GNGTS 2016 - Atti del 35° Convegno Nazionale

GNGTS 2016 S essione 2.3 423 For the current analysis themaximumfrequencydrop is between34%and46%(corresponding to a maximum roof drift of 1.6 ‰ and 1.9 ‰ respectively) with a mean value of 40% for a roof drift equal to 1.79 ‰, corresponding to the maximum displacement of 21.48 mm in the Ch.13 (as visible in the maximum displacement values reported in Fig. 3) A time-frequency analysis of the measured seismic response of the structure, carried out using time-variant AutoRegressive eXogeneous models (ARX) (Ljung, 1987), has confirmed this frequency drop during the earthquake, with a minimum reached frequency of 2.6 Hz for the first mode that implies a drop of 39% (Fig. 2). In Fig. 3 experimental displacements and driftsmeasured on the structure are comparedwith the ones obtained by the SMAV model using the median curve for the frequency drop estimation. The comparison shows a good agreement between the displacements and the inter-story drifts obtained with the SMAV model and the experimental ones, both in terms of spatial distribution and maximum values. The maximum values of deformation are for the both cases Fig. 2 – Time-frequency analysis of the first vibrational mode during the August 24, 2016 earthquake. Fig. 3 – Comparison between experimental data and the SMAV model results.