58559土木工程专业英语鲁正电子课件-普及版to bridge engineering

1、Unit 7 Introduction to Bridge EngineeringEnglish for Civil EngineeringTeacher: Prof. Zheng LuE-mail: （School of Civil Engineering, TONGJI UNIVERSITY）Unit 7 Introduction to Bridge Engineering7.1 Reinforced Concrete Girder Bridges（钢筋混凝土梁式桥） (1) Slab Bridges（板桥） (2) T-Beam Bridges （T形梁桥） (3) Box-Girder

2、 Bridges （箱梁桥）7.2 Arch Bridge（拱桥）7.3 Steel Bridges（钢桥）7.4 Truss Bridges（桁架桥）7.5 Plate and Box Girder Bridges（板箱梁桥）7.6 Cable Stayed Bridges（斜拉桥）7.7 Suspension Bridge（悬索桥）7.1 Reinforced Concrete Girder BridgesThe raw materials of concrete, consisting of water, fine aggregate, coarse aggregate, and cem

3、ent, can be found in most areas of the world and can be mixed to form a variety of structural shapes. The great availability and flexibility of concrete material and reinforcing bars have made the reinforced concrete bridge a very competitive alternative. Reinforced concrete bridges may consist of p

4、recast concrete elements, which are fabricated at a production plant and then transported for erection at the job site, or cast-in-place concrete, which is formed and cast directly in its setting location. 钢筋混凝土梁式桥 材料搭配与建造过程fine aggregate细骨料；coarse aggregate 粗骨料；cement水泥；precast concrete elements 预制

5、混凝土构件；fabricated 制造；cast-in-place 现场浇筑7.1 Reinforced Concrete Girder BridgesCast-in-place concrete structures are often constructed monolithically and continuously. They usually provide a relatively low maintenance cost and better earthquake-resistance performance. Cast-in-place concrete structures,

6、 however, may not be a good choice when the project is on a fast-track construction schedule or when the available falsework opening clearance is limited. In this unit, various structural types and design considerations for conventional cast-in-place, reinforced concrete highway girder bridge are di

7、scussed. 钢筋混凝土梁式桥 材料搭配与建造过程Monolithically 整体地；maintenance cost 维护费用；earthquake-resistance performance 抗震性能；fast-track 快速；falsework 脚手架7.1 Reinforced Concrete Girder Bridges1 Slab Bridges （板桥）Longitudinally reinforced slab bridges have the simplest superstructure configuration and the neatest appeara

8、nce. They generally require more reinforcing steel and structural concrete than do girder-type bridges of the same span. However, the design details and formworks are easier and less expensive. It has been found economical for simply supported spans up to 9 m and for continuous spans up to 12 m.钢筋混凝

9、土板桥 Longitudinally 纵向；superstructure configuration 上部结构形状； girder-type bridges 梁式桥7.1 Reinforced Concrete Girder Bridges2 T-Beam Bridges （T形梁桥）The T-beam construction consists of a transversely reinforced slab deck which spans across to the longitudinal support girders. These require a plicated form

10、work, particularly for skewed bridges, compared to the other superstructure forms. T-beam bridges are generally more economical for spans of 12 to 18 m. The girder stem thickness usually varies from 35 to 55 cm and is controlled by the required horizontal spacing of the positive moment reinforcement

11、. Optimum lateral spacing of longitudinal girders is typically between 1.8 and 3.0m for a minimum cost of formwork and structural materials. However, where vertical supports for the formwork are difficult and expensive, girder spacing can be increased accordingly.transversely reinforced slab deck 横向

12、加筋板；formwork 模板；skewed bridges 斜交桥； girder 大梁；horizontal spacing 水平间距；positive moment 正弯矩7.1 Reinforced Concrete Girder Bridges3 Box-Girder Bridges（箱梁桥）Box-girder bridges contain top deck, vertical web, and bottom slab and are often used for spans of 15 to 36 m with girders spaced at 1.5 times the s

13、tructure depth. Beyond this range, it is probably more economical to consider a different type of bridge, such as post-tensioned box girder or steel girder superstructure. This is because of the massive increase in volume and materials. They can be viewed as T-beam structures for both positive and n

14、egative moments. The high torsional strength of the box girder makes it particularly suitable for sharp curve alignment, skewed piers and abutments, superelevation, and transitions such as interchange ramp structures.top deck 顶面板；web 腹板；post-tensioned 后张法；torsional strength 抗扭强度；skewed piers and abu

15、tments 倾斜支柱和台墩；interchange ramp立交匝道7.1 Reinforced Concrete Girder Bridges7.2 Arch BridgeEven in the Middle Ages, it was appreciated that masonry arches behaved essentially as gravity structures, for which geometry and proportion dictated aesthetic appeal and stability. Compressive strength could be

16、relied upon whilst tensile strength could not. Based upon experience, many empirical relationships between the span and arch thickness were developed and applied successfully to produce many elegant structures throughout Europe. The expansion of the railway and canal systems led to an explosion of b

17、ridge building. Brickwork arches became increasingly popular. With the construction of the Coal-brookdale Bridge (1780) a new era of arch bridge construction began. By the end of the nineteenth century cast iron, wrought iron and finally steel became increasingly popular; only to be challenged by fe

18、rrocement (reinforced concrete) at the turn of the century.拱桥的历史发展masonry /Brickwork arches 石/砖拱；aesthetic appeal 美学作用；empirical 经验的；railway and canal systems 铁路和管道系统；cast /wrought iron 生/熟铁7.3 Steel BridgesStructural steel is an extremely versatile material eminently suited for the construction of

19、all forms of bridges. The material, which has a high strength-to-weight ratio, can be used to bridge a range of spans from short through to very long (151500 m), supporting the imposed loads with the minimum of dead weight. Steel bridges normally result in light superstructures which in turn lead to

20、 smaller, economical foundations. They are normally prefabricated in sections in a factory environment under strict quality control, transported to site in manageable units and bolted together in situ to form the complete bridge structure. Using this construction method the erection of a steel bridg

21、e is usually rapid, resulting in minimal disruption to traffic; a very important factor if traffic delays, be it road or rail, are properly assessed in the construction project.钢桥的优势Versatile 多面的；strength-to-weight ratio 强度质量比；imposed loads 外荷载；foundations 基础；prefabricated 预制的；bolted 螺栓连接；in situ 现场

22、；erection 建立； traffic delays 交通延误7.3 Steel BridgesFor spans in the range of about 25100 m, plate girders, again acting compositely with the deck, provide an economical solution. In order to optimise the concrete deck, which has to distribute wheel loads transversely across the bridge, it is usual to

23、 arrange for a plate girder spacing of around 3 m. For longer spans exceeding 100 m, box girders are the favoured choice. Although box girders have a higher fabrication cost than plate girders, box girders have substantially greater torsional stiffness and, if carefully profiled, good aerodynamic st

24、ability. For very long spans in excess of 250m, stiffened steel box girders with an integral orthotropically stiffened steel top plate, forming the primary support for the running surface, provide a very economical lightweight solution. Fig. 7-2 gives cross-sections taken through typical bridge stru

25、ctures using hot-rolled, plate girder and box girder sections.钢桥的优势plate girders 钢板梁；compositely 复合；profiled 外形设计；orthotropically 各向正交异性；lightweight 轻质7.4 Truss BridgesLattice truss structures have been used very successfully for both railway and highway bridges throughout the last 150 years. There

26、are three main truss configurations in use today, namely the Warren truss, the Modified Warren truss and the Pratt truss, all of which can be used as an underslung truss, a semi-through truss, or a through truss bridge. Fig. 7-3 gives details of the three truss types together with sections showing t

27、he differences between an underslung, semi-through and through truss.桁架桥梁的形式Lattice truss structures 格构式桁架；configurations 结构；Warren truss 华伦式桁架；Modified Warren truss 改进华伦式桁架；Pratt truss 普拉特桁架； underslung truss 低重心桁架7.4 Truss Bridges7.5 Plate and Box Girder BridgesAs discussed previously in this unit

28、, one of the most common forms of steel (or composite) bridge, the plate girder, is comprised of steel plate elements welded together, often of relatively slender construction. These elements are found in the webs and flanges of plate girders and also in the stiffeners, although the latter are norma

29、lly made from hot-rolled sections. The box girder, somewhat less common, is found in longer-span bridges either as a composite construction or, for very long spans, as an all-steel structure with stiffened steel decks. Such long-span girders may have additional support provided by cables such as fou

30、nd in cable-stayed or suspension bridges. Very long-span bridges can have extremely complex cross-sections of aerodynamic shape with complex stiffening arrangements. 板梁和箱梁桥Slender 细长的；webs and flanges 腹板和翼缘；composite construction 组合结构；all-steel structure 全钢结构；cable-stayed bridges 斜拉桥；suspension brid

31、ges 悬索桥；local buckling 局部屈曲7.6 Cable Stayed BridgesThe use of inclined stays as a tension support to a bridge deck was a well-known concept in the nineteenth century and there are many examples, particularly using the inclined stay as added stiffness to the primary draped cables of the suspension br

32、idge. Unfortunately, at this time, the concept was not well understood. As it was not possible to tension the stays they would e slack under various load conditions. The structures often had inadequate resistance to wind-induced oscillations. There were several notable collapses of such bridges, for

33、 example the bridge over the Tweed River at Dryburgh (Drewry, 1832), built in 1817, and collapsed in 1818 during a gale only six months after construction was completed. As a result the use of the stay concept was abandoned in England. Nevertheless, these ideas were adapted and improved by the Ameri

34、can bridge engineer Roebling who used cable stays in conjunction with the draped suspension cable for the design of his bridges. （时间顺序介绍斜拉索历史）inclined stays 斜拉索；bridge deck 桥面板；Slack 松弛；wind-induced oscillations 风振；gale 狂风； in conjunction with 连接7.6 Cable Stayed BridgesThe best known of Roeblings br

35、idges is the Brooklyn Bridge, completed in 1883. The modern concept of the cable-stayed bridge was first proposed in postwar Germany, in the early 1950s, for there construction of a number of bridges over the River Rhine. These bridges proved more economic, for moderate spans, than either the suspen

36、sion or arch bridge forms. It proved very difficult and expensive in the prevailing soil conditions of an alluvial floodplain to provide the gravity anchorages required for the cables of suspension bridges. Similarly for the arch structure, whether designed with the arch thrust carried at foundation

37、 level or carried as a tied arch, substantial foundations were required to carry these large heavy spans. By comparison the cable-stayed alternatives had light decks and the tensile cable forces were part of a closed force system which balanced these forces with the compression within the deck and p

38、ylon. Thus expensive external gravity anchorages were not required. （时间顺序介绍斜拉索历史）moderate spans 中等跨度；prevailing soil conditions 常见的土壤条件；alluvial floodplain 冲积平原；arch thrust 拱推力；pylon 桥塔7.7 Suspension Bridge The scope of this unit is restricted to consideration of the classical three-span suspension

39、bridge configuration (Fig. 7-4), with a stiffened load-carrying deck structure supported by earth-anchored cables. The bridge may have side spans of differing lengths and, depending on the site topography, the bridge deck may be suspended either in all three spans or in the main span only, when the

40、side span cables act simply as back stays to the towers. Bridges with unusual span or cable configurations, including bridges with multiple main spans, mono-cable bridges, self-anchored structures, and hybrid part suspension/part cable-stayed structures are not considered. Even with the above limita

41、tions, it is not possible in a relatively short chapter to consider in detail many important aspects of suspension bridge design in particular the analysis of cables and the aerodynamic design requirements.（悬索结构介绍）three-span suspension bridge configuration 三跨吊桥结构；earth-anchored cables 地锚；side spans

42、边跨； topography 地形；main spans 主跨； mono-cable 单索；self-anchored 自锚式7.7 Suspension BridgeTwo or more main cables formed from high-strength steel wires, with a strength-to-weight ratio of around three times that of weldable structural steels, and which support the traffic-carrying deck and transfer its loading by direct tension forces to the supporting towers and anchorages. As the deck dead load is entirely supported by the cable, towers and anchorag