Along with rapid development of high-speed railways,more and more bridges have been built in earthquake zones. 32m simply-supported box girder(SSBG) bridges structures have been adopted widely in construction of high-speed railways in China,and installation of steel shear keys has taken as the lateral falling-off prevention measure. Earthquakes induce out-of-phase vibrations between supstructures and substructures due to differences in dynamic characteristics,which results in nonlinear pounding between steel shear keys and bearing bases of reinforced concrete if their relative displacements exceed their initial gaps. In this paper,in view of the pounding phenomenon between steel shear keys and bearing bases under transverse ground motions,an eccentric pounding model considering nonlinear behavior of bearing and elasto-plastic behavior of piers was developed. Through time-history analysis on nonlinear seismic respones,the anti-seismic effect of the falling-off prevention measure was evaluated,and the effects of secondary permanent loads, linear stiffness of piers, types of cushioning block and elasto-plastic behavior of piers on seismic pounding responses were investigated. The results show as follows:The falling-off prevention measure of SS-BG bridges plays an important role in limiting lateral displacements;under strong seismic motions,pounding between steel shear keys and bearing bases generates high-magnitude impact forces that may lead to piers damages; cushioning blocks of hardwood may be installed between steel shear keys and bearing bases to appropriately reduce the pounding forces,and effectively improve the lateral seismic performance of SSBG bridges.%随着高速铁路的快速发展,越来越多的高速铁路桥梁修建于地震区.我国高速铁路32 m简支箱梁桥通常设置型钢挡块作为横向防落梁措施,强震作用下,桥梁上、下部结构由于动力特性的不同而发生不同相振动,从而引起挡块与垫石间的非线性碰撞.本文针对这种横向碰撞现象,建立考虑上部结构与垫石间偏心距、支座非线性和墩柱弹塑性的横向碰撞模型,通过非线性地震反应时程分析,评估防落梁措施的抗震性能,并研究二期恒载、桥墩线刚度、垫块类型及墩柱弹塑性等参数对结构地震响应的影响.结果表明:目前高铁桥梁中采用的防落梁措施对横向限位起到重要作用,强震作用下型钢挡块与垫石之间的碰撞可能引起桥墩破坏,在其间设置硬木垫块可以适当降低碰撞力,有效改善高铁桥梁体系的横向抗震性能.
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