Le Viaduc de Millau
I have decided to kick off my Structures & Things page with a short piece on one of my favourite pieces of civil engineering; the Millau Viaduct. Officially named le Viaduc de Millau, this record-breaking, multi-span, cable-stayed bridge lies in the South of France, spanning the Valley of the River Tarn.
My fascination with the Millau Viaduct began a few years ago, during a school trip to France in 2011. I remember driving over a viaduct during the coach journey and being in disbelief at how high off the ground we were.
As it often does, my curiosity got the better of me, and once we had returned home I tried to find out what exactly we had driven over. Without any knowledge of the context of the viaduct, finding it was a struggle. Despite many ambiguous internet searches like “really tall bridge in France” I never managed to find my answer, but I did find the Millau Viaduct instead. For a while, I thought the Millau Viaduct was the bridge we crossed while on the trip however, I soon came to realise that this doesn’t make sense geographically. The destination of our trip was in Normandy, so there was no way we would have made it all the way down to Southern France. Although I’m not entirely sure, it makes sense that it was the Normandy Bridge we had crossed, but I didn’t make this connection until much later. Despite this, I was fascinated by the immense magnitude of the bridge and spent hours wondering how erecting such a structure was possible.
The bridge was built to solve the problem of a “missing link” along the A75 autoroute which runs across a region called the Massif Central, and also created a lot of through traffic into the valley. With the bridge completing the link, the A75 was then able to provide motorists with a direct, high-speed route from Paris to the Mediterranean Coast and on to Barcelona, cutting 37 miles off of the previous route.
A Few Facts ¹ ²
- Construction of the Millau Viaduct started on 16th October 2001
- It was opened on 16th December 2004
- It has a total length of 2.46km (1.53mi)
Comprises six central sections of 342m each, with two 204m sections at either end of central span
- It has the tallest pylons in the world
Piers range from 75m to 245m with masts rising a further 87m above the road deck
- It has the highest road bridge deck in Europe
Deck height of 273m from deepest point in valley
- It superseded the Eiffel Tower as the tallest structure in France
- It was the winner of the 2006 IABSE Outstanding Structure Award
A Few Numbers ¹
- 270m: Average height of the roadway
- 4.20m: Thickness of the roadway
- 32.05m: Width of the roadway
- 85,000m³: Total volume of concrete used
- 290,000 tonnes: Total weight of the bridge
- 10,000–25,000 vehicles: Estimated daily traffic
- 20 km (12 mi): Horizontal radius of curvature of the road deck
- €400,000,000: Approximate cost of bridge
You might wonder why I’m so fascinated with this bridge, when there are longer, and higher bridges in the world. Having previously thought I had once travelled across it, I’d say my fascination for this bridge was sparked by a misplaced personal attachment. It grew, however, the more I looked at and read about it, even after realising it wasn’t the bridge I was looking for.
The engineering behind the construction of this project is what stands out to me; the height of the bridge and the distance between piers meant that cranes could not be used to hoist the deck sections into position. This problem was overcome by the sections being slowly “pushed” into place from either side, with temporary piers being built to support the deck and reduce the span. Cable-stayed pylons were used to support the overhanging sections, with a rail like structure installed below the deck. ³
Personally, this bridge balances function and aesthetics almost perfectly; its appearance, sheer size and the physics behind keeping it standing, are what keep me in awe. Even as I write this, every time I scroll up and the header image comes into view, I have to shake my head and ask how. This is an example of making the impossible, possible, and also of the kind of engineering feats I want to emulate during my career. Hopefully, I will be able to cross the right bridge some time in the future.
Originally published at abovegroundlvl.co.uk on February 23, 2016.
