Hysteretic Model of Coupler Box Assembly for Seismic Retrofitting of Severely Damaged Reinforced Concrete Buildings

Cyclic tests are conducted on interlinked reinforcing bar coupler-box assemblies, adopted to retrofit buckled reinforcing bars at the plastic hinge locations of columns in multi-storied reinforced concrete building frames. The efficacy of the proposed retrofitting technique is evaluated by comparing the hysteresis behavior, computed parameters of performance index, and failure mechanism of the reconstructed frame with the original frame. An energy-based strength deterioration hysteresis model is developed on the basis of cyclic test results for analytically computing the post-yield behavior of retrofitted reinforced concrete (RC) frame with the proposed coupler-box assembly. The experimental test results manifest that the coupler-box assembly can be a promising futuristic approach for seismic retrofitting of severely damaged reinforced concrete buildings, where buckling of longitudinal reinforcing bars at the plastic hinge location of columns is inevitable, and the process of restoration is challenging under existing gravity loads. The suggested retrofitting mechanism restrains the section from any movement against rotation and helps in shifting the yield location of reinforcing bars. The main advantage of adopting the coupler-box is that there is no observed slip of reinforcing bar from the sleeve, and the entire retrofitted section remains intact even after a lateral storey drift of 6%, which is larger than the collapse prevention drift level of 4% as per Federal Emergency Management Agency guidelines.