土木毕业设计外文翻译原文翻译桥梁

外文文件原文ThebridgecrackproducedthereasontosimplyanalyseInrecentyears,thetrafficcapitalconstructionofourprovincegetsswiftandviolentdevelopment,allpartshavebuiltalargenumberofconcretebridges.Inthecourseofbuildingandusinginthebridge,relevanttoinfluenceprojectqualityleadofcommonoccurrencereportthatbridgecollapseevenbecausethecrackappearsTheconcretecanbesaidto"oftenhaveillnesscomingon"whilefracturingand"frequently-occurringdisease",oftenperplexbridgeengineersandtechnicians.Infact,iftakecertaindesignandconstructionmeasure,alotofcrackscanbeovercomeandcontrolled.Forstrengthenunderstandingofconcretebridgecrackfurther,isitpreventprojectfromendangerlargercracktotryone'sbest,thistextmakeanmoreoverallanalysis,summarytoconcretekindandreasonofproduction,bridgeofcrackasmuchaspossible,inordertodesign,constructandfindoutthefeasiblemethodwhichcontrolthecrack,gettheresultoftakingprecautionsagainstYuWeiRan.Concretebridgecrackkind,origincauseofformationInfact,theorigincauseofformationoftheconcretestructurecrackiscomplicatedandvarious,evenmanykindsoffactorsinfluenceeachother,buteverycrackhasitsoneorseveralkindsofmainreasonsproduced.Thekindoftheconcretebridgecrack,onitsreasontoproduce,canroughlydivideseveralkindsasfollows:(1)loadthecrackcausedConcreteinroutinequiet.Isitloadtomoveandcrackthatproduceclaimtoloadthecrackunderthetimesofstressbridge,summinguphasdirectstresscracks,twokindsstresscrackoncesmainly.Directstresscrackrefertooutsideloaddirectcrackthatstressproducethatcause.Thereasonwhythecrackproducesisasfollows,1,Designthestageofcalculating,doesnotcalculateorleaksandcalculatespartlywhilecalculatinginstructure;Calculatethemodelisunreasonable;Thestructureissupposedandaccordedwithbystrengthactuallybystrength;Loadandcalculateorleakandcalculatefew;Internalforceandmatchingthemistakeincomputationofmuscle;Safetycoefficientofstructureisnotenough.Donotconsiderthepossibilitythatconstructatthetimeofthestructuraldesign;Itisinsufficienttodesignthesection;Itissimplylittleandassigningthemistakeforreinforcingbartosetup;Structurerigidityisinsufficient;Constructanddealwithimproperly;Thedesigndrawingcannotbeexplainedclearlyetc..2,Constructionstage,doesnotpileupandconstructthemachines,materiallimiting;Isitprefabricatestructurestructurereceivestrengthcharacteristic,standup,isithang,transport,installtogetupatwilltounderstand;Constructnotaccordingtothedesigndrawing,altertheconstructionorderofthestructurewithoutauthorization,changethestructureandreceivethestrengthmode;Donotdothetiredintensitycheckingcomputationsundermachinevibrationandwaittothestructure.3,Usingstage,theheavy-dutyvehiclewhichgoesbeyondthedesignloadpassesthebridge;Receivethecontact,strikingofthevehicle,shipping;Strongwind,heavysnow,earthquakehappen,explodeetc..Stresscrackoncemeansthestressofsecondarycausedbyloadingoutsideproducesthecrack.Thereasonwhythecrackproducesisasfollows,1,Indesignoutsideloadfunction,becauseactualworkingstateandroutine,structureofthingcalculatehavediscrepancyorisitconsidertocalculate,thuscausestressoncetocausethestructuretofractureinsomeposition.Twoisitjoinbridgearchfootisitisitassign"X"shapereinforcingbar,cutdownthisplaceway,sectionofsizedesignandcutwithscissorsatthesametimetoadoptoftentodesigntocutwithscissors,theorycalculateplacethiscanstorecurvedsquarein,butrealityshouldisitcanresistcurvedstilltocutwithscissors,sothatpresentthecrackandcausethereinforcingbarcorrosion.2,Bridgestructureisitdigtrough,turnonhole,setupoxleg,etc.toneedoften,difficulttouseaaccurateonediagrammatictoisitisitcalculatetoimitatetogoonincalculatinginroutine,setupandreceivethestrengthreinforcingbaringeneralfoundationexperience.Studieshaveshown,afterbeingdugtheholebythestrengthcomponent,itwillproducethediffractionphenomenonthatstrengthflows,intensiveneartheholeinautensil,producedtheenormousstresstoconcentrate.Inlongtostepprestressingforceofthecontinuousroofbeam,oftenblockthesteelbunchaccordingtotheneedsofsectioninternalforceinstepping,setuptheanchorhead,butcanoftenseethecrackintheanchorfirmsectionadjacentplace.Soifdealwithimproper,incornerorcomponentformsuddenchangeoffice,blockplacetobeeasytoappearcrackstrengthreinforcingbarofstructurethe.Intheactualproject,stresscrackonceproducedthemostcommonreasonwhichloadsthecrack.Stresscrackoncebelongtoonemorepieceofnatureofdrawing,splittingoff,shearing.Stresscrackonceisloadedandcaused,onlyseldomcalculateaccordingtotheroutinetoo,butwithmoderntocalculateconstantperfectionofmeans,timesofstresscracktocanaccomplishreasonablecheckingcomputationstoo.Forexampletosuchstresses2timesofproducingasprestressingforce,creeping,etc.,department'sfiniteelementprocedurecalculateslevelspolecorrectlynow,butmoredifficult40yearsago.Inthedesign,shouldpayattentiontoavoidingstructuresuddenchange(orsectionsuddenchange),whenitisunabletoavoid,shoulddopartdealwith,cornerforinstance,makeroundhorn,suddenchangeofficemakeintothegradationzonetransition,isitisitmixmuscletoconstructtostrengthenatthesametime,cornermixagainobliquetoreinforcingbar,astolargeholeinautensilcansetupprotectingintheperimeteratthetermsofhavinganglesteel.Loadthecrackcharacteristicinaccordancewithloadingdifferentlyandpresentingdifferentcharacteristicsdifferently.Thecrackappearpersonwhodrawmore,thecuttingareaortheseriouspositionofvibration.Mustpointout,isitgetupcoverorhavealongkeepintoshortcrackofdirectiontoappearpersonwhopress,oftenthestructurereachesthesignofbearingtheweightofstrengthlimit,itisanomenthatthestructureisdestroyed,itsreasonisoftenthatsectionalsizeispartialandsmall.Receivethestrengthwaydifferentlyaccordingtothestructure,thecrackcharacteristicproducedisasfollows:1,Thecentreisdrawn.Thecrackrunsthroughthecomponentcrosssection,theintervalisequalonthewhole,andisperpendiculartoreceivingthestrengthdirection.Whileadoptingthewhorlreinforcingbar,lieinthesecond-classcracknearthereinforcingbarbetweenthecracks.2,Thecentreispressed.Itisparallelontheshortanddenseparallelcrackwhichreceivethestrengthdirectiontoappearalongthecomponent.3,Receivecurved.Mostnearthelargesectionfromborderisitappearanddrawintodirectionverticalcracktobeginpersonwhodrawcurvedsquare,anddeveloptowardneutralizationaxlegradually.Whileadoptingthewhorlreinforcingbar,canseeshortersecond-classcrackamongthecracks.Whenthestructurematchesmusclesless,therearefewbutwidecracks,fragilitydestructionmaytakeplaceinthestructure4,Pressedbigandpartial.Heavytopressandmixpersonwhodrawmusclealessonelighttopigeonholeintothecomponentwhilebeingpartialwhilebeingpartial,similartoreceivingthecurvedcomponent.5,Pressedsmallandpartial.Smalltopressandmixpersonwhodrawmuscleamoreoneheavytopigeonholeintothecomponentwhilebeingpartialwhilebeingpartial,similartothecentreandpressedthecomponent.6,Cut.Pressobliqulywhenthehoopmuscleistoodenseanddestroy,theobliquecrackwhichisgreaterthan45??directionappearsalongthebellyofroofbeamend;Isitisitisitdestroytopresstocuttohappenwhenthehoopmuscleisproper,underpartisitinvite45??directionparallelobliquecrackeachothertoappearalongroofbeamend.7,Sprained.Componentonesidebellyappearmanydirectionobliquecrack,45??oftreaty,first,andtolaunchwithspiraldirectionbeingadjoint.8,Washedandcut.4sideisitinvite45??directioninclinedplanedrawandsplittotakeplacealongcolumncapboard,formthetangentplaneofwashing.9,Someandispressed.Sometoappearpersonwhopressdirectionroughlyparallellargeshortcrackswithpressure.(2)crackcausedintemperaturechangeTheconcretehasnatureofexpandingwithheatandcontractwithcold,lookonastheexternalenvironmentconditionorthestructuretemperaturechanges,concretetakeplaceoutofshape,ifoutofshapetorestrainfrom,producethestressinthestructure,producethetemperaturecrackpromptlywhenexceedingconcretetensilestrengthinstress.Insomebeingheavytostepfoot-pathamongthebridge,temperaturestresscanisitgobeyondlivingyearstresseventoreach.Thetemperaturecrackdistinguishesthemaincharacteristicofothercrackswillbevariedwithtemperatureandexpandedorclosedup.Themainfactorisasfollows,tocausetemperatureandchange1,Annualdifferenceintemperature.Temperatureischangingconstantlyinfourseasonsinoneyear,butchangerelativelyslowly,theimpactonstructureofthebridgeismainlytheverticaldisplacementwhichcausesthebridge,canpropupseatmoveorsetupflexiblemound,etc.nottoconstructmeasurecoordinate,throughbridgefloorexpansionjointgenerally,cancausetemperaturecrackonlywhenthedisplacementofthestructureislimited,forexamplearchedbridge,justbridgeetc.TheannualdifferenceintemperatureofourcountrygenerallychangestherangewiththeconductoftheaveragetemperatureinthemoonofJanuaryandJuly.Consideringthecreepcharacteristicoftheconcrete,theelasticmouldamountofconcreteshouldbeconsideredrollingoverandreducingwhentheinternalforceoftheannualdifferenceintemperatureiscalculated.2,Rizhao.Afterbeingtannedbythesunbythesuntothesideofbridgepanel,thegirderorthepier,temperatureisobviouslyhigherthanotherposition,thetemperaturegradientispresentedanddistributedbythelineshape.Becauseofrestrainoneselffunction,causepartdrawstresstoberelativelyheavy,thecrackappears.Rizhaoandfollowingtoisitcausestructurecommonreasonmost,temperatureofcracktolowerthetemperaturesuddenly3,Lowerthetemperaturesuddenly.Fallheavyrain,coldairattack,sunset,etc.cancausestructuresurfacetemperaturesuddenlydroppedsuddenly,butbecauseinsidetemperaturechangerelativelyslowproducingtemperaturegradient.Rizhaoandlowerthetemperatureinternalforcecanadoptdesignspecificationorconsultrealbridgematerialsgoonwhencalculatingsuddenly,concreteelasticmouldamountdoesnotconsiderconvertingintoandreducing4,Heatofhydration.Appearinthecourseofconstructing,thelargevolumeconcrete(thicknessexceeds2.0),afterbuildingbecausecementwatersendoutheat,causeinsideverymuchhightemperature,theinternalandexternaldifferenceintemperatureistoolarge,causethesurfacetoappearinthecrack.Shouldaccordingtoactualconditionsinconstructing,isitchooseheatofhydrationlowcementvarietytotryone'sbest,limitcementunit'sconsumption,reducetheaggregateandenterthetemperatureofthemould,reducetheinternalandexternaldifferenceintemperature,andlowerthetemperatureslowly,canadoptthecirculationcoolingsystemtocarryontheinsidetodispeltheheatincaseofnecessity,oradoptthethinlayerandbuilditinsuccessioninordertoacceleratedispellingtheheat.5,Theconstructionmeasureisimproperatthetimeofsteammaintenanceorthewinterconstruction,theconcreteissuddenandcoldandsuddenandhot,internalandexternaltemperatureisuneven,apttoappearinthecrack.6,PrefabricateTroofbeamhorizontalbafflewhentheinstallation,propupseatburystencilplatewithtransferflatstencilplatewhenweldinginadvance,ifweldmeasuretobeimproper,ironpiecesofnearbyconcreteeasytoisitfracturetoburn.Adoptelectricheatpiecedrawlawpiecedrawprestressingforceatthecomponent,prestressingforcesteeltemperaturecanriseto350degreesCentigrade,theconcretecomponentisapttofracture.Experimentalstudyindicates,arecausedtheintensityofconcretethatthehightemperatureburnstoobviouslyreducewithrisingoftemperaturebysuchreasonsasthefire,etc.,glueingformingthedeclinethereuponofstrengthofreinforcingbarandconcrete,tensilestrengthdropby50%afterconcretetemperaturereaches300degreesCentigrade,compressionstrengthdropsby60%,glueingthestrengthofformingtodropby80%ofonlyroundreinforcingbarandconcrete;Becauseheat,concretebodydissociateinkevaporateandcanproduceandshrinksharplyinalargeamount(3)shrinkthecrackcausedIntheactualproject,itisthemostcommonbecauseconcreteshrinksthecrackcaused.Shrinkkindinconcrete,plasticityshrinkisititshrinks(isitcontracttodo)tobethemainreasonthatthevolumeofconcreteoutofshapehappenstoshrink,shrinkspontaneouslyinadditionandthecharshrink.Plasticityshrink.About4hoursafteritisbuiltthatinthecourseofconstructing,concretehappens,thecementwaterresponseisfierceatthismoment,thestrandtakesshapegradually,secretewaterandmoisturetoevaporatesharply,theconcretedesiccatesandshrinks,itisatthesametimeconductoneselfwithdignitynotsinkingbecauseaggregate,sowhenhardenconcreteyet,itcallplasticityshrink.Theplasticityshrinkproducingamountgradeisverybig,canbeuptoabout1%.Ifstoppedbythereinforcingbarwhiletheaggregatesinks,formthecrackalongthereinforcingbardirection.Ifweb,roofbeamofTandroofbeamofcaseandcarrybaseplatehandoverofficeincomponentverticaltobecomesectionalplace,becausesinktooreallytosuperficialobeyingthewebdirectioncrackwillhappenevenlybeforehardenning.Forreducingconcreteplasticityshrink,itshouldcontrolbywaterdustwhenbeingconstructthan,lastlong-timemixing,unloadingshouldnottooquick,isitisittakecloselyknittosmashtoshake,verticaltobecomesectionalplaceshoulddividelayerbuild.Shrinkandshrink(doandcontract).Aftertheconcreteisformedhard,asthetoplayermoistureisevaporatedprogressively,thehumidityisreducedprogressively,thevolumeofconcreteisreduced,iscalledandshrunktoshrink(doandcontract).Becauseconcretetoplayermoisturelosssoon,itisslowforinsidetolose,producesurfaceshrinkheavy,insideshrinkalightoneeventoshrink,itisoutofshapetorestrainfrombytheinsideconcreteforsurfacetoshrink,causethesurfaceconcretetobearpullingforce,whenthesurfaceconcretebearspullingforcetoexceeditstensilestrength,produceandshrinkthecrack.Theconcretehardensafter-contractiontojustshrinkandshrinkmainly.Suchasmixmusclerateheavycomponent(exceed3%),betweenreinforcingbarandmoreobviousrestraintsrelativelythatconcreteshrink,theconcretesurfaceisapttoappearinthefullofcrackscrackle.Shrinkspontaneously.Spontaneoustoitshrinkstobeconcreteinthecourseofhardenning,cementandwatertakeplaceinkreact,theshrinkwithhavenothingtodobyexternalhumidity,andcanpositive(whethershrink,suchasordinaryportlandcementconcrete),cannegativetoo(whetherexpand,suchasconcrete,concreteofslagcementandcementofflyash).Thecharshrinks.Betweencarbondioxideandhyrateofcementofatmospheretakeplaceoutofshapeshrinkthatchemicalreactioncause.Thecharshrinksandcouldhappenonlyabout50%ofhumidity,andacceleratewithincreaseofthedensityofthecarbondioxide.Thecharshrinksandseldomcalculates.Thecharacteristicthattheconcreteshrinksthecrackisthatthemajoritybelongstothesurfacecrack,thecrackisrelativelydetailedinwidth,andcriss-cross,becomethefullofcracksform,theformdoesnothaveanylaw.Studieshaveshown,influenceconcreteshrinkmainfactorofcrackasfollows,1,Varietyofcement,gradeandconsumption.Slagcement,quick-hardeningcement,low-heatcementconcretecontractivityarerelativelyhigh,ordinarycement,volcanicashcement,aluminacementconcretecontractivityarerelativelylow.Cementgradelowinaddition,unitvolumeconsumptionheavyrubingdetaileddegreeheavy,thentheconcreteshrinksthemoregreatly,andshrinktimeisthelonger.Forexample,inordertoimprovetheintensityoftheconcrete,oftenadoptandincreasethecementconsumptionmethodbyforcewhileconstructing,theresultshrinksthestresstoobviouslystrengthen.2,Varietyofaggregate.Suchabsorbingwaterratesasthequartz,limestone,cloudrock,granite,feldspar,etc.aresmaller,contractivityisrelativelylowintheaggregate;Andsuchabsorbingwaterratesasthesandstone,slate,angleamphibolite,etc.aregreater,contractivityisrelativelyhigh.Aggregategrainsoffoot-pathheavytoshrinklightinaddition,watercontentbigtoshrinkthelarger.3,Watergraythan.Theheavierwaterconsumptionis,thehigherwateranddustare,theconcreteshrinksthemoregreatly.4,Mixthepharmaceuticaloutside.Itisthebettertomixpharmaceuticalwater-retainingpropertyoutside,thentheconcreteshrinksthesmaller.5,Maintainthemethod.Waterthatgoodmaintenancecanacceleratetheconcretereacts,obtaintheintensityofhigherconcrete.Keephumidityhigh,lowmaintainingtimetobethelongertemperaturewhenmaintaining,thentheconcreteshrinksthesmaller.Steammaintainwaythanmaintainwayconcreteisittakelighttoshrinknaturall.6,Externalenvironment.Thehumidityislittle,theairdrying,temperaturearehigh,thewindspeedislargeintheatmosphere,thentheconcretemoistureisevaporatedfast,theconcreteshrinksthefaster.7,Shakeandsmashthewayandtime.Machineryshakewayofsmashingthanmakefirmbyrammingortampingwayconcretecontractivitytakelittlebyhand.Shakingshoulddetermineaccordingtomechanicalperformancetosmashtime,aregenerallysuitablefor55s/time.Itistooshort,shakeandcannotsmashcloselyknit,itisinsufficientornoteveninintensitytoformtheconcrete;Itistoolong,causeanddividestorey,thickaggregatesinkstothegroundfloor,theupperstratathatthedetailedaggregatestays,theintensityisnoteven,theupperstrataincidentshrinkthecrack.Andshrinkthecrackcausedtotemperature,worthyofconstructingthereinforcingbaragainingcanobviouslyimprovetheresistingthesplittingofconcrete,structureofespeciallythinwall(thick200cmofwall).Mixmuscleshouldisitadoptlightdiameterreinforcingbar(8|?construct14|?)tohavepriority,littleintervalassign(whether@10construct@15cm)onconstructing,thewholesectionisitmixmuscletoberateunsuitabletobelowerthan0toconstruct.3%,cangenerallyadopt0.3%~0.5%.(4),crackthatcausesoutofshapeofplinthofthegroundBecausefoundationverticaltoeventosubsideorhorizontaldirectiondisplacement,makethestructureproducetheadditionalstress,gobeyondresistingtheabilityofdrawingofconcretestructure,causethestructuretofracture.Theevenmainreasonthatsubsideofthefoundationisasfollows,1,Reconnoitrestheprecisionandisnotenoughfor,testthematerialsinaccuratlyingeology.Designing,constructingwithoutfullygraspingthegeologicalsituation,thisisthemainreasonthatcausethegroundnottosubsideevenly.Suchashillsareaorbridge,districtofmountainridge,,holeintervaltobetoofarwhenreconnoitring,andgroundriseandfallbigtherock,reconnoitringthereportcan'tfullyreflecttherealgeologicalsituation.2,Thegeologicaldifferenceofthegroundistoolarge.Buildingitinthebridgeofthevalleyoftheditchofmountainarea,geologyofthestreamplaceandplaceonthehillsidechangelarger,eventhereareweakgroundsinthestream,becausethesoilofthegrounddoesnotcausesanddoesnotsubsideevenlywiththecompressing.3,Thestructureloadsthedifferencetoobig.Undertheunanimousterms,wheneveryfoundationtooheavytoloaddifferenceingeologicalsituation,maycauseevenlytosubside,forexamplehightofilloutsoilcaseshapeinthemiddlepartoftheculvertthantoisittakeheavytoloadbothsides,tosubsidesoonheavythanbothsidesmiddlepart,caseisitmightfracturetocontain4,Thedifferenceofbasictypeofstructureisgreat.Uniteitinthebridgethesamly,mixanduseanddoesnotexpandthefoundationandafoundationwiththefoundation,oradoptafoundationwhenafoot-pathoralongdifferenceisgreatatthesametime,oradoptthefoundationofexpandingwhenbasiselevationiswidelydifferentatthesametime,maycausethegroundnottosubsideevenlytoo5,Foundationbuiltbystages.Inthenewly-builtbridgenearthefoundationoforiginalbridge,ifthehalfabridgeaboutexpresswaybuiltbystages,thenewly-builtbridgeloadsorthefoundationcausesthesoilofthegroundtoconsolidateagainwhiledealingwith,maycauseandsubsidethefoundationoforiginalbridgegreatly6,Thegroundisfrozenbloatedly.Thegroundsoilofhighermoisturecontentontermsthatlowerthanzerodegreeexpandsbecauseofbeingicy;Oncetemperaturegoesup,thefrozensoilismelted,thesettingofground.Sothegroundisicyormeltscausesanddoesnotsubsideevenly.7,Bridgefoundationputonbody,cavewithstalactitesandstalagmites,activityfault,etc.ofcomingdownatthebadgeology,maycauseanddoesnotsubsideevenly.8,Afterthebridgeisbuiltup,theconditionchangeoforiginalground.Aftermostnaturalgroundsandartificialgroundsaresoakedwithwater,especiallyusuallyfilloutsuchsoilofspecialgroundasthesoil,loess,expandingintheland,etc.,soilbodyintensitymeetwaterdrop,compressoutofshapetostrengthen.Inthesoftsoilground,seasoncausesthewatertabletodroptodrawwateroraridartificially,thegroundsoillayerconsolidatesandsinksagain,reducethebuoyancyonthefoundationatthesametime,shoulderingtheobstructionofrubingtoincrease,thefoundationiscarriedonone'sshoulderorbackandstrengthened.Somebridgefoundationisitputtooshallowtobury,erode,isitdigtowashflood,thefoundationmightbemoved.Groundloadchangeofterms,bridgenearbyisitisitabolishsquare,grit,etc.inalargeamounttoputtopilewithcavein,landslide,etc.reasonforinstance,itisoutofshapethatthebridgelocationrangesoillayermaybecompressedagain.So,theconditionoforiginalgroundchangewhileusingmaycauseanddoesnotsubsideevenlyProducethestructurethingofhorizontalthrusttoarchedbridge,etc.,itisthemainreasonthathorizontaldisplacementcrackemergestodestroytheoriginalgeologicalconditionwhentothatitisunreasonabletograspincompletely,designandconstructinthegeologicalsituation.目录桥梁裂痕产生原由浅析最近几年来，我省交通基础建设获取迅猛发展，各地兴建了大批的混凝土桥梁。在桥梁建筑和使用过程中，相关因出现裂痕而影响工程质量甚至导桥梁垮塌的报导屡见不鲜。混凝土开裂能够说是“常发病”和“多发病”，常常困扰着桥梁工程技术人员。其实，假如采纳必定的设计和施工举措，好多裂痕是能够战胜和控制的。为了进一步增强对混凝土桥梁裂痕的认识，尽量防止工程中出现危害较大的裂痕，本文尽可能对混凝土桥梁裂痕的种类和产生的原由作较全面的剖析、总结，以方便设计、施工找出控制裂痕的可行方法，达到防备于已然的作用。混凝土桥梁裂痕种类、成因实质上，混凝土结构裂痕的成因复杂而众多，甚至多种要素互相影响，但每一条裂痕均有其产生的一种或几种主要原由。混凝土桥梁裂痕的种类，就其产生的原由，大概可区分以下几种：一、荷载惹起的裂痕混凝土桥梁在惯例静、动荷载及次应力下产生的裂痕称荷载裂痕，概括起来主要有直策应力裂痕、次应力裂痕两种。直策应力裂痕是指外荷载惹起的直策应力产生的裂痕。裂痕产生的原由有：1、设计计算阶段，结构计算时不计算或部分漏算；计算模型不合理；结构受力假定与实质受力不符；荷载少算或漏算；内力与配筋计算错误；结构安全系数不够。结构设计时不考虑施工的可能性；设计断面不足；钢筋设置偏少或部署错误；结构刚度不足；结构办理不妥；设计图纸交代不清等。2、施工阶段，不加限制地堆放施工机具、资料；不认识预制结构结构受力特色，任意翻身、起吊、运输、安装；不按设计图纸施工，私自改正结构施工次序，改变结构受力模式；不对结构做机器振动下的疲惫强度验算等。3、使用阶段，高出设计载荷的重型车辆过桥；受车辆、船舶的接触、撞击；发生狂风、大雪、地震、爆炸等。次应力裂痕是指由外荷载惹起的次生应力产生裂痕。裂痕产生的原由有：1、在设计外荷载作用下，因为结构物的实质工作状态同惯例计算有进出或计算不考虑，进而在某些部位惹起次应力以致结构开裂。比如两铰拱桥拱脚设计常常采纳部署“X”形钢筋、同时减少该处断面尺寸的方法设计铰，理论计算该处不会存在弯矩，但实质该铰仍旧能够抗弯，以致出现裂痕而以致钢筋锈蚀。2、桥梁结构中常常需要凿槽、开洞、设置牛腿等，在惯例计算中难以用正确的图式进行模拟计算，一般依据经验设置受力钢筋。研究表示，受力构件挖孔后，力流将产生绕射现象，在孔洞邻近密集，产生巨大的应力集中。在长跨预应力连续梁中，常常在跨内依据截面内力需要截断钢束，设置锚头，而在锚固断面邻近常常能够看到裂痕。所以，若办理不妥，在这些结构的转角处或构件形状突变处、受力钢筋截断处简单出现裂痕。实质工程中，次应力裂痕是产生荷载裂痕的最常有原由。次应力裂痕多属张拉、劈裂、剪切性质。次应力裂痕也是由荷载惹起，仅是按惯例一般不计算，但跟着现代计算手段的不停完美，次应力裂痕也是能够做到合理验算的。例如此刻对预应力、徐变等产生的二次应力，许多平面杆系有限元程序均可正确计算，但在40年前却比较困难。在设计上，应注意防止结构突变（或断面突变），当不可以回避时，应做局部办理，如转角处做圆角，突变处做成渐变过渡，同时增强结构配筋，转角处增配斜向钢筋，关于较大孔洞有条件时可在周边设置护边角钢。荷载裂痕特色依荷载不一样而异体现不一样的特色。这种裂痕多出此刻受拉区、受剪区或振动严重部位。但一定指出，假如受压区出现起皮或有沿受压方向的短裂痕，常常是结构达到承载力极限的标记，是结构损坏的先兆，其原由常常是截面尺寸偏小。依据结构不一样受力方式，产生的裂痕特色以下：1、中心受拉。裂痕贯串构件横截面，间距大概相等，且垂直于受力方向。采纳螺纹钢筋时，裂痕之间出现位于钢筋邻近的次裂痕。2、中心受压。沿构件出现平行于受力方向的短而密的平行裂痕。3、受弯。弯矩最大截面邻近从受拉区边缘开始出现与受拉方向垂直的裂痕，并渐渐向中和轴方向发展。采纳螺纹钢筋时，裂痕间可见较短的次裂痕。当结构配筋较少时，裂痕少而宽，结构可能发生脆性损坏。4、大偏爱受压。大偏爱受压和受拉区配筋较少的小偏爱受压构件，近似于受弯构件。5、小偏爱受压。小偏爱受压和受拉区配筋许多的大偏爱受压构件，近似于中心受压构件。6、受剪。当箍筋太密时发生斜压损坏，沿梁端腹部出现大于45°方向的斜裂痕；当箍筋适合时发生剪压损坏，沿梁端中下部出现约45°方向互相平行的斜裂痕。7、受扭。构件一侧腹部先出现多合约

45°方向斜裂痕，并向相邻面以螺旋方向睁开。

8、受冲切。沿柱头板内四侧发生约

45°方向斜面拉裂，形成冲切面。

9、局部受压。在局部受压区出现与压力方向大概平行的多条短裂痕。二、温度变化惹起的裂痕混凝土拥有热胀冷缩性质，当外面环境或结构内部温度发生变化，混凝土将发生变形，若变形遇到拘束，则在结构内将产生应力，当应力超出混凝土抗拉强度时即产生温度裂痕。在某些大跨径桥梁中，温度应力能够达到甚至高出活载应力。温度裂痕差异其余裂痕最主要特色是将随温度变化而扩充或合拢。惹起温度变化主要要素有：1、年温差。一年中四时温度不停变化，但变化相对迟缓，对桥梁结构的影响主假如以致桥梁的纵向位移，一般可经过桥面伸缩缝、支座位移或设置柔性墩等结构举措相协调，只有结构的位移遇到限制时才会惹起温度裂痕，比如拱桥、刚架桥等。我国年温差一般以一月和七月月均匀温度的作为变化幅度。考虑到混凝土的蠕变特征，年温差内力计算时混凝土弹性模量应试虑折减。2、日照。桥面板、主梁或桥墩侧面受太阳曝晒后，温度显然高于其余部位，温度梯度呈非线形散布。因为遇到自己拘束作用，以致局部拉应力较大，出现裂痕。日照和下述忽然降温是以致结构温度裂痕的最常有原由。3、忽然降温。突降大雨、冷空气侵袭、日落等可以致结构表面面温度忽然降落，但因内部温度变化相对较慢而产生温度梯度。日照和忽然降温内力计算时可采纳设计规范或参照实桥资料进行，混凝土弹性模量不考虑折减。4、水化热。出此刻施工过程中，大概积混凝土（厚度超出米）浇筑之后因为水泥水化放热，以致内部温度很高，内外温差太大，以致表面出现裂痕。施工中应依据实质状况，尽量选择水化热低的水泥品种，限制水泥单位用量，减少骨料入模温度，降低内外温差，并迟缓降温，必需时可采纳循环冷却系统进行内部散热，或采纳薄层连续浇筑以加快散热。5、蒸汽保养或冬天施工时施工举措不妥，混凝土骤冷骤热，内外温度不均，易出现裂痕。6、预制T梁之间横隔板安装时，支座预埋钢板与调平钢板焊接时，若焊接举措不妥，铁件邻近混凝土简单烧伤开裂。采纳电热张拉法张拉预应力构件时，预