Published: 20 October 2017
The Design Museum has been shortlisted for The Structural Awards 2017. This remarkable project saw the Grade II* Listed Commonwealth Institute building reinvigorated as a new home for London’s Design Museum. Engineers replaced the façade and internal structure, and created a significant new basement –while the 2000 tonne roof was raised on jacks 20m above ground. Here the structural engineers involved discuss the innovations featured in the project.
When we approached this project we knew that we had to create a space suitable for use by the Design Museum, while retaining the remarkable roof structure: the challenge was to introduce the minimum amount of strengthening measures required to make the building safe, while not making them visually intrusive.
The roof is a hyperbolic parabaloid structure that’s only 75mm thick, a very efficient designed produced by James Sutherland. The roof looks excellent in the sun and is one of the largest copper roofs in the world: if you converted the copper into conventional domestic wiring, the cable would stretch from the Design Museum in London to the Museum of Arts and Design in New York.
Preserving the roof would be challenging: it was never designed to be “picked up” as we intended to do, an operation that would of course cause movements and hence different forces in the structure to which it would be very sensitive.
We assessed the building using a range of non-destructive testing including ultrasound and ground-penetrating radar, to minimise damage to the fabric of the building and reduce costs. When we assessed the roof to see how sensitive it was to being “picked up”, we found that its minimal amount of steel reinforcement wasn’t enough to resist the change in forces which it would undergo - in the 1950s when the building was designed, reinforcement was expensive and the rules for reinforced concrete design didn’t require as much steel reinforcement.
We therefore had to develop a set of strengthening measures to make it able to safely resist these new forces. We did this by installing a system of temporary works incorporating the ability to adjust the forces within each of 150 support points, with live jacking provided at key locations. Movement control was critical, with limits as little as +/-5mm in places. To monitor these movements, the roof was continuously observed by automated robotic survey stations – a system that provided real-time movement data to the contractor and design team.
The roof up close
While the roof was supported the team demolished all of the internal floors and walls, and excavated a 10m deep basement – all while people were working inside and on the roof. This was an incredibly complex undertaking, and required all the structural engineer’s ability to create innovative solutions for unique challenges.
The completed Museum
Arup’s structural engineers spent a total of 21 ‘man years’ working on the Design Museum over the course of the project and we’re really proud of it. We’re thrilled to be shortlisted for the Structural Awards and to see this historic structure made available to a new generation.
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