JP2018013361A - Tension force measuring device, tension force measuring method, and tension force measuring program - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a device capable of easily measuring tension of an anchor. A tension measuring device according to one aspect of the present invention acquires acceleration waveform data indicating vibration of an existing anchor, and Fourier transforms the acquired acceleration waveform data to obtain a Fourier spectrum of the vibration. Calculated, the average value of the spectrum value in the predetermined frequency range of the calculated Fourier spectrum is calculated as a representative Fourier spectrum value, based on the correlation information indicating the correlation between the representative Fourier spectrum and the tension obtained in advance , The tension of the existing anchor corresponding to the calculated representative Fourier spectrum value is calculated. [Selection diagram] Fig. 4

Description

  The present invention relates to a tension measuring device, a tension measuring method, and a tension measuring program.

  The tension of an anchor (ground anchor or the like) installed on the slope fluctuates from moment to moment depending on the behavior of the ground constituting the slope, the temporal change in the material itself constituting the anchor, and the like. In addition, when the stability of a slope changes due to fluctuations in the tension of the anchor, various external force changes occur on the slope due to the change in stability of the slope. Will fluctuate. Therefore, in order to maintain the stability of the slope, it is extremely important to regularly measure and manage the tension of the anchor.

  As a method for measuring the tension force of the anchor, Patent Document 1 proposes a method in which a load cell (load cell) is attached to each anchor and the tension force of each anchor is measured by the load meter. However, the cost increases as much as the load cell is attached to the anchor. Also, if you want to attach a load meter to an anchor that has already been installed, you must assemble the scaffolding to the position where the anchor is installed, or remove the nut etc. while pulling the tension material of the anchor. Therefore, the work load is increased accordingly. In addition, the tension material is burdened by the amount that it is pulled out. Therefore, the method using a load cell has limited application scenes and is difficult to use widely.

  Therefore, conventionally, the tension of an anchor already installed is measured by performing a lift-off test. In the lift-off test, a tensioning jack is installed on the anchor head and the anchoring force of the anchor is measured until the anchor is separated from the bearing plate, that is, by loading a larger load on the anchor than the current tensioning load. It is a test to do. However, this lift-off test is not performed on all the anchors installed on the slope because the work process is complicated. For example, in the first year, a lift-off test is performed on 10 to 20% of the anchors, and in the next second year, a lift-off test is performed on another 10 to 20% of the anchors. Thus, it is common to change the target of the lift-off test every year. For this reason, the tension of the target anchor is measured once every few years, and the tension of the target anchor cannot be continuously monitored.

JP 2002-267593 A Japanese Patent Laying-Open No. 2015-025297

  In Patent Document 2, in order to increase the working efficiency of measuring the tension force of the anchor, the base end of the anchor is hit to generate an elastic wave, and the tension force is estimated from the dominant frequency of the reflected wave of the generated elastic wave. A method has been proposed. However, since the base end portion of the anchor is attached with a cap or the like and the base end portion of the anchor cannot be hit with a hammer or the like, an elastic wave cannot be generated. Could not be applied. In addition, since the length of the anchor free length (part where tension is applied) is generally 4 m or more, a reflected wave that can measure the dominant frequency is generated unless the anchor is hit with a very large force. I couldn't let you. Therefore, even if this estimation method was used, the tension of the anchor could not be measured easily.

  In one aspect, the present invention has been made in consideration of such points, and an object of the present invention is to provide a device that can easily measure the tension of an anchor.

  The present invention employs the following configuration in order to solve the above-described problems.

  That is, the tension measuring device according to one aspect of the present invention includes an acceleration waveform data acquisition unit that acquires acceleration waveform data indicating vibration of an existing anchor, and Fourier transform of the acquired acceleration waveform data, thereby A spectrum value calculation unit that calculates an average value of spectrum values in a predetermined frequency range of the calculated Fourier spectrum as a representative Fourier spectrum value, and a correlation between a representative Fourier spectrum acquired in advance and a tension force A tension force calculation unit that calculates the tension force of the existing anchor corresponding to the calculated representative Fourier spectrum value based on correlation information indicating the relationship.

  In this configuration, in order to measure the tension force of the existing anchor, acceleration waveform data indicating the vibration (acceleration) of the anchor along the time series is used. Acceleration waveform data is generated by, for example, installing an acceleration sensor on the head side (for example, a bearing plate) of an existing anchor and storing the output of the installed acceleration sensor in time series by a data logger or the like. can do. The tension measuring apparatus according to this configuration estimates the tension of an existing anchor by performing frequency analysis on such acceleration waveform data.

  Specifically, the tension measuring apparatus according to the configuration calculates a Fourier spectrum of the vibration of the existing anchor by performing Fourier transform on the acquired acceleration waveform data. Next, the tension measuring device according to the configuration calculates an average value of spectrum values in a predetermined frequency range of the calculated Fourier spectrum as a representative Fourier spectrum value. Then, the tension measuring apparatus according to the configuration includes the tension of the existing anchor corresponding to the calculated representative Fourier spectrum value based on the correlation information indicating the correlation between the representative Fourier spectrum value acquired in advance and the tension. Calculate the force.

  That is, the frequency component is specified by the Fourier spectrum distribution calculated from the measured acceleration waveform data. Within each identified frequency component, the tension force of the anchor is estimated by using the representative Fourier spectrum value of the frequency band mainly caused by the vibration corresponding to the tension force of the anchor. Here, vibrations having a frequency lower than 100 Hz are mainly caused by electrical noise and intermittent vibrations of peripheral work machines. Therefore, it is preferable not to employ vibrations of 100 Hz or less for estimating the tension. On the other hand, there is no particular standard on the high frequency side. For example, when the center frequency of the frequency band used for estimating the tension is set to 200 Hz, the lower limit is 100 Hz. The upper limit value may be set to 300 Hz. In this case, assuming that vibrations having a frequency between 100 Hz and 300 Hz are mainly caused by vibrations according to the tension of the anchor, the tension measuring device according to the configuration estimates the tension. However, the center frequency may not be limited to 200 Hz, and may be set as appropriate according to the embodiment. In this case, the frequency band used for tension estimation may be, for example, 100 Hz to (100 Hz + center frequency).

  According to the above, the tension force of the existing anchor can be calculated using the acceleration waveform data for the existing anchor. This acceleration waveform data can be easily obtained by using an acceleration sensor or the like. For example, when a bearing plate and a fixing tool are used in the head of the anchor, the bearing plate and the fixing tool are coupled to the anchor head so as to apply tension to the free length of the anchor. Is transmitted to the bearing plate and the fixing tool. Therefore, the vibration of the existing anchor can be measured by attaching the acceleration sensor to the bearing plate. The operation of attaching the acceleration sensor to the bearing plate is very easy because it is only necessary to attach the acceleration sensor to the surface of the bearing plate, and it is not necessary to assemble a scaffold to the position where the anchor is installed. Therefore, according to the said structure, since the tension force of the existing anchor can be calculated based on the easily obtainable acceleration waveform data, the tension force of the existing anchor can be easily measured.

  Further, as another form of the tension measuring device according to the one aspect, the tension measuring device may be configured to perform soundness of the existing anchor from the calculated tension according to a predetermined evaluation standard relating to the health of anchor tension. You may further provide the evaluation part which evaluates property. According to this configuration, along with the measurement of the tension force, the soundness of the tension force of the existing anchor can be automatically evaluated.

  Further, as another form of the tension measuring device according to the above aspect, the evaluation criterion may define an upper limit value and a lower limit value of the tension, and the evaluation unit may calculate the calculated tension. When the value is between the upper limit value and the lower limit value, it is evaluated that the tension force of the existing anchor is healthy, otherwise, the tension force of the existing anchor is not healthy. You may evaluate. According to the said structure, the tension force of the existing anchor can be evaluated absolutely.

  As another form of the tension measuring device according to the above aspect, the acceleration waveform data acquisition unit may acquire the acceleration waveform data for a plurality of the existing anchors, and the spectrum value calculation unit may The representative Fourier spectrum value may be calculated for the plurality of existing anchors, and the tension force calculating unit may calculate the tension force of each of the existing anchors. In the evaluation criteria, an allowable value of a difference in tension between adjacent anchors may be defined, and the evaluation unit may calculate the tension calculated by the target anchor and the anchor adjacent to the target anchor. Calculate the absolute value of the difference from the calculated tension, and if the calculated absolute value of the difference is within the allowable range, evaluate that the tension of the target anchor is healthy, and Otherwise, it may be evaluated that the tension of the subject anchor is not healthy. According to the said structure, the tension | tensile_strength of the adjacent existing anchor can be evaluated relatively.

  As another form of the tension measuring device according to the above aspect, the acceleration waveform data acquisition unit may acquire the acceleration waveform data a plurality of times for the existing anchor of interest, and calculate the spectrum value. The unit may calculate the representative Fourier spectrum value for the existing anchor of the target every time the acceleration waveform data is acquired, and the tension calculating unit calculates the representative Fourier spectrum value each time The tension force of the existing anchor of the object may be calculated. In the evaluation criterion, an allowable value of fluctuation in the tension of the anchor within a predetermined period may be determined, and the evaluation unit may determine the fluctuation of the tension in the predetermined period calculated by the target anchor. The absolute value is calculated, and if the calculated absolute value of the fluctuation is within the range of the allowable value, the tension of the target anchor is evaluated as healthy. It may be evaluated that the tension of the anchor is not healthy. According to the said structure, the secular change of the tension | tensile_strength of the adjacent existing anchor can be evaluated.

  In addition, as another form of the tension measuring device according to each of the above embodiments, an information processing system that realizes each of the above configurations, an information processing method, or a program may be used. However, it may be a storage medium that can be read by a computer, a device, a machine or the like in which such a program is recorded. Here, the computer-readable recording medium is a medium that stores information such as programs by electrical, magnetic, optical, mechanical, or chemical action.

  For example, in the tension measuring method according to one aspect of the present invention, a computer obtains acceleration waveform data indicating vibration of an existing anchor, and Fourier transforms the obtained acceleration waveform data, thereby A step of calculating a Fourier spectrum, a step of calculating an average value of spectrum values in a predetermined frequency range of the calculated Fourier spectrum as a representative Fourier spectrum value, and a correlation between a representative Fourier spectrum acquired in advance and a tension force And calculating a tension force of the existing anchor corresponding to the calculated representative Fourier spectrum value based on the correlation information shown.

  Further, for example, the tension measuring program according to one aspect of the present invention includes a step of acquiring acceleration waveform data indicating vibration of an existing anchor in a computer, and Fourier transforming the acquired acceleration waveform data. A step of calculating a Fourier spectrum of vibration, a step of calculating an average value of spectrum values in a predetermined frequency range of the calculated Fourier spectrum as a representative Fourier spectrum value, and a correlation between the representative Fourier spectrum acquired in advance and a tension force And a step of calculating a tension of the existing anchor corresponding to the calculated representative Fourier spectrum value based on correlation information indicating a relationship.

  ADVANTAGE OF THE INVENTION According to this invention, the apparatus which makes it possible to measure easily the tension | tensile_strength of an anchor can be provided.

FIG. 1 schematically shows an example of a scene to which the present invention is applied. FIG. 2 illustrates an example of a hardware configuration of the tension measuring device according to the embodiment. FIG. 3 illustrates an example of a functional configuration of the tension measuring device according to the embodiment. FIG. 4 illustrates an example of a processing procedure of tension calculation by the tension measuring device according to the embodiment. FIG. 5 illustrates acceleration waveform data according to the embodiment. FIG. 6 illustrates a Fourier spectrum according to the embodiment. FIG. 7A illustrates a Fourier spectrum obtained for an anchor of known tension. FIG. 7B illustrates the Fourier spectrum obtained for an anchor of known tension. FIG. 7C illustrates the Fourier spectrum obtained for an anchor of known tension. FIG. 8 illustrates the correlation information according to the embodiment. FIG. 9 illustrates the history information of tension measurement for the target anchor. FIG. 10 shows an example of a screen display according to the embodiment. FIG. 11 shows an example of a screen display according to the embodiment.

  Hereinafter, an embodiment according to an aspect of the present invention (hereinafter, also referred to as “this embodiment”) will be described with reference to the drawings. However, this embodiment described below is only an illustration of the present invention in all respects. It goes without saying that various improvements and modifications can be made without departing from the scope of the present invention. That is, in implementing the present invention, a specific configuration according to the embodiment may be adopted as appropriate. Although data appearing in the present embodiment is described in a natural language, more specifically, it is specified by a pseudo language, a command, a parameter, a machine language, or the like that can be recognized by a computer.

§1 Application scene First, the scene where the present invention is applied will be described with reference to FIG. FIG. 1 schematically illustrates an application scene of the tension measuring device 1 according to the present embodiment. In the example of FIG. 1, a plurality of anchors 70 are installed on the slope in order to stabilize the ground constituting the slope.

  Each anchor 70 includes an anchor main body that extends from the opening side to the end side of the drilling hole, and is configured to be inserted into the drilling hole and fixed by a fixing material. A male screw is formed at the proximal end of each anchor 70, and a nut 74 (fixing tool) can be fastened after a pressure plate 73 such as a flat square washer is attached. .

  Each anchor 70 is constructed as follows, for example. That is, a drilling hole is formed on the slope with a rock drill or the like, and a fixing material such as mortar is filled in the formed drilling hole. Next, each anchor 70 is inserted into the drilling hole to solidify the fixing material. Thereby, a part of the back side of each anchor 70 becomes a fixing portion 71 fixed on the ground by the fixing material. On the other hand, the portion that is not filled with the fixing material on the hand side (head side) becomes a free length portion 72 that is not fixed to the ground and can be extended according to the deformation of the ground.

  Then, the bearing plate 73 larger than the drilling hole is attached to the head side of each anchor 70, and the nut 74 is fastened until the bearing plate 73 is pressed against the wall around the opening of the drilling hole, thereby tensioning the free length portion 72. Giving power. Accordingly, each anchor 70 is driven into the drilling hole and can support the ground around the drilling hole. The tension measuring apparatus 1 according to the present embodiment is an information processing apparatus for estimating and measuring the tension of such an existing anchor 70.

  Specifically, the tension measuring device 1 according to the present embodiment acquires acceleration waveform data indicating the vibration of the existing anchor 70. The method for acquiring the acceleration waveform data may be appropriately selected according to the embodiment. For example, in this embodiment, the acceleration sensor 21 is attached to the bearing plate 73 of the anchor 70 with an adhesive or the like. A data logger 23 is connected to the acceleration sensor 21 via a general-purpose vibration meter 22. The general-purpose vibration meter 22 is a device that controls the acceleration sensor 21 to measure vibration.

  Since the bearing plate 73 and the nut 74 are coupled to the head side of the anchor 70 so as to apply tension to the free length portion 72, the vibration of the anchor 70 is transmitted to the bearing plate 73 and the nut 74. Therefore, the general-purpose vibration system 22 can measure the vibration of the anchor 70 by the acceleration sensor 21 attached to the bearing plate 73. Then, by storing the vibration data measured by the general-purpose vibrometer 22 along the time series by the data logger 23, it is possible to generate acceleration waveform data indicating the vibration of the anchor 70 along the time series. Thus, the tension measuring apparatus 1 according to the present embodiment acquires acceleration waveform data generated by the acceleration sensor 21, the general-purpose vibration meter 22, and the data logger 23.

  Next, the tension measuring apparatus 1 calculates the Fourier spectrum of the vibration of the existing anchor 70 by performing a Fourier transform on the acquired acceleration waveform data. Moreover, the tension measuring apparatus 1 calculates the average value of the spectrum values in the predetermined frequency range of the calculated Fourier spectrum as the representative Fourier spectrum value. Then, the tension measuring device 1 calculates the tension of the existing anchor 70 corresponding to the calculated representative Fourier spectrum value based on the correlation information indicating the correlation between the representative Fourier spectrum value and the tension acquired in advance. calculate.

  As described above, the vibration of the intermediate frequency excluding the low frequency and the high frequency is mainly caused by the vibration according to the tension of the anchor 70. Therefore, if a frequency range to be averaged (for example, a range of 100 Hz to 300 Hz described later) is appropriately set, the calculated representative Fourier spectrum value corresponds to the tension force of the existing anchor 70. Therefore, the tension of the anchor 70 can be calculated based on the representative Fourier spectrum value.

  Further, the acceleration waveform data used for calculating the representative Fourier spectrum value can be easily obtained by using the acceleration sensor 21, the general-purpose vibration meter 22, and the data logger 23. That is, in order to acquire the acceleration waveform data of each anchor 70, the work of attaching the acceleration sensor 21 to the bearing plate 73 of each anchor 70 is only easy to attach the acceleration sensor 21 to the surface of the bearing plate 73, and is very easy. It is.

  Therefore, the tension measuring apparatus 1 according to the present embodiment calculates the tension of the existing anchor 70 using the acceleration waveform data that can be easily acquired from the existing anchor 70. Therefore, if the tension measuring apparatus 1 according to the present embodiment is used, the tension of the existing anchor 70 can be easily measured.

  In addition, as long as the kind of anchor 70 used as the measuring object of tension | tensile_strength is an anchor provided with tension | tensile_strength, it may be suitably selected according to embodiment. The anchor 70 may be an anchor used for, for example, a VSL method, a KJS method, a SEEE method, or the like. The fixing method of the anchor 70 may be, for example, a wedge fixing method, a nut fixing method, a wedge fixing nut adjustment method, or the like. The type of support mechanism of the anchor 70 may be a tension type, a compression type, a bearing type, or the like. The purpose and application of the anchor 70 may be temporary earth retaining, retaining wall stability, suspension bridge cable reaction force, steel tower foundation, building lifting prevention, dam reinforcement, revetment / quake wall seismic reinforcement, and the like.

§2 Configuration Example Next, an example of a hardware configuration of the tension measuring device 1 will be described with reference to FIG. FIG. 2 schematically illustrates an example of a hardware configuration of the tension measuring device 1 according to the present embodiment. As illustrated in FIG. 2, the tension measuring device 1 according to the present embodiment includes a control unit 11 including a CPU (Central Processing Unit), a RAM (Random Access Memory), a ROM (Read Only Memory), and the like. 11, a storage unit 12 for storing the program 8 or the like executed by the computer 11, a communication interface 13 for performing communication via a network, an input device 14 for inputting a mouse, a keyboard, etc., and a display for displaying an image 15 is a computer in which a speaker 16 for outputting sound, an external interface 17 for connecting to an external device, and a drive 18 for reading a program stored in the storage medium 9 are electrically connected. However, in FIG. 2, the communication interface and the external interface are described as “communication I / F” and “external I / F”, respectively.

  The acceleration sensor 21 is attached so as to measure the vibration of the anchor 70 in the axial direction, for example. In the present embodiment, the acceleration sensor 21 is attached to the pressure bearing plate 73 of the existing anchor 70, thereby measuring the constant fine movement in the axial direction of the anchor 70. Therefore, the type of the acceleration sensor 21 is not limited as long as it can measure the fine movement in the axial direction of the existing anchor 70, and may be appropriately selected according to the embodiment. For example, LS-10C, LS-40C, etc. manufactured by Rion Co., Ltd. can be used for the acceleration sensor 21.

  A general-purpose vibrometer 22 is connected to the acceleration sensor 21. The general-purpose vibration meter 22 controls the acceleration sensor 21 to measure the vibration of the position where the acceleration sensor 21 is attached (in the above example, the bearing plate 73). For example, a VM-83 manufactured by Rion Co., Ltd. can be used for the general-purpose vibrometer 22.

  Furthermore, a data logger 23 is connected to the general-purpose vibration meter 22. The data logger 23 is connected to the tension measuring device 1 via the external interface 17. The data logger 23 stores vibration data (output) measured by the acceleration sensor 21 and the general-purpose vibration system 22 in time series, thereby generating acceleration waveform data indicating the vibration of the anchor 70 in time series. To do. Therefore, as long as measurement data from the acceleration sensor 21 and the general-purpose vibrometer 22 can be stored in time series, the type of the data logger 23 may not be limited and may be appropriately selected according to the embodiment. . For example, DC-204R manufactured by Tokyo Sokki Kenkyujo Co., Ltd. can be used for the data logger 23.

  The program 8 stored in the storage unit 12 is a program for causing the control unit 11 of the tension measuring device 1 to control each component and to execute each process relating to tension calculation of the anchor 70 described later. This program 8 corresponds to the “tension force measurement program” of the present invention. This program 8 may be stored in the storage medium 9.

  The storage medium 9 stores information such as a program by an electrical, magnetic, optical, mechanical, or chemical action so that information such as a program recorded by a computer or other device or machine can be read. It is a medium to do. In FIG. 2, as an example of the storage medium 9, a disk type storage medium such as a CD (Compact Disk) or a DVD (Digital Versatile Disk) is illustrated. However, the type of the storage medium 9 is not limited to the disk type and may be other than the disk type. Examples of the storage medium other than the disk type include a semiconductor memory such as a flash memory.

  It should be noted that regarding the specific hardware configuration of the tension measuring device 1, the components can be omitted, replaced, and added as appropriate according to the embodiment. For example, the control unit 11 may include a plurality of processors. Further, the tension measuring device 1 may be a general-purpose information processing device such as a personal computer in addition to the information processing device designed exclusively for the service to be provided. Furthermore, the tension measuring apparatus 1 may be configured by one or a plurality of information processing apparatuses.

[Function configuration]
Next, an example of a functional configuration of the tension measuring device 1 will be described with reference to FIG. FIG. 3 schematically illustrates an example of a functional configuration of the tension measuring device 1 according to the present embodiment. In the present embodiment, the control unit 11 of the tension measuring device 1 expands the program 8 stored in the storage unit 12 in the RAM. And the control part 11 interprets and executes the program 8 expand | deployed by RAM by CPU, and controls each component. Thereby, the tension measuring apparatus 1 functions as a computer including the acceleration waveform data acquisition unit 111, the spectrum value calculation unit 112, the tension calculation unit 113, the evaluation unit 114, and the image display unit 115.

  The acceleration waveform data acquisition unit 111 acquires acceleration waveform data 31 indicating the vibration of the existing anchor 70. The spectrum value calculation unit 112 calculates the Fourier spectrum 32 of the vibration of the anchor 70 by performing a Fourier transform on the acquired acceleration waveform data 31. Further, the spectrum value calculation unit 112 calculates an average value of spectrum values in a predetermined frequency range of the calculated Fourier spectrum 32 as the representative Fourier spectrum value SV.

  The tension force calculation unit 113 calculates the tension force TF of the existing anchor 70 corresponding to the calculated representative Fourier spectrum value SV based on the correlation information 33 indicating the correlation between the representative Fourier spectrum and the tension force acquired in advance. calculate. The evaluation unit 114 evaluates the soundness of the existing anchor 70 from the calculated tension force TF in accordance with a predetermined evaluation standard regarding the soundness of the tension force of the anchor. Then, the image display unit 115 displays the calculation result of the tension TF and the soundness evaluation result by the evaluation unit 114 on the display 15.

  In the present embodiment, an example in which these functions are realized by a general-purpose CPU has been described. However, some or all of these functions may be realized by one or more dedicated processors. Further, regarding the functional configuration of the tension measuring device 1, the omission, replacement, and addition of functions may be appropriately performed according to the embodiment. For example, when the soundness of the tension of the anchor 70 is not evaluated, the evaluation unit 114 may be omitted. Further, when the calculation result of the tension and the evaluation result of the soundness by the evaluation unit 114 are not displayed on the display 15, the image display unit 115 may be omitted. Each function will be described in detail in an operation example described later.

§3 Example of operation Next, an example of the operation of the tension measuring device 1 will be described with reference to FIG. FIG. 4 illustrates a processing procedure relating to tension force calculation of the existing anchor 70 by the tension force measuring device 1 according to the present embodiment. The processing procedure described below corresponds to the “tension force measuring method” of the present invention. However, the processing procedure relating to tension calculation described below is merely an example, and each processing may be changed as much as possible.

<Step S101>
First, in step S <b> 101, the control unit 11 functions as the acceleration waveform data acquisition unit 111 and acquires acceleration waveform data 31 indicating the vibration of the existing anchor 70. When the acceleration waveform data 31 is acquired, the control unit 11 advances the processing to the next step S102.

  As illustrated in FIG. 1, in the present embodiment, the acceleration sensor 21 is attached to the bearing plate 73 of the anchor 70 to be measured for tension, and the vibration of the anchor 70 is measured by the acceleration sensor 21. ing. The data logger 23 is connected to the acceleration sensor 21 via the general-purpose vibration meter 22 and stores the measurement result (output) of the acceleration sensor 21 in time series.

  As a result, as illustrated in FIG. 5, the data logger 23 accumulates the measurement results of the acceleration sensor 21 via the general-purpose vibration meter 22 in time series. FIG. 5 shows an example of data (acceleration waveform data 31) accumulated in the data logger 23. The control unit 11 accesses the data logger 23 via the external interface 17 and acquires data indicating the measurement result along the time series of the acceleration sensor 21 accumulated in the data logger 23 as the acceleration waveform data 31.

  When there are a plurality of anchors 70 and the tension force of all the anchors 70 is specified, the control unit 11 acquires the acceleration waveform data 31 for all the anchors 70, and the acceleration waveform data 31 for each anchor 70. The processing after step S102 described later may be applied. In this case, in order to generate acceleration waveform data for all anchors, the acceleration sensors 21 may be attached to all the anchors 70, or one or a plurality of acceleration sensors 21 may be attached to each anchor 70 sequentially. Good. Further, one data logger 23 may be connected to one acceleration sensor 21 via a general-purpose vibration meter 22 or may be connected to a plurality of acceleration sensors 21 via a plurality of general-purpose vibration meters 22. Furthermore, the measurement result (acceleration waveform data 31) of the acceleration sensor 21 collected by the data logger 23 may be stored in another storage device. However, the number of pieces of the acceleration waveform data 31 acquired in step S101 is not limited to such an example, and may be appropriately selected according to the embodiment.

<Step S102>
Returning to FIG. 4, in the next step S <b> 102, the control unit 11 functions as the spectrum value calculation unit 112, and Fourier transforms the acceleration waveform data 31 acquired in step S <b> 101, whereby the anchor 70 illustrated in FIG. 6 is illustrated. A Fourier spectrum 32 of vibration is calculated. After calculating the Fourier spectrum 32, the control unit 11 advances the processing to the next step S103.

  FIG. 6 shows an example of a Fourier spectrum 32 calculated by Fourier transforming the acceleration waveform data 31 exemplified in FIG. The calculation method of the Fourier transform may be appropriately selected according to the embodiment. For example, in this step S102, Fast Fourier Transform (FFT) may be used.

<Step S103>
Returning to FIG. 4, in the next step S103, the control unit 11 functions as the spectrum value calculation unit 112, and calculates the average value of the spectrum values in the predetermined frequency range of the Fourier spectrum 32 calculated in step S102 as the representative Fourier spectrum value SV. Calculate as After calculating the representative Fourier spectrum value SV, the control unit 11 advances the processing to the next step S104.

  As described above, the measured frequency component of the vibration of the anchor 70 is specified by the Fourier spectrum distribution calculated by the Fourier transform in step S102. In the present embodiment, the tension force of the anchor 70 is estimated by using the representative Fourier spectrum value SV of the frequency band in which the vibration corresponding to the tension force of the anchor 70 is the main cause within each identified frequency component. To do. The predetermined frequency range for obtaining the representative Fourier spectrum value SV may be appropriately set according to the embodiment. However, vibrations with a frequency lower than 100 Hz are mainly caused by electrical noise and intermittent vibrations of peripheral work machines. Therefore, it is preferable not to employ vibrations of 100 Hz or less for estimating the tension. On the other hand, there is no particular standard on the high frequency side, but for example, when the center frequency of a predetermined frequency range used for tension estimation is set to 200 Hz, the lower limit is 100 Hz. Then, the upper limit value may be set to 300 Hz. In this case, assuming that the vibration of the frequency between 100 Hz and 300 Hz is mainly caused by the vibration according to the tension of the anchor, in this step S103, the control unit 11 calculates the average value of the spectrum values of 100 Hz to 300 Hz. It calculates as a representative Fourier spectrum value SV. The center frequency is not limited to 200 Hz, and may be set as appropriate according to the embodiment. In this case, the predetermined frequency range may be set to, for example, 100 Hz to (100 Hz + center frequency).

<Step S104>
In the next step S104, the control unit 11 functions as the tension calculation unit 113, and the representative calculated in step S103 based on the correlation information 33 indicating the correlation between the representative Fourier spectrum and the tension acquired in advance. The tension force TF of the existing anchor 70 corresponding to the Fourier spectrum value SV is calculated. After calculating the tension force TF, the control unit 11 advances the processing to the next step S105.

  The correlation information 33 indicating the correlation between the representative Fourier spectrum and the tension can be generated, for example, as follows. That is, for the anchor of the same type as the anchor 70 that specifies the tension force in the tension measurement device 1 according to the present embodiment and the tension force is known, by performing the processing from the above steps S101 to S103, A plurality of sets of representative Fourier spectrum values are collected. The tension of the anchor may be measured by a known method such as a lift-off test or a method using a load meter.

  Then, by performing curve fitting on a plurality of sets of tension and representative Fourier spectrum values, a correlation equation between tension and representative Fourier spectrum values can be obtained. This correlation formula can be used as the correlation information 33. For generation of the correlation information 33, an anchor after placement may be used, or an anchor before placement may be used.

(Example of correlation information)
As an example of the correlation information 33, correlation information was generated for anchors under the following conditions. However, the correlation information 33 is not limited to the following examples, and may be appropriately generated according to the embodiment.

The anchor conditions used for generating the correlation information are as follows.
・ Anchor material: Nut anchor type anchor with total length 19.8m (fixing length 7.5m, free length 12.05m, extra length 0.25m) ・ Design anchor force: 605kN
・ Acceleration sensor: LS-10C (Rion Co., Ltd.)
・ General-purpose vibration meter: VM-83 (manufactured by Lion Co., Ltd.)
Data logger: DC-204R (manufactured by Tokyo Sokki Kenkyujo Co., Ltd.)

  The data shown in FIGS. 7A to 7C are loaded and unloaded in stages with a maximum tension of 756 kN (1.25 times the design anchor force) and an initial tension of 76 kN (about 10% of the maximum tension). It was obtained in a confirmation test (a test for confirming that the constructed anchor is safe against the design anchor force). FIG. 7A shows a Fourier spectrum calculated by applying the processing of steps S101 to S102 to the acceleration waveform data obtained at the maximum tension 756 kN. FIG. 7B shows a Fourier spectrum calculated by applying the processing of steps S101 to S102 to the acceleration waveform data obtained at 363 kN. FIG. 7C shows a Fourier spectrum calculated by applying the processing of steps S101 to S102 to the acceleration waveform data obtained at the initial tension of 76 kN. The anchor was tensioned by a center hole jack, and the load on the anchor was controlled by a Bourdon tube pressure gauge attached to the hydraulic pump. As shown in FIGS. 7A to 7C, the spectrum value from 100 Hz to 300 Hz varied greatly depending on the magnitude of the tension of the anchor. In other words, in this type of anchor, it was found that the vibration of 100 Hz to 300 Hz was mainly caused by the vibration according to the tension of the anchor.

  Therefore, for each Fourier spectrum shown in FIGS. 7A to 7C, the average value of the spectrum values of 100 Hz to 300 Hz was calculated as the representative Fourier spectrum value by the process of step S103. The representative Fourier spectrum value of an anchor having a tension of 756 kN is 40.6 (mgal · sec), the representative Fourier spectrum value of an anchor having a tension of 363 kN is 28.4 (mgal · sec), The representative Fourier spectrum value of the anchor having a tension of 76 kN was 16.1 (mgal · sec). Curve fitting was performed by logarithmic approximation on the three sets of tension and representative Fourier spectrum values calculated in this way. Then, the correlation formula shown in the following formula 1 was obtained.

x represents tension (kN), and y represents a representative Fourier spectrum value (mgal · sec). If this correlation equation is the correlation information 33 and the representative Fourier spectrum value SV is calculated to be 34.5 (mgal · sec) in step S103, the tension TF is 500 (kN) in this step S104. ) Is calculated. Note that R ² is a determination coefficient and is an index indicating the accuracy of the correlation equation obtained by curve fitting. Therefore, the value of R ² may be used as an index for determining whether or not the generated correlation equation is adopted as the correlation information 33 in step S104. That is, if the value of R ² is less than or equal to the predetermined value, the correlation formula is discarded, and a new set of tension and representative Fourier spectrum values is added, and the correlation formula is generated again. May be.

<Step S105>
Returning to FIG. 4, in the next step S <b> 105, the control unit 11 functions as the evaluation unit 114, and the existing anchor 70 is calculated from the tension TF calculated in step S <b> 104 in accordance with a predetermined evaluation criterion regarding the soundness of the tension of the anchor. Assess the health of When the evaluation of the soundness of the existing anchor 70 is completed, the control unit 11 advances the processing to the next step S106.

  The evaluation criteria for evaluating the soundness of the tension force TF of the existing anchor 70 may be appropriately set according to the embodiment. For example, the following three evaluation criteria can be used.

(1) Absolute evaluation As the first evaluation criterion, in order to absolutely evaluate the soundness of the tension force TF of each anchor 70, in the evaluation criterion used in this step S105, the upper limit value and the lower limit value of the tension force are It may be determined. The upper limit value is an index for determining overstrain, and may be, for example, a design anchor force (for example, 605 kN). On the other hand, the lower limit value is an index for determining whether the tension is insufficient. For example, the fixing tension acting on the anchor tendon at the end of the anchor tension and fixing is 605 kN (= design anchor force). If so, it may be 490 kN corresponding to 80% thereof. In the case where a tension force smaller than 605 kN is recognized as a tension force at the time of fixing, the lower limit value may be 80% of the load. However, the upper limit value and the lower limit value are not limited to such examples, and may be set as appropriate according to the embodiment.

  In this case, in step S105, the control unit 11 evaluates that the tension of the existing anchor 70 is healthy when the value of the tension TF calculated in step S104 is between the upper limit value and the lower limit value. To do. On the other hand, when that is not right, the control part 11 evaluates that the tension | tensile_strength of the existing anchor 70 is not healthy. Specifically, when the value of the tension TF calculated in step S104 exceeds the upper limit value, the control unit 11 evaluates that the existing anchor 70 is in an over tension. On the other hand, when the value of the tension TF calculated in step S104 is less than the lower limit value, the controller 11 evaluates that the existing anchor 70 is insufficient in tension. That is, in addition to evaluating the soundness of the tension force of the existing anchor 70, the control unit 11 determines that the tension force of the existing anchor 70 is not healthy. It can be determined which of the shortages has occurred.

(2) Relative evaluation As the second evaluation criterion, in order to relatively evaluate the soundness of the tension TF of each anchor 70, the evaluation criterion used in this step S105 is the difference in tension between adjacent anchors. May be determined. The allowable value is an index of a difference in tension force allowed between adjacent anchors, and may be set to 20 kN, for example. However, the allowable value is not limited to 20 kN, and may be set as appropriate according to the embodiment. Further, the allowable value may be changed as appropriate.

  In this case, in step S <b> 101, the control unit 11 acquires acceleration waveform data 31 for a plurality of existing anchors 70. In step S102 and step S103, the control unit 11 calculates a representative Fourier spectrum value SV for a plurality of existing anchors 70. In step S <b> 104, the control unit 11 calculates the tension force TF of each existing anchor 70.

  In step S105, the control unit 11 calculates the absolute value of the difference between the tension TF calculated for the target anchor 70 and the tension TF calculated for the anchor 70 adjacent to the target anchor 70. Compare the absolute value of the difference and the tolerance. The adjacent anchor 70 only needs to be adjacent to the target anchor 70 in any of the vertical and horizontal directions.

  As a result of the comparison, when the calculated absolute value of the difference is within the allowable value range (that is, the calculated absolute value of the difference is less than or less than the allowable value), the control unit 11 determines the tension of the target anchor 70. Evaluates to be healthy. On the other hand, if not, the control unit 11 evaluates that the tension of the target anchor 70 is not healthy. In this case, when the tension force TF of the target anchor 70 is larger than the tension force TF of the adjacent anchor 70, the control unit 11 can evaluate that the target anchor 70 is in an over tension. On the other hand, when the tension force TF of the target anchor 70 is smaller than the tension force TF of the adjacent anchor 70, the control unit 11 can evaluate that the target anchor 70 is insufficient in tension.

(3) Evaluation over time As a third evaluation criterion, in order to evaluate the soundness of the tension TF of each anchor 70 over time, the evaluation criterion used in this step S105 is that the tension of the anchor within a predetermined period. An allowable value of fluctuation may be determined. The allowable value is an index of the fluctuation value of the tension force allowed within a predetermined period, and may be set to 20 kN, for example. However, the allowable value is not limited to 20 kN, and may be set as appropriate according to the embodiment. Further, the allowable value may be changed as appropriate.

  In this case, steps S <b> 101 to S <b> 104 are executed a plurality of times for the target existing anchor 70 before executing step S <b> 105. That is, the step S101 is executed a plurality of times, and the control unit 11 acquires the acceleration waveform data 31 a plurality of times for the target existing anchor 70. Steps S102 and S103 are executed a plurality of times, and the control unit 11 calculates a representative Fourier spectrum value SV for the existing anchor 70 of interest every time the acceleration waveform data 31 is acquired. Step S104 is executed a plurality of times, and the control unit 11 calculates the tension TF for the existing anchor 70 as a target every time the acceleration waveform data 31 is acquired.

  At this time, as illustrated in FIG. 9, the control unit 11 may store the history of the tension TF calculated within a predetermined period in the storage unit 12 or the like. FIG. 9 illustrates the history information 34 of the tension force TF of the anchor 70. As illustrated in FIG. 9, the tension of the anchor 70 may change over time.

  Therefore, in step S105, the control unit 11 calculates the absolute value of the fluctuation of the tension force TF calculated for the target anchor 70 within a predetermined period, and compares the calculated absolute value of the fluctuation with an allowable value. The predetermined period may be, for example, one year. Since the present invention can be easily measured as compared with the lift-off test, the anchor at the boundary between healthy and unhealthy can be shortened or continuously measured and evaluated.

  Then, as a result of the comparison, if the absolute value of the calculated variation is within the allowable value range (that is, the absolute value of the calculated difference is less than or less than the allowable value), the control unit 11 determines that the target anchor 70 Assess tension is healthy. On the other hand, if not, the control unit 11 evaluates that the tension of the target anchor 70 is not healthy. In this case, when the tension force TF of the target anchor 70 increases from the past tension force TF, the control unit 11 can evaluate that the target anchor 70 is overstrained. On the other hand, for example, when the control unit 11 changes from the time point A to the time point B in FIG. 9, that is, when the tension force TF of the target anchor 70 decreases from the past tension force TF, the target anchor 70 is It can be evaluated that there is a lack of tension.

(4) Other In addition, there is a case where the representative Fourier spectrum value SV calculated in step S103 is an abnormal value in which the tension TF cannot be calculated from the correlation equation indicated by the correlation information 33 used in step S104. For example, in the case of an anchor of a type that uses a plurality of anchor tension materials such as PC steel wires and PC steel wires, when some anchor tension materials are cut and the remaining anchor tension materials are fixed, this anchor Such a case may occur. Even when this case occurs, the control unit 11 may evaluate that the tension of the existing anchor 70 is not healthy.

<Step S106>
Returning to FIG. 4, in the next step S106, the control unit 11 functions as the image display unit 115, and displays the calculation result of the tension TF in step S104 and the evaluation result of the soundness in step S105 on the display 15. . When the process of step 106 is completed, the control unit 11 ends the process related to this operation.

  The content displayed on the display 15 may be appropriately selected according to the embodiment. For example, screen display as shown in FIGS. 10 and 11 may be performed. 10 and 11 show an example of a screen displayed on the display 15 by this step S106.

  As illustrated in FIG. 10, the control unit 11 may perform a screen display on the display 15 in which the mark 151 of the anchor 70 is mapped according to the arrangement of the anchor 70 that is actually placed. And the control part 11 may distinguish and display the anchor 70 evaluated that tension force is healthy, and the anchor 70 evaluated that it is not healthy.

  For example, in the screen of FIG. 10, the anchor 70 evaluated to have a healthy tension is indicated by a dotted line 151, and the anchor 70 evaluated to have a poor tension is indicated by a solid line 151. Has been. In addition, the method of distinguishing and displaying the healthy anchor 70 and the unhealthy anchor 70 may not be limited to such an example, and may be appropriately selected according to the embodiment. For example, the control unit 11 may display the soundness of each anchor 70 in different colors. At this time, the control unit 11 displays the mark 151 of the anchor 70 with high tension (for example, over tension) in red, and the anchor 70 with low tension (for example, insufficient tension). The mark 151 may be displayed in blue.

  Here, the over-tension is a state in which the portion on the near side of the ground is pushed out and the tension of the anchor 70 is increased. In this case, since the anchor 70 may be damaged, it is better to loosen the nut 74 so as to reduce the tension of the anchor 70. Therefore, the control part 11 may perform the screen display which instruct | indicates to loosen the nut 74, and / or the audio | voice output using the speaker 16 about the anchor 70 which overstrain has arisen.

  Further, the lack of tension force is a state where the tension force of the anchor 70 is insufficient due to deterioration of the anchor 70 or the adhesion between the fixing material and the ground around the fixing portion 71 being cut off. In this case, since the ground around the hole cannot be sufficiently supported by the anchor 70, the protective cap on the head is removed, the fixing tool is inspected, and the soundness of the anchor 70 is investigated. If it is determined that the anchor 70 is healthy, the nut 74 may be tightened so as to increase the tension of the anchor 70. On the other hand, when it is determined that the anchor 70 is not healthy, emergency measures such as evacuation may be taken for the purpose of preventing damage to a third party. In this case, an additional anchor that compensates for the insufficient tension around the anchor 70 may be installed. Therefore, the control unit 11 checks the fixing tool as described above for the anchor 70 in which the tension is insufficient, tightens the nut 74, and measures the tension by other means. You may perform the screen display which instruct | indicates installation, etc. and / or the audio | voice output using the speaker 16. FIG. In addition, in the initial stage when the tension force is introduced to the anchor 70, the force acting on the head side is transmitted to the back side after the construction, and the overall tension force may be reduced. Even in such a case, lack of tension may occur.

  Further, as illustrated in FIG. 11, the control unit 11 appropriately displays a contour line 152 on the screen on which the mark 151 of the anchor 70 is mapped in order to indicate the group of the anchor 70 having the same tension. Good. The arrangement of the contour lines 152 can be determined as appropriate. For example, the control unit 11 may determine the arrangement of the contour lines 152 by specifying a group of anchors 70 in which the calculated difference in tension TF is equal to or less than a predetermined value.

  In addition, for example, the control unit 11 may display the tension TF calculated in step S104 on the mark 151. For example, when the history information 34 of the tension force TF of each anchor 70 is stored, when the mark 151 of each anchor 70 is selected via the input device 14 or the like, the control unit 11 The history information 34 illustrated in FIG. 9 may be displayed on the display 15.

  Further, for example, the control unit 11 may simultaneously display a plurality of Fourier spectra 32 calculated in step S102 on the display 15. As a result, the Fourier spectrum 32 of the target anchor 70 and the Fourier spectrum 32 of the other anchor 70 are compared, and a situation in which an abnormal value of the representative Fourier spectrum value SV occurs in the target anchor 70 occurs. I can confirm that.

<Others>
Note that, with respect to the above processing procedure, steps can be omitted, replaced, and added as appropriate according to the embodiment. For example, when the soundness of the tension of the anchor 70 is not evaluated, the process of step S105 may be omitted. Moreover, when not displaying the calculation result of the tension in step S104 and the evaluation result of the soundness in step S105 on the display 15, the process of step S106 may be omitted.

[Action / Effect]
As described above, according to the tension measuring device 1 according to the present embodiment, by applying the acceleration waveform data 31 obtained by the acceleration sensor 21 that is easy to install to the processing of the above steps S101 to S104, The tension force TF of the anchor 70 can be specified. Therefore, if the tension measuring apparatus 1 according to the present embodiment is used, the tension of the existing anchor 70 can be easily measured.

  Thereby, the frequency which measures the tension | tensile_strength of the object anchor can be increased. For example, when the acceleration sensor 21 is attached to all anchors that have been placed, the tension of each anchor can be constantly measured. Therefore, according to the tension measuring apparatus 1 according to the present embodiment, the tension of the target anchor can be continuously (always) monitored.

  Moreover, according to said step S105, the soundness of the tension | tensile_strength of each anchor 70 can be automatically evaluated with the measurement of the tension | tensile_strength TF of each anchor 70. FIG. As a result, if the target anchor falls into overtension or lack of tension, this can be quickly identified, and the administrator can be informed to resolve the overstress or lack of tension in the target anchor. .

§4 Modifications Embodiments of the present invention have been described in detail above, but the above description is merely an illustration of the present invention in all respects. It goes without saying that various improvements and modifications can be made without departing from the scope of the present invention.

  For example, in the above embodiment, the acceleration sensor 21 is attached to the pressure bearing plate 73. However, the installation location of the acceleration sensor 21 is not limited to such an example, and may be appropriately selected according to the embodiment as long as the vibration of the anchor 70 can be measured. For example, the acceleration sensor 21 may be installed on a pressure receiving plate that directly receives the tension of the anchor, an abdominal material used for temporary earth retaining, or the like. However, it is very easy to attach the acceleration sensor 21 to the surface of the bearing plate 73. Therefore, it is preferable that the acceleration sensor 21 is attached to the bearing plate 73 from the viewpoint of workability.

  Further, for example, in the above embodiment, acceleration waveform data of each anchor 70 is generated using the acceleration sensor 21 and the data logger 23. However, devices other than the acceleration sensor 21, the general-purpose vibration meter 22, and the data logger 23 may be used as long as acceleration waveform data indicating the vibration (acceleration) of each anchor 70 in time series can be generated.

1 ... tension measuring device, 8 ... program, 9 ... storage medium,
11 ... Control unit, 12 ... Storage unit, 13 ... Communication interface,
14 ... Input device, 15 ... Display, 16 ... Speaker,
17 ... External interface, 18 ... Drive,
21 ... Acceleration sensor, 22 ... General-purpose vibration meter, 23 ... Data logger 111 ... Acceleration waveform data acquisition unit, 112 ... Spectral value calculation unit,
113 ... tension calculation part, 114 ... evaluation part, 115 ... image display part,
31 ... Acceleration waveform data, 32 ... Fourier spectrum,
33 ... correlation information, 34 ... history information,
SV: representative Fourier spectrum value, TF: tension,
70 ... Anchor, 71 ... Fixing part, 72 ... Free length part,
73 ... Supporting plate, 74 ... Nut (fixing tool)

Claims (7)

An acceleration waveform data acquisition unit for acquiring acceleration waveform data indicating vibration of an existing anchor;
A spectrum value calculation unit that calculates a Fourier spectrum of the vibration by Fourier transforming the acquired acceleration waveform data, and calculates an average value of spectrum values in a predetermined frequency range of the calculated Fourier spectrum as a representative Fourier spectrum value When,
Based on the correlation information indicating the correlation between the representative Fourier spectrum and the tension acquired in advance, the tension calculating unit that calculates the tension of the existing anchor corresponding to the calculated representative Fourier spectrum value;
Comprising
Tension measuring device. According to a predetermined evaluation standard regarding the soundness of the tension of the anchor, further comprising an evaluation unit that evaluates the soundness of the existing anchor from the calculated tension.
The tension measuring device according to claim 1. In the evaluation criteria, an upper limit value and a lower limit value of the tension are defined,
The evaluation unit evaluates that the tension force of the existing anchor is healthy when the calculated tension value is between the upper limit value and the lower limit value, and otherwise, Assess the tension of existing anchors is not healthy,
The tension measuring device according to claim 2. The acceleration waveform data acquisition unit acquires the acceleration waveform data for a plurality of the existing anchors,
The spectrum value calculation unit calculates the representative Fourier spectrum value for the plurality of existing anchors,
The tension calculating unit calculates the tension of each of the existing anchors,
In the evaluation criteria, an allowable value of the difference in tension between adjacent anchors is defined,
The evaluation unit calculates an absolute value of a difference between a tension force calculated by the target anchor and a tension force calculated by an anchor adjacent to the target anchor, and the absolute value of the calculated difference is within a range of the allowable value. If it is within, evaluate the subject's anchor tension is healthy; otherwise, evaluate the subject's anchor tension is not healthy.
The tension measuring device according to claim 2 or 3. The acceleration waveform data acquisition unit acquires the acceleration waveform data multiple times for the existing anchor of interest,
The spectrum value calculation unit calculates the representative Fourier spectrum value for the existing anchor of the target every time the acceleration waveform data is acquired,
The tension calculating unit calculates the tension of the existing anchor of the target every time the representative Fourier spectrum value is calculated,
In the evaluation criteria, an allowable value of fluctuation of the tension of the anchor within a predetermined period is defined,
The evaluation unit calculates an absolute value of fluctuation within a predetermined period of the calculated tension of the target anchor, and when the calculated absolute value of the fluctuation is within the allowable value range, Assess the anchor's tension is healthy, otherwise, evaluate the anchor's tension as unhealthy,
The tension measuring device according to any one of claims 2 to 4. Computer
Obtaining acceleration waveform data indicating vibration of an existing anchor;
Calculating a Fourier spectrum of the vibration by Fourier transforming the acquired acceleration waveform data;
Calculating an average value of spectrum values in a predetermined frequency range of the calculated Fourier spectrum as a representative Fourier spectrum value;
Calculating the tension of the existing anchor corresponding to the calculated representative Fourier spectrum value based on correlation information indicating a correlation between the representative Fourier spectrum and the tension acquired in advance;
The tension measurement method to perform. On the computer,
Obtaining acceleration waveform data indicating vibration of an existing anchor;
Calculating a Fourier spectrum of the vibration by Fourier transforming the acquired acceleration waveform data;
Calculating an average value of spectrum values in a predetermined frequency range of the calculated Fourier spectrum as a representative Fourier spectrum value;
Calculating the tension of the existing anchor corresponding to the calculated representative Fourier spectrum value based on correlation information indicating a correlation between the representative Fourier spectrum and the tension acquired in advance;
Tension measurement program to execute.