Frequency domain calculation of CANDU 600 NPP structures using 3D finite element models

The dynamic response of structures excited by an earthquake is conventionally analyzed in the time domain using modal superposition procedures. It is therefore necessary to use frequency-independent parameters to represent the soil underneath the structure. These parameters are tuned to the main frequencies of the soil-structure system. In the meantime, however, analyses in the frequency domain were applied successfully to calculate the dynamic response of nuclear power plants subjected to seismic loading. This procedure is very efficient, especially in the case of significant soil-structure interaction effects (soft medium type soil) due to the more realistic results which may be obtained. Based on studies and analyses performed for building structures of Cernavoda NPP, the results obtained by means of both these methods will be compared. The advantage of the frequency domain analysis will be demonstrated and discussed with regard to different types of buildings. (authors)