Doncaster Waterfront Regeneration

Background:-
Network Rail developed a new depot on Marshgate, next to Friar’s Gate Bridge, Doncaster, in order to create a major town centre base for its regional operations which had been spread across five sites in the town.

However, the bridge – a key point of access to the development area – initially failed its assessments and was deemed in need of strengthening.

Challenge
Initial designs showed strengthening work was required to the bridge’s underslung cross girders, however, the recommended method effectively reduced clearance between the water level and the lowest point of the bridge deck.

Allied to that the overhead bracing, on top of the structure, also failed its assessment, and initial thinking was that steel ‘crucifix bracing’ – from above they look like a series of large metal ‘X’s’ spanning from left to right – should be used to give the structure renewed strength. HBPW was asked to come up with some alternative, innovative thinking.

Solution
Rather than working with the existing underslung cross girders – the original drawings sought to add steel pieces to the old metal work but, in doing so, reduced the water-to-bridge clearance level. HBPW engineers opted for temporary works.

This enabled the construction team to support and completely replace the old cross girder hangers, avoiding the need for metal strengthening ‘plates’ and the consequential reduction in water-to-bridge height, a much better solution that was acceptable to all parties.

New extra-strong horizontal sway beams running the length of the bridge were also added to the top of the structure, and the addition of height increasing steel stools paved the way for the ‘new’ bridge to take bigger and heavier vehicles.

Instead of using Crucifix Bracing, which engineers realised would be a challenge to fit because they had to be craned into place pre-assembled and drilled at four corners, they opted for single fabricated ‘half cross’ steel strips running corner to corner and requiring drilling and fixing at just two points.”

Outcome
This alternative ‘value engineering’ approach took time, material cost and effort out of the implementation process, and the bridge will be good for use by vehicles up to 40 tonnes across each of its two lanes. Doncaster Council say the improved Friar’s Gate Bridge will help unlock wider commercial development in the surrounding area.