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Beam testing key to ensure existing bridge safety

9/23/2020 McCall Macomber

Picture it. An overloaded, overweight grain wagon traveling over a local bridge causing it to collapse.

Preventing dilemmas like this is all in a day’s work for researchers at Illinois Center for Transportation and Illinois Department of Transportation.

<span style="font-size: 0.8em;">Provided by Thomas Golecki </span><span style="font-size: 0.8em;">and Bill Spencer. </span><span style="font-size: 0.8em;">Structure number 020-3087, located in central Illinois, partially collapsed after an overloaded grain wagon crossed it Oct. 1, 2019. Two of the bridge&rsquo;s six beams collapsed after the encounter.</span>
Provided by Thomas Golecki and Bill Spencer. Structure number 020-3087, located in central Illinois, partially collapsed after an overloaded grain wagon crossed it Oct. 1, 2019. Two of the bridge’s six beams collapsed after the encounter.

Just ask the University of Illinois at Urbana-Champaign’s Bill Spencer and Thomas Golecki, a professor and doctoral candidate, respectively, along with Robert Perkins, IDOT’s local bridge unit chief, all of whom lead the joint project, “Destructive Testing of IDOT Bridge Structure Number 020-3087.”

“It was a pretty unique opportunity that you don’t get ordinarily in industry or from a research perspective — to be able to test an actual specimen that was in service for over 50 years,” Golecki said.

The team got to work, taking one of the remaining prestressed beams — in which stress is introduced before it’s in service — and testing it to destruction at UIUC’s Newmark Structural Engineering Laboratory.

“There’s a lot of unknowns with how much prestress is lost over time. The environmental conditions that cause corrosion contribute to the remaining amount of prestress,” Golecki said.

“So, testing the actual specimen to figure out exactly what strength is there allows us to evaluate the accuracy of our estimates,” he added.

<span style="font-size: 0.8em;">Provided by Thomas Golecki </span><span style="font-size: 0.8em;">and Bill Spencer. </span><span style="font-size: 0.8em;">A bridge beam rests after undergoing a destructive test at the University of Illinois at Urbana-Champaign&rsquo;s&nbsp; Newmark</span><span style="font-size: 0.8em;"> Structural Engineering Laboratory. The beam supported a load of 33.14&nbsp; kips</span><span style="font-size: 0.8em;">&nbsp;(33,140 pounds) before failure.</span>
Provided by Thomas Golecki and Bill Spencer. A bridge beam rests after undergoing a destructive test at the University of Illinois at Urbana-Champaign’s  Newmark Structural Engineering Laboratory. The beam supported a load of 33.14  kips (33,140 pounds) before failure.

They determined the strength it would take to break the beam and compared it to IDOT’s current load-rating policies, which regulate how much weight a bridge can safely hold.

The result?

“This research has verified that IDOT’s current load-rating policies effectively estimate the structural capacity of deteriorated PPC deck beams,” Perkins said.

“Our current practices and policies are working, public safety is accounted for and we are setting the posting levels appropriately,” he added.

The effort was also Spencer’s first partnership with the two entities.

“It was a great opportunity to meet some of the key players in IDOT and hear their concerns and their thoughts,” Spencer said. “I hope that we have chances in the future to do other work with ICT and IDOT.”