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

Abstract

Buildings constructed with cold formed steel (CFS) framing have shown great potential as a modern efficient building system. However, full understanding of their lateral structural behavior, particularly the contribution from non-designated systems, under seismic events is limited. The current North American Standards provide information that can be used to design CFS framed steel sheet shear walls which meet the seismic demands for low- 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 primarily on experiments involving shear walls subject to quasi-static monotonic and reversed cyclic loading protocols. In the current research project, shear walls placed in-line with gravity walls were 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 by a CFS archetype building designed at 4 and 10 stories, as well as available experimental data. This paper documents the experimental response and physical damage observations of four wall specimen pairs in the test program. These particular specimens adopt compression chord stud packs with a steel tension tie-rods assembly, are either unfinished or finished on their exterior face, and laid out in a symmetric or asymmetric fashion. In addition, both Type I and “Type II” shear wall detailing are investigated.