Instantaneous identification of localized non-linearities in steel framed structures

This paper discusses the characteristics of time-frequency estimators to be used in the identification of systems with localized non-linearities. The common idea underlying this research is that, for certain classes of structural response signals, the availability of a limited number of experimental data can be partially obviated by taking into account the “localisation” in time of the frequency components of the signals. Time-frequency techniques for structural identification are reported that extend the definition of instantaneous time-frequency estimators and Gabor instantaneous estimators were extracted from non-stationary vibration signals. In order to foresee their validity on the basis of measured data, methods were applied to seismic responses obtained from numerical tests conducted on steel frames. The results obtained made it possible to evaluate the characteristics of time-frequency identification techniques as well as their efficiency when applied to non-linear structures.