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About Skyscrapers

Aon Center (Chicago) – A Lesson Learned

Posted by Jae on January 28, 2009

Aon Center (Chicago)

Aon Center (Chicago)

The Aon Center is a 1973 completed, 120 million 1973 US dollar, 83 floor, 346 m modern skyscraper in Chicago, USA. With 83 floors and a height of 346 m, it is the third tallest building in Chicago, surpassed in height by the Sears Tower and the Trump Tower.

When it was completed in 1973 it was the tallest building in Chicago and the fourth-tallest in the world. The building employs a tubular steel-framed structural system with V-shaped perimeter columns to resist earthquakes, reduce sway, minimize column bending, and maximize column-free space. This construction method was also used for the World Trade Center towers in New York City.

When completed, it was the world’s tallest marble-clad building, being sheathed entirely with 43,000 slabs of Italian Carrara marble. The marble used was thinner than previously attempted in cladding a building, this quickly proved to be a mistake. In 1974, just a year after completion, one of the marble slabs detached from the façade and penetrated the roof of the nearby Prudential Center Annex. To alleviate the problem, stainless steel straps were added to hold the marble in place. Later, from 1990 to 1992, the entire building was refaced with Mount Airy white granite at an estimated cost of over $80 million.

In recent years, the top floors of the building have been lit at night with colors to reflect a particular season or holiday. Orange is used for Thanksgiving, green or red for Christmas, and pink during Breast Cancer Awareness Month. The lighting commonly matches the nighttime lighting on the antenna of the Sears Tower, John Hancock Center, and the upper floors of the Merchandise Mart.

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