Replacement of the Siagne Viaduct
The Viaduct of Siagne is located in the town of Mandelieu-la-Napoule in the Provence-Alpes-Côte d’Azur region and overlooks the Siagne River.
This book was born in the middle of the 19th century in order to make it easier to cross the Siagne by goods, and later by travelers. This railway viaduct connects Marseille and Ventimiglia and is between two railway stations; that of Mandelieu and that of Cannes La Bocca.
Made from puddled iron, this construction consists of two flat decks, three spans and finally forms a bridge with continuous beams. The necessary rails are installed on studs fixed to the metal decking. This type of assembly is called a book with direct track laying.
Despite its historical interest, the Siagne Viaduct is not listed in the Eiffel Works Register. Its originality and the technical prowess achieved for this viaduct (including its metal arches) make it still a flagship structure of the region.
The Siagne Viaduct is one of the last iron rail bridges because the majority of these structures have been replaced over time.
The metal frame of the structure is of 360 tons
The bridge is composed of 2 decks of 83 meters.
The realization of the piers required 400m ² of concrete as well as 850m ² of backfilling.
1862: Year where the Siagne Viaduct was created
1882: The piles of the viaduct undergo heavy damage following a flood. Significant work is being done to stabilize the structure. Three additional piles are built to replace the old ones and a fourth span is installed.
1932-1936: The railway bridge must be reinforced in order to support the traffic of ever heavier vehicles. To relieve the not-so-resistant lattice bars, upper arches are added to the structure.
1944: World War II could have been fatal for the Mandelieu Bridge because the area was heavily bombed, and the central pile had been completely destroyed. It was not until 1944 that the repairs started.
2010: Fatigue cracks are discovered on three main parts of the bridge as well as an advanced corrosion on the structure, one of the main disadvantages of iron puddles.
The Viaduc de la Siagne has faced the challenges of time. Despite periodic reclamation, the book shows today signs of worrying but especially irreversible weakness.
Rail traffic is maintained but the situation of the viaduct requires an extreme slowdown of the trains during their crossing of Siagne. Indeed, while the average speed of trains is 140km / h, the crossing on the Viaduct is set at 40km / h.
Since the repair of the structure was deemed impossible, the replacement of the metal part and the reinforcement of the piles became a necessity for the region.
MBB Works – Matiere®
The replacement of the old Siagne Viaduct was awarded to our Belgian subsidiary MBB (studies, manufacturing, installation), and the installation of the metal beams was entrusted to our Matière® teams.
In order not to delay the completion of the work, the characteristics of the new structure were modeled on the old viaduct. Thus, we will find two metallic decks of 83 meters long contiguous to each other. The piles and abutments do not show any particular problem, they do not require specific interventions except for the addition of micropiles and injections.
Visually, the Siagne Viaduct has undergone some modifications. In a spirit of modernity but also of durability, metal arches give way to horizontal metal structures.
The replacement of the Siagne Viaduct is also an opportunity to review the new regulations in terms of railway traffic (seismic rules, noise pollution …) but also environmental constraints.
The work in question is in fact in a particularly protected area. During the works, care was taken to preserve the flora and fauna around the Viaduct and the classified wooded area and the wetlands.
This is the first work under MBB entity and the structure has been finalized in 2018.