KR101600813B1 - Estimating methode for the status of bar steel arrangement in the concrete - Google Patents

Abstract

The present invention relates to a method and apparatus for estimating a state of a reinforced concrete foundation capable of grasping information on a reinforced concrete state without damaging the reinforced concrete.
The method of estimating the state of the steel reinforcing bars according to the present invention is characterized by estimating the state of the reinforcing steel inside the concrete by measuring the change in the response signal of the electric signal applied to a plurality of positions of the surface of the steel reinforcing concrete.

Description

BACKGROUND OF THE INVENTION Field of the Invention < RTI ID = 0.0 > [0001] < / RTI &

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to inspection of reinforced concrete, and more particularly, to a reinforced concrete reinforced concrete And more particularly, to a method and apparatus for estimating the state of an abutment.

Reinforced concrete is a structure that reinforces the strength of concrete by arranging reinforcing bars in the inside of concrete, and is widely used in modern construction due to its durability and moldability.

Reinforced concrete structures are known to have a semi-permanent durability due to their excellent durability. However, in actual reinforced concrete structures, surface cracks, chlorine ions, and carbon dioxide penetrate from the surface to promote the corrosion of the reinforcing bars disposed therein, Fatal decrease.

Measuring the degree of corrosion of reinforcing steel of concrete is essential for checking the safety of the structure, and Korean Patent Registration No. 0867114 and No. 0822369 propose a steel corrosion confirmation device for safety diagnosis of reinforced concrete structures.

The apparatus of Patent No. 0867114 includes an optical fiber tube which is fixedly attached to the outer periphery of the reinforcing bar and deformed outwardly according to the corrosion of the reinforcing bar, a projection frame that emits light from the top of the optical fiber tube to the optical fiber, A light receiving frame, and a control unit for checking the light flux through the optical fiber and notifying the light flux when the light flux changes. According to the above apparatus, when the optical fiber tube fixedly attached to the outer periphery of each of the reinforcing bars is deformed outward due to corrosion of the reinforcing bars, it is possible to detect the difference between the light fluxes sensed by the light transmitting frame and the light receiving frame, .

In addition, the apparatus of Patent No. 0822369 has an inner cap of an elastic material to be fitted so as to enclose the outside of the reinforcing bar, a penetrating hole penetrating the reinforcing bar is formed in the vertical direction, A housing including an outer case which is fitted in the reinforcing bar so as to cover the outside; A pressure sensing means provided between the outer case and the inner cap for measuring expansion of the inner cap, a control unit connected to the pressure sensing means, and an output means connected to the control unit. According to the above apparatus, when rust is generated in the reinforcing bar, the inner cap of the housing expands due to rust, and the control unit senses the corrosion and judges corrosion of the reinforcing bar.

However, all of these devices must be installed inside the concrete, so that they can be installed only when the concrete is laid, but can not be used for diagnosis of the installed concrete.

Therefore, there is a need for a method that can grasp the internal state information of the reinforcing bars such as the position of the reinforcing bars at the surface of the structure without destroying the concrete structure.

Korea Patent No. 0867114 (Name of invention: Rebar Corrosion Checking Device for Safety Diagnosis of Reinforced Concrete Structures) Korean Patent Registration No. 0822369 (Name of invention: Rebar Corrosion Checking Device for Safety Diagnosis of Reinforced Concrete Structures)

SUMMARY OF THE INVENTION Accordingly, the present invention has been made in view of the above problems, and an object of the present invention is to provide a method and an apparatus for estimating the state of a reinforcing bar, which can grasp information about a state of a reinforcing steel in a concrete such as a position where the reinforcing steel is placed without breaking the reinforcing concrete.

According to another aspect of the present invention, there is provided a method of estimating the state of a reinforcing bar, comprising the steps of: estimating a state of a reinforcing steel in a concrete by measuring a response signal change of an electric signal applied to a plurality of positions of the surface of the reinforcing concrete .

In the present invention, it is possible to estimate whether or not the reinforcing bars are placed under the first position at which the response signal is measured by measuring the response signal change at the first position arranged in parallel along the longitudinal direction of the reinforcing concrete.

Further, in the present invention, when the response signal variation is measured over a predetermined interval along the longitudinal direction, by measuring the change in the response signal at the second position arranged at an angle different from the first position at which the change is measured, It is possible to estimate the direction of the steel bar orientation under the second position.

Further, according to the present invention, by measuring the response signal change at the third position arranged at different section distances on the extension line of the first position or the second position estimated to be reinforced immediately below the reinforcing bar, It is possible to estimate either the concrete coating thickness, the concrete resistivity, or the reinforcing resistivity.

Further, in the present invention, it is possible to estimate the state of reinforcing steel reinforcement by analyzing the change of the response signal using the following resistivity estimation model (REM).

Also, in the present invention, the resistivity estimation model (REM) can analyze the change of the response signal by using the apparent resistivity ratio, which represents the ratio of the apparent resistivity of the concrete to that of the concrete alone .

According to another aspect of the present invention, there is provided an apparatus for estimating an attitude of a reinforcing bar, comprising: a contact portion contacting a surface of a reinforced concrete to receive an electric signal and receiving a response signal; And a measurement body for measuring the measurement object.

In the present invention, the contact portion may be a pair of current electrodes for applying a current to the surface of the concrete, and a pair of voltage electrodes for measuring a voltage in accordance with the applied current.

Also, in the present invention, the measurement body may include a display unit for outputting a response signal.

Also, in the present invention, the display unit can compare and output response signals at a plurality of positions where the electrodes are moved and installed.

Also, in the present invention, the display unit may compare and output response signals at a plurality of positions arranged in the longitudinal direction or the width direction of the reinforced concrete according to the distance between the pair of contact portions on which the response signal is received.

Further, the present invention may further comprise a sensor module for detecting a moving distance of the contact portion on the concrete surface.

The method and apparatus for estimating the state of the reinforcing steel according to the present invention have the following advantages.

First, since the present invention can grasp the position of the reinforcement of the reinforcing bars without destroying the reinforcing concrete structure, it can be easily used for the stability test of the building.

Second, the present invention can grasp not only the location of the reinforcing bars in the concrete but also the direction of the reinforcing bars, the diameter of the reinforcing bars, and the thickness of the concrete covering the reinforcing bars, thereby easily analyzing the internal structure of the concrete from the outside.

Third, the present invention can increase the reliability of the estimated values according to the resistivity estimation model (REM) for diagnosing the concrete resistivity and the corrosion of the reinforcing bars by grasping the position of the reinforcement of the reinforcing bars in advance.

1 is a view showing a state of use of a device for estimating the state of an infeed of a reinforcing bar according to the present invention.
2 is a view showing the current and voltage electrode arrangement on the surface of the reinforced concrete.
3 is a block diagram of an apparatus for estimating the state of the steel bar according to the present invention.
4 is a flowchart of a method of estimating the state of the steel bars according to the present invention.
5 is a view for explaining the measurement of a response signal on a reinforced concrete surface in which reinforcing bars are arranged parallel to the width direction (Y axis) of the reinforcing concrete.
FIG. 6 is a graph showing a change in the response signal measured according to FIG.
7 is a view for explaining the measurement of a response signal on a reinforced concrete surface in which reinforcing bars are arranged at a predetermined angle with respect to the width direction of the reinforced concrete (Y axis).
FIG. 8 is a graph showing a change in the response signal at a first position arranged in parallel to the longitudinal direction of the reinforced concrete (X axis) in FIG.
Fig. 9 is a view for explaining a second position arranged at different angles from the first position in Fig. 8 on the concrete surface.
10 is a graph showing the change of the response signal at the second position in Fig.
11 is a view for explaining response signal measurement at a third position arranged at different intervals along the width direction at a position at which the reinforcing bars are assumed to be arranged.
12 is a graph showing a change in the response signal measured at the third position in Fig.
13 is a graph showing the resistance of the samples 1 to 5 according to the distance from the center of the steel bar.
FIG. 14 is a graph for explaining the influence of the thickness of the reinforced concrete coating depending on the distance from the upper portion of the reinforcing bars by the analysis of the resistivity estimation model (REM).
FIG. 15 is a graph for explaining the effect of the rebar diameter on the distance from the upper portion of the reinforcing bar by the analysis of the resistivity estimation model (REM).
16 is a graph showing the change in apparent resistivity at a position 0.05 m away from the upper portion of the reinforcing bar by analysis of the resistivity estimation model (REM).

Hereinafter, the present invention will be described in detail. Prior to this, terms and words used in the present description and claims should not be construed as limited to ordinary or dictionary terms, and the inventor should design the concept of the term appropriately in order to describe its own invention in the best way possible. It should be interpreted as meaning and concept consistent with the technical idea of the present invention.

FIG. 1 is a view showing a state of use of an apparatus for estimating the state of a steel reinforcing bar according to the present invention. (20).

The contact portion 10 is configured to contact the surface of the reinforced concrete 30 to receive an electric signal and receive a response signal. The contact portion 10 includes a pair of current electrodes 12 for applying current to the surface of the concrete 30, And a pair of voltage electrodes 11 for measuring a voltage in accordance with the applied current. 2, the voltage electrode 11 and the current electrode 12 are arranged on the surface of the reinforced concrete 30 in a straight line on the surface of the reinforced concrete 30, The voltage electrode 11 is disposed between the current electrodes 12 disposed outside and the voltage V is measured as the current I is applied.

Referring to FIG. 3 showing a configuration of the measuring body 20, a power supply unit 21, a storage unit 20, A display unit 23, a control unit 24, and a communication unit 25, as shown in Fig.

The power supply unit 21 supplies the current to the current electrode 12 of the contact unit 10. It is preferable that the supplied power source is supplied with the AC power and the response voltage corresponding to the impedance is measured.

The storage unit 22 stores the size and frequency of the current I applied to the surface of the reinforced concrete 30 and the magnitude and frequency of the voltage V as a response signal and the magnitudes and frequencies of the electrodes 11 and 12 on the surface of the reinforced concrete 30. [ And the size (a) of the gap between the electrodes 11 and 12 is stored.

The control unit 24 stores the applied current information and the voltage information, which is a response signal, in the storage unit 22, compares the amount of change in the voltage stored in the storage unit 23, and outputs the comparison result to the display unit 23. The control unit 24 receives the position of the reinforced concrete 30 from which the response signal is received from the sensor module 50 to be described later and stores it in the storage unit 23 and outputs the same to the display unit 23, And output it to the display unit 23 as a three-dimensional screen.

The display unit 23 may be a screen made up of an LCD and an LED so as to output a response signal. The form of the output can be a numerical value of one response signal measured on the surface of the reinforced concrete 30 or a plurality of response signals measured on a plurality of surfaces, which will be described later.

The communication unit 25 is a structure for transmitting and receiving data from the contact unit 10 and the sensor module 50. [

The sensor module 50 is provided for measuring the electrode position and interval size a on the surface of the concrete 30 and may be integrally installed on the electrodes 11 and 12 or installed on the surface of the reinforced concrete 30 . The sensor module 50 may be made of an element such as an optical coupler and connected to the communication unit 24 of the measurement body 20 to transmit the measured data.

FIG. 4 is a flowchart of a method of estimating the state of the steel reinforcing bars according to the present invention, and FIG. 5 is a view for explaining the measurement of response signals on a reinforced concrete surface in which reinforcing bars are arranged parallel to the width direction (Y axis) to be. Hereinafter, a method of estimating the state of the reinforcement of the reinforcing bars of the reinforcing concrete will be described with reference to FIGS.

Voltage and current electrodes are installed on the surface of the reinforced concrete 30 to be measured (S100). As shown in Figs. 2 and 5, the voltage electrode 11 is arranged between the current electrodes 12 disposed on the outside, Respectively.

Then, a current I is applied to the surface of the reinforced concrete 30 from the power supply unit 21 of the measuring main body 20 to measure a voltage V as a response signal (S200). At this time, The magnitude and frequency of the voltage V as the response signal, the electrode position on the surface of the reinforced concrete 30 and the gap size a between the electrodes, And is stored in the storage unit 22.

5, the steps S100 and S200 are repeated along the longitudinal direction of the concrete 30 (X-axis in FIG. 5) to form a plurality of parallel- The response voltage V at the 1 position (L ₁ , L ₂ , ... L _N ) is measured (S 300).

At this time, the position of the moved electrode is measured by the sensor module 50 and is transmitted to the measurement main body 20 together with the response voltage V. When the measurement is completed along the length direction, (V), and outputs the result to the display unit 23. The shape of the output can be listed as a numerical value or output as a graph. FIG. 6 is a graph showing a change in the response voltage V measured according to the first position.

When the response voltage V at the first position L ₁ , L ₂ , ..., L _N is measured, the position where the reinforcing bars 40 are buried is estimated using a resistivity estimation method (REM) can do.

The resistivity estimation model (REM) is a method in which, when a cylindrical model such as a reinforcing bar (40) is buried at a predetermined depth from a concrete surface in a semi-infinite space composed of a medium of resistivity, Is a mathematical model which can theoretically calculate the response voltage V generated by the current I as follows.

Using the above resistivity estimation model (REM), the response voltage () of the apparent resistivity ratio, which is the ratio of the apparent resistivity of concrete combined with the effect of reinforcing steel to the specific resistance of concrete, V) of the reinforcing bar 40 can be estimated.

That is, as shown in FIG. 6, at the N / 2 point of the center of the concrete, the influence of the reinforcing bars 40 is increased to decrease the apparent resistivity ratio, so that the response voltage V is small, 2, N / 2 to N), the influence of the reinforcing bar 40 is minimal, and the apparent resistivity ratio is large, so that the response voltage V is large. Therefore, the roots of the reinforcing bars can be estimated below the point N / 2 where the change in the response voltage V occurs.

In contrast to FIG. 5 in which a reinforcing bar is embedded parallel to the width direction of the concrete (Y axis), FIG. 7 shows a reinforcing bar 40 formed at a predetermined angle _K from the width direction (Y axis) Respectively.

In the case of FIG. 7, due to the reinforcing bars 40 inclined at the time of measuring the response voltage V at the first positions L ₁ , L ₂ , ... L _N , A change in the response signal is measured over a predetermined interval (N / 3 to 2N / 3). According to the present invention, as shown in FIG. 9, at a second position (? ₁ ,? ₂ , ..., L _N ) at different angles from the first position (L ₁ , L ₂ , theta] _K , [theta] _N , and the change in the response voltage V is measured. 10, a change in the response voltage V measured at the second position (? ₁ ,.? _K ,.? _N ) is shown graphically.

When the response voltage V at the second position? ₁ ,.? _K ,.? _N is measured, the orientation angle of the reinforcing bars 40 can be estimated using the above-described resistivity estimation model (REM).

10, the influence of the reinforcing bar 40 is increased in an area oriented in the same direction as the inclination angle _K of the reinforcing bars 40, so that the apparent resistivity ratio is also small and the response voltage V is small. On the other hand, (0 to? _K ,? _K to? _N ), the degree of influence of the reinforcing bars 40 is extremely small, and the apparent specific resistance ratio is large and the response voltage V is large. Therefore, the orientation of the reinforcing bars can be estimated with the inclination angle _K at which the change in the response voltage V occurs.

On the other hand, the longitudinal direction of the concrete 30 in the present invention refers to a direction in which the response voltage V changes (see FIG. 5) as a direction in which a sudden change in the response voltage V (Y-axis in FIG. 5), which can be distinguished from the initial concrete surface by two-directional measurement.

If the buried position and the orientation angle of the reinforcing bars 40 are estimated, the thickness of the concrete covering and the diameter of the reinforcing bars 40 can be estimated.

The first position estimate from the concrete surface has a reinforcement (40) has reinforcement in accordance with the measurement of the _{(L 1, L 2, ...} L N), a second position (θ _{1, K} .θ, .θ _N) After arranging the electrodes on the surface of the concrete 30 where the reinforcing bars are assumed to have been placed in the direct lower portion through the measurement (S400), the third positions M ₁ , M ₂ , ... arranged along the width direction (Y axis) M _N ) is measured (S500). The third positions M ₁ , M ₂ , ..., M _N are formed on the extension line of the first position or the second position with different intervals (a ₁ <a ₂ <a ₃ ) . When the measurement at the third position (M ₁ , M ₂ , ... M _N ) is completed, the control unit 24 compares the measured response voltage V and outputs it to the display unit 23.

FIG. 12 is a graph showing a change in the response voltage v measured through FIG. 12, when the gap of the voltage electrode 11 is a1 and a2, the change in the response voltage is small, but when the gap is a3, there is a considerable change in the response voltage V due to the influence of the reinforcing bars 40 Respectively. This is also due to the influence of the reinforcing bars 40 according to the electrode interval size a by the analysis of the resistivity estimation model (REM).

That is, in a1 and a2 where the electrode interval is narrow, the influence of the reinforcing bars included in the measurement region is minimal, and the apparent specific resistance rate is large and the response voltage V is large. However, The apparent resistivity ratio is also reduced and the response voltage V is small. By measuring the variation of the response voltage (V), it is possible to estimate the rebar diameter and the concrete covering thickness, which will be described in more detail in Experimental Examples to be described later.

According to the present invention, by analyzing the influence of the reinforcing bars on the apparent resistivity values at the surface of the concrete in which the reinforcing bars 40 are buried using the resistivity estimation model (REM), it is possible to determine the reinforcing rods, A more reliable estimation can be made on the diameter of the reinforcing bar and the thickness of the coating embedded with the reinforcing bars.

<Experimental Example>

The mortar with water cement ratio (W / C = 60) was used to make a reinforced concrete sample. Mortar was cemented for 45 days at 20 ° C in water using portland cement and steel sand, demisting after 24 hours of casting. Five types of specimens were fabricated by varying the coating thickness (T) and diameter () as shown in Table 1 below, in which the reinforcing bars were laid longitudinally in the longitudinal direction of the concrete.

The measuring electrode was coated with a conductive gel having a specific resistance of 8.3 × 10 ^-6 at a measurement position on the surface of the sample with a width of about 3 mm and a copper wire having a diameter of 1 mm was placed thereon and fixed so that the electrode did not move. The electrodes were arranged with two current electrodes on the outer side and two potential electrodes on the inner side with a constant spacing (a). The measurement range of the electrode was set to 0.14m on the right and left sides of the straight portion of the reinforcing bar. The electrode interval (a) was measured at 20, 30, and 40 mm, respectively. 13 shows a result of measuring a response signal through a voltage electrode by applying a 1-mA AC power source having a frequency of 100 Hz to a sample, and showing the resistance according to the distance from the center of the reinforcing bar. As shown in Fig. 13, the resistance at the upper portion of the reinforcing bar showed the lowest specific resistance at each electrode interval. This indicates that the reinforcing bars are most affected by the reinforcing bars with lower resistivity than the areas with the reinforcing bars directly on the concrete. The position of the reinforcing bars can be estimated by measuring the electrical response signals on the concrete surface.

<Analysis of Reinforcing Behavior of Concrete According to Resistivity Estimation Model (REM)>

Using the resistivity estimation model (REM), the state of the concrete inside the concrete was analyzed as follows. First, it is assumed that the longitudinal direction of the reinforcing bars and the measuring electrodes are arranged in parallel, and the change of the response voltage and resistance according to the relative positional relation when the measurement position is moved from the upper portion of the reinforcing bar is examined. Assuming that the resistivity of the concrete is 100 Ω · m and the specific resistance of the reinforcing bar is 0 Ω · m, the analysis condition is assumed to be 1 mA of current at the measurement site. The measurement range was set within the range of -0.2m to +0.2m (0.2m) to the left and right of the reinforcing bar.

1. Effect of Concrete Coating Thickness

The response voltage and resistance were estimated by changing the reinforcing bar diameter to Φ10 (0.01m) and the concrete covering thickness to d10 (0.01m), d20 (0.02m) and d30 (0.03m). The electrode spacing was set at three intervals of 0.01 m, 0.03 m, and 0.05 m.

First, Fig. 14a shows the result of analysis of the response voltage of d10-Φ10 (coating thickness d = 0.01m, rebar diameter Φ = 0.01m). As the measurement position moves to the center of the reinforcing bar, the response voltage decreases, And the response voltage at the top of the reinforcing bar is the lowest. However, the response voltage converges to a constant value as the measurement position moves to the position of ± 0.2 m distant from the top of the reinforcing bar.

This shows that all of the electrode intervals show similar tendency, and that the influence of the reinforcing bars increases rapidly as they approach the vicinity of the reinforcing bars, and that the influence of the reinforcing bars decreases as the distance increases.

14 (c) and (e)), the response voltage at the top of the reinforcing bars increases as the covering thickness increases. This is because the influence of the reinforcing bars in the measuring area decreases and the effect of the concrete increases due to the increase of the covering thickness . However, it can be seen that when the measurement position moves to the outer region, it converges to a constant value according to the electrode interval due to the influence of the concrete only.

As shown in Fig. 14 (b), (d), and (f) of Fig. 14, the apparent resistivity changes according to the change in the concrete covering thickness indicate that the apparent resistivity changes depending on the measurement position, , The influence of concrete is reduced and only the apparent resistivity of all the electrode intervals converges to the resistivity of 100 Ω · m of the concrete.

Also, it is shown that the influence of reinforcing bars in the resistivity measurement area decreases and the effect of concrete is increased as the result of the analysis of the apparent resistivity of the electrode relative to the increase of the coating thickness.

2. Influence of reinforcing bar diameter

The response voltage and the apparent resistivity were estimated by changing the diameter of the reinforcing bars to Φ13 (0.013m), Φ19 (0.019m) and Φ25 (0.025m) assuming the thickness of the coating to be d30 (0.03m) The electrode spacing was set to 0.02 m, 0.03 m and 0.04 m. As shown in Figs. 15 (a), (c) and (e), the response voltage decreases as the diameter of the reinforcing bars increases and approaches the vicinity of the reinforcing bars. This is due to the increase of the geometric area of the steel in the measurement area. Conversely, as the distance from the upper part of the steel reinforcement decreases, the influence of the reinforcing steel decreases and the influence of concrete only appears.

As shown in Figs. 15 (b), 15 (d), and 15 (f), the apparent resistivity decreases as the diameter of the reinforcing bar increases. However, as the distance from the reinforcing bars increases, only the influence of the concrete influences the measurement, and it can be seen that at the entire electrode interval, the concrete resistivity converges to 100 Ω · m as shown in Fig. 15 b), d) and f).

3. Apparent resistivity

The apparent resistivity ratios were calculated by the ratio of apparent resistivity combined with concrete to reinforced concrete.

FIG. 16 shows the result of calculating the apparent specific resistance at a position 0.05 m away from the upper portion of the reinforcing bar, based on the analysis results of FIG. 14 and FIG. 15 (a) shows the change in the apparent resistivity according to the variation of the concrete covering thickness at a specific position (position of 0.05 m above the reinforcing bar). As the coating thickness increases, the effect of concrete in the measurement area increases, and the effect of reinforcing bars decreases, and the apparent resistivity ratio tends to increase.

On the other hand, at 0.01 m, which is the narrow electrode interval, the degree of the effect of the reinforcing bars included in the measurement region was minimal, and the apparent resistivity ratio was 0.99 in all three coating thicknesses. 0.01m), the d20 (0.02m) is 0.76, and the d20 (0.03m) is 0.70. As the electrode spacing increases, the effect of the reinforcement contained in the measurement area increases, and the apparent resistivity ratio also decreases.

FIG. 16 (b) shows the result of analyzing the apparent resistivity ratio due to the change in the diameter of the reinforcing bars. As shown in the analysis results of the concrete covering thickness, the effect of the reinforcing bars included in the measuring area increased as the distance between the electrodes increased. It can be seen that the resistivity ratio decreases.

In particular, the apparent resistivity ratio can be estimated quantitatively by the influence of the surrounding reinforcement, so that the influence of the reinforcement on the resistivity of the concrete, which represents the corrosion environment of the reinforcing bar, .

The embodiments described in the present specification and the constitutions shown in the drawings are merely the most preferred embodiments of the present invention and are not intended to represent all of the technical ideas of the present invention. Therefore, various equivalents It should be understood that water and variations may be present.

10: measuring part 11: voltage electrode 12: current electrode
20: measuring body 21: power supply unit 22:
23: display section 24: control section 25:
30: reinforced concrete 40: reinforcing bar 50: sensor module
L ₁ , L ₂ , ... L _N : first position? ₁ ,? _K ,? _N : second position
θ _K : inclination angle M ₁ , M ₂ , ... M _N : third position a: electrode gap size

Claims (12)

As a method of estimating the state of the reinforcing steel in the reinforcing concrete,
Estimating whether or not the reinforcing bars are placed under the first position where the response signal is measured by measuring the response signal change of the electric signal applied at the first position arranged in parallel to the longitudinal direction of the reinforcing concrete on the surface of the reinforcing concrete,
When the response signal change is measured over a predetermined section along the longitudinal direction, the response signal change at the second position, which is arranged at an angle different from the first position at which the change is measured, is measured, And estimating an orientation angle of the reinforcing bars. The method according to claim 1,
And estimating the buried reinforcing bar diameter or the concrete covering thickness by measuring a change in the response signal at a third position arranged at different section distances on the extension line of the first position or the second position estimated to be reinforced immediately below the reinforcing bar Wherein the method comprises the steps of: 3. The method according to claim 1 or 2,
And estimating the state of the reinforcing steel posture by analyzing the change of the response signal using the following resistivity estimation model (REM).

The method of claim 3,
Wherein the resistivity estimation model (REM) analyzes the change in the response signal using an apparent resistivity ratio representing a ratio of an apparent resistivity value obtained by combining the effects of concrete and reinforcing steel to a resistivity value only of concrete, Estimation method. delete delete delete delete delete delete delete delete

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