Influence of lateral loading direction on seismic behavior of shear-critical reinforced concrete intermediate short columns

Abstract Most studies on the seismic performances of shear-critical, reinforced concrete columns have considered only their behavior when lateral deformations were applied parallel to one of the column faces. To investigate the influence of more general directions of loading, ten full-scale RC intermediate short columns with square cross-sections were subjected to displacement histories oriented 30° or 45° to their column faces. The columns had a variety of height-to-depth ratios (3.1 or 3.7), axial-load ratios (13% or 30%), and volumetric transverse-reinforcement ratios (0.35% or 0.70%). The performance of these columns was documented in terms of their cracking patterns, shear strengths, effective stiffnesses, degrading stiffnesses, and inelastic shear deformations. Based on these experimental results, a new model was developed to predict the envelope of cyclic force–deformation response, including the shear force and corresponding shear deformation at shear cracking, peak strength, and loss of axial-load-carrying capacity. In this model, the concrete contribution to shear strength for an intermediate short column corresponds to the force at the onset of critical shear cracking. The transverse reinforcement contribution is estimated with a spatial truss model consisting of idealized longitudinal, transverse, and diagonal truss elements, accompanied with the assumption that the diagonal crack plane is parallel to the neutral surface. Verification of the proposed model with test data from this study and an earlier study indicated that the model was applicable to be used for the seismic evaluation and rehabilitation of existing structures.