Bridge monitoring system

Abstract

The embodiment of the application provides a bridge monitoring system, and belongs to the technical field of bridge monitoring. The bridge monitoring system comprises: N fiber grating strain sensors and M fiber grating temperature sensors arranged at different positions of a bridge, the arrangement position of each fiber grating strain sensor serving as a test point; a fiber host used for demodulating detection signals collected by the N fiber grating strain sensors and the M fiber grating temperature sensors to obtain mechanical strain values ε i and environmental temperature values T j of each test point, i=1, 2, …N, j=1, 2, …M; a fiber distribution box used for distributing a fiber bus connected with the fiber host into branch lines connected with sensors at different positions, each branch line being connected with a fiber grating strain sensor or a fiber grating temperature sensor; and a power module used for supplying power to the fiber host. The bridge monitoring system has high anti-interference capability, high monitoring precision and standardized wiring.

Description

Technical Field

[0001] This application relates to the field of bridge monitoring technology, and in particular to a bridge monitoring system. Background Technology

[0002] As a core component of transportation infrastructure, the structural safety of bridges directly affects the smooth flow of transportation and the safety of public life and property. During long-term service, bridges are subjected to the combined effects of multiple factors, including vehicle loads, environmental erosion (such as temperature changes, humidity effects, and chemical corrosion), material aging, and geological settlement. This leads to structural damage such as strain accumulation, crack initiation and propagation. If timely monitoring and intervention measures are not taken, structural failure or even collapse may occur.

[0003] In existing bridge monitoring technologies, traditional electrical sensors (such as resistance strain gauges) suffer from drawbacks such as susceptibility to electromagnetic interference, poor long-term stability, complex wiring, and weak corrosion resistance, making them unsuitable for the harsh environment of long-term outdoor bridge monitoring. Furthermore, single-type strain sensors do not consider the impact of temperature changes on monitoring results, leading to significant errors in the data and failing to accurately reflect the true stress state of the bridge. In addition, the connection methods between sensors and data acquisition equipment in existing monitoring systems lack standardized design. When the number of monitoring points is large, problems such as chaotic wiring, signal transmission attenuation, and high maintenance difficulty easily arise, affecting the reliability and practicality of the monitoring system.

[0004] Therefore, developing a bridge monitoring system with strong anti-interference capabilities, high monitoring accuracy, and standardized wiring has become an urgent need in the field of bridge structural health monitoring.

[0005] It should be noted that the above content is not necessarily prior art, nor is it intended to limit the scope of patent protection of this application. Summary of the Invention

[0006] This application provides a bridge monitoring system to solve or alleviate one or more of the technical problems mentioned above.

[0007] One aspect of this application provides a bridge monitoring system, the system comprising:

[0008] N fiber Bragg grating strain sensors and M fiber Bragg grating temperature sensors are deployed at different locations on the bridge, with each fiber Bragg grating strain sensor's deployment location serving as a test point. The fiber optic host is used to demodulate the detection signals acquired by N fiber Bragg grating strain sensors and M fiber Bragg grating temperature sensors to obtain the mechanical strain value ε at each test point. i and ambient temperature value T j , i=1, 2,...N, j=1, 2,...M; The fiber optic splitter box is used to divide the fiber optic bus connected to the fiber optic host into branch lines that connect to sensors at different locations. Each branch line is connected to a fiber optic strain sensor or a fiber optic temperature sensor. A power module is used to supply power to the fiber optic host.

[0009] Optionally, the bridge includes multiple bridge decks arranged side by side, with at least one fiber optic strain sensor spaced apart on the bottom surface of each bridge deck, and at least one fiber optic strain sensor arranged in the joint between two adjacent bridge decks.

[0010] Optionally, the fiber Bragg grating strain sensor and the fiber Bragg grating temperature sensor are configured in a one-to-one correspondence, and the fiber Bragg grating temperature sensor is configured adjacent to the corresponding fiber Bragg grating strain sensor; or, multiple fiber Bragg grating strain sensors correspond to one fiber Bragg grating temperature sensor, and the fiber Bragg grating temperature sensor is set within a preset distance range of the corresponding multiple fiber Bragg grating strain sensors.

[0011] Optionally, the placement of the fiber optic strain sensor on the bottom surface of the bridge deck is determined after analyzing the stress concentration area using a finite element model of the bridge.

[0012] Optionally, the fiber optic distribution box is installed on the bridge plate located in the middle; and / or, the fiber optic host and the power module are installed at the bridgehead of the bridge.

[0013] Optionally, the outer surfaces of the fiber Bragg grating strain sensor and the fiber Bragg grating temperature sensor have stainless steel armor and / or UV-resistant coating.

[0014] Optionally, the fiber Bragg grating strain sensor and the fiber Bragg grating temperature sensor are directly bonded to the surface of the bridge using epoxy resin.

[0015] Optionally, the system further includes a strain value processing device, the strain value processing device being used for: Based on ambient temperature value T i Determine the temperature strain ε at each test point caused by ambient temperature. i ′; Based on the mechanical strain value ε at each test point i and temperature strain value ε i ′, to obtain the actual strain value Δε at each test point. i And generate a strain distribution map of the bridge; The presence of cracks in the bridge is determined based on the strain distribution diagram.

[0016] Optionally, the system further includes an alarm module, which is used for: If a crack is found in the bridge, an alarm message is sent.

[0017] Optionally, the system further includes a display terminal, the display terminal being used for: Obtain the actual strain value Δε at each test point at different data acquisition times. i ; For each test point, a line graph is used to display the actual strain value Δε at different data acquisition times. i .

[0018] The embodiments of this application employing the above-described technical solution may have the following advantages: The bridge monitoring system in this application deploys N fiber optic strain sensors and M fiber optic temperature sensors at different locations on the bridge. Leveraging the electromagnetic interference resistance, corrosion resistance, and long-term stability of fiber optic sensors, and using fiber optic splitters to standardize the fiber optic bus into branches corresponding to different sensors, it achieves distributed monitoring of multiple test points while solving the problems of messy wiring and signal attenuation in traditional monitoring systems. Simultaneously, the fiber optic host demodulates the sensor signals, enabling the determination of the mechanical strain value ε based on paired temperature sensor data. i Precise temperature compensation effectively eliminates measurement errors caused by temperature interference, ensuring the authenticity and reliability of mechanical strain data acquired at each test point. This accurately reflects the stress state and damage evolution trend of the bridge structure, providing a scientific basis for bridge maintenance decisions, significantly improving the accuracy, stability, and practicality of bridge monitoring, extending the service life of bridges, and ensuring traffic safety. Attached Figure Description

[0019] The accompanying drawings exemplify embodiments and form part of the specification, serving together with the textual description to explain exemplary implementations of the embodiments. The illustrated embodiments are for illustrative purposes only and do not limit the scope of the claims. Throughout the drawings, the same reference numerals refer to similar but not necessarily identical elements.

[0020] Figure 1 A schematic architecture diagram of a bridge monitoring system according to an embodiment of this application is shown; Figure 2 The diagram illustrates the installation of the sensor on the bridge. Detailed Implementation

[0021] To make the objectives, technical solutions, and advantages of this application clearer, the following detailed description is provided in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the scope of this application. All other embodiments obtained by those skilled in the art based on the embodiments in this application without inventive effort are within the scope of protection of this application.

[0022] It should be noted that the descriptions involving "first," "second," etc., in the embodiments of this application are for descriptive purposes only and should not be construed as indicating or implying their relative importance or implicitly specifying the number of technical features indicated. Therefore, a feature defined with "first" or "second" may explicitly or implicitly include at least one of that feature. Furthermore, the technical solutions of the various embodiments can be combined with each other, but this must be based on the ability of those skilled in the art to implement them. If the combination of technical solutions is contradictory or impossible to implement, it should be considered that such a combination of technical solutions does not exist and is not within the scope of protection claimed in this application.

[0023] It should be noted that, in any stage of this application involving the collection, storage, use, transmission, and processing of data, each stage strictly adheres to the laws, regulations, industry standards, and regulatory requirements of the data source, usage location, and relevant countries and regions to ensure the legality and compliance of data activities. In the collection stage, the purpose, method, and scope of collection are clearly communicated to the data subject in a prominent manner. Collection is conducted only after obtaining the data subject's legal authorization, ensuring that the collection process follows the "minimum necessary" principle and does not exceed the scope of data collection. In the storage stage, storage periods are limited, and data is promptly deleted or anonymized / encrypted after the storage purpose is achieved. In the usage stage, a strict data security protection mechanism is implemented, using field-level desensitization technology and processing the original data according to preset desensitization rules. For different types of data, multiple desensitization strategies, such as data generalization, data anonymization, and data encryption, are employed to effectively mitigate the risk of sensitive information leakage and ensure that all data used is securely processed and desensitized, comprehensively protecting the rights and interests of data subjects and data security. In the transmission and processing stages, the confidentiality and security of data are ensured during transmission and processing.

[0024] In the description of this application, it should be understood that the numerical labels before the steps do not indicate the order of the steps, but are only used to facilitate the description of this application and to distinguish each step, and therefore should not be construed as a limitation of this application.

[0025] First, a definition of the terminology used in this application is provided: Fiber Bragg Grating Strain Sensor (FBG): A quasi-distributed, highly sensitive, and electromagnetically interference-resistant fiber optic sensor that uses a fiber optic grating as its core sensing element to measure strain on the surface or inside a structure.

[0026] Fiber Bragg grating temperature sensor (FBG Temperature Sensor): A quasi-distributed temperature sensor that uses fiber gratings as sensing elements to infer ambient temperature by measuring the center wavelength drift.

[0027] The technical solutions of this application are described below through several embodiments. It should be understood that these embodiments can be implemented in many different forms and should not be construed as being limited to the embodiments set forth herein.

[0028] Example 1 Figure 1 A schematic architecture diagram of a bridge monitoring system according to an embodiment of this application is shown.

[0029] like Figure 1 As shown, the bridge monitoring system includes N fiber optic strain sensors 10, M fiber optic temperature sensors 20 paired with each fiber optic strain sensor 10, an optical fiber host 30, an optical fiber splitter box 40, and a power module 50.

[0030] The functions and working relationships of the fiber optic strain sensor 10, fiber optic temperature sensor 20, fiber optic host 30, fiber optic splitter box 40, and power module 50 will be introduced below.

[0031] N fiber optic strain sensors 10 (FBG strain sensors) and M fiber optic temperature sensors 20 (FBG temperature sensors) are installed at key stress points of the bridge. The location of each fiber optic strain sensor 10 is defined as a test point, for a total of N test points.

[0032] The fiber optic strain sensor 10 is used to measure the mechanical strain value of the bridge. The fiber optic strain sensor 20 is used to simultaneously measure the ambient temperature to eliminate the influence of temperature on the strain measurement.

[0033] In one embodiment, the fiber optic strain sensor 10 and the fiber optic temperature sensor 20 (FBG temperature sensor) are arranged in a one-to-one correspondence, and the fiber optic temperature sensor 10 and the corresponding fiber optic strain sensor 20 are arranged adjacent to each other.

[0034] In another embodiment, to reduce sensor cost, multiple fiber Bragg grating strain sensors 10 can also correspond to one fiber Bragg grating temperature sensor 20. The fiber Bragg grating temperature sensor 20 is positioned within a preset distance range of the corresponding multiple fiber Bragg grating strain sensors 10. The preset distance range can be set and modified according to actual conditions; for example, the preset distance range is 50 centimeters.

[0035] The value of N can be adjusted according to the bridge size, structural complexity, and monitoring accuracy requirements. For example, for long-span bridges, a value of 64 or 128 may be used. The selected fiber optic strain sensor 10 and fiber optic temperature sensor 20 are preferably paired products from the same batch. Their core parameters can be as follows: Fiber Bragg grating strain sensor 10: operating wavelength range 1525nm-1565nm, strain measurement range -2000με~+2000με, sensitivity 1.2pm / με, resolution 1με; Fiber Bragg grating temperature sensor 20: operating wavelength range 1525nm-1565nm, temperature measurement range -40℃~+85℃, sensitivity 10pm / ℃, resolution 0.1℃.

[0036] In this embodiment, both types of sensors are characterized by resistance to electromagnetic interference, waterproofing, dustproofing, and strong corrosion resistance, making them suitable for long-term outdoor service environments on bridges.

[0037] In this embodiment, the fiber Bragg grating strain sensor 10 and the fiber Bragg grating temperature sensor 20 can be connected in parallel via optical fibers to form multiple sensing links, which ultimately converge to the fiber optic distribution box 40. The fiber Bragg grating strain sensor 10 and the fiber Bragg grating temperature sensor 20 can be connected to the transmission optical fiber by fusion splicing to ensure the stability of signal transmission and anti-interference capability.

[0038] The fiber optic host 30 can be installed in the bridge monitoring center or on-site control box. It is the core demodulation device of the entire system. It has a built-in high-precision fiber Bragg grating demodulation module, which can simultaneously perform real-time scanning and demodulation of the spectral signals returned by N FBG strain sensors and M FBG temperature sensors, and output the current wavelengths λε,i and λ at each test point. T ,j. Where λε,i is the current wavelength acquired by the i-th fiber optic strain sensor; λ T Let j be the current wavelength acquired by the j-th fiber Bragg grating temperature sensor. Using a preset calibration coefficient, the fiber optic host 30 converts the wavelength drift into a mechanical strain value ε. i (i=1, 2,…, N) and ambient temperature T j (j=1, 2, ..., M). Furthermore, the fiber optic host 30 can also base its tests on the current wavelength λε,i, and λ at each test point. TThe system automatically compensates for the strain values ​​at each test point using the formulas and corresponding temperature compensation methods, thereby obtaining accurate structural strain information.

[0039] In this embodiment, the fiber optic host 30 can support high-speed sampling (such as 1Hz and above), multi-channel synchronous measurement, and has local data storage and remote communication (such as Ethernet, 4G / 5G, fiber optic communication) functions, and can upload monitoring data to the cloud platform or bridge management system in real time.

[0040] The fiber optic distribution box 40 can be installed in a convenient maintenance location on the bridge structure to distribute the fiber optic bus from the fiber optic host into multiple branches, each branch connecting to an FBG strain sensor or FBG temperature sensor. The fiber optic distribution box 40 internally utilizes a fusion splicing tray for fiber splicing and protection, and features a waterproof, dustproof, and corrosion-resistant design to meet the environmental requirements for long-term outdoor operation.

[0041] Power module 50 provides a stable power supply for the fiber optic host 30. Depending on site conditions, it can be powered by mains electricity or a combination of solar power and battery power. Power module 50 has overvoltage, overcurrent, and short-circuit protection functions, and can be equipped with an uninterruptible power supply (UPS) or battery management unit to ensure that the system can continue to operate for a certain period of time in the event of a power outage, thus ensuring monitoring continuity.

[0042] The bridge monitoring system in this application deploys N fiber optic strain sensors and M fiber optic temperature sensors at different locations on the bridge. Leveraging the electromagnetic interference resistance, corrosion resistance, and long-term stability of fiber optic sensors, and using fiber optic splitters to standardize the fiber optic bus into branches corresponding to different sensors, it achieves distributed monitoring of multiple test points while solving the problems of messy wiring and signal attenuation in traditional monitoring systems. Simultaneously, the fiber optic host demodulates the sensor signals, enabling the determination of the mechanical strain value ε based on paired temperature sensor data. i Precise temperature compensation effectively eliminates measurement errors caused by temperature interference, ensuring the authenticity and reliability of mechanical strain data acquired at each test point. This accurately reflects the stress state and damage evolution trend of the bridge structure, providing a scientific basis for bridge maintenance decisions, significantly improving the accuracy, stability, and practicality of bridge monitoring, extending the service life of bridges, and ensuring traffic safety.

[0043] In an optional embodiment, the bridge includes multiple bridge decks arranged side by side, with at least one fiber optic strain sensor 10 spaced apart on the bottom surface of each bridge deck, and at least one fiber optic strain sensor 10 arranged in the joint between two adjacent bridge decks.

[0044] In a specific scenario, refer to Figure 2The bridge consists of 12 precast bridge slabs arranged side-by-side along the transverse direction, connected by cast-in-place concrete joints or hinged joints. To monitor the local stress on the bridge slabs, the force transmission performance of the joints, and the overall collaborative working status, sensors are deployed as follows: For each bridge plate, at least two sets of sensors are arranged at intervals along the transverse direction on its bottom surface (tension zone). Each set of sensors consists of a fiber optic strain sensor (FBG strain sensor) and its paired fiber optic temperature sensor (FBG temperature sensor), which are installed close to each other (with a spacing of ≤10cm) to ensure that the strain and temperature at the same location are measured.

[0045] The selection principles for the deployment locations of each group of sensors are as follows: One of the groups ( Figure 2 A03, A04, A05, A06, A07, and A08 are located at approximately W / 3 of the bridge deck width, while another group ( Figure 2 The sensors are positioned approximately 2W / 3 (about W / 2, where W is the width of the bridge plate) near points B03, B04, B05, B06, B07, and B08. If the bridge plate is wider, a third set of sensors can be added at points W / 4, W / 2, etc., to improve spatial resolution.

[0046] If the bridge plate is long (e.g., L>15m), multiple sets of sensors can be installed along the length of the bridge plate.

[0047] At least one set of sensors shall be installed in the joint (hinged joint or cast-in-place wet joint) between every two adjacent bridge decks. Figure 2 The sensors (C04, C05, C06, and C07) are used to monitor shear slip, opening and closing degree, and lateral force transmission performance at the joint. Each sensor group contains one FBG strain sensor and one paired FBG temperature sensor. The placement principles for each sensor group are as follows: The sensor is installed on the bottom edge of the bridge plate directly below the joint, at the center line of the junction of the two plates.

[0048] To enhance sensitivity to shear deformation, FBG strain sensors can be arranged at a 45° angle (45° to the longitudinal direction of the bridge) to create a shear strain rosette effect, thereby improving the ability to capture interface slippage. Temperature sensors are also placed near the joints to eliminate the influence of ambient temperature on shear strain measurement.

[0049] If the joint is long (such as crossing multiple lanes), one set can be installed at L / 4, L / 2, and 3L / 4 along the longitudinal direction of the bridge to form a joint monitoring chain.

[0050] This implementation method achieves refined monitoring of the stress state and lateral connection performance of individual bridge plates by deploying fiber optic strain sensors on the bottom surface of each bridge plate and at adjacent joints. Compared with the traditional method of deploying sensors only at the mid-span, this method significantly improves the spatial resolution and damage identification capability of the monitoring.

[0051] In an optional implementation, the placement of the fiber optic strain sensor 10 on the bottom surface of the bridge deck is determined after analyzing the stress concentration area using a finite element model of the bridge.

[0052] A bridge finite element model is a digital model constructed using the finite element analysis method. It is based on the actual structural characteristics of the bridge (such as type, size, and material parameters) and stress conditions (such as loads and boundary constraints), and is built using specialized simulation software (such as ANSYS and Midas). Its core principle is to discretize the complex bridge structure into a finite number of elements (such as solid elements and rod elements), which are then connected at node connections to form the overall model. This model can simulate the stress, strain, and displacement mechanical responses of the bridge under different working conditions. It can be used to accurately locate stress concentration areas, verify structural safety, or provide data support for sensor deployment and structural health assessment.

[0053] In this embodiment, the stress concentration area is analyzed using the bridge finite element model. Then, fiber optic strain sensors are deployed at the determined stress concentration area locations, making the deployment of fiber optic strain sensors more targeted. This enables the accurate capture of strain changes in key stress-bearing parts of the bridge, improving the effectiveness and reliability of monitoring data and providing a scientific basis for bridge structural health assessment.

[0054] In an optional implementation, the fiber optic splitter box 40 is mounted on the bridge plate located in the middle.

[0055] In this embodiment, for a cross section with a total of M prefabricated bridge slabs in the transverse direction, when M is an odd number, the (M+1) / 2th bridge slab is taken as the middle bridge slab; when M is an even number, the M / 2th or M / 2+1th bridge slab is taken as the middle bridge slab. In this embodiment, they are uniformly referred to as "middle bridge slabs".

[0056] The central bridge deck is located in the central area of ​​the bridge deck cross section, where the lateral distribution of vehicle wheel tracks is the most dense and the structural response is the most representative. At the same time, the fiber optic paths to the sensors on the left and right sides are the shortest and the length difference is the smallest, which helps to reduce the asymmetry of wavelength drift and reduce the amount of fiber optics used. Compared with the arrangement on the bridge abutment side, it can reduce the amount of fiber optics used by about 28%, thereby reducing the cost and line loss.

[0057] In an optional implementation, the fiber optic host 30 and the power module 50 are installed at the bridgehead of the bridge.

[0058] In this embodiment, by placing the main unit 30 at the bridgehead, it can be kept away from vibration sources (expansion joints, supports), which can greatly reduce wavelength drift background noise. By installing the power module 50 at the bridgehead, routine maintenance does not require going onto the bridge, does not interfere with traffic, shortens inspection time, and improves operation and maintenance efficiency.

[0059] In an optional embodiment, the outer surfaces of the fiber optic strain sensor 10 and the fiber optic temperature sensor 20 have stainless steel armor and / or UV-resistant coating.

[0060] In this embodiment, the stainless steel armor can be made of 304 stainless steel armor tube, the length of which is the same as that of the sensor body. The two ends of the armor tube can be sealed by laser welding to wrap the sensitive area of ​​the fiber optic grating and the root of the pigtail of the sensor to prevent mechanical impact, collision or scratches from sharp objects.

[0061] In one embodiment, a layer of polyvinyl fluoride (PVDF) UV-resistant coating can be sprayed onto the outer surface of the stainless steel armored pipe, with a coating thickness of 0.1 mm to 0.2 mm. In a specific embodiment, an electrostatic spraying process is used to apply the UV-resistant coating, ensuring uniform coverage, no bubbles, and no cracks. This coating can resist ultraviolet radiation with wavelengths of 280 nm to 400 nm and has acid and alkali resistance, damp heat resistance, and aging resistance.

[0062] In another embodiment, a layer of polyvinyl fluoride (PVDF) UV-resistant coating can be directly sprayed onto the outer surface of the sensor housing.

[0063] In this embodiment, by employing stainless steel armor and / or UV-resistant coating, the stability of the sensor under harsh environments (humidity, salt spray) can be improved.

[0064] In an optional embodiment, the fiber optic strain sensor 10 and the fiber optic temperature sensor 20 are directly bonded to the surface of the bridge using epoxy resin.

[0065] In this embodiment, the sensor is directly attached to the surface of the bridge using an epoxy resin ring. This reduces construction time and eliminates the need for welding or drilling, without weakening the cross-section of the base material.

[0066] In other embodiments, the sensor can be placed on a welding base, and then the welding base can be fixed to the bridge with screws.

[0067] In an optional embodiment, the system further includes a strain value processing device, the strain value processing device being used for: Based on ambient temperature value T i Determine the temperature strain ε at each test point caused by ambient temperature. iBased on the mechanical strain value ε at each test point i and temperature strain value ε i ′, to obtain the actual strain value Δε at each test point. i A strain distribution map of the bridge is generated; based on the strain distribution map, it is determined whether the bridge has cracks.

[0068] In one embodiment, based on the ambient temperature value T i Determine the temperature strain ε at each test point caused by ambient temperature. i When ′, it can be determined according to the following formula: ε i = α×(T) i – T0), where α is the thermal expansion coefficient of the material being tested (unit µε / ℃) obtained in advance, and T0 is the temperature corresponding to the “zero strain” reference time t0 (usually the temperature measured when the sensor is just installed).

[0069] The mechanical strain value ε at each test point was obtained. i and temperature strain value ε i After that, the difference Δε between the two can be calculated. i The actual strain value Δε at each test point i .

[0070] In another embodiment, the actual strain value Δε at each test point i Alternatively, it can be calculated using the following formula:

[0071] Where εi is the actual strain value at the i-th test point. Let be the current wavelength acquired by the i-th fiber optic strain sensor. Let be the initial wavelength of the i-th fiber optic strain sensor. Let be the current wavelength acquired by the j-th fiber optic temperature sensor corresponding to the i-th fiber optic strain sensor. Let be the initial wavelength of the j-th fiber optic temperature sensor corresponding to the i-th fiber optic strain sensor. Let be the temperature coefficient of the j-th fiber Bragg grating temperature sensor. Let be the temperature coefficient of the i-th fiber optic strain sensor. Let be the strain coefficient of the i-th fiber optic strain sensor.

[0072] The actual strain value Δε at each test point was obtained. i Then, based on the actual strain value Δε at each test point... i To generate a strain distribution map of the bridge.

[0073] In this embodiment, the strain value processing device can be a local industrial control computer or a remote server. The fiber optic host 30 can transmit the mechanical strain values ​​ε at each test point in real time via a 4G / 5G module or a LoRa gateway. i and ambient temperature value T i The data is transmitted back to the strain value processing device.

[0074] In this embodiment, the strain value processing device obtains the actual strain value Δε at each test point. i Then, it can be compared with the corresponding position (in terms of coordinate x). i ,y i (The data is then represented and associated to form a coordinate-strain dataset.)

[0075] Since the test points are discretely distributed, after forming the coordinate-strain dataset, the interpolation algorithm can be used to interpolate the discrete coordinate-strain dataset to supplement the strain data between the test points, making the strain distribution continuous and obtaining the strain distribution map.

[0076] In one embodiment, based on the actual strain value Δε at each test point i Based on its location, the strain distribution map of the bridge can be generated using cubic spline interpolation.

[0077] Cubic spline interpolation refers to constructing a cubic polynomial (spline function) between two adjacent interpolation nodes, making the interpolation function continuous throughout the entire interpolation interval, and its first and second derivatives are also continuous. It can effectively fit a smooth strain distribution curve / surface, avoid the piecewise linearization problem caused by other interpolation methods (such as linear interpolation), and improve the smoothness and accuracy of the strain distribution map.

[0078] In one embodiment, determining whether the bridge has cracks based on the strain distribution map may include: determining whether there is a strain anomaly region based on the strain distribution map; if a strain anomaly region is determined to exist, extracting the maximum strain value of the strain anomaly region and comparing the maximum strain value with the yield threshold of the bridge material; when the maximum strain value is greater than the yield threshold, determining that the bridge has cracks.

[0079] In this embodiment, the yield threshold εs of the bridge material can be determined based on the type of material used in the main bridge structure and design specifications. For example: The yield threshold for ordinary C50 concrete is εs = 800με; The yield threshold of high-strength C60 concrete is εs = 900με; The yield threshold εs for reinforced concrete structures (including longitudinal reinforcing bars) is 1200με.

[0080] Anomaly regions can be identified using a strain anomaly region determination threshold Δε. This threshold Δε is determined based on historical strain data from bridges under normal service conditions, and is typically 1.5 times the maximum normal operating strain. The formula is as follows: Δε = 1.5 × ε_normal_max Where ε_normal_max is the maximum strain value of the bridge under the design load (such as standard vehicle load or crowd load) (which can be calibrated through structural mechanics simulation or previous no-load-full-load test). In this embodiment, ε_normal_max=300με, so Δε=450με.

[0081] In one specific implementation, strain anomaly regions can be identified using a two-step method of threshold screening and connected component analysis. The specific steps are as follows: Step 1: Threshold Filtering Traverse the strain values ​​of all grid nodes in the strain distribution map, and mark the nodes that satisfy ε>Δε (Δε=450με in this embodiment) as "candidate abnormal nodes" to form a preliminary set of candidate abnormal nodes; if the number of candidate abnormal nodes is 0, it is directly determined that there is no strain abnormal area in the bridge, and the result "the current strain state of the bridge is normal and there are no obvious cracks" is output.

[0082] Step 2: Connectivity Analysis Connectivity analysis of the candidate abnormal node set can be performed using the 8-neighbor connectivity rule: If the horizontal, vertical, or diagonal distance between two candidate anomaly nodes is ≤ 1 grid step, then they are considered connected. Connected candidate anomaly nodes are grouped into a "connected domain", which is the initial strain anomaly region. Set a minimum abnormal region area threshold, for example, an abnormal region area ≥ 0.3m² (corresponding to ≥ 30 grid nodes), and remove isolated connected domains with an area smaller than the threshold (considered as measurement noise) to finally determine the effective strain abnormal region.

[0083] After obtaining the effective strain anomaly regions, the following key information can be extracted and stored for each effective strain anomaly region to facilitate subsequent determination of the bridge's condition.

[0084] Region boundary coordinates: The vertex coordinates of the smallest bounding rectangle of the anomaly region, used to locate the specific position of the anomaly region; Region range parameters: length, width, and area of ​​the abnormal region; Strain data statistics: The strain values ​​of all grid nodes in the abnormal area, which may include the maximum value ε_max, the minimum value ε_min, the average value ε_avg, and the standard deviation σ_ε.

[0085] After obtaining the above data, the maximum strain value ε_max of each effective strain anomaly region can be extracted from the statistical data of that region, and the yield threshold εs of the material corresponding to the current bridge can be retrieved from the database and a comparison judgment can be performed: If ε_max > εs: it is determined that there is a crack in the abnormal region; If ε_max≤εs: the abnormal region is determined to be a normal strain concentration and there are no cracks.

[0086] This embodiment analyzes the collected mechanical strain value εi using a strain value processing device, thereby enabling accurate determination of bridge cracks.

[0087] In an optional implementation, the system further includes an alarm module, which is used to: If a crack is found in the bridge, an alarm message is sent.

[0088] In this embodiment, if it is determined that there are cracks in the bridge, the alarm module can send alarm information to the relevant bridge management personnel.

[0089] The alarm module can send alarm information via email, SMS, or other means.

[0090] In this embodiment, when the alarm module determines that there are cracks in the bridge, it sends an alarm message to prompt the management personnel to check the safety status of the bridge in a timely manner.

[0091] In an optional implementation, the system further includes a display terminal, the display terminal being used for: Obtain the actual strain value Δε at each test point at different data acquisition times. i ; For each test point, a line graph is used to display the actual strain value Δε at different data acquisition times.

[0092] In this embodiment, the actual strain value Δε is received in real time through the display terminal, and a single test point or multi-test point line graph is generated according to the preset configuration to dynamically display the strain change trend over time. In this way, managers can quickly switch test points, filter time ranges, and view historical data through the touch interface of the display terminal to intuitively grasp the strain status of each key part of the bridge.

[0093] In one implementation, remote administrators can also log in to the system via computer or mobile app to view the line graph simultaneously, enabling remote monitoring.

[0094] In this embodiment, through the above implementation method, the display terminal works in collaboration with the original components of the system to realize the real-time visualization of bridge strain monitoring data, improve the readability and practicality of the monitoring data, and provide a more convenient and efficient data analysis method for bridge structural health monitoring, which is suitable for long-term monitoring scenarios of various bridges.

[0095] In the description of this specification, it should be understood that the terms "upper", "lower", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc., indicating the orientation or positional relationship are based on the orientation or positional relationship shown in the accompanying drawings, and are only for the convenience of describing this application and simplifying the description, and are not intended to indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this application.

[0096] In this application, unless otherwise expressly specified and limited, the terms "connected" and "linked" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection, an electrical connection, or a communication connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal connection of two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in this application according to the specific circumstances.

[0097] In this application, unless otherwise expressly specified and limited, "above" or "below" the second feature can include direct contact between the first and second features, or contact between the first and second features through another feature between them. Furthermore, "above," "over," and "on top" of the second feature includes the first feature being directly above or diagonally above the second feature, or simply indicates that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature includes the first feature being directly above or diagonally above the second feature, or simply indicates that the first feature is at a lower horizontal level than the second feature.

[0098] It should be noted that although the steps of the method in this application are described in a specific order in the accompanying drawings, this does not require or imply that these steps must be performed in that specific order, or that all the steps shown must be performed to achieve the desired result. Additional or alternative steps may be omitted, multiple steps may be combined into one step, and / or one step may be broken down into multiple steps. The above drawings are merely illustrative of the processes included in the method according to exemplary embodiments of this application and are not intended to be limiting. It is readily understood that the processes shown in the above drawings do not indicate or limit the temporal order of these processes. Furthermore, it is readily understood that these processes may be performed synchronously or asynchronously in multiple modules, for example.

[0099] The foregoing disclosure provides many different implementations or examples for carrying out different structures of this application. To simplify the disclosure, specific examples of components and arrangements are described above. Of course, these are merely examples and are not intended to limit the scope of this application. Furthermore, reference numerals and / or letters may be repeated in different examples; such repetition is for simplification and clarity and does not in itself indicate a relationship between the various implementations and / or arrangements discussed.

[0100] The above description is merely a specific embodiment of this application, but the scope of protection of this application is not limited thereto. Any person skilled in the art can easily conceive of various variations or substitutions within the technical scope disclosed in this application, and these should all be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

Claims

1. A bridge monitoring system, characterized in that, The system includes: N fiber Bragg grating strain sensors and M fiber Bragg grating temperature sensors are deployed at different locations on the bridge, with each fiber Bragg grating strain sensor's deployment location serving as a test point. The fiber optic host is used to demodulate the detection signals acquired by N fiber Bragg grating strain sensors and M fiber Bragg grating temperature sensors to obtain the mechanical strain value ε at each test point. i and ambient temperature value T j , i=1, 2,...N, j=1, 2,...M; The fiber optic splitter box is used to divide the fiber optic bus connected to the fiber optic host into branch lines that connect to sensors at different locations. Each branch line is connected to a fiber optic strain sensor or a fiber optic temperature sensor. A power module is used to supply power to the fiber optic host.

2. The system according to claim 1, characterized in that, The bridge comprises multiple bridge decks arranged side by side, with at least one fiber optic strain sensor spaced apart on the bottom surface of each bridge deck, and at least one fiber optic strain sensor arranged in the joint between two adjacent bridge decks.

3. The system according to claim 1, characterized in that, The fiber Bragg grating strain sensor and the fiber Bragg grating temperature sensor are configured in a one-to-one correspondence, and the fiber Bragg grating temperature sensor is configured adjacent to the corresponding fiber Bragg grating strain sensor; or, multiple fiber Bragg grating strain sensors correspond to one fiber Bragg grating temperature sensor, and the fiber Bragg grating temperature sensor is set within a preset distance range of the corresponding multiple fiber Bragg grating strain sensors.

4. The system according to claim 3, characterized in that, The placement of the fiber optic strain sensor on the bottom surface of the bridge deck was determined after analyzing the stress concentration area using a finite element model of the bridge.

5. The system according to claim 2, characterized in that, The fiber optic distribution box is installed on the bridge plate located in the middle; and / or, the fiber optic host and the power module are installed at the bridgehead of the bridge.

6. The system according to any one of claims 1 to 5, characterized in that, The outer surfaces of the fiber optic strain sensor and the fiber optic temperature sensor are fitted with stainless steel armor and / or UV-resistant coating.

7. The system according to any one of claims 1 to 5, characterized in that, The fiber optic strain sensor and the fiber optic temperature sensor are directly bonded to the surface of the bridge using epoxy resin.

8. The system according to any one of claims 1 to 5, characterized in that, The system further includes a strain value processing device, which is used for: Based on ambient temperature value T i Determine the temperature strain ε at each test point caused by ambient temperature. i ′; Based on the mechanical strain value ε at each test point i and temperature strain value ε i ′, to obtain the actual strain value Δε at each test point. i And generate a strain distribution map of the bridge; The presence of cracks in the bridge is determined based on the strain distribution diagram.

9. The system according to claim 8, characterized in that, The system also includes an alarm module, which is used for: If a crack is found in the bridge, an alarm message is sent.

10. The system according to claim 8, characterized in that, The system further includes a display terminal, the display terminal being used for: Obtain the actual strain value Δε at each test point at different data acquisition times. i ; For each test point, a line graph is used to display the actual strain value Δε at different data acquisition times. i .

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