Size Effect on Shear Strength of FRP Reinforced Concrete Beams without Stirrups

Abstract

This paper presents the results of an experimental investigation that was carried out to examine the size effect on the shear strength and behavior of concrete beams reinforced with fiber-reinforced polymer (FRP) bars. The beams were reinforced with glass FRP, carbon FRP, and steel bars in the longitudinal direction with no transverse shear reinforcement. Twelve large-scale simply supported beams with different depths, four for each reinforcement type, were tested to determine their shear capacity. The effective depth of the beams was in the range of 300–750 mm. The axial stiffness of the reinforcement was kept the same for beams with the same reinforcement type with different depths. The test results indicated that as the member depth increased, the shear strength at failure decreased for all reinforcement types. The results were compared with Bažant’s size effect law including different parameters, and a reasonably good trend was observed. The shear strength of FRP reinforced beams were also compared with the predictions using design codes and Canadian and U.S. guideline equations. The comparisons with the equations indicated that the predicted results using one of the Canadian equations were the closest to the experimental results, while one of the U.S. equations predicted results were more conservative and gave prediction results with large scatter, especially for beams with smaller depth.