Mechanical performance of hexagonal multi-cell concrete-filled steel tubular (CFST) stub columns under axial compression

Multi-cell concrete-filled steel tubular (CFST) column is a type of composite members developing from conventional CFST columns. Featuring greater cross-sectional dimensions and the use of internal webs to separate inner concrete into smaller isolated cells, multi-cell CFST columns have been used in super high-rise buildings recently as the main vertical load bearing members. However, existing research on CFST members is mainly focused on conventional single-cell CFST members. To fill this research gap, this paper numerically investigates the mechanical performance of hexagonal multi-cell CFST stub columns under axial compression. A finite element analysis (FEA) model was initially established to simulate the mechanical performance of hexagonal multi-cell CFST columns. The FEA model was validated against existing experimental data. The mechanical performance of the multi-cell CFST columns were analysed, including the full-range load versus deformation relationships, the stress distributions of the main components and the distribution of contact stress on each concrete cell. A parametric study was then conducted to investigate the sensitivity of various geometric and material parameters on the compressive behaviour of multi-cell CFST columns. Finally, analytical formulae were derived to predict the axial compressive ultimate strength of hexagonal multi-cell CFST columns. The methods were found to be acceptable with reasonably good accuracy.