JPH09151986A - U-shaped tank type dynamic vibration absorbing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To facilitate the regulating work for providing an optimum damping performance, reduce the manufacturing cost of a tank, and wake test easy. SOLUTION: This device has a U-shaped tank 11 opened in both ends and storing a liquid in the inner part, a cover lid 13 provided on the end part of the U-shaped tank 11 and having an air chamber 14 formed in the level upper part, a through-hole 15 formed on the cover lid 13, and a slide plate 16 capable of regulating the opening of the through-hole 15. Since the cover lid for forming the air chamber in the level upper part is provided on the end part of the U-shaped tank, and the through-hole is formed on the cover lid, the oscillation of the liquid within the U-shaped tank can be damped by the air resistance generated by the coming-in and -out through the through-hole even when the liquid is oscillated, and the damping performance can be varied by the positional adjustment of the slide plate.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is used for damping vibration of structures such as bridges, high-rise buildings and ships.
The present invention relates to a character-shaped tank type dynamic vibration absorber.

[0002]

2. Description of the Related Art When a structure such as a bridge, a high-rise building, or a ship is vibrated due to an earthquake, a wave, or a wind, a viscous resistance of a fluid has been conventionally used as a means for reducing the vibration. There is a concept of damping, and U is one of them.
A character tank type dynamic vibration absorber has been proposed. A conventional U-shaped tank type dynamic vibration absorbing device 1 will be described with reference to FIG. 3. In the figure, 2 is a U-shaped tank whose both ends are open. Inside the U-shaped tank 2, for example, water 3 is stored as a liquid. Has been. When such a U-shaped tank 2 is externally vibrated, a liquid oscillation called sloshing is generated in the U-shaped tank 2, and the sloshing natural vibration of the liquid stored in the U-shaped tank 2 due to the oscillation. Number f
_T is

[0003]

(Equation 1) Is required. Therefore, such a U-shaped tank type dynamic vibration absorber 1 is attached to the structure for vibration reduction, and the U-shaped tank 2
If the effective length Le of the water column in the inside is adjusted so that the natural frequency f _T of the dynamic vibration absorbing device 1 matches the natural frequency of the target structure, the vibration energy of the target structure can be favorably reduced. .

However, when the above-mentioned U-shaped tank dynamic vibration absorber 1 is used as a damping means for a structure, not only the sloshing natural frequency f _T but also the damping capacity of this U-shaped tank dynamic vibration absorber 1 is used. Is also a very important factor. That is, FIG. 4 shows the vibration response of the target structure according to the logarithmic damping rate δ _T of the U-shaped tank dynamic vibration absorber 1.
In this graph, the broken line is the logarithmic decay rate δ _T = 0.07.
And the solid line shows the vibration response when the logarithmic damping rate δ _T = 0.4. Looking at this graph, the solid line clearly has a lower vibration response of the target structure than the broken line, and even if the natural frequency is the same,
It can be seen that the vibration of the target structure can be largely damped by setting the damping capacity of the dynamic vibration absorbing device 1 to an optimum value.

From the above description, in order to increase the reduction effect of the target structure, it is necessary to optimally adjust the sloshing natural frequency f _T and the damping capacity of the U-shaped tank dynamic vibration absorber 1. Natural frequency f _{T of} sloshing is effective length of water column L
It can be changed easily by adjusting e.
Has a relatively low viscous resistance and therefore has a small damping capacity, that is, the logarithmic damping rate of water is about δ _w = 0.05 to 0.1. Therefore, when water is stored in the U-shaped tank 2, the vibration response to the vibration energy is high, that is, a large amplitude is generated, and the damping effect is low. On the other hand, the optimum logarithmic decrement when applied to structures such as high-rise buildings is δ
It is said that _T = about 0.3 to 0.6 is necessary. That is, the logarithmic decrement [delta] _T required, the value of the logarithmic decrement of [delta] _W of the water is far.

In order to increase the logarithmic damping rate of the dynamic vibration absorber 1, it is possible to accommodate a fluid having a large viscous resistance in the U-shaped tank 2, but there is a limit to the type of fluid that can be used, and a large amount of fluid is available. Since a liquid is used, there is a problem that it becomes expensive.

On the other hand, in order to increase the flow resistance of water, conventionally, as shown in FIG. 3, a flow regulating member for regulating the flow of the water 3, for example, a wire mesh 4 made of stainless steel or the like is mounted in the U-shaped tank 2. Means have been adopted. The wire mesh 4 creates a flow resistance of water when the water 3 passes through the wire mesh 4 and attenuates the kinetic energy of the water due to this resistance, thereby reducing the vibration of the water generated in the U-shaped tank 2.
Vibration can be converged more quickly than when no is attached. However, if the damping performance is made too large, the dynamic vibration absorbing device 1 becomes a rigid body, and it becomes impossible to effectively absorb the vibration energy of the target structure. For this reason,
An optimum damping effect can be obtained by adjusting the number of wire nets 4 installed to adjust the passage resistance of water.

[0008]

However, in the conventional case, when adjusting the number of wire nets 4 to be installed in order to adjust the logarithmic decrement δ _T , vibration is applied by a vibration test, etc. And change the number of wire nets 4 to be attached, and again apply vibration in a vibration test or the like to measure the damping rate, and thereby repeat the work of adjusting the number of wire nets 4 to be attached, that is, the trial-and-error method adjustment work. There was a need.

The optimum number of the wire nets 4 obtained by such adjustment may be about 30 to 60. In this case, not only a large number of the wire nets 4 are required, but also this attachment labor is troublesome. In addition, there is a drawback that the weight of the U-shaped tank type dynamic vibration absorber 1 becomes heavy.

Further, in order to adjust the number of the wire nets 4, it is necessary to repeat the test many times, and therefore the test cost is high, and at the same time, the work is troublesome.

The present invention has been made in view of the above circumstances. The object of the present invention is that the adjustment work for obtaining the optimum damping characteristics is easy, the manufacturing cost of the tank is low, and the test is troublesome. An object of the present invention is to provide a U-shaped tank type dynamic vibration-damping device that does not hang.

[0012]

In order to solve the above-mentioned problems, the invention according to claim 1 has a U-shaped tank in which both ends are open and liquid is stored therein, and at least one end of the U-shaped tank. And a cover lid having an air chamber formed above the liquid surface of this end portion, a through hole formed in the cover lid, and an aperture ratio changing mechanism capable of freely adjusting the opening area of the through hole, It is a U-shaped tank type dynamic vibration absorbing device characterized by comprising:

According to the first aspect of the present invention, at least one end of the U-shaped tank containing the liquid is provided with a cover lid having an air chamber above the liquid surface of the end, and the through-hole is formed in the cover lid. Therefore, even if the water in the U-shaped tank rocks, the rocking of the liquid can be suppressed by the air resistance generated by the outflow and inflow of the air from the through hole. Moreover, since the opening area of the through hole can be freely adjusted by the aperture ratio adjusting mechanism, if the opening area of the through hole is adjusted, an appropriate damping effect due to the air resistance can be obtained, which is suitable for the target structure. Natural frequency and damping performance can be obtained. Therefore, the structure of the U-shaped tank becomes simple, the manufacturing cost becomes low, and the adjustment work of the damping performance becomes easy.

According to a second aspect of the present invention, the aperture ratio changing mechanism is capable of adjusting the aperture ratio of the through hole with respect to the area of the liquid surface within a range of 1/20 or less. It is a tank type dynamic vibration absorber.

According to the second aspect of the invention, the aperture ratio of the through hole to the area of the liquid surface is adjusted within the range of 1/20 or less, so that the optimum damping effect can be obtained. According to the experiments by the inventors, the damping performance cannot be significantly adjusted in the range where the aperture ratio of the through hole exceeds 1/20.

[0016]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described below based on an embodiment shown in FIGS. FIG. 1 is a side sectional view and a plan view of a U-shaped tank dynamic vibration absorber, and FIG.
It is a figure which shows the experimental result of a character tank type dynamic vibration absorber.

A U-shaped tank type dynamic vibration absorber 10 shown in FIG.
The U-shaped tank 11 constituting the main body is made of a material such as a thin metal plate, and its shape is U-shaped with both ends open. A liquid such as water 12 is stored inside the U-shaped tank 11. In the U-shaped tank 11, the sloshing natural frequency f _T can be adjusted by changing the amount of the water 12 in the U-shaped tank 11 by using the above-described number 1.

A cover lid 1 is provided on both ends of the U-shaped tank 11.
3, 13 are attached, and these cover lids 13, 1
3 forms air chambers 14, 14 between the upper surface of the water 12 and the cover lids 13, 13.

Air chambers 14, 1 are provided in the cover lids 13, 13.
4 are formed with through holes 15 and 15 for communicating the outside with each other so that air can freely flow in and out between the air chambers 14 and 14 and the outside. These through holes 15, 15
Is formed in a size corresponding to about 1/20 of the area of the liquid surface inside the U-shaped tank 11. This cover lid 13,1
Slide plates 16, 16 are slidably attached to 3 as an aperture ratio adjusting mechanism. This slide plate 1
6 and 16 are such that the aperture ratio of the through holes 15 and 15 can be freely adjusted from the fully open state to the fully closed state. When the through holes 15 and 15 are fully opened, the through hole 15
The opening ratio with respect to the liquid surface is 1/20. Guide grooves 17, 17 are formed on the left and right sides of the slide plates 16, 16 along the sliding direction, and fixing bolts 18, 18 are inserted into the guide grooves 17, 17. The fixing bolts 18, 18 are cover lids 13, 13
It is designed to be screwed on. Slide plates 16, 16
Is slidable to an appropriate position by the guide action of the fixing bolts 18, 18 and the guide grooves 17, 17, and is fixed to the cover lids 13, 13 by tightening the fixing bolts 18, 18 at this sliding position. ing. This allows the slide plates 16 and 16 to freely adjust the aperture ratio (opening area) of the through holes 15 and 15.

The U-shaped tank dynamic vibration absorber 10 having the above-described structure is attached to a bridge, a high-rise building structure, or a structure such as a ship. Then, when vibration is transmitted from the structure, the water 12 in the U-shaped tank 11 swings, that is, water flows back and forth in the U-shaped tank 11, and the water surface moves up and down at both ends. When the water surface moves upward, the air in the air chamber 14 in contact with this surface is compressed, and this air is pushed out through the through hole 15. Further, when the water surface moves downward, the air chamber 14 in contact with this surface has a negative pressure and sucks air from the outside through the through hole 15.

The inflow and outflow of the air is regulated according to the opening condition of the through holes 15, 15, that is, the inflow and outflow of the air is restricted by the throttling action of the through holes 15, 15. As a result, the water 12 in the U-shaped tank 11 suppresses the rocking and damps the wave energy.

When the amount of water 12 stored in the U-shaped tank 11 is adjusted, the effective length Le of the water column changes, so that the above-mentioned U-shaped tank type dynamic vibration absorber 10 with respect to the natural frequency of the structure.
The natural frequencies f _T of the can be matched. Further, after adjusting the amount of the water 12, the slide plates 16 and 16 provided in the through holes 15 and 15 are slid to appropriate positions, and the opening area of the through holes 15 and 15 is adjusted. δ _T can be adjusted to an optimum value. For this reason, this U-shaped tank type dynamic vibration absorbing device 10 can effectively reduce the vibration of the structure.

The experimental results using the U-shaped tank 11 constituting the U-shaped tank type dynamic vibration absorber 10 are shown in the graph of FIG. 2, which will be described below. In this graph, the vertical axis is the logarithmic damping rate δ _T and the sloshing natural frequency f
_T is taken and the horizontal axis shows the opening ratio with respect to the area of the liquid surface of the U-shaped tank 11 on a logarithmic scale. The solid line indicates the logarithmic damping rate δ _T , and the broken line indicates the natural frequency f _T.

In this experiment, no change in the logarithmic attenuation rate δ _T is observed when the aperture ratio of the through holes 15, 15 to the liquid surface area is from 1/1 to less than 1/20. That is,
When the size of the through holes 15 and 15 is large, air can freely flow in and out, and the orifice action that regulates the flow of air does not occur. Therefore, the action of suppressing the wave motion is low, and the viscous resistance does not increase, so logarithmic damping is performed. The rate δ _T does not change much.

On the other hand, when the opening area of the through holes 15, 15 is reduced from 1/20 to the area of the liquid surface,
As can be seen from the graph, the logarithmic decay rate δ _T gradually increases, and the damping effect due to the air resistance comes to be obtained. The value of this logarithmic decay rate δ _T is the through hole 15 with respect to the liquid surface area,
Although the opening ratio of 15 becomes larger and larger as it goes to 0, if the opening ratio is completely set to 0 (closed), the air in the air chambers 14, 14 does not go in and out of the outside, so that a reduction effect due to the inflow and outflow of air is obtained. However, the attenuation rate when the aperture ratio is large, that is, the point returns to point A in the graph.

From the above, if the aperture ratio of the through holes 15, 15 to the liquid surface area is adjusted in the range of 1/20 to more than 0, the logarithmic attenuation rate δ _T can be increased and the optimum range is obtained. A large logarithmic damping rate can be obtained, which is effective for damping the vibration of the target structure.

When the aperture ratio with respect to the liquid surface area of the through holes 15 and 15 is changed, the natural frequency f _T of sloshing slightly changes. This is because the movement of the liquid is regulated by the increase in the damping due to the air resistance.
However, this natural frequency f _T is equal to the effective length Le in water.
Since it can be adjusted by changing, if a deviation with respect to the natural frequency of the structure occurs, it can be easily matched with the natural frequency of the structure by adjusting the amount of water 12.

When the opening ratio of the cover lids 13 and 13 is set to 0 (closed), the air in the air chambers 14 and 14 becomes a spring, so that the sloshing natural frequency increases as indicated by point B in the graph. .

In the case of the U-shaped tank type dynamic vibration absorber 10 having the above-mentioned structure, the natural frequency of the target structure and the natural vibration of the U-shaped tank type dynamic vibration absorber 10 are adjusted only by adjusting the amount of the water 12. The number can be easily matched with the conventional one.

Further, through holes 15, 15 having an opening ratio of 1/20 with respect to the liquid surface area are formed in the cover lids 13, 13 and the opening ratios of the through holes 15, 15 can be adjusted by sliding. Aperture ratio of 1/2 due to slide plates 16 and 16
Since it is possible to appropriately adjust from about 0 to the fully closed state, by adjusting these slide plates 16, 16, it is possible to suppress the oscillation of the liquid due to the air resistance generated by the inflow and outflow of air, and the natural frequency. It is possible to obtain the optimum damping effect according to the above.

Further, the cover lids 1 are provided on both ends of the U-shaped tank 11.
Since it is a simple configuration in which only the U-shaped tank 3 and 13 are attached and the other parts of the U-shaped tank 11 do not have to be changed, the structure of the U-shaped tank dynamic vibration absorber 10 is simple and the manufacturing cost is low. Become.

The present invention is not limited to the above-described embodiment, and for example, a cover lid may be formed only on one end of the U-shaped tank 11, and the through holes 15 formed in the cover lids 13 and 13. Since the slide plates 16 adjust the aperture ratios of the sliders 15 and 15, the aperture ratios may be formed to be large in advance. Also, U
The liquid stored in the character tank 11 is not limited to water, and may be any liquid that is inexpensive and easy to handle. In particular, a highly viscous liquid is effective in increasing the damping effect. Besides, various modifications can be made without changing the gist of the present invention.

[0033]

As described above, according to the first aspect of the present invention, when the liquid in the U-shaped tank sways, the sway of the liquid can be suppressed by the resistance of the air flowing in and out through the through hole. . Moreover, since the opening area of the through hole can be adjusted by the opening ratio adjusting mechanism, an appropriate air resistance can be obtained by adjusting the opening area of the through hole, so that the damping performance can be adjusted. Therefore, it is possible to obtain the optimum natural frequency and damping capacity for the target structure. In addition, such a configuration simplifies the structure of the U-shaped tank, reduces the manufacturing cost, and facilitates the adjustment work of the damping performance. Further, according to the second aspect of the present invention, the aperture ratio of the through hole with respect to the area of the liquid surface is adjusted within the range of 1/20 or less, so that the optimum damping capacity can be obtained.

[Brief description of the drawings]

1A and 1B show a configuration of a U-shaped tank type dynamic vibration absorbing device showing an embodiment of the present invention, wherein FIG. 1A is a sectional view and FIG. 1B is a plan view.

FIG. 2 is a view showing an experimental result of the U-shaped tank dynamic vibration absorber of the same embodiment.

FIG. 3 is a sectional view showing a configuration of a conventional U-shaped tank type dynamic vibration absorber.

FIG. 4 is a diagram showing the vibration response of the target structure according to the logarithmic decrement δ _T of the dynamic vibration absorber.

[Explanation of symbols]

 10 ... U-shaped tank type dynamic vibration absorber 11 ... U-shaped tank 12 ... Water 13 ... Cover lid 14 ... Air chamber 15 ... Through hole 16 ... Slide plate 17 ... Guide groove 18 ... Fixing bolt

Claims (2)

[Claims] 1. A U-shaped tank having both ends opened and a liquid stored therein, and a cover provided at at least one end of the U-shaped tank and having an air chamber formed above the liquid surface of this end. A U-shaped tank type dynamic vibration absorbing device comprising: a lid; a through hole formed in the cover lid; and an aperture ratio changing mechanism capable of freely adjusting an opening area of the through hole. 2. The U-shaped tank type dynamic vibration absorber according to claim 1, wherein the aperture ratio changing mechanism is capable of adjusting the aperture ratio of the through hole with respect to the area of the liquid surface within a range of 1/20 or less. apparatus.