JP2017053770A - Crack occurrence diagnosing method, and crack occurrence diagnosing program - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a crack occurrence diagnosing method by which the state of crack occurrence can be assessed by merely measuring the current status of displacement of a concrete structure that is bent by loading.SOLUTION: A crack occurrence diagnosing method for concrete structures that are bent by loading comprises step S1 of loading a concrete structure sufficiently to invite its bending; step S2 of measuring over time the displacement invited by loading; steps S3 to S5 of decomposing vibration waveforms generated from the measured displacement into a positive side amplitude and a negative side amplitude; step S6 of calculating half periods that constitute time intervals of half periods making up the positive side amplitude and the negative side amplitude; step S7 of calculating from the half period the number of momentary vibrations that constitutes the number of vibrations at the time each half-wavelength occurs; and step S8 of determining the state of crack occurrence of the concrete structure by comparing the number of momentary vibrations of the positive side amplitude and the number of momentary vibrations of the negative side amplitude.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a crack occurrence diagnosis method and a crack occurrence diagnosis program for concrete structures such as bridge girders and floor slabs that are bent by loading.

  As disclosed in Patent Documents 1 and 2, there is known a method for diagnosing soundness such as whether cracks are generated in a reinforced concrete concrete structure.

  If it is a concrete structure in which cracks are visible on the surface even under normal conditions, the degree of damage or deterioration can be judged by visual observation to make a diagnosis of soundness.

  On the other hand, if the concrete structure has cracks that open only when a load is loaded, such cracks may be overlooked by visual observation alone, and the assessment of soundness may be excessive. .

  Therefore, the soundness of such a concrete structure is diagnosed by measuring the natural frequency of the concrete structure as disclosed in Patent Documents 1 and 2.

  That is, the natural frequency when the concrete structure is in a healthy state is measured, and if the natural frequency measured at the time of inspection is lower than the natural frequency at the time of soundness, the concrete structure is cracked. It can be diagnosed that there is damage or deterioration such as occurring.

JP 2011-247700 A Japanese Patent No. 3834660

  However, in the method for evaluating the soundness from the change in the natural frequency described in Patent Documents 1 and 2, it is necessary to measure the natural frequency of the concrete structure in a healthy state.

  However, innumerable existing concrete structures exist, and in all of them, the natural frequency is not measured in advance at the time of new installation or the like.

  Therefore, the present invention provides a crack occurrence diagnosis method or a crack occurrence diagnosis program that can determine a crack occurrence state only by measuring a current displacement of a concrete structure that is bent by loading. It is aimed.

  In order to achieve the above object, the crack occurrence diagnosis method of the present invention is a crack occurrence diagnosis method for a concrete structure in which bending is caused by loading, and the step of loading the concrete structure to cause bending is performed. Measuring a displacement caused by loading with time, decomposing a vibration waveform generated from the measured displacement into a positive amplitude and a negative amplitude, and the positive amplitude and the negative amplitude. Respectively, a step of calculating a half cycle that is a time interval of each half wavelength constituting each of the above, a step of calculating an instantaneous frequency that is a frequency at the time when each half wavelength is generated from the half cycle, Determining the occurrence of cracks in the concrete structure by comparing the instantaneous frequency of the side amplitude and the instantaneous frequency of the negative side amplitude; And said that there were pictures.

  Here, a free vibration waveform that becomes a residual vibration after the loaded concrete structure resonates can be used as the vibration waveform.

  Further, in order to decompose the vibration waveform generated from the measured displacement into the positive side amplitude and the negative side amplitude, an average value is calculated in a predetermined range of the vibration waveform, and the average value is to be decomposed. A configuration may be provided that includes a step of performing zero-line correction to set the vibration waveform to a zero value. Furthermore, the predetermined range for calculating the average value can be a small response range in which the amplitude width is within 0.5 mm.

  The concrete structure may be a long horizontal material, and the measured displacement may be a vertical displacement. Further, the concrete structure may be a girder member, and the measured displacement may be a vertical displacement at substantially the center in the longitudinal direction of the girder member.

  Further, the invention of the crack occurrence diagnostic program is a crack occurrence diagnostic program for a concrete structure that is bent by loading, and an input unit that captures a temporal displacement caused by loading that causes bending of the concrete structure; Waveform decomposing means for decomposing the vibration waveform generated from the captured displacement into a positive side amplitude and a negative side amplitude, and a time interval of each half wavelength constituting the positive side amplitude and the negative side amplitude, respectively And calculating an instantaneous frequency which is a frequency at the time when each half wavelength is generated from the half cycle, and an instantaneous frequency of the positive amplitude and the instantaneous frequency Output means for outputting the instantaneous frequency of the negative amplitude.

  The crack occurrence diagnosis method of the present invention configured as described above decomposes the vibration waveform generated from the displacement caused by the load causing the bending of the concrete structure into a positive amplitude and a negative amplitude.

  Then, the instantaneous vibration frequency is calculated from the decomposed positive side amplitude and negative side amplitude, and the crack occurrence state of the concrete structure is determined by comparing them.

  Here, the concrete structure in which bending is caused by loading can be presumed that the compression side of the concrete is in a healthy state, and if cracking occurs, there is a high possibility that it will occur from the tension side.

  For this reason, it is only necessary to measure the current displacement of a concrete structure that is bent by loading, decompose the vibration waveform obtained from it into a positive amplitude and a negative amplitude, and compare the respective instantaneous frequencies. The crack occurrence state can be determined.

  If a free vibration waveform that becomes a residual vibration after the loaded concrete structure resonates is used as the vibration waveform for performing such a diagnosis, it is possible to easily determine the crack occurrence state.

  Even when there is an error in the measurement of displacement and the vibration waveform is shifted to the positive side or the negative side, the vibration waveform is corrected to zero by using the average value calculated in a predetermined range. Can be decomposed into a positive amplitude and a negative amplitude.

  Furthermore, the invention of the crack occurrence diagnosis program includes waveform decomposition means for decomposing a vibration waveform generated from a displacement caused by a load that causes bending of a concrete structure into a positive amplitude and a negative amplitude.

  Further, there are provided instantaneous frequency calculating means for calculating respective instantaneous frequencies from the decomposed positive side amplitude and negative side amplitude, and output means for outputting the calculated instantaneous frequencies.

  For this reason, cracks can be easily generated just by comparing the instantaneous frequency of the positive and negative amplitudes output from the output means, calculated from the current displacement measurement results of the concrete structure that is bent by loading. The situation can be determined.

It is a flowchart explaining each step of the crack generation | occurrence | production diagnosis method of this Embodiment. It is a schematic diagram explaining the schematic structure of the bridge used as the object of crack generation | occurrence | production diagnosis. It is a block diagram explaining the crack generation | occurrence | production diagnosis program of this Embodiment. (A) is explanatory drawing which illustrated the vibration waveform produced | generated from the displacement measured by train travel, (b) is explanatory drawing which showed the result of carrying out 0 line | wire correction | amendment of the residual vibration of the vibration waveform shown to (a). is there. (A) is explanatory drawing which showed the negative side amplitude of the vibration waveform after correction | amendment shown in FIG.4 (b), (b) shows the positive side amplitude of the vibration waveform after correction | amendment shown in FIG.4 (b). FIG. It is the figure which plotted the instantaneous frequency of positive side amplitude, and the instantaneous frequency of negative side amplitude, (a) is a figure which illustrated the result judged to be healthy, and (b) that a crack has occurred. It is the figure which illustrated the result determined.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a diagram for explaining a flow of processing of a crack occurrence diagnosis method and a crack occurrence diagnosis program according to the present embodiment.

  The crack occurrence diagnosis method and crack occurrence diagnosis program of the present embodiment are applied to a concrete structure in which bending occurs due to loading. For example, a reinforced concrete structure, a prestressed concrete structure, or a structure having a composite section of steel and concrete corresponds to the concrete structure.

  Moreover, as a form of a concrete structure, the girder member, beam member, floor slab etc. which become a long horizontal material correspond. In addition, column members, wall members, piers, and the like also correspond to concrete structures that are bent by loading depending on the applied load.

  In FIG. 2, the schematic diagram of RC girder 1 illustrated as a concrete structure in this Embodiment was shown. The RC girder 1 is a long member made of reinforced concrete that is bridged between the abutment 11 and the pier 12 or between the piers 12 and 12 in the bridge 10.

  In the present embodiment, in order to simplify the description, the description will be made using a simple beam in which both ends of the RC beam 1 are supported by the support portions 13 and 13 as models. Then, the displacement in the vertical direction at the substantially central position in the longitudinal direction (axial direction) of the RC beam 1 is measured by the displacement meter 2.

  As the displacement meter 2, a known displacement meter such as a ring displacement meter or a Doppler laser displacement meter can be used. The ring-type displacement meter is a displacement meter in which a strain gauge is attached to a circularly formed leaf spring. If the probe at the tip of the ring-type displacement meter is attached to the upper surface 1a or the lower surface 1b of the RC beam 1, the leaf spring is deformed when the RC beam 1 is displaced, and is proportional to the displacement. Output can be obtained.

  On the other hand, the Doppler laser displacement meter outputs the displacement converted by integrating the velocity signal measured by the laser Doppler vibrometer. The laser Doppler vibrometer is a device that irradiates the RC beam 1 with a laser beam from a sensor head and receives the reflected laser beam.

  If the RC beam 1 vibrates due to loading, the laser beam reflected from the vibrating RC beam 1 is a Doppler-shifted laser beam, and a change in frequency (speed) is converted into a voltage and detected as a vibration phenomenon. can do. That is, the Doppler laser displacement meter is a displacement meter that converts a velocity signal measured by a non-contact vibration velocity sensor into a displacement signal and outputs the displacement signal.

  On the other hand, the loading of the bridge 10 on the RC girder 1 is performed by running the train T as shown in FIG. Here, in order to simplify the description, it is assumed that the train T is configured by connecting three vehicles T1-T3.

  When the RC girder 1 is loaded by the traveling of the train T, bending occurs such that the upper surface 1a of the RC girder 1 becomes the compression side and the lower surface 1b becomes the tension side. And since concrete has the characteristic in which the compressive strength is much larger than the tensile strength, the RC girder 1 is highly likely to crack on the tensile side (lower surface 1b side).

  Next, each step of the crack occurrence diagnosis method of the present embodiment will be described with reference to the flowchart of FIG. First, in step S <b> 1, the train T is caused to travel on the bridge 10 in which the displacement meter 2 is installed at the approximate center of the RC girder 1.

  As the train T travels, the RC girder 1 is bent, and the displacement at that time is continuously measured by the displacement meter 2 (step S2). A vibration waveform as shown in FIG. 4A can be generated from the measurement result of the displacement over time (step S3).

  In FIG. 4A, the horizontal axis indicates time, and the vertical axis indicates displacement. Further, in the displacement, the positive side (+) indicates the rise (negative bending) of the measurement point of the RC beam 1 and the negative side (−) indicates the settlement (positive bending) of the measurement point of the RC beam 1.

  The peak of the vibration waveform occurs when the train T passes. Referring to the train T schematically shown in FIG. 4A, the first peak W1 is generated by the passage of the first vehicle T1, and the next peak W2 appears by the passage of the second vehicle T2. The maximum peak W3 is obtained by passing the third vehicle T3.

  When a resonance waveform is obtained by loading with the train T, a large free vibration waveform appears as residual vibration after the train T passes. In the crack occurrence diagnosis method of the present embodiment, diagnosis is performed using the free vibration waveform that becomes the residual vibration.

  The vibration waveform can be divided into a positive side amplitude (negative bending region) and a negative side amplitude (positive bending region) with a line where the displacement becomes 0 value as a boundary, but the displacement measured by the displacement meter 2 is actually measured. Since there is a measurement error in the value, as shown on the right side of FIG. 4A, there may be a deviation d in which the zero value of the displacement does not become the center of the waveform.

  When the deviation d occurs in this way, zero-line correction is performed to match the displacement zero value with the center of the vibration waveform (step S4). In order to perform the zero-line correction, attention is first focused on a range where the response (amplitude width) of the vibration waveform is small.

  For example, as shown on the right side of FIG. 4A, an average value is calculated in a range where the amplitude falls between the deviation d and the zero value of the displacement, or the amplitude width is within 0.5 mm, and the average value is calculated. Is corrected for the free vibration waveform that becomes the residual vibration.

  FIG. 4B is a diagram showing a free vibration waveform (residual vibration) after zero line correction. The free vibration waveform is decomposed into a positive amplitude and a negative amplitude with a zero line of displacement as a boundary (step S5).

  FIG. 5A is a diagram showing the decomposed negative amplitude, and FIG. 5B is a diagram showing the decomposed positive amplitude. Each of the decomposed negative side amplitude and positive side amplitude can be regarded as a set of half wavelengths.

And the time interval of a half wavelength is called a half cycle. Since the free vibration waveform, which is residual vibration, gradually converges, the half cycle gradually decreases. Here, the time interval of the half wavelength of the negative amplitude is set as a half cycle M ₁ , M ₂ ,... M _n, and the time interval of the half wavelength of the positive amplitude is set as a half cycle P ₁ , P _2. ,... P _n ... (Step S6).

The frequency is calculated from the half periods M ₁ , M ₂ ,... M _n ... (Or half periods P ₁ , P ₂ ,... P _n ...) Calculated in this way. Can do. The frequency calculated for each half cycle is referred to as an instantaneous frequency f.

The instantaneous frequency f can be calculated by the following equation (step S7).
(Negative amplitude) f _M = 1 / (2M _n )
(For positive amplitude) f _P = 1 / (2P _n )

Then, the instantaneous frequencies f _M and f _P calculated for each half wavelength can be plotted at the time indicating each half wavelength, as shown in FIG. Moreover, the process so far can be performed by the diagnostic system (diagnostic apparatus) comprised with the computer in which the crack generation diagnostic program of this Embodiment was installed.

  FIG. 3 is a block diagram for explaining a crack occurrence diagnosis program. The input unit 3 is a unit that takes in the displacement measured by the displacement meter 2. For example, when the measurement values are collectively recorded on the storage medium, the means for reading the data from the storage medium is the input means 3. The input unit 3 may be a unit that captures the displacement measured by the displacement meter 2 in real time.

  The displacement taken into the diagnostic system by the input means 3 is sent to the calculation means 4. In the calculation means 4, a vibration waveform is generated from the displacement data with time, and the above-described zero-line correction processing is performed by the zero-line correction means 41 as necessary.

The vibration waveform in which the amplitude alternately appears on the positive side and the negative side with respect to the zero line is decomposed into a positive side amplitude and a negative side amplitude by the waveform decomposing means 42. Further, in the instantaneous frequency calculation means 43, each half period M ₁ , M ₂ ,... M _n (or P ₁ , P ₂ ,...) Of each half wavelength of the positive side amplitude and the negative side amplitude. P _n ...) Are calculated, and the instantaneous frequencies f _M and f _P are calculated from these values.

The instantaneous frequencies f _M and f _P calculated by the instantaneous frequency calculating means 43 are visualized by an output means 5 such as a monitor or a printer connected to a computer as shown in FIG. 6, for example. Note that the output means 5 may be a storage medium that records the calculated instantaneous frequencies f _M and f _P.

Based on the calculated instantaneous frequencies f _M and f _P of the positive side amplitude and the negative side amplitude, the crack occurrence degree of the RC digit 1 is determined (step S8). FIG. 6A is a diagram illustrating a calculation result determined to be healthy.

  As described above, the concrete structure (RC girder 1) can be estimated that the compression side of the concrete is in a healthy state, and when cracks are generated, the concrete structure (RC girders 1) is likely to be generated from the tension side.

When FIG. 6A is viewed based on this knowledge, the line drawn by the positive instantaneous frequency f _P plot and the line drawn by the negative instantaneous frequency f _M plot substantially coincide. . Moreover, these lines are substantially horizontal lines regardless of the magnitude of the amplitude.

  As a result, it can be judged that the tension side of the RC girder 1 is in the same sound state as the compression side of the concrete, and the crack occurrence degree is “no crack has occurred” or “a crack has occurred. Can be ignored ".

On the other hand, FIG. 6B is a diagram illustrating a calculation result determined to have cracks. Looking at this Figure, while the moment plot of frequency f _P of the positive side depicts a substantially horizontal line, the moment plot of frequency f _M of the negative side draw line, and the line of the lower left It has become.

That is, when the amplitude is large, the instantaneous frequency f _M of the instantaneous frequency f _P and the negative amplitude of the positive amplitude is separated, becomes a small value towards the instantaneous frequency f _M of the negative amplitude Yes. This separation disappears as the amplitude converges.

A decrease in the instantaneous frequency f (f _M , f _P ) indicates that there is damage or deterioration such as cracking in the concrete structure (RC girder 1) as well as a decrease in the natural frequency. Yes.

Further, since the spacing between the instantaneous frequency f _M of the instantaneous frequency f _P and the negative amplitude of the positive amplitude has disappeared with the convergence of the amplitude, the cracks, which closes with the convergence of the amplitude Can be estimated.

  Therefore, from the result of FIG. 6 (b), it can be determined that the tension side (the lower surface 1b side) of the RC girder 1 is in a damaged or deteriorated state. Can be determined.

  Next, the operation of the crack occurrence diagnosis method and crack occurrence diagnosis program of this embodiment will be described.

  The crack occurrence diagnosis method of the present embodiment configured as described above uses a vibration waveform generated from a displacement caused by a load (passing through the train T) in which the RC girder 1 bends as a positive amplitude and a negative amplitude. It breaks down into side amplitudes.

Then, the instantaneous vibration frequencies f _M and f _P are calculated from the decomposed positive side amplitude and negative side amplitude, and the crack occurrence state of the RC girder 1 is determined by comparing them.

  Here, the concrete structure in which bending is caused by loading can be presumed that the compression side of the concrete is in a healthy state, and if cracking occurs, there is a high possibility that it will occur from the tension side.

For this reason, the current displacement of the RC girder 1 that is bent by loading is continuously measured within a certain time range, and the vibration waveform obtained therefrom is decomposed into a positive amplitude and a negative amplitude. The crack occurrence state can be determined by simply comparing the instantaneous frequencies f _M and f _P.

  In short, according to the crack occurrence diagnosis method of the present embodiment, even if the state of the RC girder 1 at the time of sound, such as immediately after construction, has not been measured in advance, it cannot be visually confirmed, but the occurrence of a crack is suspected. Then, by measuring the displacement at the time of loading of the RC girder 1 at that time, it is possible to determine the presence or absence of a bending crack that occurs instantaneously.

  Here, the crack width that can be visually confirmed is said to be 0.2 mm or more. In recent years, with the development of prestressed concrete technology, the rigidity of girders can be reduced and the number of bridges with large dynamic response has increased. Appropriate evaluation is becoming necessary.

  In such a situation, if it is possible to determine the degree of occurrence of a crack with respect to a crack that opens instantaneously that cannot be visually confirmed, the soundness of the concrete structure can be accurately evaluated.

  And if the free vibration waveform used as a residual vibration after the loaded RC girder 1 resonates is used as a vibration waveform for performing such a diagnosis, the crack occurrence state can be easily determined.

  Even if there is an error in the measurement of displacement and the vibration waveform is shifted to the positive side or the negative side (deviation d), the vibration waveform is zero-line corrected using the average value calculated in a small response range. Thus, the vibration waveform can be decomposed into a positive amplitude and a negative amplitude.

  Furthermore, the crack occurrence diagnosis program according to the present embodiment includes waveform decomposition means 42 that decomposes a vibration waveform generated from a displacement caused by a load that causes bending of the RC girder 1 into a positive amplitude and a negative amplitude. ing.

Further, the instantaneous frequency calculation means 43 for calculating the respective instantaneous frequencies f _M and f _P from the decomposed positive side amplitude and negative side amplitude, and the calculated instantaneous frequencies f _M and f _P are output. Output means 5.

For this reason, it is calculated from the measurement result of the current displacement of the RC girder 1 where bending occurs due to loading, and only the instantaneous frequencies f _M and f _P of the positive and negative amplitudes output from the output means 5 are compared. Thus, it is possible to easily determine the crack occurrence status.

  The embodiment of the present invention has been described in detail above with reference to the drawings. However, the specific configuration is not limited to this embodiment, and design changes that do not depart from the gist of the present invention are not limited to this embodiment. Included in the invention.

  For example, although the RC girder 1 has been described as a concrete structure in the above-described embodiment, the present invention is not limited to this. The concrete structure can be applied.

  Moreover, although the load by passage of the train T was demonstrated as loading in the said embodiment, it is not limited to this, The case where a motor vehicle, earthquake motion, a wind, etc. are loaded as a load may be sufficient.

1 RC girder (concrete structure)
2 Displacement meter 3 Input means 4 Calculation means 41 Zero-line correction means 42 Waveform decomposition means 43 Instantaneous frequency calculation means 5 Output means f _M , f _P Instantaneous frequency M _n , P _n half cycle

Claims (7)

A method for diagnosing crack occurrence in a concrete structure in which bending occurs due to loading,
Performing a load that causes bending on the concrete structure;
Measuring the displacement caused by loading over time;
Decomposing the vibration waveform generated from the measured displacement into a positive amplitude and a negative amplitude;
Calculating each half period which is a time interval of each half wavelength constituting the positive side amplitude and the negative side amplitude, respectively;
Calculating an instantaneous frequency that is a frequency at the time when each half wavelength is generated from the half cycle;
A crack occurrence diagnosis method comprising: a step of determining a crack occurrence state of the concrete structure by comparing the instantaneous frequency of the positive amplitude and the instantaneous frequency of the negative amplitude.   The crack occurrence diagnosis method according to claim 1, wherein the vibration waveform is a free vibration waveform that becomes a residual vibration after the loaded concrete structure resonates.   In order to decompose the vibration waveform generated from the measured displacement into a positive amplitude and a negative amplitude, an average value is calculated in a predetermined range of the vibration waveform, and the average value is the vibration to be decomposed. The crack generation diagnosis method according to claim 1, further comprising a step of performing zero-line correction to set a waveform to a zero value.   The crack occurrence diagnosis method according to claim 3, wherein the predetermined range for calculating the average value is a small response range in which the amplitude width is within 0.5 mm.   The crack occurrence diagnosis method according to any one of claims 1 to 4, wherein the concrete structure is a long horizontal material, and the measured displacement is a vertical displacement.   5. The concrete structure according to claim 1, wherein the concrete structure is a girder member, and the measured displacement is a vertical displacement at a substantially center in a longitudinal direction of the girder member. Crack diagnosis method. A crack diagnosis program for a concrete structure that is bent by loading,
An input means for capturing a displacement over time caused by a load in which bending occurs with respect to the concrete structure;
Waveform decomposition means for decomposing a vibration waveform generated from the captured displacement into a positive amplitude and a negative amplitude;
Instantaneous vibration that is a frequency at the time when each half wavelength is generated from the half cycle by calculating a half period that is a time interval of each half wavelength that constitutes the positive side amplitude and the negative side amplitude, respectively. Instantaneous frequency calculating means for calculating the number;
A crack occurrence diagnosis program comprising output means for outputting the instantaneous frequency of the positive amplitude and the instantaneous frequency of the negative amplitude.