The Pyrmont Bridge, a heritage-listed swing bridge across Cockle Bay, is located in Darling Harbour, part of Port Jackson, west of the central business district in the City of Sydney local government area of New South Wales, Australia. Opened in 1902, the bridge initially carried motor vehicle traffic via the Pyrmont Bridge Road between the central business district and Pyrmont. Since 1981 the bridge has carried pedestrian and bicycle traffic only, as motor vehicles were diverted to adjacent freeway overpasses. 

The foundation stone for the new bridge was laid on 6 December 1899 by E. W. O'Sullivan and the bridge was opened for traffic on 28 June 1902 by the Governor of New South Wales, Harry Rawson.[10] The bridge was designed under the engineering supervision of Percy Allan. The bridge had one of the largest swing spans in the world at the time of its construction and it was one of the first to be powered by electricity. Allan also designed the similar Glebe Island Swing Bridge, completed in 1903.

The Pyrmont Bridge is 369 metres (1,211 ft) long and cost £112,500 to build. The bridge is made up of 14 spans with Australian ironbark timber used on 12 spans, while the two central spans, which swing, are constructed from steel. The swingspan weighs 1,000 tonnes (1,100 short tons) and is supported on a base made from concrete and Hawkesbury Sandstone. The base is filled with mass concrete and weighs 6,800 tonnes (7,500 short tons). The swingspan is 13 metres (43 ft) in diameter and 19 metres (62 ft) deep. The water is 6.5 metres (21 ft) deep and the base extends a further 10 metres (33 ft) below the sea floor.[3]

Pyrmont Bridge takes approximately 60 seconds to open completely to 83 degrees. It has to be opened for vessels more than 7 metres (23 ft) high. Vessels/barges up to 21.5 metres (71 ft) wide can pass through the channel once the Bridge has been opened. Pyrmont Bridge is driven by the original two 50 horsepower (37 kW) 600 V DC General Electric type 57 electric motors. Manual drum-type General Electric tramway controllers are used to drive the motors for the swingspan and gates. Power to operate the bridge was originally drawn from the Ultimo Power House (now the Powerhouse Museum). As a young engineer, J.J.C. Bradfield helped design the sandstone abutment walls at each end of Pyrmont Bridge.

SOURCE: https://en.wikipedia.org/wiki/Pyrmont_Bridge