JP5850231B2 - Slip isolation mechanism - Google Patents

Description

  The present invention relates to a seismic isolation structure for buildings, precision equipment, and the like, and more particularly to a sliding seismic isolation mechanism for slidably supporting an upper structure to be seismically isolated on a lower structure that supports the upper structure. .

  As is well known, laminated rubber and sliding bearings are generally used in base-isolated structures as bearings that support the weight of the base-isolated object, but laminated rubber has excellent seismic isolation performance, but is expensive. There is a problem that it is difficult to deal with excessive deformation, and the sliding bearing is low-cost and easy to deal with excessive deformation, but residual displacement becomes a problem. Moreover, although both may be used together and the displacement and residual displacement of a base isolation layer may be suppressed, in that case, the difference of both creep and axial expansion-contraction amount becomes a problem.

  For example, a so-called sliding pendulum type seismic isolation system (FPS: Friction Pendulum System) as shown in FIG. In this structure, the upper and lower sliding surfaces 3 and 4 fixed to the upper and lower structures 1 and 2 are both spherical surfaces, and a sliding member 5 serving as a mover is interposed between them. The period with the spherical radius of the sliding surface as the pendulum length without depending on the force (support load) is the natural period of the seismic isolation layer, and since the sliding surface is spherical, it has a function to restore to the original position. is there.

  However, in this sliding pendulum type seismic isolation mechanism, since the sliding surface is spherical and there is almost no gradient near the original position, the restoring force is small, and therefore it is inevitable that some residual displacement occurs. Therefore, although it can be applied to a small building with a relatively small axial force, it is necessary to increase the curvature of the spherical surface as a sliding surface even in that case, and to make it a spherical surface that is greatly curved in the vertical direction. There is a problem that the natural period is shortened and the outer dimension, particularly the required dimension in the vertical direction is increased.

  Patent Document 1 proposes a seismic isolation sliding bearing as shown in FIGS. This is because the sliding surface 6 is formed as a conical surface instead of a spherical surface, and the conical surface is supported by the top of the support body 7, thereby ensuring a predetermined restoring force even in the vicinity of the original position where the displacement is small, and remaining after the earthquake. The displacement can be suppressed.

  Further, for example, as shown in Patent Document 2, a device is proposed in which a restoring spring for restoring the sliding bearing to its original position is provided. In that case, use a rolling mechanism such as a linear guide or a bearing as a sliding bearing and make the friction coefficient sufficiently small, such as μ <0.01, and apply a large preload (initial tension) higher than the frictional resistance to the restoring spring. By giving it as a restoring force, it is possible to completely eliminate the residual displacement.

JP-A-10-73145 Japanese Patent Publication No. 7-62409

However, as shown in Patent Document 1, in the base-isolation sliding bearing in which the sliding surface 6 is a conical surface, as shown in FIG. 15, between the top of the bearing body 7 and the sliding surface 6 in the vicinity of the original position. Although a sufficient contact area (annular range shown by hatching) can be secured, the circumferential curvature of the conical surface changes inversely with the radius, so the circumferential contact increases as the displacement increases. It is inevitable that the length is reduced. Therefore, at the position where the support body 7 is displaced to the outermost peripheral portion of the sliding surface 6, a sufficient contact area cannot be secured as shown in FIG.
Therefore, this seismic isolation sliding bearing is difficult to apply to large-scale buildings where the axial force is large. In any case, the sliding surface 6 and the supporting body 7 are sufficiently robust to ensure load bearing performance. Inevitably, it must be increased in size and cost.

  Further, as shown in Patent Document 2, in the case where the restoring force is obtained by the restoring spring, it is inevitable that the seismic isolation performance is lowered due to the shortening of the period due to the spring stiffness of the restoring spring. In particular, when the restoring spring is given a large restoring force that is greater than the frictional resistance force to completely eliminate the residual displacement, the resistance force at the start of sliding greatly increases due to the spring stiffness of the restoring spring. This is the same as increasing the frictional resistance (and hence the coefficient of friction), and inevitably the original seismic isolation performance is greatly impaired.

As described above, the conventional sliding bearings and sliding seismic isolation mechanisms have their merits and demerits, and it is the actual situation that a sufficiently effective and appropriate one has not been put into practical use.
In view of the above circumstances, an object of the present invention is to provide an effective and appropriate sliding seismic isolation mechanism that is simple in configuration and can be manufactured at low cost, and that can sufficiently suppress residual displacement.

The present invention is a sliding seismic isolation mechanism for slidably supporting an upper structure to be seismically isolated in each horizontal direction with respect to a lower structure, an upper guide member fixed to the bottom of the upper structure, A lower guide member fixed to an upper portion of the lower structure, and a slider interposed between the upper guide member and the lower guide member, the slider being in contact with the upper guide member And is slidably held only in one horizontal direction and slidably held only in another horizontal direction perpendicular to the horizontal one direction with respect to the lower guide member, and the slider and the upper part The sliding surface with the guide member is an upper inclined surface that slowly inclines into a Λ shape along one horizontal direction, and the sliding surface between the slider and the lower guide member is in the other horizontal direction. It is a lower inclined surface which is slowly inclined V-shaped along the Inclination angle θ with respect to the horizontal plane of the sliding surface, characterized in that it is set so as to satisfy the relationship tanθ = (0.1~0.4) μ relative sliding friction coefficient of the dynamic surface mu .

In the present invention, it is preferable to set the pre-Symbol friction coefficient mu in the range of mu = 0.05 to 0.2. Alternatively, it is also preferable to set the tilt angle θ in a range where tan θ = 0.01 to 0.04 after setting the friction coefficient μ in a range of μ = 0.05 to 0.2.

  According to the present invention, the upper and lower sliding surfaces for sliding the slider in the two horizontal directions with respect to the upper guide member and the lower guide member are made to be inclined surfaces inclined with respect to the horizontal plane, thereby automatically restoring. Force can be obtained and residual displacement can be suppressed.

In particular, by setting the inclination angle θ of the sliding surface with respect to the horizontal plane to be related to the friction coefficient μ of the sliding surface and satisfying the relationship of tan θ = (0.1 to 0.4) μ, the sliding surface is slightly it is possible to greatly reduce minimizing One One residual displacement increases in acceleration by providing a small restoring force is inclined to.

It is a schematic block diagram which shows the assembly state of the sliding seismic isolation mechanism which is embodiment of this invention. They are a plan view and a cross-sectional view. It is a figure which shows the behavior at the time of an earthquake. It is a figure which shows the analysis model equivalent to the sliding seismic isolation mechanism of this invention. It is a figure which shows an analysis result. It is a figure which shows an analysis result. It is a figure which shows an analysis result. It is a figure which shows an analysis result. It is a figure which shows an analysis result. It is a figure which shows an analysis result. It is a figure which shows an analysis result. It is a figure which shows an analysis result. It is a figure which shows an analysis result. It is a figure which shows an example of the conventional sliding pendulum type seismic isolation mechanism. It is a figure which shows an example of the conventional seismic isolation sliding bearing. It is a figure which shows the behavior at the time of an earthquake (displaced state).

An embodiment of the sliding seismic isolation mechanism of the present invention will be described with reference to FIGS.
The sliding seismic isolation mechanism of this embodiment is for supporting the upper structure 11 which is a seismic isolation object slidably in horizontal directions with respect to the lower structure 12 which is the supporting structure. An upper guide member 13 fixed to the bottom of the body 11, a lower guide member 14 fixed to the upper portion of the lower structure 12, and a slider interposed between the upper guide member 13 and the lower guide member 14 15, and the slider 15 is slidably held only in one horizontal direction (shown as XX direction in the drawing) with respect to the upper guide member 13, and the direction with respect to the lower guide member 14 is Is mainly configured to be slidably held only in other horizontal directions orthogonal to each other (shown as Y-Y directions in the figure).

  Specifically, as shown in FIG. 1 (b), the upper guide member 13 and the lower guide member 14 are members having the same shape and the same size in the shape of a horizontally long block having a rectangular cross section, and the length direction. Are opposed to each other in a state where they are orthogonal to each other and spaced apart in the vertical direction, and in this state, as shown in FIGS. 2B and 2C, the bottom of the upper structure 11 and the upper part of the lower structure 12 Are fixed respectively.

On the opposing surface side of the upper guide member 13 and the lower guide member 14 (that is, the lower surface side of the upper guide member 13 and the upper surface side of the upper guide member 14), grooves along the respective length directions are formed, The depths of the grooves gradually decrease from the central portion toward both sides, and therefore the bottom surfaces of the grooves are inclined surfaces that are inclined in a gentle V shape.
The upper guide member 13 is fixed to the bottom of the upper structure 11 in the direction along the XX direction with the groove facing downward, so that the bottom surface of the groove formed in the upper guide member 13 is X. A downwardly inclined upper inclined surface 16 that slowly inclines in the Λ shape along the −X direction.
On the other hand, the lower guide member 14 is fixed to the upper portion of the lower structure 12 in the direction along the Y-Y direction with the groove facing upward, so that the bottom surface of the groove formed in the lower guide member 14 is Y The upper lower inclined surface 17 is gently inclined in a V shape along the −Y direction.
As will be described later, the inclination angle θ of the upper inclined surface 16 and the lower inclined surface 17 is sufficiently small, but the inclination angle θ is greatly exaggerated in the drawing.

The slider 15 is a square-shaped member that can be simultaneously disposed in the grooves of both the upper guide member 13 and the lower guide member 14, and the upper surface thereof corresponds to the upper inclined surface 16 as shown in FIG. An upward inclined surface inclined to a slow Λ shape is formed, and a lower inclined surface corresponding to the lower inclined surface 17 is inclined downward to a gentle V shape. As shown in FIG. 1 (a), such a slider 15 is integrated by superimposing one of two members having the same shape and the same dimensions while inverting one side and changing the direction by 90 °. Can be manufactured easily.
The slider 15 is held in both grooves with the upper and lower inclined surfaces in close contact with the upper inclined surface 16 and the lower inclined surface 17, respectively. It is slidable only in the direction, and can be slid only in the YY direction with respect to the lower guide member 14, and displacement and sliding in other directions are restricted.
Therefore, when an arbitrary horizontal displacement occurs between the upper structure 11 and the lower structure 12, the slider 15 is displaced relative to the upper inclined surface 16 in the XX direction. However, relative displacement in the Y-Y direction with respect to the lower inclined surface 17 is performed, so that the displacement follows the relative displacement in each horizontal direction (omnidirectional) generated between the upper structure 11 and the lower structure 12. It is what you get.

In the sliding seismic isolation mechanism of the present embodiment, the friction coefficient of each sliding surface (that is, the friction coefficient between the upper inclined surface 16 and the upper surface of the slider 15, and the lower inclined surface 17 and the lower surface of the slider 15). The friction coefficient between them and the inclination angle of the sliding surface with respect to the horizontal plane is θ, the friction coefficient μ and the inclination angle θ are expressed as tanθ = (0.1 to 0.4) μ It is preferable to set so as to satisfy the above conditions, whereby a restoring force corresponding to the friction coefficient μ and the inclination angle θ is naturally obtained, and an excellent restoring characteristic is provided.
In particular, the friction coefficient μ is preferably about μ = 0.1, which is equivalent to that of a general sliding bearing. In this case, when tanθ = (0.1 to 0.4) μ as described above, tanθ = Since it is 0.01 to 0.04, for example, it is preferable to set tan θ = 0.02 (that is, a gradient angle of 1/50, θ≈1.1 °).
With such a slight inclination angle θ, even if the horizontal displacement of the seismic isolation layer is 500 mm, the vertical displacement is only about 10 mm. Therefore, the required vertical dimension of the entire sliding seismic isolation mechanism is sufficient. The vertical seismic isolation clearance to be secured between the upper structure 11 and the lower structure 12 can be small.

The behavior and effects of the slip isolation system of this embodiment during an earthquake will be described in detail below.
(1) As schematically shown in FIG. 3, the weight of the upper structure 11 (that is, the axial force acting on the sliding seismic isolation mechanism) is set to W, and the upper guide member 13 is applied to the lower guide member 14. Assuming that the restoring force when displaced in the horizontal direction is F, the restoring force F is F = Wtanθ. Therefore, when tanθ = (0.1 to 0.4) μ as described above, F = Wtanθ = (0.1 to 0.4 ) μW, and when the friction coefficient μ = 0.1, F = (0.01 to 0.04) W.

This is structurally equivalent to the case where a restoring spring K is provided between the upper structure 11 and the lower structure 12 and a pre-tension force F is applied thereto as in the model shown in FIG. A constant restoring force F acts regardless of the displacement of the seismic layer.
In this case, when tan θ ≧ μ is set, a complete restoring force capable of completely removing the residual displacement can be obtained (in the model in which the restoring spring K shown in FIG. 4 is installed, the restoring force F is set to F ≧ μW by a constant load spring. However, by setting the restoring force F to F = (0.1 to 0.4) μW with tanθ = (0.1 to 0.4) μ as described above, that is, the restoring force F is completely restored to F = μW. If it is suppressed to about 10 to 40%, the residual displacement can be made substantially zero even by performing incomplete restoration, and the acceleration can be obtained as in the case of obtaining a complete restoring force by the restoring spring K. The original seismic isolation mechanism will not be damaged by a large increase (this will be described later).

(2) The sliding surfaces of the slider 15 and the upper guide member 13 and the lower guide member 14 are inclined planes. Therefore, no matter how much they are displaced during an earthquake, the contact area is about half the plane of the slider 15. Is always secured. For this reason, the contact area does not decrease according to the displacement as in the case of the base-isolation sliding bearing of Patent Document 1 in which the sliding surface is a conical surface, and a large axial force can be dealt with without any problem.
For example, if the reference surface pressure is 20MPa (20N / mm ² ), when the planar shape of the slider 15 is 800mm x 800mm square, the contact area at the time of horizontal displacement is 0.32m ² and its own weight (long-term axial force) W = 6.4MN = 640tonf, and a large load resistance can be easily obtained in the same way as conventional seismic isolation sliding bearings.
Further, since the sliding surface may be formed as a mere smooth flat surface that is slightly inclined, the sliding surface is formed like the sliding pendulum type seismic isolation mechanism shown in FIG. 14 or the seismic isolation sliding bearing shown in FIG. Compared to a highly accurate spherical surface or conical surface, it can be manufactured much more simply, and the cost can be reduced sufficiently.

(3) If the planar shape of the slider 15 is a square, no relative rotation (twist) around the vertical direction occurs between the upper guide member 13 and the lower guide member 14. Therefore, according to the sliding seismic isolation mechanism of this embodiment, the seismic isolation layer is not twisted (rotational displacement in the horizontal plane).

(4) In the sliding seismic isolation mechanism according to the present embodiment, when F = (0.1 to 0.4) μW and μ = 0.1 as described above, the horizontal load F ₀ when the sliding starts to occur is the inclination angle θ. Since it is small, when cos θ = 1, the following equation is obtained.
F ₀ = μW + F = (1.1 to 1.4) μW = (0.11 to 0.14) W
Therefore, the response acceleration generated in the seismic isolation structure is peaked at 110 to 140 gal. On the other hand, in the conventional general seismic isolation structure made of laminated rubber or damper, the acceleration cannot reach its peak, and the acceleration at the time of excessive input can be made smaller in the case of the sliding seismic isolation mechanism of this embodiment. In addition, when the conventional sliding pendulum type seismic isolation mechanism (FPS) and laminated rubber shown in FIG. 14 are used for seismic isolation bearings, the natural period of the seismic isolation layer exists and excitation is input at that period. In some cases, there is a characteristic that the response becomes large due to resonance, but the slip-isolation mechanism of this embodiment does not resonate because there is no natural period.

(5) The sliding seismic isolation mechanism of this embodiment has a so-called “trigger characteristic” that horizontal displacement does not occur even when the horizontal force of F ₀ or less is applied. For this reason, small disturbances such as wind and traffic vibrations do not cause vibrations and hardly cause vibration disturbances.

(6) Since the sliding seismic isolation mechanism of this embodiment uses frictional resistance for damping, a damper such as an oil damper or a lead damper is unnecessary, and a low-cost seismic isolation structure can be realized.

Hereinafter, the superiority of the present invention is demonstrated by time history response analysis with respect to a specific seismic wave.
In this analysis, for the sake of convenience, as a model that is structurally equivalent to the sliding seismic isolation mechanism of the present invention, an analysis model (as shown in FIG. 1 mass point model).
The analysis conditions are as follows: the mass of the seismic isolation object is m ₁ = 1000 tons, its own weight is W = m ₁ g (g is gravitational acceleration), a constant load spring (spring stiffness kc) is used as the restoring spring K, and the damping element C (damping Constant c ₁ : a degree of attenuation of 0.1% at a period of 4 seconds), and it is assumed that the frictional force f ₁ acts in the opposite direction to the movement of the mass m ₁ .
The analysis case is
Case 1: Restoring force F = 0 (no restoration: equivalent to the case of tanθ = 0 in the present invention)
Case 2: Restoring force F = 1 μW (complete restoration: equivalent to tanθ = μ in the present invention)
Case 3: Restoring force F = 0.1 μW (Incomplete restoration: equivalent to tanθ = 0.1 μ in the present invention)
3 cases are assumed.

The seismic wave used for analysis is
・ BCJ Level2 (Level 2)
・ El Centro 50cm / s (Level 2)
・ Taft 50cm / s (Level 2)
・ Hachinohe 50cm / s (Level 2)
・ JMA Kobe (Haranami)
5 waves.

  As an example of the analysis result, response waveforms in each case in the case of BCJ Level 2 are shown in FIGS. Each figure shows the displacement, speed, and acceleration of the seismic isolation object from the top, and the bottom shows seismic motion acceleration. (The values in the broken lines and parentheses in the top row of FIGS. 6 and 7 indicate the case 1).

From this result, in case 1 where the restoring force F = 0 (tan θ = 0), the residual displacement is about 23 cm, and naturally in case 2 where the restoring force F = 1 μW (tan θ = μ) for complete restoration, the residual displacement However, in case 3, the residual displacement is only 1.5cm, although the restoring force F = 0.1μW (tanθ = 0.1μ) and only a slight restoring force is applied. It can be seen that the displacement can be reduced to such an extent that the displacement does not become a problem.
In addition, the acceleration of case ² is about 198.38 cm / s ² compared to 102.05 cm / s ² in case 1, compared to 110.35 cm / s ² and case 1 in case 3. It can be seen that it only increases to about 1.1 times.
Therefore, when the friction coefficient μ is set to μ = 0.1 in case 3 where tanθ = 0.1μ, for example, a slight inclination of tanθ = 0.01 (gradient angle 1/100, θ≈0.57 °) is applied to restore. An excellent restoring characteristic can be obtained without providing a spring, and the acceleration is not greatly increased.

Next, FIG. 8 shows the relationship between the magnitude of the restoring force F (inclination angle θ) and the effect of reducing residual displacement and acceleration in the case of BCJ Level2.
In each figure of FIG. 8, the horizontal axis is the restoring force ratio (F / μW = tan θ / μ). When this restoring force ratio is 0, it corresponds to case 1 and when the restoring force ratio is 1, it corresponds to case 2. The case where the restoring force ratio is 0.1 corresponds to case 3.
In each figure, the upper left row shows the residual displacement (absolute value), and the lower left row shows the residual displacement reduction rate (value obtained by normalizing the residual displacement when there is a restoring force with the reduction rate from the residual displacement when there is no restoring force). Indicates. The upper right column shows acceleration (absolute value), and the lower right column shows the acceleration increase rate (acceleration magnification when there is a restoring force relative to the acceleration when there is no restoring force).

Furthermore, the analysis result about another seismic wave is shown in FIGS.
Fig. 9 shows the response displacement for each seismic wave. The results for case 3 (F = 0.1 µW, tan θ = 0.1 µ) are shown by solid lines, and the results for case 1 (F = 0, tan θ = 0) are shown in broken lines and parentheses. This is indicated by the value of. In case 2 (F = 1 μW, tanθ = μ), it has been confirmed that the residual displacement is zero for all seismic waves.
10 to 13 show the relationship between the magnitude of the restoring force F (inclination angle θ) for each seismic wave and the effect of reducing the residual displacement and acceleration.
From these results, it is clear that almost the same results as in BCJ Level 2 can be obtained for each seismic wave. However, in the case where the seismic wave is Hachinohe, the residual displacement is 1.2 cm with the restoring force F = 0.1 μW, and the reduction force F = 0.2 μW is not obtained so much as compared with 1.9 cm in case 1. Then, it has been confirmed that the residual displacement is greatly improved to 0.2 cm.

From the above analysis results, the following can be understood with respect to the inclination angle θ and the restoration characteristics.
By setting the inclination angle θ so that the restoring force ratio F / μW = tan θ / μ is in the range of 0.1 to 0.4, the restoring force F is given by about 0.1 to 0.4 times the starting load F = μW. Residual displacement can be greatly reduced to 10% or less compared to the case of no application (no tilt angle).
Moreover, the increase in acceleration at that time is proportional to the normalized restoring force ratio F / μW = tan θ / μ, and if the restoring force ratio F / μW = tan θ / μ = 0.2, the restoring force The acceleration is only 20% higher than when F is not given (when there is no tilt angle).
From the above, the residual displacement reduction rate is not proportional to the restoring force ratio, but a large reduction rate can be exhibited from a region where the restoring force ratio is small, and the restoring force is about F = (0.1 to 0.4) μW, that is, By setting tanθ = (0.1 to 0.4) μ, it is possible to sufficiently reduce the residual displacement.
Moreover, as for acceleration, when a complete restoring force is applied (when tan θ = μ and F = μW), it is twice as much as when a restoring force is not applied (when tan θ = 0 and F = 0). However, when tan θ = (0.1 to 0.4) μ and F = (0.1 to 0.4) μW are suppressed as described above, the acceleration only increases to about 1.1 to 1.4 times.
In other words, the sliding seismic isolation mechanism of the present invention has an excellent seismic isolation performance that can significantly reduce the residual displacement while suppressing the increase in acceleration as much as possible by giving a small restoring force by slightly inclining the sliding surface. It is obtained.

In the range of the restoring force ratio F / μW = tan θ / μ <0.1, the residual displacement is not sufficiently reduced (the effect of reducing the residual displacement cannot be sufficiently obtained), which is not effective. Also, in the range of restoring force ratio F / μW = tanθ / μ> 0.4, the acceleration increases proportionally, so that not only the seismic isolation performance is greatly reduced, but also the residual displacement reduction effect reaches its peak, which is useless and effective. is not.
From the above, in the present invention, the restoring force ratio tanθ / μ should be set in the range of 0.1 to 0.4, that is, tanθ = (0.1 to 0.4) μ, which is the most rational and effective. It is.
On the other hand, the friction coefficient μ is preferably in a range of μ = 0.05 to 0.2, which is a general value for a sliding bearing, and in particular, μ = 0.1 is optimal. Thus, it is preferable that tan θ is in the range of 0.01 to 0.04, that is, the gradient angle is 1/100 to 1/25, and θ≈0.57 ° to 2.3 °.

DESCRIPTION OF SYMBOLS 11 Upper structure 12 Lower structure 13 Upper guide member 14 Lower guide member 15 Slider 16 Upper inclined surface (sliding surface)
17 Lower inclined surface (sliding surface)

Claims (3)

A sliding seismic isolation mechanism for slidably supporting an upper structure subject to seismic isolation with respect to a lower structure in each horizontal direction,
An upper guide member fixed to the bottom of the upper structure, a lower guide member fixed to the upper portion of the lower structure, and a slider interposed between the upper guide member and the lower guide member Become
The slider is slidably held only in one horizontal direction with respect to the upper guide member, and is slidable only in another horizontal direction perpendicular to the one horizontal direction with respect to the lower guide member. Retained,
The sliding surface of the slider and the upper guide member is an upper inclined surface that gently slopes in a Λ shape along the horizontal direction, and the slider and the lower guide member The sliding surface is a lower inclined surface that gently slopes in a V shape along the other horizontal direction ,
The inclination angle θ of the sliding surface with respect to the horizontal plane is relative to the friction coefficient μ of the sliding surface.
A sliding seismic isolation mechanism characterized by being set to satisfy the relationship of tan θ = (0.1 to 0.4) μ . The sliding seismic isolation mechanism according to claim 1 ,
A sliding seismic isolation mechanism characterized in that the friction coefficient μ is set in a range of μ = 0.05 to 0.2. The sliding seismic isolation mechanism according to claim 1 ,
The friction coefficient μ is set in a range of μ = 0.05 to 0.2,
In addition, the sliding seismic isolation mechanism is characterized in that the inclination angle θ is set in a range where tan θ = 0.01 to 0.04.

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