Sydney Harbour Bridge

History of the Sydney Harbour Bridge

Sydney Harbour Bridge is the world's largest (but not longest) steel arch bridge, and in its beautiful harbour location, has become an international symbol of Australia.

Before the opening of the bridge there were two links between the city centre and the north. One was by ferry, which carried 40,000 people each day from Millers Point to Milsons Point; the other was a 20-kilometre road route that crosses several bridges. As the city developed, these links had turned out to be insufficient to accommodate the traffic in the Sydney/North Sydney area. Thus plans to build a bridge had been conceived as early as the 19th century. Designs and proposals were requested in 1900, but no formal proposal was accepted until 1911.

In 1912, Dr John J C Bradfield was appointed chief engineer of the bridge project. He was responsible for the concept and the general design, and documentation on which design/construct tenders specifications were based.. However, all plans for the implementation were postponed until 1922 because of outbreak of World War I. In 1922 New South Wales Government issued an international tender inviting qualified construction companies all over the world to participate. Finally, the contract went to the English firm Dorman Long and Co. Ltd on 24 March 1924. John Bradfield was appointed the supervisor of the design and engineering process. The detailed design and crucial erection process was undertaken by other contractors. The construction project itself began in 1923, with the demolition of more than 400 homes.

The Sydney Harbour Bridge, locally known as the "Coat Hanger" is one of Sydney's most famous landmarks.

The Sydney Harbour Bridge is founded on sandstone rock excavated to a depth of 12 m and filled with special reinforced high-grade concrete. Each half arch was built out from either side of the harbour, using a creeper crane that slowly progressed up the arch lifting steelwork into position as it went. The half arches were secured by wire ropes, anchored in inclined U-shaped tunnels cut into the rock. Each anchorage consisted of 128 wire ropes of 70 mm diameter, about 366 m long. The steelwork from the fabricating shops was placed onto barges, towed into position on the harbour and lifted up by creeper crane. When erection reached mid-span, the critical operation of closing the arch was achieved by lowering out on the wire rope anchorages to connect at bottom chord level, following which the required load was jacked into the top chord to make the arch two-pinned. The temporary wire rope anchorages were then removed. After the spans were connected, a deck was put in place. The deck was hung from the arch and built from the centre out so that they would not have to move the cranes.

Construction of the Sydney Harbour Bridge

The four impressive, decorative 89-metre high pylons are made of concrete, faced with granite. Three ships were specifically built to carry the 17,000 cubic metres of cut, dressed and numbered granite blocks, 300km north to Sydney.

Approximately 6 million rivets were used to make the bridge. In the 1920's welding was too unreliable and nuts and bolts were quite expensive so rivets were used. Rivets were heated to white-hot state in small furnaces located across the bridge, thrown to a catcher who passed them to the riveters. One man held the rivet firm while another hammered the other end with a pneumatic hammer. This forced the hot soft metal to mushroom out, covering the hole. Steel plates were transferred from barge to bridge by crane, often with a 'dogman' travelling with the load and then returning for the next 'delivery'. Plates were bolted into position as a temporary measure until being riveted together. The bridge was painted grey because grey is the closest colour to the natural colour of steel. In addition, it does not show dirt and dust. 485,000 square metres steelwork had to be painted which required 272,000 litres of paint to give the bridge its initial three coats. Constant inspections of the steelwork are made and painting is carried out on an 'as required' basis.

In February 1932 the Bridge was test loaded using up to 96 steam locomotives. The official opening day on Saturday 19 March 1932 was a momentous occasion, drawing remarkable crowds. The NSW Premier, the J. Lang, officially declared the Bridge open. However, when he was about to open the bridge by cutting the ribbon, Captain Francis de Groot moved forward on a horse and slashed the ribbon with a sword, declaring the bridge to be open "in the name of the people of New South Wales". He was promptly arrested and later convicted of offensive behaviour. The ribbon itself was retied and Lang continued to perform the opening ceremony. The celebrations continued with a gun-salute, a procession of passenger ships under the bridge, a fly-past, fireworks, cavalcade of decorated floats, marching groups and bands.

It took 8 years (7 years 356 days} to make the bridge at the cost of 10,057,170 pounds, 7 shillings and 9 pence. During the building of the bridge, men worked at dizzying heights without the benefit of harness or safety rails. Sixteen men died but only two fell from the arch. The workers enjoyed little in the way of safety equipment - no hard hats, safety lines, protective boots or special clothing.

The total length of the bridge 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 49 metres. The total steelwork weighs 52,800 tonnes, including 39,000 tonnes in the arch. The bridge is also made of 95,000 cubic metres of concrete. The Sydney Harbour Bridge is the widest (49 metres) long span Bridge in the world, and it has seven vehicle lanes, one bus lane, two train lines, a foot way and a cycle way.

In 1932, the annual average daily traffic volume (in both directions) was about 10,900. In June 1976, the one-billionth vehicle crossed the Sydney Harbour Bridge. In 2000, 161,000 vehicles crossed the bridge each day. Before the Harbour Tunnel opened in 1992, this figure was 181,878.