基于改进IDA的混凝土坝地震易损性研究

Study on seismic vulnerability of concrete dams based on improved IDA

针对目前混凝土坝易损性分析研究中震害等级划分多采用单一指标以及增量动力分析法(IDA)中选取步长增量时未考虑结构响应等问题,本文提出基于改进IDA的混凝土坝易损性分析方法:首先采用功效系数法以位移、应力、损伤区域为指标对坝体结构破坏进行综合评价,并应用变权模型考虑指标数值对指标权重的影响;然后通过计算得到的坝体综合破坏指数,根据坝体震害等级划分采用变增量步长法改进IDA法,从而可以更加全面地计算分析坝体在不同强度地震作用下从弹性状态到完全破坏的结构响应过程;最后,以某混凝土坝挡水坝段为例,建立有限元模型计算结构地震响应,应用改进IDA法绘制其地震易损性曲线.结果表明,该方法可以分析坝体结构在不同地震强度作用下产生各个等级破坏的概率,进而为混凝土坝结构抗震安全设计等提供理论依据.

In existing study of seismic vulnerability of concrete dams, the classification of seismic damage degrees was based on single index and the incremental step length in IDA analysis failed to consider the structural responses. In this study, a seismic vulnerability analysis method of concrete dams based on improved IDA method is proposed. To begin with, the comprehensive damage index of the dam is calculated using the efficiency coefficient method, considering the indexes of crest displacement, stress and damage area,and the variable weight model is adopted to consider the influence of index value on the index weight. In addition, the IDA method is improved by modulating incremental step length based on obtained comprehensive damage indexes and damage degree classification,so that the structural response process of a dam from elastic state to complete failure can be calculated and analyzed more comprehensively. Finally, taking one block section of a concrete dam as an example, the finite element model is established, and the seismic fragility curve is plotted utilizing the improved IDA method. The results prove that this method can be used to analyze the failure probability of concrete dams under different earthquake intensity, and can provide theoretical basis for the seismic safety design of concrete dams.