Soil-structure Interaction Analysis Of Nuclear Power Structures In Complex Sites

Soil-structure interaction analysis is an important step in seismic design and safety assessment of nuclear power structures.With the development of nuclear power in China,the proposed site of nuclear power plant is not always a regular site with horizontal layers.The complexity of local site under earthquake will cause potential safety hazards to the nuclear island structure and its accessories.The analysis of the impact of non-horizontal layered site on the seismic response of nuclear power structure has attracted much attention.In addition,structural damping is an important factor affecting the structural response in the analysis of soil-structure dynamic interaction of nuclear power structures.When the number of modes contributing to the seismic response is large,Rayleigh damping can only accurately reflect two order modal damping,and the other modal damping has errors with the real situation,which makes most modal responses distorted(especially low-frequency and high-frequency modes),resulting in a great difference between the seismic response and the real solution.Therefore,how to reasonably consider the damping is necessary for the soil-structure interaction analysis of nuclear power structures.The main work of this paper is as follows:1.Taking Cangzhou site as an example,according to the velocity profile of the site,establishes a three-dimensional finite element model of the complex site.By using the lumped-mass explicit finite element parallel calculation method and local artificial boundary conditions,the site response of threedimensional ground motion input is calculated,and the spatial distribution characteristics of ground motion are analyzed.2.Based on the finite element model of CAP1400 nuclear power structure,established the soilstructure interaction analysis model of nuclear power structure on Cangzhou site.Separate Computing Algorithms for Three-Dimensional and Efficient Time-Domain Soil-Structure Interaction Analysis,that is to say,the implicit integration method is used in the superstructure and the explicit integration method is used in the foundation and soil.The two methods can adopt different time steps and take into account the input of three-dimensional seismic waves to analyze the soil-structure interaction of the nuclear power structure.Compared with the results of site response,the influence of nuclear power structure on site response is analyzed,and the response spectrum of nuclear power structure is given,which provides input for further analysis of seismic response of relevant equipment.3.In order to reasonably consider the structural damping,the structure adopts the modal superposition method,the soil and foundation adopt the explicit time-step integration method,the method of large mass is used to realize the Separate Computing Algorithms of soil-structure interaction,which combines modal superposition and time-step integration.The method is verified by a simple example,and is applied to the soil-structure interaction analysis of CAP1400 nuclear power structure,and the modal damping and Rayleigh are compared and analyzed.The results show that there is a significant difference in the response of the damper to the nuclear power structure and site.