JP2019158834A - Optical fiber sensor installation method detecting concrete deterioration due to frost damage and method for detecting concrete structure deterioration - Google Patents

Abstract

To provide an optical fiber sensor installation method for correctly detecting a deteriorated condition of a concrete structure at an early stage.SOLUTION: The optical fiber sensor installation method for detecting concrete deterioration due to the frost damage is provided that includes at least the steps of: installing a first optical fiber sensor 101 which detects strain on the basis of characteristics of change in a propagating light wave into the inside of a concrete structure before or during placement of concrete; installing a temperature sensor in the vicinity of an FBG part 105 of the first optical sensor; and burying the first optical fiber sensor and the temperature sensor installed inside the concrete structure into concrete.SELECTED DRAWING: Figure 6A

Description

  The present invention relates to a method for installing an optical fiber sensor for detecting deterioration of concrete due to frost damage and a method for detecting deterioration of a concrete structure.

  A typical deterioration of concrete structures in cold regions is frost damage. Freezing damage is a phenomenon in which concrete is deteriorated by cracking, scaling, etc. from the concrete surface due to freezing and thawing action that repeats freezing and thawing due to the influence of ambient temperature and solar radiation on moisture in the concrete. It often impairs durability, and is one of the important issues in the maintenance of concrete structures.

  Since neutralization, salt damage, and alkali-aggregate reaction, which are typical deterioration of concrete, are accompanied by chemical changes due to deterioration, it is possible to quantitatively grasp the cause and degree of progress of deterioration. On the other hand, deterioration due to frost damage causes volume expansion when water in the concrete freezes, and if there is no gap in the concrete to absorb volume expansion, the expansion pressure will cause cracks in the concrete. Causes scaling. In other words, the deterioration due to frost damage is a physical deterioration due to the expansion of moisture in the concrete, and therefore the deterioration is often judged based on situational evidence such as surface cracks and scaling.

  Conventionally, as a method for evaluating the frost damage resistance of concrete, in laboratory experiments, the degree of deterioration of concrete due to frost damage is diagnosed using the relative dynamic elastic modulus obtained from the change in the primary resonance frequency of the specimen as a deterioration index. In general, evaluation of a concrete structure is performed by collecting the core of the concrete structure and examining the distribution of ultrasonic propagation velocity to evaluate the frost damage deterioration depth and the deterioration degree.

  On the other hand, since core removal is a destructive test and damages the structure, studies are being made to evaluate frost damage degradation using a non-destructive test. Although a method for evaluating the degree of deterioration from the concrete surface by the ultrasonic method has been reported, the method for evaluating the concrete surface to the last is not established.

  In Patent Document 1 and Patent Document 2, a frost damage deterioration curve at a predicted point reflecting a characteristic value based on concrete structure data is predicted based on a concrete frost damage deterioration curve based on an exposure test at a reference point in a natural environment. Technology is disclosed.

JP 2005-156547 A JP 2008-249733 A

  In concrete structures, deterioration due to frost damage progresses gradually from the surface, and it is important to know the depth of deterioration. However, in the evaluation method for concrete frost resistance, when evaluating a concrete structure, generally the core of the concrete structure is collected and the distribution of ultrasonic wave propagation speed is investigated, so that Evaluation is performed. Thus, since different evaluation methods are used for the indoor experiment and the actual structure, it is difficult to compare the indoor experiment with the actual structure. Moreover, since the frequency of freezing and thawing in the concrete structure differs between the shade and the sun, the degree of deterioration of the concrete also differs. In such a case, it is preferable to grasp the deterioration depth and degree of deterioration at a plurality of locations in the concrete structure, but it is difficult to perform core removal at the plurality of locations in the concrete structure.

  Patent Document 1 and Patent Document 2 are technologies for predicting a frost damage deterioration curve at a predicted point reflecting a characteristic value based on concrete structure data based on a frost damage deterioration curve of concrete based on an exposure test, It does not show the deterioration of the concrete structure itself.

  In addition, although a method for detecting strain using an optical fiber sensor has been proposed, an optical fiber sensor can be embedded in a concrete structure to accurately and efficiently detect the deterioration of the concrete structure due to frost damage. Such an optical fiber sensor installation method and a concrete structure deterioration detection method have not been established.

  This invention is made in view of such a situation, and provides the installation method of the optical fiber sensor which detects the deterioration condition in a concrete structure early and correctly, and the deterioration detection method of a concrete structure. Objective.

  (1) In order to achieve the above object, the present invention takes the following measures. That is, the installation method of the present invention is an installation method of an optical fiber sensor that detects deterioration of concrete due to frost damage, and is a characteristic of changes in propagating light waves before or during the placement of concrete. A step of installing a first optical fiber sensor for detecting strain on the basis of a concrete structure, a step of installing a temperature sensor in the vicinity of a strain detecting portion of the first optical fiber sensor, and the concrete It includes at least a step of embedding the first optical fiber sensor and the temperature sensor installed in the structure with concrete.

  In this way, before placing concrete or during placing concrete, the first optical fiber sensor that detects strain based on the characteristics of changes in the propagating light wave is installed inside the concrete structure, A temperature sensor is installed in the vicinity of the strain detection section of the first optical fiber sensor, and the first optical fiber sensor and the temperature sensor installed in the concrete structure are embedded with concrete. From this strain, it is possible to detect the deterioration status in the structure due to frost damage and accurately grasp the range that needs repair. Moreover, since the temperature sensor is installed in the vicinity of the strain detection unit, the strain of the concrete can be calculated in consideration of the strain due to the temperature change. In addition, since the temperature history of the concrete becomes clear, it can be easily judged that the deterioration due to frost damage has occurred without performing detailed analysis.

  (2) In the installation method of the present invention, the first optical fiber sensor is embedded in parallel to the surface of the concrete structure, and the temperature sensor is a strain of the first optical fiber sensor. It is embedded at substantially the same depth as the detector.

  As described above, the first optical fiber sensor is embedded in parallel to the surface of the concrete structure, and the temperature sensor is embedded at substantially the same depth as the strain detection portion of the first optical fiber sensor. Therefore, the strain can be monitored over a wide range of the structure while considering the change in strain due to the temperature change. As a result, even if there is a place where the deterioration state is different in the same structure, the deterioration portion and the deterioration state can be identified and the range where repair is necessary can be accurately grasped.

  (3) In the installation method of the present invention, the first optical fiber sensor is embedded perpendicularly to the surface of the concrete structure, and the temperature sensor is a strain of the first optical fiber sensor. It is embedded at substantially the same depth as the detector.

  As described above, the first optical fiber sensor is embedded perpendicularly to the surface of the concrete structure, and the temperature sensor is embedded at substantially the same depth as the strain detection portion of the first optical fiber sensor. Therefore, it is possible to grasp the deterioration depth of the concrete structure while taking into account the strain change due to the temperature change, and to accurately grasp the range where the repair is necessary.

  (4) In the installation method of the present invention, the first optical fiber sensor is embedded in a depth direction from the surface of the concrete structure, and the temperature sensor includes the first light. The strain sensor is buried at substantially the same depth as the strain detection part of the fiber sensor.

  As described above, the first optical fiber sensor is embedded in the depth direction from the surface of the concrete structure, and the temperature sensor is substantially the same as the strain detection unit of the first optical fiber sensor. Since it is buried in the depth, the interval between the buried depths of the strain detectors can be shortened while ensuring adhesion with the concrete, and the inside of the concrete structure can be monitored with higher accuracy.

  (5) In the installation method of the present invention, the first optical fiber sensor is spirally embedded in the depth direction from the surface of the concrete structure, and the temperature sensor includes the first light. The strain sensor is buried at substantially the same depth as the strain detection part of the fiber sensor.

  As described above, the first optical fiber sensor is spirally embedded in the depth direction from the surface of the concrete structure, and the temperature sensor is substantially the same as the strain detection unit of the first optical fiber sensor. Since it is buried in the depth, the interval between the buried depths of the strain detectors can be shortened while ensuring adhesion with the concrete, and the inside of the concrete structure can be monitored with higher accuracy.

  (6) In the installation method of the present invention, the temperature sensor includes a second optical fiber sensor that detects a temperature based on a characteristic of a change of a propagating light wave, and an outer periphery of the second optical fiber sensor. And one or more of the temperature sensors are embedded in the concrete of the concrete structure so as to be along the first optical fiber sensor.

  As described above, the temperature sensor includes the second optical fiber sensor that detects the temperature based on the characteristics of the change of the propagating light wave, and the covering that covers the outer periphery of the second optical fiber sensor. Since one or more temperature sensors are embedded along the first optical fiber sensor inside the concrete of the structure to be measured, in the concrete structure to be measured, the strain with respect to the temperature at the time of measurement is grasped in advance. Therefore, more accurate strain due to temperature change can be measured in real time. As a result, it is possible to calculate a more accurate residual strain and to grasp the deterioration state.

  (7) Further, the deterioration detection method of the present invention is a deterioration detection method for detecting deterioration of concrete due to frost damage, and the first optical fiber sensor before or during placing concrete. In the concrete structure, in the vicinity of the strain detector of the first optical fiber sensor, in the vicinity of the strain sensor, the first optical fiber sensor and the temperature installed in the concrete structure. A step of embedding the sensor with concrete, a step of measuring strain of the concrete based on a change in characteristics of light waves propagating in the first optical fiber sensor, and detecting characteristics of the measured strain over time And detecting deterioration of the concrete due to frost damage based on the characteristics of the detected strain over time. Deterioration detection method according to claim.

  In this way, before placing concrete or during placing concrete, the first optical fiber sensor that detects strain based on the characteristics of changes in the propagating light wave is installed inside the concrete structure, A temperature sensor is installed in the vicinity of the strain detection portion of the first optical fiber sensor, the first optical fiber sensor and the temperature sensor installed in the concrete structure are embedded in concrete, and the first optical fiber sensor Measure the strain of concrete based on the characteristic change of the light wave propagating through the wall, detect the characteristic of the time-dependent change of the measured strain, and reduce the concrete deterioration due to frost damage based on the characteristic of the time-dependent change of the detected strain. Since it detects, it becomes possible to embed an optical fiber sensor in the actual structure and measure the strain. As a result, it is no longer necessary to collect a core of a concrete structure in order to investigate the distribution of ultrasonic propagation velocity as has been done so far. In addition, the measurement of the relative dynamic elastic modulus cannot be applied to an actual structure. However, in the deterioration detection method according to the present invention, it is possible to measure easily and constantly by embedding an optical fiber sensor in concrete. It is possible to detect the deterioration state in the concrete early and accurately. In addition, since the temperature history of the concrete becomes clear, it can be easily judged that the deterioration due to frost damage has occurred without performing detailed analysis.

  (8) Moreover, the deterioration detection method of this invention is further characterized by including the process of removing the distortion by the temperature change measured using the said temperature sensor from the detected distortion of the concrete.

  Thus, since the distortion by the temperature change measured using the temperature sensor is removed from the detected distortion of the concrete, it is not necessary to measure the distortion at a specific temperature in advance, and versatility is enhanced.

  According to the present invention, it is possible to detect a deterioration state of a concrete structure due to frost damage with high accuracy and efficiency. Thereby, the deterioration location and deterioration condition of a concrete structure are grasped, and the range which needs repair can be specified correctly.

It is a figure which shows the test body used in order to verify whether an optical fiber sensor detects distortion by deterioration of concrete by frost damage. It is a figure which shows the distortion | strain measurement result of the optical fiber sensor in each cycle, and the value of the relative dynamic elastic modulus in each cycle. It is a figure (deterioration state) which shows the measurement result of the optical fiber sensor in a verification example 2, and a relative dynamic elastic modulus. It is a figure (deterioration state) which shows the mass change rate in the verification example 2. FIG. It is a figure (sound state) which shows the measurement result of the optical fiber sensor in relative example 2, and a relative dynamic elastic modulus. It is a figure which shows the outline of the example of installation of the optical fiber sensor in Example 1. FIG. It is a figure which shows the outline of the example of installation of the optical fiber sensor in Example 1. FIG. It is a figure which shows the outline of the example of installation of the optical fiber sensor in Example 1. FIG. It is a figure which shows the outline of the example of installation of the optical fiber sensor in Example 2. FIG. It is a figure which shows the outline of the example of installation of the optical fiber sensor in Example 2. FIG. 6 is a diagram illustrating an outline of an installation example of an optical fiber sensor in Embodiment 3. FIG. 6 is a diagram illustrating an outline of an installation example of an optical fiber sensor in Embodiment 3. FIG. It is a figure which shows the outline of the example of installation of the optical fiber sensor in Example 4. FIG.

  The inventors focused on the situation where deterioration due to frost damage to a concrete structure in a cold region is judged based on the situation evidence deterioration such as cracking and scaling of the concrete surface, and an optical fiber sensor is attached to the concrete structure. The present inventors have found an installation method of an optical fiber sensor that embeds and detects a deterioration state of a concrete structure caused by frost damage with high accuracy and efficiency, and has led to the present invention. Hereinafter, embodiments of the present invention will be described.

First, the mechanism of frost damage will be explained. Freezing damage is a deterioration phenomenon caused by expansion when moisture in concrete freezes. Water causes a 9% volume expansion when frozen. Concrete generally shrinks or expands in response to temperature changes. In the normal temperature range, the linear expansion coefficient is about 10 × 10 ⁻⁶ / ° C. When a temperature drop occurs, the moisture in the concrete freezes and an expansion pressure is generated. The water in the concrete repeatedly freezes and thaws, and the concrete expanded by the expansion pressure of water at the time of freezing does not shrink at the time of melting and remains as a residual strain. This residual strain causes cracks, scaling, etc. from the concrete surface and degrades the concrete.

  In the deterioration detection method according to the present embodiment, an optical fiber sensor is embedded in a concrete structure, thereby calculating a residual strain caused by frost damage and detecting deterioration due to frost damage. Residual strain appears as strain in the optical fiber sensor when subjected to melting in the concrete. Since the strain of the optical fiber sensor includes strain caused by the temperature effect, the strain obtained by removing the strain caused by the temperature effect from the strain of the optical fiber sensor becomes the residual strain at the time of melting.

  Thus, by measuring the strain of the optical fiber sensor during the melting period, the degree of deterioration of the concrete due to frost damage can be determined. In addition, since a plurality of sensors can be installed on one thin cable, an optical fiber sensor can measure a plurality of parts with one extremely thin optical fiber sensor when used in a concrete structure. Can do. Moreover, the deterioration depth of a concrete structure can be monitored by embedding an optical fiber sensor in the depth direction. If it is an optical fiber sensor, the cable connected to the optical fiber sensor should be extended to a place where measurement is possible even in places where it is difficult to perform core removal or ultrasonic work in concrete structures. Thus, measurement can be easily performed.

  In addition, as an evaluation method of frost damage, when an optical fiber sensor is embedded in a concrete structure, the embedded optical fiber sensor is one (one sensor unit (hereinafter also referred to as FGB unit or strain detection unit)), Multiple books are acceptable. Further, one FBG section may be provided for one optical fiber sensor, or a plurality of FBG sections may be provided. In an actual structure in which deterioration gradually proceeds from the surface, the deterioration state can be grasped in more detail by installing optical fiber sensors at as short intervals as possible in the depth direction from the surface layer portion. If the optical fiber sensor is embedded at a depth of 1 to 4 cm from the end or surface of the concrete, or at an intermediate depth of the concrete, the deterioration state of the concrete can be grasped in more detail.

[Detection method]
An optical fiber sensor having an FBG portion is embedded in concrete and connected to an optical fiber measuring instrument. The optical fiber sensor is distorted by a temperature change. The thermometer may use a thermocouple, and is not limited to a thermocouple as long as the temperature inside the concrete can be measured. In the strain of the optical fiber sensor excluding the influence (strain) due to temperature change, the strain value when the concrete is melted is measured. When the strain measured at a specific temperature is used, the strain that the optical fiber sensor receives at that temperature is constant, so that it is not necessary to correct the strain due to the temperature change.

[Verification Example 1]
FIG. 1 is a view showing a test body used for verifying whether an optical fiber sensor detects strain due to deterioration of concrete due to frost damage. The materials used in Verification Example 1 are as shown in Table 1. In addition, the composition of the materials used in Verification Example 1 is as shown in Table 2. Concrete 17 prepared by mixing the materials shown in Table 1 with the composition shown in Table 2 is poured into two steel molds 15, one with an optical fiber sensor 11 and the other with a thermometer 21. Embed in the state of hanging in the center of 15. After embedding the optical fiber sensor 11, the concrete 17 and the FBG portion 13 of the optical fiber sensor 11 need to be integrally shrunk or expanded. Therefore, when the optical fiber sensor 11 is embedded, the concrete 17 It is embedded so as to adhere to the FBG portion 13 of the fiber sensor 11. Further, the optical fiber sensor 11 may be embedded in the concrete 17 in a tensioned state (a state where tension is generated). In Verification Example 1, an FBG sensor is used as the optical fiber sensor, but the present invention is not limited to this.

  As shown in FIG. 1, the optical fiber sensor 11 is previously installed in the steel mold 15 so that the FBG portion 13 is positioned at the center of the test body (columnar shape), and concrete is poured and molded. Moreover, the test body which embedded thermometers 21, such as a thermocouple, is produced | generated similarly, and the temperature in the concrete 17 is measured. The measurement unit 23 of the FBG unit 13 and the thermometer 21 of the optical fiber sensor 11 has a vertical fog of 100 mm.

  Thereafter, water curing was performed for 28 days, and a freeze-thaw test was performed in a constant temperature and humidity chamber. The freezing and thawing conditions were one cycle (11 hours), and the concrete center temperature (environmental temperature) was changed from 5 ° C. to −20 ° C. to 5 ° C.

  FIG. 2 is a diagram showing the strain measurement result of the optical fiber sensor in each cycle and the value of the relative dynamic elastic modulus in each cycle. The strain of the optical fiber sensor shown in FIG. 2 is a value obtained by subtracting the strain caused by the change in the environmental temperature, and indicates the maximum value at the time of melting after removing the influence due to the change in the environmental temperature. The strain of the optical fiber sensor increases as the cycle progresses.

  This indicates a residual strain in which the concrete has deteriorated due to freezing and thawing. Compared with the value of the relative kinematic elastic modulus shown in Fig. 2, both values change greatly in the vicinity of 38 cycles. Therefore, the residual strain of concrete can be measured with an optical fiber sensor, and deterioration due to frost damage can be judged. It is. It was also confirmed that strain could be measured even in a range below 80% of the relative kinematic modulus indicated by JIS A 1148 that frost damage resistance is effective.

  Therefore, if this test body is used, the resistance with respect to the freeze-thaw action of concrete can be evaluated. Moreover, before using concrete for a structure, it becomes possible to evaluate freeze-thaw resistance and to develop or select concrete having high freeze-thaw resistance. In the present invention, freeze-thaw resistance is also referred to as resistance to frost damage, and the resistance to a phenomenon (frost damage) that causes deterioration and collapse of the composition due to repeated freezing and thawing of water present in the cement composition. Sex and tolerance.

[Verification Example 2]
Furthermore, using a freeze / thaw tank, the effectiveness of the judgment of deterioration due to freezing damage due to residual strain of concrete measured by an optical fiber sensor was verified. In the verification example 2, the test body A having the same material, composition, and test body shape as in the verification example 1 was different from the verification example 1 only in the air amount (air amount: 4.8%). . The freeze-thaw test was performed using a freeze-thaw test apparatus in accordance with JIS A 1148 (4 hours per cycle). In addition, when a freeze / thaw test apparatus is used, the temperature can be known without installing the thermometer 21.

  FIG. 3 is a diagram illustrating measurement results of the optical fiber sensor and the relative kinematic modulus of the test specimen A in which deterioration occurred in Verification Example 2. FIG. 4 is a diagram showing the mass change rate of the test specimen A in which deterioration occurred in the verification example 2. FIG. 5 is a diagram illustrating measurement results of the optical fiber sensor and the relative dynamic elastic modulus of a healthy test body B in which no deterioration occurs in Verification Example 2.

  As shown in FIG. 3, the specimen A is considered to be able to measure the residual strain due to freezing and thawing because the value of the relative kinematic elastic coefficient increases as the strain of the optical fiber sensor increases. In addition, the strain of the optical fiber sensor of the specimen A has increased from around 20 cycles, whereas the relative dynamic elastic modulus has not decreased. That is, the optical fiber sensor can detect even a minute deterioration that does not appear in the relative dynamic elastic modulus.

  Moreover, as shown in FIG. 4, the concrete of the test body A has increased in mass and is wet-expanded due to water absorption. That is, the residual strain shown in FIG. 3 includes a strain due to wet expansion.

  On the other hand, as shown in FIG. 5, the healthy specimen B in which residual strain due to freezing and thawing hardly occurs does not have a decreased relative dynamic elastic modulus, but the strain due to the optical fiber slightly increases. Since the strain shown in FIG. 5 is strain due to wet expansion, the strain due to wet expansion of concrete is obtained by subtracting the strain value of test body B shown in FIG. 5 from the strain value of test body A shown in FIG. Can be canceled. As a result, the accurate residual strain of the specimen A can be calculated.

  A healthy specimen B that has not deteriorated for measuring the wet expansion of concrete can be produced by increasing the amount of air by 0.5 to 4% as compared with the specimen A to be tested. If the amount of increase in the air amount is less than 0.5%, the healthy specimen B that has not deteriorated cannot be delayed more than the specimen A to be tested, or due to freezing and thawing due to frost damage. It may contain residual strain. Moreover, when the increase amount of air amount exceeds 4%, the tendency of wet expansion may deviate from the test body A. In addition, a more accurate residual strain may be calculated by preparing a specimen exactly the same as the measurement target and measuring and canceling the strain due to wet expansion by curing in water.

[Installation method]
Next, an installation method will be described. First, concrete is laid up to a position where an optical fiber sensor (first optical fiber sensor, second optical fiber sensor) is installed. After that, an optical fiber sensor is installed, and concrete is placed. The optical fiber sensor may be installed inside the concrete structure before placing concrete, or may be installed inside the concrete structure during placing concrete.

  The first optical fiber sensor 101 includes one or more FBG units 105 and is an optical fiber sensor that measures strain in a concrete structure. When embedding the first optical fiber sensor 101, the concrete 107 is embedded so as to adhere to the FBG portion 105 of the first optical fiber sensor 101. Moreover, it installs so that the FBG part 105 may be located in the measurement point in a concrete structure. Furthermore, since it is necessary for the concrete 107 and the FBG portion 105 of the optical fiber sensor 101 to integrally shrink or expand after the optical fiber sensor 101 is buried, in order to sufficiently secure the adhesion between the optical fiber sensor 101 and the concrete 107. The FBG portion 105 is preferably arranged with an interval of 50 mm or more left and right. In addition, it is preferable that the FBG portion 105 is buried at a depth of 20 mm or more, which is the maximum diameter of the aggregate used for the concrete 107.

  The second optical fiber sensor 102 is an optical fiber sensor that measures strain due to a temperature change in a concrete structure, and includes one FBG unit 105. Since the second optical fiber sensor 102 is an optical fiber sensor that measures strain due to temperature changes in the concrete structure, the second optical fiber sensor 102 is separated from the concrete 107 by a protective tube 109 or the like, and is embedded without any restraint. Moreover, the depth which embeds the 2nd optical fiber sensor 102 is the vicinity of the 1st optical fiber sensor 101, and is made into the same depth. The second optical fiber sensor is for measuring the strain caused by the temperature change, as long as it can measure the temperature in the concrete structure and the strain caused by the temperature change from the measured temperature. Therefore, the thermometer may use a thermocouple, and is not limited to an optical fiber sensor. When a thermocouple is used, the strain of the optical fiber sensor with respect to temperature is grasped. From the strain of the optical fiber sensor excluding the influence (strain) due to temperature change, measure the strain value when the concrete is melted. When measuring strain at a specific temperature, the strain experienced by the optical fiber sensor at that temperature is constant, so there is no need to correct the strain due to temperature changes.

Next, an installation example of the optical fiber sensor on the concrete structure will be described.
[Example 1]
6A to 6C are diagrams illustrating an outline of an installation example of the optical fiber sensor according to the first embodiment. An optical fiber sensor (first optical fiber sensor) 101 shown in FIG. 6A is embedded in parallel to a frozen surface of a concrete structure. An optical fiber sensor (second optical fiber sensor) 102 shown in FIG. 6B is an optical fiber sensor that measures strain due to a temperature change in a concrete structure, and is parallel to the frozen surface of the concrete structure. Buried. 6A, when the temperature inside the concrete differs greatly, as shown in FIG. 6C, the second optical fiber sensor 102 is embedded in the vicinity of each FBG portion of the first optical fiber sensor. It is preferable to measure the strain due to temperature change at each measurement point.

  Thus, by burying an optical fiber sensor in a concrete structure, a wide range of monitoring can be performed simultaneously with a single thin cable. For example, by embedding an optical fiber sensor in a place where a cryoprotectant is sprayed on a floor slab and a place where the cryoprotectant is not sprayed, it is possible to determine effects such as the effectiveness of the cryoprotectant. . In addition, even if the deterioration situation differs due to the influence of outside air temperature and solar radiation on the same concrete structure, the deterioration location is identified and repaired by measuring strain at multiple locations on the same concrete structure. It is possible to accurately grasp the range that is necessary.

[Example 2]
7A and 7B are diagrams illustrating an outline of an installation example of the optical fiber sensor according to the second embodiment. An optical fiber sensor (first optical fiber sensor) 101 shown in FIG. 7A is embedded perpendicularly to a frozen surface of a concrete structure. An optical fiber sensor (second optical fiber sensor) 102 shown in FIG. 7B is an optical fiber sensor that measures strain due to a temperature change in a concrete structure, and is embedded perpendicular to the frozen surface of the concrete structure. . When repairing concrete structures by frost damage deterioration, it is important to know the depth of deterioration. Therefore, when evaluating the progress of deterioration due to frost damage of a concrete structure, it is preferable to install an optical fiber sensor as shown in FIGS. 7A and 7B.

  Thus, by installing an optical fiber sensor in the depth direction of the concrete structure and monitoring strain, it is possible to determine the depth of deterioration and accurately grasp the range that requires repair. Further, when the temperature inside the concrete greatly changes depending on the depth, the second optical fiber sensor 102 is embedded in the vicinity of each FBG portion of the first optical fiber sensor, similarly to the first embodiment, and the measurement points are measured. It is preferable to measure strain due to temperature change.

[Example 3]
8 and 9 are diagrams schematically illustrating an installation example of the optical fiber sensor according to the third embodiment. In concrete structures, since frost damage deterioration proceeds from the surface, it is preferable that the deterioration depth can be monitored finely. As shown in FIG. 8, the optical fiber sensors 101 and 102 may be embedded with an inclination to the surface of the concrete structure. Moreover, as shown in FIG. 9, you may embed the optical fiber sensors 101 and 102 helically with respect to the depth direction of a concrete structure. By embedding the optical fiber sensor in this way, it is possible to shorten the interval of the embedding depth of the FGB portion while ensuring adhesion with concrete. As described above, it is possible to monitor in more detail by shortening the interval of the FGB unit 105.

[Example 4]
FIG. 10 is a diagram illustrating an outline of an installation example of the optical fiber sensor according to the fourth embodiment. As shown in FIG. 10, an optical fiber sensor is embedded in the floor slab overhanging part 121 and the abutment end part 123, and the cable 111 is extended to a place where measurement can be performed, so that the deterioration state of the concrete structure can be easily grasped. can do.

  By combining the installation examples described above, it is possible to embed a plurality of first optical fiber sensors in the same concrete structure, and as a result, it is possible to detect the deterioration state in the concrete structure more accurately. For example, by embedding an optical fiber sensor in a place where a cryoprotectant is sprayed on a floor slab and a place where the cryoprotectant is not sprayed, it is possible to determine effects such as the effectiveness of the cryoprotectant. . In addition, even if the deterioration situation differs due to the influence of outside air temperature and solar radiation on the same concrete structure, the deterioration location is identified and repaired by measuring strain at multiple locations on the same concrete structure. It is possible to accurately grasp the range that is necessary.

  As described above, by using an optical fiber sensor installation method that embeds an optical fiber sensor in a concrete structure and can detect the deterioration of the concrete structure due to frost damage with high accuracy and efficiency. In addition, it is possible to grasp the deterioration point and deterioration state of the concrete structure, and to accurately identify the range where repair is necessary.

DESCRIPTION OF SYMBOLS 11 Optical fiber sensor 13 FBG part 15 Steel mold 17 Concrete 21 Thermometer 23 Measuring part 101 1st optical fiber sensor 102 2nd optical fiber sensor 105 FBG part 107 Concrete 109 Protection tube 111 Cable 121 Floor slab overhanging part 123 Abutment end

Claims (8)

An optical fiber sensor installation method for detecting deterioration of concrete due to frost damage,
Installing a first optical fiber sensor in the concrete structure that detects strain based on the characteristics of changes in propagating light waves before or during placing the concrete;
Installing a temperature sensor in the vicinity of the strain detector of the first optical fiber sensor;
And a step of embedding the first optical fiber sensor and the temperature sensor installed in the concrete structure with concrete.   The first optical fiber sensor is embedded in parallel to the surface of the concrete structure, and the temperature sensor is embedded at substantially the same depth as the strain detection portion of the first optical fiber sensor. The installation method according to claim 1, wherein:   The first optical fiber sensor is embedded perpendicularly to the surface of the concrete structure, and the temperature sensor is embedded at substantially the same depth as the strain detection portion of the first optical fiber sensor. The installation method according to claim 1, wherein the installation method is performed.   The first optical fiber sensor is embedded in a depth direction from the surface of the concrete structure, and the temperature sensor is substantially the same as the strain detection unit of the first optical fiber sensor. The installation method according to claim 1, wherein the installation method is embedded at a depth.   The first optical fiber sensor is embedded in a spiral shape in the depth direction from the surface of the concrete structure, and the temperature sensor is substantially the same as the strain detection unit of the first optical fiber sensor. The installation method according to any one of claims 1 to 4, wherein the installation method is embedded to a depth. The temperature sensor includes a second optical fiber sensor that detects a temperature based on a change characteristic of a propagating light wave;
A covering portion covering an outer periphery of the second optical fiber sensor,
The installation according to any one of claims 1 to 5, wherein one or more temperature sensors are embedded along the first optical fiber sensor inside the concrete of the concrete structure. Method. A deterioration detection method for detecting deterioration of concrete due to frost damage,
Installing the first optical fiber sensor on the concrete structure before or during placing the concrete; and
Installing a temperature sensor in the vicinity of the strain detector of the first optical fiber sensor;
Burying the first optical fiber sensor and the temperature sensor installed in the concrete structure with concrete;
Measuring the strain of the concrete based on a characteristic change of a light wave propagating in the first optical fiber sensor;
Detecting a characteristic of the measured strain over time, at least,
A deterioration detection method, wherein deterioration of concrete due to frost damage is detected based on characteristics of the detected strain over time.   The deterioration detecting method according to claim 7, further comprising a step of removing strain due to temperature change measured using the temperature sensor from the detected strain of concrete.

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