Local buckling in cold-formed steel moment-resisting bolted connections : behavior, capacity and design

The research presented in this paper aimed to investigate local buckling failure occurring adjacent to moment-resisting bolted connections in cold-formed steel back-to-back channel beams connected to a gusset plate through their webs. This failure is a result of a complex stress state originating from the transfer of both shear and bending moment through the web, combined with important shear lag effects. Experimentally validated finite-element models were used, accounting for material nonlinearity, geometric imperfections, and nonlinear bolt bearing behavior. The effects of the cross-sectional shape and thickness of the beam, the bolt group configuration, and the bolt group length were investigated. It was discovered that the detrimental effect of local buckling exponentially decreases when a longer bolt group length is used, when the load is introduced at the connection with a smaller eccentricity relative to the centroid, and when the thickness of the beam is increased. The results of the investigation were employed to develop a practical design equation with a wide range of applicability. Finally, a reliability analysis was performed within the framework of various standards.