SHEAR-STRENGTH OF REINFORCED-CONCRETE DEEP BEAMS

Formulas to predict the ultimate shear strength of reinforced concrete deep beams are proposed. The derived equations are based on limit analysis theorems and associated flow rule. The lowest upper-bound solution is achieved through the work equation. With the effective strength concept, the materials are assumed to be perfectly rigid-plastic. A special constant is introduced to consider the structural effect on the effectiveness strength factor of concrete. For deep beams, this constant is equal to 1.25 - 0.25lambda, where lambda is the shear-span ratio of a deep beam. The interaction between horizontal and vertical web reinforcements is carefully analyzed. It is found that the yield condition of horizontal and vertical web reinforcements depends on the ratio of psi(h) and psi(v) or the degree of horizontal and vertical web reinforcements. Comparisons with experimental work arc performed, and they show good agreement between the proposed equations and test results.