Aggregate Interlock Role in R.C. Thin‐Webbed Beams in Shear

Abstract

The aggregate interlock mechanism gives a substantial contribution to the shear resistance of reinforced or prestressed concrete thin‐webbed beams, which are characterized by mostly linear, closely spaced, thin diagonal cracks at the onset of shear failure. Under these circumstances, the aggregate interlock effects can be adequately described by resorting to one of the few available models for aggregate interlock, such as the so‐called rough crack model, which is adopted here. On the assumption that the beam behaves like a plane truss, with shear and confinement stresses along the diagonal cracks, it is possible to determine the aggregate interlock contribution to the shear resistance and the necessary degree of shear reinforcement by solving a system of equations regarding the equilibrium of the truss, the stirrup‐to‐concrete compatibility, and the constitutive laws of the aggregate interlock, the solid concrete between the shear cracks, and the crack spacing. Results are obtained for different stirrup diameters and concrete strengths. Comparisons are made with CEB and ACI code provisions.