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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。
The performance margin ratio is used as an index to evaluate the seismic performance of the structure. The index evaluates the seismic performance margin of the structure by calculating the ratio of the median of earthquake vulnerability to the number of frequently encountered earthquakes, fortified earthquakes and rare earthquakes. Four kinds of five-story three-span RC frame structures considering different seismic fortification levels are selected as the research object. Through the vulnerability analysis, the performance margin ratio of the structure is calculated. The results show that the strength of fortified earthquakes and rare earthquakes increases with the increase of seismic fortification level, the median of earthquake vulnerability and the number of frequently encountered earthquakes corresponding to structures. However, as the former increases less than the latter, the performance margin of the structure is lower than that of the fortified level of seismic fortification. In the case of fortified earthquakes and rare earthquakes, the structure has sufficient performance margin to satisfy “Earthquake can be repaired ” and “earthquake does not fall ” performance requirements; improve the level of seismic fortification will make the structure does not meet “small earthquake is not bad ” performance requirements.