Parametric modal identification of time-varying structures and the validation approach of modal parameters

This paper investigates the problem of output-only modal parameter estimation of time-varying structures. A two-stage least square method for modal parameter estimation of time-varying structures is presented, consisting of a least square complex frequency-domain stage for the modal parameter estimation of all discrete time samples and a weighted least square stage for the estimation of continuous-time-represented modal parameters. This paper introduces a fuzzy-clustering-based approach for validating and sifting the modal parameters and develops four modal assurance criterion-based distance functions to improve the quality of clustering of operational mode shapes. Furthermore, the proposed method has been validated by a simulation example and a laboratory experiment.