page_title: World Trade Center (1973–2001)
section_title: Design
hierarchical_section_title: World Trade Center (1973–2001) / Design, construction, and criticism / Design
caption_attribution_description: Permission: please cite Rainer Halama as author of this picture. I would also appreciate it, if you inform me when using this picture about where and when it has been used. Facade of one of Twin Towers of the World Trade Center in New York, NY
context_page_description: The original World Trade Center was a large complex of seven buildings in the Financial District of Lower Manhattan, New York City, United States. It opened on April 4, 1973, and was destroyed in 2001 during the September 11 attacks. At the time of their completion, the Twin Towers—the original 1 World Trade Center, at 1,368 feet; and 2 World Trade Center, at 1,362 feet —were the tallest buildings in the world. Other buildings in the complex included the Marriott World Trade Center, 4 WTC, 5 WTC, 6 WTC, and 7 WTC. The complex contained 13,400,000 square feet of office space.
  The core complex was built between 1966 and 1975, at a cost of $400 million. During its existence, the World Trade Center experienced several major incidents, including a fire on February 13, 1975, a bombing on February 26, 1993, and a bank robbery on January 14, 1998. In 1998, the Port Authority of New York and New Jersey decided to privatize it by leasing the buildings to a private company to manage. It awarded the lease to Silverstein Properties in July 2001.
context_section_description: On September 20, 1962, the Port Authority announced the selection of Minoru Yamasaki as lead architect and Emery Roth & Sons as associate architects. Yamasaki devised the plan to incorporate twin towers. His original plan called for the towers to be 80 stories tall, but to meet the Port Authority's requirement for 10,000,000 square feet (930,000 m²) of office space, the buildings would each have to be 110 stories tall.
  Yamasaki's design for the World Trade Center, unveiled to the public on January 18, 1964, called for a square plan approximately 208 feet (63 m) in dimension on each side. The buildings were designed with narrow office windows 18 inches (46 cm) wide, which reflected Yamasaki's fear of heights as well as his desire to make building occupants feel secure. His design included building facades clad in aluminum-alloy. The World Trade Center was one of the most-striking American implementations of the architectural ethic of Le Corbusier and was the seminal expression of Yamasaki's gothic modernist tendencies. He was also inspired by Arabic architecture, elements of which he incorporated in the building's design, having previously designed Saudi Arabia's Dhahran International Airport with the Saudi Binladin Group.
  A major limiting factor in building height is the issue of elevators; the taller the building, the more elevators are needed to service it, requiring more space-consuming elevator banks. Yamasaki and the engineers decided to use a new system with two "sky lobbies"—floors where people could switch from a large-capacity express elevator to a local elevator that goes to each floor in a section. This system, inspired by the local-express train operation used in New York City's subway system, allowed the design to stack local elevators within the same elevator shaft. Located on the 44th and 78th floors of each tower, the sky lobbies enabled the elevators to be used efficiently. This increased the amount of usable space on each floor from 62 to 75 percent by reducing the number of elevator shafts. Altogether, the World Trade Center had 95 express and local elevators.
  The structural engineering firm Worthington, Skilling, Helle & Jackson worked to implement Yamasaki's design, developing the framed-tube structural system used in the twin towers. The Port Authority's Engineering Department served as foundation engineers, Joseph R. Loring & Associates as electrical engineers, and Jaros, Baum & Bolles (JB&B) as mechanical engineers. Tishman Realty & Construction Company was the general contractor on the World Trade Center project. Guy F. Tozzoli, director of the World Trade Department at the Port Authority, and Rino M. Monti, the Port Authority's Chief Engineer, oversaw the project. As an interstate agency, the Port Authority was not subject to the local laws and regulations of the City of New York, including building codes. Nonetheless, the World Trade Center's structural engineers ended up following draft versions of New York City's new 1968 building codes.
  The framed-tube design, introduced in the 1960s by Bangladeshi-American structural engineer Fazlur Rahman Khan, was a new approach that allowed more open floor plans than the traditional design that distributed columns throughout the interior to support building loads. Each of the World Trade Center towers had 236 high-strength, load-bearing perimeter steel columns which acted as Vierendeel trusses. The perimeter columns were spaced closely together to form a strong, rigid wall structure, supporting virtually all lateral loads such as wind loads, and sharing the gravity load with the core columns. The perimeter structure containing 59 columns per side was constructed with extensive use of prefabricated modular pieces, each consisting of three columns, three stories tall, connected by spandrel plates. The spandrel plates were welded to the columns to create the modular pieces off-site at the fabrication shop. Adjacent modules were bolted together with the splices occurring at mid-span of the columns and spandrels. The spandrel plates were located at each floor
caption: The exterior structure of the Twin Towers
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