The Briefing Room
General Category => National/Breaking News => Topic started by: PeteS in CA on May 14, 2021, 06:11:29 pm
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Nearly 800 Barges Stuck In Lower Mississippi River From Bridge Crack
https://www.zerohedge.com/commodities/nearly-800-barges-stuck-lower-mississippi-river-bridge-crack (https://www.zerohedge.com/commodities/nearly-800-barges-stuck-lower-mississippi-river-bridge-crack)
Earlier this week, in a routine bridge inspection, an engineer climbed onto the section of the Interstate 40 bridge over the Mississippi River and spotted a massive fracture in the frame that resulted in the immediate shutdown of the bridge on Wednesday. Traffic is being rerouted to Interstate 55 Memphis & Arkansas Bridge, creating traffic jams in the Memphis area. On the Mississippi River, the situation is much worse. Hundreds of barrages are piling up on either side of the bridge as the US Coast Guard has closed the critical waterway.
After a routine inspection, officials with the Tennessee Department of Transportation (TDOT) announced that the Hernando de Soto Bridge would be closed due to a crack on the bottom side of the bridge truss.
That is a seriously scary fracture!
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A photo of "the crack" reveals that it's MORE than just "a crack":
(https://assets.zerohedge.com/s3fs-public/styles/inline_image_mobile/public/inline-images/2021-05-12_14-02-07.png?itok=iqORnwRN)
Looks like a complete break.
Wondering if it can be patched/gusseted... or if a complete replacement of that beam is required.
If it happened to that particular beam, could others break suddenly as well...?
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Interim repair could speed up reopening of Memphis bridge, officials say
By Nick Valencia, Paul P. Murphy, Amanda Watts and Ray Sanchez, CNN 5/14/2021
https://www.cnn.com/2021/05/14/us/memphis-crack-hernando-de-soto-bridge-friday/index.html (https://www.cnn.com/2021/05/14/us/memphis-crack-hernando-de-soto-bridge-friday/index.html)
A design team is looking at an interim repair for the crack on the Interstate 40 bridge in Memphis until a new part can be made to replace the bridge's damaged section, the Tennessee Department of Transportation said Friday.
The team is working on a design concept that could use steel rods that would "span over the fractured section, and provide the needed strength to reopen the bridge to vehicular traffic," TDOT said in a release.
An initial analysis of the bridge found it to be "stable," and an independent firm was to take a second look on Friday, Tennessee's Chief Engineer Paul Degges said earlier. Officials had said emergency repairs could take months and lead to delays in a major US shipping corridor.
The design team is also looking into whether a steel plate could "beef up the fractured section and thus increase our factor of safety for the existing configuration," TDOT said.
"The interim repair would allow time for a new bridge component to be fabricated to replace the bridge's damaged 37' long section," the release said.
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A photo of "the crack" reveals that it's MORE than just "a crack":
(https://assets.zerohedge.com/s3fs-public/styles/inline_image_mobile/public/inline-images/2021-05-12_14-02-07.png?itok=iqORnwRN)
Looks like a complete break.
Wondering if it can be patched/gusseted... or if a complete replacement of that beam is required.
If it happened to that particular beam, could others break suddenly as well...?
Notice the top of the beam? Looks like it was cut, then the rest looks like a normal fracture. :shrug:
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A photo of "the crack" reveals that it's MORE than just "a crack":
(https://assets.zerohedge.com/s3fs-public/styles/inline_image_mobile/public/inline-images/2021-05-12_14-02-07.png?itok=iqORnwRN)
Looks like a complete break.
Wondering if it can be patched/gusseted... or if a complete replacement of that beam is required.
If it happened to that particular beam, could others break suddenly as well...?
That? With the corrosion?
Remove and replace the entire section. Appears to be a fatigue failure, so additional gusseting and doubling on the top and bottom would be advisable.
Should take less than a week.
But.
The entire bridge needs to be inspected most carefully now.
And example of why high margins of safety are required and why designs seek out and avoid single-point failure conditions.
Also why we can't afford to spend infrastructure money on Knee Grows and Invaders.
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Notice the top of the beam? Looks like it was cut, then the rest looks like a normal fracture. :shrug:
No.
The loading on that beam is primarily tension from axial loading, and upwards bending, meaning the beam curves up under load (I mean like a smile, or a "u"). It is a bridge, that's what they do.
So what certainly happened is that a flaw on the bottom-most fibers occurred. This would be a micro-crack. Could even have been an in-spec manufacturer's flaw. Then the cycles on the bridged expand and contract on the flaw, and the crack grows over time.
The bridge is decades old, and every car and truck, every single one, will cause that beam to flex, just like every other beam on the bridge.
And so the crack grows, following the weakest path through the grain of the metal, as can be seen zig-zagging up from the bottom. The remaining intact section has to carry the full load on the beam and the stress rises. Past a certain point, there is no longer enough section to carry the total stress and it just unzippers.
And that's what you see. About 3/4 up from the bottom, the crack stops zigging and just goes straight to the top.
A classic fatigue failure from the looks of it. Can't know for certain until the beam is cut and we can inspect the surfaces.
But I spent four years performing fatigue tests on helicopter rotors and that there is a fatigue crack.
Thing thing that should be not that the bridge was cracked. That is going to happen, it's what metal, even iron, does, and it's a fact of life. This is why bridges are inspected.
But look at the rust. How long has the beam been open to the weather? It's apparently evenly rusted, top and bottom.
When was it last inspected and, since we can determine the age of the crack, if it was missed earlier, why and what needs to be done in the future?
First thing that needs doing is to have Congress define "infrastructure" as "bridges, roads, pipelines, power grids, water distribution, and other MATERIAL articles of public use". "Knee Grows" are not infrastructure.
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And since that crack has been there for months, and the bridge hasn't dropped into the river yet, the closure of the road on the bridge should pretty much reduce the risk of collapse, at least in decent weather.
There should be a wind/current restriction on passing under the bridge, but there's no reason why cautious river traffic should not be resumed.
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Wondering if it can be patched/gusseted... or if a complete replacement of that beam is required.
(https://www.interplas.com/product_images/duct-tape/3in-x-60yds-9-mil-silver-economy-duct-tape-1000px.jpg)
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Wondering if it can be patched/gusseted... or if a complete replacement of that beam is required.
If it happened to that particular beam, could others break suddenly as well...?
Meh, fish-plate it back and front, inspect the rest, and away you go... When the replacement section shows up, install it.
This is much ado about nothing.
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(https://www.interplas.com/product_images/duct-tape/3in-x-60yds-9-mil-silver-economy-duct-tape-1000px.jpg)
For really tough jobs like this you need
(https://i.imgur.com/W5gJJ60.jpg?1)
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(https://i.pinimg.com/originals/fa/f6/3a/faf63a70277454263bdaa21e4bfca136.jpg)
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For really tough jobs like this you need
As Red Green always said "Spare the duct tape. Spoil the job!"
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A photo of "the crack" reveals that it's MORE than just "a crack":
(https://assets.zerohedge.com/s3fs-public/styles/inline_image_mobile/public/inline-images/2021-05-12_14-02-07.png?itok=iqORnwRN)
Looks like a complete break.
Wondering if it can be patched/gusseted... or if a complete replacement of that beam is required.
If it happened to that particular beam, could others break suddenly as well...?
How did the crack get to be that bad before being noticed?
Who inspects this bridge? Tennessee or Arkansas?
How often does the bridge get inspected?
Just for comparison,
Ohio inspects every bridge once a year.
I have a hard time believing that this crack
was too small to be noticed a year ago.
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How did the crack get to be that bad before being noticed?
Who inspects this bridge? Tennessee or Arkansas?
How often does the bridge get inspected?
Just for comparison,
Ohio inspects every bridge once a year.
I have a hard time believing that this crack
was too small to be noticed a year ago.
https://www.cnn.com/2021/05/14/us/memphis-crack-hernando-de-soto-bridge-friday/index.html (https://www.cnn.com/2021/05/14/us/memphis-crack-hernando-de-soto-bridge-friday/index.html)
In investigating the fracture, the Arkansas' transportation department said that a review of 2019 footage from a drone showed "evidence of damage in the same area. Not another section," according to ArDOT spokesman Dave Parker. However, at this time, the ArDOT can't conclusively say that the damage seen in the footage is the beginning of the current fracture.
"We are now investigating to see if the damage was noted in previous reports and what actions were taken," ArDOT said in a tweet.