Structure evaluation system, structure evaluation device, structure evaluation method, and computer program

Abstract

To provide a structure evaluation system, a signal processing device, a structure evaluation method, and a computer program with which it is possible to improve the accuracy of evaluating a degradation state of a structure.SOLUTION: A structure evaluation system according to an embodiment comprises a plurality of sensors, a position locating unit, a correction unit, and an evaluation unit. The plurality of sensors detect elastic waves generated from a structure. The position locating unit locates positions of generation sources of the plurality of elastic waves detected by the plurality of sensors, respectively. The correction unit corrects information based on position location by the position locating unit, by using a correction value that is determined in accordance with a temperature of the structure. The evaluation unit evaluates a degradation state of the structure on the basis of the corrected information.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] An embodiment of the present invention relates to a structure evaluation system, a structure evaluation device, a structure evaluation method, and a computer program. [Background technology]

[0002] By installing a sensor on the surface of a structure such as a bridge, it is possible to detect elastic waves generated inside the structure. Furthermore, by installing multiple sensors on the surface of the structure, it is possible to locate the position of the source of the elastic waves (hereinafter referred to as the "elastic wave source") based on the difference in arrival time of the elastic waves detected by each sensor. Elastic waves are also generated inside the structure when an impact is applied to the surface of the structure from the outside. In such cases, the position of the elastic wave source can be located based on the difference in arrival time of the elastic waves detected by each sensor.

[0003] If there is damage in the propagation path of elastic waves inside a structure, the propagation of the elastic waves will be obstructed. If the propagation of elastic waves is obstructed due to damage inside the structure, some sensors will be unable to detect the elastic waves. As a result, the accuracy of the elastic wave source location results will decrease. If a spatially uniform impact, such as raindrops hitting a road surface during rainfall, is applied to the surface of a structure and elastic waves are detected by sensors installed opposite it, a decrease in the density of elastic wave sources will be observed in areas with internal damage. This characteristic can be used to evaluate the deterioration state of a structure (whether or not there is internal damage to the structure).

[0004] Various correction methods have been proposed to improve the accuracy of assessment of the deterioration state of structures. For example, a technique has been proposed in which information based on position location is corrected using a correction value determined according to the impact, even when the impact applied to the surface of the structure is not uniform. However, none of the conventional methods specifically mentions temperature. Therefore, when measurements are taken under different temperature environments, such as those depending on the season or time of day, it is not possible to correct for temperature-related changes, and it is sometimes impossible to improve the assessment accuracy. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] International Publication No. 2017 / 217034 [Patent Document 2] International Publication No. 2022 / 014004 [Patent Document 3] Japanese Patent Publication No. 2022-70711 Summary of the Invention [Problem to be solved by the invention]

[0006] The problem to be solved by the present invention is to provide a structure evaluation system, a structure evaluation device, a structure evaluation method, and a computer program that can improve the accuracy of evaluating the deterioration state of a structure. [Means for solving the problem]

[0007] A structure evaluation system according to an embodiment includes a plurality of sensors, a position locating unit, a correction unit, and an evaluation unit. The plurality of sensors detect elastic waves generated from a structure. The position locating unit locates the positions of sources of the elastic waves based on the plurality of elastic waves detected by each of the plurality of sensors. The correction unit corrects information based on the position locating by the position locating unit using a correction value determined according to the temperature of the structure. The evaluation unit evaluates the deterioration state of the structure based on the corrected information. The structure is composed of at least a pavement on which vehicles can travel and a deck supporting the pavement. The temperature of the structure is a value related to the temperature of the pavement. [Brief explanation of the drawings]

[0008] [Figure 1] FIG. 1 is a diagram showing the configuration of a structure evaluation system according to a first embodiment. [Figure 2] FIG. 2 is a diagram showing an example of the functional configuration of a signal processing unit according to the first embodiment. [Figure 3] FIG. 2 is a diagram for explaining a method for measuring an elastic wave in the first embodiment. [Figure 4] FIG. 4 is a diagram showing the relationship between acoustic impedance and transmittance in the first embodiment. [Figure 5] FIG. 3 is a diagram for explaining the relationship between temperature and density of elastic waves in the first embodiment. [Figure 6] FIG. 3 is an explanatory diagram of a correction process performed by a correction unit according to the first embodiment. [Figure 7] FIG. 3 is a sequence diagram showing the flow of the deterioration state evaluation process performed by the structure evaluation system according to the first embodiment. [Figure 8] FIG. 4 is a diagram for explaining the effect of the first embodiment. [Figure 9] FIG. 10 is an explanatory diagram of a correction process performed by a correction unit according to the second embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0009] Hereinafter, a structure evaluation system, a structure evaluation device, a structure evaluation method, and a computer program according to embodiments will be described with reference to the drawings.

[0010] (overview) The inventors' research has revealed that the measurement results of the density of elastic wave sources vary depending on the temperature. Therefore, conventional correction methods are unable to correct for temperature-related changes, and it has been found that when measurements are taken under different temperature environments, such as different seasons or times of day, the accuracy of the assessment of the deterioration state of a structure may not be improved. Therefore, in the structure evaluation system of the embodiment, information based on the position location of elastic wave sources is corrected based on temperature information at the time of elastic wave measurement, thereby improving the accuracy of the assessment of the deterioration state of a structure by taking into account the influence of temperature at the time of measurement. Here, the information based on the position location is information used before locating the elastic wave source (e.g., the elastic wave measurement threshold) or information obtained using the location results.

[0011] (First embodiment) FIG. 1 is a diagram showing the configuration of a structure evaluation system 100 in a first embodiment. The structure evaluation system 100 is used to evaluate the soundness of a structure 50. In the following description, evaluation means determining the degree of soundness of the structure 50, i.e., the state of deterioration of the structure 50, based on a certain standard. The structure 50 in the following embodiment is made up of at least two materials that have different responses to temperature. For example, if the structure 50 is a bridge on which vehicles travel, the structure 50 is made up of a pavement on which vehicles can travel and a deck that supports the pavement. The pavement 51 is, for example, asphalt, and the deck 52 is, for example, concrete.

[0012] In the following description, the structure 50 will be described as a bridge, but the structure 50 does not have to be limited to a bridge. The structure 50 may be any structure made of at least two materials that have different temperature responses, and in which elastic waves 11 are generated in response to the occurrence or growth of cracks or external impacts (for example, rain, artificial rain, etc.). Note that bridges are not limited to structures built over rivers, valleys, etc., but also include various structures built above ground level (for example, highway viaducts).

[0013] Damage that affects the evaluation of the deterioration state of the structure 50 includes damage inside the structure that obstructs the propagation of elastic waves 11, such as cracks, cavities, and sedimentation. Here, cracks include vertical cracks, horizontal cracks, and diagonal cracks. Vertical cracks are cracks that occur in a direction perpendicular to the road surface. Horizontal cracks are cracks that occur horizontally to the road surface. Diagonal cracks are cracks that occur in a direction other than horizontal or vertical to the road surface. Sedimentation is deterioration in which concrete turns into sediment, mainly at the boundary between the asphalt and the concrete deck.

[0014] The structure evaluation system 100 includes a plurality of sensors 20-1 to 20-n, a signal processing unit 30, and a structure evaluation device 40. Each of the plurality of sensors 20-1 to 20-n and the signal processing unit 30 are connected to each other via wires so that they can communicate with each other. The signal processing unit 30 and the structure evaluation device 40 are connected to each other via wires or wirelessly so that they can communicate with each other. In the following description, when there is no need to distinguish between the sensors 20-1 to 20-n, they will be referred to as sensors 20.

[0015] As shown in FIG. 1, when a vehicle 10 passes over a structure 50, a load is applied to the road surface due to contact between the running part W of the vehicle 10 and the road surface. A large number of elastic waves 11 are generated within the structure 50 due to deflection caused by the load. Each sensor 20 installed on the underside of the structure 50 (for example, the deck slab 52) can detect the elastic waves 11 generated within the structure 50. Note that although an example in which elastic waves are generated within the structure 50 by the vehicle 10 is shown here, other methods for generating elastic waves within the structure 50 may also be used. For example, elastic waves may be generated by applying an impact to the structure 50 from the outside.

[0016] The sensor 20 has a piezoelectric element and detects elastic waves 11 generated from inside the structure 50. The sensor 20 is installed at a position where it can detect elastic waves 11 on the surface of the structure 50. For example, the sensors 20-1 to 20-n are installed on any one of the road surface, side surface, and bottom surface, spaced apart at equal or different intervals in the vehicle axis direction and in a direction perpendicular to the vehicle axis direction. The vehicle axis direction refers to the direction in which the vehicle travels on the road surface. The direction perpendicular to the vehicle axis direction refers to a direction perpendicular to the vehicle axis direction. The sensor 20 converts the detected elastic waves 11 into an electrical signal. In the following explanation, a case where the sensor 20 is installed on the bottom surface of the structure 50 will be described as an example.

[0017] A piezoelectric element having sensitivity in the range of, for example, 10 kHz to 1 MHz is used for the sensor 20. There are various types of sensors 20, such as a resonance type that has a resonance peak within a frequency range and a wideband type that suppresses resonance, but any type of sensor 20 may be used. The method by which the sensor 20 detects the elastic wave 11 includes a voltage output type, a resistance change type, and a capacitance type, but any detection method may be used.

[0018] An acceleration sensor may be used instead of the sensor 20. In this case, the acceleration sensor detects the elastic waves 11 generated inside the structure 50. Then, the acceleration sensor converts the detected elastic waves 11 into an electrical signal by performing the same processing as the sensor 20.

[0019] Between the sensor 20 and the signal processing unit 30, for example, an amplifier and an A / D converter (not shown) are provided. The amplifier amplifies the electrical signal output from the sensor 20. The amplifier outputs the amplified electrical signal to the A / D converter. The amplifier amplifies the electrical signal to a level that allows it to be processed in the A / D converter, for example. The A / D converter quantizes the amplified electrical signal and converts it into a digital signal, which is then output to the signal processing unit 30.

[0020] The signal processing unit 30 receives the digital signal output from the A / D converter as input. The signal processing unit 30 performs signal processing on the input digital signal. The signal processing performed by the signal processing unit 30 includes, for example, noise removal and parameter extraction. The signal processing unit 30 generates transmission data including the processed digital signal. The signal processing unit 30 outputs the generated transmission data to the structure evaluation device 40.

[0021] The signal processing unit 30 is configured using an analog circuit or a digital circuit. The digital circuit is realized, for example, by an FPGA (Field Programmable Gate Array) or a microcomputer. The digital circuit may also be realized by a dedicated LSI (Large-Scale Integration). The signal processing unit 30 may also be equipped with a non-volatile memory such as a flash memory or a removable memory.

[0022] 2 is a diagram showing an example of the functional configuration of the signal processing unit 30 in the first embodiment. The signal processing unit 30 includes a waveform shaping filter 301, a gate generation circuit 302, an arrival time determination unit 303, a feature extraction unit 304, a transmission data generation unit 305, a memory 306, and an output unit 307.

[0023] The waveform shaping filter 301 removes noise components outside a predetermined band from the input digital signal. The waveform shaping filter 301 is, for example, a digital band-pass filter (BPF). The waveform shaping filter 301 outputs the digital signal after the noise components have been removed (hereinafter referred to as the "noise-removed signal") to the gate generation circuit 302 and the feature extraction unit 304.

[0024] The gate generation circuit 302 receives the noise removal signal output from the waveform shaping filter 301. The gate generation circuit 302 generates a gate signal based on the received noise removal signal. The gate signal indicates whether the waveform of the noise removal signal is sustained.

[0025] The gate generation circuit 302 is realized by, for example, an envelope detector and a comparator. The envelope detector detects the envelope of the noise-removed signal. The envelope is extracted, for example, by squaring the noise-removed signal and performing a predetermined process (e.g., processing using a low-pass filter or a Hilbert transform) on the squared output value. The comparator determines whether the envelope of the noise-removed signal is equal to or greater than a predetermined threshold.

[0026] When the envelope of the noise-removed signal is equal to or greater than a predetermined threshold, the gate generation circuit 302 outputs a first gate signal indicating that the waveform of the noise-removed signal is sustained to the arrival time determination unit 303 and the feature extraction unit 304. On the other hand, when the envelope of the noise-removed signal is less than the predetermined threshold, the gate generation circuit 302 outputs a second gate signal indicating that the waveform of the noise-removed signal is not sustained to the arrival time determination unit 303 and the feature extraction unit 304. Note that while the gate generation circuit 302 is configured to determine whether the waveform of the noise-removed signal is sustained based on the envelope, the gate generation circuit 302 may also process the noise-removed signal itself or a signal to which an absolute value is applied. The threshold used for this gate generation is referred to as a measurement threshold.

[0027] The arrival time determination unit 303 receives as input a clock output from a clock source such as a crystal oscillator (not shown) and a gate signal output from the gate generation circuit 302. The arrival time determination unit 303 determines the elastic wave arrival time using the clock input while the first gate signal is being input. The arrival time determination unit 303 outputs the determined elastic wave arrival time as time information to the transmission data generation unit 305. The arrival time determination unit 303 does not perform any processing while the second gate signal is being input. The arrival time determination unit 303 generates cumulative time information since power-on based on the signal from the clock source. Specifically, the arrival time determination unit 303 may be a counter that counts clock edges, and the value of the counter's register may be used as the time information. The counter's register is determined to have a predetermined bit length.

[0028] The feature extraction unit 304 receives as input the noise-removed signal output from the waveform shaping filter 301 and the gate signal output from the gate generation circuit 302. The feature extraction unit 304 extracts a feature of the noise-removed signal using the noise-removed signal input while the first gate signal is being input. The feature extraction unit 304 does not perform processing while the second gate signal is being input. The feature is information indicating the characteristics of the noise-removed signal.

[0029] The feature quantity may be, for example, the amplitude [mV] of the waveform, the rise time [usec] of the waveform, the duration [usec] of the gate signal, the number of zero cross counts [times], the energy [arb.] of the waveform, the frequency [Hz], and the root mean square (RMS) value. The feature quantity extraction unit 304 outputs parameters related to the extracted feature quantity to the transmission data generation unit 305. When outputting the parameters related to the feature quantity, the feature quantity extraction unit 304 associates a sensor ID with the parameters related to the feature quantity. The sensor ID represents identification information for identifying the sensor 20 installed in the area (hereinafter referred to as the "evaluation area") to be evaluated for the soundness of the structure 50.

[0030] The waveform amplitude is, for example, the maximum amplitude value of the noise reduction signal. The waveform rise time is, for example, the time T1 from when the gate signal starts rising until the noise reduction signal reaches its maximum value. The gate signal duration is, for example, the time from when the gate signal starts rising until the amplitude becomes smaller than a preset value. The zero cross count is, for example, the number of times the noise reduction signal crosses a reference line that passes through a zero value.

[0031] The waveform energy is, for example, the value obtained by integrating the squared amplitude of the noise-removed signal at each time point over time. Note that the definition of energy is not limited to the above example, and may be approximated using, for example, the envelope of the waveform. The frequency is the frequency of the noise-removed signal. The RMS value is, for example, the value obtained by squaring the amplitude of the noise-removed signal at each time point and taking the square root.

[0032] The transmission data generation unit 305 receives the sensor ID, time information, and parameters related to the feature amount as input, and generates transmission data including the input sensor ID, time information, and parameters related to the feature amount.

[0033] The memory 306 stores the transmission data and is, for example, a dual-port RAM (Random Access Memory).

[0034] The output unit 307 sequentially outputs the transmission data stored in the memory 306 to the structure evaluation device 40 .

[0035] Continuing the explanation, returning to Fig. 1, the structure evaluation device 40 includes a communication unit 41, a control unit 42, a storage unit 43, and a display unit 44.

[0036] The communication unit 41 receives the transmission data output from the signal processing unit 30 .

[0037] The control unit 42 controls the entire structure evaluation device 40. The control unit 42 is configured using a processor such as a CPU (Central Processing Unit) and a memory. The control unit 42 executes a program to function as an acquisition unit 421, an event extraction unit 422, a position determination unit 423, a distribution generation unit 424, a correction unit 425, and an evaluation unit 426.

[0038] Some or all of the functional units of the acquisition unit 421, event extraction unit 422, position determination unit 423, distribution generation unit 424, correction unit 425, and evaluation unit 426 may be realized by hardware such as an ASIC (Application Specific Integrated Circuit), a PLD (Programmable Logic Device), or an FPGA, or may be realized by a combination of software and hardware. The program may be recorded on a computer-readable recording medium. Examples of computer-readable recording media include portable media such as flexible disks, magneto-optical disks, ROMs, and CD-ROMs, and non-transitory storage media such as storage devices built into a computer system, such as a hard disk. The program may be transmitted via a telecommunications line.

[0039] Some of the functions of the acquisition unit 421, the event extraction unit 422, the position determination unit 423, the distribution generation unit 424, the correction unit 425, and the evaluation unit 426 do not need to be pre-installed in the structure evaluation device 40, and may be realized by installing additional application programs in the structure evaluation device 40.

[0040] The acquisition unit 421 acquires various types of information. For example, the acquisition unit 421 acquires transmission data received by the communication unit 41. For example, the acquisition unit 421 acquires temperature information of the structure 50. The temperature information of the structure 50 is temperature information in the vicinity of the structure 50 to be evaluated. The temperature information in the vicinity of the structure 50 to be evaluated may be, for example, the air temperature in the vicinity of the structure 50 to be evaluated, or the temperature of an affected portion of the structure 50 (for example, a paved portion) that is directly affected by a temperature rise due to solar radiation or the like.

[0041] The acquisition unit 421 may acquire the temperature information of the structure 50 by any method as long as it can acquire the temperature information. For example, the acquisition unit 421 may acquire temperature information measured by a temperature sensor installed near the structure 50, may acquire temperature information near the structure 50 provided in a weather forecast or the like, or may acquire temperature information directly from the affected portion. When the acquisition unit 421 acquires temperature information measured by a temperature sensor installed near the structure 50 or when the acquisition unit 421 acquires temperature information directly from the affected portion, the structure evaluation system 100 is equipped with a temperature sensor. The acquisition unit 421 stores the acquired transmission data and temperature information in the storage unit 43. In the first embodiment, the acquisition unit 421 acquires information about the vehicle 10 that has traveled through the structure 50 to be evaluated (hereinafter referred to as "vehicle information") for a predetermined period.

[0042] The vehicle information is, for example, vehicle type information of the vehicles 10 that have traveled through the structure 50 in a predetermined period of time, and traffic volume information of the vehicles 10 on the structure 50. The vehicle type information of the vehicles 10 includes at least information on the tread width of the vehicles 10. The traffic volume information of the vehicles 10 is information indicating how many vehicles 10 of what type have passed through the structure 50 in a predetermined period of time. The acquisition unit 421 may acquire the vehicle information through user input, or may acquire the vehicle information from a server that stores traffic information.

[0043] The event extraction unit 422 extracts transmission data for one event from the transmission data stored in the memory unit 43. An event refers to an elastic wave generating event that occurs in the structure 50. In this embodiment, the elastic wave generating event is the passage of a vehicle 10 over a road surface. When one event occurs, elastic waves 11 are detected at approximately the same time by multiple sensors 20. In other words, the memory unit 43 stores transmission data related to elastic waves 11 detected at approximately the same time. Therefore, the event extraction unit 422 sets a predetermined time window and extracts all transmission data whose arrival time falls within the range of the time window as transmission data for one event. The event extraction unit 422 outputs the extracted transmission data for one event to the position determination unit 423.

[0044] The time window range Tw may be determined using the elastic wave propagation velocity v in the target structure 50 and the maximum sensor spacing dmax so as to be in the range of Tw≧dmax / v. In order to avoid erroneous detection, it is desirable to set Tw to as small a value as possible, so that Tw can essentially be set to dmax / v. The elastic wave propagation velocity v may be determined in advance.

[0045] The position locating unit 423 locates the position of the elastic wave source based on the sensor position information and the sensor ID and time information included in each of the plurality of transmission data extracted by the event extracting unit 422.

[0046] The sensor position information includes information about the installation position of the sensor 20 in association with the sensor ID. The sensor position information includes information about the installation position of the sensor 20, such as latitude and longitude, or horizontal and vertical distances from a reference position of the structure 50. The positioning unit 423 holds the sensor position information in advance. The sensor position information may be stored in the positioning unit 423 at any timing before the positioning unit 423 locates the position of the elastic wave source.

[0047] The sensor position information may be stored in the storage unit 43. In this case, the position locating unit 423 acquires the sensor position information from the storage unit 43 at the timing of performing position locating. A Kalman filter, a least squares method, or the like may be used to locate the position of the elastic wave source. The position locating unit 423 outputs the position information of the elastic wave source obtained during the measurement period to the distribution generating unit 424.

[0048] The distribution generation unit 424 receives as input the position information of the multiple elastic wave sources output from the position determination unit 423. The distribution generation unit 424 generates an elastic wave source distribution using the received position information of the multiple elastic wave sources. The elastic wave source distribution represents a distribution indicating the positions of the elastic wave sources. More specifically, the elastic wave source distribution is a distribution in which points indicating the positions of the elastic wave sources are displayed on virtual data representing the structure 50 to be evaluated, with the horizontal axis representing the distance in the traffic direction and the vertical axis representing the distance in the width direction. The distribution generation unit 424 uses the elastic wave source distribution to generate an elastic wave source density distribution. The elastic wave source density distribution represents a distribution in which density values ​​determined according to the number of elastic wave sources included in each area are displayed for each predetermined area in the elastic wave source distribution.

[0049] The correction unit 425 corrects information based on the position location by the position location unit 423, using a correction value determined according to the temperature information of the structure 50 acquired by the acquisition unit 421. The temperature information of the structure 50 is a value related to the temperature of the pavement 51, and is, for example, any of the following: air temperature, the temperature of the underside of the deck slab 52, the road surface temperature (temperature of the pavement 51) measured by a vehicle traveling on the pavement 51 or manually, the amount of solar radiation, a statistical value of the temperature during measurement, the difference between the temperature of the pavement 51 and the temperature of the deck slab 52, and the ratio between the temperature of the pavement 51 and the temperature of the deck slab 52. The temperature of the pavement 51 may be a value estimated from at least either the air temperature or the amount of solar radiation. The temperature of the deck slab 52 is the temperature of the underside of the deck slab. In the first embodiment, the correction value determined in accordance with the temperature information of the structure 50 is a correction value for correcting the density of the elastic wave source density distribution. In the first embodiment, the information based on the position location is the elastic wave source density distribution.

[0050] The evaluation unit 426 evaluates the deterioration state of the structure 50 based on the corrected information. Specifically, the evaluation unit 426 evaluates the deterioration state of the structure 50 using the corrected elastic wave source density distribution. For example, the evaluation unit 426 evaluates an area where the density of elastic wave sources is equal to or greater than a threshold as a healthy area, and evaluates an area where the density of elastic wave sources is less than the threshold as a damaged area. The evaluation area is the area through which the elastic wave sources and the wavy lines indicating the propagation paths of elastic waves to each sensor 20 pass. Therefore, the evaluation unit 426 evaluates the deterioration state of the structure within the evaluation area.

[0051] The storage unit 43 stores the transmission data, temperature information, vehicle information, and correction table acquired by the acquisition unit 421. The correction table is a table used by the correction unit 425 when making corrections. The correction table stores values ​​of Young's modulus corresponding to each temperature. For example, the correction table stores Young's modulus E at a temperature of 20°C. 20 and Young's modulus E at 25°C 25 The temperature information can then be converted into Young's modulus by the acquisition unit 421 and used in processing. The storage unit 43 is configured using a storage device such as a magnetic hard disk drive or a semiconductor storage device.

[0052] The display unit 44 displays the evaluation results under the control of the evaluation unit 426. Furthermore, under the control of the evaluation unit 426, the display unit 44 displays a group of wave lines indicating the elastic wave source and the propagation path of the elastic wave to each sensor 20, for example, by a projection method. The display unit 44 is an image display device such as a liquid crystal display or an organic EL (Electro Luminescence) display. The display unit 44 may be an interface for connecting the image display device to the structure evaluation device 40. In this case, the display unit 44 generates a video signal for displaying the evaluation results and outputs the video signal to the image display device connected to the display unit 44.

[0053] Next, the correction process performed by the correction unit 425 will be described in detail. First, the relationship between temperature and density of elastic wave sources, which is necessary for explaining the correction process performed by the correction unit 425, will be described. FIG. 3 is a diagram for explaining a method for measuring elastic waves in the first embodiment. In FIG. 3, as an example of a method for measuring elastic waves, it is considered to evaluate internal damage to a structure 50 based on elastic waves generated by a running part W (e.g., a tire) of a vehicle running on a road surface. Here, a case where the structure 50 is a road on which vehicles run will be described as an example. Note that the vehicle is not particularly limited and may be an ordinary running vehicle. By using elastic waves generated by an ordinary running vehicle, there is no need to restrict vehicles for inspection, which contributes to improving convenience for users. When the running part W of the vehicle comes into contact with the road surface, a load is applied to the road surface. This generates elastic waves within the structure 50. The generated elastic waves propagate within the structure 50 and are detected by each sensor 20 installed on a surface other than the road surface (e.g., the bottom surface).

[0054] The structure 50 is usually composed of a pavement 51 and a deck 52. The thickness of the pavement 51 is generally about 80 mm, and the thickness of the deck 52 is about 180 mm to 230 mm. An elastic wave (with amplitude A src ) propagates toward the underside of the deck 52. On the way, the elastic waves are partially reflected and partially transmitted at the interface 53 between the pavement 51 and the deck 52 due to the difference in acoustic impedance. The transmittance at this time is L t The elastic waves propagating further to the underside of the deck slab 52 reach the sensor 20 and are detected by the sensor 20. The amplitude of the detected elastic waves is designated as A. A plurality of sensors 20 are installed on the underside of the deck slab 52, and the elastic waves are detected by each sensor 20 with different time differences. The position of the elastic wave source SR is located based on the time differences when detected by each sensor.

[0055] Next, we will explain the behavior of elastic waves when temperature changes. It is known that the Young's modulus of a material is temperature-dependent. This is due to the fact that as the temperature T increases, the average interatomic distance r increases based on the potential characteristics (thermal expansion). Typically, for the asphalt of the pavement 51 and the concrete of the deck 52, the influence of thermal expansion due to temperature changes in the pavement 51, which is directly affected by solar radiation, is dominant. Young's modulus E also changes with thermal expansion. For example, as the interatomic distance r increases, Young's modulus E decreases. It is known that the relationship between temperature and Young's modulus can be approximated by the Wachtman Equation, shown below in Equation (1). The relationship between temperature and Young's modulus is specifically shown in Reference 1. (Reference 1: Yokohama National University, “Materials, Temperature, and Strength”, [online], [Retrieved September 8, 2022], Internet<URL: http: / / www.materep.ynu.ac.jp / archives / info / lec9> )

[0056]

number

[0057] The coefficient B in equation (1) is a value specific to the material. Equation (1) derives the relationship that Young's modulus E also decreases as the temperature decreases. For normal materials, the slope approaches zero at T = 0 K, but it can be considered to be nearly linear (quasi-linear relationship) around 300 K. There is a relationship between Young's modulus E and bulk modulus K via Poisson's ratio ν, as shown in equation (2) below.

[0058]

number

[0059] Equation (2) derives the relationship that as Young's modulus E decreases, the bulk modulus K also decreases. Furthermore, acoustic impedance Z is defined by density ρ and bulk modulus K as shown in the following equation (3).

[0060]

number

[0061] Equation (3) derives the relationship that as the bulk modulus K decreases, the acoustic impedance Z also decreases. Here, as shown in Figure 4, consider an elastic wave propagating through two materials (materials M1 and M2) with different acoustic impedances. In Figure 4, Z <Z ref From material M1 with acoustic impedance Z, ref The transmittance L of the elastic wave transmitted through the material M2 t can be expressed as the following equation (4). In particular, Z< <Z ref Transmittance L in the case t is 2Z / Z ref It can be expressed by the following approximate formula:

[0062]

number

[0063] The acoustic impedance of asphalt and concrete is usually such that the approximate formula shown in formula (4) can be applied. For example, material M1 corresponds to the pavement section 51, and material M2 corresponds to the deck section 52. The pavement section 51 is directly exposed to solar radiation, so the temperature change is larger than that of the deck section 52. Therefore, the transmittance L t The change in acoustic impedance Z corresponding to the pavement 51 has a large effect on the transmittance L. t If material attenuation is ignored, the amplitude A of the elastic wave arriving at the sensor 20 is reduced by the amplitude A of the elastic wave source as shown in the following equation (5): src Transmittance L t The value is multiplied by .

[0064]

number

[0065] According to equation (5), the transmittance L tThe relationship is derived such that when the logarithmic amplitude A of the elastic wave detected by the sensor 20 decreases, the logarithmic amplitude A of the elastic wave also decreases. dB A hit is recognized when the logarithmic amplitude A exceeds a predetermined measurement threshold. dB If the logarithmic amplitude A does not exceed a predetermined measurement threshold, it is not recognized as a hit. Therefore, the relationship between the elastic wave amplitude A and the number of elastic wave hits (number of AE hits) is such that the number of elastic wave hits decreases as the elastic wave amplitude A decreases. Furthermore, dB and the number of hits N ae It is empirically known that there exists a relationship between the earthquake and tsunami, as shown in the following equation (6). This is similar to the Gutenberg-Richter law in seismology. The Gutenberg-Richter law is described in Reference 2. (Reference 2: B. Gutenberg and C.F. Richter, “Seismicity of the Earth and Associated Phenomena,” Princeton University Press, 1949.)

[0066]

number

[0067] Number of hits N ae Some of the events are detected by multiple sensors 20, and the number of events N ev The event rate at this time is P ev An event represents an elastic wave generating event that has occurred in the structure 50. In this embodiment, an elastic wave generating event is, for example, a vehicle passing over the road surface. When one event occurs, elastic waves are detected (hits occur) at multiple sensors 20 at approximately the same time. Therefore, the number of events N ev is the number of hits N detected simultaneously by multiple sensors 20. ae Therefore, the number of hits N ae If decreases, the number of events N ev The relationship is that the number of passing vehicles is n carIf the measurement area is S, the density D of elastic wave sources per unit area and vehicle can be expressed as follows:

[0068]

number

[0069] According to equation (7), the number of events N ev This leads to the relationship that as the temperature T decreases, the density D of the elastic wave source also decreases. Organizing these relationships, there is a negative correlation between the Young's modulus E of the pavement 51 and the temperature T, and there is a linear relationship on a double logarithmic axis between the Young's modulus E of the pavement 51 and the density D of the elastic wave source. In other words, the relationship of the following equation (8) holds.

[0070]

number

[0071] Therefore, it is found that there is a negative correlation between temperature T and the density D of the elastic wave source. The above-mentioned dependencies are summarized to derive the relationship shown in Figure 5. Figure 5 is a diagram for explaining the relationship between temperature T and elastic wave density D. As shown in Figure 5, it can be seen that the influence propagates in the following order: temperature T of the pavement 51 → interatomic distance → Young's modulus → bulk modulus → acoustic impedance → transmittance → AE amplitude → number of AE hits → AE parameter → AE density. In the following explanation, the interatomic distance, Young's modulus, bulk modulus, acoustic impedance, transmittance, AE amplitude, number of AE hits, and AE parameter are described as intermediate parameters that indicate the relationship from temperature to AE density. The intermediate parameters are values ​​related to the temperature of the pavement 51. As a result, it can be seen that the elastic wave density D changes as the temperature T changes. For example, it can be seen that as the temperature T increases, the elastic wave density D decreases, and as the temperature T decreases, the elastic wave density D increases.

[0072] (Regarding the correction method in the first embodiment) The correction process performed by the correction unit 425 in the first embodiment will be described with reference to FIG. 6. In FIG. 6, Eex represents the Young's modulus corresponding to the temperature at the time of measurement, and D ex represents the density of the measured elastic wave source (the density of a certain area within the elastic wave source density distribution), and E ref represents the Young's modulus corresponding to a reference temperature (e.g., 20°C), and D comp represents the density of the elastic wave source after correction. In Fig. 6, E ex ,D ex ,E ref ,D comp is expressed logarithmically. Furthermore, in FIG. 6, a correction line 60 is a line used for correction based on the relationship between the density D and Young's modulus E of the elastic wave source. The correction line 60 is obtained by creating a log-log plot of the density D and Young's modulus E of the elastic wave source obtained in advance under a plurality of temperature conditions. The correction line 60 has a predetermined slope according to the density D and Young's modulus E of the elastic wave source obtained in advance under a plurality of temperature conditions.

[0073] For example, the correction line 60 is obtained as follows. The density D and Young's modulus E of the elastic wave source are obtained in advance under different temperature conditions (for example, 20°C, 25°C, 30°C, etc.). The logarithms of the density D and Young's modulus E of the elastic wave source obtained under each temperature condition are taken. A log-log plot of the logarithm of the density D and the logarithm of the Young's modulus E of the elastic wave source based on each temperature condition obtained in this way is created, thereby obtaining the correction line 60. The correction line 60 obtained in this way may be stored in the memory unit 43.

[0074] The correction unit 425 corrects the elastic wave source density distribution based on the temperature information at the time of measuring the elastic waves, the correction table stored in the storage unit 43, and the correction line 60. At this time, the correction unit 425 corrects the elastic wave source density distribution by correcting the density for each area in the elastic wave source density distribution. First, the correction unit 425 acquires temperature information from the acquisition unit 421. Next, the correction unit 425 refers to the correction table and acquires the value of Young's modulus corresponding to the temperature indicated by the acquired temperature information. For example, when the temperature is temperature T ex If so, the correction unit 425 calculates the temperature T ex The Young's modulus E corresponding to ex is obtained from the correction table.

[0075] Next, the correction unit 425 calculates the density D of the elastic wave source in one area in the elastic wave source density distribution. ex The correction unit 425 obtains the Young's modulus E on a logarithmic plot of the density D and Young's modulus E of the elastic wave source (the horizontal axis represents the logarithm of the Young's modulus E, and the vertical axis represents the logarithm of the density D of the elastic wave source). ex and the density of the elastic wave source D ex The correction unit 425 calculates the Young's modulus E corresponding to the reference temperature according to the correction line 60 set on the log-log plot of the density D and Young's modulus E of the elastic wave source. ref The density of the elastic wave source after correction, D, is derived from comp Then, the correction unit 425 calculates the density D of the elastic wave source in one area as a correction value (for example, the density D of the elastic wave source comp ) The correcting unit 425 performs the same process for each area. As a result, the elastic wave source density distribution is corrected.

[0076] 7 is a sequence diagram showing the flow of the deterioration state evaluation process by the structure evaluation system 100 in the first embodiment. The process in FIG. 7 is executed in response to the vehicle 10 traveling through the structure 50 to be evaluated. When a vehicle 10 travels over a structure 50 to be evaluated, the traveling part of the vehicle 10 comes into contact with the road surface. This causes an elastic wave 11 to be generated within the structure 50. Each of the multiple sensors 20 detects the elastic wave 11 generated within the structure 50 (step S101). Each of the multiple sensors 20 converts the detected elastic wave 11 into an electrical signal and outputs it to the signal processing unit 30 (step S102). The electrical signal output from each of the multiple sensors 20 is amplified by an amplifier (not shown). The amplified electrical signal is converted into a digital signal by an A / D converter.

[0077] The signal processing unit 30 receives the digital signal output from the A / D converter. The arrival time determination unit 303 of the signal processing unit 30 determines the arrival time of each elastic wave 11 (step S103). Specifically, the arrival time determination unit 303 determines the elastic wave arrival time using the clock input while the first gate signal is being input. The arrival time determination unit 303 outputs the determined elastic wave arrival time as time information to the transmission data generation unit 305. The arrival time determination unit 303 performs this process on all input digital signals.

[0078] The feature extraction unit 304 of the signal processing unit 30 extracts features of the denoising signal, which is a digital signal input while the first gate signal is being input (step S104). The feature extraction unit 304 outputs parameters related to the extracted features to the transmission data generation unit 305. The transmission data generation unit 305 generates transmission data including a sensor ID, time information, and parameters related to the features (step S105). The output unit 307 sequentially outputs the transmission data to the structure evaluation device 40 (step S106).

[0079] The communication unit 41 of the structure evaluation device 40 receives the transmission data output from the signal processing unit 30. The acquisition unit 421 acquires the transmission data received by the communication unit 41. The acquisition unit 421 records the acquired transmission data in the storage unit 43 (step S107). The event extraction unit 422 extracts transmission data for one event from the transmission data stored in the storage unit 43. The event extraction unit 422 outputs the extracted transmission data for one event to the position determination unit 423 and the distribution generation unit 424.

[0080] The position locating unit 423 locates the position of the elastic wave source based on the sensor ID and time information included in the transmission data output from the event extracting unit 422 and pre-stored sensor position information (step S108). Specifically, the position locating unit 423 first calculates the difference in arrival time of the elastic wave 11 to each of the multiple sensors 20. Next, the position locating unit 423 locates the position of the elastic wave source using the sensor position information and information on the difference in arrival time.

[0081] The position locating unit 423 executes the process of step S108 every time transmission data of one event is output from the event extracting unit 422 during the measurement period. In this way, the position locating unit 423 locates the positions of the multiple elastic wave sources. The position locating unit 423 outputs position information of the multiple elastic wave sources to the distribution generating unit 424. The acquiring unit 421 acquires temperature information from the outside (step S109). The acquiring unit 421 outputs the acquired temperature information to the correcting unit 425. Note that the timing at which the acquiring unit 421 acquires the temperature information is not limited to this timing, and may be any timing as long as it is before the process of FIG. 7 starts or before correction is performed by the correcting unit 425.

[0082] The distribution generation unit 424 generates an elastic wave source distribution using the position information of the multiple elastic wave sources output from the position determination unit 423. Specifically, the distribution generation unit 424 generates the elastic wave source distribution by plotting the positions of the elastic wave sources indicated by the obtained position information of the multiple elastic wave sources on virtual data. The distribution generation unit 424 generates an elastic wave source density distribution using the generated elastic wave source distribution (step S110). Specifically, first, the distribution generation unit 424 divides the elastic wave source distribution into multiple areas by dividing it into predetermined sections. Next, the distribution generation unit 424 calculates the density of elastic wave sources for each area. Then, the distribution generation unit 424 generates an elastic wave source density distribution by assigning the calculated elastic wave source density value for each area to each area. The distribution generation unit 424 outputs the generated elastic wave source density distribution to the correction unit 425.

[0083] The correcting unit 425 receives the elastic wave source density distribution output from the distribution generating unit 424, the correction table stored in the storage unit 43, and the temperature information output from the acquiring unit 421. The correcting unit 425 corrects the elastic wave source density distribution based on the input elastic wave source density distribution, correction table, and temperature information (step S111). The correcting unit 425 outputs the corrected elastic wave source density distribution to the evaluating unit 426.

[0084] The evaluation unit 426 evaluates the deterioration state of the structure using the corrected elastic wave source density distribution. The evaluation unit 426 outputs the evaluation result to the display unit 44. The display unit 44 displays the evaluation result output from the evaluation unit 426 (step S112). For example, the display unit 44 may display the corrected elastic wave source density distribution as the evaluation result, or may display areas that are considered to be damaged areas in a different display mode from other areas.

[0085] Fig. 8 is a diagram for explaining the effects of the first embodiment. The left diagram of Fig. 8 shows the evaluation results of the density of the elastic wave source when measured under different temperature environments, and the right diagram of Fig. 8 shows the temperature correction results based on the method of the embodiment. The average elastic wave source density before temperature correction (left diagram of Fig. 8) was 2.0 (+0.4 to -0.43), whereas after temperature correction (right diagram of Fig. 8) it was 2.2 (+0.28 to -0.28), indicating that the error range was reduced by 32%.

[0086] In the structure evaluation system 100 configured as described above, the elastic wave source density distribution is corrected based on the Young's modulus corresponding to temperature and the density of the elastic wave source. This makes it possible to generate an elastic wave source density distribution that takes into account the influence of temperature. By using the elastic wave source distribution obtained in this way to evaluate the deterioration state of the structure, it is possible to improve the accuracy of the evaluation of the deterioration state of the structure.

[0087] (Second embodiment) In the second embodiment, a configuration will be described in which correction is performed using a simpler method than in the first embodiment. In the second embodiment, the system configuration and the configuration of each device are the same as in the first embodiment. The second embodiment differs from the first embodiment in that a correction table is not used, and in the correction line and processing of the correction unit 425. The following description will focus on the differences.

[0088] The correction unit 425 corrects information based on the position location by the position location unit 423, using a correction value determined according to the temperature information of the structure 50 acquired by the acquisition unit 421. In the second embodiment, the correction value determined according to the temperature information of the structure 50 is a correction value for correcting the density of the elastic wave source density distribution. In the second embodiment, the information based on the position location is the elastic wave source density distribution.

[0089] (Regarding the correction method in the second embodiment) The correction process performed by the correction unit 425 in the second embodiment will be described with reference to FIG. 9. In FIG. 9, T ex represents the temperature at the time of measurement, and D ex represents the density of the measured elastic wave source (density in a certain area), and T ref represents the reference temperature (e.g., 20°C), and D comp represents the density of the elastic wave source after correction. Furthermore, in FIG. 9, a correction line 61 is a line used for correction based on the relationship between the density D of the elastic wave source and the temperature T. The correction line 61 is a line obtained by linear approximation of the slope when the density D of the elastic wave source and the temperature T are plotted, which are obtained in advance under a plurality of temperature conditions. The correction line 61 has a predetermined slope according to the density D of the elastic wave source and the temperature T, which are obtained in advance under a plurality of temperature conditions. The correction line 61 may be stored in the storage unit 43.

[0090] The correction unit 425 corrects the elastic wave source density distribution based on the temperature information at the time of measuring the elastic waves and the correction line 61. At this time, the correction unit 425 corrects the elastic wave source density distribution by correcting the density for each area in the elastic wave source density distribution. First, the correction unit 425 acquires temperature information from the acquisition unit 421. For example, if the temperature indicated by the temperature information acquired by the correction unit 425 is T ex Next, the corrector 425 calculates the density D of the elastic wave source in one area in the elastic wave source density distribution. ex The correction unit 425 obtains the temperature T on a graph showing the relationship between the density D of the elastic wave source and the temperature T (the horizontal axis represents the temperature T, and the vertical axis represents the density D of the elastic wave source). ex and the density of the elastic wave source D exThe correction unit 425 calculates the reference temperature T according to the correction line 61 set on the graph showing the relationship between the density D and the temperature T of the elastic wave source. ref The density of the elastic wave source after correction, D, is derived from comp Then, the correction unit 425 calculates the density D of the elastic wave source in one area as a correction value (for example, the density D of the elastic wave source comp ) The correcting unit 425 performs the same process for each area. As a result, the elastic wave source density distribution is corrected.

[0091] In this way, the correction unit 425 in the second embodiment corrects the density D of the elastic wave sources in a direction increasing at a predetermined rate when the temperature indicated by the acquired temperature information is high, and corrects the density D of the elastic wave sources in a direction decreasing at a predetermined rate when the temperature is low. It is generally known that there is a proportional relationship between the pavement area and the air temperature (temperature) (see, for example, Reference 3).

[0092] (Reference 3: Li. T, “Influencing Parameters on Tire-Pavement Interaction Noise: Review, Experiments”, and Design Considerations. Designs 2018, 2, 38.)

[0093] According to Reference 1, it is possible to obtain and correct the slope of a plot of the relationship between the density D of the elastic wave source and the temperature, which is determined in advance under a plurality of temperature conditions, by linear approximation. In particular, a correction value can be obtained so that when the temperature is high, the density is corrected in a direction that increases at a predetermined rate, and when the temperature is low, the density is corrected in a direction that decreases at a predetermined rate.

[0094] (Third embodiment) In the third embodiment, a configuration for correcting density based on intermediate parameters will be described. In the third embodiment, the system configuration and the configuration of each device are similar to those of the first and second embodiments. The third embodiment differs from the first and second embodiments in that a correction table is not used, and in the correction line and processing of the correction unit 425. The following description will focus on the differences.

[0095] The correction unit 425 in the third embodiment corrects the density D of the elastic wave source using a correction value obtained based on the relationship between any one of the intermediate parameters (e.g., interatomic distance, Young's modulus, bulk modulus, acoustic impedance, transmittance, AE amplitude, AE hit count, and AE parameter) and the density D of the elastic wave source.

[0096] (Regarding the correction method in the third embodiment) The correction process performed by the correction unit 425 in the third embodiment will be described. Here, the case where the acoustic impedance Z is used as the intermediate parameter will be described. When other intermediate parameters are used, the acoustic impedances shown below can be replaced with the terms of the other intermediate parameters. Here, Z ex represents the acoustic impedance during measurement, and D ex represents the density of the measured elastic wave source (density in a certain area), and Z ref represents the reference acoustic impedance at a given temperature (e.g., the acoustic impedance at 20°C), and D comp represents the density of the elastic wave source after correction. When the acoustic impedance Z is used as the intermediate parameter, the correction line is a line used for correction based on the relationship between the density D of the elastic wave source and the acoustic impedance Z. The correction line is a line obtained by linear approximation of the slope when the density D of the elastic wave source and the acoustic impedance Z are plotted, which have been obtained in advance under a plurality of acoustic impedance conditions. The correction line has a predetermined slope according to the density D and the acoustic impedance Z of the elastic wave source obtained in advance under a plurality of acoustic impedance conditions. The correction line may be stored in the storage unit 43.

[0097] The correction unit 425 corrects the elastic wave source density distribution based on the acoustic impedance information at the time of elastic wave measurement and the correction line. At this time, the correction unit 425 corrects the elastic wave source density distribution by correcting the density for each area in the elastic wave source density distribution. First, the correction unit 425 acquires acoustic impedance information from the acquisition unit 421. For example, if the acoustic impedance indicated by the acoustic impedance information acquired by the correction unit 425 is Z ex Next, the corrector 425 calculates the density D of the elastic wave source in one area in the elastic wave source density distribution. ex The correction unit 425 obtains the acoustic impedance Z on a graph showing the relationship between the density D of the elastic wave source and the acoustic impedance Z (the horizontal axis represents the acoustic impedance Z, and the vertical axis represents the density D of the elastic wave source). ex and the density of the elastic wave source D ex The correction unit 425 calculates the reference acoustic impedance Z according to the correction line set on the graph showing the relationship between the density D of the elastic wave source and the acoustic impedance Z. ref The density of the elastic wave source after correction, D, is derived from comp Then, the correction unit 425 calculates the density D of the elastic wave source in one area as a correction value (for example, the density D of the elastic wave source comp ) The correcting unit 425 performs the same process for each area. As a result, the elastic wave source density distribution is corrected.

[0098] In the structure evaluation system 100 of the third embodiment configured as described above, even when intermediate parameters are used, it is possible to generate an elastic wave source density distribution that takes into account the influence of temperature, as in the first and second embodiments. By evaluating the deterioration state of a structure using the elastic wave source distribution obtained in this manner, it is possible to improve the accuracy of the evaluation of the deterioration state of the structure.

[0099] (Fourth embodiment) In the first to third embodiments, a configuration for correcting density was described. In the fourth embodiment, a configuration for correcting the number of hits by changing a threshold for detecting hits will be described. In the fourth embodiment, the system configuration is similar to that of the first to third embodiments. In the fourth embodiment, a correction unit 425 is provided in the signal processing unit 30, and the processing of the correction unit 425 differs from that of the first to third embodiments. The following description will focus on the differences.

[0100] In the fourth embodiment, a correction unit 425 is provided in the signal processing unit 30. The correction unit 425 corrects information based on the position location by the position location unit 423, using a correction value determined in accordance with temperature information of the structure 50. In the fourth embodiment, the correction value determined in accordance with temperature information of the structure 50 is a correction value for correcting the threshold value of the gate generation circuit. In the fourth embodiment, the information based on the position location is the threshold value of the gate generation circuit. The correction unit 425 may be provided in the structure evaluation device 40. In that case, the correction unit 425 in the structure evaluation device 40 can be configured to transmit information related to the threshold value of the gate generation circuit 302 to the gate generation circuit 302 in the signal processing unit 30.

[0101] (Regarding the correction method in the fourth embodiment) The correction unit 425 corrects the number of hits by changing the threshold in the gate generation circuit 302. More specifically, the correction unit 425 refers to a correction table in which predetermined temperatures are associated with thresholds, and corrects the threshold in the gate generation circuit 302. Lowering the threshold results in more hits being detected, whereas raising the threshold results in fewer hits being detected. Because there is a correlation between the number of hits and density, the correction unit 425 performs correction so that the threshold is raised when the density D of the elastic wave sources is lowered, and lowered when the density D of the elastic wave sources is increased. For example, the correction unit 425 acquires temperature information from an external source before measurement. The temperature information may be acquired from the acquisition unit 421 of the structure evaluation device 40 or from another source. The correction unit 425 refers to the correction table and acquires a threshold corresponding to the temperature indicated by the acquired temperature information as a correction value. The correction unit 425 corrects the threshold in the gate generation circuit 302 to the acquired correction value.

[0102] In the structure evaluation device 40, the distribution generation unit 424 outputs the generated elastic wave source density distribution to the evaluation unit 426. The evaluation unit 426 evaluates the deterioration state of the structure based on the elastic wave source density distribution output from the distribution generation unit 424.

[0103] (Modification 1 common to all embodiments) The signal processing unit 30 may be provided in the structure evaluation device 40.

[0104] (Modification 2 common to all embodiments) In each of the above embodiments, a configuration has been shown in which multiple sensors 20-1 to 20-n are connected to one signal processing unit 30. The structure evaluation system 100 may include multiple signal processing units 30, and each sensor 20 may be connected to a different signal processing unit 30.

[0105] (Modification 3 common to all embodiments) Some or all of the functional units included in the structure evaluation device 40 may be included in another device. For example, the display unit 44 included in the structure evaluation device 40 may be included in the other device. When configured in this manner, the structure evaluation device 40 transmits the evaluation results to the other device that is equipped with the display unit 44. The other device that is equipped with the display unit 44 displays the received evaluation results.

[0106] According to at least one of the embodiments described above, the accuracy of evaluating the deterioration state of a structure can be improved by having a plurality of sensors 20 that detect elastic waves generated from the structure 50, a positioning unit 423 that locates the position of the source of the plurality of elastic waves based on the plurality of elastic waves detected by each of the plurality of sensors 20, a correction unit 425 that corrects information based on the positioning by the positioning unit 423 using a correction value determined according to the temperature of the structure, and an evaluation unit 426 that evaluates the deterioration state of the structure based on the corrected information.

[0107] Although several embodiments of the present invention have been described, these embodiments are presented as examples and are not intended to limit the scope of the invention. These embodiments can be implemented in various other forms, and various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. These embodiments and their modifications are included within the scope and spirit of the invention, as well as within the scope of the invention described in the claims and their equivalents. [Explanation of symbols]

[0108] 20, 20-1 to 20-n...sensor, 30...signal processing unit, 40...structure evaluation device, 41...communication unit, 42...control unit, 43...storage unit, 44...display unit, 421...acquisition unit, 422...event extraction unit, 423...positioning unit, 424...distribution generation unit, 425...correction unit, 426...evaluation unit, 301...waveform shaping filter, 302...gate generation circuit, 303...arrival time determination unit, 304...feature extraction unit, 305...transmission data generation unit, 306...memory, 307...output unit

Claims

1. a plurality of sensors for detecting elastic waves generated from the structure; a position locating unit that locates the positions of sources of the elastic waves based on the elastic waves detected by each of the sensors; a correction unit that corrects information based on the position location determined by the position location unit using a correction value determined in accordance with the temperature of the structure; an evaluation unit that evaluates a deterioration state of the structure based on the corrected information; Equipped with The structure is composed of at least a pavement portion on which vehicles can travel and a deck portion that supports the pavement portion, A structure evaluation system in which the temperature of the structure is a value related to the temperature of the pavement portion.

2. The structure evaluation system according to claim 1 , wherein the structure has a structure made of at least two materials that have different responses to temperature.

3. the location-based information includes information about density; 3. The structure evaluation system of claim 1, wherein the correction unit uses the correction value to correct the density in a direction that increases when the temperature of the pavement is high, and to correct the density in a direction that decreases when the temperature of the pavement is low.

4. The structure evaluation system according to claim 3 , wherein the correction unit calculates the correction value by referring to a correction table in which values ​​of Young's modulus at each temperature are registered.

5. 3. The structure evaluation system of claim 1, wherein the correction unit corrects the threshold for detecting the plurality of elastic waves in a lower direction when the temperature of the structure is high, and corrects the threshold in a higher direction when the temperature of the structure is low.

6. 3. The structure evaluation system according to claim 1, wherein the value related to the temperature of the pavement is air temperature.

7. 3. The structure evaluation system according to claim 1, wherein the value related to the temperature of the pavement portion is the temperature of the underside of the deck portion.

8. 3. The structure evaluation system according to claim 1, wherein the value related to the temperature of the pavement is a road surface temperature measured by a vehicle traveling on the pavement.

9. 3. The structure evaluation system according to claim 1, wherein the value related to the temperature of the pavement is the amount of solar radiation.

10. 3. A structure evaluation system according to claim 1 or 2, wherein the value related to the temperature of the pavement portion is any one of the values ​​of interatomic distance, Young's modulus, bulk modulus, acoustic impedance, transmittance, reflectance, elastic wave amplitude, number of elastic wave hits, and elastic wave parameter.

11. 3. The structure evaluation system according to claim 1, wherein the temperature of the structure is a value related to either a difference or a ratio between the temperature of the pavement portion and the temperature of the deck portion.

12. The structure evaluation system of claim 11, wherein the temperature of the pavement is a value estimated based on either air temperature or solar radiation, or the temperature of the surface of the pavement, and the temperature of the deck is the temperature of the underside of the deck.

13. 3. The structure evaluation system according to claim 1, wherein the value related to the temperature of the pavement is a statistical value of the temperature during measurement.

14. a position locating unit that locates the positions of sources of the elastic waves based on a plurality of elastic waves detected by a plurality of sensors that detect elastic waves generated from a structure; a correction unit that corrects information based on the position location determined by the position location unit using a correction value determined in accordance with the temperature of the structure; an evaluation unit that evaluates a deterioration state of the structure based on the corrected information; Equipped with The structure is composed of at least a pavement portion on which vehicles can travel and a deck portion that supports the pavement portion, A structure evaluation device, wherein the temperature of the structure is a value related to the temperature of the pavement portion.

15. Detects elastic waves generated from structures, locating a position of a source of the plurality of elastic waves based on the detected plurality of elastic waves; correcting information based on the position location using a correction value determined according to the temperature of the structure; Evaluating the deterioration state of the structure based on the corrected information; The structure is composed of at least a pavement portion on which vehicles can travel and a deck portion that supports the pavement portion, A structure evaluation method, wherein the temperature of the structure is a value related to the temperature of the pavement portion.

16. On the computer, a position locating step of locating positions of sources of the elastic waves based on a plurality of elastic waves detected by a plurality of sensors that detect elastic waves generated from a structure; a correction step of correcting information based on the position location in the position location step using a correction value determined in accordance with the temperature of the structure; an evaluation step of evaluating a deterioration state of the structure based on the corrected information; Execute The structure is composed of at least a pavement portion on which vehicles can travel and a deck portion that supports the pavement portion, A computer program for detecting a temperature of the structure, the temperature of the structure being a value related to a temperature of the pavement.

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