JP4271997B2 - Vibration inspection method inside concrete wall - Google Patents

Description

[0001]
[Industrial application fields]
The present invention relates to a vibration testing method of the internal concrete wall to be used for internal diagnostics of the concrete wall.
[0002]
[Prior art]
In recent years, deterioration of concrete structures has become a problem, and the inside diagnosis is required. Conventionally, various methods using acoustic vibration have been proposed as diagnostic methods for the inside of a concrete wall . For example, in Patent Document 1, a concrete product is tapped with a hammer using an air cylinder, the sound pressure level of sound waves generated at this time is detected with a sound level meter, and the quality is determined by the difference in the peak value of the hit sound. A method of determining is disclosed.
[0003]
Further, Patent Document 2 discloses a method for collecting a hammering sound by a manual hammer with a microphone, wavelet transforming the vibration, and performing acoustic analysis to inspect the presence or absence of a cavity inside the concrete structure.
[0004]
Further, in Patent Document 3, the ultrasonic wave is incident, the propagating ultrasonic wave is received using an accelerometer in contact with the surface of the structure, and the frequency spectrum of the received ultrasonic wave is analyzed to analyze the concrete. A method for inspecting the presence or absence of a cavity generated in a structure is disclosed.
[0005]
Further, Patent Document 4 receives vibration generated inside the solid by striking the solid wall surface, analyzes the received vibration by a linear prediction method, and determines vibration characteristics based on the resonance frequency and the Q value of the resonance. The method of inspecting and determining pass / fail is disclosed.
[0006]
[Patent Document 1]
Japanese Patent Laid-Open No. 7-20097 [Patent Document 2]
Japanese Patent No. 2610378 [Patent Document 3]
JP 2000-2692 A [Patent Document 4]
Japanese Patent Laid-Open No. 2002-202293
[Problems to be solved by the invention]
In the method for determining pass / fail based on the sound pressure level of the received sound wave, it is necessary to keep the strength of hitting the concrete product and the reception sensitivity constant, and there is a problem that false detection is likely to occur. Further, the method of wavelet transforming received vibrations or analyzing the frequency spectrum has problems that it takes time for conversion and analysis and the analysis apparatus becomes expensive. There is a similar problem in a method in which vibration generated by impact is analyzed by a linear prediction method, vibration characteristics are inspected based on the resonance frequency and the resonance Q value, and pass / fail is determined.
[0008]
[Means for Solving the Problems]
The vibration inspection method inside the concrete wall according to the present invention for solving the above-mentioned problems is
Hitting the concrete wall to be inspected;
Receiving a waveform of vibration generated by the struck concrete wall and sampling at a predetermined period;
N amplitude sample values Sn generated by this sampling Dispersion of (n = 1,2,3 ... N)
D = ^{[N Σ} _{n = 1} [(Sn -S _M ) ² ]] / (N-1)
Where S _M is a sample value S n of N amplitudes The symbol ^N Σ _{n = 1} () is the variable Sn in () Calculating the sum of 1 to N while increasing n by 1 for
It is configured to include evaluating the internal state of the concrete wall surface to be inspected based on the calculated variance.
[0009]
DETAILED DESCRIPTION OF THE INVENTION
According to one preferred embodiment of the present invention, the evaluation is performed by dividing the variance to be evaluated by a value calculated for a concrete wall surface in a known internal state.
[0010]
According to another preferred embodiment of the present invention, the internal state is evaluated based on the quality determination.
[0011]
According to still another preferred embodiment of the present invention, the degree of pass / fail is displayed according to the magnitude of the divided value.
[0012]
【Example】
FIG. 1 is a block diagram showing a configuration of a detection apparatus for carrying out a method for inspecting vibration inside a concrete wall according to an embodiment of the present invention. This detection apparatus includes a control unit 1, an excitation unit 2, a receiving element 3, a signal processing unit 4, a signal analysis unit 5, and a diagnosis output unit 6.
[0013]
When receiving the timing signal supplied from the control unit 1, the excitation unit 2 strikes the concrete wall surface to be inspected. Any suitable means can be used for this striking, but there is a device designed to prevent the concrete wall from being hit twice or more, or from being exposed to vibrations caused by prolonged contact with the wall. preferable. For example, those disclosed in Patent Document 4 (Japanese Patent Laid-Open No. 2002-202293) described above can be used.
[0014]
The vibration generated inside the wall surface by the impact of the excitation unit 2 is received by the receiving element 3. As the receiving element 3, an appropriate element such as a piezoelectric element fixed to a wall surface or a broadband microphone installed away from the wall surface can be used. The vibration received by the receiving element is supplied to the signal processing unit 4, amplified in synchronization with the timing pulse supplied from the control unit 1, filtered, and supplied to the subsequent signal analysis unit 5.
[0015]
The signal analysis unit 5 converts the processed analog signal supplied from the previous signal processing unit 4 into a digital signal while sampling, and stores the digital signal in a built-in data memory. The calculation unit in the signal analysis unit 5 reads the sampling signal stored in the memory, calculates the variance, and transfers this to the diagnosis output unit 6. The diagnosis output unit 6 determines the quality of the concrete wall to be inspected based on the received variance value and the determination condition set from the outside, and outputs the determination result by screen display or the like. The determination condition to be set is changed according to the inspection target.
[0016]
The signal analysis unit 5 first extracts N sample values _Sn (n = 1, 2, 3... N) from the sample values of the vibration waveform obtained by one hit. Next, the signal analysis unit 5 calculates an average value S _M of the extracted N sample values. Subsequently, the signal analyzing unit 5, and the average value S _M of the calculated sample values, according to the following equation from the N sample values S _n, calculating the variance D.
D = ^{[N Σ} _{n = 1} [(S _n -S _M) ^2]] / (N-1) ··· ( 1)
However, the symbol ^N Σ _{n = 1} [] in the expression (1) means that the sum in 1 to N is calculated while increasing n by 1 for the variables in [].
[0017]
Fig. 2 (A) shows the same wall with the same strength and received with the same sensitivity, with the same surface of a structure with a square tile of 50mm x 50mm and 5mm thickness on the surface of the concrete base. It is a time waveform of the generated vibration. The horizontal axis represents sampling points, and the vertical axis represents sample values. FIG. 2B shows experimental data in which the variance D calculated for 400 sample values extracted from the received waveform as described above is plotted for each number of hits. The horizontal axis is the number of hits up to 860 times, and the vertical axis is the variance D. The sampling frequency is 30 kHz and the hitting cycle is 250 msec. During 900 strikes, the dispersion value remains small, almost 0.05 or less. The experimental conditions such as the sampling frequency and the striking cycle are all the same in the following experimental data.
[0018]
FIG. 3A shows that a defective portion that may be separated from the tile on the wall surface having the structure described in FIG. 2 is hit with the same strength as in FIG. 2, and received with the same sensitivity as in FIG. It is a time waveform of the generated vibration. The horizontal axis represents sampling points, and the vertical axis represents sample values. Compared with the good wall surface shown in FIG. FIG. 3B is experimental data in which the variance D calculated for 400 sample values extracted from the received waveform as illustrated in FIG. 3A is plotted for each number of hits. The horizontal axis is the number of hits up to 860 times, and the vertical axis is the variance D. It is a large value of about 0.3 to 0.4.
[0019]
FIG. 4A is a time waveform of vibration received by hitting the same location of a good wall surface of a structure in which a mortar layer having a thickness of 10 mm is formed on the surface of the concrete with the same strength. The horizontal axis represents sampling points, and the vertical axis represents sample values. FIG. 4B shows experimental data in which the variance D calculated for 400 sample values extracted from the received waveform as described above is plotted for each number of hits. The horizontal axis is the number of hits up to 860 times, and the vertical axis is the variance D. During 900 strikes, the variance value remains small, almost 0.1 to 0.2. The reason why the dispersion has decreased since the 510th shot is that the reception sensitivity has been reduced.
[0020]
FIG. 5A shows a case where the same portion of the defective portion that may cause the peeling of the mortar layer on the wall surface of the structure described in FIG. 4 is hit with the same strength as in the experiment of FIG. Is a time waveform of vibration received under the same sensitivity. The horizontal axis represents sampling points, and the vertical axis represents sample values. Compared with the good wall surface shown in FIG. FIG. 5B is experimental data in which the variance D calculated for 400 sample values extracted from the received waveform illustrated in FIG. 5A is plotted for each number of hits. The horizontal axis is the number of hits up to 860 times, and the vertical axis is the variance D. The reason why the dispersion value after the 510th hit decreased from about 1.1 to about 0.5 is because the reception sensitivity was lowered corresponding to the case of FIG. It is clearly a large value compared to the value of FIG.
[0021]
Referring to the above data, the amplitude of the wall surface where the tile or the mortar may be peeled increases in both positive and negative directions as compared with the wall surface where the received vibration is normal. Such a difference in vibration waveform can be determined by the hearing of a skilled worker, or can be visually observed with a cathode ray tube. However, this requires ensuring the skill of the worker and visual objectivity. The present invention pays attention to the fact that the increase in the amplitude of the vibration waveform has a close relationship with the dispersion D, and by calculating the dispersion D of the vibration waveform, the normal wall surface and the abnormal wall surface on which peeling or the like has occurred are numerical values. The quantitative and objective judgment is made based on the size of the.
[0022]
An example of the determination of pass / fail of the wall surface to be inspected performed by the diagnosis output unit 6 compares the variance value calculated by the signal analysis unit 5 with a predetermined threshold value that has been set, and determines that the variance is normal if the variance is less than the threshold value. If this variance is greater than or equal to a threshold value, it is determined that there is an abnormality. Another example is setting two thresholds, high and low, and normal if the calculated variance is less than the lower threshold, caution or re-examination if between the two thresholds, abnormal if higher than the higher threshold It is determined.
[0023]
Another example of a quality determination method according to the dispersion, the dispersion D obtained for the wall to be inspected is divided by the distributed D _o pre calculation already normal wall Normality the variance normalized R = D / D _o is calculated, and the determination is performed according to the magnitude of the normality R. As the normal wall dispersion D _o , an average value of a plurality of dispersions obtained by hitting a normal wall can be used. As an example, when R is 3 or more, the possibility of peeling is large, when R is less than 3 and 1.5 or more, the possibility of peeling is medium, and when R is less than 1.5, the possibility of peeling is small.
[0024]
In the experiments of FIGS. 2 to 5, the number of hits was 860 times. However, when actually inspecting the wall surface, in particular, when striking is continued while shifting the inspection target location along the wall surface to be inspected, the number of hits per inspection target location is necessary. Depending on the reliability of the inspection result to be performed, it can be limited to several tens or several times.
[0025]
FIG. 6 is a flowchart showing a processing procedure of an example of a diagnostic output process performed by the diagnostic output unit 6 of FIG. In the first step S1, the diagnosis output unit 6 calculates the variance D _o calculated for a normal wall without separation and two threshold values R _a and R _b (R _a <R _b) used as criteria for determining the possibility of separation. ). Next, the diagnosis output unit 6 receives from the signal analysis unit 5 the variance D _n calculated by the previous signal analysis unit 5 with respect to the vibration waveform generated by the n-th hit (step S2). Next, the division value R _n = D _n / D _o is calculated (step S3), and it is determined whether or not R _n is larger than the larger threshold value R _b. Is displayed on a display device or the like (step S5).
[0026]
If the division value R _n is larger threshold R _b or less of the smaller threshold value R or not greater than _a of the determination (step S6), and larger if a warning message "peeling in danger" in the display device Is displayed and output (step S7). If the division value Rn is _equal to or smaller than the smaller threshold value Ra, _a message “Possibility of peeling small” is output (step S8). The above determination and message output processing are performed until the transfer of the variance D _n from the signal analysis unit 5 in the previous stage is completed. When it is determined in step S9 to end, the diagnostic output processing ends.
[0029]
【The invention's effect】
As described above in detail, in the vibration inspection method of the present invention, the variance is calculated for the sample value of the vibration generated by the hitting of the concrete wall to be inspected, and the internal state of the concrete wall to be inspected is calculated based on this variance. Compared to the conventional methods that perform wavelet transform, analyze frequency spectrum, and analyze by linear prediction method, using a simple and inexpensive inspection device There is an advantage that high-speed inspection is possible.
[Brief description of the drawings]
FIG. 1 is a functional block diagram illustrating an example of a configuration of a vibration inspection apparatus inside a concrete wall to which an inspection method according to an embodiment of the present invention is applied.
FIG. 2 shows a time waveform (A) of vibration generated when a wall surface having a structure in which a tile is pasted on a concrete base is hit, and variance D calculated for sample values extracted from these vibration waveforms. Is the experimental data (B) plotted for each number of hits.
FIG. 3 shows the time waveform (A) of vibrations generated when a defective part that may cause separation of tiles on the wall surface is hit, and the variance D calculated for sample values extracted from these vibration waveforms. It is the experimental data (B) plotted for every.
FIG. 4 shows a time waveform (A) of vibration generated when a wall surface having a mortar layer formed on the surface of a concrete is hit and a variance calculated for sample values extracted from these vibration waveforms. This is experimental data (B) in which D is plotted for each number of hits.
FIG. 5 shows a time waveform (A) of vibration generated when hitting a defective portion where the mortar layer on the wall surface may be peeled, and a variance D calculated for sample values extracted from these vibration waveforms. Experimental data (B) plotted for each number of times.
6 is a flowchart showing a processing procedure of an example of a diagnostic output process executed by a diagnostic output unit 6 in FIG. 1;
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Control part 2 Excitation part 3 Reception element 4 Signal processing part 5 Signal analysis part 6 Diagnosis output part

Claims (4)

Hitting the concrete wall to be inspected;
Receiving a waveform of vibration generated by the struck concrete wall and sampling at a predetermined period;
N amplitude sample values Sn generated by this sampling Dispersion of (n = 1,2,3 ... N)
D = ^{[N Σ} _{n = 1} [(Sn -S _M ) ² ]] / (N-1)
Where S _M is a sample value S n of N amplitudes The symbol ^N Σ _{n = 1} () is the variable Sn in () Means that the sum is increased from 1 to N while increasing n by 1.
Calculating
Evaluating the internal state of the concrete wall to be inspected based on the calculated variance, and a method for inspecting vibration inside the concrete wall. In claim 1,
The method for inspecting vibration inside a concrete wall, wherein the variance to be evaluated is divided by a value calculated for a concrete wall in a known internal state. In either claim 1 or 2,
The method for inspecting vibration inside a concrete wall , wherein the evaluation of the internal state is performed by determining whether the internal state is good or bad. In claim 3,
A vibration inspection method inside a concrete wall surface , wherein the degree of quality is displayed according to the magnitude of the divided value.

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