可提离式桩基础规则连续梁桥的地震响应分析

SEISMIC RESPONSE ANALYSIS OF REGULAR CONTINUOUS GIRDER BRIDGES WITH UPLIFTABLE PILE FOUNDATION

以上海嘉闵高架桥为依托,利用Open Sees软件构建有限元分析模型进行非线性时程分析,对两种不同基础体系下的规则连续梁桥的主梁、墩柱、基础等的地震响应进行对比分析,并考虑墩高变化的影响。结果表明:基础提离设计,相较常规基础设计,会显著降低墩柱的纵、横向弯矩响应,改善墩柱的受力性能,纵向降幅为20.4%~32.0%,横向降幅为2.5%~23.8%;单桩的纵向弯矩响应减小,降幅达16.2%~40.0%;桩基最大拉力受到有效控制。基于新规范体系,评估了墩柱和基础在E2地震下的抗震性能,结果表明采用提离式桩基础的规则梁桥可有效降低墩柱、基础的地震需求。在E2地震下,墩柱均处于弹性状态,单桩配筋率相较常规基础体系梁桥可随墩高增加适当降低。

The Jia-min Elevated Route in Shanghai was taken as the research object. OpenSees was adopted to establish finite element models and nonlinear time-history analyses were carried out to compare the seismic response of the girder, pier column and foundation under two kinds of pile foundation systems for a regular continuous girder bridge. The influence of change of pier height was also considered. The results show that compared with the traditional foundation system, by using pile foundation that is allowed to uplift and increasing the pier height from 5 m to 20 m, the maximum bending moment of the pier is greatly reduced by 20.4%-32.0% under longitudinal earthquake input and by 2.5%-23.8% under transverse earthquake input. The maximum longitudinal bending moment of the single pile is also decreased by 16.2%-40.0%. The maximum tensile force of a single pile is controlled effectively. Based on the new two-level seismic fortification criterion, the seismic performance of the pier column and foundation under E2 earthquake was evaluated. The results show that by allowing foundation uplift in a regular girder bridge, the seismic demand of pier column and foundation can be greatly reduced. Under E2 earthquake, all the pier columns are kept in elastic states, and the reinforcement ratio in a single pile can be reduced with the increase of pier height, compared to that of bridges using conventional pile foundation.