JP2007003475A - Method and device for concrete placement inspection - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method and a device for a concrete placement inspection that detect a concrete packing state and can simultaneously inspect a concrete setting state, a strength after completion of setting concrete, and a defect such as a crack. <P>SOLUTION: An oscillation signal of which frequency varies with time in the predetermined range is impressed to a sensor element 10A in placing the concrete. An oscillating frequency characteristic variation when the concrete comes into contact with the sensor element 10A is detected and the packing state of the concrete is determined. After the placement, the oscillation signal of a contact frequency is impressed to the sensor element 10A to generate mechanical vibration. A received signal of which elastic wave propagating in the concrete by mechanical vibration is detected is taken out by a sensor element 10B, and phase difference between the oscillation signal and the received signal is determined. The elastic wave speed is determined based on the phase difference and the distance between the sensor elements 10A and 10B, the setting and strength of the concrete is determined based on the determined elastic wave speed, and the defect including the crack is determined based on the phase difference. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a concrete placement inspection method and a concrete placement inspection apparatus for inspecting a concrete filling condition when concrete is placed in a formwork, and setting (starting and closing) after filling, and strength and defects after completion. About.

  2. Description of the Related Art Conventionally, a reinforced concrete structure for construction and civil engineering has been provided with a method in which a reinforcing bar is placed inside a mold and filled with fresh concrete. In recent years, the shape of the formwork has become complicated due to diversification of design, etc., and there is a method for easily detecting whether the concrete is correctly filled up to the end of the complicated shape by nondestructive inspection. Yes (see, for example, Patent Document 1).

  Further, as a method for measuring the setting of concrete after placing, there is a method in which a sample is taken out from the concrete before placing and is applied to an inspection device such as a hydraulic lowering bigger needle device to manage the setting process.

Also, as a method of detecting the strength of the concrete after setting (after completion) after placing, ultrasonic waves are transmitted to the concrete, and the ultrasonic waves are received at a point away from the transmission point to propagate the ultrasonic waves. There is one that measures time, obtains the sound velocity distribution in the concrete based on the measured propagation time and the position of each transmission / reception point, and estimates the strength distribution of the concrete based on the obtained sound velocity distribution (sound velocity method. For example, Patent Document 2). Other intensity detection methods include the following.
・ Repulsion strength method (Schmidt Hammer method)
・ Compressive strength method (JIS A 1108)

JP 2003-202328 A JP 2003-28844 A

However, the conventional concrete placement inspection methods have the following problems.
(1) The filling detection method disclosed in Patent Document 1 is advantageous in that it is possible to obtain information filled with concrete in real time. Defects such as strength and cracks of the concrete afterwards cannot be inspected.

(2) In the method of measuring the setting of the placed concrete, the sample is taken out from the concrete before placing and the process is managed by an inspection device such as a hydraulic pressure drop-out bigger needle device. It is not possible to directly measure the condensation.

(3) In the method of inspecting the strength of concrete after termination disclosed in Patent Document 2, in addition to the cost of the apparatus, since the measurement is performed from the outside of the structure, the influence of the shape of the structure and the influence of the reinforcing bar Therefore, high-precision measurement results cannot be obtained. In the rebound strength method, the measurement site is limited to the concrete surface layer, and the inside of the concrete cannot be inspected. Furthermore, in the method of inspecting the strength of concrete after completion by the compressive strength method (JIS A 1108), since the sample is cored from the structure and measured, it takes time to implement and repair after inspection is necessary. .

  The present invention has been made in view of such circumstances, and it is possible to obtain a concrete filling state in real time, and to inspect a setting state of concrete after placing, and a defect including strength and cracking after completion. An object of the present invention is to provide a concrete placement inspection method and a concrete placement inspection apparatus that can be used.

The above object is achieved by the following configuration.
(1) A concrete placement inspection method for inspecting defects including congealing, strength, and cracking of concrete after placement in a mold, comprising 2 sensor elements capable of reversibly converting electrical energy and mechanical energy. At least one set is used as an individual set, these are spaced apart in the mold, and after placing the concrete in the mold, an oscillation signal having a constant frequency is applied to one of the two sensor elements. A mechanical vibration is generated, and a vibration receiving signal in which an elastic wave propagating in the concrete is detected by the mechanical vibration of the one sensor element is extracted from the other sensor element, and the level of the oscillation signal and the vibration receiving signal is extracted. The phase difference is obtained, the velocity of the elastic wave is obtained based on the obtained phase difference and the distance between the two sensor elements, the setting and strength of the concrete are determined based on the obtained velocity, and further obtained. A defect including a crack of the concrete is determined from the measured phase difference.

(2) A concrete placement inspection method for inspecting the filling condition of the placed concrete in the formwork and the defects including congealing, strength and cracking of the concrete after filling, reversibly converting electrical energy and mechanical energy. At least one set of two possible sensor elements is used, and these are separated from each other in a mold, and when placing concrete into the mold, one of the two sensor elements is predetermined. An oscillation signal whose frequency changes over time in a range is applied, and the vibration frequency characteristic change when the sensor element comes into contact with the concrete is detected, and the filling state of the concrete in the mold is determined. After the concrete is placed in the formwork, an oscillation signal having a constant frequency is applied to one of the two sensor elements to generate mechanical vibration, From the sensor element, a vibration receiving signal that detects an elastic wave propagating in the concrete due to mechanical vibration of the one sensor element is taken out, a phase difference between the oscillation signal and the vibration receiving signal is obtained, and the obtained phase difference and Defects including cracks in the concrete based on the phase difference obtained by determining the velocity of the elastic wave based on the distance between the two sensor elements, determining the setting and strength of the concrete based on the obtained velocity. It is characterized by determining.

(3) A concrete placement inspection device for inspecting defects including congealing, strength and cracking of concrete after being placed in a mold, a sensor element capable of reversibly converting electrical energy and mechanical energy; A mounting means for mounting the sensor elements in a form for placing concrete by placing at least one set of the sensor elements apart from each other, and after placing the concrete in the form, An oscillating means for applying an oscillation signal having a constant frequency to one of the sensor elements; and an elastic wave propagating in the concrete by mechanical vibration generated by applying the oscillation signal to the one sensor element. A vibration receiving means for receiving vibration by the sensor element, a phase difference between the oscillation signal of the oscillation means and the vibration receiving signal of the vibration receiving means is obtained, and the obtained phase difference and the distance between the two sensor elements are obtained. Based on the above, the velocity of the elastic wave is determined, the setting and strength of the concrete are determined based on the determined velocity, and further, the setting / strength / defect is determined from the obtained phase difference to determine a defect including a crack in the concrete. Determining means.

(4) In the concrete placement inspection apparatus according to (3), when the concrete is placed in the mold, the oscillating means changes the frequency over time within a predetermined range in the one sensor element. While the oscillation signal is applied to the one sensor element, the vibration frequency characteristic change when the sensor element comes into contact with the concrete is detected. It is provided with the filling condition determination means which determines the filling condition of the said concrete.

(5) In the concrete placement inspection apparatus according to the above (3) or (4), the two sensor elements are separated from each other and arranged opposite to each other.

(6) The concrete placement inspection apparatus according to any one of (3) to (5), wherein the sensor element includes piezoelectric ceramics.

  In the concrete placement inspection method described in the above (1), it is possible to inspect the concrete setting condition after placement in the mold, and the defects including strength and cracks after completion.

  In the concrete placement inspection method described in (2) above, in addition to the concrete filling status when placing concrete into the formwork, after the placement, the setting of the cast concrete itself (starting and closing), Furthermore, it is possible to inspect defects including cracked concrete strength and cracks.

  In the concrete placement inspection apparatus according to the above (3), after placing concrete in the mold, an oscillation signal having a constant frequency is applied to one sensor element to generate mechanical vibration, and the other sensor element From the vibration signal, the vibration signal that has detected the elastic wave propagating in the concrete due to the mechanical vibration of one sensor element is taken out, the phase difference between the oscillation signal and the vibration signal is obtained, and the obtained phase difference between the two sensor elements is calculated. The velocity of the elastic wave is determined based on the distance, the setting and strength of the concrete are determined based on the determined velocity, and the defects including concrete cracks are determined from the calculated phase difference. It is possible to inspect the setting condition of concrete after placing, and the defects including strength and cracks after completion.

  In the concrete placement inspection apparatus described in (4) above, in addition to the setting of the concrete itself (starting and closing) after placement, and the defect situation including the strength and cracks of the concrete after completion, The concrete filling condition can be inspected when placing concrete.

  In the concrete placement inspection apparatus described in (5) above, since the two sensor elements are arranged to face each other, the situation between the sensor elements can be reliably inspected.

  In the concrete placement inspection apparatus described in the above (6), since the sensor element including piezoelectric ceramics is provided, the apparatus can be made inexpensive and highly accurate inspection can be performed.

  DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, preferred embodiments for carrying out the invention will be described in detail with reference to the drawings.

FIG. 1 is a block diagram showing a schematic configuration of a concrete placing inspection apparatus according to an embodiment of the present invention.
In this figure, the concrete placement inspection apparatus of the present embodiment has a filling detection function for detecting the filling state of concrete placed in the mold and the setting of the concrete after placing in the mold (first start, 2 sensor elements 10A that are used in a separated arrangement in order to realize these functions, and have the function of detecting the condition and the defects such as the strength and cracks of the concrete after completion. And 10B, a filling detection circuit 12, an oscillation circuit 13, a switching circuit 14, a vibration receiving circuit 15, a transmission arithmetic circuit 16, and a condensation / strength / defect detection information circuit 17.

Of the two sensor elements 10A and 10B, the sensor element 10A is used for filling detection, and the sensor element 10B is used for condensation, strength and defect detection. As shown in FIG. 2, the piezoelectric ceramic 101, the metal plate 102 that fixes the piezoelectric ceramic 101, the case 103 that accommodates the piezoelectric ceramic 101 together with the metal plate 102, and the case 103 are fixed. Wiring is made between the pedestal 104, the pedestal 104 and the metal plate 102 accommodated in the case 103 and preventing the concrete from entering the case 103, and the piezoelectric ceramic 101 and the metal plate 102. And a cable 106. In particular, the case 103 is formed in a size that can maintain a space around the piezoelectric ceramic 101.
As shown in FIG. 3, the two sensor elements 10A and 10B are held in a state in which the sensor elements 10A and 10B are spaced apart from each other.
The piezoelectric ceramic 101 can convert an electrical signal into a mechanical signal and vice versa. By using piezoelectric ceramics for the sensor elements 10A and 10B, the device can be manufactured at a low cost and inspection with high detection accuracy can be performed.

  FIG. 4 is a view showing an attachment stay 400 for holding the sensor elements 10A and 10B and an attachment example of the sensor elements 10A and 10B using the attachment stay 400. The mounting stay 400 is configured so that the sensor elements 10A and 10B can be attached to a reinforcing bar or a formwork. 4A shows an attachment stay 400 to which the sensor elements 10A and 10B are attached, FIG. 4B shows an example of attachment of the attachment stay 400 to the reinforcing bar 401, and FIG. 4C shows a type of the attachment stay 400. An example of attachment to the frame 402 is shown.

  As shown in FIG. 5A, the concrete placing inspection apparatus of the present embodiment attaches the sensor elements 10A and 10B between the reinforcing bars with the mounting stay 400 (see FIG. 4B), thereby reinforcing the reinforcing bar 401. The defect 403 formed between the reinforcing bars can be inspected without being affected by the above. Incidentally, as shown in FIG. 5 (b), since the sensor element 500 is conventionally attached to the surface layer of the concrete 30 structure, the detection of the defect 403 formed between the reinforcing bars is affected by the reinforcing bar 401. Can not perform high-precision inspection.

Returning to FIG. 1, the oscillation circuit 13 generates an electrical signal for exciting the sensor element 10A. As shown in FIG. 6, the synchronization signal generator 131, the variable frequency oscillator 132, the amplifier 133, and the like. And is configured.
In the oscillation circuit 13, the synchronization signal generator 131 generates a synchronization signal for repeatedly operating the variable frequency oscillator 132. The variable frequency oscillator 132 generates a sinusoidal electric signal whose frequency continuously changes in a predetermined frequency range (for example, 1 kHz to 20 kHz). In this case, every time a synchronization signal is output from the synchronization signal generator 131, a sine wave signal is repeatedly generated from an initial frequency (for example, 1 kHz). The variable frequency oscillator 132 continuously changes the frequency of an electric signal to be output in a predetermined frequency range when filling is detected, but keeps the frequency constant when detecting condensation, strength, and defect. The amplifier 133 amplifies the sine wave signal from the variable frequency oscillator 132 to a level at which the piezoelectric ceramic 101 (see FIG. 2) of the sensor element 10A can be driven, and outputs the amplified signal as an excitation signal Vr.

  The switching circuit 14 switches the sensor element 10A to either the filling detection circuit 12 side or the transmission arithmetic circuit 16 side for condensation, strength, and defect detection. In the present embodiment, the switching circuit 14 is a manual switching method in which the user manually switches, but it may be switched automatically. That is, when the filling is detected, the operation is switched to the filling detection circuit 12 side, and when the condensation / strength / defect is detected, the operation is switched to the transmission operation circuit 16 side.

  Returning to FIG. 1, the vibration receiving circuit 15 receives the elastic wave 31 (see FIG. 3) generated by the vibration of the sensor element 10 </ b> A and transmitted through the concrete 30 by the sensor element 10 </ b> B. The transfer calculation circuit 16 calculates transfer characteristics (phase difference, transfer function, etc.) of the oscillation signal of the oscillation circuit 13 and the reception signal of the vibration receiving circuit 15 and outputs the calculation result. The condensation / strength / defect detection information circuit 17 includes a display such as a liquid crystal display panel (not shown), and visually displays the result of determining the condensation, strength, and defect from the calculation result of the transfer calculation circuit 16.

  The filling detection circuit 12 is for detecting the filling state of the placed concrete 30 and, as shown in the block diagram of FIG. 6, a resistor 121, a differential amplifier 122, and a four-quadrant analog multiplier 123. And a low-pass filter 124. The resistor 121 is connected in series with the sensor element 10A via the switching circuit 14, and a voltage corresponding to the current flowing through the piezoelectric ceramics 101 of the sensor element 10A is generated at both ends thereof. Since the current flowing through the piezoelectric ceramic 101 changes with a change in frequency, the voltage appearing at both ends of the resistor 121 reflects the frequency characteristics of the piezoelectric ceramic 101. The differential amplifier 122 amplifies the voltage across the resistor 121 and outputs a voltage Vi.

  The 4-quadrant analog multiplier 123 multiplies the excitation signal Vr from the oscillation circuit 13 and the voltage Vi from the differential amplifier 122 to remove the influence of noise on these voltages. The low-pass filter 124 outputs a signal (output voltage Vo) obtained by removing cos (2ωt + α + β) described below from the output signal of the 4-quadrant analog multiplier 123.

  The signal that has passed through the low-pass filter 124 is input to a determination device (not shown), and the filling state of the placed concrete 30 is determined. That is, the determination device (not shown) uses a signal output from the low-pass filter 124 based on the characteristic vibration frequency characteristic when the concrete 30 is not brought into contact with the piezoelectric ceramic 101 of the sensor element 10A. The contact / non-contact of the concrete 30 is determined, and the result (good or bad) is visually displayed. In this case, once the inherent vibration frequency characteristic of the piezoelectric ceramic 101 is set, it is not necessary to reset it except during subsequent maintenance. The unique vibration frequency characteristic of the piezoelectric ceramic 101 is stored in the determination device.

  In the concrete placement inspection apparatus of the present embodiment, as shown in FIG. 3, the sensor elements 10A and 10B are spaced apart from each other in the placed concrete 30 and the sensor element 10A is placed on the sensor element 10A by the oscillation circuit 13. The piezoelectric ceramic 101 is vibrated by applying an electric signal. The vibration due to the vibration is transmitted inside the concrete 30 as an elastic wave 31, and the elastic wave 31 is received by the piezoelectric ceramic 101 of the sensor element 10B.

  Here, the velocity of the elastic wave 31 transmitted through the concrete 30 has a correlation with the strength of the concrete 30. That is, as shown in FIG. 7, in the initial hardening process of the concrete, when the strength of the concrete 30 is small, that is, at the start, the speed of traveling through the concrete 30 is small, and when the strength of the concrete 30 is large, that is, at the end, the concrete 30 The speed of traveling through will increase. From this speed function, the strength of the concrete 30 can be estimated to determine whether the start or the end. Specifically, as shown in the waveform diagram of FIG. 8, the phase difference Δt is obtained from the oscillation waveform and the received waveform by calculation, and the speed is calculated based on the obtained value and the distance between the sensor elements 10A and 10B. Then, the strength of the concrete 30 is estimated, and the start and end are determined. Note that the distance between the sensor elements 10A and 10B arranged to face each other is known.

  On the other hand, when inspecting the strength and defects of the concrete 30 after termination, as in the above case, an electric signal is applied from the oscillation circuit 13 to the sensor element 10A for filling detection to vibrate the piezoelectric ceramic 101. As shown in FIG. 3, the vibration due to the vibration is transmitted as elastic waves 31 in the concrete 30 after termination, and is received by the piezoelectric ceramic 101 of the sensor element 10B for detecting condensation, strength, and defect.

  Here, the velocity of the elastic wave 31 transmitted through the concrete 30 has a correlation with the compressive strength of the concrete 30. That is, as shown in FIG. 9, when the compressive strength of the concrete 30 is low, the speed transmitted through the concrete 30 is small, and when the concrete 30 is high in compressive strength, the speed transmitted through the concrete 30 is increased. The compressive strength of the concrete 30 can be estimated from this speed function. Specifically, as shown in the waveform diagram of FIG. 10, the phase difference Δt1 is obtained by calculation from the oscillation waveform and the received waveform, and the speed is calculated based on the obtained value and the distance between the sensor elements 10A and 10B. Thus, the compressive strength of the concrete 30 is estimated.

  After the termination, when a crack due to secular change or the like occurs between the sensor element 10A and the sensor element 10B as shown in FIG. 11, since there is an air layer 100 due to the crack, there is an oscillation waveform and vibration reception as shown in FIG. The phase difference Δt1 with the waveform is significantly increased. Therefore, in this case, it can be estimated that there is a defect due to cracking.

  Note that the above-described filling detection circuit 12 and a determination device (not shown) constitute a filling state determination unit. The transmission arithmetic circuit 16 and the condensation / strength / defect detection information circuit 17 constitute a condensation / strength / defect determination means.

Next, the operation of the concrete placing inspection apparatus according to the present embodiment will be described.
Here, it is assumed that one of condensation detection processing and compression strength estimation processing is selected by mode switching. Further, it is assumed that the sensor element 10A and the sensor element 10B are arranged in the concrete 30 placed in the mold by the mounting stay 400.

FIG. 13 is a flowchart showing an operation when the mode for performing the condensation detection process is selected after the filling detection process is performed.
First, the inspector operates the switching circuit 14 to connect the sensor element 10A to the filling detection circuit 12 side. After connecting, start inspection. Thereby, a filling detection process is started (step S1301). In this filling detection process, a sine wave signal generated by the variable frequency oscillator 132 of the oscillation circuit 13 is amplified by the amplifier 133 and input to the piezoelectric ceramic 101 of the sensor element 10A as the excitation voltage Vr. Mechanical vibration occurs at. The excitation voltage Vr is also input to the 4-quadrant analog multiplier 123.

  When mechanical vibration is generated in the piezoelectric ceramic 101 of the sensor element 10 </ b> A, a voltage corresponding to the current flowing through the piezoelectric ceramic 101 is generated at both ends of the resistor 121. This voltage is amplified by the differential amplifier 122 and the voltage Vi is output. The voltage Vi and the excitation voltage Vr from the oscillation circuit 13 are multiplied by the 4-quadrant analog multiplier 123. Then, the cos (2ωt + α + β) component is removed from the output by the low-pass filter 124, and the output voltage Vo is obtained.

  This output signal Vo is a signal reflecting the frequency characteristics (amplitude and phase) of the piezoelectric ceramic 101 with respect to the frequency change of the excitation voltage Vr. At this time, if the filler (concrete) is not in contact with the surface of the piezoelectric ceramic 101, a voltage having a peak at a frequency near the natural frequency of the piezoelectric ceramic 101 appears as shown in FIG. When concrete is filled around the piezoelectric ceramic 101, the vibration characteristics of the piezoelectric ceramic 101 change, and the position and magnitude of the peak voltage change as shown in FIG. The filling state of the concrete 30 can be determined from the change in the peak voltage.

The operation principle will be described using mathematical formulas as follows. here,
Vr = Asin (ωt + α)
Vi = Bsin (ωt + β)
And However, A and B are amplitudes, ωt is a frequency, and α and β are phase shifts.

Vr × Vi = Asin (ωt + α) × Bsin (ωt + β)
= AB [cos (β-α) -cos (2ωt + α + β)] / 2 (1)

  The part of cos (β−α) in the equation (1) is a direct current component that changes in accordance with the phase difference, and includes the amplitude component of the voltage Vi. The portion of cos (2ωt + α + β) is a signal having a frequency twice that of the original excitation voltage Vr and voltage Vi. Since the necessary frequency characteristic information is the amplitude (magnitude) of the voltage Vi, only cos (β−α) in the equation (1) is sufficient.

  Therefore, the component of cos (2ωt + α + β) may be removed by passing through the low-pass filter 124. In this way, frequency characteristics appear in the form of voltage in the output voltage Vo. When concrete 30 is filled in the formwork, the peak frequency and level change, and the situation can be detected.

  After filling detection is started in this way, when filling detection is completed (Yes in step S1302), a condensation detection process is then started (step S1303). In the setting detection process, it is determined whether or not the speed is the initial speed from the speed of the elastic wave 31 transmitted through the concrete 30 (step S1304). In this case, after obtaining the phase difference Δt (see FIG. 8) between the oscillation waveform obtained from the oscillation circuit 13 and the oscillation waveform obtained from the oscillation circuit 15, the velocity of the elastic wave 31 is calculated from the phase difference Δt and the sensor element 10A. 10B, based on the distance between 10B. If the obtained speed is not the initial speed, this process is repeated, and if it is the initial speed, the initial display is performed (step S1305).

When the strength of the concrete 30 is low, that is, at the first start, the speed transmitted through the concrete 30 is low, and when the strength of the concrete 30 is high, that is, at the end, the speed transmitted through the concrete 30 is increased. To do. After the initial display is performed, it is determined whether or not the speed is the end speed (step S1306). If the speed is not the end speed, this process is repeated. If the speed is the end speed, the end display is performed (step S1307).
Since this setting detection process takes time from setting the concrete 30 to setting, the oscillation circuit 13 is periodically operated to repeat vibration reception. After the termination is judged and the termination display is performed, this processing is completed.

Next, FIG. 16 is a flowchart showing an operation when the mode for performing the compression strength estimation process is selected after the filling detection process is performed.
Also in this process, the filling detection process is performed first as in the case of performing the above-described condensation detection process. Since the filling detection process is the same as described above, the description thereof is omitted. That is, steps S1601 and S1602 shown in FIG. 16 are the same processes as steps S1301 and S1302 shown in FIG.
After the filling detection process is performed, the compression strength estimation process is started (step S1603).

  In the compression strength estimation process, it is determined whether or not the phase difference Δt1 (see FIG. 10) between the oscillation waveform obtained from the oscillation circuit 13 and the oscillation waveform from the oscillation circuit 15 is significantly larger than the reference time (step S1604). If it is significantly longer than the time (ie, as shown in FIG. 12), it is estimated that there is a defect due to cracking, and the defect display is performed (step S1605). On the other hand, when the phase difference Δt1 is approximately equal to or less than the reference time, a propagation speed calculation is performed (step S1606). After the propagation velocity calculation is performed, a compression strength estimation table is created and displayed (step S1607).

  As described above, according to the concrete placement inspection apparatus of the present embodiment, the two sensor elements 10A and 10B are provided so as to be opposed to each other in the formwork, and the concrete 30 is placed in the formwork. At the time of installation, an oscillation signal whose frequency changes with time in a predetermined range is applied to the sensor element 10A, and a change in vibration frequency characteristics when the sensor element 10A contacts the concrete 30 is detected, and the concrete 30 in the formwork is detected. Judging the filling status.

  After placing the concrete 30 into the formwork, an oscillation signal having a constant frequency is applied to the sensor element 10A to generate mechanical vibration. From the sensor element 10B, the inside of the concrete 30 is caused by the mechanical vibration of the sensor element 10A. The phase difference between the oscillation signal and the vibration reception signal is obtained by extracting the vibration receiving signal that detected the elastic wave 31 propagating through the wave, and the velocity of the elastic wave 31 is determined based on the obtained phase difference and the distance between the sensor elements 10A and 10B. Based on the obtained speed, the setting and strength of the concrete 30 are determined, and further, a defect including cracks in the concrete 30 is determined from the obtained phase difference.

  As described above, the concrete placement inspection apparatus can detect the filling state of the concrete 30 in the formwork at the time of placing the concrete, and can set the concrete after placement, strength after the termination, and cracks. Including defects can be detected.

  The sensor elements 10A and 10B are not limited to the inside of the concrete 30 but can be inspected even on the surface layer of the concrete 30 by providing the sensor elements 10A and 10B in a portion to be inspected in advance. That is, it is not limited to the inside of the concrete 30, and the surface layer can be inspected freely. Further, by embedding in the concrete 30, there is no need for repair after inspection.

  In the above embodiment, two sensor elements 10A and 10B are used as a set. However, if there are a plurality of locations to be inspected at the same time, it is also possible to use a number of sensor elements corresponding to the number. is there. In this case, it is not necessary to provide a filling status determination means and a setting / strength / defect determination means for each group, and it is only necessary to switch appropriately using a switching means (such as a multiplexer).

  Needless to say, the present invention is not limited to concrete placed in a mold, but can be applied to all cases where a predetermined space is filled with a filler.

It is a block diagram which shows schematic structure of the concrete placement inspection apparatus which concerns on one embodiment of this invention. It is a figure which shows the structure of the sensor element of FIG. It is a figure which shows the arrangement | positioning relationship in the concrete of the sensor element of FIG. It is a figure which shows the example of attachment to the reinforcing bar and formwork of the attachment stay for attaching the sensor element of FIG. 1, and an attachment stay. It is a figure for demonstrating the case where the attachment stay of FIG. 4 is used, and the case of attachment by a prior art example. It is a block diagram which shows the structure of the filling detection circuit and oscillation circuit of FIG. It is a figure which shows the relationship between the intensity | strength of concrete, and the speed of an elastic wave. It is a figure which shows the signal waveform between the sensor elements in concrete. It is a figure which shows the relationship between the compressive strength of concrete, and the velocity of an elastic wave. It is a figure which shows the signal waveform between the sensor elements in concrete. It is a figure which shows the state which has an air layer in concrete. It is a figure which shows the signal waveform between sensor elements in case an air layer exists in concrete. It is a flowchart for demonstrating the filling detection process and setting detection process of the concrete placement inspection apparatus of FIG. It is an example of the measurement result of the concrete placement inspection apparatus of FIG. 1, and is an output voltage waveform diagram when there is no concrete in the mold. It is an example of the measurement result of the concrete placement inspection apparatus of FIG. 1, and is an output voltage waveform diagram when there is concrete in the mold. It is a flowchart for demonstrating the filling detection process and compressive strength estimation process of the concrete placement inspection apparatus of FIG.

Explanation of symbols

10A, 10B Sensor element 12 Filling detection circuit 13 Oscillation circuit 14 Switching circuit 15 Vibration receiving circuit 16 Transmission arithmetic circuit 17 Condensation / strength / defect detection information circuit 30 Concrete 31 Elastic wave 100 Air layer 101 Piezoelectric ceramics 102 Metal plate 103 Case 104 Base 105 Sealing material 106 Cable 121 Resistance 122 Differential amplifier 123 Four-quadrant analog multiplier 124 Low pass filter 131 Synchronization signal generator 132 Variable frequency oscillator 133 Amplifier 400 Mounting stay 401 Reinforcing bar 402 Formwork 403 Defect

Claims (6)

Using at least one pair of sensor elements capable of reversibly converting electrical energy and mechanical energy as a set, and separating them in a mold,
After placing the concrete in the mold, an oscillation signal having a constant frequency is applied to one of the two sensor elements to generate mechanical vibration, and the other sensor element mechanically transmits the one sensor element. A vibration receiving signal that detects an elastic wave propagating in the concrete by vibration is taken out, a phase difference between the oscillation signal and the vibration receiving signal is obtained, and based on the obtained phase difference and a distance between the two sensor elements. A concrete placement inspection characterized by determining the velocity of the elastic wave, determining the setting and strength of the concrete based on the determined velocity, and determining a defect including a crack of the concrete from the calculated phase difference. Method. Using at least one pair of sensor elements capable of reversibly converting electrical energy and mechanical energy as a set, and separating them in a mold,
When placing concrete into the mold, an oscillation signal whose frequency changes over time within a predetermined range is applied to one of the two sensor elements, and the sensor element is in contact with the concrete. Detecting the vibration frequency characteristic change, determining the filling state of the concrete in the mold,
After placing the concrete into the formwork, an oscillation signal having a constant frequency is applied to one of the two sensor elements to generate mechanical vibration, and the other sensor element receives the one sensor element. Taking out a vibration receiving signal in which an elastic wave propagating in the concrete is detected by mechanical vibration, obtaining a phase difference between the oscillation signal and the vibration receiving signal, and obtaining the phase difference and a distance between the two sensor elements The concrete is characterized in that the velocity of the elastic wave is obtained based on the above, the setting and strength of the concrete is judged based on the obtained velocity, and the defect including cracks of the concrete is judged from the obtained phase difference. Placement inspection method. A sensor element capable of reversibly converting electrical energy and mechanical energy;
A mounting means for mounting the sensor elements in a form in which concrete is placed with at least one set of the sensor elements spaced apart from each other.
An oscillating means for applying an oscillation signal having a constant frequency to one of the two sensor elements after placing the concrete in the mold;
Vibration receiving means for receiving an elastic wave propagating in the concrete by mechanical vibration generated by applying an oscillation signal to the one sensor element by the other sensor element;
The phase difference between the oscillation signal of the oscillation means and the vibration reception signal of the vibration receiving means is obtained, the velocity of the elastic wave is obtained based on the obtained phase difference and the distance between the two sensor elements, and based on the obtained velocity. Setting, strength and defect determination means for determining the setting and strength of the concrete, and further determining defects including cracks in the concrete from the obtained phase difference,
A concrete placement inspection apparatus comprising: The oscillating means applies an oscillating signal whose frequency changes over time within a predetermined range to the one sensor element when placing concrete into the mold,
While the oscillation signal is applied to the one sensor element, the vibration frequency characteristic change when the sensor element comes into contact with the concrete is detected to determine the filling state of the concrete in the mold The concrete placement inspection apparatus according to claim 3, further comprising a filling state determination unit.   The concrete placement inspection apparatus according to claim 3, wherein the two sensor elements are separated from each other and disposed opposite to each other.   The concrete placement inspection apparatus according to claim 3, wherein the sensor element includes piezoelectric ceramics.

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