Seismic design method of RC frame structures considering effects of aftershocks
Wen Weiping1,2 Ji Duofa1,2 Yu Yiqi1,2 Zhai Changhai1,2
1. Key Laboratory of Structures Dynamic Behavior and Control of the Ministry of Education，Harbin Institute of Technology，Harbin 150090，China；
2. Key Laboratory of Smart Prevention and Mitigation of Civil Engineering Disasters of the Ministry of Industry and
Information Technology，Harbin Institute of Technology，Harbin 150090，China
Abstract： Historical earthquakes have confirmed that aftershocks would increase the damage of structures and even make them collapse, but all the seismic design codes in the world cannot consider the effects of aftershocks directly. A total of 12 reinforced concrete (RC) frame structures were designed based on mainshock-aftershock design spectrum and mainshock design spectrum. The collapse vulnerability of RC frame structures was studied with 50 as-recorded manishock-aftershock ground motions. The collapse margin ratio CMR of mainshock-aftershock affected and mainshock affected structures was compared and analyzed. It was found that the CMR of mainshock-aftershock affected structures was smaller than that of mainshock affected structures. In order to realize the collapse margin equivalence of structures, the prediction equation of Sa, 50% collapse is firstly proposed with basic period T1 as variable. Then collapse margin equivalent equation is derived, and it is numerically solved with design spectrum. The prediction equation of T1,A is lastly proposed with T1,M as variable under the collapse margin equivalent condition. The collapse margin equivalence of mainshock-aftershock affected and mainshock affected structures can be realized by comprehensively using the prediction formula and mainshock-aftershock design spectrum.
