JP2909233B2 - Cable support 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 supporting device for supporting an end portion of a cable which is subjected to an axial tension and a secondary bending stress laterally displaced with respect to the axis. This support device can be used, for example, for a cable stretched between a girder of a suspended structure and a tower.

[0002]

2. Description of the Related Art A suspended structure supported by a cable stretched between a girder and a tower is schematically shown in FIGS. 8 and 9. The cable 1 has anchors 2 at both ends fixed to the girder 7 and the tower 8. FIG. It is stretched by being fixed to the support plate 3. By the way, the lateral displacement of the cable 1 is caused by the lateral vibration of the cable 1 and the deformation of the girder 7 and the tower 8, and in this case,
The problem is that secondary bending of the cable 1 occurs at the anchor opening 4, and the cable 1 is sharply bent at the anchor opening 4 as shown in FIGS. 10 and 11.

As shown in FIG. 11, there is a problem that the lateral displacement of the cable 1 causes a secondary bending at the anchor opening 4, thereby causing the cable 1 to be damaged. Japanese Laid-Open Patent Publication No. 52-97065 discloses an improved structure on the cable outlet side in order to solve this cable 1 breakage. In this known technique, a support for passing a cable bundle is provided, and the support surface is formed so as to be curved outward in a longitudinal sectional view.

[0004]

By providing a support having a support surface that spreads in a curved shape, the anchor cable may be bent and cut by the bending force received at the outlet from the anchor head under the influence of waves or the like. It is possible to prevent this from happening. However, it is unclear what the shape of the curve of the support surface is, and it is not clear at all how much the relief action can be achieved against the intensive bending of the anchor opening. It is clear that when applied to a cable of a suspended structure that works continuously, it has little effect on the secondary bending of the anchor opening, and this is not an appropriate solution. is there.

The present invention has been made in view of such a conventional problem, and in particular, by providing a special structure to an intermediate support provided near an anchor, rapid secondary bending concentrated at an anchor opening is provided. Can be distributed,
A main object of the present invention is to reduce and moderate bending deformation to prevent cable breakage and deterioration beforehand and to extend the life of the cable.

[0006]

In order to achieve the above-mentioned object, a cable supporting device according to the present invention has the following configuration. That is, the supporting device according to claim 1 is a device in which an end portion of a cable whose end is fixed by an anchor is near an anchor.
It becomes the intermediate support for supporting the curved surface, to this intermediate support y = αχ ² extending outwardly as the support surface further away from the anchor opening of, although α is a reference factor, a parabola
This is a cable supporting device formed on a paraboloid. The supporting device according to claim 2 includes an intermediate support member that supports the anchor near the anchor of the cable whose end is fixed by the anchor at multiple points, and a spring constant K of each support portion of the intermediate support. For the distance L to the anchor opening, K
= Α ₂ / L ² , where α ₂ is a coefficient, which is a cable supporting device. The support device according to claim 3,
The cable support device according to claim 1 or 2, wherein the intermediate support is provided in a base of the anchor port. According to a fourth aspect of the present invention, there is provided the cable supporting apparatus according to the third aspect, wherein the intermediate support has at least partially a supporting surface that is not joined to the outer periphery of the cable.

[0007]

[ Operation ] y = αχ ² , where α is a coefficient and χ is an intermediate support
The axial displacement of y, the displacement in the direction perpendicular to the axis is also
By providing an intermediate support having a parabolic curved surface as a reference, the bending stress of the cable support and the anchor opening can be evenly dispersed without concentrating on one point, and multi-point support is possible. By making the spring constant K of each support portion of the intermediate support member of the system inversely proportional to the square of the distance L, bending deformation can be moderated and bending stress can be minimized. In this case, by providing the intermediate support in the base of the anchor opening, the work of attaching the support to another place outside the anchor can be omitted, and the cable extension work can be simplified and the structure around the anchor opening can be simplified. On the other hand, by partially providing a support surface that is not joined to the outer periphery of the cable, such as by interposing a release layer, friction can be reduced and secondary bending stress can be reduced.

The secondary bending stress will be described with reference to the drawings. FIG. 12 shows a configuration in which the cable middle portion is supported at one point.
, The bending angle θ and the tension P are acting. Assuming that the intermediate support portion is laterally displaced and bends by δ, the secondary bending stress σ _b1 naturally acts on the anchor opening portion 4. This value and the secondary bending stress σ _b2 of the intermediate support portion are determined by the intermediate support portion. The spring constant K changes as shown in FIG. 13. As the spring constant K increases, σ _b1 decreases and σ _b2 increases.
In this figure, the secondary bending stress σ _b1 of the anchor opening 4 is
When the spring constant K of the intermediate supporting portion is 0, that is, when there is no supporting force, the maximum secondary bending stress becomes σ _b1max , and decreases when the spring constant K increases, that is, when the supporting force increases.

On the other hand, when the spring constant K increases, the secondary bending stress σ _b2 of the cable intermediate supporting portion becomes the maximum secondary bending stress σ _b2.
Increase to 1/2 of _b1max . In the total cable length, 2
The secondary bending stress is minimized when σ _b1 and σ _b2 are equal, and is _の of the maximum secondary bending stress σ _b1max . This indicates that the following equation is established between the bending angle theta bending angle theta _a and the intermediate support of the anchor opening 4. θ _a = θ / 3 Equation 1 From FIG. 12, the following equation is established from the balance of the horizontal force ΣH = 0 at the intermediate support portion. _{ΣH = P a cosθ a -Pcos3θ a} = 0 P a / P = (4cos 3 θ a -3cosθ a) / cosθ a = 4cos 2 θ a -3 --- load ΔP to spring in formula 2 intermediate support Is as follows. The deflection δ at the intermediate support is as follows. Therefore, the optimum spring constant K of the intermediate support is as follows. Here, P: cable tension. d: distance between supports from the cable anchor opening to the intermediate support point. θ: Bending angle at the cable middle support.

From equation (6), in order to minimize the secondary bending stress of the cable, the spring constant K of the intermediate support is determined by the cable tension P
It can be seen that it is only necessary to select an appropriate value in proportion to the cosine cos θ / 3 of the cable bending angle and in inverse proportion to the distance d between supports.

Next, FIG. 14 shows a configuration in a case where the cable middle portion is supported at multiple points. In figure, the cable is supported at multiple points, the bending angle of anchor opening 4 and theta _a, the other support point, it is assumed that there is an increase in the bending angle of 2 [Theta] _a. By doing so, it is considered that the secondary bending stress at the anchor opening 4 and each support point becomes equal.

In FIG. 14, the following equation is established from the balance ΔH = 0 of the horizontal force of the intermediate support portion at the n support point. ΣH = P _n cos [(2n-1) θ _a ] −P cos [(2n + 1) θ _a ] = 0 P _n / P = cos [(2n + 1) θ _a ] / cos [(2n-1) θ _a ] ------ Equation 7 The load ΔP _{n on} the spring of the intermediate support portion at the point _n is as follows. _{ΔP n = Psin [(2n +} 1) θ a] -P n sin [(2n-1) θ a] = P {sin [(2n + 1) θ a] -cos [(2n + 1) θ a] × tan [(2n-1) θ _a ]｝-Equation 8 The deflection δ _n of the intermediate support portion at the point _n is as follows.

[0013]

(Equation 1)

Accordingly, the optimum spring constant K _n of the intermediate support at the point _n is as follows.

[0015]

(Equation 2)

Here, the bending angle of the cable θ = (2n + 1) θ
_{If a} = 1 ° to 2 °, the following is obtained. sin [(2n + 1) θ a] ≒ (2n + 1) θ a ----- Equation 12 cos [(2n + 1) θ a] ≒ 1 ------------- Equation 13 tan [(2n-1) θ _a ] ≒ (2n-1) θ _a ----- Equation 14 By substituting Equations 12 to 14 into Equation 11, the spring constant K at n points is obtained.
_n becomes as follows.

[0017]

(Equation 3)

When Equation 15 is substituted into Equation 9, the deflection δ _n at the point _n is as follows. Deflection [delta] _n of the equation 16, since the square of the horizontal direction of the support distance nd, deflection [delta] _n is given as a parabola.

From the above description, in order to minimize the secondary bending stress of the cable 1, (a) the spring constant K _n of the n-th support point of the cable 1 is
Since it is proportional to the square of the reciprocal of the distance nd to the support point, it is given by the following equation. K _n = 2Pd / (nd) ² Equation 17 (b) On the other hand, the deflection δ _n at the point n of the cable 1 is proportional to the square of the distance nd to the support point. Given. δ _n = θ _a · (nd) ² /d=0.5θ(nd) ² / L Equation 18

In this case, in order to support the middle portion of the cable by using a fixed curved surface support without supporting the spring, the curved surface may be a parabola given by Expression 18.
In FIG. 13, the secondary bending stress σ of the cable middle support portion is shown.
_b2 is half of the maximum secondary bending stress σ _{bmax when} the spring constant K of the intermediate support portion is set to infinity, which is rigid support. This means that the distance between the anchor opening 4 and the intermediate supporting portion may be short. Therefore, by providing the intermediate supporting portion at the anchor opening 4, for example, at the base 5, the maximum secondary bending stress σ _bmax can be reduced by half. It is possible to reduce to.

[0021]

Embodiments of the present invention will be described in detail with reference to the accompanying drawings. The example of the apparatus of the present invention is applied to the anchoring portion of the cable 1 stretched over the suspension structure shown in FIGS. 8 and 9 by the anchor 2, and the first embodiment is shown in FIG. 1. That is, the intermediate support 6 is provided so as to surround a portion near the anchor 2 at the end of the cable 1, and the intermediate support 6 is fixed to a structure or the like. The intermediate support 6 has a cylindrical shape and is disposed concentrically with the cable 1 extending straight, but the support surface facing the peripheral surface of the cable 1 is in contact with or closest to the side near the anchor 2 and the anchor 2 It forms a paraboloid that spreads outward as it gets farther away from. That is, the supporting curved surface is y = αχ ² , where α is a coefficient, and χ is the intermediate support 6.
The axial displacement, y, is also based on the parabola of the displacement perpendicular to the axis .

By providing the parabolic surface as described above, the anchor opening 4 caused by the lateral displacement of the cable 1 is provided.
Sharp bending deformation can be reduced. In this case, since the bending deformation of the cable 1 is gently dispersed in the region in contact with the intermediate support 6, the concentrated bending of the anchor opening 4 is reduced. Various materials can be used as the intermediate support. For example, rubber such as chloroprene rubber and silicon rubber, or a synthetic resin such as an epoxy resin or a nylon resin is used by setting the required type and the required spring constant. It is preferred to do so.

FIG. 2 is a front view, partially in section, of a second embodiment of the present invention. The cable 1 is stretched by fixing it to a supporting plate 3 having an anchor 2 fixed to a tower or the like.
Is provided with a pipe base 5 which surrounds the end of the cable 1 and is integrally provided with the pipe end fixed by welding or the like. An intermediate support 6 is housed in the base 5 and is surrounded by the cable 1. The intermediate support 6 has a parabolic curved support surface as in the first embodiment. . This example has the advantage of providing a compact structure by providing the intermediate support 6 in the base 5, and has the same functions as the first embodiment.

FIG. 3 is a front view, partially in section, of a third embodiment of the present invention, in which a multipoint support type is used as an intermediate support 6 provided in the vicinity of the anchor 2. The shape, material, etc. of each support are set such that the spring constant K at each support point with respect to the body 6 satisfies the relationship K = α / L ² with respect to the distance L from the anchor opening 4 to the support point. It is to be selected. In the example of FIG. 3, in order to establish the above relationship, the intermediate support 6 closest to the anchor opening 4 has the largest thickness in the axial direction, and the further away from the anchor opening 4, the thinner the intermediate support 6 is. I am trying to do it. By doing so, the lateral deformation of the cable 1 becomes greater at the portion of the intermediate support 6 far from the anchor port 4, and the cable 1 is bent gently to reduce the intensive bending of the anchor port 4, Thus, the sudden bending deformation of the anchor opening 4 caused by the lateral displacement of the cable 1
It is possible to relax with the intermediate support 6 in a discontinuous arrangement.

FIG. 4 is a front view showing a partial cross section of a fourth embodiment of the present invention, and FIG. 5 is a front view showing a partial cross section of the fifth embodiment. Both examples are based on the second embodiment. The intermediate support 6 has a structure in which the intermediate support 6 has a support surface that is not bonded to the outer periphery of the cable 1. The fourth embodiment partially has a non-bonded support surface, while the fifth embodiment has a support surface in the entire axial direction.

As a method of not joining in this case, there is a method in which a hollow portion having an inner diameter slightly larger than the outer diameter of the cable 1 is formed in the intermediate support 6 to have a void.
The example shown in FIG. 4 in which a release layer 9 such as grease, rubber, or tar epoxy is inserted, and the example shown in FIG. In any of these cases, the joined structure is suitable for solving the problem that the movement of the cable 1 is restricted and the secondary bending stress is increased. To provide, only a few close to the anchor mouth 4
It may be about mm.

Although the contents of each embodiment have been described above, a secondary bending test of an actual cable is carried out to
The effect was confirmed. Specimens with a steel wire diameter of 7 mm were used.
The length of the cable bundled in parallel was 10 m. Attach anchors 2 fixed to both ends of this cable to the tester,
Pulled to 200 tons.

After pulling to 1,200 tons as shown in FIG. 6A, the central portion O is pushed up as shown in FIG. 6B to generate a bending angle θ = 0.6 °. As shown, a secondary bending stress σ _b = 9 kg / mm ² is generated at the center. Also, the the intermediate support portion M to about 50% σ _b = 2 of 4 kg / mm ²
Next bending stress occurs. On the other hand, when only the central portion O is pushed up in FIG. 6 (d), the σ _b = 9 kg / mm ² of the central portion O does not change, but the anchor opening 4 has σ _b = 9 kg as shown in FIG.
/ mm ² , which is more than twice the secondary bending stress of the intermediate support portion M in FIG. Thus, it was confirmed in the experiment that the secondary bending stress σ _b was reduced from 9 kg / mm ² to 4 kg / mm ² to 50% or less when the intermediate support in the example of the spring constant K = ∞ was performed.

FIG. 7 shows the secondary bending measured at the center O of 5.0 m in the same manner as in FIGS. Stress σ
_It is a graph which shows _b . As is apparent from this figure, the secondary bending stress σ _b of the intermediate support portion M is about 50% of that of the central support portion O, even though the bending angle of the cable is the same.

In the above embodiment, the entire cable is intermediately supported. However, if the element wires or strands, which are the components of the cable, are fixed to the anchors separately, FIG.
As shown in FIG. 16, the same effect can be obtained by intermediate support for each wire or strand.

[0031]

As described above, according to the present invention, the intermediate support 6 is provided near the anchor 2 at the end of the cable 1 and its support surface is formed as a parabolic surface. The bending stress due to the lateral displacement of the cable at the anchor opening 4 can be dispersed and uniformized.

The intermediate support 6 has a multi-point support structure, and the spring constant of the support at each support portion is inversely proportional to the square of the distance to the support point. While the secondary bending stress at the point becomes uniform,
The effect of minimizing this value is achieved.

Further, by providing the intermediate support 6 in the base 5 of the anchor port 4, uniform dispersion of the secondary bending stress can be realized with a compact structure, and the supporting surface of the intermediate support is provided. In addition, by providing a portion that is not joined to the outer periphery of the cable, there is an effect that the secondary bending stress is further reduced without restricting the free movement of the cable 1.

[Brief description of the drawings]

FIG. 1 is a partial cross-sectional front view of a first embodiment of the present invention.

FIG. 2 is a partial cross-sectional front view of a second embodiment of the present invention.

FIG. 3 is a partial cross-sectional front view of a third embodiment of the present invention.

FIG. 4 is a partial cross-sectional front view of a fourth embodiment of the present invention.

FIG. 5 is a partial cross-sectional front view of a fifth embodiment of the present invention.

FIG. 6 is an explanatory diagram of a secondary bending test of a cable.

FIG. 7 is a graph showing data of a secondary bending experiment of a cable.

FIG. 8 is a schematic perspective view of a suspension structure using a cable.

FIG. 9 is a side view of the suspension structure.

FIG. 10 is an explanatory diagram of a cable lateral displacement of the suspension structure.

FIG. 11 is an enlarged view of a cable anchor portion of the suspension structure.

FIG. 12 is an explanatory diagram of a single-point support mode of a cable.

FIG. 13 is a secondary bending stress diagram of the cable support.

FIG. 14 is an explanatory diagram of a multi-point support mode of a cable.

FIG. 15 is a diagram showing a support outline when intermediate support is performed for each wire.

FIG. 16 is a diagram showing a support outline when intermediate support is performed for each strand.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1-Cable 2-Anchor 3-Support plate 4-Anchor port 5-Base 6-Intermediate support 7-Girder 8-Tower 9-Release layer 10-Release agent 11- -Resin tube 12-Strand M ---- Intermediate support O-Center

Claims (4)

(57) [Claims] The method according to claim 1 anchor proximal portion of the cable end is anchored, made of an intermediate support for supporting the curved surface, it extends the supporting surface of the intermediate support outward as the distance from the anchor opening y = αχ ^2, but α is a coefficient, of
A cable support device formed on a paraboloid based on a parabola . 2. A cable having an end portion fixed by an anchor, comprising an intermediate support member for supporting a portion near an anchor of the cable at multiple points, and a spring constant K of each support portion of the intermediate support member is set to the anchor opening. K = α ₂ / L ² , where α ₂
Is a cable support device characterized by a coefficient. 3. The cable support device according to claim 1, wherein the intermediate support is provided in the base of the anchor port. 4. The cable support device according to claim 3, wherein the intermediate support has at least partially a support surface that is not joined to the outer periphery of the cable.