Building Bridges

If you have ever walked or driven over a bridge in Denver, you can count on one thing: Kevin Rens has been there.
Since 1997, Rens, faculty and chair of the civil engineering department in the College of Engineering and Applied Science, has inspected every one of Denver’s 600 bridges either annually or biannually, looking for any kind of change that could affect the safety of the public.
“I’m kind of like the dentist who tells a patient, ‘We are watching that crack in tooth number 15,’” says Rens. “We are observing any changes in these bridges that could create future problems.”

$45 million: Not a small deal

When Rens first met with Denver’s chief structural engineer 15 years ago, the city relied on random complaints from citizens to determine which bridges should be repaired and in what order. He proposed a more systematic plan: enlist students under his supervision to do regularly scheduled bridge inspections.

That proposal resulted in a partnership between CU Denver and the City of Denver, through which students can focus their master’s or PhD theses on bridge repair projects and have the satisfaction of seeing their maintenance recommendations implemented.
Today, the numbers testify to the program’s success.
More than 200 students have participated.

• Students have been paid more than $4 million for their work.
• More than $45 million has been invested in bridge repairs.

“That [amount of money] is not a small deal,” says Rens. “But it’s a win-win. The students get experience and their degrees. The city gets sound engineering at an economical rate.” Jim Barwick, Denver’s chief infrastructure engineer, echoes Rens when he talks about “good quality work” done by “motivated, eager” students from CU Denver. “They scratch our back and we scratch theirs,” said Barwick. “This partnership has been as enriching for us as it has been for the students.”

Inspections: A health score

Think of Rens as a bridge doctor doing annual physicals on every bridge, looking for ailments small and large, anything from minor loose nuts and bolts to major structural damage.

In fact, one of Rens’ doctoral students, Xin Jiang, developed the “Denver Bridge Health Index,” a single number indicating a bridge’s health, with 0 percent denoting a bridge in the worst possible condition and 100 percent marking one in the best condition.
Another student, Elisabeth Cole, is using work on the Evans bridge over Santa Fe Drive in her master’s thesis. She’s comparing the results of a visual inspection of the Evans bridge with a second inspection done using sensors attached to the bridge.

“I really enjoy structures,” she said. “We all need them, we all use them and I like to learn how a structure will behave during its life.”
Cole estimates that the engineering team’s second inspection will save Denver $1 million in repairs. By the time she finishes her thesis, she will have made great connections within the city. “If you do good work, there are jobs you can get right out of school,” she said.

Surrounded by police

Rens has had his share of strange encounters as, over the years, he’s made the acquaintance of every bridge in Denver, but the most bizarre experience happened in late September 2001 when the country was on heightened terror alert in the wake of 9/11. He and a team of students were working in the railroad yard under the 6th Avenue viaduct, attaching sensors to the bridge to inspect it.

“We were listening to the radio,” remembers Rens, “and we heard that the 6th Avenue viaduct had been shut down and the area evacuated because of suspicious activity. And I thought to myself ‘That’s weird. I wonder why we weren’t evacuated.’ And within minutes we were surrounded by police cars.”

It took some explaining, but Rens finally convinced the police that his sensors were no threat and, in fact, he was working to ensure the safety of the traveling public.

Eye candy

A few of the bridges Rens inspects have passed their centennial. Built to carry trains, they now carry pedestrian traffic. But they still need annual inspections and maintenance to stay safe. Rens knows that some observers might think it more cost-effective to simply replace an old bridge with a new one.

“There are some valid points to that school of thought,” he acknowledged. “But the historic nature of these bridges makes them an art form. Keeping them is historic preservation and an asset to Denver’s eye candy.”

After keeping the “eye candy” safe for the past 15 years, Rens and his students look forward to a long partnership with the city—and building more “bridges” between the university and the community.