Feast Your Eyes Upon the World’s First 3D-Printed Steel Bridge

It looks whimsical, but it could be a blueprint for fixing our woeful infrastructure in the U.S.

After four long years of planning, the world’s first 3D-printed steel bridge debuted in Amsterdam last month. If it stands up to the elements, the bridge could be a blueprint for fixing our own structurally deficient infrastructure in the U.S.—and we sorely need the help.

Dutch Company MX3D built the almost 40-foot-long bridge for pedestrians and cyclists to cross the city’s Oudezijds Achterburgwal canal. It relied on four robots, fit with welding torches, to 3D-print the structure. To do it, the machines laid out 10,000 pounds of steel, heated to 2,732 degrees Fahrenheit, in an intricate layering process. The result? An award-winning design, pushing the boundaries of what steel can do.

“A 3D-printed metal structure large and strong enough to handle pedestrian traffic has never been constructed before,” Leroy Gardner—a professor at Imperial College London’s Department of Civil and Environmental Engineering, who was involved in the work—said in a prepared statement.

For that reason, researchers at Imperial College London have developed sophisticated computer simulations to check in on the bridge, with a focus on the structure’s ability to withstand daily foot traffic and damaging weather forces.

If it all pans out, the U.S. should take notes. According to a 2019 report by the World Economic Forum, the United States ranks 13th in the world for quality of transportation infrastructure. Meanwhile, most bridges in the U.S. are only designed to last 50 years. As of 2021, about 4 in 10 bridges have already surpassed that life expectancy. Now, the American Association of State Highway and Transportation Officials requires all bridges meet a 75-year design lifespan. 

Engineers must maintain this infrastructure, while simultaneously building onto it, all with limited time and resources. Advancements in technology, like 3D printing, seem necessary to combat the country’s deteriorating infrastructure. In the search for methods to lengthen the longevity of our bridges and roads, conserve resources, and increase safety, 3D printing may be a legitimate option—and this steel bridge is the perfect case study.

Designers first came up with the concept for the bridge in 2015, with the goal of making an exceptionally efficient structure. To do so, they had to emphasize two things: simplicity and safety. To monitor the efficiency of their design, scientists at Imperial College London engineered the bridge to be a “living laboratory.”

A team of structural engineers, computer scientists, and statisticians developed a system of over one dozen embedded sensors for the bridge, which send live data to the university for further analysis of the bridge’s performance. They monitor the bridge’s movement, vibration, temperature, strain (the change in shape and size of materials under applied forces), and displacement (the amount an object shifts in a specific direction) over time.

From that data, scientists built a “digital twin”—computer science parlance for an identical, virtual rendering—of the bridge that gets more accurate over time. With machine learning, they can now look for trends that might suggest modifications are in order.

One of the advantages of 3D printing is its ability to build shapes that would otherwise require more equipment, time, and cost in a traditional manufacturing process. This allows designers to be more creative and consume less resources. 

For this bridge, designers utilized two methods of 3D printing—Direct Energy Deposit (DED) and Powder Bed Fusion (PBF). With DED, the printer feeds material (typically in powder or wire form) through a pen-like nozzle, and an intense heat source (typically a laser, but sometimes an electron beam) melts the metal on contact. 

PBF works similarly in that a laser or electron beam melts powder down to build each layer. The main advantage of PBF, though, is that it operates with much smaller (and more expensive) parts, resulting in a higher-resolution project than DED could accomplish on its own. This allows designers to take their visions a step further.

Source: Popular Mechanics