The Soil-Foundation-Structure Interaction (SFSI) is generally but controversially, believed to have beneficial consequences on structural response during an earthquake. Among the available methods of considering the SFSI in Performance-Based Design (PBD) approaches, simple yet versatile concept of Winkler Foundation is widely used. Hence, a practical application of the 'Beam on Nonlinear Winkler Foundation' approach is scrutinized in a case study on the seismic performance of Concrete Shear Wall (CSW) frames to assess the SFSI effects. A group of 3, 6, 10 and 15-story CSW frames located on hypothetically soft, medium and hard soils are designed based on FEMA450 guidelines. Then the nonlinear model of each frame is numerically constructed employing the distributed and lumped plasticity elements in addition to the flexure-shear interaction displacement-based beam-column elements, incorporating the soil-footing interface. Subsequently, the results of the nonlinear static analysis are studied through two code-based viewpoints: 1) Force-Based Design (FBD) and 2) Performance-Based Design (PBD). This paper demonstrates some degree of inaccuracy in the fixed-base assumption which is regularly applied in the analysis and design practice. An original feature of the study is its emphasize on how the fixed based assumption overestimates the design of the shear wall element.