支座布置对城市高架桥地震响应的影响分析

Influence of Bearing Arrangement Form on the Seismic Response for Urban Viaduct

为研究支座布置对城市高架桥地震响应的影响,以内蒙古呼和浩特市三环快速路高架桥主线4×30m标准跨为工程背景,支座布置为4种形式:全部为板式橡胶支座,全部为铅芯支座,每跨中一端为固定支座、一端为滑动支座,一联中只有一个固定支座、其他为滑动支座。采用有限元软件SeismoStruct建立三维模型,分析不同支座布置方案下结构的动力特性和时程响应。分析结果表明:布置有板式橡胶支座和铅芯支座的隔震结构自振频率较小,在相同地震动输入下,相比其他两种支座布置方案能有效地降低桥墩内力,降低1～4倍,但桥墩或支座位移相对较大,结构整体造价较高;隔震结构适用于处于地震活跃地区的结构或重要结构。布置固定支座和滑动支座的延性抗震体系桥墩内力较大,位移较小,结构在震后有不同程度的损伤。从结构地震响应、震后修复和工程经济性三个角度综合决定呼和浩特三环快速路高架桥主线4跨标准段采用板式橡胶支座。本文分析结果可为同类型高架桥支座选择提供参考。

In order to study the influences of bearing arrangement forms on the seismic response for urban viaducts,the 4×30 meters standard span of the main line for the Third Ring Highway Viaduct in Hohhot are used as the background.The bearings are arranged in four forms:all of them are laminated rubber bearings,all of them are lead rubber bearings,fixed bearings are at one end and sliding bearings are at the other end of each span,and there is only one fixed bearing and the others are sliding bearings in one joint bridge.The three-dimensional models are established by using the finite element software SeismoStruct,and the dynamic characteristics and time history responses of the urban viaducts with different bearing arrangement forms are analyzed.The analyses results show that the natural frequencies of the isolated structure with laminated rubber bearings and lead rubber bearings are small,which can effectively reduce the internal force of bridge pier by 1 to 4 times compared with the other two kinds of bearing arrangement forms under the same ground motion input.But the displacements of bridge piers or bearings are relatively large,and the overall cost is high.The isolation seismic resistant structures are suitable for important structures or structures that are located in earthquake active areas.The piers of ductility resistant system with fixed bearings and sliding bearings have large internal forces and small displacements,and the structures have different degrees of damage after earthquakes.From the perspectives of seismic response,post-earthquake repair and engineering economics of the structure,the isolation seismic resistant system of laminated rubber bearings is adopted for the four-span standard section of the Hohhot expressway viaduct.The analyses results can provide references for the bearing selection of the same type viaduct.