Blog Post#19 : Structural Integrity

Why couldn't the columns of the Citicorp center be built on the buildings corners? 

The building was particularly vulnerable to quartering winds (winds that strike the building at its corners). Normally, buildings are strongest at their corners, and it’s the perpendicular winds (winds that strike the building at its face) that cause the greatest strain. But this was not a normal building. The new building, suspending over St. Peter’s church had to be built around or above the church to separate the two.

What is the Citicorp building's major flaw? What could happen? Describe. 

For every year Citicorp Center was standing, there was about a 1-in-16 chance that it would collapse. It was so light weight, it could move with the wind. LeMessurier had accounted for the perpendicular winds, but not the quartering winds. He checked the math, and found that the student was right. He compared what velocity winds the building could withstand with weather data, and found that a storm strong enough to topple Citicorp Center hits New York City every 55 years.

Who discovered this flaw and tried to make it public?

LeMessurier realized that a major storm could cause a blackout and render the tuned mass damper inoperable. Without the tuned mass damper, LeMessurier calculated that a storm powerful enough to take out the building hits New York every sixteen years. LeMessurier and his team worked with the Citicorp higher-up to coordinate emergency repairs on the building. The story remained a secret until writer Joe Morgenstern overheard it being told at a party, and interviewed LeMessurier. Morgenstern broke the story in 1995. The BBC aired a special on the Citicorp Center crisis, and one of its viewers was Diane Hartley. It turns out that she was the student in LeMessurier’s story.