Behaviour of small-diameter self-compacting concrete-filled steel tubes

This study explores the effect of length to diameter (L/D) ratio on the axial load capacity of small-diameter self-compacting concrete-filled steel tube (SCFT) specimens. The SCFT specimens with L/D ratio of 2 to 14 were tested. Two different cold-formed steel tubes with diameters of 26·9 and 33·7 mm were used in the construction of the SCFT specimens. The behaviour of the SCFT specimens was compared with the unfilled steel tube (UT) specimens. The axial load capacity of SCFT specimens was found to be higher than the axial load capacity of UT specimens. The compressive failure of SCFT and UT specimens with a ratio of 2 and 4 occurred due to local buckling, and with L/D ratio ≥ 6 failure occurred due to global buckling. However, the self-compacting concrete inside the steel tubes improved the ductility and the post-peak axial load-axial deformation response of SCFT specimens compared to the UT specimens.