A5140 Longholme Bridge, Bedford

Client

Bedfordshire CC and Sir Alfred McAlpine

Project Description

This bridge carrying Longholme Way over the Great Ouse and its flood plain in Bedford was reconstructed to replace the existing degraded prestressed-concrete structure. Bailey bridges had been installed as a temporary measure. A single two lane carriageway was carried with a wide footway providing the necessary sighting on the inside of the low radius plan curve of the road. The crossing of the river was quite heavily skewed and minimal interference of bridge piers in the flood plain was required. Closed-top twin steel box girders were fabricated to a true plan curve following the road and also with a variable depth curved elevation for good aesthetic effect. The steelwork was made composite with a deck slab of insitu reinforced concrete.

The clean lines were preserved under the deck with cross frames only at the piers which are prismatic diamond-shaped columns with ship-ends aligned to the river.

Cass Hayward Role(s)

Design options study
Outline design to AIP stage for preferred option
Category III independent check of detailed design by Beds. CC
Design for revised concrete deck pour sequence for Contractor
Temporary works design checking

Project Statistics

Completed July 1996
Contract value £1.5m
Three structurally continuous spans – 42.4, 40.0m, 28.2m
Box girders curved in plan with 222m radius and variable in depth from 0.7m at mid span to 2.3m at piers

Special Features

Lighter steel concrete composite reconstruction allowed original foundations to be reused
Torsionally rigid box girders required only single bearings at supports and no cross frames other than at piers
Slender profile allowed headroom to be preserved without change to highway levels

Awards

Structural Steel Design Awards 1997: Certificate of Merit