Steel structure platform health monitoring system and method based on optical fiber sensing

Abstract

The invention relates to the technical field of optical fiber real-time monitoring, in particular to a steel structure platform health monitoring system and method based on optical fiber sensing, and the method comprises the following steps: respectively monitoring a steel beam and a bolt node of a steel structure platform by using an FBG strain sensor and a temperature sensor, and independently monitoring the bending strain of the steel beam by using an FBG curvature meter; after strain and temperature are decoupled, a real strain value is obtained, the steel beam curvature is measured by combining three gratings of a curvature meter, an eccentric threshold value is set, and when the steel beam curvature anomaly exceeds the eccentric threshold value, a steel beam deformation early warning is generated; the pre-tightening force loss rate is calculated by using the real axial strain of the bolt, the node state is dynamically evaluated by combining the curvature anomaly of the steel beam, a yellow alarm and a red alarm are set, maintenance is planned when the yellow alarm is triggered by the loss rate, and emergency disposal is performed when the red alarm is triggered. According to the system and method, thermal expansion and cold contraction errors are eliminated through strain and temperature decoupling, the bending degree of the steel beam is effectively evaluated by means of the FBG curvature meter, safety and stability of the platform are guaranteed, and a maintenance strategy is optimized.

Description

Technical Field

[0001] This invention relates to the field of fiber optic real-time monitoring technology, specifically a health monitoring system and method for steel structure platforms based on fiber optic sensing. Background Technology

[0002] In the field of steel structure platform health monitoring, traditional methods often face numerous limitations. Some monitoring methods rely on single parameters, making it difficult to simultaneously consider the critical states of steel beams and bolted joints; the coupling effect of temperature changes and strain can easily lead to measurement errors, making it difficult to accurately reflect the true stress state of the components. Monitoring of steel beam bending deformation lacks multi-directional, precise calculation methods, making it difficult to effectively identify potential risks such as load eccentricity; the assessment of bolted joint preload loss often lacks dynamic analysis, and unreasonable alarm threshold settings can easily lead to untimely maintenance or over-maintenance, affecting platform safety and stability and potentially increasing maintenance costs and wasting resources. Summary of the Invention

[0003] The purpose of this invention is to provide a health monitoring system and method for steel structure platforms based on fiber optic sensing, thereby solving the problems mentioned in the background art.

[0004] To achieve the above objectives, the present invention adopts the following technical solution:

[0005] A steel structure platform health monitoring system based on fiber optic sensing includes a sensor deployment and data acquisition module, a steel beam health status calculation module, and a bolt node health status calculation module.

[0006] The sensor deployment and data acquisition module acquires monitoring data of the steel beam and bolt joints; the steel beam health status calculation module assesses the health status by calculating the actual strain and curvature of the steel beam; the bolt joint health status calculation module processes and calculates the actual strain and preload loss of the bolts, and issues corresponding alarms according to the degree of loss.

[0007] The sensor deployment and data acquisition module includes a steel beam monitoring unit and a bolt node monitoring unit;

[0008] The steel beam monitoring unit includes an FBG strain sensor, a temperature sensor, and an FBG curvature meter installed inside the steel beam. The FBG strain sensor acquires the wavelength shift caused by strain, and the temperature sensor measures the temperature change of the steel beam. The FBG curvature meter has three built-in gratings, which are symmetrically installed in the steel beam at 120 degrees to capture strain values ​​in different directions when the steel beam is bent.

[0009] The bolt node monitoring unit includes an FBG strain sensor and a temperature sensor axially attached to the bolt shank. The FBG strain sensor acquires the wavelength offset, and the temperature sensor measures the temperature change of the bolt shank.

[0010] The steel beam health status calculation module includes a steel beam true strain value calculation unit and a bending degree calculation alarm unit;

[0011] The steel beam true strain value calculation unit eliminates errors through the strain and temperature decoupling formula to obtain the true strain value of the steel beam.

[0012] The curvature calculation alarm unit uses strain values ​​measured by the FBG curvature meter in different directions to calculate the transverse curvature of the steel beam in the X direction and the vertical curvature in the Y direction. When the ratio of the transverse curvature to the vertical curvature exceeds the eccentricity threshold set by those skilled in the art, a load eccentricity warning is triggered.

[0013] The bolt node health status calculation module includes a bolt true strain value calculation unit, a preload loss calculation unit, and a dynamic threshold alarm unit.

[0014] The bolt true strain value calculation unit eliminates the error caused by thermal expansion and contraction through the strain and temperature decoupling formula, and obtains the true strain value of the bolt.

[0015] The preload loss calculation and alarm unit calculates the preload loss rate of the bolt based on the bolt's actual strain value, combined with the bolt material's elastic modulus, effective cross-sectional area at the thread, torque coefficient, thread friction coefficient, and initial preload design value.

[0016] When the dynamic threshold alarm unit is in an unbiased state, a yellow alarm is triggered when the loss rate is between the set values ​​b and c, and a red alarm is triggered when the loss rate reaches or exceeds c. When the dynamic threshold alarm unit is in an eccentric state, a yellow alarm is triggered when the loss rate is between the set values ​​b1 and c1, and a red alarm is triggered when the loss rate reaches or exceeds c1.

[0017] A method for health monitoring of steel structure platforms based on fiber optic sensing, comprising the following specific steps:

[0018] Step S1: Use FBG strain sensors and temperature sensors to monitor the steel beams and bolt joints of the steel structure platform, and use FBG curvature meters to monitor the bending strain of the steel beams separately.

[0019] Step S2: After decoupling the strain from the temperature, the true strain value is obtained. The curvature of the steel beam is measured by the three gratings of the curvature meter. An eccentricity threshold is set. When the curvature anomaly of the steel beam exceeds the eccentricity threshold, a steel beam deformation warning is generated.

[0020] Step S3: Calculate the preload loss rate using the actual axial strain of the bolts, and dynamically assess the node status in conjunction with the curvature anomaly of the steel beam. Set yellow and red alarms. When the loss rate triggers a yellow alarm, plan maintenance; when it triggers a red alarm, take emergency measures.

[0021] Preferably, the specific steps of step S1 are as follows:

[0022] (1) FBG strain sensor, temperature sensor and FBG curvature meter are deployed in the steel beam to obtain the wavelength shift Δλ0 and temperature change value ΔT0 caused by the strain of the optical fiber. The FBG curvature meter integrates three gratings, which are symmetrically distributed at 120 degrees. When the steel structure bends, the three gratings G1, G2 and G3 measure the bending strain values ​​ε1, ε2 and ε3 respectively. The angle between grating G1 and the Y-axis of the steel beam is 0 degrees, the angle between grating G2 and the Y-axis of the steel beam is 120 degrees, and the angle between grating G3 and the Y-axis of the steel beam is 240 degrees.

[0023] (2) In order to obtain the relevant key parameters of the bolt node, the FBG strain sensor was axially attached to the bolt rod to obtain the wavelength offset Δλ1, and the temperature sensor was deployed at the bolt rod to measure the temperature change value ΔT1.

[0024] Preferably, the specific steps of step S2 are as follows:

[0025] (1) By using the strain-temperature decoupling formula, the wavelength offset of the steel beam is used to eliminate the error caused by thermal expansion and contraction, and the true strain value ε0 is obtained. The strain-temperature decoupling formula is as follows:

[0026]

[0027] In the formula, K ε α is the strain sensitivity coefficient used to convert wavelength into strain value, α is the linear thermal expansion coefficient of the steel beam (in με / ℃), and β is the correction factor (in με / ℃). 2 All settings are configured by those skilled in the art;

[0028] (2) The degree of bending of the steel beam is calculated by obtaining strain values ​​in different directions using an FBG curvature meter. The transverse curvature K in the X direction is calculated by utilizing the geometric characteristics of three 120-degree symmetrically distributed gratings. x Vertical curvature K along the Y-axis y :

[0029]

[0030] In the formula, h is the distance from the central axis of the steel beam to the fiber layer of the FBG curvature meter, and K x For the lateral curvature in the X direction, K y Vertical curvature along the Y-axis, in meters. -1 ,when When, no warning is triggered, when At that time, a load eccentricity warning is triggered. denoted as the curvature anomaly of the steel beam, and 'a' as the eccentricity threshold, which is set by those skilled in the art.

[0031] Preferably, the specific steps of step S3 are as follows:

[0032] (1) By using the strain-temperature decoupling formula, the wavelength offset of the bolt is used to eliminate the error caused by thermal expansion and contraction, and the true strain value ε of the bolt is obtained. 螺栓 The formula for decoupling strain and temperature:

[0033]

[0034] In the formula, K ε1 α1 is the bolt strain sensitivity coefficient, used to convert wavelength into strain value; β1 is the bolt linear thermal expansion coefficient, in με / ℃; and β1 is the correction coefficient, in με / ℃. 2 All settings are configured by those skilled in the art;

[0035] (2) Measure the bolt preload loss F 损失率 :

[0036]

[0037] In the formula, E is the elastic modulus of the bolt material, A is the effective cross-sectional area at the bolt thread, K is the torque coefficient, μ is the thread friction coefficient, and F0 is the initial preload design value.

[0038] (3) A yellow alarm indicates a medium risk, and a red alarm indicates a high risk;

[0039] when At that time, the bolt preload loss F 损失率 No warning is triggered when the bolt preload loss is ≤b; a warning is triggered when the bolt preload loss is <F. 损失率 When the bolt preload loss is less than c, a yellow alarm is triggered. 损失率 When b ≥ c, a red alarm is triggered. b and c are alarm thresholds, which are set by those skilled in the art.

[0040] when At that time, the bolt preload loss F 损失率 No warning is triggered when the bolt preload loss is ≤b1; a warning is triggered when the bolt preload loss is <F. 损失率 When <c1, a yellow alarm is triggered when the bolt preload loss F 损失率 When ≥c1, a red alert is triggered; b1=b / λ, c1=c / λ, where λ is an adjustment coefficient, which is set by those skilled in the art.

[0041] Compared with the prior art, the beneficial effects achieved by the present invention are as follows:

[0042] (1) By using strain and temperature decoupling technology, the interference of ambient temperature changes on sensor data is eliminated, ensuring that the actual strain values ​​of steel beams and bolts are more closely approximated to the actual state. Fiber Bragg grating (FBG) strain sensors, temperature sensors, and three-grating curvature meters are deployed in a coordinated manner, while also taking into account the critical states of steel beam and bolt joints, achieving multi-dimensional data complementarity and reducing the risk of misjudgment;

[0043] (2) The system calculates the transverse and vertical curvature of the steel beam in real time, identifies the load eccentricity state through curvature anomaly, and triggers deformation warning when the preload exceeds the preset threshold. For bolt nodes, the system quantifies the preload loss rate and dynamically adjusts the alarm threshold in combination with the eccentricity state of the steel beam: when the structure is eccentric, the loss rate threshold for triggering the alarm is automatically reduced, the warning sensitivity under high-risk conditions is improved, and real-time warning and dynamic assessment of structural anomalies are realized. The graded response mechanism balances safety and operation and maintenance efficiency.

[0044] (3) The system adopts a modular design, forming a fully automated monitoring chain from data acquisition and steel beam health analysis to bolt node evaluation; yellow alerts provide a buffer time to schedule preventive maintenance and avoid escalation of problems; red alerts force immediate intervention to prevent chain accidents, optimize the initiative and reliability of engineering operation and maintenance, reduce the risk of sudden structural failure, reduce the frequency and cost of manual inspection, and extend the overall life of the steel structure platform.

[0045] (4) By decoupling strain and temperature, thermal expansion and contraction errors are eliminated, ensuring accurate strain data; the degree of bending of steel beams can be effectively assessed with the help of FBG curvature meter, and load eccentricity warning can be triggered in time; at the same time, the bolt preload loss rate can be accurately calculated, and planned maintenance or emergency handling can be realized through graded alarms, which not only ensures the safety and stability of the platform, but also optimizes maintenance strategies and reduces resource waste. Attached Figure Description

[0046] Figure 1 This is a schematic diagram of the system of the present invention. Detailed Implementation

[0047] The technical solution of the present invention will be described in detail below with reference to the accompanying drawings and embodiments.

[0048] like Figure 1 As shown, a steel structure platform health monitoring system based on fiber optic sensing includes a sensor deployment and data acquisition module, a steel beam health status calculation module, and a bolt node health status calculation module.

[0049] The sensor deployment and data acquisition module acquires monitoring data of the steel beams and bolted joints;

[0050] The steel beam health status calculation module assesses the health status of the steel beam by calculating its actual strain and curvature.

[0051] The bolt node health status calculation module processes and calculates the actual strain and preload loss of the bolts, and issues corresponding alarms based on the degree of loss.

[0052] The sensor deployment and data acquisition module includes a steel beam monitoring unit and a bolt node monitoring unit;

[0053] The steel beam monitoring unit includes an FBG strain sensor, a temperature sensor, and an FBG curvature meter installed inside the steel beam. The FBG strain sensor acquires the wavelength shift caused by strain, and the temperature sensor measures the temperature change of the steel beam. The FBG curvature meter has three built-in gratings, which are symmetrically installed in the steel beam at 120 degrees to capture strain values ​​in different directions when the steel beam is bent.

[0054] The bolt node monitoring unit includes an FBG strain sensor and a temperature sensor axially attached to the bolt shank. The FBG strain sensor acquires the wavelength offset, and the temperature sensor measures the temperature change of the bolt shank.

[0055] The steel beam health status calculation module includes a steel beam true strain value calculation unit and a bending degree calculation alarm unit;

[0056] The steel beam true strain value calculation unit eliminates errors through strain and temperature decoupling formulas to obtain the true strain value of the steel beam.

[0057] The curvature calculation alarm unit uses strain values ​​measured by an FBG curvature meter in different directions to calculate the transverse curvature of the steel beam in the X direction and the vertical curvature in the Y direction. When the ratio of the transverse curvature to the vertical curvature exceeds the eccentricity threshold set by those skilled in the art, a load eccentricity warning is triggered.

[0058] The bolt node health status calculation module includes a bolt true strain value calculation unit, a preload loss calculation unit, and a dynamic threshold alarm unit;

[0059] The bolt true strain value calculation unit eliminates the error caused by thermal expansion and contraction through the strain and temperature decoupling formula, and obtains the true strain value of the bolt.

[0060] The preload loss calculation alarm unit calculates the preload loss rate of the bolt based on the bolt's actual strain value, combined with the bolt material's elastic modulus, effective cross-sectional area at the thread, torque coefficient, thread friction coefficient, and initial preload design value.

[0061] When the dynamic threshold alarm unit is in an unbiased state, a yellow alarm is triggered when the loss rate is between the set values ​​b and c, and a red alarm is triggered when the loss rate reaches or exceeds c. When the dynamic threshold alarm unit is in an eccentric state, a yellow alarm is triggered when the loss rate is between the set values ​​b1 and c1, and a red alarm is triggered when the loss rate reaches or exceeds c1.

[0062] Example 1

[0063] A method for health monitoring of steel structure platforms based on fiber optic sensing, comprising the following specific steps:

[0064] Step S1: Use FBG strain sensors and temperature sensors to monitor the steel beams and bolt joints of the steel structure platform, and use FBG curvature meters to monitor the bending strain of the steel beams separately.

[0065] (1) FBG strain sensor, temperature sensor and FBG curvature meter are deployed in the steel beam to obtain the wavelength shift Δλ0 and temperature change value ΔT0 caused by the strain of the optical fiber. The FBG curvature meter integrates three gratings, which are symmetrically distributed at 120 degrees. When the steel structure bends, the three gratings G1, G2 and G3 measure the bending strain values ​​ε1, ε2 and ε3 respectively. The angle between grating G1 and the Y-axis of the steel beam is 0 degrees, the angle between grating G2 and the Y-axis of the steel beam is 120 degrees, and the angle between grating G3 and the Y-axis of the steel beam is 240 degrees. The FBG strain sensor measures the wavelength shift Δλ0 = 1.2nm, the temperature sensor measures the temperature change value ΔT0 = 10℃, and the FBG curvature meter measures the bending strain values ​​ε1 = 150με, ε2 = 160με and ε3 = 140με.

[0066] (2) In order to obtain the relevant key parameters of the bolt node, the FBG strain sensor was axially attached to the bolt rod to obtain the wavelength offset Δλ1, and the temperature sensor was deployed at the bolt rod to measure the temperature change value ΔT1, Δλ1=105pm, ΔT1=0℃.

[0067] Step S2: After decoupling strain from temperature, the true strain value is obtained. The curvature of the steel beam is measured by combining the three gratings of the curvature meter. An eccentricity threshold is set. When the curvature anomaly of the steel beam exceeds the eccentricity threshold, a steel beam deformation warning is generated. The specific steps are as follows:

[0068] (1) By using the strain-temperature decoupling formula, the wavelength offset of the steel beam is used to eliminate the error caused by thermal expansion and contraction, and the true strain value ε0 is obtained. The strain-temperature decoupling formula is as follows:

[0069]

[0070] In the formula, K ε α is the strain sensitivity coefficient used to convert wavelength into strain value, α is the linear thermal expansion coefficient of the steel beam (in με / ℃), and β is the correction factor (in με / ℃). 2 Set coefficient K ε =1.2nm / με, α=12με / ℃, β=0.05με / ℃ 2 The calculation yields ε0 = 124.

[0071] (2) The degree of bending of the steel beam is calculated by obtaining strain values ​​in different directions using an FBG curvature meter. The transverse curvature K in the X direction is calculated by utilizing the geometric characteristics of three 120-degree symmetrically distributed gratings. x Vertical curvature K along the Y-axis y :

[0072]

[0073] In the formula, h is the distance from the central axis of the steel beam to the fiber layer of the FBG curvature meter, and K x For the lateral curvature in the X direction, K y Vertical curvature along the Y-axis, in meters. -1 'a' is the eccentricity threshold. With threshold a = 0.5 and h = 24 mm, the calculated value is: |K x |≈0.48,|K y |≈1.08, calculated No bias warning is triggered.

[0074] Step S3: Calculate the preload loss rate using the actual axial strain of the bolts, and dynamically assess the node status in conjunction with the curvature anomaly of the steel beam. Set yellow and red alarms. When the loss rate triggers a yellow alarm, plan maintenance; when it triggers a red alarm, take emergency measures. The specific steps are as follows:

[0075] (1) By using the strain-temperature decoupling formula, the wavelength offset of the bolt is eliminated, thus eliminating the error caused by thermal expansion and contraction, and the true strain value ε of the bolt is obtained. 螺栓 The formula for decoupling strain and temperature:

[0076]

[0077] In the formula, K ε1 α1 is the bolt strain sensitivity coefficient, used to convert wavelength into strain value; β1 is the bolt linear thermal expansion coefficient, in με / ℃; and β1 is the correction coefficient, in με / ℃. 2 Set K ε1 =1.25pm / με, α1=11.5με / ℃, β1=0.05με / ℃ 2 ε was calculated 螺栓 =84με;

[0078] (2) Measure the bolt preload loss F 损失率 :

[0079]

[0080] In the formula, E is the elastic modulus of the bolt material, A is the effective cross-sectional area at the bolt thread, K is the torque coefficient, μ is the thread friction coefficient, and F0 is the initial preload design value. We set E = 200 GPa and A = 300 mm.2 Given K = 0.18, μ = 0.12, and F0 = 150 kN, the calculation yields...

[0081] (3) A yellow alarm indicates medium risk, and a red alarm indicates high risk, with a = 0.5, b = 50%, and c = 60%; when When the bolt preload loss b < F 损失率 When <c, a yellow alert is triggered.

[0082] Example 2

[0083] A method for health monitoring of steel structure platforms based on fiber optic sensing, comprising the following specific steps:

[0084] Step S1: Use FBG strain sensors and temperature sensors to monitor the steel beams and bolt joints of the steel structure platform, and use FBG curvature meters to monitor the bending strain of the steel beams separately.

[0085] (1) FBG strain sensor, temperature sensor and FBG curvature meter are deployed in the steel beam to obtain the wavelength shift Δλ0 and temperature change value ΔT0 caused by the strain of the optical fiber. The FBG curvature meter integrates three gratings, which are symmetrically distributed at 120 degrees. When the steel structure bends, the three gratings G1, G2 and G3 measure the bending strain values ​​ε1, ε2 and ε3 respectively. The angle between grating G1 and the Y-axis of the steel beam is 0 degrees, the angle between grating G2 and the Y-axis of the steel beam is 120 degrees, and the angle between grating G3 and the Y-axis of the steel beam is 240 degrees. The FBG strain sensor measures the wavelength shift Δλ0 = 1.2nm, the temperature sensor measures the temperature change value ΔT0 = 10℃, and the FBG curvature meter measures the bending strain values ​​ε1 = 145με, ε2 = 160με and ε3 = 140με.

[0086] (2) In order to obtain the relevant key parameters of the bolt node, the FBG strain sensor was axially attached to the bolt rod to obtain the wavelength offset Δλ1, and the temperature sensor was deployed at the bolt rod to measure the temperature change value ΔT1, Δλ1=105pm, ΔT1=0℃.

[0087] Step S2: After decoupling strain from temperature, the true strain value is obtained. The curvature of the steel beam is measured by combining the three gratings of the curvature meter. An eccentricity threshold is set. When the curvature anomaly of the steel beam exceeds the eccentricity threshold, a steel beam deformation warning is generated. The specific steps are as follows:

[0088] (1) By using the strain-temperature decoupling formula, the wavelength offset of the steel beam is used to eliminate the error caused by thermal expansion and contraction, and the true strain value ε0 is obtained. The strain-temperature decoupling formula is as follows:

[0089]

[0090] In the formula, K εα is the strain sensitivity coefficient used to convert wavelength into strain value, α is the linear thermal expansion coefficient of the steel beam (in με / ℃), and β is the correction factor (in με / ℃). 2 Set coefficient K ε =1.2nm / με, α=12με / ℃, β=0.05με / ℃ 2 The calculation yields ε0 = 124.

[0091] (2) The degree of bending of the steel beam is calculated by obtaining strain values ​​in different directions using an FBG curvature meter. The transverse curvature K in the X direction is calculated by utilizing the geometric characteristics of three 120-degree symmetrically distributed gratings. x Vertical curvature K along the Y-axis y :

[0092]

[0093] In the formula, h is the distance from the central axis of the steel beam to the fiber layer of the FBG curvature meter, and K x For the lateral curvature in the X direction, K y Vertical curvature along the Y-axis, in meters. -1 'a' is the eccentricity threshold. With threshold a = 0.5 and h = 24 mm, the calculated value is: |K x |≈0.48,|K y |≈0.88, calculated A load eccentricity warning has been triggered.

[0094] Step S3: Calculate the preload loss rate using the actual axial strain of the bolts, and dynamically assess the node status in conjunction with the curvature anomaly of the steel beam. Set yellow and red alarms. When the loss rate triggers a yellow alarm, plan maintenance; when it triggers a red alarm, take emergency measures. The specific steps are as follows:

[0095] (1) By using the strain-temperature decoupling formula, the wavelength offset of the bolt is eliminated, thus eliminating the error caused by thermal expansion and contraction, and the true strain value ε of the bolt is obtained. 螺栓 The formula for decoupling strain and temperature:

[0096]

[0097] In the formula, K ε1 α1 is the bolt strain sensitivity coefficient, used to convert wavelength into strain value; β1 is the bolt linear thermal expansion coefficient, in με / ℃; and β1 is the correction coefficient, in με / ℃. 2 Set K ε1 =1.25pm / με, α1=11.5με / ℃, β1=0.05με / ℃ 2 ε was calculated 螺栓 =84με;

[0098] (2) Measure the bolt preload loss F 损失率 :

[0099]

[0100] In the formula, E is the elastic modulus of the bolt material, A is the effective cross-sectional area at the bolt thread, K is the torque coefficient, μ is the thread friction coefficient, and F0 is the initial preload design value. We set E = 200 GPa and A = 300 mm. 2 Given K = 0.18, μ = 0.12, and F0 = 150 kN, the calculation yields...

[0101] (3) A yellow alarm indicates medium risk, and a red alarm indicates high risk. a = 0.5, b = 50%, c = 60%, λ = 1.2, b1 = b / λ, c1 = c / λ. In the formula, λ is the adjustment coefficient. At that time, the bolt preload loss F 损失率 When >c1, a red alert is triggered.

[0102] Example 3

[0103] A method for health monitoring of steel structure platforms based on fiber optic sensing, comprising the following specific steps:

[0104] Step S1: Use FBG strain sensors and temperature sensors to monitor the steel beams and bolt joints of the steel structure platform, and use FBG curvature meters to monitor the bending strain of the steel beams separately.

[0105] (1) FBG strain sensor, temperature sensor and FBG curvature meter are deployed in the steel beam to obtain the wavelength shift Δλ0 and temperature change value ΔT0 caused by the strain of the optical fiber. The FBG curvature meter integrates three gratings, which are symmetrically distributed at 120 degrees. When the steel structure bends, the three gratings G1, G2 and G3 measure the bending strain values ​​ε1, ε2 and ε3 respectively. The angle between grating G1 and the Y-axis of the steel beam is 0 degrees, the angle between grating G2 and the Y-axis of the steel beam is 120 degrees, and the angle between grating G3 and the Y-axis of the steel beam is 240 degrees. The FBG strain sensor measures the wavelength shift Δλ0 = 1.2nm, the temperature sensor measures the temperature change value ΔT0 = 10℃, and the FBG curvature meter measures the bending strain values ​​ε1 = 155με, ε2 = 160με and ε3 = 140με.

[0106] (2) In order to obtain the relevant key parameters of the bolt node, the FBG strain sensor was axially attached to the bolt rod to obtain the wavelength offset Δλ1, and the temperature sensor was deployed at the bolt rod to measure the temperature change value ΔT1, Δλ1=105pm, ΔT1=0℃.

[0107] Step S2: After decoupling strain from temperature, the true strain value is obtained. The curvature of the steel beam is measured by combining the three gratings of the curvature meter. An eccentricity threshold is set. When the curvature anomaly of the steel beam exceeds the eccentricity threshold, a steel beam deformation warning is generated. The specific steps are as follows:

[0108] (1) By using the strain-temperature decoupling formula, the wavelength offset of the steel beam is used to eliminate the error caused by thermal expansion and contraction, and the true strain value ε0 is obtained. The strain-temperature decoupling formula is as follows:

[0109]

[0110] In the formula, K ε α is the strain sensitivity coefficient used to convert wavelength into strain value, α is the linear thermal expansion coefficient of the steel beam (in με / ℃), and β is the correction factor (in με / ℃). 2 Set coefficient K ε =1.2nm / με, α=12με / ℃, β=0.05με / ℃ 2 The calculation yields ε0 = 124.

[0111] (2) The degree of bending of the steel beam is calculated by obtaining strain values ​​in different directions using an FBG curvature meter. The transverse curvature K in the X direction is calculated by utilizing the geometric characteristics of three 120-degree symmetrically distributed gratings. x Vertical curvature K along the Y-axis y :

[0112]

[0113] In the formula, h is the distance from the central axis of the steel beam to the fiber layer of the FBG curvature meter, and K x For the lateral curvature in the X direction, K y Vertical curvature along the Y-axis, in meters. -1 'a' is the eccentricity threshold. With threshold a = 0.5 and h = 24 mm, the calculated value is: |K x |≈0.48,|K y |≈1.29, calculated as follows No warning was triggered.

[0114] Step S3: Calculate the preload loss rate using the actual axial strain of the bolts, and dynamically assess the node status in conjunction with the curvature anomaly of the steel beam. Set yellow and red alarms. When the loss rate triggers a yellow alarm, plan maintenance; when it triggers a red alarm, take emergency measures. The specific steps are as follows:

[0115] (1) By using the strain-temperature decoupling formula, the wavelength offset of the bolt is eliminated, thus eliminating the error caused by thermal expansion and contraction, and the true strain value ε of the bolt is obtained. 螺栓 The formula for decoupling strain and temperature:

[0116]

[0117] In the formula, K ε1 α1 is the bolt strain sensitivity coefficient, used to convert wavelength into strain value; β1 is the bolt linear thermal expansion coefficient, in με / ℃; and β1 is the correction coefficient, in με / ℃. 2 Set K ε1 =1.25pm / με, α1=11.5με / ℃, β1=0.05με / ℃ 2 ε was calculated 螺栓 =84με;

[0118] (2) Measure the bolt preload loss F 损失率 :

[0119]

[0120] In the formula, E is the elastic modulus of the bolt material, A is the effective cross-sectional area at the bolt thread, K is the torque coefficient, μ is the thread friction coefficient, and F0 is the initial preload design value. We set E = 200 GPa and A = 300 mm. 2 Given K = 0.18, μ = 0.12, and F0 = 160 kN, the calculated F... 损失率 =45.83%;

[0121] (3) A yellow alarm indicates medium risk, and a red alarm indicates high risk, with a = 0.5, b = 50%, and c = 60%; when At that time, the bolt preload loss F 损失率 <b does not trigger a warning.

Claims

1. A fiber optic sensor based steel structure platform health monitoring system, characterized in that, The sensor deployment and data acquisition module, the steel beam health state calculation module and the bolt joint health state calculation module are included. The sensor deployment and data acquisition module acquires monitoring data of the steel beam and the bolt joint; the steel beam health state calculation module evaluates the health state by calculating the real strain and the bending degree of the steel beam; The bolt joint health state calculation module calculates the real strain and the pre-tightening force loss of the bolt and issues a corresponding alarm according to the loss degree; The sensor deployment and data acquisition module includes a steel beam monitoring unit and a bolt joint monitoring unit; the steel beam monitoring unit includes an FBG strain sensor, a temperature sensor and an FBG curvature meter which are installed inside the steel beam, the FBG strain sensor acquires the wavelength offset caused by the strain, and the temperature sensor measures the temperature change of the steel beam; the FBG curvature meter has three built-in gratings which are symmetrically installed in the steel beam at an angle of 120 degrees and are used to capture strain values in different directions when the steel beam is bent; the bolt joint monitoring unit includes an FBG strain sensor and a temperature sensor which are axially pasted at the bolt rod, the FBG strain sensor acquires the wavelength offset, and the temperature sensor measures the temperature change value of the bolt rod; The steel beam health state calculation module includes a steel beam real strain value calculation unit and a bending degree calculation alarm unit; the steel beam real strain value calculation unit eliminates errors by using a strain and temperature decoupling formula to obtain the real strain value of the steel beam; The bending degree calculation alarm unit calculates the transverse curvature in the X direction and the vertical curvature in the Y axis direction of the steel beam by using the strain values in different directions measured by the FBG curvature meter, and triggers a load eccentricity warning when the ratio of the transverse curvature to the vertical curvature exceeds the eccentricity threshold value set by the person skilled in the art; The bolt joint health state calculation module includes a bolt real strain value calculation unit, a pre-tightening force loss calculation unit and a dynamic threshold alarm unit; the bolt real strain value calculation unit eliminates errors caused by thermal expansion and cold contraction by using a strain and temperature decoupling formula to obtain the real strain value of the bolt; the pre-tightening force loss calculation alarm unit calculates the pre-tightening force loss rate of the bolt according to the real strain value of the bolt, in combination with the elastic modulus of the bolt material, the effective cross-sectional area of the thread, the torque coefficient, the thread friction coefficient and the initial pre-tightening force design value; the dynamic threshold alarm unit triggers a yellow alarm when the loss rate is between the set b and c in the non-eccentric state, and triggers a red alarm when the loss rate reaches or exceeds c; when the dynamic threshold alarm unit is in the eccentric state, a yellow alarm is triggered when the loss rate is between the set b1 and c1, and a red alarm is triggered when the loss rate reaches or exceeds c1.

2. A method for monitoring the health of a steel structure platform based on fiber optic sensing based on the system of claim 1, characterized in that, The specific steps are as follows: Step S1: using FBG strain sensors, temperature sensors to monitor the steel beam and bolt joint of the steel structure platform, and FBG curvature meters to monitor the bending strain of the steel beam; Step S2: obtaining the real strain value after decoupling the strain and the temperature, combining the steel beam curvature measured by the three gratings of the curvature meter, setting the eccentricity threshold value, and generating a steel beam deformation warning when the steel beam curvature abnormality exceeds the eccentricity threshold value. Step S3: Calculate the loss rate of pre-tightening force using the axial true strain of the bolt, dynamically evaluate the node state combined with the abnormality degree of the curvature of the steel beam, set yellow and red alarms, and plan maintenance when the loss rate triggers a yellow alarm, and take emergency measures when the loss rate triggers a red alarm.

3. The method according to claim 2, wherein the method is characterized by, The specific steps of step S1 are as follows: (1) The FBG strain sensor, temperature sensor and FBG curvature meter are disposed in the steel beam to obtain the wavelength shift Δλ0 caused by the strain of the optical fiber and the temperature change value ΔT0. The FBG curvature meter internally integrates three gratings, which are symmetrically distributed at an angle of 120 degrees. When the steel structure bends, the three gratings G1, G2 and G3 measure the bending strain values ε1, ε2 and ε3 respectively. The grating G1 is at an angle of 0 degrees with the Y-axis of the steel beam, the grating G2 is at an angle of 120 degrees with the Y-axis of the steel beam, and the grating G3 is at an angle of 240 degrees with the Y-axis of the steel beam; (2) To obtain the relevant key parameters of the bolt node, the FBG strain sensor is axially pasted on the bolt rod to obtain the wavelength shift Δλ1, and the temperature sensor is disposed on the bolt rod to measure the temperature change value ΔT1.

4. The method according to claim 2, wherein the method is characterized by, The specific steps of step S2 are as follows: (1) Eliminate the error caused by thermal expansion and cold shrinkage of the wavelength shift of the steel beam by the strain and temperature decoupling formula to obtain the true strain value ε0. The strain and temperature decoupling formula is: In the formula, K ε is a strain sensitivity coefficient for converting the wavelength into a strain value, a is the linear thermal expansion coefficient of the steel beam in με / °C, and β is a correction coefficient in με / °C 2 , both of which are set by a person skilled in the art; (2) The bending degree of the steel beam is calculated by obtaining the strain values in different directions by the FBG curvature meter, and the X-direction transverse curvature K is calculated by using the geometric characteristics of the three gratings symmetrically distributed at 120 degrees x and the Y-axis direction vertical curvature K y : In the formula, h is the distance from the center axis of the steel beam to the FBG curvature sensor fiber layer, K x is the X-direction transverse curvature, K y is the Y-axis vertical curvature, with units of m -1 When , no early warning is triggered, and when , a load eccentricity warning is triggered, is the steel beam curvature abnormality, and a is the eccentricity threshold value, which is set by those skilled in the art.

5. The method of claim 2, wherein the method further comprises: The specific steps of step S3 are as follows: (1) Through the strain and temperature decoupling formula, the wavelength offset of the bolt eliminates the error caused by thermal expansion and cold shrink, and the real strain value ε of the bolt is obtained 螺栓 , strain and temperature decoupling formula: In the formula, K ε1 is the bolt strain sensitivity coefficient for converting the wavelength to the strain value, a1 is the linear thermal expansion coefficient of the bolt, with units of με / °C, and β1 is the correction coefficient, with units of με / °C 2 , which are both set by those skilled in the art; (2) Measure the loss of bolt preload force F 损失率 : In the formula, E is the elastic modulus of the bolt material, A is the effective cross-sectional area of the bolt thread, K is the torque coefficient, μ is the thread friction coefficient, and F0 is the initial pre-tightening force design value; (3) Trigger a yellow alarm for medium risk, and trigger a red alarm for high risk; When the bolt pre-tightening force loss F 损失率 ≤b, no warning is triggered, when the bolt pre-tightening force loss b 损失率 <c, a yellow warning is triggered, when the bolt pre-tightening force loss F 损失率 ≥c, a red warning is triggered, b, c are alarm thresholds, which are set by those skilled in the art; When the bolt pre-tightening force loss F 损失率 ≤b1, no early warning is triggered, when the bolt pre-tightening force loss b1 损失率 <c1, a yellow warning is triggered, when the bolt pre-tightening force loss F 损失率 ≥c1, a red warning is triggered; b1=b / λ, c1=c / λ, in the formula, λ is an adjustment coefficient, which is set by those skilled in the art.

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