4250 x 2110 px | 36 x 17,9 cm | 14,2 x 7 inches | 300dpi
Data acquisizione:
24 luglio 2009
Altre informazioni:
The Silver Jubilee Bridge or Runcorn Bridge crosses the River Mersey and the Manchester Ship Canal at Runcorn Gap between Runcorn and Widnes in Cheshire, England. It is a through arch bridge with a main arch span of 1, 082 feet (330 m). It was opened in 1961 as a replacement for the Widnes-Runcorn Transporter Bridge, and was initially known simply as the Runcorn Bridge or Runcorn–Widnes Bridge. In 1975–77 it was widened, after which it was given its official name in honour of the Queen's Silver Jubilee. It carries the A533 road and a cantilevered footway. The bridge has been designated by English Heritage as a Grade II listed structure The new bridge had to allow the passage of shipping along the Manchester Ship Canal. Many ideas were considered, including a new transporter bridge or a swing bridge. These were considered to be impractical and it was decided that the best solution was a high-level bridge upstream from the railway bridge. This would allow the least obstruction to shipping and would also be at the narrowest crossing point. The first plan for a high-level bridge was a truss bridge with three or five spans, giving a 24 feet (7 m) dual carriageway with a cycle track and footpaths. This was abandoned because it was too expensive, and because one of the piers would be too close to the wall of the ship canal. The next idea was for a suspension bridge with a span of 1, 030 feet (314 m) between the main towers with a 24 feet (7 m) single carriageway and a 6-foot (2 m) footpath. However aerodynamic tests on models of the bridge showed that, while the bridge itself would be stable, the presence of the adjacent railway bridge would cause severe oscillation. The finally accepted design was for a steel through arch bridge with a 30-foot (9 m) single carriageway. The design of the bridge is similar to that of Sydney Harbour Bridge but differs from it in that the side spans are continuous with the main span rather than being separate from them. This design feat
