Manufacture and testing of a novel FRP tube confinement system

Fiber reinforced polymer (FRP) tubes are an attractive form of concrete confinement, where the tubes can fulfill multiple functions of: (i) formwork, (ii) confinement reinforcement, (iii) protective shell against corrosion, weathering, and chemical attacks. This paper reports on the development and testing of a new type of rectangular FRP tube that is designed to improve the inherently low confinement effectiveness of rectangular FRP tubes. Axial compression tests were conducted to investigate confinement effectiveness of rectangular tubes with various arrangements. The tubes were designed as column confinement reinforcement and were manufactured using unidirectional carbon fiber sheets. The effects of the tube corner radius and the presence of internal FRP reinforcement were investigated experimentally. The results of the experimental investigation indicate that confinement of rectangular columns with FRP tubes leads to substantial improvement in the ductility of the columns. Confinement provided by the FRP tube may also improve the axial load-carrying capacity of the rectangular columns if the confinement effectiveness of the FRP tube is sufficiently high. The results also indicate that the FRP tube developed by the authors and presented in this study provides significantly higher confinement effectiveness than that of conventional rectangular FRP tubes.