Harmonic scaling of mode shapes for operational modal analysis

Mode shapes from operational modal analysis are normally unscaled, since the forces acting on the structure are not measured. Several methods for obtaining scaled mode shapes have been proposed in the past, some of them rather elaborate. In this paper we present and investigate using harmonic excitation at (or close to) the natural frequencies to obtain the mode shape scaling. The method is explored through simulated data, and on data from a staircase. Results are validated by comparing the results of applying the harmonic force in different points. The method is found to work very well.