The new A11 viaduct at Porte des Gesvres in Nantes was erected by Sarens, on behalf of Bouygues Travaux Publics Régions France and Vinci Autoroutes. This was a delicate, precise operation, since the curved steel structure, 110 m long and weighing 740 tonnes, had to be positioned in just 6 hours! Indeed, the A11, a freeway currently used by over 90,000 vehicles a day, could only be closed during this overnight window.
Sarens Technical Solutions & Engineering therefore opted for a combination of 4 Kamag SPMTs (Self-Propelled Modular Transports) with 6 axle lines. In addition, they used 4 CS450 towers with 12 elements on one side, and 4 CS450 towers with 10 elements on the other side to cover the 70 m before dismantling the bridge using a jack. The choice of these lathes enabled the team to complete the jacking work more quickly, which was particularly important given the time constraints.
This is the second viaduct to be installed in the region, the first being the connection between the A11 and the eastern ring road, which was completed in early 2023.
The extension of this section will link the Nantes ring road to the A11 freeway. This route links Paris and Nantes, and the extension work should cut journey times by 30%. They will increase road traffic on the section, which has a capacity of 115,000 vehicles per day, by up to 25%, and reduce journey times by 30%.
