JP6893161B2 - Non-destructive diagnostic method for mounting jigs for heavy objects in tunnels - Google Patents

Description

The present invention relates to a non-destructive diagnosis method for a mounting jig for a heavy object in a tunnel, which nondestructively diagnoses the fixed state of the mounting jig used for a heavy object provided on a ceiling surface or the like in the tunnel.

Various heavy objects such as jet fans (ventilation blowers), signs, alarm display boards, cable racks, and lighting are installed on the ceilings of tunnels such as general roads and highways.

These heavy objects are attached by a hanging jig fixed to a ceiling surface, a wall surface, or the like after the mounting jig composed of mounting brackets and anchor bolts is fixed.

The fixing force of the mounting jig to a heavy object may decrease with the passage of time, and if the limit is exceeded, the heavy object may fall and a serious accident may occur. Therefore, after mounting a heavy object, it is necessary to periodically check the fixing state of the mounting jig to the heavy object and maintain it. However, since the number of mounting jigs (mounting brackets and anchor bolts) to be inspected is enormous at each site, in the past, only visual inspection was performed to check for deformation of the mounting brackets and anchor bolts. However, it was not a sufficient inspection.

Therefore, if necessary, a tapping sound inspection is also performed, but since the evaluation by this tapping sound is not constant depending on the skill level of the technician, the inspection / evaluation method of the mounting jig does not depend on the skill level of the technician. Is desired.

Under such circumstances, the present inventor has performed mechanical anchor inspection technology (Non-Patent Documents 1 and 2) by tapping sound inspection using an AE sensor, and non-destructive anchor bolts for metal anchors and adhesive anchors. We propose inspection technology (Patent Documents 1 and 2).

Ryota Ogawa et al., "Development of mechanical anchor inspection technology by tapping sound inspection system using AE sensor", 70th Annual Scientific Lecture Meeting of Japan Society of Civil Engineers, (September 2015), pp325-326 Ryota Ogawa et al., "Development of Mechanical Anchor Inspection Technology by Striking Sound Inspection System Using AE Sensor 2", 71st Annual Academic Lecture Meeting of Japan Society of Civil Engineers, (September 2016), pp1423-1424

Japanese Unexamined Patent Publication No. 2016-24609 Japanese Unexamined Patent Publication No. 2015-45637

However, although these inspection techniques can evaluate the state of the anchor bolt itself, they cannot evaluate the decrease in the fixing force of the mounting bracket to a heavy object. In addition, since it is not assumed that the vibration of the mounting bracket affects the evaluation, the accuracy of the judgment regarding the quantitative evaluation of the axial force (tightening torque value) of the anchor bolt that affects the fixed state of the mounting bracket is high. It wasn't high enough yet.

In the above, the "fixed state of the mounting bracket" means a state when the mounting bracket is fixed by several anchor bolts, and a good fixed state means a predetermined shaft by a plurality of anchor bolts. It means that the bolts are firmly fixed by force, and the poor fixing state means that the axial force of some of the multiple anchor bolts is reduced and the bolts are loosened, and the bolts are sufficiently fixed. It means no state.

The present invention is a mounting jig by accurately and quantitatively evaluating the fixed state of the mounting bracket and the axial force of the anchor bolt while the heavy object in the tunnel is suspended without relying on the skill level of the engineer. An object of the present invention is to provide a non-destructive diagnosis method for mounting jigs capable of non-destructively diagnosing the fixed state of an entire heavy object.

The invention according to claim 1
This is a non-destructive diagnosis method for mounting jigs for heavy objects in tunnels, which non-destructively diagnoses the fixed state of the mounting jigs that fix heavy objects in the tunnel with mounting brackets and anchor bolts.
After acquiring the vibration waveform generated by the vibration of the mounting jig to the mounting bracket on the mounting bracket and the vibration waveform generated by the vibration of the mounting jig to the anchor bolt on the anchor bolt, The frequency distribution acquisition step to obtain each frequency distribution by frequency analysis of each obtained vibration waveform,
The frequency distribution obtained from the vibration to the mounting bracket is compared and evaluated with the frequency distribution obtained from the vibration to the anchor bolt, and the frequency distribution obtained from the vibration to the anchor bolt is used for mounting. A frequency distribution evaluation step that excludes the vibration peaks caused by the metal fittings and sets the frequency distribution including only the vibration peaks caused by the anchor bolts as the frequency distribution to be evaluated.
The evaluation peak frequency acquisition step of acquiring the natural vibration peak frequency selected based on a predetermined condition as the evaluation peak frequency from the natural vibration peak frequencies in the frequency distribution to be evaluated, and the evaluation peak frequency acquisition step.
Mounting of a heavy object in a tunnel, which comprises a fixed state diagnosis step of evaluating the axial force of the anchor bolt based on the obtained evaluation peak frequency and diagnosing the fixed state of the mounting jig. This is a non-destructive diagnosis method for jigs.

The invention according to claim 2
Between the frequency distribution acquisition step and the frequency distribution evaluation step,
A comparison step is provided to compare the frequency distribution obtained from the vibration to the mounting bracket with the frequency distribution obtained from the vibration to the mounting bracket that has been diagnosed as having a good fixed state in advance.
The claim is characterized in that, based on the result of comparison, a mounting jig that can be diagnosed as having a good fixed state is screened, and only a mounting jig that cannot be diagnosed as having a good fixed state proceeds to the evaluation peak frequency acquisition step. It is a non-destructive diagnosis method of a mounting jig for a heavy object in a tunnel according to 1.

The invention according to claim 3
The non-destructive diagnosis method for a mounting jig for a heavy object in a tunnel according to claim 1 or 2, wherein the vibration waveform is acquired by a sensor.

The invention according to claim 4
The non-destructive diagnosis method for a mounting jig for a heavy object in a tunnel according to claim 3, wherein the sensor is an AE sensor.

The invention according to claim 5
A primary regression line is created in advance based on the change in the evaluation peak frequency accompanying the change in the axial force of the anchor bolt, and the axial force of the anchor bolt is calculated from the obtained evaluation peak frequency using the primary regression line. The non-destructive diagnosis method for mounting jigs for heavy objects in a tunnel according to any one of claims 1 to 4, characterized in that evaluation is performed.

According to the present invention, mounting is performed by quantitatively evaluating the fixed state of the mounting bracket and the axial force of the anchor bolt with high accuracy while the heavy object in the tunnel is suspended without relying on the skill level of the engineer. It is possible to provide a non-destructive diagnosis method of a mounting jig capable of non-destructively diagnosing the fixed state of the entire jig with respect to a heavy object.

It is a figure which shows an example of the vibration waveform acquired in one Embodiment of this invention. In one embodiment of the present invention, it is a figure which shows an example which the frequency distribution acquired from the vibration to a mounting bracket differs depending on whether the fixing state of a mounting bracket is good or bad. It is a figure explaining the acquisition of the evaluation peak frequency in one Embodiment of this invention. In one embodiment of the present invention, to the anchor bolt fixed to the mounting bracket by changing the frequency distribution of the mounting bracket acquired by vibration to the mounting bracket to which the anchor bolt is sufficiently fixed and the axial force. It is a figure which shows the frequency distribution of the anchor bolt acquired by the excitation of. It is a figure which shows the relationship between the evaluation peak frequency and the axial force in one Embodiment of this invention. It is external drawing of the mounting bracket in one Example of this invention. In one embodiment of the present invention, it is a figure which shows the frequency distribution of the mounting bracket acquired by the vibration to the mounting bracket.

[1] Basic Concept in the Present Invention First, the basic concept in the present invention will be described.

While diligently studying the solution to the above problems, the present inventor vibrates based on the vibration of the anchor bolt itself when the mounting bracket and the anchor bolt are hit (vibrated) against the fixed mounting jig. We focused on acquiring the vibration waveform and frequency distribution in which the components and the vibration components based on the vibration of the mounting bracket itself are superimposed.

Then, if the vibration component of the mounting bracket can be removed from the obtained frequency distribution, the frequency distribution based on the original vibration component of the anchor bolt can be obtained, and the change in the axial force of the anchor bolt can be evaluated and diagnosed. As a result of various experiments and studies on the specific means thereof, it was found that it is possible based on the following embodiments, and the present invention has been completed.

[2] Embodiment of the present invention Next, the present invention will be specifically described with reference to the drawings based on the embodiment.

In the present embodiment, the fixed state of the mounting jig can be diagnosed non-destructively by going through each of the following steps.

1. 1. Frequency distribution acquisition step First, the frequency distribution acquisition step for acquiring the frequency distribution by vibrating the mounting bracket and the anchor bolt will be described.

(1) Acquisition of vibration waveform (a) Vibration waveform of mounting bracket First, the sensor is installed at a predetermined position on the mounting bracket. Then, a hammer is used to hit (vibrate) the mounting bracket, and the vibration waveform generated by the vibration is acquired by the sensor. An example of the acquired vibration waveform is shown in FIG. In FIG. 1, the vertical axis represents the amplitude (Amplitude: mV), and the horizontal axis represents the elapsed time (Time: ms) from the start of vibration, and the vibration is attenuated with the passage of time.

As described above, the obtained vibration waveform contains a mixture of the vibration component of the mounting bracket and the vibration component of the anchor bolt (however, the vibration component of the mounting bracket is the main component).

(B) Vibration waveform of anchor bolt Next, the sensor is installed at a predetermined position on the anchor bolt. Then, an impact (vibration) is applied to the anchor bolt using a hammer, and the vibration waveform generated by the vibration is acquired by the sensor. Also in this case, as in the case of the mounting bracket described above, the vibration is attenuated with the passage of time.

In this case as well, the obtained vibration waveform contains a mixture of the vibration component of the mounting bracket and the vibration component of the anchor bolt (however, the vibration component of the anchor bolt is the main component).

When acquiring the above two vibration waveforms, a test hammer that is generally used for hammering inspection, has a light weight, and is convenient to carry is preferably used. However, a plastic hammer and a rubber hammer are used. , A wooden hammer, an iron hammer other than a test hammer, or any other hammer that can give vibration to the target and obtain a vibration waveform may be used instead of the test hammer.

Further, as the sensor, it is preferable to use an AE (Acoustic Emission) sensor from the viewpoint of acquiring the vibration generated by the impact with high accuracy, but depending on the accuracy of the diagnosis, an accelerometer or the like capable of acquiring the vibration may be used. It may be used, or the striking sound may be acquired by a microphone.

(2) Acquisition of frequency distribution Next, the obtained two vibration waveforms are frequency-analyzed to obtain a frequency distribution based on each vibration waveform.

2. Frequency distribution evaluation step Next, the frequency distribution evaluation step of selecting the frequency distribution including only the vibration peak caused by the anchor bolt from the frequency distribution obtained from the vibration to the anchor bolt as the frequency distribution to be evaluated will be described. ..

(1) Frequency distribution of anchor bolts As described above, the frequency distribution acquired by exciting the anchor bolts also includes vibration components caused by vibrations generated in the surrounding environment, that is, mounting brackets. Therefore, compared with the frequency distribution of the mounting bracket, the vibration peak caused by the mounting bracket is excluded from the frequency distribution of the anchor bolt, and the frequency distribution is selected as the frequency distribution for evaluating the axial force of the anchor bolt.

That is, in the evaluation of the fixed state between the anchor bolt and the mounting bracket, the lowest natural vibration peak frequency in the frequency distribution acquired by the impact of the anchor bolt is usually adopted as the evaluation peak frequency, and the change in the evaluation peak frequency is adopted. Do by. However, when the frequency distribution acquired by the impact of the anchor bolt is adopted as it is, as described above, the vibration component caused by the vibration generated in the surrounding environment, that is, the mounting bracket is also included, so that the anchor The natural vibration peak of the anchor bolt that changes due to the axial force of the bolt does not always appear at the lowest frequency, and the "natural vibration peak of the anchor bolt" that originally changes due to the axial force may be overlooked. It was not highly evaluated. Therefore, in the present embodiment, the vibration peak caused by the mounting bracket is excluded from the frequency distribution of the anchor bolt, and the frequency distribution is selected as the frequency distribution for evaluating the axial force of the anchor bolt.

Specifically, as described above, in addition to acquiring the vibration waveform of the anchor bolt, the vibration waveform of the mounting bracket is also acquired. Then, by comparing and evaluating each frequency distribution obtained from the vibration waveform, the vibration peak caused by the mounting bracket is excluded from the frequency distribution of the anchor bolt.

As a result, the frequency distribution of the obtained anchor bolts shows the frequency distribution from which the influence of the surrounding environment (vibration component caused by the vibration generated in the mounting bracket) is removed. Therefore, the evaluation peak is evaluated from this frequency distribution. By selecting the frequency, the original "natural vibration peak of the anchor bolt" is not overlooked, and the fixed state of the mounting bracket and the axial force of the anchor bolt can be quantitatively evaluated with high accuracy.

(2) Frequency distribution of mounting brackets On the other hand, when looking at the frequency distribution acquired by hitting the mounting brackets, it can be seen that the frequency distribution changes significantly depending on the fixed state of the anchor bolts, and the frequency distribution of the mounting brackets. It was found that it is possible to easily judge whether the anchor bolt is fixed or not.

FIG. 2 shows a specific example in which the frequency distribution of the mounting bracket differs depending on whether the mounting bracket is in a good or bad state. In FIG. 2, the upper row shows the frequency distribution of the mounting bracket obtained when the fixed state is good, and the lower row shows the frequency distribution of the mounting bracket obtained when the fixed state is poor. From FIG. 2, it can be seen that the frequency distribution is clearly different depending on whether the fixed state is good or bad, and the good or bad of the fixed state can be easily diagnosed only by observing the frequency distribution of the mounting bracket.

In this way, by observing the frequency distribution acquired by hitting the mounting bracket, it is possible to easily distinguish between the mounting bracket that can be judged to be in a good fixed state and the mounting bracket that cannot be judged to be in a good fixed state (screening). can do.

As a result, instead of the time-consuming 100% inspection, it is possible to narrow down the mounting brackets that cannot be judged to be in a good fixed state in advance. Then, only for the mounting brackets whose narrowed-down fixed state cannot be judged to be good, the process proceeds to the evaluation peak frequency acquisition step described later, and the decrease in the axial force of the anchor bolt is evaluated based on the frequency distribution of the anchor bolt. Therefore, even if there are a large number of mounting jigs to be inspected, the fixed state can be efficiently and non-destructively diagnosed.

3. 3. Evaluation peak frequency acquisition step Next, in order to specifically evaluate the degree of axial force of the anchor bolt with respect to the mounting bracket in the mounting jig, the natural vibration peak frequency was obtained from the frequency distribution selected above and obtained. From the natural vibration peak frequencies, the natural vibration peak frequency selected based on a predetermined condition is acquired as the evaluation peak frequency.

FIG. 3 is a diagram for explaining the acquisition of the evaluation peak frequency, in which the horizontal axis represents the frequency (Frequency: Hz) and the vertical axis represents the normalized vibration intensity (Magnitude). As shown in FIG. 3, among the natural vibration peak frequencies exceeding a predetermined intensity (generally set to "0.5") as a threshold value, the minimum (lowest frequency side) natural vibration peak frequency (2641 Hz in FIG. 3) is acquired as an evaluation frequency peak (evaluation peak frequency).

4. Fixed state diagnosis step As described above, the frequency distribution acquired by hitting the anchor bolt includes the frequency distribution based on the frequency component caused by the anchor bolt and the frequency distribution based on the frequency component caused by the mounting bracket. There is. The natural vibration peak frequency caused by the mounting bracket hardly changes, while the natural vibration peak frequency caused by the anchor bolt matches the change in the fixed state with respect to the mounting bracket, specifically, the change in the axial force of the anchor bolt. And change. Therefore, by acquiring the evaluation peak frequency from the natural vibration peak frequency caused by the anchor bolt, the change in the axial force of the anchor bolt can be grasped, and the quality of the fixed state of the anchor bolt can be judged.

FIG. 4 is a diagram showing the frequency distribution in the mounting bracket in which the anchor bolt is fixed by a sufficient axial force and the frequency distribution in the anchor bolt in which the mounting bracket is fixed with different axial forces, which will be described later. This is the data when the anchor bolt 1 of the example is vibrated. In FIG. 4, the part surrounded by a square is the natural vibration peak frequency caused by the mounting bracket, and the part surrounded by a circle is the evaluation peak frequency acquired from the natural vibration peak frequency caused by the anchor bolt. is there. The description in parentheses is the axial force of the anchor bolt (tightening torque: Nm).

From FIG. 4, it can be seen that the evaluation peak frequency of the mounting jig shifts to the low frequency side as the axial force of the anchor bolt decreases, and the axial force of the anchor bolt and the evaluation peak frequency correlate with each other. You can see that.

Therefore, each measured value in FIG. 4 was plotted to obtain FIG. 5 showing the relationship between the evaluation peak frequency and the axial force. Then, a first-order regression line (shown by a broken line in FIG. 5) was created. By using this first-order regression line, it is possible to easily obtain the axial force of the anchor bolt corresponding to the acquired evaluation peak frequency and to know the decrease in the axial force of the anchor bolt due to the deterioration of the fixed state of the mounting jig. it can. Then, based on the reduced axial force, the anchor bolt can be retightened to the axial force when the fixed state of the mounting jig is good, so that the fixed state of the mounting jig can be restored. Efficient maintenance is possible with reduced costs and labor.

And these tasks do not have to rely on the proficiency of the technician. Therefore, by applying this embodiment, the fixed state of the mounting bracket and the axial force of the anchor bolt can be quantitatively evaluated with high accuracy in a non-destructive manner without relying on the skill level of the engineer, and the mounting jig It is possible to diagnose the fixed state of the body and take appropriate measures.

As described above, in the present embodiment, when diagnosing the fixed state of the anchor bolt, after obtaining the frequency distribution of the anchor bolt excluding the vibration caused by the mounting bracket and selecting the evaluation peak frequency, the anchor bolt Since the fixed state of the mounting jig is diagnosed by using the change in the evaluation peak frequency that correlates with the change in the axial force, it is possible to perform a non-destructive and sufficiently high-precision diagnosis.

Further, in the present embodiment, since the mounting jig having a good fixed state can be screened in advance at the time of diagnosis, a huge number of mounting jigs can be efficiently diagnosed in a short time.

Hereinafter, a more specific description will be given based on the examples. In this embodiment, the above method is applied to the mounting brackets and anchor bolts of the jet fan.

FIG. 6 is an external view of the mounting bracket. Anchor bolts 1 to 4 are arranged at the four corners, and the mounting bracket 5 is fixed to the jet fan. Then, the anchor bolts 1 to 4 were sequentially hit, and the vibration waveform in each anchor bolt was acquired by an AE sensor (not shown) arranged in each anchor bolt. On the other hand, a predetermined portion of the mounting bracket 5 was hit, and the vibration waveform of the mounting bracket was acquired by the AE sensors arranged at the vibration measurement points of the two mounting brackets. As the anchor bolt, a mechanical anchor for a jet fan of M24 was used.

At this time, in order to change the axial force of the anchor bolts, a torque wrench was used to gradually reduce the tightening torque of each bolt as shown in Table 1, and the No. Specimens 1 to 17 were prepared. Here, assuming that the fixed state is defective when the tightening torque is less than 120 Nm, No. Specimens 1 to 3 are specimens in a good fixed state, No. Specimens after 4 are specimens with a poor fixed state.

FIG. 7 shows the frequency distribution of the mounting brackets obtained by vibrating the mounting brackets for each test piece. From FIG. 7, the test piece No. which has a good fixed state. In Nos. 1 to 3, peaks (peaks caused by anchor bolts) are scattered even on the low frequency side surrounded by a square broken line, and it can be seen that the vibration caused by the anchor bolts has sufficiently reached the sensor.

On the other hand, the test piece No. In 4 to 17, as the fixed state deteriorates, the peak on the low frequency side surrounded by the solid square line decreases, and it can be seen that the vibration caused by the anchor bolt does not sufficiently reach the sensor. From this result, it can be seen that the case where the fixed state is good and the case where the fixed state is bad can be clearly distinguished.

The reason why such a result was obtained is that the fixing force by the anchor bolt weakened due to the decrease in the axial force of the anchor bolt, and the frequency component of the vibration in the mounting bracket became the main vibration obtained by the AE sensor. This is because the natural vibration mode, which indicates the natural vibration peak of the anchor bolt, has decreased.

In this embodiment, the axial force of the anchor bolt is specified in advance, but by obtaining the evaluation peak frequency from the frequency distribution and using the linear regression line shown in FIG. 5, how much the axial force of the anchor bolt is. It is possible to know whether the fixed state is defective.

Although the present invention has been described above based on the embodiments, the present invention is not limited to the above embodiments. Within the same and equal scope as the present invention, various modifications can be made to the above embodiments.

1-4 Anchor bolt 5 Mounting bracket

Claims (5)

This is a non-destructive diagnosis method for mounting jigs for heavy objects in tunnels, which non-destructively diagnoses the fixed state of the mounting jigs that fix heavy objects in the tunnel with mounting brackets and anchor bolts.
After acquiring the vibration waveform generated by the vibration of the mounting jig to the mounting bracket on the mounting bracket and the vibration waveform generated by the vibration of the mounting jig to the anchor bolt on the anchor bolt, The frequency distribution acquisition step to obtain each frequency distribution by frequency analysis of each obtained vibration waveform,
The frequency distribution obtained from the vibration to the mounting bracket is compared and evaluated with the frequency distribution obtained from the vibration to the anchor bolt, and the frequency distribution obtained from the vibration to the anchor bolt is used for mounting. A frequency distribution evaluation step that excludes the vibration peaks caused by the metal fittings and sets the frequency distribution including only the vibration peaks caused by the anchor bolts as the frequency distribution to be evaluated.
The evaluation peak frequency acquisition step of acquiring the natural vibration peak frequency selected based on a predetermined condition as the evaluation peak frequency from the natural vibration peak frequencies in the frequency distribution to be evaluated, and the evaluation peak frequency acquisition step.
Mounting of a heavy object in a tunnel, which comprises a fixed state diagnosis step of evaluating the axial force of the anchor bolt based on the obtained evaluation peak frequency and diagnosing the fixed state of the mounting jig. Non-destructive diagnostic method for jigs. Between the frequency distribution acquisition step and the frequency distribution evaluation step,
A comparison step is provided to compare the frequency distribution obtained from the vibration to the mounting bracket with the frequency distribution obtained from the vibration to the mounting bracket that has been diagnosed as having a good fixed state in advance.
The claim is characterized in that, based on the result of comparison, a mounting jig that can be diagnosed as having a good fixed state is screened, and only a mounting jig that cannot be diagnosed as having a good fixed state proceeds to the evaluation peak frequency acquisition step. The non-destructive diagnosis method for mounting jigs for heavy objects in tunnels according to 1. The non-destructive diagnosis method for a mounting jig for a heavy object in a tunnel according to claim 1 or 2, wherein the vibration waveform is acquired by a sensor. The non-destructive diagnosis method for a mounting jig for a heavy object in a tunnel according to claim 3, wherein the sensor is an AE sensor. A primary regression line is created in advance based on the change in the evaluation peak frequency accompanying the change in the axial force of the anchor bolt, and the axial force of the anchor bolt is calculated from the obtained evaluation peak frequency using the primary regression line. The non-destructive diagnosis method for mounting jigs for heavy objects in a tunnel according to any one of claims 1 to 4, wherein the evaluation is performed.

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