The ultimate tall challenge: build a Gulf mountain

09 February 2007

The Burj Dubai, soaring heavenwards to more than 1,000 feet, is at its most impressive close up. In January, construction reached the 100th floor. Another level is being added every three-four days. Some time in mid-May, the Burj will become the world's highest tower. Its target height is more than 2,000 feet.

Dubai and the GCC are at the cutting edge of a tall building revolution. Work has started on Doha's 80-storey Dubai Tower. Nakheel is working on a tower for its Dubai Waterfront project that could be the tallest yet. A dozen other Gulf super-tall projects are on the drawing board.

The MEED Building Tall conference in January explored the challenges presented by vertical structures of increasing height. It also dismissed several Gulf construction myths.

It has been proven by the Burj al-Arab and Emirates Towers that skyscrapers can be built on the southern littoral of the Gulf. Beneath the sand is a thick band that comprises compacted ancient sea shells. Piles driven deep enough into it can support unlimited weight.

Arabia is seismically benign. New York, the birthplace of the skyscraper, is more prone to earthquakes than the UAE. The Shamal (North) wind that blows for up to 40 consecutive days down the Gulf normally never rises above 40 kilometres an hour. It is less powerful at more than 500 feet than it is below.

Fire risks in tall buildings are smaller than in low ones. Sprinklers are invariably successful in extinguishing fires. Modern steel and concrete can survive the most intense heat. New thinking about evacuating tall buildings prompted by the 9/11 attacks has produced reassuring solutions.

Every building sways. Horizontal movement increases with height. New York structural engineer and managing principal of Thornton Tomasetti, Dennis Poon, who worked on Taipei 101, showed how a circular shape steel damper internally suspended within the building reduced swaying to such an extent that it became imperceptible. Tall buildings cause strong winds at their base which can drive away visitors. The Burj Dubai deals with the problem by changing shape as it rises.

There are only two serious constraints to vertical construction. One is that the higher the structure is, the wider it must be at the base. This makes it impossible to build tall where land is limited and expensive. The other is the challenge of moving people and materials vertically.

Lift numbers increase with storeys and people in tall buildings. But more lifts means a larger central core that displaces revenue-generating office, hotel and living space. People can't travel vertically in comfort at more than 40 kilometres an hour. In Taipei 101, the fast lifts are pressurised.

Perhaps the moment has come to think differently about vertical building. About 5,000 years ago, the Egyptians erected the pyramids, the tallest manmade structures until the invention of the lift at the end of the 19th century. They have a wide base to ensure stability and allow easy human access to the top.

The modern answer to vertical building might involve drawing inspiration from the pharaohs, but building on a far larger scale. With a gentler gradient, all outside surfaces could be used for housing and leisure. Hidden inside could be power, water and sewage plants. Warehousing, manufacturing and even offices could be accommodated. A huge artificial environment usable in the Gulf's summer months might be formed by the hollow peak.

The scale would have to be enormous, perhaps 1 kilometre to the top and 10 kilometres across. But a city mountain built vertically in layers would be internally coherent and externally pleasing. Built properly, it could cut per capita carbon emissions. And by reducing urban sprawl, it would preserve more of the natural environment now being lost as Gulf cities expand horizontally.

In the Middle East, humans for the first time rejected the supremacy of nature and

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