OUR APPROACH TO THE BRIDGE ENGINEERING
Starting with a blank sheet, Whitbybird set out to understand the needs of the pedestrians and cyclists who would become the everyday users of this bridge.
It was quickly realised that there was a strong need to make two connections: the viaduct and the quay both needed to link to the opposite bank. After much consultation and modelmaking, it was decided to span the river from the viaduct with a boomerang-shaped bridge linked by a 'gang plank' to the corner of the quay.
We investigated a series of structures, opting to use the hard rock near the surface on the town side as a base for a double mast built on the inside of the elbow. The whole bridge could then hang from these masts.
The site was difficult: access was limited by low bridges and a vicious tide. Lifting-in the masts demanded a mammoth crane and calm weather, and building the spans required special permission to protect the migrating salmon. The foundations revealed ancient timbers, possibly from the medieval bridge, a reminder of the two previous bridges on the site.
The main deck of the bridge is a 600mm deep steel box girder fabricated from stiffened plate. The masts, of varying diameter, are tubular in form and fabricated from bent plate. Cable stays support the span and the triangulations formed by the tie-down cables on each side maintain the stability of the masts.
Project data
bridge length ... 140m
bridge span ... 64m
mast height ... 40m
s u m m a r y
twin-masted cable stayed pedestrian + cycle bridge, box girder deck
m a t e r i a l s
steel, concrete piers
Services we provided
bridge design
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