桥梁工程最新外文翻译：箱梁的设计与研究.docx

西南交通大学本科毕业设计（论文）外文资料翻译年级:学号:姓名:专业:指导老师:2023年6月外文资料原文:13Boxgirders13.1 Genera1Theboxgirderisthemostf1exib1ebridgedeckform.Itcancoverarangeofspansfrom25muptothe1argestnon-suspendedconcretedecksbui1t,oftheorderof300m.Sing1eboxgirdersmaya1socarrydecksupto30mwide.Forthe1ongerspanbeams,beyondabout50m,theyarepractica11ytheon1yfeasib1edecksection.Fortheshorterspanstheyareincompetitionwithmostoftheotherdecktypesdiscussedinthisbook.Theadvantagesoftheboxformareprincipa11yitshighstructura1efficiency(5.4),whichminimisestheprestressforcerequiredtoresistagivenbendingmoment,anditsgreattorsiona1strengthwiththecapacitythisgivestore-centreeccentric1ive1oads,minimisingtheprestressrequiredtocarrythem.Theboxform1endsitse1ftomanyofthehigh1yproductivemethodsofbridgeconstructionthathavebeenprogressive1yrefinedoverthe1ast50years,suchasprecastsegmenta1constructionwithorwithoutepoxyresininthejoints,ba1ancedcanti1evererectioneithercastin-situorcoup1edwithprecastsegmenta1construction,andincrementa11aunching(Chapter15).13.2 Cast-in-situconstructionofboxes13.2.1 Genera1Oneofthemaindisadvantagesofboxdecksisthattheyaredifficu1ttocastin-situduetotheinaccessibi1ityofthebottoms1abandtheneedtoextracttheinterna1shutter.Eithertheboxhastobedesignedsothattheentirecrosssectionmaybecastinonecontinuouspour,orthecrosssectionhastobecastinstages.13.2.2 CastingthedeckcrosssectioninstagesThemostcommonmethodofbui1dingboxdecksinsituistocastthecrosssectioninstages.Either,thebottoms1abiscastfirstwiththewebsandtops1abcastinasecondphase,orthewebsandbottoms1abconstitutethefirstphase,comp1etedbythetops1ab.Whenthebottoms1abiscastfirst,theconstructionjointisusua11y1ocatedjustabovethes1ab,givingakickerforthewebformwork,position1inFigure13.1.Ajointinthis1ocationhassevera1disadvantageswhicharedescribedinFigure13.1A1ternativepositionsofconstructionjointA1ternative1y,thejointmaybeinthebottoms1abc1osetothewebs,oratthebeginningofthehaunches,position2.Theadvantagesof1ocatingthejointinthebottoms1abarethatitdoesnotcrossprestressingtendonsorheavyreinforcement;itisprotectedfromtheweatherandisa1so1essprominentvisua11y.Themaindisadvantageisthatthes1abon1yconstitutesasma11proportionofthetota1concretetobecast,1eavingamuch1argersecondpour.Thejointmaybe1ocatedatthetopoftheweb,justbe1owthetops1ab,position3.Thisretainsmanyofthedisadvantagesofposition1,name1ythattheconstructionjointiscrossedbyprestressingductsatasha11owang1e,anditisdifficu1ttoprepareforthenextpourduetothepresenceofthewebreinforcement.Inaddition,mostofthedifficu1tyofcastingthebottoms1abhasbeenre-introduced.Theadvantagesarethatthejointis1essprominentvisua11yandisprotectedfromtheweatherbythesidecanti1ever,thequantityofconcreteineachpourissimi1arand1essoftheshutteristrappedinsidethebox.Castingacrosssectioninphasescausesthesecondphasetocrackduetorestraintbythehardenedconcreteofthefirstphase.A1thoughthesectionmaybereinforcedto1imitthewidthofthecracks,itisnotdesirab1eforaprestressedconcretedecktobecrackedunderpermanent1oads.E1iminatingcracksa1togetherwou1drequireveryexpensivemeasuressuchascoo1ingthesecondphaseconcreteto1imittheriseintemperatureduringsettingoradoptingcracksea1ingadmixtures13.2.3 CastingthecrosssectioninonepourTherearetwoapproachestocastingaboxsectioninonepour.Thebottoms1abmaybecastfirstwiththehe1poftrunkingpassingthroughtemporaryho1es1eftinthesoffitformofthetops1ab.Thisrequiresaccessfor1abourerstospreadandvibratetheconcrete,andison1ygenera11ypossib1efordecksthatareat1east2mdeep.Thecastingofthewebsmustfo11owonc1ose1y,sothatco1djointsareavoided.Thef1uidityoftheconcreteneedstobedesignedsuchthattheconcretewi11nots1umpoutofthewebs.Thisisassistedifthereisastripoftopshuttertothebottoms1ababout500mmwidea1ongeachweb.Thismethodputsnorestrictiononthewidthofthebottoms1ab,Figure13.2(a).A1ternative1ythedeckcrosssectionmaybeshapedsothatconcretewi11f1owfromthewebsintothebottoms1ab,whichnorma11yhasacomp1etetopshutter,Figure13.2(b).Thismethodofconstructionismostsuitab1eforboxeswithre1ative1ynarrowbottomf1anges.Thecompactionofthebottoms1abconcreteneedstobeeffectedbyexterna1vibrators,whichimp1iestheuseofstee1shutters.Theconcretemaybecastdownbothwebs,withinspectionho1esintheshutterthata11owairtobeexpe11edandthecomp1etefi11ingofthebottoms1abtobeconfirmed.A1ternative1y,concretemaybecastdownonewebfirstwiththesecondwebbeingcaston1ywhenconcreteappearsatitsbase,demonstratingthatthebottoms1abisfu11.Theconcretemixdesigniscritica1andfu11-sca1etria1srepresentingboththegeometryofthecrosssectionanddensityofreinforcementandprestresscab1esareessentia1.(AiA*iUtcakavk八56)MmQKA*sGb力ith3adu皿卜Figure13.2CastingdeckinonepourHoweverthesectioniscast,thecoreshuttermustbedismant1edandremovedthroughaho1einthetops1ab,ormadeco11apsib1esoitmaybewithdrawn1ongitudina11ythroughthepierdiaphragm.Despitethesedifficu1ties,castingthesectioninonepourisunder-used.Therecentdeve1opmentofSe1rCOmPaCtingconcretecou1drevo1utionisetheconstructionofdecksinthismanner.Thiscou1dbeparticu1ar1yimport