JPH0756188B2 - Vibration suppression device for structures - Google Patents

Description

TECHNICAL FIELD The present invention relates to a vibration suppressing device 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 structures have become larger, diversified in form, and lightweight. As it becomes more and more popular, the structure is becoming more flexible. And
In such a lightweight and flexible structure, the natural frequency is 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.

For this reason, aerodynamic measures may be taken on the outer shape of the structure for the purpose of cutting off this type of vibration source. However, the outer shape of the structure has various restrictions in terms of function or design. It is difficult to rely on this aerodynamic measure alone.

Therefore, the inventor of the present application has filed Japanese Patent Application No. 60-241045
-101764) In the specification, at the required position of the building,
Proposal of a vibration suppression device that can hold a tank that stores a liquid that vibrates in the same cycle as the building's unique vibration cycle and with a phase difference, and suppress the rolling of the building due to the vibration of the liquid However, the above-mentioned problem is solved.

However, in addition to rolling,
When the center of gravity and the center of gravity of the building are deviated from each other, a rotational motion that is generated by the aerodynamic force of the wind, that is, a swinging rotation of the building may occur, and vibration of the liquid causes the building to swing. There was a problem that it continued even after the vibration stopped, which had the opposite effect of suppressing the vibration of the building.

In view of the above problems, the present invention has been made by developing the vibration suppressing device proposed by the inventor of the present application, in which vibration mainly caused by rolling of a structure caused by wind, and swinging. An object of the present invention is to provide a vibration suppressing device for a structure that can suppress both vibrations due to rotation and that can quickly dampen vibrations of a liquid.

"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, which allows the vibration of the liquid, and a plurality of rotary blades that rotate with the vibration of the liquid are provided inside the tank. is there.

“Action” When vibrations are applied to a structure due to an earthquake or wind, the liquid stored in the tank vibrates in the same natural vibration cycle as the structure and with a phase shift In addition to suppressing vibrations mainly due to rolling, when vibration such as swinging rotation occurs in the structure due to earthquake or wind, the liquid moving in the circumferential direction of the tank rotates the rotating blades due to swinging rotation, Vortices are generated in the liquid by the rotation of the blades, and the liquid becomes a turbulent flow to damp the vibration of the liquid and suppress the swinging rotation of the structure.

[Example] Hereinafter, a structure vibration suppressing device of the present invention will be described with reference to the drawings. 1 to 3 show a first embodiment of the present invention, and FIG. 1 shows a structure of a vibration suppressing device for a structure of the present invention (hereinafter, simply referred to as “vibration suppressing device”) in a high-rise building. It shows a state of being installed on the roof of a building such as.

In the building 1 of this embodiment, a support base 2 having a laminated structure of an elastic body such as rubber and a steel plate is provided on the roof, which is said to be most effective against vibrations caused by wind. A tank 3 for suppressing vibration is provided on the above.

The tank 3 is a cylindrical tank for storing drinking water of the building 1 or fire protection water, and has a structure with an open upper part, as shown in FIGS. 2 and 3. The liquid W is formed to have an outer dimension and has the same natural vibration period as that of the building 1.
By storing the water, the vibration of the building caused by the wind etc. is suppressed. The tank 3 has a space above the liquid surface of the liquid W in a stationary state to allow the vibration of the liquid W, and the bottom surface of the tank 3 is spaced apart from the center of the tank 3 by a predetermined distance. Five shaft bodies 3a are erected radially, and rotary blades 3b rotatable around the shaft body are attached to the shaft body 3a. The rotary blade 3b in this embodiment is formed with a swastika plane so as to rotate in one direction, and a cylindrical mounting portion 3c is formed in the central portion thereof so that it can be inserted into the shaft body 3a. , Tank 3
It has a predetermined width in the height direction so as to be immersed in the liquid W stored in and receive a predetermined fluid resistance.

Then, the liquid W in the tank 3 is stored at a depth such that the natural vibration cycle is the same as the natural vibration cycle of the building 1, and thus the vibration of the structure 1 caused by the wind is suppressed. Further, when the center of gravity and the center of gravity of the building 1 are deviated, and when the building 1 swings and swings, the liquid inside the tank tends to flow in the circumferential direction of the tank 3. In this case, the rotary blade 3b serves as a flow resistance of the liquid flowing in the circumferential direction, but on the other hand, the liquid W is rotated around the shaft 3a in one direction to generate a vortex in the liquid and to make the liquid turbulent. The liquid is prevented from flowing in the tank 3 in the circumferential direction, and the swinging rotation of the building is also suppressed.

Therefore, according to the vibration suppressing device having the above-described structure, both the vibration mainly caused by the rolling of the building 1 and the vibration mainly caused by the swinging rotation of the building 1 can be suppressed, and the rotary vanes become a flow resistance and can be quickly obtained. The vibration of the liquid can be damped.

By the way, the liquid W stored in the tank 3 is required to generate vibrations out of phase with the same cycle as the cycle of the building 1.
Therefore, when the tank 3 having no rotary vane is used, the damping rate for the vibration of the liquid W itself is small,
On the contrary, unless a liquid having a higher viscosity than water is used, the effect of vibrating may be brought about. However, in the structure of the present invention, no matter what kind of building 1 is applied, the rotary blade
The damping rate of the liquid itself stored in the tank 3 can be adjusted by adjusting the shape, width, number, arrangement position, etc. of 3b, and by extension, the damping rate of the entire structure can be controlled.

FIG. 7 shows a second embodiment of the present invention, in which a plurality of (four in this embodiment) swastikas are provided for each shaft body 3a which is erected so that its tip reaches near the liquid surface. A predetermined number of rotating blades 3b are detachably and rotatably provided. The rotary blade 3b attached to the shaft body 3a is
You may make it rotate by connecting with each other.

In the second embodiment, the same effect as that of the first embodiment can be obtained, and by appropriately adjusting the number of the rotating blades 3b, the damping is performed according to the amount and viscosity of the stored liquid W. The rate can be controlled, and the optimum vibration damping effect can be exhibited.

Here, the vibration analysis of the building 1 and the tank performed in the specification of Japanese Patent Application No. 60-241045 (Japanese Patent Laid-Open No. 62-101764) will be described. First, if a tank without the rotary vanes 3b is analyzed, this tank and the building 1 exhibit vibration characteristics similar to the vibration model shown in FIG.

The vibration model shown in Fig. 4 is based on the mass of spring 4A with spring constant K _0.
A vibration system A (a vibration model of a building) that supports a body 5A of M ₀ and adds a dashpot 6A with a damping rate h ₀ , and a body of effective mass M ₁ to a spring 4B having a spring constant K ₁ 5B
Vibration system B (vibration model inside the tank) that supports a dashpot 6B with damping rate h ₁
It consists of and.

Then, in such a vibration model, when the vibration system A starts to vibrate due to an external force applied to the object 4A, the vibration system B
Starts to vibrate with a phase difference of 1/4 cycle, so that the vibration of the vibration system A can be suppressed by matching the natural vibration cycles of the vibration systems A and B.

Here, the natural vibration period of the vibration system is And the natural vibration period T ₀ of the building 1 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 make the natural vibration period T ₁ of the liquid W stored in the tank 3 coincide with the above T ₀ ,
The size and the capacity of the tank 3 are set so that they match.

That is, according to the Hausner theory that holds for the behavior of the stored liquid in the tank, the tank 3
The free water effective mass (mass acting as a vibrating body) M ₁ that can move inside is given by the following equation (2).

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

Further, from the natural frequency ω, the natural vibration period T is obtained 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 in the tank and the natural vibration period T ₀ of the building obtained by the above formula, T ₀ = T ₁ ……………… (5) Formula is established. As described above, each size and storage amount of the tank 3 are set.

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 W and the mass M of the building ₁ 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 effect to the contrary. Since it is necessary to perform this, it is better to set the ratio of M to M ₁ as in the above equation (6).

It should be noted that the shape of the tank 3 is not limited to the cylindrical shape as shown in the above-mentioned embodiment, but may be changed into various shapes such as a plane quadrangle, a sphere, and a plane ellipse depending on the installation conditions. In this case, the Hausner's theory may be applied to set the vibration period and the mass based on an equation corresponding to the shape.
Further, the structure vibration suppression device of the present invention is not limited to the building as shown in the above-mentioned embodiment, but can be used for any structure.

[Advantages of the Invention] As described above, the present invention has a configuration in which a tank provided at a required position of a structure stores a liquid that vibrates with a phase difference in the same cycle as the structure and that vibrates the liquid. In order to suppress the vibration of the structure, it is possible to obtain the vibration suppressing effect against the earthquake and the wind. Further, against the vibration caused by the swinging rotation of the structure, when the liquid tries to flow in the circumferential direction in the tank, the rotary vanes act as a fluid resistance, while the liquid is rotated by the liquid and swirls occur in the tank. As a result, the liquid is made to be in a turbulent state, which prevents the liquid from flowing and suppresses the vibration, and it is possible to suppress the vibration associated with the swinging rotation of the structure, and at the same time, the liquid vibrates quickly. By dampening, it is possible to suppress the vibration effect exerted by the liquid on the structure. Further, if the water supply tank or fire protection water tank provided in the structure is used as the vibration suppression tank, it is not necessary to install the tank specially, and there is an advantageous effect in terms of equipment cost.

[Brief description of drawings]

1 to 3 show an embodiment of the present invention. FIG. 1 is an elevation view of a building equipped with a vibration suppressing device, FIG. 2 is a plan view of a tank, and FIG. FIG. 4 is a longitudinal sectional view of a tank, FIG. 4 is a vibration model of a building, FIG. 5 is a displacement response magnification diagram of the device of the present invention, FIG. 6 is a displacement response magnification diagram in the case of an empty tank, and FIG. It is a longitudinal cross-sectional view of a tank showing a second embodiment of the invention. W ... Liquid, 1 ... Building (structure), 2 ... Support base,
3 ... Tank, 3a ... Shaft, 3b ... Rotating blade.

Claims (1)

[Claims] 1. A tank provided in a structure stores therein a liquid vibrating in a natural vibration cycle that is the same as a natural vibration cycle of the structure, and the tank stores the liquid in a stationary state. There is a space above the liquid surface that allows vibration of the liquid, and a plurality of rotary blades that rotate with the vibration of the liquid are provided inside the tank, and vibration suppression of the structure apparatus.