Bridge laying high-voltage cable mechanical fatigue evaluation method and system

Abstract

The invention discloses a bridge laying high-voltage cable mechanical fatigue evaluation method and system, and relates to the field of cable fatigue evaluation. Existing methods for evaluating cable fatigue caused by factors such as bridge expansion and vibration are lacked. The method comprises the following steps: arranging a test cable on a mobile test platform, and collecting sensor data to obtain bending, stretching and compression stress of the cable; data are repeatedly acquired by moving the movable box body, and the stress condition of the cable is simulated; carrying out a slice test on the cable, and measuring the elongation at break of a cable sheath and insulation; in combination with sensor data and cable material fatigue characteristics, shape parameters and scale parameters of Weibull joint distribution are fitted, and the fatigue life, the fault probability and the mechanical failure risk of the cable are predicted based on a fitting result, so that whether the fatigue failure of the cable occurs or not is judged. According to the technical scheme, through combination of the test platform and the Weibull distribution model, the mechanical fatigue of the bridge laying high-voltage cable is accurately evaluated, and the accuracy of cable life prediction is improved.

Description

Technical Field

[0001] The invention relates to the field of cable fatigue assessment, and in particular to a method for mechanical fatigue assessment of high-voltage cables laid on bridges. Background Art

[0002] When laying high-voltage cables on bridges, the cables need to withstand the expansion and contraction of the bridge structure and dynamic loads. Due to the different materials and geometric structures of the bridges, the expansion and contraction varies in different types of bridges. According to existing bridge observation data, the expansion and contraction of suspension bridges is usually 1 to 2 meters, while the expansion and contraction of steel frame bridges is about 1 meter. Therefore, during the laying of bridge cables, effective measures must be taken to absorb the stress caused by the expansion and contraction of the bridge to prevent the cable from breaking or excessive bending.

[0003] Especially in flexible structures such as suspension bridges and cable-stayed bridges, the truss structures of the central span and the two side spans will bend significantly when subjected to heavy loads, which causes the ends of the bridge trusses to shrink or stretch. Over time, the bridge will produce periodic expansion and contraction and vibration due to dynamic loads. These factors together cause the cables to bend, stretch and creep during use.

[0004] In this case, the cable must not only consider its own thermal expansion and contraction, but also cope with the expansion and bending of the bridge structure. For long-span bridges, the expansion and contraction of the bridge itself may be very large. If appropriate expansion and contraction absorption measures are not taken, the cable may be subjected to excessive stretching or bending. When the bridge contracts, the cable will be subjected to excessive bending, resulting in local bending exceeding its limit, which may cause cable damage. When the bridge stretches, the cable may be subjected to excessive tension, especially due to the difference in elastic modulus between the various layers of the cable material and the bridge, which may cause destructive stress on the cable metal sheath and insulation layer, thereby affecting the service life of the cable.

[0005] The mechanical fatigue of cables caused by the expansion and creeping of bridges, especially the breakage of cable metal sheath and insulation layer breakdown, directly affects the long-term reliability and safety of cables. At present, there is still a lack of evaluation methods for the mechanical fatigue of high-voltage cables laid on bridges, and there is no mature technical means to effectively predict the mechanical fatigue of cables caused by expansion and contraction, vibration and other factors during the operation of bridges. Therefore, it is urgent to develop an effective evaluation method to predict the fatigue failure risk that bridge cables may face during long-term operation, so as to provide a scientific basis for the design, maintenance and replacement of cables. Summary of the invention

[0006] The technical problem to be solved and the technical task proposed by the present invention are to improve and perfect the existing technical solutions, and provide a method and system for evaluating the mechanical fatigue of high-voltage cables laid on bridges, so as to achieve the purpose of evaluating the mechanical fatigue of cables laid on bridges. To this end, the present invention adopts the following technical solutions.

[0007] A method for evaluating mechanical fatigue of high-voltage cables installed on bridges, comprising the following steps: 1) A plurality of hinge connection devices and fixing devices are arranged on the test cable, and the hinge connection devices and the fixing devices are arranged alternately. The test cable is installed on a mobile test platform, and the mobile test platform includes a plurality of boxes, wherein the first box is fixed, and the other boxes can move left and right, and each box is provided with a hanging point, and the cable is connected to the hinge through the hinge connection device and is hung on the hanging point on the top of the box, and the fixing device is fixedly connected to the side wall of the box, and the hinge connection device on the test cable is higher than the fixing device, so as to form a serpentine test cable; a plurality of first sensors are arranged on the test cable on both sides of the middle hinge connection device, and second sensors are arranged at both ends of the hinge; 2) Collecting information from the first sensor and the second sensor to obtain the initial bending stress, tensile stress and compressive stress of the test cable; 3) Move the movable box, collect information from the first sensor and the second sensor, obtain the stress condition of the test cable, repeatedly move the movable box and continuously collect sensor information until the set number of movements is reached; 4) Carry out a cable slice test to measure the elongation at break of the cable sheath and insulation, and combine the collected sensor data to fit the shape parameters and scale parameters of the Weibull joint distribution based on the fatigue characteristics of the cable material. Then, use the fitting results to predict the fatigue life, failure probability and mechanical failure risk of the cable, and determine whether the cable will suffer fatigue failure.

[0008] This technical solution can monitor the stress state (including bending, tensile and compressive stress) of the cable in real time under actual working conditions by installing multiple sensors on the test cable and combining the fatigue characteristics of the cable material. The collected sensor data can accurately predict the fatigue problems that may occur in the long-term operation of the cable, making the prediction of fatigue life more accurate and avoiding the errors in predicting life through experience and assumptions in the past.

[0009] The fatigue failure of cables is modeled and evaluated using the Weibull joint distribution model. Weibull distribution is a probability distribution widely used in life prediction and reliability analysis, which can provide detailed failure probability and risk analysis for parts such as cable sheath and insulation layer. By fitting the shape parameters and scale parameters of the Weibull distribution, the mechanical failure risk of the cable can be evaluated more scientifically, which is crucial for identifying potential problems in advance.

[0010] The present invention combines actual bridge expansion and contraction and temperature changes on the simulation platform to perform stress tests on cables under real working conditions. By moving the test platform multiple times, the mechanical load and stress changes experienced by the cable during actual use are simulated, making the evaluation results more consistent with actual working conditions, rather than just a single load condition in a laboratory environment. This method can truly reflect the fatigue behavior of bridge cables in actual use.

[0011] Based on accurate fatigue life prediction, maintenance and replacement plans can be formulated in advance before the cable is seriously damaged or fatigue fails, thereby avoiding safety hazards and high maintenance costs caused by sudden cable damage or breakage, significantly improving the operational reliability of the cable, extending its service life, and reducing the risk of unexpected downtime and damage.

[0012] This technical solution not only takes into account the overall failure of the cable, but also conducts slice tests on the cable sheath and insulation layer to measure the elongation at break. It makes accurate predictions on the fatigue failure of different components and provides a scientific basis for design optimization and subsequent maintenance.

[0013] By repeatedly moving the box and collecting sensor information multiple times, the cyclic stress changes that the cable is subjected to during actual use can be simulated, avoiding the accidental errors that may exist in a single measurement and ensuring the reliability of the evaluation results. Repeated tests can better reflect the fatigue accumulation effect that the cable may experience in long-term use, and thus make a more accurate prediction of the safety and life of the cable.

[0014] This technical solution realizes fatigue testing of cables in different working environments by moving the box left and right and simulating different stretching and compression. It effectively simulates the actual stress conditions of cables under the influence of bridge expansion and contraction and external environment.

[0015] Through a systematic evaluation method, there is no longer a need for overly complex theoretical derivations or a large amount of field test data. The fatigue life and failure probability of the cable can be accurately evaluated only through the combination of known material properties and sensor data, thereby simplifying the complexity and workload of cable fatigue evaluation and improving work efficiency.

[0016] As a preferred technical means: the mobile test platform is provided with three boxes, and the second box and the third box are synchronously applied with pulling force or pushing force through the hydraulic workstation.

[0017] The mobile test platform with three boxes can accurately simulate the expansion and contraction deformation of the cable on the bridge. The second and third boxes simultaneously apply tension or thrust through the hydraulic workstation, which can achieve a high degree of restoration of the cable's stretching and compression process. This simulation process is closer to the actual working conditions, so that the test results can reflect the stress conditions of the cable in the real bridge environment.

[0018] The hydraulic workstation can accurately control the applied tension and thrust to ensure that the rate and amplitude of force change are consistent with the stress fluctuations of the cable under actual working conditions. By applying tension and thrust synchronously, the mechanical response (such as bending, stretching, compression, etc.) experienced by the cable on the simulation platform can be made more realistic. This synchronous control helps to more accurately capture the fatigue characteristics and mechanical failure process of the cable.

[0019] The synchronous control of the hydraulic system makes the applied force more uniform and controllable, avoiding the inconsistency caused by external factors (such as human operating errors). By accurately controlling the pulling or pushing force applied each time, the repeatability and consistency of the test can be ensured, thereby obtaining more stable and reliable test data. This is crucial for fatigue life prediction.

[0020] Since bridges usually undergo periodic expansion and contraction (such as temperature changes, load changes, etc.), the hydraulic workstation can simulate this dynamic expansion and contraction process, and simulate various deformation modes of the cable (such as bending, stretching and compression) through the design of the three-section box. It can more comprehensively consider the stress changes of the cable under multiple loads and reflect the real fatigue process of the cable.

[0021] By adjusting the hydraulic workstation, it can adapt to the expansion and contraction requirements of different types of bridges. Whether it is a short bridge or an extra-long bridge, its specific expansion and contraction process can be simulated by adjusting the parameters of the hydraulic system (such as pressure, stroke, etc.). This flexibility ensures that the test platform can be applied to a variety of bridge structures, further improving the versatility of the technical solution.

[0022] Since the force applied by the hydraulic workstation can be precisely controlled and adjusted, combined with the arrangement of sensors on the cable, the stress conditions of the cable under different stress conditions (such as tensile stress, bending stress, compressive stress, etc.) can be fully monitored, providing high-quality data support for subsequent fatigue assessment.

[0023] The hydraulic system can accurately control the cyclic changes in load application and is suitable for long-term fatigue testing. Through multiple, long-term cyclic loading, the repeated expansion and contraction loads that cables bear on bridges are simulated, thus providing more data support for the fatigue life prediction of cables.

[0024] The automatic control system of the hydraulic workstation can accurately implement the predetermined loading / unloading process, reduce the manual operation errors that may occur during the test, and ensure the accuracy of the experimental data. Compared with the traditional mechanical loading method, the hydraulic system can complete a large number of loading / unloading cycles in a short time, and can accurately control the applied tension and thrust, which significantly improves the test efficiency. In addition, the hydraulic system can stably repeat the loading, reducing the time for manual setting and adjustment, and saving the experimental cycle.

[0025] As a preferred technical means: the two ends of the test cable are fixed to the first and third box sections respectively through fixing devices; the test cable located in the first box section is provided with two fixing devices and a hinge connection device, and the test cables in the second and third box sections are provided with a fixing device and a hinge connection device.

[0026] By setting fixtures on the first and third boxes respectively, and setting fixtures on both ends of the test cable, it is possible to ensure that the cable is stably fixed on the test platform during the test, avoiding inaccurate testing due to cable sliding or position changes. This helps to ensure that the test cable is evenly stressed and the force transmission is clear, making the collected data more reliable.

[0027] Two fixtures and a hinge connection are set on the test cable of the first section of the box, which can provide more degrees of freedom during the stress process, so that the cable can bend and deform flexibly during the expansion and contraction process. It simulates the real response of the cable when it is stressed in an actual bridge, especially at the expansion joint, where the cable may bend and stretch.

[0028] Setting up a hinge connection device not only allows the cable to swing freely when subjected to stress, but also simulates the mechanical behavior of the cable in actual bridges, such as rotation, twisting and bending. The hinge design provides a fulcrum to make the deformation of the cable more in line with the actual situation, helping to analyze the mechanical properties of the cable under different load conditions. This design better simulates the complex stress process of the cable in actual bridge operation.

[0029] A fixing device and a hinge connection device are provided on the cable of the second and third boxes to ensure a smoother force transition between the boxes. Through the combination of the hinge connection and the fixing device, the cable can smoothly transmit force changes between the test sections, thereby avoiding inaccurate test results caused by sudden changes or uneven force transmission.

[0030] There are multiple fixtures and hinged connections on the cable, which allows the cable to generate different bending stresses and tensile / compressive stresses at different locations, making it easier to arrange sensors at different test points to obtain more detailed stress data. This is crucial for evaluating the fatigue condition of the cable at different locations, enabling multi-point monitoring, thereby providing more comprehensive data support for fatigue life prediction and fault diagnosis.

[0031] The arrangement of the fixing devices and hinged connection devices at both ends of the cable can be flexibly adjusted according to the specific structure of the bridge. On different types of bridges (such as suspension bridges, cable-stayed bridges, etc.), the cable fixing and connection methods can be adjusted as needed to better simulate the stress conditions of the cable on different bridge structures. This flexibility makes this solution applicable to a variety of different bridge cable testing scenarios.

[0032] By setting up multiple fixing devices and hinge connection devices, it is possible to effectively simulate the repeated expansion and contraction, bending and other conditions of the cable in the actual environment, so as to comprehensively evaluate the fatigue performance of the cable. It is helpful to evaluate whether the cable will be damaged, cracked or other mechanical failures will occur under different working conditions, so as to make accurate judgments on the service life, maintenance cycle and replacement time of the cable.

[0033] The fixture and hinge connection make the test equipment more stable and easy to operate. During the test, the cables do not need to be frequently adjusted or rearranged, the operation process is more simplified, and the test efficiency can be improved. At the same time, the system has a high degree of automation, which reduces the impact of human operation and helps to improve the accuracy and repeatability of the test results.

[0034] Combined with the arrangement of the fixing device and the hinge connection device, this solution can accurately capture the stress changes of the cable under different tension, bending and compression conditions, and combined with the data collected by the sensor, accurate fatigue assessment can be performed. Through multi-point stress measurement, the fatigue characteristics of the cable material are evaluated, and finally, through mathematical models such as Weibull distribution, the prediction accuracy of the cable mechanical fatigue life, failure probability and risk is improved.

[0035] As a preferred technical means: a plurality of first sensors are provided on the surface of the test cable in the two fixing devices on both sides of the hanging point of the second box section and between the two fixing devices, wherein the first sensor located between the two fixing devices is tightly attached to the outer circumference of the cable through a cable clamp.

[0036] Sensors are installed in the key area of ​​the cable (i.e., the cable surface between the fixtures on both sides of the second section box suspension point), which not only monitors the stress at the highest point, but also monitors the stress at the lowest point, which can more accurately monitor the stress changes of the cable during the stress process. These areas are highly sensitive areas where the cable is stressed. The arrangement of sensors helps to capture the local stress conditions when the cable is bent, stretched or compressed, ensuring high accuracy of the monitoring data. The first sensor located between the two fixtures is close to the outer periphery of the cable through the cable clamp, which can ensure that the sensor is in close contact with the cable surface, thereby improving the accuracy of data collection. The close contact between the cable surface and the sensor can avoid signal loss or errors caused by poor contact and enhance the reliability of stress measurement.

[0037] By placing sensors on the cable surface between two fixtures, the tensile, compressive or bending stress of the cable in this area can be accurately measured. The stress concentration or deformation that may occur in the local area of ​​the cable can be identified in time to avoid cable damage or failure.

[0038] By placing multiple sensors in the key stress-bearing areas of the cable and combining the fatigue characteristics of the cable material, the shape parameters and scale parameters of the Weibull joint distribution can be fitted more accurately, thereby improving the prediction accuracy of the cable fatigue life and mechanical failure risk. This helps to optimize cable design and maintenance strategies and extend the service life of the cable.

[0039] The sensor fits tightly to the outer surface of the cable and can provide accurate data feedback when there is a slight change in the force on the cable. It increases the sensitivity of detecting cable fatigue damage and can promptly detect fatigue damage accumulated by the cable during long-term use, providing a basis for early maintenance or replacement, and reducing the risk of accidents in bridge facilities.

[0040] By using multiple sensors to simultaneously monitor stress changes at multiple key locations of the cable, the stress distribution of the cable during the entire test process can be more comprehensively analyzed. Combined with real-time data collection, adjustments and optimizations can be made in real time during the cable stress process, thereby improving the real-time and responsiveness of the test.

[0041] As the preferred technical means: the length of the hinge is 0.5-1.5 meters; the working stroke of the hydraulic workstation is 0.5-1.5 meters; the length of the box is 4-10 meters. By reasonably setting the hinge length, hydraulic working stroke and box length, not only the accuracy, reliability and controllability of the test are improved, but also the test requirements of different cables can be flexibly adapted. The overall solution optimizes the test process, improves the representativeness and efficiency of the test, and ensures more accurate prediction of cable fatigue life and failure risk.

[0042] As a preferred technical means: the Weibull joint distribution function is used to evaluate the probability of mechanical failure of the cable, wherein the Weibull distribution function of the mechanical failure of the protective layer is: ; The Weibull distribution function for insulation mechanical failure is: ; The Weibull joint distribution function of cable mechanical failure is:

[0043] Where: is the shape parameter of the protective layer, is the scale parameter of the protective layer; is the shape parameter of the insulating layer, is the scale parameter of the insulation layer; Fatigue life evaluation is performed based on the shape parameters and scale parameters obtained by fitting the test data.

[0044] This technical solution models the mechanical failure of the cable sheath, insulation and cable body respectively, and combines the Weibull distribution function of the sheath and insulation with the joint distribution function of the overall cable failure to ensure a comprehensive evaluation of the overall performance of the cable; better understand the aging and breakage of each component of the cable in actual use, so as to conduct a more comprehensive risk assessment. The Weibull joint distribution function is used to evaluate the probability of mechanical failure of the cable, and by accurately fitting the shape parameters and scale parameters, it can provide a reliable prediction of the fatigue life and failure risk of the cable. It not only comprehensively considers the failure characteristics of each part of the cable, but also can accurately model according to the test data, which significantly improves the scientificity and accuracy of the evaluation.

[0045] As a preferred technical means: in step 4), the number of repeated movements is 30 times, corresponding to 30 changes in bending stress during 30 years of operation and 60 times of bending stress borne by the metal sleeve.

[0046] By setting the number of repeated movements to 30 times, the bending stress changes experienced by the cable during 30 years of operation and the bending stress borne by the metal sheath are simulated. This makes the test closer to the actual stress conditions of the cable during actual use, reflecting the stress changes and fatigue accumulation that the cable may encounter during many years of operation, so as to more accurately evaluate the long-term reliability and fatigue life of the cable.

[0047] Another object of the present invention is to provide a mechanical fatigue assessment system for high-voltage cables installed on bridges. The mechanical fatigue assessment system for high-voltage cables installed on bridges comprises: A mobile test platform, the platform is composed of a plurality of boxes, the plurality of boxes include at least one fixed box and at least two movable boxes, and the movable boxes can reciprocate along the axial direction of the platform; A hinge connection device and a fixing device, wherein the hinge connection device and the fixing device are alternately arranged on the test cable to fix the test cable in a serpentine shape on the mobile test platform; A sensor device, the sensor device comprising a plurality of first sensors and a plurality of second sensors, the first sensors being mounted on both sides of a hinge connection device in the middle of the test cable, and the second sensors being mounted at both ends of the hinge, respectively used to collect bending stress, tensile stress and compressive stress of the cable; A control unit, used for controlling the movement of the movable box, recording the measurement data of the sensor, and performing fatigue life evaluation of the cable based on the measurement data; A slice test device, used for performing a slice test on the cable, measuring the elongation at break of the cable sheath and insulation, and feeding back the elongation at break data to the control unit; The data analysis unit is used to fit the shape parameters and scale parameters of the Weibull joint distribution function based on the measurement data and the elongation at break data, so as to predict the fatigue life and failure probability of the cable.

[0048] This system installs the cable in a serpentine shape through a mobile test platform, hinged connection devices and fixing devices, and combines multiple sensors to collect stress data of the cable at different positions in real time. It can more comprehensively simulate the dynamic mechanical changes and environmental stresses that the cable is subjected to in actual applications such as bridges, and improve the authenticity and effectiveness of the test.

[0049] The system collects the bending stress, tensile stress and compressive stress of the cable through sensors, measures the elongation at break of the cable sheath and insulation through slice tests, and uses the Weibull joint distribution model to predict fatigue life and failure probability. This makes cable fatigue assessment more accurate, helps to accurately judge the use status and remaining life of the cable, and thus provides early warning and formulates maintenance plans.

[0050] The control unit of the system can accurately control the reciprocating motion of the movable box, simulate the long-term stress of the cable, and record the sensor data in real time. The data analysis unit can obtain more scientific cable fatigue assessment results by processing and fitting these data, and further enhance the reliability of the assessment by combining the elongation at break data, avoiding errors caused by a single test method.

[0051] The design of the system takes into account the actual long-term operating conditions of the cable. By repeatedly simulating the stress changes of the cable in long-term use, the fatigue life prediction is more in line with the actual use cycle of the cable.

[0052] The data analysis unit combines the slice test and stress test data for analysis, and uses the fitted Weibull distribution parameters to conduct an in-depth assessment of the mechanical failure of the cable, providing accurate remaining life and failure probability information, providing regular assessment reports for power companies, and optimizing the life cycle management of the cable.

[0053] As a preferred technical means: the mobile test platform includes three sections of boxes, wherein the second and third sections of boxes are synchronously applied with pulling force or pushing force through a hydraulic workstation.

[0054] As the preferred technical means: the length of the hinge connection device is 0.5-1.5 meters, the fixing device is fixedly connected to the side wall of the box, and the cable is connected to the hanging point on the top of the box through the hinge connection device; the working stroke of the hydraulic workstation is 0.5-1.5 meters, which is used to simulate the thermal expansion and contraction process of the bridge and provide tension and pressure corresponding to the cable; the length of the box is 4-10 meters, and each box is provided with a hanging point, and the cable is connected to the hanging point through a hinge device.

[0055] By applying tension or thrust synchronously through the hydraulic workstation, the stress changes of the cable during the thermal expansion and contraction of the bridge can be simulated, so that the experimental platform can accurately reproduce the working state of the bridge cable under different temperature environments, thereby more realistically evaluating the fatigue life and failure risk of the cable. The introduction of the hydraulic workstation can flexibly apply precise tension and thrust during the test, further enhancing the dynamic loading capacity of the experiment. It enables the cable to simulate the actual stress in long-term use during the stress process, ensuring that the working performance of the cable under different environments and conditions is fully evaluated.

[0056] The system adopts a three-section box design, each box has a suspension point, and the cable is fixed to the suspension point through a hinge connection device, which can simulate the serpentine arrangement of the cable and further restore the mechanical performance in actual operation. The length of the box is 4-10 meters, which provides enough space for long-term fatigue testing while avoiding the test limitations caused by too small a space.

[0057] The second and third boxes are synchronously applied with tension or thrust through the hydraulic workstation to ensure that the movement and mechanical force of the two boxes remain synchronized, avoiding inaccurate signal interference caused by asynchronous movement. This design improves the accuracy of the experiment, makes the stress changes more consistent with the actual situation, and can more effectively evaluate the performance of the cable in long-term use.

[0058] This technical solution can accurately control the stress state of the cable and perform mechanical tests at multiple stress points (through different suspension points and hinge connection devices), thereby improving the accuracy and reliability of the experiment. It helps to conduct more comprehensive cable fatigue tests under different working conditions, ensuring that the evaluation results are more accurate and scientific.

[0059] Beneficial effects: This technical solution achieves accurate evaluation of mechanical fatigue of high-voltage cables laid on bridges by combining the test platform and the Weibull distribution model. It improves the accuracy of cable life prediction, effectively reduces the cost of maintenance and replacement, and reduces the risk of sudden cable failure. Through a comprehensive analysis of cable fatigue failure, the present invention provides an important theoretical basis and practical guidance for the design, use, and maintenance of cables. Specifically: 1. This technical solution can monitor the stress state (including bending, tensile and compressive stress) of the cable under actual working conditions in real time by installing multiple sensors on the test cable and combining the fatigue characteristics of the cable material. The collected sensor data can accurately predict the fatigue problems that may occur in the long-term operation of the cable, making the prediction of fatigue life more accurate and avoiding the errors in predicting life through experience and assumptions in the past.

[0060] 2. Use the Weibull joint distribution model to model and evaluate the fatigue failure of the cable. Weibull distribution is a probability distribution widely used in life prediction and reliability analysis, which can provide detailed failure probability and risk analysis for parts such as cable sheath and insulation layer. By fitting the shape parameters and scale parameters of the Weibull distribution, the mechanical failure risk of the cable can be evaluated more scientifically, which is crucial to identifying potential problems in advance.

[0061] 3. The present invention combines actual bridge expansion and contraction and temperature changes on the simulation platform to perform stress tests on cables under real working conditions. By moving the test platform multiple times, the mechanical load and stress changes experienced by the cable during actual use are simulated, making the evaluation results more consistent with actual working conditions, rather than just a single load condition in a laboratory environment. This method can truly reflect the fatigue behavior of bridge cables in actual use.

[0062] 4. This technical solution not only takes into account the overall failure of the cable, but also conducts slice tests on the cable sheath and insulation layer to measure the elongation at break. It makes accurate predictions on the fatigue failure of different components and provides a scientific basis for design optimization and subsequent maintenance.

[0063] 5. By repeatedly moving the box and collecting sensor information multiple times, it is possible to simulate the periodic stress changes that the cable suffers during actual use, avoiding the accidental errors that may exist in a single measurement and ensuring the reliability of the evaluation results. Repeated tests can better reflect the fatigue accumulation effect that the cable may experience in long-term use, and thus make a more accurate prediction of the safety and life of the cable.

[0064] 6. This technical solution realizes fatigue testing of cables in different working environments through left and right movement of the box and different stretching and compression simulations, effectively simulating the actual stress conditions of cables under the influence of bridge expansion and contraction and external environment.

[0065] 7. Through the systematic evaluation method, there is no need for overly complex theoretical derivations or a large amount of field test data. Only through the combination of known material properties and sensor data, the fatigue life and failure probability of the cable can be accurately evaluated, thereby simplifying the complexity and workload of cable fatigue evaluation and improving work efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0066] Figure 1 It is a working principle diagram of the present invention.

[0067] Figure 2 This is a schematic diagram of the installation of the first sensor of the present invention.

[0068] Figure 3 This is a schematic diagram of the installation of the second sensor of the present invention.

[0069] In the figure: 1. Box; 2. Suspension point; 3. Hinge; 4. Hinge connection device; 5. Fixing device; 6. Test cable; 7. First sensor; 8. Second sensor; 9. Cable clamp; 10. Bolt; 11. Cable sheath; 12. Insulation layer; 13. Hydraulic workstation; 14. Steel pipe. DETAILED DESCRIPTION

[0070] The technical solution of the present invention is further described in detail below in conjunction with the accompanying drawings.

[0071] Embodiment 1: A method for evaluating mechanical fatigue of high-voltage cables installed on bridges, comprising the following steps: S1: A plurality of hinge connection devices 4 and fixing devices 5 are arranged on the test cable 6, and the hinge connection devices 4 and the fixing devices 5 are arranged alternately, and the test cable 6 is installed on a mobile test platform, wherein the mobile test platform comprises a plurality of boxes 1, wherein the first box 1 is fixed, and the other boxes 1 can move left and right, and each box 1 is provided with a suspension point 2, and the cable is connected to the hinge 3 through the hinge connection device 4 and is suspended on the suspension point 2 at the top of the box 1, and the fixing device 5 is fixedly connected to the side wall of the box 1, and the hinge connection device 4 on the test cable 6 is higher than the fixing device 5, thereby forming a serpentine test cable 6; a plurality of first sensors 7 are arranged on the test cable 6 on both sides of the middle hinge connection device 4, and second sensors 8 are arranged at both ends of the hinge 3; In this embodiment, three-section box 1 is used, the first section box 1 is fixed, and the second section box 1 and the third section box 1 are synchronously applied with tension or thrust through the hydraulic workstation 13. By setting up three sections of box 1 and using the hydraulic workstation 13 to synchronously apply tension or thrust, this technical solution can accurately simulate the stress conditions of the cable during the actual bridge expansion and contraction process, comprehensively evaluate the fatigue performance of the cable, reduce experimental errors, and provide an efficient and accurate cable mechanical fatigue evaluation method.

[0072] The two ends of the test cable 6 are fixed to the first box 1 and the third box 1 respectively through the fixing devices 5; the test cable 6 located in the first box 1 is provided with two fixing devices 5 and a hinge connection device 4, and the test cables 6 in the second box 1 and the third box 1 are provided with one fixing device 5 and one hinge connection device 4. By arranging multiple fixing devices 5 and hinge connection devices 4 at both ends of the test cable 6, the actual stress condition of the cable in the bridge environment can be effectively simulated, ensuring the stability of the cable, the uniformity of stress and the smoothness of stress transition during the test.

[0073] A plurality of first sensors 7 are arranged on the surface of the test cable 6 in the two fixing devices 5 on both sides of the suspension point 2 of the second box body 1 and between the two fixing devices 5. The first sensor 7 located between the two fixing devices 5 is closely attached to the outer periphery of the cable through a cable clamp 9, such as Figure 2 As shown, in this embodiment, the cable clamp 9 is butt-jointed and fixed at both ends with bolts 10 to fix the first sensor 7 on the test cable 6. The outermost layer of the test cable 6 is a cable sheath 11, the middle layer is an insulating layer 12, and the innermost layer is a conductive core. The first sensor 7 is tightly attached to the outer side of the cable sheath 11.

[0074] like Figure 3 As shown, the second sensor 8 is arranged between the suspension point 2 and the hinge 3 of the second section box 1.

[0075] In this embodiment, the length of the hinge 3 is 1 meter; the working stroke of the hydraulic workstation 13 is 1 meter; and the length of the box 1 is 6 meters. By reasonably setting the length of the hinge 3, the hydraulic working stroke, and the length of the box 1, not only the accuracy, reliability, and controllability of the test are improved, but also the test requirements of different cables can be flexibly adapted. The overall solution optimizes the test process, improves the representativeness and efficiency of the test, and ensures a more accurate prediction of the fatigue life and failure risk of the cable.

[0076] S2: Collecting information from the first sensor 7 and the second sensor 8 to obtain initial bending stress, tensile stress and compressive stress of the test cable 6; S3: Move the movable box 1, collect information from the first sensor 7 and the second sensor 8, obtain the stress condition of the test cable 6, repeatedly move the movable box 1 and continuously collect sensor information until reaching 30 times; During the test, the first step is to measure the stress values ​​of the cable in the expansion joint section under normal conditions; the second step is compression, measuring the stress values ​​at various locations; the third step is stretching, measuring the stress values ​​at various locations; the fourth step is swinging, measuring the torsional stress values.

[0077] Considering that the cable will run on the bridge for more than 30 years, there will be a maximum elongation in winter and a maximum compression in summer every year. At the maximum elongation, the cable is subjected to tensile stress, and the bending radius can basically meet the bending requirements, but the wrinkles on the metal sheath of the cable will produce a bend, and the telescopic compensation device and the fixed transition section cable will also be subjected to a stress change at the same time; at the maximum compression, the bending radius of the cable may be less than the specified value, the cable metal sheath will be bent again, and the transition point will also be subjected to a stress change. Therefore, the cable must meet 30 bending stress changes during the 30-year operation period, and the bending stress of the metal sheath should reach 60 times. Therefore, a complete measurement of 30 times is required.

[0078] S4: Perform a slice test on the cable to measure the elongation at break of the cable sheath 11 and the insulation, and combine the collected sensor data to fit the shape parameters and scale parameters of the Weibull joint distribution based on the fatigue characteristics of the cable material. Then use the fitting results to predict the fatigue life, failure probability and mechanical failure risk of the cable, and determine whether the cable has fatigue failure.

[0079] The Weibull joint distribution function is used to evaluate the probability of mechanical failure of the cable, where the Weibull distribution function of the mechanical failure of the protective layer is:

[0080] The Weibull distribution function for insulation mechanical failure is:

[0081] The Weibull joint distribution function of cable mechanical failure is:

[0082] Where: is the shape parameter of the protective layer, is the scale parameter of the protective layer; is the shape parameter of the insulating layer, is the scale parameter of the insulation layer; Fatigue life evaluation is performed based on the shape parameters and scale parameters obtained by fitting the test data.

[0083] The Weibull joint distribution function is used to evaluate the probability of mechanical failure of cables. By accurately fitting shape parameters and scale parameters, a reliable prediction of fatigue life and failure risk of cables can be provided. This method not only comprehensively considers the failure characteristics of each part of the cable, but also can accurately model according to test data, significantly improving the scientificity and accuracy of the evaluation.

[0084] This technical solution achieves accurate evaluation of mechanical fatigue of high-voltage cables laid on bridges by combining the test platform and the Weibull distribution model. It improves the accuracy of cable life prediction, effectively reduces the cost of maintenance and replacement, and reduces the risk of sudden cable failure. Through a comprehensive analysis of cable fatigue failure, the present invention provides an important theoretical basis and practical guidance for the design, use, and maintenance of cables.

[0085] Calculate and analyze based on the measured data. When the data is less than the allowable value of the cable, it means that there is no problem with the design; when the measured data exceeds the allowable value, confirm whether the cable is damaged (including inside and outside) under such circumstances. If damage occurs, find out the cause.

[0086] The specific effects that can be achieved in this embodiment are as follows: (1) The fatigue assessment method based on Weibull joint distribution can more accurately predict the fatigue life of cables under actual working conditions, thereby improving the accuracy of the assessment.

[0087] (2) The failure probability and life distribution of cables under different environments can be predicted more accurately, thereby reducing the risk and cost of future maintenance and replacement.

[0088] (3) By taking fatigue characteristics into account more comprehensively, this approach helps to identify potential problems and risk points in advance and reduce the occurrence of accidents.

[0089] Embodiment 2: A mechanical fatigue assessment system for high-voltage cables installed on bridges includes: Mobile test platforms, such as Figure 2 As shown, the platform is composed of three boxes 1, including a fixed box 1 and two movable boxes 1, and the movable boxes 1 can reciprocate along the axial direction of the platform; A hinge connection device 4 and a fixing device 5, wherein the hinge connection device 4 and the fixing device 5 are alternately arranged on the test cable 6 to fix the test cable 6 in a serpentine shape on the mobile test platform; A sensor device, the sensor device comprises a plurality of first sensors 7 and a plurality of second sensors 8, the first sensors 7 are installed on both sides of the hinge connection device 4 in the middle of the test cable 6, and the second sensors 8 are installed at both ends of the hinge 3, respectively used to collect bending stress, tensile stress and compressive stress of the cable; A control unit, used for controlling the movement of the movable box 1, recording the measurement data of the sensor, and performing a fatigue life assessment of the cable according to the measurement data; A slice test device, used to perform a slice test on the cable, measure the elongation at break of the cable sheath 11 and the insulation, and feed back the elongation at break data to the control unit; The data analysis unit is used to fit the shape parameters and scale parameters of the Weibull joint distribution function based on the measurement data and the elongation at break data, so as to predict the fatigue life and failure probability of the cable.

[0090] This system effectively improves the prediction accuracy of cable fatigue life by accurately simulating the long-term use stress of cables in bridge laying environments and combining slice test data for comprehensive analysis. By using the Weibull joint distribution model for fatigue assessment, the system can provide a scientific basis for the maintenance, monitoring and replacement of power facilities, reduce the risk of failures, and ensure the long-term stable operation of the power system.

[0091] To facilitate the movement of the box 1, a steel pipe 14 can be installed at the bottom of the box 1 for support, and a slide rail can be installed at the bottom of the steel pipe 14 for linear motion. The synchronous hydraulic workstation 13 installed at the steel pipe 14 at the bottom of the two moving boxes 1 applies tension and pressure to the box 1 to simulate the thermal expansion and contraction process of the bridge.

[0092] It can be understood that the detailed functional implementation of the above-mentioned platform, device and unit can be found in the introduction of the aforementioned method embodiment, and no further details are given here.

[0093] The above-mentioned method and system for mechanical fatigue assessment of high-voltage cables laid on bridges are specific embodiments of the present invention, which have embodied the substantial characteristics and progress of the present invention. According to actual use needs and under the guidance of the present invention, equivalent modifications in shape, structure, etc. can be made to the method and system, which are all within the protection scope of this scheme.

Claims

1. A method for evaluating mechanical fatigue of high-voltage cables installed on bridges, characterized in that The following steps are involved: 1) A plurality of hinge connection devices (4) and fixing devices (5) are arranged on a test cable (6), and the hinge connection devices (4) and the fixing devices (5) are arranged alternately. The test cable (6) is installed on a mobile test platform, and the mobile test platform comprises a plurality of boxes (1), wherein the first box (1) is fixed, and the remaining boxes (1) can move left and right, and each box (1) is provided with a suspension point (2). The cable is connected to the hinge (3) through the hinge connection device (4) and is suspended on the suspension point (2) at the top of the box (1). The fixing device (5) is fixedly connected to the side wall of the box (1), and the hinge connection device (4) on the test cable (6) is higher than the fixing device (5), so as to form a serpentine test cable (6); a plurality of first sensors (7) are arranged on the test cable (6) on both sides of the middle hinge connection device (4), and second sensors (8) are arranged at both ends of the hinge (3); 2) collecting information from the first sensor (7) and the second sensor (8) to obtain initial bending stress, tensile stress and compressive stress of the test cable (6); 3) moving the movable box (1), collecting information from the first sensor (7) and the second sensor (8), obtaining the stress condition of the test cable (6), repeatedly moving the movable box (1) and continuously collecting sensor information until a set number of movements is reached; 4) Conduct a cable slice test to measure the elongation at break of the cable sheath (11) and insulation, and combine the collected sensor data to fit the shape parameters and scale parameters of the Weibull joint distribution based on the fatigue characteristics of the cable material. Then use the fitting results to predict the fatigue life, failure probability and mechanical failure risk of the cable, and determine whether the cable will suffer fatigue failure.

2. The method for mechanical fatigue assessment of high-voltage cables installed on bridges according to claim 1 is characterized in that: The mobile test platform is provided with three boxes (1), and the second box (1) and the third box (1) are synchronously applied with pulling force or pushing force through a hydraulic workstation (13).

3. The method for mechanical fatigue assessment of high-voltage cables installed on bridges according to claim 2 is characterized in that: The two ends of the test cable (6) are fixed to the first box section (1) and the third box section (1) respectively through fixing devices (5); wherein the test cable (6) located on the first box section (1) is provided with two fixing devices (5) and a hinge connection device (4), and the test cables (6) on the second box section (1) and the third box section (1) are provided with one fixing device (5) and a hinge connection device (4).

4. The method for mechanical fatigue assessment of high-voltage cables installed on bridges according to claim 3 is characterized in that: A plurality of first sensors (7) are provided in two fixing devices (5) on both sides of the suspension point (2) of the second section housing (1) and on the surface of the test cable (6) therebetween, wherein the first sensor (7) located between the two fixing devices (5) is tightly attached to the outer circumference of the cable via a cable clamp (9).

5. The method for mechanical fatigue assessment of high-voltage cables installed on bridges according to claim 4 is characterized in that: The length of the hinge (3) is 0.5-1.5 meters; the working stroke of the hydraulic workstation (13) is 0.5-1.5 meters; and the length of the box (1) is 4-10 meters.

6. The method for mechanical fatigue assessment of high-voltage cables installed on bridges according to claim 1 is characterized in that: The Weibull joint distribution function is used to evaluate the probability of mechanical failure of the cable, where the Weibull distribution function of the mechanical failure of the protective layer is: The Weibull distribution function for insulation mechanical failure is: The Weibull joint distribution function of cable mechanical failure is: Where: is the shape parameter of the protective layer, is the scale parameter of the protective layer; is the shape parameter of the insulating layer, is the scale parameter of the insulation layer; Fatigue life evaluation is performed based on the shape parameters and scale parameters obtained by fitting the test data.

7. The method for mechanical fatigue assessment of high-voltage cables installed on bridges according to claim 1 is characterized in that: In step 4), the number of repeated movements is 30 times, corresponding to 30 changes in bending stress during 30 years of operation and 60 times of bending stress borne by the metal sleeve.

8. A mechanical fatigue assessment system for high-voltage cables installed on bridges, characterized in that include: A mobile test platform, the platform comprising a plurality of boxes (1), the plurality of boxes (1) comprising at least one fixed box (1) and at least two movable boxes (1), and the movable boxes (1) are capable of reciprocating along the axial direction of the platform; A hinge connection device (4) and a fixing device (5), wherein the hinge connection device (4) and the fixing device (5) are alternately arranged on the test cable (6) so as to fix the test cable (6) in a serpentine shape on the mobile test platform; A sensor device, the sensor device comprising a plurality of first sensors (7) and a plurality of second sensors (8), the first sensors (7) being mounted on both sides of a hinge connection device (4) in the middle of a test cable (6), and the second sensors (8) being mounted on both ends of the hinge (3), respectively used to collect bending stress, tensile stress and compressive stress of the cable; A control unit, used for controlling the movement of the movable box (1), recording the measurement data of the sensor, and performing a fatigue life assessment of the cable based on the measurement data; A slice test device, used for performing a slice test on a cable, measuring the elongation at break of the cable sheath (11) and the insulation, and feeding back the elongation at break data to a control unit; The data analysis unit is used to fit the shape parameters and scale parameters of the Weibull joint distribution function based on the measurement data and the elongation at break data, and predict the fatigue life and failure probability of the cable.

9. A mechanical fatigue assessment system for high-voltage cables installed on bridges according to claim 8, characterized in that: The mobile test platform comprises three sections of boxes (1), wherein the second section and the third section of boxes (1) are synchronously applied with pulling force or pushing force through a hydraulic workstation (13).

10. A mechanical fatigue assessment system for high-voltage cables installed on bridges according to claim 9, characterized in that: The hinge connection device (4) has a length of 0.5-1.5 meters, the fixing device (5) is fixedly connected to the side wall of the box (1), and the cable is connected to the suspension point (2) at the top of the box (1) through the hinge connection device (4); the hydraulic workstation (13) has a working stroke of 0.5-1.5 meters and is used to simulate the thermal expansion and contraction process of the bridge and provide tension and pressure corresponding to the cable; the box (1) has a length of 4-10 meters, and each box (1) is provided with a suspension point (2), and the cable is connected to the suspension point (2) through a hinge (3) device.

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