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Millau Viaduct

Millau Viaduct

General Information

Structural Type: Cable-stayed bridge with semi-fan system
Multiple-span cable-stayed bridge
Function / usage: Motorway bridge / freeway bridge
Construction method: Longitudinal launching
Other name(s): Viaduc de Millau
Built: 2001 - 2004
Duration of works: 38 months
Status: in use

Geographic Information & Related Structures

Location: Millau, Aveyron (12), Midi-Pyrénées, France, Europe
Carries
  • Autoroute A75
Crosses
  • Tarn River
Part of:
Next to Centre d'information du viaduc de Millau
Near Millau Viaduct Toll Gate (2004)
Coordinates: 44° 5' 6.00" N    3° 1' 18.00" E

Technical Information

Dimensions

total length 2 460 m
span lengths 204 m - 6 x 342 m - 204 m
horizontal radius of curvature 20 000 m
deck deck depth 4.20 m
height above valley floor or water 270 m
total width 32.050 m
longitudinal slope 3.025 %
pier P1 height 94.50 m
pier P2 height 244.96 m
pier P3 height 221.05 m
pier P4 height 144.21 m
pier P5 height 136.42 m
pier P6 height 111.94 m
pier P7 height 77.56 m
pylons pylon height (above deck) 88.92 m
pylon height (above ground) max. 343 m

Quantities

volume of earthworks 350 000 m³
deck structural steel S355: 23 500 t
S460: 12 500 t
foundation slabs concrete volume 13 000 m³
reinforcing steel 1 300 t
foundations reinforcing steel 13 450 t
piers concrete volume 53 000 m³
prestressing steel 200 t
reinforcing steel 10 000 t
piles concrete volume 6 000 m³
reinforcing steel 1 200 t
pylons structural steel S355: 3 200 t
S460: 1 400 t
stay cables steel for cable-stays 1 500 t
temporary works structural steel S 355: 3 200 t
S 460: 3 200 t
concrete volume 7 500 m³
reinforcing steel 400 t

Cost

cost of construction Euro 300 000 000

Materials

deck steel
piers reinforced concrete
pylons steel
abutments reinforced concrete
stay cables steel

Products, Services & Reports

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Chronology

1987

CETE (Aix-en-Provence) establishes the first possible alignments for the A75 at Millau.

1990

Decision by the ministry to cross the Tarn valley by a 2500-meter long bridge.

1993
- 1994

Seven architectural offices and eight engineering offices are consulted separately for proposals.

1995
- 1996

Second design phase with five groups each associating an architecture and engineering office.

1996

The jury retains the solution proposed by Lord Norman Foster in association with Sogelerg.

1998

The decision is made to operate the Millau Viaduct under a concession agreement.

2000

Competition is launched for the concession/construction tender.

March 2001

Eiffage is awarded the first prize of the competition and declared concessionaire.

May 2001

The construction contract is signed.

August 2001

The concession is awarded to Eiffage.

16 October 2001

Construction begins.

November 2002

Pier P2 (to be the highest) reaches 100 meters in height.

26 February 2003

Launching of the deck commences.

28 May 2003

Pier P2 surpasses the height of 180 m and thus becomes the highest pier in the world, a record previously held by the Kochertal Viaduct. The record will be broken again when the highest pier reaches 245 meters.

25 August 2003
- 26 August 2003

Launching phase L4.

November 2003

Completion of piers.

26 March 2004

Launching phase L10 from the south end. The deck reaches Pier P3.

Night of 4 April 2004
- 5 April 2004

The metal deck is launched onto P2, the highest pier in the world. The launching operation is slowed down by wind and mist which perturb the laser guidance system. A this phase, 1 947 m of deck have been launched.

20 April 2004

End of launching of the deck from the north side. The end of the canitlever reaching out beyond pier P2 is at midspan over the Tarn. Two launch phases remain from the south side.

28 May 2004

The deck is completed.

End of July 2004

Completion of the construction of the pylons.

November 2004

Expected completion of the dismantling of the temporary piers.

17 November 2004

Load testing begins with a total load of 920 tons.

14 December 2004

Inauguration by President Jacques Chirac.

16 December 2004, 09:00

Opened to traffic.

2006

Outstanding Structure Award 2006 (IABSE)

About the Millau Viaduct

The Millau Bridge and the Rion-Antirion Bridge are the most modern and most important examples for series of cable-stayed bridges. They answer the main questions for series individually: –How can the inner towers be stabilized to avoid too large beam deflections due to spanwise live loads? –How can the changes in beam lengths of these long bridges, e. g. due to temperature,be taken into account, together with longitudinal forces, e.g due to breaking, together with the forces from earthquake?

In 2004 the large viaduct of Millau was opened for traffic, thereby closing the last gap in the second north–south highway A 75. The bridge has earned its title „Record Bridge“ not only because it is the highest in the world, crossing the Tarn River at a height of 270 m, but also the construction period of only 38 months and the costs of about € 400 m are outstanding. For the second north–south highway the main obstacle was the wide valley of the Tarn River near the city of Millau, well-known for its seemingly endless queues during the summer. It was decided to cross the valley by a 2 460 m long viaduct. In 1996 a series of cable-stayed bridges with two side spans of 204 m, and sixmain spans of 342 m was selected. For the financial success of the concession company it was important to keep the construction period to a minimum in order to receive tolls as early as possible. For this reason the French contractor Eiffel Construction Métallique proposed an alternate with steel beam and steel towers above deck against the tender design of a post-tensioned concrete bridge. This alternate was selected in March 2001 and construction started in October 2001. The advantages of the steel design against the original concrete design are:

  • light-weight and slenderness of the beam (36 t against 120 t)
  • reduction of the depth of the beam to 4.2 m, meaning smaller wind loads
  • improved safety: less work at great height due to pre-assembly on ground and incremental launching construction
  • minimizing the number of stay cables and the size of foundations
  • reduction in total costs – the over-riding advantage.

Within two and a half years nearly 43 t of steel were fabricated for the beam, the towers and the auxiliary piers. For the complete design phase Michel Virlogeux was the engineer- in-charge for the French Highway Authority SETRA, and during the construction phase he was an important advisor.

Design

The Millau Bridge has a total length of 2 460 m and comprises eight spans: two side spans with 204 m and six inner spans with 342 m. The cross-section consists of a steel box with orthotropic deck, two vertical inner webs and two inclined outer plates. The vertical webs are required for construction by incremental launching, and the triangular outside boxes create a streamlined cross-section which reduces the wind load on the bridge. On the outside of the beam, wind shields are installed which prevent the overturning of high-sided vehicles. The rounded edges on both outsides improve the aerodynamic behavior and the appearance. Due to the great height above the valley a central girder, with one cable plane only, was the most effective design for avoiding twin piers. The required torsional stiffness is provided by the box girder. Governing the design of the bridge was the condition that the up to 230 m high piers are stiff enough to carry unsymmetrical loads in the longitudinal direction. Also they have to be flexible enough to follow the beam’s longitudinal changes due to temperature. The solution is a strong concrete box girder for the piers with a vertical slot underneath the beam. This bisectioning of the box provides for the required flexibility. The 87 m high towers above deck form stiff A-frames in the longitudinal direction. The spread legs of the towers meet at the beam the spread upper pier halves. In this way an overall system from pier and tower is created which converts the moment from loads acting at the tower tips into a couple of tension and compression and thus restrains the tower head. The 90 m long pier shafts are vertically post-tensioned to counteract the tensile stresses due to wind in the inner piers and due to temperature changes in the outer piers. Bearings are located between the steel girder and the concrete piers, which are stressed down against uplift. Unsymmetrical loads and extreme winds cause support reactions on each pier of up to 100 MN. A new type of spherical bearing was used. The towers above deck are made from steel to make them as light and slender as possible. The central cable plane is anchored at the tower heads between longitudinal steel plates. Due to architectural reasons the towers extend beyond the upper cables.

Construction

Piers

The piers have varying cross-sections, but dimensions were selected in such a way that they could be formed easily. Four sides have constant dimensions, and the others vary uniformly in each construction section. This permits construction with outer jumping forms and inner forms which are stepwise lifted by the tower crane. Sliding forms could have made the correct positioning of the built-in items difficult.

Beam

About 2100 stiffened panels, four per work day, were fabricated from plates and stiffeners in the shops of Eiffel Construction Métallique in Lauterbourg (Alsace). After transportation to site they were welded in the two 170 m long pre-assembly yards. The central boxes were prewelded ahead in Fos-sur-Mer. Up to 75 welders were working in each pre-assembly yard.

Launching the beam

The detailed design and construction engineering of the steel parts – beam, towers and auxiliary piers – was provided by the consultant Greisch from Liège, Belgium. The engineer-in-charge was Jean- Marie Crémer. During launching from both abutments several special measures were introduced to control the large cantilever moments. The spans were reduced by half with temporary telescopic piers, a launching nose was used and the front tower with some of the final stay cables was launched together with the beam. These cables were not ad- justed during launching! After joint closure on 28 May 2004, the re- maining towers and stay cables were installed and the auxiliary piers removed. The steel beams were launched from both ends at the same time with a closure joint above the Tarn River. In the center of the large span trussed auxiliary truss piers were installed with the exception of the center span which was bridged by cantilevering from both sides. The launching bearings on top of the piers with a distance of 20 m reduced the beam moments quite significantly in the ratio of span lengths (151 / 171)2 = 0.78.

The auxiliary piers are built from prefabricated sections with 12 m heights. They are designed like a crane. The elements prefabricated on the ground from steel sections are lifted with an inside lifting device in such way that the next sections could be installed from underneath and also lifted until these telescoping auxiliary piers reached a height of up to 175 m. Their highest load came to 7 000 t roughly equal to the total weight of the Eifel Tower. The final piers were only provided with an auxiliary scaffolding for launching. A unique characteristic of this launching was that, for cost rea- sons, the pre-assembly yard was located at the level of the future road gradient, 4.8 m above the final bridge deck elevation. A shortened view during launching shows the elasticity of the steel beam by overcoming the gradient offset. Each of the two beam halves was launched over an auxiliary pier and a launching nose across the outer side spans. After that the final tower was installed at the front end as auxiliary support, but with a reduced height of 70 m instead of 87 m to minimize the transverse wind loads during launching. The highest wind speed permitted during launching was 3 km/h. Due to the extreme heights of the piers the friction forces during launching had to be equalized, so on top of each pier two active launching bearings were installed in each support axis. Horizontal hydraulic jacks acted between the beam and the piers in such a way that the pier tips remained in place during launching, centrally controlled by sensors. Finally the center span was bridged from each side with cantilevers, supported by towers. The design and construction on site was an extraordinary engineering achievement.

Towers

After the steel beam was in place, the remaining steel towers were pre-assembled behind the abutments. Each tower was then moved with crawler cranes over the bridge beam to its final position. The total weight of such a convoy came to 8 MN, thus acting as a test loading. The towers were lifted from their horizontal position with the help of a temporary guyed tower. Finally, they were connected with the beam, and the stay cables were installed.

Completed Bridge

The Millau Bridge is an important example for a series of cablestayed bridges. A structure with impressive elegance has been built in an impressive landscape, where it gracefully crosses the valley at great height.

Excerpt from: Svensson, Holger; Cable-Stayed Bridges, Wilhelm Ernst & Sohn Verlag für Architektur und technische Wissenschaften GmbH, Berlin (Germany), ISBN 343302992X; pp. 411-417. References to figures and literature were omitted.

Participants

Conceding authority
Agent of the conceding authority
Concessionaire
Client
Design studies
Design
Meteorological data
Wind tunnel testing
Technical advisor to the owner
Structural engineering
Construction engineers
Geotechnical engineering
Main contractor
Civil works
Steel construction
Subcontractor
Earthworks
Welding checks
Stay cables
Concrete supplier
Cement supplier
Concrete plant
Concrete testing
Steel supplier
Stay cable steel supplier
Prestressing steel
Reinforcing steel
Steel connections
Bearings
Expansion joints
Safety barriers
Roadway cover
Roadway cover studies
Water proofing
Paint
Temporary shoring
Temporary piers
Formwork & scaffolding
Tower cranes
Sliding bearings
Hydraulics
Lifting
Large transports
Computer equipment
Electricity (high & low voltage)
Elevators
Piping
Monitoring equipment
Remote monitoring system

Relevant Web Sites

Relevant Publications

Internal Information
Structure-ID: s0000351
Created: 02/09/1999
Last Updated: 21/02/2014