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Ever taller skyscrapers made possible by steel
Dubai, Shanghai, New York, London, Moscow: All around the world, ever taller and more striking new skyscrapers are being designed and built. Major cities are giving clear indications that the race to reach new heights is on. A city gains prestige by having the world’s tallest skyscraper but skyscrapers are also important for another reason. As more people move to cities, skyscrapers will become crucial to the development of urban living by taking advantage of limited construction space. Steel as a key construction material will inevitably have a role to play in the process of urbanisation in years to come.
Steel and skyscrapers: A brief history
The story of skyscrapers goes back to the second part of the 19th century when steel became one of the cornerstones of the world’s industrial economy. Thanks to the invention of the Bessemer process, steel became available in large quantities at a competitive price and soon supplanted iron in buildings. Steel framing and steel reinforced concrete made curtain-wall architecture possible, leading to the first skyscrapers. A curtain wall is a term used in architecture to describe the outer facade of a building. It is usually made of lightweight material and is supported by a load-bearing framed structure, typically made of structural steel and steel reinforced concrete.
The use of steel made the evolution of skyscrapers possible by allowing them to reach new heights. The 10-storey Home Insurance Building built in 1895 in Chicago was the first tall building to be supported by a steel skeleton of vertical columns and horizontal beams. It rose to a height of 42m. As skyscrapers grew taller and taller, architects and engineers were faced with a new enemy: wind. They had to experiment with new styles and building methods in order to build taller and more innovative structures.
10-storey Home Insurance Building, Chicago, US
- Woolworth Building, New York, US
Today a beautiful historical landmark, the 242m tall Woolworth Building, erected in New York City in 1913, was first to combine all of the components of a true skyscraper and it was to become the highest skyscraper in the world. The extensive foundations made up of closely spaced steel beams and concrete act as support to the steel structure of the building designed to resist expected wind forces. Innovative high-speed elevators provided service to its 60 floors.
- Empire State Building, New York, US
In 1931, the Empire State Building in New York City rose to a height of 281m. It would remain the world's tallest office building for 42 years.
Chicago’s Willis Tower (formerly Sear’s Tower) was the tallest building in the western hemisphere from 1973 to 1998. By 2000, only six other buildings in the world would surpass its height. The Willis Tower uses a tubular steel structure, a design concept invented by Fazlur Khan, a Bangladeshi-American structural engineer and architect from the world renowned architecture firm Skidmore, Owings and Merrill (SOM).
Tubular designs replaced conventional steel framing in most buildings rising above 40 storeys since the 1960s. The tubular system revolutionised tall building design by using all the exterior wall perimeter structure of a building to simulate a thin-walled tube. In addition to offering architects greater creative freedom, tubular designs use less steel and provide improved resistance to lateral loads such as wind forces, seismic forces, etc.
Reaching new heights thanks to steel
The last decade has seen an unprecedented number of skyscrapers rising higher and higher on the horizon of major cities, particularly in China and the Middle East. The sleek Burj Khalifa in Dubai today holds the title of tallest skyscraper in the world but the race to be the tallest changes all the time as new buildings are completed.
At present, the tallest skyscrapers in four regions of the world; the Middle East, North America, Asia and Europe are:
Burj Khalifa, Dubai, UAE, Middle East
Rising at 829.8m over the Gulf City of Dubai, the Burj Khalifa is the tallest man-made structure in the world.
Designed by Skidmore Owings and Merill (SOM), the Burj Khalifa used a bundled tube design and a composite of steel and concrete to hit its record height. The bundled tube system is a system that uses a number of interconnected tube frames. A total of 39,000 tonnes of steel rebar was needed for the construction and 15,500m2 of embossed stainless steel for cladding. Proportionally, the design uses half the amount of steel used in the construction of the Empire State Building thanks to the tubular system. The Burj Khalifa houses a mix of residential spaces, corporate suites, retail spaces and a Georgio Armani Hotel.
Planned for 2018 and under construction in Saudi Arabia, the Kingdom Tower is the most ambitious project so far and is no doubt set to take pole position in the ranking of the tallest skyscraper in the world with a staggering height of 1 km. It will use an estimated 80,000 tonnes of steel in its structure.
Shanghai Tower, Shanghai, Asia
Standing at 632m with 128 storeys and a floor area of 380,000m2, the Shanghai Tower is located in Shanghai’s Financial district of Lujiazui, Pudong. Its completion is scheduled for 2015. Following its topping out on 3 August 2013, the Shanghai Tower is the tallest building in China and the second-tallest in the world, surpassed only by the Burj Khalifa in Dubai.
Designed by Gensler and owned by a consortium of Chinese state-owned companies, the Shanghai Tower is the tallest of a group of three adjacent supertall buildings in Pudong. Gensler’s design team anticipated that three important design strategies— the asymmetry of the tower’s shape, its tapering profile, and rounded corners - would allow the building to withstand typhoon wind forces common to Shanghai.
Baosteel Construction took advantage of the research work carried out by steelmaker Baosteel to produce high strength steel, ultra-thick plates of over 100mm in thickness, in addition to other high-end construction steels. When the Shanghai Tower is completed, an estimated 100,000 tonnes of steel will have been used in the steel structure supporting the curtain wall.
One World Trade Centre, New York, North America
Designed by architects David Childs of Skidmore Owings Merrill (SOM), the 104-storey One World Trade Centre boasts a height of 417m and 242,000 m2 floor space. Including the spire, the total height reaches 541m, or 1,776 feet, a tribute to 1776, the year of US independence. A new landmark for New York, the One World Trade Centre is the tallest building in the US.
The tower's structure is designed around a strong steel frame made of beams and columns. The reinforced concrete core wall system at the centre of the tower acts as the main spine and provides support for gravitational loads as well as resistance to wind and seismic forces. The building incorporates highly advanced state-of-the-art life-safety systems that exceed the requirements of the New York City Building Code.
Steelmaker ArcelorMittal contributed to the design by supplying 14,000 tonnes of Histar® grade structural steel shapes from ArcelorMittal Differdange, Luxembourg and 20 to 30,000 tonnes of steel plates from ArcelorMittal Coatesville, Pennsylvania, US. By substituting common steel with high-strength Histar®, the weight of steel columns is reduced by 32% and beams by 19%. The lighter structures enable savings in greenhouse gases, with a 30% reduction in carbon emissions during construction. The 70 elevators and nine escalators for the One World Trade Center were provided by ThyssenKrupp.
The Shard, London, UK, Europe
The 72-storey Shard is a glass-clad pyramidal tower rising above the City of London. It was completed in 2012, stands at 245m high and has a floor area of 110,000 m2. The design uses an intelligent combination of steel and concrete: steel structures were used from ground floor to level 40, then up to floor 69 concrete takes over as the framing material, before the design reverts back to steel. Construction required 12,000 tonnes of steel which were supplied by the Tata Steel Scunthorpe works, North Lincolnshire, England.
Federation Tower, Moscow, Russia, Europe
The Federation Tower is a complex of skyscrapers being built in the Moscow International Business Centre. Construction is planned to be completed in 2015. The construction of the towers began in 2003. In November 2008, due to the world economic recession and lack of funding, the tower construction was suspended, to resume in September 2011.The complex consists of two towers built on one podium. Tower East or Vostok Tower is to be a 97-storey structure and is to become the tallest structure in Europe. The Vostok Tower uses ArcelorMittal Histar® high-strength steel. An estimated 9,500 tonnes of steel were required in the construction.
Over more than a century, steel has been a major contributor to the development of taller and ever more resistant skyscrapers and the acceleration of urbanisation in the decades to come is not set to slow down the pace of development.
