Dynamic Response And Damage Evolution Of AP1000 Nuclear Island Structure Under Sequence-type Earthquakes

At present,the seismic performance research of nuclear island structures at home and abroad mostly uses single earthquake as input.In fact,there are many strong aftershocks after the main earthquake.Whether the nuclear island structure has enough performance to resist strong aftershocks after the main earthquake,and how the seismic performance of the nuclear island structure under multiple earthquakes remains to be further studied.This paper takes AP1000 nuclear island structure as the research object,establishes AP1000 nuclear island structure analysis model considering equipment gate and personnel gate by using ABAQUS,a large-scale general finite element software,and compares the modal analysis results with domestic and foreign literatures to verify the accuracy of the model;analyses the influence of shear wave velocity of different types of soil on seismic response of AP1000 nuclear island structure;constructs AP1000 nuclear island structure by repetitive method;Seven main and aftershock sequence earthquake motions are analyzed,and the seismic response and damage development of the nuclear island structure in the main and aftershock stages are analyzed.Three seismic waves with five aftershocks are constructed by stochastic method,and the seismic response and damage development of the nuclear island structure in the main and each aftershock stage are analyzed.Two main and aftershock structural methods are compared and analyzed in the aftershocks of different working conditions.The plastic displacement increment at the apex of the shielded workshop,the tensile damage nephogram of the concrete of the shielded workshop in each aftershock stage,and the change of the natural vibration period of the structure.Through the above research,the following conclusions are drawn:1.Under the same peak acceleration of ground motion,the seismic wave with high shear wave velocity has greater response to the acceleration and displacement of AP1000 nuclear island structure.It is more appropriate to select seismic wave with shear wave velocity greater than 700 m/s for seismic analysis of AP1000 nuclear island structure.2.The horizontal and vertical acceleration responses of the shield building and the containment vessel are slightly larger than the horizontal and vertical acceleration responses of the aftershock period under the main aftershock input of 0.3g,0.6g and 0.9g.The peak displacement of the shield building during the aftershock period is larger than the peakdisplacement of the main shock period under some working conditions.The plastic damage of the shielded building is aggravated.The displacement response of the containment vessel in the main earthquake period is slightly larger than that in the aftershock period,and the containment vessel is in the safe elastic stage.3.When the input acceleration peak value is in the range of 0.3g~1.2g,the period corresponding to the peak value of the main aftershock response spectrum constructed by the random method is closer to the basic period of the nuclear island structure than that of the main shock,and the difference between the peak acceleration and displacement of the top of the shielding building and the shell is large in the main and aftershock stages.When the aftershock intensity is less than that of the main shock,the acceleration response and displacement response of the joint in some cases exceed that of the main shock.With the increase of the earthquake intensity,the plastic displacement deformation of the shielded workshop appears to varying degrees.After the main shock is completed,the secondary damage to the shielded workshop is caused by the aftershock,which enhances the plastic displacement deformation of the shielded workshop,and no obvious plastic displacement of the containment vessel occurs.It is still in the stage of elasticity.4.The plastic displacement on the top of the shield building is different in the main shock period and the aftershock period.The vertical plastic displacement of the aftershock period relative to the main shock period is much smaller than the plastic displacement of the main shock period.The horizontal plastic displacement of the aftershock period relative to the main shock period in a small part of cases exceeds the plastic displacement of the main shock period.The aftershock is vertical to the shielded workshop.The cumulative damage can not be neglected.5.Under the two main aftershocks,the first natural frequency of the nuclear island structure decreases with the occurrence of the main shock and the aftershocks in different degrees.The first natural frequency of the structure in each working condition is greater than that in the aftershocks.Under the main aftershocks constructed by stochastic method,the natural frequency of the structure under the main shock and the first and third aftershocks decreases greatly,and the natural vibration of the latter two aftershocks is larger.The frequency decreases slightly.