Need a Bridge? Just Press "Print"

Come 2017, the denizens of Amsterdam may be able to stroll across the most unique pedestrian bridge in the world - a bridge 3D printed in midair. The project is a collaboration between R&D startup MX3D, Dutch construction company Heijmans, and Autodesk.

 Artist's rendering of the proposed 3D printed bridge (courtesy of MX3D)

Artist's rendering of the proposed 3D printed bridge (courtesy of MX3D)

According to this FastCompany article, the bridge will be approximately 24 feet in length, and will take just two months to print, though the exact location of the bridge has yet to be determined. The 3D printing method used by MX3D is entirely different from the traditional methods for metals. There's no printer bed here, no powder layers or lasers. Instead, the additive process appears to be a little bit like accumulating a million tack welds in a line. Robots with six-axis arms will start at either end of the bridge, printing both the bridge and their own rails as they move along. This method of fabrication raises some interesting questions as to what the material properties and behavior will be.

The sketches of the proposed bridge suggest that topology optimization is being used in the design. I won't pretend to understand the required mathematics, but my bare-bones understanding is that topology optimization can optimize material for a given load (often yielding non-intuitive solutions). This is similar to what I suspect Arup did when they optimized a steel node for a building - which to date is just about the only other application of 3D printing that I know of in Structural Engineering.

The art of structure is where to put the holes
— Robert le Ricolais
 Sketches of the bridge concept (courtesy of MX3D)

Sketches of the bridge concept (courtesy of MX3D)

Joris Laarman is listed as the designer on the MX3D website. The Dutch artist graduated from Design Academy Eindhoven in 2003, founded Laarman Labs in 2004, and received the Innovator of the Year award from the Wall Street Journal in 2011. He has 3D printed works in resin, metal, and ceramic, with work on display at MoMA, V&A, and Centre Pompidou. While his work in 3D printing is impressive, the first question in my mind is..."but what about the structural engineers?!" It may well be yet another case of heaping public praise on the architect while the engineer is treated as a silent partner. At least, I hope it is. The project may have an undeniable 'cool' factor, but without a structural engineer involved it's hard to see it as anything more than an art project.

 Autobots roll out! (courtesy of MX3D)

Autobots roll out! (courtesy of MX3D)