Repair and retrofitting of external RC beam-to-column joints using the hybrid NSM + EBR method

Abstract

In this study, the repair and retrofitting of external reinforced-concrete (RC) beam-to-column joints using FRP composites is investigated by performing experimental tests. The seismic design detailing for the panel zone is not considered in the design of the tested joints. The test program was performed in three stages. At the first stage, the specimens were loaded until reaching different levels of damage. Subsequently, the damaged specimens were repaired and retrofitted by the NSM and hybrid EBR + NSM methods using FRP composites. Finally, the retrofitted joints were loaded cyclically until their failure. This study is intended to investigate the influence of the utilized retrofitting methods on improving load carrying capacity, stiffness, and ductility of damaged RC joints. For this purpose, eight RC beam-to-column joints, including seven non-seismically designed (NS) and one seismically designed joint (S), were cast and tested. The attained experimental results for the load-carrying capacity, stiffness reduction, and the cumulative dissipated energy of NS specimens were compared with the S specimen. The results showed the proposed hybrid retrofitting methods can recover the lost capacities of joints and even increase their capacities to levels higher than the seismic control specimen. In addition, it is found that according to Park and Ang damage index, the tested specimens are repairable up to 2.6% drift ratio.