Combined Asymptotic Method in Seismic Analysis of High-Rise Building: Impact of SSI
Combined Asymptotic Method in Seismic Analysis of High-Rise Building: Impact of SSI

Combined Asymptotic Method in Seismic Analysis of High-Rise Building: Impact of SSI

Authors:  

Тяпин Александр Георгиевич Tyapin A.G.
Dr.Sci.Tech., JSC Atomenergoproject. Moscow, Russian Federation


Rubric:     Theoretical and experimental studies   
Annotation:
Combined Asymptotic Method (CAM) has been developed and used for SSI analysis of stiff and heavy NPP structures. However, some of civil structures nowadays are comparable with NPP structures in terms of size and mass. The question is whether SSI is significant for such structures and whether it should be accounted for in the design process. In the previous paper the authors applied CAM to the seismic analysis of the high-rise structure resting on a sample homogeneous half-space modeling soil. In the present paper the results are investigated to estimate the overall impact of SSI or, in other words, the applicability of the fixed-base seismic analysis. It turns out that this question must be asked separately for separate directions of seismic response - horizontal&rocking in two different vertical planes, vertical, and torsional (for non-symmetrical structures). Impact of SSI may be different for one and the same structure in different directions. Hence, fixed-base seismic analysis may be applicable in some directions and non-applicable in others. The results were checked against empirical criteria from nuclear ASCE Standard, based on the comparison of the first natural frequencies of flexible structure resting on rigid soil and of rigid structure resting on flexible soil. Criteria were confirmed, if the comparison is performed separately for different directions. Otherwise, if the comparison is performed for the whole set of frequencies, one can get wrong result. The considered case gives an example of such a situation. 

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