Composite Structures, vol.309, 2023 (SCI-Expanded)
© 2023 Elsevier LtdBoth experimental and numerical investigations are performed to determine complete inelastic behavior of circular concrete filled double skin steel tubes (CFDSTs) with different compositions. In the experimental part, 8 circular tubes including 2 DSTs (double skin steel tubes without infill) and 6 CFDSTs are tested under concentric axial compression to failure. Presence/absence of infill concrete, hollow ratio (χ = 0.47 ∼ 0.70), and concrete type (plain, polypropylene and steel fibers added) are the parameters. To cover more parameters such as further hollow ratios, inner and outer tube thicknesses, a numerical work is added. AISC 360–16 and Eurocode 4 (EC4) are employed to evaluate their applicability for CFDSTs. Results show that the hollow ratio and outer/inner tube slendernesses (D/t) have a significant impact on the behavior. Experimental and numerical results reveal that, independent of the concrete composition (i.e. with or without any fibers) and hollow section ratio, concrete infill has significantly improved axial strength (up to 86 %) and ductility (up to 314 %) by delaying local buckling. Polypropylene and steel fibers improve the overall behavior with an enhanced displacement ductility and energy absorbtion. CFDSTs with smaller hollow ratios (say 0.47 or smaller) present much better inelastic behavior mainly from the enhanced confinement effect.