How do you construct a bridge in an historic location that presents a set of unique and challenging site conditions? That was the burning question facing the engineering team behind Cornwall’s new Tintagel Bridge.
Set on a rugged coastline in the south west of England, the new footbridge has been built on behalf of client English Heritage. The aim of the project was to restore a pathway that had collapsed five centuries before, and in doing so reconnect the mainland to the ancient medieval castle, birthplace of the legends of Merlin and King Arthur.
But with no easy access and set in a location that was open to the elements, this was no easy feat. To add to the logistical challenges, Tintagel Castle’s rich history was such that the bridge had to complement its surroundings in a subtle and culturally sensitive way.
“It’s very difficult to build something in this context because you have a lot of communities and organisations to convince that this is a good project for the place in several aspects,” begins Matthieu Mallié, partner at civil engineering firm NEY Partners, who won the design competition for the new bridge in partnership with architects William Matthews Associates.
“There was no road and no sea access, so we couldn’t build the bridge in arch pieces, with temporary scaffolding as support during construction, as you would normally do. So, we had to find a way to build a bridge in a place where it was impossible.”
Their solution was to use helicopters to transport some materials and prefabricated sections on to site, at the same time as adopting a specialised technique used to cross mountain ranges like the Alps. This involves a suspended cable crane that lifts equipment into place without the need for scaffolding.
A bridge to the past
The Tintagel bridge itself is formed out of two 30-metre cantilever pieces, made from locally sourced steel and slate. These materials also allowed the team to address some of the project’s key logistical challenges.
As Mallié explains, “We needed a light structure since we had a very limited lifting capacity during construction so we had to find materials that could be light and at the same time resistant and the only material that can do that in the construction world is steel.”
“We had to find materials that could be light and at the same time resistant and the only material that can do that in the construction world is steel.” – Matthieu Mallié, NEY Partners
For the client, steel also provided an answer to the some of their concerns over how the new bridge would fit in aesthetically, as English Heritage’s head of national projects, Nichola Tasker, explained:
“Materials were particularly selected so we could design a bridge that was in keeping with the landscape. The steel allows us to have a very slender bridge, so it has minimum impact on the views of the castle.”
The origin of the steel was also important to English Heritage, which is why they chose Plymouth-based steel fabricator, Underhill Engineering, to supply the 18 main sections for the bridge. The ability for the steel sections to be prefabricated offsite with extreme precision also contributed to the success of the project as it minimised construction time.
“The steel allows us to have a very slender bridge, so it has minimum impact on the views of the castle.” – Nichola Tasker, English Heritage
Picking the right steel also had to be done with the environmental considerations in mind, given that the bridge would be located next to the sea and vulnerable to corrosion.
This meant the designers were unable to use weathering steel, which naturally forms a protective layer of oxidised metal that wards against corrosion as this process would be prevented by the conditions of a marine environment.
Stainless steel doesn’t rust but was not a viable option due to aesthetic requirements, so the team instead selected a painted steel solution. This provided English Heritage with a low maintenance and visually impressive solution that reopened a walkway to the public that had been lost for so many years.
Combining modern engineering and material excellence with a timeless aesthetic that complements its historic setting, the Tintagel bridge is a triumph of carefully planned and executed design.