Damage diagnosis device, damage diagnosis method, and recording medium in which damage diagnosis program is stored

A damage diagnosis device is provided with: a detection unit for detecting that, immediately after a vehicle crossing a bridge has exited from the bridge, another vehicle is not crossing the bridge; a determination unit for determining whether the weight of the vehicle satisfies a criterion; and a diagnosis unit that, when the detection unit has detected that no other vehicle is crossing the bridge and the determination unit has determined that the weight of the vehicle satisfies the criterion, diagnoses damage to the bridge on the basis of information representing free vibration generated in the bridge due to the crossing of the vehicle, thereby improving the precision of diagnosis when damage to a bridge is diagnosed on the basis of information representing free vibration generated in the bridge due to the crossing of a vehicle.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a National Stage of International Application No. PCT/JP2018/044341 filed Dec. 3, 2018, claiming priority based on Japanese Patent Application No. 2017-234804 filed Dec. 7, 2017, the disclosure of which is incorporated herein in its entirety by reference.

TECHNICAL FIELD

The invention of the present application relates to a technique of diagnosing damage occurring in a bridge, based on information representing free vibration occurring in the bridge due to crossing of a vehicle.

BACKGROUND ART

Expectation has been rising for a technique of more accurately diagnosing damage occurring in a structure, in such a way that occurrence of an accident resulting from damage occurring in an aging structure such as a bridge can be prevented.

As a technique pertaining to such a technique, PTL 1 discloses a structure state determination device including a vibration detection means for detecting vibration of a structure, and a calculation means for performing calculation processing with regard to vibration waveform data acquired by the vibration detection means. The calculation means in this device performs an attenuated waveform analysis, and determines, based on a result of the analysis, a state of the structure, with regard to vibration waveform data at and after a time point when an absolute value of a peak is maximum in the vibration waveform data.

PTL 2 discloses a crack occurrence diagnosis method for a concrete structure to which strain is caused by a load. This diagnosis method performs, on a concrete structure, loading by which strain occurs, and measures, with time, displacement caused by the loading. This method resolves a vibration waveform generated from the measured displacement into a positive-side amplitude and a negative-side amplitude, and calculates each half cycle being a time interval of each half wavelength constituting each of the positive-side amplitude and the negative-side amplitude. Then, this method calculates, from the half cycle, an instantaneous frequency being a frequency at a time point when each half wavelength occurs, and determines a crack occurrence situation of the concrete structure by comparing the instantaneous frequency of the positive-side amplitude with the instantaneous frequency of the negative-side amplitude.

PTL 3 discloses a road monitoring system that detects, by use of one kind of sensor, the number of vehicle passages, a traveling speed, and vehicle weight, being necessary for road management. This system includes vibration sensors being placed in a roadbed of a road, and spaced apart from each other in a traveling direction of a vehicle, and derives the number of vehicle passages by counting the number of vibration detections by the vibration sensors. This system also derives a traveling speed of a vehicle, based on a detection time difference between the vibration sensors, and further estimates weight of the vehicle, based on magnitude of an amplitude of detected vibration and the traveling speed.

PTL 4 discloses a characteristic display system that visualizes and displays vibration measurement data relating to physical quantities such as displacement, a speed, acceleration, and sound pressure in a measured target such as a rotor or a vibrator. This system removes, minimizes, or extracts a specific vibration component in the measured target from the measurement data, and then displays the measurement data on a Campbell diagram.

CITATION LIST

Patent Literature

Non Patent Literature

SUMMARY OF INVENTION

Technical Problem

A general structure changes in a mechanical characteristic (rigidity, viscosity, or the like) thereof due to occurrence and advance (aggravation) of damage, and therefore, damage occurring in a structure can be diagnosed by concentrating on vibration occurring in the structure. When a damage diagnosis target is a bridge, damage can be diagnosed by measuring free vibration occurring in the bridge after a vehicle crosses the bridge, for example, as described in NPL 1.

However, when diagnosing damage to a bridge by the method described above, there is fear that a wrong diagnosis is made due to the following factors. Specifically, when, in a state where free vibration occurs in a bridge after a vehicle crosses the bridge, another vehicle (a vehicle behind the former vehicle) travels on the bridge, vibration occurring due to the traveling of the another vehicle is mixed into the free vibration, and therefore, it becomes difficult to accurately measure the free vibration. Alternatively, when the vehicle is not, for example, a large-size vehicle (weight thereof does not satisfy a criterion), free vibration that occurs is small, and thus, it becomes difficult to extract, with high precision, a change in a mechanical characteristic of a bridge being indicated by the free vibration.

Specifically, the present inventors have found out that elimination of the above-described factor of a wrong diagnosis is a problem when diagnosing damage to a bridge by measuring free vibration occurring in the bridge after a vehicle crosses the bridge. PTLs 1 to 4 do not refer to this problem. A main object of the invention of the present application is to provide a damage diagnosis device and the like that solve this problem.

Solution to Problem

A damage diagnosis device according to one aspect of the invention of the present application includes: a detection means for detecting that, after a vehicle crossing a bridge exits from the bridge, crossing of another vehicle over the bridge does not occur; a determination means for determining whether weight of the vehicle satisfies a criterion; and a diagnosis means for diagnosing damage to the bridge, based on information representing free vibration occurring in the bridge due to crossing of the vehicle, when the detection means detects that crossing of the another vehicle over the bridge does not occur and the determination means determines that the weight of the vehicle satisfies the criterion.

In another viewpoint of achieving the object described above, a damage diagnosis method according to one aspect of the invention of the present application includes: by an information processing device, detecting that, after a vehicle crossing a bridge exits from the bridge, crossing of another vehicle over the bridge does not occur; determining whether weight of the vehicle satisfies a criterion; and diagnosing damage to the bridge, based on information representing free vibration occurring in the bridge due to crossing of the vehicle, when detecting that crossing of the another vehicle over the bridge does not occur and determining that the weight of the vehicle satisfies the criterion.

In still another viewpoint of achieving the object described above, a damage diagnosis program according to one aspect of the invention of the present application is a program causing a computer to execute: detection processing of detecting that, after a vehicle crossing a bridge exits from the bridge, crossing of another vehicle over the bridge does not occur; determination processing of determining whether weight of the vehicle satisfies a criterion; and diagnosis processing of diagnosing damage to the bridge, based on information representing free vibration occurring in the bridge due to crossing of the vehicle, when the detection processing detects that crossing of the another vehicle over the bridge does not occur and the determination processing determines that the weight of the vehicle satisfies the criterion.

Furthermore, the invention of the present application is also achievable by a computer-readable non-volatile recording medium in which the damage diagnosis program (computer program) is stored.

Advantageous Effects of Invention

The invention of the present application enables improvement in diagnosis precision, when diagnosing damage occurring in a bridge, based on information representing free vibration occurring in the bridge due to crossing of a vehicle.

EXAMPLE EMBODIMENT

Hereinafter, example embodiments of the invention of the present application will be described in detail with reference to the drawings.

First Example Embodiment

FIG.1is a block diagram conceptually illustrating a configuration of a damage diagnosis system1according to a first example embodiment of the invention of the present application. The damage diagnosis system1broadly includes a damage diagnosis device10, acceleration sensors30-1to30-n(n is any integer equal to or more than 3), and a measurement data aggregator31. Note that there exist a total of at least three acceleration sensors30-1to30-nincluding those that are placed in the vicinity of expansion/contraction devices21and22, and those that collect measurement data relating to information (an acceleration time history characteristic) representing an acceleration-time-history-waveform140used when a diagnosis unit13performs diagnosis, as described later. The acceleration-time-history-waveform140, inclusive of information representing the acceleration-time-history-waveform140, is hereinafter simply referred to as the acceleration-time-history-waveform140in the present application. The damage diagnosis device10is a device that diagnoses damage occurring in the bridge20. The damage diagnosis device10diagnoses damage occurring in the bridge20, based on data acquired by measuring free vibration occurring in the bridge20after a vehicle41crosses the bridge20.

In the present example embodiment, it is assumed, for convenience of description, that a traveling direction of the vehicle41traveling on the bridge20is one direction, and a vehicle facing the vehicle41(traveling in a direction opposite to the vehicle41) travels, for example, on a bridge different as a structure from the bridge20. The expansion/contraction device21is placed in a part where the vehicle41enters (goes into) the bridge20, and the expansion/contraction device22is placed in a part where the vehicle41exits (goes out) from the bridge20. The expansion/contraction devices21and22are placed on road surface ends of the bridge20(an entrance part onto the bridge20and an exit part from the bridge20), and are devices that absorb expansion/contraction of the bridge20resulting from a temperature change, deformation of the bridge20due to crossing of the vehicle41, and the like.

As exemplified inFIG.1, the acceleration sensor30-1is placed in the vicinity of the expansion/contraction device21, and the acceleration sensor30-nis placed in the vicinity of the expansion/contraction device22. The acceleration sensor other than the acceleration sensors30-1and30-namong the acceleration sensors30-1to30-nis placed in any part between the expansion/contraction device21and the expansion/contraction device22on the bridge20. The acceleration sensors30-1to30-nare sensors capable of measuring acceleration at which the bridge20vibrates. Specifically, the acceleration sensors30-1to30-nmeasure acceleration at which the bridge20vibrates, in the vicinity of the expansion/contraction devices21and22in order.

The measurement data aggregator31acquires, at a predetermined timing, measurement data collected by the acceleration sensors30-1to30-nand relating to acceleration at which the bridge20vibrates, by performing, for example, wireless communication with the acceleration sensors30-1to30-n. The measurement data aggregator31transmits the acquired measurement data to the damage diagnosis device10at a predetermined timing by, for example, wireless communication.

The damage diagnosis device10includes a detection unit11, a determination unit12, the diagnosis unit13, a storage unit14, and a communication unit15.

The communication unit15receives measurement data collected by the acceleration sensors30-1to30-nand relating to acceleration at which the bridge20vibrates, by performing, for example, wireless communication with the measurement data aggregator31.

The storage unit14is a storage device such as an electronic memory or a magnetic disk. The storage unit14stores the measurement data received by the communication unit15, collected by the acceleration sensors30-1to30-n, and relating to acceleration at which the bridge20vibrates. In the present example embodiment, it is assumed that the storage unit14stores the acceleration-time-history-waveform140generated based on the measurement data. It is assumed that the acceleration-time-history-waveform140is a waveform representing acceleration of vibration varying with elapse of time, and is generated by, for example, the measurement data aggregator31, or the damage diagnosis device10or the like, based on the measurement data collected by the acceleration sensors30-1to30-n. The storage unit14is capable of storing information (data) generated by the detection unit11, the determination unit12, and the diagnosis unit13that are described later.

FIGS.2A and2Bare diagrams exemplifying the acceleration-time-history-waveforms140relating to vibration occurring due to the vehicle41crossing the bridge20and measured by the acceleration sensors30-1and30-naccording to the present example embodiment.FIG.2Arepresents the acceleration-time-history-waveform140relating to vibration occurring due to the vehicle41and measured by the acceleration sensor30-1placed on an entrance side (in the vicinity of the expansion/contraction device21) onto the bridge20.FIG.2Brepresents the acceleration-time-history-waveform140relating to vibration occurring due to the vehicle41and measured by the acceleration sensor30-nplaced on an exit side (in the vicinity of the expansion/contraction device22) from the bridge20. A vertical axis of a graph representing the acceleration-time-history-waveform140represents acceleration (meter per second) of vibration, and a horizontal axis represents elapsed time (second).

The acceleration-time-history-waveforms140exemplified inFIGS.2A and2Brepresent acceleration-time-history-waveforms when three vehicles (vehicles A, B, and C) cross the bridge20in order. As exemplified in each ofFIGS.2A and2B, the acceleration-time-history-waveform140includes a peak point (a point indicating a moment when acceleration of vibration becomes maximum within a certain period of approaching on a time axis). The peak point inFIG.2Ais a point representing a moment when an axle (a pair of tires) included in the vehicle41passes an upper part of the expansion/contraction device21. The peak point inFIG.2Bis a point representing a moment when the axle included in the vehicle41passes an upper part of the expansion/contraction device22. In the examples illustrated inFIGS.2A and2B, a point, on a positive-value side of acceleration, indicating a moment when acceleration of vibration becomes maximum is designated as a peak point but a point, on a negative-value side of acceleration, indicating a moment when acceleration (an absolute value) of vibration becomes maximum may be designated as a peak point.

The peak points exist, for each vehicle, as many as the number of axles included in the vehicle. Specifically, since, for example, a general passenger car includes two axles (i.e., four tires), peak points occurring due to passage of the passenger car across the upper part of the expansion/contraction device21or22are “2”. Moreover, peak points occurring due to passage of a large-size vehicle such as a truck including three axles (i.e., six tires) across the upper part of the expansion/contraction device21or22are “3”.

Vibration occurring due to the vehicle41crossing the bridge20becomes greater as weight of the vehicle41is greater. Therefore, the acceleration-time-history-waveforms140illustrated inFIGS.2A and2Bindicate that the vehicles A and C are vehicles having great weight, and the vehicle B is a vehicle having small weight.

The detection unit11illustrated inFIG.1generates a band-limiting signal (an acceleration-time-history-waveform after frequency-band-limiting-processing is applied) by applying the frequency-band-limiting-processing with regard to the acceleration-time-history-waveform140, in order to extract a peak point in the acceleration-time-history-waveform140stored in the storage unit14. The frequency-band-limiting-processing refers to, for example, finite impulse response (FIR) type or infinite impulse response (IIR) type band pass filter processing.

The detection unit11calculates a difference value relating to adjacent sample points with regard to the generated band-limiting signal, and extracts, as a peak point, a point where a sign of the difference value is inverted from positive to negative. Specifically, the detection unit11extracts a peak point by performing peak picking processing of extracting a sign change point of a first derivative.

Alternatively, the detection unit11may generate integral information acquired by integrating acceleration in relation to time, in relation to a plurality of different periods in the generated band-limiting signal, and extract a peak point, based on a plurality of pieces of generated integral information. More specifically, the detection unit11divides, for example, a band-limiting signal for 10 seconds into 0.1-second100periods, and derives an integral value acquired by integrating in relation to time at each of the periods. In this instance, the detection unit11may derive the integral value by calculating a root-mean-square as indicated in Equation 1, for example, with regard to acceleration at times of a plurality of different sample points included in each period.

In Equation 1, N represents the number of sample points included in each period (a period of 0.1 seconds in the example described above). In Equation 1, xirepresents acceleration at a time of each sample point.

Then, the detection unit11generates a time history waveform relating to a derived integral value, calculates a difference value relating to adjacent sample points with regard to the generated time history waveform, and extracts, as a peak point, a point where a sign of the difference value is inverted from positive to negative.

The detection unit11detects, based on the peak point extracted from the acceleration-time-history-waveform140, that a relation between a timing indicated by the extracted peak point at which the vehicle41exits from the bridge20and a timing indicated by the extracted peak point at which another vehicle42behind the vehicle41enters the bridge20satisfies a predetermined condition. This predetermined condition is a condition equivalent to a fact that, after the vehicle41crossing the bridge20exits from the bridge20, crossing of the another vehicle42over the bridge20does not occur.

The acceleration-time-history-waveform140includes a plurality of peak points related to the individual axles included in the vehicle41. Since the plurality of peak points related to the individual axles included in the vehicle41are proximate on a time axis, it is easy for the detection unit11and the later-described determination unit12to recognize that the plurality of peak points relate to one vehicle41, and recognize the plurality of peak points in distinction from a peak point relating to the another vehicle42. Specifically, the detection unit11and the later-described determination unit12can accurately recognize which vehicle each peak point included in the acceleration-time-history-waveform140relates to.

The detection unit11according to the present example embodiment stipulates, as the above-described predetermined condition, that a time interval from exit of the vehicle41from the bridge20to entrance of the another vehicle42onto the bridge20is equal to or more than a first time interval. This first time interval is equivalent to a value minimally required as a time interval from exit of the vehicle41from the bridge20to entrance of the another vehicle42onto the bridge20, in order for the damage diagnosis device10according to the present example embodiment to acquire measurement data sufficient to diagnose, with high precision, damage occurring in the bridge as a result of free vibration occurring in the bridge20due to crossing of the vehicle41.

Specifically, for example, when the another vehicle42enters the bridge20before the vehicle41exits from the bridge20, a time interval from exit of the vehicle41from the bridge20to entrance of the another vehicle42onto the bridge20becomes a negative value, and therefore, the detection unit11determines that the above-described predetermined condition is not satisfied. Alternatively, for example, when, after the vehicle41exits from the bridge20, the another vehicle42enters the bridge20, but a time interval from exit of the vehicle41from the bridge20to entrance of the another vehicle42onto the bridge20is short (less than the first time interval), the detection unit11determines that the above-described predetermined condition is not satisfied.

FIG.3is a diagram describing that the detection unit11according to the present example embodiment detects, based on the acceleration-time-history-waveforms140exemplified inFIGS.2A and2B, that, after the vehicle41exits from the bridge20, the another vehicle42crossing the bridge20does not exist. The acceleration-time-history-waveform illustrated inFIG.3is composed of the acceleration-time-history-waveforms140exemplified inFIGS.2A and2Bthat are displayed over each other by matching time axes thereof.

In the example illustrated inFIG.3, since the vehicle A, and the vehicle B behind the vehicle A travel in proximity to each other, a time interval from exit of the vehicle A from the bridge20to entrance of the vehicle B onto the bridge20is less than the first time interval. Therefore, in this case, the detection unit11determines that the above-described predetermined condition is not satisfied.

In the example illustrated inFIG.3, since the vehicle B, and the vehicle C behind the vehicle B travel apart from each other, a time interval from exit of the vehicle B from the bridge20to entrance of the vehicle C onto the bridge20is equal to or more than the first time interval. Therefore, in this case, the detection unit11detects that the above-described predetermined condition is satisfied. The detection unit11reports a result of the above-described detection to the diagnosis unit13. The detection unit11may store the detection result in the storage unit14.

The determination unit12illustrated inFIG.1extracts a peak point in the acceleration-time-history-waveform140stored in the storage unit14, by performing processing similar to that of the detection unit11described above. Then, the determination unit12determines, based on the peak point extracted from the acceleration-time-history-waveform140, whether weight of the vehicle41crossing the bridge20satisfies a criterion. The determination unit12according to the present example embodiment determines, based on the number of axles of the vehicle41indicated by the peak point extracted from the acceleration-time-history-waveform140, whether the weight of the vehicle41satisfies the criterion.

FIGS.4A and4Bare diagrams describing an example in which the determination unit12according to the present example embodiment determines, based on the acceleration-time-history-waveforms140exemplified inFIGS.2A and2B, that the weight of the vehicle41does not satisfy the criterion.FIGS.4A and4Bare diagrams displaying the acceleration-time-history-waveforms140illustrated inFIGS.2A and2B, respectively, in such a way that a part representing vibration due to the vehicle B is enlarged in a time-axis direction and an acceleration-axis direction.

As exemplified inFIGS.4A and4B, the determination unit12derives the number of peak points in a second time interval serving as a criterion when deriving the number of axles of the vehicle41. This second time interval is a value indicating a general time required from passage of the most front (head) axle included in the vehicle41across the upper part of the expansion/contraction device21(or the expansion/contraction device22) to passage of the most rear (end) axle included in the vehicle41across the upper part of the expansion/contraction device21(or the expansion/contraction device22).

In the acceleration-time-history-waveforms140illustrated inFIGS.4A and4B, the number of peak points in the second time interval is “2”, and therefore, the number of axles of the vehicle41(the vehicle B) is also “2”. In this case, the determination unit12determines that the vehicle41is not a large-size vehicle, and the weight of the vehicle41does not satisfy the criterion.

FIGS.5A and5Bare diagrams describing an example in which the determination unit12according to the present example embodiment determines, based on the acceleration-time-history-waveforms140exemplified inFIGS.2A and2B, that the weight of the vehicle41satisfies the criterion.FIGS.5A and5Bare diagrams displaying the acceleration-time-history-waveforms140illustrated inFIGS.2A and2B, respectively, in such a way that a part representing vibration due to the vehicle C is enlarged in a time-axis direction and an acceleration-axis direction.

As exemplified inFIGS.5A and5B, the determination unit12derives the number of peak points in the second time interval.

In the acceleration-time-history-waveforms140illustrated inFIGS.5A and5B, the number of peak points in the second time interval is “3”, and therefore, the number of axles of the vehicle41(the vehicle C) is also “3”. In this case, the determination unit12determines that the vehicle41is a large-size vehicle, and the weight of the vehicle41satisfies the criterion.

The determination unit12reports a result of the above-described detection to the diagnosis unit13. The determination unit12may store the detection result in the storage unit14.

When a condition is satisfied, the diagnosis unit13illustrated inFIG.1diagnoses damage occurring in the bridge20, based on the acceleration-time-history-waveform140representing free vibration occurring in the bridge20due to crossing of the vehicle41. The condition is as follows. A detection result by the detection unit11satisfies a condition equivalent to a fact that, after the vehicle41crossing the bridge20exits from the bridge20, crossing of the another vehicle42over the bridge20does not occur. A detection result by the determination unit12is that the weight of the vehicle41satisfies the criterion.

The diagnosis unit13diagnoses damage occurring in the bridge20, based on an attenuation part included in the acceleration-time-history-waveform140, starting at a peak point relating to the vehicle41and indicating exit from the bridge20, and indicating that free vibration occurring in a bridge60due to crossing of the vehicle41attenuates with elapse of time. In this instance, the diagnosis unit13uses the acceleration-time-history-waveform140at a specific position in the bridge20. The specific position in the bridge20is assumed to be a position other than both ends (i.e., places where the expansion/contraction devices21and22are placed) and a central part of the bridge20. Specifically, the diagnosis unit13uses the acceleration-time-history-waveform140based on measurement data by at least one of the acceleration sensors30-2to30-(n−1). The diagnosis unit13calculates a frequency spectrum by performing Fourier transform for the acceleration-time-history-waveform140of the above-described specific position in the bridge20.

The diagnosis unit13extracts a peak position in the derived frequency spectrum. The diagnosis unit13extracts a frequency or an attenuation rate (sharpness of a peak) at the peak position. The diagnosis unit13calculates, with regard to the extracted frequency or attenuation rate, a rate of change of the frequency or the attenuation rate from a criterion value. A criterion value of a frequency or an attenuation rate is, for example, a value of a frequency or an attenuation rate acquired when damage to be paid attention to does not occur in the bridge20.

When a calculated change rate is equal to or more than a threshold value, the diagnosis unit13diagnoses that damage to be paid attention to (to be taken care of) occurs in the bridge20. When a calculated change rate is less than a threshold value, the diagnosis unit13diagnoses that damage to be paid attention to does not occur in the bridge20.

Since a technique of diagnosing, by the above-described diagnosis unit13, damage occurring in the bridge20, based on a rate of change of a frequency spectrum from a criterion value thereof relating to a frequency or an attenuation rate at a peak position is an existing technique, more detailed description relating to the technique is omitted in the present application. Note that using the above-described existing technique when the diagnosis unit13diagnoses damage occurring in the bridge20is one example, and a technique used by the diagnosis unit13is not limited to the above-described existing technique.

Next, an operation (processing) of the damage diagnosis device10according to the present example embodiment is described in detail with reference to flowcharts inFIGS.6A and6B.

The detection unit11and the determination unit12generate a band-limiting signal by performing the above-described frequency-band-limiting-processing for the acceleration-time-history-waveforms140acquired by the acceleration sensors30-1to30-n(step S101). The detection unit11and the determination unit12generate a plurality of pieces of integral information by integrating acceleration in relation to time, in relation to a plurality of different periods in the generated band-limiting signal (step S102). The detection unit11and the determination unit12extract, based on the generated integral information, peak points in the acceleration-time-history-waveforms140where each of the axels of the vehicle41and the another vehicle42passes the expansion/contraction devices21and22(step S103).

The detection unit11derives, based on the extracted peak point, a time interval from exit of the vehicle41from the bridge20to entrance of the another vehicle42onto the bridge20(step S104). When the derived time interval is not equal to or more than the first time interval (No in step S105), the diagnosis unit13determines that diagnosis of damage based on the acceleration-time-history-waveform140relating to the vehicle41is not a target (step S108), and the overall processing ends.

When the derived time interval is equal to or more than the first time interval (Yes in step S105), the determination unit12derives the number of axles of the vehicle41, based on the number of extracted peak points included in the second time interval (step S106). When the derived number of axles is not equal to or more than “3” (i.e., equal to or less than “2”) (No in step S107), the diagnosis unit13determines that diagnosis of damage based on the acceleration-time-history-waveform140relating to the vehicle41is not a target (step S108), and the overall processing ends.

When the derived number of axles is equal to or more than “3” (Yes in step S107), the diagnosis unit13calculates a frequency spectrum by performing Fourier transform for an attenuation part starting at a peak point relating to the vehicle41and indicating exit from the bridge20in the acceleration-time-history-waveform140acquired by the acceleration sensor (at least one of the acceleration sensors30-2to30-(n−1)) placed at a specific position in the bridge20(step S109).

The diagnosis unit13determines a peak position of the frequency spectrum at the specific position (step S110). The diagnosis unit13extracts a frequency or an attenuation rate (sharpness of a peak) at the peak position (step S111).

The diagnosis unit13calculates, with regard to the extracted frequency or attenuation rate, a rate of change of the frequency or the attenuation rate from a criterion value, and determines whether the calculated change rate is equal to or more than a threshold value (step S112). When the calculated change rate is not equal to or more than the threshold value (No in step S113), the diagnosis unit13diagnoses that damage to be paid attention to does not occur in the bridge20(step S114), and the overall processing ends. When the calculated change rate is equal to or more than the threshold value (Yes in step S113), the diagnosis unit13diagnoses that damage to be paid attention to occurs in the bridge20(step S115), and the overall processing ends.

The damage diagnosis device10according to the present example embodiment can improve diagnosis precision when diagnosing damage to a bridge, based on information representing free vibration occurring in the bridge due to crossing of a vehicle. A reason for this is that the damage diagnosis device10diagnoses damage to the bridge20, based on the acceleration-time-history-waveform140representing free vibration occurring in the bridge20due to crossing of the vehicle41, when, after the vehicle41crossing the bridge20exits from the bridge20, crossing of the another vehicle42over the bridge20does not occur, and the weight of the vehicle41satisfies the criterion.

An advantageous effect achieved by the damage diagnosis device10according to the present example embodiment is described below in detail.

When diagnosing damage to a bridge, the damage can be diagnosed by measuring free vibration occurring in the bridge after a vehicle crosses the bridge. However, in this case, there is fear that a wrong diagnosis is made due to the following factor. Specifically, when, in a state where free vibration occurs in a bridge after a vehicle crosses the bridge, another vehicle travels on the bridge, vibration occurring due to the traveling of the another vehicle is mixed into the free vibration, and therefore, it becomes difficult to accurately measure the free vibration. Alternatively, when weight of the vehicle does not satisfy a criterion, free vibration that occurs is small, and thus, it becomes difficult to extract, with high precision, a change in a mechanical characteristic of a bridge indicated by the free vibration. Therefore, when diagnosing damage to a bridge by measuring free vibration occurring in the bridge after a vehicle crosses the bridge, elimination of the above-described factor of wrong diagnosis is a problem.

For such a problem, the damage diagnosis device10according to the present example embodiment includes the detection unit11, the determination unit12, and the diagnosis unit13, and operates, for example, as described above with reference toFIGS.1to6(FIGS.6A and6B). Specifically, the detection unit11detects that, after the vehicle41crossing the bridge20exits from the bridge20, crossing of the another vehicle42over the bridge20does not occur. The determination unit12determines whether the weight of the vehicle41satisfies a criterion. Then, the diagnosis unit13diagnoses damage to the bridge20, based on the acceleration-time-history-waveform140representing free vibration occurring in the bridge20due to crossing of the vehicle41, when the detection unit11detects that crossing of the another vehicle42over the bridge20does not occur, and the determination unit12determines that the weight of the vehicle41satisfies the criterion.

Specifically, the acceleration-time-history-waveform140representing free vibration used when the damage diagnosis device10diagnoses damage occurring in the bridge20represents free vibration into which vibration occurring due to crossing of the another vehicle42over the bridge20is not mixed, and which represents free vibration occurring due to crossing of the vehicle41the weight of which satisfies a criterion on the bridge20. Therefore, the damage diagnosis device10according to the present example embodiment can improve diagnosis precision when diagnosing damage occurring in a bridge, based on an acceleration-time-history-waveform representing free vibration occurring in the bridge due to crossing of a vehicle.

The damage diagnosis device10according to the present example embodiment detects, by extracting a peak point from the acceleration-time-history-waveform140, that, after the vehicle41crossing the bridge20exits from the bridge20, crossing of the another vehicle42over the bridge20does not occur, and determines whether the weight of the vehicle41satisfies a criterion. Specifically, the damage diagnosis device10according to the present example embodiment can perform the above-described detection and determination, based on the acceleration-time-history-waveform140, and therefore, achieve, with a simple configuration, improvement in diagnosis precision when diagnosing damage occurring in a bridge.

The determination unit12according to the present example embodiment can determine, with a simple configuration, whether the weight of the vehicle41satisfies a criterion, by concentrating on a fact that, generally, a vehicle having small weight, such as a passenger car, tends to include two axels, and a vehicle having great weight, such as a truck, tends to include three or more axels.

Note that both the detection unit11and the determination unit12include a function of extracting a peak point in the acceleration-time-history-waveform140in the present example embodiment described above, but one of the detection unit11and the determination unit12may include a function of extracting a peak point. Specifically, for example, when the detection unit11alone includes a function of extracting a peak point, the detection unit11may input information indicating the extracted peak point to the determination unit12.

The detection unit11according to the present example embodiment may detect that, after the vehicle41crossing the bridge20exits from the bridge20, crossing of the another vehicle42over the bridge20does not occur, for example, by analyzing a video in which the bridge20is captured with an external imaging device (camera). Note that a camera capturing the bridge20may be an infrared camera as long as the camera is capable of detecting crossing of the vehicle or determining a kind of vehicle.

The determination unit12according to the present example embodiment may determine whether the weight of the vehicle41satisfies a criterion, for example, based on a video in which the bridge20is captured, or information acquired by a weight sensor placed on the bridge20. In this case, the determination unit12may determine whether the weight of the vehicle41satisfies a criterion, for example, by collating an image representing the vehicle41included in a video in which the bridge20is captured, with information (a database) associating the image representing the vehicle41with the weight of the vehicle41. The determination unit12can identify a type (e.g. a model name) of the vehicle41included in the video, for example, by using an image analysis technique in recent years. Alternatively, the determination unit12is also capable of determining whether the weight of the vehicle41satisfies a criterion, as illustrated in the present example embodiment described above, based on the number of axles of the vehicle41acquired by analyzing the image representing the vehicle41.

At least one of the detection unit11and the determination unit12according to the present example embodiment may display the acceleration-time-history-waveform140relating to an entrance part (the expansion/contraction device21) in the bridge20and the acceleration-time-history-waveform140relating to an exit part (the expansion/contraction device22) in the bridge20, over each other on a display device (not illustrated inFIG.1), by matching time axes thereof, for example, as illustrated inFIG.3. Specifically, the damage diagnosis device10according to the present example embodiment can improve user's convenience by presenting the acceleration-time-history-waveform140in such a way that the user can easily understand.

Note that the damage diagnosis device10according to the present example embodiment described above targets, for diagnosis, the bridge20including a one-way lane, but the damage diagnosis device10may target, for diagnosis, a bridge including lanes (opposite lanes) in both directions. In this case, the detection unit11may detect, with regard to both the lane and an opposite lane, that, after the vehicle41crossing one of the lanes exits from the bridge20, crossing of the another vehicle42over the bridge20does not occur, based on the acceleration-time-history-waveforms140relating to the lanes in both the directions.

Second Example Embodiment

FIG.7is a block diagram conceptually illustrating a configuration of a damage diagnosis system50according to a second example embodiment of the invention of the present application.

The damage diagnosis device50according to the present example embodiment includes a detection unit51, a determination unit52, and a diagnosis unit53.

The detection unit51detects that, after a vehicle71crossing a bridge60exits from the bridge60, crossing of another vehicle72over the bridge60does not occur.

The determination unit52determines whether weight of the vehicle71satisfies a criterion.

The diagnosis unit53diagnoses damage to the bridge60, based on information representing information530representing free vibration occurring in the bridge60due to crossing of the vehicle71, when the detection unit51detects that crossing of the another vehicle72over the bridge60does not occur, and the determination unit52determines that the weight of the vehicle71satisfies the criterion.

The damage diagnosis device50according to the present example embodiment can improve diagnosis precision when diagnosing damage to a bridge, based on information representing free vibration occurring in the bridge due to crossing of a vehicle. A reason for this is that the damage diagnosis device50diagnoses damage to the bridge60, based on the information530representing free vibration occurring in the bridge60due to crossing of the vehicle71, when, after the vehicle71crossing the bridge60exits from the bridge60, crossing of the another vehicle72over the bridge60does not occur, and the weight of the vehicle71satisfies the criterion.

Hardware Configuration Example

Each unit in each of the damage diagnosis devices illustrated inFIGS.1and7in each of the example embodiments described above can be achieved by dedicated hardware (HW) (electronic circuit). InFIGS.1and7, at least the following configuration can be considered as a functional (processing) unit (software module) of a software program.Detection units11and51,determination units12and52, anddiagnosis units13and53.

Classification of each unit illustrated in the drawings is a configuration serving for convenience of description, and various configurations are conceivable during implementation. One example of a hardware environment in this case is described with reference toFIG.8.

FIG.8is a diagram exemplarily describing a configuration of an information processing device900(computer) being capable of executing the damage diagnosis device according to each example embodiment of the invention of the present application. Specifically,FIG.8represents a hardware environment being a configuration of a computer (information processing device) capable of achieving the damage diagnosis devices10and50illustrated inFIGS.1and7, and being capable of achieving each function in the example embodiments described above.

The information processing device900illustrated inFIG.8includes the following as components.A central processing unit (CPU)901,a read only memory (ROM)902,a random access memory (RAM)903,a hard disk (storage device)904,a communication interface905with an external device,a bus906(communication wire),a reader/writer908capable of reading and writing data stored in a recording medium907such as a compact disc read only memory (CD-ROM), andan input/output interface909(including a display device or the like).

Specifically, the information processing device900including the components described above is a general computer to which these components are connected via the bus906. The information processing device900may include a plurality of CPUs901, or include a multicore CPU901.

The invention of the present application described with the above-described example embodiments as examples supplies the information processing device900illustrated inFIG.8with a computer program capable of achieving the following function. The function is a function of the above-described configuration in the block configuration diagrams (FIGS.1and7) referred to in the description of the example embodiments, or the flowchart (FIGS.6A and6B). Thereafter, the invention of the present application is accomplished by reading the computer program in the CPU901of the hardware, and then interpreting and executing the computer program. The computer program supplied into the device may be stored in a readable/writable volatile memory (the RAM903), or a non-volatile storage device such as the ROM902or the hard disk904.

In the above-described case, a nowadays general procedure can be adopted as a method of supplying a computer program into the hardware. As the procedure, there is, for example, a method that installs the program into the device via various recording media907such as a CD-ROM, a method that downloads the program from outside via a communication line such as the Internet, or the like. In such a case, it can be considered that the invention of the present application is configured by a code constituting the computer program, or the recording medium907storing the code.

Note that some or all of the above-described example embodiments may be also described as in the following supplementary notes. However, the invention of the present application exemplarily described with each of the above-described example embodiments is not limited to the following.

A damage diagnosis device including:

a detection means for detecting that, after a vehicle crossing a bridge exits from the bridge, crossing of another vehicle over the bridge does not occur;

a determination means for determining whether weight of the vehicle satisfies a criterion; and

a diagnosis means for diagnosing damage to the bridge, based on information representing free vibration occurring in the bridge due to crossing of the vehicle, when the detection means detects that crossing of the another vehicle over the bridge does not occur and the determination means determines that the weight of the vehicle satisfies the criterion.

The damage diagnosis device according to Supplementary Note 1, wherein,

when an acceleration sensor being capable of acquiring information necessary for generation of information representing an acceleration-time-history-waveform relating to the free vibration acquires information representing peak points in the acceleration-time-history-waveform indicating that the vehicle and the another vehicle enter the bridge and exit from the bridge,

the detection means extracts a plurality of the peak points included in the acceleration-time-history-waveform, and detects that a relation between a timing indicated by the extracted peak point at which the vehicle exits from the bridge, and a timing indicated by the extracted peak point at which the another vehicle enters the bridge satisfies a predetermined condition.

The damage diagnosis device according to Supplementary Note 1, wherein,

when an acceleration sensor being capable of acquiring information necessary for generation of information representing an acceleration-time-history-waveform relating to the free vibration acquires information representing a peak point in the acceleration-time-history-waveform, the peak point indicating that each of a plurality of axles included in the vehicle passes a predetermined place on the bridge,

the determination means extracts a plurality of the peak points included in the acceleration-time-history-waveform, and determines that the weight of the vehicle satisfies the criterion when a number of the axles indicated by the peak points being extracted satisfies a predetermined condition.

The damage diagnosis device according to Supplementary Note 2 or 3, wherein

at least one of the detection means and the determination means generates a band-limiting signal by performing frequency-band-limiting-processing on information representing the acceleration-time-history-waveform, and then extracts the peak point, based on the band-limiting signal being generated.

The damage diagnosis device according to Supplementary Note 4, wherein

at least one of the detection means and the determination means generates a plurality of pieces of integral information by integrating acceleration in relation to time, in relation to a plurality of different periods in the band-limiting signal, and then extracts the peak point, based on the plurality of pieces of integral information being generated.

The damage diagnosis device according to Supplementary Note 5, wherein

the integral information indicates a value acquired by deriving a root-mean-square with regard to the acceleration at a plurality of different times included in the period.

The damage diagnosis device according to Supplementary Note 1, wherein

the detection means detects that the crossing of the another vehicle over the bridge does not occur, by analyzing a video in which the bridge is captured.

The damage diagnosis device according to Supplementary Note 1, wherein

the determination means determines whether the weight of the vehicle satisfies the criterion, based on a video in which the bridge is captured, or information acquired by a weight sensor placed on the bridge.

The damage diagnosis device according to Supplementary Note 8, wherein

the determination means determines whether the weight of the vehicle satisfies the criterion, by collating an image representing the vehicle included in the video in which the bridge is captured, with information associating the image representing the vehicle with the weight of the vehicle.

The damage diagnosis device according to any one of Supplementary Notes 7 to 9, wherein

the video is captured by an infrared camera.

The damage diagnosis device according to any one of Supplementary Notes 2 to 6, wherein

the diagnosis means diagnoses damage occurring in the bridge, based on an attenuation part included in the acceleration-time-history-waveform, the attenuation part starting at the peak point that indicates exit from the bridge relating to the vehicle, and indicating that the free vibration occurring in the bridge due to the crossing of the vehicle attenuates with elapse of time.

The damage diagnosis device according to Supplementary Note 11, wherein

the diagnosis means calculates a frequency spectrum by performing Fourier transform on the attenuation part, determines a peak position of the frequency spectrum being calculated, calculates a change rate relative to a referential frequency or a referential attenuation rate, in relation to a frequency or attenuation rate at the peak position being determined, and determines whether the change rate being calculated is equal to or more than a threshold value.

The damage diagnosis device according to Supplementary Note 2 or 3, wherein

at least one of the detection means and the determination means displays the acceleration-time-history-waveform relating to an entrance part of the bridge and the acceleration-time-history-waveform relating to an exit part of the bridge, with overlapping each other on a display device, by matching time axes thereof.

A damage diagnosis system including:

the damage diagnosis device according to Supplementary Note 2 or 3; and

the acceleration sensor.

A damage diagnosis method including, by an information processing device:

detecting that, after a vehicle crossing a bridge exits from the bridge, crossing of another vehicle over the bridge does not occur;

determining whether weight of the vehicle satisfies a criterion; and

diagnosing damage to the bridge, based on information representing free vibration occurring in the bridge due to crossing of the vehicle, when detecting that crossing of the another vehicle over the bridge does not occur and determining that the weight of the vehicle satisfies the criterion.

A recording medium storing a damage diagnosis program for causing a computer to execute:

detection processing of detecting that, after a vehicle crossing a bridge exits from the bridge, crossing of another vehicle over the bridge does not occur;

determination processing of determining whether weight of the vehicle satisfies a criterion; and

diagnosis processing of diagnosing damage to the bridge, based on information representing free vibration occurring in the bridge due to crossing of the vehicle, when the detection processing detects that crossing of the another vehicle over the bridge does not occur and the determination processing determines that the weight of the vehicle satisfies the criterion.

This application is based upon and claims the benefit of priority from Japanese Patent Application No. 2017-234804, filed on Dec. 7, 2017, the disclosure of which is incorporated herein in its entirety by reference.

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