JP7350310B2 - Crack detection device and crack detection system - Google Patents

Description

The present invention relates to a crack detection device and a crack detection system that detect cracks that occur in a concrete structure before a concrete block falls off.

Conventionally, a spalling prevention structure for a concrete structure that prevents spalling is known, although it does not detect cracks (see Patent Document 1).
This spalling prevention structure prevents concrete pieces that have peeled off from the wall surface of a concrete structure such as a tunnel from falling, and consists of a lattice-shaped reinforcing material that extends over the entire wall surface and a part of the lattice-shaped reinforcing material. The concrete structure includes a reinforcing material fixture that holds down the reinforcing material fixture, and an anchor material that fixes the reinforcing material fixture to the concrete structure.
The lattice reinforcement material is composed of an FRP mesh sheet consisting of a mesh surface and a lattice frame, and covers the entire wall surface of the target concrete structure. The reinforcing material fixing device is formed of a steel plate or the like, and has a frame-shaped support part corresponding to one lattice frame of the lattice-shaped reinforcing material, a central part in which a bolt hole for an anchor material is formed, and a support part on a diagonal line. and a band-shaped bending portion connecting the central portion and the central portion. An open window is formed inside the support portion as a portion other than the central portion and the bending portion. Further, the anchor material is composed of an expansion anchor driven into a mandrel.
The reinforcing material fixing device presses and fixes the lattice-shaped reinforcing material against the wall surface of the concrete structure using anchor materials that are driven into the concrete structure through bolt holes.

Patent No. 6046302

In this type of conventional concrete structure spalling prevention structure, the FRP mesh sheet (lattice-like reinforcing material) can prevent concrete pieces from falling off, and can also visually identify cracks that occur on the wall surface through the FRP mesh sheet. can do. However, there is a problem that the equipment is large-scale and the cost increases. Further, the expansion anchor, which is an anchor material, has low reliability in terms of falling off due to vibrations, etc., and cannot deal with cracks that occur at a deeper position than the anchor material. That is, the conventional spalling prevention structure has the problem that although it can cope with spalling in a narrow area of a concrete structure, it cannot cope with spalling in a wide area.
On the other hand, cracks that cause concrete structures to peel off occur inside the concrete structure and progress from the inside to the surface (wall surface). Therefore, when cracks are observed on the surface of a concrete structure, it can be said that spalling may occur at any time.

SUMMARY OF THE INVENTION An object of the present invention is to provide a crack detection device and a crack detection system that can visually and historically detect cracks generated inside a concrete structure from the outside.

The crack detection device of the present invention is a crack detection device that is installed in a pilot hole drilled in a concrete structure and detects cracks in the concrete structure that occur across the pilot hole, and is loosely fitted into the pilot hole. At the same time, a rod-shaped anchor whose tip end is fixed to the concrete structure at the back of the prepared hole, a sleeve section whose tip is fixed to the concrete structure at the opening side of the prepared hole, and a state in which the sleeve section is in contact with the sleeve section from the outside. and an occurrence detection mechanism section provided at the base end of the rod-shaped anchor, and when a crack occurs, the occurrence detection mechanism section undergoes a slight movement outward of the sleeve section and visually changes its state. It is characterized by

According to this configuration, the rod-shaped anchor provided in the concrete structure is fixed to the concrete structure with its distal end at the deep part of the prepared hole, and the generation detection mechanism provided at the base end of the rod-shaped anchor. is in contact with the proximal end of the sleeve portion fixed on the opening side of the prepared hole. Therefore, when cracks occur inside the concrete structure, bulges occur on the surface of the concrete structure. In response to the slight outward movement of the sleeve portion due to this bulge, the state of the occurrence detection mechanism portion changes. Due to this state change, it is visually and historically detected from the outside that a crack has occurred inside the concrete structure so as to intersect with the pilot hole. Therefore, the occurrence of cracks can be detected before they appear on the surface of the concrete structure.

In this case, the occurrence detection mechanism part is exposed to the outside and is located between the visual recognition head that abuts the sleeve part, the mechanism body attached to the base end of the rod-shaped anchor, and the visual recognition head and the mechanism body. It is preferable to have a neck portion that is interposed and breaks when a crack occurs.

According to this configuration, when the sleeve portion moves slightly outward, the neck portion interposed between the viewing head and the mechanism body breaks. That is, due to the breakage of the neck portion, the visible head exposed to the outside is separated from the mechanism body. Therefore, by detaching the visual recognition head, it is possible to clearly confirm visually that a crack has occurred inside the concrete structure.

In this case, it is preferable that the mechanism main body is screwed into the base end of the rod-shaped anchor, and the visual recognition head and the mechanism main body are each provided with a tool hook for screwing.

According to this configuration, after the rod-shaped anchor is driven into the concrete structure, the occurrence detection mechanism section can be attached to the base end of the rod-shaped anchor. In particular, by adjusting the threading of the mechanism main body to the rod-shaped anchor, it is possible to appropriately adjust the abutment force of the viewing head against the sleeve portion.

The prepared hole has a straight hole portion into which the rod-shaped anchor is loosely fitted, and a fixing hole portion on the opening side that is connected to the straight hole portion by missing the annular step portion and to which the sleeve portion is fixed, and the mechanism body It is preferable that the fixing hole be disposed inside the sleeve part in the fixing hole and formed to have a diameter larger than the diameter of the straight hole.

By the way, there is a possibility that concrete pieces will come off soon after cracks occur.
According to this configuration, since the mechanism body is formed to have a larger diameter than the diameter of the straight hole, the annular stepped portion of the prepared hole formed in the concrete piece will be attached to the mechanism body at the beginning of flaking of the concrete piece. It will be used. Thereby, if the weight of the concrete piece is less than the proof strength of the rod-shaped anchor, it is possible to effectively prevent the concrete piece from falling off.

In this case, it is preferable that the prepared hole further has a counterbore portion continuous to the outside of the fixing hole portion, and the visual recognition head is disposed within the counterbore portion.

According to this configuration, since the visible head exposed to the outside is disposed within the counterbore, it is possible to prevent the visible head from being accidentally damaged or falling off due to external force (false detection). can.

In addition, the occurrence detection mechanism part is exposed to the outside and is attached to a plate-shaped visual body that abuts the proximal end of the sleeve part and to the proximal end of the rod-shaped anchor that passes through the visual body. It is preferable to have a destruction body that is brought into contact with the proximal end of the sleeve part, and the visual recognition body is destroyed when a crack occurs.

According to this configuration, when the sleeve portion moves slightly outward, the destructive body relatively presses the visible body via the rod-shaped anchor and destroys it. In other words, the visible body exposed to the outside is where cracks occur. Therefore, it is possible to clearly confirm visually that a crack has occurred inside the concrete structure due to the crack in the visual object.

In this case, the visual object has a through hole through which the destructible object passes, and the destructible object is attached to the proximal end of the rod-shaped anchor, and has a destructible body main body formed to have the same diameter as the through hole, and a destructible body that is exposed to the outside. It is preferable to have a head portion formed to have a larger diameter than the through hole, and a tapered portion interposed between the destroyer main body and the head portion.

According to this configuration, when a crack occurs, the tapered portion of the destruction body bites into the through hole of the visual recognition body, thereby destroying the visual recognition body. That is, the visual object destroys the destructive object by forcefully pushing the through hole wide. For this reason, the visible object that has cracked is separated from the destroyed object in a manner that it scatters around. Therefore, it is possible to visually confirm the occurrence of cracks inside the concrete structure more clearly.

The occurrence detection mechanism part is fixed to the proximal end of the rod-shaped anchor in an externally exposed state, and has a visual recognition piece part that abuts the sleeve part, and a visual recognition piece part that is attached to the rod-shaped anchor adjacent to the sleeve part side of the visual recognition piece part. It is preferable to have a weak part that is provided and breaks when a crack occurs.

According to this configuration, when the sleeve portion moves slightly outward, the fragile portion provided in the rod-shaped anchor breaks. That is, due to the breakage of the fragile portion, the visible piece portion exposed to the outside is separated from the rod-shaped anchor. Therefore, by detaching the visual recognition piece, it is possible to clearly visually confirm that a crack has occurred inside the concrete structure.

Similarly, the occurrence detection mechanism section is exposed to the outside and is interposed between a translucent pressure receiving piece attached to the proximal end of the rod-shaped anchor, and the pressure receiving piece and the sleeve section. It is preferable to have a pressurized color changing body that changes color when .

According to this configuration, when the sleeve portion moves slightly outward, the pressure-applied color changing body interposed between the pressure receiving piece portion and the base end portion of the sleeve portion changes color. That is, it is possible to visually confirm that the pressurized color-changing body has changed color through the transparent pressure-receiving piece portion exposed to the outside. Therefore, the occurrence of cracks inside the concrete structure can be clearly confirmed visually due to the color change of the pressurized color change body.

Similarly, the occurrence detection mechanism section is attached to the proximal end of the rod-shaped anchor in a state exposed to the outside, and has a visual recognition piece that abuts on the sleeve part. Preferably, it falls off the proximal end of the anchor.

According to this configuration, when the sleeve portion moves slightly outward, the visual recognition piece falls off from the base end of the rod-shaped anchor. That is, when the visible piece exposed to the outside falls off, it is possible to clearly confirm visually that a crack has occurred inside the concrete structure.

In this case, the visual recognition piece is preferably screwed onto the base end of the rod-shaped anchor, made of a softer material than the rod-shaped anchor, and falls off from the rod-shaped anchor when the screw thread is damaged.

According to this configuration, after the rod-shaped anchor is driven into the concrete structure, the visual recognition piece can be easily set at the base end of the rod-shaped anchor.

Further, it is preferable that the visual recognition piece is constituted by a retaining ring attached to the base end of the rod-shaped anchor.

According to this configuration, after the rod-shaped anchor is driven into the concrete structure, the retaining ring (visible piece) can be easily set at the base end of the rod-shaped anchor.

The crack detection system of the present invention includes a metal anchor fixed to a concrete structure, and the above-mentioned crack detection device provided in the prepared hole that is adjacent to the metal anchor and has approximately the same length as the metal anchor. The present invention is characterized in that the crack detection device detects occurrence of cone-shaped fracture in a concrete structure caused by a metal anchor.

According to this configuration, the tensile strength of the metal anchor is determined by the strength that leads to cone-shaped failure of the concrete structure or the tensile strength of the anchor bolt of the metal anchor. That is, when an excessive tensile load is applied to a metal anchor, a cone-shaped fracture occurs or a bolt breaks, and cone-shaped fractures often pose a problem.
According to this configuration, the occurrence of a cone-shaped fracture within the concrete structure is detected by the crack detection device provided in the concrete structure adjacent to the metal anchor. Specifically, due to a change in the state of the occurrence detection mechanism, the occurrence of a cone-shaped crack, which is the initial stage of cone-shaped fracture, inside a concrete structure is visually and historically detected from the outside. .

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a front view (a) and a side view (b) illustrating how the crack detection device and crack detection system according to the embodiment are used. FIG. 2 is a structural diagram of the crack detection device according to the first embodiment, showing a steady state (a) and a detection state (b). FIG. 3 is an exploded view of the crack detection device. FIG. 3 is a structural diagram of a crack detection device according to a second embodiment. It is a structural diagram of the crack detection apparatus based on 3rd Embodiment, Comprising: It is a figure (a) of a steady state, and a figure (b) of a detection state. They are a structural diagram (a) of a crack detection device according to a first modification of the third embodiment, and a construction diagram (b) of a crack detection device according to a second modification. They are a structural diagram (a) of a crack detection device according to a fourth embodiment, and a structural diagram (b) of a crack detection device according to a modification thereof. It is a structural diagram of the crack detection apparatus of 5th Embodiment. FIG. 1 is a structural diagram of a crack detection system according to an embodiment. FIG. 2 is an explanatory diagram of a state in which a cone-shaped crack is detected in the crack detection system.

DESCRIPTION OF THE PREFERRED EMBODIMENTS A crack detection device and a crack detection system according to an embodiment of the present invention will be described below with reference to the accompanying drawings. This crack detection device detects early-stage cracks that occur inside a concrete structure. It is known that when cracks that occur inside a concrete structure progress and appear on the surface of the concrete structure, pieces of concrete will come off. The crack detection device of this embodiment detects cracks in the initial stage that cause peeling.

On the other hand, a crack detection system consists of a metal anchor fixed to a concrete structure and a crack detection device placed adjacent to the metal anchor. This detects the early stages of structural failure (cone-shaped cracks). In this case as well, cone-shaped cracks progress and appear on the surface of the concrete structure, resulting in cone-shaped fracture.

[overview]
Figure 1 shows an example of how the crack detection device and crack detection system are used. This figure shows the structure around a jet fan F in an expressway tunnel.A concrete structure C that makes up the ceiling of the tunnel is equipped with a jet fan for ventilation inside the tunnel through six support fittings S. A fan F is suspended and supported. Four metal anchors 10 are driven into the concrete structure C corresponding to the base plate Sa of each support fitting S. That is, a jet fan F, which is an object to be supported, is suspended and supported on the concrete structure C by four metal anchors 10, which are attached to one base plate Sa cast into the concrete structure C.

On the other hand, the concrete structure C is provided with first crack detection devices 12A at a rate of, for example, one device per 1 m ² over its entire area. Further, a second crack detection device 12B is provided adjacent to each metal anchor 10. The first crack detection device 12A detects the initial stage of cracks that cause concrete pieces to fall off in the concrete structure C, and the second crack detection device 12B detects the initial stage of cone-shaped fracture (cone-shaped fracture). It is used to detect cracks in The metal anchor 10 that supports the jet fan F and the second crack detection device 12B constitute the crack detection system 14 of this embodiment. Note that the first crack detection device 12A and the second crack detection device 12B have the same basic structure.

[First embodiment]
FIG. 2 is a structural diagram of the first crack detection device 12A according to the first embodiment, in which (a) shows a steady state, and (b) shows a detection state. Moreover, FIG. 3 is an exploded view of the first crack detection device 12A. Note that each of the figures after FIG. 2 shows a part of FIG. 1 upside down and enlarged.
As shown in these figures, the first crack detection device 12A is provided in a prepared hole BH drilled in the concrete structure C.

The prepared hole BH is bored so that the assumed crack intersects with the assumed crack, and extends to a position deeper than the assumed crack. In addition, the prepared hole BH consists of a long straight hole portion BHa forming the main body and a short fixing hole portion BHb on the opening side, and on the same axis, the straight hole portion BHa and the fixing hole portion BHb have an annular stepped portion BHc. exist and communicate. A counterbore portion BHd, which is chamfered in the shape of an inverted truncated cone, is formed in the opening portion of the fixing hole portion BHb.

As shown in FIGS. 2 and 3, the first crack detection device 12A includes a rod-shaped anchor 21 that is inserted into the prepared hole BH and is fixed to the concrete structure C, and a concrete It includes a sleeve part 22 fixed to the structure C, and an occurrence detection mechanism part 23 attached to the proximal end of the rod-shaped anchor 21 in contact with the sleeve part 22 from the outside. The rod-shaped anchor 21 and the sleeve portion 22 are made of steel, stainless steel, or the like, and the occurrence detection mechanism portion 23 is made of aluminum, ceramic, plastic, or the like.

The rod-shaped anchor 21 is composed of a fully threaded bolt, and includes an anchor body 25 that is loosely fitted into a straight hole BHa of a prepared hole BH, and a tip of the anchor body 25 that is connected to the innermost part of the prepared hole BH (straight hole BHa). It has an anchor fixing part 26 which is fixed to the concrete structure C at the anchor fixing part 26. An anchor fixing section 26 is screwed into the distal end of the anchor body 25, and an occurrence detection mechanism section 23 located within the sleeve section 22 is screwed into the proximal end.

Although details will be described later, the rod-shaped anchor 21 is fixed at its distal end to the innermost part of the prepared hole BH via the anchor fixing section 26, and at its base end, a part of the threaded occurrence detection mechanism section 23 is fixed. It is in contact with the proximal end surface of the sleeve portion 22 . Note that the anchor body 25 may have male threads formed only at the proximal end and the distal end.

The anchor fixing part 26 has an expansion part 32 on the distal end side, a cylindrical body 31 whose base end side is screwed into the anchor body 25, an expansion collar 33 inserted into the cylindrical body 31, and an expansion collar 33 that is inserted into the cylindrical body 31 by driving. It has an expansion cone 34 that expands the expansion part 32 via the expansion cone 34 (see FIG. 3). In this anchor fixing part 26, the cylindrical main body 31 incorporating the expansion collar 33 and the expansion cone 34 is inserted into the innermost part of the prepared hole BH (straight hole part BHa), and the expansion cone 34 is driven using a driving rod. Do it like this.

When the expansion cone 34 is driven in, the expansion collar 33 expands, and the expanded expansion collar 33 causes the expansion portion 32 of the cylindrical main body 31 to expand. The expanded portion 32 expanding outward is pressed against the circumferential surface of the prepared hole BH, and the cylindrical main body 31 is fixed at the innermost part of the prepared hole BH. Then, the distal end portion of the anchor body 25 is screwed into the fixed cylindrical body 31 (anchor fixing portion 26). Note that in order to ensure the fixation of the cylindrical body 31 and to ensure that the tip of the anchor body 25 is adhered to the cylindrical body 31 (to prevent loosening), an adhesive (not shown in the figure) is applied to the innermost part of the prepared hole BH in advance. (omitted) is preferably injected.

The sleeve portion 22 is made of steel, stainless steel, or the like, and is fixed in the fixing hole portion BHb of the prepared hole BH, with a mechanism main body 42 of the generation detection mechanism portion 23, which will be described later, accommodated therein. A male screw 22a or a ring-shaped unevenness is formed on the outer peripheral surface of the sleeve portion 22 (the one shown is a male screw 22a: see FIG. 3), and is driven into the fixing hole BHb to attach the concrete structure C. will be established.

The occurrence detection mechanism section 23 includes a disk-shaped visual recognition head 41 that contacts the proximal end surface 22b of the sleeve section 22 from the outside, a mechanism main body 42 that is screwed into the proximal end of the rod-shaped anchor 21, and a visual recognition head 41. and a neck portion 43 interposed between the mechanism body 42 and the mechanism body 42. Further, the visual recognition head 41, the mechanism body 42, and the neck portion 43 are integrally formed of a relatively brittle metal material such as aluminum, brittle plastic, ceramic, or the like. When a crack occurs in the concrete structure C, the neck portion 43 receives a bulge (bulge) generated on the surface of the concrete structure C and breaks.

The visual recognition head 41 is formed to have the same diameter as the sleeve portion 22, is exposed to the outside together with the proximal end portion of the sleeve portion 22, and is in contact with the proximal end surface 22b of the sleeve portion 22. In this case, the visual recognition head 41 is located within the counterbore BHd of the prepared hole BH, and its surface is disposed substantially flush with the surface of the concrete structure C. Thereby, the visible head 41 is protected from damage due to external force, and is attached to the base end of the sleeve portion 22 so that it can be visually recognized.

Further, a main tool hanging portion 45 is formed in the visual recognition head 41 and is D-cut at a 180° point symmetrical position (see FIG. 3). The occurrence detection mechanism section 23 is screwed to the rod-shaped anchor 21 in the mechanism body 42, and the final tightening adjustment is made by a torque wrench engaged with the main tool hook section 45. . As a result, a slight tension is applied to the rod-shaped anchor 21, and the visual recognition head 41 is brought into contact with the sleeve portion 22 with a predetermined pressure. Note that the visible head 41 is preferably colored with a fluorescent color or the like so that it stands out.

The mechanism main body 42 has the form of a so-called cap nut, and is screwed into the proximal end of the rod-shaped anchor 21 within the sleeve portion 22 . By this screwing, the occurrence detection mechanism section 23 is attached to the rod-shaped anchor 21, and the visual recognition head 41 comes into contact with the proximal end surface 22b of the sleeve section 22. The end of the mechanism main body 42 screwed into the rod-shaped anchor 21 has sufficient clearance with respect to the annular stepped portion BHc of the prepared hole BH, so that the neck portion 43 does not have any trouble in breaking.

Further, the mechanism main body 42 is formed to have a larger diameter than the diameter of the straight hole BHa. For this reason, even if a piece of concrete falls off soon after a crack occurs, the annular stepped portion BHc of the pilot hole BH will hold against the mechanism body 42, and the rod-shaped anchor 21 will be able to detach from the concrete piece via the mechanism body 42. becomes a state of support. Thereby, if the weight of the concrete piece is equal to or less than the tensile strength of the rod-shaped anchor 21, it is possible to prevent the concrete piece from falling off.

On the other hand, the mechanism main body 42 is also formed with a D-cut auxiliary tool hanging part 46 similarly to the visual recognition head 41 (see FIG. 3). In this case, the auxiliary tool hanging part 46 is for removing the mechanism body 42 remaining on the rod-shaped anchor 21 when the visual recognition head 41 accidentally separates from the mechanism body 42 (breakage of the neck part 43). This makes it possible to replace the occurrence detection mechanism section 23 with respect to the rod-shaped anchor 21.

The neck portion 43 is a portion that breaks when a crack occurs in the concrete structure C, and is cut into a substantially “V”-shaped cross section at the boundary between the visible head 41 and the mechanism body 42. That is, the cut depth of the neck portion 43 is adjusted so that the surface of the concrete structure C bulges due to the occurrence of cracks, and the neck portion 43 is fractured by receiving minute outward movement of the sleeve portion 22 (see FIG. 2(b)). The occurrence of cracks inside the concrete structure C due to the breakage of the neck portion 43 is visually detected from the outside.

Here, with reference to FIG. 2, the construction procedure of the first crack detection device 12A will be briefly explained, and the function of the occurrence detection mechanism section 23 will be explained.
In this first crack detection device 12A, adhesive is first injected into the innermost part of the prepared hole BH using an adhesive injector or the like. Next, the cylindrical main body 31 incorporating the expansion collar 33 and the expansion cone 34 is inserted into the innermost part of the prepared hole BH, and the expansion cone 34 is driven in to fix the cylindrical main body 31 in the prepared hole BH. Next, before the adhesive hardens, the anchor body 25 is inserted into the prepared hole BH and screwed into the cylindrical body 31.

Further, before and after the construction of the rod-shaped anchor 21, the sleeve portion 22 is driven into the fixing hole portion BHb, and the sleeve portion 22 is fixed to the concrete structure C. Finally, the occurrence detection mechanism section 23 is screwed into the base end of the rod-shaped anchor 21, and the contact pressure of the visual recognition head 41 against the base end surface 22b of the sleeve section 22 is adjusted using a torque wrench (see FIG. 2). a)).

In this manner, when a crack occurs inside the concrete structure C with the first crack detection device 12A installed, the surface of the concrete structure C rises slightly (sagging on the ceiling surface). When the surface of the concrete structure C rises, the sleeve part 22 fixed thereto moves outward, and a tensile force acts on the rod-shaped anchor 21 whose tip part is fixed at the innermost part of the prepared hole BH. . In this state, the visible head 41 of the occurrence detection mechanism section 23 is suspended by the sleeve section 22, and the neck section 43 is broken. When the neck portion 43 breaks, the visual recognition head 41 separates from the mechanism body 42, and the occurrence of cracks in the concrete structure C is visually detected (see FIG. 2(a)).

On the other hand, based on this detection, the administrator takes the following countermeasures, for example. First, the crack area is inspected by keystrokes. If the crack area is narrow and a portion of the crack appears on the surface of the concrete structure C, the crack is repaired by injecting a resin or the like. In this case, the mechanism main body 42 is removed from the rod-shaped anchor 21, and the occurrence detection mechanism section 23 is newly attached. If the crack area is wide, chip away the floating part of the concrete structure C that borders the crack, and replace this part. In this case, a new first crack detection device 12A is installed.

As described above, according to the first crack detection device 12A of the first embodiment, when a crack occurs inside the concrete structure C, the visible head 41 of the occurrence detection mechanism section 23 separates from the mechanism body 42. Therefore, the occurrence of cracks can be detected visually.

Further, upon receiving this detection, appropriate countermeasures can be taken, so that the concrete structure C can be properly inspected and managed, and it is possible to effectively prevent concrete pieces from falling off due to cracks.

[Second embodiment]
Next, with reference to FIG. 4, a first crack detection device 12AA according to a second embodiment will be described. In this first crack detection device 12AA, in the rod-shaped anchor 21 consisting of an anchor body 25 and an anchor fixing part 26, the anchor fixing part 26 is made of adhesive 28. Further, the structure around the occurrence detection mechanism section 23A is different from that of the first embodiment. An adhesive 28 is injected into the innermost part of the prepared hole BH (straight hole portion BHa), and the tip of the anchor body 25 composed of a fully threaded bolt is fixed in the prepared hole BH via the adhesive 28. .

On the other hand, the occurrence detection mechanism section 23A in this case is fixed to the proximal end of the rod-shaped anchor 21, and includes a visual recognition piece 51 that abuts the proximal end surface 22b of the sleeve part 22, and a visual recognition piece 51 on the rod-like anchor 21 side of the visual recognition piece 51. A weakened portion 52 is provided on the rod-shaped anchor 21 adjacent to the weakened portion 52 .

The viewing piece portion 51 has the same form as the viewing head 41 of the first embodiment, and is in contact with the proximal end surface 22b of the sleeve portion 22 in a state of being exposed to the outside. The visual recognition piece 51 and the rod-shaped anchor 21 may be formed integrally, but in the embodiment, a hole having the same diameter as the rod-shaped anchor 21 is formed in the center of the visual recognition piece 51, and the rod-shaped anchor is inserted into the hole. It is formed by inserting and welding the tip of 21. Also in this case, the visual recognition piece 51 is located within the counterbore BHd of the prepared hole BH, and its surface is disposed substantially flush with the surface of the concrete structure C. In this second embodiment, the rod-shaped anchor 21 to which the visual recognition piece 51 is fixed is inserted into the prepared hole BH into which the adhesive 28 is injected, and the visual recognition piece 51 is brought into contact with the proximal end surface 22b of the sleeve part 22. This state of contact is maintained until the adhesive 28 hardens (curing).

The fragile portion 52 is formed on the rod-shaped anchor 21 (anchor main body 25) adjacent to the visual recognition piece portion 51. The fragile portion 52 in this case is obtained by cutting the anchor body 25 into a semicircular cross section, and similarly to the neck portion 43 described above, the surface of the concrete structure C swells due to the occurrence of cracks, and the sleeve portion 22 It breaks due to slight outward movement. In this case as well, it is preferable that the visual recognition piece 51 is colored with a fluorescent color or the like so that it stands out.

In this manner, in the first crack detection device 12AA of the second embodiment as well, when a crack occurs inside the concrete structure C, the visual recognition piece portion 51 of the occurrence detection mechanism portion 23A separates, so that the occurrence of a crack can be prevented. , can be detected through vision.
Further, upon receiving this detection, appropriate countermeasures can be taken, so that the concrete structure C can be properly inspected and managed, and it is possible to effectively prevent concrete pieces from falling off due to cracks.

[Third embodiment]
Next, with reference to FIG. 5, a first crack detection device 12AB according to a third embodiment will be described. In this first crack detection device 12AB, the structure around the occurrence detection mechanism section 23B is different from that of the first embodiment.

This occurrence detection mechanism part 23B is exposed to the outside and has a visual recognition body 54 that abuts on the proximal end surface 22b of the sleeve part 22, and a visual recognition body 54 that penetrates through the visual recognition body 54 and is screwed into the base end of the rod-shaped anchor 21, so that it can be visually recognized. It has a destructive body 55 that brings the body 54 into contact with the proximal end surface 22b of the sleeve portion 22. The visual recognition body 54 is destroyed when a crack occurs inside the concrete structure C. In this case, the rod-shaped anchor 21 and the destructive body 55 are made of steel, stainless steel, or the like, whereas the visual recognition body 54 is made of a fragile ceramic or the like.

The visual recognition body 54 is formed into a disk shape and has a through hole 54a in the axial center thereof through which the destruction body 55 passes. In response to the pressing force acting on the visible body 54 due to cracks, the likelihood of destruction in the visible body 54 is adjusted by its thickness.

The destructible body 55 is attached to the base end of the rod-shaped anchor 21 and includes a destructible body main body 56 formed to have the same diameter as the through hole 54a, and a head portion exposed to the outside and formed to have a larger diameter than the through hole 54a. 57, and a tapered part 58 interposed between the destroyer main body 56 and the head part 57, and these are integrally formed. The destroyer main body 56 that is screwed onto the rod-shaped anchor 21 has the form of a cap nut. A tool hanging groove 57a in the shape of a single letter or a cross is formed in the head part 57, and by using this tool hanging groove 57a, the visual recognition body 54 seated (in contact with) the proximal end surface 22b of the sleeve part 22 is lightly pressed. The destructible body 55 is screwed onto the rod-shaped anchor 21 so as to do so.

In this state, the tapered portion 58 of the destructive body 55 is in contact with the through hole 54a of the visual recognition body 54 so that its tip side slightly bites into the through hole 54a (see 5(a)). When a crack occurs in the concrete structure C, the surface of the concrete structure C swells, and the sleeve portion 22 moves slightly outward, causing the visible body 54 to be damaged by the proximal end surface 22b of the sleeve portion 22 and the destructive body 55. , subjected to strong clamping force. As a result, the tapered portion 58 of the destruction body 55 strongly bites into the through hole 54a of the visual recognition body 54, and destroys it by pushing the through hole 54a wider (see 5(b)). The destroyed visual object 54 is divided into a plurality of fragments and separated from the destroyed object 55. Note that, also in this case, it is preferable that the visual recognition body 54 is colored with a fluorescent color or the like so that it stands out.

[Modified example]
Next, with reference to FIG. 6, a modification of the first crack detection device 12AB of the third embodiment will be described.
FIG. 6A shows a first crack detection device 12AB according to a first modification. In this first crack detection device 12AB, the destroyer 55 does not have a tapered portion 58, and the destroyer 55 has a destroyer main body 56. It is formed integrally with the head portion 57. On the other hand, the through hole 54a of the visual recognition body 54 is formed in a tapered shape. The destroyer 55 is screwed onto the rod-shaped anchor 21 so that its lower end lightly presses the viewer 54 seated (in contact with) the proximal end surface 22b of the sleeve portion 22. In this case as well, the visual recognition body 64 is destroyed by the slight outward movement of the sleeve portion 22 due to the crack, and the destruction body 55 strongly bites into the tapered through hole 54a.

FIG. 6(b) shows a first crack detection device 12AB according to a second modification, and in this first crack detection device 12AB, the destructive body 55 has the form of a nut having a tapered portion 58, The proximal end portion of the rod-shaped anchor 21 protrudes from the proximal end surface 22b of the sleeve portion 22 and is screwed into the proximal end portion. On the other hand, the visual recognition body 54 has the same form as that of the third embodiment. In this case as well, the visual recognition body 54 is destroyed by the slight outward movement of the sleeve portion 22 due to the crack, and the tapered portion 58 of the destruction body 55 strongly bites into the through hole 54a.

As described above, in the first crack detection device 12AB of the third embodiment including the modified example, when a crack occurs inside the concrete structure C, the visible body 54 of the occurrence detection mechanism section 23B is destroyed and scattered. Therefore, the occurrence of cracks can be detected visually.
Further, upon receiving this detection, appropriate countermeasures can be taken, so that the concrete structure C can be properly inspected and managed, and it is possible to effectively prevent concrete pieces from falling off due to cracks.

[Fourth embodiment]
Next, a first crack detection device 12AC according to a fourth embodiment will be described with reference to FIG. 7(a). Also in this first crack detection device 12AC, the structure around the occurrence detection mechanism section 23C is different from that in the first embodiment. The occurrence detection mechanism section 23C has a visual recognition piece 61 that is screwed into the proximal end of the rod-shaped anchor 21 and abuts on the proximal end surface 22b of the sleeve section 22. The rod-shaped anchor 21 is made of steel, stainless steel, or the like, whereas the visual recognition piece 61 is made of a softer material than the rod-shaped anchor 21, such as gunmetal or plastic. The visual recognition piece 61 has the form of a disc-shaped plate nut with a female thread 61a formed in the center.

The proximal end portion of the rod-shaped anchor 21 slightly protrudes from the proximal end surface 22b of the sleeve portion 22, and the visual recognition piece 61 is screwed into this protruding portion so as to abut on the proximal end surface 22b of the sleeve portion 22. In this case, the rod-shaped anchor 21 is adjusted to be threaded onto the anchor fixing section 26 (cylindrical main body 31) so that the proximal end of the rod-shaped anchor 21 slightly protrudes from the proximal end surface 22b of the sleeve section 22. Then, the visual recognition piece 61 is screwed into this protruding portion. Thereby, the visible piece 61 exposed to the outside is attached to the base end of the rod-shaped anchor 21 and can be visually recognized. Further, the visual recognition piece 61 is located within the counterbore BHd of the prepared hole BH, and its surface is disposed substantially flush with the surface of the concrete structure C.

In the first crack detection device 12AC configured as described above, when a crack occurs in the concrete structure C, the surface of the concrete structure C swells, and the sleeve portion 22 moves slightly outward, causing the visible piece 61 In this case, the female thread 61a is broken and falls off from the base end of the rod-shaped anchor 21. As a result, the occurrence of cracks can be visually detected. In this case as well, it is preferable that the visible piece 61 is colored with a fluorescent color or the like so that it stands out.

[Modified example]
Next, a modification of the first crack detection device 12AC according to the fourth embodiment will be described with reference to FIG. 7(b). In this first crack detection device 12AC, a retaining ring 63 is attached to the base end of the rod-shaped anchor 21 protruding from the base end surface 22b of the sleeve portion 22 in place of the visual recognition piece 61. The retaining ring 63 is made of thin metal or plastic. In this case, the retaining ring 63 falls off from the base end of the rod-shaped anchor 21 when a crack occurs in the concrete structure C.

As described above, in the first crack detection device 12AC of the fourth embodiment including the modified example, when a crack occurs inside the concrete structure C, the visual recognition piece 61 or the retaining ring 63 of the occurrence detection mechanism section 23C has a rod-like shape. Since the anchor 21 falls off from the base end, the occurrence of a crack can be visually detected.
Further, upon receiving this detection, appropriate countermeasures can be taken, so that the concrete structure C can be properly inspected and managed, and it is possible to effectively prevent concrete pieces from falling off due to cracks.

[Fifth embodiment]
Next, with reference to FIG. 8, a first crack detection device 12AD according to a fifth embodiment will be described. Also in this first crack detection device 12AD, the structure around the occurrence detection mechanism section 23D is different from that in the first embodiment. The occurrence detection mechanism section 23D includes a pressure receiving piece 65 screwed to the base end of the rod-shaped anchor 21, a pressurized discoloration body 66 interposed between the pressure receiving piece 65 and the base end surface 22b of the sleeve section 22, have.

The pressure-receiving piece 65 is made of a transparent (transparent in the embodiment) hard plastic or the like, and is attached to the rod-shaped anchor 21 so that the pressurized color change body 66 is sandwiched between the pressure-receiving piece 65 and the proximal end surface 22b of the sleeve portion 22. are screwed together. On the other hand, the pressure color change body 66 is made of a film or a piece of plastic that changes color from white to red under pressure. The magnitude of the pressure applied to the pressurized color-changing body 66 after the color change is confirmed by comparing it with a color sample.

Although not shown in the drawings, in the embodiment, a color sample is attached to the base end of the rod-shaped anchor 21, etc., and the color of the pressurized color change body 66 that is visually recognized through the pressure receiving piece 65 and this color sample are are compared. The color of the color sample in this case corresponds to the pressure that the pressurized discoloration body 66 receives from the pressure receiving piece portion 65 based on tension when tension is applied to the rod-shaped anchor 21 due to a crack. That is, when tension based on cracks acts on the rod-shaped anchor 21, the pressure-receiving piece portion 65 presses the pressurized discoloration body 66 relatively to the proximal end surface 22b of the sleeve portion 22, so that the pressurized discoloration body 66 is held in a predetermined position. The color changes.

In this manner, in the first crack detection device 12AD of the fifth embodiment, when a crack occurs inside the concrete structure C, the pressurized color change body 66 of the occurrence detection mechanism section 23D changes color to a predetermined color. , the occurrence of cracks can be detected visually.
Further, upon receiving this detection, appropriate countermeasures can be taken, so that the concrete structure C can be properly inspected and managed, and it is possible to effectively prevent concrete pieces from falling off due to cracks.
Note that in the third, fourth, and fifth embodiments, the anchor fixing portion 26 may be made of adhesive 28.

[Crack detection system]
FIG. 9 is a structural diagram of the crack detection system 14 of this embodiment. As shown in the figure, the crack detection system 14 includes a metal anchor 10 that supports the jet fan F, and a second crack detection device 12B having the same basic form as the first crack detection device 12A described above. There is. The illustrated second crack detection device 12B follows the structure of the first crack detection device 12A of the first embodiment, and in this crack detection system 14, the first crack detection device 12AA, 12AB of other embodiments is used. , 12AC, and 12AD can be applied. The second crack detection device 12B detects the initial stage of cone-shaped fracture (cone-shaped crack) occurring in the metal anchor 10.

On the other hand, the metal anchor 10 is a so-called post-installed metal expansion anchor (mechanical anchor), and its main parts including an anchor bolt 71, which will be described later, are made of steel, stainless steel, or the like.

The concrete structure C has an anchor hole AH with an enlarged diameter portion AHa formed in the inner part thereof, and the metal anchor 10 is fixed by being driven into the anchor hole AH. In the metal anchor 10 fixed in the anchor hole AH (concrete structure C), the base end of the anchor bolt 71 protrudes from the surface of the concrete structure C, and is screwed into this part via the washer W. The base plate Sa of the jet fan F (fixed object) is fastened by the fixing nut N.

The metal anchor 10 includes an anchor bolt 71 made of a fully threaded bolt, and a fixing mechanism section 72 that fixes the tip of the anchor bolt 71 to the enlarged diameter portion AHa of the anchor hole AH.

The fixing mechanism section 72 includes an expansion nut 74 screwed onto the tip of the anchor bolt 71, and a driving sleeve 75 disposed to surround the anchor bolt 71. The expansion nut 74 is integrally formed with a nut main body 76 in the lower half shown, which is screwed onto the anchor bolt 71, and an expansion part 77 in the upper half shown, which is divided into four parts by a slit 77a. A cone portion 78 is formed at the tip of the driving sleeve 75, and by driving the driving sleeve 75, the expanding portion 77 of the expanding nut 74 expands radially outward. The expanded expanded portion 77 expands toward the peripheral wall of the expanded diameter portion AHa and is fixed to the expanded diameter portion AHa. The anchor bolt 71 exhibits a wedge effect due to the cooperation between the expanded portion 77 and the expanded diameter portion AHa.

On the other hand, the second crack detection device 12B has the same structure as the first crack detection device 12A described above. That is, the second crack detection device 12B includes a rod-shaped anchor 21 that is inserted into the prepared hole BH and is fixed to the concrete structure C, and a sleeve that is fixed to the concrete structure C in the fixing hole portion BHb of the prepared hole BH. portion 22, and a fracture detection mechanism portion 81 provided at the proximal end portion of the rod-shaped anchor 21 in a state of contacting the sleeve portion 22 from the outside.

In this case, the prepared hole BH is bored adjacent to the anchor hole AH, and is formed parallel to and approximately the same length as the anchor hole AH. Further, the base plate Sa of the jet fan F is formed with a circular opening Saa into which the sleeve portion 22 is loosely inserted. The sleeve portion 22 in this case is fixed to the concrete structure C by driving its lower half in the figure into the fixing hole BHb. Further, in this state, the sleeve portion 22 penetrates the base plate Sa at the circular opening Saa and protrudes from the surface of the base plate Sa. In addition, when the position of the second crack detection device 12B is removed from the base plate Sa, it is preferable to provide a counterbore portion BHd as described above and accommodate the visual recognition head 41 of the destruction detection mechanism portion 81 in this.

FIG. 10 shows a state in which a cone-shaped fracture has occurred in the concrete structure C. That is, a large tensile load is applied to the metal anchor 10 (anchor bolt 71), and the tensile strength of the concrete structure C is lower than the tensile strength of the anchor bolt 71. In this state, a cone-shaped crack is generated inside the concrete structure C starting from the enlarged diameter portion AHa of the anchor hole AH. This crack gradually progresses toward the surface of the concrete structure C, but on the other hand, a bulge is generated on the surface of the concrete structure C due to this crack.

When it rises to the surface of the concrete structure C, the sleeve part 22 fixed to the concrete structure C moves outward, and applies a tensile force to the rod-shaped anchor 21 fixed at the innermost part of the prepared hole BH with its tip end. acts. In this state, the visible head 41 of the destruction detection mechanism section 81 is suspended by the sleeve section 22, and the neck section 43 is broken. When the neck portion 43 breaks, the visual recognition head 41 separates from the mechanism body 42, and the occurrence of a cone-shaped fracture (cone-shaped crack) is visually detected.

As described above, according to the crack detection system 14 of the present embodiment, when a cone-shaped fracture occurs in the concrete structure C due to the metal anchor 10 receiving a large tensile load, the second crack detection device 12B Since the visual recognition head 41 of the fracture detection mechanism section 81 is detached, the occurrence of cone-shaped fracture can be visually detected. Thereby, anchor bolts 71 can be prevented from falling off from concrete structure C.

In the above embodiment, a metal expansion anchor is used as an example of the metal anchor 10, but the crack detection system 14 of the present invention can be fixed to the concrete structure C regardless of whether it is installed first or later (post-installed). It is applicable to various metal anchors 10. Further, it goes without saying that the crack detection device of the present invention can be applied to concrete structures C such as columns and outer walls.

DESCRIPTION OF SYMBOLS 10... Metal anchor, 12A, 12AA, 12AB, 12AC, 12AD... First crack detection device, 12B... Second crack detection device, 14... Crack detection system, 21... Rod-shaped anchor, 22... Sleeve part, 22b... Base end surface , 23, 23A, 23B, 23C, 23D... Occurrence detection mechanism part, 25... Anchor body, 26... Anchor fixing part, 28... Adhesive, 41... Visual recognition head, 42... Mechanism body, 43... Neck part, 51... Visible piece part, 52... Fragile part, 54... Visible body, 54a... Through hole, 55... Destroyed body, 56... Destroyed body main body, 57... Head part, 58... Tapered part, 61... Visible piece, 61a... Female screw, 63...Retaining ring, 65...Pressure receiving piece part, 66...Pressure discoloration body, 71...Anchor bolt, 72...Fixing mechanism part, 81...Destruction detection mechanism part, AH...Anchor hole, AHa...Expanded diameter part, BH...Bottom Hole, BHa...Straight hole, BHb...Fixing hole, BHc...Annular step, BHd...Counterbore, C...Concrete structure, F...Jet fan, Sa...Base plate

Claims (13)

A crack detection device that is installed in a prepared hole drilled in a concrete structure and detects a crack in the concrete structure that occurs so as to intersect with the prepared hole,
a rod-shaped anchor that is loosely fitted into the prepared hole and whose tip end is fixed to the concrete structure in the deep part of the prepared hole;
a sleeve portion fixed to the concrete structure on the opening side of the prepared hole;
an occurrence detection mechanism provided at the proximal end of the rod-shaped anchor in contact with the sleeve from the outside;
The crack detection device is characterized in that, when the crack occurs, the occurrence detection mechanism section undergoes a minute movement outward of the sleeve section and visually changes its state. The occurrence detection mechanism section includes:
a visible head that abuts the sleeve portion while being exposed to the outside;
a mechanism main body attached to the proximal end of the rod-shaped anchor;
2. The crack detection device according to claim 1, further comprising a neck portion that is interposed between the visual recognition head and the mechanism body and breaks when the crack occurs. The mechanism main body is screwed into a proximal end portion of the rod-shaped anchor,
3. The crack detection device according to claim 2, wherein the visual recognition head and the mechanism body are each provided with a tool hook for the screwing. The prepared hole has a straight hole portion into which the rod-shaped anchor is loosely fitted, and a fixing hole portion on the opening side that is connected to the straight hole portion without an annular step portion and to which the sleeve portion is fixed. ,
The crack crack according to claim 2 or 3, wherein the mechanism main body is disposed inside the sleeve portion and within the fixing hole portion, and is formed to have a larger diameter than the diameter of the straight hole portion. Detection device. The prepared hole further has a counterbore portion continuous to the outside of the fixing hole portion,
The crack detection device according to claim 4, wherein the visual recognition head is disposed within the counterbore. The occurrence detection mechanism section includes:
a plate-shaped visual recognition body that abuts the proximal end portion of the sleeve portion while being exposed to the outside;
a destruction body that penetrates the visual body and is attached to the proximal end of the rod-shaped anchor, and brings the visual body into contact with the proximal end of the sleeve part,
The crack detection device according to claim 1, wherein the visual recognition body is destroyed when the crack occurs. The visual recognition body has a through hole through which the destruction body passes,
The destructible body is attached to the base end of the rod-shaped anchor and includes a destructible body main body formed to have the same diameter as the through hole, and a head portion exposed to the outside and formed to have a larger diameter than the through hole. The crack detection device according to claim 6, further comprising: a tapered portion interposed between the destruction body body and the head portion. The occurrence detection mechanism section includes:
a visibility piece portion that is fixed to the proximal end portion of the rod-shaped anchor in an externally exposed state and abuts the sleeve portion;
2. The crack detection device according to claim 1, further comprising a fragile portion that is provided on the rod-shaped anchor adjacent to the sleeve portion side of the visual recognition piece portion and that breaks when the crack occurs. The occurrence detection mechanism section includes:
a translucent pressure-receiving piece attached to the proximal end of the rod-shaped anchor in a state exposed to the outside;
2. The crack detection device according to claim 1, further comprising a pressurized color changing body that is interposed between the pressure receiving piece portion and the sleeve portion and changes color when the crack occurs. The occurrence detection mechanism section includes:
a visual recognition piece attached to the proximal end portion of the rod-shaped anchor in a state exposed to the outside and abutting the sleeve portion;
2. The crack detection device according to claim 1, wherein the visual recognition piece falls off from the base end of the rod-shaped anchor when the crack occurs. 11. The visual recognition piece is screwed to the base end of the rod-shaped anchor, is made of a material softer than the rod-shaped anchor, and falls off from the rod-shaped anchor when the screw thread is damaged. Crack detection device as described. 11. The crack detection device according to claim 10, wherein the visual recognition piece is comprised of a retaining ring attached to a base end of the rod-shaped anchor. A metal anchor anchored to a concrete structure;
The crack detection device according to any one of claims 1 to 12, provided in the prepared hole bored adjacent to the metal anchor and having approximately the same length as the metal anchor,
A crack detection system, wherein the crack detection device detects occurrence of cone-shaped fracture in the concrete structure caused by the metal anchor.

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