Seismic Response Subjected To Strong Earthquakes And Fragility Analysis Of Nuclear Island

Reinforced concrete structure of NPP is the significant infrastructure to ensure the safety of nuclear power engineering,and the safety of NPP during operation service is the key issue of the construction and development of the nuclear power.Due to the randomness of earthquake.Nuclear power plants may suffer beyond design basis ground motion,resulting in the destruction of nuclear structure and nuclear accident.And related experiments and research shows that the influence of water tank fluid-solid coupling on seismic response of nuclear island plant under earthquake grounds isn't negligible.Therefore,the seismic safety of nuclear power plant is analyzed numerically,to understand the damage probability and the seismic response of nuclear power plant under different earthquake intensity and water level,which plays an important role in fully estimating the seismic performance and ensuring the normal operation of nuclear power plant.From the aspect of the effects of FSI on structure's seismic response of nuclear plant under strong earthquake,gravity tank shock absorption problem of water tank,different optimization design scheme of water tank,structural fragility under different water level and fragility of nuclear plant subjected to far-field and near-field earthquake,this paper make a thorough study,.the specific work is as follows:(1)Based on the ALE fluid-solid coupling algorithm,the seismic response of the improved and optimized shielding building is analyzed under the RG1.60 seismic wave and EI-Centro wave.The relationship between the seismic response and the height of the water level,the height ratio of the water level,the mass ratio and the frequency ratio of the different points of the improved shield plant are studied.The law of variation between them is revealed and the optimal shock absorption level is obtained.Under the condition of standard water level,two baffle optimization schemes are put forward.The optimal design scheme is put forward and the internal structure of the water tank is optimized.(2)Based on the ALE fluid-solid coupling algorithm,fragility analysis of the traditional shield building is performed by he regression analysis method,the moment estimation method and the truncated maximum likelihood estimation method and three methods verified the reliability of the conclusions each other.In the analysis of fragility,the first strength theory is chosen as the structural yield criterion.Based on the requirement that the nuclear island can only be in linear elastic state,the fragility analysis of different water level conditions is performed.Under the premise of the standard water level,four baffle optimization schemesare developed and the damage probability of the structure under different positions is studied.The optimal shock absorption design scheme is put forward.(3)In this paper,the finite element model and infinite element soil model of AP1000 non isolated and isolated island buildings are established.Performance levels of nuclear building are divided.Tensile strain of rebar and compressive strain of concrete are used as the damage index and The limit value of each damage state is given,which can be used to judge the damage state of the nuclear island in the elastic-plastic stage.The paper selects 15 sets of far-field ground motions recommended by ATC-63,by using IDA and MSA method to perform fragility analysis,the fragility curves subjected to far-field ground motions are obtained and the two methods were compared and analyzed.The results of the two methods are basically consistent,which proves rationality of the results.(4)In this paper,the 14 groups of pulsed near-field ground motions recommended by ATC-63 are analyzed,and the fragility curves of isolated and non-isolated island buildings are obtained by using the analysis method of the previous chapter.The paper compares damage probability between non-isolated and isolated nuclear island,isolated shield building and auxiliary building and non-isolation shield building and auxiliary building.At the end of this paper,the comparative analysis of the fragility of the nuclear island subjected to the near-field and far-field earthquakes is carried out and the their fragility is evaluated.