A novel identification procedure from ambient vibration data
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MODELLING AND ANALYSIS OF MECHANICAL SYSTEMS DYNAMICS
A novel identification procedure from ambient vibration data A. Di. Matteo . C. Masnata . S. Russotto . C. Bilello . A. Pirrotta
Received: 9 March 2020 / Accepted: 15 November 2020 Ó The Author(s) 2020
Abstract Ambient vibration modal identification, also known as Operational Modal Analysis, aims to identify the modal properties of a structure based on vibration data collected when the 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 attractive for 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 sophisticated and based on stochastic mechanics. In this context, this contribution will introduce an innovative ambient identification method based on applying the Hilbert Transform, to obtain the analytical representation of the system response in terms of the correlation function. In particular, it is worth stressing that the analytical signal is a complex representation of a time domain signal: the real part is the time domain signal itself, while the imaginary part is its Hilbert transform. A 3DOF numerical example will be presented to show the accuracy of the proposed procedure, and A. Di. Matteo (&) C. Masnata S. Russotto A. Pirrotta Dipartimento di Ingegneria, Universita` degli Studi di Palermo, Viale delle Scienze, 90128 Palermo, Italy e-mail: [email protected] C. Bilello ABGroup Ingegneria e Servizi Tecnici integrati, Sciacca, Italy
comparisons with data from other methods assess the reliability of the approach. Finally, the identification method will be extended to the real case study of the Chiaramonte Palace, a historic building located in Palermo and known as ‘‘Steri’’. Keywords Operational modal analysis Hilbert transform Correlation function Analytical signal
1 Introduction Most of the literature concerning dynamic identification deals with the estimation of the modal parameters (frequencies, damping coefficients and mode shapes) of a structure starting from the measurement of both the dynamic input and structural response signals. In the past, the dynamic identification of the modal characteristics of buildings was generally based on force vibration tests involving impact tests or other complex setups, applying several types of input exciters directly in-situ. In this context, it is customary to refer to the modal analysis based on artificial forced excitations as Experimental Modal Analysis (EMA) which presupposes the use of both known input and structural response measurements to estimate modal parameters [1, 2]. Based on the number of reference points used to measure data, numerous modal identification algorithms have been developed such as Single-Input/
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Meccanica
Single-Output (SISO), Single-Input/ Multi-Output (SIMO)
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