UMaine student develops affordable option for shoring up Maine’s aging bridges

the same orientations.

“The fiber-reinforced polymer composites are really strong in the direction of the fiber,” Loring says. “If you have fibers that run in one direction and you pull on the composite in that direction, it takes tens of thousands of pounds to break it. What we end up doing is kind of combining the fiber orientations in different directions, giving it different properties.

We looked at different fiber orientations for the core fibers in order to ensure the threaded rods can develop sufficient capacity.”

Loring used glass and carbon because they are lighter than steel. Glass is usually cheaper than carbon, but tends to deteriorate in the environment faster. The hybrid system was chosen because it would be cheaper — due to the glass — and durable enough for short-term use — because of carbon’s superior durability properties.

After conducting durability studies on effects of saltwater, freezing and thawing, the four systems were whittled down to the two glass-carbon hybrid systems.

“The performance of the glass-carbon system was much more superior so we had that manufactured in large strips so we could apply them to reinforced concrete beams,” Loring says.

Working with Kenway Corp. of Augusta, the strips were manufactured and tested on beams designed to mimic flat-slab bridges.

“There has been a big constructability focus with everything we’ve done,” Loring says. “The ability to make the materials, the ability of the materials to perform properly, the ease of installing on a bridge. Everything we’ve done for testing, we’ve done overhead, because you can’t just pick a bridge up and roll it over.”

Loring found the glass-carbon systems performed the best.

“We were able to get about a 47 (percent) to 49 percent increase in the flexural capacity of the beam compared to an unreinforced beam,” she says.

Loring says the system looks promising, although some fine-tuning could increase efficiency.

Another student is planning to perform fatigue testing after Loring graduates this summer. Fatigue testing is essential before any field application.

Although Loring does not yet have an exact dollar figure on how much using her retrofitting system would cost, she is confident it is cheaper than what is available and could save the department tens of thousands of dollars per bridge compared to other methods of strengthening.

“There are commercially available systems out there for the same type of product that I’ve engineered from the ground up, but they’re proprietary systems,” Loring says. “Basically what that means is you pay for the product from the company at whatever price they say it’s worth.”

Loring’s main goal for the project is to be able to give the MaineDOT an alternative option. She wants to present the department with a comprehensive report on a low-cost retrofitting system they could have manufactured instead of defaulting to a proprietary option.

“A lot of the time MaineDOT puts out to bid its work and sees what companies can do,” Loring says. “With this they would be able to present the design specifications to a composite manufacturer and say, ‘Here’s what we want. How much can you make it for?’”

For Loring, working in an environment that forced her to apply what she learned in college was overwhelming at first, but she credits her department, adviser and the Advanced Structures and Composites Center with making her feel comfortable and capable throughout the process.

“The department’s awesome, there’s always been a really close-knit community with the Civil and Environmental Engineering Department,” Loring says. “Professors go by their first names. It’s just friendly, it’s welcoming. I come from a big family so having a family environment at school has just been great.”

The release notes that Loring chose to study civil and environmental engineering after developing a love of buildings at an early age. Growing up visiting worksites with her father who is a carpenter, Loring knew she wanted to have a hand in creating buildings. Following in the footsteps of her father and several siblings, she decided to come to UMaine to pursue her goal of becoming an engineer.

This is Loring’s first project working with bridges.

— Read more in The Fix We’re In For: The State of Our Bridges (Transportation for America, 2013)