Experimental Study on Load-Carrying Capacity and Failure Modes of Composite Double Skin Tubular Columns

The given research is an experimental research on the axial compressive performance of composite double-skin tubular columns, i.e. Steel-Confined Double Skin Tubular (SCDST) columns and Glass Fiber Reinforced Polymer-Steel Double Skin Tubular (GSDST) columns. The study is aimed at considering the impact of the following parameters on the load-carrying capacity, failure mechanism, and the load-strain behavior, including fiber orientation, diameter-thickness (Do/t) ratio, confinement thickness, hollow section ratio, and concrete grade. Axial compression tests were performed in the series on stub columns manufactured with different GFRP fiber orientations (0deg, 45deg and 0deg/90 deg) and with different confinement arrangements. It was found that experimental results showed that SCDST columns had a 30-40% higher ultimate load capacity than GSDST columns because of the better confinement of the steel. Nonetheless, GSDST columns exhibited high strength improvement when high fiber orientation and confinement thickness was used. GSDST specimens with an orientation of the fiber of 0deg and a Do/t ratio of 35 gave the highest load capacity of 1400 kN. Failures were different in nature with SCDST columns mainly failing through buckling of the outer steel tube, and GSDST column failing through fiber rupture, delamination, and splitting with respect to fiber orientation. The behavior of loads was nonlinear, and it was found to increase the level of stiffness and ductility with reduced Do/t ratios and increased confinement levels. Its results can be useful in optimizing composite tubular columns in case of high load and duration-sensitive structural issues.