考虑主余震作用下的核岛厂房结构易损性研究

一次强震常伴随着多次余震作用,且时间间隔较短。研究表明,主震诱发的系列余震会对原有结构造成进一步的累积损伤。核岛厂房结构作为核反应堆的最后一道防线,其在服役期间可能遭受主震和余震的累积作用。参考我国现行规范,定义了四类性能水准(PL)和三种极限状态(LS),以混凝土最大应变作为结构破坏指数(DI),以谱加速度S_a作为地震动强度指标(IM),提出一种考虑主余震序列作用下核岛厂房结构的易损性评估方法。选取PEER数据库地震记录,采用增量动力分析方法,给出了AP1000核岛厂房在420条主余震序列地震作用下的易损性曲线。定量分析了主震强度和主余震谱加速度比对核岛厂房结构易损性的影响。结果表明:核岛厂房的超越概率随着余震强度的增大而增大;余震在主震对结构损伤的基础上会加重核岛厂房的附加损伤;随着主余震谱加速度比从0.5增加到1.0时,核岛厂房结构破坏状态超越概率提高了10%～40%。

Fragility analysis of nuclear island structure under mainshock-aftershock sequences

A strong earthquake is often accompanied by multiple aftershocks with short time intervals.Studies have shown that the series of aftershocks triggered by the mainshock might result in cumulative damage.Nuclear island structure severs as the last line of defense for nuclear reactors and may suffer from the cumulative effects of mainshock and aftershocks during the service life.With reference to China current codes,four categories of performance levels(PL),and three limit states(LS)are defined.The maximum strain of concrete,and the spectral acceleration S a are used as the structural destroy index(DI)and seismic intensity measure(IM).A fragility assessment method of nuclear island structure is proposed under main and aftershock sequences.Based on the PEER seismic records of the database,the effect of mainshock and mainshock-aftershock ratio S a on the fragility of the structure are quantitatively analyzed.The results indicate that the proceeding probability of nuclear island structure increases with the increase of aftershock,the aftershock can cause more additional damage to the structure.The fragility of nuclear island structure increases by 10%~40%for different damage levels with an increase of S a from 0.5 to 1.0.