An eccentric resonant seismic metasurface

Abstract

This invention discloses an eccentric resonant seismic metasurface. This small-sized, easily constructed surface wave defense array can prevent surface waves from propagating into densely populated urban areas, significantly improving the seismic safety of urban building structures. The invention includes multiple eccentric resonators arranged in a ring around the protected building. Each eccentric resonator includes an eccentric steel column, vertically fixed to the ground surface. The eccentric steel column comprises a vertical section and an eccentric section; the vertical section is fixed to the ground, and the eccentric section is fixed to the top of the vertical section. A mass block is fixed to the top of the eccentric section. The central axis of the vertical section is a certain distance from the center of gravity of the mass block. The eccentric seismic metasurface of this invention is separated from the protected building and does not participate in the vertical stress on the protected building, making both the protected building and the seismic-resistant metasurface less prone to damage.

Description

Technical Field

[0001] This invention belongs to the field of seismic resistance technology for buildings, and specifically relates to an eccentric resonant seismic metasurface. Background Technology

[0002] Earthquakes pose a serious safety threat to densely populated cities, their immense destructive power capable of causing building collapse and damage. To mitigate earthquake damage, various seismic isolation and vibration reduction measures targeting the structure itself have been gradually implemented. While these structural earthquake-resistant measures can reduce the risk of damage and collapse during earthquakes, both the measures and the structure itself can suffer irreparable damage under moderate and major earthquakes.

[0003] Therefore, seismic metamaterials, placed at a certain distance from the structure and around its perimeter, have been developed. However, existing seismic metamaterials suffer from problems such as needing to be buried in the soil and being too large to be practically constructed in engineering projects. During an earthquake, faults generate body waves and surface waves. Seismic surface waves travel long distances and their energy does not easily attenuate, affecting the widest area. Realizing small-sized, easily constructed surface wave defense arrays could prevent surface waves from propagating to densely populated urban areas, significantly improving the seismic safety of urban building structures. Subwavelength seismic metasurface structures, with their small size, can directly block seismic surface waves. Summary of the Invention

[0004] To overcome the shortcomings of existing technologies, this invention provides an eccentric resonant seismic metasurface. By setting an initial eccentricity, it achieves resonant coupling between the subwavelength structure and the Earth's surface, strongly attenuating seismic surface waves, thereby achieving the purpose of blocking seismic surface waves and protecting designated urban areas.

[0005] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0006] An eccentric resonant seismic metasurface is characterized by comprising multiple eccentric resonators arranged in a ring around the protected building.

[0007] The eccentric resonator includes an eccentric steel column, which is vertically fixed to the ground surface; the eccentric steel column includes a vertical section and an eccentric section, the vertical section is vertically fixed to the ground, and the eccentric section is fixed to the top of the vertical section; a mass block is fixed to the top of the eccentric section.

[0008] The central axis of the vertical segment is a certain distance away from the center of gravity of the mass block.

[0009] Furthermore, the eccentric resonators are arranged at equal intervals;

[0010] Furthermore, the material parameters of the eccentric steel column are as follows: Young's modulus is 210 GPa, Poisson's ratio is 0.3, and mass density is 7850 kg / m³. 3 ;

[0011] Furthermore, the mass block is spherical or square in shape;

[0012] Furthermore, the eccentric segment is either arc-shaped or straight-line-shaped;

[0013] Furthermore, the ratio e of the distance Δ between the central axis of the vertical segment and the center of gravity of the mass block to the length L of the steel column satisfies:

[0014] The beneficial effects of this invention are:

[0015] 1) The eccentric resonant seismic metasurface of the present invention consists of only two components, and both components can be made of the same material, making it easy to mass-produce and construct;

[0016] 2) The eccentric earthquake metasurface of the present invention is separated from the protected building and does not participate in the vertical force of the protected building, making both the protected building and the earthquake-resistant metasurface less prone to damage.

[0017] 3) The object protected by this invention can be a designated area, a proposed building, or an existing building, and it can provide earthquake protection for ancient buildings. Attached Figure Description

[0018] Figure 1 This is a cross-sectional view of the eccentric resonant seismic metasurfaces deployed around the building according to the present invention.

[0019] Figure 2 This is a layout plan of a region of any specified shape protected by the present invention;

[0020] Figure 3 This is an elevation view of the eccentric resonance seismic metasurface of the curved steel column of this invention;

[0021] Figure 4 This is a stress analysis diagram of the eccentric resonant seismic metasurface of the curved steel column of the present invention;

[0022] Figure 5 This is an elevation view of the eccentric resonance seismic supersurface of the polygonal steel column of the present invention. Detailed Implementation

[0023] The present invention will now be described in detail with reference to specific embodiments.

[0024] According to the effective medium theory, the eccentric resonant seismic metasurface in this invention can achieve direct coupling vibration with the earth's surface through eccentric resonance, strongly attenuating seismic surface waves and realizing seismic surface wave protection for designated buildings.

[0025] like Figure 1 , Figure 2 As shown, the present invention includes multiple eccentric resonators, which are arranged in a ring around the protected building. The eccentric resonators are evenly spaced and closely surround the protected building, thus enclosing the protected building in the middle. According to the effective medium theory, the seismic metasurface of the eccentric resonator can directly couple vibrations with the ground surface, preventing seismic surface waves from affecting the building.

[0026] The eccentric resonator includes an eccentric steel column. The material parameters of the eccentric steel column are: Young's modulus of 210 GPa, Poisson's ratio of 0.3, and mass density of 7850 kg / m³. 3 The eccentric steel column consists of a vertical section and an eccentric section. The vertical section is fixed to the ground, and the eccentric section is fixed to the top of the vertical section. A mass block is fixed to the top of the eccentric section. The central axis of the vertical section is a certain distance away from the center of gravity of the mass block.

[0027] The ratio e of the distance Δ between the central axis of the vertical segment and the center of gravity of the mass block to the length L of the steel column satisfies: Different regions have different soil properties, and the eccentricity of the steel column is determined based on the properties of the soil.

[0028] The mass block is spherical or square in shape, with a mass greater than 1000 kg. It can be made of the same steel as the steel column or a material with a higher density, and is fixed to the top of the steel column by welding or other methods.

[0029] The eccentric segment can be circular or straight. The initial eccentricity of an eccentric steel column can be formed by making the central axis of the steel column into a curve, or the steel column can be divided into two or more segments, and the central axis of the steel column can be made into a broken line to form the initial eccentricity.

[0030] Eccentric resonant seismic metasurfaces are divided into curved steel columns and mass blocks. Figure 3 The meaning of each calculation quantity is clearly indicated. Figure 4 The stress analysis of the eccentric resonant seismic metasurface is shown, and the following assumptions are made about the model in the figure:

[0031] 1) Ignore the deformation of the mass block and only consider minor vertical vibrations;

[0032] 2) The bottom support structure is completely fixed to the ground;

[0033] 3) The soil is a linearly elastic homogeneous medium;

[0034] 4) The material nonlinearity of the steel column is not considered;

[0035] At this time, let Figure 3The displacement of the mass block is W1(x,t), the displacement of the ground is U0(x,t), the mass of the mass block is m, the bending stiffness of the steel column is EI, the initial eccentricity is Δ, and the bottom support width is d. When the seismic wave excites the seismic hypersurface, the mass block is subjected to an inertial force F. a (x,t), and an eccentric steel column provides an elastic restoring force F. k (x,t), as shown in equation (1):

[0036]

[0037] At this point, the part of the support in contact with the ground can be equivalent to two forces: the equivalent vertical force F. e (x,t) and equivalent bending moment M e (x,t), the equivalent lateral force and equivalent bending moment are shown in equations (2) and (3):

[0038]

[0039] F e (x,t)=F k (x,t) (3)

[0040] The curved steel column resonant seismic metasurface is fixedly connected to the ground surface through a support; therefore, the support will exhibit... Figure 4 The forces are distributed in a triangular pattern. It can be seen that when the resonator is subjected to seismic excitation, the entire resonator will experience an equivalent bending moment M. e (x,t) and equivalent vertical force F e (x,t) interacts with the ground. This interaction is controlled by the mass m of the mass block and the initial eccentricity Δ of the steel column. Since soil is a semi-infinite homogeneous medium, the energy of its surface waves is concentrated within a single wavelength range at the surface, and the amplitude decays exponentially with increasing soil depth z. When the resonator can interact with the ground, it can directly modulate the propagation of seismic surface waves and suppress their propagation in the low-frequency range.

[0041] like Figure 5 As shown, the eccentric resonator of the eccentric resonant metasurface consists of a steel column and a mass block. The initial eccentricity of the steel column is a polygonal central axis. The degree of initial eccentricity is determined by the initial eccentricity Δ and the length L of the steel column, with a ratio of e, as shown in the equation: When an earthquake propagates to the seismic metasurface, the seismic waves will cause the eccentric structure to produce vertical eccentric vibrations.

[0042] The content of this invention is not limited to the embodiments listed. Any equivalent modifications made by those skilled in the art to the technical solutions of this invention by reading this specification are covered by the claims of this invention.

Claims

1. An eccentric resonant seismic metasurface device, characterized in that: It includes multiple eccentric resonators, which are arranged in a ring around the protected building; The eccentric resonator includes an eccentric steel column, which is vertically fixed to the ground surface; the eccentric steel column includes a vertical section and an eccentric section, the vertical section is vertically fixed to the ground, and the eccentric section is fixed to the top of the vertical section; a mass block is fixed to the top of the eccentric section. The central axis of the vertical segment is a certain distance away from the center of gravity of the mass block.

2. The eccentric resonant seismic metasurface device according to claim 1, characterized in that: The eccentric resonators are arranged at equal intervals.

3. The eccentric resonant seismic metasurface device according to claim 2, characterized in that: The material parameters of the eccentric steel column are: Young's modulus of 210 GPa, Poisson's ratio of 0.3, and mass density of 7850 kg / m³.

4. The eccentric resonant seismic metasurface device according to claim 3, characterized in that: The mass block is spherical or square in shape.

5. The eccentric resonant seismic metasurface device according to claim 4, characterized in that: The eccentric segment is either arc-shaped or straight.

6. The eccentric resonant seismic metasurface device according to claim 5, characterized in that: The ratio e of the distance Δ between the central axis of the vertical segment and the center of gravity of the mass block to the length L of the steel column satisfies: .

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