A skyscraper that could have toppled over in the wind (1995)

https://www.newyorker.com/magazine/1995/05/29/the-fifty-nine-story-crisis-citicorp-center

by prismatic • 3 years ago

110 21 3 years ago

mherdeg• 3 years ago

Wow, the last time I read about this, I had not seen

* the 2019 update that someone re-evaluated the risks and thinks the retrofit might not have been necessary after all ( https://www.nist.gov/publications/wind-effects-tall-building... )

* the identification of the person who called LeMessurier in 1978 and whose questions made him redo the math (whose name is not listed in the New Yorker article) as Lee DeCarolis ( https://onlineethics.org/node/41606 )

In the version of the story I read, Diane Hartley flagged the risk to the engineer by writing a whole thesis about the building (see e.g. writeup at https://www.lemessurier.com/sites/default/files/publications... and https://onlineethics.org/cases/engineers-and-scientists-beha... ).

It's interesting how, the closer you look, reality grows more complex than the stories we tell about it.

velcrovan• 3 years ago

In 2014, the 99% Invisible podcast did an episode on this story. Not only did they credit Diane Hartley and her thesis, but they interviewed her about it: https://99percentinvisible.org/episode/structural-integrity/

intrasight2• 3 years ago

So the New Yorker article is embellished - as it recounts two conversations he had with a "young man" - when it fact it was a young woman and it was one of his associates and not LeMessurier who had those conversations.

edit:Wikipedia says that Lee DeCarolis came forward in 2022 to identify himself as the person who had spoken to LeMessurier. His story is here: https://onlineethics.org/node/41606

JeremyNT• 3 years ago

Link to said wikipedia story [0], which includes a lot of context and subsequent developments that are missing from the OP.

[0] https://en.wikipedia.org/wiki/Citicorp_Center_engineering_cr...

m463• 3 years ago

Impressive engineering - not the tech, the being a good engineer part.

repelsteeltje2• 3 years ago

(Sorry to be bit of a skunk at the picnic, but...)

I'm sure someone payed for the adjustments deemed necessary. And this probably wasn't the engineer's pocket money.

Zooming out, many/most/all larger projects have budget overruns. The root cause is usually that politically the plan is not viable unless it's pitched below a realistic estimate.

This is often where "clever engineering" comes into the picture, but also where risks are taken that are responsible for budget overruns (or physical disasters when undressed) are rooted. I don't know enough about this project to allege that this is what was going on here, but it kinda fits the picture:

1. Try something novel (aluminum construction, unusual foundation)

2. Start (or even finish) construction; ie.: sunk cost fallacy

3. "Discover" potential issue with significant budgetary impact

psd1• 3 years ago

The structural members in question were steel, not aluminium.

The original costings were done assuming welded joints. It was a contractor who cavilled that expense, and the change to bolted joints was done without notice to the lead engineer.

What you describe does happen, I've seen it in the field of software; but it's not the issue described in TFA.

fiksie• 3 years ago

https://archive.ph/BC2Ix

conqueso• 3 years ago

Great story, and LeMessurier is certainly deserving of praise. I'm curious about his initial mistake. The article mentions that he placed the pillars at the middle edges, as opposed to corners, because this is beter for resisting the quarterly winds. So he clearly knew they were a thing. Why then did he not do the calculations for how they would effect the chevon braces until the call from the student? That seems like a pretty huge lack of oversight. Was it pride? The moment of inspiration is described romantically, sprawling designs on the back of a napkin and such, and he was disappointed that the chevrons would be hidden behind the aluminum skin/facade - consoling himself with the thought "It'd be there for God to see".

The article describes the whole situation as a perfect storm of sorts (no violation of building code, industry standard of bolts instead of welding, etc), but I can't get past how he didn't crunch the numbers for something that seems like it should go without saying.

wiredfool• 3 years ago

I'm not sure about the initial mistake either. But then again, this was a lesson in one of my structural classes, so you don't forget about that sort of issue.

Basically, I'm surprised that no one did the basic worst case sigma=MY/I for the side and quartering loads. The old grizzled supervising engineer generally will run through a bunch of ballpark estimates to see if the designer has actually checked all the worst case combinations.

I don't really buy the article's factor of safety discussion -- the factor of safety is for uncertainty, not blunders. I _might_ save you from a blunder, but that's not what it's for. It's for variation in material dimension, quality, and loading variation.

As for the bolts vs welding, There's definitely scope for changes at the shop drawing stage. When an engineering firm designs a building, they'll generally design a set of typical connections, but when the shop goes to build them, they have to take this column:floor beam connection and actually turn it into "cut this cope, drill here, ..." and they'll generally do the simplest, cheapest thing they can.

The engineers have to review the shop drawings, and if they don't have a good set of calcs for what the loads are in that particular bit, then they aren't going to necessarily see that this substitution of bolts won't work. (Note -- bolts can be just as good, and potentially better than welds, depending on what you're doing, how you're erecting, and the space you have available. Full Penetration welds are a pain, but they're the easiest way to specify a full strength join. But doing them on site, in the air, when you're putting the thing together is not something that you'd generally want to spec.)

There have been a significant number of historical disasters connected to shop drawing changes that the engineers didn't pick up. (e.g., the Hyatt Regency walkway collapse).

Also remember, this was done in the 70's, so they wouldn't have had Finite element models of the building where it's super easy to just run a couple more loads. Everything there would have been indeterminate elastic analysis, so it's not quick to run an accurate calculation if you're trying to find beam sizes.

sublinear• 3 years ago

[SERENE:] Special Engineering Review of Events Nobody Envisioned

continuitylimit• 3 years ago

To clear space for the new church, Hugh Stubbins and Bill LeMessurier (he pronounces his name “LeMeasure”) set

Sure, repeat his name n times and then ‘oh, by the way, it’s pronounced this way’. New Yorker does this all the time.

ubermonkey• 3 years ago

Honestly, one of my favorite pieces I've read in 30+ years of reading that magazine.

ycom13__• 3 years ago

I remember buying a Visual Basic 4 (Oreilly) book in the Barnes and Noble that was in that building

swader999• 3 years ago

That could have been a disaster. Those books has serious ballast.

teladee• 3 years ago

LeMessurier gave a talk on this at my school when I was studying architecture and structural engineering. The narrative very much follows the lines of this story, but also appreciate the added detail in the article. His voiceover definitely emphasized the complex ethical considerations of engineering more than the technical: Balancing the interests of insurance, client brand, public sentiment and trust, government relations, and his own professional and firm. Don't get me wrong, the technical details and Delta P effect were super interesting. But the professional practice aspects were what he wanted students to take away from it.

PhasmaFelis• 3 years ago

The young man, whose name has been lost in the swirl of subsequent events

Not a man. Her name was Diane Hartley.

gedy• 3 years ago

From another comment, it was, Lee DeCarolis: https://onlineethics.org/node/41606

intrasight2• 3 years ago

I was a consultant and worked for Citicorp in that tower in the mid 90s. Someone that I worked with told me this story. I don't remember anything else about the project, but I remember him explaining how they had gone in every night to weld plates across the joints.

A skyscraper that could have toppled over in the wind (1995)

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