JP2001208733A - Device for measuring degradation of concrete structure - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a device for measuring the degree of degradation capable of non-destructively, appropriately, and simply measuring and detecting the degree of degradation of a deep-layer section inside a concrete structure. SOLUTION: The device for oscillating a concrete structure and measuring a resonance frequency and the degradation of the reinforced concrete structure is provided with a moving means to move at a fixed distance from the surface of concrete to be measured. The moving means is provided with both an acoustic means capable of oscillating the concrete structure and a sound detecting means to detect the sound transmitted into the concrete structure from the acoustic means in the vicinity of the acoustic device.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention belongs to the technical field of measuring the degree of deterioration of the internal structure of a concrete structure without destroying the concrete structure.

[0002]

2. Description of the Related Art Deterioration of reinforced concrete structures is caused by corrosion of reinforcing steel, alkali-aggregate reaction, and frost damage.
Softening of cement, that is, reduction of pressure resistance due to destruction of the internal structure of the concrete, cracking, that is, cracking, concrete cracking due to corrosion and rusting of the reinforcing steel, separation of the reinforcing steel from the concrete, etc. Before doing so, it is desirable to know the extent of its degradation. Conventionally, in order to measure the degree of deterioration of the internal structure of a concrete structure, a sample is taken from a predetermined portion of the concrete structure, a compression test is performed, the composition is further made into powder, and the composition is analyzed to determine the degree of lime alteration. Deterioration measurement method to detect,
It is generally known as a means for surely knowing the degree of deterioration, and, as disclosed in JP-A-8-29413, drilling a plurality of thin inspection holes in a concrete structure,
Methods of inserting a fiberscope or the like to inspect the progress of cracks and the like are known, but in any case, it is necessary to collect a sample or drill an inspection hole. Therefore, a method of nondestructively detecting the degree of deterioration of the internal structure of a concrete structure is required. Conventionally, the approximate degree of deterioration can be known visually from the appearance of a concrete structure by its color, etc. Various methods of detecting the degree of deterioration of concrete structures have been proposed in order to make it difficult to obtain an evaluation and to obtain an objective evaluation in a non-destructive manner.

[0003] For example, a method is known in which a displacement gauge or a strain gauge is installed on the surface of a concrete structure, and the degree of deterioration is determined by measuring the deformation caused by corrosion of the reinforcing bar over time. Also, as proposed in Japanese Patent Application Laid-Open No. 8-15126, each surface of the concrete structure is scanned with ultrasonic waves, and the obtained distance measurement value is compared with a preset reference value of a healthy part. And the degree of deterioration is detected. Further, as proposed in Japanese Patent Application Laid-Open No. H11-30510, unevenness on the surface of a concrete structure is measured by scanning a distance sensor on a straight line, and a deterioration state is detected from the measured unevenness. Furthermore, as disclosed in JP-A-5-108796, the surface temperature distribution of the concrete structure is detected by an infrared sensor, and compared with the temperature distribution of the concrete structure in a healthy state, a unique temperature distribution is obtained. When it was detected, it was judged and evaluated as a deteriorated part. At present, as a method of measuring deterioration of a concrete structure, which has been relatively well-established, there is known a self-potential measurement method of measuring self-potential and analyzing the degree of deterioration. Inspection of the degree of non-destructive deterioration of the above-mentioned conventional concrete structures
In a measurement method, for example, in a method of measuring a shape change over time with a strain gauge or the like, deterioration at a shallow portion from the surface can be detected relatively accurately, but the degree of deterioration of an internal tissue, particularly at a deep portion, is not always accurate. In the method of measuring and detecting the surface temperature using an infrared sensor, deterioration at a shallow part from the surface can be detected relatively accurately, but the degree of deterioration of internal tissues, especially at deep parts, is not always accurate. In addition to the problem that measurement and detection are not possible, temperature control is difficult, and the self-potential measurement method is most suitable mainly for detecting the degree of deterioration of reinforcing steel, but it does not cause deterioration or cracking of concrete itself. Not suitable for detection.

[0004] The inventors of the present invention have proposed in Japanese Patent Application No. 11-193942.
As a reference, we have proposed a means of measuring the deterioration of concrete structures that can non-destructively measure and detect the degree of deterioration in deep parts inside concrete structures. The outline of the first invention of Japanese Patent Application No. 11-193942 is that, in a concrete structure having a portion having almost the same thickness, a resonance portion is measured by exciting a sound portion of the concrete structure to be measured in advance. Create a reference resonance frequency spectrum of the sound part, vibrate another measurement part, measure the resonance frequency of the measurement part, create the resonance frequency spectrum of the measurement part, and superimpose the created two resonance frequency spectra. hand,
By analyzing the degree of deviation between the two resonance frequency spectra, the degree of deterioration of the internal structure is determined, and the degree of complexity that is more complicated than the spectrum of the healthy part is analyzed, or the peak of the spectrum is analyzed. By analyzing the degree of the dulling, the degree of softening, cracking, and separation of the reinforcing steel from the concrete at the measuring point is measured, and the outline of the second invention is that the thickness of the cement is almost the same. In a concrete structure having a portion, a sound portion of the concrete structure to be measured is vibrated in advance to detect a reference resonance frequency of a fundamental mode of vibration in the sound portion,
While calculating the value of the reference phase velocity from the reference resonance frequency, the other measurement unit is excited to detect a resonance frequency peak of the vibration measurement unit near the reference resonance frequency, and the measurement unit at the peak is detected. Calculate the phase velocity value of the vibration from the resonance frequency of the vibration, compare the two phase velocity values and analyze the value of the difference to determine the degree of deterioration of the internal tissue, and quantitatively determine the phase velocity value of the vibration. This is to judge the degree of deterioration of the internal structure of the reinforced concrete structure. Each of the above two inventions uses an impact hammer as a means for vibrating a concrete structure, and vibrates the concrete structure to be measured by hitting it with an impact hammer. The frequency is detected by an acceleration pickup fixed to a concrete structure.

[0005]

However, in the invention of Japanese Patent Application No. 11-193942, an impact hammer is used as a means for vibrating a concrete structure, and the concrete structure to be measured is impacted. Because it is a method of hitting with a hammer to vibrate, there is a problem that it is usually necessary to hit the concrete surface manually, which is troublesome and requires a lot of labor.
There was a problem that how to hit was not constant. further,
When detecting the resonance frequency due to vibration, the acceleration pickup must be fixed to the concrete structure, which requires a lot of labor, and the data varies depending on the fixing method. was there. The present invention has been made in view of the above-described problems, and an object thereof is to provide a deterioration measuring device for a reinforced concrete structure that measures a resonance frequency by vibrating a concrete structure. It is another object of the present invention to provide a concrete structure deterioration measuring device which has a configuration in which the vibration means and the detection means can be automated with almost no need for manual labor, and which reduces variations in data obtained.

[0006]

In order to solve the above-mentioned problems, the present invention is directed to an apparatus for measuring a resonance frequency by vibrating a concrete structure and measuring deterioration of the reinforced concrete structure. A sound means capable of exciting the concrete structure is provided at a predetermined distance from the concrete surface to be measured, and a sound detecting means for detecting sound propagated from the sound means into the concrete structure is provided from the concrete surface to be measured. This is a deterioration measuring device for a reinforced concrete structure provided at a predetermined distance. In order to solve the above-mentioned problem, an invention according to claim 2 is an apparatus for measuring the resonance frequency by vibrating a concrete structure and measuring the deterioration of the reinforced concrete structure, wherein the device has a certain distance from the concrete surface to be measured. Moving means for moving while keeping the sound, the moving means provided with an acoustic means capable of vibrating the concrete structure, and the moving means includes a sound for detecting a sound transmitted from the acoustic means into the concrete structure. This is a device for measuring deterioration of a reinforced concrete structure, wherein a detecting means is provided near the acoustic device.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Here, an apparatus for measuring the degree of deterioration of the internal structure of a concrete structure according to the present invention will be described. First, the principle of the method for measuring the degree of deterioration of the internal structure of a concrete structure employed in the present invention will be described. Will be described. We have:
In general, one of the physical quantities representing the strength of an object is Young's modulus E. The larger the Young's modulus E, the higher the compressive strength of the object. To measure the strength,
Researched as proposed in -193942. The above method for measuring the Young's modulus E is based on the resonance frequency (resonance frequency) of the object.
There is a method of measuring the Young's modulus E of the object by measuring the elastic body of a finite size such as a concrete structure has a number of natural vibration modes, Is a numerical value determined by the material, shape and dimensions of the concrete structure. When a concrete structure that is an elastic body is hit, a natural vibration mode of the concrete structure is excited by a finite size, for example, a thickness or a dimension, and vibrates at the natural frequency (resonance phenomenon). Is excited depends on the hitting position and how to hit. For example, there are many natural vibration modes of a floor slab concrete structure of a bridge, but as described above, the mode to be excited generally differs depending on the hitting position. The present inventors have found that in a floor slab concrete structure, when the thickness of the floor slab concrete is substantially constant, there are several modes that are excited regardless of the hitting position.

These are vibration modes of transverse and longitudinal waves in the thickness direction of the floorboard, and the frequencies of the fundamental modes of these vibrations are given by the following equations (1) to (4). (1) Shear wave resonance frequency fs = vs / 2h (2) Shear wave propagation velocity vs = √1 / 2 (1 + σ) E / ρ (3) Longitudinal wave resonance frequency fp = vp / 2h (4) Longitudinal wave The propagation velocity vp = √ (1−σ) / (1 + σ) (1-2σ) · E / ρ where h: thickness of the floorboard, σ: Poisson's ratio, ρ: density,
It is. However, in practice, the above-mentioned transverse wave and longitudinal wave are complex waves and cannot be strictly distinguished, so strictly speaking, in the present invention and the examples, the transverse wave is “transverse wave” and the longitudinal wave is “longitudinal wave”. However, in this specification, they are simply defined as “lateral wave” and “longitudinal wave”.

As described above, the deterioration of the reinforced concrete structure is caused by the softening of cement, cracking,
Although the phenomenon such as separation of the reinforcing bars occurs, the present inventors have found that the relationship between the deterioration of the reinforced concrete structure and the above-described resonance frequency is related to h: the thickness of the floorboard, σ: Poisson's ratio, and ρ: density, In concrete structures having the same thickness,
With respect to the phenomenon of cement softening, it has been found that any of the above resonance frequencies shifts to a lower one and the peak of the spectrum becomes dull. In addition, it has also been found that the spectrum becomes complicated and the peak of the resonance frequency (resonance frequency) becomes indistinct with respect to phenomena such as cracks and loosening of reinforcing bars.

In this embodiment, based on the above findings, FIG.
The measurement system shown in Fig. 1 was assembled and used, and the system will be described below with reference to the drawings. The reinforced concrete structure to be measured to confirm the above principle is
As shown in FIG. 2, this is a sound floor model of reinforced concrete having a thickness h = 0.23 m and a floor plate of 1 m square. First, in FIG. 1, a reinforced concrete structure 10 is a speaker model as a vibration means for applying vibration to a reinforced concrete floor plate model or a reinforced concrete to be measured.
Although a speaker 11 is used, a speaker 11 which is an acoustic means is provided on a movable carriage 12 which moves in parallel while maintaining a position about 1 m away from the measurement surface of the reinforced concrete structure 10. In this example, the distance between the reinforced concrete structure and the measurement surface was set to about 50 cm. However, it is better that the detection sensitivity is shorter, and it is advantageous that the detection time is longer. A range from centimeters to several meters is practical. In addition, a distance sensor 13 for detecting the distance of the movable trolley 12 from the measurement surface and controlling the position is provided on the measurement surface side. In this embodiment, the sound emitted from the speaker 11 has an excitation frequency spectrum similar to the striking sound generated when the reinforced concrete structure 10 is hit with an impact hammer. The striking similar sound having the excitation frequency spectrum is generated by the waveform signal generator 14, and the output signal from the waveform
It is pronounced as a blow-like sound. Therefore, the striking similar sound is a short, short-time pulse sound that is uniform like a so-called white noise containing various frequencies.

[0011] A similar sound A struck from the speaker 11
First, the sound reaches the reinforced concrete structure 10 and partly reflects, but partly propagates inside the concrete B, reflects on the back side of the concrete structure 10 and further partly propagates outside C and detects sound A microphone 16 is reached. The loudspeaker 11 used in this embodiment is preferably directional, and the distance X between the loudspeaker 11 and the concrete 10 to be measured.
If the distance is too far, the sharpness of the peak of the resonance frequency disappears.
The acoustic pulse is generated repeatedly and intermittently, and can be automatically measured while moving on the movable trolley 12, thereby significantly improving the work efficiency as compared with the prior art.
Also, since the speaker 11 and the microphone 16 are integrated, when the reflected sound reaches the microphone 16 so as not to directly detect the striking similar sound from the microphone 16 while the speaker 11 is producing the striking similar sound. Only the microphone
16 conduction must be turned on and off at other times. For this reason, the acoustic pulse needs to have a short and short width, but in this embodiment, since the speaker 11 and the microphone 16 are integral with each other and have a distance X of 50 cm, the reciprocating distance is 1 m, and the sound speed is at room temperature. 342m / sec (18
° C), there is no interference if the pulse width is 1/342 sec or less and the pulse interval is longer. In order to further enhance the above operation, it is preferable that the microphone 16 has high directivity. However, if necessary, as shown in FIG. Loudspeaker 1 and the speaker 1 as shown in FIG. 2 (b).
The microphone 16 may be provided at the bottom of the cone 111 using the fact that the cone 111 itself has a sound collecting shape, and the speaker 11 itself may be switched each time and used as a microphone, in these cases Makes the device more compact. In the present embodiment, at the same time as outputting a sound pulse of a striking similar sound from the waveform signal generator 14 to the speaker 11,
FTT analyzer 15 (fast four
ier transform) FFT analyzer (not shown)
Input to channel 151. On the other hand, the striking similar sound that propagates through the inside of the reinforced concrete structure 10 and is emitted to the outside is collected by the microphone 16 attached near the speaker 11. The vibration signal 17 detected by the microphone 16 is amplified by an amplifier 18 and input to a second channel 152 of an FFT analyzer (not shown) of the FTT analyzer 15.

The FFT analyzer section A / D converts the input vibration signal 151 of the speaker 11 and the vibration signal 152 (17) detected by the microphone 16, and performs Fourier transform by computer processing to generate a vibration signal. The waveform is analyzed into a frequency spectrum. By the way, in the analysis of the frequency spectrum, the sound pulse of the impact similar sound of the impact hammer has a frequency spectrum that is not flat, so that the ratio of the frequency spectrum of the impact similar sound to the detected frequency spectrum is normalized. The frequency response is measured. The frequency response obtained by analyzing the frequency collected by the microphone 16 and converted into an electric signal, amplified by the amplifier 18 and input to the second channel 152 of the FFT analyzer (not shown) of the FTT analyzer 15 is analyzed. The function (frequency spectrum) is displayed on the display screen. If necessary, the output of the frequency spectrum may be input to the peak reading device 19, and the necessary data may be extracted and printed out from the printer 21 via the personal computer 20, and the analyzed frequency spectrum data may be obtained. Record on a recording medium such as a floppy disk (FD). FTT analyzer 15
Is configured using a microcomputer including an input device, an arithmetic processing device, a storage device, an output device, and the like. The storage device stores in advance the items necessary for the shape measurement calculation processing, such as the resonance condition formula, the related calculation formula, and the calculation processing program set based on the above-described principle. And microphone 16
Then, a frequency spectrum is calculated from the output of the FTT analyzer, that is, a graph of the frequency response function is output via an output device such as the display of the FTT analyzer 15 or the printer 21.

The reinforced concrete structure 10 to be measured here is a healthy slab model 101 of a reinforced concrete slab having a thickness of h = 0.23 m and a square of 1 m, as shown in FIG. FIG. 4 is a graph showing the result of measurement using the system. As described above, in the concrete floor structure, there are several modes that are excited even if the position of the speaker 11 is moved in parallel, and the transverse and longitudinal vibration modes in the thickness direction of the floor plate exist. The fundamental mode frequency is given by the above (1) to (4). In the graph of FIG. 3, the horizontal axis represents the resonance frequency and the vertical axis represents the vibration intensity function. Signal) and the frequency spectrum of the vibration signal of the microphone 16 (the input signal of the second channel 152) are normalized by taking the ratio of the frequency spectrum of the signal and the value standardized by the FTT analyzer 15 measured as the frequency response. It is a dimension value. In this case, it is sufficient that the peak frequency of the frequency response can be detected, and the present invention does not particularly require the value of the vibration intensity itself. Therefore, the volume of the speaker 11 may be set to a volume that can detect the peak frequency of the frequency response. The measurement results show that since the floor panel model 101 is a square prism of finite length 1 m square and a thickness h: 0.23 m, a number of frequency peaks appear in the graph of FIG. The frequencies of the fundamental modes of the transverse and longitudinal vibration modes of the obtained concrete structure also appear as relatively sharp peaks with the following values. In addition, as described later, the thickness h: 0.23 as an actual measurement portion
In a sound part such as a wall having a large area of m, the spectrum is relatively simple and the number of peaks is small.

(1) Resonance frequency of shear wave: fs = 5.3 kHz Propagation velocity of shear wave for the above frequency: vs = 2.4 km / s (2) Resonant frequency of longitudinal wave: fp = 8.3 kHz Wave propagation speed: vp = 3.8km / s

Based on the above fact, the spectrum of the resonance frequency of the actual reinforced concrete structure was measured. In fact, we measured the part of the concrete wall of the floorboard where the thickness of the Tohoku Expressway Toyosawa River Bridge was about 0.23m. And the thickness
h: In the sound part of a concrete structure with a floor panel of 0.23 m, the fundamental mode frequency of transverse and longitudinal wave modes is fs = 5.3
kHz, fp = 8.3kHz
Analyze the frequency spectrum of the resonance frequency in the vicinity, calculate the phase velocity value from the peak frequency value, and collect a sample of the concrete structure part, and then check the actual state of the cracked state and free lime state Was analyzed and the two were compared.

[Use Example 1] Next, a first use example of measuring the deterioration of a reinforced concrete structure by measuring the resonance frequency using the deterioration measuring device of the present invention will be described. As a result of measuring and analyzing the resonance frequency of the concrete structure with a thickness of h: 0.23 m, which is a striking sound, the actual concrete structure of the healthy part was 5 kHz.
It turned out that the peak of the transverse resonance frequency appears clearly near z, but the peak of the longitudinal resonance frequency that should appear near 8 kHz is unclear. It is considered that disturbance noise is apt to be mixed in at a high frequency of 8 kHz, and at present, only a low-sensitivity measuring instrument can be obtained. Further, it was found that the spectrum of the cracked portion became complicated and the peak of the resonance frequency was not clear. As a matter of course, if the peak of the resonance frequency can be clearly determined depending on the target concrete structure or the measuring instrument even at the high frequency of 8 kHz, the measurement may be performed using the high frequency longitudinal vibration of 8 kHz.

Next, a specific result obtained by measuring an actual concrete structure will be described with reference to FIG. The concrete structure having the spectrum of FIG. 5 is a healthy part,
The spectrum is relatively simple, the peak of the resonance frequency of the shear wave clearly appears around 5 kHz, and the vibration intensity function represented by the vertical axis is large. Note that the vibration intensity function on the vertical axis in the spectrum diagram is a value related to the vibration intensity, but is the output of the FTT analyzer 15 when conditions such as the sensitivity of the measured value are constant, and the vibration intensity at each frequency. Is a value specified by the FTT analyzer 15 and is dimensionless. On the other hand, the concrete structure having the spectrum shown in FIG. 6 is a deteriorated part, the spectrum is relatively complicated, the peak of the resonance frequency of the shear wave is gentle around 5 kHz, and the vibration intensity function is low. Has become. Further, the concrete structure having the spectrum shown in FIG. 7 is a crack, and the resonance frequency spectrum is complicated, and the peak of the resonance frequency of the transverse wave is not clear around 5 kHz. In particular, one of the features of this crack detection is that it is a clear detection means that a deep and sharp valley appears in the resonance frequency spectrum and cannot be obtained by other known deterioration measurement means.

From these facts, the method and apparatus for measuring the degree of deterioration of a concrete structure according to the embodiment of the present invention vibrate a reinforced concrete structure to be measured, measure a resonance frequency spectrum, and measure the internal structure of the reinforced concrete structure. Is determined based on the following criteria, and whether or not the part is sound is checked. (1) When the resonance frequency spectrum has a complex uneven, deep and sharp valley, and the peak of the resonance frequency of the inherent transverse wave due to the thickness is unclear → It is determined that there is a crack. (2) If the peak of the resonance frequency of the inherent shear wave due to the thickness of the resonance frequency spectrum is gentle and the vibration intensity function is low, it is determined that free lime is present. (3) When the above does not correspond to (1) and (2), and the peak of the resonance frequency of the inherent transverse wave due to the thickness of the resonance frequency spectrum is clear and the vibration intensity function is high → it is determined to be a sound part.

In the states (1), (2), and (3), an average resonance frequency spectrum of a sound part is created and used as a reference resonance frequency spectrum. Is visually determined.
By calculating the degree of displacement quantitatively, the degree of deterioration of the internal structure of the reinforced concrete structure can be measured.

The specific configuration of the measuring device is as follows:
A known FTT analyzer 15 is used, and the shape calculation device is configured using a microcomputer including an input device, a calculation processing device, a storage device, an output device, and the like. The storage device stores a reference resonance frequency spectrum. Recall this reference resonance frequency spectrum, superimpose the measured resonance frequency spectrum measured in the above-described procedure on the display, and display the area where the measured resonance frequency spectrum is lower than the reference resonance frequency spectrum in red. In addition, the area outside the upper value is displayed in green, and the above (1) (2)
According to the criteria of (3), the operator visually determines the degree of deterioration from the screen, or quantitatively calculates the degree of deviation to determine the degree of deterioration inside the reinforced concrete structure. The configuration of the apparatus at this time may be appropriately selected from screen analysis software such as peak analysis software suitable for the above-described measurement method. Also, if necessary, if the comparison spectrum is output on paper via an output device such as a printer, it can be used as objective degradation data of a reinforced concrete structure, unlike a simple visual inspection of a reinforced concrete structure. Available.

In the first embodiment described above, the thickness
It is intended for reinforced concrete structures with 0.23m concrete wall shape, road surface and ceiling, but of course, concrete of almost constant thickness other than 0.23m, for example, 1m thick concrete wall shape, road surface and ceiling structure Also for the object, the average resonance frequency spectrum of the sound part is created in the same procedure as the above and used as the reference resonance frequency spectrum, and the measured resonance frequency spectrum of the measurement site is superimposed, and the above (1) (2) ( The degree of deterioration of the internal structure of the reinforced concrete structure can be measured by visually determining the degree of deviation or quantitatively calculating the degree of deviation based on the criterion 3). Also, in a concrete structure having many places of the same geometrical shape and dimensions, if the same thickness h is present, the spectrum becomes complicated, but a transverse wave and a vertical wave in the thickness direction with respect to the same thickness h. Since the reference resonance frequency of the wave vibration mode exists, the measurement target is not limited to the floor plate, but is applied to concrete structures having the same geometric shape and dimensions, for example, cubic and polyhedral concrete structures. Of course.

[Usage Example 2] Next, a second usage example of measuring the deterioration of a reinforced concrete structure by measuring the resonance frequency using the deterioration measuring device of the present invention will be described. At present, the relationship between the self-potential of the self-potential measurement method which is relatively well-established and the phase velocity of the shear wave at the peak of the resonance frequency of the shear wave at around 5 kHz according to the present invention was analyzed. And Table 1 of FIG.

[Table 1] in FIG. 9 will be described.
First, as described in the above (1), when the resonance frequency spectrum has a complex irregularity, there is a deep and sharp valley, and the peak of the resonance frequency of the shear wave is unclear, the crack portion at a glance without measuring. Was excluded from the comparison, but the compressive strength of the concrete X to be measured was extremely brittle, σc = 238, and the degree of deterioration was clearly inferior. In order to determine whether the part was sound or free lime, a concrete sample was taken from the part, a compression test was performed, and the composition was further analyzed using powder to detect the degree of lime alteration.

In the above-described method of measuring the natural potential, the possibility of corrosion of the steel material of the reinforced concrete structure is determined as follows. If the value of the natural potential mV is: (1) -200 mV <E, there is no probability of corrosion of 90% or more. If -350mV <E ≤ -200mV, the degree of corrosion is uncertain. (3) If E ≤ -350mV, the probability of corrosion is 90% or more. Then, the natural potential in the natural potential measurement method for the reinforced concrete structure to be measured and the phase velocity of the shear wave at the peak of the resonance frequency of the shear wave near 5 kHz are calculated from the equation (1) the resonance frequency fs = vs / 2h FIG. 8 shows a comparison between the phase velocity value obtained by calculating back and vs.
As shown in the graph, there is a correlation and reliability. That is, in the graph of FIG. 8, it can be seen that the self-potential of the healthy part is located on the left side and above.

From the above measurement results of [Table 1] in FIG.
When the value of the phase velocity vs. km / s of the shear wave at the peak of the resonance frequency of the shear wave near kHz is 1. (1) 2.25> vs (km / s), the amount of free lime is large and the free lime portion ( Y1 to Y6: Compressive strength of concrete σc = 270 (kg · f / cm2)) (2) If 2.25 ≧ vs (km / s)> 2.28, the degree of free lime is uncertain (3) vs (km If / s) ≥ 2.28, there is almost no free lime and it can be determined that the part is sound (Z1 to Z4: compressive strength of concrete σc = 288 (kg · f / cm2)). In order to make the above judgment as a more definitive judgment criterion in comparison with the result of the self potential measurement method,
Data Y6 and Z1 are (2) -350mV
<E ≦ −200 mV, and the degree of corrosion is in an uncertain range. In this range, if the degree of free lime is uncertain, the following 2. And become more qualified.

2. (1) In the case of 2.23> vs (km / s) (Y1 to Y5), the amount of free lime is large, and the free lime portion is (2) 2.23 ≧ vs (km / s)> 2.44 (Y6, Z1) In the case of, the degree of free lime is uncertain. (3) In the case of vs (km / s) ≥ 2.44 (Z2 to Z4), there is almost no free lime and there is a healthy part.

As described above, the resonance frequency measuring apparatus according to the second usage example vibrates the concrete structure to be measured,
Measure the resonance frequency of the concrete structure,
In the case of h: 0.23 m, a peak of the resonance frequency of the shear wave clearly appears around 5 kHz. The phase velocity value of the shear wave at the peak of the resonance frequency of the shear wave near 5 kHz is calculated, and the value of this phase speed vs. When (km / s) is (1) 2.25> vs (km / s), more certainly, when 2.23> vs (km / s), it is judged that the amount of free lime is large and free lime is contained, and (2) 2.25 ≧ vs (km / s)> 2.28, more specifically, if 2.23 ≧ vs (km / s)> 2.44, the degree of free lime is determined to be uncertain, and (3) vs (km / s) In the case of ≧ 2.28, more certainly vs (km / s) ≧ 2.44, it is judged that there is almost no free lime and that it is healthy. However, the resonance frequency measuring method of the second usage example is based on the following: (1) Resonance frequency of transverse wave fs = vs / 2h (2) Resonance frequency of longitudinal wave fp = vp / 2h If the thickness of the concrete structure to be measured changes from h: 0.23 m, the above-mentioned (1) resonance frequency fs = vs / 2h of the transverse wave and (2) resonance frequency fp = vp / 2h of the longitudinal wave also change, The peak of the resonance frequency of the shear wave also moves from around 5 kHz. Each time, the reference resonance frequency value of the shear wave and the reference phase velocity value of the shear wave of the sound part at the thickness are set, and the same procedure as above is performed. Then, the degree of deterioration of the internal structure may be measured and determined.

Then, the configuration of the above specific measuring device is as follows:
As in the usage example 1, the FTT analyzer 15 is used, and the shape calculation device is configured using a microcomputer including an input device, a calculation processing device, a storage device, an output device, and the like. In the case of a floor plate having a thickness of h: 0.23 m, a peak of the shear wave resonance frequency is detected at around 5 kHz, a value of the phase velocity vs of the shear wave at the peak of the resonance frequency is detected, and the value of vs. s) The value of 1. Or 2. (1) When the amount of free lime is free lime, the degree of free lime is uncertain, and (3) There is almost no free lime and it is healthy Are displayed by classification, and the configuration of the apparatus at this time may be selected as appropriate from screen analysis software suitable for the above-described known measurement method. In addition, if paper output is performed via an output device such as a printer as needed, it can be used as objective deterioration degree data of the reinforced concrete structure, unlike a simple visual appearance determination of the reinforced concrete structure.

In the second use example, the thickness
The same applies to 0.23m concrete wall-shaped, road-surface and ceiling structures. The average resonance frequency spectrum of the healthy part is created as the reference resonance frequency spectrum by the procedure described above, and the phase velocity there is calculated and compared with the phase velocity in the healthy part, so that the internal structure of the reinforced concrete structure can be quantitatively deteriorated. The degree can be measured. Also, in the case of a concrete structure having a large number of places having the same geometric shape and dimensions, for example, a cube or a polyhedron, if the same thickness h is present, the spectrum becomes complicated. Since the reference resonance frequency exists in the transverse and longitudinal vibration modes, the measurement target is not limited to the floorboard, and is of course applied to concrete structures having the same geometric shape and dimensions. It is.

It is needless to say that the present invention is not limited to the above two embodiments unless the characteristics of the present invention are impaired. For example, the sound pulse of the sound means is set to be the same as the striking sound. Any sound may be used as long as it includes a wide range of frequencies continuously and evenly. In addition, as described above, the measurement target was a floor plate, but it is a matter of course that the measurement target may be a concrete structure of a geometric shape having the same thickness, and the thickness may be other than 23 cm. Of course, it is possible to measure concrete structures as a measurement object, and a relatively low resonance frequency (5 kHz) of a shear wave or a shear wave was measured. Even at the resonance frequency (8 kHz), if the peak of the resonance frequency can be clearly determined depending on the target concrete structure or the measuring instrument, the measurement may be performed with a high-frequency acoustic pulse. In this embodiment, the impact similar sound is a short pulse sound, but the FFT analyzer deletes the signal waveform of the emitted sound as a continuous sound, and analyzes the sound propagated inside the concrete structure. You may do so. Or
Extremely high directivity of the speaker 11 and the microphone 16,
If the striking similar sound from the speaker 11 is not directly transmitted to the microphone 16, the striking similar sound from the speaker 11 can be changed to a continuous sound instead of a pulse.

[0031]

As described above, according to the first aspect of the present invention, there is provided an apparatus for measuring deterioration of a reinforced concrete structure by vibrating the concrete structure and measuring a resonance frequency. Sound means capable of exciting the sound is provided at a predetermined distance from the concrete surface to be measured, and sound detecting means for detecting sound transmitted from the sound means into the concrete structure is provided at a predetermined distance from the concrete surface to be measured. Because it is a deterioration measuring device for reinforced concrete structures that is provided while being held, the effect that the working efficiency can be significantly improved compared to a device that hits and shakes the concrete structure with an impact hammer manually is obtained. Also, the method of hitting the concrete surface by hand was not constant and the data fluctuated, but it was said that vibration could be applied under the same constant conditions. Effect is obtained, further, there is also an effect that the handling because the acoustic means and the sound detecting means is separated from the concrete structure becomes simple. According to the second aspect of the present invention, in a device for measuring deterioration of a reinforced concrete structure for measuring a resonance frequency by vibrating a concrete structure, the device moves while maintaining a certain distance from a concrete surface to be measured. Since the moving means is provided with sound means capable of vibrating the concrete structure, the moving means is a deterioration measuring device for a reinforced concrete structure provided with a sound detecting means arranged integrally with the sound means. In addition to the effect according to the first aspect of the present invention, since the acoustic means and the sound detecting means can be integrated, the effect that the measuring instrument can be made compact can be obtained, and the moving means can be kept constant from the concrete surface to be measured. Moving at a constant distance, the vibration can always be applied under the same conditions, and the effect of automatically measuring the deterioration of a wide range of concrete structures is obtained. That.

[Brief description of the drawings]

FIG. 1 is an explanatory view schematically illustrating a system of a measuring device used in a method for measuring deterioration of a concrete structure according to one embodiment of the present invention.

FIG. 2 (a) shows another embodiment of the sound means and sound detection means of the present invention, and FIG. 2 (b) shows another embodiment.

FIG. 3 is a perspective view of a floor panel model of a reinforced concrete structure.

FIG. 4 is a spectrum diagram of a resonance frequency of a floor panel model.

FIG. 5 is a spectrum diagram of a resonance frequency of a sound part of a reinforced concrete structure to be measured.

FIG. 6 is a spectrum diagram of a resonance frequency of a free lime portion of a reinforced concrete structure to be measured.

FIG. 7 is a spectrum diagram of a resonance frequency of a crack portion of a reinforced concrete structure to be measured.

FIG. 8 shows the natural potential and 5 kHz in the method for measuring the natural potential.
A graph showing the relationship between the shear wave phase velocity at the peak of the shear wave resonance frequency in the vicinity,

FIG. 9 shows the natural potential and 5 kHz in the method of measuring the natural potential.
It is the figure which showed as Table 1 the relationship of the phase velocity of the shear wave at the peak of the resonance frequency of the shear wave in the vicinity.

[Explanation of symbols]

 10: Reinforced concrete structure to be measured 101: Reinforced concrete floor plate model 11: Speaker 111: Cone 12: Moving trolley 13: Distance sensor 14: Wave signal generator for striking similar sound 15: FTT analyzer 151: First of FFT analyzer section Channel 152: Second channel 16: Microphone 161: Sound collector 17: Vibration detection signal 18: Amplifier 19: Peak reading device 20: Personal computer 21: Printer

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Yoshio Moriai 2-28-27 Kuromatsu, Izumi-ku, Sendai City, Miyagi Prefecture (72) Inventor Yoshiyasu Matsumura 5-9-9, Nagamachi, Tashiro-ku, Sendai City, Miyagi Prefecture 10-1003 F-term (Reference) 2G047 AA10 BA04 BC04 CA01 CB02 GG12

Claims (2)

[Claims] An apparatus for measuring the resonance frequency of a reinforced concrete structure by vibrating the concrete structure to measure the deterioration of the reinforced concrete structure, wherein an acoustic means capable of vibrating the concrete structure is maintained at a predetermined distance from the concrete surface to be measured. Provided
An apparatus for measuring deterioration of a reinforced concrete structure, wherein sound detection means for detecting sound transmitted from the acoustic means to the inside of the concrete structure is provided at a predetermined distance from the concrete surface to be measured. 2. An apparatus for measuring a resonance frequency by vibrating a concrete structure to measure deterioration of a reinforced concrete structure, comprising: moving means for moving the concrete structure at a predetermined distance from a concrete surface to be measured; And sound means capable of vibrating the concrete structure is provided, and sound moving means for detecting sound propagated from the sound means into the concrete structure is provided near the sound device. Characteristic degradation measuring device for reinforced concrete structures.