JPH0426004B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Application Field] The present invention relates to a vibration damping device for vertical members such as lighting poles installed on roads, bridges, etc. [Prior Art] In this type of lighting pole, resonance phenomena occur due to wind, earthquakes, passing vehicles, etc., causing large vibrations.
It may cause damage to lighting lamps and lighting pillar members. Conventionally, two methods have been known as methods for preventing resonance phenomena. (1) A method of changing the natural frequency of the columnar body by changing the weight, shape, and rigidity of the vertical and/or horizontal members of the columnar body. (2) As seen in Utility Model Application Publication No. 59-24412,
A physical pendulum and a contact tool are installed in the lighting lamp so that the physical pendulum collides with the contact tool when vibrating.
A method to have a control effect. [Problems to be Solved by the Invention] However, all of the above conventional methods have the following problems. Method (1) not only reduces the degree of freedom in design, but also reduces the flexibility of the columnar body (lighting pole) because the excitation period acting on the columnar body changes depending on the wind speed when excitation is caused by wind, etc. Methods of changing weight, shape, and stiffness are less effective. Method (2) is effective in damping vibrations with a frequency that almost matches the natural frequency of the physical pendulum, but is ineffective against excitation forces with a wide frequency range caused by wind, etc. Less is. Moreover, the structure is somewhat complex, and it is economically difficult to install it on each of a large number of lighting poles, and it is difficult to store complex objects in the narrow space inside the lighting. , and if it is made small for storage, the vibration damping effect will not be sufficient. SUMMARY OF THE INVENTION Therefore, the main object of the present invention is to provide a vibration damping device for vertical members that can effectively cope with vibrations in a wide range of frequencies, exhibits a high damping effect regardless of the vibration direction, and has a simple and economical structure. Our goal is to provide the following. [Means for Solving the Problems] In order to solve the above problems, the present invention provides a vertical member that is attached to the outside or inside of the vertical member, or constituted by itself when the vertical member is a hollow member. A steel chain or wire rope is suspended with an unfixed free vibration part provided inside the vertical hollow member, and the steel chain or wire rope is fixed with an equal distance from the inner wall of the vertical hollow member. At the same time, the vertical hollow member is arranged at a plurality of positions in the longitudinal direction where the vibration increases under the vibration mode in which the vertical member vibrates. [Function] In the present invention, a free vibration part is provided inside a vertical hollow member to suspend a steel chain or wire rope, and the distance between the steel chain or wire rope and the inner wall of the vertical hollow member is equalized. It is fixed as a state. Therefore, when external excitation is applied to the vertical member, the steel chain and the like vibrate together with the vertical hollow member. During this vibration,
The free vibrating section of the steel chain vibrates in a different manner than the vertical hollow member. As a result, the free vibrating part of the chain collides with the inner wall surface of the vertical hollow member, the vibration energy of the vertical hollow member, in other words the vibration energy of the vertical member, is dissipated, and the vibration of the vertical member is damped. In addition, in the present invention, since a steel chain or the like is used as the colliding body, the chain has easy flexibility at its link joints, and the wire rope has flexibility, so it can be used uniformly in any direction. Because it vibrates, it can exert a damping effect regardless of the direction of vibration. In addition, since it vibrates in various vibration shapes depending on the frequency and collides with the inner wall of the hollow member, it exhibits a damping effect against excitation forces over a wide frequency range. Further, since the distance between the steel chain and the inner wall of the vertical hollow member is equal, a uniform vibration damping effect is exerted over the entire circumferential direction. Furthermore, in the present invention, based on the findings based on the examples, in order to obtain a large vibration damping effect, it is recommended to install the vibration damping device at the position showing the maximum displacement amplitude, and to install it separately in order to deal with each vibration mode. Since it has been found to be effective, it has been decided to arrange the vertical members at a plurality of longitudinal positions where the vibrations increase under the vibration mode in which the vertical member vibrates. [Specific Examples of the Invention] The present invention will be explained in more detail below with reference to the drawings. Fig. 2 shows an example of the entire lighting column 1, in which a vertical member 3 made of, for example, an octagonal steel pipe is erected on a foundation 2, and a horizontal member 4 overhangs almost horizontally from its upper end. A lighting lamp 5 is attached to the projecting end of the member 4. 6 is a reinforcing stay. The present invention aims at the vibration damping effect of the vertical member 3 described above. For this purpose, in the illustrated example, the vibration damping devices X are attached at two locations outside the vertical member 3. That is, the vibration damping device 3) to be fixed to the vertical member 3. The hollow member 10 is provided externally and parallel to the vertical member 3. The chain 11 is suspended and fixed by a hook 15 fixed to an end plate 14 bolted to a nut 13 welded to the upper outer periphery of the hollow member 10. Thus, the chain 11 has a free vibration section other than the hook attachment section. In such a vibration damping device, when the vertical member 3 is now excited by an external factor, the hollow member 10 also vibrates, and the chain 11 inside thereof also vibrates. The chain 11 as a whole vibrates freely, and its mode of vibration is almost independent of the vibration of the hollow member 10 due to inertial force or the like. As a result, chain 11
collides with the inner surface of the hollow member 10, and at this time, a part of the vibrational energy of the hollow member 10, in other words the vertical member 3, is dissipated and damped. Incidentally, from the viewpoint of strength and durability, it is desirable to use a steel pipe as the hollow member, and it is also desirable to use steel for the chain, but this increases the noise of mutual collision. Therefore, it is preferable to line the outer surface of each link of the chain 11 with rubber, to cover the entire chain 11 with a fairly soft tube, for example, a rubber tube, or to line the inner surface of the hollow member 10 with, for example, a rubber-based material. The vibration damping device X should preferably be installed at the maximum amplitude point of the vertical member, such as at the top end of the lighting column shown in FIG. Considering secondary and subsequent vibration modes, the vibration damping device X may also be provided, for example, in the central portion of the vertical member 3, as shown in FIG. This point will be explained in detail later. As inferred from the vibration damping principle described above, a flexible wire can be used instead of the chain 11 as long as it is relatively heavy and has sufficient flexibility; Flexibility per thickness is somewhat difficult. Also, the fourth
As shown in the figure, for example, sand 16B is attached to the bag body 16A.
The suspension member may also be made of a material filled with iron powder and connected by a wire 16C. However, the steel chain 11 is optimal because it can easily bend in all horizontal directions due to its structure. On the other hand, when the vertical member 3 is hollow, the chain 11 may be suspended within the vertical member 3 by using the vertical member 3 itself as a hollow member without preparing a separate hollow member 10. Alternatively, a hollow member may be installed inside the vertical member 3, and the chain may be suspended within the hollow member. If the aesthetic appearance is important, an interior design is preferable. However, if the structure for storing and fixing the damping device is complicated and it is difficult to install it internally, an exterior method in which the damping device is mounted outside the vertical member 3 is desirable. It is desirable that the cross-sectional shape of the hollow member 10 is substantially circular. This point will be considered next. First, for comparison, as shown in FIGS. 5 and 6, circular and square hollow members 10, 10'
Considering that, we set the conditions that their wall thickness and weight are the same, and the outer diameter of the circular hollow member Ro = 89.1 mm,
Assuming wall thickness t = 4.2 mm, inner diameter Ri = 80.7 mm, the square hollow member has outer dimension Xo = 70.9 mm, wall thickness t = 4.2 mm,
Inner dimension Xi = 62.5mm. Assume that the same chain with a nominal diameter of 16 mm and one link size of 74.8 mm x 56 mm is installed in each of these chains. At this time, the separation distance (amplitude length) between the circular hollow member 10 and the chain 11 is constant at 24.7 mm in all directions, whereas in the case of the square hollow member 10', the amplitude length of the chain 11 is 6.5 mm. Varies between ~25.8mm. However, according to the inventors' actual measurements, the relationship between the amplitude length (the distance between the chain and the hollow member) and the attenuation constant is as shown in FIG. According to Figure 8, the damping constant in the case of a circular hollow member is constant at 0.94% for vibrations in all directions, while the damping constant in the case of a square hollow member is R-R.
In the case of the direction, it is 0.95%, which is almost the same as in the circular case, but in the case of the P-P direction or the Q-Q direction, it is 0.83%, which is a 12% decrease in the damping constant compared to the case of a circular hollow member. . Consider that under certain design conditions, the damping constant of a square hollow member may be 12% lower than that of a circular hollow member, and that the damping effect differs depending on the vibration direction. It is clear that a circular shape is more suitable when it is desired to obtain a uniform damping effect in all directions. In addition, in the above comparison, a square was used as the rectangular hollow member, but a square is originally close to a circle, so
It is clear that the above-mentioned difference becomes even more obvious when considering, for example, rectangular shapes with different side ratios. 9 to 11 show examples of vibration damping devices with further different aspects. FIG. 9 is basically the same as the example in FIG. 4, but a protrusion 17 is inserted into the hollow member 10. The aim is to obtain a control effect over a wide range of vibration frequencies by changing the length of the protrusion. In FIG. 10, the shape of the bag body 16A is changed to achieve the same effect. In FIG. 11, mounting plates 18A and 18B are provided within the vertical member 3, and the chain 11 is arranged in a V-shape with slack between them. In this example, the chain 11 is fixed to the upper and lower mounting plates 18A and 18B, but only the upper mounting plate 18A may be fixed. The vertical members targeted by the present invention are not limited to the above-mentioned lighting pillars, but for example, the 12th
The suspension towers 19 and the like in the suspension bridges shown in Figures a and b can also be targeted. 20 is a cable, and 21 is a hanger rope. [Example] Next, the effects of the present invention will be clarified through examples. In particular, the mounting location of the vibration damping device mentioned in the above description and the vibration damping effect depending on the presence or absence of the vibration damping device will be explained using forced vibration experiment results. [Example 1] The target was a lighting column with the dimensions and shape shown in Figure 13 (weight and weight).
750Kg), this was fixed to the foundation, an exciter was attached to the upper end of the vertical member, and an accelerometer was attached at the positions shown in the figure. At this speed, we investigated the presence or absence of a vibration damping device and its installation location. The vibration damping device used is an exterior type, and its hollow member (exterior tube) has an outer diameter of 76.3 mm.
Wall thickness: 4.2mm, length: 1.1mm, weight: 8.2Kg, chain nominal diameter: 16mm, 1 link size: 74.8 x 56
mm, weight: 5.56Kg, length: 1.0m.
The relationship between displacement amplitude/excitation force and measurement position in each vibration mode is shown in FIGS. 14 to 16. Note that with a damping device means that the damping device X is installed at position A.
This is a case where two vibration damping devices X are installed at position B. Further, the natural frequencies in each vibration mode are shown in Table 1.

[Table] From the results, it was found that the device of the present invention has a high vibration damping effect on the secondary to quartic vibration modes, and that the vibration damping effect can be obtained over a wide range of vibration frequencies. . (Example 2) When the vibration damping effect was investigated by changing the mounting position and number of vibration damping devices, the effects shown in FIGS. 17 to 19 were obtained, and the following was found.・In order to obtain a large vibration damping effect, it is more effective to install a vibration damper at the position where the maximum displacement amplitude occurs than to increase the weight of the chain.・In order to deal with each vibration mode, it is desirable to install the vibration damping device in separate mounting positions A and B. This will allow you to obtain an average and high vibration damping effect in each vibration mode. I can do it. (Example 3) A free vibration experiment was conducted in the manner shown in Figure 20,
We investigated the difference in damping effects between chains and wire ropes installed inside hollow members. The specifications of the hollow member 10 are an outer diameter of 34.0 mm and a wall thickness of 3.4 mm.
mm, inner diameter 27.2mm, length 2.3m, weight 5.91Kg.
In addition, the length of the chain is 37 mm as the dimension of 1 link.
mm x width 16 mm, length 50 cm, and weight 200 g. The wire rope has an outer diameter of 11.2 mm and a length of 50 mm.
cm, and weighs 205g. In the experiment, the upper end of the hollow member was pulled by hand and instantly released to allow the hollow member to vibrate freely, and the vibration was measured by an accelerometer 22 attached to the upper end. The results are shown in Table 2.

〔Effect of the invention〕

As described above, according to the present invention, a large vibration damping effect can be obtained over a wide frequency range and regardless of the vibration direction, and the structure is simple and economical.

[Brief explanation of drawings]

Figure 1 is a front view of an exterior-type vibration damping device, Figure 2 is a front view of an example of installation on a lighting pole, Figure 3 is an enlarged longitudinal sectional view of the main part of Figure 1, and Figure 4 is a vibration damping device. 5 to 7 are explanatory diagrams of the chain amplitude due to differences in the shape of the hollow member, and FIG. 8 is a correlation diagram between the separation distance between the chain and the hollow member and the attenuation constant, 9 to 11 are longitudinal cross-sectional views of vibration damping devices with further different aspects, FIG. 12a is a front view of a hanging tower as another example of an installation target, FIG.
The figure is a front view of the lighting column used in the forced vibration experiment.
4 to 19 are experimental results, and FIG. 20 is a diagram of the free vibration experiment. 1... Lighting column, 3... Vertical member, 10... Hollow member, 11... Chain, 12... Mounting piece, 16
A...Bag body, 16B...Sand, 16C...Wire,
19... Hanging tower, X... Vibration damping device.

Claims (1)

[Claims] 1. A steel chain or wire rope with an unfixed free vibrating part inside the vertical hollow member, which is attached to the outside or inside of the vertical member, or constituted by itself when the vertical member is a hollow member. is suspended, and the distance between the steel chain or wire rope and the inner wall of the vertical hollow member is fixed in an even state, and the vibration of the vertical hollow member increases under a vibration mode in which the vertical member vibrates. A vibration damping device for a vertical member, characterized in that it is arranged at multiple positions in the longitudinal direction.