Abstract: To evaluate the effectiveness of different stiffening measures, the comparative study on the axial compression behavior of the stiffened and unstiffened concrete-filled thin-walled high-strength square steel tube stub co-lumns was carried out in this paper. Firstly, the axial compression experiments of the stiffened specimens and the reference unstiffened specimens were designed and carried out, and the influence of yield strength of steel tube and type of stiffening measures on the failure patterns, load versus axial displacement (strain) curves and the mechanical indexes, e.g. bearing capacity, composite elastic modulus and ductility index, of the specimens was investigated. The results show that the stiffening measures can alter the destruction process of the specimens and the failure patterns of steel tube and improve the mechanical indexes of the specimens. However, there are no stiffening mea-sures that can thoroughly enhance the mechanical indexes of the specimens. Secondly, by determining the reasonable constitutive model of steel and core concrete, the finite element model of the stiffened and unstiffened concrete-filled thin-walled high-strength square steel tube stub columns under axial compression was developed and verified through experiments. Eventually, the effect of major parameters on the axial compression behavior of the stiffened concrete-filled thin-walled high-strength square steel tube stub columns was further analyzed with the verified finite element model. The results show that, the demarcation points in different stages of load versus axial displacement curves and mechanical indexes of the stiffened composite stub columns are different, and the stiffening measure of diagonal binding ribs is more effective to improve bearing capacity and ductility, while the stiffening measure of double-row steel ribs is more effective to improve composite elastic modulus.

Key words: concrete-filled thin-walled steel tube, square section, stub columns, stiffening measures, high-strength steel, axial compression behavior, experiment, finite element model