Large cantilever flange steel box girder bridge anti-overturning early warning device, early warning method thereof and early warning threshold determination method

Abstract

The invention discloses an anti-overturning early warning device and method for a large cantilever flange steel box girder bridge and an early warning threshold value determining method. The core of the device is that a closed box-shaped lower flange of a cantilever beam is transformed into a high-sensitivity liquid level type inclination angle sensing unit. The device further comprises a data acquisition and transmission box and an early warning controller which are used for signal processing, wireless transmission and intelligent analysis. The invention further provides a corresponding early warning method and a key early warning threshold value determining method, the method is based on the bridge overturning critical state, the precise deformation form of the cantilever beam is obtained through finite element simulation, and the corresponding critical liquid level variable quantity is obtained through comprehensive calculation and serves as an early warning basis. The structure is ingeniously used as a sensor, the problems that a traditional displacement monitoring technology is insufficient in precision, difficult to install and poor in environmental adaptability are solved, direct, high-precision and high-reliability real-time online early warning on the overturning risk of the large cantilever steel box girder bridge is achieved, the structure is simple, and applicability is high.

Description

Technical Field

[0001] This invention relates to the field of bridge safety monitoring technology, and in particular to an anti-overturning early warning device and method for large cantilever flange steel box girder bridges, as well as a method for determining the early warning threshold. Background Technology

[0002] Large cantilever flange steel box girder bridges are widely used in urban viaducts, ramps, and overpasses due to their lightweight structure, aesthetically pleasing design, and high utilization of the space beneath the bridge. However, while these bridge structures offer numerous advantages, they also present inherent safety hazards—overturning stability issues. Because the main structure is biased towards one side of the bridge's centerline, under adverse conditions such as overloading or uneven loading (e.g., heavy vehicles driving close to the side or congestion on one side), the box girder will generate extremely large torsional moments. When this moment exceeds the pull-out force of the pier supports and its own stabilizing moment, it can easily lead to the overall overturning and instability of the bridge. This is a sudden, brittle failure with few prior warning signs but extremely catastrophic consequences, seriously threatening people's lives and property. In recent years, numerous bridge overturning accidents have occurred both domestically and internationally, repeatedly sounding the alarm for bridge overturning safety monitoring.

[0003] Currently, traditional technologies for monitoring the structural condition of bridges, especially displacement and deformation monitoring, have many limitations and are difficult to apply effectively to the specific scenario of overturning early warning. Communicating vessel type liquid level sensor: Although this method is low in cost, it requires laying long pipelines at different locations on the bridge, which is extremely inconvenient for on-site installation, has poor reliability, and the liquid flow in the pipeline has a lag, making it impossible to achieve rapid real-time monitoring. Its accuracy is easily affected by factors such as temperature and liquid evaporation, making it difficult to meet the requirements of high-precision micro-deformation measurement.

[0004] Laser displacement / range sensors: While these sensors offer high accuracy, they rely on point-to-point measurement. This requires an absolutely stable installation foundation and a highly clean environment. In large outdoor structures like bridges, the installation points themselves may settle or shift. Furthermore, harsh environments such as vehicle dust, rain, snow, and vibration can severely affect laser propagation and reception, leading to distorted or even invalid measurement data, and resulting in high long-term maintenance costs.

[0005] Global Positioning System (GPS) monitoring: GPS technology can be used to measure the three-dimensional displacement of the bridge deck, but its accuracy is typically at the centimeter level, while the critical deformation of a bridge before it collapses may only be at the millimeter or even sub-millimeter level. GPS's low accuracy cannot capture these crucial, minute signs, making it unsuitable for accurate overturning warnings. Furthermore, GPS signals are easily blocked in areas such as under bridges and in urban canyons, resulting in unstable reception.

[0006] Conventional strain gauges / fiber grating sensors: These sensors are typically used to measure local stress and strain, but the stability problem of overturning needs to be transformed into the stress value at a certain point in the structure for judgment. This requires complex theoretical conversions and assumptions, with many intermediate steps, reduced reliability, and a large number of sensors deployed, making the system complex.

[0007] In summary, existing monitoring technologies, due to insufficient accuracy, complex installation, poor environmental adaptability, or inability to directly and effectively characterize overturning states, struggle to construct a reliable, accurate, and applicable real-time overturning early warning system for large cantilever steel box girder bridges. Therefore, there is an urgent need in this field for a novel, direct, effective, highly accurate, and environmentally adaptable specialized technology and device to achieve early detection and intelligent warning of overturning risks for such bridges. Summary of the Invention

[0008] In view of this, the purpose of this invention is to provide an anti-overturning early warning device for large cantilever flange steel box girder bridges, its early warning method, and a method for determining the early warning threshold. Compared with the problems of insufficient accuracy, difficult installation, and poor environmental adaptability of traditional displacement monitoring technology, this invention has a simple structure, wide applicability, and can perform real-time online overturning risk monitoring for various large cantilever steel box girder bridges. It has high accuracy, strong reliability, and issues early warnings directly and promptly.

[0009] To achieve the above objectives, the present invention adopts the following technical solution: an anti-overturning early warning device for a large cantilever flange steel box girder bridge. This device is installed inside the lower flange of the cantilever beam of the large cantilever steel box girder. The lower flange of the cantilever beam is a closed, sealed box-shaped structure and is inclined. The device includes: a liquid level sensing subsystem, a data acquisition and transmission box, and an early warning controller. The liquid level sensing subsystem consists of a liquid medium and a sensor unit. The liquid medium is medical white oil encapsulated at the bottom of the cavity of the closed lower flange. The sensor unit is a float-type liquid level transmitter, which is fixed to the inner top wall of the closed lower flange by a mounting bracket. Its float is suspended on the surface of the medical white oil, used to detect the liquid level height in real time and output a liquid level signal.

[0010] In a preferred embodiment: the data acquisition and transmission box is a waterproof and explosion-proof enclosure, fixedly installed on the web or outer wall of the cantilever beam; it integrates a signal conditioner and a wireless transmission module; the signal conditioner is connected to the electrical interface of the float-type liquid level transmitter through a shielded signal line, and is used to filter, amplify, and convert the liquid level signal to digital; the wireless transmission module is used to transmit the digitized liquid level data through a 4G / 5G or LoRa wireless network.

[0011] In a preferred embodiment: the early warning controller includes a cabinet, an industrial computer installed inside the cabinet, and an audible and visual alarm and a remote communication terminal connected thereto; the industrial computer is equipped with a data receiving port for receiving liquid level data from the wireless transmission module, and internally stores an early warning threshold and comparison logic. When the real-time liquid level data reaches or exceeds the early warning threshold, it drives the audible and visual alarm and the remote communication terminal to issue an early warning.

[0012] In a preferred embodiment, the tilt angle α of the closed lower flange is in the range of 5° to 30°.

[0013] In a preferred embodiment, the amount of medical white oil added ensures that when the bridge is unloaded and without live load, the float has sufficient buoyancy and keeps the liquid level within the effective range of the float-type level transmitter.

[0014] In a preferred embodiment: the device is independently installed in the lower flange of each cantilever beam of the bridge that needs to be monitored, and the early warning controller can receive and process the data from all monitoring points, and perform comprehensive analysis and early warning.

[0015] This invention also provides a method for anti-overturning early warning of large cantilever flange steel box girder bridges, using the anti-overturning early warning device for large cantilever flange steel box girder bridges as described above, characterized by including the following steps: S1: System Calibration: Under the condition of no live load after the bridge is completed, record the initial liquid level measurement value of the float-type liquid level transmitter. H 0; S2: Real-time monitoring: The device continuously collects and transmits real-time liquid level height data H within the lower flange of the cantilever beam; S3: Data Analysis: The early warning controller calculates the real-time liquid level change Δ H = H - H 0; S4: Threshold determination: Set Δ H Compared with the preset warning threshold ΔH in the controller alert Compare; S5: Warning Triggered: When Δ H ≥ΔH alert When this happens, the warning controller initiates the warning procedure.

[0016] In a preferred embodiment, the system calibration in step S1 further includes a warning threshold Δ H alert The steps to determine: S01: Through theoretical calculations, determine the expected change in the height Δ of the liquid level inside the closed lower flange caused by the bending deformation of the cantilever beam under the ultimate load that would cause the bridge to overturn. Hcritical ; S02: According to the formula Δ H alert = K ×Δ H critical The warning threshold is calculated, where K For safety factors, the value ranges from 0.8 to 0.95.

[0017] In a preferred embodiment, the expected deformation Δ in step S01 L critical The calculation method is as follows: Step S011: Calculate the critical load combination for bridge overturning and the corresponding ultimate bending moment at the root of the cantilever beam. M critical ; Step S012: Establish a finite element model including the steel box girder and cantilever beam, and simulate the... M critical Under the influence of gravity, the cantilever beam undergoes bending deformation. Based on the geometric shape of the cantilever beam after bending deformation, the constant initial liquid filling volume of the closed lower flange, and the effect of gravity, a geometric model is constructed to calculate the theoretical change value Δ of the liquid level height at the installation position of the float-type level transmitter. H critical .

[0018] This invention provides a method for determining the overturning warning threshold of a large cantilever flange steel box girder bridge, applied to the anti-overturning device of the aforementioned large cantilever flange steel box girder bridge, comprising the following steps: (1) Determine the critical overturning state: According to the bridge design code, calculate the critical load when the overall overturning stability coefficient of the bridge is 1.0 under the most unfavorable load combination; (2) Calculate the critical bending moment: Based on the critical load, calculate the critical bending moment at the root of the cantilever beam using structural mechanics methods. M critical ; (3) Refined finite element simulation: Establish a finite element analysis model of the large cantilever and apply... M critical To obtain the precise geometric shape of the cantilever beam after bending deformation; (4) Calculation of critical liquid level change: Define the coordinate system after deformation: A new spatial coordinate system is established with the centerline of the box body after deformation and the lower flange of the closed flange as the reference; Establish the liquid surface equation: Based on the physical principle that the liquid volume is incompressible and the liquid surface always remains horizontal under the action of gravity, solve the liquid surface equation that satisfies the initial filling volume in the geometric space of the deformed box. Calculate the height difference: Calculate the height difference between the current liquid level and the liquid level under the initial no-load condition at the installation point of the float-type level transmitter. This value is the critical liquid level height change Δ. H critical ; (5) Set the warning threshold: Introduce a safety factor K and calculate the final warning threshold Δ H alert The calculation formula is: Δ H alert = K·|Δ H critical |, of which 0.8 <K<0.95; (6) Threshold input: The calculated Δ H alert The data is pre-stored in the database of the early warning controller as a criterion for triggering an early warning.

[0019] Compared with existing technologies, this invention has the following advantages: the early warning device has a simple structural design and wide applicability, enabling high-precision and high-reliability real-time online overturning monitoring of various large cantilever steel box girder bridges. Its core advantage lies in its ability to directly capture risk signs and provide timely early warnings. Attached Figure Description

[0020] Figure 1 This is a schematic diagram of the cross-sectional structure of the early warning device of the present invention installed on a large cantilever steel box girder.

[0021] Figure 2 This is a schematic diagram (enlarged detail view) of the installation of the core part (liquid level sensing subsystem) of the early warning device of the present invention in the closed lower flange.

[0022] Figure 3 This is a block diagram illustrating the internal working principle of the data acquisition and transmission box of this invention.

[0023] Figure 4 This is a schematic diagram of the system configuration and connection of the early warning controller of the present invention.

[0024] Figure 5 This is a flowchart of the early warning method of the present invention.

[0025] Figure 6 This is a schematic diagram illustrating the calculation principle of the early warning threshold determination method of the present invention.

[0026] In the picture: 1. Bridge deck; 2. Mounting bracket; 3. Float-type level transmitter 4. Medical white oil; 5. Float ball; 6. Main beam; 7. Cantilever beam; 8. Data acquisition and transmission box; 9. Signal conditioner; 10. Wireless transmission module; 11. Waterproof cable; 12. Early warning controller; 13. Data receiving server / industrial computer; 14. Audible and visual alarm; 15. Remote communication terminal; H0. Initial liquid level height; H. Real-time liquid level height; ΔH. Liquid level change; α. Lower flange inclination angle. Detailed Implementation

[0027] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0028] It should be noted that the following detailed descriptions are illustrative and intended to provide further explanation of this application. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains.

[0029] It should be noted that the terminology used herein is for the purpose of describing particular implementations only and is not intended to limit the exemplary implementations according to this application; as used herein, the singular form is intended to include the plural form as well, unless the context clearly indicates otherwise; furthermore, it should be understood that when the terms “comprising” and / or “including” are used in this specification, they indicate the presence of features, steps, operations, devices, components and / or combinations thereof.

[0030] The first aspect of this application discloses as follows: Figure 1-6 The overturning warning device for a large cantilever flange steel box girder bridge shown includes: 1. Bridge deck; 2. Mounting bracket; 3. Float-type liquid level transmitter; 4. Medical white oil; 5. Float; 6. Main girder; 7. Cantilever beam; 8. Data acquisition and transmission box; 9. Signal conditioner; 10. Wireless transmission module; 11. Waterproof cable; 12. Warning controller; 13. Data receiving server / industrial computer; 14. Audible and visual alarm; 15. Remote communication terminal.

[0031] The device is installed inside the lower flange of the cantilever steel box girder, and the lower flange of the cantilever girder is a closed sealed box-shaped structure and is inclined.

[0032] The inclination angle α of the closed lower flange ranges from 5° to 30°.

[0033] The liquid level sensing subsystem consists of a liquid medium and a sensor unit. The liquid medium is medical white oil 4 encapsulated at the bottom of the cavity of the lower flange of the closed opening. The sensor unit is a float-type liquid level transmitter 3, which is fixed to the inner top wall of the lower flange of the closed opening by a mounting bracket 2. Its float 5 is suspended on the surface of the medical white oil and is used to detect the liquid level height in real time and output the liquid level signal.

[0034] The amount of medical white oil added ensures that when the bridge is unloaded and without live load, the float has sufficient buoyancy and keeps the liquid level within the effective range of the float-type level transmitter.

[0035] The early warning controller 12 includes a cabinet, an industrial computer 13 installed inside the cabinet, and an audible and visual alarm 14 and a remote communication terminal 15 connected to it by a waterproof cable 11.

[0036] The industrial computer 13 is equipped with a data receiving port for receiving liquid level data from the wireless transmission module 10. It stores a warning threshold and comparison logic. When the real-time liquid level data reaches or exceeds the warning threshold, it drives the audible and visual alarm 14 and the remote communication terminal 15 to issue a warning.

[0037] The device is independently installed in the lower flange of each cantilever beam of the bridge that needs to be monitored. The early warning controller can receive and process the data from all monitoring points and perform comprehensive analysis and early warning.

[0038] The overturning warning method for box girder bridges comprises the following steps: S1 System calibration: Under the condition of no live load after bridge construction, record the initial liquid level measurement value H0 of the float-type liquid level transmitter; S2 Real-time monitoring: Continuously collect and transmit real-time liquid level height data H within the lower flange of the cantilever beam through the device; S3 Data analysis: The controller calculates the deviation ΔH from the initial value (ΔH = H - H0); finally, compare this deviation with the preset warning threshold ΔH. alert Comparison; S4 threshold judgment and early warning trigger: if ΔH reaches or exceeds ΔH alert If so, an early warning will be activated immediately.

[0039] The method for determining the overturning warning threshold of a large cantilever flange steel box girder bridge includes the following steps: (1) Determining the critical overturning state: According to the bridge design specifications, calculate the critical load when the overall overturning stability coefficient of the bridge is 1.0 under the most unfavorable load combination; (2) Calculating the critical bending moment: Based on the critical load, calculate the critical bending moment at the root of the cantilever beam using structural mechanics methods. M critical (3) Refined finite element simulation: Establish a finite element analysis model of the large cantilever and apply... M critical, obtain the exact geometric shape of the cantilever beam after bending deformation; (4) Critical liquid level change calculation: Define the deformed coordinate system: Take the center line of the box body of the closed lower flange after deformation as the reference to establish a new spatial coordinate system; Establish the liquid level equation: According to the physical principle that the volume of the liquid is incompressible and the liquid level always remains horizontal under the action of gravity, solve the liquid plane equation that satisfies the initial filling volume in the geometric space of the box body after deformation; Calculate the height difference: Calculate the height difference between this liquid plane and the liquid plane in the initial unloaded state at the installation point of the float type liquid level transmitter, and this value is the critical liquid level height change amount Δ H critical ; (5) Set the warning threshold: Introduce the safety factor K and calculate the final warning threshold Δ H alert , and the calculation formula is: Δ H alert = K·|Δ H critical |, where 0.8 < K < 0.95; (6) Threshold input: Pre-store the calculated Δ H alert into the database of the warning controller as the criterion for triggering a warning.

[0040] The second aspect of this application discloses a warning method for an anti-overturning warning device of a large cantilever flange steel box girder bridge as shown in Figure 5-6 : The main difference between the second embodiment and the first embodiment is that Figure 5 , in step S1, the determination of the warning threshold Δ H alert includes two steps: First, theoretically calculate the limit value ΔHcritical of the liquid level height change in the closed lower flange caused by the bending deformation of the cantilever beam when the bridge is in the critical state of overturning. Then, to ensure the advance and safety of the warning, multiply the above limit value by a safety factor K less than 1 to finally obtain the warning threshold Δ H alert = K ×Δ H critical , where the value range of K is 0.8~0.95.

[0041] Figure 6 , in step S01, the method for calculating the expected deformation amount Δ L critical is as follows: a) First, theoretically calculate the critical load that causes the bridge to overturn and the corresponding ultimate moment at the root of the cantilever beam M critical ; b) Furthermore, use finite element software to establish the models of the steel box girder and the cantilever beam and analyze under M criticalc) The specific bending deformation under the action; finally, based on the deformed cantilever beam shape and assuming that the liquid volume in the lower flange remains constant, the change in liquid level height Δ at the location of the level transmitter is calculated through geometric relationships. H critical In addition, Δ H critical It can also be obtained directly through indoor physical model testing technology.

[0042] The above describes one or more embodiments of the present invention in a relatively specific and detailed manner, but it should not be construed as limiting the scope of the present invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the protection scope of the present invention. Therefore, the protection scope of this patent should be determined by the appended claims.

Claims

1. An anti-overturning early warning device for large cantilever flange steel box girder bridges, characterized in that: The device is installed inside the lower flange of the cantilever beam of a large cantilever steel box girder. The lower flange of the cantilever beam is a closed, sealed box-shaped structure and is inclined. The device includes: a liquid level sensing subsystem, a data acquisition and transmission box, and an early warning controller. The liquid level sensing subsystem consists of a liquid medium and a sensor unit. The liquid medium is medical white oil encapsulated at the bottom of the cavity of the closed lower flange. The sensor unit is a float-type liquid level transmitter, which is fixed to the inner top wall of the closed lower flange by a mounting bracket. Its float is suspended on the surface of the medical white oil and is used to detect the liquid level height in real time and output a liquid level signal.

2. The anti-overturning early warning device for large cantilever flange steel box girder bridges according to claim 1, characterized in that: The data acquisition and transmission box is a waterproof and explosion-proof box, which is fixedly installed on the web or outer wall of the cantilever beam. It integrates a signal conditioner and a wireless transmission module; the signal conditioner is connected to the electrical interface of the float-type liquid level transmitter through a shielded signal line, and is used to filter, amplify and convert the liquid level signal into digital data; the wireless transmission module is used to send the digitized liquid level data out through a 4G / 5G or LoRa wireless network.

3. The anti-overturning early warning device for large cantilever flange steel box girder bridges according to claim 2, characterized in that: The early warning controller includes a cabinet, an industrial computer installed inside the cabinet, and an audible and visual alarm and a remote communication terminal connected thereto. The industrial computer is equipped with a data receiving port for receiving liquid level data from the wireless transmission module. It stores an early warning threshold and comparison logic internally. When the real-time liquid level data reaches or exceeds the early warning threshold, it drives the audible and visual alarm and the remote communication terminal to issue an early warning.

4. The anti-overturning early warning device for large cantilever flange steel box girder bridges according to claim 1, characterized in that: The inclination angle α of the closed lower flange ranges from 5° to 30°.

5. The anti-overturning early warning device for large cantilever flange steel box girder bridges according to claim 1, characterized in that: The amount of medical white oil added ensures that when the bridge is unloaded and without live load, the float has sufficient buoyancy and keeps the liquid level within the effective range of the float-type level transmitter.

6. The anti-overturning early warning device for large cantilever flange steel box girder bridges according to claim 1, characterized in that: The device is independently installed in the lower flange of each cantilever beam of the bridge that needs to be monitored. The early warning controller can receive and process the data from all monitoring points and perform comprehensive analysis and early warning.

7. A method for early warning of overturning of large cantilever flange steel box girder bridges, characterized in that, The anti-overturning early warning device for large cantilever flange steel box girder bridges as described in any one of claims 1-6 is characterized by comprising the following steps: S1: System Calibration: Under the condition of no live load after the bridge is completed, record the initial liquid level measurement value of the float-type liquid level transmitter. H 0; S2: Real-time monitoring: The device continuously collects and transmits real-time liquid level height data H within the lower flange of the cantilever beam; S3: Data Analysis: The early warning controller calculates the real-time liquid level change Δ H = H - H 0; S4: Threshold determination: Set Δ H Compared with the preset warning threshold ΔH in the controller alert Compare; S5: Warning Triggered: When Δ H ≥ΔH alert When this happens, the warning controller initiates the warning program.

8. The overturning early warning method for large cantilever flange steel box girder bridges according to claim 7, characterized in that, The system calibration in step S1 also includes an early warning threshold Δ H alert The steps to determine this are: S01: Through theoretical calculations, determine the expected change in the height Δ of the liquid level inside the closed lower flange caused by the bending deformation of the cantilever beam under the ultimate load that would cause the bridge to overturn. H critical ; S02: According to the formula Δ H alert = K ×Δ H critical The warning threshold is calculated, where K For safety factors, the value ranges from 0.8 to 0.

95.

9. The overturning early warning method for large cantilever flange steel box girder bridges according to claim 8, characterized in that, The expected deformation Δ mentioned in step S01 L critical The calculation method is as follows: Step S011: Calculate the critical load combination for bridge overturning and the corresponding ultimate bending moment at the root of the cantilever beam. M critical ; Step S012: Establish a finite element model including the steel box girder and cantilever beam, and simulate the... M critical Under the influence of gravity, the cantilever beam undergoes bending deformation. Based on the geometric shape of the cantilever beam after bending deformation, the constant initial liquid filling volume of the closed lower flange, and the effect of gravity, a geometric model is constructed to calculate the theoretical change value Δ of the liquid level height at the installation position of the float-type level transmitter. H critical .

10. A method for determining the overturning early warning threshold of a large cantilever flange steel box girder bridge, characterized in that, The anti-overturning device for large cantilever flange steel box girder bridges as described in claim 1 includes the following steps: (1) Determine the critical overturning state: According to the bridge design code, calculate the critical load when the overall overturning stability coefficient of the bridge is 1.0 under the most unfavorable load combination; (2) Calculate the critical bending moment: Based on the critical load, calculate the critical bending moment at the root of the cantilever beam using structural mechanics methods. M critical ; (3) Refined finite element simulation: Establish a finite element analysis model of the large cantilever and apply... M critical To obtain the precise geometric shape of the cantilever beam after bending deformation; (4) Calculation of critical liquid level change: Define the coordinate system after deformation: A new spatial coordinate system is established with the centerline of the box body after deformation and the lower flange of the closed flange as the reference; Establish the liquid surface equation: Based on the physical principle that the liquid volume is incompressible and the liquid surface always remains horizontal under the action of gravity, solve the liquid surface equation that satisfies the initial filling volume in the geometric space of the deformed box. Calculate the height difference: Calculate the height difference between the current liquid level and the liquid level under the initial no-load condition at the installation point of the float-type level transmitter. This value is the critical liquid level height change Δ. H critical ; (5) Set the warning threshold: Introduce a safety factor K and calculate the final warning threshold Δ H alert The calculation formula is: Δ H alert = K·|Δ H critical | where 0.8 < K < 0.95; (6) Threshold input: The calculated Δ H alert The data is pre-stored in the database of the early warning controller as a criterion for triggering an early warning.

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