不同弯矩增大系数钢筋混凝土框架结构地震易损性分析

设计3个不同柱端弯矩增大系数的钢筋混凝土框架结构模型，考虑结构材料、荷载及地震动参数的随机性，分别对其进行随机增量动力分析（IDA），以地震峰值加速度（a _pg）作为地震动强度指标，结构的顶点最大位移角θ_max作为结构的反应参数，得到各结构模型的IDA曲线。在IDA分析的基础上，对各结构模型进行地震需求概率分析，通过定义4个抗震性能水平，对各模型进行随机pushover分析，确定各性能水平的限值，分别对各结构模型进行易损性分析，得出各结构的地震易损性曲线。计算分析结果表明：弯矩增大系数的取值对结构的易损性有一定的影响，其取值越大时，结构在地震作用下倒塌的概率越小；在一定的范围内(0.2g≤a _pg≤1.0g)，当结构的塑性程度发展越大时，提高弯矩增大系数对结构抗震性能的贡献越明显；建议规范修订时可适当增加柱端弯矩增大系数的取值。

Seismic fragility analysis for RC frame structures with various moment magnifying coefficients

Three RC frame structure models were designed with various moment magnifying coefficients of columns and analyzed based on randomly incremental dynamic analysis in consideration of the parameter randomness of material, loads and the ground motion, using seismic peak acceleration as the vibration intensity indicators and the maximum vertex displacement angle as the reaction parameters of the structures to obtain the IDA curves of the structures; on the basis of the IDA, the seismic demand probability model of each structure was established, and four seismic performance levels were defined. Then the random pushover analysis for each structure was carried out to determine the various performance level limit value. Finally, seismic fragility analysis was carried out for each structure to obtain fragility curves. The results show that the moment magnifying coefficient value has a certain impact on the fragility of the structure. The greater its value is, the smaller the collapse probability of the structure under a specific earthquake motion is. Within a certain range (0.2_g≤a _pg≤1.0g), the larger the plastic degree of the structure is, the more obviously the seismic performance of the structure with a larger moment magnifying coefficient value is improved; the paper proposes that it may be appropriate to increase the moment magnifying coefficient value in the subsequent code revision.