JP7029303B2 - Non-destructive diagnostic method for PC grout filling state - Google Patents

Description

Application of Article 30, Paragraph 2 of the Patent Act At the "2017 Annual Conference of the Japan Society of Civil Engineers 72nd Annual Academic Lecture DVD-ROM Version Lecture Summary" published by the Japan Society of Civil Engineers on August 1, 2017. Release

The present invention relates to a non-destructive diagnostic method for a PC grout-filled state in which a prestressed concrete structure (PC structure) is non-destructively evaluated and diagnosed.

In PC structures such as prestressed concrete bridges (PC bridges), the sheath is filled with PC grout for the purpose of ensuring the integration of member concrete and PC steel and protecting the PC steel from corrosion. Is done.

At this time, if the PC grout is not densely filled, a cavity is formed in the sheath, and rainwater or the like may enter the cavity to corrode the internal PC steel material, leading to breakage or protrusion of the PC steel material. be. Therefore, in order to properly maintain and manage the PC structure, it is necessary to accurately evaluate the filling degree of the PC grout (PC grout filling rate).

Therefore, for example, there is a method of identifying the place where the PC steel material is placed, then drilling the hole and checking the inside to evaluate the filling state of the PC grout, but this method takes a lot of time. There is a problem that labor is required and a part of the PC structure must be destroyed to make a hole, and non-destructive evaluation methods as listed below have been proposed (Patent Documents 1 to 1). 3).

(1) Radiation transmission method (X-ray method)
The radiation transmission method (X-ray method) is a method of inspecting the details inside concrete using X-rays, and utilizes the property that the transmittance of X-rays changes depending on the density of the substance to create cavities in the sheath. Non-destructive detection.

Specifically, when the PC grout filling rate is low, a cavity is formed in the sheath, and the cavity increases the transmittance of X-rays, so that the image appears dark. On the other hand, in the portion where the PC grout filling rate is high, since it is solid and has almost no cavities, the transmittance of X-rays is low and the image appears faint. Therefore, by discriminating the shade of the image, the presence or absence of a cavity in the sheath can be directly detected.

However, this X-ray method becomes difficult to distinguish when the concrete becomes thick. Further, when using X-rays, it takes time to set and measure the radiation controlled area, so that there is a problem that it is difficult to improve the test efficiency.

(2) Impact elastic wave method (impact echo method)
The impact elastic wave method (impact echo method) is a method of identifying the unfilled position of the PC grout by focusing on the frequency characteristics of the reflected wave (impact echo). The elastic wave is propagated to the concrete, the reflected wave from the object is received by the sensor installed on the striking surface side, and the thickness of the member, the presence or absence of internal defects, and the depth thereof are estimated nondestructively from the frequency characteristics.

Specifically, when the sheath is completely filled with PC grout, reflected waves are generated on the bottom surface of the plate. On the other hand, when the PC grout unfilled portion is present in the sheath, reflected waves are also generated on the surface of the sheath in which the cavity is formed. The longitudinal resonance phenomenon is excited by repeating the reflection of each of these reflected waves with the concrete surface. Therefore, the presence or absence of internal defects (cavities) and their depth can be estimated by detecting the peak frequency due to longitudinal wave resonance corresponding to the plate thickness and sheath depth.

However, in this impact echo method, when the sheath diameter is small or the sheath is in a deep position, the reflected wave does not repeat, so that the resonance phenomenon due to the repeatedly reflected wave with the sheath surface of the unfilled portion described above occurs. There is a problem that it is not excited, the peak frequency cannot be detected, and it cannot be determined.

(3) Impact elastic wave method (striking vibration method)
The impact elastic wave method (striking vibration method) is a method of grasping the average PC grout filling status inside the sheath by focusing on the propagation velocity of elastic waves calculated by impact input, and impacts from the end of the PC steel material. The elastic wave generated when the above is given is detected by a sensor installed at the other end, and the PC grout filling status inside the sheath is non-destructively grasped from the propagation velocity in the PC steel material.

Specifically, when an impact is applied from the end of a PC steel material, if the sheath is not sufficiently filled with PC grout, the earliest propagated elastic wave among the input elastic waves propagates through the steel rod. Therefore, the apparent elastic wave velocity is close to the propagation velocity of the steel rod alone. On the other hand, when the PC grout is filled, the elastic wave propagates in the composite member in which the steel rod and the PC grout are integrated. In this case, since the tip position of the propagating wave in the steel rod and the tip position of the wave propagating in the peripheral PC grout portion are the same, the propagating speed is smaller than that in the unfilled case. Therefore, by knowing the elastic wave propagation velocity, it is possible to determine the filling defect of the PC grout.

However, although this tapping vibration method can determine the filling defect of the PC grout in the entire sheath through which the PC steel material is inserted, it cannot specify the location where the filling defect of the PC grout occurs. There is a problem.

(4) Wideband ultrasonic method In the wideband ultrasonic method, ultrasonic waves are input from a transmitter probe placed on the concrete surface directly above the sheath, and the reflected waves from the sheath are received and analyzed to improve the filling property of the PC grout. It is a non-destructive guessing technique.

Specifically, if a cavity exists in the sheath, it is reflected there and a reflected wave is generated. On the other hand, if it is solid, the reflected wave becomes small because the reflectance is low. Since this sheath reflected wave is dominated by waves in the high frequency band, when the PC grout is poorly filled (hollow in the sheath), the wave in the high frequency band is predominantly received. On the other hand, in the case of a packed sheath in which PC grout is densely filled, waves in the low frequency band are predominantly received. Therefore, the filling property of the PC grout can be estimated by analyzing the reflected wave from the sheath.

However, in this broadband ultrasonic method, since the reflected waves include reflected waves from concrete reinforcing bars and aggregates and reflected waves propagating on the concrete surface, these reflected waves are transmitted from the unfilled portion of the PC grout. It is necessary to separate it from the reflected wave of concrete and extract it efficiently, and there is a problem that it takes time to measure. In addition, if the concrete surface is not smooth, it takes time and effort to scrape it and apply a contact medium to place the probe on the concrete surface, which requires a lot of time and effort for evaluation, and the PC structure at the present time. Considering the total number of things, it is not a realistic method.

Japanese Unexamined Patent Publication No. 2005-265817 Japanese Unexamined Patent Publication No. 2011-21163 Japanese Unexamined Patent Publication No. 2016-118466

As described above, the conventional method of non-destructively evaluating and diagnosing the filling state of PC grout takes time for measurement and has high accuracy regardless of which method is adopted. There are problems such as difficulty in measurement.

Therefore, the present invention provides a non-destructive diagnostic method for a PC grout filling state, which can evaluate and diagnose the filling state of the PC grout with high accuracy while being a simple method that does not require time for measurement. The challenge is to provide.

As a result of diligent studies, the present inventor has found that the above-mentioned problems can be solved by the invention described below, and has completed the present invention.

The invention according to claim 1 is
It is a non-destructive diagnosis method of the PC grout filling state for non-destructively diagnosing the filling state of the PC grout filled around the PC steel material in the sheath embedded in the PC structure.
The vibration waveform acquisition step for acquiring the vibration waveform of the impact elastic wave generated by the vibration of the PC structure on the concrete surface, and the vibration waveform acquisition step.
An evaluation index acquisition step of acquiring at least one of the vibration duration, period, and natural vibration frequency as an evaluation index based on the acquired vibration waveform.
It is equipped with a filling state diagnosis step for diagnosing the filling state of the PC grout based on the acquired evaluation index.
The filling state diagnosis step using the cycle as an evaluation index is a non-destructive diagnosis method for the PC grout filling state, characterized in that the longer the cycle is, the lower the filling state of the PC grout is diagnosed.

The invention according to claim 2 is
It is a non-destructive diagnosis method of the PC grout filling state for non-destructively diagnosing the filling state of the PC grout filled around the PC steel material in the sheath embedded in the PC structure.
The vibration waveform acquisition step for acquiring the vibration waveform of the impact elastic wave generated by the vibration of the PC structure on the concrete surface, and the vibration waveform acquisition step.
An evaluation index acquisition step of acquiring at least one of the vibration duration, period, and natural vibration frequency as an evaluation index based on the acquired vibration waveform.
It is equipped with a filling state diagnosis step for diagnosing the filling state of the PC grout based on the acquired evaluation index.
The PC grout is characterized in that the elapsed time from the start of vibration of the PC structure to the concrete surface until the amplitude of the vibration waveform falls within a predetermined amplitude or less from the maximum amplitude is used as the vibration duration. This is a non-destructive diagnostic method for the filled state.

The invention according to claim 3 is
The non-destructive diagnostic method for a PC grout filling state according to claim 2 , wherein the elapsed time is an elapsed time until the amplitude of the vibration waveform is within ± 10% of the maximum amplitude.

The invention according to claim 4 is
The PC grout filling according to claim 1, wherein the period is the first period obtained by performing autocorrelation analysis on the vibration waveform immediately after the vibration of the PC structure on the concrete surface. It is a non-destructive diagnostic method for the condition.
The invention according to claim 5 is
The PC grout filling state according to claim 2, wherein the filling state diagnosis step using the vibration duration as an evaluation index diagnoses that the filling state of the PC grout is lower as the vibration duration is longer. It is a non-destructive diagnostic method.

According to the present invention, there is a non-destructive diagnostic method for a PC grout filling state that can non-destructively evaluate and diagnose the filling state of the PC grout with high accuracy while being a simple method that does not require time for measurement. Can be provided.

It is a figure explaining the relationship between the vibration duration of the impact elastic wave of a PC structure, and the filling state of a PC grout. It is a figure explaining the relationship between the period of the impact elastic wave of a PC structure, and the filling state of a PC grout. It is a figure explaining the relationship between the natural vibration frequency of the impact elastic wave of a PC structure, and the filling state of a PC grout. It is a figure which shows an example of the vibration waveform acquired in the PC structure. It is a figure which shows an example of the result of performing the autocorrelation analysis on the vibration waveform. It is a figure explaining the acquisition of a natural vibration frequency. It is a perspective view which showed the structure of the PC concrete specimen produced in the Example of this invention as an image. It is sectional drawing from the side surface side of the PC concrete specimen shown in FIG. 7. It is a figure which shows the vibration waveform of the impact elastic wave acquired in the Example of this invention. It is a figure which shows the relationship between the vibration duration measured in the Example of this invention, and the PC grout filling rate. It is a figure which shows the measurement point which performed the area diagnostic measurement in the Example of this invention. FIG. 3 is a contour diagram created in a plane based on a period in an embodiment of the present invention. FIG. 3 is a contour diagram created in a plane based on the natural vibration frequency in the embodiment of the present invention. It is a figure which shows the relationship between the evaluation peak frequency and the filling rate of PC grout in the Example of this invention.

Hereinafter, the present invention will be described based on the embodiments.

[1] Techniques behind the present invention First, the techniques behind the present invention will be described.

While diligently studying the solution to the above problems, the present inventor closely correlates the vibration duration, period, and natural vibration frequency of impact elastic waves with each other, as described below. By using these as an index for evaluation, it was found that the filling state of PC grout can be evaluated with high accuracy in a short time. Hereinafter, the relationship between the vibration duration, the period, and the natural vibration frequency and the filling state of the PC grout will be described.

1. 1. Vibration duration FIG. 1 is a diagram for explaining the relationship between the vibration duration of the impact elastic wave of the PC structure and the filling state of the PC grout, and (a) is the vibration duration depending on the degree of the filling rate of the PC grout. It is a figure which shows how it changes, and (b) is a figure explaining the reason why the vibration duration is different. In FIG. 1 (b), 1 is a PC structure, 2 is concrete, 3 is a sheath, 4 is a PC steel material, and 5 is a PC grout. Here, in order to facilitate understanding, 0% is taken as an example of a low filling factor of PC grout, and 100% is taken as an example of a high filling factor.

The vibration duration is the time from the start of vibration until the vibration waveform falls within a constant amplitude, and as shown in FIG. 1 (a), it becomes longer when the filling rate is low. This is because, as shown on the right side of FIG. 1 (b), when the filling rate of the PC grout 5 is low (0%) and there is a cavity between the inner wall of the sheath 3 and the PC steel material 4, the surface of the concrete 2 is formed. This is because the vibration is likely to occur, so that the vibration is sustained for a long time in the PC structure 1.

2. 2. Period FIG. 2 is a diagram for explaining the relationship between the period of the impact elastic wave of the PC structure and the filling state of the PC grout, and (a) is how the period changes depending on the degree of the filling rate of the PC grout. (B) is a diagram for explaining the reason why the period is different.

The period is the time required for one cycle of vibration in the vibration waveform, and as shown in FIG. 2A, it becomes longer when the filling rate is low. As shown on the right side of FIG. 2B, when the filling rate of the PC grout 5 is low (0%) and there is a cavity between the inner wall of the sheath 3 and the PC steel material 4, it vibrates in a detoured path. This is because it takes time for the reflected wave to arrive from the opposite surface.

3. 3. Natural vibration frequency FIG. 3 is a diagram for explaining the relationship between the natural vibration frequency of the impact elastic wave of the PC structure and the filling state of the PC grout, and (a) shows the natural vibration frequency depending on the degree of the filling rate of the PC grout. It is a figure which shows how it changes, and (b) is a figure which explains the reason why a difference occurs in a natural vibration frequency.

The natural vibration frequency is the natural vibration frequency indicated by the vibrating body when vibrated freely without applying an external force, and as shown in FIG. 3A, when the filling rate is low, the natural vibration frequency shifts to the low frequency side. come. This is because, as shown on the right side of FIG. 3B, when the filling rate of the PC grout 5 is low (0%) and there is a cavity between the inner wall of the sheath 3 and the PC steel material 4, the surface of the concrete 2 is formed. This is because it easily vibrates even at a low frequency.

As described above, the vibration duration, period and natural vibration frequency of impact elastic waves are related to the filling state of the PC grout, and by using these as evaluation indexes, the filling state of the PC grout can be evaluated with high accuracy. It turned out that it can be diagnosed. Then, it is preferable that these evaluation indexes can be evaluated and diagnosed with higher accuracy by making a comprehensive judgment using two or more. Since these evaluation indexes can be calculated by changing the analysis method after obtaining one vibration waveform, high-speed measurement is possible even when a plurality of indexes are used, and the measurement can be performed in a short time. , It was found that it can be evaluated and diagnosed with higher accuracy.

The diagnostic method according to the present embodiment can not only evaluate the filling state of the PC grout non-destructively, but also has the following advantages over the conventional diagnostic methods described above.

That is, in the case of a method for diagnosing the PC grout filling state by ultrasonic waves such as the broadband ultrasonic method, if the concrete surface is not smooth, the surface is scraped smoothly or the probe is placed on the concrete surface on the smooth surface. It takes time to apply the contact medium for the purpose, and it takes time for evaluation and diagnosis. However, this embodiment is a tapping sound inspection using a sensor, and the diagnosis is made within a few seconds from the installation of the sensor to the hitting. Since it can be started, high-speed measurement is possible and the time required for diagnosis can be significantly reduced.

Then, the impact elastic wave method (impact echo method) diagnoses the filling defect of the PC grout by capturing the resonance phenomenon due to the repeatedly reflected wave between the defective filling portion of the PC grout and the sheath surface, but when the sheath diameter is small. When the sheath is deep, the resonance phenomenon does not occur because the reflected wave does not repeat, and the diagnosis cannot be made. On the other hand, according to the present embodiment, each index targets the vibration characteristics of the PC structure including the filling state of the PC grout, and the PC structure including the cavity formed by the insufficient filling of the PC grout. Since changes in the elasticity coefficient and density of the entire object are captured in each index, it is more stable as an index than using the resonance frequency due to repeated reflected waves as an index, and it is possible to make a highly accurate diagnosis with little variation. ..

In addition, the impact elastic wave method (striking vibration method) is a diagnostic method that can identify the cable that has caused the filling failure of the PC grout, but it is difficult to specifically identify the unfilled part. rice field. On the other hand, according to the present embodiment, it is possible to accurately identify the location where the filling is insufficient.

Further, in the diagnostic method according to the present embodiment, by displaying each of the above-mentioned indexes on a surface, the entire surface can be relatively diagnosed and the filling defect of the PC grout can be identified.

[2] Embodiment of the present invention Next, a method for diagnosing a PC grout filling state according to the present embodiment based on the above findings will be specifically described.

In the present embodiment, as described above, the vibration waveform of the impact elastic wave generated by the vibration to the PC structure is acquired, and the vibration duration, period and natural vibration frequency are obtained based on the acquired vibration waveform. Is determined as an index for evaluation, so that the PC grout filling state is diagnosed non-destructively. Specifically, the PC grout filling state is diagnosed according to each step shown below.

1. 1. Vibration waveform acquisition step First, the vibration waveform generated by the impact (vibration) on the concrete surface of the PC structure is acquired.

Specifically, after attaching a sensor to a predetermined location on the surface of the construction concrete of the PC structure to be diagnosed, vibration is applied by hitting it with a hammer, and the impact generated in response to this vibration is applied. The vibration waveform of the elastic wave is acquired by the sensor.

An example of the acquired vibration waveform is shown in FIG. In FIG. 4, the horizontal axis is the elapsed time from the start of vibration (Time: 10 ^-3 s), and the vertical axis is the amplitude (Amplitude). The amplitude is shown as a relative value with the maximum amplitude as 100%. From FIG. 4, it can be seen that the vibration is attenuated with the passage of time.

As the jig used for hitting sound, a test hammer that is generally used for hitting sound inspection, is light in weight, and is convenient to carry is preferable, but a plastic hammer, a rubber hammer, a wooden hammer, an iron hammer, etc. , If the hammer can give vibration to the target and can acquire the vibration waveform, it may be used instead of the test hammer. Further, instead of the hammer, an iron ball may be used to make a striking sound.

Further, as the sensor, it is preferable to use an AE (Acoustic Measurement) 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. 2. Evaluation index acquisition step Next, based on the vibration waveform acquired above, at least one of the vibration duration, period, and natural vibration frequency is acquired as an evaluation index.

(1) Acquisition of vibration duration As described above, the vibration duration is defined as the vibration duration by obtaining the elapsed time from the start of vibration until the vibration waveform falls below a certain amplitude.

Specifically, as shown in FIG. 4, the vibration is sustained by finding the elapsed time from the start of vibration of the PC structure to the concrete surface until, for example, the amplitude of the vibration waveform becomes ± 10% or less of the maximum amplitude. It's time.

(2) Acquisition of cycle As described above, the cycle is defined as the time required for one cycle of vibration in the vibration waveform.

Specifically, as shown in FIG. 4, the time from the time when the amplitude peaks in the first vibration cycle to the time when the amplitude peaks in the next vibration cycle is defined as the cycle.

However, if the vibration waveform is complicated and it is difficult to obtain the period as it is, the acquired vibration waveform is converted into a simple vibration waveform as shown in FIG. 5 by performing autocorrelation analysis. , The first cycle may be used.

(3) Acquisition of natural vibration frequency The natural vibration frequency can be obtained by frequency analysis of the acquired vibration waveform.

Specifically, a frequency analysis is performed on the acquired vibration waveform using a fast Fourier transform (FFT transform) or the like to acquire a frequency distribution as shown in FIG. In FIG. 6, the horizontal axis is frequency (Frequency: Hz), and the vertical axis is standardized vibration intensity (Magnitude).

As shown in FIG. 6, many peaks appear in the frequency distribution, but usually, the natural vibration peak exceeding a predetermined intensity (generally set to "0.5") as a threshold value is exceeded. The minimum (lowest frequency side) peak frequency among the frequencies of is used as the natural vibration frequency (evaluation peak frequency) used as the evaluation index.

3. 3. Filling state diagnosis step Next, the filling state of the PC grout is diagnosed using each index, vibration duration, period and natural vibration frequency obtained above.

Specifically, as described above, since each index has a good correlation with the filling state of the PC grout, the filling state of the PC grout in the PC structure to be diagnosed is variously changed and acquired in advance. By comparing with each index, the filling state of PC grout can be quantitatively diagnosed.

The diagnosis may be made based on at least one of the above three indexes, but a more accurate diagnosis can be made by making a diagnosis based on two or more indexes. At this time, since each index can be acquired from one vibration waveform at the same time, it is not necessary to change the acquisition method to acquire the index when using different indexes, and the diagnosis can be completed in a short time. ..

Since these indexes are indexes that capture changes in the elastic modulus and density of the entire body including the cavity caused by insufficient filling of PC grout, they are stable as indexes and have little variation. Highly accurate diagnosis is possible.

Then, in the PC structure to be diagnosed, a plurality of positions (measurement points) for acquiring the vibration waveform are provided at predetermined intervals, and the index at each measurement point is represented as, for example, a contour diagram (isoline diagram). Since it is possible to relatively evaluate the filling state of the PC grout in the entire PC structure and identify the portion where the filling rate of the PC grout is low, the PC grout in the entire PC structure can be identified. It is possible to diagnose the variation of the filling rate with high accuracy.

Hereinafter, the diagnosis based on each index will be specifically described with reference to examples.

1. 1. Preparation of specimen Prior to diagnosis, a concrete base with a width of 2000 x depth of 1500 x height of 300 mm was first made, and then a concrete base with a size of 400 mm in thickness and 1800 mm in height was placed in the center of the depth of this base. A PC structure was prepared and used as a concrete specimen. A sheath simulating insufficient filling of the PC grout was inserted through the central portion of the PC structure in the thickness direction.

FIG. 7 is a perspective view showing the configuration of the produced PC concrete specimen as an image, and FIG. 8 is a cross-sectional view from the side surface side. In FIGS. 7 and 8, 11 is a PC concrete specimen, 12 is a PC structure, and 13 is a base.

Each of A1, A2, B1, B2, and B3 is a sheath inserted through the central portion of the PC structure 12 in the thickness direction along the width direction. A PC steel rod (SBPR930 / 1180) (outer diameter 32 mmφ) is inserted in the sheaths A1 and A2 (inner diameter 38 mmφ), the filling rate of PC grout in A1 is 100%, and the filling rate of PC grout in A2 is 100%. It was set to 0%. Further, a PC stranded wire (12s15.2 (SWPR7BL)) is inserted in the sheaths B1, B2, and B3 (inner diameter 80 mmφ), the filling rate of the PC grout in B1 is 100%, and the filling rate of the PC grout in B2 is 100%. The rate was 50%, and the filling rate of PC grout in B3 was 0%. Each of 21 is a cavity (thickness 50 × width 200 × height 150 mm) formed inside the PC structure 12 along the reinforcing bar.

2. 2. Example 1 (Diagnosis using vibration duration as an index)
In this example, it was confirmed that the filling state of the PC grout can be diagnosed using the vibration duration as an index.

(1) Acquisition of vibration waveform A sensor was installed at a location corresponding to B1, B2, and B3 on the surface A (FIG. 8) of the PC structure 12, and the vicinity thereof was hit 5 times each to acquire a vibration waveform. The acquired vibration waveform is shown in FIG. In FIG. 9, the horizontal axis is the elapsed time from the start of vibration (10 ^-3 s), and the vertical axis is the amplitude (Amplitude). From FIG. 9, it can be seen that the vibration waveform continues for a long time (vibration duration is long) as surrounded by a broken line as the filling rate of the PC grout changes from a high state to a low state.

(2) Acquisition of vibration duration Next, the vibration duration for each impact is obtained based on each acquired vibration waveform, and the average value of the vibration duration at each filling rate of the PC grout is calculated as the PC grout filling rate. 10 was obtained, showing the relationship between the vibration duration and the PC grout filling rate. In addition, in FIG. 10, the variation of the vibration duration is also described as an error bar (a straight line connecting MAX and MIN).

(3) Diagnosis of PC grout filling state From Fig. 10, it was found that there is a correlation between the vibration duration and the PC grout filling rate that the vibration duration becomes shorter as the PC grout filling rate increases. It was confirmed that the filling rate of PC grout can be quantitatively diagnosed by using the duration as an index.

3. 3. Example 2 (Diagnosis using cycle as an index)
In this example, it was confirmed that the filling state of the PC grout can be diagnosed by using the period in the vibration waveform as an index. Here, a face-to-face diagnosis was performed on the PC structure.

(1) Acquisition of Vibration Waveforms Using the same PC concrete specimen 11 as the specimens shown in FIGS. 7 and 8, a plurality of vibration waveforms were acquired with the points marked with ◯ in FIG. 11 as measurement points. As specific measurement points, 11 measurement points are provided so that the interval is 200 mm at the position corresponding to each sheath and the intermediate position thereof, and 100 mm above the sheath A1 and below the sheath B2. Twenty-one measurement points were provided.

(2) Acquisition of period Next, the period was calculated based on each vibration waveform acquired at each measurement point. Next, each obtained period (ms) was plotted at the corresponding position on the graph with the horizontal position as the horizontal axis and the height position as the vertical axis, and a contour diagram was created. The obtained contour diagram is shown in FIG.

(3) Diagnosis of PC grout filling state From Fig. 12, in sheaths A1 and A2 through which PC steel rods are inserted, when the PC grout filling rate decreases from 100% to 0%, there are many places where the cycle becomes long. You can see that it appears. It can be seen that even in the sheaths B1, B2, and B3 through which the PC stranded wire is inserted, many places where the cycle becomes longer appear as the PC grout filling rate decreases from 100% to 50% and 0%.

From the above results, it can be seen that the period of the portion where the PC grout filling rate is low tends to be clearly longer than that of the portion where the PC grout filling rate is high, regardless of the PC steel rod and the PC stranded wire. It was confirmed that the filling rate of PC grout can be quantitatively diagnosed by using the above as an index.

4. Example 3 (Diagnosis using natural vibration frequency as an index)
In this example, it was confirmed that the filling state of the PC grout can be diagnosed using the natural vibration frequency obtained by frequency analysis of the vibration waveform as an index. Here, as in Example 2, a face-to-face diagnosis was performed on the PC structure.

(1) Acquisition of vibration waveform In this example, the vibration waveform acquired in Example 2 was used as the vibration waveform.

(2) Acquisition of natural vibration frequency Next, the frequency analysis of each vibration waveform acquired at each measurement point was performed to obtain the evaluation peak frequency. Next, as in Example 2, each of the obtained evaluation peak frequencies (Hz) is plotted at the corresponding positions on the graph with the horizontal position as the horizontal axis and the height position as the vertical axis, and a contour diagram is created. did. The obtained contour diagram is shown in FIG.

(3) Diagnosis of PC grout filling state From FIG. 13, in the sheaths A1 and A2 through which the PC steel rod is inserted, when the PC grout filling rate decreases from 100% to 0%, many places where the evaluation peak frequency is low appear. You can see that. It can be seen that even in the sheaths B1, B2, and B3 through which the PC stranded wire is inserted, many places where the evaluation peak frequency is low appear as the PC grout filling rate decreases from 100% to 50% and 0%.

From the above results, the evaluation peak frequency (natural vibration frequency) at the location where the PC grout filling rate is low tends to be clearly lower than that at the location where the PC grout filling rate is high, regardless of the PC steel rod or PC stranded wire. It was confirmed that the filling rate of PC grout can be quantitatively diagnosed by using the evaluation peak frequency (natural vibration frequency) as an index.

Next, the average value of the evaluation peak frequency is obtained for each line in which the PC steel rod or the sheath through which the PC stranded wire is inserted is installed, and the filling rate of the PC grout is set on the horizontal axis and the evaluation peak frequency is set on the vertical axis. ◯ or Δ was plotted at the corresponding positions on the graph to obtain FIG. In FIG. 14, as in FIG. 10, the variation in the evaluation peak frequency is also shown as an error bar.

From FIG. 14, in the sheath through which the PC steel rod is inserted, the filling factor is 5146 Hz when the filling rate is 100% and 4803 Hz when the filling rate is 0%, and it can be seen that a decrease of 343 Hz is observed. In the sheath through which the PC stranded wire is inserted, the filling factor is 4906 Hz when the filling rate is 100%, 4436 Hz when the filling rate is 50%, and 4377 Hz when the filling rate is 0%, and the maximum decrease is 529 Hz. You can see that it can be seen.

From the above, by using the value averaged at multiple points as the evaluation index as described above, the variation in construction and the random influence of concrete aggregates, reinforcing bars, etc. are averaged, and the effect of poor PC grout filling can be improved. It was confirmed that it was possible to make a clear evaluation, and that it was possible to make a more accurate diagnosis of PC grout filling by face-to-face evaluation and averaging.

Although the present invention has been described above based on the embodiments, the present invention is not limited to the above embodiments. It is possible to make various modifications to the above embodiments within the same and equal range as the present invention.

1, 12 PC structure 2 Concrete 3, A1, A2, B1, B2, B3 Sheath 4 PC steel 5 PC grout 11 PC concrete specimen 13 Base 21 Cavity

Claims (5)

It is a non-destructive diagnosis method of the PC grout filling state for non-destructively diagnosing the filling state of the PC grout filled around the PC steel material in the sheath embedded in the PC structure.
The vibration waveform acquisition step for acquiring the vibration waveform of the impact elastic wave generated by the vibration of the PC structure on the concrete surface, and the vibration waveform acquisition step.
An evaluation index acquisition step of acquiring at least one of the vibration duration, period, and natural vibration frequency as an evaluation index based on the acquired vibration waveform.
It is equipped with a filling state diagnosis step for diagnosing the filling state of the PC grout based on the acquired evaluation index.
A non-destructive diagnosis method for a PC grout filling state , wherein the filling state diagnosis step using the cycle as an index diagnoses that the longer the cycle is, the lower the filling state of the PC grout is. It is a non-destructive diagnosis method of the PC grout filling state for non-destructively diagnosing the filling state of the PC grout filled around the PC steel material in the sheath embedded in the PC structure.
The vibration waveform acquisition step for acquiring the vibration waveform of the impact elastic wave generated by the vibration of the PC structure on the concrete surface, and the vibration waveform acquisition step.
An evaluation index acquisition step of acquiring at least one of the vibration duration, period, and natural vibration frequency as an evaluation index based on the acquired vibration waveform.
It is equipped with a filling state diagnosis step for diagnosing the filling state of the PC grout based on the acquired evaluation index.
The PC grout is characterized in that the elapsed time from the start of vibration of the PC structure to the concrete surface until the amplitude of the vibration waveform falls within a predetermined amplitude or less from the maximum amplitude is used as the vibration duration. Non-destructive diagnostic method for filled state. The non-destructive diagnostic method for a PC grout filling state according to claim 2 , wherein the elapsed time is an elapsed time until the amplitude of the vibration waveform is within ± 10% of the maximum amplitude. The PC grout filling according to claim 1, wherein the period is the first period obtained by performing autocorrelation analysis on the vibration waveform immediately after the vibration of the PC structure on the concrete surface. Non-destructive diagnostic method for the condition. The PC grout filling state according to claim 2 , wherein the filling state diagnosis step using the vibration duration as an evaluation index diagnoses that the filling state of the PC grout is lower as the vibration duration is longer. Non-destructive diagnostic method.

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