Behavior of Circular Concrete Members Reinforced with Carbon-FRP Bars and Spirals under Shear

Abstract

Considerable research in recent years has exclusively considered concrete members with rectangular cross sections in developing fiber-reinforced polymer (FRP) shear design provisions. Although there is no evidence that these provisions do not apply equally well to nonrectangular sections, the behavior of circular sections has yet to be confirmed with experimental results. This paper reports experimental data about the shear strength of circular concrete beams reinforced with carbon-FRP (CFRP) bars and spirals. A total of five full-scale concrete beams with a total length of 3,000 mm and diameter of 500 mm were constructed and tested up to failure. The test parameters included the type of reinforcement (CFRP versus steel) and the ratio of shear reinforcement (spiral spacing). The investigation revealed that the beams reinforced with CFRP bars and spirals exhibited high load-carrying capacity and performance comparable with that of the control beam reinforced with steel. The experimental shear strengths of the CFRP-reinforced concrete beams were compared with theoretical predictions provided by current codes and design guidelines. The comparison indicated that some of the available design methods provide reasonable predictions. However, a more precise formula for the shear strength Vsf was proposed to account for the mechanical properties and geometry of CFRP spirals. The proposed equation provided more reasonably accurate and conservative predictions.