How to detect the location of cracks on a concrete surface

Abstract

To detect positions of cracks more precisely even if intervals of cracks are small.SOLUTION: A detection method comprises: an optical fiber installing process of installing an optical fiber 10 on a surface 101 of concrete 100; and a crack position detecting process of detecting a position of a crack 102 made on the surface 101 based upon strain occurring on the optical fiber 10 installed on the surface 101 in the optical fiber installing process. In the optical fiber installing process, the optical fiber 10 is installed on the surface 101 so that the optical fiber 10 has a fixed part 21 fixed to the surface 101 and a non-fixed part 22 not fixed to the surface 101 alternately, and in the crack position detecting process, the position of the crack 102 is detected based upon the strain occurring on the optical fiber 10 at each of non-fixed parts 22. A strain detection result at the non-fixed part 22 is not affected by strain at other non-fixed parts 22 because of the fixed parts 21, so the position of the crack 102 can be detected more precisely even when intervals of the cracks 102 are small.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a method for detecting the location of cracks on the surface of concrete. [Background technology]

[0002] Techniques have been proposed for detecting the positions of cracks on the surface of concrete. For example, Patent Document 1 discloses a technique in which an optical fiber is arranged at an angle of 45° with respect to the direction in which cracks are predicted to occur on the surface of concrete, and the position of the cracks on the surface of concrete is detected based on the strain generated in the optical fiber. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2002-267575 A Summary of the Invention [Problem to be solved by the invention]

[0004] In the above-mentioned technology, the optical fiber measures the average strain in a set measurement section in the axial direction of the optical fiber. When the cracks on the surface of the concrete are spaced widely apart, the optical fiber follows the sudden increase in strain at the crack position, increasing the strain of the optical fiber in a certain section around the crack, and the position of the crack can be detected based on the strain of the optical fiber.

[0005] However, when the cracks on the concrete surface are spaced apart, the effects of increased strain due to multiple cracks are mixed within one measurement section of the optical fiber, making it difficult to identify the location of the crack. In other words, because optical fiber adapts to the surrounding strain, even a local crack is detected as its strain is adapted over a large range. Therefore, one measurement section of the optical fiber measures the strain of the surrounding measurement sections mixed in. Therefore, when the cracks on the concrete surface are spaced apart, it makes it difficult to identify the location of the crack.

[0006] Therefore, an object of the present invention is to provide a method for detecting the position of a crack on the surface of concrete, which can detect the position of the crack with higher accuracy even if the cracks on the surface of the concrete are spaced apart closely. [Means for solving the problem]

[0007] The present invention is a method for detecting the position of a crack on the surface of concrete, comprising an optical fiber installation process for installing an optical fiber on the surface of concrete, and a crack position detection process for detecting the position of a crack on the surface of concrete based on strain generated in the optical fiber installed on the surface of concrete in the optical fiber installation process, wherein in the optical fiber installation process, the optical fiber is installed on the surface of concrete so that the optical fiber has alternately fixed portions fixed to the surface of concrete and non-fixed portions not fixed to the surface of concrete, and in the crack position detection process, the position of a crack on the surface of concrete is detected based on strain generated in the optical fiber in each of the non-fixed portions.

[0008] According to this configuration, a method for detecting the position of a crack on the surface of concrete is provided, the method comprising an optical fiber installation step of installing an optical fiber on the surface of concrete, and a crack position detection step of detecting the position of a crack on the surface of concrete based on the strain generated in the optical fiber installed on the surface of concrete in the optical fiber installation step. In the optical fiber installation step, the optical fiber is installed on the surface of concrete so that the optical fiber has alternately fixed parts fixed to the surface of concrete and non-fixed parts not fixed to the surface of concrete. In the crack position detection step, the position of a crack on the surface of concrete is detected based on the strain generated in the optical fiber in each of the non-fixed parts provided between the fixed parts. Since the detection result of the strain generated in the optical fiber in each non-fixed part is not affected by the strain generated in the optical fiber in the other non-fixed parts by the fixed parts adjacent to the non-fixed parts, the position of the crack can be detected with higher accuracy even if the interval between the cracks on the surface of concrete is small.

[0009] In this case, in the optical fiber installation step, it is preferable that the length of the unfixed portion is longer than the interval of the spatial resolution of the optical fiber and shorter than the expected interval of cracks on the surface of the concrete.

[0010] According to this configuration, in the optical fiber installation process, the length of the non-fixed portion is longer than the section of the spatial resolution of the optical fiber, so it is possible to prevent the length of the non-fixed portion from being too short and exceeding the evaluation range of the strain generated in the optical fiber. Also, in the optical fiber installation process, the length of the non-fixed portion is shorter than the expected interval between cracks on the surface of the concrete, so it is possible to prevent the length of the non-fixed portion from being too long and being unable to detect the position of each crack. Therefore, it is possible to detect the position of each crack generated on the surface of the concrete with higher accuracy.

[0011] In this case, it is also preferable that the spacing of expected cracks on the surface of the concrete is determined based on the covering of the reinforcing bars embedded in the concrete, the center-to-center spacing of each of the reinforcing bars, and the diameter of the reinforcing bars.

[0012] With this configuration, the expected spacing of cracks on the surface of the concrete is determined based on the cover of the rebars embedded in the concrete, the center-to-center spacing of each of the rebars, and the diameter of the rebars, so that it is possible to determine an appropriate spacing for cracks that are expected to occur at regular intervals on the surface of the concrete, and to determine an appropriate length of the non-fixed portion based on the spacing of the cracks.

[0013] In addition, in the optical fiber installation step, it is preferable to install the optical fiber on the surface of the concrete so that the direction of expected cracks on the surface of the concrete intersects with the axial direction of the optical fiber.

[0014] According to this configuration, in the optical fiber installation process, the optical fiber is installed on the surface of the concrete so that the expected direction of cracks on the surface of the concrete intersects with the axial direction of the optical fiber, so that in the crack position detection process, strain generated in the optical fiber can be detected more accurately, and the position of cracks generated on the surface of the concrete can be detected more accurately.

[0015] It is also preferable that the method further comprises a crack width detection step of detecting the width of a crack occurring in the non-fixed portion by integrating the strain occurring in the non-fixed portion.

[0016] The integral value of the strain distribution measured by the optical fiber in the non-fixed parts provided between the fixed parts approximates the total crack width generated in the non-fixed parts. Therefore, according to this configuration, for example, by setting the non-fixed parts and the fixed parts so that one crack occurs in one non-fixed part, it is possible to quantitatively evaluate not only the crack position but also the crack width. Effect of the Invention

[0017] According to the method for detecting the positions of cracks on the surface of concrete of the present invention, the positions of cracks can be detected with high accuracy even if the cracks on the surface of concrete are spaced apart closely. [Brief description of the drawings]

[0018] [Figure 1] FIG. 1(A) is a side view showing the concept of a method for detecting the positions of cracks on the surface of concrete according to a first embodiment, and FIG. [Diagram 2] 4 is a flowchart showing a method for detecting the position of a crack on the surface of concrete according to the first embodiment. [Diagram 3] 1 is a diagram illustrating the concept of spatial resolution and measurement interval of an optical fiber. [Figure 4] FIG. 1(A) is a side view showing a method for detecting the positions of cracks on the surface of concrete according to a first embodiment, and FIG. [Diagram 5] FIG. 13(A) is a side view showing a method for detecting the positions of cracks on the surface of concrete according to a second embodiment, and (B) is a bottom view of (A). [Figure 6] (A) is a side view showing a state in which multiple edge cutting sheets have been pre-installed at regular intervals on the surface of concrete in a method for detecting the position of cracks on the surface of concrete in the third embodiment, and (B) is a side view showing a state in which optical fiber has been laid on the surface of the concrete in (A) and adhesive has been applied. [Figure 7] FIG. 11 is a perspective view showing a method for detecting the position of a crack on the surface of concrete according to a fourth embodiment. [Figure 8] FIG. 1A is a diagram showing the results of crack detection using an optical fiber when the cracks are spaced apart widely, and FIG. 1B is a diagram showing the results of crack detection when the cracks are spaced apart narrowly. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0019] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. As shown in Fig. 1(A), Fig. 1(B) and Fig. 2, in a method for detecting the position of a crack on the surface of concrete according to a first embodiment of the present invention, for example, the position of a crack 102 occurring on the surface 101 of concrete 100 in which reinforcing bars 103 are embedded is detected. The crack 102 on the surface 101 of concrete 100 whose position is detected by the detection method of this embodiment means, for example, a structural crack that is known to occur at regular intervals on the surface 101 of concrete 100.

[0020] In the method for detecting the position of a crack on the surface of concrete according to this embodiment, an optical fiber installation step is performed in which an optical fiber 10 is installed on the surface 101 of concrete 100 (S1). In addition, in the method for detecting the position of a crack on the surface of concrete according to this embodiment, a crack position detection step is performed in which the position of a crack 102 that has occurred on the surface 101 of concrete 100 is detected based on the strain that has occurred in the optical fiber 10 installed on the surface 101 of concrete 100 in the optical fiber installation step (S2).

[0021] 1(A) and 1(B), in the optical fiber installation step, the optical fiber 10 is installed on the surface 101 of the concrete 100 so that the optical fiber 10 has alternately fixed portions 21 that are fixed to the surface 101 of the concrete 100 and non-fixed portions 22 that are not fixed to the surface 101 of the concrete 100. In the crack position detection step, the position of a crack 102 that has occurred on the surface 101 of the concrete 100 is detected based on the strain generated in the optical fiber 10 in each of the non-fixed portions 22.

[0022] In the optical fiber installation process, the length L of the non-fixed portion 22 is longer than the interval S of the spatial resolution of the optical fiber 10. The interval g1 of the measurement points 23 at which each position of the strain generated in the optical fiber 10 can be resolved and detected as shown in FIG. 3 is determined by the measurement method of the strain generated in the optical fiber 10. For example, in an existing measurement system, the interval g1 of the measurement points 23 at which each position of the strain generated in the optical fiber 10 can be resolved and detected as the interval for acquiring data of the strain generated in the optical fiber 10 is 50 mm as a standard. In addition, in this measurement system, the interval S of the spatial resolution is 100 mm, which is twice the interval g1 at which each position of the strain generated in the optical fiber 10 can be resolved and detected as a standard. The spatial resolution means, for example, that an average strain in the interval S of the spatial resolution is detected.

[0023] 1A and 1B, in the optical fiber installation process, the length L of the non-fixed portion 22 is shorter than the expected interval g2 of the cracks 102 on the surface 101 of the concrete 100. The expected interval g2 of the cracks 102 on the surface 101 of the concrete 100 is calculated by multiplying the cover c of the reinforcing bars 103 embedded in the concrete 100 and the center-to-center interval c of the reinforcing bars 103 by the distance between the centers of the reinforcing bars 103. s and the diameter φ of the reinforcing bar. For example, the expected spacing g2 of cracks 102 on the surface 101 of concrete 100 is spacing g2 = 4 × cover c + 0.7 (center spacing c s -Diameter φ) can be used to calculate the

[0024] Furthermore, in the optical fiber installation step, the optical fiber 10 is installed on the surface 101 of the concrete 100 so that the expected direction of cracks 102 on the surface 101 of the concrete 100 intersects with the axial direction of the optical fiber 10. In the optical fiber installation step, it is preferable that the expected direction of cracks 102 on the surface 101 of the concrete 100 intersects with the axial direction of the optical fiber 10 at right angles.

[0025] For example, the frequency of the Brillouin scattered light changes in proportion to the magnitude of the strain in the optical fiber 10. Therefore, in the crack position detection process, an optical pulse of a predetermined frequency is input from one end of the optical fiber 10, and the change in optical frequency in the Brillouin scattered light generated by the optical pulse is measured at one end of the optical fiber along with the time indicating the generation position, thereby measuring the axial strain of the optical fiber 10.

[0026] When a crack 102 occurs at a position on the surface 101 of the concrete 100 corresponding to a non-fixed portion 22 where the optical fiber 10 is not fixed to the surface 101 of the concrete 100, the elongation of the optical fiber 10 at the non-fixed portion 22, with the fixed portion 21 where the optical fiber 10 is fixed to the surface 101 of the concrete 100 as a reference point, is approximately equal to the width of the crack 102. The elongation of the optical fiber 10 at the non-fixed portion 22 is found by integrating the strain of the optical fiber 10 between the fixed portions 21, which are the reference points, in the axial direction of the optical fiber 10. Therefore, as shown in Fig. 2, a crack width detection step may be performed in which the width of the crack 102 generated in the non-fixed portion 22 is detected by integrating the strain generated in the non-fixed portion 22 (S3).

[0027] That is, since the fixed portion 21 is firmly fixed to the surface 101 of the concrete 100, if strain is detected in the non-fixed portion 22, the elongation of the optical fiber 10 in the non-fixed portion 22 becomes the width of the crack 102. If no strain is detected in the non-fixed portion 22, this means that there is no crack 102 in that non-fixed portion 22 or in the fixed portion 21 adjacent to that non-fixed portion 22.

[0028] The elongation of the optical fiber 10 in the non-fixed portions 22 caused by the cracks 102 is limited between the non-fixed portions 22 where the optical fiber 10 is not fixed to the surface 101 of the concrete 100, so it is possible to identify the position where the cracks 102 have occurred. In other words, the strain generated in the optical fiber 10 is detected using each of the fixed portions 21 as an independent reference point, and there is no interference between the detection results of the strain in the non-fixed portions 22. In this embodiment, the position where the cracks 102 have occurred is limited to the non-fixed portions 22. From the strain of the optical fiber 10 in each of the non-fixed portions 22, the cracks 102 in the surface 101 of the concrete 100 at the locations corresponding to each of the non-fixed portions 22 are identified.

[0029] Regarding a specific method of installing the optical fiber 10 in the optical fiber installation step, for example, as shown in Fig. 4, the optical fiber 10 may be installed on the surface 101 of the concrete 100 via a member such as a plate material 31. The optical fiber 10 is adhered to the plate material 31. The plate material 31 is fixed to the surface 101 of the concrete 100 at regular intervals with anchors 32 or adhered with an adhesive. Fixed portions 21 are formed at the sites where the plate material 31 is fixed or adhered to the surface 101 of the concrete 100, and non-fixed portions 22 are formed at the sites where the plate material 31 is not fixed or adhered to the surface 101 of the concrete 100.

[0030] Members such as the plate material 31 are required to have high elasticity, a small elastic modulus, uniform distortion, and high durability in order to follow the width of the crack 102. Suitable materials for members such as the plate material 31 that satisfy these conditions include, for example, carbon fiber reinforced plastics (CFRP) and basalt fiber reinforced plastics (BFRP).

[0031] For comparison with the conventional technology, as shown in Fig. 8(A) and Fig. 8(B), the optical fiber 10 was installed over the entire length of the surface 101 of the concrete 100 as a test specimen, so that there was no unfixed portion, and cracks 102 that occurred on the surface 101 of the concrete 100 were detected. In the figures, the "crack width" is a value measured by a pie-shaped displacement meter installed on the surface 101 of the concrete 100 as a test specimen. As shown in Fig. 8(A), when the interval between the cracks 102 is large, the optical fiber 10 follows the sudden increase in strain at the crack position, and the strain of the optical fiber 10 in a certain section around the crack 102 increases, and it can be seen that the position of each crack 102 can be detected from the detection result by the optical fiber 10.

[0032] However, as shown in FIG. 8B, when the intervals between the cracks 102 are small, the influence of the increase in strain due to the multiple cracks 102 is mixed in the measurement section of one point of the optical fiber 10 where the average strain of the measurement section is obtained, so the position of each crack 102 cannot be identified from the detection result of the strain distribution by the optical fiber 10 attached by the conventional method. In other words, as described above, the optical fiber 10 adapts to the surrounding strain, so even if the crack 102 is localized, the strain is detected by adapting to a large range. Therefore, in one measurement section of the optical fiber 10, the strain of the surrounding measurement sections is also measured. Therefore, when the intervals between the cracks 102 generated on the surface 101 of the concrete 100 are small, it is difficult to identify the position of the crack 102.

[0033] On the other hand, in this embodiment, a method for detecting the position of a crack on the surface of concrete is provided, which includes an optical fiber installation process for installing an optical fiber 10 on the surface 101 of the concrete 100, and a crack position detection process for detecting the position of a crack 102 that has occurred on the surface 101 of the concrete 100 based on the distortion generated in the optical fiber 10 installed on the surface 101 of the concrete 100 in the optical fiber installation process.

[0034] In the optical fiber installation step, the optical fiber 10 is installed on the surface 101 of the concrete 100 so that the optical fiber 10 has alternately fixed portions 21 fixed to the surface 101 of the concrete 100 and non-fixed portions 22 not fixed to the surface 101 of the concrete 100. In the crack position detection step, the position of a crack 102 occurring on the surface 101 of the concrete 100 is detected based on the strain occurring in the optical fiber 10 in each of the non-fixed portions 22 provided between the fixed portions 21.

[0035] Since the detection results of the strain generated in the optical fiber 10 in each non-fixed portion 22 are not affected by the strain generated in the optical fiber 10 in other non-fixed portions 22 by the fixed portion 21 adjacent to the non-fixed portion 22, the resolution for detecting cracks 102 is improved, and the position of each crack 102 can be detected more accurately even if the cracks 102 generated on the surface 101 of the concrete 100 are spaced apart closely.

[0036] Furthermore, when the entire optical fiber 10 is fixed to the surface 101 of the concrete 100, if a crack 102 occurs on the surface 101 of the concrete 100, the strain of the optical fiber 10 increases rapidly in the vicinity of the position of the crack 102, limiting the elongation of the optical fiber 10, and there is a possibility that measurement will become impossible due to deviation from the measurement range and early breakage of the optical fiber 10. On the other hand, in this embodiment, the strain is averaged within the range of the length L of the non-fixed portion 22 where the optical fiber 10 is not fixed to the surface 101 of the concrete 100, so that it is possible to reduce the possibility of deviation from the measurement range and early breakage of the optical fiber 10, making measurement impossible.

[0037] Furthermore, in this embodiment, in the optical fiber installation process, the length L of the non-fixed portion 22 is longer than the section S of the spatial resolution of the optical fiber 10, so it is possible to prevent the length L of the non-fixed portion 22 from being too short and exceeding the evaluation range of the strain generated in the optical fiber 10. Furthermore, in the optical fiber installation process, the length L of the non-fixed portion 22 is shorter than the expected interval g2 of the cracks 102 on the surface 101 of the concrete 100, so it is possible to prevent the length L of the non-fixed portion 22 from being too long and being unable to detect the position of each of the cracks 102. Therefore, it is possible to detect the position of each of the cracks 102 generated on the surface 101 of the concrete 100 with greater accuracy.

[0038] In this embodiment, the expected interval g2 of the cracks 102 on the surface 101 of the concrete 100 is calculated by dividing the cover c of the reinforcing bars 103 embedded in the concrete 100 and the center interval c of each of the reinforcing bars 103. s Since the spacing g2 of the cracks 102 that are expected to occur at regular intervals on the surface 101 of the concrete 100 can be determined, and a reasonable length L of the non-fixed portion 22 can be determined based on the spacing g2 of the cracks 102.

[0039] Furthermore, in this embodiment, in the optical fiber installation process, the optical fiber 10 is installed on the surface 101 of the concrete 100 so that the expected direction of the crack 102 on the surface 101 of the concrete 100 intersects with the axial direction of the optical fiber 10. Therefore, in the crack position detection process, the distortion occurring in the optical fiber 10 can be detected more accurately, and the position of the crack 102 occurring on the surface 101 of the concrete 100 can be detected more accurately.

[0040] Moreover, the integral value of the strain distribution measured by the optical fiber 10 in the non-fixed parts 22 provided between the fixed parts 21 approximates the total value of the crack widths that have occurred in the non-fixed parts 22. Therefore, according to this embodiment, for example, by setting the non-fixed parts 22 and the fixed parts 21 so that one crack 102 occurs in one non-fixed part 22, it is possible to quantitatively evaluate not only the crack position but also the crack width.

[0041] A second embodiment of the present invention will be described below. In the optical fiber installation process of this embodiment, the optical fiber 10 is fixed to the surface 101 of the concrete 100 in the fixed portion 21 so that the optical fiber 10 cannot move freely, and the optical fiber 10 is supported on the surface 101 of the concrete 100 in the non-fixed portion 22 so that the optical fiber 10 can move freely. As shown in Figures 5(A) and 5(B), the optical fiber 10 is surrounded by a plurality of protective tubes 34, each having an inner diameter larger than the outer diameter of the optical fiber 10, at regular intervals in the axial direction.

[0042] Throughout the entire length of the measurement range of the optical fiber 10, the portion of the optical fiber 10 that is not surrounded by the protective tube 34 and the protective tube 34 are fixed to the surface 101 of the concrete 100 by the adhesive 33. The portion of the optical fiber 10 that is not surrounded by the protective tube 34 is fixed to the surface 101 of the concrete 100 so that the optical fiber 10 cannot move freely. However, the portion of the optical fiber 10 that is surrounded by the protective tube 34 is cut off from the adhesive 33 and the surface 101 of the concrete 100, and is supported by the surface 101 of the concrete 100 so that the optical fiber 10 can move freely in the protective tube 34. That is, in this embodiment, the fixed portion 21 is formed in the portion of the optical fiber 10 that is not surrounded by the protective tube 34, and the non-fixed portion 22 is formed in the portion of the optical fiber 10 that is surrounded by the protective tube 34. In this embodiment, the fixed portion 21 and the non-fixed portion 22 can be easily formed by using the protective tube 34.

[0043] A third embodiment of the present invention will be described below. As shown in Fig. 6(A), in the optical fiber installation process of this embodiment, a plurality of edge cutting sheets 35 or edge cutting seals are installed at regular intervals on a surface 101 of concrete 100 in advance. As shown in Fig. 6(B), an optical fiber 10 is laid on the surface 101 of concrete 100 on which the edge cutting sheets 35 or edge cutting seals are installed at regular intervals, and an adhesive 33 is applied.

[0044] In the area where the edge cutting sheet 35 or edge cutting seal is not installed, the optical fiber 10 is fixed to the surface 101 of the concrete 100 by the adhesive 33. However, in the area where the edge cutting sheet 35 or edge cutting seal is installed, the optical fiber 10 is cut off from the surface 101 of the concrete 100. That is, in this embodiment, the fixed portion 21 is formed in the area where the edge cutting sheet 35 or edge cutting seal is not installed, and the non-fixed portion 22 is formed in the area where the edge cutting sheet 35 or edge cutting seal is installed. In this embodiment, the fixed portion 21 and the non-fixed portion 22 can be easily formed by using the edge cutting sheet 35 or edge cutting seal.

[0045] A fourth embodiment of the present invention will be described below. As shown in Fig. 7, in the optical fiber installation process of this embodiment, the optical fiber 10 is mechanically fixed to the surface 101 of the concrete 100 at regular intervals in the axial direction by fasteners 36 such as screws or staples of a stapler. In this embodiment, fixed portions 21 are formed at the sites where the optical fiber 10 is fixed by the fasteners 36, and non-fixed portions 22 are formed at the sites between the fasteners 36. In this embodiment, the fixed portions 21 and non-fixed portions 22 can be easily formed by using the fasteners 36.

[0046] Although the embodiment of the present invention has been described above, the present invention is not limited to the above embodiment and can be embodied in various forms. [Explanation of symbols]

[0047] 10...optical fiber, 21...fixed part, 22...non-fixed part, 23...measurement point, 31...plate material, 32...anchor, 33...adhesive, 34...protective tube, 35...edge cutting sheet, 36...fixing device, 100...concrete, 101...surface, 102...crack, 103...reinforcing bar, L...length, g1, g2...spacing, S...section, c...cover, c s ...Center spacing, φ...Diameter.

Claims

1. an optical fiber installation step of installing an optical fiber on a surface of the concrete; a crack position detection step of detecting a position of a crack occurring on the surface of the concrete based on a strain occurring in the optical fiber installed on the surface of the concrete in the optical fiber installation step; Equipped with In the optical fiber installation step, the optical fiber is fixed to the surface of the concrete such that the optical fiber has alternately fixed portions fixed to the surface of the concrete and non-fixed portions not fixed to the surface of the concrete; In the crack position detection step, a position of the crack occurring on the surface of the concrete is detected based on the strain occurring in the optical fiber in each of the non-fixed portions; In the optical fiber installation step, A pipe member or a cutting member is installed on the surface of the concrete at regular intervals in advance along the axial direction of the optical fiber, The optical fiber is installed so that the pipe member or the edge-cutting member is interposed between the surface of the concrete and the optical fiber at a plurality of locations where the pipe member or the edge-cutting member is installed; A method for detecting the position of cracks on the surface of concrete, comprising applying an adhesive to a measurement range of the optical fiber including the multiple locations to fix the optical fiber, thereby forming the fixed portion and the non-fixed portion.

2. The method for detecting the position of cracks on the surface of concrete as described in claim 1, wherein, in the optical fiber installation process, the length of the non-fixed portion is longer than the spatial resolution interval of the optical fiber and shorter than the expected spacing of the cracks on the surface of the concrete.

3. 3. The method for detecting the location of cracks on the surface of concrete according to claim 2, wherein the expected spacing of the cracks on the surface of the concrete is determined based on the cover of rebars embedded in the concrete, the center-to-center spacing of each of the rebars, and the diameter of the rebars.

4. A method for detecting the position of a crack on the surface of concrete as described in any one of claims 1 to 3, wherein in the optical fiber installation process, the optical fiber is installed on the surface of the concrete so that the predicted direction of the crack on the surface of the concrete intersects with the axial direction of the optical fiber.

5. The method for detecting the position of a crack on the surface of concrete according to any one of claims 1 to 4, further comprising a crack width detection step of detecting the width of the crack occurring in the non-fixed portion by integrating the strain occurring in the non-fixed portion.

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