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The Citigroup Center in Midtown Manhattan is also known by its address, 601 Lexington Avenue, at which it’s been standing for 47 years, longer than the median New Yorker has been alive. Though still a fairly handsome building, in a seventies-corporate sort of way, it now pops out only mildly on the skyline. At street level, though, the building continues to turn heads, placed as it is on a series of stilt-looking columns placed not at the corners, but in the middle of the walls. A visitor with no knowledge of structural engineering passing the Citigroup Center for the first time may wonder why it doesn’t fall down — which, for a few months in 1978, was a genuinely serious concern.
This story, told with a special explanatory vividness in the new Veritasium video above, usually begins with a phone call. An unidentified architecture student got ahold of William LeMessurier, the structural engineer of the Citicorp Center, as it was then known, to relay concerns he’d heard a professor express about the still-new skyscraper’s ability to withstand “quartering winds,” which blow diagonally at its corners. LeMessurier took the time to walk the student through the elements of his then-groundbreaking lightweight design, which included chevron-shaped braces that directed tension loads down to the columns and a 400-ton concrete tuned mass damper (or “great block of cheese,” as it got to be called) meant to counteract oscillation movements.
LeMessurier was a proud professional, but his professionalism outweighed his pride. When he went back to check the Citicorp Center’s plans, he received an unpleasant surprise: the construction company had swapped out the welded joints in those chevron braces for cheaper bolted ones. His office had approved the change, which made sense at the time, and had also taken into account only perpendicular winds, not quartering winds, as was then standard industry practice. Performing the relevant calculations himself, he determined that the whole tower could be brought down — and much in the surrounding area destroyed with it — by the kind of winds that have a one-in-sixteen chance of blowing in any given year.
It didn’t take LeMessurier long to realize that he had no choice but to reveal what he’d discovered to Citicorp, whose leadership cooperated with the accelerated, semi-clandestine project of shoring up their gleaming emblem’s structural joints by night. The work could hardly fail to draw the attention of the New York press, of course, but it received scant coverage thanks to an impeccably timed newspaper strike, and on its completion made the skyscraper perhaps the safest in the city. In fact, the story of the Citicorp Center disaster that wasn’t only came out publicly in a 1995 New Yorker piece by Joseph Morgenstern, which made LeMessurier a kind of hero among structural engineers. But it was the students who’d identified the building’s faults, not just one but two of whom came forward thereafter, who personified the life-saving power of asking the right questions.
Related content:
How This Chicago Skyscraper Barely Touches the Ground
New York’s Lost Skyscraper: The Rise and Fall of the Singer Tower
Based in Seoul, Colin Marshall writes and broadcasts on cities, language, and culture. His projects include the Substack newsletter Books on Cities and the book The Stateless City: a Walk through 21st-Century Los Angeles. Follow him on the social network formerly known as Twitter at @colinmarshall.
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