Drivers on the A12 between Genoa and Rapallo cross the valley of the Sori torrent in a few seconds, without realising they are travelling 105 metres above the valley floor. The viaduct carrying that roadway is a piece of Italian engineering history: commissioned by Società Autostrade, designed by the engineers Silvano Zorzi and Sergio Tolaccia, built by the Mondelli firm. It was here that the Dywidag system, with self-supporting cantilever formwork, was used for the first time in Italy; the motorway section opened to traffic on 18 December 1966.
What to see
The viaduct is 393 metres long and has six spans of varying length: the two largest measure 100 metres, flanked by two of 65 metres and, on the Genoa side, by three access spans of 35 metres. It is all reinforced concrete. The deck is single for both carriageways and 19.10 metres wide.
The three main piers are 6 metres wide and 14.55 metres deep. From each of them spring two cantilevers of 35 metres, one per side, cast with the self-supporting method that avoids resting scaffolding on the ground: a decisive choice when the valley floor is taken up by houses, or when the height is this one. Two adjacent cantilevers are then joined by a precast beam of 30 metres, and the beams of the access spans are precast as well.
Visiting
This is not a monument you visit: it is working infrastructure, and from the motorway you see nothing of it. To look at it properly you have to stand underneath, walking up the valley of the Sori torrent from the village towards the interior, along the roads that serve the upper hamlets. From there the bulk of the piers and the sequence of cantilevers become readable, and you understand why that building system was devised for narrow valley floors already covered in houses.
Our editors' tip
If you like a comparison, the twin is a few kilometres away: the Nervi viaduct has identical dimensions and construction method and differs only in total length, having two access spans instead of three. Together with the Veilino and Bisagno viaducts they form the Dywidag quartet of the Genoa-Rapallo section. Looking at two of them in the same morning is the quickest way to grasp how much that technique changed the way Ligurian valleys were crossed.