JP7409911B2 - Anti-vibration structure - Google Patents

Description

The present invention relates to a vibration isolation structure.

In facilities such as live music halls and dance studios, vertical vibrations (so-called vertical vibrations) may occur due to the bending and stretching movements of a large number of guests. Anti-vibration structures are known (for example, see Patent Documents 1 to 3). In such an anti-vibration structure, the structural frame is partially recessed, and a floating floor supported by springs is provided in the recessed part.

The floating floor is spring-supported vertically to the structural frame. Since the frequency at which vertical vibration causes vibration problems is said to be approximately 2 to 3.5 Hz, the vertical natural frequency of a floating floor is generally set to about 1 Hz, and the vertical displacement during normal use of the floating floor is The mass of the floating floor and the specifications of the springs are set so that the difference is about 1 to 2 cm or less.
However, for a typical floating floor with a natural frequency of 1 Hz, if the vertical excitation frequency is 2 Hz, more than 1/3 of the excitation force will be transmitted to the structural frame supporting the floating floor, resulting in a significant vibration isolation effect. cannot be expected.

In the vibration isolation structure disclosed in Patent Document 1, the inertial mass device is installed in parallel with the support spring. As a result, it is possible to reduce the excitation force transmitted to the foundation (structural frame) to approximately 1/10 or less at frequencies of 2 to 4 Hz, where vibration disturbance caused by vertical vibration is a problem, and a significant vibration-proofing effect is expected. can.

In the vibration isolation structure 100 shown in FIG. 8, the ratio R/F of the basic reaction force R to the excitation force F from above the floating floor 103 is defined as the reaction force magnification, and the excitation frequency f and the reaction force magnification R/F are The relationship (frequency transfer function) is shown in FIG. In FIG. 8, the structural frame is shown as 102, the support spring k is shown as 105, the damping element c is shown as 107, and the inertial mass ψ is shown as 109. It can be seen that by adding the inertial mass, the reaction force at the excitation frequency of 2 to 3 Hz, including the cut-off frequency, is greatly reduced, and the reaction force magnification R/F becomes approximately 1/10 or less at 2 to 4 Hz. The frequency transfer function is obtained by plotting the amplitude ratio of the reaction force to the amplitude of the excitation force for each frequency under the following conditions for harmonic vibration (sinusoidal vibration). The unit system for each specification is ton for mass and inertial mass, mm for displacement, kN/mm for spring stiffness, kN for excitation force and reaction force, kNm/sec for damping coefficient, time in sec, and frequency. is Hz, the attenuation constant, ratio, and magnification are unitless numbers (dimensionless quantities).

Here, in order to suppress an excessive response at the time of resonance, a model of a vibration isolation structure to which a damping element with a damping constant h=0.05 is added will be considered.
The natural frequency f ₀ of the floating floor is set as follows.

In the vibration isolation structure disclosed in Patent Document 2, the floating floor has a two-tiered structure, upper and lower. In the vibration isolation structure disclosed in Patent Document 2, a first floating floor is provided on the structure via a first support spring, and a second floating floor is provided on the first floating floor via a second support spring. It has a laminated structure with . A rotating inertial mass device is provided between the first floating floor and the structure in parallel with the first support spring. A natural frequency set by the spring constant of the second support spring and the mass of the first floating floor, and a fixed frequency set by the spring constant of the first support spring and the rotating inertial mass by the rotating inertial mass device, Both are made to match a predetermined frequency, and the reaction force magnification is greatly reduced at this frequency.

Therefore, as disclosed in Patent Document 3, the applicant created a floating floor with an upper and lower two-tiered structure, which greatly reduces the reaction force multiplier in a specific frequency range, while maintaining the same structure as the conventional floating floor even in high frequency ranges. We have proposed a vibration isolation structure that does not increase the reaction force multiplier compared to the previous model.

Specifically, the vibration isolation structure includes a first floating floor provided on the structure foundation via a first support spring, and a second floating floor provided on the first floating floor via a second support spring. It has a laminated structure with . By providing a damping element in parallel with the first support spring between the first floating floor and the foundation, the response at resonance can be reduced. Moreover, by providing an inertial mass device in parallel with the second support spring between the first floating floor and the second floating floor, the reaction force magnification can be significantly reduced in a specific frequency range.

JP2008-082541A JP2009-085362A Patent Application No. 2019-219599 (unpublished at the time of filing)

However, in the vibration isolation structure disclosed in Patent Document 1, as shown in FIG. 7, in a high frequency region (for example, 3.5 Hz or higher), the case with an inertial mass device is better than the case without an inertial mass device. There is a problem that the reaction force magnification becomes larger than that of the conventional method, and the vibration damping effect becomes inferior.
In addition, in the vibration isolation structure disclosed in Patent Document 2, it is possible to greatly reduce the reaction force multiplier at a specific frequency, but when vibration is applied at a frequency different from this frequency, the reaction force multiplier The problem is that it is not possible to significantly reduce the

The vibration isolation structure disclosed in Patent Document 3 has excellent vibration isolation characteristics in terms of reaction force reduction effect, but the displacement amplitude (vertical vibration) is lower than that of conventional floating floors in the frequency band where vertical vibration is a problem. ) becomes large. If the displacement amplitude of the floating floor becomes large, there is a concern that the audience on the floating floor (second floating floor) may feel uncomfortable.

Therefore, an object of the present invention is to provide a vibration isolation structure that can significantly reduce both the reaction force multiplier and the displacement amplitude in a specific frequency range.

In order to achieve the above object, a vibration isolation structure according to the present invention includes a structure, a first spring element provided on the structure, and a vibration isolation structure provided on the structure via the first spring element. a second vibrating body provided on the first vibrating body, a second spring element provided on the first vibrating body, and a second vibrating body provided on the first vibrating body via the second spring element; an inertial mass device provided in parallel with the first spring element between the structure and the first vibrating body, and the mass of the first vibrating body is greater than or equal to the mass of the second vibrating body. The spring stiffness of the first spring element is set to be smaller than the spring stiffness of the second spring element, and the inertial mass of the inertial mass device is set as shown in the following formula. .

In the present invention, in a specific frequency range, the displacement of the excited floor is reduced while greatly reducing the reaction force multiplier (the ratio R/F of the basic reaction force R to the excitation force F from the second vibrating body). The magnification (ratio v/v ₀ of the displacement amplitude v during excitation to the displacement v 0 when the excitation force F acts statically) can also be significantly reduced.
In the present invention, the cut-off frequency at which the reaction force multiplier becomes minimum is determined by the inertial mass ψ ₁ of the inertial mass device and the spring stiffness k ₁ of the first spring element. The mooring frequency at which the displacement amplitude becomes minimum is determined by the mass M ₁ of the first vibrating body, the inertial mass ψ ₁ of the inertial mass device, the spring stiffness k ₁ of the first spring element, and the spring stiffness k ₂ of the second spring element. be done. Both the cut-off frequency and the mooring frequency do not change due to the mass _M2 of the second vibrating body. Therefore, even if the mass of the second vibrating body changes due to an increase or decrease in the weight of the upper floor (second floating floor on the upper side) serving as the second vibrating body or the number of spectators, the anti-vibration properties (particularly effective frequency) is maintained. Furthermore, by setting the mass of the first vibrating body to be greater than or equal to the mass of the second vibrating body, making the spring stiffness of the first spring element smaller than that of the second spring element, and defining the cutoff frequency and the mooring frequency separately, , it is possible to widen the frequency range in which the response reduction effect is exhibited.
Since the second spring element only supports the mass of the second vibrating body, the supporting load is smaller than that of the first spring element that supports both the mass of the first vibrating body and the mass of the second vibrating body. Further, since the spring stiffness _k2 of the second spring element is set larger than the spring stiffness k1 of the first spring element, the deflection of the _second spring element is smaller than the deflection of the first spring element, and the deflection of the second spring element is smaller than the deflection of the first spring element. A spring that is lighter and cheaper than the spring element can be used.

Moreover, the vibration isolation structure according to the present invention may include a first damping element provided in parallel with the first spring element between the structure and the first vibrating body.
With such a configuration, the response during resonance can be reduced.

Further, the vibration isolation structure according to the present invention may include a second damping element provided between the first vibrating body and the second vibrating body in parallel with the second spring element.
With such a configuration, it is possible to evaluate the frictional resistance of the device and reduce the response at high frequencies.

Moreover, in the vibration isolation structure according to the present invention, the inertial mass device may be a rotating inertial mass damper.
With such a configuration, it is possible to downsize the inertial mass device.

According to the present invention, both the reaction force magnification and the displacement amplitude can be significantly reduced in a specific frequency range.

1 is a schematic diagram showing an example of a vibration isolator according to an embodiment of the present invention. FIG. 1 is a schematic diagram showing an example of an inertial mass device. It is a graph showing the relationship between the excitation frequency and the reaction force magnification of the vibration isolation structure according to the present embodiment. It is a graph showing the relationship between the excitation frequency and the displacement magnification of the vibration isolation structure according to the present embodiment. It is a graph showing the relationship between the excitation frequency and the reaction force magnification when the mass of the second floating floor is doubled in the vibration isolation structure according to the present embodiment. It is a graph showing the relationship between the excitation frequency and the displacement magnification when the mass of the second floating floor is doubled in the vibration isolation structure according to the present embodiment. It is a graph showing the relationship between the excitation frequency and the reaction force magnification of a conventional vibration isolation structure. FIG. 1 is a schematic diagram showing an example of a conventional vibration isolator.

Hereinafter, a vibration isolation structure according to an embodiment of the present invention will be described based on FIGS. 1 to 6.
As shown in FIG. 1, the vibration isolation structure 1 according to the present embodiment includes a structure 2, a first floating floor 3 (first vibrating body) installed above the structure 2, and a first floating floor 3 (first vibration body) installed above the structure 2. A second floating floor 4 (second vibrating body) installed above, a first support spring 5 (first spring element) interposed between the structure 2 and the first floating floor 3, and a first floating floor a second support spring 6 (second spring element) interposed between the structure 2 and the second floating floor 4; a first damping element 7 interposed between the structure 2 and the first floating floor 3; 2 and the first floating floor 3, and a second damping element 9 interposed between the first floating floor 3 and the second floating floor 4.
The vibration isolation structure 1 according to the present embodiment is adopted, for example, in a building such as a large-scale music hall, and people and objects are placed on the upper part of the second floating floor 4. In the vibration isolation structure 1, when the second floating floor 4 is excited by a large number of guests bending and stretching in time with the music on the upper part of the second floating floor 4, vertical vibration ( It is assumed that so-called vertical vibration) will occur.

The structure 2 has, for example, a foundation made of RC construction. The structure 2 has a recess 21 that opens upward. The structure 2 has a base part 22 that is below the recess 21 and a side wall part 23 that is located on the side of the recess 21.
The upper surface of the base portion 22 is formed into a horizontal surface.
The first floating floor 3 and the second floating floor 4 are each formed into a flat plate shape, and are arranged in the recess 21 of the structure 2 with the plate surfaces facing the horizontal plane. The first floating floor 3 is arranged to overlap above the base portion 22, and the second floating floor 4 is arranged to overlap above the first floating floor 3.

The first floating floor 3 is arranged above the base 22 via a first support spring 5 , an inertial mass device 8 and a first damping element 7 . The first support spring 5, the inertial mass device 8 and the first damping element 7 are arranged in parallel. The first support spring 5 is arranged so that the spring axis direction is in the up-down direction (vertical direction).
The first floating floor 3 is configured to be vertically displaceable with respect to the structure 2 within a deformable range of the first support spring 5 , the inertial mass device 8 , and the first damping element 7 .

The second floating floor 4 is arranged above the first floating floor 3 via a second support spring 6 and a second damping element 9. The second support spring 6 and the second damping element 9 are provided in parallel. The second support spring 6 is arranged with the spring axis direction being in the vertical direction.
The second floating floor 4 is configured to be vertically displaceable with respect to the structure 2, and is vertically displaceable with respect to the first floating floor 3 within the deformable range of the second support spring 6 and the second damping element 9. It is configured to be able to be displaced in the direction.

The mass M ₁ of the first floating floor 3 is set to be greater than or equal to the mass M ₂ of the second floating floor 4 (M ₁ ≧M ₂ ). The mass _M2 of the second floating floor 4 also includes the mass of the audience assumed to be on the second floating floor 4 and the fixtures assumed to be installed.
The spring stiffness k ₁ of the first support spring 5 is set smaller than the spring stiffness k ₂ of the second support spring 6 (k ₁ <k ₂ ).
The second support spring 6 has a smaller displacement than the first support spring 5 and has a smaller supporting load than the first support spring 5, so in this embodiment, a spring that is lighter than the first support spring 5 is used. ing.

As shown in FIG. 2, the inertial mass device 8 is a so-called rotating inertial mass damper, which converts linear displacement (vertical displacement) into rotational displacement using a ball screw mechanism 81 or the like to rotate a rotating weight 82 (flywheel). It has become. The inertial mass device 8 can provide an inertial mass several hundred to several thousand times larger than the mass of the rotating weight 82.
The force borne by the inertial mass device 8 is as follows, where the diameter D of the rotating weight 82, the rotational moment of inertia I _θ , the mass m _s , the lead L _d , the device borne force P, the displacement x, the weight rotation angle θ, and the inertial mass ψ Expressed by the formula.

When the density ρ and the thickness t of the rotating weight 82 are expressed as follows, it can be seen that the inertial mass ψ is proportional to the fourth power of the weight diameter.

The inertial mass ψ ₁ of the inertial mass device 8 shown in FIG. 1 is set as follows.
Let f ₁ be the natural frequency of the vibration isolation structure when the inertial mass device 8 is not provided (there is no inertial mass ψ ₁ ). Let f _min be the lower limit frequency of "a specific frequency range in which the reaction force magnification is desired to be significantly reduced," and let f _max be the upper limit frequency. As mentioned above, k ₁ is the spring stiffness of the first support spring 54 . The reaction force magnification indicates the ratio R/F of the basic reaction force R to the excitation force F from above the second floating floor 4.
The inertial mass ψ ₁ is set such that the lower limit frequency is f _min and the upper limit frequency is f _max to satisfy the following formula.

Note that the expression between f _min and f _max is the cutoff frequency f _S . The cutoff frequency _fS is shown below.

The spring stiffness _k2 of the second support spring 6 is set to satisfy the following, assuming that the "specific frequency range in which the displacement multiplier is desired to be significantly reduced" is the same as the "frequency range in which the reaction force multiplier is desired to be reduced" do. The displacement magnification indicates the ratio v/v ₀ of the maximum response displacement v to the displacement v ₀ of the second floating floor 4 when the excitation force F acts as a static force.

Note that the expression between f _min and f _max is the mooring frequency f _k at which the displacement magnification becomes minimum. The mooring frequency f _k is shown below.

Regarding the vibration isolation structure 1 of the present embodiment described above, the following specifications are set so as to be compared with the specifications set using the conventional vibration isolation structure shown in FIG. 8 and the above equation (1).
Mass of first floating floor 3 M ₁ =0.9M
Mass of second floating floor 4 M ₂ =0.1M
Rigidity k ₁ of first support spring 5 = 1.07k
Rigidity k ₂ of second support spring 6 = 6k
Natural frequency f _{1 of vibration isolation structure 1 excluding inertial mass ψ 1 =} 1.03Hz
Damping of the first damping element 7 between the foundation 22 and the first floating floor 3 c ₁ =1.0c
Damping of the second damping element 9 between the first floating floor 3 and the second floating floor 4 c ₂ =1.5c
Inertial mass ψ ₁ =0.188M
When the damping is ignored, the cutoff frequency f _S at which the reaction force multiplier becomes minimum is 2.39 Hz.
The mooring frequency f _k at which the displacement magnification of the second floating floor 4 becomes minimum is 2.55 Hz when damping is ignored.

These specifications are set based on the calculations below. Let f ₀ be the natural frequency of the floating floor in a vibration isolation structure with a single-stage floating floor.

Here, since we want to emphasize the vibration damping effect near 2.5 Hz, ψ ₁ /M=0.188.
Note that the cutoff frequency at damping c ₁ =0 is as follows.

The cut-off frequency at which the reaction force multiplier becomes minimum when damping _c1 is applied is 2.42 Hz, which is a slight increase from the cut-off frequency (2.39 Hz) at which the reaction force multiplier becomes minimum when damping is ignored. do.
On the other hand, since we want to reduce the shaking (vertical amplitude) of the second floating floor 4 in the same frequency range, we set the mooring frequency at which the displacement magnification (response displacement) of the second floating floor 4 is minimal by adjusting f _min and f _max . Set between.

Here, since we want to emphasize the vibration damping effect near 2.5 Hz, we set k ₂ /k=6.
The mooring frequency at damping c ₂ =0 is:

The relationship (frequency transfer function) between the excitation frequency f and the reaction force magnification R/F of the vibration isolation structure 1 according to the present embodiment _is shown in FIG. The relationship is shown in Figure 4. In addition, FIG. 3 shows the relationship between the excitation frequency f and the reaction force magnification R/F (frequency transfer function) in the case with and without the conventional inertial mass device 8 of the vibration isolation structure shown in FIG. are also shown for comparison. In FIG. 4, the relationship between the excitation frequency f and the displacement magnification v/v ₀ is also shown for comparison in the case where the inertial mass device 8 of the vibration-proof structure is present and the case where it is not.

According to the vibration isolation structure 1 according to the present embodiment, it can be seen that the reaction force is approximately 1/10 or less of the excitation force in a specific frequency range (2 to 3.5 Hz) where vertical vibration becomes a problem. In addition, the shaking (vertical vibration) of the second floating floor 4 (upper floor) where the audience enters shall be approximately 1/10 or less of the "displacement of the second floating floor 4 when the excitation force acts statically". I understand.
From FIG. 3, the reaction force magnification R/F is 0.334 at an excitation frequency of 2 Hz for the conventional floating floor with one-stage structure and no inertial mass device 8, but when the inertial mass device 8 is added to this, the reaction force multiplier R/F is 0.334. This makes it 0.100. In the vibration isolation structure 1 according to the present embodiment, the reaction force magnification R/F is 0.108 at an excitation frequency of 2 Hz, which is approximately equivalent to a floating floor with a one-stage structure and an inertial mass device 8. It can be seen that the reaction force reduction effect is exhibited.
From FIG. 4, the displacement magnification v/v ₀ is 0.34 at an excitation frequency of 2 Hz for the conventional floating floor with one-stage structure and no inertial mass device 8, but when the inertial mass device 8 is added to this, the displacement magnification v/v 0 is 0.34 This results in a slight decrease to 0.271. In the vibration isolation structure 1 according to the present embodiment, the displacement magnification v/v ₀ is 0.120 at an excitation frequency of 2 Hz, which indicates that a significant displacement reduction effect is exhibited.

Next, the functions and effects of the vibration isolation structure according to the present embodiment described above will be explained.
The vibration isolation structure according to the present embodiment described above can significantly reduce the displacement amplitude (vertical shaking) of the excited floor while significantly reducing the reaction force magnification in a specific frequency range. As a result, the reaction force multiplier is reduced to 1/10 or less for excitation frequencies (2 to 3.5 Hz) that are 2 to 3.5 times the resonance frequency (1.0 Hz), and the second floating floor 4 is It is possible to achieve unprecedented vibration damping characteristics in which the displacement amplitude is approximately 1/10 or less of the static deflection (displacement) caused by the excitation force. Note that in a conventional general vibration isolation mechanism that does not use the inertial mass device 8, it was not possible to reduce the reaction force magnification to ⅓ or less at an excitation frequency that is twice the resonance frequency.

In the vibration isolation structure according to this embodiment, the cutoff frequency that minimizes the reaction force magnification is determined by the inertial mass ψ ₁ of the inertial mass device 8 and the spring stiffness k ₁ of the first support spring 5. The mooring frequency at which the displacement magnification becomes minimum is the mass M ₁ of the first floating floor 3, the inertial mass ψ ₁ of the inertial mass device 8, the spring rigidity k ₁ of the first support spring 5, and the spring rigidity of the second support spring 6. It is determined by _k2 . Both of these do not change depending on the weight of the second floating floor 4 or the number of spectators (fixed load or live load), so even if the weight of the second floating floor 4 or the number of spectators increases or decreases, the anti-vibration characteristics (particularly effective vibration frequency) is maintained. In addition, the mass _M1 of the first floating floor 3 is set to be greater than or equal to the mass M2 of the second floating floor ₄ , and the spring rigidity _k1 of the first support spring 5 is made smaller than the spring rigidity k2 of the second support spring ₆ , thereby interrupting vibration. By individually defining the number and mooring frequency, it is possible to widen the frequency range in which the response reduction effect is exerted.
Figure 5 shows the relationship between the excitation frequency f and the reaction force magnification R/F when the mass (M ₂ ) of the second floating floor 4 is twice the above value (M ₂ =0.2M). 6 shows the relationship between the excitation frequency f and the displacement magnification v/v ₀ when the mass (M ₂ ) of the second floating floor 4 is twice the above value (M ₂ =0.2M).
Comparing FIG. 5 with FIG. 3 and FIG. 6 with FIG. 4, it is found that the reaction force magnification R/F and displacement magnification v/v are the same as the cut-off frequency and mooring frequency at which ₀ is the minimum. It can be seen that there is not much difference in the vibration-proofing characteristics of the vibration-proofing structures.

Since the spring stiffness k 2 of the second support spring ₆ only supports the mass M ₂ of the second floating floor 4, it supports the mass M ₁ of the first floating floor 3 and the mass M ₁ of the second floating floor 4. The supporting load is smaller than the spring stiffness _k1 of the first supporting spring 5. Further, since the spring stiffness _k2 of the second support spring 6 is set larger than the spring stiffness k1 of the first support spring 5, the deflection of the second support spring ₆ is smaller than the deflection of the first support spring 5. Therefore, a spring that is lighter and cheaper than the first support spring 5 can be used.

Further, in the vibration isolation structure according to the present embodiment, by having the first damping element 7 provided between the structure 2 and the first floating floor 3 in parallel with the first support spring 5, response can be reduced.

Moreover, in the vibration isolation structure according to the present embodiment, by having the second damping element 9 provided in parallel with the second support spring 6 between the first floating floor 3 and the second floating floor 4, It is possible to evaluate the frictional resistance of the device and reduce the response at high frequencies.

Further, in the vibration isolation structure according to the present embodiment, the inertial mass device 8 is a rotating inertial mass damper, so that the inertial mass device 8 can be downsized.

The smaller the damping _c1 of the first damping element 7 in parallel with the first support spring 5, the higher the vibration isolation effect at the cut-off frequency with respect to the reaction force. The response magnification (reaction force magnification) tends to increase in inverse proportion to the attenuation. Therefore, in this embodiment, the specifications are set so that the response magnification during resonance is within 10 times, but if only the vibration isolation characteristics are to be focused on, the performance will be better if the attenuation is made smaller.
The smaller the damping _c2 of the second damping element 7 in parallel with the second support spring 5, the higher the vibration isolation effect at the mooring frequency with respect to displacement. The displacement response magnification tends to increase. Therefore, in this embodiment, the specifications realized by the current device are set, but if only the vibration damping characteristics are to be focused on, the performance will be better if the damping is made smaller.

Although the embodiments of the vibration isolation structure according to the present invention have been described above, the present invention is not limited to the above-described embodiments, and can be modified as appropriate without departing from the spirit thereof.
For example, in the above embodiment, an example was described in which the vibration isolation mechanism of the present proposal is applied to a live hall or the like, but the present proposal can also be applied to a lower support stand of a device that vibrates vertically at a specific frequency. If the cut-off frequency and mooring frequency in this proposal are made to match specific frequencies, it is possible to eliminate the vibration disturbance caused by shaking the surrounding area due to mechanical vibration, and the vertical vibration of the equipment itself does not occur, making it easy to connect the equipment to the outside. It has the characteristic that problems are less likely to occur.

Further, in the above embodiment, the first damping element 7 is provided between the structure 2 and the first floating floor 3 in parallel with the first support spring 5, but the structure 2 and the first floating floor 3, the first damping element 7 may not be provided.
Furthermore, in the above embodiment, the second damping element 9 is provided between the first floating floor 3 and the second floating floor 4 in parallel with the second support spring 6; The second damping element 9 may not be provided between the two floating floors 4.

Further, in the above embodiment, the inertial mass device 8 is a rotating inertial mass damper, but it may be other than a rotating inertial mass damper, such as a mechanism that generates an inertial mass using a lever and a weight.

1 Vibration isolation structure 2 Structure 3 First floating floor (first vibrating body)
4 Second floating floor (second vibrating body)
5 First support spring (first spring element)
6 Second support spring (second spring element)
7 First damping element 8 Inertial mass device 9 Second damping element

Claims (4)

structure and
a first spring element provided on the structure;
a first vibrating body provided on the structure via the first spring element;
a second spring element provided on the first vibrating body;
a second vibrating body provided on the first vibrating body via the second spring element;
an inertial mass device provided in parallel with the first spring element between the structure and the first vibrating body,
_The mass M1 of the first vibrating body is set to be greater than _or equal to the mass M2 of the second vibrating body,
Spring stiffness k1 of the first spring element is set smaller than spring _stiffness k2 of the _second spring element,
The ratio R/F of the basic reaction force R to the excitation force F from above the second vibrating body is a reaction force magnification,
If the lower limit frequency of a specific frequency range in which the reaction force multiplier is desired to be significantly reduced is f _min and the upper limit frequency is f _max , then the relationship shown in equation (1) below is obtained.
A vibration isolation structure characterized in that the inertial mass of the inertial mass device is set as shown in the following formula (2) .

The vibration isolation structure according to claim 1, further comprising a first damping element provided in parallel with the first spring element between the structure and the first vibrating body. The vibration isolation structure according to claim 1 or 2, further comprising a second damping element provided in parallel with the second spring element between the first vibrating body and the second vibrating body. The vibration isolation structure according to any one of claims 1 to 3, wherein the inertial mass device is a rotating inertial mass damper.

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