抄録
The simultaneous occurrence of different load conditions such as gravity loads, lateral and vertical loads due to seismic event in various combinations should be considered to generate most critical design conditions. The aim of the paper is to evaluate the behaviour and the structural response in form of in-structure response spectra of the reactor building internal structures, under site specific seismic loading, and to determine whether these ones satisfy current international safety regulations. A preliminary conceptual analysis and design of a nuclear building with different foundation embedding depths for the most critical conditions were discussed in this paper with reference to solutions considered for a Near Term generation Nuclear Power Plant. The seismic input motion was considered as a free field response spectra of 0.2g PGA, while the Soil-Structure Interaction (SSI) effects were taken into account through appropriate features. To achieve the purpose of this study, the foundations can be seen as a stable base for the superstructure able to transfer safely all loads from ground to the internals. The general approach was consistent with up-to-date design conditions for evaluation and upgrade of nuclear power plant facilities. The project's major objectives may be summarized as follows: study of available data for preliminary design and as built conditions, creation of 3-D detailed finite element models, determination of dynamic characteristics, verification of capability of structure to resist relevant design load combinations, calculation of all important characteristics for specific parts of the structure, determination of possible feature and components mostly affected by the assumed seismic loads. The results of the performed analyses, the possible effects of SSI and the response of internal components (e.g. Nuclear Building, Vessel-GVs and GV-tubes system) seem to confirm the possibility to achieve an upgrading of the geometry and the performances of the proposed solutions for the considered NPP.
