Damage identification method based on full-field displacement monitoring of natural texture features
By using a full-field displacement monitoring method based on natural texture features, and employing image processing techniques and fixed-point analysis, the problem of incomplete monitoring data in structural damage identification was solved, and accurate damage identification of bridge structures was achieved.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- Filing Date
- 2022-10-25
- Publication Date
- 2026-04-21
AI Technical Summary
In existing technologies, the limited number of measurement points leads to incomplete monitoring data during structural damage identification, making it difficult to obtain sufficient useful information and thus hindering damage identification.
A full-field displacement monitoring method based on natural texture features is adopted. Through image feature extraction and superposition processing, the continuous deflection curve of the bridge edge is obtained. Combined with fixed point analysis, mismatched full-field displacement vectors are screened out, and damage is identified by the rotation rate of the full-field displacement vector.
This effectively alleviated the problem of incomplete test data, enabled accurate damage identification of bridge structures, and improved the accuracy and reliability of damage identification.
Smart Images
Figure CN115682951B_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of damage identification techniques, and more specifically, to a damage identification method based on full-field displacement monitoring of natural texture features. Background Technology
[0002] Currently, methods for structural damage identification, such as deploying sensors at a limited number of measurement points on a structure to obtain dynamic response information, all assume that the degrees of freedom of the structural model and the degrees of freedom of observation are consistent. However, in practical engineering, various conditions often lead to incomplete observation data. To fundamentally solve this problem, as many measurement points as possible are needed, but the number of measurement points that can be deployed on a real structure is finite. For structural damage identification, if the monitoring data is incomplete, the useful information obtained is insufficient, which means that the damage identification problem can only be solved without sufficient known information. Therefore, parametric damage identification methods face the problem of difficulty in damage identification due to insufficient test data.
[0003] Any structure can be viewed as a mechanical system composed of stiffness, mass, and damping matrices. Once structural damage occurs, the structural parameters change, leading to alterations in the system's response. Therefore, changes in structural morphology can be considered a marker of early structural damage. The rapid rise of computer image processing technology in recent years has provided technical support for parametric damage identification methods to overcome the limitations of insufficient measured data. On the other hand, parametric damage identification focuses on constructing the relationship between structural mechanical characteristics and damage, forming the fundamental theoretical system for structural damage identification. It can provide a theoretical framework for the mechanical behavior of structures for image processing-based structural damage identification methods, linking images with structural mechanical behavior. Therefore, research on the fusion of parametric damage identification methods and digital images has broad application prospects. Summary of the Invention
[0004] To address the problems in related technologies, this invention proposes a damage identification method based on full-field displacement monitoring of natural texture features, in order to overcome the aforementioned technical problems existing in the existing related technologies.
[0005] Therefore, the specific technical solution adopted by the present invention is as follows:
[0006] A damage identification method based on full-field displacement monitoring of natural texture features, comprising the following steps:
[0007] S1. Extract the edge profile of the bridge using image feature extraction method, and obtain the continuous deflection curve of the bridge edge by overlay method.
[0008] S2. By setting fixed points around the bridge, the relative position changes of the bridge feature points before and after deformation are analyzed, and the initial calculation results of the full-field displacement vector of the bridge structure are obtained.
[0009] S3. Using the continuous deflection values of the bridge structure edge obtained in S1, the mismatches of the full-field displacement vector of the bridge structure are screened out, and the accurate full-field displacement vector of the bridge structure is obtained.
[0010] S4. Damage identification of bridge structures is performed by using the rate of change of the displacement vector angle across the entire field.
[0011] Furthermore, the step of extracting the edge profile of the bridge under various working conditions using image feature extraction and obtaining the continuous deflection curve of the bridge edge through overlay processing includes the following steps:
[0012] S11. Extract the equivalent orthophoto images of the bridge under various working conditions using the image perspective transformation method.
[0013] S12. The monitoring resolution of the equivalent orthophoto image of the bridge is obtained by calibrating the pixel size, and the pixel size of the equivalent orthophoto image of the bridge is converted to the deformation monitoring size using the monitoring resolution. The measured deformation value of the structure is obtained by the pixel position difference.
[0014] S13. Use image feature extraction method to extract the feature points of the bridge in the equivalent orthophoto image of the bridge. After deleting the useless feature points around it, retain the edge points of the main body of the bridge.
[0015] S14. Fit the extracted structural edge points to obtain the edge line shape of the structure. Subtract the initial edge line under this working condition from the extracted structural edge line to obtain the overall structural deformation deflection curve that can be compared with the dial gauge.
[0016] Furthermore, the analysis of the relative positional changes of bridge feature points before and after the analytical deformation, and the initial calculation results of the bridge structure's total displacement vector, include the following steps:
[0017] S21. The displacement of the entire field is approximated by replacing the corresponding points with feature points on the surface of the bridge structure before and after deformation.
[0018] S22. The feature matching results of the bridge images before and after deformation obtained by SIFT feature point matching method constitute the source data for the full-field displacement extraction of the bridge structure.
[0019] S23. Arrange fixed points around the bridge and ensure that the fixed points are in the image. Relate the positions of the feature points to the positions of the fixed points and calculate the change in the position of the feature points in the plane through the fixed points.
[0020] S24. Extract the initial result of the full-field displacement vector of the bridge structure by solving the vector set of the initial matching feature point pairs before and after the deformation of the bridge structure.
[0021] Furthermore, the process of filtering out mismatches in the full-field displacement vector of the bridge structure using the continuous deflection values at the edge of the bridge structure obtained in S1 includes the following steps:
[0022] Determine whether the matched full-field displacement vector of the structure satisfies the deformation compatibility law of the structure. If it is consistent with the deformation compatibility law of the structure, it is a correct match; if it is inconsistent, it can be determined as a mismatch.
[0023] Determine if there are any obvious anomalies in the rotation angle θ of the matched structural full-field displacement vector. If there are none, it is a correct match; if there are, the vector is considered an incorrect match and is filtered out.
[0024] Vector length mismatches are filtered out by extracting the maximum deflection value of the edge line. If there is no obvious abnormality in the vector length, it is a correct match; if there is an obvious abnormality, it is a mismatch and is filtered out.
[0025] If there are still abnormal vectors that cannot be determined, the vector length at the corresponding position should be accurately compared and analyzed using the edge holographic deformation information. If there are concentrated continuous abnormal changes in angle or deflection in a local area of the full-field displacement vector on the structural surface, and the deformation continuity of this area is closely related to that of its adjacent areas, and it is developed from the deformation of its surrounding areas and meets the structural deformation coordination requirements, then the vector screening of the abnormality in this area should be handled with caution.
[0026] Furthermore, the angular consistency constraint is the cross-sectional rotation angle of the bridge structure edge deflection, and the calculation formula for the cross-sectional rotation angle is as follows:
[0027]
[0028] In the formula, θ represents the turning angle, y represents the deflection, f(x) represents a continuous function of the abscissa x of the bridge structure, and f'(x) represents the derivative of the function f(x).
[0029] Furthermore, the damage identification index based on the full-field displacement vector of the bridge structure for bridge structure damage identification includes the following steps:
[0030] S41. Analyze the damage identification index of the bridge structure with the rotation angle change rate set as the damage identification index of the bridge structure's total displacement vector, and solve for the rotation angle change rate of the bridge structure's total displacement vector.
[0031] S42. Use the damage identification index of the rate of change of rotation angle to determine the location of damage to the bridge structure;
[0032] S43. After the location of the damage is determined, the degree of damage is identified by the difference between adjacent angles at locations with abnormal angle change rates.
[0033] Furthermore, the formula for calculating the rate of change of the rotation angle of the total displacement vector of the bridge structure is as follows:
[0034]
[0035] Where, θ' n Let θ be the rotation angle of the total displacement vector of the structure after damage. n θ represents the rotation angle of the structural displacement vector in the undamaged state, and K is the rate of change of rotation, a damage index.
[0036] The beneficial effects of this invention are as follows:
[0037] 1) This invention can extract the natural texture features of the structural surface through image scale-invariant feature transformation, and extract the full-field position vector of the structural surface by calculating the relative position relationship between the feature points before and after deformation and the planar reference system, thereby solving the problem of incomplete test data.
[0038] 2) This invention proposes a damage identification index applicable to full-field structural displacement monitoring, which can realize damage identification of bridges and effectively alleviate the problem of difficulty in structural damage identification caused by incomplete test data. Attached Figure Description
[0039] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.
[0040] Figure 1 This is a flowchart illustrating a damage identification method based on full-field displacement monitoring of natural texture features according to an embodiment of the present invention.
[0041] Figure 2 This is a schematic diagram of the specimen arrangement in the damage identification method based on full-field displacement monitoring of natural texture feature structure according to an embodiment of the present invention;
[0042] Figure 3 This is a schematic diagram of the pixel size calibration model in the damage identification method based on full-field displacement monitoring of natural texture feature structure according to an embodiment of the present invention;
[0043] Figure 4 This is a schematic diagram of the generation model of relative position change of corresponding point pairs in the damage identification method based on full-field displacement monitoring of natural texture feature structure according to an embodiment of the present invention. Detailed Implementation
[0044] To further illustrate the various embodiments, the present invention provides accompanying drawings, which are part of the disclosure of the present invention. These drawings are mainly used to illustrate the embodiments and can be used in conjunction with the relevant descriptions in the specification to explain the operating principles of the embodiments. With reference to these drawings, those skilled in the art should be able to understand other possible implementation methods and the advantages of the present invention. The components in the drawings are not drawn to scale, and similar component symbols are generally used to represent similar components.
[0045] According to embodiments of the present invention, a damage identification method based on full-field displacement monitoring of natural texture feature structures is provided.
[0046] The present invention will now be further described in conjunction with the accompanying drawings and specific embodiments, such as... Figure 1-4 As shown, the damage identification method based on full-field displacement monitoring of natural texture feature structures according to an embodiment of the present invention includes the following steps:
[0047] S1. Extract the edge profile of the bridge using image feature extraction method, and obtain the continuous deflection curve of the bridge edge by overlay method.
[0048] The step of extracting the edge profile of the bridge under various working conditions using image feature extraction and obtaining the continuous deflection curve of the bridge edge through overlay processing includes the following steps:
[0049] S11. Extract the equivalent orthophoto images of the bridge under various working conditions using the image perspective transformation method.
[0050] In practical applications, it is necessary to find descriptors that can mathematically represent corresponding image points on the structural surface. The natural texture features of the bridge surface are consistent before and after deformation, and can constitute natural corresponding points. As long as the photogrammetric accuracy is high enough, these texture features can be detected and represented as extrema in the scale space of the image. Currently, the most common method for finding and detecting extrema in the scale space of an image is to use the Scale-invariant Feature Transform (SIFT) algorithm. The SIFT feature point extraction algorithm can detect image feature points in multi-scale space, and the extracted feature points have the characteristics of scale, position, and orientation invariance. These features can be matched using the generated feature vector descriptors.
[0051] In this embodiment, bridge images are acquired using a pre-prepared monitoring camera. The selection of the monitoring camera is based on a comprehensive analysis of factors such as measurement accuracy, field of view, and focal length; the Fujifilm GFX 100 general-purpose camera is chosen. A suitable lens with a suitable focal length is selected based on the actual shooting distance; the Fujifilm GF 32-64 / 4R LM WR lens is selected. The technical parameters of the camera and lens are shown in Table 1.
[0052] Table 1 Camera and Lens Parameters
[0053]
[0054] Camera calibration was performed using a self-calibrated bundle adjustment method based on a planar grid. The calibration board parameters are shown in Table 2. The main calibration parameters included the interior orientation elements (x0, y0), camera principal distance f, radial distortion coefficients K1 and K2, eccentric distortion coefficients P1 and P2, pixel size, and image size. The camera's internal parameters were calculated using the camera orientation element calculation method. The initial values for the GFX 100 camera's interior orientation elements were set to 0, the focal length to 50mm, and the pixel size to 3.76μm. The camera calibration parameter results are shown in Table 3.
[0055] Table 2 Calibration Plate Parameter Table
[0056]
[0057] Table 3 Camera Calibration Results
[0058]
[0059] Because directly acquired specimen images are affected by natural perspective, they exhibit a significant near-large and far-small characteristic, making them unable to accurately reflect structural deformation. Therefore, perspective transformation of the specimen images is necessary. An image perspective transformation method is used to process the test beam image, obtaining the orthographic projection of the test beam after perspective transformation. The specimen image after perspective transformation is no longer affected by perspective, eliminating the "near-large and far-small" imaging characteristic, and thus possesses orthographic projection characteristics, allowing for the analysis of structural deformation information.
[0060] S12. The monitoring resolution of the equivalent orthophoto image of the bridge is obtained by calibrating the pixel size, and the pixel size of the equivalent orthophoto image of the bridge is converted to the deformation monitoring size using the monitoring resolution. The measured deformation value of the structure is obtained by the pixel position difference.
[0061] In bridge structural deformation monitoring, the size of the image area occupied by the structure is a key focus. Structural deformation is reflected in the image as a change in the position of the pixels covered by the deformed area. Under the same shooting conditions, the magnitude of deformation required to cause a change in pixel position becomes a resolution issue in bridge image deformation monitoring. Theoretically, the deformation value must be larger than the image size of the pixels to be identifiable by bridge structural deformation monitoring methods. Figure 2 As can be seen, the yellow calibration lines drawn in the strut represent a series of regular pixel matrices on the image. The size of these pixel matrices relative to the actual physical dimensions of the specimen constitutes the monitoring resolution. The calibration model is as follows: Figure 3As shown. The monitoring resolution calibration calculation method is: R = L / n (mm / pixel). The test beam has a total of 15 vertical bars, and a yellow calibration line was drawn in the middle of each vertical bar during the test. The precise length of each calibration line was measured, and the number of pixels covered by the corresponding calibration line was counted on the image to obtain the monitoring resolution. The monitoring resolution of the bridge image was obtained by calibrating the pixel size. This resolution can be used to convert the pixel size of the bridge image to the deformation monitoring size, and then the measured deformation value of the structure can be obtained through the pixel difference when the structure deforms.
[0062] S13. Use image feature extraction to extract the feature points of the bridge in the equivalent orthophoto image of the bridge. After deleting the useless feature points around it, retain the edge points of the main body of the bridge.
[0063] S14. Fit the extracted structural edge points to obtain the edge line shape of the structure. Subtract the initial edge line under this working condition from the extracted structural edge line to obtain the overall structural deformation deflection curve that can be compared with the dial gauge.
[0064] S2. By setting fixed points around the bridge, the relative position changes of the bridge feature points before and after deformation are analyzed, and the initial calculation results of the full-field displacement vector of the bridge structure are obtained.
[0065] The process of analyzing the relative positional changes of bridge feature points before and after deformation by setting fixed points around the bridge to obtain the initial calculation results of the bridge structure's total displacement vector includes the following steps:
[0066] S21. The displacement of the entire field is approximated by replacing the corresponding points with feature points on the surface of the bridge structure before and after deformation.
[0067] S22. The feature matching results of the bridge images before and after deformation obtained by SIFT feature point matching method constitute the source data for the full-field displacement extraction of the bridge structure.
[0068] The difficulty in determining the relative displacement of feature points in the bridge image measurement plane lies in the fact that the images before and after deformation are completely free, and all bridge feature points are in their own independent measurement planes. Therefore, a standard reference system is needed to run through all images under different working conditions to provide unified constraints for each working condition image in order to solve the relative positional relationship of feature points before and after deformation. Hence, S23 is executed.
[0069] S23. Arrange fixed points around the bridge and ensure that the fixed points are in the image. Relate the positions of the feature points to the positions of the fixed points and calculate the change in the position of the feature points in the plane through the fixed points.
[0070] S24. Extract the initial result of the full-field displacement vector of the bridge structure by solving the vector set of the initial matching feature point pairs before and after the deformation of the bridge structure;
[0071] To achieve accurate calculation of displacement values of feature points in structural images before and after deformation, a mathematical model of the relative positional changes of feature point pairs is proposed, such as... Figure 4 As shown.
[0072] Figure 4 In this example, the large square area serves as a planar reference frame. Theoretically, any feature point on the chessboard can be used as a fixed point O. In this embodiment, the feature point at the very center of the chessboard is selected as the fixed point of the reference frame. For example... Figure 4 As shown, starting from the initial endpoint A before deformation i and termination endpoint A′ i Composition of displacement vector This displacement vector is a fundamental element of the total displacement vector of the structure, such as Figure 4 As shown by the dashed vector, M i express.
[0073] Specifically, the feature points of the bridge structure images before and after deformation are represented by M... i This indicates that the bridge structure image feature points M before and after deformation are... i The generation includes the following steps:
[0074] Let the bridge images before and after deformation be (i1, i2); extract feature points from the bridge images, denoted as A. i and A′ i And obtain n initial matches C, C = {(A i ,A' i ):i=1,2,...,n}, where A i ∈i1, A' i ∈i2; The feature point A i and A′ i Projecting onto the specified fixed point O, we obtain the coordinates A of the feature point. i (x i ,y i ), A' i (x' i ,y' i Feature point A is extracted in the preset photogrammetric coordinate system. i A′ i The coordinates (x) between the fixed point O and the fixed point O i ,y i ), (x' i ,y' i ),get An M i A displacement vector has two attributes: length L and rotation angle θ, both of which pass through the known feature point coordinates A. i (x i ,y i ), A'i (x' i ,y' i The initial matching feature point pairs before and after structural deformation can generate n M values. i The set M = {M i :i=1,2,...,n}. Based on the above method, the full-field deformation vector of the structural surface can be extracted by solving the vector set M, i.e., executing S24.
[0075] S3. Set vector field consistency constraints, and use the continuous deflection values of the bridge structure edge obtained in S1 to filter out mismatches of the full field displacement vector of the bridge structure, so as to obtain the accurate full field displacement vector of the bridge structure.
[0076] Deflection y and rotation angle θ are two fundamental quantities for measuring bridge displacement. Deflection y varies with the cross-sectional position and can be represented by a continuous function of the structural transverse coordinate x, i.e., y = f(x). This is the equation of the beam's deflection curve. The ordinate of any point on the deflection curve represents the deflection of the cross-section at that point, and the inclination angle of its tangent is the rotation angle θ of that cross-section. Under small deformation conditions, θ is very small, so the rotation angle equation can be expressed as:
[0077]
[0078] In the formula, θ represents the turning angle, y represents the deflection, f(x) represents a continuous function of the abscissa x of the bridge structure, and f'(x) represents the derivative of the function f(x).
[0079] Unlike conventional methods that use functions to represent deflection curves, the structural edge deflection obtained in this embodiment is directly extracted from the structural image, representing the change in the actual edge shape of the structure. The above formula can be used to solve for the cross-sectional rotation angle of the structural edge deflection, and the obtained cross-sectional rotation angle can be used as an angular consistency constraint for the entire field displacement vector.
[0080] The step of filtering out mismatches in the full-field displacement vector of the bridge structure using the continuous deflection values at the edge of the bridge structure obtained by S1 includes the following steps:
[0081] Determine whether the matched full-field displacement vector of the structure satisfies the deformation compatibility law of the structure. If it is consistent with the deformation compatibility law of the structure, it is a correct match; if it is inconsistent, it can be determined as a mismatch.
[0082] Determine if there are any obvious anomalies in the rotation angle θ of the matched structural full-field displacement vector. If there are none, it is a correct match; if there are, the vector is considered an incorrect match and is filtered out.
[0083] Vector length mismatches are filtered out by extracting the maximum deflection value of the edge line. If there is no obvious abnormality in the vector length, it is a correct match; if there is an obvious abnormality, it is a mismatch and is filtered out.
[0084] If there are still abnormal vectors that cannot be determined, the vector length at the corresponding position should be accurately compared and analyzed using the edge holographic deformation information. If there are concentrated continuous abnormal changes in angle or deflection in a local area of the full-field displacement vector on the structural surface, and the deformation continuity of this area is closely related to that of its adjacent areas, and it is developed from the deformation of its surrounding areas and meets the structural deformation coordination requirements, then the vector screening of the abnormality in this area should be handled with caution.
[0085] S4. Damage identification of bridge structures is performed by using the rate of change of the displacement vector angle across the entire field.
[0086] The method of identifying damage to bridge structures by measuring the rate of change of the full-field displacement vector rotation includes the following steps:
[0087] S41. Analyze the damage identification index of the bridge structure with the rotation angle change rate set as the damage identification index of the bridge structure's total displacement vector, and solve for the rotation angle change rate of the bridge structure's total displacement vector.
[0088] The essence of abnormal holographic morphological changes in structures is that damage disrupts the deformation compatibility of the structural system, and damage information is expressed through the abnormal distribution of rotation angles in the full-field vector. This property can be used to analyze the rate of change of rotation angles of the full-field displacement vectors before and after damage. The formula for calculating the rate of change of rotation angles is as follows:
[0089]
[0090] Where K is the damage index of rotation rate of change. Analysis of this formula shows that the rotation rate of change in the undamaged area is affected by the continuity and coordination of structural deformation, and theoretically should be consistent. However, at the damaged location, the structural displacement vector rotation angle undergoes abrupt changes, deviating from the vector rotation angle at the corresponding location in the undamaged structure. The rotation angle difference begins to appear and is amplified through the rate of change, thus demonstrating the sensitivity of the damage index.
[0091] S42. Use the damage identification index of the rate of change of rotation angle to determine the location of damage to the bridge structure;
[0092] In this embodiment, the rotation angle information of the structural full-field displacement vector is used to propose a damage identification index based on the rotation angle change rate. This index has a strong response capability to abnormal rotation angle changes caused by damage to the structure and has a clear indication of the damage location. It can be used as a discrimination index for the damage occurrence area and specific location.
[0093] S43. After the location of the damage is determined, the degree of damage is identified by the difference between adjacent angles at locations with abnormal angle change rates.
[0094] Once the location of the damage is determined, the degree of damage can be identified by using the difference between adjacent angles at locations with abnormal angle change rates, based on existing theories and numerical simulations.
[0095] In summary, by means of the above-mentioned technical solution of the present invention, the present invention can extract the natural texture features of the structural surface through image scale-invariant feature transformation, and extract the full-field position vector of the structural surface by calculating the relative position relationship between the feature points before and after deformation and the planar reference system, thereby solving the problem of incomplete test data.
[0096] Furthermore, this invention proposes a damage identification index applicable to full-field structural displacement monitoring, which can realize damage identification of bridges and effectively alleviate the problem of difficulty in structural damage identification caused by incomplete test data.
[0097] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.
Claims
1. A damage identification method based on full-field displacement monitoring of natural texture features, characterized in that, The method includes the following steps: S1. Extract the edge profile of the bridge using image feature extraction method, and obtain the continuous deflection curve of the bridge edge by overlay method. S2. By setting fixed points around the bridge, the relative position changes of the bridge feature points before and after deformation are analyzed, and the initial calculation results of the full-field displacement vector of the bridge structure are obtained. S3. Set vector field consistency constraints, and use the continuous deflection values of the bridge structure edge obtained in S1 to filter out mismatches of the full field displacement vector of the bridge structure, so as to obtain the accurate full field displacement vector of the bridge structure. S4. Damage identification of bridge structures is performed by the rate of change of the rotation angle of the full-field displacement vector. The step of extracting the edge profile of the bridge under various working conditions using image feature extraction and obtaining the continuous deflection curve of the bridge edge through overlay processing includes the following steps: S11. Extract the equivalent orthophoto images of the bridge under various working conditions using the image perspective transformation method. S12. The monitoring resolution of the equivalent orthophoto image of the bridge is obtained by calibrating the pixel size, and the pixel size of the equivalent orthophoto image of the bridge is converted to the deformation monitoring size using the monitoring resolution. The measured deformation value of the structure is obtained by the pixel position difference. S13. Use image feature extraction method to extract the feature points of the bridge in the equivalent orthophoto image of the bridge. After deleting the useless feature points around it, retain the edge points of the main body of the bridge. S14. Fit the extracted structural edge points to obtain the edge line shape of the structure. Subtract the initial edge line under this working condition from the extracted structural edge line to obtain the overall structural deformation deflection curve that can be compared with the dial gauge. The analysis of the relative positional changes of bridge feature points before and after deformation, and the initial calculation results of the bridge structure's total displacement vector, include the following steps: S21. The displacement of the entire field is approximated by replacing the corresponding points with feature points on the surface of the bridge structure before and after deformation. S22. The feature matching results of the bridge images before and after deformation obtained by SIFT feature point matching method constitute the source data for the full-field displacement extraction of the bridge structure. S23. Arrange fixed points around the bridge and ensure that the fixed points are in the image. Relate the positions of the feature points to the positions of the fixed points and calculate the change in the position of the feature points in the plane through the fixed points. S24. Extract the initial result of the full-field displacement vector of the bridge structure by solving the vector set of the initial matching feature points before and after the deformation of the bridge structure.
2. The damage identification method based on full-field displacement monitoring of natural texture features according to claim 1, characterized in that, The process of filtering out mismatches in the full-field displacement vector of the bridge structure using the continuous deflection values at the edge of the bridge structure obtained by S1 includes the following steps: Determine whether the matched full-field displacement vector of the structure satisfies the deformation compatibility law of the structure. If it is consistent with the deformation compatibility law of the structure, it is a correct match; if it is inconsistent, it can be determined as a mismatch. Determine the rotation angle of the matched structural full-field displacement vector If there are no obvious anomalies, the match is correct; if there are, the vector is considered an incorrect match and is filtered out. Vector length mismatches are filtered out by extracting the maximum deflection value of the edge line. If there is no obvious abnormality in the vector length, it is a correct match; if there is an obvious abnormality, it is a mismatch and is filtered out. If there are still abnormal vectors that cannot be determined, the vector length at the corresponding position is accurately compared and analyzed using edge holographic deformation information. If there are concentrated, continuous, and abnormal changes in rotation or deflection in a local area of the full-field displacement vector on the structural surface, and the deformation continuity of this area is closely related to that of its adjacent areas, originating from the deformation of its surrounding areas, and satisfies the structural deformation coordination requirement, then the vector screening of the abnormality in this area should be handled with caution.
3. The damage identification method based on full-field displacement monitoring of natural texture features according to claim 1, characterized in that, The vector field consistency constraint is the cross-sectional rotation angle of the bridge structure edge deflection, and the calculation formula for the cross-sectional rotation angle is as follows: ; In the formula, y represents the turning angle, and y represents the deflection. Represents a continuous function of the x-coordinate of the bridge structure. Representation function The derivative of .
4. The damage identification method based on full-field displacement monitoring of natural texture feature structures according to claim 1, characterized in that, The damage identification index based on the full-field displacement vector of the bridge structure for bridge structure damage identification includes the following steps: S41. Analyze the damage identification index of the bridge structure with the rotation angle change rate set as the damage identification index of the bridge structure's total displacement vector, and solve for the rotation angle change rate of the bridge structure's total displacement vector. S42. Use the damage identification index of the rate of change of rotation angle to determine the location of damage to the bridge structure; S43. After the location of the damage is determined, the degree of damage is identified by the difference between adjacent angles at locations with abnormal angle change rates.
5. The damage identification method based on full-field displacement monitoring of natural texture feature structures according to claim 4, characterized in that, The formula for calculating the rate of change of the rotation angle of the total displacement vector of the bridge structure is as follows: ; in, The angle is the total displacement vector of the structure after damage. θ represents the rotation angle of the structural displacement vector in the undamaged state, and K is the rate of change of rotation, a damage index.