SCINTILLA '11

Pandulipi invites comments or reviews for the golden jubilee annual college magazine 2011 , "Scintilla '11" . You may write to the Secretary, Pandulipi at pandulipi10@gmail.com

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Friday, December 24, 2010

SKYSCRAPERS, HIGH-RISES, AND A BENGALI MIND

What I am about to put in words in the next few paragraphs , may not necessarily be exactly what you would call a modern development of science, but I believe it to be the essence of innovation.

Today, high-rises crop up around us at an abominable speed. Humankind seems to have a difficulty in satiating its soaring ambition to reach greater and even greater heights. Well, long live our so called civilization, and our so called humanity; A hundred stories above you, and a million sad stories in one thousand minds around you, but I’d rather not go out of topic.

The thing is, today we cannot imagine a metropolitan city without skyscrapers. We wonder at their immense heights, and often do we admire their architecture. But trust me, they were as complicated and cumbersome as they look, until a certain person came into the limelight and revolutionized the entire idea of their construction.

Fazlur Rahman Khan was born in Shibchar, Dhaka Division, Bangladesh on 3rd April, 1929. In a conservative middle class family, where education is usually the ornament of one’s personality, Khan grew up and lived up to his family tradition in flying colors. He pursued his undergraduate degree at Bengal Engineering College, University of Calcutta (now B.E.S.U., Shibpur), and attained his bachelor’s degree in Civil Engineering from the Engineering Faculty of the University of Dhaka (now B.U.E.T) in 1951. Subsequently, two scholarships, one of them being a Fulbright, allowed him to travel to the United States, to pursue post-graduate studies, at the University of Illinois, Urbana-Champaign. Khan, as shining as he always was, earned two Master degrees by 1954, one in Structural Engineering, and another in Theoretical and Applied Mechanics. He further obtained his Ph.D. Degree in Structural Engineering in the following years.

Khan was employed by a firm called Skidmore, Owings and Merrill, in 1955 and he started working as an engineer for the first time at Chicago, Illinois. Though some of his most notable works are in the United States, he is also renowned for his works in Saudi Arabia, and Bangladesh.

What makes Fazlur Rahman Khan such a remarkable persona in the civil engineering society is his innovation and research in the field of multistoried buildings (Pardon me, for henceforth, I am compelled to move on to more technical terms). By the 1960’s, Multistoried buildings were already very popular and they seemed to be a plausible solution to the ever growing population of the world. But an engineer must consider ten other possibilities, besides aesthetic and social reasons, before he would build something as immense as a skyscraper. For example, one of the major problems with very tall buildings lies in the lateral forces they are subjected to. These may be wind forces, earthquake forces, possible sudden loads, and it is only obvious that for the building to be safe, it must be able to sustain such loads effectively.

As I have already stated, by the 1960’s, skyscrapers had already made a successful entrance into the construction sector. One of the most notable skyscrapers built in the 1931 was the Empire State Building. However, there lied one object of concern. Such buildings were, until then, made of rigid jointed steel space frames. Steel, being a very costly raw material, posed a problem where extremely tall buildings (of say more than 35 stories) were involved. It is at this juncture that Khan makes an appearance, with his ingenious theory of “Tube Structural System”.

Khan’s theory was based on the fact, that for any tall building, the entire wall perimeter of the structure is used to simulate a thin walled equivalent tube structure. This thin external wall (the word thin not in its usual meaning, of course) is informally referred to as the “skin” of the building. Such buildings tend to be much more efficient, economical, have reduced penalty for taller heights, and increased resistance to lateral forces. Khan further divided his tube structure into three categories, and some of the greatest buildings of the latter part of the 20th century followed suit of his theory.

The first category, the framed tube structure, the very first one Khan is known to have implemented into a real design, was an instant success. In such a structure, three, four or more, frames were joined at their edges to form a vertical tube like structure. Each of the concerned frames is cantilevered from the foundation towards the top. The remaining periphery of the structure is formed by exterior columns aligned along the extern of the building. These columns are further inter-connected, as well as with the frames. As such, any lateral load, such as earthquake or wind load is resisted by the structure as one single unit. Such buildings, thus, are automatically much more efficient from seismic point of view. In addition to this, the tubular structure is quite stable, hence eliminating the need for interior columns and shear walls. This enables more usable floor space. Another wonderful aspect of such buildings lies in the fact that, in spite of the extern of the building being occupied by columns, about 50% of the perimeter is available for openings such as windows and doors. For larger openings, the exterior column setup requires some minor modification. Possibly, the most notable Framed Tube Structure, (though not designed by Khan himself), was the World Trade Centre.

The Tube and X-Bracing structure was a modification of the framed tube structure. Here, exterior columns are more spaced apart, but are interconnected by cross bracings (X- Shaped truss like members). In such buildings, the so called skin (the thin walled extern) of the tubular structures becomes vivid as an integral part of the structure itself. Here, nearly all the lateral loads are transferred to the exterior columns, thus almost eliminating the need for interior columns in the building. Such a tubular system enables the building to stand upright during earthquakes and wind-storms. Also, X-Braced tube structures have more available allowance for openings. The John Hancock centre in Chicago, designed by Khan in 1965 (completed in 1969) is the most notable cross braced tubular structure. Not only is it noted as a high performance high-rise, but also as an architectural icon. From another point of view, John Hancock centre was much more economically sound, requiring 145 Kg of steel per square meter, compared to the Empire State Building (an earlier rigid steel framed structure) which required 206 Kg of steel per square meter.

The final and most important variation was the bundled tube structure. It is not only the most economically efficient type of structure among the three, but also the most versatile type for its allowances of architectural essence. Tubes no longer needed to be box like, since in such structures, bundles of exterior columns (interconnected as well as intra-connected), could take any possible shape at the extern. The most notable building of this type is the Sears Tower (currently known as Willis Tower), designed by Khan again, and completed 1974. At the time of its construction, it was the tallest building of the United States.

From then on, the influence of Khan’s tubular structure spread around the world like wildfire. Some of the most notable structures in the entire world followed along his lines of design. These include the World Trade Centre, Petronas Twin Towers, Willis Tower (formerly Sears Tower), Jin Mao Building, Onterie Centre, One Magnificent Mile, Citigroup Centre, Bank of China Tower, and the Burj Khalifa (which is currently the tallest building in the World).

Khan continued his wizardry in the field of structural engineering in the subsequent years. The first “Sky Lobby” was also designed by Khan. Buildings with sky lobbies at that time include the WTC, Twin Towers, and the Taipei 101. John Hancock centre also featured a sky lobby in its 44th floor. Khan’s dream of “people working and living in the sky” had finally come true. Khan also designed the Hajj Terminal, King Abdulaziz International Airport, and King Abdulaziz University in Jeddah. He was awarded the “Aga Khan Award” for his works at Jeddah. Most notably, Khan’s very first design in his career, the “DeWitt Chestnut Apartments” in Chicago, and his very last, The Onterie Centre and One Magnificent Mile were astonishingly, concrete framed tubular structures.

Fazlur Rahman Khan was as versatile a human being as he was an engineer. After an early death on March 27th, 1982, at an age of 52, the world of structural engineering lost a pioneer in his field. During his lifetime, he was cited five times among “Men Who Served the Best Interests of the Construction Industry” by Engineering-News Record. He was named “Construction’s Man of the Year” in 1972. He was posthumously awarded The John Parmer Award in 1987 by the Structural Engineer’s Association of Illinois. The Government of Bangladesh posthumously awarded him the “Independence Day Medal”, the highest honor of the state, for creating public opinions and amassing emergency fund during its War of Liberation in 1971. All records of his pioneering work, which are included in manuscripts, sketches, audio tapes and slides, found in his office at the time of his death, are currently held in custody by the Ryerson and Burnham Libraries at the Art Institute of Chicago.

It is only fitting and respectable, that I conclude my article with one of the sayings of Fazlur R. Khan himself,

“The technical man must not be lost in his own technology; he must be able to appreciate life, and life is an art, drama, music,

And most importantly, people”

Dr. Fazlur Rahman Khan was honored by U.S. President Barack Obama in his speech at Cairo, Egypt in 2009.

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