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Origin and history

Viaduct du Viaur is a steel railway built between 1895 and 1902 to cross the Viaur valley on the Carmelaux-Rodez line. Designed by engineer Paul Bodin (Société des Batignolles), it uses an innovative technique of cantilever beams, unique in France. Its central span of 220 meters, articulated in three points, allows movements without additional stresses. The abutments of local gneiss masonry and Sidobre granite anchor the structure, while 3,800 tons of steel (including 3 245 rolled) compose its riveted structure. Inaugurated on October 5, 1902, it was the longest metal arc in the world at its completion, without fatal accidents during the construction site.

The construction was led by Jean Compagnon, veteran of the viaducts of Garabit and the Eiffel Tower, who died in 1900 before its completion. His successor, Gaboris, finished the assembly, whose junction of the two halves on 4 July 1902 showed only a 2 mm deviation from the planes. The viaduct symbolizes the disenclavation of the Segala, an isolated agricultural region, thanks to the political will of the elected representatives of Aveyron and Tarn. Ranked a historic monument in 2021, it was restored between 2014 and 2017 for 26 million euros, preserving its status as a technical and landscape icon.

The originality of the viaduct lies in its railway line located at the top of the structure, as opposed to the traditional girder bridges. Its five joint points (central key and abutment hooves) allow deformations under the effect of loads or temperature. The triangulated farms, located 33.39 metres apart at the base, provide optimal wind stability. The assembly used a 131-ton rolling platform, nicknamed "the whale", to assemble the half-archs in a fender. The pieces, manufactured at Creusot and Denain, were pre-assembled in Paris before they were shipped on site.

The project, which won an 1887 competition against Gustave Eiffel, was modified in 1891 to reduce the range from 250 to 220 metres, in accordance with a new regulation on metal works. The first stone was laid in 1895 by Minister Dupuy-Dutemps, and the masonries completed in 1899. The resistance tests took place in December 1902, validating his ability to withstand exceptional loads. The viaduct inspired artistic works, such as the painting Construction of a Viaduct by Henri-Marcel Magne or Joan Bodon's new Lo Pan de Froment, highlighting its cultural and economic impact on the Rouergue.

Today, the viaduct remains a major testimony of the French engineering of the Industrial Revolution. Its slender silhouette, with a height of 116 meters above the Viaur, makes it an emblematic visual landmark of the Occitanie. The cantilever technique, further developed at the Québec Bridge (1917), reached a remarkable maturity. The initial cost of 2.7 million francs (equivalent to 10 million euros) reflects the ambition of a work designed as a technological showcase, while meeting a crucial local need: connecting Rodez to Albi and the national network.

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