Infrastructure: Memphis I40 bridge over Mississippi river closed indefinitely after stress fracture discovered

[crimsonaudio]

When I was living in Memphis, the northbound lane of the Perkins Road bridge over Nonconnah Creek collapsed. A couple of people died. If memory serves, one of them was an All American safety for Memphis State.

One person died, MSU safety Bill Austin.

 

[Go Bama]

One person died, MSU safety Bill Austin.

Thanks. My girlfriend at that time lived just off Perkins. She crossed that bridge daily.

 

[Elefantman]

This is probably more engineering detail that you may want to know. But it does a good job explaining the complexity of the repair and return to service of this bridge.

 

[TIDE-HSV]

I thought that was excellent...

 

[jthomas666]

This is probably more engineering detail that you may want to know. But it does a good job explaining the complexity of the repair and return to service of this bridge.

Thanks! I'm passing this along to my wife the physics teacher...

 

[TIDE-HSV]

I went back and looked at old pix and I think the long piece of the fractured chord has displaced upwards by and inch or so. Lack of traffic?

 

[Elefantman]

I went back and looked at old pix and I think the long piece of the fractured chord has displaced upwards by and inch or so. Lack of traffic?

Possible, I'm not sure how thermal expansion would effect it.

 

[NationalTitles18]

We crossed this bridge way back in 2016 when we moved to CA. To think it may have had a crack in it already then and didn't fall into the river...Lots of people have been unknowingly fortunate.

 

[dayhiker]

I went back and looked at old pix and I think the long piece of the fractured chord has displaced upwards by and inch or so. Lack of traffic?

I didn't look back up the condition, so this is from memory, but It's probably just a difference in restraint. One side of the fracture has a really stiff connection that is connected to the hangers. The other side is not, well, at least not in the very close vicinity.

 

[TIDE-HSV]

I didn't look back up the condition, so this is from memory, but It's probably just a difference in restraint. One side of the fracture has a really stiff connection that is connected to the hangers. The other side is not, well, at least not in the very close vicinity.

John, IIRC, it is the longer section which has risen slightly, consistent with what you say...

 

[dayhiker]

John, IIRC, it is the longer section which has risen slightly, consistent with what you say...

It's also possible cantilever action that's lifting it as well. When you have a long span and a short cantilever, the beam design yields weird sizes because you're trying to keep the free end of that diving board from popping up in the air. In this instance, you have a long cantilevered end because it's going from whatever the last support was to the location of the fracture. That distance might be long enough to keep that end from popping up, but it could also explain what's happening. It would just depend on what those different span lengths are.

I watched part of that video. I was glad to hear that my off the cuff initial remarks weren't totally out in left field. He did a good job explaining the structural mechanics and the graphics seemed to be really good examples. One thing I didn't hear him mention is that while yes, the thrust could have gone into the piers and caused problems, it's also possible that the thrust was ultimately resisted as the whole assembly acting as a column and ultimately get resisted where it connected back to mother earth. I was doing some fast forwarding, so that may have come up.

 

[TIDE-HSV]

It's also possible cantilever action that's lifting it as well. When you have a long span and a short cantilever, the beam design yields weird sizes because you're trying to keep the free end of that diving board from popping up in the air. In this instance, you have a long cantilevered end because it's going from whatever the last support was to the location of the fracture. That distance might be long enough to keep that end from popping up, but it could also explain what's happening. It would just depend on what those different span lengths are.

I watched part of that video. I was glad to hear that my off the cuff initial remarks weren't totally out in left field. He did a good job explaining the structural mechanics and the graphics seemed to be really good examples. One thing I didn't hear him mention is that while yes, the thrust could have gone into the piers and caused problems, it's also possible that the thrust was ultimately resisted as the whole assembly acting as a column and ultimately get resisted where it connected back to mother earth. I was doing some fast forwarding, so that may have come up.

If it did come up, I missed it. The upward deflection may just be the natural progression and would have happened without traffic, I suppose...

 

[CrimsonNagus]

That video was very interesting. It is sad that they fired one guy as a scapegoat, entire teams should be fired for this blunder.

 

[DogPatch]

Here's one that will seem........really weird.

Ever since I was 10 years old, I've ALWAYS had a phobia about bridges collapsing. If I'm on a long one and I'm driving, I take a deep breath and exhale slowly. It may go back to seeing a bridge that had collapsed in my county in 1979 when a crane being transported across it hit the top of it and it knocked it down sort of in a triangle shape.

The bridge that has always given me the most stress? The I-55 in Memphis.

To avoid that stress when possible? I always took the I-40.

Holy moses.

You probably remember the Sunshine Skyway collapse, too.

 

[selmaborntidefan]

You probably remember the Sunshine Skyway collapse, too.

Not only do I recall that, I have an interesting story about it.

When I was at Keesler AFB back in 1992, one of my trainers was a guy who attended Florida A/M prior to his military career. He had a friend who that was heading home for the weekend and was sitting at the bus station to get on that bus that went off and killed those people. By chance, this trainer and some other friends had decided they were going back up Florida somewhere (honestly, I didn't totally absorb every detail he said), so they picked him up at the Greyhound bus station mere moments before it left. He figured he'd rather spend the time riding with friends than strangers on a bus, so he went with them.

He was supposed to be on the bus, and they wound up saving his life by coincidence. I still recall this guy - he was a black man and so was his friend - saying, "He walked around whiter than a white dude for a couple of weeks after that realizing what would have happened if he had been on that bus."

 

[Elefantman]

You probably remember the Sunshine Skyway collapse, too.

Similar thing happened in 1993 in Alabama. A barge hit a railroad bridge outside Mobile causing an Amtrak train to derail. 47 died in that accident.

Amtrak Sunset Limited disaster 23 years later: 1993 Bayou Canot train wreck remembered

Twenty-Three years, visitors -- including a first responder and the brother of an engineer who died -- returned to the scene of a deadly rail disaster.

www.al.com

 

[dayhiker]

If it did come up, I missed it. The upward deflection may just be the natural progression and would have happened without traffic, I suppose...

Since that member doesn't directly have traffic on it, I doubt the movement has anything to do with the traffic.

 

[TIDE-HSV]

Since that member doesn't directly have traffic on it, I doubt the movement has anything to do with the traffic.

I would have thought the load imposed by traffic would be distributed throughout the structure, including the damaged part...

 

[dayhiker]

I would have thought the load imposed by traffic would be distributed throughout the structure, including the damaged part...

Yes and no. The fractured member was a tension member. The amount of tension in the member would have varied with the amount of traffic. With 0 traffic, that member is still supposed to be in tension. Once it fractured, it's really not doing anything and is just along for the ride at the whims of gravity.

 

[TIDE-HSV]

Interesting. Since the arch is still flexing and pulling on that member, I'd guess it'll continue to move some. It still seems to be that the arch would be flexing more with traffic load. There's a lot to be learned here...