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.