Shear strength of reinforced high strength concrete beam without web reinforcement

Abstract

Twenty singly reinforced high strength concrete beams without web reinforcement were tested to investigate their behaviour and to determine their ultimate shear capacities. Test variables were longitudinal steel ratio (ρ), shear span to depth ratio (a/d) and effective depth (d). The cylinder compressive strength (f′c) of concrete used in this study was 53·7MPa. One type of reinforcing bar with yield strength of 477MPa was used. All beams were loaded with two equal concentrated loads. Test results were analysed and compared with the strengths predicted by BS 8110 equation, ACI code equation, CEB–FIP model code equation, Zsutty's equation and Bazant's equation. With regard to the results, the CEB–FIP model code equation predicts shear strength of test beams relatively well, whereas BS 8110 equation is excessively conservative for most test beams and the ACI code equation gives unsafe results for beams with d of 915 mm. It was shown that the effects of ρ and a/d on the shear strength of beams are not significantly influenced by the concrete strength. Within the scope of this study, there was no clear difference in size effect with increasing compressive strength of concrete.