JP6847813B2 - Cover thickness inspection method - Google Patents

Description

The present invention determines the cover thickness of reinforcing bars in a reinforced concrete structure including a large structure such as a railway bridge among structures including railway structures, road structures, etc. (hereinafter, simply referred to as "structure"). It relates to a cover thickness inspection method and a cover thickness inspection device to be inspected.

The cover thickness, which indicates the shortest distance from the reinforcing bar to the concrete surface in reinforced concrete, plays a role of protecting the reinforcing bar from oxidation and the like, and if this is insufficient, deterioration of the reinforcing bar may be promoted and the strength of the reinforced concrete may be significantly reduced.

For this reason, it is necessary for concrete structures to have an appropriate cover thickness specified in the design standards, but there are structures in which the required cover thickness is not secured due to causes such as poor construction. there is a possibility. Therefore, it is necessary to measure the cover thickness of the reinforced concrete structure and inspect it appropriately.

There is a chipping inspection as a conventional method for inspecting the cover thickness. This method is a method of measuring the cover thickness after actually peeling the concrete from the surface of the reinforced concrete to expose the reinforcing bars. The most reliable method is to destroy the concrete surface.

As a non-destructive inspection method for inspecting a concrete surface without destroying it, there is an inspection method called an electromagnetic wave radar method (see, for example, Patent Document 1). This method utilizes the fact that electromagnetic waves transmitted into concrete are reflected at the interface between substances with different properties. The device is pressed against the concrete surface to transmit electromagnetic waves and receive the reflected electromagnetic waves. By detecting reinforcing bars and cavities, the cover thickness is measured.

As another non-destructive inspection method, there is an inspection method called an electromagnetic induction method (see, for example, Patent Document 2). In this method, when a test probe that generates an alternating current by passing an alternating current through an exciting coil is pressed against the concrete surface, a current flows when a reinforcing bar, which is a magnetic material, exists in the magnetic field, and a further magnetic field is formed. By detecting and analyzing this change in the magnetic field, the position of the reinforcing bar and the cover thickness are measured.

Of these cover thickness inspection methods, the electromagnetic wave radar method or the electromagnetic induction method, which is a non-destructive inspection method, is preferable as the inspection method because it is necessary to actually peel off the concrete to expose the reinforcing bars in the chipping inspection.

JP-A-2010-107259 Japanese Unexamined Patent Publication No. 2003-106806 JP-A-2017-166922

However, all of the above-mentioned cover thickness inspection methods based on the conventional non-destructive inspection method transmit electromagnetic waves into concrete to measure the cover thickness. Therefore, if a magnetic material such as metal is present at the measurement location, this magnetism Due to the influence of the body, there is a possibility that errors may occur in the measured values of the cover thickness and the reinforcing bar diameter.

For example, in the cover thickness inspection method by the electromagnetic induction method, the magnetic flux of the magnetic field formed based on the magnetic field generated by the exciting coil becomes large due to the influence of the magnetic material, the amount of metal is estimated to be large, and the cover thickness is small. Reinforcing bar diameter may be estimated large.

Therefore, an object of the present invention is to provide a cover thickness inspection method and a cover thickness inspection device capable of accurately measuring the cover thickness of a reinforced concrete structure.

In order to achieve the above object, it has a small unmanned aircraft, a moving mechanism provided on the side facing the surface of the structure of the small unmanned aircraft, and a cover thickness measuring sensor provided on the moving mechanism side of the small unmanned aircraft. The cover thickness inspection method of the present invention for inspecting the cover thickness of the reinforcing bar in the reinforced concrete structure by the cover thickness inspection device measures the cover thickness of the reinforcing bar in the concrete test piece in which the reinforcing bar having a known cover thickness is embedded. The relationship between the measured value of the cover thickness of the reinforcing bar in the test piece measured by the measurement sensor and the actual cover thickness measured by the cover thickness measurement sensor is obtained, and the cover thickness measured by the cover thickness measurement sensor is based on this relationship. It is characterized by correcting the measured value of.

Here, the cover thickness of the reinforcing bar in the test piece can be measured by the cover thickness measuring sensor while the small unmanned aerial vehicle is in operation.

Further, the cover thickness inspection device of the present invention for inspecting the cover thickness of the reinforcing bar in the reinforced concrete structure includes a small unmanned aerial vehicle, a moving mechanism provided on the side facing the surface of the structure of the small unmanned aerial vehicle, and a small unmanned vehicle. The cover thickness measurement sensor provided on the moving mechanism side of the aircraft, the storage unit that stores the relationship between the measured value of the cover thickness of the reinforcing bar measured by the cover thickness measurement sensor and the actual cover thickness, and the storage unit are stored in the storage unit. It has a correction unit that corrects the measured value of the cover thickness measured by the cover thickness measurement sensor based on the above relationship.

Here, the above-mentioned relationship can be configured based on the measured value of the cover thickness of the reinforcing bar measured by the cover thickness measurement sensor in a state where the small unmanned aerial vehicle is operated.

In the cover thickness inspection method of the present invention configured as described above, the cover thickness of the reinforcing bar in the concrete test piece in which the reinforcing bar having a known cover thickness is embedded is measured by the cover thickness measuring sensor, and the cover thickness measuring sensor is used. The relationship between the measured value of the cover thickness of the reinforcing bar in the measured test piece and the actual cover thickness is obtained, and the measured value of the cover thickness measured by the cover thickness measuring sensor is corrected based on this relationship.

By doing so, the measured value by the cover thickness measuring sensor can be appropriately corrected, and the cover thickness of the reinforced concrete structure can be accurately measured.

Here, since the cover thickness of the reinforcing bar in the test piece is measured by the cover thickness measuring sensor while the small unmanned aerial vehicle is operating, the condition that the cover thickness of the structure is actually measured by the cover thickness inspection device. The correction can be performed in a state closer to the above, and the measured value can be corrected more appropriately.

Further, in the cover thickness inspection device of the present invention, the relationship between the cover thickness measurement sensor provided on the moving mechanism side of a small unmanned aircraft, the measured value of the cover thickness of the reinforcing bar measured by the cover thickness measurement sensor, and the actual cover thickness. It has a storage unit in which is stored, and a correction unit that corrects the measured value of the cover thickness measured by the cover thickness measurement sensor based on the relationship stored in the storage unit.

By doing so, the value measured by the cover thickness measuring sensor can be appropriately corrected by the correction unit, and a cover thickness inspection device suitable for the cover thickness inspection method of the present invention can be realized.

Here, since the above-mentioned relationship is based on the measured value obtained by measuring the cover thickness of the reinforcing bar with the cover thickness measurement sensor while operating the small unmanned aerial vehicle, the cover thickness of the structure is actually measured by the cover thickness inspection device. The correction can be performed in a state closer to the specified condition, and the measured value can be corrected more appropriately.

It is a perspective view which shows the structure of the cover thickness inspection apparatus which is this embodiment. It is a side view which shows the structure of the cover thickness inspection apparatus which is this embodiment. It is a top view which shows the structure of the cover thickness inspection apparatus which is this embodiment. It is a front view which shows the structure of the cover thickness inspection apparatus which is this embodiment. It is a schematic side view which shows the structure of the cover thickness measurement sensor. It is a figure for demonstrating the principle of the electromagnetic induction method. It is a figure for demonstrating the method of measuring the cover thickness of a reinforcing bar. It is a figure for demonstrating the cover thickness measurement operation by the cover thickness inspection apparatus which is this embodiment. It is a block diagram which shows the schematic structure of the cover thickness measurement system including the cover thickness inspection apparatus which is this embodiment. It is a figure for demonstrating the cover thickness measurement method using the cover thickness inspection apparatus which is this embodiment. It is a figure for demonstrating the cover thickness measurement method using the cover thickness inspection apparatus which is this embodiment. It is a figure for demonstrating the cover thickness measurement method using the cover thickness inspection apparatus which is this embodiment. It is a side view which shows an example of the test piece used in the cover thickness inspection system which is this embodiment. It is a bottom view which shows an example of the test piece used in the cover thickness inspection system which is this embodiment. It is a side view which shows another example of the test piece used in the cover thickness inspection system which is this embodiment. It is a bottom view which shows another example of the test piece used in the cover thickness inspection system which is this embodiment. It is a figure which shows an example of the relationship between the measured value of the cover thickness by a cover thickness measurement sensor, and the cover thickness of a test piece. It is a figure which shows an example of the relationship between the measured value of the reinforcing bar diameter by a cover thickness measurement sensor, and the reinforcing bar diameter of a test piece.

Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a perspective view for explaining the overall configuration of the cover thickness inspection device 10 of the present embodiment, FIG. 2 is a side view of the same, FIG. 3 is a top view of the same, and FIG. 4 is a front view of the same. First, an outline of the cover thickness inspection device 10 will be described.

The cover thickness inspection device 10 is a device using a small unmanned aerial vehicle 1 equipped with a cover thickness measuring sensor 3 for measuring the cover thickness of reinforcing bars in a reinforced concrete structure by using the above-mentioned electromagnetic induction method. The cover thickness measurement by the electromagnetic induction method is advantageous in that non-destructive inspection can be performed on a reinforced concrete structure.

Then, by using the small unmanned aerial vehicle 1, it becomes possible to inspect high places without scaffolding and places that are difficult for workers to approach. For example, the inspection can be performed on the lower surface or the side surface of a structure such as a bridge, a building or a retaining wall. In the following, as shown in FIG. 8, the girder lower surface M1 of the concrete girder M of the bridge, which is a structure, will be described as the surface to be inspected.

As shown in FIGS. 1 to 4, the cover thickness inspection device 10 of the present embodiment is the same as the small unmanned aerial vehicle 1 and the moving mechanism 2 provided on the side of the small unmanned aerial vehicle 1 facing the lower surface M1 of the girder. It is mainly composed of a cover thickness measuring sensor 3 provided on the moving mechanism 2 side.

The small unmanned aerial vehicle 1 includes a main body 11, a plurality of propellers 12 as flight means, and a flight control unit 13. The main body portion 11 of the present embodiment is a support portion that connects a pair of cross beam portions 11a erected in the width direction (vertical direction in FIG. 3) and these cross beam portions 11a in the length direction (horizontal direction in FIG. 2). It has an 11b and a leg portion 11c connected to the lower portion of the support portion 11b.

Propellers 12 are provided at a total of four locations, one on each side of the pair of cross beam portions 11a of the main body portion 11. The propeller 12 is rotated by being driven by the motor unit 121, and power is supplied to the motor unit 121 from the drive power supply unit (not shown). The drive power supply unit includes a converter and the like in addition to the battery.

The flight control unit 13 controls the flight such as the ascent and progress of the small unmanned aerial vehicle 1 by controlling the rotation speed of each propeller 12. The flight control unit 13 has a gyro or the like, and the gyro or the like detects the attitude of the small unmanned aerial vehicle 1 and uses it for flight control. Further, the small unmanned aerial vehicle 1 according to the present embodiment has a GPS antenna 14, and flight control is performed based on information from a GPS communication satellite 37 (see FIGS. 8 and 9) received via the GPS antenna 14. The unit 13 controls the attitude and flight of the small unmanned aerial vehicle 1. Further, the flight control unit 13 has a wireless communication unit 13a (see FIG. 9), and wirelessly communicates with the ground side control device 30 (see FIG. 9) arranged on the ground side, which will be described later, to perform various information. To send and receive.

The flight control unit 13 can store flight data such as a route in advance, but it can also be operated from the ground via the above-mentioned ground side control device 30. In addition to controlling the rotation speed of the propeller 12, the flight control unit 13 also controls the moving mechanism 2.

A camera 15 for observing the surface of the structure (the lower surface M1 of the girder in the present embodiment) is provided at the front end portion (left end portion in FIG. 2) of the small unmanned aerial vehicle 1. The image captured by the camera 15 is transmitted to the ground side control device 30 via the flight control unit 13.

The moving mechanism 2 is provided at both the left and right ends in FIGS. 1 and 4 on the upper surface side of the small unmanned aerial vehicle 1. The moving mechanism 2 is provided on a belt 21 having an endless track, four pulleys 22 on which the belt 21 is laid, and one of these pulleys 22 (the right end in FIG. 2), and the pulley 22 is provided. It has a motor and a gearbox (both are not shown) for rotating the drive.

Then, the pulley 22 is rotationally driven in a state where the surface of the belt 21 is in contact with the lower surface M1 of the girder, so that the belt 21 hung around the pulley 22 moves, whereby the small unmanned aerial vehicle 1 is moved by the belt 21. It can be moved along the length direction. At this time, by measuring the amount of rotation of the pulley 22 with a rotation sensor or the like, it is possible to obtain data on the moving distance of the small unmanned aerial vehicle 1.

The surface of the belt 21 is formed so that the coefficient of friction is high. That is, if the cover thickness inspection device 10 pressed against the girder lower surface M1 by the buoyancy of the small unmanned aerial vehicle 1 is to be driven by the rotational drive of the belt 21, a certain amount of frictional resistance is required. The surface of the belt 21 can have a structure having high adsorption performance such as rubber, a fine suction cup structure, and an ultrafine hair structure (using Van der Waals force).

Next, the details of the cover thickness measuring sensor 3 will be described with reference to FIGS. 1 to 4 and 5.

As best shown in FIG. 5, the cover thickness measuring sensor 3 is formed in a substantially rectangular parallelepiped shape, and the end portion 3b of the upper surface 3a in FIG. 5 which is a contact surface in contact with the girder lower surface M1 which is the surface of the structure is formed. By chamfering the upper surface 3a in a curved shape, the upper surface 3a is formed as a smooth surface.

As described above, the cover thickness measuring sensor 3 is a sensor 3 capable of measuring the cover thickness by the electromagnetic induction method. The principle of the electromagnetic induction method and the cover thickness measuring method will be described with reference to FIGS. 6 and 7.

As shown in FIG. 6, an exciting coil 3c and a detection coil 3d are built in the cover thickness measuring sensor 3, and an exciting current is supplied to the exciting coil 3c from the drive power supply unit of the small unmanned aerial vehicle 1. When this exciting current is supplied to the exciting coil 3c, a magnetic flux is generated along the vertical direction in FIG. 6, a current is generated in the reinforcing bar F by the electromagnetic induction of the magnetic flux H, and further, the magnetic flux H is also generated by this induced current. Occurs. Then, the magnetic flux H based on the induced current of the reinforcing bar F is detected by the detection coil 3d and taken out as a detection signal.

Therefore, the exciting coil 3c and the detection coil 3d built in the cover thickness measuring sensor 3 can detect the magnetic flux H from the reinforcing bar F in the concrete girder M most efficiently when the upper surface 3a is in contact with the girder lower surface M1. The position, size, etc. are set in.

As shown in FIG. 7, when the upper surface 3a of the cover thickness measuring sensor 3 is brought into contact with the lower surface M1 of the concrete girder M and the exciting current is supplied to the exciting coil 3c in this state, it is detected based on the magnetic flux H from the reinforcing bar F. The detection signal detected by the coil 3d becomes smaller as _{the cover thickness is thicker (h 1} > h _{2), as schematically shown by an arrow in the figure.} Although not shown, the larger the reinforcing bar diameter, the larger the detection signal detected by the detection coil 3d.

Accordingly, the cover thickness h _1, h ₂ rebar F measurement can be detected based on the detection signal. Further, by scanning the cover thickness measuring sensor 3 in the left-right direction of FIG. 7, since the place where the detection signal is the largest is directly under the reinforcing bar F, the position of the reinforcing bar F can also be detected. Further, if the cover thickness is known, the reinforcing bar diameter can be measured and detected.

Returning to FIG. 5, the cover thickness measuring sensor 3 is fixed and supported on the support portion 11b of the small unmanned aerial vehicle 1 by the urging portion 4, which is also an urging mechanism. The urging portion 4 has a support cylinder 4a made of an elastic member such as a cylindrical rubber and an urging member 4b such as a spring housed in the support cylinder 4a, and the support cylinder 4a and the urging member 4a. The cover thickness measuring sensor 3 is supported from below by 4b, and an urging force is applied to urge the cover thickness measuring sensor 3 toward the lower surface M1 of the girder.

A displacement meter 5 is interposed between the cover thickness measuring sensor 3 and the support portion 11b. The displacement meter 5 detects the displacement of the cover thickness measuring sensor 3 by the urging unit 4 along the urging force on the lower surface M1 of the girder. The measurement result (displacement result) by the displacement meter 5 is transmitted to the ground side control device 30 via the flight control unit 13.

Further, a marker 6 which is a recording unit is attached to the side surface of the cover thickness measuring sensor 3. The tip 6a of the marker 6, that is, the part to be marked, is in contact with the lower surface M1 of the girder while the upper surface 3a of the cover thickness measurement sensor 3 is in contact with the lower surface M1 of the girder. The movement locus along the girder lower surface M1 of the cover thickness measuring sensor 3 is recorded.

Further, a hollow tubular electromagnetic wave shielding portion 7 formed of a substance (for example, ferrite) that shields electromagnetic waves is provided so as to surround the side of the cover thickness measuring sensor 3. The upper end portion 7a of the electromagnetic wave shielding portion 7 is in contact with the lower surface M1 of the girder so that the upper end portion 7a is slightly lower than the upper surface 3a of the cover thickness measurement sensor 3, that is, for the cover thickness measurement by the cover thickness measurement sensor 3. The height is set so as not to come into contact with the lower surface M1 of the girder even when the girder is being used. The electromagnetic wave shielding unit 7 is shown only in FIGS. 3 and 5 for the sake of simplification.

Further, as shown in FIG. 12, a locus sensor 8 for detecting a movement locus recorded by the marker 6 is provided at one end (left end in the illustrated example) of the cross beam portion 11a of the small unmanned aerial vehicle 1. The method of detecting the movement locus by the locus sensor 8 may be appropriately selected from well-known ones, and as an example, a method of identifying the marking by the marker 6 by color with a small camera is preferably mentioned. The detection result of the movement locus by the locus sensor 8 is transmitted to the ground side control device 30 via the flight control unit 13.

Next, the cover thickness inspection system including the cover thickness inspection device 10 according to the present embodiment will be described with reference to FIGS. 8 and 9.

The cover thickness inspection system according to the present embodiment includes a cover thickness inspection device 10 and a ground side control device 30 arranged on the ground. The ground side control device 30 receives and manages a wireless communication unit 31 capable of wireless communication with the wireless communication unit 13a of the flight control unit 13 of the cover thickness inspection device 10 and measurement results by the cover thickness inspection device 10. It has a side control unit 32, a storage unit 33 for storing measurement results and the like, and a display unit 34 for displaying images and measurement results captured by the cover thickness inspection device 10 and the like.

Further, a video camera 35 is connected to the ground side control device 30, and the image pickup result by the video camera 35 is input to the ground side control unit 32 via the input interface (I / O) 36 and displayed on the display unit 34 as appropriate. To. The video camera 35 is a camera for grasping the position of the cover thickness inspection device 10. Therefore, a tracking target (not shown) is provided at a suitable position of the small unmanned aerial vehicle 1, and the video camera 35 is the tracking target. It is preferable to track.

Next, a cover thickness inspection method using the cover thickness inspection system according to the present embodiment will be described with reference to FIGS. 8 to 12.

First, as shown in FIG. 8, the cover thickness inspection device 10 is levitated toward the girder lower surface M1 of the concrete girder M of the bridge to be inspected.

When the cover thickness inspection device 10 is pressed against the girder lower surface M1 by the buoyancy obtained by the rotational drive of the propeller 12 of the small unmanned aerial vehicle 1, the belt 21 of the moving mechanism 2 comes into contact with the girder lower surface M1 and the cover thickness inspection device 10 is stable. It becomes a posture.

The cover thickness inspection device 10 and the ground side control device 30 during flight are in a state of communication by radios W1 and W2. From the ground side control device 30, a control signal of the small unmanned aerial vehicle 1, a measurement start instruction signal, and the like are transmitted by wireless W1.

In the concrete girder M to be inspected by the cover thickness inspection system according to the present embodiment, the reinforcing bar F to be inspected is a reinforcing bar extending in the longitudinal direction (left-right direction in the figure) of the girder M as shown in FIG. Is. Therefore, in the cover thickness inspection system of the present embodiment, the small unmanned aerial vehicle 1 is moved in the direction across the girder M (from bottom to top in FIG. 10), and the cover thickness measurement sensor 3 is used along the movement locus. The cover thickness of the reinforcing bar F is inspected from the lower surface M1 of the girder.

From the ground side control device 30, a maneuvering signal is transmitted by wireless W1 so that the cover thickness measurement sensor 3 reaches the inspection start position of the girder lower surface M1, and a tracking target provided on the small unmanned aerial vehicle 1 by the video camera 35. The actual position of the small unmanned aerial vehicle 1 is grasped by photographing the image, and the control signal is adjusted so as to actually reach the inspection start position.

In the flight control unit 13 of the small unmanned aerial vehicle 1, the cover thickness measurement sensor 3 starts inspection based on the control signal from the ground side control device 30 and the information received from the GPS communication satellite 37 (see FIGS. 8 and 9). The rotation speed of the propeller 12 and the belt 21 is controlled so as to reach the position. Further, the flight control unit 13 transmits the image of the lower surface M1 of the girder imaged by the camera 15 to the ground side control device 30 by wireless W2, and the ground side control device 30 is small while checking the image of the camera 15. It controls the position of the unmanned aerial vehicle 1 and confirms and determines the inspection position.

The inspection positions are positions spaced apart from each other in the traveling direction of the belt 21 (that is, the direction across the girder M). By marking the marker 6 along the traveling direction of the belt 21, the survey line L, which is the movement locus, is recorded. At the inspection position P shown in FIG. 11, the flight control unit 13 acquires the cover thickness measurement result by the cover thickness measurement sensor 3, that is, the cover thickness and the reinforcing bar diameter, and wirelessly performs the mileage from the inspection start position and the time when the inspection is performed. It is transmitted to the ground side control device 30 by W2.

The inspection start position can be determined from the bar arrangement plan of the reinforcing bar F in the concrete girder M, and each inspection position is set by transmitting a signal specifying the amount of rotation of the belt 21 from the ground side control device 30. be able to. Further, the above-mentioned mileage can also be measured based on the actual amount of rotation of the belt 21. By collecting the position data in this way, the actual travel distance can be accurately grasped.

Various data transmitted to the ground side control device 30 are temporarily stored in the storage unit 33 and displayed on the display unit 34 as appropriate.

In order to inspect the entire cover thickness of the concrete girder M under the girder surface M1, first, as shown in FIG. 12A, the small unmanned aerial vehicle 1 is moved in the direction across the girder M (from bottom to top in the figure). The inspection is performed by the cover thickness measuring sensor 3. At this time, the marker 6 records the survey line L on the lower surface M1 of the girder. Next, as shown in FIG. 12B, the trajectory sensor 8 detects the survey line L, and the cover thickness measurement sensor 3 similarly performs the inspection at the inspection position separated from the survey line L by a predetermined distance. Then, as shown in FIG. 12 (c), the cover thickness measurement sensor 3 is used for inspection at the measurement positions arranged in a grid pattern. At this time, the interval of the survey lines L can be adjusted by the installation position of the locus sensor 8.

Next, with reference to FIGS. 13 to 18, a method for inspecting the cover thickness of the reinforced concrete structure using the cover thickness inspection system according to the present embodiment, particularly a method for correcting the cover thickness measured by the cover thickness measurement sensor 3. explain.

The cover thickness measurement sensor 3 used in the cover thickness inspection system according to the present embodiment is a sensor that measures the cover thickness by a so-called electromagnetic induction method. Therefore, if a magnetic material exists in the vicinity of the exciting coil 3c of the cover thickness measurement sensor 3, there is a possibility that an error may occur in the measured values of the cover thickness and the reinforcing bar diameter due to the influence of this magnetic material.

In particular, in the cover thickness inspection system of the present embodiment, the small unmanned aerial vehicle 1 of the cover thickness inspection device 10 is levitated and inspected by the cover thickness measurement sensor 3, and the small unmanned aerial vehicle 1 has a metal portion. In addition, there is a possibility of being affected by electromagnetic waves due to the rotation of the motor unit 121. Therefore, in the cover thickness inspection device 10 of the present embodiment, the electromagnetic wave shielding portion 7 is provided to suppress the influence of electromagnetic waves other than the electromagnetic waves from the reinforcing bar F as much as possible, but no error occurs in the measured values. It is difficult to completely guarantee that.

Therefore, in the cover thickness inspection system of the present embodiment, the cover thickness of the reinforcing bar F in the reinforced concrete structure, which is the inspection target, for example, the lower surface M1 of the girder of the concrete girder M in the present embodiment, is actually inspected. Prior to this, measurement was performed by the cover thickness measurement sensor 3 using a test piece whose cover thickness and reinforcing bar diameter are known, and the relationship between the measured value and the actual cover thickness was obtained in advance and actually inspected. By correcting the measured values of the cover thickness measurement sensor 3 based on this relationship, more accurate cover thickness and reinforcing bar diameter can be inspected.

13 and 14 are diagrams showing an example of a test piece used in the cover thickness inspection system according to the present embodiment.

The test piece 40 shown in FIGS. 13 and 14 has reinforcing bars F arranged in concrete 41 so as to have a predetermined cover thickness. In the illustrated example, the thickness of the concrete 41 (length in the vertical direction in FIG. 13) is 100 mm, the reinforcing _{bar F 1} is 20 mm from the upper surface of the concrete 41 (upper surface in FIG. 13), and the reinforcing bar F ₂ is the concrete 41. Reinforcing bars are arranged with a cover thickness of 40 mm from the upper surface of the concrete. Therefore, when viewed from the lower surface of the concrete 41 (lower surface in FIG. 13), the reinforcing _{bar F 1} has a covering thickness of 80 mm, and the reinforcing _{bar F 2} has a covering thickness of 60 mm.

Such a test piece 40 is suspended by a support member (preferably a non-magnetic material such as wood) so that the upper surface or the lower surface in FIG. 13 is downward, and in this state, the cover thickness inspection device 10 as described above. Is floated and brought into close contact with the upper surface or the lower surface of the test piece 40, and the cover thickness measuring sensor 3 is moved to points A to D shown in FIG. ), The cover thickness of the reinforcing bars F ₁ and F _{2 is measured.}

At this time, it is preferable to actually rotate the motor unit 121 at a rotation speed substantially equal to that at the time of measuring the cover thickness on the girder lower surface M1 to more accurately correct the influence of the electromagnetic wave by the motor unit 121.

Alternatively, the test piece 40 is fixed on the cover thickness measurement sensor 3 in a state where any of the four points (points A to D) of the test piece 40 faces the cover thickness measurement sensor 3, and the cover thickness inspection device is in this state. By floating 10 and _{measuring the cover thickness of the reinforcing bars F 1} and F ₂ , and performing this operation while changing the relative positions of the test piece 40 and the cover thickness measurement sensor 3, the test piece 40 is operated by the sensor 3. Measure the cover thickness _{of the reinforcing bars F 1} and F ₂ at the four points (points A to D).

The ground-side control unit 32 of the ground-side control device 30 temporarily stores the measurement result received from the cover thickness inspection device 10 in the storage unit 33. After that, the ground side control unit 32 reads out the measured value of the cover thickness measuring sensor 3 at points A to D from the measurement result temporarily stored in the storage unit 33, and this measured value and the actual reinforcing bars F ₁ and F Find the relationship with the cover thickness of _2.

The method for obtaining the relationship between the measured value of the cover thickness measurement sensor 3 and the actual cover thickness can be appropriately selected from well-known methods, but the cover thickness inspection system according to the present embodiment best matches the measured value. The method of finding the regression equation to be used is used.

First, as shown in FIG. 17, the measured value of the cover thickness measuring sensor 3 is taken on the X-axis and the actual cover thickness is taken on the Y-axis, and the measured value and the points corresponding to the actual cover thickness are plotted. If there is no error in the measured values, the points plotted on the Y = X straight line shown by the dotted line in FIG. 17 are located, but in the example shown in FIG. 17, the points plotted on this dotted line are located. Not done. Therefore, the regression equation that best matches the plotted points is set as Y = f (X), and the parameters of this regression equation Y = f (X) are obtained by, for example, the least squares method. The ground side control unit 32 stores this regression equation and parameters in the storage unit 33.

Next, when the cover thickness of the girder lower surface M1 is actually measured by the cover thickness measurement sensor 3 of the cover thickness inspection device 10 and the measurement result is transmitted to the ground side control device 30, the ground side control unit 32 receives the cover thickness. The measured value of the measurement sensor 3 is applied to the regression equation, and this measured value is corrected by the regression equation and used as the inspection result. Therefore, in the cover thickness inspection system of the present embodiment, the ground side control unit 32 functions as a correction unit.

Next, FIGS. 15 and 16 are diagrams showing another example of the test piece used in the cover thickness inspection system according to the present embodiment.

The test piece 42 shown in FIGS. 15 and 16 is formed _{by arranging reinforcing bars F 3 to} F ₆ having a predetermined reinforcing bar diameter in concrete 41 with substantially the same covering thickness.

Such a test piece 42 is suspended by a support member (preferably a non-magnetic material such as wood) so that the upper surface or the lower surface in FIG. 15 is downward, and in this state, the cover thickness inspection device 10 as described above. Is floated and brought into close contact with the upper surface or the lower surface of the test piece 42, and the cover thickness measuring sensor 3 is moved to points A to D shown in FIG. ), The reinforcing bar diameters of the reinforcing _{bars F 3 to F 6 are measured.}

Alternatively, the test piece 42 is fixed on the cover thickness measurement sensor 3 in a state where any of the four points (points A to D) of the test piece 42 faces the cover thickness measurement sensor 3, and the cover thickness inspection device is in this state. By floating 10 and _{measuring the reinforcing bar diameters of the reinforcing bars F 3 to} F ₆ and performing this operation while changing the relative positions of the test piece 42 and the cover thickness measuring sensor 3, the test piece 42 is operated by the sensor 3. Measure the reinforcing bar diameters of the reinforcing _{bars F 3 to F 6} at the four points (points A to D) of.

The ground-side control unit 32 of the ground-side control device 30 temporarily stores the measurement result received from the cover thickness inspection device 10 in the storage unit 33. After that, the ground side control unit 32 reads out the measured value of the cover thickness measuring sensor 3 at points A to D from the measurement result temporarily stored in the storage unit 33, and this measured value and the actual reinforcing bars F _{3 to} F Find the relationship with the reinforcing bar diameter of _6.

The method for obtaining the relationship between the measured value of the cover thickness measuring sensor 3 and the actual reinforcing bar diameter may be the same as in the case of the cover thickness described above. That is, as shown in FIG. 18, the measured value of the cover thickness measuring sensor 3 is taken on the X-axis and the actual reinforcing bar diameter is taken on the Y-axis, and the measured value and the points corresponding to the actual reinforcing bar diameter are plotted. If there is no error in the measured values, the points plotted on the Y = X straight line shown by the dotted line in FIG. 18 are located, but in the example shown in FIG. 18, the points plotted on this dotted line are located. Not done. Therefore, the regression equation that best matches the plotted points is set as Y = f (X), and the parameters of this regression equation Y = f (X) are obtained by, for example, the least squares method.

After that, as in the case of the cover thickness, the measured value of the cover thickness measurement sensor 3 may be corrected based on the regression equation and used as the inspection result.

In the cover thickness inspection method according to the present embodiment configured as described above, the cover thickness of the reinforcing bar F in the concrete test piece 40 in which the reinforcing bar F having a known cover thickness is embedded is measured by the cover thickness measuring sensor 3. Then, the relationship between the measured value of the cover thickness of the reinforcing bar F in the test piece 40 measured by the cover thickness measuring sensor 3 and the actual cover thickness is obtained, and the cover thickness measured by the cover thickness measuring sensor 3 is based on this relationship. The measured value of is corrected.

By doing so, the measured value by the cover thickness measuring sensor 3 can be appropriately corrected, and the cover thickness of the reinforced concrete structure can be accurately measured.

Here, since the cover thickness of the reinforcing bar F in the test piece 40 is measured by the cover thickness measuring sensor 3 in the state where the small unmanned aerial vehicle 1 is operated, the cover thickness of the structure is actually measured by the cover thickness inspection device 10. The correction can be performed in a state closer to the measurement condition, and the measured value can be corrected more appropriately.

Further, the cover thickness inspection device 10 according to the present embodiment is a cover thickness measurement sensor 3 provided on the moving mechanism side of the small unmanned aircraft 1, and a measurement value of the cover thickness of the reinforcing bar F measured by the cover thickness measurement sensor 3. The ground is a correction unit that corrects the measured value of the cover thickness measured by the cover thickness measurement sensor 3 based on the storage unit 33 in which the relationship between the image and the actual cover thickness is stored and the relationship stored in the storage unit 33. It has a side control unit 32.

By doing so, the value measured by the cover thickness measurement sensor 3 can be appropriately corrected by the ground side control unit 32, and the cover thickness inspection device 10 suitable for the cover thickness inspection method described above can be realized. ..

Although the embodiments of the present invention have been described in detail with reference to the drawings, the specific configuration is not limited to the embodiments and examples, and design changes are made to the extent that the gist of the present invention is not deviated. Is included in the present invention.

For example, in the cover thickness inspection system according to the above-described embodiment, the test pieces 40 and 42 are measured with the small unmanned aerial vehicle 1 floating, but as a simple correction method, the small unmanned aerial vehicle 1 is stationary. The correction value (regression formula) may be calculated by measuring the test pieces 40 and 42 in this state. Alternatively, the test pieces 40 and 42 may be measured with the small unmanned aerial vehicle 1 fixed on the ground and the motor unit 121 rotated.

On the other hand, as a more precise correction method, the test pieces 40 and 42 are measured in a state where the rotation speed of the motor unit 121 of the small unmanned aerial vehicle 1 is changed stepwise, and the rotation speed of the motor unit 121 and the correction value at that time are measured. A nomogram that organizes the relationship with (return equation) is created, and the measured value when the cover thickness of a structure such as the girder lower surface M1 is actually measured by the cover thickness measurement sensor 3 is corrected with reference to this nomogram. May be good.

Further, in the cover thickness inspection device 10 according to the above-described embodiment, the endless track type moving mechanism 2 has been described, but the present invention is not limited to this. For example, even if the moving mechanism 2 has wheels, it is a small unmanned aerial vehicle. Can be moved along the surface of the structure.

Further, in the above-described embodiment, the inspection of the lower surface M1 of the girder of the bridge has been described as an example, but the present invention is not limited to this, and the inspection of a high place of a reinforced concrete structure such as a high-rise building is also performed. The cover thickness inspection device 10 can be applied. Further, when inspecting the side surface of a pier, a retaining wall, a building, or the like, the present invention is made by using a small unmanned aerial vehicle having a structure in which the upper half of the fuselage provided with a moving mechanism stands up. Be able to apply.

1 Small unmanned aerial vehicle 2 Mobile mechanism 3 Cover thickness measurement sensor 10 Cover thickness inspection device 32 Ground side control unit (correction unit)
33 Storage units 40, 42 Test piece F Reinforcing bar M Concrete girder (Reinforced concrete structure)
M1 girder lower surface (front surface)

Claims (1)

It has a small unmanned aerial vehicle, a moving mechanism provided on the side facing the surface of the structure of the small unmanned aerial vehicle, and a cover thickness measuring sensor by an electromagnetic induction method provided on the moving mechanism side of the small unmanned aerial vehicle. This is a cover thickness inspection method that inspects the cover thickness of reinforcing bars in a reinforced concrete structure using a cover thickness inspection device.
The cover thickness of the reinforcing bar in the concrete test piece in which the reinforcing bar having a known cover thickness is embedded is measured by the cover thickness measuring sensor in a state where the small unmanned aerial vehicle is operated.
The relationship between the measured value of the cover thickness of the reinforcing bar in the test piece measured by the cover thickness measurement sensor and the actual cover thickness was obtained.
In the method of correcting the measured value of the cover thickness measured by the cover thickness measurement sensor based on the above relationship,
A cover thickness inspection method , wherein the test piece is in a suspended state or in a state of being fixed on the cover thickness measurement sensor.

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