Compressive Behavior of Double-Skin Tubular Columns with High-Strength Concrete and a Filament-Wound FRP Tube
Hybrid fiber-reinforced polymer (FRP)-concrete-steel double-skin tubular columns (DSTCs) consist of an outer FRP tube and an inner steel tube, with the space between them filled with concrete. Many experimental studies have been conducted on the axial compressive behavior of hybrid DSTCs, but these studies have generally been limited to small-scale specimens with a wet-layup FRP tube. In particular, there has been no systematic experimental study on the axial compressive behavior of hybrid DSTCs with a filament-wound tube and high-strength concrete (HSC), which are the two desirable features of hybrid DSTCs in practical implementation. This paper therefore presents an experimental study on hybrid DSTCs under monotonic axial compression with a particular focus on three important issues: the use of HSC, the use of filament-wound tubes, and the use of large-scale specimens. The experimental results indicate that hybrid DSTCs can possess excellent ductility even when high-strength concrete is used. The axial stress-strain curves of concrete in hybrid DSTCs feature a bilinear ascending shape if the concrete is well confined by the FRP tube, but exhibits stress fluctuations or even a sudden stress drop if this confinement is less effective. An existing stress-strain model, which was developed on the basis of test results of small-scale hybrid DSTCs with normal-strength concrete and a wet-layup FRP tube, is capable of providing reasonably accurate predictions for the present test specimens with a bilinear ascending stress-strain curve or with small fluctuations in the axial stress, but it overestimates the results of the specimens with a sudden load drop.