A standard, industrial robotic arm has “printed” about a third of a 12-meter pedestrian bridge that is destined to span an old Amsterdam canal in the Netherlands as early as next year.

在当地艺术家和设计师Joris Laarman的带领下，一支小型团队正在使用数字控制的焊接工艺在3D打印公司MX3D的阿姆斯特丹车间中建立了形状较高的桥梁元素。

该公司首席技术官兼共同所有人蒂姆·盖特金斯（Tim Geurtjens）表示，大约6米吨，不锈钢桥的所有元素应在2018年中期全面形成和组装，以进行全面测试。

Geurtjens希望运河现场准备好在明年年底之前接收整个桥梁。但是在此之前，该结构需要确保城市官员的保险和批准。

“There is an issue, particularly with permitting. This is not a codified project,” says Mathew Vola, an associate director in the Amsterdam office of London-based Arup Group, which is advising MX3D. “There are no [other] 3D-printed bridges with this technique.”

Geurtjens说，Laarman的团队建立了MX3D，使用其软件使用标准焊接技术和机器人形成大型钢元素。该团队在获得了工业合作伙伴的网站并获得了支持后，于2016年5月完成了设计。

盖尔特詹斯（Geurtjens）承认，这个概念“与桥相关”，但太复杂了。“我们发现，现在的结构工程还没有准备好[这种]复杂的几何形状。”

Geurtjens说，该团队在罗斯马伦承包商Heijmans N.V.的建筑顾问使用了一种分析模型，该模型“太简化”了他们想要的“酷”结构。因此，他们于去年年底重新设计了Arup。

MX3D最初的桥梁设计“was made of trusses, much like a 3D space frame,” says Vola. That statically indeterminate structure, with high stress concentrations, added to other uncertainties, such as the material’s brittleness and fatigue performance.

So, Arup remodeled the bridge as a U-section channel that is curved in plan. The engineers developed and structurally analyzed the essentially 2D, folded plate using 3D parametric modeling software in a totally digital operation. “We don’t do drawing any more,” says Vola.

Although the team has done extensive theoretical work on the bridge, “there are a lot of unknowns about the material,” says Geurtjens.

MX3D正在使用314类不锈钢，该钢在高温下具有良好的性能。该项目的ARUP工程师Bertrand Le说，焊接产品的均匀较低。但是它的强度特性与常规钢的特性相同，而材料相对没有内置应力。

Because of all the uncertainties, MX3D will validate its design with a full-scale prototype. Geurtjens is optimistic that the structure will secure the required permits next year.

If tests reveal the bridge needs reinforcing, “we can print extra parts,” says Geurtjens. And if all goes to plan, he adds, future structures will be printed entirely on site.