SHEAR TESTS ON REINFORCED CONCRETE BEAMS WITH LOW AMOUNTS OF STIRRUPS

This paper presents an experimental study on the shear resistance of reinforced concrete beams with low amounts of shear reinforcement. The experimental program consists of four simply supported beams subjected to concentrated loads, one simply supported beam and four cantilevers subjected to uniformly distributed loads. For the shear reinforcement, closed stirrups with the
reinforcement ratio in the range of 0.6-1.1 times of the required minimum shear reinforcement ratio (ρ w,min ) according to EC2 (2010) were used. The test results showed considerable effects of the support and loading conditions on the crack development and shear resistance of beams with low
amounts of stirrups. It was found that shear reinforcement lower than the required minimum reinforcement did not contribute to the shear resistance of the simply supported beams subjected to concentrated loads. In contrast, a very low amount of stirrups, which corresponds to approx. 0.6ρ w,min , could effectively improve the shear resistance of the specimens subjected to uniformly
distributed loads. The effects of the static system and shear reinforcement were further investigated by analyzing the failure mode and location. Comparison to the shear resistances predicted by formulas included in some codes of practice is also provided.