1970: Willis Tower – Chicago, Illinois
Innovation: Willis Tower
Location: Chicago, Illinois
Architect: Skidmore, Owings, and Merrill
Engineer: Skidmore, Owings, and Merrill
Formerly known as the Sears Tower, the Willis Tower, standing at 108 stories, held the title for the world’s tallest building for nearly 25 years, between the years 1973-1998. The architects and engineers of Skidmore, Owings, and Merrill were tasked with the job to build one of the tallest office buildings in the world. With little ground area to work with and the requirement for a building fit to contain around 3 million people, they came up with the idea to create a 3×3 matrix of bundled rectangular “tubes.” Originally introduced by Fazlur Rahman Khan, “tubes” were a relatively new concept in structural engineering; in which, they acted like hollow cantilevers that could resist lateral loads. Furthermore, bundling the tubes would allow an extremely tall structure to stand because it would spread the lateral loads and vertical loads through a greater area throughout and at the bottom of the tower. Also, because of this discovery, “buildings no longer need be box-like in appearance, they could become sculpture.” For this reason, sections of the 3×3 matrix vary in height. The concept of bundling “tubes” was a new design innovation that would be incorporated into many future projects.