Effect of different size of joint enlargement on seismic behavior of gravity load designed RC beam-column connections

Effect of different size of planer joint enlargement as a noninvasive and practical strategy for seismic retrofit of gravity load designed external reinforced concrete beam-column connections was experimentally investigated. The joint region was enlarged using steel angles that are mounted using prestressed cross-ties. Reverse cyclic load tests on five half-scale control and retrofitted external RC beam-column connections were conducted. Three different size of planer joint enlargement being 180, 140, and 90 mm were considered for retrofitted specimens. The performance of the retrofitted specimens is compared with that of the control gravity load designed beam-column connections, in terms of load-displacement hysteresis curve, energy dissipation and ductility capacities, and global strength and stiffness degradation behavior. The experimental results showed that increasing the size of planer joint enlargement significantly enhances the seismic capacity of the retrofitted connections, in terms of strength, stiffness, energy dissipation, and ductility capacity and also planer joint enlargement can relocate beam plastic hinges to outside the joint panel.