Watching the welds
The project team kept a particularly close eye on welds. These were necessary because the roof had been designed to have no visible bolts, just lateral fixings hidden between the steel members. Seele was only able to start welding after they had completed a weld to JMP’s satisfaction and agreed to a benchmark.
Once the roof had been complete, all that was left to do was remove the temporary scaffolding supporting the 1200 tonnes of steel. It was removed in July when the roof finally became self supporting. Deflections of 120mm had been accounted for, but in the event they the structure moved only half this amount.
For the last six months workers have been preparing the retails units and installing JMP’s sci-fi designs for the counters and ticket machines. King’s Cross station may not trump Sir George Gilbert Scott’s Gothic grandeur at St Pancras, but it’s now got an unashamedly modern piece of station architecture.
Funnelling the load
The load of the 1,200 tonne steel roof is taken through the steel funnel and 16 tree columns around the perimeter of the Western Concourse. Steel members were fixed to the tree columns through steel nodes weighing 1.5 tonnes.
Each node, which look like bagpipes shorn of their pipes, was cast to the design created by JMP. The finish is the texture of the sand that was used in the casting.
JMP visited Seele’s factory in the Czech Republic to check the first castings for imperfections before giving approval for casting of all 16. This level of rigour was repeated for every design element on the site.
A lot of time was spent refining the design of the tree columns. Their final tapered design combined with the curvy nodes helped to soften the appearance. ‘We had weekly meetings with Seele to ensure the design detail wasn’t lost,” says JMP associate director Simon Goode. “The checks continued onsite to ensure the quality was maintained as the installation took place.”