Crack Detection Method

Abstract

To suppress a detection failure of a crack of a structure in the structure for detecting the crack of the structure with light emission due to radiation of light by breaking a shielding layer.SOLUTION: A crack detection method includes: an irradiation step of emitting light to a reinforcement structure which includes: a fiber sheet that is arranged on a surface of a structure and includes fiber that emits phosphorescence with radiation of the light; an adhesive layer that bonds the fiber sheet to the surface; and a shielding layer that shields the light radiated to the fiber sheet, and in which the adhesive layer and the shielding layer break before the fiber sheet when a punching load test is performed to the fiber sheet, the adhesive layer and the shielding layer; and a detection step of detecting a crack generated in the structure by detecting the phosphorescence emitted from the fiber sheet with radiation of the light in the radiation step, a detection range of the phosphorescence including a range where the radiation of the light ends in the radiation step.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a crack detection method. [Background technology]

[0002] Patent Document 1 discloses a method for inspecting deterioration of a structure, which comprises forming a highly elastic first coating layer on a base constituting the structure, which contains a fluorescent dye that emits light when exposed to excitation light and which stretches without breaking even when a crack occurs in the base, and forming a low-elastic second coating layer on this first coating layer, which contains a shielding material that blocks the transmission of excitation light and which generates cracks in response to cracks that occur in the base when they occur, and then irradiating the structure with excitation light to detect cracks that occur in the base after the coating layer formation by passing the excitation light through the cracks that occur in the second coating layer and causing the first coating layer to emit light.

[0003] Patent Document 2 discloses a stress-luminescence measuring device including: a storage unit that stores a conversion formula for converting pixel values ​​into luminance values ​​in association with the characteristics of an imaging means used for imaging and the type of stress-luminescent material; a light source that irradiates excitation light onto the stress-luminescent material applied to or mixed into the measurement object; an imaging unit that images the luminescence of the stress-luminescent material applied to or mixed into the measurement object; a pixel extraction unit that extracts pixel values ​​from image data obtained by imaging by the imaging unit; an input unit that allows input of the characteristics of the imaging unit and the type of stress-luminescent material applied to or mixed into the measurement object; a conversion formula readout unit that reads out from the storage unit the conversion formula corresponding to the characteristics of the imaging unit and the type of stress-luminescent material applied to or mixed into the measurement object, which have been input to the input unit; and a conversion unit that converts the pixel values ​​extracted by the pixel extraction unit into luminance values ​​using the conversion formula readout by the conversion formula readout unit. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent No. 5562310 [Patent Document 2] Patent Publication No. 2021-32740 Summary of the Invention [Problem to be solved by the invention]

[0005] A crack detection method having, for example, an irradiation step and a detection step can be applied to a structure that includes a light-emitting layer that is placed on the surface of a structure and emits light when irradiated with light, and a shielding layer that is placed on the surface of the light-emitting layer and blocks the light irradiated onto the light-emitting layer, and in which the elongation of the shielding layer is smaller than that of the light-emitting layer so that only the shielding layer breaks when a crack occurs in the structure.

[0006] In the above structure, when a crack occurs in the structure, the light-emitting layer stretches with the crack, and only the shielding layer breaks, exposing the light-emitting layer from the broken portion.

[0007] In the crack detection method, for example, in the irradiation step, light is irradiated onto the structure. As a result, the light passes through the broken portion of the shielding layer, causing the light-emitting layer to emit light. Furthermore, in the crack detection method, for example, in the detection step, the light emitted from the light-emitting layer is detected to detect a crack that has occurred in the structure.

[0008] Here, if the light emitted from the light-emitting layer is fluorescent, the light-emitting layer emits light only during the period when light is irradiated, and therefore if no light emission is detected during that period, cracks cannot be detected.

[0009] Furthermore, when the light-emitting layer emits fluorescence, the light-emitting layer emits light only while it is being irradiated with light, and therefore the light emission from the light-emitting layer must be detected in the area where the light emitted from the light-emitting layer overlaps with the light reflected from the surface of the structure, making it difficult to detect.In particular, when detecting the light emitted from the light-emitting layer visually from a distance from the detection point, it is difficult to detect the light emitted from the light-emitting layer, which may result in failure to detect cracks in the structure.

[0010] The present invention aims to suppress failure to detect cracks in a structure in a crack detection method that detects cracks in a structure by emitting light due to irradiation with light. [Means for solving the problem]

[0011] A first aspect of the crack detection method includes a reinforcement structure that is arranged on the surface of a structure and includes a fiber sheet containing fibers that emit phosphorescence when irradiated with light, an adhesive layer that adheres the fiber sheet to the surface, and a shielding layer that blocks light irradiated to the fiber sheet, and when a punching load test is performed on the fiber sheet, the adhesive layer, and the shielding layer, the adhesive layer and the shielding layer break before the fiber sheet, and the method includes an irradiation step of irradiating the reinforcement structure with light, and a detection step of detecting a crack that has occurred in the structure by detecting the phosphorescence emitted from the fiber sheet by the light irradiation in the irradiation step, wherein the detection range of the phosphorescence includes the range where the light irradiation in the irradiation step is completed.

[0012] In the reinforced structure according to the first aspect of the crack detection method, when a punching load test is performed on the fiber sheet, adhesive layer, and shielding layer, the adhesive layer and shielding layer break before the fiber sheet. In the punching load test, a tensile force in a direction along the surface of the structure and a shear force in a direction normal to the surface act on the fiber sheet, adhesive layer, and shielding layer. Therefore, in the reinforced structure, when a tensile force in a direction along the surface of the structure or a shear force in a direction normal to the surface act on the fiber sheet, adhesive layer, and shielding layer, the adhesive layer and shielding layer break before the fiber sheet. Therefore, when a crack occurs in the structure and the surface of the structure expands in a direction along the surface, or when a crack occurs in the structure and the surface of the structure shifts in a shear direction, the adhesive layer and shielding layer can break, exposing the fiber sheet.

[0013] In the crack detection method of the first aspect, the irradiation step irradiates the reinforcement structure with light, and the detection step detects cracks that have occurred in the structure by detecting phosphorescence emitted from the fiber sheet due to the light irradiation in the irradiation step.

[0014] In the detection step, the phosphorescence detection range includes the end range where the light irradiation in the irradiation step ends. In the end range, no light is reflected from the surface of the structure due to the light irradiation, so the reflected light from the surface of the structure is less likely to enter the detection range, making it easier to detect the phosphorescence from the fiber sheet. As a result, failure to detect cracks in the structure can be reduced.

[0015] A second aspect of the crack detection method is a reinforcement structure comprising a fiber sheet placed on the surface of a structure and containing fibers that emit phosphorescence when irradiated with light, an adhesive layer that adheres the fiber sheet to the surface, and a shielding layer that blocks light irradiated to the fiber sheet, wherein the reinforcement structure is such that when a crack occurs in the structure, the adhesive layer and the shielding layer break, exposing the fiber sheet from the broken portion, and the method includes an irradiation step of irradiating the light onto the reinforcement structure; and a detection step of detecting a crack that has occurred in the structure by detecting the phosphorescence emitted from the fiber sheet as a result of the light irradiation in the irradiation step, wherein the detection range of the phosphorescence includes the range where the light irradiation in the irradiation step is completed.

[0016] In the reinforced structure according to the second aspect of the crack detection method, when a crack occurs in the structure, the adhesive layer and the shielding layer are broken, and the fiber sheet is exposed from the broken portion.

[0017] In the second aspect of the crack detection method, the irradiation step irradiates the reinforcement structure with light, and the detection step detects cracks that have occurred in the structure by detecting phosphorescence emitted from the fiber sheet due to the light irradiation in the irradiation step.

[0018] In the detection step, the phosphorescence detection range includes the end range where the light irradiation in the irradiation step ends. In the end range, no light is reflected from the surface of the structure due to the light irradiation, so the reflected light from the surface of the structure is less likely to enter the detection range, making it easier to detect the phosphorescence from the fiber sheet. As a result, failure to detect cracks in the structure can be reduced.

[0019] In the crack detection method of the third aspect, the irradiating step irradiates light onto a reinforcement structure in which the shielding layer also serves as the adhesive layer.

[0020] In the reinforcement structure where light is irradiated in the irradiation step, the shielding layer also serves as the adhesive layer, which effectively shields the fiber sheet, thereby reducing false detections caused by inadvertent exposure of the fiber sheet in the detection step.

[0021] In a fourth aspect of the crack detection method, the irradiation process irradiates light from an irradiation device onto the reinforcement structure, and the detection process detects cracks that have occurred in the structure by detecting the phosphorescence with a detection device, and the detection range of the detection device is shifted from the irradiation range of the irradiation device.

[0022] In this way, in the detection process, the detection range of the detection device is offset from the irradiation range of the irradiation device, so that reflected light from the surface of the structure that occurs within the irradiation range of the irradiation device is less likely to enter the detection range compared to when the detection range of the detection device coincides with the irradiation range of the irradiation device. This makes it easier to detect phosphorescence from the fiber sheet, and reduces the risk of failing to detect cracks in the structure.

[0023] In a crack detection method of a fifth aspect, in the detection step, the detection range of the detection device is separated from the irradiation range of the irradiation device.

[0024] In this way, in the detection process, since the detection range of the detection device is separated from the irradiation range of the irradiation device, reflected light from the surface of the structure generated in the irradiation range of the irradiation device is less likely to enter the detection range compared to when the detection range of the detection device is adjacent to the irradiation range of the irradiation device. This makes it easier to detect phosphorescence from the fiber sheet, and reduces failure to detect cracks in the structure.

[0025] In a crack detection method of a sixth aspect, the detection step is performed such that the detection range of the detection device is spaced 0.1 m or more from the irradiation range of the irradiation device.

[0026] In this way, in the detection process, because the detection range of the detection device is at least 0.1 m away from the irradiation range of the irradiation device, reflected light from the surface of the structure within the irradiation range of the irradiation device is less likely to enter the detection range compared to when the detection range of the detection device is less than 0.1 m away from the irradiation range of the irradiation device. This makes it easier to detect phosphorescence from the fiber sheet, and reduces the risk of failing to detect cracks in the structure.

[0027] In the crack detection method of the seventh aspect, the detection device used in the detection step is a digital camera with a minimum subject illuminance of 1 lux or less.

[0028] The detection device used in the detection process is a digital camera with a minimum subject illumination of 1 lux or less, so the detection accuracy of phosphorescence is high and failure to detect cracks in the structure can be reduced.

[0029] In the crack detection method of the eighth aspect, the afterglow luminance of the fiber that emits phosphorescence when irradiated with light in the irradiating step is 10 mcd / m even 10 minutes after the light is turned off after 30 minutes of irradiation with 1000 lux using a D65 light source. 2 Exceeds.

[0030] The afterglow brightness of the phosphorescent fiber, which is irradiated with light during the irradiation process, is 10 mcd / m even after 10 minutes of turning off the light after 30 minutes of irradiation with a D65 light source at 1000 luxL. 2 , the afterglow luminance exceeds 10mcd / m after 30 minutes of irradiation at 1000 lux using a D65 light source and 10 minutes after the light is turned off. 2 Compared to the case where the value is less than or equal to the above, the phosphorescence detection accuracy is higher and failure to detect cracks in the structure can be reduced.

[0031] In the crack detection method of the ninth aspect, the irradiating step irradiates parallel light.

[0032] In this way, because parallel light is irradiated in the irradiation step, reflected light from the surface of the structure within the irradiation range of the irradiation device is less likely to enter the detection range compared to when diffused light is irradiated in the irradiation step, making it easier to detect phosphorescence from the fiber sheet and reducing failures in detecting cracks in the structure.

[0033] In the crack detection method of the tenth aspect, the irradiating step irradiates light including ultraviolet light.

[0034] In this way, in the irradiation step, light containing ultraviolet light may be irradiated. [Effects of the Invention]

[0035] The present invention employs the above method, and therefore has the excellent effect of being able to suppress failure to detect cracks in a structure in a crack detection method that detects cracks in a structure by light emission caused by irradiation with light. [Brief explanation of the drawings]

[0036] [Figure 1] 1 is a cross-sectional view showing a reinforcement structure related to a crack detection method of the present embodiment. [Figure 2] 1 is a cross-sectional view showing a state in which a shielding layer is broken in a reinforcement structure according to the crack detection method of this embodiment. [Figure 3] 1 is a schematic diagram for explaining a crack detection method according to an embodiment of the present invention; [Figure 4] 3 is a schematic diagram showing the positional relationship between a detection range and an irradiation range in the crack detection method of the present embodiment. FIG. [Figure 5] 10 is a schematic diagram showing another example of the positional relationship between the detection range and the irradiation range in the crack detection method of the present embodiment. FIG. [Figure 6] 10 is a schematic diagram showing another example of the positional relationship between the detection range and the irradiation range in the crack detection method of the present embodiment. FIG. [Figure 7] FIG. 10 is a cross-sectional view showing a reinforcing structure according to a modified example. [Figure 8] FIG. 10 is a cross-sectional view showing a reinforcing structure according to a modified example. DETAILED DESCRIPTION OF THE INVENTION

[0037] An example of an embodiment of the present invention will be described below with reference to the drawings.

[0038] First Embodiment (Reinforcement structure 10 relating to the crack detection method of this embodiment) First, a reinforcement structure 10 relating to the crack detection method of this embodiment will be described. Fig. 1 is a cross-sectional view showing the reinforcement structure 10. Fig. 2 is a cross-sectional view showing the reinforcement structure 10 in a state where a shielding layer 50, which will be described later, is broken.

[0039] The reinforcement structure 10 shown in Fig. 1 is a structure that reinforces a structure 90 and prevents the structure 90 from spalling or falling off. An example of the structure 90 is a concrete structure. An example of the concrete structure is a lining wall of a railway or road tunnel.

[0040] The concrete structure is not limited to the lining walls of railway or road tunnels, but may be, for example, a building, a bridge, a bridge pier, etc., as long as it is a structure to be reinforced. Furthermore, the structure is not limited to concrete, but may be, for example, a structure made of mortar, ceramics, metal, glass, etc., as long as it is a structure to be reinforced.

[0041] 1, the reinforcement structure 10 specifically includes a primer 20, an unevenness correction material 30, a fiber sheet 40, and a shielding layer 50. In the reinforcement structure 10, the primer 20, the unevenness correction material 30, and the shielding layer 50 are laminated in this order, and the fiber sheet 40 is disposed inside the shielding layer 50.

[0042] The primer 20 is applied to the surface of the structure 90. The primer 20 has the function of improving the bonding (adhesion) between the structure 90 and a layer formed on the structure 90. As an example, a resin such as an epoxy resin is used for the primer 20. Note that the primer 20 is not limited to an epoxy resin, and may be, for example, a resin other than an epoxy resin, such as a thermosetting resin, and various other materials can be used.

[0043] The unevenness correction material 30 is applied to the surface of the primer 20. The unevenness correction material 30 has the function of smoothing out the irregularities on the surface of the structure 90. As an example, a resin such as an epoxy resin is used for the unevenness correction material 30. Note that the unevenness correction material 30 may be a resin other than epoxy resin, such as a thermosetting resin, and various other materials may be used.

[0044] The fiber sheet 40 is placed on the surface of the unevenness correction material 30. That is, the fiber sheet 40 is placed on the surface of the structure 90 to which the primer 20 and the unevenness correction material 30 have been applied. Note that the entire structure 90 to which the primer 20 and the unevenness correction material 30 have been applied may be considered as the "structure" in the claims.

[0045] The fiber sheet 40 has the function of reinforcing the surface of the structure 90. The fiber sheet 40 contains fibers (hereinafter referred to as luminous fibers) that emit light when irradiated with light (for example, excitation light including ultraviolet rays).

[0046] The luminescent fiber is made of a thermoplastic resin containing a luminescent material that emits light when irradiated with light. Examples of the thermoplastic resin used for the luminescent fiber include polyester, nylon, polyolefins such as polypropylene, vinylon, and the like. The resin used for the luminescent fiber is not limited to the above, and other resins may also be used. Furthermore, the luminescent fiber may be a composite fiber with carbon fiber or glass fiber.

[0047] As an example of the luminous material used in the luminous fiber, a phosphorescent material is used, which stores irradiated light and continues to emit light even after the light irradiation stops. That is, a material that emits phosphorescence is used as the luminous material. An example of the phosphorescent material is a phosphorescent pigment using strontium aluminate.

[0048] The luminescent fiber is formed into a thread-like luminescent fiber by spinning a thermoplastic resin containing a luminescent material. Examples of the spinning method include melt spinning, dry spinning, and wet spinning.

[0049] In melt spinning, the raw material is melted by heat, extruded through a spinneret to form fibers, and then cooled and solidified. In dry spinning, the raw material is dissolved in a solvent that vaporizes by heat, and extruded through a spinneret in a hot atmosphere to evaporate the solvent and form fibers. In wet spinning, the raw material is dissolved in a solvent, and extruded through a spinneret in a solution called a coagulation bath to cause a chemical reaction, and then the solvent is removed to form fibers.

[0050] The luminescent fiber may be a bundle or twist of spun luminescent fibers. Furthermore, the luminescent fiber may be a luminescent fiber obtained by subjecting a spun fiber (fiber not containing a luminescent material) to a surface treatment with a chemical containing a luminescent material.

[0051] Although a nonwoven fabric using short fibers can be used for the fiber sheet 40, a continuous fiber sheet using continuous fibers is preferable from the viewpoint of strength, detection performance, etc. Specifically, the fiber sheet 40 may be a UD (Unidirectional) material (i.e., a unidirectional material in which fibers are aligned in one direction) made of luminescent fiber, a woven fabric, a knitted fabric, or the like. Examples of woven fabrics include those woven by plain weave, twill weave, satin weave, etc. Examples of knitted fabrics include weft knitted fabrics such as plain knit, rib knit, and purl knit, and warp knitted fabrics (tricot, etc.) such as denbi knit, cord knit, and atlas knit.

[0052] The fiber sheet 40 need not be entirely made of luminescent fibers, as long as it contains luminescent fibers. In other words, the fiber sheet 40 may contain non-luminescent fibers that do not emit light. For example, a woven fabric can be used in which one of the warp and weft threads is luminescent fiber and the other is non-luminescent fiber. The fiber sheet 40 may contain, for example, 5% or more by volume of luminescent fibers.

[0053] Furthermore, multiple fiber sheets 40 may be stacked as the fiber sheet 40. When multiple UD materials are stacked, they are used, for example, stacked so that the fiber directions of the sheets are perpendicular to each other. This allows the fibers to be aligned in the perpendicular direction, increasing the tensile strength in the perpendicular direction and improving the reinforcing effect of the fiber sheet 40. Also, a UD material made of non-luminescent fibers and a UD material containing luminescent fibers can be stacked. Note that even when woven fabrics, knitted fabrics, etc. are used as the fiber sheet 40, multiple fiber sheets 40 may be stacked.

[0054] An example of the light that causes the fiber sheet 40 to emit light is excitation light such as ultraviolet light. Note that the light is not limited to ultraviolet light, and may be, for example, blue light (blue visible light), and various other types of light can be used.

[0055] The shielding layer 50 has the function of blocking light irradiated onto the fiber sheet 40. The shielding layer 50 contains a shielding material that blocks light.

[0056] Specifically, the shielding layer 50 is formed by applying a resin containing a shielding material (hereinafter referred to as a shielding resin) to the surface of the unevenness correcting material 30 and then curing the resin. The shielding layer 50 also has the function of adhering the fiber sheet 40 to the surface of the unevenness correcting material 30.

[0057] As an example, a resin such as an epoxy resin is used for the shielding layer 50. Note that the material for the shielding layer 50 is not limited to epoxy resin, and may be a thermosetting resin other than epoxy resin, such as an acrylic resin, and various materials may be used, but a solvent-free room-temperature curing epoxy resin is preferably used.

[0058] The shielding material may be any material that can physically or chemically shield the light (for example, ultraviolet light) that causes the fiber sheet 40 to emit light, and inorganic fillers or absorbents are used.

[0059] The inorganic filler as a shielding material is not particularly limited in material or shape as long as it can physically block the light that causes the fiber sheet 40 to emit light, but carbon black or titanium oxide is preferably used.

[0060] The absorbent used as the shielding material is capable of chemically absorbing the light that causes the fiber sheet 40 to emit light. When the light that causes the fiber sheet 40 to emit light is ultraviolet light, an ultraviolet absorbing material that absorbs ultraviolet light is used as the shielding material. Note that the ultraviolet absorbing material may also absorb light of wavelengths other than ultraviolet light. Furthermore, the shielding material may be a combination of the inorganic filler and the absorbent.

[0061] The shielding layer 50 is an example of a shielding layer in the claims, and is also an example of an adhesive layer in the claims. That is, the shielding layer 50 also serves as an adhesive layer.

[0062] Here, in the reinforcement structure 10, when a punching load test is performed on the fiber sheet 40 and the shielding layer 50, the shielding layer 50 breaks before the fiber sheet 40. In the punching load test, a tensile force in a direction along the surface of the structure 90 (hereinafter referred to as the planar direction) and a shear force in a direction normal to the surface act on the fiber sheet 40 and the shielding layer 50. Therefore, in the reinforcement structure 10, when a tensile force in the planar direction or a shear force in the direction normal to the surface of the structure 90 acts on the fiber sheet 40 and the shielding layer 50, the shielding layer 50 breaks before the fiber sheet 40.

[0063] Therefore, when a crack occurs in the structure 90 and the surface of the structure 90 expands in the planar direction, or when a crack occurs in the structure 90 and a displacement in the shear direction occurs on the surface of the structure 90, the shielding layer 50 breaks while the fiber sheet 40 remains intact, as shown in Fig. 2. Therefore, the reinforcement structure 10 is configured such that when a crack occurs in the structure 90, the shielding layer 50 breaks and the fiber sheet 40 is exposed from the broken portion.

[0064] For example, the "Punching Load Test" described in Appendix 17-2, Test Methods for Concrete Surface Coating Methods, of the Standard Specifications for Civil Engineering Works (edited by East Japan Railway Company) and the Japan Railway Facilities Association (September 2016) is used as the punching load test.

[0065] Furthermore, in the reinforcement structure 10, when the fiber sheet 40 and the shielding layer 50 are compared in terms of tensile elongation (elongation) in the plane direction, the fiber sheet 40 has a greater tensile elongation (elongation) than the shielding layer 50. Specifically, the elongation of the fiber sheet 40 is, for example, 20-something percent, and the elongation of the shielding layer 50 is, for example, 3% or less, preferably 0.5% to 3%, and more preferably 0.5% to 2.5% (all elongations at 23°C). Note that this elongation is the breaking elongation (i.e., the value obtained by dividing the elongation between the gauge points of the tensile test piece after breaking by the gauge length and expressing it as a percentage).

[0066] In addition, the reinforcing structure 10 may have a protective layer formed on the surface of the shielding layer 50 to protect the shielding layer 50. The protective layer is formed to protect the shielding layer 50 from deterioration due to ultraviolet rays, exhaust gas, etc. As an example, the protective layer is made of a resin material such as an acrylic urethane resin, a water-based acrylic resin, or a fluororesin, or polymer mortar, which has the same tensile elongation (elongation) as the shielding layer 50.

[0067] The reinforcing structure 10 may not have the primer 20. Therefore, the structure may be configured so that the unevenness correcting material 30 is applied directly to the surface of the structure 90. The reinforcing structure 10 may also have a structure that does not have the primer 20 or the unevenness correcting material 30. Therefore, the shielding layer 50 may be formed directly on the surface of the structure 90. The reinforcing structure 10 may also have a structure that has the primer 20 but does not have the unevenness correcting material 30. Therefore, the shielding layer 50 may be formed directly on the surface of the primer 20.

[0068] (Construction method of reinforcement structure 10) Next, a description will be given of a construction method for constructing the above-mentioned reinforcement structure 10 on the structure 90. Note that, since the reinforcement structure 10 is formed by this construction method, this construction method can also be said to be a manufacturing method for manufacturing the reinforcement structure 10.

[0069] In this construction method, first, a surface preparation is carried out to remove protrusions on the surface of the structure 90 and deposits (for example, deteriorated layers) attached to the surface, and then the primer 20 is applied.

[0070] Next, the unevenness correcting material 30 is applied to the surface to which the primer 20 has been applied, to smooth out the irregularities on the surface.

[0071] Next, a fiber sheet 40 is adhered to the surface coated with the unevenness correction material 30 using a shielding resin. Specifically, a base coat of shielding resin is applied, and the fiber sheet 40 is attached to the base coat of shielding resin and degassed. Then, a top coat of shielding resin is applied and degassed. The shielding resin is hardened, for example, by exposure to ambient temperature or by heating. This forms a shielding layer 50 with the fiber sheet 40 disposed therein.

[0072] When a protective layer is formed on the surface of the shielding layer 50 , the resin that forms the protective layer is applied to the surface of the shielding layer 50 .

[0073] (Crack detection method applied to reinforced structure 10) Next, a description will be given of a crack detection method for detecting a crack that has occurred in the structure 90 in the reinforcement structure 10. In this embodiment, as an example, a crack detection method will be described for the case where the structure 90 is a tunnel structure.

[0074] This crack detection method includes an irradiation step and a detection step. Here, in this crack detection method, as shown in FIG. 3, a vehicle 60 for crack detection is used. This vehicle 60 travels in the extension direction of the tunnel (the direction of arrow X). The vehicle 60 is equipped with an irradiation device 62 and a detection device 64. Specifically, the irradiation device 62 and the detection device 64 are provided, for example, on a roof 63 of the vehicle 60 at positions offset in the width direction of the vehicle 60 (see FIG. 4). Furthermore, as shown in FIG. 3, the irradiation device 62 is disposed on the front side of the vehicle 60 with respect to the detection device 64.

[0075] The irradiation device 62 irradiates light (for example, excitation light including ultraviolet rays) onto a covering wall 92 (i.e., an inner wall) of the structure 90. Specifically, the irradiation device 62 irradiates light upward in front of the vehicle 60.

[0076] The detection device 64 may be, for example, a digital camera with a minimum subject illumination of 1 lux or less. The digital camera may be a CCD or CMOS image sensor as long as it is capable of recording phosphorescence. However, since the shutter speed for still image capture is slow depending on the shooting environment, it is preferable to use a digital video camera capable of capturing continuous images from the perspective of inspection efficiency. If a digital still camera is used, it is preferable to use one with an ISO sensitivity of 25600 or higher. The detection range of the detection device 64 is the upper side facing forward of the vehicle 60. Light containing phosphorescence emitted from the fiber sheet 40 is incident on the detection device 64, and information about the light (such as the amount of light and position) is recorded.

[0077] In the present crack detection method, in the irradiation step, the reinforcement structure 10 is irradiated with light from the irradiation device 62. Specifically, in the irradiation step, the shielding layer 50 of the reinforcement structure 10 is irradiated with parallel light from the irradiation device 62.

[0078] Here, in the reinforcement structure 10, as described above, when a punching load test is performed on the fiber sheet 40 and the shielding layer 50, the shielding layer 50 breaks before the fiber sheet 40. That is, in the reinforcement structure 10, when a tensile force in the planar direction or a shear force in the normal direction to the surface of the structure 90 acts on the fiber sheet 40 and the shielding layer 50, the shielding layer 50 breaks before the fiber sheet 40.

[0079] Therefore, when a crack occurs in the structure 90 and the surface of the structure 90 expands in the planar direction, or when a crack occurs in the structure 90 and a shear shift occurs on the surface of the structure 90, the shielding layer 50 can be broken and the fiber sheet 40 can be exposed, as shown in Figure 2, while the fiber sheet 40 is not broken.

[0080] That is, in the reinforcement structure 10, when a crack occurs in the structure 90, the shielding layer 50 breaks and the fiber sheet 40 is exposed from the broken portion. As a result, when light is irradiated toward the shielding layer 50, the exposed fiber sheet 40 emits phosphorescence. In each figure including FIG. 2, the light irradiated toward the shielding layer 50 is indicated by the symbol L1, and the phosphorescence emitted by the fiber sheet 40 is indicated by the symbol L2.

[0081] Here, the afterglow brightness of the phosphorescent fiber irradiated with light in the irradiation process is 10 mcd / m even after 10 minutes of turning off the light after 30 minutes of irradiation with 1000 lux using a D65 light source. 2 Exceeds.

[0082] Next, in the detection step, the detection device 64 detects the phosphorescence emitted from the fiber sheet 40 due to the light irradiation in the irradiation step, thereby detecting cracks that have occurred in the structure 90. As shown in FIG. 4 , the phosphorescence detection range 64A of the detection device 64 includes the range where the light irradiation in the irradiation step ended (specifically, the range opposite the traveling direction (arrow X direction) relative to the irradiation range 62A). Specifically, the detection range 64A of the detection device 64 is shifted toward the opposite side of the traveling direction (arrow X direction) relative to the irradiation range 62A of the irradiation device 62. More specifically, the detection range 64A of the detection device 64 is spaced away from the irradiation range 62A of the irradiation device 62 in the opposite side of the traveling direction (arrow X direction). Furthermore, the detection range 64A of the detection device 64 is spaced away from the irradiation range 62A of the irradiation device 62 in the opposite side of the traveling direction (arrow X direction) by 0.1 m or more. Furthermore, it is desirable that the distance between the detection range 64A and the irradiation range 62A is 0.1 m or more, and that the distance is within a range that allows detection within 60 seconds after irradiation with the excitation light. In Figure 4, the phosphorescence in the fiber sheet 40 is indicated by the symbol 40A.

[0083] The occurrence of a crack is a concept that includes both a case where a crack occurs from a state where no cracks have occurred and a case where an opening of an already occurring crack propagates. Therefore, a crack that has occurred in the structure 90 is a concept that includes a crack that has occurred in the structure 90 in a state where no cracks have occurred and a crack that has occurred as a result of the opening of an already occurring crack propagating, and can also be considered as "crack damage." Furthermore, the mode of the crack includes not only a case where an opening occurs in the surface direction, but also a case where a step occurs in the shear direction.

[0084] As described above, in the detection step of this crack detection method, cracks occurring in the structure 90 are detected by detecting phosphorescence emitted from the fiber sheet 40. Note that this crack detection method may use a method in which the vehicle 60 travels in the traveling direction while the illumination device 62 (illumination range 62A) and the detection device 64 (detection range 64A) scan the structure 90 in the circumferential direction. Alternatively, a method may be used in which the positions of the illumination range 62A and the detection range 64A are changed in the circumferential direction of the structure 90 each time the vehicle 60 travels in the tunnel extension direction, and the vehicle 60 travels back and forth multiple times.

[0085] (Effects of this embodiment) Next, the effects of this embodiment will be described.

[0086] The crack detection method according to this embodiment detects cracks occurring in the structure 90 by detecting phosphorescence emitted from the fiber sheet 40 due to the irradiation of light in the irradiation step.

[0087] Here, when detecting cracks that have occurred in the structure 90 by detecting the fluorescence emitted from the fiber sheet 40 (hereinafter referred to as comparison example A), the fiber sheet 40 emits light only during the period when light is irradiated, and therefore if the emission cannot be detected during that period, the crack cannot be detected.

[0088] Furthermore, in Comparative Example A, the fiber sheet 40 emits light only while it is being irradiated with light, and therefore the fiber sheet 40 must emit light in the area where the light emitted by the fiber sheet 40 overlaps with the light reflected from the surface of the structure 90, making it difficult to detect the light emitted by the fiber sheet 40. In particular, when visually detecting from a distance from the detection location, it is difficult to detect the light emitted by the fiber sheet 40, which may result in failure to detect cracks in the structure 90.

[0089] In contrast, in the crack detection method according to the present embodiment, cracks occurring in the structure 90 are detected by detecting phosphorescence emitted from the fiber sheet 40 during the irradiation step, so the fiber sheet 40 continues to emit light even after the light irradiation has ended. Therefore, even if the light emission cannot be detected during the light irradiation period, the crack can be detected by detecting the light emission after the light irradiation has ended.

[0090] Furthermore, in the crack detection method of this embodiment, the fiber sheet 40 continues to emit light even after the light irradiation has ended, so there is no need to detect the emission of light from the fiber sheet 40 in the area where the emission of light from the fiber sheet 40 overlaps with the reflected light from the surface of the structure 90.

[0091] Therefore, as in the crack detection method according to this embodiment, the detection range 64A of phosphorescence by the detection device 64 may include the range where the light irradiation in the irradiation step is completed (see FIG. 4). In the completion range, no light is reflected from the surface of the structure 90 due to the light irradiation, so the reflected light from the surface of the structure 90 is less likely to be incident on the detection range 64A, making it easier to detect the phosphorescence from the fiber sheet 40. As a result, failure to detect cracks in the structure 90 can be reduced.

[0092] 4, in the crack detection method according to this embodiment, the detection range 64A of the detection device 64 is shifted relative to the irradiation range 62A of the irradiation device 62. Therefore, compared to when the detection range 64A of the detection device 64 coincides with the irradiation range 62A of the irradiation device 62, reflected light from the surface of the structure 90 that occurs in the irradiation range 62A of the irradiation device 62 is less likely to be incident on the detection range 64A. This makes it easier to detect phosphorescence from the fiber sheet 40, reducing the chance of failing to detect cracks in the structure 90.

[0093] Furthermore, in the crack detection method according to this embodiment, the detection range 64A of the detection device 64 is spaced apart from the irradiation range 62A of the irradiation device 62, so that reflected light from the surface of the structure 90 generated in the irradiation range 62A of the irradiation device 62 is less likely to be incident on the detection range 64A, compared to when the detection range 64A of the detection device 64 is adjacent to the irradiation range 62A of the irradiation device 62. This makes it easier to detect phosphorescence from the fiber sheet 40, and reduces failure to detect cracks in the structure 90.

[0094] Furthermore, in the crack detection method according to this embodiment, the detection range 64A of the detection device 64 is 0.1 m or more away from the irradiation range 62A of the irradiation device 62, so that reflected light from the surface of the structure 90 that occurs in the irradiation range 62A of the irradiation device 62 is less likely to be incident on the detection range 64A, compared to when the detection range 64A of the detection device 64 is less than 0.1 m away from the irradiation range 62A of the irradiation device 62. This makes it easier to detect phosphorescence from the fiber sheet 40, and reduces failure to detect cracks in the structure 90.

[0095] Furthermore, in the crack detection method according to this embodiment, parallel light is irradiated in the irradiation step. Therefore, compared to when diffused light is irradiated in the irradiation step, reflected light from the surface of the structure 90 generated in the irradiation range 62A of the irradiation device 62 is less likely to enter the detection range 64A. This makes it easier to detect phosphorescence from the fiber sheet 40, reducing the chance of failing to detect cracks in the structure 90.

[0096] Furthermore, in the reinforcement structure 10 that is irradiated with light in the irradiation step, the shielding layer 50 also serves as the adhesive layer 70, which is highly effective in shielding the fiber sheet 40. Therefore, in the detection step, false detection due to inadvertent exposure of the fiber sheet 40 can be suppressed.

[0097] Furthermore, in the crack detection method according to this embodiment, the detection device 64 used in the detection process is a digital camera with a minimum subject illumination of 1 lux or less, so that the detection accuracy of phosphorescence is high and failure to detect cracks in the structure 90 can be reduced.

[0098] Furthermore, in the crack detection method according to this embodiment, the afterglow luminance of the fiber that emits phosphorescence when irradiated with light in the irradiation step is 10 mcd / m even 10 minutes after the light is turned off after 30 minutes of irradiation at 1000 lux using a D65 light source. 2 , so the afterglow luminance is 10mcd / m after 10 minutes of turning off the light after 30 minutes of irradiation with a D65 light source at 1000 lux. 2 In comparison with the case where the value is less than the above, the accuracy of detecting phosphorescence is high, and failure to detect cracks in the structure 90 can be reduced.

[0099] (Modification of detection range 64A of detection device 64) In the present embodiment, the detection range 64A of the detection device 64 is spaced apart from the irradiation range 62A of the irradiation device 62 on the opposite side of the traveling direction (the direction of the arrow X), but this is not limited thereto. For example, as shown in Fig. 5, the detection range 64A of the detection device 64 may be adjacent to the irradiation range 62A of the irradiation device 62. In Fig. 5, the detection range 64A of the detection device 64 is adjacent to the irradiation range 62A of the irradiation device 62 on the opposite side of the traveling direction (the direction of the arrow X).

[0100] 6, a part of the detection range 64A of the detection device 64 may overlap a part of the irradiation range 62A of the irradiation device 62. In Fig. 6, the detection range 64A of the detection device 64 is shifted to the opposite side of the traveling direction (the direction of the arrow X) with respect to the irradiation range 62A of the irradiation device 62, and the part of the detection range 64A of the detection device 64 on the traveling direction side overlaps with the part of the irradiation range 62A of the irradiation device 62 on the opposite side of the traveling direction (the direction of the arrow X).

[0101] (Reinforcement structure 12 according to modified example) The reinforcement structure related to the crack detection method of this embodiment may be a reinforcement structure 12. Fig. 7 is a cross-sectional view showing a reinforcement structure 12 according to a modified example. Note that parts having the same functions as those in the first embodiment are given the same reference numerals, and descriptions thereof will be omitted as appropriate.

[0102] In the reinforced structure 10, the fiber sheet 40 was adhered to the surface of the structure 90 by the shielding layer 50, but in the reinforced structure 12, the adhesive layer that adheres the fiber sheet 40 and the shielding layer are formed as separate layers. In other words, the reinforced structure 12 is a structure in which the adhesive function of adhering the fiber sheet 40 and the shielding function of shielding the fiber sheet 40 are functionally separated.

[0103] Specifically, as shown in FIG. 7, the reinforcement structure 12 of the second embodiment includes a primer 20, an unevenness correcting material 30, a fiber sheet 40, an adhesive layer 70, and a shielding layer 50.

[0104] The adhesive layer 70 has the function of adhering the fiber sheet 40 to the structure 90. Specifically, the adhesive layer 70 is formed by applying an adhesive resin to the surface of the unevenness correction material 30 and then curing it. As an example, a resin such as an epoxy resin is used for the adhesive layer 70. Note that the adhesive layer 70 is not limited to an epoxy resin, and may be a resin other than an epoxy resin, such as an acrylic resin, or other thermosetting resin. Although various materials can be used for the adhesive layer 70, a solvent-free room-temperature curing epoxy resin is preferably used.

[0105] The adhesive layer 70 does not contain any shielding material and is a transparent layer, allowing the fiber sheet 40 to transmit light that produces a luminous effect.

[0106] In the reinforcing structure 12, the shielding layer 50 is specifically formed by applying a shielding resin to the surface of the adhesive layer 70 and then curing it.

[0107] Here, in the reinforced structure 12, when a punching load test is performed on the fiber sheet 40, the adhesive layer 70, and the shielding layer 50, the adhesive layer 70 and the shielding layer 50 break before the fiber sheet 40. In the punching load test, a tensile force in a direction along the surface of the structure 90 (hereinafter referred to as the planar direction) and a shear force in a direction normal to the surface act on the fiber sheet 40, the adhesive layer 70, and the shielding layer 50. Therefore, in the reinforced structure 12, when a tensile force in the planar direction or a shear force in the direction normal to the surface of the structure 90 acts on the fiber sheet 40, the adhesive layer 70, and the shielding layer 50, the adhesive layer 70 and the shielding layer 50 break before the fiber sheet 40.

[0108] Therefore, when a crack occurs in the structure 90 and the surface of the structure 90 expands in the planar direction, or when a crack occurs in the structure 90 and a displacement occurs in the shear direction on the surface of the structure 90, the adhesive layer 70 and the shielding layer 50 will break while the fiber sheet 40 remains intact, as shown in Fig. 6. Therefore, the reinforcement structure 12 is configured such that when a crack occurs in the structure 90, the adhesive layer 70 and the shielding layer 50 break and the fiber sheet 40 is exposed from the broken portion.

[0109] For example, the "Punching Load Test" described in Appendix 17-2, Test Methods for Concrete Surface Coating Methods, of the Standard Specifications for Civil Engineering Works (edited by East Japan Railway Company) and the Japan Railway Facilities Association (September 2016) is used as the punching load test.

[0110] Furthermore, in the reinforcement structure 12, when the tensile elongation (elongation) in the plane direction of the fiber sheet 40 is compared with that of the adhesive layer 70 and the shielding layer 50, the fiber sheet 40 has a greater tensile elongation (elongation) than the adhesive layer 70 and the shielding layer 50. Specifically, the elongation of the fiber sheet 40 is, for example, 20-something percent, and the elongation of the adhesive layer 70 and the shielding layer 50 is, for example, 3% or less, preferably 0.5% or more and 3% or less, and more preferably 0.5% or more and 2.5% or less (all elongations at 23°C). Note that these elongations are the breaking elongation (i.e., the value obtained by dividing the elongation between the gauge points of the tensile test specimen after breaking by the gauge length and expressing it as a percentage).

[0111] Regarding the tensile elongation (elongation) in the plane direction between the adhesive layer 70 and the shielding layer 50, the tensile elongation (elongation) of the shielding layer 50 is set to be equal to or less than that of the adhesive layer 70. If the adhesive layer 70 has a larger elongation, the adhesive layer 70 will remain even if the shielding layer 50 breaks, which will physically block the light emission of the light-emitting fiber due to the excitation light, which is not preferable.

[0112] Similar to the reinforcing structure 10, the reinforcing structure 12 may also have a protective layer formed on the surface of the shielding layer 50 to protect the shielding layer 50. Examples of the protective layer include resin materials such as acrylic urethane resin, water-based acrylic resin, and fluororesin, which have the same tensile elongation (elongation) as the shielding layer 50, or polymer mortar.

[0113] (Reinforcement structure 13 according to modified example) The reinforcement structure related to the crack detection method of this embodiment may be a reinforcement structure 13. Fig. 8 is a cross-sectional view showing a reinforcement structure 13 according to a modified example. Note that parts having the same functions as those in the first embodiment are given the same reference numerals, and descriptions thereof will be omitted as appropriate.

[0114] As shown in FIG. 8, the reinforcing structure 13 includes a reinforcing member 15 having a fiber sheet 40 and a shielding layer 50, and an adhesive layer 17.

[0115] The shielding layer 50 is formed by impregnating the fiber sheet 40 with the above-mentioned shielding resin and then curing the resin. In the reinforcing member 15, the fiber sheet 40 is disposed inside the shielding layer 50.

[0116] The adhesive layer 17 is a layer made of an adhesive and has the function of adhering the reinforcing member 15 to the surface of the structure 90. Specifically, the adhesive layer 17 is formed by applying an adhesive to at least one of the surface of the structure 90 and the adhesive surface of the reinforcing member 15, and then curing the adhesive after the surface of the structure 90 and the adhesive surface of the reinforcing member 15 are adhered to each other.

[0117] An example of the adhesive is a resin such as an epoxy resin. The adhesive is not limited to an epoxy resin, and may be a thermosetting resin other than an epoxy resin, such as an acrylic resin, and various materials can be used, but a solvent-free room-temperature curing epoxy resin is preferably used.

[0118] The present invention is not limited to the above-described embodiment, and various modifications, changes, and improvements are possible without departing from the spirit of the present invention. For example, the above-described modified examples may be appropriately combined to form a configuration. [Explanation of symbols]

[0119] 10, 12, 13 Reinforcement structure 15 Reinforcement member 17 Adhesive layer 20 Primers 30 Unevenness correction material 40 Fiber Sheet 50 shielding layer 60 vehicles 62 Irradiation device 62A Irradiation Range 63 Roof 64 Detection Device 64A detection range 70 Adhesive layer 90 Structures 92 Covering wall

Claims

1. a reinforcement structure including a fiber sheet disposed on a surface of a structure and containing fibers that emit phosphorescence when irradiated with light, an adhesive layer that adheres the fiber sheet to the surface, and a shielding layer that blocks light irradiated to the fiber sheet, wherein when a punching load test is conducted on the fiber sheet, the adhesive layer, and the shielding layer, the adhesive layer and the shielding layer break before the fiber sheet; a detection step of detecting a crack generated in the structure by detecting phosphorescence emitted from the fiber sheet due to the light irradiation in the irradiation step, wherein the detection range of the phosphorescence includes a range where the light irradiation in the irradiation step is completed; A crack detection method having

2. a reinforcement structure including a fiber sheet disposed on a surface of a structure and containing fibers that emit phosphorescence when irradiated with light, an adhesive layer that adheres the fiber sheet to the surface, and a shielding layer that blocks light irradiated to the fiber sheet, wherein the reinforcement structure has been subjected to breakage of the adhesive layer and the shielding layer due to the occurrence of a crack in the structure, exposing the fiber sheet from the broken portion, and an irradiation step of irradiating the reinforcement structure with light; a detection step of detecting a crack generated in the structure by detecting phosphorescence emitted from the fiber sheet due to the light irradiation in the irradiation step, wherein the detection range of the phosphorescence includes a range where the light irradiation in the irradiation step is completed; A crack detection method having

3. The irradiation step irradiates light onto the reinforcing structure in which the shielding layer also serves as the adhesive layer. The crack detection method according to claim 1 or 2.

4. The irradiation step includes irradiating the reinforcement structure with light from an irradiation device, The detecting step detects the cracks generated in the structure by detecting the phosphorescence with a detecting device, and detects if the detection range of the detecting device is shifted from the irradiation range of the irradiating device. The crack detection method according to any one of claims 1 to 3.

5. In the detecting step, a detection range of the detection device is separated from an irradiation range of the irradiation device. The crack detection method according to claim 4.

6. In the detecting step, the detection range of the detection device is separated from the irradiation range of the irradiation device by 0.1 m or more. The crack detection method according to claim 5 .

7. The detection device used in the detection step is a digital camera with a minimum subject illumination of 1 lux or less. The crack detection method according to any one of claims 4 to 6.

8. The afterglow brightness of the phosphorescent fiber irradiated with light in the irradiation step is 10 mcd / m even after 10 minutes of turning off the light after 30 minutes of irradiation at 1000 lux using a D65 light source. ２ exceed The crack detection method according to any one of claims 1 to 7.

9. The irradiation step irradiates parallel light. The crack detection method according to any one of claims 1 to 8.

10. The irradiation step involves irradiating with light containing ultraviolet light. The crack detection method according to any one of claims 1 to 9.

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