3rd TAGRA

In the modeling of soil-structure interaction (SSI) using the finite element method, the dimensions of the finite soil domain and the boundary conditions can affect the calculated dynamic properties of the system. This study used the five-story reinforced concrete frame structure examined by Kamal et al. (2022) as a reference to create three-dimensional soil–structure interaction models using ANSYS software and investigated the effect of soil geometry on the system’s dynamic behavior. The soil depth was set to 45 m, the raft foundation dimensions (B×L) to 25×20 m, and the soil mesh size to 1.25 m. Bottom boundary conditions were fixed for the soil region, while viscous boundary conditions were applied to the horizontal boundaries. The plan dimensions of the soil, while remaining the same in the X direction, were modified in the Y direction by taking 2, 4, 5.5, and 6.5 times the length of the structure’s edge in the Y direction (20 m), resulting in 110×40 (Model-1), 110×80 (Model-2), 110×110 (Model-3), and 110×130 (Model-4). When the dominant periods in the X and Y directions were evaluated based on the modal analysis results, negligible differences were observed in the X direction. In the Y direction, however, the differences decreased as the dimensions increased and became negligible after Model-3. Furthermore, the models were analyzed under the effects of the Erzincan earthquake, revealing that the ground geometry had an impact on the dynamic responses. The results demonstrated that the distance of the boundaries in the soil region from the structure can influence the directional system behavior. The findings indicate that in direct ZYE analyses, the dimensions of the soil region must be evaluated not only in terms of computational cost but also to minimize boundary effects and obtain reliable dynamic system characteristics.