JPH0472949B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a cylindrical body having a vibration prevention function such as a lighting pole, a lightning rod, a telephone pole, a steel pipe pile, a chimney, a pillar, etc.

[Conventional technology]

In this type of columnar body, fluids such as wind and currents cause a resonance phenomenon and shake greatly, which in the case of lighting columns can cause damage to the lighting lamp and lighting column members, and in general columns, it can also cause fatigue of the steel material. This may cause breakage, collapse, etc.

It is known that when an external circular columnar body is placed in an airflow, it vibrates (vortex excitation) due to Karman vortices. The following several methods are known as measures to prevent vibrations caused by this Karman vortex.

(1) As shown in Figures 13 and 14, the columnar body P
A method of wrapping a rope 50 and ribs 51 in a spiral shape.

(2) A method of attaching fin-like protrusions 60 intermittently as shown in Fig. 15.

(3) As shown in Figure 16, a flat plate 7 is attached to one side of the columnar body P.
0 parallel to the generatrix at a predetermined interval d, specifically d
= D/24 to D/2 (D is the pipe diameter) and continuous mounting method (see Japanese Patent Application Laid-Open No. 53-88227).
(hereinafter referred to as prior art).

[Problem that the invention seeks to solve]

However, with methods (1) and (2) above, in the case of structures that require aesthetic appearance, such as lighting pillars, the presence of protrusions gives a sense of discomfort, resulting in an extremely poor appearance, and the drag coefficient is significantly increased, which is not desirable.

On the other hand, in the method (3) as well, the flat plate must be attached over the entire length of the cylindrical body, which requires time and effort to manufacture, and the manufacturing cost is also high. Furthermore, since the flat plate is attached only to one side of the columnar body, the appearance is unbalanced, and the both edges of the flat plate hit against each other during transportation, making it difficult to handle. Furthermore, as is clear from Figure 9 of the above-mentioned publication, it is only effective when the angle of attack α of the wind is −4° < α < 4°, and is not considered to be effective over a wide range of angles of attack. It will be done.

Therefore, the main object of the present invention is to provide a method that does not damage the appearance, has excellent handling properties, is effective over a wide range of angles of attack, has a large vibration damping effect, is inexpensive to manufacture, and has a manufacturing cost that is low in manufacturing costs. The purpose is to provide a columnar body that is easy to form.

[Means for solving problems]

In order to solve the above problem, the device of the present invention is provided at a longitudinal position where the amplitude increases under the vibration mode in which a single external circular columnar body vibrates, and at outward symmetrical positions on both sides of the position. The present invention is characterized in that two circular arc plates for damping are attached at a predetermined distance from the outer surface of the columnar body so that the arcs thereof are located substantially concentrically with the columnar body.

[Effect]

In the present invention, the central angle of the circular arc plate is limited to a range of 80 to 90 degrees because if the opening angle is small, the damping effect will be small, and if the opening angle is large, the appearance will be impaired. Therefore, the arc plate appears to be integrated with the columnar body, so that the appearance is hardly impaired. Furthermore, since the columnar body is surrounded by an arcuate plate, it has excellent handling properties during transportation.

As a result of conducting a wind tunnel experiment described below under the shape of the circular arc plate described above, it was found that two circular arc plates for vibration damping were arranged so that their arcs were located substantially concentrically with the columnar body, and the circular arc plates and the columnar body The velocity of the separation shear layer of the fluid flowing around the cylindrical body can be increased by attaching it so that the distance d from the surface is 15 to 28% as a ratio (d/D) to the outer diameter D of the cylindrical body. By making the slope gentler, the amplitude of the Karman vortex is reduced to 1/1 compared to the case without the arc plate.
It can be reduced by 10 to 1/20, and a suppression effect can be expected over a wide range of wind directions.

Regarding the mounting position of the columnar body of the circular arc plate in the longitudinal direction, based on the knowledge of the test results described later, for example, it is possible to achieve a sufficient effect by installing it only at the location where the vibration amplitude is large in the assumed vibration mode, and the manufacturing process This simplifies the process and provides an excellent appearance.

[Specific examples of the invention]

The present invention will be explained in more detail below with reference to the drawings.

As shown in FIG. 3, the vibration damping device X of the present invention is installed at, for example, two locations where the displacement amplitude of the lighting column 1 is large. 2 is a columnar body (hereinafter also referred to as a column) having a circular outer surface, for example, a tube;
is a lighting lamp.

In the present invention, as shown in FIGS. 1 and 2, two vibration-damping circular arc plates 4, 4 are provided at outwardly symmetrical positions on both sides of the column 2 at a predetermined distance d from the outer surface of the column 2.
is installed so that its arc is located on the concentric circles of the two pillars.

In this mounting method, for example, as shown in FIG.
0 can be fixed by welding or the like, and bolts 11 can be fastened through insertion holes formed in the web portion of the mounting seat 10 and the circular arc plate 4, respectively.

Further, as shown in FIG.
Alternatively, it may be fixed to the pillar 2 by welding or the like.

As shown in FIG. 6, the bolts 11
It may also be concluded.

As shown in FIG. 7, the arcuate plates 4, 4 are fixed to the outer surfaces of the bands 14, 14 via fan-shaped pieces 15, 15, and the bands 14, 14 are attached to the outer periphery of the column 2 by fastening the bolts 11. It can also be fixed.

Furthermore, as shown in FIG.
7 with bolts 11, semicircular plates 17, 17
There is also an example in which the arcuate plate 4 is fixed to the inner peripheral edge.

In addition, various attachment modes are possible.

By the way, in the symbols shown in FIG. 1, as described later, d/D is preferably 15 to 28%, and the opening angle θ is preferably 80 to 90 degrees. If the opening angle θ is small, the damping effect will be small, and if the opening angle is large, the arcuate plate will protrude from the column, spoiling the appearance. However, depending on the application, a range of 45 to 135 degrees may be acceptable.
FIG. 17 shows, as an application example, an example in which vibration-damping circular arc plates 4 are attached to each support column 31 of a marine work scaffold 30.

〔Example〕

Next, experimental examples will be shown to further clarify the effects of the present invention.

Experimental Example 1 In order to determine the optimal gap between the columnar body and the circular arc plate and to demonstrate the damping effect, a wind tunnel experiment was conducted using a two-dimensional rigid spring support model. This experimental method is a general method in which both ends of a rigid model are supported in a wind tunnel measurement section so that it can vibrate, and airflow is applied.

The results are shown in FIGS. 9 and 10. Figure 9 shows an arc plate with a central angle of 80 to 90 degrees, and d/D (d: 〓
This is an example of the relationship between the wind speed V and the displacement response amplitude (y/D) when the distance D is the diameter of the columnar body). The wind direction is α=0. From this result, the maximum displacement amplitude (ymax/D) in each case is determined and plotted, as shown in FIG. 10. Δamax in the figure is the maximum value of the excitation aerodynamic force in each case (the greater the negative value, the greater the excitation force).

According to these results, d/
The displacement amplitude and the excitation aerodynamic force become small when D is in the range of 15 to 28%, and reach a minimum value when d/D≈21%. Moreover, this value is 1/10 to 1/20 compared to the case without the arc plate, and it is clear that installing the arc plate according to the present invention brings about a large vibration damping effect. .

Experimental Example 2 When the influence of the wind direction α when d/D=21% was investigated, the results shown in FIG. 11 were obtained. −30゜＜α＜
The damping effect can be seen over a wide range of wind directions of 30 degrees.

Experimental Example 3 FIG. 12 shows the results obtained in a wind tunnel experiment using a 1/10 scale elastic model for a lighting column with a height of 12 m and a taper of 1/100, as shown in the figure.
The response amplitude of acceleration (Y¨) and displacement (Y) in the illumination lamp section is shown on the vertical axis.

From the results shown in the figure, in the case without an arc plate, when exposed to wind in the direction of α = 0°, the maximum amplitude of the acceleration response of out-of-plane fourth-order vibration is as high as 1.5 g, which has a negative effect on the lighting lamp. On the other hand, if arc plates are installed at two locations corresponding to the antinodes of the vibration mode, in the wind direction range of -45° < α < 45°,
It can be seen that the maximum amplitude of the acceleration response is reduced to less than 1/6 of the above value. In this way, in the present invention, by calculating the vibration mode in which a single columnar body vibrates and arranging the vibration damping device according to the present invention at a position where the vibration amplitude becomes large, a sufficient vibration suppressing effect can be obtained. It turns out that this can be expected. Therefore, the arc plate only needs to be attached to a portion of the outer circular columnar body in the longitudinal direction, which simplifies production and provides an excellent appearance.

〔Effect of the invention〕

As described above, according to the present invention, a product having an excellent appearance and an excellent vibration damping effect can be obtained.

[Brief explanation of the drawing]

FIG. 1 is a schematic plan view of the vibration damping device of the present invention, and FIG.
The figure is a perspective view, Figure 3 is a front view of a lighting column as a columnar body, and Figures 4 to 8 show examples of mounting an arc plate. A broken front view, FIGS. 9 to 12 are correlation diagrams showing experimental results, and FIGS. 13 to 16 show conventional examples.
FIG. 13 is a perspective view, FIG. 14 is a front view, FIG. 15 a is a plan view, FIG. 1... Lighting column, 2, P... Column body, 4... Arc plate for vibration damping.

Claims (1)

[Claims] 1 Under the vibration mode in which a single external circular columnar body vibrates, a distance d from the external surface of the columnar body is set at a longitudinal position where the amplitude becomes large and at an outwardly symmetrical position on both sides of said position. The ratio (d/D) to the outer diameter D of the body is 15 to 28%, and two damping circular arc plates with a central angle of 80 to 90 degrees are placed so that the arcs are substantially concentric with the columnar body. A cylindrical body having a vibration prevention function, characterized in that it is attached so as to prevent vibrations.