Consideration of soil's response in dynamic analysis is equally important as modeling superstructure to capture all nonlinear behavior in evaluating its seismic performance. This becomes more important if an adjacent building exists nearby, which can alter dynamic response of both structures. Also, soft soil makes effect of interaction between superstructure and soil more pronounced due to low stiffness which can be improved by implementation of some stiffer elements inside the soil. In this study, effects of soil-structure and structure-soil structure interaction are investigated with consideration of improved soil consideration. Fixed base, soil structure and adjacent frames with soil and improved soil conditions are modeled, and nonlinear time history analyses are performed. Results are given in terms of maximum story drift and residual drift demand. In addition, fragility curves are obtained performing incremental dynamic analysis and adjusted based on results of seismic hazard analysis on considered site. Collapse probability of frames in fifty years is also shown. The results indicate that stone column improvement reduces demand on superstructure and collapse probability of frames.