考虑桥墩及支座影响的梁桥竖向地震反应分析

VERTICAL EARTHQUAKE RESPONSE ANALYSIS OF GIRDER BRIDGES CONSIDERING INFLUENCE OF PIERS AND SUPPORTS

将桥墩和支座简化为竖向串联弹簧系统,考虑桥墩及支座轴向变形的影响,建立了竖向地震作用下梁桥动力分析模型。考虑边界条件,采用微分求积法对桥梁连续模型进行空间离散,将其转化为多自由度体系,采用逐步积分数值方法求解多自由度体系在竖向地震动下的反应。在此基础上,通过算例数值分析,研究了空间离散点数量、桥墩及支座轴向效应对桥梁竖向动力反应的影响;分析了不同外部激励下,桥墩及支座轴向刚度变化对桥梁竖向动力反应的影响。研究表明:不考虑桥墩及支座影响时,空间离散点数量对计算收敛性及计算结果影响很小;考虑桥墩及支座影响时,空间离散点数量对计算收敛性影响很大。不同外部激励下,桥墩及支座对梁桥反应的作用不同,需要根据地震地面运动的频谱特性来判断。

The piers and supports are simplified as a vertical series spring system and the vertical dynamic analysis model of the girder bridge considering effects of axial deformation of piers and supports is established.Considering the boundary conditions,the differential quadrature method（DQM） is applied to discretize the continuous model of the bridge to a MDOF（multi-degree-of-system） system in spatial domain.Then the responses of the MDOF system are calculated by step-by-step integration method.In addition,effects of discrete point number of spatial domain and axial deformation of piers and supports to vertical dynamic responses of bridge are studied,and the effect of stiffness of piers and supports to bridge seismic response is analyzed due to different external excitations.The research found the effects of discrete point number of spatial domain to calculation convergence and results are very small without considering the influence of piers and supports,but the effects of discrete point number of spatial domain have an enormous influence on calculation convergence with considering the effect of piers and supports.For different external exactions,the effects of piers and supports to dynamic response of bridge are different and the effects depend on the spectrum characteristic of earthquake-induced ground motion.