Infrastructure: Memphis I40 bridge over Mississippi river closed indefinitely after stress fracture discovered
- Thread starter crimsonaudio
- Start date
Yes, that's what I was trying to convey with the pre engineered building analogy.fifyOur engineering curriculums only merged in 100 level classes.
I think I understand what happens in this bridge is that the weight makes the arch want to flatten and the ends of the arch move away from the center. The beam that cracked keeps the ends of the arch from moving away from each other. I would guess that without this beam in place there is thrust on the foundation (maybe why it's being inspected?).
Yes, that's probably a better analogy to use. Most folks don't visualize a PEMB. I only used it as the example since it's a three hinged arch and the bridge is what's called a tied arch.
I like how they keep calling it a crack. A crack is something that hasn't broken yet. That thing is not a crack.
If that were a tooth it would be called a fracture. The fracture happens after the crack.I like how they keep calling it a crack. A crack is something that hasn't broken yet. That thing is not a crack.
A fracture or rupture is generally what you hear on a tension failure like this.
I haven't seen drawings, just a few photos of the bridge, but I just wonder if the bridge deck acted like a diaphragm and the other tension tie on the opposite side is now taking 100% of the thrust and maybe that's the only thing keeping it up. Heck, the reinforcing steel in the bridge deck may be acting like the tie strut. Something is, otherwise....
Fulmer drove over it. The engineers did not account for the extra weight.
Local news is saying they're currently in the mode of determining whether the bridge can even sustain it's own weight right now.
I drove over that bridge and back this past Sunday...
I can't imagine how long it would take to build that analysis model. I bet it already exists though, since there was the seismic upgrade project. Still, the computer model won't necessarily be able to take into account the things that are helping that aren't necessarily supposed to be helping.Local news is saying they're currently in the mode of determining whether the bridge can even sustain it's own weight right now.
I drove over that bridge and back this past Sunday...
Get some Gorilla Glue and duck tape. It will be good as new.
I was just about to post the same thing.I like how they keep calling it a crack. A crack is something that hasn't broken yet. That thing is not a crack.
I don't know what all the fuss is about, a little calking putty and some paint will have that good as new in no time.
In this case, it's not just vehicular traffic on the bridge. The way I read this quote from the article in your post #61 above is that it's unsafe to pass under the bridge, so traffic on the Mississippi River is stopped as well.
"Traffic is non-existent on the famed “M” bridge. The U.S. Coast Guard reported 16 vessels and 229 barges at a standstill, all due to this crack in the bridge’s support beam discovered by inspectors Tuesday."
I certainly don't know, but the Mississippi River is such a major commercial artery that I wouldn't be surprised if that's a bigger economic issue than diverting vehicular traffic.
If there's a legitimate question as to whether the bridge can support its own weight, I don't know how you put personnel on it to fix the problem. It might have to be demolished.
This is bad news. The amount of product that moves up and down the Mississippi is staggering.
If I had to guess, I think the river will be reopened eventually to a coordinated one way, daylight only traffic situation.
When I was taking steel design for architecture, we decided to see if it is at all possible to design a beam that could not support its own weight. How big would it need to be?
Pretty much any beam size made can be proportioned to collapse under it's own weight. If it's long enough without any bracing of the compression flange, down it will go.
Also, I'm sure you've seen precast girders being transported on flat beds. Notice how they have camber and are lifted off the flatbed. If those get laid on their side, or turned upside down, they can fold like a playing card. The internal tension from the cables is balanced with the weight of the girder. If you take away that self weight, the tension wins and concrete goes flying.
Yes it is possible. See dayhiker's post above. I don't remember the size but it was pretty darn big.
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