High strength steel cold-formed hollow sections: implication of cross-section aspect ratio and slenderness characteristics on flexural behavior

Cold-formed tubular sections are widely applicated for a variety of structural solutions, primarily due to their advantageous structural properties, inherent aesthetic characteristics and ease of prefabrication and mass production. High strength steels (HSS) are attaining growing attention from structural engineers and researchers due to their potential on the design of lightweight and more economic structures. In combination with cold-formed tubular sections HSS might serve as improvement on structural efficiency as well as solution for structural problems when usage of normal steel is limited due to insufficient strength. However, innovative structural solutions are often faced problems related with absence of appropriate design procedures. In most of the design codes cross-section design is performed following the traditional classification procedure based on the slenderness of the individual constituents without respect to their interaction. Moreover, tubular sections are generally treated in the same manner without respect to their formation route, embedding an elastic-perfectly plastic material model, without reference to the cold-formed sections increased strength and reduced ductility over the flat material. This paper reports on the numerical study of cold-formed HSS tubular beams deformation response, with a focus on the effect of cross-section constituent’s interaction and strength enhancement influence on the cross-section slenderness. Finite element (FE) models were first developed and validated against existing test results. Upon validation against the experimental results, parametric studies were carried out to expand the available flexural response data over a range of cross-section aspect ratio, cross-section slenderness and steel grades. The obtained numerical results were used to assess the suitability of the current design codes cross-sections classification for cold-formed HSS tubular beams.