JP2898205B2 - Damping cable - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention is used for cables for suspension structures, for example, cables such as cable-stayed bridge cables and suspension bridge hangers, and cables for power transmission lines, and does not cause an increase in wind load acting on the cables. And a vibration damping cable for suppressing vibration caused by wind and rain.

[0002]

2. Description of the Related Art Cables having a circular cross section coated with polyethylene have come to be widely used as anticorrosion measures for suspension structure cables such as cable-stayed bridges and transmission line cables. However, in a cable having a circular cross section, in addition to vortex excitation with minute amplitude due to wind, rain vibration oscillating with large amplitude due to the interaction between rain and wind occurs. In particular, when a polyethylene-coated circular cross section cable is placed at an angle, a water channel due to rainfall is likely to be formed on the surface of the anticorrosion coating, divergent vibration occurs in a certain wind speed range, and a large angular change occurs at the cable fixing part Since the occurrence of cracks and the possibility of breakage due to large bending stress or fatigue is a concern, the following conventional techniques can be mentioned as measures to suppress this vibration.

For example, JP-A-63-197703,
As shown in FIG. 11 (a), (b) or (c), (d), a cable 3 as shown in FIG. By providing a linear projection 7 or a groove 6 having a height of about several mm over the entire length in the axial direction, the air flow around the anticorrosion cable is controlled, the formation of a water channel that causes the occurrence of rain vibration is prevented, and the vibration is reduced. Method to suppress.

As shown in FIG. 12, a method in which a number of cables 3 supporting a bridge girder 9 are connected to each other by a wire rope 8 to suppress vibration by increasing the apparent rigidity and damping performance of the cables.

As shown in FIG. 13, there is a method in which dampers 10 using an oil damper or a viscoelastic body are attached near the fixing portion of the cable 3 to increase the damping effect, thereby suppressing vibration.

[0006]

However, these prior arts have the following problems.

In the above, the surface of the anticorrosion coating has a height of several meters.
By providing a linear projection or groove with a width of about m and a width of about several mm, the formation of a water channel generated on the cable surface is inhibited,
This is a method of suppressing the occurrence of rain vibration. In this case, in order to prevent the formation of a water channel, a projection or a groove having a height of about 2 to 3% of the cable diameter is provided over the entire surface of the cable. The drag coefficient of the cable cross section is significantly increased as compared with a circular cable having For this reason, in a structure such as a cable-stayed bridge, the wind load acting on the cable increases, and the design cross section of the girder or the tower may be excessively large. In addition, when performing the installation work, it is necessary to prevent the occurrence of damage such as cracks from the notch of the anticorrosion coating, and when the cable is twisted at the time of cable installation, the grooves and protrusions rotate, and the original function Therefore, there is a problem in that significant restrictions must be set on the handling in the production and erection because there is a possibility that the method cannot be exhibited.

In order to connect the cables with each other with a wire rope, it is necessary to tighten the cables with a jig such as a clamp. However, the anticorrosive coating made of polyethylene constituting the cable surface layer is a material having a large creep. As a result, the tightening force is weakened, and regular maintenance is required to maintain a sufficient safety factor against slippage. In addition, the wire rope connecting the cables impairs the view of the cable-stayed bridge.

In this case, since the vibration damper is attached to all cables, it is necessary to provide an accessory structure near the cable fixing portion. In addition, when the bridge becomes large and the cable length becomes long, a sufficient damping effect cannot be obtained in the vicinity of the bridge girder, and it becomes necessary to provide a high position, which is not preferable from the viewpoint of aesthetics.

The inventor of the present invention has made it possible to manufacture the cable relatively easily without attaching an additional member to the cable as in the above-mentioned prior art and without greatly affecting the strength characteristics of the anticorrosion coating. Japanese Patent Application No. 05-63867 ( Japanese Unexamined Patent Application Publication No. 6-27) discloses a vibration damping cable in which the occurrence of rain vibration is suppressed without increasing the acting wind load.
No. 2180 ). This vibration damping cable has a plurality of round or polygonal concave or convex gatherings on the entire surface of the anticorrosion coating made of polyethylene for corrosion protection of the cable, and disturbs the smooth airflow on the cable surface. This prevents the formation of a water channel and suppresses vibration, and the ratio of the sum of the areas of the concave or convex gatherings to the unit surface area (including irregularities) of the cable is 10%.
-30%. According to the present invention, in the above-mentioned invention, the processing area of the cable surface is reduced, and the appearance is further improved.

[0011]

SUMMARY OF THE INVENTION The gist of the present invention is to provide an aerial suspension cable in which the surface of the anticorrosion coating has a concave or convex shape, and a plurality of circular or polygonal concave portions on the surface of the anticorrosion coating. Or, the sum of the concave or convex areas corresponding to the unit surface area of the cable is 3% to 1
A vibration damping cable formed in a large number so as to be in a range of less than 0%.

(Action) The vibration phenomenon called rain vibration generated in the circular anticorrosion cable due to the interaction between rain and wind is considered to be caused by the formation of a wide water channel at specific positions on the upper and lower surfaces of the anticorrosion cable. Therefore, the prevention of the formation of the water channel is a measure for suppressing the rain vibration.

According to the present invention, a plurality of circular or polygonal concave or convex gatherings are provided on the surface of the anticorrosion coating to prevent the formation of water channels. This concave or convex portion can prevent the formation of a water channel by disturbing a smooth airflow on the cable surface, and suppresses the occurrence of rain vibration.

A large number of concave or convex aggregates are arranged or randomly arranged over the entire length of the cable, and the sum of their areas accounts for less than 3% to 10% of the unit surface area (including concave or convex) of the cable. Range. The reason for this is to suppress rain vibration without causing an increase in wind load acting on the cable. In order to suppress the rain vibration, it is better to provide as many concave or convex parts as possible, but when the concave or convex parts on the cable surface increase, the smooth surface decreases and as a result, the drag coefficient increases. Wind load increases. The drag coefficient of the circular cross section is the smallest when the surface has a smooth surface, and when the cable has a diameter of 10 to 20 cm, the wind speed is 50 m / s.
The extent, drag coefficient C _D is 0.5 to 0.6. When grooves or projections are formed on the surface of the cable, the greater the degree and the larger the processing area, the greater the deformation from the smooth surface, and as a result, the drag coefficient increases. In the conventional example, C _D = 1. Some also indicate 2. The drag coefficient can be reduced by reducing the concave or convex processing area on the cable surface, but if it is less than 3%, the effect of suppressing rain vibration is lost. In the present invention, the concave or convex processing area on the cable surface is set to 3% to less than 10% to suppress the increase in the drag coefficient, and the drag coefficient C _D even at a wind speed of 50 m / s.
Is about 0.6, which is almost equivalent to a circular section without any concave or convex. Further, the concave or convex formed on the cable surface is not a single one, but a plurality of concaves or convexes are arranged as an assembly. This is to make the turbulence of the air flow more effective. As a result, the wind load on the cable can be significantly reduced and the occurrence of rain vibration can be suppressed, as compared with the drag coefficient of a conventional vibration damping cable having grooves or projections on the surface as 1.0 to 1.2. The amount of recesses or protrusions on the cable surface can be reduced, making it easier to manufacture and improving the aesthetics of the installed cable.

[0015]

【Example】

Embodiment 1 FIG. 1 shows a first embodiment of the present invention. A corrosion prevention coating 2 made of polyethylene is applied to the surface of a cable composed of an aggregate of cable strands 1, and a coating portion of the corrosion protection cable 3. A plurality of (four) sets of elliptical concave portions 4a on the surface are arranged and arranged.

FIG. 2 shows details of the shape of the concave portion.

The specific dimensions are as follows: Cable outer diameter 150m
1m 4 oval 3mm x 5mm concave portions
It is an aggregate, which is arranged at eight equally spaced intervals in the circumferential direction of the cable and parallel in the axial direction. The sum of the areas of the concave portions corresponding to the unit surface area of the cable is about 4%. If one recess is large, the turbulence effect will decrease and it will be difficult to obtain the vibration suppression effect.
A plurality of small aggregates 4 were formed, and the area of one recess 4a was about 12 mm ^2, and four aggregates were arranged to form one aggregate 4.

The depth of the recess 4a is 2 to 2 of the cable diameter.
If it is 3% or more, the drag coefficient increases as the ratio of the concave portion to the cable surface area increases, so that the wind load acting on the cable increases. For this reason, in order to obtain a vibration damping effect and a range where the drag coefficient does not increase, the depth of the concave portion 4a is set to 1 to 1.5 mm, which is about 1% or less of the cable diameter.

Embodiment 2 FIG. 3 shows a second embodiment of the present invention. A cable similar to that of the first embodiment is provided with a plurality of circular concave portions 5a.
G) The assembled parts 5 are arranged and arranged.

FIG. 4 shows details of the shape of the concave portion 5a.

3 mm ×
The five 5 mm elliptical concave portions 5a are arranged as a set, and are arranged at equal intervals in the circumferential direction of the cable at eight intervals in parallel in the axial direction. In this case, the sum of the areas of the concave portions corresponding to the cable unit surface area is about 5%.

Comparative Example 1 FIGS. 5 and 6 show Comparative Example 1 in which the sum of the areas of the concave portions corresponding to the cable unit surface area is less than 3%, and an ellipse of 3 mm × 5 mm is added to the area of the cable outer diameter of 150 mm. Three of the shape concave portions 6a are arranged as a set and eight are arranged at equal intervals in the circumferential direction of the cable and are arranged in parallel in the axial direction.

Comparative Example 2 FIG. 7 shows a comparative example 2 in which the area of one concave portion is increased to 230 mm ^2, and the concave portions are individually arranged.

FIGS. 8 and 9 show the results of wind tunnel experiments of the first embodiment, the second embodiment, the comparative example, and the conventional example of the present invention. As shown in FIG. 8, divergent vibration, that is, rain vibration occurs at a wind speed of about 9 to 10 m / s in the unmeasured cable having a smooth surface and Comparative Example 1, but the first and second embodiments of the present invention. No rain vibration occurs in the cable of the embodiment. Further, as shown in FIG. 7, in the case of Comparative Example 2 in which the area of one concave portion was increased and arranged alone, the turbulence effect was reduced at 15 m / s or more, and a rain vibration occurred.

FIG. 9 shows the concave shape and the drag coefficient C according to the present invention.
_This is an experiment of the relationship of _D , and shows the result of measuring the drag coefficient by changing the circular surface processing area of the depth (height) of the concave portion of 1% of the cable diameter. According to this, when the degree of processing on the cable surface is 30% or less of the sum of the areas of the concave portions corresponding to the unit surface area, the drag coefficient C _D decreases. When the sum is 20% or less, the drag coefficient of the circular cross section is 0.5. It is almost equivalent. In Examples 1 and 2 of the present invention, the drag coefficient is substantially the same as that of the circular cross section. Further, it is known that a circular cross section is affected by the Reynolds number, and the drag coefficient greatly changes depending on the degree of the depression. Figure 10 is a representation comparing the drag coefficient C _D for the Reynolds number of the damping cable smooth cable and conventional damping cable and the present invention. No-measure cable No. with smooth surface
In the low Reynolds number region, the drag coefficient C _D is 1.2, and reaches the critical Reynolds number at 3 to 4 × 10 ⁵ , after which the drag coefficient slightly increases and corresponds to the design wind speed of 50 m / s. Drag coefficient C at Reynolds number 5.5 × 10 ⁵
_D was 0.52.

The cable No. of the first and second embodiments of the present invention described above. In the case of 2, the critical Reynolds number was about 1 × 10 ⁵ , after which no increase in the drag coefficient was observed, and the Reynolds number 5.5 × 10 5 corresponding to the design wind speed region of 50 m / s.
Drag coefficient C _D In ⁵ became 0.63. Therefore,
In the embodiment of the present invention, the drag coefficient C _D of the cable for calculating the wind load in the design of the bridge only slightly increases in comparison with the smooth cross section.

On the other hand, a conventional damping cable No. having a cross section as shown in FIG. In 3,
Since the shape change is large, the critical Reynolds number is reached at 4 to 5 × 10 ⁴ , the drag coefficient _CD is 1.2 at a wind speed of 50 m / s, and the drag coefficient is the vibration-damping cable of the present invention or no countermeasures having a smooth surface. More than twice the cable. Therefore,
With such a cross-sectional shape, the design wind load of the damping cable may be excessive, and even if the damping effect of the rain vibration can be obtained, a reasonable bridge design cannot be achieved.

Although the embodiment in which the anticorrosion coating of the cable is made of polyethylene resin has been described above, the same effect can be obtained by applying the present invention when the surface of the cable is coated with fluororesin.

The same effect can be obtained when the concave shape in the present invention is circular, elliptical, polygonal such as hexagonal, quadrangular, pentagonal or convex.

[0030]

According to the present invention, a plurality of circular or polygonal concave or convex gatherings corresponding to the unit surface area of the cable are formed on the anticorrosion coating 2 on the surface of the cable 1. By forming and arranging a large number so that the sum of the areas is within a range of 3% to less than 10%, formation of a water channel caused by the interaction of rain and wind on the surface of the anticorrosion cable can be prevented with a small amount of processing, and rain vibration Generation can be suppressed, and the drag coefficient does not increase with a change in the cable surface shape. The drag coefficient can be suppressed to substantially the same level as a smooth circular cross section, and the appearance is not spoiled. As a result, the wind load on the cable can be significantly reduced as compared with the conventional vibration damping cable, and a rational design of the bridge becomes possible. In particular, in the case of a long cable-stayed bridge, since many cables are densely arranged, the load capacity in the direction perpendicular to the bridge axis of the girder is governed by the wind load generated on the cables. Above is very effective.

Further, as the length of the bridge increases, the cable length also increases, so that the effect of the installation of the damping device is reduced, and aerodynamic measures are effective. The use of the aerodynamic measures according to the invention does not require the addition of additional structures as in the case of damping devices and does not impair the appearance.

[Brief description of the drawings]

FIGS. 1A and 1B are explanatory views of a vibration damping cable according to a first embodiment of the present invention, in which four elliptical concave portions are arranged on a cable surface;

FIG. 2 is a diagram showing details of the shape of a concave portion according to the first embodiment of the present invention.

FIGS. 3 (a) and 3 (b) are explanatory views of a vibration damping cable according to a second embodiment of the present invention, in which five elliptical recesses are collectively arranged on the cable surface.

FIG. 4 is a diagram showing details of the shape of a concave portion according to a second embodiment of the present invention.

FIGS. 5A and 5B are explanatory views of Comparative Example 1 in which a ratio corresponding to a cable unit surface area of a concave area is set to less than 3%.

FIG. 6 is a view showing details of the shape of a recess shown in FIG. 5;

FIG. 7 is a diagram showing details of the shape of a concave surface of a conventional vibration damping cable.

FIG. 8 is a diagram showing a result of a rain vibration wind tunnel experiment.

FIG. 9 is a graph showing a relationship between a cable surface processing area and a drag coefficient.

FIG. 10 is a graph showing the relationship between the Reynolds number and the drag coefficient in the damping cable of the present invention and the conventional example.

FIG. 11 is a diagram showing a cross section of a conventional vibration damping cable (a).
Is a perspective view, (b) is a partially enlarged view, (c) is a perspective view of another example, and (d) is a partially enlarged view.

FIG. 12 is a diagram showing a conventional technique of a vibration damping method by stretching a wire rope.

FIG. 13 is a diagram showing a conventional technique of a vibration damping method by attaching a damping device.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Cable strand 2 ... Anticorrosion coating 3 ... Cable 4 ... Concave part 4a ... Concave part 5 ... Concave part 5a ... Concave part 6 ... Groove 7 ... Protrusion 8 ... Wire rope 9 ... Girder 10 ... Attenuation device

Claims (1)

(57) [Claims] 1. An aerial suspension cable in which a concave or convex processing is applied to a surface of the anticorrosion coating, wherein a plurality of round or polygonal concave or convex aggregates are formed on the anticorrosion coating surface.
A vibration damping cable formed in a large number such that the sum of the concave or convex areas corresponding to the unit surface area of the cable is in a range of 3% to less than 10%.