Due to the advanced and even "advanced" design concepts, there are many unique problems in the construction of Olympic venues. There are no ready-made reference answers in the world, and they can only be solved independently by relying on their own technological innovation.
The outer cover of the "Bird's Nest" is woven from irregular steel structural members. The concrete structure and steel structure inside are independent of each other. The architect designed a new structure in the space between the concrete stands and the steel structure outer cover. Many sloping concrete columns 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 demonstrations by domestic engineers, a solution that had the best of both worlds was born. First, tie the steel cage like other concrete structures, and then cover the upper steel pipes section by section. 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 columns are not visible, which is safe and beautiful, but makes the construction more difficult.
Square steel tubes with a side length of one meter are connected into more than 120 steel columns of different lengths and angles of inclination. More than 70% of them are double inclined columns - one column twists twice on the vertical plane. . The tallest steel column is 21 meters long and spans the first to fourth 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...
To be in Pouring concrete in these tall, sloping and seemingly messy special-shaped steel pipes is already quite a challenge. What's more, the inside of the steel pipe is densely covered with a steel grid - 32 steel bars are arranged longitudinally, and dense rows of steel bars are arranged every ten centimeters horizontally. Only three fingers at most can fit into such a densely packed steel mesh. How easy is it to fill the inside with concrete and make it closely adhere to the steel pipe?
At first, the construction unit could only try to pour into the steel pipe from the top, and could only pour four to five meters from morning to night every day. After independent research, the National Stadium Project General Contracting Department proposed a new plan: jack up the concrete, inject concrete from the bottom of the steel pipe, and gradually fill it from the bottom up.
This is a method that has never been used before, but the results are very ideal. Jacking concrete is not only fast, but also of good quality and without delamination. When completed, it was two months and two days shorter than the scheduled construction period.
On January 20, 2006, this process was named "Construction Technology of Ultra-High Rectangular Steel Tube Permanent Formwork Reinforced Concrete Diagonal Columns" and officially applied for an invention patent from the State Intellectual Property Office. This is a mature fruit of independent innovation produced by the Olympic project.