Seismic performance assessment of GFRP-steel double-skin confined rubber concrete composite columns

Rubber concrete, recognized as an eco-friendly composite material, tackles the problem of "black pollution" stemming from discarded tires, while conforming to green, low-carbon, energy-saving, and environmental protection standards. Despite its benefits, an increase in rubber content in rubber concrete leads to a decline in compressive strength and modulus of elasticity, limiting its application in structural engineering. To overcome this limitation, a novel strategy involves the use of glass fiber reinforced polymer (GFRP) and steel tubes for the dual confinement of rubber concrete, resulting in the development of GFRP-steel double-skin confined rubber concrete composite columns. This innovative method anticipates delivering enhanced ductility, energy absorption, and deformation abilities, rendering it suitable for seismic-prone regions and extreme environmental conditions. To shed light on the behavior of these composite columns, including the confinement and ductility mechanisms and failure modes, as well as their seismic performance regarding energy dissipation, strength, stiffness, and residual deformation, seven specimens were produced and subjected to quasi-static loading tests with varying axial compression ratios, rubber contents, and GFRP tube thicknesses. Findings indicate that the dual-tube setup substantially confines the rubberized concrete and offers superior shock absorption and energy dissipation, which mitigates damage in the plastic hinge areas. Under horizontal low cyclic loads, the composite columns' hysteretic curves is markedly plump, facilitating the efficient absorption and dissipation of seismic energy. Finally, the study introduces an accurate method to calculate the horizontal ultimate bearing capacity using sectional analysis, and the computed outcomes closely match the experimental results.