JPH0427768B2 - - Google Patents

Description

[Detailed Description of the Invention] <Industrial Application Field> The present invention relates to a method for laying power cables at the end of a bridge, and more specifically, a method for laying a power cable to the ground from the end of a bridge where expansion and contraction and angle changes occur. It is about the method.

<Background of the invention and problems> Normally, at the end of a small-scale bridge with a short span, expansion and contraction occurs mainly due to temperature changes in the girder, and the amount of expansion and contraction is small, for example, about 50 to 100 mm. Recently, large-scale bridges with long spans such as suspension bridges and cable-stayed bridges have become more common, and in such bridges, large expansion and contraction of about 1 to 1.5 m occurs at the end of the bridge, and the horizontal direction perpendicular to the bridge axis and the vertical direction An angular change in direction (hereinafter referred to as angular folding) occurs.

In addition, the amount of corner bending is often about 1 to 3 degrees.

When lowering power cables to the ground from the bridge ends of such large-scale bridges, even if there is a relative displacement between a moving point on the bridge and a fixed point on the ground, there will be no local strain on the power cables. It is necessary to avoid bending or twisting.

Conventionally, there has been no suitable installation method for lowering power cables to the ground at the bridge ends while absorbing the expansion and contraction of the bridge as well as corner bends at the same time.With the increase in the number of large-scale bridges, an effective method for laying power cables at the bridge ends has been developed. Currently, proposals are awaited.

<Purpose of the invention> This invention has been made in view of the above-mentioned points, and is intended to simultaneously absorb the expansion and contraction of the bridge and corner bends in the power cable installation section at the end of the bridge, and to prevent local stress on the power cable. It is an object of the present invention to provide a method for laying power cables at the end of a bridge that can prevent bending and twisting.

<Means for Achieving the Object> In order to achieve the above-mentioned object, the present invention provides a structure in which an attachment frame is provided with a slack part that can be bent and expanded and contracted by connecting with a hinge, so that it can be moved in the axial direction of the bridge. Installed on a bridge, maintain a certain distance between one end of the attachment frame located on the bridge end side and the bridge end side ground fixing point with a support, and fix the other end of this attachment frame on the bridge. Then, one end of the supporting frame and the ground are connected by an arch frame in which the frame bodies are sequentially connected by three pairs of hinges, the lowest hinge point of this arch frame is fixed to the ground, and the bridge is pulled out from the end of the bridge to the ground. A power cable is laid from inside the attachment frame along the inside of the arch frame, and the attachment frame and arch frame , as well as a power cable.

<Function> When the bridge expands or contracts in the axial direction, the slack part of the support frame is deformed because the support point of the support column is fixed, and the power cable follows this slack part and changes its bending radius uniformly. It corresponds to the expansion and contraction of the bridge.

When a corner bend occurs in the horizontal or vertical direction perpendicular to the bridge axis at the end of the bridge, the displacement that occurs due to the corner bend will be applied to the upper end of the arch frame, causing the arch frame to bend and deform at each hinge. , the power cable changes to follow the deformation of the arch frame, absorbing the corner bends.

<Example> Hereinafter, an example of the present invention will be described based on the accompanying drawings.

As shown in FIGS. 1 to 3, the attachment frame 2 installed near the end of the bridge 1 consists of a plurality of frame bodies 2a.
Connect sequentially 2e to 2e with hinges 3a to 3d,
It is formed to be bendable in the horizontal direction, and supported by a sliding plate 4 so as to be slidable in the axial direction of the bridge 1.

The attachment frame 2 is provided with a slack part 5 in the middle that can be expanded and contracted while being bent, and the frame body 2e at one end located near the end of the bridge 1 is provided with connection ports in two directions at right angles. A support 6 is interposed between the frame body 2e and the ground-side fixed point facing the bridge end, and a constant distance is maintained between the frame body 2e and the ground-side fixed point.

In the attachment frame 2, the frame body 2a located on the inside of the bridge 1 is fixed on the bridge 1 by the fixing member 7, and when the bridge 1 expands or contracts, this frame body 2a moves by the amount of expansion or contraction, The attachment frame 2 absorbs the expansion and contraction of the bridge 1 by expanding and contracting the slack portion 5 between it and the immovable one frame 2e fixed to the support column 6.

Note that the frame body 2e is fixed to the bridge 1 by guide rails 8 to prevent sideways movement.

The arch frame 9 connecting the frame body 2e of the supporting frame 2 and the ground is connected to the frame bodies 9a, 9b and 9c by hinges 10.
b and 10c, and the uppermost frame 9a is connected to the frame 2e with a hinge 10a, and a total of three pairs of hinges 10a, 10b, 10c connect the frames 2e, 9a to 9c horizontally at right angles to the bridge axis of the bridge 1. It has a link structure that is connected so that it can be bent freely in both the direction and the vertical direction.

When viewed from above, the arch frame 9 has a straight line as shown in FIG. 2, and when viewed from the side, it has an arc shape as shown in FIG. 3, and has hinges 10a, 10b, 10c.
There is a pair on each side of each frame, and
The lowest hinge 10c is a support 11 installed on the ground.
It is supported by a fixed point.

The power cable A that is lowered to the ground from above the bridge 1 is laid along the inside of the support frame 2 and the inside of the arch frame 9.

As shown in FIG. 2, the power cable A in the support frame 2 is laid so that it is slack along the shape of the slack portion 5, and the cleats 12a, 12b, 1
2c, it is fixed to the frames 2a, 2c, and 2e.

In addition, the power cable A in the arch frame 9
The cleats 13a are installed so as to have an arc shape when viewed from the side as shown in FIG. 3, and a snake shape when viewed from the top and front as shown in FIG. or fixed at 13d,
Furthermore, it is supported by rollers 14 at positions between the respective cleats.

The reason for distributing the rollers 14 and shortening the support interval for the power cable A is to increase the natural vibration frequency of the cable system so that the power cable A does not resonate with vibrations propagating from the bridge end. This is a consideration for

The power cable installation method of the present invention is carried out by laying the power cable A along the supporting frame 2 and the arch frame 9 having the above-described structure, and then absorbing the expansion/contraction and corner bends that occur in the bridge 1. Explain.

Expansion and contraction absorption As shown in Fig. 4, if the bridge 1 extends by ΔM in the direction of arrow B in the figure, the frame 2e supported by the pillars 6 remains stationary, while
The frame body 2a fixed to the bridge 1 is ΔM together with the bridge 1.
3, the slack portion 5 is deformed as shown by the broken line in the figure by the link mechanism of the hinges 3a to 3d.

At this time, the cleats 12a to 12c that fix the power cable A to each frame move in the same way as the frame moves, so the bending radius of the power cable A changes uniformly to correspond to the elongation of the bridge 1. Become.

Furthermore, since the frame body 2e of the auxiliary frame 2 is stretched by the supports 6, the power cable A responds to the expansion and contraction of the bridge 1 by slackening on the bridge 1, and the arch frame 9 is not affected at all. do not have.

Corner bend absorption As shown in Fig. 5, if a corner bend occurs in the bridge 1 in the horizontal direction perpendicular to the bridge axis by Δθ with the center point of the bridge end as the fulcrum, then 7, since it is fixed to the bridge 1 and the frame 2e is prevented from moving sideways by the guide rail 8,
Horizontal displacements of ΔN ₁ and ΔN ₂ are applied to the upper end of the arch frame 9 corresponding to Δθ.

Strictly speaking, ΔN ₁ and ΔN ₂ are slightly different in magnitude, but since Δθ is small, they can be considered to be approximately equal.

In addition, without the guide rail 8, the frame body of the slack portion 5 of the supporting frame 2 would sway sideways, becoming unstable against earthquakes, strong winds, etc., and causing the arch frame 9 to be displaced more than designed. Undesirable.

Similarly, vertical displacement is applied to the upper end of the arch frame 9 when the arch frame 9 is bent vertically.

The principle of absorption of expansion and contraction in the horizontal direction perpendicular to the bridge axis and in the vertical direction is shown in FIGS. 6 and 7.

FIG. 6 shows the absorption of the displacement caused by the bending in the horizontal direction perpendicular to the bridge axis.
Since the lengths a and 9b remain unchanged, the hinge position after the change is determined geometrically, and it suffices if it takes the shape of the broken line.

FIG. 7 shows absorption of displacement caused by vertically downward corner bending, and the same applies to ΔH as in FIG. 6.

Here, the distance between the fixed cleats 13b and 13c changes from S to S', and the power cable itself expands and contracts due to temperature changes, but the length changes between the cleats due to the horizontal snake installation of the power cable A. can be absorbed by changing the snake width.

<Effects> As described above, according to the present invention, an arch frame is provided between the auxiliary frame attached to the end of the bridge and the ground, and the power cable is laid along the auxiliary frame and the arch frame. It will be possible to lower power cables to the ground while absorbing expansion, contraction, and corner bends at the same time.

In addition, by absorbing expansion/contraction and corner bends in separate locations, the degree of deformation of the power cable is reduced, and since the arch frame is a link mechanism using three pairs of hinges, vertical bends and bends that occur due to corner bends can be reduced. It can follow displacement in the horizontal direction perpendicular to the axis, and does not exert unnecessary reaction force on the bridge girder.

Furthermore, the arch frame consisting of three pairs of hinges becomes a stable structure against its own weight and external forces applied during earthquakes and typhoons, and by removing the horizontal snake of the power cable within the arch frame, the power cable's own thermal expansion and Changes in distance between hinges due to changes in arch frame can be absorbed by changes in snake width.

[Brief explanation of drawings]

FIG. 1 is a perspective view showing the installation state of the installation method according to the present invention, FIG. 2 is a plan view of the same, FIG. 3 is a side view of the same, and FIG.
Fig. 5 is a plan view illustrating absorption of corner folds, Fig. 6 is an explanatory diagram illustrating absorption of horizontal angle folds perpendicular to the bridge axis of the arch frame, and Fig. 7 is an explanatory diagram illustrating absorption of corner folds in the vertical direction. FIG. 8 is a developed view showing the power cable installation state of the arch frame. 1... Bridge, 2... Addition frame, 2a to 2e... Frame body, 3a to 3d... Hinge, 5... Sagging part,
6, 11... Support column, 7... Fixing member, 8... Guide rail, 9... Arch frame, 9a-9c... Frame body, 10a-10c... Hinge, 12a-12c
... Cleat, 13a-13d ... Cleat, A
...Power cable.

Claims (1)

[Claims] 1. An attachment frame having a slack part that can be bent and expanded and contracted by connecting with a hinge is installed on a bridge so as to be movable in the bridge axis direction, and the attachment frame is located on the bridge end side. A fixed distance is maintained between one end of the attachment frame and the ground fixing point on the bridge end side using a support, the other end of this attachment frame is fixed on the bridge, and the distance between one end of the attachment frame and the ground is The frames are connected by an arch frame in which the frame bodies are successively connected by three pairs of hinges, the lowest hinge point of this arch frame is fixed to the ground, and a power cable is drawn out from the bridge end to the ground from within the attached frame and along the inside of the arch frame. against expansion and contraction in the horizontal direction perpendicular to the bridge axis and in the vertical direction caused by expansion and contraction in the bridge axis direction and angular changes.
A method of laying power cables at the end of a bridge, characterized by making the power cables follow the supporting frame, the arch frame, and the power cables. 2. The method of laying power cables at the end of a bridge according to claim 1, wherein the power cables are laid in a snake shape within the arch frame and fixed to each frame.