Day 345/365 of Steel – Sydney Harbour Bridge

Official opening of the Sydney Harbour Bridge on March 19,1932.

The Sydney Harbour Bridge is a steel through arch bridge in Sydney. The view of the bridge, the harbor, and the nearby Sydney Opera House is widely regarded as an iconic image of Sydney. Nicknamed “The Coathanger” because of its arch-based design, the bridge carries rail, vehicular, bicycle and pedestrian traffic.

Sydney Harbour Bridge, Sydney, New South Wales, Australia
Fig 1: Sydney Harbour Bridge, Sydney, New South Wales, Australia
Photo: Dietmar Rabich / Wikimedia Commons / “Sydney (AU), Harbour Bridge — 2019 — 2179” / CC BY-SA 4.0

The bridge was designed and built by British firm Dorman Long. The bridge’s general design 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 at the center of the arch to 57 m at the ends next to the pylons. The arch has a span of 504 m and its summit is 134 m above mean sea level. The total weight of the steelwork of the bridge, including the arch and approach spans, is 52,800 tons.

Sydney Harbour shot taken from the air.
Fig 2: Sydney Harbour shot taken from the air.
Photo: Rodney Haywood / Wikimedia

The bridge is held together by six million Australian-made hand-driven rivets supplied by the McPherson company of Melbourne. 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 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.

The most noticeable maintenance work on the bridge involves painting. A special fast-drying paint is used, so that any paint drops have dried before reaching the vehicles or bridge surface.

About the Author:

Bruno Dursin – Managing Director at Believe in Steel. Bruno has more than 30 years of experience in promoting steel & steel solutions. His clients benefit from his extensive network within the building industry.

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