JPH1172481A - Detector and method for detecting fracture of reinforcing bar - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fracture detector for reinforcing bar which can detect the fracturing position of a reinforcing bar in a CP(concrete pole) with accuracy. SOLUTION: A fracture detector for reinforcing bar is provided with a reinforcing bar locating sensor which locates reinforcing bars in a concrete pole, two fracturing position detecting sensors A and B which detect the fracturing position of a reinforcing bar, a sensor moving guide 6 which positions the sensors A and B in accordance with the arranging pitch of the spiral hoop reinforcement in the concrete pole and the arranging interval of the main reinforcement in the pole, a main body 4 incorporating an arithmetic section which specifies the fracturing position of the reinforcing bar from the difference between the signals received by means of the sensors A and B, and a display section 20 which displays the fracture of the reinforcing bar when the fracture is detected.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for detecting a rupture of a reinforcing bar in a concrete pole using an eddy current flaw detection method.
The present invention relates to a method for accurately detecting a reinforcing bar break position using two sensors.

[0002]

2. Description of the Related Art In order to lay telephone cables and power cables in homes, concrete poles (hereinafter referred to as C) are provided along roads.
P), and telephone cables are laid on the CP. As shown in FIG.
1, a pulling force 8 by a cable 7 laid is always used in a loaded state. The pulling forces 8 from both sides are balanced so that they are the same. The situation where the pulling forces 8 from both sides cancel each other is called an equilibrium state.

On the other hand, as shown in FIG.
For example, at an intersection, the laying direction of the cable 7 may bend at a right angle. In this case, a tensile force 8 in one direction is applied to CP1 instead of a balanced tensile force. This force is called an unbalanced load. Generally, in order to cancel the unbalance force, as shown in FIG. 7C, the branch line 9 and the like are installed in a direction opposite to the direction of the unbalance force. However, there may be cases where a branch line cannot be constructed, such as when there is a private house. In this case, an unbalanced load is always applied to CP1.

[0004] Concrete is carbon dioxide in the air,
It changes from alkaline to neutral due to salt content. When the concrete becomes neutral, the reinforcing steel in the concrete is easily corroded. Generally, as the corrosion of reinforcing bars progresses, the diameter of the reinforcing bars decreases, and the strength of the reinforcing bars decreases, leading to fracture. However, when an unbalanced load is applied to the CP, a break may occur suddenly before the thickness of the reinforcing bar progresses. This phenomenon is called stress corrosion cracking. Stress corrosion cracking is a type of delayed fracture and is very dangerous because it occurs one day without warning. Although there is a slight accident that the CP breaks due to the stress corrosion cracking, it has occurred. Therefore, a technique for non-destructively detecting the breakage of the rebar included in the CP is desired.

As a method for detecting corrosion of a reinforcing bar, there is a self potential method. However, in the self-potential method, it is necessary to remove concrete at only one location to expose the reinforcing bar. For this reason, the workability is deteriorated, and after the measurement is completed, the shaved concrete is repaired. However, since there is a possibility that salt and the like in the air may enter from the repaired portion, this is not an actual measuring method.

As shown in FIGS. 8A and 8B, there is an eddy current flaw detection method as a method for detecting a flaw 11 on the surface of a metal plate 10. Reference numeral 12 denotes a sensor moving direction. Generally, it is considered that in the eddy current flaw detection method, the measurement accuracy is improved by minimizing the distance between the surface of the inspection object and the eddy current sensor to improve the inspection accuracy. The distance between the eddy current sensor and the surface of the inspection object is called lift-off. Since concrete has a magnetic permeability equal to that of air (that is, it is considered to have a magnetic permeability of 1), when the eddy current flaw detection method is applied, lift-off, that is, the distance between the eddy current sensor surface and the reinforcing bar becomes 20 mm or more. For this reason, the magnetic field transmitted from the eddy current flaw detection sensor does not reach the reinforcing bar in currently marketed devices, and it is difficult to detect the reinforcing bar itself.

[0007]

As described above, in the conventional eddy current flaw detection method, it is difficult to detect a flaw on the metal surface when the lift-off is 20 mm. Further, even if the above problem is solved, as shown in FIG. 9A, the CP1 has the main reinforcing bar 101 in the longitudinal direction, and the spiral reinforcing bar 201 exists so as to surround the main reinforcing bar 101. . Main rebar 101
If only the position of the break 5 can be detected relatively easily by the eddy current flaw detection method as shown in FIG. 10B by moving the surface of the CP1 as shown in FIG. 10A. But,
The signal obtained by the eddy current flaw detection method by the spiral reinforcing bar 201 of FIG. 9 (a) is, as shown in FIG.
03. In particular, when the position of the break 5 of the main reinforcing bar 101 is close to the spiral reinforcing bar 201, it is very difficult to separate both signals.

The present invention has been made in view of such a problem, and an object of the present invention is to provide a rebar break detector and a rebar break detection method capable of accurately detecting a break position of a reinforcing bar in a CP. Is to provide.

[0009]

In order to achieve the above object, a reinforcing bar breakage detector according to a first aspect of the present invention includes a reinforcing bar exploring sensor for detecting the position of a reinforcing bar on a concrete pole,
Means for detecting two rebar break position detecting sensors for detecting a rebar break position, and means for installing the rebar break position detecting sensor in accordance with the pitch of the spiral rebar in the concrete pole and the rebar spacing of the main rebar. The apparatus includes a main body having a built-in operation unit for specifying a break position of a reinforcing bar based on a difference between signals received by the two reinforcing bar break position detecting sensors, and a display unit for displaying the break of the reinforcing bar when a break is detected.

[0010] Further, a reinforcing bar rupture detector according to a second aspect of the present invention is the reinforcing bar rupture detector according to the first aspect of the present invention, wherein the reinforcing bar exploring sensor comprises a transmitting coil, a receiving coil, and a rod-shaped core. Is 800 Hz to 20 kHz.

[0011] A reinforcing bar rupture detector according to a third aspect of the present invention is the rebar rupture detector according to the first aspect, wherein the reinforcing bar rupture position detecting sensor comprises one transmitting coil, two receiving coils, and an iron core. And the transmission frequency of the transmission coil is 800 Hz to 20 kHz.

[0012] In addition, a method of detecting a reinforcing-bar rupture according to a fourth aspect of the present invention includes a first step of specifying the positions of a main reinforcing bar and a spiral reinforcing bar of a concrete pole, and installing a sensor moving guide parallel to the spiral reinforcing bar. A second step of installing two rebar breakage position detection sensors on the main rebar, and a third step of moving the two rebar breakage position detection sensors on the main rebar and in the height direction of the concrete pole. Fourth step of calculating the signal transmitted from the two reinforcing bar breakage position detection sensors by the arithmetic unit of the main body and calculating the difference, and the case where the amplitude value of the obtained difference signal exceeds a predetermined value. The method includes a fifth step of determining whether a reinforcing bar has fractured and a sixth step of displaying a reinforcing bar fracture.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In the present embodiment, in order to solve the above-mentioned problems, a method commonly used as an eddy current flaw detection method is described.
800 Hz to 2 lower than 0 kHz to 100 kHz
By using a relatively low measurement frequency near 0 kHz, the magnetic field transmitted from the eddy current detection sensor can reach the rebar, and by using two eddy current detection sensors, the rebar breaking position can be accurately determined. It is something that is often detected.

Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings. FIG. 1 is a flowchart for explaining an embodiment of the present invention. "Step 1" In this step, the positions of the main reinforcing bar and the spiral reinforcing bar of the CP are searched for using an I-type sensor as shown in FIG. The transmission frequency of I-type sensor is 800Hz ~ 20kHz
Set near z. The I-type sensor is a sensor for simply confirming the presence / absence of a metal object.
And a receiving coil 15 and a rod-shaped metal iron core 17.

FIG. 2B shows the principle of measurement. An eddy current is generated in the metal iron core 17 by the magnetic field 16 generated from the transmission coil 14. Then, the eddy current causes the magnetic field 1
6 occurs again. The magnetic field 16 is received by the receiving coil 15 of the I-type sensor. From transmitting coil 14 to receiving coil 1
The current generated by the magnetic field directly entering 5 is adjusted to zero before measurement.

In the actual measurement, as shown in FIG. 2B, the longitudinal direction of the I-type sensor 13 is installed perpendicular to the CP1 and is moved up, down, left and right. I-type sensor 1
FIG. 2 (c) shows the waveform obtained by step 3. When the amplitude value of the waveform from the reinforcing bar exceeds a certain value V1, the operator is notified by a buzzer or the like. With this method, the positions of the main reinforcing bar and the spiral reinforcing bar of CP1 can be determined.

[Steps 2 and 3] Next, as shown in FIG. 3, the sensor moving guide 6 is set so as to be parallel to the spiral reinforcing bar 201. The eddy current flaw detection sensors A (3) and B (2) are attached to the installed sensor movement guide 6. Sensors A (3) and B (2) are main rebars 101 and 102
Installed directly above The sensors A (3) and B (2) are connected to a main body 4 having a built-in calculation unit for calculating a difference between signals received by the two sensors and specifying a break position of a reinforcing bar.
The main body 4 has a display section 20 for displaying the breakage of the reinforcing bar.

FIGS. 4 (a) and 4 (b) are views showing the installation pattern when CP1 is viewed from directly above. As shown in FIG. 4A, the sensor A (3) is placed just above the main reinforcing bar 101,
The sensor B (2) is arranged directly above the sensor B (02). FIG.
As shown in (b), the sensor A
In (3), the sensor B (2) is arranged right above the reinforcing bar 103.

FIG. 5 shows the sensors A (3) and B
It is a figure which shows the structure of (2), It consists of the transmission coil 14, two reception coils a and b (15), and the iron core 17. FIG.
The transmission frequency of the transmission coil 14 is 800 Hz to 20 kHz
It is. Since the two receiving coils a and b (15) are differentially connected, the output voltage is 0 if the sensor does not move. Voltage is generated when the sensor moves and the transmission / reception balance is lost. By detecting the change in the voltage, the breaking position of the reinforcing bar is detected.

[Steps 4 and 5] In this state, the sensors A (3) and B (2) are simultaneously moved in the direction of arrow 12 in FIG. The sensors A (3) and B (2) are connected to the main reinforcing bars 101,1.
6 (a) and 6 (b) show waveforms obtained by setting the sensor A (3) and B (2) on the sensor 02.
Here, it is assumed that the main reinforcing bar 101 is broken. FIG.
FIG. 6A shows a waveform obtained by the sensor A (3), and FIG.
(B) is a waveform obtained by the sensor B (2). FIG.
In (a), since the main reinforcing bar 101 has a break, a waveform in which the waveforms 301 and 302 of the spiral reinforcing bar and the waveform 303 of the main reinforcing bar overlap are observed. Since there is no break in the main reinforcing bar 102, as shown in FIG.
Only waveforms 301 and 302 from 1 can be observed.

Therefore, the difference between the waveforms of FIGS. 6A and 6B is calculated. Then, the spiral reinforcing bar 201 common to both
Are removed, leaving only the waveform 303 from break 5. Thereby, the break 5 of the main reinforcing bar 101 can be detected with high accuracy. Further, as shown in FIG. 6C, when the value of the amplitude value of the waveform obtained as a result of the difference processing is larger than a certain value V2, a means such as a buzzer or a lamp is used. Notify or display the presence of the break to the operator.

[Steps 6 and 7] If the main reinforcing bar 102 is also broken and the distance between the spiral reinforcing bar 201 of each of the main reinforcing bars 101 and 102 and the breaking position is the same, the break cannot be detected. Therefore, the sensor B (2) is moved to another main reinforcing bar by the sensor moving guide 6, and the same measurement is performed. Since the probability that the distance between the spiral reinforcing bar 201 and the breaking position 5 in the main reinforcing bar and that of the main reinforcing bar 101 is the same is considered to be small, the main reinforcing bar 10
Even when 2 has broken, the breaking position can be measured. That is, if a combination of two main rebars is selected from all the main rebars and the measurement is performed a plurality of times using the sensor movement guide, the detection performance is further improved.

[0023]

According to the present invention, the following effects can be obtained. (1) Since the rebar rupture of the CP can be accurately detected, the CP
Accidents due to collapse can be prevented beforehand.

(2) When the worker goes up and down on the CP to perform various operations, if the measurement is performed in advance by this method, it is possible to prevent the CP from collapsing at the time of going up and down and save human lives. it can.

[Brief description of the drawings]

FIG. 1 is a flowchart for explaining an embodiment of the present invention.

FIG. 2A is a diagram showing a configuration of an I-type sensor,
(B) is a diagram for explaining the principle of measurement, (c)
FIG. 4 is a diagram showing a waveform obtained by measurement.

FIG. 3 is a diagram for explaining a reinforcing bar rupture detection method according to the present embodiment.

FIG. 4 is a diagram showing a pattern of installation when the CP is viewed from directly above.

FIG. 5 is a diagram showing a structure of sensors A and B.

6A and 6B are diagrams showing waveforms obtained by installing and moving sensors A and B on a main reinforcing bar, and FIG. 6C is a diagram showing a result of a difference between two waveforms. FIG.

FIG. 7 is a diagram showing a configuration when a telephone cable or the like is laid on a concrete pole.

FIG. 8 is a diagram for explaining an eddy current flaw detection method for detecting a flaw on a metal surface.

FIG. 9 is a diagram for explaining a problem of a conventional method of detecting a reinforcing bar rupture.

FIG. 10 is a diagram for explaining an eddy current flaw detection method when only a main reinforcing bar is present.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Concrete pole (CP), 2 ... Sensor B, 3 ... Sensor A, 4 ... Eddy current flaw detector main body, 5 ... Rebar breakage position, 6 ... Sensor movement guide, 7 ... Cable, 8 ... Tension force, 9 ... Branch line Reference numeral 10: metal plate, 11: scratch, 12: sensor moving direction, 13: I-type sensor, 14: transmission coil, 15: reception coil, 16: magnetic field, 20: display unit, 101: main reinforcing bar, 102: main reinforcing bar Reference numeral 201: spiral rebar, 300: waveform from spiral rebar, 302: waveform from spiral rebar, 303: waveform from fracture of main rebar

Claims (4)

[Claims] 1. A reinforcing bar exploring sensor for detecting the position of a reinforcing bar of a concrete pole, two reinforcing bar breaking position detecting sensors for detecting a breaking position of a reinforcing bar, a pitch of a spiral reinforcing bar in the concrete pole and a main reinforcing bar. Means for installing the reinforcing bar break position detecting sensor in accordance with the arrangement interval of the reinforcing bars, and a main body having a built-in arithmetic unit for specifying the reinforcing bar break position based on a difference between signals received by the two reinforcing bar break position detecting sensors; A display unit for displaying a break of a reinforcing bar at the time of detection, and a reinforcing bar break detector for a concrete pole. 2. The rebar exploration sensor according to claim 1, comprising a transmission coil, a reception coil, and a rod-shaped iron core.
2. The detector according to claim 1, wherein the frequency is 0 Hz to 20 kHz. 3. The sensor according to claim 1, wherein the rebar breakage position detecting sensor includes one transmission coil, two reception coils, and an iron core, and a transmission frequency of the transmission coil is 800 Hz to 20 kHz. Rebar break detector for concrete pole. 4. A first step of specifying the positions of the main rebar and the spiral rebar of the concrete pole, and a sensor moving guide is installed in parallel with the spiral rebar, and two sensors for detecting the rebar break position are provided on the main rebar. The second step of installation, the third step of moving the two reinforcing bar rupture position detection sensors on the main reinforcing bar and in the height direction of the concrete pole, and the two steps have been transmitted from the two reinforcing bar rupture position detection sensors. A fourth step of calculating the signal in the arithmetic unit of the main body and obtaining the difference, a fifth step of determining the breakage of the rebar when the amplitude value of the obtained difference signal exceeds a predetermined value, And a sixth step of displaying a rupture of the reinforcing bar.