Experimental and numerical investigation of liner-stiffened thin-walled CFST columns under axial compression

This paper presents an experimental and numerical investigation into the structural performance of thin-walled square concrete-filled steel tubular (CFST) columns stiffened with internal steel liners under axial compression, mainly focusing on performance optimization through rational steel allocation, enhanced constructability via tube discontinuity at the ends, and the exploration of corrugated liners and self-tapping screw connections. A total of 14 short column specimens were tested, including unstiffened, circular liner-stiffened (SC), and octagonal liner-stiffened (SO) types. The results demonstrate that both liner types can significantly enhance the axial load-bearing capacity, ductility, and buckling resistance of thin-walled CFST; discontinuing the thinner tube at the column ends effectively addressed joint constructability with minimal compromise to performance. Finite element models are developed to investigate the bearing mechanism. The results of parametric analysis indicate that the liner-to-tube steel allocation ratio ( γ ) critically influences optimal performance. Finally, the method for predicting axial resistance proposed in the previous study was modified to adapt to a wider range of parameters, showing excellent agreement with experimental and numerical results.