NTSB Extended Animation - The Fern Hollow Bridge Accident
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- Опубликовано: 7 июл 2024
- This animation with video excerpts describes the circumstances surrounding the
collapse of the Fern Hollow Bridge, which occurred about 6:37 a.m. eastern standard
time on January 28, 2022, in Pittsburgh, Allegheny County, Pennsylvania.
The animation begins with a photograph of the collapsed bridge (viewed looking
west from the east abutment) including four passenger vehicles and a port authority
articulated bus, followed by a satellite image showing the location of the bridge
about five miles east of the city center. A higher magnification satellite image shows
the vicinity of the bridge, which ran east and west and carried Forbes Avenue over
the north of the Frick Park. A picture of the bridge (looking east) shows the two lanes
on the bridge in each direction, with text indicating the bridge opened in 1973.
A series of graphics are used to depict the structure of the bridge. A three-
dimensional model of the bridge is shown, and text annotations indicate the main
girders running east and west, the four legs which are connected by cross-bracing,
and the east and west abutments. The design of the bridge called a K frame is
introduced, and the shape of the bridge being like a letter K tipped on its side is
indicated with a graphic.
Another series of graphics illustrate the construction of the legs, with the components
identified with arrows and text labels. Each leg has an I-shaped cross section, with the
main load-carrying outer flanges connected by a central web plate. Each leg also
includes longitudinal and transverse stiffener plates welded to the flanges and the
web plate. The steel legs narrowed from top to bottom, and then tapered to a shoe
that rested on a reinforced concrete thrust block. The change in taper at the top of
the shoe caused the compression forces carried in the flanges to push outward in that
area. The outward push is illustrated by arrows, with narration that the outward push
was resisted by tension in the web and a transverse tie plate at the top of the shoe.
The tie plate was thicker than the other transverse stiffeners in each leg because of its
critical location at the top of the shoe.
The nature of the weathering steel used in the construction is indicated with text
surrounding the image of the three-dimensional bridge model. The text notes that
weathering steel forms a protective surface coating called a patina, and its use
eliminated the need for painting or coating.
What’s amazing is how thoroughly the inspectors did their job and EVERYONE above them did nothing.
Literally the lowest paying job in the chain of responsibility did everything correctly but the higher ups ignored the issues.
The strange thing is politicians seem to feel that if some structure is questionable, they will pore more money into more inspections rather than use that same money for a coating that would slow the corrosion. They seem to feel that more inspections will some how solve the problem when inspections do nothing to actually fix the problem.
@@crissd8283 Management's solution to any problem is just ask for more reporting about it (this is true in every sector and industry)
This is why whistleblower protections are so important. Or even just having a healthy relationship with workers, like in Japan, workers can immediately shut down a production line for any reason. Safety inspectors should have the power to shut down traffic if they deem it unsafe.
@@andrewahern3730 Hate to break it to you, but that "stop work authority" as we call it, exists at nearly all industrial facilities. You are apparently a few decades late.
@@crissd8283 it obviously doesn't apply here, Mr. UmAckshully
That 2017 picture at 4:56 is wild. I'm not a chartered engineer, but when there's that many large fasteners holding two bits of metal together, that's some serious structural load, and one half of that bolted connection is almost completely corroded away at what looks to be the very foot of the bridge. Incredible that that was still considered structurally sound.
The leg looked like that in 2013, and nearly nothing done in 9 years. Wow.
Bus driver reflexes saved lives that day!
Mind boggling that the structural elements were that far gone and no remediation took place...
Yeah, that footage of the bus braking was impressive! 👍
Grady from Practical Engineering channel gave an excellent explanation of what went wrong
And then also explained why the recommendations probably won't really help in the long run. Because they mostly just make more paperwork rather than give individuals close to the inspection the ability to take responsibility for the bridge.
The video says the final report identified "poor quality of inspections", but it doesn't elaborate on why the inspections were faulty. Which is ironic, considering that the inspections are one of the major reasons why we have such clear documentation on the degradation of critical load bearing bridge structures. I wonder if it was the responsibility of inspectors to determine if the bridge had fracture critical components, and if it was also their responsibility to oversee the load calculations which they requested due to the crippled state of the bridge.
I feel like the inspectors are being unfairly judged, since anyone with common sense would look at a giant hole almost a foot in diameter, and say "that's not safe, we should do something about that". In the social media presence, the inspectors did their job very well, documenting the progression of the collapse, and the lack of basic maintenance that led to clogged drains, and the lack of repairs that were requested, and never delivered. The inspectors even pushed for the updated load calculations that, if done correctly, would have shown that the bridge would have only been able to safely hold a single car or two, which would have shut it down permanently. It's because of the yearly inspections that we know that the city literally did nothing to even attempt to repair this bridge for over a decade, when everyone already knew that the bridge structure was compromised back in 2009 when they installed the "temporary" reinforcements. It's unforgivable that such a serious problem could go on for so long without any repairs.
It's exceedingly ironic that the bridge collapsed literally hours before the President was visiting Pittsburg explicitly to promote his infrastructure repair bill, for these exact type of problems. The horrid state of infrastructure in the US is so bad that it's become a national issue. Blaming the inspectors is wrong, since they recommended repairs and the most basic maintenance tasks that were never completed. Had the drains been cleared, and rust resistant coating been applied, the bridge would still be standing. Although arguably, the bridge collapse was a good thing, since no one died, and the timing turned this into a public issue. People don't feel safe when they know the bridges they're driving on could have foot wide holes in critical parts, and the collapse of a similar bridge was on national news.
To me, the failure was in management. The inspections shouldn't be a different department from the maintenance department, with zero ability to force repairs and maintenance to be done in a timely manner. If they inspectors had the ability to force the bridge to either receive repairs, or close down the bridge, then I expect the bridge would have either closed down, or been properly repaired. What we need is more power in the hands of the inspectors to force these types of issues to be resolved properly.
I agree with you that the on-site inspection personnel that collected the data did a good job. I did have a reaction similar to your reaction about the inspectors being considered as the problem.
But I realized that the NTSB isn't actually pointing at the on-site personnel that collected the data. They are faulting the related engineering work that should happen before and after the on-site work. They consider that as part of the inspection.
There is a considerable amount of off site work that is supposed to go into bridge inspections. After the I-35 bridge collapse in Minneapolis in 2007 bridge the NTSB recommended that periodically the initial design of bridges be evaluated as part of the inspection process. Put another way inspections should periodically include a complete re-engineering of each bridge to check for design flaws. Due to this recommendation a couple bridges in the Puget Sound area (greater Seattle area) were closed for upgrades. The initial designs were found to have problems.
From this video it is not clear to me if the NTSB is recommending a higher level of authority for the inspector. Should they have the authority to close a bridge? If yes should that authority be related to immediate failure risk? (Was this bridge at risk of immediate failure ten years ago? It seems like it. But ten years doesn't seem very immediate.) What authority should they have to get things like the storm drains fix? (That is what lead to the corrosion that caused the failure.) Can you imagine how upset drivers would be about a bridge closure due to clogged storm drains. Those inspectors would probably loss their jobs.
'I feel like the inspectors are being unfairly judged, since anyone with common sense would look at a giant hole almost a foot in diameter, and say "that's not safe, we should do something about that"'
Except that they didn't. The inspectors who documented the problems with the bridge described the problems as at worst a Priority 2 rather than P1 or P0, eg a high priority but not actually imminently critical. No, the video doesn't go into details about this but all of it is in the actual NTSB reports. And this is one of the reasons why the report cites the inspections.
Thank you for sharing. Transparency like this is a foundation of good government.
The conversation probably went like this:
Engineer:"The Fern Hollow bridge is in very bad shape."
Boss: "How bad?"
Engineer: "Structural members are failing."
Boss: "How much time do we have?"
Engineer: "To be honest, we're lucky it is still standing. It should have already failed."
Boss: "Yeah, but it is still in use and it seem to be okay."
Boss: "So do we have another year?"
Engineer: "I don't know. But I know I won't use it."
Boss: "This is a bad budget year --we'll deal with this next year."
Engineer: "For the love of all that is good... DO SOMETHING!"
Boss: "With WHAT?"
Boss: "Nobody gets kudos for preventing a disaster, but we get all kinds of help after one."
Boss: "I hear you, and if we had the budget, I'd do something."
(Repeat for 13 years)
There are Federal programs that dole out money to the States and then further divided among the Cities and Counties to repair existing bridges. It is SOLELY the responsibility of the bridge owners (State, County, City) to inspect and request funds for repairs through the well documented funding process. Granted, repair requests are evaluated and ranked by severity/risk ranking. I would be shocked if this bridge did not qualify for repair funds had someone at the City actually made the grant request. This is a failure at the highest political rungs at the State and City officials charged with this structure.
Except that the engineers doing the inspection didn't say that. They never put high enough priorities on the issues.
@@xuthnet what evidence do you have to state that? If you have a copy of the many inspection reports, please provide so we all can benefit from your statement of fact.
@@steveo4749 This is a case where the book is better than the movie. Read the actual NTSB report rather than depending on their short video synopsis. The report is public and on the NTSB website but if I include a URL this comment will be deleted instantly.
Wow they really did a great job inspecting the bridge structure regularly. But nothing was done to act on the inspection results. Way to go!
Imagine all the money saved by not having those drains unclogged! ;-)
The inspectors were the strongest link in the chain of responsibility for the safety, maintenance and upkeep of the bridge yet the NTSB unfairly put the blame on them. No good deed goes unpunished!
Read the actual NTSB report as to why the inspectors were cited as a problem (the report covers lots of things that were not in this short synopsis video and this is one of those). Among the problems was that while they documented many of the issues, they never gave them accurate severity/priority levels.
what is the use of inspecting it every year if nothing suitable is done
This is the first I’ve even heard of NTSB animated videos, and now I want to see more of them.
I think this provides a good service for informative purposes, as it easily disseminates relevant information in a way that is easy for most of us to understand.
A few years ago I found what I consider a major flaw in the engineering work on the City of Santa Fe's water supply. I wrote letters to everyone I could think of. The government did what it does best, ignore the problem and attack the whistleblower.
As a bus driver, this makes me fear every bridge I ever cross.
The officials responsible for ensuring that the bridge was kept in a good, safe, legal condition should be charged with dereliction of duty and endangering public safety.
Someone should have (at least) been fired!
I have said this before several times: if you spread responsibility thinly enough, pretty soon nobody is responsible for anything. There probably wasn't any one person responsible for this debacle. There probably should have been, but there wasn't.
@@jakebrodskypeyou explained it well.
@@OldePeteyeah, and someone should close the barn doors, too, now that the horses are out.
City of Pittsburgh always keeping us safe
yay! another NTSB video!
Apparently, the NTSB needs the same animators as the CSB has.
when it will have thesame sort of results quality (in terms of Analysis and easily readable reports respected by those who read them & showing clear and actionable ways to improve safety) the request might be considered.
@@stanislavkostarnov2157 NTSB reports are dry, very clear and factual. CSB is like watching the History Channel. I keep waiting for the narrator to "Was it aliens?"
If non-engineers looked at those inspection photos and were given the choice, they would have closed the bridge.
They did look at the photos and they did chose.
They chose to not close the bridge and to use taxpayer money on other things
Does anyone know who to contact on a federal level when you come across extreme corrosion on bridges that are being ignored by the city or county?
Crash, because this was avoidable.
Wow , the damaged material looks catastrophic corroded . Traffic HAD TO be stopped there years before the bridge collapsed.
In Germany bridge inspectors would get a heart attack , seing these pre-collaps-damages......
In Germany you could pay a visit to the local Bauhof and show them photos of it, that would lead to them closing the road the next day.
@@Ink_25 , immer noch schneller als in Pittsburgh, aber ich bezweifle sowieso, das die die richtigen Ansprechpartner dafür wären.
BABE WAKE UP NEW NTSB VIDEO DROPPED
Do you watch the Chemical Safety Board ones too? They have great animations! (Sadly the last one was about 11 months ago. - Not sure that I really mean "sadly" there though! 🤔) youtube.com/@USCSB/videos
I was thinking that exact same thing lmao.
Frickin Bridge!
🤔 I wonder how long this bridge was getting ready to fall down until it finally gave way to gravity and collapsed?
I’ve had this happen in my dreams a few times
NTSB covering a structure I used to use daily 🤩
NTSB covering a structure I used to use daily 😱
Pittsburgh mentioned
After that last inspection, they bridge should have been shut down. N.B.: when a bridge across the lower Mississippi showed a fraction of that much damage it was shut down in minutes. Looks like the Southern "Good Old Boys" did a better job of preserving public safety than the workers for the Steel City. (The "Good Old Boy" that drew a salary for inspecting the bridge did screw up.)
Anyone a LOT of folks should have lost their jobs starting with the people that would assigned the jobs of cleaning out the drains.
Penn Dot at its best
This is going to mean no driver is going to ever cross a bridge in the USA from now on. The whole system of checks and balances is apparently garbage.
The additional environmental regulations and restrictions do cause some added costs with working where the bridge was located. That said everyone passing the buck on responsibilities is depressing but not unexpected.
no point in having inspections with this type of management. may as well be having donuts and coffee with the cops. la la la la.
Just like everywhere else in the USA; don't fix it unless it's broke
I work on infastructure and sadly because of the burocracy, it is often cheaper to let it fail. If my group wants to upgrade a failing piece of infastructure proactively, we must spend years getting permits, spend a fortune on environmental studies, have months of public comment (where we pay someone to respond to every comment, study traffic patters and develop alternate routes and mitigation, and if one person protests (which they always do) we have to spend a small fortune on lawyers. However, if we let that infastructure fail, we get instant permits, the environmental review is waved, no public comment period, no traffic studies, sometimes the state or fed will throw money at us, and we start before anyone can sue. The project takes a tenth of the time and a third of the budget. Since most of my stuff is not life safety, we have a few projects with all the plans and parts sitting around just waiting for it to fail. When it does, we'll upgrade, get the exact same product as a preventative upgrade, and save a lot of money. It is sad, but the burocracy incentives us to let stuff fail.
But they collected the taxes through it all, avoided repairs, endangered the public, The legs needed replacement in 2013 and they had the tax base to do that, so WHO was lining thier pockets? WHO was paid off? WHO is going to jail? I could have told you in 2013 the bridge steel was a danger and needed replacing, SO WHO allowed this to happen? Stop this training stuff, it had nothing to do with training, THAT is negligence, CRIMINAL NEGLIGENCE.
i understand how you feel and agree with you, however the NTSB is not a blame-laying organization and has repeatedly stated their job is only to determine the chain of events, the causes, and recommend improvements. That is all they do. That said, these findings could (and imo should) be used in criminal hearings against the responsible parties brought by the proper legal authorities.
Pennsylvania rainy day fund is now over 6 billion dollars, that's up from 300 thousand some time ago. Our state Reb bragged about this in his reelection campaign. Absolutely Disgusting. 6 billion of taxpayers money sitting around and this stuff happens. Our government needs accountability this is unacceptable. They will probably eventually dip into the rainy day funds to cover pensions but we won't hear about that.
Unfortunately, to the best of my knowledge, only an NSTB investigation was done. Generally NTSB reports can't be used for litigation. This is the reason that the DOJ and other law enforcement agencies also investigated the collapse of the Francis Scott Key Bridge in Baltimore. Litigation can be based on the information from the reports from those investigation.
Criminal neglect and misuse of taxpayer money. Not ONE person will be held accountable. You can do inspections yearly, but if NO money is used on repairs, what's the point? Structural steel in advance stages of corrosion and steel cable bracing was the only thing done over MANY years of inspections? They couldn't even be bothered to clean out the drain inlets. I am ashamed of my engineering profession that this occurred.
4:08 why do these documents have a ton of redactions? What is being hidden??
Probably redacting the name of the inspectors
Would've assumed that the legs would've been pre-weathered before installation - that'd've assured integrity of the resulting structure \m/
wake up babe there's a new ntsb investigation animation
Who did the inspections, Helen Keller? The pictures I saw were absolutely awful.
I believe the issue is not the inspectors, but whomever it was who is responsible for bridge safety. In other words, someone reading the reports and responsible to see that remediation is done.
Whether or not the inspection reports were sufficient. It was obvious to engineers and non-engineers alike that the bridge was in serious need of attention. It was ignored and not maintained for years.
@@donmoore7785 Part of the problem is that while the inspectors documented the problems with photos they described and coded them as significantly less critical than they really were. And as is the case in so many other things, the book is better than the movie. This was in the full report but not the video.
If the higher ups had spent little to clean the drains they'd still be able to party away the taxpayer's dollar but no, now they gotta stop and buy a new bridge.
Oh well.
How about a closed profile bridge deck with such strength that it could momentarily hold its own weight without any legs and give it similarly simple closed profile standard legs and make the design a reference for such small spans. With closed profiles there would be fewer cavities for water to linger and with a bit of strength surplus and entire leg could be removed and replaced with relative ease. The deck should be slightly slanted with no opportunities for water to linger. The railing could be mounted on the underside.
Why make each bridge a completely unique design every time with all the overhead that entails. Why all the engineering art details when rust just destroys them. It's not a 2 mile span that strains materials to their limit. Closed profile is plenty good. It's used on our longest bridges in Denmark anyway.
With a simple 'dumb' robust design there should be fewer allergic reactions to maintenance costs. Jennifer Homendy will have a bruised forehead from all the facepalming she has to do at you people :)
The narrator sounds far to calm. He should be much more angry.
Nope. The findings speak for themselves. Analysis is best done objectively.
No, the narrator's job is not to judge. It is to report findings in an unbiased manner.