Three-dimensional face-centered cubic seismic metamaterial structure with low-frequency forbidden band characteristic

Abstract

The utility model discloses a three-dimensional face-centered cubic seismic metamaterial structure with a low-frequency forbidden band characteristic. The three-dimensional face-centered cubic seismic metamaterial structure comprises a cubic shell, a cubic shell surface plate and a cubic core structure, regular octagonal through holes are formed in the centers of six surfaces of the cubic shell; the thickness of the cubic shell surface plate is the same as that of the cubic shell, the cubic shell surface plate comprises square thin plates and long and thin strip-shaped structures, the long and thin strip-shaped structures are arranged in parallel at intervals, a solid cube of the cubic core structure is located in the center of the cubic shell, and six side faces of the solid cube are connected with the square thin plates through cylindrical connecting pieces. The structure has the advantages of small size, large wavelength control and effective attenuation of seismic wave body waves and surface waves in a certain frequency range.

Description

Technical Field

[0001] The utility model relates to the field of seismic reduction and isolation of rock and soil earthquake engineering, and more precisely to a three-dimensional face-centered cubic seismic metamaterial structure with low-frequency forbidden band characteristics. Background Art

[0002] Earthquakes are sudden and destructive geological disasters. They not only cause serious direct economic losses, but also trigger different types of secondary disasters, such as landslides, mud-rock flows, subsidence, and floods, which seriously endanger people's lives and property safety and have a huge impact on the country's social life and economic activities.

[0003] In view of the significant losses caused by earthquake disasters, it is necessary to take seismic isolation measures for residential buildings and important public buildings or structures to protect them from serious damage caused by earthquake disasters. Traditional seismic design mainly reduces the damage caused by earthquake disasters to the protected buildings through measures such as structural seismic resistance, seismic energy dissipation, and seismic isolation. Structural seismic resistance refers to improving the seismic resistance of the main load-bearing structural components and using the plasticity and ductility of the structural components to "force" seismic resistance; seismic energy dissipation refers to setting damping elements in certain parts of the structure to dissipate part of the energy input by the seismic wave through the deformation of the damping elements to reduce the seismic response of the main structure. Seismic isolation measures refer to introducing a flexible structure at the bottom of the protected building to consume part of the seismic wave energy through the deformation of the flexible structure to protect the safety of the main structure. "Forced" earthquake resistance of structures will cause some degree of damage to some internal structures, affecting the normal use of buildings, and the damaged structural components are difficult to repair in the later stage; shock absorption and energy dissipation are difficult to resist strong earthquakes with high magnitude and great damage; the flexible structure introduced by the isolation measures will produce a certain degree of lateral displacement after an earthquake, so there is a risk of the overall structure overturning. Therefore, it is necessary to develop a new type of seismic isolation technology that can overcome the limitations of traditional seismic isolation measures.

[0004] In recent years, in the field of solid-state physics, the emergence of acoustic metamaterials based on phononic crystals has enabled us to control the propagation of elastic waves. Phononic crystals refer to periodic artificial structures with bandgap characteristics, which can attenuate the propagation of elastic waves within a certain frequency range, thereby controlling the propagation of elastic waves. Given that phononic crystals have the characteristics of controlling the propagation of elastic waves, the civil engineering field has borrowed from the basic theory of phononic crystals and proposed a new type of seismic isolation technology, namely, seismic metamaterials that can suppress the propagation of seismic waves within a certain frequency range, and applied seismic metamaterials to the field of civil engineering seismic isolation.

[0005] Seismic metamaterials are divided into two types according to the formation mechanism of the bandgap, namely Bragg scattering type seismic metamaterials and local resonance type seismic metamaterials. Bragg scattering type seismic metamaterials produce the lowest frequency range of the bandgap.

[0006] Related to the lattice constant, the wavelength of seismic waves corresponding to the lowest frequency range is of the same order of magnitude as the lattice constant. To produce a lower frequency bandgap, a larger structure needs to be designed, which is not conducive to its application in actual seismic isolation projects. At the same time, most existing seismic metamaterials are one-dimensional or two-dimensional periodic structures designed for seismic surface waves, which can only effectively attenuate the energy of seismic waves within (1-3)λ below the surface, and fail to effectively attenuate the body and surface waves of seismic waves.

[0007] In summary, there is an urgent need for the invention of a local resonance type three-dimensional seismic metamaterial that has the characteristics of small size controlling large wavelength and effectively attenuating seismic body waves and surface waves. Utility Model Content

[0008] The technical problem to be solved by the utility model is to provide a three-dimensional face-centered cubic seismic metamaterial structure with low-frequency bandgap characteristics, which has the advantages of small size controlling large wavelength and effectively attenuating seismic body waves and surface waves in a certain frequency range.

[0009] In order to solve the above technical problems, the utility model adopts the following technical means:

[0010] A three-dimensional face-centered cubic seismic metamaterial structure with low-frequency bandgap characteristics, comprising a cubic shell, a surface plate of the cubic shell, and a cubic core structure;

[0011] The centers of the six surfaces of the cubic shell each have a regular octagonal through hole penetrating the cubic shell;

[0012] The surface plate of the cube shell is located in the center of the six regular octagonal through holes on the surface, the thickness of the surface plate of the cube shell is the same as the thickness of the cube shell, and the surfaces of the two are flush; the surface plate of the cube shell includes a square thin plate and a slender strip structure, 2-5 slender strip structures are arranged in parallel at intervals, and the slender strip structure is used to connect the square thin plate to the cube shell;

[0013] The cube core structure includes a solid cube and a cylindrical connector. The solid cube is located at the center of the cube shell. A cylindrical connector is provided at the center of each of the six sides of the solid cube. One end of the cylindrical connector is connected to the solid cube, and the other end is connected to the center of the square thin plate of the surface panel of the cube shell.

[0014] The utility model provides a solid cube, and connects the solid cube with a square thin plate, so that each face and the solid cube form a stable local resonance unit body connected together, which not only improves the compression, tension and shear strength of the unit body, but also increases the shock absorption and energy absorption effect.

[0015] The slender strip structures are arranged in parallel at intervals, which increases the stability of the connection force between the square thin plate and the cubic shell, so that the force on the components is more balanced when local resonance occurs. At the same time, the parallel arrangement at intervals can maximize the low-frequency bandgap range of the three-dimensional seismic metamaterial structure and enhance the attenuation performance of seismic waves within the bandgap frequency range.

[0016] By setting a high-density solid cube in the center of the cube shell, the low-frequency bandgap range can be significantly widened, the upper frequency limit of the bandgap range is increased by 5Hz, and the attenuation performance of seismic waves in the bandgap range is improved. At the same time, the solid cube has the advantages of high strength, high rigidity and good stability, which can improve the mechanical properties of the three-dimensional seismic metamaterial, improve the shear strength of the soil in the area, and resist the vibration and extrusion damage caused by upper human activities, vehicle driving, etc.

[0017] As the thickness of the surface plate of the cube shell increases, the bandgap range of the three-dimensional seismic metamaterial remains almost unchanged, and the thickness of the surface plate of the cube shell is set to be consistent with that of the cube shell, which can greatly improve the attenuation performance of the three-dimensional seismic metamaterial structure to seismic waves, while saving materials of the surface plate of the cube and reducing production costs. The surface of the surface plate of the cube shell and the surface of the cube shell are flush, which increases the contact area between the cells, facilitates the mutual connection of the three-dimensional seismic metamaterial cells, improves the connection strength between the cells, and ensures that the overall structure formed by the three-dimensional seismic metamaterial cells has good stability.

[0018] The utility model provides that the slender strip structures arranged in parallel at intervals can widen the bandgap range of the three-dimensional seismic metamaterial structure. As the number of the slender strip structures increases, the bandgap range of the three-dimensional seismic metamaterial structure gradually increases. At the same time, the slender strip structures are regular rectangular structures, which are convenient for factory processing and on-site installation.

[0019] The working principle of this utility model:

[0020] The utility model is stacked and arranged around the foundation of the building, and the cross-section is rectangular. When an earthquake occurs, the seismic wave propagates outward from the source, thereby causing vibration and damage to the soil and upper structure in the propagation area. When the seismic wave propagates to the three-dimensional seismic metamaterial structure designed by the utility model patent, the seismic wave in a part of the frequency range is close to or equal to the natural frequency of the designed three-dimensional seismic metamaterial structure, so that the designed three-dimensional seismic metamaterial structure resonates locally, thereby suppressing the propagation of the seismic wave in the frequency range.

[0021] The three-dimensional seismic metamaterial structure designed by the utility model patent is arranged in a circular ring shape and buried around the protected building, so that seismic waves in the forbidden frequency range cannot propagate to the protected building. At the same time, the three-dimensional seismic metamaterial arranged in a circular ring shape can effectively attenuate seismic waves in all directions, thereby reducing the damage caused by earthquakes to the protected buildings.

[0022] The utility model belongs to the local resonance type seismic metamaterial, which has the characteristics of small size controlling large wavelength; it can simultaneously attenuate seismic body waves and surface waves within a certain frequency range; the geometric structure of the components is simple, which is convenient for factory processing and production; the materials used are commonly used materials for engineering construction, which are easy to obtain. By changing the thickness of the cube shell, the size of the cube core, the number of slender strip structures, the radius and longitudinal thickness of the cylindrical connector, the range of the low-frequency band gap can be adjusted.

[0023] Further preferred technical solutions are as follows:

[0024] The regular octagonal through holes on each surface have the same structure, the square thin plates and the elongated strip structures have the same structure, and the cylindrical connectors have the same structure.

[0025] The same arrangement of the above structures makes component processing and assembly simpler and more convenient.

[0026] Three slender strip structures are evenly distributed between the four sides of the square thin plate and the cubic shell, and the spacing between the slender strip structures is 4 mm.

[0027] By setting up three slender strip structures, the connection between the four sides of the square thin plate and the cubic shell is more balanced and stable.

[0028] The side length of the square thin plate is the same as the side length of the solid cube.

[0029] Keeping the side length of the square thin plate consistent with that of the solid cube can not only improve the compressive, tensile and shear strength of the three-dimensional cubic seismic metamaterial, but also enhance its attenuation performance for seismic waves within the bandgap range.

[0030] The side lengths of the square thin plate and the solid cube are 1 / 3-1 / 2 of the side lengths of the cube shell. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 : Schematic diagram of the patent structure of this utility model.

[0032] Figure 2 : Schematic diagram of the surface panel structure of the cube shell.

[0033] Figure 3 : Schematic diagram of the cube core structure.

[0034] Figure 4 : A front view schematic diagram of the buried position of the utility model patent.

[0035] Figure 5 : Schematic diagram of the top view of the buried position of the utility model patent.

[0036] Figure 6 : Energy band structure diagram of the unit cell of the utility model patent.

[0037] Figure 7 : Frequency response transmission loss diagram of this utility model patent.

[0038] Description of reference numerals:

[0039] 1: Cube shell; 2: Cube shell surface plate; 21: Square thin plate; 22: Slender strip structure; 3: Cube core structure; 31: Solid cube; 32: Cylindrical connector; 4: Building; 5: Embedded seismic metamaterial. DETAILED DESCRIPTION

[0040] The present invention will be further described below in conjunction with the embodiments.

[0041] See also Figure 1 It can be seen that the utility model is a three-dimensional face-centered cubic seismic metamaterial structure with low-frequency bandgap characteristics, which consists of three parts: a cubic shell 1, a cubic shell surface plate 2, and a cubic core structure 3.

[0042] There is a regular octagonal through hole penetrating the cubic shell 1 at the center of each of the six surfaces of the cubic shell 1 .

[0043] The surface plate 2 of the cubic shell includes a square thin plate 21 and a thin and long strip structure 22. The thin and long strip structure 22 is used to connect the square thin plate 21 with the cubic shell 1. 2 to 5 thin and long strip structures 22 are arranged in parallel at intervals.

[0044] See also Figure 1 , Figure 2 It can be seen that three slender strip structures 22 are evenly distributed between the four sides of the square thin plate 21 and the cubic shell 1, with a spacing of 4 mm.

[0045] The surface plate 2 of the cube shell is located in the center of the six regular octagonal through holes on the surface, and the thickness of the surface plate 2 of the cube shell is the same as that of the cube shell 1, and the surfaces of the two are flush.

[0046] The cube core structure 3 includes a solid cube 31 and six cylindrical connectors 32. The solid cube 31 is located at the center of the cube shell 1. A cylindrical connector 32 is provided at the center of each of the six sides of the solid cube 31. One end of the cylindrical connector 32 is connected to the solid cube 31, and the other end is connected to the center of the square thin plate 21 of the surface panel 2 of the cube shell.

[0047] The centers of the cubic shell 1 , the cubic shell surface plate 2 , and the cubic core structure 3 coincide with each other, and the central axes of each square thin plate 21 , the solid cube 31 , and the cylindrical connecting member 32 coincide with each other.

[0048] The regular octagonal through holes on each surface have the same structure, the square thin plates 21 and the elongated strip structures 22 have the same structure, and the cylindrical connectors 32 have the same structure.

[0049] The side length of the square thin plate (21) is the same as the side length of the solid cube (31)

[0050] In the embodiment of the present invention, the side length of the cubic shell 1 is 100 mm; the radius of the circumscribed circle of the regular octagonal through hole is 45 mm; the side length of the square thin plate 21 is 48 mm and the thickness is 5 mm; the longitudinal length of the slender strip structure 22 is 21 mm, the transverse width is 5 mm, and the thickness is 5 mm; the radius of the cylindrical connecting piece 32 is 18 mm and the longitudinal height is 25 mm; the side length of the solid cube 31 is 48 mm.

[0051] The utility model of the utility model adopts epoxy resin as the outer shell 1, polyurethane as the slender strip structure 22, polyurethane as the cylindrical connector 32, steel as the square plate 21, and steel as the solid cube 31. The specific material parameters are as follows: epoxy resin, density 1200kg / m 3 , Poisson's ratio is 0.38, and the elastic modulus is 4.4×10 9 Pa; polyurethane, density 1100kg / m 3 , Poisson's ratio is 0.472, and the elastic modulus is 1.62×10 5 Pa; steel, density is 7850kg / m 3 , Poisson's ratio is 0.3, and the elastic modulus is 2.1×10 11 .

[0052] See also Figure 4 , 5 The three-dimensional face-centered cubic seismic metamaterial unit cell proposed in the utility model can be periodically arranged in the x, y, and z directions of space and buried around the protected building 4 or structure (only the left and right sides of the building 4 are shown in the figure, and the layout of the front and back sides is the same as the left and right sides), which can effectively attenuate seismic waves within a certain frequency range.

[0053] See also Figure 4 , 5 The three-dimensional face-centered cubic seismic metamaterial unit cells proposed in the utility model can be periodically arranged in the x, y, and z directions of space to form a circular ring-shaped seismic wave barrier 5. The seismic wave barrier 5 composed of the three-dimensional face-centered cubic seismic metamaterial unit cells resonates locally with the seismic waves, thereby attenuating the energy carried by the seismic waves in the forbidden frequency range, and the circular ring-shaped seismic wave barrier 4 can effectively attenuate seismic waves from different directions, thereby avoiding serious damage to the protected building 4.

[0054] See also Figure 6 The energy band structure diagram of the seismic metamaterial unit cell designed by the utility model shows that there is a forbidden band in the frequency range of 0-50, wherein the forbidden band range is 6.08-35.1 Hz.

[0055] See also Figure 7 The frequency response transmission function diagram of the seismic metamaterial unit cell proposed by the utility model is formed by periodically arranging the wave barrier structure in the x, y, and z directions. The transmission function is 20log 10 (A1 / A2). A1 is the displacement at the input; A2 is the displacement at the output. The frequency response transfer function diagram of the seismic wave passing through the designed seismic metamaterial is obtained through numerical simulation. From the frequency response transfer function diagram, it can be concluded that the area below 0dB corresponds to the forbidden band range of the band structure, indicating that the utility model can effectively attenuate seismic waves within the forbidden band range.

[0056] The above description is only a preferred feasible embodiment of the present utility model, and does not limit the scope of rights of the present utility model. All equivalent structural changes made using the contents of the specification and drawings of the present utility model are included in the scope of rights of the present utility model.

Claims

1. A three-dimensional face-centered cubic seismic metamaterial structure with low-frequency bandgap characteristics, comprising a cubic shell (1), a cubic shell surface plate (2), and a cubic core structure (3), characterized in that: The centers of the six surfaces of the cubic shell (1) each have a regular octagonal through hole penetrating the cubic shell (1); The cubic shell surface plate (2) is located in the six regular octagonal through holes on the surface and is located at the center. The thickness of the cubic shell surface plate (2) is the same as that of the cubic shell (1), and the surfaces of the two are flush. The cubic shell surface plate (2) comprises a square thin plate (21) and a slender strip structure (22). The slender strip structures (22) are arranged in parallel at intervals of 2 to 5. The slender strip structures (22) are used to connect the square thin plate (21) to the cubic shell (1). The cubic core structure (3) comprises a solid cube (31) and a cylindrical connector (32). The solid cube (31) is located at the center of the cubic shell (1). A cylindrical connector (32) is provided at the center of each of the six sides of the solid cube (31). One end of the cylindrical connector (32) is connected to the solid cube (31), and the other end is connected to the center of the square thin plate (21) of the cubic shell surface plate (2).

2. The three-dimensional face-centered cubic seismic metamaterial structure with low-frequency bandgap characteristics according to claim 1, characterized in that: The regular octagonal through-hole structures on each surface are the same, the structures of each square thin plate (21), the structures of each slender strip structure (22) are the same, and the structures of each cylindrical connecting piece (32) are the same.

3. The three-dimensional face-centered cubic seismic metamaterial structure with low-frequency bandgap characteristics according to claim 1, characterized in that: Three slender strip structures (22) are distributed at equal intervals between the four sides of the square thin plate (21) and the cubic shell (1), and the interval between the slender strip structures (22) is 4 mm.

4. The three-dimensional face-centered cubic seismic metamaterial structure with low-frequency bandgap characteristics according to claim 1, characterized in that: The side length of the square thin plate (21) is the same as the side length of the solid cube (31).

5. The three-dimensional face-centered cubic seismic metamaterial structure with low-frequency bandgap characteristics according to claim 1, characterized in that: The side lengths of the square thin plate (21) and the solid cube (31) are 1 / 3 to 1 / 2 of the side length of the cubic shell (1).

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