The Minimum Seismic Shear Coefficient Of Super High-rise Building Structure With Long Period

With the increase of high-rise building height, the fundamental period of the structure becomes longer and longer. Since the seismic force calculated by modal decomposition response spectrum method is small, the specification set the minimum shear coefficient requirements in order to ensure the safety of the structure. The consideration of advisable design and the minimum shear coefficient which meets the specification requirements has become an important problem in high-rise building structure design for engineers. In the high-rise structure design, adjustment rigidity or strength to meet the minimum shear coefficient has aroused heated debate. Therefore, researches have been carried out in this thesis as follows:(1) Through comparing the differences of shear coefficient requirement in the codes of United States, Europe and China. The reasons of setting minimum shear coefficient in these standards were analyzed, and the disadvantages exist in the base shear coefficient set of our country standard were pointed out.(2)An 82-storys high-rise buildings given as an engineering example, the influences of different factors on the structural seismic shear coefficient were analyzed. The results show that: with the decrease of the period reducti on factor, base shear increases; with the increases of the damping ratio, the structure of the base she ar decreases to a certain extent, but it is unobvious; with the changes of the site conditions, the top floor displacement and the interlayer displacement angle of the structure is increased; the differences of displacement responses of structures in site ? and site ? ground are more than 50%, the former base shear is 1.8 times of the latter, which reflect the former structure conform to the standard minimum shear coefficient requirements but should be taken effective and reliable measures. These results illustrate that the influence of different fields to the shear resistance coefficient values is not fully considered by China seismic code of building.(3) Two structure models are established. One structure model adjusts structure strength to meet the minimum shear strength requirements of the specifications, while another one change the structural stiffness to meet the specification requirements. The floor displacements of two models are similar under rarely occurred earthquake and both structures can satisfy the design requirements. However, the cost of structure which adjusted rigidity is larger, and the component strength have not been efficiently used.The improvement measures of minimum shear coefficient and its application in engineering design was also discussed in this thesis. Shear coefficient reflects the structure stiffness, mass distribution, such as macroeconomic indicators. How to control the strength and stiffness of the structures in high-rise structure design is still a project worth researching deeply.