桥梁外文翻译 荷兰跨线高架桥.docx
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桥梁外文翻译 荷兰跨线高架桥.docx
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桥梁外文翻译荷兰跨线高架桥
附录4外文文献翻译
RAILWAYSUSPENSIONBRIDGE
INWOERDEN,THENETHERLANDS
SUMMARY
InWoerden,asmalltowninthewestoftheNetherlands,arailwayfly-overhasbeenbuiltwheretworailwaytracksmeet.Thefly-overconsistsofasingle-trackviaduct.Thishasalengthof438.5m.Thecrossingangleis10degrees.Atthefly-oversitetheviaductissuspendedfromapylonthathasbeenconstructedovertwotrackspassingunderneath.
1.INTRODUCTION
ArailwaybridgewasconstructedinWoerdenaspartofthetrackexpansionoftheNetherlandsRailways.Moretrainswillberun,therunningspeedswillbeincreasedandthepossibilityofdelaysmustbereduced.Inordertomakethispossible,manylinesectionsmustbefour-trackandtrainsmustbeabletocrosseachotheratdifferentlevels.
Thispaperexaminesthefly-overinWoerden.
2.SITUATIONANDREQUIREMENTS
Thefly-overinWoerdenmustbridgethefollowingelements:
-twoexistingtracks;
-twofuturetracks;
-apolderdrainagepool;
-anunderpassforalltraffic.
Thesubsoilexhibitsagreatvariationincompressibility.Theforecastforsettlementafter30yearsfortheadjacenttrackbedononesideisabout0.5mandontheothersideabout3m.Tolimitsettlement,andduetothelackofspaceforaccess,theconstructionheightofthebridgemustbeaslowaspossible.
Theexistingtracksandtheunderpassmustremaininoperationduringtheconstruction.Theflowcapacityofthepolderdrainagepoolmaynotberestricted.
3.GENERALDESCRIPTION
Thetotallengthoftheviaductis438.5m,comprisingsixsections(fig.1).
SectionIcrossestheunderpassandhasalengthof82.3m.Thetwointermediatesupportsaresituatedimmediatelyadjacenttotheconcretecasingoftheunderpass,settingthespansat22.7m,35mand22.65m.
SectionsIItoVhavealengthof47.3mandeachconsistsoftwospansof22.65m.ThelengthsandspansweredeterminedbytheremainingspacebetweensectionsIandVIandcostoptimisation.SectionIIcrossesthepolderdrainagepool.
SectionVI,withalengthof167m,crossesthetwoexistingandthetwofuturetracks.Thespansrangebetween26.3and46.7m,withthesupportsstaggeredunderthesidebeams.Allbridgeshavebeenmadefrompre-stressedconcrete.
Tolimittheconstructionheight,itwasdecidedtoemployaU-shapedcross-section(fig.2).Thetrackfloorlieslowbetweenthetwoload-bearingperimeterbeamswithabreadthof1.4m.Theheightofthebeamsis1.5mforthesmallspansand2.8mforthelarger.Theappearanceofagradualtransitionfromlowtohighbeamsiscausedbywallsthatincreaseinheightattheendsofthelowbeams,connectingtothehighbeams.
Thetrackconstructionconsistsofacontinuousballastbed.OnlyforthetransitionfromsectionVItothetrackbedaretwocompensationweldsusedintherailstoabsorbchangesinlengthduetotemperatureshifts.Attheotherjoinsbetweenthebridgesectionstherailsruncontinuouslythrough.
Thelackofspaceatthesitemeansthatthecrossinganglewiththetracksthataretobenewlylaidisonly10degrees.Inaddition,pointsareprojectedtobepositionedinthetrackspassing
underneath,sothatnocolumnscanbelocatedbetweenthenewtracks.Forsuchsituations,‘pergolaconstructions’areoftenbuilt,consistingoflongrowsofcolumnsalongthetrackwhichsupportaconcretedeckwithaspandirectionperpendiculartothetrackspassingunderneath.Thepergolawouldinthissituationbe160mlongandvarybetween14mand28minwidth.
Foraestheticandeconomicreasons,aninnovativesolutionhasbeendeveloped:
ThesuspensionofthecrossingU-shapedbridgefromapylonwhichisconstructedoverthetracksthatwillberunningunderneath(fig.3).Thiscreatesatransparentconstructionthatguaranteesaviewofthecountrysideandclearlyexpressestheforcesatwork.ThisbridgeisthefirstofitskindintheNetherlands.
Despitethehighconstructioncostofthepylon,thetotalcostofthesolutionchosenislowerthanforapergola.
ThesuspensionfromthepylonissuchthattheforcesintheU-shapedbridgeworkasevenlyaspossibleandhighpeakstressesareavoided.TheloadfromtheU-shapedbeamsisdivertedtothethreesuspensioncableanchorsperbeamunderneath.Thecablesrunviaconduitsthroughthebeamstotheintersectionoftheridgebeamandtheslantingpyloncolumns(fig.4).
ThehorizontalloadsfromthebridgearefeddirectlytothecolumnsofthepylonviaridgeslocatedontheoutsideoftheU-shapedbeams.
4.CONSTRUCTIONASPECTS
4.1Staticsystemsuperstructure
Thefly-overisconstructedfromsixbridgesections.Thebridgepartsaremountedonreinforcedrubberbearings.Attheirextremes,thesectionsarefixedhorizontallyinthecrossdirectionbysteelguidingconstructionsthatprimarilyabsorbthehorizontalthrustforcesandcentrifugalforces;theendsofthebridgearefreetomoveinthelongitudinaldirection.ThesectioncrossingthetrackisalsofixedatthepylonbothinthecrossdirectionandinthelongitudinaldirectionbyhorizontalstrutsbetweentheU-shapedfloorandthepylon.
4.2Substructure
Thefoundationsofthefly-overareprimarilypre-fabricatedpre-stressed450x450mm2
concretepileswithalengthvaryingbetween13mand18mandwithapiledepthvaryingfrom12.50mto18.00mbelowgroundlevel.BothabutmentshaveafoundationofsteelpipepilesØ508mmwithawallthicknessof16mm.Thepilesarefilledwithconcreteandfittedwithreinforcement.Theuseofsteelpipepilesfortheabutmentswasmadenecessarybythesettlementoftheconnectingraisedtrackbedsasaresultofthecompressiblesubsoilwhichmightsubjectthepilestobending.Prestressedconcretedrivenpilesturnedoutnottobeabletoabsorbthesebendingmoments.
ThecolumnsundertheU-shapedbridgeendsarecoupledcrosswayswithabeamconstructionduetothehorizontalforcesthataredivertedthereviatheguidingconstructions.Inordertobeabletoquantifytheinteractionofthetrackwiththesubstructure,atracklongitudinalforcesprogramhasbeendevelopedinwhichthewholesystemisdividedintodiscretecomponentsbymeansofthefollowingelements:
-railelements;
-ballastelements;
-bridgeelements;
-bearingelements;
-pileelements;
-foundationelements.
Thebridgesystemisphysicallydescribedwiththeseelements,andtheaccompanyingparametersareenteredforeachtype.
Generally,CWRtrackisused.If,however,theexpandingbridgelengthsbecometoogreat,‘compensation’weldsorcompensationconstructions,inwhichthetrackhasoverlapping‘tongues’andsoisfreetoundergodeformation,mustbeusedduetotherailforcesreachingtoohighalevelasaresultofbrakingforcesandtemperatureeffects.Atthelocationofoneoftheintermediatesupports,bridgesectionVIissuspendedfromapylonconstructionwherethebridgeisalsofixedhorizontally.Duetothehighstiffnessofthisconstruction,thisdeterminesthefreeexpansionlengthtotheabutment.Thislengthisgreaterthan60m,themaximumfreeexpansionlengthtoanabutmentforballastedtrack.Forthisreasontwocompensationweldsareusedattheabutment.
4.3Pre-stressing
TheU-shapedbridgesareconstructedfrompre-stressedconcrete.
Thefollowingcanbedistinguished:
-longitudinalpre-stressingintheU-shapedbeams,throughwhichthebeam’sownweight,thepermanentloadandtheworkingloadarediverted;
-crosspre-stressingoftheU-shapedendsinthebase.Thisabsorbsthesheartensionsthataregeneratedasaresultofthelongitudinalpre-stressing.
Forthe167mlongtrack-crossingsectionVI,a27-strandlongitudinalpre-stressingsystemwaschosenwithstrandsØ15,2mm,FeP1860.Eightunitsareusedforeachbeam.Forthecrosspre-stressing,theBBRVsystem,whichisnotliabletowedge-settlement,waschosen.Thiswasduetotherelativelyshortlength(approx.7.50m),whichmeansthattheeffectofwedgesettlementwouldhavebeentoogreatontheextentofthepre-stressing.
Theaveragepre-stressinglevelintheU-shapedbridgesisbetween4.5and5.5N/mm2.
Anadditionalcomplicationaroseatthepylonwherethebridgeissuspendedwithverticalguycables.TherearethreeguycablesforeachU-shapedbeamwhicharecarriedviasteelconduitsØ400mmthroughthe1.40mwideU-shapedbeams.Thisprovidedmuchconcernwithrespecttoaccommodatingtheeightpre-stressingcables,theshearforcesthatariseandthesoftsteelreinforcementconnectedwiththisasaresultofthebendingofthetensiontrajectoriesthroughthisdeformation.Thecriterionforthemaximumpermissiblestress(0,45f'‘ck)wastheguidelineatthissite.
TheU-shapedbridgeswerecalculatedwithafinite-elementmodelinwhichsuchfactorsas,withaviewtofatigue,themainpullintheconcretewouldnotexceedthevalueof0,5f’'ck.
4.4Pylon
Thepylonwascalculatedbymeansofdividingitintodiscretebarelementsinafinite-elementmodel.Thehorizontalstruts,thatcanonlybearcompressiveforces,weredividedintospringelementswiththecharacteristicthattheyareinactiveforanpullingload,sothatitisanonlinearcalculation.
Thehorizontalstruts(figs.5and6)thatfixtheU-shapedbridgebothinthelongitudinalandinthecrossdirection,thusbearthelongitudinalforces(primarilybraking,startingandtrackforces)andthecrossforces(mainlythrust,centrifugalandwindforces).
ThehorizontalstrutscomprisefoursteelpipesØ508mmwithawallthicknessof30mm.Thelengthvariesfrom1025mmto2285mm.Thebracketsareconstructedinsuchawaythattheyareableonlytobearcompressiveforces.Thesteelpipesprovidesupportforconcretebracketsatthebaselevelofthebridge.Thisconnection,thatcannotabso
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