Will Arnold, Senior Structural Engineer, and Giancarlo Torpiano, Structural Engineer, ARUP, discuss how city sculptures can serve beyond aesthetic value.
The ‘Solar Gate’ sculpture in Hull is the latest work in a series of ethereal structures that Arup and Architect Tonkin Liu have pioneered over the past decade. We refer to these undulating, perforate, and incredibly lightweight works as Shell Lace, inspired by an approach that is grounded in the design teams’ mutual interest in natural structures.
In nature, material is used sparingly, and strength is often derived through geometry. Nature also avoids adding material where it would not be needed, an approach we follow that leads to lace-like and highly efficient structures, like Solar Gate.
Preservation of History Solar Gate is a prime example of how a structure can serve a crucial purpose beyond its aesthetic value; its form also evokes other stories. It is reminiscent of a sail and sits in what was once an old dock, known as Queen’s Gardens, and thus reminds its citizens of Hull’s past as a prominent port-town. The sculpture is made entirely of steel plate as an evocative reference point to Hull’s ship building and industrial past. The sculpture itself is designed to act as an elegant sundial, marking sixteen specific times and dates celebrating Hull’s history and world events.
City of Culture
The artwork forms part of Arup’s wider involvement in the renewal of Hull as 2017 UK City of Culture. Its fabrication relied and made use of local industry expertise, allowing this local knowledge and industrial history to reinvent itself for the production of cutting-edge, contemporary art. It is the latest in a series of Arup and Tonkin Liu commissions outside of London; the previous being Rain Bow Gate in Burnley, and the next being Tower of Light in Manchester. We believe that projects like this serve as a reminder of the UK’s cultural richness of beyond London.
At Solar Gate, the shell lace technique allowed for the three-storey high sculpture to be produced entirely from steel plate only four millimetres thick. As the height increases and the structural demand diminishes, material is removed, allowing wind loads to be reduced and for the sculpture to become more delicate. All removed material is recycled.
The careful removal of material exposes the insides of the sculpture, in the process exposing the parallel stories of how it works as a structure, and how it was made. There is no supporting structure other than the undulating plates forming the sculpture that have been cut, bent and welded to each other: structure is architecture.
Solar Gate was realised using advanced computational design techniques, which coupled structural engineering and fabrication logics with the aesthetic ambition for the sculpture. Arup developed custom algorithms that integrated seamlessly with Tonkin Liu’s models so that the plate arrangement could be optimised in response to movement and stresses in the steelwork.
Placing team effort at the centre of the design process, and enabling this with the latest digital techniques, has resulted in a truly integrated and symbiotic architectural and engineering installation.