JP3902503B2 - Sensor mounting structure for concrete structures - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a structure for mounting a deterioration diagnosis sensor on a concrete structure, and in particular, the prestressed concrete structure of a sensor such as an AE sensor for accurately detecting breakage of a tension material used in a prestressed concrete structure. The present invention relates to an attachment structure to an object.
[0002]
[Prior art]
For example, since concrete structures such as road bridges and railway bridges are subjected to repeated load over time, prestressed concrete structures in which tendons are embedded are used.
In such a prestressed concrete structure, it is very important to detect the breaking of the tendon because the collapse of the entire structure can be predicted in advance.
[0003]
Here, an acoustic emission (hereinafter abbreviated as AE) method has been conventionally known as a method for detecting the breakage of the tension material embedded in the prestressed concrete structure.
This AE method is a method of diagnosing an abnormality in a concrete structure or the like by detecting an elastic wave generated by energy released when a solid is deformed or broken and analyzing the elastic wave.
[0004]
By this AE method, when it is attempted to detect the breakage of the tension material embedded in the prestressed concrete structure, many of the conventional materials are applied to the surface of the concrete structure near the site where the tension material is embedded. An AE sensor for detecting elastic waves has been attached.
[0005]
[Problems to be solved by the invention]
Here, generally as a tension material which makes prestress act on a concrete structure, a PC steel rod or PC steel wire is used, and in recent years, more wire is used than PC steel which has good adhesion to the structure. Has been.
[0006]
When a PC steel bar is used as a tension material, there is a large release of energy when it breaks, and strong elastic waves propagate through the concrete structure, so even a sensor attached to the surface of the concrete structure is sufficient. Detection was possible.
However, in the case of a PC strand, the breakage of the strand from the PC rope does not occur at a stretch, but one or several pieces are gradually broken, so that a large amount of energy is not released, and weak elasticity Waves will only propagate through the concrete structure. For this reason, even if the strands of the PC rope are actually broken, the sensor attached to the surface of the concrete structure may not be able to detect the elastic wave based on the fracture, and the PC strands are frequently used. In recent years, it has been a big issue.
[0007]
In addition, since the concrete structure is outdoors, the sensor attached to its surface picks up natural environmental sounds such as rain and wind, and the sound becomes noise and generates elastic waves based on the fracture of the tendon. Sensors attached to the surface of concrete structures have been subject to temperature changes, are exposed to wind and rain, and are also subject to corrosion due to salinity along the ocean. I had a problem to say.
[0008]
On the other hand, it is important for the sensor to have a long life and be easily replaced in order to construct a system that continuously monitors the breakage of the tendon material over a long period of time.
[0009]
Accordingly, an object of the present invention is to provide a structure in which a sensor such as an AE sensor that detects breakage of a tension material used in a prestressed concrete structure is attached to the concrete structure with high detection accuracy and can be easily replaced. It is in.
[0010]
[Means for Solving the Problems]
In order to achieve the above-mentioned object, the present invention provides a drilling hole drilled in a prestressed concrete structure from the surface toward the position where the tendon is buried, and near the position, and more elastic than the concrete fixed to the inner surface of the drilling hole. A cylindrical holder made of a material with a small coefficient, the above-mentioned sensor detachably mounted in the cylindrical holder, a jig attached to the tip toward the tension material side, and loaded in the cylindrical holder The sensor is attached to a concrete structure made of the filled material.
[0011]
According to the sensor mounting structure to the concrete structure according to the present invention described above, for example, since the sensor is mounted in a drilling hole near the embedding position of the tension material such as the protective grout surface of the tension material, natural environmental sound, for example, Since it rarely picks up sounds such as rain and wind, and the sensor is located in the vicinity of the tendon, even if the tendon is a strand of PC steel, it is possible to accurately detect weak elastic waves based on the breakage. It becomes. In addition, since the sensor is mounted in the drilling hole by a cylindrical holder fixed to the inner surface of the drilling hole with an adhesive or the like and a jig detachably mounted in the cylindrical holder, the sensor can be easily replaced. It will be a thing.
Further, the cylindrical holder fixed to the inner surface of the drilling hole is made of a material having a smaller elastic coefficient than concrete, for example, plastic, and is filled with a filler. It is easy to follow and hardly peel off from the inner surface of the drilling hole, and the filler loaded inside the cylindrical holder is installed inside the drilling hole to block moisture and salt entering from the outside. The above-described sensor and the tendon located in the vicinity of the drilling hole are sufficiently protected from the external environment. As described above, the sensor mounting structure for a concrete structure according to the present invention is a sensor for detecting breakage of a tension material used in the concrete structure, and is easy to replace with a high detection accuracy. It is possible to construct a system that can monitor the breakage of the tendon over a long period of time.
[0012]
Here, in the present invention, it is preferable to use a grout filling state inspection hole for protecting the tendon as the hole for attaching the sensor.
This is because the hole for inspection of the filling condition of the grout reaches the protective grout of the tension material very close to the position where the tension material is buried, and when a sensor is attached to the hole, It is preferable because breakage can be detected with high accuracy and there is no need to form a new hole, and the influence on the structure can be minimized.
[0013]
The concrete structure referred to in the present invention is not particularly limited as long as it is a prestressed concrete structure in which a tension material is used, but there are bridges such as roads and railways, high-rise buildings, dams, tunnels, and the like. Can be mentioned.
The sensor referred to in the present invention is a sensor that detects an elastic wave generated by energy released when a solid is deformed or broken, and includes an AE sensor, an ultrasonic sensor, an acceleration sensor, a microphone, and the like. .
Furthermore, the filler referred to in the present invention is an ointment-like substance that does not harden, and includes mineral oil-based grease, silicon-based grease, fluorine-based grease, and the like.
[0014]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, a sensor mounting structure for a concrete structure according to the present invention will be described in detail with reference to the drawings.
[0015]
1 to 3 conceptually show an embodiment in which the sensor mounting structure for a concrete structure according to the present invention is applied to AE sensor mounting to a prestressed concrete structure such as a road bridge or a railway bridge. It is a figure.
[0016]
In the figure, reference numeral 1 denotes a concrete structure, and the concrete structure 1 is prestressed by a tension material 2 made of a PC steel wire. The tendon 2 is protected by a grout 4 filled in the sheath tube 3 and is embedded in the concrete structure 1 through the grout 4.
[0017]
The concrete structure 1 is formed with a hole 5 for checking the filling state of the grout 4. The hole 5 reaches the sheath tube 3, and a hole 6 communicating with the hole 5 is formed in the sheath tube 3.
[0018]
The outer peripheral surface of the cylindrical holder 8 is integrally fixed to the inner peripheral surface of the hole 5 with an adhesive 7. The cylindrical holder 8 is formed into a cylindrical shape with both ends open by a non-metallic material having a smaller elastic coefficient than concrete, such as plastic, and a female screw 9 is formed on the inner peripheral surface of the rear end as shown in FIG. It is engraved.
[0019]
A jig 11 having an AE sensor 10 attached to the tip is mounted in the cylindrical holder 8, and the jig 11 cuts the AE sensor 10 in close contact with the surface of the grout 4 through the hole 6. It is installed in the hole 5. The jig 11 is made of a non-metallic material having an elastic coefficient smaller than that of concrete, such as plastic, as shown in FIG. 3, and includes a front end cylindrical portion 11a for attaching the AE sensor 10 as shown in FIG. The connecting portion 11c that connects the cylindrical portions 11a and 11b is integrally formed. A concave portion 12 for mounting the AE sensor 10 (this concave portion 12 is closed by another member when used at the time of grout filling as will be described later) is formed in the tip cylindrical portion 11a. The end column portion 11b is provided with a male screw 13 which is engaged with the female screw 9 of the cylindrical holder 8 on the outer peripheral surface thereof, and a knob portion 14 is formed on the rear end surface thereof. In addition, a pore 15 into which the lead wire 10a of the AE sensor 10 is inserted is formed through the tip cylindrical portion 11a, the connecting portion 11c, and the rear end cylindrical portion 11b.
[0020]
The cylindrical holder 8 is filled with a filler 16 that is an ointment-like substance such as silicon grease that prevents moisture and salt from entering the cylindrical holder 8.
[0021]
Next, an example of the attachment procedure for realizing the sensor attachment structure to the concrete structure according to the present invention will be described. In this example, the concrete structure is constructed and the grout filling inspection before grout filling is used, or after the concrete structure is constructed and the grout filling is incomplete. This is an example in the case of using a hole for grout filling state inspection that requires new grouting.
[0022]
First, the cylindrical holder 8 is fixed to the grout 5 for grout filling state inspection using the adhesive 7.
[0023]
Subsequently, the jig 11 is inserted into the fixed cylindrical holder 8, and the male screw 13 formed on the rear end cylindrical portion 11 b of the jig 11 is replaced with the female screw formed on the cylindrical holder 8. The jig 11 is mounted in the cylindrical holder 8 by being screwed to 9. At this time, by using the knob portion 14 formed on the rear end cylindrical portion 11b of the jig 11, it can be easily mounted.
The concave portion 12 for attaching the AE sensor formed in the distal end cylindrical portion 11a of the jig 11 is mounted on the cylindrical holder 8 in a state where the distal end surface is closed by a separate member.
[0024]
Subsequently, the grout 4 is filled into the sheath tube 3 provided with the tension material 2 from a grout injection hole (not shown) provided separately.
[0025]
After the filled grout 4 is cured, the jig 11 attached to the cylindrical holder 8 is removed, and the filling state of the grout 4 is inspected.
[0026]
After confirming that the grout 4 is satisfactorily filled, the above-mentioned jig 11 in which the grease 16 is filled in the cylindrical holder 8 and the AE sensor 10 is attached to the concave portion 12 is cylinderized by the same method as described above. Is mounted in the holder 8.
[0027]
Thereby, the AE sensor 10 can be mounted in the drilling hole 5 in close contact with the grout 4 that protects the tendon 2, and the elastic wave propagating in the concrete structure 1 detected by the AE sensor 10 is As shown in FIGS. 1 and 2, for example, an amplifier, an A / D converter, and a control unit (none of which are shown) led to the measurement box 20 through the lead wire 10 a and provided in the measurement box 20. If the elastic wave detected by the AE sensor 10 is based on breakage of the tendon 2, the warning lamp 21 is turned on to notify the manager of the structure.
[0028]
As mentioned above, although one embodiment of the sensor mounting structure to the concrete structure according to the present invention has been described, the present invention is not limited to the above-described embodiment, and is within the scope of the technical idea of the present invention. Of course, various modifications and changes are possible.
[0029]
For example, in the above-described embodiment, the description has been given on the use of the grout filling state inspection hole 5 as the hole for attaching the sensor. However, the tension material 2 is embedded in the concrete structure 1. A drill hole approaching the position may be newly drilled for sensor mounting. In this case, the mounting is performed in a state where the grouting steps described in the paragraph numbers [0022] to [0024] are omitted.
Further, as described above, an acceleration sensor or an ultrasonic sensor may be used instead of the AE sensor 10 as the sensor.
Furthermore, in the above embodiment, as a structure in which the jig is detachably attached to the cylindrical holder, the male screw 13 formed on the jig 11 is screwed onto the female screw 9 formed on the cylindrical holder 8. Although the structure has been described, this is merely an example. For example, a structure in which an annular convex portion formed on the outer peripheral surface of the jig is fitted to an annular concave portion formed on the inner peripheral surface of the cylindrical holder, or Various known structures that can easily fix and remove the jig from the cylindrical holder, such as a structure using various fasteners using a clamp mechanism, can be employed.
[0030]
【The invention's effect】
As described above, according to the sensor mounting structure to the concrete structure according to the present invention described above, the sensor for detecting the breakage of the tension material used in the prestressed concrete structure can be easily detected and replaced in the concrete structure. It is possible to construct a system that can be attached to the monitor and keep monitoring the breakage of the tendon over a long period of time.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view conceptually showing an embodiment of a sensor mounting structure for a concrete structure according to the present invention.
FIG. 2 is a longitudinal sectional view conceptually showing an embodiment of a sensor mounting structure for a concrete structure according to the present invention.
FIG. 3 is an exploded perspective view conceptually showing an embodiment of a sensor mounting structure for a concrete structure according to the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Concrete structure 2 Tensile material 3 Sheath tube 4 Grout 5 Drilling hole 6 Hole 7 Adhesive 8 Cylindrical holder 9 Female screw 10 AE sensor 10a Lead wire 11 Jig 12 Recess 13 Male screw 14 Knob part 15 Pore 16 Filler 20 Measurement box 21 Warning light

Claims (2)

A sensor mounting structure for detecting a breakage of a tendon material embedded in a prestressed concrete structure, and a drilling hole drilled in the concrete structure from the surface toward the position where the tendon material is embedded, to the vicinity of the position, A cylindrical holder made of a material having a smaller elastic coefficient than the concrete fixed to the inner surface of the drilling hole, and the sensor detachably mounted in the cylindrical holder were attached to the tip toward the tendon side A sensor mounting structure for a concrete structure, comprising a jig and a filler loaded in the cylindrical holder. 2. The sensor mounting structure for a concrete structure according to claim 1, wherein the hole is a hole for grout filling state inspection that protects the tendon.

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