In central Italy, BESIX is doubling State Road 318, in partnership with Donati S.p.A. This is an essential infrastructure project for the region as it will greatly improve the connection and traffic flow between the cities of Perugia and Ancona.
Alongside two two-lane tunnels and a bridge, another notable feature of the project is the Tre Vescovi viaduct. The ‘Viadotto Tre Vescovi’ is a mixed steel-concrete viaduct of 129.5 metres length, composed of three segments of 37 metres, 55.5 metres, and 37 metres. This single deck bridge has a total width of 11.45 metres with a road width of 9.35 metres for two traffic lanes in the same direction and weighs 458 tonnes (367 tonnes for the viaduct itself and 91 tonnes for the metal bars), quite a mastodont!
After careful preparations, the viaduct was launched in the first phase from 22 February to 27 February using a spindle bar system. This system involves steel bars connected to the back of the viaduct and hydraulic jacks pulling them, and therefore the viaduct too. The method pulls about 12 metres a day.
The spindle bar system is a method used to gradually move and position bridge parts into place during construction, allowing for the construction of a bridge from one side only. In Valfabbrica, the bridge is being assembled and launched with this system in three phases, because there is not enough space to assemble it entirely and launch it in one or even two phases. The first part of the bridge was assembled on one side of the bridge with the steel nose, the structure used for the launch, and then gradually moved horizontally till enough space had been freed up to build the second part of the bridge. This will take about two months, after which the second phase and later the third phase of the launch will take place.
The main advantage of the spindle bar system is for bridges uphill or downhill, so with a slope higher than 5°. This system allows for a controlled and precise launching of the bridge.
Congratulations to our colleagues in Italy for reaching this major milestone of launching the first part of the bridge. After the second and third phases of the launching have taken place, the bridge deck will completely span above the valley, another essential milestone in this major infrastructure project.
