Tests on Shear Capacity of Reinforced Concrete

Abstract

The purpose of this research is to contribute to the definition of maximum carrying capacity and rational reinforcement schemes for structures such as deep beams, corbels, and dapped-end beams. The research included laboratory testing of 28 prismatic beam samples with a higher percentage of steel than currently permitted in design practice. The tests revealed that the nominal shear capacity may significantly exceed the current limits of both the American and Canadian codes if proper reinforcement is provided. The ratio of nominal shear stress to the compressive strength of concrete ( v u /f′) can be as much as 0.42 when horizontal reinforcement is used, and 0.85 when a sufficient inclined reinforcement is provided. Strut and tie models, composed of multiple compression struts and tension ties corresponding to the configuration of the reinforcement, were used to analyze the test results. In all cases, the strut and tie models rendered results comparable with those from the laboratory tests. The ultimate shear capacity may be governed either by the compression struts (concrete) or the tension ties (steel). The maximum capacity occurs when the amount of reinforcement at least corresponds with the balanced condition, where the capacity of the tension ties is equal to, or greater than, that of the compression struts.