Building bridges during major A1 upgrade, with our propping expertise

The challenge

The A1 is a critical part of the UK’s highway network, with the Newcastle Gateshead Western Bypass in particularly being one of the most congested sections in the North East. With traffic levels expected to only increase, National Highways planned improvements to the A1 via the Birtley to Coal House scheme, including widening the north and southbound carriageway and replacing the existing Allerdene railway bridge which carries the highway over the East Coast Mainline.
The new bridge structure consists of 16 central girders, installed as braced pairs, comprising over 3000 tonnes of structural steel and decking. Understandably, the assembly and installation of the bridge presented project teams with a considerable logistical challenge, requiring a bespoke series of temporary works.
Ben Adcock, Lead Temporary Works Co-ordinator at Costain, principal contractor on the project, said: “Due to the poor ground conditions experienced in the local area, the geotechnical team anticipated a significant movement could occur at the back-span embankment and abutments during the construction of the embankment. As a result, we were unable to land the new bridge deck directly onto the new abutments, as the bridge bearings would be unable to cope with the movement and loads experienced.
“Due to this, the temporary works proved critical to continuing to meet the programme requirements. We needed a temporary propping and trestle scheme that would provide additional support to the back span beams of the bridge deck at both the east and west abutment locations during the initial install, before we could remove gradually and transfer the deck loads to the permanent abutment.