Bruno Postle was part of a team behind an incredible sculpture built to celebrate the anniversary of BMW. The sculpture, which formed the centrepiece attraction at the 2016 Goodwood Festival of Speed, has been shortlisted for The Structural Awards 2017.

My qualification is in architecture, but Hooman Baghi and Stuart Holdsworth, my fellow team members, are both experienced structural engineers and our approach is very much cross-disciplinary. 
As a team we have worked on a variety of challenging and unusual projects including the 2012 Olympics, Commonwealth Games 2014, Lord’s Cricket Ground, and many more. Our structural technique has been refined through a series of sculptures, all for car companies, each one exploring a new possibility.

With monumental sculptures, and I suppose with building in general, there has to be some overlap between different professions - these structures wouldn’t be possible without artists that understand about engineering and engineers that understand about aesthetics. It isn’t plausible that an artist could create a design and then hand it over to technically minded people to implement. The entire team has to be able to consider aspects of the whole project. From our perspective it is difficult to imagine art and STEM as separate worlds, or that art is purely creative and engineering not creative, they are simply two aspects of the same creative design process.

The structural challenges of the BMW sculpture are familiar to any engineer: stability, buildability, schedule, cost, loading and dynamics. The structure had to span seventy metres, with huge cantilevers sticking out in all directions, but appear to be slender and effortless.

Technology plays a big part in making structures like this possible. We wouldn’t have been able to achieve what we did without CNC controlled laser cutting: the pieces are cut to millimetre accuracy or they just won’t fit. Grinding and bashing hand-cut plate to force it together would not only take much longer, but would lose all the dimensional accuracy we need to be able to take multiple prefabricated sections to site and assemble them together without fuss.

The software tools needed to generate the shapes are surprisingly commonplace, but a good understanding of what families of shape are usable is essential. You can’t just draw any blobby shape in a 3D modeller and expect it to be buildable; these kind of shell structures have to be made from ‘developable surfaces’, meaning that they can be rolled and unrolled from flat plate into conical and cylindrical forms. We do this actual rolling and unrolling in custom software I developed in house, but it is conceptually a straightforward geometrical process, and the code we use is short and simple.

The sculpture’s monocoque construction technique has application elsewhere in engineering, as it’s well suited to creating extremely accurate, light and stiff curved members. In fact, the curvature plays an essential part providing rigidity – where the curvature flattens out we had to stiffen the sections internally with bulkheads to avoid buckling. The technique is very suitable for bridge construction, where light and rigid elements are always called for. Also, because the raw materials are simply laser-cut decoiled plate, which is commonly available, the time between finalising design and starting fabrication can be very short.

BMW Sculpture Goodwood 2016

It was really interesting to listen-in on the public’s conversations about the structure. People love to speculate on how it stands up, as this isn’t at all obvious, just as it isn’t obvious what material it is made from – the steel is flawless up close, with no bolts, fixtures or visible joints, so many tap on the side to see if it is concrete, metal, plaster or wood.  

The Festival’s centrepiece helps differentiate each event: everyone goes to have a close-up look, take a photo and express an opinion as to whether it is better than previous years. This is quite a contrast to a lot of abstract public art that gets completely ignored - nobody ever questions the purpose of this sculpture. It’s wonderful to have produced something that not only created spectacle, but caused discussion about the engineering behind its dazzling form.

Explore The Structural Awards shortlist 2017.

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