The Brivio bridge, built between June 1912 and May 1917, crosses the Adda river between the small towns of Brivio and Cisano Bergamasco, about 50 km North-East of Milan. The overall structure is 132.0 m long and consists of three reinforced concrete tied arches spanning 44.0 m each, with the arches being in principle perfectly equal; the three spans are supported by two piers, whose foundations are built in the river bed, and two end abutments. As the historic bridge still represents a crucial node for the vehicular traffic in Lombardy and a joint research between Lombardy Region and Politecnico di Milano is ongoing to define guidelines for the assessment and maintenance of key infrastructures, it was decided to install a continuous dynamic monitoring system in the Brivio bridge. Before the monitoring, preliminary investigations were carried out and included documentary research in the archives of Brivio town hall and National Roadway Authority (ANAS), visual inspection and geometric survey of the arches intrados, ambient vibration survey, mechanical characterization of the concrete materials (arches and hangers), finite element modeling of each span and vibration-based model tuning. The present paper, after a concise summary of the multidisciplinary activities carried out on the different spans of the bridge, is mainly focused on structural modeling and vibration-based model updating; in order to take advantage of the similarity of the different tied arches, a simple system identification technique was used to update the models. The application of this technique provided optimal models accurately fitting the identified modal parameters of each bridge; in addition, the identified structural parameters are in good agreement with the available characterization of the materials.