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at Over, Gloucester
The lowest crossing of the river Severn before the Severn Crossings, this masonry bridge was built by Thomas Telford in 1828.
Over Bridge, also known as Telford's Bridge, is a single span stone arch bridge spanning the canalised West Channel of the River Severn near Gloucester. It links Over to Alney Island.
Although there was a crossing at Over recorded in the Domesday Book, this famous bridge was built by Thomas Telford between 1825 and 1828, to carry traffic east-west. It was opened in 1830 and remained in use for traffic until 1974. Until the Severn Bridge was built in the 1960s this was the lowest point downstream that the Severn could be crossed by road bridge.
The arch spans 150 feet (46 m), and was based on Jean-Rodolphe Perronet's 1774 design for a bridge over the River Seine at Neuilly. It combines both an elliptical profile over most of the soffit with a segmental profile at its faces. This feature is known as a corne de vache.
When built, the arch sank by 2 inches when
150 ft span, with 35 ft rise, although the tapered haunches give the impression of a flatter arch, while also aiding the flow of water during floods.
There is a noticeable dip at mid-span. The centre of the arch dropped 3" on removal of the wooden centring, and a further 7" due to displacement of the eastern abutment, which, due to false economy, had inadequate foundations. The western abutment was on firmer ground.
The design was based on a much earlier bridge at Neuilly on the Seine, designed by Jean-Rodolphe Perronet.
The spandrels are not solid, there being five cells across the width of the bridge, 2 ft 6" wide, as can be seen in a drawing in the above link.
The bridge has been bypassed, but is accessible on foot. Access from the fast and busy A48 needs to be well researched before attempting to reach the footpaths!