Vibration suppression structure and method for forming the vibration suppression structure

Abstract

To provide a vibration suppression structure or the like which can be easily constructed and can suitably suppress vibration of a cable caused by wind.SOLUTION: A cable 4 supports a main girder of a cable-stayed bridge from a main tower. In the cable 4, a mantle tube 42 that can vibrate with respect to a cable body 40 is provided so as to cover the periphery of the cable body 40 having a strand S. The mantle tube 42 generates an external force due to an air pressure difference caused by a turbulent flow around the mantle tube 42 when receiving a wind. However, by vibrating only the mantle tube 42 to dissipate kinetic energy, it is possible to reduce vibration applied to the cable main body 40.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to a vibration suppression structure for a cable used to support a structure, etc., and a method for forming the same. [Background technology]

[0002] A cable-stayed bridge is constructed so that the bridge's main girders are supported by cables from a main tower located halfway along the bridge's length.

[0003] The vibrations generated by the wind in the cables have a great impact on the support structure of the structure, especially on the cable anchorage, and can cause fatigue failure. Therefore, measures to prevent cable vibrations may be taken by adding shapes such as protrusions or dimples to the outer surface of the cable, or by providing additional vibration damping means such as vibration-damping wires, high-damping rubber, oil dampers, and viscous dampers.

[0004] For example, Patent Document 1 describes a method for preventing vibration of cables in a cable-stayed bridge by providing the outer layer of the cable body with a plurality of parallel protrusions along the axial direction of the cable. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Publication No. 7-119058 Summary of the Invention [Problem to be solved by the invention]

[0006] As mentioned above, various measures against vibration of cables have been proposed, but no fundamental and economically advantageous solution has been found. For example, various research results have been obtained on adding protrusions or dimples to the outer layer of the cable body, and the effectiveness of such methods has been demonstrated. However, the manufacturing process of the outer layer is complicated, which imposes restrictions on the manufacturing and transportation aspects of construction, and when a tubular body of a fixed length is used as the outer layer, it is necessary to connect the tubular body of a length determined by the restrictions.

[0007] In addition, measures to prevent cable vibrations are generally considered and adopted when constructing a new cable-stayed bridge, but there are cases where vibrations that were not anticipated at the time of design occur, and there is the issue that it is difficult to take measures to prevent vibrations in existing cables after an incident has occurred.

[0008] The present invention has been made in consideration of the above problems, and has an object to provide a vibration suppression structure etc. that can be easily constructed and can effectively suppress cable vibration caused by wind. [Means for solving the problem]

[0009] The first invention for solving the above-mentioned problems is, It is erected at an angle, A structure for suppressing wind-induced vibration of a cable supporting an object, comprising: a mantle tube that vibrates relative to a cable body having strands and that covers the cable body; The outer tube is in contact with the cable body at one point on the cross section when placed on the cable body. The vibration suppression structure is characterized by the above.

[0010] In the present invention, a mantle tube that can vibrate relative to the cable main body is provided so as to cover the cable main body that supports the support object. When the mantle tube is exposed to wind, an external force is generated due to the difference in air pressure caused by turbulence in the surrounding area, but by vibrating only the mantle tube and dissipating the kinetic energy, the vibration applied to the cable main body can be suppressed. Furthermore, the vibration suppression structure of the present invention is easy to install because no special processing is required for the cable main body, and is also effective as a vibration countermeasure for existing cables.

[0011] The cable is, for example, a cable that supports a bridge from a main tower in a cable-stayed bridge. It is desirable that the outer tube is provided over the entire length of the cable body, and that the upper end of the outer tube on the main tower side is not fixed in position and the lower end is placed on the main girder of the bridge so that no tension is applied to the outer tube. This makes it possible to apply the present invention as a measure against vibration in cables of cable-stayed bridges.

[0012] The outer surface of the outer tube preferably has a recess or protrusion for reducing vibrations caused by wind. This makes it possible to reduce vibration of the outer tube, and to suppress vibration of the cable main body due to vibration of the outer tube.

[0013] The outer tube is preferably a strip of tubular material wound in a spiral shape, and adjacent tubular materials in the axial direction of the outer tube are preferably fitted together at fitting portions at side ends in the width direction of the tubular materials. Furthermore, it is also preferable that the outer tube is made of a plurality of types of the pipe materials arranged adjacent to each other in the axial direction of the tube. By winding a strip of pipe material in a spiral shape to form an outer tube, it becomes easy to arrange the outer tube continuously and it becomes possible to install the outer tube on-site. The outer tube can be appropriately maintained in its shape by fitting adjacent pipe materials in the axial direction of the outer tube by means of projections and recesses or the like.

[0014] The second invention is a method for forming a vibration suppression structure of the first invention, characterized in that a pipe making device is installed on the cable body of an existing cable-stayed bridge, and the outer tube is formed by spirally winding a strip-shaped pipe material around the cable body using the pipe making device. The second invention is a method for forming a vibration suppression structure for the cable body of an existing cable-stayed bridge. Effect of the Invention

[0015] The present invention can provide a vibration suppression structure that can be easily constructed and can effectively suppress cable vibration caused by wind. [Brief description of the drawings]

[0016] [Figure 1] A diagram showing cable-stayed bridge 1. [Diagram 2] FIG. 2 is a diagram showing a radial cross section of the cable 4. [Diagram 3] A diagram showing the outer tube 42. [Figure 4] 4 shows an example of an aerodynamic shape of the outer tube 42. [Diagram 5] An example in which multiple types of pipe materials 421 (421a, 421b) are used. [Figure 6] 4A to 4C are diagrams for explaining a method of installing the outer tube 42. [Figure 7] FIG. 4 is a diagram showing a radial cross section of a cable 4a. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0017] Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the drawings.

[0018] (1. Cable-stayed bridge 1) FIG. 1 is a diagram showing a cable-stayed bridge 1 having a cable 4 to which a vibration suppression structure according to an embodiment of the present invention is applied.

[0019] As shown in Figure 1, a cable-stayed bridge 1 supports the main girder 2 of the bridge, which is the object of support, with cables 4 from a main tower 3 installed halfway along the bridge's extension direction. The cables 4 are installed on both sides of the main tower 3 and are erected diagonally between the main tower 3 and the main girder 2, with both ends fixed to the main tower 3 and the main girder 2.

[0020] (2. Vibration suppression structure of cable 4) FIG. 2(a) is a diagram showing a radial cross section (hereinafter sometimes simply referred to as a cross section) of the cable 4. FIG.

[0021] 2(a), the cable 4 is provided with an outer jacket tube 42 separated from the cable main body 40 so as to cover the periphery of the cable main body 40. The cable main body 40 is configured such that a plurality of strands S are housed in a protective tube 41 having a circular cross section, and the outer jacket tube 42 has a circular cross section with a larger diameter than the cable main body 40. A gap is provided between the outer jacket tube 42 and the cable main body 40 due to the difference between the inner diameter of the outer jacket tube 42 and the outer diameter of the cable main body 40.

[0022] If the cable 4 has the above-mentioned structure (vibration suppression structure), when vibration occurs in the cable 4 due to wind, the kinetic energy can be dissipated by vibrating only the outer tube 42, thereby suppressing wind-induced vibration of the cable main body 40 supporting the main girder 2.

[0023] The mantle tube 42 is provided over the entire length of the cable main body 40, but in order to prevent tension from being applied to the mantle tube 42, the upper end of the mantle tube 42 on the main tower 3 side is not fixed in position, and the lower end is placed on the main girder 2. The mantle tube 42 is normally in contact with the cable main body 40 at one point on the cross section while resting on the cable main body 40 as shown in Fig. 2(b). Therefore, when the mantle tube 42 receives wind, a pressure difference caused by surrounding turbulence causes a pendulum-like vibration with the contact point with the cable main body 40 as the center of rotation, as shown by arrow a.

[0024] Since wind conditions (wind direction and wind force) are not constant over the entire length of the cable 4, the position of contact between the outer tube 42 and the cable body 40 changes at different positions in the longitudinal direction of the cable 4, as shown in Fig. 2(c), for example. Therefore, when looking at the entire length of the cable 4, local vibrations of the outer tube 42 are combined in a complex manner, and these vibrations interfere with each other, allowing the kinetic energy of the wind to be dissipated.

[0025] 3(a) shows the mantle tube 42 as seen from the side. The mantle tube 42 is formed by spirally winding a strip-shaped pipe material 421. Joints (not shown) are formed at both longitudinal ends of the pipe material 421, and the pipe materials 421 are connected to each other at the connecting portion c, so that the mantle tube 42 can be continuously extended. At the connecting portion c, the longitudinal ends of the pipe material 421 can also be fitted together, bonded, welded, etc.

[0026] Fig. 3(b) is a diagram showing a cross section of the mantle tube 42 in the pipe wall thickness direction along line bb in Fig. 3(a). As shown in Fig. 3(b), a convex fitting portion 422 is provided at one side end in the width direction of the pipe material 421, and a concave fitting portion 423 that fits with the convex shape is provided at the other side end. The mantle tube 42 is formed by continuously and integrally forming the pipe materials 421 in a spiral shape by fitting the fitting portions 422, 423 of the pipe materials 421 adjacent to each other in the pipe axis direction.

[0027] Various materials can be selected for the pipe material 421, including flexible metals such as steel and aluminum, resins such as polyethylene and polypropylene, and FRP (fiber reinforced plastic). It is also possible to combine the pipe material 421 with different types of reinforcing materials to maintain its shape. For example, it is possible to embed a strip-shaped metal plate as an elastic reinforcing material in the resin pipe material 421 along the longitudinal direction of the pipe material 421.

[0028] As for the outer tube 42, it is also possible to reduce vibration by adding concaves and convexities to the outer surface as an aerodynamic measure. That is, when the outer tube 42 vibrates with an amplitude exceeding the width of the gap between the outer tube 42 and the cable main body 40, the vibration of the outer tube 42 causes vibration of the cable main body 40. Therefore, by taking an aerodynamic measure for the outer tube 42 in advance, the vibration of the outer tube 42 can be reduced, and as a result, the vibration of the cable main body 40 can be suppressed.

[0029] The aerodynamic shape of the mantle tube 42 can be formed by simultaneously forming recesses and protrusions in the pipe material 421 during the manufacturing process of the pipe material 421. The specific shapes of the recesses and protrusions are not particularly limited, but for example, a continuous convex rib 424 (protrusion) can be formed along the longitudinal direction of the pipe material 421 as shown in Fig. 4(a), a continuous groove 425 (recess) can be formed along the longitudinal direction of the pipe material 421 as shown in Fig. 4(b), or dimples 426 (recess) can be formed at intervals along the longitudinal direction of the pipe material 421 as shown in Fig. 4(c).

[0030] By changing the width of the pipe material 421 or the helical pitch of the pipe material 421, it is possible to change the spacing in the pipe axis direction and the angle relative to the pipe axis direction of these aerodynamic shapes, making it possible to select the optimal spacing and angle that suits the pipe diameter of the outer tube 42 and the wind conditions.

[0031] Furthermore, the mantle tube 42 is not limited to being formed from one type of pipe material 421, but can also be formed by adjacently forming multiple types of pipe materials 421 (421a, 421b) in the pipe axial direction as shown in Fig. 5, and the aerodynamic shape, material strength, quality, color, presence or absence of reinforcing material, etc. can be varied between these pipe materials 421. Furthermore, when multiple types of pipe materials 421 (421a, 421b) are used, by shifting the axial position of the connecting parts c between these pipe materials 421, it is possible to prevent the connecting parts c from concentrating locally and becoming structurally weak parts.

[0032] (3. Method of Installing the Outer Tube 42) In this embodiment, as shown in Figure 6, for an existing cable-stayed bridge in which the main girder 2 of the bridge is supported by a cable main body 40 from a main tower 3, the above-mentioned vibration suppression structure can be formed by post-constructing an outer jacket tube 42 around the cable main body 40.

[0033] In this embodiment, a known pipe making machine described in JP 05-018478 A, JP 05-312276 A, JP 06-143420 A, JP 2021-98364 A, etc. can be used as the pipe making device 5 for constructing the jacket pipe 42. These pipe making machines pull in a strip-shaped pipe material with rollers or the like and wind it spirally to produce a pipe body, and at this time, fitting is performed between adjacent pipe materials in the axial direction by fitting parts located on both side ends of the pipe material in the width direction.

[0034] In this embodiment, as shown in Fig. 6, the pipe making device 5 is installed at the end of the cable body 40 on the main girder 2 side, and a belt-shaped pipe material 421 is spirally wound around the cable body 40 to make the jacket tube 42, which is then sent out along the cable body 40 to the main tower 3 side while rotating. This allows the jacket tube 42 to be installed over the entire length of the cable body 40. The jacket tube 42 installed in this manner can be replaced or its specifications changed even if it is physically or chemically damaged or deteriorates over time. The pipe making device 5 may be installed at the end of the cable body 40 on the main tower 3 side, in which case the jacket tube 42 is manufactured by the pipe making device 5 and sent out to the main girder 2 side while rotating.

[0035] It is also possible to attach a jig to the tip of the mantle tube 42 after pipe making, and use this jig to lift or push up the tip of the mantle tube 42 toward the main tower 3. It is preferable that this jig be rotatable in accordance with the spiral winding of the pipe material 421. Also, as described in JP 2011-240634 A, it is also possible to use a pipe making machine that moves in the pipe axial direction of the pipe body as the band-shaped pipe material is wound to produce the pipe body, and the mantle tube 42 can be installed while moving the pipe making machine along the cable main body 40.

[0036] As described above, in this embodiment, the outer jacket tube 42 that can vibrate with respect to the cable main body 40 is provided so as to cover the periphery of the cable main body 40 that supports the main girder 2 of the bridge. When the outer jacket tube 42 receives wind, an external force is generated due to a pressure difference caused by surrounding turbulence, but by vibrating only the outer jacket tube 42 to dissipate kinetic energy, it is possible to suppress the vibration applied to the cable main body 40. Furthermore, the vibration suppression structure of this embodiment is easy to install because no special processing or the like is required for the cable main body 40, and is also effective as a vibration countermeasure for existing cables.

[0037] Furthermore, by providing the outer surface of the outer tube with the aerodynamic shape illustrated in FIG. 4, the vibration of the outer tube can be reduced, and the vibration of the cable main body 40 due to the vibration of the outer tube can be suppressed.

[0038] In this embodiment, the outer tube 42 is formed by winding the strip-shaped pipe material 421 in a spiral shape, which makes it easy to arrange the outer tube 42 continuously and also makes it possible to install the outer tube 42 on-site. The pipe materials 421 adjacent to each other in the axial direction of the outer tube 42 are fitted together by projections and recesses, etc., so that the shape of the outer tube 42 is appropriately maintained.

[0039] However, the present invention is not limited to the above embodiment. For example, in this embodiment, the outer jacket tube 42 is provided on the cable main body 40 of an existing cable-stayed bridge, but the vibration suppression structure of the present invention can also be applied to the cable of the cable-stayed bridge when a new cable-stayed bridge 1 is constructed. Figure 7 shows a radial cross section of the cable 4a at this time, and in this case, the outer jacket tube 42 is provided around the cable main body 40a, which does not include the protective tube 41, and the protective function and the aerodynamic countermeasure function are integrated into the outer jacket tube 42, thereby improving the economic efficiency of the cable 4a. In addition, the construction of the outer jacket tube 42 can also be performed using the above-mentioned pipe making device 5 after erecting the required number of strands S between the main girder 2 and the main tower 3.

[0040] In addition to the reinforcing material, an optical fiber sensor can be built into the pipe material 421 in advance, and the vibration of the entire mantle tube 42 can be detected by a known technology using the sensor (e.g., JP 2021-156822 A, etc.) to visualize the vibration suppression effect, making it possible to monitor during construction and use. Damage to the mantle tube 42 can also be detected by a known technology using an optical fiber sensor (e.g., JP 2019-70594 A, etc.). The optical fiber sensor can be built into the pipe material 421 in advance, or the optical fiber sensor can be installed simultaneously during pipe manufacturing of the mantle tube 42 shown in FIG. 6, etc.

[0041] In addition, in a cable-stayed bridge 1 in a cold region, a heating means (not shown) such as a heater or a fan can be used to heat the gap inside the jacket tube 42 or to supply heat such as hot air to warm the jacket tube 42, thereby melting the snow on the interface of the jacket tube 42 and promoting early snow fall. It is also preferable to perform a waterproofing treatment on both ends of the jacket tube 42 to prevent water from entering the inside of the jacket tube 42, and it is also preferable to provide a drying means (not shown) for drying the inside of the jacket tube 42 and keep the gap inside the jacket tube 42 dry to prevent corrosion of the strands S. It is also possible to provide an elastic body such as rubber between the jacket tube 42 and the cable body 40 and use it as a cushioning material or vibration absorbing material.

[0042] Furthermore, although this embodiment has been described as an example of vibration countermeasures for the cable 4 of a cable-stayed bridge 1, the vibration suppression structure using the outer tube 42 can be applied not only to the cable-stayed bridge 1 but also to all structures that support objects using cables, such as various suspension bridges, buildings, temporary structures, mechanical equipment, etc., and, as described above, it is possible to suppress cable vibration caused by wind.

[0043] Although the preferred embodiment of the present invention has been described above with reference to the attached drawings, the present invention is not limited to the examples. For example, it is clear that a person skilled in the art, such as a designer, constructor, or material supplier of cable-stayed bridges, can come up with various modified or revised examples within the scope of the technical ideas disclosed in this application, and it is understood that such modified or revised examples naturally belong to the technical scope of the present invention. [Explanation of symbols]

[0044] 1: Cable-stayed bridge 2: Main girder 3: Main tower 4, 4a: Cable 5: Pipe making equipment 40, 40a: Cable body 41:Protection tube 42: Mantle tube 421: Pipe manufacturing 422, 423: Fitting part 424: Convex stripe 425: Groove 426: Dimple

Claims

1. A structure for suppressing wind vibration of a cable that is erected in an oblique direction and supports a support object, comprising: a mantle tube that vibrates relative to a cable body having a strand so as to cover the cable body; A vibration suppression structure characterized in that the outer tube contacts the cable main body at one point on the cross section when placed on the cable main body.

2. 2. The vibration suppression structure according to claim 1, wherein the cable is a cable that supports a bridge from a main tower in a cable-stayed bridge.

3. The outer jacket tube is provided over the entire length of the cable body, A vibration suppression structure as described in claim 2, characterized in that the upper end of the outer tube on the main tower side is not fixed in position, and the lower end is placed on the main girder of the bridge so that no tension is applied to the outer tube.

4. 4. The vibration suppression structure according to claim 1, wherein the outer tube is made by winding a strip of tubular material in a spiral shape.

5. A vibration suppression structure as described in claim 4, characterized in that the outer tube is made of multiple types of the pipe material adjacent to each other in the axial direction of the tube.

6. A method for forming the vibration suppression structure according to claim 4 or 5, comprising the steps of: A method for forming a vibration suppression structure, characterized in that a pipe-making device is installed on the cable body of an existing cable-stayed bridge, and the outer tube is formed by spirally winding a strip-shaped pipe material around the cable body using the pipe-making device.

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