ArDOT Engineers Review Troubled Bridge Over Water


ArDOT Engineers Review Troubled Bridge Over Water
Steve Frisbee, assistant chief engineer of operations, and Michael Hill, heavy bridge maintenance engineer, both of the Arkansas Department of Transportation (Karen E. Segrave)
Steve Frisbee, 47, and Michael Hill, 53, are monitoring repairs on the Interstate 40 bridge over the Mississippi River in Memphis after the bridge was closed May 11 when a crack was discovered in a steel support beam.
Frisbee, of North Little Rock, is the assistant chief engineer of operations for the Arkansas Department of Transportation. He joined the department after earning a civil engineering degree from the University of Arkansas at Fayetteville.
Hill, of Benton, is the state’s heavy bridge maintenance engineer. He earned a civil engineering degree from the UA and worked for a consulting firm before joining ArDOT.
The Interstate 40 bridge opened in 1973. Since the crack was discovered, traffic has been diverted to the I-55 bridge, which opened in 1949.

How close was the Memphis I-40 bridge to collapsing?

Frisbee: It’s always a complicated answer. With different engineers, there are different opinions. We will probably never know. We hope to never know. It was very serious. It was rare to see a fracture of this size.

Hill: We can’t say for sure if it would have completely failed or stopped at the joints.

How rare of an event was this crack?

Hill: I would say it was really rare to get something that went to this point without getting caught beforehand. We will find cracks in bridges in inspections. Usually they are not in a [critical support] member of this size. We can address those cracks pretty quickly when they are small. This member is a pretty major member, and the crack was to the point it was a rather large thing to take care of. We calculated that it had enough material left to carry the loads, but anytime you have a crack in a member for precaution, you have to assume that crack might grow and take away some of the material you are counting on.

Once you fix it, is it going to be a long-term repair and the bridge will be back to full strength?

Hill: Yes, this will be a long-term repair. They are trying to make sure we don’t have any other places that may have a similar issue. They are doing a lot of ultrasonic testing of all the joints to make sure we don’t have anything that we can’t see yet. You can’t guarantee that in 20 years it will be fine, but they are making sure there is nothing in the near future.

Frisbee: This is a 50-year-old bridge and I’m approximately that age, as well. It is similar to the lifespan of a person. A person gets a diagnosis of skin cancer and it is serious. When you do that, you get a full body scan to make sure there aren’t any other spots. The good news of this story is we are checking this bridge, and the day it is open it is going to be in its best condition possible and healthier than it ever could be — for a 50-year-old bridge.

How much is this going to end up costing?

Frisbee: It is in the millions but we are sharing the costs [with the Tennessee Department of Transportation]. Both states are in this together. It is reasonable; it’s not anything we can’t manage.


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