基于性能的重力式挡墙地震易损性分析

Seismic vulnerability assessment of gravity retaining walls based on performance

位于高烈度地震区的支挡结构时刻面临着特大震灾的严峻考验,迄今国内外还没有人针对重力式挡墙系统地做过易损性方面的研究工作。采用增量动力分析方法,考虑地震动输入的不确定性,选取PGA为地震强度参数,挡墙的位移指数DI为性能参数,基于振动台模型试验划分了挡墙的抗震性能水准,利用FLAC3D对8m高的重力式挡墙进行了地震动力响应分析和地震易损性分析,通过易损性曲线对挡墙在不同地震动作用下的易损性进行了评估和对比分析。研究表明:PGA与挡墙的位移指数近似呈指数关系,当地震动加速度小于0.4g时,场地条件对墙体位移指数的影响不显著,当地震动加速度大于0.4g时,土质场地挡墙位移指数与岩石场地挡墙相比显著增大,墙体位移指数受场地条件的影响显著。当PGA<0.4g时,挡墙基本保持完好或以轻微损伤破坏为主;当PGA>0.6g时,挡墙已完全损伤,发生严重损坏的概率也较大;当PGA>0.8g时,会造成挡墙的严重损坏,甚至可能造成整体倒塌,需要采取一定的抗震加固措施。

The retaining structures in the high earthquake intensity areas face the severe tests of devastating earthquake, and so far, the seismic vulnerability of gravity retaining walls has not been studied systematically at home and abroad. The increment dynamic analysis method is used in this study. Taking into account the uncertainty of seismic input, the PGA and displacement index are selected as the seismic intensity parameter and performance parameter, respectively, and the classification of the performance level of retaining walls is determined based on shaking table tests. The seismic response and seismic vulnerability of a 8 m-high gravity retaining wall are analyzed by applying FLAC3D, and the fragility curves are derived to assess and compare the seismic performances of the retaining wall under different ground motions. It is shown that the displacement index exponentially relates to the PGA. When the PGA is less than 0.4 g, the displacement index increases slowly. When it exceeds 0.4 g, the displacement index increases quickly, and it is greatly affected by site conditions. When the PGA is less than 0.4 g, the retaining wall keeps slight damage or good situation;when it is more than 0.6 g, the retaining wall is damaged completely, and the probability of severe damage increases. When the PGA is more than 0.8 g, the retaining wall suffers serious damage, and even collapse is caused, and reinforcing measures should be taken to maintain the stability of the retaining wall.