大跨双层斜拉桥的行波效应

以目前跨度最大的双层公路斜拉桥——上海闵浦大桥为例,研究行波效应对大跨双层斜拉桥地震响应的影响。建立考虑双层桥面间不同腹杆的梁壳空间有限元模型,通过静力几何非线性分析获取全桥的初始平衡态,在此基础上进行特征值分析与几何非线性动力分析,分别获取全桥的动力特性与地震响应。分析了3组不同地震波在不同视波速下的大跨双层斜拉桥的地震响应,给出了视波速对主塔、辅助墩地震响应以及塔梁、墩梁纵桥向相对位移的影响规律。研究表明,行波效应对大跨双层斜拉桥地震响应的影响对地震波特性以及视波速具有一定的依赖性,因此选定合适的地震波与确定合理的视波速范围尤为重要。

Influence of Waves Traveling on Seismic Response of Double-Deck Long-Span Cable-Stayed Bridges

The influence of traveling wave on the seismic response of long-span double-deck cable-stayed bridge, especially taking into account the web members between decks, has not been studied thoroughly. Shanghai Minpu Bridge, which is the longest double-deck long-span cable-stayed highway bridge, is taken as an example to study the traveling wave on the seismic response in this paper. Finite element model with beam and shell element is established, in which the web members between decks are also modeled. Initial equilibrium configuration for the bridge is acquired through nonlinear static analysis. The modal analysis and geometric nonlinear dynamic analysis are carried out based on the initial equilibrium configuration to get the dynamic characters and seismic responses respectively. The influence of traveling wave on the seismic response is demonstrated by three groups of earthquake motions with different apparent wave velocities. The effect of apparent wave velocities on the seismic response of tower, subsidiary piers and the relative displacement between tower and girder and between subsidiary piers and girder are discussed in detail. It is concluded that the seismic responses of double-deck long-span cable-stayed bridges depend heavily on the apparent wave velocities and the earthquake motions inputted. Therefore the selection of a ppropriate earthquake motions and the determination of reasonable apparent wave velocities are of much importance to seismic response of bridges.