F. R. Khan "Einstein of structural engineering"


F. R. Khan “Einstein of structural engineering”

Fakruddin M. Khan

Fazlur Rahman Khan (April 3, 1929 – March 27, 1982) was a Bangladeshi American Architect and Structural Engineer. He is a central figure behind the “Second Chicago School” of architecture, and is regarded as the “Father of tubular design for high-rises”. F.R. Khan, “more than any other individual, ushered in a renaissance in skyscraper construction during the second half of the twentieth century.” He has been called the “Einstein of structural engineering” and the “Greatest Structural Engineer of the 20th Century” for his innovative use of structural systems that remain fundamental to modern skyscraper construction. He is widely known for his work on the John Hancock Center and the Willis Tower (formerly Sears Tower), which was the world’s tallest building for several decades.

Fazlur Rahman Khan was born on April 3, 1929 in Dhaka, British India. He was brought up in the village of Bhandarikandii near Dhaka. His father, Khan Bahadur Abdur Rahman Khan, BES was ADPI of Bengal and after retirement served as Principal of Jagannath College, Dhaka.

F.R. Khan received his matriculation from Armanitola Government High School, in Dhaka. He received his bachelor degree from Bangladesh University of Engineering and Technology (BUET), Dhaka, Bangladesh. He received a Fulbright Scholarship and a Pakistani Government scholarship enabled him to travel to the United States in 1952 where he pursued advanced studies at the University of Illinois at Urbana-Champaign. He was able to travel because he finally had enough money. In three years F.R. Khan earned two Master’s degrees — one in structural engineering and one in theoretical — and a PhD in structural engineering.

In 1955, employed by Skidmore, Owings and Merrill, he began working in Chicago, Illinois. He was made a partner in 1966 and became a naturalized American citizen in 1967. During the 1960s and 1970s, he became noted for his designs for Chicago’s 100-story John Hancock Center and 108-story Sears Tower, the tallest building in the world in its time and still the tallest in the United States since its completion in 1974. He is also responsible for designing notable buildings in Bangladesh and Saudi Arabia.
F.R. Khan realized that the rigid steel frame structure that had “dominated tall building design and construction so long was not the only system fitting for tall buildings”, marking “the beginning of a new era of skyscraper revolution in terms of multiple structural systems.” F.R. Khan’s design innovations significantly improved the construction of high-rise buildings, enabling them to withstand enormous forces generated on these super structures. These new designs opened an economic door for contractors, engineers, architects, and investors, providing vast amounts of real estate space on minimal plots of land.

Tube structural systems
F.R. Khan’s central innovation in skyscraper design and construction was the idea of the “tube” structural system for tall buildings, including the “framed tube”, “trussed tube” and “bundled tube” variations. His “tube concept,” using “all the exterior wall perimeter structure of a building to simulate a thin-walled tube, revolutionized tall building design.” The constructions of most super tall skyscrapers since the 1960s, including the construction of the World Trade Center, Petronas Towers and Jin Mao Building, employ a tube structural system.

Framed tube
Since 1963, the new structural system of framed tubes became highly influential in skyscraper design and construction. F.R. Khan defined the framed tube structure as “a three dimensional space structure composed of three, four, or possibly more frames, braced frames, or shear, joined at or near their edges to form a vertical tube-like structural system capable of resisting lateral forces in any direction by cantilevering from the foundation.” Closely spaced interconnected exterior columns form the tube. Horizontal loads, for example from wind and earthquakes, are supported by the structure as a whole. About half the exterior surface is available for windows. Framed tubes allow fewer interior columns, and so create more usable floor space. The bundled tube structure is more efficient for tall buildings, lessening the penalty for height. The structural system also allows the interior columns to be smaller and the core of the building to be free of braced frames or shear walls that use up valuable floor space. Where larger openings like garage doors are required, the tube frame must be interrupted, with transfer girders used to maintain structural integrity. The first building to apply the tube-frame construction was the DeWitt-Chestnut Apartments building that F.R. Khan designed and was completed in Chicago in 1963. This laid the foundations for the framed tube structure used in the construction of the World Trade Center.

Trussed tube and X-bracing
F.R. Khan pioneered several other variations of the tube structure design. One of these was the concept of X-bracing, or the “trussed tube”, first employed for the John Hancock Center. This concept reduced the lateral load on the building by transferring the load into the exterior columns. This allows for a reduced need for interior columns thus creating more floor space. This concept can be seen in the John Hancock Center, designed in 1965 and completed in 1969. One of the most famous buildings of the structural expressionist style, the skyscraper’s distinctive X-bracing exterior is actually a hint that the structure’s skin is indeed part of its ‘tubular system’. This idea is one of the architectural techniques the building used to climb to record heights (the tubular system is essentially the spine that helps the building stand upright during wind and earthquake loads). This X-bracing allows for both higher performance from tall structures and the ability to open up the inside floor plan (and usable floor space) if the architect desires. Original features such as the skin, pioneered by F. R. Khan, have made the John Hancock Center an architectural icon.

Bundle tube
One of F.R. Khan’s most important variations of the tube structure concept was the “bundled tube,” which he used for the Sears Tower and One Magnificent Mile. The bundle tube design was not only the most efficient in economic terms, but it was also “innovative in its potential for versatile formulation of architectural space. Efficient towers no longer had to be box-like; the tube-units could take on various shapes and could be bundled together in different sorts of groupings.”
Concrete tube structures
The last major buildings engineered by F.R. Khan were the One Magnificent Mile and Onterie Center in Chicago, which employed his bundled tube and trussed tube system designs respectively. In contrast to his earlier buildings, which were mainly steel, his last two buildings were concrete. His earlier DeWitt-Chestnut Apartments building, built in 1963 in Chicago, was also a concrete building with a tube structure.

Sky lobby
The first sky lobby was also designed by F.R. Khan for the John Hancock Center. Later buildings with sky lobbies include the World Trade Center, Petronas Twin Towers and Taipei 101. The 44th-floor sky lobby of the John Hancock Center also features the first rise indoor swimming pool, which remains the highest in America. This was the first time that people could have the opportunity to work and live “in the sky”.
Professional milestones

List of buildings
Some the most famous buildings F.R. Khan was responsible for performing as structural engineer include the following:
DeWitt-Chestnut Apartments, Chicago, 1963
John Hancock Center, Chicago, 1965–1969
Sears Tower, Chicago, 1970–1973
Hajj Terminal, King Abdulaziz International Airport, Jeddah, 1974–1980
King Abdulaziz University, Jeddah, 1977–1978
One Magnificent Mile, Chicago, completed 1983
Onterie Center, Chicago, completed 1986
U.S. Bank Center, Milwaukee, 1973
Other honors
Among F.R. Khan’s other accomplishments, he received the Wason Medal (1971) and Alfred Lindau Award (1973) from the American Concrete Institute (ACI); the Thomas Middlebrooks Award (1972) and the Ernest Howard Award (1977) from ASCE; the Kimbrough Medal (1973) from the American Institute of Steel Construction; the Oscar Faber medal (1973) from the Institution of Structural Engineers, London; the International Award of Merit in Structural Engineering (1983) from the International Association for Bridge and Structural Engineering IABSE; the AIA Institute Honor for Distinguished Achievement (1983) from the American Institute of Architects; and the John Parmer Award (1987) from Structural Engineers Association of Illinois (Engineering Legends, Richard Weingardt).

F.R. Khan died of a heart attack on March 27, 1982 while on a trip in Jeddah, Saudi Arabia, at age 52. He was a general partner in SOM, the only Engineer holding that high position at the time. His body was returned to the USA and was buried in Chicago.

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