🤖 AI Summary
Overview
This episode unravels the gripping story of the Citicorp Center in Manhattan, a groundbreaking skyscraper that nearly collapsed due to a critical design flaw. It explores the engineering challenges, the discovery of the flaw, the ethical dilemma faced by its structural engineer, and the extraordinary efforts to avert disaster—all while keeping the public in the dark.
Notable Quotes
- Here I am, the only man in the world who knew this. This thing is in real trouble.
– Bill LeMessurier, on realizing the building's fatal flaw.
- If you see something that is a social risk—good heavens, this thing would kill thousands—you must do something.
– Bill LeMessurier, on the responsibility of engineers.
- I mixed a martini for myself and dialed The New York Times. It was one minute past six, and they had just gone on strike.
– Bill LeMessurier, on narrowly avoiding media exposure during the crisis.
🏗️ The Innovative Design of Citicorp Center
- The Citicorp Center was built on stilts to accommodate St. Peter’s Church, which required two-thirds of its space to remain open.
- Structural engineer Bill LeMessurier designed a unique chevron bracing system to transfer gravity and wind loads to the building’s mid-face stilts.
- A tuned mass damper (TMD), a 400-ton concrete block, was installed to reduce the building’s sway—a first for skyscrapers.
🌬️ The Discovery of a Fatal Flaw
- In 1978, LeMessurier learned that the chevron braces were bolted instead of welded, weakening the structure.
- A student’s inquiry about quartering winds (diagonal wind forces) prompted LeMessurier to recalculate the building’s stability.
- The analysis revealed that under quartering winds, the building had a 1 in 16 chance of collapse in any given year, especially if the TMD lost power.
⚖️ The Ethical Dilemma and Crisis Response
- LeMessurier faced a moral crossroads: stay silent and risk catastrophe or confess and risk professional ruin.
- He chose to act, initiating secret overnight repairs (Project Serene) to weld steel plates onto over 200 joints.
- A 10-block evacuation plan was prepared in case of a hurricane, but the public and office workers were kept unaware to avoid panic.
🌪️ Hurricane Ella and a Narrow Escape
- As repairs were underway, Hurricane Ella threatened New York with winds strong enough to topple the building.
- The storm veered off course at the last moment, sparing the city and allowing repairs to be completed.
🌍 Legacy and Lessons in Engineering Ethics
- The Citicorp crisis became a landmark case in engineering ethics, emphasizing the responsibility to act on potential risks.
- The building’s TMD inspired its adoption in skyscrapers worldwide, including Taipei 101.
- Despite the heroic resolution, the incident remains a sensitive topic, with Citicorp and LeMessurier’s firm reluctant to discuss it publicly.
AI-generated content may not be accurate or complete and should not be relied upon as a sole source of truth.
📋 Video Description
How a single phone call from a student helped uncover a flaw that nearly toppled Citicorp. Get an exclusive 15% discount on Saily data plans! Use code veritasium at checkout. Download Saily app or go to https://saily.com/veritasium
If you’re looking for a molecular modeling kit, try Snatoms, a kit I invented where the atoms snap together magnetically - https://ve42.co/SnatomsV
Note: From construction images of Citicorp, sharp-eyed viewers might see that the mid-V columns are still there. Those columns help prevent buckling of the diagonal and the weight of people on the floor above, but do not take the majority of the gravity load. So we left them out of our diagram to clearly explain the load paths. See page 70 of this source for more details - https://drive.google.com/file/d/1ODFo66-_V7Y9vKANbj53mQ0z20RZ2Uai/view
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0:00 Why is the citicorp building on stilts?
4:44 How wind load works
7:49 Tuned Mass Dampers
11:17 The Anonymous Student
14:00 Quartering Winds
18:38 What were the odds of collapse?
20:31 How was the citicorp building fixed?
25:40 Hurricane Ella
27:00 TMDs Take Over The World
28:36 Conspiracies and Cover Ups
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A big thank you for the incredible people without whom we couldn't have done this! 🖤
To Michael Greenburg, author of The Great Miscalculation, for his insights that really brought the story and its context to life. He gave us a pre-copy of his upcoming book, and it is fantastic: https://ve42.co/Miscalc
To Eric Hines for all his help with the technical details, fact-checking, and making sure we got the engineering right.
To Michael J. Vardaro for helping us uncover the details of the story and the resources he provided.
To Brock Hedegaard for helping us dive deep into the Citicorp structural analysis. Learn the fundamentals of structural analysis on his brilliant channel, @StructuresProfH, and see here for his analysis of the citicorp center; https://www.youtube.com/watch?v=lE_DspFE2ZM
To Michele Barbato from UC Davis for his inputs on the load calculations.
https://faculty.engineering.ucdavis.edu/barbato/
Matt from @mvvvc for talking us through his wind load analysis.
To Prof. Chris Letchford who helped us understand the impact of wind on Citicorp's structure.
To DongHun Yeo from NIST for discussing his research about wind effects on buildings similar to citicorp: https://ve42.co/WindLoad
Finally, to Team Columbia —who built the epic TMD and ran wind tunnel experiments that made this story come alive.
This includes the folks at the Mechanical Engineering Teaching Laboratory
(Follow all the cool stuff they’re doing: @mechcu, @columbiaengineering or visit https://teachinglab.me/)
Amanda Lombardo, Manager of Instructional Laboratories
Daniela Durón García, Assistant Manager of Instructional Laboratories
Jorge Casas, Machinist
And the amazing seniors from the Columbia Space Initiative:
(Support their awesome work here: columbiaspace.org/support-us/, Follow them: @columbiaspaceinitiative)
Michael Sheehan
Claudio Solano
Jessica Bolar
Kathryn Lampo
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References:
Michael M. Greenburg. The Great Miscalculation via. nyupress.org - https://ve42.co/Miscalc
Joe Morgenstern. The Fifty-Nine-Story Crisis via. The New Yorker - https://ve42.co/59Crisis
National Academy of Engineering. William LeMessurier-The Fifty-Nine-Story Crisis: A Lesson in Professional Behavior - https://www.youtube.com/watch?v=um-7IlAdAtg
Diane Lee Hartley. Implications of a Major Urban Office Complex: The Scientific, Social and Symbolic Meanings of Citicorp Center via. princeton.edu - https://ve42.co/CitiSymbol
Caroline Whitbeck. William LeMessurier: The Fifty-Nine-Story Crisis, A Lesson in Professional
Addition References here: https://ve42.co/citiref
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Special thanks to our Patreon supporters:
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Written and Directed by Sulli Yost
Edited by Trenton Oliver
Additional Editing by Axel Oliver, James Horsley and Peter Nelson
3D Modeling by Maydelis Anaya Romero
Animation by Mike Radjabov, Andrew Neet, Fabio Albertelli, Jakub Misiek, and Emma Wright
Illustration by Jakub Misiek, Maria Gusakovich and Cainejan Esperanza
Filmed by Sulli Yost, Henry van Dyck, Andrew Abballe, Derek Muller
Produced by Sulli Yost, Derek Muller, Casper Mebius, Zoe Heron, Rob Beasley Spence and Tori Brittain
Additional research by Geeta Thakur
Thumbnail contributions by Ren Hurley and Ben Powell
Additional video/photos supplied by Getty Images, Pond5, Axiom Images and Storyblocks
Music from Epidemic Sound