Bridge crack 3D construction system and method

Abstract

The present invention provides a system and method for constructing three-dimensional bridge cracks. The system includes a crack status display layer fixed to the outer surface of the bridge, and a sensing fiber arranged on the outer surface of the crack status display layer. When a crack appears at a corresponding location on the bridge, strain occurs at the corresponding location on the sensing fiber, and the crack status at the corresponding location on the crack status display layer changes accordingly. A strain measurement system measures the strain on the sensing fiber, determines the location on the sensing fiber where the strain change occurred, and transmits the location information and the corresponding strain magnitude to a data processing device. The data processing device determines image information corresponding to the location based on the location information and image information captured by an image acquisition device, indicating the crack status at the location on the crack status display layer. Based on the corresponding strain magnitude and image information, the data processing device determines the relative positional relationship between the two sides of the crack in three-dimensional space. The present invention provides a simple three-dimensional crack construction method.

Description

Technical Field

[0001] The present invention belongs to the field of bridge crack detection, and in particular relates to a three-dimensional construction system and method for bridge cracks. Background Art

[0002] With the rapid development of society, bridges, as a vital piece of infrastructure, are increasing in number. Over time, bridges are subject to environmental erosion and vehicle pressure, causing cracks to form. Cracks are crucial to bridge safety, and crack monitoring has become a key indicator for bridge health monitoring. Traditionally, bridge crack monitoring involves on-site monitoring personnel using monitoring equipment such as crack width gauges placed close to the surface of the bridge structure to conduct manual monitoring and recording. This approach not only results in long monitoring cycles, low efficiency, and large monitoring errors, but also makes it difficult to visually determine the location of cracks on the bridge, impacting the efficiency of subsequent bridge maintenance.

[0003] To this end, image recognition technology has recently been proposed for identifying and monitoring bridge cracks. However, this approach typically requires pre-established models and image processing, making it complex. Furthermore, the resulting cracks are constructed with the sides aligned on the same plane, meaning they can only be positioned relative to each other in the left-right direction. In reality, cracks can shift not only in the left-right direction but also in the up-down and front-back directions. The three-dimensional crack morphology constructed using existing techniques cannot accurately reconstruct the three-dimensional shape of the cracks, effectively limiting their relative positional relationship in three-dimensional space. Summary of the Invention

[0004] The present invention provides a three-dimensional construction system and method for bridge cracks to solve the problem that the current method requires building a model to construct bridge cracks in three dimensions, which is relatively complicated and the constructed three-dimensional shape of the bridge crack cannot reflect the relative position relationship between the two sides of the crack in three-dimensional space.

[0005] According to a first aspect of an embodiment of the present invention, a three-dimensional bridge crack construction system is provided, comprising an image acquisition device, a sensing fiber, a strain measurement system, and a data processing device. A crack status display layer is fixed to the outer surface of the bridge, and the sensing fiber is arranged on the outer surface of the crack status display layer. When a crack appears at a corresponding position on the bridge, strain occurs at the corresponding position of the sensing fiber, and the crack state at the corresponding position of the crack status display layer changes accordingly. The strain measurement system measures the strain on the sensing fiber, determines the corresponding position on the sensing fiber where the strain change occurs, and transmits the position information and the strain corresponding to the position to the data processing device.

[0006] The data processing device determines the image information corresponding to the position based on the crack state of the position corresponding to the crack state display layer in the image information collected by the image collection device; and determines the relative position relationship between the two sides of the crack in three-dimensional space based on the strain size and image information corresponding to the position.

[0007] In an optional implementation, the crack state display layer includes an elastic layer and two stripe line combinations coated on the elastic layer. The elastic layer is fixed to the bridge, and the sensing optical fiber is fixed to the elastic layer. The two stripe line combinations are respectively located on the upper and lower sides of the sensing optical fiber, and each stripe line combination is composed of multiple side-by-side strip lines, and each strip line is perpendicular to the arrangement direction of the stripe line combination.

[0008] The crack state includes the closing and separation states of the strip lines in the combination of two strip lines on the elastic layer. When the strip lines in the combination of two strip lines are in the closing state, it indicates that no cracks appear on the bridge, or cracks appear but the two sides of the crack only undergo a front-to-back relative displacement. When the strip lines in the combination of two strip lines are in the separation state, it indicates that the two sides of the crack only undergo a left-right relative displacement, or both left-right relative displacement and up-down relative displacement occur simultaneously.

[0009] In another optional implementation, the elastic layer is a rubber layer, and in an initial state, the arrangement directions of the two strip line combinations are both parallel to the sensing optical fiber.

[0010] According to a second aspect of an embodiment of the present invention, a method for constructing a three-dimensional bridge crack is provided, which is applied to the above-mentioned three-dimensional bridge crack construction system, comprising:

[0011] Step S100: The strain measurement system detects the strain magnitude on the sensing optical fiber, determines the corresponding position where the strain changes on the sensing optical fiber, and sends the position information and the strain magnitude corresponding to the position to a data processing device;

[0012] Step S200: The data processing device determines the image information corresponding to the position based on the crack state of the position corresponding to the crack state display layer in the image information collected by the image collection device;

[0013] Step S300: The data processing device determines the relative position relationship between two sides of the crack in three-dimensional space according to the strain magnitude and image information corresponding to the position.

[0014] In an optional implementation, the crack state includes the closing and separation states of the strip lines in the combination of two strip lines of the crack state display layer, and the step S200 specifically includes:

[0015] Step S210: The data processing device drives the image acquisition device to move to the vicinity of the position according to the position information, and roughly adjusts the acquisition position of the image acquisition device;

[0016] Step S220: The data processing device drives the image acquisition device to search within a set range to the left and right of the current position, and determines whether there are strip lines in a separated state in the image returned by the image acquisition device. After finding the strip lines in the separated state, image acquisition is performed so that all the strip lines in the separated state are located in the acquired image, and the acquired image is used as the image information corresponding to the position.

[0017] In another optional implementation, in step S220, if a strip line in a separated state is found, step S300 specifically includes:

[0018] Step S310: For a stripe line combination located on the sensing optical fiber, the upper leftmost pixel point or the lower leftmost pixel point of the stripe line in the stripe line combination that is in a separated state is used as the first pixel point; the upper rightmost pixel point or the lower rightmost pixel point of the stripe line in the stripe line combination that is in a separated state is used as the second pixel point;

[0019] Step S320: For the stripe line combination located below the sensing optical fiber, determine the third pixel point corresponding to the first pixel point as the upper rightmost pixel point or the lower rightmost pixel point of the stripe line in the separated state in the stripe line combination; determine the fourth pixel point corresponding to the second pixel point as the upper leftmost pixel point or the lower leftmost pixel point of the stripe line in the separated state in the stripe line combination;

[0020] Step S330: Connect the first pixel point and the third pixel point to obtain a first length L1, and connect the second pixel point and the fourth pixel point to obtain a second length L2. Assume that the left-right relative displacement of the two sides of the crack is Δx, that is, the left-right lateral change of the stripe line is Δx, and the up-down relative displacement of the two sides of the crack is Δy, that is, the up-down vertical change of the stripe line is Δx. In the initial state, the vertical distance between the two stripe lines is L0, then establish the equation:

[0021]

[0022] Solve for Δx and Δy;

[0023] Step S340: Determine the left-right strain and the top-bottom strain of the sensing optical fiber segment at the position corresponding to the fringe line combination based on Δx and Δy;

[0024] Step S350 : Subtract the left-right strain and the up-down strain from the detected strain at the position on the sensing fiber segment to obtain the strain caused by the front-back relative displacement of the crack, thereby determining the front-back relative displacement Δz of the crack.

[0025] In another optional implementation, in step S220, if no strip line in a separated state is found, step S300 specifically includes: determining the relative displacement Δz before and after the crack occurs based on the strain magnitude detected at the position on the sensing fiber segment.

[0026] In another optional implementation, the relative distance between the image acquisition device and the crack status display layer is equal during each acquisition.

[0027] The beneficial effects of the present invention are:

[0028] 1. The present invention provides a crack state display layer and a sensing fiber, so that when the relative position of the two sides of the crack in three-dimensional space changes, the crack state on the crack state display layer and the strain on the sensing fiber both change. An image acquisition device is used to capture a two-dimensional plane image of the crack state, and the two-dimensional plane image reflects the relative displacement of the two sides of the crack in the left-right and up-down directions. After determining the relative displacement of the two sides of the crack in the left-right and up-down directions, the relative displacement of the two sides of the crack in the front-to-back direction is determined based on the strain on the sensing fiber. In this way, the present invention can construct a three-dimensional crack morphology without pre-establishing a model. The method is very simple, and the constructed three-dimensional crack morphology can reflect the relative positional relationship of the two sides of the crack in three-dimensional space.

[0029] 2. In the present invention, two strip line combinations are provided on the elastic layer in the crack state display layer. By utilizing the relative position relationship of the two strip line combinations, the relative displacement of the two sides of the crack in the left-right and up-down directions can be accurately determined. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 This is a schematic structural diagram of an embodiment of the system for constructing three-dimensional bridge cracks according to the present invention;

[0031] Figure 2 1 is a schematic structural diagram of an embodiment of a crack state display layer of the present invention;

[0032] Figure 3 Schematic diagram of three states of the crack state display layer of the present invention;

[0033] Figure 4 It is a schematic diagram for determining the relative displacement of the two sides of the crack up and down and left and right;

[0034] Figure 5This is a flow chart of an embodiment of the method for constructing three-dimensional bridge cracks of the present invention. DETAILED DESCRIPTION

[0035] In order to enable those skilled in the art to better understand the technical solutions in the embodiments of the present invention and to make the above-mentioned purposes, features and advantages of the embodiments of the present invention more obvious and easy to understand, the technical solutions in the embodiments of the present invention are further described in detail below with reference to the accompanying drawings.

[0036] In the description of the present invention, unless otherwise specified and limited, it should be noted that the term "connection" should be understood in a broad sense. For example, it can be a mechanical connection or an electrical connection, or it can be the internal connection between two elements. It can be a direct connection or an indirect connection through an intermediate medium. For ordinary technicians in this field, the specific meaning of the above terms can be understood according to the specific circumstances.

[0037] See also Figure 1 , is a schematic structural diagram of an embodiment of a bridge crack 3D construction system according to the present invention. This underground event location and monitoring system may include an image acquisition device, a sensing fiber 1, a strain measurement system, and a data processing device. A crack status display layer 3 is fixed to the outer surface of a bridge 2, and the sensing fiber 1 is arranged on the outer surface of the crack status display layer 3. When a crack appears at a corresponding location on the bridge 2, strain occurs at the corresponding location on the sensing fiber 1, and the crack status at the corresponding location on the crack status display layer 3 changes accordingly. The strain measurement system measures the strain on the sensing fiber 1, determines the location on the sensing fiber 1 where the strain change occurs, and transmits this location information and the corresponding strain magnitude to the data processing device. The data processing device determines image information corresponding to the location based on this location information and the crack status at the location on the crack status display layer in the image information captured by the image acquisition device. Based on the strain magnitude and image information corresponding to the location, the data processing device determines the relative positional relationship between the two sides of the crack in three-dimensional space.

[0038] In this embodiment, the sensing optical fiber 1 can be connected to the input end of the strain measurement system, the output end of the strain measurement system is connected to the first end of the data processing device, and the image acquisition device is connected to the second end of the data processing device. The strain measurement system can be an OFDR optical frequency domain reflectometer measurement system, and the camera direction of the image acquisition device can be perpendicular to the bridge 2 (i.e., perpendicular to the crack state display layer 3). Figure 2 and Figure 3As shown, the crack state display layer 3 may include an elastic layer 31 and two stripe line combinations 32 coated on the elastic layer 31, the elastic layer 31 is fixed on the bridge 2, the sensing optical fiber 1 is fixed on the elastic layer 31, the two stripe line combinations 32 are respectively located on the upper and lower sides of the sensing optical fiber 1, and each stripe line combination 32 is composed of a plurality of side-by-side strip lines 33, each strip line 33 is perpendicular to the setting direction of its stripe line combination 32, the crack state may include the closing and separation states of the stripe lines 33 in the two stripe line combinations 32 on the elastic layer 31, wherein when the stripe lines 33 in the two stripe line combinations 32 are in the closing state, it indicates that there is no crack on the bridge or there is a crack but the two sides of the crack only undergo a relative displacement forward and backward, as shown in FIG. Figure 3 (a); when the two strip line combinations 32 in the strip line 33 are in a separated state, it means that the two sides of the crack only have a relative displacement to the left and right, as shown in FIG. Figure 3 (b), or the left-right relative displacement and the up-down relative displacement occur simultaneously, as shown in Figure 3 (c) The elastic layer 31 may be a rubber layer, and in the initial state, the two strip line assemblies 32 may be arranged in directions parallel to the sensing optical fiber 1, and the strip lines in the strip line assembly 32 may be equal.

[0039] Since the crack state display layer and the sensing optical fiber will change as the relative positional relationship of the two sides of the crack in three-dimensional space changes, when the camera direction of the image sampling device is perpendicular to the crack state display layer and the crack state on the crack state display layer is captured, the relative displacement of the two sides of the crack in the left-right and up-down directions can actually be determined based on a strip line combination. For example, the strip line combination in the currently captured image can be compared with the strip line combination in the image captured in the initial state. If the strip line combination in the current image is not tilted and the strip lines are in a separated state, it can be determined that the two sides of the crack have undergone relative displacement in the left-right direction, but not in the up-down direction. If the strip line combination in the current image is tilted and the strip lines are in a separated state, it can be determined that the two sides of the crack have undergone relative displacement in both the left-right and up-down directions. However, before determining the relative displacement of the two sides of the crack, the two images at different times need to be aligned. The alignment process is relatively complicated and reduces the accuracy of the relative displacement determination. To this end, the present invention provides two strip line combinations on the elastic layer in the crack state display layer. The relative position relationship of the two strip line combinations can be used to accurately determine the relative displacement of the two sides of the crack in the left and right and up and down directions.

[0040] Specifically, combined Figure 4As shown, when the stripe line is in a separated state, for the stripe line combination located on the sensing optical fiber, the upper leftmost pixel point or the lower leftmost pixel point of the stripe line in the separated state in the stripe line combination is used as the first pixel point; the upper rightmost pixel point or the lower rightmost pixel point of the stripe line in the separated state in the stripe line combination is used as the second pixel point;

[0041] For a stripe line combination located below the sensing optical fiber, determining a third pixel point corresponding to the first pixel point as: the upper rightmost pixel point or the lower rightmost pixel point of the stripe line in the separated state in the stripe line combination; determining a fourth pixel point corresponding to the second pixel point as: the upper leftmost pixel point or the lower leftmost pixel point of the stripe line in the separated state in the stripe line combination;

[0042] Connect the first pixel point with the third pixel point to obtain a first length L1, and connect the second pixel point with the fourth pixel point to obtain a second length L2. Assume that the left-right relative displacement of the two sides of the crack is Δx, that is, the left-right lateral change of the stripe line is Δx, and the up-down relative displacement of the two sides of the crack is Δy, that is, the up-down vertical change of the stripe line is Δx. In the initial state, the up-down distance between the two stripe lines is L0, then establish the equation:

[0043]

[0044] Solve for Δx and Δy.

[0045] After determining the relative displacements Δx and Δy of the two sides of the crack in the left-right and up-down directions, the left-right strain and up-down strain of the sensing fiber segment at the corresponding position of the stripe line combination can be determined based on Δx and Δy; the left-right strain and up-down strain are subtracted from the detected strain at that position on the sensing fiber segment to obtain the strain caused by the relative displacement before and after the crack occurs, thereby determining the relative displacement Δz of the crack before and after the crack occurs.

[0046] As can be seen from the above embodiments, the present invention provides a crack state display layer and a sensing optical fiber, so that when the relative positions of the two sides of the crack in three-dimensional space change, the crack state on the crack state display layer and the strain on the sensing optical fiber both change. The image acquisition device is used to acquire a two-dimensional plane image of the crack state, and the two-dimensional plane image reflects the relative displacement of the two sides of the crack in the left and right and up and down directions. After determining the relative displacement of the two sides of the crack in the left and right and up and down directions, the relative displacement of the two sides of the crack in the front-to-back direction is determined according to the strain on the sensing optical fiber. Therefore, the present invention can construct the three-dimensional shape of the crack without pre-establishing a model. The method is very simple, and the constructed three-dimensional shape of the crack can reflect the relative position relationship of the two sides of the crack in three-dimensional space.

[0047] Also, see Figure 5 The present invention also provides a three-dimensional construction method for bridge cracks, which is applied to the above-mentioned three-dimensional construction system for bridge cracks. The method may include:

[0048] Step S100: The strain measurement system detects the strain magnitude on the sensing optical fiber, determines the corresponding position where the strain changes on the sensing optical fiber, and sends the position information and the strain magnitude corresponding to the position to a data processing device;

[0049] Step S200: The data processing device determines the image information corresponding to the position based on the crack state of the position corresponding to the crack state display layer in the image information collected by the image collection device;

[0050] Step S300: The data processing device determines the relative position relationship between two sides of the crack in three-dimensional space according to the strain magnitude and image information corresponding to the position.

[0051] The crack state may include the close-together and separate states of the strip lines in the combination of two strip lines of the crack state display layer. The step S200 specifically includes:

[0052] Step S210: The data processing device drives the image acquisition device to move to the vicinity of the position according to the position information, and roughly adjusts the acquisition position of the image acquisition device;

[0053] In step S220, the data processing device drives the image acquisition device to search within a set range to the left and right of the current position, and determines whether the image returned by the image acquisition device contains any separated strip lines. After finding any separated strip lines, the device performs image acquisition so that all separated strip lines are located within the acquired image, and uses the acquired image as the image information corresponding to the position. The image acquisition device maintains a constant relative distance from the crack status display layer during each acquisition, ensuring that each acquired image has the same reference standard.

[0054] In step S220, if a strip line in a separated state is found, step S300 may specifically include:

[0055] Step S310: For a stripe line combination located on the sensing optical fiber, the upper leftmost pixel point or the lower leftmost pixel point of the stripe line in the stripe line combination that is in a separated state is used as the first pixel point; the upper rightmost pixel point or the lower rightmost pixel point of the stripe line in the stripe line combination that is in a separated state is used as the second pixel point;

[0056] Step S320: For the stripe line combination located below the sensing optical fiber, determine the third pixel point corresponding to the first pixel point as the upper rightmost pixel point or the lower rightmost pixel point of the stripe line in the separated state in the stripe line combination; determine the fourth pixel point corresponding to the second pixel point as the upper leftmost pixel point or the lower leftmost pixel point of the stripe line in the separated state in the stripe line combination;

[0057] Step S330: Connect the first pixel point and the third pixel point to obtain a first length L1, and connect the second pixel point and the fourth pixel point to obtain a second length L2. Assume that the left-right relative displacement of the two sides of the crack is Δx, that is, the left-right lateral change of the stripe line is Δx, and the up-down relative displacement of the two sides of the crack is Δy, that is, the up-down vertical change of the stripe line is Δx. In the initial state, the vertical distance between the two stripe lines is L0, then establish the equation:

[0058]

[0059] Solve for Δx and Δy;

[0060] Step S340: Determine the left-right strain and the top-bottom strain of the sensing optical fiber segment at the position corresponding to the fringe line combination based on Δx and Δy;

[0061] Step S350 : Subtract the left-right strain and the up-down strain from the detected strain at the position on the sensing fiber segment to obtain the strain caused by the front-back relative displacement of the crack, thereby determining the front-back relative displacement Δz of the crack.

[0062] In the step S220 , if no separated strip line is found, the step S300 may specifically include determining a front-to-rear relative displacement Δz of the crack according to the detected strain at the position on the sensing fiber segment.

[0063] As can be seen from the above embodiments, the present invention provides a crack state display layer and a sensing optical fiber, so that when the relative positions of the two sides of the crack in three-dimensional space change, the crack state on the crack state display layer and the strain on the sensing optical fiber both change. The image acquisition device is used to acquire a two-dimensional plane image of the crack state, and the two-dimensional plane image reflects the relative displacement of the two sides of the crack in the left and right and up and down directions. After determining the relative displacement of the two sides of the crack in the left and right and up and down directions, the relative displacement of the two sides of the crack in the front-to-back direction is determined according to the strain on the sensing optical fiber. Therefore, the present invention can construct the three-dimensional shape of the crack without pre-establishing a model. The method is very simple, and the constructed three-dimensional shape of the crack can reflect the relative position relationship of the two sides of the crack in three-dimensional space.

[0064] Other embodiments of the present invention will readily occur to those skilled in the art after considering the specification and practicing the invention disclosed herein. This application is intended to cover any variations, uses, or adaptations of the present invention that follow the general principles of the invention and include common knowledge or customary techniques in the art not disclosed herein. The description and examples are to be considered as exemplary only, with the true scope and spirit of the invention being indicated by the following claims.

[0065] It will be appreciated that the present invention is not limited to the precise construction that has been described above and shown in the accompanying drawings, and that various modifications and variations can be made without departing from its scope, which is governed solely by the appended claims.

Claims

1. A three-dimensional construction system for bridge cracks, characterized by: The system comprises an image acquisition device, a sensing fiber, a strain measurement system, and a data processing device. A crack status display layer is fixed to the outer surface of the bridge, and the sensing fiber is arranged on the outer surface of the crack status display layer. When a crack appears at a corresponding position on the bridge, strain occurs at the corresponding position of the sensing fiber, and the crack status at the corresponding position of the crack status display layer changes accordingly. The strain measurement system measures the strain on the sensing fiber, determines the corresponding position on the sensing fiber where the strain changes, and transmits the position information and the corresponding strain magnitude to the data processing device. The data processing device determines the image information corresponding to the position based on the position information and the crack state at the position corresponding to the crack state display layer in the image information collected by the image collection device; and determines the relative position relationship between the two sides of the crack in three-dimensional space based on the strain size corresponding to the position and the image information; The crack state display layer includes an elastic layer and two stripe line combinations coated on the elastic layer. The elastic layer is fixed to the bridge, and the sensing optical fiber is fixed to the elastic layer. The two stripe line combinations are respectively located on the upper and lower sides of the sensing optical fiber, and each stripe line combination is composed of a plurality of side-by-side strip lines, and each strip line is perpendicular to the arrangement direction of the stripe line combination. The crack state includes the states of the strip lines in the combination of two strip lines on the elastic layer being close together and being separated. When the strip lines in the combination of two strip lines are close together, it indicates that no cracks have occurred on the bridge, or cracks have occurred but the two sides of the crack have only undergone front-to-back relative displacement. When the strip lines in the combination of two strip lines are separated, it indicates that the two sides of the crack have only undergone left-to-right relative displacement, or have undergone both left-to-right and up-to-down relative displacement. The elastic layer is a rubber layer. In an initial state, the arrangement directions of the two strip line combinations are both parallel to the sensing optical fiber.

2. A three-dimensional construction method for bridge cracks, applied to the three-dimensional construction system for bridge cracks according to claim 1, characterized in that: include: Step S100: The strain measurement system detects the strain magnitude on the sensing optical fiber, determines the corresponding position where the strain changes on the sensing optical fiber, and sends the position information and the strain magnitude corresponding to the position to a data processing device; Step S200: The data processing device determines the image information corresponding to the position based on the crack state of the position corresponding to the crack state display layer in the image information collected by the image collection device; Step S300: The data processing device determines the relative position relationship between two sides of the crack in three-dimensional space according to the strain magnitude and image information corresponding to the position.

3. The three-dimensional construction method of bridge cracks according to claim 2, characterized in that: The crack state includes the close-together and separate states of the strip lines in the combination of two strip lines of the crack state display layer. The step S200 specifically includes: Step S210: The data processing device drives the image acquisition device to move to the vicinity of the position according to the position information, and roughly adjusts the acquisition position of the image acquisition device; Step S220: The data processing device drives the image acquisition device to search within a set range to the left and right of the current position, and determines whether there are strip lines in a separated state in the image returned by the image acquisition device. After finding the strip lines in the separated state, image acquisition is performed so that all the strip lines in the separated state are located in the acquired image, and the acquired image is used as the image information corresponding to the position.

4. The three-dimensional construction method of bridge cracks according to claim 3, characterized in that: In step S220, if a strip line in a separated state is found, step S300 specifically includes: Step S310: For a stripe line combination located on the sensing optical fiber, the upper leftmost pixel point or the lower leftmost pixel point of the stripe line in the stripe line combination that is in a separated state is used as the first pixel point; the upper rightmost pixel point or the lower rightmost pixel point of the stripe line in the stripe line combination that is in a separated state is used as the second pixel point; Step S320: For the stripe line combination located below the sensing optical fiber, determine the third pixel point corresponding to the first pixel point as the upper rightmost pixel point or the lower rightmost pixel point of the stripe line in the separated state in the stripe line combination; determine the fourth pixel point corresponding to the second pixel point as the upper leftmost pixel point or the lower leftmost pixel point of the stripe line in the separated state in the stripe line combination; Step S330: Connect the first pixel point and the third pixel point to obtain a first length L1, and connect the second pixel point and the fourth pixel point to obtain a second length L2. Assume that the left-right relative displacement of the two sides of the crack is Δx, that is, the left-right lateral change of the stripe line is Δx, and the up-down relative displacement of the two sides of the crack is Δy, that is, the up-down vertical change of the stripe line is Δx. In the initial state, the vertical distance between the two stripe lines is L0, then establish the equation: Solve for Δx and Δy; Step S340: Determine the left-right strain and the top-bottom strain of the sensing optical fiber segment at the position corresponding to the fringe line combination based on Δx and Δy; Step S350 : Subtract the left-right strain and the up-down strain from the detected strain at the position on the sensing fiber segment to obtain the strain caused by the front-back relative displacement of the crack, thereby determining the front-back relative displacement Δz of the crack.

5. The three-dimensional construction method of bridge cracks according to claim 3 or 4, characterized in that: In the step S220 , if no separated strip line is found, the step S300 specifically includes: determining the relative displacement Δz of the crack according to the strain magnitude detected at the position on the sensing fiber segment.

6. The three-dimensional construction method of bridge cracks according to claim 2, characterized in that: The relative distance between the image acquisition device and the crack state display layer is equal during each acquisition.

Images