Diagnosis method and diagnosis device for concrete structure

Abstract

To provide a diagnosis method and diagnosis device for a concrete structure capable of sensitively detecting any of sparse adhesion failure and uneven distribution failure of fixing means such as an adhesive for fixing a conductive rod to a prepared hole of a concrete structure, a filling state where a gap part is generated and a failure due to a gap.SOLUTION: A coil 23 is arranged on an exposed portion 12 of an anchor bolt 10 that is partially embedded in a prepared hole 2 of concrete 1 to generate an elastic wave in the anchor bolt 10. A sensor 22 is placed at the end of the exposed portion 12 to receive the elastic wave. A temporal axis waveform and a frequency spectrum are obtained from the received signal. When determining a construction failure of the anchor bolt 10 in the concrete 1 on the basis of the result of data processing, the construction failure is determined by obtaining a high-frequency band evaluation index on the basis of a comb-like ripple Wc which appears due to multiple reflections in a high-frequency band equal to or greater than a predetermined frequency in the frequency spectrum.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present invention relates to a method for diagnosing a concrete structure in which a conductor bar such as an anchor bolt is partially embedded in concrete and a diagnostic apparatus therefor.

Background Art

[0002] Conventionally, a non-destructive inspection technique is known for non-destructively detecting defects such as deterioration in the fixing portion of a conductor bar partially embedded in concrete using the electromagnetic pulse method. The electromagnetic pulse method is a kind of inspection method using elastic waves (acoustics). By applying a large pulse current to a coil, the "magnetic force" generated is utilized to generate elastic waves from the conductor bar of the object to be inspected non-contact, and the elastic waves are received and analyzed to grasp the state of the object. This is a non-destructive inspection technique.

[0003] Patent Documents 1, 2, etc. describe a method for diagnosing a concrete structure for diagnosing defects such as deterioration in the fixing portion of a conductor bar (for example, a post-construction anchor bolt) partially embedded in concrete using the electromagnetic pulse method. A post-construction anchor bolt is formed by drilling a hole in concrete and partially embedding and fixing an anchor bolt.

[0004] In the diagnostic methods described in Patent Documents 1, 2, etc., a post-construction anchor bolt partially embedded in concrete is taken as the object to be diagnosed, a coil is arranged around the exposed portion exposed from the concrete surface of the anchor bolt, and a sensor is arranged on the concrete surface around the anchor bolt. Then, a pulse current output from a power supply unit is passed through the coil to generate a pulse magnetic field from this coil. The generated pulse magnetic field acts on the anchor bolt to generate elastic waves. The elastic waves pass through the inside of the concrete and are received by a sensor arranged on the concrete surface, and the received results are analyzed by an analysis processing device to diagnose defects such as deterioration in the fixing portion of the anchor bolt and construction defects.

[0005] In the diagnostic methods of these Patent Documents 1 and 2, the analysis results analyzed by the analysis processing device are displayed on a display screen or the like, and mainly, the inspector visually discriminates the construction defects of the anchor bolts. Therefore, due to the experience of the inspector, etc., not only does the discrimination accuracy of the construction defects vary, but the discrimination process is complicated and disadvantageous. Therefore, in Patent Document 3, signals received by a sensor at the end of the anchor bolt and the surrounding concrete surface are processed to obtain a time-axis waveform and its frequency spectrum, and this data processing result is scored (hereinafter referred to as NG points) using a plurality of evaluation indices and integrated to determine the construction defects of the anchor bolt in the concrete.

Prior Art Documents

Patent Documents

[0006]

Patent Document 1

Patent Document 2

Patent Document 3

Summary of the Invention

Problems to be Solved by the Invention

[0007] However, in the conventional diagnostic method for concrete structures such as Patent Document 3, although it is possible to highly detect construction defects in which fixing means such as adhesives for fixing the anchor bolt in the lower hole are unevenly present in the longitudinal direction of the anchor bolt while the fixing means such as adhesives filled in the lower hole are insufficient, further improvement is desired for the detection sensitivity of construction defects (hereinafter referred to as sparse attachment defects) in which the fixing means such as adhesives are sparsely present in the longitudinal direction of the anchor bolt.

[0008] Therefore, the first object of the present invention is to provide a diagnostic method for a concrete structure capable of sensitively detecting any of the looseness defect, deviation defect, filling state with voids, and defects due to voids of fixing means such as an adhesive for fixing a conductor bar in a hole of the concrete structure by the amplitude of the frequency spectrum, and a diagnostic apparatus for the concrete structure. The second object is to provide a diagnostic method for a concrete structure capable of sensitively detecting a looseness defect of an adhesive and a void portion where no adhesive exists together with the looseness defect of the fixing means such as an adhesive for fixing a conductor bar in a hole of the concrete structure by the phase of the frequency spectrum, and a diagnostic apparatus for the concrete structure.

Means for Solving the Problems

[0009] When the present inventors generated elastic waves in a conductor bar partially embedded in concrete and obtained a frequency spectrum from the time-axis waveform received at the exposed portion, when there was a looseness defect, comb-shaped ripples due to multiple reflections appeared in a high-frequency band of a predetermined frequency or higher, and moreover, the larger the degree of the looseness defect, the larger the amplitude of the comb-shaped ripples. Furthermore, the present inventors obtained a waveform of the phase component from the complex amplitude of the frequency spectrum, and found that a void portion where no adhesive exists together with the looseness defect can be sensitively detected by this waveform, thus completing the present invention.

[0010] That is, in the method for diagnosing a concrete structure of the present invention, a coil is disposed on the exposed portion of a conductor bar partially embedded in a hole of the concrete and fixed by fixing means and / or on the concrete surface around the conductor bar, and an elastic wave is generated in the conductor bar by a pulse magnetic field generated by passing a pulse current through the coil (elastic wave generation process); a sensor is disposed on the exposed portion, and an elastic wave is received by the sensor to generate a received signal (reception process); a time-axis waveform is obtained from the received signal, and a frequency spectrum is obtained by Fourier-transforming the time-axis waveform (data process); and based on the result of the data process, it is determined whether there is a construction defect of the conductor bar in the concrete (determination process). In the method for diagnosing a concrete structure, a high-frequency band evaluation index is obtained based on comb-shaped ripples appearing due to multiple reflections of elastic waves in a high-frequency band of a predetermined frequency or higher in the frequency spectrum, and the construction defect is determined based on the high-frequency band evaluation index, or in the data process, a waveform of a phase component is obtained from the complex amplitude of the frequency spectrum, and in the determination process, the construction defect is determined based on the waveform of the phase component of the frequency spectrum. Here, the high-frequency band may be, for example, a frequency band from 40 kHz to 110 kHz.

[0011] According to the present invention, a coil is disposed on the exposed portion of the conductor bar to generate an elastic wave, the elastic wave is received by a sensor at the end of the conductor bar to obtain a frequency spectrum, a high-frequency band evaluation index is obtained based on comb-shaped ripples appearing in a high-frequency band of a predetermined frequency or higher due to multiple reflections of the elastic wave, and the construction defect is determined based on this high-frequency band evaluation index. Therefore, it is possible to detect a poor embedding defect of the conductor bar with high sensitivity. Further, since the construction defect is determined based on the waveform of the phase component, even if the difference in the structure around the conductor member is small, the difference can be detected. Therefore, it is possible to improve the detection accuracy when detecting the structure nondestructively by applying an elastic wave to the conductor member.

[0012] In the method for diagnosing a concrete structure of the present invention, a time-domain signal may be obtained by cutting out a predetermined frequency region of the comb-shaped ripple and performing inverse Fourier transform, and a high-frequency band evaluation index may be obtained based on an echo waveform periodically appearing in the time-domain signal.

[0013] By doing so, by extracting a predetermined frequency region of the comb-shaped ripple and performing inverse Fourier transform, echoes periodically appear due to multiple reflections. When substantially the entire portion of the conductor bar embedded in the concrete is completely fixed by fixing means such as an adhesive, no echo appears. When there is a poor compaction defect, an echo appears. Therefore, by using this to obtain a high-frequency band evaluation index, the poor compaction defect can be detected with high sensitivity.

[0014] In the method for diagnosing a concrete structure of the present invention, the high-frequency band evaluation index includes the amplitude of the second echo in the echo waveform, and when the amplitude is equal to or greater than a threshold value, it may be determined as a construction defect. By doing so, since the waveform in which the elastic wave generated by the coil reaches the sensor directly rather than by multiple reflections can be excluded from the determination, the echo waveform due to multiple reflections can be reliably detected.

[0015] In the method for diagnosing a concrete structure of the present invention, the high-frequency band evaluation index includes the attenuation coefficient of the second and subsequent echoes in the echo waveform, and when the attenuation coefficient is smaller than a threshold value, it may be determined as a construction defect. By doing so, since the greater the degree of the poor compaction defect, the slower the attenuation of the echo amplitude, the degree of the poor compaction defect can be determined by determining that there is a construction defect when the attenuation coefficient of the second and subsequent echoes is smaller than the threshold value.

[0016] In the method for diagnosing a concrete structure of the present invention, a high-frequency band evaluation index may be obtained from the integrated value in a predetermined frequency range of the comb-shaped ripple. In this way, the size of the comb-shaped ripple in the high-frequency band due to the multiple reflection of elastic waves can be easily quantified, and the degree of sparse attachment defect can be easily determined. In the determination process, an evaluation index obtained from the waveform of the phase component of the frequency spectrum may be obtained, and the suitability of the construction may be determined by comparing the evaluation index with a threshold value obtained from the evaluation index of normal construction. In this way, since the difference in the waveform of the phase component of the frequency spectrum between the structure to be diagnosed and the normal construction product is large, the structure around the conductor member of the structure to be diagnosed can be easily compared with the normal construction product, and the diagnosis of the building structure using the concrete structure is easy.

[0017] In the method for diagnosing a concrete structure of the present invention, an adhesive for adhering a conductor rod to a hole in the concrete may be determined as a construction defect if it is in a sparse state where it is sparsely present in the axial direction, a bias defect where the adhesive is present in a biased state, a filling state where voids are generated, or any of the voids.

[0018] In the method for diagnosing a concrete structure of the present invention, in the reception process, sensors are arranged on each of the exposed part and the concrete surface around the conductor rod, elastic waves are received by both sensors to generate received signals respectively, in the data processing, frequency spectra are obtained from each received signal respectively, and in the determination process, the sparse state is determined from the high-frequency band of the frequency spectrum, and a low-frequency band evaluation index is obtained from the low-frequency band of a predetermined frequency in the frequency spectrum, and the biased state where the adhesive is present in a biased manner in the axial direction may be determined using the low-frequency band evaluation index. Here, the low-frequency band may be, for example, a frequency band from 0 kHz or more to 100 kHz. By doing so, as a construction defect where the adhesive for fixing the conductor rod is insufficient, together with the sparse attachment defect of the adhesive as described above, the bias defect where the adhesive is present in a biased state can be collectively detected.

[0019] In the method for diagnosing a concrete structure of the present invention, in the determination process, evaluation points may be respectively assigned to a plurality of evaluation indicators including a high-frequency band evaluation indicator and a low-frequency band evaluation indicator based on a threshold value, and construction defects may be determined based on the total of the evaluation points. By doing so, the sparse state and the bias state of the adhesive can be stably determined while suppressing variations and labor, and stable diagnosis can be performed.

[0020] In the diagnostic apparatus for a concrete structure of the present invention, a coil and a sensor disposed on an exposed portion of a conductor rod partially embedded in a hole of the concrete and fixed by fixing means, an elastic wave generating unit that generates elastic waves in the conductor rod by a pulse magnetic field generated by flowing a pulse current through the coil, a reception processing unit that receives the elastic waves with the sensor and generates a reception signal, a data processing unit that obtains a time-axis waveform from the reception signal and obtains a frequency spectrum by Fourier-transforming the time-axis waveform, and a determination processing unit that determines construction defects in the concrete of the conductor rod based on the processing result of the data processing unit. In the diagnostic apparatus for a concrete structure having these components, the determination processing unit obtains a high-frequency band evaluation indicator based on comb-shaped ripples appearing due to multiple reflections of elastic waves in a high-frequency band of a predetermined frequency or higher in the frequency spectrum, and determines construction defects based on the high-frequency band evaluation indicator, or the data processing unit obtains a waveform of a phase component of the frequency spectrum, and the determination processing unit is an apparatus that determines construction defects based on the waveform of the phase component of the frequency spectrum. Here, the high-frequency band may be, for example, a frequency band from 40 kHz to 110 kHz.

[0021] In the diagnostic apparatus for a concrete structure of the present invention, the sensor is disposed on the exposed portion and on the concrete surface around the conductor rod, the reception processing unit receives the elastic waves with both sensors and generates reception signals respectively, and the determination processing unit may determine construction defects using a high-frequency band evaluation indicator and a low-frequency band evaluation indicator obtained from a low-frequency band of a predetermined frequency or lower in the frequency spectrum.

Advantages of the Invention

[0022] According to the method and apparatus for diagnosing a concrete structure of the present invention, it is possible to provide a method for diagnosing a concrete structure capable of sensitively detecting a defective state of fixing means such as an adhesive for fixing a conductor rod in a blind hole of the concrete structure or a filling state with voids, and a diagnostic apparatus for a concrete structure.

Brief Description of the Drawings

[0023]

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Embodiments for Carrying Out the Invention

[0024] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. (Diagnostic Device for Concrete Structures) FIGS. 1(a) and (b) are schematic configuration diagrams showing a diagnostic device 28 for a concrete structure in an embodiment of the present invention. FIG. 1(a) is an overall configuration diagram of the diagnostic device 28, and FIG. 1(b) is a configuration diagram of a waveform receiving unit (for example, an analog / digital conversion device, hereinafter referred to as an "AD conversion device") in (a). FIG. 2 is a functional block diagram showing a configuration example of the information processing device 30 in FIG. 1.

[0025] The diagnostic device 28 of the present embodiment is a device for determining construction defects of the post - construction anchor bolt 10 as a conductor bar partially embedded in the under - hole 2 of the concrete 1, as shown in FIG. 1(a). Subsequently, the post-construction anchor bolt 10 is provided with a pilot hole in the concrete 1, and the anchor bolt 10 is partially embedded in this pilot hole and fixed by fixing means. In this embodiment, as an example of an adhesive anchor bolt, an adhesive is used as the fixing means. The anchor bolt 10 is fixed by an adhesive filled in the pilot hole 2 in a state where it is partially inserted into the pilot hole 2 of the concrete 1.

[0026] As shown in Fig. 1(a), the diagnostic device 28 for a concrete structure diagnoses the post-construction anchor bolt 10 as a conductor bar partially embedded in the concrete 1, and can diagnose various construction defects such as defects and deficiencies in the fixed portion where the post-construction anchor bolt 10 is embedded. In this embodiment, as an example of a construction defect where the adhesive for fixing the anchor bolt 10 is insufficient, an example of detecting a sparse state where the adhesive is sparsely present in the axial direction and a biased state where the adhesive is biased in the axial direction will be used for explanation.

[0027] On the surface of the concrete 1 around the anchor bolt 10, a plurality of first sensors for detecting elastic waves, for example, AE (Acoustic Emission) sensors 21-1 to 21-4 are arranged and fixed, for example, with a resin adhesive tool (glue gun), etc. The plurality of sensors 21-1 to 21-4 are fixed on the concrete surface at four positions, for example, at 90° intervals on a circumference centered on the anchor bolt 10. Also, a second sensor (for example, a small AE sensor) 22 for detecting elastic waves is arranged at the upper end of the exposed portion of the anchor bolt 10 exposed from the concrete surface and fixed with a glue gun, etc. Note that the second sensor 22 is arranged at the tip of the exposed portion in Fig. 1, but it may be arranged at any position of the exposed portion, not limited to the upper end, and may be installed between the lower end and the upper end.

[0028] Furthermore, around the exposed portion of the anchor bolt 10, a coil for generating a pulsed magnetic field, for example, a ring coil 23 is arranged. The upper end of the coil 23 is installed, for example, to coincide with the upper end of the anchor bolt 10.

[0029] A coil unit 24 for generating a pulsed current is connected to the coil 23 via a cable. Further, an electromagnetic pulse power supply 25 for supplying power is connected to the coil unit 24 via a cable. The coil unit 24 and the electromagnetic pulse power supply 25 constitute an elastic wave generating unit that passes a pulsed current through the coil 23 to generate a pulsed magnetic field from this coil 23 and acts this pulsed magnetic field on the anchor bolt 10 to generate an elastic wave.

[0030] An AD conversion device 26 as a waveform receiving unit is connected to the plurality of sensors 21-1 to 21-4 and 22 via a cable. The AD conversion device 26 is a device that amplifies the analog elastic wave signals received by the sensors 21-1 to 21-4 and then converts them into a first received signal S26a consisting of a digital signal, and also amplifies the analog elastic wave signal received by the sensor 22 and then converts it into a second received signal S26b consisting of a digital signal.

[0031] The concrete sensors 21-1 to 21-4 are, for example, AE sensors weighing 70 g. The second sensor 22 for the exposed part of the anchor bolt 10A is, for example, a small AE sensor weighing 8 g. The distance between the anchor bolt 10A and the sensors 21-1 to 21-4 is, for example, 100 mm. The five sensors 21-1 to 21-4 and 22 are fixed, for example, with glue gun and measured simultaneously. The measurement of the sensors 21-1 to 21-4 is not limited to being simultaneous, and they may be measured one by one sequentially.

[0032] As shown in Fig. 1(b), the AD conversion device 26 converts an analog elastic wave signal into a digital signal, for example, at a sampling frequency of 100 MHz and a data length of 10 ms. An information processing device 30 as a data processing unit is connected to this AD conversion device 26 via a signal line. The information processing device 30 is a device that calculates the input received signals S26a and S26b and evaluates defects such as deterioration in the fixing part of the anchor bolt 10, and is composed of, for example, a personal computer (PC), etc.

[0033] FIG. 2 is a functional block diagram showing a configuration example of the information processing apparatus 30 in FIG. 1. This information processing apparatus 30 includes a time-axis waveform processing unit 40 and a frequency spectrum processing unit 50 that perform data processing on the first received signal S26a and the second received signal S26b output from the AD conversion apparatus 26, a waveform evaluation index unit 60 connected to the output side of the time-axis waveform processing unit 40, a spectrum evaluation index unit 70 connected to the output side of the frequency spectrum processing unit 50, and a determination evaluation unit 90 connected to the output sides of the waveform evaluation index unit 60 and the spectrum evaluation index unit 70.

[0034] The time-axis waveform processing unit 40 receives the first received signal S26a and the second received signal S26b output from the AD conversion apparatus 26, filters the first received signal S26a to obtain a signal of the first time-axis waveform S44a, and filters the second received signal S26b to obtain a signal of the second time-axis waveform S44b. The time-axis waveform processing unit 40 includes, for example, a 2 MHz low-pass filter (hereinafter referred to as "LPF") 41 that allows only low-frequency components of the received signals S26a and S26b to pass through, a file conversion unit 42 that converts the output signal of the LPF 41 into a text file, for example, a CSV (Comma Separated Values) file, a decimation unit 43 that performs decimation to simplify the processing of the signal after file conversion, and a 2.5 kHz high-pass filter (hereinafter referred to as "HPF") 44 that allows only high-frequency components of the signal after decimation to pass through. The HPF 44 has a function of outputting signals of the first time-axis waveform S44a and the second time-axis waveform S44b with a sampling frequency of 1 MHz and a data length of 10 ms, for example.

[0035] The frequency spectrum processing unit 50 receives the first received signal S26a and the second received signal S26b output from the AD conversion device 26, performs Fourier transform (for example, fast Fourier transform, hereinafter referred to as "FFT") on the received signal S26a to obtain the first frequency spectrum, and performs FFT on the received signal S26b to obtain the second frequency spectrum. It has an FFT unit 51 and a file conversion unit 52 that converts the first and second frequency spectra output from this FFT unit 51 into a text file (for example, a CSV file). The first frequency spectrum S52a and the second frequency spectrum S52b converted into a text file have, for example, a frequency range of 0 to 100 kHz, a frequency resolution of 200 Hz, and an FFT point number of 250.

[0036] The waveform evaluation index unit 60 obtains various evaluation indexes based on the signals of the first and second time-axis waveforms S44a and S44b output from the HPF 44. Examples of the evaluation indexes obtained by the waveform evaluation index unit 60 include a waveform energy ratio SR (first evaluation index EI1), a waveform duration TC (second evaluation index EI2), a time-axis correlation coefficient, and the like. The spectrum evaluation index unit 70 includes a low-frequency band evaluation index unit 71 that obtains a low-frequency band evaluation index from a low-frequency band, for example, a frequency band below 50 kHz in the frequency spectrum, based on the signals of the first and second frequency spectra S52a and S52b after file conversion, and a high-frequency band evaluation index unit 72 that obtains a high-frequency band evaluation index from a high-frequency band, for example, a frequency band of 40 kHz or higher in the frequency spectrum. Here, as will be described later, the high-frequency band is, for example, a frequency band of 40 kHz to 110 kHz. Also, the frequency for obtaining the low-frequency band evaluation index can be a low-frequency band of 0 kHz or higher to 100 kHz in the frequency spectrum. The low-frequency band can be, for example, 0 kHz or higher and 40 kHz or lower, 0 kHz or higher and 50 kHz or lower, 0 kHz or higher and 60 kHz or lower, 0 kHz or higher and 70 kHz or lower, 0 kHz or higher and 80 kHz or lower, 0 kHz or higher and 90 kHz or lower.

[0037] The low-frequency band evaluation index unit 71 obtains various evaluation indices based on signals in the low-frequency band below 50 kHz of the first and second frequency spectra S52a and S52b. Examples of the evaluation indices obtained by the low-frequency band evaluation index unit 71 include the center frequency SC of the spectrum (the third evaluation index EI3), the standard deviation SD of the spectrum (the fourth evaluation index EI4), the number of peaks SP of the spectrum (the fifth evaluation index EI5), the spectral correlation coefficient CF (the sixth evaluation index EI6), and the like. The high-frequency band evaluation index unit 72 obtains high-frequency band evaluation indices based on the comb-shaped ripple Wc that appears in the high-frequency band generally from 40 to 50 kHz or higher of the first and second frequency spectra S52a and S52b. The comb-shaped ripple Wc appears due to multiple reflections of elastic waves inside the anchor bolt 10, and the high-frequency band evaluation indices based on this will be described later.

[0038] Here, the waveform energy ratio SR that becomes the first evaluation index EI1 is the ratio of the waveform energy on the concrete surface to the waveform energy on the exposed part of the anchor bolt. It expresses, by ratio, the phenomenon that the waveform energy on the concrete surface becomes small and the waveform energy on the exposed part of the anchor bolt becomes large due to poor construction. The waveform duration TC that becomes the second evaluation index EI2 is the time until the amplitude attenuates to, for example, less than 10% of the maximum amplitude of the wave head in the time-axis waveform. It expresses the phenomenon that the restraint of the anchor bolts 10A and 10B becomes loose and the convergence time of the time-axis waveform becomes long due to poor construction. The center frequency SC of the spectrum that becomes the third evaluation index EI3 is the center frequency of a specific frequency spectrum, and it expresses the phenomenon that the frequency spectrum shifts to the low-frequency side due to poor construction. The standard deviation SD of the spectrum that becomes the fourth evaluation index EI4 is the sharpness of the peak of a specific frequency spectrum, and it expresses the degree of concentration of the frequency spectrum that appears due to poor construction. The number of peaks SP of the spectrum that becomes the fifth evaluation index EI5 is the number of peaks in the frequency spectrum, and particularly represents the number of peaks in a plurality of frequency spectra that appear due to poor construction of a mechanical anchor bolt having a particularly complex structure (for example, the metal sleeve expansion type anchor bolt 10B). The correlation coefficient CF of the spectrum that becomes the sixth evaluation index EI6 represents the correlation coefficient between the frequency spectrum that appears due to poor construction and the FFT waveform obtained by averaging the spectra of a plurality of standard constructions.

[0039] In the present embodiment, as a high-frequency band evaluation index based on the comb-shaped ripple Wc, a time-domain signal is obtained by cutting out a predetermined frequency region of the comb-shaped ripple Wc, for example, a region from 60 to 80 kHz, and performing inverse Fourier transform (hereinafter referred to as inverse FTT), and a high-frequency band evaluation index is obtained based on the echo waveform We that periodically appears in the time-domain signal. For example, the amplitude of the second echo in the echo waveform We, the attenuation coefficient α of the echoes after the second echo in the echo waveform We, etc. can be used.

[0040] The determination evaluation unit 90 assigns evaluation points to one or more evaluation indexes including the high-frequency band evaluation index based on a threshold value in the evaluation point assignment unit 80 connected to the output sides of the waveform evaluation index unit 60 and the spectrum evaluation index unit 70, and determines poor construction based on the total of the evaluation points. Evaluation points for poor construction evaluation are assigned to the input high-frequency band evaluation index based on a threshold value. In the low-frequency band evaluation index unit 71, for example, for at least one of the first, second, third, fourth, fifth, and sixth evaluation indexes EI1 to EI6, evaluation points for poor construction evaluation are respectively assigned based on a threshold value, and the total of the evaluation points, etc. are used. The assignment of the evaluation points of the low-frequency band evaluation index unit 71 is disclosed in Patent Document 3. In particular, a method for determining poor construction by a high-frequency band evaluation index for sparse attachment failure of the conductor bar of the present invention will be described in more detail.

[0041] (Diagnosis method for concrete structures) A method for diagnosing a test specimen using the diagnostic apparatus 28 for a concrete structure according to the present embodiment shown in FIGS. 1 and 2 will be described. FIG. 3 is a longitudinal sectional view showing a test specimen fabricated as a concrete structure, and FIG. 4 is a flowchart showing a diagnostic method for a concrete structure according to an embodiment of the present invention. In this diagnostic method for a concrete structure, the following elastic wave generation process ST1, reception process ST2, data process ST3, evaluation index process ST4, and evaluation point assignment process ST5 are performed in order.

[0042] Note that the test specimen shown in FIG. 3 is a rectangular parallelepiped concrete of 900 mm × 900 mm × 600 mm, in which a plurality of blind holes 2 with a depth of 400 mm are provided, and anchor bolts A to E with a nominal diameter of 16 mm and a length of 1050 mm are respectively embedded 400 mm in the concrete 1 and exposed 650 mm outside, and are fixed by different amounts of epoxy adhesives.

[0043] In the test specimen, the anchor bolt A is in a state where the adhesive exists in all of the embedded 400 mm, and the amount of the adhesive present is a normal construction product of 25 da. Here, da is a value obtained by indicating the length in the axial direction of the adhesive existing around the anchor bolt by the nominal diameter of the anchor bolt, and 25 da indicates that the adhesive exists for a length of 25 times the nominal diameter of 16 (400 mm). For the anchor bolts B - E, as described in FIG. 3, the total amount of the adhesives sparsely present in the axial direction is 20 da, 13 da, 9 da, and 7 da respectively, and they are defective construction products in a state of sparse attachment defect. In these defective construction products with sparse attachment defects, in all cases, the adhesive exists around the anchor bolt at the opening end of the blind hole 2, and the presence or absence of the internal adhesive cannot be visually confirmed.

[0044] (I) Elastic wave generation process ST1 Turn on the electromagnetic pulse power supply 25 to start the process. Power is output from the electromagnetic pulse power supply 25 and supplied to the coil unit 24. A pulse current is output from the coil unit 24, and this pulse current flows through the coil 23 disposed on the exposed portion 12 of the anchor bolt 10. Then, a pulse magnetic field is generated from the coil 23, causing the anchor bolt 10 to vibrate and generate elastic waves. The generated elastic waves propagate inside the anchor bolt 10 and pass through the inside of the concrete 1, and then propagate to the concrete surface around the anchor bolt 10. Here, in order to reinforce the pulse magnetic field generated in the coil 23, a magnet (not shown) may be disposed at the upper end of the exposed portion 12 of the anchor bolt 10, and the second sensor 22 may be disposed via this magnet. Thereby, a bias static magnetic field is applied in the axial direction of the anchor bolt 10.

[0045] (II) Reception processing ST2 It is received by the second sensor 22 disposed at the end of the exposed portion 12 of the anchor bolt 10. Also, the elastic waves propagated to the concrete surface are received by a plurality of sensors 21-1 to 21-4 disposed on the concrete surface. At the same time, the elastic waves propagated inside the anchor bolt 10 are received by the sensor 22 disposed on the exposed portion 12 of the anchor bolt 10. The analog reception signals received by the plurality of sensors 21-1 to 21-4 and the analog reception signal received by the second sensor 22 are sent to the AD conversion device 26. In the AD conversion device 26, the analog reception signals supplied from the plurality of sensors 21-1 to 21-4 and 22 are converted into digital signals at a sampling frequency of 100 MHz and a data length of 10 ms, and the first reception signal S26a is output to the information processing device 30. At the same time, the analog reception signal supplied from the second sensor 22 is converted into a digital signal, and the second reception signal S26b is output to the information processing device 30.

[0046] (III) Data processing ST3 In the time-axis waveform processing unit 40 and the frequency spectrum processing unit 50 in the information processing apparatus 30, data processing ST3 including the time-axis waveform processing ST3a by the time-axis waveform processing unit 40 and the frequency spectrum processing ST3b by the frequency spectrum processing unit 50 is performed.

[0047] That is, in the time-axis waveform processing unit 40, the input first received signal S26a and second received signal S26b have their high-frequency components removed by the 2 MHz LPF 41 and are converted into CSV files by the file conversion unit 42. The converted CSV files have their data decimated by the decimation unit 43, their low-frequency components removed by the 2.5 kHz HPF 44, and signals of the first time-axis waveform S44a and second time-axis waveform S44b with a sampling frequency of 1 MHz and a data length of 10 ms are generated and output to the waveform evaluation index unit 60.

[0048] Also, in the frequency spectrum processing unit 50, the input first received signal S26a and second received signal S26b are subjected to fast Fourier transform by the FFT unit 51, and signals of the frequency spectrum are generated. The generated signals of the frequency spectrum are converted into CSV files by the file conversion unit 52, and signals of the first frequency spectrum S52a and second frequency spectrum S52b with a frequency range of 0 to 50 kHz, a frequency resolution of 200 Hz, and an FFT point number of 250 are generated and output to the low-frequency band evaluation index unit 71 of the spectrum evaluation index unit 70.

[0049] Furthermore, in the frequency spectrum processing unit 50, among the signals of the frequency spectrum generated by converting the first and second received signals S26a and S26b by the FFT unit 51 and the file conversion unit 52, the signal of the second frequency spectrum S52b with a frequency range of 40 kHz or higher, preferably 40 kHz to 110 kHz, is output to the high-frequency band evaluation index unit 72 of the spectrum evaluation index unit 70.

[0050] (IV) Evaluation Index Processing ST4 The waveform evaluation index unit 60 and the spectrum evaluation index unit 70 perform the evaluation index processing ST4 as follows. In the waveform evaluation index unit 60 of the present embodiment, a first evaluation index EI1 of a waveform energy ratio SR between the waveform energy of the first time-axis waveform and the waveform energy of the second time-axis waveform, and a second evaluation index EI2 of a waveform duration TC for each of the maximum amplitudes of the respective wave heads in the first time-axis waveform and the second time-axis waveform until the amplitude decays to less than, for example, 10% are obtained. The second evaluation index EI2 of the waveform duration TC for each of the first time-axis waveform and the second time-axis waveform is, for example, the maximum amplitude of the wave head, but may also be the maximum amplitude in the waveform of the first time-axis waveform and / or the second time-axis waveform. Further, the waveform duration TC until the decay is not limited to less than 10%, and may be set to a predetermined amplitude.

[0051] Also, in the low-frequency band evaluation index unit 71 of the present embodiment, a third evaluation index EI3 of the center frequency SC of each spectrum in the first frequency spectrum and the second frequency spectrum, a fourth evaluation index EI4 of the standard deviation SD of the spectrum, a fifth evaluation index EI5 of the number of peaks SP of the spectrum, and a sixth evaluation index EI6 of the correlation coefficient CF of the spectrum are obtained. Furthermore, in the high-frequency band evaluation index unit 72 of the present embodiment, a high-frequency band evaluation index is obtained from a high-frequency band of 40 kHz to 110 kHz in the frequency spectrum.

[0052] Here, the waveform energy is represented by the sum of the squares of the amplitude values at each sampled point and can be calculated by Equation (1).

Equation

[0053] The waveform energy ratio SR is, as shown in Equation (2), the ratio between the waveform energy of the concrete surface and the waveform energy of the anchor bolt exposed portion 12. That is, the values of the waveform energy in the four directions of the concrete surface are respectively divided by the value of the waveform energy of the anchor bolt exposed portion 12.

Number

[0054] Since the waveform energy ratio SR changes more significantly than the waveform energy alone, it becomes easier to identify poor construction. The waveform energy ratio SR is an index based on the ratio of the waveform energy of the concrete surface in case of poor construction to the waveform energy of the anchor bolt exposed part 12. Therefore, it becomes easy to compare with standard construction, and in some cases, it may not be necessary to compare with standard construction.

[0055] The waveform duration TC is the time t2 from the vibration initial arrival time t1 to when the amplitude attenuates to less than, for example, 10% of the maximum amplitude (MAX) of the wave crest in the time-axis waveform. Therefore, it can be seen that due to poor construction, the restraint of the anchor bolts 10A and 10B becomes loose, and the convergence time of the time-axis waveform becomes longer.

[0056] The center frequency SC of the spectrum, the standard deviation SD of the spectrum, and the number of peaks SP of the spectrum are obtained as follows from (a) to (d). (a) Extract spectra with an intensity of a certain ratio (for example, the extraction level EL is 30% of the maximum peak) or more with respect to the maximum peak of the spectrum. (b) Extract the spectrum Sfmin with the lowest frequency from among those in (a). (c) For the spectrum Sfmin with the lowest frequency extracted in (b), when F30 ≧ 5 kHz, within the range of the maximum value ±2.5 kHz, calculate the center of gravity SC of the spectrum using Equation (3) and calculate the standard deviation SD of the spectrum using Equation (4). When F30 < 5 kHz, within the range of F30, calculate the center of gravity SC of the spectrum using Equation (3) and calculate the standard deviation SD of the spectrum using Equation (4). (d) Count the number of peaks SP of the spectrum extracted in (a). That is, count the points where the slope of the graph changes from positive to negative.

Number

Number

[0057] The correlation coefficient CF(E16) of the frequency spectrum can be obtained as follows. (1) First, obtain the average value of the frequency spectra acquired when the standard construction is performed N times. The frequency spectrum is the FFT waveform obtained by performing a fast Fourier transform on the data of the time-axis waveform. The average value of the frequency spectrum can be obtained by calculating the average value of the amplitudes at each frequency. (2) Next, taking the evaluation target as a construction different from the standard construction, for example, a defective construction, calculate the correlation coefficient (CF) between the average (x) of the FFT waveforms of the standard construction and the amplitude (y) of the evaluation target spectrum using the following formula (5) or formula (6).

[0058]

Equation

Equation

[0059] Furthermore, an index part for evaluating the cross-correlation function XF(E17) of the time-axis waveform may be added as necessary. The cross-correlation function XF(E17) of the time-axis waveform will be described. (1) First, obtain the average value of the time-axis waveforms acquired when the standard construction is performed N times. The time-axis waveform is the data of the time-axis waveform processing. (2) Next, taking the evaluation target as a construction different from the standard construction, for example, a defective construction, calculate the cross-correlation function (R) and the normalized cross-correlation function (Rnorm) between the average (f(i)) of the time-axis waveforms of the standard construction and the evaluation target time-axis waveform (g(i)) using the following formula (7) and formula (8), respectively. The cross-correlation function (R) and the normalized cross-correlation function (Rnorm) are in a so-called discrete system and can be calculated by digital operations.

[0060]

Equation

[0061] However, n is the number of data of i per 10 -6 seconds in the time-axis waveform, i is an integer from 1 to n, and the points at predetermined intervals in the time-axis waveform are sequentially indicated by numbers. τ is the deviation with respect to i and is a variable indicating the phase.

[0062]

Number

[0063] However, n is the number of data of i per 10 -6 seconds, i is an integer from 1 to n, τ is the deviation with respect to i, and f bar, g bar are the average values of f(i) and g(i), respectively. Here, Equation (8) is for obtaining the normalized cross-correlation function (Rnorm) normalized by the magnitudes of the functions f(i) and g(i - τ) with respect to Equation (7). The normalized cross-correlation function (Rnorm) has a value between 0 and 1.

[0064] Since the normalized cross-correlation function Rnorm takes a value between 0 and 1, the level of the cross-correlation function can be easily grasped. Also, if the difference in amplitude between the time-axis waveform in the case of construction defects to be evaluated for cross-correlation and the time-axis waveform of standard construction is large, the cross-correlation function R may become large, and there is a possibility of misjudging that the time-axis waveforms are similar. However, in the case of the normalized cross-correlation function Rnorm, it is not affected by the amplitude level of the time-axis waveform in the case of construction defects to be evaluated, a more accurate correlation function can be obtained, and the determination of construction defects can be performed more accurately.

[0065] Thus, the construction defects of the post-construction anchor bolts can also be evaluated by waveform evaluation based on the time-axis waveform instead of spectrum evaluation based on the FFT waveform of the frequency spectrum. Furthermore, when calculating the cross-correlation function between the average (f(i)) of the time-axis waveform of standard construction and the time-axis waveform (g(i)) of the object to be evaluated, the differential time i of the time-axis waveform of the object to be evaluated is shifted by τ. Therefore, even if there is a phase shift, the correlation can be confirmed without being greatly affected by this phase shift, and it is possible to more accurately evaluate the construction defects of the concrete structure.

[0066] Next, the high-frequency band evaluation index based on the comb-shaped ripple Wc can be obtained as follows. As shown in FIG. 5, for the second received signal S26b obtained by converting the analog received signal supplied from the second sensor 22 into a digital signal by the elastic wave generation process ST1 and the reception process ST2, as shown in FIGS. 6(1)-(5) by the data process ST3, a frequency spectrum obtained by performing fast Fourier transform by the FFT unit 51 is generated. Here, FIGS. 6(1)-(5) respectively correspond to the anchor bolts A-E.

[0067] In these frequency spectra, if there is a sparse attachment defect, a comb-shaped ripple Wc appears in the high-frequency band of 40 kHz or higher, for example, 40 kHz to 110 kHz or lower, due to the multiple reflection of elastic waves inside the anchor bolts B-E as shown in FIGS. 6(2)-(5). Therefore, the high-frequency band evaluation index can be obtained using this. It has been found that the frequency of the above high-frequency band changes depending on the diameter and length of the anchor bolt to be constructed, the diameter and length of the under-hole, etc. Therefore, the range of the high-frequency band is set to 40 kHz to 110 kHz or lower. The frequency of the high-frequency band may be set appropriately according to the dimensions of the anchor bolt and under-hole to be constructed. Similarly, since the frequency of the low-frequency band for obtaining the low-frequency band evaluation index also changes depending on the diameter and length of the anchor bolt to be constructed, the diameter and length of the under-hole, etc., it may be set appropriately.

[0068] At that time, a time-domain signal as shown in FIGS. 7(1)-(5) is generated by extracting a predetermined frequency region of the comb-shaped ripple Wc, for example, a region of 60-80 kHz, and performing an inverse Fourier transform. Here, FIGS. 7(1)-(5) respectively correspond to the anchor bolts A-E. In the time-domain signals of FIGS. 7(2)-(5) where there are sparse attachment defects, echo waveforms that periodically appear due to multiple reflections are formed. Therefore, a high-frequency band evaluation index can be obtained based on this echo waveform.

[0069] The time interval of this echo approximately matches the time interval calculated from the Young's modulus, density, length, etc. of the anchor bolt. Here, since the first echo of the echo waveform is directly propagated from the coil 23 and has nothing to do with multiple reflections, when the amplitude of the second echo in the echo waveform is equal to or greater than the threshold value, it may be determined as a construction defect and a high-frequency band evaluation index may be obtained.

[0070] In this embodiment, as the high-frequency band evaluation index, the attenuation coefficient of the second and subsequent echoes in this echo waveform is used. Specifically, as shown in FIGS. 7(2)-(5), as the number of repetitions increases, the echo height attenuates. Representing the nth echo height (amplitude) as Hn, the time as t, the attenuation coefficient as α, and A as a constant, the nth echo height Hn is approximated by an exponential function as in the following formula (9).

Equation

[0071] Regarding the echo waveforms of FIGS. 7(2)-(5), when the attenuation coefficient α is obtained by formula (9), as shown in the figure respectively, they are 0.842, 1.07, 1.563, 2.945, and the greater the degree of sparse attachment defect of the anchor bolts B-E, the greater the attenuation coefficient. This is presumably because the more the filling amount of the adhesive increases, the greater the degree of dissipation of the elastic wave from the anchor bolts B-E to the surrounding concrete 1. Therefore, in the present embodiment, this attenuation coefficient α can be used as a high-frequency band evaluation index for the evaluation point assignment process ST5 in the evaluation point assignment unit 80.

[0072] (V) Evaluation Point Assignment Process ST5 In the evaluation point assignment unit 80, an evaluation point assignment process ST5 is performed to assign evaluation points for construction defect evaluation based on threshold values for the evaluation index obtained by the waveform evaluation index unit 60, and the low-frequency band evaluation index and high-frequency band evaluation index obtained by the spectrum evaluation index unit 70. In the evaluation point assignment process ST5, evaluation points are assigned to each of the evaluation indexes based on threshold values as follows in (i) and (ii) below. (i) A threshold value for performing a defect (NG) evaluation is set for each evaluation index. At this time, a margin is set so as not to perform a defect (NG) evaluation as much as possible even if the data of standard construction varies. (ii) In each evaluation index, an evaluation point is assigned based on the threshold value.

[0073] Examples of aggregating the evaluation indexes by the evaluation point assignment process ST5 are shown in FIGS. 8 and 9. FIG. 8 shows only the NG points for the high-frequency band evaluation index using the attenuation coefficient α as bar graphs for each of the five anchor bolts A - E, and the tensile strength of the tensile test is plotted. As is clear from FIG. 8, the NG points can evaluate the differences in the filling amount of the adhesive and the degree of tensile strength. Also, it can be seen that the detection sensitivity is high enough to detect construction defects even when the tensile strength is high, as in the case of anchor bolt B.

[0074] Figure 9 shows the results of assigning evaluation points to each of five anchor bolts A - E. Here, the total of the NG points for the high - frequency band evaluation index using the attenuation coefficient α and the NG points for all other evaluation indices are shown as bar graphs for each anchor bolt. Also, the tensile strength in the tensile test is plotted. As is clear from Figure 9, the total of the NG points can evaluate the differences in the filling amount of the adhesive and the degree of tensile strength. Also, even when it is difficult to detect only by other evaluation indices such as anchor bolt B - 001, the detection sensitivity can be improved by adding the NG points for the high - frequency band evaluation index using the attenuation coefficient α.

[0075] According to the diagnostic apparatus 28 and diagnostic method for a concrete structure of the present embodiment as described above, a coil 23 is arranged on the exposed portion 12 of the anchor bolt 10 to generate elastic waves, and elastic waves are received by the second sensor 22 at the end of the anchor bolt 10 and a plurality of sensors 21 - 1 to 21 - 4 arranged on the concrete surface to obtain a frequency spectrum. Based on the comb - like ripple Wc that appears in the high - frequency band of a predetermined frequency or higher due to the multiple reflection of elastic waves, a high - frequency band evaluation index is obtained, and construction defects are determined based on this high - frequency band evaluation index. Therefore, construction defects of the anchor bolt 10 can be detected with high sensitivity, and in particular, it is possible to detect sparse defects where an adhesive or the like is sparsely present in the longitudinal direction of the anchor bolt. Note that the second sensor 22 and the plurality of sensors 21 - 1 to 21 - 4 may be appropriately selected according to the detected signals. Any one of the second sensor 22 and the plurality of sensors 21 - 1 to 21 - 4 may be used. Also, when the waveform energy ratio SR is not obtained, any one of the plurality of sensors 21 - 1 to 21 - 4 may be used.

[0076] In this embodiment, a time-domain signal is obtained by extracting a predetermined frequency region of the comb-shaped ripple Wc and performing inverse Fourier transform, and a high-frequency band evaluation index is obtained based on the echo waveform that periodically appears in the time-domain signal. As a result, when substantially the entire portion of the anchor bolt 10 embedded in the concrete 1 is completely fixed by a fixing means such as an adhesive, no echo appears, and an echo appears when there is a poor densification defect. Therefore, the poor densification defect can be detected with high sensitivity.

[0077] Also, in this embodiment, the high-frequency band evaluation index includes the amplitude of the second echo in the echo waveform, and when the amplitude of this second echo is equal to or greater than a threshold value, it is determined that there is a construction defect. Therefore, the waveform in which the elastic wave generated by the coil 23 directly reaches the second sensor 22 can be excluded from the determination, and the echo waveform due to multiple reflections can be reliably detected.

[0078] In particular, in this embodiment, the high-frequency band evaluation index includes the attenuation coefficient of the second and subsequent echoes in the echo waveform, and when this attenuation coefficient is smaller than the threshold value, it is determined that there is a construction defect. Here, the greater the degree of the poor densification defect, the slower the attenuation of the echo amplitude. Therefore, by determining that there is a construction defect when the attenuation coefficient of the second and subsequent echoes is smaller than the threshold value, the degree of the poor densification defect can be determined.

[0079] Furthermore, in this embodiment, the densification state is determined from the high-frequency band of the frequency spectrum in the determination process, and a low-frequency band evaluation index is obtained from the low-frequency band below a predetermined frequency in the frequency spectrum, and the deviation state in which the adhesive exists biased in the axial direction can also be determined using the low-frequency band evaluation index. Therefore, as construction defects in which the adhesive for fixing the anchor bolt is insufficient, in addition to the poor densification defect of the adhesive, other defects such as a deviation defect in which the adhesive exists in a biased state can be collectively detected.

[0080] Furthermore, when determining construction defects based on the sum of evaluation points by assigning evaluation points to a plurality of evaluation indicators including a high-frequency band evaluation indicator and a low-frequency band evaluation indicator with respect to a threshold value in the determination process, it is possible to stably determine construction defects as compared with the case of evaluating only with the low-frequency band evaluation indicator. Thereby, when determining construction defects based on the sum of evaluation points by the high-frequency band evaluation indicator and the low-frequency band evaluation indicator, the detection sensitivity is improved with respect to the conventional method for diagnosing concrete structures as disclosed in Patent Document 3, and construction defects can be determined at a higher speed.

[0081] [Second Embodiment] FIGS. 10 and 11 are diagrams for explaining a diagnostic apparatus and a diagnostic method for a concrete structure according to the second embodiment. The diagnostic apparatus according to the second embodiment is the same as the diagnostic apparatus and the diagnostic method of the first embodiment in all respects except that the method for obtaining the high-frequency band evaluation indicator by data processing ST3 is different in the high-frequency band evaluation indicator unit 72 of the spectrum evaluation indicator unit 70.

[0082] In the high-frequency band evaluation indicator unit 72 of the second embodiment, when obtaining the high-frequency band evaluation indicator from the frequency spectrum generated by the fast Fourier transform of the second received signal S26b, it is performed by integrating the comb-shaped ripple Wc appearing in the high-frequency band of frequencies from 40 kHz to 110 kHz in the frequency spectrum. That is, from the frequency spectrum shown in FIGS. 6(1)-(5), for example, the integrated value of the amplitude of the comb-shaped ripple Wc in a predetermined frequency region such as 40 kHz or more and 110 kHz or less is obtained, and an NG point can be assigned by comparing this with a threshold value as the high-frequency band evaluation indicator.

[0083] For example, as shown in FIG. 10, for each of five anchor bolts A-E, the integrated value of the amplitude of the comb-shaped ripple Wc is obtained. Then, as shown in FIG. 11, the integrated value of the amplitude of each anchor bolt A-E is compared with the threshold value to obtain an NG point for each. In FIG. 11, only the NG points for the high-frequency band evaluation index are illustrated as bar graphs for each anchor bolt, and the tensile strength of the tensile test is plotted. As is clear from this figure, the NG points can evaluate the difference in the filling amount of the adhesive and the degree of tensile strength. Also, it can be seen that the detection sensitivity is high enough to detect construction defects even when the tensile strength is high as in the case of the anchor bolt B.

[0084] Also in such a diagnostic apparatus and diagnostic method of the second embodiment, the same operational effects as those of the first embodiment can be obtained. In particular, in the second embodiment, the size of the comb-shaped ripple Wc in the high-frequency band due to the multiple reflection of elastic waves can be easily quantified, and the degree of looseness defect can be easily determined.

[0085] [Third Embodiment] FIG. 12 is a schematic configuration diagram showing a diagnostic apparatus 28A for a concrete structure according to the third embodiment. In the diagnostic apparatus 28A for a concrete structure of the third embodiment, the second sensors 22 are arranged only at the ends of the exposed portions 12 of the anchor bolts 10 without providing the first sensors 21-1 to 21-4 on the surface of the concrete 1. Other aspects are the same as those of the diagnostic apparatus 28 of the first embodiment.

[0086] Even with such a diagnostic apparatus 28A, similarly to the first embodiment, the low-frequency band evaluation index and the high-frequency band evaluation index can be obtained, and only the NG points based on the high-frequency band evaluation index can be accurately obtained. Therefore, similarly to the diagnostic method for a concrete structure of the first embodiment, it is possible to accurately detect looseness defects.

[0087] Note that each of the above embodiments can be appropriately changed within the scope of the present invention. For example, in the above embodiment, an example of a post-construction anchor bolt is used as the anchor bolt 10 partially embedded in the under-hole 2 of the concrete 1, but it is not particularly limited as long as it is a rod-shaped conductor partially embedded and fixed in the under-hole 2 of the concrete 1.

[0088] In the above-described embodiment, an example in which an adhesive filled in a hole is used as the fixing means for fixing the anchor bolt 10 has been described. However, other fixing means may be used. For example, in the case of other adhesive-type anchor bolts, an adhesive that is accommodated in a capsule manner in the lower hole 2 provided in the concrete and cured may be used. Further, in the case of a metal-type anchor bolt, a sleeve that expands in the lower hole previously drilled in the concrete and is mechanically fixed to the inner wall of the lower hole may be used.

[0089] In the diagnostic apparatus for a concrete structure according to the third embodiment, the information processing apparatus 30 may be provided with only the high-frequency band evaluation index unit 72 without providing the waveform evaluation index unit 60 and the low-frequency band evaluation index unit 71 of the spectrum evaluation index unit 70.

[0090] [Fourth Embodiment] Next, the fourth embodiment of the present invention will be described in detail with reference to the drawings. The diagnostic method and diagnostic apparatus for a building structure according to the fourth embodiment are another method and apparatus for diagnosing a diagnostic structure around a conductor member disposed in a building structure. The diagnostic structure to be diagnosed may be any structure that can be determined from information obtained by receiving and processing elastic waves generated in the conductor member, and various structures can be diagnosed.

[0091] In the fourth embodiment, as a concrete structure in which a conductor member is disposed, an example of a concrete structure in which a post-construction anchor bolt is partially embedded in concrete is used, and as a diagnostic structure around the conductor member, an example of a fixing structure in which a post-construction anchor bolt is fixed with an adhesive is described.

[0092] (Diagnostic Apparatus for Building Structure) FIGS. 13(a) and (b) are schematic configuration diagrams showing a diagnostic apparatus 28B for a building structure according to the fourth embodiment of the present invention. FIG. 13(a) is a configuration diagram of the entire diagnostic apparatus 28B, and FIG. 13(b) is a configuration diagram of a waveform receiving unit (for example, an AD conversion device) in FIG. 13(a). FIG. 14 is a functional block diagram showing a configuration example of the information processing apparatus 30A in FIG. 13.

[0093] Subsequently, as will be described with reference to FIG. 3, the post-construction anchor bolt 10 is provided with a lower hole 2 in the concrete 1, and the anchor bolt 10 is partially embedded in the lower hole 2 and fixed by fixing means. In the fourth embodiment, it is an adhesive anchor bolt, and an adhesive is used as the fixing means. The anchor bolt 10 is fixed by the adhesive filled in the lower hole 2 in a state where it is partially inserted into the lower hole 2 of the concrete 1.

[0094] The diagnostic device 28B of the fourth embodiment is a device for determining construction defects of the post-construction anchor bolt 10 partially embedded in the lower hole 2 of the concrete 1. This diagnostic device 28B can diagnose various construction defects such as defects and deficiencies in the fixed portion where the post-construction anchor bolt 10 is embedded. In this embodiment, as an example of a construction defect where the adhesive for fixing the anchor bolt 10 is insufficient, an example of detecting a sparse state where the adhesive is sparsely present in the axial direction will be described.

[0095] As shown in FIG. 13(a), around the exposed portion of the anchor bolt 10 exposed from the concrete surface, a coil for generating a pulsed magnetic field, for example, a ring coil 23, is arranged. The upper end of the coil 23 is installed, for example, to coincide with the upper end of the anchor bolt 10.

[0096] A coil unit 24 for generating a pulsed current is connected to the coil 23 via a cable. Further, an electromagnetic pulse power supply 25 for supplying power is connected to the coil unit 24 via a cable. The coil unit 24 and the electromagnetic pulse power supply 25 constitute an elastic wave generating portion that passes a pulsed current through the coil 23 to generate a pulsed magnetic field from this coil 23 and acts this pulsed magnetic field on the anchor bolt 10 to generate elastic waves.

[0097] At the upper end of the exposed portion of the anchor bolt 10, a second sensor 22 for detecting elastic waves, for example, an AE (Acoustic Emission) sensor, is arranged and fixed with glue gun or the like. The second sensor 22 is connected via a cable to an AD conversion device 26 as a waveform receiving unit. The AD conversion device 26 is a device that amplifies the analog elastic wave signal received by the second sensor 22 and then converts it into a received signal S26b consisting of a digital signal.

[0098] As shown in Fig. 13(b), the AD conversion device 26 converts, for example, an analog elastic wave signal into a digital signal at a sampling frequency of 100 MHz and a data length of 10 ms. The AD conversion device 26 is connected via a signal line to an information processing device 30A as a data processing unit.

[0099] The information processing device 30A is a device that calculates the input received signal S26b and evaluates defects and deficiencies such as deterioration in the fixed portion of the anchor bolt 10, and is composed of, for example, a personal computer (PC) or the like.

[0100] Fig. 14 is a functional block diagram showing a configuration example of the information processing device 30A in Fig. 12. This information processing device 30A includes a frequency spectrum processing unit 50A that performs data processing on the received signal S26b output from the AD conversion device 26, a spectrum evaluation index unit 70A connected to the output side of the frequency spectrum processing unit 50A, and a determination evaluation unit 90A connected to the output side of the spectrum evaluation index unit 70A. The difference between the information processing device 30A of the building structure diagnostic device 28B in the fourth embodiment and the information processing device 30 in the first embodiment is that it includes a frequency spectrum processing unit 50A, and in the frequency spectrum processing unit 50A, as will be described later, a frequency spectrum S52A consisting of the waveform of the phase component of the frequency spectrum is obtained.

[0101] The frequency spectrum processing unit 50A includes an FFT unit 51A that obtains a time-axis waveform from the received signal S26b output from the AD conversion device 26 and performs FFT on the time-axis waveform to obtain a frequency spectrum S52A composed of the waveform of the phase component of the frequency spectrum, and a file conversion unit 52 that converts the second frequency spectrum output from the FFT unit 51A into a text file (for example, a CSV file). The frequency spectrum S52A converted into a text file has, for example, a frequency range of 0 to 100 kHz, a frequency resolution of 200 Hz, and an FFT point number of 250.

[0102] The FFT unit 51A of the fourth embodiment includes a complex amplitude processing unit 51a that obtains the complex amplitude of the frequency spectrum obtained by performing Fourier transform on the time-axis waveform, and a phase processing unit 51b that obtains the waveform of the phase component from the complex amplitude obtained by the complex amplitude processing unit 51a.

[0103] The spectrum evaluation index unit 70A includes an evaluation index unit 71 that obtains an evaluation index based on the waveform of the phase component of the frequency spectrum after file conversion, which is the signal of the frequency spectrum S52A. Other evaluation indexes may be obtained together with the evaluation index based on the waveform of the phase component.

[0104] The determination evaluation unit 90A is connected to the evaluation point assigning unit 80A on the output side of the spectrum evaluation index unit 70A. It assigns evaluation points to the evaluation index based on the waveform of the phase component with reference to a threshold value, and determines construction defects based on the evaluation points. When other evaluation indexes are obtained together with the evaluation index based on the waveform of the phase component in the evaluation index unit 70A, the construction defects may be determined based on the sum of the evaluation points based on each evaluation index.

[0105] (Diagnosis method of building structures) A method for diagnosing a test piece using the building structure diagnosis device 28B of the fourth embodiment shown in FIGS. 13 and 14 will be described. The test piece fabricated as a building structure is the same as that in FIG. 3, and FIG. 15 is a flowchart showing the diagnosis method of the building structure in the fourth embodiment of the present invention.

[0106] As shown in Fig. 3, in the test specimen, anchor bolts A - E with a nominal diameter of 16 mm and a length of 1050 mm are each fixed with different amounts of epoxy adhesive in a state where 400 mm is embedded in concrete 1 and 650 mm is exposed outside.

[0107] In the test specimen, for anchor bolt A, adhesive exists throughout the entire 400 mm of the embedded part, and the amount of adhesive present is a normal construction product of 25 da. Here, the diagnosed structure is a structure with adhesive applied to anchor bolt A. The normal construction product is the structure that serves as the standard for the evaluation index described later and is called the control structure. For anchor bolts B - E, as described in Fig. 3, the total amount of adhesives sparsely present in the axial direction is 20 da, 13 da, 9 da, and 7 da respectively, and they are construction defective products in a state of sparse application defects. In these construction defective products with sparse application defects, in all cases, adhesive exists around the anchor bolt at the opening end of the under - hole 2, and the presence or absence of internal adhesive cannot be visually confirmed.

[0108] In the diagnostic method for the building structure of the fourth embodiment, as shown in Fig. 15, the following elastic wave generation process ST1, reception process ST2, data process ST3, evaluation index process ST4, and evaluation point assignment process ST5 are performed in sequence. (I) Elastic wave generation process ST1 Turn on the electromagnetic pulse power supply 25 to start the process. Power is output from the electromagnetic pulse power supply 25 and supplied to the coil unit 24. A pulse current is output from the coil unit 24, and this pulse current flows through the coil 23 arranged at the exposed part 12 of the anchor bolt 10. Then, a pulse magnetic field is generated from the coil 23, the anchor bolt 10 vibrates, and elastic waves are generated. The generated elastic waves propagate inside the anchor bolt 10 and also pass through the inside of the concrete 1 and propagate around the anchor bolt 10.

[0109] (II) Reception process ST2 The elastic wave propagated inside the anchor bolt 10 is received by the second sensor 22 disposed at the exposed portion 12 of the anchor bolt 10. The analog reception signal received by the second sensor 22 is sent to the AD conversion device 26. In the AD conversion device 26, the analog reception signal supplied from the second sensor 22 is converted into a digital signal at a sampling frequency of 100 MHz and a data length of 10 ms, and the reception signal S26b is output to the information processing device 30A.

[0110] (III) Data processing ST3 In the frequency spectrum processing unit 50A in the information processing device 30A, the input reception signal S26b is subjected to fast Fourier transform by the FFT unit 51A, and a signal of the frequency spectrum is generated. Here, data processing ST3 is performed to obtain a time-axis waveform from the reception signal S26b and perform Fourier transform on the time-axis waveform to obtain a waveform of the phase component of the frequency spectrum.

[0111] In the fourth embodiment, in the complex amplitude processing unit 51a, a complex amplitude processing ST3c (see FIG. 15) for obtaining the complex amplitude of the frequency spectrum as shown in, for example, FIG. 16(a) is performed by obtaining a time-axis waveform and performing FFT on the time-axis waveform. Then, in the phase processing unit 51b, phase processing ST3d (see FIG. 15) is performed from the complex amplitude output from the complex amplitude processing unit 51a, and a waveform of the phase component of the frequency spectrum as shown in FIG. 16(b) is obtained.

[0112] That is, assuming that the value on the real axis is a and the value on the imaginary axis is b in the complex plane, the change of X1(f) is a(f)+jb(f)=(a 2 +b 2 ) 1 / 2 {cosθ+jsinθ}=(a 2 +b 2 ) 1 / 2 exp(jθ), and the absolute value r is (a 2 +b 2 ) 1 / 2That is. In the complex amplitude processing unit 51a, the complex amplitude with respect to the frequency is obtained. Then, by obtaining the phase (θ) from the complex amplitude according to the following formula (10), the waveform of the phase component of the frequency spectrum is obtained.

[0113] [Number]

[0114] The waveform of the phase component of the generated frequency spectrum is converted into a CSV file by the file conversion unit 52, and a signal of the frequency spectrum S52A with a frequency range of 0 to 100 kHz, a frequency resolution of 200 Hz, and the number of FFT points of 250 is generated and output to the spectrum evaluation index unit 70A.

[0115] When diagnosing the fixing structure by the adhesive of the post-construction anchor bolt 10 like the test piece shown in FIG. 3, an example of the waveform of the phase component of the obtained frequency spectrum is shown in FIG. 17. In FIG. 17, FIG. 17(a) is an example of the waveform obtained by the normal construction product in which the adhesive exists in all the embedded parts like the anchor bolt A, and FIGS. 17(b) and 17(c) are examples of the waveforms obtained by the construction defective products with sparse defects in which the adhesive exists sparsely in the axial direction like the anchor bolts C - E, for example. Compared with FIG. 17(b), FIG. 17(c) is the waveform of the construction defective product with less amount of the adhesive and a greater degree of sparse defect. Thus, the waveform of the phase component of the frequency spectrum obtained in the data processing ST3 changes according to the difference in the adhesive structure around the anchor bolts A - E.

[0116] (IV) Evaluation index processing ST4 In the spectrum evaluation index unit 70A, evaluation index processing ST4 is performed to obtain an evaluation index based on the waveform of the phase component of the frequency spectrum, which can compare the fixing structure by the adhesive of the post-construction anchor bolt 10, the structure to be diagnosed, with the control structure which is a normal construction product. In the fourth embodiment, a phase component correlation coefficient of the frequency spectrum between the fixing structure of each anchor bolt AE and the fixing structure of anchor bolt A, which is a control structure, is obtained as an evaluation index.

[0117] The correlation coefficient of the phase component of the frequency spectrum can be calculated as follows. (1) First, calculate the average value of the phase components of the frequency spectrum obtained when the standard construction is performed N times. The frequency spectrum is an FFT waveform obtained by fast Fourier transforming the data from the time-domain waveform processing. The average value of the phase component of the frequency spectrum can be obtained by calculating the average value of the phase at each frequency. (2) Next, the evaluation target is a construction different from the standard construction, for example, a poor construction, and the correlation coefficient (CF) between the average phase component (x) of the standard construction and the phase component (y) of the evaluation target is calculated using the following formula (11) or formula (12).

[0118]

number

number

[0119] In the fourth embodiment, the correlation coefficient in the fixing structure of each anchor bolt AE obtained in this manner is calculated as an evaluation index and sent to the evaluation point assigning unit 80A. Figure 18(a) shows the correlation coefficients calculated for the phase waveforms of the frequency spectrum for the AE of the five anchor bolts of the test specimen shown in Figure 3. As a comparative example, Figure 18(b) shows the correlation coefficients calculated from the complex amplitudes (absolute values) of the frequency spectrum for the same anchor bolts. The correlation coefficient of the phase waveform shown in Fig. 18(a) clearly has improved detection accuracy compared to the correlation coefficient found from the complex amplitude shown in Fig. 18(b). In particular, the difference between anchor bolt A of 25 da, which is a properly installed product, and anchor bolt B of 20 da, which is a defective product with a small degree of loosening defect, is more pronounced, and the detection accuracy has improved to the point where even slight differences can be detected.

[0120] (V) Evaluation Point Assignment Process ST5 In the evaluation point assignment unit 80A, an evaluation point assignment process ST5 for assigning an evaluation point for construction defect evaluation is performed by comparing the correlation coefficient of the waveform of the phase of the frequency spectrum obtained for each anchor bolt A - E of the diagnosed structure with the threshold value indicating the control structure. In the evaluation point assignment process ST5, the evaluation points are respectively assigned based on the threshold value for each of the following (i) and (ii) for each evaluation index. (i) Set a threshold value for evaluating non - conforming (NG) for each evaluation index. At this time, set it with a margin so as not to evaluate non - conforming (NG) as much as possible even if the data varies. (ii) For each evaluation index, assign an evaluation point based on the threshold value.

[0121] An example of the evaluation points assigned by the evaluation point assignment process ST5 is shown in Fig. 19. Fig. 19 shows, for each of 5 pieces of each of the anchor bolts A - E, the NG points using the correlation coefficient of the waveform of the phase of the frequency spectrum are illustrated as a bar graph on the left axis for each anchor bolt, and the maximum tensile strength (kN) of the tensile test is plotted on the right axis. The normal construction products as the control structure are A - 001 to A - 003, and A - 004 to A - 005 and the anchor bolts B (B - 001 to B - 005) - E (E - 001 to E - 005) are the diagnosed structures, that is, the evaluation objects. As is clear from Fig. 19, the NG points were able to evaluate the differences in the degree of looseness defect and the degree of tensile strength. Also, it can be seen that for A - 004, A - 005 and the anchor bolts B (B - 001 to B - 005) with a small degree of looseness defect as the diagnosed structures, NG points are assigned with respect to the normal construction products (A - 001 to A - 003) as the control structure and they are completely separated.

[0122] According to the diagnostic device 28B and diagnostic method of the building structure of the fourth embodiment as described above, an elastic wave is generated in the anchor bolt 10 which is a conductor member, received by the second sensor 22, a time-axis waveform is obtained and Fourier-transformed, thereby obtaining a waveform of the phase component of the frequency spectrum, and the difference between the diagnosed structure and the reference structure is determined based on the waveform of this phase component. Therefore, even if the difference in the structure around the anchor bolt 10 is small, the difference can be detected. Therefore, it is possible to improve the detection accuracy when detecting the structure non-destructively by applying an elastic wave to the anchor bolt 10.

[0123] In the fourth embodiment, the waveform of the phase component is obtained from the complex amplitude of the frequency spectrum obtained by Fourier-transforming the time-axis waveform in the data processing ST3. Therefore, even in a device in which only the complex amplitude of the frequency spectrum can be obtained by obtaining the time-axis waveform from the received signal and performing Fourier transformation, the detection accuracy can be improved by obtaining the waveform of the phase component using the complex amplitude.

[0124] In the fourth embodiment, in the evaluation index process ST4, the correlation coefficient between the waveform of the phase component of the frequency spectrum in the diagnosed structure and the waveform of the phase component of the frequency spectrum in the reference structure is obtained, and the suitability of the diagnosed structure is determined by comparing the correlation coefficient with a threshold value. As a result, since the difference in the waveform of the phase component of the frequency spectrum between the diagnosed structure and the reference structure is large, it is possible to easily determine construction defects by obtaining the correlation coefficient for the waveform of the phase component of the frequency spectrum, and the diagnosis of the building structure is easy.

[0125] In the fourth embodiment, in the evaluation index process ST4, an evaluation index of the diagnosed structure obtained from the waveform of the phase component of the frequency spectrum is obtained, and the suitability of the diagnosed structure is determined by comparing the evaluation index with a threshold value indicating the reference structure. As a result, since the difference in the waveform of the phase component of the frequency spectrum between the diagnosed structure and the reference structure is large, it is possible to easily compare the structure around the anchor bolt 10 which is the conductor member of the diagnosed structure with the reference structure, and the diagnosis of the building structure is easy.

[0126] In the fourth embodiment, the diagnostic method and diagnostic apparatus 28B of the building structure of the present invention are applied to the fixing structure of the anchor bolt 10, which is a conductor bar partially embedded in the concrete 1 and fixed by a fixing means, to determine construction defects. In particular, a sparse state in which the adhesive for adhering the anchor bolt 10 to the hole in the concrete 1 is sparsely present in the axial direction is determined as a construction defect. Therefore, it is possible not only to detect a construction defect in which the fixing strength of the partially embedded anchor bolt 10 with respect to the concrete 1 is significantly inferior to that of a properly constructed product, but also a construction defect in which the fixing strength is slightly inferior to that of a properly constructed product, or a sparse defect that is difficult to distinguish by the waveform of the time-axis component of the frequency spectrum. However, since the difference in the waveform of the phase component of the frequency spectrum is large, the construction defect can be easily determined.

[0127] Note that the fourth embodiment can be appropriately modified within the scope of the present invention. For example, in the above-described first embodiment, an example in which the waveform of the phase component of the frequency spectrum is obtained from the received signal by two processing units, i.e., a complex amplitude processing unit 51a that performs Fourier transform on the time-axis waveform in the FFT unit 51 to obtain the complex amplitude of the frequency spectrum, and a phase processing unit 51b that obtains the waveform of the phase component from the complex amplitude obtained by the complex amplitude processing unit 51a, has been described. However, the present invention is not particularly limited thereto, and in one processing unit of the FTT unit 51, the waveform of the phase component of the frequency spectrum may be obtained from the time-axis waveform without outputting the complex amplitude.

[0128] Further, in the fourth embodiment, the second sensor 22 is provided at the upper end of the exposed portion of the anchor bolt 10. However, as in the first embodiment, the sensor may be provided on the surface of the concrete. FIG. 1 shows four sensors 21-1 to 21-4 disposed at positions separated by 90 degrees on the surface of the concrete. FIG. 20 is a diagram showing the amplitude of the frequency spectrum received from the sensor provided on the surface of the concrete. The horizontal axis in FIG. 20 is the frequency (kHz), and the vertical axis is the amplitude. As shown in Fig. 20, it can be seen that even for the sensor disposed on the surface of the concrete, the amplitude is observed at a high frequency of 40 kHz or more, similar to the second sensor 22 provided at the upper end of the exposed portion of the anchor bolt 10 shown in Fig. 16(a). Thus, since the echo reciprocating inside the anchor bolt 10 leaks out to the concrete 1, that is, propagates in the concrete 1, it can be seen that the first received signal S26a received on the surface of the concrete 1 also contains a high-frequency component.

[0129] In the above embodiment, as a method of comparing the structural differences using the waveform of the phase of the frequency spectrum, an example using the correlation coefficient of the waveform of the phase of the frequency spectrum as an evaluation index has been described. However, the method is not limited to the correlation function, and it is also possible to compare by other methods. For example, the number of zero crossings where the phase in the waveform of the phase of the frequency spectrum of the structure to be diagnosed becomes 0 (rad) may be compared with the number of zero crossings in the waveform of the phase of the frequency spectrum of the reference structure. Here, the number of zero crossings is the number of times the phase becomes 0 rad on the frequency axis.

[0130] Fig. 21 is a diagram showing the number of zero crossings of the phase of the frequency spectrum for the anchor bolts A - E. The horizontal axis in Fig. 20 indicates the type of the anchor bolt, and the vertical axis indicates the number of zero crossings. Here, the second sensor 22 is provided at the upper end of the exposed portion of the anchor bolt 10 as in Fig. 18. As shown in Fig. 21, for the normal construction products A - 001 to A - 005, the number of zero crossings is approximately 40 or more for the anchor bolts B - E with a degree of sparse attachment defect. It can be seen that if the threshold value is set to about 35, the normal construction products and the defective construction can be completely discriminated.

[0131] (Diagnostic method for voids) Regarding the structure around the conductor member of a building structure where the conductor member is arranged, as the structure to be diagnosed, in the fixing structure of the post-construction anchor bolt 10 solely by an adhesive, the state where the adhesive for bonding the conductor bar is sparsely present in the axial direction was described as a construction defect. However, as a construction defect of the anchor bolt 10, a construction defect (also called a void defect) where the adhesive for bonding the conductor bar does not exist in the axial direction and there is a void can also be determined, and this will be described in detail below.

[0132] Figure 22 is a diagram for explaining a construction defect with a void portion 6. Figure 22(a) is a side cross-sectional view showing normal construction, and Figure 22(b) is a cross-sectional view taken along the line a-a of Figure 22(a). As shown in Figure 22(a), an anchor bolt 10 with a length of 200 mm is partially embedded by 130 mm in a pilot hole 2 with a diameter of 20 mm, fixed to the concrete by an adhesive 3, and the exposed portion of the anchor bolt 10 is 70 mm. As shown in Figure 22(b), the void portion 6 of the construction-defective anchor bolt 10 occurs on the inner side of the concrete, and the adhesive-filled portion, which is the portion filled with the adhesive, is a so-called front filling, and it appears visually as if the adhesive is filled from the outside. Therefore, the void defect is a construction defect that cannot be found by visual inspection. To evaluate the construction defect of the void, test specimens of the anchor bolt 10 with a filling dimension from 23% to 100% are shown in Table 1. Here, the filling rate indicates the ratio of the adhesive filled in the gap between the concrete 1 and the anchor bolt 10 in %, and it is 100% if it is filled completely without a gap. In this test specimen, a hole with a diameter of 19 mm and a depth of 130 mm is made in the concrete 1, and an anchor bolt 10 with a diameter of 16 mm is inserted to the bottom of the hole. Since the amount of the adhesive in the radial direction of the anchor bolt 10 is the same in the construction defect with the void portion 6 (see Figure 22), as shown in Table 1, the filling rate when the filling dimension d is 130 mm is 100%, and the filling rate when d is 65 mm is 50%, etc.

[0133]

Table 1

[0134] Fig. 23 shows the correlation coefficients obtained for the test specimens shown in Table 1 in the same manner as in Fig. 18. Fig. 23(a) shows the correlation coefficients obtained from the waveforms of the phases of the frequency spectra, and Fig. 23(b) shows, as a comparative example, the correlation coefficients obtained from the complex amplitudes (absolute values) of the frequency spectra. For both the phase in Figure 23(a) and the amplitude in Figure 23(b), five poles from 01d-100% to 09d-100% were selected as the evaluation standard (control structure) from the 12 poles that were normally constructed, and seven poles from 11d-100% to 23d-100% were evaluated as the evaluation targets (diagnosed structure), and the threshold value was set to the minimum value of the five poles of the control structure. In the correlation coefficient of the phase waveform shown in FIG. 23(a), all seven of the diagnosed structures that were properly constructed were greater than the threshold value and were determined to be non-defective. Next, for the 12 anchor bolts with a filling rate of 73%, which was the least defective, all had values ​​below 0.6, and it was found that they were completely separated from the 7 anchor bolts with properly constructed structures that were the subject of the diagnosis. In the correlation coefficient of the complex amplitude shown in FIG. 23(b), six of the diagnosed structures were determined to be below the threshold and therefore to be defective. Next, it was found that for the 12 anchor bolts with a filling rate of 73%, which is a small degree of defect, the correlation coefficient was near the threshold value, making it difficult to distinguish them from the seven properly constructed bolts that were the subject of the evaluation. Comparing the correlation coefficients by phase in Figure 23(a) and amplitude in Figure 23(b), it is clear that the correlation coefficient by phase shown in Figure 23(a) has improved detection accuracy. In particular, the difference between the properly installed anchor bolts with a filling rate of 100% (No.01-100% to No.23-100%) and the anchor bolts with a filling rate 27% lower, i.e., 73% (No.01-73% to No.23-73%), is more pronounced, demonstrating that even slight differences in voids can be detected.

[0135] FIG. 24 is a diagram showing the evaluation points given in the evaluation point assignment process ST5 based on the waveform of the phase of the frequency spectrum, and shows the NG points for each anchor bolt with respect to the evaluation index using the correlation coefficient. The horizontal axis in FIG. 24 indicates anchor bolts with filling rates of 100%, 73%, 50%, and 23%, and the vertical axis is the NG points. As is clear from FIG. 24, it can be seen that the NG points can evaluate the degree of void defects. Also, for the control structure, that is, the regular construction product with a filling rate of 100%, all are 0 points, and the anchor bolts with a small degree of void defects of 73% (from No. 01-73% to No. 23-73%) have large NG points, indicating that voids can be accurately detected.

[0136] FIG. 25 is a diagram showing the NG points based on the evaluation index regarding the amplitude, instead of the evaluation using the evaluation points based on the phase of the frequency spectrum, as a comparative example of FIG. 24. The horizontal axis in FIG. 25 indicates anchor bolts with filling rates of 100%, 73%, 50%, and 23%, and the vertical axis is the NG points. As shown in FIG. 25, as the evaluation index regarding the amplitude, the amplitude correlation coefficient, the centroid, the standard deviation, the waveform duration, and the number of peaks are obtained and plotted, and the NG points based on the phase shown in FIG. 24 are also shown together. As shown in FIG. 25, it can be seen that the NG points based on the amplitude correlation coefficient are also present for the regular construction product with a filling rate of 100%, and the change in the NG points is small even when the filling rate decreases. On the other hand, when the NG points based on the phase shown in FIG. 24 are added to the evaluation index regarding the amplitude in FIG. 25, large NG points also appear at a filling rate of 73%, indicating that construction defects can be accurately discriminated even when the degree of void defects is small.

[0137] Note that the above embodiments can be appropriately changed within the scope of the present invention. For example, in the above embodiments, as the evaluation index regarding the amplitude, an example of assigning evaluation points by adding the amplitude correlation coefficient, the centroid, the standard deviation, the waveform duration, the number of peaks, and the phase correlation coefficient has been described. Needless to say, the selection of various evaluation indexes regarding the amplitude and the combination with the phase correlation coefficient are selected so that the evaluation of the NG points can be accurately performed.

Explanation of Symbols

[0138] 1: Concrete 2: Borehole (hole) 3: Resin 5: Specimen 6: Void portion 10, 10A, 10B: Anchor bolt 11: Fixing portion 12: Exposed portion 21-1 to 21-4: First sensor 22: Second sensor 23: Coil 24: Coil unit 25: Electromagnetic pulse power supply 28, 28A, 28B: Diagnostic device 30, 30A: Information processing device 40: Time-axis waveform processing unit 50, 50A: Frequency spectrum processing unit 51a: Complex amplitude processing unit 51b: Phase processing unit 60: Waveform evaluation index unit 70, 70A: Spectrum evaluation index unit 71: Low-frequency band evaluation index unit 72: High-frequency band evaluation index unit 80, 80A: Evaluation point assignment unit 90, 90A: Judgment evaluation unit ST1: Elastic wave generation processing ST2: Reception processing ST3: Data processing ST3a: Time-axis waveform processing ST3b: Frequency spectrum processing ST3c: Complex amplitude processing ST3d: Phase processing ST4: Evaluation index processing ST5: Evaluation point assignment processing Wc: Comb-like ripple We: Echo waveform

Claims

1. A coil is disposed on an exposed portion of a conductor bar partially embedded in a hole in concrete and fixed by fixing means, and an elastic wave is generated in the conductor bar by a pulse magnetic field generated by flowing a pulse current through the coil. An elastic wave generation process, A sensor is disposed on the exposed portion and / or the concrete surface around the conductor bar, and a reception process of receiving the elastic wave by the sensor and generating a reception signal, A data process of obtaining a time-axis waveform from the reception signal and performing a Fourier transform on the time-axis waveform to obtain a frequency spectrum, In a diagnostic method for a concrete structure having a determination process of determining a construction defect of the conductor bar in the concrete based on the result of the data process, In a high-frequency band of a predetermined frequency or higher in the frequency spectrum, a high-frequency band evaluation index is obtained based on comb-like ripples appearing due to multiple reflections of the elastic wave, and the construction defect is determined based on the high-frequency band evaluation index. A diagnostic method for a concrete structure.

2. The high-frequency band is a frequency band from 40 kHz to 110 kHz. The diagnostic method for a concrete structure according to claim 1.

3. The time-domain signal is obtained by cutting out a predetermined frequency region of the comb-like ripple and performing an inverse Fourier transform, and the high-frequency band evaluation index is obtained based on an echo waveform that periodically appears in the time-domain signal. The diagnostic method for a concrete structure according to claim 1.

4. The high-frequency band evaluation index includes the amplitude of the second echo in the echo waveform, and when the amplitude is equal to or greater than a threshold value, it is determined that there is a construction defect. The diagnostic method for a concrete structure according to claim 3.

5. The high-frequency band evaluation index includes the attenuation coefficient of the second and subsequent echoes in the echo waveform, and when the attenuation coefficient is smaller than a threshold value, it is determined that there is a construction defect. The diagnostic method for a concrete structure according to claim 3.

6. The method for diagnosing a concrete structure according to claim 1, wherein the high-frequency band evaluation index is obtained from the integrated value in a predetermined frequency range of the comb-shaped ripple.

7. In the determination process, an evaluation index obtained from the waveform of the phase component of the frequency spectrum is obtained, and the suitability of the construction is determined by comparing the evaluation index with a threshold value obtained from the evaluation index of normal construction. The method for diagnosing a building structure according to claim 1.

8. The adhesive for adhering the conductor rod to the hole in the concrete is determined as any one of a sparse state in which the adhesive is sparsely present in the axial direction, a bias defect in which the adhesive is present in a biased state, a filling state in which voids are generated, and voids as the construction defect. The method for diagnosing a concrete structure according to any one of claims 1 to 7.

9. In the reception process, the sensor is arranged on each of the exposed portion and the concrete surface around the conductor rod, and the elastic wave is received by both sensors to generate the reception signal respectively. In the data processing, the frequency spectrum is obtained from each of the received signals respectively. In the determination process, the sparse state is determined from the high-frequency band of the frequency spectrum, and a low-frequency band evaluation index is obtained from the low-frequency band of 0 kHz or more to 100 kHz in the frequency spectrum, and the bias state in which the adhesive is present in a biased manner in the axial direction is determined using the low-frequency band evaluation index. The method for diagnosing a concrete structure according to claim 7.

10. In the determination process, an evaluation point is given to each of a plurality of evaluation indexes including the high-frequency band evaluation index and the low-frequency band evaluation index based on a threshold value, and the construction defect is determined by the sum of the evaluation points. The method for diagnosing a concrete structure according to claim 9.

11. A coil and a sensor arranged on an exposed portion of a conductor rod partially embedded in a hole in concrete and fixed by fixing means. An elastic wave generation unit that generates an elastic wave in the conductor bar by a pulsed magnetic field generated by passing a pulsed current through the coil, A reception processing unit that receives the elastic wave with the sensor and generates a reception signal, A data processing unit that obtains a time-axis waveform from the reception signal and performs a Fourier transform on the time-axis waveform to obtain a frequency spectrum, In a diagnostic device for a concrete structure having a determination processing unit that determines a construction defect of the conductor bar in the concrete based on the processing result of the data processing unit, The determination processing unit obtains a high-frequency band evaluation index based on a comb-shaped ripple appearing due to multiple reflections of the elastic wave in a high-frequency band of a predetermined frequency or higher in the frequency spectrum, and determines the construction defect based on the high-frequency band evaluation index, or The data processing unit obtains a waveform of a phase component of the frequency spectrum, The determination processing unit determines the construction defect based on the waveform of the phase component of the frequency spectrum. A diagnostic device for a concrete structure.

12. The high-frequency band is a frequency band from 40 kHz to 110 kHz. The diagnostic device for a concrete structure according to claim 11.

13. The sensor is disposed on the exposed portion and on the concrete surface around the conductor bar, The reception processing unit receives the elastic wave with both sensors and generates the reception signals respectively, The determination processing unit determines the construction defect using the high-frequency band evaluation index and a low-frequency band evaluation index obtained from a low-frequency band of less than a predetermined frequency in the frequency spectrum. The diagnostic device for a concrete structure according to claim 11.

14. The low-frequency band is a frequency band from 0 kHz or higher to 100 kHz. The diagnostic device for a concrete structure according to claim 13.

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