Sydney Harbour Bridge: Construction & History

Instructor: Christopher Muscato

Chris has a master's degree in history and teaches at the University of Northern Colorado.

The opera house isn't Sydney Harbour's only notable landmark. In this lesson, we'll check out the bridge that spans this harbor and see what role it played in Australian history.

The Sydney Harbour Bridge

Most cities in the world share a basic policy when it comes to their bridges: no climbing. Considering the numerous issues of public and personal safety that immediately come to mind, it's understandable. Sydney, Australia is apparently not like most cities. Amongst the iconic landmarks of the city's famed harbor is the Sydney Harbour Bridge, the tallest of its kind in the world. Rather than telling people to stay off, however, the city promotes climbing the sides of this towering structure as a recreational activity. Equipped with climbing gear and led by professional guides, the bold can trek to the top of the bridge for an unparalleled view of the city. It might sound crazy, but Australians are pretty proud of the Sydney Harbour Bridge.

The Sydney Harbor Bridge
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History

The history of the Sydney Harbor Bridge dates back to about 1815, the first time that proposals were made to connect the north and south shores of Sydney Harbour. At that point, the only ways to make this trip were to take a ferry across the harbour or travel the roughly 12-mile journey around the shore. A bridge was needed, but it would take a while before serious efforts were made.

Part of the concern was technology. It wasn't until the mid- to late-19th century that wrought iron construction became readily available, and it was even later that steel construction was possible. After World War I, efforts to use the technological advancements encouraged serious efforts to create a bridge that could span the harbour without impeding boat traffic. The government of New South Wales opened up an international commission for the bridge, based on the rough design their Public Works had come up with, and in 1922 awarded the project to Dorman Long and Co., an English company. Construction started in 1924 and 8 years, 4.2 million Australian pounds, six million rivets, and 53,000 tons of steel later, the bridge opened to the public in 1932.

Construction began on either end of the harbor and worked towards the center
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Design

The Sydney Harbour Bridge is roughly 440 feet tall, 3,770 feet long, and an incredible 160 feet wide. All of these numbers made it a sight to see in 1932, but what was really novel at the time were the materials and design. The foundations and other parts of the bridge are set with reinforced concrete, which at that time was still a new technique. Most of the bridge, however, is made of steel. Remember, this is the same time that the Empire State Building was being constructed. Steel-frame construction was still also new and a symbol of modern technology and ingenuity. So, this steel-frame bridge that left the skeleton exposed as opposed to covered by a concrete or stone façade, was a strong statement about Sydney's place in the modern world.

The design itself is both ancient and new. In the most basic terms, the Sydney Harbour Bridge is an arch bridge, distributing the weight of the structure across a distance by dispersing it outwards through the arch. This is an ancient design, beloved especially be the ancient Romans. However, the Romans never built bridges of this size. It's the steel that makes that possible.

Still, if you look at the bridge then you may notice something strange about it. In the traditional arch bridge, the arch is under the bridge. That's not the case here. The deck crosses right through the arch. So, the base of the arch is below the deck, but the top of the arch is far above it. Steel cables support the deck, which is actually suspended from the arch rather than resting on top of it. Technically, that makes this a through-arch bridge, not just an arch bridge. This system is very effective, so much so in fact that those massive pylons (which traditionally anchor the cables or support the arch) are almost useless. They're more decorative than functional.

From this angle you can see the arch pass through the deck
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