Random Seismic Response Analysis Of Nuclear Power Plant Structures

Dynamic analyses of nuclear power plant structure are very important for aseismicdesign. However, it is more important and significant to use stochastic methods todesign engineering structures. To date, it is not studied completely on nuclear powerplant structures using stochastic method and considering the SSI effect. The results ofstochastic analyses are only references to deterministic methods. Of course, it is notpractical to use it in the real design yet. In this dissertation, a systematic study on thestochastic seismic response theory is presented firstly, and then a simulation ofnuclear power plants subjected to earthquakes were performed considering the SSIeffect and parameter uncertainties. The primary innovative points embodied in thisdissertation are listed as follows:(1)According to the differences of nuclear power plant structures from normalcivil structures, an analytical system based on stochastic analysis method was comeup with. The analytical system includes the establishment of the Finite Element Model(FEM) of a nuclear power plant, the introduction of uncertain parameters of soil, theconsideration the soil-structure dynamic interaction effect, and so on. The comparisonof the numerical results of the stochastic method with those of the determinedanalyses indicates that this system is practical, and it can clearly demonstrate theinfluences of SSI effect and of parameter uncertainties on the seismic response ofnuclear power plant to earthquakes.(2) A reactor building with a 1000MW Pressurized Water Reactor (PWR) nuclearstation was analyzed. The soil-structure dynamic interaction is modeled with thespring and damping elements nested in the analytical program ANSYS. Theuncertainty of the dynamical parameter of soil can be simulated by adjusting thevalues of these parameters of the corresponding elements. The numerical results of theboth methods indicate that this system based on stochastic analysis method is practical.It also can clearly show the effects of SSI on structural responses. (3)The model of the nuclear power plant analyzed by stochastic method isestablished in the program ANSYS. The time-history analyses are conducted bywriting relevant command streams. The sensitivity of the nuclear plant structure to theuncertain parameters of soil was analyzed. Some valuable conclusions were obtained.Furthermore, the conclusions provide some references for evaluating the sensitivity ofthe response of seismic nuclear power plant structure to uncertain parameters.(4)The stochastic series of seismic response were transformed by FFT (FastFourier Transform) after the time-history analysis and in turn the Floor AccelerationSpectra (FRS) of structure response was achieved .The analysis in the frequencydomain indicates that SSI effects and parameter uncertainties of soils have someinfluences on the PSD of structure response.