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Mangere Bridge, officially also called the Manukau Harbour Crossing, is a motorway bridge over the Manukau Harbour in south-western Auckland, New Zealand, crossing between the suburb also known as Mangere Bridge (southern side) and the suburb of Onehunga (northern side). Completed in 1983, the current bridge carries a four-lane motorway (carrying approximately 80,000 vehicles daily)〔 with a cycle and pedestrian path also suspended underneath the western side of the bridge. In April 2008, work began on a duplication of the bridge to cater for increased traffic (completed in 2010),〔(Manukau Harbour Crossing, January 2009 ) - NZTA newsletter. Accessed 2009-08-09.〕 and to serve up to 160,000 vehicles per day in 2021.〔 The process had been delayed by disagreements over design and funding, as well as over the scope of the bridge project and an associated interchange - with the interchange being scaled down after concerns from the local community. ==Original bridges== ;Initial bridge The initial bridge in this location was built of timber and opened in January 1875. Rather narrow, it also soon began to be attacked by shipworms, and in 1910, more than 30 of the piles had been replaced, as well as the decking.〔(Appendix 11 - Archaeological and Heritage Assessment ) (Opus for Transit New Zealand, May 2006, Page 23-26. Accessed 2008-06-12.)〕 The bridge was also single-lane, and so narrow, even pedestrians could barely pass a vehicle safely.〔 The bridge was eventually considered structurally unsound and closed in 1914,〔 before being fully demolished. ;Old Mangere Bridge In January 1914 (according to some sources, only in 1915),〔 a 246 m long replacement bridge was opened instead. Designed by R.F. Moore, the designer of Grafton Bridge, it was also built by the same company, the Ferro-Concrete Company of Australasia (in a time when almost all bridges in the country were being built by the Public Works Department). The ferro-concrete bridge with driven concrete piles was considered a substantial engineering achievement in its time. With a width of 11.6m, it allowed for a double tram track. The bridge however did not provide for enough clearance to let anything but small boats pass under it.〔 In World War II, an anti-tank road block was erected on the bridge near the middle of the spans, with a small sentry shelter close by. The structure has since been removed, and it is unclear whether the bridge had also been mined.〔 However, the new bridge also soon proved to have too little capacity, and sinking foundation piles created issues.〔 The old bridge was closed in the 1970s to motor vehicles〔 and is slowly deteriorating as of today, especially after it sustained damage when a ship accidentally rammed it some years ago. A second ship, the 300 ft container transport ''Spirit of Resolution'', also crashed into the old bridge on 8 October 2005 as it attempted to leave a nearby Port of Onehunga berth during winds estimated later on as being between 30-40 knots (with stronger gusts) and against a strong incoming tide. The collision occurred despite the ship's bow thrusters working at full power and a small harbour tug assisting.〔(Accident Report - Collision with Bridge, ''Spirit of Resolution'' ) (from the Maritime New Zealand Investigation Report, October 2005. Accessed 2008-06-12.)〕 Due to problems with the quality of the concrete and steel of the 'Old Mangere Bridge',〔 it was initially envisioned that the bridge would be dismantled and replaced by a newly designed footbridge. Due to complaints about this course of action plans for its removal were not finalised until 2012.〔(New Zealand Transport Authority - NZTA welcomes great response for new harbour link in Auckland )〕 Construction of a replacement structure, designed for walking, cycling and fishing, is scheduled for 2015, the centenary of the opening of the old bridge.〔 ;Motorway Bridge The current Mangere Bridge was opened for traffic in 1983, and now carries approximately 80,000 vehicles a day.〔 The motorway bridge took 8 years to build, including a 2-year stoppage due to industrial action and other delays. A duplication of the structure, to increase capacity, was completed in 2010. 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「Mangere Bridge (bridges)」の詳細全文を読む スポンサード リンク
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