大跨度混合梁斜拉桥弹塑性极限承载力分析

Analysis of Elasto-Plastic Ultimate Load Bearing Capacity of Long Span Hybrid Girder Cable-Stayed Bridge

为研究混合梁斜拉桥的弹塑性极限承载力,基于连续体三维虚功增量方程,建立空间薄壁梁单元的U.L.列式增量平衡方程,采用分段分块变刚度法计算单元的弹塑性刚度矩阵,并编制相应的斜拉桥弹塑性极限承载力空间分析程序ULCA。采用ULCA对某主跨480m的双塔三跨空间双索面混合梁斜拉桥成桥进行弹塑性极限承载力分析,分析结果表明:该桥的荷载安全系数k=3.146 5,因混凝土主梁受压区破坏而达到极限状态;材料非线性对边跨位移、索力及桥塔位移的影响远大于对中跨的影响;极限荷载作用下,材料非线性对主梁和桥塔的轴力基本无影响,但弯矩重分布比较明显。

To study the elasto-plastic ultimate load bearing capacity of long span hybrid girder cable-stayed bridge, the incremental equilibrium equation of U.L. formulation for a spacial thinwalled beam element was developed on the basis of the incremental virtual work equation of 3-dimensional continuum. The eiasto-plastic stiffness matrix of the beam element was calculated by the segment and block variable stiffness method and the corresponding spacial analysis program ULCA for the elasto-plastic ultimate load bearing capacity of the cable-stayed bridge was com plied. The ULCA was then used to analyze the elasto-plastic ultimate load bearing capacity of a completed three-span hybrid girder cable-stayed bridge with double pylons, double spacial cable planes and with a main span 480 m. The results of the analysis demonstrate that the load safety factor of the bridge is k=3. 146 5 and the bridge reaches the ultimate state on account of failure of the compression areas of main girder of the bridge. The influences of material nonlinearity on the displacement and cable forces of the side span and on the displacement of pylons are far greater than those on the central span. Under the action of the ultimate load, the material nonlinearity basically has no influence on the axial forces of the main girder and pylons, however the redistri- bution of bending moment in such case is quite notable.