地震动空间变异性对千米级斜拉桥结构随机地震反应的影响

Influence of spatial variation of seismic ground motion on thousand-meter scale cable-stayed bridge

基于随机振动理论,以苏通长江公路大桥为背景,对超大跨度斜拉桥在随机地震荷载作用下的动力响应展开研究,详细分析地震动空间变化特性对千米级斜拉桥结构动力响应的影响。研究结果表明:相干效应对主梁纵向弯矩影响比较大,尤其是中跨部位;而局部场地效应相对影响较小。对于主梁轴力而言,行波效应影响较为显著,主梁轴力的最大值增大约70%之多,但对竖向剪力并无突出影响。与一致激励比较,行波效应使得跨中竖向位移均方根增大约74%,相干效应为60%,而局部场地效应为13%。对于不同的内力和位移响应,地震动空间变化特性的影响程度和规律不尽相同,必须区别对待,具体问题具体分析。

Based on the stochastic vibration theory and taking the Sutong Yangtze River Highway Bridge as an example, the seismic response of super-long-span cable-stayed bridge is studied. The spatial variation of the seismic ground motion influecing the response of super-long-span cable - stayed bridges is studied. The results indicate that the vertical bending moment of girders, especially the girders of middle span, are influenced more obviously by coherence effect than by local site effect. The axial force of girder is influenced greatly by wave traveling effect and increases 70% than that under uniform excitation. However, the vertical shear force is influenced lightly. The root mean square of vertical displacement for middle span girders is increased 74% by wave traveling effect, 60% by coherence effect and 13% by local site effect, compared with those under uniform seismic excitation.