This iconic New York skyscraper could have fallen in a storm: Here’s the construction error that almost made it happen

When construction was finished on Citicorp Center in 1977, the New York skyscraper was the seventh tallest building in the world. Its unique design made it appear to levitate above the ground, supported by four stilts at the center of each side.

William LeMessurier, the engineer who designed the building now designated a New York City landmark, had done so in order to accommodate Saint Peter’s Lutheran Church which is located on one of the corners under the tower above.

However, a year after it was completed, a design flaw was discovered that could’ve resulted in the building coming crashing down and killing thousands of New Yorkers. What LeMessurier did next has become a lesson in professional ethics for engineering students.

Fatal flaw discovered in Citicorp Center

LeMessurier was consulted by the architect for the Citicorp Center project, Hugh Stubbins, to help him solve the problem of accommodating the Saint Peter’s Lutheran Church, whose pastor had refused to sell the property outright. The idea was hatched to put the building on four stilts positioned in the middle of each side, not at the corners.

In order to provide the structural support and distribute the buildings weight and stress from wind, he envisioned a series of distinctive V-shaped chevrons. To provide further stability in the event of strong winds, he placed a tuned mass damper, a 400-ton concrete block on a film of oil, in the upper floors to counteract sway.

Everything looked good on paper and passed wind tunnel tests, so the project moved forward and ground was broke in 1974. Three years later the building was completed. At the same time, a young engineering student Diane Hartley at Princeton University was beginning her final year.

Citicorp Center was a perfect fit to be featured in her thesis, and LeMessurier’s firm happily provided her with all the information that she needed. However, she found a problem with the building’s design. The numbers didn’t add up if it were hit by diagonal winds and if that happened it could result in a catastrophic failure of the structure.

If the building were to topple over, it would begin a domino affect that would cause skyscraper after skyscraper to topple as well. She alerted LeMessurier’s firm to the problem but was told that her calculations were wrong. Around the same time, Lee DeCarolis, a freshman architect student, reportedly also discovered the fatal flaw and contacted LeMessurier.

A stitch in time saves nine: Repairs save Citicorp Center from doom

Whose message got through to LeMessurier is unknown, but the structural engineer began to investigate and found that there was a 100% chance that the building would collapse before the end of the century.

Not only was there his engineering miscalculation that could doom the building but also that the bracing system had been bolted together and not welded to save money and time. He made the choice to scuttle his professional reputation and get the problem fixed.

Secretly during the night, construction crews began to make the necessary repairs to strengthen the building’s structure to avoid catastrophe. Evacuation plans were made for the surrounding area and the Red Cross called in to prepare for the worse. With hurricane season under way, private weather forecasters were hired to monitor the winds and sound the alarm should they present danger.

Within two months the repairs were completed, and no one was the wiser, thanks in part to a newspaper strike going on at the same time. How close New York came to having a mass casualty event did not come out until 1995 when an article on the affair was published in the New Yorker.

LeMessurier career didn’t end, although he is best known for the mistake, thanks to his honesty and professional ethics which has become a lesson passed on to other aspiring engineers.

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