Shear Strength of Circular Concrete Beams Reinforced with Glass Fiber-Reinforced Polymer Bars and Spirals

Recent years have witnessed noticeable advances in incorporating shear design provisions for fiber-reinforced polymers (FRPs) into guidelines and standards. These provisions were developed based on experimental work on rectangular concrete members reinforced with FRP bars and bent FRP stirrups. In contrast, no research seems to have investigated circular concrete members reinforced with FRP bars and spirals under shear loads. This paper reports experimental data on the shear strength of concrete beams reinforced with glass FRP (GFRP) bars and spirals. A total of seven full-scale concrete beams with a total length of 3000 mm (118.11 in.) and a diameter of 500 mm (20 in.) were constructed and tested up to failure. The test parameters included the type and ratio of shear reinforcement (spiral diameter and spacing). The test specimens comprised five beams reinforced with sand-coated GFRP bars and spirals, one beam with only longitudinal GFRP bars, and a reference beam reinforced with conventional steel bars and spirals. As designed, the beams failed in shear due to GFRP spiral rupture. The experimental results were compared to current codes and design guidelines. The comparison indicates that the shear capacity of GFRP-reinforced concrete members with circular cross sections may be determined with the approaches developed for rectangular sections, provided that certain modifications are made to take into account the effective shear depth, equivalent breadth, and the mechanical properties and geometry of GFRP spirals.