Error correction method for continuous beam bridge deflection monitoring based on digital image measurement

Abstract

The present invention discloses a method for correcting the error in monitoring the deflection of a continuous beam bridge based on digital image measurement. By calculating the deflection angle of the main span and the mid-span deflection of continuous beam bridges with different spans, deflection test experiments are carried out on the deflectometer and target targets under different deflection angle conditions. The deflection error-deflection angle relationship curve obtained by monitoring the deflectometer and target targets is fitted according to the test results, and a deflection monitoring error model library for continuous beam bridges with different spans is constructed. At the same time, inclinometers are respectively installed on the deflectometer and the target target. Based on the inclinometer test values ​​and the continuous beam bridge deflection monitoring error model library, the errors caused by the deflection of the deflectometer and the change of the center of the target target light source are corrected. The present invention does not require the use of a reference target, eliminates the possibility of reverse error caused by the reference target, reduces the number and cost of target installation, realizes the correction of the error of the deflection of the deflectometer and the change of the center of the target target light source, and provides support for improving the reliability of the image deflectometer in the long-term monitoring of the static and dynamic deflections of continuous beam bridges.

Description

Technical Field

[0001] The invention relates to a continuous beam bridge deflection monitoring method, and in particular to a continuous beam bridge deflection monitoring error correction method based on digital image monitoring. Background Art

[0002] The static and dynamic deflections of bridges reflect the overall vertical stiffness of the bridge structure and are important indicators for assessing the structural condition and performance of bridges, thus playing a crucial role in bridge health monitoring. Currently, there are over one million active highway bridges in China. Continuous beam bridges account for a significant proportion of these bridges due to their advantages, such as the ability to resist positive mid-span bending moments at their supports, their light weight, sophisticated construction techniques, excellent integrity, and a minimal number of expansion joints on the deck. However, with the increasing volume of traffic and heavy vehicles, the deterioration of material properties, and the emergence of untimely maintenance, a significant number of bridges have experienced concrete cracking, such as vertical, transverse, and diagonal cracks in the top, bottom, and mid-span webs. This results in insufficient overall vertical stiffness and reduced safety margins. Therefore, accurate and convenient monitoring of the static and dynamic deflections of continuous beam bridges during operation is a pressing need for evaluating bridge performance and providing timely structural safety warnings. Currently, the main methods for measuring the static and dynamic deflections of continuous beam bridges include displacement meters, levels, connecting pipes, GPS, and millimeter-wave radar.

[0003] However, displacement meters need to be mounted on fixed brackets before use and cannot be applied to bridges across rivers or deep valleys; optical levels cannot measure dynamic deflection; connecting pipes lack real-time monitoring capabilities due to liquid flow resistance, and are limited in range and cannot be applied to large-span bridges with large longitudinal slopes; GPS is easily affected by satellite clock errors, satellite orbit errors, ionospheric errors, etc., making it difficult to ensure long-term stability of the positioning accuracy of the receiving terminal; millimeter-wave radar devices are expensive and difficult to deploy in large quantities.

[0004] With the development of machine vision and photoelectric sensing technologies, bridge static and dynamic deflection measurement methods based on digital image correlation technology have been gradually applied to long-term monitoring of bridge structure displacement due to their advantages of non-contact, multi-point simultaneous monitoring, high measurement accuracy, and low equipment cost. However, in actual applications, through monitoring studies on a large number of continuous beam bridges, it has been found that the deflection monitoring method based on digital image correlation still has the following shortcomings:

[0005] Currently, in long-term displacement monitoring of continuous beam bridges, an image deflectometer is typically installed on the top of a chamber near the mid-support, taking into account on-site construction and subsequent equipment maintenance. Targets are then placed on the top of the chamber at the quarter, mid-span, and three-quarter positions of the main span, respectively, while a reference target is placed on the top of the chamber near the opposite mid-support. However, variable-section continuous beam bridges experience deflection at the supports under vehicle loads, causing some deflection and vertical deformation of the image deflectometer (CMOS), target, and reference targets, introducing errors into the test results. The image deflectometer and reference target are installed near the mid-support, resulting in minimal vertical deformation. This primarily results in a depression angle, which affects the accuracy of the image point deflection test and introduces significant uncertainty into the deflection test. In particular, when the reference target experiences a depression angle, correction of the image deflectometer is difficult and may even result in reverse error.

[0006] The above problems make it difficult for digital image correlation technology to fully exert its advantages in deflection monitoring. Summary of the Invention

[0007] In response to the above-mentioned deficiencies in the prior art, the present invention proposes a continuous beam bridge deflection monitoring error correction method based on digital image measurement, with the aim of eliminating the possibility of reverse errors caused by the reference target, reducing the implementation cost of the bridge health monitoring system, improving the system installation efficiency, and providing data support for more accurate and reliable continuous beam bridge health assessment and safety warning.

[0008] Technical solution: A method for correcting the deflection monitoring error of a continuous beam bridge based on digital image measurement, comprising the following steps:

[0009] (1) Select typical span and typical cross-section continuous beam bridges and calculate the main span deflection angles of different continuous beam bridges through finite element simulation;

[0010] (2) The deflection angle of the main span calculated by finite element simulation is the maximum limit and the maximum deflection, and deflection test of the image deflectometer and / or target under different deflection angle conditions is carried out;

[0011] (3) Based on the deflection test results, the relationship curve between the deflection monitoring error and the deflection angle is fitted to construct a deflection monitoring error model library for continuous beam bridges with different spans. The deflection monitoring error refers to the error of the deflection measurement value from the reference value;

[0012] (4) installing an inclinometer on the image deflectometer and / or the target, wherein the inclinometer is used to monitor the deflection angle of the image deflectometer and / or the target;

[0013] (5) Determine the deflection type through the inclinometer. Based on the deflection type and the inclinometer test value, query the deflection monitoring error corresponding to the deflection type and the inclinometer test value in the continuous beam bridge deflection monitoring error model library. According to the current measured mid-span deflection, correct the error caused by the image deflectometer deflection and / or the target deflection.

[0014] In one embodiment, the deflection test experiment of step (2) adjusts the deflection angle of the image deflectometer and / or the target, records the deflection measurement value at each deflection angle in real time, and takes the difference between the deflection measurement value at each deflection angle and the reference value as the deflection error value.

[0015] In one embodiment, the deflection test in step (2) further includes a step of adjusting the vertical displacement of the target.

[0016] Specifically, when the deflection monitoring error comes from the deflection of the deflectometer, the calculation process of the deflection monitoring error is as follows:

[0017] Define the target imaging height as W1, the target height as W2, the focal length as f, the distance between the target and the image deflectometer lens as L, and the deviation caused by the deflection of the deflectometer as Δh1;

[0018] The mapping relationship between the image 2D pixel coordinate system and the world 3D coordinate system is shown in the following formula:

[0019]

[0020] Where s represents the scale factor; R represents the rotation matrix; T represents the translation matrix; u, v represent the pixel coordinates; u0, v0 represent the horizontal and vertical pixel differences between the center pixel coordinates of the image and the target pixel coordinates, respectively; α, β represent the unit pixel displacement; X w ,Y w Represents world coordinates;

[0021] Substituting the vertical pixel deviation Δh1 into the formula, we can obtain the deviation Y1 caused by the deflection of the deflectometer;

[0022]

[0023] Y1 is the deflection monitoring error caused by the deflection of the deflectometer.

[0024] When the deflection monitoring error comes from the optical center deflection caused by the target deflection, the calculation process of the deflection monitoring error is as follows:

[0025] Define the target imaging height as W1, the target height as W2, the focal length as f, the distance between the target and the image deflectometer lens as L, and the vertical pixel deviation caused by the change of the target light source center as Δh2;

[0026] The mapping relationship between the image 2D pixel coordinate system and the world 3D coordinate system is shown in the following formula:

[0027]

[0028] Where s represents the scale factor; R represents the rotation matrix; T represents the translation matrix; u, v represent the pixel coordinates; u0, v0 represent the horizontal and vertical pixel differences between the center pixel coordinates of the image and the target pixel coordinates, respectively; α, β represent the unit pixel displacement; X w ,Y w Represents world coordinates;

[0029] Substituting the vertical pixel deviation Δh2 into the formula, we can obtain the deviation Y2 caused by the change of the target light source center;

[0030]

[0031] Y2 is the deflection monitoring error caused by the target deflection.

[0032] When the deflection monitoring error comes from the combination of the deflection of the deflectometer and the target deflection, the deflection monitoring error is calculated as follows:

[0033] Define the target imaging height as W1, the target height as W2, the focal length as f, the distance between the target and the image deflectometer lens as L, the vertical pixel deviation caused by the deflection of the deflectometer as Δh1, and the vertical pixel deviation caused by the change of the target light source center as Δh2;

[0034] The mapping relationship between the image 2D pixel coordinate system and the world 3D coordinate system is shown in the following formula:

[0035]

[0036] Where s represents the scale factor; R represents the rotation matrix; T represents the translation matrix; u, v represent the pixel coordinates; u0, v0 represent the horizontal and vertical pixel differences between the center pixel coordinates of the image and the target pixel coordinates, respectively; α, β represent the unit pixel displacement; X w ,Y w Represents world coordinates;

[0037] Substituting the vertical pixel deviations Δh1 and Δh2 into the formula, we can obtain the deviations Y1 and Y2 caused by the deflection of the deflectometer and the change of the target light source center;

[0038]

[0039]

[0040] The deflection monitoring error Δh caused by the deflection of the deflectometer and the change of the target light source center is:

[0041] Δh=Y1+Y2.

[0042] Compared with the existing methods, the present invention has the following beneficial effects:

[0043] 1. The finite element simulation results are used to guide the setting of subsequent test conditions, making the test conditions of support deflection angle and mid-span deflection more targeted;

[0044] 2. Through deflectometer and target deflection testing, the distribution range and distribution patterns of related errors were analyzed, and a deflection monitoring error model library for continuous beam bridges of different spans was constructed. Based on the inclinometer test values ​​and the continuous beam bridge deflection monitoring error model library, errors caused by deflection meter deflection and target light source center change were corrected, providing support for improving the reliability of image deflectometers in long-term monitoring of static and dynamic deflections of continuous beam bridges.

[0045] 3. This correction method no longer relies on the reference target, eliminating the possibility of reverse error caused by the reference target and reducing the number and cost of target installation. BRIEF DESCRIPTION OF THE DRAWINGS

[0046] Figure 1 This is a flow chart of a method for correcting errors in monitoring deflection of a continuous beam bridge according to an embodiment of the present invention;

[0047] Figure 2 The deflection test result of the deflectometer under the working condition of 2 cm downward deflection in one embodiment of the present invention is shown;

[0048] Figure 3 This is the deflection test result of the deflectometer under the working condition of 3cm downward deflection in one embodiment of the present invention;

[0049] Figure 4 Schematic diagram of the deflection monitoring error caused by looking down at the deflectometer and looking up at the target. DETAILED DESCRIPTION

[0050] To make the above-mentioned objects, features, and advantages of the present application more clearly understood, the specific embodiments of the present application are described in detail below with reference to the accompanying drawings. The following description sets forth many specific details to facilitate a full understanding of the present application. However, the present application can be implemented in many other ways than those described herein, and those skilled in the art can make similar improvements without violating the scope of the present application. Therefore, the present application is not limited to the specific embodiments disclosed below.

[0051] In the description of this application, it should be understood that if there are terms indicating orientation or positional relationships, these terms are based on the orientation or positional relationships shown in the accompanying drawings and are only for the convenience of describing this application and simplifying the description. They do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation. Therefore, they cannot be understood as limitations on this application.

[0052] like Figure 1 As shown, a method for correcting the error in monitoring the deflection of a continuous beam bridge based on digital image measurement comprises the following steps:

[0053] (1) A typical span and typical cross-section continuous beam bridge is selected, and the deflection angle at the support to be tested and the corresponding mid-span deflection are obtained through finite element simulation. The deflection angle and mid-span deflection obtained by simulation are used to guide the setting of the working conditions of subsequent tests, that is, within the deflection range of the finite element simulation, relevant test conditions are set to make the test conditions of the mid-span deflection more targeted.

[0054] (2) Conduct deflection tests on the image deflectometer and target under different deflection angle conditions, with the finite element calculation results as the maximum limit of the deflection test;

[0055] (3) Based on the deflection test results, the relationship curves between the deflection monitoring error and the deflection angle of the image deflectometer and the target are fitted to construct a deflection monitoring error model library for continuous beam bridges with different spans. The deflection monitoring error refers to the error of the deflection measurement value from the reference value. Figure 2 、 Figure 3 These are the deflection test results of the deflectometer when the deflection is 2cm and 3cm respectively; the selection of the deflection reference value during the test process should be based on the mid-span deflection in the finite element calculation results, and the relevant test conditions should be set within the deflection range;

[0056] (4) Installing an inclinometer on the image deflectometer and / or the target, the inclinometer is used to monitor the deflection angle of the image deflectometer and / or the target;

[0057] (5) Determine the deflection type through the inclinometer. Based on the deflection type and the inclinometer test value, query the deflection monitoring error corresponding to the deflection type and the inclinometer test value in the continuous beam bridge deflection monitoring error model library. According to the current measured mid-span deflection, correct the error caused by the image deflectometer deflection and / or the target deflection.

[0058] Preferably, step (3) uses MATLAB to fit the relationship curve between the deflection monitoring error and the deflection angle of the image deflectometer and the target.

[0059] Example 1

[0060] The deflection test process of this embodiment is as follows:

[0061] By adjusting the deflection angle of the image deflectometer, the deflection measurement value at each deflection angle (i.e., the actual deflection measurement value) is recorded in real time; since the deflection reference value is known, the difference between the deflection measurement value at each deflection angle and the reference value is taken as the deflection error value.

[0062] Among them, the principle of calculating the corresponding deflection error based on the deflection angle is as follows:

[0063] Define the target imaging height as W1, the target height as W2, the focal length as f, the distance between the target and the image deflectometer lens as L, and the deviation caused by the deflection of the deflectometer as Δh1.

[0064] The mapping relationship between the image 2D pixel coordinate system and the world 3D coordinate system is shown in the following formula:

[0065]

[0066] In formula (1), s represents the scale factor; R represents the rotation matrix; T represents the translation matrix; u, v represent the pixel coordinates; u0, v0 represent the horizontal and vertical pixel differences between the center pixel coordinates of the image and the target pixel coordinates, respectively; α, β represent the unit pixel displacement; X w ,Y w Represents world coordinates.

[0067] Different deflection angles of the deflectometer will cause changes in pixel coordinates such as u0, v0, u, and v. The changes in these pixels are a direct reflection of the test error.

[0068] The deflection error caused by the deflection of the deflectometer is calculated through the mapping relationship between the two-dimensional pixel coordinate system of the image and the three-dimensional coordinate system of the world.

[0069] Substituting the vertical pixel deviation Δh1 into equation (1), we can obtain the deviation Y1 caused by the deflection of the deflectometer;

[0070]

[0071] Y1 is the deflection monitoring error caused by the deflection of the deflectometer.

[0072] Example 2

[0073] In addition to image deflectometer deflection, target deflection can also cause optical center deflection, leading to deflection monitoring errors. In this embodiment, when the target deflects from a top-down perspective, the deflection error caused by the target deflection is also calculated using the mapping relationship between the image's 2D pixel coordinate system and the world's 3D coordinate system.

[0074] Define the vertical pixel deviation caused by the change of the target light source center as Δh2; Substitute the vertical pixel deviation Δh2 into formula (1) to obtain the deviation Y2 caused by the change of the target light source center;

[0075]

[0076] Y2 is the deflection monitoring error caused by the target deflection.

[0077] Example 3

[0078] In addition to the deflection of a single deflectometer or target, it is common in actual working conditions for the deflectometer and target to deflect simultaneously.

[0079] like Figure 4 As shown, the deflectometer on the right side of the arrow produces a downward deflection, while the target produces an upward deflection. Similarly, through the mapping relationship between the image two-dimensional pixel coordinate system and the world three-dimensional coordinate system, the deflection errors caused by the two deflections are equivalent to the imaging image on the left side of the arrow.

[0080] Specifically, the vertical pixel deviations Δh1 and Δh2 are substituted into formula (1) to obtain the deviations Y1 and Y2 caused by the deflection of the deflectometer and the change of the target light source center;

[0081] The deflection monitoring error Δh caused by the deflection of the deflectometer and the change of the target light source center is:

[0082] Δh=Y1+Y2.

[0083] The present invention measures the numerical relationship between the deflectometer, target pitch and measurement error through a deflection test, analyzes the deformation measurement error law caused by the deflectometer and target pitch, and fits the specific functional relationship between the deflectometer, target pitch and measurement error through MATLAB to simulate and study the influence of the deflection meter deflection and target pitch on the displacement test accuracy. Later, the inclinometer reading is substituted into the error compensation function to obtain a more accurate deformation value.

[0084] Furthermore, based on the adjustment of the deflectometer and the pitch and deflection angle of the target, the deflection test also includes the step of adjusting the vertical displacement of the target.

[0085] The technical features of the above-mentioned embodiments can be combined arbitrarily. In order to make the description concise, not all possible combinations of the technical features in the above-mentioned embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0086] The above-described embodiments merely represent several implementation methods of the present application. While the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the patent application. It should be noted that a person of ordinary skill in the art may make various modifications and improvements without departing from the spirit of the present application, and these modifications and improvements fall within the scope of protection of the present application. Therefore, the scope of protection of the present patent application shall be determined by the appended claims.

Claims

1. A method for correcting the deflection monitoring error of a continuous beam bridge based on digital image measurement, characterized in that: The steps include: (1) Select typical span and typical cross-section continuous beam bridges and calculate the main span deflection angles of different continuous beam bridges through finite element simulation; (2) Taking the main span deflection angle calculated by finite element simulation as the maximum limit, conduct deflection test of the image deflectometer and / or target under different deflection angle conditions; (3) Based on the deflection test results, the relationship curve between the deflection monitoring error and the deflection angle is fitted to construct a deflection monitoring error model library for continuous beam bridges with different spans. The deflection monitoring error refers to the error of the deflection measurement value from the reference value; (4) installing an inclinometer on the image deflectometer and / or the target, wherein the inclinometer is used to monitor the deflection angle of the image deflectometer and / or the target; (5) Determine the deflection type through the inclinometer. Based on the deflection type and the inclinometer test value, query the deflection monitoring error corresponding to the deflection type and the inclinometer test value in the continuous beam bridge deflection monitoring error model library. According to the current measured mid-span deflection, correct the error caused by the image deflectometer deflection and / or the target deflection.

2. The continuous beam bridge deflection monitoring error correction method according to claim 1 is characterized in that: In step (2), the deflection test is performed by adjusting the deflection angle of the image deflectometer and / or the target, recording the deflection measurement value at each deflection angle in real time, and taking the difference between the deflection measurement value at each deflection angle and the reference value as the deflection error value.

3. The continuous beam bridge deflection monitoring error correction method according to claim 1, characterized in that: In step (2), the deflection test also includes a step of adjusting the vertical displacement of the target.

4. The continuous beam bridge deflection monitoring error correction method according to claim 1, characterized in that: When the deflection monitoring error comes from the deflection of the deflectometer, the calculation process of the deflection monitoring error is as follows: Define the target imaging height as W1, the target height as W2, the focal length as f, the distance between the target and the image deflectometer lens as L, and the deviation caused by the deflection of the deflectometer as Δh1; The mapping relationship between the image 2D pixel coordinate system and the world 3D coordinate system is shown in the following formula: Where s represents the scale factor; R represents the rotation matrix; T represents the translation matrix; u, v represent the pixel coordinates; u0, v0 represent the horizontal and vertical pixel differences between the center pixel coordinates of the image and the target pixel coordinates, respectively; α, β represent the unit pixel displacement; X w ,Y w Represents world coordinates; Substituting the vertical pixel deviation Δh1 into the formula, we can obtain the deviation Y1 caused by the deflection of the deflectometer; Y1 is the deflection monitoring error caused by the deflection of the deflectometer.

5. The continuous beam bridge deflection monitoring error correction method according to claim 1, characterized in that: When the deflection monitoring error comes from the optical center deflection caused by the target deflection, the calculation process of the deflection monitoring error is as follows: Define the target imaging height as W1, the target height as W2, the focal length as f, the distance between the target and the image deflectometer lens as L, and the vertical pixel deviation caused by the change of the target light source center as Δh2; The mapping relationship between the image 2D pixel coordinate system and the world 3D coordinate system is shown in the following formula: Where s represents the scale factor; R represents the rotation matrix; T represents the translation matrix; u, v represent the pixel coordinates; u0, v0 represent the horizontal and vertical pixel differences between the center pixel coordinates of the image and the target pixel coordinates, respectively; α, β represent the unit pixel displacement; X w ,Y w Represents world coordinates; Substituting the vertical pixel deviation Δh2 into the formula, we can obtain the deviation Y2 caused by the change of the target light source center; Y2 is the deflection monitoring error caused by the target deflection.

6. The continuous beam bridge deflection monitoring error correction method according to claim 1, characterized in that: When the deflection monitoring error comes from the deflection of the deflectometer and the target deflection, the calculation process of the deflection monitoring error is as follows: Define the target imaging height as W1, the target height as W2, the focal length as f, the distance between the target and the image deflectometer lens as L, the vertical pixel deviation caused by the deflection of the deflectometer as Δh1, and the vertical pixel deviation caused by the change of the target light source center as Δh2; The mapping relationship between the image 2D pixel coordinate system and the world 3D coordinate system is shown in the following formula: Where s represents the scale factor; R represents the rotation matrix; T represents the translation matrix; u, v represent the pixel coordinates; u0, v0 represent the horizontal and vertical pixel differences between the center pixel coordinates of the image and the target pixel coordinates, respectively; α, β represent the unit pixel displacement; X w ,Y w Represents world coordinates; Substituting the vertical pixel deviations Δh1 and Δh2 into the formula, we can obtain the deviations Y1 and Y2 caused by the deflection of the deflectometer and the change of the target light source center; The deflection monitoring error Δh caused by the deflection of the deflectometer and the change of the target light source center is: Δh=Y1+Y2.

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