The unloading process for the bird's nest-shaped steel skeleton of the National Stadium for the Beijing Olympic Games awaited the ultimate moment on Sunday morning: 78 bracketing structures that support the weight of its steel skeleton will be gradually removed.

Therefore, parts of its steel skeleton will be lowered for less than 30cm, according to the experts.

The large steel skeleton of the project weighs 42,000 tons, with the roof and the hanging parts around it accounting for 11,200 tons. To bear such a heavy load, 78 supporting structures were temporarily installed and distributed in different points under stress, with 24 structures along the outer circle, 24 in the middle circle and 30 in the inner circle. What awaits the technicians and workers is to discharge all these supporting objects from a weight of 11,200 tons.

The unloading process of the supporting structures is divided into seven steps and each step is conducted in the order of outer circle, middle circle, inner circle, middle circle and inner circle. Therefore, 35 sub-steps are needed to complete the whole process.

According to the plan, the outer circle will vertically drop by 67-70mm, the middle by 161-178mm and the inner by 208-286mm.