Location
Millau Viaduct is located at 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 autoroute, (la Méridienne) from Clermont-Ferrand to Pézenas (to be extended to Béziers by 2010). The A75, with the A10 and A71, provides a continuous high-speed route south from Paris through Clermont-Ferrand to the Languedoc region and through to Spain, considerably reducing 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 Pézenas, except for the bridge itself.
The Eiffage group operates the viaduct as a toll bridge, with the toll currently (Nov 2006) set at €5.10 for light automobiles (€6.80 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.
Description
The Millau Viaduct consists of an eight-span steel roadway supported by seven concrete piers. The roadway weighs 36,000 tons and is 2,460 m long, measuring 32 m wide by 4.2 m deep. The six central spans each measure 342 m with the two outer spans measuring 204 m. The roadway has a slope of 3% descending from south to north, and curves in plan section on a 20 km radius to give drivers better visibility. It carries two lanes of traffic in each direction.
The piers range in height from 77–246 m, and taper in their longitudinal section from 24.5 m at the base to 11 m at the deck. Each pier is composed of 16 framework sections, each weighing 2,230 tons. These sections were assembled on site from pieces of 60 tons, 4 m wide and 17 m long, made in factories in Lauterbourg and Fos-sur-Mer by Eiffage. The piers each support 97 m 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 every 4 minutes.
The viaduct is nearly twice as tall as the previous tallest vehicular bridge in Europe, the Europabrücke in Austria.
The Millau Viaduct is the second-highest vehicular bridge measured from the roadway elevation. Its deck, about 270 m above the Tarn, is slightly higher than the New River Gorge Bridge in West Virginia in the United States, which is 267 m above the New River. The Royal Gorge Bridge in Colorado, United States has a deck considerably higher than either, at 321 m above the Arkansas River.
Construction began on 10 October 2001 and was intended to take three 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 inaugurated by President Chirac on 14 December 2004 to open for traffic on 16 December, several weeks ahead of the revised schedule. The construction of the bridge is depicted in an episode of the Discovery Channel "Megastructures" series.
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 28 June 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 2,300 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, hurt the town, cost more, and lengthened the driving distance.
After the choice of the high viaduct's path, five teams of architects and researchers worked on a technical solution. The concept for the bridge was devised by French designer Michel Virlogeux. The architects of the bridge are the British firm Foster and Partners. They worked with the Dutch engineering firm ARCADIS, responsible for the technical design of the bridge.
Implementation
The bridge deck was constructed on land at the ends of the viaduct and rolled lengthwise from one tower to the next, with seven temporary towers providing additional support. The movement was accomplished by a computer-controlled system of pairs of wedges under the deck; the upper and lower wedges of each pair pointed in opposite directions. These were hydraulically operated, and moved repeatedly in the following sequence:
- Lower wedge slides under the upper wedge, raising it to the roadway above and then forcing the upper wedge still higher to lift the roadway.
- Both wedges move together, advancing the roadway a short distance.
- Lower wedge retracts from under the upper wedge, lowering the roadway and then allowing the upper wedge to drop away from the roadway.
- Upper wedge moves backward, placing it into position farther (back) along the roadway, ready to repeat the cycle and advance the roadway again.
PERI Formwork technology for the construction of the highest bridge pier
PERI Formwork technology for the construction of the highest bridge pier
Four consortia competed for the building contract:
- One led by Dragados (Spanish), with Skanska (Swedish) and Bec (French);
- Société du viaduc de Millau, made up of ASF, Egis, GTM, Bouygues Travaux Publics, SGE, CDC Projets, Tofinso (all French) and Autostrade (Italian); and
- One led by Générale Routière, with Via GTI (French), and Cintra, Necso, Acciona, and Ferrovial Agroman (all Spanish).
- The successful bidders, led by the Eiffage group, product of the Fougerolles-SEA fusion, the third-largest French group in public works, and the sixth-largest in Europe.
The formwork technology for the bridge piers came from PERI.
Costs and resources
The bridge's construction cost up 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 steel for the cables and shrouds. The builder claims that the bridge's lifetime will be at least 120 years.
Statistics
- 2,460 m: total length of the roadway
- 7: number of piers
- 77 m: height of Pier 7, the shortest
- 343 m: height of Pier 2, the tallest (245 m at the roadway's level)
- 87 m: height of a pylon
- 154: number of shrouds
- 270 m: average height of the roadway
- 4.20 m: thickness of the roadway
- 32.05 m: width of the roadway
- 85,000 m³: total volume of concrete used
- 290,000 tonnes: total weight of the bridge
- 10,000–25,000 vehicles: estimated daily traffic
- €4.90–6.50: typical automobile toll, as of 2005
- 20 km: horizontal radius of curvature of the road deck
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