Millau Viaduct

From Academic Kids

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Millau_Bridge_over_Tarn_River_France.jpg
Millau viaduct in France, currently the world's tallest vehicular bridge.

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 master-architect Lord Foster, it is the tallest vehicular bridge in the world, with one pier's summit at 341 metres (1,118 ft)—slightly higher than the Eiffel Tower and only 40 m (132 ft) shorter than the Empire State Building. It was formally opened on 14 December 2004 and opened to traffic on 16 December 2004.


Contents

Location

The bridge is the last link on the A75 autoroute, providing a continuous high-speed route from Paris through Clermont-Ferrand to Bziers. Prior to the bridge's construction, 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. Many tourists heading to southern France and Spain follow this route because it is direct and mostly toll free.

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The nearly completed bridge in September 2004

The A75 (la Mridienne) is a developmental project with the aim of speeding up and reducing the cost of car travel from Paris southwards, and it is entirely free for the 340 km between Clermont-Ferrand and Bziers. However, the viaduct was constructed under a government contract with the Eiffage group, the French construction company that built the Eiffel Tower, effective for 75 years. The corporation will impose tolls at agreed upon rates: about 4.90 for light automobiles, excluding the peak months of July and August (6.60), and 20 for heavy goods vehicles.

The bridge crosses the Tarn valley at its lowest point, linking the causse du Larzac to the causse rouge. The bridge is within the perimeter of the Grands Causses regional natural park.

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 slight 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.

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

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 road bridge in Europe, the Europabrcke in Austria. It is also the second highest vehicular bridge measured by roadway level. Its deck, at "almost 270 m" (886 ft) above the Tarn, is apparently 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, in the United States has a deck considerably higher than either, at 321 m (1,053 ft) above the Arkansas River.

Construction

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

Construction began on October 10, 2001 and was meant 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 (http://www.arcadis-global.com/), responsible for the technical design of the bridge.

The builders

Four consortia were in competition for the building contract:

  • one led by Dragados (Spanish), with Skanska (Swedish) and Bec (French);
  • Socit 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 Gnrale Routire, with Via GTI (French), and Cintra, Necso, Acciona, and Ferrovial Agroman (all Spanish).
  • the successful bidders, lead 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 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 dpartement), 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  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.

Statistics

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End view
  • 2,460 metre: total length of the roadway
  • 7: number of piers
  • 77 m: height of Pier 7, the shortest
  • 336 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: typical height of the roadway
  • 4.20 m: thickness of the roadway
  • 32.05 m: width of the roadway
  • 85,000 : total volume of concrete used
  • 290,000 metric tons: total weight of the bridge
  • 10,000–25,000 vehicles: estimated daily traffic
  • 4.90–6.60: typical automobile toll

Project timeline

  • June 28, 1989: governmental approval of the middle route
  • October 19, 1991: selection of the high solution, with the viaduct at 2500 m
  • January 10, 1995: declaration of utilit publique (public usefulness), as needed to apply eminent domain
  • July 9, 1996: choice of the cable-stayed bridge type
  • 1998: decision to contract out both construction costs and future tolls to a private enterprise
  • October 16, 2001: work begins
  • December 14, 2001: laying of the first stone
  • January 2002: laying pier foundations
  • March 2002: start of work on the pier support C8
  • June 2002: support C8 completed, start of work on piers
  • July 2002: start of work on the foundations of temporary, height adjustable roadway supports
  • August 2002: start of work on pier support C0
  • September 2002: assembly of roadway begins
  • November 2002: first piers complete
  • February 25February 26, 2003: laying of first pieces of roadway
  • November 2003: completion of the last piers (Piers P2 at 221 m and P3 at 245 m are the highest piers in the world.)
  • May 28, 2004: the pieces of roadway are several centimeters apart, their juncture to be accomplished within two weeks
  • 2nd half of 2004: installation of the pylons and shrouds, removal of the temporary roadway supports
  • December 14, 2004: official inauguration
  • December 16, 2004: opening of the viaduct, ahead of schedule
  • January 10, 2005: initial planned opening date
  • 2044: French government can assume control of the bridge if the toll concession is very profitable
  • 2080: Eiffage toll concession runs out

See also

External links

ca:Viaducte de Millau de:Viaduc de Millau es:Viaducto de Millau eo:Viadukto de Millau fr:Viaduc de Millau nl:Brug van Millau pl:Wiadukt Millau sl:Viadukt Millau sr:Мост Мијо zh:密佑高架橋

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