Footbridge to the Future
Eindhoven University of Technology in the Netherlands is home to the world’s first footbridge built completely with biocomposite materials. The 46-foot-long bridge was a collaborative effort by a consortium that included several regional universities and composite manufacturer NPSP.
The bridge weighs approximately 3,300 pounds and is designed to carry loads of 102 pounds per square foot. Its biocomposite material includes hemp and flax fibers. “We had the idea that flax fibers would be able to fulfill the mechanical requirements for a bridge like this,” says Patrick Teuffel, professor of innovative structural design at Eindhoven University. The fibers were also readily available from the project’s industrial partners.
To manufacture the bridge, workers attached the fibers to a biological polylactic acid (PLA) foam core, then introduced a bio-resin using a vacuum injection process.
The bridge, installed over a stream in October 2016, includes 28 sensors that continue to measure its strength, stiffness and deformation (creep behavior) over time. The university staff is also testing the behavior of the bridge materials in the lab.
“There is still not a lot of experience about how [the bio-material] will behave long term,” Teuffel says. “If you really intend to have these kinds of projects for 10, 20 or even 60 years, you have to define a certain stress level that should not be exceeded to avoid creep problems.”
The team has acquired a grant to build a small biocomposite pavilion and hopes to construct another bridge in Eindhoven this year. “I’m sure there will be more applications in the future,” Teuffel says.