The Millau Viaduct (French: le Viaduc de Millau, IPA: is a cable-stayed bridge that spans the valley of the River Tarn near Millau in southern France.
Designed by the French structural engineer Michel Virlogeux and British architect Norman Foster, it is the tallest bridge in the world with one mast's summit at 343.0 metres (1,125 ft) above the base of the structure. It is the 15th highest bridge deck in the world, being 270 metres (890 ft)between the road deck and the ground below.The Millau Viaduct is part of the A75-A71 autoroute axis from Paris to Béziers and Montpellier. The cost of construction was approximately €400 million. It was formally inaugurated on 14 December 2004, and opened to traffic on 16 December. The bridge has been consistently ranked as one of the great engineering achievements of all time. The bridge received the 2006 International Association for Bridge and Structural Engineering Outstanding Structure Award.
History
Because of problems with traffic on the route from Paris to Spain along the stretch passing through the Tarn valley near the town of Millau, leading to congestion in the summer from holiday traffic, construction of a bridge to span the valley was required. The first plans were discussed in 1987 by CETE, and by October 1991, the decision was made to build a high crossing of the Tarn River by a structure of around 2,500 m (8,200 ft) in length. During 1993–1994 the government consulted with seven architects and eight structural engineers. During 1995–1996, a second definition study was made by five associated architect groups and structural engineers. In January 1995, the government issued a declaration of public interest to solicit design approaches for a competition. In July 1996, the jury decided in favour of a cable-stayed design with multiple spans, as proposed by the Sogelerg consortium (Michel Virlogeux and Norman Foster). The decision to proceed by grant of contract was made in May 1998; then in June 2000 the contest for the construction contract was launched, open to four consortia. In March 2001 Eiffage established the subsidiary Compagnie Eiffage du Viaduc de Millau (CEVM) and was declared winner of the contest and awarded the prime contract in August.
Possible routes
Routes of the four projects of the A75 autoroute around Millau
In initial studies, four options were examined:
Great Eastern (grand Est) ( yellow route ) passing east of Millau and crossing the valleys of the Tarn and Dourbie on two very high and long bridges (spans of 800 and 1,000 m or 2,600 and 3,300 ft) whose construction was acknowledged to be problematic. This option would have allowed access to Millau only from the Larzac plateau, using the long and tortuous descent from La Cavalerie. Although this option was shorter and better suited to through traffic, it did not satisfactorily serve the needs of Millau and its area . Great Western (grand Ouest) ( black route ), longer than the eastern option by 12 km (7.5 mi), following the Cernon valley. Technically easier (requiring four viaducts), this solution was judged to have negative impacts on the environment, in particular on the picturesque villages of Peyre and Saint-Georges-de-Luzençon. It was more expensive than the preceding option, and served the region badly. Near RN9 (proche de la RN9) ( red route ), would have served the town of Millau well, but presented technical difficulties and would have had a strong impact on existing or planned structures. Intermediate (médiane), west of Millau ( blue route ) was supported by local opinion, but presented geological difficulties, notably on the question of crossing the valley of the Tarn. Expert investigation concluded that these obstacles were not insurmountable.
The fourth option was selected by ministerial decree on 28 June 1989. It encompassed two possibilities:
the high solution, envisaging a 2,500 m (8,200 ft) long viaduct more than 200 m (660 ft) above the river; the low solution, descending into the valley and crossing the river on a 200 m (660 ft) long bridge, then a viaduct of 2,300 m (7,500 ft) extended by a tunnel on the Larzac side.
After long construction studies by the Ministry of Public Works, the low solution was abandoned because it would have intersected the water table, had a negative impact on the town, cost more, and lengthened the driving distance. The choice of the "high" solution was decided by ministerial decree on 29 October 1991.
After the choice of the high viaduct, five teams of architects and researchers worked on a technical solution. The concept and design for the bridge was devised by French designer Michel Virlogeux. He worked with the Dutch engineering firm ARCADIS, responsible for the structural engineering of the bridge.
Choosing the definitive route
Satellite image of the route before construction of the bridge
The "high solution" required the construction of a 2,500 m (8,200 ft) long viaduct. From 1991 to 1993, the structures division of Sétra, directed by Michel Virlogeux, carried out preliminary studies and examined the feasibility of a single structure spanning the valley. Taking into account technical, architectural and financial issues, the Administration of Roads opened the question for competition among structural engineers and architects to widen the search for realistic designs. By July 1993, 17 structural engineers and 38 architects applied as candidates for the preliminary studies. With the assistance of a multidisciplinary commission, the Administration of Roads selected eight structural engineers for a technical study and seven architects for the architectural study.
Choice of technical design
Simultaneously, a school of international experts representing a wide spectrum of expertise (technical, architectural and landscape), chaired by Jean-François Coste, was established to clarify the choices that had to be made. In February 1995, on the basis of proposals of the architects and structural engineers, and with support of the school of experts, five general designs were identified.
The competition was relaunched: five combinations of architects and structural engineers, drawn from the best candidates of the first phase, were formed; each was to conduct in-depth studies of one of the general designs. On 15 July 1996, Bernard Pons, minister of Public Works, announced the decision of the jury, which was constituted of elected artists and experts and chaired by Christian Leyrit, the director of highways. The solution of a cable-stayed bridge, presented by the structural engineering group Sogelerg, Europe Etudes Gecti and Serf and the architects Foster + Partners was declared the best.
Detailed studies were carried out by the successful consortium, steered by the highways authority until mid-1998. After wind tunnel tests, the shape of the road deck was altered and detailed corrections were made to the design of the pylons. When the details were eventually finalised, the whole design was approved in late 1998.