Seismic performance of K-EBF structures considering aftershock sequences and link failure

Abstract

Aiming at the problems that the failure of members can change the stress state of the structure, and the building may be severely damaged or even collapsed due to aftershock sequences, the effect of aftershock sequences and link failure on the seismic performance of K-eccentrically braced steel frames (K-EBF) was investigated. Incremental dynamic analysis, fragility analysis, and collapse-resistant performance evaluations of 12-story and 18-story K-EBF were conducted by using the maximum inter-story drift as the seismic demand parameter and peak seismic acceleration as the ground motion intensity parameter. The results show that compared with non-considering the effect of aftershock sequences and link failure, under the fortification earthquakes, the two factors (aftershock sequences and link failure) make the θmax of the 12-story and 18-story K-EBF structures increase by 2.3% and 8.4%, and the probability of severe damage increase by 0.6% and 2.8%, respectively; Under rare earthquakes, the θmax of the 12-story and 18-story K-EBF structures increase by 21.0% and 42.1%, and the probability of severe damage failure increase by 11.6% and 19.4%, respectively; In addition, the minimum structural collapse reserve factor decreases by 32.1% and 31.2% for 12-story and 18-story structures, respectively; Overall, aftershock sequences will aggravate the structure damage accumulation, and the negative effect on the structure increases with the intensity of the earthquakes;The failure probabilities of different limit state will further increase after considering the link failure, which will result in a further decrease with the minimum structural collapse reserve factor; Therefore, the effects caused by aftershock sequences and link failure should be fully considered in the seismic performance analysis of K-EBF to reveal the structural real dynamic response under earthquakes. Taking both the damage failure of link failure and the effect of aftershocks into consideration can comprehensively analyze the seismic performance of K-EBF structures, which provides a more reliable basis for seismic design.

Keywords

• structural designs; eccentrically braced steel structures; main-aftershock sequence; collapse resistance; fragility analysis; link failure