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

Buildings constructed with cold-formed steel (CFS) framing have shown great potential as a modern load resisting system. However, understanding regarding their structural behavior, particularly the contributions from non-designated systems, under earthquake events is limited. The current North American Standards, AISI S240-15 (2015) and AISI S400-15 (2015), provide guidance for design of CFS-framed shear walls, which meet the seismic demands for low-rise to mid-rise (3-6 story) buildings. However, there is a paucity in experimental data to support design guidelines for taller, mid-rise (>6 stories) and high-rise buildings (>10 stories), where large lateral load resistance is required. Moreover, existing code guidelines are based on experiments involving individual shear walls subject to quasi-static monotonic and/or reversed cyclic loading protocols. In the current research project, single and pairs of shear walls are placed in-line with gravity walls and tested at full-scale first under a sequence of increasing amplitude (in-plane) earthquake motions, and subsequently (for select specimens) under slow monotonic pull conditions to failure. Experiments were performed at the NHERI Large High-Performance Outdoor Shake Table at the University of California, San Diego. The selection of wall details was motivated using a designed CFS archetype building, of 4 and 10 stories, harmonized with available experimental data. Shear wall segments were detailed with tie-down assemblies consisting of compression stud packs and tension tie-rods with a single face sheathed with steel sheet. This report documents the experimental program, response and physical damage observations of specimen configurations in the test program which include specimens in an unfinished or finished, symmetric or asymmetric, Type I or “Type II” design configuration, with or without a window opening.

Part I: Shake Table Test Phase. Structural Systems Research Report SSRP-19/05, University of California San Diego, La Jolla, CA