Lateral Response of Cold-Formed Steel Framed Steel Sheathed In-line Wall Systems Detailed for Mid-Rise Buildings

The North American construction industry has seen substantial growth in the use of cold-formed steel (CFS) framing for mid-rise buildings in recent years. In seismic zones, CFS-framed buildings utilize shear walls to provide the primary lateral resistance to earthquake induced loads. While OSB (Oriented Strand Board) 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 non-combustible material, amongst other benefits. While CFS framing systems have the potential to support the need for resilient housing, the use of steel sheet sheathed CFS framed walls has been restricted due to gaps in understanding its structural behavior and by the limited guidelines provided in design standards. Additionally, the contribution from non-designated lateral systems and portions of the building system not specifically designated by the design engineers, has not been substantially investigated through experiments. To address the paucity of data regarding CFS-framed wall response within actual wall lines of buildings, a two-phased experimental effort was conducted. In the first phase, CFS-framed wall lines were tested on the large high performance outdoor shake table at UC San Diego. Subsequently, select specimens were tested using the fixed reaction wall facilities at UC San Diego by imposing simulated seismic loading at quasi-static rates. The present report documents the second phase of this effort. Interested readers may refer to Singh et al. (2021b) and Singh et al. (2021a) for details of the first test phase. In the quasi-static phase, wall line assemblies were fabricated and tested with shear walls placed in-line with gravity walls under a reverse cyclic displacement controlled loading CUREE protocol. The selection of wall details was motivated using a designed CFS archetype building, of 4 and 10 stories, harmonized with available experimental data. The shear walls chord stud packs include tie-down assemblies consistent with multi-story detailing. Specimens were either unfinished or finished, and the shear walls 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 report, the impact of test variables governing the structural and nonstructural detailing of CFS framed walls are quantified.

Part II: Quasi-Static Test Phase. Structural Systems Research Report SSRP-19/06, University of California San Diego, La Jolla, CA