Corrosion prevention method for structural cables and structural cables treated with the corrosion prevention method

Abstract

To easily view and confirm degradation or the like of components of an existing or new structural cable that is used in suspension structures such as a suspension bridge and a cable-stayed bridge and exposed to outdoor atmosphere, after conducting a corrosion control method of the structural cable.SOLUTION: In a corrosion control method of a structural cable that is used in suspension structures including a suspension bridge and a cable-stayed bridge and exposed to outdoor atmosphere, the structural cable is enclosed and covered with a visible, transparent, adhesive, and thin resin film. Preferably, the raw material of the adhesive thin resin film is a fluororesin, especially ETFE. Preferably, the form of the adhesive thin resin film is a tape-like form or a sheet-like form.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a corrosion prevention technology for existing structural cables that are used in suspended structures such as suspension bridges and cable-stayed bridges and are exposed to the outdoors, or for newly installed structural cables that are exposed to the outdoors, and in particular to a corrosion prevention method that aims to extend the life of structural cables when preventing corrosion of such structural cables or when the structural cable becomes corroded (rather than replacing the structural cable when the corrosion is minor and replacement is difficult), and to a structural cable that has been treated with this corrosion prevention method. [Background technology]

[0002] Structural cables used in suspension bridges and cable-stayed bridges are exposed to harsh outdoor weather conditions and therefore require painting to prevent deterioration such as rust. Conventionally, structural cables have been painted with weather-resistant paint, but the harsh weather conditions to which the painted structural cables are exposed may require periodic repainting. However, due to poor access to the structural cables caused by the fact that such structural cables are installed on the towers at high positions of suspension bridges and cable-stayed bridges, this repainting requires a considerable amount of cost. In addition, in order to repaint properly, it is necessary to remove the existing paint before repainting, which further increases the cost.

[0003] In contrast to such repairs by repainting, it has been discovered recently that structural cables can be protected from outdoor exposure more permanently by spirally wrapping a polychloroprene covering material such as neoprene (the covering material can be in the form of a tape that can be easily wrapped in a spiral shape, for example) around structural cables of different lengths depending on the location, even in a suspended structure. However, this type of neoprene covering material needs to match or harmonize with the appearance of other elements (girders, towers, hangers, etc.) other than the structural cables in the suspended structure (suspension bridge, cable-stayed bridge, etc.) in which it is used, but it is usually not possible to properly color it before construction. Therefore, after spirally wrapping the bridge structural cables with neoprene covering material, the outer surface of the covering material is painted to properly match the color between the structural cables and other bridge elements, but this painting process is very time-consuming and therefore very expensive.

[0004] Furthermore, when structural cables for suspension bridges are spirally wrapped with neoprene tape, it is important that each turn of tape be firmly bonded to the previous turn to adequately seal the seam between them and thereby prevent the ingress of moisture and dust at the interface between the cover and the structural cables. It has been found that when using this type of neoprene tape (wrapped spirally around the structural cables), a reliable and adequate seal can be achieved by providing a significant overlap between successive turns of tape and using a solvent to bond the overlapping layers together. However, the application of the solvent is laborious and therefore expensive, and many of the solvents present environmental, health and safety hazards and require careful handling and disposal.

[0005] In view of such various problems, U.S. Patent No. 5,390,386 (Patent Document 1) discloses a corrosion prevention method for outdoor-exposed structural cables used in suspension bridges and cable-stayed bridges, which can be advantageously protected from exposure to severe weather conditions by spirally wrapping the structural cables with a flexible and appropriate synthetic rubber chlorosulfonated polyethylene material. The corrosion prevention method disclosed in Patent Document 1 is a method for protecting structural cables used in suspension bridges, cable-stayed bridges, etc., by spirally wrapping a flexible synthetic rubber tape (chlorosulfonated polyethylene), and the wrapping method involves wrapping the tape in a half-wrap (half-wrap) to form a double layer of uniform thickness, heating the tape to heat-seal the overlapped layers to seal the joints, and shrinking the tape to reliably and sufficiently fit (integrate) the flexible synthetic rubber tape (chlorosulfonated polyethylene) to the structural cables. According to this corrosion prevention method, it is possible to prevent the infiltration of air and moisture by wrapping a synthetic rubber tape (chlorosulfonated polyethylene) around corroded structural cables, thereby slowing down the progression of corrosion. Furthermore, since this flexible synthetic rubber tape can be colored before carrying out the corrosion prevention method, it is possible to properly match the color of the structural cables with other elements by coloring the flexible synthetic rubber tape the same color as the structural cables were originally colored. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] U.S. Pat. No. 5,390,386 Summary of the Invention [Problem to be solved by the invention]

[0007] However, in the corrosion prevention method disclosed in Patent Document 1, the structural cable wrapped with the tape (or sheet) used for corrosion prevention as a coating material makes the cable itself invisible due to the coating material, so that after construction, it is not possible to visually check the deterioration and other conditions of the structural cable's components (the presence or absence and progress of rust in the structural cable (steel material) itself, the presence or absence and progress of rust in the rust prevention layer in the structural cable (steel material) such as zinc plating, wax, or rust prevention paint, the deterioration of the outer tube such as a PE pipe (polyethylene pipe), etc.). Therefore, at present, in order to check the deterioration and other conditions of the structural cable's components, it is necessary to remove the coating material formed by the tape (or sheet) used for corrosion prevention, or to check using a non-destructive inspection method that can detect rust, etc., which poses a problem of extremely poor workability.

[0008] The present invention was developed in consideration of the above-mentioned problems of the prior art, and its purpose is to provide a corrosion prevention method for existing structural cables that are used in suspended structures such as suspension bridges and cable-stayed bridges and are exposed to the outdoors, or for newly installed structural cables that are exposed to the outdoors, which prevents corrosion of such structural cables, or, in the event that the structural cable becomes corroded (instead of replacing the structural cable especially when the corrosion is minor and replacement is difficult), makes it possible to easily visually confirm the condition of deterioration, etc. of the components of the structural cable after the construction of a corrosion prevention method that aims to extend the life of the structural cable, and to provide a structural cable that has been treated with this corrosion prevention method. [Means for solving the problem]

[0009] In order to achieve the above-mentioned object, the corrosion prevention method for a structural cable and the structural cable to which the corrosion prevention method has been applied according to the present invention have the following technical means. In other words, a corrosion protection method for structural cables relating to one aspect of the present invention is a corrosion protection method for structural cables exposed to the outdoors and used in suspended structures including suspension bridges and cable-stayed bridges, and is characterized in that the structural cable is wrapped and covered in a visible, transparent, and weldable thin resin film.

[0010] Preferably, the resin is a fluororesin. More preferably, the resin thin film is tape-shaped, and the tape-shaped resin thin film is overlapped over at least a portion of the tape width and spirally wound around the structural cable, thereby enveloping and covering the structural cable with the tape-shaped resin thin film.

[0011] More preferably, the resin thin film is in sheet form, and the sheet-like resin thin film is wrapped around the structural cable so that the sheet-like resin thin film forms a single-layer tube, and the ends of the sheet in a direction perpendicular to the longitudinal direction of the structural cable are overlapped, thereby wrapping and covering the structural cable with the sheet-like resin thin film. More preferably, the resin thin films may be laminated together, and then the laminated portions may be heated and thermally welded.

[0012] More preferably, a substance that reacts to water or moisture may be disposed between the structural cable and the thin resin film. In addition, a structural cable to which a corrosion prevention method according to another aspect of the present invention has been applied is any one of the above-mentioned The cable is characterized in that it is an outdoor-exposed structural cable used in suspended structures including suspension bridges and cable-stayed bridges, to which the corrosion prevention method described above has been applied. Preferably, the structural cable may be configured so that a structure is provided in which dry air supplied from outside the structural cable flows between the thin resin film and the structural cable. Effect of the Invention

[0013] According to the corrosion prevention method and structural cable treated with the corrosion prevention method of the present invention, the method is a corrosion prevention method for existing structural cables that are used in suspended structures such as suspension bridges and cable-stayed bridges and are exposed to the outdoors, or for newly installed structural cables that are exposed to the outdoors.When corrosion of such structural cables is prevented, or when the structural cable becomes corroded (rather than replacing the structural cable when the corrosion is minor and replacement is difficult), the deterioration and other conditions of the components of the structural cable can be easily visually confirmed after the application of the corrosion prevention method, which aims to extend the life of the structural cable, and a structural cable treated with the corrosion prevention method can be provided. [Brief description of the drawings]

[0014] [Figure 1] FIG. 1 is a diagram illustrating a corrosion protection method for structural cables according to an embodiment of the present invention, in which a structural cable is wrapped and covered with a transparent fluororesin (preferably ETFE) tape, where (A) the tape is spirally wrapped with less than a half wrap, and (B) the tape is spirally wrapped with a half wrap. [Diagram 2] 1 is a diagram for explaining a state in which a structural cable is wrapped and covered with a transparent fluororesin (preferably ETFE) sheet in a corrosion protection method for a structural cable according to an embodiment of the present invention. FIG. [Diagram 3] FIG. 3 is a diagram showing a state in which an air blowing and drying system is applied to a structural cable that has been subjected to a corrosion prevention method in which the structural cable is wrapped and covered with a fluororesin (preferably ETFE) sheet shown in FIG. 2. [Figure 4] FIG. 2 is a diagram showing the state in which an air blowing and drying system is applied to a structural cable that has been subjected to a corrosion prevention method in which the structural cable is wrapped and covered with a fluororesin (preferably ETFE) tape shown in FIG. 1(A). DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0015] The corrosion prevention method for structural cables according to the embodiment of the present invention and the structural cables to which the corrosion prevention method has been applied will be described in detail below with reference to the drawings. The structural cables to which the corrosion prevention method for structural cables according to the embodiment of the present invention has been applied as described below are structural cables (to which the corrosion prevention method has been applied) according to the embodiment of the present invention. The following description will be of a corrosion prevention method for existing structural cables used in suspended structures such as suspension bridges and cable-stayed bridges and exposed outdoors, which aims to extend the life of the structural cables when the structural cables are corroded (instead of replacing the structural cables when the corrosion is minor and replacement is difficult), but the corrosion prevention method according to the present invention is not limited to being applied to existing structural cables exposed outdoors, and may also be applied as a corrosion prevention method to prevent corrosion of newly installed structural cables exposed outdoors.

[0016] The figures referred to in the following description are basically schematic diagrams in which detailed structures have been omitted in order to facilitate understanding of the present invention, and in some cases parts that should be represented by their external form rather than their internal form are represented as if looking through the interior, parts that should be represented by a cross section rather than an external form are represented by an external form, and parts that should be represented by an external form rather than a cross section are represented by a cross section.

[0017] A corrosion protection method for structural cables according to an embodiment of the present invention will be described in detail with reference to Fig. 1 to Fig. 5. Fig. 1 shows a corrosion protection method for structural cables according to the present embodiment, in which a fluororesin (preferably ETFE) tape is used as a weldable resin thin film, and Fig. 2 shows a corrosion protection method for structural cables according to the present embodiment, in which a fluororesin (preferably ETFE) sheet is used as a weldable resin thin film. As shown in these Figs. 1 and 2, the corrosion protection method for a structural cable according to the present embodiment includes the following steps: It has the following features:

[0018] The corrosion prevention method for structural cables according to the present embodiment is a corrosion prevention method for structural cables exposed outdoors and used in suspended structures including suspension bridges and cable-stayed bridges, in which the structural cables are wrapped and covered with a transparent and weldable resin thin film that allows the structural cables to be visually recognized. As described below, the material of the transparent and weldable resin thin film that allows the structural cables to be visually recognized is preferably a transparent fluororesin, and particularly preferably ETFE. As described below, the shape of the transparent and weldable resin thin film that allows the structural cables to be visually recognized is preferably a tape or sheet shape, and is transparent so that the structural cables can be visually recognized even after construction. Here, visual recognition originally means recognizing (the state of deterioration of the structural cables after construction of the corrosion prevention method according to the present invention) by the sense of sight, which is one of the five human senses, but in the present invention, it also includes recognizing) the state of deterioration of the structural cables after construction of the corrosion prevention method according to the present invention by taking an image using a device other than a human, such as a camera, and analyzing the image data.

[0019] Here, the material of this thin resin film is preferably a fluororesin, and among fluororesins, transparent ETFE (Ethylene tetrafluoroethylene, ethylene-tetrafluoroethylene copolymer) is particularly preferable. Fluorocarbon polymers is a general term for synthetic resins obtained by polymerizing olefins containing fluorine. They are characterized by their high heat resistance, chemical resistance, and low coefficient of friction. The fluoroplastic that is most widely produced is polytetrafluoroethylene (tetrafluororesin). It has high resistance to chemicals, high electrical insulation, the lowest coefficient of friction of any known substance, and is stable at high temperatures and non-flammable, making it an engineering plastic. The first polytetrafluoroethylene developed had a heat resistance of 260°C, but it did not exhibit thermoplasticity and was not easy to process. To improve moldability, various chlorotrifluoroethylene resins and polyvinylidene fluoride resins were developed by replacing part of the fluorine group of the fully fluorinated polytetrafluoroethylene with hydrogen or chlorine, or by replacing it with olefins. Although these resins are inferior to polytetrafluoroethylene in terms of heat resistance, they are highly processable and can be compressed, extruded, and injected.

[0020] (1) Fully fluorinated resins include polytetrafluoroethylene (tetrafluororesin, abbreviated as PTFE), (2) partially fluorinated resins include polychlorotrifluoroethylene (trifluororesin, abbreviated as PCTFE or CTFE), polyvinylidene fluoride (abbreviated as PVDF), and polyvinyl fluoride (abbreviated as PVF), and (3) fluorinated resin copolymers include perfluoroalkoxy fluororesin (abbreviated as PFA), tetrafluoroethylene-hexafluoropropylene copolymer (abbreviated as FEP), ethylene-tetrafluoroethylene copolymer (abbreviated as ETFE), and ethylene-chlorotrifluoroethylene copolymer (abbreviated as ECTFE).

[0021] On the other hand, polyethylene (PE), a representative of common synthetic resins, is a resin with the simplest molecular structure, and is inexpensive and mass-produced, but its strength and heat resistance are extremely weak. This characteristic also makes it a resin with good thermal responsiveness, and it can be easily molded at relatively low temperatures, making it an extremely easy-to-use resin. For this reason, PVDF and ETFE were developed as resins with the properties of both PE and PTFE, and both are copolymerized (copolymerized) with PE parts (C2H4) and PTFE parts (C2F4). Unlike PVDF, which is roughly copolymerized, ETFE is carefully alternating polymerized. PE chains are the cause of deterioration, but ETFE reduces the number of PE chains by carefully alternating polymerizing them by devising reaction conditions, etc. The mobility of the PE parts reduces the melt viscosity of ETFE, and it softens at just under 180°C, making it possible to perform extrusion molding such as film molding, while at the same time, the decomposition between PE parts by radicals is blocked by F, making it extremely resistant to decomposition by ultraviolet rays, etc. Therefore, it is preferably used in applications where it is not used in high temperature environments but weather resistance is required. In this way, ETFE has the properties of both PTFE and PE, and has better moldability than PTFE, and can be injected or molded into films, etc., and can be easily processed into tape or sheet shapes. In addition, it can be colorless and transparent, colored and transparent, or opaque, and resin thin films of various colors (including transparent) can be realized.

[0022] It should be noted that ETFE welding does not require half-wrapping because strength can be obtained even with a narrow bonding width (overlap width). For this reason, when a transparent fluororesin tape (especially ETFE tape) is used instead of an opaque synthetic rubber tape, the weight per unit length of the fluororesin tape itself is lighter than that of the synthetic rubber tape, and further, since the ETFE tape is overlapped by about 1 / 4 of the width to form an incomplete double structure instead of overlapping by about 1 / 2 of the width to form a complete double structure, the corrosion prevention method shown in Fig. 1(A) significantly improves workability (in addition to improving visual confirmation workability by easily visually confirming the deterioration of the structural cable components after the corrosion prevention method is applied, since the structural cable is wrapped with a visible, transparent, and weldable ETFE tape, the deterioration of the structural cable components can be easily visually confirmed after the corrosion prevention method is applied) compared to the corrosion prevention method disclosed in Patent Document 1 (half-wrapped with synthetic rubber) in that the corrosion prevention method shown in Fig. 1(A) significantly improves workability (in addition to improving workability by visually confirming the deterioration of the structural cable components after the corrosion prevention method is applied, since the structural cable is wrapped with a visible, transparent, and weldable ETFE tape). Furthermore, since the weight per unit length of the fluororesin tape itself is lighter than that of synthetic rubber tape, the workability of the corrosion prevention method shown in Figure 1(B) (half-wrap with thin resin film) is improved compared to the corrosion prevention method disclosed in Patent Document 1 (half-wrap with synthetic rubber).

[0023] Moreover, it is preferable that the resin thin film is in the form of a tape (ETFE tape), and the tape-like resin thin film is overlapped by less than half the tape width and spirally wound around the structural cable (however, the present invention does not exclude less than half wrap (about 1 / 4 wrap) in which less than half the tape width (for example, about 1 / 4) is overlapped and spirally wound around the structural cable), thereby wrapping and covering the structural cable with the tape-like resin thin film. In this case, the half wrap disclosed in Patent Document 1 overlaps half the tape width and spirally winds the structural cable, so that the complete synthetic rubber tape covering layer (wrapping layer) constitutes a complete two-layer structure, whereas in this embodiment, it includes an incomplete two-layer structure in which less than half the tape width (for example, about 1 / 4) is overlapped and has a single-layer portion. Then, it is preferable that the resin thin films are overlapped each other, and then the overlapped portion (here, the overlapped portion is about half or less than half, i.e., about 1 / 4, of the tape width) is heated and thermally welded. In this way, in the corrosion prevention method for structural cables according to the present embodiment, a transparent fluororesin tape (ETFE tape) is used instead of an opaque synthetic rubber tape as in Patent Document 1, and a coating layer is formed on the structural cable in an incomplete two-layer structure (partially one-layer structure) that is an optional configuration (not a complete two-layer structure with half-wrap, but an overlap of less than half the tape width (approximately 1 / 4 of the tape width)), so that the weight of the coating material is reduced as described below (the structural cable is wrapped in a transparent and weldable ETFE tape that allows the structural cable to be visually confirmed, and the deterioration of the structural cable components can be easily confirmed after the corrosion prevention method is applied, thereby improving the visual confirmation workability). Note that the width of the overlapped tape is not particularly limited in the present invention, as long as the tape-shaped resin thin film is overlapped at least partially over the tape width and wound spirally around the structural cable.

[0024] Here, with reference to FIG. 1, a description will be given of an embodiment in which a tape-shaped resin thin film (ETFE tape) is spirally wound around a structural cable to encase and cover the structural cable with the tape-shaped resin thin film. Fig. 1(A) shows a state where the ETFE tape 150 is wound spirally with less than half-lap (approximately 1 / 4 of the tape width overlap), and Fig. 1(B) shows a state where it is wound spirally with half-lap. Note that it is also possible to directly apply anticorrosive paint to the cable wire 110 without providing an outer jacket tube 120 for anticorrosive purposes.

[0025] The state shown in Figure 1 (A) shows a structural cable 100 in the middle of undergoing corrosion protection construction, in which a cable wire 110 and an outer tube (an FRP pipe, PE pipe, etc. for corrosion protection purposes) 120 covering the outer periphery of the cable wire 110 are spirally wrapped with ETFE tape 150 with less than a half wrap, and the structural cable is enveloped in a tape-shaped thin resin film.

[0026] The state shown in FIG. 1(B) shows a structural cable 102 undergoing anticorrosion construction. The cable wire 110 and the outer tube (PE tube) 120 covering the outer periphery of the cable wire 110 are spirally wrapped with ETFE tape 152 in a half-wrap manner, so that the structural cable is enveloped in a tape-like resin thin film. 1(A) and 1(B), the overlapping portions (approximately 1 / 4 of the tape width) of the ETFE tapes 150 spirally wound around the cable wire 110 and the outer tube (PE tube) 120, or the overlapping portions (approximately 1 / 2 of the tape width) of the ETFE tapes 152 are heated and thermally welded. This thermal welding welds the ETFE tapes together, suppressing the infiltration of air and moisture from the overlapping portions and slowing the progress of corrosion.

[0027] Furthermore, since the structural cable is wrapped in a visible, transparent, and weldable thin resin film (here, ETFE tape 150 or ETFE tape 152), it is preferable in that the deterioration and other conditions of the structural cable components can be easily visually confirmed after the corrosion prevention method is applied. Next, referring to Figure 2, we will explain an embodiment in which a sheet-shaped resin thin film (ETFE sheet) is wrapped around a structural cable so that the sheet-shaped resin thin film forms a single-layer tube, and the ends of the sheet perpendicular to the longitudinal direction of the structural cable are overlapped to encase and cover the structural cable with the sheet-shaped resin thin film.

[0028] The state shown in Figure 2 shows a structural cable 104 in the middle of undergoing corrosion prevention construction, in which a single ETFE sheet 160 is wrapped around the cable wire 110 and an outer tube (corrosion-resistant FRP pipe, PE pipe, etc.) 120 covering the outer periphery of the cable wire 110 to form a single-layer tube, and the sheet ends 162 perpendicular to the longitudinal direction of the structural cable are overlapped, so that the structural cable is wrapped in a sheet-like thin resin film.

[0029] 2, one ETFE sheet 160 is wound around the cable wire 110 and the outer tube (PE tube) 120 to form a single-layer tube, and overlapping portions of the sheet ends 162 of the ETFE sheet 160 are heated and thermally welded. This thermal welding welds the sheet ends 162 of the ETFE sheet 160 together, suppressing the infiltration of air and moisture from the overlapping portions and slowing the progress of corrosion.

[0030] It should be noted that since the ETFE sheet is strong even when it is a single layer (completely single-layered structure), there is no need to half-wrap it to create a complete double-layered structure.For this reason, when a fluororesin sheet (particularly an ETFE sheet) is used in place of synthetic rubber tape, the workability is significantly improved in the corrosion prevention method shown in Figure 2 compared to the corrosion prevention method disclosed in Patent Document 1 (half-wrapped with synthetic rubber) in that the weight per unit area of ​​the fluororesin sheet itself is lighter than that of the synthetic rubber tape, and further, the weight of the covering material can be significantly reduced by using a completely single-layered ETFE sheet rather than half-wrapped by overlapping about 1 / 2 of the ETFE tape width to create a complete double-layered structure.

[0031] Note that there may be an air gap between the outer tube 120 covering the outer periphery of the cable wire 110 and the ETFE sheet 160, so long as the infiltration of air and moisture from the outside to the inside of the covering material can be suppressed. Furthermore, since the structural cable is wrapped in a visible, transparent, and weldable thin resin film (here, ETFE sheet 160), this is advantageous in that the deterioration and other conditions of the structural cable's components can be easily visually confirmed after the corrosion prevention method is applied.

[0032] Here, whether in the embodiment shown in Fig. 1 or the embodiment shown in Fig. 2, it is also preferable to place a substance that reacts to water or moisture between the structural cable and the thin resin film (ETFE tape 150, ETFE tape 152, or ETFE sheet 160). As described above, the problem with the conventional technology is that the tape (or sheet) used for corrosion prevention cannot visually check the state of deterioration (the presence or absence and progress of rust in the structural cable (steel material) itself, the presence or absence and progress of rust in the rust prevention layer in the structural cable (steel material) such as zinc plating or wax, the deterioration state of the outer pipe such as a PE pipe (polyethylene pipe), etc.). In contrast to this, in the corrosion prevention method for structural cables according to the present embodiment, as described above, a transparent fluororesin (preferably TEFE, which has excellent weather resistance) tape or fluororesin (preferably TEFE, which has excellent weather resistance) sheet is used, and since the covering material is transparent even after the application of the corrosion prevention method for structural cables, the deterioration status of the structural cable (the presence or absence and progress of rust in the structural cable (steel material) itself, the presence or absence and progress of rust in the rust prevention layer in the structural cable (steel material) such as zinc plating or wax, the deterioration status of the jacket pipe such as a PE pipe (polyethylene pipe) and the like) can be visually confirmed. Note that the "transparent" of the thin resin film in the corrosion prevention method according to the present invention includes both "colorless transparent" and "colored transparent", and is not particularly limited to "colorless transparent" or "colored transparent" as long as the deterioration status of the structural cable after the application of the corrosion prevention method according to the present invention can be visually confirmed. In this regard, it is not possible to visually confirm the deterioration of the structural cable after the application of the corrosion prevention method of the present invention; for example, "opaque (only)" is excluded from the "transparency" of the resin thin film in the description of the present invention.

[0033] In addition, it is preferable to place a powder, paint, or sheet that discolors or changes in quality due to moisture or humidity between the structural cable and the thin resin film (TEFE tape, TEFE sheet). This makes it possible to visually check the intrusion of moisture, which is a cause of corrosion, and helps to determine the progress of corrosion of the steel material. In this way, microcapsules, silica gel, and cobalt chloride hexahydrate are possible materials that discolor due to moisture or humidity, and water-absorbing sheets are possible materials that change quality due to moisture or humidity. The corrosion protection method for structural cables according to the present embodiment described above will now be described in more detail.

[0034] As mentioned above, there are two possible cases for structural cables used in suspended structures such as suspension bridges and cable-stayed bridges: [1] cables protected from corrosion by being covered with an outer tube such as an FRP (reinforced plastic) pipe or a PE (polyethylene) pipe, and [2] cables protected from corrosion by having an anti-corrosive paint applied directly to the cable. The implementation form differs depending on the case. Furthermore, with regard to the scope of application of the corrosion protection method for structural cables in this embodiment, it may be applied over the entire length of the structural cable that is the target of the corrosion protection method, or it may be applied only to the parts that have been deformed and to which waterproofing and airtightness are to be imparted.

[0035] [1] A cable that is protected from corrosion by being covered with an outer tube such as an FRP or PE tube. When only a part of the jacket tube is damaged but the majority of it is sound, the ETFE tape is wrapped directly around the jacket tube. There are two ways to wrap the tape: the manner shown in Fig. 1 and the manner shown in Fig. 2. If the jacket tube is severely damaged and cannot be directly wrapped with tape, the jacket tube is removed and the same treatment as for cables protected by direct application of anticorrosive paint as described below in [2] is carried out.

[0036] [2] Cables protected from corrosion by applying anticorrosive paint directly to them If the unevenness of the cable surface is small and the tape can fit, the same procedure as [1] can be used. However, if the surface is very uneven, such as when multiple cables are bundled together, the uneven areas will be filled with molding material to smooth out the unevenness, and then the same procedure as [1] will be used. In this case, it is preferable to use transparent resin or transparent clay as the covering material (molding material) so that the inside of the steel material (cable) can be seen, and it is also desirable to place a substance that will discolor or change its quality when exposed to moisture or humidity, as described below, so that the infiltration of corrosion factors can be visualized.

[0037] This explains how, after the application of corrosion protection methods for structural cables, it is possible to visually check the deterioration status of the structural cables (the presence or absence and progress of rust on the structural cable (steel) itself, the presence or absence and progress of rust on the anti-rust layer of the structural cable (steel) such as zinc plating or wax, the deterioration status of the outer pipe such as a PE pipe (polyethylene pipe), etc.). Next, visual confirmation of corrosion of structural cables (steel materials) will be described. Since the corrosion rate of structural cables (steel materials) varies greatly depending on the external environment, when the corrosion rate is slow, the judgment of the progress of corrosion may differ depending on the worker who performs the visual confirmation or the frequency of the visual confirmation. Therefore, if the following measures are taken to visualize the penetration of corrosion factors, the internal visual confirmation effect of this embodiment will have a more beneficial effect.

[0038] -Method of visualizing the penetration of corrosion factors The presence or absence of moisture or humidity is a major factor in the corrosion of structural cables in suspension bridges, cable-stayed bridges, and the like, which are the subject of the corrosion protection method for structural cables according to the present invention. Therefore, visualization of the intrusion of moisture or humidity is important as a criterion for judging the progress of corrosion. Therefore, in this embodiment, a method for visualizing the intrusion of moisture or humidity even through a transparent fluororesin thin film is to place a substance that discolors or changes in quality due to moisture or humidity. Specific examples include the following substances.

[0039] (1) Water-soluble microcapsules containing pigments When moisture penetrates, the microcapsules are destroyed and the dye is released, detecting the presence of moisture. (2) Silica gel used for dehumidification, etc. This method detects moisture or humidity by detecting the discoloration of silica gel. This method is expected to have an anti-corrosive effect on structural cables (steel materials) during the period when the silica gel absorbs moisture or humidity. (3) Cobalt chloride hexahydrate powder or solution It is detected by the change in color due to moisture or humidity. (4) Water-absorbent sheet When it absorbs moisture, its volume expands, and this change in volume can be detected visually.

[0040] In addition, with these visualization methods, it is preferable to arrange the structural cables (steel materials) in a way that allows them to be seen, as the condition of the structural cables (steel materials) cannot be seen if they are covered entirely. However, since the presence of moisture affects the progression of corrosion, it is acceptable to cover the entire structure. In this way, the structural cables are covered with a thin, transparent resin film that allows visual confirmation of the deterioration of the structural cable components (deformations such as the presence or absence and progression of rust in the structural cable (steel) itself, the presence or absence and progression of rust in the rust-preventive layer of the structural cable (steel) such as zinc plating or wax, and the deterioration of the outer pipe such as a PE pipe (polyethylene pipe)). Furthermore, by visualizing the intrusion of moisture or humidity, which is the cause of the deterioration, the accuracy of visual detection of abnormalities can be improved.

[0041] As described above, a structural cable treated with the corrosion prevention method of this embodiment and a structural cable treated with the corrosion prevention method are a corrosion prevention method for structural cables exposed to the outdoors and used in suspended structures such as suspension bridges and cable-stayed bridges, and in the event that such a structural cable becomes corroded (especially when the corrosion is minor and replacement is difficult), the structural cable is not replaced but rather the deterioration and other conditions of the components of the structural cable can be easily visually confirmed after the application of the corrosion prevention method, which aims to extend the life of the structural cable, and a structural cable treated with the corrosion prevention method can be provided.

[0042] <Modification> A modified example of the embodiment of the present invention will be described below. This modified example is a case where an air blowing and drying system is applied to a structural cable to which the anticorrosive method of the present invention has been applied (i.e., a case where a structural cable to which the anticorrosive method of the present invention has been applied is suitably provided with an air blowing and drying function), and will be described with reference to Fig. 3 and Fig. 4. Here, Fig. 3 is a diagram showing a state where an air blowing and drying system is applied to a structural cable to which the anticorrosive method of the present invention has been applied, in which the structural cable is wrapped and covered with a fluororesin (preferably ETFE) sheet shown in Fig. 2, and Fig. 4 is a diagram showing a state where an air blowing and drying system is applied to a structural cable to which the anticorrosive method of the present invention has been applied, in which the structural cable is wrapped and covered with a fluororesin (preferably ETFE) tape shown in Fig. 1(A).

[0043] In addition, this air supply drying system can be suitably applied to a structural cable that has been subjected to the corrosion prevention method of the present invention, whether it is an existing structural cable or a newly installed structural cable, in the same manner as the corrosion prevention method of the present invention. In addition, in the above-mentioned embodiment, the description includes the outer jacket tube 120 such as a PE pipe, but in the present invention, the outer jacket tube 120 is not an essential component, and the following modified examples will be described without the outer jacket tube 120. In the above-mentioned embodiment, the outer jacket tube 120 may not be provided, and in the modified examples shown below, the outer jacket tube 120 may be provided (as long as the dry air described below can be circulated so as to achieve its function and effect).

[0044] First, the air blowing and drying system will be briefly described. As described above, the corrosion prevention method according to the present invention can provide a sufficient rust prevention effect, but it is preferable to introduce an air blowing and drying system in addition to the above. In this case, it is preferable to use a structural cable to which the corrosion prevention method according to the present invention has been applied, since the air blowing and drying system can be suitably introduced. That is, the corrosion prevention method according to the present invention can realize a structure in which dry air in the air blowing and drying system flows between the resin thin film (fluororesin (preferably ETFE sheet 160, ETFE tape 150)) and the structural cable (here, referring to a plurality of cable wires 110 wrapped around a steel wire bundle 130).

[0045] The air blowing and drying system is a system that realizes more effective water blocking. For example, dry air is produced by removing salt and the like from the outside air using air blowing equipment installed on the main tower and stiffening girder of a suspension bridge, and the dry air is passed through the air blowing pipe and sent into the structural cable 100. The humid air that has passed through the gaps in the structural cable 100 is discharged from the exhaust bar and the tower top / anchorage saddle, so that the inside of the structural cable 100 is always dry. In the air blowing equipment, a filter unit is installed to remove dust and salt from the outside air, and the outside air is dried by a dehumidifier, pressurized by an air blower, and sent to the cable. Here, it has been confirmed through literature and tests that the cable wire 110, which is a steel wire (steel material), hardly corrodes at a relative humidity of 60% or less. Therefore, in order to reliably maintain a relative humidity of 60% or less, it is preferable that the management target value of the dry air in the cable is set to a relative humidity of 40%.

[0046] As shown in Figure 3, in a structural cable 104 after completion of the corrosion prevention method of the present invention, dry air supplied from outside the structural cable 104 is divided into dry air A (1) flowing through the space between the thin resin film (here, ETFE sheet 160) and the structural cable (here, referring to multiple cable wires 110 wrapped around a steel wire bundle 130), and dry air A (2) flowing through the gaps between the multiple cable wires 110 wrapped around the steel wire bundle 130. As a result, there is little resistance to air flow, and the entire cable wires 110 in the structural cable 104 can always be effectively dried without partial bias without causing extreme differences in the amount of air flow within the structural cable 104.

[0047] As shown in Figure 4, in a structural cable 100 after completion of the corrosion prevention method of the present invention, dry air supplied from outside the structural cable 100 is divided into dry air A (1) flowing through the space between the resin thin film (here, ETFE tape 150) and the structural cable (here, referring to multiple cable wires 110 wrapped around a steel wire bundle 130), and dry air A (2) flowing through the gaps between the multiple cable wires 110 wrapped around the steel wire bundle 130. As a result, there is little resistance to air flow, and the entire cable wires 110 in the structural cable 100 can always be effectively dried without partial bias without causing extreme differences in the amount of air flow within the structural cable 100.

[0048] As described above, when a structural cable is subjected to the corrosion prevention method of the present invention, the rust prevention effect can be further enhanced by suitably introducing an air drying system as in this modified example. It should be noted that the embodiments disclosed herein are illustrative and not restrictive in all respects. The scope of the present invention is defined by the claims, not the above description, and is intended to include all modifications within the meaning and scope of the claims. [Industrial Applicability]

[0049] The present invention relates to corrosion prevention technology for structural cables exposed outdoors and used in suspended structures such as suspension bridges and cable-stayed bridges, and is particularly preferred as a corrosion prevention method that aims to extend the life of such structural cables rather than replacing them when they become corroded (especially when the corrosion is minor and replacement is difficult). [Explanation of symbols]

[0050] 100, 102, 104, 202 Structural cables undergoing anti-corrosion construction 110 Cable wire 120 Mantle tube 150, 152 ETFE tape 160 ETFE sheet 162 Sheet end 252 Synthetic rubber tape

Claims

1. A corrosion protection method for existing structural cables exposed outdoors or new structural cables exposed outdoors, which is used in suspended structures including suspension bridges and cable-stayed bridges, comprising: The structural cable is wrapped and covered with a visible transparent and weldable resin thin film; A corrosion protection method for structural cables, characterized in that a substance that visualizes the intrusion of moisture or humidity between the structural cable and the thin resin film is placed between the structural cable and the thin resin film, and the intrusion is visually confirmed through the transparent thin resin film using the substance.

2. 2. The corrosion protection method for structural cables according to claim 1, wherein the resin is a fluororesin.

3. A corrosion protection method for structural cables as described in claim 1 or claim 2, characterized in that the resin thin film is tape-shaped, and the tape-shaped resin thin film is overlapped over at least a portion of the tape width and spirally wound around the structural cable, thereby wrapping and covering the structural cable with the tape-shaped resin thin film.

4. A corrosion protection method for structural cables as described in claim 1 or claim 2, characterized in that the resin thin film is in sheet form, and the sheet-like resin thin film is wrapped around the structural cable so that the sheet-like resin thin film forms a single-layer tube, and the ends of the sheet in a direction perpendicular to the longitudinal direction of the structural cable are overlapped to wrap and cover the structural cable with the sheet-like resin thin film.

5. 5. The method for preventing corrosion of a structural cable according to claim 3, further comprising the steps of: overlapping the resin thin films together; heating the overlapped portion to thermally weld the overlapped portion;

6. A corrosion protection method for structural cables as described in any one of claims 1 to 5, characterized in that a substance that changes color in response to moisture or humidity is placed between the structural cable and the resin thin film.

7. 7. A structural cable exposed outdoors and used in a suspended structure including a suspension bridge and a cable-stayed bridge, the structural cable being treated with the corrosion prevention method according to any one of claims 1 to 6.

8. The structural cable according to claim 7 , further comprising a structure for allowing dry air supplied from outside the structural cable to flow between the resin thin film and the structural cable.

Images