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How OSU researchers help keep Oklahoma's bridges up to code

When construction faults were discovered in the I-235 bridge in Oklahoma City, the Oklahoma Department of Transportation (ODOT) needed a team of experts to help with repairs. They contacted researchers at Oklahoma State University to monitor the restoration.

OSU Research Matters is a bi-weekly look inside the work of Oklahoma State University faculty, staff and students.

In this episode, Meghan Robinson speaks with Dr. Robert Emerson, a faculty member at OSU’s College of Engineering, Architecture and Technology. His research, which focuses on bridges and load testing, has helped the Oklahoma Department of Transportation keep their bridges up to code.

TRANSCRIPT:

ROBINSON: What is load testing, and why is it important to bridge safety?

DR. EMERSON: We go in there, and we attach all of these sensors. Then after we've attached the sensors in the known locations that we would expect those highest stresses, we then will drive trucks of known weights at particular speeds, which are really, really slow speeds. We're measuring where that truck is along the bridge, and then we measure the response with those sensors. So then we can monitor the bridge more locally. So, if we say, okay, the area of problem was on the left side of the bridge when you're driving along it. And so then that's where this one would have been.

Then on the right side, which would be a mirror image, it's all solid. So we can instrument both sides, and we can compare the response of the side that maybe has a problem to the response of our control side and see if they're behaving similarly or if they're behaving differently.

Then, the other thing that we can do, and we've done -- this is a multi-year project -- is that we can look at our response of five years ago and three years ago with the response that we did this summer. Then we can see, as over time, is there a difference in behavior? And if there's a difference in behavior that showing that it's more flexible, so there's larger deformations, then we could potentially have a problem that we have to investigate even more closely I would say.

ROBINSON: And with the load testing, you're driving a truck over a bridge that if it goes wrong, it goes wrong. Is that stressful, or do you do that with confidence, knowing that your repair has sort of worked?

DR. EMERSON: Well, we have an idea of what we would think would be the ultimate strength or a load that would result truly in damage. So what we're doing is we're using trucks that are lower than what that damage load would be. We run one truck across of a known weight -- which they're about 50,000 pounds -- and then we can run an almost identical truck to that and run the two groups of trucks, and then we do four trucks.

So we can see the behavior as the load increases on there. And we can determine, is it staying in that safe, linear elastic behavior zone? Or does it look like it's going to start to have deformations that aren't going to be recoverable?

ROBINSON: For OSU Research Matters, I’m Meghan Robinson.

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