Corrosion prevention methods and structural cables treated with these corrosion prevention methods

Abstract

To easily visually recognize and confirm the state of deterioration or the like of components of a structural cable periodically or irregularly after the subjection of a corrosion prevention method of the structural cable.SOLUTION: A corrosion prevention method for structural cables is a corrosion prevention method for outdoor exposed structural cables used for suspension structures including suspension bridges and cable-stayed bridges, the structural cables are wrapped and covered together with a moisture-detecting material 122 by a corrosion prevention tape 150 which is an example of a resin thin film which is adhesively bondable to each other and has a waterproof function and can be peeled off, as the aging deterioration confirmation, the corrosion prevention tape 150 covered by the structural cable is peeled off (when the corrosion prevention tape 150 is replaced periodically or non-periodically), and the degree of the corrosion prevention of the structural cable is confirmed by visual recognition of the degeneration such as discoloration and alteration (shape change) of the moisture detecting material 122.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present invention relates to an anticorrosion technique for an existing object that needs anticorrosion measures exposed outdoors or a new object that needs anticorrosion measures to be exposed outdoors (especially when the object is used for a suspension structure such as a suspension bridge or a cable-stayed bridge, and is an existing structural cable exposed outdoors or a new structural cable to be exposed outdoors). In particular, when preventing corrosion of such a structural cable as an example of the object, or when the structural cable is corroded (especially when the corrosion is mild and it is difficult to replace the structural cable, instead of replacing the structural cable), it relates to an anticorrosion method for prolonging the life of the structural cable as an example of the object and a structural cable to which the anticorrosion method has been applied. Note that the object to which the anticorrosion method according to the present invention is preferably applied is not limited to such a structural cable, and may be, for example, a metal pipe or the like as long as it is an existing object that needs anticorrosion measures exposed outdoors or a new object that needs anticorrosion measures to be exposed outdoors.

Background Art

[0002] A structural cable used for a suspension bridge or a cable-stayed bridge, which is an example of an object to which an anticorrosion method is preferably applied, is exposed to severe outdoor weather conditions, so painting or the like is required to prevent deterioration such as rusting. Conventionally, structural cables were painted with weather-resistant paints, but periodic repainting may have been required due to the severe weather conditions to which the painted structural cables were exposed. However, due to the poor accessibility to such structural cables, such as being provided on the main towers at high positions such as suspension bridges and cable-stayed bridges, a considerably high cost was required for this repainting. Also, in order to properly repaint, it was necessary to remove the existing paint before repainting, further increasing the cost.

[0003] Recently, it has been discovered that, in contrast to repairs involving repainting, wrapping structural cables, which vary in length even within a single suspension structure, with polychloroprene coverings such as neoprene (often in the form of tape that is easy to wrap spirally) provides more permanent protection against outdoor exposure. However, this type of neoprene covering needs to match or harmonize with the appearance of other elements (girders, main towers, hangers, etc.) in the suspension structure (suspension bridges, cable-stayed bridges, etc.) other than the structural cables, but it is usually not possible to properly color them before installation. Therefore, after spirally wrapping the bridge structural cables with neoprene coverings, the outer surface of the covering is painted to achieve appropriate color matching between the structural cables and other bridge elements. However, this painting process is very time-consuming and therefore very expensive.

[0004] Furthermore, when spirally wrapping the structural cables of a suspension bridge with neoprene sheathing (tape), it is crucial to firmly adhere each turn of the sheathing (tape) to the preceding turn, properly sealing the joints between them, thereby preventing moisture and dust from entering the interface between the cover and the structural cables. When using this type of neoprene sheathing (spirally wrapping tape-like sheathing around structural cables), it was known that a reliable and sufficient seal could be achieved by providing considerable overlap between consecutive turns of the sheathing (tape) and bonding the overlapping layers together using a solvent. However, the application of solvents is time-consuming and expensive, and many solvents pose environmental, health, and safety problems, requiring careful handling and disposal.

[0005] In view of these various problems, U.S. Patent No. 5,390,386 (Patent Document 1) discloses a corrosion protection method that can advantageously protect exposed structural cables used in suspension bridges and cable-stayed bridges from exposure to harsh climatic conditions by spirally wrapping the structural cables with a flexible and appropriate synthetic rubber chlorosulfonated polyethylene material. The corrosion protection method disclosed in Patent Document 1 is a method of protecting structural cables used in suspension bridges or cable-stayed bridges by spirally wrapping them with a flexible synthetic rubber tape (chlorosulfonated polyethylene). The wrapping method involves overlapping the tape by half and wrapping it in a half-wrap manner to form a double layer of uniform thickness, then heating the tape to heat-seal the overlapping layers together to seal the joints, and shrinking the tape as well, thereby ensuring that the synthetic rubber tape (chlorosulfonated polyethylene) fits (integrates) securely and sufficiently to the structural cable. This corrosion prevention method involves wrapping corroded structural cables with synthetic rubber tape (chlorosulfonated polyethylene) to suppress the intrusion of air and moisture, thereby slowing down the progression of corrosion. Furthermore, since this flexible synthetic rubber tape can be colored before the corrosion prevention method is implemented, it is possible to color the flexible synthetic rubber tape to match the original color of the structural cables, thereby ensuring proper color matching between the structural cables and other elements. [Prior art documents] [Patent Documents]

[0006] [Patent Document 1] U.S. Patent No. 5390386 [Overview of the project] [Problems that the invention aims to solve]

[0007] However, in the corrosion protection method disclosed in Patent Document 1, structural cables wrapped with tape (or sheets) used for corrosion protection as a covering material become invisible due to the covering material. Therefore, after construction, it is not possible to visually inspect the deterioration status of the structural cable components (such as the presence and progression of rust on the structural cable (steel material) itself, the presence and progression of rust on the rust-preventive layer on the structural cable (steel material) such as zinc plating, wax, or rust-preventive paint, and the deterioration status of the outer pipe such as PE pipe (polyethylene pipe)). Consequently, in the current situation, it is necessary to remove the covering material formed by the tape (or sheets) used for corrosion protection in order to check the deterioration status of the structural cable components, which presents a problem of extremely poor workability.

[0008] Furthermore, when removing the covering material formed by the tape (or sheet) used for corrosion protection to check the condition of the structural cable components, it is extremely important to confirm that moisture is blocked from reaching the structural cable in order to achieve reliable corrosion protection. However, in the corrosion protection method disclosed in Patent Document 1, even if the covering material is removed and checked, it is not easy to confirm whether moisture is reliably blocked from reaching the structural cable.

[0009] The present invention was developed in view of the above-mentioned problems of the prior art, and its purpose is to provide a corrosion protection method for objects that require corrosion protection measures, such as existing structural cables exposed outdoors or newly installed structural cables exposed outdoors, used in suspension structures such as suspension bridges and cable-stayed bridges, and which are used in suspension structures, such as suspension bridges and cable-stayed bridges, and which are used in preventing corrosion of such structural cables, or when structural cables, etc. have corroded (especially when the corrosion is minor and replacement is difficult, the structural cables, etc. are not replaced), and which provides a corrosion protection method that allows for easy visual inspection of the deterioration of components of structural cables, etc., periodically or irregularly after the application of the corrosion protection method, and provides structural cables to which the corrosion protection method has been applied. [Means for solving the problem]

[0010] To achieve the above objective, the corrosion prevention method and the structural cable to which this corrosion prevention method is applied according to the present invention comprises the following technical means.

[0011] In other words, a corrosion protection method according to a certain aspect of the present invention is a corrosion protection method for an existing object exposed outdoors that requires corrosion protection measures or a newly constructed object exposed outdoors that requires corrosion protection measures, wherein the object has a shape in which one longitudinal direction is longer than the other direction, and the object is wrapped and covered together with a moisture detection material by a peelable resin thin film that is adhesive to each other and has a waterproof function, and the degree of corrosion protection of the object is confirmed by peeling off the resin thin film covering the object as confirmation of deterioration over time.

[0012] Furthermore, a corrosion protection method relating to another aspect of the present invention is a corrosion protection method for suspension structures, including suspension bridges and cable-stayed bridges, for existing structural cables exposed outdoors or newly installed structural cables exposed outdoors, wherein the structural cables are bonded to each other and have a waterproofing function using a resin thin film. The present invention is characterized by encasing and covering the structural cable together with a moisture detection material using a peelable resin thin film, and then peeling off the resin thin film covering the structural cable to confirm the degree of corrosion protection of the structural cable as a way to check for deterioration over time.

[0013] Preferably, the moisture detection material can be configured to be provided together with a filler that is filled between the object or the structural cable and the resin thin film.

[0014] More preferably, the moisture detection material can be configured to be provided in a portion of the object or structural cable that is covered by the resin thin film along its longitudinal direction.

[0015] More preferably, the moisture detection material is provided in a portion of the object or structural cable covered by the resin thin film along its longitudinal direction, and a water-conducting member can be further provided in the portion of the object or structural cable covered by the resin thin film along its longitudinal direction so as to be in contact with the moisture detection material.

[0016] More preferably, the resin thin film is in the form of a tape, and the object or structural cable can be wrapped and covered by the tape-shaped resin thin film by overlapping at least a portion of the tape width and winding it spirally around the object or structural cable.

[0017] Furthermore, a corrosion protection method relating to another aspect of the present invention is a corrosion protection method for existing structural cables exposed to the outdoors or newly installed structural cables exposed to the outdoors, used in suspension structures including suspension bridges and cable-stayed bridges, characterized in that the structural cables are wrapped and covered with a resin thin film that is adhesive to each other and has a waterproof function, together with a moisture detection material and a sensor that detects the deterioration of the moisture detection material, and the degree of corrosion protection of the structural cables is confirmed by the sensor as confirmation of deterioration over time.

[0018] Furthermore, a corrosion protection method relating to another aspect of the present invention is a corrosion protection method for existing structural cables exposed to the outdoors or newly installed structural cables exposed to the outdoors, used in suspension structures including suspension bridges and cable-stayed bridges, characterized in that the structural cables are wrapped and covered with a resin thin film that is adhesive to each other and has a waterproof function, together with a sensor that detects moisture, the sensor can be connected to a measuring instrument by peeling off the resin thin film or without peeling off the resin thin film, and the degree of corrosion protection of the structural cables is confirmed by the sensor and the measuring instrument as confirmation of deterioration over time.

[0019] Also, a structural cable applied with the anticorrosion method according to another aspect of the present invention is an outdoor-exposed structural cable used in a suspension structure including a suspension bridge and a cable-stayed bridge, to which the anticorrosion method described in any of the above is applied.

Advantages of the Invention

[0020] According to the anticorrosion method and the structural cable applied with the anticorrosion method according to the present invention, it is an anticorrosion method for an object that requires anticorrosion measures, such as an existing outdoor-exposed structural cable or a newly installed outdoor-exposed structural cable used in a suspension structure such as a suspension bridge or a cable-stayed bridge. When preventing corrosion of such a structural cable or the like, or when the structural cable or the like is corroded (especially when the corrosion is mild and it is difficult to replace, instead of replacing the structural cable or the like), after the construction of the anticorrosion method for extending the life of the structural cable or the like, it is possible to easily visually recognize and confirm the deterioration status of the components of the structural cable or the like regularly or irregularly, and a structural cable applied with the anticorrosion method can be provided.

Brief Description of the Drawings

[0021] [Figure 1] In the anticorrosion method of the structural cable according to the embodiment of the present invention, it is a diagram for explaining a mode in which the structural cable is wrapped and covered with an anticorrosion tape, (A) a state of being spirally wound with less than a half lap, and (B) a state of being spirally wound with a half lap. [Figure 2] It is a diagram (part 1) for explaining a state in which the structural cable is wrapped and covered with an anticorrosion tape in the anticorrosion method of the structural cable according to the embodiment of the present invention. [Figure 3] It is a diagram (part 2) for explaining a state in which the structural cable is wrapped and covered with an anticorrosion tape in the anticorrosion method of the structural cable according to the embodiment of the present invention. [Figure 4] It is a diagram for explaining a state in which the structural cable is wrapped and covered with an anticorrosion tape in the anticorrosion method of the structural cable according to the second modification of the embodiment of the present invention. [Figure 5] In the anti-corrosion method for the structural cable shown in FIG. 4, it is a diagram (part 1) for explaining the state where water immersion is confirmed. [Figure 6] In the anti-corrosion method for the structural cable shown in FIG. 4, it is a diagram (part 2) for explaining the state where water immersion is confirmed.

Embodiments for Carrying out the Invention

[0022] Hereinafter, the anti-corrosion method for the structural cable according to the embodiment of the present invention and the structural cable to which the anti-corrosion method has been applied will be described in detail with reference to the drawings. Note that the structural cable to which the anti-corrosion method (anti-corrosion construction method) for the structural cable according to the present embodiment has been constructed as described below is the structural cable according to the embodiment of the present invention (to which the anti-corrosion method has been applied). In the following description, it is an anti-corrosion method for an existing structural cable used in a suspension structure such as a suspension bridge or a cable-stayed bridge and exposed outdoors. When the structural cable is corroded (especially when the corrosion is mild and it is difficult to replace the structural cable, the structural cable is not replaced), an anti-corrosion method for extending the life of the structural cable will be described. However, the anti-corrosion method according to the present invention is not limited to being constructed for an existing structural cable exposed outdoors, and it may be constructed as an anti-corrosion method for preventing corrosion of a newly installed structural cable exposed outdoors. Further, the structural cable to be anti-corroded may be one provided with cable strands and an outer sleeve (such as an FRP (fiber reinforced plastic) pipe or a PE (polyethylene) pipe for anti-corrosion purposes) covering the outer peripheral side of the cable strands, or one in which an anti-corrosion paint is directly applied to the cable strands without such an outer sleeve for anti-corrosion purposes, or any other structure.

[0023] Herein, the objects to which the corrosion protection method according to the present invention is suitably applied are not limited to structural cables, but may also be existing objects exposed outdoors that require corrosion protection measures, or new objects exposed outdoors that require corrosion protection measures, such as existing or new metal pipes exposed outdoors that require corrosion protection measures. In the following, the objects to which the corrosion protection method according to the present invention is suitably applied will be described as existing structural cables exposed outdoors or new structural cables exposed outdoors. Furthermore, when the corrosion protection method is implemented, if there are steps or other irregularities in the structural cable when wrapping and covering it with a peelable resin thin film that is adhesive to each other and has a waterproof function, a filler may be filled between the structural cable and the resin thin film to alleviate such steps or irregularities.

[0024] Herein, the diagrams referenced in the following explanation are basically schematic diagrams that omit detailed structures in order to facilitate understanding of the present invention. In some cases, parts that should be represented by their external shape rather than their internal shape are shown as if the internal structure is visible through them, parts that should be represented by a cross-section rather than their external shape are shown as external shapes, and parts that should be represented by an external shape rather than a cross-section are shown as cross-sections.

[0025] A corrosion protection method for structural cables according to an embodiment of the present invention will be described in detail with reference to Figures 1 to 3. Figure 1 shows a corrosion protection tape being used as the weldable resin thin film in the corrosion protection method for structural cables according to this embodiment, and Figures 2 and 3 are diagrams illustrating the state in which the structural cable is wrapped and covered with the corrosion protection tape in the corrosion protection method for structural cables according to this embodiment. In all of the figures, the corrosion protection method for structural cables employs a resin thin film tape that is adhesive to each other, has a waterproof function, and is peelable (sometimes referred to as corrosion protection tape in the above description and sometimes as corrosion protection tape in the following description). However, the resin thin film may be in sheet form, and the structural cable may be wrapped and covered by covering the periphery of the structural cable with the sheet-like resin thin film and bonding both ends perpendicular to the longitudinal direction of the structural cable to each other.

[0026] As shown in Figures 1 to 3, the corrosion protection method for structural cables according to this embodiment has the following features.

[0027] The corrosion protection method according to this embodiment is for existing objects exposed outdoors that require corrosion protection measures or This invention relates to a corrosion protection method for newly installed objects requiring corrosion protection that are exposed outdoors, wherein the objects have a shape in which one longitudinal direction is longer than the other. As described above, although not limited thereto, the objects of the corrosion protection method according to the present invention will be described as existing structural cables requiring corrosion protection that are exposed outdoors and used in suspension structures, including suspension bridges and cable-stayed bridges, or newly installed structural cables requiring corrosion protection that are exposed outdoors. The corrosion protection method according to this embodiment is based on the premise that such structural cables are wrapped and covered together with a moisture detection material by a peelable resin thin film that is adhesive to each other and has a waterproof function. Furthermore, as confirmation of deterioration over time (such as when the resin thin film is replaced periodically or irregularly), the resin thin film covering the structural cable is peeled off, and the degree of corrosion protection of the structural cable is confirmed by visually observing changes such as discoloration or deterioration of the moisture detection material (change in shape is one example of deterioration).

[0028] Here, as an example of a removable resin thin film that is adhesive to itself and has waterproofing properties, the anti-corrosion tape used in the Antimec® method, manufactured and sold by the applicant, can be used. This anti-corrosion tape is suitable for corrosion protection of structural cables, and is made by impregnating a plastic-based cloth (which can be said to be equivalent to the resin thin film itself) with a compound mainly composed of a specially formulated drying oil. This anti-corrosion tape is an oxidative polymerization-curing type tape that hardens its surface by oxidative polymerization by absorbing sunlight, heat, and oxygen, forming a hardened film, and has excellent corrosion resistance, weather resistance, heat resistance, flexibility, and displacement following ability. This anti-corrosion tape does not become impossible or difficult to remove after application, such as welding, where a part of the anti-corrosion tape is melted by heat to bond it to each other, but rather the resin thin films themselves (in this case, the anti-corrosion tape) have adhesive properties that allow them to become one when joined to each other, or the resin thin films are bonded to each other by applying an adhesive with adhesive properties to the resin thin films (in this case, the anti-corrosion tape), and it is possible to peel it off after application.

[0029] In this process, structural cables are wrapped spirally around and covered with this type of anti-corrosion tape. To improve the adhesion of the anti-corrosion tape, a rust-preventive primer is applied to the structural cables. Fillers are used to smooth out any steps caused by cable bands or cable bundles, and a topcoat is applied to the surface of the anti-corrosion tape to quickly form a coating that prevents dust and other particles from adhering, thereby enhancing the tape's corrosion resistance and weather resistance. Thus, the main steps in the application of anti-corrosion tape are: (1) surface preparation, (2) application of primer, (3) filling with filler (shaping of steps), (4) wrapping with anti-corrosion tape, and (5) application of topcoat.

[0030] Referring to Figure 1, we will now describe an embodiment in which a structural cable is wrapped and covered with a tape-shaped resin film (corrosion-resistant tape) that is adhesive to itself, has waterproof properties, and is peelable.

[0031] Figure 1(A) shows the state in which the anti-corrosion tape 150 is wrapped spirally with less than a half-wrap (approximately 1 / 4 of the tape width overlapping), and Figure 1(B) shows the state in which it is wrapped spirally with a half-wrap. Here, it is assumed that there is no outer sheath for the purpose of corrosion protection, and the anti-corrosion paint is applied directly to the cable strands 110.

[0032] Figure 1(A) shows a structural cable 100 in the process of undergoing corrosion protection treatment. The cable strands 110 have been filled with a filler 120, which has formed any stepped sections (such as those caused by cable bands or cable bundles, not shown) on the cable strands 110. Furthermore, corrosion protection tape 150 is wrapped spirally around the cable with less than a half-wrap, so the structural cable is completely encased in the corrosion protection tape 150.

[0033] Figure 1(B) shows a structural cable 102 undergoing corrosion protection treatment. The cable strands 110 have been filled with a filler 120, which has formed any stepped sections (such as those caused by cable bands or cable bundles, not shown). Furthermore, corrosion protection tape 150 is wrapped spirally around the cable in a half-wrap fashion, encasing the structural cable in the corrosion protection tape 150.

[0034] In either Figure 1(A) or Figure 1(B), the cable strands 110 and the charge In the overlapping portions (approximately 1 / 4 of the tape width) of the anti-corrosion tapes 150 spirally wrapped around the filler 120, or in the overlapping portions (approximately 1 / 2 of the tape width) of the anti-corrosion tapes 152, the anti-corrosion tapes 150 (anti-corrosion tapes 152) are bonded together (without, for example, heat welding) by possessing adhesive properties that cause them to integrate when joined (when they come into contact), or by applying an adhesive with adhesive properties to the anti-corrosion tapes 150 (anti-corrosion tapes 152), and can be peeled off after installation. The anti-corrosion tapes 150 (anti-corrosion tapes 152) bonded together in this way suppress the intrusion of air and moisture from the overlapping portions, thereby slowing down the progression of corrosion. Furthermore, by making it peelable, it is preferable that the degree of corrosion protection of the structural cable can be easily confirmed by peeling off the corrosion protection tape 150 (corrosion protection tape 152) covering the structural cable and visually inspecting the deterioration of the moisture detection material, etc., as part of checking for deterioration over time after construction (such as when replacing the corrosion protection tape 150 (corrosion protection tape 152) periodically or irregularly). From here on, corrosion protection tape 150 will be used as a representative example when describing corrosion protection tape 150 and corrosion protection tape 152.

[0035] Here, as shown in Figures 1 to 3, the moisture detection material 122 is provided together with the filler 120 that is filled between the structural cable (more specifically, the cable strands 110) and the corrosion-resistant tape 150. The moisture detection material 122 provided together with the filler 120 will now be described in detail.

[0036] The presence or absence of moisture or humidity is a major factor in the corrosion of structural cables such as suspension bridges or cable-stayed bridges, which are targeted by the corrosion prevention method according to the present invention. Therefore, visualizing the intrusion of moisture or humidity is important for determining the progression of corrosion. For this reason, in this embodiment, the intrusion of moisture or humidity can be detected by placing a substance (moisture detection material 122) that changes color or deteriorates when exposed to moisture or humidity. Specific examples include the following substances. (1) Water-soluble microcapsules containing a dye (dye-encapsulated microcapsules) The detection method works by having microcapsules rupture upon contact with moisture, releasing a dye. (2) Silica gel used for dehumidification, etc. This method detects moisture or humidity by observing the discoloration of the silica gel. Furthermore, this method can be expected to provide corrosion protection for structural cables (steel materials) during the period in which the silica gel absorbs moisture or humidity. (3) Cobalt chloride hexahydrate powder or solution This method detects moisture or humidity by causing a change in color. (4) Absorbent sheet Because its volume expands when it absorbs moisture, this change in volume is visually observed and detected. (5) Water-soluble sheet Because it dissolves by absorbing moisture, for example, letters or other characters can be printed on the sheet with ink, and the dissolution of the ink of these characters can be visually observed to detect the problem.

[0037] For example, the moisture detection materials (1) to (3) in powder form are mixed into the filler 120 and placed together with the filler 120 between the anti-corrosion tape 150 and the cable strands 110, while the sheet-like materials (4) to (5) are placed between the filler 120 and the anti-corrosion tape 150.

[0038] Next, the effects of this moisture detection material 122 (discoloration or deterioration due to moisture or humidity) were confirmed as shown below. (A) A simple test specimen was prepared by placing a filler and dye-encapsulated microcapsules on a steel plate simulating a structural cable, and then wrapping it with anti-corrosion tape. A notch was made in the simple test specimen from above the anti-corrosion tape to reach the filler, and it was immersed in water for several days before being removed. When the removed simple test specimen was disassembled, it was confirmed that the microcapsules and filler were discolored only in the areas where water had penetrated, making it possible to visually determine that water had penetrated. (B) A filler containing cobalt chloride hexahydrate was prepared as a simple test specimen. When water was intentionally added to this simple test specimen to simulate the state of water penetration, it turned into a red solution, confirming that water penetration could be visually determined. (C) A simple test specimen was prepared by placing a filler on a steel plate that mimicked a structural cable, and then wrapping the filler with a polyvinyl alcohol sheet (water-soluble sheet) printed with black ink. When water was sprayed onto the simple test specimen to simulate water infiltration, the polyvinyl alcohol sheet dissolved and the ink appeared to dissolve, confirming that it was possible to visually determine that water had infiltrated the specimen.

[0039] Next, the arrangement of the moisture detection material 122 will be explained with reference to Figures 2 and 3.

[0040] Here, it is preferable that such moisture-detecting material is provided in the portion covered by the anti-corrosion tape 150, which is a thin resin film, along the longitudinal direction of the structural cable 100 (in this Figure 2, cable strands 110 are shown). Furthermore, it is also preferable that such moisture-detecting material is provided in a part of the portion covered by the anti-corrosion tape 150, which is a thin resin film, along the longitudinal direction of the structural cable 100 (in this Figure 3, cable strands 110 are shown), and that a water-conducting member 130 is further provided in the portion covered by the anti-corrosion tape 150, which is a thin resin film, along the longitudinal direction of the structural cable (in this Figure 3, cable strands 110 are shown), so as to be in contact with the moisture-detecting material 122. Here, one example of this water-conducting member 130 is a sheet that easily transmits moisture.

[0041] In Figures 2 and 3, the moisture detection materials (1) to (3), such as powders, are mixed into the filler 120 and placed together with the filler 120 between the anti-corrosion tape 150 and the cable strands 110. For this reason, the moisture detection material 122 is shown in the figure with a parenthetical reference numeral in the filler 120.

[0042] As described above, in the corrosion prevention method according to this embodiment, a moisture detection material 122, such as a powder, paint, or sheet that changes color or deteriorates with moisture, is installed between a structural cable 100 or structural cable 102, which is composed of multiple cable strands 110, and a resin thin film (corrosion prevention tape 150). This makes it possible to visually confirm the intrusion of moisture, which is a cause of corrosion, and to assist in determining the progression of steel corrosion. As described above, suitable materials that change with moisture or humidity for the moisture detection material 122 include materials that change color with moisture or humidity, such as microcapsules, silica gel, and cobalt chloride hexahydrate, and materials that change (change shape) with moisture or humidity, such as water-absorbing sheets and water-soluble sheets. Thus, it should be confirmed that the modification (change in properties) in this invention includes, as an example, discoloration (change in color) and deterioration (change in shape).

[0043] Furthermore, it is preferable that, as part of checking for deterioration over time (such as when replacing the resin thin film anti-corrosion tape 150 periodically or irregularly), the degree of corrosion protection of the structural cable can be easily confirmed by peeling off the resin thin film anti-corrosion tape 150 covering the structural cable and visually inspecting the deformation of the moisture detection material. In particular, as part of post-installation maintenance, the resin thin film anti-corrosion tape 150 often needs to be replaced periodically or irregularly. For this reason, without the need to make the anti-corrosion tape and filler transparent, moisture intrusion can be easily confirmed by visually inspecting the deformation of the moisture detection material (discoloration, alteration (change in shape), etc.) when replacing the anti-corrosion tape as part of this maintenance. <First variation> Incidentally, the visual inspection of discoloration or deterioration of such moisture-detecting materials may be influenced by the operator's subjectivity, and the inability to visually inspect the discoloration or deterioration of moisture-detecting materials outside of maintenance periods could be a problem. The following measures can be taken to address these problems.

[0044] The corrosion protection method according to this modified example is based on the premise of wrapping and covering structural cables together with a moisture detection material 122 using a resin thin film (corrosion protection tape 150) that is adhesive to each other and has waterproofing properties, and also includes a sensor that detects the deterioration of the moisture detection material 122 in addition to the moisture detection material 122. It is characterized by encasing and covering the structural cable. Furthermore, it is characterized by using a sensor to check the degree of corrosion protection of the structural cable as a way to confirm deterioration over time.

[0045] More specifically, for example, an optical fiber is installed as a sensor along the longitudinal direction of the structural cable so as to detect discoloration or deterioration (discoloration is preferred here) of the moisture detection material 122. That is, the structural cable is installed so as to wrap and cover it with corrosion-resistant tape 150 together with the moisture detection material 122 and the sensor. Then, the degree of corrosion protection (degree of moisture intrusion) of the structural cable is checked using the optical fiber as a check for deterioration over time. In this case, the color of the moisture detection material 122 is recorded as data, and by comparing this color data with the previous detection data, discoloration or deterioration (discoloration here) of the moisture detection material 122 can be accurately detected. This makes it possible to accurately and easily check for discoloration or deterioration (discoloration here) of the moisture detection material without being influenced by the subjective judgment of the worker based on visual inspection, etc., and even outside of maintenance. <Second variation> The problems in the first modification described above can also be addressed with the following second modification. While this modification will be explained in detail below with reference to Figures 4 to 6, the same reference numerals are used for structures identical to those in Figures 1 to 3, and their explanations will not be repeated here.

[0046] Figure 4 corresponds to Figures 2 and 3 and illustrates the state in which the structural cable is wrapped and covered with corrosion-resistant tape in the corrosion protection method for structural cables according to this modified example. In Figure 4, the moisture detection material 122 is not used (the moisture detection material 122 is not kneaded and mixed into the filler 120), and instead of the moisture detection material 122 described above, one or more conductors 230 are provided between the filler 120 and the corrosion-resistant tape 150 as sensors that detect moisture (in this specification, this means the same as detection) (including the case where there is one pair of conductors 230). In Figure 4, two conductors 230 are provided between the filler 120 and the corrosion-resistant tape 150. That is, in the structural cable according to this modified example, the cable strands 110 and the filler 120 are wrapped and covered together with the conductors 230, which are sensors that detect moisture, by the corrosion-resistant tape 150, which is a resin thin film that is adhesive to each other and has a waterproof function. Specifically, as shown in Figure 4, after filling the unevenness of the cable strands 110 with the filler 120, one or more conductors 230 (two in this case) are placed on the surface of the filler 120, and then corrosion-resistant tape 150 is wrapped around the upper layer.

[0047] The reason for providing two or more conductors 230 is to improve reliability. If there is only one conductor, and the corrosion-resistant tape 150 is damaged or otherwise exposed to moisture only downwards due to gravity acting on the structural cable, then the presence of a conductor only above would prevent detection of this moisture ingress. Furthermore, the sensor used to detect moisture is not particularly limited as long as it is an electrically-detectable sensor. Here, a time-domain reflectometry (TDR) method using conductors 230 is employed, but instead of such an electrical method (it does not have to be a conductor), an optical time-domain reflectometry (OTDR) method using optical fibers as the moisture-detecting sensor may also be employed (it does not have to be an optical fiber).

[0048] Furthermore, the conductor 230 is configured to be connectable to a measuring instrument 240 located outside the structural cable, either by peeling off the anti-corrosion tape 150, which is a thin resin film, or without peeling off the anti-corrosion tape 150. That is, when checking for moisture intrusion into the structural cable (which has the same meaning as moisture immersion in this specification), the end of the conductor 230, which is a moisture-sensing sensor, is electrically connected to the measuring instrument 240, and the presence or absence of moisture (whether or not moisture immersion has occurred) is confirmed by a change in an electrical signal (called characteristic impedance in TDR). It is advantageous to leave the end of the conductor 230 exposed in advance through the gap in the anti-corrosion tape 150, as this eliminates the need to peel off the anti-corrosion tape 150 when checking for moisture intrusion (as this could cause moisture to enter). However, if the end of the conductor 230 is wrapped in the anti-corrosion tape 150, the anti-corrosion tape 150 wrapped around the end of the conductor 230 is peeled off when checking for moisture intrusion. That's fine too.

[0049] Furthermore, in this modified example configured as shown in Figure 4, it was confirmed that it is actually possible to detect moisture intrusion, as shown in Figures 5 and 6.

[0050] Figure 5(A) is a cross-sectional view of the structural cable along its longitudinal direction, and Figure 5(B) is a cross-sectional view taken along the line 5B-5B shown in Figure 5(A).

[0051] Here, as shown in Figure 5, we artificially created a damaged area in the anti-corrosion tape 150 and immersed that area in water to observe the signal change. Note that the triangular marks in Figure 5(A) (both white and black) correspond to the triangular marks in Figure 6.

[0052] As shown in Figure 6, before immersing the damaged area in water, the waveform outside the structural cable (i.e., the part where the conductor 230 is exposed to the atmosphere) had a mountain-shaped peak. However, after immersing the damaged conductor 230 and the conductor 230 itself outside the structural cable for comparison in water, in addition to the two mountain-shaped peaks, a waveform with a trough-shaped peak similar to the waveform of the conductor 230 itself outside the water-immersed structural cable was observed at the damaged area of ​​the water-immersed corrosion-resistant tape 150 using the measuring instrument 240. This allows for the detection of moisture ingress into the structural cable due to damage to the corrosion-resistant tape 150 inside the structural cable, similar to the detection of moisture in the conductor 230 itself outside the structural cable. This eliminates the influence of subjective observations by workers, and even outside of maintenance, the moisture-detecting sensor (in this case, the conductor 230 because the TDR method was used) can be electrically connected to the measuring instrument 240 to check the waveform (change in characteristic impedance), thereby accurately and easily confirming moisture intrusion into the structural cable due to damage to the corrosion-resistant tape 150.

[0053] As described above, the corrosion prevention method according to this embodiment and the structural cables etc. to which this corrosion prevention method is applied provide a corrosion prevention method for exposed structural cables etc. used in suspended structures such as suspension bridges and cable-stayed bridges, which, when such structural cables etc. corrode (especially when the corrosion is minor and replacement is difficult), does not replace the structural cables etc. but takes measures to extend the life of the structural cables etc. After the application of the corrosion prevention method, it is possible to easily visually check the condition of deterioration, etc. of the components of the structural cables etc. periodically or irregularly, and it is possible to provide structural cables etc. to which this corrosion prevention method is applied.

[0054] It should be noted that the embodiments disclosed herein are illustrative and not restrictive in all respects. The scope of the present invention is indicated by the claims rather than by the foregoing description, and all modifications within the meaning and scope equivalent to the claims are intended to be included. [Industrial applicability]

[0055] The present invention relates to corrosion prevention technology for exposed structural cables used in suspension structures such as suspension bridges and cable-stayed bridges, and is particularly preferable to a corrosion prevention method that extends the lifespan of such structural cables rather than replacing them when they corrode (especially when the corrosion is minor and replacement is difficult). [Explanation of Symbols]

[0056] 100, 102 Structural cables under construction using corrosion protection method 110 Cable strands 120 Filler 122 Moisture detection material 130 Water-conducting member 230 Wire (as a sensor for detecting moisture) 240 Measuring Instruments

Claims

1. A corrosion protection method for an existing object exposed outdoors that requires corrosion protection measures, or a newly constructed object exposed outdoors that requires corrosion protection measures, wherein the object has a shape in which one longitudinal direction is longer than the other directions. The aforementioned object is covered and encased together with a moisture detection material by a peelable resin thin film that is adhesive to each other and has a waterproof function. A corrosion protection method for objects requiring corrosion protection measures, characterized by peeling off a thin resin film covering the object as confirmation of deterioration over time, and confirming the degree of corrosion protection of the object.

2. A corrosion protection method for existing structural cables exposed outdoors or newly installed structural cables exposed outdoors, used in suspension structures including suspension bridges and cable-stayed bridges, The structural cable is wrapped and covered together with a moisture detection material by a peelable resin thin film that is adhesive to each other and has waterproof properties. A corrosion protection method characterized by peeling off the resin thin film covering the structural cable as a way to check for deterioration over time, and confirming the degree of corrosion protection of the structural cable.

3. The corrosion protection method according to claim 1 or 2, characterized in that the moisture detection material is provided together with a filler that is filled between the object or the structural cable and the resin thin film.

4. The corrosion protection method according to claim 1 or claim 2, characterized in that the moisture detection material is provided in a portion of the object or structural cable that is covered by the resin thin film along its longitudinal direction.

5. The moisture detection material is provided in a portion of the object or structural cable that is covered by the resin thin film along its longitudinal direction. The corrosion protection method according to claim 1 or claim 2, characterized in that a water-conducting member is further provided in a portion of the object or structural cable that is covered by the resin thin film along its longitudinal direction, so as to be in contact with the moisture detection material.

6. The corrosion protection method according to claim 1 or claim 2, characterized in that the resin thin film is in the form of a tape, and the tape-shaped resin thin film is wrapped spirally around the object or the structural cable by overlapping at least a portion of the tape width, thereby enclosing and covering the object or the structural cable with the tape-shaped resin thin film.

7. A corrosion protection method for existing structural cables exposed outdoors or newly installed structural cables exposed outdoors, used in suspension structures including suspension bridges and cable-stayed bridges, The structural cable is enclosed and covered with a resin thin film that is adhesive to itself and has waterproof properties, together with a moisture detection material and a sensor that detects the deformation of the moisture detection material. A corrosion protection method characterized by confirming the degree of corrosion protection of the structural cable using the aforementioned sensor as a confirmation of deterioration over time.

8. A corrosion protection method for existing structural cables exposed outdoors or newly installed structural cables exposed outdoors, used in suspension structures including suspension bridges and cable-stayed bridges, The structural cable is encased and covered with a resin thin film that is adhesive to itself and has waterproof properties, along with a conductor that acts as a sensor for electrically detecting moisture. The sensor can be connected to a measuring instrument by peeling off the resin thin film, or without peeling off the resin thin film. A corrosion protection method characterized by confirming the degree of corrosion protection of the structural cable using the aforementioned sensor and measuring instrument, and by a time-domain reflectance measurement method using the aforementioned conductor, as a confirmation of deterioration over time.

9. Outdoor exposed structural cables used in suspension structures, including suspension bridges and cable-stayed bridges, which are subjected to the corrosion protection method described in any one of claims 2, 7, or 8.

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