Blind modal identification of non‐classically damped structures under non‐stationary excitations. Issue 6 (12th August 2016) - Ghahari, S. F.
Summary: In the present paper, we extend a previously developed blind modal identification method to systems with non‐classical damping, which have complex‐valued mode shapes. Unlike conventional output‐only identification methods, blind modal identification method can provide modal property estimates when the input excitations are unknown and non‐stationary (e.g., for systems equipped with added dampers or soil–structure problems). In earlier work, we have developed a technique that can be used for non‐classically damped systems, but it is only applicable to stationary (i.e., ambient) excitations. Herein, we present an extension to non‐classically damped systems under non‐stationary (e.g., seismic) excitations. The proposed method yields mode shapes, natural frequencies and damping ratios, sequentially. A critical ingredient in this new method is a combination of generalized eigen‐decomposition and rough–fuzzy c ‐means clustering techniques, which are employed to identify the complex‐valued mode shapes. The accuracy of the proposed method is verified through a simulated but realistic example. Copyright © 2016 John Wiley & Sons, Ltd.