斜拉桥的发展.ppt

2003-11-28 武汉理工大学　汪国相 Evolution of cable-stayed bridges Examples of cable-stayed bridges can be found from the earliest days of bridges building Evolution of cable-stayed bridges But these early examples have no decisive influence on the design of modern cabled-stayed bridges Evolution of cable-stayed bridges 加之，19世纪20年代前后修建的几座斜拉桥因人群超载或风振作用而遭受破坏，法国人纳维(Navier)调查后得出悬索桥优于斜拉桥的结论。 所以，直到第二次世界大战后德国重新采用前，斜拉桥几乎已被工程师们遗忘。 Evolution of cable-stayed bridges 但是，历史上斜拉桥破坏的真正原因并不是斜拉桥在结构上不及悬索桥，只是因为当时材料强度低，以及当时还不能正确计算斜拉桥这样高次超静定结构，致使斜拉桥被人们遗忘达一个世纪之久。 The start of a new era for cable-stayed bridges was to a large extent due to the improved techniques of structural analysis allowing calculation of cable forces throughout the erection period and thereby assuring the efficiency of all cables in the final structure. Evolution of cable-stayed bridges 斜拉桥发展的原因： 考虑挠曲影响的超静定结构计算理论的发展。 这种理论便于电子计算机计算。 不仅能正确进行结构计算，还能精确作出施工控制计算。 正交异性板作为主梁。 使用正交异性板的桥梁比以往具有纵向联结系的结构具有更高的横向刚性。 高强度钢索和高疲劳强度锚具的发展。 模型试验技术的发展。由于斜拉桥是高次超静定结构，某些部位应力分布较为复杂，要依靠各种模型试验来探求其设计参数和验证设计的安全性。 Evolution of cable-stayed bridges 通过斜拉索与悬索体系相组合以获取更有效的结构体系的构思，最早出现在1883年建成的布洛克林大桥。 该桥由罗勃林（John A. Roebling）设计，被认为是现代悬索桥的鼻祖。 主跨486m，边跨286m。John A. Roebling生涯中最伟大的桥梁 Evolution of cable-stayed bridges 跨越纽约东河的布洛克林桥（Brooklyn Bridge） Evolution of cable-stayed bridges The idea of combining the suspension system with stays to achieve more efficient structural systems had not been completely forgotten after the days of the Brooklyn Bridge. In 1938 Dischinger proposed a system in which the central part of the span was carried by a suspension system whereas the outer parts of the span was carried by stays radiating from the pylon top. Evolution of cable-stayed bridges In connection with the reconstruction of German bridges after the war, the Dischinger’s system was proposed on several occasions but it was never used for actual construction. Evolution of cable-stayed bridges The Dischinger’s system was never adopted for actual construction, but it undoubtedly