JP2000353880A - Damper for structure - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a damper for structure in which natural oscillation can be regulated through a simple arrangement or arbitrarily and an appropriate damping can be attained easily. SOLUTION: An insulator type arrestor 1 is supported fixedly at the top plate part 2a of a frame 2. The arrestor 1 comprises a nonlinear resistor element of metal oxide (not shown) contained in a hollow insulating tube 1a. The arrestor 1 and the frame 2 constitute an objective structure for damping oscillation. The damper 3 comprises three cables 4 suspended from the top plate part 2a of the frame 2, and spacers 5 for separating the three cables 4 at two intermediate positions and at the end part thereof. Upon occurrence of earthquake, seismic energy is absorbed through oscillation of the cables 4 and oscillation of the frame 2 mounting the arrestor 1 is suppressed. The cable 4 comprises strands 4a which are oscillated and deformed upon occurrence of earthquake and a substantially optimal damping coefficient is obtained through friction among the strands.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a vibration damping device for a structure, such as a structure to be damped, on which an electric device having an insulator or an insulator tube is mounted.

[0002]

2. Description of the Related Art Generally, the natural frequency of a power insulator / porcelain pipe mounted on a gantry is within a natural frequency range (0.
5 to 10 Hz), which tends to cause some resonance and increase the response.

As a countermeasure, for example, the natural frequency is increased as much as possible by the following method. With regard to the gantry, measures are taken to widen the gantry, reduce the height of the gantry, adopt a large cross-sectional shape as a gantry constituent member, insert a large number of cross beams and oblique beams, and increase rigidity. Take measures such as adopting large diameter insulators and insulators. However, there was a limit in increasing the natural frequency.

On the other hand, aggressive application of a vibration damping device has not been adopted because of a complicated structure, a demand for a long-term operation, and a demand for reliable operation in the event of an earthquake. .

What is similar in principle to the present invention is a vibration damping device using a pendulum. This is because by adding a pendulum device close to the natural frequency of the structure to be damped to the device whose vibration response is to be reduced, that is, the structure to be damped, the vibration energy input as disturbance is applied to the structure to be damped. It is intended to be absorbed by the pendulum damping device without telling.

FIG. 7 is a block diagram showing a conventional pendulum type vibration damping device described in, for example, the document “Seismic Design and Structural Dynamics” edited by the Japan Society of Mechanical Engineers (Nippon Kogyo Shuppan, published in September 1985). In FIG. 7, a gantry 2 which is a structure to be damped
The pendulum 10 of the pendulum device 7 is connected via a connecting plate 6. The pendulum 10 has a rod portion 10a, one end of which is rotatably supported on a support base 8 by a pin 9;
And a weight 10b fixed to the tip of the rod, and the connecting plate 6 is connected to the rod 10a by a pin.

[0007] Such a pendulum type vibration damping device operates as follows. As an example of vibration, when an earthquake is encountered, the seismic force from ground motion causes the gantry 2 to vibrate. At this time, if there is no pendulum type vibration damping device, the natural frequency of the gantry 2 alone falls within the natural frequency range of the earthquake If so, the gantry 2 resonates and large vibrations are generated. On the other hand, if a pendulum type vibration damping device having a natural frequency close to the natural frequency of the stand 2 alone is provided,
The seismic energy input to the gantry from the ground motion is first absorbed by the pendulum type vibration damping device, and the transmission of the seismic energy to the gantry 2 is reduced, and the response of the gantry 2 can be reduced.

[0008]

In the above-described conventional pendulum type vibration damping device, it is necessary to make the gantry 2 rigid in order to mount the pendulum type vibration damping device. For this reason, the weight of the gantry 2 increases and the manufacturing cost also increases.

A pendulum 1 for absorbing seismic energy
In order to make the vibration response of zero as low as possible, a damping device (not shown in FIG. 7) such as an oil damper having an appropriate damping is required. Since it is necessary to design the mounting structure of the pins 9 of the support base 7 of the apparatus in consideration of environmental resistance such as corrosion and sticking, there is a problem that the vibration damping apparatus becomes complicated.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-described problems, and has a simple structure, a natural frequency can be arbitrarily adjusted, and a proper damping can be easily obtained. The purpose is to obtain a vibration damping device.

[0011]

In order to achieve the above object, a vibration damping device for a structure according to the present invention comprises a string-like elastic member suspended from a structure to be damped and having elasticity. It is provided. The string-shaped elastic member vibrates during an earthquake to absorb seismic energy and suppress vibration of the structure to be damped. Further, the natural frequency and the spring constant of the vibration damping device are set by setting the shape, the number, and the mass of the elastic member to predetermined values. Therefore, the configuration of the vibration damping device is simplified,
Also, the natural frequency can be set arbitrarily, and the setting of the spring constant is easy.

The elastic member is a cable in which a plurality of strands are twisted, and its mass is in the range of 1 to 5% of the equivalent mass of the structure to be damped, and its natural frequency is controlled. It is characterized by being in the range of 95 to 99% of the natural frequency of the structure to be vibrated. When a cable is used as the elastic member and the mass and the natural frequency are practically set in the above ranges, the weight of the cable can be reduced and the vibration can be effectively suppressed. Also, due to friction between the wires generated when the cable is vibrated and deformed, an almost optimal damping constant is obtained, and it is not necessary to provide a separate damping device.

Further, the invention is characterized in that a plurality of cables are provided, and a spacer for separating the plurality of cables from each other is provided. By adjusting the spacer spacing,
The spring constant can be easily set.

[0014] Further, an additional mass is added to the cable. By adjusting the value of the added mass,
The natural frequency can be easily set.

The structure to be damped is a gantry and an electric device mounted on the gantry. Since electrical equipment often uses an insulator or an insulator tube that is vulnerable to vibration for insulation, it is effective to apply the electrical equipment to a gantry that supports the electrical equipment.

[0016]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiment 1 FIG. 1A is a configuration diagram of a vibration damping device applied to a mount on which an insulator type lightning arrester according to an embodiment of the present invention is mounted. FIG.
FIG. 2B is a detailed configuration diagram of the vibration damping device of FIG.
In FIG. 1A, an insulator type lightning arrester 1 is fixedly supported on a top plate 2 a of a gantry 2. The lightning arrester 1 contains a non-linear resistance element (not shown) formed of a metal oxide in a hollow insulator tube 1a. The lightning arrester 1 and the gantry 2 are the structures to be damped in the present invention.

The vibration damping device 3 includes three cables 4 (FIG. 1 (b)) suspended from the top plate 2a of the gantry 2 and three cables 4 at two places in the middle and at the end. It has three spacers 5 of a triangular shape (FIG. 1 (b)) which are separated so as not to contact. As shown in FIG. 1B, the cable 4 is formed by twisting a number of strands 4a made of steel, aluminum, copper, or the like.

The gantry 2 on which the lightning arrester 1 shown in FIG. 1 is mounted does not have the vibration damping device 3 and, when encountering an earthquake, resonates with the seismic wave and generates a large vibration. On the other hand, if the vibration damping device 3 is provided, the vibration of the gantry 2 and the lightning arrester 1 can be suppressed because the vibration damping device 3 absorbs the seismic energy.

Here, the principle of vibration damping of the vibration damping device 3 having the cable 4 will be described. For easy understanding of the explanation, consider a vibration model of a two-mass system shown in FIG. This is referred to as a tuned mass damper, and the idea is theoretically established. In FIG. 2, it is assumed that the mass point A, the spring A, and the damping A correspond to the lightning arrester 1 and the gantry 2 system. The mass B, the spring B, and the damping B
Cable 4 and spacer 5 system.

Here, a sinusoidal continuous wave that can best represent the vibration suppression effect as an earthquake input will be considered. In the vibration system of FIG. 2, the natural frequency determined by the mass point A and the spring A (corresponding to the natural frequency of the lightning arrester 1 and the gantry 2) is f0, and the natural frequency determined by the mass point B and the spring B is f1 (separated by the spacer 5). Cable 4
).

If the amplitude of the sine wave input to the vibration system of FIG. 2 is kept constant and the frequency is changed variously, the response characteristic of the mass point A becomes as shown in FIG. In FIG. 3, a curve C is a response characteristic when no vibration damping device is provided, and a curve D is a response characteristic when a vibration damping device is provided.

As shown in this figure, when the vibration damping device is provided, the response of the mass point A is considerably reduced. That is, when an appropriate additional vibration system (the cable 4 fixed by the spacer 5 in this embodiment) is selected and attached to the main vibration system, that is, the structure to be damped, the response of the main vibration system is considerably reduced. Can be.

The optimum value of the additional vibration system has been theoretically derived and is expressed by the following equations (1) and (2).
That is, the optimum natural frequency ratio r = (f1 / f0) = 1 / (1 + μ) (1) The optimum damping ratio ζ = √ (3μ / 8 (1 + μ)) (2)

Here, μ is the mass ratio (mass of mass B / mass of mass A), but the mass of each mass is not the total mass but an equivalent mass derived theoretically. Regarding the calculation of the equivalent mass, see, for example, the latest Seismic Structural Analysis by Akinori Shibata (Morikita Publishing Co., Ltd., June 1981)
Monthly).

The approximate application range is μ = 0.01 to
0.4 and ζ = 0 to 0.15. However, in application to an actual machine, it is better to reduce the mass ratio μ as much as possible (that is, to reduce the weight of the cable 4) to reduce the total weight of the vibration damping device 3. It is desirable because it leads to reduction and cost reduction.

From the above equations (1) and (2), the specific relationship between the mass ratio μ, the optimum natural frequency ratio r, and the optimum damping ratio ζ is calculated in a range that can be adopted in an actual design.
As shown in FIG. From this result, it is clear that the normal cable 4
Is considered to be about 0.06 to 0.13, the mass ratio μ is substantially in the range of 0.01 to 0.05, and the natural frequency ratio r is substantially 0.95 to 0. .99
It is appropriate from the viewpoints of the structure of the actual structure to be damped and the manufacturing of the damping device 3.

Under these optimum conditions, the characteristics corresponding to the curve D shown in FIG. 3, that is, the magnitudes of the two peaks can be made substantially equal and minimum. In an actual machine, the mass of the cable 4 may be determined so that the natural frequency ratio r is as close to 1 as possible. The required mass can be easily set by appropriately selecting the thickness and the number of the cables 4.

The setting of the spring constant for determining the natural frequency can be easily set by changing the number of spacers 5 and their intervals.

Regarding the required attenuation constant, since the cable 4 itself is a stranded wire obtained by twisting a plurality of strands 4a (FIG. 1B), the strand generated when the cable 4 is vibrated and deformed. It has been found that an almost optimal damping constant is obtained by the friction between 4a. Therefore, there is a great advantage that a damping device such as a conventional vibration damping device is not required.

As described above, if the cable 4 and the spacer 5 are selected to constitute the vibration damping device 3, the response of the lightning arrester 1 and the gantry 2 can be reduced even if an earthquake is encountered. Here, the sinusoidal continuous wave input has been described, but in the case of an actual seismic wave, the effect is sufficiently reduced although the reduction effect is lower than the response characteristics shown in FIG. If such a vibration damping device is employed, it is not necessary to increase the rigidity of the gantry 2 as in the related art. A further damping effect can be exhibited.

Embodiment 2 FIG. 5 is a configuration diagram showing a vibration damping device according to another embodiment of the present invention.
5A shows the case where the number of the cables 4 is two, and FIG. 5B shows the case where the number of the cables 4 is eight. Other configurations are the same as those of the first embodiment shown in FIG. Of course, one cable 4 may be used.

Embodiment 3 FIG. FIG. 6 is a configuration diagram showing a vibration damping device according to another embodiment of the present invention. In FIG. 6, weights 11 are provided at lower ends of the cables 4 respectively. Other configurations are the same as those of the first embodiment shown in FIG.

As described above, the setting of the magnitude of the mass for determining the natural frequency depends on the weight of the weight 11 in addition to the weight of the cable 4.
Can also be easily set.

In each of the above embodiments, the case where the structure to be damped is the lightning arrester 1 and its gantry 2 has been described. However, it is a gantry on which other electrical equipment such as a disconnecting switch, a bushing and a circuit breaker is mounted. The same effect can be obtained even with a general structure without being limited to the one equipped with the electric device.

[0035]

Since the present invention is constructed as described above, it has the following effects.

That is, since the string-shaped elastic member is suspended from the structure to be damped and provided with elastic string-shaped elastic members, the string-shaped elastic members vibrate in the event of an earthquake to generate seismic energy. Absorbs and suppresses vibration of the target structure. Further, by setting the shape, number, and mass of the elastic member to predetermined values, the natural frequency and the spring constant of the vibration damping device can be set. Therefore, the configuration of the vibration damping device is simplified, the natural frequency can be arbitrarily adjusted, and the spring constant can be easily set.

The elastic member is a cable in which a plurality of strands are twisted, and its mass is in the range of 1 to 5% of the equivalent mass of the structure to be damped, and its natural frequency is controlled. Since the characteristic frequency is in the range of 0.95 to 1 with respect to the natural frequency of the structure to be vibrated, a cable is used as the elastic member, and its mass and natural frequency are practically set in the above ranges. Therefore, the weight of the cable can be reduced, and the vibration can be effectively suppressed. Also, due to friction between the wires generated when the cable is vibrated and deformed, an almost optimal damping constant is obtained, and it is not necessary to provide a separate damping device. As a result, the vibration damping device becomes lightweight and simple.

Further, since a plurality of cables are provided and spacers are provided to separate the plurality of cables from each other, the spring constant can be easily set by adjusting the spacing between the spacers.

Further, since the additional mass is added to the cable, the natural frequency can be easily set by adjusting the value of the additional mass.

Since the structure to be damped is characterized by a gantry and an electric device mounted on the gantry, an insulator or a porcelain tube which is often vulnerable to vibration for insulation is used. It is effective when applied to a frame that supports.

[Brief description of the drawings]

FIG. 1 shows an embodiment of the present invention, in which FIG. 1 (a) is a configuration diagram showing a vibration damping device for a structure on which an electric device is mounted, and FIG. 1 (b) is a detailed configuration diagram of the vibration damping device. is there.

FIG. 2 is a vibration model of a two-mass system for explaining a vibration suppression principle.

FIG. 3 is a characteristic diagram showing a response characteristic obtained from the vibration model of FIG.

FIG. 4 is a diagram showing a relationship among a mass ratio, an optimal natural frequency ratio, and an optimal damping ratio.

5A and 5B are configuration diagrams showing a vibration damping device according to another embodiment of the present invention. FIG. 5A shows a case where there are two cables, and FIG. 5B shows a case where there are eight cables. is there.

FIG. 6 is a configuration diagram showing a vibration damping device according to another embodiment of the present invention.

FIG. 7 is a configuration diagram showing a conventional pendulum type vibration damping device.

[Explanation of symbols]

1 lightning arrester, 1a insulator tube, 2 gantry, 2a top plate, 3
Damping device, 4 cables, 4a strands, 5 spacers, 11 weights.

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 3J048 AA05 AD06 BE10 BF09 CB01 DA01 EA13 EA38 4E360 AB02 AB52 AB64 EA05 EB03 EC03 ED17 FA02 GA14 GA28 GB99

Claims (5)

[Claims] 1. A vibration damping device for a structure which is suspended from a structure to be damped and provided with a string-like elastic member having elasticity. 2. The elastic member is a cable in which a plurality of strands are twisted, the mass of which is in the range of 1 to 5% of the equivalent mass of the structure to be damped, and the natural frequency of which is controlled. The structure vibration damping device according to claim 1, wherein the vibration frequency is in a range of 95% to 99% of the natural frequency of the structure to be vibrated. 3. The vibration damping device for a structure according to claim 2, wherein a plurality of cables are provided, and a spacer is provided to separate the plurality of cables from each other. 4. The structure vibration damping device according to claim 2, wherein an additional mass is added to the cable. 5. The vibration damping device for a structure according to claim 1, wherein the structure to be damped is a gantry and an electric device mounted on the gantry.