Flexural Strength of CFSS Beams with Single and Double Web Holes

Abstract

Web openings in structural beams facilitate building services; however, their influence on cold-formed stainless steel (CFSS) members, particularly under multiple openings, remains underexplored. This study addresses the gap in understanding of how single and double web holes affect the flexural performance and failure behavior of CFSS beams. A total of 90 finite element models of ferritic and lean duplex CFSS beams were analyzed using ABAQUS under four-point bending. Parameters included varied cross-sections, hole diameters (20–90% of web depth), and single or double openings. Results were compared with existing design rules using reliability analysis. Web openings up to 20% of web depth showed negligible impact on flexural strength. Increasing from one to two holes caused minimal additional strength reduction, though larger openings (≥50%) led to more pronounced capacity loss. All specimens failed by flexural buckling interacting with local buckling. Existing design methods yielded conservative predictions with safety indices exceeding the recommended minimum of 2.5. The minimal impact of multiple openings confirms the web's limited contribution to flexural resistance under pure bending, even considering stainless steel's nonlinear behavior. Current design rules remain reliable for beams with up to two openings. CFSS beams can safely accommodate single or double web openings up to 20% of web depth without significant strength loss, enabling practical service integration while maintaining structural safety.