JP4662890B2 - Functional diagnosis method for concrete structures - Google Patents

Description

  The present invention relates to a function diagnosis method for a concrete structure. More specifically, the present invention relates to a deterioration diagnosis technique for prestressed concrete pipes (hereinafter referred to as PC pipes) that are buried in the ground and used for a long time.

  A concrete structure that has passed many years may be aged due to environmental conditions, the influence of land use in the surrounding area, and an increase in traffic load.

  For example, in order to actively promote the maintenance and management of PC pipes etc. that have been buried underground for a long period of time, there is a strong demand for diagnostic methods for elucidating the basic aging mechanism and evaluating the soundness from inside and outside the pipe. It has been. The PC pipe is pre-stressed on the outer periphery of the PC steel wire by applying a pre-stress on the outer periphery of the reinforced concrete pipe with a diameter of about 3 to 6 mm. It has a structure with a cover coat (covered concrete) of about 25 mm. PC pipes are mainly buried in the ground and used as water conduits and water and sewage pipes.

  A technique for diagnosing reinforcing bars in concrete from the outside of the concrete is known. For example, methods such as an electromagnetic induction method, a radiation trap, an electromagnetic wave method, and an electromagnetic radar have been developed as means for confirming the position of a reinforcing bar.

  As a technique for detecting changes in defects, materials, dimensions, etc. of conductive members, there is a technique using electromagnetic induction (see, for example, Patent Document 1).

  In this technique, a sensor in which an excitation coil and a detection coil are coaxially integrated is used, and an eddy current generated in a reinforcing bar or the like by an alternating magnetic flux generated from the excitation coil is detected by the detection coil. Non-destructive inspection can be performed on reinforcing bars in concrete. If there are scratches or cracks in the reinforcing bars, eddy currents are disturbed, and this can be detected by detecting coils to detect defects. Can do.

  In such an electromagnetic induction sensor, inspection is performed by scanning a sensor in which an excitation coil and a detection coil are integrally formed along a reinforcing bar or the like. A sensor with an integrated excitation coil and detection coil increases the size of the sensor, and a conventional cylindrical coil-shaped sensor accurately applies only the steel material to be inspected to a concrete structure with complex reinforcement. It may be difficult to capture and a desired measurement may not be possible.

  On the other hand, it is also important to measure the change in the thickness of the concrete member in order to diagnose the deterioration of the concrete structure. There is an ultrasonic method as a means for accurately measuring the thickness of a concrete member and the thickness reduction (thickness reduction) of a steel material. In concrete structures such as PC pipes, the strength characteristics of the concrete frame and the cover coat may differ depending on the manufacturing process of the product (centrifugal force method or roll rolling method) and the size of the tube (type of diameter). Since the propagation speed of ultrasonic waves depends on these physical property conditions, it is necessary to collect and analyze and evaluate data relating to these physical property conditions in advance. In the thickness measurement by the ultrasonic method, since the propagation speed of the ultrasonic wave in the measurement object is known and the transmission or reflection time is measured and the thickness is calculated backward, the calculation of the propagation speed is the most important in diagnostic evaluation.

  In particular, a PC pipe is composed of a concrete inner pipe (framed concrete), a PC steel wire wound around its circumference, and a cover coat covering the PC steel wire. From the viewpoints of geology, water quality, surrounding land use, and increased traffic load, the cover coat may have become obsolete due to the thinning of the cover coat, and it is necessary to grasp the decrease in the thickness of the cover coat. .

  Possible causes of the decrease in the thickness of the cover coat include chemical corrosion or wear due to a high-speed flow due to water leakage from the pipe joint. In general, it is estimated that there are many cases of chemical corrosion caused by soil components, groundwater quality and fluctuation, and exudation of harmful substances from agricultural land. In the case of such chemical corrosion, the loss of alkalinity (neutralization) based on the disappearance of calcium hydroxide in the concrete at the initial stage of erosion, and the loss of mortar due to weakening of the mortar forming the cover coat Based on these, it is considered that corrosion and fracture of the PC steel wire will eventually occur.

  Therefore, in order to diagnose and evaluate the soundness of PC steel wires, assuming that PC pipes are basically subject to chemical corrosion, it is necessary to understand the thickness of the cover coat and to check the soundness of the PC steel wires themselves. It is necessary to check the degree (corrosion status and presence / absence of breakage).

In other words, in order to actively promote the maintenance and management of PC pipes that have been buried underground for a long period of time, the basic aging mechanism will be elucidated, and functional diagnosis methods for evaluating the soundness from inside and outside the pipe, and these The establishment of management standards based on the
Japanese Patent Laid-Open No. 2001-318080 (page 2-4, FIG. 1)

  The problem to be solved by the present invention is to develop an electromagnetic induction sensor specialized in the detection of corrosion and fracture of reinforcing bars in concrete structures, and to use this to improve the soundness of PC steel and reinforcing bars in concrete. It is to provide a way to evaluate.

  Furthermore, the present invention is particularly targeted for deterioration diagnosis of PC pipes, etc., and measures the status of PC steel wires and cover coats based on different physical exploration techniques, and obtains a diagnostic index according to these measured values. An object of the present invention is to provide a function diagnosis technique using a diagnosis matrix in which these are combined.

  The present invention has been made to solve the above-described problems. The reference sensor and the diagnostic sensor of the electromagnetic induction flaw detector are separated so as to be independently movable, and the reference sensor is brought close to the steel material in the concrete structure. The concrete is characterized in that it is placed in one position and the diagnostic sensor is brought close to another position of the steel material in the concrete structure or moved along the steel material to determine the breaking / corrosion status of the steel material. This is a function diagnostic method for a structure.

  The reference sensor and the diagnostic sensor can be appropriately used in correspondence with the bar arrangement of the target structure or the like by making the shape rod-shaped, gate-shaped or horseshoe-shaped.

As the concrete structure, for example, it can be applied to the PC pipe, reinforced concrete pipes, box culverts, joint groove, bridges deck or ground anchors or the like.

  Furthermore, when the concrete structure is a PC pipe, a reinforced concrete pipe, or a box culvert, the thickness of the concrete member is measured with a thickness meter, and the soundness of these concrete structures is comprehensively determined together with the measurement data. To do.

  These measurements can be performed from the inside of the installed PC pipe or the like, and external earth and sand such as the buried pipe can be locally removed by boring or the like, and the measurement can be performed from the outside.

  In addition, the secular change of soundness can be grasped | ascertained by diagnosing the concrete structure before use beforehand and determining the condition after use on the basis of the diagnostic result.

  According to the present invention, the reference sensor and the diagnostic sensor are separated into separate bodies, and the sensor uses a small electromagnetic induction sensor having a shape corresponding to the reinforcing bar arrangement of the target structure to be diagnosed. Since these reference sensors and diagnostic sensors can be moved independently, it is possible to quickly and accurately measure and judge the entire state of a desired reinforcing bar or the like. Furthermore, only the abnormal part can be diagnosed in detail based on these determinations.

  In addition, for PC pipes, etc., it is possible to quantitatively and comprehensively grasp the soundness of the pipe body by periodically diagnosing the degree of progress of cover coat deterioration and the progress of corrosion of PC steel wire. It became.

  Therefore, as preventive maintenance, unforeseen circumstances such as water leakage or tube rupture can be avoided as much as possible, and it is highly effective in preventing social damage to the economy, people, the environment, and the like.

  In particular, in industrial and agricultural water pipelines using PC pipes, an effective function diagnostic method for evaluating the soundness of pipes has not yet been established, so the role played by the function diagnostic technique of the present invention is extremely important. There is a significant contribution.

  First, characteristics of a general electromagnetic induction sensor will be described. An electromagnetic induction sensor generates an eddy current in an object when it is irradiated with an alternating magnetic flux generated from an excitation coil, and the generated eddy current generates a reaction magnetic flux that cancels the magnetic flux from the excitation coil. To do. Here, if there is a discontinuous part (damaged part such as scratches or cracks) in the object, eddy current flows around it, and the magnetic flux generated by the eddy current at this time is normal (healthy state) And different. By detecting this abnormal magnetic flux, it becomes possible to detect defects such as scratches and cracks present in the object.

    FIG. 8 shows a block diagram of an electromagnetic induction flaw detection system used in the present invention. The electromagnetic induction flaw detection system includes a reference sensor (excitation coil) 121 and a diagnostic sensor (detection coil) 122. In the electromagnetic induction sensor used in the present invention, the reference sensor 121 and the diagnostic sensor 122 are separately formed and can be moved independently. Information from the reference sensor 121 and information detected by the diagnostic sensor 122 are input from the low-frequency electromagnetic induction flaw detector 123 to the measurement personal computer 125 via the A / D converter 124. The measurement personal computer 125 calculates and analyzes the phase angle and voltage value of the magnetic flux caused by the eddy current in the healthy part and damaged part of the measurement object, and displays the voltage value. The measurement personal computer 125 displays the calculation result, stores it, and outputs it to a printer or the like.

  In the present invention, for example, in order to facilitate the damage investigation of the PC steel wire of the PC pipe, the sensor part is separated into a reference sensor (excitation coil) 121 and a diagnostic sensor (detection coil) 122, which can be moved independently. By adopting a simple format, it became possible to explore the inside of the PC tube in a short time along its longitudinal direction.

  Furthermore, the reference sensor and the diagnostic sensor are each specially shaped so that measurement can be performed while avoiding the influence of the bar arrangement condition of the PC tube as much as possible. For example, a rod sensor, a portal sensor, and a horseshoe sensor. Hereinafter, the example of the shape specification of each sensor is shown.

  5 (a) is a side view of the rod-shaped sensor 110a, FIG. 5 (b) is a cross-sectional view taken along the line BB, and FIG. 5 (c) is a detailed cross-sectional view of part A of FIG. 5 (a). This rod-shaped sensor 110a has a length of 250 mm, a cross-section of 25 mm square, and a superposition of 72 directional silicon steel plates having a thickness of 0.35 mm in order to obtain a high magnetic flux density with a low iron loss as the iron core 111. ing.

  As shown in FIG. 5C, the coil 112 has a winding 112a double-wound, and a shield plate 113 is interposed between the upper and lower sides and the middle. In this embodiment, urethane wire φ0.2 mm is used as the winding 112a, the coil 112 is a flat winding, and the number of single turns is 800.

  6A is a side view of the portal sensor 110b, FIG. 6B is a cross-sectional view taken along the line C-C, and FIG. 6C is a detailed view of a portion D in FIG. 6A. The portal sensor 110b has a portal shape including both legs and a beam connecting the legs. In the example shown in FIG. 6A, the length of both legs is 55 mm and the length of the beam is 265 mm.

  In order to obtain a high magnetic flux density with low iron loss, the iron core is made of directional silicon steel sheets, and 72 directional silicon steel sheets with a thickness of 0.35 mm are overlapped, and windings 112b are respectively wound on both legs and beams. And 112a are wound. As shown in detail in FIG. 6 (c), the coil is made of urethane wire φ0.2mm, and the winding 112a is double wound. The number of each single winding is 70 turns on both legs and 660 turns on the beam. Are coupled in series. Shield plates 113 are interposed between the upper and lower sides and the middle of the winding 112a.

  FIG. 7A is a side view of the horseshoe sensor 110c, and FIG. 7B is a cross-sectional view taken along the line EE. The illustrated embodiment of the horseshoe sensor 110 c has a semicircular shape with an inner diameter of 175 mm and an outer diameter of 225 mm, and a winding 112 is wound around an iron core 111.

  The iron core 111 is a laminate of 84 directional silicon steel sheets having a thickness of 0.3 mm, the winding 112 is a formal wire φ0.2 mm, and the number of windings of the coil is doubled. The details of the portion of the winding 112 are the same as those shown in FIG.

  Next, examples of the method of the present invention will be described.

  An explanatory view of a method of diagnosing the soundness of the PC steel wire of the PC pipe is shown in FIG. FIG. 1 is an explanatory view schematically showing a longitudinal section of a PC tube 30 which is an object of an embodiment of the method of the present invention.

  A PC steel wire 32 is wound around the outer periphery of a casing of a PC tube 30 containing a reinforcing bar 31 while applying prestress, and the outer surface thereof is covered with a cover coat 33. In FIG. 1, in order to display the distribution of the PC steel wire 32 in an easy-to-understand manner, the figure showing the distribution of the PC steel wire through the frame concrete is drawn. The dimensions of the PC tube 30 are, for example, an inner diameter of 1 to 2 m and a length of about 4 m.

  Measurement was performed using the electromagnetic induction flaw detection system shown in FIG. Prior to this measurement, the arrangement position of the structural muscle 31 of the target PC tube 30 was confirmed by an electromagnetic wave radar or the like, and a sensor having a shape that is hardly affected by the structural muscle 31 was selected and measured.

  There are two types of measurement methods, the line method and the spot method. In the line method, the diagnostic sensor 22 is brought close to the PC steel wire 32 while avoiding the space between the structural bars 31 and measured along the longitudinal direction of the PC tube 30 at intervals of 0.1 to 0.5 m. In the spot method, measurement is performed in a spot manner with respect to the gluteal muscles at intervals of 60 to 80 mm. In the line method, a bar sensor or a portal sensor is used. In the spot method, a horseshoe sensor is mainly used.

  The examples were performed from the inside of the PC tube 30 by the line method. As shown in FIG. 1, a reference sensor (excitation coil) 21 is installed at one position of an end portion in the PC tube 30, and diagnostic sensors (measurement coils) 22 are arranged at intervals of 0.2 m along the longitudinal direction of the PC tube. It was measured.

  FIG. 2 shows an example of function diagnosis and determination by the method of the present invention. A change in the output voltage of the diagnostic sensor is measured along the longitudinal direction (distance 0 to 4 m) of the PC tube 30.

  This is a technique for evaluating the soundness of a PC steel wire based on the voltage change in the measurement range and the maximum voltage difference (Vmax) as diagnostic parameters. For the voltage change in the measurement range, the coefficient of variation (Cv) is calculated, the maximum voltage difference (Vmax) in the measurement data is obtained, and the soundness level is classified.

  The meaning of obtaining the coefficient of variation (Cv) is determined from the fact that there is almost no voltage change in a sound PC steel wire as judged from experimental data, and the voltage change width increases with the deterioration of the PC steel wire. The In other words, the change in voltage within the measurement range is due to the deterioration of the steel wire (progress of rust) when the cover coat part deteriorates due to the neutralization or chemical erosion of the concrete. The resistance value of the wire increases. As a result, the voltage value varies. The coefficient of variation (Cv) of the voltage data is calculated for the voltage change data at the scanning distance (3 m excluding 0.5 m at both ends of the measurement tube (PC tube)) obtained from the healthy state by the electromagnetic induction method. The coefficient of variation (Cv) is often used in statistics as a measure of the degree of variation in numerical values, but here it is used as a deterioration diagnosis parameter for steel wires.

Incidentally, the coefficient of variation (Cv) is expressed by the following equation: Cv = standard deviation ÷ average value × 100
Calculate with The standard deviation σ is

Where x = standard average (numerical values 1, 2,...)
n = number of samples. Practically, using the computer software “Excel”, calculation is performed using the function STDEV (when the argument is regarded as a sample of the population) or the function STDEVP (when the specified numerical value is the entire population). . The standard deviation is calculated using the non-bias method or the (n-1) method. The average value is calculated using the Excel function AVERAGE.

  On the other hand, for the maximum voltage difference (Vmax), the absolute value of the voltage showing the maximum value in the scanning distance 3 m range excluding 0.5 m at both ends of the tube is used as the deterioration diagnosis parameter. From the experimental data, the absolute value of the maximum voltage difference (Vmax) when the steel wire breaks is larger than that of the steel wire in a healthy state. Therefore, the absolute value of the maximum voltage is considered to increase as the deterioration progresses on site. That is, the progress of deterioration and the maximum value of voltage are considered to be correlated with each other, and are judged as effective diagnostic parameters. If the oxidation is likely to occur due to the neutralization of the concrete or changes in the cover coat due to chemical erosion, the steel wire rusts, causing a change in resistance value due to differences in the soundness and degree of corrosion, inducing a potential difference. It is estimated that the voltage increases.

The electromagnetic induction method is diagnosed using the above two types of deterioration diagnosis parameters (variation coefficient Cv and maximum output voltage difference Vmax). The classification that is generally the basis of diagnosis was calculated by the corrosion experiment that corroded the steel wire. FIG. 2 shows the classification of both and the voltage change pattern.
(1) F1 classification (sound): The coefficient of variation Cv is 50% or less and the maximum voltage difference Vmax is 1.5V or less.
(2) F2 classification (local corrosion): coefficient of variation is 50 to 100% or less, maximum voltage difference is 1.5 to 2.5 V or less.
(3) F3 classification (local corrosion): coefficient of variation is 100 to 150% or less, maximum voltage difference is 2.5 to 4.0 V or less.
(4) F4 category (large corrosion progress, high possibility of breakage) Fluctuation coefficient is 150% or more, maximum voltage difference is 4.0V or more.

  When the relationship between the maximum voltage difference Vmax and the coefficient of variation Cv at that time is obtained from samples having different degrees of corrosion, the relationship shown in FIG. 3 is obtained. In Fig. 3, black circles are data of PC pipes with PC steel wires rusted and broken (F4 category), gray circles are data of PC tubes with PC steel wires rusted (F2 and F3 categories), and white circles are sound PC tubes. Data (F1 classification).

    FIG. 3 shows the maximum output voltage difference Vmax and the coefficient of variation Cv in these data as deterioration diagnosis parameters.

The relationship between the deterioration diagnosis parameters is the following cubic function y = 4.1571x ³ −7.9506x ² + 301048x + 21.789 (1)
Can be approximated by The correlation coefficient ^{R 2} of the above equation (1) is 0.9869. From FIG. 3, it can be determined that the influence of the maximum voltage difference Vmax is larger than the variation coefficient Cv. Since the pipes embedded in the field have various moisture characteristics and the electrical characteristics (dielectric constant) of the pipes also change, the relationship between these diagnostic parameters varies in function slope depending on the degree of dielectric constant. There is a possibility. In addition, the relationship between the two when there is no simple corrosion mechanism, such as stress corrosion (when external fluid permeates into fine cracks at the initial stage of production and causes brittle fracture, etc.) or combined with oxidative corrosion is also estimated. Is done.

  On the other hand, in the case of measuring actual pipes with secular changes at the site, it is determined that the polynomial function equation as described above can be regarded as a deterioration curve when it is arranged on the function degradation and time axis.

  Although the deterioration mechanism of PC steel wire has not yet been elucidated in detail, it is estimated that the aging equation from corrosion to steel wire breakage can be evaluated by these functions.

  Next, with respect to the PC pipe, the management standard of the embodiment of the present invention in which the damage of the PC steel wire by the electromagnetic induction method and the thickness measurement of the cover coat are combined will be described with reference to FIG.

  The thickness of the cover coat is measured by ultrasonic thickness measurement. Since PC pipes have different ultrasonic propagation speeds for concrete and cover coat depending on the pipe diameter, manufacturing method, and aging, basic data is collected and analyzed for each of these factors.

  The total thickness of the PC tube is measured with an ultrasonic thickness gauge. The above factor data is applied to this measurement data to correct the thickness measurement value, and then the thickness of the cover concrete is assumed to be unchanged, and the cover coat thickness is calculated. Excludes data where the thickness of the concrete frame appears to have decreased due to water flow.

  The basic diagnostic categories in ultrasonic thickness measurement were as follows.

  (1) The cover coat thickness remains 75% or more of the design value.

  (2) The cover coat thickness is less than 75% to 20% of the design value.

  (3) The cover coat thickness is less than 20% of the design value.

  The diagnostic criteria determined as described above are combined with the measurement and evaluation of PC steel wire by the electromagnetic induction method to evaluate the soundness comprehensively. The flow of this deterioration diagnosis evaluation is shown in a flowchart in FIG.

  (A) In the ultrasonic thickness measurement, when the judgment 61 of whether or not it falls under the A1 category (75% or more of the design value) is YES, the corrosion / breakage category of the PC steel wire is the F1 category (the coefficient of variation Cv is 50). %, The maximum output voltage difference Vmax is less than 1.5V), and if this is YES, it will be classified as A1 / F1 71 and periodic diagnosis will be performed once every 5 years .

  (B) In the ultrasonic thickness measurement, the judgment 61 as to whether or not it falls under the A1 category (75% or more of the design value) is YES, and the PC steel wire category is F2 to F3 (variation coefficient Cv is 50). % Or more and 150% or less, and when the determination 52 is YES whether the maximum output voltage difference Vmax is between 1.5V and 4.0V (local corrosion stage), that is, A1 · F2 to F3 In Category 72, a periodic diagnosis is conducted once every three years to check for the progress of damage.

  (C) In ultrasonic thickness measurement, the judgment 62 of whether or not it falls under the A2 category (less than 75% to 20% of the design value) is YES, and the corrosion / breakage of the PC steel wire is F1 category (variation) When the determination 52 whether or not the coefficient Cv is 50% or less and the maximum output voltage difference Vmax is 1.5 V or less is YES, in the A2 / F1 category 73, a diagnosis is made every year, and the cover coat thickness Confirm progress of thinning. If there is no progress in thinning, regular diagnoses are performed at intervals of 3-5 years. If there is progress in reducing the thickness of the cover coat, in A2 / F2 to F3 classification 74, exploratory investigation and cause elucidation of the target pipe will be implemented immediately and countermeasures will be implemented.

  (D) In the ultrasonic thickness measurement, the judgment 63 as to whether or not it falls under the A3 category (less than 20% of the design value) is YES, and the corrosion / breakage of the PC steel wire is the F2 to F3 category (variation coefficient Cv). Is 50% or more and 150% or less and the maximum output voltage difference Vmax is 1.5V or more and 4.0V or less), when the determination 52 is YES, in A3 / F2-F3 classification 75, the prospecting survey is conducted. After implementing and elucidating the cause, implement anti-corrosion measures.

  (E) In the ultrasonic thickness measurement, the judgment 63 as to whether or not it corresponds to the A3 category is YES, the PC steel wire category is the F4 category (variation coefficient Cv is 150% or more, and the maximum output voltage difference Vmax is 4). If the judgment 53 of whether or not it falls within the range of 0 V or higher) is YES, in the A3 / F4 division 76, either an immediate exploration check is carried out, and emergency measures are taken or a new update is made Implement countermeasures.

  Table 1 summarizes the above PC pipe deterioration judgments.

  As shown in Example 3, the PC steel wire was cut and corroded by electromagnetic induction flaw detection from the inside of the PC tube, and the thickness of the cover coat covering the PC steel wire was measured with an ultrasonic thickness gauge. It has become possible to comprehensively evaluate the integrity of the PC tube by combining the indicators of both the electromagnetic induction method and the ultrasonic thickness measurement.

  Note that when applying the method of the present invention, even when there is always water in the PC tube and measurement from the inside of the PC tube is impossible, a PC tube using a boring machine or an auger drill having a diameter of about 66 mm to 150 mm is used. A plurality of holes reaching the outer periphery can be drilled, and a reference sensor and a diagnostic sensor can be pressure-bonded to separate hole bottoms to check the fracture / corrosion status of the PC steel wire. Of course, the reference sensor and the diagnostic sensor may be inserted into the same hole bottom.

  In the method of the present invention, for example, a concrete structure such as a box culvert, a joint groove, a bridge deck, or a ground anchor can be a target of diagnosis. The PC steel wire of the PC tube has a diameter of about 3 mm to 6 mm. However, in other reinforced concrete, a rebar having a diameter of 13 mm or more is used, and therefore measurement is easier than the PC tube.

  According to the method of the present invention, management data can be provided to the user as a guarantee of the aging performance evaluation of the product by measuring at the time of product shipment. In particular, for cover coat soundness assessment, accurate assessment of the completed thickness at the time of shipment and provision of management data greatly benefit the assessment of changes in performance over time. It is extremely effective in doing.

It is a longitudinal cross-sectional view of the PC pipe explaining the method of the present invention. It is explanatory drawing which shows the measurement division of the PC pipe | tube of a various step. It is a graph which shows the relationship between the maximum output voltage amount and a variation coefficient. It is a flowchart of the Example of this invention method. It is a side view of the sensor of an Example. It is BB arrow sectional drawing of Fig.5 (a). FIG. 6 is a detailed view of part A in FIG. It is a side view of the sensor of another Example. It is CC sectional view taken on the line of Fig.6 (a). It is the D section detailed drawing of Drawing 6 (a). It is a side view of the sensor of another Example. It is EE arrow sectional drawing of Fig.7 (a). It is a block diagram which shows the system of an Example.

Explanation of symbols

21 Reference Sensor 22 Diagnostic Sensor 26 Scan Line 27 Arrow 30 PC Tube 31 Reinforcing Bar (Structural Bar)
32 PC steel 33 Cover coat 51-53 Judgment of voltage change pattern classification 61-63 Judgment of cover coat thickness classification 71-76 Classification 110, 110a, 110b, 110c Sensor 111 Iron core 112, 112a, 112b Winding (coil)
113 Shield plate 121 Reference sensor 122 Diagnostic sensor 123 Flaw detector 124 A / D converter 125 PC for measurement

Claims (4)

  The reference sensor and diagnostic sensor of the electromagnetic induction flaw detector are separated so as to be independently movable, the reference sensor is placed in one position close to the steel material in the concrete structure, and the diagnostic sensor is installed in the steel material in the concrete structure. A method for diagnosing a function of a concrete structure, characterized by determining whether the steel material is broken or corroded by being moved close to another position or moved along the steel material. The concrete structure is, PC tube, reinforced concrete pipes, box culverts, joint groove, function diagnosis method of claim 1 concrete structure of wherein a is slab or ground anchor bridge.   The concrete structure is a PC pipe, a reinforced concrete pipe, a joint groove or a box culvert, and the thickness of the concrete member is measured by a thickness meter, and the soundness of the concrete pipe is comprehensively determined together with the measurement data. The method for diagnosing a function of a concrete structure according to claim 1.   The method for diagnosing a function of a concrete structure according to any one of claims 1 to 3, wherein a concrete structure before use is diagnosed in advance, and a situation after use is determined based on the diagnosis result.

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