Sydney Harbour Bridge

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Lore & Background

Under the direction of John Bradfield of the New South Wales Department of Public Works, the bridge was designed and built by British firm Dorman Long of Middlesbrough, and opened in 1932. The bridge's general design, which Bradfield tasked the NSW Department of Public Works with producing, was a rough copy of the Hell Gate Bridge in New York City. The design chosen from the tender responses was original work created by Dorman Long, who leveraged some of the design from its own Tyne Bridge. The arch is composed of two 28-panel arch trusses; their heights vary from 18 m (59 ft) at the centre of the arch, to 57 m (187 ft) at the ends next to the pylons. The arch has a span of 504 m (1,654 ft), and its summit is 134 m (440 ft) above mean sea level; expansion of the steel structure on hot days can increase the height of the arch by 18 cm (7.1 in). The total weight of the steelwork of the bridge, including the arch and approach spans, is 52,800 tonnes (52,000 long tons; 58,200 short tons), with the arch itself weighing 39,000 tonnes (38,000 long tons; 43,000 short tons). About 79% of the steel, specifically those technical sections constituting the curve of the arch, was imported pre-formed from England, with the rest being sourced from the Newcastle Steelworks. The bridge is held together by six million Australian-made hand-driven rivets supplied by the McPherson company of Melbourne, the last being driven through the deck on 21 January 1932.

Reader's Guide

The Sydney Harbour Bridge is the eleventh-longest spanning-arch bridge in the world and the tallest steel arch bridge, measuring 134 m (440 ft) from top to water level. It was also the world's widest long-span bridge, at 48.8 m (160 ft) wide, until construction of the new Port Mann Bridge in Vancouver was completed in 2012. The road over the bridge is currently owned by the state government through NSW Motorways. The main roadway 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 southern end of the bridge is located at Dawes Point in The Rocks area, and the northern end at Milsons Point on the lower North Shore. There are six original lanes of road traffic through the main roadway, plus an additional two lanes of road traffic on its eastern side, using lanes that were formerly tram tracks. Adjacent to the road traffic, a path for pedestrian use runs along the eastern side of the bridge, whilst a dedicated path for bicycle use runs along the western side. Between the main roadway and the western bicycle path lies the North Shore railway line. At each end of the arch stands a pair of 89-metre-high (292 ft) concrete pylons, faced with granite. The pylons were designed by the Scottish architect Thomas S. Tait, a partner in the architectural firm John Burnet & Partners. The pylons themselves have no structural purpose; they were included to provide a frame for the arch panels and to give better visual balance to the bridge, and were only added to allay public concern about the structural integrity of the bridge. The south-eastern pylon contains a museum and tourist centre, with a 360° lookout at the top providing views across the harbour and city. The south-western pylon is used by Transport for NSW to support its CCTV cameras overlooking the bridge and the roads around that area. The two pylons on the north shore include venting chimneys for fumes from the Sydney Harbour Tunnel, with the base of the southern pylon containing the Transport for NSW maintenance shed for the bridge, and the base of the northern pylon containing the traffic management shed for tow trucks and safety vehicles used on the bridge. In 1942, the pylons were modified to include parapets and anti-aircraft guns designed to assist in both Australia's defence and general war effort.

Did You Know?

• The bridge's nickname 'the Coathanger' comes from its arch-based design.
• The arch's height can increase by 18 cm (7.1 in) on hot days due to expansion of the steel.
• The bridge is held together by six million Australian-made hand-driven rivets, the last driven on 21 January 1932.
• The largest rivets used weighed 3.5 kg (8 lb) and were 39.5 cm (15.6 in) long.
• The four granite-faced pylons have no structural purpose; they were added to allay public concern about the bridge's integrity.

Design & Engineering Heritage

The bridge's general design, which John Bradfield tasked the NSW Department of Public Works with producing, was a rough copy of the Hell Gate Bridge in New York City. However, the design chosen from the tender responses was original work created by Dorman Long, who leveraged some of the design from its own Tyne Bridge. The resulting structure is a steel through arch with a span of 504 m (1,654 ft), and its summit is 134 m (440 ft) above mean sea level. The arch is composed of two 28-panel arch trusses; their heights vary from 18 m (59 ft) at the centre of the arch, to 57 m (187 ft) at the ends next to the pylons. Expansion of the steel structure on hot days can increase the height of the arch by 18 cm (7.1 in). The total weight of the steelwork of the bridge, including the arch and approach spans, is 52,800 tonnes (52,000 long tons; 58,200 short tons), with the arch itself weighing 39,000 tonnes (38,000 long tons; 43,000 short tons). About 79% of the steel, specifically those technical sections constituting the curve of the arch, was imported pre-formed from England, with the rest being sourced from the Newcastle Steelworks. At the time of its 1932 opening, it was the world's widest long-span bridge, at 48.8 m (160 ft) wide, until construction of the new Port Mann Bridge in Vancouver was completed in 2012. It remains the tallest steel arch bridge, measuring 134 m (440 ft) from top to water level.

The Pylons & the Granite Story

At each end of the arch stands a pair of 89-metre-high (292 ft) concrete pylons, faced with granite. The pylons were designed by the Scottish architect Thomas S. Tait, a partner in the architectural firm John Burnet & Partners. The pylons themselves have no structural purpose; they were included to provide a frame for the arch panels and to give better visual balance to the bridge, and were only added to allay public concern about the structural integrity of the bridge. Some 250 Australian, Scottish, and Italian stonemasons and their families relocated to a temporary settlement at Moruya, 300 km (186 mi) south of Sydney, where they quarried around 18,000 m3 (635,664 ft3) of granite for the bridge pylons. The stonemasons cut, dressed, and numbered the blocks, which were then transported to Sydney on three ships built specifically for this purpose. The Moruya quarry was managed by John Gilmore, a Scottish stonemason who emigrated with his young family to Australia in 1924, at the request of the project managers. The concrete used was also Australian-made and supplied from Kandos. Today, all four pylons serve practical roles: the south-eastern pylon contains a museum and tourist centre, with a 360° lookout at the top providing views across the harbour and city; the south-western pylon is used by Transport for NSW to support its CCTV cameras; the two pylons on the north shore include venting chimneys for fumes from the Sydney Harbour Tunnel, with the base of the southern pylon containing the Transport for NSW maintenance shed for the bridge, and the base of the northern pylon containing the traffic management shed for tow trucks and safety vehicles used on the bridge. In 1942, the pylons were modified to include parapets and anti-aircraft guns designed to assist in both Australia's defence and general war effort.

Steel, Rivets & the Craft of Assembly

The bridge's steelwork involved a trans-Pacific supply chain. About 79% of the steel, specifically those technical sections constituting the curve of the arch, was imported pre-formed from England, with the rest being sourced from the Newcastle Steelworks. On site, Dorman Long & Co set up two workshops at Milsons Point, at the site of the present-day Luna Park, and fabricated the steel into the girders and other required parts. The entire structure is held together by six million Australian-made hand-driven rivets supplied by the McPherson company of Melbourne, the last being driven through the deck on 21 January 1932. The rivets were heated red-hot and inserted into the plates; the headless end was immediately rounded over with a large pneumatic rivet gun. The largest of the rivets used weighed 3.5 kg (8 lb) and was 39.5 cm (15.6 in) long. The practice of riveting large steel structures, rather than welding, was, at the time, a proven and understood construction technique, whilst structural welding had not at that stage been adequately developed for use on the bridge.

A Living Corridor of Traffic

The bridge carries rail, vehicular, bicycle and pedestrian traffic. The southern end of the bridge is located at Dawes Point in The Rocks area, and the northern end at Milsons Point on the lower North Shore. There are six original lanes of road traffic through the main roadway, plus an additional two lanes of road traffic on its eastern side, using lanes that were formerly tram tracks. Adjacent to the road traffic, a path for pedestrian use runs along the eastern side of the bridge, whilst a dedicated path for bicycle use runs along the western side. Between the main roadway and the western bicycle path lies the North Shore railway line. The main roadway 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 road over the bridge is currently owned by the state government through NSW Motorways. The view of the bridge, the harbour, and the nearby Sydney Opera House is widely regarded as an iconic image of Sydney, and of Australia itself. Its nickname, 'the Coathanger,' comes from its arch-based design.

Common Misconceptions (Editorial)

Some people believe the Sydney Harbour Bridge was designed solely by John Bradfield or entirely by the New South Wales Department of Public Works. In fact, while Bradfield directed the project and his department produced a general design based on the Hell Gate Bridge, the final design chosen from the tender responses was original work created by Dorman Long, who also leveraged some of its own design from the Tyne Bridge.

Why It Matters (Editorial)

The Sydney Harbour Bridge endures as a symbol of engineering ambition and national pride, connecting not just two sides of the harbour but also the city's past to its present. Its iconic silhouette, set against the Opera House and the water, continues to define Sydney’s identity and inspire recognition worldwide.

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