Inspection device and method for internal reinforcing bars in reinforced concrete structures

Abstract

To provide an inspection device and inspection method capable of determining whether there is a break point inside reinforcing bars even for a reinforced concrete structure to which equipment is attached.SOLUTION: An inspection device 1 includes a thermometer and an arithmetic device 100. The thermometer is for measuring a change over time in the temperature distribution of the surface of a reinforced concrete structure. The arithmetic device 100 is for generating data related to an imposed stress variation image showing an imposed stress variation of the reinforced concrete structure on the basis of a change over time in the temperature distribution measured by the thermometer. The thermometer is an infrared camera 2 that generates a temperature image indicating the temperature distribution of the surface of the reinforced concrete structure. The arithmetic device 100 may generate data related to an imposed stress variation image indicating an imposed stress variation of the reinforced concrete structure on the basis of the temperature image generated by the infrared camera 2.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to an inspection device and an inspection method for internal reinforcing bars in a reinforced concrete structure. [Background technology]

[0002] In order to prevent reinforced concrete columns from breaking, periodic visual inspections are performed. Since visual inspections of reinforced concrete columns do not adequately grasp the state of the internal reinforcing bars, development of a method for non-destructively inspecting the broken parts of the internal reinforcing bars in reinforced concrete columns is underway. For example, Patent Document 1 discloses an inspection method for determining the presence or absence of broken parts of the internal reinforcing bars by magnetizing the internal reinforcing bars of a reinforced concrete column from the outside and measuring the minute magnetic flux leaking from the broken parts of the internal reinforcing bars. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2006-177747 A Summary of the Invention [Problem to be solved by the invention]

[0004] The inspection method of Patent Document 1 has a problem that if equipment such as overhead wire fittings, electric wires, and machinery is attached to a reinforced concrete pole, the internal reinforcing bar cannot be magnetized and the presence or absence of a fracture in the internal reinforcing bar cannot be determined. For this reason, it is necessary to remove various equipment from the reinforced concrete pole before magnetizing the internal reinforcing bar, and the inspection work takes a lot of time. This problem is not limited to the case of determining the presence or absence of a fracture in the internal reinforcing bar in a reinforced concrete pole, but also exists in the case of determining the presence or absence of a fracture in the internal reinforcing bar in other reinforced concrete structures.

[0005] The present invention has been made against this background, and aims to provide an inspection device and an inspection method that can determine whether or not there are any broken internal rebars, even in reinforced concrete structures with equipment attached. [Means for solving the problem]

[0006] In order to achieve the above object, an inspection device according to the present invention comprises: An inspection device for detecting the presence or absence of fractures in internal reinforcing bars in a reinforced concrete structure, Due to thermoelastic effect A thermometer for measuring a change over time in the temperature distribution on the surface of the reinforced concrete structure; a calculation device that generates data relating to a stress fluctuation image showing stress fluctuations in the reinforced concrete structure based on the change over time in temperature distribution measured by the thermometer; and Equipped with. Effect of the Invention

[0007] According to the present invention, it is possible to provide an inspection device and an inspection method that can determine whether or not there is a break in the internal reinforcing bars, even in a reinforced concrete structure to which equipment is attached. [Brief description of the drawings]

[0008] [Figure 1] 1 is a schematic diagram showing a configuration of an inspection device according to a first embodiment of the present invention. [Diagram 2] 1 is a block diagram showing a hardware configuration of a calculation device according to a first embodiment of the present invention. [Diagram 3] FIG. 1(a) is a diagram showing an example of a data table stored in a temperature video memory unit according to embodiment 1 of the present invention, and FIG. 1(b) is a diagram showing an example of a data table stored in a stress fluctuation image memory unit according to embodiment 1 of the present invention. [Figure 4] 5 is a diagram showing a procedure by which the arithmetic device according to the first embodiment of the present invention calculates a temperature difference for each pixel of a temperature image. FIG. [Diagram 5] 4 is a flowchart showing the flow of an inspection method according to the first embodiment of the present invention. [Figure 6] 4 is a flowchart showing a flow of calculation processing according to the first embodiment of the present invention. [Figure 7] FIG. 11 is a schematic diagram showing a configuration of an inspection device according to a second embodiment of the present invention. [Figure 8] FIG. 10(a) is a perspective view showing a configuration of a wind type coil according to a second embodiment of the present invention, and FIG. 10(b) is a perspective view showing a configuration of a spot type coil according to the second embodiment of the present invention. [Figure 9] 10 is a flowchart showing the flow of an inspection method according to a second embodiment of the present invention. [Figure 10] FIG. 2 is a cross-sectional view showing a test piece of a reinforced concrete column in Example 1. [Figure 11] 1A and 1B are photographs of the bending test in Example 1 taken from above and from the side, respectively. [Figure 12] 4(a) and 4(b) are diagrams showing stress variation images of a test piece of a reinforced concrete column in Example 1. [Figure 13] 4A to 4C are diagrams showing temperature change images and stress fluctuation images of a test piece of a reinforced concrete column to which a mounting bracket was attached in Example 1. [Figure 14] 13(a) and 13(b) are diagrams showing the state in which a wind coil and a spot coil are set on a test piece of a reinforced concrete column in Example 2. [Figure 15] 1A is a diagram showing a temperature image of a test piece of a reinforced concrete pillar in Example 2, and FIG. 1B is a diagram showing a temperature image of a test piece of a reinforced concrete pillar to which a mounting bracket in Example 2 is attached. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An inspection apparatus and an inspection method according to embodiments of the present invention will now be described in detail with reference to the drawings. In the drawings, the same or equivalent parts are designated by the same reference numerals.

[0010] (Embodiment 1) An inspection device and an inspection method according to a first embodiment will be described with reference to Fig. 1 to Fig. 6. In the first embodiment, a method for detecting a broken portion of an internal rebar in a reinforced concrete column (hereinafter abbreviated as "CP") will be described when an unbalanced load occurs at the broken portion of the internal rebar and the internal stress is constantly fluctuating. The inspection device and the inspection method according to the first embodiment are useful when the internal rebar in the middle part of the CP is broken and an unbalanced load is occurring at the broken portion due to stress concentration.

[0011] In the inspection method according to the first embodiment, a thermoelastic stress measurement technique is used to determine whether or not there is a fracture in the internal rebar of a CP in a stress-varying state. Specifically, an infrared camera is first used to measure the temperature distribution on the surface of the CP in a stress-generated state. The temperature distribution on the surface of the CP reflects the temperature distribution of the internal rebar due to heat transfer. Next, a stress variation image is generated that shows the distribution of stress variations in the CP based on the change over time in the measured temperature distribution on the surface of the CP.

[0012] If the generated stress fluctuation image shows a location where the stress fluctuation is large compared to the surrounding area, the location where the stress fluctuation is large is determined to be the location where the internal rebar is broken. This is because in a sound CP, the load is applied evenly to the internal rebar and concrete, and no locations of stress concentration occur, whereas in a CP where the internal rebar is broken, the broken internal rebar cannot withstand the tensile load, and the load is concentrated on the internal rebar that receives the compressive load on the opposite side.

[0013] The mechanism of thermoelastic stress measurement technology, which is the premise of the inspection method according to the first embodiment, will be described below. It is widely known that adiabatic expansion of gas reduces the temperature, and adiabatic compression of gas increases the temperature, but a similar phenomenon also occurs when stress is applied to a solid. The phenomenon in which temperature change occurs due to elastic deformation of a solid is called the "thermoelastic effect." The relationship between the amount of change ΔT in the temperature of the measurement object in the thermoelastic effect and the fluctuation width Δσ of the sum of the principal stresses of the measurement object is expressed by the following formula. ΔT=-K*T*Δσ …(1)

[0014] Principal stress is the stress acting on the principal stress surface of the measurement object. The principal stress surface is the surface of the measurement object where the shear stress is zero and the normal stress is maximum or minimum. In addition, T in formula (1) is the absolute temperature of the measurement object at the time of measurement, and K is the thermoelastic coefficient. The thermoelastic coefficient K is a unique value set for each material of the measurement object. For example, in the case of CP, K = 4.0 x 10 -6 MPa -1 It is.

[0015] In thermoelastic stress measurement technology, an infrared camera is used to measure the minute amount of temperature change ΔT when a stress fluctuation occurs in the measurement object, and the measured amount of temperature change ΔT is substituted into equation (1) to convert it into the fluctuation width Δσ of the sum of principal stresses. An infrared camera is used to measure the temperature of the measurement object because it measures the temperature of the measurement object without contacting it, thereby not disturbing the temperature field of the measurement object. This is how thermoelastic stress measurement technology works.

[0016] Next, the configuration of an inspection device 1 according to the first embodiment will be described with reference to Fig. 1. The inspection device 1 includes an infrared camera 2 that captures a temperature image (thermography) that is an image showing the temperature distribution on the surface of a CP to be measured, and a calculation device 100 that generates a stress fluctuation image that is an image showing stress fluctuations in the CP based on the temperature image captured by the infrared camera 2. The calculation device 100 is, for example, a general-purpose computer. The infrared camera 2 and the calculation device 100 are connected to each other so as to be able to communicate with each other via a wired or wireless communication line.

[0017] The infrared camera 2 is an example of a thermometer that measures the temperature distribution on the CP surface. The temperature image captured by the infrared camera 2 is, for example, a video (temperature video) showing the change in temperature distribution on the CP surface. The temperature video is a chronological arrangement of frames showing the temperature distribution on the CP surface acquired at a constant sampling period. The stress fluctuation image is an image that expresses the distribution of stress fluctuations on the CP using a color distribution.

[0018] The infrared camera 2 detects infrared energy emitted from the measurement object and converts it into a signal indicating the intensity of the infrared energy. The converted signal is then processed to generate a temperature image in which the temperature distribution of the measurement object is visualized as a color distribution. The infrared camera 2 preferably has a highly accurate temperature resolution, for example, 0.02 K or less. This is because the temperature change of a solid is extremely minute, and in order to improve the accuracy of the converted value of the stress variation, it is necessary for the infrared camera 2 to have a highly accurate temperature resolution. The infrared camera 2 may be supported by, for example, a tripod. The inspection device 1 has the above configuration.

[0019] Next, a hardware configuration of the arithmetic device 100 according to the first embodiment will be described with reference to Fig. 2. The arithmetic device 100 includes an operation unit 110, a display unit 120, a communication unit 130, a storage unit 140, and a control unit 150. The units of the arithmetic device 100 are connected to each other via an internal bus (not shown).

[0020] The operation unit 110 receives an instruction from a user, and supplies an operation signal corresponding to the received operation to the control unit 150. The operation unit 110 includes, for example, a mouse and a keyboard.

[0021] The display unit 120 includes a display drive circuit, and displays various images to the user based on data supplied from the control unit 150.

[0022] The communication unit 130 is a communication interface for the arithmetic device 100 to communicate with an external device. The communication unit 130 communicates with the external device via a communication network such as the Internet and an input / output terminal. The input / output terminal is, for example, a Universal Serial Bus (USB).

[0023] The storage unit 140 includes, for example, a random access memory (RAM), a read only memory (ROM), a flash memory, and a hard disk. The storage unit 140 stores programs executed by the control unit 150 and various data, for example, the formula (1) and the value of the thermoelastic coefficient K for each material. The storage unit 140 also temporarily stores various information and functions as a work memory for the control unit 150 to execute processing. The storage unit 140 further includes a temperature video storage unit 141 and a stress variation image storage unit 142.

[0024] 3(a), the temperature video storage unit 141 stores the temperature video captured by the infrared camera 2 in association with the CP identification number and the capture position. The CP identification number is a unique identification number assigned to each CP. The capture position is expressed by, for example, the axial position (height) z1, z2, ... of the CP and the angle r1, r2, ... around the CP axis.

[0025] As shown in FIG. 3(b), the stress fluctuation image storage unit 142 stores the stress fluctuation image generated by the arithmetic device 100 based on the temperature change image in association with the CP identification number and the imaging position.

[0026] Returning to Fig. 2, the control unit 150 includes a processor and controls each unit of the arithmetic device 100. The processor is, for example, a CPU (Central Processing Unit). The control unit 150 executes the program stored in the storage unit 140 to perform the arithmetic processing of Fig. 6. The control unit 150 functionally includes an acquisition unit 151, a temperature difference calculation unit 152, a stress variation image generation unit 153, and an output unit 154.

[0027] The acquiring unit 151 acquires a temperature video showing the temperature distribution on the CP surface captured by the infrared camera 2, and stores the temperature video in the temperature video storage unit 141 in association with the CP identification information and the capture position. The acquisition of data by the acquiring unit 151 includes reading out data stored in the storage unit 140.

[0028] The temperature difference calculation unit 152 calculates the temperature difference for each pixel of the temperature video based on the temperature video acquired by the acquisition unit 151. Specifically, a certain number of analysis points of frames may be extracted from the temperature video acquired by the acquisition unit 151, and a difference between the maximum and minimum temperature values ​​may be calculated for each pixel from the collection of extracted frames. The number of analysis points is the number of frames to be extracted, for example, 250 frames. As shown in FIG. 4, the extraction of frames may be performed for each certain analysis step from the first frame, and the temperature differences ΔT1, ΔT2, ΔT3, ΔT4, ... may be calculated one after another from the collection of extracted frames. The analysis step is the position at which the extraction of frames starts, and may be, for example, every 150 steps from the first frame. The temperature difference calculation unit 152 may generate a temperature change image showing a change in the temperature distribution of the CP surface by expressing the calculated value of the temperature difference for each pixel as a color distribution.

[0029] The stress variation image generating unit 153 generates a stress variation image showing the stress variation of the CP based on the calculated value of the temperature difference showing the temperature change of the CP surface for each pixel calculated by the temperature difference calculating unit 152, and stores the generated stress variation image in the stress variation image storage unit 142 in association with the CP identification information and the shooting position. Specifically, the calculated value ΔT of the temperature difference for each pixel of the temperature variation image is substituted into equation (1) to convert it into a converted value Δσ of the stress variation. Next, a stress variation image showing the stress variation of the CP is generated by expressing the converted value of the stress variation for each pixel as a color distribution. Note that the generation of the stress variation image includes the generation of data (image data) related to the stress variation image and the generation of a latent image of the stress variation image.

[0030] The output unit 154 outputs to the outside the data of the stress variation image converted by the stress variation image generating unit 153. For example, the stress variation image may be displayed on the display unit 120. The hardware configuration of the arithmetic device 100 has been described above.

[0031] Next, a flow of an inspection method executed by a user using the inspection device 1 according to the first embodiment will be described with reference to Fig. 5. First, the infrared camera 2 is set up facing the CP (step S11). Specifically, a tripod is attached to the infrared camera 2, and the tripod is set on the ground so that the infrared camera 2 faces the CP.

[0032] Next, a temperature video showing the temperature distribution on the CP surface is captured using the infrared camera 2 installed in step S11 (step S12). The frame rate and capture time of the temperature video are preset by the user. In order to grasp the temperature change on the CP surface, it is preferable to capture images of, for example, 2000 frames or more.

[0033] Next, based on the temperature video captured by the infrared camera 2 in the process of step S12, the arithmetic device 100 executes the arithmetic processing of FIG. 6, thereby causing the display unit 120 of the arithmetic device 100 to display a stress variation image of the CP (step S13).

[0034] Next, based on the stress variation image obtained in the process of step S13, the presence or absence of fractured parts of the rebar inside the CP is determined (step S14). Specifically, there is almost no stress variation in parts where the internal rebar is not fractured, whereas at fractured parts of the internal rebar, the load remains unbalanced and the stress fluctuates greatly. Therefore, the user can observe the color distribution of the stress variation image of the CP and determine whether there are any parts where the color distribution is significantly different from the surrounding areas, thereby determining the fractured parts of the internal rebar. The above is the flow of the inspection method.

[0035] (Calculation processing) Next, a flow of the arithmetic processing executed by the arithmetic device 100 according to the first embodiment will be described with reference to Fig. 6. The arithmetic processing starts when an instruction from a user is received after a temperature video of the CP surface is captured by the infrared camera 2.

[0036] First, the acquisition unit 151 acquires a temperature video obtained by capturing the temperature distribution on the surface of the CP (step S21).

[0037] Next, the temperature difference calculation unit 152 calculates a temperature difference indicating a temperature change on the CP surface for each pixel based on the temperature video acquired in the process of step S21 (step S22). Specifically, a certain number of frames are extracted from the temperature video acquired in the process of step S21, and the difference between the maximum and minimum temperatures for each pixel is calculated from the collection of extracted frames.

[0038] Next, the stress fluctuation image generating unit 153 generates a stress fluctuation image showing the stress fluctuation of the CP based on the calculated temperature difference showing the temperature change of the CP surface for each pixel calculated in the process of step S22 (step S23). Specifically, the calculated temperature difference ΔT for each pixel of the temperature image is substituted into formula (1) to convert it into a converted value Δσ of the stress fluctuation.

[0039] Next, the output unit 154 causes the display unit 120 to display the stress variation image obtained in the process of step S23 (step S24), and the process ends. The above is the flow of the calculation process.

[0040] As described above, the inspection device 1 according to the first embodiment includes an infrared camera 2 that measures the change over time in the temperature distribution on the surface of the CP, and a calculation device 100 that generates a stress variation image showing the stress variation of the CP based on the change over time in the temperature distribution measured by the infrared camera 2. Therefore, even in a place where equipment is attached to the CP, it is possible to determine the presence or absence of a fractured part of the internal rebar, and as a result, the degree of deterioration of the CP can be determined quickly and accurately. This reduces the cost required for the maintenance management of the CP and the burden of inspection by workers.

[0041] (Embodiment 2) An inspection device and an inspection method according to the second embodiment will be described with reference to Figs. 7 to 9. In the first embodiment, the temperature of the CP surface in a stressed state is measured, but in the second embodiment, the temperature of the CP surface is measured after the internal rebar of the CP in a stationary state is heated by an induction coil. The inspection device and the inspection method according to the second embodiment can also be applied to cases where no unbalanced load due to stress concentration is occurring. The following mainly describes the differences between the two.

[0042] The configuration of the inspection device 1 according to the second embodiment will be described with reference to Fig. 7. The inspection device 1 includes an induction heating coil 3 that heats the internal rebar of the CP from the outside, and an infrared camera 2 that measures the temperature distribution on the surface of the CP after the internal rebar is heated by the induction heating coil 3.

[0043] The infrared camera 2 is equipped with a monitor that displays a temperature image showing the temperature distribution on the CP surface. The temperature image captured by the infrared camera 2 may be a still image showing the temperature distribution on the CP surface, or a temperature video showing the change in the temperature distribution on the CP surface.

[0044] The induction heating coil 3 is an example of a heating means for externally heating the internal rebar of the CP. The induction heating coil 3 utilizes the principle of electromagnetic induction to heat the internal rebar without contacting it. The principle of electromagnetic induction is that when an alternating current is passed through the coil's conductor, a fluctuating magnetic field is generated around it, and when metal is placed in this magnetic field, an induced current flows due to electromagnetic induction, and this induced current generates Joule heat in the metal.

[0045] The induction heating coil 3 may be a wound coil 3A shown in Fig. 8(a), a spot coil 3B shown in Fig. 8(b), or another type. The wound coil 3A heats the internal rebar while wound around the CP. The spot coil 3B is a water-cooled spiral coil, and is suitable for pinpoint heating of cracked areas.

[0046] Next, with reference to Fig. 9, a flow of an inspection method executed by a user using the inspection device 1 according to the second embodiment will be described. First, the infrared camera 2 and the induction heating coil 3 are placed relative to the CP (step S31). Specifically, a tripod is attached to the infrared camera 2, and the tripod is placed on the ground so that the infrared camera 2 faces the CP. The induction heating coil 3 may be wrapped around the surface of the CP or placed in the vicinity of the surface.

[0047] Next, the internal rebar of the CP is heated by the induction heating coil 3 installed in step S31 (step S32). Specifically, a high frequency is supplied to the induction heating coil 3 to generate a fluctuating magnetic field in the vicinity of the induction heating coil 3, which generates an eddy current in the internal rebar, thereby generating Joule heat in the internal rebar.

[0048] Next, the infrared camera 2 installed in step S31 is used to capture a temperature image showing the temperature distribution on the surface of the CP after the internal rebar is heated in step S32 (step S33). The temperature image may be either a still image or a video image.

[0049] Next, the temperature image obtained in step S33 is displayed on a monitor (step S34), and the presence or absence of a fractured portion of the rebar inside the CP is determined based on the temperature image displayed on the monitor (step S35), and the process ends. Specifically, in areas where the internal rebar is not fractured, the surface of the CP also heats up due to the heat generated by the internal rebar, whereas in areas where the internal rebar is fractured, the surface of the CP does not heat up as a result of no induction heating of the internal rebar. Therefore, the user can determine the presence or absence of a fractured portion of the internal rebar by observing the color distribution of the temperature image. Even if equipment is attached to the CP, the heat generated by the equipment does not affect the temperature distribution of the CP over a wide area, so the presence or absence of a fractured portion of the internal rebar can be determined except for areas overlapping with the equipment. The above is the flow of the inspection method according to the second embodiment.

[0050] In addition to the infrared camera 2 and the computing device 100, the inspection device 1 according to the second embodiment includes an induction heating coil 3 that is installed near the CP and heats the internal rebar of the reinforced concrete structure from the outside. Therefore, even if no stress fluctuation occurs in the internal rebar, the presence or absence of a fracture can be determined by using the induction heating coil 3. Also, unlike the inspection device 1 of the invention according to the first embodiment, analysis of temperature images is not required, so the presence or absence of a fracture in the internal rebar can be determined quickly on-site.

[0051] The present invention is not limited to the above-described embodiment, and the following modifications are possible.

[0052] (Modification) In the above embodiment, there is one infrared camera 2, but the present invention is not limited to this. For example, two or more infrared cameras 2 may be provided in order to quickly capture an image of the entire CP.

[0053] In the above embodiment, the infrared camera 2 is used as a thermometer, but the present invention is not limited to this. For example, a non-contact thermometer other than the infrared camera 2 may be used.

[0054] In the above embodiment, the infrared camera 2 captures a temperature image showing the temperature distribution on the CP surface, but the present invention is not limited to this. If data showing the temperature distribution on the CP surface can be obtained, it is not necessary to capture a temperature image, and the data showing the temperature distribution on the CP surface may be treated as numerical data corresponding to pixel positions.

[0055] In the above-mentioned first embodiment, the calculation device 100 generates a stress variation image, and the user judges whether or not there is a fractured part in the internal rebar by referring to the stress variation image displayed on the display unit 120 of the calculation device 100, but the present invention is not limited to this. For example, the control unit 150 of the calculation device 100 may detect whether or not there is a fractured part in the internal rebar based on the stress variation image.

[0056] Specifically, the converted value of the stress variation is compared with a preset stress variation threshold for each pixel in the stress variation image, and if there is a pixel whose converted value of the stress variation is equal to or greater than the stress variation threshold, it is determined that the internal rebar is fractured at the location corresponding to that pixel. At this time, it is not necessary to display the stress variation image on the display unit 120 of the computing device 100, and it is sufficient to simply compare the converted value of the stress variation at each pixel of the stress variation image with the stress variation threshold and display the comparison result.

[0057] In the above-mentioned second embodiment, the monitor of the infrared camera 2 displays a temperature image, and the user judges whether or not there is a fractured part in the internal rebar by referring to the temperature image displayed on the monitor of the infrared camera 2, but the present invention is not limited to this. For example, the calculation device 100 may be communicatively connected to the infrared camera 2, and the control unit 150 of the calculation device 100 may detect whether or not there is a fractured part in the internal rebar based on the temperature image captured by the infrared camera 2.

[0058] Specifically, the area corresponding to the internal rebar is recognized in the temperature image, the measured temperature value is compared with a preset temperature threshold for each pixel in the recognized area, and if there is a pixel whose measured temperature value is equal to or lower than the temperature threshold, it is determined that the internal rebar is broken at the location corresponding to that pixel. At this time, it is not necessary to display the temperature image on the display unit 120 of the computing device 100, and it is sufficient to simply compare the measured temperature value at each pixel of the temperature image with the temperature threshold and display the comparison result.

[0059] In the above-mentioned second embodiment, one induction heating coil 3 is applied to the CP, but the present invention is not limited to this. The number of induction heating coils 3 to the CP is arbitrary, and for example, two or more may be used in order to heat a wide range of the internal rebar.

[0060] In the above-mentioned first embodiment, various data are stored in the storage unit 140 of the arithmetic device 100, but the present invention is not limited to this. For example, all or part of the various data may be stored in an external control device or computer via a communication network.

[0061] In the above-mentioned first embodiment, the arithmetic devices 100 operate based on the programs stored in the storage units 140, but the present invention is not limited to this. For example, the functional configuration realized by the programs may be realized by hardware.

[0062] In the first embodiment, the arithmetic device 100 is, for example, a general-purpose computer, but the present invention is not limited to this. For example, the arithmetic device 100 may be realized by a computer provided on a cloud.

[0063] In the above-mentioned embodiment 1, the processing performed by the arithmetic device 100 is realized by a device having the above-mentioned physical configuration executing a program stored in the memory unit 140, but the present invention may also be realized as a program or as a storage medium on which the program is recorded.

[0064] In addition, a program for executing the above-mentioned processing operations may be stored and distributed on a non-transitory computer-readable recording medium such as a flexible disk, a CD-ROM (Compact Disk Read-Only Memory), a DVD (Digital Versatile Disk), or an MO (Magneto-Optical Disk), and the program may be installed on a computer to configure an apparatus that executes the above-mentioned processing operations.

[0065] In the above embodiment, the inspection object is a reinforced concrete pillar, which is an example of a long reinforced concrete structure, but the present invention is not limited to this. Other reinforced concrete structures, such as bridge decks, bridge piers, and building beams, girders, and columns, may also be inspected.

[0066] The above-mentioned embodiments are merely examples, and the present invention is not limited to these, and various embodiments are possible without departing from the spirit of the invention described in the claims. The components described in each embodiment and modification can be freely combined. In addition, inventions equivalent to the inventions described in the claims are also included in the present invention.

[0067] The present invention will be specifically described below with reference to examples, although the present invention is not limited to these examples.

[0068] Example 1 In Example 1, bending stress was artificially generated in the middle of the CP sample, and it was verified whether or not the presence or absence of a fractured portion of the internal rebar could be determined using the method according to the first embodiment.

[0069] First, as shown in Fig. 10, a radial cut was made in the middle of a CP having 12 internal rebars, and 4 internal rebars were cut to create a CP sample (fractured sample). Next, bending deformation was applied to the CP sample so that a tensile load was applied to the fractured parts of the internal rebars, and the surface (compressed surface) of the CP sample on the side where the compressive load was applied was photographed with an infrared camera for about 20 seconds (about 2000 frames). Specifically, as shown in Fig. 11(a), a bending test was performed using a bending test device of JIS (Japanese Industrial Standards) A 5373. At this time, with the middle part of the CP fixed with a wire as shown in Fig. 11(b), the end of the CP was pulled so that a tensile load was applied to the fractured parts of the internal rebars. The load on the fractured sample was in the range of 2.5kN to 3kN.

[0070] Next, a stress fluctuation image was generated based on the temperature video of the compression surface of the CP specimen taken by infrared camera 2. Specifically, the measured temperature difference for each pixel obtained from the temperature video was converted into an equivalent value of stress fluctuation using equation (1). Then, it was confirmed whether the fracture location of the internal rebar could be detected based on the stress fluctuation image. For comparison, a similar experiment was also conducted on a sound specimen in which the rebar was not cut. The loading load on the sound specimen was 7kN (the standard value for fracture of CP).

[0071] As a result, in the sound specimen, as shown in Fig. 12(a), the stress was dispersed overall and there were no points of stress concentration. On the other hand, in the fractured specimen, as shown in Fig. 12(b), it was confirmed that there were points of stress concentration, i.e., fractured points of the internal rebars, even in the load range of 2.5kN to 3kN.

[0072] Next, we verified whether it was possible to identify the fracture location of the internal rebar even when the overhead wire fittings were attached to the middle of the CP. All other experimental conditions were the same as when the overhead wire fittings were not attached. As a result, as shown in the stress fluctuation image in Figure 13, it was confirmed that there were stress concentration locations in the internal rebar even when the overhead wire fittings were attached to the middle of the CP.

[0073] Example 2 In Example 2, a CP sample was heated from the outside, and it was verified whether or not the presence or absence of fractures in the internal rebars could be determined using the method according to the second embodiment.

[0074] First, a CP test specimen was taken from the middle of the CP of an actual facility where part of the internal rebar had broken. Next, as shown in Figures 14(a) and (b), the surface of the taken CP test specimen was photographed with an infrared camera 2 while the internal rebar of the CP test specimen was heated, and an attempt was made to identify the location of the fracture in the internal rebar based on the temperature image obtained by the infrared camera 2. Note that a wind-type coil 3A and a spot-type coil 3B were used as the induction heating coils 3 used to heat the internal rebar. Hereinafter, the method using the wind-type coil will be referred to as the "wind method," and the method using the spot-type coil will be referred to as the "spot method."

[0075] As a result, as shown in the temperature image in Figure 15(a), in both the wind method and the spot method, the internal rebar generated heat, resulting in a significant temperature difference between the fracture point of the internal rebar and the surrounding area, making it possible to clearly distinguish between the two.

[0076] Next, we verified whether it was possible to identify the location of the fractured internal rebar even when overhead wire fittings were attached to the middle of the CP. All other experimental conditions were the same as when overhead wire fittings were not attached. As a result, as shown in the temperature images in Figure 15(b), with both the wind method and the spot method, a significant temperature difference was apparent between the fractured location of the internal rebar and other locations, except for the location where the overhead wire fittings were attached, making it possible to clearly distinguish between the two. [Explanation of symbols]

[0077] 1. Inspection equipment 2. Infrared camera 3. Induction heating coil 100 Computing equipment 150 Control section 152 Temperature difference calculation section 153 Stress Variation Image Generation Unit

Claims

1. An inspection device for detecting the presence or absence of fractures in internal reinforcing bars in a reinforced concrete structure, a thermometer for measuring a change over time in the temperature distribution on the surface of the reinforced concrete structure due to a thermoelastic effect; a calculation device that generates data relating to a stress fluctuation image showing stress fluctuations in the reinforced concrete structure based on the change over time in temperature distribution measured by the thermometer; and An inspection device comprising:

2. the thermometer is an infrared camera that generates a temperature image showing the temperature distribution on the surface of the reinforced concrete structure; The computing device generates data on a stress fluctuation image showing stress fluctuations in the reinforced concrete structure based on the temperature image generated by the infrared camera.

2. The inspection device according to claim 1.

3. The thermal resolution of the infrared camera is 0.02 K or less.

3. The inspection device according to claim 2.

4. The computing device includes: Calculating a temperature difference indicating a temperature change on the surface of the reinforced concrete structure for each pixel of the temperature image based on the temperature image generated by the infrared camera; generating data relating to a stress fluctuation image showing stress fluctuations in the reinforced concrete structure based on the temperature difference calculated for each pixel of the temperature image; 4. The inspection device according to claim 2 or 3.

5. The arithmetic device displays the generated stress fluctuation image on a display unit. The inspection device according to any one of claims 1 to 3.

6. An inspection device for detecting the presence or absence of fractures in internal reinforcing bars in a reinforced concrete structure, comprising: an infrared camera for generating a temperature image showing the temperature distribution on the surface of the reinforced concrete structure; a calculation device that calculates a temperature difference indicating a temperature change on the surface of the reinforced concrete structure for each pixel of the temperature image based on the temperature image generated by the infrared camera, and generates data relating to a stress fluctuation image indicating stress fluctuations of the reinforced concrete structure based on the temperature difference calculated for each pixel of the temperature image; Equipped with The infrared camera generates a temperature video showing a change in temperature distribution on a surface of the reinforced concrete structure; The arithmetic device extracts frames of a certain number of analysis points from a first frame in the temperature video generated by the infrared camera at regular intervals, and calculates a temperature difference between a maximum temperature value and a minimum temperature value for each pixel from the collection of extracted frames. Inspection equipment.

7. An inspection method for detecting the presence or absence of fractures in internal reinforcing bars in a reinforced concrete structure, comprising: a measuring step of measuring a change over time in the temperature distribution on the surface of the reinforced concrete structure due to a thermoelastic effect; a generating step of generating data relating to a stress fluctuation image showing stress fluctuations in the reinforced concrete structure based on the change over time in the temperature distribution measured in the measuring step; The inspection method includes:

8. The method further includes a display step of displaying the stress fluctuation image generated in the generation step on a display unit. The inspection method according to claim 7.

9. The reinforced concrete structure is a reinforced concrete column. The inspection method according to claim 7 or 8.

10. An inspection method for detecting the presence or absence of fractures in internal reinforcing bars in a reinforced concrete structure, comprising: generating a temperature image showing a temperature distribution on a surface of the reinforced concrete structure; A step of calculating a temperature difference indicating a temperature change on the surface of the reinforced concrete structure for each pixel of the temperature image based on the temperature image generated in the step of generating the temperature image; and generating data relating to a stress fluctuation image showing stress fluctuations in the reinforced concrete structure based on the temperature difference calculated for each pixel of the temperature image in the step of calculating the temperature difference, In the step of generating a temperature image, a temperature video showing a change in temperature distribution on a surface of the reinforced concrete structure is generated, In the step of calculating the temperature difference, frames having a certain number of analysis points are extracted from the first frame in the generated temperature video at regular intervals, and a difference between a maximum temperature value and a minimum temperature value is calculated for each pixel from the collection of extracted frames as a temperature difference. Testing method.

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