Millau Viaduct - World's Tallest Vehicular Bridge

Millau Viaduct - World's Tallest Vehicular Bridge
The Millau Viaduct (French: le Viaduc de Millau, Occitan: lo Viaducte de Milhau) is an enormous cable-stayed road-bridge that spans the valley of the river Tarn near Millau in southern France.

Designed by the structural engineer Michel Virlogeux and British architect Norman Foster, it is the tallest vehicular bridge in the world, with one mast's summit at 343 metres (1,125 ft) — slightly taller than the Eiffel Tower and only 37 m (121 ft) shorter than the Empire State Building.

The viaduct is part of the A75-A71 autoroute axis from Paris to Montpellier. Construction cost was around €400 million.

It was formally dedicated on 14 December 2004, inaugurated the day after and opened to traffic two days later.

The bridge won the 2006 IABSE Outstanding Structure Award.

The bridge’s construction broke three world records:

• The highest pylons in the world: pylons P2 and P3, 244.96 metres (803 ft 8 in) and 221.05 metres (725 ft 3 in) in height respectively, broke the French record previously held by the Tulle and Verrières Viaducts (141 m/460 ft), and the world record previously held by the Kochertal Viaduct (Germany), which is 181 metres (590 ft) at its highest;
• The highest bridge tower in the world: the mast atop pylon P2 peaks at 343 metres (1,130 ft).
• The highest road bridge deck in the world, 270 m (890 ft) above the Tarn River at its highest point. It is nearly twice as tall as the previous tallest vehicular bridge in Europe, the Europabrücke in Austria. It is slightly higher than the New River Gorge Bridge in West Virginia in the United States, which is 267 m (880 ft) above the New River. Only the bridge deck of the Royal Gorge Bridge in Colorado, United States (mainly a pedestrian bridge over the Arkansas River, occasionally also used by motor vehicles) is higher with 321 m (1,050 ft), and is considered the highest bridge in the world.

The Millau Viaduct consists of an eight-span steel roadway supported by seven concrete pylons. The roadway weighs 36,000 tonnes and is 2,460 m (8,100 ft) long, measuring 32 m (100 ft) wide by 4.2 m (14 ft) deep, making it the world's longest cable-stayed deck. The six central spans each measure 342 m (1,120 ft) with the two outer spans measuring 204 m (670 ft). The roadway has a slope of 3% descending from south to north, and curves in a plane section with a 20 km (12 mi) radius to give drivers better visibility. The pylons range in height from 77 m (250 ft) to 246 m (810 ft), and taper in their longitudinal section from 24.5 m (80 ft) at the base to 11 m (36 ft) at the deck. Each pylon is composed of 16 framework sections, each weighing 2,230 tons. These sections were assembled on site from pieces of 60 tons, 4 m (13 ft) wide and 17 m (56 ft) long, made in factories in Lauterbourg and Fos-sur-Mer by Eiffage. The pylons each support 87 m (290 ft) tall masts.

The enormous pylons were built first, together with intermediate temporary pylons which were in themselves a massive record-breaking construction project.

Remarkably, the entire length of deck surface (that is to say, the bridge itself, the actual kilometers of roadway) was slid out, into the valley, across the pylons from both sides.

This feat was achieved using hydraulic rams that moved the deck about 600 mm every 4 minutes, over the course of many days.

While the kilometers of roadway was being slid-out through space, it was supported by both the final pylons and the temporary pylons.

Only after the roadway was completely slid-out in to the final position, were the masts erected on top of the deck (that is to say, over the pylons). To be clear, the masts on top are not continuing elements of the pylons underneath, although they appear to be. The masts are separate constructions which were built on land, wheeled out to position only after the pylons and roadway were complete, raised (with difficulty), and emplaced.

The construction of the massive cable-stay system between the masts and deck then followed.

Finally, the massive temporary pylons in the valley were removed.

Construction began on 10 October 2001 and was intended to take three years, but weather conditions put work on the bridge behind schedule. A revised schedule aimed for the bridge to be opened in January 2005. The viaduct was inaugurated by President Chirac on 14 December 2004 to open for traffic on 16 December, several weeks ahead of the revised schedule.

The construction of the bridge was depicted in an episode of the National Geographic Channel MegaStructures series, as well as Discovery Channel's Extreme Engineering, both of which included time-lapse footage of the ultimate astonishing feat of sliding the roadway out over the valley, on to the plyons, to create the bridge.

Source: wikipedia.org, yawoot.com