For the first time in history, a bio-based movable bridge for cyclists is tested within TU Delft’s laboratories. It was made out of flax and resins derived from plants. This structure is actually a 12-meter long prototype and it’s the first time this bio composite material is used on this scale. The bridge, that will actually be built in 2020 in the province of Friesland, is an important project to promote more eco-friendly materials and sway the construction industry to turn to a greener page.
After clicking on a series of buttons, Assistant Professor Dr. Marko Pavlović turns on a machine. Two pistons, one per side, start a rhythmic up-and-down bending of the structure’s extremities. This 1:3 scale replica of the swing bridge, designed to pivot horizontally around a central pin, is going to be built in Leeuwarden, in the North of the Netherlands. “Regarding flexibility, the structure is very promising,” comments Pavlović. “It behaves like chewing gum, and it is very strong.”
Bio-based is the new black
The machine keeps on running for weeks under Pavlović’s eye. Bending, hammering, twisting and loading the structure to simulate how deformations affect it when crossed, or while opened and closed for 30 times a day for a lifetime of 100 years. Pavlović set his heart on this research as an expert in Structural Engineering and Fibre Reinforced Polymer (FRP) composites — obtained by mixing two or more different constituent materials. He aims to present the bridge in one piece and without significant deformations to the conservative construction industry. To prove once more that there is more to play with than the classic trio of Concrete, Steel and Wood. “Concrete suffers corrosion of the embedded steel reinforcement within 30-40 years of its lifetime, and steel needs repainting every 20 years to avoid corrosion to impact the structure’s performances,” says Pavlović. “The bio-based composite material used for the bridge — laminated and painted to resist UV rays and moisture — aims to achieve more durability and less maintenance than traditional steel.”
Research and sacrifices to slow down global warming
“We must learn to reduce our comfort standards to slow down emissions from human activities,” says Pavlović. The construction industry, at the moment, is responsible for 39% of energy-related CO2 emissions on Earth. It is mandatory that Civil Engineering plays its part to increase the funds into research for solutions with lower carbon footprints. “This means investigating new solutions to use greener materials and sacrifice comfort if needed. For instance, letting structures shake a little more when stepping on them, without compromising their safety.”
Greener materials for more sustainable economies
More innovative businesses like sport and automotive, already use bio-based materials. Such industries have lighted the starry night to inspire engineers like Pavlović to research new fruitful routes while promoting innovation and more circular economies. “Looking out of the box is the key”, says Pavlović. “By doing that, it soon came out that composite materials can be used in Civil Engineering as well. If well-designed, bio-based structures could be crafted out of modular parts similar to LEGO, to be re-used in new constructions after periods of 50 years.”
Setting foot onto the future
One day in 2020, the first pedestrians will set foot on the bridge. They will walk or cycle on a milestone: crossing the world's first movable bio-based composite bridge. “I hope they do not only feel safe but, that they also understand the message of the structure,” comments Pavlović. “If you are brave enough to look for alternatives, you can make the world a better place for yourself, your family and many more generations to come.”
FRP Composites in Structural Engineering
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