JP7819040B2 - Seismic isolation device - Google Patents

Description

This invention relates to a seismic isolation device.

Conventional seismic isolation devices include those equipped with a laminated structure having hard and soft material layers stacked alternately in the vertical direction (see, for example, Patent Document 1).

Patent No. 6482974 specification

However, conventional seismic isolation devices had room for improvement in terms of high surface pressure.

The purpose of this invention is to provide a seismic isolation device that can withstand high surface pressure.

The seismic isolation device of the present invention comprises:
A seismic isolation device comprising a laminated structure having hard material layers and soft material layers alternately stacked in a vertical direction,
The following formula (1) is satisfied.
Here, in the above formula (1),
In the above formula (2),
_S1 : Ratio of the constrained area of the soft material layer to the free area per layer of the soft material layer _S2 : Ratio of the width of the soft material layer to the total thickness of all the soft material layers _S3 : Value obtained by multiplying the ratio of the thickness per layer of the hard material layer to the width of the soft material layer by 1000 σ: Short-term allowable surface pressure (MPa)
is.
The seismic isolation device of the present invention allows for high surface pressure.

In the seismic isolation device of the present invention,
It is preferable that the soft material layer has a shear modulus of elasticity of 0.35 MPa or more.
In this case, it is easy to obtain a seismic isolation device that satisfies formula (1).

In the seismic isolation device of the present invention,
It is preferable that the total thickness of all the soft material layers is 160 mm or more.
In this case, it is possible to increase the period and also ensure a large limit deformation.

This invention makes it possible to provide a seismic isolation device that can withstand high surface pressure.

1 is an axial cross-sectional view schematically showing a seismic isolation device according to one embodiment of the present invention. FIG. 1 is a perspective view schematically showing a seismic isolation device model used in the analysis. 10A and 10B are diagrams showing analysis results of comparative examples and examples of the seismic isolation device of the present invention. 10A and 10B are diagrams showing analysis results of comparative examples and examples of the seismic isolation device of the present invention. 10A and 10B are diagrams showing analysis results of comparative examples and examples of the seismic isolation device of the present invention. 10A and 10B are diagrams showing analysis results of comparative examples and examples of the seismic isolation device of the present invention. 10A and 10B are diagrams showing analysis results of comparative examples and examples of the seismic isolation device of the present invention. 10A and 10B are diagrams showing analysis results of comparative examples and examples of the seismic isolation device of the present invention.

The seismic isolation device of the present invention is suitable for use between the superstructure and substructure of a structure (for example, buildings such as buildings, condominiums, detached houses, warehouses, and bridges) to prevent earthquake vibrations from being transmitted to the structure. The seismic isolation device of the present invention is suitable for use on pillars to support the pillars of the structure, and is suitable for use, for example, on each pillar.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, an embodiment of a seismic isolation device according to the present invention will be described with reference to the drawings. Common components in the various drawings are designated by the same reference numerals.

Fig. 1 is a diagram for explaining a seismic isolation device 1 according to one embodiment of the present invention. Fig. 1 is an axial cross-sectional view that schematically shows the seismic isolation device 1 according to this embodiment in a state where no horizontal deformation occurs.
As shown in FIG. 1 , the seismic isolation device 1 of this embodiment includes a laminated structure 3 , a pair of upper and lower connecting steel plates 7 , and a pair of upper and lower flanges 8 .

In this specification, the "central axis O" of the seismic isolation device 1 (hereinafter simply referred to as the "central axis O") is the central axis of the laminated structure 3. The central axis O of the seismic isolation device 1 is oriented to extend vertically. In this specification, the "axial direction" of the seismic isolation device 1 is a direction parallel to the central axis O of the seismic isolation device 1. The "axial inner side" of the seismic isolation device 1 refers to the side closer to the axial center of the laminated structure 3 in the axial direction, and the "axial outer side" of the seismic isolation device 1 refers to the side farther from the axial center of the laminated structure 3 in the axial direction. Furthermore, the "direction perpendicular to the axis" of the seismic isolation device 1 is a direction perpendicular to the axial direction of the seismic isolation device 1. Furthermore, the "inner peripheral side," "outer peripheral side," "radial direction," and "circumferential direction" of the seismic isolation device 1 refer to the "inner peripheral side," "outer peripheral side," "radial direction," and "circumferential direction," respectively, when the central axis O of the seismic isolation device 1 is the center. Additionally, "up" and "down" refer to "up" and "down" in the vertical direction, respectively.

The laminated structure 3 has multiple hard material layers 4, multiple soft material layers 5, and a coating layer 6. The hard material layers 4 and soft material layers 5 are stacked alternately in the vertical direction. Each hard material layer 4 and each soft material layer 5 are arranged coaxially; that is, the central axis of each hard material layer 4 and each soft material layer 5 is located on the central axis O of the seismic isolation device 1. It is preferable that soft material layers 5 are arranged at both the top and bottom ends of the laminated structure 3.

The hard material layer 4 is made of a hard material. As the hard material constituting the hard material layer 4, metal is preferable, and steel is more preferable.
The thickness of each hard material layer 4 is preferably the same as in the example of FIG. 1, but may be different from each other.
The widths of the hard material layers 4 are preferably the same as each other as in the example of FIG. 1, but may be different from each other.

The soft material layer 5 is made of a soft material that is softer than the hard material layer 4. An elastic body is preferable as the soft material that makes up the soft material layer 5, and rubber is more preferable. Suitable rubber that can make up the soft material layer 5 is natural rubber or synthetic rubber (such as high-damping rubber).
The thickness of each soft material layer 5 is preferably the same as in the example of FIG. 1, but may be different from each other.
The width of each soft material layer 5 is preferably the same as that of each hard material layer 4, as in the example of Fig. 1. However, the widths of each soft material layer 5 may be different from each other.

The covering layer 6 covers the outer peripheral surfaces of the hard material layer 4 and the soft material layer 5. The material constituting the covering layer 6 is preferably an elastic body, more preferably rubber. The material constituting the covering layer 6 may be the same as the soft material constituting the soft material layer 5, or may be different from the soft material constituting the soft material layer 5.
The covering layer 6 is formed integrally with the soft material layer 5 .
1 , the coating layer 6 covers the entire outer peripheral surfaces of the hard material layer 4 and the soft material layer 5, and thus constitutes the entire outer peripheral surface of the laminated structure 3. However, the coating layer 6 may cover only a portion of the outer peripheral surfaces of the hard material layer 4 and the soft material layer 5, and thus may constitute only a portion of the outer peripheral surface of the laminated structure 3.
Furthermore, the laminated structure 3 may not have the covering layer 6 .

The hard material layer 4, the soft material layer 5, and the coating layer 6 (and thus the laminated structure 3) may each have any outer edge shape, such as a polygonal shape (e.g., a square), a circle, or the like, in a cross section perpendicular to the axis. When the hard material layer 4, the soft material layer 5, and the coating layer 6 (and thus the laminated structure 3) each have a polygonal shape in a cross section perpendicular to the axis, the corners of the polygonal shape may be angular or may be curved by, for example, chamfering.

The width of the laminated structure 3 is preferably constant along the axial direction, as in the example of Figure 1, but may also vary along the axial direction.

In this specification, the "width" of components such as the laminated structure 3, hard material layer 4, soft material layer 5, connecting steel plates 7, and flanges 8 refers to the distance between the two intersections of a line passing through the center of gravity of the outer edge shape of the component in a cross section perpendicular to the axis and the outer edge shape, in the direction where the distance between these two intersections is smallest. For example, if the outer edge of the component is circular in a cross section perpendicular to the axis, the "width" corresponds to the diameter of the circle. If the outer edge of the component is square in a cross section perpendicular to the axis, the "width" corresponds to the length of one side of the square.

In the example shown in Figure 1, the laminated structure 3 has each hard material layer 4 and each soft material layer 5 configured as a solid core, but this is not limited to this. For example, the laminated structure 3 may have each hard material layer 4 and each soft material layer 5 configured as an annular ring, with the central holes of each hard material layer 4 and each soft material layer 5 forming a central hole extending axially on its central axis O. In this case, a pillar may be disposed in the central hole. The pillar is preferably configured to absorb vibration energy through plastic deformation. The pillar may be composed of, for example, lead, tin, a tin alloy, or a thermoplastic resin.

The laminated structure 3 is disposed between a pair of flanges 8 .
Of the pair of flanges 8, the upper flange 8 is configured to be connected to a superstructure (such as a building itself; more specifically, a column of the building itself) of a structure (such as a building, condominium, detached house, warehouse, or bridge) by fastening or the like when the superstructure is placed on top of the upper flange 8. Of the pair of flanges 8, the lower flange 8 is configured to be connected to a substructure (such as a foundation) of the structure by fastening or the like.
The flange 8 is preferably made of metal, more preferably steel.
The flange 8 may have any outer edge shape in a cross section perpendicular to the axis, such as a polygonal shape (such as a square), a circle, or the like.

The pair of connecting steel plates 7 are arranged between the laminated structure 3 and the pair of flanges 8 .
The pair of connecting steel plates 7 are respectively connected to the upper and lower surfaces of the laminated structure 3 by, for example, adhesion (vulcanization adhesion and/or adhesion with an adhesive, etc.), etc. The pair of connecting steel plates 7 are also connected to the pair of flanges 8 by fastening via fastening members f, etc.
The connecting steel plates 7 are made of a hard material. As the hard material constituting the connecting steel plates 7, metal is preferable, and steel is more preferable.

However, the seismic isolation device 1 does not necessarily have to include a pair of connecting steel plates 7. In this case, it is preferable that the pair of flanges 8 are connected to the upper and lower surfaces of the laminated structure 3, respectively, by, for example, bonding (vulcanization bonding and/or bonding with an adhesive, etc.).

The seismic isolation device 1 of this embodiment preferably has a long-term allowable surface pressure of 18 MPa or more and 25 MPa or less.
Here, "long-term allowable surface pressure" corresponds to "Fc/3" of "allowable stress against long-term forces" as defined in Article 6 of the "Ministry of Construction Notification No. 2009 of 2000."

Furthermore, the seismic isolation device 1 of this embodiment satisfies the following formula (1).
Here, in the above formula (1),
In the above formula (2),
S ₁ : ratio of the constrained area of the soft material layer 5 to the free area per layer of the soft material layer 5 (i.e., S ₁ = (constrained area of the soft material layer 5)/(free area per layer of the soft material layer 5))
S ₂ : the ratio of the width of the soft material layer 5 to the total thickness of all the soft material layers 5 (i.e., S ₂ = (width of the soft material layer 5)/(total thickness of all the soft material layers 5))
S ₃ : the ratio of the thickness of each hard material layer 4 to the width of each soft material layer 5 multiplied by 1000 (i.e., S ₃ = (thickness of each hard material layer 4) × 1000/(width of each soft material layer 5))
σ: Short-term allowable surface pressure (MPa)
is.
The above _S1 is generally called a primary shape factor. Regarding the above _S1 , the "constrained area of the soft material layer 5" corresponds to the area of the soft material layer 5 in a cross section perpendicular to the axis.
Regarding _S1 above, the "free area per soft material layer 5" corresponds to the area of the outer peripheral surface of one soft material layer 5.
The above _S2 is generally called the quadratic shape factor.
Furthermore, the "short-term allowable surface pressure (σ)" corresponds to "2Fc/3" of the "allowable stress against short-term forces" stipulated in Article 6 of the Ministry of Construction Notification No. 2009 of 2000. The short-term allowable surface pressure σ is, for example, approximately twice (usually twice) the long-term allowable surface pressure. In the event of an earthquake, it can be assumed that a maximum surface pressure equivalent to the short-term allowable surface pressure will be applied to the seismic isolation device.
In formula (2), "Max(25, -7.5S ₃ +62.5)" means the larger value of "25" and "-7.5S ₃ +62.5".
In addition, when the width and/or thickness of each soft material layer 5 is not the same, the above-mentioned "constrained area of the soft material layer 5,""free area per soft material layer 5," and "width of the soft material layer 5" shall be the values of the soft material layer 5 with the smallest thickness among the soft material layers 5 with the smallest width.
Furthermore, if the thicknesses of the hard material layers 4 are not the same, the "thickness per hard material layer 4" is the value of the hard material layer 4 with the smallest thickness.

In the above formula (1), the left side (X(1- ^eY )) represents the buckling strain, that is, the shear strain of the seismic isolation device 1 when buckling occurs in the seismic isolation device 1 during horizontal deformation of the seismic isolation device 1. Generally, the buckling strain can be adjusted by the structure of the seismic isolation device.
In the above formula (1), the right-hand side (4) represents the fracture strain, i.e., the shear strain of the seismic isolation device 1 when fracture occurs in the seismic isolation device 1 during horizontal deformation of the seismic isolation device 1. Generally, the fracture limit strain is defined as 400%. Therefore, the fracture strain corresponds to a shear strain of 400%. The number "4" on the right-hand side of the above formula (1) represents a shear strain of 400%. Generally, shear strain cannot be adjusted by the structure of the seismic isolation device.
The above formula (1) is designed especially for seismic isolation devices with a long-term allowable surface pressure of 18 MPa or more and 25 MPa or less. The above formula (1) is an empirical formula newly discovered by the inventor of the present invention based on the results of FEM analysis of comparative examples and examples described later. Specifically, formula (1) is an empirical formula derived from FEM analysis in which _S2 contributes linearly to buckling, and _S1 and _S3 contribute exponentially to buckling.

To obtain a seismic isolation device 1 that satisfies the above formula (1), it is sufficient to adjust the dimensions and number of hard material layers 4 and soft material layers 5, the shear modulus of the soft material layers 5, etc. The shape of the laminated structure 3 in the cross section perpendicular to the axis does not significantly affect whether the above formula (1) is satisfied.

The above formula (1) indicates that when a high surface pressure equivalent to a short-term allowable surface pressure σ, which is approximately twice the long-term allowable surface pressure of, for example, 18 MPa or more and 25 MPa or less, is applied to the seismic isolation device 1, fracture occurs before buckling during horizontal deformation of the seismic isolation device 1; in other words, buckling does not occur until the fracture strain (shear strain 400%) is reached.
Generally, when a high surface pressure is applied to a seismic isolation device, the seismic isolation device is prone to buckling during horizontal deformation. Conventional seismic isolation devices do not satisfy the above formula (1), and when a high surface pressure equivalent to a short-term allowable surface pressure σ, which is approximately twice the long-term allowable surface pressure of 18 MPa to 25 MPa, is applied, there is a risk that the seismic isolation device will buckle before breaking during horizontal deformation.
On the other hand, in the case of the seismic isolation device 1 of this embodiment that satisfies the above formula (1), when a high surface pressure equivalent to a short-term allowable surface pressure σ, which is approximately twice the long-term allowable surface pressure of, for example, 18 MPa to 25 MPa, is applied to the seismic isolation device, fracture occurs before buckling during horizontal deformation of the seismic isolation device 1, so that the occurrence of buckling can be suppressed over a longer shear strain region, thereby improving stability. Therefore, even if large horizontal deformation occurs under high surface pressure during an earthquake, the device can withstand it without buckling; in other words, high surface pressure is possible.
Generally, when a seismic isolation device is installed on a column, the surface pressure of the seismic isolation device corresponds to the axial force of the column divided by the cross-sectional area of the soft material layer of the seismic isolation device. In recent years, the axial force of columns has been increasing, and there is a demand for seismic isolation devices that can support such high axial forces. Two methods can be considered to meet such demands: increasing the surface pressure of the seismic isolation device or increasing the width of the laminated structure of the seismic isolation device. However, because there is a limit to the size of the machines (e.g., vulcanizers) used to manufacture seismic isolation devices, there is a practical limit to increasing the width of the laminated structure of the seismic isolation device. On the other hand, according to this embodiment, the surface pressure of the seismic isolation device 1 can be increased, allowing the seismic isolation device 1 to support a higher axial force without having to be enlarged.
Furthermore, according to this embodiment, the surface pressure of the seismic isolation device 1 can be increased, which enables the structure to have a longer period (in other words, the structure will sway more slowly), thereby improving the seismic isolation performance of the seismic isolation device 1. The period T of a structure is expressed by the following equation (3), where m (mass) in equation (3) is proportional to the surface pressure, so the period T can be lengthened by increasing the surface pressure of the seismic isolation device 1.

In addition, from the viewpoint of high surface pressure, etc., assuming a breaking strain of more than 400%, it is preferable that the seismic isolation device 1 satisfies the following formula (4), and it is even more preferable that it satisfies the following formula (5).

The long-term allowable surface pressure of the seismic isolation device 1 is preferably greater than 18 MPa, more preferably 20 MPa or more, and is preferably, for example, 20 MPa.
The short-term allowable surface pressure σ of the seismic isolation device 1 is preferably 36 MPa or more, more preferably more than 36 MPa, and even more preferably 40 MPa or more. The short-term allowable surface pressure σ of the seismic isolation device 1 is preferably 50 MPa or less. For example, the short-term allowable surface pressure σ of the seismic isolation device 1 is preferably 40 MPa.

The shear modulus of elasticity of the soft material layer 5 is preferably 0.350 MPa or more. In this case, it is easy to obtain a seismic isolation device 1 that satisfies formula (1). This also makes the seismic isolation device 1 less susceptible to buckling.
From the same viewpoint, the shear modulus of elasticity of the soft material layer 5 is more preferably 0.390 MPa or more, for example, 0.392 MPa or more, and particularly preferably 0.392 MPa or more.
The shear modulus of elasticity of the soft material layer 5 is preferably, for example, 0.6 MPa or less.
In this specification, the "shear modulus" of the soft material layer 5 refers to the static shear modulus measured in accordance with JIS K 6254:2016.
The higher the shear modulus of elasticity of the soft material layer 5, the greater the buckling strain.

It is preferable that the width of the laminated structure 3 (and therefore the hard material layer 4 and soft material layer 5) be 1800 mm or less. In this case, the seismic isolation device 1 is easier to manufacture.

The total thickness of all the soft material layers 5 is preferably 160 mm or more, which allows for a long period and ensures a large limit deformation.
From the same viewpoint, the total thickness of all the soft material layers 5 is more preferably 200 mm or more, and even more preferably 250 mm or more.

FEM analysis was performed on Comparative Examples 1 to 10 (including Comparative Example 4-2) and Examples 1 to 10 (including Example 4-2) of the seismic isolation device of the present invention, and the results are described below.
Analysis was performed for each comparative example and each example using a seismic isolation device model 1' as schematically shown in Figure 2. The seismic isolation device model 1' for each comparative example and each example comprises a pair of connecting steel plates 7' and a laminated structure 3' connected between the pair of connecting steel plates 7', and does not include a flange. The laminated structure 3' is formed by alternately stacking hard material layers 4' and soft material layers 5' along the axial direction and does not include a coating layer. The connecting steel plates 7' have a square cross section perpendicular to the axis, with its four angular corners. The laminated structure 3' has a square cross section perpendicular to the axis, with its four curved corners formed by C-chamfering. The width of the laminated structure 3' is constant along the axial direction. Other specifications for each comparative example and example are as shown in Tables 1 to 3 below. As shown in Tables 1 to 3, each comparative example does not satisfy the above formula (1), while each example satisfies the above formula (1).
Comparative Example 4-2 and Example 4-2 differ from Comparative Example 4 and Example 4, respectively, only in the shear modulus of the soft material layer.

For each of the comparative examples except for Comparative Example 4-2 and each of the examples except for Example 4-2, the seismic isolation device model 1' was loaded in the 0° direction and the 45° direction under a surface pressure of 20 MPa and 40 MPa, respectively, until the shear strain reached 400% or until buckling occurred, thereby causing horizontal deformation. For Comparative Example 4-2 and Example 4-2, the model was loaded in the 45° direction under a surface pressure of 40 MPa until the shear strain reached 400% or until buckling occurred, thereby causing horizontal deformation. The shear stress-shear strain curves obtained for each of the comparative examples and examples are shown in Figures 3 to 8. The points where the shear stress-shear strain curves change from a positive gradient to a negative gradient indicate the timing at which buckling occurred.
As shown in FIG. 2, the "0° direction" is a direction parallel to one side of the laminated structure 3', and the "45° direction" is a direction parallel to a diagonal line of the laminated structure 3'.

As can be seen from Figures 3 to 8, in Comparative Examples 1 to 10, excluding Comparative Example 4-2, buckling occurred under a high surface pressure of 40 MPa, both in horizontal deformation in the 0° direction and in the 45° direction, just before the shear strain reached 400%. Furthermore, in Comparative Example 4-2, buckling occurred under a high surface pressure of 40 MPa, both in horizontal deformation in the 45° direction, just before the shear strain reached 400%. On the other hand, in Examples 1 to 10, excluding Example 4-2, buckling did not occur under a high surface pressure of 40 MPa, both in horizontal deformation in the 0° direction and in the 45° direction, even up to a shear strain of 400%. Furthermore, in Example 4-2, buckling did not occur under a high surface pressure of 40 MPa, both in horizontal deformation in the 45° direction, even up to a shear strain of 400%. Therefore, it can be seen that Examples 1 to 10 (including Example 4-2) can more effectively withstand high surface pressure than Comparative Examples 1 to 10 (including Comparative Example 4-2), and as a result, can withstand higher surface pressures.

The seismic isolation device of the present invention is suitable for placement between the superstructure and substructure of a structure (e.g., buildings such as buildings, condominiums, detached houses, warehouses, and bridges) to prevent earthquake vibrations from being transmitted to the structure. The seismic isolation device of the present invention is suitable for installation on pillars, for example, to support the pillars of the structure, and it is suitable for installation of one or more devices on each pillar, for example.

1: seismic isolation device, 3: laminated structure, 4: hard material layer, 5: soft material layer, 6: covering layer, 7: connecting steel plate, 8: flange,
f: fastening member, O: central axis,
1': seismic isolation device model, 3': laminated structure, 4': hard material layer, 5': soft material layer, 7': connecting steel plate, O': central axis

Claims (3)

A seismic isolation device comprising a laminated structure having hard material layers and soft material layers alternately stacked in a vertical direction,
A seismic isolation device that satisfies the following formula (1).
Here, in the above formula (1),
In the above formula (2),
_S1 : Ratio of the constrained area of the soft material layer to the free area per layer of the soft material layer _S2 : Ratio of the width of the soft material layer to the total thickness of all the soft material layers _S3 : Value obtained by multiplying the ratio of the thickness per layer of the hard material layer to the width of the soft material layer by 1000 σ: Short-term allowable surface pressure (MPa)
is. The seismic isolation device described in claim 1, wherein the shear modulus of the soft material layer is 0.35 MPa or greater. The seismic isolation device described in claim 1 or 2, wherein the total thickness of all of the soft material layers is 160 mm or more.