JPH0814088B2 - Vibration isolation structure for construction cables - Google Patents

Description

The present invention relates to cable-stayed bridges, suspension bridges, cables erected on structures such as towers and chimneys, and cables for power transmission and communication installed between towers. It relates to a vibration-proof structure.

(Prior Art) Figure 5 shows the structure of a typical cable-stayed bridge.
The cable (3) is stretched between the bridge girder and the bridge girder (2), and the bridge girder (2) is supported from the main tower (1).

In general, two cables (3) are generally stretched in parallel as shown in FIG. 6, and are usually arranged at a center distance from the size of the mounting socket and at least three times the cable diameter. .

When wind (4) blows on the parallel cable, the downstream cable (3b) is connected to the upstream cable (3b) as shown in FIG.
The separated flow (5) generated from a) causes wake gear locking that vibrates greatly in the direction (6) at right angles to the wind (4).

This wake gear roping is designed with the cable (3
The separated flow (5) generated from a) is the downstream cable (3b)
Switch to the upper and lower surfaces of the
It is considered that the cause is a gap flow between a) and (3b).

Conventionally, in order to suppress the vibration, as shown in FIG. 8, a wire (7) fixed substantially at right angles to each cable (3) is stretched toward the legs of the main tower (1). Further, as shown in FIG. 9, a cable vibration-proof structure in which a wire (7) is stretched between the cables (3) substantially parallel to the bridge girder (2) has been adopted.

(Problems to be Solved by the Invention) The conventional vibration-proof structure in which a wire is stretched between cables may damage the wrapping material wound around the outer periphery of the cable in order to protect the cable.

In addition, the structure in which the wires are stretched between the cables as described above is not aesthetically preferable in the bridges that become the starting and ending points of roads and the monuments of towns and ports.

The present invention has been proposed in view of the above problems of the prior art, and an object thereof is to prevent vibration of a structure erection cable that does not vibrate by wind without laying a wire between the cables. The point is to provide the structure.

(Means for Solving the Problem) In order to achieve the above-mentioned object, the vibration isolating structure for a structure erection cable according to the present invention has a center interval between parallel cables erected on a structure that is 1.2 times the cable diameter. It is configured to be doubled.

(Operation) In the present invention, as described above, the center distance between the parallel cables laid on the component is set to be 1.2 times the cable diameter.
By squeezing the cable to twice or twice, the downstream cable enters completely inside the separated flow generated from the upstream cable,
The separated flow does not switch to the upper and lower surfaces of the downstream side cable, wake gear locking does not occur, and vibration does not occur.

(Example) Hereinafter, an illustrated example in which the present invention is applied to a cable vibration-proof structure in a cable-stayed bridge will be described.

In FIG. 1, (11) is a main tower, and a pair of parallel cables (13) are stretched between the main tower (11) and the bridge girder (12), and the bridge girder (12) is connected to the main tower (11). ) Is suspended from.

Thus, the pair of cables (13) are arranged by the spacer (14) so that the center interval is 1.2 to 2.0 times the cable diameter in most of the longitudinal direction.

In addition, the cable interval in the vicinity of the attachment portion of the cable (13) to the main tower (11) or bridge girder (12) is set arbitrarily.

According to the illustrated embodiment, as described above, the center distance λ of the pair of cables (13) stretched between the main tower (11) and the bridge girder (12) is 1.2 to 2.0 times the cable diameter d. Since it is narrowed, as shown in Fig. 2, the downstream cable (13b)
Completely enters the separated flow (5) generated from the upstream cable (13a), the separated flow (5) does not switch to the upper and lower surfaces of the downstream cable (13b), and vibration occurs. Will not do.

When the value of λ / d exceeds 2, a gear trap flow is generated between the cables (13a) and (13b) as in the conventional cable, and wake gear locking occurs.

When the value of λ / d becomes smaller than 1.2, the cable (13a)
The gap between (13b) becomes smaller and both cables (13a) (13
b) comes to show the characteristics as one body. That is, when a slightly inclined wind (α described later is small) acts, a large lift is generated in the negative direction. This is a phenomenon based on a well-known principle as a mechanism of gear-lopping vibration, and is also stable when α = 0 or α ≧ 10 ° as described later.

Further, by disposing the downstream cable (13b) close to the upstream cable (13a), the shape of the water flowing on the surface of the cable during wind and rain is changed, and vibration due to rain vibration is eliminated.

FIG. 3 is a diagram showing a wind tunnel experiment result in which the cable center interval λ and the generation state of vibration of the twin cables (13) arranged in parallel with respect to the wind from the direction of the arrow are examined, and are shown by dotted lines in the figure. The arrow indicates the vibration direction of the downstream cable.

The experimental wind speed v was 0 to 25 m / s, and the test cable diameter was d = 1.
60mmφ, length = 27.00mm.

4a to 4d show the wind velocity (vm / s) and the cable amplitude (Δ) with respect to the cable diameter (d) in the four regions of λ / d in FIG. 3, where λ is the center distance of the cable, α is the wind direction entering the cable.

The stability here means that the vibration amplitude (Δ) is 5% or less of the cable diameter (d).

Fig. 4a shows α = 3 when one pair of cables are closely attached.
And the data of α = 5 °. However, it is stable when α = 0 °, and the amplitude is small even when α ≧ 10 °.

Fig. 4b shows the stable range, where the vibration amplitude Δ is the cable diameter d.
It can be seen that it is in the stable range of 5% or less.

FIG. 4C shows data at λ = 4d and α = 0 °, and similar results can be obtained at λ = 5d.

Fig. 4d shows the case where λ = 10d and α ≈ 18 °, and the wake side cable "wobbles".

In the embodiment shown in FIG. 1, the main tower (11) may be replaced with a long structure such as an antenna tower or an observation tower, and the bridge girder (12) may be used as the ground. The present invention can be applied to a hanger rope that suspends a bridge girder from a main cable.

(Effect of the invention) According to the present invention, as described above, the distance between the parallel cables laid on the structure is set to 1.2 times to 2 times the cable diameter, so that the vibration due to the wake gear locking of the cable is suppressed. It is possible to prevent the occurrence of vibrations and to prevent the vibration due to the rain vibration by disposing the front side cable in the vicinity of the rear side cable.

As described above, according to the present invention, it is possible to prevent vibration without tensioning wires between the structure erection cables as in the related art.

[Brief description of drawings]

FIG. 1 is a perspective view showing an embodiment of a vibration isolating structure for a structure erection cable according to the present invention, FIG. 2 is a table showing a relationship between wind speed and vibration amplitude, and FIG. 3 is a wind tunnel test result. Figures 4a to 4d are charts showing the relationship between the wind speed in each area in Fig. 3 and the amplitude of the cable with respect to the cable diameter. Fig. 5 is a front view of the cable-stayed bridge. Fig. 6 is its part. FIG. 7 is a perspective view, FIG. 7 is a conceptual diagram of wake gear locking vibration, and FIGS. 8 and 9 are front views showing a conventional cable vibration damping structure. (11)… Main tower, (12)… Bridge girder, (13)… Cable

Front page continuation (72) Inventor Kosuke Watanabe 1-1, Atsunoura-cho, Nagasaki-shi, Nagasaki Mitsubishi Heavy Industries, Ltd. Nagasaki Research Institute (72) Inventor Masaru Miyake 12 Nishiki-cho, Naka-ku, Yokohama-shi Kanagawa Mitsubishi Heavy Industries, Ltd. Inside the Yokohama Works (72) Inventor Noboru Tomita 12 Nishiki-cho, Naka-ku, Yokohama, Kanagawa Mitsubishi Heavy Industries, Ltd. (72) Inventor Shozaburo Miura 12 Nishiki-machi, Naka-ku, Yokohama Mitsubishi Heavy Industries, Ltd. In-house Examiner, Ryoji Kawashima (56) References JP-A-53-58136 (JP, A) SAIKAI-SHO 61-184716 (JP, U) JP-B-47-27984 (JP, B1)

Claims (1)

[Claims] 1. A vibration isolating structure for a structure-installed cable, wherein a center interval between parallel cables installed in the structure is 1.2 to 2 times the cable diameter.