Cyclic Behavior of Seismically Non-Conforming Interior Reinforced Concrete Beam-Column Joints

The cyclic behavior of reinforced concrete (RC) beam-column joints (BCJs) is still one of the critical issues in structural engineering. In this context, for the purpose of gaining a more in-depth insight about the sophisticated behavior of BCJs under cyclic loading scenarios, the current work aims to investigate the cyclic behavior of reinforced concrete beam-column joints. The cyclic behavior of four interior reinforced concrete beam-column joints, with plain and deformed bars, which are representative of the seismically non-conforming structures from the 1970s, were experimentally investigated. The corresponding results of the specimens were compared with each other to better understand and highlight the differences between the force-drift curves and envelopes and damage patterns of each of the specimens. Furthermore, a numerical validation of the laboratory testing results was established with the DIANA FEA code for both monotonic and cyclic loading scenarios, and the force-displacement plots were compared with the associated laboratory results for validation purposes. The crack propagation and final damage states of the numerical models of beam-column joints are presented and discussed in detail. The results showed good agreement between the numerical and experimental behavior, and a graphical representation of the critical regions affected by damages was also shown, which could ultimately contribute to future retrofitting solutions for strengthening the BCJ region in existing RC structures.