Rehabilitation and seismic upgrading of the masonry arch bridge over the Magra river in Villafranca

The paper deals with the rehabilitation of an historical masonry bridge crossing the Magra river and connecting the small towns of Mulazzo and Villafranca in the northern part of Tuscany (I).The masonry arch bridge, characterized by eight arches spanning 19 m around each and by around 12 m height intermediate masonry piers on shallow foundations, was built in 1874. Since the original carriageway width was not sufficient to allow two lanes, in 1961 it was widened by means of two lateral prestressed concrete beams, supported by the piers, so hiding the arches and modifying severely the original aspect of the bridge itself. In 2011, during the Magra flooding, two arches on the Mulazzo side collapsed due to scour of the extreme pier. The reconstruction the collapsed arches and rehabilitation and the strengthening of the bridge, which has been completed last year, is discussed and the execution of the interventions, which has performed without erection of temporary support in the riverbed, is also illustrated. Particular attention is devoted to the original solutions which have been adopted for the full seismic upgrading of the bridge according to the Italian Building Code currently in force, recovering the original architectural aspect of the bridge and widening the carriageway as well.