Numerical investigation of cold-formed stainless steel elliptical hollow sections subjected to bending

The paper presents a numerical investigation on the cold formed stainless steel (CFSS) elliptical hollow section (EHS) subjected to pure bending. In this study, numerical modeling methodologies for cold-formed (CF) tubular beams with both the moment span and full span were first developed and validated, in which the local imperfection magnitude, plastic strains and residual stresses were predicted numerically. Based upon the validated numerical models, an extensive parametric study was carried out for CFSS EHS beams; covering two loading conditions of both the minor-axis bending and major-axis bending, the lateral-torsional buckling (LTB) effect, three stainless steel alloys, a large range of cross-section aspect ratios and sizes as well as slenderness values. A total of 391 generated numerical data together with the collected test data were used to assess the design equations and slenderness limits specified in the existing design codes of ASCE/SEI 8–22, AS/NZS-4673 and prEN 1993-1-4:2023 (E) for the design of CFSS EHS beams. In addition, the direct strength method (DSM) specified in AISI for CF square and rectangular tubular beams and the existing continuous strength method (CSM) for CFSS circular hollow section (CHS) beams were also assessed. It can be found that the aforementioned design methods were conservative for CFSS EHS beams. In this paper, new slenderness limits were proposed for CFSS EHS beams. Appropriate modifications on the design guidelines were also proposed for the CFSS EHS beams.