地震作用下LRB隔震桥梁碰撞临界间隙分析

采用LRB隔震支座增大了梁体在地震作用下碰撞的可能性,确定隔震梁桥邻跨间避免地震碰撞的最小间隙对于桥梁减隔震措施的设计有着显著意义.以隔震连续梁桥梁端相对位移为研究对象,通过桥梁结构拆分,运用振型分解法推导梁体在地震作用下相对位移的最大值反应谱计算方法.采用等效双线性铅销橡胶支座模型,通过迭代计算梁端相对位移并分析SRSS和CQC振型组合法适用性.采用非线性时程分析法计算连续梁的相对位移,验证了反应谱方法预测梁端地震临界间隙的可行性.结果表明:地震作用下梁端相对位移与相邻结构的周期和阻尼比有关,梁端采用CQC组合的反应谱方法能较好预测梁体在地震作用下梁体避免碰撞的临界间隙.提出了基于反应谱方法隔震桥梁间隙设计方法,可供设计人员参考.

Study on Critical Gap Length of Seismic Pounding for LRB Isolated Bridges

Girder pounding of bridge isolated with LRB may be occur easily at the exciting of earthquake, determining the critical gap length between adjacent spans to avoid pounding has great significance to seismic isolating design of bridge.Taken the girder end relative displacement of isolated continuous girder bridge as object, through division of bridge, the analysis method using response spectrum for maximum relative displacement between girders in earthquake was derived based on mode analysis method.The equivalent bilinear LRB model and iteration were used to calculate the relative displacement of girder end, and the applicability for SRSS and CQC mode combination method was studied.The relative displacement of continuous girder was calculated using nonlinear time history analysis method, and the feasibility of predicting the critical gap between girders using response spectrum theory was verified.The results show that (1) the relative displacement between adjacent span structures is relative to period and damping ratio of the two adjacent structures; (2) using CQC mode combination method based on response spectrum can easily predict critical gap to avoid pounding when bridge encounter earthquake.Designing method for gap between girders of isolated bridge was put forward and designer can take it as a reference.