近断层高墩大跨梁桥在河谷地形效应作用下的破坏机理与设计方法研究

强地震动观测数据表明，河谷场地迎波侧与背波侧地震动有异常放大现象，宏观震害调查亦显示其致灾效应显著加剧。河谷地形效应影响下地震动输入机制（如何定量反映河谷地形效应）、抗震设计理论（考核河谷两侧地震动差异效应带来的有效抗震设计方法）是亟待解决的问题，也是地震学界关注的热点问题。本项目拟以川藏线上跨河谷且靠近断层的高墩大跨梁桥为研究对象，围绕强地震动输入机制、河谷地形效应对桥梁致灾机理与分析方法两个关键科学问题，从地震动模拟、桥梁破坏机理及抗震设计方法等方面对河谷场地桥梁抗震防灾性能进行研究。拟提出考虑近断层效应和河谷地形效应的地震动模拟方法；通过试验与数值分析，揭示河谷场地桥梁震害机理；继而，建立其抗震性能科学评价方法，形成面向设计的基于性能抗震设计理论。项目是地震学和工程抗震的交叉学科，研究成果可为河谷场地桥梁震灾分析提供理论支撑，服务于川藏铁路桥梁建设，具有重要的科学意义和工程应用价值。

Strong ground motions presented that seismic records at canyons were significantly amplified due to the topography. Moreover, prior investigations of structural damages under earthquakes proved that compared with structures in plain areas, the canyon-crossing structures were more likely to be damaged under earthquakes. This phenomenon has been termed the canyon topographic effect (CTE). To design bridges in canyons properly, two problems need to be addressed urgently. The first problem is that when ground motions of canyons are used as inputs of seismic simulations of bridges, how can the amplification of the ground motions be considered properly. The second problem is that a seismic design methodology of bridges needs to be developed with the consideration of CTE. The research of seismic performance of canyon-crossing bridges has been an important issue in the seismological community. In this research, the long-span girder bridges with high piers located in canyon and near active fault will be taken as case studies. The project will mainly focus on the input mechanism of strong ground motions, and the influence of CTE on seismic disaster-causing mechanism and analysis method of the bridges. Three aspects will be performed: the consideration of the amplification of ground motions, the failure mechanism of the bridges, and the seismic design methodology. A simulation methodology of ground motions will be proposed with the considerations of the near-fault effect and CTE. Based on experimental tests and numerical simulations, the seismic behavior of the canyon-crossing bridges will be explored. Afterward, the scientific criteria for evaluating the seismic performance of the bridges will be developed. Finally, a performance-based seismic design methodology will be put forward. Two disciplines will be involved in this project, which is the seismology engineering and earthquake engineering. Outcomes of this study will offer theoretical supports for seismic analyses of bridges located in canyon and near active fault and will assist the construction of bridges in Sichuan-Tibet railway. It will be of great significance in scientific research and engineering application.