One Illinois Center vs Aon Center

Comparing the One Illinois Center and the Aon Center is interesting because they both stand in Chicago, IL, and were completed within 3 years of each other, but they were designed by different architects.

This offers a unique glimpse at how rival designers approached projects in the same city during the same era.

The Aon Center is clearly the larger tower of the two, both in terms of height and number of floors. It rises to 1135ft (346m) with 83 floors above ground, while the One Illinois Center reaches 361ft (110m) with 30 floors above ground.

Of course, each project may have faced different briefs or regulatory constraints, which we don't really know about and could also explain the outcome.

Both the One Illinois Center and the Aon Center were designed in line with the aesthetic conventions of the International Style style.

The Aon Center was designed at a moment when the International Style style was already in decline, making it more of a lingering expression of the movement. In contrast, the One Illinois Center was built when the style still carried greater cultural weight.

Both the One Illinois Center and the Aon Center were designed to serve as commercial towers, and that has remained their main use since their completion, serving similar roles in the urban fabric.

Both towers provide significant parking capacity, with One Illinois Center offering 866 spaces and the Aon Center offering 679.

The two towers rely on different structural systems, reflecting distinct engineering strategies.

The One Illinois Center uses a Frame structural system, which relies on a regular grid of columns and beams to sustain its weight, while the Aon Center uses a Framed Tube In Tube system, that combines a strong central core with a perimeter tube of columns.

Yet, when it comes to their facade, they both employed the same solution, a Curtain Wall facade.

A curtain wall is a non-load-bearing facade hung from the structural frame. It is anchored to floor slabs and transfers only its own weight and wind loads, allowing for sleek, glassy exteriors.