Numerical modeling and design of cold-formed stainless steel elliptical hollow section beam-column members

This paper aims to investigate the structural behavior of cold-formed stainless steel (CFSS) elliptical hollow section (EHS) members under combined axial load plus biaxial bending by using numerical method . By using a validated finite element (FE) model for cold-formed (CF) tubular beam-column members, an extensive parametric study was conducted in this study. In order to cover various stainless steel alloys , a wide range of cross-section geometries, aspect ratios, cross-section slenderness values, member slenderness values as well as loading angles and eccentricities of the CFSS EHS beam-column members were examined. The FE predicted ultimate loads were compared with the design strengths predicted from the current interaction design expressions for CFSS structures specified in prEN 1993–1-4:2023, AS/NZS 4673 and ASCE/SEI 8–22 together with their codified slenderness limits for CFSS circular hollow sections (CHS). The Direct Strength Method (DSM) was recently proposed in the literature to predict the compression and bending resistances of CF normal grade steel EHS subjected to combined actions. The design expressions in AS/NZS 4673 and ASCE/SEI 8–22 associated with the DSM end points were also evaluated for CFSS EHS beam-column members. As the existing versions of Continuous Strength Method (CSM) were only suitable for CFSS square (SHS) and rectangular (RHS) hollow section as well as CHS members subjected to axial load plus uniaxial bending. Therefore, in this study, a modified CSM was proposed for the design of CFSS EHS beam-column members, by developing new CSM end points for CFSS EHS as well as the modified CSM interaction factors and modified CSM design formulae for CFSS EHS subjected to axial load plus biaxial bending. The comparisons revealed that the existing codified interaction design curves provided scattered and conservative predictions. By adopting the Chen and Young’s modified DSM to predict the end points, the accuracy of the design formulae in AS/NZS 4673 and ASCE/SEI 8–22 can be highly improved. However, the proposed modified CSM can achieve more accurate and reliable design predictions for CFSS EHS beam-column members than the existing codified methods and DSM. • Advanced FE modeling of cold-formed stainless steel (CFSS) EHS beam-column members. • Extensive parametric study for CFSS EHS beam-column members under combined actions. • Compared FE data with column strengths predicted from existing design codes and DSM. • Modified CSM is proposed for CFSS EHS beam-column members with different alloys.