Inspection method and inspection device

Abstract

This inspection method includes: a selection step in which at least one cable band to be measured is selected from among a plurality of cable bands; a measurement step in which the current gripping force with which the cable band to be measured grips a main cable is measured; a calculation step in which a rate of decrease in the gripping force of the cable band to be measured is calculated on the basis of the measured value of the gripping force of the cable band to be measured as measured in the measurement step and the initial value of the gripping force of the cable band to be measured; and an estimation step in which the current gripping force of a cable band to be subjected to estimation differing from the cable band to be measured is estimated on the basis of the initial value of the gripping force of the cable band to be subjected to estimation and the rate of decrease in the gripping force of the cable band to be measured.

Description

Inspection Method and Inspection Apparatus

[0001] The present disclosure relates to an inspection method and an inspection apparatus for bridges. This application claims the benefit of priority based on Japanese Patent Application No. 2025-066213 filed on April 14, 2025, the content of which is incorporated herein by reference in its entirety.

[0002] For example, Patent Document 1 discloses a suspension bridge in which the upper end of a hanger rope is connected to a main cable stretched between two towers, and the lower end of the hanger rope is connected to a bridge girder.

[0003] Japanese Unexamined Patent Application Publication No. 11-264114

[0004] In general, a cable band is provided between the upper end of the hanger rope and the main cable. The cable band fixes the position of the hanger rope relative to the main cable by gripping the main cable. The gripping force of the cable band decreases over time. When the gripping force of the cable band decreases, the function of fixing the position of the hanger rope relative to the main cable deteriorates, which may possibly lead to degradation or damage of the bridge in some cases. Therefore, inspection of the gripping force of the cable band is sometimes performed. However, since a large number of cable bands are provided, the inspection of the gripping force of the cable bands requires enormous labor.

[0005] An object of the present disclosure is to provide an inspection method and an inspection apparatus capable of reducing the labor required for inspecting the gripping force of cable bands.

[0006] To solve the above problems, an inspection method according to one aspect of the present disclosure is an inspection method for a bridge having a main cable, a plurality of hanger ropes for suspending a bridge girder from the main cable, and a plurality of cable bands for fixing the upper ends of the hanger ropes to the main cable by gripping the main cable, the method comprising: a selection step of selecting at least one cable band to be measured from among the plurality of cable bands; a measurement step of measuring the current gripping force of the cable band to be measured that grips the main cable; a calculation step of calculating the rate of decrease in the gripping force of the cable band to be measured based on the measured value of the gripping force of the cable band to be measured measured in the measurement step and the initial value of the gripping force of the cable band to be measured; and an estimation step of estimating the current gripping force of an estimated cable band, which is different from the cable band to be measured, based on the initial value of the gripping force of an estimated cable band and the rate of decrease in the gripping force of the cable band to be measured.

[0007] A cable band has one or more bolts fastened to grip the main cable, and the gripping force is determined by the number of bolts and the axial force of the bolts. In the measurement process, the current gripping force of the cable band to be measured may be measured by measuring the axial force of one or more bolts of the cable band to be measured.

[0008] In the height direction of the bridge, the cable band under measurement may be assumed to be installed at a lower position than the cable band under estimation.

[0009] In the estimation process, the estimated current gripping force of the cable band to be estimated may be calculated by multiplying the value obtained by subtracting the rate of decrease in the gripping force of the cable band to be measured from 1 by the initial value of the gripping force of the cable band to be estimated.

[0010] The process may further include a determination step of determining whether the gripping force of the cable band to be estimated is acceptable or not by comparing the estimated current gripping force of the cable band to be estimated with a preset threshold.

[0011] To solve the above problems, an inspection device according to one aspect of the present disclosure is a bridge inspection device having a main cable, a plurality of hanger ropes for suspending a bridge girder from the main cable, and a plurality of cable bands for fixing the upper ends of the hanger ropes to the main cable by gripping the main cable, and comprises a calculation device for performing calculations related to the bridge, the calculation device calculates the rate of decrease in the gripping force of the cable band to be measured based on the measured value of the gripping force of the cable band to be measured and the initial value of the gripping force of the cable band to be measured, estimates the current gripping force of the estimated target cable band based on the initial value of the gripping force of an estimated target cable band different from the cable band to be measured and the rate of decrease in the gripping force of the cable band to be measured, and determines whether the gripping force of the estimated target cable band is acceptable or not by comparing the estimated value of the current gripping force of the estimated target cable band with a preset threshold.

[0012] To solve the above problems, an inspection method according to one aspect of the present disclosure is an inspection method for a bridge having a main cable, a plurality of hanger ropes for suspending a bridge girder from the main cable, and a plurality of cable bands for fixing the upper ends of the hanger ropes to the main cable by gripping the main cable, wherein the cable band has one or more bolts fastened to grip the main cable, the gripping force of the cable band on the main cable is determined by the number of bolts and the axial force of the bolts, and the inspection method includes a selection step of selecting at least one cable band to be measured from among the plurality of cable bands, a measurement step of measuring the current axial force of each bolt of the cable band to be measured that grips the main cable, and an estimation step of estimating the current gripping force of the cable band to be estimated based on the number of bolts of the cable band to be estimated, which is different from the cable band to be measured, and the measured value of the axial force of the bolts of the cable band to be measured.

[0013] In the estimation step, the axial forces of the bolts are extracted from the measured bolt axial forces, corresponding to the number of bolts in the cable band to be estimated. The estimated current gripping force of the cable band to be estimated is calculated by summing the extracted bolt axial forces. The process of extracting bolt axial forces and calculating the estimated current gripping force of the cable band to be estimated is repeated multiple times with different combinations of bolt axial forces to be extracted, thereby creating a distribution of the estimated current gripping force of the cable band to be estimated. The inspection method further includes a judgment step, in which, based on the distribution, the ratio of the number of estimated gripping force values ​​that are less than a preset first threshold relative to the total number of calculated gripping force estimates is calculated. The pass / fail status of the gripping force of the cable band to be estimated is determined by comparing this ratio with a preset second threshold.

[0014] According to this disclosure, it is possible to reduce the effort required to test the gripping force of cable bands.

[0015] Figure 1 is a side view showing an example of the configuration of a bridge according to the first embodiment. Figure 2 is a side view showing an example of the configuration of a cable band according to the first embodiment. Figure 3 is a cross-sectional view showing an example of the configuration of a cable band according to the first embodiment. Figure 4 is a diagram showing an example of the change in axial force of a bolt according to the first embodiment over time. Figure 5 is a flowchart showing an example of the flow of a bridge inspection method according to the first embodiment. Figure 6 is a block diagram showing an example of the configuration of a bridge inspection device according to the first embodiment. Figure 7 is a flowchart showing an example of the flow of a bridge inspection method according to the second embodiment. Figure 8 is a diagram showing an example of the current axial force distribution of a bolt in a cable band to be measured according to the second embodiment. Figure 9 is a diagram showing an example of the distribution of the estimated current gripping force of a cable band to be estimated according to the second embodiment.

[0016] Embodiments of this disclosure will be described in detail below with reference to the attached drawings. The dimensions, materials, and other specific numerical values ​​shown in these embodiments are merely illustrative for ease of understanding and do not limit this disclosure unless otherwise specified. In this specification and drawings, elements having substantially the same function or configuration are denoted by the same reference numerals to avoid redundant explanations, and elements not directly related to this disclosure are omitted from the illustrations.

[0017] [First Embodiment] [Bridge Structure] Figure 1 is a side view showing an example of the structure of a bridge 1 according to the first embodiment. The bridge 1 is, for example, a suspension bridge. The bridge 1 has a bridge girder 10, towers 12, anchors 14, main cables 16, a plurality of hanger ropes 18, and a plurality of cable bands 20.

[0018] The bridge girder 10 extends in the longitudinal direction of the bridge 1 and supports the bridge plate that constitutes the road on the bridge. The towers 12 extend in the height direction that intersects the longitudinal and horizontal directions of the bridge 1, respectively. The towers 12 may include, for example, a first tower 12A located on the first end side of the center of the bridge 1, and a second tower 12B located on the second end side of the center of the bridge 1. Although two towers 12 are shown as an example in Figure 1, the number of towers 12 is not limited to two; there may be one, three or more, etc.

[0019] The anchor 14 is made of a structure such as a concrete block and is installed on the ground at the end of the bridge 1. The anchor 14 may include, for example, a first anchor 14A at the first end of the bridge 1 and a second anchor 14B at the second end of the bridge 1.

[0020] The main cable 16 is formed, for example, by bundling together multiple steel wires. The outer surface of the main cable 16 may be covered with a coating made of, for example, synthetic resin.

[0021] The main cable 16 is connected to the tower 12 at least at one end. The main cable 16 may include, for example, a first main cable 16A, a second main cable 16B, and a third main cable 16C.

[0022] One end of the first main cable 16A is connected to the upper end of the first tower 12A. The other end of the first main cable 16A is connected to the first anchor 14A. In other words, the first main cable 16A is stretched between the upper end of the first tower 12A and the first anchor 14A. One end of the second main cable 16B is connected to the upper end of the second tower 12B. The other end of the second main cable 16B is connected to the second anchor 14B. In other words, the second main cable 16B is stretched between the upper end of the second tower 12B and the second anchor 14B. One end of the third main cable 16C is connected to the upper end of the first tower 12A. The other end of the third main cable 16C is connected to the upper end of the second tower 12B. In other words, the third main cable 16C is stretched between the upper end of the first tower 12A and the upper end of the second tower 12B.

[0023] The hanger ropes 18 are installed between the main cable 16 and the bridge girder 10. The hanger ropes 18 extend in the height direction of the bridge 1. The upper end of the hanger ropes 18 is connected to the main cable 16 via a cable band 20. The lower end of the hanger ropes 18 is connected to the bridge girder 10. Multiple hanger ropes 18 are arranged in parallel along the length direction of the bridge 1. That is, the multiple hanger ropes 18 suspend the bridge girder 10 from the main cable 16.

[0024] The cable band 20 is installed between the main cable 16 and the upper end of the hanger rope 18. The cable band 20 secures the upper end of the hanger rope 18 to the main cable 16 by gripping the main cable 16. The cable band 20 will be described in detail later.

[0025] Thus, the bridge girder 10 is supported by the tower 12, anchors 14, main cables 16, multiple hanger ropes 18, and multiple cable bands 20.

[0026] Figure 2 is a side view showing an example of the configuration of the cable band 20 according to the first embodiment. Figure 3 is a cross-sectional view showing an example of the configuration of the cable band 20 according to the first embodiment. The cable band 20 has a first piece 30A, a second piece 30B, and one or more bolts 34.

[0027] The first piece 30A and the second piece 30B are formed in the shape of a cylinder roughly cut in half. The first piece 30A and the second piece 30B are positioned opposite each other with the main cable 16 in between.

[0028] The first piece 30A has a first hole 36A into which a bolt 34 can be inserted. The second piece 30B has a second hole 36B into which a bolt 34 can be inserted. The number of first holes 36A and second holes 36B are substantially the same as the number of bolts 34. The first piece 30A and the second piece 30B are positioned opposite each other such that the central axis of the first hole 36A and the central axis of the second hole 36B are coaxial.

[0029] Figure 2 shows an example where 10 bolts 34 are provided on one cable band 20. However, the number of bolts 34 on the cable band 20 is not limited to this example; at least one or more bolts are sufficient.

[0030] The bolts 34 are inserted into the first hole 36A and the second hole 36B. The first piece 30A and the second piece 30B are positioned opposite each other with the main cable 16 in between, and are tightened toward each other by the bolts 34 inserted into the first hole 36A and the second hole 36B. The first piece 30A and the second piece 30B are substantially integrated by the tightened bolts 34. In this way, the bolts 34 are fastened so that the cable band 20 grips the main cable 16.

[0031] The first piece 30A has a first guide 38A formed thereon that can support the hanger rope 18. The second piece 30B has a second guide 38B formed thereon that can support the hanger rope 18. When the first piece 30A, the second piece 30B and the bolt 34 are substantially integrated, the upper end of the first guide 38A and the upper end of the second guide 38B are roughly continuous. After the first piece 30A, the second piece 30B and the bolt 34 are substantially integrated, the upper end of the hanger rope 18 is attached to the first guide 38A and the second guide 38B.

[0032] As shown in Figure 1, the inclination angle of the main cable 16 with respect to the horizontal plane increases as it approaches the tower 12. Consequently, as shown in Figure 2, the inclination angle of the central axis C10 of the cable band 20 with respect to the horizontal plane increases as the position of the cable band 20 approaches the tower 12. For convenience of explanation, the inclination angle of the central axis C10 of the cable band 20 with respect to the horizontal plane is sometimes simply referred to as the inclination angle of the cable band 20.

[0033] In order to prevent the cable band 20 from shifting position, the gripping force of the cable band 20 on the main cable 16 must be increased as the inclination angle of the cable band 20 increases. For the sake of explanation, the gripping force of the cable band 20 on the main cable 16 is sometimes simply referred to as the gripping force of the cable band 20.

[0034] Here, the gripping force of the cable band 20 on the main cable 16 can be determined by the number of bolts 34 provided in the cable band 20 and the axial force of the bolts 34 provided in the cable band 20.

[0035] Based on this, the number of bolts provided on the cable band may vary depending on the position of the cable band. More specifically, the number of bolts 34 provided on the cable band 20 may increase as the inclination angle of the cable band 20 becomes relatively larger. As the number of bolts 34 provided increases relatively, the gripping force of the cable band 20 becomes relatively larger.

[0036] Furthermore, the initial value of the axial force of the bolts 34 may be substantially the same regardless of the position of the bolts 34 within the cable band 20. Also, the initial value of the axial force of the bolts 34 may be substantially the same regardless of the cable band 20 (i.e., regardless of the position of the cable band 20). Even if the initial value of the axial force of the bolts 34 is common in this way, the gripping force of the cable band 20 can be adjusted for each cable band 20 by varying the number of bolts 34 as described above. Note that the initial value refers to the value at the time the bridge 1 was constructed.

[0037] Figure 4 shows an example of the change in axial force of a bolt 34 over time according to the first embodiment. Specifically, Figure 4 shows the actual measurement of the axial force of a bolt 34 over time in a specific bridge 1, and the change in axial force of the bolt 34 over time. The horizontal axis in Figure 4 shows the position of the cable band 20 (in other words, the bolt 34) in the longitudinal direction of the bridge 1. In Figure 4, it is assumed that the initial value of the axial force of the bolt 34 was substantially the same regardless of the position of the cable band 20.

[0038] In Figure 4, the circles "○" indicate an example of the measured axial force of the bolts 34 at the first measurement point, which is one period after the completion of construction of bridge 1. The triangles "△" indicate an example of the measured axial force of the bolts 34 at the second measurement point, which is two periods after the first measurement point. The squares "□" indicate an example of the measured axial force of the bolts 34 at the third measurement point, which is three periods after the second measurement point.

[0039] As shown by the triangle "△" in Figure 4, the axial force of the bolt 34 at the second measurement point decreases uniformly by a predetermined first ratio compared to the axial force of the bolt 34 at the first measurement point, regardless of the position of the cable band 20. Also, as shown by the square "□" in Figure 4, the axial force of the bolt 34 at the third measurement point decreases uniformly by a predetermined second ratio compared to the axial force of the bolt 34 at the first measurement point, regardless of the position of the cable band 20.

[0040] Based on these considerations, it can be assumed that the axial force of the bolt 34 decreases uniformly regardless of the position of the cable band 20.

[0041] In the inspection method of the first embodiment, the gripping force of the cable band 20 of the bridge 1 is inspected by utilizing the tendency of the axial force of the bolt 34 to decrease in this way.

[0042] [Inspection Method] Figure 5 is a flowchart showing an example of the flow of the inspection method for bridge 1 according to the first embodiment. As shown in Figure 5, the inspection method of the first embodiment includes a selection step (S10), a measurement step (S11), a calculation step (S12), an estimation step (S13), and a determination step (S14).

[0043] Each step of the inspection method according to the first embodiment may be performed by a person, by a machine such as a computer, or by cooperation between a person and a machine. In the inspection method according to the first embodiment, at least some of the steps may be performed by a machine, and the other steps may be performed by a person.

[0044] The inspection method according to the first embodiment may be performed, for example, by an administrator who manages the bridge 1 that is the target of the inspection method, or may be performed by any entity corresponding to the actual operation status of the bridge 1, such as a third party entrusted with management by the administrator. The administrator may be the same entity that constructed the bridge 1, or may be an entity different from the entity that constructed the bridge 1. Further, the present invention is not limited to an aspect in which all steps of the inspection method are performed by the same entity, and the inspection method according to the first embodiment may be realized as a result by having at least some of the steps performed by another entity. In the following, for convenience of explanation, the description will be given on the assumption that the administrator performs each step.

[0045] For convenience of explanation, the cable band 20 for which the gripping force of the cable band 20 on the main cable 16 is measured may be referred to as a measurement target cable band. A cable band 20 that is a different cable band 20 from the measurement target cable band and is targeted for gripping force estimation may be referred to as an estimation target cable band.

[0046] [Selection Step (S10)] First, in the selection step, the administrator selects at least one measurement target cable band from the plurality of cable bands 20. For example, the administrator may select one cable band 20 as the measurement target cable band.

[0047] The administrator may select, as the measurement target cable band, the cable band 20 installed at a position lower than the estimation target cable band in the height direction of the bridge. In other words, the administrator may select the measurement target cable band such that the inclination angle of the measurement target cable band with respect to the horizontal plane is smaller than the inclination angle of the estimation target cable band with respect to the horizontal plane. The cable band 20 at the position with a relatively small inclination angle has a relatively low position in the height direction from the bridge girder 10. For example, the administrator may select the cable band 20 located near the center of the third main cable 16C as the measurement target cable band. In this case, the estimation target cable band may be the cable band 20 located near the first tower 12A of the third main cable 16C, or the cable band 20 located near the second tower 12B of the third main cable 16C.

[0048] Accordingly, in the inspection method of the first embodiment, by selecting the cable band 20 at a relatively low position in the height direction (the cable band 20 at the position where the inclination angle is relatively small) as the measurement target cable band, the labor for measuring the measurement target cable band in the measurement step described later can be reduced. In this case, furthermore, the inspection method of the first embodiment can suppress the time and cost required for the measurement step.

[0049] In addition, when the current inspection is the second or subsequent inspection in time series, the administrator may select, as the current measurement target cable band, the cable band 20 that is substantially the same as the cable band 20 selected as the measurement target cable band in the previous inspection.

[0050] In this case, in the inspection method of the first embodiment, the secular change between the previous inspection and the current inspection can be reflected in the measurement target cable band, and the reliability of the measured value of the measurement target cable band can be improved.

[0051] [Measurement Process (S11)] In the measurement process, the administrator measures the current gripping force of the cable band to be measured, which was selected in the selection process. The measured gripping force may be referred to as the measured value of the gripping force. The current gripping force may also be referred to as the current value of the gripping force.

[0052] More specifically, the administrator may measure the current gripping force of the cable band under test by measuring the axial force of one or more bolts 34 of the cable band under test.

[0053] As a result, the inspection method of the first embodiment makes it possible to appropriately obtain the current gripping force of the cable band being measured.

[0054] For example, the administrator may measure the axial force of all bolts 34 included in the cable band under measurement. In this case, the administrator may obtain a measurement of the current gripping force of the cable band under measurement by summing the axial forces of the measured bolts 34.

[0055] Furthermore, for example, the administrator may measure the axial force of some of the bolts 34 included in the cable band under measurement. In this case, the administrator may estimate the axial force of the unmeasured bolts 34 included in the cable band under measurement based on the axial force of the measured bolts. For example, the administrator may use the average or median value of the axial force of the measured bolts 34 as the estimated value of the axial force of the unmeasured bolts 34. The administrator may obtain a measurement value of the current gripping force of the cable band under measurement by summing the axial force of the measured bolts 34 and the estimated value of the axial force of the unmeasured bolts 34 in the cable band under measurement, for all bolts 34 included in the cable band under measurement.

[0056] [Calculation Process (S12)] In the calculation process, the administrator calculates the rate of decrease in gripping force of the cable band to be measured based on the measured gripping force of the cable band to be measured in the measurement process and the initial value of the gripping force of the cable band to be measured. The rate of decrease in gripping force refers to the ratio of the decrease in gripping force relative to the initial value of the gripping force.

[0057] Here, assuming that the axial force of bolt 34 is substantially the same regardless of the position of the cable band 20, the gripping force of the cable band 20 can be expressed by the following equation (1): Gripping force = Number of bolts × Axial force of each bolt ... (1)

[0058] As described above with reference to Figure 4, the axial force of the bolt 34 decreases uniformly regardless of the position of the cable band 20 (in other words, the bolt 34). Therefore, for a single bolt 34, the rate of decrease in axial force relative to the initial value of the axial force is expressed by the following equation (2): Rate of decrease in axial force = (Initial value of axial force - Current value of axial force) / Initial value of axial force ... (2)

[0059] Applying equation (1) to the right-hand side of equation (2), equation (2) can be expressed as equation (3) below: Axial force reduction rate = ((Initial gripping force / Number of bolts) - (Current gripping force / Number of bolts)) / ((Initial gripping force / Number of bolts)) ... (3)

[0060] Equation (3) can be expressed as equation (4) by removing the "number of bolts". The right-hand side of equation (4) essentially represents the rate of decrease in the gripping force of the cable band 20. That is, the rate of decrease in the gripping force of the cable band 20 can be considered to be essentially the same as the rate of decrease in the axial force of one bolt 34. Rate of decrease in axial force = (Initial value of gripping force - Current value of gripping force) / Initial value of gripping force ... (4)

[0061] Therefore, in the calculation process, the administrator may calculate the rate of decrease in gripping force of the cable band 20 using the following formula (5). That is, the administrator may obtain the rate of decrease in gripping force of the cable band to be measured by multiplying the value obtained by subtracting the current value of gripping force from the initial value of gripping force by the initial value of gripping force. Rate of decrease in gripping force = (Initial value of gripping force - Current value of gripping force) / Initial value of gripping force ... (5)

[0062] [Estimation Process (S13)] In the estimation process, the administrator estimates the current gripping force of the cable band to be estimated based on the initial value of the gripping force of the cable band to be estimated and the rate of decrease in the gripping force of the cable band to be measured. The estimated gripping force is sometimes referred to as the estimated gripping force value.

[0063] As described above with reference to Figure 4, the axial force of the bolt 34 decreases uniformly regardless of the position of the cable band 20 (in other words, the bolt 34). Therefore, it can be estimated that the rate of decrease in gripping force of the estimated target cable band is substantially the same as the rate of decrease in gripping force of the measured target cable band.

[0064] Therefore, in the estimation process, the administrator may calculate the estimated current gripping force of the cable band to be estimated using the following formula (6). That is, the administrator may calculate the estimated current gripping force of the cable band to be estimated by multiplying the value obtained by subtracting the rate of decrease in the gripping force of the cable band to be measured from 1 by the initial value of the gripping force of the cable band to be estimated. Estimated current gripping force of the cable band to be estimated = (1 - rate of decrease in the gripping force of the cable band to be measured) × initial value of the gripping force of the cable band to be estimated ... (6)

[0065] As a result, the inspection method of the first embodiment makes it possible to appropriately obtain an estimated value of the current gripping force of the cable band to be estimated.

[0066] [Determination Process (S14)] In the determination process, the administrator determines whether the gripping force of the cable band to be estimated is acceptable or not by comparing the estimated current gripping force of the cable band to be estimated with a preset threshold. The preset threshold may be, for example, the gripping force required by the design of the cable band to be estimated.

[0067] The administrator may determine that the gripping force test of the cable band in question has passed if the estimated current gripping force of the cable band in question is equal to or greater than a predetermined threshold. On the other hand, the administrator may determine that the gripping force test of the cable band in question has failed if the estimated current gripping force of the cable band in question is less than a predetermined threshold.

[0068] As a result, in the inspection method of the first embodiment, the inspection result of the gripping force of the target cable band can be easily obtained by using the estimated value of the current gripping force of the target cable band.

[0069] The determination step may be omitted.

[0070] As described above, the inspection method of the first embodiment includes a selection step of selecting at least one cable band to be measured from among a plurality of cable bands. The inspection method of the first embodiment includes a measurement step of measuring the current gripping force of the cable band to be measured that grips the main cable. The inspection method of the first embodiment includes a calculation step of calculating the rate of decrease in gripping force of the cable band to be measured based on the measured value of the gripping force of the cable band to be measured measured in the measurement step and the initial value of the gripping force of the cable band to be measured. The inspection method of the first embodiment includes an estimation step of estimating the current gripping force of an estimated cable band, which is different from the cable band to be measured, based on the initial value of the gripping force of an estimated cable band and the rate of decrease in gripping force of the cable band to be measured.

[0071] As a result, in the inspection method of the first embodiment, it is only necessary to actually measure the gripping force of the cable band 20 designated as the target cable band among the multiple cable bands 20 of the bridge 1. In other words, in the inspection method of the first embodiment, the number of cable bands 20 whose gripping force is actually measured can be significantly reduced. Therefore, according to the inspection method of the first embodiment, it is possible to reduce the effort required to inspect the gripping force of the cable bands 20.

[0072] [Inspection device] Next, an example of mechanically executing each step of the inspection method of the first embodiment will be described. Figure 6 is a block diagram showing an example of the configuration of the inspection device 100 for the bridge 1 according to the first embodiment. As shown in Figure 6, the inspection device 100 includes an input / output device 110, a storage device 112, and a computing device 114.

[0073] The input / output device 110 includes an optional output device that presents various types of information to an administrator or the like. The output device may include a display device, such as a liquid crystal display, that displays various types of images and various types of information. The input / output device 110 also includes an input device, such as a keyboard or touch panel, that accepts input operations from an administrator or the like.

[0074] The storage 112 is composed of non-volatile memory elements, such as a hard disk drive or flash memory. The storage 112 may store various data used by the computing unit 114, such as the initial value of the axial force of each bolt 34, the number of bolts 34 in the cable band 20, the initial value of the gripping force of the cable band 20, and the threshold value in the judgment process.

[0075] The arithmetic unit 114 comprises one or more processors 130 and one or more memories 132 connected to the processors 130. The memories 132 include ROM for storing programs and RAM as a work area. The processors 130 work in cooperation with the programs contained in the memories 132 to perform various processes. By executing the programs, the processors 130 function as a processing unit 140 that performs various calculations related to the bridge 1, for example.

[0076] The processing unit 140 may perform the calculation step (S12), estimation step (S13), and determination step (S14) among the steps shown in Figure 5. The selection step (S10) and measurement step (S11) in Figure 5 may be performed by a person such as an administrator, or by a machine capable of performing measurements. The processing unit 140 only needs to be able to use the current gripping force of the cable band to be measured, which was measured in the measurement step (S11).

[0077] More specifically, the processing unit 140 calculates the rate of decrease in the gripping force of the cable band to be measured based on the measured value of the gripping force of the cable band to be measured and the initial value of the gripping force of the cable band to be measured. For example, the processing unit 140 may calculate the rate of decrease in the gripping force of the cable band to be measured using the above formula (5).

[0078] The processing unit 140 estimates the current gripping force of the cable band to be estimated based on the initial value of the gripping force of the cable band to be estimated, which is different from the cable band to be measured, and the rate of decrease in the gripping force of the cable band to be measured. For example, the processing unit 140 may calculate an estimated value of the current gripping force of the cable band to be estimated using the above formula (6).

[0079] The processing unit 140 determines whether the gripping force of the target cable band is acceptable or not by comparing the estimated current gripping force of the target cable band with a preset threshold.

[0080] Furthermore, the details of each process performed by the processing unit 140 are substantially the same as those of each process in the inspection method for bridge 1 described above, so they are omitted from this description.

[0081] As described above, the calculation unit 114 of the inspection device 100 of the first embodiment calculates the rate of decrease in gripping force of the cable band to be measured based on the measured value of the gripping force of the cable band to be measured and the initial value of the gripping force of the cable band to be measured. The calculation unit 114 of the inspection device 100 of the first embodiment estimates the current gripping force of the cable band to be estimated based on the initial value of the gripping force of the cable band to be estimated, which is different from the cable band to be measured, and the rate of decrease in gripping force of the cable band to be measured. The calculation unit 114 of the inspection device 100 of the first embodiment determines whether the gripping force of the cable band to be estimated passes or fails by comparing the estimated value of the current gripping force of the cable band to be estimated with a preset threshold.

[0082] As a result, in the inspection device 100 of the first embodiment, it is only necessary to actually measure the gripping force of the cable band 20 that is designated as the target cable band among the multiple cable bands 20 of the bridge 1. In other words, the inspection device 100 of the first embodiment can significantly reduce the number of cable bands 20 whose gripping force is actually measured. Therefore, according to the inspection device 100 of the first embodiment, it is possible to reduce the effort required to inspect the gripping force of the cable bands 20.

[0083] [Second Embodiment] [Inspection Method] In the inspection method of the first embodiment, the rate of decrease in the gripping force of the cable band to be measured was calculated based on the measured value of the gripping force of the cable band to be measured, and the current gripping force of the cable band to be estimated was estimated based on the rate of decrease in the gripping force of the cable band to be measured. In contrast, in the inspection method of the second embodiment, the current gripping force of the cable band to be estimated is directly estimated based on the axial force of the bolt 34 of the cable band to be measured.

[0084] Figure 7 is a flowchart showing an example of the flow of the inspection method for bridge 1 according to the second embodiment. As shown in Figure 7, the inspection method of the second embodiment includes a selection step (S30), a measurement step (S31), an estimation step (S32), and a determination step (S33).

[0085] Each step of the inspection method in the second embodiment may be performed by a person, by a machine such as a computer, or by a combination of a person and a machine, similar to the inspection method in the first embodiment. In the inspection method in the second embodiment, at least some steps may be performed by a machine and other steps may be performed by a person.

[0086] The inspection method of the second embodiment may be carried out by various entities, similar to the first inspection method. For the sake of explanation, the following description will assume that the manager responsible for the bridge 1 that is the subject of the inspection method performs each step.

[0087] Furthermore, in the second embodiment, the cable band to be measured means a cable band containing a bolt whose axial force is measured. The cable band to be estimated means a cable band 20 different from the cable band to be measured that is the subject of gripping force estimation.

[0088] Furthermore, the cable band 20 has one or more bolts 34 that are fastened to grip the main cable 16. The gripping force of the cable band 20 on the main cable 16 is determined by the number of bolts 34 and the axial force of the bolts 34.

[0089] [Selection Process (S30)] In the selection process (S30), the administrator selects at least one cable band to be measured from among the multiple cable bands 20. For example, the administrator may select a number of cable bands 20 that is less than the total number of cable bands 20 on the bridge 1 as the cables to be measured.

[0090] Furthermore, the administrator selects the cable bands to be measured such that the number of bolts 34 included in the cable bands to be measured is equal to or greater than the number of bolts 34 in the estimated cable bands.

[0091] In addition, similar to the selection process (S10) of the first embodiment, the administrator may select a cable band 20 installed at a lower position than the estimated target cable band in the height direction of the bridge as the cable band to be measured.

[0092] Furthermore, similar to the selection step (S10) of the first embodiment, if the current inspection is the second or subsequent inspection in chronological order, the administrator may select a cable band 20 as the cable band to be measured for this inspection that is substantially the same as the cable band 20 selected as the cable band to be measured during the previous inspection.

[0093] [Measurement process (S31)] In the measurement process (S31), the administrator measures the current axial force of each bolt 34 of the cable band to be measured that grips the main cable 16.

[0094] For example, the administrator may measure the axial force of all bolts 34 in the cable band 20 selected as the cable band to be measured. Alternatively, the administrator may measure the axial force of some of the bolts 34 in the cable band 20 selected as the cable band to be measured. Alternatively, the administrator may measure the axial force of some of the bolts 34 in each of the multiple cable bands 20 selected as the cable bands to be measured.

[0095] For example, the administrator measures the current axial force of a number of bolts 34 in the cable band to be measured that is equal to or greater than the number of bolts 34 in the cable band to be estimated.

[0096] Figure 8 shows an example of the distribution of measured axial force values ​​of bolts 34 in a cable band under measurement according to the second embodiment. The administrator may create a distribution of measured axial force values ​​of bolts 34 in a cable band under measurement, as shown in Figure 8, based on the measured axial force values ​​of multiple bolts 34 in the cable band under measurement.

[0097] [Estimation Process (S32)] In the estimation process (S32), the administrator estimates the current gripping force of the cable band to be estimated based on the number of bolts 34 of the cable band to be estimated and the measured values ​​of the axial force of multiple bolts 34 of the cable band to be measured.

[0098] More specifically, in the estimation process (S32), the administrator extracts the axial forces of the bolts 34 from the measured axial forces of the bolts 34, equal to the number of bolts 34 in the cable band to be estimated (S321). At this time, the administrator may extract multiple axial forces in any combination.

[0099] The administrator calculates an estimated value of the current gripping force of the target cable band by summing the axial forces of the extracted bolts 34 (S322).

[0100] The administrator determines whether the number of estimated current gripping force values ​​for the target cable bands has exceeded a predetermined number (S323). The predetermined number is set to an arbitrary value that allows for the creation of the distribution of estimated current gripping force values ​​for the target cable bands, as described later.

[0101] If the number of estimated values ​​for the current gripping force of the target cable band is less than a predetermined number (NO in S323), the administrator returns to S321 and extracts the axial force of the bolts 34 again, using a different combination of axial forces (S321).

[0102] In other words, the administrator extracts the axial force of the bolts 34 and calculates an estimated value of the current gripping force of the cable band to be estimated, performing this process multiple times with different combinations of axial forces of the bolts 34 to be extracted.

[0103] If the number of estimated current gripping force values ​​for the target cable band exceeds a predetermined number (YES in S323), the administrator creates a distribution of estimated current gripping force values ​​for the target cable band based on the multiple estimated values ​​calculated in S321 to S323 (S324).

[0104] Figure 9 shows an example of the distribution of estimated current gripping forces of the target cable band according to the second embodiment. As shown in Figure 9, the estimated current gripping forces of the target cable band vary depending on the combination of axial forces of the extracted bolts 34, resulting in variability.

[0105] [Determination Process (S33)] After the estimation process (S32), the administrator performs the determination process (S33). For the sake of explanation, the ratio of the number of estimated gripping force values ​​that are less than a predetermined first threshold to the total number of estimated gripping force values ​​is sometimes referred to as the specific ratio. In the determination process (S33), the administrator calculates the specific ratio (S331).

[0106] The total number of calculated gripping force estimates corresponds to the number of calculations performed in S322 and represents the entire distribution in Figure 9. The hatched area in Figure 9 represents an example of the number of times the gripping force estimate is less than a predetermined first threshold. The first threshold may be, for example, the gripping force required by the design of the cable band being estimated. The specific percentage corresponds to the ratio of the hatched area to the entire distribution in Figure 9. That is, the specific percentage corresponds to the probability that the gripping force estimate is less than the first threshold.

[0107] In the determination step (S33), the administrator determines whether the gripping force of the estimated target cable band is acceptable or not by comparing a specific percentage with a pre-set second threshold. The second threshold may be set to various values ​​depending on the desired level of confidence in the estimated gripping force.

[0108] The administrator may determine that the gripping force test of the estimated target cable band is passed if the specific percentage is less than a predetermined second threshold. On the other hand, the administrator may determine that the gripping force test of the estimated target cable band is failed if the specific percentage is equal to or greater than the predetermined second threshold.

[0109] The determination step (S33) may be omitted.

[0110] As described above, the inspection method of the second embodiment includes a selection step of selecting at least one cable band to be measured from among a plurality of cable bands. The inspection method of the second embodiment includes a measurement step of measuring the current axial force of each bolt of the cable band to be measured that grips the main cable. The inspection method of the second embodiment includes an estimation step of estimating the current gripping force of the cable band to be estimated based on the number of bolts of the cable band to be estimated, which is different from the cable band to be measured, and the measured values ​​of the axial force of the bolts of the cable band to be measured.

[0111] As a result, in the inspection method of the second embodiment, the axial force of the bolts 34 only needs to be measured for the cable band 20 designated as the target cable band among the multiple cable bands 20 of the bridge 1. In other words, in the inspection method of the second embodiment, the number of cable bands 20 for which the axial force of the bolts 34 is actually measured can be significantly reduced. Therefore, according to the inspection method of the second embodiment, it is possible to reduce the effort required to inspect the gripping force of the cable bands 20.

[0112] Furthermore, in the estimation step of the inspection method of the second embodiment, the axial forces of bolts are extracted from the measured axial forces of bolts, up to the number of bolts in the cable band to be estimated. In the estimation step of the inspection method of the second embodiment, the estimated current gripping force of the cable band to be estimated is calculated by summing the extracted axial forces of bolts. In the estimation step of the inspection method of the second embodiment, the extraction of axial forces of bolts and the calculation of the estimated current gripping force of the cable band to be estimated is performed multiple times with different combinations of axial forces of bolts to be extracted, thereby creating a distribution of the estimated current gripping force of the cable band to be estimated. The inspection method of the second embodiment further includes a determination step. In the determination step of the inspection method of the second embodiment, based on the distribution, the ratio of the number of estimated gripping force values ​​that are less than a preset first threshold to the total number of calculated estimated gripping force values ​​is calculated. In the determination step of the inspection method of the second embodiment, the pass or fail of the gripping force of the cable band to be estimated is determined by comparing the ratio with a preset second threshold.

[0113] As a result, in the inspection method of the second embodiment, the reliability of the inspection results for the gripping force of the target cable band can be improved by utilizing the distribution of the estimated current gripping force of the target cable band.

[0114] Furthermore, when each step of the inspection method of the second embodiment is performed mechanically, the processing of each step may be performed using an inspection device having substantially the same configuration as the inspection device 100 of the first embodiment.

[0115] While embodiments have been described above with reference to the attached drawings, it goes without saying that this disclosure is not limited to the embodiments described above. It is clear to those skilled in the art that various modifications or alterations can be conceived within the scope of the claims, and these will naturally also fall within the technical scope of this disclosure.

[0116] 1: Bridge 10: Bridge girder 16: Main cable 18: Hanger rope 20: Cable band 34: Bolt 100: Inspection device 114: Calculation device S10, S30: Selection process S11, S31: Measurement process S12: Calculation process S13, S32: Estimation process S14, S33: Judgment process

Claims

1. A method for inspecting a bridge having a main cable, a plurality of hanger ropes for suspending a bridge girder from the main cable, and a plurality of cable bands for fixing the upper ends of the hanger ropes to the main cable by gripping the main cable, the method comprising: a selection step of selecting at least one cable band to be measured from among the plurality of cable bands; a measurement step of measuring the current gripping force of the cable band to be measured that grips the main cable; a calculation step of calculating the rate of decrease in the gripping force of the cable band to be measured based on the measured value of the gripping force of the cable band to be measured measured in the measurement step and the initial value of the gripping force of the cable band to be measured; and an estimation step of estimating the current gripping force of the estimated cable band based on the initial value of the gripping force of an estimated cable band different from the cable band to be measured and the rate of decrease in the gripping force of the cable band to be measured.

2. The inspection method according to claim 1, wherein the cable band has one or more bolts fastened to grip the main cable, the gripping force is determined by the number of bolts and the axial force of the bolts, and in the measurement step, the current gripping force of the cable band to be measured is measured by measuring the axial force of one or more of the bolts of the cable band to be measured.

3. The inspection method according to claim 1, wherein, in the height direction of the bridge, the cable band to be measured is installed at a lower position than the cable band to be estimated.

4. The inspection method according to claim 1, wherein in the estimation step, an estimated value of the current gripping force of the cable band to be estimated is calculated by multiplying the value obtained by subtracting the rate of decrease in the gripping force of the cable band to be measured from 1 by the initial value of the gripping force of the cable band to be estimated.

5. The inspection method according to claim 1, further comprising a determination step of determining whether the gripping force of the cable band to be estimated is acceptable or not by comparing the estimated current gripping force of the cable band to be estimated with a preset threshold.

6. An inspection device for a bridge comprising: a main cable; a plurality of hanger ropes for suspending a bridge girder from the main cable; and a plurality of cable bands for fixing the upper ends of the hanger ropes to the main cable by gripping the main cable, the device further comprising a calculation unit for performing calculations related to the bridge, wherein the calculation unit calculates the rate of decrease of the gripping force of the cable band to be measured based on the measured value of the gripping force of the cable band to be measured and the initial value of the gripping force of the cable band to be measured; estimates the current gripping force of the estimated cable band based on the initial value of the gripping force of an estimated cable band different from the cable band to be measured and the rate of decrease of the gripping force of the cable band to be measured; and determines whether the gripping force of the estimated cable band passes or fails by comparing the estimated value of the current gripping force of the estimated cable band with a preset threshold.

7. A method for inspecting a bridge, comprising: a main cable; a plurality of hanger ropes for suspending a bridge girder from the main cable; and a plurality of cable bands for fixing the upper ends of the hanger ropes to the main cable by gripping the main cable, wherein each cable band has one or more bolts fastened to grip the main cable, the gripping force of the cable band on the main cable is determined by the number of bolts and the axial force of the bolts, and the inspection method comprises: a selection step of selecting at least one cable band to be measured from the plurality of cable bands; a measurement step of measuring the current axial force of each bolt of the cable band to be measured that grips the main cable; and an estimation step of estimating the current gripping force of the estimated cable band based on the number of bolts of an estimated cable band different from the cable band to be measured and the measured value of the axial force of the bolts of the cable band to be measured.

8. The inspection method according to claim 7, wherein in the estimation step, the axial forces of the bolts are extracted from the measured axial forces of the bolts, the number of bolts in the cable band to be estimated is equal to the number of bolts in the cable band to be estimated, the current estimated gripping force of the cable band to be estimated is calculated by summing the extracted axial forces of the bolts, and a distribution of the current estimated gripping force of the cable band to be estimated is created by performing the extraction of the axial forces of the bolts and the calculation of the current estimated gripping force of the cable band to be estimated multiple times with different combinations of the axial forces of the bolts to be extracted, and the inspection method further includes a determination step, in which, based on the distribution, the ratio of the number of estimated gripping force values ​​that are less than a preset first threshold to the total number of estimated gripping force values ​​is calculated, and the pass / fail status of the gripping force of the cable band to be estimated is determined by comparing the ratio with a preset second threshold.

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