JPH0545314A - Method for detecting defective part of concrete structure - Google Patents

Abstract

PURPOSE:To make it possible to detect a defect highly accurately in a short time without the skill of an engineer by emitting the infrared rays having the specified wavelength on a concrete structure, receiving the infrared rays reflected from the structure, and analyzing the infrared-ray data. CONSTITUTION:Infrared-rays (a) are emitted from an infrared-ray heater 2 as an infrared-ray source on an object 1 as a concrete structure. As the infrared rays, the rays having the wavelength of 1-15 microns are optimal. The infrared rays are reflected in conformity with the state of a defect 4 of the object 1. The image of the reflected infrared rays is picked up with an infrared-ray camera 3. The image of the intensity distribution of the photographed infrared rays is analyzed. The image analysis is performed on the monitored image or by printing out the image with a personal computer and printer. At the part where the defective part 4 is present, the intensity of the infrared rays appears at the low level. Therefore, the part is found at a glance. In the image analysis, e.g., the intensities of the infrared rays are compared for the individual pixels, and the pixel indicating the difference exceeding a certain level is plotted as one method.

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 defects such as cracks, dents and corner breaks in concrete structures such as bridges and dams.

[0002]

2. Description of the Related Art As a method of detecting a defective portion of a concrete structure, a method of detecting by visual inspection, a method of detecting by performing detailed inspection of appearance, a method of analyzing a visible image (photograph) and detecting it And the detection method by infrared image analysis are generally used.

A visual inspection is conducted by an engineer using binoculars or the like to confirm a defect such as a crack, sketching it on a field notebook, and drawing it. This method is performed by an engineer. There is a disadvantage that it requires skill and also requires man-hours and time.

In the detailed inspection of the appearance, the crack width is measured using a crack scale, and the grasping of the floating portion is confirmed by percussion, so that the defective portion can be surely detected. It has to be done by contacting each other, and it is necessary to construct a scaffold etc. each time, which requires a lot of time and a large amount of cost.

A detection method by analyzing a visible image (photograph) is
This is a method of analyzing the photographed data by image processing, but the photographing is usually performed by close-up photography, so a scaffold is required, and it is inefficient because the photographer must take a number of times while repeating small movements.

The infrared image analysis method is a method of measuring the intensity of infrared rays radiated from the concrete structure itself in a natural or forced heating state, that is, the temperature distribution. This method is effective only for detecting surface defects such as floats and cavities inside concrete by analyzing the surface temperature distribution. A linear defect such as a crack is affected by the temperature of its adjacent portion, and as a result, the temperature distribution is averaged and cannot be captured in a phenomenon-like manner.

[0007]

DISCLOSURE OF THE INVENTION The present invention eliminates the disadvantages of detecting a defective portion of a concrete structure, such as the skill and the scaffolding, which are found in the conventional methods. Moreover, it is an object to provide a detection method with high detection accuracy.

[0008]

SUMMARY OF THE INVENTION The present invention solves the above problems in a method for detecting a defective portion of a concrete structure by irradiating the structure with infrared rays and receiving the infrared rays reflected by the concrete structure with an infrared camera. , It solved by using the non-contact means to the structure of analyzing the infrared data.

(Principle of measurement) The concrete surface is smooth from a macro point of view, but has numerous microscopic irregularities. Therefore, similar to paper or the like, when it is exposed to light, it is diffusely reflected uniformly. If the concrete is cracked, the assumption of diffuse reflection is broken, and the reflection density (strength) of the cracked part is reduced. The present invention detects a defect such as a crack by irradiating infrared rays at a higher level than the infrared rays emitted by the structure itself and capturing the reflected waves (a conceptual diagram is shown in FIG. 2).

(Reason for using infrared rays) Infrared rays have the properties of both visible rays and microwaves, and like visible rays, they are condensed by a lens or a mirror, refracted and reflected, and at the same time, are converted into microwaves. It also propagates through the object. When a concrete structure is irradiated with infrared rays, it is reflected, absorbed, and transmitted on the concrete surface. Therefore, the cracks and irregularities on the surface reflect differently from a smooth concrete surface. (FIG. 2) In this case, it is not affected by visible rays, ultraviolet rays, X-rays, microwaves and the like. Therefore, the amount of infrared rays appears as a clear difference, and it becomes easy to detect the defective portion.

Since visible light has a large difference in absorption and reflection when there is dirt (brightness and darkness) or a pattern, it is unsuitable for mechanical image analysis of cracks in concrete. It is unsuitable for structures in the atmosphere because it is largely absorbed by ozone and oxygen gas. X-rays penetrate relatively low-density X-rays such as concrete structures and do not meet this purpose. There is also a problem with safety, because the wavelength of microwaves becomes long and the resolution deteriorates, so when cracks of about 0.1 mm in concrete structures are detected, the accuracy becomes poor and detection becomes impossible, and absorption by water vapor etc. Is not appropriate because it affects.

Therefore, in the present invention, the advantages of infrared rays are utilized, but infrared rays in the short wavelength range of about 1 to 15 microns are most preferable. When the wavelength of infrared rays becomes long, the resolution and the straightness thereof may be deteriorated, and the resolution accuracy may be slightly lowered.

[0013]

[Operation] When the concrete structure is irradiated with infrared rays,
Infrared rays are reflected, but due to the defective shape of the concrete structure, the reflection direction changes and the infrared intensity is different, and the intensity difference is photographed by the infrared camera.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 schematically shows an embodiment of the present invention, in which 1 is a subject as a concrete structure, 2 is an infrared heater as an infrared source, and 3 is an infrared camera. First, the subject 1 is irradiated with infrared rays by an infrared heater. The infrared rays are reflected according to the defect condition of the subject 1. The reflected infrared rays are photographed.

Next, image analysis of the intensity distribution of the photographed infrared rays is performed. Image analysis is performed on the monitor screen or by printing out with a personal computer and printer. Infrared intensity appears low where there is a defect, so it is obvious. Although various methods can be considered for image analysis,
For example, there is also a method of comparing infrared intensities of respective pixels and plotting pixels showing a difference of a certain level or more.

[0016]

INDUSTRIAL APPLICABILITY The present invention is a method for detecting a defective portion by irradiating the concrete structure to be surveyed with infrared rays to photograph reflected infrared rays with an infrared camera and analyzing the infrared data, so No skill required,
Universal results are obtained in a short time because there is no personal difference. Moreover, the defect can be detected more reliably as compared with the conventional imaging of infrared rays emitted by the structure itself by natural or forced heating. It also eliminates the disadvantages of constructing a scaffold, such as contact investigations using a scale or close-up photography.

[Brief description of drawings]

1 diagrammatically shows an embodiment of the invention.

FIG. 2 is an explanatory diagram of diffused reflection of infrared rays applied to a concrete structure.

[Explanation of symbols]

 1 Subject as concrete structure 2 Infrared heater as infrared source 3 Infrared camera 4 Crack of concrete

Front Page Continuation (72) Inventor Hiroaki Mishima 2-1049 Nakanahata, Ikoma-shi, Nara Waka Royal Building 302

Claims (2)

[Claims] 1. A concrete structure is characterized in that a concrete structure is irradiated with infrared rays from an infrared source, infrared rays reflected from the concrete structure are received by an infrared camera, and the infrared data is analyzed to detect a defective portion of the concrete. Method for detecting defects in concrete structures. 2. The infrared rays with which the concrete structure is irradiated have a wavelength of 1 to 15 microns.
For detecting defective parts of concrete structures in.