高烈度区快速施工跨线桥基础隔震性能研究

Study on seismic performance of rapid construction overpass bridges with base isolation in areas with higher seismic fortification intensity

为适应高烈度区跨线桥快速施工的需要,提出基础隔震跨线桥的设计理念。以某2×25m高速公路跨线桥为工程背景,将铅芯橡胶支座作为基础隔震装置进行研究。采用Midas/Civil建立桥梁动力分析模型,选取7条时程曲线作为地震动输入,对跨线桥进行顺桥向和横桥向时程分析,对比采用基础隔震体系前后跨线桥抗震性能的变化,并分析弹性挡块对跨线桥地震位移的控制效果。结果表明:基础隔震跨线桥将主梁与中墩作为整体预制安装,最大限度地减少了现场作业时间,理论上可作为跨线桥快速施工的一种方式;相比于常规结构体系,基础隔震体系既能降低中墩地震内力,又能减小梁端支座位移,可显著提升跨线桥在顺桥向和横桥向的抗震性能;弹性挡块可有效控制基础隔震跨线桥的地震位移,但使得桥墩的地震内力明显增大,设计时应注意二者的平衡,合理选择弹性挡块的力学参数。

In order to meet the demands of rapid construction of overpass bridges in areas with higher seismic fortification intensity,the design concept of base isolation for overpass bridges is proposed.Based on an expressway overpass bridge with span layout of 2×25 m,lead rubber bearings were adopted as base isolation devices.The dynamic analysis model of the bridge was established by using software Midas/Civil,and time⁃history analysis was done in longitudinal and transverse directions by selecting 7 earthquake waves as ground motion inputs.The changes in seismic performance of the overpass bridge were studied before and after adopting base isolation system,and control effects of elastic block on seismic displacement of the overpass bridge were analyzed.The results show that overpass bridges with base isolation system could minimize on⁃site operation time,which prefabricated the girder and middle pier as a whole.In theory,it could be used as a method for rapid construction of overpass bridges.Compared with conventional structural system,the base isolation system could not only reduce the seismic force of middle pier,but also reduce the seismic displacement between girder and transition pier,which could significantly improve the seismic performance of bridges in longitudinal and transverse directions.The elastic block could effectively control the seismic displacement of overpass bridges with base isolation system,but the seismic force of pier was significantly increased.The balance of displacement and force should be paid more attention to,and the mechanical parameters of the elastic block should be selected reasonably.