Axial compression behaviour of bolted-flange composite column-column connection

Reliable column-column connection contributes to a reduction in waste materials and enables structures to be demountable after their service life. This paper demonstrates the feasibility of using a bolted-flange connection with concrete-filled steel tube (CFST) columns subjected to axial compression load. Compression capacity, ductility, axial stiffness and toughness, as well as failure modes are discussed. The specimens are grouped into two categories: group I-connection without stiffeners and group II-connections supported by stiffeners. Three thicknesses of 2, 4 and 6 mm were used to manufacture the bolted flanges and stiffeners. The results showed that the proposed connection was effective to avoid a reduction in compression capacity. The various thicknesses of bolted flanges in group I specimens had a slight influence on the axial stiffness value and that influence was doubled in group II specimens. The stiffeners played a significant role in the toughness value and this was reduced with a reduction in the thickness of the stiffeners. In addition, an improvement in ductility was noticeable in stiffened specimens. Consequently, it can be inferred that bolted-flange joints have the potential to produce reliable and economical designs for CFST columns.