Comparison Between EBR Method and a NSM New Technique for Strengthening Concrete Beam–Column Joints

This research investigats the behavior of external concrete beam–column joints strengthened by carbon fiber-reinforced polymer sheets under reversed cyclic loads. The objective of this study is to compare two strengthening techniques. One specimen was strengthened by external bonding reinforcement (EBR) method while two other specimens were strengthened by manually made FRP bars with the near-surface mounted (NSM) method. One of these specimens had only side bars while the other used L-shaped bars in addition to side bars as strengthening components. Manually made FRP rods had cores with wood or steel materials wrapped with CFRP sheets with different widths. The behavior of the strengthened specimens was compared with a reference specimen having no strengthening. Conclusions were drawn on the basis of load versus the drift angle of the beam’s tip curves, hysteresis envelope curves, energy dissipation capacity, damping ratio, stiffness degradation, and ductility ratio. The results show that the use of suggested manually made FRP bars with NSM technique, especially on both sides of the specimen, is more effective for strengthening the exterior beam–column joints, compared to the EBR method. Moreover, the specimen with only side NSM rebars had better energy-based parameters, while the specimen with both L-shaped with side NSM rebars was better in load capacity-based parameters.