Numerical Study of Unstiffened Cold-Formed Steel Sections Moment Connection

Abstract

Cold-Formed Steel sections are commonly used in residential and commercial buildings as purlins, side girts, portal frames and moment resisting frames. The bolted moment connections can be used to connect the different structural components of these buildings together. These connections allowing the transfer of the internal forces of the structures such as axial forces, shear forces, bending moments and torsion. The main objective of this paper is to study numerically the behaviour of the apex bolted moment connection for cold formed sections. The deflection and the stress distribution at critical sections for unstiffened 2C (double back-to-back) CFS were investigated for two cases. Connecting single gusset plate was used in the first case, while two connecting double gusset plates in the second case. A finite element modelling was developed by using the ANSYS workbench to simulate the apex connection of cold-formed steel sections. The considered beams had span lengths of 4000 mm with nominal web depths of 150 mm and wall thickness 2.0 mm. A numerical model was developed and verified using the experimental results. The parametric study was carried out to investigate the effect of connecting gusset plate thickness, bolts patterns, and bolts pretension force on the resistance of the cold-formed steel sections. Based on this analysis the deflections, ultimate failure load, failure modes of specimens were studied and different failure modes, including local yielding in cold formed section, flexuraldistortional buckling in the connecting gusset plate, and bearing failure near bolts are observed. Moreover, moment resistance ratio and rotations for this type of connection are deduced.