基于随机振动理论确定桥梁地震碰撞的临界间隙

确定梁桥邻跨间避免地震碰撞的最小间隙,对于梁桥地震碰撞危险性预测及防地震碰撞措施的设计有着显著意义。本文基于随机振动理论建立梁桥地震碰撞邻跨临界间隙的计算方法,分析模型采用跨径不等的两跨简支梁桥,且考虑隔震支座非线性恢复力的影响。文中首先建立了系统的非线性运动方程;随后运用随机等效线性化理论将其线性化;最后在复模态空间推导了临界碰撞间隙的均值与方差的计算方法。人工地震动的非线性时程分析结果验证了本文算法的正确性。参数分析表明,临界间隙随邻跨长度比增大而增大,随支座屈服力与上部结构重量比值减小而增大,随隔震支座屈服位移增大而增大,随桥墩振动周期增大而增大。隔震支座屈服前后刚度比值对临界间隙大小影响很小。

Determination of critical gap length of seismic pounding for bridges based on random vibration theory

Determining the critical gap length between adjacent spans to avoid pounding has great significance to pounding risk prediction and designing methods to prevent pounding.In this paper,the method to calculate critical gap length is founded based on random vibration theory.A two span simple supported bridge with different span lengths is taken as an analyzing model,and the nonlinear restoring force of seismic isolation bearing is also considered. Systems' nonlinear equations of motion are set up firstly,and then linearized by stochastic equivalent linearization method.The mean and standard deviation of the critical gap length are obtained in the complex modal space.The proposed method is verified by the results of nonlinear time history analysis using artificial ground motions.Parametric study shows that critical gap length increases with increasing the length ratio between adjacent girders,with decreasing the ratio of bearing's yield force to superstructure's weight,with increasing bearing's yield displacement and with increasing piers' natural periods.The bearing's post-yield to pre-yield stiffness ratio has little influence on critical gap length.