Measurement of the vibration response of the medieval Maddalena Bridge (Italy).

Nowadays the structural health monitoring of ancient masonry constructions is a key issue. In this context, one very important approach is the use of wholly nondestructive techniques, such as measurement of the environmental vibrations affecting structures. This paper reports on a vibration measurements campaign performed on the medieval Maddalena Bridge in Borgo a Mozzano, near Lucca, also known as "Ponte del Diavolo" (Devil's Bridge), one of the most fascinating old masonry bridges in Italy. The bridge, built in the 11th century, crosses the Serchio River for about one hundred meters with four circular arcades. The monitoring system has been mainly aimed at evaluating the dynamic response of the bridge to vibrations originating in the adjacent railway and two nearby roads. Analysis of the recorded data via Operational Modal Analysis techniques has furnished the natural frequencies and mode shapes of the structure and the corresponding damping ratios.