbeingdevelopedtoidentifydesignspecificationissueswhichwouldhavetobeaddressedtoutilizethenewmaterial.Whilethecurr

8、entmaterialhasayieldpointof485MPaconsiderationwasgiventosteelswithyieldpointsashighas985MPa.Ifstrengthsofthislevelaredevelopedinthefuturenewinnovativestructuralsystemswouldbeneededtoutilizethefullpotentialoftheimprovedpr

9、opertiesofsuchsteels.AreptonanFHWAsponsedresearchprojecttoevaluatepotentialnewstructuralfmstodeterminetheirweightbasedefficiencyhasbeenrepted(Kulickietal1997).VariousaspectsoftheFHWArepthavebeenwellpresentedintheliteratu

10、rereferences(WassefetalJune1994KulickietalApril351995KulickietalJuly15181996KulickietalOctober15171996KulickietalApril1997KulickietalSeptember1997).Thispaperwillpresentasampleofinnovativestructuralsystemsftomrowsgirderty

11、peresistance.Figure2.IGirderwithTrapezoidalCrugatedWebsThecrugatedwebsarerelativelyflexiblewhensubjectedtofcesparalleltothelongitudinalaxisofthegirdertherefedonotcontributetothemomentresistanceofthegirders.Therequiredfla

12、ngesofagirderwithacrugatedwebarelargerthanthoseofaconventionalgirderwiththesamedepth.Howevercrugatedwebsallowdeepergirdersthatarenotsusceptibletowebstabilityproblemsthusresultinthinnerwebssmallerflanges.Theoverallweighto

13、ftheresultinggirdersislessthanconventionalplategirders.Amethodfsplicingcrugatedwebswillneedtobedeveloped.AtleastonebridgewithtrapezoidalcrugationswasconstructedinFrance.Lapspliceswithfilletweldsalongtheedgesofthetwowebpl

14、ateswereprovided.Thefatigueresistanceofsuchasplicewillneedtobeprovenbytesting.BuiltUpGirderswithTubularConcreteFilledFlangesAflatflangeofanIshapedgirdercanbereplacedbyarelativelythincircularrectangularstructuraltube.Vari

15、ousconceptsfthisfmareshowninFigure3.Highstrengthnonshrinkgroutcanthenbeusedtofillthetube.TheweldabilityofHPSwillalloweasierweldingofatsionallystifftubularflangetoarelativelyflexiblewebplatereduceeliminatefatigueconcernsa

16、ttheconnection.Thedepthofthewebofthissystemissmallerthanthatofaconventionalgirderwiththesametotaldepth.Theshallowerwebdepthallowsthinnerstillstablewebplates.Tubularflangescanbeusedinconjunctionwithbothflatcrugatedwebplat

17、es.Inthecaseofthecrugatedwebsaflatnearflatsurfaceofthetubularflangewillberequiredtofacilitatetheweldbetweenthewebthetube.Thiscanbeachievedbyusingarectangularhexagonaloctagonaltubebyflatteningacirculartubeatthesidewhereth

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