Study On Calculation Method Of Seismic Action Of Long Span Grid Structure

With the widely application ofthe grid structure, people found that there areso many damage factorsof long-span grid structure. And when the structure is damaged, the direct and indirect losses cannot be measured. In order to enhance the ability of structures to resist earthquake disaster, as early as the 19 th century scholars began to research in earthquake action theory, so far the development of the theory of structural aseismic analysis has undergone a static method, response spectrum method and dynamic time history analysis method, etc.First,in this paper the author introduces the characteristics of the grid structure and research status of seismic action calculation methods about long-span grid structure,and expounds the research background, significance and content. The author expounds principle of development of the three seismic analysis methods including static method,response spectrum method and time history analysis method and the different characteristics of specific method to calculate the seismic action. The authors designed a long-span grid structure and used the static method, response spectrum method and time history analysis method for the computation of seismic action, completed the content of the modal analysis and time history analysis.According to the analysis of the results in this paper, we can find that the static method is the most simple way but the result should be conservative, that is safe enoughin structure design. Although in modal theory decomposition response spectrum method is clear and understandable, but it only considers the maximum acceleration response, and does not take into account the factor of time, and the method of modal combination is obtained by probability and statistics calculation under the action of earthquake internal force and displacement is not accurate. In addition, the author does not take into account the current application of the design response spectrum of ground motion duration, at the same time, it does not take into account structure may be the accumulation of plastic and plastic deformation process. In fact, it is also a kind of static methods. In theory, the time history analysis method of calculation is more accurate, but it is affected by selected seismic wave is very obvious. So, when we choose to seismic wave, not only can’t just input general several typical seismic waves, but also take into account different ground conditions. So the results of the calculation will produce large discreteness.