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

[dayhiker]

Ok, this gives a much different feel to it. That diagonal we saw and were talking about isn't doing much of anything for what we were speculating. It looks to me like it's there to stabilize the bottom of the perpendicular plate girder.

Note to the left of the big bolted connection. You can see some waviness in the member there too.

 

[dayhiker]

What I previously meant by "how it works," is if the truss up in the air is actually doing all of the work and then these low girders just span from cable to cable. If that's the case, then the upper girder in the photo above would seem to be doing the work. In which case, what's this broken one actually doing? I'm curious now. I may have to see what I can dig up.

 

[NationalTitles18]

View attachment 16368

Ok, this gives a much different feel to it. That diagonal we saw and were talking about isn't doing much of anything for what we were speculating. It looks to me like it's there to stabilize the bottom of the perpendicular plate girder.

Note to the left of the big bolted connection. You can see some waviness in the member there too.

does it look to you like the part to the left has a similar “crack” developing?

 

[dayhiker]

I've read a few things about it now, but nothing is in detail talking about how you analyze one of these. I'm going to back off my fatigue comment at this time.

As far as a crack in the other side, if this member was overloaded in tension, maybe both sides were starting to fail and the right one just popped first. I don't know.

 

[dayhiker]

So this is a tied arch bridge. Picture a metal building frame. You push down on the middle of it and the ends try to spread. In this case the ends are tied together. Those ties appear to be what's broken.

My bridge knowledge puts this all above my pay grade. I'm going to have to do some reading later. I'm pushing to get stuff finished since I'm heading out of town next week. Maybe this will be some airplane reading for me.

 

[dayhiker]

PS, I didn't find someone's Master's Thesis on testing and monitoring of this very bridge. One photo looked like it could be the same place as this failure and all looked good there/then. The thesis was form 2017

 

[dayhiker]

One last comment....when you see test results from steel beams, they frequently paint them. It's almost like a chalky white wash. Then they'll bend or stretch them and you'll see this stuff flake off. As the steel elongates, this stuff comes off. I don't know if "real" paint does that too. Note that you don't see any distress in the paint. Nothing looks like this member was being stretched or necked down before it fractured. In strength of materials class, we'd break steel and you could see a steel rod neck down a pretty substantial amount before it finally failed. These photos are from a drone and probably not that close, but the lack of any type of necking down just sort of struck me.

 

[TexasBama]

What I previously meant by "how it works," is if the truss up in the air is actually doing all of the work and then these low girders just span from cable to cable. If that's the case, then the upper girder in the photo above would seem to be doing the work. In which case, what's this broken one actually doing? I'm curious now. I may have to see what I can dig up.

Just looking at the pictures, that beam is getting loaded pretty much laterally (as you described). Curious how much torsion it might see. Judging by the rust visible, its been that way for a little while.

 

[crimsonaudio]

Friend just sent me this:

 

[TexasBama]

Friend just sent me this:

View attachment 16371

 

[crimsonaudio]

If true, this is likely a lot longer than a few months to repair. And that's going to crush shipping / distribution for a huge part of the US. Memphis Airport is so busy due in large part to the amount of shipping companies with warehouses here - I forget the exact number, but something like 80% of the population of the US is within a 900 mile radius of Memphis.

Goodness.

 

[DzynKingRTR]

Good news for a structural engineer. They get some work to do. Probably won't go with the original company.

 

[Jon]

over/under on the number of hours before the conspiracy crowd wraps this into Q?

 

[dayhiker]

Just looking at the pictures, that beam is getting loaded pretty much laterally (as you described). Curious how much torsion it might see. Judging by the rust visible, its been that way for a little while.

It looks solely axially loaded to me. I don’t see any lateral loading.

 

[TexasBama]

It looks solely axially loaded to me. I don’t see any lateral loading.

What I was trying to say. Not well, but trying

 

[92tide]

UPS, FEDEX, Amazon - Memphis is a major shipping hub - Memphis International is the busiest cargo airport in the world.

This is almost certain to impact prices of a lot of goods in the near future.

2020 cargo tonnage by airport:
View attachment 16367

supply/logistics chains around the world were already pretty jacked up prior to covid. it has gotten a lot worse since then, and throw in suez, the pipeline, this.

 

[92tide]

Friend just sent me this:

View attachment 16371

absolutely huge that they caught this when they did.

 

[TIDE-HSV]

That may or may not be totally true. These type of cable bridges can be a different animal. That's why I was vague in my wording. I didn't want to mispeak. I can look at a truss and pretty well know what's going on. I can't say that about these type of structures.

Cable or no, it seems it has to be hanging from the arch. I don't see how it can be resting on that bottom chord...

 

[TexasBama]

over/under on the number of hours before the conspiracy crowd wraps this into Q?

how big is the Russian community in Memphis?

 

[TexasBama]

supply/logistics chains around the world were already pretty jacked up prior to covid. it has gotten a lot worse since then, and throw in suez, the pipeline, this.

I read that they also shut down the river. It may be open now.