Material properties and buckling behaviour of double-sided stainless-clad bimetallic stub columns

Double-sided stainless-clad bimetallic steel (SBS) is a novel structural material developed for members exposed to corrosive environments on both inner and outer surfaces, such as H-sections and other open sections. However, unlike single-sided SBS, the buckling behaviour of double-sided members has not yet been systematically investigated. To address this critical gap, this study presents the first systematic experimental and numerical investigation on the buckling behaviour of double-sided SBS members. The experimental programme comprised twelve tensile coupon tests and ten stub column tests covering a wide range of plate slenderness. Both H-sections and channel sections were examined, with particular emphasis on the effects of width-to-thickness ratio, material type, and cross-sectional form. The test results indicated that the stress-strain responses predicted using the weighted superposition method show close agreement with the experimental results, demonstrating its effectiveness in representing the constitutive behaviour of double-sided SBS. Based on this approach, advanced finite element (FE) models employing a homogeneous single layer were developed and validated against the experimental results. The obtained test results were further used to assess the existing design methods, and a benchmark assessment against the experimental data indicates that the current design provisions in EN 1993–1–1 (2022), AS 4100 (2020) and AISC 360 (2022) underestimate the axial resistance of double-sided SBS stub columns. For the cladding ratio of 0.16 considered in this study, the local buckling behaviour was governed primarily by the carbon steel substrate, resulting in good agreement between the experimental results and carbon steel-based design predictions, with only a limited contribution from the stainless steel cladding.