A node plate service performance degradation monitoring system and monitoring method

Abstract

The present invention discloses a node plate service performance degradation monitoring system and monitoring method. The system includes an ultrasonic transducer, an ultrasonic excitation receiving module, an embedded processing module, and a power supply module. The ultrasonic excitation receiving module excites ultrasonic guided waves and longitudinal waves according to a predetermined mode and frequency. The ultrasonic transducers deployed on the node plate surface and the tail of the high-strength bolt receive the ultrasonic guided waves and longitudinal waves, and reflect the waves transmitted to the node plate and the high-strength bolt back to the ultrasonic excitation receiving module. The ultrasonic excitation receiving module converts the ultrasonic signal into an electrical frequency signal and transmits it to the embedded processing module. The embedded processing module performs noise reduction processing on the signal and evaluates the node plate service performance and the high-strength bolt tightening force. The present invention improves the reliability of the node plate service performance test by monitoring the node plate and the high-strength bolt tightening force in the target area. At the same time, it can timely locate the node plate with degraded performance and the high-strength bolt with reduced tightening force, providing support for the maintenance decision-making of the management and maintenance unit.

Description

Technical Field

[0001] The present invention relates to monitoring of gusset plates of steel structure bridges, and in particular to a monitoring system and method for monitoring degradation of service performance of gusset plates. Background Art

[0002] The gusset plates of steel bridges primarily bear shear forces, and their shear strength is provided by high-strength bolts. High-strength bolts apply axial tightening force, effectively clamping the bolts and nuts to the connected plates, generating significant friction when subjected to shear. High-strength bolts are widely used in steel bridges in my country due to their advantages, including simple construction, good load-bearing performance, removable and replaceable, and fatigue resistance. However, during operation, steel bridges are subject to factors such as cyclic vehicle loads, wind loads, and bolt material failure and relaxation, which can lead to a reduction in the tightening force of high-strength bolts in the gusset plates. This reduction in tightening force can affect the local bearing capacity and stiffness of the gusset plates. When the actual bearing capacity of the gusset plate is significantly less than the designed bearing capacity, brittle failure of the gusset can occur. If not promptly detected and re-tightened, this can lead to damage to the entire structure or even collapse. Furthermore, reduced tightening force can cause the bolts to loosen and fall off, potentially striking pedestrians and vehicles under the bridge, posing a serious safety hazard to life and property. Therefore, monitoring the tightening force of high-strength bolts in the gusset plates of steel bridges during operation should be strengthened.

[0003] Currently, the tightening force of high-strength bolts is primarily tested using methods such as rotation angle, strain measurement, reverse pull, ultrasonic longitudinal wave, ultrasonic guided wave, imaging, and piezoresistive impedance. The rotation angle method is simple to use, but the torque coefficient is easily affected by the friction coefficients of the thread surface, the bolt-node plate, and the nut-node plate interface, resulting in large measurement errors. Furthermore, the rotation angle method cannot monitor the tightening force of high-strength bolts in real time, requiring only periodic, individual inspections. This results in low testing efficiency and real-time performance. The strain method offers higher measurement accuracy, but the visible portion of the bolt in actual bridges is unloaded, and strain gauges cannot be attached to the unloaded portion due to its invisibility. This makes it unsuitable for inspecting bolts that have already been tightened. The reverse pull method offers high accuracy, but requires the deployment of a jack, resulting in low test frequency and high costs. It is also difficult to implement, making it unsuitable for bridge monitoring applications. Ultrasonic longitudinal waves align their vibration direction with their propagation direction, making them suitable for testing the normal tightening force of high-strength bolts. However, most of the waves are reflected by the contact bolts, resulting in low energy transmission. In practical applications, one sensor is often deployed per bolt, resulting in low monitoring efficiency and high hardware and installation costs, limiting their widespread application in bridge monitoring. Ultrasonic guided waves can penetrate farther within the gusset plate, and the modulated wave frequency range is concentrated, carrying more contact information between the bolt and the gusset plate. Only a few sensors are required to monitor a large area of ​​the gusset plate, offering high testing efficiency and low sensor cost. However, because ultrasonic guided waves primarily propagate along the plate plane, they are susceptible to surface adhesions such as rain and snow, often leading to misjudgments of bolt tightening force. Image-based testing methods offer low cost and high frequency, but many bolts do not rotate when tightening force is reduced, resulting in significant lag in bolt relaxation testing and inability to provide real-time early warning of loosening of high-strength bolts in the gusset plate. The piezoresistive impedance method has strong anti-interference ability and high sensitivity, but it will only respond to changes in electrical signals when under pressure. It is generally installed together with high-strength bolts during the construction phase and is not suitable for monitoring the tightening force of high-strength bolts during the operation period.

[0004] Furthermore, steel bridges have numerous high-strength bolts, and their loosening is random. Currently, some manufacturers monitor each bolt individually, but this approach consumes a large number of sensors, resulting in high equipment and installation costs, making it difficult to implement on a large scale. Furthermore, even if some gusset plate high-strength bolts loosen, this does not necessarily cause the overall gusset plate's load-bearing capacity to fall below the design value.

[0005] In summary, within the allowable range of the node plate bearing capacity, it is neither necessary nor objective to monitor the tightening force of high-strength bolts one by one. At the same time, each high-strength bolt tightening force test method has its advantages and disadvantages. If only one test method is used in actual engineering, there will be corresponding shortcomings. In addition, Article 3.5.6 of the "Highway Bridge and Culvert Maintenance Code" (JTG 5120-2021) stipulates that "the inspection of the superstructure of steel bridges should include bolt loosening", and Article 11.2.7 of the "Highway Bridge Structure Monitoring Technical Code" (JT / T1037-2022) mentions that "the monitoring data of high-strength bolt tightening force should be analyzed in terms of quantity, location, degree and change trend". Neither of them provides clear regulations on the inspection and monitoring methods and locations of high-strength bolt tightening force. This brings great confusion to the designers of steel structure bridge inspection and monitoring programs. At present, many regular inspection and health monitoring projects for steel bridges also lack inspection and monitoring items for high-strength bolt tightening force, which brings great hidden dangers to structural safety. Summary of the Invention

[0006] Purpose of the invention: In view of the problems existing in the prior art, the purpose of the present invention is to provide a node plate service performance degradation monitoring system, and at the same time provide a node plate service performance degradation monitoring method, so as to solve the problem of high-strength bolt tightening force inspection and monitoring of steel structure bridges, clarify the key test node plates, evaluate the service performance of node plates, promote the automation, intelligence and standardization of high-strength bolt tightening force inspection and monitoring of steel bridges, and improve the service life and durability of steel structure bridges.

[0007] Technical solution: A node plate service performance degradation monitoring system, including:

[0008] Ultrasonic transducers are deployed on the surface of the gusset plate and the tail of the high-strength bolts;

[0009] The ultrasonic excitation receiving module excites ultrasonic guided waves and longitudinal waves according to a predetermined mode and frequency; the ultrasonic transducer receives the ultrasonic guided waves and longitudinal waves excited by the ultrasonic excitation receiving module, and reflects the waves transmitted to the gusset plate and high-strength bolts back to the ultrasonic excitation receiving module; the ultrasonic excitation receiving module converts the reflected ultrasonic signal into an electrical frequency signal and sends it to the embedded processing module;

[0010] An embedded processing module, electrically connected to the ultrasonic excitation receiving module, for performing noise reduction processing on the electric frequency signal and calculating and evaluating the service performance of the node plate and the tightening force of the high-strength bolts; and

[0011] Power module, used to supply power to the system.

[0012] Specifically, the ultrasonic transducer includes an ultrasonic guided wave piezoelectric sensor and an ultrasonic longitudinal wave piezoelectric sensor; preferably, the ultrasonic guided wave piezoelectric sensor is continuously deployed in the longitudinal and transverse positions in the middle of the key control node plate; the ultrasonic longitudinal wave piezoelectric sensor is arranged in alternating rows in the target area of ​​the node plate with degraded performance. The ultrasonic excitation receiving module includes an ultrasonic guided wave excitation receiving module and an ultrasonic longitudinal wave excitation receiving module, the ultrasonic guided wave piezoelectric sensor is electrically connected to the ultrasonic guided wave excitation receiving module, and the ultrasonic longitudinal wave piezoelectric sensor is electrically connected to the ultrasonic longitudinal wave excitation receiving module. The embedded processing module includes a signal preprocessing module, and the signal preprocessing module is electrically connected to the ultrasonic guided wave excitation receiving module and the ultrasonic longitudinal wave excitation receiving module, respectively, for performing noise reduction processing on the electrical frequency signal.

[0013] Furthermore, the embedded processing module includes a node plate fastening force calculation module, a node plate service performance evaluation module, a high-strength bolt fastening force calculation module, and a high-strength bolt fastening force evaluation module;

[0014] Among them, the node plate fastening force calculation module is electrically connected to the signal preprocessing module, and the node plate fastening force is determined according to the ultrasonic guided wave energy; the node plate service performance evaluation module is electrically connected to the node plate fastening force calculation module, and the node plate service performance evaluation is performed according to the node plate fastening force; the high-strength bolt fastening force calculation module is electrically connected to the signal preprocessing module, and the high-strength bolt fastening force is determined according to the ultrasonic longitudinal wave sound time difference; the high-strength bolt fastening force evaluation module is electrically connected to the high-strength bolt fastening force calculation module, and the high-strength bolt fastening force evaluation is performed according to the high-strength bolt fastening force.

[0015] The system further includes a wireless communication module electrically connected to the gusset plate service performance evaluation module and the high-strength bolt tightening force evaluation module, respectively, for transmitting evaluation results of the gusset plate service performance and high-strength bolt tightening force. Furthermore, the system includes a visualization terminal communicatively connected to the wireless communication module for displaying the evaluation results of the gusset plate service performance and high-strength bolt tightening force.

[0016] Furthermore, the system also includes a storage module.

[0017] A monitoring method based on the node plate service performance degradation monitoring system comprises the following steps:

[0018] 1) The gusset plate shear strength and high-strength bolt tightening force are selected as evaluation indicators of node performance degradation. The gusset plate shear strength is provided by the tightening force of multiple high-strength bolts on a gusset plate to resist shear force;

[0019] 2) Conduct a finite element simulation model of the bridge structure and determine the key control nodes of the entire bridge based on the principles of maximum stress and maximum modal curvature;

[0020] 3) Based on the finite element shear calculation results at key control nodes, the node performance degradation level is divided into multiple levels according to the percentage of deviation;

[0021] 4) Divide the gusset plate high-strength bolt tightening force into multiple levels according to the percentage of different degrees of decrease in the gusset plate high-strength bolt tightening force;

[0022] 5) Use ultrasonic guided wave and ultrasonic longitudinal wave methods to calibrate the normal working state and failure state of the gusset plate and high-strength bolts, respectively, and perform temperature compensation; establish a monitoring baseline for the tightening force of the gusset plate and high-strength bolts;

[0023] 6) Determine the gusset plate fastening force based on the received ultrasonic guided wave energy and evaluate the gusset plate service performance;

[0024] 7) The node performance threshold is determined based on the node performance degradation level, the node plate high-strength bolt tightening force level, and the node plate and high-strength bolt tightening force monitoring baseline. The area where the node plate service performance is lower than the node performance threshold is defined as the node plate target area. Based on the received ultrasonic longitudinal wave sound time difference, the high-strength bolt tightening force in this area is calculated and evaluated, and the bolts with reduced tightening force are locally located.

[0025] Compared with the prior art, the present invention has the following beneficial effects:

[0026] This invention avoids the subjectivity of gusset plate service performance testing. By monitoring the fastening force of high-strength bolts in the gusset plate and target area, it expands the test scope and improves test efficiency. This replaces the traditional large-scale single-point monitoring of high-strength bolt fastening force, significantly reducing the number and cost of sensor installations and improving the reliability of gusset plate service performance testing. The monitoring system also enables edge-side data collection, analysis, and wireless transmission, resolving the latency issues of traditional cloud services. It can promptly locate degraded gusset plates and high-strength bolts with reduced fastening force, providing support for maintenance decisions by management and maintenance units. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 This is a module diagram of a gusset plate service performance degradation monitoring system according to an embodiment of the present invention;

[0028] Figure 2 This is a flow chart of a method for monitoring service performance degradation of a gusset plate according to an embodiment of the present invention. DETAILED DESCRIPTION

[0029] To make the above-mentioned objects, features, and advantages of the present application more clearly understood, the specific embodiments of the present application are described in detail below with reference to the accompanying drawings. The following description sets forth many specific details to facilitate a full understanding of the present application. However, the present application can be implemented in many other ways than those described herein, and those skilled in the art can make similar improvements without violating the scope of the present application. Therefore, the present application is not limited to the specific embodiments disclosed below.

[0030] Reference Figure 1 ,A node plate service performance degradation monitoring system includes an ultrasonic transducer, an ultrasonic excitation receiving module, an embedded processing module and a power supply module.

[0031] Among them, the ultrasonic transducer is deployed on the surface of the node plate and the tail of the high-strength bolt. The ultrasonic transducer includes an ultrasonic guided wave piezoelectric sensor and an ultrasonic longitudinal wave piezoelectric sensor. The ultrasonic excitation receiving module includes an ultrasonic guided wave excitation receiving module and an ultrasonic longitudinal wave excitation receiving module. The ultrasonic guided wave piezoelectric sensor and the ultrasonic guided wave excitation receiving module are electrically connected, and the ultrasonic longitudinal wave piezoelectric sensor and the ultrasonic longitudinal wave excitation receiving module are electrically connected. Preferably, the ultrasonic longitudinal wave piezoelectric sensor is adsorbed on the magnetic contact and is electrically connected to the ultrasonic excitation receiving module through the magnetic contact. The magnetic contact serves as an auxiliary installation device and supports quick disassembly.

[0032] The embedded processing module mainly includes a signal preprocessing module, a node plate tightening force calculation module, a node plate service performance evaluation module, a high-strength bolt tightening force calculation module and a high-strength bolt tightening force evaluation module.

[0033] The ultrasonic excitation receiving module excites ultrasonic guided waves and longitudinal waves according to the predetermined mode and frequency; the ultrasonic transducer receives the ultrasonic guided waves and longitudinal waves, and reflects the waves transmitted to the node plate and high-strength bolts back to the ultrasonic excitation receiving module. The ultrasonic excitation receiving module converts the ultrasonic signal into an electrical frequency signal and transmits the signal to the embedded processing module. The embedded processing module performs noise reduction on the signal and evaluates the service performance of the node plate and the tightening force of the high-strength bolts.

[0034] The node plate fastening force calculation module is electrically connected to the signal preprocessing module, and determines the node plate fastening force according to the ultrasonic guided wave energy; the node plate service performance evaluation module evaluates the node plate service performance according to the node plate fastening force provided by the node plate fastening force calculation module.

[0035] Specifically, the ultrasonic guided wave energy E is calculated based on the electrical frequency signal, and the calculation formula is:

[0036] E=0.5×ρ×v×A×f 2 ×s 2

[0037] Where E is the energy of the ultrasonic guided wave, ρ is the density of the medium, v is the propagation velocity of the ultrasonic guided wave in the medium, A is the propagation area of ​​the ultrasonic guided wave, f is the frequency of the ultrasonic guided wave, and s is the amplitude of the ultrasonic guided wave.

[0038] Because the ultrasonic guided wave energy transmitted through the bolted joint interface is closely related to the contact state of the joint surfaces, the transmitted guided wave energy can be directly used as an indicator of high-strength bolt tightening strength. This method is also known as guided wave energy dissipation. The shear strength of a gusset plate is provided by the combined tightening force of numerous high-strength bolts within the gusset plate. If the joint performance in a particular area degrades below the joint performance threshold, further localization of the bolts with reduced tightening force in that area is necessary.

[0039] The high-strength bolt tightening force calculation module and the signal preprocessing module are electrically connected to determine the high-strength bolt tightening force according to the ultrasonic longitudinal wave sound time difference; the high-strength bolt tightening force evaluation module evaluates the high-strength bolt tightening force according to the high-strength bolt tightening force provided by the high-strength bolt tightening force calculation module.

[0040] The calculation formula for the tightening force of high-strength bolts is as follows:

[0041]

[0042] Where σ is the axial stress in the bolt, K L is the tightening axial force, T L0 is the propagation time of ultrasonic longitudinal wave in the bolt under stress-free state, T L is the propagation time of ultrasonic longitudinal wave in the bolt under σ stress state.

[0043] Preferably, the system further comprises a wireless communication module for remotely transmitting the evaluation results of the embedded processing module. Preferably, the evaluation results can be sent to a visual terminal for display.

[0044] Further preferably, the system also includes a storage module to provide storage space for operation data.

[0045] Based on the above monitoring system, the present invention also proposes a method for monitoring the service performance degradation of a node plate, comprising the following steps:

[0046] 1) The gusset plate shear strength and high-strength bolt tightening force are selected as evaluation indicators of node performance degradation. The gusset plate shear strength is provided by the tightening force of multiple high-strength bolts on a gusset plate to resist shear force.

[0047] 2) Establish a finite element simulation model of a real bridge to analyze the load-bearing performance and vibration mode change trends of the components connected to the node plate and the overall structure under the action of vehicle load and wind load when the bearing capacity of the node plate of the main load-bearing component of the bridge structure degrades by 5%, 10%, 15%, 20%, 25%, and 30%. Based on the principle of maximum force and maximum vibration mode curvature, determine the key control nodes of the entire bridge.

[0048] 3) Based on the finite element shear calculation results at key control nodes, the node performance degradation levels are divided into 5 levels according to deviations of 5%, 10%, 15%, 20% and more.

[0049] 4) According to the provisions of Appendix H.1.3 of the "Specifications for the Fabrication and Installation of Highway Steel Structure Bridges" (JTG / T 3651-2022), the fastening force of the node plate high-strength bolts is divided into five levels according to the decrease of 5%, 10%, 15%, 20%, 25% and 30% in the fastening force of the node plate high-strength bolts.

[0050] 5) Use the ultrasonic guided wave method to calibrate the normal working state and failure state of the node plate; use the ultrasonic longitudinal wave method to calibrate the normal working state and failure state of the high-strength bolt, and perform temperature compensation; establish a baseline for monitoring the tightening force of the node plate and high-strength bolt.

[0051] 6) Multiple ultrasonic transducers are continuously pasted longitudinally and transversely in the middle of the key control node plate, and the ultrasonic transducers are connected to the node plate fastening force calculation module and the node plate service performance evaluation module to perform a rapid regional test on the fastening force of the entire node plate.

[0052] 7) Based on the above-mentioned node performance degradation level, node plate high-strength bolt tightening force level, and node plate and high-strength bolt tightening force monitoring baseline, the node performance threshold is determined to determine whether there is a node plate area whose performance has degraded to below the node performance threshold; if so, the area is designated as the node plate target area, and the high-strength bolt tightening force monitoring is performed on the node plate target area. Preferably, a plurality of ultrasonic longitudinal wave piezoelectric sensors are arranged in alternate rows in the node plate target area, and each ultrasonic longitudinal wave piezoelectric sensor is individually connected to a test channel, connected to the high-strength bolt tightening force calculation module and the high-strength bolt tightening force evaluation module, to locate the bolts with reduced local tightening force. In order to achieve quick disassembly, the ultrasonic longitudinal wave probe can be arranged in a magnetic manner.

[0053] 8) After monitoring the decrease in the tightening force of high-strength bolts in the target area of ​​the node plate, an early warning message is issued to provide data support for the maintenance unit to tighten the high-strength bolts, improve the service level of the node plate, and reduce the risk of safe operation of the structure.

[0054] In summary, the present invention uses ultrasonic guided waves to achieve rapid testing of the normal tightening force of the entire node plate, monitors the long-term service performance change trend of the node plate, and evaluates the service performance of the node plate. At the same time, the ultrasonic longitudinal wave method is used to monitor the high-strength bolts with reduced tightening force of the local node plate, thereby reducing the misjudgment of the ultrasonic guided wave method, improving the reliability of the node plate service performance evaluation, providing support for maintenance decisions of management and maintenance units, reducing the risk of structural safety operation, and is suitable for monitoring the service performance of node plates assembled from steel trusses and segmental steel box girders. At the same time, this system can realize edge-side data collection, storage, analysis and wireless transmission, solving the problem of traditional cloud service delays, and can timely locate node plates with degraded performance and high-strength bolts with reduced tightening force, and issue early warning information.

[0055] The technical features of the above-mentioned embodiments can be combined arbitrarily. In order to make the description concise, not all possible combinations of the technical features in the above-mentioned embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0056] The above-described embodiments merely represent several implementation methods of the present application. While the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the patent application. It should be noted that a person of ordinary skill in the art may make various modifications and improvements without departing from the spirit of the present application, and these modifications and improvements fall within the scope of protection of the present application. Therefore, the scope of protection of the present patent application shall be determined by the appended claims.

Claims

1. A node plate service performance degradation monitoring system, characterized in that: include: Ultrasonic transducers are deployed on the surface of the gusset plate and the tail of the high-strength bolts; The ultrasonic excitation receiving module excites ultrasonic guided waves and longitudinal waves according to a predetermined mode and frequency; the ultrasonic transducer receives the ultrasonic guided waves and longitudinal waves excited by the ultrasonic excitation receiving module, and reflects the waves transmitted to the gusset plate and high-strength bolts back to the ultrasonic excitation receiving module; the ultrasonic excitation receiving module converts the reflected ultrasonic signal into an electrical frequency signal and sends it to the embedded processing module; An embedded processing module is electrically connected to the ultrasonic excitation receiving module and is used to perform noise reduction processing on the electric frequency signal and calculate and evaluate the service performance of the node plate and the tightening force of the high-strength bolt; the embedded processing module includes a signal preprocessing module, which is electrically connected to the ultrasonic guided wave excitation receiving module and the ultrasonic longitudinal wave excitation receiving module respectively, and is used to perform noise reduction processing on the electric frequency signal; the embedded processing module includes a node plate tightening force calculation module, a node plate service performance evaluation module, a high-strength bolt tightening force calculation module, and a high-strength bolt tightening force evaluation module; The node plate fastening force calculation module is electrically connected to the signal preprocessing module, and determines the node plate fastening force according to the ultrasonic guided wave energy; the node plate service performance evaluation module is electrically connected to the node plate fastening force calculation module, and performs a node plate service performance evaluation according to the node plate fastening force; the high-strength bolt fastening force calculation module is electrically connected to the signal preprocessing module, and determines the high-strength bolt fastening force according to the ultrasonic longitudinal wave acoustic time difference; the high-strength bolt fastening force evaluation module is electrically connected to the high-strength bolt fastening force calculation module, and performs a high-strength bolt fastening force evaluation according to the high-strength bolt fastening force; Power module, used to supply power to the system.

2. The gusset plate service performance degradation monitoring system according to claim 1, characterized in that: The ultrasonic transducer includes an ultrasonic guided wave piezoelectric sensor and an ultrasonic longitudinal wave piezoelectric sensor.

3. The gusset plate service performance degradation monitoring system according to claim 2, characterized in that: The ultrasonic guided wave piezoelectric sensors are continuously deployed in the middle longitudinal and transverse positions of the key control node plate; the ultrasonic longitudinal wave piezoelectric sensors are arranged in alternate rows in the target area of ​​the node plate with degraded performance.

4. The gusset plate service performance degradation monitoring system according to claim 2, characterized in that: The ultrasonic excitation receiving module includes an ultrasonic guided wave excitation receiving module and an ultrasonic longitudinal wave excitation receiving module. The ultrasonic guided wave piezoelectric sensor is electrically connected to the ultrasonic guided wave excitation receiving module, and the ultrasonic longitudinal wave piezoelectric sensor is electrically connected to the ultrasonic longitudinal wave excitation receiving module.

5. The gusset plate service performance degradation monitoring system according to claim 1, characterized in that: It includes a wireless communication module, which is electrically connected to the node plate service performance evaluation module and the high-strength bolt tightening force evaluation module respectively, and is used to send the evaluation results of the node plate service performance and the high-strength bolt tightening force.

6. The gusset plate service performance degradation monitoring system according to claim 5, characterized in that: It includes a visualization terminal and a communication connection with a wireless communication module, and is used to display the evaluation results of the service performance of the node plate and the tightening force of the high-strength bolts.

7. The gusset plate service performance degradation monitoring system according to claim 1, characterized in that: Including storage module.

8. A monitoring method based on the gusset plate service performance degradation monitoring system according to any one of claims 1 to 7, characterized in that: The steps include: 1) The gusset plate shear strength and high-strength bolt tightening force are selected as evaluation indicators of node performance degradation. The gusset plate shear strength is provided by the tightening force of multiple high-strength bolts on a gusset plate to resist shear force; 2) Conduct a finite element simulation model of the bridge structure and determine the key control nodes of the entire bridge based on the principles of maximum stress and maximum modal curvature; 3) Based on the finite element shear calculation results at key control nodes, the node performance degradation level is divided into multiple levels according to the percentage of deviation; 4) Divide the gusset plate high-strength bolt tightening force into multiple levels according to the percentage of different degrees of decrease in the gusset plate high-strength bolt tightening force; 5) Use ultrasonic guided wave and ultrasonic longitudinal wave methods to calibrate the normal working state and failure state of the gusset plate and high-strength bolts, respectively, and perform temperature compensation; establish a monitoring baseline for the tightening force of the gusset plate and high-strength bolts; 6) Determine the gusset plate fastening force based on the received ultrasonic guided wave energy and evaluate the gusset plate service performance; 7) The node performance threshold is determined based on the node performance degradation level, the node plate high-strength bolt tightening force level, and the node plate and high-strength bolt tightening force monitoring baseline. The area where the node plate service performance is lower than the node performance threshold is defined as the node plate target area. Based on the received ultrasonic longitudinal wave sound time difference, the high-strength bolt tightening force in this area is calculated and evaluated, and the bolts with reduced tightening force are locally located.

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