Design and global buckling behaviour of slender concrete-filled double-skin corrugated steel tubular columns for modular construction

Slender concrete-filled double-skin corrugated steel tubular (CFDSCT) columns offer a promising solution for modular composite buildings, where storey-height members must combine high load capacity, reduced self-weight, and reliable global buckling performance. Despite their potential for prefabricated construction, the axial behaviour and design of slender CFDSCT columns remain unregulated due to the absence of systematic studies addressing global buckling. This study addresses this gap by providing the first comprehensive numerical dataset and design guidance for slender square CFDSCT columns under axial compression, with direct relevance to modular applications. A detailed finite element model is developed in ABAQUS and rigorously validated against experimental results for both short CFDSCT columns and slender conventional concrete-filled double-skin steel tubular columns. A geometrically and materially nonlinear analysis with imperfections is employed to capture second-order effects and instability behaviour. An extensive parametric study comprising 120 numerical models is conducted to investigate the influence of slenderness ratio, hollow ratio, material strengths, corrugation profile, and cross-sectional dimensions. The results demonstrate that the slenderness ratio is identified as the dominant parameter governing global behaviour, defining a clear transition from section-controlled response to global buckling–controlled failure. Practical slenderness limits suitable for storey-height modular columns are proposed. While the corrugated outer tube enhances performance in short and intermediate-length columns by improving confinement and delaying local buckling, its influence diminishes in slender members governed by elastic global buckling. The hollow ratio significantly affects the absolute capacity but has limited influence on normalised strength. Comparisons with current design standards (EC4, AISC 360–22, and AS/NZS 2327) reveal varying degrees of conservatism and inconsistency. Consequently, two practical design models—a modified EC4-based approach and a calibrated power-law model—are proposed, both showing excellent agreement with numerical results across the full slenderness range. The findings provide essential behavioural insight and validated design tools to enable the safe and efficient use of slender CFDSCT columns in modular composite buildings.