In structural engineering, the tube is a system where, to resist lateral loads, a building is designed to act like a hollow cylinder, cantilevered perpendicular to the ground. This system was introduced by Fazlur Rahman Khan while at the architectural firm Skidmore, Owings & Merrill (SOM), in their Chicago office. The first example of the tube's use is the 43-story Khan-designed DeWitt-Chestnut Apartment Building, since renamed Plaza on DeWitt, in Chicago, Illinois, finished in 1966.
John Hancock Center in Chicago, designed in 1965 and finished in 1969, is an example of the trussed tube structural design
Willis Tower, finished in 1973, introduced the bundled tube structural design and was the world's tallest building until 1998
Fazlur Rahman Khan was a Bangladeshi-American structural engineer and architect, who initiated important structural systems for skyscrapers. Considered the "father of tubular designs" for high-rises, Khan was also a pioneer in computer-aided design (CAD). He was the designer of the Sears Tower, since renamed Willis Tower, the tallest building in the world from 1973 until 1998, and the 100-story John Hancock Center.
Fazlur Rahman Khan
A sculpture honoring Fazlur Khan at the Willis Tower
John Hancock Center is the world's first mixed use tower. When built, it was the second tallest building in the world. It demonstrated how much more efficient and feasible building very tall skyscrapers could be, in comparison to the older design and technology used by the tallest buildings up to that time.
In 1960, buildings over 20 stories were still newsworthy. Apartments in the John Hancock Center in Chicago – shown here with its distinctive exterior X-bracing – are located as high as the 90th floor.