JPH0756190B2 - Vibration suppression device for structures - Google Patents

Description

TECHNICAL FIELD The present invention relates to a vibration suppression device for a structure that suppresses vibration caused in a structure by an earthquake, wind, or the like.

"Conventional technology and its problems" Due to factors such as the development of high-strength materials, the progress of machining technology, and the development of structural analysis technology using computers, recent buildings have become larger, more diverse in form, and lighter in weight. With the progress of, the structure has become more flexible. And in such a lightweight and flexible building, the natural frequency tends to be low and the vibration damping tends to be small.
In particular, various unexpected vibrations may occur due to the influence of aerodynamic external force due to wind.

Therefore, for the purpose of cutting off this type of vibration source, it is conceivable to take aerodynamic measures on the outer shape of the structure, but the outer shape of the structure has restrictions from the functional or design viewpoint, It is difficult to rely solely on this aerodynamic measure.

Therefore, the inventor of the present application has filed Japanese Patent Application No. 60-241045
-101764), a tank for storing a liquid that vibrates at the required position of the structure with the same vibration period as the structure and with a phase difference is provided. Has proposed a vibration suppressing device for suppressing the rolling motion of the above, and solved the above-mentioned problems.

By the way, since this vibration suppressing device suppresses the vibration of the structure by the liquid in the tank vibrating the same as the structure, the vibration of the structure is suppressed by the action of the vibration suppressing device, On the contrary, the vibration suppressing device may act as a vibration exciter. Normally, the liquid in the tank is configured so that its vibration is damped due to collision with the wall surface of the tank or viscosity of the liquid itself, but it is appropriate depending on the structure of the structure and the scale of the vibration suppression device. The realization of means capable of damping the vibration of liquid has been a subject for study.

In view of the above problems, the present invention has been developed by previously developing the vibration suppressing device proposed by the inventor of the present application, and provides a vibration suppressing device capable of easily damping the vibration of liquid in a tank. The purpose is to do.

"Means for Solving the Problems" The present invention relates to a tank provided in a structure, in which a liquid vibrating in the same natural vibration cycle as the natural vibration cycle of the structure is stored, and The tank has a space above the liquid surface of the liquid in a stationary state to allow vibration of the liquid, and a plurality of floats for adjusting vibration damping of the liquid are provided inside the tank in a state of floating on the liquid. It is what has been.

[Operation] In the vibration suppressing device for a structure according to the present invention, a tank is provided at a predetermined position of the structure, and the inside of the tank has the same natural vibration cycle as the natural vibration cycle of the structure and the structure. When a structure vibrates due to an earthquake, wind, etc. by storing a liquid that vibrates with a phase difference that is unique to the vibration of the structure, the liquid stored in the tank has the same cycle and phase as the structure's vibration cycle. By vibrating in a deviated state, suppressing the vibration centering on the rolling of the structure, and by providing a plurality of floats in the tank that adjust the vibration damping of the liquid while floating in the liquid. When the liquid vibrates, the collision of the floats causes the wave energy to be attenuated, whereby the vibration of the liquid is damped. Since the vibration of the liquid is dampened, the vibration of the structure is dampened and the vibration of the vibration suppression device itself is also damped. Therefore, the vibration suppression device acts as a shaker for the structure. There is no.

[Embodiment] A first embodiment of the present invention will be described below with reference to FIGS. 1 to 3.

The structure vibration suppression device 1 of this embodiment is installed on the roof of a high-rise building 2 (structure) which is said to be most effective against vibrations caused by wind.
Support base 3 having a laminated structure of an elastic body such as rubber and a steel plate
And a tank 4 placed on the support base 3 and a liquid 5 stored in the tank 4.

The tank 4 is a cylindrical tank for storing drinking water of the building 2, water for fire prevention, water for cooling and heating equipment, etc., and its upper part is open, It has a structure having a space above which the vibration of the liquid 5 is allowed. The liquid 5 has a liquid surface height (H shown in FIG. 3) and the like appropriately adjusted according to its specific gravity, so that the liquid 5 has a natural vibration period that is the same as the natural vibration period of the building 2. Are stored in this tank 4.

A plurality of floats 6 are floated on the liquid surface of the liquid 5. The float 6 is made of plastic or the like having a smaller specific gravity than the liquid 5, and is moored by an anchor 7 attached to the bottom of the tank 4 while floating on the liquid surface of the liquid 5. Its range of movement is limited. The shape of the float 6 is spherical,
It may have a plate shape or the like, but may have any other shape. Further, the float 6 may be moored by an anchor 7 attached to a part other than the bottom of the tank 4,
The anchor 7 may be left floating without mooring. However, if the floating positions of the floats 6 are significantly deviated, it is not possible to sufficiently damp the vibration of the liquid 5, so it is desirable to limit the movement of the floats by the anchor 7 or the like.

By the way, the liquid 5 stored in the tank 4 needs to generate vibrations out of phase with the same cycle as the cycle of the building. Therefore, when the float 6 is not floated on the liquid 5 in the tank 4, since the damping rate against the vibration of the liquid 5 itself is small, it is possible to bring about the effect of vibrating conversely unless a liquid having a viscosity higher than that of water is used. There is. However, in the structure of the present invention, the damping rate of the liquid itself stored in the tank 4 can be adjusted by adjusting the material shape, size, and number of the floats 6 regardless of what kind of building is applied. Therefore, the damping rate of the entire structure can be adjusted.

Next, the operation of the vibration suppressing device 1 will be described.

A vibration system including the building 2 and the vibration suppression device 1 has a fourth structure.
It exhibits vibration characteristics similar to the vibration model shown in the figure.

The vibration model shown in Fig. 4 is based on the mass of spring 8A with spring constant K _0.
A vibration system A (a vibration model of the building 2) that supports an object 9A of M ₀ and adds a dashpot 10A with a damping rate h ₀ and a spring 8B with a spring constant K ₁ of effective mass M ₁ object
Supports 9B and dashpot 10B with damping rate h ₁
Is added to the vibration system B (vibration model in the tank 4).

In such a vibration system, when the vibration system A starts to vibrate due to an external force applied to the object 8A, the vibration system B becomes 1 / 4th.
Since the vibration starts with the phase difference of the cycle, the vibration system A
By matching the natural vibration period of B, the vibration of the vibration system A can be suppressed.

Here, the natural vibration period of the vibration system is And the natural vibration period T ₀ of the building 2 is given by
Since it is uniquely determined by the mass M ₀ and the spring constant K ₀ determined from the viewpoint of structural design, in order to match the natural vibration period T ₁ of the liquid 5 stored in the tank 4 with the above T ₀ ,
The size and the capacity of the tank 4 are set so that they match each other. That is, according to the Hausner theory that holds for the behavior of the stored liquid in the tank, the free water effective mass (mass acting as a vibrating body) M ₁ that can move in the tank 4 as shown in the illustrated example is It is given by the equation (2).

However, H: distance from the bottom of the tank 4 to the water surface R: radius of the tank 4 M: mass of the liquid 5 actually stored in the tank 4 and natural frequency ω of the liquid 5 (so-called The natural frequency of sloshing) is given by the following equation (3).

Further, the vibration period T is obtained from the natural frequency ω as shown in the following equation (4).

If, for example, R = 15 m H = 2 m M = 1414 t (subsequently, M = 812 t) is substituted for the above parameters, T = 11.7 seconds.

Then, between the natural vibration period T ₁ of the liquid 5 in the tank 4 and the natural vibration period T ₀ of the building 2 obtained by the above formula, T ₀ = T ₁ ………… (5) Each dimension and storage amount of the tank 4 are set so that

The characteristics shown in FIGS. 5 and 6 were obtained from the experimental results of the displacement response magnification excited by the vibrating table. Fifth
The figure shows the result of an experiment carried out with the liquid (water) stored in the tank, and FIG. 6 shows the result of the experiment carried out with the tank being empty.

That is, as shown in FIG. 6, by providing a tank in a building having a large amplitude at a frequency close to the natural frequency and storing a liquid, the vibration can be suppressed as shown in FIG.

Further, as a result of the experiment, it is effective when the ratio of the effective mass M ₁ of the liquid 5 and the mass M of the building 2 is set to M ₁ / M = 1/50 to 1/100 ………… (6) It was possible to exert the vibration suppression effect. Here, if the effective mass is 1/100 or less, a sufficient vibration damping effect cannot be obtained, and if it is 1/50 or more, the liquid may cause the vibration exciting effect to the contrary, so again the structural design of the building 2 Therefore, it is better to set the ratio of M to M ₁ as in the equation (6).

7 and 8 are diagrams showing a second embodiment of the present invention.

In the vibration suppressing device 1a of this embodiment, a plurality of mesh members 11 for damping the vibration of the liquid 5 are provided on the bottom surface of the tank 4 so as to project upward, and the upper portion of the mesh member 11 is the liquid 5 above. The height is set so as not to come into contact with the float 6 that is floating on the bottom. This mesh member 11 is
A mesh made by weaving various fibers and fibers such as metal wires is stretched around a frame body made of metal or the like, and a plurality of the meshes are arranged in a lattice in the tank 4. The number and scale of the mesh members 11 may be appropriately determined depending on the storage amount of the liquid 5 stored in the tank 4, the physical property value of the liquid 5, and the like. In this vibration suppressing device 1a, the plurality of mesh members 11 do not necessarily have to be arranged in a lattice shape, but may be arranged in a concentric circle shape or a star shape.

A large number of stoppers 12 for fixing the mesh member 11 are provided on the bottom surface of the tank 4, and the mesh member 11 is positioned in the tank 4 by the stoppers 12. The stopper 12 is an expected mesh member.
It is preferable to provide in advance a number larger than the number of 11 installed, which facilitates adjustment of the number and scale of the mesh members 11 described above.

According to this vibration suppressing device 1a, since the mesh member 11 is provided inside the tank 4, when the liquid vibrates in the tank 4 due to the vibration of the building 2, when the liquid 5 passes through the gap of the mesh member 11. Then, the transfer energy is lost, so that the vibration of the liquid 5 can be damped more effectively.

In the vibration suppressing device of the present invention, the shape of the tank does not necessarily have to be cylindrical, and may be changed into various shapes such as a flat quadrangle, a sphere, and a flat ellipse according to the installation conditions. . In this case, the above Hausner theory may be applied to set the vibration period and the mass based on the equation corresponding to the shape.

[Effect of the Invention] According to the structure vibration suppression device of the present invention, the tank is provided at a predetermined position of the structure, and inside the tank, at the same vibration cycle as the unique vibration cycle of the structure, Moreover, since the liquid that vibrates with the phase difference and the vibration peculiar to the structure is stored, when the structure vibrates due to an earthquake, wind, etc., the liquid stored in the tank has the same cycle as the vibration cycle of the structure, and By vibrating in a phase-shifted state, it is possible to suppress the vibration centering on the rolling of the structure, and a float for adjusting the vibration damping of the liquid is provided inside the tank while floating on the liquid. Therefore, when the liquid vibrates, the energy of the wave is attenuated due to the collision of the floats, whereby the vibration of the liquid is damped. Further, since the vibration of the liquid is damped, the vibration of the structure is also dampened at the same time as the vibration of the structure is dampened. Therefore, the vibration suppressor acts on the structure like an exciter. The vibration of the structure can be reliably suppressed.

[Brief description of drawings]

1 to 3 are views showing a first embodiment of the present invention, wherein FIG. 1 is a schematic configuration diagram of a building provided with a vibration suppressing device, and FIG. 2 is a plan view of the vibration suppressing device. 3 is a vertical sectional view of the same. FIG. 4 is a vibration model diagram of a building, FIG. 5 is a displacement response magnification diagram of a tank according to the present invention, FIG. 6 is a displacement response magnification diagram of an empty tank, and FIGS. It is a figure which shows 2nd Example, Comprising: FIG. 7 is a longitudinal cross-sectional view of a vibration suppressing device, and FIG. 1 ... Vibration suppressor, 2 ... Structure (building), 4 ...
Tank, 5 ... Liquid, 6 ... Float.

Claims (1)

[Claims] 1. A liquid tank vibrating at a natural vibration cycle identical to the natural vibration cycle of the structure is stored inside a tank provided in the structure, and the tank is filled with the liquid of the liquid in a stationary state. A structure having a space for allowing vibration of liquid above the liquid level, and a plurality of floats for adjusting vibration damping of the liquid are provided inside the tank in a state of floating in the liquid. Vibration suppression device for objects.