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Millau Viaduct

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Panoramic view of Millau Viaduct from south-east side
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Panoramic view of Millau Viaduct from south-east side

The Millau Viaduct (French: le Viaduc de Millau) is a cable-stayed road bridge that spans the valley of the River Tarn near Millau in southern France. Designed by French bridge engineer Michel Virlogeux in collaboration with British architect Norman Foster, it is the tallest vehicular bridge in the world, with one pier's summit at 343 metres (1,125 ft)—slightly higher than the Eiffel Tower and only 38 m (125 ft) shorter than the Empire State Building. It was formally opened on 14 December 2004 and opened to traffic on 16 December 2004.

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Location

Millau Viaduct's coordinates are [44.077165° N 3.022887° E]. Before the bridge was constructed, traffic had to descend into the Tarn River valley and pass along the route nationale N9 near the town of Millau, causing heavy congestion at the beginning and end of the July and August vacation season. The bridge now traverses the Tarn valley above its lowest point, linking the causse du Larzac to the causse rouge, and is inside the perimeter of the Grands Causses regional natural park.

The bridge forms the last link of the A75 (la Méridienne) autoroute, providing a continuous high-speed route south from Paris through Clermont-Ferrand to Béziers. The purpose of the A75 is to increase the speed and reduce the cost of vehicle traffic travelling along this route. Many tourists heading to southern France and Spain follow this route because it is direct and without tolls for the 340 km between Clermont-Ferrand to Béziers, except for the bridge itself.

The Eiffage group operates the viaduct as a toll bridge, with the toll currently set at €4.90 for light automobiles (€6.50 during the peak months of July and August). The bridge was constructed by the Eiffage group, which also built the Eiffel Tower, under a government contract which allows the company to collect tolls for up to 75 years.

The nearly completed bridge in September 2004
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The nearly completed bridge in September 2004

Description

The Millau Viaduct consists of an eight-span steel roadway supported by seven concrete piers. The roadway weighs 36,000 metric tons and is 2,460 m (8,071 ft) long, measuring 32 m (105 ft) wide by 4.2 m (13.8 ft) deep. The six central spans each measure 342 m (1,122 ft) with the two outer spans measuring 204 m (670 ft). The roadway has a slope of 3% descending from south to north, and curves in plan section on a 20 km (12.4 mile) radius to give drivers better visibility. It carries two lanes of traffic in each direction.

The piers range in height from 77–246 m (253–807 ft), and taper in their longitudinal section from 24.5 m (81 ft) at the base to 11 m (36 ft) at the deck. Each pier is composed of 16 framework sections, each section weighing 2,230 metric tons. These sections were assembled on site from pieces of 60 metric tons, 4 m (13 ft) wide and 17 m (56 ft) long, made in factories in Lauterbourg and Fos-sur-Mer by Eiffage. The piers each support 97 m (319 ft) tall pylons. The piers were assembled first, together with some temporary supports, before the decks were slid out across the piers by satellite-guided hydraulic rams that moved the deck 600 mm (23.6 inches) every 4 minutes.

The viaduct is the tallest vehicular bridge in the world, nearly twice as tall as the previous tallest vehicular bridge in Europe, the Europabrücke in Austria. The proposed Strait of Messina Bridge in Italy, if constructed, would be taller still and would also be the world's largest suspension bridge. Current plans call for towers 382.6 m high.

The Millau Viaduct is the second highest vehicular bridge measured from the roadway elevation. Its deck, at approximately 270 m (886 ft) above the Tarn, is slightly higher than the New River Gorge Bridge in West Virginia in the United States, which is 267 m (876 ft) above the New River. The Royal Gorge Bridge in Colorado, United States has a deck considerably higher than either, at 321 m (1,053 ft) above the Arkansas River.

Panoramic view of the Millau Viaduct, as seen from the south. The red temporary supports are still visible in this June 29, 2004 photograph.
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Panoramic view of the Millau Viaduct, as seen from the south. The red temporary supports are still visible in this June 29, 2004 photograph.

Construction

The viaduct under construction, seen from the south in early 2004.
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The viaduct under construction, seen from the south in early 2004.

PERI Formwork technology for the construction of the highest bridge pier worldwide, Viaduc de Millau, France
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PERI Formwork technology for the construction of the highest bridge pier worldwide, Viaduc de Millau, France

Construction began on October 10, 2001 and was intended to take 3 years, but weather conditions put work on the bridge behind schedule. A revised schedule aimed for the bridge to be opened in January 2005. The viaduct was officially inaugurated by President Chirac on December 14, 2004 to open for traffic on December 16, several weeks ahead of the revised schedule.

Preliminary studies

In initial studies, four options were examined:
  1. bypass Millau to the east, requiring two large bridges over the Tarn and the Dourbie;
  2. bypass Millau to the west (12 km longer), requiring four bridges;
  3. follow the path of Route Nationale 9, providing good access to Millau but at the cost of technical difficulties and intrusion on the town; and
  4. traverse the middle of the valley.
The fourth option was selected by the government on June 28, 1989. It consisted of two possibilities: the high solution, and the low solution, requiring the construction of a 200 m bridge to cross the Tarn, then a viaduct of 2300 m extended by a tunnel on the Larzac side. After long construction studies, the low solution was abandoned because it would have intersected the water table, had negative effects on the town, cost more, and the driving distance would have been longer.

After the choice of the high viaduct's path, five teams of architects and researchers simultaneously worked on a technical solution. The original concept for the bridge was devised by French designer Michel Virlogeux. The architects of the bridge are the British firm Foster and Partners. He worked together with the Dutch engineering firm [ARCADIS], responsible for the technical design of the bridge.

The builders

Four consortia were in competition for the building contract:

The work leader is the Compagnie Eiffage du Viaduc de Millau, owner of the government contract. The construction consortium is made up of the Eiffage TP company for the concrete part, the Eiffel company for the steel roadway (Gustave Eiffel built the Garabit viaduct in 1884, a train bridge in the neighboring Cantal département), and the Enerpac company for the roadway's hydraulic supports. The engineering group Setec has authority in the project, with SNCF engineering having partial control.

Costs and resources

The bridge's construction costs amount to €394 million, with a toll plaza 6 km north of the viaduct costing an additional €20 million. The builders, Eiffage, financed the construction in return for a concession to collect the tolls for 75 years, until 2080. However, if the concession is very profitable, the French government can assume control of the bridge in 2044.

The project required about 127,000 m³ of concrete, 19,000 metric tons of steel for the reinforced concrete, and 5,000 metric tons of pre-stressed concrete for the cables and shrouds. The builder claims that the bridge's lifetime will be at least 120 years.

Single segment of the constructionon the small exhibition under viaduct
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Single segment of the construction
on the small exhibition under viaduct

Statistics

Project timeline

Large numbers of people stop to view the viaduct from the viewing area on the northern side
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Large numbers of people stop to view the viaduct from the viewing area on the northern side

See also

External links

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