angle-left Fazlur Rahman Khan, the visionary of skyscrapers
TUNGSTENO

Fazlur Rahman Khan, the visionary of skyscrapers

What we owe to Fazlur Rahman Khan is the design of the structural system of tubes, essential for the construction of skyscrapers. Credit: Wikimedia / Skidmore, Owings & Merrill LLP .

ISABEL RUBIO ARROYO | Tungsteno

The skyscraper Burj Khalifain Dubai is currently the tallest building in the world at 828 metres high and 163 stories. The construction of this great architectural work, and of many other structures that seem to touch the sky, would not have been possible without Fazlur Rahman Khan. Considered by many as "the Einstein of structural engineering," he is praised for his legacy, as most modern skyscrapers use his tubular designs.

Rahman first saw a skyscraper when he was 21 years old. At that time, he did not imagine that he would become a giant among the engineers who today construct this type of building, hallmarks of modern cities such as New York, Chicago or Hong Kong. But two decades later, he would become the architect of the Sears Tower (now called the Willis Tower) of Chicago, which was, thanks to its revolutionary design for the time, the tallest building in the world for 24 years at 442 metres high.

To understand how this Asian engineer came to design what is currently the third tallest tower in North America (only the CN Tower in Toronto and the One World Trade Center in New York are taller), we must go back to his origins 90 years ago. Rahman Khan was born on April 3, 1929 in Dhaka, which was then part of British India that later became Bangladesh (1971). He was raised in a village and his father, who was a professor of mathematics, encouraged him to study civil engineering. He did so at the Indian Institute of Engineering and Technology and at the University of Engineering and Technology of Bangladesh.

Thanks to his academic excellence, he obtained two scholarships —one Fulbright and one from the government of Pakistan— and moved to the United States in 1952. In just three years he obtained three degrees at the University of Illinois: two masters degrees in structural engineering and applied mechanics, and a doctorate in structural engineering.

Considered "the Einstein of structural engineering," Rahman Khan knew how to look beyond traditional designs and adapt them to the needs of people. Credit: Paula Abrahao.

The structural system of tubes

Rahman began his professional career against that background, determined to look beyond the structures of conventional buildings. The growth in the US population in the first half of the 20th century, fueled by the baby boom of the 1950s, intensified the need to build taller buildings that would house more homes and offices. However, building skyscrapers such as the Empire State Building, which allowed for a large amount of usable space in a small footprint, was prohibitively expensive.

What’s more, before the 1960s it was not possible to provide lateral support to buildings of more than 20 or 30 stories. The Asian engineer was aware of this when in 1955 he started working in Chicago at the architecture firm SOM (Skidmore, Owings & Merrill). There he developed his great contribution to the modern world: the structural system of tubes for tall buildings.

Rahman's idea was to create a building not supported by central steel supports, but by an external frame constructed of separate and interconnected columns. In other words, the building was designed to act as a hollow cylinder that would allow it to better resist lateral loads such as strong winds, and free up the interior space that was normally used for central supports. Khan tested this structure for the first time with the 42-story DeWitt-Chestnut building in Chicago. While it did not exceed the Empire State Building in height, it won in terms of efficiency. The building used 145 kg of steel per square metre, a figure significantly below the 206 kg per square metre of the Empire State Building. Construction costs were also significantly reduced.

The Hajj Terminal, known for its tent-like roof structure,was specially built for the annual pilgrimage to Mecca.. Credit: Courtesy SOM.

Beyond the skyscrapers

This design marked the beginning of a new era in the world of construction. Most buildings greater than 40 stories built since the 1960s have employed this structure. An example is the John Hancock Center, one of the classic skyscrapers of Chicago, which was also designed by Rahman together with the architect Bruce Graham. With 108 stories and 344 metres in height, it became the second tallest building in the world in 1968.

Rahman continued to set milestones until he died of a heart attack in 1982 at the age of 52. In 1971 he also designed in Chicago the structure that for more than 20 years was the tallest building in the world: the Sears Tower. He also won the Construction’s Man of the Year award, and not just for designing skyscrapers. He is also the architect of other structures such as the Hajj terminal of King Abdulaziz International Airport; King Abdulaziz University; the United States Air Force Academy in Colorado Springs and the Hubert H. Humphrey Metrodome in Minneapolis.

But he has gone down in history for his structural tube system, which today many of the tallest buildings in the world use. This pioneer in the design of modern skyscrapers knew how to look beyond traditional designs and adapt them to the needs of people. He was convinced that his work had a positive impact on society. Nowadays he is an example to follow for numerous engineers, who years ago he encouraged to never lose sight of the objective of their profession: "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."

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Tungsteno is a journalism laboratory to scan the essence of innovation. Devised by Materia Publicaciones Científicas for Sacyr’s blog.

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