强震作用下桩-土-上部结构达到极限状态时的性能分析及抗震措施

Recently，as strong earthquakes happened one after another, and high-speed way and railway are developing quickly, the technique and design code about pile foundations cannot satisfy seismic resistance. As it is reasonable to think that the mechanical behavior of the pile foundation and surrounding ground is nonlinear, in a major earthquake, the limit state design method has become predominant in the design of foundations for railway bridges and other structure. In another way, before modifying the design code, the existed piles, which are not satisfied for seismic resistance, should be enhanced. The study include: (1) investigate the mechanical behavior of piles and soils subjected to lateral roading up to ultimate state and the axial force dependent of pile; (2) conduct shaking table test and numerical calculation to study dynamic behavior of pile-soil-structure system in sand ground, and provide an applicable numerical way of evaluating seismic resistance of pile-soil-structure system by the comparison between test results and calculation results; (3) propose an effective seismic reinforcement method for the existed pile foundations which are not satisfied for seismic resistance, then verify the proposed method through shaking table test and numerical simulation on pile-soil-structure system. The study will be useful for establishing an evaluation system for seismic resistance of pile-soil-structure, and promoting the application of ultimate state design method in pile foundations of high-speed way, high-speed railway and huge buildings.

近年我国强地震不断发生，伴随着高架道路桥、铁路桥梁的建设高潮，相关研究和技术规范不能满足要求。强震作用下桩与周围土处于非线性状态，极限状态设计法 在高架桥和其它建筑物桩基础的设计上起着非常关键的作用。然而,在修改设计规范之前,对于既存不满足抗震要求的桩基础应实施抗震加强措施。研究包括：（1）考察桩与土在水平荷载作用下达到极限状态时的力学性能及桩的轴力依存性；（2）实施振动台试验和数值计算来研究桩-土-上部结构整体系统处于砂土地基的动态性能，对比试验结果与计算结果，建立桩-土-上部结构系统抗震评价的高性能数值模拟方法；（3）针对既存不满足抗震要求的结构物桩基础，提出经济高效的抗震加强方案，通过桩-土-上部结构系统的振动台试验与数值计算来验证所提方案的有效性。本项目研究成果可为桩-土-上部结构系统的抗震提供完善系统的评价方法，推动极限状态设计法在我国在高速道路铁路及其它建筑物桩基础上的应用。

20世纪60年代以来的全球多次强震中可液化地基中桩基础的震害屡见不鲜，使得桩基础的抗震研究成为了一个热点。伴随着高架道路桥、铁路桥梁的建设高潮，相关研究和技术规范不能满足要求。强震作用下桩与周围土处于非线性状态，极限状态设计法 在高架桥和其它建筑物桩基础的设计上起着非常关键的作用。然而,在修改设计规范之前,对于既存不满足抗震要求的桩基础应实施抗震加强措施。本项目研究完成了：（1）考察桩与土在水平荷载作用下达到极限状态时的力学性能及桩的轴力依存性；（2）实施振动台试验和数值计算来研究桩-土-上部结构整体系统处于砂土地基的动态性能，对比试验结果与计算结果，建立桩-土-上部结构系统抗震评价的高性能数值模拟方法；（3）针对既存不满足抗震要求的结构物桩基础，提出经济高效的抗震加强方案，通过桩-土-上部结构系统的振动台试验与数值计算来验证所提方案的有效性。本项目的资助下，以第一作者已经发表SCI论文3篇，EI论文3篇，其它论文2篇，参加国际国内会议5次，培养硕士研究生1名，另外还有2名在读硕士研究生。本项目研究成果可为桩-土-上部结构系统的抗震提供完善系统的评价方法，推动极限状态设计法在我国在高速道路铁路及其它建筑物桩基础上的应用。研究成果有广阔的工程应用前景和重要的社会意义。