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Fazlur Rahman Khanফজলু�র রহমা�ন খা�ন

Fazlur Rahman Khan

BornApril 3, 1929Dhaka, Bangladesh

DiedMarch 27, 1982 (aged 52)Jeddah, Saudi Arabia

Resting placeGraceland Cemetery,Chicago, Illinois

Nationality Bangladeshi

Education

Bengal Engineering and Science University, Shibpur, Bangladesh University of Engineering and Technology, University of Illinois at Urbana-Champaign

WorkEngineering discipline

Architectural, civil, structural

Significant design

John Hancock Center, Willis Tower, Hajj Terminal, King Abdulaziz University, One Magnificent Mile, Onterie   Center

Significant Aga Khan Award for Architecture,

awardsIndependence Day Award,[1] AIA Institute Honor for Distinguished Achievement

Fazlur Rahman Khan (Bengali: ফজলু�র রহমা�ন খা�ন, Fozlur Rôhman Khan) (April 3, 1929 - March 27, 1982) was a Bangladeshi structural engineer and architect, who initiated structural systems that form the basis of tall building construction today.[2][3][4][5] Considered the Father of tubular designs for high-rises,[6] Khan became an icon in both architecture and structural engineering.[7] He is the designer of Willis Tower – the tallest building in the United States (and tallest in the world for many years) and John Hancock Centre, a 100-story tall building. He also designed structures that are not high rises such as the Hajj Terminal and helped in initiating the widespread usage of computers for structural engineering. Khan, more than any other individual, ushered in a renaissance in skyscraper construction during the second half of the twentieth century[8] and made it possible for people to live and work in "cities in the sky".[9] Khan in his short life created a legacy of innovations that is without peer and left an unprecedented and lasting influence on the profession, both nationally and internationally.[10][11] 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.[2] CTBUH named an award after him called Fazlur Khan Lifetime Achievement Medal. Khan's seminal work of developing tall building structural systems are still used today as starting point when considering design options for tall buildings.[12]

Contents

1 Biography o 1.1 Education o 1.2 Career o 1.3 Personal interests

2 Innovations o 2.1 Tube structural systems

2.1.1 Framed tube 2.1.2 Trussed tube and X-bracing 2.1.3 Bundle tube 2.1.4 Concrete tube structures 2.1.5 Influence

o 2.2 Sky lobby 3 Hajj Terminal and non skyscrapers 4 Computers for structural engineering and architecture 5 Professional milestones

o 5.1 List of buildings o 5.2 Awards and Chair

6 Charity 7 Death 8 See also 9 References

10 Further reading 11 External links

Biography

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

Education

Khan received his matriculation from Armanitola Government High School, in Dhaka. He received his Bachelor of Civil Engineering degree from Ahsanullah Engineering College, University of Dhaka, (now Bangladesh University of Engineering and Technology). He received a Fulbright Scholarship and a Pakistan 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. 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.

Career

In a career marked by innovation in structural engineering and collaboration between engineering and architecture, Khan introduced design methods and concepts that set new standards for efficient use of material and suggested new possibilities for building architecture. 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.[13] 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, topping out the Empire State Building (1931), and still the tallest in the United States since its completion in 1974. He is also responsible for designing notable buildings in Bangladesh, Australia and Saudi Arabia.

Fazlur Khan had a unique understanding of forces, materials, behavior, as well as art, literature, and architecture. Fazlur Khan was not only a creative structural engineer, he was also a philosopher, visionary, educator and humanitarian. He said, "Think logically and find the relationships which exist in every system, because it will help you understand nature itself, making living more meaningful and exciting." According to John Zils, senior engineer and associate partner with Skidmore, Owings & Merrill (SOM), "It was his unique ability to bridge the gap between architectural design and structural engineering that truly set Faz apart from other structural engineers." Because of that, Khan became an icon in both architecture and structural engineering. Khan 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."[10]

Fazlur Khan's personal papers, the majority of which were found 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.

Personal interests

Outside of work, Khan enjoyed spending time with his family (wife Liselotte and daughter Yasmin). He enjoyed singing, poetry - his favorite poet was Rabindranath Tagore. He also liked playing table tennis.

Innovations

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.[14]

Tube structural systems

See also: Tube (structure)

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.[15] Most buildings over 40-storeys constructed since the 1960s now use a tube design derived from Khan’s structural engineering principles.[16]

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.[17] 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.[18][19] 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 more than any other individual brought in a rebirth in skyscrapers construction after a hiatus for over thirty years.[10][20]

Khan's tubular designs have dominated skyscraper construction design since the 1960s. The tubular systems have yet to reach their limit when it comes to height.[21] The beauty of Khan’s tubular systems is that buildings can be constructed using steel or concrete, or a composite of the two to reach lofty heights. His clear approaches to structural systems have often led to expressive structures.

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.[22] 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."[23]

Khan's initial projects were the 43 stories DeWitt-Chestnut (1964) and 35 stories Brunswick Building (1965). He then did the John Hancock Center (1969), a 100 stories tall building and would later go on to America's tallest building the iconic Willis Tower (formerly called Sears 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."[24] 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.[16]

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.[25] This laid the foundations for the framed tube structure used in the construction of the World Trade Center.

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 are located as high as the 90th floor.

Trussed tube and X-bracing

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 floorplan (and usable floor space) if the architect desires. Original features such as the skin, pioneered by Fazlur Khan, have made the John Hancock Center an architectural icon.[16][26]

In contrast to earlier steel-frame structures, such as the Empire State Building (1931), which required about 206 kilograms of steel per square metre and Chase Manhattan Bank Building (1961), which required around 275 kilograms of steel per square metre, the John Hancock Center was far more efficient, requiring only 145 kilograms of steel per square metre.[25] The trussed tube concept was applied to many later skyscrapers, including the Onterie Center, Citigroup Center and Bank of China Tower.[27]

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.

Onterie Center, an award winning high rise

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."[26][28]

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.[16] The Brunswick Building, a 35 stories tall building built in 1965 also used this structural system.[29]

Influence

Khan's seminal work of developing tall building structural systems in structural steel and reinforced concrete based on building height are still used today as starting point when considering design options for tall buildings.[12] 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.[16] 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.[30]

These pioneering structural systems shaped skyline of cities around the world. Khan is the foremost structural engineer of the 20th century whose contributions to the design of tall buildings have had a profound impact on the profession of architecture and engineering. In his short life, Khan re-shaped the concept of super-tall buildings and man’s ability to live and work in the sky. His developments are among today’s “conventional” systems for skyscraper design. Khan never acquired a household name, but a quarter-century after his death, his legacy lives on in the lives and work of a new generation of structural engineers.[9]

Sky lobby

The first sky lobby was also designed by Khan for the John Hancock Center. Later buildings with sky lobbies include the World Trade Center, Petronas Twin Towers, Taipei 101 and the Burj Khalifa. The 44th-floor sky lobby of the John Hancock Center also features the first high-rise indoor swimming pool, which remains the highest in America.[31] This was the first time that people could have the opportunity to work and live "in the sky".[26]

A sky lobby is an intermediate floor, where people change from an express elevator that stops only there to a local elevator that stops at every floor within a segment of the building. When designing very tall buildings supplying enough elevators is a problem. Travellers wanting to reach a specific higher floor may conceivably have to stop at a very large number of other floors on the way up to let other passengers off and on. This increases travel time, and indirectly requires many more elevator shafts to still allow acceptable travel times – thus reducing effective floor space on each floor for all levels. To resolve this issue he invented the sky lobby.

Hajj Terminal and non skyscrapers

The Hajj terminal was the world’s largest cable-stayed, fabric-roofed structure. The Hajj terminal serves as the physically welcoming, culturally symbolic, and structurally innovative portal for over one million pilgrims annually.

Besides designing many notable super tall buildings with his groundbreaking structural systems, Khan also designed other notable structures that are not skyscrapers. Examples include the Hajj Terminal (completed in 1981), which consists of tent like roofs that are folded up when not in use. The Hajj terminal's structure is unique and 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 Hajj Terminal has won the Aga Khan Award for Architecture - "An outstanding contribution to architecture for muslims"; 2010 • AIA • National 25 Year Award; 1983 • AIA • National Honor Award for Architecture; 1983 • World Architecture • AIA - New York City Chapter • Distinguished Architecture Award; 1982 • Industrial Fabrics Association • International President's Award of Merit; 1981 • Progressive Architecture • P/A Award: Architectural Design.[32]

King Abdulaziz International Airport, King Abdulaziz University, United States Air Force Academy, Colorado Springs, Hubert H. Humphrey Metrodome in Minneapolis, and the Baxter Travenol Laboratories in Deerfield, III., whose roof is suspended from cables were also designed by Khan.[23]

Computers for structural engineering and architecture

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.[22][33]

Professional milestones

List of buildings

Some the most famous buildings Khan was responsible for performing as structural engineer include the following:

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

FR Khan in ENR

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).[34]

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 honored 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.[5]

The Council on Tall Buildings and Urban Habitat (CTBUH) named an award after him called the Fazlur Khan Lifetime Achievement Medal and several other awards have been established in his honor since his passing, along with a chair at Lehigh University. Promoting educational activities and research, the Fazlur Rahman Khan Endowed Chair of Structural Engineering and Architecture honors Khan’s legacy of engineering advancement and architectural sensibility.[5]

Charity

In 1971 the Bangladesh liberation war brokeout. Khan was heavily involved with creating public opinion and garnering emergency funding for Bengali people during the 1971 Bangladesh Liberation War. He created the Chicago-based organization known as Bangladesh Emergency Welfare Appeal.

Death

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.[10]

See also

Architecture of Bangladesh Engineering Legends

References

1. ̂ "List of Independence Awardees". Cabinet Division, Government of Bangladesh. Retrieved 2012-11-29.

2. ^ a b Ali Mir (2001), Art of the Skyscraper: the Genius of Fazlur Khan, Rizzoli International Publications, ISBN 0-8478-2370-9

3. ̂ File:Skyscraper structure.png4. ̂ Hong Kong   : PHigh-Rise Structural Systems . Darkwing.uoregon.edu. Retrieved on

2012-06-26.5. ^ a b c http://www.lehigh.edu/~infrk/2011.08.article.html6. ̂ Weingardt, Richard (2005). Engineering Legends. ASCE Publications. p. 75. ISBN 0-

7844-0801-7

7. ̂ Richard Weingardt (10 August 2005). Engineering Legends: Great American Civil Engineers   : 32 Profiles of Inspiration and Achievement . ASCE Publications. pp. 75–. ISBN 978-0-7844-0801-8. Retrieved 26 June 2012.

8. ̂ Richard Weingardt (10 August 2005). Engineering Legends: Great American Civil Engineers   : 32 Profiles of Inspiration and Achievement . ASCE Publications. pp. 78–. ISBN 978-0-7844-0801-8. Retrieved 26 June 2012.

9. ^ a b Designing 'cities in the sky'. Lehigh University, Engineering & Applied Science. Retrieved on 2012-06-26.

10. ^ a b c d http://www.structuremag.org/article.aspx?articleID=121111. ̂ IALCCE 2012: Keynote Speakers Details. Ialcce2012.boku.ac.at. Retrieved on 2012-

06-26.12. ^ a b https://ialcce2012.boku.ac.at/keynote_details.php?profile=513. ̂ "Obama Mentions Fazlur Rahman Khan". The Muslim Observer. June 19, 2009.

Retrieved October 11, 2011.14. ̂ Mir M. Ali, Kyoung Sun Moon. "Structural developments in tall buildings: current

trends and future prospects". Architectural Science Review (September 2007). Retrieved 2008-12-10

15. ̂ Weingardt, Richard (2005). Engineering Legends. ASCE Publications. p. 76. ISBN 0-7844-0801-7

16. ^ a b c d e Ali, Mir M. (2001). "Evolution of Concrete Skyscrapers: from Ingalls to Jin mao". Electronic Journal of Structural Engineering 1 (1): 2–14. Retrieved 2008-11-30

17. ̂ https://docs.google.com/viewer?a=v&q=cache:8B4PPiZ3LjMJ:www.efka.utm.my/thesis/images/4MASTER/2004/1JSB/Part1/NGSOOKJENMAC021035D04TT2.doc+chapter+2+design+philosophy+of+reinforcement+concrete+tall+building&hl=en&pid=bl&srcid=ADGEESiU-qZPyMFTJOL3UBsS7ViutQOurhn4BA8QC-XAd73cvV2HFtIcSIphPpkVU4lzwEvwyKrMppAtnHz5NE3og62jLT9CwtuGWVXUHyEeF3sfh1G9GVRZUgFOYQLLEutyyyoSn49d&sig=AHIEtbSA_8S1o-jYf1G7B4H_i3b0TiON2Q

18. ̂ On the rise. Constructionweekonline.com (2011-01-31). Retrieved on 2012-06-26.19. ̂ Bayley, Stephen. (2010-01-05) Burj Dubai: The new pinnacle of vanity. Telegraph.

Retrieved on 2012-06-26.20. ̂ https://docs.google.com/viewer?

a=v&q=cache:2RHuSbYRzRMJ:www.crcnetbase.com/doi/abs/10.4324/NOE0415232418.ch32+fazlur+khan+transformed+city+skyline&hl=en&pid=bl&srcid=ADGEESihn5j7rJIRtFoJCbwq8wShPOaHpe58yoE73coq6B9k34MzK5KG_g4uiZBYe3eN3-tzyegycQt0R19bl_DyxG3n6VhbUB22qDRSmc7qpRhhOFaROXHdb6uDXuP8wMukBd_aP404&sig=AHIEtbTdAXBk_8DZzecEJPiR1Tubq-RmxQ

21. ̂ http://darkwing.uoregon.edu/~struct/resources/pencil/systems.htm#types22. ^ a b http://www.gostructural.com/magazine-article-gostructural.com-4-2011-

fazlur_rahman_khan__ph.d.__1929_1982_-8285.html23. ^ a b http://www3.lehigh.edu/News/RCEASnews_story.asp?iNewsID=207524. ̂ "Evolution of Concrete Skyscrapers". Retrieved 2007-05-14.25. ^ a b Alfred Swenson & Pao-Chi Chang (2008). "Building construction: High-rise

construction since 1945". Encyclopædia Britannica. Retrieved 2008-12-09.

26. ^ a b c "Khan, Fazlur Rahman". Banglapedia. Retrieved 2008-12-09.27. ̂ [1], pg 34, Introduction to Tall building Structures, Dr. D.M Chan28. ̂ "Fazlur R. Khan". Encyclopædia Britannica. 2008. Retrieved 2008-12-10.29. ̂ http://www.som.com/content.cfm/brunswick_building30. ̂ Stephen Bayley (5 January 2010). "Burj Dubai: The new pinnacle of vanity". The Daily

Telegraph. Retrieved 2010-02-26.31. ̂ John Hancock Center, Emporis32. ̂

http://www.som.com/content.cfm/king_abdul_aziz_international_airport_hajj_terminal/33. ̂ http://www.som.com/content.cfm/blackbox_technological_trajectory_3

Tube (structure)

In structural engineering, the tube is the system where in order to resist lateral loads (wind, seismic, etc.) 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 Skidmore, Owings and Merrill's (SOM) Chicago office.[1] The first example of the tube’s use is the 43-story Khan-designed DeWitt-Chestnut Apartment Building in Chicago, Illinois, completed in 1963.[2]

The system can be constructed using steel, concrete, or composite construction (the discrete use of both steel and concrete). It can be used for office, apartment and mixed-use buildings. Most buildings in excess of 40 stories constructed since the 1960s are of this structural type.

Contents

1 Concept 2 History 3 Variations

o 3.1 Framed tube o 3.2 Trussed tube o 3.3 Bundled tube

4 Diagram 5 References

Concept

The tube system concept is based on the idea that a building can be designed to resist lateral loads by designing it as a hollow cantilever perpendicular to the ground. In the simplest incarnation of the tube, the perimeter of the exterior consists of closely spaced columns that are tied together with deep spandrel beams through moment connections. This assembly of columns and beams forms a rigid frame that amounts to a dense and strong structural wall along the exterior of the building.[3]

This exterior framing is designed sufficiently strong to resist all lateral loads on the building, thereby allowing the interior of the building to be simply framed for gravity loads. Interior columns are comparatively few and located at the core. The distance between the exterior and the core frames is spanned with beams or trusses and intentionally left column-free. This maximizes the effectiveness of the perimeter tube by transferring some of the gravity loads within the structure to it and increases its ability to resist overturning due to lateral loads.

History

By 1963, a new structural system of framed tubes had appeared in skyscraper design and construction. Fazlur 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."[4] Closely spaced interconnected exterior columns form the tube. Horizontal loads, wind for example, 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. 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 apartment building which Khan designed and which was completed in Chicago by 1963.[5] This laid the foundations for the tube structural design of many later skyscrapers, including his own John Hancock Center and Willis Tower, and the construction of the World Trade Center, Petronas Towers, Jin Mao Building, and most other supertall skyscrapers since the 1960s.[6]

Variations

From its conception, the tube has been varied to suit different structural requirements:

Framed tube

WTC Twin Towers structures was one of the first in use the framed tube design.

This is the simplest incarnation of the tube. It can take a variety of floor plan shapes from square and rectangular, circular, and freeform. This design was first used in Chicago's DeWitt-Chestnut apartment building, designed by Khan and completed in 1965, but the most notable examples are the Aon Center and the original World Trade Center towers.

Trussed tube

Also known as the braced tube, it is similar to the simple tube but with comparatively fewer and farther-spaced exterior columns. Steel bracings or concrete shear walls are introduced along the exterior walls to compensate for the fewer columns by tying them together. The most notable examples incorporating steel bracing are the John Hancock Center, the Citigroup Center and the Bank of China Tower. When the outer columns are insuffient to support the load, interior cores can be used. 780 Third Avenue on Manhattan, a 50-story concrete frame office building, is an example of using concrete shear walls for bracing while also incorporating an off-center core.[7]

Bundled tube

Breakdown of the bundled tube structure of the Willis Tower with simplified floor plans.

Instead of one tube, a building consists of several tubes tied together to resist the lateral forces. Such buildings have interior columns along the perimeters of the tubes when they fall within the building envelope. Notable examples include Willis Tower and One Magnificent Mile.

Willis Tower, completed in 1973, introduced the bundled tube structural design and was the world's tallest building until 1998

The bundle tube design was not only highly 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."[8] The bundled tube structure meant that "buildings no longer need be boxlike in appearance: they could become sculpture."[9]

Structural systemFrom Wikipedia, the free encyclopediaJump to: navigation, search

The term structural system or structural frame in structural engineering refers to load-resisting sub-system of a structure. The structural system transfers loads through interconnected structural components or members.

Commonly used structures can be classified into five major categories, depending on the type of primary stress that may arise in the members of the structures under major design loads. However any two or more of the basic structural types described in the following may be combined in a single structure, such as a building or a bridge in order to meet the structures functional requirements.[1]

Tensile structures : Members of tensile structures are subjects to pure tension under the action of external loads. Because the tensile stress is uniformly distributed over the cross-sectional area of members, the material of such a structure is utilized in the most efficient manner.

Compressive structures : Compression structures develop mainly compressive stresses under the action of axial loads. Because compressive structures are susceptible to buckling or instability, the possibility of such a failure should be considered in their designs if necessary, adequate bracing must be provided to avoid such failures.

Trusses : Trusses are composed of straight members connected at their ends by hinged connections to form a stable configuration. Because of their light weight and high strength, are among the most commonly used type of structure.

Shear structures : These are structures such as reinforced concrete shear walls, which are used in multistory buildings to reduce lateral movements due to wind loads and earthquake excitations. Shear structures develop mainly in-plane shear with relatively small bending stresses under the action of external loads.

Bending structures: Bending structures develop mainly bending stresses under the action of external loads. The shear stresses associated with the changes in bending moments may also be significant should be considered in their designs.

Contents

1 High-rise buildings 2 See also 3 References 4 External links

High-rise buildings

The structural system of a high-rise building is designed to cope with the vertical gravity loads and lateral loads caused by wind or seismic activity. The structural system consists only of the members designed to carry the loads, all other members are referred to as non-structural.

A classification for the structural system of a high-rise was introduced in 1969 by Fazlur Khan and was extended to incorporate interior and exterior structures. The primary lateral load-resisting system defines if a structural system is an interior or exterior one.[2] The following interior structures are possible:

Hinged frame Rigid frame Braced frame and Shear-walled frame Outrigger structures

The following exterior structures are possible:

Tube Diagrid Space Truss Exoskeleton Superframe