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

crimsonaudio

crimsonaudio

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This is bad - over 50k vehicles a day use this bridge, over a quarter of which are tractor-trailers (Memphis is a major distribution hub). The "crack" as it was described, was discovered during routine inspections yesterday and the bridge was closed immediately. For now, all traffic is being re-routed over the Mississippi via the smaller (and older) I55 bridge.

Latest news says they've no idea how long this major bridge will be closed but it "could be several months" before repairs are completed...

The 'crack' (aka a stress fracture):
IMG_1273.JPG

I fear this is the first of many failures we'll see in the near future as our infrastructure has largely been ignored as it's not something 'sexy' to spend money on...
 
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92tide

92tide

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NationalTitles18 said:
We've needed to invest in infrastructure for 40 years or more and have just ignored the problem, pretending it didn't exist. The bridge in MN (I think) collapsing a few years ago should have been a wake up call, but obviously wasn't.
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i was in grad school studying regional planning in 2003-05 and the backlog was already absurd at that point and it has gotten a lot worse since then.
 
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Jon

Jon

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NationalTitles18 said:
We've needed to invest in infrastructure for 40 years or more and have just ignored the problem, pretending it didn't exist. The bridge in MN (I think) collapsing a few years ago should have been a wake up call, but obviously wasn't.
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if there is one consistent theme in American politics over my lifetime it is missing wake up calls when they do not involve defense spending
 
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dayhiker

dayhiker

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I'm not sure what kind of a crack ISN'T a stress fracture. Things break because more stress is put on them than their capacity. I don't deal with bridges, but I bet that's due to fatigue. You have to take into account an estimate of how many millions of cycles something might experience and then "act" like the steel is weaker than it is by a modifier. At least, that's a close description of how it used to be done. There may be different methods now.

I'm curious what's taking the load that used to be carried by that member. There is a diagonal visible beyond that broken member. I bet those parts of the truss are now taking more load than intended to compensate for what this one used to carry.
 
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dayhiker

dayhiker

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I guess I'll be going through Nashville instead of Memphis as I head to STL in a few weeks. The drive time was basically the same....before this popped up. I had planned to go up one way and back the other.
 
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Jon

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dayhiker said:
I guess I'll be going through Nashville instead of Memphis as I head to STL in a few weeks. The drive time was basically the same....before this popped up. I had planned to go up one way and back the other.
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It won't be the same now with Traffic doubling on your route, but then again with gas shortages....
 
TIDE-HSV

TIDE-HSV

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dayhiker said:
I'm not sure what kind of a crack ISN'T a stress fracture. Things break because more stress is put on them than their capacity. I don't deal with bridges, but I bet that's due to fatigue. You have to take into account an estimate of how many millions of cycles something might experience and then "act" like the steel is weaker than it is by a modifier. At least, that's a close description of how it used to be done. There may be different methods now.

I'm curious what's taking the load that used to be carried by that member. There is a diagonal visible beyond that broken member. I bet those parts of the truss are now taking more load than intended to compensate for what this one used to carry.
Click to expand...
The bottom chord is what's broken, so there's nothing left but the diagonals. The whole weight of the arch is coming down right there to the piling, so the arch suspension is just hanging, depending on its structural integrity. It reminds me of the situation I told you about where my trusses' bottom chords were missing the wall plate, so the roof was hanging on the end of the top chord which was resting on the wall. It looks like a very dangerous situation...
 
crimsonaudio

crimsonaudio

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dayhiker said:
I guess I'll be going through Nashville instead of Memphis as I head to STL in a few weeks. The drive time was basically the same....before this popped up. I had planned to go up one way and back the other.
Click to expand...
Yah, talking to locals this is adding between 45 minutes (dead times) and a couple of hours to their commutes across the river. Best to go through Nashville.
 
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dayhiker

dayhiker

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TIDE-HSV said:
The bottom chord is what's broken, so there's nothing left but the diagonals. The whole weight of the arch is coming down right there to the piling, so the arch suspension is just hanging, depending on its structural integrity. It reminds me of the situation I told you about where my trusses' bottom chords were missing the wall plate, so the roof was hanging on the end of the top chord which was resting on the wall. It looks like a very dangerous situation...
Click to expand...
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.
 
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