SIESMIC PERFORMANCE OF REGULAR AND IRREGULAR BRB FRAMES UNDER SEISMIC SEQUENCE

The Buckling-restrained braces were introduced in 1989 for the first time, in which compression buckling of bracing could be avoided by its confinement (Kersting et al., 2015). Buckling-restrained braces yield in tension and compression, and show an ideal hysteretic behavior (Sabelli et al., 2003). However, these braces have a low post-yield stiffness, which can lead to large permanent deformations or occurrence of soft story during a seismic sequence. This also can be intensified by irregularity of the structure. Chen et al. (2015) showed that earthquake influence coefficients for irregular frames are larger than values of the design code. On the other hand, recently it is proved that seismic sequence is a phenomenon that can cause more extensive damages in comparison to mainshock only. The key parameter for structures to withstand against aftershocks is residual drift under mainshock (Tesfamariam & Goda, 2015). In this study, behavior of regular and irregular frames with BRB under seismic loads has been investigated. Eight 4-, and 8- story frames have been modeled. Time history and incremental dynamic analysis were analyzed for structures. Next, response of these structuresunder seismic sequence is investigated.

Keywords:

BRB , Nonlinear dynamic analysis , IDA , Seismic sequence , Irregular frame