Evolution of Modal Characteristics and Model Comparison for a 10-Story Cold-Formed Steel Framed Building under Seismic Excitation

A 10-story cold-formed steel-framed building, coined CFS10, was constructed and tested at the 6-DOF Large High-Performance Outdoor Shake Table (LHPOST6) at UC San Diego in the summer of 2025. Seismic tests targeted Service-Level Earthquake (SLE), Design Earthquake (DE) and risk-targeted Maximum-Considered Earthquake (MCER) hazards and were followed by live fire compartment tests. This landmark full-scale building specimen was designed beyond current code limits with advances in steel sheet sheathed shear walls and heavy chord stud details proofed in complementary component test programs, while also incorporating a wide range of realistic nonstructural systems (stairs, fire sprinkler, gas piping, glazing, etc.). The shake table testing captures the accumulation of damage to the building and its nonstructural elements during realistic seismic scenarios. In preparation for predicting building performance and to aid in ground motion selection and test protocols, a practice-oriented, phenomenological finite element (FE) model was developed. This model aimed for efficient simulation run speeds, with only essential degrees-of-freedom defined, while still seeking to capture the salient features of the specimen’s behavior to earthquake excitation. This paper discusses the modal characteristics of the CFS10 building and how those characteristics evolve as damage accumulates during the seismic testing phase. Importantly, a preliminary comparison of the experimentally extracted modal characteristics, which evolve during the test program, are compared with the aforementioned FE model predictions.

Proceedings of the International Modal Analysis Conference (IMAC) XLIV, Palm Springs, CA.