基于易损性的钢筋混凝土框架结构抗震性能裕度评估

采用性能裕度比作为评估结构抗震性能的指标，该指标通过计算地震易损性中位值与多遇地震、设防地震和罕遇地震强度的比值来评估结构的抗震性能裕度。选择4种考虑不同抗震设防水平的5层3跨钢筋混凝土平面框架结构作为研究对象，通过易损性分析，计算得到结构的性能裕度比。研究结果表明：随着结构抗震设防水平的提高，结构的地震易损性中位值和结构所对应的多遇地震、设防地震和罕遇地震的强度随之增加。然而，由于前者的增加幅度要小于后者的，因此，结构的性能裕度比随其抗震设防水平的提高而降低；在设防地震和罕遇地震作用下，结构具有足够的性能裕度以满足“中震可修”和“大震不倒”的性能要求；抗震设防水平的提高会使结构不满足“小震不坏”的性能要求。

Fragility-based assessment of seismic performance margin for RC frame structures

Performance margin ratio (PMR) was presented to assess structural performance under earthquake. The PMR was calculated by the ratio of the median of fragility function to the earthquake intensities corresponding to frequent earthquake (FE), design based earthquake (DBE) and rare earthquake (RE). Four kinds of 5-story and 4-bay RC plane frames were selected as study cases, which were designed for different seismic fortification levels. Then the PMRs of the reference structures were calculated by fragility analysis. The results show that increasing seismic fortification levels leads to the increase of both fragility medians and the seismic actions with respect to FE, DBE and RE. Nevertheless, the resultant increment of fragility medians is less than that of seismic actions, thus a decreasing trend of PMR is found according to the increased seismic fortification levels. Under DBE and RE, the structures show sufficient performance margins to satisfy the performance requirements of ‘no unrepairable damages under DBE’ and ‘no collapse under RE’, respectively. The increase of seismic fortification level may probably cause the structure cannot satisfy the performance requirement of ‘no damage under FE’.