JPH0868011A - Vibration controlling cable - Google Patents

Abstract

PURPOSE: To restrain rain vibration while reducing wind load working on cables by providing recesses or projections to a cable or the like for suspension structure with coating applied to its surface. CONSTITUTION: In a cable 3, made of an aggregate of strands 1, with anti-corrosive coating 2 applied to its surface, a number of aggregates 4, 5, each composed of a number of circular or polygonal recesses 4a or projections 5a are arranged regularly or at random to the coated surface. Thereby, turbulance is made in wind, and vibration is prevented from occurring to the cable 3. The area for the recess or the projection should be less than 3-10% of unit area on the surface of the cable, and thereby increase of drag coefficient for the cable can be restrained without causing in incrfease of wind load working on the cable while improving the appearances of the cable.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is used for cables for suspension structures, such as cables for cable-stayed bridges, hangers for suspension bridges, cables for power transmission lines, etc. without increasing the wind load acting on the cables. It also relates to a vibration damping cable that suppresses vibrations caused by wind and rain.

[0002]

2. Description of the Related Art Polyethylene-coated cables having a circular cross section have come to be widely used as cables for suspending structures such as cable-stayed bridges and cables for power transmission lines as an anticorrosion measure. However, in a cable with a circular cross section, in addition to vortex excitation accompanied by a small amplitude due to wind, rain vibration that vibrates with a large amplitude occurs due to the interaction between rain and wind. In particular, when a polyethylene-coated circular cross-section cable is placed at an inclination, water channels are easily formed on the surface of the anticorrosion coating part due to rainfall, and divergent vibration occurs in a certain wind speed range, causing a large angle change in the cable fixing part. Therefore, the following conventional techniques can be cited as a measure for suppressing this vibration because a large bending stress or a fracture due to fatigue may occur.

For example, JP-A-63-197703,
A cable 3 as shown in FIGS. 11 (a), 11 (b) or 11 (c), 11 (d) is formed on the entire surface of an anticorrosion coating made of polyethylene for protecting the cable as disclosed in JP-A-1-146006. By providing the linear protrusions 7 or the grooves 6 with a height of about several mm over the entire axial length, the air flow around the anticorrosion cable is controlled, the formation of water channels that cause rain vibration is prevented, and vibration is prevented. Method to suppress.

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

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

[0006]

However, these conventional techniques have the following problems.

In the above, the height of the surface of the anticorrosion coating is several meters.
By forming a linear protrusion or groove with a width of about several mm in m, formation of a water channel generated on the cable surface is hindered,
Although this is a method of suppressing the occurrence of rain vibration, in order to prevent the formation of water channels in this case, a projection or groove having a height of about 2 to 3% of the cable diameter is provided over the entire surface of the cable, so that a smooth surface is provided. The drag coefficient of the cable cross section is significantly increased as compared with the circular cable with. Therefore, in a structure such as a cable-stayed bridge, the wind load acting on the cable increases, which may result in an excessively large design cross section of the girder or tower. In addition, when performing erection work, it is necessary to prevent damage such as cracks from the notch of the anticorrosion coating, and when the cable is twisted when installing the cable, the grooves and protrusions rotate and the original function is Therefore, there is a problem in that it is necessary to set a large limit to the handling in manufacturing and erection because there is a possibility that the product cannot be exhibited.

In the above method, the cables need to be clamped by a jig such as a clamp in order to connect the cables with a wire rope. However, the anticorrosion coating made of polyethylene forming the cable surface layer is a material having a large creep. Because of this, the tightening force is weakened, which requires regular maintenance to maintain a sufficient safety factor against slipping. In addition, the wire rope connecting the cables spoils the view of the cable-stayed bridge.

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

The present inventors did not attach additional members to the cable as in the above-mentioned prior art, and do not have a great adverse effect on the strength characteristics of the anticorrosion coating, and are relatively easy to manufacture. Japanese Patent Application No. 05-63867 has filed for a damping cable that suppresses the occurrence of rain vibration without increasing the wind load that acts. This anti-vibration cable has multiple circular or polygonal concave or convex aggregates on the entire surface of the anticorrosion coating made of polyethylene to protect the cable. This prevents the formation of water channels and suppresses vibration, and the sum of the areas of the concave or convex aggregates is 10 to 30% of the unit surface area of the cable (including irregularities). Is. The present invention is the above-mentioned invention of the already filed application, in which the processed area of the cable surface is reduced to further improve the aesthetic appearance.

[0011]

SUMMARY OF THE INVENTION The gist of the present invention is to provide a plurality of circular or polygonal concaves on the surface of an anticorrosion coating in an aerial suspension cable in which the surface of the anticorrosion coating has concave or convex processing. Alternatively, the sum of convex or concave areas corresponding to the unit surface area of the cable is 3% to 1
It is a vibration-damping cable characterized by being formed in large numbers in a range of less than 0%.

(Operation) It is considered that the vibration phenomenon called rain vibration generated in the circular anticorrosion cable due to the interaction between rain and wind is caused by the formation of a water channel having a certain width on the upper and lower surfaces of the anticorrosion cable. Therefore, the prevention of this water channel formation is a measure to suppress rain vibration.

To prevent the formation of water channels, the present invention provides a plurality of circular or polygonal concave or convex aggregates on the surface of the anticorrosion coating. The concave portion or the convex portion can prevent the formation of a water channel by disturbing the smooth air flow on the cable surface, and suppress 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 the areas occupies 3% to less than 10% of the unit surface area of the cable (including concave or convex portions). To be within the range. The reason for this is to prevent rain vibration without increasing the wind load acting on the cable. In order to suppress rain vibration, it is better to make as many recesses or protrusions as possible, but if the number of recesses or protrusions on the surface of the cable increases, the smooth surface decreases, resulting in an increase in the drag coefficient. Wind load increases. The drag force coefficient of the circular cross section is the smallest for a shape with a smooth surface, and the wind velocity is 50 m / s for a cable with a diameter of 10 to 20 cm.
To a degree, the drag coefficient C _D is between 0.5 and 0.6. When grooves or protrusions are formed on the surface of the cable, the larger the extent and the larger the processing area, the greater the deformation from the smooth surface, resulting in a larger drag coefficient. In the conventional example, C _D = 1. Some show 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 of the drag coefficient. Therefore, the drag coefficient C _D is reduced even at a wind speed of 50 m / s.
Is about 0.6, which is almost equivalent to a circular cross section without a concave or convex shape. Moreover, the concaves or convexes formed on the surface of the cable are not single, but a plurality of concaves or convexes are arranged as a collective portion. This is to make the turbulent action of the air flow more effective. As a result, compared to the drag coefficient of 1.0 to 1.2 of the conventional vibration damping cable having grooves or protrusions, the wind load on the cable can be significantly reduced and the occurrence of rain vibration can be suppressed. The amount of recesses or protrusions on the cable surface can be reduced, manufacturing is easier, and the aesthetic appearance of the erected cable is also improved.

[0015]

【Example】

Example 1 FIG. 1 shows a first example of the present invention, in which a surface of a cable composed of an assembly of cable strands 1 is provided with an anticorrosion coating 2 made of polyethylene, and a coating portion of the anticorrosion cable 3 thereof. A plurality of (four) elliptical concave portions 4a are gathered on the surface, and a gathering portion 4 is arranged in an array.

FIG. 2 shows details of the shape of the recess.

The concrete dimensions are as follows: cable outer diameter 150 m
One 3 mm x 5 mm elliptical recess 4a on the surface of m
The assembly is arranged in eight equal intervals in the circumferential direction of the cable and arranged in parallel in the axial direction, and the total area of the concave portions corresponding to the unit surface area of the cable is about 4%. If one recess is made larger, the turbulence effect will be reduced and the damping effect will be difficult to obtain.
A plurality of smaller gathering portions 4 are formed. The area of one concave portion 4a is about 12 mm ^2, and four gathering portions 4a are arranged to form one gathering portion 4.

The depth of the recess 4a is 2 to 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, 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, in order to obtain a vibration damping effect and not increase the drag coefficient.

Embodiment 2 FIG. 3 shows a second embodiment of the present invention, in which a cable similar to the first embodiment is provided with a plurality of circular recesses 5a (5).
(3) The gathering units 5 gathered are arranged in an array.

FIG. 4 shows details of the shape of the recess 5a.

3 mm x on the surface of the outer diameter of the cable 150 mm
The five 5 mm elliptical recesses 5a are treated as one aggregate and are arranged in parallel in the axial direction at eight equal intervals in the cable circumferential 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 formed in an area having a cable outer diameter of 150 mm. The three shaped recesses 6a are arranged as one assembly and arranged in parallel in the axial direction at eight equal intervals in the cable circumferential direction.

Comparative Example 2 In FIG. 7, the area of one concave portion in Comparative Example 2 was increased to 230 mm ^2, and the concave portions were arranged independently.

FIGS. 8 and 9 show the results of wind tunnel experiments of the first and second embodiments of the present invention, the comparative example, and the conventional example. As shown in FIG. 8, in the non-measured cable having a smooth surface and in Comparative Example 1, divergent vibration, that is, rain vibration occurs at a wind speed of about 9 to 10 m / s, but the first embodiment and the second embodiment of the present invention Rain vibration does not occur at all in the example cable. Further, as shown in FIG. 7, in the case of Comparative Example 2 in which the area of one concave portion was increased and the concave portions were individually arranged, at 15 m / s or more, the turbulent flow effect was reduced and rain vibration occurred.

FIG. 9 shows the concave shape and drag coefficient C in the present invention.
_This is an experiment result of the relationship of _D , and shows the result of measuring the drag coefficient by changing the surface processing area of the circular shape having the depth (height) of the recess of 1% of the cable diameter. According to this, when the sum of the areas of the concave portions corresponding to the surface area of the cable is 30% or less, the drag coefficient C _D is decreased, and when the sum is 20% or less, the drag coefficient of the circular cross section is 0.5. It is almost the same. In Examples 1 and 2 of the present invention, the drag coefficient is almost equal to that of the circular cross section. It is known that the circular cross section is affected by the Reynolds number, and the drag coefficient greatly changes depending on the degree of the depression. FIG. 10 shows a comparison of the drag coefficient C _D with respect to the Reynolds number of the smooth cable, the conventional damping cable and the damping cable of the present invention. No countermeasure cable with smooth surface.
In the low Reynolds number range, 1 has a drag coefficient C _D of 1.2, reaches the limit Reynolds number at 3 to 4 × 10 ⁵ , and thereafter the drag coefficient slightly increases and corresponds to the design wind speed of 50 m / s. Drag coefficient C at Reynolds number of 5.5 × 10 ⁵
_D was 0.52.

Cable Nos. 1 and 2 of the first and second embodiments of the present invention described above. At 2, the limit Reynolds number was about 1 × 10 ⁵ , and after that no increase in the drag coefficient was observed, and the Reynolds number 5.5 × 10 5 equivalent to the design wind speed of 50 m / s region.
^{At 5} , the drag coefficient C _D was 0.63. Therefore,
The drag coefficient C _D of the cable for calculating the design wind load of the bridge only slightly increases in the embodiment of the present invention as compared with the smooth cross section.

On the other hand, the conventional damping cable No. 1 having a cross section as shown in FIG. In 3,
Since the shape change is large, the limit Reynolds number is reached at 4 to 5 × 10 ⁴ , the drag coefficient C _D is 1.2 at a wind speed of 50 m / s, and the drag coefficient is the damping cable of the present invention or no countermeasure with a smooth surface. It is about twice as much as the cable. Therefore,
With such a cross-sectional shape, there is a risk that the design wind load of the vibration damping cable will become excessive, and even if the vibration damping effect of the rain vibration can be obtained, it will not be a rational bridge design.

Although the embodiment in which the anticorrosive 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 concave shape in the present invention may be circular, elliptical, polygonal such as hexagonal, quadrilateral, pentagonal, or convex, and the same effect can be obtained.

[0030]

According to the present invention, the anticorrosion coating 2 on the surface of the cable 1 is provided with a plurality of concave or convex aggregates of circular or polygonal shape, which are processed into a concave or convex shape corresponding to the unit surface area of the cable. By forming and arranging a large number of areas so that the sum of the areas is in the range of 3% to less than 10%, it is possible to prevent the formation of water channels caused by the interaction of rain and wind on the surface of the anticorrosion cable with a small amount of processing, and to prevent rain vibration. It is possible to suppress the occurrence of the stress, to prevent an increase in the drag coefficient due to the change of the cable surface shape, to suppress the drag coefficient to a level almost equal to that of a smooth circular cross section, and to not impair the appearance. As a result, the wind load on the cable can be significantly reduced compared to the conventional damping cable, and the rational design of the bridge becomes possible. In particular, in the case of a long cable-stayed bridge, many cables are densely arranged, and the wind-bearing capacity of the girder is governed by the wind load generated on the cable. Very effective above.

Further, as the length of the bridge becomes longer, the cable length also becomes longer, so that the effect of mounting the damping device is reduced and the aerodynamic countermeasure becomes effective. If the aerodynamic measures according to the present invention are used, it is not necessary to add an additional structure like a damping device and the appearance is not spoiled.

[Brief description of drawings]

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

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

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

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

5 (a) and 5 (b) are explanatory views of Comparative Example 1 in which the ratio of the area of the recess to the cable unit surface area is less than 3%.

FIG. 6 is a diagram showing the detailed shape of a recess in FIG. 5;

FIG. 7 is a view showing details of a shape of a surface recess 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 the relationship between the cable surface processing area and the drag coefficient.

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

FIG. 11 is a view showing a cross section of a vibration damping cable of a conventional example (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 mounting a damping device.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Cable strand 2 ... Anticorrosion coating 3 ... Cable 4 ... Recessed assembly part 4a ... Recessed part 5 ... Recessed assembly part 5a ... Recessed part 6 ... Groove 7 ... Projection 8 ... Wire rope 9 ... Girder 10 ... Damping device

Claims (1)

[Claims] 1. An air-suspended cable in which a surface of an anticorrosion coating is processed to have a concave or convex shape, and a plurality of circular or polygonal concave or convex aggregates are formed on the surface of the anticorrosion coating.
A vibration-damping cable characterized in that a large number of concave or convex areas corresponding to a unit surface area of the cable are formed in a range of 3% to less than 10%.