Sydeny Horbour 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" on account of its arch-based design.
The bridge was the city's tallest structure until 1967. It is the widest bridge in the world. It is the world's largest single-arch bridge, but not the longest (as millions of Australian school children were erroneously taught). The bridge was officially opened on 19 March 1932. The Bayonne Bridge in the United States, opened four months earlier on 15 November 1931, is 70 cm (or 2.3 feet) longer.
The design bears a marked resemblance to that of the New York Hell Gate Bridge. Its design was used as a basis for the Tyne Bridge in Newcastle, England, which is almost identical, except to a smaller scale.
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 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 pass 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 the southern east pylon. 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. Otherwise, the pylons serve no structural purpose and are primarily to visually balance the bridge itself. They were originally not part of the design but were added later to allay concerns about structural integrity - ironically, as the pylons do not actually touch the bridge (except at road level).
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 tonnes, and six million hand-driven rivets hold the bridge together.

 
From: www.wikipedia.org