JPH09281065A - Method of detecting defects in structures - Google Patents

Abstract

(57) [Abstract] [PROBLEMS] To improve the detection accuracy of a defect portion on the surface of a structure. Further, it is possible to detect a defect of a structure reinforced by a steel plate. SOLUTION: The temperature distribution on the surface of the structure in each time zone is obtained by performing detection by the infrared radiometer in each time zone during daytime and nighttime. These temperature distributions are subtracted from each other to obtain the subtracted temperature distributions. Defects in the structure are detected based on the subtracted temperature distribution.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for detecting a defect in an outdoor structure such as a building or a bridge, which detects defects such as rising of tiles and mortar and peeling of a steel plate of a steel plate reinforced structure. The present invention relates to a method for detecting a defect in a structure to be detected.

[0002]

2. Description of the Related Art When a structure is used for many years, defects such as cracks on outer walls, peeling of mortar, and floating of tiles occur. If these defects are left unchecked, they will cause water leakage or the exfoliation of outer walls and tiles, so these defects must be detected and repaired as early as possible and reliably. Conventionally, as a method of detecting these defects, there is known a method of hitting the surface of the structure with a wooden hammer or the like and making a judgment by an operator based on the sound. However, this method not only has poor workability, but also lacks reliability.

Therefore, a method of detecting a defect having excellent workability and high reliability has been sought. One of them is a method of detecting the radiant energy from the surface of a structure by an infrared radiometer and detecting a portion on the surface of the structure where the temperature difference is large to detect the presence or absence of a defect in the structure.

The conventional detection method of this type will be briefly described. The radiant energy on the surface of the structure is measured by an infrared radiometer, the temperature distribution on the surface of the structure is determined from the measurement result, and image processing is performed. And displays it as a thermal image on the CRT screen. The inspector who visually inspects the CRT screen judges, based on his own experience, that there is a defect in a portion showing a temperature distribution different from other portions. This method
It is basically an excellent method, and various proposals have been made for its improvement.

[0005]

By the way, in order to detect a defect by this type of detection method, it is a prerequisite that the defect portion and the defect-free portion have different temperature distributions and are displayed as a thermal image. In particular, since the inspector visually judges the presence or absence of defects, it is desirable that the difference in temperature distribution between the defect portion and the defect-free portion is clear.

However, there are various environments surrounding actual structures, and there are no defective parts due to the influence of the season and time of measurement, the difference in the amount of solar radiation received by the structure, and the shadows of other structures. Defects may have similar temperature distributions, or conversely, different defect distributions or defect-free parts may exhibit different temperature distributions, and the difference between defect and defect-free parts may not be clear.

In such a case, the temperature distribution on the surface of the structure is measured by an infrared radiometer, the measurement result is displayed on a CRT screen, and the presence or absence of a defect is detected only by visually inspecting the CRT screen. It was very difficult.

Further, since the inspector who visually inspects the CRT screen judges whether or not the structure has a defect based on his own experience, there is a large reliance on the inspector's subjectivity. It was unavoidable that the detection accuracy was low.

On the other hand, this type of detection method using an infrared radiometer has not hitherto been aimed at detecting defects in a steel plate reinforced concrete structure. The reason is that the size of the steel plate itself is much larger than that of the tile, unlike the case where the floating of the tile is detected.
Therefore, not enough energy is actually given to the structure reinforced by steel plates, and even if the radiant energy from the surface is detected by an infrared radiometer, the temperature difference is too small,
This is probably because it was presumed that the defect could not be detected.

Therefore, an object of the present invention is to improve the detection accuracy of the defect portion on the structure surface by making it possible to clearly determine the temperature difference between the defect portion and the defect-free portion on the structure surface.

Another object is to measure the radiant energy from the surface of the structure with an infrared radiometer,
It may be possible to detect a defect in a steel plate reinforced structure.

[0012]

According to the present invention, which has solved the above-mentioned problems, the radiant energy from the surface of a structure is detected by an infrared radiometer, the temperature distribution on the surface of the structure is obtained, and defects in the structure are detected. In the method, in each time zone of daytime and nighttime, detection by the infrared radiometer is performed to obtain the temperature distribution of the structure surface in each time zone, and the difference temperature is obtained by differentially processing these temperature distributions. The feature is that a distribution is obtained and defects of the structure are detected based on the difference temperature distribution.

During the daytime, the temperature of the surface of the structure rises due to solar radiation. A part of the solar energy projected on the surface is reflected, but the rest is absorbed in the area, and the absorbed thermal energy is eventually transferred to the wall thickness direction. The surface temperature of the structure is determined by the relationship between this heat energy and its heat transfer rate. However, when there is a defect such as a floating tile, heat transfer is hindered in the floating part, so that the absorbed heat energy is transferred slowly, so that the surface temperature of the defect is a defect-free part. Will be higher than.

At night, heat transfer in the opposite direction occurs in which the heat energy absorbed by the structure is dissipated to the outside air having a low temperature. Therefore, a reversal phenomenon occurs in which the temperature of the surface is lower than that of the inside of the structure. Under this reversal phenomenon,
Regarding the temperature difference between the defective portion and the non-defective portion, the temperature of the defective portion is lower than that of the non-defective portion, that is, "a reversal phenomenon of the temperature difference" occurs.

Therefore, in the present invention, radiant energy is detected by an infrared radiometer during daytime and nighttime,
The temperature distribution on the structure surface is measured. Then, the temperature distribution on the surface of the structure detected in the daytime and the temperature distribution on the surface of the structure detected at night are subjected to a difference process to obtain a difference temperature distribution. Since the "temperature difference reversal phenomenon" occurs between daytime and nighttime, the temperature difference between the defective portion and the non-defective portion is amplified by obtaining the differential temperature distribution. Therefore, the temperature difference between the defective portion and the non-defective portion becomes very clear, and when the difference temperature distribution is displayed as an image, an inspector who visually checks the difference temperature distribution can easily detect the defect.

At this time, preferably, the differential temperature distribution is further subjected to time integration processing to obtain an integrated temperature distribution, and a defect of the structure is detected based on the integrated temperature distribution. The difference temperature distribution thus obtained is subjected to time integration processing to obtain the integrated temperature distribution, whereby the temperature difference between the defect portion and the defect-free portion is further amplified, and the defect detection becomes easier.

Further, in the present invention, it can be judged that there is a defect in a portion having a temperature difference of ± 0.3 ° C. or more in the difference temperature distribution or the integrated temperature distribution.

As described above, the presence or absence of a defect is clearly indicated by a numerical value, specifically, when there is a temperature difference of ± 0.3 ° C. or more, it is determined that there is a defect, and the CRT screen is displayed. It is possible to detect a defect with high objectivity as compared with the case where the visually inspected person judges the presence or absence of the defect based on his own experience and intuition.

On the other hand, in the present invention, the structure is
It may be a structure in which the surface of the concrete slab is integrated with a crocodile steel plate and reinforced with a steel plate. According to the present invention, since the temperature difference between the defect portion and the defect-free portion is amplified as described above,
For example, if the steel plate is too large and sufficient energy is not given to the structure reinforced by the steel plate, and the radiant energy from the surface is detected by an infrared radiometer, the temperature difference between the defective part and the non-defective part is small. Also, the defect can be sufficiently detected.

[0020]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be specifically described below. The defect detection method on which the present invention is based will be described. An infrared radiation thermometer (thermal image detector) is provided by glaring at the surface of the target structure, and the thermal energy radiated from the target structure surface is radiated by infrared radiation. Detect with a thermometer. This detection signal is taken into the image analysis device to obtain the temperature and temperature distribution image within the target imaging range, the part where the temperature is different from the surrounding is extracted from this temperature distribution image, and that part is detected as a defect. is there.

In the present invention, thermal energy is detected by this basic infrared radiation thermometer during the daytime and nighttime, respectively, and thermal images in both time zones are obtained. Then, in the image analysis device, for example, a temperature distribution image obtained by daytime detection is used as a subtracted image, and a temperature distribution image obtained by nighttime detection is used as a subtraction image to perform subtraction processing to obtain a subtraction processed image. In this subtraction-processed image, a portion having a temperature higher than that of the surrounding area is extracted, and it is determined to be a defective portion. In this subtraction processing image, the temperature difference between the defective portion and the non-defective portion is amplified, so that the defective portion can be easily detected.

Further, the subtracted image is time-integrated with respect to the subtracted image to obtain an integrated image. In this integration-processed image, a portion having a temperature higher than that of the surrounding is extracted, and it is determined that the image is a defective portion. By performing this integration process, the temperature difference between the defective portion and the non-defective portion is further amplified, so that the defective portion can be detected more easily.

The calculation processing such as the subtraction processing and the time integration processing can be easily performed by using the thermal image processing software "TVS-2000" provided by Japan Avionics Co., Ltd., for example.

In the subtraction-processed image or the integration-processed image thus obtained, it can be determined that the temperature difference from the surroundings is ± 0.3 ° C. or more and there is a defect in the low-temperature area. . When the subtracted image and the subtracted image are reversed, it is determined that there is a defect in the low temperature region. It has been found from many other experiments that when a temperature difference of less than ± 0.3 ° C. is used as an index for determining the presence / absence of a defect, the probability of misjudgment of the defect is high.

(Basic Experiment) As shown in FIG. 1, each structure has a width of 5 m and a height of 1.8 m on the roof of an existing structure 10 in a local city as a structure to be detected. A model structure 1 having new edge tiles attached was constructed. As shown in FIG. 2, the outer wall 1A of this model structure 1
Then, a simulated defect portion (tile peeling defect portion) having an area of about 7% was artificially created. Here, assuming that the simulated defect portion also determines whether there is a difference due to the area of the defect region,
An area for 32 tiles, an area for 16 tiles, an area for 8 tiles, and an area for 4 tiles were formed. The area value of 7% is an average value of the actual situation when the tile defect portion investigation is requested.

In order to detect defects on the outer wall surface, an infrared radiation thermometer (thermal image detector) 2 that gazes at the outer wall surface is installed on the roof.

The detection signal from the infrared radiation thermometer 2 is input to the image analysis device 20, and the analysis signal is further sent to the CRT.
It is displayed on the display device 21 or the like, or recorded on a flexible disk or the like.

In the apparatus constructed as described above, the infrared radiation energy from the outer wall 1A is detected by the infrared radiation thermometer 2 and each is arbitrarily divided in the image analysis apparatus 20 according to the purpose within the area to be processed. The average temperature per unit area is obtained, and the presence or absence of defects is determined based on the temperature difference between adjacent unit areas.

In the experiment, on a sunny day in spring, the infrared radiation thermometer continuously measured at intervals of 10 minutes from the sunrise for about 25 hours.

FIG. 3 shows the surface temperature change of the defective portion in the area corresponding to 32 tiles, and FIG. 4 shows the surface temperature change of the defective portion in the area corresponding to 8 tiles.

As can be seen from FIG. 3, regarding the defect in the area corresponding to 32 tiles, the time period when the temperature difference from the surroundings is ± 0.3 ° C. or less is 4:30 to 5:00, 10:00 to 10:00. 1
The time is extremely short such as 1:30 and 15:00 to 17:30, and defects can be detected in almost all other time zones, specifically 20 hours per day.

However, regarding the defect in the area corresponding to eight tiles, the time zone when the temperature difference from the surroundings is ± 0.3 ° C. or more is 5:30 to 9:30, 13:00 to 15:30,
It is a very short time from 0:00 to 3:00, and tile 3
Contrary to the area corresponding to two sheets, the time period in which defects can be detected is shorter, that is, 9.5 hours per day.

Therefore, according to the present invention, the temperature distribution on the surface of the structure detected during the day and the temperature distribution detected at night are subtracted. The process of the subtraction process will be schematically described by using the thermal image displayed on the CRT display screen 21A shown in FIGS. In FIG. 5, it is 10:00 during the day.
6 schematically shows a thermal image showing the temperature distribution on the surface of the model structure 1 detected in FIG. 6, and FIG. 6 schematically shows a thermal image showing the temperature distribution on the surface of the model structure 1 detected at 23:00 at night. .

In the temperature distributions shown in FIGS. 5 and 6, the defective portions in the area corresponding to the eight tiles are about + 0.2 ° C. and −0.2 ° C., respectively, as compared with the ambient temperature, so that there is an error. Taking this into account, this portion cannot be determined as a defect. However, when these thermal images are subjected to subtraction processing by the image analysis device as the image to be subtracted using the image shown in FIG. 5 and the image shown in FIG. 6 as the subtraction image, as shown schematically in FIG. Since the temperature difference of is amplified to + 0.4 ° C., the defect can be detected with high accuracy.

Further, by performing integration processing on the image shown in FIG. 5 with respect to the image shown in FIG. 7, the temperature difference in the area corresponding to the eight tiles is amplified to + 0.6 ° C., so that the detection accuracy is further improved. be able to.

On the other hand, for the area corresponding to 32 tiles,
Since the temperature difference is amplified to + 0.8 ° C, the accuracy of detection can be increased.

(Applied Experiment) In order to examine whether or not the result of the basic experiment described above can be applied to a steel plate reinforced structure, a steel plate reinforced structure is actually used. An applied experiment was conducted on the bridge. This applied experiment was conducted on a bridge on a highway over a first-class river in Tokyo.

As shown in FIG. 8, in this bridge 50, a pavement 52 is formed on a floor slab 51 in which a reinforcing steel plate 51B is adhered to a lower portion of a concrete floor slab 51A. It is supported by the main girder 53. Further, below the floor slab 51, there is a water main 54 as an attachment.
Is passing. FIG. 9 schematically shows the bottom surface of a certain length region in the two-lane portion of this bridge. In the region of FIG. 9, a boom car was used in advance to detect the reinforcing steel plate under the floor slab by a hammering method using a test hammer, and the defective portion K was marked with chalk. This defective portion K is
It was presumed by the tapping method that the adhesive covering about 500 cm ² was a peeled portion.

In the experiment, as shown in FIG. 8, the infrared radiation thermometer 2 was installed on the ground below the bridge, and the thermal radiation energy of the X part was calculated by the infrared radiation thermometer 2. The detection signal from the radiation thermometer 2 was analyzed by the image analysis device 20 and displayed on the CRT display device 21 as needed.

Then, in the image analysis apparatus 20, the temperature difference between the defect portion and the defect-free portion examined by the tapping method was obtained. This measurement was performed about every 10 minutes for about 24 hours. The result is shown in FIG.

From FIG. 10, it can be seen that the time zone in which the temperature difference between the defect portion and the defect-free portion is 0.3 ° C. or more is 1:00 to 10:00. In this time zone, the defective portion and the non-defective portion can be clearly distinguished, so that the defect can be detected relatively easily. However, for example, the temperature difference is ± 0.0
If the measurement is performed at 22:00, which is 0 ° C., the defect cannot be detected.

Then, during the daytime, for example, 12:00
Thermal image detected at night and night time, for example 23: 0
The thermal image detected at 0 is subtracted. Then, the temperature difference between the defective portion and its surrounding becomes about 1.0 ° C., and this defective portion can be detected with high accuracy. Furthermore, if the thermal image that has been subjected to the difference calculation is subjected to time integration calculation, the temperature difference between the defect portion and its surroundings becomes 1.5 ° C., and detection with higher accuracy can be performed.

As a result of the above-mentioned applied experiments, the method of detecting defects in a structure, which was carried out in the basic experiment, can be used for detecting defects in a structure reinforced by steel plates, and is effective in an actual bridge. Proved to be.

The present invention is not limited to the bridge diagnosis shown in the above-mentioned applied experiments, but can be applied to steel plates such as buildings, roofs, chimneys, dams, levees, tunnels, subways, and roads (highways) where steel plates are reinforced. It can be used for diagnosis.

[0045]

As is apparent from the above description, according to the present invention, the temperature difference between the defect portion and the defect-free portion on the structure surface can be clearly determined, so that the defect portion on the structure surface can be detected. The detection accuracy can be improved.

Further, by measuring the radiant energy from the surface of the structure with an infrared radiometer, it becomes possible to detect defects in the structure reinforced by the steel plate.

[Brief description of drawings]

FIG. 1 is a schematic diagram of a model structure used in a basic experiment of the present invention.

FIG. 2 is a schematic view showing an example of a wall surface of a target structure.

FIG. 3 is a graph showing the results of basic experiments of the present invention.

FIG. 4 is a graph showing the results of basic experiments of the present invention.

FIG. 5 is a schematic diagram of a thermal image of the wall surface of the target structure.

FIG. 6 is a schematic diagram of a thermal image of the wall surface of the target structure detected at another time.

FIG. 7 is a schematic diagram of these subtracted images.

FIG. 8 is a schematic diagram of a bridge used in an application experiment of the present invention.

FIG. 9 is a bottom view of a steel plate reinforced floor slab of the bridge.

FIG. 10 is a graph showing the results of application experiments of the present invention.

[Explanation of symbols]

1 ... Model structure, 2 ... Infrared radiometer, 10 ... Building,
20 ... Image analysis device, 21 ... VTR display device, 51 ... Steel plate reinforced floor slab, 51A ... Floor slab, 51B ... Reinforced steel plate, 50 ...
Bridges, 52 ... Paved roads, 53 ... Main girders, 54 ... Additives, K ...
Defective part.

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Susumu Harashima 1-5-1, Marunouchi, Chiyoda-ku, Tokyo Nitto Kagaku Kogyo Co., Ltd.

Claims (4)

[Claims] 1. A radiant energy from a structure surface is detected by an infrared radiometer to obtain a temperature distribution on the structure surface,
In the method of detecting a defect in a structure, the infrared radiation meter is used to detect the temperature distribution on the surface of the structure in each time zone during the daytime and nighttime, and the temperature distribution between these temperature distributions is calculated. Is detected to obtain a difference temperature distribution, and a defect of the structure is detected based on the difference temperature distribution. 2. The method for detecting a defect of a structure according to claim 1, wherein the differential temperature distribution is further subjected to time integration processing to obtain an integrated temperature distribution, and the defect of the structure is detected based on the integrated temperature distribution. 3. The method for detecting a defect in a structure according to claim 1, wherein it is judged that there is a defect in a portion having a temperature difference of ± 0.3 ° C. or more in the differential temperature distribution or the integrated temperature distribution. 4. The method for detecting a defect in a structure according to claim 1, wherein the structure is a structure in which a steel plate is integrally formed on the surface of a concrete slab to reinforce the steel plate.