Retrofit of RC buildings using vertical shear links and hybrid connections

Abstract

This study employs a retrofit system with a vertical shear link inside a steel frame to improve the structural behavior of an existing reinforced concrete (RC) frame. The steel frame is connected to the RC frame through a hybrid connection system. The hybrid connection not only provides a rigid, strong connection between the steel and RC frames but also increases the shear strength of RC columns and beams. It is referred to as a hybrid connection in light of such combined measures. The connection is composed of thin steel plates, bolts, and infilling grout. This study tested four one-bay one-story RC frames. One of the RC frames was the benchmark, while the three remaining RC frames were retrofitted under different schemes. The scale factor of the frames was set to 1/3 ∼ 1/4 to model a low-rise RC building. The experimental results of the retrofitted RC frames by vertical shear links demonstrated that the boundary steel frame played a key role in obtaining a stable hysteretic response. Moreover, the hybrid connection strongly withstood the shear force between the RC frame and the steel frame. A series of calculation approaches were proposed to find the lateral strength of retrofitted frames under different failure mechanisms. The calculated lateral strengths were observed to agree with the experimental results.