Bridging technology and design gap

By Matthew Knight for CNN

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(CNN) -- There can be few less glamorous modern problems in the world than traffic congestion and often the solution of a bypass displaces people, wildlife and creates a vast ugly swathe of concrete through what was once a picturesque landscape.

But the people of the ancient town of Millau in the Languedoc region of Southern France now not only have quieter streets, but a bridge of breathtaking beauty and a modern structure which is a tourist attraction in its own right.

The fusion of modern technology, engineering and design displayed by the Millau Bridge has been seldom matched.

From its conception at the offices of world-leading architect Norman Foster to completion by the French construction company Eiffage, it has set new standards for design and construction.

Spanning two plateaus in the Massif Central mountains (France's paragliding capital) the bridge, at its highest point, towers over 340 meters above the floor of the Tarn valley. That's higher than the Eiffel Tower and tall enough to squeeze London's Canary Wharf underneath it.

The Millau Bridge is a cable-stayed structure consisting of seven reinforced concrete pillars ranging from 75 to 235 meters tall.

The masts which rise above the roadway and the multi-span cables are all made of steel. The height of the pillars meant that the usual way of laying the road deck -- using cranes to lift sections into place -- was not an option, so a new untried method in cable-stayed bridge construction was sought.

Using hundreds of hydraulic cylinders and pumps, the road deck (made from high grade steel) was literally rolled out from either end of the bridge.

Using GPS satellite system, 2000 pre-assembled pieces of road deck were painstakingly laid 60 cm at a time, finally meeting in the middle in June 2004, whereupon Felix Baumgartner, the famous BASE jumper put another notch on his skydiving bedpost and leapt from the newly completed platform.

In total the bridge weighs in the region of 290,000 tonnes and is a vast structure, but set against the landscape it succeeds in Foster's aims of having "the delicacy of a butterfly" and "fusing with nature."

Indeed when the fog shrouds the valley below, the sensation of floating above the clouds, when crossing the bridge, is palpable. The cables which anchor the road deck can take on the appearance of the masts and sails of seven ships. To counteract any sense of disorientation and reassure drivers who pass through the tollgates, the bridge was designed with a gentle curve and has a 3% incline which also improves visibility.

Jean Pierre Martin, the project director believes that the bridge is proof of the speed with which engineering techniques are improving. "Ten years ago", he said, "These problems might not have been overcome".

Delivered on budget -- €400m -- and on time -- opening to drivers on 16th December 2004 -- the bridge has exceeded the best expectations its designers and builders had for it and has become a modern engineering wonder to look at again and again.

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