Behaviour of FRP–rubber concrete–steel double-skin tubular long columns under axial compression: An experimental and theoretical study

As a green and innovative structure, FRP–rubber concrete–steel double-skin tubular columns (RC-DSTCs) not only reduce the environmental harm caused by waste rubber and promote its recycling, but also enhance their own ductility by utilizing the high toughness of rubber concrete. However, current research has been limited to the axial compressive behaviour of short columns, without addressing the stability issues of RC-DSTCs at higher slenderness ratios. Therefore, this study investigates the influence of slenderness ratio (6.69, 13.39, 20.08, 26.78, and 33.47), rubber volume replacement rate (0%, 5%, and 10%), GFRP tube thickness (2, 4, and 6 mm), and void area ratio (0.3, 0.4, and 0.5) on the axial compressive performance of RC-DSTCs. Experimental results indicate that with an increase in the slenderness ratio, the failure modes of RC-DSTCs transition from axial compressive failure to flexural instability failure and their peak load, GFRP tube confinement effect, and ductility significantly decrease. When the rubber volume replacement rate is 5%, the ductility coefficient of RC-DSTCs increases by 15%, and its peak load does not change significantly. Furthermore, the effect of GFRP tube thickness and void area ratio on the peak load of RC-DSTCs is insignificant, but their ductility notably increases. Ultimately, the theoretical axial compressive capacities of RC-DSTCs consider the cross-sectional shape and stability factors, showing good agreement with the experimental results. This study can provide a valuable reference for future engineering applications.