Seismic Response Analysis Of Nuclear Power Structure With Pile Foundation

In order to expand the site selection of nuclear power plants,it is necessary to conduct seismic safety evaluation of nuclear power structures in the case of pile foundations in non-rock site.Among the current pile-soil-structure interaction analysis methods,the Winkler foundation model and the P-Y method simplify the pile-soil interaction problem,which cannot reflect the complex foundation situation.In addition,the actual seismic records of nuclear power plants site often exceed its design basis.The nonlinearity of soil needs to be considered under earthquake beyond design basis.The frequency domain method can only consider the weak nonlinearity of soil,and the strong nonlinearity of soil needs to be considered by the time domain method.At present the direct method can consider complex site conditions and the strong nonlinearity of soil,but the efficiency is low,which is difficult to be used in large-scale practical engineering problems.Therefore,how to realize the efficient analysis method of pile-soil-structure interaction which can reflect the complex foundation situation is worth studying.Furthermore,the influence of the location and thickness of the soft soil layer and its nonlinear in the non-rock site on the seismic response of piles and nuclear power structures are still not fully understood.Based on the efficient partitioned method of soil-structure interaction,the high-efficiency time domain analysis method of pile-soil-structure interaction has been studied,and the influence of the location,thickness and nonlinearity of soft soil layer on the seismic response of pile foundation and nuclear power structures has been analyzed in this paper,which could provide technology for the seismic response analysis of nuclear power structures with pile foundation on non-rock site.The main work of this article is as follows:(1)Based on the partitioned method of soil-structure interaction,an efficient asynchronous algorithm for the analysis of pile-soil-structure interaction has been proposed.The structure adopts the implicit integration scheme,the pile and soil adopt the explicit integration scheme.Interpolation to the response of soil nodes adjacent to the pile is carried out to realize the calculation of the pile and soil using different time step,so as to avoid the pile small stable time step in calculation of the soil and unnecessary calculation.The validity of the asynchronous algorithm has been verified by examples of pile-soil-nuclear structure interaction through pulse wave input.Also,the maximum shear force and bending moment of the pile has been analyzed considering the kinetic interaction and the inertial interaction.(2)By setting several cases with different positions and thicknesses of soft soil layer,and the comparison and analysis of the seismic response results,the influence of the location and thickness of soft soil layer on the seismic response of pile-soil-nuclear power structure system has been clarified.(3)The modified Davidenkov model has been used to analyze the nonlinear soil-pile-structure interaction under earthquake.First,the method of freefield input considering the nonlinearity of soil was discussed.Then,by comparing the seismic response of pile-soil-nuclear power structure considering the nonlinearity of soil and considering the soil as linear elasticity,the influence of nonlinearity of soil on the response of piles and nuclear power structure was analyzed.