Citicorp Center engineering crisis

Uncommon card · No. 161203

In July 1978, a possible structural flaw was discovered in Citicorp Center (now Citigroup Center), a skyscraper that had recently been completed in New York City. After investigations from a number of third parties, the building was found to be in danger of possible collapse due to its design; workers surreptitiously made repairs over the next few months, avoiding disaster. The building's structural engineer, William LeMessurier, incorporated numerous unconventional features into the design. Among these are a raised base supported by four offset stilts, diagonal bracing to absorb wind loads from upper stories, and a tuned mass damper on the roof. It was the first building that used active mechanical elements (the tuned mass damper) for stabilization. Concerned about "quartering winds" directed diagonally toward the corners of the building, Princeton University undergraduate student Diane Hartley investigated the structural integrity of the building and found it wanting. Nearly simultaneously...

Read on Wikipedia · Image Andrew Moore from Johannesburg, South Africa, Arnold Reinhold, CC BY-SA 2.0