The top of the National Stadium is saddle-shaped, with a major axis of 332.3 meters, a minor axis of 296.4 meters, a height of 68.5 meters at the highest point and a height of 42.8 meters at the lowest point ... On the premise of keeping the architectural style of the "Bird's Nest" unchanged, the new design scheme has greatly adjusted and optimized the structural layout, building cross-sectional form and material utilization rate. The openable roof in the original design scheme was cancelled, the opening of the roof was increased, and the steel consumption was greatly reduced by optimizing the steel structure. The long-span roof is supported on 24 truss columns with an interval of 37.96 meters. The main trusses are radially arranged around the opening in the middle of the roof, and 22 main trusses are straight or nearly straight. In order to avoid too complicated joints, a few main trusses are truncated near the inner ring. A large number of steel structures are box-shaped members welded by steel plates, and the cross-arranged main trusses, together with the substructure of the roof and facade, form a special architectural shape of "Bird's Nest". The main stand adopts reinforced concrete frame-shear wall structure system, which is completely separated from long-span steel structure.
The "Bird's Nest" is surrounded by a huge steel net, covering the stadium of 9 1 000 people. Sightseeing stairs naturally become an extension of the structure; The pillars are gone, and the net with uniform stress has no clear direction like branches, which makes people feel that every seat is equal, and being in it is like returning to the forest; Filter sunlight into a diffusion inflatable membrane, so that the stadium bid farewell to the shadow of sunlight; The whole terrain rises by 4 meters, and the interior is used as an auxiliary facility, which avoids the huge investment consumed by excavation.
Bird's Nest is a long-span curved structure with a large number of curved box structures. Design and installation are extremely challenging, and scientific and technological support is indispensable everywhere in the construction process. The "Bird's Nest" adopts today's advanced construction technology, and there are twenty or thirty technical problems in the whole project, among which the steel structure is unique in the world. The total weight of the "Bird's Nest" steel structure is 42,000 tons, and the maximum span is 343 meters. And the structure is quite complicated, and its three-dimensional distortion is treated like a twist. Problems such as settlement, deformation and hoisting after construction are gradually being solved, and related construction technical problems are also listed as key research projects of the Ministry of Science and Technology.
Now, the "Bird's Nest" has completed the concrete construction and started the steel structure construction. In order to effectively control the maximum wall thickness of members, reduce the welding workload and make the connection structure more reasonable, high-strength Q460 steel is adopted in the design.
Speaking of Q460 steel, most people may not understand it. The structural design of "Bird's Nest" is strange and novel, and the steel structure Q460 built this time has many unique features: Q460 is a low-alloy high-strength steel, which will only undergo plastic deformation when the stress intensity reaches 460 MPa, which is greater than that of ordinary steel, so it is very difficult to produce. This is the first time that Q460 steel has been used in building structures in China. The thickness of the steel plate used this time is 1 10 mm, which is unique in the past. In the national standard, the maximum thickness of Q460 is only100 mm. In the past, this kind of steel was generally imported from Luxembourg, South Korea and Japan. In order to provide a "suitable" Q460 for the Bird's Nest, from September 2004, the researchers of Henan Wuyang Special Steel began to tackle scientific and technological problems for more than half a year, and the trial production was finally successful three times. Nowadays, mass production of Q460 steel for "Bird's Nest" has begun. In 2008, 400 tons of domestic Q460 steel with independent innovation and intellectual property rights will support the "Bird's Nest".