Abstract—In this paper, a real 10-story base isolated structure, designed according to IBC, 2009 guidelines, is selected as a case study. A semi-infinite cone model has been used to evaluate base soil characteristics of buildings embedded in layered flexible half space. Three different soil types are selected according to soil classifications in the code. The analysis has been performed using Loma Prieta and Northridge’s time history earthquakes considering the Soil-Structure Interaction (SSI) effects or base isolated system. The comparison of natural period, base shear and total relative displacements of the structure has been realized based on analytical models. Numerical results show that Soil-Structure Interaction has negligible effects on the base shear ratios of this type of buildings on very stiff soil. Also, damped periods of base isolated buildings resting on the soft soils, have been increased regardless of the height of the building or shear-wave velocity.