JP4113100B2 - Method for investigating structures with infrared camera - Google Patents

Description

  The present invention relates to a method for investigating an internal damage state of a structure such as concrete or tile with an infrared camera.

  Concrete structures such as bridges and overpasses are affected by weather changes, ground changes and load loads over the years in addition to their own deterioration. When these are collected and the adverse conditions overlap, partial destruction or peeling of the concrete structure may occur, leading to damage to third parties or accidents.

  Therefore, in order to prevent the concrete structure from peeling off, it is necessary to continuously inspect and monitor the concrete structure.

  At present, the hammering sound survey method is widely implemented as an inspection method for concrete structures.

  However, the hammering sound investigation method is a method in which a human actually strikes a site to be investigated to investigate a damaged state, and it is necessary to approach a concrete structure. However, in reality, there are many places where it is difficult to approach easily due to crossing conditions such as underpass roads, railways, rivers, etc., and the survey area is also large.

  For this reason, the sound inspection method still has problems to be solved in terms of efficiency such as traffic regulation, processing capacity, and cost. In addition, it is difficult to conduct an accurate survey because the sound-taping survey method depends on experience and intuition.

  Therefore, in recent years, since it is not necessary to approach a concrete structure and a wide range of surveys can be performed with high efficiency, the infrared survey method has been studied as an auxiliary inspection method for extracting the places where the sound inspection is necessary.

  In the infrared survey method, the concrete surface temperature is measured by an infrared camera, and the healthy part and the damaged part without damage are discriminated by the temperature difference.

  The principle of the infrared survey method will be described with reference to FIGS.

  FIGS. 1A and 1B are schematic diagrams showing heat flow and temperature change in concrete accompanying environmental temperature change.

  As shown in FIG. 1 (a), since the damaged portion 2 such as a void near the surface layer portion of the concrete structure 1 serves as a heat insulation tank against heat flow, the outside air temperature is higher than the concrete and the heat flow from the concrete surface such as daytime. When going inside, the surface in the vicinity of the damaged portion 2 becomes a high temperature region, and the healthy portion 3 becomes a low temperature region. On the other hand, when the heat flow goes from the inside of the concrete to the surface, such as at night, the damaged part 2 becomes a low temperature region and the healthy part 3 becomes a high temperature region.

  FIG. 2 illustrates the daily temperature change of the outside air temperature, the sound part 3 and the damaged part 2 in the concrete viaduct.

  In FIG. 2, if the surface of the investigation target part of the concrete structure 1 is photographed with an infrared camera when the temperature difference between the healthy part 3 and the damaged part 2 exceeds a predetermined value, the surface of the concrete structure with a temperature difference Thus, it is possible to obtain an image of the temperature distribution and to determine that the investigation target site is damaged.

  However, the temperature difference between the healthy part 3 and the damaged part 2 depends on the environmental conditions of the site to be investigated, that is, location, season, time zone, and the like.

  For this reason, in order to conduct an infrared survey method, even if a person visits the site and takes an image with an infrared camera, the temperature difference between the healthy part 3 and the damaged part 2 is small at the time of taking the image. In spite of this, it may be misjudged that there is no abnormality. For this reason, not only was the cost associated with the survey wasted, but the reliability of the survey results was lacking.

  In addition, since the infrared inspection method is an auxiliary inspection method for extracting a portion where a sound hitting check is necessary, it should be possible to accurately determine whether or not the sound hitting check should be performed and the priority of the sound hit checking at each location.

  In other words, depending on the depth and shape of the damaged portion 2 inside the concrete structure, damage may progress by hitting the hammering sound survey method and the peeling time may be advanced. In other words, as a result of the infrared inspection method, if it was determined that there was an abnormality inside the structure, it would be sufficient if the concrete on the surface could be knocked down, but it would be damaged without being knocked down. May occur and may cause damage to third parties due to peeling. In addition, as a result of infrared survey method implementation, it was determined that there was an abnormality inside the structure, so if we decided to implement the sound impact survey method uniformly, depending on the survey area and position, a great deal of time and labor would be spent on the survey. Therefore, an efficient inspection cannot be performed.

  The present invention has been made in view of such a situation, and it is possible to determine the time when the survey by the infrared survey method can be accurately performed, to reduce useless costs associated with the survey, and to improve the reliability of the survey results. This is a first problem to be solved.

  In addition, the present invention makes it possible to accurately determine the depth and shape of the damaged portion inside the structure, and from the determination result, whether or not to perform the hammering investigation, and accurately prioritize the hammering investigation at each location. The second solution is to make the determination possible.

  The following Non-Patent Document 1 is a document showing a general technical level related to the infrared survey method.

In this non-patent document 1,
1) Create a test piece with a simulated defect (damaged part), attach this test piece to the surface of the concrete structure, and photograph the temperature distribution of the concrete structure surface and the temperature distribution of the test piece with an infrared camera. And the invention of determining the time when the infrared survey method should be carried out from the comparison result is described.

2) An invention is described in which an image of a temperature distribution on the surface of a concrete structure is taken for a predetermined time, and the depth of a defect (damaged portion) inside the structure is estimated from a change in the temperature distribution image.

  However, the technique disclosed in Non-Patent Document 1 has to approach the concrete structure and attach the test piece. In addition, when there are a plurality of investigation target parts, a test piece must be attached to each investigation target part. For this reason, as with the hammering sound investigation method, problems associated with the approach of the structure occur, and a test piece has to be installed at each investigation target site, so the labor required for the work is enormous and the work efficiency is reduced. To do.

  In addition, the technique disclosed in Non-Patent Document 1 must continue to image a site to be investigated for a long time in order to determine the depth of a defective part (damaged part) inside the structure. For this reason, it takes time for the survey, and when the site to be surveyed covers a large area, a huge amount of time is required.

  In addition, the technique disclosed in Non-Patent Document 1 may be able to determine the depth of the defective portion (damaged portion) inside the structure, but cannot determine the shape of the defect. Unless it is possible to determine not only the depth of the damaged portion but also the shape, it is not possible to determine whether or not the investigation by the hitting sound investigation method should be performed.

That is, according to the technique disclosed in Non-Patent Document 1, the first solution problem and the second solution problem of the present invention cannot be achieved.
Pamphlet of Sumitomo Osaka Cement Co., Ltd. “Non-destructive inspection technology using infrared thermography”

In order to achieve the first solution, the first invention provides:
When photographing the surface of the structure with an infrared camera and investigating the damage inside the structure based on the temperature distribution of the photographed structure surface,
Prepare a test body of a structure that has a damaged part inside and is provided with a temperature sensor that detects each temperature of the healthy part and the damaged part,
The test specimen is installed in a different location from the survey target site under the same environmental conditions as the survey target site of the structure.
The site to be investigated of the structure is photographed by an infrared camera at a time when the temperature difference between the healthy part and the damaged part obtained from the detection result of the temperature sensor of the specimen becomes a predetermined value or more.

The second invention is the first invention,
Collect the detection results of the temperature sensor of the test body, obtain in advance the data of the correspondence between the temperature difference between the healthy part and the damaged part and the season, the time zone during the day,
Determine the season and time zone in which the temperature difference between the healthy part and the damaged part is greater than or equal to a predetermined value from the data, as the season and time zone for shooting with an infrared camera,
In this determined season and time zone, the investigation target part of the structure is photographed with an infrared camera.

The third invention is the first invention,
It is characterized in that a plurality of test bodies are installed corresponding to a plurality of investigation target parts of the structure.

  According to the present invention, as shown in FIG. 4, the test specimens 10 and 10 ′ are installed on the ground having the same environmental conditions as the investigation target parts 21 and 22 and different from the investigation target parts 21 and 22. Then, as shown in FIG. 7, the test is performed by the infrared camera at the time t1 when the temperature difference between the healthy part 3 and the damaged part 2 obtained from the detection results of the temperature sensors 15 and 16 of the test body 10 exceeds a predetermined value. An investigation target region 21 having the same environmental conditions as the body 10 is photographed.

  According to the present invention, it is possible to reliably image a region to be investigated under the condition that the temperature difference is equal to or greater than a predetermined value, and an accurate investigation result can be obtained. In addition, the test body only needs to be installed at a location different from the site to be investigated, and it is not necessary to approach the structure to be investigated as in the hitting investigation method, so that the work can be performed efficiently.

  As described above, according to the present invention, it is possible to determine the time when the survey by the infrared survey method can be accurately performed, so that it is possible to reduce useless costs associated with the survey and improve the reliability of the survey results. be able to.

In order to achieve the second solution, the fourth invention provides
In the structure investigation method using an infrared camera, the surface of the structure is photographed with an infrared camera, and the damage state inside the structure is investigated based on the temperature distribution of the photographed structure surface.
Define multiple damage patterns with different depth and shape of the damage inside the structure,
Create a plurality of FEM analysis models corresponding to the plurality of damage patterns,
Prepare a test body of a structure that has a damaged part inside and is provided with a temperature sensor that detects each temperature of the healthy part and the damaged part,
The same environmental conditions as the structure, and the test body is installed in a different place from the structure,
At the time when the temperature difference between the healthy part and the damaged part obtained from the detection result of the temperature sensor of the test specimen is equal to or greater than a predetermined value, the surface of the structure is photographed by an infrared camera and the temperature sensor of the test specimen is detected. From the result, calculate the heat flow given to the structure from the time when the temperature difference between the healthy part and the damaged part is equal to the time of shooting,
FEM analysis is performed for each of the plurality of models using the heat flow rate, and the surface temperature distribution of each model obtained as a result is compared with the surface temperature distribution of the photographed structure surface to obtain a matched model. It is characterized in that it is determined that the corresponding damage pattern is a damage state of the actual structure.

  According to the present invention, as shown in FIG. 4, the test body 10 is installed in a place having the same environmental conditions as the investigation target region 21. Then, as shown in FIG. 7, the test is performed by the infrared camera at the time t1 when the temperature difference between the healthy part 3 and the damaged part 2 obtained from the detection results of the temperature sensors 15 and 16 of the test body 10 exceeds a predetermined value. An investigation target region 21 having the same environmental conditions as the body 10 is photographed. Then, the heat flow rate given to the investigation target region 21 from the detection results of the temperature sensors 15 and 16 of the test body 10 to the imaging time t1 is calculated. Then, using the calculated heat flow rate, the FEM analysis is performed for each of the plurality of FEM analysis models 31 to 35 in FIG. 10, and the surface temperature distribution for each of the FEM analysis models 31 to 35 is acquired. . Then, by matching the surface temperature distribution of each of the obtained FEM analysis models 31 to 35 with the surface temperature distribution of the photographed investigation target region 21, a matched FEM analysis model (for example, FEM analysis model 31) It is determined that the damage pattern corresponding to (for example, the damage pattern (1)) is the actual damage state of the site to be investigated 21 (for example, the damaged portion 2 is a “cavity portion 4 cm deep from the surface”: see FIG. 8). Not only can the depth and shape of the actual damaged portion 2 be known from the damage pattern, but also the priority of the sounding investigation (for example, damage) from the correspondence between the damage pattern and the sounding investigation priority shown in FIG. Pattern (1) can accurately determine “observation”).

  As described above, according to the present invention, it is possible to accurately determine the depth and shape of the damaged portion 2 inside the concrete structure. It is possible to accurately determine the priority of the sound survey. In addition, unlike the prior art (Non-Patent Document 1), it is not necessary to perform photographing for a long time in order to determine the depth of the damaged portion, so that the work can be performed efficiently.

  Embodiments of a structure investigation method using an infrared camera according to the present invention will be described below with reference to the drawings.

  FIG. 3 shows the appearance of the test body 10 used to determine the implementation time of the infrared survey method.

  The test body 10 includes a cube 11 made of concrete having a cavity 12 as a damaged portion 2 inside, a heat insulating material 14 provided so as to cover the concrete cube 11 leaving the surface 11a (photographing surface), and a concrete cube. Temperature sensors 15 and 16 embedded in locations corresponding to the cavity portion 12 (damaged portion 2) and the concrete filling portion 13 (healthy portion 3) other than the cavity portion 12, and the concrete cube 11 inside. The reinforcing bar 17 is made of.

  Phenomena such as “peeling” and “floating” in a concrete structure means that the reinforcing bar corrodes and expands, and the adhesion between the concrete and the reinforcing bar is broken, and the part that has reached such a state may peel off. Many.

  Therefore, the cavity 12 is provided in the vicinity of the reinforcing bar 17 and on the surface 11a side of the concrete cube 11.

  As the temperature sensors 15 and 16, for example, a thermistor type small digital thermometer was used. Of the surface 11a of the concrete cube 11, the part corresponding to the cavity 12 was scraped off, and the temperature detection part of the temperature sensor 15 was bonded with embedded concrete bond. Similarly, the portion corresponding to the concrete filling portion 13 of the surface 11a of the concrete cube 11 was scraped off, and the temperature detection portion of the temperature sensor 16 was bonded with an embedded concrete bond.

  Desirably, the test body 10 is set to a size and weight that can be moved by an investigator alone.

  However, when the test body 10 is downsized, the temperature change differs from that of the concrete structure 1 such as an actual bridge. Therefore, in order to bring the test body 10 closer to an actual bridge or the like, the surface other than the imaging surface 11a is covered with a heat insulating material 14 such as fiberglass, natural rubber, or wood. As the heat insulating material 14, for example, a fiber glass having a thermal conductivity of 0.05 W / m · K can be used.

  FIG. 4 shows the installation location of the test body 10.

  In the embodiment, it is assumed that the bridge 20 is an investigation target, and the wall height column portion 21 and the base portion 22 of the bridge 20 are investigated as respective investigation target portions.

  The test body 10 has the same environmental conditions as the survey target portions 21 and 22 of the bridge 20 and is installed at a location different from the survey target portions 21 and 22.

  Since the wall height column 21 of the bridge 20 has a relatively large amount of solar radiation and a well-ventilated environmental condition, the test body 10 for judging the investigation time of the wall height column 21 is near the bridge 20 and is similarly exposed to sunlight. It is installed on a lot of airy ground. In addition, since the base portion 22 of the bridge 20 has a relatively low solar radiation and poorly ventilated environmental conditions, the test body 10 ′ for determining the investigation period of the base portion 22 is near the bridge 20 and is similarly exposed to the solar radiation. It is installed on the ground where there are few and poor ventilation.

  When the equipment for judging the survey time is prepared as described above, the survey time is judged by the following procedure.

・ Determining the season and time zone for the infrared survey method As explained with reference to FIGS. 1 and 2, when the temperature difference between the damaged portion 2 and the healthy portion 3 in the survey target portion exceeds a predetermined value, the infrared survey is performed. The legal investigation can be done accurately.

  However, throughout the year, the temperature difference between the damaged part 2 and the healthy part 3 changes, and there are seasons in which the temperature difference is relatively large, and there are seasons in which the temperature difference is relatively small. In addition, there are time periods in which the temperature difference is relatively large during one day, and there are time periods in which the temperature difference is relatively small.

  Therefore, temperature data detected by the temperature sensors 15 and 16 of the test specimens 10 and 10 'are collected throughout the year, and analyzed to obtain a concrete filling portion 13 (healthy portion 3) and a cavity portion 12 (damage portion 2). Data on the correspondence relationship between the temperature difference and the season and time zone is acquired in advance. If the temperature difference between the concrete filling portion 13 and the cavity portion 12 detected by the temperature sensors 15 and 16 of the test specimens 10 and 10 'is a predetermined value or more, the test specimens 10 and 10' Similarly, the healthy part 3 and the damaged part 2 of the investigation target parts 21 and 22 having the same environmental conditions are considered to have a temperature difference equal to or more than a predetermined value. For example, accurate survey results can be obtained.

  5 (a), (b), (c), and (d) show the daily temperature transition detected by the temperature sensors 15 and 16 of the test body 10 for each season.

  If the daily range of the day (the difference between the minimum temperature and the maximum temperature in the day) is large (over 10 ° C), the temperature difference between the damaged part 2 and the healthy part 3 becomes large. It is said.

  However, as shown in FIG. 5, the temperature difference between the concrete filling part 13 (healthy part 3) and the cavity part 12 (damaged part 2) appears depending on the season even if the daily temperature difference is 10 ° C or more from the detection result of the outside air temperature. You can see that there is a difference. In winter (December-February), the temperature difference during the day is around 0.5 ° C, while the temperature difference in spring (March-May) and autumn (September-November) is about It is moving around 1.0 ° C. This is because not only the daily difference but also environmental conditions such as ventilation and wind speed affect the temperature difference.

  By collecting such data, data on the correspondence relationship between the season and time zone that can be investigated is acquired as shown in the table of FIG. 6, for example.

  As shown in Fig. 6, during the daytime of winter (December-February), the survey can be conducted only for 3 hours, while during the daytime of spring (March-May), the survey is conducted for 6 hours. It is possible, and it can be determined that the spring daytime is more suitable for long-term surveys.

  From the data shown in FIG. 6, the investigator determines the season and time zone in which the temperature difference is greater than or equal to a predetermined value and is convenient for visiting the site.

  As a result, it is possible that the temperature difference is likely to be smaller than the predetermined value and it is possible to avoid going to the site during the season and time that are not suitable for the survey, so it is possible to control the expenditure of unnecessary survey costs. Can do.

・ Confirmation of the temperature difference at the site However, even if you actually visit the site, the temperature difference may be small due to the effects of rainfall, etc., and may not be suitable for the survey. Therefore, when the user visits the site, the data of the detection values of the temperature sensors 15 and 16 of the specimen 10 are acquired before the investigation, and after confirming that the temperature difference has become a predetermined value or more, the image is taken by the infrared camera. It is desirable to implement.

  FIG. 7 shows the time variation of the cavity 12 (damaged part 2) and the concrete filling part 13 (healthy part 3) obtained from the outside air temperature on the survey day, the detection results of the temperature sensors 15 and 16 of the test body 10. . A time zone in which the temperature difference between the cavity portion 12 (damaged portion 2) and the concrete filling portion 13 (healthy portion 3) is a predetermined value or more is determined as a time zone suitable for the investigation.

  If a time zone suitable for such a survey does not appear, the survey is postponed.

・ Shooting with an infrared camera The investigator uses an infrared camera during the time zone when the temperature difference between the healthy part 3 and the damaged part 2 obtained from the detection results of the temperature sensors 15 and 16 of the test body 10 exceeds a predetermined value. An investigation target region 21 having the same environmental conditions as the test body 10 is photographed.

  Similarly, the investigator uses the infrared camera to detect the test object during the time zone when the temperature difference between the healthy part 3 and the damaged part 2 obtained from the detection results of the temperature sensors 15 and 16 of the test object 10 ′ exceeds a predetermined value. An investigation target region 22 having the same environmental condition as 10 'is photographed.

  As a result, it becomes possible to image the investigation target region under the condition that the temperature difference is surely equal to or greater than the predetermined value, and an accurate investigation result can be obtained. In addition, the test body only needs to be installed at a location different from the site to be investigated, and it is not necessary to approach the structure to be investigated as in the hitting investigation method, so that the work can be performed efficiently.

  As described above, according to the present embodiment, it is possible to determine the time when the survey by the infrared survey method can be accurately performed, so that it is possible to reduce the wasteful cost associated with the survey and improve the reliability of the survey result. Can be made.

  Next, a method for determining the depth and shape of the damaged portion 2 of the concrete structure 1 will be described.

Damage pattern FIG. 8 shows five damage patterns (1), (2), (3), (4), and (5) with different depths and shapes of the damaged portion 2 of the concrete structure 1 and the hitting sound. The correspondence with the priority of the survey is shown.

  The accidental fall of the concrete piece is that the rebar 17 expands and the concrete on the surface peels off, and the concrete block falls. The priority of the hit sound investigation differs depending on the depth and shape of the damaged portion 2.

  The damage pattern (1) is a pattern of a damage situation in which a sufficient covering is ensured but the damaged portion 2 is present 4 cm behind the surface. When the hitting investigation is performed, it is a case where only the abnormal sound does not come off. The priority of the sounding investigation is “observation”, and it is not particularly necessary to conduct the sounding investigation quickly.

  The damage pattern (2) is a pattern of a damage situation in which the damaged portion 2 exists about 2 cm from the surface. When the hammering sound investigation is performed, there is a case where a hole is made in the damaged portion 2 and then the concrete piece may fall. The priority of the sounding investigation is “caution”, and it is necessary to conduct the sounding investigation while monitoring.

  The damage pattern (3) has a cover depth of 4 cm, the same as the damage pattern (1), but damage proceeds from the damage pattern (1) and a part of the damaged part 2 is at an angle of 45 ° toward the concrete surface. It is the pattern of the damage situation which inclines and has reached 2 cm from the surface. When the hammering sound investigation is performed, there is a possibility that the concrete piece will fall due to a heavy hit. The priority of the sounding investigation is “caution”, and it is necessary to conduct the sounding investigation while monitoring.

  The damage pattern (4) has a covering depth of 2 cm, the same as the damage pattern (2), but damage proceeds from the damage pattern (2) so that a part of the damaged part 2 is at an angle of 45 ° toward the concrete surface. It is the pattern of the damage situation which inclines and has reached the surface vicinity. When the hammering survey is conducted, there is a high possibility that the concrete piece will fall due to a heavy hit. The priority of the sounding investigation is “Caution”, and it is necessary to conduct the sounding investigation and drop the concrete pieces in advance.

  The damage pattern (5) is a damage state pattern in which damage has progressed from the damage pattern (3) and a part of the damaged portion 2 has reached the vicinity of the surface. When the hammering survey is conducted, there is a high possibility that the concrete piece will fall due to a heavy hit. The priority of the sounding investigation is “Caution”, and it is necessary to conduct the sounding investigation and drop the concrete pieces in advance.

-Creation of FEM analysis model When five damage patterns are determined as described above, FEM analysis models 31 to 35 are created for each of the damage patterns (1) to (5).

  FIG. 9 shows an FEM analysis model 31 as a representative.

  The FEM analysis model 31 is a three-dimensional model having each of an x axis (concrete surface horizontal direction), a y axis (concrete surface vertical direction), and a z axis (concrete surface depth direction). 4 can be modeled.

Preparation and installation of test specimens The test specimens 10 and 10 'described with reference to FIG. 3 are prepared, and as described with reference to FIG. 4, the environment is the same as each of the survey target portions 21 and 22 of the bridge 20 that is an actual concrete structure. Specimens 10, 10 'are installed at the conditions.

-Photographing with an infrared camera Hereinafter, the specimen 10 will be described as a representative.

  FIG. 7 shows the transition of each temperature of the cavity 12 (damaged part 2) and the concrete filling part 13 (healthy part 3) detected by the temperature sensors 15 and 16 of the test body 10. Here, the time when the temperature difference between the cavity portion 12 (damaged portion 2) and the concrete filling portion 13 (healthy portion 3) is equal was t0 (8:45 minutes). The temperature difference became 0.8 ° C. at time t1 when 3 hours passed from this time t0, and an image of the surface of the investigation target region 21 was taken by the infrared camera at time t1.

Calculation of heat flow, FEM analysis Next, the investigator calculates the heat flow given to the site to be investigated 21 by the imaging time t1 from the detection results of the temperature sensors 15 and 16 of the specimen 10, and this heat flow The FEM analysis is performed for each of the plurality of FEM analysis models 31 to 35 using the above.

  That is, the calculation was performed by unsteady three-dimensional heat conduction analysis while changing the heat flow rate. However, it is difficult to generally indicate the magnitude of the thermal conductivity between the air and the concrete because the thermal conductivity changes with the temperature of the air at the same time as the air convection occurs.

  Therefore, the heat flow transferred from the air to the object surface is changed and inputted within the time period from time t0 to time t1, and the cavity 12 (damaged part 2) and concrete filling part 13 (healthy part) of the FEM analysis model are input. The convergence calculation is repeated until each surface temperature corresponding to 3) reaches each temperature detected at time t1 in FIG.

  FIG. 10 shows the calculation results for each of the FEM analysis models 31 to 35. Each mesh on the concrete surface (xy plane) of the FEM analysis models 31 to 35 can be shown as a hue (or density) corresponding to the temperature.

-Judgment of the damage state of an actual structure As shown in the same figure 10, according to the difference of each damage pattern (1)-(5), the concrete surface (xy plane) of the models 31-35 for FEM analysis It can be seen that the hue (or density) appears differently.

  Therefore, the temperature distribution, that is, the hue (or density) distribution on the concrete surface photographed by the infrared camera is the hue (or density) distribution on the concrete surface (xy plane) of any of the FEM analysis models 31-35. , It can be determined that the damage pattern corresponding to the matched FEM analysis model is the actual damaged state of the concrete structure 1.

  Therefore, the investigator calculates the surface temperature distribution (hue (or density) distribution) for each of the FEM analysis models 31 to 35 calculated and the surface temperature distribution (hue (or density) distribution) of the photographed investigation target region 21. Match. For example, as shown in FIG. 10, if a captured image 41 of the investigation target region 21 is obtained, the surface temperature distribution (hue (or density) distribution) of the surface temperature distribution (hue (or hue (or density) distribution)) of the FEM analysis model 31 is obtained. Therefore, it is determined that the damage pattern (1) corresponding to the matched FEM analysis model 31 is the actual damage state of the site 21 to be investigated. Similarly, if a captured image 42 of the investigation target region 21 is obtained, it is determined that the damage pattern (2) corresponding to the FEM analysis model 32 that matches the actual image is the damage state of the investigation target region 21. If the captured image 43 of the investigation target region 21 is obtained, it is determined that the damage pattern (3) corresponding to the FEM analysis model 33 corresponding to the captured image 43 is the actual damage state of the investigation target region 21, and the investigation target If the captured image 44 of the part 21 is obtained, it is determined that the damage pattern (4) corresponding to the FEM analysis model 34 corresponding to the captured image 44 is the actual damage state of the part 21 to be investigated. If the captured image 45 is obtained, it is determined that the damage pattern (5) corresponding to the FEM analysis model 35 corresponding to the captured image 45 is the actual damage state of the investigation target region 21.As a result, the investigator can know the actual depth and shape of the damaged portion 2 from the damage pattern determined to be the actual damage state of the investigation target region 21, and the damage pattern and the hitting sound shown in FIG. It is possible to accurately determine the priority of the hitting sound investigation from the correspondence relationship of the investigation priorities.

  Similarly, the investigator also photographs the other investigation target parts 22 in the same manner, similarly calculates the FEM analysis models 31 to 35, and calculates the surface temperature distribution for each of the FEM analysis models 31 to 35. By comparing the surface temperature distribution of the photographed investigation target region 22 with each other, it is possible to determine that the damage pattern corresponding to the matched FEM analysis model is the actual damage state of the investigation target region 22. The depth and shape of the damaged portion 2 can be known, and the priority of the hitting investigation can be accurately determined from the correspondence between the damage pattern and the priority of the hitting investigation shown in FIG.

  As described above, according to this embodiment, it is possible to accurately determine the depth and shape of the damaged portion 2 inside the concrete structure. It is possible to accurately determine the priority of the sounding investigation. In addition, unlike the prior art (Non-Patent Document 1), it is not necessary to perform photographing for a long time in order to determine the depth of the damaged portion, so that the work can be performed efficiently.

  Next, an embodiment in which the depth and shape of the damaged portion 2 can be determined without performing FEM analysis will be described.

-Determination of damage pattern Also in this embodiment, five damage patterns (1) to (5) are determined according to the damage state as in the above-described embodiment.

Correlation between damage pattern and temperature transition pattern The temperature line graphs 51 to 55 in FIG. 10 show the temperature transition in the y-axis direction on the concrete surface (xy plane) of each FEM analysis model 31 to 35, respectively. Yes. The temperature line graphs 51 to 55 show the transition of the temperature from the center of the damaged portion 2 toward the healthy portion 3. Looking at each temperature line graph 51-55, it can be seen that the shape and gradient of the temperature line graph are different for each FEM analysis model 31-35, that is, for each damage pattern (1)-(5). .

  That is, the temperature line graph has a gentle slope as it goes from the surface of the damaged portion 2 to the back. When the shape of the damaged portion 2 advances toward the surface, the temperature line graph shifts from a bell shape to a trapezoid shape. The damage pattern can be inferred from the characteristics of the shape of the temperature transition and the magnitude of the gradient.

  Therefore, as shown in FIG. 10, each temperature transition pattern, that is, the shape and gradient of each temperature line graph 51 to 55 is associated with each of the five damage patterns (1) to (5). Further, the damage pattern is not limited to the case where the damaged portion 2 is a hollow portion, and a damaged pattern such as a sand line or a crack may be prepared.

  For example, even in the case of a damage pattern in which the damaged portion 2 is sand streaks and cracks, the temperature line graph shows a triangular shape.

  Damage patterns (1) to (5) when the damaged portion 2 is a hollow portion, damage patterns (6) when the damaged portion 2 is sand streaks and cracks, the shape of the temperature line graph, temperature gradient (temperature transition) FIG. 11 shows the correspondence with the (pattern). For example, when a temperature transition pattern having a “bell shape” and a temperature gradient of “10 or more” is obtained, it can be determined that the damage pattern is (2).

・ Shooting with an infrared camera When the preparations as described above are completed, the investigator can determine the temperatures of the healthy part 3 and the damaged part 2 obtained from the detection results of the temperature sensors 15 and 16 of the specimen 10 as in the above-described embodiment. In the time zone when the difference is equal to or greater than the predetermined value, the investigation target region 21 having the same environmental conditions as the test body 10 is photographed by the infrared camera.

-Determination of temperature transition pattern from imaging result Then, the temperature transition in the y-axis direction (left-right direction) of the surface of the investigation target region 21 is obtained from the imaging result. Then, a temperature transition pattern that matches the obtained temperature transition is determined.

  FIG. 12 shows a line in the y-axis direction (left-right direction) of the surface of the investigation target region 21 photographed by the infrared camera as a temperature line graph, and illustrates the change with time. The temperature gradient of the temperature line graph is shown for each time in the figure. For example, at time 11:00, the temperature gradient of the temperature line graph is 11.42.

  For example, a thermal line graph can be created from an infrared image by using infrared image analysis software made by GORATEC of Germany and PE Professional.

  The shape of the temperature line graph shown in FIG. 12 is “bell-shaped” and the temperature gradient is “10 or more”, so that the shape of the temperature line in FIG. 10 is “bell-shaped” and the gradient is “10 or more”. It can be determined that the temperature transition pattern is the same as that of the graph 52 (see FIG. 11), and the damage pattern (2) corresponding to the temperature line graph 52 can be determined to be the actual damage state of the site to be investigated 21.

  Similarly, if it is determined that the temperature line graph created from the infrared image has the same temperature transition pattern as the temperature line graph 51 of FIG. 10, the damage pattern (1) corresponding to the temperature line graph 51 is actually If the temperature line graph created from the infrared image is determined to have the same temperature transition pattern as the temperature line graph 53 of FIG. 10, the temperature line is determined. It is determined that the damage pattern (3) corresponding to the graph 53 is the actual damage state of the site to be investigated 21, and the temperature line graph created from the infrared image has the same temperature transition as the temperature line graph 54 of FIG. If it is determined that the pattern is a pattern, the damage pattern (4) corresponding to the temperature line graph 54 is the actual damage of the site 21 to be investigated. If the temperature line graph created from the infrared image is determined to be the same temperature transition pattern as the temperature line graph 55 of FIG. 10, the damage pattern corresponding to the temperature line graph 55 is determined. (5) is determined to be the actual damaged state of the site to be investigated 21.

  If it is determined that the temperature line graph created from the infrared image has a triangular temperature transition pattern as shown in FIG. 11, the damage pattern (6) corresponding to the triangular temperature transition pattern, that is, sand It is determined that the crack is actually a damaged state of the investigation target site 21.

  As a result, the investigator determines the actual depth and shape of the damaged portion 2 or the type of the damaged portion (a hollow portion or sand line, It is possible to know whether it is a crack or not, and it is possible to accurately determine the priority of the sounding investigation from the correspondence between the damage pattern and the priority of the sounding investigation shown in FIG.

  In this embodiment, as in the above-described embodiment, it is assumed that the shooting date by the infrared camera is determined, the shooting date is taken to the site, and shooting is performed at a specific time zone and time. It is also possible to install an infrared camera on the site and continue shooting until a specific shape and gradient as shown in FIG. 12 are obtained.

Similarly, the investigator also captures images of other investigation target parts 22 in the same manner, similarly creates a temperature line graph from the infrared image, and uses the damage pattern corresponding to the temperature transition pattern that matches the temperature line graph to actually The damage state of the site 22 to be investigated can be determined, whereby the actual depth and shape of the damaged portion 2 or the type of the damaged portion can be known. From the correspondence of the priorities, the priority of the hit sound investigation can be accurately determined.

  As described above, according to this embodiment, it is possible to accurately determine the depth and shape of the damaged portion 2 inside the concrete structure. It is possible to accurately determine the priority of the sounding investigation. In addition, unlike the prior art (Non-Patent Document 1), it is not necessary to perform photographing for a long time in order to determine the depth of the damaged portion, so that the work can be performed efficiently.

  In the above description, the description has been made assuming a concrete structure such as a bridge. However, the present invention is not limited to a concrete structure, and there is a possibility that damage may occur inside. Any structure that can be captured as a difference can be applied to any structure such as a tile or a brick. The present invention has been described on the assumption that a concrete structure is a bridge, an elevated structure, or the like, but the present invention can naturally be applied to a case where buildings, general houses, and the like are to be investigated.

FIGS. 1A and 1B are diagrams showing a difference in temperature between a damaged part and a healthy part inside a concrete structure in the daytime and at night. FIG. 2 is a graph showing temperature changes of the outside air temperature, the damaged part, and the healthy part. FIG. 3 is a perspective view showing the structure of the test body 10. FIG. 4 is a diagram showing the installation location of the test specimen. FIGS. 5A, 5B, 5C, and 5D are graphs showing the outside air temperature and the temperature change of the damaged part and the healthy part for each season. FIG. 6 is a table showing the correspondence between the season and time zone and the time available for photographing by the infrared camera. FIG. 7 is a graph illustrating a time zone suitable for photographing in one day. FIG. 8 is a table showing a correspondence relationship between the damage pattern and the actual damage situation, the necessity of the hit sound investigation, and the priority. FIGS. 9A and 9B are diagrams used for explaining the FEM analysis model. FIG. 10 is a table showing the correspondence between the damage pattern, the FEM analysis model, the temperature distribution image of the concrete surface photographed by the infrared camera, and the temperature line graph. FIG. 11 is a table showing the correspondence between the damage pattern and the temperature transition pattern. FIG. 12 is a diagram used to explain how a temperature line graph is created from an infrared image.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Concrete structure 2 Damaged part 3 Healthy part 10, 10 'Test body 12 Cavity part 13 Concrete dense part 20 Bridge 21, 22 Investigation object part 31-35 Model for FEM analysis 41-45 Temperature distribution of structure surface 51-55 Temperature line graph

Claims (4)

When photographing the surface of the structure with an infrared camera and investigating the damage inside the structure based on the temperature distribution of the photographed structure surface,
Prepare a test body of a structure that has a damaged part inside and is provided with a temperature sensor that detects each temperature of the healthy part and the damaged part,
The test specimen is installed in a different location from the survey target site under the same environmental conditions as the survey target site of the structure.
When the temperature difference between the healthy part and the damaged part obtained from the detection result of the temperature sensor of the test body is equal to or greater than a predetermined value, the investigation target part of the structure is photographed by the infrared camera. Structure survey method. Collect the detection results of the temperature sensor of the test body, acquire in advance the data of the correspondence between the temperature difference between the healthy part and the damaged part and the season, the time zone during the day,
The season and time zone in which the temperature difference between the healthy part and the damaged part is greater than or equal to a predetermined value from the data are determined as the season and time zone for shooting with an infrared camera,
The method for investigating a structure with an infrared camera according to claim 1, wherein the investigation target part of the structure is photographed with an infrared camera during the determined season and time zone.   2. The structure investigation method using an infrared camera according to claim 1, wherein a plurality of test bodies are installed corresponding to a plurality of investigation target parts of the structure. In the structure investigation method using an infrared camera, the surface of the structure is photographed with an infrared camera, and the damage state inside the structure is investigated based on the temperature distribution of the photographed structure surface.
Define multiple damage patterns with different depth and shape of the damage inside the structure,
Create a plurality of FEM analysis models corresponding to the plurality of damage patterns,
Prepare a test body of a structure that has a damaged part inside and is provided with a temperature sensor that detects each temperature of the healthy part and the damaged part,
The same environmental conditions as the structure, and the test body is installed in a different place from the structure,
At the time when the temperature difference between the healthy part and the damaged part obtained from the detection result of the temperature sensor of the test specimen is equal to or greater than a predetermined value, the surface of the structure is photographed by an infrared camera and the temperature sensor of the test specimen is detected. From the result, calculate the heat flow given to the structure from the time when the temperature difference between the healthy part and the damaged part is equal to the time of shooting,
FEM analysis is performed for each of the plurality of models using the heat flow rate, and the surface temperature distribution of each model obtained as a result is compared with the surface temperature distribution of the photographed structure surface to obtain a matched model. A method for investigating a structure using an infrared camera, wherein the corresponding damage pattern is determined to be a damaged state of the actual structure.

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