Influence of shear reinforcement on the shear cracking and shear resistance of simply supported beams subjected to concentrated loads and cantilevers subjected to uniformly distributed loads

This paper presents an experimental program on reinforced, rectangular concrete beams with varying amounts of shear reinforcement. A total of ten simply supported beams subjected to two concentrated loads and twenty-four cantilevers subjected to uniformly distributed loads were tested. The specimens had the same cross-sectional properties and stirrup spacing. The single variable was the bar diameter of the stirrups; this was done so that five shear reinforcement ratios ranging between zero and two times the required minimum shear reinforcement ratio, as stipulated by Eurocode 2, could be obtained. The test results indicate significant differences in the shear crack pattern and shear resistance of the simply supported beams and cantilevers – each with the same longitudinal and shear reinforcement. For each amount of shear reinforcement investigated, the shear resistance of the cantilevers subjected to a uniformly distributed load was higher than that of the simply supported beams. Additionally, the amounts of shear reinforcement, specifically amounts below the threshold for the minimum shear reinforcement, could considerably increase the shear resistance of the cantilevers, while having almost no influence on the shear resistance of the simply supported beams. However, the difference in the shear resistance between these two structural types tends to decrease with an increase in the amount of shear reinforcement. A comparison of the shear resistance predicted by formulas included in some of the codes of practice and by a model recently developed by the authors is also provided.