Millau Viaduct France (In French le Viaduc de Millau) is one of the most awesome civil engineering project. It is a large cable-stayed road-bridge that spans the valley of the River Tarn near Millau in France. It was designed by structural engineer Michel Virlogeux and architect Norman Foster.One of the summit of this bridge is at a height of 343 meters)1125 ft) which makes it is the tallest vehicular bridge in the world.
The Millau Viaduct consists of an eight-span steel roadway supported by seven concrete pylons. The roadway weighs 36,000 tons and is 2,460 m (8,100 ft) long, measuring 32 m (100 ft) wide by 4.2 m (14 ft) deep, making it the world’s longest cable-stayed deck. The six central spans each measure 342 m (1,120 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 a plane section with a 20 km (12 mi) radius to give drivers better visibility. It carries two lanes of traffic and one safety lane in each direction.
The pylons range in height from 77 m (250 ft) to 246 m (810 ft), and taper in their longitudinal section from 24.5 m (80 ft) at the base to 11 m (36 ft) at the deck. Each pylon is composed of 16 framework sections, each weighing 2,230 tons. These sections were assembled on site from pieces of 60 tons, 4 m (13 ft) wide and 17 m (56 ft) long, made in factories in Lauterbourg and Fos-sur-Mer by Eiffage. The pylons each support 97 m (320 ft) tall masts.
The pylons were assembled first, together with some intermediate temporary pylons, before the decks were slid out across the piers by satellite-guided hydraulic rams that moved the deck 600 mm every 4 minutes. Then the masts were driven over the new deck, erected on top of the pylons, connected to the deck and the temporary pylons removed.
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.
Pylons and abutments
Each pylon is supported by four deep shafts, 15 m (49 ft) deep and 5 m (16 ft) in diameter.Height is given below for each
P1 = 94.501 m (310 ft 0.5 in) P2 = 244.96 m (803 ft 8 in)
P3 = 221.05 m (725 ft 3 in) P4 = 144.21 m (473 ft 2 in)
P5 = 136.42 m (447 ft 7 in) P6 = 111.94 m (367 ft 3 in)
P7 = 77.56 m (254 ft 6 in)
Deck
The metallic deck, which appears very light despite its total mass of around 36,000 metric tons (40,000 short tons), is 2,460 m (8,100 ft) long and 32 m (100 ft) wide. It comprises eight spans. The six central spans measure 342 m (1,120 ft), and the two outer spans are 204 metres (670 ft). These are composed of 173 central box beams, the spinal column of the construction, onto which the lateral floors and the lateral box beams were welded. The central box beams have a 4 m (13 ft) cross-section and a length of 15–22 m (49-72 ft) for a total weight of 90 metric tons (99 short tons). The deck has an inverse airfoil shape, providing negative lift in strong wind conditions.
Masts
The seven masts, each 87 m (290 ft) high and weighing around 700 metric tons (770 short tons), are set on top of the pylons. Between each of them, eleven stays (metal cables) are anchored, providing support for the road deck.
Stays
Each mast of the viaduct is equipped with a monoaxial layer of eleven pairs of stays laid face to face. Depending on their length, the stays were made of 55 to 91 high tensile steel cables, or strands, themselves formed of seven strands of steel (a central strand with six intertwined strands). Each strand has triple protection against corrosion (galvanisation, a coating of petroleum wax and an extruded polyethylene sheath). The exterior envelope of the stays is itself coated along its entire length with a double helical weatherstrip. The idea is to avoid running water which, in high winds, could cause vibration in the stays and compromise the stability of the viaduct.The stays were installed by the Freyssinet company.
Surface To allow for deformations of the metal deck under traffic, a special surface of modified bitumen was installed by research teams from Appia. The surface is somewhat flexible to adapt to deformations in the steel deck without cracking, but it must nevertheless have sufficient strength to withstand motorway conditions (fatigue, density, texture, adherence, anti-rutting, etc.). The “ideal formula” was found only after ten years of research.
Statistics : The Millau Viaduct Bridge
* 2,460 m (8,071 ft): total length of the roadway
* 7: number of piers
* 77 m (253 ft): height of Pier 7, the shortest
* 343 m (1,125 ft): height of Pier 2, the tallest (245 m/804 ft at the roadway’s level)
* 87 m (285 ft): height of a mast
* 154: number of shrouds
* 270 m (886 ft): average height of the roadway
* 4.20 m (13 ft 9 in): thickness of the roadway
* 32.05 m (105 ft 2 in): width of the roadway
* 85,000 m³ (111,000 cu yd): total volume of concrete used
* 290,000 metric tons (320,000 short tons): total weight of the bridge
* 10,000–25,000 vehicles: estimated daily traffic
* €5.40–7.00: typical automobile toll, as of July 2007
* 20 km (12 mi): horizontal radius of curvature of the road deck
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