It is a structural typology that mimics natural forms such as seashells, resulting in optimised curvilinear geometries that gain strength and lock in stiffness through curvature and corrugation.
The first stage is to digitally model the Shell Lace as a series of conjoined developable surfaces. These surfaces are then isolated, unzipped at their seams, unrolled and nested onto a flat surface – allowing efficient computer-aided cutting from flat sheet material.
Once cut, the profiles are laid onto curved formwork where their self weight bends them down into the correct developable shapes. Each panel is then fixed to the next along their shared seams, and the result is the desired strong and stiff composite form.
Lightness and transparency is achieved by perforating the flat sheets during the lasercutting stage. This creates highly efficient and responsive structures with minimum weight and wastage.
Shell Lace can be built from a range of different sheet materials such as metal, plastic, wood and card. The fabrication & construction system is tailored to each material, which results in a different cutting process (i.e. laser or plasma cutting, milling, etc), as well as unique connection details (welding, bolting, tabbed joints, etc).
To date Tonkin Liu have produced a series of different Shell Lace designs for buildings, bridges, canopies and art installations. In 2011 they completed the Rainbow Gate sculpture in Burnley, the first built Shell Lace structure.
My work on Shell Lace involved designing proposals for 2 new Shell Lace structures:
· A large-span canopy for an extension to Bluewater Shopping Centre in Kent.
· A design for the Cadogan Cafe competition, organised by the RIBA.
At the same time I also developed general digital design tools and methodologies for each stage of the process:
· Creating initial forms (and parametric tools to automate this stage).
· Assessing and improving developability of the individual panels.
· Arraying perforations across the surfaces, which can be based on different criteria such as structural efficiency, desired light levels, and so on.
· The next stage of the process is to produce scripting tools that automate production of formwork for each unique panel.
Different strategies for removing material and reducing panel weight, while retaining strength:
Designer: Tonkin Liu
Structural Engineer: ARUP (Ed Clark)
Project Role: Architectural Assistant at Tonkin Liu
· Read Tonkin Liu’s Shell Lace book… both of my projects with them – the Bluewater Shopping Centre extension and Cadogan Cafe competition entry – are documented in this publication.