31 January 2015

Newport - Transporter Bridge

Newport Transporter Bridge is one of only 16 such bridges ever built to completion, worldwide (counting only once the bridge at Bizerta that was rebuilt at Brest). It was one of four built in the UK. To properly qualify as such, a transporter bridge must be a high-level structure that carries a gondola suspended at grade, and leaves the crossed waterway unobstructed. As such, these bridges can be better thought of as aerial ferries. The first working example, Puente Vizcaya, was opened in 1893, between Portugalete and Las Arenas, near Bilbao, Spain, designed by Spaniard Alberto de Palacio and Frenchman Ferdinand Arnodin, patentee holders.

The Newport aerial ferry was designed to enable workers from the city, on the west side of the River Usk, to reach the developing industries on the east side, without an eight mile round walk. A ferry had operated nearby, but the extreme tidal range made use impossible at low tide. A conventional bridge would have required very long approach ramps to provide for ships to pass beneath, and tunnelling would have been too expensive.

The Borough Engineer, Robert Haynes, arranged for the council to visit the transporter bridge at Rouen, France, opened 1899. The Newport bridge received parliamentary approval in 1900. Arnodin undertook the design, and he and Haynes were appointed joint engineers. The contract was awarded to Alfred Thorne, of Westminster. Work commenced in 1902, and the bridge opened in 1906.

The high-level boom, 774 feet long and with a main span (between the tower centres) of 645 feet, is slung between towers, the tops of which are 242 feet above road level. Rail tracks are carried by the boom, and upon these runs a traveller. In turn from this is suspended a gondola (second photo), pulled across the river at ten feet per second by a continuous cable, the winding of which is powered by two 35 horsepower electric motors. The winding house is situated at the eastern end of the bridge (below). The 1,326 ton steel structure is of the suspension bridge form, a series of three-inch wide suspension cables carried over the top of the towers. The anchorages are each formed of 2,200 tons of ashlar, their centres 1,545 feet apart.

Grade I-listed in 1982, the bridge was closed in 1985 due to safety concerns. It cost £98,000 to build originally, and £3m to refurbish. It re-opened in 1995, only to close again in 2007. A further £1.23m of work enabled the bridge to operate once more from July 2010.

Nine of the 16 bridges survive. Of these, seven are in use in transporter form: Puente Vizcaya in Spain; Rochefort in France; Osten and Rendsburg in Germany; Newport and Middlesbrough in the UK; and Buenos Aires in Argentina. An eighth, that at Duluth, Minnesota, USA, although still in use, was converted to a lift bridge, reopening as such in 1930. The one other survivor, at Warrington in the UK, lies derelict.

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