Static strength of stainless-clad bimetallic steel CHS T- and K-joints

This paper presents an experimental investigation into the structural behaviour and strength of stainless-clad (SC) bimetallic steel circular hollow section (CHS) T- and gapped K-joints. The SCCHS joints consisted of chord and brace members made up of SC bimetallic steel tubes, which were cold-formed from SC bimetallic steel plates with nominal thicknesses of 8 mm, composed of 2 mm 304 L cladding stainless steel and 6 mm Q235 substrate carbon steel. A total of eight SCCHS joints, including four T-joints and four K-joints, were tested. For the T-joints, the axial loading was applied at the brace members, while the axial loading was applied at the chord members for K-joints. In the experimental programme, the brace to chord diameter ratio β ranged from 0.56 to 0.75, the chord diameter to thickness ratio 2γ varied from 25.00 to 33.25, and the gap distance between two braces to chord diameter ratio g/d₀ of K-joints changed from 0.139 to 0.408. The load-deformation curves, joint strengths, as well as failure modes of the SCCHS T- and K-joints have been presented. The test results of SCCHS T- and K-joints demonstrated similar failure modes and joint strengths to those of carbon steel joints reported in the literature. Finally, the test results have been used to evaluate the applicability of current design recommendations for normal strength steel joints in ANSI/AISC 360–22, EN 1993–1–8 and API 2A-LRFD to the design of SCCHS T- and K-joints. Results indicate that the ANSI/AISC 360–22, EN 1993–1–8 and API 2A-LRFD characteristic strength equations are conservative for the design of SCCHS T-joints under axial brace load. The ANSI/AISC 360–22 characteristic strength equations tend to underestimate the SCCHS K-joint strengths, while those specified in EN 1993–1–8 and API 2A-LRFD produce marginal predictions to the test joint strengths.