欧洲土木工程建筑外文翻译外文文献英文文献欧洲桥梁研究

Bridge researchin Europe

A brief outl ine is given of the developmentof the EuropeanUnion, togetherwiththe researchplatform in Europe.The special caseof post-tensionedbridgesin the UKis discussed. In order to i l lustrate the type of Europeanresearchbeing undertaken,anexample is given from the University of Edinburgh portfol io: relating to theidentification of voids in post-tensionedconcretebridgesusing digital impulse radar.

Introduction

The chal lenge in any research arena is to harness the findings of differentresearch groups to identify a coherent mass of data,which enables research andpractice to be better focused.A particular chal lenge exists with respect to Europewhere language barriers are inevitably very significant.The European Communitywas formed in the 1960s basedupon a pol itical wi l l within continental Europe toavoid theEuropeancivi l wars,which developedinto World War 2 from 1939 to 1945.The strong pol itical motivation formed the original community of which Britain wasnot a member.Many of the continental countriessawBritain ’sinterestasbeing purelyeconomic.The 1970s saw Britain joining what was then the European EconomicCommunity (EEC) and the 1990s has seen the widening of the community to aEuropean Union, EU,with certain pol itical goals together with the objective of acommonEuropeancurrency.

Notwithstanding these financial and pol itical developments, civi l engineeringand bridge engineeringin particular have found greatdifficulty in forming anykind ofcommon thread. Indeed the educational systems for University training are quitedifferent between Britain and the European continental countries.The formation ofthe EU funding schemes—e.g. Socrates, Brite Euram and other programs havehelped significantly.The Socrates scheme is based upon the exchangeof studentsbetween Universities in different member states. The Brite Euram scheme hasinvolved technical research grants given to consortia of academics and industrialpartnerswithin a number of the states—a Brite Euram bid would normal ly be led byan industrial ist.

In terms of dissemination of knowledge, two quite different strands appear tohaveemerged.The UK andthe USA haveconcentratedprimari ly upon disseminatingbasic research in refereed journal publ ications:ASCE, ICE and other journals.Whereas the continental Europeans have frequently disseminatedbasic researchat

conferenceswherethe circulation of the proceedingsis restricted.

Additional ly, languagebarriers have proved to be very difficult to break down.In countries where Engl ish is a strong second languagethere has been enthusiasticparticipation in international conferences based within continental Europe—e.g.Germany, Italy,Belgium,The Netherlands and Switzerland.However,countrieswhere Engl ish is not a strong secondlanguagehavebeenhesitantparticipants}—e.g.F ran ce.

Eu ropean research

Examples of researchrelating to bridges in Europe can be divided into threetypesof structu re:

Masonry arch bridges

Britain has the largest stock of masonry arch bridges. In certain regions of theUK up to 60%of the road bridges are historic stone masonryarch bridges original lyconstructedfor horsedrawn traffic.This is lesscommon in other parts of Europe asmany of thesebridgeswere destroyedduring World War 2.

Concretebridges

A large stock of concretebridges was constructedduring the 1950s, 1960s and1970s.At the time, thesestructureswere seenasmaintenancefree.Europe also hasalarge number of post-tensionedconcretebridges with steel tendon ducts preventingradarinspection.This is a particular problem in Franceandthe UK.

Steelbridges

Steelbridges went out of fashion in the UKdue to their needfor maintenanceasperceived in the 1960s and 1970s. However, they have been used for long spanand rai l bridges, andthey are now returning to fashion for motorway wideningschemesin the UK.

Researchactivityin Europe

It gives an indication certain areasof expertise and work being undertaken inEurope,but is by no meansexhaustive.

In order to i l lustrate the type of Europeanresearchbeing undertaken,an exampleis given from the University of Edinburgh portfol io. The example relates to theidentification of voids in post-tensionedconcretebridges,using digital impulse radar.

Post-tensionedconcreterai l bridgeanalysis

Ove Arup and Partners carried out an inspection and assessmentof thesuperstructure of a 160 m long post-tensioned,segmental rai lway bridge in

Manchester to determine its load-carrying capacity prior to a transfer of ownership,for usein the Metrol ink l ight rai l system. .

Particular attention was paid to the integrity of its post-tensionedsteelelements.Physical inspection,non-destructiveradar testingand other exploratory methodswereusedto investigatefor possibleweaknessesin the bridge.

Since the suddencol lapse of Ynys-y-Gwas Bridge in Wales,UK in 1985, therehasbeenconcern about the long-term integrity of segmental ,post-tensionedconcretebridges which may be prone to ‘ brittle fai lure’without warning. The corrosionprotection of the post-tensionedsteel cables,where they passthrough joints betweenthe segments,hasbeenidentified as a major factor affecting the long-term durabi l ityand consequentstrengthof this type of bridge.The identification of voids in groutedtendon ducts at vulnerable positions is recognized as an important step in thedetectionof suchcorrosion.

Descriptionof bridge

General arrangement

Besseso’th ’Barn Bridge is a 160 m long, three span,segmental ,post-tensionedconcreterai lway bridge bui lt in 1969.The main span of 90 m crossesover both theM62 motorway and A665 Bury to Prestwick Road.Minimum headroom is 5.18 mfrom the A665 andthe M62 is clearedby approx 12.5 m.

The superstructureconsistsof a central hol low trapezoidal concretebox section

6.7 m high and 4 m wide.The majority of the south andcentral spansare constructedusing 1 .27 m long pre-cast concrete trapezoidal box units, post-tensionedtogether.This box section supports the in site concrete transversecanti lever slabs at bottomflange level ,which carry therai l tracks andbal last.

The center and south span sections are of post-tensioned construction.Thesepost-tensionedsectionshavefive typesof pre-stressing:

1.Longitudinal tendonsin groutedductswithin the top andbottom flanges.

2. Longitudinal internal draped tendons located alongside the webs.These aredeflectedat internal diaphragmpositions andareencasedin in site concrete.

3. Longitudinal macal loy bars in the transversecanti lever slabs in the centralspan.

4.Vertical macal loy barsin the 229 mm wide websto enhanceshearcapacity.

5.Transversemacal loy bars through the bottom flange to support thetransverse canti lever slabs.

Segmentalconstruction

The pre-castsegmentalsystemof constructionusedfor the southand centerspansections was an alternative method proposed by the contractor.Current thinkingsuggeststhat such a form of construction can lead to ‘ brittle fai lure’ of the entirestructure without warning due to corrosion of tendons across a construction joint The original designconcepthadbeenfor in site concreteconstruction.

Inspectionandassessment

Inspection

Inspection work was undertakenin a number of phasesand was l inked with thetesting required for the structure.The initial inspectionsrecordeda numberof visibleproblemsincluding:

Defective waterproofing on theexposedsurfaceof thetop flange.

Watertrappedin the internal spaceof thehol low box with depthsup to 300 mm.

Variousdrainageproblemsat joints andabutments.

Longitudinal cracking of the exposedsoffit of the central span.

Longitudinal cracking on sidesof the top flange of thepre-stressedsections.

Widespread sapl ing on some in site concrete surfaces with exposed rustingre i n force m e n t.

Assessment

The subjectof anearl ier paper,the objectives of the assessmentwere:

Estimatethe presentload-carrying capacity.

Identify any structural deficienciesin theoriginal design.

Determinereasonsfor existing problemsidentified by the inspection.

Conclusionto the inspectionand assessment

Fol lowing the inspection and the analytical assessmentone major element ofdoubt stil l existed.This concernedthe condition of the embeddedpre-stressingwires,strands,cables or bars.For the purpose of structural analysis these elements、 hadbeenassumedto be sound.However, due to the very high forces involved, 、 a riskto the structure,causedby corrosion to theseprimary elements,wasidentified.

The initial recommendationswhich completed the first phaseof the assessmentwere:

1. Carry out detai led material testing to determine the condition of hiddenstructuralelements, in particularthe groutedpost-tensionedsteelcables.

2.Conduct concretedurabil ity tests.

3.Undertakerepairsto defective waterproofing andsu rfacedefectsin concrete.

Testi ngproced u res

Non-destructive radar testing

During the first phaseinvestigation at a joint betweenpre-castdeck segmentstheobservationof a void in a post-tensionedcable duct gaverise to seriousconcernaboutcorrosion and the integrity of the pre-stress.However, the extent of this problem wasextremely difficult to determine.The bridge contains 93 joints with an averageof 24cables passing through each joint, i .e. there were approx. 2200 positions whereinvestigations could be carried out.A typical section through such a joint is that the 24draped tendons within the spine did not give rise to concern becausethesewereprotectedby in site concretepouredwithout joints after the cableshadbeenstressed.

As it was clearly impractical to consider physical ly exposing al l tendon/jointintersections, radar was used to investigate a large numbers of tendons and hencelocate duct voids within a modesttimescale. It was fortunate that the corrugatedsteelducts around the tendons were discontinuous through the joints which al lowed theradarto detectthe tendonsand voids.The problem,however,was sti l l highly complexdue to the high density of other steel elementswhich could interfere with the radarsignalsand the fact that the areaof interest was at most 102 mm wide andembedded between150 mm and800 mm deepin thick concreteslabs.

Trial radarinvestigations.

Threecompanieswere invited to visit the bridge and conducta trial investigation.One company decided not to proceed.The remaining two were given 2 weeks tomobi lize, test andreport.Their resultswere then comparedwith physical explorations.

To make the comparisons,observation holes were dril led vertical ly downwardsinto the ducts at a selectionof 10 locations which included severalwhere voids werepredicted and several where the ducts were predicted to be ful ly grouted.A 25-mmdiameter hole was required in order to faci l itate use of the chosen horoscope.Theresultsfrom the University of Edinburgh yielded anaccuracyof around60%.

Main radar survey,horoscopeverification of voids.

Having completed a radar survey of the total structure,a baroscopic was thenusedto investigateal l predictedvoids and in more than 60%of casesthis gavea clearconfirmation of the radar findings. In several other cases some evidence ofhoneycombingin the in site stitch concreteabovethe duct was found.

When viewing voids through the baroscopic, however, it proved impossible todeterminetheir actual size or how far they extendedalong the tendon ducts althoughthey only appearedto occupy less than the top 25%of the duct diameter.Most ofthesevoids, in fact,were smal ler than the diameter of the flexible baroscopic beingused(approximately 9 mm)and were seenbetween the horizontal top surfaceof thegrout and the curved upper l imit of the duct. In a very few casesthe tops of the pre-stressingstrandswere visible above the grout but no sign of any trapped water wasseen. It was not possible, using the baroscopic, to see whether those cables werecorroded.

Digitalradar testing

The testmethod involved exciting the joints using radio frequencyradarantenna: 1 GHz, 900 MHz and 500 MHz. The highest frequency gives thehighest resolution but has shal low depth penetration in the concrete. The lowestfrequency gives the greatestdepthpenetrationbut yields lower resolution.

The data col lected on theradar sweepswere recordedon a GSSI SIR System

10.This system involves radar pulsing and recording.The data from the antenna istransformedfrom an analoguesignal to a digital signal using a16-bit analoguedigitalconverter giving a very high resolution for subsequentdata processing.The data isdisplayed on site on a high-resolution color monitor.Fol lowing visual inspection it isthen stored digital ly on a 2.3-gigabyte tape for subsequentanalysis and signalprocessing.The tape first of al l records a ‘ headernoting’ the digital radar settingstogether with the trace number prior to recording the actual data.When the data isplayed back, one is able to clearly identify al l the relevant settings—making foraccurateandrel iable datareproduction.

At particular locations along the traces, the trace was marked using a markerswitch on the recording unit or theantenna.

Al l the digital records were subsequentlydownloaded at the University NDT’ slaboratory on to a micro-computer. The raw data prior to processingconsumed35megabytes of digital data.  Post-processingwas undertaken using sophisticatedsignal processingsoftware.Techniquesavai lable for the analysisinclude changingthecolor transform and changing the scalesfrom l inear to a skewed distribution in order tohighl ight 、突出 certain features.Also, the color transforms could be changedtohighl ight phasechanges. In addition to these color transform faci l ities, sophisticatedhorizontal andvertical fi ltering proceduresareavai lable.Using alarge screenmonitor

it is possible to display in spl it screensthe raw data and the transformed processeddata.Thus one is ableto get an accurateindication of the processingwhich hastakenplace.The computer screen displays the time domain cal ibrations of the reflectedsignalson the vertical axis.

A further faci l ity of the software was the abi l ity to display the individual radarpulses as time domain wiggle plots.This was a particularly valuable feature whenlooking at individual recordsin the vicinity of the tendons.

Interpretationof findings

A ful l analysis of findings is given elsewhere, Essential ly the digitized radarplots were transformed to color l ine scans and where double phase shifts wereidentified in thejoints, then voiding was diagnosed.

Conclusions

1.An outl ine of the bridge researchplatform in Europeis given.

2. The use of impulse radar has contributed considerablyto the level ofconfidencein the assessmentof the Besseso’th ’Barn Rai l Bridge.

3.The radar investigations revealedextensive voiding within the post-tensionedcable ducts.However, no sign of corrosion on the stressing wires had been foundexceptfor the very first investigation.

欧洲桥梁研究

欧洲联盟共同的研究平台诞生于欧洲联盟。为了说明欧洲的研究方法已经被这种方式所替代一个典型的案例是后张桥在英国爱丁堡大学进行了讨论对数字脉冲雷达识别后张预应力混凝土桥梁孔隙互补的情况。

引言

利用各研究小组的研究结果验证了大量的相关参数是所有研究领域面临的挑战这是使研究和实践更有针对性的的结合。此外在欧洲语言是不能忽视的是一个巨大的障碍 为了避免类低于 1939到1945第二次世界大战一样的欧洲内战 60年代的第二十世纪的欧洲共同体的建立是基于欧盟各个国家这样共同的目的。它是建立在一个强大的政治动机之上但英国不是欧盟一员 因此许多欧洲国家视英国的为纯粹的经济利益直到 20世纪70年代英国加入欧洲共同体进入欧洲经济共同体。在 90年代 欧洲经济共同体扩展为欧洲联盟在这个时候欧洲联盟既有共同的政治目标也有建立一个共同的欧洲货币体系的经济目标。

随着经济和政治的发展土木工程特别是桥梁工程一直没有能够形成统一战线。这是由于英国和其他欧洲国家不同的大学教育培训体系欧洲基金计划如苏格拉底计划英国欧洲计划等。扮演一个独特的角色来改变这种状况苏格拉底方案是以国内交换生学习为主而英国的欧洲计划则是给一些国家的学术机构和产业界的合作伙伴提供研究援助这通常是由一个工业国家领导的。

传播知识现在似乎已经出现了两个非常不同的方式英国和美国主要集中在将研究结果发表在相关的期刊例如ASCE、 LCE和其他期刊和欧洲大陆国家主要集中于重要研究专题会议上展示研究成果后者在研究成果上发布具有局限性。

此外语言是很难克服的障碍在英语是一种强势语言的国家里在欧洲内陆国家积极参加各种国际会议如德国意大利 比利时荷兰和瑞士。然而英语不是一种强大的语言国家里在国际会议上不活跃如法国。

欧洲的研究

在欧洲桥梁的研究方向可分为三种类型

1圬工拱桥

英国有最大的砖砌拱桥。在英国的某些地区多达60%的道路桥梁是石砌石拱桥这些最初为马拉交通建造的。这在欧洲其他地方不太常见 因为它们在二战期间它们大多数已经破坏了。

2混凝土桥

在20世纪50年代、到70年代的时候欧洲出现了大量的混凝土结构桥梁在那时这一结构被认为是免维护的。欧洲还使用了很多后张法建造的混凝土桥梁但铁制锚索套管会影响桥梁雷达监测。这个问题只存在于英法两国。

3钢结构桥

在上世纪60年代和70年代被认为是对维修的需求这种桥在英国被冷落了。但它仍然被用于大跨度桥梁和铁路桥梁现在这种桥应用于英国正在进行的公路扩建工程行。

欧洲的研究活动

一个明确的信息表明在这一领域的研究工作正在欧洲星期但它并不意味着这中研究的方法没有缺陷。

为了说明欧洲研究正在进行的类型爱丁堡大学给出了一个这种资源互补的案例运用数字化脉冲雷达对后张法建造的混凝土桥梁的孔隙进行检测。

后张法混凝土铁路桥研究

Ove Arup和他的合作者对曼彻斯特的一座长 160M的后张法分段预制施工建造的铁路桥的上部结构的长期稳定性进行了检测和评估这种技术已被运用于城市轻轨系统。

特别需要关注的是后张力法施工的桥梁的完整性。物理检查、非损伤雷达检测及其它的研究方法均已被用来去调查桥梁中潜在的缺陷。

自从1985年2月1 日英国威尔士地区的一座名叫 Ynys-y-Gwas桥梁突然坍塌以来。采用后张力法分段预制施工的桥梁在长期稳定性方面受到关注。因为这种桥梁可能会毫无预兆地出现脆性断裂后张法钢绞线在预制段搭接部位的防腐工作是影响这种类型桥梁长期稳定性的主要因素。对容易发生脆性破坏处锚索套管中的沙浆孔隙的鉴定被认为是防腐检测中最为重要的步骤之一。

总体布局

Besses o’ th ’ Barn大桥始建于 1969年是一座三跨总长 160m的后张法分段预制施工的混凝土铁路桥。它的主跨跨径 90米横跨M62公路和巴利A665公路 Prestwick 公路衔接与 A665公路最小桥下净空高度 5.18米与 为

与M62公路的桥下净空则大约为 12.5米。

桥梁上部结构由空心梯形混凝土箱梁组成。箱体横截面高 6.7m宽4m。桥梁南部分引桥和中央主跨径均采用这种长为 1 .27M的梯形混凝土箱梁结构后张法施工。这种箱形构件的作用是支撑用来承受铁轨和行车荷载的现浇混凝土悬臂梁。

大桥中跨和南部引桥跨径均采用后张法装配式预制结构这些后张法预制构件构件包括五种类型的预应力张拉措施。