Fazlur Rahman Khan was a Bangladeshi-American structural engineer known as the "Einstein of structural engineering" for revolutionizing skyscraper design with his innovative tubular structural system. Key innovations included the framed tube, trussed tube, and bundled tube designs, which use the entire exterior structure of a building acting as a thin-walled tube to resist lateral forces. This allowed for taller, more efficient buildings and opened new possibilities for skyscraper construction and urban development. Major projects designed with these tubular systems include the Sears Tower and John Hancock Center.

1. Dr Fazlur Rahman Khan, Ph.D. (1929-1982)…….. Einstein of structural engineering and
father of tubular designs,
Dr Ganesh S Kame, Professor,
Department of Civil Engineering.
Fazlur Rahman Khan was a Bangladeshi-American structural engineer and architect who
initiated important structural systems for skyscrapers. Considered the "father of tubular designs"
for high-rises, Khan was also a pioneer in computer-aided design (CAD). He was the designer of
the Sears Tower (now Willis Tower), the tallest building in the world until 1998 and the 100-
story John Hancock Center.
Khan, more than any other individual, usher in a renaissance in skyscraper construction during
the second half of the 20th 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. The Council on Tall
Buildings and Urban Habitat established the Fazlur R. Khan lifetime achievement medal in his
honor.
Although best known for skyscrapers, Khan was also an active designer of other kinds of
structures, including the Hajj airport terminal, the McMath–Pierce solar telescope, and several
stadium structures.
Biography

2. Fazlur Rahman Khan was born 3 April 1929 in Dhaka, East Bengal (Pakistan after 1947 and now
Bangladesh since 1971). He was brought up in the village of Bhandarikandii, in the Faridpur
district near Dhaka. His father Abdur was a high school mathematics teacher and textbook
author. He eventually became the Director of Public Instruction in the region of Bengal and after
retirement served as Principal of Jagannath College, Dhaka.
Khan attended Armanitola Government High School, in Dhaka. After that, he received his
Bachelor of Civil Engineering degree from Ahsanullah Engineering College, University of
Dhaka, e received a Fulbright Scholarship and a Pakistan government scholarship, which enabled
him to travel to the United States in 1952. There he studied at the University of Illinois at
Urbana-Champaign. In three years Khan earned two master's degrees — one in structural
engineering and one in theoretical and applied mechanics — and a PhD in structural engineering.
with thesis titled Analytical study of relations among various design criteria for rectangular
prestressed concrete beams.
Career
Khan helped introduce design methods and concepts for efficient use of material in building
architecture. His first building to employ the tube structure was Chestnut De-Witt apartment
building.[17]
In 1955, employed by Skidmore, Owings and Merrill, he began working in Chicago, Illinois,
United States. 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 110-story Sears Tower, the tallest building in the world in its time. He is
also responsible for designing notable buildings in Bangladesh, Australia and Saudi Arabia.
Of his design process, Khan said "When thinking design, I put myself in the place of a whole
building, feeling every part. In my mind I visualize the stresses and twisting a building
undergoes." He believed that engineers needed a broader perspective on life, saying, "The
technical man must not be lost in his own technology; he must be able to appreciate life, and life
is art, drama, music, and most importantly, people."
Khan's personal papers, the majority of which were in his office at the time of his death, are held
by the Ryerson & Burnham Libraries at the Art Institute of Chicago. The Fazlur Khan Collection
includes manuscripts, sketches, audio cassette tapes, slides and other materials regarding his
work. The International Association for Life Cycle Civil Engineering named their Life-Cycle
Civil Engineering Medal after Khan.
Innovations
Khan discovered 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 construction.

3. Tube structural systems
John Hancock Center is the world's first mixed use tower. It was the tallest building in the world
outside New York City
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. Most buildings over 40-
storeys constructed since the 1960s now use a tube design derived from Khan's structural
engineering principles.
The tubular designs are for resisting lateral loads (horizontal forces) such as wind forces, seismic
forces, etc. The primary important role of structural system for tall Buildings is to resist lateral
loads. The lateral loads begin to dominate the structural system and take on increasing
importance in the overall building system when the building height increases. Forces of winds
become very substantial and forces of earthquake etc. are very important as well. It is the tubular
designs that are used for tall buildings to resist such forces. Tube structures are very stiff and
have numerous significant advantages over other framing systems. They not only make the
buildings structurally stronger and more efficient, they significantly reduce the usage of
materials while simultaneously allowing buildings to reach even greater heights. The reduction
of material makes the buildings economically much more efficient and reduces environmental
issues as it results in the least carbon emission impact on the environment. Tubular systems
allow greater interior space and further enable buildings to take on various shapes, offering
unprecedented freedom to architects. 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. Khan was among a group of engineers who encouraged a rebirth in
skyscrapers construction after a hiatus for over thirty years.

4. The tubular systems have yet to reach their limit when it comes to height. Another important
feature of the tubular systems is that buildings can be constructed using steel or reinforced
concrete, or a composite of the two to reach greater heights. Khan pioneered the use of
lightweight concrete for high-rise buildings, at a time when reinforced concrete was utilized
primarily for low-rise construction of only a few stories in height. Most of Khan's designs were
conceived considering pre-fabrication and repetition of components so projects could be quickly
built with minimal errors.
The population explosion, beginning with the baby boom of the 1950s, created widespread
concern about the amount of available living space. Khan had the solution — building up.[33]
More than any other 20th-century engineer, Fazlur Rahman Khan made it possible for people to
live, and work in “cities in the sky.” Mark Sarkisian (Director of Structural and Seismic
Engineering at Skidmore, Owings & Merrill) said, "Khan was a visionary who transformed
skyscrapers into sky cities while staying firmly grounded in the fundamentals of engineering."
Khan's initial projects were the 43 stories DeWitt-Chestnut (1964) and 35 stories Brunswick
Building (1965). His most important projects were the John Hancock Center and the Willis
Tower.
Framed tube
Since 1963, the new structural system of framed tubes became highly influential in skyscraper
design and construction. Khan defined the framed tube structure as "a three dimensional space
structure composed of three, four, or possibly more frames, braced frames, or shear walls, 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 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 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.

5. Trussed tube and X-bracing
In 1960, buildings over 20 stories were still newsworthy; by the close of the decade, people were
“living in the sky.” Apartments in the John Hancock Center in Chicago - shown here with its
distinctive exterior X-bracing - are located as high as the 90th floor.
Khan pioneered several other variations of the tube structure design. One of these was the
concept of applying X-bracing to the exterior of the tube to form a "trussed tube". X-bracing
reduces the lateral load on a building by transferring the load into the exterior columns, and the
reduced need for interior columns provides a greater usable floor space. Khan first employed
exterior X-bracing on his design of the John Hancock Center in 1965, and this can be clearly
seen on the building's exterior, making it an architectural icon.
In contrast to earlier steel-frame structures, such as the Empire State Building (1931), which
required about 206 kilograms of steel per square meter and Chase Manhattan Bank Building
(1961), which required around 275 kilograms of steel per square meter, the John Hancock Center
was far more efficient, requiring only 145 kilograms of steel per square meter. The trussed tube
concept was applied to many later skyscrapers, including the Onterie Center, Citigroup Center
and Bank of China Tower.

6. Sears Tower (now Willis Tower), engineered by Khan and designed by Bruce Graham, was the
tallest building in the world for over two decades. The design for this 1450-foot-tall tower
introduced the bundled tube structural system, as well as a new vocabulary in architectural form.
Bundle tube
One of 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."
Tube in tube
Tube-in-tube system takes advantage of core shear wall tubes in addition to exterior tubes. The
inner tube and outer tube work together to resist gravity loads and lateral loads and to provide
additional rigidity to the structure to prevent significant deflections at the top. This design was
first used in One Shell Plaza. Later buildings to utilize this structural system include the Petronas
Tower.
Outrigger and belt truss
The outrigger and belt truss system is a lateral load resisting system in which the tube structure is
connected to the central core wall with very stiff outriggers and belt trusses at one or more levels.
BHP House was the first building to utilize this structural system followed by US Bank Center.
The US Bank Center rises 601 feet, with three belt trusses at the bottom, middle and top of the
building. The exposed belt trusses serve for both aesthetic and structural purposes. Later
buildings to utilize this include Shanghai World Financial Center.
Concrete tube structures
The last major buildings engineered by 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. Trump Tower in New York City is also another example that
adapted this system.
Shear wall frame interaction system
Khan developed the shear wall frame interaction system for mid high-rise buildings. This
structural system uses combinations of shear walls and frames designed to resist lateral forces.
The first building to utilize this structural system was the 35-stories Brunswick Building. The
Brunswick building was completed in 1965 and became the tallest reinforce concrete structure of
its time. The structural system of Brunswick Building consists of a concrete shear wall core

7. surrounded by an outer concrete frame of columns and spandrels. Apartment buildings up to 70
stories high have successfully utilized this concept.
Legacy
Khan's seminal work of developing tall building structural systems are still used today as the
starting point when considering design options for tall buildings. Tube structures have since been
used in many skyscrapers, including the construction of the World Trade Center, Aon Centre,
Petronas Towers, Jin Mao Building, Bank of China Tower and most other buildings in excess of
40 stories constructed since the 1960s. The strong influence of tube structure design is also
evident in the world's current tallest skyscraper, the Burj Khalifa in Dubai. According to Stephen
Bayley of The Daily Telegraph:
Khan invented a new way of building tall. So Fazlur Khan created the unconventional
skyscraper. Reversing the logic of the steel frame, he decided that the building's external
envelope could – given enough trussing, framing and bracing – be the structure itself. This made
buildings even lighter. The "bundled tube" meant buildings no longer need be boxlike in
appearance: they could become sculpture. Khan's amazing insight – he was name-checked by
Obama in his Cairo University speech last year – changed both the economics and the
morphology of supertall buildings. And it made Burj Khalifa possible: proportionately, Burj
employs perhaps half the steel that conservatively supports the Empire State Building. Burj
Khalifa is the ultimate expression of his audacious, lightweight design philosophy.
Other architectural work
Khan designed several notable structures that are not skyscrapers. Examples include the Hajj
terminal of King Abdulaziz International Airport, completed in 1981, which consists of tent-like
roofs that are folded up when not in use. The terminal's structure has been made to adapt to the
harsh desert conditions. The tent-like tensile structures advanced the theory and technology of
fabric as a structural material and led the way to its use for other types of terminals and large
spaces. The King Abdulaziz International Airport received several awards, including the Aga
Khan Award for Architecture, which described it as an "outstanding contribution to architecture
for Muslims".
Khan also designed the King Abdulaziz University, the United States Air Force Academy in
Colorado Springs and the Hubert H. Humphrey Metrodome in Minneapolis. With Bruce
Graham, Khan developed a cable-stayed roof system for the Baxter Travenol Laboratories in
Deerfield.
Khan and Mark Fintel conceived ideas of shock absorbing soft-stories, for protecting structures
from abnormal loading, particularly strong earthquakes, over a long period of time. This concept
was a precursor to modern seismic isolation systems.
Computers for structural engineering and architecture

8. In the 1970s, engineers were just beginning to use computer structural analysis on a large scale.
SOM was at the center of these new developments, with undeniable contributions from Khan.
Graham and Khan lobbied SOM partners to purchase a mainframe computer, a risky investment
at a time when new technologies were just beginning to take shape. The partners agreed, and
Khan began programming the system to calculate structural engineering equations and, later on,
to develop architectural drawings.
Professional milestones
List of buildings
Buildings on which Khan was structural engineer include:
 DeWitt-Chestnut Apartments, Chicago, 1963
 Brunswick Building, Chicago, 1965
 John Hancock Center, Chicago, 1965–1969
 One Shell Square, New Orleans, Louisiana, 1972
 140 William Street (formerly BHP House), Melbourne, 1972
 Sears Tower, Chicago, 1970–1973
 U.S. Bank Center, Milwaukee, 1973
 Hajj Terminal, King Abdulaziz International Airport, Jeddah, 1974–1980
 King Abdulaziz University, Jeddah, 1977–1978
 Hubert H. Humphrey Metrodome, Minneapolis, Minnesota, 1982
 One Magnificent Mile, Chicago, completed 1983
 Onterie Center, Chicago, completed 1986
 United States Air Force Academy, Colorado Springs, Colorado
Awards and chair
Among 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 and Illinois
Engineering Hall of Fame from Illinois Engineering Council (2006).
Khan was cited five times by Engineering News-Record as among those who served the best
interests of the construction industry, and in 1972 he was honoured with ENR's Man of the Year
award. In 1973 he was elected to the National Academy of Engineering. He received Honorary
Doctorates from Northwestern University, Lehigh University, and the Swiss Federal Institute of
Technology (ETH) Zurich.

9. The Council on Tall Buildings and Urban Habitat named the Fazlur Khan Lifetime Achievement
Medal after him, and other awards have been established in his honour, along with a chair at
Lehigh University. Promoting educational activities and research, the Fazlur Rahman Khan
Endowed Chair of Structural Engineering and Architecture honours Khan's legacy of engineering
advancement and architectural sensibility. Dan Frangopol, the first holder of the chair, said, "Dr.
Khan's legacy is the creativity, practicality, efficiency and cost-effectiveness of his work. I try to
incorporate these same qualities into my own work."