LAUSR

Abstract In this study, the effectiveness of two retrofitting solutions for the repair and upgrading of severely damaged substandard RC beam-column joints is examined and compared. Both solutions are made of CFRP reinforced SHCC (Strain Hardening Cementitious Composite). However, whilst one of the solutions follows a cast-in-situ retrofitting strategy, the other is based on bonding prefabricated Hybrid Composite Plates (HCP). Chemical anchors were used to prevent or delay debonding of the retrofitting layer. The effectiveness of the proposed techniques was evaluated by retrofitting two severely damaged full-scale identical interior substandard RC joints. The retrofitting solutions were applied to the front and rear faces of the damaged specimens. The retrofitted specimens were subjected to the same loading history that caused the severe damage before retrofitting. This loading was composed of a simultaneous column axial load and lateral reversal cyclic displacements. The seismic performance of the retrofitted specimens was examined and compared in terms of hysteretic response, ultimate and residual strengths, stiffness, ductility, and energy dissipation capacity. According to the tests results, both retrofitting strategies restored or enhanced the most relevant seismic features of the damaged beam-column joints. However, retrofitting by bonding HCP plates to the damaged specimen outperformed the cast-in-situ solution in all the examined features except displacement ductility. The test results revealed that the bond between the retrofitting system and the concrete plays a determining role in the performance of the proposed techniques. In the case of the cast-in-situ solution, the chemical anchors were critical in delaying the debonding progress at the SHCC-to-concrete interface and in preventing detachment of the retrofitting layer.