基于极限状态法的钢桁梁公铁斜拉桥结构分析

Analysis of Property of Ultimate States of Steel Truss Road and Rail Cable-Stayed Bridges

以某钢桁梁公铁斜拉桥为研究对象,采用空间有限元方法,计入几何非线性影响,进行基于极限状态法的斜拉索初应力计算及桥梁结构特性的数值分析。提出基于极限状态法的计入主梁恒载增大系数的斜拉索初应力计算方法,计算了两组斜拉索初应力:不考虑恒载增大系数和考虑恒载增大系数。进行该斜拉桥自振特性分析,以及两种极限状态下的静力特性分析:承载能力极限状态和正常使用极限状态。讨论以极限状态法为基础的分析方法的有效性。研究结果表明:斜拉索初应力大小对钢桁梁斜拉桥主塔和主梁构件静力响应的影响显著;以极限状态法为基础的考虑提高系数计算出的斜拉索初应力能使斜拉桥在外荷载作用下具有更加良好的结构性能;按照承载能力极限状态法来进行大跨度钢桁梁公铁斜拉桥的设计和分析更经济合理。

Take a long span truss rail and road cable-stayed bridge as the example, using nonlinear finite element method, properties of the truss rail and road cable stayed bridge under load ultimate limit state and serviceability limit state are studied. Two different methods to calculate the initial stress of the cable were adopted： one is concerned with safety factor and partial load factors and the other is unconcerned with these factors. Dynamic characteristics of the truss rail and road cable-stayed bridge were studied and static responses of the bridge under basic loads combination and long-term effect loads combination were calculated respectively. Based on comaprative study, the initial cable stress had great effect on vertical members and cables. In addition, the influence of the initial cable stress on dynamic properties of cablestayed bridges was little and can be neglected. The result showed that truss rail. and road cable-stayed bridges having the initial cable stress which was calculated by considering the safety and partial loads factors had more rasonable statuses and better mechanical behavious.