Time-Frequency Blind Source Separation Using Independent Component Analysis for Output-Only Modal Identification of Highly Damped Structures
Publication: Journal of Structural Engineering
Volume 139, Issue 10
Abstract
Output-only algorithms are needed for modal identification when only structural responses are available. The recent years have witnessed the fast development of blind source separation (BSS) as a promising signal processing technique, pursuing to recover the sources using only the measured mixtures. As the most popular tool solving the BSS problem, independent component analysis (ICA) is able to directly extract the time-domain modal responses, which are viewed as virtual sources, from the observed system responses; however, it has been shown that ICA loses accuracy in the presence of higher-level damping. In this study, the modal identification issue, which is incorporated into the BSS formulation, is transformed into a time-frequency framework. The sparse time-frequency representations of the monotone modal responses are proposed as the targeted independent sources hidden in those of the system responses which have been short-time Fourier-transformed (STFT); they can then be efficiently extracted by ICA, whereby the time-domain modal responses are recovered such that the modal parameters are readily obtained. The simulation results of a multidegree-of-freedom system illustrate that the proposed output-only STFT-ICA method is capable of accurately identifying modal information of lightly and highly damped structures, even in the presence of heavy noise and nonstationary excitation. The laboratory experiment on a highly damped three-story frame and the analysis of the real measured seismic responses of the University of Southern California hospital building demonstrate the capability of the method to perform blind modal identification in practical applications.
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Acknowledgments
The authors thank the researchers at Helsinki University of Technology for sharing the FastICA software package (available at http://www.cis.hut.fi/projects/ica/fastica/). Partial funding for this study provided by Fugro International is gratefully acknowledged. The authors also acknowledge useful discussions with Dr. Sriram Narasimhan of University of Waterloo.
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© 2013 American Society of Civil Engineers.
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Received: Sep 2, 2011
Accepted: Mar 30, 2012
Published online: Apr 11, 2012
Published in print: Oct 1, 2013
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