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Across Nova Scotia, there are nearly 200 bridges constructed using prestressed concrete girders.

While prestressed concrete is considered a durable, long-lasting solution, bridges from this era are beginning to show their age, especially under the province’s harsh and unpredictable weather.

One of those bridges is the St. Croix overpass on Highway 101, built in 1970, which now sits at the centre of Dalhousie Engineering master’s student Donavon Beatty’s research.

“It’s worse in a climate like Nova Scotia because of the salty air and moisture that can progress corrosion faster,” explains Donavon, adding that decades of freeze and thaw cycles have accelerated deterioration and allowed water to seep into the girders and crack the concrete.

It's certainly a different climate than Donavon is used to. Originally from a farm in Saskatchewan, he relocated to Nova Scotia in 2017 to play Junior A hockey in the Annapolis Valley.

“On the farm, we were always doing little side projects,” he says. “There were always challenges with each project that you had to overcome and engineer. I’ve always liked learning how things work and fit together, and I love hands-on work.”

That curiosity led him into civil engineering and eventually into a master’s degree where he now gets the chance to use his hands every day, testing and analyzing girders that have supported Nova Scotia’s roads for decades.

Aging Infrastructure

That work is happening at Dalhousie University’s Centre for Innovation in Infrastructure’s Structural Assessment and Research (SAR) group, a team dedicated to studying infrastructure durability and developing innovative methods for assessing and repairing existing structures.

Under the supervision of Dr. Fadi Oudah and Dr. John Newhook, Donavon’s research focuses on understanding how environmental stress has affected these prestressed concrete girders. The work is being funded by the Province of Nova Scotia in partnership with NSERC.

The process began in the summer of 2024 when several prestressed concrete girders were removed from the St. Croix Bridge on Highway 101 during a rehabilitation project by the Province. “I was on site to watch the removal process, seeing how they chipped them free from the bridge and lifted them out with a crane,” says Donavon. “From there, they were taken to the storage yard.”

This rehabilitation project created the opportunity for Faculty of Engineering and the Province to collaborate on testing some of those girders in the labs at Dalhousie. Once the girders arrived at the yard, the team began initial testing using both destructive and non-destructive methods to assess the condition of the concrete

“We had a contractor drill some concrete cores so we could test their strength, and we also used a Schmidt hammer to get an approximate value of the concrete’s compressive strength.”

After their preliminary work, the girders were cut into shorter lengths so they could be lifted by a crane and transported to the John Wilson Heavy Structures Lab on Sexton Campus for full-scale analysis.

Each girder underwent testing to see how it would perform under controlled stresses that simulate real-world conditions. “There are three separate girders,” Donavon explains. “The first one we brought in was the longest, about 60 feet, and we had to cut it down. The next two are around 47 feet, reduced to 36 to fit in the lab.”

He says testing focused on different failure modes, which “provided us with different data. It helps us understand how the deteriorated girders behave,” he adds.


 

Early Findings
 

“It’s too early to say how long these particular bridges will last,” says Donavon. “The goal is to use the data from these girders to help engineers assess other bridges. Our results will help calibrate the computerized tools they use for those assessments.”

But the research isn’t just about the assessment. “One other aspect of the project is looking at whether the girders can be repaired instead of being replaced,” he explains.

“Could we strengthen them so that they meet code requirements? Repairing instead of replacing saves money and even helps the environment by avoiding casting entirely new girders.”

Hands-On-Learning
 

For Donavon, one of the most exciting aspects of working with the SAR group is getting hands-on experience with new technologies while collaborating closely with other students in the lab.

“There are a few other students with related projects. I am testing the girders, another student is building the assessment software, and another is using some of my non-destructive testing results in his paper,” he says. “Even if it’s not directly related to my project, I like being involved and helping them out, whether that’s discussing ideas and challenges or lending a hand in the lab.”

While he loves the hands-on work, the experience has also been an opportunity for him to discover parts of engineering he never considered during his undergrad.

“During my undergrad, some of the labs and resources we have access to here, I didn’t really know existed,” he admits. “Now doing the master’s, it’s opened a lot of doors for me. I’ve learned a lot and I’ve also met so many great people: professors, my supervisors, lab technicians, others in the research group and our provincial partners. It’s been really rewarding to grow both academically and personally through those experiences and relationships.”

“And, when I finish this project, I hope the work we’ve done will have a meaningful impact on the province.”