Concrete-Filled Steel Tubular (CFST) columns are widely recognized as efficient composite structural members due to their superior strength, stiffness, and ductility. The composite action between the outer steel tube and the inner concrete core provides enhanced confinement, resulting in improved load-carrying capacity and energy dissipation compared to conventional reinforced concrete or steel members. Owing to these advantages, CFST columns have been extensively studied under various loading conditions, including axial compression, bending, torsion, buckling, and their combined effects.

This paper presents a structured and critical review of the existing literature on CFST behaviour, systematically organized according to different loading regimes. Particular emphasis is placed on the diameter-to-thickness (D/t) ratio, which plays a crucial role in governing confinement effectiveness, strength enhancement, and overall stability of the member. The review also highlights recent advances in nonlinear finite element modelling, with a focus on the application of the Concrete Damaged Plasticity (CDP) model in ABAQUS for accurately simulating the complex interaction between steel and concrete.

To strengthen the findings of the review, a finite element model is developed and validated against available experimental data. The numerical results demonstrate good agreement with experimental observations, with deviations limited to within 5%, confirming the reliability of the adopted modelling approach.

Despite the substantial body of research, significant gaps remain, particularly in the limited understanding of combined axial–bending–torsion behaviour and the lack of comprehensive design provisions addressing such complex loading conditions. This study provides a comparative synthesis of existing findings and identifies key areas requiring further investigation. The outcomes are expected to contribute towards the development of more unified and reliable design methodologies for CFST structures.

Keywords— CFST; column; axial; bending; torsion; buckling; combined loading; D/t ratio; Concrete Damaged Plasticity; finite element analysis; confinement.