Ground Motion Selection and Scaling Considerations for the CFS-NHERI Capstone 10-Story Building Specimen

Lightweight structures constructed of cold-formed steel (CFS) framing have demonstrated robust structural performance under shake table testing. However, the use of CFS framing for taller structures (>65-ft) in the North American construction industry is prohibited due to code restrictions. To contribute to understanding the seismic performance of tall CFS-constructed buildings, a 10-story full-scale CFS-framed building is planned to commence construction and preparation for shake table testing in late summer 2024. This unique specimen serves as the capstone effort to the NSF-funded Collaborative Research Program entitled: Seismic Resiliency of Repetitively Framed Mid-Rise Cold-Formed Steel Buildings (CFS-NHERI). This benchmark test, coined the CFS-NHERI 10-story building, will be conducted atop the newly upgraded 6-DOF Large High-Performance Outdoor Shake Table (LHPOST6) at NHERI@UC San Diego Experimental Facility. This test will provide a unique opportunity to investigate the system-level performance of tall CFS buildings under multi-directional seismic excitation. The selection of the test motion protocol during the planning stages is crucial to ensure that the building specimen is subject to a range of performance scenarios, most notably considering hazards scaled towards service, design, and maximum considered events with varying motion characteristics. To this end, a review of ground motion candidates and testing protocols adopted in previous large-scale tests is conducted. Performance targets of the CFS-NHERI 10-story capstone building test are subsequently defined. Candidate ground motions include twenty-two far-field and twenty-eight near-field ground motion suites from FEMA P695 and near-field ground motions as well as motions from the most recent 2023 Türkiye/Syria Earthquake sequence. The characteristics of these ground motion records are studied and different scaling methodologies, accounting for the characteristics of the test building, are employed. The final set of ground motions and scaling factors will ultimately be selected based on a comprehensive review of the available data, cross-comparison, consultation with the LHPOST6 facility, and results of a sensitivity analysis. At this stage, a preliminary testing protocol is developed to target the performance levels of the 10-story test building.

18th World Conference on Earthquake Engineering, Milan, Italy.