“Old” and “New” Nodes in Modeling of Complicated Soil Environment
“Old” and “New” Nodes in Modeling of Complicated Soil Environment

“Old” and “New” Nodes in Modeling of Complicated Soil Environment

Authors:  

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


Rubric:     Theoretical and experimental studies   
Key words: seismic response, complicated soil environment, upgraded soil pad, combined asymptotic method
Annotation:
Complicated soil environment” means that under the basement there is a certain finite soil volume with properties breaking horizontally-layered initial soil composition. The author discusses two alternatives in modeling such volume. The “old nodes” approach means that one and the same set of internal nodes is used both for the outcropped soil and for the substituting soil. The “new nodes” approach means that a new set of the internal nodes (with the same coordinates) is introduced for the substituting soil. The author shows that the difference in the results is caused by special feature of the SASSI program: after the outcrop the old internal nodes stay with certain “residual” non-zero stiffness. If the substituting soil
is hard enough, this difference is negligible: “new nodes” approach will not give new results. But in case of soft substituting soil this “residual” stiffness can spoil the results of the “old nodes” approach. In such cases the “new nodes” approach is justified in spite of the increase of the problem size. Combined Asymptotic Method (CAM) is extended for the case of the “new nodes” approach; the capability of CAM is further extended. The topic is important because of the implementation of the upgraded soil pads under the base mats of the heavy structures in seismic regions.

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