Axial force estimation device, axial force estimation method, and program

Abstract

To provide an axial force estimation device, an axial force estimation method, and a program for simply and accurately measuring an axial force present in a member of a large-scale structure.SOLUTION: An axial force estimation device 1 includes: a measurement unit that measures acceleration, velocity, displacement, or strain generated in a member of a large-scale structure due to input of environmental vibration, vibration generated by a natural phenomenon, or vibration generated by a vibration exciter installed in advance; and an estimation unit that estimates an axial force generated in the member according to a vibration mode ratio on the basis of measurement data from the measurement unit.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to an axial force estimation device, an axial force estimation method, and a program, and in particular to a technique for easily and highly accurately measuring the axial force inherent in members of large-scale structures such as steel towers and bridges. [Background technology]

[0002] In the maintenance and management of large-scale structures, it is important to be able to detect any abnormalities that occur easily and with high accuracy.

[0003] For example, during inspections of steel towers, deformation or other abnormalities may be found in the main pillars. The main causes of such abnormalities are various, including landslides on mountain slopes and subsidence or liquefaction of soft ground. If the ground subsides unevenly due to such factors, eccentricity (variation in the load on multiple pillars) occurs, reducing the load-bearing capacity of the entire steel tower. If the load-bearing capacity of a steel tower decreases, for example, in the event of a disaster such as an earthquake, there is a risk of an accident such as collapse, even if the external forces acting on the steel tower are within the design tolerance.

[0004] Therefore, in the maintenance and management of large-scale structures, it is necessary to accurately measure the degree of deformation that has occurred in components, conduct analytical evaluations, and then take measures such as repairing components, installing reinforcing materials, replacing components, or rebuilding the structure.

[0005] However, it is difficult to directly observe the axial force and deformation inherent in the components of large-scale structures. The current common method for measuring axial force is to remove important structural components suspected of generating large stress from the structure, install sensors in the stress-released state, and then return the components to the structure to measure the stress state. This method requires a very large-scale operation and is expensive, making it difficult to apply to large-scale surveys.

[0006] Therefore, there is a demand for a technology that can easily and accurately determine the axial forces inherent in the components of large-scale structures using analytical methods.

[0007] As related techniques, Patent Documents 1 to 5 disclose a method of estimating axial force by applying vibration to a target component (mainly a bolt) and inputting the response obtained from a single sensor installed on the target component into an estimation formula.

[0008] Furthermore, Patent Document 6 and Non-Patent Document 1 disclose a method for estimating axial force by applying vibration to a columnar target member and inputting responses obtained from multiple sensors installed on the target member into an estimation formula. [Prior art documents] [Patent documents]

[0009] [Patent Document 1] Patent Publication No. 2021-175957 [Patent Document 2] Japanese Patent Publication No. 2020-148504 [Patent Document 3] Japanese Patent Application Publication No. 2019-128193 [Patent Document 4] Japanese Patent Application Laid-Open No. 2002-340710 [Patent Document 5] Japanese Patent Application Laid-Open No. 2002-168708 [Patent Document 6] CN-B-102252792 [Patent Document 7] Japanese Patent Publication No. 2020-201146 [Patent Document 8] Patent application 2022-086465 [Non-patent literature]

[0010] [Non-Patent Document 1] Vibration-based estimation of axial force for a beam member with uncertain boundary conditions, Suzhen Li et al., Journal of Sound and Vibration 332 (2013) 795-806, November 8, 2012 [Non-patent document 2] Data Assimilation for Elastic-Plastic Finite Element Analysis Using Ensemble Kalman Filter, Satoshi Nakano and two others, Proceedings of the 31st Annual Conference on Computational Mechanics (CMD2018), No. 18-8, Japan Society of Mechanical Engineers, November 23, 2018 [Non-patent document 3] Vibration-based improvement identification of axial force for bar members, YUAN Yong-qiang and 2 others, Journal of Dalian University of Technology, Vol.55 No.5, September 2015 Summary of the Invention [Problem to be solved by the invention]

[0011] In particular, the prior art described in Patent Document 6 and Non-Patent Document 1 can serve as a theoretical basis for measuring the axial force inherent in columnar members of large-scale structures. However, these documents do not disclose the specific technical innovations required to apply this theory to large-scale structures.

[0012] The present invention has been made to solve these problems, and aims to provide an axial force estimation device, an axial force estimation method, and a program that can measure the axial force inherent in components of large-scale structures easily and with high accuracy. [Means for solving the problem]

[0013] According to one embodiment, the axial force estimation device includes a measurement unit that measures acceleration, velocity, displacement, or strain that occurs when environmental vibrations, vibrations due to natural phenomena, or vibrations caused by a pre-installed vibrator are input to a member of a large-scale structure, and an estimation unit that estimates the axial force that occurs in the member depending on the vibration mode ratio based on the measurement data of the measurement unit. According to one embodiment, the measurement unit is a plurality of sensors installed on the member. According to one embodiment, the measurement unit is an image measurement device that performs the measurement by a digital image correlation method at a position remote from the member. According to one embodiment, the measurement unit performs the measurement by a digital image correlation method using compressed sensing. According to one embodiment, the axial force estimation method includes a measurement step of measuring acceleration, velocity, displacement, or strain caused by input of environmental vibration, vibration due to natural phenomenon, or vibration caused by a pre-installed vibrator to a member of a large-scale structure, and an estimation step of estimating the axial force caused in the member according to a vibration mode ratio based on measurement data measured in the measurement step. According to one embodiment, a program causes a computer to carry out the above method. [Effects of the Invention]

[0014] The present invention can provide an axial force estimation device, an axial force estimation method, and a program for easily and accurately measuring the axial force inherent in members of a large-scale structure. [Brief explanation of the drawings]

[0015] [Figure 1] 1 is a block diagram showing a configuration of an axial force estimation device 1 according to a first embodiment. [Figure 2] FIG. 10 is a block diagram showing a configuration of an axial force estimation device 1 according to a second embodiment. [Figure 3] FIG. 10 is a diagram illustrating an axial force estimation method. DETAILED DESCRIPTION OF THE INVENTION

[0016] <Embodiment 1: Implementation example using an accelerometer> FIG. 1 is a block diagram showing a configuration of an axial force estimation device 1 according to a first embodiment of the present invention.

[0017] The axial force estimation device 1 includes a measurement unit 11 and an estimation unit 13.

[0018] The measurement unit 11 includes a plurality of sensors 12 that measure and output acceleration, velocity, displacement, or strain occurring in the measurement object. The plurality of sensors 12 are installed at arbitrary positions on the surface of the columnar member (hereinafter simply referred to as member) that is the measurement object. In this case, there is no need to remove the member from the structure, and of course there is no need to reattach it to the structure. The sensors 12 are connected to the estimation unit 13 so that they can communicate with each other, and the measurement data from the sensors 12 is sent to the estimation unit 13.

[0019] In the past, it was common for a person to strike the test object with a hammer or other device and measure the resulting vibrations with a sensor for each test. In contrast, in this embodiment, environmental vibrations (such as those occurring in daily life, such as traffic vibrations caused by automobiles or trains, mechanical vibrations caused by large machinery operating in factories, and floor vibrations inside buildings), natural vibrations (such as those caused by wind, water currents, tides, and earthquakes), or vibrations from a pre-installed vibrator (such as acoustic vibrations from a speaker that generates sound while in contact with or facing the test object, or vibrations caused by inertial vibrations) are input to the test object. These vibrations are characterized by the fact that they do not require special work each time they are applied and are continuous. Sensor 12 measures the acceleration, velocity, displacement, or strain that occurs when these vibrations are input to the test object and outputs the resulting measurement data. This method allows sensor 12 to acquire measurement data at any time, for example, at a specific time period on a specific day. Furthermore, by utilizing vibrations that continue for a certain period of time or longer, it is possible to obtain measurement data that is suitable for image measurement.

[0020] The estimation unit 13 is an information processing device that performs the axial force estimation process for a member, and typically includes a processor, a memory, an input device, and an output device. The processor reads out programs and data stored in the memory and executes predetermined processes, thereby logically realizing the processing unit described below. The input device is a device for inputting data and instructions required for processing, and typically includes a character input device such as a keyboard, an instruction device such as a mouse, and a communication device for receiving information from an external storage device or a communication line. The measurement data output by the sensor 12 is also input to the input device via a communication line and then passed to the processor. The output device is a device for outputting processing results and various notifications, and typically includes a display device such as a monitor, and a communication device for transmitting information to an external storage device or a communication line.

[0021] The estimation unit 13 includes the following processing units: a measurement data receiving unit 131 that receives measurement data from the sensor 12, an estimation processing unit 133 that estimates the axial force of the member based on the measurement data, and an output unit 135 that outputs the estimation result.

[0022] The measurement data receiving unit 131 receives measurement data from each of the plurality of sensors 12 .

[0023] The estimation processing unit 133 estimates the axial force based on the vibration mode ratio. The vibration mode ratio refers to the mode ratio of acceleration, velocity, displacement, or strain. The formula for calculating the vibration mode ratio differs depending on whether the measurement results of acceleration, velocity, or displacement are used or whether the measurement results of strain are used; in the former case, Equation 1 is used, and in the latter case, Equation 2 is used. Below, an overview of this method will be explained using an example of the method using Equations 1 and 2. Assume that five sensors are installed along the longitudinal direction of a columnar member with length L (Fig. 3).

[0024] (1) When the sensor 12 measures acceleration, velocity, or displacement From the measured data of acceleration, velocity, or displacement, the mode value φ (acceleration, velocity, or displacement) corresponding to the frequency ω and ω at five points along the columnar member, which corresponds to a specific order mode, is extracted. In this case, the vibration mode ratio at any two points i and j can be calculated using Equation 1.

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[0025] (2) When the sensor 12 measures strain From the strain measurement data, the mode value δ (strain) corresponding to the frequency ω and ω at five points along the columnar member corresponding to a specific order mode is extracted. In this case, the vibration mode ratio at any two points i and j can be calculated using Equation 2.

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[0026] The factor q2 in the equation is inversely proportional to the factor q1, which is related to the measured angular frequency, and the axial force N is a function of q1 and q2. At least one non-zero solution must exist for [C1, C2, C3, C4] in the equation, so the determinant of the matrix composed of these coefficients must be equal to zero. If the determinant contains only the unknown N and the value is zero, the value of N can be found using a numerical analysis method.

[0027] As mentioned above, for long and slender members, the modal ratio is calculated using Equation 1 or Equation 2, while for thick and short members that take shear effects into account, a different equation is used. The calculation equation corresponding to Equation 1 that can be applied to thick and short members is Equation 3 (see Non-Patent Document 3).

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[0028] The calculation formula corresponding to Equation 2, which is applicable to thick and short members, can also be derived from Equation 3.

[0029] The output unit 135 outputs the axial force estimated by the estimation processing unit 133. Typically, the estimation result is displayed on a screen.

[0030] According to the first embodiment, the estimation unit 13 analytically estimates the axial force of a member based on the measured values of acceleration, velocity, displacement, or strain caused by inputting environmental vibrations or vibrations due to natural phenomena into the member. In other words, there is no need to artificially vibrate the member with a hammer or the like. Once the sensor 12 is installed on a member of a large-scale structure, there is no need to directly manipulate the member, and the axial force can be measured remotely. Compared to conventional methods, the work process can be dramatically simplified, and high-precision axial force measurement is possible at low cost.

[0031] <Embodiment 2: Implementation example using image measurement> FIG. 2 is a block diagram showing a configuration of an axial force estimation device 1 according to a second embodiment of the present invention.

[0032] The axial force estimation device 1 includes a measurement unit 11 and an estimation unit 13.

[0033] In the second embodiment, the measurement unit 11 is an image measurement device 15. The image measurement device 15 is an information processing device that measures and outputs the acceleration, velocity, displacement, or strain occurring in a component by image measurement. The image measurement device 15 typically includes a processor, memory, input device, output device, photographing device, and lighting device. The functions of the processor, memory, input device, and output device are similar to those of the estimation unit 13 in the first embodiment, and therefore will not be described here. The photographing device is a photographing device capable of acquiring image data, including one or more cameras. While a single camera capable of acquiring two-dimensional images may be used, a device capable of acquiring image data including three-dimensional information using multiple cameras, such as a stereo camera, is preferable because it can acquire more accurate observation data. The photographing device exposes light at a predetermined timing based on instructions from the processor to generate image data. The image data is passed to the processor. The lighting device emits light at a predetermined timing based on instructions from the processor.

[0034] The image measurement device 15 includes the following processing units: an image measurement unit 151 that measures the acceleration, velocity, displacement, or strain occurring in a member by image measurement, and an output unit 153 that outputs the measurement results.

[0035] The image measurement unit 151 uses digital image correlation (DIC) to measure the acceleration, velocity, displacement, or strain occurring in a component. Specifically, this method involves capturing an image of a measurement target having a mark or pattern on its surface with a camera, and then tracking the movement and deformation of the pattern through image analysis to obtain the acceleration, velocity, displacement, or strain of the measurement target surface in a non-contact manner. Examples of marks or patterns that can be used include natural patterns on the target surface, naturally occurring patterns such as dirt or scratches, and artificial paint or stickers (patterns such as regular grids, shapes such as circles or squares, QR codes (registered trademark), etc.). Because this method is non-contact, it can be used even in cases where it is difficult to directly install a sensor 12, such as on components of large structures located at high altitudes. A general measurement method using DIC is disclosed in Patent Document 7 and Non-Patent Document 2, and therefore will not be described here.

[0036] It is said that to measure vibration, sampling must be performed at a frequency twice the vibration frequency (the Nyquist frequency) (sampling theorem). Therefore, if the imaging device can capture images at a higher frequency (number of still images per second) than the expected mode, DIC can be applied using a conventional method. However, such imaging devices are relatively expensive. On the other hand, if the imaging device can only capture images at a lower frequency than the expected mode, compressed sensing can be used to measure the acceleration, velocity, displacement, or strain occurring in a component. A method for implementing DIC using compressed sensing is disclosed in Patent Document 8, and therefore will not be described here. This embodiment also employs a technique in which a light source randomly emits light during continuous exposure by the imaging device, as described in Embodiment 1 of Patent Document 8. Alternatively, under conditions where strong natural light is available outdoors, compressed sensing can be performed without a light source such as a lighting device by controlling the imaging device to expose at random times during continuous emission (natural light), as described in Embodiment 2 of Patent Document 8. In any case, compressed sensing enables DIC to be used with relatively inexpensive imaging devices. However, the condition is that the vibrations must continue during continuous exposure or continuous light emission (as a rough guide, the vibrations must continue for a period of time sufficient to take several dozen images).

[0037] The output unit 153 transmits the acceleration, velocity, displacement, or strain measured by the image measurement unit 151 to the estimation unit 13 as measurement data.

[0038] The measurement data receiving unit 131 of the estimation unit 13 receives the measurement data output by the output unit 153. The functions of the estimation processing unit 133 and the output unit 135 are the same as those in the first embodiment, and therefore description thereof will be omitted.

[0039] According to the second embodiment, the image measuring device 15 measures the acceleration, velocity, displacement, or strain occurring in the member by image measurement. This method eliminates the need to install the sensor 12 directly on the member, and all processes can be performed remotely. Compared to the first embodiment, this method enables highly accurate axial force measurement while being simpler and less expensive.

[0040] Furthermore, the image measurement device 15 in the second embodiment measures acceleration, velocity, displacement, or strain caused by environmental vibrations or vibrations due to natural phenomena input to a component. Such vibrations tend to last longer than artificial vibrations, such as those generated by hammers, which have often been used in conventional axial force estimation methods. Preferably, if the vibration duration is long enough to capture several dozen images, for example, several tens of seconds to several minutes, DIC using compressed sensing, i.e., DIC using a relatively inexpensive imaging device, can be employed. This allows for simpler and more cost-effective measurement of axial force.

[0041] Although the embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments and can be modified as appropriate without departing from the spirit and scope of the present invention. Any of the components of the embodiments can be modified or omitted within the scope of the present invention.

[0042] For example, in the above-described embodiment, steel towers (electric power towers, communication towers, etc.) are used as examples of large-scale structures, but the application of the present invention is not limited to this and can be applied to frame structures made up of slender columnar members, such as bridges, buildings, machinery and equipment, chimneys supported by steel plate steel towers, etc. Also, in the above-described embodiment, the members are mainly assumed to be the web members of steel towers, but the application of the present invention is not limited to this and, for example, the axial force of horizontal members and main members can also be estimated.

[0043] Furthermore, the information processing of the present invention may be realized by hardware or by a CPU executing a computer program, which may be supplied to a computer by various types of non-transitory computer-readable medium or transitory computer-readable medium. [Explanation of symbols]

[0044] 1 Axial force estimation device 11 Measuring part 12 sensors 13 Estimation part 131 Measurement data receiver 133 Estimation processing unit 135 Output section 15 Image measurement device 151 Image Measurement Unit 153 Output section

Claims

1. a measuring unit that measures acceleration, velocity, displacement, or strain caused by input of environmental vibrations, vibrations due to natural phenomena, or vibrations generated by a pre-installed vibrator to a component of a large-scale structure; an estimation unit that estimates an axial force generated in the member due to a vibration mode ratio based on measurement data from the measurement unit. Axial force estimation device.

2. The measuring unit is a plurality of sensors installed on the member. The axial force estimation device according to claim 1 .

3. The measuring unit is an image measuring device that performs the measurement by a digital image correlation method at a location remote from the member. The axial force estimation device according to claim 1 .

4. The measurement unit performs the measurement by a digital image correlation method using compressed sensing. The axial force estimation device according to claim 3.

5. a measuring step of measuring acceleration, velocity, displacement, or strain caused by input of environmental vibration, vibration due to natural phenomenon, or vibration caused by a pre-installed vibrator to a member of a large-scale structure; and an estimation step of estimating an axial force generated in the member due to a vibration mode ratio based on the measurement data measured in the measurement step. Axial force estimation method.

6. A program that causes a computer to execute the method according to claim 5.

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