大跨悬索桥抖振内力响应分析

Buffeting induced internal forces of long span suspension bridges

基于虚拟激励法和有限元法,在频域建立了一种新的桥梁抖振内力响应分析的随机振动方法。该方法与传统随机振动方法相比具有如下两个特点:(1)单元抖振内力响应同时考虑了保留模态多模态耦合产生的动力效应和保留模态外高频模态产生的拟静力效应;(2)单元抖振内力响应同时考虑了单元杆端位移产生的单元杆端力和单元上分布荷载产生的单元固端力。以香港青马悬索桥为例,分析了保留模态多模态耦合产生的动力效应、高频模态拟静力效应、单元上分布荷载产生的单元固端力及主缆上的抖振荷载等因素对主梁抖振内力响应的贡献。结果表明:保留模态多模态耦合产生的动力效应对主梁抖振内力响应占据主导地位,高频模态拟静力效应、单元上分布荷载产生的单元固端力等因素对主梁抖振内力响应均有一定的影响,主缆上的抖振荷载对主梁侧向抖振内力响应有较大贡献。

Based on the pseudo-excitation method and the finite element method,a new random vibration method is developed for predicting buffeting internal forces of long-span bridges in the frequency domain.This method have two features：（1）the dynamic effect of the retain modes to the element internal forces is performed using traditional modal superposition method,while the contribution of the higher modes to the element internal forces is considered by pseudo-static method;（2）the element forces at the element ends include those caused by the node displacements as well as the element distributed loads.The method is then applied to the Tsing Ma suspension bridge to investigate the internal force responses of the bridge deck due to dynamic effect of multi-mode coupling,pseudo-static effect of higher modes,the effect of the element distributed loads and the buffeting loads acting on the main cables.The results show that the dynamic effect of multi-mode coupling is dominant in the internal force responses of the bridge deck,both the pseudo-static effect of higher modes and the effect of element distributed loads have modest influence,while the lateral buffeting internal forces increase significantly when the contributions of the buffeting loads acting on the main cables are considered.