TIME-FREQUENCY DSP TO IDENTIFY MODAL PARAMETERS UNDER NON-STATIONARY AMBIENT EXCITATION APPLICATION TO REAL STRUCTURES

摘要

The importance of global vibration tests resides essentially in two aspects: they can corroborate realistic numerical models and, secondly, may constitute a starting point for localising anomalous local behaviours and possible damage occurrences. Most of the techniques currently used in structural identification under ambient excitation typically require the hypothesis of stationarity, though, in the field of civil engineering, excitation may be markedly non stationary. This consideration prompted in the past some proposals for new identification methods that, being based on time-frequency transformations, were designed to handle current types of non-stationary excitation. Hence, a novelty is that identification is based solely on the properties of slowly modulated harmonics. The second part of the paper reports some recent applications of ambient vibration testing over two ancient towers sited in Piedmont, Italy. The results of a structural identification from the signals constituted a first stage for the definition of a predictive model, which might support the intervention of consolidation.