Modeling seismic response of a full-scale cold-formed steel-framed building

The objective of this paper is to present finite element modeling protocols and validation studies for the seismic response of a two-story cold-formed steel-framed building with oriented strand board sheathed shear walls. Recently, shake table testing of this building was completed by the authors. The building provides an archetype for modern details of cold-formed steel construction, and provides benchmarks for the seismic response of the building system, subsystem, and components. The seismic response of buildings framed from cold-formed steel has seen little study in comparison with efforts on isolated members and shear walls. Validated building-scale models are needed to expand our understanding of the seismic response of these systems. Finite element models corresponding to the archetype building during its various test phases are developed in OpenSees and detailed herein. For cold-formed steel framed buildings accurate seismic models require consideration of components beyond the isolated shear walls, e.g. the stiffness and capacity of the gravity framing is included in the model. Such decisions require model refinement beyond what is typically performed and details for completing this effort accurately and efficiently are described herein. In addition, nonstructural components, including exterior sheathing of the gravity framing, interior gypsum sheathing for the shear walls and gravity framing, and interior partition walls, are included in the building model based on nonlinear surrogate models that utilize experimental characterization of member-fastener-sheathing response. Comparisons between the developed models and testing for natural period, story drift, accelerations, and foundation hold-down forces validate the model. Performance of the tested archetype building is better than predicted by design or typical engineering assumptions. The model developed herein provides insights into how the building achieves its beneficial performance and will be used to further quantify the lateral resistance of each subsystem and the extent of their coupling. In addition, the protocols used to develop the model herein provide a first examination of the necessary modeling characteristics for wider archetype studies of cold-formed steel-framed buildings and the development and substantiation of seismic response modification coefficients. (C) 2017 Elsevier Ltd. All rights reserved.