Numerical investigation of retrofitting techniques for substandard exterior reinforced concrete beam–column joints

Abstract Being a critical component of reinforced concrete (RC) structures, retrofitting beam-to-column joints (BCJs) has been extensively investigated, particularly for substandard designs. These investigations attempted to avoid possible shear failure in the joint region; however, careful consideration of the most effective and potentially practical solution was limited. Therefore, this study systematically evaluates three retrofitting techniques that are assumed to be both effective and replicable in real applications. The three techniques were carbon-fiber-reinforced polymers (CFRP), steel angles with pretension bolts, and U-shaped steel bars. First, finite element (FE) models were validated against experimental data to confirm the accuracy of the proposed numerical model. Then, a parametric study was conducted to explore the effect on the joint performance. The considered parameters for CFRP: bond shear stress and the ply count; for steel angles with pretension bolts: angle’s leg size, component thickness, and bolt diameter; for U-shaped bar technique: diameter and length of the bar. Based on the parametric analysis, a comparison between the three techniques was performed to achieve the most robust designs possible. Results indicated that the overall joint strength in terms of ultimate load was enhanced using the CFRP and U-shaped techniques compared to the control joint by 103.93% and 43.55%, respectively. Steel angles with pretension bolts exhibited the highest performance, with a 148.50% increase in ultimate load, and was the most effective in relocating the failure to the beam.