Model to Assess the Seismic Response of Shear-Critical Rectangular Columns

Abstract

This paper describes a complete shear force–lateral displacement model for predicting the response envelope of shear-critical rectangular columns comprising (1) an effective stiffness, (2) nominal shear strength, and (3) softening, including the loss of gravity load–carrying capacity. The effective stiffness of shear-critical columns was found to correlate well with a simplified equation from the literature for the effective stiffness of flexural-dominated columns. In the model, the shear strength is estimated based on the classical approach of the sum of two independent mechanisms of shear resistance, which uses a new definition for computing the section’s effective depth. Softening in the response was defined in two parts. The first part that occurs at the onset of softening was correlated to a single-dimensional parameter, making this portion of the degrading response dependent on the column size. The second part was conservatively made a sole function of the column’s longitudinal reinforcement, which can either reach plastic buckling or form a local sidesway mechanism.