The Progressive Collapses Analysis Of High Steel Tower

The definition of "Progressive Collapses" can be basically summarized like this: the structure may collapse partly or even totally when local failure under the normal service condition or accident happens, because of the limited ductility and continuity of the structure. The accident refers to the factors which are not considered in structural design, such as construction mistake, gas explode, the vehicle impact, the terrorist attack etc. As the flourishing development of constructions in China, more and more large-scale public buildings are accomplished. Among them, a large number of high steel towers are built up one after another. For these steel towers, although the design method of structures could meet the demand when structures are in regular service and maintained normally, the alternative defensive ability of structures has not been researched in case of accidental events and severe local overloading. Because of these important status and higher security grade, the resisting progressive collapses ability should be fully estimated, such as analyzing the strength, stiffness and stability due to their significance and higher security grade. It means that structures should be able to adjust the internal forces automatically, thereby resisting the continuation of damage and maintaining the whole structural stability when local members failed suddenly as a result of accidental events and severe local overloading. There have been a lot of disasters caused by that the structure which are lack of the resisting progressive collapses ability in history. Some large-scale public buildings which were finished recently, have already reflected the defect in this respect too. So, it's very important to carry on the progressive collapses analysis of high steel towers.This paper introduces the basic concepts of progressive collapse. On the basis of composite progressive collapse analytical methods and knowledge of risk evaluation, "key index method" is proposed to estimate the importance of these members. Then, a research on the resisting progressive collapses analysis of HeNan Broadcast and Television Tower is carried on. In the end, some measures to enhance the resisting progressive collapses ability are proposed in this paper.