Tube (structure)
Hollow cantilever tube system for lateral load resistance.
The tube is a structural system for tall buildings designed to resist lateral loads such as wind, seismic, and impact by making the building act like a hollow cylinder cantilevered from the ground. Introduced by structural engineer Fazlur Rahman Khan while at Skidmore, Owings & Merrill (SOM) in Chicago, the system was first used in the 43-story DeWitt-Chestnut Apartment Building (later renamed Plaza on DeWitt), completed in 1966. Most buildings over 40 stories built since the 1960s use this structural type.
- Introduced by
- Fazlur Rahman Khan
- Firm
- Skidmore, Owings & Merrill (SOM), Chicago office
- First building
- DeWitt-Chestnut Apartment Building (Plaza on DeWitt), Chicago, Illinois
- Year first used
- 1966
- Materials
- steel, concrete, or composite construction
- Building types
- office, apartment, mixed-use
Lore & Background
Fazlur Rahman Khan, a structural engineer born in British India (present-day Bangladesh), defined the framed tube structure as a three-dimensional space structure composed of frames, braced frames, or shear walls joined at their edges to form a vertical tube. Khan did not see his first skyscraper in person until age 21 and had not stepped inside a mid-rise building until moving to the United States for graduate school.
The simplest incarnation of the tube uses closely spaced exterior columns tied together with deep spandrel beams through moment connections, forming a rigid frame that resists all lateral loads. This allows interior columns to be few and located at the core, maximizing usable floor space. Variants include the framed tube, trussed or braced tube, hull and core, bundled tube, hybrid, concrete tube, and lattice towers with steel tube elements.
Reader's Guide
The tube system revolutionized tall building design by enabling efficient resistance to lateral forces while allowing column-free interior spaces and greater architectural flexibility. Its bundled tube variant, notably used in Willis Tower, allowed towers to take on various shapes and become sculptural. The system has been applied to many iconic skyscrapers since the 1960s, including the John Hancock Center, Sears Tower, World Trade Center, Petronas Towers, Jin Mao Building, and the Burj Khalifa. Khan's later buildings, One Magnificent Mile and Onterie Center in Chicago, employed bundled tube and trussed tube designs in concrete, while his earlier DeWitt-Chestnut Apartments was also concrete. The tube remains the dominant structural system for most tall buildings over 40 stories.
Did You Know?
- The first building to use the tube-frame construction was the DeWitt-Chestnut Apartment Building, completed in Chicago in 1966.
- About half the exterior surface of a framed tube building is available for windows.
- The bundled tube variant allowed buildings to become sculpture by enabling versatile formulation of architectural space.
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