桥梁外文翻译 ---荷兰跨线高架桥

附录4 外文文献翻译RAILWAY SUSPENSION BRIDGEIN WOERDEN, THE NETHERLANDSSUMMARYIn Woerden, a small town in the west of the Netherlands, a railway fly-over has been builtwhere two railway tracks meet. The fly-over consists of a single-track viaduct. This has alength of 438.5 m. The crossing angle is 10 degrees. At the fly-over site the viaduct issuspended from a pylon that has been constructed over two tracks passing underneath.1. INTRODUCTIONA railway bridge was constructed in Woerden as part of the track expansion of theNetherlands Railways. More trains will be run, the running speeds will be increased and thepossibility of delays must be reduced. In order to make this possible, many line sections mustbe four-track and trains must be able to cross each other at different levels.This paper examines the fly-over in Woerden.2. SITUATION AND REQUIREMENTSThe fly-over in Woerden must bridge the following elements:- two existing tracks;- two future tracks;- a polder drainage pool;- an underpass for all traffic.The subsoil exhibits a great variation in compressibility. The forecast for settlement after 30years for the adjacent track bed on one side is about 0.5 m and on the other side about 3 m. To limit settlement, and due to the lack of space for access, the construction height of thebridge must be as low as possible.The existing tracks and the underpass must remain in operation during the construction. Theflow capacity of the polder drainage pool may not be restricted.3. GENERAL DESCRIPTIONThe total length of the viaduct is 438.5 m, comprising six sections (fig. 1).Section I crosses the underpass and has a length of 82.3 m. The two intermediate supports aresituated immediately adjacent to the concrete casing of the underpass, setting the spans at22.7 m, 35 m and 22.65 m.Sections II to V have a length of 47.3 m and each consists of two spans of 22.65 m. Thelengths and spans were determined by the remaining space between sections I and VI and costoptimisation. Section II crosses the polder drainage pool.Section VI, with a length of 167 m, crosses the two existing and the two future tracks. Thespans range between 26.3 and 46.7 m, with the supports staggered under the side beams. Allbridges have been made from pre-stressed concrete.To limit the construction height, it was decided to employ a U-shapedcross-section (fig. 2). The track floor lies low between the two load-bearing perimeter beams with a breadth of 1.4m. The height of the beams is 1.5 m for the small spans and 2.8 m for the larger. Theappearance of a gradual transition from low to high beams is caused by walls that increase inheight at the ends of the low beams, connecting to the high beams.The track construction consists of a continuous ballast bed. Only for the transition fromsection VI to the track bed are two compensation welds used in the rails to absorb changes inlength due to temperature shifts. At the other joins between the bridge sections the rails runcontinuously through.The lack of space at the site means that the crossing angle with the tracks that are to be newlylaid is only 10 degrees. In addition, points are projected to be positioned in the tracks passingunderneath, so that no columns can be located between the new tracks. For such situations, ‘pergola constructions’ are often built, consisting of long rows of columns along the trackwhich support a concrete deck with a span direction perpendicular to the tracks passingunderneath. The pergola would in this situation be 160 m long and vary between 14 m and 28m in width.For aesthetic and economic reasons, an innovative solution has been developed: Thesuspension of the crossing U-shaped bridge from a pylon which is constructed over the tracksthat will be running underneath (fig. 3). This creates a transparent construction thatguarantees a view of the countryside and clearly expresses the forces at work. This bridge isthe first of its kind in the Netherlands.Despite the high construction cost of the pylon, the total cost of the solution chosen is lowerthan for a pergola.The suspension from the pylon is such that the forces in the U-shaped bridge work as evenlyas possible and high peak stresses are avoided. The load from theU-shaped beams is divertedto the three suspension cable anchors per beam underneath. The cables run via conduitsthrough the beams to the intersection of the ridge beam and the slanting pylon columns (fig. 4).The horizontal loads from the bridge are fed directly to the columns of the pylon via ridgeslocated on the outside of the U-shaped beams.4. CONSTRUCTION ASPECTS4.1 Static system superstructureThe fly-over is constructed from six bridge sections. The bridge parts are mounted onreinforced rubber bearings. At their extremes, the sections are fixed horizontally in the crossdirection by steel guiding constructions that primarily absorb the horizontal thrust forces andcentrifugal forces; the ends of the bridge are free to move in the longitudinal direction. Thesection crossing the track is also fixed at the pylon both in the cross direction and in thelongitudinal direction by horizontal struts between the U-shaped floor and the pylon.4.2 SubstructureThe foundations of the fly-over are primarily pre-fabricated pre-stressed 450 x 450 mm2concrete piles with a length varying between 13 m and 18 m and with a pile depth varyingfrom 12.50 m to 18.00 m below ground level. Both abutments have a foundation of steel pipe piles Ø 508 mm with a wall thickness of 16mm. The piles are filled with concrete and fitted with reinforcement. The use of steel pipepiles for the abutments was made necessary by the settlement of the connecting raised trackbeds as a result of the compressible subsoil which might subject the piles to bending. Prestressedconcrete driven piles turned out not to be able to absorb these bending moments.The columns under the U-shaped bridge ends are coupled crossways with a beam constructiondue to the horizontal forces that are diverted there via the guiding constructions. In order to be able to quantify the interaction of the track with thesubstructure, a tracklongitudinal forces program has been developed in which the whole system is divided intodiscrete components by means of the following elements:- rail elements;- ballast elements;- bridge elements;- bearing elements;- pile elements;- foundation elements.The bridge system is physically described with these elements, and the accompanyingparameters are entered for each type.Generally, CWR track is used. If, however, the expanding bridge lengths become too great, ‘compensation’ welds or compensation constructions, in which the track has overlapping ‘tongues’ and so is free to undergo deformation, must be used due to the rail forces reachingtoo high a level as a result of braking forces and temperature effects. At the location of one of the intermediate supports, bridge section VI is suspended from apylon construction where the bridge is also fixed horizontally. Due to the high stiffness of thisconstruction, this determines the free expansion length to the abutment. This length is greaterthan 60 m, the maximum free expansion length to an abutment for ballasted track. For thisreason two compensation welds are used at the abutment.4.3 Pre-stressingThe U-shaped bridges are constructed from pre-stressed concrete.The following can be distinguished:- longitudinal pre-stressing in the U-shaped beams, through which thebeam’s ownweight, the permanent load and the working load arediverted;- cross pre-stressing of the U-shaped ends in the base. This absorbs theshear tensionsthat are generated as a result of the longitudinalpre-stressing.For the 167 m long track-crossing section VI, a 27-strand longitudinalpre-stressing systemwas chosen with strands Ø 15,2 mm, FeP 1860. Eight units are used for each beam. For thecross pre-stressing, the BBRV system, which is not liable to wedge-settlement, was chosen. This was due to the relatively short length (approx.7.50 m), which means that the effect ofwedge settlement would have been too great on the extent of the pre-stressing.The average pre-stressing level in the U-shaped bridges is between 4.5 and 5.5N/mm2.An additional complication arose at the pylon where the bridge is suspended with vertical guycables. There are three guy cables for each U-shaped beam which are carried via steelconduits Ø 400 mm through the 1.40 m wide U-shaped beams. This provided much concernwith respect to accommodating the eight pre-stressing cables, the shear forces that arise andthe soft steel reinforcement connected with this as a result of the bending of the tensiontrajectories through this deformation. The criterion for the maximum permissible stress (0,45f'‘ck) was the guideline at this site.The U-shaped bridges were calculated with a finite-element model in which such factors as, with a view to fatigue, the main pull in the concrete would not exceed the value of 0,5 f’'ck.4.4 PylonThe pylon was calculated by means of dividing it into discrete bar elements in a finite-elementmodel. The horizontal struts, that can only bear compressive forces, were divided into springelements with the characteristic that they are inactive for an pulling load, so that it is a nonlinearcalculation.The horizontal struts (figs. 5 and 6) that fix the U-shaped bridge both in the longitudinal andin the cross direction, thus bear the longitudinal forces (primarily braking, starting and trackforces) and the cross forces (mainly thrust, centrifugal and wind forces).The horizontal struts comprise four steel pipes Ø 508 mm with a wall thickness of 30 mm. The length varies from 1025 mm to 2285 mm. The brackets are constructed in such a waythat they are able only to bear compressive forces. The steel pipes provide support for concretebrackets at the base level of the bridge. This connection, that cannot absorb pull forces, isfitted with a conical dowel, a ‘seeker dowel’, that ensures that the support construction iscentred at all times, even when it is disengaged by a few millimetres from the connection tothe U-shaped bridge.The maximum compressive force that occurs in the most heavily loaded strut is 3020 kN. Themaximum cross force has been calculated at 248 kN.4.5 Guy cablesAt the pylon, the bridge is suspended with two groups of vertical guy cables. Three cables arefitted to each beam, which move as a group in relation to the axis of this support (fig. 5). Thecables are fed through the U-shaped beam and pylon viain-built steel conduits, with theanchor-heads are supported to accurately horizontally positioned steel anchor plates. The cables are ‘Hiam cables’, composed of 253 strands Ø 7 mm, FeP 1670.Load on the cables:- the six cables absorb a maximum reactive force of 20970 kN, 22% ofwhichis causedby the working load;- the most heavily loaded cable absorbs a maximum reactive force of3880 kN;- the least heavily loaded cable absorbs a reactive force of 3070 kN.In the design of the cables, the following requirements were set:-the maximum deformation due to the working load must be less than1/800 part of theadjoining span;- collapse safety criteria;- fatigue criteria;- changing a cable under the own weight of the bridge and permanentload;- taking over the load after sudden failure of a cable under maximumload;- preservation requirements.荷兰跨线高架桥摘要在荷兰西部的一个小镇两条铁路相交的地方，一座跨线铁路桥已经修建。