One-year dynamic monitoring of a centenary iron arch bridge

The San Michele bridge is an iron arch bridge that crosses the Adda river about 50 km far from Milan. The bridge, built in 1889, is the most important monument of XIX century iron architecture in Italy and is still used as roadway and railway bridge. In order to assess the bridge structural condition, ambient vibration tests were performed in 2009 and suggested the opportunity of installing a dynamic monitoring system in the bridge with Structural Health Monitoring purpose. Hence, a continuous monitoring system was designed and it is now active on the bridge since late November 2011. The paper, after a brief summary of the experimental studies developed since 2009, describes the monitoring system and the software developed in LabVIEW for automated processing the collected data. Subsequently, the tracking of modal frequencies automatically identified over more than one year is presented and the effects of environmental and operational conditions on the bridge dynamic response are discussed.