Cyclic Performance of Innovative Stiffener-Free Cold-Formed Steel Moment-Resisting Connections with Folded Flange Sections

While cold-formed steel (CFS) elements are increasingly used in modern construction as cost-effective alternatives to conventional hot-rolled steel members, designing momentresisting connections for these systems remains challenging due to the low buckling resistance of their thin-walled sections. Although CFS members with folded flanges have demonstrated improved structural performance, their application in moment-resisting beam–column connections has received limited investigation, particularly for practical stiffener-free configurations. This study presents a numerical investigation of a new generation of bolted moment-resisting connections in CFS structures, introducing new practical stiffener-free connection configurations with the focus on the use of folded flange beam (FFB) sections as a practical substitute for curved flange beams (CFB) in order to promote constructability and manufacturing efficiency. Finite element (FE) models were developed and validated against existing experimental and numerical data under cyclic loading. A comparative assessment was performed to evaluate the structural performance of FFB connections relative to conventional CFB connections, followed by an analysis of enhanced FFB joint designs. Results confirm that FFB connections offer comparable cyclic moment–rotation performance to CFB systems, while providing additional benefits such as simplified floor-system integration. Moreover, practical connection enhancements were found to improve joint behaviour and increase the flexural capacity of the joint by up to 29% without the need for stiffeners, supporting wider implementation in cold-formed steel construction.