Linear-elastic And Elastic-plastic Analysis Of Pile-soil-structure Dynamic Interaction Of Nuclear Power Plant On Soft Foundation

With the development of global economic,energy demands continue to expand,while the traditional non-renewable resources such as oil,coal and other resources are dwindling.They have caused serious environmental pollution.It's time to find new energy to replace the existing energy.As an efficient and clean energy,nuclear power has been widely used in the world.After Chinese government has lifted the ban on nuclear power project since the Fukushima nuclear accident in Japan,more and more nuclear power plants are being built.Nuclear power plant is different from the general industrial and civil buildings,its security is particularly important,once an accident occurs,the consequences is unbearable to contemplate.The Fukushima nuclear accident drew the attention of the whole world on the safety of nuclear power plants under earthquake.China locates in the world's two major earthquake zone,it's one of the countries that suffered the most serious earthquake disaster in the world,so it is urgent to solve the problem of earthquake resistance and disaster reduction of nuclear power plant.One of the key seismic design of nuclear power plant is the seismic performance of the nuclear island building structure analysis.Numerical simulation is an effective research method for those complex engineering projects,which were restricted by some factors and could not be efficiently settled by theory and experimental verification.In this paper,the finite element analysis software LS-DYNA is used to conduct the linear-elastic and elastic-plastic FEM analysis of a nuclear power plant structure-pile-soil coupled system under seismic excitation,which aim to provide some reference for the seismic research and improve the level of seismic analysis of nuclear power plant for our country.The main work and conclusions of this thesis are as follows:(1)Taking a nuclear power plant which is being designed and built in China as the engineering application background,the whole three-dimensional nuclear power plant structure-pile-soil coupled finite element model is established according to the geological survey data and design drawings.The model considers the interaction between different parts of system,such as the pile and soil foundation,the nuclear island and soil foundation.The whole model is approximative to the real situation.The dynamic time history analysis of the model was conducted by LS-DYNA software.The response of structure under seismic excitation was studied,and the seismic performance of structure was evaluated.Results show that the acceleration has amplification effect in the earthquake process.Under the design earthquake excitation,the structure deformation is small and will not lead to the damage of the internal device.The maximum stress of pile foundation is less than that of conventional concrete.Overall,the structure can meet the seismic safety requirements,but the connections of pile and raft are vulnerable to damage.(2)Study the effect of pile foundation on the seismic response of nuclear island structure.Input earthquake excitation to pile foundation model and non pile foundation model from three directions respectively.Compare the response of different models in the same earthquake excitation.Results show that under the horizontal earthquake,the pile has a certain effect of vibration reduction,with the increase of height,the effect increases.However,under the vertical earthquake,the seismic response of the pile foundation to the raft and structure has an amplification effect.(3)Study the effect of raft extension plate on the seismic response of nuclear island structure.Input earthquake excitation to raft extension plate model and non raft extension plate model from three directions respectively.Compare the response of different models in the same earthquake excitation.Results show that under the horizontal earthquake,the raft extension plate has a certain effect of vibration reduction.With the increase of height,the effect increases.However,under the vertical earthquake,there is no uniform increase or decrease effect of seismic response of the raft extension plate to the raft and structure has occurred.