考虑场地效应的非一致激励下桥梁地震响应特点分析

本研究拟从常规桥梁（跨径不超过150m且桥长不超过600m）出发,考虑局部场地效应,对某工程场地的地震反应进行三维动力有限元分析。将计算得到的地表地震动作为桥梁桥墩处的非一致输入,然后再通过有限元时程分析计算得到桥梁的地震反应。通过与一致激励及考虑行波效应激励的地震反应计算结果进行比较,得出以下结果:由于局部场地条件对地震动的频谱、峰值加速度都有影响,与一致激励相比,考虑局部场地的非一致激励对于桥梁的下部结构反应影响较小,而对于上部结构响应影响明显;考虑行波效应的非一致激励对于桥梁地震响应有减弱效果。研究结果表明,仅考虑行波效应引起的地震动非一致性开展桥梁地震响应分析并不具备保守性。

Characteristics of Earthquake Performances of Bridge under Multi-support Excitation with Consideration of Site Effects

In this study, we intend to start from the conventional bridge (span is less than 150m and length is less than 600m), calculating the earthquake response of an engineering field through three-dimensional dynamic finite element simulation for multi-support excitation with consideration of local site effect. Then the seismic response of the bridge is calculated through the finite element time history analysis. By comparing the traveling wave effect and uniform excitation we obtained the following results:Because of the Fourier spectrum and peak acceleration of the input wave have been changed due to the site effect, compared with the uniform excitation, multi-support excitation consider local site effect has little effect on lower part of the bridge structure, but for the upper structure of the bridge is relatively large; multi-support excitation consider traveling wave effect on the seismic response of the bridge is decreased obviously. We conclude out that multi-support excitation consider traveling wave effect only is not conservative.