Anchor non-destructive inspection method, and anchor non-destructive inspection device

Abstract

To suppress deterioration of workability in an anchor non-destructive inspection.SOLUTION: A frequency responce derivation step is configured to derive a frequency responce of an anchor when oscillation is applied. A frequency characteristic derivation step is configured to repeat the frequency responce derivation step while changing an oscillation frequency, and derive a frequency characteristic of the anchor. A largest maximal value acquisition step is configured to acquire a largest maximal value of the frequency characteristic, and a corresponding oscillation frequency. A pick-up step is configured to pick up the maximal value in which the oscillation frequency is smaller than that acquired in the largest maximal value acquisition step, of the maximal value of the frequency characteristic. An inclination acquisition step is configured to set each maximal value to an objective variable, and set a coefficient of an explanatory variable obtained by logarithm single regression analysis with the oscillation frequency as the explanatory variable to an inclination. A determination step is configured to determine whether an anchor is in a deterioration state on the basis of two parameters of the oscillation frequency acquired in the largest maximal value acquisition step and the inclination.SELECTED DRAWING: Figure 3

Description

[Technical field]

[0001] The present disclosure relates to a non-destructive inspection method and an apparatus for non-destructive inspection of an anchor. [Background technology]

[0002] In this disclosure, the term "anchor" refers to a structural material whose embedded part is embedded in a structure and whose protruding part protruding from the structure is fixed to another structure. That is, the term "anchor" in this disclosure includes, for example, an anchor bolt whose embedded part on one side is embedded in a concrete foundation and whose protruding part on the other side is fixed to another structure. The term "anchor" also includes, for example, an anchor bar that is provided in a state in which a reinforcing bar protrudes upward from a concrete skeleton and fixes another concrete structure cast on the skeleton to the skeleton. The term "anchor" also includes, for example, a set anchor that is an assembly in which one or both of an anchor bolt and an anchor bar are combined into one piece. The term "anchor" also includes, for example, a linear body (so-called "tendon") whose one end is embedded in an anchor body, which is a structure provided in the ground, and whose other end is fixed to a retaining wall, which is a structure provided on a slope. "Anchor" also includes, for example, a rock bolt, one of whose buried parts is buried in a ground structure and the other of whose protruding part protrudes from the ground structure and is fixed to a slope protection work. "Anchor" also includes, for example, a foundation pile, the lower of which is buried in a ground structure and the upper protruding part is fixed to the foundation of a building.

[0003] There is a need for a non-destructive inspection method for inspecting "anchors" without destroying the structure in which the embedded portion is embedded. For example, the following Patent Document 1 discloses a technique in which a vertical probe is attached via an angle wedge to the upper end of an anchor bolt embedded in concrete that protrudes from the concrete, and deterioration of the anchor bolt is judged from the reflected echo (waveform of the reflected wave) of the ultrasonic inspection signal. In this technique, the angle wedge to which the vertical probe is fixed is rotated once at the upper end of the anchor bolt, without moving the vertical probe in the up / down or left / right directions, to inspect the entire circumference of the anchor bolt. Then, deterioration of the anchor bolt is judged from the height of the reflected echo reflected from each thread of the anchor bolt detected in this inspection. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent No. 6088088 Summary of the Invention [Problem to be solved by the invention]

[0005] In the conventional technology disclosed in the above Patent Document 1, if the upper end of the anchor bolt is uneven or inclined, the angle wedge and vertical probe will be unstable and accurate detection will be impossible, and deterioration of the anchor bolt will not be judged correctly. Therefore, in order to detect the reflected echo with high accuracy, the above conventional technology requires additional work to check whether the upper end of the anchor bolt is uneven or inclined, and if it is uneven or inclined, to polish the upper end of the anchor bolt flat. This work deteriorates the workability of non-destructive testing of anchors.

[0006] The present disclosure provides a method and device for non-destructive testing of an anchor, which suppresses deterioration of workability in non-destructive testing of an anchor. [Means for solving the problem]

[0007] According to one aspect of the present disclosure, there is provided a non-destructive inspection method for an anchor, in which an anchor with a buried portion buried in a structure and a protruding portion protruding from the structure is judged to be in a deteriorated state without destroying the structure. This non-destructive inspection method for an anchor includes a frequency response deriving step, a frequency characteristic deriving step, a maximum local maximum value acquiring step, a pick-up step, a tilt acquiring step, and a judging step, each of which will be described later. Here, in the frequency response deriving step, the frequency response of the anchor when vibration of a predetermined vibration frequency is applied is derived based on the measurement value of a sensor set on the protruding portion of the anchor. In addition, in the frequency characteristic deriving step, the frequency response deriving step is repeatedly executed while changing the vibration frequency of the vibration, thereby deriving the frequency characteristic of the anchor. In addition, in the maximum local maximum value acquiring step, the maximum local maximum value in the frequency characteristic and the vibration frequency corresponding to this local maximum value are acquired. In the picking step, a maximum value in the frequency characteristics is picked up that satisfies the condition that the vibration frequency corresponding to the maximum value is smaller than the vibration frequency acquired in the maximum maximum value acquisition step. In the slope acquisition step, a logarithmic simple regression analysis is performed with the maximum value acquired in the maximum maximum value acquisition step and the maximum value picked up in the picking step as objective variables, and the vibration frequency corresponding to these maximum values ​​as explanatory variables, and the coefficient of the explanatory variable obtained is acquired as a slope. In the determination step, it is determined whether or not the anchor is in a deteriorated state based on two parameters, the vibration frequency acquired in the maximum maximum value acquisition step and the slope.

[0008] Here, when the term "logarithm" is used simply in this disclosure, it refers to a logarithm that satisfies the condition that the base is greater than 1. Furthermore, in this disclosure, "logarithmic simple regression analysis" refers to a process that is equivalent to "a process of performing a simple linear regression analysis in which the logarithm of the objective variable (whether the base is less than or greater than 1) is used as a new objective variable without changing the explanatory variables."

[0009] The present inventor discovered that the difference between a normal anchor and an anchor in a deteriorated state is manifested in that the vibration frequency corresponding to the maximum local maximum value (peak) in the frequency characteristics of the anchor is large, and in the region where the vibration frequency is smaller than this vibration frequency, the slope in the logarithm of the frequency characteristics is large, and thus the present disclosure was made. That is, according to the above method, it is determined whether or not the anchor is in a deteriorated state from the magnitude of the vibration frequency corresponding to the maximum local maximum value in the frequency characteristics of the anchor and the slope in the logarithm of the frequency characteristics. Therefore, according to the above method, it is possible to eliminate the need for additional work for detecting the waveform of the reflected wave of the vibration with high accuracy, and to suppress deterioration of the workability in the nondestructive testing of the anchor.

[0010] In one preferred embodiment, the determination step executes the following process: In this process, the anchor is determined to be in a deteriorated state when a condition is established that is equivalent to the vibration frequency acquired in the maximum local maximum value acquisition step being large in light of a first criterion, which is a predetermined criterion, and the absolute value of the slope is large in light of a second criterion, which is a criterion set separately from the first criterion.

[0011] In the above case, the judgment in the judgment step can be a simple process that combines two judgments based on simple conditions.

[0012] In another preferred embodiment, the means for applying vibration is a vibrating speaker that reproduces a sweeping sound.

[0013] Here, "sweep sound" refers to a sound whose vibration frequency gradually increases (or decreases) over time. Also, "playback" refers to referencing sound information fixed to an object and generating a sound corresponding to this sound information.

[0014] In the above case, the frequency characteristic deriving step can be executed by repeatedly measuring with the sensor while applying the sweep sound from the vibration speaker to the anchor, and deriving the frequency characteristic based on each measured value. This can improve the workability when performing the nondestructive testing method for anchors. In addition, since the vibration speaker generates the sweep sound by playback, it is possible to generate the same sweep sound every time. This can provide a nondestructive testing method for anchors in which the conditions for applying vibration to the anchor are uniform and the influence of differences in the application conditions on the testing results is suppressed.

[0015] In another preferred embodiment, a uniaxial vibration exciter that generates uniaxial vibration is used as the vibration applying means, and a vibration sensor having one or more axes for measuring vibration is used as the sensor.The uniaxial vibration exciter and the vibration sensor are opposed to each other, and one of the axes of measurement of the vibration sensor is aligned with the axis of vibration generated by the uniaxial vibration exciter, and the frequency response deriving step is performed in this state.

[0016] In this case, the vibration generated by the uniaxial vibrator reaches the sensor without being deflected from its axial direction. Also, the sensor can measure the vibration generated by the uniaxial vibrator only with the measurement axis that is aligned with the axis of this vibration. This makes it possible to provide a nondestructive inspection method for anchors in which the influence of vibration noise acting from a direction other than the vibration generated by the uniaxial vibrator on the inspection results is suppressed.

[0017] In another preferred embodiment, the frequency response deriving step is performed in a state where the sensor is set at the tip of the protruding portion protruding from the structure.

[0018] In an anchor, the protruding portion protruding from a structure is more susceptible to vibration than the embedded portion embedded in the structure. This tendency is most pronounced at the tip of the protruding portion. In the above case, the sensor measures the vibration at the tip of the protruding portion where the vibration acting on the anchor is the largest. This makes it possible to provide a non-destructive inspection method for an anchor in which the magnitude of the vibration input to the sensor is increased and the signal-to-noise ratio is improved.

[0019] In another preferred embodiment, the sensor is either an accelerometer, which measures the acceleration waveform of the vibration, or a velocimeter, which measures the velocity waveform of the vibration.

[0020] There are three types of sensors that enable the derivation of the frequency response when vibration is applied to an object: a displacement meter that measures the displacement waveform of the vibration, a speed meter that measures the velocity waveform of the vibration, and an accelerometer that measures the acceleration waveform of the vibration. Here, the displacement meter captures the "result of the movement of the object due to the application of vibration", so there is a time difference between the timing of the application of the vibration and the timing of the measurement by the sensor. On the other hand, the speed meter captures the "movement of the object due to the application of vibration", so there is less of a time difference between the timing of the application of the vibration and the timing of the measurement by the sensor. In addition, the accelerometer captures the "force acting on the object when the vibration is applied", so there is less of a time difference between the timing of the application of the vibration and the timing of the measurement by the sensor. Therefore, according to the above embodiment, it is possible to provide a non-destructive inspection method for an anchor in which the influence of the time difference between the timing of the application of the vibration and the timing of the measurement by the sensor on the inspection result is suppressed.

[0021] According to another aspect of the present disclosure, there is provided a non-destructive inspection device for an anchor, which determines whether an anchor, whose embedded portion is embedded in a structure and whose protruding portion protrudes from the structure, is in a deteriorated state without destroying the structure. The non-destructive inspection device for an anchor includes a vibrator that repeatedly applies vibration to the anchor while changing the vibration frequency of the vibration. The non-destructive inspection device for an anchor also includes a sensor that is set on the protruding portion of the anchor. The non-destructive inspection device for an anchor also includes a frequency response derivation means that derives the frequency response of the anchor when the vibration is applied based on the measurement value of the sensor. The non-destructive inspection device for an anchor also includes a frequency characteristic derivation means that derives the frequency characteristic of the anchor by associating the vibration frequency of the vibration applied by the vibrator with the frequency response derived by the frequency response derivation means. The non-destructive inspection device for an anchor also includes a maximum maximum value acquisition means that acquires the maximum local maximum value in the frequency characteristic and the vibration frequency corresponding to the local maximum value. The non-destructive testing device for anchors also includes a pick-up means for picking up a maximum value among the maximum values ​​in the frequency characteristics that satisfies the condition that the vibration frequency corresponding to the maximum value is smaller than the vibration frequency acquired by the maximum maximum value acquisition means. The non-destructive testing device for anchors also includes a slope acquisition means for performing a logarithmic simple regression analysis with the maximum value acquired by the maximum maximum value acquisition means and the maximum value picked up by the pick-up means as objective variables and the vibration frequency corresponding to these maximum values ​​as explanatory variables, and acquiring the coefficient of the explanatory variable obtained as a slope. The non-destructive testing device for anchors also includes a determination means for determining whether or not the anchor is in a deteriorated state based on two parameters, the vibration frequency acquired by the maximum maximum value acquisition means and the slope.

[0022] The nondestructive testing device determines whether or not the anchor is in a deteriorated state based on the magnitude of the vibration frequency corresponding to the maximum local maximum value in the frequency characteristics of the anchor and the slope of the logarithm of the frequency characteristics. Therefore, the nondestructive testing device does not require additional work for detecting the waveform of the reflected wave of the vibration with high accuracy, and can suppress deterioration of the workability in the nondestructive testing of the anchor. Effect of the Invention

[0023] According to the present disclosure, it is possible to provide a non-destructive inspection method and a non-destructive inspection device for an anchor, in which deterioration of workability in non-destructive inspection of an anchor is suppressed. [Brief description of the drawings]

[0024] [Figure 1] FIG. 1 is a schematic diagram showing a non-destructive inspection device according to an embodiment. [Diagram 2] FIG. 2 is an enlarged view of part II in FIG. [Diagram 3] 1 is a flow chart illustrating a series of steps performed in a method for non-destructive testing of an anchor according to one embodiment. [Figure 4] 13 is a graph showing the Fourier amplitude spectrum obtained by performing a discrete Fourier transform on the acceleration waveform when a sweep sound is applied to eight sets of control anchors. [Diagram 5] 1 is a graph showing a Fourier amplitude spectrum obtained by performing a discrete Fourier transform on an acceleration waveform when a sweep sound is applied to four sets of anchors in a cutting and worn state. [Figure 6] 1 is a scatter plot for showing the relationship between a vibration frequency corresponding to a peak in the frequency characteristics and the slope of the logarithm of the frequency characteristics in a region where the vibration frequency is smaller than this vibration frequency. [Figure 7] 7 is a graph showing a Fourier amplitude spectrum of the data plotted as point a in FIG. 6. [Figure 8]7 is a graph showing a Fourier amplitude spectrum of the data plotted as point b in FIG. 6. [Figure 9] FIG. 13 is an enlarged view of a main portion showing a modified example of the setting position of a sensor in a non-destructive inspection device. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0025] Hereinafter, embodiments of the present disclosure will be described with reference to the drawings.

[0026] First, the configuration of a non-destructive inspection device 10 according to one embodiment will be described with reference to Figures 1 and 2. As shown in Figure 1, this non-destructive inspection device 10 determines whether or not an anchor 90, a part of which (see embedded portion 90B in Figure 1) is embedded in foundation concrete 92, is in a deteriorated state without destroying the foundation concrete 92.

[0027] Here, the term "deteriorated state" refers to a state in which the bending stiffness of an object is reduced, regardless of the reason. In other words, the "deteriorated state" includes, for example, a state in which the bending stiffness of an object is reduced due to wear or spalling on the surface of the object. The "deteriorated state" also includes, for example, a state in which the bending stiffness of an object is reduced due to microscopic or macroscopic scale cracks that occur in the object. The "deteriorated state" also includes, for example, a state in which the bending stiffness of an object is reduced due to corrosion such as rust or salt damage. The "deteriorated state" also includes, for example, a state in which the bending stiffness of an object is reduced due to a combination of the above states. In this embodiment, the nondestructive inspection device 10 judges the above states as "deteriorated state" without distinguishing between them.

[0028] As shown in FIG. 1, the concrete foundation 92 is a structure that is poured into the ground 94 and supports a column base 93 provided thereon. In this embodiment, the column base 93 is a structure that is separate from the concrete foundation 92 and has a base plate 93A at its lower end. The column base 93 may be, for example, a column base for supporting a road illumination lamp or a column base for supporting a road information display device. Mortar 92A is filled between the upper surface of the concrete foundation 92 and the lower surface of the base plate 93A as a joint material. In the following, the mixed structure formed by combining the concrete foundation 92, the anchor 90, the mortar 92A, and the column base 93 is also referred to as a "mixed structure 93B."

[0029] The anchor 90 is a metal set anchor in which a plurality of anchor bolts 91 and a plurality of reinforcing bars 90A are combined in a cage shape. Each anchor bolt 91 is arranged with its threaded portion 91A facing upward and its head portion 91B facing downward. Each reinforcing bar 90A is horizontally stretched between the anchor bolts 91 to connect these anchor bolts 91. In this embodiment, each anchor bolt 91 is arranged with its vertical position aligned. Also, one reinforcing bar 90A is arranged at each of three positions vertically spaced apart on the head portion 91B of each anchor bolt 91.

[0030] The threaded portion 91A of each anchor bolt 91 protrudes upward from the upper surface of the foundation concrete 92 and penetrates the mortar 92A and the base plate 93A. That is, each threaded portion 91A corresponds to the "protruding portion" in this disclosure. In this embodiment, each anchor bolt 91 is fixed to the base plate 93A by a configuration in which nuts 91C and 91D screwed onto the threaded portion 91A sandwich the base plate 93A from both above and below. In the following, the portion of the threaded portion 91A that penetrates the mortar 92A is also referred to as the "root portion 91E."

[0031] Further, in the anchor 90, the portion below each screw portion 91A is an embedded portion 90B embedded in the foundation concrete 92. In other words, the anchor 90 is in a state in which the embedded portion 90B is embedded in the foundation concrete 92 and each screw portion 91A protrudes from the foundation concrete 92.

[0032] The nondestructive testing device 10 includes a vibration speaker 11, a sensor 12, and a computer 13. As shown in Fig. 2, the vibration speaker 11 applies uniaxial vibration 11B to an object (threaded portion 91A of an anchor bolt 91 in Fig. 2) with its contact plate 11A in contact with the object, thereby making the object emit a sound. In other words, the vibration speaker 11 corresponds to the "uniaxial vibrator" in this disclosure.

[0033] The vibration speaker 11 is connected to a computer 13 (see FIG. 1) and reproduces a sound specified by the computer 13. In this embodiment, the vibration speaker 11 reproduces a sweep sound in which the vibration frequency increases stepwise over time. In this case, the vibration speaker 11 repeatedly applies vibration 11B to the threaded portion 91A of the anchor 90 while changing the vibration frequency so that it increases stepwise. In other words, the vibration speaker 11 corresponds to the "vibrator" in this disclosure.

[0034] As shown in Fig. 2, the sensor 12 is a three-axis (X-axis, Y-axis, Z-axis) vibration sensor, and is set in a position in the threaded portion 91A of the anchor 90 where the threaded portion 91A is sandwiched together with the vibration speaker 11. The sensor 12 is installed so that its X-axis direction is the horizontal direction toward the vibration speaker 11 (left-right direction in Fig. 2), its Y-axis direction is the horizontal direction perpendicular to the X-axis direction (direction perpendicular to the paper surface in Fig. 2), and its Z-axis direction is the up-down direction (up-down direction in Fig. 2). In this embodiment, the sensor 12 is an accelerometer that measures the acceleration waveform of vibration on each of the three axes and outputs the measured values ​​to the computer 13 (see Fig. 1).

[0035] Here, the sensor 12 is set in a state where its side surface on the positive side in the X-axis direction (the right side in FIG. 2) is in contact with the screw portion 91A. The vibration speaker 11 is set in a position where the screw portion 91A of the anchor 90 is sandwiched between the sensor 12 and the vibration speaker 11, with the contact plate 11A in contact with the screw portion 91A. This causes the vibration speaker 11 and the sensor 12 to face each other. In this embodiment, the sensor 12 is set in a state where the X-axis 12A, which is one of the axes of measurement, coincides with the axis 11C of the vibration 11B generated by the vibration speaker 11.

[0036] The computer 13 is equipped with a touch panel 13B, which is a human-machine interface that inputs and outputs information to and from the outside, and a recording medium 13A that records various data and programs in a computer-readable format. This recording medium 13A records a file of the sweep sound reproduced by the vibration speaker 11. In other words, the recording medium 13A is a medium in which sound information referenced by the vibration speaker 11 when the vibration speaker 11 reproduces the sweep sound is fixed.

[0037] Furthermore, the recording medium 13A stores a program (hereinafter, simply referred to as a "program") for causing the computer 13 to function as each of the means described below. Each of these means causes the nondestructive testing device 10 to realize a function of executing a nondestructive testing method for an anchor, which determines whether or not the anchor 90 is in a deteriorated state without destroying the foundation concrete 92.

[0038] Here, a series of steps executed by the computer 13 by the program in the non-destructive testing method for anchors will be described with reference to the flowchart shown in Fig. 3. When the computer 13 is to execute each of the series of steps, an engineer executes step S10 in advance.

[0039] In step S10, the engineer sets up the nondestructive testing device 10 described above. The engineer also turns on the vibration speaker 11, the sensor 12, and the computer 13, and prepares the computer 13 so that when the program is started, each step of the program is executed smoothly. Then, the engineer starts the program. In response to this, the computer 13 first executes step S20.

[0040] In step S20, the computer 13 designates the file of the sweep sound recorded on the recording medium 13A, and starts reproduction of the sweep sound by the vibration speaker 11. Then, the computer 13 advances the process to step S30.

[0041] In response to this, the vibration speaker 11 refers to the information of the file specified by the computer 13 and plays the sweep sound for a predetermined time defined by this information. In this embodiment, the vibration speaker 11 plays the sweep sound while outputting to the computer 13 information on the sound currently being generated as the vibration 11B and information on the playback position in the playback of the sweep sound.

[0042] In step S30, the computer 13 repeatedly executes the process of step S40 described later. This repetition is executed until the reproduction of the sweep sound by the vibration speaker 11 ends. When the reproduction of the sweep sound by the vibration speaker 11 ends, the computer 13 stops the repeated process of step S30 and advances the process to step S50.

[0043] In this embodiment, the computer 13 determines, based on the information of the reproduction position output by the vibration speaker 11, whether or not the reproduction of the sweep sound by the vibration speaker 11 has ended.

[0044] In step S40, the computer 13 acquires information on the sound currently being generated by the vibration speaker 11 as the vibration 11B, and extracts the vibration frequency of the vibration 11B from this information. The computer 13 also acquires the measurement value of the sensor 12 at the current time, and extracts the vibration frequency of the vibration measured by the sensor 12 from this measurement value. The computer 13 then compares the vibration frequency of the vibration 11B with the vibration frequency of the vibration measured by the sensor 12 to derive the frequency response of the anchor 90. In other words, the computer 13 derives the frequency response of the anchor 90 when the vibration 11B of a predetermined vibration frequency is applied based on the measurement value of the sensor 12 set on the threaded portion 91A of the anchor 90. That is, step S40 corresponds to the "frequency response derivation step" in this disclosure. The computer 13 executing step S40 corresponds to the "frequency response derivation means" in this disclosure.

[0045] Here, the vibration 11B generated by the vibration speaker 11 is a sweep sound vibration whose vibration frequency increases stepwise over time. Therefore, in the repeated processing of step S30, step S40 (frequency response derivation step) is repeatedly executed while changing the vibration frequency of the vibration 11B. Here, a set of frequency responses derived for each different vibration frequency is the frequency characteristic itself. Therefore, in the repeated processing of step S30, the frequency characteristic of the anchor 90 is derived. That is, the repeated processing of step S30 corresponds to the "frequency characteristic derivation step" in this disclosure. In addition, the computer 13 executing the repeated processing of step S30 can be said to be a frequency characteristic derivation means that derives the frequency characteristic of the anchor 90 by associating the vibration frequency of the vibration 11B applied by the vibration speaker 11 with the frequency response derived by the computer 13 executing step S40 (frequency response derivation means).

[0046] In step S50, the computer 13 analyzes the frequency characteristics of the anchor 90 derived in the repeated process of step S30 executed immediately before, and acquires the maximum local maximum value in the frequency characteristics (hereinafter also referred to as the "maximum local maximum value") and the vibration frequency corresponding to this maximum local maximum value. Then, the computer 13 advances the process to step S60. Here, step S50 corresponds to the "maximum local maximum value acquisition step" in this disclosure. Moreover, the computer 13 executing step S50 corresponds to the "maximum local maximum value acquisition means" in this disclosure.

[0047] In step S60, the computer 13 picks up all maximum values ​​(hereinafter also referred to as "pickup maximum values") that satisfy a predetermined pick-up condition among the maximum values ​​in the frequency characteristics analyzed in the immediately preceding step S50. Specifically, this pick-up condition is that "the vibration frequency corresponding to the maximum value is smaller than the vibration frequency corresponding to the maximum maximum value acquired in step S50 (maximum maximum value acquisition step)." Then, the computer 13 advances the process to step S70. Here, step S60 corresponds to the "pick-up step" in this disclosure. Moreover, the computer 13 executing step S60 corresponds to the "pick-up means" in this disclosure.

[0048] In step S70, computer 13 performs a logarithmic simple regression analysis using each of the maximum maximum value and the pickup maximum value as a response variable and the vibration frequency corresponding to these maximum values ​​as an explanatory variable. Computer 13 also obtains the coefficient of the explanatory variable obtained in the logarithmic simple regression analysis as a slope. Computer 13 then advances the process to step S80. Here, step S70 corresponds to the "slope acquisition step" in this disclosure. Moreover, computer 13 executing step S70 corresponds to the "slope acquisition means" in this disclosure.

[0049] In this embodiment, a logarithm having a base greater than 1 is used as the logarithm when performing the logarithmic simple regression analysis in the gradient acquisition step. In addition, since the maximum maximum value is the maximum maximum value in the frequency characteristics of the anchor 90, the pickup maximum value always has a value smaller than the maximum maximum value. Therefore, the gradient acquired in the gradient acquisition step of this embodiment always has a positive value.

[0050] In step S80, the computer 13 performs a first determination to determine whether or not the vibration frequency corresponding to the maximum local maximum value is large in light of a first criterion. The computer 13 also performs a second determination to determine whether or not the absolute value of the slope is large in light of a second criterion. Here, the first criterion and the second criterion are predetermined criteria that are set separately. In this embodiment, a constant reference value is used for each of the first criterion and the second criterion.

[0051] As described above, the inclination acquired in the inclination acquisition step of this embodiment is always a positive value. Therefore, the condition "the absolute value of the inclination is large in light of the second criterion" is equivalent to the condition "the inclination is large in light of the second criterion." Therefore, the second determination may be replaced with "processing for determining whether or not the inclination is large in light of the second criterion."

[0052] If the determination result of the first determination and the determination result of the second determination are both "large" (or if a condition equivalent thereto is established), the computer 13 determines that the anchor 90 is in a deteriorated state. If at least one of the determination results of the first determination and the determination result of the second determination is "not large," the computer 13 determines that the anchor 90 is not in a deteriorated state.

[0053] After determining whether the anchor 90 is in a deteriorated state, the computer 13 advances the process to step S90. Here, step S80 is a step of determining whether the anchor 90 is in a deteriorated state based on two parameters, the vibration frequency corresponding to the maximum local maximum value and the slope, and corresponds to the "determination step" in the present disclosure. Moreover, the computer 13 executing step S80 corresponds to the "determination means" in the present disclosure.

[0054] In step S90, the computer 13 outputs the result of the determination of whether or not the anchor 90 is in a deteriorated state, which was performed in the immediately preceding step S80, to the touch panel 13B. Then, the computer 13 ends a series of processes by the program.

[0055] According to the above-mentioned non-destructive testing method for an anchor (hereinafter also simply referred to as the "method"), it is determined whether or not the anchor 90 is in a deteriorated state from the magnitude of the vibration frequency corresponding to the maximum local maximum value in the frequency characteristics of the anchor 90 and the slope of the logarithm of the frequency characteristics. Therefore, according to the method, it is possible to eliminate the need for additional work for detecting the waveform of the reflected wave of the vibration with high accuracy, and to suppress deterioration of the workability in the non-destructive testing of the anchor 90.

[0056] Furthermore, according to the method, the judgment in the judging step can be a simple process that combines two judgments based on simple conditions (that is, a first judgment and a second judgment).

[0057] According to the method, the frequency characteristic derivation step can be executed by repeatedly performing measurements by the sensor 12 while applying the sweep sound from the vibration speaker 11 to the anchor 90, and deriving the frequency characteristic based on each measurement value. This improves the workability when carrying out the method. Furthermore, since the vibration speaker 11 generates the sweep sound by playback, it is possible to generate the same sweep sound every time. This makes it possible to uniform the application conditions of the vibration 11B to the anchor 90 and suppress the influence of differences in the application conditions on the test results.

[0058] Furthermore, according to the method, the vibration 11B generated by the vibration speaker 11 reaches the sensor 12 without being deflected from the axial direction of its axis 11C. Furthermore, the sensor 12 can measure the vibration 11B generated by the vibration speaker 11 only by the measurement X-axis 12A that is aligned with the axis 11C of the vibration 11B. This makes it possible to suppress the influence of vibration noise acting from a direction different from that of the vibration 11B generated by the vibration speaker 11 on the test results.

[0059] Incidentally, in the anchor 90, the threaded portion 91A protruding from the foundation concrete 92 is more susceptible to vibration than the buried portion 90B buried in the foundation concrete 92. Here, according to the method, the vibration 11B generated by the vibration speaker 11 acts directly on the threaded portion 91A of the anchor 90. Also, the vibration resulting from the vibration 11B generated by the vibration speaker 11 acting on the anchor 90 is directly input to the sensor 12 that sandwiches the threaded portion 91A together with the vibration speaker 11. This increases the magnitude of the vibration input to the sensor 12, improving the signal-to-noise ratio.

[0060] In addition, in the method, an accelerometer that measures the acceleration waveform of vibration is used as sensor 12. Here, since the accelerometer captures the "force acting on the object when vibration is applied," there is little time lag between the timing of application of vibration 11B and the timing of measurement by sensor 12. This is in contrast to a displacement meter that captures the "result of the object moving due to application of vibration," in which a time lag occurs between the timing of application of vibration and the timing of measurement by the sensor. Therefore, according to the method, the effect of the time lag between the timing of application of vibration 11B and the timing of measurement by sensor 12 on the inspection result can be suppressed.

[0061] Moreover, the above-mentioned nondestructive testing device 10 judges whether or not the anchor 90 is in a deteriorated state from the magnitude of the vibration frequency corresponding to the maximum local maximum value in the frequency characteristics of the anchor 90 and the slope of the logarithm of the frequency characteristics. Therefore, the nondestructive testing device 10 makes it possible to eliminate the need for additional work for detecting the waveform of the reflected wave of the vibration with high accuracy, and to suppress deterioration of the workability in the nondestructive testing of the anchor 90.

[0062] Now, the present inventor has come to the present disclosure by discovering that "the difference between a normal anchor and an anchor in a deteriorated state is manifested in that the vibration frequency corresponding to the maximum local maximum value (peak) in the frequency characteristics of the anchor is large, and the slope of the logarithm of the frequency characteristics in the region where the vibration frequency is smaller than this vibration frequency is large." This knowledge is a new knowledge that the present inventor discovered through various researches. Below, one of the studies that led the present inventor to discover the above knowledge will be explained mainly with reference to Figs. 4 to 8.

[0063] The present inventor prepared 12 sets of paired anchors having the same configuration as the above-mentioned anchor 90 (see FIG. 1), and randomly divided these paired anchors into 8 sets of "paired anchors A" and 4 sets of "paired anchors B." The present inventor also cut the threads of the root part of the threaded part (corresponding to the root part 91E of anchor 90), which is the protruding part, of each paired anchor B, to cause the threads to be cut and worn. The present inventor did not perform any treatment on each paired anchor A, in order to use them as controls.

[0064] Next, the present disclosure created eight mixed structures (hereinafter also referred to as "mixed structure A") having a configuration similar to the above-mentioned mixed structure 93B (see FIG. 1) by using each of the eight sets of paired anchors A. Similarly, the present disclosure created four mixed structures (hereinafter also referred to as "mixed structure B") having a configuration similar to the mixed structure 93B by using each of the four sets of paired anchors B.

[0065] Next, the present inventor set up device A having a configuration similar to the above-mentioned non-destructive inspection device 10 (see FIG. 1) for each of the eight mixed structures A, and applied a sweep sound from its vibration speaker to the protruding portion of the pair of anchors A. Then, the present inventor derived a Fourier amplitude spectrum (see FIG. 4) of each measurement value by performing a discrete Fourier transform on the measurement values ​​(acceleration waveforms) of each axis of the sensor of device A. This Fourier amplitude spectrum is a parameter corresponding to the frequency characteristics of the pair of anchors A.

[0066] Similarly, the present inventor set up a device B having a similar configuration to the non-destructive inspection device 10 for each of the four mixed structures B, and applied a sweep sound from its vibration speaker to the protruding portion of the set anchor B. The present inventor then performed a discrete Fourier transform on the measured values ​​(acceleration waveforms) of each axis in the sensor of the device B to derive the Fourier amplitude spectrum (see FIG. 5) of each measured value. This Fourier amplitude spectrum is a parameter corresponding to the frequency characteristics of the set anchor B.

[0067] The graphs in Figures 4 and 5 are compared. In the Fourier amplitude spectrum (see Figure 4) corresponding to the frequency characteristics of paired anchor A, the vibration frequencies corresponding to the maximum maximum values ​​(peaks) are scattered over a relatively wide range of about 1500 [Hz] to 5000 [Hz]. Also, in the Fourier amplitude spectrum of paired anchor A, there is a tendency for the value (amplitude) to increase as the vibration frequency decreases.

[0068] On the other hand, in the Fourier amplitude spectrum (see FIG. 5) corresponding to the frequency characteristics of group anchor B, the vibration frequencies corresponding to the maximum maximal values ​​(peaks) are concentrated in a relatively narrow range of about 3000 [Hz] to 4000 [Hz]. Also, in the Fourier amplitude spectrum of group anchor B, in the region where the vibration frequency is lower than the peaks, there is a tendency that the value (amplitude) of the Fourier amplitude spectrum becomes smaller as the vibration frequency becomes smaller.

[0069] From this, the present inventor focused on two parameters: "the vibration frequency corresponding to the peak in the frequency characteristics (hereinafter also referred to as the "peak vibration frequency")" and "the logarithmic slope of the frequency characteristics in a region where the vibration frequency is smaller than the peak vibration frequency (hereinafter also simply referred to as the "slope")".

[0070] Therefore, the present inventor plotted a logarithmic graph 95 (see FIG. 7) of the Fourier amplitude spectrum (see FIG. 4) of each measured value corresponding to the frequency characteristic of the set anchor A. The present inventor also picked up a peak 95A and a peak vibration frequency 95B in the graph 95, as well as a maximum value 95D in a region 95C where the vibration frequency is lower than the peak vibration frequency 95B. The present inventor then determined a regression line 95E of the peak 95A and each maximum value 95D from each of the picked up data, and plotted the slope and the peak vibration frequency 95B on a scatter diagram (see FIG. 6). This plot is displayed as "control" in FIG. 6.

[0071] Similarly, the present inventor plotted a logarithmic graph 96 (see FIG. 8) of the Fourier amplitude spectrum (see FIG. 5) of each measured value corresponding to the frequency characteristic of the set anchor B. The present inventor also picked up a peak 96A and a peak vibration frequency 96B in the graph 96, as well as a maximum value 96D in a region 96C where the vibration frequency is lower than the peak vibration frequency 96B. The present inventor then determined a regression line 96E of the peak 96A and each maximum value 96D from each of the picked up data, and plotted the slope and the peak vibration frequency 96B on the same scatter diagram (see FIG. 6) as above. This plot is displayed as "Cutting Wear" in FIG. 6.

[0072] Consider Figure 6. Focusing only on the "peak vibration frequency," the peak vibration frequencies of "cutting wear" are concentrated in a relatively narrow range of about 3000 [Hz] to 4000 [Hz]. In contrast, the peak vibration frequencies of "control" are scattered in a relatively wide range of about 1500 [Hz] to 5000 [Hz]. This means that if you focus only on the "peak vibration frequency," you cannot distinguish between "cutting wear" and "control."

[0073] On the other hand, when focusing on both the "peak vibration frequency" and the "slope", the "cutting wear" exists only in the range where the peak vibration frequency is about 3000 [Hz] to 4000 [Hz] and the slope is greater than 0.007. In contrast, when the peak vibration frequency is greater than 3000 [Hz], the "control" exists only in the range where the slope is less than 0.007. However, when the peak vibration frequency is less than 2500 [Hz], the slope of the "control" varies in a relatively wide range of 0 to 0.05. This means that when focusing on both the "peak vibration frequency" and the "slope", it is possible to distinguish between the "cutting wear" and the "control".

[0074] The above describes the embodiment of the present disclosure. However, it is clear to those skilled in the art that various substitutions, modifications, and changes are possible without departing from the purpose of the present disclosure. In other words, the embodiment of the present disclosure may include all substitutions, modifications, and changes that do not deviate from the spirit and purpose of the claims attached to this specification. For example, the following various embodiments can be implemented as the embodiment of the present disclosure.

[0075] (1) In the present disclosure, the "anchor" to be determined whether it is in a deteriorated state is not limited to an anchor 90 (assembly anchor) in which a plurality of anchor bolts 91 are combined, and can be changed as appropriate. That is, the present disclosure may be for determining whether an assembly anchor in which an anchor bar is combined in addition to an anchor bolt (or instead of an anchor bolt) is in a deteriorated state. The present disclosure may also be for determining whether an anchor bolt or an anchor bar used alone is in a deteriorated state. The present disclosure may also be for determining whether a tendon used in a ground anchor construction method or a rock bolt used in a rebar insertion reinforcement earth construction method is in a deteriorated state. The present disclosure may also be for determining whether a foundation pile used in a pile foundation is in a deteriorated state. In this case, the foundation pile may be made of, for example, metal or concrete.

[0076] (2) In the present disclosure, the aspect of the sensor set is not limited to the aspect described in the above-mentioned embodiment. That is, in the present disclosure, for example, a method can be adopted in which the measurement axis of a three-axis sensor is shifted from the axis of vibration by a vibration speaker, and the measurement values ​​of the three axes of the sensor are analyzed to obtain the measurement values ​​of the vibration by the vibration speaker.

[0077] In the above method, it is preferable to execute the frequency response deriving step in a state where a sensor is set at the tip of the protruding portion of the anchor that protrudes from the structure (see sensor 12 set at the tip of threaded portion 91A of anchor 90 in FIG. 9). That is, in an anchor, the protruding portion that protrudes from the structure is more likely to vibrate than the embedded portion that is embedded in the structure. This tendency is most noticeable at the tip of the protruding portion. Here, in the above case, the sensor measures the vibration at the tip of the protruding portion where the vibration acting on the anchor is the largest. This makes it possible to provide a nondestructive inspection method for an anchor in which the magnitude of the vibration input to the sensor is increased and the signal-to-noise ratio is improved.

[0078] (3) In the present disclosure, the mode of application of vibration to the anchor is not limited to the mode of applying a sweep sound whose vibration frequency increases stepwise over time to the anchor by a vibration speaker. That is, the vibration applied to the anchor by the vibration speaker may be, for example, a sweep sound whose vibration frequency decreases stepwise over time, or a sound whose vibration frequency increases or decreases over time. In addition, the vibration applied to the anchor may be, for example, vibration caused by hitting with a hammer. In this case, the position of the hit by the hammer may be changed as appropriate.

[0079] (4) In the present disclosure, the sensor set on the protruding portion of the anchor is not limited to a three-axis (X-axis, Y-axis, Z-axis) accelerometer. That is, the sensor used in the present disclosure may be a displacement meter that measures the displacement waveform of vibration or a speed meter that measures the speed waveform of vibration. Here, since the speed meter captures the "movement of the object due to the application of vibration", a time difference is unlikely to occur between the timing of the application of vibration and the timing of the measurement by the sensor. This is in contrast to a displacement meter that captures the "result of the movement of the object due to the application of vibration", in which a time difference occurs between the timing of the application of vibration and the timing of the measurement by the sensor. Therefore, according to the method of adopting a speed meter as a sensor, the influence of the time difference between the timing of the application of vibration and the timing of the measurement by the sensor on the inspection result can be suppressed. In addition, the sensor used in the present disclosure may be, for example, a one-axis or two-axis vibration sensor.

[0080] (5) In the embodiment described above, a logarithm with a base greater than 1 is used as the logarithm when performing the logarithmic simple regression analysis in the slope acquisition step. However, the base of the logarithm when performing the logarithmic simple regression analysis in the slope acquisition step may be a positive number smaller than 1. In this case, the positive and negative signs of the slope acquired in the slope acquisition step will be reversed, but in the determination step, the "absolute value of the slope" is compared with the second criterion, so that a determination similar to that in the embodiment described above can be made.

[0081] (6) In the present disclosure, the judgment step is not limited to a combination of the first judgment and the second judgment described above. For example, a case can be considered in which there is a large amount of sample data for anchors of the same type as the anchor to be judged, in which the magnitude of the vibration frequency corresponding to the maximum local maximum value in the frequency characteristics and the slope in the logarithm of the frequency characteristics are associated with information on whether the anchor is in a degraded state. When these sample data include sample data of anchors in a degraded state and sample data of normal anchors, the judgment step can be a hypothesis testing process that examines whether the null hypothesis that "the anchor to be judged is not in a degraded state" can be rejected. [Explanation of symbols]

[0082] 10. Non-destructive testing equipment 11 Vibration speaker (single-axis vibrator, vibrator) 11A contact plate 11B Vibration 11C axis 12 Sensors (vibration sensors, accelerometers) 12A X-axis (axis) 13 Computer (frequency response deriving means, frequency characteristic deriving means, maximum maximum value acquiring means, pickup means, tilt acquiring means, judgment means) 13A Recording media 13B Touch Panel 90 Anchor 90A Steel Bar 90B Buried part 91 Anchor bolt 91A Threaded part (protruding part) 91B Head 91C Nut 91D Nut 91E Base part 92 Foundation concrete (structure) 92A Mortar 93 Pillar base 93A Base Plate 93B Mixed structure 94 Ground 95 Graphs 95A peak 95B Peak Vibration Frequency 95C area 95D Maximum 95E Regression Line 96 Graphs 96A Peak 96B Peak vibration frequency 96C area 96D Maximum 96E Regression Line

Claims

1. A non-destructive inspection method for an anchor, the method comprising the steps of: determining whether or not an anchor, the embedded portion of which is embedded in a structure and the protruding portion of which protrudes from the structure, is in a deteriorated state without destroying the structure, the method comprising the steps of: a frequency response deriving step of deriving a frequency response of the anchor when vibration of a predetermined vibration frequency is applied based on a measurement value of a sensor set on the protruding portion of the anchor; a frequency characteristic deriving step of deriving a frequency characteristic of the anchor by repeatedly executing the frequency response deriving step while changing a vibration frequency of the vibration; a maximum maximum value acquisition step of acquiring a maximum maximum value in the frequency characteristics and a vibration frequency corresponding to the maximum maximum value; a picking step of picking out a maximum value from among the maximum values ​​in the frequency characteristic, the maximum value satisfying a condition that a vibration frequency corresponding to the maximum value is smaller than the vibration frequency acquired in the maximum maximum value acquisition step; a slope acquisition step of performing a logarithmic simple regression analysis using the maximum value acquired in the maximum maximum value acquisition step and the maximum value picked up in the picking step as objective variables and vibration frequencies corresponding to these maximum values ​​as explanatory variables, and acquiring the coefficient of the explanatory variable obtained as a slope; and, a determining step of determining whether or not the anchor is in the deteriorated state based on two parameters, that is, the vibration frequency acquired in the maximum maximum value acquiring step and the slope; It has Non-destructive testing methods for anchors.

2. A non-destructive inspection method for an anchor according to claim 1, comprising: a process of determining that the anchor is in the deteriorated state when a condition is satisfied in the determination step that is equivalent to the vibration frequency acquired in the maximum maximum value acquisition step being large in light of a first criterion, which is a predetermined criterion, and the absolute value of the slope being large in light of a second criterion, which is a criterion set separately from the first criterion. Non-destructive testing methods for anchors.

3. A non-destructive inspection method for the anchor according to claim 1 or 2, comprising: A vibration speaker that reproduces a sweep sound is used as the means for applying the vibration. Non-destructive testing methods for anchors.

4. A non-destructive inspection method for the anchor according to claim 1 or 2, comprising: As a means for applying the vibration, a one-axis vibration exciter that generates the vibration on one axis is used, As the sensor, a vibration sensor having one or more axes for measuring the vibration is used, The frequency response deriving step is performed in a state where the one-axis vibration exciter and the vibration sensor are opposed to each other and one of the measurement axes of the vibration sensor is aligned with the axis of the vibration generated by the one-axis vibration exciter. Non-destructive testing methods for anchors.

5. A non-destructive inspection method for the anchor according to claim 1 or 2, comprising: The frequency response deriving step is performed in a state where the sensor is set at a tip of the protruding portion protruding from the structure. Non-destructive testing methods for anchors.

6. A non-destructive inspection method for the anchor according to claim 1 or 2, comprising: As the sensor, an accelerometer that measures an acceleration waveform of the vibration or a speedometer that measures a velocity waveform of the vibration is used. Non-destructive testing methods for anchors.

7. A non-destructive inspection device for an anchor, which determines whether or not an anchor having an embedded portion embedded in a structure and a protruding portion protruding from the structure is in a deteriorated state without destroying the structure, comprising: a vibration exciter that repeatedly applies vibration to the anchor while changing a vibration frequency of the vibration; a sensor set on the protruding portion of the anchor; a frequency response deriving means for deriving a frequency response of the anchor when the vibration is applied based on a measurement value of the sensor; a frequency characteristic deriving means for deriving a frequency characteristic of the anchor by associating a vibration frequency of the vibration applied by the vibration exciter with the frequency response derived by the frequency response deriving means; A maximum maximum value acquiring means for acquiring a maximum maximum value in the frequency characteristic and a vibration frequency corresponding to the maximum maximum value; a pick-up means for picking out a maximum value from among the maximum values ​​in the frequency characteristic, the maximum value satisfying a condition that a vibration frequency corresponding to the maximum value is smaller than the vibration frequency acquired by the maximum maximum value acquisition means; a slope acquisition means for performing a logarithmic simple regression analysis using the maximum value acquired by the maximum maximum value acquisition means and the maximum value picked up by the pickup means as objective variables and vibration frequencies corresponding to these maximum values ​​as explanatory variables, and acquiring the coefficient of the explanatory variable as a slope; a determination means for determining whether or not the anchor is in the deteriorated state based on two parameters, that is, the vibration frequency and the slope, acquired by the maximum maximum value acquisition means; Equipped with Non-destructive testing equipment for anchors.

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