JP2018151168A - Nondestructive inspection method and nondestructive inspection device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a nondestructive inspection method which can easily reduce the effect of magnetism from multiple long-sized steel materials of non-inspection objects arranged crossing a long-sized steel material of inspection object and can correctly detect the existence of a damaged portion, and a nondestructive inspection device.SOLUTION: The nondestructive inspection method comprises: magnetizing a long-sized steel material of inspection object and multiple long-sized steel materials of non-inspection object crossing the steel material of inspection object by a magnet from the outside a concrete body in which the steel material of inspection object and the steel materials of non-inspection object are embedded; then measuring a magnetic flux density outside the concrete body by a magnetic sensor; extracting the magnetic flux density at a substantially intermediate point between the multiple steel materials of non-inspection object adjacent to each other from the magnetic flux density; calculating the amount of change or the rate of change along a longitudinal direction of the steel material of inspection object about the extracted magnetic flux density; and detecting the existence of a damaged portion of the steel material of inspection object by comparing the calculated amount of change or the calculated rate of change with a preset threshold.SELECTED DRAWING: Figure 6

Description

  The present invention relates to a nondestructive inspection method and a nondestructive inspection apparatus for detecting the presence or absence of a damaged portion of a long steel material such as a reinforcing bar provided in the body of a reinforced concrete structure such as a bridge, a building, or a concrete pole.

Conventionally, a non-destructive inspection method for detecting a fracture portion of a long steel material provided in a concrete body is known.
For example, in the non-destructive inspection method described in Japanese Patent No. 3734822 (Patent Document 1), a permanent magnet is placed along the longitudinal direction of a long steel material such as a reinforcing steel bar to be inspected embedded in concrete. The long steel material is magnetized by moving on the surface, then the magnetic flux density leaking from the surface of the concrete is measured, and the differential value of the measured value obtained is calculated to determine whether the long steel material is broken or not. It is to detect.

  However, in general, a large number of long steel materials with different positions and arrangement directions are embedded in the concrete body. Therefore, when the magnetism of the steel material to be inspected is detected by the magnetic sensor outside the concrete body, the magnetism from the long steel material other than the steel material to be inspected is often detected at the same time. However, in the non-destructive inspection method described in Patent Document 1, no means for removing or reducing the influence of magnetism emitted from other than the steel material to be inspected is provided. May be missing.

  Japanese Patent Laying-Open No. 2015-42975 (Patent Document 2) discloses a first magnetization step in which a magnet is moved along the longitudinal direction of a long steel material to be inspected to magnetize the steel material to be inspected, and then concrete. A first magnetic flux density measuring step for measuring the magnetic flux density on the surface of the body, a second magnetization step for magnetizing the steel to be inspected by moving the magnet in the opposite direction to the first magnetization step, and then the surface of the concrete body The second magnetic flux density measuring step for measuring the upper magnetic flux density and the magnetic flux density measured by the first and second magnetic flux density measuring steps are added together to obtain the sum of both magnetic flux densities. A non-inspection magnetic flux removal step that cancels and removes the magnetic flux density, and a fracture portion detection step that detects the presence or absence of a fracture portion of the steel to be inspected based on the sum of the two magnetic flux densities obtained by the non-inspection magnetic flux removal step. Non-destructive inspection method There has been described.

And, according to such a non-destructive inspection method, it is possible to reduce the influence of magnetism from a large number of non-inspection-target long steel materials that are arranged so as to cross the inspection-target long steel material, It is said that the presence or absence of a part can be accurately detected.
However, since the nondestructive inspection method described in Patent Document 2 requires two magnetization steps and two magnetic flux density measurement steps, it takes time and effort to detect the fracture portion of the steel material to be inspected. There is a problem.

Japanese Patent No. 3734822 Japanese Patent Laid-Open No. 2015-42975

  Therefore, the present invention can easily reduce the influence of magnetism from a large number of non-inspection target long steel materials that are arranged to intersect with the long steel material to be inspected, and the inspection target steel material has a damaged portion. It is an object of the present invention to provide a nondestructive inspection method and a nondestructive inspection apparatus capable of detecting the presence or absence of a damaged portion extremely accurately by utilizing the property of change in magnetic flux density that appears characteristically in some cases.

  The above problems have been solved by the following means.

[1] From the outside of a concrete body in which a long steel material to be inspected and a plurality of long non-inspecting steel materials arranged in parallel intersecting the steel material to be inspected are embedded by a magnet. A non-destructive inspection method for detecting the presence or absence of a damaged portion of the inspection target steel material by magnetizing the inspection target steel material and the non-inspection target steel material and then measuring the magnetic flux density outside the concrete body by a magnetic sensor. The magnetized surface of the magnet is arranged close to the surface of the concrete body so that both magnetic poles of the magnet are along the longitudinal direction of the steel material to be inspected, and then the magnet is disposed along the longitudinal direction of the steel material to be inspected. After magnetizing the steel material to be inspected and the steel material not to be inspected by moving, a magnetizing step of removing the magnet, and placing the magnetic sensor close to the surface of the concrete body Then, the plurality of the magnetic flux density measuring step for measuring the magnetic flux density along the longitudinal direction of the steel material to be inspected by appropriately moving or without moving, and the magnetic flux density measured by the magnetic flux density measuring step. A magnetic flux density at a substantially middle point between adjacent ones of the non-inspection target steel materials, and a calculation step of calculating a change amount or a change rate along the longitudinal direction of the inspection target steel materials for the extracted magnetic flux density; A damaged portion detecting step of detecting the presence or absence of a damaged portion of the steel material to be inspected by comparing the amount of change or the rate of change obtained by the calculation step with a predetermined threshold value. Non-destructive inspection method.

  Here, the long steel material is not limited to a round steel bar with a round cross-section, which is a reinforcing bar often used in general reinforced concrete structures, or a deformed steel bar with protrusions on the surface, but a rectangular cross-section shape, etc. It may be a polygonal steel material or an H-shaped steel. Moreover, the inside of the pipe used for water flow or ventilation may be a hollow steel pipe, and further, PC steel material such as PC steel rod, PC steel wire or PC steel twisted wire used for prestressed concrete construction method, or these inside It may be a sheath tube used through a PC steel material in the sheath tube.

  Moreover, in the case of the steel material which consists of a bundle of many steel wires like the part where the long steel material is completely fractured, for example, a PC steel wire or a PC steel twisted wire, the damaged part of the steel material In addition, a part where a part of many steel wires is broken is also included.

  In order to arrange the magnetized surface of the magnet close to the surface of the concrete body when magnetizing the long steel material in the magnetizing step of the invention of [1], the magnetized surface of the magnet is a predetermined part near the surface of the concrete body. It is only necessary to temporarily approach the position, and it is not always necessary to bring the magnetized surface of the magnet into direct contact with the surface of the concrete body, and it is not necessary to make it stationary.

  Here, the magnetized surface of the magnet refers to the one surface of the magnet that is closest to the concrete body when the reinforcing bar is magnetized. Such a magnetized surface is not limited to a single plane as long as both magnetic poles of the magnet can be along the longitudinal direction of the steel material to be inspected.

  Also, in the magnetic flux density measurement process, in order to place the magnetic sensor close to the surface of the concrete body, as in the case of the magnet, the magnetic sensor may be temporarily brought close to a predetermined position near the surface of the concrete body. Well, it is not necessary to directly contact the surface of the concrete body, and it does not need to be stationary.

However, in order to obtain the magnetic flux density along the longitudinal direction of the steel material to be inspected, it is necessary to measure the magnetic flux density to the inspection range of the damaged portion of the steel material to be inspected and, if necessary, the peripheral range.
For that purpose, the magnetic flux density may be measured while appropriately moving one or a plurality of magnetic sensors. For example, while moving the magnetic sensor near the surface of the concrete body along the longitudinal direction of the steel material to be inspected. Magnetic flux density can be measured. Alternatively, the magnetic sensor arranged on the surface of the concrete body is moved back and forth in a direction perpendicular to the longitudinal direction of the steel material to be inspected while being close to the surface of the concrete body, and gradually shifted in the longitudinal direction of the steel material to be inspected. Thus, the magnetic flux density of the steel material to be inspected can be measured, and the magnetic flux density along the longitudinal direction of the steel material to be inspected can be calculated from the measurement result.

  For example, when using a long magnetic sensor unit in which a large number of magnetic sensors are connected in a straight line, the magnetic sensor unit is placed on the surface of the concrete body along the longitudinal direction of the steel material to be inspected. The magnetic flux density along the longitudinal direction of the steel material to be inspected can be measured simply by placing them close to each other and without moving them thereafter.

[2] Based on the position information of the non-inspection target steel material obtained by investigating in advance, the magnetic flux density is extracted at a substantially intermediate point between adjacent ones of the plurality of non-inspection target steel materials in the calculation step. The nondestructive inspection method according to claim 1.

  Here, the position information of the non-inspection target steel material obtained by investigating in advance is a plurality of long non-inspection targets arranged substantially in parallel when viewed from the direction perpendicular to the surface of the concrete body. The location information of each part where the steel material intersects with the long steel material to be inspected, which is investigated or inspected in advance by a general radar type or electromagnetic induction type reinforcing bar probe This is position information obtained by examining design drawings of reinforced concrete structures.

[3] Local convex shape apex that appears when the magnetic flux density measured by the magnetic flux density measurement step is represented in a graph in which the horizontal axis indicates the longitudinal position of the steel material to be inspected and the vertical axis indicates the magnetic flux density It is estimated that a non-inspection target steel material exists at the position of the magnetic field, and the magnetic flux density is extracted at a substantially middle point between the adjacent non-inspection target steel materials in the calculation step. The nondestructive inspection method according to 1.

  A curve S1 in FIG. 3 and a curve D1 in FIG. 6 are graphs showing the vertical direction component of the magnetic flux density measured by the magnetic flux density process, the horizontal axis showing the longitudinal position of the steel material to be inspected, and the vertical axis showing the magnetic flux density. In this example, both the curved line S1 and the curved line D1 have a large number of local convex portions toward the bottom of the graph. The apex (lowermost point) of the downward convex portion is a plurality of long, non-inspected steel materials arranged in parallel when viewed from the direction perpendicular to the surface of the concrete body. It is known that it appears at each location that intersects the steel material to be inspected. Therefore, it can be estimated that the non-inspection target steel material exists at the position of the apex (lowermost point) of the convex portion.

[4] From the outside of the concrete body in which a long steel material to be inspected and a plurality of substantially non-inspecting steel materials arranged in parallel intersecting the steel material to be inspected are embedded by a magnet. A non-destructive inspection device that detects the presence or absence of a damaged portion of the inspection target reinforcing bar by magnetizing the inspection target reinforcing bar and the non-inspecting target steel, and then measuring the magnetic flux density outside the concrete body by a magnetic sensor. The magnetic poles are arranged close to the surface of the concrete body so that both magnetic poles are along the longitudinal direction of the inspection object rebar, and are moved along the longitudinal direction of the inspection object rebar, so that the inspection object rebar is moved. And a magnet for magnetizing the non-inspection target steel material, and the concrete member disposed close to the surface of the concrete body and moved appropriately or without moving. A magnetic sensor for measuring the magnetic flux density along the longitudinal direction of the inspection target reinforcing bar on the surface of the steel body, and a plurality of non-inspection target steel materials set in advance from the magnetic flux density measured by the magnetic sensor. Based on the position information, the magnetic flux density at a substantially intermediate point between adjacent ones of each non-inspection steel material is extracted, and the amount of change or rate of change along the longitudinal direction of the inspected steel material for the extracted magnetic flux density Computing means for calculating
And a damaged portion detecting means for detecting the presence or absence of a damaged portion of the steel material to be inspected by comparing the amount of change or the change rate obtained by the calculating means with a preset threshold value. Destructive inspection equipment.

  Here, the position information of the non-inspection target steel material obtained by investigating in advance is, as described above, a plurality of elongated shapes arranged substantially in parallel when viewed from the direction perpendicular to the surface of the concrete body. The non-inspected steel material is the location information of each part intersecting with the long inspected steel material, and it is investigated in advance with a general rebar probe or the design drawing of the reinforced concrete structure It is the positional information obtained by doing.

  According to the nondestructive inspection method according to the invention of [1], in the calculation process, from the magnetic flux density measured by the magnetic flux density measurement process, a substantially intermediate point between adjacent ones of the plurality of non-inspection steel materials. As a result, it is possible to remove a locally large change portion of the magnetic flux density caused by the presence of the non-inspection target steel material. Therefore, it becomes possible to accurately determine the change state of the magnetic flux density of the magnetic flux generated from the steel material to be inspected, and the presence / absence of the damaged portion can be detected with high accuracy.

Moreover, according to the nondestructive inspection method according to the invention of [2], each of the plurality of non-inspection target steel materials in the calculation step is adjacent to each other on the basis of the positional information of the non-inspection target steel materials obtained in advance by investigation. Since the magnetic flux density is extracted at a substantially middle point between the matching pieces, a locally large change portion of the magnetic flux density caused by the presence of the non-inspection steel material can be surely removed.
Therefore, the magnetic flux density can be automatically and reliably extracted at a substantially intermediate point between adjacent ones of the plurality of non-inspection steel materials by, for example, data processing by the CPU.

  Further, according to the nondestructive inspection method according to the invention of [3], the magnetic flux density measured by the magnetic flux density measurement process is shown, the horizontal axis indicates the longitudinal position of the steel material to be inspected, and the vertical axis indicates the magnetic flux density. It is estimated that there is a non-inspection target steel material at the position of the apex of the local convex shape portion that appears in the case of, and at a substantially intermediate point between each of the plurality of non-inspection target steel materials in the calculation process Since the magnetic flux density is extracted, there is no need to separately investigate the position information of the non-inspected steel material, which is convenient.

  Further, according to the nondestructive inspection apparatus according to the invention of [4], the nondestructive inspection method according to the invention of [2] can be automatically and reliably carried out, and the presence or absence of a damaged portion is very accurately detected. Can be detected.

It is explanatory drawing which shows a X direction cross section at the time of arrange | positioning a magnet on the surface of the concrete body by which the to-be-inspected reinforcing bar which does not include a fracture | rupture part and three crossing reinforcing bars were embed | buried. A cross section in the X direction when a magnet arranged in a position substantially directly above the inspection target reinforcing bar is moved in the X direction on the surface of the concrete body in which the inspection target reinforcing bar and the three crossing reinforcing bars are not embedded. It is explanatory drawing shown. It is a graph which shows the measurement result of the perpendicular | vertical component of the magnetic flux density on the surface of the concrete body by which the test object reinforcing bar which does not include a fracture | rupture part, and seven crossing reinforcing bars were embed | buried. Description showing a cross section in the X direction when a magnet arranged at a position substantially directly above the main reinforcing bar is moved in the X direction on the surface of the concrete body in which the reinforcing bar including the fracture portion and the three crossed reinforcing bars are embedded. FIG. It is explanatory drawing which shows the state of the magnetic flux on a magnetic force line and a concrete body surface when the test object reinforcing bar containing a fracture | rupture part is magnetized. It is a graph which shows the measurement result of the perpendicular | vertical component of the magnetic flux density on the surface of the concrete object by which the test object reinforcement containing a fracture | rupture part and seven crossing reinforcing bars were embed | buried. It is a graph which shows an example of the measurement result of the perpendicular | vertical component of the magnetic flux density on the concrete other surface in which the test | inspection PC steel material and many cross rebars of non-inspection object were embed | buried. It is a graph which shows the other example of the measurement result of the perpendicular | vertical component of magnetic flux density on the concrete other surface in which the inspection object PC steel material and many cross rebars of non-inspection object were embed | buried. It is a graph which shows the approximate value of the measurement result of the perpendicular | vertical component of the magnetic flux density in FIG. It is a graph which shows the approximate value of the measurement result of the perpendicular | vertical component of the magnetic flux density in FIG. It is a graph which shows the example of the variation | change_quantity and threshold value for every 1 section (190 mm) of the approximate value in FIG. It is a graph which shows the example of the variation | change_quantity and threshold value for every 1 section (190 mm) of the approximate value in FIG. It is a graph which shows the example of the variation | change_quantity and threshold value for every 2 area (380 mm) of the approximate value in FIG. It is a graph which shows the example of the variation | change_quantity and threshold value for every 2 area (380 mm) of the approximate value in FIG. 10 is a graph showing an example of a change rate and a threshold value for each section (190 mm) of the approximate value in FIG. 9. It is a graph which shows the example of the change rate and threshold value for every 1 section (190 mm) of the approximate value in FIG. It is a graph which shows the example of the integrated value of the negative value of the change rate in FIG. It is a graph which shows the example of the integral value of the negative value of the change rate in FIG. It is a perspective view which shows an example of a U-shaped magnet. It is a schematic block diagram which shows an example of a nondestructive inspection apparatus.

  Embodiments of a nondestructive inspection method and a nondestructive inspection apparatus according to the present invention will be described below.

A: Principle of the nondestructive inspection method of the present invention
Aa: Inspected reinforcing bar and crossed reinforcing bar FIGS. 1 and 2 show a cross section in the X direction of the concrete body 1 in which the inspected reinforcing bar 2 having no fracture portion is embedded. 3 and 4 show a cross section in the X direction of the concrete body 1 in which the inspection target reinforcing bar 2 (2N, 2P) having the fracture portion H is embedded.
In these drawings, in a concrete body 1, an inspection rebar 2 and a cross rebar 3, which is a non-inspection object arranged so as to be substantially orthogonal to the inspection target rebar 2, are embedded. .

Ab: When the inspection target reinforcing bar does not have a broken portion The case where the inspection target reinforcing bar 2 has no broken portion will be described.
As shown in FIG. 1, a magnet 5 is magnetized on the surface 1A of the concrete body 1 so that both magnetic poles thereof are along the longitudinal direction of the rebar 2 to be inspected and the N pole is on the left side of the figure and the S pole is on the right side of the figure. If the magnetized surface 5A of the magnet 5 is placed close to each other, the inspection target reinforcing bar 2 is magnetized to the S pole on the left side of the drawing and to the N pole on the right side of the drawing due to the influence of the magnetic force line 51 from the magnet 5. A magnetic flux 2A directed in the X direction is generated inside.
Further, the portion near the magnet 5 of the cross rebar 3L on the left side of the figure is magnetized to the south pole by the influence of the magnetic field lines 51, so that a magnetic flux 3LA directed in the Z direction is generated on the concrete body surface 1A. Since the portion of the reinforcing bar 3R close to the magnet 5 is magnetized to the N pole, a magnetic flux 3RA directed in the -Z direction is generated on the concrete body 1A.

Here, the position where the magnet 5 is arranged is preferably a position where the separation distance between the magnetized surface 5A of the magnet 5 and the inspection target reinforcing bar 2 is the shortest in order to sufficiently magnetize the inspection target reinforcing bar 2 which is the inspection target. In the example as shown in FIG. 1, the magnet 5 is positioned on the surface 1 </ b> A of the concrete body 1 directly above the inspection target rebar 2 (that is, the position of the magnet 5 in the Y direction and the position of the inspection rebar 2 in the Y direction). In the same case).
However, if the distance between the magnet 5 and the rebar 2 to be inspected is too short, extra magnetism that hinders inspection may occur. If there is such a fear, the magnet 5 is slightly above the concrete body surface 1A. What is necessary is just to arrange | position in the position distant from.
Further, the orientations of the two magnetic poles of the magnet 5 to be arranged may be the S pole on the left side and the N pole on the right side, contrary to the present embodiment.

  The magnet 5 in the present embodiment is a rectangular parallelepiped (100 mm in length, 100 mm in width, 60 mm in height) made of a rare earth metal such as Nd, but is not limited to this, for example, an electromagnet instead of a permanent magnet. The shape is not limited to a rectangular parallelepiped, and may be a U shape or a U shape. Further, the magnet 5 may be in a bare state as it is, but is housed in a case having a function for facilitating movement while being close to the surface of the concrete body, or is unitized by combining a plurality of magnets. There may be.

Next, as shown in FIG. 2, the magnet 5 disposed on the concrete body surface 1 </ b> A substantially directly above the rebar 2 to be inspected is moved by moving it to the X direction side along the longitudinal direction of the rebar 2 to be inspected. Do magnetism. FIG. 2 shows a cross section in the X direction, which is the longitudinal direction of the rebar 2 to be inspected, of the concrete body 1.
At this time, the reinforcing bar 2 to be inspected is magnetized, and a magnetic flux 2A in the X direction is generated therein. Further, a portion of the crossing reinforcing bar 3 that is located immediately below the trajectory to which the magnet 5 has moved is magnetized to the S pole under the influence of the N pole of the magnet 5 that has finally passed through the vicinity thereof. Therefore, the magnetic flux density Z is relatively high on the concrete body surface 1A above the portion magnetized to the south pole of the crossed reinforcing bar 3 (the portion of the crossed reinforcing bar 3 positioned immediately above the inspection target reinforcing bar 2). Directional magnetic flux 3A is generated.

In FIG. 2, in order to facilitate understanding of the present invention, the magnetic flux 3A and the crossing reinforcing bar 3 are shown to overlap each other. However, the magnetic flux 3A is exactly the same as the magnetic flux 3LA shown in FIG. This is a magnetic flux in the Z direction generated on the body surface 1A.
Similarly, in FIG. 4 and FIG. 20, the magnetic flux 3 </ b> A represented so as to overlap the crossed reinforcing bar 3 is precisely a magnetic flux generated on the concrete body surface 1 </ b> A above the crossed reinforcing bar 3.
In addition, the direction of the arrow showing each magnetic flux has shown the direction of each magnetic flux.

  Here, the trajectory for moving the magnet 5 does not necessarily have to be directly above the rebar 2 to be inspected. Similarly, the description “along the longitudinal direction of the reinforcing bar” does not necessarily mean that it should always be along the reinforcing bar. However, in order to sufficiently magnetize the inspection target rebar 2 of the inspection object, it is desirable that the moving trajectory has the shortest separation distance between the magnet 5 and the inspection target rebar 2. It is desirable to move the magnetized surface 5A of the magnet 5 close to the concrete body surface 1A and move the inspection object rebar 2 directly along the longitudinal direction thereof.

In the concrete body 1 in which the inspected reinforcing bar 2 and the seven crossed reinforcing bars 3 without the rupture portion are embedded, the N pole is placed on the concrete body surface 1A along the longitudinal direction of the inspected reinforcing bar 2 as shown in FIG. When the magnet 5 having the S pole on the right side of the figure is moved in the X direction and magnetized to magnetize the reinforcing bar 2 and the crossed reinforcing bar 3, the magnetic sensor is used to inspect the concrete surface 1A. When the vertical component (Z-direction or -Z-direction component) of the magnetic flux density along the longitudinal direction directly above the target reinforcing bar 2 is measured, a curve S1 in FIG. 3 is obtained.
Such a curve S1 represents a change according to the X-direction position of the vertical component of the magnetic flux density on the concrete body surface 1A along the longitudinal direction directly above the inspection target reinforcing bar 2 after magnetization.

  The horizontal axis of the graph in FIG. 3 represents the position in the X direction (unit: mm) on the concrete body surface 1A, and the vertical axis represents the vertical component (unit: μT) of the magnetic flux density at this position. ing.

  Since a total of seven cross rebars 3 are embedded in each position of -750 mm, -500 mm, -250 mm, 0 mm, 250 mm, 500 mm, and 750 mm on the horizontal axis of FIG. A vertex (the lowest point) of the downward convex portion appears on the curve S1.

  In the example of FIG. 3, the rebar 2 to be inspected is a rebar having a diameter of 16 mm (deformed bar), and the cover thickness of concrete is 100 mm. The crossed reinforcing bar 3 is a reinforcing bar (deformed bar) having a diameter of 13 mm embedded so as to be substantially orthogonal to the reinforcing bar 2 to be inspected, and the concrete cover thickness is 62 mm. Moreover, the concrete cover thickness is the shortest distance from the surface of the concrete body to the surface of the reinforced steel bar.

Next, from the magnetic flux density measured by the above method, the magnetic flux density at a substantially intermediate point between the seven non-inspection steel materials adjacent to each other is extracted. That is, -625 mm which is an intermediate point between -750 mm and -500 mm, -375 mm which is an intermediate point between -500 mm and -250 mm, -125 which is an intermediate point between -250 and 0 mm, 125 mm which is an intermediate point between 0 mm and 250 mm, The magnetic flux density (vertical component) is extracted at each position of 375 mm, which is an intermediate point between 250 mm and 500 mm, and 625 mm, which is an intermediate point between 500 mm and 750 mm.
A curve S2 in the graph of FIG. 3 is obtained by connecting the magnetic flux densities (vertical components) at the respective intermediate points with straight lines. The curve S2 does not have a large convex portion as compared with the curve S1, and shows a gentle upward shape.

Ac: When the main reinforcing bar has a broken part Next, a case where the inspection target reinforcing bar 2 has a broken part will be described.
FIG. 4 shows a cross section in the X direction of the concrete body 1 in the case where the inspection target reinforcing bar 2 has a fracture H.

First, as shown in FIG. 4, on the concrete body surface 1A along the longitudinal direction of the inspection target reinforcing bar 2 (2N and 2P), the magnet 5 with the N pole on the left side and the S pole on the right side is connected to the inspection target reinforcing bar. After being arranged at a position almost directly above 2N, magnetization is performed by moving in the X direction to magnetize the reinforcing bars 2N and 2P to be inspected and the crossing reinforcing bar 3. Then, portions other than the rupture portion H of the inspection target reinforcing bar 2 are magnetized, but the rupture portion H is not magnetized, and inside the inspection target rebar 2N located on the X direction negative side with the rupture portion H as the origin position. , A magnetic flux 2AN in the X direction is generated, and a magnetic flux 2AP in the X direction is generated in the inside of the inspection target reinforcing bar 2P located on the positive side in the X direction.
Further, a portion of the crossing reinforcing bar 3 that is located immediately below the trajectory to which the magnet 5 has moved is magnetized to the S pole under the influence of the N pole of the magnet 5 that has finally passed through the vicinity thereof. Therefore, a magnetic flux 3A in the Z direction is generated on the concrete body surface 1A above the portion magnetized to the south pole of the crossed reinforcing bar 3 (the portion of the crossed reinforcing bar 3 positioned immediately above the inspection target reinforcing bar 2). .

  In FIG. 4, in order to facilitate understanding of the present invention, the magnetic flux 3 </ b> A and the crossed reinforcing bar 3 are shown to overlap each other, but the magnetic flux 3 </ b> A is precisely a magnetic flux in the Z direction generated on the concrete body surface 1 </ b> A. .

FIG. 5 shows the state of the lines of magnetic force generated from the inspection reinforcing bars 2N and 2P after magnetization. The magnetic force line 61 is generated from the inspection target reinforcing bar 2N, and the magnetic force line 62 is generated from the inspection target reinforcing bar 2P.
In this case, a magnetic flux 6N1 in the Z direction is generated on the concrete body surface 1A above the left end of the inspection target rebar 2N, while a magnetic flux 6N2 opposite to 6N1 is generated above the right end of the inspection target rebar 2N. Further, a magnetic flux 6P1 in the Z direction is generated above the left end of the inspection target rebar 2P, while a magnetic flux 6P2 opposite to 6P1 is generated above the right end of the inspection target rebar 2P.
Therefore, the vertical component of the magnetic flux density on the surface 1A of the concrete body above the inspection target rebar 2N is influenced by the magnetic flux in the Z direction such as 6N1 near the end of the moving range of the magnet 5 away from the fracture portion H. Appears strongly, and at the position close to the fracture portion H, the influence of the magnetic flux in the −Z direction such as 6N2 appears strongly. Similarly, the vertical component of the magnetic flux density on the concrete body surface 1A above the rebar 2P to be inspected is the magnetic flux in the −Z direction like 6P2 near the end of the moving range of the magnet 5 away from the fracture portion H. The influence appears strongly, and the influence of the magnetic flux in the Z direction such as 6P1 appears strongly at a position near the fracture portion H.

Therefore, when the vertical component of the magnetic flux density on the concrete body surface 1A along the entire inspection object reinforcing bar 2 including the inspection object reinforcing bars 2N and 2P is measured, as shown in the graph of FIG. On the left and right of the 0 mm position on the horizontal axis), a curve having an upward convex portion and a downward convex portion due to a change in magnetic flux density is obtained. Further, the inclination of the line segment connecting these two convex portions is very steep. That is, in the vicinity of the position of the fracture portion H, a large change in magnetic flux density of a substantially S shape appears from the upward convex shape portion to the downward convex shape portion.
As described above, when the inspection target reinforcing bar 2 has the fracture portion H, the vertical component of the magnetic flux density on the concrete body surface 1A changes abruptly. By detecting this characteristic sudden change, the fracture portion H It can be determined whether or not.

  The example of FIG. 6 is the same as the example of FIG. 3 except that the inspection target reinforcing bar 2 has a broken portion H at the 0 mm position on the horizontal axis of the graph. That is, the rebar 2 to be inspected is a 16 mm diameter rebar (deformed bar), the concrete cover thickness is 100 mm, the cross rebar 3 is a 13 mm diameter rebar (deformed bar), and the concrete cover thickness is 62 mm. . In addition, the crossed reinforcing bars 3 are embedded in each position of −750 mm, −500 mm, −250 mm, 0 mm, 250 mm, 500 mm, and 750 mm on the horizontal axis of the graph so that a total of seven bars are substantially orthogonal to the reinforcing bar 2 to be inspected. ing.

  The curve D1 in FIG. 6 shows the N pole on the left side of the figure and the S pole on the right side of the concrete body surface 1A along the longitudinal direction substantially directly above the rebar 2 (2N and 2P) to be inspected as shown in FIG. When the magnet 5 is moved in the X direction to magnetize the inspected reinforcing bar 2 and the crossed reinforcing bar 3, the magnetic flux density along the longitudinal direction directly above the inspected reinforcing bar 2 on the concrete body surface 1A (vertical) Component).

  Next, from the magnetic flux density (vertical component) along the longitudinal direction directly above the inspection target rebar 2, the magnetic flux density at a substantially intermediate point between the seven adjacent non-inspection steel materials is extracted. That is, -625 mm which is an intermediate point between -750 mm and -500 mm, -375 mm which is an intermediate point between -500 mm and -250 mm, -125 which is an intermediate point between -250 and 0 mm, 125 mm which is an intermediate point between 0 mm and 250 mm, The magnetic flux density (vertical component) is extracted at each position of 375 mm, which is an intermediate point between 250 mm and 500 mm, and 625 mm, which is an intermediate point between 500 mm and 750 mm.

A curve D2 in the graph of FIG. 6 is obtained by connecting the magnetic flux densities (vertical components) at the respective intermediate points with straight lines. The curve D2 has fewer local convex portions than the curve D1, has one large upward convex portion slightly on the negative side from the 0 mm position on the horizontal axis of the graph, and slightly from the 0 mm position on the horizontal axis. There is only a large downward convex part on the positive side.
From this, it can be seen that the upward convex portion and the downward convex portion of the curve D2 and the steep line segment connecting these appear due to the presence of the fracture portion H in the rebar 2 to be inspected. .

B: Embodiment of nondestructive inspection method of the present invention By the nondestructive inspection method of the present invention, a PC steel material which is a long steel material arranged on the back side of a long non-inspected steel material in a concrete body is inspected. The results of the investigation are shown in FIGS.
Magnetization was carried out in the range of 0 to 4600 mm with the S pole of the magnet unit facing the right side of the graphs of FIGS. 7 and 8, including magnetizing. The measurement result of the component perpendicular to the concrete body surface of the magnetic flux density is the curve of the graphs of FIGS. Moreover, the position of the non-inspection target steel material investigated separately is shown as many vertical lines in the graph of FIG.7 and FIG.8. The investigation of the position of the non-inspected steel material can be easily performed with a general commercially available reinforcing bar probe (radar type, electromagnetic induction type, etc.). The investigation of the position of the non-inspection target steel material may be information from the design drawing as long as an accurate position is known.

  Here, the “PC steel material” includes a PC steel bar, a PC steel wire, and a PC steel stranded wire, and there are those in which one or a plurality are arranged in a bundle. Some (post-tension) are arranged in a sheath (made of steel or polyethylene). In addition, damage to the steel material to be inspected includes not only complete fracture but also severe cross-sectional defects due to wire breakage or corrosion.

7 and 8, in the measurement result of the magnetic flux density, in addition to the component due to the steel material to be inspected, the influence component of the long non-inspection steel material (hereinafter referred to as crossed reinforcing bars) straddling the steel material on the surface side. Is also included. In the former case, if the steel material to be inspected is not damaged, the curve of the graph has a smooth distribution that rises to the right, and if there is damage, it shows a distribution that falls to the right near the damaged portion. The latter shows the distribution of convex shape (convex upward or convex downward) at the position where the non-inspection target steel material and the inspection target steel material intersect.
The present invention is a method of data processing and determination from the measurement result of the magnetic flux density, excluding the influence component of the crossed reinforcing bar that hinders the damage inspection of the steel material to be inspected.

(1) Data processing excluding influence components of crossed reinforcing bars Since the distribution of convex shape is shown at the position where the crossing reinforcing bars exist, and the magnetic flux density attenuates with distance, the magnetic flux density distribution obtained as a result of the measurement From this, only the middle point of the position of the crossed reinforcing bar separately investigated is extracted and used as an approximate value (black circle on the curve in the graphs of FIGS. 9 and 10 and a line connecting them). Such an intermediate point does not have to be a strict intermediate point, and may not be a mechanically (automatically) calculated position, but may be an approximately intermediate position obtained from a visual measurement of the graph. Further, it is desirable to extract an intermediate point and its value after removing obvious noise and local change (change within a range of several tens of mm) from the measurement result of magnetic flux density. As a method of extracting mechanically (automatically), for example, a measurement result closest to the intermediate point is obtained except a portion where there is a change of 10 μT within a range of 10 mm.

(2) Data processing and determination method 1
From the approximate value of the magnetic flux density distribution, the amount of change for a range of about 140 to 400 mm is calculated. For example, in the example of FIG. 9 and FIG. 10, since the pitch (interval) of the crossed reinforcing bar positions is 190 mm on average, the amount of change for each 1 section (190 mm) and 2 sections (380 mm) is calculated (FIG. 11 and FIG. FIG. 12, FIG. 13 and FIG. 14).

In the experimental result of the strand breakage of the PC steel material, the range of the downward-sloping distribution indicating the damage of the steel material to be inspected when the break width of the broken strand is 1 to 300 mm was in the range of about 140 to 400 mm. . Here, since the amount of change is a value obtained by subtracting the value of the left position from the value of the right position, the amount of change indicates a negative value if the distribution is a downward-sloping distribution indicating damage to the steel material to be inspected.
A common threshold value is provided in FIGS. 11, 12, 13, and 4, and when the threshold value is less than or equal to this threshold value, the strand break is suspected.
As an example of the criteria for determining the damaged part, when the cover of the PC steel material to be inspected is 150 mm, “possibility of wire breakage cannot be denied” at −40 μT or less, “possibility of wire breakage” at −80 μT or less “Yes”, and “−Possible to break” at −160 μT or less.

(3) Data processing and determination methods 2, 3
Similarly, a method of calculating the rate of change (FIGS. 15 and 16), a method of calculating an integral value of the negative value of the rate of change (FIGS. 17 and 18), or a method of providing a threshold value for these criteria Can be adopted. The integral value may be an approximate integral value that can be calculated by simple calculation.

C: Nondestructive inspection apparatus FIG. 20 is a schematic configuration diagram of the nondestructive inspection apparatus of the present invention.
The nondestructive inspection apparatus is a magnet separate from the main body 20, and both magnetic poles are arranged along the longitudinal direction of the rebar 2 to be inspected, and the magnetized surface 5 </ b> A is disposed close to the concrete body surface 1 </ b> A to be inspected. The magnet 5 (refer FIG. 2 and FIG. 4) which magnetizes the test | inspection reinforcement 2 etc. by moving along the longitudinal direction of the reinforcement 2 is provided.

The nondestructive inspection apparatus (main body) 20 includes a magnetic detection unit 210, and the magnetic detection unit 210 is provided with a magnetic sensor 211 that measures a vertical component of magnetic flux density on the concrete body surface 1A. As the magnetic sensor 211, a highly sensitive MI sensor, fluxgate sensor, Hall element, superconducting quantum interference element, or the like can be suitably used.
Further, since the distance traveled by the magnetic detection unit 210 can be measured by incorporating the distance sensor 212 into the magnetic detection unit 210, the position of the magnetic detection unit 210 and the magnetic flux density at that position can be calculated.
When the nondestructive inspection apparatus (main body) 20 according to the present invention has a high-precision positioning mechanism, the position of the magnetic detection unit 210 and the magnetic flux density at the position are detected without the distance sensor 212. can do.

  Further, the nondestructive inspection device (main body) 20 is configured based on the position information of a plurality of cross reinforcing bars 3 (non-inspection steel materials) set in advance from the vertical component of the magnetic flux density measured by the magnetic sensor 211. A calculation unit 220 that extracts the magnetic flux density at a substantially middle point between adjacent ones of the crossed reinforcing bars 3 and calculates the amount of change or rate of change along the longitudinal direction of the inspection reinforcing bar 2 with respect to the extracted magnetic flux density (the invention described above). Corresponds to [4] computing means).

Further, the nondestructive inspection apparatus (main body) 20 detects the presence or absence of a damaged portion of the inspection target reinforcing bar 2 by comparing the change amount or change rate of the magnetic flux density obtained by the calculation unit 220 with a preset threshold value. A fracture determination unit 230 (corresponding to the damaged part detection means of the invention [4]) is provided.
In addition, the nondestructive inspection device (main body) 20 preferably includes a memory 250 that holds and reads / writes various data used in detecting a damaged portion.

Furthermore, the display unit 240 displays various graphs and data generated by the calculation unit 220.
In addition, although embodiment of the above-mentioned nondestructive inspection apparatus calculates the vertical component of magnetic flux density, you may calculate the other direction component of magnetic flux density, for example, a horizontal component.
Further, the invention of the present application is not limited to the above-described embodiment, and design changes and additions are permitted without departing from the gist of the invention according to each claim of the claims.

  The nondestructive inspection method and nondestructive inspection apparatus of the present invention can be used for nondestructive inspection for detecting the presence or absence of a damaged portion of a long steel material provided in a concrete body such as a bridge, a building, or a concrete pole. is there.

DESCRIPTION OF SYMBOLS 1 Concrete body 1A Concrete body surface 2 Main rebar 2A Magnetic flux generated inside magnetized main rebar 3 Cross rebar 3A Magnetic flux generated from magnetized cross rebar 4A Magnet trajectory 5 Magnet 5A Magnetized surface 20 Nondestructive inspection device (main body )
210 Magnetic detection unit 211 Magnetic sensor 220 Calculation unit (calculation means)
230 Break determination unit (break determination means)
240 display portion 250 memory C center line of both magnetic poles H broken portion

Claims (4)

From the outside of a concrete body in which a long steel material to be inspected and a plurality of substantially non-inspecting steel materials arranged in parallel intersecting the steel material to be inspected are embedded by a magnet, the steel material to be inspected And non-destructive inspection method for detecting the presence or absence of a damaged portion of the inspection target steel by magnetizing the non-inspection target steel, and then measuring the magnetic flux density outside the concrete body by a magnetic sensor,
The magnetized surface of the magnet is arranged close to the surface of the concrete body so that both magnetic poles of the magnet are along the longitudinal direction of the steel to be inspected, and then the magnet is moved along the longitudinal direction of the steel to be inspected After magnetizing the steel material to be inspected and the non-inspection steel material by allowing the magnet to be removed,
After arranging the magnetic sensor close to the surface of the concrete body, by appropriately moving or measuring the magnetic flux density along the longitudinal direction of the steel material to be inspected without moving, a magnetic flux density measuring step;
From the magnetic flux density measured by the magnetic flux density measuring step, extract the magnetic flux density at a substantially intermediate point between adjacent ones of the plurality of non-inspection steel materials, and the length of the inspected steel material for the extracted magnetic flux density A calculation process for calculating a change amount or a change rate along the direction;
And a damaged portion detecting step of detecting presence or absence of a damaged portion of the steel material to be inspected by comparing the amount of change or the rate of change obtained by the calculation step with a predetermined threshold value. Destructive inspection method.   Based on the position information of the non-inspection target steel material obtained by investigating in advance, the magnetic flux density is extracted at a substantially intermediate point between adjacent ones of the plurality of non-inspection target steel materials in the calculation step. The nondestructive inspection method according to claim 1.   The magnetic flux density measured by the magnetic flux density measurement step, the horizontal axis represents the longitudinal position of the steel material to be inspected, and the vertical axis represents the magnetic flux density. 2. The magnetic flux density is extracted at a substantially intermediate point between adjacent ones of the plurality of non-inspection steel materials in the calculation step, assuming that the non-inspection steel material is present. Non-destructive inspection method. From the outside of a concrete body in which a long steel material to be inspected and a plurality of substantially non-inspected steel materials that are arranged in parallel to intersect with the steel material to be inspected are magnetized from the outside of the concrete object. And non-destructive inspection apparatus for detecting the presence or absence of a damaged portion of the inspection target reinforcing bar by magnetizing the non-inspection target steel material and then measuring the magnetic flux density outside the concrete body by a magnetic sensor,
Both magnetic poles are along the longitudinal direction of the inspection object rebar, the magnetized surface is arranged close to the surface of the concrete body, and moved along the longitudinal direction of the inspection object rebar, so that the inspection object rebar and A magnet for magnetizing the non-inspected steel material;
A magnetic sensor for measuring the magnetic flux density along the longitudinal direction of the rebar to be inspected on the surface of the concrete body, without being moved, by being arranged close to the surface of the concrete body, or moving appropriately;
From the magnetic flux density measured by the magnetic sensor, based on the preset position information of the plurality of non-inspection target steel materials, the magnetic flux density at a substantially intermediate point between the adjacent non-inspection target steel materials is extracted. And calculating means for calculating the amount of change or rate of change along the longitudinal direction of the steel material to be inspected for the extracted magnetic flux density,
And a damaged portion detecting means for detecting the presence or absence of a damaged portion of the steel material to be inspected by comparing the amount of change or the change rate obtained by the calculating means with a preset threshold value. Destructive inspection equipment.

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