Tags: architecture, bridge
The Narrows Bridge is a freeway crossing of the Swan River in Perth, Western Australia, at The Narrows between Mill Point and Mount Eliza. Made up of two road bridges and a railway bridge, it connects the Mitchell and Kwinana Freeways, linking the city's northern and southern suburbs.
Opened in 1959 with the first stage of the Kwinana Freeway, The Narrows Bridge was a single five-span concrete structure designed by G Maunsell & partners and built by Christiani & Nielsen and J O Clough & son.
It was the first bridge in Australia to use segmental construction and a lighter web construction using pre-stressing cables. The unusually soft soil conditions at the site forced the use of 160 "Gambia piles" for the bridge's foundations, named after the country in which they were first used. The 79 cm diameter piles have steel shells and conical noses. The hollow piles were driven by a drop hammer falling within them, then when they had sufficient resistance to driving, they were filled with reinforced concrete.
At the time of its construction, the 97.5 metre central span was the largest precast prestressed concrete bridge span in the world. The new bridge had a traffic capacity of 6,000 cars per hour in each direction, over a total of six traffic lanes.
The bridge was entered on the state's heritage register in January 1999, and was named a national engineering landmark by the Institution of Engineers, Australia, in November 1999.