Strength and Axial Behavior of Circular Concrete Columns Reinforced with CFRP Bars and Spirals

The behavior of concrete members reinforced with fiber-reinforced polymer (FRP) bars has been the focus of many studies in recent years. However, limited research work has been conducted to examine the axial behavior of concrete columns reinforced with FRP bars. In this paper, the behavior and compression strength of 11 full-scale circular concrete columns reinforced with carbon fiber-reinforced polymer (CFRP) bars and spirals were investigated. The test variables included reinforcement type (CFRP versus steel); longitudinal CFRP reinforcement ratio; and the volumetric ratio, size, and spacing of CFRP spirals. The test results indicated that the CFRP and steel reinforced concrete (RC) columns behaved in a similar manner up to their peak loads. The CFRP bars were effective in resisting compression until after crushing of concrete, and contributed on average 12% of column capacity. The design equation is modified to accurately predict the ultimate load capacities of CFRP RC columns. A new factor (alpha c) is introduced in the modified equation to account for the FRP bars' compressive strength properties as a function in their ultimate tensile strength.