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1、.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
2、 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. incl
3、ined 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
4、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
5、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 app
6、lication 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 desig
7、n, 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 f
8、actors 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 bui
9、lt 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 lar
10、ge 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, bu
11、t 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
12、 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
13、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 plac
14、e. 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 thi
15、s 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 b
16、ridges 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 p
17、articipation 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
18、 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
19、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
20、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 Staple
21、s 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
22、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
23、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。在过去的仅仅十年内，它们在传统的桥梁体系中已占一席之地，斜拉桥的发展如此迅猛，真让人惊叹，但事实上并没有新的重大发现。这种体系的桥的开始出现可以追溯到那个年代，就是刚性结构可以通过铰接形成的时代。尽管早期的大多数斜拉桥设计都基于扎实的理论基础和假设，由斜拉索控制的主梁还是出了问题，致使人们放弃了该种桥型。然而，这种体系本身并
24、不是不可用的。因为解决问题时不幸地利用了错误的假设方法。一方面，高次超静定体系的平衡问题没有得到足够的认识和控制，另一方面，受压构件由木材圆钢筋或钢束组成，他们认为只有当梁发生较大的变形时，这些低强度材料应力才得以提高。这就是为什么斜拉桥体系在以下条件下才可应用：（1） 结构体系的正确分析。（2） 由于高应力存在，使受拉构件有相当强的刚性，并且当超出该应力值后，结构还可以有足够的应力储备去承受活载。（3） 施工方法的选用能保证设计时的假设满足经济可行性的原则。 然而，仅在上个年代斜拉桥体系就可以复兴并最终成功应用。现代斜拉桥由加劲梁横向和纵向连接系正交异性板和支撑结构如受压的塔和受拉的索组成，并呈现出三维空间结构。这种三维空间结构的重要特性是横向结构可以完全参与到纵向主梁的受力中，这意味着大大增大结构的惯性矩，从而做到降低主梁的高度并节省钢材。斜拉桥体系的出现在桥梁美学上是一个真正的创新，斜拉桥是钢建筑中的杰作。它们不仅外形美观，结构概念明确，而且完全没有多余的装饰。这时因为斜拉桥的设计不仅要满足经济性、可行性和技术要求，而且在很大程度上要考虑美学和建筑风格。在设计现代斜拉桥时，一个主要的客观因素就是要保证桥型引人注目并与周围环境协调。这些斜拉桥是现代社会的真正代言人，也是现代工程科学的产物。工程科学同它的法则不断发展，并被二十世纪的工程师赋予新的内容和形式。*;