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Clackline Bridge is a road bridge in Clackline, Western Australia, east of Perth in the Shire of Northam, that carried the Great Eastern Highway until 2008. It is the only bridge in Western Australia to have spanned both a waterway and railway, the Clackline Brook and the former Eastern Railway alignment. The mainly timber bridge has a unique curved and sloped design, due to the difficult topography and the route of the former railway. The bridge was designed in 1934 to replace two dangerous rail crossings and a rudimentary water crossing. Construction began in January 1935, and was completed relatively quickly, with the opening ceremony held in August 1935. The bridge has undergone various improvement and maintenance works since then, including widening by in 1959–60, but remained a safety hazard, with increasing severity and numbers of accidents through the 1970s and 1980s. Planning for a highway bypass of Clackline and the Clackline Bridge began in the 1990s, and it was constructed between January 2007 and February 2008. The local community had been concerned that the historic bridge would be lost, but it remains in use as part of the local road network, and has been listed on both the Northam Municipal Heritage Inventory and the Heritage Council of Western Australia's Register of Heritage Places. ==Description== Clackline Bridge is a timber bridge spanning the Clackline Brook and the former Eastern Railway alignment, in the Shire of Northam, east of Perth. Constrained by the topography of the site, the route of the Eastern Railway tracks, and the previous alignment of Great Eastern Highway, the bridge has a unique curved and sloping design. It has 18 spans over a length, with a 1 in 20 slope and a horizontal curve radius of . There are 18 numbered piers, starting from pier 1 at the eastern end.〔 The double tracks of the Eastern Railway, which linked Perth and Northam until its removal in 1981,〔 passed between piers 16 and 17. Piers 14 to 17 are parallel to that former railway, at an angle of approximately 40 degrees to the bridge. This resulted in spans of various lengths: heading out from the western abutment, then a span between piers 16 and 17, followed by a length, two spans, and 13 spans of . The bridge has undergone multiple alterations, but the original piers remain. They were constructed as "four rounded braced wandoo piles supported from horizontal 450mm timber sills, adzed to 400mm, fixed to concrete footings",〔 with the footings designed to bear on foundation rocks beneath the surface. The bridge's original spans were made up of seven rounded timber wandoo stringers, of at least diameter, bearing on jarrah corbels, supported by jarrah half caps in size. The span over the railway alignment was originally supported on four steel beams, weighing each.〔 Various aspects of Clackline Bridge have since been modified. Originally wide, with a footpath, the bridge was widened by , with two additional piles installed at each pier. At the same time the railway span was strengthened, with eight additional steel beams installed, and steel plates welded to the flanges of the existing girders. The approaches to the bridge were also widened, over a length of to the west, and to the east. The timber decking was upgraded to a concrete slab that has been repaired a number of times, especially around pier 13. Some of the connecting bolts in the structure have been replaced, and a concrete approach slab was installed at the western end. In 2008, the bridge was assessed as being in a well-maintained condition.〔 Main Roads Western Australia identifies Clackline Bridge as Structure Number 0608. , the bridge dimensions are recorded as in length and in width, with a distance of between kerbs, a deck area of , and maximum span length of .〔(【引用サイトリンク】url=http://gis.mainroads.wa.gov.au/roadinformationmap/ )〕 , it is the only bridge in Western Australia to have crossed both a railway line and a waterway.〔 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「Clackline Bridge」の詳細全文を読む スポンサード リンク
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