Seismic isolation structure

Abstract

To provide a base isolation structure capable of prolonging a natural period without extending a tensile material.SOLUTION: A base isolation structure 1 is provided between a substructure 2 and a superstructure 3. The base isolation structure 1 comprises an upper structure 10 fixed to the superstructure 3; a lower structure 20 fixed to the substructure 2; a tensile material 30 that is supported by an upper structure lower end part 10b at the lower end part of the upper structure 10 and a lower structure upper end part 20b of the upper end part of the lower structure 20; and a base isolation bearing device 40 that is provided between the lower structure upper end part 20b and an upper end part 30a of the tensile material 30, and bears in a base isolating manner the tensile material 30 with respect to the lower structure upper end part 20b.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a seismic isolation structure provided between a lower structure and an upper structure.

Background Art

[0002] In structures such as buildings, in order to reduce vibrations transmitted from the ground during an earthquake, there is known a structure in which a seismic isolation structure is provided between a lower structure such as a foundation and an upper structure.

[0003] As such a seismic isolation structure, conventionally, a plurality of diagonal bars fixed to the lower structure, a plurality of reverse diagonal bars fixed to the upper structure, an upper casing provided at the upper end of the diagonal bar, and a lower end of the reverse diagonal bar And a tension member (connecting member) connected to a lower casing disposed below the upper casing, and a configuration in which the upper structure is supported by the tension member in a simple pendulum manner with respect to the lower structure is known (see, for example, Patent Document 1).

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] The seismic isolation structure can generally enhance the seismic isolation performance by increasing the natural period. In the above-described conventional seismic isolation structure, since the natural period is determined by the length of the pendulum constituted by the tension member, it is necessary to make the tension member longer in order to obtain higher seismic isolation performance.

[0006] However, in order to lengthen the tension member in the above-described conventional seismic isolation structure, it is necessary to increase the vertical space between the lower structure and the upper structure. Therefore, it is necessary to increase the height of the first floor of the building or deepen the position of the foundation base plate, and accordingly, there is a problem that the cost for installing the seismic isolation structure increases.

[0007] An object of the present invention is to provide a seismic isolation structure capable of lengthening the natural period without lengthening the tension member.

Means for Solving the Problems

[0009] The seismic isolation structure of the present invention is A seismic isolation structure provided between a lower structure and an upper structure, comprising an upper structure fixed to the upper structure, a lower structure fixed to the lower structure, a lower end portion of the upper structure supported by an upper end portion of the upper structure and an upper end portion of the lower structure, a tension member supported by the upper end portion of the lower structure and the upper end portion of the tension member, and a seismic isolation support device provided between the upper end portion of the lower structure and the upper end portion of the tension member for seismic isolation supporting the tension member with respect to the upper end portion of the lower structure, wherein the seismic isolation support device is a sliding support .

Effects of the Invention

[0010] According to the present invention, it is possible to provide a seismic isolation structure capable of lengthening the natural period without lengthening the tension member.

Brief Description of the Drawings

[0011]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Modes for Carrying Out the Invention

[0012] Hereinafter, the seismic isolation structure according to the present invention will be described in detail with reference to the drawings by way of example.

[0013] As shown in FIG. 1, a seismic isolation structure 1 according to an embodiment of the present invention is provided between a lower structure 2 and an upper structure 3. The seismic isolation structure 1 can reduce horizontal vibrations transmitted from the ground through the lower structure 2 to the upper structure 3.

[0014] The seismic isolation structure 1 can stably support the upper structure 3 by installing three or more between the lower structure 2 and the upper structure 3. The arrangement pattern and the number of arrangements when arranging a plurality of seismic isolation structures 1 between the lower structure 2 and the upper structure 3 can be changed as appropriate.

[0015] The lower structure 2 is a structure fixed directly or indirectly to the ground. The upper structure 3 is a structure constructed above the lower structure 2. In the present embodiment, the lower structure 2 is the foundation of a building, and the upper structure 3 is a building such as a building, a warehouse, or a wooden building.

[0016] Note that the lower structure 2 is not limited to the foundation of a building as long as it is a structure fixed to the ground, and may be other structures such as a part constituting the lower floor of a building. When the lower structure 2 is a part constituting the lower floor of a building, the upper structure 3 is a part constituting the upper floor of the building.

[0017] The seismic isolation structure 1 includes an upper structure 10, a lower structure 20, a tension member 30, and a seismic isolation bearing device 40.

[0018] The upper structure 10 is fixed to the upper structure 3. The upper structure 10 can be, for example, a truss structure in which the lower ends of two inclined column portions 10a are joined to each other and fixed to the upper structure 3 at the upper ends of these column portions 10a. The upper structure 10 is configured to have a predetermined rigidity capable of supporting the load of the upper structure 3 by, for example, steel materials or the like. The lower end portion of the upper structure 10 is the lower end portion 10b of the upper structure.

[0019] The upper structure 10 is not limited to the above-described truss structure as long as it has a configuration in which the lower end portion of the upper structure 10b is provided at the lower end portion and is fixed to the upper structure 3. For example, it can have a portal configuration, and its shape or configuration can be variously changed.

[0020] The lower structure 20 is fixed to the lower structure 2. The lower structure 20 can be, for example, a truss structure in which the upper ends of two inclined column portions 20a are joined to each other and are fixed to the lower structure 2 at the lower ends of these column portions 20a. The lower structure 20 is configured to have a predetermined rigidity capable of supporting the load of the upper structure 3, for example, by steel materials or the like. The upper end portion of the lower structure 20 is the upper end portion 20b of the lower structure. The upper end portion 20b of the lower structure is disposed at a predetermined interval above the lower end portion 10b of the upper structure.

[0021] The lower structure 20 is not limited to the above-described truss structure as long as it has a configuration in which the upper end portion of the lower structure 20b is provided at the upper end portion and is fixed to the lower structure 2. For example, it can have a portal configuration, and its shape or configuration can be variously changed.

[0022] The tension member 30 is supported by the lower end portion 10b of the upper structure at its lower end side and is supported by the upper end portion 20b of the lower structure at its upper end side. Thereby, the tension member 30 suspends and holds the upper structure 10 fixed to the upper structure 3 with respect to the lower structure 20 fixed to the lower structure 2. The tension member 30 can be, for example, a rod-shaped member made of steel materials or the like that extends along the vertical direction (vertical direction) and has a tensile strength capable of supporting the weight of the upper structure 3, but it can also be a wire, a chain, or the like having a tensile strength capable of supporting the weight of the upper structure 3.

[0023] The tension member 30 can tilt (rotate) in any horizontal direction with respect to each of the lower end portion 10b of the upper structure and the upper end portion 20b of the lower structure. Thereby, when the lower structure 2 vibrates horizontally with respect to the upper structure 3 due to an earthquake or the like, the tension member 30 can tilt in the vibration direction like a pendulum between the lower end portion 10b of the upper structure and the upper end portion 20b of the lower structure due to the vibration.

[0024] The seismic isolation bearing device 40 is provided between the upper end portion 20b of the lower structure and the upper end portion 30a of the tension member 30. The seismic isolation bearing device 40 seismically isolates the tension member 30 in the horizontal direction with respect to the upper end portion 20b of the lower structure.

[0025] As shown in FIG. 2, in the present embodiment, the seismic isolation bearing device 40 serves as a sliding bearing. As shown in FIGS. 2, 3, and 4, in the present embodiment, the upper end portion 20b of the lower structure is formed in a rectangular plate shape, and its upper surface is a flat sliding surface 41 parallel to the horizontal direction. A circular through hole 42 having an inner diameter larger than the outer diameter of the tension member 30 is provided at the center of the upper end portion 20b of the lower structure, and the tension member 30 passes through the through hole 42 and protrudes above the upper end portion 20b of the lower structure.

[0026] A base plate 43 is disposed on the sliding surface 41. The base plate 43 has a rectangular plate-shaped friction material 43a that contacts the sliding surface 41 over the entire lower surface, and a plate-shaped spherical seat receiving member 43b to which the friction material 43a is fixed on the lower surface. The base plate 43 can move in the horizontal direction with respect to the upper end portion 20b of the lower structure by the friction material 43a sliding on the sliding surface 41. A circular through hole 43c having an inner diameter larger than the outer diameter of the tension member 30 and penetrating the friction material 43a and the spherical seat receiving member 43b in the vertical direction is provided coaxially with the through hole 42 of the upper end portion 20b of the lower structure at the center of the base plate 43, and the upper end portion 30a of the tension member 30 passes through the through hole 42 and the through hole 43c and protrudes above the base plate 43.

[0027] On the upper surface of the socket receiving member 43b, a hemispherical socket receiving surface 43d is provided that is coaxial with the through hole 43c and recesses downward from the upper surface of the socket receiving member 43b. On the other hand, a socket 32 is attached to the upper end portion 30a of the tension member 30 using a nut 31. The socket 32 has the same radius as the socket receiving surface 43d and is hemispherical, protruding downward, and its hemispherical outer peripheral surface 32a is in contact with the socket receiving surface 43d. The tension member 30 passes through the axis of the socket 32, and the nut 31 is screwed to the tension member 30 above the socket 32. The upward movement of the socket 32 relative to the tension member 30 is restricted by the nut 31.

[0028] In this embodiment, the tension member 30 can tilt (rotate) in any horizontal direction with respect to the upper end portion 20b of the lower structure as the outer peripheral surface 32a of the socket 32 slides along the socket receiving surface 43d.

[0029] When the lower structure 2 vibrates horizontally with respect to the upper structure 3 due to an earthquake or the like, the friction material 43a slides on the sliding surface 41, and the base plate 43 moves horizontally with respect to the upper end portion 20b of the lower structure, so that the position supported by the upper end portion 20b of the lower structure of the tension member 30 can be changed horizontally.

[0030] The seismic isolation structure 1 can be configured to include an elastic support member 50 for vertical seismic isolation between the lower end portion 10b of the upper structure and the lower end portion 30b of the tension member 30 or between the seismic isolation bearing device 40 and the upper end portion 30a of the tension member 30. In this embodiment, a case is shown in which an elastic support member 50 for vertical seismic isolation is provided between the lower end portion 10b of the upper structure and the lower end portion 30b of the tension member 30.

[0031] As shown in FIG. 4, in the present embodiment, the lower end portion 10b of the upper structure is formed in a plate shape, and a circular through-hole 10c having an inner diameter larger than the outer diameter of the tension member 30 is provided at the center thereof. The tension member 30 penetrates through the through-hole 10c and protrudes below the lower end portion 10b of the upper structure. A flange 51 that faces the lower end portion 10b of the upper structure with a predetermined interval therebetween is fixed to the lower end portion 30b of the tension member 30 that protrudes below the lower end portion 10b of the upper structure.

[0032] The elastic support member 50 is a compression coil spring and is disposed in a compressed state between the lower end portion 10b of the upper structure and the flange 51. When the lower structure 2 vibrates in the vertical direction (the vertical direction) with respect to the upper structure 3 due to an earthquake or the like, the elastic support member 50 expands and contracts by elastic deformation, so that the length of the tension member 30 between the lower end portion 10b of the upper structure and the upper end portion 20b of the lower structure changes according to the change in the distance between the lower structure 2 and the upper structure 3 due to the vibration, and the vertical vibration can be suppressed from being transmitted from the lower structure 2 to the upper structure 3. The elastic support member 50 is not limited to a compression coil spring, and may be other elastic members such as disc springs stacked in a plurality in the vertical direction.

[0033] In the present embodiment, the tension member 30 is supported by the lower end portion 10b of the upper structure with the through-hole 10c as a fulcrum, and the elastic support member 50 elastically deforms in the inclined direction, so that the tension member 30 can tilt (rotate) in any horizontal direction with respect to the lower end portion 10b of the upper structure.

[0034] As shown in FIG. 5, when the lower structure 2 vibrates horizontally with respect to the upper structure 3 due to an earthquake or the like, the seismic isolation structure 1 of the present embodiment having the above configuration performs seismic isolation operation by the tension member 30 tilting in the vibration direction like a pendulum between the lower end portion 10b of the upper structure and the upper end portion 20b of the lower structure due to the vibration, and the vibration of the lower structure 2 can be suppressed from being transmitted to the upper structure 3.

[0035] Moreover, the seismic isolation structure 1 of the present embodiment having the above configuration is provided with a seismic isolation bearing device 40 in series with the seismic isolation mechanism by the pendulum motion of the tension member 30 between the upper end portion 20b of the lower structure and the upper end portion 30a of the tension member 30. Therefore, when the lower structure 2 vibrates horizontally with respect to the upper structure 3 due to an earthquake or the like, as shown in FIGS. 5 and 6, the friction material 43a slides on the sliding surface 41, so that the base plate 43 moves horizontally with respect to the upper end portion 20b of the lower structure, and the position where the tension member 30 is supported by the upper end portion 20b of the lower structure changes horizontally in accordance with the tilting motion (pendulum motion) of the tension member 30. As a result, as shown in FIG. 5, the rotation radius R1 due to the pendulum motion of the tension member 30 during the seismic isolation operation is larger than the rotation radius R2 when the seismic isolation bearing device 40 is not provided by the amount that the base plate 43 moves horizontally with respect to the upper end portion 20b of the lower structure. Therefore, the natural period of the seismic isolation structure 1 with respect to horizontal vibration becomes longer compared to the case where the seismic isolation bearing device 40 is not provided.

[0036] As described above, in the seismic isolation structure 1 of the present embodiment, in addition to the seismic isolation mechanism by the pendulum motion of the tension member 30 supported by the upper end portion 20b of the lower structure and the lower end portion 10b of the upper structure, a seismic isolation bearing device 40 for seismic isolating the tension member 30 with respect to the upper end portion 20b of the lower structure is provided between the upper end portion 20b of the lower structure and the upper end portion 30a of the tension member 30. Therefore, without increasing the length of the tension member 30, the natural period during the seismic isolation operation of the seismic isolation structure 1 can be made longer.

[0037] Moreover, in the seismic isolation structure 1 of the present embodiment having the above configuration, since the natural period during the seismic isolation operation can be made longer without increasing the length of the tension member 30, in order to expand the vertical space between the lower structure 2 and the upper structure 3, it is not necessary to increase the height of the first floor of the building or deepen the position of the base of the foundation, and the cost for installing the seismic isolation structure 1 can be reduced.

[0038] Furthermore, in the seismic isolation structure 1 of the present embodiment, since the seismic isolation bearing device 40 can be arranged inside the upper structure 10 having a truss structure, the space for arranging the seismic isolation bearing device 40 can be reduced. Also, when the superstructure 3 is a building, it is not necessary to arrange the seismic isolation bearing device 40 in the living space or the like of the building, and the space of the building can be effectively utilized.

[0039] Thus, according to the seismic isolation structure 1 of the present embodiment, the natural period can be lengthened without increasing the installation cost, and the seismic isolation performance of the seismic isolation structure 1 can be enhanced.

[0040] The natural period T of the seismic isolation structure 1 with respect to horizontal vibration is as follows.

[0041] That is, in the seismic isolation structure 1 of the present embodiment having the above configuration, when the pendulum angle θ during the pendulum motion of the tension member 30 is small, sinθ≒θ, so the horizontal rigidity K of the seismic isolation mechanism due to the pendulum motion of the tension member 30 p is given by the following (Equation 1) where the supported weight of the tension member 30 is mg and the pendulum length of the tension member 30 (the length from the center of the spherical seat 32 of the tension member 30 to the lower end portion 10b of the upper structure) is L.

[0042] [Mathematical formula] K p =mg / L (Equation 1)

[0043] On the other hand, the equivalent rigidity K of the seismic isolation bearing device 40 s is given by the following (Equation 2) where the displacement amount of the seismic isolation bearing device 40 in the horizontal direction is d and the friction coefficient between the friction material 43a and the sliding surface 41 is μ.

[0044] [Mathematical formula] K s =μN / d=μmgcos 2 θ / d (Equation 2)

[0045] Note that when the tension during the pendulum motion of the tension member 30 is F t then F t =mgcosθ, N=F tSince it becomes cosθ, the overall stiffness K of the seismic isolation structure 1 in which the pendulum mechanism by the tension member 30 and the seismic isolation bearing device 40 are arranged in series is 1 / K = 1 / K p + 1 / K s = (μLcos 2 θ + d) / μmgcos 2 θ, and it becomes the following (Equation 3).

[0046] [Mathematical formula] K = μmgcos 2 θ / (μLcos 2 θ + d) (Equation 3)

[0047] Therefore, the natural period T of the seismic isolation structure 1 with respect to horizontal vibration becomes the following (Equation 4).

[0048] [Mathematical formula] T = 2π / ω = 2π{(μLcos 2 θ + d) / μgcos 2 θ} 1 / 2 = 2π{(L / g)+(d / μgcos 2 θ)} 1 / 2 (Equation 4)

[0049] Thus, the natural period T of the seismic isolation structure 1 with respect to horizontal vibration is extended from the natural period 2π(L / g) when the seismic isolation bearing device 40 is not provided. 1 / 2 More extended.

[0050] In the seismic isolation structure 1 of the present embodiment having the above configuration, the friction coefficient μ between the friction material 43a and the sliding surface 41 can be variously changed.

[0051] For example, by setting the friction coefficient μ to be relatively small, when the lower structure 2 vibrates horizontally with respect to the upper structure 3 due to an earthquake or the like, the seismic isolation bearing device 40 actively performs a vibration isolation operation, and the vibration can be effectively suppressed from being transmitted to the upper structure 3 by the seismic isolation structure 1 with a lengthened natural period T. In this case, since the seismic isolation bearing device 40 has no restoring function, it is necessary to return the seismic isolation bearing device 40 to the origin position using a jack or the like even after a small earthquake.

[0052] On the other hand, by setting the friction coefficient μ to be relatively large, the seismic isolation bearing device 40 can also be used in a fail-safe manner. That is, by setting the friction coefficient μ to be relatively large, the friction material 43a does not slide on the sliding surface 41 during a small earthquake, and the friction material 43a slides on the sliding surface 41 only during a large earthquake with a predetermined seismic intensity or higher. In this case, during a small earthquake, since the seismic isolation bearing device 40 does not operate, the natural period T of the seismic isolation structure 1 cannot be lengthened, but after a small earthquake, the restoration work of the seismic isolation bearing device 40 can be made unnecessary. On the other hand, during a large earthquake, when the friction material 43a slides on the sliding surface 41, the natural period T of the seismic isolation structure 1 can be lengthened, and large vibrations caused by the large earthquake can be effectively vibration-isolated by the seismic isolation structure 1. Further, by making the friction coefficient μ relatively large, the frictional resistance generated between the friction material 43a and the sliding surface 41 during the seismic isolation operation can be increased, and the effect of attenuating vibrations can be obtained.

[0053] It goes without saying that the present invention is not limited to the above-described embodiments, and various modifications can be made without departing from the gist thereof.

[0054] For example, the seismic isolation bearing device 40 is not limited to a sliding bearing, and may have other configurations as long as it can isolate horizontal vibrations, such as a rolling bearing, a laminated rubber bearing, etc.

[0055] When a spherical roller bearing is used as the seismic isolation bearing device 40, between the upper end portion 20b of the lower structure and the spherical seat receiving member 43b, instead of the friction material 43a, an upper dish and a lower dish each having a spherical surface are arranged vertically with their spherical surfaces facing each other, and a piece in contact with the spherical surface is arranged between these upper and lower dishes. In this case, the radius (rotation radius) of the spherical surface of the seismic isolation bearing device 40 is set to be larger than the rotation radius R2 when the seismic isolation bearing device 40 of the tension member 30 is not performing the vibration isolation operation. By using a spherical roller bearing as the seismic isolation bearing device 40, after an earthquake, the seismic isolation bearing device 40 can be automatically returned to the origin position.

[0056] When using a laminated rubber bearing as the seismic isolation bearing device 40, a laminated rubber bearing is arranged between the upper end portion 20b of the lower structure and the spherical seat receiving member 43b instead of the friction material 43a. As the laminated rubber bearing, it is preferable to use a flat-shaped one in order to resist the rotational load applied thereto. By using a laminated rubber bearing as the seismic isolation bearing device 40, after an earthquake, the seismic isolation bearing device 40 can be easily returned to the origin position. Further, by using a laminated rubber bearing using high damping rubber as the laminated rubber bearing, a damping function can also be imparted to the seismic isolation bearing device 40.

[0057] The seismic isolation structure 1 is not limited to the configuration in which the elastic support member 50 for vertical seismic isolation is provided between the lower end portion 10b of the upper structure and the lower end portion 30b of the tension member 30, and the elastic support member 50 for vertical seismic isolation may be provided between the seismic isolation bearing device 40 and the upper end portion 30a of the tension member 30. Further, the seismic isolation structure 1 can also be configured not to include the elastic support member 50. In these cases, the lower end portion 30b of the tension member 30 is connected to the lower end portion 10b of the upper structure by various connection structures such as, for example, pin connection, universal joint, and ring member, which can transmit the tensile load to the lower end portion 10b of the upper structure and enable the tension member 30 to tilt (rotate) with respect to the lower end portion 10b of the upper structure.

[0058] In the above-described embodiment, the upper structure 10 and the lower structure 20 have been described as truss structures each having two column portions 10a and 20a, but the upper structure 10 and the lower structure 20 may be truss structures each having three or more column portions 10a and 20a. By making the upper structure 10 and the lower structure 20 into truss structures each having three or more column portions 10a and 20a, a more stable seismic isolation structure 1 can be obtained. Further, even when the upper structure 10 and the lower structure 20 are each configured to have one column portion 10a and 20a, by installing three or more seismic isolation structures 1, the upper structure 3 can be stably supported.

Explanation of Reference Numerals

[0059] 1 Seismic isolation structure 2 Lower structure 3 Upper structure 10 Upper structure 10a Column part 10b Lower end of the upper structure 10c Through hole 20 Lower structure 20a Column part 20b Upper end of the lower structure 30 Tension member 30a Upper end 30b Lower end 31 Nut 32 Ball seat 32a Outer peripheral surface 40 Seismic isolation bearing device 41 Sliding surface 42 Through hole 43 Base plate 43a Friction material 43b Ball seat receiving member 43c Through hole 43d Ball seat receiving surface 50 Elastic support member 51 Flange R1 Radius of rotation R2 Radius of rotation

Claims

Claim 1 A seismic isolation structure provided between a lower structure and an upper structure, an upper structure fixed to the upper structure, a lower structure fixed to the lower structure, a tension member supported by an upper end portion of the upper structure and an upper end portion of the lower structure of the lower end portion of the upper structure, a seismic isolation bearing device provided between the upper end portion of the lower structure and the upper end portion of the tension member, and seismically isolating the tension member with respect to the upper end portion of the lower structure, comprising: the seismic isolation bearing device being a sliding bearing A seismic isolation structure characterized by this.

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