Effect of soil dimensions on the dynamic behavior of a multi-story building considering soil-structure interaction

In traditional structural design, soil-structure interaction is ignored, and structure responses are calculated with fixed base approach. This is because the soil-structure interaction is thought to play a positive role in reducing overturning moments and base shear forces. However, rocking of the foundation may increase the horizontal displacements of the structure. In addition, the soil flexibility increases the number of degrees of freedom of the system considered, reduces the effective stiffness, and can lengthen the period. The main purpose of this study is to examine the relative effects of different soil properties, frequency content of the ground motion and soil volume on the dynamic responses of a 10-storey structure based on three-dimensional finite element analyses. For this purpose, considering three earthquake ground motions with different frequency contents, three soil conditions with different stiffnesses, fixed base condition, four different soil widths from each face of the structure in both horizontal directions, and four different bedrock depths from the foundation base, the stresses, accelerations and displacements were calculated. In the modeling, the behavior of the soil and structure was defined as linear elastic, and the soil-structure interaction mechanism was taken into account with the massless foundation approach. The results revealed that the aforementioned responses may vary significantly depending on soil interaction, frequency content and bedrock depth, but soil width has a negligible effect on the responses.