JPH0739032A - Corner-breakage absorbing snake - Google Patents

Abstract

PURPOSE:To balance the difference, in the expansion and contraction amounts of power cables, which is generated when a bridge is broken at a corner, i.e., a reaction force, and to reduce the strength of a cleat which fixes the middle of two snakes on the power cables by a method wherein the size of a snake on two power cables connected in series inside a corner breakage beams is changed. CONSTITUTION:Lengths L1, L2 of snakes 15, 16 on two power cables connected in series inside a corner breakage beam are changed respectively or their widths F1, F2 are changed respectively. Thereby, a difference, in the expansion and contraction amount of the power cables, which is generated when a bridge is broken at a corner, i.e., a reaction force, can be balanced and the strength of a cleat which fixes the middle of the two snakes on the power cables can be reduced. In addition, in the case of a metal-clad power cable, a core cannot be moved inside a metal sheath, and it is possible to prevent the cable from being degraded due to the damage of the core.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a corner break absorbing snake used in a method of laying a power cable on a long bridge such as a suspension bridge.

[0002]

2. Description of the Related Art When a power cable is installed on a long bridge or the like, in order to cope with corner breaks occurring at the joints of bridge girders, as shown in FIG.
Cable bridge girders 3 and 5 and corner break girders 4 provided on bridge girders 1 and 2.
Are connected via universal joints 6 and 7 to form a cable girder that can be folded freely.
The method of mounting the power cable on the 5 and the corner bending girder 4 is adopted. Then, even when the joint between the bridge girders 1 and 2 is bent as shown in FIG. 3 and the gap is opened, on the contrary, even when the gap is narrowed, the power cable laid in the girder 4 is bent into a corner. The slack called snake that absorbs the expansion and contraction of the power cable that accompanies it is attached to the power cable for installation. When the corner folding girder 4 becomes long, two snakes of the power cable may be provided in series.

[0003]

When the two snakes formed on the power cable mounted on the bridge with the same length are formed and used, the corner break of the bridge and the position of the corner break girder and the universal Depending on the positional relationship of the joint, the two snakes may have different amounts of expansion and contraction to be absorbed. As a result, the difference in reaction force generated between the two snakes becomes large, and excessive force acts on the cleat that secures the two snakes, causing the power cable to shift, or in the case of a metal-clad power cable. There is a problem that only the core inside moves.

The present invention has been made in view of the above circumstances, and an object thereof is to solve the drawbacks of the prior art and to provide a corner bending absorbing snake that balances the reaction forces of two snakes in series in a power cable. And

[0005]

According to the present invention, the size of the snakes of two series power cables in a corner bending girder is set at the corner bending part provided at the joint of the bridge girder when the power cable is installed on the bridge. It is a corner bending absorption snake that changes the balance between the reaction forces of the two snakes and absorbs the amount of expansion and contraction.

[0006]

[Operation] It is possible to balance the reaction force of the two snakes by changing the length and width of the two snakes formed on the power cable or by changing either the snake length or the snake width. become.

[0007]

Embodiments of the present invention will be described below with reference to the drawings. First, the relationship between the bridge and the corner bending of the power cable bridge girder will be described with reference to FIGS. 2 and 3. In Fig. 2, both ends of the universal joint 6, between the power cable bridge girders 3 and 5 are arranged so as to cross the joint between the adjacent bridge girders 1 and 2.
The corner folding girder 4 connected at 7 is installed. As shown in Fig. 3, when the bridge is broken, the relative angles of the bridge girders 1 and 2 change, and the joint between the bridge girders 1 and 2 expands.
The corner break girder 4 and the undercarriage girder 5 are bent at the universal joints 6 and 7, and the bridge girder 2 and the undercarriage girder 5 move relatively.

Next, with reference to FIG. 4, description will be given of the change in length when the carriage girder is folded. If a corner break occurs between the bridge girders 1, and the corner break girder 4 and the undercarriage girder 5 are moved to 4 ', 5'as indicated by the two-dot chain line, the center axes of the corner bends 8, 9 shown by the one-dot chain line are shown. Will be displaced as 8, 6, 7 ', 9'. At this time, the length of the central axis does not change, but the side separated from the central axis, for example, 10, 1 of the mounting girder 3.
The line connecting 1 and 12 and 13 of the suspension girder 5 extends 10,
It becomes like 11, 12 ', and 13', and when it is folded in the opposite direction, it is similarly shrunk.

At this time, as shown in FIG. 3, the corner bending occurs at the same time as the expansion and contraction of the bridge girders 1 and 2, so that the positions of the universal joints 6 and 7 are not always symmetrical with respect to the joint of the bridge girders. .

Next, referring to FIG. 5, it will be described that when the power cable is formed of the two snakes 15 and 16 to absorb the expansion and contraction, the snakes 15 and 16 have a difference in expansion and contraction amount.
As shown in Fig. 3, when there is a corner break between the bridge girders 1 and 2,
In FIG. 4, the angle θ formed by the central axis 8-6 of the mount girder 3 and the central axis 7'-9 'of the mount girder 5'when the mount girder 5 is bent is the bending angle. At this time, the bending angles θ ₁ and θ ₂ of the universal joints 6 and 7 are different from each other, and the two snakes 15 and 16 of the power cable laid on the lines 10 to 13 separated from the central axis of the angle bending absorb it. There will be a difference in the amount of expansion and contraction. In addition, 14 is an intermediate fixed point of two mountain snakes.

Next, the relationship between the expansion and contraction of the snake and the reaction force will be described with reference to FIG. As shown in FIG. 6, when both ends of the power cable 17 snaked into a mountain shape are mechanically pushed in by m, the rigidity of the power cable 17 is EI, the elasticity is E,
Given the size of the snake (width B and length L), reaction force F commensurate with this size is generated at both ends of the power cable 17. This reaction force F is defined by the following equation.

F = κ · E · (EI) · f (L, B, m) (1)

Therefore, a difference in reaction force occurs between the two snakes 15 and 16 of the power cable shown in FIG. 5, resulting in the above-mentioned inconvenience. Therefore, the lengths L ₁ and L ₂ of the _two snakes 15 and 16 are changed as shown in FIG. 1 (A) by the difference of m, or the widths F ₁ and F are changed as shown in FIG. 1 (B). By changing ₂ , the reaction force is balanced as a whole and the amount of expansion and contraction is absorbed.

[0014]

As described above, when the corner bending absorbing snake of the present invention is applied, it is possible to balance the difference in the amount of expansion and contraction of the power cable caused by the corner bending of the bridge, that is, the reaction force. The strength of the cleat that fixes the middle of the two snakes of the cable can be reduced. Further, in the case of a metal-clad power cable, movement of the core within the metal sheath is eliminated, and deterioration of the cable due to damage to the core can be prevented.

[Brief description of drawings]

FIG. 1 is a diagram showing a state in which two snakes are formed in a power cable to which an embodiment of the present invention is applied. (A) shows a case where the length is changed, (B) shows a case where the width is changed,

FIG. 2 is a diagram showing a neutral state in which a cable bridge girder is placed inside a J bridge girder.

FIG. 3 is a diagram showing a relative positional relationship between a bridge girder and a cable girder when a corner is broken,

FIG. 4 is an explanatory diagram showing that the length of the power cable changes when the undercarriage is broken.

FIG. 5 is a diagram for explaining that a double snake is formed on a power cable and a difference occurs in the amount of expansion and contraction thereof.

FIG. 6 is a diagram for explaining that a reaction force is generated when the snake is expanded and contracted.

[Explanation of symbols]

1, 2 Bridge girders 3, 5 Cable bridge girders 4 Bent girders 6, 7 Universal joints 8, 9 Bent center axes 10, 11, 12, 13 Center line for cable laying 14 Intermediate fixing point for double snake 15 , 16 snaked cables

Front Page Continuation (72) Inventor Naohide Urakawa 6-27 Nakanoshima, Kita-ku, Osaka "Kansai Electric Power Co., Inc. Central Transmission Construction Office" (72) Inventor Sadao Mizutani 5-chome Hidakacho, Hitachi City, Ibaraki Prefecture 1-1 "Hitachi Electric Cable Co., Ltd. Hidaka Plant" (72) Inventor Tadashi Kawamata 1-20-19 Shimanouchi, Chuo-ku, Osaka "Inside New Jec Co., Ltd." (72) Inventor Takashi Matsui Shimaya, Konohana-ku, Osaka 1-3 1 "inside Sumitomo Electric Industries, Ltd. Osaka Works"

Claims (1)

[Claims] 1. The anti-snapping of two snakes by changing the size of the snakes of the two power cables in series in the corner girder at the corner bending part provided at the joint of the girder when the power cable is laid under the bridge. A corner bending absorption snake characterized by absorbing the amount of expansion and contraction so as to balance the force.