JPH01210507A - Vibrationproof structure for cable constructed for structure - Google Patents

Abstract

PURPOSE:To prevent vibrations by a wind by bringing the space of two parallel cables constructed to a diagonal cable bridge, a steel tower, etc. to fixed times as long as the diameter of the cable. CONSTITUTION:A pair of parallel cables 13 are disposed in tension between a main tower 11 and a bridge girder 12 for a diagonal cable bridge, arranging spacers 14 so that a space between the centers of each cable is brought to 1.2-2.0 times as long as the diameter of the cable. Accordingly, when a wind blows against the cables, wake-galopping, in which the rear stream side cable is vibrated largely in the direction rectangular to the wind by the peeling current of the front stream side cable, can be prevented.

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention is applicable to cables installed on structures such as cable-stayed bridges, suspension bridges, and steel towers and chimneys, and cables for power transmission and communications installed between steel towers. This relates to vibration-proof structure.

(Prior art) Figure 5 shows a structural diagram of a general cable-stayed bridge, in which a cable (3) is stretched between the main tower (]) and the bridge girder (2),
) is suspended from the main tower (1).

Generally, two cables (3) are often installed in parallel as shown in Fig. 6, and they are usually spaced apart from each other by at least three times the cable diameter based on the size of the mounting socket. .

When the wind (4) blows on the parallel cable, the wake side cable (3b) blows on the front side cable (3) as shown in Fig. 7.
The separated flow (5) generated by a) causes wake galloping, which vibrates greatly in the direction (6) perpendicular to the wind (4).

This wake galloping is performed using the upstream cable (3a
) The separation flow (5) generated from the downstream cable (3b)
As a result, both cables (3
This is thought to be caused by a gap flow occurring between a) and (3b).

Conventionally, in order to suppress the vibration, wires (7) fixed at almost right angles to each cable (3) were strung toward the legs of the main tower (1), as shown in Figure 8. And also the 9th
As shown in the figure, a cable vibration isolation structure was adopted in which wires (7) were stretched between each cable (3) almost parallel to the bridge girder (2).

(Problems to be Solved by the Invention) The conventional vibration isolation structure in which a wire is stretched between cables has the risk of damaging the wrapping material wrapped around the outer periphery of the cable to protect the cable.

Furthermore, for bridges that serve as monuments at the beginning and end of roads, towns, and ports, structures in which wires are stretched between cables as described above are undesirable from an aesthetic point of view.

The present invention was proposed in view of the problems of the prior art, and its purpose is to provide vibration isolation for cables installed in structures that do not vibrate due to wind, without having to stretch wires between the cables. The point is to provide structure.

(Means for Solving the Problems) In order to achieve the above-mentioned object, the vibration isolation structure for a cable installed in a structure according to the present invention sets the distance between the centers of parallel cables installed in a structure to 1.0% of the cable diameter. It is configured to be twice or twice as large.

(Function) As described above, in the present invention, the center distance between parallel cables installed in a structure is set to 1.2 of the cable diameter.
By narrowing down to twice or twice, the wake cable completely enters the separation flow generated from the front cable,
The separation flow does not switch to the upper and lower surfaces of the downstream cable, so wake galloping does not occur, and vibrations do not occur.

(Example) The illustrated example in which the present invention is applied to a cable vibration isolation structure in a cable-stayed bridge will be described below.

In Figure 1, 01) is the main tower, and a pair of parallel cables 09 are stretched between the main tower (11) and the bridge girder (12+), and the bridge girder 09 is suspended from the main tower (11). ing.

The two cable surfaces are arranged by spacers 04 in most of their longitudinal directions so that the distance between the centers is 1.2 to 2.0 times the cable diameter '0).

Note that the cable spacing near the attachment point between the main tower (11) or the bridge girder and the cable surface is set arbitrarily.

According to the illustrated embodiment, as described above, the center distance λ of the pair of cables stretched between the main tower (11) and the bridge girder is 1.2 to 2.0 times the cable diameter d. As shown in Part 2, the downstream cable ('13
b) completely enters the inside of the turbulent flow (5) generated from the upstream side cable (13a), and the separated flow (5) does not switch to the upper and lower surfaces of the downstream side cable (13b). ,
Vibration will no longer occur.

Note that when the value of λ/d exceeds 2, a gap flow occurs between the cables (13a) and (13b) as in the conventional cable, and wake galloping occurs.

Moreover, when the value of λ/4 becomes smaller than 1.2, the cable (13
a) The gap between (13b) becomes smaller and both cables (
13a) (13b) now exhibits the characteristics of a single body.

That is, when a slightly tilted wind (α, which will be described later is small) acts, a large lift force is generated in the negative direction. This is a phenomenon based on a well-known principle as a generation mechanism of gearropping vibration, and is also the reason why it becomes stable when α=0 or when α≧10＠, as will be described later.

Furthermore, by arranging the downstream cable (13b) close to the upstream cable (13a), the shape of the water path flowing on the cable surface changes during wind and rain, and vibrations caused by rain vibrations are eliminated.

Figure 3 is a diagram showing the results of a wind tunnel experiment that investigated the cable center spacing λ and vibration generation state in response to wind from the arrow direction of a pair of cables θ9 arranged in parallel. Indicates the direction of vibration of the downstream cable.

The experimental wind speed V was 0 to 25 m/s, the test cable diameter was d-160 mm φ, and the length was 27.00 mm.

Figures 4a to 4d are 4 of λ/4 in Figure 3 above.
Figure 3 shows the cable amplitude (Δ) versus wind speed (vm/s) and cable diameter (d) in two regions, where λ is the cable center spacing and α is the wind direction entering the cable.

Stability here means that the vibration amplitude (Δ) is equal to the cable diameter (d
) below 5%.

Figure 4a shows α-3 when one pair of cables are in close contact with each other.
°, and α-5° data. However, it is stable when α=0″, and the amplitude is small even when α≧10″′.

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

FIG. 4C shows data for λ=4d1α=0″, and similar results can be obtained for λ=5d.

Figure 4d shows the case where λ=10d and αζ18@, and the downstream cable "wobbles around."

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 observatory, and the bridge girder 02) may be used as the ground. The present invention can also be applied to hanger ropes for suspending bridge girders from cables.

(Effects of the Invention) According to the present invention, as described above, by setting the distance between the parallel cables installed in the structure to 1.2 to 2 times the cable diameter, wake galloping of the cables is prevented. It is possible to prevent vibrations from occurring, and by arranging the upstream cable in close proximity to the downstream cable in this way, it is possible to prevent vibrations caused by rain vibrations.

As described above, according to the present invention, vibration can be prevented without having to stretch wires between cables for constructing a structure as in the conventional case.

[Brief explanation of the drawing]

Fig. 1 is a perspective view showing an example of the vibration isolation structure for cables installed in structures according to the present invention, Fig. 2 is a chart showing the relationship between wind speed and vibration amplitude, and Fig. 3 shows the results of wind tunnel experiments. Figures 4a to 4d are diagrams showing the relationship between wind speed and cable amplitude in each region in Figure 3 and cable diameter, Figure 5 is a front view of the cable-stayed bridge, and Figure 6 is its part. FIG. 7 is a conceptual diagram of wake galloping vibration, and FIGS. 8 and 9 are front views showing conventional cable vibration isolation structures, respectively. (11)--Main tower 0 powder...Bridge girder flush--Cable agent Patent attorney Shige Okamoto 2 people shoulder 2m outside the building Diagram Aq

Claims (1)

[Claims] A vibration isolation structure for cables installed in a structure, characterized in that the distance between the centers of parallel cables installed in the structure is 1.2 to 2 times the cable diameter.