Aon Center

The Aon Center is an International Style skyscraper designed by Edward Durell Stone, in association with Perkins & Will Partnership, and built between 1970 and 1973, for a reported $120 million dollars, in Chicago, IL.

Aon Center is not the only name you might know this building by though. It is common for companies to want to attach their names to iconic buildings when they move in, or for the general public to come up with nicknames, and this one is no exception. The Aon Center is also known, or has been known as, Standard Oil Building, or Amoco Building.

Its precise street address is 200 E.Randolph Street, Chicago, IL. You can also find it on the map here.

Although this building is unrelated to the Twin Towers in NYC, many have highlighted the similarities between both projects. The structure type of choice in both cases was a "framed tube-in-tube", which naturally creates narrow windows and, depending on the materials used, the distinctive vertical stripes which both projects share.

The building underwent a major restoration between 1990 and 1992.

Edward Durell Stone was the architecture firm in charge of the architectural design, in association with Perkins & Will Partnership.

That being said, architecture is a complex discipline involving many professionals from different fields, without whom this building would have not been possible. We will surely be leaving out a lot of names here, but here is a list of the people we do know also played their part in making the Aon Center a reality:

• Perkins & Will in charge of Structural Engineering
• Turner Construction as the Main Contractor
• Otis as the company in charge of the elevators system
• Standard Oil Company of Indiana as the Main Developer

The Aon Center can be categorized as an International Style building.

The Aon Center uses a framed tube-in-tube structure , with steel columns and concrete slabs.

A framed tube-in-tube structure uses a central core, known as inner tube, which usually holds stairs, lifts and installations, and a perimeter of columns around it, which form the exterior tube. The interior tube is tipically more massive (often made of reinforced concrete), and the exterior tube is "lighter" (made of steel or concrete columns). Both tubes are conencted via horizontal elements which make up the floors and also transmit any horizontal froces from the facade to the core.

The facade of the building is load bearing. This is a direct consequence of the integration of the exterior "tube" into the facade, something which most framed tube-in-tube buildings do in order to liberate the interior space from structural elements and achieve a more flexible interior.

So the facade of the builing is techinically load-bearing, yes, however, in between the load-bearing colums we find a curtain-wall type of facade, which by itself would not be cosnidered load-bearing.

From an aesthetic point of view, the facade features a curtain wall consisting of 15 vertical bands of windows with dark glass and metal frames on each side, embedded in white Carrara marble triangular pillars, which are part of the building's structure. So yes, the facade is both structural, and a curtain wall.

The facade transfers horizontal wind loads to the main building structure through connections in the floors or columns..