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The heritage-listed village of Peyre offers one of the finest views of the Millau Viaduct.
Discover this unusual site, carved into the cliff. From Millau, take the D 41 towards Comprégnac. The village of Peyre is located 7 km west of Millau.
Viaduc Expo, located in Millau Viaduct rest area
* Opening hours change when the clocks change in France.
The exhibition space is open year round, 7 days a week – except for New Year's Day and Christmas Day.
The piers of the Millau Viaduct are numbered 1 to 7, from north to south of the structure. The world record for pier height has been achieved with P2, at 245 m. The heights of the piers vary depending on the topography of the site and the viaduct's longitudinal profile.
P1: 94.5 m - P2: 245 m - P3: 221 m - P4: 144 m - P5: 136 m - P6: 112 m - P7: 77.5 m
The shape and size of the piers were designed to withstand the vertical load imposed by the deck, movements of their heads due to thermal expansion of the deck, as well as the wind.
Transversally, the width of P2 ranges from 27 m at its base to 10 m at the top. The piers are monolithic at the base and split in the upper part. This was done to overcome certain constraints such as expansion of the deck.
Underneath each pier, four 4 to 5 m-diameter well foundations from 9 to 18 m deep were dug and covered with a 3 to 5 m-thick spread footing. Concreting the spread footings (up to 2,100 m³) was done by pumping, in a single phase.
Construction of the Millau Viaduct involved the construction of a site access track and two bridges: one over the Tarn and the other over the RD 992 road between Creissels and Saint-Georges-de-Luzençon. This 8.5 km-long track provided access to all the significant points related to the project. It is still used for maintenance operations and is one of the major sections of the route taken by the Course Eiffage, feared by runners because of its steep incline.
First held in 2007, the Course Eiffage du Viaduc de Millau has become an important event in the world of running. Year after year, its success is confirmed: 10,500 runners registered in 2007, 13,500 in 2012 and 14,500 in 2014, to take on the viaduct that soars above Millau and the beautiful Tarn valley.
On arrival at the foot of the viaduct, at the pier P2, runners take the former northern site access track that winds its way uphill beneath the structure. Leaving to take on the viaduct, you feel so very small... but with the spirit of a winner ! Once at the top of the plateau, runners embark on the viaduct itself for a fantastic 5 km crossing (3.025% incline oriented north-south).
Each pylon of the Millau Viaduct is fitted with 11 pairs of stays.
Inside protective enclosures, the strands, composed of seven twisted wires, have been placed under a tension specified by the engineering office. Depending on the length and tension of each stay, 45 to 91 strands are needed.
Preparation: stays equipped for the toughest challenges
The stays benefited from all the technology developed by the company Freyssinet. Each strand has been given a triple protection against corrosion: galvanisation, a petroleum wax coating and an extruded polyethylene sheath.
The outer sheath of the stays is itself equipped with a double helical rib along its entire length.
The abutments were built at the same time as the piers, on the Causse du Larzac and the Causse Rouge. These are concrete structures that anchor the deck to solid ground.
These hollow, 13 m-wide abutments are narrower than the deck. Their lateral cantilevers extend the shape of the deck up to the natural terrain of the valley wall.
It is at the north abutment, the one closest to the toll gate, that the technical facilities needed to keep the viaduct operational are located.
Two open construction sites were set up behind the abutments, to the north and south of the viaduct. All welding and assembly work was carried out there, limiting the risks associated with working at great heights.
The deck truly is the viaduct's steel spine. From both ends of the construction site, the deck was pushed at regular intervals, moving each part of the deck towards the other.
Launching these thousands of tonnes of steel into the void, as it were, was an operation made possible thanks to the ingenuity and precision of the teams on site.
The metal deck is made up of central box girder sections onto which the lateral panels and deck plates were welded.
In total, 173 central box girder sections – assembled at a factory in Fos-sur-Mer from parts that had been prefabricated in Lauterbourg in Alsace – were transported to Millau in lorries.Eighteen launching operations brought the two parts of the deck together above the Tarn. Each time, several thousands of tonnes were shifted 171 m. 1,743 metres of deck were assembled at the southern end, compared to 717 at the northern end. A tour de force made possible thanks to the use of 64 translation mechanisms: an innovative system custom-designed and -conceived by the Civil Engineering Works Manager.
Each translation mechanism consisted of a structure supporting the deck. Inside this structure, two sliders (wedges) were driven by hydraulic cylinders. The lower wedge would lift the slider above that was supporting the deck. Two cylinders thus enabled the whole system to be moved 60 cm. The lifting wedge would then retract and the translation mechanisms would return to their original positions. Each mechanism was connected to a central computer that controlled the movement ensuring it was perfectly synchronous.
The inverted-Y-shaped pylons were oriented lengthwise to form an extension of the split shafts of the piers.
These metal structures allowed stays to be anchored high above the deck, ensuring it is well-supported.
Two partially-stayed pylons were placed in front of each section of the deck during launching operations in order to limit overhang. The five other pylons were prefabricated behind the abutments, transported in a horizontal position by multi-wheel transport vehicles, and then set upright and welded onto the deck.
The road surface: custom-made, tested and approved
To address the issue of deck expansion, a special surface was developed by the Eiffage group's research teams.
The road surface of the Millau Viaduct is the result of several years of research.
It was designed to withstand distortion of the deck while remaining perfectly comfortable to drive on. Flexible enough to account for distortions in the steel without cracking, it also had to be strong enough to meet the requirements of a motorway (density, texture, adhesion, rut-resistant, etc.). Two years of work were needed to find "the" ideal solution.
Several operations preceded application of the road surface.
High-pressure blasting of 1-mm diameter steel shot (peening) removed all traces of rust from the deck.
A primary bonding layer was applied to the rust-free steel before applying a 4-mm-thick bituminous sheet that had been heat-sealed at 400°C. This is a perfect protection against the risk of corrosion.
Smooth and without a wrinkle, it covers the steel to a thickness of 6.7 cm.
A total of 10,000 tonnes of asphalt concrete was needed to lay the wearing course. Two asphalt production plants with a total capacity of 380t/h were specially set up to the north of the viaduct. Twenty five articulated lorries ensured the two finishers had a continuous supply. No supply disruption would stop the progress of the machines applying the asphalt.
Instruments: A viaduct scrutinised from every angle
Piers, deck, pylons and stays alike are equipped with a multitude of sensors. They are designed to detect the slightest movement of the viaduct and measure its wear resistance.
Air speed indicators, accelerometers, inclinometers and temperature sensors are all part of the toolbox of measuring instruments used. Twelve fibre-optic strain gauges were integrated into the footing of the pier P2. As the tallest pier of the viaduct, P2 is subjected to the most intense forces. These sensors detect movements as small as one thousandth of a millimetre.
Other strain gauges – electrical this time – are spread out all the way up P2 and P7. These devices are capable of providing up to 100 measurements per second. In high winds, they can continuously monitor the viaduct's reactions to extreme conditions.
Accelerometers, strategically placed on the deck, control the oscillatory phenomena that could affect the metal structure.
Movements of the deck at the abutments are monitored to the millimetre. The stays are also equipped with instruments, and their ageing is carefully analysed.
The data collected is transmitted via network to a computer located in the nearby operations centre at the toll gate.
The canopy: A twisted "leaf" of concrete
The buildings reserved for the viaduct's commercial and technical operations team and the toll gate are located 4 km north of the structure. The toll gate is protected by a twisted "leaf"-shaped concrete canopy. Composed of 53 parts (concrete segments), the canopy is 98 metres long and 28-metres wide, and rests on 48 metal poles. It weighs around 2,500 tonnes.
Construction of the toll gate canopy involved the use of a special, high-performance concrete, BSI Ceracem®. This contains metal fibres that give it enormous strength. It had never been used for a structure of this size before.