Seismic Metamaterials And Their Applications In Seismic Reduction Of Nuclear Power Structures

In recent years,at the forefront of acoustic physics,the introduction of new concepts such as "phononic crystals" and "acoustic metamaterials" has opened up a new chapter in the study of "manipulating wave propagation in elastic media and structures",and has also reduced structural Earthquake theory and technology provide new ideas.Phononic crystals and acoustic metamaterials are a class of materials / structures composed of periodically arranged artificial structural units.Elaxtic waves propagate in such materials will produce a series of special physical effects and characteristics,such as suppressing the propagation of elastic waves.The frequency ranges are called band gaps.By adjusting the geometry / material parameters of the artificial periodic structure,the position and width of the band gap and its ability to suppress wave propagation can be artificially adjusted.With the above ideas,"seismic metamaterials" can be designed to control the propagation of seismic waves,thereby achieving the purpose of structural vibration reduction and isolation.In addition,when an earthquake occurs,the energy of the Rayleigh wave accounts for 67% of the energy of the entire wave field,and along with the increase of the distance from the earthquake source along the surface,the energy decay is also slower than that of the body wave.Therefore,in the seismic design of the building structure,it is necessary to consider the influence of Rayleigh wave.According to the idea of phononic crystals and acoustic metamaterials,this paper designs seismic metamaterials,analyzes their band gap and ground motion transmission characteristics,and explores their application possibilities in structural vibration reduction and isolation.The main work of this article is as follows:(1)The Rayleigh wave fields of the homogeneous elastic half-space and the horizontal layered elastic half-space are synthesized,which provide input for the characteristic analysis of seismic metamaterials.The analytical solution and the thin-layer stiffness method were used to calculate the Rayleigh wave field in the uniform elastic half-space and the horizontal layered elastic half-space,respectively,and the propagation characteristics of the Rayleigh wave were analyzed.The Rayleigh wave field was used as the free field input,and the wave field simulation was performed through finite element and artificial boundary conditions,and compared with the Rayleigh wave free field,the correctness of the free field input and finite element calculation was verified.(2)Based on two band-gap mechanisms of Bragg scattering and local resonance of phononic crystals,two(surface and underground)seismic metamaterials are designed,and their band-gap characteristics and vibration transmission characteristics for Rayleigh waves are analyzed.,It was applied to the design of shock absorption of two-dimensional frame structure,and its vibration reduction effect on frame structure under Rayleigh wave input was verified.By improving the underground seismic metamaterial,band gap characteristics appears for Rayleigh and SV waves,and verified that the improved underground seismic metamaterial can reduce the shock of the frame structure under the input of Rayleigh and SV waves.(3)A partition algorithm based on soil-junction interactions and designing two-dimensional periodic seismic metamaterials around nuclear power structures,analyzing the response of three-dimensional nuclear power structures under seismic wave input,and comparing the different response of nuclear power structures with and without seismic metamaterials.It is verified that seismic metamaterials have a certain shock-absorbing effect on nuclear power structures,whether under surface or bulk waves.