JPH01131766A - Vibration damper for structure - Google Patents

Abstract

PURPOSE: To attenuate vibration by storing liquid, which vibrates at the same frequency as the frequency of a structure with a phase difference provided from the natural frequency of the structure, in a tank, and also providing waveform irregularities at the bottom part of the tank. CONSTITUTION: A supporting stand 2 formed with a laminated structure comprising an elastic body such as rubber and a steel plate is provided on a roof of a building 1. Also, a tank 3 is put on the supporting stand 2, and a liquid W, which vibrates at the same frequency as a frequency of the building 1 with a phase difference provided from a natural frequency of the building 1, in the tank 3. Then projected parts 3a and recessed parts 3b extending radially from a center are installed on the bottom surface of the tank 3 alternately along the circumferential direction of the tank 3. Thus, when an oscillating rotation is caused on the building 1 by an earthquake, the projected and recessed parts 3a and 3b act as flow resistance against the liquid W, the liquid W flows in the circumferential direction of the tank 3 to attenuate the vibration, and the oscillating rotation is attenuated.

Description

DETAILED DESCRIPTION OF THE INVENTION "Field of Industrial Application" The present invention relates to a vibration suppressing device that suppresses vibrations caused in structures by earthquakes, wind, etc.

"Conventional technology and its problems" Due to factors such as the development of high-strength materials, progress in manufacturing technology, and development of structural analysis technology using computers, structures in recent years have become larger, more diverse in form, and lighter. As technology advances, structures are becoming more flexible. In addition, such lightweight and flexible structures tend to have low natural frequencies and low vibration damping, and as a result, various unpredictable vibrations occur due to the influence of external aerodynamic forces, especially those caused by wind. there's a possibility that.

For this reason, it is conceivable to take aerodynamic measures to the external shape of the structure for the purpose of cutting off this type of vibration source, but there are various restrictions on the external shape of the structure from a functional and design perspective. Therefore, it is difficult to rely solely on this aerodynamic measure.

Therefore, in the specification of Japanese Patent Application No. 60-241045, the inventor of the present application stored a liquid that vibrates at a predetermined position of a building at the same period as the natural vibration period of the building, but with a phase difference. We have proposed a vibration suppression device that can suppress the horizontal shaking of a building by the vibration of this liquid, which solves the above-mentioned problems.

However, in addition to horizontal shaking, there are other types of vibrations that affect buildings.
If the center of gravity of the building is misaligned with the closing point, the rotational movement that occurs due to the aerodynamic force of the wind, that is, the swinging rotation of the building, may occur, and the vibration of the liquid may cause the building to vibrate. This continued even after the vibrations had stopped, causing problems such as having the opposite effect on suppressing vibrations in buildings.

In view of the above-mentioned problems, the present invention has been made by developing the vibration suppression device previously proposed by the inventor of the present invention, and is designed to suppress vibrations mainly caused by horizontal shaking of structures caused by wind.
Another object of the present invention is to provide a vibration suppressing device for a structure that is capable of suppressing both vibrations caused by oscillating rotation and attenuating liquid vibrations at an early stage.

``Means for Solving the Problems'' In order to solve the above problems, the present invention provides a tank provided at a predetermined position of a structure, and inside the tank, the vibration period unique to the structure is detected. A liquid that vibrates at the same vibration frequency and with a phase difference from the vibration unique to the structure is stored, and at the bottom of this tank, a wave-shaped unevenness is formed to adjust the attenuation of the liquid. .

"Effect" When vibrations are applied to a structure due to earthquakes, wind, etc., the liquid stored in the tank vibrates in the same phase as the structure's vibration period, but out of phase, causing the structure's horizontal shaking to be the main cause. In addition to suppressing vibrations caused by earthquakes or wind, when vibrations such as swing rotation occur in the structure, the liquid moving in the circumferential direction of the tank due to the swing rotation is resisted by the corrugated unevenness of the bottom, and the liquid Turbulent flow is generated in the structure, preventing movement in the circumferential direction and suppressing the swinging rotation of the structure.

"Example" Hereinafter, a vibration suppressing device for a structure according to the present invention will be described using the drawings. 1 to 3 show a first embodiment of the present invention, and FIG. 1 shows a structure in which the structure vibration suppressing device (hereinafter simply referred to as "vibration suppressing device") of the present invention is installed in a high-rise building. This shows the state where it is installed on the roof of a building such as.

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

The tank 3 is a cylindrical tank for storing drinking water for the building l or fire prevention water, and has an open top structure, as shown in FIGS. 2 and 3. The vibration of the building caused by wind or the like is suppressed by storing the liquid W under conditions such that the external dimensions are the same and the vibration period is the same as that of the building I. The bottom surface of the tank 3 is provided with convex portions 3a and concave portions 3b, which extend radially from the center toward the outer periphery, alternately along the circumferential direction, thereby forming a corrugated bottom surface.

The liquid W in the tank 3 is stored at a depth such that the vibration period is the same as that of the building l, thereby suppressing vibrations of the structure l caused by wind. In addition, if the center of gravity of the building 1 and the closing position are misaligned, and if the building 1 swings, the liquid inside the tank will try to flow in the circumferential direction of the tank 3. In this case, since the uneven portions 3a and 3b on the bottom surface act as flow resistance for the liquid, the liquid flows in the circumferential direction of the tank 3 with the same period as the swing period of the building l but out of phase. The liquid also suppresses the swinging rotation of this building.

Therefore, according to the vibration suppressing device configured as described above,
It is possible to suppress both vibrations mainly caused by the horizontal shaking of the building l and vibrations mainly caused by swinging rotation, and the uneven portions act as flow resistance and can quickly attenuate the vibrations of the liquid.

By the way, the liquid W stored in the tank 3 needs to vibrate in a phase-shifted manner with the same period as the period of the building l.

Therefore, when using a tank 3 that does not have uneven portions 3a and 3b on the bottom, the vibration damping rate of the liquid W itself is small. may result in However, the structure of the present invention can be applied to any building by appropriately setting the number, height, shape, etc. of the protrusions 3a and recesses 3b at the bottom of the tank 3.
It becomes possible to adjust the attenuation rate of the liquid itself stored in the
Furthermore, the attenuation rate of the entire structure can also be controlled.

7 and 8 show a second embodiment of the present invention, in which convex portions 3a and concave portions 3b are alternately provided in the diametrical direction on the bottom surface of the tank 3, and the bottom surface is formed into a wave shape. . This second
In this embodiment, the same effect as in the first embodiment can be obtained, and the uneven parts 3a and 3b formed on the bottom surface can be adjusted to accommodate different vibration states that occur depending on the shape of the building. By appropriately changing the direction, a more efficient vibration damping effect can be achieved.

Here, the vibration analysis of the building I and the tank conducted in the specification of Japanese Patent Application No. 1988-241045 will be described. First, if we analyze a tank with no uneven bottom surface, this tank and the building 1 exhibit vibration characteristics similar to the vibration model shown in FIG. 4.

The vibration model shown in Fig. 4 has a spring constant K. Spring 4A quality ff1M. In addition to supporting the object 5A, the attenuation rate. A vibration system A (vibration model of a building) to which Dashbot 6A is added, and a spring 4B with a spring constant of
supports an object 5B of effective quality ff1M, and
It consists of a vibration system B (vibration model in the tank) to which a dashpot 6B with a damping rate h1 is added.

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 period.
By matching the vibration periods of vibration systems A-H, vibration of vibration system A can be suppressed.

Here, the vibration period of the vibration system is Also, the vibration period T of the building 1 is given by the formula.

is the mass M determined from the viewpoint of structural design. , and spring constant K. Since it is uniquely determined by, the vibration period T1 of the liquid W stored in the tank 3 is T. The dimensions and capacity of the tank 3 are set to match the two.

That is, according to the Hausner (1-1 Ousner) theory that holds true regarding the behavior of the liquid stored in the tank, the effective mass of free water that can move in the tank 3 (mass that acts as a vibrating body) Ml as shown in the example shown is as follows. It is given by equation (2).

However, H... Distance R from the bottom of tank 3 to the water surface.
...Radius M of the tank 3...The mass of the liquid actually stored in the tank 3, and the natural vibration ω (so-called natural frequency of sloshing) of the stored liquid W are as follows. According to equation (3), the vibration period T can be determined from the natural frequency ω as shown in equation (4) below.

If, for example, R=15m H=2m M=1414t (M=812t from equation 2) is substituted into each of the above parameters, then T=11.7 seconds.

Then, the vibration period of the liquid in the tank and the vibration period T of the building obtained from the above equation. Between T o ” T I
. . . Each dimension and storage amount of the tank 3 are set so that equation (5) holds true.

As a result of experiments on the displacement response magnification caused by vibration using a vibration table, characteristics as shown in FIGS. 5 and 6 were obtained. Fifth
The figure shows the results of an experiment conducted with liquid (water) stored in the tank, and FIG. 6 shows the results of an experiment conducted with the tank empty.

That is, as shown in FIG. 6, vibrations can be suppressed 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 liquid therein.

Furthermore, as a result of the experiment, the ratio between the effective mass M of the liquid W and the mass M of the building L is M, /M = 1150 to 1/100...
. . . When the equation (6) was set, the vibration suppressing effect could be effectively exhibited. Here, the effective mass is 1/
If it is less than 100, sufficient vibration damping effect cannot be obtained;
In the above case, it is better to set the ratio of M and M as in the above equation (6) because the liquid may cause the vibration effect in the opposite direction and it is necessary to perform the structural design of the building again. good.

Furthermore, if it is necessary to keep the liquid in the tank in a fixed state (closely filled in a closed tank) due to various factors, instead of the above formula (2), use this formula. The volume of the tank and other various numerical values may be determined from the results obtained using equation (2).

The shape of the tank 3 is not limited to the cylindrical shape shown in the above embodiment, but may be changed to various shapes depending on the installation conditions, such as a square planar shape, a spherical shape, and a planar elliptical shape. In this case, it is sufficient to apply Hausner's theory and set the vibration period and mass based on a formula depending on the shape. Further, the structure vibration suppression device of the present invention is not limited to buildings as shown in the above embodiments, but can be used for any structure.

"Effects of the Invention" As explained above, the present invention has a structure in which a liquid that vibrates at the same period as the structure and has a phase difference is stored in a tank provided at a predetermined position of a structure. Since this vibration suppresses the vibration of the structure, it is possible to obtain a vibration suppression effect against earthquakes and wind.

Furthermore, when the liquid tries to flow in the circumferential direction within the tank due to the vibration caused by the swinging rotation of the structure, the unevenness of the bottom surface becomes a fluid resistance, causing turbulent flow within the tank, causing the above-mentioned In order to attenuate the vibrations of the liquid, it is possible to suppress the vibrations accompanying the swinging rotation of the structure, and by attenuating the vibrations of the liquid at an early stage, it is possible to suppress the excitation effect exerted by the liquid on the structure. Can be done. Further, if a water supply tank or a fire prevention water tank provided in a structure is used as a vibration suppression tank, there is no need to specially install a tank, which is advantageous in terms of equipment costs.

[Brief explanation of the drawing]

1 to 3 show one embodiment of the present invention, in which FIG. 1 is an elevation view of a building equipped with a vibration suppression device, and FIG.
The figure is a plan view of the tank, Figure 3 is a vertical cross-sectional view of the tank, and Figure 4 is a longitudinal sectional view of the tank.
The figure is a vibration model diagram of a building, Figure 5 is a displacement response magnification diagram of the device of the present invention, Figure 6 is a displacement response magnification diagram for an empty tank, and Figures 7 and 8 are the displacement response magnification diagram of the device of the present invention. Example 7
The figure is a plan view of the tank, and FIG. 8 is a longitudinal sectional view of the tank. W...Liquid, l...Building (structure), 2...
- Support stand, 3...tank, 3a...convex portion, 3b...concave portion.

Claims (1)

[Claims] A tank is provided at a predetermined position of the structure, and inside this tank there is a liquid that vibrates at the same vibration period as the vibration period unique to the structure and with a phase difference from the vibration unique to the structure. A vibration suppressing device for a structure, characterized in that the liquid is stored therein, and a wave-shaped unevenness is formed on the bottom of the tank to adjust attenuation of the liquid.