SYDNEY HARBOUR BRIDGE
The Sydney Harbour Bridge is one of the major landmarks of Sydney, Australia, connecting the Sydney central business district (CBD) with the North Shore commercial and residential areas, both of which are located on Sydney Harbour.
The dramatic water vista of the bridge together with the nearby Sydney Opera House is an iconic image of both Sydney and Australia. The bridge is affectionately known as "the Coathanger" by many Sydney residents on account of its arch-based design. It was the city's tallest structure until 1967.
Its design was used as a basis for the Tyne Bridge in Newcastle, England, which is almost identical, except to a smaller scale, which resulted in it being completed 4 years earlier than the Sydney bridge in 1928.
The Bayonne Bridge in the United States, opened on 15 November 1931, is 70 cm (or 2.3 feet) longer. However, that fact was not generally known, and millions of Australian school children throughout the next 50 years were taught, erroneously, that the Sydney Harbour Bridge was the world's longest single-arch bridge. However, it remains the world's largest (but not the longest) steel arch bridge.
The bridge's two ends are located in at Dawes Point (in Sydney's Rocks area) and Milsons Point (in Sydney's lower North Shore area). It carries six lanes of road traffic on its main roadway, two lanes of road traffic (formerly two tram tracks) and a footpath on its eastern side, and two railway tracks and a bicycle path along its western side. The road carried across the bridge is known as the Bradfield Highway and is about 2.4 km/1.5 mi long, making it one of the shortest highways in Australia. (The shortest, also called the Bradfield Highway, is found on the Story Bridge in Brisbane). At 48.8 m/151.3 ft wide, it is the widest bridge in the world (Guinness World Records, 2004).
The bridge deck portion of the highway is 1.149 km/.71 mi long. It is concrete and lies on trimmers (beams that run along the length of the bridge). The trimmers themselves rest on steel beams that run along the width of the bridge. The trimmers and beams are visible to boats that go underneath the bridge.
The arch is composed of two 28-panel arch trusses. Their heights vary from 18 m/55.8 ft (at the center of the arch) to 57 m/176.7 ft (beside the pylons). The arch span is 503 m/1559 ft and the weight of the steel arch is 39,000 tons. The arch's summit is 134 m/415.4 ft above mean sea level, though it can increase by as much as 180 mm/7 in on hot days as the result of steel expanding in heat. Two large metal hinges at the base of the bridge accommodate these expansions and contractions and thereby prevent the arch from being damaged.
The two pairs of pylons at each end are about 89 m/276 ft high and are made of concrete and granite. A museum and tourist centre with a lookout of the harbour is in one of the southern pylons. Abutments, which support the ends of the bridge, are contained at the base of the pylons. They prevent the bridge from stretching or compressing due to temperature variations.
The steel used for the bridge was largely imported. About 79% came from Redcar in the North East of Britain, the rest was Australian-made. The granite used was quarried in Moruya, New South Wales, and the concrete used was also Australian made.
The total weight of the bridge is 52,800 t, and six million hand-driven rivets hold the bridge together.
Motor vehicle access to the bridge is normally via York Street, the Cahill Expressway, or the Western Distributor. Drivers on the northern side will find themselves on the Warringah Freeway, though it is easy to turn off the freeway to drive westwards into North Sydney or eastwards to Neutral Bay and beyond upon arrival on the northern side.
To travel across the bridge there is a toll for vehicles of AUD$3.00. This toll is only charged for traffic headed into the CBD (southbound). No toll is charged for pedestrian traffic or bicycles. There are toll plazas at the northern and southern ends. The eastern-most southbound lanes (which continue over the Cahill Expressway after leaving the bridge) have their tollbooths at the northern end of the bridge, with the remainder being at the southern end of the bridge.
Pedestrian access from the northern side involves climbing an easily-spotted flight of stairs at Milsons Point. Pedestrian access on the southern side is more complicated, but signposts in the Rocks area now direct pedestrians to the long and sheltered flight of stairs that leads to the bridge's southern end. These stairs are located near Gloucester Street and Cumberland Street in the Sydney Rocks area.
It can also be accessed from the south by getting on Cahill Walk, which runs along the Cahill Expressway. Pedestrians can access this walkway it from Circular Quay from a flight of stairs, or a lift, alternately they can be accessed from The Botanical Gardens.
The bridge lies between Milson's Point and Wynyard railway stations, located on the north and south shores respectively. Both are part of the North Shore line.
 PLANNING OF THE SYDNEY HARBOUR BRIDGE
There had been plans to build a bridge as early as 1815, when Francis Greenway proposed that a bridge be built across the harbour. Nothing came of this.
The building of the current bridge can be said to have started in 1890, when a royal commission determined that there was a heavy level of ferry traffic in the Sydney Harbour area, best relieved with the construction of a bridge. Vehicular access to the north shore was undertaken with a series of smaller bridges located further westwards in the harbour, but this was insufficient for the traffic in the Sydney/North Sydney area.
Designs and proposals were requested in 1900, but a formal proposal was not accepted until 1911. In 1912, John Bradfield was appointed chief engineer of the bridge project, which also had to include a railway. He completed a formal design - the now familiar single arch shape - in 1916, but plans to implement the design were postponed until 1922, primarily because of World War I.
In November 1922 the NSW parliament passed laws that allowed the bridge's construction. Construction tenders for the bridge were requested the same year, and the British firm Dorman Long and Co Ltd, Middlesbrough won. To offset concerns about a foreign firm participating in the project, assurances were given by Bradfield that the workforce building the bridge would all be Australians.
The building of the bridge coincided with the construction of a system of underground railways in Sydney's CBD, known today as the City Circle, and the bridge was designed with this in mind. The bridge was designed to carry six lanes of road traffic, flanked by two railway tracks and a footpath on each side. Both sets of rail tracks were linked into the underground Wynyard railway station, on the south side of the bridge, by symmetrical ramps and tunnels. The eastern-side railway tracks were used to carry trams from the north into a terminal within that station.
CONSTRUCTION OF THE SYDNEY HARBOUR BRIDGE
The building of the bridge was under the management of Bradfield. Three other persons were involved in the bridge's design and construction: Laurence Ennis, the engineer-in-charge at Dorman Long and Co was the main supervisor (Bradfield visited occasionally throughout the project, and in particular at the many key stages of the project, to inspect progress and make managerial decisions); Edward Judge was Chief Technical Engineer of Dorman Long and later became President of the British Iron and Steel Federation; Sir Ralph Freeman was hired by the company to design the accepted model in further detail. Later a bitter disagreement broke out between Bradfield and Freeman as to who actually designed the bridge. Another name connected with the bridge's design is that of Arthur Plunkett.
The construction project itself began in 1923, with the demolition of 800 homes. The owners of these homes received compensation, but their occupants did not.
The first stage of the bridge project was the building of two worksheds at Milson's Point to assist in building the bridge - the light and heavy workshops. Their purpose was to build the bridge's many parts.
The first sod for the bridge was turned that same year. In January 1925, the excavations to build the abutments and approach spans began. In October 1925, the building of the abutments and approach spans themselves began, and these were completed in September 1928. Construction of the bridge itself began in December 1928, with the construction of the bridge parts in the workshops.
Construction of the arch of the bridge began in 1929, with two separate teams building the arch on each side using creeper cranes. The first panel was erected on the southern side in March 1929. The southern end of the bridge was worked on a month ahead of the northern end, in order to detect any errors and to ensure that they did not happen on the northern side.
The arch was successfully joined on the afternoon of 19 August 1930. Ennis and four associates personally witnessed this whilst standing on top of the bridge. Following a parting that occurred due to the contracting of metal in the evening, the ends were rejoined at 10 pm, and have remained joined since then.
The road and the two sets of tram and railway tracks were completed in 1931. Power and telephone lines, and water, gas and drainage pipes were also all added to the bridge in that year. On 19 January 1932, the first test train, a steam locomotive, safely crossed the bridge. About 90 others also crossed the bridge in the months that followed as part of a series of tests to ensure the bridge's safety.
The construction worksheds were demolished after the bridge was completed, and the land that they were on is now occupied by Luna Park and the North Sydney swimming pool.
The standards of industrial safety during construction were poor by today's standards. Sixteen workers died during construction, mainly from falling off the bridge. Several more were injured from unsafe working practices undertaken whilst heating and constructing its rivets, and deafness experienced by many of the workers in later years was blamed on the project.
The total financial cost of the bridge was £10,057,170/7/9. This was not paid off in full until 1988.
Retrieved from Wikipedia.org, the Free Encyclopedia
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