Shake Table Testing of a Three‐Story Nonstructural Bypass‐Framed Cold‐Formed Steel Façade With Drift Clips

Interstory drift is a primary cause of seismic damage to building elements that span vertically between floors, such as exterior façade walls. To study this issue, a three‐story bypass‐framed cold‐formed steel exterior wall subassembly was incorporated into a recent test of a full‐scale 10‐story mass timber building at the LHPOST6 shake table facility at UC San Diego. A major objective of the test was to investigate seismically resilient details for nonstructural elements. Thus, the subassembly was designed with drift clips and a corner expansion joint to prevent interstory drift‐induced seismic damage. This paper discusses the design, detailing, and performance of the subassembly during the shake table test program. Overall, the drift clip system was found to be effective at reducing wall drifts as intended, and the expansion joint prevented corner damage entirely. However, binding of the drift clips was observed, preventing the wall from sliding freely as assumed during design. One result of this binding was that screw pullout occurred at many clip connections on the uppermost floor over the course of repeated earthquake excitations. Ultimately, damage to sheathing, windows, and exterior cladding was avoided altogether despite connection pullout. Lessons learned offer valuable insight toward improving the design and detailing practice of similar assemblies being considered for implementation.