Millau ViaductCopyright: phbcz 123rf.com

Millau Viaduct

The Millau Viaduct was born out of the need to speed up transport between Spain and France across the Millau and Tarn Valley region of southern France as well as a crossing of the Tarn River. During the summer months this region became grid locked with holiday makers as well as the regular traffic.

Construction began on 14th December 2001 and was opened on 10th January 2005. British designer, Norman Foster wanted a design that was 'as delicate as a butterfly', a bridge that would enhance the natural beauty of its surroundings and the region. This vision can be seen shortly after sunrise in the Autumn where the bridge is above the fog as though it is floating on the clouds, 'as delicate as a butterfly'.

The construction was a technical challenge as no crane was able to reach the height. It was decided that the roadway was to be built in separate halves on each side. As each half grew it was literally rolled out to the next pylon until it met in the middle. It was a massive engineering and technological risk as nothing like it had ever been attempted before, but it proved successful and cost effective.

The deck itself is an inverse aerofoil, like an upside-down aeroplane wing, giving it a negative lift and weighs 360,000kg (36,000 tonnes). The deck surface is a specially formulated bitumen that is designed to be very flexible as well as hard wearing. The structure is subjected to high temperature variations which stresses the metallic deck structure and not forgetting very high winds in the Millau Valley and it took 2 years of research to find the right surface material.

To the top of the pylons the structure is 343m (1,125ft) which is 9m (30ft) taller than the Eiffel Tower. Each pylon is brimming with high tech instruments that measure movement in the bridge as small as a micrometer, 0.001mm and doing this a hundred times per second! All this requires 30km (18.5 miles) of electrical cable. Other instrumentation measure the wind and temperature as well as others that monitor traffic numbers, speed and pollution.

The maximum speed limit was originally set at 130km/h (80mp/h) but was reduced to 110km/h (70mp/h) due to people stopping to admire the incredible views.

The bridge is a toll and the booths along with other buildings for maintenance and monitoring are 4km (2.5 miles) north of the crossing itself.

Millau ViaductCopyright: Tamas Sebestyen Flickr

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