page_title: Tube (structure)
section_title: Framed tube
hierarchical_section_title: Tube (structure) / Variants / Framed tube
caption_attribution_description: English: Typical WTC tower architectural floor plan
context_page_description: 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, 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.
  The system can be built using steel, concrete, or composite construction. It can be used for office, apartment, and mixed-use buildings. Most buildings of over 40 stories built since the 1960s are of this structural type.
context_section_description: This is the simplest incarnation of the tube. It can appear in a variety of floor plan shapes, including square, rectangular, circular, and freeform. This design was first used in Chicago's DeWitt-Chestnut Apartment Building, designed by Khan and finished in 1965, but the most notable examples are the Aon Center and the original World Trade Center towers.
caption: The World Trade Center's Twin Towers were some of the first structures to use a framed tube design.  The many columns of the tube can be seen around the exterior of this horizontal cross section.  The towers had a core for services, seen in the center.  The design was not tube-in-tube since the core had 47 columns spaced relatively evenly, rather than around the edge of the core.
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