Shear strength of reinforced concrete beam-column joints with crossed inclined bars

Abstract

A new analytical approach for the evaluation of the shear strength of reinforced concrete beam-column joints with crossed inclined reinforcement is developed. The proposed model considers that a joint member resists to the applied shear via three mechanisms, the concrete diagonal strut, the steel conventional shear reinforcement truss and the X-bars truss. Failure criteria are adopted in order to quantify the contribution of the crossed inclined bars to the shear capacity of the joint. The joint shear strength is calculated using a simple expression as a function of the shear resistance of the joint without X-bars. The developed procedure is applicable to beam-column joint elements with crossed inclined reinforcement as the only shear reinforcement in the joint region or with the combination of X-bars and conventional horizontal or/and vertical shear reinforcement. The proposed approach is verified by comparisons between analytically predicted shear strength values and experimentally obtained ones derived from the literature. The parameters that influence the shear capacity of joints with X-bars have been investigated and special design graphs have been plotted for designing the crossed inclined reinforcement in the joint area. The application of the proposed approach has been illustrated by three numerical examples.