Bi-directional interaction of joint shear strength in non-seismically designed corner RC beam-column connections under seismic loading

Non-seismically designed (NSD) beam-column joints are susceptible to joint shear failure under seismic loads. Although significant research is available on the seismic behavior of such joints of planar frames, the information on the seismic behavior of joints of space frames (3D joints) is insufficient. The 3D joints are subjected to bi-directional excitation, which results in an interaction between the shear strength obtained for the joint in the two orthogonal directions separately. The bi-directional seismic behavior of corner reinforced concrete (RC) joints is the focus of this study. First, a detailed finite element (FE) model using the FE software Abaqus, is developed and validated using the test results from the literature. The validated modeling procedure is used to conduct a parametric study to investigate the influence of different parameters such as concrete strength, dimensions of main and transverse beams framing into the joint, presence or absence of a slab, axial load ratio and loading direction on the seismic behavior of joints. By subjecting the models to different combinations of loads on the beams along perpendicular directions, the interaction of the joint shear strength in two orthogonal directions is studied. The comparison of the interaction curves of the joints obtained from the numerical study with a quadratic (circular) interaction curve indicates that in a majority of cases, the quadratic interaction model can represent the strength interaction diagrams of RC beam to column connections with governing joint shear failure reasonably well.