地震动特性对公路桥梁板式橡胶支座滑动反应影响

EFFECT OF GROUND MOTION CHARACTERISTICS ON SLIDING RESPONSE OF ELASTOMERIC PAD BEARINGS IN HIGHWAY BRIDGES

针对我国常见的板式橡胶支座类型公路桥梁因支座与墩梁间无连接措施、在地震作用下频发主梁移位甚至落梁等震害的现状,采用平滑动支座单元模拟板式橡胶支座的滑动效应,通过对一单墩模型的非线性地震反应时程分析,探讨了影响板式橡胶支座滑动反应的主要因素,研究了包括地震动峰值加速度、地震动频谱特性以及地震动加速度时程曲线形状细节等地震动特性对公路桥梁板式橡胶支座滑动反应的影响。研究表明:板式橡胶支座滑动反应是随地震动峰值加速度Ap、地震动峰值加速度与峰值速度比值Ap/vp变化的函数;地震动加速度时程曲线形状细节也是影响支座滑动反应的一个重要因素。设计人员在对板式橡胶支座类型桥梁进行抗震设计时,应注意选择与场地条件相匹配的地震动输入;利用工程经验判断支座滑动反应时,应重视地震动加速度时程曲线形状细节的反常影响。

Facing the frequently occurred seismic damage of shifting or even unseating ot glroers m mgnway bridges whose elastomeric pad bearings are not connected appropriately with the pier and girder, this paper discusses the main influencing factors and presents the effect of ground motion characteristics on sliding response of elastomeric pad bearings based on non-linear time-history analysis of a single pier model, in which the sliding effect of elastomeric pad bearings is characterized by a fiat sliding bearing element. The ground motion characteristics studied in this paper include peak ground acceleration, dominant frequency and energy content, and details of the pulses contained in ground motions. The results show that the sliding response of elastomeric pad bearings is a function of the peak ground acceleration and the ratio of peak ground acceleration to peak ground velocity. Besides, the details of the pulses contained in ground motions may have significant influence on the sliding response. Thus, in order to conduct a correct seismic design of highway bridges on elastomeric pad bearings, the seismic ground motions should be chosen according to the characteristics of the bridge site, and particular attention should be paid to the possible unexpected effect of the details of pulse in ground motion when using empirical statistical correlations to predict the sliding response in individual cases.