Method and system for evaluating the plastic deformation capacity of a component.

Abstract

To provide a method and a system for evaluating the plastic deformation capability of a member, in which the plastic deformation capability of the member can be appropriately evaluated.SOLUTION: An evaluation device 20 includes a control part 21 for evaluating the plastic deformation capability of the steel frame beam which is buckled and deformed by applying an external force. A control part 21 evaluates the plastic deformation capability by using the standard deviation of the strain distribution in an evaluation target region in a lower flange of the steel frame beam. In this case, the region, which is specified by a first length between more than or equal to half the beam height and less than or equal to the beam height of the steel beam and a second length corresponding to the width of the steel beam from a point where the steel beam joins to a pillar, is used as an evaluation object region.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a method and a system for evaluating the plastic deformation capacity of a member for evaluating the plastic deformation capacity of a member such as a steel frame member used in a building that undergoes buckling deformation.

Background Art

[0005] An evaluation method to solve the above problem is an evaluation method for evaluating the plastic deformation capacity of a member that buckles when an external force is applied, wherein the standard deviation of the strain distribution of the evaluation target area on the evaluation surface of the member is... Based on the external force when it falls within a predetermined range, The plastic deformation capacity is evaluated. [Effects of the Invention]

[0006] According to the present invention, the plastic deformation capacity of a component can be appropriately evaluated. [Brief explanation of the drawing]

[0007] [Figure 1] This is an explanatory diagram of the configuration of the evaluation device in the embodiment. [Figure 2] This is an explanatory diagram of an example hardware configuration of the evaluation device in the embodiment. [Figure 3] This is an explanatory diagram of a structure equipped with steel beams to be evaluated in the embodiment. [Figure 4] This is an explanatory diagram of the buckling deformation of a steel frame structure in an embodiment. [Figure 5] This is an explanatory diagram of the configuration of the test apparatus in the embodiment. [Figure 6] This graph shows the relationship between the steel frame members used in the test and the generalized width-to-thickness ratio in the embodiment. [Figure 7] This graph shows the range of beam member types identified from the values ​​based on the web and flange of the steel beam used in the test in the embodiment. [Figure 8]This is a cross-sectional view illustrating the dimensions of a steel beam used to specify the range of member types for the beam in the embodiment. [Figure 9] The standard deviation of the strain distribution measured by image correlation in the evaluation area of ​​the embodiment, and the image at that time, showing a small standard deviation, are shown. [Figure 10] The standard deviation of the strain distribution measured by image correlation method in the evaluation target area of ​​the embodiment, and the image at that time, showing a state where the standard deviation is large, are shown. [Figure 11] In the embodiment, the plastic deformation capacity of steel members with the same generalized width-to-thickness ratio is evaluated by standard deviation, and the results are shown below: (a) shows the case when member type is A, (b) shows the case when member type is B, and (c) shows the case when member type is C. [Figure 12] The graphs show the evaluation of the plastic deformation capacity of steel members with the same generalized width-to-thickness ratio using conventional technology, with (a) showing the case where member type is A, (b) showing the case where member type is B, and (c) showing the case where member type is C. [Modes for carrying out the invention]

[0008] Below, an embodiment of a method and system for evaluating the plastic deformation capacity of a structural member will be described using Figures 1 to 11. In this embodiment, the plastic deformation capacity of a steel beam that buckles under external force is evaluated. This evaluation uses the standard deviation of the strain distribution measured using the image correlation method. For this purpose, a random pattern is formed on the surface of the steel structural member to be evaluated, and images are taken while applying an external force (stress) to this member. As shown in Figure 1, in this embodiment, an evaluation device 20 is used to evaluate the plastic deformation capacity of a steel beam.

[0009] (Description of hardware configuration) Using FIG. 2, the hardware configuration of the information processing device H10 that constitutes the evaluation device 20 will be described. The information processing device H10 includes a communication device H11, an input device H12, a display device H13, a storage device H14, and a processor H15. Note that this hardware configuration is an example, and it is also possible to be realized by other hardware.

[0010] The communication device H11 is an interface that establishes a communication path with other devices and executes data transmission and reception, such as a network interface or a wireless interface.

[0011] The input device H12 is a device that accepts input of various information and input from users, etc., such as a mouse, a keyboard, a camera (imaging device), etc. The display device H13 is a display, a touch panel, etc. that display various information. The input device H12 constitutes at least a part of the input unit 15 described later, and the display device H13 constitutes at least a part of the output unit 16 described later.

[0012] The storage device H14 is a storage device that stores data and various programs for executing various functions of the evaluation device 20. Examples of the storage device H14 include a ROM, a RAM, a hard disk, etc.

[0013] The processor H15 controls each process in the evaluation device 20 (for example, the process in the control unit 21 described later) using the programs and data stored in the storage device H14. Examples of the processor H15 include a CPU, an MPU, etc. This processor H15 expands the program stored in the ROM, etc. to the RAM and executes various processes corresponding to various processes.

[0014] Processor H15 is not limited to performing software processing for all the processes it executes. For example, processor H15 may include a dedicated hardware circuit (e.g., an application-specific integrated circuit) that performs hardware processing for at least a part of the processes it executes. That is, processor H15 can be configured as circuitry including the following.

[0015] [1] One or more processors that operate according to a computer program (software) [2] One or more dedicated hardware circuits that execute at least a part of various processes [3] A combination thereof

[0016] The processor includes a CPU and memories such as a RAM and a ROM. The memories store program codes or instructions configured to cause the CPU to execute processes. The memory, i.e., the computer-readable medium, includes any available medium accessible by a general-purpose or dedicated computer.

[0017] (Configuration of steel structure) As shown in FIG. 3, in this embodiment, the plastic deformation capacity of the steel beam 32 that undergoes local buckling is evaluated. Here, a structure 30 in which the steel beam 32 is fixed by welding to the center of the column 31 is used. This steel beam 32 is an H-shaped steel and includes an upper flange 32a, a lower flange 32b, and a web 32f. The web 32f is attached to the central position (the position on the central axis) between the upper flange 32a and the lower flange 32b. Then, as shown in FIG. 4, the steel beam 32 of this embodiment undergoes local buckling due to an external force.

[0018] (Functions of evaluation device 20) Next, each function of the evaluation device 20 will be described using FIG. 1. The evaluation device 20 is a computer system that measures the standard deviation of the strain distribution in the evaluation target area of the evaluation target member. This evaluation device 20 is connected to an input unit 15 and an output unit 16.

[0019] The input unit 15 acquires information about the member to be evaluated (generalized width-to-thickness ratio, material, etc.) and images of the subject (evaluation target area) acquired by the image correlation method. In this embodiment, the image correlation method acquires images taken before the application of the external force and images taken consecutively at different times during the application of the external force.

[0020] Then, the output unit 16 outputs the evaluation results obtained by image processing of the captured image by the evaluation device 20. Here, the standard deviation of the strain distribution is obtained as an evaluation result. The evaluation device 20 comprises a control unit 21, an image information storage unit 25, and a component information storage unit 26.

[0021] The control unit 21 performs the processes described later (including the evaluation management stage, strain measurement stage, and standard deviation calculation stage). By executing programs for each of these processes, the control unit 21 functions as the evaluation management unit 211, the strain measurement unit 212, and the standard deviation calculation unit 213, etc.

[0022] The evaluation management unit 211 performs processing to manage information on the components to be evaluated and images taken of the evaluation area. The strain measurement unit 212 performs a process to evaluate the displacement of the surface of the evaluation target area (the surface of the object being evaluated) using the image correlation method. This strain measurement unit 212 measures, for example, the change in position (displacement) of measurement points arranged in a random pattern formed on the evaluation target area (surface) in a series of images taken over time. In this embodiment, the strain in two dimensions (width direction and axial direction) of the surface is determined from the surface displacement (strain) measured based on images taken at different times. The standard deviation calculation unit 213 calculates the standard deviation of the strain calculated by the strain measurement unit 212 in the evaluation target area.

[0023] The image information storage unit 25 stores image management data for images taken of the object to be evaluated. This image management data is recorded when an image is acquired from the input unit 15. The image management data consists of data relating to the object to be evaluated identifier, image identifier, timestamp, captured image, area range, strain distribution, and standard deviation.

[0024] The evaluation target identifier data area stores data related to identifiers used to identify each evaluation target. The image identifier data area records data related to identifiers used to identify each captured image of the object being evaluated.

[0025] The timestamp data area records data related to the time the image was taken. The image data area records images of the object being evaluated. The region range data area records data relating to the coordinates that define the range of the evaluation area in the captured image. This evaluation area is the range specified in the initial image before the application of external force, and the corresponding range is identified in the image used for the image correlation method.

[0026] The strain distribution data area records data on the strain distribution measured using the image correlation method. This strain distribution is the strain distribution for a state where the strain is "0" before the application of external force (before the loading test), and is calculated based on the displacement in each captured image. The standard deviation data region records data regarding the standard deviation of the strain distribution within the region in this captured image.

[0027] The component information storage unit 26 stores data relating to the detailed information of the component to be evaluated. This component information data is recorded when information about the component to be evaluated is obtained from the input unit 15. The component information data consists of data relating to the object to be evaluated identifier, dimensions, material, generalized width-to-thickness ratio, type, and maximum load-bearing capacity.

[0028] The evaluation target identifier data area contains data related to an identifier used to identify each evaluation target. This evaluation target identifier links component information data and image management data.

[0029] The dimension data area and material data area record data regarding the dimensions (size) and material of the object (component) being evaluated. The generalized width-to-thickness ratio data area records data related to the generalized width-to-thickness ratio of the object being evaluated. Here, the generalized width-to-thickness ratio for the flange and web is recorded.

[0030] The type data area records data that identifies the type of the member being evaluated, according to its generalized width-to-thickness ratio. The maximum load-bearing capacity data area records data related to the maximum load-bearing capacity of the member being evaluated. In this embodiment, this maximum load-bearing capacity is recorded by identifying the load at which the standard deviation of the strain distribution identified from the image using the image correlation method is 1%.

[0031] (Configuration of the test apparatus) Figure 5 shows a test apparatus 40 that applies force to the structure 30 shown in Figure 3. The test apparatus 40 is equipped with the structure 30 having the configuration described above. In this case, the column 31 of the structure 30 is positioned at the lower end, and the steel beam 32 is positioned to extend upward. Here, the column 31 is fixed at both ends at distances L1 from the central axis C1 of the steel beam 32. An out-of-plane restraint member 36 is provided at a distance L2 (=1200 mm) from the beam end on the column 31 side. Furthermore, one end of a load-bearing jack 41 is fixed at a distance L3 (=3375 mm) from the beam end. The load-bearing jack 41 is positioned so that the direction of extension of its central axis C2 is perpendicular to the direction of extension of the central axis C1 of the steel beam 32. The other end of the load-bearing jack 41 is fixed to a wall W1 or the like. In its natural state, the load-bearing jack 41 is positioned so that the central axis C1 of the steel beam 32 extends vertically. The load jack 41 vibrates the steel beam 32 by repeatedly applying the same load Q in the positive direction (pushing the steel beam 32 away from the wall W1) and the negative direction (pulling the steel beam 32 toward the wall W1) a predetermined number of times in the direction of extension of the central axis C2.

[0032] In this embodiment, for example, a square steel pipe with a plate thickness of 25 mm and dimensions of 450 mm in length and width is used as the column 31. Also, as will be described later, all steel beams 32 used as test specimens have a flange width B1 of 600 mm. The evaluation is performed using an image taken from arrow V1, from the lower flange 32b of the steel beam 32 to a distance L5 from the end of the column 31. This image includes the evaluation target area A1 on the lower flange 32b of the steel beam 32. In this embodiment, the lower flange 32b corresponds to the evaluation surface. Furthermore, the evaluation target area A1 is a rectangular area composed of the distance from the end of the steel beam 32 (where the steel beam 32 is joined to the column 31) to half the beam depth D1 of the steel beam 32 (first length) and the flange width B1 (second length).

[0033] (Evaluation method for steel beam 32) Next, the evaluation method for the steel beam 32 of this embodiment will be described. In this embodiment, the steel beam 32 with the dimensions and materials shown in Figure 6 is used. In this case, the generalized width-to-thickness ratios for the flange and web are 0.24 and 1.5 for type A, 0.27 and 1.5 for type B, and 0.18 and 2.0 for type C.

[0034] As shown in Figure 7, types A and B in Figure 6 are located within beam member type FA, while type C in Figure 6 is located at the boundary between beam member types FA and FB. Here, the beam member type refers to the beam member type shown in the Building Standards Act related notification "Showa 55 Kenko No. 1792".

[0035] As shown in Figures 6 to 8, B1 is the flange width of the steel beam 32, b1 is the half width of the flange of the steel beam 32, D1 is the beam depth, d1 is the web depth, tf is the flange thickness, tw is the web thickness, F is the F-value of the material (steel), and E is the Young's modulus of the material (steel). The F-value of the steel is 235 N / mm² for SS400 material (400N steel). 2 For SN490B material (490N steel), the load capacity is 325 N / mm². 2 TMCP385 material (550N steel) has a rating of 550 N / mm 2 The Young's modulus is 205 kN / mm². 2 That is the case.

[0036] Then, various steel beams 32 shown in Figure 6 were installed in the test apparatus 40 described above, and a loading test was conducted. Before and during this loading test, the standard deviation of the strain distribution was calculated using an image correlation method with images taken of the evaluation target area A1 on the lower flange 32b.

[0037] Figures 9 and 10 show images taken during the loading test, as well as the strain distribution and standard deviation calculated from each image. Figure 9 shows the case where buckling is small, and the standard deviation of the strain distribution of the lower flange 32b is 0.11%. Figure 10 shows the case where buckling is large, and the standard deviation of the strain distribution of the lower flange 32b is 6.74%.

[0038] In the image captured in Figure 10, it can be seen that the surface of the lower flange 32b is significantly wavy. Furthermore, Figures 11(a) to (c) show the ratio of load Q to maximum load Qmax (normalized load) according to the standard deviation of the strain distribution on the surface of the lower flange 32b. Figures 11(a) to (c) show the normalized loads of types A to C shown in Figure 6, respectively. The circles, triangles, and squares on the line in Figure 11 indicate the standard deviation when the normalized load is "1".

[0039] In other words, Figure 11 shows that for all three materials (400N steel, 490N steel, and 550N steel), the maximum load Qmax occurs when the standard deviation is around 1%. Therefore, the load at which the standard deviation is approximately 1% (0.4% to 1.2%) can be evaluated as the maximum load-bearing capacity of the member.

[0040] Furthermore, the standard deviation at maximum load falls within the ranges of "0.5% to 1.2%" for type A (Figure 11(a)), "0.4% to 0.9%" for type B (Figure 11(b)), and "0.8% to 1.2%" for type C (Figure 11(c)). In other words, unlike when using the plasticity ratio, when the generalized width-to-thickness ratio is the same, the range of variation in the standard deviation at maximum load is narrower, allowing for a more appropriate evaluation of the maximum load-bearing capacity.

[0041] (action) In cases of localized buckling, the strain distribution becomes highly biased. By evaluating this bias using the standard deviation of the strain distribution, the plastic deformation capacity (maximum load-bearing capacity) can be assessed.

[0042] According to this embodiment, the following effects can be obtained. (1) In this embodiment, the maximum load-bearing capacity of the steel beam 32 is reached when the standard deviation of the strain distribution on the surface of the lower flange 32b of the steel beam 32 being evaluated is approximately 1%. Therefore, the plastic deformation capacity of the locally buckling steel beam 32 can be accurately evaluated using the standard deviation.

[0043] (2) In this embodiment, the evaluation area A1 of the steel beam 32 is a rectangular area formed by the flange width B1 and the distance from the column end of the steel beam 32 to half the beam depth D1 of the steel beam 32. Normally, displacements leading to local buckling can be observed in the range from the column end of the steel beam 32 to the beam depth D1, but the plastic deformation capacity of the steel beam 32 can be accurately evaluated using the standard deviation of the strain distribution in a narrow area of ​​half the beam depth D1.

[0044] (3) In this embodiment, the standard deviation of the strain distribution of each member is calculated using an image correlation method with images captured when a load test is performed in the test apparatus 40. This makes it possible to appropriately evaluate the plastic deformation capacity of newly generated materials using the standard deviation in the future.

[0045] This embodiment can be implemented with the following modifications. This embodiment and the following modifications can be combined with each other to the extent that they do not contradict each other technically. In the above embodiment, the evaluation target area A1 of the steel beam 32 was a rectangular area composed of the flange width B1 and the distance from the column end of the steel beam 32 to half the beam depth D1 of the steel beam 32. The evaluation target area for calculating the standard deviation of the strain distribution is not limited to this. For example, it may be a rectangular area composed of the distance from the column end of the steel beam 32 to the beam depth D1 of the steel beam 32 (first length) and the flange width B1 (second length). Alternatively, the first length may be the length from the column end to half the beam depth D1 of the steel beam 32 to the beam depth D1 (length in the range of D1 / 2 to D1). Furthermore, in the evaluation target area, instead of the flange width B1, the second length may be the size of the flange width excluding the end portion (length after subtracting a predetermined distance from the end).

[0046] In the above embodiment, a structure 30 equipped with steel beams 32 was installed in the test apparatus 40, and the standard deviation of the strain distribution of the steel beams 32 was calculated using the image correlation method. The standard deviation of the strain distribution is not limited to being calculated based on values ​​measured by actually applying external force in the test apparatus 40, but may also be calculated by simulation using, for example, finite element analysis.

[0047] In the above embodiment, the plastic deformation capacity of the steel beam 32 was evaluated using the load at which the standard deviation of the strain distribution of the steel beam 32 was 1% as the maximum load-bearing capacity. The plastic deformation capacity is not limited to being evaluated using the load at which the standard deviation of the strain distribution is 1%. For example, as shown in Figure 11, the maximum load-bearing capacity may be set to a load within a predetermined range (around 1%) relative to 1%, determined according to the generalized width-to-thickness ratio. Alternatively, the plastic deformation capacity may be evaluated from the standard deviation corresponding to the generalized width-to-thickness ratio, or from the standard deviation identified according to the experimental results described above. Furthermore, the plastic deformation capacity may also be evaluated using a conversion formula calculated using the normalized load or the load value. In the above embodiment, a steel beam 32 was used as the member to be evaluated. The member to be evaluated is not limited to the steel material of the steel beam 32, but can be any material that exhibits local buckling.

[0048] Next, the technical concepts that can be understood from the above embodiments and alternative examples are described below. (a) The evaluation method according to claim 1 or 2, characterized in that the yield strength of the member when the standard deviation is 1% is evaluated as the elastic yield strength of the member as the plastic deformation capacity. [Explanation of Symbols]

[0049] A1...Evaluation target area, B1...Flange width, C1, C2...Center axis, H10...Information processing device, H11...Communication device, H12...Input device, H13...Display device, H14...Storage device, H15...Processor, L1, L2, L3, L5...Distance, W1...Wall, 15...Input unit, 16...Output unit, 20...Evaluation device, 21...Control unit, 25...Image information storage unit, 26...Component information storage unit, 30...Structure, 31...Column, 32...Steel beam, 32a...Upper flange, 32b...Lower flange, 32f...Web, 36...Out-of-plane restraint member, 40...Testing device, 41...Loading jack, 211...Evaluation management unit, 212...Measurement unit, 213...Standard deviation calculation unit.

Claims

1. An evaluation method for evaluating the plastic deformation capacity of a member that undergoes buckling deformation when an external force is applied, An evaluation method characterized by evaluating the plastic deformation capacity based on the external force at which the standard deviation of the strain distribution of the area to be evaluated on the evaluation surface of the member falls within a predetermined range.

2. The aforementioned member is a steel beam, The evaluation method according to claim 1, characterized in that the evaluation target area is an area defined by a first length from the point where the steel beam is joined to the column, between more than half the beam depth of the steel beam and less than or equal to the beam depth, and a second length corresponding to the width of the steel beam.

3. The evaluation method according to claim 1 or 2, characterized in that the standard deviation is determined by an image correlation method using captured images obtained for the evaluation target area while the member is being vibrated.

4. An evaluation system comprising a control unit for evaluating the plastic deformation capability of a member that undergoes buckling deformation when an external force is applied, The control unit, An evaluation system characterized by evaluating the plastic deformation capacity based on the external force at which the standard deviation of the strain distribution of the area to be evaluated on the evaluation surface of the member falls within a predetermined range.

Images