Seismic strengthening of external reinforced concrete beam-column joint by square hollow steel bracings

Abstract

Non-Seismically designed reinforced concrete buildings are susceptible to the earthquake loading, severely damaging the joint and columns. This article presents a strengthening of external reinforced beam-column joints that are not designed to withstand the seismic loads. Two identical beam-column joint specimens were made and one was seismic strengthened by easy-to-install square hollow steel braces. The cross-sectional dimensions of the beam and columns are 0.15x0.40 meter and 0.15x0.15 meter , respectively. The half-span length of the beam is 1.15 meter and the haft-height of the column is 1.91 meter. Then, the two specimens were tested under the lateral cyclic loads until failure. From the experimental results, the original specimen was damaged at columns near to the joint and the joint. It had low lateral sway and low ductility. For the strengthened specimen, the column length was shortened and the joint area was increased resulting to the higher lateral load capacity compared with that of the original specimen. In addition, the failure mode from the beam-column joint was changed to the beam, resulting in increasing the ductility and stiffness of the strengthened specimen.