Performance Evaluation of Concrete Columns Reinforced Longitudinally with FRP Bars and Confined with FRP Hoops and Spirals under Axial Load

Nowadays, AASHTO LRFD Bridge Design Specifications and the Canadian Highway Bridge Design Code contain flexural and shear provisions for the design of concrete bridge members reinforced with fiber-reinforced polymer (FRP) bars. Because of a lack of research, these standards do not recommend using FRP bars to resist compressive stresses in compression members. This paper reports on 14 full-scale circular RC columns tested under concentric axial load. The columns were reinforced with longitudinal FRP bars and confined with circular FRP spirals or hoops. Sand-coated glass-FRP (GFRP) and carbon-FRP (CFRP) reinforcement was used. The test parameters included configuration of the confinement reinforcement (spirals versus hoops), hoop lap length, volumetric ratio, and FRP reinforcement type (glass versus carbon). The test results indicate that the GFRP and CFRP RC columns behaved similarly to columns reinforced with steel. Using GFRP and CFRP spirals or hoops according to the provisions of the Canadian Standards Association S806-12 yielded sufficient restraint against the buckling of the longitudinal FRP bars and provided good confinement of the concrete core in the postpeak stages. The results of this study can be used as a fundamental step toward code provisions for using GFRP or CFRP spirals and hoops as internal confinement reinforcement in bridge pier and pile foundations. (C) 2014 American Society of Civil Engineers.