Behavior of large-scale hybrid FRP-concrete-steel double-skin tubular columns subjected to eccentric compression

Hybrid FRP-concrete-steel double-skin tubular columns (DSTCs), consisting of an outer FRP tube, an inner steel tube and a concrete infill between the two tubes, are a novel form of hybrid columns which possess excellent mechanical performance and durability. Extensive studies have been conducted on such columns under concentric axial compression. However, limited research has been focused on the behavior of hybrid DSTCs subjected to eccentric compression which is a common loading case in practice. Therefore, an experimental program on nine large-scale hybrid DSTCs subjected to concentric or eccentric compression was conducted in the present study. The load eccentricity and the thickness of the filament wound FRP tube were the main test var-iables. The test results demonstrated that the hybrid DSTCs exhibited a highly ductile behavior under eccentric compression. A theoretical column model was then adapted by incorporating three stress-strain models for FRP -confined concrete for predicting the behavior of test DSTCs under eccentric compression. It was found that all the three stress-strain models provided reasonably accurate predictions for the axial load-carrying capacities of the test columns. However, the concentric loading stress-strain model led to significant underestimation in the deformation capacities of the test columns due to the neglect of the effect of eccentric compression.