Stability behaviour and design approach of slender concrete-filled double-skin corrugated steel tubes under axial compression

Concrete-filled double-skin corrugated steel tube (CFDCST) members have been proven to exhibit superior mechanical performance, durability, and construction efficiency. In practice, hollow-section CFDCSTs are often designed as slender components in piers, towers, and high-rise buildings; however, their stability behaviour has not been clarified. Therefore, this study aims to reveal the working mechanisms of slender CFDCSTs under axial compression and propose design methods. This study first experimentally investigated eight large-scale slender CFDCST specimens under axial compression, including four variables: nominal slenderness ratio from 27 to 42, hollow ratio from 0.3 to 0.7, outer CST thickness from 1.2 mm to 1.6 mm, and longitudinal rebar ratio from 1.06% to 2.70%. Subsequently, solid finite element models were established, and stress analysis was performed to quantify the working mechanisms. Results indicated that the outer CST can provide effective confinement, with the nominal hoop stress generally ranging from 0.4 to 0.8 times the yield strength in the compressive side and 0.25–0.7 times the yield strength in the tensile side, while the inner CST mainly provides internal support. On this basis, a fiber-based finite element method was developed, and a systematic parametric analysis was then performed to investigate the stability bearing capacity. Finally, a calculation method for the axial compressive stability coefficient was proposed with satisfactory prediction accuracy.