FIU had grand plans for 'signature' bridge. But the design had a key mistake
miamiherald.com
miamiherald.com
I've always found it useful to hone in on anything that is done purely for aesthetic reasons.
We build a house recently. I really wanted exposed rafters, there was some complexity around insulation, and the architect responded by proposing some "faux" rafters. The idea was so revolting that it prompted more examination, which identified some mistakes. In the end, a simpler, better, cheaper solution was found that did not have faux elements in it.
I have a similar design philosophy that honesty is more aesthetically pleasing than deception.
When designers resort to faux materials and structures, the truth still tends to peek through, resulting in an 'uncanny valley' of forms. For example: * Brickwork veneers bend in the wrong spots * Faux beams are placed in the wrong locations with the wrong joints, announcing that they can't bear a load
There's certainly a place for decorative elements, just not decorative elements pretending to be something else.
I spent several summers framing houses, so I'm looking forward to an opportunity to design my own house - and maybe 3D printing it.
EDIT: Added examples of fake garage door handles and hinges. I'm seeing that a lot more and don't understand the point.
Isn't this the core principle of Brutalism? As they say, beauty is in the eye of the beholder.
I'm not an expert, but it seems that Brutalism requires one to reduce all forms to their mechanical function. I think there are plenty of other good reasons to include a form, e.g. Corinthian columns are modeled after acanthus leaves, and I think that's just great. The form is telling a story about our connection with nature, and nobody is pretending that the column is actually an acanthus.
https://www.youtube.com/watch?v=MtxA20Q-Uss&feature=youtu.be...
'If something is 100% functional, it's always beautiful'
https://makezine.com/2015/03/20/18-lessons-smart-prototyping...
Fascinating guy:
https://spie.org/membership/spie-professional-magazine/spie-...
It bugs me that FIGG (one of the contractors) appears to be threatening the professional licenses of the engineers who helped the Miami Herald's investigation, by suggesting that doing so was unethical.
As a licensed Professional Engineer, you have to be quite careful criticizing other engineers. As long as the engineer signing off met "standard practices", he is covered and saying that he is not could get you in quite hot water.
In addition, while it is certainly possible that the engineer screwed up, it is also not impossible that the concrete may have been substandard, installation instructions may not have been followed, etc.
For example, in the Citibank Tower, the design was incorrect for quartering winds. However, Bethlehem Steel, the steel supplier, suggested cheaper bolted connections which made the problem worse.
http://www.engineersjournal.ie/2015/12/08/citicorp-centre-to...
Engineering failures are often a chain. That's why the NTSB has to be allowed to do its work.
As long as both the critic and the criticized are supporting their arguments with reasons and engaged in dialogue, the outcome should be net good for everyone.
On the other, criticising a collegue for a mistake that is only obvious in retrospect is also poor sportsmanship.
2. "After you've dropped a bridge...": Until the investigation is complete, no one has any business assigning responsibility. (In fact, the investigation probably won't assign responsibility; that will be the job of the court system in the subsequent lawsuits.)
http://to70.com/why-aviation-safety-experts-dont-talk-about-...
Criticism, behind closed doors or strictly in the company of other engineers with the correct training and experience, is not dangerous.
Criticism shared with non-engineers amounts to second-guessing and degrades the trust of the public in the profession as a whole, which has tangible negative outcomes for everyone.
Imagine if every project you'd been on had another developer bending the ear of management saying "oh, that's the wrong editor...oh, that's not the right algorithm to use..."! It'd be awful.
For mechanical and structural engineering, both much more difficult and unknowable than software, it is of the utmost importance not to foment doubt and uncertainty in people who are by definition unqualified to properly understand the criticisms and weight them.
It works precisely until there is a scandal too big to cover-up.
Why do you think otherwise?
Also makes it ever so easy to bury the negligence and mistakes. Leaving the public devoid of trust and potentially with some very tangible negative outcomes. For instance:
"Yes your condition should have been identified, it's clear from the first X-rays in your history. No it's too late to do anything about it now, you just have to live with it. Put that in writing? I couldn't possibly do that."
Repeat several times.
Applicable to many of the professions in varying degree.
The Citibank tower continues to sway and creak, more noticeably than most comparable buildings, in a strong wind.
I would be very interested in any law or regulation you can find that says otherwise.
I would also add that most of the involvement of engineers during lawsuits is to establish exactly what state of practice is in the local area. It would be hard to do that if all these other engineers didn't have or couldn't give an opinion.
It's also not so much a matter of law as it is professionalism.
Being an expert witness is completely different than being an engineer talking to the public. Generally speaking an engineer close to the details of the project is going to know more than you. If you have concerns, you call up the engineer and you have a discussion. If he's dismissive you still have the choice to escalate the matter, but it's usually to someone in the government, not the public at large. Engineers need to be trusted by the public and shooting your mouth off about another engineer degrades public trust.
I am disagreeing with the statement that you could get in "quite hot water" by noting that the only liability you are exposing yourself to by stating your opinion is looking stupid. Yours and my opinions on public trust and how someone should conduct themselves is orthogonal to the question.
An engineer in a lawsuit as an expert witness is a VERY different beast from making public statements about an engineering failure.
Much of the way this is being played out in the press is that the statements by the outside engineers are implying that the engineering firm didn't due sufficient analysis.
That's a statement that they do NOT have the facts to support and falls under "libel". Under a "libel" charge, the defendant has to prove that the statements made are true rather than the plaintiff showing that they are false.
In addition, it's quite easy to take a known failure point and then backfill the analysis to find the mistake. The more interesting question would be to take the design and give it to a firm that doesn't know about the failure and see if they can find the flaw in the analysis.
FIU built a fake one that was more expensive than a real one.
[1] https://en.wikipedia.org/wiki/Don_Burnett_Bicycle-Pedestrian...
https://twitter.com/EdwardTufte/status/1007395311541682176
> A+ This is beautifully executed technical report by the Miami Herald, an instant classic of news reporting. Note that this report is a document not a deck. The FIU admistration loaded the bridge design down with features.
They are structured to put critical information up front, so that a reader can stop whenever they lose interest without missing anything more important than what they already read, but include additional detail below for those who are more deeply interested.
This leads to the same main points being repeated several times, which can be a jarring style for readers who are not used to reading newspapers. Long magazine articles are typically structured quite differently.
Quote from one of the expert engineers from OA. It is the last sentence in the article, and I think a very effective final comment.
However, the article does quote two of the expert engineers as saying that the faux suspension bridge design could have been perfectly stable, had the trusses been strong enough.
I was interested in the comment that had the two end pieces been in place, then the bridge may well have been fine - the plan was to swing the main bridge section into position then build the two end pieces in situ. One wonders about the design calculations for each stage of the proposed construction.
I think there is a book length work around the details of the decision making process once the investigation is complete and the legal fall-out has been dealt with.
---
"Why do you want me to think that this is great architecture?" He pointed to the picture of the Parthenon.
"That," said the Dean, "is the Parthenon!"
"So it is."
"I haven't the time to waste on silly questions."
"All right, then." Roark got up, he took a long ruler from the desk, he walked to the picture. "Shall I tell you what's rotten about it?"
"It’s the Parthenon!" said the Dean.
"Yes, God damn it, the Parthenon."
The ruler struck the glass over the picture.
"Look, " said Roark. "The famous flutings on the the famous columns—what are they there for? To hide the joints in the wood—when columns were made of wood, only these aren't, they're marble. The triglyphs, what are they? Wood. Wooden beams, the way they had to be laid when people began to build wooden shacks. Your Greeks took marble and they made copies of their wooden structures out of it, because others had done it that way. Then your masters of the Renaissance came along and made copies in plaster of copies in marble of copies in wood. Now here we are, making copies in steel and concrete of copies in plaster of copies in marble of copies in wood. Why?"
What building by modern architects will even be around 500 years from now, much less revered as an example of beautiful architecture?
I don't say it's as beautiful as the Parthenon, and it might not last 500 years, but we moderns aren't completely shabby...
https://en.wikipedia.org/wiki/Cathedral_of_Saint_Mary_of_the...
> Its saddle roof is composed of eight segments of hyperbolic paraboloids, in such a fashion that the bottom horizontal cross section of the roof is a square and the top cross section is a cross.
The interior is open.
https://goo.gl/maps/R2arUkpaZeD2
The top cross section is also a cross on this one.
In fitting with the theme of the GP, not only is it structurally sound (to my knowledge) because of how the pillars are constructed, but it successfully pays homage to Gothic architecture and the oldest inspiration, Nature, while also being new and innovative.
Religious communities have the motivation to build something that lasts and use the best of materials. They see the building as an act of worship, in and of itself. Cathedrals often took extremely long times to build. In some cases, such as the beautiful Sheikh Zayed Grand Mosque, they also have the money to build it both well and quickly.
Within many modern protestant Christian communities, building grand buildings is seen as a poor use of money that could be better spent helping people. These grand buildings are seen as less comfortable, efficient and flexible for modern congregations that would prefer lower cost, environmentally friendly and low energy building with community facilities.
https://en.wikipedia.org/wiki/UTS_Tower
Something about those big blocky Brutalist style concrete box buildings you just know the thing is nigh indestructible and is going to be around forever and that to me is the beauty of the thing it has such as permanence about it. It just kind of sticks out there and says 'here I am deal with it'.
Go to some modern temples/shrines in Japan. Check out the torii gates and any other classical looking structure. Compare the ones in wood to the ones in stone or concrete. They look identical.
If you look close, you'll notice the little details sticking out of parts of the design. It's almost always a part of Japanese wood joinery. But it's still in the stone copies. Is it bad design? Of course not. That simple, striking, beautiful, complicated wood joinery has its own unique aesthetic appeal, and shaving off features just because they aren't necessary is completely beside the point of aesthetic beauty. To say nothing of honoring the tradition of a difficult and highly effective craft.
I’m inclined to believe that, if the original masterful wood-crafters had instead began their professions with stone, that they would have created beautiful structures that fully explored the capabilities of stone, and that their contributions to architecture may have looked a little different, but no less aesthetic.
So, assuming the will of the original craftsmen was to simply make the most aesthetic structures that their materials would allow (and maybe I’m wrong about that), would it be paying homage to them by making stone copies of their wooden accomplishments while working in a new medium with different characteristics, or would it be paying homage to them by continuing their pursuit and fully exploring the capabilities of stone, as the forefathers had done with wood?
That’s a question with no right answer... but I personally believe that homage is not to copy one’s output, but to copy one’s input.. To seek what they sought. To do as they would have done if they had stone instead of wood.
Beauty is subjective and the development of taste is path-dependent. A thing can be beautiful because it evokes features that make a designar successful for functional reasons in historical media.
In the case of many of these structures, their physical form is a reflection of some spiritual aspect. They're basically religious icons. Their design may be carried forward in part just because not doing so would be disrespectful on a spiritual level, or because they remind people of something. But they're not all the same.
There are probably thousands of different torii gates with slightly different designs. Some show an extended nuki with kusabi wedges, a modified mortise and tenon style joinery. But many torii gates don't feature these. Nuki joints are actually widely used as ornamental carpentry, and can be found in several non-wooden objects.
The construction of most torii, regardless of their material, seems to be about aesthetics (and honoring whoever paid to put it up) before the rest.
If you want maximum accomplishment with a material, check out their multi story pagodas that use a massive wooden beam in the middle. It acts as a mass damper and prevents the different floors from sliding off the building during an earthquake, as they aren't attached to each other. Hard to do that with stone! :)
I spent 13 years, in various capacities, studying architecture and working as an architect.
Bullshit like this reminds me why I don't miss it. Vapid pasted-on "signifiers" that are not merely devoid of sensibility, but aggressively hostile towards it. Engineers fighting to coerce the pastiche into something that won't kill people.
If you're not an architect and you're feeling generous -- like, maybe you're just having your daily dose of Dunning Kruger, and that maybe the architecture profession is like this for a good reason -- don't bother. It's genuinely as idiotic as you think.
This reads a lot like every startup that tries to convince themselves that their run-of-the-mill CRUD app is "changing the world".
Also, I'm not even an engineer and I can tell you that uneven strut design would give you uneven loading on the span. Christ. Why didn't they just build a damn cable stayed bridge?! If traffic was a concern, they could have built it half cantilever, half guyed. No formwork, strong, still visually appealing, no stupid truss design, and no concrete.
Adding the tower or cables would have done nothing to strengthen the bridge. The engineers in the article suggest that the second shorter section of the bridge to be built afterwards may have alleviated some of the stresses on the north truss beam, but the truss itself was unorthodox, so they cannot say anything for certain.
The worst case would be a marching parade, on just one side, during a hurricane.
Technical description of the bridge from the engineering firm:
https://facilities.fiu.edu/projects/BT_904/MCM_FIGG_Proposal...
Page 3: "The stay cable pipes increase stiffness for pedestrian loads."
Page 18: "The stays and pylon provide the required structural design to meet the pedestrian loads for harmonic conditions of natural frequencies"
Page 64: "HORIZONTAL FREQUENCY In the lateral direction, the fundamental frequency of the pedestrian bridge shall be greater than 1.3 hertz. VERTICAL FREQUENCY The fundamental frequency in a vertical mode shall be greater than 3.0 hertz to avoid the first harmonic."
Page 65: "The pylon stiffness was designed to provide significant benefit to the overall stiffness of the structure."
The bridge that they built did not use the stays as structural elements, and any vibration dampening would have been minimal, i.e., a side-effect of stiffening the bridge rather than the reason for including them.
Unless you can find such a document: the stays were structural elements.
A structural engineer is quoted in the article that this uneven strut design would have worked if if that end beam was more solid.
They were very unconventional in this design (new type of concrete, single row of struts, prefabricated construction, concrete instead of steel, uneven struts, computer-only analysis instead of civil engineering 101 static analysis) that it demanded extreme care.
Conventional bridge design patterns are robust as in they still work when they're old, under unexpected loads, analyzed by below-average engineers, or built with less-than-perfect materials. Deviating from them demands extra extra care, or people die. :/
I'm sure you noticed that sky-scraper shapes are getting weirder and more unstable-looking:
https://www.designbuild-network.com/wp-content/uploads/sites...
It's very easy to be seduced into assuming a computer model's results are correct. Computer models of critical bits should always be double-checked by a separate independent calculation.
For this bridge, a simple analysis of static forces should have been sufficient for a cross-check, despite the article repeatedly implying this was a difficult/tricky computation. It is not.
Designing how those members resist/react to those loads is dependent on the material though.
Again, what I am talking about is using statics to determine the minimum loadings to check against the computer models, which should predict higher values or they are wrong.
This is not difficult.
It's an extreme scenario, yes, as I'm sure/hope the software goes through rigorous testing.
The city I grew up in is a larger one, and currently seems to be entirely in the hands of private developers - who just dump closed-off groups of blocks at random throughout the city, hoping to sell the apartments, without any consideration to things like neighborhood, surrounding architecture or road throughput.
Often it is good to wait for an entire report to nail down the facts before the witch hunt should begin, is there something in this case that means this isn't the best idea?
One of the undercurrent themes of this story is that, according to the herald, the construction company and FIU officials are well-connected politically. Possibly related to this is the fact that the Herald is suing the state for records related to the bridge [0]. These records were determined to be public but have so far been withheld from public release.
[0] http://www.miamiherald.com/news/state/article212489364.html
It certainly doesn't look good from this quoted paragraph...
"Public records made and received by the Department from February 20 until the bridge collapsed on March 15 obviously were not obtained by the Department during an investigation because there had been no accident, much less an investigation into an accident,'' he wrote in a response to the FDOT motion to dismiss the lawsuit.
"Florida law is clear that if an agency’s record is a public record at the time it is made or received, then that document does not lose its character as a public record if the document is later given to an investigative agency in the course of a subsequently initiated investigation."
Still could be to prevent a public outcry before the facts are in, but that does seem mighty fishy...
I'd suggest that it's not an issue of bad faith regarding the NTSB, but rather that the NTSB doesn't (and shouldn't!) care about the political fallout from this, whereas a newspaper very much has an interest in uncovering the political side of this.
Beyond them, there are a large number of potential officials that could have leaned on / been leaned on or through nepotism or laziness been a part (or not part) of the planning, design, implementation etc of the bridge that are partly or largely responsible for design/funding choices to this bridge.
There are countless examples of people receiving undue flak before being conclusively proven as guilt free, it is often prudent to wait before leveling accusations - that is what the NTSB does in it's processes - often to a fault.
I think it is unnecessary snark to ask me if the bridge collapsed, please don't be crude.
To be clear, I fully trust the NTSB. It’s more that I want to make sure that there are checks and balances — even when a just agency is doing the reporting. It adds another protection layer to the system.
People are often very forgiving when they know what actually happened. But being shut out of the information flow is a problem.
I'm not saying we need to find the guilty and punish them, but there are people that have a real stake in finding out the story.
The Miami Herald is suing to get more material so that it can run more speculative headlines, which doubtless is great for the Miami Herald, because it drives revenue from selling papers and from advertising. But unlike the NTSB the Miami Herald has no real interest in the prevention of future harm.
Accident investigators like the NTSB need legal protection so that they get honest answers, in the service of the prevention of future harm. The harder you make it for them to do that job, the less effective they are.
There's often a fantasy in play in which people suppose that surely if everything was out in the open we'd fix all these problems, wouldn't we? But we've actually run that experiment already and the results were not good. Without the methodical independent investigation big vested interests are able to direct the narrative as they choose. And their interest isn't preventing future harm... except to themselves. So nothing improves, you will read the same stories, and be pointed at the same scapegoats, forever.
The specific focus on _preventing future harm_ is what's important about accident investigators. You might think a court seems like the right place, but courts are about _justice_ which isn't interested in future harm at all. Here's a nice modern British example that shows this difference:
A young woman drunkenly leans against a train as it departs, to the horror of those inside the train she falls and is killed.
The accident investigators look at that and their concern is: How should we prevent similar things happening? They look at lots of evidence as to exactly what happened and when, they interview people, they review the technology in place, and they make recommendations for how we can prevent the same tragedy re-occurring.
The court says: The train guard has a legal responsibility towards passengers, the evidence shows he did not do everything by the book, and a passenger died. If you have a legal responsibility but you don't do things by the book and someone dies, that's manslaughter. Guilty. Prison.
https://www.amazon.com/Just-Culture-Balancing-Safety-Account...
That is to be expected. Real world projects are usually resilient enough, that only when a lot of things align catastrophic failure happens, AKA Swiss Cheese model [1]
Not with all of the facts, yet interesting to see the conjecture and reasoning of trying to figure out what went wrong.
>“This is not a big project," Beck said. "It’s a darn pedestrian bridge.”
There is something to be said about not over-complicating designs, whether it be in actual construction or in software.
https://en.wikipedia.org/wiki/Don_Burnett_Bicycle-Pedestrian...
This problem will re-appear. When a bridge collapses, if they found out the company building it hired the cheapest engineers right out of school, denied them access to tools or training needed to do their job, kept them removed from decisions about scheduling, ignored any concerns voiced about needing more time for proper development and testing, multiple people (the ones who wear suits) would go to prison and the company would likely be destroyed. If a few executives were put in prison over shoddily made software rushed to market, I imagine we would see changes in how software is developed of monumental proportions. But not until then, apparently. And that day doesn't seem to be coming soon. Perhaps self-driving cars will herald such a wake-up call. I know I'm certainly not trusting one until things change drastically.
Developers, meanwhile, generally don't like the idea because it raises the barrier to entry, and it would establish standards that are extremely likely to be disagreed with by large numbers of people. Other professions have dealt with this, however, so it's not a completely unsolvable problem. I'd personally think that 'registered, licensed software engineers' might be something that a company would only need if producing certain kinds of products. If you're building an in-house processing system whose behavior and outputs your business is entirely legally responsible for, you probably don't need the licensed engineers. If you're building self-driving cars, though, yeah, you'd have to follow some standard practices and such. One would hope they would be fairly high-level, such as simply requiring static analysis be performed rather than getting as specific as mandating a specific tool be used.
It's understandable that there is hesitation, but I worry that the hesitation will bite us badly. A government stepping in and mandating programming languages and libraries and creating a regulatory body and all of that wouldn't be completely unheard of for things dealing with infrastructure. And nobody wants that.
Now this is an interesting idea. I wonder if one write a static analysis tool that output a printable 3D model...
If you included all the software that ran just to service a key press, the OS, drivers, etc...
Thinking about it, I do believe that would be an ugly machine.
https://www.google.com/maps/place/Sweetwater,+FL/@25.7618825...
You can see some remnants of the construction on street view.
The satellite view is slightly newer, with a near-completed span about ready to be moved into place.
They did the obvious thing to design the bridge, given that a hangbridge was requested. They started from a standard hang bridge and then eliminated the parts above the bridge itself, realizing that if you can just pull the cables inward the bridge will support itself like a hang bridge would.
But the installable part did not look like a hangbridge, and so the contractor treated it like a non-hangbridge, that only needs support at the sides.
Then, total idiocy struck. They mismeasured. The support could not actually be placed where it was planned when the bridge was designed. It needed to move ~2m to the left. And they did that, put the bridge over it, and left.
So let's go over that last part again. They had a bridge that hung from a pole (the pole was just cut off at a certain point, and a horizontal tension structure put into it's place. Actually pretty cool. Also: despite the article's claims, that definitely works). Then the contractors removed the structure that supported the pole, placing a different support ... at a different place. So they interrupted the foundation of the bridge, making it discontinuous.
(in their defense, with 99.9% of bridges you can do that without causing a problem, which is probably why this mistake was made)
This is like interrupting a building's foundation, and having everything from the 1st floor up supported by a window. The window has some strength, of course, to hold itself up, to hold the side wall up, and generally to not be too easy to destroy, so this will work ... for a short while.
And the of course the predictable thing happens : the bridge breaks in half, at almost exactly the point where the support SHOULD have been, but wasn't ... (and let's just ignore that there would have been loud cracking for a double-digit amount of seconds before the collapse, which clearly was not judged a good reason for the contractors to stop what they were doing).
Who's at fault ? Well the original mistake is mismeasuring where the support should have been. I would not place blame on the designer, because he was working from faulty data. And yes, there were some different designs that would not have had this problem, but the sponsor explicitly asked for this design. Then there were a LOT of opportunities to detect this mistake, all of which were missed. And then there is the fatal decision, made by the contractors installing the bridge as far as I can tell. Oh we can't place the support here, let's just move it a bit. What could go wrong ? And they did move it. Then the bridge showed obvious signs of stress (cracks), right in front of them. Again, somehow this was missed (despite camera footage showing some worker pointing it out to some guy that looks important). They ignored those signs and just left after cleaning things up.
And then ... tiny little shock overloads the weak component (which is the concrete surrounding that cable/beam thing they show, obviously NOT that cable itself). And boom.
If you analyze the blame, it seems like somebody really wants the contractor's decision to just place the bridge on different supports (which, again, is not a problem with 99.9% of bridges) to be the right call. If you force that decision to be reasonable, then there's little choice but to blame the design for not allowing for that. It seems unlikely in the extreme that the design firm hadn't warned the contractors about this though.
But also let's be real, you're not going to cross a 10-lane stroad, bridge or no bridge and feel like you're in 'a college town'. It was never gonna happen.
They aren't joking about the "variety of different shapes and sizes" for the diagonal supports. It's really incredibly ugly. In my view any "aesthetics" gained from the fake cables on the bridge are far outweighed by how goofy the whole thing looks when viewed from the side. It's really jarring, and I imagine that it would look rather cobbled together when walking over it.
I also was shocked by the reported "2000 pages of calculations" that 3 different structural engineers signed off on. I have a hard time imagining that none of these experts might have said at some point, "this is a bad bridge that should not be built!" even if mathematically it could have survived magnitude 10 earthquake. Which it clearly couldn't. I'm not an engineer but it ought to be outside the ethics of an engineer's role in approving a bridge design that appears to have redundancy (the cable stays AND the diagonal supports) when the cable stays are merely a foolish aesthetic choice. Doesn't seem much different than selling a car with an airbag icon on the steering wheel when no such airbag exists. It's a false claim to structural integrity.
One final thought- the PURPOSE for this bridge seems ill-conceived in the first place. Why is the campus divided by a highway to begin with?? But that's neither here nor there.
That's probably more circumstance than anything else. The area immediately north of the campus has a lot of residential housing, attractive to both students and employees, moreso because Miami's public transit is gawdawful; if you can walk to school/work, avoiding the traffic, that's a bonus.
Additionally, the campus wasn't always the behemoth it is now. The highway they speak of is SW 8th Street, or Tamiami Trail, if memory serves. It's a main road in the area The campus was always adjacent, but only semi-recently has it begun to truly crowd the road, likely a byproduct of all the insane construction going on in the school. FIU is far from the only school spending ridiculous money on infrastructure. The school was never really plopped down next to a major highway...they both just grew, and city planning has never been the area's strong point.
That's not how engineering works at all. Structures are either safe for the conditions or not.
They don't have features that the public derives safety ratings for because that's impossible for the public to do under any kind of complex forces.
A cable from a bridge doesn't mean anything about it's safety or support. It's nothing like the airbag example.
That's a weird claim to make. False claim to who? Joe on the street?
This was my exact point: as a Joe on the street you just have to assume that the engineers got it right. A two set strutted bridge can still fail if the struts are two thin, or not of the right kind of steel/concrete. Do you really evaluate all buildings when you enter them, especially the modern weird and unstable looking ones? Have you ever avoided entering a building just because it has a crazy unstable looking design?
Sure, I would never cross that bridge if I saw those fake stayed cables damaged after a storm, because again, I am in no position to judge the design of the bridge, but it is obviously damaged and I must assume that it is unsafe. Maybe a structural engineer would immediately spot that those stayed cables are fake and wouldn't worry about cross it. But if the bridge looks intact, I would just assume that the engineers knew what they were doing.