A sensor for monitoring bridge deflection

Abstract

The present invention discloses a sensor for monitoring bridge deflection. The sensor comprises an elastic rod, a strain fiber Bragg grating (FBG), and a temperature fiber Bragg grating (TFG). The elastic rod is linear and flexible, with multiple annular monitoring sections evenly arranged along its axis. A temperature fiber Bragg grating (TFG) is deployed on the surface of the elastic rod at a preset distance from each monitoring section. A strain fiber Bragg grating (FBG) is installed in each groove on the surface of each monitoring section. The four strain fiber Bragg gratings (FBGs) and the corresponding temperature fiber Bragg gratings (TFGs) on a monitoring section form a monitoring link. The aforementioned sensor, which utilizes a linear fiber Bragg grating (FBG) sensor, can effectively address data lag, external interference, stability, and maintainability issues inherent in bridge deflection monitoring. It can effectively obtain dynamic and static deflection deformations of the bridge, thereby more effectively providing data support for bridge structural safety assessments.

Description

Technical Field

[0001] The present invention relates to the technical field of bridge deflection monitoring, and in particular to a sensor for monitoring bridge deflection. Background Art

[0002] The linear performance of a bridge directly reflects its structural safety. On the one hand, excessive beam deformation can lead to more severe impacts and vibrations, significantly impacting traffic safety. On the other hand, excessive beam deformation can damage the bridge structure, threatening the overall structural safety of the bridge. Therefore, linear monitoring of bridges is of great significance. Typically, linear monitoring of bridges is primarily achieved by monitoring changes in bridge deflection, including measuring both dynamic and static deflection. Currently, the main sensor types used for monitoring bridge deflection include connecting pipe sensors, reflective photoelectric sensors, inclination sensors, and CCD sensors. These sensors have been widely used for long-term monitoring of bridge deflection changes, achieving reasonable results. However, these sensor types still present some challenges in monitoring bridge deflection changes. For example, connecting tube sensors are easily affected by the expansion, evaporation, leakage of liquid in the connecting tube during the process of monitoring deflection changes, resulting in a decrease in monitoring accuracy; when using reflective photoelectric sensors, they are extremely susceptible to interference from passing vehicles; inclination sensors are only suitable for deflection monitoring of simply supported beam bridges and have a narrow monitoring range; CCD monitoring has a low coverage range and is easily affected by external natural environmental factors.

[0003] In summary, the existing sensors for monitoring bridge deflection currently have problems such as low long-term stability, difficult maintenance, weak anti-interference ability, and delayed monitoring data. Affected by these factors, it is difficult for existing sensors to accurately obtain changes in bridge deflection. Summary of the Invention

[0004] The purpose of the present invention is to solve the problems of the above-mentioned background technology and to propose a sensor for monitoring the deflection of a bridge.

[0005] The purpose of the present invention can be achieved through the following technical solutions:

[0006] An embodiment of the present invention provides a sensor for monitoring bridge deflection, comprising an elastic rod, a strain fiber Bragg grating, and a temperature fiber Bragg grating;

[0007] The elastic rod as a core rod is linear and flexible, and a plurality of annular monitoring sections are evenly arranged along the axis of the elastic rod. A temperature fiber Bragg grating is deployed at a preset distance from each monitoring section on the surface of the elastic rod.

[0008] There are four grooves on the surface of each monitoring section. The distance between two adjacent grooves is one quarter of the circumference of the monitoring section. A strained fiber Bragg grating is installed in each groove.

[0009] The four strain fiber Bragg gratings of the monitoring section and the corresponding temperature fiber Bragg gratings form a monitoring link.

[0010] An embodiment of the present invention further provides a bridge deflection measurement method based on the above-mentioned sensor for monitoring bridge deflection, wherein the sensor for monitoring bridge deflection is arranged along the bridge direction of the target bridge, and the method includes:

[0011] Acquire monitoring data of each monitoring link; the monitoring data includes strain measurement data of all strain fiber Bragg gratings of the monitoring link, temperature measurement data of the temperature fiber Bragg gratings, and a position number code of the monitoring link;

[0012] Correcting the strain measurement data according to the temperature measurement data to obtain strain correction data;

[0013] Calculating a measured deflection value at a location of the monitoring link based on the strain correction data;

[0014] The deployment position of the monitoring link on the target bridge is determined according to the position number code, and the measured deflection values ​​of all monitoring links are matched with the deployment position to obtain the deflection change data of the target bridge.

[0015] Optionally, the strain measurement data is corrected according to the temperature measurement data to obtain the strain correction data:

[0016]

[0017] Among them, α f is the thermal expansion coefficient of each fiber Bragg grating, ξ is the thermo-optical coefficient of each fiber Bragg grating, P e is the photoelastic constant of each fiber Bragg grating, ΔT is the real-time value monitored by the temperature grating, and Δε is the strain correction data.

[0018] Optionally, calculating the measured deflection value at the location of the monitoring link according to the strain correction data includes:

[0019] Calculating a target angle of the monitoring link according to the strain correction data;

[0020] Calculating the deformation radius of the monitoring link location according to the target angle; the deformation radius is the radius of a virtual circle with the monitoring section as an arc;

[0021] The measured deflection value at the location of the monitoring link is calculated according to the deformation radius.

[0022] Optionally, the target angle of the monitoring link is calculated according to the strain correction data as follows:

[0023]

[0024] Wherein, α is the target angle, and ε1, ε2, ε3 and ε4 are the strain correction data.

[0025] Optionally, the deformation radius of the monitoring link location is calculated according to the target angle as follows:

[0026]

[0027] Wherein, R is the deformation radius, and r is the cross-sectional radius of the elastic rod.

[0028] Optionally, the measured deflection value at the location of the monitoring link is calculated according to the deformation radius as follows:

[0029]

[0030] Where ω(x) is the measured deflection value.

[0031] Beneficial effects of the present invention:

[0032] An embodiment of the present invention provides a sensor for monitoring bridge deflection, comprising an elastic rod, a strain fiber Bragg grating (FBG), and a temperature fiber Bragg grating (TFG). The elastic rod, serving as a core member, is linear and flexible, with multiple annular monitoring sections evenly arranged along its axis. A temperature fiber Bragg grating (TFG) is deployed on the surface of the elastic rod at a preset distance from each monitoring section. Each monitoring section has four grooves on its surface, with the distance between two adjacent grooves being one-quarter the circumference of the monitoring section. A strain fiber Bragg grating (FBG) is installed in each groove. The four strain fiber Bragg gratings and the corresponding temperature fiber Bragg gratings on the monitoring section form a monitoring link. This sensor, which utilizes a linear fiber Bragg grating (FBG) sensor, can effectively address data lag, external interference, stability, and maintainability issues inherent in bridge deflection monitoring. It can effectively obtain dynamic and static deflection deformations of the bridge, thereby more effectively providing data support for bridge structural safety assessments. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] The present invention will be further described below with reference to the accompanying drawings.

[0034] Figure 1 A three-dimensional diagram of a sensor for monitoring bridge deflection provided by an embodiment of the present invention;

[0035] Figure 2 A front view of a sensor for monitoring bridge deflection provided by an embodiment of the present invention;

[0036] Figure 3 A flow chart of a bridge deflection measurement method provided by an embodiment of the present invention;

[0037] In the figure: 1. Elastic rod; 2. Strain fiber Bragg grating; 3. Temperature fiber Bragg grating; 4. Grooves; 5. Monitoring section. DETAILED DESCRIPTION

[0038] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making any creative efforts shall fall within the scope of protection of the present invention.

[0039] The embodiment of the present invention provides a sensor for monitoring bridge deflection. Figure 1 and Figure 2 , Figure 1 A three-dimensional diagram of a sensor for monitoring bridge deflection provided by an embodiment of the present invention, Figure 2 A front view of a sensor for monitoring bridge deflection according to an embodiment of the present invention. The device comprises an elastic rod 1, a strain fiber Bragg grating 2, and a temperature fiber Bragg grating 3.

[0040] The elastic rod 1 as the core rod is linear and flexible. A plurality of annular monitoring sections 5 are evenly arranged along the axis of the elastic rod 1. A temperature fiber Bragg grating 3 is deployed at a preset distance from each monitoring section 5 on the surface of the elastic rod 1.

[0041] There are four grooves 4 on the surface of each monitoring section 5. The distance between two adjacent grooves 4 on the monitoring section 5 is one quarter of the circumference of the monitoring section 5. A strained fiber Bragg grating 2 is installed in each groove 4.

[0042] The four strain fiber Bragg gratings 2 and the corresponding temperature fiber Bragg gratings 3 of the monitoring section 5 form a monitoring link.

[0043] Based on an embodiment of the present invention, a sensor for monitoring bridge deflection is provided. The linear sensor using optical fiber sensing can effectively solve the data lag, external interference, stability, and maintainability problems in bridge deflection monitoring. The dynamic and static deflection deformation of the bridge can be effectively obtained, thereby more effectively providing data support for the safety assessment of the bridge structure.

[0044] In one implementation, the elastic rod 1, serving as the core rod, is linear and flexible. It can be a PC rod coated with high-elasticity, thick acrylic, or other resin, plastic, or rubber rods. The elastic rod 1, serving as the primary sensor for changes in bridge deflection, is arranged along the length of the bridge. Changes in bridge deflection drive changes in the elastic rod, influencing the rod's behavior and generating varying bending moments and axial stretch at each monitoring section 5. This in turn drives axial deformation of the strain fiber Bragg grating 2 within the groove 4. The temperature-dependent effects of the strain fiber Bragg grating 2 are compensated by the temperature-dependent fiber Bragg grating 3, resulting in the actual strain measurement of the strain fiber Bragg grating 2. This allows the calculation of the elastic rod's deflection at that monitoring section 5.

[0045] In one implementation, Figure 1 Here, FBG0A01, FBG0A02, FBG0A03, FBG0A04, FBG0B01, FBG0B02, FBG0B03, and FBG0B04 are the names and numbers of the strain fiber Bragg grating 2, and FBG-T is the name and number of the temperature fiber Bragg grating 3. In actual deployment, the name and number can be used as a position code to be associated with the deployment location of each fiber Bragg grating.

[0046] In one implementation, Figure 2 The distance between two adjacent grooves 4 in the monitoring section 5 is shown to be one-quarter the circumference of the monitoring section 5, meaning that the two grooves 4 form a 90° angle with the center of the monitoring section 5. The groove depth and length of the grooves 4 on the elastic rod surface are consistent with the diameter and length of the strain fiber Bragg grating 2. The grooves 4 are arranged in sections, with four grooves per section evenly distributed along the axis of the elastic rod. The grooves 4 on each section are located at 90° angles along the circumference of the elastic rod surface. The longer the elastic rod, the more sections containing grooves 4. The strain fiber Bragg grating 2, serving as the primary sensing element, is tightly embedded within the grooves. Each section has four grooves, corresponding to four embedded strain fiber Bragg gratings 2. The temperature fiber Bragg grating 3 is surface-mounted and arranged between the monitoring sections 5. Four strain fiber Bragg gratings 2 and one temperature fiber Bragg grating 3 on each monitoring section 5 are connected in series to form a monitoring link.

[0047] Based on the above-mentioned sensor for monitoring bridge deflection, an embodiment of the present invention provides a bridge deflection measurement method, see Figure 3 , Figure 3 This is a flow chart of a bridge deflection measurement method provided by an embodiment of the present invention. The sensors for monitoring bridge deflection are arranged along the bridge direction of the target bridge. The method includes:

[0048] S301: Acquire monitoring data of each monitoring link.

[0049] S302 , correcting the strain measurement data according to the temperature measurement data to obtain strain correction data.

[0050] S303: Calculate the measured deflection value at the location of the monitoring link according to the strain correction data.

[0051] S304: Determine the deployment position of the monitoring link on the target bridge according to the position number code, match the measured deflection value of the monitoring link with the deployment position, and obtain deflection change data of the target bridge.

[0052] The monitoring data includes the strain measurement data of all strain fiber Bragg gratings in the monitoring link, the temperature measurement data of the temperature fiber Bragg gratings, and the position number code of the monitoring link.

[0053] Based on the embodiment of the present invention, a bridge deflection measurement method is provided. The linear sensor using optical fiber sensing can effectively solve the data lag, external interference (influence of expansion coefficient and temperature), stability and maintainability problems existing in bridge deflection monitoring. The dynamic and static deflection deformation of the bridge can be effectively obtained, thereby more effectively providing data support for the safety assessment of the bridge structure.

[0054] In one implementation, elastic rods serve as the primary sensors for bridge deflection changes, arranged along the length of the bridge. Changes in bridge deflection drive these rods, influencing the rods and inducing varying bending moments and axial stretching at each grooved section. This in turn induces axial deformation in the strain-sensitive fiber Bragg gratings within the grooves. The changes in bridge deflection can be calculated using the strain-sensitive fiber Bragg grating measurements.

[0055] In one implementation, by correcting the strain measurement data based on the temperature measurement data, the temperature effect on the deformation of the strain fiber Bragg grating can be compensated, making the strain correction data closer to the deformation of the target bridge, thereby improving the accuracy of the bridge deflection measurement.

[0056] In one implementation, a high-speed data collector is used to acquire real-time fiber Bragg grating data, thereby acquiring changes in the dynamic deflection of the bridge without data lag.

[0057] In one embodiment, step S302 is specifically as follows:

[0058]

[0059] Among them, α f is the thermal expansion coefficient of the strained fiber Bragg grating, ξ is the thermo-optical coefficient of the strained fiber Bragg grating, P e is the photoelastic constant of the strained fiber Bragg grating, ΔT is the real-time value of the temperature grating monitoring, and Δε is the strain correction data of the strained fiber Bragg grating.

[0060] In one embodiment, step S303 includes:

[0061] Step 1: Calculate the target angle of the monitoring link based on the strain correction data;

[0062] Step 2: Calculate the deformation radius of the monitoring link location based on the target angle; the deformation radius is the radius of a virtual circle with the monitoring section as an arc;

[0063] Step three: Calculate the measured deflection value at the location of the monitoring link based on the deformation radius.

[0064] In one embodiment, the target angle of the monitoring link is calculated based on the strain correction data as follows:

[0065]

[0066] Among them, α is the target angle, and ε1, ε2, ε3, and ε4 are strain correction data.

[0067] In one implementation, α is the angle between the line connecting the bending direction of the elastic rod and the center of the curvature circle and the normal line (perpendicular to the ground). ε1, ε2, ε3, and ε4 are the strain correction data calculated by each strain fiber Bragg grating in the same monitoring section according to formula (1).

[0068] In one embodiment, the deformation radius of the monitoring link location is calculated based on the target angle as follows:

[0069]

[0070] Where R is the deformation radius and r is the cross-sectional radius of the elastic rod.

[0071] In one embodiment, the measured deflection value at the location of the monitoring link is calculated based on the deformation radius as follows:

[0072]

[0073] Where ω(x) is the measured deflection value.

[0074] The above is a detailed description of an embodiment of the present invention. However, the content described is only a preferred embodiment of the present invention and should not be considered to limit the scope of the present invention. All equivalent changes and improvements made within the scope of the present invention should still fall within the scope of the patent coverage of the present invention.

Claims

1. A bridge deflection measurement method using a sensor for monitoring bridge deflection, characterized in that: A sensor for monitoring bridge deflection is provided, wherein the sensor for monitoring bridge deflection comprises an elastic rod (1), a strain fiber Bragg grating (2) and a temperature fiber Bragg grating (3); The elastic rod (1) is a core rod member that is linear and flexible, and a plurality of annular monitoring sections (5) are evenly arranged along the axis of the elastic rod (1). A temperature fiber Bragg grating (3) is deployed at a preset distance from each monitoring section (5) on the surface of the elastic rod (1). There are four grooves (4) on the surface of each monitoring section (5), the distance between two adjacent grooves (4) on the monitoring section (5) is one quarter of the circumference of the monitoring section (5), and a strain fiber Bragg grating (2) is installed in each groove (4); The groove depth and length of the groove (4) on the surface of the elastic rod are consistent with the diameter and length of the strained fiber grating (2); The four strain fiber Bragg gratings (2) and the corresponding temperature fiber Bragg gratings (3) of the monitoring section (5) are connected in series to form a monitoring link; The sensors for monitoring bridge deflection are arranged along the target bridge along the bridge direction, and the method includes: Acquire monitoring data of each monitoring link; the monitoring data includes strain measurement data of all strain fiber Bragg gratings of the monitoring link, temperature measurement data of the temperature fiber Bragg gratings, and a position number code of the monitoring link; Correcting the strain measurement data according to the temperature measurement data to obtain strain correction data; Calculating a measured deflection value at a location of the monitoring link based on the strain correction data; Determine the deployment position of the monitoring link on the target bridge according to the position number code, correspond the measured deflection values ​​of all monitoring links to the deployment position, and obtain the deflection change data of the target bridge; Correcting the strain measurement data according to the temperature measurement data to obtain the strain correction data is specifically: ； in, is the thermal expansion coefficient of the strained fiber Bragg grating, is the thermo-optical coefficient of the strained fiber Bragg grating, is the photoelastic constant of the strained fiber Bragg grating, Real-time value of temperature fiber Bragg grating monitoring, is the strain correction data of the strained fiber Bragg grating.

2. A bridge deflection measurement method according to claim 1, characterized in that: Calculating the measured deflection value at the location of the monitoring link according to the strain correction data includes: Calculating a target angle of the monitoring link according to the strain correction data; Calculating the deformation radius of the monitoring link location according to the target angle; the deformation radius is the radius of a virtual circle with the monitoring section as an arc; The measured deflection value at the location of the monitoring link is calculated according to the deformation radius.

3. A bridge deflection measurement method according to claim 2, characterized in that: The target angle of the monitoring link is calculated based on the strain correction data as follows: ， ； in, The angle formed by the line connecting the bending direction of the elastic rod and the center of the curvature circle and the normal line perpendicular to the ground, that is, the torsion angle, 、 、 and is the strain correction data.

4. A bridge deflection measurement method according to claim 3, characterized in that: The deformation radius of the monitoring link location is calculated based on the target angle as follows: ； in, is the deformation radius, is the cross-sectional radius of the elastic rod.

5. A bridge deflection measurement method according to claim 4, characterized in that: The measured deflection value at the location of the monitoring link is calculated based on the deformation radius as follows: ； in, To measure the deflection value.

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