冲刷作用下群桩基础桥梁地震破坏机理及抗震设计方法

Highway bridges are the essential components of the transportation infrastructure. Increasing reliability of bridges is an important strategy to mitigate the direct and indirect losses caused by natural hazards. The structural behavior of bridge structures under multiple hazards intrigued a strong interest in recent decades. This research focuses on the stability and seismic performance of bridge foundations under scour effect, including: (1) to perform quasi-static tests on the bridge pier with pile foundations subjected to different scour depths, propose a hysteretic model for the pier, and build a numerical model of soil-structure-interaction that can be applied to different scour depths, (2) to perform shake table tests on the small-scale bridge model subjected to different scour depths, investigate the soil-structure-interaction mechanism under different scour depths for the validation and modification of the proposed numerical models (3) based on the reliability theory, to develop an approach for seismic analysis and seismic design of highway bridges with pile foundation considering different scour depths. This research integrate theoretical analyses, experimental studies and numerical simulations, develop an accurate and efficient seismic analysis approach for bridge systems under scour effect, and provide a solid theoretical basis for improving the reliability of bridge structures subjected to multiple hazards.

桥梁是交通基础设施系统的枢纽工程，提高桥梁结构的可靠度是减少自然灾害造成直接和间接损失的重要手段之一。近年来，基于多种灾害作用下桥梁结构的性能化设计引起了广泛关注。本项目拟对河流冲刷作用对桥梁基础的稳定性和抗震性能展开研究，具体内容包括：（1）开展不同冲刷深度群桩桥墩拟静力试验研究，提出冲刷作用下群桩桥墩的滞回模型，并给出适用不同埋置深度的桩土相互作用的数值模型；（2）开展不同冲刷深度下带群桩基础梁桥的模拟地震振动台试验研究，分析各种冲刷深度下桩土相互作用的受力全过程，进一步完善和校核提出的数值模拟方法；（3）基于可靠度理论，结合试验和数值模拟结果，提出考虑桥梁冲刷深度的桥梁抗震性能分析和设计方法。上述工作结合理论分析、试验研究和数值模拟，建立一种准确、高效的整体结构抗震分析方法，为提高公路桥梁在多种灾害下的可靠度打下理论基础并提供技术支撑。

近年来由于洪水冲刷作用导致桥梁基础力学性能的劣化已引起研究和设计人员的重视。在本项目的资助下，针对河流冲刷作用下桥梁基础的稳定性和抗震性能，开展了以下研究内容：.（1）讨论了考虑冲刷影响的桩土相互作用动力p-y模型参数取值方法，以及桥梁重要构件非线性力学行为的建模方法；（2）开展了群桩基础模拟地震振动台试验，分析了场地和结构的动力特性，以及冲刷条件下桩基桥梁结构的地震反应规律；（3）以某独塔斜拉桥为例，全面分析了冲刷深度、地震动特性对桥梁地震响应的影响；（4）考虑极端偶然荷载与非极端荷载，建立了桥梁多灾害可靠度评估方法，针对选择的9座桥梁开展了桥梁抗震可靠度评估。