Seismic Retrofitting of Reinforced Concrete Buildings with Buckling-Restrained Braces (BRBs) with a Technical Focus on Vertical Irregularity

The aim of this paper is to evaluate the effectiveness of buckling-restrained braces (BRBs) in improving the seismic performance of reinforced concrete (RC) buildings with and without vertical irregularity. To this end, two RC buildings with ۵ and ۸ stories were first modeled and designed in SeismoStruct as vertically regular systems and then with a mass irregularity applied at the roof level (a ۵۰% mass increase). Following an initial design in accordance with Iranian Standard No. ۲۸۰۰ (۵th Edition) and ACI ۳۱۸-۱۹, the buildings were retrofitted using BRBs with an A۳۶ steel core and a confining concrete cover, and were subjected to nonlinear static (pushover) analysis. The results indicate that, for the regular ۵-story building, BRBs reduce base shear by ۴۲% (from ۱,۸۵۰ kN to ۱,۰۷۰ kN) and decrease roof displacement by ۵۵% (from ۲۲ cm to ۹.۸ cm). For the ۸-story building with vertical irregularity, BRBs reduce base shear by ۵۸% (from ۳,۲۰۰ kN to ۱,۳۴۴ kN), reduce roof displacement by ۶۷% (from ۴۸ cm to ۱۶ cm), increase absorbed energy by a factor of ۳.۲ (from ۴۵۰ kJ to ۱,۴۴۰ kJ), and enhance the ductility factor from ۳.۸ to ۸.۹. Moreover, BRBs compensate for up to ۷۵% of the adverse effects associated with vertical irregularity, such as stress concentration at the top story. The paper underscores the importance of BRBs as an effective, minimally invasive, and economical retrofit strategy for existing RC buildings—particularly those with vertical irregularities—and recommends considering this system in national seismic rehabilitation programs (e.g., for schools and hospitals).

کلیدواژه ها:

Buckling-restrained brace (BRB) ، seismic retrofit ، Reinforced concrete building ، Vertical irregularity ، nonlinear static (pushover) analysis ، SeismoStructure