JP2993403B2 - Cable-stayed bridge diagonal cable damping device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cable-stayed bridge diagonal cable damping device for suppressing vibration of a diagonal cable caused by wind or the like.

[0002]

2. Description of the Related Art Since a cable for a cable stayed bridge is likely to vibrate due to wind or earthquake, it is necessary to avoid damage due to fatigue caused by the vibration. 7 are added.

FIG. 5 shows a method of connecting a plurality of diagonal cables with ropes to suppress vibration due to interference between the diagonal cables. FIG. 6 shows an oil damper near a fixing portion of the diagonal cable to a main girder. FIG. 7 shows a method of connecting a viscous shear type damper to suppress vibration, and FIG. 7 shows a method of restricting vibration by disposing a spacer between the parallel diagonal cables when the diagonal cables are arranged in parallel.

In the method shown in FIG. 5, if the rope is not directed in the direction of the vibration of the diagonal cable, the efficiency is reduced, so that a sufficient vibration damping effect cannot be expected. Although the effect of the damper increases as the amplitude of the diagonal cable increases, the damping effect is small in the method of FIG. 6 because the damper is installed near the fixing portion having a small amplitude. In the method shown in FIG. 7, a new vibration is generated at the installation position of the spacer, so that it is not an effective vibration suppression method.

The present invention proposes an apparatus for effectively suppressing the vibration of a diagonal cable from the above background.

[0006]

According to the present invention, the vibration of the diagonal cable is restrained by a part of the diagonal cable using the attractive force between the magnetic material and the magnet, and the force at the time of the vibration opposite to the attractive force is applied. The vibration mode of the diagonal cable is changed by releasing the restraint by using, and the vibration of the diagonal cable is effectively and easily suppressed.

[0007] A vibration damping device for switching between restraining and releasing vibration of a diagonal cable is provided with a gap between a cylindrical magnetic body attached to a part of the diagonal cable and surrounding the outer circumference of the diagonal cable. It consists of a cylindrical magnet that surrounds the magnetic material at a distance and is fixed to the main girder. When the diagonal cable generates vibration with a certain amplitude or more, the magnetic material is attracted by the magnet and the vibration of the diagonal cable Is restrained at the position of the magnetic material, and the diagonal cable vibrates in the opposite phase to that of the restraint, and the diagonal cable is released from the restraint when the force applied to the magnetic material exceeds the attractive force of the magnet.

[0008] The vibration of the diagonal cable generated by the wind is considered to be a kind of self-excited vibration, and mainly vibrates in the primary mode. When one point near the anchoring portion of the oblique cable vibrating in the primary mode is constrained as shown in FIG. 3, the vibration shifts to a mode in which the constrained point is a node as shown in FIGS. .

According to the vibration damping device of the present invention, the diagonal cable starts to vibrate, and when the amplitude reaches a certain value, the magnetic material attached to the diagonal cable is attracted to the magnet by the magnetic force, and the two come into contact with each other. In this state, the diagonal cable is restrained at the vibration control device installation position.

Conversely, if the restraint of the diagonal cable is released when the central part of the diagonal cable is displaced to the opposite phase, FIG.
As shown in (1) and (2), the vibration in the first mode is disturbed, and the vibration in the higher mode is generated. This indicates that the primary mode vibration energy has shifted to the higher mode as shown in FIG. 4, and as a result, the primary mode vibration amplitude decreases.
On the other hand, the vibration of the higher-order mode immediately attenuates and disappears.

According to the vibration damping device, the vibration of the diagonal cable vibrates in a phase opposite to that of the restraint, and when the force applied to the restraint point exceeds the holding force of the magnet, the magnetic material separates from the magnet and The cable is released from the restraint.

The energy of the primary vibration mode is shifted to the higher-order vibration mode by alternately repeating the above-described restraint and release of the vibration, whereby the growth of the vibration is suppressed, and the steady vibration is reduced. Can be attenuated.
In order to shift the energy of the first mode to the higher mode more effectively, the holding force of the magnet may be set so that the oblique cable can be restrained and released when the displacement of the central portion of the oblique cable is maximum. .

[0013] By repeating the restraining and releasing operation of the diagonal cable, vibration due to wind and earthquake can be suppressed, and all vibrations such as wake galloping, rain vibration, and vortex excitation can be suppressed.

In the present invention, the attraction between the cylindrical magnetic body surrounding the diagonal cable and the cylindrical magnet spaced apart from the outer periphery is used for the operation of restraining and releasing the vibration. Therefore, vibration of the diagonal cable in any direction can be suppressed.

Further, since the device is composed of only a magnetic material and a magnet, the structure is simple. In particular, if a permanent magnet is used as the magnet, the device does not require any power, and the vibration of the diagonal cable can be easily suppressed. I can do it.

[0016]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A vibration damping device 1 according to the present invention has a cylindrical magnetic body 2 attached to a part of a diagonal cable 6 so as to surround the outer periphery thereof, as shown in FIGS. 2 around the magnetic body 2 with a space between it and the outer periphery of the main girder 7.
And is installed on a part of the diagonal cable 6 while being supported by the main girder 7 to suppress vibration of the diagonal cable 6.

A permanent magnet or an electromagnet is used for the magnet 3, and the magnet 3 is protected by a protector 4 surrounding the whole magnet, and a fixing member 5 supported by a main girder 7 is fixed to the outer periphery of the protector 4. As a result, it is indirectly fixed to the main girder 7.
In the neutral state where the diagonal cable 6 is not vibrating, the diagonal cable 6 is located at the center of the magnet 3.

The vibration damping device 1 is configured such that when the diagonal cable 6 starts to vibrate and the magnetic material 2 is vibrated by the attraction force of the magnet 3 and vibrates with a certain amplitude or more to the extent that they come into contact with each other. 2 contacts the magnet 3 and restrains the diagonal cable 6 at the position of the magnetic body 2. This state corresponds to FIG.

When the diagonal cable 6 vibrates in a phase opposite to that of the restraint and acts on the contact point between the magnetic body 2 and the magnet 3 when the force in the opposite direction to the attractive force exceeds the attractive force of the magnet 3, Release the material cable 6 from the restraint. This state corresponds to FIG.

The attractive force of the magnet 3 and the force (maximum holding force of the magnet) acting on the restraint point when the diagonal cable 6 is released can be set by the strength of the magnet 3 to be used (in the case of an electromagnet, the coil is not connected to the coil). The amount of displacement required to restrain the vibrating diagonal cable 6 is the distance between the outer circumference of the magnetic body 2 and the inner circumference of the magnet 3 (the magnetic body 2 and the magnet 3 are cylindrical). In the case of a shape, it is determined by the difference between the outer diameter of the magnetic body 2 and the inner diameter of the magnet 3).

[0021]

According to the present invention, the vibration of the diagonal cable is restrained by a part of the diagonal cable by utilizing the attractive force between the magnetic material and the magnet, and the restraint is released by using the force at the time of the vibration opposite to the attractive force. By changing the vibration mode of the diagonal cable, the vibration of the primary vibration mode is shifted to the higher vibration mode by alternately repeating the restraint and release of the vibration, thereby suppressing the growth of vibration. In order to reduce the vibration, it is possible to attenuate the vibration of the diagonal cable at an early stage, and to suppress all the vibrations such as wake galloping, rain vibration, vortex excitation, etc. in addition to the vibration of the diagonal cable due to wind and earthquake. Can be.

In addition, since the attractive force between the cylindrical magnetic body surrounding the diagonal cable and the cylindrical magnet spaced apart from the outer periphery is used for the operation of restraining and releasing the vibration, the Therefore, vibration of the diagonal cable in any direction can be suppressed.

Further, the structure is simple because it is composed of only a magnetic material and a magnet. In particular, if a permanent magnet is used for the magnet,
The device requires no power at all, and can easily suppress the vibration of the diagonal cable.

[Brief description of the drawings]

FIG. 1 is an elevation view showing a state in which a vibration damping device is attached to a diagonal cable.

FIG. 2 is an axial sectional view of a diagonal cable showing a configuration of the vibration damping device.

FIG. 3 is a schematic diagram showing a change in vibration when one point of a diagonal cable is restrained and released.

FIG. 4 is a graph showing energy transfer by restraining and releasing a diagonal cable.

FIG. 5 is an elevational view showing a conventional method of damping a diagonal cable.

FIG. 6 is an elevation view showing a conventional method of damping a diagonal cable.

FIG. 7 is an elevational view showing a conventional method of damping a diagonal cable.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Vibration suppression device, 2 ... Magnetic body, 3 ... Magnet, 4 ... Protector, 5 ... Fixing member, 6 ... Diagonal cable, 7 ...
Main girder.

Claims (1)

(57) [Claims] 1. A vibration damping device that is installed on a part of a diagonal cable while being supported by a main girder and suppresses vibration of the diagonal cable. A cylindrical magnet to be attached, and a cylindrical magnet fixed to the main girder, surrounding the magnetic body at an interval between the magnetic body and the outer periphery of the magnetic body. At the time of vibration, the magnetic material is attracted by the magnet and restrains the vibration of the diagonal cable at the position of the magnetic material, and the diagonal cable vibrates in the opposite phase to the restraint, and the force applied to the magnetic material exceeds the attractive force of the magnet A cable-stayed bridge diagonal cable damping device that sometimes releases the diagonal cable from restraint.