Behavior of double-skinned circular composite columns infilled with mortar, SCC, and SIF materials under axial and eccentric loads

Failure of column components in structures can result in catastrophic collapse, highlighting the need for improved ductility and energy dissipation capacities. Cocrete-filled steel tubular (CFST) columns have demonstrated superior performance because of their combined resistance, enhanced ductility, and effectiveness under seismic and fire conditions. This experimental study investigated the behavior of double-skinned concrete-filled hollow steel tubular CFHST columns under axial and eccentric loading using three different filler materials: cement mortar (CM), self-compacting concrete (SCC), and slurry-infiltrated fiber concrete (SIFCON). A total of 12 specimens were cast and tested to evaluate their load-deflection behavior, ductility index (DI), and strength index (SI). The results show that columns filled with SIFCON achieved the highest strength load-bearing capacity and deformation capabilities, with a 14.39 % increase in strength compared with those of CM-filled columns. Eccentric loading (30 mm) led to an average reduction of 8.04 % in the load capacity. Among the design codes evaluated, the Australian Standard (AS 5100) provided the most accurate strength predictions compared to AISC 360 and EC4. These findings suggest that the use of high-performance filler materials, specifically SIFCON, significantly enhances the axial and eccentric loading resistance of offering CFSTs, indicating promising potential for application in critical infrastructure where enhanced strength and ductility are essential.