Seismic strengthening of exterior reinforced concrete beam–column joints using post-installed shear reinforcement bars

Abstract

Beam–column joints (BCJs) are key components of reinforced concrete (RC) moment-resisting frame structures subjected to seismic loading to ensure integrity and overall stability. Many past earthquakes have highlighted the vulnerability of BCJs in non-seismically designed (NSD) RC moment-resisting frame structures. Typically, exterior BCJs are more susceptible to seismic action than interior BCJs owing to the inherent confinement of interior BCJ. This study investigates the possibility of seismic strengthening of exterior RC BCJ using post-installed reinforcement. These reinforcements may act as joint transverse reinforcements. Eight specimens were investigated, where three were CSs, the other three were strengthened specimens with bent-in bottom beam bars, one was strengthened with straight bottom beam reinforcement, and the last one evaluated the post-damage performance of a joint strengthened with bent-in bottom beam bars. The results show that there is a capacity increment of 14%–44% in the upward direction and 15.9%–72% in the downward direction. In addition to capacity enhancement, restraining side (edge) concrete cover spalling and altering the mode of failure from joint shear failure to combined beam reinforcement yielding (which is the onset of the formation of beam hinge) and joint shear failure mode were observed from the strengthened specimens. This significant improvement and finding show that the proposed strengthening technique is promising for enhancing the seismic performance of NSD BCJs.