Construction Facts

• Two major obstacles faced in building this Megastructure were crossing the River Tarn, and spanning the huge gap from one plateau to the other. The solution proposed is unique- to use seven pylons instead of the usual two or three.

• SETEC’ approached the British Architect Sir Norman Foster to design a bridge to last 120 years.

• Tests revealed problems for drivers that how could the journey time be only about a minute using such a high, long and thin structure (just two lanes either way). The solution was to incline the bridge slightly (3%) to improve road visibility, and to make the whole structure curved (The curve is 20km in range;to lessen the sensation of floating) — even though this would lengthen the bridge to 2.5 km and add to the cost.Please note: The red towers in the picture were removed after completion of the Bridge.
  

• To prevent drivers from the distraction of the beautiful scenery, the hard shoulder on both sides was increased in width to three meters.

• Emergency phones were designed for every 500 metres along the full length on each side.

• It has been designed to look as delicate and transparent as possible. It uses the minimum amount of material, which made it less costly to construct,light and decreased the wind load : the deck, the masts rising above the road deck and the multi-span cables are all in steel.
• The steel deck was pre-constructed in 2,000 pieces at Eiffage’s Lauterbourg factory in Alsace and GPS-aligned, 60cm at a time.The factory was given just 20 months to supply the elements for the deck and the piers of the viaduct.

• To accommodate the expansion and contraction of the concrete deck, there is 1m of empty space at its extremities and each column is split into two thinner, more flexible columns below the roadway, forming an A-frame above the deck level.

• A 3m-wide emergency lane provides increased security. It will, in particular, prevent drivers from seeing the valley from the viaduct.

• As the bridge is exposed to winds of up to 151km/hr, side screens are used to reduce the effects of the wind by 50%. The speed of the wind at the level of the road therefore reflects the speed of the wind found at ground level.

• Construction work used approx. 127,000m³ of concrete, 19,000t (tonnes)of steel-reinforced concrete and 5,000t of pre-constraint steel (cables and shrouds). The project needed 205,000t of concrete, of which 50,000m³ will be reinforced concrete. In total, the viaduct weighs 290,000t.

• An 18-lane toll station 6km north of the Millau Viaduct is housed under a structure made of a special concrete patented by the group Eiffage.