Effectiveness of concrete filled FRP tubes under axial loading

Concrete filled tube (CFT) has been widely used as an effective column structure because of the improved strength, ductility and stiffness as well as significantly reduced cost. Considerable studies have established that the improved performance of CFT columns results from the advantageous characteristics of both the tubes and concrete cores. It has been demonstrated that while the lateral confinement provided by the tube can improve the strength and ductility of the concrete, the concrete core will enhance the buckling strength of the tube. Currently, steels are the primary materials for the tubes because of their high strength and high stiffness. Over the past few years, fiber reinforcement polymer (FRP) has increasingly been used in structural application because of a number of its advantages over steels such as lightness, and reduced installing and maintenance costs among the other advantages. In line with this trend, a number of studies were reported on the use of FRP tubes in the CFT structures. This paper presents a brief state-of-art review of the application of FRP ‘can’ in structural engineering together with partial results from an experimental study of the behavior of a concrete filled FRP tubes under axial loading. The compressive strength of the FRP CFT and failure modes were obtained by varying the slenderness ratios of CFTs. The results are analyzed and discussed in terms of the effects of both slenderness ratio and lateral confinement due to the FRP tubes on the stress state and therefore, on failure mode and strength behavior.