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Sydney Harbour Bridge

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Engineering materials

Concrete

The bridge structure sits on four large concrete ‘skewbacks’. Two are on the south shore and two on the north. The excavation for these was directly into the solid sandstone. More…

Steel

The Sydney Harbour Bridge is a steel structure, with the steel arch carrying the live and dead loads out to the underground concrete abutments. The steel used by Dorman, Long & Co. Ltd. was not mild steel or plain-carbon steel. They chose to use a precursor to modern day structural steels: silicon steel. More…

Corrosion

The Sydney Harbour Bridge’s use of ferrous alloy presents a significant challenge in terms of protecting the structure from the ravages of corrosion. Unfortunately steel oxidises to form rust, a corrosion product that is porous which means that the rust exposes more metal to oxidation. More…

Cable sockets

During the construction of the bridge, each half arch was built out from each shore supported on each of the main bearings. As the main bearings are designed to allow a small amount of rotation (to take up changes in loads, and expansion and contraction due to temperature change) each half-arch had to be supported in some way to prevent it from falling into the harbour. This support was provided using cables mounted to 'link plates' near the top of the half arch and passing through 'U' shaped tunnels underground. More…

Rivets

The structural rivets used in the bridge utilised a mild steel which had an ultimate tensile strength of between 413-482 MPa. This steel had sufficient tensile strength and shear strength for its use as rivets in the construction of the bridge. More…

Testing

During the building of the bridge many different forms of testing were carried out to ensure the quality of materials being used and to ensure that structural members were capable of withstanding the applied loads. When the bridge was complete it was tested to determine that no one member ,or group of members, within the structure were likely to be over-stressed during service. More…

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