Issue 46

S. Ivorra et alii, Frattura ed Integrità Strutturale, 46 (2018) 203-215; DOI: 10.3221/IGF-ESIS.46.19 208 Figure 5 : Devices used for the dynamic monitoring of the tower. Left: National Instruments DAQ. Right: Seismic Piezoelectric accelerometers situated on the top of the tower. With this setup several signals have been recorded to analyze the resonance effects generated by the bell’s swinging. Each recording had a duration of 720 s and a sampling frequency of 1024 Hz. The recordings were acquired in five different dynamic forcing conditions:  Ambient Noise;  Swinging of the bigger bell (SS Medici) alone; (N-S direction)  Swinging of the second bigger bell (Aurelio Marena) alone; (N-S direction)  Swinging of the bell Isabella Ciccolella alone; (N-S direction)  Swinging of all bells together. (N-S direction) P RELIMINARY RESULTS AND ANALYSIS o understand the response of the bell tower to the dynamic forces generated by the bells, the top N-S and E-W accelerometers were firstly considered. Fig. 6 shows the ambient response of these accelerometers. Figure 6 : Acceleration recorded on the top of the tower under ambient vibrations at 1024 Hz sampling frequency. Up: E-W direction. Bottom: N-S direction Time [s] 700s 650s 600s 550s 500s 450s 400s 350s 300s 250s 200s 150s 100s 50s 0s Accelertaion (g) 0,005 0 -0,005 Time [s] 700s 650s 600s 550s 500s 450s 400s 350s 300s 250s 200s 150s 100s 50s 0s Accelertaion (g) 0,005 0 -0,005 T