JPH0756189B2 - 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 corrugated unevenness for adjusting the damping of the vibration of the liquid is formed at the bottom of the tank.

“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 an earthquake or wind, the liquid that moves in the circumferential direction of the tank due to swinging rotation resists due to the unevenness of the waveform at the bottom. Accordingly, turbulent flow is generated in the liquid, movement in the circumferential direction is blocked, and swinging rotation of the structure is suppressed.

[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 has a convex portion extending radially from the center toward the outer peripheral portion. By arranging the recesses 3a and the recesses 3b alternately in the circumferential direction, the bottom surface is corrugated.

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 rotates, the liquid inside the tank tends to flow in the circumferential direction of the tank 3. In this case, since the concave-convex portions 3a and 3b on the bottom face become the flow resistance of the liquid, the liquid flows in the circumferential direction of the tank 3 in the same cycle as the swing cycle of the building 1 and with a phase shift. The liquid also suppresses swinging rotation of this building.

Therefore, according to the vibration suppressing device configured as described above,
It is possible to suppress both the vibration mainly due to the rolling of the building 1 and the vibration mainly due to the swinging rotation, and at the same time, it is possible to damp the vibration of the liquid at an early stage, because the uneven portion serves as a flow resistance.

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 uneven portions 3a and 3b at the bottom is used, the damping rate for the vibration of the liquid W itself is small, and therefore, the effect of vibrating conversely unless a liquid having a viscosity higher than that of water is used. May bring. However, in the structure of the present invention, even when applied to any building 1, it is stored in the tank 3 by appropriately setting the number, height, shape, etc. of the convex portions 3a and the concave portions 3b at the bottom of the tank 3. The damping rate of the liquid itself can be adjusted, and thus the damping rate of the entire structure can be controlled.

FIG. 7 and FIG. 8 show a second embodiment of the present invention, in which convex portions 3a and concave portions 3b are alternately provided on the bottom surface of the tank 3 in the diameter direction, and the bottom surface is formed in a corrugated shape. . In the second embodiment, the same effect as that of the first embodiment can be obtained, and the uneven portion 3a formed on the bottom surface is adapted to the different vibration states generated according to the shape of the building. , 3
By changing the direction of b as appropriate, a more efficient 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 an analysis is performed on a tank having no uneven surface, the 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, when the liquid tries to flow in the circumferential direction in the tank against the vibration caused by the swinging rotation of the structure, the unevenness of the bottom surface becomes a fluid resistance, which causes a turbulent flow in the tank to cause the liquid to flow. In order to damp the vibration, it is possible to suppress the vibration associated with the swinging rotation of the structure, and to damp the vibration of the liquid at an early stage, so that the vibration effect exerted on the structure by the liquid can be suppressed. . 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 THE DRAWINGS FIG. 1 to FIG. 3 show an embodiment of the present invention. FIG. 1 is an elevation view of a building equipped with a vibration suppressing device, and FIG. Plan view, FIG. 3 is a longitudinal sectional view of the tank, FIG. 4 is a vibration model of the building, FIG. 5 is a displacement response magnification diagram of the device of the present invention, and FIG. 6 is a displacement response magnification in the case of an empty tank FIGS. 7, 7 and 8 show a second embodiment of the present invention, FIG. 7 is a plan view of the tank, and FIG. 8 is a longitudinal sectional view of the tank. W ... Liquid, 1 ... Building (structure), 2 ... Support base,
3 ... tank, 3a ... convex portion, 3b ... concave portion.

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. A vibration suppressing device for a structure, comprising a space for allowing vibration of liquid above the liquid surface, and corrugated unevenness for adjusting damping of the vibration of the liquid is formed at the bottom of the tank.