Beijing National Stadium,The Bird's Nest-China

China's National Stadium known as the Bird's Nest 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.

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 to be inspiring and be 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 36 kilometer of steel struts, was combined with an inventive 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 a single 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 50 million US Dollars. The structure is covered with a polymer membrane, rain-proof but translucent, allowing sunlight for the grass.
Construction of the National Stadium started on 24 December 2003 and was completed in March, 2008. The total cost was more than 423 million dollars, a tiny fraction of the 40 billion US Dollars 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.

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.