Aran Chadwick discusses his work on Chadstone Shopping Centre in Melbourne. Shortlisted for The Structural Awards 2017, the Centre features a remarkable catenary steel gridshell roof.
During my career I’ve been privileged to work on many remarkable projects, and was especially proud to act as Director of the structural team on the London 2012 Olympic opening and closing ceremonies.
Chadstone Shopping Centre was an interesting structural engineering challenge in its own right: we were asked to develop a freeform gridshell roof structure and were provided with a roof boundary to match the programme of the shopping centre extension below. However, as the programme developed, so did the boundary - a non-planar orderless curve. That meant that the roof shape needed to be constantly updated to match the boundary line.
The exciting result was a roof structure glazed with quadrilateral panels of varying sizes, arranged in an efficient double curvature, covering an area of approximately 7000m² and spanning up to 32m.
To achieve this form we were pleased to work with Chris Williams at Bath University, one of many academics with whom we have enjoyed successful collaborations. With initial work from Chris, we further developed bespoke software in-house, creating an efficient geometry using a steel gridshell and cold bent quadrilateral double glazed panels. Software tools are amazing at trying many options and iterations within a set of defined constraints (although you still need engineering skills to know whether what you put in and take out makes any sense). The software developed in the design could have many other useful applications, and we are currently using several spin offs from it on other projects.
I think the link between the design, fabrication and installation is also opening up new doors. Not too long ago structural engineers tried to achieve as much uniformity in nodes, members, and panels as possible, then assemble them in interesting forms. New digital fabrication techniques have changed all this: we are much freer in what we can specify and this opens up the possibilities of what’s achievable in the overall design.
There were many challenges on this project but we wanted to do something exceptional on a budget and had to refine our design process as a result. Throughout this process we asked how we could do more with less: how do we make the structural form more efficient? How do we minimise material wastage? How do we make sure all items can be easily transported? How can we simplify the elements?What is the most effective method of fabrication?
We were pleased to deliver on many of these questions: the planar quadrilateral grid reduced both the weight of structural steel we used and the wastage from glass cutting– and by developing the geometry alongside the structural engineering analysis, we produced a highly efficient form combining geometric and structural considerations.
We’re really proud of the roof at Chadstone Shopping Centre and are thrilled to see the project shortlisted for The Structural Awards.
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