Fazlur Khan (1929-82)
American Architecture Series
One of the most acclaimed American architects involved in supertall skyscraper architecture, Fazlur Khan was a Bangladesh-born structural engineer and designer, who developed a number of structural systems that revolutionized the construction of high-rise towers, like the 110-story Willis (Sears) Tower (1970-74) and the 100-story John Hancock Center (1967-70). A man who revolutionized the art of architecture, through his advances in structural design, he is regarded as the Father of tubular designs for skyscrapers - the "Einstein of structural engineering" - and a key contributor to American public art of the late 20th century. Associated with the influential Second Chicago School of architecture, Khan was a partner in the firm of Skidmore, Owings & Merrill, the world famous American architects whose most recent projects have included the 2,717-foot tall Burj Khalifa Dubai tower, United Arab Emirates (2010), the tallest man-made structure on the planet - Fazlur Khan's design innovations led to a resurgence of skyscraper construction and vertical architecture across the globe. To do justice to his contribution to urban American art, the US Council on Tall Buildings and Urban Habitat (CTBUH) created a special award in his honour, named the Fazlur Khan Lifetime Achievement Medal. As well as his architectural systems for skyscrapers, Khan also designed a number of other important buildings including the Haj Terminal, Jeddah, Saudi Arabia (1972-81).
In 1955, Fazlur Khan joined Skidmore, Owings and Merrill, and began working in Chicago. He was made a partner in 1966 and took American citizenship in 1967. During the 1960s and 1970s, after designing the 43-story DeWitt-Chestnut (1964) and the 35-story Brunswick Building (1965), he achieved international recognition for his International Style of modern architecture, notably his designs for Chicago's John Hancock Center and the Sears Tower (as was) - still the tallest building in the United States - which reflected his unique insight into the relationship between architectural design and structural engineering.
Based on the concept that the building's external "skin" could provided it had enough trussing, framing and bracing act as the structure itself, Fazlur Khan designed a set of new structural systems to replace the rigid steel-frame structure, used in most skyscrapers, with a number of different tubular steel systems which offered greatly improved strength and stability (notably greater resistance to lateral forces), while using less steel. Usable in both steel and concrete buildings, these systems included the "framed tube", "trussed tube" and "bundled tube" designs. Most buildings over 40-storys erected since the 1960s now use Khan's tube design, not least because tubular systems provide greater interior space and facilitate a greater variety of building shapes.
According to Fazlur Khan, the "framed tube" structure was a three-dimensional structure consisting of three, four, or more frames, or shear walls, connected at their edges to form a vertical tube-like structure capable of resisting lateral pressures (from wind and so on) by cantilevering from the foundation upwards. (Think of Fazlur Khan tube system as like a huge bendable spine, made up of connected frames.) Framed tubes require fewer interior columns, thus allowing more usable floor space, and roughly half the exterior surface is available for windows. The "bundled tube" structure is even better for supertall tower buildings.
The first building designed by Fazlur Khan using his patented tube-frames was the DeWitt-Chestnut Apartments, Chicago (1964), which paved the way for the framed tube structure used by Minoru Yamasaki (1912-86) in the construction of buildings 1 and 2 of the World Trade Center (1965-66).
Khan also invented the "trussed tube" (also called X-bracing), first used in the John Hancock Center, Chicago (1967-70). Considered to be one of the most famous examples of the structural expressionist style (the anti-minimalist idiom also known as decorative formalism), the tower's distinctive X-bracing facade exemplifies the technique of using a building's formal elements for both engineering and aesthetic purposes. In this case, aside from its decorative attribute, the X-bracing is part of the tubular structure.
Like other tubular designs, the "trussed tube" used far less steel than the traditional rigid steel-frame structure. The Empire State Building (1931), for instance, consumed 206 kilograms of steel per square metre, whereas the John Hancock Center needed only 145 kilograms of steel per square metre. The trussed tube system was used in the Onterie Center, Chicago (1986), the Citigroup Center, New York (formerly Citicorp Center, now called 601 Lexington Avenue) and the Bank of China Tower, Hong Kong (1982-89).
Fazlur Khan also designed the first sky lobby, which he incorporated into the John Hancock Center. A sky lobby functions as a connecting point for elevator passengers. They are the only stopping-off points for express elevators (which provide rapid vertical transport), allowing passengers to connect with a local elevator that stops at every floor within a section of the building. Sky lobbies reduce the number of elevator shafts required, while simultaneously maintaining acceptable travel times. Khan's concept was later employed at the World Trade Center, the Petronas Twin Towers, Kuala Lumpur, Malaysia (1993-4), Taipei 101, Taiwan (2004) and the Burj Khalifa, United Arab Emirates (2010).
At the age of only 52, Khan died of a heart attack while on a trip in Saudi Arabia. His body was returned to the United States and was buried in Chicago.
Acknowledged to be one of the greatest architects and structural engineers, who combined art, science and design, his innovations transformed high-rise 20th-century architecture, and won him numerous awards. These included: the Oscar Faber medal (1973), from the Institute of Structural Engineers (London); the International Award of Merit in Structural Engineering (1983) from the International Association for Bridge and Structural Engineering (IABSE); and the Distinguished Achievement Award (1983) from the American Institute of Architects (AIA). In addition, Lehigh University endowed the Fazlur Rahman Khan Chair of Structural Engineering and Architecture to celebrate his contribution to both structural and architectural design.
Here is a short list of the most famous buildings engineered by Khan:
- United States Air Force Academy, Colorado