橋梁設計存在的主要問題中英文翻譯

1、THEMAINPROBLEMSOFDOMESTICRIDGEDESIGNINGNow,thecountry'sstructuraldesignprocess,suchtendencies:moreintensityconsideredinthedesignanddurabilityconsiderlessattentionintensitylimittotheuseofstatewithoutlimitstate,andthroughoutthelifecycleofthemostimportantwhenitispreciselytheuseofperformance;attenti

2、ontotheconstructionofthestructurewithoutattentiontothemaintenanceofthestructure.Infact,thecurrentdesignofthebridgeformoredurabilityisaconcern,asaconcept,didnotexplicitlyputforwardtherequestoftheuseoflife,northedurabilityofspecializeddesign.Thesetendenciestoacertainextent,ledtothecurrentprojectaccide

3、nts,theuseofpoorperformance,theshortlifeoftheadverseconsequencesofstructuralengineeringwiththeincreasingemphasisoninternationaldurability,safety,contrarytothetrendofapplicability;doesnotconformtothestructuredynamicandcomprehensiveeconomyrequirements.Bridgesafety,durability,themainreasonforpoor1) Con

4、structionandmanagementoflowlevelMorebridgesathomeandabroaddestructionandthesuddencollapseofthebridgehasbeenengineeringmoreconcernedaboutsecurityissues.Thegeneralviewisthatthecurrentprojectisbarbaricincidentmanagementandconstructioncausedbycorruption.Fortheshortterm,suchasthedestructionandcollapseofa

5、sudden,mostlybecauseofconstructionqualitydidnotmeetspecificationsanddesignrequirements,typicalproblemsincludeinadequateandconstructionmaterialsintensityoffailure;alsoexist,suchasindividualbridgejerryseriousmanagementissues,butalsoonbridgesafetyofthefataldamage.Andalargenumberofbridgesinthefardidnota

6、chievetheexpectedlifetime,therehasbeenaffectingthenormaluseofdiseaseanddeterioration,especiallyinanumberofbridgesinuseonlyafewyears,orevenjustcompletedsoonontheseriousproblemofinsufficientdurability,whichandthelowqualityofconstructionisanimportantrelationship,thetypicalproblemsofinadequateprotection

7、ofreinforcedandthecurrentwidespreadintheconstructionsiteoftheseriousproblemofcrackingcomponent.Theseconstruction,althoughshort-termdeficienciesofthebridgewillnotbethenormaluseofaclearimpact,butthelong-termdurabilityofthestructurewillhaveaverynegativehazards.2) Designtheoryandstructureofthesystemisno

8、tperfectenoughWhileacknowledgingtheexistenceoftheproblem,butitalso,itisundeniablethatbridgedesignfields,inparticularonthebridgeconstructionanduseoftheissueofsafetythereisstillmuchimprovement.Structuraldesignfirstandforemosttaskisthechoiceofreasonableeconomicprogrammer,followedbythestructuralanalysis

9、anddesignofcomponentsandconnections,andaccesstoregulatethesafetyfactorspecifiedorreliabilityofindicatorstoensurethesafetyofthestructure.Manydesignersoftencomplacentwithnormsonthestructuralstrengthofthesafetyoftheneed,andignorethestructuralsystem,structure,structure,structureofmaterials,structuremain

10、tenance,aswellasfromthestructuraldurabilityofthedesignandconstructionprocesstomakeuseofthatoftenappearintheman-madewrongareastostrengthenandguaranteethesafetyofthestructure.Somestructuralintegrityandductilityinadequateredundancysmall,butsomeofSchemaandtheuncertaintyoftheline,causingpartialexcessivef

11、orce;someconcretestrengthgradetoolowtoprotectslicethroughsmalldiametersteelmicromanage,athincross-sectioncomponentsofthesestructureshaveweakenedthedurability,itwouldseriouslyaffectthesafetyofthestructure.Manybridges,althoughthedesignspecificationsmeettherequirementsofthestrengthofonly5to10yearsbecau

12、seofthedurabilityoftheproblemsaffectingstructuralsafety.StructuralDurabilityshortagehasbecomeoneofthemostrealisticsecurityissues,fromdesigntoconstructionandmaterials,suchasangleofmeasurestostrengthenthedurabilityofthestructure.Oftheenvironmentandtheuseofdifferentconditions,differentdesignofthestruct

13、uralsystemwilltargetdifferentaspectsofthelayoutandstructurerequirements.Normscannotcoverindetailthedesignstaffshouldsolvethevariousproblemsintheupdatednormsfastercanalsoadapttonewunderstanding,newtechnologies,newmaterials,rapiddevelopmentofthestructureofthenewrequirements.Therefore,reasonableandreli

14、ableadditiontothestructuresisdesignedtomeettherequirementsofnorms,andtodesignastructuretothecorrectunderstandingofnature,richexperienceandaccuratejudgments.Andtheneedtoimproveeffortsinthedirection1) ShouldpaymoreattentiontothedurabilityofstructuralproblemsBridgeintheconstructionanduseoftheprocess,wi

15、llbesubjecttoenvironmental,andtheerosionofharmfulchemicalsubstances,andtobearvehicles,wind,earthquake,fatigue,overloading,humanfactors,suchasexternalrole,andbridgematerialsusedbytheself-degradationofperformancewillcontinue,resultinginthestructureofthedifferentdegreesofdamageanddeterioration.Inthefie

16、ldoflong-spanbridges,andfromthecountrysincethe1980s,theconstructionofalargenumberofcable-stayedbridge,althoughsofartherecollapseorseriousdamagetothefewexamples,buthasmorebridgesbecauseofthedurabilityofcabletotheproblemadvanceforcable,andthisnotonlyaffectstheuseofincreasedeconomiclosses.Needstobepoin

17、tedoutisthatmanyoftheseproblemsanddidnotconductareasonabledurabilityofthedesign,whichhasalsopromptedrenewedawarenessofdurabilityofthebridge.Diseasesarealotofexamplesofthat,inadditiontoconstructionmaterialsandthereasonsforadecisiveimpactonthedurabilityofthestructurefromthestructuralfactors(isdesign)f

18、laws.Fromthecountryinthe1990sstartedtoattachimportancetothedurabilityofthestructureofthestudy,hasalsomadequiteafewsuccesses.Mostofthesestudiesandstatisticsfromtheanalysisofthematerialpointofview,onhowtostructureanddesignfromtheperspectiveofhowandthedesignandconstructionstafftobereadilyacceptedandope

19、rationofthebridgeapproachtoimprovingthedurabilityhasbeenlittleresearch.Moreover,foralongtime,peoplehavealwaysbeenemphasisonthemethodsofcalculationonthestructure;itignoresthedetailsoftheoverallstructureandprocessingconcern.Designanddurabilityofthestructureofthestructuraldesignofaconventionalnatureoft

20、hedifferencebetweenthecurrenteffortswillbeneededonthedurabilityofthequalitativeanalysistothequantitativeanalysisofdevelopment.2) EmphasisonthestudyoffatiguedamageBridgestructuretowithstandthevehicleloadandwindloadaredynamicloadwillbeinacycleofchangewithinthestructureofthestress,notonlywillcausethevi

21、brationofthestructure,butalsofromthestructureoftheaccumulatedfatiguedamage.Thebridgeisnotusedbythematerialisuniformandcontinuous,infacttherearemanytinyflawsintheroleofcyclicloading,thesedeficiencieswillbeprogressivedevelopmentofmicro,amergerofinjury,andgraduallyformedinthematerialmacrocracks.Ifthecr

22、ackisnoteffectivemacro-control,isverylikelytocausematerial,thestructureofbrittlefracture.Earlyfatiguedamageisnotalwayseasytobedetected,buttheconsequencesareoftendisastrous.Fatiguedamagehasbeenconsideredinthedesignofsteelbridgeisthecoreissueoffatiguecausedbythesteelstructureofsteelcrackmorecases,many

23、causedbyfatiguefracturebridgecollapseexample.Overthepast20years,fatigueinjuryresearchhasenteredtheconcretestructure,butbytheuseofcorrosionofreinforcedconcretestructuresdynamicperformanceandfatiguepropertiesofneedtobestrengthened.Onthefatiguedamageofnotonlyreferstotheentirestructure,thebridgestructur

24、eoftenasamatteroffactsomeofthekeypartsoflocalfatiguefailureoftheentirestructureandleadtofailure,suchasthecable-stayedbridgecablesanchoringendofthefatiguedamage.3) PayfullattentiontotheproblemofoverloadingthebridgeTherearethreemainvehicleoverloading:Oneistheearlyconstructionoftheoldbridgeoverageloadc

25、arriersandtheotheristhepassageofvehiculartrafficbridgeovertheoriginaldesign;theotheris川egaloverloadingofvehicles.Thefirsttwoarethemainreasonsforthechangesinthedesignloadandtheincreaseinthevolumeoftraffic;usersofthelatterare川egaloverloadingofvehiclesoperating,thelattertwophenomenaofoverloadinginroadt

26、ransportinChinaismorecommon.Ontheonehand,overloadingthebridgemaytriggerfatigue.Overloadingbridgewouldincreasetherateoffatiguestressinjuryaggravated,orevensomestructuraldamagecausedbyoverloadingaccidents.Ontheotherhand,duetooverloadingofthebridgecausedinternaldamagecannotberestored,thebridgewillbemad

27、eoftheworkundernormalloadconditionschange,whichcouldendangerthesafetyofbridgesanddurability.Forexample,theconcretebridgehasalwaysbeenregardedasanadequatedurability,buttheoverloadingofthevehicle,crackingmayoccur;cracksevenintheloadwillbeabletodivestclosed,buttheinternalstructureofconcretehasbeendamag

28、e,crackingcomponentfromthelowerbend,Stiffnessdeclinewasinthenormaluseofload,shouldnothavebeencrackingorstructuralcrackshavebecomesmallercracksinexcessofthenormstoallowalargercracksordeformation.Thesewillbeusedforstructuralperformanceandlong-termdurabilityhasanegativeimpact,inadditiontotheTrafficCont

29、roldepartmentsshouldstrengthenmanagement,butalsotheneedforoverloadingtheconsequencesofresearch,analysis.4) ActivelylearnfromforeignexperienceandresultsDomesticbridgedesignthemainproblemsistheuseofthenormalstructureofpoorperformance(referringcomparedwiththedesignexpectationscanbeattributedtopoorperfo

30、rmanceoftheapplication,includingthebridgetoomuchvibration,linearirregularity,joints,diarrhea,excessivestructuralcrackinganddeformation,etc.),durabilityandsafetyofthepoor(includingshortlifespan,highmaintenancecosts,andmorefrequentaccidents,etc.).Whiletheseissueshavewiththecurrentdomesticconstructionq

31、ualityandmanagementlevellower,buttobefair,sincethissituationcannotberesolvedintheshortterm,thenasengineersweshouldaddressthisissueinthepremise,arefullytakenintoaccountstageofconstructionandmanagementandmaterialstechnology,theuseofappropriatesecurity,theappropriatewaytoensurethatthedesignofabridgetot

32、heuseoftheperformance,thisisamoreproactiveandeffectivemeans.Especiallythedurabilityofthebridgeandsafetyofmanyproblemswiththestructureortheuseofmaterialselectionareunreasonableandimproperhandlingofthestructuraldetails.InEuropeancountries(suchasGermany,Denmark,etc.),attachedgreatimportancetothestructu

33、reofaperformance-baseddesign(PBD,PerformanceBasedDesign),whichincludesstructuraldeformation,cracks,vibration,strong,handsome,durability,fatigueandsoon.PBDstudyistoenableoperatorsinthestructureoftheprocess,inadditiontotheguaranteedminimumsecurityrequirements;theideaoftheuseofperformanceshouldbegood(i

34、ncludinglifeanddurability,corrosionresistance,fatigueresistance,aesthetics,etc.).Bytheirverynature,theEuropeancountriesPBDtheory,researchintheuseofstructureinthecourseofperformanceoutofservice,theperformancebytheweakeningofthereasonsforitsoccurrenceandthemechanismofthelaw,toseekanewstructuraldesignc

35、onceptsandmethods.FromthepointofviewofEuropeans,PBDseemstobetothedurabilityofthestructureatthecoreofthecomprehensiveuseofperformanceindicatorstoconsider.ThisisthedomesticengineeringshouldbebasedontheEnlightenment.Atpresentthedomesticdesigncanbeseenasstaticdesign,builtonlyatthedesigndefinitionofastru

36、cture'sabilityandperformance,andduringtheperformanceofoperatingtimeandtheactualdeteriorationoftheperformanceofthelackofsufficientawarenessandconsideration;Inotherwords,theeconomicpointofviewistoconsideronlytheconstructioncost,theexpenseofoperatingandmaintenancecostsandservicelifeshouldbetherelat

37、ivecost-effectiveness.Bridgesafetyanddurabilityshortagehasbecomeanurgentneedtoaddresstheproblem,weshouldactivelylearnfromsuccessfulforeignexperiencesandpractices,inadditiontostrengtheningtheconstructionqualitymanagement,bridgedesignconceptsandfromthestructureandtectonicperspectivetothedesignofdurabi

38、lity.Atthesametimeneedtostudyfatigueandoverloadingthedurabilityofthebridgestructureeffects.國內(nèi)橋梁設計存在的主要問題現(xiàn)在，國內(nèi)的結構設計過程中，有這樣的傾向：設計中考慮強度多而考慮耐久性少;重視強度極限狀態(tài)而不重視使用極限狀態(tài)，而結構在整個生命周期中最重要的卻恰恰是使用時的性能表現(xiàn)；重視結構的建造而不重視結構的維護。實際上，目前的橋梁設計中，對于耐久性更多的只是作為一種概念受到關注，既沒有明確提出使用年限的要求，也沒有進行專門的耐久性設計。這些傾向在一定程度上導致了當前工程事故頻發(fā)、結構使用性能差、使用

39、壽命短的不良后果；也與國際結構工程界日益重視耐久性、安全性、適用性的趨勢相違背；也不符合結構動態(tài)和綜合經(jīng)濟性的要求。橋梁安全性、耐久性差的主要原因1 ）施工和管理水平低國內(nèi)外多座橋梁的突然破壞與倒塌，已使工程界對橋梁安全性問題倍加關注。一般的看法認為當前的工程事故主要是野蠻施工和管理腐敗所導致。對于短期內(nèi)發(fā)生的諸如突然破壞與倒塌，多是由于施工質量沒有達到規(guī)范和設計要求，典型的問題包括材料強度不足和施工工藝不合格等；也有個別橋梁存在諸如偷工減料、以次充好等嚴重的管理問題，更是對橋梁安全造成致命的損害。而大量的橋梁在遠沒有達到預期使用壽命時，出現(xiàn)了影響正常使用的病害與劣化；特別是一些橋梁在只使用了

40、幾年、甚至剛建成不久就出現(xiàn)嚴重的耐久性不足的問題，這也與施工質量低下有重要關系，典型的問題有鋼筋保護層不足及目前廣泛存在于施工現(xiàn)場的嚴重的構件開裂問題。這些施工上的缺陷雖然短期不會對橋梁的正常使用產(chǎn)生明顯的影響，但卻會對結構的長期耐久性產(chǎn)生非常不利的危害。2 ）設計理論和結構構造體系不夠完善在承認施工存在問題的同時，也不可否認，在橋梁設計領域，特別是關于橋梁施工和使用期安全性的問題還有許多可以改進的地方。結構設計的首要任務是選擇經(jīng)濟合理的結構方案，其次是結構分析與構件和連接的設計，并取用規(guī)范規(guī)定的安全系數(shù)或可靠性指標以保證結構的安全性。許多設計人員往往只滿足于規(guī)范對結構強度計算上的安全度需要，

41、而忽視從結構體系、結構構造、結構材料、結構維護、結構耐久性以及從設計、施工到使用全過程中經(jīng)常出現(xiàn)的人為錯誤等方面去加強和保證結構的安全性。有的結構整體性和延性不足，冗余性??；有的計算圖式和受力路線不明確，造成局部受力過大；有的混凝土強度等級過低、保護層厚度過小、鋼筋直徑過細、構件截面過薄；這些都削弱了結構耐久性，會嚴重影響結構的安全性。不少橋梁、雖然滿足了設計規(guī)范的強度要求，僅用了510年就因為耐久性出了問題影響結構安全。結構耐久性不足已成為最現(xiàn)實的一個安全問題，設計時要從構造、材料等角度采取措施加強結構耐久性。不同的環(huán)境和使用條件、不同的設計對象都會對結構體系提出不同的布局和構造等方面的要求

42、。規(guī)范再詳細也不能包羅本應由設計人員解決的各種問題、規(guī)范更新得再快也適應不了新認識、新技術、新材料快速發(fā)展對結構提出的各種新的要求。因此，合理可靠的結構設計除了滿足規(guī)范的要求外，還要求設計人員具有對結構本性的正確認識、豐富的經(jīng)驗和準確的判斷。需要改進和努力的方向1）應該更加重視結構的耐久性問題橋梁在建造和使用過程中，一定會受到環(huán)境、有害化學物質的侵蝕，并要承受車輛、風、地震、疲勞、超載、人為因素等外來作用，同時橋梁所采用材料的自身性能也會不斷退化，從而導致結構各部分不同程度的損傷和劣化。在大跨橋梁領域，國內(nèi)從上世紀80年代以來，修建了大量的斜拉橋；雖然迄今為止出現(xiàn)倒塌或嚴重損害的例子很少，但已

43、經(jīng)有多座橋梁因為拉索的耐久性問題而不得不提前換索，既影響了使用又增大了經(jīng)濟損失。需要指出的是，很多這類問題與沒有進行合理的耐久性設計有關，這也促使人們重新認識橋梁的耐久性問題。大量的病害實例也證明，除了施工和材料方面的原因，影響結構耐久性的決定性因素是來自構造上（也即設計上）的缺陷。國內(nèi)從上世紀90年代開始重視了對結構耐久性的研究，也取得了不少成果。這些研究大多是從材料和統(tǒng)計分析的角度進行的，對如何從結構和設計的角度及如何以設計和施工人員易于接受和操作的方式來改善橋梁耐久性卻很少有人研究。而且，長期以來，人們一直偏重于結構計算方法的研究，卻忽視了對總體構造和細節(jié)處理方面的關注。結構的耐久性設計與常規(guī)的結構設計有著本質的區(qū)別，目前需要努力將耐久性的研究從定性分析向定量分析發(fā)展。2）重視對疲勞損傷的研究橋梁結構所承受的車輛荷載和風荷載都是動荷載，會在結構內(nèi)產(chǎn)生循環(huán)變化的應力，不但會引起結構的振動，還會引起結構的累積疲勞損傷。由于橋梁所采用的材料并非是均勻和連續(xù)的，實際上存在許多微小的缺陷，在循環(huán)荷載作用下，這些微缺陷會逐漸發(fā)展、合并形成損傷，并逐步在材料中形成宏觀裂紋。如果宏觀裂紋不得到有效控制，極有可能會引起材料、結構的脆性斷裂。早期疲勞損傷往往不易被檢測到，但其帶來的后果往往是災難性的。疲勞損傷過去