Narrows Bridge

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For the bridge in Tacoma, Washington, United States, see Tacoma Narrows Bridge.

Location of Narrows Bridge

The Narrows Bridge is a bridge that connects the Mitchell Freeway and Kwinana Freeway in Perth, Western Australia. It runs over the Swan River at "The Narrows" between Mt Eliza and Mill Point, connecting the northern and southern suburbs of the city. Prior to its construction the only connection between the northern and southern shores of the Swan River between Fremantle and Perth was The Causeway at the eastern side of Perth Water, which is two bridges making connections via Heirisson Island.

Upstream of the bridge, the river widens to an expanse known as Perth Water, and downstream an even larger widening occurs into Matilda Bay and Melville Water.

1 History
- 1.1 Design
2 Gallery
3 References
4 External links

[edit] History

The Narrows Bridge viewed from South Perth, prior to the 2006 construction of the centre railway bridge. The original bridge is in the right foreground. The piers for the 2001 duplication can be just seen to the left.

The first Narrows Bridge was opened to traffic on November 13, 1959 by the Governor of Western Australia, Sir Charles Gairdner. A lane was later allocated for "peak hour" usage, with automated gates to alternate the direction between north and sound bound depending upon the time of day.

Due to Perth's increasing traffic volumes, a new bridge was built immediately west of the existing bridge and opened in 2001, effectively doubling its carrying capacity. Although nearly identical in appearance the new bridge is very different structurally, being an incrementally launched post-tensioned concrete structure.

A third bridge for the Southern Suburbs Railway was built in 2006 in the 6 metre (19.7 ft) gap between the existing structures. The bridge is made up of nine steel girders, each weighing up to 94 tonnes (103.6 t) and up to 54 metres (177.2 ft) in length. This bridge will be used for the southbound track of the railway, with the existing northbound busway being strengthened and used for the northbound railway track.

[edit] Design

The original bridge was designed by G Maunsell & Partners of London. Its length was 335 metres (1100 ft) between abutments, with 5 spans, the central span 98 metres (320 ft). The width of 24 metres (80 ft) designated 21 metres (70 ft) for 6 traffic lanes and 3 metres (10 ft) for footpaths. At the time of completion, the bridge was the world's largest precast prestressed concrete bridge.^[1]

The 2001 duplication included carbon fiber reinforcement.

The 2001 duplication was designed by Connell Wagner and constructed by Leighton Contractors. The rail bridge and associated modifications to the original two structures were built by Leighton and designed by GHD. Piling design was by Coffey Geoscience.