考虑多次余震作用的地下结构抗震性能研究

Aseismic performance of underground structure considering multiple aftershocks

一次强地震过后通常伴有多次余震发生,结构在历次地震中的损伤累计会降低其面临再一次强震作用时的安全储备。针对地下结构抗震设计与性能提升不考虑多次余震影响的现实情况,以1995年日本阪神地震中的大开地铁站为原型,选取含有多次余震的真实主余震记录,对比研究了多次余震作用、地震单独作用以及仅考虑最大峰值加速度(peak ground acceleration,PGA)余震与主震构成主余震序列等3种不同工况下的结构地震响应特征。结果表明:余震作用对地下结构造成的地震损伤通常要比仅考虑单次地震激励时严重,余震强度较小时该现象不明显;在多次余震作用下,结构的峰值位移大于或等于相应单独地震的激励结果,但小于各单独地震的累计值;中柱的残余变形随余震次数的增多呈现出一定增大趋势,这将不利于结构的震后修复工作。

After a strong earthquake,it is usually accompanied by multiple aftershocks,and cumulative damage of a structure in previous earthquakes can reduce its security reserve when facing another strong earthquake.Here,aiming at the present situation of underground structure seismic design and performance improvement not considering effects of multiple aftershocks,taking Daikai subway station in 1995 Japan Hanshin earthquake as the prototype,real mainshock-aftershock records containing multiple aftershocks were chosen to study contrastively structural seismic response characteristics under 3 different working conditions of multiple aftershock actions,earthquake action alone,and only considering main shock-aftershock sequences composed of mainshock and aftershocks with peak ground acceleration(PGA).The results shows that the seismic damage of underground structure due to aftershocks is usually more severe than that when considering only a single seismic excitation,and this phenomenon is not obvious when aftershock intensity is smaller;under multiple aftershocks actions,structural peak displacement is larger than or equal to that due to each single earthquake,but less than their cumulative value;residual deformation of central column reveals a certain increasing trend with increase in aftershocks,this trend will be detrimental to structural repair work after earthquake.