两次地震作用下RC框架结构抗震能力分析方法研究

Seismic analysis method of RC frame structure considering the excitations of twice earthquakes

为研究钢筋混凝土(RC)框架结构在两次地震作用下的抗震能力,给出了一种考虑两次地震作用的结构分析方法。首先采用动力时程分析,得到第一次地震作用下结构的顶点位移,并将其作为目标位移;然后采用静力往复加载方式对结构加载到该目标位移并卸载到零,然后反向加载到结构能力极限(即结构倒塌时的顶点位移),并对反向加载曲线进行坐标变换作为结构经历一次地震后的能力曲线,用此能力曲线对结构进行Pushover分析,得到结构经历两次地震后的损伤状态与抗震能力。利用所提方法对某3层典型RC框架结构进行分析,得到了其在两次地震作用下的抗震能力曲线与损伤状态。结果表明:连续两次地震作用下,RC框架结构损伤累积效应明显,与单次地震作用相比,其损伤水平提高较大,对本文结构来说提高约30%。因此,目前仅考虑单次地震的设计理论与方法是不完备和不安全的,建议在设计时提高结构的抗震设防水平。该文方法、结果与结论可供结构抗震设计、结构抗震分析等工作参考。

To obtain the seismic capacity of reinforced concrete （RC） frame structure under the excitations of twice earthquakes, this paper presents a structural analysis method considering twice earthquake actions. Firstly, the dynamic time history analysis is adopted, and the top displacement of a structure under the first earthquake was got as the target displacement. Then, the structure was reciprocally loaded to the target displacement and unloaded to zero by the static loading method; and the reverse loading was conducted to the structural capacity limit （i. e. , the maximum displacement of the structure when the structure collapses）. The reverse loading curve was used as the capacity curve of the structure after an earthquake through coordinate transformation, and the pushover analysis of structure was performed. Finally, the damage state and seismic capacity of the structure under the excitations of twice earthquakes were obtained. By using the proposed method, the seismic capacity and damage state of a typical 3 - story RC frame structure are obtained. The results show that the damage accumulation effect of RC frame structure is obvious under continuous twice earthquakes, and the damage level is increased compared with the single earth-quake action, and the damage level increases about 30% for the structure used in this paper. Therefore, the design theory about the single earthquake action is not complete. It is suggested that the seismic fortification level of structure should be increased in the design. The method, result and conclusion of this paper can be used as reference for the seismic design and seismic analysis of structures.