3d Printed Structures – What Does It Mean for Structural Engineers?

3D Bridge in Amsterdam – The Future?


Image Courtesy of Construction-Manager

Comment was requested on the 3D printing process and what it might mean for structural engineering. The bridge in the image is a Dutch Start-up project (MX3D) intended to be created by multi-axis robots which print metals, plastics and combinations of materials.

The image above is an artists impression by Joris Laarman, in conjunction with the printing company, Heijmans.

To quote from the Laarman: “This bridge will show how 3D printing finally enters the world of large-scale, functional objects and sustainable materials while allowing unprecedented freedom of form.”

See also…. Cablestay.com Blog

Structural Engineers – What Role to Play?

This is a very interesting development which offers construction techniques which minimise site labour and, like offsite construction methods, places greater degree of control in the hands of specialist structural designers.

Individual designs (ignoring any aesthetics aspects) would be, it is surmised, a collaboration between stress engineers, product engineers and materials scientists in terms of selection of materials, with structural and civil engineers placed in the position of delivering the site specific matters. Ground conditions, foundations, design brief assessment, defining loadings, buildability and so on, traditionally are civil and structural engineering skills.

Taking a historic analogy with the eminent structural engineer Peter Rice  in the design of the Pompidou Centre in Paris, the conceptual design of the structural tied-back frame support and the ends of the building involved cast steel gerberettes in which the design of the castings and materials relied on the specialist technical knowledge of the foundry and materials specialists.

Structural engineers in day to day design may select materials ‘off the shelf’ – such as steel sections, timber or engineered joists, precast concrete sections, and have sufficient knowledge to put these together into a coherent whole. They seldom need the input of specialists for this purpose.

Limitations of The Current 3D Printing Process?

The MX3D bridge  appears to be a ‘tree-like’ structure rather like a truss in which the principle loadings within the individual elements is compression. It is assumed that 3D printing, at the present time,  will not be able to reproduce the benefits of extruding or rolling processes (among others) of manufacture which temper the strengths of many materials so that they usefully act in tension. The writer does not profess to be an expert in this subject.

At present, perhaps, for foot bridges and lightly loaded structures, 3D printing is not far from practical application.

As for sustainability it is not easy to comment. The materials used would need a high degree of processing before they were ready for use – along with the design and manufacture of the robots building the bridge. Is not the use of minimally manufacturing intensive materials, such as timber, and unskilled local labour less sustainable? Its sustainability is a matter of conjecture, at best, for the time being, it is contended.

Having said all this, taking the example of the medieval builders, who produced beautiful structures, even with the limitations of compression, perhaps it is not beyond the imagination, that a combination of 3D printing with designs generated by fractals and fractal mechanics  (invented by the mathematician Benoit Mandelbrot with applications in various fields) might create some beautiful structures hitherto un-imagined? It would need a set of specific rules, which are defined by structural parameters.

Now there’s a thought for the next generation of engineers!


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