Seismic Response Analysis Of The Superlong Space Grids Structures Under Multi-Dimensional And Multi-Support Earthquake Excitations

Theoretical research and experience about earthquake damage are all showed that, earthquake ground motion is a complex multi-dimensional movement. For the important and complex structure, only considering one-dimensional seismic is not enough, it's necessary to consider the combined effects of multiple seismic ground motion. In essence, ground motion is in the changes of space. Because of the limited wave spread velocity, loss of coherence, and different local site conditions, all these things can lead to the differences of seismic excitation appears significant in points of support. For the long-span structures, it has the characteristics of high freedoms, closely spaced frequencies, complex vibration mode and multidimensional vibration. Moreover, the structure strongly affected by spatial variation of ground motion for its large-scale. Therefore, for the long-span structures, it's necessary to take into account the Multidimensional and multiple ground motion excitation.On the basis of the investigation background mentioned above, the text investigates on the multi-dimension and multi-support seismic reaction analysis of the large-span spatial grids structure from various aspects, and following achievements have been obtained:1) Relationship of structural length and multi-support excitation. The text compared the difference of structural response from the non-uniform excitation and uniform excitation by using large amount of counting examples, to which the influence of apparent wave velocity and structural length has also been analyzed. On the other hand, the minimum structural span which originated from the consideration of uniform excitation rather than non-uniform excitation was concluded by quantity of dangerous poles.2) Influence on overlong large-span spatial grids structure by wave passage effect. During the research of multi-dimension and multi-support input case, the influence on overlong large-span spatial structure by wave passage effect appears obvious, which is a most important factor among all the considerations. The text has made the analysis by using large amount of counting examples to cover the influence on large-span spatial structure and its dangerous poles by multi-dimension and multi-support input in terms of four different apparent wave velocity. 3) Influence on overlong large-span spatial grids structure by partial coherence effect. As one of the most important factors which affect the excitation difference of seism wave, partial coherence effect has been widely investigated by many scholars. It is demonstrated by most results that for multi-support excitation, whether the partial coherence effect should be considered has not reached a unified. For this situation, the text judges influence to the structure caused by partial coherence effect based on the dangerous poles, and an apparent result has been obtained.