Experimental and theoretical study on elliptical rubber concrete filled double-skin GFRP short tubes under axial compression

This study proposed a double-skin section consisted of an elliptical glass fiber reinforced polymer (GFRP) outer tube, a circular steel inner tube and rubber concrete filled between them, which had the features of aesthetic appeal, structural efficiency and waste recycle. Axial compressive test was conducted on the elliptical rubber concrete filled double-skin GFRP tubular (CFDST) short columns with various void ratios and rubber contents. Load-axial strain-hoop strain data was obtained from the experiments and the contribution of each component (i. e., concrete, GFRP tube, steel tube) to resist the applied load was clarified. Experimental results indicated that the void ratio and rubber content had the most significant effects on the dilation property (i.e., hoop and axial strains) and confinement effect of the rubber concrete. Nevertheless, effects of steel tube thickness and rubber particle size were insignificant. Based on the experimental results and confining concrete theories, a theoretical model, with proper considerations on the effects of void ratio, rubber content and aspect ratio, was proposed to estimate the ultimate load-carrying capacity and ultimate strain of the stub columns under axial compression. Finally, reasonability and accuracy of the proposed model were verified by the experimental results.