JP2018084507A - Reinforcing-bar corrosion ae detection method and device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an AE detection method and an apparatus for reinforcing bar corrosion capable of identifying AE generated at an AE source on a reinforcing bar from noise and detecting it with high accuracy. A sensor arrangement step S1, a delay time calculation step S2, a received waveform storage step S3, and a waveform synthesis step S4 are included. In step S1, a plurality of AE sensors are arranged at intervals of the sensors on the surface of the concrete in which the reinforcing bars are arranged inside. In step S2, the individual delay time t of the AE arriving at each AE sensor from the AE source on the reinforcing bar is calculated. In step S3, the plurality of AE sensors receive the AEs generated at the AE source, respectively, and store the plurality of received waveforms 5. In step S4, a composite waveform 6 is created by delaying each of the received waveforms 5 based on the individual delay time t and synthesizing them. [Selection diagram] Fig. 4

Description

  The present invention relates to a rebar corrosion AE detection method and apparatus for detecting AE associated with rebar corrosion inside concrete.

It is known that AE occurs with the corrosion of reinforcing bars inside concrete.
AE (Acoustic Emission) is an elastic wave generated in the process of solid deformation, destruction, or corrosion.

The AE generated in the concrete has a frequency band of several tens of kHz to several hundreds of kHz, and can be detected by an AE sensor (for example, a piezoelectric element sensor) in principle.
Further, it is possible to evaluate the reinforcement corrosion inside the concrete from the detected maximum amplitude value of AE, count number, energy, signal duration, rise time and the like.

  For example, Patent Document 1 has already been proposed as a method for evaluating the reinforcement corrosion inside concrete using such AE.

Patent Document 1 “Quantitative Evaluation Method of Reinforcing Bar Corrosion of Concrete Structure by AE” detects AE generated by installing a piezoelectric element sensor in a reinforced concrete structure. The number of hits in which the peak frequency f of the AE satisfies f ₁ ≦ f <f ₂ with respect to an arbitrary frequency f ₁ , f ₂ , f ₃ , f ₄ (f ₁ <f ₂ ≦ f ₃ <f ₄ ) Rebar corrosion is evaluated by the ratio of Hl to the number of hits Hh that satisfies f ₃ ≦ f <f ₄ .

JP 2011-133448 A

  Corrosion of reinforcing bars in concrete is accompanied by volume expansion of oxides during corrosion, and compressive stress is generated between the reinforcing bars and concrete, thereby generating AE along with destruction and rubbing of oxidized corrosion products. Furthermore, if corrosion of the reinforcing bar progresses, the concrete will crack and shift to more serious damage.

  However, the AE associated with corrosion of the reinforcing bar inside the concrete is very weak, and particularly in the initial state of the reinforcing bar corrosion, it is difficult to distinguish it from noise (noise caused by wind and rain).

  For example, in Patent Document 1, AE detected from the concrete surface cannot be confirmed as a significant change in frequency at each loading cycle, and a part of the reinforcing bar of the concrete structure is exposed, and a piezoelectric element sensor is installed at that part. doing.

  The present invention has been developed to solve the above-described problems. That is, an object of the present invention is to provide an AE detection method and apparatus for rebar corrosion that can accurately detect and detect AE generated at an AE generation source on a rebar without exposing the rebar in concrete. It is to provide.

According to the present invention, a sensor placement step of placing a plurality of AE sensors at a distance from each other on the surface of the concrete in which reinforcing bars are arranged,
A delay time calculating step for calculating an individual delay time of the AE arriving at each AE sensor from the AE generation source on the reinforcing bar;
A received waveform storage step of receiving the AE generated at the AE generation source by a plurality of the AE sensors and storing a plurality of received waveforms;
There is provided a method for detecting AE of corrosion of reinforcing bars, comprising: a waveform synthesis step of creating a synthesized waveform obtained by delaying the received waveforms based on the individual delay time.

Further, according to the present invention, a plurality of AE sensors disposed on the surface of the concrete in which reinforcing bars are arranged with a sensor interval therebetween,
A delay time calculation device for calculating an individual delay time of AEs arriving at each AE sensor from an AE generation source on a reinforcing bar;
A received waveform storage device for receiving the AE generated at the AE generation source by a plurality of the AE sensors and storing a plurality of received waveforms;
There is provided an AE detection apparatus for reinforcing steel corrosion, comprising: a waveform synthesizer that creates a synthesized waveform obtained by delaying the received waveforms based on the individual delay time.

  According to the present invention, based on the individual delay time of the AE arriving at each AE sensor from the AE generation source on the reinforcing bar, the combined waveform is created by delaying the received waveforms. As a result of this synthesis, AEs (referred to as “received AE waveforms”) included in each received waveform are added synchronously based on the individual delay time, so that the synthesized waveform is enhanced (amplified) in proportion to the number of AE sensors. ) Received AE waveform. In addition, the noise included in each received waveform is attenuated by canceling each other because its generation position is different from that of the AE generation source.

  Therefore, according to the present invention, the AE generated at the AE generation source on the reinforcing bar can be identified from the noise without exposing the reinforcing bar in the concrete, and the initial state of the reinforcing bar corrosion can be accurately detected.

It is explanatory drawing of the detection method of AE. It is a schematic diagram of the reception waveform of AE. It is an embodiment figure of the AE detection apparatus of rebar corrosion by the present invention. It is a whole flowchart which shows embodiment of the AE detection method of the reinforcement corrosion by this invention. It is a schematic diagram of a received waveform and a synthesized waveform. It is a figure which shows the case where a some sensor is arrange | positioned on the straight line orthogonal to the length direction of a reinforcing bar. It is a figure which shows the simulation waveform of AE used by simulation. It is a figure which shows the synthetic | combination waveform which synthesize | combined the pseudo | simulation AE which generate | occur | produced on the upper surface (generation source) of the reinforcing bar of FIG. 6 by the method of this invention. It is a figure which shows the synthetic | combination waveform synthesize | combined by the method of this invention based on the pseudo | simulation AE which generate | occur | produced in the depth different from the generation source of FIG. It is a relationship diagram between the depth of the sound source and the amplitude value ratio. FIG. 6 is a relationship diagram between a position in a width direction of a sound source and an amplitude value ratio. It is a figure which shows the example of arrangement | positioning of the sensor with respect to the support | pillar of a road bridge. It is a relational diagram between sensor interval and amplitude value ratio. The composite waveform of the noise which comes from the distant of the support | pillar in the case of the distance between sensors which satisfy | fills Formula (3) is shown.

  Embodiments of the present invention will be described below with reference to the drawings. In each figure, common portions are denoted by the same reference numerals, and redundant description is omitted.

FIG. 1 is an explanatory diagram of an AE detection method.
In this figure, 1 is the concrete surface, 2 is the AE source of the reinforcing bar B, and 4 is the AE sensor. This figure shows a two-dimensional cross section that passes through the AE generation source 2 and is orthogonal to the reinforcing bar B.

In this figure, the position of the surface 1 closest to the AE generating source 2 (directly above in the figure) is the origin O, one axis along the surface 1 is the X axis, and the axis orthogonal to the surface 1 is the Z axis.
The AE generation source 2 is located on the Z axis at the position of the reinforcing bar B, that is, the depth d from the origin O. The AE sensor 4 is located on the X axis at a surface distance L from the origin O.

In this case, the propagation distance R from the AE generation source 2 to the reception surface (position of the surface 1) of the AE sensor 4 is geometrically obtained by the equation (1).
R ² = d ² + L ² (1)
In addition, the individual delay time t from the generation of AE3 to the detection by the AE sensor 4 from the sound speed v of AE3 can be obtained by Expression (2).
t = R / v (2)
The sound speed v of AE3 is a sound wave in the concrete, and is, for example, about 4250 to about 5250 m / s.

The position of the reinforcing bar B in the concrete is usually known from the drawings and the like. Even if it is not known, the position of the reinforcing bar B can be actually measured by a radar or the like. The sound velocity v in the concrete can also be measured in advance. Furthermore, the surface distance L from the origin O of the AE sensor 4 can be freely set.
Therefore, by setting the position of the AE generation source 2 on the reinforcing bar in advance, the individual delay time t can be calculated from the equations (1) and (2).

FIG. 2 is a schematic diagram of the received waveform 5 of AE, where the horizontal axis represents time and the vertical axis represents AE intensity.
In this figure, S is a threshold value, T1 is a duration, T2 is a rise time, Hm is a maximum amplitude value, black circles (●) are count points, and hatched areas indicate energy.
As shown in this figure, the received waveform 5 includes noise 8 in addition to the waveform of AE3 (“received AE waveform 5a”). Therefore, as described above, when AE3 is weak, it is difficult to distinguish the received AE waveform 5a from the noise 8.

FIG. 3 is a diagram showing an embodiment of the AE detection apparatus 10 for reinforcing steel corrosion according to the present invention.
In this figure, the AE detection device 10 includes a plurality of AE sensors 12, a delay time calculation device 14, a received waveform storage device 16, a waveform synthesis device 18, and an evaluation device 20.

  The plurality of AE sensors 12 are, for example, piezoelectric element sensors, and are arranged on the concrete surface 1 in which the reinforcing bars B are arranged at an interval from each other. Hereinafter, the AE sensor 12 is simply referred to as “sensor 12” unless necessary.

FIG. 3 is a view of the surface 1 of the concrete as viewed from above (in a direction orthogonal to the surface 1). The surface position closest to the AE source 2 on the reinforcing bar is the origin O, and the axes are orthogonal to each other along the surface 1. Are the X and Y axes.
In this example, eleven sensors 12 are arranged on the X axis with the sensor interval ΔL from the origin O centered on the origin O. The sensor interval ΔL may be constant or random.
Further, the plurality of sensors 12 is not limited to the X axis, and if the surface distance L from the origin O is the same (on a circle centered on the origin O), as shown by the broken line in the figure, the Y axis It may be on or other positions.

The delay time calculation device 14, the received waveform storage device 16, the waveform synthesis device 18, and the evaluation device 20 are configured as one computer (PC) as a whole, for example. This computer has an input / output device, a computing device, and a storage device.
Note that a part of the delay time calculation device 14, the received waveform storage device 16, the waveform synthesis device 18, and the evaluation device 20 may be configured by another device. Moreover, the evaluation apparatus 20 is not essential and may be omitted.

  The delay time calculation device 14 calculates the individual delay time t of the AE 3 that arrives at each sensor 12 from the AE generation source 2 on the reinforcing bar.

  When the position of the AE generation source 2 on the reinforcing bar is known or predetermined, the individual delay time t is based on the known or measured position of the reinforcing bar B and the sound velocity v, and the above-described equations (1) and (2). Can be calculated in advance.

The reception waveform storage device 16 receives the AE 3 generated by the AE generation source 2 by the plurality of sensors 12 and stores a plurality of reception waveforms 5.
The waveform synthesizer 18 creates a synthesized waveform 6 that is synthesized by delaying the received waveform 5 based on the individual delay time t.
The evaluation device 20 evaluates corrosion of reinforcing bars in the concrete from the maximum amplitude value, count number, energy, signal duration, rise time, and the like of the created composite waveform 6.

In FIG. 3, when the position of the AE generation source 2 on the reinforcing bar is unknown, the AE detection device 10 preferably further includes a position locating device 15. As with the delay time calculation device 14, the position locating device 15 is composed of, for example, one computer (PC) as a whole.
The position locator 15 determines the position of the AE source 2 from the difference in detection time of AE3 that has arrived at three or more AE sensors 12.
Based on the determined position of the AE generation source 2, the delay time calculation device 14 calculates the individual delay time t, and the waveform synthesis device 18 creates the synthesized waveform 6.

FIG. 4 is an overall flowchart showing an embodiment of the AE detection method for reinforcing steel bar corrosion according to the present invention.
In this figure, this AE detection method has each step (process) of S1-S6.

  In the sensor arrangement step S1, a plurality of sensors 12 are arranged with a sensor interval ΔL from the origin O on the concrete surface 1 in which the reinforcing bars B are arranged.

As shown in FIG. 3, this arrangement is not limited to the X axis, and as long as the surface distance L from the origin O is the same (on a circle centered on the origin O), as shown by a broken line in the figure. In addition, it may be on the Y axis or at other positions.
That is, the AE sensors 12 may be arranged on a plurality of circles on the surface where the propagation distances R from the AE generation source 2 to the AE 3 are different from each other.

In the delay time calculation step S2, the individual delay time t of AE3 arriving at each AE sensor 12 from the AE generation source 2 on the reinforcing bar is calculated.
As described above, when the position of the AE generation source 2 on the reinforcing bar is known or predetermined, it is calculated in advance from the above-described equations (1) and (2). In this case, step S2 is performed prior to step S3.

When the position of the AE generation source 2 on the reinforcing bar is unknown, the position determination step S6 is provided, and the position of the AE generation source 2 is determined from the detection time difference of AE3 that has arrived at three or more AE sensors 12. In this case, the individual delay time t is calculated in step S2 based on the determined position of the AE generation source 2, and the composite waveform 6 is created in step S3.
Note that step S6 may be omitted.

  In received waveform storage step S3, AE3 generated by the AE generating source 2 is received by the plurality of sensors 12, and a plurality of received waveforms 5 are stored.

FIG. 5 is a schematic diagram of the received waveform 5 and the synthesized waveform 6. FIG. 5A is a schematic diagram of two received waveforms 5, each including an AE3 waveform (received AE waveform 5a) and noise 8. FIG.
The two received AE waveforms 5a are obtained by detecting the same received waveform 5 generated by a single AE generation source 2. Accordingly, the two received AE waveforms 5a have the same waveform although the delay time ta between them is different.
On the other hand, the noise 8 included in the two received waveforms 5 is generated from various positions and the delay time to reach each AE sensor 12 is also different, so the waveforms of the noises 8a to 8d are different. .

  In the waveform synthesis step S4, a synthesized waveform 6 is created by synthesizing the received waveform 5 with delay based on the individual delay time t.

  By synthesizing the two received waveforms 5 in FIG. 5A based on the delay time ta between them, the received AE waveforms 5a having the same waveform are added and emphasized (amplified). Moreover, since the waveforms of the noises 8a to 8c are different due to the synthesis, they are canceled and attenuated.

Therefore, as shown in FIG. 5B, the combined waveform 6 includes a reception waveform (reception AE waveform 5a) of AE3 that is emphasized (amplified) in proportion to the number of sensors 12 (for example, five). Become.
In this example, for the sake of explanation, the reception AE waveform 5a and the noise 8 are generated at different times, but the same applies when the generation times overlap.

In the evaluation step S5, the reinforcement corrosion inside the concrete is evaluated from the maximum amplitude value, count number, energy, signal duration, rise time, and the like of the created composite waveform 6.
This step S5 is preferably performed using the evaluation device 20, but may be performed artificially without using this.

  Hereinafter, the effects of the present invention will be described based on simulation results.

FIG. 6 is a diagram illustrating a case where a plurality of sensors 12 are arranged on a straight line orthogonal to the length direction of the reinforcing bar B.
AE3 generated by the AE generation source 2 on the reinforcing bar in the concrete reaches the plurality of sensors 12 linearly as shown in this figure, and at this time, it corresponds to the difference in the propagation distance R of AE3 (that is, sound wave). A time difference is produced by each sensor 12.

  A case was simulated in which the depth d (covering depth) of the AE generating source 2 on the reinforcing bar was 70 mm, and 11 sensors 12 were arranged at a sensor interval ΔL (50 mm) in a direction orthogonal to the reinforcing bar B.

  FIG. 7 is a diagram showing a simulated waveform of AE3 (hereinafter referred to as “pseudo AE7”) used in the simulation. The pseudo AE 7 has a wavelength of 32 mm and a maximum amplitude value Hm of about 1.0.

FIG. 8 is a diagram showing a composite waveform 6 obtained by synthesizing the pseudo AE 7 generated on the upper surface (AE generation source 2) of the reinforcing bar B in FIG. 6 by the method of the present invention. In this simulation, the noise 8 is not assumed, and it is assumed that the pseudo AE 7 (AE 3 generated by the AE generation source 2) reaches each sensor 12 without being attenuated.
In this figure, the maximum amplitude value Hm of the combined waveform 6 is amplified to about 11. That is, when the pseudo AE 7 is generated at the preset AE generation source 2, it is understood that the combined waveform 6 includes the received AE waveform 5 a that is emphasized (amplified) in proportion to the number of sensors 12. .

FIG. 9 is a diagram showing a composite waveform 6 synthesized by the method of the present invention based on the pseudo AE 7 generated at a different depth from the AE generation source 2 of FIG. That is, the pseudo AE 7 in this case corresponds to the noise 8 generated at a position deeper than the AE generation source 2 (200 mm).
In this figure, the maximum amplitude value Hm of the composite waveform 6 is attenuated to about 2. That is, when the pseudo AE 7 is generated at a depth different from that of the preset AE generation source 2, even if the plurality of reception waveforms 5 have the same waveform, the delay time is different from that of the AE generation source 2, and thus the phase is different. In contrast, it can be seen that a plurality of received waveforms 5 cancel each other out due to synthesis.

FIG. 10 is a relational diagram between the depth of the sound source and the amplitude value ratio, and shows the change of the maximum amplitude value Hm with the depth.
In this figure, the case where the pseudo AE 7 is generated at a preset depth d (= 70 mm) of the AE generation source 2 is the point A, and the other is the case where the pseudo AE 7 is generated at a different depth. Further, the width direction position X is the same (X = 0 in FIG. 3).
The horizontal axis in the figure is the depth at which the pseudo AE 7 is generated, and the vertical axis is the ratio of the maximum amplitude value Hm to the point A.

  In this figure, the amplitude value ratio is the maximum at point A, and sharply decreases at other depths. That is, even when the same level of AE3 (or noise 8) is generated from a depth different from the preset depth d of the AE generation source 2, a plurality of received waveforms 5 cancel each other out and attenuate. Accordingly, it can be seen that only the received AE waveform 5a generated at the preset depth d (= 70 mm) of the AE generation source 2 can be emphasized.

FIG. 11 is a relationship diagram between the position in the width direction of the sound source and the amplitude value ratio, and shows how the maximum amplitude value Hm changes when the position of the sound source is shifted in the width direction.
In this figure, the case where a pseudo AE7 occurs at a preset width direction position X (X = 0 in FIG. 3) is point A, and the other is the case where a pseudo AE7 occurs at a different width direction position X. Further, the depth at which the pseudo AE 7 is generated is the same (d = 70 mm).
The horizontal axis in the figure is the width direction position X where the pseudo AE 7 is generated, and the vertical axis is the ratio of the maximum amplitude value Hm to the point A.

  In this figure, the amplitude value ratio is maximum at point A, and sharply decreases in the case of other width direction positions X. That is, even when AE3 (or noise 8) of the same level is generated from a position X in the width direction different from the preset AE generation source 2, a plurality of received waveforms 5 are canceled and attenuated by synthesis. Therefore, it can be seen that only the received AE waveform 5a generated at the preset width direction position X (= 0 mm) can be emphasized.

  According to the first embodiment described above, the method according to the present invention emphasizes the received AE waveform 5a based on the preset AE generation source 2 and attenuates AE3 (or noise 8) generated at different positions in the depth and width directions. Can be made. Therefore, according to the present invention, it was confirmed that the intended received AE waveform 5a can be detected from the noise 8 with high accuracy.

  FIG. 12 is a diagram illustrating an arrangement example of the sensor 12 with respect to the support 9 of the road bridge. In this figure, (A) is an example in which a plurality of sensors 12 are arranged on a straight line in the axial direction and perpendicular to the reinforcing bar B, and (B) is a plurality of sensors on a straight line in the orthogonal direction with respect to the reinforcing bar B. 12 is an example.

In a road bridge or the like, the support column 9 is elongated in the vertical direction (longitudinal direction), and the reinforcing bar B is often arranged in the longitudinal direction. In this case, for noise 8 propagating in the concrete from above (or below), signal processing by the sensor 12 arranged in the width direction of the reinforcing bar B is not very effective as shown in FIG. . This is because each sensor 12 detects the noise 8 almost simultaneously.
In this case, it is effective to arrange a plurality of sensors 12 along the reinforcing bar B.

In particular, as shown in FIG. 12A, it is preferable to arrange a plurality of sensors 12 on the straight lines in the axial direction and the orthogonal direction with respect to the reinforcing bar B, respectively.
In this case, the signal processing of the present invention is performed in the plurality of sensors 12 in the axial direction and the orthogonal direction of the reinforcing bar B, respectively, and AE3 is intended only when both the combined waveform 6 in the axial direction and the orthogonal direction exceed the threshold value. A counting method is effective.

  In the second embodiment, the optimum sensor interval ΔL for discriminating the noise 8 propagating from far away (above or below) the support column 9 from the AE 3 generated in the preset AE generation source 2 will be examined. The wavelength of AE3 (pseudo AE7) assumed here is 32 mm.

  First, the sensor 12 is arranged as shown in FIG. In this case, the noise 8 from a distance travels through the concrete and is simultaneously transmitted to the plurality of sensors 12 arranged.

FIG. 13 is a relationship diagram between the sensor interval ΔL and the amplitude value ratio. In this figure, when the sensor interval ΔL for identifying noise 8 from an infinite distance is changed by a plurality of sensors 12 arranged on a straight line orthogonal to the reinforcing bar B when the depth d of the reinforcing bar B is 70 mm. It is the result of simulating the reduction situation of the noise 8.
From this figure, it can be seen that the effect of reducing the noise 8 periodically changes depending on the sensor interval ΔL. From this, it can be said that the noise 8 is most effectively reduced when the propagation distance R to the reinforcing bar B changes by a half wavelength.

That is, in the sensor placement step S1, it is preferable to set the sensor interval ΔL so that the difference in the propagation distance R between the AE generation source 2 and the adjacent sensor 12 becomes a half wavelength of the sound wave in the concrete.
In this case, the following formula (3) is established.
R ² = d ² + L (n) ² = {d + (λ / 2) (2n−1)} ² (3)
Here, λ is the wavelength of the sound wave in the concrete, L (n) is the nth surface distance from the center, and n is an integer.

  FIG. 14 shows a combined waveform 6 of the noise 8 coming from the far side of the column 9 when the sensor interval ΔL satisfies Expression (3). It is assumed that the noise 8 from a distance is not attenuated.

  In this figure, the maximum amplitude value Hm of the composite waveform 6 is attenuated to about 1. In this case, the phases of the detection waveforms of the sensors 12 of n (1) to n (5) and the sensors 12 of n (-1) to n (-5) in FIG. 6 are reversed. That is, even when the noise 8 coming from the far side of the column 9 is detected by a plurality (11) of sensors 12 and each received waveform 5 has the same waveform without being attenuated, the synthesized waveform 6 cancels each other because the phases are different. Attenuating together.

As described above, in the present invention, the received waveform of AE3 associated with corrosion is emphasized and measured by synthesizing waveforms by providing individual delay times t associated with the shortest time difference between each sensor position and the reinforcing bar B.
Therefore, when AE3 is received by one sensor, the waveform of the other sensor 12 is synthesized in consideration of the predicted individual delay time t, so that the received waveform of AE3 accompanying corrosion using the reinforcing bar B as a sound source is It is emphasized and can be easily distinguished from noise 8 generated from other parts.

  According to the embodiment of the present invention described above, based on the individual delay time t of the AE 3 arriving at each sensor 12 from the AE generation source 2 on the reinforcing bar, the combined waveform 6 is created by delaying the received waveform 5 and synthesizing. . As a result of this synthesis, the received AE waveform 5a included in each received waveform is added synchronously based on the individual delay time t, so that the synthesized waveform 6 is enhanced (amplified) in proportion to the number of sensors 12. Includes an AE waveform 5a. Further, since the noise 8 included in each received waveform is different from the AE generation source 2, the noise 8 is canceled and attenuated.

  Therefore, according to the present invention, the AE 3 generated at the AE generation source 2 on the reinforcing bar can be identified from the noise 8 without exposing the reinforcing bar B in the concrete, and the initial state of the corrosion of the reinforcing bar can be accurately detected.

  In addition, this invention is not limited to embodiment mentioned above, Of course, it can change variously in the range which does not deviate from the summary of this invention.

B rebar, d depth, Hm maximum amplitude value, L, L (n) surface distance,
ΔL sensor interval, O origin, R propagation distance, S threshold, t individual delay time,
ta delay time, T1 duration, T2 rise time, v sound speed, λ wavelength,
1 Concrete surface, 2 AE source, 3 AE, 4 AE sensor,
5 received waveform, 5a received AE waveform, 6 synthesized waveform, 7 pseudo AE,
8 (8a-8c) noise, 9 struts, 10 AE detector,
12 AE sensors (sensors), 14 delay time calculation device,
16 received waveform storage device, 18 waveform synthesis device, 20 evaluation device

Claims (8)

A sensor placement step of placing a plurality of AE sensors at a distance from each other on the surface of the concrete in which reinforcing bars are arranged;
A delay time calculating step for calculating an individual delay time of the AE arriving at each AE sensor from the AE generation source on the reinforcing bar;
A received waveform storage step of receiving the AE generated at the AE generation source by a plurality of the AE sensors and storing a plurality of received waveforms;
And a waveform synthesis step of creating a synthesized waveform obtained by delaying the received waveforms based on the individual delay time.   2. The AE detection method of reinforcing bar corrosion according to claim 1, wherein, in the sensor arranging step, a plurality of the AE sensors are arranged on a straight line in an axial direction or an orthogonal direction with respect to the reinforcing bar of the AE generation source. In the sensor arrangement step, a plurality of the AE sensors are arranged on a straight line in an axial direction and an orthogonal direction with respect to the reinforcing bar of the AE generation source,
In the waveform synthesis step, the synthesized waveform is created from each of the plurality of received waveforms in the axial direction and the orthogonal direction,
2. The AE detection method for reinforcing steel corrosion according to claim 1, wherein one or both of the combined waveforms are output when both of the combined waveforms in the axial direction and the orthogonal direction exceed a threshold value.   The reinforcing bar corrosion AE detection method according to claim 1, wherein, in the sensor arrangement step, the AE sensors are arranged on a plurality of circles on surfaces having different propagation distances of the AE from the AE generation source.   2. The sensor interval according to claim 1, wherein in the sensor placement step, the sensor interval is set so that a difference in propagation distance from the AE generation source to the adjacent AE sensor becomes a half wavelength of a sound wave in the concrete. AE detection method for rebar corrosion.   The AE detection method of rebar corrosion according to claim 1, further comprising a position locating step of locating the position of the AE generation source from a difference in detection time of the AE arriving at three or more AE sensors. A plurality of AE sensors arranged on the surface of the concrete in which reinforcing bars are arranged with a sensor interval between them;
A delay time calculation device for calculating an individual delay time of AEs arriving at each AE sensor from an AE generation source on a reinforcing bar;
A received waveform storage device for receiving the AE generated at the AE generation source by a plurality of the AE sensors and storing a plurality of received waveforms;
An AE detection apparatus for reinforcing steel corrosion, comprising: a waveform synthesizer that creates a synthesized waveform obtained by delaying the received waveforms based on the individual delay time.   The rebar corrosion AE detection device according to claim 7, further comprising a position locating device for locating the position of the AE generation source based on a difference in detection time of the AE that has arrived at three or more AE sensors.

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