Development and cyclic performance of a small-fastener connection for cold-formed steel framing

The use of cold-formed steel (CFS) sections as the primary load-carrying members in low-rise residential and industrial buildings is on the rise. The literature reports that the lateral strength and performance of commonly used CFS stud-wall frames are predominantly limited by failure mechanisms occurring at the sheathing-to-stud connections, such as cracking of panel boards, self-drilling screws (SDS) pull-out, and sheathing pull-over. Furthermore, conventional bolted-framing systems exhibit similar performance due to high concentration of forces near bolts, which lead to component buckling. To overcome these drawbacks of the existing framing system, appropriate design modifications are necessary. To achieve this, a beam-to-column connection using SDS and gusset plates was developed to distribute the forces effectively, eliminate the reliance on sheathing boards for lateral strength. The performance of the developed connection was evaluated in terms of hysteretic moment-rotation behaviour, energy dissipation, ductility, and failure modes through experimental studies. Numerical analyses were carried out to assess the influence of key design variables on the connection behaviour. Additionally, experimental studies on performance SDS lap joints were conducted under tensile shear loading to assess the validity of the existing guidelines and adopt them to the current configuration of connection components. The results obtained from the numerical studies were then compared with the envelopes of the experimental hysteresis curves. Based on the findings, the developed connection demonstrates adequate strength and ductility for CFS framing systems intended to use as moment-resistant connection. This paper presents the details of the proposed connection along with component-level and full-scale experimental investigations. The studies indicate that the proposed connection successfully overcomes the drawbacks of the bolted connections and it can be effectively adopted in the development of CFS framing systems, such as low-rise residential buildings, parking structures, mezzanine floors and similar applications.