Suspension Bridge - Wikipedia, The Free Encyclopedia

5/10/2015 SuspensionbridgeWikipedia,thefreeencyclopedia

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Suspensionbridge

TheAkashiKaikyBridgeinJapan,world'slongestmainspan.

Ancestor Simplesuspensionbridge

Related Underspannedsuspensionbridgeseealsocablestayedbridgeandthrougharchbridge

Descendant Selfanchoredsuspensionbridge

Carries Pedestrians,bicycles,livestock,automobiles,trucks,lightrail

Spanrange Mediumtolong

Material Steelrope,multiplesteelwirestrandcablesorforgedorcastchainlinks

Movable No

Designeffort

medium

Falseworkrequired

No

SuspensionbridgeFromWikipedia,thefreeencyclopedia

Asuspensionbridgeisatypeofbridgeinwhichthedeck(theloadbearingportion)ishungbelowsuspensioncablesonverticalsuspenders.Thefirstmodernexamplesofthistypeofbridgewerebuiltintheearly19thcentury.[3][4]Simplesuspensionbridges,whichlackverticalsuspenders,havealonghistoryinmanymountainouspartsoftheworld.

Thistypeofbridgehascablessuspendedbetweentowers,plusverticalsuspendercablesthatcarrytheweightofthedeckbelow,uponwhichtrafficcrosses.Thisarrangementallowsthedecktobelevelortoarcupwardforadditionalclearance.Likeothersuspensionbridgetypes,thistypeoftenisconstructedwithoutfalsework.

Thesuspensioncablesmustbeanchoredateachendofthebridge,sinceanyloadappliedtothebridgeistransformedintoatensioninthesemaincables.Themaincablescontinuebeyondthepillarstodecklevelsupports,andfurthercontinuetoconnectionswithanchorsintheground.Theroadwayissupportedbyverticalsuspendercablesorrods,calledhangers.Insomecircumstances,thetowersmaysitonablufforcanyonedgewheretheroadmayproceeddirectlytothemainspan,otherwisethebridgewillusuallyhavetwosmallerspans,runningbetweeneitherpairofpillarsandthehighway,whichmaybesupportedbysuspendercablesormayuseatrussbridgetomakethisconnection.Inthelattercasetherewillbeverylittlearcintheoutboardmaincables.

Contents

1History1.1Precursor1.2First1.3Wirecable

2Structuralbehavior2.1Structuralanalysis2.2Advantages2.3Disadvantages

3Variations3.1Underspanned3.2Suspensioncabletypes
http://en.wikipedia.org/wiki/File:Akashi_Bridge.JPGhttp://en.wikipedia.org/wiki/Light_railhttp://en.wikipedia.org/wiki/Canyonhttp://en.wikipedia.org/wiki/Towerhttp://en.wikipedia.org/wiki/Suspension_bridge_typeshttp://en.wikipedia.org/wiki/Cable_stayed_bridgehttp://en.wikipedia.org/wiki/Akashi_Kaiky%C5%8D_Bridgehttp://en.wikipedia.org/wiki/Wire_ropehttp://en.wikipedia.org/wiki/Japanhttp://en.wikipedia.org/wiki/Underspanned_suspension_bridgehttp://en.wikipedia.org/wiki/Falseworkhttp://en.wikipedia.org/wiki/Steel_ropehttp://en.wikipedia.org/wiki/Falseworkhttp://en.wikipedia.org/wiki/Through_arch_bridgehttp://en.wikipedia.org/wiki/Simple_suspension_bridgehttp://en.wikipedia.org/wiki/Simple_suspension_bridgehttp://en.wikipedia.org/wiki/Bridgehttp://en.wikipedia.org/wiki/Self-anchored_suspension_bridge



ThedoubledeckedGeorgeWashingtonBridge,connectingNewYorkCitytoBergenCounty,NewJersey,USA,istheworld'sbusiestsuspensionbridge,carrying102millionvehiclesannually.[1][2]

3.2Suspensioncabletypes3.3Deckstructuretypes

4Forces4.1Useotherthanroadandrail

5Constructionsequence(wirestrandcabletype)6Longestspans7Otherexamples8Notablecollapses9Gallery10Seealso11References12Externallinks

History

Theearliestsuspensionbridgeswereropesslungacrossachasm,withadeckpossiblyatthesamelevelorhungbelowtheropessothattheropehasacatenaryshape.

Precursor

TheTibetansaintandbridgebuilderThangtongGyalpooriginatedtheuseofironchainsinhisversionofearlysuspensionbridges.In1433,GyalpobuilteightbridgesineasternBhutan.ThelastsurvivingchainlinkedbridgeofGyalpo'swastheThangtongGyalpoBridgeinDuksumenroutetoTrashiYangtse,whichwasfinallywashedawayin2004.[5]Gyalpo'sironchainbridgesdidnotincludeasuspendeddeckbridgewhichisthestandardonallmodernsuspensionbridgestoday.Instead,boththerailingandthewalkinglayerofGyalpo'sbridgesusedwires.Thestresspointsthatcarriedthescreedwerereinforcedbytheironchains.BeforetheuseofironchainsitisthoughtthatGyalpousedropesfromtwistedwillowsoryakskins.[6]Hemayhavealsousedtightlyboundcloth.

First

ThefirstdesignforabridgeresemblingthemodernsuspensionbridgeisattributedtoVenetianpolymathFaustoVeranzio,whose1595bookMachinaeNovaeincludeddrawingsbothforatimberandropesuspensionbridge,andahybridsuspensionandcablestayedbridgeusingironchains(seegallerybelow).

ThefirstAmericanironchainsuspensionbridgewastheJacob'sCreekBridge(1801)inWestmorelandCounty,Pennsylvania,designedbyinventorJamesFinley.[7]Finley'sbridgewasthefirsttoincorporateallofthenecessarycomponentsofamodernsuspensionbridge,includingasuspendeddeckwhichhungbytrusses.Finleypatentedhisdesignin1808,andpublisheditinthePhiladelphiajournal,ThePortFolio,in1810.[8]

EarlyBritishchainbridgesincludedtheDryburghAbbeyBridge(1817)and137mUnionBridge(1820),withspansrapidlyincreasingto176mwiththeMenaiBridge(1826),"thefirstimportantmodernsuspensionbridge".[9]TheCliftonSuspensionBridge(designedin1831,completedin1864witha214mcentralspan)isoneofthelongestoftheparabolicarcchaintype.
http://en.wikipedia.org/wiki/Westmoreland_County,_Pennsylvaniahttp://en.wikipedia.org/wiki/James_Finley_(engineer)http://en.wikipedia.org/wiki/Fausto_Veranziohttp://en.wikipedia.org/wiki/Trashi_Yangtsehttp://en.wikipedia.org/wiki/Dryburgh_Abbey_Bridgehttp://en.wikipedia.org/wiki/The_Port_Foliohttp://en.wikipedia.org/wiki/Republic_of_Venicehttp://en.wikipedia.org/wiki/Bergen_Countyhttp://en.wikipedia.org/wiki/Union_Bridge_(Tweed)http://en.wikipedia.org/wiki/Bhutanhttp://en.wikipedia.org/wiki/Clifton_Suspension_Bridgehttp://en.wikipedia.org/wiki/New_Jerseyhttp://en.wikipedia.org/wiki/Stress_(mechanics)http://en.wikipedia.org/wiki/Thangtong_Gyalpohttp://en.wikipedia.org/wiki/Tibetan_peoplehttp://en.wikipedia.org/wiki/Jacob%27s_Creek_Bridgehttp://en.wikipedia.org/wiki/New_York_Cityhttp://en.wikipedia.org/wiki/File:George_Washington_Bridge_from_New_Jersey-edit.jpghttp://en.wikipedia.org/wiki/Duksumhttp://en.wikipedia.org/wiki/Wrought_ironhttp://en.wikipedia.org/wiki/Suspended_deck_bridgehttp://en.wikipedia.org/wiki/George_Washington_Bridgehttp://en.wikipedia.org/wiki/Menai_Suspension_Bridgehttp://en.wikipedia.org/wiki/Catenaryhttp://en.wikipedia.org/wiki/Cable-stayed_bridge



Wirecable

ThefirstwirecablesuspensionbridgewastheSpiderBridgeatFallsofSchuylkill(1816),amodestandtemporaryfootbridgebuiltfollowingthecollapseofJamesFinley'snearbyChainBridgeatFallsofSchuylkill(1808).Thefootbridge'sspanwas124m,althoughitsdeckwasonly0.45mwide.

DevelopmentofwirecablesuspensionbridgesdatestothetemporarysimplesuspensionbridgeatAnnonaybuiltbyMarcSeguinandhisbrothersin1822.Itspannedonly18m.[10]ThefirstpermanentwirecablesuspensionbridgewasGuillaumeHenriDufour'sSaintAntoineBridgeinGenevaof1823,withtwo40mspans.[10]ThefirstwithcablesassembledinmidairinthemodernmethodwasJosephChaley'sGrandPontSuspenduinFribourg,in1834.[10]

IntheUnitedStates,thefirstmajorwirecablesuspensionbridgewastheWireBridgeatFairmountinPhiladelphia,Pennsylvania.DesignedbyCharlesEllet,Jr.andcompletedin1842,ithadaspanof109m.Ellet'sNiagaraFallsSuspensionBridge(184748)wasabandonedbeforecompletion.ItwasusedasscaffoldingforJohnA.Roebling'sdoubledeckerrailroadandcarriagebridge(1855).

TheOttoBeitBridge(193839)wasthefirstmodernsuspensionbridgeoutsidetheUnitedStatesbuiltwithparallelwirecables.[11]

DrawingoftheChakzambridgesouthofLhasa,constructedin1430,withcablessuspendedbetweentowers,andverticalsuspendercablescarryingtheweightofaplankedfootwaybelow.

Veranzio'ssuspendedbridgedesign(1595)

"ViewoftheChainBridgeinventedbyJamesFinleyEsq."(1810)byWilliamStrickland.Finley'sChainBridgeatFallsofSchuylkill(1808)hadtwospans,100feetand200feet.

WireBridgeatFairmount(1842,replaced1874).

Structuralbehavior

Structuralanalysis
http://en.wikipedia.org/wiki/John_A._Roeblinghttp://en.wikipedia.org/wiki/Annonayhttp://en.wikipedia.org/wiki/Spider_Bridge_at_Falls_of_Schuylkillhttp://en.wikipedia.org/wiki/Fausto_Veranziohttp://en.wikipedia.org/wiki/File:View_of_the_Chain_Bridge_The_Port_Folio_June_1810.jpghttp://en.wikipedia.org/wiki/Scaffoldinghttp://en.wikipedia.org/wiki/Bridge#Double-decker_bridgehttp://en.wikipedia.org/wiki/Marc_Seguinhttp://en.wikipedia.org/wiki/Spring_Garden_Street_Bridge#2nd_bridge:_Wire_Bridge_at_Fairmounthttp://en.wikipedia.org/wiki/Spring_Garden_Street_Bridge#2nd_bridge:_Wire_Bridge_at_Fairmounthttp://en.wikipedia.org/wiki/Chain_Bridge_at_Falls_of_Schuylkillhttp://en.wikipedia.org/wiki/Joseph_Chaleyhttp://en.wikipedia.org/wiki/Guillaume_Henri_Dufourhttp://en.wikipedia.org/wiki/File:The_New_Suspension_Bridge_at_Fairmount,_Philadelphia_by_George_Lehman_circa_1842.jpghttp://en.wikipedia.org/wiki/Charles_Ellet,_Jr.http://en.wikipedia.org/wiki/William_Strickland_(architect)http://en.wikipedia.org/wiki/File:Chakzampa.pnghttp://en.wikipedia.org/wiki/Fribourghttp://en.wikipedia.org/wiki/Otto_Beit_Bridgehttp://en.wikipedia.org/wiki/File:Pons_ferrevs_by_Faust_Vran%C4%8Di%C4%87.jpghttp://en.wikipedia.org/wiki/Niagara_Falls_Suspension_Bridgehttp://en.wikipedia.org/wiki/Genevahttp://en.wikipedia.org/wiki/Chain_Bridge_at_Falls_of_Schuylkill



Comparisonofacatenary(blackdottedcurve)andaparabola(redsolidcurve)withthesamespanandsag.Thecatenaryrepresentstheprofileofasimplesuspensionbridge,orthecableofasuspendeddecksuspensionbridgeonwhichitsdeckandhangershavenegligiblemasscomparedtoitscable.Theparabolarepresentstheprofileofthecableofasuspendeddecksuspensionbridgeonwhichitscableandhangershavenegligiblemasscomparedtoitsdeck.Theprofileofthecableofarealsuspensionbridgewiththesamespanandsagliesbetweenthetwocurves.

Themainforcesinasuspensionbridgeofanytypearetensioninthecablesandcompressioninthepillars.Sincealmostalltheforceonthepillarsisverticallydownwardsandtheyarealsostabilizedbythemaincables,thepillarscanbemadequiteslender,asontheSevernBridge,ontheWalesEnglandborder.

TheslenderlinesoftheSevernBridge

Inasuspendeddeckbridge,cablessuspendedviatowersholduptheroaddeck.Theweightistransferredbythecablestothetowers,whichinturntransfertheweighttotheground.

Assuminganegligibleweightascomparedtotheweightofthedeckandvehiclesbeingsupported,themaincablesofasuspensionbridgewillformaparabola(verysimilartoacatenary,theformtheunloadedcablestakebeforethedeckisadded).Onecanseetheshapefromtheconstantincreaseofthegradientofthecablewithlinear(deck)distance,thisincreaseingradientateachconnectionwiththedeckprovidinganetupwardsupportforce.Combinedwiththerelativelysimpleconstraintsplacedupontheactualdeck,thismakesthesuspensionbridgemuchsimplertodesignandanalyzethanacablestayedbridge,wherethedeckisincompression.

Advantages

LongermainspansareachievablethanwithanyothertypeofbridgeLessmaterialmayberequiredthanotherbridgetypes,evenatspanstheycanachieve,leadingtoareducedconstructioncostExceptforinstallationoftheinitialtemporarycables,littleornoaccessfrombelowisrequiredduringconstruction,forexampleallowingawaterwaytoremainopenwhilethebridgeisbuiltaboveMaybebettertowithstandearthquakemovementsthanheavierandmorerigidbridgesBridgedeckscanhavedecksectionsreplacedinordertowidentrafficlanesforlargervehiclesoraddadditionswidthforseparatedcycling/pedestrianpaths.

Disadvantages

Considerablestiffnessoraerodynamicprofilingmayberequiredtopreventthebridgedeckvibrating
http://en.wikipedia.org/wiki/Cable-stayed_bridgehttp://en.wikipedia.org/wiki/Tension_(mechanics)http://en.wikipedia.org/wiki/Severn_Bridgehttp://en.wikipedia.org/wiki/File:Comparison_catenary_parabola.svghttp://en.wikipedia.org/wiki/Parabolahttp://en.wikipedia.org/wiki/Compression_(physical)http://en.wikipedia.org/wiki/File:Severn_bridge-panoramic.jpghttp://en.wikipedia.org/wiki/Columnhttp://en.wikipedia.org/wiki/Severn_Bridgehttp://en.wikipedia.org/wiki/Force_(physics)http://en.wikipedia.org/wiki/Catenary



Asuspensionbridgecanbemadeoutofsimplematerialssuchaswoodandcommonwirerope.

MicklewoodBridgeasillustratedbyCharlesDrewry,1832

SquibbParkBridge,Brooklyn,built2013

EyebarchaincablesofCliftonSuspensionBridge

underhighwindsTherelativelylowdeckstiffnesscomparedtoother(nonsuspension)typesofbridgesmakesitmoredifficulttocarryheavyrailtrafficwherehighconcentratedliveloadsoccurSomeaccessbelowmayberequiredduringconstruction,tolifttheinitialcablesortoliftdeckunits.Thisaccesscanoftenbeavoidedincablestayedbridgeconstruction

Variations

Underspanned

Inanunderspannedsuspensionbridge,themaincableshangentirelybelowthebridgedeck,butarestillanchoredintothegroundinasimilarwaytotheconventionaltype.Veryfewbridgesofthisnaturehavebeenbuilt,asthedeckisinherentlylessstablethanwhensuspendedbelowthecables.ExamplesincludethePontdesBerguesof1834designedbyGuillaumeHenriDufour[10]JamesSmith'sMicklewoodBridge[12]andaproposalbyRobertStevensonforabridgeovertheRiverAlmondnearEdinburgh.[12]

Roebling'sDelawareAqueduct(begun1847)consistsofthreesectionssupportedbycables.Thetimberstructureessentiallyhidesthecablesandfromaquickview,itisnotimmediatelyapparentthatitisevenasuspensionbridge.

Suspensioncabletypes

Themainsuspensioncableinolderbridgeswasoftenmadefromchainorlinkedbars,butmodernbridgecablesaremadefrommultiplestrandsofwire.Thiscontributesgreaterredundancyafewflawedstrandsinthehundredsusedposeverylittlethreat,whereasasinglebadlinkoreyebarcancausefailureoftheentirebridge.(ThefailureofasingleeyebarwasfoundtobethecauseofthecollapseoftheSilverBridgeovertheOhioRiver).Anotherreasonisthatasspansincreased,engineerswereunabletoliftlargerchainsintoposition,whereaswirestrandcablescanbelargelypreparedinmidairfromatemporarywalkway.

Deckstructuretypes

Mostsuspensionbridgeshaveopentrussstructurestosupporttheroadbed,particularlyowingtotheunfavorableeffectsofusingplategirders,discoveredfromtheTacomaNarrowsBridge(1940)bridgecollapse.Recentdevelopmentsinbridgeaerodynamicshaveallowedthereintroductionofplatestructures.InthepictureoftheYichangBridge,notetheverysharp
http://en.wikipedia.org/wiki/Guillaume_Henri_Dufourhttp://en.wikipedia.org/wiki/Eyebarhttp://en.wikipedia.org/wiki/Passenger_rail_terminology#Heavy_railhttp://en.wikipedia.org/wiki/File:Micklewood-bridge.pnghttp://en.wikipedia.org/wiki/Redundancy_(engineering)http://en.wikipedia.org/wiki/Robert_Stevenson_(civil_engineer)http://en.wikipedia.org/wiki/Tacoma_Narrows_Bridge_(1940)http://en.wikipedia.org/wiki/Brooklynhttp://en.wikipedia.org/wiki/File:Squibb_Park_Bridge_uncut_jeh.jpghttp://en.wikipedia.org/wiki/File:Uk_bristol_csbchains.jpghttp://en.wikipedia.org/wiki/Roebling%27s_Delaware_Aqueducthttp://en.wikipedia.org/wiki/Yichang_Bridgehttp://en.wikipedia.org/wiki/Cable-stayed_bridgehttp://en.wikipedia.org/wiki/Ohio_Riverhttp://en.wikipedia.org/wiki/Clifton_Suspension_Bridgehttp://en.wikipedia.org/wiki/Edinburghhttp://en.wikipedia.org/wiki/File:Suspension_bridge.jpghttp://en.wikipedia.org/wiki/Eyebarhttp://en.wikipedia.org/wiki/Silver_Bridge



TheYichangBridge,aplatedecksuspensionbridge,overtheYangtzeRiverinChina

CablesuspendedfootbridgeatDallasFortWorthAirportTerminalD

NewLittleBeltsuspensionbridge,1970Denmark

entryedgeandslopingundergirdersinthesuspensionbridgeshown.Thisenablesthistypeofconstructiontobeusedwithoutthedangerofvortexsheddingandconsequentaeroelasticeffects,suchasthosethatdestroyedtheoriginalTacomaNarrowsbridge.

Forces

Threekindsofforcesoperateonanybridge:thedeadload,theliveload,andthedynamicload.Deadloadreferstotheweightofthebridgeitself.Likeanyotherstructure,abridgehasatendencytocollapsesimplybecauseofthegravitationalforcesactingonthematerialsofwhichthebridgeismade.Liveloadreferstotrafficthatmovesacrossthebridgeaswellasnormalenvironmentalfactorssuchaschangesintemperature,precipitation,andwinds.Dynamicloadreferstoenvironmentalfactorsthatgobeyondnormalweatherconditions,factorssuchassuddengustsofwindandearthquakes.Allthreefactorsmustbetakenintoconsiderationwhenbuildingabridge.

Useotherthanroadandrail

Theprinciplesofsuspensionusedonthelargescalemayalsoappearincontextslessdramaticthanroadorrailbridges.Lightcablesuspensionmayprovelessexpensiveandseemmoreelegantforafootbridgethanstronggirdersupports.Wheresuchabridgespansagapbetweentwobuildings,thereisnoneedtoconstructspecialtowers,asthebuildingscananchorthecables.Cablesuspensionmayalsobeaugmentedbytheinherentstiffnessofastructurethathasmuchincommonwithatubularbridge.

Constructionsequence(wirestrandcabletype)

Typicalsuspensionbridgesareconstructedusingasequencegenerallydescribedasfollows.Dependingonlengthandsize,constructionmaytakeanywherebetweenayearandahalf(constructionontheoriginalTacomaNarrowsBridgetookonly19months)uptoasadecade(theAkashiKaikyBridge'sconstructionbeganinMay1986andwasopenedinMay,1998atotaloftwelveyears).

1. Wherethetowersarefoundedonunderwaterpiers,caissonsaresunkandanysoftbottomisexcavatedforafoundation.Ifthebedrockistoodeeptobeexposedbyexcavationorthesinkingofacaisson,pilingsaredrivento
http://en.wikipedia.org/wiki/File:Yichang_Yangtze_Highway_Bridge.JPGhttp://en.wikipedia.org/wiki/File:Cable-suspended_footbridge_at_DFW_terminal_D.JPGhttp://en.wikipedia.org/wiki/Bedrockhttp://en.wikipedia.org/wiki/File:Little_Belt_Bridge2.jpghttp://en.wikipedia.org/wiki/Tubular_bridgehttp://en.wikipedia.org/wiki/Caisson_(engineering)http://en.wikipedia.org/wiki/Yangtze_Riverhttp://en.wikipedia.org/wiki/Little_Belthttp://en.wikipedia.org/wiki/Yichang_Bridgehttp://en.wikipedia.org/wiki/Dallas-Fort_Worth_International_Airport



ManhattanBridgeinNewYorkCitywithdeckunderconstructionfromthetowersoutward.

SuspendercablesandsuspendercablebandontheGoldenGateBridgeinSanFrancisco.Maincablediameteris36inches(910mm),andsuspendercablediameteris3.5inches(89mm).

thebedrockorintooverlyinghardsoil,oralargeconcretepadtodistributetheweightoverlessresistantsoilmaybeconstructed,firstpreparingthesurfacewithabedofcompactedgravel.(Suchapadfootingcanalsoaccommodatethemovementsofanactivefault,andthishasbeenimplementedonthefoundationsofthecablestayedRioAntiriobridge.Thepiersarethenextendedabovewaterlevel,wheretheyarecappedwithpedestalbasesforthetowers.

2. Wherethetowersarefoundedondryland,deepfoundationexcavationorpilingsareused.

3. Fromthetowerfoundation,towersofsingleormultiplecolumnsareerectedusinghighstrengthreinforcedconcrete,stonework,orsteel.Concreteisusedmostfrequentlyinmodernsuspensionbridgeconstructionduetothehighcostofsteel.

4. Largedevicescalledsaddles,whichwillcarrythemainsuspensioncables,arepositionedatopthetowers.Typicallyofcaststeel,theycanalsobemanufacturedusingrivetedforms,andareequippedwithrollerstoallowthemaincablestoshiftunderconstructionandnormalloads.

5. Anchoragesareconstructed,usuallyintandemwiththetowers,toresistthetensionofthecablesandformasthemainanchorsystemfortheentirestructure.Theseareusuallyanchoredingoodqualityrock,butmayconsistofmassivereinforcedconcretedeadweightswithinanexcavation.Theanchoragestructurewillhavemultipleprotrudingopeneyeboltsenclosedwithinasecurespace.

6. Temporarysuspendedwalkways,calledcatwalks,arethenerectedusingasetofguidewireshoistedintoplaceviawinchespositionedatopthetowers.Thesecatwalksfollowthecurvesetbybridgedesignersforthemaincables,inapathmathematicallydescribedasacatenaryarc.Typicalcatwalksareusuallybetweeneightandtenfeetwide,andareconstructedusingwiregrateandwoodslats.

7. Gantriesareplaceduponthecatwalks,whichwillsupportthemaincablespinningreels.Then,cablesattachedtowinchesareinstalled,andinturn,themaincablespinningdevicesareinstalled.

8. Highstrengthwire(typically4or6gaugegalvanizedsteelwire),ispulledinaloopbypulleysonthetraveler,withoneendaffixedatananchorage.Whenthetravelerreachestheoppositeanchoragetheloopisplacedoveranopenanchoreyebar.Alongthecatwalk,workersalsopullthecablewirestotheirdesiredtension.Thiscontinuesuntilabundle,calleda"cablestrand"iscompleted,andtemporarilybundledusingstainlesssteelwire.Thisprocessisrepeateduntilthefinalcablestrandiscompleted.Workersthenremovetheindividualwrapsonthecablestrands(duringthespinningprocess,theshapeofthemaincablecloselyresemblesahexagon),andthentheentirecableisthencompressedbyatravelinghydraulicpressintoacloselypackedcylinderandtightlywrappedwithadditionalwiretoformthefinalcircularcrosssection.Thewireusedinsuspensionbridgeconstructionisagalvanizedsteelwirethathasbeencoatedwithcorrosioninhibitors.

9. Atspecificpointsalongthemaincable(eachbeingtheexactdistancehorizontallyinrelationtothenext)devicescalled"cablebands"areinstalledtocarrysteelwireropescalledSuspendercables.
http://en.wikipedia.org/wiki/Manhattan_Bridgehttp://en.wikipedia.org/wiki/File:Manhattan_Bridge_Construction_1909.jpghttp://en.wikipedia.org/wiki/File:Golden_Gate_Bridge_architecture_10.jpghttp://en.wikipedia.org/wiki/Rio-Antirio_bridgehttp://en.wikipedia.org/wiki/Active_faulthttp://en.wikipedia.org/wiki/Eyebarhttp://en.wikipedia.org/wiki/Cable-stayed_bridgehttp://en.wikipedia.org/wiki/Catenary



Lions'GateBridgewithdeckunderconstructionfromthespan'scenter

Eachsuspendercableisengineeredandcuttopreciselengths,andareloopedoverthecablebands.Insomebridges,wherethetowersareclosetoorontheshore,thesuspendercablesmaybeappliedonlytothecentralspan.Earlysuspendercableswerefittedwithzincjewelsandasetofsteelwashers,whichformedthesupportforthedeck.Modernsuspendercablescarryashackletypefitting.

10. Specialliftinghoistsattachedtothesuspendersorfromthemaincablesareusedtoliftprefabricatedsectionsofbridgedecktotheproperlevel,providedthatthelocalconditionsallowthesectionstobecarriedbelowthebridgebybargeorothermeans.Otherwise,atravelingcantileverderrickmaybeusedtoextendthedeckonesectionatatimestartingfromthetowersandworkingoutward.Iftheadditionofthedeckstructureextendsfromthetowersthefinishedportionsofthedeckwillpitchupwardrathersharply,asthereisnodownwardforceinthecenterofthespan.Uponcompletionofthedecktheaddedloadwillpullthemaincablesintoanarcmathematicallydescribedasaparabola,whilethearcofthedeckwillbeasthedesignerintendedusuallyagentleupwardarcforaddedclearanceifoverashippingchannel,orflatinothercasessuchasaspanoveracanyon.Archedsuspensionspansalsogivethestructuremorerigidityandstrength.

11. Withcompletionoftheprimarystructurevariousdetailssuchaslighting,handrails,finishpaintingandpavingareinstalledorcompleted.

Longestspans

Suspensionbridgesaretypicallyrankedbythelengthoftheirmainspan.Thesearethetenbridgeswiththelongestspans,followedbythelengthofthespanandtheyearthebridgeopenedfortraffic:

1. AkashiKaikyBridge(Japan),1991m(6532ft)19982. XihoumenBridge(China),1650m(5413ft)20093. GreatBeltBridge(Denmark),1624m(5328ft)19984. YiSunsinbridge(SouthKorea),1545m(5069ft)20125. RunyangBridge(China),1490m(4888ft)20056. FourthNanjingYangtzeBridge(China),1418m(4652ft)20127. HumberBridge(England,UnitedKingdom),1410m(4626ft)1981(longestspanfrom1981until

1998)8. JiangyinSuspensionBridge(China),1385m(4544ft)19979. HardangerBridge(Norway),1380m(4528ft)201310. TsingMaBridge(HongKong),1377m(4518ft)1997(longestspanwithbothroadandmetro)

Otherexamples

(Chronological)

UnionBridge(England/Scotland,1820),thelongestspan(137m)from1820to1826.Theoldestintheworldstillinusetoday.Roebling'sDelawareAqueduct(USA,1847),theoldestwiresuspensionbridgestillinserviceinUnitedStates.JohnA.RoeblingSuspensionBridge(USA,1866),thenthelongestwiresuspensionbridgeinthe
http://en.wikipedia.org/wiki/Union_Bridge_(Tweed)http://en.wikipedia.org/wiki/Tsing_Ma_Bridgehttp://en.wikipedia.org/wiki/File:Lions%27_Gate_Bridge_1938.jpghttp://en.wikipedia.org/wiki/Yi_Sun-sin_bridgehttp://en.wikipedia.org/wiki/Great_Belt_Bridgehttp://en.wikipedia.org/wiki/Hardanger_Bridgehttp://en.wikipedia.org/wiki/Cantileverhttp://en.wikipedia.org/wiki/Runyang_Bridgehttp://en.wikipedia.org/wiki/Parabolahttp://en.wikipedia.org/wiki/Jiangyin_Suspension_Bridgehttp://en.wikipedia.org/wiki/Akashi_Kaiky%C5%8D_Bridgehttp://en.wikipedia.org/wiki/Fourth_Nanjing_Yangtze_Bridgehttp://en.wikipedia.org/wiki/Lions%27_Gate_Bridgehttp://en.wikipedia.org/wiki/Roebling%27s_Delaware_Aqueducthttp://en.wikipedia.org/wiki/Xihoumen_Bridgehttp://en.wikipedia.org/wiki/Humber_Bridgehttp://en.wikipedia.org/wiki/John_A._Roebling_Suspension_Bridge

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