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The Narrows Bridge is a freeway crossing of the Swan River in Perth, Western Australia. Made up of two road bridges and a railway bridge located over a section of water known as ''The Narrows'', located between Mill Point and Point Lewis, it connects the Mitchell and Kwinana Freeways, linking the city's northern and southern suburbs. The original road bridge was opened in 1959 and was the largest precast prestressed concrete bridge in the world. Construction of the northern interchange for this bridge necessitated the reclamation of a large amount of land from the river. The bridge formed part of the Kwinana Freeway which originally ran for only . Over the following decades, the freeway system was expanded to the north and south, greatly increasing the volume of traffic using the bridge. As a result, in 2001, a duplicate traffic bridge was opened to the west of the original bridge, and in 2005, the railway bridge was constructed in the gap between the two traffic bridges. Passenger trains first traversed the Narrows in 2007 with the opening of the Mandurah railway line. == First road bridge: 1959 == The close distance between Mill Point and Point Lewis at the foot of Mount Eliza meant the site was suggested as a suitable location for a bridge as early as 1849.〔 A bridge was proposed for the site in 1899, but its expected cost of £13,000 was deemed too high. Preliminary planning for a bridge at the site finally began in 1947, but was suspended so that a replacement, The Causeway, could be built at Heirisson Island, at the city's eastern end.〔Gregory, p. 107〕 The new Causeway bridges were opened in 1952, and by 1954 traffic using them to enter the city had doubled, renewing calls for a bridge at The Narrows.〔 Site investigations for the bridge began in August 1954.〔 The bridge was proposed for The Narrows site by the Town Planning Commission under the chairmanship of Harold Boas. The chosen site drew public protest on the basis that the bridge would spoil the view to and from the city.〔 Also, residents of the wealthy Mill Point area were angry that they would have a major highway running beside their houses.〔 The site also necessitated the reclamation of of land from Mounts Bay for the bridge approach and interchange.〔 This land reclamation, which started in October 1954, saw the addition of of sand, much of which was dredged from Melville Water.〔 The State started saving for the new bridge in September 1954,〔 and the construction of the bridge was approved by the Hawke state Labor government in November 1954, before the Hepburn-Stephenson metropolitan roads plan had been finalised, such was the urgency of a new traffic link.〔Gregory, p. 106〕 The construction of the bridge was subsequently endorsed in the 1955 Hepburn–Stephenson plan,〔 which later developed into the Metropolitan Region Scheme. The river bed at the site of the proposed bridge was not ideal for bridge building, with soft mud extending down up to , with sand beds below that going a further down.〔"''Narrows Opening''", p. 33〕 Ernie Godfrey, a bridge engineer with the Main Roads Department, travelled overseas to inspect bridges in similar geological locations and to source a designer for the proposed bridge.〔 The design contract for the bridge was won by British engineering firm Maunsell & Co.〔 Construction on the road system began in 1956,〔 and the contract for construction of the bridge was signed by Commissioner of Main Roads J. Digby Leach on 16 March 1957.〔 The bridge was built by Danish firm Christiani and Nielsen in conjunction with Western Australian engineering firm J. O. Clough & Son.〔 Leif Ott Nilsen oversaw construction on behalf of Christiani and Nielsen.〔"''Narrows Opening''", p. 31〕 The first timber pile for the temporary staging for the construction was driven at noon on 8 June 1957.〔"''Narrows Opening''", p. 34〕 The first permanent pile for the bridge was driven home on 18 August 1957.〔 Work on the bridge's precast concrete beams began in September 1957, and the first of these was lifted into place by the gantry crane in February 1958. The last river pile was driven home in November 1958, and the final concrete beam was lowered into position in June 1959.〔 During construction on 10 February 1959, John Tonkin, then the Deputy Premier and Minister for Works, announced that the new bridge was to be named the Golden West Bridge.〔 However, Golden West was also the name for a popular soft drink; the proposal encountered scorn from commentators and was quietly dropped.〔Gregory, p. 108〕 The bridge cost £1.5 million, as part of a wider road system costing £3.5 million.〔"''Narrows Opening''", p. 25〕 Construction on the bridge took 2 years and 5 months.〔 It was officially opened by Governor Charles Gairdner on 13 November 1959. He unveiled a plaque on the bridge together with Premier Sir David Brand, Commissioner of Main Roads J. Digby Leach and Works Minister Wild.〔 Gairdner was also the first person to drive across the new bridge.〔 It was hoped at this stage that the debt raised to pay for the bridge would be repaid by the Government within 12 months.〔 The bridge formed part of the new Kwinana Freeway, which originally ran from the Narrows to Canning Highway.〔"''Narrows Opening''", p. 27〕 This was described as the "most modern highway" in Western Australia, with a speed limit of .〔 The bridge was also the largest precast prestressed concrete bridge in the world at the time of its opening.〔Anon. 1959, ''World's largest precast prestressed concrete bridge completed'', Roads and Road Construction, v. 37, n. 444, pp. 364–367.〕 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Narrows Bridge (Perth)」の詳細全文を読む スポンサード リンク
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