In this thesis, uncertainties in dynamic soil structure interaction (SSI) of nuclear power plants subject to seismic loading are studied considering of the random characteristics of soils surrounding the structure. Firstly, sensitivity analysis is performed to study the effect of uncertain dynamic soil properties on the response of the structure. Secondly, to take into account of the nondeterministic characteristics in analysis caused by random characteristic of the soil properties, Perturbation method and the Rosenblueth's two point estimates were used for this study. The procedure is based on the complex response method which is constituted by a combined usage of the conventional finite elements for the near field and infinite elements for the far field. Results of the sensitivity analysis show that dynamic soil properties greatly affect the response of the structure. Results of the probabilistic analysis show that the two point estimates produce good agreements with perturbation method.
