A new model for determining the shear strength of reinforced concrete deep beams is proposed in this paper. An explicit formula that considers the shear strength contributions provided by the strut-and-tie mechanism due to the diagonal concrete strut and the longitudinal main reinforcement, as well as the vertical stirrups and the horizontal web reinforcement, is derived. The coefficients of each contribution are calibrated on 240 test results relevant to both normal and high strength concrete deep beams, available in the literature. The obtained expression is compared to the ACI Code and to the most recently formulae and computing procedures, and it results as the one best fitting the measured shear strengths. A design formula is then proposed.
