Shear Strength of Short Rectangular Bridge Columns

Abstract

Four short shear-critical rectangular columns were constructed and tested under monotonic shear loading and a constant compressive axial load. The main variable in these tests was the amount of shear reinforcement. The objectives were to examine the behavior of columns with small shear span-to-depth ratios and develop a method for predicting the shear strength of such columns. An inclined compressive strut was found to form between the column ends and contribute to the column shear capacity. The observed column responses were compared with predictions made using sectional analyses, combined strut and compression field models, and nonlinear finite-element analyses. Failure shears predicted by the sectional analyses were conservative. The proposed model, which considers the contribution of strut action gave reasonable estimates of the shear strength with Vexp/Vpred varying from 0.93 to 1.00. Nonlinear finite-element analysis gave accurate predictions of shear strength, as well as predictions of the complete behavior of the columns. It was determined that the strut effect is significant for reinforced axially loaded columns with shear span-to-depth ratios of less than about 2.5 but should not be considered if the columns undergo large deflections.