24 August 2014

Yorkshire Bridges: 5. Scammonden Bridge

This is the last, and largest, in a set of Yorkshire motorway bridges which I visited earlier this year.

Spanning 125m, it is the biggest concrete arch bridge in the UK. It carries a local highway across the motorway where it passes through a huge cutting. In some photographs, Scammonden Bridge can appear almost "small", as it is scaled appropriately to its setting.

Its sheer size becomes more apparent only when passing underneath. A construction photo from 1969 showing the scaffolding used to erect the arch also gives a much better idea of quite what an enormous structure it actually is.

The concrete arch comprises a twin-cell reinforced concrete box section, supporting slender spandrel columns. These are hinged at the top to allow thermal movement of the deck to take place. The deck is built from conventional precast, prestressed concrete "T" beams.

As with the other bridges I visited in the area, this structure was designed by the West Riding County Council. Sri Sriskandan was credited with a key role in an obituary published by the New Civil Engineer.

The bridge provides spectacular views along the motorway and onto the moorland that the road bisects. It's startling to try and imagine this setting before the motorway was built, as the huge "valley" that the road passes through is entirely artificial.

The bridge seems to be in generally good condition, with the notable exception of the parapets, which are in serious need of repainting.

Aesthetically, it is appropriate to the place, and generally well-proportioned. The only "wrong note" is the way that the profile of the arch at its crown cuts into the deck profile, but this is a minor matter.

It would be fascinating to see what kind of bridge would be built today if a new motorway were built in the UK requiring a similar span. However, it's hard to imagine such a road being allowed to be built, given the visual impact on the rural landscape.

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