Bridges That Last a Century Will Be Big Stuff BY MATT ROUSH
24 | TechCentury | SUMMER 2018
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ompared to giant structures like the Mackinac Bridge, the bridge carrying I-75 over the Sexton and Kilfoil Drain in Allen Park wouldn’t seem to be all that impressive. But appearances can be deceiving. It’s what’s inside the bridge–or more precisely, what’s inside its reinforced prestressed bulb-T sections—that really counts. Because what’s inside them isn’t the usual steel reinforcing bars. Instead, there are innovative strands made of continuous carbon fiber, which is far lighter than steel and far more durable, because it doesn’t corrode. At 150 feet, the I-75 bridge is the longest carbon-fiber reinforced and prestressed highway bridge ever built in the Western Hemisphere. And it’s built to last a century. The work is part of the lifelong research focus of Nabil Grace, dean of the College of Engineering at Lawrence Technological University in Southfield. Grace is principal investigator on two research contracts totaling about $500,000 to study the benefits of carbon fiber prestressing strands. Mena Bebawy, assistant professor of civil and architectural engineering at LTU, is co-principal investigator. The research contracts are funded by the federal government and state departments of transportation in Maine, Michigan, North Carolina and Ohio. The research is being conducted in the field, where MDOT jointly with LTU has supervised the construction of seven highway bridges using the material already. A bridge in Southfield carrying Bridge Street over the Rouge River was the first, in 2001. Others include