考虑波速影响的斜拉桥非一致激励地震响应研究.doc

考虑波速影响的斜拉桥非一致激励地震响应研究 　　摘要：为研究地震波传播速度对大跨度斜拉桥地震响应的影响，以某主跨跨长406 m的双塔钢箱梁斜拉桥为研究对象，建立动力有限元模型。对非一致地震激励输入方法进行理论分析，对比研究了相对运动法、大刚度法和大质量法的计算特点。通过对视波速无穷大时非一致激励法与一致激励法的计算结果进行对比，校验地震动输入方法的正确性。在此基础上，分别选择天津地震波、El Centro地震波和汶川地震波，根据软土区和岩石区地震波传播特点，对视波速在50～4 000 m?s-1之间的不同波速工况进行计算。结果表明：波速对斜拉桥地震响应有显著影响，软土区视波速对结构影响更加突出，对位于深厚软土区的大跨度斜拉桥进行行波效应分析时，需要关注结构的内力和位移响应，而岩石区仅需关注结构的内力响应。 　　关键词：桥梁工程；相对运动法；大跨度斜拉桥；行波效应；多点激励；视波速 　　中图分类号：U448.27文献标志码：A 　　Abstract： In order to investigate the effects of propagation velocity of ground motions on the seismic response of cablestayed bridge， a cablestayed bridge with span length of 406 m was taken as an example and the dynamic finite element model was built. The multisupport excitation method was analyzed theoretically， and the characteristics of the relative motion method， the large mass method and the large stiffness method were compared. When the current wave velocity is infinity， the calculation results under asynchronous excitation were compared with those under uniform excitations to verify the accuracy of the method of ground input. On this basis， considering the different characteristics of ground motions in soft soil area and rock area， Tianjin wave， El Centro wave and Wenchuan wave were chosen with different propagation velocities ranging from 50 m?s-1 to 4 000 m?s-1. The results show that different velocities have significant influence on seismic response of cablestayed bridge， and the influence of apparent wave velocity on structure is more prominent in soft soil area. The internal force and displacement should be considered when longspan cablestayed bridge in deep soft soil area is analyzed， while the internal force will be only concerned in rock area. 　　Key words： bridge engineering； relative motion method； longspan cablestayed bridge； wavepassage effect； multisupport excitation； apparent wave velocity 　　0引言 　　由于斜拉桥跨度大，自振周期长，考虑到地震动的空间变异性特征，一致激励已不能满足工程抗震需求，采取非一致激励分析方法可更好地反映出结构响应规律。Housner[1]很早注意到了这一问题，1965年Bongdanoff等[2]率先研究了行波效应对大跨度结