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• Two large-scale thin-walled CFDST columns with different stud spacing were tested under axial compression. • The stiffened studs delayed the occurrence of local buckling in these specimens significantly. • The arrangement of the studs leads to a obvious effect of section confinement, thus improving the overall compressive performance of the specimen. • The variability of the Poisson's ratio of concrete and steel during loading resulted in different stresses on the studs. • The current design specifications for calculating the peak load of CFDST columns are modified and used for the evaluation of the two large-scale thin-walled CFDST specimens in this study. Wind turbine towers offer good application potential for concrete-filled double-skin steel tubular columns with large hollow ratios (LHR-CFDST). With the increasing size of this engineering structure, the requirement to reduce construction expenses can be met by enhancing the diameter-to-thickness ratio of steel tubes. Few studies have been conducted to report on thin-walled LHR-CFDST columns. Meanwhile, local buckling and size effect shall be considered for this type of structure. Based on this, the first experimental investigation on large-scale stiffened thin-walled LHR-CFDST columns under axial compression is reported in this paper. Two large-scale thin-walled LHR-CFDST columns with different stud spacings are discussed. Failure modes, local buckling behaviours, load-strain responses, and some common mechanical indexes are investigated. According to the test results, adding studs was an effective method to increase the ultimate capacity of LHR-CFDST columns, as evidenced by the 16.6% increase in peak load for the specimen with smaller stud spacing than the other. Besides, the arrangement of studs leads to an obvious effect of section confinement, thus improving the overall compressive performance of the specimens. Then, four existing specifications all give a conservative prediction for the ultimate capacity of the specimen with smaller stud spacing, indicating that the large-scale thin-walled LHR-CFDST can be evaluated utilizing the present specifications with suitable stiffening measures. [ABSTRACT FROM AUTHOR]

• 1) Completing the monotonic axial loading test on the STCLAC stub columns. • 2) Proposing a formula that calculated the equivalent lateral confining stress. • 3) Proposing formulae that calculated the compressive stress and the corresponding strain for confined LAC. • 4) Proposing the constitutive model for confined LAC. To study the constitutive model of lightweight aggregate concrete (LAC) constrained by the circular steel tube, the monotonic axial loading test was carried out on steel tube confined LAC (STCLAC) stub columns, considering the effects of the diameter-to-thickness (D / t) ratio (30.4, 19 and 12.7) and steel grade (Q235 and Q355). The test results showed that the steel tubes of STCLAC columns were bulging outward as a whole without local buckling during the loading process. The D / t ratio for the STCLAC column is recommended that be greater than 19.0. Due to friction stress accumulating at the interface between the steel tube and the LAC core, the steel tube is subjected to longitudinal stress. When the confinement factor (ξ) is less than 2.313, the transverse stress of the steel tube reached its yield strength before the peak load, otherwise it reached the proportional stress without yielding. Using the average transverse stresses along the height of the steel tube, this study calculated the equivalent lateral confining stress of the STCLAC column. The calculation formulas of the compressive stress and corresponding strain of confined LAC were proposed based on the test results. And the constitutive model was also proposed, which is more capable of predicting the stress–strain relationship of the constrained LAC by a circular steel tube. [ABSTRACT FROM AUTHOR]