Strength and Ductility of Steel Cold-Formed Section Beam to Column Bolted Connections

Recently, there has been a rapid growth in the construction of low to medium rise houses and portal frames with moderate spans using steel cold-formed sections (CFS) as primary structural elements. However, the strength and stability of steel frames depend largely on the nature of the connections between their elements. This paper presents a study of the structural performance of three configurations of beam to column bolted connections of single-lipped channel CFS. In the first model, a sleeve element is used to connect the beam to the column. The sleeve element has a channel cross section with a tapered web. This enables the transmission of forces through the flanges as well as the webs. In the second model, the beam is connected to the column by a tapered gusset plate. Bolts connect the webs of the beam and column sections to the gusset plate. The third model depends on placing a knee-bracing element between the beam and the column; consequently, forces are transmitted mainly from beam to column as shear forces. Finite element models are established with the use of shell elements to model the sections while beam elements are used to model the bolted fasteners. The model is verified by comparing its results with published experimental results. The dimensions of the cross section of the members studied are 200 mm for the web, 60 mm for the flanges, and 20 mm for the lip. The thicknesses of the connected CFS members and connection plates are the main parameters of the study.