The North American construction industry has seen substantial growth in the use of cold-formed steel (CFS) framing for midrise buildings in recent years. In seismic zones, CFS-framed buildings utilize shear walls to provide the primary lateral resistance to earthquake induced loads. Although oriented strand board (OSB) and plywood panels have been traditionally used as the sheathing material for these essential components, more recently, steel sheet sheathing has emerged as a novel strategy due to its strength, ductility, ease of installation, and use of noncombustible material, among other benefits. To address the paucity of data regarding CFS-framed shear wall response within actual wall lines of buildings, a two-phased experimental effort was conducted. Wall-line assemblies were fabricated and tested with shear walls placed in-line with gravity walls. The shear walls chord stud packs include tie-rod assemblies consistent with multistory detailing. Specimens were either unfinished or finished, and the shear walls were laid out in a symmetrical or unsymmetrical fashion within in the wall line. In addition, both Type I and Type II shear wall and anchorage detailing were investigated. In this paper, the impact of test variables governing the structural detailing of CFS-framed walls are quantified through dynamic and quasi-static tests, and a companion paper presents findings regarding the impact of architectural variations on seismic performance.

The primary objective of this work is to provide connection-level force-deformation response appropriate for standard cold-formed steel (CFS) framed steel sheet sheathed shear walls under cyclic loads. Common CFS framing designs increasingly are exploring thicker framing options so that walls can meet gravity demands, overturning demands, and seismic overstrength requirements. For the seismic performance of self-drilling screw-fastened steel sheet sheathed shear walls, the cyclic nonlinear response of the screw-fastened connection is particularly important and should incorporate the impact of shear buckling of the steel sheet on the strength and ductility of the connection. Minimal cyclic connection-level shear test data exist, especially for combinations of screw-fastened thin steel sheet and thick framing steel. A unique lap shear test following current test standards was proposed to elucidate and characterize the cyclic screw-fastened connection behavior. An asymmetric cyclic loading protocol was selected with a small displacement applied in the direction that buckles the thin steel sheet, followed by progressively larger displacements in the opposite direction. A total of 93 tests were conducted, and characterization of the observed cyclic connection response with a multilinear backbone curve appropriate for use in models is provided. Connection strength is sensitive to whether the thin steel sheet ply is buckling away from or toward the fastener head in some test series. Performance of the screw shear strength as per the standard’s provisions is evaluated. The work is intended to provide critical missing information for CFS framed steel sheet sheathed shear walls for use in both simulation and design.

Cold-formed steel (CFS) framed buildings have shown potential towards innovative and efficient building design in high seismic regions. The objective of this study is to expand the knowledge and breadth of design options of CFS construction into higher capacity lateral force resisting systems; as such, the lateral performance of CFS shear walls sheathed with fiber cement board (FCB) and composite steel-gypsum (SG) panels are the focus of this work. Three-dimensional finite element shell modeling is used by focusing on the impact of sheathing type, screw type and fastener pattern. The computational method includes fastener-based modeling which necessitates the use of experimentally-derived connection behavior. An experimental program of monotonic and cyclic fastener testing was conducted to provide shear response of CFS-to-sheathing connections with various sheathings (FCB, SG), screws, and screw spacing. Monotonic connection means are derived from the experiments and introduced in the finite element model. The numerical results demonstrate significant capacity benefits and different failure modes from traditional wood-sheathed shear walls. This work not only aims to provide an innovative and accurate computational tool for FCB- and SG-sheathed shear walls to the research community, but also to expand CFS practice through higher capacity design options. To enable adoption by practitioners, prescriptive design recommendations are provided. As the developed finite element model is computationally expensive, Pinching4 parameters from the cyclic testing are also provided to aid in the development of reduced- order models.

Cold-formed steel (CFS) framed construction has been widely adopted and used toward a modern, lightweight, and cost-efficient engineering practice across the United States. The primary objective of this work is to numerically assess the performance of CFS-framed shear walls sheathed with oriented strand board (OSB) and subjected to seismic events. A robust three-dimensional high-fidelity shell finite element model is developed and aims to provide a benchmark modeling approach able to accurately capture strength, stiffness, and failure mechanisms in these systems. Particular attention is given to the fundamental role of the connections between the CFS members and the OSB sheathing to the overall shear wall lateral response. To understand the variability in this critical connection, a series of 30 identical connection tests are performed. The robustness of the proposed computational model is validated by nine different CFS shear wall experimental studies and by a parametric analysis. The developed model is applied to provide an accurate experimentally-derived fastener-based computational tool of CFS-framed shear walls with potential use in design code expansion.