LTU, MDOT Building Another Bridge Using Carbon-Fiber Technology

Another semester, another bridge test at Lawrence Technological University’s Nabil F. Grace Center for Innovative Materials Research. 

In the latest test, on Feb. 18, a novel design for a bridge beam stood up to a load of 220,000 pounds of pressure, administered by two giant presses called actuators.

And since bridges are made up of many beams, that means a bridge made of these could stand up to millions of pounds of load.

The goal of Lawrence Tech’s decades of bridge research remains the same—sturdy bridges that last a century, decades longer than the current state of the art.

“The major advantage is that [carbon-fiber reinforced polymer] is corrosion free, so we don’t have to worry about corrosion of prestressing steel strands and having to replace them”

– Mena Bebawy

The secret ingredient is no longer a secret. It’s reinforcing concrete bridge beams with prestressed cables made of carbon-fiber reinforced polymer, rather than the steel that’s been used since the late 19th century. It’s the product of the research career of Nabil Grace, former longtime LTU Dean of Engineering who now serves the university as Senior Vice President of Research and Economic Development.

Under a $400,000 state and federal grant, LTU will continue to research improving bridges with CFRP through 2027.

“The major advantage is that it’s corrosion free, so we don’t have to worry about corrosion of prestressing steel strands and having to replace them,” said Mena Bebawy, LTU associate professor of civil engineering. “And since construction using this material has been mainstreamed for a few years, construction has become fairly easy. We have contractors now who are trained to build this kind of bridge.”

There are over a dozen CFRP-reinforced bridges throughout Michigan, carrying everything from two-lane roads to freeways over waterways and highways. Currently, a CFRP-reinforced bridge is under construction to carry M-30 over US-10 near Bay County’s village of Sanford. The bridge will feature two spans of beams, both 90 feet in length. Bebawy said the beams are now under construction, and that construction is going “very smoothly.”

“MDOT is the leader in these bridges among all other states,” Bebawy said. “Since 2013, we and the MDOT have built a bridge per year with CFRP. I would say it’s gaining momentum, especially in Michigan. Other states are also picking up the technology and are building their own bridges, but they are not as active as Michigan. MDOT is for sure ahead of the game.”

The latest CFRP bridges, Bebawy said, are “hybrids,” using CFRP for the main reinforcement, and traditional steel for secondary reinforcement that is less directly involved in the integrity of the bridge. Even so, he said, the cost of CFRP is “slowly going down.” Thanks to efforts of state and LTU officials, Tokyo Rope Co. has built a factory to produce CFRP strands in the Detroit area, and, Bebawy said, “with the increase in production comes a decrease in cost.”