JP6554065B2 - Method and system for evaluating deterioration state of metal structure - Google Patents

Description

  The present invention relates to a method and system for evaluating the deterioration state of a metal structure.

  For example, metal structures typified by infrastructure equipment such as steel pipe columns, supporting anchors and piping thereof are used in a state where the whole or a part thereof is buried in the ground. Such an underground metal structure may be reduced in strength due to thinning of a metal member to be formed due to corrosion or the like due to moisture in the ground. In general, a state in which there is no or slight degree of deterioration such as thinning and the underground metal structure performs its original function is called a sound state. On the other hand, a state in which the underground metal structure may lose its original function due to a high degree of deterioration such as thinning is called a deteriorated state.

  Among the underground metal structures, for example, for piping, it is possible to know the state where the original function has been lost by detecting the leakage of the fluid flowing in the pipe, and to identify and replace that part. May be taken. However, in the case of underground metal structures that secure the strength as a structure, a state in which the original strength function is lost may lead to an accident such as breakage, destruction, or collapse, and so it is not post-maintenance, Preventive maintenance is required.

  As a method of preventive maintenance, a deterioration state is detected and detected by inspection including inspection of the target structure, and all or some of the members constituting the structure are replaced with healthy new ones. Alternatively, it is common to replace it with an equivalent to secure the health condition. Here, the inspection generally refers to a simple inspection, and in many cases, using a visual or a simple tool.

  However, in underground metal structures that are entirely or partly buried in the ground, it is often difficult for humans to observe the deterioration state of the buried parts in the ground. In the inspection, it can hardly be judged whether it is a deteriorated state. On the other hand, as an inspection device for detecting the deterioration state of the part buried in the ground of the underground metal structure, for example, ultrasonic waves are used for inspection using a branch wire rod for fixing a branch line supporting the pole to the ground. Flaw detection equipment has been developed. (Refer the following nonpatent literature 1).

Sohei Yamada "Development of branch rod ultrasonic flaw detector" Rust prevention management 2016-2, pp45-50. IRVING A. DENISON, MELVIN ROMANOFF, "Corrosion of Low-Alloy Irons and Steels in Steels", J. Res. Nat. Bur. Standards, 492, No. 5, p. 315-323 Development of technology to visualize "invisible" hazards-simultaneously diagnose structural defects and their hazard levels with stress light emitters-http://www.aist.go.jp/aist_j/press_release/pr2008/pr20081114/pr20081114. html (viewed March 3, 2016)

  Of course, in such inspection equipment using ultrasonic waves, it is indispensable that the ultrasonic waves propagate to the site to be inspected in the underground metal structure. Moreover, even if it propagates, it is necessary that a signal indicating a deterioration state different from a signal indicating a sound state is detected with sufficient intensity. The same applies to inspection equipment based on the principle of using probes other than ultrasonic waves.

  In the case of an underground metal structure composed of a plurality of members instead of an integral shape such as a branch rod, ultrasonic waves can not propagate from the members to the members at the points where the members are connected, or Even when propagating from member to member, the intensity of the ultrasonic wave is extremely attenuated. That is, in the case of an underground metal structure composed of a plurality of members, the application range of the inspection equipment using ultrasonic waves is limited to the range of the members that first propagate the ultrasonic waves. As an example of the underground metal structure composed of a plurality of metal members, there is a branch anchor used to fix the branch line to the ground in the same manner as the branch rod of Non-Patent Document 1. A branch anchor 401, which is also schematically shown in FIG. 1 to be described later, includes a plurality of metal members including a rod 402 connected to a ground branch line, in addition to a plurality of main body members embedded in the ground.

  In the case of such a branch anchor, it is required to secure a reaction force against a tensile load of the branch by a metal member in the ground as a strength function. The maximum value of reaction force is called proof stress. In practice, branch anchors are used under conditions where the tensile load is well below the proof stress. When a tensile load is applied, the positions of the branch anchors slightly change, and the tensile load and the reaction force are balanced with a certain displacement. When the branch anchor is deteriorated and cannot withstand the tensile load, a displacement that can be visually recognized may appear. A state in which such a displacement appears is called floating or the like. The uplift condition is already dangerous and it is necessary to detect the deterioration condition of the branch anchor from the small displacement value before the uplift condition. However, if there is a small displacement, it can not be easily determined by visual observation whether the displacement is in the range of the healthy state or the range of the deteriorated state.

  This invention is made | formed in view of the said subject, Comprising: It aims at evaluating the deterioration state of an underground metal structure.

In order to solve the above-described problems and achieve the object, the present invention can be configured as follows.
(Structure 1 of the Invention)
Regarding metal structures that are completely or partially buried in the ground,
A processing step of performing a thinning process on the sample A equivalent to the metal structure;
A test A step of embedding the sample A and applying a force to the embedded sample A and performing a test of measuring a displacement according to the applied force;
Based on the result of the test A step, a recording A step for obtaining and recording a curve A indicating the relationship between force and displacement;
Defining the deterioration state based on the curve A;
A test B step of performing a test for applying a force to the sample B equivalent to the metal structure and measuring a strain according to the applied force;
Based on the result of the test B step, a recording B step for obtaining and recording a curve B indicating the relationship between force and strain,
A strain measurement process for measuring a strain in a use state which is provided for a while after the burying, provided with a device for measuring the strain before burying the metal structure;
For the metal structure, a displacement measurement step for measuring displacement in a use state that has passed for a while after the embedding, and
A method for evaluating the deterioration state of a metal structure, comprising
(Structure 2 of the Invention)
Regarding metal structures that are completely or partially buried in the ground,
A processing step of performing a thinning process on the sample A equivalent to the metal structure;
A test A step of embedding the sample A and applying a force to the embedded sample A and performing a test of measuring a displacement according to the applied force;
Based on the result of the test A step, a recording A step for obtaining and recording a curve A indicating the relationship between force and displacement;
Defining the deterioration state based on the curve A;
A recording B ′ step of obtaining a Young's modulus for a metal material equivalent to the metal structure, obtaining a relationship between a force applied to the metal structure and a strain, and recording;
A strain measurement process for measuring a strain in a use state which is provided for a while after the burying, provided with a device for measuring the strain before burying the metal structure;
A displacement measuring step of measuring displacement of the metal structure in a use state which has been in progress for a while after the embedding;
A degradation state evaluation method for a metal structure, characterized by comprising:
(Composition 3 of the Invention)
For a metal structure that is completely or partially buried in the ground, the sample A, which has been subjected to thickness reduction processing to a sample equivalent to the metal structure, is embedded and loaded with force, and displacement according to the applied force A recording unit A for recording a curve A indicating a relationship between force and displacement based on the result of the test A for measuring the value as an index value of the deterioration state of the metal structure,
A database unit for storing stress-strain curve B of the metal structure or Young's modulus of the metal material of the metal structure;
An interface unit for performing input / output for searching a stress-strain curve B or Young's modulus of a metal structure from the database unit,
An apparatus for measuring strain before embedding in the metal structure is provided, and a value of strain obtained as a result of measuring strain in a use state a while after embedding is obtained and input to the interface unit. A recording unit C for recording a result C, which is a combination of a stress and a displacement, by combining the value of the stress with the result of measuring the displacement in a use state which has passed for a while after the embedding,
A degradation state evaluation system of a metal structure, comprising: a determination portion which compares the curve A of the recording portion A with the result C and determines the deterioration state of the metal structure.

  According to the present invention, the deterioration state of the underground metal structure can be evaluated with high accuracy.

It is a figure which shows the installation state of the branch line anchor which is a underground metal structure in one this embodiment of this invention. It is a figure which illustrates the tensile load-displacement curve A obtained by the test A process of the sample A of this embodiment, and a recording A process, and the result of having evaluated the degradation state. It is a figure which illustrates the stress distortion curve B obtained at the test B process of the sample B of this embodiment, and a recording B process. It is a flowchart which shows the evaluation processing procedure which concerns on one Embodiment of this invention.

  Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings. In addition, this invention is not limited by this embodiment. Further, in the description of the drawings, the same portions are denoted by the same reference numerals.

  FIG. 1 is a view showing an installation state of an underground metal structure to be evaluated in one embodiment of the present invention.

  FIG. 1 exemplifies the installation state of a branch anchor as described above as an example of the underground metal structure. Most of the main body of the branch anchor 401 composed of a plurality of metal members is buried in the ground, and another structure to be supported by the branch anchor 401 via a metal rod 402 partially exposed to the ground. It is connected with a thing (not shown) by a branch line. The rod 402 is in a state of being subjected to a tensile load which is received from another structure.

  In an example of the embodiment of the present invention, a strain gauge 403 is attached to the rod 402 of the branch anchor 401, and the strain accompanying the tensile load is measured. As shown in FIG. 3 described later, if it is in the range of elastic deformation, it is possible to know the tensile load actually applied from the measured strain using the linear portion of the stress-strain curve B or the Young's modulus.

  Further, by measuring the position of the representative point 404 on the rod 402 in FIG. 1 by applying an appropriate load, a load-displacement curve can be obtained.

  FIG. 2 is a diagram showing such a tensile load-displacement relationship when a branch anchor is taken as an example.

  The upper curve A0 in FIG. 2 is a curve showing the relationship between the tensile load and the displacement in a new state without deterioration such as corrosion immediately after the branch anchor is buried.

  In a state of use that has passed for a while after the structure is buried, the strength of the structure is reduced in a state where the deterioration has progressed to some extent, and the displacement increases with a smaller load. In this state, the curve indicating the relationship between tensile load and displacement moves downward in FIG. This curve A is measured using a sample A of a structure that simulates deterioration, and defined as a reference for judgment of deterioration.

  FIG. 2 also shows the displacement measured when a specific tensile load is applied to the further deteriorated metal structure to be actually evaluated, as a point C of the measured value in the use state. In FIG. 2, since the point C is below the curve A, it is evaluated that the metal structure to be evaluated is in a deteriorated state.

  Thus, based on the relationship between the point C represented by the combination of tensile load and displacement and the curve A, it can be determined whether or not the underground metal structure is in a deteriorated state.

  FIG. 4 is a flow chart showing the processing procedure of the evaluation method according to the embodiment of the present invention. Hereinafter, description will be made based on FIG.

[Thickening process of sample A]
S101 in FIG. 4 is a processing step of applying a thinning process to all or a part of the members of the sample A equivalent to the metal structure by simulating deterioration due to corrosion. As a specific processing method for reducing the thickness, for example, processing using an NC lathe or a milling machine may be used, or a metal structure may be dissolved using chemical etching, and the degree of thickness reduction after dissolution may be vernier etc. It is also possible to obtain a desired degree of thinning by repeating chemical etching while measuring.

  The final desired degree of thickness reduction may be determined similar to the metal structure to be evaluated, and may be determined by imitating the metal structure in the degraded state already recovered after installation and use, or has already been disclosed If there is data on aging of the amount of corrosion reduction of the metal material, it may be determined by reference (see Non-Patent Document 2).

[Test A step for reduced-thickness sample A]
S102 of FIG. 4 embeds the thickness-reduced sample A obtained by the thickness-reduction processing process of the above-mentioned sample A on the ground equivalent to the ground where embedding of a metal structure is assumed, and is embedded with respect to the sample A embedded. This is a test A step in which a test is performed in which a force is applied and a displacement of the structure generated according to the applied force (tensile load) is measured.

  In the test A step, for example, if the sample A is large, a load cell for measuring a tensile load applied between the heavy machine and the sample A is disposed in the test for pulling the embedded sample A using the heavy machine. This can be implemented by measuring the displacement of sample A as the movement of a representative point on sample A.

  The movement of the representative point may be obtained sequentially by positioning with a laser by positioning with the fixed point on the ground, or more simply, with a heavy machine as the fixed point, a non-stretching thread attached to the representative point on the sample A The yarn may be wound up according to the tensile direction of the tensile test, and the yarn winding length may be taken as a displacement. In the following, a tensile load will be applied as a force unless otherwise specified, using a branch anchor as an example.

[Recording process A of tensile load-displacement curve A for thinned sample A]
S103 in FIG. 4 is a step of obtaining and recording a tensile load-displacement curve A (FIG. 2) based on the data obtained in the test A step on the thickness-reduced sample A. In general, the tensile load is taken on the vertical axis and the displacement is taken on the horizontal axis, and the data obtained in the test A step are described, and the intervals are connected by curves (including straight lines). If the data obtained in the test A step is discrete, a curve A may be obtained by complementing the discrete data using a cloud ruler, a spline function or the like.

[Defined state regulation process]
S104 in FIG. 4 is a step of defining the deterioration state based on the obtained curve A. Taking the case of a branch anchor as an example, generally, for the maximum tensile load in curve A (tensile load at the highest point of curve A in FIG. 2), the ratio to the yield strength is calculated, and the ratio is used Degradation can be defined.

  For example, the strength of the original new product is designed with a margin for strength, and the margin is often expressed as a safety factor, but if the safety factor is 1.5, the maximum tensile load resistance in curve A If the ratio to is two thirds corresponding to the reciprocal of 1.5, a state showing less than two thirds of the proof stress can be defined as a deteriorated state.

  On the contrary, assuming that the condition showing less than two thirds of the proof stress is the deteriorated condition, if the maximum tensile load on the curve A is more than two thirds or less than two thirds, the entire curve A is multiplied by a constant New curve A in which the maximum tensile load is two thirds of the proof stress, or a new sample A is prepared, and steps 101 to 104 are performed again to obtain a new one. Step 101 to step 104 may be repeated so that the maximum tensile load in the curve A is about two thirds.

  The proof stress may be a new proof strength or a design proof strength depending on the intention of using the present invention.

[Test B step for sample B]
S105 in FIG. 4 is a step of applying a force to the sample B equivalent to the metal structure not to be subjected to wall thinning processing and performing a test to measure strain according to the applied force.

  Prepare a sample B equivalent to the metal structure not to be reduced in thickness processing and apply a force in the non-embedding state to obtain stress-strain characteristics (FIG. 3) of the metal structure not to be reduced in thickness processing and evaluate It is a basis to measure the tensile load applied to the target metal structure.

  The site to which force is applied is the whole or a part of sample B, but in the case of a partial site, the site to which most of the applied force is applied is not the site to which force is hard to be applied. desirable. Taking a branch anchor as an example of sample B not subjected to thinning processing, the branch anchor is mounted on a device that measures strain, and tension is applied to a rod portion that is a portion that receives a tensile load applied to the branch in actual use. Load the load. Although a tensile tester is generally used as a device that applies a tensile load and measures strain, a device such as a load cell that can know the applied load may be used. Although a slight displacement of the rod portion corresponding to the applied tensile load may be measured to correct the strain, the strain may be measured directly using a strain gauge or the like.

[Record B process of tensile load-strain curve B for sample B]
S106 in FIG. 4 is a step of obtaining and recording a curve B indicating the relationship between the force and the strain in the sample B not subjected to the thickness reduction processing based on the result of the test B step. Taking the case of a branch anchor as an example, a curve B showing the relationship between tensile load and strain as shown in FIG. 3 is obtained and recorded.

  The part where the force is applied is a part of the metal structure, has a uniform shape in the direction in which the force is applied, and the constituent material is a general metal material, and the Young's modulus of the material is If the data is clear in the literature, etc., instead of using the sample B, instead of the test B step (S105) and the recording B step (S106), from the data of the shape of the member and the Young's modulus data of the material constituting the member, It is good also as record B 'process which acquires and records relation between load and distortion of metal structure.

[Strain measurement process of metal structure]
S107 in FIG. 4 is a strain measurement step of performing strain measurement on the metal structure to be actually evaluated in order to determine the tensile load actually applied in the use state after a while after being embedded.

  The metal structure that is actually the object of evaluation is equipped with a device for measuring strain before being embedded in the ground.

  As a device for measuring the strain, a device such as the strain gauge 403 shown in FIG. 1 is simple, but a device or method other than the strain gauge may be used. The part of the metal structure whose strain is to be measured is the same as the part of the sample B where the strain was measured (see Non-Patent Document 3).

  S108 in FIG. 4 is a step of calculating the tensile load applied to the metal structure to be evaluated using the stress-strain curve B described above. Since the distortion of the metal structure in the use state after a while has passed since embedding is obtained in the step S107, the tensile load actually applied to the metal structure to be evaluated using the curve B (FIG. 3) recorded in S106. (Stress) can be obtained.

[Displacement measurement process of metal structure]
S109 of FIG. 4 is a displacement measurement process which measures the displacement which generate | occur | produces actually in the use condition which passed for a while after embedding with respect to the metal structure made into evaluation object.

  The method of measuring the displacement is determined, for example, based on the fixed point around the metal structure in the use state immediately after embedding, and the space coordinate 1 of the representative point of the specified part of the metal structure is determined by surveying Keep it. Then, in the use state after a while since embedding, the space coordinate 2 of the representative point is determined by surveying on the basis of the fixed point, and the length of the line segment 1 indicating the distance between the space coordinate 1 and the space coordinate 2 is actually generated There is a way to determine it as a moving displacement.

  Alternatively, there is a method in which the length of the line segment 2 obtained by projecting the line segment 1 onto the straight line indicating the direction in which the force is applied is displaced. As a surveying method, triangulation using a plurality of fixed points can be used. As the fixed point, it is possible to use a benchmark, a triangle, or a point set according to the benchmark or triangle used in surveying.

  Through the above steps, a point C (FIG. 2) representing the tensile load and displacement applied to the metal structure to be evaluated in the actual use state that has passed for a while after the embedding is obtained.

  In S110 of FIG. 4, the tensile load is taken along the vertical axis obtained in S103, and the curve A (FIG. 2) when displacement is taken along the horizontal axis, and the combination of the tensile load and the displacement in a used state a while after embedding is expressed. The positional relationship with the point C (FIG. 2) is compared.

  In S111 of FIG. 4, as described with reference to FIG. 2, when the position of the point C is below the curve A defined as the reference of the deterioration state, it may be evaluated that the metal structure is in the deterioration state. it can.

  The above-mentioned FIG. 3 is a figure which shows the tensile load or stress of sample B, and the relationship of distortion or displacement by making the rod which is a site | part which comprises a branch line anchor into sample B as an example of the metal structure which does not carry out thickness reduction processing. .

   The curve B may be obtained experimentally using a tensile tester or the like. However, if the material constituting the target region is a general material and the stress-strain curve is known, the known curve is represented by the curve B. It may be used as The tensile loads applied in normal use of the metal structure do not lead to a large strain reaching the plastic region, but in the range of strain in the elastic region. Therefore, stress and strain are in a proportional relationship, and when the material constituting the target portion is a general material, the curve B is replaced by the data of the known Young's modulus of the material, and the corresponding value is obtained from the strain. A stress value can be obtained, and the stress value can be converted into a tensile load from the shape (cross-sectional area) of the sample B.

[Embodiment as a system]
The present invention can also be implemented as an embodiment of a system implemented by a personal computer or the like.

  That is, the deterioration evaluation system for a metal structure of the present invention first applies a sample A obtained by reducing the thickness of a sample equivalent to the metal structure for a metal structure that is entirely or partially embedded in the ground. A curve A indicating the relationship between force and displacement based on the result of test A in which a force is applied by embedding and measuring the displacement according to the applied force is used as an index value (reference value) of the deterioration state of the metal structure. A recording unit A for recording is provided.

  The system also comprises a database unit that stores the stress-strain curve B of the metal structure or the Young's modulus of the metal material of the metal structure, and from the database unit, the stress-strain curve B or Young of the metal structure It has an interface unit that performs input and output to search rates.

  The present system is also equipped with an instrument for measuring the strain before embedding in the metal structure, and the strain value obtained as a result of measuring the strain in the use state after a while after embedding is used as the interface section. It has recording part C which records result C which is a group of the value of stress and displacement together with the result of performing the measurement of displacement under the condition of use where the value of the stress obtained by input has passed for a while after embedding. .

And this system is a degradation state evaluation system of the metal structure characterized by having a judgment part which compares curve A of the above-mentioned recording part A, and the above-mentioned result C, and judges a deterioration state of a metal structure. .

  As described above, in the evaluation method or the evaluation system according to the present embodiment, the metal structure to be entirely or partially embedded in the ground is first subjected to the thickness reduction process for the equivalent sample A. The sample A is embedded, and a load is applied to the embedded sample A. A test A is performed to test the displacement according to the applied force. Based on the curve A obtained, the sample A is deteriorated. Define judgment criteria.

  In addition, a force is applied to the sample B which is not subjected to the thickness reduction processing equivalent to the metal structure to be evaluated, and a test is performed to perform a test to measure strain according to the applied force. A curve B showing the relationship is obtained.

  Then, for the metal structure to be evaluated, strain and displacement are measured immediately after embedding and in use after a short time after embedding, and a combination of tensile load and displacement is obtained, and a combination of tensile load and displacement is displayed. The relationship between the point C of interest and the curve A is obtained. Thereby, the deterioration state of the underground metal structure can be evaluated.

  The embodiment of the deterioration state evaluation method and evaluation system for a metal structure to which the present invention has been applied has been described above.

  The present invention is not limited by the description and the drawings that form a part of the disclosure of the present invention according to the present embodiment. That is, other embodiments, examples, operation techniques and the like made by those skilled in the art based on the present embodiment are all included in the scope of the present invention.

401 Branch anchor 402 Rod 403 Strain gauge 404 Representative point

Claims (3)

Regarding metal structures that are completely or partially buried in the ground,
A processing step of performing a thinning process on the sample A equivalent to the metal structure;
A test A step of embedding the sample A and applying a force to the embedded sample A and performing a test of measuring a displacement according to the applied force;
Based on the result of the test A step, a recording A step for obtaining and recording a curve A indicating the relationship between force and displacement;
Defining the deterioration state based on the curve A;
A test B step of performing a test for applying a force to the sample B equivalent to the metal structure and measuring a strain according to the applied force;
Based on the result of the test B step, a recording B step for obtaining and recording a curve B indicating the relationship between force and strain,
A strain measurement process for measuring a strain in a use state which is provided for a while after the burying, provided with a device for measuring the strain before burying the metal structure;
For the metal structure, a displacement measurement step for measuring displacement in a use state that has passed for a while after the embedding, and
A degradation state evaluation method for a metal structure, characterized by comprising: For metal structures, all or part of which are buried underground
A processing step of performing a thinning process on the sample A equivalent to the metal structure;
A test A step of embedding the sample A and applying a force to the embedded sample A and performing a test of measuring a displacement according to the applied force;
Based on the result of the test A step, a recording A step for obtaining and recording a curve A indicating the relationship between force and displacement;
Defining the deterioration state based on the curve A;
A recording B ′ step of obtaining a Young's modulus for a metal material equivalent to the metal structure, obtaining a relationship between a force applied to the metal structure and a strain, and recording;
A strain measurement process for measuring a strain in a use state which is provided for a while after the burying, provided with a device for measuring the strain before burying the metal structure;
For the metal structure, a displacement measurement step for measuring displacement in a use state that has passed for a while after the embedding, and
A degradation state evaluation method for a metal structure, characterized by comprising: For a metal structure that is completely or partially buried in the ground, the sample A, which has been subjected to thickness reduction processing to a sample equivalent to the metal structure, is embedded and loaded with force, and displacement according to the applied force A recording unit A for recording a curve A indicating a relationship between force and displacement based on the result of the test A for measuring the value as an index value of the deterioration state of the metal structure,
A database unit for storing the stress-strain curve B of the metal structure or the Young's modulus of the metal material of the metal structure;
An interface unit for performing input / output for searching the stress-strain curve B or Young's modulus of the metal structure from the database unit;
An apparatus for measuring strain before embedding in the metal structure is provided, and a value of strain obtained as a result of measuring strain in a use state a while after embedding is obtained and input to the interface unit. A recording unit C for recording a result C, which is a combination of a stress and a displacement, by combining the value of the stress with the result of measuring the displacement in a use state which has passed for a while after the embedding,
A deterioration state evaluation system for a metal structure, comprising: a determination unit that compares the curve A of the recording portion A with the result C and determines the deterioration state of the metal structure.

Images