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\n On October 12, 1977, banking giant Citicorp opened the tallest new skyscraper in New York City since the early 1930s. From afar, the 915-foot tower\u2019s distinctive sloped roof cut through the Midtown skyline like a scalpel. Close up, at ground level, its 59 floors appeared to levitate above a sunken public plaza, a generous architectural gesture to passersby.\n <\/p>\n
\n Citicorp Center\u2019s design was not universally loved. But the scale and ambition of its engineering were undeniable. In a review, the Times\u2019 architecture critic Paul Goldberger concluded<\/a> that the bank\u2019s new office, despite lacking in originality, would \u201cprobably give more pleasure to more New Yorkers than any other high\u2010rise building of the decade.\u201d\n <\/p>\n \n This prediction almost proved disastrously far from the truth. In fact, were it not for two college students who helped uncover a grave flaw in the building\u2019s engineering, Citicorp Center might have killed thousands of New Yorkers.\n <\/p>\n \n Citicorp Center still stands today, though it has since been renamed 601 Lexington. But in some ways, it is not the same structure it was in 1977.\n <\/p>\n \n Unbeknownst to its owners, occupants and even architects, the brand-new $128-million skyscraper was far more vulnerable to wind than previously believed. If a storm knocked out the power to its stabilizing device, a strong enough gust could make it collapse \u2014 and, on average, winds powerful enough to topple the building would occur in New York every 16 years. When the tower\u2019s engineer realized this in July 1978, hurricane season was already underway.\n <\/p>\n \n Within months, welders had carried out corrective work under the cover of darkness. A newspaper strike at the time meant knowledge of how close New York came to disaster remained largely hidden from the public until the mid-1990s.\n <\/p>\n \n Now, a comprehensive new book<\/a> on the crisis, \u201cThe Great Miscalculation: The Race to Save New York City\u2019s Citicorp Tower,\u201d delves into the human stories behind the events of 1978 \u2014 especially that of William LeMessurier, the structural engineer who blew the whistle on himself after being alerted to potential errors in his calculations.\n <\/p>\n \n \u201cYou have this one man who\u2019s put in the impossible position of discovering a terrible structural flaw with, at the time, the seventh tallest building in the world,\u201d the book\u2019s author, Michael M. Greenburg, said in a Zoom call. \u201cAnd he knows \u2014 at least in his own mind \u2014 that disclosure of this problem was going to ruin his career.\u201d\n <\/p>\n \n \u201cBut it was a real race against time,\u201d he added.\n <\/p>\n \n The tower\u2019s susceptibility to wind stemmed from its unusual design \u2014 which arose from a quirk of the Manhattan site on which it stood.\n <\/p>\n \n Citicorp\u2019s attempts to buy an entire midtown block for its new office had been thwarted by a lone holdout, St. Peter\u2019s Lutheran Church, which had occupied a corner of the proposed plot since the early 1900s. The church\u2019s pastor stubbornly resisted a sale that might force his congregation to relocate from the Midtown East neighborhood with which it had longstanding historical ties.\n <\/p>\n \n Instead, he negotiated an agreement: St Peter\u2019s would sell its neo-gothic building and, crucially, the air rights above it, on the condition that the bank build it a new church on the same corner. Under the agreement, this new church had to be distinct, physically and architecturally, from the skyscraper.\n <\/p>\n \n For the tower\u2019s architect Hugh Stubbins, who had never designed a New York high-rise, this posed a major quandary. He presented the problem to LeMessurier, a well-regarded structural engineer. Could the tower cantilever entirely over the corner housing the new church? Might they also free up space for a ground-level plaza?\n <\/p>\n \n Sketching on a napkin over lunch, LeMessurier began envisaging a unique answer to these questions: a skyscraper raised at not just one, but all four of its corners. In other words, a tower on stilts.\n <\/p>\n \n \u201cThere\u2019s nothing wrong with the building, nobody knows anything\u2019s wrong. There\u2019s no cracks; the building behaves itself perfectly. So, what do you do?\u201d\n <\/p>\n \n William LeMessurier, structural engineer\n <\/p>\n \n To achieve this, the building\u2019s four main support columns would run through the middle of the building\u2019s four faces, not its corners. This created an inherent instability that Greenburg compared to sitting on a chair with legs positioned at the middle of each side. \u201cNow put a 59-story building on top of those legs, and you begin to understand the complexity here,\u201d he added.\n <\/p>\n \n To compensate, LeMessurier developed a structural bracing system to act like an exoskeleton. A series of V-shaped chevrons, intersected by mast columns, effectively divided the building into six structurally independent segments. In each, the stress of wind and gravitational loads (those produced by the weight of the building itself) would be safely distributed, via trusses, to the columns, which would be drilled around 50 feet into the bedrock below.\n <\/p>\n \n To reduce movement during strong winds, LeMessurier also proposed installing a huge counterweight, known as a tuned mass damper, in the tower\u2019s upper floors. The stabilizing device featured a 400-ton concrete block on a film of oil that would slide in the opposite direction to the building\u2019s motion to counteract swaying.\n <\/p>\n \n Calculations were completed and models tested in wind tunnels. The project broke ground in 1974 and, when it opened three years later, it proved to be a \u201cspringboard\u201d for LeMessurier\u2019s career, Greenburg said.\n <\/p>\n \n \u201cHe\u2019s receiving awards, he\u2019s receiving notoriety, his business is exploding and things are just going well. And then, all of a sudden, he gets this telephone call.\u201d\n <\/p>\n \n Diane Hartley, a young engineering student, was starting her final year of undergraduate studies at Princeton University when Citicorp Center opened. She decided to feature the tower in her thesis on the history and impact of tall buildings.\n <\/p>\n \n LeMessurier\u2019s firm helpfully provided her with drawings, plans and figures. She visited the skyscraper to see its mass damper in action. But as Hartley modeled the tower\u2019s response to wind loads, something didn\u2019t add up.\n <\/p>\n \n According to her calculations, so-called \u201cquartering\u201d winds \u2014 gusts hitting the tower diagonally, thus exerting pressure on two sides of the building simultaneously \u2014 produced 42% more stress than perpendicular ones. Yet the numbers given to her failed to account for this.\n <\/p>\n \n \u201cIt never occurred to me that I had discovered something unusual,\u201d said Hartley, who is now aged 69, in a Zoom call. \u201cI was trying to figure out why I was wrong.\u201d\n <\/p>\n A short history of the world’s tallest buildings\n <\/p>\n A short history of the world’s tallest buildings<\/p>\n 4:24 <\/p>\n \n With her thesis already overdue, she rang LeMessurier\u2019s office and spoke with one of his project engineers, who \u201cconvinced\u201d the student that her \u201ccalculation was not correct, and the building was inherently stronger,\u201d said Hartley, who went on to have a successful real estate career. \u201cAnd at that point, being behind and waiting to graduate, I footnoted that conversation and turned the thesis in.\u201d\n <\/p>\n \n Hartley all but forgot about the interaction until the 1990s, when she saw a documentary about the tower saying that a mystery student had raised the alarm. It is not known for certain whether the engineer she spoke with passed her concerns on to LeMessurier. Nonetheless, she is widely credited with beginning a chain of events that led to the discovery of Citicorp Center\u2019s potentially fatal flaw.\n <\/p>\n \n However, another student, whose identity only came to light in 2011, is also thought to have contacted LeMessurier in 1978. Lee DeCarolis, then a freshman architecture student at the New Jersey Institute of Technology, has written<\/a> that he directly relayed his professor\u2019s concerns about the columns\u2019 placement to the engineer over the phone.\n <\/p>\n \n LeMessurier died in 2007, and inconsistencies in his recollections mean we may never know who alerted him to the miscalculation. In Greenburg\u2019s new book, the author diplomatically concludes that although neither student \u201cdefinitively claims to have exclusively influenced LeMessurier\u2019s actions, there is little doubt that each, to some degree, profoundly impacted what would happen next.\u201d\n <\/p>\n \n LeMessurier was both an engineer and a Harvard University educator. While preparing a college lecture about Citicorp Center, he reconsidered his wind load calculations in light of the student\u2019s \u2014 or both students\u2019 \u2014 concerns.\n <\/p>\n \n New York City\u2019s building codes did not explicitly address quartering winds. Nor was accounting for them universally practiced by structural engineering firms at the time. LeMessurier claimed that he had considered diagonal wind, yet it emerged that Citicorp Center\u2019s unconventional bracing system was more susceptible to it than his team had grasped.\n <\/p>\n \n \u201cAs LeMessurier is doing the calculations, he realizes what he calls some \u2018very peculiar behavior,\u2019\u201d explained Greenburg. He found that in a quartering wind, the wind stresses in half of the exoskeleton\u2019s bracing members would be zero. But in the remaining half, they would rise by 40%. a figure he had not accounted for. \u201cIt becomes a matter of great concern,\u201d the author added.\n <\/p>\n \n At that stage, LeMessurier still \u201cwasn\u2019t panicking,\u201d Greenburg said. The engineer believed the tower was, nonetheless, sufficiently strong. But upon speaking to his steel fabricator, he discovered that the tower\u2019s bracing had been bolted together, not welded \u2014 without his knowledge, he claimed \u2014 to save time and money. LeMessurier also realized his engineers had miscalculated how much stress would be offset by the building\u2019s weight during quartering winds.\n <\/p>\n \n Armed with this new information, he determined that every splice that connected parts of the chevron bracing system should have been joined with 14 bolts. Yet each splice had only been fitted with four bolts.\n <\/p>\n \n \u201cThis thing is in real trouble,\u201d LeMessurier recalled<\/a> thinking, in a lecture years later. He asked his wind tunnel experts to run more tests, and the findings made his reassessment \u201ceven worse,\u201d he added.\n <\/p>\n \n LeMessurier traveled with the data and his wife to their summer retreat in Maine to think the matter through. He was especially concerned about the bolted joints on the 30th floor, which he believed were most likely to fail. The building was designed with \u201cno redundancy,\u201d Greenburg said, meaning that the failure of just one connection would lead to total collapse \u2014 one that could have a domino effect on surrounding buildings.\n <\/p>\n \n Looking at weather data, LeMessurier concluded that a storm strong enough to take down Citicorp Center occurs in New York City once every 50 years. If power to the tuned mass damper failed (a plausible occurrence in a hurricane), this probability fell to once every 16 years. In a subsequent analysis of events, LeMessurier wrote there had been \u201ca 100% probability of total collapse by the end of the century,\u201d adding: \u201cWhen collapse occurred, it would have come suddenly, without warning, and would have killed thousands of people.\u201d\n <\/p>\n \n \u201cHere I am, the only person in the world who knew,\u201d he recounted in the aforementioned lecture. \u201cThere\u2019s nothing wrong with the building, nobody knows anything\u2019s wrong. There\u2019s no cracks; the building behaves itself perfectly. So, what do you do?\u201d\n <\/p>\n \n Facing legal, professional and reputational ruin, LeMessurier had little choice but to blow the whistle on himself.\n <\/p>\n \n \u201cHe\u2019s emotionally cornered,\u201d said Greenburg, who spoke with LeMessurier\u2019s daughters while researching his book and paints a sympathetic portrait of the engineer. \u201cHe was concerned to the point of contemplating suicide.\u201d (LeMessurier said as much himself, half-joking: \u201cI thought briefly about driving into an abutment \u2026 but then I said, \u2018I would miss the end of the story.\u2019\u201d)\n <\/p>\n \n LeMessurier briefed colleagues, collaborators and the bank to his miscalculation. One of the Twin Towers\u2019 engineers, Leslie Robertson, was brought in to oversee the response, but LeMessurier was given the chance to fix his own mistake. His proposal was straightforward enough: weld steel plates over the bolted joints. But planning for the worst-case scenario, in the meantime, was far from simple.\n <\/p>\n \n Robertson hired a private weather forecasting company to provide data on any tropical storms forming in the Atlantic. Gauges measuring stresses at key points in the building were installed to alert engineers to any dangerous movement. Secret evacuation plans were made, too. LeMessurier informed city officials of his findings, and the Red Cross was consulted to understand what a building collapse in densely populated Manhattan might look like.\n <\/p>\n \n Around halfway through the repairs, Hurricane Ella formed in the Atlantic and threatened to barrel toward New York City. To LeMessurier\u2019s relief, the storm veered away. Even then, the extent of the danger remained unknown to the public. While some reporters asked questions, that year\u2019s newspaper strike meant the corrective measures went largely unscrutinized. They were carried out over two months, by crews working inconspicuously at night, and the parties then quietly resolved compensation and insurance claims.\n <\/p>\n \n While some critics have questioned the secrecy with which repairs were made, LeMessurier was \u201calmost universally commended for his disclosure and cooperation,\u201d Greenburg writes. The tale of Citicorp Center has since become a morality tale of professional ethics, the author added: \u201cIt\u2019s really become the seminal story when training engineers.\u201d\n <\/p>\n \n The full extent of the danger was not publicized until 1995, when the New Yorker magazine published an article<\/a> by Joseph Morgenstern (whose transcripts underpin Greenburg\u2019s book) detailing the crisis. LeMessurier was, after then, increasingly open with students, contemporaries and the press about his error. It did not prove to be career-ending, though he will always be best known for the mistake he made \u2014 and fixed.\n <\/p>\n![\"The](\"https:\/\/www.europesays.com\/us\/wp-content\/uploads\/2025\/08\/gettyimages-1637574746.jpg\")
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