ACI 440.1R design provisions provide conservative estimates for the flexural design strength of glass fiber-reinforced polymer (GFRP) reinforced concrete (RC) members with rectangular sections. These provisions do not apply equally well to nonrectangular sections, which motivated this study. This study investigated the flexural strength and behavior of concrete members with circular section and reinforced with GFRP bars and spirals both experimentally and theoretically. Large-scale specimens with a total length of 6000 mm (236.22 in.) and diameter of 500 mm (20 in.) were constructed and tested under four-point bending. The test parameters included reinforcement flexural stiffness (GFRP versus steel) and GFRP longitudinal reinforcement ratio. In this paper, ductility and deformability of the tested specimens were defined, calculated, and evaluated. Test results show that the deformability of the tested GFRP-RC circular members ranged between 19 and 40, which significantly exceeds the requirements of North American codes. Moreover, the nominal flexural strengths of the GFRP-RC specimens were 1.5 and 3.0 times that of the steel counterpart specimen, when considering a similar reinforcement ratio and equivalent longitudinal axial stiffness, respectively. An analytical strain compatibility model capable of predicting the flexural strength of circular GFRP-RC members, including the sequential progressive failure, was developed and verified with the experimental results. Moreover, a simplified method, including design equations and a design chart, is presented using noniterative analysis. This method accurately and simply predicted the flexural capacity and can be considered a simple and more straightforward method for practicing engineers. |
