China's National Stadium, or the Bird's Nest, as it has become known, is the world's largest steel structure and the most complex stadium ever constructed. It is "one of the key engineering marvels in the world today."
As a testament to its significance, it's on the city's north-south axis, which also includes the Forbidden City, Tian’anmen Square and the Temple of Heaven, travelling south. It is on the Olympic Green about 8km from the center of Beijing.
The Bird’s Nest was designed by Swiss Architects, Herzog & de Meuron, and a Chinese Architect, Li Xinggang. The requirements for its design were that it had tobe inspiring andbe able to withstand an earthquake.
In order to make the structure 'light weight' but earthquake-proof, the strength in 110 000 tons of a new grade of steel, the purest ever developed in China, including 36km of steel struts, was combined with an ingenious design.
It is saddle-shaped, but the interlocking steel parts resembling a lattice of twigs, make the name Bird's Nest an obvious alias.
The design came from the idea of asingle thread wrapped round a ball. Layers of logical geometry give the appearance of randomness and an organic shape. Multiple pentagrams in the interlocking fabric of the elliptical structure are like the stars of the Chinese flag.
An international steel shortage meant that the idea for a retractable roof was scrapped, saving 50M USD. Anew grade of steel had to be produced to withstand pulling forces within the structure without the addition of extra columns, which would have blocked spectators' views.
The structure is covered with a polymer membrane, rain-proof but translucent, allowing sunlight for the grass. This special membrane enhances lighting within the stadium by diminishing glare and shadowing, giving a more favorable competition environment.
Construction of the National Stadium began on December 24, 2003, and was completed in March, 2008. The total cost was more than 423 million dollars, a tiny fraction of the 40 billion USD spent on Beijing in preparation for the Olympics.
It is 333 meters long from north to south, 294 meters wide from east to west, and the highest point is 68.5 meters.
Ground Work: Pile foundations had to be dug 37m below ground level to bear the weight and horizontal forces generated by the structure. Then the functional inner body of the stadium was built. 14700 precast concrete slabs, all formed within 2mm tolerance to hold the seating, were slotted together. Each of the 24 supporting columns weighs 1000 tons, no lifting equipment in the world is able to lift it.
Because of Beijing's location, the stadium had to be able to withstand an earthquake. The purest steel ever developed in China allowed the designers to combine light weight with strength to provide maximum resistance to seismic forces.
Welders had to be specially trained to join the interlocking steel sections together due to the low sensitivity to welding of the new type of metal.
The 11200 ton roof was supported by temporary columns until the moment of truth when the jacks were released and the web of the Bird's Nest held its own weight.
The Bird's Nest was the main venue of the 2008 Beijing Olympic Games, when it had a capacity of 91,000 spectators. The stadium now has a capacity of 80,000, after temporary seating was removed.
The Bird's Nest hosted the opening ceremony, athletic events, the football final and the closing ceremony of the 2008 Beijing Olympic Games, which took place from August 8 to August 24, 2008.
It was also the venue for the 2008 Beijing Paralympics athletics and ceremonies from September 6 to September 17, 2008. The stadium will continue to host international and domestic sporting events, such as football matches.
There is a revealing series of five Youtube video clips that cover the construction of this amazing structure.
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