Formulation of a shear resistance mechanism for inclined cracks in RC beams

Abstract

The shear capacity of reinforced concrete (RC) members is often associated with sliding across inclined planes often referred to as critical diagonal cracks. However, quantifying the shear capacity of the RC member in terms of the sliding resistance of an inclined plane as a result of shear-friction has been found to be a very complex problem. This is because these sliding planes transcend both initially cracked and uncracked planes, their capacity is also a function of the separation between these sliding planes, and invariably the shear-friction sliding capacity overestimates the shear capacity of the member. In this paper, a structural mechanics model that incorporates shear-friction is developed for quantifying the various components of the shear resistance across a critical diagonal crack because of both longitudinal reinforcement and stirrups. It is shown that the shear resistance is less than would be anticipated from the direct application of shear-friction theory because the compressive force in the uncracked region of concrete is less than can be anticipated and because the shear resistance must provide shear forces to maintain equilibrium prior to resisting the direct shear force. © 2011 American Society of Civil Engineers.