Diagonal smear failure and size effect in RC beams without web reinforcement

This paper describes a formal theory, which explains the mechanism of shear failure in reinforced concrete (RC) ordinary (slender) beams without web reinforcement. The theory determines the type of splitting of concrete responsible for the diagonal shear failure of beams under concentrated loads and the location along the shear span where this splitting occurs. A simple expression is derived for the shear stress at failure as the product of the ratio of the neutral axis depth to the effective depth of beam times the splitting tensile strength of concrete. It is also shown how the nominal shear strength can be adjusted to take into account the size effect. The derived formula from this analysis is verified by comparisons to extensive sets of experimental data from the literature, which have been obtained on slender beams with various strengths of concrete (low and high), steel ratios, shear span to depth (a/d) ratios, and geometrical sizes.