Experimental Behavior of Nonconforming RC Columns with Deformed Bars under Constant Axial Load and Fixed Biaxial Bending

Although recent efforts have been made to understand the behavior of RC members subjected to cyclic biaxial bending, the experimental data available in the literature are still limited for making conclusions about the influence of biaxial actions on the inelastic response of RC columns. To analyze the effects of biaxial bending on the seismic behavior of existing RC columns with design characteristics nonconforming to modern seismic codes, the results of an experimental program on RC columns under constant axial load and cyclic uniaxial/biaxial bending are presented in this paper. The experimental data set consists of ten tests (seven new tests and three previously published by the authors) on full-scale columns reinforced with deformed bars: six square columns and four rectangular columns. The square columns are tested with diagonal cyclic displacement paths with inclination angles of 0°, 30°, and 45° with respect to the cross section principal axes and axial load ratios of 0.1 and 0.2. Rectangular columns are subjected to horizontal displacements with inclination angles of 0°, 30°, 45°, and 90° with respect to the cross section principal axes and an axial load ratio 0.1. The effects of different horizontal displacement orientations on column performance is investigated and discussed in terms of strength, deformation capacity, and damage at failure.