Required time gap between mainshock and aftershock for dynamic analysis of structures

Abstract

Despite the various studies carried out to evaluate the effects of seismic sequences on structures, the matter of the time gap required to be considered between the mainshock and its corresponding aftershocks in dynamic analyses has never been focused on directly. This subtle but in the meantime effective subject, influences on the amount of accumulated damage caused by earthquake sequences. In the present study, 244 near fault ground motion components from 122 earthquakes were applied to a wide variety of single degree of freedom systems having vibrating period of 0.05 to 7 seconds with linear and nonlinear behavior. Furthermore, 2 planar steel moment-resisting frames, having 3 and 12 stories, were subjected to a set of 30 ground motion components. The purpose of this investigation was to estimate the required time for the structures to cease the free vibration at the end of the mainshock. The main purpose is to generate an estimation that is function of structural system's parameters and the strong motion duration. Excellent correlations were obtained between the rest time and the following parameters: the combination of natural period of single degree of freedom systems, as well as the strong motion duration of earthquake sequences. In consequence, a formula is proposed which estimates the required optimized rest-time of a structure based on natural vibration period, as well as the duration of strong motion. Additionally, results obtained from the dynamic analysis of the steel frames validate the rest-time values achieved from the proposed formula.

Seismic behavior of RC moment resisting structures with concrete shear wall under mainshock–aftershock seismic sequences

“…The shear wave velocity of ground motion records agrees with the seismic design assumptions (375< 𝑉 𝑠 (m/s) <750). Furthermore, a 5-second zero acceleration interval between mainshock and aftershock (time gap) was considered (Pirooz et al, 2021). To provide a comprehensive evaluation of the behavior of structures under seismic sequences, an effort has been made that selected records have a different ratio of aftershock to mainshock acceleration, frequency content, and magnitude.…”

Probabilistic seismic performance assessment of steel moment‐resisting frames considering exposed column‐base plate connections with ductile anchor rods

“…This time interval with zero acceleration is assumed sufficient to ensure that the 2‐ and 4‐story frame models cease vibration (due to GM1) in dynamic analyses. It is worth noting that such a required time interval is strongly correlated with the fundamental period of the assessed structure 57 …”

Peak and Cumulative Response of Reinforced Concrete Frames with Steel Damper Columns under Seismic Sequences

“…Similarly, they concluded that the influence of major aftershocks on the damage potential is significant because the energybased damage index of tall RC buildings increases due to the seismic sequences. In addition to these studies, Zhai et al [30][31][32], Di Sarno et al [33][34][35][36], Abdelnaby et al [37][38][39][40][41], Kagermanov and Gee [42,43], Yang et al [44,45], Yaghmaei-Sabegh et al [46], Qiao et al [47], Orlacchio et al [48], Hoveidae and Radpour [49], and Pirooz et al [50] investigated the nonlinear response of building structures under seismic sequences. Although most of those studies were analytical in nature, one experimental study used a shaking table [47].…”