River Parrett Structures

Huntworth Viaduct


Bridge Name:   Huntworth Viaduct
No.:   36
Build Date:   begun in 1971 and opened in 1973
Engineer:   Cementation Ltd
Southeast of Bridgwater the motorway crosses the River Parrot, the Bristol-Exeter Railway, the Taunton to Bridgwater Canal and two minor roads; furthermore as the alluvium at the site would only support a lightweight embankment, a viaduct carrying the motorway for about half a mile over these facilities was an economic proposition. The design was a twin steel box girder construction with a composite reinforced concrete deck. The main spans are 166 ft. and there are seventeen spans with columns founded on large diameter bored piles which extend well into the keuper marl beneath the alluvium.

The design of the structure was undertaken before the publication of the report of the Merrison Committee on Box Girder Bridges. However during the preparation of the design the Engineers in the Sub-Unit worked closely with experts at the Imperial College of Science. Advice which emerged from the University enabled factors to be included in the design which minimized the ultimate problems at the reappraisal stage. In fact only a small amount of extra steel was required mainly in the webs of the box girder compression flanges.

The embankments to the north of the viaduct were constructed in PFA and surcharged to accelerate settlement. In addition to the viaduct six other bridges were constructed as part of the contract.1

References:   1.http://www.ukmotorwayarchive.org/page1.htm