Assessing the effects of mainshock-aftershock sequences on the seismic collapse of rocking buckling restrained braced frames

Buckling Restrained Braces (BRBs) show high ductility and energy dissipation capacity under seismic excitations. It is possible to improve these features by modifying the BRB configuration and the structural system including these braces. Buckling Restrained Braced Frames (BRBFs) may have drift concentration in one story, which leads to the instability of structure due to P-Delta effects and residual drift. To solve the problem of non-uniform damage distribution along the height of structure, which is a disadvantage of BRBFs, researchers have proposed the Rocking Buckling Restrained Braced Frame (RBRBF) system. Each braced bay in this system consists of a conventional brace on one side, a BRB on the other side and a connecting element at the middle of the bay. The conventional brace in one side of the braced bay with the side column and the connecting element form a pin-supported vertical truss system like a rocking wall that behaves elastically until near the collapse of structure. In this study, 4-, 8- and 12-story RBRBFs and BRBFs are considered. Then, by performing non-linear dynamic analyses, the effects of mainshock-aftershock sequences on the seismic collapse of the structures are evaluated, and the results obtained for the two structural systems are compared. The results show that the seismic collapse resistance of each RBRBF under mainshock-aftershock sequences is significantly higher than that of its corresponding BRBF.