How was the Bird's Nest built?

The "Bird's Nest" National Stadium, known as the "fourth generation stadium", is the landmark of the 2008 Beijing Olympic Games. It is located in Beijing's North Fourth Ring Road and is listed in the Olympic National Forest Park. It covers an area of 204,000 square meters with a total construction area of 258,000 square meters. It has 96,5438+0,000 fixed seats, a dining room, an athlete's lounge and a dressing room. During the 2008 Olympic Games, it will host the opening and closing ceremonies, track and field competitions, men's football finals and other events. With a total investment of US$ 450 million, this project is the largest building in the world and the most modern and humanized stadium in the world. The "Bird's Nest" is named because its main body is composed of a series of radial steel structures, which looks like a bird's nest. The top of the building is saddle-shaped, with a major axis of 332.3 meters and a minor axis of 297.3 meters. After the main frame is completed, a layer of milky translucent polytetrafluoroethylene (ETFE) inflatable plastic film will be pasted on the outer surface of the grid structure at the top of the "Bird's Nest". After using this film, sunlight will not directly enter the stadium, but will spread into the stadium, making the light softer. The diffused light formed in this way can also solve the maintenance problem of the lawn in the stadium, and can also play a role in sheltering the seats in the stadium from the wind and rain. It is the originality of the "Bird's Nest" in architectural structure and exterior decoration that makes her and the National Swimming Center, Beijing Capital International Airport, Shanghai World Financial Center, National Grand Theatre, CCTV and other buildings selected as the top ten architectural wonders of China by American Business Week at the end of 2005. At the beginning of April, CMTM reporter walked into the "Bird's Nest" site being hoisted. The main body of the "Bird's Nest" is a combination of seismic wall structure and reinforced concrete frame. This brand-new structural system has the characteristics of high earthquake resistance, high safety and strong bearing capacity. Its external structure consists of 24 huge steel structure columns, which are triangular lattice columns with large upper end and small lower end. The highest pillar is in the east-west direction, 78 meters high, and the lowest pillar is in the north-south direction, 60 meters high. The thickness of steel for steel structure is 1 1 cm, and the total amount of steel for engineering design is 50,000 tons. The whole project has a unique shape, and there are a lot of curved structures in heavy steel structure, which has great challenges in steel quality, steel structure design, processing and installation. According to experts, the "Bird's Nest" is a large-scale steel structure project with the largest amount of steel, the largest scale, the most difficult construction and many world-class construction technical problems. The "Bird's Nest" project is generally contracted by Beijing Urban Construction Group, and Beijing Urban Construction and Zhejiang Seiko Urban Construction Seiko and CITIC Guohua are subcontractors, each responsible for half of the "Bird's Nest" project. Mamte Heavy Equipment Transportation and Installation Co., Ltd. undertook the hoisting of urban construction precision steel structures with a total hoisting capacity of 25,000 tons, with an average hoisting capacity of 1 15 tons every two days. Guan Xinyu, the manager of the company, introduced to us: "Mamt officially entered the" Bird's Nest "site in August 2005. The company is equipped with 800 tons of Demag CC4800 crawler crane, 600 tons of Demag CC2800 crane and 300 tons of Demag CC 1800 crane for hoisting, of which 300 tons of cranes have just entered the site and are still being assembled. The 800-ton crane is mainly used to hoist these columns, especially the upper part of the columns. After the upper and lower parts are docked, the workers start welding. " Because there are a large number of building materials, various transport vehicles and small and medium tonnage auxiliary hoisting cranes at the "Bird's Nest" site, the construction site is very narrow, and the crane station is limited, so it can't be close to the steel structure installation position, which increases the working radius of the crane. Under such circumstances, it is also a big problem to accurately install the entire steel structure of the 800-ton column in place. According to the engineering characteristics, structural form, component weight and site conditions, in order to reduce the difficulty of component assembly and ensure the welding quality of nodes, the construction designer decided to hoist the columns in sections. First, steel structures are assembled on the ground like building blocks and welded on site. The structure formed in this way is called assembled structural members, and then these welded assembled structural members are hoisted and welded. Even so, the lifting of the upper part of the column with strange appearance and complex structure and the docking with the lower part are also a great test for cranes and lifting companies. How to choose lifting points and supporting points during hoisting requires accurate hoisting calculation. The hoisting of the beam above the Bird's Nest is also one of the difficulties in the project. The maximum area of these beams can reach 25m×20m, the minimum weight is100t, and the maximum weight can reach136t. Inside the "Bird's Nest", we saw many tall steel beams standing around the infield. Manager Guan explained to us: "These are temporary supports, which are divided into outer ring, middle ring and inner ring. They are used to temporarily support the steel beam of the "Bird's Nest". When all the beams and columns are welded, all these temporary supports will be removed. " During the conversation, we saw a beam hanging in the air by a crane, ready to be in place. Because of the large area and high position of the beam, engineers also pulled two ropes on the beam, and the ground personnel pulled the ropes to help the crane lift the beam in place. Two engineering commanders standing on the roof of the "Bird's Nest" are communicating with the crane commanders on the ground with gestures to determine the exact position of the beam. In the other half of the "Bird's Nest", the construction machinery company of China Nuclear Industry Zhongyuan Construction Company undertook the steel structure hoisting project of CITIC Guohua, which was also a scene of great enthusiasm. A yellow Liebherr crane is hoisting the upper part of the external column. "We used an 800-ton Liebherr LR 1800 crawler crane and a 600-ton crane for hoisting. Because the height of the column can reach 78m, and the working radius is 22-24m, the maximum lifting counterweight of the 800t crane can reach 350t. After the installation of this part of the main steel structure that we undertake hoisting is completed, it will be docked with that part of the steel structure undertaken by Mamt, thus completing the external steel structure of the "Bird's Nest" and then completing a small number of internal steel structure hoisting projects. " During the interview, Zhang Xin, manager of the hoisting and transportation department of CNNC Zhongyuan Company, introduced us. Steel structure members are bulky, heavy and complicated, so it is extremely difficult to hoist, erect, locate, stabilize at high altitude and control installation accuracy in winter and spring when the wind and sand are heavy and the temperature is low in Beijing. When asked about the difficulties in the hoisting project, Manager Guan and Manager Zhang both thought: "Because of the large tonnage and large windward area of the hoisted object, the wind load will be very large during the hoisting process, and hundreds of tons of hoisted objects will sway back and forth in the wind, which is a great test for the safe operation of the crane. The steel structure is not allowed to touch anything during the hoisting process, so it CNNC only run when the wind speed does not exceed12m/s". It only took less than a year from the arrival of equipment to the end of hoisting of large steel structures. Modern hoisting technology and hoisting equipment provide favorable technical support for the successful completion of the hoisting project.