Theory of interface shear capacity of reinforced concrete

A softened strut-and-tie model for determining interface shear capacity is proposed in this paper. Contrary to the sheer-friction concept, the proposed theory predicts that ultimate failure is caused by the crushing of concrete in the compression struts formed after cracking of the concrete. The shear strength predictions of the proposed model and the empirical formulas of the ACI 318-95 building code are compared with collected experimental data from 147 specimens. Examination of existing experimental data indicated that the softened strut-and-tie model developed in this study is capable of predicting the interface shear strengths of both the push-off and the pull-off specimens with or without the precracked shear planes. The comparison shows that the performance of the softened strut-and-tie model is better than the ACI Code approach for the parameters under comparison. The parameters reviewed include concrete strength and amount of shear transfer reinforcement.