Modes, Mechanisms, and Likelihood of Seismic Shear Failure in Rectangular Reinforced Concrete Columns

Abstract

A multimechanism, shear-assessment procedure has been developed by combining and modifying a shear-strength model for truss-tension failures with a softened strut-and-tie model for strut-compression failures. The procedure also includes new equations to account for diagonal-tension and truss-compression failures. The procedure was calibrated using the results of 390 cyclic tests of rectangular reinforced concrete columns. For the 175 columns that failed in shear or flexure-shear, the ratio of the measured shear strength to the calculated strength had a mean of 1.01 and a coefficient of variation of 0.15. The procedure correctly identified the critical shear-resistance mechanism for 86% (43/50) of the columns in which the calculated shear-mechanism capacities differed by at least 6%. The procedure also correctly identified the failure mode for all of the 215 columns that failed in flexure. By combining the lognormal characterizations of the accuracy of the shear demand and capacity models, the procedure accurately estimates the likelihood of shear failure at a given level of column deformation.