Concrete structure monitoring system and concrete structure monitoring method

Abstract

The objective is to provide a concrete structure monitoring system 10 and a concrete structure monitoring method that can estimate the location of elastic wave generation even in a box girder 1 having a lower slab 4 and side wall portions 5 with different thickness directions. [Solution] A concrete structure monitoring system 10 for calculating the estimated fracture location of PC steel members 2 in a box girder 1 in which PC steel members 2 are embedded in the lower slab 4 and side wall 5, characterized in that it comprises multiple acceleration sensors arranged on the main surface of the lower slab 4 and the main surface of the side wall 5, a main surface identification means (terminal control unit 45) that identifies the main surface of the lower slab 4 or side wall 5 on which the acceleration sensors are arranged as a detection surface based on the position information of the acceleration sensors that have detected elastic waves and the detection order of elastic waves, and a calculation means (terminal control unit 45) that calculates the estimated fracture location of the PC steel members 2 based on the position information of the multiple acceleration sensors on the detection surface and the difference in arrival times of elastic waves detected by the acceleration sensors.

Description

Technical Field

[0001] The present invention relates to a concrete structure monitoring system and a concrete structure monitoring method for monitoring elastic waves propagating inside a prestressed concrete structure such as a bridge, for example, and calculating the location where damage to the concrete structure occurs based on the elastic waves.

Background Art

[0002] Concrete structures such as bridges on roads and railways may be damaged over time after being put into service, such as cracks in the concrete structure or breakage of PC steel materials embedded inside the concrete structure. For example, in a prestressed concrete structure constructed by the post-tensioning method, it is known that the PC steel materials embedded inside break due to corrosion caused by insufficient filling of grout.

[0003] Since such damage causes a decrease in the durability of the concrete structure, it is desirable to detect the occurrence and location of damage in the concrete structure at an early stage. Therefore, a technique has been proposed for detecting elastic waves caused by damage in a concrete structure and calculating the estimated generation position of the elastic waves based on the difference in arrival times of the detected elastic waves.

[0004] For example, Patent Document 1 detects elastic waves generated when PC steel materials break in a prestressed concrete structure using an AE sensor arranged on the surface of the prestressed concrete structure as elastic wave detection means, and calculates the estimated breakage position of the PC steel materials based on the difference in arrival times of the detected elastic waves.

[0005] By the way, some concrete structures have a first part and a second part with different thickness directions, such as a floor slab and a side wall in a box girder extending in the bridge axis direction.

[0006] In such concrete structures, it is conceivable to place multiple elastic wave detection means on both the main surface of the first section and the main surface of the second section, and to calculate the estimated location of the elastic wave generation based on the arrival times of all elastic waves detected by the elastic wave detection means.

[0007] However, in this case, for example, a body wave, which is an elastic wave generated at the first site, will propagate to the second site through the bent portion, which is the boundary between the first and second sites, attenuating at a much larger rate than a surface wave, which is an elastic wave propagating along the surface of the first site.

[0008] Therefore, while elastic wave detection means close to the source of the elastic wave detects the body wave, elastic wave detection means located further away from the source of the elastic wave are more likely to detect surface waves as elastic waves, which have higher energy and are less susceptible to attenuation than body waves.

[0009] Consequently, the estimated location of the elastic wave generation is calculated using the arrival times of the body wave and the surface wave, which tends to reduce the accuracy of the calculated estimated location. For this reason, there was a problem in calculating the estimated location of the elastic wave generation in concrete structures that have a first and second section with different thickness directions. [Prior art documents] [Patent Documents]

[0010] [Patent Document 1] Special Publication No. 5-64299 [Overview of the Initiative] [Problems that the invention aims to solve]

[0011] In view of the above-mentioned problems, the present invention aims to provide a concrete structure monitoring system and a concrete structure monitoring method that can estimate the location of elastic wave generation even in a concrete structure having a first part and a second part with different thickness directions. [Means for solving the problem]

[0012] This invention relates to a concrete structure monitoring system for calculating the estimated location of elastic waves caused by damage to a concrete structure having a first portion and a second portion having different thickness directions and intersecting at a predetermined angle, and is characterized by comprising: multiple elastic wave detection means provided on the main surface of the first portion and the main surface of the second portion, respectively, for detecting the elastic waves generated in the concrete structure; main surface identification means for identifying the main surface of the first portion or the main surface of the second portion on which the elastic wave detection means is provided as a detection surface based on the position information of the elastic wave detection means that detected the elastic waves and the detection order of the elastic waves; and calculation means for calculating the estimated location of the elastic waves based on the position information of the multiple elastic wave detection means on the detection surface and the difference in arrival times of the elastic waves detected by the elastic wave detection means.

[0013] Furthermore, this invention relates to a concrete structure monitoring method for calculating the estimated generation location of elastic waves caused by damage to a concrete structure having a first portion and a second portion having different thickness directions and intersecting at a predetermined angle, characterized in that it performs an elastic wave detection step in which a plurality of elastic wave detection means provided on the main surface of the first portion and the main surface of the second portion respectively detect the elastic waves generated in the concrete structure; a main surface identification step in which a main surface identification means identifies the main surface of the first portion or the main surface of the second portion provided with the elastic wave detection means as a detection surface based on the position information of the elastic wave detection means that detected the elastic waves and the detection order of the elastic waves; and a calculation step in which a calculation means calculates the estimated generation location of the elastic waves based on the position information of the plurality of elastic wave detection means on the detection surface and the difference in arrival times of the elastic waves detected by the elastic wave detection means.

[0014] The first and second parts mentioned above refer to parts with different thickness directions in a closed cross-sectional shape with a roughly rectangular cross-section, such as a pair of floor slabs and a pair of side walls in a box girder, or parts with different thickness directions in a roughly L-shaped cross-section.

[0015] The above-mentioned concrete structures refer to prestressed concrete structures with embedded PC steel bars, or concrete structures without embedded PC steel bars, such as bridges, box culverts, and precast concrete structures over which automobiles and railway vehicles pass. The principal surface of the first part described above refers to both of the two principal surfaces that are opposite each other in the thickness direction, or to one of the two principal surfaces. Similarly, the principal surface of the second part described above refers to both of the two principal surfaces that are opposite each other in the thickness direction, or to one of the two principal surfaces.

[0016] When we say that multiple units are provided on the main surface of the first unit and the main surface of the second unit, we mean that they are provided in a state of contact with the main surface or in a state of non-contact with the main surface. The above-mentioned elastic wave detection means refers to an acceleration sensor, vibration sensor, or AE sensor provided in contact with the main surface, or a laser Doppler vibrometer provided in non-contact with the main surface.

[0017] According to this invention, the main surface of the first part or the main surface of the second part is identified as the detection surface based on the positional information of the elastic wave detection means that detected the elastic wave and the detection order of the elastic wave, so that it is possible to estimate whether the elastic wave originated in the first part or the second part. In particular, the concrete structure monitoring system can estimate whether the elastic wave originated in the first part or the second part, even if the damage occurred inside the concrete structure.

[0018] Furthermore, since the estimated location of the elastic wave is calculated based on the difference in arrival times of elastic waves detected by the elastic wave detection means on the detection surface, the concrete structure monitoring system can prevent the arrival times of elastic waves detected by elastic wave detection means installed on main surfaces other than the detection surface from being used in calculating the estimated location of the elastic wave.

[0019] As a result, the concrete structure monitoring system and the concrete structure monitoring method can improve the positional accuracy of the calculated estimated occurrence position compared to the case where the estimated occurrence position is calculated based on the arrival times of the elastic waves respectively detected by the plurality of elastic wave detection means provided for the main surfaces of the first part and the main surface of the second part.

[0020] Therefore, the concrete structure monitoring system and the concrete structure monitoring method can estimate the generation position of the elastic wave even in a concrete structure having a first part and a second part with different thickness directions.

[0021] As an aspect of this invention, the main surface specifying means may be configured to specify the main surface of the first part or the main surface of the second part provided with the elastic wave detection means that first detected the elastic wave and the elastic wave detection means that second detected the elastic wave as the detection surface.

[0022] According to this configuration, the detection surface can be specified more efficiently compared to the case where the detection surface is specified based on the detection order of the elastic waves detected by three or more elastic wave detection means. For this reason, the concrete structure monitoring system can efficiently calculate the estimated generation position of the elastic wave.

[0023] Also, as an aspect of this invention, four or more elastic wave detection means may be provided for each of the main surface of the first part and the main surface of the second part, and the calculation means may be configured to calculate the estimated generation position based on the elastic waves detected by four or more of the elastic wave detection means on the detection surface.

[0024] According to this configuration, since the estimated generation position is calculated based on the elastic waves detected by four or more elastic wave detection means provided for the detection surface, for example, compared to the case where the estimated generation position is calculated based on the elastic waves detected by two elastic wave detection means, the positional accuracy of the calculated estimated generation position can be further improved.

[0025] As an aspect of the present invention, four or more elastic wave detection means may be provided for the main surfaces of the first part and the second part, respectively, and the calculation means may calculate the estimated generation position based on the arrival times of the elastic waves detected by the elastic wave detection means that first detected the elastic waves and the elastic wave detection means located at a position spaced apart from the elastic wave detection means in a predetermined direction.

[0026] The above-mentioned predetermined direction refers to, for example, the longitudinal direction of the detection surface, the lateral direction of the detection surface, or the crossing direction crossing the longitudinal direction of the detection surface. According to this configuration, since the estimated generation position is calculated based on the elastic waves detected by two elastic wave detection means spaced apart in a predetermined direction, at least the generation position of the elastic wave in the predetermined direction can be estimated.

[0027] As an aspect of the present invention, four or more elastic wave detection means may be provided for the main surfaces of the first part and the second part, respectively. The calculation means includes a first calculation means for calculating the estimated generation position based on the arrival times of the elastic waves detected by four or more elastic wave detection means on the detection surface, and when the estimated generation position calculated by the first calculation means is not located within the detection surface, a second calculation means for calculating the estimated generation position based on the arrival times of the elastic waves detected by the elastic wave detection means that first detected the elastic waves and the elastic wave detection means located at a position spaced apart from the elastic wave detection means in a predetermined direction.

[0028] According to this configuration, even when the calculation accuracy of the estimated generation position by the first calculation means is reduced because the elastic waves detected by four or more elastic wave detection means include elastic waves that become noise, the generation position of the elastic wave in the predetermined direction can be estimated by the second calculation means.

[0029] In another aspect of this invention, the concrete structure is provided with a haunch portion having an inclined surface at the bending portion between the first portion and the second portion, and at least one of the plurality of elastic wave detection means is provided with respect to the inclined surface of the haunch portion, and the main surface identification means is configured to identify the inclined surface of the haunch portion as the main surface of the first portion or the main surface of the second portion, depending on the combination of the elastic wave detection means that first detected the elastic wave and the elastic wave detection means that second detected the elastic wave.

[0030] With this configuration, the elastic wave detection means provided for the haunch portion can be considered as an elastic wave detection means provided for the first portion, or an elastic wave detection means provided for the second portion. Therefore, the concrete structure monitoring system can reduce the number of elastic wave detection means compared to, for example, a system that provides four elastic wave detection means for each of the first and second parts. This allows the concrete structure monitoring system to estimate the location of elastic wave generation while keeping costs down.

[0031] In another aspect of this invention, the concrete structure may be formed in a closed cross-sectional shape extending in a predetermined direction, and the plurality of elastic wave detection means may be provided on the inner surface of the closed cross-sectional shape.

[0032] With this configuration, the elastic wave detection means is not directly exposed to wind, rain, or direct sunlight, making it possible not only to calculate the estimated location of elastic wave generation but also to monitor the generation of elastic waves over a long period of time.

[0033] Furthermore, in an embodiment of this invention, the concrete structure may be a prestressed concrete structure in which PC steel members are embedded in both the first and second portions, and the estimated fracture position of the PC steel members may be calculated as the estimated generation position of the elastic wave. The above-mentioned prestressed concrete structures refer to concrete structures constructed using either the post-tensioning or pre-tensioning method.

[0034] This configuration allows for monitoring of PC steel fractures in prestressed concrete structures, such as those caused by corrosion due to insufficient grout filling, and enables the calculation of the estimated fracture location of the PC steel when fracture occurs. [Effects of the Invention]

[0035] The present invention provides a concrete structure monitoring system and a concrete structure monitoring method that can estimate the location of elastic wave generation even in concrete structures having first and second portions with different thickness directions. [Brief explanation of the drawing]

[0036] [Figure 1] A schematic diagram illustrating the basic structure of a box girder. [Figure 2] An explanatory diagram illustrating the general structure of PC steel materials embedded in a box girder. [Figure 3] A block diagram showing the internal configuration of a concrete structure monitoring system. [Figure 4] An explanatory diagram showing the locations of the eight accelerometers. [Figure 5] An explanatory diagram illustrating the unfolded structure of the registered data. [Figure 6] A flowchart illustrating the processing flow in a monitoring device. [Figure 7] An explanatory diagram illustrating the monitoring screen that displays the estimated fracture location. [Figure 8] A flowchart illustrating the flow of processing operations in an information processing terminal. [Figure 9] An explanatory diagram illustrating the estimated fracture location of PC steel. [Figure 10] An explanatory diagram illustrating the propagation state of elastic waves. [Figure 11] A schematic diagram illustrating the outline of a box girder in another embodiment. [Modes for carrying out the invention]

[0037] One embodiment of this invention will be described below with reference to the drawings. The concrete structure monitoring system 10 in this embodiment is a PC steel member 2 fracture monitoring system that monitors elastic waves propagating inside the box girder 1 of a bridge, which is a prestressed concrete structure, and calculates the estimated fracture location of the PC steel member 2 based on the elastic waves. This concrete structure monitoring system 10 will be explained with reference to Figures 1 to 5.

[0038] Figure 1 is a schematic diagram illustrating the outline of the box girder 1, with Figure 1(a) showing an external perspective view of the box girder 1, Figure 1(b) showing a front view of the box girder 1, and Figure 2 showing an explanatory diagram illustrating the outline of the PC steel members 2 embedded in the box girder 1. Furthermore, Figure 3 shows a block diagram of the concrete structure monitoring system 10, Figure 4 shows an explanatory diagram illustrating the locations of the eight acceleration sensors, and Figure 5 shows an explanatory diagram illustrating the unfolded view 47 of the registered data 46.

[0039] Furthermore, to clarify the illustration, the upper floor slab 3 is shown as a dashed line in Figure 2, and the lower surface of the upper floor slab 3, the inclined surface 6a of the upper haunch portion 6, and the inner surface 5a of the right side wall portion 5 are shown as dashed lines in Figure 4.

[0040] Furthermore, in Figure 1(a), the upper side is considered to be above box girder 1, and the lower side is considered to be below box girder 1. In the figure, arrow X indicates the bridge axis direction of box girder 1 (hereinafter referred to as bridge axis direction X), and arrow Y indicates the direction perpendicular to the bridge axis, which is approximately perpendicular to the bridge axis direction X in a plan view (hereinafter referred to as bridge axis perpendicular direction Y).

[0041] First, as shown in Figure 1(a), the box girder 1 of the bridge in this embodiment is a prestressed concrete structure constructed using a post-tensioning method, and is formed in a closed cross-sectional shape extending in the bridge axis direction X of the bridge.

[0042] Specifically, the box girder 1 is formed by tensioning the PC steel members 2 (see Figure 2) inside the sheath pipes (not shown) that are pre-embedded in the concrete after the poured concrete has hardened, and then filling the sheath pipes with grout to anchor them to the concrete.

[0043] Such a box girder 1 is integrally formed from an upper deck 3 and a lower deck 4 facing each other at a predetermined distance in the vertical direction, a pair of side wall sections 5 facing each other in the direction Y perpendicular to the bridge axis, a pair of upper haunch sections 6 spanning from the upper deck 3 to the upper part of the side wall section 5, and a pair of lower haunch sections 7 spanning from the lower deck 4 to the lower part of the side wall section 5.

[0044] More specifically, as shown in Figure 1, the upper deck slab 3 has thickness in the vertical direction and is formed as a flat plate with a roughly rectangular shape in plan view, elongated in the bridge axis direction X. The upper surface of this upper deck slab 3 is formed flat so that it becomes, for example, a road through which vehicles pass.

[0045] Furthermore, as shown in Figure 1, the lower deck slab 4 has thickness in the vertical direction and is formed as a flat plate with a roughly rectangular shape when viewed from the bottom, having a length X in the bridge axis direction that is roughly the same as that of the upper deck slab 3. This lower deck slab 4 is formed with a length Y in the direction perpendicular to the bridge axis that is shorter than the length Y in the direction perpendicular to the bridge axis of the upper deck slab 3. Furthermore, as shown in Figure 2, multiple PC steel members 2 extending in the bridge axis direction X are embedded inside the lower deck slab 4 at predetermined intervals in the direction perpendicular to the bridge axis Y.

[0046] Furthermore, as shown in Figure 1, the pair of side wall sections 5 have thickness in the direction Y perpendicular to the bridge axis and are formed in a flat plate shape with a roughly rectangular shape in side view, having a length X in the bridge axis direction that is roughly the same as the upper deck slab 3. The upper end of each side wall section 5 is connected to the upper deck slab 3 via an upper haunch section 6, which will be described later, and the lower end is connected to the lower deck slab 4 via a lower haunch section 7. Furthermore, as shown in Figure 2, multiple PC steel members 2 extending in the bridge axis direction X are embedded inside the pair of side wall sections 5 at predetermined intervals in the vertical direction.

[0047] Furthermore, as shown in Figure 1(b), the pair of upper haunch portions 6 are bent portions provided at the point where the upper floor slab 3 and the side wall portion 5 intersect, and are formed in a shape having inclined surfaces 6a that are inclined with respect to both the lower surface of the upper floor slab 3 and the inner surface 5a of the side wall portion 5.

[0048] Furthermore, as shown in Figure 1(b), the pair of lower haunch portions 7 are bent portions provided at the point where the lower floor slab 4 and the side wall portion 5 intersect, and are formed in a shape having an inclined surface 7a that is inclined with respect to both the upper surface 4a of the lower floor slab 4 and the inner surface 5a of the side wall portion 5.

[0049] For the sake of clarity in the following explanation, of the pair of side wall sections 5, the side wall section 5 located on the right side in Figure 1(b) will be referred to as the right side wall section 5, and the side wall section 5 located on the left side in Figure 1(b) will be referred to as the left side wall section 5.

[0050] Furthermore, of the pair of lower haunch sections 7, the lower haunch section 7 located on the right side in Figure 1(b) is designated as the right lower haunch section 7, and the lower haunch section 7 located on the left side in Figure 1(b) is designated as the left lower haunch section 7.

[0051] In the concrete structure monitoring system 10 described later, the box girder 1 with the above configuration is identified as having the upper surface 4a of the lower slab 4 and the inclined surfaces 7a of the pair of lower haunch sections 7 as the main surface 4A of the lower slab 4, the inner surface 5a of the right side wall section 5 and the inclined surface 7a of the right lower haunch section 7 as the main surface 5A of the right side wall section 5, and the inner surface 5a of the left side wall section 5 and the inclined surface 7a of the left lower haunch section 7 as the main surface 5A of the left side wall section 5.

[0052] Next, the concrete structure monitoring system 10 in this embodiment will be described. The concrete structure monitoring system 10 has the function of remotely monitoring the condition of the PC steel members 2 embedded inside the box girder 1, the function of calculating the estimated fracture location of the PC steel members 2 when fracture occurs, and the function of notifying the system user of the condition of the PC steel members 2.

[0053] As shown in Figure 3, this concrete structure monitoring system 10 consists of a monitoring device 20 attached to the box girder 1 to monitor the condition of the PC steel members 2, and an information processing terminal 40 located in a remote location away from the box girder 1 and connected to the monitoring device 20 via a communication line 11.

[0054] The monitoring device 20 operates on power from an external power source (not shown) and has the function of detecting elastic waves associated with the fracture of the PC steel material 2, and the function of transmitting data including time-series waveform data of the elastic waves to the information processing terminal 40 via the communication line 11.

[0055] As shown in Figure 3, the monitoring device 20 is positioned in contact with the main surface 4A of the lower floor slab 4 and the main surface 5A of the side wall portion 5, and consists of eight acceleration sensors that detect elastic waves generated inside the box girder 1, and a device body 21 that is attached to the box girder 1 and to which the eight acceleration sensors are connected.

[0056] More specifically, the eight acceleration sensors of the monitoring device 20 have the function of detecting elastic waves propagating inside the box girder 1 and the function of outputting an electrical signal indicating the detected elastic waves. Of these eight acceleration sensors, four constitute the four acceleration sensors positioned on the main surface 5A of the right side wall 5 as described above, and the remaining four acceleration sensors constitute the four acceleration sensors positioned on the main surface 5A of the left side wall 5 as described above.

[0057] Furthermore, two of the four acceleration sensors located on the main surface 5A of the right side wall 5, and two of the four acceleration sensors located on the main surface 5A of the left side wall 5, constitute the four acceleration sensors located on the main surface 4A of the lower floor slab 4 as described above.

[0058] More specifically, of the eight acceleration sensors, two constitute the first right-side sensor 22 and the second right-side sensor 23, which are located on the inner surface 5a of the right-side wall portion 5, as shown in Figures 3 and 4.

[0059] Furthermore, of the eight acceleration sensors, two constitute the first left side sensor 24 and the second left side sensor 25, which are located on the inner surface 5a of the left side wall portion 5, as shown in Figures 3 and 4.

[0060] The remaining four acceleration sensors, as shown in Figures 3 and 4, constitute the first haunch sensor 26, the second haunch sensor 27, the third haunch sensor 28, and the fourth haunch sensor 29, which are positioned on the inclined surface 7a of the lower haunch portion 7.

[0061] As shown in Figure 4, the first right-side sensor 22 is positioned on the inner surface 5a of the right-side wall portion 5, on one side in the bridge axis direction X, and at the upper corner. Furthermore, as shown in Figure 4, the second right-side sensor 23 is positioned on the inner surface 5a of the right-side wall portion 5, on the other side in the bridge axis direction X, and at the upper corner.

[0062] Furthermore, as shown in Figure 4, the first left-side sensor 24 is positioned on the inner surface 5a of the left side wall portion 5, on one side in the bridge axis direction X, and at the upper corner. Furthermore, as shown in Figure 4, the second left-side sensor 25 is positioned on the inner surface 5a of the left side wall portion 5, on the other side in the bridge axis direction X, and at the upper corner.

[0063] Furthermore, as shown in Figure 4, the first haunch sensor 26 is positioned on the inclined surface 7a of the right-side lower haunch portion 7 at approximately the same bridge axis direction X as the first right-side sensor 22. Furthermore, as shown in Figure 4, the second haunch sensor 27 is positioned on the inclined surface 7a of the right-side lower haunch portion 7 at approximately the same bridge axis direction X as the second right-side sensor 23.

[0064] Furthermore, as shown in Figure 4, the third haunch sensor 28 is positioned on the inclined surface 7a of the left lower haunch portion 7 at approximately the same bridge axis direction X as the first left side sensor 24. Furthermore, as shown in Figure 4, the fourth haunch sensor 29 is positioned on the inclined surface 7a of the left lower haunch portion 7 at approximately the same bridge axis direction X as the second left side sensor 25.

[0065] These eight acceleration sensors consist of a first right-side sensor 22, a second right-side sensor 23, a first haunch sensor 26, and a second haunch sensor 27, which constitute four acceleration sensors positioned on the main surface 5A of the right-side wall portion 5 described above, and a first left-side sensor 24, a second left-side sensor 25, a third haunch sensor 28, and a fourth haunch sensor 29, which constitute four acceleration sensors positioned on the main surface 5A of the left-side wall portion 5 described above.

[0066] Furthermore, the first haunch sensor 26, the second haunch sensor 27, the third haunch sensor 28, and the fourth haunch sensor 29 constitute four acceleration sensors that are positioned on the main surface 4A of the lower floor plate 4 as described above.

[0067] Furthermore, as shown in Figure 3, the main body 21 of the monitoring device 20 includes a line connection unit 30 that connects to the communication line 11, a sensor connection unit 31 to which eight acceleration sensors are connected, and a control unit 32 that controls the operation of these sensors and processes various information.

[0068] Specifically, the line connection unit 30 is composed of, for example, a wireless LAN module or a wireless WAN module, and has the function of connecting to the communication line 11 and the function of sending and receiving various information via the communication line 11.

[0069] Furthermore, the sensor connection unit 31 is composed of, for example, a preamplifier, and has the function of acquiring electrical signals from multiple acceleration sensors, assigning a unique identifier to each acceleration sensor for the acquired electrical signals, and amplifying and outputting each of the acquired electrical signals.

[0070] Furthermore, the control unit 32 is composed of hardware such as a CPU and memory, and software such as a control program. This control unit 32 has processing functions for sending and receiving various signals with the line connection unit 30 and the sensor connection unit 31, and functions for controlling the operation of each of the above-mentioned parts.

[0071] Furthermore, the control unit 32 has the function of generating time-series waveform data representing elastic waves for each acceleration sensor based on the electrical signal acquired from the sensor connection unit 31, the function of generating transmission data that associates the identifier for each acceleration sensor with the time-series waveform data, and the function of outputting the generated transmission data to the information processing terminal 40 via the line connection unit 30.

[0072] On the other hand, the information processing terminal 40 is a terminal used by users who monitor the condition of the PC steel material 2, for example, in a monitoring office. This information processing terminal 40 has the function of calculating the estimated fracture location of the PC steel material 2 based on the transmission data acquired from the monitoring device 20, and the function of notifying the user of the estimated fracture location of the PC steel material 2.

[0073] As shown in Figure 3, such an information processing terminal 40 consists of a line connection unit 41 that connects to a communication line 11, a display unit 42 that displays various information to the user, an operation reception unit 43 that accepts various operations from the user, a storage unit 44 that stores various information, and a terminal control unit 45 that controls the operation of these units.

[0074] More specifically, the line connection unit 41 is composed of a wireless LAN module, a wired LAN module, etc., and has the function of connecting to the communication line 11 and the function of sending and receiving various information via the communication line 11. Furthermore, the display unit 42 is composed of, for example, a liquid crystal display and has the function of displaying various information based on control signals from the terminal control unit 45.

[0075] Furthermore, the operation reception unit 43 is composed of, for example, a keyboard or mouse, and has the function of receiving input operations from the user and the function of outputting information indicating the received input operations to the terminal control unit 45. Furthermore, the storage unit 44 is composed of, for example, a hard disk or non-volatile memory, and has the function of writing and storing various types of information, and the function of reading and storing various types of information.

[0076] As shown in Figure 3, this memory unit 44 stores a processing program (not shown) that calculates the estimated fracture location of the PC steel material 2 from the transmitted data, as well as registered data 46 containing various information about the box girder 1 and the eight acceleration sensors.

[0077] Specifically, the registered data 46 is data in which coordinate information indicating the position coordinates on a predetermined planar coordinate system where the bridge axis direction X is the X-axis direction and the direction perpendicular to the bridge axis Y is the Y-axis direction is registered. The coordinate information obtained by replacing the positions of the inner surface of the box girder 1 and the acceleration sensors with position coordinates on the predetermined coordinate plane is associated with a unique identifier that identifies the eight acceleration sensors.

[0078] For example, the registered data 46 includes the position coordinates of a developed drawing 47, which shows the inner surface of a box girder 1 with the inclined surfaces 7a of a pair of lower haunch sections 7 and the inner surfaces 5a of a pair of side wall sections 5 unfolded so as to be substantially flat with respect to the upper surface 4a of the lower deck slab 4, when placed on a predetermined coordinate plane, as shown in Figure 5.

[0079] Furthermore, the registered data 46 is registered in association with the position coordinates of the eight acceleration sensors on the unfolded diagram 47 showing the inner surface of the box girder 1, and a unique identifier for each acceleration sensor.

[0080] Furthermore, the terminal control unit 45 is composed of hardware such as a CPU and memory, and software such as a control program. This terminal control unit 45 has processing functions for exchanging various signals with the line connection unit 41, display unit 42, operation reception unit 43 and storage unit 44, functions for controlling the operation of the above-mentioned units, and various processing functions for exchanging various information with the monitoring device 20.

[0081] Furthermore, the terminal control unit 45 has a function to calculate the arrival time of elastic waves based on the transmission data acquired from the monitoring device 20, and a function to calculate the estimated fracture location, which is the estimated location of the fracture in the PC steel material 2, based on the difference in the arrival times of the elastic waves.

[0082] Next, the processing operations of the monitoring device 20 and the information processing terminal 40 in the concrete structure monitoring system 10 with the above configuration will be explained using Figures 6 to 10. Figure 6 shows a flowchart of the processing operation in the monitoring device 20, Figure 7 shows an explanatory diagram of the monitoring screen 200 displaying the estimated fracture location, and Figure 8 shows a flowchart of the processing operation in the information processing terminal 40.

[0083] Furthermore, Figure 9 is an explanatory diagram illustrating the estimated fracture locations of the PC steel material 2, Figure 9(a) shows an explanatory diagram illustrating the locations of the estimated fracture locations E1, E2, and E3 calculated by the comparative example, Figure 9(b) shows an explanatory diagram illustrating the locations of the estimated fracture locations E1, E2, and E3 calculated by this embodiment, and Figure 10 shows an explanatory diagram illustrating the propagation state of elastic waves.

[0084] First, as shown in Figure 6, when power is supplied, the control unit 32 of the monitoring device 20 determines whether at least two of the eight acceleration sensors have detected elastic waves generated in conjunction with the fracture of the PC steel material 2 (step S101). In this case, the control unit 32 determines that it has detected an elastic wave generated by the fracture of the PC steel material 2 if the amplitude of the elastic wave detected by the acceleration sensor exceeds a threshold indicating the upper limit of noise.

[0085] If none of the eight acceleration sensors detect elastic waves associated with the fracture of the PC steel material 2 (step S101: No), the control unit 32 waits until at least two of the eight acceleration sensors detect elastic waves associated with the fracture of the PC steel material 2.

[0086] On the other hand, if at least two of the eight acceleration sensors detect elastic waves associated with the fracture of the PC steel material 2 (step S101: Yes), the control unit 32 generates transmission data to be sent to the information processing terminal 40, as shown in Figure 6 (step S102).

[0087] Specifically, the control unit 32 generates time-series waveform data representing elastic waves for each acceleration sensor based on the electrical signals acquired from the acceleration sensors, and assigns a unique identifier to each acceleration sensor for the generated time-series waveform data. Furthermore, the control unit 32 generates transmission data by associating identification information for identifying the box girder 1 with time-series waveform data to which an identifier for each acceleration sensor has been assigned.

[0088] Once the transmission data is generated, the control unit 32 transmits the transmission data to the information processing terminal 40 via the communication line 11, as shown in Figure 6 (step S103), then returns the process to step S101, and repeats the process from step S101 to step S103 until the external power supply is interrupted.

[0089] Meanwhile, when the terminal control unit 45 of the information processing terminal 40 receives a user's operation and executes a processing program, it displays a monitoring screen on the display unit 42 showing the status of the PC steel material 2 embedded in the box girder 1. On the right side of this monitoring screen 200, as shown in Figure 7 for example, there is a monitoring target information field 201 that displays the name of the bridge and the current date and time, a status display field 202 that displays the current status of the PC steel material 2, a selection button 203 for selecting another box girder 1, and a stop button 204 for stopping the monitoring of box girder 1.

[0090] Furthermore, as shown in Figure 7, the monitoring screen 200 displays an unfolded diagram 47 read from the registered data 46 on the left side of the screen. If the estimated fracture location of the PC steel material 2 is calculated, this unfolded diagram 47 displays a black circle indicating the estimated fracture location of the PC steel material 2, along with the number assigned to the black circle, superimposed on the diagram.

[0091] The status display area 202 shows either "Normal" or "Fracture Occurred," indicating the current status of PC steel 2, along with a numbered black circle indicating the estimated fracture location of PC steel 2, and the date and time when the fracture of PC steel 2 was detected.

[0092] Subsequently, the terminal control unit 45 determines whether or not it has received the transmitted data from the monitoring device 20 via the communication line 11, as shown in Figure 8 (step S121). If no transmission data is received from the monitoring device 20 (step S121: No), the terminal control unit 45 determines that the PC steel material 2 is in a healthy state without fracture and waits for the device to receive transmission data from the monitoring device 20.

[0093] On the other hand, if data is obtained from the monitoring device 20 (step S121: Yes), the terminal control unit 45 assumes that a fracture of the PC steel material 2 has occurred at any part of the lower floor slab 4 or the pair of side wall sections 5, and calculates the arrival time of the elastic wave for each acceleration sensor based on the transmitted data (step S122).

[0094] Specifically, the terminal control unit 45 applies the Akaike Information Criterion to the time-series waveform data of the transmitted data to calculate the AIC value. Furthermore, the terminal control unit 45 detects the point where the calculated AIC value is minimized as the initial phase of the elastic wave, and obtains the detection time of the detected initial phase of the elastic wave as the arrival time of the elastic wave.

[0095] After calculating the arrival time of the elastic wave, the terminal control unit 45 identifies either the main surface 4A of the lower floor slab 4 or the main surfaces 5A of the pair of side wall sections 5 as the detection surface where the fracture of the PC steel material 2 was detected, based on the position coordinates of the acceleration sensor and the arrival time of the elastic wave for each acceleration sensor (step S123).

[0096] Specifically, the terminal control unit 45 identifies the acceleration sensor with the earliest arrival time of the elastic wave as the first acceleration sensor, and the acceleration sensor with the second earliest arrival time of the elastic wave as the second acceleration sensor.

[0097] In other words, the terminal control unit 45 identifies the acceleration sensor that first detects the elastic wave as the first acceleration sensor, and the acceleration sensor that second detects the elastic wave as the second acceleration sensor.

[0098] Furthermore, the terminal control unit 45 estimates whether the location of the elastic wave generation is on the lower floor slab 4, the right side wall 5, or the left side wall 5, based on the unique identifiers for the first and second acceleration sensors and the position coordinates of the acceleration sensors registered in the registration data 46.

[0099] In this case, the terminal control unit 45 identifies the lower haunch portion 7 as the lower floor plate 4, the right side wall portion 5, or the left side wall portion 5, based on the combination of the first and second acceleration sensors.

[0100] For example, if both the first and second acceleration sensors are the first haunch sensor 26, the second haunch sensor 27, the third haunch sensor 28, or the fourth haunch sensor 29, the terminal control unit 45 identifies the pair of lower haunch sections 7 as the lower floor plate 4 and estimates the lower floor plate 4 as the site where elastic waves are generated.

[0101] Alternatively, if one of the first and second acceleration sensors is the first haunch sensor 26 or the second haunch sensor 27, and the other is the first right side sensor 22 or the second right side sensor 23, the terminal control unit 45 identifies the right lower haunch portion 7 as the right side wall portion 5 and estimates the right side wall portion 5 as the elastic wave generation site.

[0102] Alternatively, if one of the first and second acceleration sensors is the third haunch sensor 28 or the fourth haunch sensor 29, and the other is the first left side sensor 24 or the second left side sensor 25, the terminal control unit 45 identifies the lower left haunch portion 7 as the left side wall portion 5 and estimates the left side wall portion 5 as the elastic wave generation site.

[0103] Once the location of the elastic wave generation is estimated, the terminal control unit 45 identifies the estimated location of the elastic wave generation as the fracture location of the PC steel material 2, and also identifies the main surface of the elastic wave generation location as the detection surface.

[0104] For example, if the estimated location of the elastic wave generation is the lower floor slab 4, the terminal control unit 45 identifies the upper surface 4a of the lower floor slab 4 and the inclined surfaces 7a of the pair of lower haunch portions 7 as the main surface 4A of the lower floor slab 4, and identifies the identified main surface 4A of the lower floor slab 4 as the detection surface.

[0105] Alternatively, if the estimated location of the elastic wave generation is the right side wall portion 5, the terminal control unit 45 identifies the inner surface 5a of the right side wall portion 5 and the inclined surface 7a of the right lower haunch portion 7 as the main surface 5A of the right side wall portion 5, and identifies the identified main surface 5A of the right side wall portion 5 as the detection surface.

[0106] Alternatively, if the estimated location of the elastic wave generation is the left side wall portion 5, the terminal control unit 45 identifies the inner surface 5a of the left side wall portion 5 and the inclined surface 7a of the left lower haunch portion 7 as the main surface 5A of the left side wall portion 5, and identifies the identified main surface 5A of the left side wall portion 5 as the detection surface.

[0107] Once the detection surface is identified, the terminal control unit 45 calculates the position coordinates indicating the estimated fracture location, which is the estimated location of the fracture in the PC steel material 2, based on the difference in the arrival times of elastic waves acquired by the four acceleration sensors located on the detection surface, as shown in Figure 8 (step S124). Furthermore, since the estimated fracture location of the PC steel material 2 is calculated using a known method that assumes a constant propagation speed of elastic waves, a detailed explanation of this method is omitted in this embodiment.

[0108] When the estimated fracture location of the PC steel material 2 is calculated, the terminal control unit 45 determines whether the position coordinates indicated by the estimated fracture location are within the range of position coordinates indicating the detected surface registered in the registration data 46 (step S125). If the position coordinates indicated by the estimated fracture location are within the range of the position coordinates indicating the detection surface (step S125: Yes), the terminal control unit 45 has identified the fracture location of the PC steel material 2 and proceeds to step S127, which will be described later.

[0109] On the other hand, if the position coordinates indicated by the estimated fracture location are outside the range of position coordinates indicating the detection surface (step S125: No), the terminal control unit 45 is unable to accurately calculate the position in the bridge axis direction X and the position in the direction perpendicular to the bridge axis Y at the fracture site of the PC steel material 2, and therefore only calculates the estimated fracture location in the bridge axis direction X (position in the X axis direction of the predetermined coordinate plane) (step S126).

[0110] Specifically, the terminal control unit 45 identifies the first acceleration sensor identified in step S123 described above, and an acceleration sensor located at a position separated from the first acceleration sensor in the bridge axis direction X (the X axis direction of a predetermined coordinate plane). Based on the difference in arrival times of elastic waves detected by the two identified acceleration sensors, it calculates the estimated fracture position in the bridge axis direction X. The estimated fracture location in the bridge axis direction X is calculated using a known calculation method that assumes a constant elastic wave propagation speed, similar to step S124.

[0111] For example, if the first acceleration sensor is the first left-side sensor 24, the terminal control unit 45 calculates the estimated fracture position in the bridge axis direction X based on the difference between the arrival time of the elastic wave detected by the first left-side sensor 24 and the arrival time of the elastic wave detected by the second left-side sensor 25.

[0112] Then, if the position coordinates indicated by the estimated fracture location in step S125 are within the range of position coordinates indicating the detection surface, or if the estimated fracture location in the bridge axis direction X is calculated in step S126, the terminal control unit 45 displays the calculated estimated fracture location as the fracture location of the PC steel member 2 on the monitoring screen 200 (step S127).

[0113] In this case, as shown in Figure 7, the terminal control unit 45 displays a black circle indicating the fracture position of the PC steel material 2 on the unfolded diagram 47 based on the position coordinates indicating the estimated fracture position. Furthermore, the terminal control unit 45 changes the current status of the PC steel material 2 in the status display field 202 from "normal" to "fracture occurred," and displays the number of the black circle indicating the estimated fracture location of the PC steel material 2, as well as the date and time when the fracture of the PC steel material 2 was detected, in the status display field 202.

[0114] Subsequently, the terminal control unit 45 returns the process to step S121 and repeatedly performs the processes from step S121 to step S127 until the processing program is terminated by user operation.

[0115] In this way, the concrete structure monitoring system 10 in this embodiment can accurately calculate the estimated fracture location of the PC steel member 2 in a box girder 1, which is a prestressed concrete structure having a lower slab 4 and side wall portions 5 with different thickness directions, by identifying the main surface (detection surface) where elastic waves are generated.

[0116] Here, as a comparative example, we compare the estimated fracture location calculated based on the difference in arrival times of elastic waves detected by eight acceleration sensors with the estimated fracture location calculated by the concrete structure monitoring system 10 of this embodiment.

[0117] In the comparative example and this embodiment, the estimated fracture location is calculated using elastic waves generated when a predetermined striking point on the outer surface of the box girder 1 is struck once with a Schmidt hammer, instead of elastic waves generated by the fracture of the PC steel material 2. Furthermore, in the comparative example and this embodiment, the estimated fracture position was calculated for each impact, and this process was repeated three times to calculate three estimated fracture positions for each impact position.

[0118] Furthermore, the striking positions of the Schmidt hammer are as shown by the black circles in Figure 9(a): the first striking position P1 is approximately in the center of the lower deck slab 4 in a plan view; the second striking position P2 is approximately in the center of the bridge axis direction X and near the lower end of the right side wall 5; and the third striking position P3 is approximately in the center of the bridge axis direction X and near the lower end of the left side wall 5.

[0119] First, the comparative example skips the identification of the detection surface in step S123 of Figure 8, and in step S124 of Figure 8, calculates the estimated fracture location of the PC steel 2 based on the difference in arrival times of elastic waves detected by all eight acceleration sensors.

[0120] In this comparative example, as shown in Figure 9(a), the estimated fracture position E1 (circle in the figure) for the first impact position P1, the estimated fracture position E2 (diamond in the figure) for the second impact position P2, and the estimated fracture position E3 (triangle in the figure) for the third impact position P3 all failed to converge near the impact position. Furthermore, the estimated fracture position E2 for the second impact position P2 did not overlap with the right side wall portion 5.

[0121] This is likely because the calculation accuracy decreased due to the use of both the arrival time of the body wave and the arrival time of the surface wave in the calculation of the estimated fracture location. Specifically, for example, if an elastic wave is generated in the right side wall 5, the elastic wave generated in the side wall 5 will propagate through the side wall 5 as an elastic wave (surface wave) that travels toward the lower floor slab 4 via the propagation path indicated by arrow R1 in Figure 10, and as an elastic wave (body wave) that travels toward the lower floor slab 4 via the propagation path indicated by arrow R2 in Figure 10.

[0122] In this case, the elastic waves (surface waves) propagating along the surface of the side wall 5 propagate to the lower floor slab 4 via the lower haunch 7 without significant attenuation while retaining their energy, whereas the elastic waves (body waves) propagating inside the side wall 5 propagate to the lower floor slab 4 via the lower haunch 7 attenuate at a much higher rate than the elastic waves (surface waves) propagating along the surface of the side wall 5. Of the body waves (P-waves and S-waves), the P-waves propagate along the surface of the sidewall 5, similar to surface waves, but unlike surface waves, they propagate to the lower floor slab 4 via the lower haunch 7 while being significantly attenuated.

[0123] Therefore, while the first right-side sensor 22 and the second right-side sensor 23, which are close to the source of the elastic wave, detect P-waves, acceleration sensors located further away from the source of the elastic wave, such as the first left-side sensor 24 and the second left-side sensor 25, which are located on the left side wall 5, are more likely to detect S-waves and surface waves, which have higher energy than P-waves and are less susceptible to attenuation, rather than P-waves.

[0124] Therefore, in the comparative example where the estimated fracture location is calculated based on the difference in arrival times of elastic waves detected by eight acceleration sensors, the estimated fracture location is calculated using the arrival times of the body wave and the surface wave, resulting in a significant decrease in the accuracy of the estimated fracture location calculation.

[0125] In contrast, as shown in Figure 9(b), in this embodiment, the estimated fracture position E1 for the first impact position P1, the estimated fracture position E2 for the second impact position P2, and the estimated fracture position E3 for the third impact position P3 all converge near the impact position.

[0126] As described above, in this embodiment, in step S123 of Figure 8, the main surface (detection surface) of the elastic wave generation site is identified, and in step S124 of Figure 8, the estimated fracture position is calculated based on the difference in arrival times of the elastic waves detected by four acceleration sensors located on the detection surface. Therefore, in this embodiment, since the arrival time of the surface wave is difficult to use in calculating the estimated fracture location, the accuracy of calculating the estimated fracture location was improved compared to the comparative example.

[0127] Even if the estimated fracture location does not coincide with the unfolded view 47 of the inner surface of the box girder 1, this embodiment makes it possible to inform the user of the approximate fracture location of the PC steel member 2 by calculating the estimated fracture location in the bridge axis direction X in step S126 of Figure 8.

[0128] As described above, the concrete structure monitoring system 10 in this embodiment is a PC steel material 2 fracture monitoring system that calculates the estimated fracture location of the PC steel material 2 in a box girder 1 in which PC steel material 2 is embedded in both the lower slab 4 and the side wall portion 5, which have different thickness directions and intersect at a predetermined angle.

[0129] This concrete structure monitoring system 10 is provided with multiple accelerometers on the main surface 4A of the lower slab 4 and the main surface 5A of the side wall section 5, respectively, and is equipped with accelerometers that detect elastic waves caused by fractures in the PC steel members 2 of the box girder 1.

[0130] Furthermore, the concrete structure monitoring system 10 includes a main surface identification means (terminal control unit 45) that identifies the main surface 4A of the lower floor slab 4 or the main surface 5A of the side wall portion 5, which is equipped with an acceleration sensor, as the detection surface based on the position information of the acceleration sensor that detected the elastic wave and the detection order of the elastic wave.

[0131] Furthermore, the concrete structure monitoring system 10 includes a calculation means (terminal control unit 45) that calculates the estimated fracture location of the PC steel material 2 based on the positional information of multiple acceleration sensors on the detection surface and the difference in arrival times of elastic waves detected by the acceleration sensors.

[0132] Furthermore, the concrete structure monitoring method in this embodiment is a method for monitoring the fracture of PC steel members 2 in a box girder 1 in which PC steel members 2 are embedded in both the lower slab 4 and the side wall portion 5, which have different thickness directions and intersect at a predetermined angle.

[0133] This concrete structure monitoring method involves an elastic wave detection process (steps S102 and S105) in which multiple acceleration sensors are installed on the main surface 4A of the lower slab 4 and the main surface 5A of the side wall 5 to detect elastic waves caused by fractures in the PC steel members 2 of the box girder 1.

[0134] Furthermore, the concrete structure monitoring method performs a main surface identification step (step S123) in which the main surface identification means identifies the main surface 4A of the lower floor slab 4 or the main surface 5A of the side wall portion 5, on which the acceleration sensor is installed, as the detection surface, based on the position information of the acceleration sensor that detected the elastic wave and the detection order of the elastic wave.

[0135] The concrete structure monitoring method involves a calculation step (step S124) in which a calculation means calculates the estimated fracture location of the PC steel material 2 based on the positional information of multiple acceleration sensors on the detection surface and the difference in arrival times of elastic waves detected by the acceleration sensors.

[0136] With this configuration, based on the positional information of the acceleration sensor that detected the elastic wave and the detection order of the elastic wave, the main surface 4A of the lower slab 4 or the main surface 5A of the side wall portion 5 is identified as the detection surface, making it possible to estimate whether the fracture of the PC steel material 2 that occurred inside the box girder 1 occurred in the lower slab 4 or the side wall portion 5.

[0137] Furthermore, since the estimated fracture location of the PC steel material 2 is calculated based on the difference in the arrival times of elastic waves detected by acceleration sensors on the detection surface, the concrete structure monitoring system 10 can prevent the arrival times of elastic waves detected by acceleration sensors installed on main surfaces other than the detection surface from being used in calculating the estimated fracture location.

[0138] As a result, the concrete structure monitoring system 10 and the concrete structure monitoring method can improve the positional accuracy of the calculated estimated fracture location compared to when the estimated fracture location is calculated based on the arrival time of elastic waves detected by eight acceleration sensors installed on the main surface 4A of the lower slab 4 and the main surface 5A of the side wall portion 5.

[0139] Therefore, the concrete structure monitoring system 10 and the concrete structure monitoring method can estimate the fracture location of the PC steel members 2 even in the case of a box girder 1 having a lower slab 4 and side wall portions 5 with different thickness directions.

[0140] Furthermore, the main surface identification means (terminal control unit 45) is configured to identify the main surface 4A of the lower floor slab 4 or the main surface 5A of the side wall portion 5 as the detection surface, where the first acceleration sensor that first detected the elastic wave and the second acceleration sensor that second detected the elastic wave are provided.

[0141] This configuration allows for more efficient identification of the detection surface compared to identifying the detection surface based on the detection order of elastic waves detected by three or more acceleration sensors. As a result, the concrete structure monitoring system 10 can efficiently calculate the estimated fracture location of the PC steel material 2.

[0142] Furthermore, four acceleration sensors are provided on the main surface 4A of the lower floor slab 4 and on the main surface 5A of the side wall portion 5. The calculation means (terminal control unit 45) is configured to calculate the estimated fracture position based on the elastic waves detected by the four acceleration sensors on the detection surface.

[0143] With this configuration, the estimated fracture position is calculated based on the elastic waves detected by four acceleration sensors placed on the detection surface. Compared to, for example, calculating the estimated fracture position based on elastic waves detected by two acceleration sensors, the positional accuracy of the calculated estimated fracture position can be improved.

[0144] Furthermore, four acceleration sensors are provided on the main surface 4A of the lower floor slab 4 and on the main surface 5A of the side wall portion 5. The calculation means includes a first calculation means (terminal control unit 45) that calculates the estimated fracture position based on the arrival time of elastic waves detected by four acceleration sensors on the detection surface.

[0145] Furthermore, the calculation means includes a second calculation means (terminal control unit 45) that calculates the estimated fracture position based on the arrival time of the elastic wave detected by the first acceleration sensor that first detected the elastic wave, and by an acceleration sensor located at a position spaced apart from the first acceleration sensor in the bridge axis direction X, if the estimated fracture position calculated by the first calculation means is not located within the detection surface.

[0146] With this configuration, even if the accuracy of the estimated fracture location calculated by the first calculation means decreases due to the inclusion of noise-inducing elastic waves in the elastic waves detected by the four acceleration sensors, the second calculation means can still estimate the fracture location of the PC steel member 2 in the bridge axis direction X.

[0147] Furthermore, the box girder 1 is equipped with a lower haunch section 7 having an inclined surface 7a at the bent portion between the lower floor slab 4 and the side wall section 5. Furthermore, of the eight acceleration sensors, four are mounted on the inclined surface 7a of the lower haunch portion 7.

[0148] The main surface identification means is configured to identify the inclined surface 7a of the lower haunch section 7 as the main surface 4A of the lower floor slab 4 or the main surface 5A of the side wall section 5, depending on the combination of the first acceleration sensor that first detected the elastic wave and the second acceleration sensor that second detected the elastic wave.

[0149] With this configuration, the acceleration sensor provided on the lower haunch portion 7 can be considered as an acceleration sensor provided on the lower floor slab 4, or as an acceleration sensor provided on the side wall portion 5. Therefore, the concrete structure monitoring system 10 can reduce the number of acceleration sensors compared to, for example, a case where four acceleration sensors are provided for each of the lower floor slab 4 and the side wall 5. This allows the concrete structure monitoring system 10 to estimate the fracture location of the PC steel 2 while keeping costs down.

[0150] Furthermore, the box girder 1 is formed in a closed cross-sectional shape extending in the bridge axis direction X. Multiple acceleration sensors are provided on the inner surface of the closed cross-sectional shape. With this configuration, the acceleration sensor is not directly exposed to wind, rain, or direct sunlight, so it is possible not only to calculate the estimated fracture location of the PC steel 2, but also to monitor the fracture of the PC steel 2 over a long period of time.

[0151] Furthermore, the box girder 1 is a prestressed concrete structure in which PC steel members 2 are embedded in both the lower slab 4 and the side wall section 5. The concrete structure monitoring system 10 is configured to calculate the estimated fracture location of the PC steel members 2 as the estimated location of elastic wave generation.

[0152] With this configuration, in a box girder 1 which is a prestressed concrete structure, it is possible to monitor for fractures of PC steel members 2 due to corrosion caused by, for example, insufficient grout filling, and to calculate the estimated fracture location of the PC steel members 2 when a fracture occurs.

[0153] In the correspondence between the structure of this invention and the embodiments described above, The first part of this invention corresponds to the lower floor slab 4 of the embodiment, The same applies to the following: The second part corresponds to the side wall portion 5, The concrete structure and prestressed concrete structure correspond to box girder 1, The estimated location of the elastic wave generation corresponds to the estimated fracture location of PC steel 2. The main surface of the first part corresponds to the main surface 4A of the lower floor slab 4. The main surface of the second part corresponds to the main surface 5A of the side wall portion 5. The elastic wave detection means corresponds to acceleration sensors (first right side sensor 22, second right side sensor 23, first left side sensor 24, second left side sensor 25, first haunch sensor 26, second haunch sensor 27, third haunch sensor 28 and fourth haunch sensor 29), The main surface identification means, calculation means, first calculation means and second calculation means correspond to the terminal control unit 45. The predetermined direction corresponds to the bridge axis direction X, The haunch section corresponds to the lower haunch section 7. The elastic wave detection process corresponds to step S101, The main surface identification process corresponds to steps S122 and S123. The calculation process corresponds to steps S124 to S126, This invention is not limited to the configuration of the embodiments described above, and many other embodiments can be obtained.

[0154] For example, in the embodiment described above, the box girder 1 was constructed using a post-tensioning method, but it is not limited to this, and the box girder 1 may also be constructed using a pre-tensioning method. Furthermore, although the box girder 1 is configured to have an internal space penetrating in the bridge axis direction X, it is not limited to this configuration. As shown in Figure 11(a), which is a schematic diagram illustrating the outline of the box girder 1 in another embodiment, the box girder 1 may also be provided with at least one substantially flat partition wall portion 8 with the bridge axis direction X as the thickness direction, at appropriate positions within the internal space of the box girder 1. Furthermore, this bulkhead section 8 is a substantially flat plate with a substantially rectangular opening 8a formed through it in the bridge axis direction X, and unlike the lower deck slab 4 and side wall section 5, PC steel members 2 are not embedded in it.

[0155] In a box girder 1 equipped with such a partition wall 8, if, for example, an elastic wave is generated on one side of the lower deck slab 4 in the bridge axis direction X, the elastic wave (surface wave) propagating along the surface of the lower deck slab 4 will propagate along the inner surface 5a of the side wall 5 and the main surface of the partition wall 8 on one side of the partition wall 8 in the bridge axis direction X.

[0156] On the other hand, elastic waves (body waves) propagating inside the lower deck slab 4 not only propagate inside the partition wall 8, but also propagate from one side in the bridge axis direction X inside the side wall 5, across the partition wall 8, to the other side in the bridge axis direction X, and also propagate from one side in the bridge axis direction X inside the lower deck slab 4, across the partition wall 8, to the other side in the bridge axis direction X.

[0157] Therefore, even with a box girder 1 equipped with a partition wall 8, the concrete structure monitoring system 10 can detect elastic waves generated in the lower slab 4, for example, using eight acceleration sensors, thus achieving the same effects as in the above-described embodiment.

[0158] Furthermore, the box girder 1 may have a configuration that includes a vertical wall portion 9 connecting the upper deck 3 and the lower deck 4 at approximately the center in the direction Y perpendicular to the bridge axis, as shown in Figure 11(b), which is a schematic diagram illustrating the outline of the box girder 1 in another embodiment.

[0159] This vertical wall section 9 is substantially flat, with the bridge axis direction X as its thickness direction, and is arranged to face a pair of side wall sections 5. In this case, the vertical wall section 9 may have a configuration in which PC steel members 2 extending in the bridge axis direction X are embedded, or it may not have a configuration in which PC steel members 2 are embedded.

[0160] Furthermore, although a box girder 1, which is a prestressed concrete structure, was used as an example of a concrete structure in the explanation, the explanation is not limited to this, and any suitable concrete structure may be used as long as it has a first part and a second part that have different thickness directions and intersect at a predetermined angle.

[0161] For example, prestressed concrete structures with closed cross-sectional shapes such as box culverts, prestressed concrete structures with roughly portal or U-shaped cross-sections, or prestressed concrete structures with roughly L-shaped, mountain-shaped, or T-shaped cross-sections may also be used.

[0162] Furthermore, the prestressed concrete structure is not limited to a structure made up of flat plate-shaped sections, but may also be a prestressed concrete structure made up of, for example, a first flat plate-shaped section in which PC steel members 2 are embedded and a second columnar section in which PC steel members 2 are embedded. In this case, the columnar second section is arranged so as to intersect the first flat plate-shaped section at a predetermined angle. The second columnar portion may be a column with a roughly circular cross-section, a column with a roughly ring-shaped cross-section, or a column with a roughly elongated elliptical cross-section.

[0163] Furthermore, the concrete structure is not limited to a prestressed concrete structure; it may also be a concrete structure in which PC steel members 2 are not embedded. In this case, elastic waves caused by damage such as cracks occurring inside or on the surface of the concrete structure are detected, and the estimated location of the damage is calculated based on the detected elastic waves.

[0164] Furthermore, although the PC steel members 2 are embedded in the lower slab 4 and the pair of side walls 5 in this prestressed concrete structure, the design is not limited to this. For example, the PC steel members 2 may be embedded in the upper slab 3 in addition to the lower slab 4 and the pair of side walls 5 in this prestressed concrete structure. In this case, similar to the lower haunch section 7, acceleration sensors are placed on the inclined surfaces 6a of the pair of upper haunch sections 6.

[0165] Furthermore, although the box girder 1 is provided with an upper haunch section 6 and a lower haunch section 7, it is not limited to this, and a box girder without an upper haunch section 6 and a lower haunch section 7 may also be provided. In this case, for example, acceleration sensors are placed at the four corners of the inner surface 5a of the side wall section 5 and at the four corners of the upper surface 4a of the lower floor slab 4.

[0166] Furthermore, while the concrete structure monitoring system 10 is described as a monitoring device 20 attached to the box girder 1 and an information processing terminal 40 connected to the monitoring device 20 via a communication line 11, this is merely an example and is not limited to this configuration. The concrete structure monitoring system 10 may be configured as appropriate.

[0167] For example, it may be a concrete structure monitoring system consisting of a monitoring device 20 and a server and information processing terminal connected via a communication line 11. In this case, the server receives the transmitted data from the monitoring device 20, and after the server performs the processing from steps S121 to S126 in Figure 8, it transmits location information indicating the estimated fracture location to the information processing terminal. In this case, the information processing terminal displays a monitoring screen 200 based on location information indicating the estimated fracture location obtained from the server.

[0168] Furthermore, although an acceleration sensor was described as an example of an elastic wave detection means for detecting elastic waves, the means is not limited to this. The elastic wave detection means may be a vibration sensor or AE sensor provided in contact with the main surface 4A of the lower floor slab 4 and the main surface 5A of the side wall portion 5, as long as it is capable of detecting elastic waves. Alternatively, the elastic wave detection means may be a laser Doppler vibrometer provided in a non-contact state with the main surface 4A of the lower floor slab 4 and the main surface 5A of the side wall portion 5.

[0169] Furthermore, the installation locations of the eight acceleration sensors are not limited to the embodiments described above, and may be installed at appropriate locations depending on the shape of the prestressed concrete structure. Furthermore, although the monitoring device 20 is described as having eight acceleration sensors, it is not limited to this, and the number of acceleration sensors may be set to an appropriate number.

[0170] For example, acceleration sensors may be placed at 12 locations: the four corners of the upper surface 4a of the lower deck 4, the four corners of the inner surface 5a of the side wall 5, and both ends of the lower haunch section 7 in the bridge axis direction X.

[0171] Furthermore, although acceleration sensors are placed on the inclined surface 7a of the lower haunch portion 7, the system is not limited to this. Instead of placing acceleration sensors on the lower haunch portion 7, acceleration sensors may be placed at the four corners of the inner surface 5a of the side wall portion 5 and at the four corners of the upper surface 4a of the lower floor slab 4.

[0172] Furthermore, although acceleration sensors are placed on the inner surface of the box girder 1, the design is not limited to this, and acceleration sensors may also be placed on the outer surface of the box girder 1, i.e., the outer surface of the side wall portion 5 and the lower surface of the lower floor slab 4. Alternatively, acceleration sensors may be placed on both the inner surface and the outer surface of the box girder 1, such as the inner surface 5a and outer surface of the side wall portion 5. In this case, the acceleration sensors placed on the inner surface of the box girder 1 and the acceleration sensors placed on the outer surface of the box girder 1 are positioned so that they do not face each other in the thickness direction.

[0173] Furthermore, although the monitoring device 20 was described as having eight acceleration sensors in a continuously operating state, it is not limited to this. It may also be a monitoring device equipped with a wake-up function that switches the eight acceleration sensors to a dormant state when the PC steel material 2 is in a sound state, and switches the acceleration sensors from the dormant state to the operating state when the PC steel material 2 breaks.

[0174] More specifically, the control unit 32 may, for example, lower the supply voltage to the acceleration sensor to put it into a standby state, and when elastic waves are generated due to the fracture of the PC steel material 2, increase the supply voltage to a predetermined voltage to switch the standby acceleration sensor to an operational state.

[0175] Furthermore, the monitoring screen 200 in Figure 7 is just an example, and a monitoring screen with an appropriate configuration may be used. Furthermore, the processing flow in the monitoring device 20 and the processing flow in the information processing terminal 40 are merely examples and are not limited to the embodiments described above; any appropriate processing flow may be used.

[0176] Furthermore, in the processing operation of the information processing terminal 40, after identifying the detection surface in step S123, the estimated fracture position on the detection surface is calculated in step S124. However, the process is not limited to this, and only the estimated fracture position in the bridge axis direction X may be calculated.

[0177] Specifically, the terminal control unit 45, which identified the detection surface in step S123, skips the processing in steps S124 and S125, and in step S126 calculates the estimated fracture position based on the arrival time of the elastic wave detected by the first acceleration sensor that first detected the elastic wave, and by the acceleration sensor located at a position separated from the first acceleration sensor in the bridge axis direction X.

[0178] Then, the terminal control unit 45 estimates the fracture position in the bridge axis direction X calculated in step S126 as the fracture position of the PC steel member 2. In this case, the estimated fracture location is calculated based on elastic waves detected by two acceleration sensors positioned at intervals in the bridge axis direction X, making it possible to estimate the fracture location of the PC steel member 2 in at least the bridge axis direction X.

[0179] Furthermore, in step S126, an acceleration sensor located at a position separated from the first acceleration sensor in the bridge axis direction X (the X-axis direction of the predetermined coordinate plane) was identified, but this is not limited to this. Specifically, if the configuration identifies the first acceleration sensor identified in step S123 and another acceleration sensor placed on the detection surface where the first acceleration sensor is located, the predetermined direction is not limited to the bridge axis direction X (the X-axis direction of the predetermined coordinate plane). However, the predetermined direction is preferably a direction that substantially coincides with the axis direction of the PC steel member 2.

[0180] For example, an acceleration sensor may be identified that is positioned at a distance from the first acceleration sensor in a direction approximately perpendicular to the bridge axis direction X (the Y axis direction of a predetermined coordinate plane). Alternatively, an accelerometer located at a distance from the first accelerometer in a direction intersecting the bridge axis direction X may be identified. [Explanation of symbols]

[0181] 1... Box girders 2…PC steel material 4…Subfloor version 4A…Main surface 5... Side wall section 5A…Main surface 7...Lower haunch section 7a…Slope surface 10…Concrete structure monitoring system 22...First right side sensor 23…Second right side sensor 24…First left side sensor 25…Second left side sensor 26…First Hunt Sensor 27...Second Hunt Sensor 28...Third Hunt Sensor 29...4th Hunt Sensor 32…Control Unit 45…Terminal Control Unit E1, E2, E3... Estimated fracture locations X…Bridge axis direction

Claims

1. A concrete structure monitoring system for calculating the estimated location of elastic waves generated by damage to a concrete structure having a first portion and a second portion that have different thickness directions and intersect at a predetermined angle, Multiple elastic wave detection means are provided on the main surface of the first part and the main surface of the second part, respectively, for detecting the elastic waves generated in the concrete structure. A main surface identification means that identifies the main surface of the first part or the main surface of the second part on which the elastic wave detection means is provided as a detection surface, based on the position information of the elastic wave detection means that detected the elastic wave and the detection order of the elastic wave, The system includes a calculation means for calculating the estimated generation position of the elastic wave based on the positional information of the plurality of elastic wave detection means on the detection surface and the difference in arrival times of the elastic waves detected by the elastic wave detection means. Concrete structure monitoring system.

2. The main surface identification means is, The configuration identifies the main surface of the first portion or the main surface of the second portion, where the elastic wave detection means that first detected the elastic wave and the elastic wave detection means that second detected the elastic wave are provided, as the detection surface. The concrete structure monitoring system according to claim 1.

3. The elastic wave detection means is Four or more are provided on the main surface of the first part and on the main surface of the second part, The calculation means is The configuration is such that the estimated generation position is calculated based on the elastic waves detected by four or more elastic wave detection means on the detection surface. The concrete structure monitoring system according to claim 1.

4. The elastic wave detection means is Four or more are provided on the main surface of the first part and on the main surface of the second part, The calculation means is The configuration is such that the estimated generation position is calculated based on the arrival time of the elastic wave detected by the elastic wave detection means that first detects the elastic wave, and by the elastic wave detection means located at a predetermined distance from the elastic wave detection means. The concrete structure monitoring system according to claim 1.

5. The elastic wave detection means is Four or more are provided on the main surface of the first part and on the main surface of the second part, The calculation means is A first calculation means calculates the estimated generation position based on the arrival time of the elastic wave detected by four or more elastic wave detection means on the detection surface, If the estimated generation position calculated by the first calculation means is not located within the detection surface, the system comprises a second calculation means that calculates the estimated generation position based on the arrival time of the elastic wave detected by the elastic wave detection means that first detected the elastic wave, and the elastic wave detection means located at a predetermined distance from the elastic wave detection means. The concrete structure monitoring system according to claim 1.

6. The aforementioned concrete structure is A haunch portion having an inclined surface is provided at the bent portion between the first portion and the second portion. Of the plurality of elastic wave detection means, at least one of the elastic wave detection means is provided with respect to the inclined surface of the haunch portion, The main surface identification means is, The configuration identifies the inclined surface of the haunch portion as the main surface of the first portion or the main surface of the second portion, depending on the combination of the elastic wave detection means that first detected the elastic wave and the elastic wave detection means that second detected the elastic wave. The concrete structure monitoring system according to claim 1.

7. The aforementioned concrete structure is formed in a closed cross-sectional shape extending in a predetermined direction, Multiple elastic wave detection means are provided on the inner surface of the closed cross-sectional shape The concrete structure monitoring system according to claim 1.

8. The concrete structure is a prestressed concrete structure in which PC steel members are embedded in both the first and second portions. The configuration is such that the estimated fracture position of the PC steel material is calculated as the estimated generation position of the elastic wave. A concrete structure monitoring system according to any one of claims 1 to 7.

9. A concrete structure monitoring method for calculating the estimated location of elastic wave generation due to damage occurring in a concrete structure having a first portion and a second portion that have different thickness directions and intersect at a predetermined angle, A plurality of elastic wave detection means are provided on the main surface of the first part and the main surface of the second part, respectively, to detect the elastic waves generated in the concrete structure. A main surface identification step in which, based on the position information of the elastic wave detection means that detected the elastic wave and the detection order of the elastic wave, the main surface identification means identifies the main surface of the first part where the elastic wave detection means is provided or the main surface of the second part as a detection surface, A calculation step is performed in which a calculation means calculates the estimated generation position of the elastic wave based on the positional information of the plurality of elastic wave detection means on the detection surface and the difference in arrival times of the elastic wave detected by the elastic wave detection means. Methods for monitoring concrete structures.

Images