Finite Element Modeling for Concrete-Filled Steel Tube Stub Columns Under Axial Compression

Concrete-filled steel tube (CFST) columns exhibit remarkable structural performance due to the combined effects of lateral confinement provided by the steel tube and the capacity of the core concrete to delay steel local buckling. This interaction enhances the axial capacity, peak-load strain, and ductility behavior of CFST columns. However, accurately modeling CFST stub columns using finite element (FE) simulations is a challenging task, requiring accurate representation of concrete behavior under tri-axial stress conditions. The concrete damaged plasticity (CDP) model in ABAQUS software is commonly used but has limitations, particularly for confined concrete. In addition, most introduced confinement models are constrained by the type of confining material and column dimensions. This study addresses these limitations by introducing an enhanced CDP model that properly accounts for the hardening/softening rule, yielding surface, and flow rule. In addition, a new confinement ratio is proposed for steel-confined concrete columns to calculate the dilation angle. The suggested model was validated through FE analysis on 1041 previously tested CFST stub columns. It was found that the proposed model successfully predicts load–strain curves and axial capacity for various cross-section shapes and confinement levels.