部分吊杆失效对“X”形钢结构系杆拱人行天桥结构性能的影响分析

Influence of Failure of Some Hangers on Structural Performance of X-Shaped Steel Tied Arch Footbridge

上海某人行天桥平面布置为"X"形和中心椭圆环组合的钢结构系杆拱桥,两交叉方向主桥跨度分别为80m和58m;桥面结构为箱形梁板架。对该桥进行检测发现,有4根吊杆失效引起结构状态改变,吊杆索力分布与原设计存在一定偏差。为了解吊杆失效后结构性能,建立有限元模型,计算结构静、动力性能。结果表明:4根吊杆失效后,与其相邻的部分吊杆索力变化较大,其余索力变化不大;结构在各工况下的最大应力及挠曲变形均有不同程度的增大,但仍能满足规范要求,吊杆失效对结构静力安全影响有限;结构整体刚度降低,前10阶自振频率均有所减小,结构振型发生了一定改变。

A footbridge in Shanghai is an X-shaped steel tied arch bridge .From a bird′s-eye view ,the bridge looks like a structure of an “X” shape superimposed with a central elliptical ring . The spans of the main bridge in the two intersection directions are 80 m and 58 m ,respectively . The bridge deck adopts the box-shaped frame with filled-in plates .The inspection of the bridge demonstrated that the failure of four hangers led to the change of the structural condition of the bridge and the distribution of hanger forces were not in accord with the original design values .To analyze the structural performance of the bridge in the context of hanger failure ,the finite element model of the bridge was built to calculate the static and dynamic property of the bridge .The re-sults of the calculation demonstrated that when four hangers failed ,the forces of some of their neighboring hangers showed great change and the forces of the remaining hangers showed minor change .The maximum stress ,deflection-induced deformation of the structure under different con-ditions increased with different degrees ,but still met the code requirements ,which means hanger failure has limited influence on the structural static safety .The overall stiffness of the structure has decreased ,the natural vibration frequency of the first 10 orders all reduced and the structural vibration has changed to a certain extent .