JPH07119058A - Vibration-damping cable - Google Patents

Abstract

PURPOSE:To provide a function capable of damping rain vibration generated by wind and rain to slant cables in a cable-stayed bridge. CONSTITUTION:Plural numbers of strands 1 formed by bundling wires are intertwisted to constitute a cable core material 10 and the outer periphery of inner layer 2 obtained by coating this cable core material 10 with a high- density polyethylene layer is coated with an outer layer 3 of high-density polyethylene and plural parallel projections 4 are provided along the axial direction of the cable in the outer layer 3. Thereby, raindrops 6 are divided by parallel projections 4 and the raindrops are prevented from concentrating on the cable surface and, simultaneously, air flow in the circumference of the cable is controlled by the parallel projections 4 to suppress causing of vibration.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a vibration damping cable applied to a diagonal cable of a cable-stayed bridge cable. It can also be applied to strands of Nielsen Bridge and suspension bridge.

[0002]

2. Description of the Related Art Generally, a cable-stayed bridge is constructed as shown in FIG.
Multiple girders 13 with bridge girder 11 installed diagonally from main tower 12
It is configured to be suspended by. As shown in FIG. 7 or FIG. 8, the cable 13 is a strand 14 formed by bundling steel wires in parallel or semi-parallel.
And a high-density polyethylene 15 coated on the outer periphery of the strand 14 to protect the strand 14. In the figure, reference numeral 16 indicates a rust preventive material, and reference numeral 20 indicates a spacer strand.

By the way, in such a cable 13, when a wind including rain blows, raindrops on the surface gather on the upper and lower parts of the cable 13 to form a steady water channel. Due to the formation of this channel, the separation point of the wind is fixed at the position where vibration occurs, and at the same time, the instability of the diagonal cable itself is amplified, so that rain vibration (vibration caused by rain and wind) occurs. In order to suppress this vibration, conventionally, as shown in FIG. 9, the cables 13 are connected by wires 17, and
As shown in 10, vibration was suppressed by installing a viscous damper 18 at the cable fixing portion of the bridge girder 11 or the main tower 12.

[0004]

By the way, when connecting the cables 13 with the wire 17, it is necessary to fix the cables 13 near the center of the cable 13 via the cable band 19 as shown in FIG. External force acts on the part,
There is a risk of damaging the high density polyethylene 15. Also,
Since vibrations occur in several types of modes, all vibrations cannot be suppressed. Furthermore, there are problems such as impairing the appearance and aesthetics.

When the damper 18 is installed, the cable may be damaged in the same manner as above, and the structure near the fixing portion of the cable 13 becomes complicated, and the damper 18 is installed near the fixing portion. There is also a problem that the damper effect is small and the vibration cannot be effectively suppressed. In order to solve these problems, Japanese Patent Laid-Open No. 63-197703 proposes to provide a strip-shaped or bump-shaped projection on a wrapping material wound around the outer circumference of a strand in which strands are bundled.

However, when streak-like or bump-like projections are provided on the wrapping material, depending on the conditions such as the installation position, the number of pieces, the size, and the angle, it may cause vibrations on the contrary, so that the condition setting is necessary. Become. This is, for example,
It is clear from the experimental data shown in 12. That is, FIG.
Shows the relationship between the wind speed (horizontal axis) and the amplification factor (vertical axis) when the angle ζ of the ridge b protruding from the cable a having a circular cross-section is changed with respect to the wind blowing direction. From this figure, it can be seen that the position where the ridge b is provided affects the amplification degree.

Experiments shown in FIGS. 13 (a) to 13 (c) were also conducted. That is, as shown in FIG. 13 (a), in the wind tunnel experiment of the cylindrical model d wound with the trip wire C, when the ratio of the diameter d of the wire to the diameter D of the cylinder is 0.066 and 0.10, and θ = 30. When three, four, or six coils were wound at a degree, the regular vortex could be completely eliminated. However, when the number of trip wires is 7 or more, and when the wires are attached in parallel to the cylinder (θ = 0 °), vortices are regularly generated, and the effect does not appear. It was

Further, in the case of FIG. 13 (b) in which the flat plate e is straightly aligned with the surface of the circular cylinder d, the height h of the flat plate e is set to the cylindrical diameter D.
Although 6 sheets were mounted in parallel as 10% of the above, almost no effect was exhibited. However, as shown in FIG. 13 (c), the effect was recognized when the short flat plate f was attached by shifting the position for each certain length. It was also found by experiments that when parallel protrusions are installed at 60 ° intervals, the cross section becomes a hexagonal shape and galloping occurs.

Further, by providing a protrusion on the wrapping material itself which is coated for the purpose of protecting the cable, there is a possibility that damage such as cracks is likely to occur during the operation or after the service. It is an object of the present invention to provide a vibration damping cable that solves the above-mentioned problems in the conventional vibration damping cable.

[0010]

In order to achieve the above object, a damping cable according to a first aspect of the present invention is a strand formed by bundling strands of a cable stretched between fixing members. Of the cable core material and a high-density polyethylene layer covering the same core material, the outer periphery of the polyethylene layer is covered with an outer layer of high-density polyethylene, It is characterized in that a plurality of parallel protrusions are provided along the axial direction of the cable. The vibration damping cable according to claim 2 is the vibration damping cable according to claim 1, wherein the parallel protrusions have a pitch of 28 to 32 °, a height of 3 to 7 mm, and a width of 9 to 13 mm. It is characterized by being.

[0011]

In the above-described vibration damping cable of the present invention, the parallel protrusions having a predetermined pitch, height and width provided on the surface of the outer layer prevent raindrops from concentrating on the cable surface and the presence of the parallel protrusions. As a result, the air flow around the cable is controlled, and the action of suppressing the induction of vibration is performed.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A damping cable as an embodiment of the present invention will be described below with reference to the drawings. FIG. 1 and FIG. 2 are sectional views of the damping cable, and FIG. 3 is a sectional view of the damping cable for explaining the operation. 4 and 5 are graphs showing experimental data.

The damping cable of this embodiment is also constructed by diagonally suspending the bridge girder from the main tower to form a cable-stayed bridge.
In FIG. 2, reference numeral 1 denotes a strand, and a cable core 10 is formed by twisting a plurality of strands 1. The outside of the core material 10 is covered with a high-density polyethylene layer to form the inner layer 2. Further, the outer side of the inner layer 2 is covered with an outer layer 3 made of high density polyethylene. The outer layer 3 is provided with a plurality of parallel protrusions 4 having a substantially rectangular cross section and parallel to the axis of the vibration damping cable at a predetermined pitch, height and width.
Are configured.

Next, an example of an experiment conducted on the vibration damping cable having the above-mentioned structure will be described. [Experiment 1] The dimensions of each part of the cable 5 used in the experiment are shown in FIGS. That is, the outer diameter of the inner layer 2 is 14
Twelve protrusions 4 were provided on the outer layer 3 on the outer side of the outer layer 3 with a pitch of 30 ° from the top. The width of the protrusion 4 was 11 mm, the height was 5 mm, and the film thickness of the outer layer 3 was 4 mm. The film thickness of the inner layer 2 was 10.5 mm. In the experiment, the cable 5 was suspended, and rain and wind were blown directly onto it (see FIG. 3). The wind speed at this time was about 3 m / s to 24 m / s, and the rainfall was 20 mm / h. As a result of this experiment, raindrops 6 were divided by the parallel protrusions 4 on the way, and formation of concentrated water channels was not found.

In FIG. 4A, the vertical axis represents the vibration (amplitude) of the cable when there is no protrusion, and the horizontal axis represents the wind tunnel wind speed (m / m).
s) is shown and the experimental results are shown in FIG.
FIG. 4 (a) shows the experimental results by taking the vibration (amplitude) of the cable 5 of this embodiment on the vertical axis and the wind tunnel wind speed (m / s) on the horizontal axis. The graph of FIG. 4 (b) shows that when there is no protrusion, the vibration generated in the wind speed range of 9 to 16 m / s can be suppressed by the cable of this embodiment. The symbols in FIG. 4 (a) and FIG. 4 (b) are as shown in FIG.

[Experiment 2] The pitch of the protrusions 4 (12 places)
28-32 °, height 3-7mm, width 9-13,
The experiment was conducted under the same conditions as above. As a result, there is no concentration of raindrops,
The vibration was similar to that of Experiment 1.

[Experiment 3] The height of the protrusion 4 is set to 5, 10, 15 mm.
The test was performed under the same conditions as in Experiment 1 except that unevenness was added. As a result, cracks (corner) occur in the 10 and 15 mm areas where raindrops concentrate.
Was found. This crack stopped at the outer layer 3.

In the vibration-damping cable of the present invention, the reason why the protrusions provided on the outer surface of the outer layer are parallel protrusions is mainly for the following reason. That is, the cable is formed by bundling the strands in parallel at the time of manufacturing and extruding and forming a high-density polyethylene pipe on the bundle. At this time, since the cable always moves in a straight line, the parallel protrusion is the easiest to manufacture.
In addition, it is necessary that the protrusions are parallel to each other in order to obtain the damping effect on the entire cross section of the cable. Further, in order to avoid the influence of heat, it is better to make the outer layer thinner, and therefore it is easier to manufacture the protrusions than to form the grooves in the outer layer.

[0019]

As described in detail above, according to the vibration damping cable of the present invention, the parallel projections provided on the cable surface
It can prevent raindrops from concentrating on the cable surface, and
The air flow around the cable can be controlled to prevent unstable vibrations. Also, with respect to external damage to the parallel protrusions, the coating has a double structure,
Moreover, since the parallel protrusions are provided on the outer layer, the damage on the surface does not extend to the inside, which is advantageous in preventing rust of the cable.

[Brief description of drawings]

FIG. 1 is a sectional view of a vibration damping cable as an embodiment of the present invention.

FIG. 2 is a sectional view of the modified example.

FIG. 3 is a sectional view for explaining the same action.

FIG. 4 (a) is a graph showing the results of the same experiment. (b) A graph showing the results of the same experiment.

FIG. 5 is an explanatory diagram of each symbol in FIGS. 4 (a) and 4 (b).

FIG. 6 is a side view of a general cable-stayed bridge.

FIG. 7 is a cross-sectional view of a conventional cable.

FIG. 8 is a cross-sectional view of another conventional cable.

FIG. 9 is a side view of a cable-stayed bridge provided with conventional cable vibration suppressing means.

FIG. 10 is a side view of a cable-stayed bridge provided with another conventional cable vibration suppressing means.

FIG. 11 is a side view showing an enlarged main part of FIG. 9.

FIG. 12 is a graph showing vibration damping performance test data of a conventional vibration damping cable.

[FIG. 13] (a) A front view (left) and a side view (right) of the first experimental vibration damping cable. (b) A front view (left) and a side view (right) of the second experimental damping cable. (c) Front view (left) and side view (right) of the third experimental damping cable.

[Explanation of symbols]

 1,14 Strand 2 Inner layer 3 Outer layer 4 Parallel protrusion 5 Damping cable 6 Raindrop 10 Cable core material 11 Bridge girder 12 Main tower 13 Cable

Front Page Continuation (72) Inventor Akinobu Kishi 1-1-1 Wadazakicho, Hyogo-ku, Kobe Sanbishi Heavy Industries Ltd. Kobe Shipyard (72) Inventor Tsutomu Saito 1-1 Atsunoura-cho, Nagasaki-shi Mitsubishi Heavy Industries Ltd. Meeting President Saki Institute (72) Inventor Masaru Matsumoto 45-33, Kibata Mikurayama, Uji-shi, Kyoto Prefecture (72) Inventor Masahiko Kitazawa 4-6-1-205 Yamada Nishi, Suita City, Osaka Prefecture

Claims (2)

[Claims] 1. A cable stretched between fixing members, comprising: a cable core material formed by twisting a plurality of strands formed by bundling strands; and a high-density polyethylene layer covering the core material. The outer periphery of the polyethylene layer is covered with an outer layer of high-density polyethylene,
A vibration damping cable, wherein a plurality of parallel protrusions are provided on the outer layer along the axial direction of the cable. 2. The vibration damping cable according to claim 1, wherein the parallel protrusions have a pitch of 28 to 32 ° and a height of 3 to 7.
mm, width is set to 9 to 13 mm,
Damping cable.