JP7600066B2 - Compression detector - Google Patents

Description

This disclosure relates to a compression detection device that detects the compressive force acting on concrete.

Patent Publication No. 6145344 describes an impact detection method and detection device that uses an FBG sensor (Fiber Bragg Grating Sensor) to detect impacts on a structure. This detection device includes an FBG sensor that is attached to the structure, an optical fiber amplifier, an optical circulator, and a coupler. An optical filter for measuring strain, an optical filter for measuring temperature, and a photoelectric converter are connected to the coupler. When strain occurs in the structure, reflected light from the FBG sensor is input to the light source converter via the optical fiber amplifier and the coupler, and the light source converter obtains the history of impact force application to the structure.

Patent Publication No. 4187250 describes a method and system for diagnosing a structure using optical fibers. In this system, an optical fiber is attached to a target component of the structure, and the initial strain of the target component is measured by the optical fiber. The optical fiber continuously monitors the strain history of a specific part of the target component, and diagnoses the soundness of the structure from the initial strain and strain history.

JP 2013-250120 A describes a method for detecting damage to a structure. In the damage detection method, a damage detection device is attached to the underside of a bridge girder arranged between a pair of bridge piers. The damage detection device includes a first base and a second base that are fixed to the test surface of the bridge girder, and a detection member that is disposed between the first base and the second base. An optical fiber with a built-in optical strain detection means is used as the detection member.

JP 2001-59796 A describes a strength prediction device for oil tanks. The strength prediction device comprises a base on which the side plate of the oil tank is erected, an optical fiber laid on the side plate of the oil tank, a strain gauge, and a monitoring device. The strain gauge measures strain caused by an external force on the oil tank via the optical fiber. The monitoring device monitors the occurrence of cracks based on the amount of strain measured by the strain gauge.

Patent No. 6145344 Patent No. 4187250 JP 2013-250120 A JP 2001-59796 A

However, concrete structures have a problem in that it is difficult to grasp the compressive force applied to the concrete structure due to an earthquake or the like after the fact. As mentioned above, there is a known method of detecting the strain of a concrete structure using an optical fiber cable. However, the strain detected by the optical fiber cable is the strain at the moment when the pulsed light is incident, and it is not possible to grasp the past history or maximum response of the compressive force that the concrete has received. In other words, the current situation is that it is not possible to grasp the maximum compressive force that the concrete structure has received in the past after the fact in response to the behavior of the concrete structure due to an earthquake or the like.

The purpose of this disclosure is to provide a compression detection device that can retroactively determine the maximum compressive force that a concrete structure has ever been subjected to.

The compression detection device according to the present disclosure is a compression detection device that is embedded in concrete, and includes a plurality of rigid materials that have a higher rigidity than concrete and are stacked in one direction, a detection material that is disposed between two rigid materials that are aligned in one direction, and a detection device that detects irreversible deformation of the detection material due to a compressive force in one direction applied to the rigid materials.

This compression detection device includes a plurality of rigid materials having a higher rigidity than concrete, a detection material interposed between two rigid materials arranged in one direction, and a detection device that detects the deformation of the detection material that deforms irreversibly due to a compressive force. The detection material deforms irreversibly when the rigid material receives a compressive force of a predetermined value or more. Specifically, even if a plurality of rigid materials having a higher rigidity than concrete receive a compressive force, the detection material does not deform if the compressive force is not equal to or greater than the predetermined value. On the other hand, the detection material deforms irreversibly when the compressive force is equal to or greater than the predetermined value. By detecting the irreversible deformation of this detection material with the detection device, it is possible to know whether the compressive force received was equal to or greater than the predetermined value. In other words, when the detection device detects the irreversible deformation of the detection material, it is possible to know after the fact that the maximum compressive force received by the concrete is equal to or greater than the predetermined value, and when the detection device does not detect the irreversible deformation of the detection material, it is possible to know after the fact that the maximum compressive force is not equal to or greater than the predetermined value. Therefore, it is possible to know after the fact whether the concrete has received a compressive force of equal to or greater than the predetermined value in the past.

The detection material may include a dowel that is interposed between two rigid materials and breaks when a compressive force equal to or greater than a predetermined value is applied to the rigid material. In this case, the detection device detects whether the dowel has broken, making it easy to know whether the compressive force received by the concrete was equal to or greater than a predetermined value. Note that the present disclosure is not limited to dowels that break, and may also be a mechanism that causes residual deformation.

The detection device may include multiple rigid materials and an optical fiber cable that contacts the detection materials. In this case, the optical fiber cable can detect irreversible deformation of the detection materials with high accuracy. Since the optical fiber cable can detect strain continuously or distributed along the points where the optical fiber cable contacts, for example, when the optical fiber cable is installed across multiple detection materials, it can detect which detection materials have been deformed. In other words, since the optical fiber cable can detect the presence or absence of deformation in multiple detection materials, it is possible to grasp the history of compressive force that has been applied from the past with high accuracy. The predetermined value at which irreversible deformation occurs may be set to a different value in stages for each of the multiple detection materials. In this case, by detecting which detection materials have been deformed, it is possible to retroactively grasp the maximum compressive force that the concrete has been subjected to in the past.

The optical fiber cable may be spirally wound around multiple rigid materials and the sensing material. In this case, by spirally winding the optical fiber cable that detects deformation of the sensing material, the number of measurement points of the optical fiber cable in one direction can be increased. Therefore, deformation of the sensing material by the optical fiber cable can be detected with higher accuracy.

The method for replacing a compression detector according to the present disclosure is a method for replacing the above-mentioned compression detector, which is embedded in concrete and has a linear detector that detects the compressive force on the concrete. A storage member in which the detector is stored is embedded in the concrete, and the method includes the steps of exposing the compression detector from a hole formed by scraping the concrete, removing the compression detector from the hole by cutting the detector extending from the compression detector, pulling the detector from the storage member into the hole, placing a new compression detector in the hole, connecting the pulled-out detector to the detector of the new compression detector, and filling the hole with concrete.

In this method of replacing a compression detector, the compression detector and a storage member that stores the linear detector are embedded in concrete, and the compression detector is removed from a hole formed by scraping the concrete. The compression detector is exposed from the hole formed by scraping the concrete, and the linear detector is cut and removed from the exposed compression detector. The linear detector stored in the storage member is pulled out into the hole, and a detector of a new compression detector is connected to the pulled out detector. After the new compression detector is installed in the hole in this state, the hole is filled with concrete. Therefore, the compression detector can be easily attached and detached from the hole. In addition, since the above-mentioned compression detector is used in this replacement method, the history of compressive force received from the past can be grasped with high accuracy.

This disclosure makes it possible to retrospectively determine the maximum compressive force that a concrete structure has ever been subjected to.

1 is a cross-sectional view showing a concrete structure in which a compression detection device according to an embodiment is used. FIG. 2 is a vertical cross-sectional view of the concrete structure of FIG. 1 . FIG. 2 is a vertical cross-sectional view showing the compression detection device according to the embodiment. 4A and 4B are longitudinal sectional views for explaining the behavior of the compression detection device of FIG. 3 . 4A and 4B are a vertical cross-sectional view and a plan view for explaining a hole through which a detection device of the compression detection device according to the embodiment is inserted. Fig. 6(a) is a vertical cross-sectional view showing an optical fiber cable inserted into the hole of Fig. 5. Fig. 6(b) is a vertical cross-sectional view for explaining the behavior of the optical fiber cable of Fig. 6(a). 13A, 13B, and 13C are longitudinal cross-sectional views for explaining a method of arranging an optical fiber cable according to a modified example. FIG. 11 is a vertical cross-sectional view showing a compression detector according to a modified example. 5A, 5B, and 5C are vertical cross-sectional views showing steps of a method for replacing a compression detection device according to an embodiment.

Below, an embodiment of the compression detection device and the replacement method for the compression detection device according to the present disclosure will be described with reference to the drawings. In the description of the drawings, the same or corresponding elements are given the same reference numerals, and duplicated descriptions will be omitted as appropriate. In addition, the drawings may be partially simplified or exaggerated to facilitate understanding, and the dimensional ratios, etc. are not limited to those shown in the drawings.

Figure 1 is a cross-sectional view showing a concrete structure S in which a compression detection device 1 according to an embodiment is embedded. As shown in Figure 1, the compression detection device 1 detects a compressive force F (see Figure 3) acting on the concrete structure S while embedded in the concrete structure S. As an example, the concrete structure S is a part of the base of a bridge pier. The concrete structure S has, for example, multiple structural reinforcing bars S1 and concrete S2. As an example, the structural reinforcing bars S1 include multiple axial reinforcing bars S11 extending in the vertical direction D1 and hoop reinforcing bars S12 extending in the horizontal direction D2.

The axial reinforcing bars S11 and the tie bars S12 are arranged in a grid pattern. The spacing W1 between the two tie bars S12 is, for example, 200 mm, and the surface-to-surface distance W2 between the two tie bars S12 is 165 mm or more and 175 mm or less. The compression detection device 1 is embedded in a rectangular area defined by the two axial reinforcing bars S11 and the two tie bars S12. Therefore, since the compression detection device 1 is embedded in a position where there is no structural reinforcing bar S1, the compression detection device 1 can be easily attached and detached to the concrete S2 without interfering with the structural reinforcing bar S1.

The compression detector 1 comprises a main body 10 and a linear detector 20 extending from the main body 10. In this embodiment, the detector 20 comprises an optical fiber cable 21 and a measuring instrument 22 provided at the end of the optical fiber cable 21. The optical fiber cable 21 extending from the main body 10 is arranged, for example, so as to run along the structural reinforcing bar S1 (axial reinforcing bar S11 as an example).

The measuring instrument 22 measures the irreversible deformation of the sensing material 12 (see FIG. 3) as strain, for example, by measurement using Rayleigh scattered light using the optical fiber cable 21. However, the measuring instrument 22 may also measure the strain by Brillouin measurement using the optical fiber cable 21. When the measuring instrument 22 inputs the measurement light K1 to the optical fiber cable 21, backscattered light K2 is generated in the optical fiber cable 21. The spectrum (intensity per frequency) of the backscattered light K2 changes depending on the strain. The intensity of the backscattered light K2 is smaller than the intensity of the measurement light K1. In the measurement using Rayleigh scattered light, the strain generated in the optical fiber cable 21 is detected by measuring the change in the spectrum of the backscattered light K2. Since the intensity of Rayleigh scattered light is greater than that of Brillouin scattered light, the measurement using Rayleigh scattered light has the advantage of being highly accurate and relatively resistant to light loss. With the optical fiber cable 21, it is possible to detect the irreversible deformation of the sensing material 12 with an accuracy of, for example, 1 μm of strain.

Figure 2 is a vertical cross-sectional view showing a concrete structure S and a compression detection device 1. As shown in Figures 1 and 2, for example, a storage member 30 that stores a detection device 20 (optical fiber cable 21) is buried in the concrete S2. As an example, multiple storage members 30 are buried in the concrete S2.

In the storage member 30, for example, the optical fiber cable 21 is wound in a spiral shape. As an example, the storage member 30 has a reel around which the optical fiber cable 21 is wound in a spiral shape. By storing the optical fiber cable 21 wound in this manner in the storage member 30, it is possible to efficiently store a long optical fiber cable 21. For example, a casing tube 31 extends from the storage member 30, and the optical fiber cable 21 is freely movable inside the casing tube 31.

For example, one of the multiple storage members 30 is interposed between the measuring device 22 and the main body 10. In this case, the optical fiber cable 21 extending from the storage member 30 is connected to the optical fiber cable 21 extending from the main body 10, and the optical fiber cable 21 extending from the storage member 30 to the opposite side to the main body 10 is connected to the measuring device 22.

For example, one of the two storage members 30 is arranged on the side of the measuring instrument 22, and the other of the two storage members 30 is arranged on the opposite side of the measuring instrument 22. A pair of optical fiber cables 21 extend from the main body 10. One of the pair of optical fiber cables 21 is connected to the storage member 30 on the side of the measuring instrument 22, and the other of the pair of optical fiber cables 21 is connected to the storage member 30 on the opposite side of the measuring instrument 22.

Figure 3 is a vertical cross-sectional view of the compression detection device 1, showing an enlarged view of the main body 10 of the compression detection device 1. As shown in Figure 3, the main body 10 comprises a plurality of rigid materials 11 and a detection material 12 disposed between the two rigid materials 11. The main body 10 according to this embodiment further comprises an unevenness adjusting material 13 interposed between the two rigid materials 11, a soft material 14 which is a tubular sponge surrounding the plurality of rigid materials 11, and a tubular member 15 surrounding the soft material 14.

The compression detector 1 (main body 10) is, for example, cylindrical. For example, the optical fiber cable 21 penetrates multiple rigid materials 11 so as to extend along the axis L of the compression detector 1. The height H1 (length in one direction A1) of the compression detector 1 is, for example, 100 mm or more and 160 mm or less (120 mm as an example). By setting the height H1 to 160 mm or less, the compression detector 1 can be reliably embedded in the rectangular area defined by the two axial reinforcing bars S11 and the two tie bars S12.

The diameter R of the compression detection device 1 is, for example, 40 mm or more and 100 mm or less (50 mm as an example). The height (length in one direction A1) of the rigid material 11 is, for example, 10 mm or more and 20 mm or less. However, the lower limit of the height of the rigid material 11 may be determined by the spatial resolution of the optical fiber cable 21. The thickness (length in one direction A1) of the unevenness adjustment material 13 is, for example, a few mm (5 mm as an example).

For example, the rigid material 11 protrudes further toward the end in one direction A1 than the soft material 14 and the tubular member 15. This makes it easier to apply a compressive force F to the rigid material 11. The rigid material 11 is a rigid material that has a higher rigidity than the concrete S2. The rigid material 11 is made of, for example, steel. As an example, the material of the rigid material 11 is iron. However, the material of the rigid material 11 is not limited to iron, and may be, for example, fiber-reinforced concrete that has a higher strength than the concrete S2.

The multiple rigid materials 11 are stacked along one direction A1. One direction A1 is, for example, a direction that coincides with the vertical direction D1. In this case, the compression detection device 1 can detect a compression force F in the vertical direction D1. However, one direction A1 may be a direction other than the vertical direction D1, and can be any direction.

For example, the multiple rigid materials 11 include a pair of first rigid materials 11A located at the ends in one direction A1, and a second rigid material 11B located between the pair of first rigid materials 11A. FIG. 3 shows an example having two first rigid materials 11A aligned along one direction A1, and three second rigid materials 11B located between the two first rigid materials 11A. The first rigid material 11A and the second rigid material 11B are, for example, cylindrical.

The first rigid material 11A has a pressure-receiving surface 11b that receives a compressive force F in one direction A1, an inclined surface 11c facing the opposite side of the pressure-receiving surface 11b, and an outer peripheral surface 11d. The pressure-receiving surface 11b and the inclined surface 11c are, for example, flat. The inclined surface 11c is inclined with respect to the pressure-receiving surface 11b. The inclination angle θ1 of the inclined surface 11c with respect to the pressure-receiving surface 11b is, for example, 20° or more and 30° or less. However, the inclination angle θ1 is a design value calculated based on the component force of the compressive force F received by the pressure-receiving surface 11b, and is not limited to the above angle.

The second rigid material 11B has a first inclined surface 11f, a second inclined surface 11g facing the opposite side to the first inclined surface 11f, and an outer peripheral surface 11h. The first inclined surface 11f and the second inclined surface 11g are, for example, flat. Each of the first inclined surface 11f and the second inclined surface 11g is inclined with respect to a plane perpendicular to the axis L of the second rigid material 11B.

The direction of inclination of the first inclined surface 11f and the direction of inclination of the second inclined surface 11g are different from each other. For example, the first inclined surface 11f is inclined to one side of the one direction A1 (e.g., diagonally upward) as it progresses in the radial direction A2 of the rigid material 11, and the second inclined surface 11g is inclined to the other side of the one direction A1 (e.g., diagonally downward) as it progresses in the radial direction A2 of the rigid material 11.

The inclination angle θ2 of the first inclined surface 11f relative to the plane perpendicular to the axis L, and the inclination angle θ3 of the second inclined surface 11g relative to the plane perpendicular to the axis L are the same as the inclination angle θ1. As a result, when the second rigid material 11B is layered between a pair of first rigid materials 11A, the pressure-receiving surface 11b of each first rigid material 11A extends parallel to the plane perpendicular to the axis L.

As described above, since the first rigid material 11A and the second rigid material 11B each have an inclined surface (inclined surface 11c, first inclined surface 11f, second inclined surface 11g), when a compressive force F acts on the pressure-receiving surface 11b, the first rigid material 11A and the second rigid material 11B are displaced in the radial direction A2 of the compression detection device 1 (see Figures 4(a) and 4(b)). The unevenness adjustment material 13 is provided between the inclined surface 11c and the first inclined surface 11f, between the first inclined surface 11f and the second inclined surface 11g, and between the second inclined surface 11g and the inclined surface 11c.

The unevenness adjustment material 13 is made of, for example, cement paste. By providing the unevenness adjustment material 13, even if there are minute irregularities on the inclined surface 11c, the first inclined surface 11f, or the second inclined surface 11g, the positional deviation of the rigid material 11 in the radial direction A2 caused by the compressive force F on the pressure-receiving surface 11b can be smoothed. However, in cases where the smoothness of the inclined surface 11c, the first inclined surface 11f, and the second inclined surface 11g is ensured, the unevenness adjustment material 13 can be omitted.

The detection material 12 includes, for example, a first detection material 12A, a second detection material 12B, a third detection material 12C, and a fourth detection material 12D. The first detection material 12A, the second detection material 12B, the third detection material 12C, and the fourth detection material 12D are arranged in this order along one direction A1.

The first sensing material 12A is, for example, interposed between the first rigid material 11A at one end of the direction A1 and the second rigid material 11B, and the second sensing material 12B is interposed between the second rigid material 11B on one side of the direction A1 and the second rigid material 11B in the center. The third sensing material 12C is, for example, interposed between the second rigid material 11B in the center and the second rigid material 11B on the other side of the direction A1, and the fourth sensing material 12D is interposed between the second rigid material 11B on the other side of the direction A1 and the first rigid material 11A on the other side of the direction A1.

The first detection material 12A, the second detection material 12B, the third detection material 12C, and the fourth detection material 12D are each composed of dowels 12b, 12c, and 12d that break when a compressive force F of a predetermined value or more acts on the pressure-receiving surface 11b. The dowels 12b, 12c, and 12d are made of, for example, steel. However, the dowels 12b, 12c, and 12d may be made of a material other than steel as long as they are made of a material whose shear strength is known. "A material whose shear strength is known" refers to a material whose strength against a shear force is known, or a material whose deformation against a shear force is known.

Each of the dowels 12b, 12c, and 12d is inserted, for example, into a hole formed in advance in the rigid material 11. The compressive force F when the dowel 12b of the first detection material 12A breaks, the compressive force F when the dowel 12d of the second detection material 12B breaks, the compressive force F when the dowel 12c of the third detection material 12C breaks, and the compressive force F when the dowel 12c of the fourth detection material 12D breaks are different from each other.

As an example, the first detection material 12A is composed of two dowels 12b, the second detection material 12B is composed of two dowels 12d, the third detection material 12C is composed of two dowels 12c, and the fourth detection material 12D is composed of four dowels 12c. For example, the thickness of the dowels 12b, 12c, and 12d are different from each other. As an example, the dowel 12b is the thickest, the dowel 12c is the second thickest, and the dowel 12d is the thinnest.

The first detection material 12A, the second detection material 12B, the third detection material 12C, and the fourth detection material 12D have different shear strengths. The dowels 12b, 12c, and 12d are made of materials having different shear strengths (e.g., 80 N/mm ² , 105 N/mm ² , 120 N/mm ² ). The dowels 12b, 12c, and 12d may be made of materials having different shear strengths.

As described above, by making the arrangement of the dowels 12b, 12c, and 12d in the first detection material 12A, the second detection material 12B, the third detection material 12C, and the fourth detection material 12D different from one another, the strengths of the first detection material 12A, the second detection material 12B, the third detection material 12C, and the fourth detection material 12D can be made different from one another. However, the arrangement (e.g., thickness and number) of the dowels 12b, 12c, and 12d in the first detection material 12A, the second detection material 12B, the third detection material 12C, and the fourth detection material 12D is not limited to the above-mentioned example and can be changed as appropriate.

For example, the fourth detection material 12D has the highest resistance, the first detection material 12A has the second highest resistance, the third detection material 12C has the third highest resistance, and the second detection material 12B has the lowest resistance. In this case, when a compressive force F acts on the pressure-receiving surface 11b, the second detection material 12B (two dowels 12d) breaks first, as shown in Figures 3, 4(a) and 4(b). Next, depending on the magnitude of the compressive force F acting on the pressure-receiving surface 11b, the third detection material 12C, the first detection material 12A and the fourth detection material 12D break in this order.

As described above, the first detection material 12A, the second detection material 12B, the third detection material 12C, and the fourth detection material 12D are irreversibly deformed (e.g., broken) when a compressive force F acts on the pressure-receiving surface 11b. This irreversible deformation is detected by the detection device 20 (optical fiber cable 21), making it possible to know after the fact how much compressive force F acted on the concrete structure S.

Figure 4(a) shows an example in which only the second detection material 12B has undergone irreversible deformation, while Figure 4(b) shows an example in which the second detection material 12B and the third detection material 12C have undergone irreversible deformation. Figure 4(b) shows an example in which a larger compressive force F has been received than in the case of Figure 4(a), and more of the detection material 12 has become irreversibly deformed than in the case of Figure 4(a). In this way, the degree to which the detection material 12 deforms changes depending on the magnitude of the compressive force F received by the pressure-receiving surface 11b, so by detecting the degree to which the detection material 12 has undergone deformation, it is possible to know after the fact how much compressive force F the concrete structure S has received in the past.

That is, the detection device 20 detects which of the first detection material 12A, the second detection material 12B, the third detection material 12C, and the fourth detection material 12D has undergone irreversible deformation, thereby making it possible to know after the fact the maximum compressive force F that the concrete structure S has received in the past. In the above example, the detection material 12 includes the first detection material 12A, the second detection material 12B, the third detection material 12C, and the fourth detection material 12D (four layers). However, the number of layers of the detection material 12 and the number of rigid materials 11 may be two, three, five or more layers and can be changed as appropriate.

When the first detection material 12A, the second detection material 12B, the third detection material 12C, and the fourth detection material 12D are irreversibly deformed, the rigid material 11 shifts in the radial direction A2, and a part of the rigid material 11 compresses the soft material 14. The soft material 14 is made of, for example, a sponge that can freely deform as the rigid material 11 enters. The tubular member 15 is made of, for example, polyvinyl chloride, steel, or acrylic. The tubular member 15 is preferably made of a material with a small elastic modulus that is unlikely to hinder the behavior of the compression detection device 1 in one direction A1. However, the material of the tubular member 15 is not particularly limited.

Figures 5, 6(a) and 6(b) are diagrams for explaining examples of the arrangement of the optical fiber cable 21 in the compression detection device 1. For example, each of the first rigid material 11A and the second rigid material 11B has a hole 11j through which the optical fiber cable 21 is inserted. The hole 11j has an extension portion 11k extending along one direction A1 and an expanding portion 11m that opens into the inclined surfaces (inclined surface 11c, first inclined surface 11f, second inclined surface 11g) of the rigid material 11 and expands in diameter toward the inclined surfaces.

The optical fiber cable 21 is inserted into the hole 11j while being housed in the casing tube 23, for example. The casing tube 23 is made of a flexibly deformable material and has, for example, a bellows shape. In addition, a pair of enlarged diameter portions 11m face each other on a pair of inclined surfaces arranged in one direction A1 in the plurality of rigid materials 11. Therefore, the optical fiber cable 21 (casing tube 23) can be gently deformed in the area where the pair of enlarged diameter portions 11m face each other, thereby reducing the possibility of the optical fiber cable 21 breaking.

The above describes an example in which the optical fiber cable 21 is arranged along the axis L of the compression detection device 1. However, the arrangement of the optical fiber cable 21 is not limited to the above example. Figures 7(a), 7(b), and 7(c) are diagrams showing modified examples of the arrangement of the optical fiber cable 21.

As shown in FIG. 7(a), the optical fiber cable 21 may be attached to multiple rigid materials 11 so as to follow the surfaces of the multiple rigid materials 11. In this case, for example, the optical fiber cable 21 is arranged linearly in one direction A1 so as to follow the outer peripheral surface 11d of the first rigid material 11A and the outer peripheral surface 11h of the second rigid material 11B.

As shown in FIG. 7(b), multiple optical fiber cables 21 may be attached to the compression detection device 1. The optical fiber cables 21 may include a first optical fiber cable 21b arranged along the surfaces of the multiple rigid materials 11, and a second optical fiber cable 21c arranged inside the multiple rigid materials 11. FIG. 7(b) shows an example in which one first optical fiber cable 21b and two second optical fiber cables 21c are provided.

As shown in FIG. 7(c), the optical fiber cable 21 may be spirally wound around multiple rigid materials 11. In this case, by spirally winding the optical fiber cable 21 around multiple rigid materials 11, the number of measurement points by the optical fiber cable 21 in one direction A1 can be increased.

Next, a compression detection device 41 according to a modified example will be described with reference to FIG. 8. Since part of the configuration of the compression detection device 41 is the same as part of the configuration of the compression detection device 1 described above, the same reference numerals will be used below to omit the description of the same configuration as that of the compression detection device 1 as appropriate. As shown in FIG. 8, in the compression detection device 41, the configuration of the detection material 42 is different from the configuration of the detection material 12 described above. Also, the optical fiber cable 21 is spirally wound around multiple rigid materials 11.

The compression detection device 41 does not have dowels 12b, 12c, 12d and unevenness adjustment material 13, and instead of the unevenness adjustment material 13, a damage detection material 43 is provided in the compression detection device 41. The compressive strength of the damage detection material 43 is smaller than the compressive strength of the rigid material 11. The damage detection material 43 includes, for example, a first damage detection material 43b, a second damage detection material 43c, a third damage detection material 43d, and a fourth damage detection material 43f.

The compressive strengths of the first damage detection material 43b, the second damage detection material 43c, the third damage detection material 43d, and the fourth damage detection material 43f are different from one another. As an example, the compressive strength of the first damage detection material 43b is the smallest, the compressive strength of the second damage detection material 43c is the second smallest, the compressive strength of the third damage detection material 43d is the third smallest, and the compressive strength of the fourth damage detection material 43f is the largest. In this case, the first damage detection material 43b is most susceptible to damage (easily cracked) due to the compressive force F on the pressure-receiving surface 11b, the second damage detection material 43c is second most susceptible to damage, the third damage detection material 43d is third most susceptible to damage, and the fourth damage detection material 43f is least susceptible to damage.

As described above, the first damage detection material 43b, the second damage detection material 43c, the third damage detection material 43d, and the fourth damage detection material 43f are irreversibly deformed (cracks are generated) when a compressive force F acts on the pressure-receiving surface 11b. By detecting this irreversible deformation with the detection device 20, it is possible to know after the fact how much compressive force F acted on the concrete structure S.

In addition, instead of the damage detection material 43, multiple types of plastic materials may be laminated between the two rigid materials 11, and the strength of plasticization of the multiple types of plastic materials may differ from one another. In this case, the detection device 20 can detect the presence or absence of remaining deformation of the plastic material, thereby detecting the maximum response of the past compressive force F. In addition, the friction coefficient between the two rigid materials 11 (inclined surfaces) may be controlled to control the timing at which the inclined surfaces shift (start to slide).

Next, a method for replacing a compression detector according to this embodiment will be described with reference to Figs. 9(a), 9(b), and 9(c). Below, an example of a method for replacing an existing compression detector 1 with a new compression detector 1 will be described. The timing for replacing an existing compression detector 1 can be, for example, when the dowels 12b, 12c, and 12d of the existing compression detector 1 break, making it necessary to install a new compression detector 1.

First, as shown in FIG. 9(a), concrete S2 is scraped to form a hole S4, and the existing compression detector 1 is exposed in the hole S4 (process of exposing the compression detector). For example, concrete S2 in a rectangular area (see FIG. 1) defined by two axial reinforcing bars S11 and two tie bars S12 is scraped with a core drill to expose the compression detector 1 that was embedded in the concrete S2.

Next, as shown in FIG. 9(b), the detector 20 (optical fiber cable 21) extending from the existing compression detector 1 is cut and the existing compression detector 1 is removed from the hole S4 (step of removing the compression detector). After that, the detector 20 is pulled out from the storage member 30 into the hole S4 (step of pulling out the detector). At this time, the detector 20 extending from the storage member 30 into the inside of the casing tube 31 is pulled into the hole S4.

Then, as shown in FIG. 9(c), a new compression detector 1 is placed in the hole S4 (step of placing the compression detector). At this time, the compression detector 1 is placed in the hole S4 so that, for example, one direction A1 (the stacking direction of the multiple rigid materials 11) of the compression detector 1 coincides with the vertical direction, and the optical fiber cable 21 is pulled out from the compression detector 1 in both the up and down directions.

Next, the detection device 20 pulled out from the storage member 30 into the hole S4 is connected to the detection device 20 of the new compression detection device 1 (process of connecting the detection device). After that, concrete S2 is filled into the hole S4 (process of filling concrete). Then, after the filled concrete S2 has hardened, the series of steps of the replacement method is completed.

Next, the effects obtained from the compression detection device 1 and replacement method according to this embodiment will be described in detail. As illustrated in Figures 3 and 8, the compression detection device 1 includes a plurality of rigid materials 11 having a higher rigidity than concrete S2, detection materials 12, 42 interposed between two rigid materials 11 arranged in one direction A1, and a detection device 20 that detects the deformation of the detection materials 12, 42 that deform irreversibly due to a compressive force F.

The detection materials 12, 42 deform irreversibly when subjected to a compressive force F equal to or greater than a predetermined value. Therefore, even if multiple rigid materials 11 having higher rigidity than the concrete S2 are subjected to a compressive force F, the detection materials 12, 42 will not deform if the compressive force F is not equal to or greater than the predetermined value. On the other hand, the detection materials 12, 42 deform irreversibly if the compressive force F is equal to or greater than a predetermined value. By detecting the irreversible deformation of the detection materials 12, 42 with the detection device 20, it is possible to determine whether the compressive force F that the concrete S2 has been subjected to has been equal to or greater than a predetermined value.

In other words, when the detection device 20 detects irreversible deformation of the detection materials 12, 42, it can be determined that the maximum compressive force F received by the concrete S2 is equal to or greater than a predetermined value, and when the detection device 20 does not detect irreversible deformation of the detection materials 12, 42, it can be determined that the maximum compressive force F is not equal to or greater than the predetermined value. Therefore, it is possible to retroactively determine the past history or maximum response of the compressive force F received by the concrete S2.

The detection device 20 may include a plurality of rigid materials 11 and an optical fiber cable 21 that contacts the detection materials 12, 42. In this case, the optical fiber cable 21 can detect irreversible deformation of the detection materials 12, 42 with high accuracy. Since the optical fiber cable 21 can detect strain along the point where the optical fiber cable 21 contacts, it can detect which detection material 12, 42 has deformed when the optical fiber cable 21 is installed across multiple detection materials 12, 42. In other words, the optical fiber cable 21 can detect the presence or absence of deformation of multiple detection materials 12, 42, so it can grasp the history of the compressive force F that has been applied in the past with high accuracy.

The detection material 12 may include dowels 12b, 12c, and 12d that are interposed between two rigid materials 11 and break when a compressive force F of a predetermined value or more is applied to the rigid material 11. In this case, the detection device 20 detects whether the dowels 12b, 12c, and 12d have broken, making it easy to know whether the compressive force F applied to the concrete S2 was a predetermined value or more.

The optical fiber cable 21 may be spirally wound around multiple rigid materials 11 and the sensing materials 12, 42. In this case, the optical fiber cable 21 that detects the deformation of the sensing materials 12, 42 is spirally wound, so that the number of measurement points of the optical fiber cable 21 in one direction A1 can be increased. Therefore, the detection of the deformation of the sensing materials 12, 42 by the optical fiber cable 21 can be performed with higher accuracy.

In the method for replacing the compression detector 1 according to this embodiment, as shown in FIG. 9(a) to FIG. 9(c), the compression detector 1 and the storage member 30 for storing the linear detector 20 (optical fiber cable 21) are embedded in the concrete S2, and the compression detector 1 is taken out from a hole S4 formed by scraping the concrete S2. The compression detector 1 is exposed from the hole S4 formed by scraping the concrete S2, and the linear detector 20 of the exposed compression detector 1 is cut and taken out from the hole S4. The linear detector 20 stored in the storage member 30 is pulled out to the hole S4, and the detector 20 of the new compression detector 1 is connected to the pulled out detector 20. After the new compression detector 1 is installed in the hole S4 in this state, the hole S4 is filled with concrete S2. Therefore, the compression detector 1 can be easily attached and detached from the hole S4. In addition, since the compression detector 1 described above is used in this replacement method, the history of the compressive force received from the past can be grasped with high accuracy.

The above describes embodiments of the compression detection device and replacement method according to the present disclosure. However, the compression detection device and replacement method according to the present disclosure are not limited to the above-mentioned embodiments or various examples, and can be modified as appropriate within the scope of the gist described in the claims. In other words, the configuration, shape, size, material, number and arrangement of each part of the compression detection device, as well as the content and order of the steps of the replacement method, can be modified as appropriate within the scope of the above-mentioned gist.

For example, in the above embodiment, a detection device 20 having an optical fiber cable 21 has been described. However, the detection device may not have an optical fiber cable 21. For example, the detection device may have a heating wire instead of the optical fiber cable 21. For example, the compression detection device may have multiple heating wires arranged on multiple rigid materials 11, and estimate the compression force F from the state of the broken heating wires.

In the above embodiment, an example was described in which the multiple rigid materials 11 include a first rigid material 11A having an inclined surface 11c and a second rigid material 11B having a first inclined surface 11f and a second inclined surface 11g. However, the multiple rigid materials 11 may not have an inclined surface, and the shape of the rigid materials, etc. can be changed as appropriate. The same applies to the detection material.

In the above embodiment, an example was described in which the compression detection device 1 was embedded in a concrete structure S provided at the base of a pier. However, the compression detection device can also be applied to concrete structures other than the base of a pier. In other words, the compression detection device according to the present disclosure can be applied to various concrete structures.

Reference Signs List 1, 41...Compression detection device, 10...Main body, 11...Rigid material, 11A...First rigid material, 11B...Second rigid material, 11b...Pressure receiving surface, 11c...Inclined surface, 11d...Outer peripheral surface, 11f...First inclined surface, 11g...Second inclined surface, 11h...Outer peripheral surface, 11j...Hole, 11k...Extended portion, 11m...Expanded diameter portion, 12, 42...Detection material, 12A...First detection material, 12B...Second detection material, 12C...Third detection material, 12D...Fourth detection material, 12b, 12c, 12d...Dowel, 13...Unevenness adjustment material, 14...Soft material, 15...Tubular member, 20...Detection device, 21...Optical fiber cable , 21b...first optical fiber cable, 21c...second optical fiber cable, 22...measuring instrument, 23...casing tube, 30...storage member, 31...casing tube, 43...damage detection material, 43b...first damage detection material, 43c...second damage detection material, 43d...third damage detection material, 43f...fourth damage detection material, A1...one direction, A2...radial direction, D1...vertical direction, D2...horizontal direction, F...compressive force, H1...height, L...axis, S...concrete structure, S1...structural rebar, S2...concrete, S4...hole, S11...axial rebar, S12...hoop rebar, W1...spacing.

Claims (5)

A compression detection device embedded in concrete, comprising:
A plurality of rigid materials having a higher rigidity than the concrete and laminated in one direction;
A sensing material disposed between two of the rigid materials aligned along the one direction;
a sensing device that senses irreversible deformation of the sensing material due to a compressive force in the one direction on the rigid material;
A compression sensing device comprising: The detection material includes a dowel that is interposed between two of the rigid materials and breaks when a compressive force equal to or greater than a predetermined value is applied to the rigid materials.
2. The compression sensing device of claim 1. the sensing device includes a plurality of the rigid materials and a fiber optic cable in contact with the sensing materials;
3. A compression sensing device according to claim 1 or 2. the fiber optic cable is helically wrapped around a plurality of the stiffening materials and the sensing material;
4. The compression sensing device of claim 3. A method for replacing a compression detection device according to any one of claims 1 to 4, which is embedded in concrete and includes a linear detection device that detects a compressive force on the concrete, comprising:
A housing member housing the detection device is buried in the concrete,
exposing the compression detection device through a hole formed by scraping the concrete;
removing the compression detector from the hole by cutting the detector extending from the compression detector;
Pulling the detection device out of the storage member into the hole;
placing the novel compression sensing device in the hole;
connecting the extracted detector to the detector of the new compression detector;
filling the hole with concrete;
An exchange method comprising:

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