JP2012168022A - Method for diagnosing quality of concrete-based structure - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for diagnosing quality of concrete-based structures, which is uninfluenced by accuracy of a set value or the like, high in certainty of diagnosis, and applicable even to an object to which it has been difficult to apply an existing diagnostic method.SOLUTION: In a method for diagnosing quality of concrete-based structures, time characteristic wave forms of exciting force and time characteristic wave forms of sound pressure response are compared to diagnose. When a positive sign of the exciting force is regarded as a direction where compression force works on an impact contact surface of impact means and a positive sign of the sound pressure response is regarded as a direction where a pressure is higher than a resting pressure, it is diagnosed that there is an abnormality in an object 7 to be measured when at least one of the following phenomena is observed: a positive or negative sign of the sound pressure response is observed and the sign being positive is observed when an absolute value of the sound pressure response, for the first time, exceeds a prescribed value which is a threshold value determining whether or not sound pressure that is equal to or greater than background noise has been sensed to a sound receiving system while the exciting force works on the object 7 to be measured or in a subsequent process; and a high frequency component that is equal to or higher than an excitation frequency appears on the sound pressure response while the exciting force works on the object to be measured.

Description

  The present invention relates to a method for diagnosing quality of a concrete structure, and more particularly, a sound part and a surface layer part of a concrete structure are peeled off, cracked, or a cavity is generated due to insufficient filling of a formwork when placing concrete. The present invention relates to a quality diagnostic method for a concrete structure that can be used for non-destructive inspection from the outside to determine and diagnose an abnormal part.

  There have been many proposals for a method of diagnosing the presence or absence of cavities due to insufficient peeling of cracks in the surface layer of concrete-based structures, as well as insufficient filling of the formwork during concrete placement. The present applicant has also made a plurality of proposals as shown in Patent Documents 1 and 2, for example.

  Many of the prior arts, including the prior art proposed by the present applicant, are based on the conventional methods that have been sensuously judged by the human sense of sound from hitting the surface of the structure with a hammer or the like. Instead, it is intended to be able to quantitatively discriminate without relying on a sense and requiring skill by performing analysis using measuring instruments such as various sensors.

  The Applicant continued further research on the technology, and found that the traditional method of discriminating the quality type of a structure by human hearing was discriminating by distinguishing the tone of the hitting sound. It has been found that the prior art for discriminating the quality type of a structure by analysis is classified into a method of discriminating based on the volume of the hitting sound and a method of discriminating based on the amount corresponding to the timbre.

  The technique described in Patent Document 1 is a method for determining the quality type of a structure based on the sound pressure level of a striking sound. A concrete surface is struck by a striking means to generate vibrations, and is separated from the striking position. In the method of judging the soundness of concrete by analyzing the sound, collecting sound (striking sound) propagating through the concrete and radiating into the air with a microphone placed at a position, Sound is struck by using a hammer with a known change in the impact input value over time, and analyzing the known amount of the impact input and the sound radiated in the air that propagates through the concrete (striking sound). It is a concrete soundness judgment method characterized by judging the degree.

  The technique described in Patent Document 2 is a method for determining the quality type of a structure based on the amount corresponding to the tone color of the impact sound, and a response signal obtained by applying an impact to the structure to be measured is added. This is a method that uses the normalized response obtained by dividing by the magnitude of the impact force, and uses a late response or a full time response of the normalized response, and 1 / N octave band analysis for each signal in the signal set. Average values μ1 and μ2 and standard deviations σ1 and σ2 for each quality type in each frequency band using a healthy data set and an abnormal data set as a teacher signal are obtained from the obtained level values. The standardized distance δ is obtained by a specific equation (1), and an arbitrary number of values are extracted from the obtained values of the standardized distance δ from the largest value, and the structure value is extracted from the extracted value. Able to determine the quality type in each part A.

  However, these diagnosis methods require a process of defining corresponding parameters for each category such as a healthy part and an abnormal part in advance and setting the discrimination boundary value thereof. Further, there is a problem that the diagnostic accuracy is greatly influenced by the accuracy of the set value or the selected parameter, and the range of applicable problems is limited.

JP 2001-31724 A JP2010-060286

  Therefore, an object of the present invention is to focus on a qualitative phenomenon that is always observed as a phenomenon that occurs in an abnormal part such as peeling, and is highly reliable in diagnosis regardless of the accuracy of the set value or the selected parameter. An object of the present invention is to provide a method for diagnosing the quality of a concrete structure that can be applied to an object that has been difficult to apply with existing diagnostic methods.

The object of the present invention is achieved by the following means.
1. The concrete structure to be measured is struck by any striking means such as an impact hammer, the excitation force obtained from the striking means, and the sound receiving system installed at a position close to the striking location. In a method for diagnosing the quality of a concrete structure by measuring the sound pressure response obtained by the sound receiving means,
A method of making a diagnosis by comparing a time characteristic waveform of the excitation force and a time characteristic waveform of the sound pressure response,
When the positive sign of the excitation force is the direction in which the compressive force acts on the striking contact surface of the striking means, and the positive sign of the sound pressure response is the direction of pressure higher than the static pressure,
(A-1) Whether or not the absolute value of the sound pressure response senses a sound pressure higher than background noise in the sound receiving system while the excitation force is acting on the object to be measured or in the subsequent process. When the specified value, which is a threshold value to be distinguished, is exceeded for the first time, the sign of the sign is observed, and the sign of the sound pressure response is positive,
(A-2) While the excitation force is acting on the object to be measured, a high frequency component higher than the excitation frequency appears in the sound pressure response.
Among these, when at least one phenomenon of the above (A-1) and (A-2) is observed, it is diagnosed that there is an abnormality in the object to be measured. Method.

2. The time characteristic waveform of the excitation force and the sound pressure response is normalized by the maximum value of the excitation force and the negative maximum value of the sound pressure response while the excitation force is working. A quality diagnostic method for a concrete structure according to 1.

3. (B-1) A sine half wave in which the time characteristic waveform of the excitation force has a sine half wave shape, and the time characteristic waveform of the sound pressure response is obtained by inverting the sign of the waveform indicating the time characteristic of the excitation force. Have a shape,
(B-2) the time at which the negative maximum value in the time characteristic waveform of the sound pressure response occurs is delayed from the time at which the maximum value in the time characteristic waveform of the excitation force occurs;
(B-3) The first rise of the time characteristic waveform of the sound pressure response occurs later than the first rise of the time characteristic waveform of the excitation force.
The concrete according to 1 or 2 above, wherein when the at least one phenomenon of (B-1) to (B-3) is observed, the object to be measured is diagnosed as being healthy. Quality diagnosis method for system structures.

4). The abnormality of the measurement target diagnosed by the quality diagnostic method for a concrete structure according to any one of 1 to 3,
(C-1) A state in which a part of the concrete structure is peeled off,
(C-2) A state in which a cavity exists inside the concrete structure,
(C-3) A state in which there is a crack leading from the inside to the outside of the concrete structure,
(C-4) A state in which there is a cavity due to insufficient filling of the formwork when placing concrete,
(C-5) The other relatively thin material with respect to the base material of the concrete-based structure is (1) not in the prescribed adhesion state, but in a state of having peeling properties, and / or (2) cracking Or having a cavity,
Among them, the method for diagnosing quality of a concrete structure according to any one of the above items 1 to 3, which is at least one of the states (C-1) to (C-5).

According to the first aspect of the present invention, it is possible to mobilize and discriminate a plurality of parameters without requiring a process such as parameter pre-adjustment for discrimination, and the diagnosis is highly reliable. It is possible to provide a method for diagnosing the quality of a concrete structure that can be applied even to an object that is difficult to apply by the diagnostic method.
Moreover, it is a method based on independent information different from the conventional diagnostic method, and can be used in combination with the conventional diagnostic method, thereby improving the accuracy of the quality diagnosis. Furthermore, since the method is based on independent information, it may be possible to determine a phenomenon that could not be detected by a conventional diagnostic method.

  According to the invention shown in 2, the time characteristic waveform of the exciting force is normalized by normalizing the maximum value of the exciting force and the negative maximum value of the sound pressure response while the exciting force is working, Comparison with the time characteristic waveform of the sound pressure response is facilitated, and the ease of diagnosis is improved.

  According to the third aspect of the present invention, not only an abnormal part to be measured but also a healthy part can be discriminated and diagnosed, and the accuracy of diagnosis is improved.

  According to the fourth aspect of the present invention, it can be understood that there is any abnormality in the measurement object.

The schematic block diagram which shows an example of a measurement means structure used for the quality diagnostic method of the concrete type structure concerning this invention Schematic explanatory diagram explaining changes in measurement target when hitting healthy part Schematic explanatory diagram explaining changes in measurement target when hitting abnormal parts such as cavities and peeling Schematic explanatory diagram explaining changes in measurement target when hitting abnormal parts such as cracks Waveform graph showing the characteristics of the healthy part Waveform graph showing characteristics of abnormal part (existence of positive minute peak in initial sound pressure response) Waveform graph showing the characteristics of abnormal parts (existence of high frequency components above the excitation frequency or presence of high frequency components based on secondary vibration)

  The method for diagnosing the quality of a concrete structure according to the present invention is a concrete in which the object to be measured is a structure such as a building or a tunnel using concrete in whole or in part, and the object to be measured by impact means such as an impact hammer. The excitation force applied to the system structure and the sound pressure response obtained by the sound receiving means of the sound receiving system such as a microphone installed at a position close to the hitting point are measured, and each time characteristic waveform (so-called This is a method of diagnosing the quality of a concrete structure by observing a “time waveform”) to distinguish between a healthy part and an abnormal part.

  "Excitation force" is a physical quantity with a unit of force measured using a force sensor (force sensor) using a piezoelectric element, etc., and is adjusted to output the magnitude of the force applied to the target. It can be measured by a measuring instrument (for example, an impact hammer).

  “Sound pressure response” refers to a sound pressure sensor, such as a microphone, that uses vibration to generate sound (air vibration, close-packed waves) radiated into the air due to impact. Say.

  In the present invention, the term “concrete structure” is not limited to concrete, but includes a wide range of materials used as building structures, civil structures, or parts thereof, such as bricks, asphalt, metals, stones, wood, and other various materials. The present invention can also be applied to structures using these as materials.

First, an example of the structure of the measuring means used for the quality diagnosis method for a concrete structure according to the present invention will be described.
FIG. 1 shows a schematic configuration diagram showing an example of a configuration of a measuring means used in the quality diagnosis method for a concrete structure according to the present invention. The components required for the measurement are the striking means 1, excitation force detector / amplifier 2, sound receiving means 3, sound pressure detector / amplifier 4, AD converter 5, and computer 6.

The hitting means 1 is a publicly known means used in this type of sound inspection technology field, and means for giving an impact under a substantially constant condition can be used without any particular limitation. Examples of the means include striking with an impact hammer capable of striking the surface of the structure with a substantially constant excitation force capable of obtaining a shock wave.
The impact hammer here refers to a hammer having a built-in sensor (force sensor) using a piezoelectric element or the like so that the change with time of the hitting input value is known. In other words, the hammer has the functions of the striking means 1 and the excitation force detector / amplifier 2 shown in FIG.

  The sound receiving means 3 may be a publicly known means used in this type of sound inspection technology field. For example, in the position close to the impact point (for example, impact point of impact hammer) to which the impact is given by the impacting means, the propagation impact sound (vibration) propagated through the concrete structure itself to be measured is air-vibrated. As a sound receiving means 3 composed of a microphone 31 to be sampled and a hood member 32 which has the microphone and the sound receiving direction is released, the sound receiving means 3 is used in a state close to or in close contact with the surface of the concrete structure. The structure which performs a measurement can be mentioned.

  The hood member 32 of the microphone with the hood propagates to the member to be diagnosed rather than the sound generated from the point-like local deformation of the position vibrated by the hammer, and structural features of the member to be diagnosed. For example, the effect described in Japanese Patent Application Laid-Open No. 2001-31724 can be expected.

An excitation force obtained from the striking means 1 and the excitation force detector / amplifier 2 and a sound pressure response obtained from the sound receiving means 3 and the sound pressure detector / amplifier 4 are connected via the AD converter 5. By converting to a digital signal, the computer 6 can display the excitation force and sound pressure response measurement data as a time characteristic waveform.
The method for diagnosing the quality of a concrete structure according to the present invention compares the excitation force obtained as described above with the time characteristic waveform of the sound pressure response, thereby comparing the concrete structure being measured. It is a method of diagnosing quality.

In each time characteristic waveform, the positive sign of the excitation force is the direction in which the compressive force acts on the hammering contact surface, and the positive sign of the sound pressure response is the direction of pressure higher than the static pressure (atmospheric pressure, reference pressure). When the healthy part is vibrated, the half-wave of vibration is observed as positive, and the sound pressure response of a nearby microphone is observed as negative.
Moreover, it is preferable to normalize the time characteristic waveform of the excitation force and the sound pressure response with the maximum value of the excitation force and the negative maximum value of the sound pressure response while the excitation force is working. That is, for the excitation force, the value obtained by dividing the obtained excitation force by the maximum value of the excitation force is used. For the sound pressure response, the obtained sound pressure response is applied to the measurement target. A value obtained by dividing by the negative maximum value of the sound pressure response while the force is working is preferably a time characteristic waveform displayed as a vertical axis.

  Next, a specific method for diagnosing the quality of the concrete structure to be measured will be described by comparing the excitation force obtained by the above configuration and the time characteristic waveform of the sound pressure response.

Generally, a sound part of a concrete structure has a vibration response characteristic integrated with a base material with respect to an excitation force such as an impact hammer. That is, the ratio between the input force F and the vibration response speed V is an amount corresponding to the driving point impedance Z.
Z = F / V

  On the other hand, the characteristic of the abnormal part of the concrete structure is that there is a part (hereinafter also referred to as “micro member”) that can vibrate minutely due to the presence of peeling or cracking. As a result, even when a vibration is applied by an impact hammer similar to a healthy case, the vibration response characteristic unique to the small member is different from the vibration response characteristic of the base material.

  The present invention relates to a method for diagnosing the quality of an object to be measured by paying attention to the vibration response characteristic unique to the small member, thereby determining the presence or absence of an abnormal part.

First, the characteristics of the sound part in the comparison of the time characteristic waveforms of the excitation force and the sound pressure response will be described.
The excitation force and the sound pressure response were measured by the measuring means described above, and the excitation force waveform and the sound pressure response waveform were obtained from these measured values. In the observation comparing the above, when there is any of the following characteristics, the concrete structure to be measured can be determined to be healthy.

(B-1) A sine half wave in which the time characteristic waveform of the excitation force has a sine half wave shape, and the time characteristic waveform of the sound pressure response is obtained by inverting the sign of the waveform indicating the time characteristic of the excitation force. Have a shape.
(B-2) The time at which the negative maximum value in the time characteristic waveform of the sound pressure response occurs is delayed from the time at which the maximum value in the time characteristic waveform of the excitation force occurs.
(B-3) The first rise of the time characteristic waveform of the sound pressure response occurs later than the first rise of the time characteristic waveform of the excitation force.

  Further, although not included in the present invention, it is a guideline for determining a sound part that “the absolute value of the sound pressure response after the excitation time does not greatly exceed the negative maximum value (absolute value) of the sound pressure response”. As a reference.

  Next, the characteristics of the abnormal part in the comparison of the time characteristic waveforms of the excitation force and the sound pressure response will be described.

In addition, the abnormal part in this invention refers to the part which peeling etc. in the concrete structure which is a to-be-measured object generate | occur | produced, and peeling etc. show the following phenomena.
(C-1) A state where a part of the structure is peeled off (a state where a gap is generated between a material near the surface and a member near the center).
(C-2) A state in which a cavity exists inside the concrete structure.
(C-3) A state in which there is a crack leading from the inside to the outside of the concrete structure.
(C-4) A state in which there is a cavity due to insufficient filling of the formwork when placing concrete.
(C-5) The other relatively thin material with respect to the base material of the concrete-based structure is (1) not in the prescribed adhesion state, but in a state of having peeling properties, and / or (2) cracking A state of having a cavity.

  The excitation force and the sound pressure response were measured by the measuring means described above, and the excitation force waveform and the sound pressure response waveform were obtained from these measured values. In the observation comparing the above, when there is the following feature (A-1) or (A-2), it can be determined that the concrete structure to be measured has an abnormality such as peeling. .

(A-1) Presence of a positive minute peak in the initial sound pressure response.
The absolute value of the sound pressure response is a threshold value that distinguishes whether or not the sound receiving system has detected a sound pressure higher than background noise while the excitation force is acting on the measurement target or in the subsequent process. When the specified value is exceeded for the first time, the sign of the sign is observed, and if the sign of the sound pressure response is positive, it can be diagnosed that the measurement target is abnormal.

  As described in (A-1) above, a minute positive peak in the sound pressure response is observed when an abnormal part such as peeling exists in the object to be measured. This is the sound pressure of the opposite sign from the negative response observed in the healthy part. Such sound pressure is generated because there is a minute independent part that can move in the opposite direction due to an abnormal part such as peeling in the object to be measured, which is not a solid / homogeneous member, That is, it indicates the presence of a peeling site.

The reason why a positive minute peak related to the initial response occurs is that, as shown in FIG. 3 or FIG. 4, the sound receiving point (the position where the microphone or the like as the sound receiving means is installed) is separated from the excitation point. This is considered to be because displacement in the direction opposite to the excitation direction occurs. In order for such a displacement in the opposite direction to occur, it is necessary that a minute part exists due to the presence of peeling, cracking, etc., and this is not considered to occur when there is a solid and homogeneous wide member. Therefore, the observation of a positive minute peak in the initial sound pressure response can be said to be equivalent to the presence of a part such as peeling.
In addition, since there is no abnormal part such as peeling or cracking in the object to be measured in the healthy part, it is a solid and homogeneous wide member, so that a displacement in the direction opposite to the excitation direction occurs as shown in FIG. It is thought that there is nothing.

  In the method for diagnosing an abnormal portion of the measurement target according to (A-1), the absolute value of the sound pressure response exceeds the specified value for the first time while the excitation force is acting on the measurement target or in the subsequent process. Therefore, it can be determined whether the sign is positive or negative, which is a very simple diagnostic method.

  The specified value indicates a threshold value for distinguishing whether or not the sound pressure above the background noise is detected in the sound receiving system, and is a value unique to the sound receiving system, so once this value is set, There is no need for prior adjustment of parameters.

(A-2) Presence of high frequency components higher than the excitation frequency or presence of high frequency components based on secondary generated vibrations.
When a high frequency component equal to or higher than the excitation frequency appears in the sound pressure response while the excitation force is acting on the measurement target, it can be diagnosed that the measurement target is abnormal.

  As described in the above (A-2), when there is an abnormal part such as peeling on the object to be measured, a minute member exists due to the peeling or the like, and the vibration of the minute member is caused by vibration. Since excited, it is considered that a sound pressure response of a high frequency component higher than the maximum excitation frequency by the striking means is generated. In the case of a homogeneous and large member (a member having no separation or the like), it is considered that a sound pressure response above the excitation frequency does not occur in principle. Due to the presence of delamination, the size of the object to be measured is reduced, and an excitation force that extends to the high frequency range occurs due to a collision between the delamination site and the base material other than vibration, and the influence of reflected waves from the boundary It is considered that a high frequency component is generated in the sound pressure response due to reasons such as appearing. The high frequency component of the sound pressure response is observed as intense vibration, that is, vibration that repeats positive / negative and increase / decrease many times in the time characteristic waveform of the sound pressure response within the excitation time.

The method for diagnosing an abnormal part to be measured according to (A-2) will be described in detail.
In the sound part, while the excitation force is acting on the measurement target (excitation process), the sign of the sound pressure response is reversed or the sign of the sound pressure response is differentiated (differential wave) frequently. Absent. Therefore, whether or not there is an abnormal part in the measurement target is determined by detecting whether the sound pressure is positive or negative during the excitation process by detecting a high frequency component from the frequency analysis of the sound pressure during the excitation process. It is possible to determine whether or not the sign inversion of the differential wave occurs more frequently than the specified value.

  In the comparison between the time characteristic waveform of the excitation force and the time characteristic waveform of the sound pressure response, when there is a feature of the above (A-1) or (A-2), the concrete structure to be measured is The present invention, which can be judged to have an abnormality such as peeling, is a method based on information completely independent of the existing quality diagnosis method, and is therefore used in combination with the above-mentioned Patent Documents 1 and 2 and other existing methods. The diagnostic accuracy can be improved, and there is a significant effect that discrimination that cannot be diagnosed and discriminated by existing methods can be made.

  In addition, it is not a diagnostic method that sets diagnostic parameters for a specific purpose, such as a frequency center of gravity or a parameter that quantifies part of the frequency characteristics, but observes whether a specific phenomenon has occurred in the measurement target. It is also possible to set a plurality of judgment criteria for judging the presence or absence of a phenomenon, and this has a significant effect that the accuracy and certainty of diagnosis can be improved.

  The method for diagnosing the quality of a concrete structure according to the present invention is performed by comparing the time characteristic waveform of the excitation force and the time characteristic waveform of the sound pressure response. For these waveforms, one or more times. It is also possible to perform quality diagnosis of concrete structures by observing and comparing waveforms that have been subjected to differential processing.

An embodiment in which a quality diagnosis of a concrete structure is performed using the method for diagnosing a quality of a concrete structure according to the present invention will be described below.
As described above, as a means for obtaining the excitation force and the sound pressure response, the concrete structure to be measured was hit with an impact hammer, the excitation force was measured, and it was close to the hit location. A method of measuring the sound pressure response using a sound receiving means (a combination of a microphone and a hood member) installed at a position was used. The object to be measured is a concrete building.

The excitation force and sound pressure response obtained by using the above method are normalized and displayed as a time characteristic waveform in FIGS. 5 to 7, the vertical axis represents a value obtained by normalizing the excitation force or the sound pressure response, and the horizontal axis represents time (msec.).

The six waveform graphs shown in FIG. 5 are all waveforms showing the characteristics of the healthy part.
The waveform graph is standardized by the above method.
In addition, first, the present inventors measure the sound pressure response in Japanese Patent Laid-Open No. 2010-060286 (hereinafter referred to as “proposed”) because the sound pressure response is proportional to the vibration velocity of the vibration surface. This is equivalent to measuring the vibration speed of the vibration surface, and this proposal can also be used when vibration acceleration is used instead of vibration speed. I showed that it can be used as well. In the present invention, since the value corresponding to the vibration speed is measured by sound pressure, the measurement using the hooded microphone is equivalent to the measurement performed by attaching the vibration sensor to the surface to be diagnosed. Therefore, the same result can be obtained not only with a microphone with a hood but also with a vibration measurement performed with a pickup attached to the surface to be diagnosed.

As mentioned above,
(B-1) A sine half wave in which the time characteristic waveform of the excitation force has a sine half wave shape, and the time characteristic waveform of the sound pressure response is obtained by inverting the sign of the waveform indicating the time characteristic of the excitation force. Have a shape.
(B-2) The time at which the negative maximum value in the time characteristic waveform of the sound pressure response occurs is delayed from the time at which the maximum value in the time characteristic waveform of the excitation force occurs.
(B-3) The first rise of the time characteristic waveform of the sound pressure response occurs later than the first rise of the time characteristic waveform of the excitation force.
It can be seen that all the features of.

The six waveform graphs shown in FIG. 6 are all waveforms that indicate abnormal portions.
It can be seen that in the waveform diagram, the “existence of a positive minute peak in the initial sound pressure response”, which is the characteristic of the above (A-1), appears in a circled portion.

The six waveform graphs shown in FIG. 7 are all waveforms that indicate abnormal portions.
It can be seen that the feature (A-2), “existence of high frequency components higher than the excitation frequency or presence of high frequency components based on secondary generated vibration” appears.

DESCRIPTION OF SYMBOLS 1 Impact means 2 Excitation force detector / amplifier 3 Sound receiving means 31 Microphone 32 Hood member 4 Sound pressure detector / amplifier 5 AD converter 6 Computer 7 Object to be measured 71 Concrete part 72 Parts other than concrete such as steel

Claims (4)

The concrete structure to be measured is struck by any striking means such as an impact hammer, the excitation force obtained from the striking means, and the sound receiving system installed at a position close to the striking location. In a method for diagnosing the quality of a concrete structure by measuring the sound pressure response obtained by the sound receiving means,
A method of making a diagnosis by comparing a time characteristic waveform of the excitation force and a time characteristic waveform of the sound pressure response,
When the positive sign of the excitation force is the direction in which the compressive force acts on the striking contact surface of the striking means, and the positive sign of the sound pressure response is the direction of pressure higher than the static pressure,
(A-1) Whether or not the absolute value of the sound pressure response senses a sound pressure higher than background noise in the sound receiving system while the excitation force is acting on the object to be measured or in the subsequent process. When the specified value, which is a threshold value to be distinguished, is exceeded for the first time, the sign of the sign is observed, and the sign of the sound pressure response is positive,
(A-2) While the excitation force is acting on the object to be measured, a high frequency component higher than the excitation frequency appears in the sound pressure response.
Among these, when at least one phenomenon of the above (A-1) and (A-2) is observed, it is diagnosed that there is an abnormality in the object to be measured. Method.   The time characteristic waveform of the excitation force and the sound pressure response is normalized by the maximum value of the excitation force and the negative maximum value of the sound pressure response while the excitation force is working. Item 10. A method for diagnosing the quality of a concrete structure according to Item 1. (B-1) A sine half wave in which the time characteristic waveform of the excitation force has a sine half wave shape, and the time characteristic waveform of the sound pressure response is obtained by inverting the sign of the waveform indicating the time characteristic of the excitation force. Have a shape,
(B-2) the time at which the negative maximum value in the time characteristic waveform of the sound pressure response occurs is delayed from the time at which the maximum value in the time characteristic waveform of the excitation force occurs;
(B-3) The first rise of the time characteristic waveform of the sound pressure response occurs later than the first rise of the time characteristic waveform of the excitation force.
3. The diagnosis according to claim 1, wherein the measurement target is healthy when at least one phenomenon of (B-1) to (B-3) is observed. Quality diagnosis method for concrete structures. The abnormality of the measurement target diagnosed by the quality diagnostic method for a concrete structure according to any one of claims 1 to 3,
(C-1) A state in which a part of the concrete structure is peeled off,
(C-2) A state in which a cavity exists inside the concrete structure,
(C-3) A state in which there is a crack leading from the inside to the outside of the concrete structure,
(C-4) A state in which there is a cavity due to insufficient filling of the formwork when placing concrete,
(C-5) The other relatively thin material with respect to the base material of the concrete-based structure is (1) not in the prescribed adhesion state, but in a state of having peeling properties, and / or (2) cracking Or having a cavity,
The method for diagnosing quality of a concrete structure according to any one of claims 1 to 3, wherein at least one of the states (C-1) to (C-5) is included.

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