Experimental Performance of Full-Scale Cold-Formed Steel Buildings Under Seismic Excitations

The NSF NEESR project: Enabling the Performance-Based Design of Multi-Story Cold-Formed Steel (CFS) Structures, known simply as CFS-NEES, has entered its final year of research. Testing of two full-scale cold-formed steel framed buildings under seismic excitation at the University at Buffalo Structural Engineering Earthquake Simulation Lab (SEESL) was performed in the summer of 2013. The two-story buildings, approximately 23’ x 50’ in plan and 19’ in height, were tested in two different configurations. In the first, the engineered lateral force resisting system (LFRS), consisting of OSB sheathed shear walls, and OSB sheathed floors/diaphragms was tested—gravity walls were left unsheathed, and interior gypsum on the shear walls and interior walls were absent. In effect, this first configuration examines the LFRS that is specifically designed by the engineer. In the second building configuration the building was completely fit-out, thus the influence of the sheathed gravity walls, interior walls, etc. were all captured, providing insight on the engineered LFRS and the full building system response. System identification tests and earthquake excitations utilizing the Canoga Park and Rinaldi records were both performed. The buildings were densely instrumented and provide video, displacement, acceleration, and force measurements both globally and in local systems throughout. While the response of the entire structure is investigated, the performance of several sub-systems is also of interest, including: the ledger-framing system, floor diaphragm, multi-story shear walls, stud-sheathing-fastener connections, and non-structural elements. Aligned with the overall CFS-NEES effort, these experiments will also provide benchmarks for advancing the computational models necessary for improving performance-based design for CFS structures.