Experiments on special-shaped CFST stub columns under axial compression

• A set of new test on special-shaped CFST stub columns is reported.
• The influence of different parameters on the composite columns is investigated.
• Simplified model for predicting the strength of the composite columns is discussed.

This paper is an attempt to study the behavior of axially loaded concrete filled steel tubular (CFST) stub columns with special-shaped cross-sections, i.e. triangular, fan-shaped, D-shaped, 1/4 circular and semi-circular. A total of forty-four specimens including CFST stub columns and reference hollow steel tubular stub columns were tested. The effects of the changing steel tube wall thickness and the infill of concrete on the behavior of the composite columns were investigated. The results showed that the tested special-shaped CFST stub columns behaved in a ductile manner, and the composite columns showed an outward local buckling model near the middle section. Generally, the failure modes of these five kinds of special-shaped specimens were similar to those of the square CFST stub columns. Finally, simplified model for predicting the cross-sectional strength of the special-shaped CFST sections was discussed and proposed.