JPS6260512B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a coated cable with spiral ribs, such as a bridge, an architectural suspension structure, or an electric wire cable, and particularly to prevention of vibration of the cable due to wind.

[Conventional technology]

Conventionally, the Langar Bridge (arch bridge) shown in Figure 2
Alternatively, in bridges such as the cable-stayed bridge shown in FIG. 3, a cable 1 made of twisted or parallelly bundled high-tensile piano wires with a diameter of 5 mm or 7 mm is used as a tension member. In order to prevent corrosion and protect the cable 1, the cable 1 is coated with a synthetic resin material such as polyethylene resin, as shown in FIG.
Cables coated with

By the way, as is well known, when an object with a circular cross section is placed vertically in a flow of water, air, etc., a Karman vortex is generated on the wake side of the object, and the periodic forcing force of this vortex is It is known that objects in the flow vibrate due to this phenomenon, and this phenomenon has also been confirmed experimentally.

Actually, in the bridge shown in FIGS. 2 and 3, the cable 1 vibrates due to the Karman vortex caused by the wind and generates noise. In order to prevent the vibration of the cable 1, a vibration prevention wire 3 is connected between the cables 1 and a special damper is used, but the effect is not perfect, and furthermore, due to the appearance and cost was also not satisfactory.

On the other hand, it has been experimentally confirmed that wrapping a spiral rib plate 5 around an object 4 having a circular cross section as shown in FIG. 5 has a significant effect on preventing Karman vortex vibrations. That is, Figures 6 and 7
The figure shows the converted wind speed (dimensionalless wind speed) V/fD when the wind speed is V, the frequency is f, and the diameter of object 4 is D.
The horizontal axis is the dimensionless amplitude A/D of the amplitude A, and the vertical axis is the dimensionless amplitude A/D. Here, FIG. 6 shows a case where the spiral rib plate 5 is not wound around the object 4, and FIG. 7 shows a case where the spiral rib plate 5 is wound around the object 4. Note that δ in the figure represents the attenuation rate. As is clear from FIGS. 6 and 7, when the spiral rib plate 5 is not wrapped around the object 4, vortex-excited vibration is generated, but when the spiral-shaped rib plate 5 is wrapped around the object 4, vortex-excited vibration is generated. It has a remarkable effect on preventing. In fact, the 8th
As shown in the figure, there are examples in which lobes 6 or the like are spirally wound around a cylindrical object such as a cable 1 or a gas pipe bridge, or a spiral rib plate is attached to a chimney to achieve a vibration-preventing effect.

[Problem that the invention seeks to solve]

The conventional method for preventing vortex vibrations as described above is to simply wrap rib plates, ropes, wires, etc. around the cable 1 after the construction using the cable 1 is completed on-site, so the strength is not sufficient. Over the years, there have been problems in which the rib plates etc. have become misaligned or loosened from the cable 1, and the ribs have not been sufficiently high, resulting in insufficient vibration-proofing effects.

Furthermore, winding the cable around the cable 1 was difficult and dangerous as it required work at high places on site.

Furthermore, cables coated with polyethylene resin, etc., which are often used in bridges these days, have a cylindrical shape with a smooth surface, so it is difficult to install rib plates, etc. on site to prevent vortex vibrations caused by wind. There was also the problem that.

This invention was made to solve this problem, and the object is to obtain a coated cable with spiral ribs that can reliably prevent excessive vibration caused by wind without requiring on-site work. It is.

[Means for solving problems]

The coated cable with spiral ribs according to the present invention has a spiral rib plate formed integrally with the synthetic resin coating of the cable.

[Effect]

In this invention, when coating the cable with a synthetic resin material, by integrally molding or welding a spiral rib plate with a predetermined shape to the cable surface, it is possible to prevent the cable from wind damage. Prevents vortex vibration.

〔Example〕

FIGS. 1a and 1b show an embodiment of the present invention, and a
is a front view, and b is a cross-sectional view. In the figure, 7a,
Reference numerals 7b and 7c each designate a rib plate integrally formed into a spiral shape with a synthetic resin material 2, such as polyethylene resin, coated on the cable 1.

The shapes of the spiral rib plates 7a, 7b, 7c are as shown in FIGS. 1a and 1b as a result of experiments. The pitch l is approximately 5 times the diameter D, the height h is approximately 0.1 times the diameter D, and the spiral rib plates 7a, 7b, 7
The vibration damping effect is highest when the number of c is about three.
Therefore, this shape is molded as a standard.

As mentioned above, the synthetic resin material such as polyethylene resin that is molded and coated on the cable 1 is relatively flexible and has elasticity, so after being molded and coated at the factory, it is transported wrapped around a reel and deployed at the site. The shape is only temporarily deformed, but it quickly returns to its original shape. Therefore, vortex vibrations caused by wind can be prevented simply by tensioning this coated cable with spiral ribs as a tension member at the site.

In the above example, the spiral rib plate was molded integrally with the cable sheath, but
A similar effect can be obtained by welding a spiral rib plate when covering the cable.

〔Effect of the invention〕

As explained above, in this invention, when covering and molding a cable with a synthetic resin material, a spiral rib plate of a fixed shape is integrally molded or welded, so that the installation strength of the rib plate is sufficient, and the rib plate can be prevented from changing over time. It is possible to exhibit a sufficient vibration-proofing effect to prevent the plates from shifting. In addition, there is no need to wrap rib plates or the like around cables when working at high places on-site, which has the effect of increasing the safety of on-site work.

The coated cable with spiral ribs is not limited to bridge cables, but can also be widely applied to architectural cables used in suspended roofs, membrane structures, etc., power cables, communication cables, and the like.

[Brief explanation of the drawing]

Figures 1a and 1b show embodiments of the invention, where a is a front view, b is a sectional view, Figures 2 and 3 are front views of a bridge, and Figure 4 is a perspective view of a synthetic resin coated cable. , Fig. 5 is a front view of a cable wrapped with a conventional spiral rib plate, Figs. 6 and 7 are wind speed-amplitude characteristic diagrams, and Fig. 8 is a perspective view of a cable wrapped with a conventional rope. . 1... Cable, 2... Synthetic resin material, 7a, 7b,
7c...Spiral rib plate.

Claims (1)

[Claims] 1. A coated cable with spiral ribs, which is characterized by having a spiral ribbed plate integrally formed with the synthetic resin coating, in a cable whose surface is coated with a synthetic resin material for corrosion prevention and protection.