Conservazione e uso dei ponti metallici: il caso del ponte della Becca

Since 18th century, progresses in iron industry allowed the spread of metal bridges in UK, US and France. These bridges were characterized by various construction types. In Italy, apart from some rare previous example, metal bridges spread only after 1860s. In a first phase, financial capital, materials, and designers were mainly foreigners; only since the end of the century Italian enterprises developed. Most of the bridges were continuous beam bridges on masonry piers; initially the most common type was the lattice truss bridge, subsequently trusses made of square panels with double bracing prevailed. Many bridges built before World War II were demolished and rebuilt because they no longer met the needs of traffic and safety, or because damaged by exceptional events. The Ponte della Becca – at the confluence of Po and Ticino rivers, next to Pavia – is a 1040 m long continuous-beam trussed bridge. The bridge was inaugurated in 1912, but bombings of 1944 made him unfit for use until 1950. Nowadays the state of preservation of the bridge is poor: in addition to widespread oxidation, some piers suffered settlements. In November 2010, a pier underwent a major settlement and the bridge was strengthened building two new piers adjacent to the settled one, which collapsed in March 2011. Since then, heavy vehicles are prohibited from passing on the bridge. Conservation, strengthening and use of the Ponte della Becca are complex issues. The bridge has a fundamental role in the local transport. A performance adjustment would involve significant investments, but also invasive interventions without solving the problems due to poor track width; the Provincial Administration has intention to build a new bridge parallel to the existent, which would be preserved for pedestrian use; the limitation of the importance of the bridge as a transit route is likely to limit the possibility of access to adequate funding for its conservation. The article presents some critical reflections on this issue.