Investigation the effect of soil-foundation interaction defined by finite grid method on the structural performance

The behavior of structures under the effect of seismic force constitutes a wide area of research in Turkey, where the majority of the population lives in earthquake zones. The fact that the construction of building on soft soil area increases over time for several reasons makes the soil-structure interaction more important under the effect of earthquake forces. However, the fact that the elastic soil and the superstructure are generally studied separately causes the interaction of these two sub-systems to be neglected. In methods that directly take into account the elastic soil effect, the soil is considered to be composed of a bearing coefficient described by the Winkler spring, and the bearing coefficient is modelled as a vertical lumped spring at the nodal points of the foundation plate. Within the scope of this study, the two-parameter elastic soil, which includes the effects of displacement in the vertical axis and rotation around the 2 horizontal axes, has been taken into account with the distributed (continuous) spring model. This effect is directly integrated to the structural model by transforming thin plates into an equivalent grid system according to the finite grid method, and solving the grid element differential equation and calculating the element stiffness, mass and load matrices including the continuous spring effect. This model has been compared with analytical, semi-analytical and numerical methods in the literature. Regarding the analyzes performed under the external loads and free vibration analysis results, it has been shown that this method is applicable despite some disadvantages. The thin plate model, which includes the 2 parameter elastic soil effect described above, has been modelled mathematically, and then the dynamic behavior of the structure has been investigated by integrating it with the superstructure. Afterwards, the response spectrum analysis has been performed under earthquake loads defined in the principal horizontal axes, and story shear force and story displacement has been studied. The analysis results have been compared with the results obtained from analysis made with the finite element method regarding the lumped model. Considering the results obtained from these analyzes are evaluated as a whole, it is concluded that the complex dynamic behavior of the superstructure is affected by the elastic soil model, and the lumped model gives unsafe results in some cases.