Citigroup Center, Tuned Mass Dampers and a lesson in professional ethics

THE 59-FLOOR, 915-FOOT CITIGROUP CENTER, LOCATED AT 53RD ST AND 3RD AVENUE in midtown Manhattan was one of the first skyscrapers in the world to incorporate a Tuned Mass Damper to combat the wind’s effect on a building. Constructed upon four columns located at the center rather than the corners, it is a unique architectural and engineering accomplishment, while the repair of a potentially disastrous flaw, after its construction, is recounted today as a positive lesson in professional ethics.
800px-citigroupcenter

The structural engineer, William LeMessurier, was alerted to the possibility that the building was structurally unsound by a Princeton University student in 1978. LeMessurier found the building’s bolted joints were too weak to sustain a prolonged 70mph wind, something that occurs in New York City, on average, every 16 years. Once discovered, workers welded the internal joints at night while the Red Cross implemented an evacuation plan for the surrounding neighborhood.

I will not get into the entire story, which is detailed much better here.

What is most interesting to me, however, is the Tuned Mass Damper that sits in the building’s crown, atop the 59th floor. The TMD is a 400 ton slab of concrete resting on oil-film bearings and electronically controlled actuators for building stability. The inertia of the damper reduces the swaying of the building by up to 40%.

An example of a TMD:

200px-tuned_mass_damper

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~ by jaskim on February 14, 2009.

2 Responses to “Citigroup Center, Tuned Mass Dampers and a lesson in professional ethics”

  1. Great website!!!

    The tuned mass damper on the New York (City) Citicorp tower is an engineering is… in a word… fascinating!

    –30–

  2. I ran this project in the 70’s for MTS Systems out of Minneapolis and I could tell many stories about the challenge of designing it and installing at the top of a building in New York City using organized labor. Note that we were not able to fully test the system with the mass connected until it was fully assembled in the Citicorp Center.
    Bob Berdahl

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