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Modeling and analysis of multi-story cold-formed steel building for performance-based seismic design

The objective of talk is to present the modeling and analysis effort of the nonlinear seismic response of a cold-formed steel framed building. The two-story building of the Cold-Formed Steel – Network for Earthquake Engineering Simulation (CFS-NEES) project is analyzed using OpenSees. Full-scale shake table tests show that the building designed and built to current specifications is far more rigid than previous simulation models with the shear wall stiffness only. The stiffness of steel frames, gravity and internal walls and semi-rigid diaphragm was added to 3D finite element model for its calibration using test data. P-Delta effects are included in the model with the consideration of system stability. Free vibration analysis and time history analyses results of the updated model are compared with test results. Recorded responses of simulation: story drift, base shear, and more local measures, such as hold down forces, are employed as indicators of structural performance and possible failure. Incremental dynamic analysis (IDA) of the model using the far field earthquake record suite of FEMA P695 provides statistical insights into the seismic response of this cold-formed steel building. Post processing of IDA outputs initiates the modification of response modification factor in current design specifications. The combined results of simulation and test are expected to foster understanding of full system-performance of cold-formed steel framed buildings under earthquake excitation and to provide engineers with practical guidance on the level of model sophistication required to predict behavior.

Author(s):

Jiazhen Leng    
Johns Hopkins Univeristy
United States

Benjamin Schafer    
Johns Hopkins Univeristy
United States

Stephen Buonopane    
Bucknell University
United States