Mimicking Nature to Save Bridges

First posted on 09-03-2010

Borrowing a lesson from nature, Xiong “Bill” Yu has come up with an array of sensors to detect river bottom scouring around bridges. His inspiration for these sensors came from salmon.

Scouring is the removal of river bottom around bridge foundations. The speed and turbulence of flooding rivers or streams increases scouring and that impedes how well bridge foundations can do their jobs. The resulting deterioration can cause bridges to collapse and fail, costing millions to repair and potentially leading to injury or loss of life.

Yu, an assistant professor of civil engineering at Case School of Engineering, estimates that scouring around bridge foundations has caused over 60 percent of bridge failures in the United States over the past 30 years. Currently, “there is no way to determine risk during these crucial events,” he said. “We don’t fully understand how scouring takes place.”

So he began designing underwater sensors that can provide real-time data about the condition of the river bottom under bridges. He based his design for the sensors on a tiny, hair-like apparatus found on salmon, which have thousands of them along the sides of their bodies. Salmon can gauge the direction of water flow by which way those tiny hairs point. They also use them to determine the velocity of the flow by the time delay as water passes over different hairs on their bodies.

In the laboratory, Yu and his team constructed metal sensors that closely mimicked those tiny hairs. Capable of sending electrical signals to indicate water flow velocity and direction, Yu’s sensors have proven to be accurate, durable and sensitive in river bottoms that lie 10-20 feet below the surface.

Yu said his next step is to determine how deep he can place the sensors and still receive accurate, real-time information from them. He also thinks they might be adapted to provide data about the stability of the bridge structure itself.

Thanks to a complex set of sensors lining the outside of salmon, highway departments and engineers may become armed with valuable, up-to-the-minute data about the health of bridges. Early problem diagnosis can lead to quicker repairs that could save millions of dollars and possibly even human lives.

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