Mode shape scaling and implications in modal identification with known input

This study proposes a mode shape scaling and parameterization scheme for modal identification with known input. Through the derivation of the equations for known input modal identification using the proposed mode shape scaling and parameterization scheme, the study provides insight into the relationship between the identified modal parameters and information required in the forced vibration test. In typical applications of modal identifications, when there is sufficient amount of data, the formulation using the proposed mode shape scaling and parameterization scheme shows that it allows modal parameters to be determined efficiently in a globally identifiable manner. An illustrative example using synthetic data is provided in this study. The findings show that an appropriate mode shape scaling and normalization scheme could reduce the information required in the modal identification procedure for some modal parameters, i.e. natural frequencies, damping ratios and mode shapes. This significantly simplifies the procedure of the forced vibration test, and hence, it can be carried out in a more robust manner.