Reinforced Concrete Deep Beams - Shear Strength Model and Design Formula

Reinforced concrete (RC) deep beams are used as load-distributing structural elements including transfer girders, pile caps, foundation walls, and offshore structures. In this article, the authors propose a new model for determining the shear strength of RC deep beams. They derive a 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. The coefficients of each contribution are then calibrated on 240 test results relevant to both normal and high strength concrete deep beams, available in the literature. The authors compare the obtained expression to the ACI Code and to the most recently formulae and computing procedures. The authors note that, in deep beams, the horizontal web reinforcement is less effective in providing shear strength than the vertical web reinforcement. They conclude by proposing a design formula.