JPH0571104A - Overcoat protective tube of laid cable - Google Patents

Abstract

PURPOSE:To restrain the vibration of a cable by providing a spiral projecting portion in the longitudinal direction on the outer peripheral surface of an overcoat protective tube for covering and protecting a laid cable. CONSTITUTION:A longitudinal projecting portion 3 is provided on the outer peripheral surface 2a of a synthetic resin tube 2 to form an overcoat protective tube 1. In the case where wind blows at declination, at the back of a section of the overcoat protective tube 1, wind directing in the axial direction collides with the projecting portion 3 to be disturbed, so that a steady axial flow is checked. Further, the vertical flow velocity fluctuation can be restrained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a vibration damping device for cables of cable-stayed bridges and general erection cables.

[0002]

2. Description of the Related Art Conventionally, for example, a cable in a cable-stayed bridge is used by being exposed outdoors, and therefore it is necessary to prevent a cable made of a bundle of steel wires from being cut due to corrosion. Therefore, as shown in FIG. 4, a synthetic resin pipe (hereinafter referred to as a jacket protection pipe) 1 is provided on the steel wire bundle 15 via a rust preventive material 16.
It is covered with 7. Further, the outer jacket protection tube 17 has a cylindrical shape.

[0003]

However, the mantle protection tube 17 of the cable of the cable-stayed bridge described above vibrates when the vehicle is running or an earthquake occurs or when it receives strong winds, causing the cable to be fatigued and the strength of the cable to be reduced. There was a flaw that said it would decline early. Among these vibrations, a particularly remarkable vibration is the occurrence of vibration called rain vibration due to wind and rain, and an early solution to prevent this is desired.

In the rain vibration, a path for rainwater to flow along the bottom surface of the cable stayed bridge is formed, which makes the outer surface of the mantle protection tube irregular, and a lift is generated by horizontal wind to cause a so-called galloping phenomenon. ..

Therefore, as shown in FIG. 3, the mantle protective tube 1
4 is provided with protrusions 12 and 13 on the outer peripheral surface and in the longitudinal direction, it is proposed to suppress lift generation due to asymmetrical flow of the outer flow of the mantle protective tube 14 and prevent the rain vibration, and its vibration damping effect is proposed. It is recognized.

However, as shown in FIG. 3, when the mantle protection tube 14 has an angle of deviation (β in FIG. 3) with respect to the direction of the wind α (this case is common), the mantle protection is performed. Tube 1
Axial flow 11 is generated behind the cross section of No. 4 and toward the rear part of the outer jacket protection tube 14 and becomes extremely aerodynamically unstable, resulting in a vertical flow velocity fluctuation of about 1 Hz, and the vibration suppression of the outer jacket protection tube 14 is caused. A wind tunnel test revealed that the effect was adversely affected. The present invention has been made in view of the above problems, and a mantle protection that suppresses the vibration of the erection cable by suppressing the generation of the axial flow 11 in the mantle protection pipe of the cable-stayed bridge cable and other general erection cables. Intended to provide a tube.

[0007]

Means for Solving the Problems The object of the present invention to solve the above problems and achieve the above objects is to provide a mantle protection tube for covering and protecting a erection cable, in which an outer peripheral surface and a spiral projection in the longitudinal direction. It is due to the establishment of the department. Also,
If the protrusion is formed by attaching a wire or the like, the outer protective tube of the present invention can be easily obtained.

[0008]

As described above, according to the mantle protection tube of the cable-stayed cable according to the present invention, the projection behind the spiral winding causes the cross section behind the mantle protection tube when the wind blows at an angle β. In the above, the axial wind collides with and is disturbed by the projections to prevent the steady flow of the axial flow, thereby suppressing the vertical flow velocity fluctuation.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, the present invention will be described with reference to the drawings. FIG. 1 is a perspective view of a jacket protection tube 1 according to the present invention. FIG. 2 is a front view showing a usage state.

The mantle protection tube 1 is formed of a synthetic resin (for example, FRP, PE, etc.) tube 2 with a projection 3 spirally formed on its outer peripheral surface 2a and in the longitudinal direction of the mantle protection tube 1 as shown in the drawing. Be provided in a shape.

As a method of forming the protrusions 3, the projections 3 may be integrally molded with the tube 2, or may be wound by using wires or flexible hoses. Then, in order to construct a method for damping a cable of a cable-stayed bridge using the mantle protection tube 1 according to the present invention, as shown in FIG. The outer sheath protection tube 1 is successfully connected, and the cable-stayed bridge cable is completed. It should be noted that reference numerals 8 and 9 denote a tower and a roadway girder, respectively.

As a result, even if wind blows on the cable stayed bridge during rain or no rain, the steady axial flow behind the cross section of the mantle protection tube 1 is blocked, and fluctuations in the vertical flow velocity occur. The cable staying bridge cable will be effectively damped.

The wind tunnel test was conducted at the Japan Automobile Research Institute, using a JARI small wind tunnel tester, and the frequency of the vortices was measured using a probe of a hot-wire anemometer (manufactured by DANTEC) and FFT. Frequency analysis was performed with an analyzer (manufactured by HP), and the flow was visualized by injecting smoke into the air flow as a tracer and irradiating it with a laser light.

[0014]

As described above, the mantle protection tube for the erection cable according to the present invention is the mantle protection tube for covering and protecting the erection cable, in which the spiral projection is provided on the outer peripheral surface and in the longitudinal direction. Therefore, the generation of the axial flow due to the wind is prevented, the fluctuation of the flow velocity in the vertical direction is eliminated, and the shaking of the cable-stayed bridge cable and the general erection cable is suppressed. In addition, if the wire or the like is wound around in a spiral shape, the mantle protection tube can be easily formed, which is convenient.

[Brief description of drawings]

FIG. 1 is a perspective view of a mantle protection tube according to the present invention.

FIG. 2 is a front view showing a usage state of the mantle protection tube.

FIG. 3 is an explanatory view of a wind tunnel test state of a conventional mantle protection tube.

FIG. 4 is a cross-sectional view of a conventional mantle protection tube of the same.

[Explanation of Codes] 1 mantle protection tube, 2 tubes, 3 projections, 6 steel wire bundle, 7 rust preventive material, 11 axial flow.

Claims (2)

[Claims] 1. An outer sheath protection tube for a erection cable, characterized in that, in the outer sheath protection tube for covering and protecting the erection cable, a spiral projection is provided on the outer peripheral surface thereof in the longitudinal direction. 2. The mantle protection tube for an erection cable according to claim 1, wherein the protrusion is formed by attaching a long object such as a wire or a hose.