How do you construct a footbridge over a 58-metre drop, when it’s exposed to some exceptionally brutal weather?
The answer is, you build it off-site, and use a cable crane to put the different elements of the bridge into place.
That’s how engineers Ney & Partners handled the building of the new footbridge between mainland Cornwall and the island where Tintagel Castle stands.
Created in partnership with architecture studio William Matthews Associates, the bridge design includes two 30-metre cantilevered spans that don’t quite meet in the middle – I’ll talk more about that in a moment.
The design was selected deliberately to avoid needing any scaffolding during construction. In fact, after being constructed off site over the course of 12 months, the bridge only took two weeks to put in place.
Resurrecting the old land bridge
When the castle was originally built in the 13th century, its inhabitants would have crossed back and forth from the mainland to the headland on a narrow land bridge as high as the cliffs. But this disappeared between the 14th and 17th century.
More recently, visitors to the English Heritage attraction have endured a challenging climb, with over a hundred steep steps to navigate to the castle ruins.
And so it made sense to put in a bridge over the drop, so that visitors could simply cross to visit the site – which is popular due to its strong links with the legends of King Arthur.
One challenge the engineers and architects had was to design a bridge that could handle the weather conditions and extremes of temperature at the coastal site. And this is what led to them leaving a 40mm gap in the middle of the bridge. As well as allowing the structure to expand and contract, this creates a novelty for visitors, as bridges do not generally have such a visible empty space in the middle.
The bridge is made of steel and slate, and unusually the slate is stacked vertically to create a contemporary finish to the surface that people are walking across. Visitors can hold onto the oak handrail as they cross the gap.
To fix the bridge in place, specialists hung over the edge of the cliffs and drilled supports into the cliff face. This is a technique used in the Alps, but is rarely seen in the UK.
This new bridge means that visitors to the medieval castle are now able to walk a route that hasn’t been travelled for 500 years.
Perhaps if you decide to visit, you will walk across it too.
Meanwhile, if you need assistance with the structural elements of an upcoming project, please do get in touch.