Load and Moment Interaction Diagram for Circular Concrete Columns Reinforced with GFRP Bars and GFRP Helices

This paper presents analytical and experimental studies on the axial load-bending moment behavior of glass fiber-reinforced polymer (GFRP) bars and helices RC columns. The nominal axial load and bending moment of the columns were analyzed based on the stress-strain behavior of the cross-sectional components. A numerical integration method was used to determine the compressive force of concrete in the compression region. The analytical results were verified with experimental results of 12 circular specimens reinforced with GFRP bars and GFRP helices. Out of these 12 specimens, eight specimens were taken from available literature and four specimens were tested in this study. The influences of different parameters such as loading conditions, spacing of the GFRP helices, and wrapping the specimens with carbon fiber-reinforced polymer (CFRP) sheets on the behavior of GFRP-RC specimens were investigated. A parametric study was also carried out to investigate the effects of longitudinal and transverse GFRP reinforcement ratio and slenderness ratio on the axial load-bending moment diagrams of GFRP-RC columns. It was found that the slenderness effect is more pronounced on the confined cross sections under eccentric loads at the ultimate state condition. (C) 2016 American Society of Civil Engineers.