GNGTS 2015 - Atti del 34° Convegno Nazionale

GNGTS 2015 S essione 2.3 223 ambient vibration survey of these bridges. In this research project, ambient vibration testing was adopted to determine the dynamic characteristics of the bridge (with five-six cars per hour, approximately, the typical traffic entity). This working assumption for the experimental tests – strictly required by the Municipality of Pietratagliata – enabled the use of additional excitation sources and resulted in additional difficulty for the experimental analysis and interpretation of test measurements (Alaggio et al., 2015). The instrumentation chain was based on a 16-channels data acquisition system, connected to a remote PC. The sensors consisted in 16 Sprengnether mono-axial servo-accelerometers operating in the frequency range 0-25 Hz. Each sensor was provided with a pre-amplifier having variable gain controlled by the remote computer. The signal was transmitted in differential modality to the acquisition system, where it was converted in single-ended modality to be filtered and passed to a 16-bit A/D converter, before being stored Fig. 1 – Pietratagliata bridge: a) general view; b) technical drawings with lateral view, plan and transversal cross- section (U= upstream; D= downstream); c) stays-to-tower and stays-to-deck connection details.