MDOT and LTU driving the future of durable bridges
January 11, 2022
The Michigan Department of Transportation (MDOT) is leading the way in carbon fiber reinforced bridge beams - an evolutionary step forward - with the goal of a 100-year bridge in sight.
"The aim is bridges that last a century with minimal maintenance," said State Transportation Director Paul C. Ajegba. "This technology, developed here in Michigan, is becoming wildly popular all over the country."
Since 2001, MDOT has been collaborating with Lawrence Technological University (LTU) in Southfield on researching carbon fiber reinforced polymer materials in concrete bridge beams. That research has moved from the lab into the field, with projects now being deployed.
To understand why carbon fiber is such a game-changing technology, it helps to understand how modern bridges are built to withstand the loads of thousands of vehicles every day and extreme temperature changes for decades. Prestressing concrete with high-strength materials is one method of strengthening concrete. Traditionally, in this method, steel cables are installed inside forms before concrete is poured. The strands are then tensioned with a significant force, causing them to elongate. Once the concrete has gained strength but before it carries loads, the strands are released, compressing the concrete. Any subsequent loads on the beam would then have to overcome this built-in compression to actually stress the beam. Prestressing also reduces or eliminates cracking from concrete shrinkage; it allows thinner and longer spans.
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