Cyclic behaviour of square concrete-filled steel tubular columns at cold-region low temperatures

This paper studied the cold-region seismic behaviours of square concrete-filled steel tubular (SCFST) columns through five cyclic loading tests on them at low temperatures of 20, −30, −60, and −80 °C. The cyclic loading tests showed that SCFST columns failed in outward plastic local buckling of steel tube and concrete-core crushing. Subjected to low-temperature cyclic loading, the hysteretic shear resistance-lateral displacement curves of SCFSTs exhibited full spindle-shaped loops with slight pinching. The low temperature had only marginal effects on the failure modes and the shape of hysteretic loops. As T decreased from 20 °C to −80 °C, the peak bending resistance ( M m ) of SCFST columns was increased by 12.8%; the cumulative energy dissipation capacity ( E a ) of SCFST columns at θ = 6% was increased by 20.7%, but their ductility ratio ( μ ) was decreased by 20.5%. Moreover, analytical models were developed to predict the skeleton load-displacement curves of SCFST columns under low-temperature cyclic loading. The developed models offer reasonable estimations on the load-displacement behaviours of SCFST columns under lateral cyclic shear loads.