Modal parameter identification based on variational mode decomposition

An out-put only modal parameter identification technique based on variational mode decomposition (VMD) was developed for civil structures. The free decay response (FDR, which can be recorded in free vibration tests or reconstructed from ambient vibration responses) of a structure was decomposed into modal responses using VMD. The instantaneous modal frequencies were calculated from the modal responses with the empirical envelope (EE) method, while the instantaneous modal damping ratios were calculated using a newly developed procedure. Mode shape vectors were indentified using the modal responses extracted from the FDRs by processing all the available sensors data on the structure. The calculated instantaneous modal frequencies and instantaneous modal damping ratios can capture any transient modal parameter variations. A series of numerical and experimental case studies were conducted to demonstrate the efficiency and highlight the superiority of the proposed method in modal parameter identification using free vibration or ambient vibration data. The proposed method was proved to be efficient in modal parameter identification for both linear and nonlinear systems, and can be applied to systems with closely spaced modes and sudden modal parameter variations. © 2020, Editorial Office of Journal of Vibration and Shock. All right reserved.