Millau Bridge, France

When it was opened on 17 December 2004, the spectacular Millau Viaduct set new standards in both planning design and construction - without mentioning the record it set as the largest cable-stayed bridge in Europe.

At 2.4km long, and 270m above the river at its highest point, the Millau viaduct spans a 2km valley in the Massif Central mountain range and forms the final link in the A75 highway from Paris to Barcelona. Despite its huge length, journey time over the structure is expected to be just one minute.

Two major challenges were identified in building the structure: crossing the River Tarn, and spanning the huge gap from one plateau to the other. The solution proposed is unique, using seven pylons instead of the typical two or three. It is several metres taller than that other famous French landmark, the Eiffel Tower.

Famous British architect Norman Foster was in charge of the viaduct's appearance. It has been designed to look as delicate and transparent as possible. Each of its sections spans 342m and its columns range in height from 75m to 235m over the river Tarn. It uses the minimum amount of material, which made it less costly to construct: the deck, the masts rising above the road deck and the multi-span cables are all in steel.

The seven piers of the Millau Viaduct are sunk in shafts of reinforced concrete in a pyramidal shape, being divided in an overturned V, and the shrouds are anchored and distributed in semi harps. The program utilised hundreds of high-pressure hydraulic cylinders and pumps to push-launch the deck spans in place and a PC-synchronised lifting system to lift the auxiliary piers. Enerpac was awarded the major contract to supply the hydraulic system for lifting and pushing the bridge spans and piers for the bridge.

Intriguingly, the Millau Viaduct is not straight. A straight road could induce a sensation of floating for drivers, which a slight curve remedies. The curve is 20km in range. Moreover, the road has a light incline of 3% to improve the visibility and reassure the driver.

The Millau Viaduct is supported by multi-span cables placed in the middle. 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.

Construction work used approx. 127,000m³ of concrete, 19,000t 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

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

As the bridge will be 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 around Larzac and Sauveterre.

Sydney Harbour Bridge

Sydney Harbour Bridge is the world's largest (but not longest as thats the New River Gorge in the USA) steel arch bridge, and, in its beautiful harbour location, has become a renowned international symbol of Australia.

The Sydney Harbour Bridge, also affectionately known as the 'Coathanger', was opened on March 19th 1932 by Premier Jack Lang, after six years of construction. Made of steel the bridge contains 6 million hand driven rivets. The surface area that requires painting is equal to about the surface area of 60 sports fields. The Bridge has huge hinges to absorb the expansion caused by the hot Sydney sun. You will see them on either side of the bridge at the footings of the Pylons.

Its total length including approach spans is 1149 metres and its arch span is 503 metres. The top of the arch is 134 metres above sea level and the clearance for shipping under the deck is a spacious 49 metres. The total steelwork weighs 52,800 tonnes, including 39,000 tonnes in the arch. The 49 metre wide deck makes Sydney Harbour Bridge the widest Longspan Bridge in the world.

After inviting worldwide tenders in 1922, the New South Wales Government received twenty proposals from six companies and on 24 March 1924; the contract was let to the English firm Dorman Long and Co of Middlesbrough.

You can have a close hand look while you are in Sydney by visiting the South Eastern Pylon. It is a walking trip and recommended for the fit only. It is a longish walk to get to the base of the Pylon and then there are 200 steps to the top.

The general design was prepared by Dr J.J.C Bradfield and officers of the NSW Department of Public Works, while the detailed design and crucial erection process were undertaken by the contractors consulting engineer Mr (later Sir) Ralph Freeman of Sir Douglas Fox and Partners and his associate Mr. G.C Imbault.

As Chief Engineer of Sydney Harbour Bridge and Metropolitan Railway Construction from 1912, Dr Bradfield is regarded as the "father" of the Bridge as it was his vision, enthusiasm, engineering expertise and detailed supervision of all aspects of its construction which brought Sydney's long held dream into reality.

The official opening day on Saturday 19 March 1932 was a momentous occasion, drawing remarkable crowds (estimated between 300,000 and one million people) to the city and around the harbour foreshores. The NSW Premier, the Hon. John T. Lang, officially declared the Bridge open. However, the Premier enlivened proceedings when Captain Francis De Groot of the para-military group, the New Guard, slashed the ribbon prematurely with his sword, prior to the official cutting. This incident caused both amusement and dismay on the day and has since become part of Australian folklore.