Base isolation structure

Abstract

To provide a base isolation structure in which even when an external force occurs in a direction in which one structure and the other structure separate from each other, the external force is attenuated and a base isolation function of a bearing can be exhibited.SOLUTION: A base isolation structure of a bridge is configured to prevent vibrations generated in a bridge pier 4 due to an earthquake or the like from being transmitted to a bridge girder 5, and comprises: a sliding bearing 1 that is arranged between the bridge pier 4 and the bridge girder 5, and supports the bridge girder 5 while allowing the bridge girder 5 to move relative to the bridge pier 4 in a direction perpendicular to a bridge axis Y; a damper 2 that is arranged between the bridge pier 4 and the bridge girder 5, and has a restoration function for generating a tensile force against an external force in a vertical direction Z in which the bridge pier 4 and the bridge girder 5 separate from each other; and a tension adjustment device 3 that adjusts the tensile force of the damper 2.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a seismic isolation structure that suppresses the transmission of vibrations caused by earthquakes or the like from one structure to another structure.

Background Art

[0002] Conventionally, a seismic isolation structure using a bearing has been known. In this type of seismic isolation structure, the bearing is disposed between an upper structure and a lower structure, and while supporting the upper structure, by allowing a horizontal relative displacement between the upper structure and the lower structure, at the time of an earthquake or the like, the swaying of the lower structure is suppressed from being transmitted to the upper structure. As the bearing, a sliding bearing composed of a sliding plate and a sliding material that slide on each other, a laminated rubber bearing formed by alternately bonding rubber plates and metal plates, or a combination thereof (for example, Patent Document 1) is used.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] By the way, depending on the type, design, etc. of the upper structure, at the time of an earthquake or the like, an uplifting force may be generated in the upper structure, and the upper structure may move in a direction away from the lower structure. In this case, there is a possibility that the seismic isolation function by the bearing cannot be exerted. That is, in the case of a sliding bearing, the sliding plate and the sliding material may separate from each other, and there is a possibility that the damping function by sliding cannot be exerted. Further, when the upper structure and the lower structure are fixed by a laminated rubber bearing or the like, not only the bearing but also mounting bolts and anchor bolts used for joining with concrete are pulled, so that the seismic isolation function may be reduced due to an excessive uplifting force.

[0005] The present invention has been made in view of the above circumstances, and an object thereof is to attenuate an external force even when an external force is generated in a direction in which one structure and the other structure are separated, and to exhibit a seismic isolation function of a support. The purpose is to provide a seismic isolation structure that can

Means for Solving the Problems

[0006] In order to solve the above problems, in the present invention, between one structure and the other structure, while supporting the other structure, a support that allows relative translational movement of the one structure and the other structure, and one A damper having a restoring function that generates a tensile force with respect to an external force in a direction in which the structure and the other structure are separated, and a tension adjusting device that adjusts the tensile force of the damper are arranged. Here, the damper has two spring characteristics, and until an external force equivalent to the trigger resistance force is generated in the extension direction, it has a high spring constant (primary spring constant) and hardly extends (trigger function). When an external force exceeding the trigger resistance force is generated, it has a spring constant (secondary spring constant) lower than the primary spring constant, generates a resistance force (tensile force) while extending (attenuation function), and as the external force decreases, it shrinks until it returns to its original length (restoring function). It is preferable to use a so-called damper with a tensile type restoring function. In this case, the tension adjusting device preferably adjusts the damper with a tensile type restoring function so that an external force equivalent to the trigger resistance force is generated.

[0007] For example, the present invention is A seismic isolation structure that suppresses the transmission of vibrations generated in one structure to the other structure, A support disposed between the one structure and the other structure, while supporting the other structure, allowing relative translational movement of the one structure and the other structure, A damper having a restoring function that is disposed between the one structure and the other structure and generates a tensile force with respect to an external force in a direction in which the one structure and the other structure are separated, And a tension adjusting device that adjusts the tensile force of the damper.

Effects of the Invention

[0008] According to the present invention, by means of a bearing, while supporting one structure by the other structure, relative parallel movement of the one structure and the other structure is allowed, and by means of a damper, a tensile force (resistance force) adjusted by a tension adjusting device is generated with respect to an external force in a direction in which the one structure and the other structure are separated. Thereby, even when an external force is generated in a direction separating from the one structure and the other structure, this external force can be attenuated and the seismic isolation function of the bearing can be exhibited.

Brief Description of the Drawings

[0009]

Figure 1

Figure 2

Figure 3

Figure 4

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Figure 6

Figure 7

Embodiments for Carrying Out the Invention

[0010] Hereinafter, an embodiment of the present invention will be described by taking the seismic isolation structure of a bridge as an example.

[0011] FIG. 1 is a schematic view of the seismic isolation structure according to the present embodiment.

[0012] The seismic isolation structure is for suppressing the transmission of vibrations generated in the pier 4, which is the lower structure of the bridge, to the bridge girder 5, which is the upper structure of the bridge, due to an earthquake or the like. As shown in Fig. 1, it is composed of a sliding bearing 1 and a damper 2 arranged between the pier 4 and the bridge girder 5, and a tension adjustment device 3 provided for each damper 2. In Fig. 1, the case where two sliding bearings 1, four sets of dampers 2 and tension adjustment devices 3 are arranged between the pier 4 and the bridge girder 5 is illustrated, but the number of these installations can be changed as appropriate.

[0013] The sliding bearing 1 supports the bridge girder 5 in the vertical direction Z while allowing relative translational movement (movement in the direction perpendicular to the bridge axis Y) between the pier 4 and the bridge girder 5. As shown in Fig. 1, as the sliding bearing 1, a rigid sliding bearing having a sliding plate 10 fixed to the upper surface of the pier 4 and a sliding material 11 fixed to the lower surface of the bridge girder 5 and sliding on the sliding plate 10 is used.

[0014] The damper 2 is a so-called damper with a tension-type restoring function, and generates a resistance force (tensile force) in the vertical direction Z against an external force in the direction in which the pier 4 and the bridge girder 5 are separated.

[0015] Fig. 2 is a diagram showing the resistance-displacement characteristics of the damper 2.

[0016] Here, the vertical axis is the resistance force (tensile force), and the horizontal axis is the displacement (change in the length of the damper 2). And the symbol 20 is the resistance-displacement characteristic graph of the damper 2.

[0017] As shown in the figure, the damper 2 has two spring characteristics. In the extension direction, until an external force equivalent to the trigger resistance force Ft is generated, it has a high spring constant (primary spring constant) and hardly extends, acting like a rigid body (trigger function). And when an external force above the trigger resistance force Ft is generated, it has a spring constant lower than the primary spring constant (secondary spring constant), generates a resistance force (tensile force) while extending until it reaches the maximum resistance force Fmax, and absorbs the energy of the external force (attenuation function). After that, when the external force decreases, it contracts accordingly, and when the external force becomes zero, it restores to the original length (restoring function).

[0018] As the damper 2 having such a trigger function, damping function, and restoring function, the damper described in Japanese Patent No. 4432208 with the applicant as the patentee can be used.

[0019] This damper includes a cylinder main body, a piston disposed in the cylinder main body so as to partition the cylinder main body into two chambers and having an orifice communicating the two chambers, a large-diameter piston rod having one end connected to the piston and protruding outside the cylinder main body through one end of the cylinder main body, a small-diameter piston rod having one end connected to the piston and protruding outside the cylinder main body through the other end of the cylinder main body, and a pressurized fluid filled in the two chambers of the cylinder main body.

[0020] According to this damper, in the extension direction, unless an external force equal to or greater than the force (trigger resistance force Ft) based on the area difference between the large-diameter piston rod and the small-diameter piston rod and the pressure of the pressurized fluid is applied, it behaves like a rigid body (trigger function). When an external force equal to or greater than the trigger resistance force Ft is applied, the pressurized fluid passing through the orifice absorbs the external kinetic energy as quickly as possible to attenuate the movement of the structure (damping function). Further, as the external force decreases, it contracts to its original length by the force based on the area difference between the large-diameter piston rod and the small-diameter piston rod and the pressure of the pressurized fluid, that is, its own tensile force (restoring function).

[0021] The tension adjusting device 3 adjusts the tensile force (resistance force) of the corresponding damper 2. The tension adjusting device 3 is, for example, a turnbuckle disposed between the damper 2 and the pier 4 or the bridge girder 5, and adjusts the tensile force of the damper 2 by adjusting the external force in the extension direction applied to the damper 2. In the present embodiment, when the pier 4 and the bridge girder 5 are in the standard state (a state where there is no displacement in the relative positions of the pier 4 and the bridge girder 5 in either the vertical direction Z or the direction perpendicular to the bridge axis Y), adjustment is made so that an external force equivalent to the trigger resistance force Ft is applied to the damper 2 (so that the damper 2 generates a resistance force (tensile force) equivalent to the trigger resistance force Ft).

[0022] FIG. 3 is a diagram showing the state of the seismic isolation structure when an external force (lateral sway) in the direction perpendicular to the bridge axis Y is applied to the pier 4 due to an earthquake or the like.

[0023] In this case, since an external force equivalent to the trigger resistance force Ft is applied to the damper 2 by the tension adjusting device 3, the damper 2 immediately exhibits a damping function by operating with the secondary spring constant, generates a resistance force while extending, and absorbs the energy of the external force due to an earthquake or the like. Further, in the sliding bearing 1, the sliding member 11 slides on the sliding plate 10. As a result, the bridge girder 5 is supported in the vertical direction Z by the sliding bearing 1 and moves in the direction perpendicular to the bridge axis Y with respect to the pier 4. Thereafter, when the external force in the direction perpendicular to the bridge axis Y acting on the bridge girder 5 due to an earthquake or the like weakens, the damper 2 contracts due to its own tensile force, and when this external force becomes zero, it returns to its original length. Accordingly, the sliding member 11 of the sliding bearing 1 slides on the sliding plate 10, and the pier 4 and the bridge girder 5 return to the standard state.

[0024] FIG. 4 is a diagram showing the state of the seismic isolation structure when an external force (uplift force) in the vertical direction Z is applied to the bridge girder 5 due to an earthquake or the like.

[0025] In this case, since an external force equivalent to or greater than the trigger resistance force Ft is applied to the damper 2 by the tension adjusting device 3, the damper 2 immediately exhibits a damping function by operating with the secondary spring constant, generates a resistance force while extending, and absorbs the energy of the external force due to an earthquake or the like. On the other hand, in the sliding bearing 1, the sliding member 11 separates from the sliding plate 10 and the seismic isolation function cannot be exhibited. Thereafter, when the external force in the vertical direction Z acting on the bridge girder 5 due to an earthquake or the like weakens, the damper 2 contracts due to its own tensile force, and when this external force becomes zero, it returns to its original length. As a result, the pier 4 and the bridge girder 5 return to the standard state, the sliding member 11 comes into contact with the sliding plate 10, and the seismic isolation function of the sliding bearing 1 is restored.

[0026] The above describes one embodiment of the present invention.

[0027] According to this embodiment, when an external force (lateral sway) in the direction Y perpendicular to the bridge axis is applied to the pier 4, the sliding bearing 1 allows the relative movement of the pier 4 and the bridge girder 5 in the direction Y perpendicular to the bridge axis while supporting the bridge girder 5. Thereby, the seismic isolation function is exhibited. Further, the damper 2 generates a tensile force (resisting force) adjusted by the tension adjusting device 3 against this external force, attenuates this external force, and contracts until it returns to its original length as this external force decreases. Thereby, the bridge girder 5 and the pier 4 can be returned to the standard state. Further, when an external force (uplift force) in the vertical direction Z is applied to the bridge girder 5, the damper 2 generates a tensile force (resisting force) adjusted by the tension adjusting device 3 against this external force, attenuates this external force, and contracts until it reaches its original length as this external force decreases. Thereby, the bridge girder 5 and the pier 4 can be returned to the standard state, and the seismic isolation function of the sliding bearing 1 can be exhibited.

[0028] In this embodiment, a so-called damper with a tensile type restoring function is used as the damper 2, and a resisting force (tensile force) is generated only when the piston rod acts in the extending direction. In the compression direction, it does not act due to the presence of the sliding bearing 1. For this reason, it is not necessary to consider buckling, bending of the piston rod during compression, or leakage of internal fluid due to damage to the seal portion at the base of the piston rod. Therefore, countermeasures for this are not required, and the cost of the damper 2 can be reduced.

[0029] Note that the present invention is not limited to the above-described embodiment, and numerous modifications are possible within the scope of the gist thereof.

[0030] For example, in the above-described embodiment, the unit including the sliding bearing 1, the damper 2, and the tension adjusting device 3 is arranged in the direction Y perpendicular to the bridge axis between the pier 4 and the bridge girder 5, thereby attenuating the external force in the direction Y perpendicular to the bridge axis. However, the present invention is not limited to this. For example, as in the modification shown in FIG. 5, the unit including the sliding bearing 1, the damper 2, and the tension adjusting device 3 is arranged in the bridge axis direction X (the unit of the damper 2 and the tension adjusting device 3 is arranged on the front surface 40 side and the rear surface 41 side of the pier 4 with the sliding bearing 1 interposed therebetween), and by arranging it between the pier 4 and the bridge girder 5, the external force in the bridge axis direction X may be attenuated. Alternatively, as in the modification shown in FIG. 6, the sliding bearing 1 is arranged between the abutment 6 and the bridge girder 5, and the unit of the damper 2 and the tension adjusting device 3 is arranged between the front surface 60 side of the abutment 6 and the bridge girder 5, thereby attenuating the external force in the bridge axis direction X.

[0031] Also, in the above-described embodiment, the unit of the damper 2 and the tension adjusting device 3 is arranged between the bridge girder 5 and the pier 4 (the abutment 6 in the modified example shown in FIG. 6) in the vertical direction Z. However, the present invention is not limited to this. For example, as in the modified example shown in FIG. 7, the unit of the damper 2 and the tension adjusting device 3 may be arranged between the bridge girder 5 and the pier 4 or the abutment 6 in the direction perpendicular to the bridge axis Y. In the modified example shown in FIG. 7, fixing devices 8 formed of concrete blocks or the like are installed at the edge portions on both sides of the upper surface of the pier 4 or the abutment 6, and for each fixing device 8, between the side surface 80 of the fixing device 8 and the side surface 50 of the bridge girder 5 facing this fixing device 8, the unit of the damper 2 and the tension adjusting device 3 is arranged. In FIG. 7, reference numeral 7 is a displacement restraint portion that restrains a displacement of the sliding bearing 1 in the direction perpendicular to the bridge axis Y that is equal to or greater than a predetermined value. Even when the unit of the damper 2 and the tension adjusting device 3 is arranged between the bridge girder 5 and the pier 4 or the abutment 6 in the direction perpendicular to the bridge axis Y as in the modified example shown in FIG. 7, when an external force (uplift force) in the vertical direction Z is applied to the bridge girder 5, the damper 2 generates a tensile force (resistance force) adjusted by the tension adjusting device 3 against this external force, attenuates this external force, and shrinks until it returns to its original length as this external force decreases. Thereby, the bridge girder 5 and the pier 4 or the abutment 6 can be returned to the standard state, and the seismic isolation function of the sliding bearing 1 can be exhibited.

[0032] Also, in the above-described embodiment, as the sliding bearing 1, a rigid sliding bearing having a sliding plate 10 fixed to the upper surface of the pier 4 and a sliding material 11 fixed to the lower surface of the bridge girder 5 and sliding on the sliding plate 10 is used, but the present invention is not limited to this. The sliding bearing 1 may be an elastic sliding bearing having laminated rubber arranged between the bridge girder 5 and the sliding plate 10 instead of the sliding material 11. Alternatively, a laminated rubber bearing may be used instead of the sliding bearing.

[0033] In addition, in the above-described embodiment, a tension-type damper with a restoring function having two spring characteristics is used as the damper 2, but the present invention is not limited thereto. The damper 2 may be any damper as long as it has a restoring function that generates a tensile force against the force in the direction in which the pier 4 and the bridge girder 5 are separated, and may be an oil damper, a viscous damper, or a combination of these and a spring member.

[0034] In addition, in the above-described embodiment, the case where the seismic isolation structure is arranged between the pier 4 and the bridge girder 5 of the bridge has been described as an example. However, the present invention is not limited thereto. The seismic isolation structure may be arranged between one structure and the other structure. That is, the seismic isolation structure is arranged between one structure and the other structure, and while supporting the other structure, a sliding bearing that allows relative translational movement of the one structure and the other structure, and a damper that is arranged between the one structure and the other structure and has a restoring function of generating a tensile force against an external force in the direction in which the one structure and the other structure are separated, and a tension adjusting device that adjusts the tensile force of the damper.

Explanation of Reference Numerals

[0035] 1: Sliding bearing 2: Damper 3: Tension adjusting device 4: Pier 5: Bridge girder 6: Abutment 7: Displacement restraint portion 8: Fixing device 10: Sliding plate 11: Sliding material

Claims

1. A seismic isolation structure for suppressing the transmission of vibrations generated in one structure to another structure, a bearing disposed between the one structure and the other structure, supporting the other structure while allowing relative translational movement of the other structure with respect to the one structure; a damper having a restoring function, disposed between the one structure and the other structure, and generating a tensile force against an external force in a direction in which the one structure and the other structure move apart; and a tension adjusting device for adjusting the tensile force of the damper. The seismic isolation structure is characterized by the above.

2. The seismic isolation structure according to Claim 1, wherein the damper has two spring characteristics, and has a trigger function of having a predetermined primary spring constant and not extending until an external force equivalent to a trigger resistance force is generated in the extension direction, a damping function of having a secondary spring constant lower than the primary spring constant and generating a resistance force while extending when an external force equal to or greater than the trigger resistance force is generated, and a restoring function of shrinking until it returns to its original length as the external force decreases; and the tension adjusting device is adjusted so that a pretension equivalent to the trigger resistance force is applied to the damper. The seismic isolation structure is characterized by the above.

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