Characteristic Analysis For Seismic Response Of3D Soil-structure Interaction Of Nuclear Power Plant On The Complex Site Conditions

Many nuclear power plants (NPP) in China are being or plan to be built recently on a non-uniform field condition. The effect of Soil Structure Interaction (SSI) on seismic response analysis is needed to be considered to the NPP on a complex site condition. However, the analysis of this kind of nuclear SSI system based on conversional method and software popular in the past (such as SASSI, FLUSH, CLASSI, etc) often suffer from some computational difficulties because of the complexity of the site and the increasing requirements of NPP safety. The unreasonable or simplified analysis models may bring about uncertain security risks on nuclear island and equipments. This thesis aims to develop computational models that are more efficient and accurate than the conversional ones. Moreover, in accordance with the presented models, the dynamic characteristics and strong seismic response characteristics of the NPP are discussed in detail. Some significant results are given. The studies done in the paper include:1. The existing methods and models for dynamic SSI system are summarized. Moreover, Base on the existing lumped-mass explicit finite element method (FEM) with a local transmitting boundary condition, an explicit procedure in the time domain is developed for the analysis of three-dimensional dynamic SSI analysis.2. Based on the proposed computational procedure, the nature frequencies are given in accordance with the NPP SSI systems on various of site conditions. Comparing with the results without SSI effect, the characteristics of frequency change are discussed in detail for these NPP SSI systems.3. According to a large number of strong ground motion records, the characteristics of strong ground motion records are summarized with distance and frequency spectrum.5large magnitude of far field outcrop bedrock strong ground motion records respectively from Wenchuan and Fukushima are used as earthquake incident wave of NPP SSI system. Based on the proposed procedure, the equivalent seismic inputs and response specta are computated from various of NPP SSI models. Comparing with the corresponding results given by uniform site conditions and complex site conditions without the SSI effect, the changes of the seismic input, response spectrum and floor spectrum characteristics are discussed and summarized. The results show that it is neccessory for NPP system to consider the effects of soil-structure interaction on the strong seismic even in far field.