Study on mechanical properties of hollow square steel composite columns embedded steel fiber ceramsite concrete

Abstract In the evolving landscape of structural engineering, concrete‐filled double skinned tubes (CFDST) attract attention due to their enhanced bearing capacities and deformation capabilities, pivotal for seismic and fire resistance. This study explores the structural behavior and mechanical performance of hollow square steel composite columns embedded with steel fiber‐reinforced ceramsite concrete, in contrast to conventional solid steel tube concrete (CFST) columns with equivalent material composition and external dimensions. The experimental program includes axial and eccentric compression tests on a series of nine CFDST specimens and one CFST specimen. The manipulated parameters include the ceramsite aggregate replacement rate (0%, 50%, 100%), hollow ratio (0, 0.22, 0.42), and eccentricity (0, 30, 50 mm). The documentation of failure modes meticulously highlights shear failure and drum‐like wrinkling in axially loaded specimens at ultimate loads, along with concrete crushing on the compression side accompanied by tension‐side cracking in eccentrically loaded setups. Analysis reveals that the ultimate bearing capacities of CFDST specimens exceed those of their CFST counterparts, with the highest recorded at 1726 kN for axially compressed columns, and decrease progressively with increased hollow ratios and eccentricities. Notably, the study establishes that increasing the ceramsite replacement rate adversely affects the ultimate bearing capacity, illustrating a decrement trend with higher aggregate replacement rates, where the maximum bearing decrease is observed in specimens with a 100% replacement rate, achieving only 1521 kN. The study identifies a significant enhancement in the ductility coefficients of CFDST specimens over traditional CFST designs, underscoring the beneficial integration of steel fibers and optimized geometric parameters. This advancement underscores the potential for CFDST in high‐performance applications, suggesting that strategic modifications in ceramsite replacement rate, hollow ratios, and load eccentricities can yield substantial improvements in structural resilience and durability.