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1、Structures 2008: Crossing Borders 2008 ASCENew Innovative Features of Maines First Cable Stay BridgeAuthor:Chrisstoppherr J. Buurgeess, P.E., S.E., FIIGG, Deenveer, CO, cbburggesssmThe ssteeel ssusppenssionn Waaldoo-Haancoock Briidgee caarriied U.SS. RRoutte 11 trraveelerrs ooverr thhe PPenoobsccot
2、Rivver, neear thee toown of Bucckspportt, MMainne ffor 74 yeaars. Thhis vittallly iimpoortaant traanspporttatiion linnk proovidded saffe ppasssagee foor ccarlloadds oof ttourristts tthrooughh thhe yyearrs, in addditiion to siggnifficaant commmerrciaal ttraffficc reelatted to reggionnal papper-makkin
3、gg, ggrannitee-quuarrryinng, boaat bbuilldinng,mmanuufaccturred houusinng pprodducttionn annd aa hoost of freeighht iitemms, succh aas ddeliiverry oof hhomee heeatiing oill. IIn 220022, aa scchedduleed rrenoovattionn beegann annd iin tthe summmerr off 20003, thhe mmainn suuspeensiion cabbless weere
4、unwwrapppedd too prrepaare forr a vissuall innspeectiion of thee inndivviduual wirres in thee 377 caablees in eacch mmainn caablee. DDeteerioorattionn off thhe mmainn caablee onn thhe ssoutth ssidee off thhe bbriddge wass muuch morre aadvaanceed tthann exxpecctedd, lleaddingg thhe bbriddge ownner, M
5、aainee Deeparrtmeent of Traanspporttatiion, too simmulttaneeoussly undderttakee a strrenggtheeninng pprojjectt onn thhe WWalddo-HHanccockk Briidgee annd tthe dessignn off thhe PPenoobsccot Narrrowws BBriddge & OObseervaatorry oon aa paaralllell allignnmennt to thee exxisttingg brridgge.FIGURE 1THE W
6、ALDO-HANCOCK BRIDGE AND NEW PENOBSCOT NARROWS BRIDGE & OBSERVATORY SIDE-BY-SIDE OVER THE PENOBSCOT RIVER, LINKING WALDO AND HANCOCK COUNTIES IN MAINE. THE NEW BRIDGE OPENED TO TRAFFIC ON DECEMBER 30, 2006, JUST 42 MONTHS AFTER THE EMERGENCY REPLACMENT NEED WAS IDENTIFIED.In orrderr too sppeedd thhe
7、pproccesss, MMainne uundeertoook thee reeplaacemmentt inn ann innnovvatiive ownner-facciliitatted dessignn buuildd prroceess andd grrounnd wwas brookenn inn Deecemmberr off 20003 forr thhe nnew cabble-staayedd briidgee, aa fiirstt foor MMainne. A kkey eleemennt iin tthe dessignn off thhe nnew casst-
8、iin-pplacce cconccrette seggmenntall brridgge iis tthe connsidderaablee atttenntioon aand efffortt innvesstedd too prroviide a dduraablee annd eeasyy too maainttainn sttruccturre wwithh a plaanneed sservvicee liife excceeddingg 1000 yyearrs. Thee brridgge iis tthe firrst to utiilizze aa unniquue cco
9、mbbinaatioon oof ffeatturees ddesiigneed sspeccifiicallly to prootecct tthe briidgee annd oonlyy thhe seccondd too beeneffit froom aa piioneeeriing craadlee syysteem, devveloopedd annd ppateenteed bby tthe briidgees dessignner.FIGURE 2ADJACENT CRADLES POSITIONED IN THE UPPER PYLON ALONG WITH FORMWOR
10、K, AS THE JUMP FORMS ARE BEING PREPARED TO MOVE UP AND CAST THE NEXT SECTION. THE CRADLES ARE FABRICATED, DELIVERED TO THE SITE, POSITIONED AND SURVEYED IN POSITION IN THE FRAMEWORK, THEN LIFTED INTO PLACE AND THE ENTIRE ASSEMBLY SURVEYED FOR CORRECT POSITIONING PRIOR TO CASTING.An innnovvatiive nit
11、troggen gass prroteectiion andd moonittoriing sysstemm prroviidess ann enncloosedd envviroonmentt off prresssuriizedd innertt gaas aarouund eacch ccablle sstayy. TThe maiin ccompponeentss off thhe sysstemm arre tthe gass, HHDPEE shheatthinng, resservvoirr taankss, aanchhoraage-seaalinng ccapss annd
12、mmoniitorringg harrdwaare. Niitroogenn gaas wwas sellectted duee too itts nnon-corrrossivee prropeertiies andd eaase of avaailaabillityy.Ann ennvirronmmentt off prresssuriizedd puure nittroggen esssenttiallly eliiminnatees ooxyggen, chhlorridees aand moiistuure, alll ppoteentiiallly ccorrrosiive ele
13、emennts.A priimarry ggoall waas tto ccostt-efffecctivvelyy crreatte aa gaas-ttighht ssealled sysstemm thhat commpleetelly encclosses thee sttayss. AAfteer iinsttalllatiion of thee sttayss, ttheyy weere purrgedd off mooistturee annd nnitrrogeen ggas injjectted to purrge thee exxisttingg aiir ffromm t
14、hhe cclossed envviroonmeent. Thhe nnitrrogeen wwas theen preessuurizzed to twoo pooundds pper squuaree innch.A seaalinng ccap covverss thhe sstraand taiils at eacch aanchhoraage andd fuullyy enncappsullatees aall ancchorragee harrdwaare. A cleear endd pllatee alllowws ddireect vissuall innspeectiion
15、 of thee annchoor aareaa. EEachh sttay is proovidded witth aa 3000 ccubiic ffoott niitroogenn gaas rreseervooir to reccharrge thee gaas iin tthe eveent of a ddropp inn preessuure. Gaaugees rrecoord alll fllucttuattionns iin ppresssurre aand serrve as a ttooll foor tthe Depparttmennt tto eassilyy moo
16、nittor thee sttatuus oof tthe sysstemm annd ttakee coorreectiive acttionn, iif nneceessaary. Thhe aannuularr spaace bettweeen tthe cabble staay sstraand andd thhe ccraddle sleeevees aalloows gass too fllow freeelyy thhrouugh thee staay ssysttem in an isoolatted envviroonmeent.To thhe bbestt off ouur
17、 kknowwleddge, thhe sstayy caablee gaas pprottecttionn syysteem uutillizeed iin tthe neww Pennobsscott Naarroows Briidgee iss a worrld firrst. Thhis uniiquee syysteem pprovvidees ttwo addditiionaal llayeers of prootecctioon bby ccompplettelyy suurroounddingg thhe sstayys wwithh ann innertt gaas, and
18、d thhrouugh auttomaaticc anndcoontiinuaal mmoniitorringg off thhe ggas preessuure levvel. Moonittoriing alllowss thhe MMainne DDepaartmmentt off Traanspporttatiion reaal-ttimee knnowlledgge oof aany pottenttiall coomprromiise in thee syysteem. Theere aree a tottal of fouur nnestted levvelss off prro
19、teectiion, prroviidinng rreduundaancyy: Epooxy coaatinng oon tthe staay sstraandss Outter layyer of HDPPE ssheaathiing arooundd thhe sstayys Sysstemm fiilleed wwithh niitroogenn gaas tto ppurgge ppoteentiial corrrossivees Seaaledd syysteem wwithh moonittoriing equuipmmenttThis prooacttivee appprooac
20、hh alllowws mmainntennancce ccrewws tto iidenntiffy aand adddresss ppoteentiial proobleems at an earrly staage, wiith minnimaal mmoniitorringg effforrt.An adddittionnal monnitoorinng ttooll foor tthe Pennobsscott Naarroows Briidgee iss a serriess off foorcee monnitoorinng ssysttemss onn eaach staay.
21、 Dywwidaag SSysttemss Innterrnattionnal proovidded thee foorcee moonittoriing sysstemms, whiich cann acccurrateely dettermminee thhe fforcce wwithhin 1% usiing a pporttablle ffielld llapttop uniit.TThe sysstemm iss veery rugggedd, rrequuirees nno mmainntennancce, hass noo moovinng ppartts aand willl
22、 pprovvidee monnitoorinng tthrooughhoutt thhe pprojjectted serrvicce llifee off thhe bbriddge, alllowwingg Deeparrtmeent empployyeess easse iin rreguularrly monnitoorinng tthe forrcess inn thhe ccablle aas ppartt off thheirr innspeectiion prooceddurees, witthouut thee neeed forr liift-offf eqquippme
23、nnt oor tthe utiilizzatiion of speeciaal eexpeensiive tecchniiquees ssuchh ass viibraatioon meaasurremeentss. WWithh thhis monnitoorinng ssysttem, thhe fforcce iin tthe cabble is obttainned in minnutees wwithhoutt anyy innterrferrencce wwithh thhe ttraffficc onn thhe bbriddge. Thhe lleadds ffromm th
24、he ssenssorss arre iin aa gaas ttighht boxx loccateed iinsiide thee boox ggirdder jusst uundeer tthe cabble ancchorragee, mmainntaiininng tthe inttegrrityy off thhe seaaledd syysteem oof tthe gass moonittoriing sysstemm.FIGURE 3CONSTRUCTION TOOK PLACE IN THREE DIRECTIONS ON BOTH PYLONS TWO CANTILEVE
25、RS EXTENDING FROM THE PYLON AS THE PYLONS WERE CAST TO THEIR FULL HEIGHT OF 420. THE TOP OF THE WESTERN PYLON HOUSES A THREE STORY GLASS PUBLIC OBSERVATORY WHICH IS ACCESSED BY AN ELEVATOR THAT RUNS UP THROUGH THE CORE OF THE PYLON.As prreviioussly menntioonedd, tthe Pennobsscott Naarroows Briidgee
26、allso inccluddes thee usse oof aa caablee-sttay craadlee syysteem (U.SS. PPateent No. 6,8800,1993) dessignned by FIGGG, thee ennginneerr off reecorrd ffor thee proojecct; it is thee seeconnd ssuchh innstaallaatioon. Thee crradlle ssysttem alllowss foor tthe usee off coontiinuoous strrandds ffromm br
27、ridgge ddeckk too brridgge ddeckk, ccarrryinng eeachh sttay thrrouggh aa sttainnlesss ssteeel ssleeeve in thee craadlee asssemmblyy. TThe inddiviiduaal ssleeevess inncreeasee duurabbiliity by eliiminnatiing thee pootenntiaal ffor strrandd-too-sttrannd cconttactt. TThe craadlee syysteem alsso eelimmi
28、naatess annchooragges in thee pyylonn, rreduucess tennsille fforcces in thee pyylonn annd aalloows forr moore strreammlinned pyllon dimmenssionns. Anyy giivenn sttrannd mayy bee reemovved, innspeecteed aand repplacced witth aa neew sstraand at sellectted inttervvalss too veeriffy tthe conndittionn o
29、ff thhe sstayys, witthouut ccompprommisiing thee brridgges iinteegriity. Siix mmontths aftter thee opeeninng oof tthe neww brridgge tto ttraffficc onn Deecemmberr 300, 220066, ssix reffereencee sttrannds werre rremoovedd andd reeplaacedd wiith carrbonn fiiberr sttrannds. Thhis is thee fiirstt suuch
30、insstalllattionn inn thhe UU.S. Monnitoorinng of thee sttrannds, booth steeel andd caarboon ffibeer pprovvidees ffeeddbacck oon tthe usee off thhis innnovaativvemaaterriall annd wwilll heelp furrtheer iincrreasse dduraabillityy ass fuuturre bbriddgess wiill be dessignned utiilizzingg thhis tecchnool
31、oggy.FIGURE 4A LARGE PLAZA GREETS VISITORS TO THE WORLDS TALLEST PUBLIC BRIDGE OBSERVATORY ENTRANCE, ALONG THE BANKS OF THE PENOBSCOT RIVER. THE ENTRANCE IS FRAMED IN GRANITE, IN CONCERT WITH THE BRIDGE AESTHETIC THEME OF GRANITE. DETAILS REFLECT ON THE ADJACENT HISTORIC FORT KNOX. AN ELEVATOR TAKES
32、 VISITORS TO THE OBSERVATORY AT THE TOP OF THE PYLON.The pproaactiive andd piioneeeriing appproaachees eencoouraagedd byy thhe MMainne DDepaartmmentt off Traanspporttatiion havve aadvaanceed sstanndarrds forr fuuturre ccablle-sstayyed briidgee deesiggns. Thheree wiill be oppporttuniitiees tto aanall
33、yzee annd eevalluatte tthe monnitoorinng rrecoordss frrom thee sttay sysstemm, wwhicch wwilll ressultt inn coontiinueed aadvaanceemennts in unddersstanndinng ccablle-sstayy brridgge pperfformmancce aand enhhancced lonng ttermm duurabbiliity. Thhe PPenoobsccot Narrrowws BBriddge & OObseervaatorry iis
34、 pprovvidiing saffe ppasssagee forr trraveelerrs ooverr thhe PPenoobsccot Rivver, whhilee neearlly 775,0000 vissitoors in thee fiirstt seeasoon hhavee traavelled to thee woorldds ttalllestt puubliic bbriddge obsservvatoory (4220 abbovee thhe rriveer) to enjjoy vieews of coaastaal MMainne ffromm thhe
35、 ttop of thee weesteern pyllon.ReferrenccesThe AAuthhor of thiis ppapeer, Chrristtophher J. Burrgesss, P.EE., S.EE., siggnedd annd ssealled thee deesiggn pplanns forr thhe bbriddge andd reeloccateed tto tthe sitte ffor twoo yeearss duurinng cconsstruuctiion of thee brridgge.结构20008：穿穿越边缘缘 20008美国国土木
36、工工程师协协会缅因州第一一座斜拉拉桥的新新创新作者：Chhrisstoppherr J. Buurgeess, P.E., S.E., FIIGG, Deenveer, CO缅因州的沃沃尔多汉汉考克刚刚桁架桥桥是美国国的1号号旅客干干线，它它位于诺诺斯科特特河附近近的巴克克斯波特特，已近近有744年的历历史了。这这非常重重要的交交通枢纽纽，这些些年来通通过该道道路提供供的车辆辆安全通通道的货货物，除除了巨大大的商业业联系与与区域造造纸，花花岗岩采采石，造造船，制制造工业业和民用用住房还还有货主主运送的的物品，如如，家庭庭取暖用用油。220022年，由由于桥的的南侧主主缆恶化化，比预预期的更更快
37、些，一一个翻修修计划开开始并于于20003年开开始，计计划准备备在每一一个主索索分成337个小小的钢索索。为了加快这这一进程程，利用用缅因州州运输部部拥有较较早的桥桥梁，以以现有的的桥梁同同时开展展对沃尔尔多汉考考克桥梁梁加固工工程和诺诺斯科特特纳罗斯斯桥的设设计，并并将其与与天文台台于平行行排列。缅缅因州决决定用一一个新的的具有创创新意识识的业主主对桥梁梁进行设设计和建建造，该该斜拉桥桥于20003年年12月月破土动动工。这这是缅因因州第一一座斜拉拉桥图片1沃尔多的，汉考克大桥，新诺斯科特纳罗斯上空的诺斯科特河大桥及天文台台，两端连接这缅因州沃尔多和汉考克县。2006年12月30日新大桥建成
38、通车，但仅仅42个月后就需要维修并更换新的零部件。其中的一个个现浇混混凝土桥桥梁，人人们给予予了相当当大的关关注，它它的投资资计划是是要提供供超过1100年年寿命的的服务。其其中易于于维护的的结构设设计工作作的关键键因素。这这座桥是是第一个个利用一一个专为为保护桥桥梁而做做的现浇浇梁，第第二个是是受益于于创新的的摇篮制制度，制制定桥梁梁设计专专利保护护功能的的独特组组合。图片2吊篮与模板一起定位在上部吊架，图中为正在准备移动吊篮的下一节。吊篮是先制造在运送到工地，先定位同时在架构的地方测量，然后再吊装到设计好的地方。其中一个创创新是氮氮气保护护和监测测系统提提供在每每个斜拉拉索加压压惰性气气体
39、的密密封环境境。该系系统的主主要组成成部分是是气体，高高密度聚聚乙烯护护套，储储水箱，锚锚固密封封帽和监监测硬件件。氮气气被选为为保护气气体是由由于其非非腐蚀性性和易于于储存，纯纯氮气环环境的压压力基本本上消除除了氧，氯氯化物、水水分和所所有潜在在的腐蚀蚀因素。该系统的一一个主要要目标是是有效地地创建一一个不透透气的密密封系统统，完全全将索揽揽包围。安安装后，缆缆索将注注入清洁洁的水分分和氮气气用以清清除封闭闭的环境境中现有有的空气气，此时时的氮加加压至22磅每平平方英寸寸。然后用一个个密封帽帽将各锚锚具的尾尾部、钢钢绞线锚锚固端和和所有硬硬件充分分封装。再再预留一一个明显显的端板板可以直直接
40、目视视检查的的锚区。每每个端部部都提供供了一个个3000立方英英尺氮气气水库补补给施工工中的压压力下降降。仪表表会记录录施工中中的气体体的所有有波动压压力，并并作为该该部分的的数据，轻轻松监控控系统的的状态，并并采取纠纠正措施施。如有有必要，电电缆之间间的环形形空间和和吊篮空空间可以以让气体体流经在在隔离的的环境下下。据我们所知知，利用用在新诺诺斯科特特纳罗斯斯桥的斜斜拉索气气体保护护系统是是世界第第一。这这种独特特的系统统提供了了完全周周围的惰惰性气体体的环境境，并通通过气体体压力自自动监测测水平和和连续的的两个附附加保护护层。交交通监措措施使系系统中的的任何潜潜在的威威胁都可可以及时时通知
41、给给缅因州州交通部部。该系系统有四四嵌套级级别的保保护，共共提供冗冗余的保保护措施施：有环氧树树脂涂层层的钢索索外层的聚聚乙烯护护套 整个系系统充满满氮气以以清除潜潜在的腐腐因素密封系统统的监测测设备这种积极的的措施使使维修人人员可以以确定和和解决在在早期阶阶段可能能出现的的问题以以减少的的监测工工作。一个为诺斯斯科特纳纳罗斯桥桥工作的的监测工工具是监监测系统统对每个个要素的的监控。狄狄伟德提提供的监监测系统统，可以以精确到到1，可可供人使使用便携携式笔记记本电脑脑监测，这这是非常常坚固监监测系统统，无需需维护，没没有移动动部件，并并提供整整个预计计使用寿寿命监控控桥梁的的测试数数据，让让员工
42、安安心定期期监测，而而钢索是是作为其其检查程程序的一一部分，而而不剥离离设备或或技术，可可以使用用特殊的的技术，如如振动测测量的需需要。有有了这个个监控系系统，设设备在几几分钟内内没有受受到任何何关于大大桥交通通的干扰扰。引线线从传感感器的气气密箱梁梁内设下下的锚索索框通过过，保持持了气体体监测系系统密封封系统的的完整性性。图片3建造分三个部分，两个主塔、中间和双悬臂，主塔的高度420m。在西面吊架设有一个三层玻璃公众观测站，是由电梯运行向上通过核心去到的主塔顶部。正如前面提提到的，诺诺斯科特特纳罗斯斯桥还包包括电缆缆停留吊吊篮系统统（美国国专利号号688801993）由由菲格设设计的使使用，
43、有有记录的的项目工工程，这这是第二二次这样样的安装装。吊篮篮式系统统可以连连续从桥桥面到桥桥面使用用，携带带通过的的吊篮每每次逗留留带不锈锈钢套筒筒以增加加耐用性性。通过过消除对对吊篮对对锁链的的摩擦，吊吊篮式系系统也消消除了在在塔锚的的磨损，同同时也减减少对主主塔的拉拉力以便便用更精精简的尺尺寸建造造主塔。多多余的任任何部分分都可能能会被删删除，并并在指定定的时间间间隔用用一新的的钢绞线线取代验验证实验验条件，而而不影响响桥梁的的完整性性。 66个月后后的122月300日新桥桥梁贯通通，20006年年通车，66参考索索被拆除除，被碳碳纤维束束所取代代。这是是首次在在美国监监测索，钢钢铁和碳碳
44、纤维等等的安装装提供了了关于这这些材料料的使用用反馈，并并将有助助于进一一步提高高高耐久久性未来来的桥梁梁的设计计并在不不久的将将会利用用这种技技术。图片4这是一个迎接游人的大型广场，是世界上最高的供游人参观的桥梁天文台，沿着诺斯科特河岸。入口是花岗岩制成的大门，与桥梁花岗岩属于一样的审美主题。有一部电梯将载这游客到桥塔顶部天文台。缅因州交通通运输部部的鼓励励办法已已为未来来先进标标准的斜斜拉索桥桥的设计计提供了了积极开开始。这这将有机机会来分分析和评评价系统统的性能能，这将将有利于于持续了了解和记记录电缆缆的性能能和增强强桥梁耐耐久性的的长期监监测记录录。诺斯斯科特纳纳罗斯桥桥及天文文台可提提供诺斯斯科特河河旅客安安全的通通行，而而近7550000名游客客载第一一个季度度前往世世界上最最高的公公共桥梁梁天文台台，她在在河流上上方4220米的的地方，人人们可以以享受从从桥梁顶顶部沿缅缅因州参参观。参考资料本文的作者者，Chhrisstoppherr J. Buurgeess, P.E, S.EE签字盖盖章，他他在设计计计划中中桥梁和和搬迁过过程中的的两年时时间里设设计建立立了关于于这座桥桥梁的网网站。