Experimental Study of Screw Connections in Plywood-Sheathed CFS Wall Panels Subjected to In-Plane Shear Loading

Abstract

Sheathed cold-formed steel (CFS) wall panels are a primary load-carrying component in CFS buildings in which the wall panel is under shear loading, and the resistance offered by the wall panels depends on the screw connection between CFS frame and sheathing. In this study, a set of 48 small-scale tests was conducted to study the behavior of screw connections in CFS wall panels sheathed with plywood under in-plane shear loading. The studies were conducted using both monotonic and cyclic loading (24 specimens each) to investigate the effect of various parameters, including sheathing thickness, type of screws, stud thickness, and sheathing orientations. It was found that screw failure was the most common mode of failure in plywood-sheathed wall panels when conventional flat head screws were employed, and a screw with a washer increased the wall panel’s stiffness and strength significantly. The performance of the specimens was evaluated based on their load-carrying capacity, initial stiffness, failure mechanisms, ductility, and energy dissipation. The failure mode sequence of different types of fasteners connected to various CFS studs and plywood thicknesses under in-plane shear loading are discussed. The study’s findings show that screw head type and sheathing thickness are the governing parameters that determine screw connection capacity under in-plane shear loading. The screw failure mechanism for various parameters provides an understanding of a wall panel under in-plane shear load and helps facilitate the design of the CFS shear walls sheathed with plywood. This research evaluated the performance of screw connections in cold-formed steel–framed assemblies with plywood sheathing under in-plane shear loading. The study highlights the benefits of using 12-mm-thick plywood sheathing, which increases connection strength, ductility, and energy dissipation. The use of hexagonal head screws with washers is recommended due to their higher load-carrying capacity and energy dissipation, making them ideal for buildings in disaster-prone areas. This combination is especially advantageous in seismic zones, in which flexibility and strength are crucial. Additionally, the findings suggest that although increasing CFS stud thickness from 1.5 to 2 mm offers minor improvements in shear strength and stiffness, it significantly enhances the seismic performance of sheathed panels. This knowledge can guide engineers in optimizing material choices for earthquake-resistant designs. The study results also can inform construction standards, promoting the use of screws with washers and appropriate sheathing thickness to ensure safer and more durable buildings.