Seismic performance of seismic‐damaged reinforced concrete frames strengthened with section steel

Abstract Seismic‐damaged reinforced concrete (RC) frames are required to be quickly repaired after the earthquake, and methods to strengthen the local structures and improve the seismic capacity of the whole structure are supposed to be considered. Considering the stress characteristics and failure mode of the RC frame in the earthquake, the column was partially strengthened with wrapped angle steel and batten plates, and then the whole frame was reinforced with the steel plate, diagonal bracing, and V‐shaped buckling restrained brace (V‐shaped BRB). A quasi‐static test was conducted on the RC frame after strengthening to study the seismic performance. The results showed a great improvement in the seismic performance of the strengthened RC frames, according to the seismic requirements of “strong joints and weak members; strong columns and weak beams.” The bracket and steel plate were destroyed before the frame, effectively avoiding the premature destruction of the main frame. The bearing capacity, initial stiffness, ductility, and cumulative energy dissipation of the strengthened RC frames were significantly better than those of the unreinforced. The bearing capacity and stiffness of the strengthened RC frames deteriorated slowly. The failure of strengthened RC frames was caused by cumulative damage. The seismic performance and ductility of the RC frame strengthened by the V‐shaped BRB were better than those strengthened with the other two methods due to its multiple energy dissipation capacity. Considering the seismic behavior and failure mode of the strengthened RC frames, the V‐shaped BRB was recommended for strengthening. Parameter analysis was conducted for an in‐depth study of the seismic performance of strengthened RC frames. The results indicated that the most effective way of improving the seismic performance of RC frames damaged in the earthquake and strengthened with V‐shaped BRB was to increase the thickness of the gusset plate. As the increase of axial compression ratio, the energy dissipation capacity of the frames strengthened with the three methods decreased to some extent.