JPH1144338A - Small stroke base isolation device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To attain efficient base isolation while restraining relative displacement by setting vibrations of a base isolation object and a support structure body in the almost same phase by adding a rotational inertia system such as ball screws between the base isolation object and the support structure body. SOLUTION: A base isolation object 1 is supported on a support structure body 2 through a small friction bearing such as a rolling bearing or a sliding bearing. The base isolation object 1 and the support structure body 2 are connected to each other by springs 4 or the like, and an origin returning function is imparted. The support structure body 2 and the base isolation object 1 are connected to each other by a rotational inertia mechanism such as ball screws 6 and 9, and relative displacement of the support structure body 2 and the base isolation object 1 is converted into spiral rotary motion, and the base isolation object 1 is vibrated in the almost same phase as the support structure body 2 in setting the rotational inertia mechanism.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a small-stroke seismic isolator for seismic isolation of a floor or a building frame of a building.

[0002]

2. Description of the Related Art As a seismic isolation structure for reducing the vibration of a building during an earthquake, a seismic isolation device mainly using a laminated rubber bearing is conventionally used.

In the case of a relatively lightweight seismic isolation target such as a floor or a lightweight structure, a seismic isolation device in which a rolling bearing or a sliding bearing is combined with a damper or a coil spring as a home return mechanism has been put into practical use. I have.

[0004]

However, the conventional seismic isolation device has a large relative displacement between a seismic isolation target such as a floor or a building frame and a supporting structure, and requires a considerably large clearance in a building plan. In the case of an extremely large earthquake, it is conceivable that the seismic isolation target collides with the wall of the structure or the rising portion of the support structure.

Therefore, in order to limit such an excessive relative displacement, a damping device such as a damper is usually provided. However, when the damping device is provided (particularly when the damping coefficient is large), the effect of reducing the vibration in the high frequency range is reduced. As a result, an effective seismic isolation effect cannot be obtained.

The reason why the response displacement is large in the conventional seismic isolation device is that there is a phase difference between the vibration of the object to be isolated and the supporting structure on which it is installed.

If the seismic isolation target can be vibrated in the same phase as the support structure, a more effective seismic isolation effect can be obtained even with the same relative displacement.

However, no matter how much the parameters of the spring and the damper are adjusted, a system that vibrates in the same phase while maintaining the seismic isolation effect cannot be realized.

The present invention has been made to solve the above-mentioned problem in the conventional seismic isolation device, and by adding a rotary inertia system such as a ball screw between the seismic isolation target and the support structure. It is an object of the present invention to provide a small-stroke seismic isolation device capable of performing an effective seismic isolation while suppressing relative displacement by making the vibrations of the seismic isolation target and the support structure substantially in phase.

[0010]

According to a first aspect of the present invention, there is provided a small-stroke seismic isolation device which supports a seismic isolated object via a rolling bearing or a sliding bearing between the supporting structure and the supporting structure. And a seismic isolation device comprising a spring element that suppresses displacement of the seismic isolation target due to an earthquake input and provides a return-to-origin function between the seismic isolation target and the seismic isolation target. The seismic isolation object vibrates in almost the same phase as the support structure by connecting the relative displacement of the support structure and the seismic isolation target in a specific direction to a spiral inertial mechanism that converts the relative displacement in a specific direction into a spiral rotational motion. It is characterized by doing so.

The object to be seismically isolated here is an upper floor of a seismic isolated floor or an upper structure (building body) separated from a base of a seismic isolated structure. The support structure is a slab of a building in the case of a base-isolated floor, and a lower foundation slab in the case of a base-isolated structure.

A rolling bearing or a sliding bearing is a bearing mechanism having small friction, and as described above, there are some which are also used in the conventional seismic isolation device.

[0013] The spring element that provides the origin return function can be considered in the same manner as in the prior art. Usually, a damper is installed together with a spring acting in the horizontal direction. The spring element is not limited to a coil spring, rubber, or the like, but may be an element using electromagnetic force or an element using potential energy with a sliding surface as a curved surface. The damper may be an elastic-plastic damper, a viscous damper or the like, or a damper utilizing frictional force.

According to the invention of the present application, by further interposing a rotary inertia mechanism between such a support structure and the seismic isolation target, the seismic isolation target vibrates in substantially the same phase as the support structure. The reason why the vibration can be performed in substantially the same phase and the reason that the effective seismic isolation can be achieved with a small stroke will be described in detail later.

According to a second aspect of the present invention, in the small-stroke seismic isolator according to the first aspect, a spring element and a damper element acting in the specific direction are interposed between the rotary inertia mechanism and the object to be isolated. Thus, the rotational inertia force from the rotational inertia mechanism is transmitted to the seismic isolation target.

According to the configuration of the first aspect, as will be described in detail later, it is possible to reduce the external vibration force such as the seismic motion at a constant reduction rate almost independently of the frequency. However, on the other hand, even in the case of vibration in a high frequency range where a high response reduction rate can be obtained with the conventional seismic isolation device, only a reduction rate comparable to that in the low frequency range can be obtained.

That is, in the invention according to the first aspect, the rotary inertia mechanism works efficiently in the low frequency range where displacement is large, and in the high frequency range where displacement is small and acceleration is large, stroke reduction is small, and Seismic performance will be degraded.

On the other hand, if the force applied from the rotary inertia mechanism to the seismic isolation target is transmitted only in a low frequency range, more efficient seismic isolation can be performed.

According to the second aspect of the present invention, in order to realize such a function, a spring element and a damper element are further interposed between the rotary inertia mechanism and the object to be isolated.

In a third aspect of the present invention, in the small-stroke seismic isolation device according to the first or second aspect, the case where the rotary inertia mechanism is a ball screw connecting the support structure and the object to be isolated is limited.

As the rotary inertia mechanism required in the present invention, a ball screw which can replace horizontal movement with rotation in a state where friction is small is suitable, and a ball screw having an existing structure can be used. it can.

Note that, depending on the cross-sectional shape of the seismic isolation target,
It is also conceivable to perform seismic isolation in only one direction, in which case the axial direction of the rotary inertia mechanism consisting of a ball screw etc. should be matched in only one direction, but it is usually necessary to deal with seismic motion in all directions. In such a case, for example, the X and Y2 directions orthogonal to each other are set as specific directions, and a ball screw and an associated spring element as an origin return mechanism are used in the two directions.
In the case of the invention according to claim 2, a spring element, a damper element, and the like are further disposed between the rotary inertia mechanism and the seismic isolation target.

The principle of the provision of the rotary inertia mechanism in which the seismic isolation target and the supporting structure vibrate in substantially the same phase is as follows.

FIG. 1 shows a model diagram of a vibration system according to the first aspect of the present invention. However, here, the theoretical formula in only one direction of a seismic isolation device to which a ball element is added as a spring element, a damper element (a spring element connecting the support structure and the seismic isolation target, a damper element), and a rotary inertia mechanism will be described.

[0025] m = seismic isolation target amount of substance (kg) I = moment of inertia of the ball screw (kg · m ²⁾ r = pitch circle radius (m) L _e = lead angle of the pitch (m) φ = ball screw of the ball screw of the ball screw (Rad) _mr = Equivalent inertial mass of ball screw (kg) x = absolute displacement of seismic isolation target (m) y = absolute displacement of support structure (m) θ = rotation angle of ball screw (rad) x _r = immunity Relative displacement of the object to be supported relative to the supporting structure (m) k = spring coefficient of spring element (N / m) c = damping coefficient of damper element (N · s / m) F _i = ball screw is added to the seismic object Force (N) _Fo = Spring and damper apply force to seismic isolation target (N) M = Moment applied to ball screw (N · m) First, the following equation of motion holds for the seismic isolation target and ball screw .

M (d ² x / dt ² ) = F _o + F _i (1) I (d ² θ / dt ² ) = M (2) The equation of motion (1) of the seismic isolated object is unknown. Force F _o
And can be solved if F _i is known.

Firstly F _{o is, F o = - {k ·} x r + c (dx r / dt)} = k (y-x) + c {(dy / dt) - (dx / dt)} ... (3) Becomes

[0028] Then, F _i is a = ball screw rotation angle and the relative displacement relationship ^{d 2 θ / dt 2 (2π} / L e) · (d 2 x r / dt 2) ... (4), and F _i · relationship M = -F _i of the moment M applied to the ball screw (sinφ / cosφ) · r = -F i · (L e / 2π) ... (5) of and substituting the two equations (2) to the equation F _i = −m _r (d ² x _r / dt ² ) = m _r {(d ² y / dt ² ) − (d ² x / dt ² )} (6) Here, m _r = I · (2π / L _e ) ² .

F _o and F _i obtained by the equations (3) and (6) are
Substituting into equation (1), d ² x / dt ² = (1 / m) · [k (y−x) + c ｛(dy / dt) − (d x / dt)｝ + m _r ｛(d ² y / Dt ² ) − (d ² x / dt ² )｝] (7) When obtaining the transfer function of the x it from y by Laplace transformation, the X (s) / Y (s ) = (m r s 2 + cs + k) / {(m + m r) s 2 + cs + k) ... (8) . In the case of k = 0 and c = 0, X (s) / Y (s) = _mr / (m + _mr ) (9), and becomes a constant value regardless of the frequency.

From equation (8), if the values of k and c are reduced, the vibration transmissibility m _r / (m + m
_r ) shows that a system with almost no phase delay can be realized.

FIG. 2 is a graph relating to the vibration transmissibility of the system represented by the equation (8). The horizontal axis represents frequency (Hz), and the vertical axis represents phase difference (degree) and gain (dB).

From this figure, it can be seen that the frequency is 0.1 (period 10
It can be seen that the phase shift occurs near (seconds) and the gain increases, but the other portions have almost no phase shift and the gain is stable.

FIG. 3 is a diagram comparing the conventional seismic isolation device with the seismic isolation device according to claim 1 of the present application. FIG. 3A shows the relationship between the input displacement and the response displacement when the conventional seismic isolation device is installed. Indicates that
(b) shows the relationship between the input displacement and the response displacement when the small-stroke seismic isolation device according to claim 1 of the present application is installed.

In (b), the phases of the input displacement and the response displacement overlap, and the relative displacement between the support structure (installation foundation) and the seismic isolation target is the same as (a) and (b), but (b) It can be seen that the absolute value of the displacement amount becomes smaller. In other words, more effective damping is performed.

FIG. 6 similarly shows a model diagram of a vibration system according to the second aspect of the present invention. That is, in the invention according to claim 1, a spring element and a damper element for transmitting the rotational inertia force are further added between the rotary inertia mechanism (ball screw) and the seismic isolation target. The theoretical formula in the case is shown. In addition, the part which overlaps with the above description of the invention according to claim 1 is partially omitted.

M = Amount of substance to be isolated (kg) m _r = Equivalent inertial mass of ball screw (reaction plate is ignored)
(Kg) x ₁ = absolute displacement of the seismic isolation target (m) x ₂ = absolute displacement on the ball screw side (m) y = absolute displacement of the support structure (m) θ = rotation angle of the ball screw (rad) x _r = Relative displacement of the seismic isolation target with respect to the support structure (m) k ₁ = spring coefficient of a spring element as an origin return mechanism (N /
m) c ₁ = damping coefficient of damper element (N
S / m) k ₂ = spring coefficient (N / m) of a spring element as a rotary inertia force transmission mechanism c ₂ = damping coefficient (N · s / m) of a damper element as a rotary inertia force transmission mechanism F _i = The force (N) applied to the seismic isolation target by the rotary inertia force transmission mechanism (k ₂ , c ₂ ) _Fo = the home return mechanism (k ₁ , c ₁ ) The force applied to the seismic isolation target (N) The following equation of motion holds for the object and the ball screw.

M (d ² x ₁ / dt ² ) = F _o + F _i (1a) _mr {(d ² x ₂ / dt ² ) − (d ² y / dt ² )} = − F _i ( 2a) However, F _{o is, F o = k 1 (y} -x 1) + c 1 - the {(dy / dt) (dx 1 / dt)} ... (3a), F i is, F _i = k ₂ (X ₂ −x ₁ ) + c ₂ {(dx ₂ / dt) − (dx ₁ / dt)} (4a).

By substituting the equations (3a) and (4a) into the equation (1a) and performing Laplace transform, X ₁ ｛ms ² + (c ₁ + c ₂ ) s + k ₁ + k ₂ ｝ −X ₂ (c ₂ s + k ₂ ) −Y (c ₁ s + k ₁ ) = 0 (5a) Further, by substituting equation (4a) into equation (2a) and performing Laplace transform, X ₂ (m _rs ² + c ₂ s + k ₂ ) −X ₁ a _{(c 2 s + k 2)} -Ym r s 2 = 0 ... (6a).

From equations (5a) and (6a), X_TwoIf you delete, X₁｛Ms^Two+ (C₁+ C_Two) S + k₁+ K_Two− (C_Twos + k_Two)^Two/ (M _r s^Two+ C_Twos + k_Two)｝-Y ｛c₁s + k₁+ M_rs^Two(C_Twos + k_Two) / (M_rs^Two+ C_Twos + k_Two)｝ = 0 (7a).

From this, when a transfer function from Y to X ₁ is obtained, X ₁ / Y = {c ₁ s + k ₁ + m _rs ² (c ₂ s + k ₂ ) / (m _rs ² + c ₂ s + k ₂ )} / {Ms ² + (c ₁ + c ₂ ) s + k ₁ + k ₂ − (c ₂ s + k ₂ ) ² / (m _rs ² + c ₂ s + k ₂ )} (8a).

For the purpose of comparing the performance of the devices, the device 1 (seismic isolation device according to claim 2), the device 2 (conventional seismic isolation device), and the device 3 (according to claim 1) shown as a vibration model in FIG. With respect to three types of seismic isolation devices (seismic isolation devices), examples of the vibration transmissibility from the installation foundation, which is the support structure, to the seismic isolation target were obtained.

The numerical value for each parameter of the model is m
_{= 1.0, m r = 1.0,} k 1 = 2.0, k 2 = 8.
Calculated as 0, c ₁ = 1.5, c ₂ = 3.0.

FIG. 8 is a graph showing the obtained vibration transmissibility, with the horizontal axis representing the frequency (Hz) and the vertical axis representing the vibration transmissibility. In addition, as the vibration transmissibility in this figure, the upper graph represents the absolute displacement of the seismic isolated object with respect to the absolute displacement of the installed foundation, and the lower graph represents the relative displacement of the seismic isolated object with respect to the absolute displacement of the installed foundation. I have.

For performance comparison, consider four regions from region 1 to region 4 in the figure.

In the low frequency (long period) region 1,
The three devices show almost the same performance.

In the area 2, the stroke (relative displacement with respect to the installation foundation) of the device 1 according to claim 2 is the smallest, and the device 1 is the device corresponding to claim 1 with respect to the seismic isolation performance (absolute displacement). Although it is slightly inferior to 3, it is better as compared with the device 2 corresponding to the conventional seismic isolation device.

In the region 3, the seismic isolation performance of the device 1 is inferior to those of the devices 2 and 3, but a certain reduction rate is secured. The stroke is about the size between the device 2 and the device 3.

In the region 4, the seismic isolation performance is inferior to that of the device 2, but is very good as compared with the device 3.
Further, the stroke is as large as that of the device 3. From the above,
The seismic isolation device according to claim 2 has a small stroke in a low frequency region, and has a certain level of seismic isolation performance, and has a performance close to that of the seismic isolation device according to claim 1, and high Although the stroke is hardly reduced at the frequency, the seismic isolation performance is maintained at a high level, indicating that the seismic isolation device has performance close to that of the conventional seismic isolation device.

[0049]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 4 conceptually shows a small-stroke seismic isolation device according to claim 1, wherein (a) is a plan view and (b) is an elevation view.

In this example, the seismic isolation target 1 such as a building superstructure is shown.
Is a rolling bearing 3 (ball bearing), which is supported on a supporting structure 2 such as a foundation slab. In addition, seismic isolation target 1
Is connected to the support structure 2 by a horizontal spring 4 so that horizontal vibration is suppressed. These structures are the same as those of the conventional seismic isolation device using the rolling bearing 3, and although not shown, a damper is also used as necessary.

In the figure, reference numeral 5 denotes a rotary inertia mechanism comprising ball screws in the X direction and the Y direction which are two horizontal directions orthogonal to each other, and the support structure 2 and the seismic isolation target 1 are connected via the rotary inertia mechanism 5. Then, the relative displacement of the support structure 2 and the seismic isolation target 1 in the X direction and the Y direction is converted into rotation about the axis of a ball screw constituting the rotary inertia mechanism 5, and the seismic isolation target 1 is converted to the support structure. By vibrating in substantially the same phase as 2, a small stroke is realized (see FIG. 3 described above).

FIGS. 5A and 5B show details of the rotary inertia mechanism 5, wherein FIG. 5A is a plan view and FIG. 5B is an elevation view.

In this example, two ball screws 6 are arranged in the X direction of the support structure 2 and supported by bearings 7 fixed to the support structure 2. Each of these ball screws 6 is provided with a stage 8 to be screwed to the screw.
A bearing 10 for supporting the ball screw 9 in the direction is provided.

Further, the stage 11 is screwed into the ball screw 9 in the Y direction, and the seismic isolation target 1 is fixed to the stage 11. The linear guide rails 12 and 13 are provided on the stage 8 moving in the X direction and the stage 11 moving in the Y direction, respectively.
Are provided, and can be moved along the ball screws 6 and 9.

When the seismic isolation target 1 is relatively displaced with respect to the support structure 2, the stages 8, 11 move and the ball screws 6, 9 rotate, so that rotational inertia is obtained. By properly setting the specifications of the ball screw in this case based on the above-described theoretical formula, the seismic isolation target 1 and the support structure 2
Vibrates in almost the same phase, and compared with the conventional seismic isolation device,
With the same relative displacement, a larger seismic isolation effect can be obtained, and conversely, the relative displacement that gives the same seismic isolation effect becomes smaller, and the stroke can be reduced.

FIG. 9 conceptually shows a small-stroke seismic isolation device according to claim 2, wherein (a) is a plan view and (b) is an elevation view.

The object 1 to be isolated is supported on a support structure 2 such as a foundation slab by a rolling bearing 3.
Are connected by a horizontal spring 4 and a damper 14, which is the same as the conventional seismic isolation device or the seismic isolation device according to claim 1.

In this example, a rotary inertia mechanism 5 composed of ball screws 6 and 9 in the X direction and the Y direction, which are two horizontal directions orthogonal to each other, is separately provided.
A spring 17 and a damper 18 are provided between the base 1 and the seismic isolation target 1 via reaction plates 15 and 16.

In the illustrated example, the seismic isolation target 1
The reaction plate 16 on the side moves along the rail 19.

By interposing the spring 17 and the damper 18, the ball screws 6, 9 serving as a rotary inertia mechanism are provided.
Therefore, the force applied to the seismic isolation target 1 becomes difficult to be transmitted in the high frequency range, and more efficient seismic isolation can be performed.

[0061]

In the seismic isolation device according to claim 1 of the present application, since the vibration of the support structure and the vibration of the seismic isolation target can be substantially in phase,
Compared to the conventional seismic isolation device, a larger seismic isolation effect can be obtained with the same relative displacement amount, and conversely, the stroke for obtaining the same seismic isolation effect can be reduced. In the seismic isolation device according to claim 2 of the present application, the disadvantages of the seismic isolation device of claim 1 in which the stroke is small and the seismic isolation performance is degraded in a high frequency range where displacement is small and acceleration is large are eliminated, and high frequency More efficient seismic isolation is possible for the area.

[Brief description of the drawings]

FIG. 1 is a model diagram of a vibration system using a small-stroke seismic isolation device according to claim 1.

FIG. 2 is a graph relating to the vibration transmissibility of the system represented by equation (8).

FIG. 3 is a graph comparing the performance of a conventional seismic isolation device and the seismic isolation device according to claim 1, wherein (a) is a graph showing a relationship between input and response when the conventional seismic isolation device is installed; (b) is a graph showing the relationship between input displacement and response displacement when the small-stroke seismic isolation device according to claim 1 is installed.

FIG. 4 is a conceptual diagram of the small-stroke seismic isolation device according to claim 1, wherein (a) is a plan view and (b) is an elevation view.

FIG. 5 is a schematic view of a ball screw portion as a rotary inertia mechanism in the small-stroke seismic isolation device according to claim 1, (a) is a plan view, and (b) is an elevation view.

FIG. 6 is a model diagram of a vibration system using the small-stroke seismic isolation device according to claim 2;

FIG. 7 is a diagram in which respective vibration system models are arranged for comparison of the performance of a conventional seismic isolation device and the seismic isolation device according to claims 1 and 2.

8 is a graph comparing the vibration transmissibility of the absolute response (upper side) and the vibration transmissibility of the relative response (lower side) with respect to the model of each vibration system of FIG. 7;

FIG. 9 is a conceptual diagram of a small-stroke seismic isolation device according to claim 2, wherein (a) is a plan view and (b) is an elevation view.

[Explanation of symbols]

1 ... seismic isolation target, 2 ... support structure, 3 ... rolling bearing, 4
... Spring, 5 ... Rotary inertia mechanism, 6 ... Ball screw (X direction), 7 ... Bearing (X direction), 8 ... Stage (X direction), 9 ... Ball screw (Y direction), 10 ... Bearing (Y direction), 11 ... Stage (Y direction), 12 ... Linear guide (X direction), 13 ... Linear guide (Y direction), 1
4 damper, 15 reaction plate (ball screw side), 16 reaction plate (isolation target side), 17 spring, 18 damper, 1
9 ... Rail

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Norihide Oga 1-2-7 Moto-Akasaka, Minato-ku, Tokyo Inside Kashima Construction Co., Ltd. (72) Isao Nishimura 1-2-2 Moto-Akasaka, Minato-ku, Tokyo No. 7 Inside Kashima Corporation (72) Inventor Katsuyasu Sasaki 1-2-7 Moto-Akasaka, Minato-ku, Tokyo Kashima Corporation (72) Inventor Yoshitaka Suzuki 1-2-2 Moto-Akasaka, Minato-ku, Tokyo 7 Kashima Construction Co., Ltd.

Claims (3)

[Claims] A seismic isolation target is supported between a supporting structure and a rolling bearing or a sliding bearing, and the seismic isolation target is subjected to an earthquake input between the supporting structure and the seismic isolation target. In a seismic isolation device provided with a spring element that suppresses displacement and provides a return-to-origin function, the support structure and the seismic isolation target are moved relative to each other in a specific direction between the support structure and the seismic isolation target in the specific direction. A small-stroke seismic isolation device, characterized in that the object is vibrated in substantially the same phase as the supporting structure, by being connected by a rotary inertia mechanism that converts the rotational motion into a spiral rotational motion having an axial direction. 2. A rotary inertia force from the rotary inertia mechanism is transmitted to the seismic isolation target by interposing a spring element and a damper element acting in the specific direction between the rotary inertia mechanism and the seismic isolation target. 2. The small-stroke seismic isolation device according to claim 1, wherein: 3. The rotary inertia mechanism is a ball screw for connecting a support structure and a seismic isolation target.
The described small stroke seismic isolation device.