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The Ordinary Engineering Behind the Horrifying Florida Bridge Collapse (wired.com)
An anonymous reader quotes a report from WIRED: The people of Sweetwater, Florida were supposed to wait until early 2019 for the Florida International University-Sweetwater University City Bridge to open. Instead, they will wait about that long for an official assessment from the National Transportation Safety Board of why it collapsed just five days after its installation, killing at least six people. In the immediate aftermath of the disaster, many queries have centered on the unconventional technique used to build the bridge, something called Accelerated Bridge Construction, or ABC. But ABC is more complicated than its acronym suggests -- and it's hardly brand new. ABC refers to dozens of construction methods, but at its core, it's about drastically reducing on-site construction time. Mostly, that relies on pre-fabricating things like concrete decks, abutments, walls, barriers, and concrete topped steel girders, and hauling them to the work site. There, cranes or specialized vehicles known as Self-Propelled Modular Transporter install them. A video posted online by Florida International University, which helped fund the bridge connects to its campus, showed an SPMT lifting and then lowering the span into place.
In a now-deleted press release, the university called the "largest pedestrian bridge moved via SPMT in U.S. history," but that doesn't seem to mean much, engineering-wise. SPMTs have been around since the 1970s, and have moved much heavier loads. In 2017, workers used a 600-axle SPMT to salvage the 17,000 ton ferry that sank off the coast of South Korea in 2014. The ABC technique is much more expensive than building things in place, but cities and places like FIU like it for a specific reason: Because most of the work happens far away, traffic goes mostly unperturbed. When years- or months-long construction projects can have serious effects on businesses and homes, governments might make up the money in the long run. Workers installed this collapsed span in just a few hours. These accelerated techniques are also much safer for workers, who do most their work well away from active roads. The report goes on to note that the bridge collapse is still under investigation and the search for a culprit is ongoing. "The answers could run the gamut, from design flaws to fabrication flubs to installation issues," reports WIRED. As of publication, The Washington Post is reporting that an engineer called the state to report cracking two days before its collapse.
In a now-deleted press release, the university called the "largest pedestrian bridge moved via SPMT in U.S. history," but that doesn't seem to mean much, engineering-wise. SPMTs have been around since the 1970s, and have moved much heavier loads. In 2017, workers used a 600-axle SPMT to salvage the 17,000 ton ferry that sank off the coast of South Korea in 2014. The ABC technique is much more expensive than building things in place, but cities and places like FIU like it for a specific reason: Because most of the work happens far away, traffic goes mostly unperturbed. When years- or months-long construction projects can have serious effects on businesses and homes, governments might make up the money in the long run. Workers installed this collapsed span in just a few hours. These accelerated techniques are also much safer for workers, who do most their work well away from active roads. The report goes on to note that the bridge collapse is still under investigation and the search for a culprit is ongoing. "The answers could run the gamut, from design flaws to fabrication flubs to installation issues," reports WIRED. As of publication, The Washington Post is reporting that an engineer called the state to report cracking two days before its collapse.
Seems only fair, he wants to claim credit for the stock market rising. Never mind that it has risen steadily for the eight preceding years.
If he can take credit for that, I think he deserves credit for everything else that happens.
It's called Cuban construction.
Like every engineering disaster, somebody found the problem, and failed to communicate its severity. In this case, they decided it wasn't a safety issue (cracks in a brand new bridge!) and left a voice mail with somebody else who was out of the office for a few days.
There's no substitute for risk assessments by fully qualified engineers, of course. But those engineers also need communication skills â" including persuasive skills. Engineers who can find somebody in authority and convince them to take action save lives.
The engineering drawings I have seen show a tall tower with suspension supports coming down to support the span. Was the tower complete and the suspension in place when it broke or was that for completion later? Also the suspension when to both sides of the tower so it was balanced. Are there any pictures of the bridge while it was "good" to compare with the engineering drawing?
See here for a 3d view of the design. As far as I could tell the tower, the section over the water and the suspension lines were not in place when it collapsed.
https://youtu.be/Q2A1wS09p0k?t=5
To start, it was a truss bridge, self-supported. The stays shown in final drawings are pipes for stiffening and harmonics in high winds.
The structure was non-redundant. A failure of any truss was near guaranteed to lead to collapse. It's theorized by some that truss member #11 at the junction of the pier was initial failure point.
In preliminary drawings, #11 is shown with no post-tensioning bars, but the actual construction shows it with two. While those bars in #11 may have been necessary due to the move, since the ends of the bridge were cantilevered (which is different than shown in the preliminary drawings), they likely weren't needed after placement; not needed to be post-tensioned, since #11 would be in high compression.
It appears workers were post-tensioning #11 using a crane and other equipment attached to one of the post-tension rods. It appears tensioner (blue) and part of the bar is sticking out several feet in photos of the collapse. According to some, this likely lead to the collapse.
were the building materials fake? fake concrete, fake steel? someone should audit who built it and who their suppliers were
The ABC technique is much more expensive than building things in place, but cities and places like FIU like it for a specific reason: Because most of the work happens far away, traffic goes mostly unperturbed.
Nope!! That span was assembled right next to the road where it was placed. I drive by it every day and I can assure you, even though it wasn't on the road, it disrupted traffic due to rubbernecking for over a year.
Seemingly, it was designed as a cable-stayed bridge. This means the deck's main support is a central pylon and the cables attached to it. Except they only built one half of the bridge and no pylon. It was supported by literally nothing.
Circumcision is child abuse.
Am I supposed to know what an SPTM is??? (As it seems to be too much trouble to explain the initialism before throwing it at us over and over again...)
First it goes on a paragraph of rambling about accelerated bridge construction, then it sidetracks into some irrelevant korean ship, and all while there is no indication the accelerated bridge construction had anything to do with what happened.
It will be interesting as one of the prime's MCM, has had issues in the past. MCM gives generously to Christie and Rubio.
In my town we have a footbridge that was installed this way, several years ago. It was factory-built in Phoenix, hauled 100 miles up I-17 using one of the smaller roadable version of the SPMT, and installed overnight to cross a creek. There hasn't been a problem since.
Offsite construction should be safer than site-built, so in this disaster let's focus on the design itself, rather than rushing to judgement on the offsite construction.
Don't you people know the truth? A single line of army ants marching across a bridge in step can cause it to collapse!
Scientifically proven beyond a shadow of a doubt.
End sarcasm. Just in case you thought I was being serious.
Here is a story of another seemingly similar bridge. Tower with stays pedestrian bridge. The deck was originally planned to be concrete but design revisions changed it to steel. Would be interesting to look into that decision.
http://johnsankey.ca/path2014.html
From the 13 April link in above: http://www.davidmckie.com/airport-parkway-bridge-undergoes-new-design-after-pricey-deficiencies/
"Delcan reviewed the partially completed structure and found that there were many deficiencies, including cracks in the concrete tower and in the bridge deck-these are obvious safety concerns."
If you still think America is Number One...
I have a bridge in Florida to sell you.
Those who do not learn from commit history are doomed to regress it.
https://youtu.be/KtiTm2dKLgU Seems there was a construction flaw , sounds likely!
engineering-wise. SPMTs have been around since the 1970s, and have moved much heavier loads
Depends what you call a SPTM. Bridges have been prefabricated and moved into place since pre-historic times, starting with carved tree trunks. It does not matter how the bridge gets put there, what matters is its strength and that of its supports. Here is a much more ambitious construction, overseen by Robert Stephenson and Brunel no less, over dangerous water too, 150 years ago :- Britannia Bridge, Menai Strait
The complexity and risk of the intermediate stages of a project are the most impressive things to me about civil engineering. It's one thing to design a dam, it's another to build that dam in the middle of an actual river; you need a dam to build a dam. It's one thing to draw a bridge that's perfectly stable once built, it's another to ensure the partially completed structure is in perfect equilibrium at every point from the time the moment the ground is cleared until the last cable is tightened.
If you think about what ABC involves, it really ought to make bridge construction safer, but I think in this case people simply put too much faith in it. Any time you put something heavy over someone's head, you're taking a terrible risk. For a completed bridge, engineering reduces that risk to negligible, but if you're going to be building that bridge while people pass under it every intermediate step has to be as safe as the completed structure. I wonder if that's even possible.
Post may contain irony: discontinue use if experiencing mood swings, nausea or elevated blood pressure.
This video goes into some detail analysing from available information : https://www.youtube.com/watch?v=KtiTm2dKLgU
Seriously, in Montreal, the new "turcot interchange" is being build using prefab units. The only things that aren't prefab, are the support pillars. Which are a bit too thin for comfort, IMO, but apparently those are harder than the massive pillars of the old exchange...
We already have at least one lane that was opened and so far it's holding up.
Lets hope we do better with the rebuilt spillway on the Oroville dam.
next time.
They slide this 950 ton slab onto the pilings and congratulated themselves. Great job of building a suspension bridge without you know the suspension part that holds it up.
Only the State obtains its revenue by coercion. - Murray Rothbard
the 7ongest or not so bad. To the
Is there any huge advantage to making something out of concrete/rebar when it's designed to handle only foot traffic? I thought concrete was mainly used when you need a large bulky structure to take huge compression loads that would normally make steel too expensive by comparison.
They were tightening the cables that run through the structure - it's called post tension concrete - Concrete is strong in compression but weak in tension, so the idea is to preload the structure with large cables under tension - which squeezes the concrete.
This is extremely common with slab on grade houses these days.
If you consider a beam supported between two supports, there's a bending moment - the top is in compression, the bottom is in tension. If you externally apply a force to squeeze the ends together then you can make it so that the bottom is in compression and the top is in even more compression, both of which are easily handled by the concrete.
In this bridge that is done by cranking cables through the bridge. In something like, say, the Roman Arch, it's done by having massive side supports. In Gothic cathedrals, it's flying buttresses.
This isn't exactly new engineering - although the details change over time.
Concrete is cheap and easy to make withstand things like hurricane winds.
Other alternatives are steel beam truss (very expensive for the span)
or some sort of suspension bridge (requires a strong vertical support and often more room for the backstays on the support) - Calatrava's bridge in Chico, CA, or the Golden Gate.
The possible explanation to the failure (over tightening of one or more post tension rods) as detailed in this AvE video, seem to make sense. https://www.youtube.com/watch?...
As a long time player of Bridge Constructor (including stunt version) with over 50% of the achievements I can say with great authority that the bridge should never have been left for too long without the cables. I bet the final investigation turns up someone cutting corners and pocketing money from construction material savings.....
Now imagine what would happen if enough people say "Fuck this, I am not voting for any shitty candidate."
What happens it you get Trump or someone similarly repugnant in the White House with a fraction of the people voting. Someone is going to win and some people are always going to vote. If you don't vote then you are just letting someone else vote for you and you might not like what they decide.
Maybe the "innovation" was a side product of "realizing" some things can be built in reverse: that bridges don't actually need support structures. "Real engineering" must work inside boring tolerances, sequential construction and safety measures. This is the way software maintenance works today: thanks to the internet we can patch stuff in real time.
Have gnu, will travel.
The Reason Foundation has published an article about the bridge was funded by a federal program that has come under repeated fire for awarding money based on politics rather than merit:
Collapsed FIU Bridge Was Funded by Federal Grant Program Criticized for Shoddy, Politicized Review Process - The TIGER grant program has come under fire for putting politics ahead of technical concerns.
AvE over on youtube did a very good commentary on how and why the bridge collapsed. Video 1 (overview): https://www.youtube.com/watch?... Video 2 (technically in depth): https://www.youtube.com/watch?...
Perhaps "fabrication flubs" is not the correct way to describe something that killed people? Crushed and rent limb from limb you say? Bit of a flub, that, eh?
If 6 people died while we were inventing a new technique that improves construction for a decade, it's a sad growing pain. If 6 people died because of a fuckup in traditional design, it's horrific.
Your ad here. Ask me how!
In my opinion, it was wrong to keep the road open until the 1000 tons bridge was fully functional and well tested.
But they could not close the road because there are basically no other modes of transportation. No bicycle routes worth mentioning, no pedestrian alleys, no trams.
Close the road for two days and the town collapses.
The Florida attorney general needs subpoena all communications and records whether electronic, paper, phone logs, digital, etc from anyone who touched this project including the lunch truck for the construction workers (selling a morning pot hit on the side?) . I fear a mass paper shredding and disk hammering party even as we speak. Unfortunately there is not much that can be done with the mass amnesia that is common in instances of this kind.
It may look like one to you, but if you were able to read any of the reporting, you could have learned that it actually was a truss bridge. But that would require a) comprehension skills and b) you passing up an opportunity to be a cunt, which would be something of a break from tradition.
1) the original Bridge design was safe, having been created by an actual engineer, not a DIVERSITY HIRE as used as 'lead' engineers by all the sub-contracting companies who actually build and deployed the PARTIAL bridge.
2) the key aspect of the original design is the cable system that is 95% intended to prevent the concrete spans from SAGGING and thus going into tension (a catastrophic disaster for reinforced concrete spans).
3) the cables do not hold the entire weight of the span, but this does not mean the anti-sagging force they exert is not essential. Without cables, a concrete span must be built on a partial ARCH design to provide the counter force.
4) the diversity hire lead engineer (hispanic woman) had no fundamental idea about the principles involved. She simply ramped up the cable tension values on the CAD program used to model the concrete span until the computer program seemed to imply the concrete span could support its own weight (impossible in the circumstances).
5) this was made worse by the fundamental misunderstanding that the cables existed only to prevent vibrations and swaying in the concrete spans.
6) criminal forces exploited this fundamental misunderstanding about the role of the cables to game the approval system to allow the ABC method of assembly to proceed in the cheapest and most convenient way possible.
Reinforced concrete cannot be self supporting (without devices like an arch). Let me give you an analogy...
You have a washing line, that appears 'level'. But when you put washing on it, it sags annoyingly. A diversity hire 'engineer' will simply say "no probs, just tighten the line. And to prove this is so,will go to their CAD program and push the slider to max tension, not understanding that the simulation is physically incorrect beyond certain parameter limits. In reality the washing line will break (as you increase its tension) before the washing is pulled up into a level position.
So in this accident the span started to SAG, as it had to. And as it sagged, the concrete went from compression to tension, causing multiple points of gradual failure. In panic, the diversity hires attempted to increase the tension of the cables 'reinforcing' the concrete- at some point this simply causes disasterous buckling as you overcome the natural strength of the materials involved.
For ever, properly trained engineers knew that (significant) concrete spans can't support their own weight without sagging, and that sagging must cause failure. So you use arches, cables, or regular 'props' (columns beneath the span at correct distances). But diversity hire 'engineers' lack the brains to comprehend the principles or even respect the 'rules of thumb'. Instead all they 'know' they learn from playing with the computer CAD and simulation packages. These simulations are notoriously only correct under very limited parameter and design situations (and sometimes not even then).
The computer tools were designed to ASSIST skilled engineers, not replace the the awareness of physics held by said engineers.
The IDIOCRACY is now very real- but the idiocracy is self-supporting so statements like mine will be trashed, and you will be told it was only "white pivilege lies" that ever suggested reinforced concrete spans could not be self supporting.
Thats the phrase in gov circles to ensure job survival +/- pleasantly.
Cannot imagine that if the engineer raised a stink for each crack, that he'd do well on his yearly perf reviews. Sadly, that's not how the world works.
Lookit both shuttle crashes.
Were they sure EVERYONE working on the project knew it was a truss bridge?
Laws are rules for the court, but merely a bottom bar to hit for life. Think beyond laws in your actions always.
A reinforced concrete span (reinforced concrete is 'stone' sythetically placed under compression by steel cables running with the concrete, usually embedded- material science 101) cannot support its own weight without disasterous sagging beyond a certain point.
Despite the lies repeated here again and again, the cable system (cables above the span connected to a tower) were essential in this case to prevent the very long span from sagging.
The moment the span started to sag under its own weight, it was lost. An abuse of a computer simulation package allowed a very incompetent lead engineer to believe all she had to do was increase the tension of the reinforced concrete cables to compensate. But taking the reinforced concrete cables beyond safe limits simply increased buckling forces to disaster.
For ever concrete spans have been supported from above, propped up from below (regular columns) or given weight supporting arch designs. Them came the idiocracy, and diversity hires playing with CAD/simulation packages with no understanding. Ramp up the onscreen reinforced concrete tension cable values and lookie- it was all a white male conspiracy to keep unsupported concrete spans short. The computer doesn't lie, after all.
A child of three could explain why the cables were essential on this bridge, and would have no interest in the gamed papers written by diversity hires saying otherwise. The cables were designed to prevent the span sagging (which is not the same as taking its entire weight- when the span doesn't sag, the concrete under compression continues to safely bare to majority of the load).
There are videos showing propagandists associated with this disaster decry RIGOUR in engineering as a "white privilege tactic to keep minorities out of the field" - for real. Even though the original design was correct (if the anti-sag cables had been attached before the supports beneath the span had been removed), the building of the bridge was 100% a SJW project.
Anyway the public blame will be placed on "imperfect manufacturing", as if the laws of physics could have been confounded if only the span had been built "better". But behind the scenes the truth will be accepted, and such bridges in the future will always have the anti-sag cables applied first. And you will still be told those cables are "decorative" or for "vibration supression" only for you are the idiots that make the idiocracy possible in the first place.
or build the bridge. Instead, only woman or minority owned business were picked from. The president of FIU even bragged about that during the ground breaking ceremony. I bet he already regrets saying that.
https://youtu.be/KtiTm2dKLgU
In GOD we trust, all others we monitor.
Was potential harmonic stress from seismic vibration induced by road traffic adequately accounted for?
A diversity hire 'engineer' sat infront of the CAD/simulation package, forcing the reinforced concrete cables to higher and higher tension until she convinved herself such an insanely long span could be self-supporting. She was unaware that the simulation simply throws up dreadully incorrect results in all edge cases- expecting the user to understand fundamental rule-of-thumb and sanity limitations themselves.
To PROVE the quality of diversity hires, standard operating procedures were binned on the basis of her 'evidence'.
She didn't design the bridge- the original design was fine- but the cables were essential to prevent the span from sagging under its own weight. Somehow the FAKE NEWS lie that the cables were 'cosmetic' or for 'vibration' protection only spread- probably for the simple commercial reason that ABC had become the political nonsense of the day for new bridge builds- to be hyped at any cost.
ABC works, but only when the engineering is correct. Indeed it needs MORE correct engineering than older construction methods. With ABC it is essential you do your homework and have all your ducks in a row.
In this case, ABC was used as the excuse to forego the cable support system in the first phase (yes the cables DO support weight- being the anti-sag system that is essential to allow such a long span).
Many have pointed out that the span could have had a temp column supporting the middle and still allowed traffic flow. The arrogance that eliminated even this cheap simple sane precaution was all down to the SJW need to TRUST the calculations of the lead diversity hire 'engineer'- to prove the faith in her 'competence'.
When the span started to fail, as it sagged under its own weight, the 'genius' engineer felt that increasing the tension on the reinforced concrete cables would 'fix' the problem. After all, it worked on the computer. And thus the span was made to undergo catastrophic buckling forces.
The idiocracy is dribblers here saying they've read papers saying insanely long concrete spans can be self-supporting, so obviously only racist white engineers claim the laws of physics still apply. And the fact such an unsupported span collapsed proves NOTHING- for facts are racist, don't you know. And that even if the finished plan had support cables, the cables were not for support cos some piece of paper, written by a diversity hire, says so.
Of course the people murdered by this atrocity were diverse too, but that never matters to the SJW types.
Anyone who went to uni knows that most students on an engineering, maths or computer course are scary bad, regardless of their background. Now imagine some of those no-hopers end up in powerful positions simply cos of their skin colour or gender. Diversity hires where the fundamental lack of ability is not an issue. So long as the diversity hire can be well dressed and present a good impression in a brochure- well that's all that is needed to sell them to the unwashed masses as 'experts'.
To argue with morons in this forum as to why extremely long concrete spans need a seperate mechanism (arches, columns, above support cables) to act against the sag is depressing and sickening. The building 'accidents' in the USA are going to reach third-world proportions.
One of my favorite youtube personalities has a couple interesting things to say about this, and presents a well reasoned conclusion....
https://www.youtube.com/watch?...
and
https://www.youtube.com/watch?...
I don't know many details about this canadian fellow but he's he's no idiot and funny af.
enjoy...
chris watts íë¦ìS ì(TM)ì
In other words, the blood is still wet on the pavement, but we're already hard at work on the most important issue: figuring out how to blame eveything on the political party we don't like.
...it needed a woman's touch.
https://squawker.org/culture-wars/a-female-led-construction-company-built-the-florida-bridge-that-collapsed/
We have imported all kinds of cheap, no quality stuff from China
Someone must have save a buck by buying this cheap, pre-cracked bridge from China, too !
The bridge was put in to active service before it was even complete. The required suspension system was literally not even there. Oh know, great scam! Even a toddler would have recognized this problem. There are too many idiots in this world.
This is what happens when today's "engineers" design with form-before-function approach.
Putin made bridge to collapse and kill fellow americans
In Ontario, there was a case of a rather large pre-fabricated bridge having part of it installed upside-down.
https://www.thestar.com/news/gta/2016/12/16/pickering-pedestrian-bridge-contractor-strikes-back-against-auditor-generals-report.html
Simply put, if the installed span was inverted, the stresses would easily destroy the integrity of the bridge, and it would fail. Likely, in a spectacular way.
Not specifically saying that was indeed the case, but it wouldn't be a first, if it was the problem.
Either way, the failure should be squarely on the contractor, and not the buyer. After all, they paid for a functional and sound product, and that is what is supposed to be delivered. Any fallout and subsequent cleanup, should be covered by the contractor at their expense. If they were cutting corners, or underestimated the costs, too bad for them. The buyer shouldn't have to suffer and pay out extra.
It's a crying shame that governmental contract work never follows that simple procedure, though. Cost overruns are rampant, and it's always the taxpayer that ends up on the hook for it.
You ASSUME that the cause could be the worst possible factor until you know for sure, especially when public safety is concerned!
It's really not that complicated. Even if it holds up the project by a day or a week, or a year, of might result in your boss getting fired, you're basically NEVER wrong to err on the side of safety if any reasonable suspicion of actual risk exists.
But...
That bridge looked absurdly over-engineered to me.
Why is a pedestrian bridge made out of tons and tons of concrete? Wouldn't a suspension bridge of steel wire and wood planking have worked. It would have been much light and not crushed cars should it have failed.
If 6 people died, it's horrific.
https://imgur.com/qsj8RbB
If the culprit it white, he/she will rot for life in jail.
If not, the authorities will find an excuse to blame a white somewhere.
Are we now going to hear from the gun-control crowd that we need more "bridge control" ?
Just because you found it on the internet doesn’t mean it’s real.
Reason is usually pretty even-handed in placing blame on both Republicans and Democrats. They've also been known to blame private companies as well. There is probably plenty to go around in this instance.
It was a federal grant for improving transportation. It would have only improved pedestrian transportation for students at a single university. Hardly an appropriate use of federal funds... In addition, it was a massively over-expensive artistic bridge instead of a simple, practical one. But hey, I guess you need a gateway to the expensive luxury apartments for those broke college students saddled with unsustainable debt right?
http://myinvestmentbrokers.com...
Yes it's an anecdote! Were you expecting original research in a Slashdot comment?