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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 12th highest bridge deck in the world, being 270 metres (890 ft) between the road deck and the ground below. Millau Viaduct is part of the A75-A71 autoroute axis from Paris to Béziers and Montpellier. Construction cost 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.
n 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) 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) 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
The "high solution" required the construction of a 2,500 m (8,200 ft) long viaduct (about one and a half miles). 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.
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.
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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.
nce the Ministry of Public Works had taken the decision to offer the construction and operation of the viaduct as a grant of contract, an international call for tenders was issued in 1999. Four consortia tendered:
Compagnie Eiffage du Viaduc de Millau (CEVM), led by Eiffage
PAECH Construction Enterprise (Poland)
a consortium led by the Spanish company Dragados, with Skanska (Sweden), and Bec (France)
Société du Viaduc de Millau, including the French companies ASF, Egis, GTM, Bouygues Travaux Publics, SGE, CDC Projets, Tofinso and the Italian company Autostrade
a consortium led by Générale Routière, with Via GTI (France) and Cintra, Nesco, Acciona and Ferrovial Agroman (Spain).
Piers were built with LAFARGE high performance cement. The pylons of the Millau viaduct, which are the tallest elements (the tallest pylon – 244.96 m) were produced and mounted by PAECH Construction Enterprise from Poland.
The Compagnie Eiffage du Viaduc de Millau, working with the architect Sir Norman Foster, was successful in obtaining the tender. Because the government had already taken the design work to an advanced stage, the technical uncertainties were considerably reduced. A further advantage of this process was to make negotiating the contract easier, reducing public expense and speeding up construction, while minimising such design work as remained for the contractor.
All the member companies of the Eiffage group had some role in the construction work. The construction consortium was 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 railway bridge in the neighbouring 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. Appia was responsible for the job of the bituminous coating on the bridge deck, and Forclum for electrical installations. Management was handled by Eiffage Concessions.
The only other business that had a notable role on the building site was Freyssinet, a subsidiary of the Vinci Group specialising in prestressing. It installed the cable stays and put them under tension, while the prestress division of Eiffage was responsible for prestressing the pillar heads.
The steel deck and the hydraulic action of the deck were designed by the Walloon engineering firm Greisch from Liège, Belgium, also an Information and communication technologies company of the Walloon Region. They carried out the general calculations and the resistance calculations for winds of up to 225 km/h (140 mph). They also applied the launching technology.
The sliding shutter technology for the bridge piers came from PERI.
o weeks after the laying of the first stone on 14 December 2001, the workers started to dig the deep shafts. There were 4 per pylon; 15 m (49 ft) deep and 5 m (16 ft) in diameter, assuring the stability of the pylons. At the bottom of each pylon, a tread of 3–5 m (10–16 ft) in thickness was installed to reinforce the effect of the deep shafts. The 2,000 m3 (2,600 cu yd) of concrete necessary for the treads was poured at the same time.
In March 2002, the pylons emerged from the ground. The speed of construction then rapidly increased. Every three days, each pylon increased in height by 4 m (13 ft). This performance was mainly due to sliding shuttering. Thanks to a system of shoe anchorages and fixed rails in the heart of the pylons, a new layer of concrete could be poured every 20 minutes.
The bridge deck was constructed on land at the ends of the viaduct and rolled lengthwise from one pylon to the next, with eight 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 pointing in opposite directions. These were hydraulically operated, and moved repeatedly in the following sequence: The 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 forward together, advancing the roadway a short distance. The lower wedge retracts from under the upper wedge, lowering the roadway and allowing the upper wedge to drop away from the roadway; the lower wedge then moves back all the way to its starting position. There is now a linear distance between the two wedges equal to the distance forward the roadway has just moved. The upper wedge moves backward, placing it further back along the roadway, adjacent to the front tip of the lower wedge and ready to repeat the cycle and advance the roadway by another increment. It worked at 600 mm per cycle which was roughly four minutes long.
The mast pieces were driven over the new deck lying down horizontally. The pieces were joined to form the one complete mast, still lying horizontally. The mast was then tilted upwards, as one piece, at one time in a tricky operation. In this way each mast was erected on top of the corresponding pylon. The stays connecting the masts and the deck were then installed, and the bridge was tensioned overall and weight tested. After this, the temporary pylons could be removed.
Timeline
16 October 2001: work begins
14 December 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
25–26 February 2003: laying of first pieces of roadway
November 2003: completion of the last piers (Piers P2 at 245 m (804 ft) and P3 at 221 m (725 ft) are the highest piers in the world.)
28 May 2004: the pieces of roadway are several centimetres 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
14 December 2004: official inauguration
16 December 2004: opening of the viaduct, ahead of schedule
10 January 2005: initial planned opening date
Since opening in 2004, the deck height of Millau has been surpassed by several suspension bridges in China, including Siduhe, Balinghe and two spans (Beipanjiang River 2003 Bridge and Beipanjiang River 2009 Bridge) over the Beipanjiang River. In 2012, Mexico's Baluarte Bridge surpassed Millau as the world's highest cable-stayed bridge. The Royal Gorge suspension bridge in the U.S. state of Colorado is also higher, with a bridge deck approximately 291 metres (955 ft) over the Arkansas River
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