JP2000186984A - Abnormality detecting method of piers, and system, and recording medium for bridge - Google Patents

Abstract

PROBLEM TO BE SOLVED: To properly and regularly monitor variations in bridge pier supporting force due to scouring or the like to exactly announce/cancel operation regulation, by simple constitution and processing. SOLUTION: Fast Fourier transformation is applied by an FFT(fast Fourier transformation) processing part 4, to a detected data detected by an accelerometer 1 which is attached to a top end of a bridge pier P to provide Fourier spectra. An averaging processing part 5 addition-averages the Fourier spectra as to a prescribed time to find an average in the time, and finds a moving average on a frequency axis as to a prescribed frequency width, so as to smooth a Fourier spectrum waveform. A weighting processing part 6 weights the smoothed Fourier spectrum by a weight function, based on a response magnification curve of a single freedom system based on a transfer function of the pier P at sound state. An area calculating normalizing processing part 7 finds an areas surrounded by a curve of the weighted Fourier spectra and a base line to normalize it, so as to be used for comparison evaluation with a threshold by a normalization area reduction evaluating part 8.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a technique for detecting an abnormality in a pier, and more particularly to a technique for effectively detecting a decrease in pier support force due to scouring phenomena of a pier and monitoring and maintaining the bridge against river flooding. TECHNICAL FIELD The present invention relates to a pier abnormality detection method, system, and recording medium suitable for, for example, a pier.

[0002]

2. Description of the Related Art Bridges built on rivers are often
It constitutes a main route for transportation such as railroad tracks and roads. When the supporting capacity of the pier is reduced due to scouring phenomenon of the pier caused by the rising water of the river, the danger such as a decrease in the supporting capacity of the bridge is increased. Therefore, if the support capacity of the pier supporting the bridge is predicted to be reduced to a dangerous state due to scouring phenomena, railway operation regulations and traffic regulations for vehicles etc. will be implemented to prevent disasters before they occur. Will be issued. However, scouring of piers when the river rises is a phenomenon that proceeds under the surface of turbid currents, and it is difficult to visually monitor the situation.

[0003] In particular, in the case of railways, since the unit transport volume is large, during the passage of the bridge, the support capacity of the piers decreases, and so on.
If a bridge is damaged, there is a danger of a major disaster. For this reason, when it is anticipated that the bearing capacity of the piers will decrease, operation restrictions are imposed. Conventionally, a method of estimating a scouring depth from a water level by a hydraulic equation has been generally used. That is, the girder water level at which the stability of the pier is impaired is calculated, and the presence or absence of scour is determined.

[0004]

However, this method is only an estimation by calculation, and in a situation where complicated movements of flowing water are developed like an actual river, the riverbed lowering is difficult to predict by the estimation formula. Can cause disaster. For this reason, scouring detection devices for predicting dangers due to scouring have been studied in the past, but it is difficult for conventional devices to reliably perform scouring detection over a long period of time, and the reliability is poor. Was.

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and makes it possible to appropriately and constantly monitor a change in the supporting force of a pier caused by scouring or the like, with a simple configuration and processing. It is an object of the present invention to provide a method, a system and a recording medium for detecting an abnormality of a pier. In particular, an object of the present invention is to provide a pier abnormality detection method capable of monitoring and determining the supporting force of a pier more accurately than any conventional technique. An object of the invention described in claim 2 is to provide a method for detecting an abnormality of a bridge pier which can obtain a high detection accuracy and easily determine a state. An object of the invention described in claim 3 is to provide an abnormality detection system for a pier, which can be relatively easily configured, and can realize high safety and accurate determination.

It is an object of the present invention to provide a pier abnormality detection system which facilitates high-speed processing. An object of the invention described in claim 5 is, in particular, to provide a bridge pier abnormality detection system capable of clarifying required information among measurement information and improving substantial detection accuracy and detection speed. An object of the present invention described in claim 6 is to store a program for realizing an abnormality detection system for a pier that can be relatively easily configured and that can realize high security and accurate determination. It is to provide a computer-readable recording medium.

[0007]

According to a first aspect of the present invention, there is provided a method for detecting an abnormality of a pier according to the present invention. A weight setting step of setting a weighting spectrum substantially corresponding to a magnification curve; and an accelerometer disposed at the top end of the pier detects an acceleration of the pier at a constant fine motion, performs a fast Fourier transform, and performs a fast Fourier transform on the acceleration information. A fast Fourier transform step for obtaining a Fourier spectrum;
An averaging step of averaging in time and frequency the Fourier spectrum related to the constantly fine movement of the pier obtained in the fast Fourier transform step, and the weighting is performed on the Fourier spectrum averaged in the averaging step. A weighting step of performing weighting with a weighted spectrum of the bridge pier in the healthy state set by the setting step, and an area calculating step of determining an area of the spectrum weighted by the weighting step and normalizing the area of the weighted spectrum in the healthy state, An evaluation step of comparing the normalized area obtained in the area calculation step with a preset threshold value to evaluate the normalized area.

According to a second aspect of the present invention, in the pier abnormality detection method, the averaging step includes a time averaging step of sequentially averaging the Fourier spectrum for a predetermined time in the past, and the time averaging step. A smoothing step of obtaining a moving average over a predetermined frequency range for the Fourier spectrum averaged as needed.

In order to achieve the above-mentioned object, an abnormality detection system for a pier according to the third aspect of the present invention is provided at an upper end of the pier, and detects acceleration of the pier during a slight movement of the pier. A fast Fourier transforming means for obtaining a Fourier spectrum of the acceleration information from the acceleration information detected by the acceleration detecting means; and a Fourier spectrum related to the constantly fine movement of the pier obtained by the fast Fourier transforming means. Averaging means for averaging in frequency, and the Fourier spectrum averaged by the averaging means is weighted by a weighting spectrum substantially corresponding to a response magnification curve of a one-degree-of-freedom system based on a transfer function of a pier in a normal state. Weighting means for performing weighting, and determining the area of the spectrum weighted by the weighting means. An area calculating means for normalizing according to the area of the attached spectrum, and an evaluation means for evaluating the normalized area by comparing the normalized area obtained by the area calculating means with a preset threshold value. I have.

According to a fourth aspect of the present invention, in the pier abnormality detection system, the acceleration detecting means includes an accelerometer, and an output of the accelerometer is provided between the acceleration detecting means and the fast Fourier transform means. It is further characterized by further including a signal conditioner for adjusting a signal, and an analog-digital converter for converting an analog signal output from the signal conditioner into a digital signal. An abnormality detection system for a pier according to the invention as set forth in claim 5, wherein the averaging means is a time averaging means for averaging the Fourier spectrum sequentially for a predetermined time in the past, and
And a smoothing means for obtaining a moving average over a predetermined frequency range with respect to the Fourier spectrum averaged as needed by the time averaging means.

According to a sixth aspect of the present invention, there is provided a computer-readable recording medium in which a computer is provided at a top end of a pier, and a horizontal acceleration caused by a fine movement of the pier is provided to achieve the above object. Fast Fourier transforming means for obtaining a Fourier spectrum of the acceleration information from the acceleration information detected by the accelerometer for detecting the Fourier spectrum obtained by the fast Fourier transforming means relating to the constantly fine movement of the pier. Weighting means for weighting the Fourier spectrum averaged by the averaging means with a weighting spectrum substantially corresponding to a response magnification curve of a one-degree-of-freedom system based on a transfer function of a pier in a healthy state. Means, determine the area of the spectrum weighted by said weighting means, said healthy state Area calculation means for normalizing by the area of the spotting spectrum, and a program for functioning as evaluation means for evaluating the normalized area by comparing the normalized area obtained by the area calculation means with a preset threshold value. Have recorded.

[0012]

According to a first aspect of the present invention, there is provided a method for detecting an abnormality of a pier, which sets a weighting spectrum substantially corresponding to a response magnification curve of a one-degree-of-freedom system in advance based on a transfer function of a pier in a healthy state. The accelerometer disposed at the top of the pier detects the acceleration of the pier during the microtremor, performs a fast Fourier transform to obtain a Fourier spectrum of the acceleration information, and calculates the Fourier spectrum in terms of time and frequency. The Fourier spectrum averaged is weighted by a weighted spectrum of the pier at the time of sound, the area of the weighted spectrum is obtained, normalized by the area of the weighted spectrum at the time of sound, and The normalized area is compared and evaluated with a preset threshold. This makes it possible to quantitatively monitor and evaluate the bearing capacity of the pier based on microtremors at all times. With a simple configuration and processing, changes in the bearing capacity of the pier caused by scouring can be safely monitored. In addition, it is possible to monitor and determine more accurately and constantly than any conventional method, and it is possible to issue / cancel the operation regulation more accurately.

According to a second aspect of the present invention, in the method for detecting an abnormality of a pier, in the averaging, the Fourier spectrum is averaged sequentially for a predetermined time in the past, and the Fourier spectrum averaged as needed. about,
A moving average for a predetermined frequency range is obtained. In this way, it is possible to obtain a high detection accuracy particularly for the component related to the required natural vibration of the pier, and to facilitate the state determination.

According to a third aspect of the present invention, there is provided an abnormality detection system for a pier, wherein the acceleration detecting means provided at the top end of the pier detects the acceleration of the pier at a constant fine movement, and uses the fast Fourier transform means. After obtaining a Fourier spectrum of the acceleration information, and averaging the Fourier spectrum relating to the constantly fine movement of the pier temporally and frequencyly by averaging means, The weighting means performs weighting with a weighting spectrum substantially corresponding to a response magnification curve of a one-degree-of-freedom system based on a transfer function of a pier in a healthy state,
The area of the weighted spectrum is obtained by the area calculating means, normalized by the area of the weighted spectrum in the normal state, and the evaluation means evaluates the normalized area by comparing with a preset threshold value. With such a configuration, the pier supporting force can be quantitatively monitored and evaluated based on microtremors at all times. With a simple configuration and processing, supporting the pier caused by scouring while maintaining high safety can be achieved. It is possible to accurately and constantly monitor and determine the change in force, and it is possible to issue / cancel the operation regulation accurately.

According to a fourth aspect of the present invention, in the pier abnormality detection system, the acceleration detection means includes an accelerometer, and the output signal of the accelerometer is appropriately adjusted by a signal conditioner. To convert the analog signal into a digital signal and supply it to the fast Fourier transform means. With such a configuration, particularly, high-speed processing can be easily realized. An abnormality detection system for a pier according to the invention as set forth in claim 5, wherein the averaging means sequentially averages the Fourier spectrum for a predetermined time in the past by a time averaging means. , A moving average over a predetermined frequency range is obtained by the smoothing means. With such a configuration, in particular, it is possible to clarify required information of the measurement information and to substantially improve detection accuracy and detection speed.

According to a sixth aspect of the present invention, there is provided a computer-readable recording medium, wherein the computer is configured to execute a high-speed Fourier transform based on an acceleration in a microtremor of the pier detected by an accelerometer provided at a top end of the pier. A Fourier spectrum of the acceleration information is obtained by using a converting means, and a Fourier spectrum relating to the constantly tremor of the pier is averaged in time and frequency by an averaging means, and then the averaged Fourier spectrum is obtained. , Weighting is performed by a weighting spectrum by a weighting spectrum substantially corresponding to a response magnification curve of a one-degree-of-freedom system based on a transfer function of a bridge pier in a healthy state.
The area of the weighted spectrum is obtained, normalized by the area of the weighted spectrum at the time of soundness, and compared with a threshold set in advance by an evaluation means to function as a pier abnormality detection system for evaluating the normalized area. For recording programs. With such a recording medium, the supporting force of the pier can be quantitatively monitored and evaluated based on the microtremor using a computer, and scouring and the like can be performed while maintaining high safety by a simple configuration and processing. Thus, it is possible to accurately and constantly monitor and determine the change in the supporting force of the pier caused by the above, and it is possible to construct a system capable of accurately issuing / releasing the operation regulation.

[0017]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, based on an embodiment of the present invention, a pier abnormality detecting system of the present invention will be described in detail with reference to the drawings. FIG. 1 shows a configuration of an abnormality detection system for a pier according to one embodiment of the present invention. FIG.
Is an accelerometer 1, a signal conditioner 2, an analog-to-digital converter (hereinafter, referred to as an "A / D converter") 3, and a fast Fourier transform (FFT) processing unit. (Hereinafter, referred to as “FFT processing unit”) 4, averaging processing unit 5,
It comprises a weighting processing section 6, an area calculation normalization processing section 7, a normalized area reduction evaluation section 8 and an output section 9. Averaging section 5, weighting section 6, area calculation normalizing section 7
And the normalized area reduction evaluation unit 8 constitutes the evaluation processing unit 11, and includes the FFT processing unit 4, the output unit 9, and the evaluation processing unit 11.
Constitutes the observation processing device 12.

The accelerometer 1 constitutes an acceleration detecting means,
Attached to the top of the pier P, the acceleration fluctuation of the vibration of the pier P is constantly measured. Therefore, by accelerometer 1,
The microtremor of the pier P is always measured. The accelerometer 11 is configured using, for example, a strain gauge, a differential transformer, a semiconductor magnetic sensor, and the like. The signal conditioner 2 adjusts the signal level and waveform of the measurement output of the accelerometer 1,
Output an appropriate acceleration waveform. The A / D converter 3 converts an acceleration waveform, which is an analog signal output from the signal conditioner 2, into digital information and outputs the digital information.

The FFT processing section 4 is a fast Fourier transform means, and performs a fast Fourier transform on the output of the A / D converter 3 as a high-speed operation of a discrete Fourier transform by a computer to obtain a Fourier spectrum. . The averaging processing unit 5 is an averaging unit, and obtains a temporal average by adding and averaging the Fourier spectrum obtained by the FFT processing unit 4 for each frequency for a predetermined time set in advance. Further, the averaging processing unit 5 smoothes, that is, smoothes the Fourier spectrum waveform by obtaining a moving average on a frequency axis for a predetermined frequency width set in advance. Further, the averaging processing unit 5 normalizes the smoothed Fourier spectrum so that the maximum value in the entire frequency band is 1.0.

An example of a specific process in the averaging unit 5 will be described. The averaging unit 5 performs Hanning for each time history data of the acceleration measurement signal, for example, for 32 seconds.
ing) A Fourier spectrum obtained by applying a window function is obtained for, for example, data for the past 30 minutes, and each spectrum is averaged for each frequency to obtain a temporal average. A smoothing obtained by obtaining a moving average for each 6 Hz is normalized by the maximum value.

The weighting processing unit 6 is a weighting means. The Fourier spectrum smoothed and normalized by the averaging processing unit 5 is added to the transfer function H ( A weighting function substantially corresponding to the response magnification curve of the one-degree-of-freedom system based on f) is multiplied. The weighting function of the weighting processing unit 6 is typically a displacement transfer function, that is, when the vibration frequency (frequency) is fr and the natural vibration frequency of the pier P is fn, f = fr / fn, and the pier P The transfer function H _D (f) expressed by the following equation is used, where 減 衰 is the attenuation constant of.

[0022]

(Equation 1)

It should be noted that the damping constant ξ of the pier P is as follows: When the response at the natural vibration frequency fn is 1, the frequencies at which the response is attenuated to 1 / (2) ^1/2 are f1 and f2. (F1−f2) / 2fn (see FIG. 6B).

It is desirable that the weighting processing unit 6 further normalizes the Fourier spectrum multiplied by the weighting function with the maximum value when sound. The area calculation normalization processing unit 7 is an area calculation unit, and is an area of a region surrounded by the curve of the weighted Fourier spectrum obtained by the weighting processing unit 6 and the base line (hereinafter, simply referred to as “area of Fourier spectrum”).
That is, the integral value of the frequency of the weighted Fourier spectrum is obtained. The area calculation normalization processing unit 7 previously sets the area of the same weighted Fourier spectrum when the pier is healthy, and calculates the newly measured and calculated weighted Fourier spectrum by the area of the weighted Fourier spectrum when the pier is healthy. Normalize the area.

The normalized area reduction evaluation unit 8 is an evaluation unit, and evaluates the normalized weighted Fourier spectrum area obtained by the area calculation normalization processing unit 7 by comparing it with a preset threshold value. The evaluation processing unit 11 including the averaging processing unit 5, the weighting processing unit 6, the area calculation normalization processing unit 7, and the normalized area reduction evaluation unit 8 is the most characteristic part in the present invention. The output unit 9 outputs a warning signal or a warning signal when the supporting force of the pier P is reduced and the bridge pier P enters a dangerous state based on the evaluation result compared with the threshold value by the normalized area reduction evaluation unit 8. Urgent inspections and operation regulations.

The FFT processing unit 4, the averaging processing unit 5, the weighting processing unit 6, the area calculation normalization processing unit 7, the normalized area reduction evaluation unit 8, and the output unit 9, ie, the FFT processing unit
The processing unit 4, the output unit 9, and the evaluation processing unit 11 constitute an observation processing device 12, and the observation processing device 12 can execute all processing in software, and is usually a computer such as a personal computer. Configured by system.

Next, the operation and function of the pier abnormality detection system shown in FIG. 1 will be described in detail. The pier anomaly detection system of the present invention mounts the accelerometer 1 on the top end of the pier P of the bridge, detects the microtremor of the pier P constantly, and detects the pier P
Is to observe a decrease in the supporting force of the pier P due to a decrease in the natural vibration frequency of the bridge. The pier P is configured, for example, as shown in FIG. FIG. 2A is a front view of an example of the pier P, and FIG. 2B is a plan view thereof. The overall height of the pier P shown in FIG. 2 is about 7 m, and about 1.5 m at the lower end thereof is buried in the riverbed. The pier P has a lower end surface abutting on a solid ground such as a bedrock of a riverbed, and is buried with ordinary soil or the like up to about 1.5 m from the lower end surface.

Therefore, the supporting force of the pier P is about 1.5.
m depending on the depth of the buried part by soil or the like. When the burial depth becomes shallow due to scouring, etc., the bearing capacity gradually decreases,
Accordingly, the natural vibration frequency also decreases as the free vibration portion of the pier P increases. The signal due to the free tremor movement of the pier P, which is measured by the accelerometer 1 whose sensing direction is horizontally set at the top end of the pier P, for example, is conditioned by the signal conditioner 2 and A / D converted. It is digitized by the device 3 and supplied to the observation processing device 12 composed of a personal computer or the like.

The digital measurement signal of the microtremor supplied to the observation processing unit 12 is given to the FFT processing unit 4,
Fast Fourier transform processing, which is a high-speed processing method of discrete Fourier transform by computer processing, is performed, and a Fourier spectrum, which is a frequency spectrum of the microtremor of the pier P, is obtained. The Fourier spectrum obtained in the FFT processing unit 4 is subjected to the evaluation processing of the evaluation processing unit 11. FIG. 3 shows a flow of the evaluation processing by the evaluation processing unit 11, and FIGS. 4 and 5 show a healthy state, that is, an initial state before scouring, and a decrease in the supporting force of the pier due to the scouring, thereby lowering the natural vibration frequency. The process of each process in the state in which it was done is shown typically.

The evaluation processing shown in FIG.
Is periodically executed at predetermined time intervals by the evaluation processing unit 11. The Fourier spectrum obtained by the processing of the FFT processing unit 4 is continuously measured in a predetermined time unit, and the predetermined time is buffered. Specifically, the FFT processing unit 4 stores, for example, 32
A Fourier spectrum is repeatedly obtained based on the time history data for each second, and a predetermined past time of the Fourier spectrum is accumulated in a buffer (not shown). The Fourier spectrum provided to the evaluation processing unit 11 is supplied to the averaging processing unit 5, and the temporal average is calculated by adding and averaging the Fourier spectrum for each frequency for a predetermined time set in advance. (Step S11).
In step S11, a Fourier spectrum based on the time history data of the acceleration measurement signal is obtained for, for example, data for the past 30 minutes, and each spectrum is averaged for each frequency to obtain a temporal average.

Next, the averaging section 5 smoothes the Fourier spectrum waveform by obtaining a moving average on the frequency axis for a predetermined frequency width set in advance (step S12). In step S12, step S
For example, a moving average at every 0.6 Hz of the Fourier spectrum averaged at 11 is obtained and smoothed. Desirably, in step S12, the smoothed Fourier spectrum is further normalized with its maximum value.
FIG. 4 (a) shows a Fourier spectrum in a healthy state smoothed and normalized in this way, and FIG. 5 (a) shows a Fourier spectrum in a state in which the bearing capacity is reduced due to smoothing and normalized scouring. The spectrum is shown.

The weighting processor 6 converts the Fourier spectrum smoothed and normalized by the averaging processor 5 in step S12 into a transfer function H (f) of the pier P obtained by an impact vibration test of the pier P in a normal state. Are multiplied by a weighting function substantially corresponding to the response magnification curve of the one-degree-of-freedom system based on the above (Step S13). FIG. 4 (b) and FIG.
(B) shows an example (same waveform) of the transfer function H (f) in a healthy state before scouring used for such weighting. The weighting function used in step S13 is typically the displacement transfer function shown in Expression 1, and is set beforehand when it is sound and obtained by an impact vibration test of the pier P in advance. As the weighting function, a function having a peak position at a frequency common to the peak position of the response magnification curve of the one-degree-of-freedom system of the pier P and gradually decreasing as the distance from the peak frequency is used.

In this case, as the weighting function, in this case, the displacement transfer function H _D (f) shown in Expression 1, that is, FIG.
As shown in the figure, the frequency f = 1, which is the maximum value, is centered, and gradually decreases to a finite value on the low frequency side (f <1), and gradually decreases to zero on the high frequency side (f> 1). Use a weighting function. As the weighting function, in addition to the above, a function obtained by combining the velocity transfer function H _V (f), the acceleration transfer function H _A (f), the displacement transfer function H _D (f), and the acceleration transfer function H _A (f), etc. Can be used. The velocity transfer function H _V (f) is expressed by the following equation (2). As shown in FIG. 7, the frequency transfer function H _V (f) has a characteristic that the frequency f = 1, which is the maximum value, is centered on the low frequency side and the high frequency side. Have.

[0034]

[Number 2] _{H V (f) = f ·} H D (f) acceleration transfer function H _A (f) is represented by the number 3, the center frequency f = 1 to the maximum value as shown in FIG. 8 On the low frequency side, it gradually decreases to zero, and on the high frequency side, it gradually decreases to a finite value.

[0035]

H _A (f) = f ² · H _D (f) The weighting function combining the displacement transfer function H _D (f) and the acceleration transfer function H _A (f) has a low frequency side (f <1 )), The acceleration transfer function H _A (f) is used, and the high-frequency side (f
> 1) uses the displacement transfer function H _D (f) and has the characteristic shown in FIG.

The weighting process in step S13 is as follows.
The weighting function mainly related to the natural vibration of the pier P in a healthy state acts to emphasize the natural vibration element of the Fourier spectrum, and the waveform (area) of the weighted spectrum as the natural vibration frequency departs (decreases) from the healthy state. However, it is significantly reduced. In step S13, it is desirable that the Fourier spectrum multiplied by the weighting function in the weighting processing unit 6 be further normalized by the maximum value when sound.

FIG. 4C shows a weighted Fourier spectrum after weighting in a healthy state. FIG. 5 (c) shows a weighted Fourier spectrum after weighting in a state where the supporting force is reduced by scouring, and the scouring clearly reduces the weighted Fourier spectrum. The area calculation normalization processing unit 7 obtains the area of the weighted Fourier spectrum (integrated value of the frequency of the weighted Fourier spectrum) obtained in step S13 (step S14). The area calculation normalization processing unit 7 sets in advance the area of the weighted Fourier spectrum when the pier is sound, and uses the area of the weighted Fourier spectrum obtained in step S14 as a reference based on the area of the weighted Fourier spectrum when sound. (Step S15).

That is, as shown in FIG. 4D, the area S of the weighted Fourier spectrum in a healthy state is expressed as S =
As shown in FIG. 5D, the area S = 0.3 of the weighted Fourier spectrum in a state where the supporting force is reduced by scouring as shown in FIG. Normalized area reduction evaluation unit 8
Evaluates by comparing the normalized weighted Fourier spectrum area obtained in step S15 with a preset threshold value (step S16). Normalized area reduction evaluation unit 8
Determines the result of the comparison between the normalized weighted Fourier spectrum area and the threshold (step S17), and if the normalized weighted Fourier spectrum area is smaller than the threshold, the supporting force of the pier P decreases. Since it is in a dangerous state, an alarm and a warning signal are output via the output unit 9 (step S18), and the process is terminated to return to the standby state.

If the normalized weighted Fourier spectrum area is equal to or larger than the threshold value in step S17, the supporting force of the pier P is maintained in the normal range.
It returns to the standby state without any action without issuing an alarm.
The output of the warning or warning signal by the output unit 9 based on the evaluation result compared with the threshold value by the normalized area reduction evaluation unit 8 indicates that the support force of at least the pier P is reduced as described above. It is used to encourage detailed inspections and operation regulations. However, since the normalized area obtained in the above is for quantitatively evaluating the bearing capacity corresponding to scouring of the pier P, threshold values corresponding to several bearing capacity levels are further set,
A signal for instructing inspection or the like according to each state may be output. The above-described evaluation processing can be realized as a hardware device or a system by configuring each function by hardware, but is suitable for being realized by a computer program using software.

The effectiveness of the pier abnormality detection system according to the present invention described above will be verified based on experiments conducted by the present inventors. 15cm (length) × 30 as a pier model
9 cm (width) x 90 cm (height)
As shown in FIG. 10, the lower part of the pier model was excavated at a predetermined depth in order to simulate scouring by embedding about 40 cm of the lower part in the soil to make it sound healthy. In each state, an impact vibration test and a microtremor measurement based on the present invention were performed, and a vibration transfer function of the pier model PM and an acceleration Fourier spectrum of the microtremor were obtained for each excavation depth.

FIGS. 11 to 14 show transfer functions detected by an accelerometer at the top of a pier by performing an impact vibration test on the pier model described above, and show waveforms of response magnification. Among them, FIG. 11 shows the characteristics in a healthy state without excavation, FIG. 12 shows the characteristics when the excavation depth is 15 cm, FIG. 13 shows the characteristics when the excavation depth is 30 cm, and FIG. This is a characteristic in the case of 40 cm, and this response magnification is normalized by the maximum value in each test. In calculating the natural vibration frequency of the pier model, a change in the phase characteristic curve of the one-degree-of-freedom system was applied to a phase characteristic curve (not shown) to determine a position where the phase was shifted by -90 °.

FIG. 15 shows the relationship between the excavation depth and the natural vibration frequency at each number of tests, obtained from the results of the shock vibration test when such excavation and backfilling were performed three times. According to FIGS. 11 to 14 and 15, it is understood that the natural vibration frequency gradually decreases as the excavation depth increases. Next, the averaging Fourier spectrum of the microtremor for the same pier model was verified. The averaging Fourier spectrum in this case is about 32
A Fourier spectrum obtained by multiplying a Hanning window function for each second of the time history data for seconds is obtained for all data for about 30 minutes, and these spectra are averaged for each frequency.

FIG. 16 shows (a) a healthy state where no excavation is performed, (b) an excavation depth of 15 cm, (c) an excavation depth of 3
0d, and (d) the averaged Fourier spectrum of the microtremor at an excavation depth of 40cm is about 0.
The characteristics smoothed by the 6 Hz width moving average are shown by solid lines, and the one-degree-of-freedom response magnification curves obtained based on the transfer function of the impact vibration test at the excavation depth of 0 cm are shown by broken lines. FIG. 16 is a graph normalized by the maximum value at each excavation depth. The peak position of the solid line in FIG. 16 substantially corresponds to the frequency of the natural vibration, and the peak position moves with the change in the natural vibration frequency depending on the excavation depth.

FIG. 17 shows each state of FIG. 16, that is, (a) a healthy state where no excavation is performed, and (b) an excavation depth 15c.
m, (c) the digging depth of 30 cm, and (d) the averaging spectrum at the digging depth of 40 cm, which is weighted by the one-degree-of-freedom response magnification curve. The values are normalized by a value of 0 cm. FIG. 18 shows the change in the area of the weighted spectrum at each excavation depth in (a) to (d) of FIG. 17, which is also normalized by the sound state, that is, the value of the excavation depth of 0 cm. The change in the area of the weighted spectrum shown in FIG. 18 depending on the excavation depth corresponds to the change in the natural vibration frequency in the shock vibration test shown in FIG. 15, and the change is more remarkably shown.

From the results shown in FIGS.
When the area comparison of the weighted spectrum according to the present invention is used, the rate of decrease in the area of the weighted Fourier spectrum due to excavation decreases at a rate of approximately the square of the rate of decrease in the natural vibration frequency. It is clear that the sensitivity for detection is improved. In reality, a bridge is not a single pier, but a plurality of piers are connected by a girder, and the measured Fourier spectrum is affected by the vibration characteristics of the girder and neighboring piers connected by the girder. Will be. However, in such a case, the influence of the vibration of the target pier on which the measurement accelerometer is installed is the most remarkable, and components other than the characteristics related to the vibration of the target pier are effectively suppressed by appropriate weighting. You. Therefore, compared to the measurement of the natural vibration frequency by the shock vibration test, the girder and the neighboring piers connected by the girder are less susceptible to the influence, so that a very effective measurement and monitoring can be performed.

The pier abnormality detection system of the present invention can be realized by using a general-purpose computer system instead of being configured as a dedicated system. For example, a floppy disk storing a program for executing the above-described processing is provided. By installing the program in a computer system from a recording medium such as a disk, CD-ROM, or DVD-ROM, an abnormality detection system for a pier that realizes the above-described functions can be configured. The installed program is stored in a storage medium such as a hard disk in the computer system and used for execution, whereby the computer system constructs a pier abnormality detection system.

The medium for supplying the program to the computer is not limited to a recording medium in a narrow sense, but also includes a communication medium such as a communication line for temporarily and fluidly storing information such as a program. It may be a storage medium.
Further, it goes without saying that the present invention is not limited to the embodiments described above and shown in the drawings, and can be carried out in various modifications without departing from the gist thereof.

[0048]

As described above, according to the present invention, a weighting spectrum substantially corresponding to the response magnification curve of the one-degree-of-freedom system is set in advance based on the transfer function of the pier in a normal state, and the weighted spectrum is set at the top of the pier. With the accelerometer arranged, the acceleration of the pier in the constant micromotion is detected, a fast Fourier transform is performed to obtain a Fourier spectrum of the acceleration information, and the Fourier spectrum is averaged in time and frequency. The averaged Fourier spectrum is weighted by a weighted spectrum of the pier in the healthy state to obtain an area of the weighted spectrum, normalized by the area of the weighted spectrum in the healthy state, and the normalized area is By comparing and evaluating with a preset threshold value, it is possible to quantitatively monitor and evaluate the supporting force of the pier quantitatively based on microtremors. With a simple configuration and processing, it is possible to appropriately and constantly monitor a change in the supporting force of a pier caused by scouring and the like without danger, and to accurately issue / cancel operation regulations. An abnormality detection method, system, and recording medium for a pier can be provided.

In particular, according to the first aspect of the present invention, it is possible to provide a pier abnormality detecting method capable of monitoring and determining the supporting force of a pier more accurately than any conventional technique. According to the pier abnormality detection method according to the second aspect of the present invention, in the averaging, the Fourier spectrum is averaged sequentially for a predetermined time in the past, and the Fourier spectrum averaged as needed is By obtaining a moving average over a predetermined frequency range, in particular,
It is possible to obtain a high detection accuracy for a component related to the required natural vibration of the pier, and to facilitate the state determination.

According to the pier abnormality detecting system according to the third aspect of the present invention, the acceleration in the microtremor of the pier is detected by the acceleration detecting means provided at the top end of the pier, and the fast Fourier transform means is used. The Fourier spectrum of the acceleration information is obtained using the Fourier spectrum, and the Fourier spectrum related to the microtremor of the pier is averaged in time and frequency by averaging means. The weighting means weights a weighted spectrum substantially corresponding to the response magnification curve of the one-degree-of-freedom system based on the transfer function of the pier in a healthy state, and the area of the weighted spectrum is obtained by the area calculating means. Normalized by the area of the weighted spectrum of, in the evaluation means, compared with a preset threshold, The arrangement for evaluating a normalized area,
The pier support capacity can be quantitatively monitored and evaluated based on microtremors at all times, and with a simple configuration and processing, changes in pier support capacity due to scouring etc. can be accurately maintained while maintaining high safety. In addition, it is possible to constantly monitor and determine, and it is possible to issue / cancel the operation regulation accurately.

According to the system for detecting abnormality of a pier according to the fourth aspect of the present invention, the acceleration detecting means includes an accelerometer, and the accelerometer output signal is appropriately adjusted by a signal conditioner, and is converted into an analog-digital signal. In particular, high-speed processing can be easily realized by a configuration in which an analog signal is converted into a digital signal by a device and supplied to the fast Fourier transform means. According to the abnormality detection system for a pier according to the invention of claim 5, the averaging means averages the Fourier spectrum sequentially for a predetermined time in the past by the time averaging means. , By the smoothing means,
With the configuration for calculating the moving average in the predetermined frequency range, it is possible to clarify the necessary information among the measurement information and improve the substantial detection accuracy and the detection speed.

According to the computer-readable recording medium of the present invention, the computer can be controlled at a high speed based on the acceleration in the fine movement of the pier detected by the accelerometer provided at the top end of the pier. A Fourier spectrum of the acceleration information is obtained using Fourier transform means, and a Fourier spectrum relating to the microtremor of the pier is averaged temporally and frequencyly by the averaging means, and then the averaged Fourier spectrum is obtained. The spectrum is weighted by a weighting means with a weighting spectrum substantially corresponding to a response magnification curve of a one-degree-of-freedom system based on a transfer function of a pier in a healthy state, and the area of the weighted spectrum is calculated by an area calculating means. Normalized by the area of the weighted spectrum obtained at the time of sound, the evaluation means Compared to preset threshold value,
By recording a program for functioning as a pier abnormality detection system for evaluating the normalized area, using a computer, it is possible to quantitatively monitor and evaluate the supporting force of the pier based on microtremors, With a simple configuration and processing, it is possible to accurately and constantly monitor and judge changes in the bearing capacity of piers due to scouring while maintaining high safety, and to accurately issue / cancel operation regulations. It is possible to construct a system that can perform the operation.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of an abnormality detection system for a pier according to one embodiment of the present invention.

2 shows an example of a pier which is an object of the pier abnormality detection system of FIG. 1, in which (a) is a front view and (b) is a plan view. FIG.

FIG. 3 is a flowchart showing a flow of an evaluation process in the abnormality detection system for a pier in FIG. 1;

4A and 4B show a smoothed Fourier spectrum corresponding to a healthy state (initial state) without scouring, and FIG. 4B shows a transfer function for weighting, for explaining the operation of the pier abnormality detection system of FIG. It is a schematic diagram which respectively shows (c) weighted Fourier spectrum and (d) normalized area S.

FIGS. 5A and 5B show the operation of the pier abnormality detection system of FIG. 1 corresponding to a state where the natural vibration frequency is reduced by scouring, and FIG.
It is a schematic diagram which respectively shows the transfer function for weighting, (c) weighted Fourier spectrum, and (d) normalized area S.

6A is a schematic waveform diagram showing a displacement transfer function used for weighting in the pier abnormality detection system of FIG. 1, and FIG. 6B is a schematic diagram for explaining a damping constant thereof.

FIG. 7 is a schematic waveform diagram showing a speed transfer function that can be used for weighting instead of the displacement transfer function in the pier abnormality detection system of FIG. 1;

FIG. 8 is a schematic waveform diagram showing an acceleration transfer function that can be used for weighting in place of the displacement transfer function in the pier abnormality detection system of FIG. 1;

9 is a schematic diagram showing a pier model used in an experiment for verifying the operation of the pier abnormality detection system of FIG. 1 and a cross-section for explaining an excavation state thereof.

FIG. 10 is a schematic perspective view showing a mounting position of a pier model and an accelerometer in the experiment of FIG. 9;

FIG. 11: Excavation depth 0c of the pier model of FIGS. 9 and 10
FIG. 6 is a diagram showing a waveform of a response magnification of a transfer function detected by an accelerometer at the top of a pier in an impact vibration test in a healthy state of m.

FIG. 12: Excavation depth 15 of the pier model of FIGS. 9 and 10
It is a figure which shows the waveform of the response magnification of the transfer function detected by the accelerometer of the pier top part in the shock vibration test in the state of cm.

FIG. 13 shows the excavation depth 30 of the pier model of FIGS. 9 and 10.
It is a figure which shows the waveform of the response magnification of the transfer function detected by the accelerometer of the pier top part in the shock vibration test in the state of cm.

FIG. 14 shows the excavation depth 40 of the pier model of FIGS. 9 and 10.
It is a figure which shows the waveform of the response magnification of the transfer function detected by the accelerometer of the pier top part in the shock vibration test in the state of cm.

FIG. 15 is a diagram showing the relationship between the excavation depth and the natural vibration frequency obtained in the shock vibration test of the pier models of FIGS. 9 and 10;

FIG. 16: (a) healthy state without digging, (b) digging depth of 15 cm of the pier model of FIGS. 9 and 10,
(C) One-degree-of-freedom response obtained based on a smoothed Fourier spectrum of each microtremor and a transfer function of an impact vibration test at an excavation depth of 0 cm at an excavation depth of 30 cm and at an excavation depth of 40 cm. It is a figure which shows a magnification curve respectively.

FIG. 17 shows the bridge pier model shown in FIGS. 9 and 10 in the case of (a) a sound state without digging, and (b) a digging depth of 15 cm.
(C) When the excavation depth is 30 cm, and (d) When the excavation depth is 40 cm, the averaged spectrum of each microtremor is 1
It is a figure which shows the curve weighted by the degree-of-freedom response magnification curve, respectively.

FIG. 18 is a diagram showing a change in the area of a weighted spectrum at each excavation depth of the pier model of FIGS. 9 and 10;

[Explanation of symbols]

 Reference Signs List 1 accelerometer 2 signal conditioner 3 A / D (analog-digital) converter 4 FFT (fast Fourier transform) processing unit 5 averaging processing unit 6 weighting processing unit 7 area calculation normalization processing unit 8 normalized area reduction evaluation Part 9 Output part 11 Evaluation processing part 12 Observation processing device P Pier PM Pier device

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Junichi Tanaka 2-2-2 Yoyogi, Shibuya-ku, Tokyo East Japan Railway Company (72) Inventor Mitsugu Sakata 3-chome, Chofugaoka, Chofu City, Tokyo F-5 term at Kyowa Dengyo Co., Ltd. (Reference) 2D059 AA03 2G024 AD34 BA27 CA11 FA04 FA06 FA11

Claims (6)

[Claims] 1. Based on a transfer function of a bridge pier in a healthy state,
A weight setting step for setting a weighting spectrum substantially corresponding to the response magnification curve of the degree of freedom system; and an accelerometer arranged at the top end of the pier detects acceleration in the microtremor of the pier and performs fast Fourier transform. A fast Fourier transform step of obtaining a Fourier spectrum of the acceleration information, and an averaging step of temporally and frequency averaging the Fourier spectrum related to the constantly tremor of the pier obtained in the fast Fourier transform step. A weighting step of weighting the Fourier spectrum averaged in the averaging step with a weighted spectrum of the pier in a healthy state set in the weight setting step; and obtaining an area of the spectrum weighted in the weighting step. Time weighted spectrum An abnormality of a pier, comprising: an area calculation step of normalizing by area; and an evaluation step of evaluating the normalized area by comparing the normalized area obtained in the area calculation step with a preset threshold. Detection method. 2. The averaging step includes: a time averaging step of sequentially averaging the Fourier spectrum for a predetermined time in the past; and a Fourier spectrum averaged as needed in the time averaging step. 2. The method according to claim 1, further comprising a smoothing step of obtaining a moving average. 3. An acceleration detecting means disposed at the top end of the pier, for detecting acceleration of the pier during constant fine movement, and a fast Fourier for obtaining a Fourier spectrum of the acceleration information from the acceleration information detected by the acceleration detecting means. Conversion means; averaging means for averaging temporally and frequency-wise a Fourier spectrum related to the constantly fine movement of the pier obtained by the fast Fourier transformation means; and the Fourier spectrum averaged by the averaging means. Weighting means for performing weighting with a weighting spectrum substantially corresponding to a response magnification curve of a one-degree-of-freedom system based on a transfer function of a pier in a healthy state; and determining the area of the spectrum weighted by the weighting means. Area calculating means for normalizing according to the area of the spectrum; and The normalized area compared with preset thresholds, the abnormality detection system of piers, characterized in that it comprises an evaluation means for evaluating the normalized area. 4. A signal conditioner including an accelerometer, wherein a signal conditioner for adjusting a signal of an accelerometer output is provided between the acceleration detector and the fast Fourier transform means, and an output of the signal conditioner. An analog-to-digital converter for converting an analog signal to a digital signal;
The pier abnormality detection system according to claim 3, further comprising: 5. The averaging means, comprising: a time averaging means for averaging the Fourier spectrum sequentially for a predetermined time in the past; and a Fourier spectrum averaged as needed by the time averaging means for a predetermined frequency range. 5. The pier abnormality detection system according to claim 3, further comprising a smoothing means for obtaining a moving average. 6. A high-speed Fourier transforming means for disposing a computer at a top end of a pier and obtaining a Fourier spectrum of the acceleration information from acceleration information detected by an accelerometer for detecting a horizontal acceleration of the pier at a constant fine movement. Averaging means for averaging temporally and frequency-wise the Fourier spectrum related to the constantly fine movement of the pier obtained by the fast Fourier transforming means; Weighting means for weighting with a weighting spectrum substantially corresponding to a response magnification curve of a one-degree-of-freedom system based on a transfer function of a bridge pier, and obtaining an area of a spectrum weighted by the weighting means, and normalizing the area of the weighting spectrum in a healthy state. Area calculating means, and obtained by the area calculating means Compared to preset threshold-normalized area, computer-readable recording medium storing a program to function as an evaluation means for evaluating the normalized area.