I think that I have missed something important here.
I have no doubt that the repair work will ensure that that beam never breaks again.
BUT
Did I miss the reason why it broke?
Why is this important?
What about the three remaining identical tie beams?
If we don't know why the first one broke..........
Sorry if I have missed the answer.
Bill
-------------------- Ohm's law
Not just a good idea; It's the LAW!
I think the answer is 'they don't know yet'. They only just removed the fractured piece on Friday, presumably it's gone back to a lab or testing facility for analysis and testing.
"According to him, the fault was not visible from the angle of the snooper truck because it could not go far enough outboard..."
The snooper bucket launches from the bridge deck and then articulates outboard on its way for inspectors to access structure under the deck. The bucket is absolutely outboard of the structure far enough to see the crack, even if there is some distance bridge length-wise.
The crack is very visible viewed from above, and from anywhere outboard. Not visible from directly below or inboard.
Heck, this crack was visible in photos taken by kayakers 100' below.
Something else must explain why it was missed... Repeatedly.
Two comments:
1. I had wondered why the beam had failed and if the failure was isolated to this member or could be more widespread.
I am glad to see that the consulting engineers had the same thought and tested and identified other problems.
2. Does this now look like an error in the original design? Are there any bridges of similar design and construction that should be rigorously inspected?
Bill
-------------------- Ohm's law
Not just a good idea; It's the LAW!
According to the article, it is/was an Aspen-A75. Here's a bit of an excerpt from the article:
Also, this:
Since it sounds like the procedure always had the same start points and number of stops, it seems like you could potentially end up with consistent 'blind spots'.
He said if you took the basket outside of the tie girder to move along the outside, the A-75 was unstable. He also said that he once moved it out there, and one of the tires lifted off the ground.
That’s a great article, Craig. Regarding the “one person” statement, it seems pretty clear that Frazier is a scapegoat. From the article:
To clarify the reasons for Frazier’s firing, The Daily Memphian and Arkansas Nonprofit News Network relayed a series of questions to ArDOT’s public information officer, Dave Parker. In response to a specific question about Frazier’s termination, Parker responded that, “we have verified that Monty Frazier was the only inspector of the tie girder that was cracked between 2016 and 2020.” In a follow-up call on the evening of July 20, ArDOT’s Director, Lori Tudor, emphasized this point: “Monty Frazier was the only inspector who looked at that particular tie girder.”
This contention is contradicted by years of inspection reports provided to The Daily Memphian and ANNN. The ArDOT inspection reports include a description of each structural element of the bridge, identified by number. The tie girders on the DeSoto Bridge correspond to element #107, “Steel Open Girder/Beam.” At least five inspectors are listed as having inspected the bridge during that time. Monty Frazier is only one of them.
Another photo shows the same crack in an image dated Oct. 24, 2014. The photo is from a French tourist, Philipe Suissa, who traveled to Memphis for two days in October 2014, during a road trip from New Orleans to Chicago. “We had a boat trip and I took the photo,” he said in an email to The Daily Memphian. Metadata analysis by The Daily Memphian confirmed the date of Suissa’s photo.
Frazier has been on staff at ArDOT since 2006, but didn’t participate in DeSoto inspections until 2016. DeSoto Bridge inspections have gone through multiple lead bridge inspectors — and dozens of inspectors — since 2014.
It's really difficult to believe none of the inspectors involved over the years raised a big red flag about not being able to do a proper inspection because the truck wasn't suitable for the job or it required too many stops along the bridge to see all of the tie beam.
However, looking at the pictures of the Aspen A-75, I can see why they might have to make stops pretty close together and do a backtrack/skip procedure to inspect all of the tie beam. If you divided the beam into sections A,B,C,D,E,F...., you'd park the truck at B to inspect A and C, then move to C to inspect B and D, then move to F to inspect E and G, etc. That's a bit confusing and time consuming, but doable. A good inspector would figure it out, and write a procedure to get the job done right.
Maybe they should have the inspectors draw a crack on the structure with a big sharpie or paint or whatever and then see if the next crew two years later actually find it.
Just kidding, sort of.
On a serious level, did anyone figure out what was going on on that beam to cause the fracture years ago, and then cause the fracture to deflect that much (a lot) and yet have the remaining part of the beam to NOT fail??
I've seen a lot of fractured steel (in machinery, mostly), but if loads are enough to break it half way through, you would think the remaining bit would fail soon after. Not be still hangin in there years later.
Edit: And man did they go big with the sistering plates!! That is a lot of steel added. CYA is strong here!!
Craig Neth quoted that 16 plate repairs will be required. Maybe each repair is unique and won't require the same amount of plating? Then again, it sounds like the failures are systemic so they'll all require the same repair.
