Experimental strengthening of the deficient reinforced concrete beam-column joint

During an earthquake, the energy dissipation and ductility capacities of the structures depend on the performance of the beam-column joints where the load transfer is performed. It is stated in the research reports that the shear failure observed in the joints with deficient reinforcement detail and strength causes the collapse of many structures. Therefore, it is necessary to strengthen the joints in order to ensure structural safety. In this study, the strengthening of interior RC beam-column joints with deficient shear strength with CFRP fabrics by using externally bonded reinforcement on grooves (EBROG) and bore-epoxy anchorage was investigated. The debonding behavior of CFRP fabrics seriously affects the efficiency of strengthening. It is aimed to improve the shear capacities and seismic behaviors of the joints by postponing the debonding with applied the new strengthening methods. The thesis consists of two different studies, experimental and numerical. In the experimental study, half scale interior RC beam-column joints designed with deficient shear capacity were produced. One reference and five strengthened specimens with various errors and deficiencies were subjected to displacement-controlled cyclic loading. The effectiveness of EBROG and bore-epoxy anchorage strengthening methods in preventing premature debonding and their contribution to the overall performance of the joints were investigated. Damage states of the specimens were observed. In the numerical study, numerical models of beam-column joints were developed by using the ABAQUS program and finite element analyses were performed. The proposed models were verified by using experimental results and the load-displacement behavior of the specimens were predicted. Crack distributions and failure modes of the specimens were evaluated at the end of the test. EBROG and bore-epoxy anchorage methods significantly postponed debonding in the CFRP fabrics by increasing the interfacial bond strength. Shear failures observed in the strengthened specimens were delayed to advanced displacement levels. The new methods increased the load carrying and energy dissipation capacities of the specimens up to 64% and 104% respectively, compared to the reference (REF) specimen. The results revealed that the EBROG and bore-epoxy anchorage methods were successful in improving the seismic performance of the specimens. The superiority of EBROG and bore-epoxy anchorage methods over the externally bonded reinforcement (EBR) method was proven.