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.""
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/
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.
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.
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]
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.
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:
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.
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'
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.