Seismic upgrade of deficient RC frames using different configurations of eccentric steel braces

Abstract

Deficient reinforced concrete frames in many developing countries need upgrade and effective retrofitting techniques to enhance the strength, stiffness and energy dissipation capacity of the system. This paper presents eccentric steel braces (ESB) retrofitting technique for deficient reinforced concrete moment-resisting frames. A hollow box steel brace was connected to the beam at different lengths from the beam-column joint that is at Lbeam/8, Lbeam/6 and Lbeam/4. A nonlinear static analysis was carried out on three-story deficient and ESB retrofitted frames and the force–deformation hysteretic response was noted. The ESB retrofitted frames considerably changed the lateral forces load transfer path and as a result increased the strength, stiffness and hysteretic damping of the frames as opposed to the deficient bare frame. Furthermore, a dynamic time history analysis was performed on five and seven-story ESB retrofitted frames and story drift demands were identified. ESB retrofitted frames significantly reduced story drift demands as compared to bare frames.