The Design Flaw That Almost Wiped Out an NYC Skyscraper 183
Hugh Pickens DOT Com (2995471) writes "Joel Werner writes in Slate that when Citicorp Center was built in 1977 it was, at 59 stories, the seventh-tallest building in the world but no one figured out until after it was built that although the chief structural engineer, William LeMessurier, had properly accounted for perpendicular winds, the building was particularly vulnerable to quartering winds — in part due to cost-saving changes made to the original plan by the contractor. "According to LeMessurier, in 1978 an undergraduate architecture student contacted him with a bold claim about LeMessurier's building: that Citicorp Center could blow over in the wind," writes Werner. "LeMessurier realized that a major storm could cause a blackout and render the tuned mass damper inoperable. Without the tuned mass damper, LeMessurier calculated that a storm powerful enough to take out the building hit New York every 16 years." In other words, for every year Citicorp Center was standing, there was about a 1-in-16 chance that it would collapse." (Read on for more.)
Pickens continues:
"LeMessurier and his team worked with Citicorp to coordinate emergency repairs. With the help of the NYPD, they worked out an evacuation plan spanning a 10-block radius. They had 2,500 Red Cross volunteers on standby, and three different weather services employed 24/7 to keep an eye on potential windstorms. Work began immediately, and continued around the clock for three months. Welders worked all night and quit at daybreak, just as the building occupants returned to work. But all of this happened in secret, even as Hurricane Ella, the strongest hurricane on record in Canadian waters, was racing up the eastern seaboard. The hurricane became stationary for about 24 hours, and later turned to the northeast away from the coast. Hurricane Ella never made landfall. And so the public—including the building's occupants—were never notified.Until his death in 2007, LeMessurier talked about the summer of 1978 to his classes at Harvard. The tale, as he told it, is by turns painful, self-deprecating, and self-dramatizing--an engineer who did the right thing. But it also speaks to the larger question of how professional people should behave. "You have a social obligation," LeMessurier reminded his students. "In return for getting a license and being regarded with respect, you're supposed to be self-sacrificing and look beyond the interests of yourself and your client to society as a whole.""
Nuh-uh! (Score:4, Insightful)
No way! This is America! You're supposed to extract as much wealth as you can for yourself! Society as a whole doesn't exist!
So what if the building blows over and kills thousands - I guess we won't buy another building from those guys will we! The market takes care of that sort of thing - it's like magic!
HW
yes, I've used a Professional Engineer. also a CPA (Score:5, Insightful)
Yes, it does, pretty well. I've used a PE (Professional Engineer) for exactly that reason - they "sell" trustworthiness, objectivity. The person I bought my house from and I paid the PE precisely because we know they sell the truth, rather than telling either of us what we want to hear.
That's the same thing CPAs sell - the market pays Price Waterhouse Coopers to find the truth, rather than skewing things.
Re:yes, I've used a Professional Engineer. also a (Score:5, Insightful)
Yeah, I remember how well that worked in the 90's
Remember when Arther Anderson stood up to Enron and refused to sign their books. And in turn sacrificed the lucrative consulting contracts with Enron for only CPA fees.
As opposed to simply adding a footnote disavowing the report before signing it anyway.
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Why look there only?
Look at all the software hiding behind various licenses that include clauses to try and escape responsibility?
Many EULA's from corps such as Microsoft and Adobe for example. Then there's Open Source licenses such as GPL and BSD.
That's actually an interesting engineering ethics issue: Can you, as a licensed software engineer, in good conscience release software under any license with such clauses, without totally violating your responsibilities and duties as an engineer?
My personal take o
Re:yes, I've used a Professional Engineer. also a (Score:4, Interesting)
What jurisdiction do you live in that actually licenses software engineers?
Licensed Software Engineer new in USA. Ethics old (Score:2)
Many states in the US now license software engineers because the national organization now has criteria. A problem is that you need sign-off from an existing PE who knows your work, so there is a bootstrapping problem. A new software PE has to be approved by an existing PE, but there are virtually no existing software PEs to approve the first generation.
Of course, it's always been possible to work under the same ethical guidelines voluntarily. More than once I've told a client I won't do something because
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This is less of an issue than you make it out to be. I got my PE license with the computer engineering test, and I'd happily sign off on somebody taking the software engineering exam. I would have taken the software engineering PE exam, except it was not offered in my stated at the time (Texas). Coincidentally, Texas was the first to offer that exam.
I'd love to talk to you in more detail (Score:2)
I called the Texas licensing board asking how this is supposed to work and the person who answered pretty much said "yeah, you're screwed, unless you've been working as some other type of engineer".
I'd really like to talk to you about just how you went about getting licensed, and under what conditions you'd sign off on someone else. If you're nearby, maybe I can buy you lunch sometime. I can be reached at deepmagicbeginshere AT gmail.
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Yes and no. There should be barriers to entry for professions where lives are on the line.
Frankly, getting a PE license is not difficult, provided you are not a totally shitty engineer.
most engineers aren't PEs, not excluding anyone (Score:2)
Most engineering graduates aren't PEs - you don't need the credential to work as an engineer. It indicates a certain level of professionalism, so people can choose to hire a PE. Of course in some life-safety situations there might be a regulation saying you can't do X (build a highway bridge) until a PE signs off the design.
It's not like a union where it's illegal to hire people that have identical qualifications. It pretty much just defines the label "Professional Engineer" to mean someone who has passed
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Why not? As long as you explicitly note that you are NOT guaranteeing it under your engineering license, and you aren't providing it under conditions where signed-off software would be required, why would it be unethical?
Ethics -- in general, not in the sense of a
Yes, sure...with conditions. (Score:2)
Can you, as a licensed software engineer, in good conscience release software under any license with such clauses, without totally violating your responsibilities and duties as an engineer?
I have an engineering degree, but am not a "professional engineer". I've worked for over a decade on proprietary embedded projects based largely on open-source software.
We generally write good code (though there will always be known issues) and we provide extensive support for our products, and charge accordingly.
On the other hand, we also contribute features and bugfixes back to the upstream open-source projects.
I don't see a conflict.
which cost Arthur Anderson $9B in market value (Score:2)
Arthur Anderson was a 100-year old brand worth $9.3 billion. Because they violated the public trust, they are now worth about $0. The company still exists, but noone will buy from them.
Sony, on the other hand, is still selling electronics after rooting their customers' computers wholesale. Electronics company does something unethical - they have a PR problem for a few months. CPA does something unethical - the market executed them.
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I thought the shredding was technically legal because it was presubponea
Re:yes, I've used a Professional Engineer. also a (Score:4, Informative)
Thats only if its your general practice and not being done out of the blue *and* you have no reasonable grounds to suspect you may need them..
You can't go 'well I see a court case coming.. I *might* be up for a subpoena, better start shredding'
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> Yeah, those CPAs auditing Enron did a bang-up job of it, didn't they?
The 100-year old firm that audited Enron was worth over nine BILLION dollars at the time. It's now worth a few thousand, because nobody will ever hire them. The market executed them.
Compare Sony and their root kit.
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The 100-year old firm that audited Enron was worth over nine BILLION dollars at the time. It's now worth a few thousand, because nobody will ever hire them. The market executed them.
A system that makes sure a failure doesn't occur a second time is better than nothing, but it's not as good as a system that makes sure the first failure doesn't happen. (Whether it's "good enough" depends on how acceptable it is to suffer that first failure)
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The insurance premium on that building must have been astronomical until it was fixed!
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You ignore the fact that he can be held criminally liable. Let a skyscraper fall and you're talking casualties in the 5 digit range. There is no way to stop that avalanche of outrage. In fact, I'd be surprised if the engineer didn't have to be taken into protective custody for his own safety. The people responsible for building safety will catch hell too. Catastrophic destruction gets catastrophic response.
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Example: Hyatt Regency walkway collapse [wikipedia.org]
The contractor made changes to save money. Only in this case they got the PE to sign off on their changes without evaluating them.
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Only 114 dead. Compared to a falling skyscraper it's nothing. Bad but not bad enough to generate the hysteria neccessary for a lynching.
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Yepper.
Pure fucking magic!
Re:Nuh-uh! (Score:4, Insightful)
Re:Nuh-uh! (Score:4, Insightful)
By the time it fails, that's 15 jobs ago for the management. They already got their bonus for short term cost savings and are doing the same thing to bigger and better projects now. There's a reason job hopping is so common in senior management levels.
numb3rs (Score:2)
That sounds familiar. Wasn't there an episode of Numb3rs based on that?
This is from the 99% Invisible Podcast. (Score:5, Informative)
It's not clear at all to me why the OP or the editors wouldn't at least mention that this information is taken nearly word-for-word from the really excellent weekly podcast 99% Invisible, so I'm making this comment to get it on the record. Also, here's a gratuitous link to the podcast: http://99percentinvisible.org/ and the episode: http://99percentinvisible.org/episode/structural-integrity/
Not the first to break the story (Score:2)
I don't see it -- the summary was taken word-for-word from a podcast? As in, someone transcripted and submitted it, including the quotes?
That podcast certainly wasn't the first source to report on the Citicorp Center design flaw -- there was article in the New Yorker in 1995 about it ( http://www.newyorker.com/archi... [newyorker.com] ).
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Its right in the byline at the top of the article so it seems well-covered for those who click-through already. Also, I hate podcasts, so I'm glad they didn't link to that instead.
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Did I miss something? Where does it mention 99% invisible?
Re:This is from the 99% Invisible Podcast. (Score:4, Insightful)
In the actual story. You might know it as the thing nobody reads before posting comments.
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Haha. Found it! Thanks.
They kept it SECRET so lots can be kept secret? (Score:2, Insightful)
Re:They kept it SECRET so lots can be kept secret? (Score:5, Informative)
The repairs were only "secret" because no one was asking questions about it.
Press strike? (Score:2)
Re:Press strike? (Score:5, Insightful)
So all the newspapers of the USA were closed and no TV stations were broadcasting news? Certainly today it would make a strong story - after all we're resurrecting it after all these years; I'm dubious that the fact that the newspapers of New York were shut would be a such a barrier then.
Those were much different times. There were no 24 hour news channels, no internet, and radio was somewhat different then. Print was just about the only place this kind of thing would have showed up. And since most papers were more focused on the city they were based in, it's unlikely it would be reported in another cities paper. Remember, TV news was an hour, at best, in the evening. Even if it would have ended up on the evening news, it would probably have been mentioned in a 30 second bit at best. There wouldn't have been a 2 hour "special report" on it.
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I am more curious about what the reply was to the undegrad student and how did they keep him quiet. Also, did he get a congressional medal for saving 1000s of lives?
Re:They kept it SECRET so lots can be kept secret? (Score:5, Informative)
According to TFA the undergrad student was a she not a he. From the article:
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But the story DID come out.
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Um, this story is posted on /. The original architect spoke about the incident regularly and educated thousands of students using it as a lesson. I also remember seeing an entire special on PBS about this incident.
It was only a secret during the remediation phase.
According to Slate, the story wasn't public for over 15 years:
The story remained a secret until writer Joe Morgenstern overheard it being told at a party, and interviewed LeMessurier. Morgenstern broke the story in The New Yorker in 1995.
A tidbit that would explain why the city would let them keep it secret and not evacuate during the mediation phase (from the people.duke.edu link):
LeMessurier didn't think an evacuation would be necessary. He believed that the building was safe for occupancy in all but the most violent weather, thanks to the tuned mass damper, and he insisted that the damper's reliability in a storm could be assured by installing emergency generators. Robertson conceded the importance of keeping the damper running--it had performed flawlessly since it became operational earlier that year---but, because, in his view, its value as a safety device was unproved, he flatly refused to consider it as a mitigating factor. (In a conversation shortly after the World Trade Center bombing, Robertson noted dryly that the twin towers' emergency generators "lasted for fifteen minutes.")
They probably believed LeMessurier, not Robertson. As to secrecy after the mediation: standard nondisclose agreements, probably.
@AC 15:53 - Re:They kept it SECRET ... ? (Score:2)
In my experience most secrets come out eventually..
How would you know?
There was even a case of a British royal heir that was likely murdered, a situation that would have endangered the monarch who did it (ordered it done). It took several centuries but they think they've found the body (it was found under a staircase).
It wasn't a royal heir, it was a king (Edward V), after being deposed in 1483 by his successor, King Richard III. The probable body (alongside his supposed younger brother) was found about 200 years later in Charles II's reign. Ironically, Richard III's own remains also remained hidden until last year. Historians still cannot agree who was responsible for killing Edward V, but modern thought is that the rumour that it was Richard was no more than Tudor propaganda - so the "secret" sti
What happened to that undergrad? (Score:5, Insightful)
Re:What happened to that undergrad? (Score:5, Informative)
I'm not sure what the author means when he says that the student was "lost to history", because at the end of the article he says that it was Diane Hartley.
The BBC aired a special on the Citicorp Center crisis, and one of its viewers was Diane Hartley. It turns out that she was the student in LeMessurier’s story.
Her name is also mentioned in some papers on engineering ethics:
http://www.onlineethics.org/cm... [onlineethics.org]
http://www.theaiatrust.com/whi... [theaiatrust.com]
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"I was very nice to this young man," LeMessurier recalls. "But I said, 'Listen, I want you to tell your teacher that he doesn't know what the hell he's talking about, because he doesn't know the problem that had to be solved.' I promised to call back after my meeting and explain the whole thing."
None of the sources agree on the details of how the problem was discovered.
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Hyatt Regency Walkway Collapse (Score:4, Informative)
Another engineering fail is the collapse of indoor walkways at a Kansas City hotel. Except the fail actually killed over 100 people:
http://en.wikipedia.org/wiki/Hyatt_Regency_walkway_collapse
Interestingly, the _original_ designs for both the walkways and the Citigroup Center tower case were safe. In both cases contractors requested design changes, and the engineering firms didn't do a proper review when approving them.
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I don't know about "safe" but the original design for the Hyatt Regency walkway would not have been up to KC's building code.
source [engineering.com]
Re:Hyatt Regency Walkway Collapse (Score:5, Interesting)
The design is fine if you can magically materialize the rods, retaining nuts, and walkways in place, as they appeared on paper. But it's one of those designs where it's completely impractical to get from the disassembled parts to the completed design. The contractor correctly called out this idiotic design and suggested splitting the rods in half - one for the upper walkway, the other for the lower walkway. That way they could connect the rods to the upper walkway, lift it in place and mount it to the ceiling. Then attach the rods to the lower walkway, lift it in place to mount it to the upper walkway.
It was the architect/engineers who didn't properly vet the change. If the two rods had been above/below each other with a mating connector (emulating the original single-rod design), all would have been fine. But the contractor had suggested offsetting the two rods sideways so they could both be sent through the upper walkway, using the walkway itself as the mating connector. That offset (1) transferred the entire load of the lower walkway onto the upper walkway instead of just the rods, and (2) converted what was supposed to be entirely axial loads on the rods into a torque on the walkway floor; a floor whose structure wasn't designed to withstand that much torque, and didn't on the night of the disaster. The engineers should have caught that and come up with a different design.
Missing the obvious? (Score:3)
I know hindsight is 20/20 but not considering the effect of wind hitting the corners of the building seems unbelievable. With no support at the corners it seems obvious* that the easiest way to cause a failure would be to apply force directed towards a corner. TFA does say that wind at the corners is not usually an issue, but when designing something so radically different you have to consider the effects of those differences.
*For anyone who has ever played with Lego: imagine building something that looks like that building and think of the easiest way to push it over. Consider how you control the direction when felling a tree.
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And it was obvious enough for an undergrad to discover. Even though it passed the (at the time) tried and true methods that proved the fitness of many designs. It even became a cautionary tale that improved our procedures without the building falling down and killing people (which I find to be the truly amazing part of this story).
However, your lego example could point out why wind wasn't tested at the corners. In pushing over legos you assume a constant force from any direction (since you're pushing with y
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True, which is why that is not normally considered. But in this case the lack of support at the corners made the building particularly vulnerable to diagonal forces. That was the point I was trying to make with the Lego example. And if you're designing such an unusual building maybe you should consider more than just the first "first obvious choice" for what could go wrong.
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No, they didn't.
With only the forces of the perpendicular winds considered and reported, the contractor's decision was ok. While it is true that the bolts were weaker than the welds would have been, they were strong enough to handle the forces the design specified. There's a quote by LeMessurier in the podcast that says this.
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http://people.duke.edu/~hpgavin/cee421/citicorp1.htm
When LeMessurier called the student back, he related this with the pride of a master builder and the elaborate patience of a pedagogue; he, too, taught a structural-engineering class, to architecture students at Harvard. Then he explained how the peculiar geometry of the building, far from constituting a mistake, put the columns in the strongest position to resist what sailors call quartering winds--those which come from a diagonal and, by flowing across two sides of a building at once, increase the forces on both. For further enlightenment on the matter, he referred the student to a technical article written by LeMessurier's partner in New York, an engineer named Stanley Goldstein. LeMessurier recalls, "I gave him a lot of information, and I said, 'Now you really have something on your professor, because you can explain all of this to him yourself.'"
What poetry is this? (Score:5, Insightful)
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Holy tongue twister Batman!
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Or flip the view:
A towering bank undercut by a small church.
----------------------
In the intersection between religion and the modern world
Religion razes grandeur to the ground for 20 pieces of silver.
In the intersection between religion and the modern world
Religion refuses to budge from barren historical ground.
In the intersection between religion and the modern world
A towering bank undercut by a small church nearly kills us.
-
Risk (Score:2)
LeMessurier realized that a major storm could cause a blackout and render the tuned mass damper inoperable. Without the tuned mass damper, LeMessurier calculated that a storm powerful enough to take out the building hit New York every 16 years.
Sonds like he forgot to account for systematic risk. Mutiple failures caused by one underlying event having a higher probability than unrelated failures. Its a common problem with the quantitative approach to analyzing failures.
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http://people.duke.edu/~hpgavin/cee421/citicorp1.htm
LeMessurier didn't think an evacuation would be necessary. He believed that the building was safe for occupancy in all but the most violent weather, thanks to the tuned mass damper, and he insisted that the damper's reliability in a storm could be assured by installing emergency generators. Robertson conceded the importance of keeping the damper running--it had performed flawlessly since it became operational earlier that year---but, because, in his view, its value as a safety device was unproved, he flatly refused to consider it as a mitigating factor. (In a conversation shortly after the World Trade Center bombing, Robertson noted dryly that the twin towers' emergency generators "lasted for fifteen minutes.")
I wonder if the emergency generators are in a basement that could flood?
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I wonder if the emergency generators are in a basement that could flood?
No, that'd be stupid. The generators are on the top floor. But the fuel is under the basement for safety (and not fully sealed from water contamination).
Or, as I have seen in person, the grid power comes in the basement, and the generator feeds the basement cutover switch, but they put the generators on the roof, and the fuel on the roof of the parking structure (to reduce fire risk to the building), with a safe and reliable connection between the fuel and generators. When the flood hits, the electron
Ahh Unions... (Score:5, Insightful)
I want to be in support of unions, but then you read about shit like this. Basically, "Hey, let's render inoperative some vital equipment necessary to make the determination on whether 10 blocks of Manhattan need to be evacuated because they weren't wired by union electricians"...
One time, the readings went off the chart, then stopped. This provoked more bafflement than fear, since it seemed unlikely that a hurricane raging on Lexington and Fifty-third Street would go otherwise unnoticed at Forty-sixth and Park. The cause proved to be straightforward enough: When the instrumentation experts from California installed their strain guages, they had neglected to hire union electricians. "Someone heard about it," LeMessurier says, "went up there in the middle of the night, and snipped all the wires."
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I'm not sure how my post is offtopic considering I quoted one of the linked articles...
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Someone who has mod points today and has been involved with a union saw this and went 'how dare you badmouth unions', probably.
Conditional probability... (Score:2)
In other words, for every year Citicorp Center was standing, there was about a 1-in-16 chance that it would collapse.
Well, no. That figure only applies if a power outage (affecting both the city power and the building's emergency power, so as to disable the building's tuned mass damper) occurs simultaneously with every occurrence of high winds. Or if the building's owners decide to just turn off the tuned mass damper for giggles, and leave it turned off for a decade and a half.
Far more interesting - and potentially scary - was the fact that even with the mass damper, the building would expect to see winds sufficient
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In other words, for every year Citicorp Center was standing, there was about a 1-in-16 chance that it would collapse.
Well, no. That figure only applies if a power outage (affecting both the city power and the building's emergency power, so as to disable the building's tuned mass damper) occurs simultaneously with every occurrence of high winds. Or if the building's owners decide to just turn off the tuned mass damper for giggles, and leave it turned off for a decade and a half.
...
True, but even restating is as "Every 16 years the building was in a state where if the power failed, it would collapse" is pretty serious especially since these events are always in the middle of severe storms.
Challenger and Fukushima (Score:3, Insightful)
“How the hell can you ignore this?” - Robert Boisjoly, Thiokol booster rocket engineer for the Challenger
http://www.nytimes.com/2012/02... [nytimes.com]
“They completely ignored me in order to save Tepco money,” - Kunihiko Shimazaki, a retired professor of seismology at the University of Tokyo
http://www.nytimes.com/2012/03... [nytimes.com]\
For things that are too big to fail and would cause major disaster, the corporate shield must be removed and executive management must be held directly responsible. Financially and criminally.
never cross the unions (Score:2)
Makes me think of the Hancock Tower in Boston (Score:2)
Math (Score:2)
LeMessurier calculated that a storm powerful enough to take out the building hit New York every 16 years." In other words, for every year Citicorp Center was standing, there was about a 1-in-16 chance that it would collapse."
Umm, actually that would be p=1-(1/E)^(1/16)=0.0605869 (about 1-in-16.5052).
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Actually no, the odds of collapse would be much lower, unless you are assuming that any storm capable of knocking down the building would automatically also cause a blackout that disabled the tuned mass damper that would otherwise allow it to survive. Without knowing the conditional probability of a blackout occurring during such a storm it's impossible to calculate the chances of a collapse.
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what? where the hell did you pull that from? why 1/e?
if a storm hit every two years, your method would give a probability of 0.393. what sense does that make?
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what? where the hell did you pull that from? why 1/e?
if a storm hit every two years, your method would give a probability of 0.393.
Right.
what sense does that make?
Imagine you're throwing a 100-sided dice 100 times in two years (i.e. 50 times a year). Then you statistically throw a particular number (say, 1) once every two years. The chance of throwing that number in one year (i.e. in 50 throws) is 1-(99/100)^50=0.395 (=the inverse of not throwing that number 50 times in a row). There you go. If you transition from discrete to continuous probabilities, the number of dice sides and throws approaches infinity, and lim_{x->infinity} (1-1/x)^x = 1/E.
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uh, sure, except these aren't independent trials. to clarify, the event of being in a storm now, and the event of being in a storm one minute from now are almost perfectly correlated. this means you can't use the product rule.
by contrast, the event of a storm happening this year vs. a storm happening next year are closer to independent exactly because the blocks are bigger (a storm on Dec. 31 will make a storm on Jan. 1 more likely, but apart from that...).
your 'improvement' rests on assumptions which are n
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Standard Engineering ethics case study (Score:4, Informative)
This case is one of the usual case studies that make up many Engineering Ethics courses (at least it was brought up in mine). The nice thing about this case is that in the end, it all worked out for the better, and is a good news story rather than a disaster.
The other typical case studies are the Therac 25 [wikipedia.org], Challenger Disaster [wikipedia.org], Hyatt Walkway Collapse [wikipedia.org] and in Canada the Quebec Bridge [wikipedia.org] collapse (which also lead to the creation of the Iron Ring [wikipedia.org].
There is a significant portion of the Engineering education that is dedicated to reminding prospective Engineers of their responsibilities to society, and the power they can potentially wield. Ethics is also a significant portion of the licensure to get one's professional designation.
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Precisely. I taught on this exact case study for three semesters while attached as a Teaching Assistant to my university's Engineering Ethics course, which had the guy who literally wrote the book on the subject teaching there.
One interesting tidbit left out in the summary is the fact that this wasn't necessarily so much an oversight on the architect or engineer's part, so much as it was an oversight in the regulations of the time. Back then, quartering winds were not required to be taken into account in th
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(e.g. the late Roger Boisjoly, who was the Morton Thiokol engineer that strongly warned of the O-ring failure and tried to postpone Challenger's launch)
I saw a documentary on that. What's sad is that despite all the good work he did to try and avert the disaster, when given a last chance to object on the conference call to NASA he remained silent.
Old story. (Score:2)
Read this when it was in the New Yorker in 1995. [smith.edu]
A clear lack of taste (Score:2)
I particularly like the part where LeMessurier, the structural engineer given most of the credit for this giant ugly glass-and-steel rectangle on stilts (with a *gasp* slanted roof, how exciting!) calls the Old Saint Peters Church [nyc-architecture.com] that it was built to accommodate “a crummy old building the lowest point in Victorian architecture."
If that's the sentiment of the people designing our buildings, then it's no wonder that US cities are such colossal eyesores.
I'm no engineer, but (Score:2)
...at least according to the summary, wasn't this a little histrionic?
"Without the tuned mass damper, LeMessurier calculated that a storm powerful enough to take out the building hit New York every 16 years." In other words, for every year Citicorp Center was standing, there was about a 1-in-16 chance that it would collapse."
No, the "lack of a tuned mass damper" was already presupposing that the POWER was out. The power doesn't go out in NYC all that often, and even if it did...Would it have been impossibl
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Since this happened in the 70s some of us have actually heard about this plenty of times by now. =D
Re:Dupe (Score:5, Informative)
Damninteresting:
Diane Hartley contacted him to ask some technical questions about the design, which he was delighted to address. Hartley's professor had expressed doubts regarding the strength of a stilted skyscraper where the support columns were not on the corners. ... But the conversation got him thinking, and he started doing some calculations on just how much diagonal wind the structure could withstand. He was particularly interested in the effects of an engineering change made during construction which had seemed benign at the time: numerous joints were secured with bolts rather than welds.
Slate:
According to LeMessurier, in 1978 an undergraduate architecture student contacted him with a bold claim about LeMessurier’s building: that Citicorp Center could blow over in the wind. The student (who has since been lost to history) was studying Citicorp Center and had found that the building was particularly vulnerable to quartering winds (winds that strike the building at its corners). Normally, buildings are strongest at their corners, and it’s the perpendicular winds (winds that strike the building at its faces) that cause the greatest strain. But this was not a normal building. LeMessurier had accounted for the perpendicular winds, but not the quartering winds. He checked the math and found that the student was right. He compared what velocity winds the building could withstand with weather data and found that a storm strong enough to topple Citicorp Center hits New York City every 55 years. But that’s only if the tuned mass damper, which keeps the building stable, is running. LeMessurier realized that a major storm could cause a blackout and render the tuned mass damper inoperable. Without the tuned mass damper, LeMessurier calculated that a storm powerful enough to take out the building his New York every 16 years.
people.duke.edu:
The student wondered about the columns--there are four--that held the building up. According to his professor, LeMessurier had put them in the wrong place. "I was very nice to this young man," LeMessurier recalls. "But I said, 'Listen, I want you to tell your teacher that he doesn't know what the hell he's talking about, because he doesn't know the problem that had to be solved.' I promised to call back after my meeting and explain the whole thing." When LeMessurier called the student back, he related this with the pride of a master builder and the elaborate patience of a pedagogue; he, too, taught a structural-engineering class, to architecture students at Harvard. Then he explained how the peculiar geometry of the building, far from constituting a mistake, put the columns in the strongest position to resist what sailors call quartering winds--those which come from a diagonal and, by flowing across two sides of a building at once, increase the forces on both. For further enlightenment on the matter, he referred the student to a technical article written by LeMessurier's partner in New York, an engineer named Stanley Goldstein. LeMessurier recalls, "I gave him a lot of information, and I said, 'Now you really have something on your professor, because you can explain all of this to him yourself.'"
...
LeMessurier had long since established the strength of those braces in perpendicular winds--the only calculation required by New York City's building code. Now, in the spirit of intellectual play, he wanted to see if they were just as strong in winds hitting from forty-five degrees. His new calculations surprised him. In four of the eight chevrons in each tier, a quartering wind increased the strain by forty per cent. Under normal circumstances, the wind braces would have absorbed the extra load without so much as a tremor. But the circumstances were not normal. A few weeks before, during a meeting in his office, LeMessurier had learned of a crucial change in the way the braces were joined.
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Only the New Yorker story where LeMessurier supposedly talked directly to a male engineering student directly conflicts with the others. Maybe the New Yorker made that part up for color.
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An engineering student named Diane Hartley contacted him to ask some technical questions about the design, which he was delighted to address. Hartley's professor had expressed doubts regarding the strength of a stilted skyscraper where the support columns were not on the corners. "Listen, I want you to tell your teacher that he doesn't know what the hell he's talking about," LeMessurier told Hartley, "because he doesn't know the problem that had to be solved."
then later giving credit to Hartley:
Diane Hartley--the engineering student who had originally identified the error and alerted LeMessurier--almost certainly saved hundreds of lives and millions of dollars with her sharp eye and intrepid action.
I
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You might niot have parsed the summary correctly. LeMessurier, an engineer, did the structural design. An undergraduate architecture student caught the error.
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A "simplification of design" that would certainly kill a lot of people counts as an error, no?
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it was wilful cutting costs by simplifying the design by the contractor.
Was the building not built per the drawing? If this is the case, the building inspectors should have caught it and it was their error. If LeMessurier failed to specify structural details accurately or allowed the contractor to pressure him into an inadequate design, it was his (the engineer's) error.
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That has happened quite often here in the US. (Score:5, Interesting)
I wish I could find an appropriate citation - the example I recall was a bridge which needed to be torn apart and repaired because of the use of a different type of bolt securing the framework. The replacement had similar tensile and shearing strength, but several years later the bolts started failing at a much higher than expected rate, requiring the bridge to be retrofitted with the original fastener. It turned out that the new bolt (while actually stronger in some respects than originally required) was subject to vibration stresses. The review permitting the substitution focused on the strength of the bolt required for the application, but the data showing that the bolt was subject to metal fatigue if subjected to extended vibration wasn't available or considered at that time.
Changes such as these are actually not too rare; I suspect that in most cases, the substitutions work exactly as expected, but when we're discussing infrastructure elements of this scope a single failure is not merely troublesome but often catastrophic.
Kansas City Hyatt Regency Skywalk (Score:5, Interesting)
I've heard news reporting before on this subject. The way it goes is this: the architect submits his designs, which are subject to review. Once the green light's given, construction begins. Now, engineers on the project notice a way that they can cut costs or construction time, or somebody requests a modification to the original design (perhaps to add a restroom or breakroom, perhaps to add or remove a wall or subdivide a floor differently). ...
I wish I could find an appropriate citation ...
The Kansas City Hyatt Regency Skywalk disaster [wikipedia.org], 17 July 17 1981, is an excellent case study. Before the collapse of the WTC South Tower it was the deadiest structural collapse in U.S. histories (dam failures are another story entirely). Until 9-11 the CitiCorp Center was well placed to beat it.
In the Hyatt Regency case the design of the double skywalk was changed during constructution, replacing a continuous steel rod that supported both skywalks with two rods, one from the roof to the upper skywalk, and one from the upper skywalk to the lower. Problem was the design had the continuous rod bearing the full load, the change made the upper skywalk bear the load of the lower skywalk (and the people on it) when it was only supposed to be holding up people on the upper skywalk and nothing else.
As built the skywalk was so overloaded that eventual collapse was possible even without any load. Naturally when it did fail it would be at a time when both the upper and lower skywalks were heavily loaded with people, and the floor crowded below. 114 died, 216 were injured - many seriously.
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n this case it failed when there was a celebration in progress. The ground floor level was crammed with dancing people and the crowd had overflowed onto the skywalks. Pogo dancing was current at the time, and apparently the failure occurred when people on the bridges, synchronized by the live music, were jumping up and down in unison. (It's the inverse of the way soldiers are required NOT to march in step when crossing a bridge.)
Thus you can expect such structures to go when there are a lot of people aro
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...Pogo dancing was current at the time, and apparently the failure occurred when people on the bridges, synchronized by the live music, were jumping up and down in unison....
Nope. You are imagining this. You can see the actual videotape of the dancing as the dance party and the collapse as it happened here [youtube.com]. Those codgers were not "pogo dancing".
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I agree. My takeaway point is . . . (Score:3)
They treated the walkways as a 'black box' condition. It didn't matter to the buildings being connected if it was done using one support rod or two, from the standpoint of t
Re:That has happened quite often here in the US. (Score:5, Informative)
structural engineer here. couldn't let the idea that an architect is responsible for the primary structure of a building slip by.......
Traditionally, an architect's remit is in with the form and function of a structure in accordance with a client's wishes (+ understanding of basic building regs on fire, acoustics, M&E strategies etc);
it is the structural engineer's job consider and design the physics of a building in meeting the architects intended form.
Depending on the nature of the contract, a main contractor (read builders, rarely design engineers) may influence the design of the building....to make savings usually, or solving buildability issues etc. contractors typically have temporary works engineers, and for a big job may employ a checking engineer to encourage savings etc.
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Re:Cost-saving is the key here (Score:5, Insightful)
No. They had an idea to save time and money (to use bolts instead of welds for certain braces), and they submitted it to LeMessurier's firm, which approved it after some analysis, which turned out to have been done wrong. It wasn't the contractor's fault, they didn't have the expertise to evaluate whether the change would work or not, and they properly submitted it to those who did.
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No, still a design flaw. This risk would not exist if they had used a more traditional design. If that church made it impossible to do so, they should have bought the church and demolished it, or built elsewhere, instead of risking lives with that less secure design!
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