The outer cover of the "Bird's Nest" is made of irregular steel members, and the concrete structure and steel structure inside are independent of each other. In the space between the concrete stand and the steel structure shell, the architect designed many inclined concrete columns to support the building. How to ensure the structural requirements of these concrete columns without affecting the overall beauty of the "Bird's Nest"?
After several arguments by domestic engineers, a plan with the best of both worlds was born. First, tie the reinforcing cage like other concrete structures, and then cover the steel pipe section by section from the top. After the steel pipes are connected, concrete is poured into the steel pipes to form a concrete column integrated with the steel pipes. In this way, the concrete column can't be seen, which is safe and beautiful, but it increases the construction difficulty.
Square steel tubes with a side length of one meter are connected into 120 steel columns with different lengths and inclinations, of which more than 70% are double inclined columns-one column is twisted twice on the vertical plane. The tallest steel column has a total length of 2 1 m and spans one to four floors of the stadium. The angle between the most inclined steel column and the ground reaches 59 degrees, and the maximum rotation angle of the steel column exceeds 45 degrees. ...
It is a great challenge to pour concrete in these tall, inclined and seemingly messy special-shaped steel pipes. What's more, the inside of the steel pipe is densely covered with steel bars-32 steel bars are arranged vertically, and a row of dense steel bars is arranged every ten centimeters horizontally. Such a dense steel mesh can only reach three fingers at most. How easy is it to fill the porcelain bottle with concrete and let it stick to the steel pipe?
At first, the construction unit can only try to fill the steel pipe from above, and can only fill four or five meters every day from morning till night. After independent research, the General Contracting Department of the National Stadium Project put forward a new scheme: concrete jacking, pouring concrete from the bottom of the steel pipe and gradually filling it from bottom to top.
This is a method that no one has ever used, but the result is very ideal. The jacking concrete is not only fast in progress, but also good in quality and not layered. When it was completed, it was two months and two days shorter than the scheduled deadline.
From June 5, 2006 to October 20, 2006/KLOC-0, this technology was named "Construction Technology of Reinforced Concrete Oblique Torsion Column with Super-high Rectangular Steel Tube Permanent Formwork", and officially applied to China National Intellectual Property Administration for invention patent. This is the mature fruit of independent innovation produced by the Olympic project.