Method for hammering test, hammering test apparatus, and hammering test vessel

Abstract

To improve the accuracy of a hammering test.SOLUTION: A hammering test method (M10) includes: a striking step (S11) of applying an impact to a structure; a conversion step (S13) of obtaining a spectrum representing the frequency dependence of an amplitude by performing Fourier transformation on a hammering sound; and an evaluation step (S14) of evaluating the soundness of the structure by comparing average values or integral values of amplitudes in a low-frequency region and a high-frequency region which are separated by a first frequency.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a hammering inspection method, a hammering inspection device, and a hammering inspection ship. [Background technology]

[0002] Patent Document 1 describes a technique for conducting a hammering test on the surface of a target concrete section to evaluate the presence or absence of cavities inside the target concrete section. The technique described in Patent Document 1 involves applying an impact to the target concrete section using a flying object, and acquiring hammering data representing the hammering sounds generated by the impact. Then, if the hammering data has a peak at a specific frequency, it is determined that a cavity is present (see paragraph 0037 of Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2019-174131 Summary of the Invention [Problem to be solved by the invention]

[0004] However, when the inventors of the present application conducted hammering tests, they found that peaks sometimes appeared in the hammering data even when there were no cavities inside the concrete. Furthermore, when they obtained multiple hammering data from test locations that contained cavities inside the concrete, they found that the peak positions varied and it was sometimes difficult to identify a clear peak.

[0005] As described above, there is room for improving the inspection accuracy of the hammering inspection method described in Patent Document 1. This tendency is particularly noticeable when the inspection targets are not models used in simulations or test specimens, but buildings used in real society.

[0006] One aspect of the present invention has been made in consideration of the above-mentioned problems, and an object of the present invention is to improve the inspection accuracy in hammering inspection. [Means for solving the problem]

[0007] In order to solve the above-mentioned problems, a hammering inspection method according to one embodiment of the present invention includes: a hammering step of applying a hammering force to a structure; a transformation step of obtaining a spectrum whose amplitude is frequency-dependent by Fourier transforming the hammering sounds generated by the hammering step; and an evaluation step of evaluating the soundness of the structure by comparing the average values ​​or integral values ​​of the amplitudes in two regions included in the spectrum, the two regions separated by a predetermined first frequency, which are defined as a low-frequency region and a high-frequency region.

[0008] In order to solve the above problems, a hammering inspection device according to another aspect of the present invention includes: a hammering unit that applies a hammering force to a structure; a sound collection unit that acquires hammering sounds generated by applying a hammering force to the structure; a conversion unit that obtains a spectrum in which the amplitude is frequency-dependent by performing a Fourier transform on the hammering sounds; and an evaluation unit that evaluates the soundness of the structure by comparing the average value or integral value of the amplitude in each of the low-frequency region and the high-frequency region, which are two regions included in the spectrum and have a predetermined first frequency as their boundary.

[0009] In order to solve the above problems, a hammering inspection vessel according to yet another embodiment of the present invention comprises a hammering unit that strikes a structure, a sound collection unit that acquires the hammering sounds generated by striking the structure, a conversion unit that obtains a spectrum in which the amplitude is frequency dependent by performing a Fourier transform on the hammering sounds, and an evaluation unit that evaluates the soundness of the structure by comparing the average value or integral value of the amplitude in each of two regions included in the spectrum, the two regions having a predetermined first frequency as a low frequency region and a high frequency region. [Effects of the Invention]

[0010] According to one aspect of the present invention, it is possible to improve the inspection accuracy in hammering inspection. [Brief explanation of the drawings]

[0011] [Figure 1] 1 is a flowchart of a hammering test method according to a first embodiment of the present invention. [Figure 2] 2 is a graph showing sounds including hammering sounds obtained by the sound collection process shown in Fig. 1. The upper graph shows sounds obtained from a test specimen that does not have a cavity near the test target location, and the lower graph shows sounds obtained from a test specimen that does have a cavity near the test target location. [Figure 3] 1 is a graph showing the spectrum of hammering sounds obtained as a result of performing the hammering inspection method according to the first embodiment of the present invention on the surveyed locations 1 to 4 and the test piece 1. [Figure 4] 1 is a graph showing the spectrum of hammering sounds obtained as a result of performing the hammering inspection method according to the first embodiment of the present invention on survey points 5 to 8. [Figure 5] 1 is a graph showing spectra of hammering sounds obtained as a result of performing the hammering inspection method according to the first embodiment of the present invention on test specimens 2 to 5. [Figure 6] 1 is a graph showing evaluation indexes obtained as a result of performing the hammering test method according to the first embodiment of the present invention on the inspection target locations 1 to 8 and the test specimens 1 to 5. [Figure 7] 1 is a graph showing the natural frequencies of test specimens 2 to 5, which were subjected to the hammering test method according to embodiment 1 of the present invention. The plots of circles represent values ​​obtained by FEM analysis, and the plots of triangles represent experimental values ​​obtained from test specimens 2 to 5. [Figure 8] 1 shows plan views (top) and cross-sectional views (bottom) of specimens 2 to 5, which are specimens 2 to 5 that were subjected to the hammering inspection method according to embodiment 1 of the present invention and include cavities. The plan view and cross-sectional view on the left show specimens 2 and 3, which include cavities that are square with sides measuring 200 mm in plan view, and the plan view and cross-sectional view on the right show specimens 4 and 5, which include cavities that are square with sides measuring 500 mm in plan view. [Figure 9] FIG. 10 is a block diagram of a hammering inspection device according to a second embodiment of the present invention. [Figure 10] FIG. 10 is a schematic diagram of a hammering inspection vessel according to a third embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0012] [Embodiment 1] <Hit sound inspection method> A hammering inspection method M10 according to a first embodiment of the present invention will be described with reference to FIG. 1. FIG. 1 is a flowchart of the hammering inspection method M10. The hammering inspection method M10 is a technique for evaluating the presence or absence of defects inside an inspection target portion of a building by performing a hammering inspection on the surface of the inspection target portion. It is preferable that the surface of the building to be inspected by the hammering inspection method M10 is covered with concrete. Examples of such buildings include piers, bridges, retaining walls, and buildings such as buildings and apartment buildings. In this embodiment, the hammering inspection method M10 will be described using a pier as an example of a building.

[0013] As shown in FIG. 1, the hammering inspection method M10 includes a hammering step S11, a sound collection step S12, a conversion step S13, and an evaluation step S14.

[0014] (Impact process) The impact step S11 is a step of impacting the structure. In this embodiment, an object having a certain weight is launched toward the pier from a location away from the structure (i.e., a remote location), and the launched object is caused to collide with the structure, thereby impacting the structure. The kinetic energy of the object impacting the structure depends on the mass and velocity of the object. Therefore, by appropriately determining the mass and velocity, it is possible to control the magnitude of the impact applied to the structure by the object. Note that in this embodiment 1, the impact testing method M10 will be described hereinafter using a pier as the structure.

[0015] In this embodiment, the object to be shot toward the pier is a spherical metal (steel in this embodiment) member with a diameter of 25 mm and a weight of 60 g. However, the size of the object, represented by its diameter, the weight of the object, and the material from which the object is made are not limited to these and can be determined as appropriate.

[0016] (Sound collection process) The sound collection step S12 is a step of collecting impact sounds generated by carrying out the impact step S11, that is, impact sounds generated when the object hits the pier, and converting the collected impact sounds into audio signals, which are electrical signals representing sounds including the impact sounds. The sound collection step S12 can be performed by, for example, a microphone. Note that, although details will be described later in the examples, an example of sounds including impact sounds is shown in FIG. 2. Note that the timing and period for recording the sounds by the microphone are determined so that at least the impact sounds are included.

[0017] (Conversion process) The conversion step S13 is a step of obtaining a spectrum, which is a frequency-dependent amplitude, by Fourier transforming the hitting sounds generated in the hitting step S11. This spectrum is also called a frequency spectrum. Note that, although details will be described later, examples of the spectrum obtained by the Fourier transform in the conversion step S13 are shown in Figs. 3 and 4.

[0018] (Evaluation process) In the evaluation step S14, the two regions included in the spectrum, which are separated by a predetermined first frequency f1, are defined as the low frequency region RL and the high frequency region RH, and the soundness of the pier (whether or not it contains any defective areas) is evaluated by comparing the average or integral values ​​of the amplitude in each of the low frequency region RL and the high frequency region RH. In this embodiment, μL / μH, which is the ratio of the average value μL of the amplitude in the low-frequency region RL to the average value μH of the amplitude in the high-frequency region RH, is used as an evaluation index. More specifically, whether or not the pier contains a defective part is evaluated according to the magnitude relationship between the evaluation index μL / μH and a predetermined threshold value th. For example, 1 can be cited as an example of the threshold value th. When μL / μH≤th, it is determined that no defective part is included, and when th<μL / μH, it is determined that a defective part is included.

[0019] Note that since there are also minute defective parts that cannot be judged as to whether there is floating by the tapping sound in the tapping sound inspection by a person, in the evaluation step S14, when μL / μH<th, it is determined that no defective part is included, and in order to ensure more soundness, it can also be configured to determine that a defective part is included when th≤μL / μH.

[0020] Also, IL / IH, which is the ratio of the integrated value IL of the amplitude in the low-frequency region RL to the integrated value IH of the amplitude in the high-frequency region RH, may be used as an evaluation index.

[0021] Also, in this embodiment, 5 kHz is adopted as the first frequency f1. However, the first frequency f1 is not limited to 5 kHz, and can be appropriately set according to the structure of the building (for example, the thickness of the building) to be the target of the tapping sound inspection method M10. When setting the first frequency f1, a method of performing the striking step S11 to the conversion step S13 of the tapping sound inspection method M10 on a building for which the presence or absence of defective parts such as cavities and floating is known in advance, and obtaining the spectra for each case where a defective part is included and where a defective part is not included is conceivable. By comparing a group of spectra obtained from a building containing a defective part with a group of spectra obtained from a building not containing a defective part, a preferable first frequency f1 for determining the presence or absence of a defective part according to the structure of the target building can be set.

[0022] Note that the upper limit value of the high-frequency region RH can be determined as appropriate. In this embodiment, the upper limit value of the high-frequency region RH is 10 kHz.

[0023] In one aspect of the hammering test method M10, a frequency lower than the first frequency f1 is defined as the second frequency f2, and the lower and upper limits of the low-frequency region RL are preferably defined by the second frequency f2 and the first frequency f1, respectively. In other words, the lower limit of the low-frequency region RL is preferably defined by the second frequency f2, and the upper limit of the low-frequency region RL is preferably defined by the first frequency f1. In this embodiment, 1 kHz is used as the second frequency f2. However, the second frequency f2 is not limited to 1 kHz and can be set appropriately depending on the structure of the building to be subjected to the hammering test method M10.

[0024] [Example] An embodiment of the hammering inspection method M10 shown in FIG. 1 will be described with reference to FIGS.

[0025] Fig. 2 is a graph showing sounds including hammering sounds obtained by the sound collection step S12 shown in Fig. 1. The upper graph in Fig. 2 shows the sound obtained from test piece 1, which does not have a cavity near the location to be inspected, and the lower graph in Fig. 2 shows the sound obtained from test piece 3, which has a cavity near the location to be inspected.

[0026] FIG. 3 is a graph showing the spectrum of hammering sounds obtained as a result of applying hammering test method M10 to surveyed locations 1 to 4 of the pier and test piece 1.

[0027] FIG. 4 is a graph showing the spectrum of hammering sounds obtained as a result of carrying out hammering test method M10 at survey points 5 to 8 on the pier.

[0028] FIG. 5 is a graph showing the spectrum of hammering sounds obtained as a result of applying hammering test method M10 to pier specimens 2 to 5.

[0029] FIG. 6 is a graph showing the evaluation index μL / μH obtained as a result of performing hammering test method M10 on survey locations 1 to 8 and test specimens 1 to 5.

[0030] 7 is a graph showing the natural frequencies of specimens 2 to 5, which were subjected to hammering test method M10. The plots of circles represent the natural frequencies obtained by FEM analysis, and the plots of triangles represent the natural frequencies obtained from specimens 2 to 5.

[0031] Figure 8 shows plan views (top) and cross-sectional views (bottom) of specimens 2 to 5, which were subjected to hammering test method M10 and include a cavity C. The plan view and cross-sectional view on the left side of Figure 8 show specimens 2 and 3, which include a square cavity C with a side length of 200 mm in plan view. The plan view and cross-sectional view on the right side of Figure 8 show specimens 4 and 5, which include a square cavity C with a side length of 500 mm in plan view.

[0032] In this example, a pier built for testing hammering inspection method M10, with its surface covered with concrete, was used as the structure to be investigated. This pier had floats, which are a type of defect, installed at predetermined positions. On this pier, the areas without floats were designated as investigation areas 1 to 4, and the areas with floats were designated as investigation areas 5 to 8.

[0033] In this example, specimens 1 to 5 were blocks made of concrete, each of whose two main surfaces had a square shape when viewed in plan, and these specimens 1 to 5 were also investigated. Specimens 1 to 5 had a side length L of 900 mm on their main surfaces and a thickness T of 300 mm. As shown in Table 1 below, specimen 1 was a block that did not contain a cavity C inside, and specimens 2 to 5 were blocks that had a cavity C formed inside.

[0034] As shown in Figure 8, the cavity C in specimens 2 to 5 is square in plan view and is formed in the center of each specimen in plan view. The length of one side LC of cavity C in plan view, the thickness t of cavity C, and the cover h are as shown in Table 1. The cover h refers to the shorter distance from one main surface of the specimen to cavity C. The cover h can also be said to be the depth at which cavity C is formed in the specimen. [Table 1] In this example, as described above, the hammering test method M10 was carried out on the pier's inspection target locations 1 to 8 and test specimens 1 to 5, and an experiment was conducted to determine whether the presence or absence of defective areas could be correctly determined. The object to be fired at the pier was a spherical iron member with a diameter of 25 mm and a weight of 60 g.

[0035] An example of a sound obtained as a result of carrying out the striking step S11 and the sound collection step S12 is shown in Fig. 2. As shown in Fig. 2, the obtained sound includes a firing sound generated when the object is fired in the striking step S11 and a hitting sound generated when the object collides with the object to be investigated.

[0036] Next, the spectrum of each sound was obtained by performing a Fourier transform in a conversion step S13 on the sounds obtained in the sound collection step S12. Figure 3 shows the spectra obtained for survey locations 1 to 4 and test piece 1, Figure 4 shows the spectra obtained for survey locations 5 to 8, and Figure 5 shows the spectra obtained for test pieces 2 to 5.

[0037] As explained in the first embodiment, in the hammering inspection method M10, 5 kHz is used as the first frequency f1 and 1 kHz is used as the second frequency f2 (see FIGS. 3 and 4). That is, the low frequency region RL is a frequency band of 1 kHz or more and less than 5 kHz, and the high frequency region RH is a frequency band of 5 kHz or more and 10 kHz or less.

[0038] Comparing the spectrum shown in Figure 3 with the spectrum shown in Figure 4, it was found that when there were no defective parts in the vicinity of the investigated parts (investigation parts 1, 2, 3, 4), the hammering sounds contained relatively more high-frequency components (high-pitched sounds), and when there were defective parts in the vicinity of the investigated parts (investigation parts 5, 6, 7, 8), the hammering sounds contained relatively more low-frequency components (low-pitched sounds).

[0039] The evaluation index μL / μH obtained by the conversion step S13 is shown in FIG. 6. In this example, the threshold value of the evaluation index μL / μH used to evaluate the soundness (whether or not a defective part is included) of the building to be investigated was set to 1.0. The evaluation index μL / μH obtained from each of the test specimens was less than 1, which is consistent with the absence of any defective areas. In addition, the evaluation index μL / μH obtained from test specimens 5 to 8 and test specimens 2 to 5 was greater than 1, which is consistent with the presence of any defective areas.

[0040] As described above, by carrying out the hammering inspection method M10, it was possible to accurately determine whether or not there was a defect. In the hammering inspection method M10, unlike the hammering inspection described in Patent Document 1, only the peak amplitudes contained in the spectrum of the hammering sounds are used, but the average amplitude value is used.

[0041] Referring to FIG. 3, a peak is observed near 6 kHz at survey point 1, but no portion with a large enough amplitude to be called a clear peak is observed at survey points 2-4 and specimen 1. Referring to FIG. 4, a peak is observed near 3 kHz at survey points 5-7, but no portion with a large enough amplitude to be called a clear peak is observed at survey point 8. Referring to FIG. 5, one or more peaks are observed in the low-frequency region RL for specimens 2-5. The frequencies of the peaks observed in the low-frequency region RL for specimens 2-5 differ for each specimen, and the number of peaks also differs. Thus, it was found that there is room for improvement in the inspection accuracy when determining the presence or absence of defects by focusing only on peaks occurring at specific amplitude frequencies, as in the technology described in Patent Document 1.

[0042] On the other hand, according to the hammering inspection method M10, it is possible to determine the presence or absence of a defect by taking into account frequency components with small amplitudes contained in the low frequency region RL and the high frequency region RH. Therefore, the hammering inspection method M10 can improve the inspection accuracy in hammering inspection compared to the technique described in Patent Document 1.

[0043] Furthermore, referring to Figure 7, it can be seen that the natural frequencies obtained by performing hammering test method M10 on specimens 2 to 5 are in good agreement with the theoretical natural frequency values ​​obtained by FEM analysis. This proves that hammering test method M10 has high inspection accuracy.

[0044] [Embodiment 2] <Heat testing device> A hammering inspection device 10 according to a second embodiment of the present invention will be described with reference to FIG. 9. FIG. 9 is a block diagram of the hammering inspection device 10. The hammering inspection device 10 is an apparatus that performs the hammering inspection method M10 shown in FIG. 1. The hammering inspection device 10 is an invention that expresses the hammering inspection method M10 as an object. Therefore, in this embodiment, the description of the first embodiment can be referred to as appropriate, and descriptions of the pier, which is the structure to be inspected, the hammering inspection method M10, and the like will be omitted.

[0045] 9, the hammering inspection device 10 includes a hammering unit 11, a sound collection unit 12, and a control unit 13. The control unit 13 also includes a conversion unit 131 and an evaluation unit 132.

[0046] The hammering unit 11, sound collection unit 12, conversion unit 131, and evaluation unit 132 of the hammering inspection device 10 respectively perform the hammering step S11, sound collection step S12, conversion step S13, and evaluation step S14 of the hammering inspection method M10.

[0047] (Striking part) The striking unit 11 is configured to strike the pier, and performs a striking step S11. In this embodiment, an object having a certain weight is fired toward the pier from a location a predetermined distance away from the pier (i.e., a remote location), and the fired object strikes the pier, thereby striking the pier.

[0048] In this embodiment, as in the first embodiment, a spherical metal (iron in this embodiment) member with a diameter of 25 mm and a weight of 60 g is used as the object to be fired toward the pier. The material constituting the object is preferably a metal with a heavy specific gravity, such as iron or stainless steel, rather than a metal with a light specific gravity, such as aluminum. This is because, if the speed at which the object impacts the target area is constant, a heavier object is more likely to generate a louder impact sound due to the greater kinetic energy. Furthermore, when an object is fired toward a pier from the sea, the object will come into contact with seawater after impacting the pier. Therefore, for such use, a metal that is resistant to rust, such as stainless steel, is preferable over a metal that is prone to rust, such as iron. However, the size, represented by the diameter of the object, the weight of the object, and the material constituting the object are not limited to these and can be determined as appropriate.

[0049] In this embodiment, the pressure of a compressed fluid (air in this embodiment) is used as the force that urges the object when it is launched. By adjusting the magnitude of this pressure, the initial velocity of the launched object can be controlled, and therefore the velocity of the object that hits the pier can be controlled.

[0050] The force that biases the object when it is launched is not limited to the pressure of compressed air and can be determined as appropriate. Other examples of this force include the repulsive force of an elastic body, such as a spring or rubber.

[0051] The object launched from a remote location toward the location to be investigated may be attached with a string used for retrieving the object from the remote location. With this configuration, the object can be retrieved by reeling in the string from the remote location.

[0052] Furthermore, the method of striking the pier is not limited to striking the pier with an object launched from a remote location. For example, the pier may be struck by swinging a hammer in a location close to the pier.

[0053] (Sound collection part) The sound collection unit 12 is configured to collect impact sounds generated by striking the pier, i.e., when the object collides with the pier, and convert the collected impact sounds into audio signals, which are electrical signals representing sounds including the impact sounds. The sound collection unit 12 performs the sound collection step S12. The configuration of the sound collection unit 12 is not limited, and for example, a microphone or a directional microphone connected to a computer can be used.

[0054] (Conversion section) The conversion unit 131, which constitutes a part of the control unit 13, is configured to obtain a spectrum, which is the frequency dependency of amplitude, by performing a Fourier transform on the impact sound generated by striking the building. The conversion unit 131 performs the conversion step S13.

[0055] (Control unit) The functions of the hammering inspection device 10 (hereinafter referred to as the "device") can be realized by a program that causes a computer to function as the device, and a program that causes a computer to function as each control block of the device (particularly the conversion unit 131 and evaluation unit 132 included in the control unit 13).

[0056] In this case, the device includes a computer having at least one control device (e.g., a processor) and at least one storage device (e.g., a memory) as hardware for executing the program. The control device and storage device execute the program, thereby realizing the functions described in each of the above embodiments.

[0057] The program may be non-transitory and may be recorded on one or more computer-readable recording media. The recording media may or may not be included in the device. In the latter case, the program may be supplied to the device via any wired or wireless transmission medium.

[0058] (Evaluation Department) The evaluation unit 132, which constitutes a part of the control unit 13, is configured to evaluate the soundness of the pier (whether or not a defective portion is included) by comparing the average value or integral value of the amplitude in each of the low-frequency region RL and the high-frequency region RH, which are two regions included in the spectrum and have a predetermined first frequency f1 as a boundary. The evaluation unit 132 performs the evaluation step S14.

[0059] [Embodiment 3] <Heat Test Ship> A hammering inspection vessel 1 according to a third embodiment of the present invention will be described with reference to Fig. 10. Fig. 10 is a schematic diagram of the hammering inspection vessel 1.

[0060] The hammering inspection vessel 1 is equipped with a hammering inspection device 10 shown in Fig. 9. That is, as shown in Fig. 10, it is equipped with a hammering unit 11, a sound collecting unit 12, and a control unit 13.

[0061] By carrying out the hammering inspection method M10 (see FIG. 1) using a hammering inspection vessel 1 equipped with a hammering inspection device 10, hammering inspection can be easily carried out on structures that are built on water and at a high altitude above the water surface, such as piers and bridges.

[0062] For example, when conducting a hammering inspection using a hammer on a pier where the position of the pier superstructure components is higher than the water level, a suspended scaffolding is set up and an inspector uses the suspended scaffolding to go close to the area of ​​the pier to be inspected and hammer the area. However, by using the hammering inspection vessel 1, hammering inspection can be carried out without using the dangerous suspended scaffolding, which reduces the cost of the hammering inspection and ensures the safety of the inspector.

[0063] Furthermore, when conducting hammering inspections on piers where the components of the pier superstructure are located low, depending on the tide conditions, inspectors on a ship or boat may not be able to access the component locations. In such cases, inspectors may have to access the component locations by boarding a raft instead of a ship or boat. Hammering inspections using a raft are not considered to be very safe due to the raft's low stability. Safety is particularly likely to decrease when the raft is prone to significant rocking due to high waves, etc. By using the hammering inspection vessel 1, inspectors no longer need to access the component locations, allowing hammering inspections to be conducted without worrying about the inspector's safety.

[0064] Preferably, the hammering inspection vessel 1 is radio-controlled and can be operated from a remote location without the need for a crew or inspector on board. Furthermore, the hammering inspection vessel 1 is preferably small and low in height above the waterline so that hammering inspection method M10 can be performed even on piers where components are located at low heights. Furthermore, it is preferable that the hammering inspection vessel be equipped with a camera, and by linking the orientation of the camera with the orientation of the striking unit 11 and sound collection unit 12, an inspector can perform the hammering inspection while visually viewing the image from the camera.

[0065] [Additional Notes] The present invention is not limited to the above-described embodiments, and various modifications are possible within the scope of the claims. Embodiments obtained by appropriately combining the technical means disclosed in different embodiments are also included in the technical scope of the present invention.

[0066] 〔summary〕 In order to improve the inspection accuracy in the hammering inspection, the hammering inspection method according to the first aspect of the present invention comprises: a striking process of striking the structure; a transforming step of obtaining a spectrum of frequency-dependent amplitude by Fourier transforming the hitting sound generated in the striking step; The method includes an evaluation process in which two regions included in the spectrum, which are defined as a low-frequency region and a high-frequency region with a predetermined first frequency as their boundary, are used to evaluate the soundness of the building by comparing the average or integral values ​​of the amplitudes in the low-frequency region and the high-frequency region.

[0067] According to the above configuration, the hammering test is performed using an average value or an integral value that reflects information in a frequency range having a width, rather than a peak that reflects information of a specific frequency as in the technology described in Patent Document 1. Therefore, this hammering test method can improve the test accuracy in the hammering test even when the test object is complex, such as a building used in real society.

[0068] Furthermore, in the hammering inspection method according to the second aspect of the present invention, in addition to the configuration of the hammering inspection method according to the first aspect, a frequency lower than the first frequency is defined as a second frequency, The low frequency region has a lower limit and an upper limit defined by the second frequency and the first frequency, respectively.

[0069] The inventors of the present application have discovered that there is a frequency band that is likely to contain hammering sound components regardless of the presence or absence of defects such as cavities or lifts. The hammering sound components contained in this frequency band are likely not to reflect the presence or absence of defects. Therefore, the hammering sound components contained in this frequency band are likely to become noise when used to evaluate sound quality. According to the above configuration, by appropriately setting the second frequency lower than the first frequency, it is possible to eliminate frequency bands that are likely to become noise in the evaluation process. Therefore, the inspection accuracy of hammering sound inspection can be further improved.

[0070] Furthermore, a hammering inspection method according to a third aspect of the present invention employs the same configuration as the hammering inspection method according to the second aspect described above, but in addition, the second frequency is 1 kHz.

[0071] Furthermore, a hammering inspection method according to a fourth aspect of the present invention employs a configuration in which the first frequency is 5 kHz in addition to the configuration of the hammering inspection method according to any one of the first to third aspects described above.

[0072] Furthermore, a hammering inspection method according to a fifth aspect of the present invention employs a configuration in which the structure is a pier or a bridge, in addition to the configuration of the hammering inspection method according to any one of the first to third aspects described above.

[0073] When the surface of the structure to be inspected is made of concrete, 5 kHz and 1 kHz can be suitably used as the first frequency and the second frequency, respectively. Examples of the structure include a pier or a bridge.

[0074] In order to improve the inspection accuracy in hammering inspections, a hammering inspection device according to a sixth aspect of the present invention includes: a hammering unit that applies a hammering force to a structure; a sound collection unit that acquires hammering sounds generated by applying a hammering force to the structure; a conversion unit that obtains a spectrum in which the amplitude is frequency-dependent by performing a Fourier transform on the hammering sounds; and an evaluation unit that evaluates the soundness of the structure by comparing the average value or integral value of the amplitude in each of the low-frequency region and the high-frequency region, which are two regions included in the spectrum and have a predetermined first frequency as their boundary.

[0075] In order to improve the inspection accuracy in hammering inspections, a hammering inspection vessel according to a seventh aspect of the present invention comprises: a hammering unit that applies hammering to a structure; a sound collection unit that acquires hammering sounds generated by applying hammering to the structure; a conversion unit that obtains a spectrum of frequency-dependent amplitude by performing a Fourier transform on the hammering sounds; and an evaluation unit that evaluates the soundness of the structure by comparing the average value or integral value of the amplitude in each of two regions included in the spectrum, the two regions separated by a predetermined first frequency, which are defined as a low-frequency region and a high-frequency region.

[0076] The hammering inspection device according to the sixth aspect and the hammering inspection ship according to the seventh aspect configured in this manner have the same effects as the hammering inspection method according to the first aspect.

[0077] The hammering inspection device according to each aspect of the present invention may be realized by a computer. In this case, the hammering inspection program for the hammering inspection device, which causes the computer to operate as each unit (software element) of the hammering inspection device, thereby realizing the hammering inspection device on the computer, and a computer-readable recording medium on which the program is recorded, also fall within the scope of the present invention. [Explanation of symbols]

[0078] 1 ship 10. Hammering inspection device 11 Striking section 12 Sound collection section 13 Control Unit 131 Conversion Unit 132 Evaluation Department M10 Hammering inspection method S11 Impact process S12 Sound collection process S13 Conversion process S14 Evaluation process

Claims

1. a striking process of striking the structure; a transforming step of obtaining a spectrum of frequency-dependent amplitude by Fourier transforming the hitting sound generated in the striking step; an evaluation step of evaluating the soundness of the building by comparing average values ​​or integral values ​​of amplitudes in two regions included in the spectrum, the two regions having a predetermined first frequency as a low-frequency region and a high-frequency region.

2. a frequency lower than the first frequency is defined as a second frequency, a lower limit value and an upper limit value of the low frequency region are defined by the second frequency and the first frequency, respectively; The hammering inspection method according to claim 1.

3. the second frequency is 1 kHz; The hammering inspection method according to claim 2.

4. the first frequency is 5 kHz; The hammering inspection method according to any one of claims 1 to 3.

5. The structure is a pier or a bridge. The hammering inspection method according to any one of claims 1 to 3.

6. a striking unit that strikes the structure; a sound collection unit for acquiring a striking sound generated by striking the structure; a transform unit that performs a Fourier transform on the beat sounds to obtain a spectrum that is a frequency dependency of amplitude; an evaluation unit that evaluates the soundness of the building by comparing average values ​​or integral values ​​of amplitudes in two regions included in the spectrum, the two regions having a predetermined first frequency as a low-frequency region and a high-frequency region.

7. a striking unit that strikes the structure; a sound collection unit for acquiring a striking sound generated by striking the structure; a transform unit that performs a Fourier transform on the beat sounds to obtain a spectrum that is a frequency dependency of amplitude; an evaluation unit that evaluates the soundness of the building by comparing the average value or integral value of the amplitude in each of two regions included in the spectrum, the two regions having a predetermined first frequency as a low-frequency region and a high-frequency region; A hammering inspection vessel equipped with the following:

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