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Smart Structures and Systems
  Volume 15, Number 1, January 2015 , pages 081-97

Blind modal identification of output-only non-proportionally-damped structures by time-frequency complex independent component analysis
Satish Nagarajaiah and Yongchao Yang

    Recently, a new output-only modal identification method based on time-frequency independent component analysis (ICA) has been developed by the authors and shown to be useful for even highly-damped structures. In many cases, it is of interest to identify the complex modes of structures with non-proportional damping. This study extends the time-frequency ICA based method to a complex ICA formulation for output-only modal identification of non-proportionally-damped structures. The connection is established between complex ICA model and the complex-valued modal expansion with sparse time-frequency representation, thereby blindly separating the measured structural responses into the complex mode matrix and complex-valued modal responses. Numerical simulation on a non-proportionally-damped system, laboratory experiment on a highly-damped three-story frame, and a real-world highly-damped base-isolated structure identification example demonstrate the capability of the time-frequency complex ICA method for identification of structures with complex modes in a straightforward and efficient manner.
Key Words
    output-only modal identification; complex modes; non-proportional damping; blind source separation; complex independent component analysis; time-frequency analysis
Satish Nagarajaiah: Department of Civil and Environmental Engineering and Department of Mechanical Engineering,
Rice Univ., Houston, TX, USA
Yongchao Yang: Department of Civil and Environmental Engineering, Rice Univ., Houston, TX, USA

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