Seismic Retrofit of Reinforced Concrete Moment Frame Using a BRB with U-Plate Connections

Abstract

Since their first use in 1989, buckling-restrained braces (BRBs) have proven to be an efficient energy dissipation device. Two reduced scale quasi-static cyclic experiments were conducted for a reinforced concrete (RC) moment frame with substandard seismic details retrofitted with a BRB to examine its performance. In the first experiment, the BRB was attached to the RC frame utilizing post-installed U steel plates designed using the uniform force method. The RC frame was tested utilizing the BRB retrofit until the BRB steel core fractured in tension, at which point the BRB was removed. A second experiment was carried out on the damaged RC frame, following removal of the BRB, with the U steel plates still attached. The two experiments showed that the RC frame retrofit using a BRB and U steel plates is an effective approach to doubling the strength, stiffness, and total hysteretic energy dissipation of the original RC frame with substandard seismic details. In addition, a method of proportioning the seismic retrofit components, including the size of the BRB and U steel plates, is developed. Nonlinear pushover and cyclic analyses were used to compare the experimental results to OpenSees numerical models.