Flexural behavior and design enhancement of slender shelf-type cold-formed steel members: an experimental and numerical investigation

Abstract This study presents an integrated experimental, numerical, and reliability-based analytical framework for investigating the flexural behavior of solid cold-formed steel (CFS) shelf-type members fabricated from high-ductility steel ( f u /f y > 3) subjected to minor-axis bending. Six full-scale tests were conducted on inverted C-channel shelves and were used to validate detailed nonlinear finite element (FE) models, which showed excellent agreement with the experimental results. Within the proposed analytical framework, a parametric study comprising 90 FE models was performed, covering width-to-thickness ratios (b/t) from 30 to 600, plate thicknesses of 1.0–2.0 mm, and spans of 1000–2000 mm. The results indicate that flexural behavior is governed by local buckling of the compression flange. Increasing b/t reduced the ultimate moment capacity by approximately 20–25% for thin shelves, while thicker shelves exhibited a smaller reduction of about 5–10% due to enhanced post-buckling and strain-hardening effects. The accuracy and reliability of the AISI S100-24 Direct Strength Method (DSM) were evaluated within a code-consistent reliability framework. While DSM predictions were satisfactory for thin sections, a systematic thickness-dependent conservatism was identified for thicker shelves fabricated from high-ductility steel with f u /f y > 3, with strength underestimations reaching up to 74%. To address this limitation, a simple thickness-dependent refinement to the DSM flexural strength equation is proposed. The refinement is applied within the developed analytical framework, preserves the original DSM formulation, reduces the strength bias to within 3–5%, and restores reliability indices to values close to the target level. The proposed refinement is intended specifically for shelf-type members fabricated from steel with f u /f y > 3, where the unusual material ductility influences the post-buckling response. The proposed framework improves the applicability of DSM for the design of high-slenderness CFS shelf-type members used in modern industrial storage systems.