An innovative ambient identification method

Ambient modal identification, also known as Operational Modal Analysis (OMA),aims to identify the modal properties of a structure based on vibration data collected whenthe structure is under its operating conditions, i.e., no initial excitation or known artificial excitation.This procedure for testing and/or monitoring historic buildings, is particularly attractivefor civil engineers concerned with the safety of complex historic structures. However,since the external force is not recorded, the identification methods have to be more sophisticatedand based on stochastic mechanics. In this context, this contribution will introduce aninnovative ambient identification method based on applying the Hilbert Transform, to obtainthe analytical representation of the system response in terms of the correlation function. Inparticular, it is worth stressing that the analytical signal is a complex representation of a timedomain signal: the real part is the time domain signal itself, while the imaginary part is itsHilbert transform. A 3DOF numerical example will be presented to show the accuracy of theproposed procedure, and comparisons with data from other methods assess the reliability ofthe approach.