Study On Two Key Problems In Seismic Design And Theseismic Fragility Of Factory Building Structures In Nuclear Power Plant

In recent years, destructive earthquakes occurred frequently. On March11th2011, acatastrophic Mw9.0earthquake hit the land of Japan, and the following tsunami caused severe nuclear leak accident to Fukushima Daiichi nuclear power plant. More and more attentions are drawn to the impact on nuclear power plant due to earthquakes. American codes and European codes demand the prevention and relief for severe accidents, the improvment of safety reliabilities and the improvment of the human factors engineering. In past20years, the third generation nuclear power technology has been developed with the second edition standard on the basis of over8000ractor years’operating experiences from more than400nuclear power plants all over the world. Correspondingly, the referencable international policies, codes and regulations have been updated mostly. However, at the time of lack of experiences and references, Code for Seismic Design of Nuclear Power Plants (GB50267-1997) of China was issued16years ago. Therefore, it is necessary to revise Code for Seismic Design of Nuclear Power Plants of China on the basis of our own and advancedinternational experiences. This thesis provides case studies on comparison for several design provisions about earthquake resistance issues between Chinese code, French code and American code. Revision suggestions for GB50267were developed correspondingly. The main work is as follows:1. Based on extensive literature review about related references, the assessment method for nuclear power plantunder unexpected earthquake impacts beyond the design level is briefly introduced, and some key problems currently focused are also summarised.2. The comparison for earthquake resistance design provisions about presure pipingof nuclear safety class Ⅱ level between the ChineseCode for Seismic Design of Nuclear Power Plants (GB50267-1997), the French RCC-M (Edition2000&addendum2002) and American ASME (Edition2007) is carried out in detail. The different emphasis and the conservative characters are compared and summarized on the basis of a case study. Moreover, recommended values for standard response spectrum and primary stressindice B1are suggested to GB50267.3. The comparison for soil-structure interaction impedance functions between the ChineseCode for Seismic Design of Nuclear Power Plants (GB50267-1997), the French RCC-G and American ASCE4-98is performed and cased studied in detail. The conservative level between the three codes are compared Fitting formulas about constants in GB and ASCE4-98are suggested, and fitting formulas about the stiffness and damping coefficient in RCC-G are also established. The formula of equivalent radius of rectangular base is suggested for GB50267.4. Based on the test results, constitutive model parameters for nonlinear finite element analysis of reinforced concrete structure under dynymic loads were revised. Corresponding comparison of the Equivalent-Static Method and the Time History Analyses Method were studied. As examples, the fragility analyses for a reactor fuel factory building and a diesel engine factory building in nuclear power plant were carried out respectively by using the three dimentional Time History analysis. Corresponding structure fragility curves vs the acceleration parameter were developed.