Pre-test Numerical Modeling of the CFS-NHERI 10-Story Capstone Building

The use of cold-formed steel (CFS) framing for taller structures in the North American construction industry is limited within current codified guidelines, despite its robust structural performance as observed in shake table and component-level tests. To fully utilize this form of construction and meet the growing needs of urban housing, a full-scale 10-story CFS-framed building is planned to commence construction and preparation for shake table testing at the UC San Diego 6-DOF Large High-Performance Outdoor Shake Table (LHPOST6) in late summer 2024. This landmark test program will serve as the capstone effort to the Collaborative Research Program entitled: Seismic Resiliency of Repetitively Framed Mid-Rise Cold-Formed Steel Buildings (CFS-NHERI). Courtesy of the newly upgraded LHPOST6, this unique test program will provide an opportunity to investigate the system-level performance of tall CFS buildings under multi-directional seismic excitation. In preparation for the capstone test phase, two finite element (FE) models are under development, namely: model 1 is a design-level phenomenological-based model, while model 2 is a refined, stacked wall-line FE model, each undertaken using the OpenSeesPy framework. The aim of these models is to predict the dynamic characteristics and response of this 10-story test building under different intensities of earthquake input. Model 1, a design-level FE model, is developed using a strategy adopted to predict the response of a full-scale 6-story CFS building that was tested under unidirectional shaking. The robustness of this modeling approach has been evaluated and compared against prior test results and good agreement was observed. This simplistic strategy boasts efficiency in computing by minimizing model degrees-of-freedom, assuming rigid diaphragms, lumped masses, and uniaxial spring elements to capture the lumped behaviors of the lateral load resisting shear walls, gravity walls, and tie-down systems. Model 2 boasts higher fidelity, though requires parallel computing to enhance the computational speed, with wall lines captured with a suite of discrete beam and truss elements and interconnecting springs at boundary and other connections to capture local behaviors induced along the lateral force resisting system and associated boundaries. These numerical models will be cross-compared and used for pre-test analyses and to support selection and scaling of ground motions during the full-scale shake table program.

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