外文翻译---斜拉桥体系.docx

附录： THE CABLE-STAYED BRIDGE SYSTEMDuring the past decade cable-stayed bridges have found wide application, especially in Western Europe, and to a lesser extent in other parts of the world.The renewal of the cable-stayed system in modern bridge engineering was due to the tendency of bridge engineers in Europe, primarily Germany, to obtain optimum structural performance from material which was in short supply during the post-war years. Cable-stayed bridges are constructed along a structural system which comprises an orthotropic deck and continuous girders which are supported by stays, i.e. inclined cables passing over or attached to towers located at the main piers. The idea of using cables to support bridge spans is by no means new, and a number of examples of this type of construction were recorded a long time ago .Unfortunately the system in general met with little success, due to the fact that the static were not fully understood and that unsuitable materials such as bars and chains were used to form the inclined supports or stays. Stays made in this manner could not be fully tensioned and in a slack condition allowed large deformations of the deck before they could participate in taking the tensile loads for which they were intendedWide and successful application of cable-stayed systems was realized only recently, with the introduction of high-strength steels, orthotropic decks, development of welding techniques and progress in structural analysis. The development and application of electronic computers opened up new and practically unlimited possibilities for the exact solution of these highly statically indeterminate systems and for precise statically analysis of their three-dimensional performance. Existing cable-stayed bridges provide useful data regarding design, fabrication, erection and maintenance of the new system. With the construction of these bridges many basic problems encountered in their engineering are shown to have been successfully solved. However, these important data have apparently never before been systematically presented.The following factors helped make the successful development of cable-stayed bridges possible:(1) The development of methods of structural analysis of high statically indeterminate structures and application of electronic computers. (2) The development of orthotropic steel decks. (3) Experience with previously built bridges containing basic elements of cable-stayed bridges. (4) Application of high strength steels new methods of fabrication and erection. (5)The ability to analysis such structures through model studies.BASIC CONCEPTS The application of inclined cables gave a new stimulus to construction of large bridges. The importance of cable-stayed bridges increased rapidly and within only one decade they have become so successful that they have taken their rightful place among classical bridge systems. It is interesting to note how this development which has so revolutionized bridges construction, but which in fact is no new discovery, came out. The beginning of this system, probably, may be traced on back to the time when it was realized that rigid structures could be formed by joining triangles together. Although most of these earlier designs were based on sound principles and assumptions，the girder stiffened by inclined cables suffered various misfortunes which regrettably resulted in abandonment of the system. Nevertheless, the system in itself was not at all unsuitable. The solution of the problem had unfortunately been attempted in the wrong way. On the one hand, the equilibrium of these highly indeterminate systems dad not been clearly appreciated and controlled, and on the other, the tension members were made of timber, round bars or chains. They consisted therefore of low-strength material which was fully stressed only after a substantial deformation of the girder took place. This may explain why the renewed application of the cable-stayed system was possible only under the following conditions:(1) The correct analysis of the structural system.(2) The use of tension members having under dead load a considerable degree of stiffness due to high pre-stress and beyond this still sufficient capacity to accommodate the live load.(3) The use of erection methods which ensure that the design assumptions are realized in an economic manner.The renaissance of the cable-stayed system, however, was finally successfully achieved only during the last decadeModern cable-stayed bridges present a three-dimensional system consisting of stiffening girders, transverse and longitudinal bracings, orthotropic-type deck and supporting parts such as towers in compression and inclined cables in tension. The important characteristics of such a three-dimensional structure is the full participation of the transverse construction in the work of the main longitudinal structure. This means a considerable increase in the moment of inertia of the construction which permits a reduction in the depth of the girders and economy in steel.The introduction of the cable-stayed system is a true pioneering development in bridge architecture. Existing cable-stayed bridges are masterpieces of steel construction. They are pleasing in outline, clean in their anatomical conception and totally free of meaningless ornamentation. This is because the design of cable-stayed bridges was governed not only by financial, practical and technical requirements, but also, to a great extent, by aesthetic and architectural considerations. In the design of modern cable-stayed bridges, one objective is to produce an aesthetically appealing bridge which blends with its surroundings.These bridges are truly representative of modern times. They are the product of engineering science, which is continuously advancing in accordance with its own laws and has been given form and substance by the twentieth century engineer. From : “Cable-Stayed Bridges Theory and Design” by M. S. Troitsky CrosbLockwood Staples London 1999 译文： 斜拉桥体系在过去的几十年中，斜拉桥得到了广泛的应用，尤其是在西欧应用最多，在别的地方应用也较多。在现代桥梁工程中，斜拉桥的应用之所以兴起是由欧洲桥梁工程师的研究方向决定的，大多数在德国。他们当时（二战后）为了获得材料的最佳结构使用性能，而在那时这些材料是很紧缺的。斜拉桥是按如下结构体系建造的，它由正交各向异性桥面板和由拉索控制的连续梁组成，拉索是通过位于主桥墩上的索塔顶部或固定于索塔顶部的倾斜缆索。使用拉索来支撑桥跨的观点现在来说决不是什么新奇的，很早以前就有这种结构的记载。遗憾的是，这中体系的桥很少成功应用，主要是因为内力并不能完全解出，斜支撑或支座所使用的材料如钢筋和拉索对斜拉桥来说是不适用的。这种拉索不能充分拉紧而处于松弛状态，因而仅在桥面发生很大变形时，拉索才能承受使用时的拉力。伴随着高强度材料和正交各向异性板的产生，焊接技术的发展和结构动力性能分析的进步，斜拉桥体系才得到广泛的发展并成功的应用。电子计算机的应用使斜拉桥的高次超静定体系的精确分析成为可能，并提供了可行的精确的解决方案，也为三维空间结构提供了准确的静力分析。斜拉桥的存在为新体系的设计、构造、建设和维护提供了有用的数据资料，随着这些桥的兴建，在实际工程中遇到的许多基本问题将得到很好的解决。然而，这些重要数据以前不能从体系中得出。以下因素是建造一座斜拉桥应该考虑的：（1） 高次超静定结构性能的分析方法和电子计算机的应用。（2） 正交刚性异性板的发展。（3） 先前的建桥经验，其中包括斜拉桥的基本组成部分。（4） 高强度钢材的使用，组装和施工的新方法。（5） 利用模型分析结构的能力。基本概念斜拉索的应用促进了大型桥梁的建设，斜拉桥的重要性也明显提高。在过去的