Patent Application
20240272036
The present disclosure relates to a measurement device, a measurement system, a measurement method, and a program capable of estimating strength from deformation of a structure.
Structures are required to have designs that can sufficiently withstand loading in use environments based on the strength of materials to be used. Accordingly, it is assumed that characteristics of the materials to be used are sufficiently ascertained in the design. However, strength of materials of structures to be used for a long period of time may be changed due to deterioration or the like. Since deterioration in strength of materials of structures directly results in deterioration in proof stress of the structures, responsible owners of the structures are required to appropriately ascertain the deterioration in the material strength.
For example, resin concrete (hereinafter referred to as “REC”) is a material widely used for structures and the like. There are 100,000 or more communication manholes (hereinafter referred to as “RECMHs”) of NTT manufactured of REC all over the country. REC is also a material of a sewer manhole (see Non Patent Literature 1).
Many studies for the material characteristics of REC have been carried out so far, and the strength (flexural strength, compressive strength, tensile strength, shear strength, and the like) thereof is 3 to 5 times that of cement concrete (see Non Patent Literature 2). On the other hand, unclear points regarding changes in material characteristics due to aging of REC over time have been considerable for many years. However, in recent year, there has been a report that strength deteriorates over time (see Non Patent Literature 3).
Methods of examining the material strength of structures vary depending on materials, but most directly, there is a method of taking out a part of a structure as a sample and performing a compression test, a tensile test, and the like.
There is a non-destructive inspection technique in which ultrasonic measurement is utilized for strength measurement of RECMH (see Non Patent Literature 4).
The above-described destructive test is often not preferred in that it generally takes time and incurs costs, and that it may not be allowed to damage a structure from the viewpoint of safety or the like in the first place. For RECMH, it is not realistic to perform a destructive test on 100,000 RECMHs across the country.
Although a non-destructive inspection is superior to a destructive inspection in terms of cost, there are problems that a dedicated device is required, preprocessing for an ultrasonic measurement surface is required, and it takes time for measurement.
An object of the present disclosure is to provide a measurement device, a measurement system, a measurement method, and a program capable of estimating a material flexural strength of a structure simply through simple length measurement.
According to an embodiment, a measurement device includes: a height difference acquisition unit configured to acquire a height difference which is a difference in vertical displacement between two points on a bottom surface of a structure; and a material flexural strength calculation unit configured to calculate a material flexural strength of the structure based on the height difference.
According to another embodiment, a measurement system includes: the foregoing measurement device; and measurement equipment. The measurement equipment includes a horizontal member, a first vertical member that is fixed to the horizontal member to be able to move in a vertical direction with respect to the horizontal member and includes a displacement presentation unit indicating first displacement in the vertical direction; and a second vertical member that is fixed at a position different from the first vertical member on the horizontal member to be able to move in a vertical direction with respect to the horizontal member, and includes a displacement presentation unit indicating second displacement in the vertical direction. The measurement device acquires a height difference based on the first displacement and the second displacement.
According to still another embodiment, a measurement method includes: a height difference acquisition step of acquiring a height difference which is a difference in vertical displacement between two points on a bottom surface of a structure; and a material flexural strength acquisition step of obtaining a material flexural strength of the structure based on the height difference information.
According to still another embodiment, a program causes a computer to function as the measurement device.
According to the present disclosure, it is possible to provide a measurement device, a measurement system, and a measurement method capable of estimating a material flexural strength only through simple length measurement when a structure is loaded.
As described above, there are proposed a measurement device, a measurement system, and a measurement method capable of estimating material strength only through simple length measurement by utilizing characteristics that the degree of deformation differs depending on material flexural strength when a structure is loaded. A deformation behavior of a structure at the time of loading of the structure differs depending on a loading position, a size, material strength, a structure shape, and the like. These are stored as a database and can be ascertained at the time of inspection. Examples of a target structure include a resin concrete manhole made of resin concrete of which strength changes over time. In the present embodiment, the technology will be described by exemplifying a case where the structure is an RECMH.
The upper floor slab 11 has a circular opening 11o, and each short side wall 12 has a rectangular opening 12o. The number of openings or the shapes of the openings provided in the RECMH 10 can be changed.
The RECMH 10 is an underground structure, and the load applied to the RECMH 10 after installation includes a soil pressure applied at all times and a vehicle load applied when a vehicle or the like passes thereover. Since the vehicle does not travel on the RECMH 10 during inspection of the RECMH 10, deformation only by an earth pressure may be considered.
A vertical soil pressure on the RECMH 10 is caused by soil on the upper floor slab 11. Strictly speaking, the horizontal earth pressure should also be considered, but it is considered that an influence of the horizontal earth pressure on the deformation of the RECMH 10 can be ignored. Here, the description of the horizontal earth pressure will be omitted.
According to the tunnel standard specifications (refer to “Tunnel Standard Instruction (edited by the Japan Society of Engineers of Japan)”, 1986, the upper part of p. 22.), a unit volume weight of backfilled soil (a groundwater level or less) is 2.0 t/m3=19.6 kN/m3. A depth from the ground surface to the upper floor slab 11 of the RECMH 10, that is, a soil thickness, is generally 0.5 m. In this case, the vertical soil pressure to the RECMH 10 is 19.6×0.5=9.8 kN/m2.
In order to examine a deformation behavior when a load corresponding to the vertical earth pressure was applied to the RECMH 10, a test RECMH 10′ equivalent to the RECMH 10 was prepared and a loading test was performed. Since the test RECMH 10′ has the same constituents as the RECMH 10, the constituents of the test RECMH 10′ are denoted by the same reference numerals as the RECMH 10.
The test RECMH 10′ used at this time has a known material flexural strength (hereinafter simply referred to as “flexural strength” in this document) of REC according to JIS A 1181: 2005, which is 6.5 MPa.
Although there are several sets of dimensions for the RECMH, an RECMH with a length of 3000×a width of 1400×a height of 1700 mm of which there are a large number, was used for the test RECMH 10′.
In the loading test, loading was performed, as illustrated in
In order to examine the deformation behavior of the test RECMH 10′, a strain gauge 30 was attached along the longitudinal direction of the lower floor slab 14 at a position illustrated in
In the 10 MN structure tester 20 illustrated in
It is considered that the deformation illustrated in
When measurement on a site is considered, as illustrated by the sketch in
In the embodiment, the deformation of the end portion of the cut plane C taken in the longitudinal direction through the center of the test RECMH 10′ is examined, but an extension direction between the end portion and the center may be changed. For example, referring to
As a method other than the method directly measuring the displacement difference d between the end portion and the central portion, as described above, there is a method of deriving the displacement difference between the end portion and the central portion from the displacement (strain) in the horizontal direction by calculation. Hereinafter, an example of the method will be described. First, for example, at the center of the lower floor slab 14, an elongation along the center line extending in the longitudinal direction is calculated from the strain in the longitudinal direction of the lower floor slab 14. Thereafter, the displacement difference d between the end portion and the central portion can be calculated by calculating the vertical displacement at the central portion of the center line of the lower floor slab 14 from the elongation along the center line of the lower floor slab 14. A specific example will be described below.
When an end portion of the lower floor slab 14 in a direction other than the longitudinal direction is examined, strain of the lower floor slab 14 corresponding to this direction is measured.
The displacement of the central portion in the vertical direction when the strain of the lower floor slab 14 in the horizontal direction is 12×10−6 is considered. The strain measured here is a maximum at the center of the lower floor slab 14 on the center line (indicated by a two-dot chain line) in the longitudinal direction of the lower floor slab 14 as illustrated in
A minute section on the center line in the longitudinal direction of the lower floor slab 14 is defined as Δ×. The elongation in this section is defined as ΔL×. The maximum value of ΔL×/Δ× is 12×10−6, and the minimum value is 0. Since the deformation of the center line (length L=3000 mm) before the deformation is bilaterally symmetrical, the deformation of the half section L1/2 (here, 1500 mm) is considered. At this time, this half section can be divided into L1/2/Δ× pieces. Of sections obtained by dividing the half section into L1/2/Δ×, a section with a maximum strain (12×10−6) is a section closest to the center, and the section with a minimum strain (0) is a section closest to the end.
In such a case, it is difficult to calculate all ΔLx corresponding to the minute section Δ×. Therefore, as the most general case, assuming that the strain value decreases from the maximum value ΔL×max equally for L1/2/Δ× times and finally becomes the minimum value 0, the elongation ΔL1/2 at the half section length L1/2 can be expressed as follows. According to the foregoing assumption, the elongation on the center line of the lower floor slab 14 can be calculated as an accurate approximate solution to some extent.
Here, it is necessary to appropriately set Δ× so that L1/2/Δ× takes an integer value. The foregoing expression is a sum of an arithmetic progression and is expressed as follows with n as an integer.
Since ΔL1/2 is an elongation of the half section, the elongation ΔL of the entire section is obtained by doubling ΔL.
By solving the above expression, the elongation at the time of the deformation of the RECMH can be estimated.
In this test, when L1/2=1500 mm, ΔL×max=12×10−6, and Δ×=1 mm, the following first expression is obtained, and the expression is further developed.
Accordingly, the length of the upper surface along the center line after the deformation is about 3000.018 mm.
In the fields of material mechanics, deformation due to beam bending is approximately calculated as an arc (see, for example, the following Reference Literature 1). In particular, when the angle θ of the arc is minute, it is more approximate. Therefore, as illustrated in
Then, the arc length of the arc is expressed as follows.
The following expression is established from the definition of the triangular ratio with respect to a right triangle.
In this condition, L′=3000.018 and L=3000 are satisfied. Therefore, when these are substituted and the above two expressions (Math. 5 and Math. 6) are solved as simultaneous equations, θ≈0.012 (rad) and r≈2.50×105 (mm) are obtained. 0 is minute, and it can be said that the foregoing approximation of the arc is appropriate. At this time, a maximum displacement amount y in the vertical direction is expressed by the following expression. Here, a is a length of a perpendicular drawn from the center of the arc to the axial center line before the deformation.
Therefore, y≈4.5 is obtained. Accordingly, on the surface of the lower floor slab 14 in the test RECMH 10′, the maximum vertical displacement at the center line is 4.5 mm, and the difference from the end (displacement 0 mm) is 4.5 mm.
As described above, the test RECMH 10′ used this time has a known flexural strength which is 6.5 MPa. Accordingly, for an RECMH in an environment where only soil pressure is applied in the vertical direction, when the difference in the vertical direction between the central portion and the end portion on the center line of the lower floor slab 14 in the longitudinal direction is 4.5 mm, the material flexural strength of the RECMH can be estimated to be 6.5 MPa.
In this way, the material strength can be estimated by obtaining the relationship between the material strength and the vertical displacement from the result of the loading test or a result of the simulation by a finite element method or the like and measuring the vertical displacement on a site.
When the relationship between the material strength and the vertical displacement is acquired under a plurality of conditions, an approximate line indicating correlation between the material strength and the displacement can be obtained, and the material strength in a wider range can be estimated. For example, for the RECMH, a loading test was carried out for an RECMH that has a flexural strength of 15.9 MPa in accordance with the same method as the above-described method. As a result, the strain at the time of loading of the pressure of 9.8 N/m2 corresponding to the vertical earth pressure on the upper floor slab 11 of the test RECMH 10′ was 5×10−6. At this time, on the surface of the lower floor slab 14 in the test RECMH 10′, the vertical displacement at the center line was 2.9 mm. Therefore, as illustrated in
Next, an approximate line (flexural strength)=−5.875×(vertical displacement)+32.938, which is a straight line connecting these two points, can be derived. The reason for the linear approximation is that a stress-strain relationship at the time of applying of stress to the test RECMH 10′ is a linear relationship in the minute strain region as this time (see, for example, the following Reference Literature 2).
It is possible to draw a better approximation by increasing the number of conditions and obtaining more plots. In order to obtain an approximate expression, for example, a least squares method can be used. For example, when strength is estimated with another material or the like, the approximate expression may indicate a curve.
When the displacement of the actual RECMH in the vertical direction is measured, it is easy to perform measurement by using retained water 90 which is in many RECMHs 10 as in
Next, a measurement system that measures strength of a structure using the results of the loading test or the simulation will be described below. A bird's eye view of the measurement system is illustrated in
The measurement equipment 1010 includes a horizontal member 1011, a first vertical member 1012, and a second vertical member 1013.
It is desirable that the horizontal member 1011 can be stretched in an axial direction. It is desirable that the horizontal member is not displaced in a radial direction. The horizontal member 1011 may be fixed by a screw or the like in a state in which the horizontal member 1011 is stretched in the axial direction.
Preferably, the first vertical member 1012 and the second vertical member 1013 have the same shape and are rigid. In this embodiment, the first vertical member 1012 and the second vertical member 1013 are cylindrical. The first vertical member 1012 and the second vertical member 1013 are not completely bonded to the horizontal member 1011, but are fixed to the horizontal member 1011 to be able to be moved only in a direction perpendicular to the axial line of the horizontal member 1011. This configuration can be implemented, for example, by providing slight gaps between the horizontal member 1011, and the first vertical member 1012 and the second vertical member 1013. Movable ranges of the first vertical member 1012 and the second vertical member 1013 with respect to the horizontal member 1011 may be limited by providing unevenness in any member.
As illustrated in
The surface of the RECMH 10 has fine unevenness and a ground point is not necessarily horizontal. Therefore, the radius of the cross section of the first vertical member 1012 and the second vertical member 1013 is preferably 1 cm or more, and a grounding portion of the first vertical member 1012 and the second vertical member 1013 is preferably hemispherical.
When the height difference of the lower floor slab 14 of the RECMH 10 is measured, the first vertical member 1012 is grounded to an end portion of the lower floor slab 14 in the longitudinal direction, and the second vertical member 1013 is grounded to the central portion (or vice versa), and thus a displacement difference (height difference) between the end portion and the central portion can be measured simply and with high accuracy.
Displacement sensors serving as displacement presentation units may be provided in the first vertical member 1012 and the second vertical member 1013, and signals corresponding to the protrusion amounts of the first vertical member 1012 and the second vertical member 1013 in the vertical direction may be output to a height difference acquisition unit 131 of the measurement device 1020.
In another embodiment, instead of the measurement equipment 1010 automatically measuring the protrusion amount, circumferential surfaces of the first vertical member 1012 and the second vertical member 1013 can be used as rulers, and scales indicating the protrusion amounts in the vertical direction can be provided. The scale can also be printed on the circumferential surface. The scale may be formed of unevenness on the circumferential surface. In this case, a user can input a confirmed protrusion amount to the height difference acquisition unit 131 of the measurement device 1020. Hereinafter, the protrusion amount of the first vertical member 1012 in the vertical direction is referred to as a first protrusion amount, and the protrusion amount of the second vertical member 1013 in the vertical direction is referred to as a second protrusion amount.
The height difference acquisition unit 131 is an input interface that is connected to the measurement equipment 1010 illustrated in
The material flexural strength calculation unit 132 obtains material flexural strength of the structure from the vertical height difference acquired by the height difference acquisition unit 131. Specifically, for example, a relational expression between the vertical displacement and the flexural strength illustrated in
The material strength display unit 133 displays the material flexural strength of the structure obtained by the material flexural strength calculation unit 132 on a display or the like. The measurement device 1020 may further include a display that displays the material flexural strength of the structure obtained by the material flexural strength calculation unit 132.
In the above-described configuration, the relational expression between the vertical displacement and the flexural strength is stored in advance in the material flexural strength calculation unit 132. On the other hand, in the configuration illustrated in
The measurement device 1020 illustrated in
In the storage unit 145, for example, two sets (flexural strength MPa, vertical displacement: mm)=(6.5, 4.5) and (15.9, 2.9) of the vertical displacement and the flexural strength which are plotted in
The strength-displacement relationship deriving unit 142 derives a function indicating a relationship between flexural strength and vertical displacement based on two or more sets of the vertical displacement and the flexural strength stored in the storage unit 145. For example, as described above, the strength-displacement relationship deriving unit 142 can derive the function (flexural strength)=−5.875×(vertical displacement)+32.938 based on (flexural strength MPa, vertical displacement: mm)=(6.5, 4.5) and (15.9, 2.9) which are two sets of the vertical displacement and the flexural strength. A derivation method will not be described again.
The material flexural strength calculation unit 141 calculates the flexural strength with respect to a height difference which is a difference in the vertical displacement by using the function derived by the strength-displacement relationship deriving unit 142.
The strain-flexural strength acquisition unit 143 can receive input of a flexural strength and a set of pressures caused by a loading load against strain. For example, the user can input flexural strength of 6.5 MPa in the test structure subjected to the loading test to the strain-flexural strength acquisition unit 143 and input a set of pressures due to the loading against the strain illustrated in
The vertical displacement calculation unit 144 can obtain the vertical displacement from the horizontal strain and the direction in which the strain is measured. Since the calculation method has been described above, the description thereof will be omitted.
The strength-displacement relationship deriving unit 142, the strain-flexural strength acquisition unit 143, the vertical displacement calculation unit 144, or the storage unit 145 may be provided outside of the measurement device 1020. The measurement device 1020 illustrated in
Next, a measurement method according to an embodiment will be described.
The preprocessing will be described below. As described above, the preprocessing is generally performed in the loading test performed in a laboratory or the like instead of on a site.
In step S151 of
In step S152, the storage unit 145 of the measurement device 1020 stores a set of the vertical displacement calculated in step S151 and the material flexural strength of the RECMH 10′. In the above-described example, the storage unit 145 stores (flexural strength MPa, vertical displacement: mm)=(6.5, 4.5), (15.9, 2.9).
In step S153, the strength-displacement relationship deriving unit 142 of the measurement device 1020 derives a function indicating a relationship between the material flexural strength and the vertical displacement of the RECMH 10′. In the above-described example, a function (flexural strength)=5.875×(vertical displacement)+32.938 is derived. Here, the preprocessing ends.
Hereinafter, referring to
In step S162, the material flexural strength calculation unit 132 or 141 of the measurement device 1020 obtains the material flexural strength of the structure based on the height difference information. For example, when the height difference is 3.5 mm, the material flexural strength calculation unit 141 estimates that (flexural strength)=−5.875×3.5+32.938=12.376 Mpa.
In step S162, the material strength display unit 133 of the measurement device 1020 displays the material flexural strength of the structure obtained by the material flexural strength calculation unit 132 or 141 on a display or the like. The process ends here.
In the foregoing processing, the user can acquire the estimated result of the material strength of the structure only through simple length measurement. The user performs maintenance or the like of the structure as necessary according to the estimated material flexural strength.
In order to function as the above-described measurement device 1020, it is also possible to use a computer capable of executing a program instruction. Here, the computer may be a general-purpose computer, a dedicated computer, a workstation, a personal computer (PC), an electronic note pad, or the like. The program instruction may be a program code, a code segment, or the like for executing a necessary task.
The computer includes a processor, a storage unit, an input unit, an output unit, and a communication interface. The processor is a central processing unit (CPU), a micro processing unit (MPU), a graphics processing unit (GPU), a digital signal processor (DSP), a system on a chip (SoC), or the like and may be configured with the same type or different types of a plurality of processors. The processor reads and executes the program from the storage unit to perform control of each of the above-described configurations and various types of arithmetic processing. At least a part of these processing content may be implemented by hardware. The input unit is an input interface that receives a user input operation and acquires information based on a user operation and is a pointing device, a keyboard, a mouse, or the like. The output unit is an output interface that outputs information and is a display, a speaker, or the like. The communication interface is an interface for communication with an external device.
The program may be recorded on a computer-readable recording medium. When such a recording medium is used, the program can be installed in the computer. Here, the recording medium on which the program is recorded may be a non-transitory recording medium. The non-transitory recording medium is not particularly limited, but may be, for example, a CD-ROM, a DVD-ROM, a Universal Serial Bus (USB) memory, or the like. The program may be downloaded from an external device via a network.
The following supplements for the foregoing embodiments will be further disclosed.
A measurement device including:
The measurement device according to Supplement 1, further including:
The measurement device according to Supplement 1 or 2, wherein the control unit calculates the material flexural strength based on an extension direction of a straight line connecting the two points.
A measurement system including: the measurement device according to any one of Supplements 1 to 3; and measurement equipment,
A measurement method including:
The measurement method according to Supplement 5, further including:
The measurement method according to Supplement 5 or 6,
A non-transitory storage medium storing a program which is able to be executed by a computer,
The above-described embodiments have been described as representative examples and it is apparent to those skilled in the art that many modifications and substitutions can be made within the spirit and scope of the present disclosure. Accordingly, it should not be understood that the present invention is limited by the above-described embodiments, and various modifications or changes can be made without departing from the scope of the claims. For example, a plurality of configuration blocks described in the configuration diagrams of the embodiment can be integrated, or one configuration block can be divided.
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/JP2021/021643 | 6/7/2021 | WO |
