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The Design Flaw That Almost Wiped Out an NYC Skyscraper
- bayouborne 13y agoThis has always been a fascinating story - I can't believe Slate's just now discovering it. There's a much longer, more detailed account somewhere.
- marklabedz 13y agoThere's a pretty good one in the New Yorker (paywall, though I've seen scans of the article floating around): http://www.newyorker.com/archive/1995/05/29/1995_05_29_045_TNY_CARDS_000370292 http://www.newyorker.com/archive/1995/05/29/1995_05_29_045_T...
- mkarr 13y agoA full text of the article can be found here: http://people.duke.edu/~hpgavin/cee421/citicorp1.htm http://people.duke.edu/~hpgavin/cee421/citicorp1.htm This is much more comprehensive and interesting than the source linked in OP and elsewhere. I discovered this a few years back while doing some reading for an ethics class, and was fascinated by it.
- millstone 13y agoIt was dramatized in the "Structural Corruption" episode of NUMB3RS, though they added in a suicide / murder element.
- philgr 13y agoThis podcast is fantastical.
- gkop 13y agoThe original source is at http://99percentinvisible.org/episode/structural-integrity/ http://99percentinvisible.org/episode/structural-integrity/
- tcas 13y agoAnother good source is: http://www.damninteresting.com/a-potentially-disastrous-design-error/ http://www.damninteresting.com/a-potentially-disastrous-desi... Apparently it costed $8 million to repair.
- matthewmcg 13y agoJoe Morgenstern's 1995 _New Yorker_ article "The Fifty-Nine Story Crisis" is also an excellent telling of this story. http://people.duke.edu/~hpgavin/cee421/citicorp1.htm http://people.duke.edu/~hpgavin/cee421/citicorp1.htm
- lexcorvus 13y agoUse asterisks for emphasis, like this: New Yorker
- paul_f 13y agoMaybe this is a dumb question, but why couldn't they have found another location for the new church? Why did it have to be on the same plot as the Citicorp building?
- mimiflynn 13y agoIt was an old church. The chuch allowed the Citicorp building to be built around it, which ended up being above it. EDIT: spelling
- paul_f 13y agoThey tore down the old church and built a new, modern one on the site. This is what makes this whole story so absurd to me.
- Jtsummers 13y agoChurches are parts of their community. Moving them isn't always an option. In NYC the Catholic churches are particularly tied to their neighborhoods, historically, so there really aren't many places to move to and still provide a place for that same community.
- mapt 13y agoThe church could have been established as floors 2 through 10 (or indeed, floors 70 through 80) of a conventional rectangular box skyscraper, instead of building what is effectively a large shack at ground level, and designing a risky skyscraper without corner supports because one of those corners would pierce the shack. http://www.saintpeters.org/your-church/the-building/ http://www.saintpeters.org/your-church/the-building/
- jeffdavis 13y agoThat makes logical sense in the same way as turning central park into a "park skyscraper" makes logical sense.
- morley 13y agoMaybe this is covered in the New Yorker article marklabedz linked to, but I'm curious what their solution to quartering winds was. (They mention welding as a part of the solution but don't go into more detail.)
- morley 13y agoI found the answer in the Wikipedia article[1]: > For the next three months, a construction crew welded two-inch-thick steel plates over each of the skyscraper's 200 bolted joints during the night, after each work day, almost unknown to the general public. [1] http://en.wikipedia.org/wiki/Citigroup_Center http://en.wikipedia.org/wiki/Citigroup_Center
- dm2 13y agoReminds me of: http://en.wikipedia.org/wiki/File:CCTV_Beijing_April_2008.jpg http://en.wikipedia.org/wiki/File:CCTV_Beijing_April_2008.jp... I'm sure the CCTV building is safe, but I get a small panic attack just thinking about walking or jumping up and down in that overhanging corner of the building. How did they fix it? The article says they "welded" but doesn't say what was added to increase the strength of the building.
- salem 13y agoThe documentary is interesting. Some of the steel structure held together by bolts were welded together with some extra steel braces.
- sscalia 13y agoMore interesting reading around "Tuned Mass Dampers" http://en.wikipedia.org/wiki/Tuned_mass_damper http://en.wikipedia.org/wiki/Tuned_mass_damper
- jwise0 13y agoThe first I had heard of a tuned mass damper was in the installation on Taipei 101. There's a good video of it moving that gives you an idea of just how colossal these things are: https://www.youtube.com/watch?v=NYSgd1XSZXc https://www.youtube.com/watch?v=NYSgd1XSZXc
- tapia 13y agoWhat I also find very interesting are the "tuned column liquid dampers", which applies the same idea of "tuning" the period of the liquid system to one period of the structure. They are found to be very effective in dissipating energy after seismic events or constant wind. I'm a civil engineering student (currently writing my thesis) and I just loved this systems when I learned from them.
- salem 13y agoThis fantastic validation for a person's undergraduate thesis. It's a real shame that she wasn't given proper credit at the time.
- wallflower 13y agoWhat this story leaves out is that the EVP of Citicorp at the time was a MIT-trained scientist (physical metallurgy). So when this crisis bubbled up - there was no hesitation in action since there was a scientist/engineer in top leadership who was able to communicate to the board the severity of the situation. "Together they flew to New York City to confront the executive officers of Citicorp with the dilemma. "I have a real problem for you, sir," LeMessurier said to Citicorp's executive vice-president, John S. Reed. The two men outlined the design flaw and described their proposed solution: to systematically reinforce all 200+ bolted joints by welding two-inch-thick steel plates over them." http://www.damninteresting.com/a-potentially-disastrous-design-error/ http://www.damninteresting.com/a-potentially-disastrous-desi... http://en.wikipedia.org/wiki/John_S._Reed http://en.wikipedia.org/wiki/John_S._Reed
- matt_trentini 13y agoSo I presume the bolts and added welded plates were actually stronger than the originally specified welded joins? In the interview with Bill LeMessurier it seemed the problem existed even with the original joins - the bolted joins just made the issue significantly worse...
- wallflower 13y agoYes, it is more akin to bridge construction. http://en.wikipedia.org/wiki/Gusset_plate http://en.wikipedia.org/wiki/Gusset_plate "The building now stands as one of the safest skyscrapers in New York City, able to withstand a 700-year[1] storm without the aid of the tuned mass damper." http://www.theaiatrust.com/whitepapers/ethics/study.php http://www.theaiatrust.com/whitepapers/ethics/study.php [1] Approximately 140mph gusts. http://civil.unm.edu/classes/content//CE%20491-002/ASCE%207-10.pdf#page=294 http://civil.unm.edu/classes/content//CE%20491-002/ASCE%207-...
- kchoudhu 13y agoThis must have been in the golden age before Citigroup was run by idiots.
- cmapes 13y agoThat was a great read, I usually HATE stories that come from Slate but this partially redeemed them in my mind.
- Timothee 13y agoOne point that this article doesn't mention but the video does (starting about here: http://www.youtube.com/watch?v=TZhgTewKhTQ#t=350 http://www.youtube.com/watch?v=TZhgTewKhTQ#t=350) is that the building wasn't built exactly as designed. In particular, the 8-story-high diagonal parts were done in multiple splices that were supposed to be welded together but ended up being bolted together. It sounds like it made things much worse.
- pat2man 13y agoThe fix was to rip the building apart and weld everything together.
- kevinchen 13y agoAccording to wallflower below, it was to weld thick steel plates to the joints. That's not the same as following the original design.
- jzwinck 13y agoThis reminds me of the 1981 Hyatt Regency walkway collapse [1]. The blueprints called for continuous suspension rods with walkways attached along their length. This would mean that the load on any single joint between rod and walkway would be limited to the load on one walkway. But as built, the rods were not continuous, rather they connected each walkway to the one below. This meant the load on the topmost rod-walkway joint was the aggregate of the load of all walkways hanging below it. The builders did not notify the designers of the change, and 114 people were killed as a result. [1] http://en.wikipedia.org/wiki/Hyatt_Regency_walkway_collapse http://en.wikipedia.org/wiki/Hyatt_Regency_walkway_collapse
- wiredfool 13y agoAnd not only that, instead of using a box section for the steel piece, they used two c sections welded together like this: []. A box section is strong, that built up section, not so much. The thing is, that design would have been a horrible pain to build as designed. It's a design failure. To build it, you'd need to slide a large steel section up two screws, following it by a nut up 30 feet. It needed to be redesigned by someone who knew more about fabrication and erection, and then checked closely to make sure that there weren't material changes in the performance.
- cratermoon 13y agoIf only software flaws in large commercial proprietary/closed source systems were subject this kind of discovery and mitigation before things break.
- CaveTech 13y agoThe flaws in computer software cause damage because people are quick to exploit them. Mother nature is not quite as driven by money and corruption.
- rdl 13y agoA terrifying thing is that one could hack a building management system or the controls for the tuned mass damper specifically and essentially "self destruct" the building, or at least make it much more vulnerable to mother nature.
- rajacombinator 13y agoThat's really scummy that the student did not receive appropriate credit at the time or after. That should have been a career maker story.
- malcolmwhy 13y agoThe 99% Invisible story covers that a bit if you're interested. http://99percentinvisible.org/episode/structural-integrity/ http://99percentinvisible.org/episode/structural-integrity/
- sea6ear 13y agoI think there was an episode of Numb3rs that was based on this. Maybe Season 1 episode 4 (Structural Corruption)? It was fun to see the premise turn up in the show and go, oh, I think I know where they got this idea from.
- sitkack 13y ago"But what I found out at that meeting were that all factors of safety were gone." Many catastrophic "accidents", and I use quotes because they could have been averted had people not cut corners w/o knowing the full context. * Chernobyl (after hours test by an untrained crew with an inverted fail safe design) * http://en.wikipedia.org/wiki/Hyatt_Regency_walkway_collapse (design change in the field, very similar to the citicorp flaw) * 3 Mile Island (indicator that triggered on switch rather than valve) * Fukashima (cost cutting on seawall and generator snorkels) * Ariane-5 (code reuse, dead code) If you want to look at good engineering, look at the Brooklyn Bridge[5] and the DC-3[6]. Too many people don't design with proper safety factors. You build it, you test it, you test it till it fails and you understand those failures. I would trust another citicorp wouldn't happen because we can do realistic wind model, we can do an earthquake model, an anything model. Maybe we can get to a safety factor of 1 when everything is automated, when everyone has an off-site backup of their own brain but until then. Safety factor 6. [5] http://www.asce.org/People-and-Projects/Projects/Landmarks/Brooklyn-Bridge/ http://www.asce.org/People-and-Projects/Projects/Landmarks/B... [6] http://en.wikipedia.org/wiki/Douglas_DC-3 http://en.wikipedia.org/wiki/Douglas_DC-3
- sitkack 13y agoThis is fascinating, http://www.onlineethics.org/cms/24528.aspx http://www.onlineethics.org/cms/24528.aspx It also reminds me of the Mars Climate Orbiter. http://en.wikipedia.org/wiki/Mars_Climate_Orbiter http://en.wikipedia.org/wiki/Mars_Climate_Orbiter
- darkmighty 13y agoSafety factors also exist because we don't know what we don't know. Models sometimes break down unexpectedly, so a factor >1 is sort of a "meta safety factor 1", taking into account that our models/people somewhat predictably fail.
- hrktb 13y agoAnother direction would be to build by default with as much margins as realistic. The original design with the welded joints would have allowed the building to withstand the corner winds, but it was replaced by bolts because builders thought it was overkill. Perhaps the consensus (or law?) should be to build with at least 2-3 times the calculated resistance, with only some justified exceptions. Buildings would cost way more, but Intuitively it wouldn't be a bad thing (they would last longer and they would a bit less of a "mine's bigger" attitude)
- ot 13y agoReminded me of the design flaw of the Millennium Bridge in London, where the engineers accounted for all resonance modes but one, the one that can be caused by pedestrians: > Resonant vibrational modes due to vertical loads (such as trains, traffic, pedestrians) and wind loads are well understood in bridge design. In the case of the Millennium Bridge, because the lateral motion caused the pedestrians loading the bridge to directly participate with the bridge, the vibrational modes had not been anticipated by the designers. The crucial point is that when the bridge lurches to one side, the pedestrians must adjust to keep from falling over, and they all do this at exactly the same time. http://en.wikipedia.org/wiki/Millennium_Bridge_(London) http://en.wikipedia.org/wiki/Millennium_Bridge_(London)
- cantbecool 13y agoThere was a similar issue with pedestrian ramps at Lincon Financial Field in Philadelphia, where the Eagles play. http://articles.philly.com/2007-01-14/news/25221645_1_ramps-engineering-problem-london-bridge http://articles.philly.com/2007-01-14/news/25221645_1_ramps-...
- abduhl 13y agoAccounting for "all resonance modes" is physically impossible as there are an infinitely many number of resonance modes. It's more precise to say "accounted for most dominant resonance modes".
- sp332 13y ago"Accounting for" means they made sure it was strong enough for the expected loads.
- happyscrappy 13y agoThe first Tuned Mass Damper was in the John Hancock Tower. http://en.wikipedia.org/wiki/John_Hancock_Tower http://en.wikipedia.org/wiki/John_Hancock_Tower From an engineering standpoint that is a pretty depressing read.
- nashashmi 13y agoThis sort of story never gets old.
- drewsears 13y agoDRTA, but I listened to the podcast. In it, they say that if the Citicorp tower fell, it would topple nearby skyscrapers like dominoes. Out of morbid curiosity, what's the worst case scenario for something like this? Let's assume terrorists could detonate a bomb large enough to knock over any one skyscraper in the world. Where should they put it to maximize the chain reaction of destruction?
- billmalarky 13y agoI think most skyscrapers fall straight down under the load rather than topple. Similar to what happened to the WTC towers. Not that I have any credibility in this area, but according to that documentary people seemed especially concerned that this particular building would topple instead of collapse straight down.
- stillsut 13y agoA bug that would make even Heartbleed blush.
- stillsut 13y agoI'm curious: since this flaw was pointed out in 1977, has NYC had such winds? How many times? Would Sandy have done it?
- n6mac41717 13y agoI wish the author had referenced "Why Buildings Fall Down," the book that first made me aware of the Citicorp Building problem: http://www.amazon.com/Why-Buildings-Fall-Down-Structures/dp/039331152X http://www.amazon.com/Why-Buildings-Fall-Down-Structures/dp/...
- smoorman1024 13y agoYeah. I work in this building and it terrifies me everyday. It does sway in the wind. You can hear the walls creek when the winds are high. Besides the complete fear that is instilled in my heart because this building was built in a flawed way it also has an absolute terrible elevator design. The elevators are double-deckers. So the elevator actually has two rooms that move together. In the morning if you want to go to an even floor you have to enter from the basement level and if you want to go to an odd floor you have to enter from the lobby level. This results in the weird sensation that if you are going to a higher floor the elevators often stop but the doors do not open. Probably related to the weird design the elevators break down often and with or without an elevator set out of commission there are high queue times during peak hours. This is a building that could REALLY benefit from an elevator call system where you enter a floor and it assigns you which elevator to get into to. Why they haven't installed a relatively simple fix like this is beyond me. My final gripe about this building is its sheer ugliness IMHO. The steel facade pegs it as one of those buildings that was built in a particularly time. It's not timeless like the Empire State Building or perpetually modern like the Willis Tower or One World Trade center. I guess its only redeeming factor is the very nice public plaza it has both inside and outside, its direct access to the E and 6 trains (super convenient for me), and the fact that it has not fallen down yet.