Stamford’s Antique Shop Conundrum

A Grade II listed antique shop posed a unique challenge for HBPW’s engineers when they were called on to strengthen the Network Rail (NR) bridge running beneath it.

Barnack Road in Stamford, Leicestershire is used by local traffic, but part of it also forms the NR cut and cover tunnel running over the Felixstowe to Nuneaton cross country freight line directly below it.

However, the bridge’s original cast iron beams dating back to 1847, were found to be understrength.

Partner, Jon Livesey, takes up the story: “Three sections of the bridge had previously been replaced with pre-stressed beams, but the two remaining cast iron beam sections were discovered to be under-strength, even though one had previously had some remedial work carried out on it.

“Under normal circumstances this might have been a relatively straightforward exercise in replacing the ironwork but, with a Grade II structure being supported above, we just couldn’t do that.”

The steel grillage used to strengthen one section of the bridge several decades earlier, was badly corroded leaving engineers with a double challenge.  

“Our remit was to provide an engineering solution for the replacement of the steel grillage in section three of the tunnel and add another to section two directly below the antique shop,” said Jon, “and we had to be sure that we minimised any impact on the shop itself” he added.

Twenty eight heavyweathering steel girders supported on gallows brackets with six rock anchors per bracket, were designed along with innovative temporary works which enabled each girder to be moved into place, one at a time, with the minimum of effort.

Working with Amco-Giffen’s in house fabrication team, we developed a central stub column featuring a spherical bearing, which enabled each two-tonne beam to be positioned into place, courtesy of a road rail machine, and ‘rotated’ into place ahead of ‘sliding’ gallows brackets being anchored into each side of the tunnel wall.

“It was a challenging project in that we had to:

• Maintain clearance of the railway line.
• Maintain the integrity of the Grade II listed building above
• Ensure all the pre-fabricated beams fit perfectly and were capable of being installed in short possessions
• ….and it all had to fit together seamlessly!

“But we did it! Everyone came together brilliantly to make a technically difficult job run smoothly thanks to meticulous advancing planning that delivered on the day.”

Client:                Network Rail
Contractor:         AmcoGiffen