公路大跨度桥梁建设期抗震设防标准研究

Research on Seismic Fortification Criterion for Long-Span Highway Bridges in Construction Stage

针对桥梁结构建设期间的抗震性能存在较大风险、国内公路桥梁在建设期一般没有考虑地震作用影响的问题,基于现行桥梁抗震设计规范重要性系数的概念,根据设计基准期、烈度、超越概率及地震重现期关系,研究了公路大跨度桥梁建设期的设防标准和抗震重要性系数,通过数值模拟,采用所推荐标准与抗震重要性系数评估了西部高烈度区一座T形刚构桥在建设期的抗震性能,并与成桥状态桥梁抗震性能比较。结果表明:大跨度桥梁建设过程中地震响应规律与成桥状态不同,对于桥梁建设期抗震,建议建设期在5年内的桥梁采用5年设计基准期超越概率10%的地震动,建设期超过5年的桥梁采用桥梁抗震设防类别E1地震作用;要求建设期桥梁在地震作用下处于弹性状态。

Bridge structures undergoing construction also face the risk of exposure to seismic damages,and the seismic effect on the highway bridges in the construction stage are not given enough concern in the Chinese specifications.To address this issue,the seismic fortification criterion and coefficient for importance of a structure are studied for long-span highway bridges in the construction stage,which follows the concept of coefficient for importance of a structure in current bridge seismic design specifications and takes into account relations among design reference period,intensity,exceedance probability and return period.By numerical simulation,the recommended criterion and coefficient for importance of a structure were used to evaluate the seismic performance of a T rigid-frame bridge in a high seismic intensity region in western China,and the results were compared with seismic performance of the bridge in the completion state.It is shown that the seismic responses of the long-span bridge in the construction stage and in the completion state are different.For the seismic protection of the bridges with five-year construction schedule,the ground motions with exceedance probability of 10%in five-year design reference period is recommended,while for the bridges with construction schedule longer than five years,E1 seismic effect is recommended.And it is required that the bridges under construction should be in elastic state in an earthquake event.