Shear friction strength of monolithic concrete interfaces

This paper presents an integrated model for the shear friction strength of monolithic concrete interfaces derived from the upper-bound theorem of concrete plasticity. The model accounts for the effects of applied axial stresses and transverse reinforcement on the shear friction action at interfacial shear cracks. Simple equations are also developed to generalise the effectiveness factor for compression, the ratio of effective tensile to compressive strengths and the angle of concrete friction. The reliability of the proposed model is verified through comparisons with previous empirical equations and 103 push-off test specimens compiled from different sources in the literature. The previous equations considerably underestimate the concrete shear transfer capacity and the underestimation is notable for interfaces subjected to additional axial stresses. The proposed model provides superior accuracy in predicting the shear friction strength, resulting in a mean between experimental and predicted friction strengths of 0·97 and low scatter. Moreover, the proposed model shows consistent trends with the test results in evaluating the effects of various parameters on the shear friction strength.