Local stresses and crack displacements in reinforced concrete elements

The average stress condition in a reinforced concrete (RC) element is not identical to the local stress condition at a crack because of bond slip between the concrete and the reinforcement. After a review of previous research concerning local stresses at cracks, this paper presents local equilibrium and compatibility equations for RC elements given constitutive models for bond and friction. A procedure is described for analyzing the in-plane pure shear response of orthogonally reinforced concrete panels. The procedure considers stress variations between cracks, the crack formation process, and the slip delta(t) accompanying the friction across a crack. Corresponding analytical results are compared with previous experimental work. It is shown that after the residual tension at the crack is lost, the slip delta(t) increases almost proportionally to the normal crack displacement delta(n). Accompanying local shears tau(ct) remain because of friction even when the normal crack displacement continues to increase.