Resistance of cold-formed built-up stainless steel columns - Part I: Experiment

Nowadays, the codified procedure for design of centrically compressed cold-formed stainless steel (CFSS) built-up members is absent in Europe. Besides, there are no published research information and experimental data in this structural area. This paper focuses on a comprehensive experimental investigation of closely spaced CFSS built-up columns and addresses their flexural buckling capacity about the minor principal axis. Two series with a total of 36 built-up members were assembled, each formed by two discontinuously and directly connected channel chords oriented back-to-back to form an I-section. The chords were press-braked from flat strips of austenitic stainless steel EN 1.4301 as non-slender channel sections. The chords were uniformly interconnected by bolts or by welds. To identify the effects of interconnection spacing on chords' composite action, the overall and chord slenderness ratios were varied. Material properties, cross-section response and initial imperfections were quantified before testing. As a result, the overall flexural buckling without any local-overall interactions was observed as the dominant failure mode. All findings were used in the accompanying paper [1] to establish qualitative data base through numerical simulations of flexural buckling tests. Additionally, a quantitative accuracy assessment of the design methods for carbon steel built-up columns provided in Eurocode and American Specification was reported on the basis of their ability to predict flexural buckling resistances of the tested columns. This enabled numerical parametric studies and proposing design rules for CFSS built-up columns with non-slender sections that capture interconnection shear stiffness, overall and chord slenderness ratio and strain hardening effects.