The analysis of shear strength of only longitudinally reinforced concrete beams, in which a constant shear force acts throughout the shear span, has lead to a shear strength formula predicting the experimental behavior in a more accurate and uniform way than other Codes or authors expressions. On the basis of the shear strength expression found for beams without stirrups, a formula able to predict the shear strength of NSC and HSC beams with transverse reinforcement is here proposed. It is obtained by adding the resisting contribution provided by concrete to that provided by stirrups. The shear strength contribution due to stirrups inclusion takes into account not only the truss mechanism, but also the interaction between the truss action and the beam action. The mutual influence of the truss action on beam and arch strength contribution is here considered. The reliability of the proposed formula has been verified using 1326 experimental results found in the literature. The here provided expression has found to predict the experimental shear behavior in a more accurate and uniform way than other Codes formulas or analytical expressions recently proposed by other authors.
