Vibration-Based Structural Health Monitoring of a Historic Arch Bridge

The Brivio bridge is a reinforced concrete tied-arch bridge composed of three spans of 44m that crosses the Adda River in the Province of Lecco (northern Italy). The structure was completed in 1917, and - despite its age - it is still a crucial node for the vehicular traffic of the Lombardy regional network. Within a research program promoted by the Lombardy Region, a dynamic monitoring system was installed in the bridge. The paper presents the preliminary activities carried out before the monitoring period and selected results of the first two years of continuous monitoring. Special emphasis is given to the Structural Health Monitoring methodology implemented for the detection of anomaly occurrence using natural frequencies and mode shapes. A fully automated modal estimation and tracking software was developed and led to the identification of seven vibration modes for each span. As expected, temperature variations significantly affect natural frequencies, whereas no remarkable changes in mode shapes have been detected so far.