Effects On Seismic Response Of Nuclear Power Station Due To Foundation Embedment

With the rapid development of nuclear power industry in China, seismic performance of nuclear power plant has become increasingiy important. As to the reactor building of a 1000MW nuclear power plant, the effect of foundation embedment on the dynamic response of the sites and the upper structures is studied. In addition, two approaches in the content of the scaled boundary finite element method for solving the dynamic stiffness of semi-infinite foundation have been investigated. At last, based on the continued-fraction technique, a time domain procedure is developed to analyze dynamic unbounded soil-structure interaction problems, with applying to the seismic analysis of nuclear power plants.(1) High-frequency asymptotic expansion and continued-fractions techniques are two main ways in the content of SBFEM for solving dynamic stiffness of unbounded domain; their main features are investigated carefully with emphasis on accuracy and dependency of the initial condition. In order to avoid the numerical error pertinent to the two approaches in high order expansion, the dimensional analysis is performed. The relationship between the dynamic stiffness under dimensionless frequencies and the actual frequencies is derived, so those are calculated. Then, the dynamic stiffness under the actual frequencies can be obtained using this relationship. Numerical results show that the proposed approach is feasible, and can effectively reduce the error in high expansion.(2) Because the lumped parameter models suggested by the major seismic specifications of nuclear power plants can not well reflect the dependency of dynamic impedance on excitation frequencies, with the unbounded foundation modelled by viscoelastic boundary, a harmonic analysis method is introduced, which is used to analyze the effects on foundation embedment. In addition, coupling the lumped-mass simplified model for the reactor buildingand and using the time history analysis method, this paper studies the earthquake response of the structure. The results illustrate that both the dynamic impedance and the earthquake response are affected by the foundation embedment.(3) Based on the continued-fraction technique in the framework of the scaled boundary finite element method, a time domain method is developed to analyze dynamic unbounded soil-structure interaction problems. Compared to the similar methods, this method avoids solution of the unit impulse response function and convolution integral, thus simplifing calculation. The proposed approach is validated by seismic analysis of a nuclear power plant...