JPH10115599A - Detecting method for crack in concrete structure - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a detecting method, for a crack in a concrete structure, in which the occurrence place of the crack can be specified, in which a plurality of cracks can be detected with a simple configuration and in which the occurrence cause of the crack can be estimated. SOLUTION: A pulsed signal is input, by a pulse transmitting means 3, to a conductive conductor 2 which is buried in a body 1a constituting a concrete structure 1. Reflected waves, from the conductor 2, which are generated due to the input of the pulsed signal are detected by a reflected-wave receiving means 4. The impedance in every position of the conductor 2 is detected on the basis of the pulsed signal and the reflected waves. On the basis of a detected result, the existence of a crack in the body 1a is detected.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for detecting a crack in a concrete structure for detecting a crack generated in a skeleton of the concrete structure.

[0002]

2. Description of the Related Art Investigation of cracks and their occurrence in concrete structures is indispensable for grasping the strength and durability of the structures and confirming the soundness of the structures. ing.

[0003] Such investigations are often carried out visually, but in order to more accurately grasp the state of cracks, a technique of installing a strain gauge in a place where cracks are likely to occur has been used. . In addition, recently, the presence or absence of cracks is detected by burying conductive fibers such as carbon fibers formed in a lattice shape in a concrete structure and measuring the electrical resistance value of those fibers. And other techniques have also been developed.

[0004]

However, when trying to grasp the state of cracks in a structure using a strain gauge, if a crack occurs at a position different from the place where the strain gauge is installed, the crack is removed. There was a problem that detection was impossible. Further, the strain gauge is used by being attached to the outer surface of a structure to be subjected to crack detection, and it has been difficult to grasp the state of occurrence of cracks inside the structure.

On the other hand, when conductive fibers are embedded in a concrete structure, the occurrence of cracks inside the structure can be detected, and depending on the arrangement and shape of the conductive fibers, it can be both planar and Although it is possible to investigate the occurrence of cracks in a wide range, this method makes it possible to confirm that the electrical resistance of the conductive fiber has changed at any point on the conductive fiber due to cracking or distortion. Even so, it was difficult to grasp where these cracks and the like occurred on the conductive fiber. Particularly, in a situation where a plurality of cracks are generated on one conductive fiber, it is difficult to detect the crack. Furthermore, it was impossible to determine whether the cause of the cracks or the like was caused by, for example, the load of the structure, the external force applied to the structure, or the salt damage.

[0006] In view of such circumstances, the present invention can specify the location of the occurrence of cracks, can detect cracks at a plurality of locations with a simple configuration, and can also estimate the cause of the occurrence of cracks. It is an object of the present invention to provide a method for detecting cracks in a concrete structure.

[0007]

In the present invention, the following means are employed in order to solve the above-mentioned problems. That is, a method for detecting cracks in a concrete structure according to claim 1 is a method for detecting cracks in a concrete structure for detecting cracks generated in a skeleton of a concrete structure, wherein a conductive wire having conductivity is connected to at least one end thereof. Is embedded in the skeleton in a state of being exposed from the surface of the skeleton, and at one end of the conductor exposed from the skeleton, a pulse transmitting means for inputting a pulse signal to the conductor, and the pulse signal is generated by the input of the pulse signal A reflected wave receiving means for detecting a reflected wave from the conducting wire is connected, and a pulse signal is input to the conducting wire by the pulse transmitting means, and a reflection from the conducting wire caused by the input of the pulse signal is provided. A wave is detected by the reflected wave receiving means, and impedance at each position of the conductor is detected based on the pulse signal and the reflected wave. , Based on the detection result, and detecting the presence of cracks in the building frame.

In this method for detecting cracks in a concrete structure, the state of occurrence and the cause of the cracks can be grasped from the results of impedance detection at each position on the conductor. Specifically, when the impedance value increases at a certain position on the conductor, it can be estimated that the conductor near that position has been extended by cracking. In the case of cracks due to salt damage, the conductivity of concrete near the cracks increases, so that the conductor is in the same state as insulated insulation, and the impedance is reduced. Therefore, when a decrease in the impedance value is detected at a certain position on the conductive wire, it can be estimated that cracking due to salt damage has occurred.

A method for detecting cracks in a concrete structure according to a second aspect is the method for detecting cracks in a concrete structure according to the first aspect, wherein a plurality of the conductive wires are arranged in parallel in the frame. By the pulse transmitting means,
It is characterized in that a pulse signal is input to these conductors, and a state of cracks generated in the skeleton is detected based on a detection result obtained from these conductors.

In this method for detecting a crack in a concrete structure, since a plurality of conductive wires are arranged in the skeleton of the concrete structure, it is possible to specify a crack generation site in a wide area. In particular, it is possible to determine whether or not cracks due to salt damage have penetrated these conductors, based on impedance-related signals obtained between adjacent conductors.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a method for detecting cracks in a concrete structure according to the present invention will be described below with reference to the drawings. FIG. 1 is a view showing an embodiment of the present invention, and reference numeral 1 denotes a concrete structure to be inspected for occurrence of cracks. The conducting wire 2 is buried in the skeleton 1a of the concrete structure 1 in advance from the time of construction. The conducting wires 2 are arranged in parallel and at equal intervals in the frame 1a, and both ends thereof are concrete structures 1
Is exposed from the outer surface 1b. A pulse transmitting means 3 capable of transmitting a pulse signal to the conductive wire 2 and a pulse signal transmitted from the pulse transmitting means 3 are provided at one end 2a of the conductive wire 2 exposed from the outer surface 1b. The reflected wave receiving means 4 capable of detecting the generated reflected wave from the conducting wire 2 is connected to the pulse transmitting means 3 and the reflected wave receiving means 4. The impedance detecting means 5 for detecting the impedance at the position is connected. Further, the impedance detecting means 5 is provided with a display means 6 for displaying the impedance at each position on the conductor 2.

The above is the configuration of the apparatus and the like necessary for executing the method for detecting a crack in a concrete structure according to the present embodiment. Next, details regarding the execution of the method for detecting a crack in a concrete structure will be described. I do.

In general, when a pulse is input to an electric circuit, a reflected wave from the electric circuit itself, or a reflected wave from a flaw on a cable constituting the electric circuit or a defective insulation portion is obtained as a response. Can be With these reflected waves, the impedance at each position on the cable that constitutes the electric circuit can be measured.For example, if there is a scratch on the cable, it becomes difficult for electricity to flow at that position, so the impedance is high. Measured.
In addition, when there is a poor insulation location on the cable, the impedance at that location is measured low.

The above-described phenomenon relating to impedance is usually used to find a defective insulation portion or a broken wire position in an electric circuit. In the present embodiment, this phenomenon occurs in a concrete structure. Used to detect cracks. That is, when a crack is generated in the skeleton 1a by the action of a load or the like, the conductive wire 2 penetrating the crack is extended. For this reason, it is difficult for the conductor 2 to conduct electricity in the vicinity of the place where the crack occurs, and as a result, the impedance of the conductor 2 at that position increases. Further, when a crack occurs due to salt damage in the frame 1a, since the conductivity of the concrete in the vicinity of the crack increases, the same phenomenon as the occurrence of the insulation failure portion in the above example of the electric circuit occurs. Will occur. That is, the impedance of the conductor 2 near the crack is reduced. Therefore, a pulse signal is transmitted to the conductor 2 by the pulse transmission means 3, and the impedance at each position on the conductor 2 is measured based on the reflected wave generated by the pulse signal. It is possible to detect where the crack has occurred.

In the present embodiment, cracks in the skeleton 1a of the concrete structure 1 are detected by utilizing the above-described action relating to impedance. The specific procedure will be described below.

First, a pulse signal is input to the conductor 2 by the pulse transmitting means 3. The reflected wave is returned from the conducting wire 2 with the transmission of the pulse signal, and the reflected wave is received by the reflected wave receiving means 4. On the other hand, a pulse signal similar to that input to the conductor 2 from the pulse transmission means 3 is also input to the impedance detection means 5. Similarly, the reflected wave detected by the reflected wave receiving means 4 is also input to the impedance detecting means 5.

The impedance detecting means 5 detects the impedance at each position in the conductor 2 from the pulse signal and the reflected wave, and the detection result is displayed by the display means 6. Specifically, for example, FIG.
As shown in the graph shown in FIG. 7, the impedance at each position on the conductor 2 is displayed, with the vertical axis representing the impedance value Z and the horizontal axis representing the distance 1 from the end 2 a of the conductor 2.

FIG. 2 is a graph showing an example of the impedance detection result in the present embodiment. According to this graph, the impedance is high at the point indicated by point A. Is observed. Therefore, it is considered that cracks have occurred in the frame 1a near the point _A , that is, near the position at a distance lA from the end 2a on the conductor 2. Further, in this case, as a cause of the occurrence of the crack, a load on the concrete structure 1 itself or an external force acting on the concrete structure 1 is assumed.

In addition, a drop in impedance is observed at a point indicated by point B in FIG. Therefore, B point, that is, in the vicinity of the position of the distance l _b from the end 2a of the conductor 2, during building frame 1a, cracks were caused by salt damage is assumed to have occurred.

Further, when a crack due to salt damage occurs, it is possible to check whether the crack penetrates the adjacent conductors 2 by measuring the impedance between the adjacent conductors 2. . In this case, as shown in FIG. 3, the pulse transmitting means 3 is connected to one of the conductors 2b, and the reflected wave receiving means 4 is connected to the other 2c. When a pulse signal is transmitted to the conductor 2b by the pulse transmitter 3, if the crack caused by salt damage does not penetrate the conductors 2b and 2c, no response is detected by the reflected wave receiver 4. However, FIG.
As shown in the figure, cracks 7 caused by salt damage
In the case of passing through c, the conducting wires 2b and 2c are conducted by the crack 7 due to salt damage, and the response is detected by the reflected wave receiving means 4. In this manner, in the present embodiment, when a crack occurs in the skeleton 1a due to salt damage, it is possible to determine the approximate crack width.

As described above, the method for detecting a crack in a concrete structure according to the present embodiment is an application of a method for detecting a defective insulation location or a broken wire position in an electric circuit. Frame 1a of object 1
It is possible to find cracks inside. Especially,
By using the configuration and the procedure as described above, it is possible to specify a crack location with an accuracy of several centimeters, and it is also possible to specify a plurality of crack locations on one conductive wire. As described above, in the present embodiment, it is possible to detect cracks in a wide range with high accuracy as compared with the conventional crack detection method for concrete structures.

Further, the present embodiment makes it possible to detect a cracked portion with high accuracy with a simple device configuration.
Conventionally, many strain gauges must be installed on the outer surface of a concrete structure in order to accurately know the state of occurrence of cracks, and it is difficult to perform such measurements in terms of cost and workability. However, according to the present embodiment, a wide range of cracks can be detected with a simple device configuration, so that the soundness of the concrete structure can be easily and at low cost.

Further, in the present embodiment, it is possible to estimate the cause of crack generation, which is difficult in the conventional crack detection method. In particular, since the occurrence of cracks due to salt damage can be detected, the present embodiment is preferably applied to a concrete structure or the like in a seaside part. In addition, when cracks occur due to salt damage, it is possible to know the approximate length of the cracks, and it is possible to more accurately grasp the damage status of concrete structures due to salt damage as compared to conventional technology. Becomes

In the above embodiment, the type of the concrete structure 1 is not specified, but the present invention is applied to various structures by utilizing the features of the present invention as described above. Can be considered. For example, as described above, the present invention may be applied to a concrete structure in a seaside area, or a soundness of a large-scale concrete structure such as a crack due to a ground load in a tunnel or a crack in a concrete embankment of a dam. The present invention may be used for the determination of. In addition, the present invention may be applied to a structure, such as monitoring of an outer peripheral concrete of an underground tank and maintenance and management of a tower-like structure, in which crack investigation was conventionally difficult. In addition, taking advantage of the feature of the present invention that it is possible to detect crack locations with high accuracy, nuclear facilities,
It is also conceivable to apply the present invention to a structure requiring a high level of security, such as a reprocessing facility.

[0025]

As described above, the method for detecting cracks in a concrete structure according to the first aspect of the present invention embeds a conductor in a skeleton of a concrete structure, inputs a pulse signal to the conductor, and outputs a pulse signal to the conductor. The impedance at each position of the conductor is detected based on the waves and the reflected waves generated by the conductor, and based on the detection results, the presence of cracks in the skeleton is detected. Since it is possible to detect a plurality of cracks on a single conductor, it is possible to specify a wide range of cracks depending on the arrangement of the conductors. Further, it is possible to guess the cause of crack generation (whether due to load / external force or salt damage), and it is suitable to be used for crack investigation of a concrete structure in a seaside area. Claim 2
According to the concrete structure crack detection method described, a plurality of conductors are arranged in parallel in the skeleton of the concrete structure, a pulse signal is input to these conductors, and based on the detection result, The invention according to claim 1 can be realized over a wide area in order to detect the state of cracks generated in the skeleton. In particular, it is possible to determine whether or not cracks due to salt damage have penetrated these conductors, based on impedance-related signals obtained between adjacent conductors.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of a concrete structure schematically showing one embodiment of the present invention.

FIG. 2 is an example of a graph showing the impedance at each position on a conductive wire obtained by the method for detecting a crack in a concrete structure according to the present invention.

FIG. 3 is a partially enlarged view of the concrete structure shown in FIG.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Concrete structure 1a Frame 2 Conductor 2a End part 3 Pulse transmitting means 4 Reflected wave receiving means 5 Impedance detecting means 7 Crack

Claims (2)

[Claims] 1. A method for detecting cracks in a concrete structure for detecting cracks generated in a skeleton of the concrete structure, the method comprising: providing a conductive wire having conductivity at least one end thereof exposed from the surface of the skeleton. A pulse transmitting unit configured to input a pulse signal to the conductor at one end of the conductor exposed from the framework, and a reflected wave detected by the input of the pulse signal to detect a reflected wave from the conductor; A pulse signal is input to the conductor by the pulse transmitting means, and a reflected wave from the conductor generated with the input of the pulse signal is detected by the reflected wave receiving means. The impedance at each position of the conductor is detected based on the pulse signal and the reflected wave. Crack detection method of the concrete structure, characterized in that to detect the presence of. 2. A method for detecting cracks in a concrete structure according to claim 1, wherein a plurality of said conductors are arranged in parallel in said frame, and said pulse transmission means applies pulses to said conductors. A method for detecting a crack in a concrete structure, comprising: inputting a signal; and detecting a state of a crack generated in the skeleton based on a detection result obtained from the conductor.