GNGTS 2015 - Atti del 34° Convegno Nazionale

224 GNGTS 2015 S essione 2.3 in different formats. Based on the dynamic estimations obtained from preliminary FE studies carried out on a simplified numerical model of the bridge (Alaggio et al., 2015), the instruments were located at 16 selected points, according to two different setups (Fig. 2a). Time acquisition during tests was set equal to 45’, corresponding to about 1600 times the expected vibration period of the fundamental mode of the bridge. The sampling rate used during acquisition was 400 Hz. During post-processing analysis, the signal data were further decimated in time by a factor 10, giving a baseband for the analysis ranging till to 20 Hz. Natural frequencies, damping ratios and mode shape components were estimated by means of the Enhanced frequency Domain Decomposition (EFDD) technique available in the commercial software ARTeMIS (ARTeMIS Extractor Software, 2002). Several repeated identifications were performed separately, either on the same data set or on partial data using different baseband and different sets of data, so that the estimation of the detected vibration modes could be optimized. In the case of the damping factors, obtained from the experimental power spectral density measurements, the Fig. 2 – Dynamic experiments. a) instrumental layout; b) overview and details of the FE-OPT model (ABAQUS/ Standard); c) 3D view of the identified modal shapes (ABAQUS/Standard).