GNGTS 2014 - Atti del 33° Convegno Nazionale

number of floors (N) (Goel and Chopra, 1997; Hong and Hwang, 2000; Messele and Tadese, 2002; Crowley and Pinho, 2006; Panzera et al. , 2013). In the present study ��� ������� �������� �� ��������� �� ��������� ������� ������������ the dynamic response of buildings is estimated through experimental measurements based on microtremor recordings. ��� ���������� �� �������� ����� ����� The horizontal to vertical noise ratio (HVNR) and the standard noise spectral ratio (SSNR) techniques were used to identify the building’s frequencies. Measurements were performed in 5 buildings distinguished according to their construction typology 2 masonry (MA) and 3 reinforced concrete (RC) buildings. As fundamental period for each building we considered the peak with the higher amplitude in both HVNR and SSNR. In each building, 10 minutes length of ambient noise were recorded both at the top and at the ground floor. ��������� �� ��� ���������� ��������� �� ��� ������ ������� According to the guidelines suggested by the SESAME (2004), time windows of 10 s were considered, selecting the most stationary part and not including transients associated to very close sources. Fourier spectra were calculated �� ��� ��������� in the frequency band 0.5–15 Hz ��� �������� ����� � ���������� ������� �� ��������� ��������� �� � �� �� ��� and smoothed using a triangular average on frequency intervals of ± 5% of the central frequency. Fig. 2 – a-b) examples of HVNR, directional resonance diagrams and polarization plots observed in the plateau (a) and cliff (b) areas of Lampedusa; c) map of the fundamental frequencies experimentally detected at Lampedusa. 206 GNGTS 2014 S essione 2.2