The first half of the story is that the stakeholders wanted an over-the-top bridge design, complete with fake cable stays, and out of hubris decided they would use an all-concrete single-truss Accelerated Bridge Construction (ABC) design because all-concrete would look better and the university's (FIU's) engineering department sort of specialized in promoting ABC.
What could have been a much cheaper nice looking normally-designed bridge (which would be open today) ballooned (or you could say, was hijacked) into a $10mm+ bridge disaster that would be comedy if people hadn't been hurt and killed. A majority of it was even paid for by federal grants.
This is why we can't have nice things. They were so focused on building a nice looking bridge — and meeting deadlines — that they didn't/couldn't allocate sufficient resources to verify the design, verify it was built and moved into place correctly.
 see page 9 of https://www.transportation.gov/sites/dot.gov/files/docs/brie...
Nothing wrong with that!
> They were so focused on building a nice looking bridge — and meeting deadlines
These are also good things.
To me sounds like the civil engineers started behaving more like software engineers. The independent peer reviewer they hired was not qualified to do the review.
> Louis Berger was not qualified by the Florida Department of Transportation to conduct an independent peer review and failed to perform an adequate review of the FIGG Bridge Engineers design plans and to recognize the significant under-design of the steel reinforcement within the 11/12 node, which was unable to resist the horizontal shear between diagonal 11 and the bridge deck.
This whole business of the engineers ignoring the cracks that the contractors kept needing reassurance about is also insane.
Things like these were common in construction before software engineering was a thing. It always makes me chuckle when someone defers to "if we built buildings like we build software" trope. We do, and worse.
Lots of constructions standing around the world are not up to the codes in zillion different ways. They are still standing because redundant nature of physical construction is more forgiving than execution on a Turing machine.
I read in an architect's memoirs that when he was a student back in the 1940s whenever his Architecture faculty teacher and his students visited a construction site to maybe change some small details (or at least they were perceived as "small" by said architects) oftentimes they were met with very angry construction site workers who would make the above architects think again about trying to force the implementation of those small changes. A similar story was told to me by my father (also a civil engineer) as happening in the 1980s, though the level of implied violence coming from the construction workers was a little more subdued. Wish that we in the software industry would be like those construction workers from time to time.
Why do you think I'm a fan of Ada?
(And looking to get into VHDL, too.)
A cluster of burly construction workers holding spanners is probably more physically intimidating than whatever we software developers could typically muster.
Joke's on you, 100% of my code is redundant.
> Nothing wrong with that!
Well, in this case, apart from the structural problems, the bridge just looked cheap and kitschy because of the fake cable stays. So yes, there was something very wrong with that, but this problem is so common in contemporary architecture that we don't seem to recognize it anymore. There is just no way for an over-the-top designed building to have any dignity.
Except that it's not private money. It's public money.
This is the bridge equivalent of a town using a state grant to buy a Cadillac for the code inspector to drive around in. There is no place for that kind of behavior with other people's money.
If the university wants to build a bridge with all the bells and whistles with their own money that's fine. When they do that with public money there is an opportunity cost of the other improvements to society that money could have bankrolled. To claim that it is ok to spend public money on frills like this is to claim that the net difference between a boring pedestrian bridge and a fancy one (i.e, the "frills") is more important to society than the other things that money could have done.
Well, there's nothing wrong as long as they are not spending their money.
This exactly parallels the disaster that is the new span of the (SF-Oakland) Bay Bridge. What would have been a $400M fully-functional replacement instead became an $8 billion art piece that is less safe and needs far more maintenance.
To be fair, you can make that criticism of almost every monument and famous building in the world. If the Sagrada Familia didn't have all those over-the-top arched ceilings and all those do-nothing decorative carvings, it'd have been finished decades ago!
"The structure of the chapel, built in a great hurry in the 1470s, had given trouble from the start, with frequent cracks appearing. At Christmas in 1525 a Swiss Guard was killed when entering the chapel with the pope when the stone lintel to the doorway split and fell on him. The site is on sandy soil, draining a large area, and the preceding "Great Chapel" had had similar problems."
According to the narrator, although FIU has a department for ABC they weren't consulted nor involved with the bridge project (and were not happy about it?). No idea how accurate that statement by the narrator is.
Municipalities really need to carefully consider the balance of aesthetics, costs, and risks.
Part of the reason for that is Gray Davis wanted the bridge construction to start as soon as possible because he wanted to show the voters he was competent and effective instead of the hapless fool he is.
There was a process that involved many people and it failed.
The bridge was supposed to self-support without them during assembly, without a hurricane or marching band. This does not mean the cable stays were entirely decorative. They had a structural purpose, primarily to change the resonance frequency to be outside the range of ordinary human motion. They were intended to bear some of the load.
To me there were obvious problems, particularly the sharp non-articulated corners in the the concrete at the truss edges (high stress points), but of course my concerns would have been dismissed prior to the collapse. Lots of people, with even minimal understanding of mechanical design, should have been alarmed. Maybe that was the point of the design: make something that looks alarming and thus dramatic.
Shouldn't they be experts at building them properly then?
> A bad design with a good presentation is doomed eventually. A good design with a bad presentation is doomed immediately.
-- Akin's Laws of Spacecraft Design
The only reason this got noticed is because people died and bodies create opportunities for all the parties that should have stopped this stuff before it started to score virtue points and look like they're doing something cleaning up the mess.
If the (metaphorical or literal) tar and feathers came out every time taxpayer money was spent on a boondoggle like this you wouldn't have nearly as many boondoggles like this.
The bridge was the most hideously ugly bridge ever, behold:
Welp, that's a lawsuit laid out cold right there, setting aside even the fact that
> the probable cause of the ... bridge collapse was the load and capacity calculation errors made by FIGG Bridge Engineers, Inc.
> Errors in design may occur, but systems should be in place to catch those errors when they do occur. In this case, a firm was hired to independently review the bridge design for errors. However, [...] Although the design reviewer recognized that he should have examined the nodes and stages, he indicated that there was not enough budget or time to evaluate those factors. Contributing to this review failure was the reviewing firm’s lack of qualification to do this work.
Like even with software there's a point where I tell folks "Look if we're not going to do this X far, it's not of any value to do it half way and claim we did anything here."
You'd think there would be some engineering standard where "No this isn't a legitimate review because we didn't do enough." and that might set off some alarms...
I've heard many other examples of viciously denying that anything is wrong, all the way until something becomes very very wrong, to wonder whether this is an inherent part of human nature or a futile effort to avoid liability for knowingly screwing it up.
Effectively, playing with apparent risk/reward, in the sense of overstating or understating the potential benefits or costs/hazards of an activity or phenomenon, is a form of rent-seeking. It allows an asset to appreciate (or a risk to be discounted), without doing any real work.
Whether that's done through a deliberate calculation, through inherent psychological bias, through group or peer pressure, or other mechansism, seems to vary. But you'll find this across activities, technical domains, space, and time.
It's a major element of Bernhard J. Stern's "Resistances to the Adoption of Technological Innovations", from 1937, which looks at the history of numerous innovations across multiple areas. You'll find this repeatedly in all kinds of technical and technological disasters: Chernobyl, Fukushima, Three Mile Island, numerous aircraft disasters, military campaigns, entire wars, business decisions, and any number of mundane accidents. In the use of lead, asbestos, tobacco, CFCs, and CO2.
One common element is that risks, whilst occasionally somewhat apparent, are not unambiguously manifest. Failures are almost always highly nonlinear. At one moment, things are mostly OK, though there are possible signs of trouble. Moments later, everything is gone to hell.
Up until that point, it's possible to argue otherwise. Occasionally even past it.
It also makes sense both intuitively and mathematically. If you screwed up and don't admit it, there's a chance (say X) nobody will find out (that it was you, or that anything was screwed up in the first place). Conversely, there's a (1-X) chance it'll be found out and you'll pay the costs - which my be huge and very personal, including tarnished reputation, monetary damage or even jail time. Now, if you admit to the error yourself, you get 100% certainty of slightly lower punishment. As long as the "slightly lower" isn't lower than (1-X), it makes sense to keep quiet mathematically. And of course, once you add fear into this, people tend to overestimate X.
Consequences to others turn this from a small to huge moral issue, but the mechanism is still arguably dominated by fear. That's why punishments are a tricky thing. Threat of losing license is a good deterrent from screwing up, but also a good motivator to hide your failure if you screwed up.
There is no practical alternative to taking away a licence in cases like this, at least temporarily in less egregious cases. What meaning would the licence have if the person responsible here retained it? He has demonstrated an appalling lack of judgement which goes beyond this one disaster. Removing the threat of revoking the licence would not fix the incentives issue, as even with that off the table, the engineer is to blame for the cost and delays of his failure, even if he does not care about the risk to other people.
Here's an example of an engineer doing the right thing - though the prospect of failure was so appalling that it probably focused his mind on what mattered most.
This reminds me of all the nuclear power plants that are operating beyond their design life and keep increasing their allowable crack tolerance.
The ntsb and us chemical safety board channels are amazing.
The bridge slowly and visibly announced its impending collapse, which - as I understand it - is exactly what engineers want. The thing nobody wants is a bridge like the Morandi bridge in Genua, where the signs of impending collapse were hidden under thick layers of concrete, until the structure suddenly and unexpectedly gave way.
... and (only for the record) behind false or falsified inspection reports.
"WARNING Cracking bridge, proceed at own risk, age 18+ only, do not stop near the bridge."
We need a way to have something like that be viable from a legal perspective.
For less money, they could have had a real cable-stayed bridge, like the one over I-280 near Apple HQ. That cost $14 million, but it's a 375-foot clear span over the freeway.
A 620 ft concrete suspension bridge  in Chicago was $23 million, or ~$37k/ft
A 1470 ft concrete and steel bridge  in Chicago was $33 million, or ~$22k/ft
This ugly monstrosity in Florida was $9 million for 174 feet, or ~$51k/ft
It's awfully pathetic.
"Denney Pate, who stamped the plans for the bridge, told a judge June 12 that his wife accidentally put his pants with the phone in the pocket into a washing machine, inflicting damage that destroyed any call records or images."
10. Train your staff on the proper use of Pc (the permanent net compressive force normal to the shear plane) when calculating nominal interface shear resistance.
Pretty humiliating. I wonder how bad the damage is to FIGG.
I get that mistakes do happen but this was a bloody footbridge...
The bridge collapsing was one of the most surreal experiences of my life.
The highest required factor of safety in engineering is AFAIK 5 and is used for things like lifts, cablecars and similar.
But the short version of the story is that for LRFD there are two main factors which affect “factor of safety” in the traditional sense (eg - structural capacity / structural demand) which are load factors and resistance factors (as you’d guess). Load factors increase applied forces while resistance factors decrease assumed strengths. Load factors vary depending on the type of load but typically they’re between 1.2 to 1.6. Resistance factors vary based on failure mechanism under consideration and are between 0.6 to 0.9 for structural work.
So the range is 1.2/0.9 to 1.6/0.6 or ~1.35 to ~2.75.
There are secondary sources of additional factors of safety. For example, material properties assumed in design are the minimums that are allowed and so chances are you’ll get something on site that exceeds by 25-50% or so because nobody wants to deliver material that doesn’t meet the minimums and open themselves to claims liability. There’s also a redundancy factor which is touched on in the report where loads are increased if no redundant load path exists, for concrete there’s some additional caps/limitations on a couple values due to time effects like creep, etc.
I would say most modern construction has an overall factor of safety of 3-5 with bleeding edge construction sitting at around 2 and public works construction (utilities or highways - things where architects aren’t involved) at over 5.
It is a small (but good) thing, though it would have IMHO not been enough to save this particular bridge, here the issue is evidently a wrong static model, or - less likely - a wrong assessment of loads.
Besides the initial (huge) calculation error, what is really preoccupying is that they didn't consider as serious the cracks, which as seen in the video/photos on youtube are the typical (severe) shear cracks, that should have been ringing all alarms.
The poor structure, as often happens, did all it could to "signal" the issue, what I find bordering being criminal is ignoring or severely underestimating those clear signals.
I suspect current designs are far nearer critical tolerances. Even under the ridiculous dynamics of the Tacoma Narrows incident, ultimate failure took hours.
It took 4 months from construction to failure, during which time it was already flexing far more than normal.
Contrast Tacoma Narrows, whose final throes were long enough for crowds to form and traffic to be cleared.
Morandi, Genoa, Italy:
I-35W, Minneapolis, MN:
The bridge was connecting FIU with a large student residence. Negligence during construction notwithstanding, to say that a simple crosswalk was enough is disingenuous.
Someone with a PE license has met the minimum requirements from the state. Nothing else can be garnered from someone possessing a license. The minimum requirements have, historically, resulted in engineers who put out public facing designs that, more often than not, do not bring harm to the public. I can tell you first hand that sometimes the guy with a license who is actually at “the minimum” does not always put out something that is safe.
Still, I'm glad professional licensure is required. That's what will prevent these folks from quietly rebranding and designing another disasterous bridge tomorrow.
Particularly lately I have seen an increase of (otherwise very good, smart and qualified) engineers and architects with no or very little on-site experience, that produce beautiful and valid drawings/designs that cannot be "as they are" realized in practice.
Why am I not surprised?
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