Method and system for evaluating safety of bridge after continuous fracture of suspension bridge cable and medium

Abstract

The application discloses a kind of suspension bridge cable continuity fracture bridge safety evaluation method, system and medium.Method includes: in finite element analysis software, establish suspension bridge whole bridge model, define state variable and field variable for cable material;User-defined field variable subprogram is set as calculation subprogram, real-time monitoring equivalent stress of cable, construct continuous damage variable by stress ratio and quantize as hierarchical damage variable, control hierarchical progressive degradation of elastic modulus;When stress reaches threshold value, elastic modulus gradually reduces to residual strength, tension is redistributed to adjacent cable after cable fracture, and continuous fracture simulation is automatically repeated;Data is collected by bridge deck displacement monitoring point, and multi-stage early warning is issued according to the proportion of allowable value of bridge design specification, and bridge damage is evaluated.The application solves the problems of traditional method, such as node suspension, matrix singularity, and the need to preset fracture position, and realizes the simulation and safety evaluation of cable continuity fracture in real scene.

Description

Technical Field

[0001] This invention belongs to the technical field of safety evaluation of suspension bridge cable structures, and specifically relates to a method, system and medium for bridge safety assessment after the continuous fracture of suspension bridge cables. Background Technology

[0002] Various unforeseen events, such as disrepair over time, earthquakes, or vehicle fires, can lead to cable breakage. Furthermore, cable breakage causes stress redistribution, resulting in a sharp increase in stress in adjacent cables on both sides, potentially leading to a continuous break and causing bridge deck tilting. Therefore, this paper proposes a method for assessing bridge safety after continuous cable breakage in suspension bridges, which will contribute to the study of the structural safety performance of suspension bridge cables.

[0003] Currently, existing research on bridge safety assessment methods after the continuous fracture of suspension bridge cables largely focuses on simulating cable fracture by using software to hide or delete cable units (such as the component removal method), which has significant shortcomings in practical engineering applications.

[0004] Firstly, traditional methods that rely on the software's own functions often result in phenomena such as floating nodes, mesh distortion, and abnormal contact in the model, causing the model to fail to converge.

[0005] Secondly, traditional methods for controlling cable breakage require prior assumptions about where the cable will break, which does not align with the suddenness and potential for continuous cable breakage in actual engineering projects.

[0006] Third, the traditional method of controlling the behavior of cable breakage is to directly delete the cable element (such as ANSYS birth and death elements), which does not match the actual breakage conditions and is very likely to cause matrix singularities, making the model unable to be calculated;

[0007] Fourth, traditional methods mostly focus on simulation studies of the continuity fracture of suspension bridge cables, lacking an assessment of bridge safety after continuity fracture.

[0008] Therefore, existing methods for simulating suspension bridge cable fracture not only struggle to simulate the continuous fracture of suspension bridge cables in real-world scenarios, but also fail to adequately assess bridge safety after such fracture. This results in blind spots when predicting the safety and reliability of suspension bridge cable continuity fracture under extreme environments (such as fires and earthquakes), making it difficult to meet the safety assessment requirements for suspension bridges. Developing a method capable of assessing bridge safety after suspension bridge cable continuity fracture in real-world environments has significant theoretical and engineering application value. Summary of the Invention

[0009] To address the shortcomings of existing technologies, this invention provides a method for assessing bridge safety after the continuity of suspension bridge cables breaks, thereby resolving technical issues such as the simulation of continuity failure of suspension bridge cables.

[0010] To achieve the above objectives, the present invention adopts the following technical solution:

[0011] A method for safety assessment of a suspension bridge after the continuity of its cables breaks, comprising the following specific steps:

[0012] S1. Establish a suspension bridge model in finite element analysis software, and define state variables and field variables for the cable material. The state variables are used to store the stress state, damage degree and failure indicator information of the cable.

[0013] S2. Set the user-defined field variable subroutine as the calculation subroutine for the suspension bridge model, monitor the equivalent stress of each cable in real time, construct a continuous damage variable D based on the stress ratio, and then quantify it into a graded damage variable. , are assigned to field variables to control the graded degradation of the elastic modulus;

[0014] S3. When the equivalent stress of the sling reaches the stress threshold, the subroutine drives the field variable through graded damage variables. The field variable couples with the material constitutive model to realize a graded progressive elastic modulus degradation method, gradually reducing the elastic modulus of the sling to residual strength in N levels, simulating the sling losing its load-bearing capacity and breaking. Its tensile force is redistributed to adjacent slings. The elastic modulus degradation follows the following formula:

[0015] ;

[0016] in, It is the initial elastic modulus; It is the residual modulus;

[0017] S4. The subroutine continues to monitor the equivalent stress of adjacent slings after redistribution. If the stress of the slings on both sides exceeds the stress threshold after stress redistribution, the sling will automatically repeat the above damage judgment and failure process in subsequent load increment steps to realize the simulation of the continuous fracture process of the sling.

[0018] S5. Before and after the cable breakage process, the bridge deck displacement data is collected in real time through displacement monitoring points set in key locations on the bridge deck.

[0019] S6. Based on the displacement of the bridge deck caused by the breakage of the suspension cable, issue multi-level early warnings according to the ratio of the displacement to the allowable value in the specification, and make a bridge damage assessment.

[0020] Furthermore, in step S2, the stress ratio is calculated according to the following formula:

[0021] ;

[0022] in, It is the stress ratio; It is the equivalent stress of the suspension cable; It is the stress threshold;

[0023] Construct a continuous damage variable D based on the stress ratio:

[0024] ;

[0025] in, The initial damage stress ratio; For the complete failure stress ratio, 0 < < ;

[0026] The continuous damage variable D is quantified into a graded damage variable. :

[0027] ;

[0028] Among them, round( ) represents the rounding function, where N is a positive integer greater than or equal to 2, representing the number of levels;

[0029] The graded damage variables The value is assigned to the field variable to control the graded degradation of the elastic modulus.

[0030] Furthermore, the stress threshold value mentioned in step S2 is 1.0 times the ultimate tensile strength of the sling material.

[0031] Furthermore, the state variables include a first state variable, a second state variable, and a third state variable, wherein the first state variable is used to store the stress ratio, the second state variable is used to store the damage level, and the third state variable is used to store the failure flag.

[0032] Furthermore, step S1 specifically includes:

[0033] S11. After establishing the main cable, suspension cables, bridge deck, and bridge tower components of the suspension bridge in the finite element analysis software, assemble them into a full suspension bridge model.

[0034] S12. For the material corresponding to the sling, check Depvar and user-defined field variable attributes.

[0035] Furthermore, the residual modulus mentioned in step S3 Initial elastic modulus 1%.

[0036] Furthermore, step S5 specifically includes the following sub-steps:

[0037] S51. Displacement monitoring points shall be set on the bridge deck directly above the suspension cables, at the mid-span of the bridge deck, on both sides of the bridge tower, and on the bridge deck at the ends of the entire bridge.

[0038] S52. Real-time collection of vertical displacement value, lateral displacement value, displacement development rate and displacement difference of bridge deck with the number of cable failures through monitoring point equipment;

[0039] S53. Data preprocessing: Based on the assumption that the displacement change rate is less than 1% for three consecutive time steps, noise reduction is performed to remove numerical oscillation interference during the simulation process. The valid displacement data is then retained and transmitted to the backend.

[0040] Furthermore, in step S6, the multi-level early warning is a three-level early warning, and the specific criteria are as follows:

[0041] A Level 1 warning is issued when the vertical displacement of each monitoring point does not exceed 50% of the allowable value specified in the standard.

[0042] A Level II warning is issued when the vertical displacement of each monitoring point is between 50% and 80% of the allowable value specified in the standard.

[0043] A Level III warning will be issued when the vertical displacement of each monitoring point exceeds 80% of the allowable value specified in the standard or when the lateral displacement of the bridge deck exceeds the limit specified in the standard.

[0044] Another aspect of the present invention proposes an assessment system for bridge safety after the continuity failure of suspension bridge cables, comprising:

[0045] One or more processors;

[0046] Memory, used to store one or more programs;

[0047] When the one or more programs are executed by the one or more processors, the one or more processors implement the method.

[0048] A third aspect of the present invention provides a computer-readable storage medium having a computer program stored thereon, which, when executed by a processor, implements the method described thereon.

[0049] Beneficial effects:

[0050] (1) This invention uses a graded progressive elastic modulus degradation method to simulate the failure process of the suspension cable, through continuous damage variable D and graded damage variable D. By gradually reducing the elastic modulus to residual strength in N levels, the problems of node suspension, mesh distortion and matrix singularity caused by "instantaneous deletion of elements" in the traditional birth and death element method are avoided, and the degradation process of cable stiffness conforms to the physical asymptotic characteristics of real fracture.

[0051] (2) This invention quantifies continuous damage variables into discrete graded damage variables, so that the material stiffness remains constant within each analysis step and the stiffness variation between adjacent grades is controllable; at the same time, residual modulus is used. It avoids the element stiffness from suddenly dropping to zero, effectively eliminates structural impact and numerical oscillation, and significantly improves the convergence and stability of structural analysis under complex nonlinear conditions.

[0052] (3) The present invention monitors the stress of the sling in real time and automatically determines the damage through the USDFLD subroutine. When the sling breaks, the tension is redistributed to the adjacent slings. The subroutine automatically repeats the monitoring-determination-failure process without pre-assuming the fracture location, which truly simulates the suddenness and continuity of sling breakage in actual engineering.

[0053] (4) The present invention uses stress ratio as failure judgment index, and performs dimensionless processing on the equivalent stress of the sling and the stress threshold. As a dimensionless index, stress ratio is convenient for unified comparison between different materials and working conditions, realizing unified and standardized sling failure judgment, and improving the applicability and reliability of the evaluation method.

[0054] (5) This invention sets up displacement monitoring points at key locations on the bridge deck to collect multi-dimensional data such as vertical displacement, lateral displacement, displacement development rate and displacement difference in real time, and establishes a three-level early warning mechanism according to the proportion of allowable values ​​in the bridge design specifications. This invention realizes a complete technical closed loop from suspension cable fracture simulation to bridge safety assessment, and provides effective technical support for the safe operation of in-service suspension bridges.

[0055] (6) This invention is based on a general finite element analysis software platform and does not rely on specific commercial software. The method has a clear principle and flexible parameter settings. It can adjust key parameters such as the grading level and damage threshold according to the structural characteristics and material properties of different bridges. It is applicable to the safety assessment of various long-span suspension bridges. Attached Figure Description

[0056] Figure 1 This is a flowchart of the technical solution evaluation method of this invention;

[0057] Figure 2 This is a schematic diagram of a suspension bridge cable model;

[0058] Figure 3 This is a schematic diagram of a suspension bridge cable model when a cable reaches its maximum stress.

[0059] Figure 4 yes Figure 3 A magnified view of a portion of the image;

[0060] Figure 5 This is a schematic diagram of a suspension bridge cable model where one of the cables has lost its load-bearing capacity.

[0061] Figure 6 yes Figure 5 A magnified view of a portion of the image;

[0062] Figure 7This is a schematic diagram of a suspension bridge cable model experiencing cable breakage;

[0063] Figure 8 This is a schematic diagram of the continuity failure of the suspension cable of a suspension bridge;

[0064] Figure 9 yes Figure 8 A magnified view of a portion of the image;

[0065] Figure 10 This is a diagram illustrating the limits for issuing warnings on bridges;

[0066] Figure 11 This is a schematic diagram showing the vertical displacement of the bridge deck due to the breakage of a suspension cable.

[0067] Figure 12 yes Figure 11 A magnified view of a portion of the image;

[0068] Figure 13 This is a mid-span displacement-time curve of a suspension bridge;

[0069] Figure 14 This is a schematic diagram of the early warning trigger and displacement change;

[0070] Figure 15 This is the core logic flowchart of the USDFLD subroutine. Detailed Implementation

[0071] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0072] It should be noted that the illustrations in this invention are merely to illustrate the basic concept and do not represent the actual dimensions of the physical object. In actual manufacturing, specific analysis should be conducted considering the actual manufacturing difficulties and other factors. This specification only provides a structure, proportion, and size, and is solely for explaining this invention. To enable those skilled in the art to better understand and learn this invention, it is hereby declared that the above-described technical solutions, specific implementation methods, structural designs, and preparation techniques are not intended to limit the implementation of this invention. This description should not be construed as a substantial limitation on the technical details. Any adjustments to the structure, modifications to the proportional relationships, or changes in dimensions are applicable to the technical scope of this invention without affecting the effects and objectives achieved. Therefore, those skilled in the art can modify the structure or adjust the parameters according to actual needs to meet the requirements of specific application scenarios. This flexibility ensures the applicability and wide applicability of this invention, enabling various related technical personnel to better understand, apply, and promote the technical content of this invention.

[0073] As attached Figure 1 As shown, this embodiment provides a method for assessing bridge safety after the continuous fracture of a suspension bridge cable. The method includes: establishing a suspension bridge model in ABAQUS and defining state variables STATEV and field variables FIELD for the cable material to assess the degree of material damage. Before model calculation, the ABAQUS subroutine USDFLD, written in FORTRAN, is set as the model's calculation subroutine. During model operation, the subroutine monitors the equivalent stress MISES of the cable and compares it with the stress threshold THRESHOLD to determine damage. When the equivalent stress of the cable reaches the stress threshold, the subroutine changes the state variables, reducing the material strength to one percent of its original strength. The cable loses its load-bearing capacity, and its tension is redistributed to adjacent cables on both sides. By repeating the cable damage determination and failure process, the continuous fracture process of the cable can be simulated. Afterwards, monitoring equipment is used to collect bridge deck displacement, and an early warning is issued based on the magnitude of the bridge displacement, and a bridge damage assessment is performed.

[0074] The method for assessing the safety of a suspension bridge after the continuity of its cables breaks, as described in this embodiment, specifically includes the following steps:

[0075] S1, as attached Figure 1 As shown, a suspension bridge model is first established in ABAQUS. Two state variables, STATEV and FIELD, are added to the material corresponding to the cables. These two state variables are used to store the cable stress ratio, remember the damage evolution history, and mark the element failure state. The field variables are transformed to carry the graded damage variables and couple the material constitutive model, thereby controlling the cable failure. The specific steps include the following:

[0076] S11. After creating the main cable, suspenders, bridge deck, bridge towers and other components of the suspension bridge in ABAQUS, assemble them into the entire suspension bridge in the assembly process.

[0077] S12. For the material corresponding to the sling, the Depvar and User Defined Field attributes need to be checked additionally. The state variable STATEV is used to store the stress ratio, damage level and failure indicator of the sling, etc.; the field variable FIELD is used to pass the calculated graded damage variable to the material constitutive model to control the graded degradation of the elastic modulus.

[0078] S2, as attached Figure 1 As shown, a USDFLD subroutine adapted to ABAQUS is written as the core of damage assessment and set as the calculation subroutine of the model. Damage assessment is performed by monitoring the equivalent stress MISES of the sling and comparing it with the stress threshold. The specific steps include:

[0079] S21. The beginning of the USDFLD subroutine should be written in accordance with the relevant specifications in the ABAQUS user manual;

[0080] S22. The present invention uses the ABAQUS built-in subroutine interface GETVRM function to realize the real-time extraction of the stress results of the unit integration point, extracts the equivalent stress of the current integration point based on the ABAQUS built-in variable SINV, and stores the extraction results in the array ARRAY (1).

[0081] S23. Calculate the stress ratio, continuous damage variable and graded damage variable through a subroutine, and assign the graded damage variable to the field variable to control the graded degradation of the elastic modulus.

[0082] Specifically, the subroutine monitors the equivalent stress of each sling in real time. And calculate the stress ratio according to the following formula. :

[0083] ;

[0084] in, It is the stress ratio; It is the equivalent stress of the suspension cable; It is the stress threshold;

[0085] stress ratio Substitute into the following formula to construct the continuous damage variable D:

[0086] ;

[0087] in, The initial damage stress ratio is preferably set to 0.8. The value of α must ensure that the suspender cable will not be damaged during normal use, while also being able to respond promptly to overload conditions. According to the "Design Code for Highway Suspension Bridges" (JTG / T D65-05), the safety factor of the suspender cable is usually not less than 2.5. In this invention, α = 0.8 is used, which is equivalent to 80% of the ultimate tensile strength. That is, the suspender cable is in a fully elastic working state before the stress ratio reaches 0.8. This value has been verified in numerical simulations of several long-span suspension bridges (main span 800m~2000m). The complete failure stress ratio is greater than or equal to 1, preferably 1.0. β corresponds to the critical point at which the sling completely loses its load-bearing capacity. Taking β=1.0 means that when the equivalent stress of the sling reaches the ultimate tensile strength of the material, it is judged as a complete failure. This value is consistent with the provisions of the "Design Code for Highway Steel Structure Bridges" (JTG D64) regarding the ultimate strength of steel as a failure criterion.

[0088] The continuous damage variable D is quantified into a graded damage variable. :

[0089] ;

[0090] Where N is the number of levels, and N is preferably 5. N=5 can reduce the elastic modulus from... The system has been steadily declining at level 5. To avoid abrupt failures, when N is too high, the USDFLD subroutine will frequently update field variables, significantly reducing computational efficiency. When N is too low, the reduction in each stage is too large, leading to severe redistribution of internal forces and potential stress shocks. The value of N=5 is the result of an optimized trade-off between computational efficiency and numerical stability. Comparative tests (N=3, 5, 10, 20) show that when N=5, the elastic modulus degrades by 20% per stage. This ensures the smoothness of the stiffness degradation process, avoiding stress shocks caused by excessive single reductions, while also preventing the USDFLD subroutine from frequently updating field variables in each increment step due to an excessive number of stages, thus avoiding a significant reduction in computational efficiency.

[0091] The recommended values ​​for the above parameters (α=0.8, β=1.0, N=5) are general preferred values ​​for conventional long-span suspension bridges. When conducting safety assessments for other types of suspension bridges, the three sets of parameters can be adapted and modified according to the bridge design parameters, structural form, and material type.

[0092] The graded damage variables Assign values ​​to field variables to control the graded degradation of the elastic modulus;

[0093] The core logic flowchart of the USDFLD subroutine can be found here. Figure 15The diagram illustrates the core logic of this invention: obtaining equivalent stress → calculating stress ratio → determining damage initiation and evolution → hierarchical quantification → updating field variables to drive elastic modulus degradation → marking failure state. Based on the above code and the textual description in the specification, those skilled in the art can adapt this subroutine to ABAQUS to implement hierarchical progressive fracture simulation of slings without any inventive effort.

[0094] S3, as attached Figure 1 As shown, USDFLD controls the state variable STATEV(1) of the sling material in the model calculation; as attached Figure 2 As shown, when the equivalent stress of the sling does not reach the stress threshold, the state variable STATEV(1) is 1 and the material strength is at normal value; as shown in the attached figure. Figures 3-4 As shown, when the equivalent stress of the sling reaches the stress threshold, the subroutine adjusts the state variable STATEV(1) of the material that has reached the stress threshold to 0; as shown in the attached figure. Figures 5-6 As shown, when the stress in the sling reaches its stress threshold, its material strength decreases to... If its original strength is reduced to one percent, the sling will lose its load-bearing capacity and break; as shown in the attached... Figure 7 As shown, the material strength of the sling decreases and it loses its load-bearing capacity. The program determines that the sling has failed and fractures. Furthermore, as the model continues to run, the tension borne by the fractured sling will be distributed to other slings. If the stress threshold is reached again, continuous fracture will occur. The USDFLD subroutine is automatically called by the ABAQUS solver at each load increment step and each element integration point. Within each increment step, the subroutine sequentially completes stress extraction, failure state determination, state variable update, and field variable assignment. The state variables are passed between increment steps and maintain their historical state, while the field variables are passed to the material constitutive model in real time to control the degradation of the elastic modulus, ensuring real-time simulation and numerical stability of the continuous fracture process of the sling.

[0095] residual modulus Convergence verification:

[0096] By comparing the number of convergence iterations and the stress fluctuation amplitude at key nodes when the residual modulus proportions are 0.1%, 1%, and 5%, the results show that a 1% residual modulus can minimize the stress redistribution error caused by residual stiffness while ensuring computational convergence. In summary, a 1% residual modulus achieves the optimal balance between convergence stability and computational accuracy.

[0097] To avoid the problem of floating nodes caused by deleting elements in the traditional "birth and death element method", this invention adopts the following technical measures to handle the boundary conditions after fracture:

[0098] Specifically, the degradation of the elastic modulus follows the following formula:

[0099] ;

[0100] in, It is the initial elastic modulus; It is the residual modulus, preferably 1%.

[0101] S4, Automatic Iterative Simulation of Continuous Fracture Process:

[0102] As attached Figures 8-9 As shown, the subroutine is embedded in the solver of the model. During the model calculation process, when cable ① breaks, the stress of cable ① will be redistributed to the adjacent cables ② and ③. If cables ② and ③ also break, the stress will continue to be redistributed to cables ④ and ⑤. The subroutine will automatically repeat the cable damage judgment and failure process to simulate the continuous fracture process of the cables.

[0103] S5. Before and after the cable breakage process, bridge deck displacement data is collected in real time through monitoring points, specifically including the following sub-steps:

[0104] S51. Displacement monitoring points shall be set on the bridge deck directly above the area of ​​cable breakage, at the mid-span of the bridge deck, on both sides of the bridge tower, and on the bridge deck at the end of the entire bridge to cover the main areas affected by the redistribution of tension after cable failure.

[0105] S52. Real-time collection of vertical displacement value, lateral displacement value, displacement development rate and displacement difference of bridge deck with the number of cable failures through monitoring point equipment;

[0106] S53. Data preprocessing: Remove numerical oscillation interference during the simulation process and retain valid displacement data.

[0107] S6, as attached Figure 10 As shown, based on the displacement of the bridge deck caused by the breakage of the suspension cable, a bridge displacement early warning and a bridge damage assessment are made. Specifically, the multi-level early warning is divided into three levels:

[0108] When the vertical displacement of each monitoring point is less than or equal to 50% of the allowable value specified in the standard, a first-level warning for bridge displacement is issued. The displacement development rate is stable and there is no significant displacement difference.

[0109] When the vertical displacement of each monitoring point is between 50% and 80% of the allowable value specified in the code, a level II warning for bridge displacement is issued, the displacement development rate accelerates, and significant displacement differences appear in local areas.

[0110] When the vertical displacement of each monitoring point exceeds 80% of the allowable value in the specification, or when the lateral displacement of the bridge deck exceeds the limit in the specification, the bridge issues a level three warning, the displacement difference increases sharply, and the bridge deck tilts significantly.

[0111] Preferably, the bridge design specification is the "Specification for Testing and Evaluation of Bearing Capacity of Highway Bridges" (JTG / T J21).

[0112] Standard example verification:

[0113] To verify the effectiveness and reliability of the method of the present invention, a numerical simulation was conducted on a double-tower suspension bridge with a main span of 2000m.

[0114] Applying a localized overload (simulating a fire or vehicle collision) to the mid-span area triggers a break in the continuity of the suspension cables.

[0115] Simulation results are as follows Figures 11-14 The results show that the method of the present invention did not experience any convergence failures during the simulation of continuous fracture of 5 suspension cables, verifying the effectiveness of the hierarchical progressive degradation strategy and the setting of residual modulus.

[0116] This embodiment also provides a bridge safety assessment system after the continuity of suspension bridge cables breaks, including:

[0117] One or more processors;

[0118] Memory, used to store one or more programs;

[0119] When the one or more programs are executed by the one or more processors, the one or more processors implement the bridge safety assessment method after the suspension bridge cable continuity failure as described in any of the above embodiments.

[0120] Specifically, the processor can be a central processing unit (CPU), graphics processing unit (GPU), digital signal processor (DSP), or other programmable logic devices. The memory can be read-only memory (ROM), random access memory (RAM), flash memory, hard disk, or solid-state drive. The program can be stored in the memory as software code and loaded and executed by the processor. This system can be integrated into existing bridge health monitoring systems or used as a standalone safety assessment terminal.

[0121] This embodiment also provides a computer-readable storage medium storing a computer program that, when executed by a processor, implements the bridge safety assessment method after the suspension bridge cable continuity failure described in any of the above embodiments.

[0122] Computer-readable storage media can be any tangible medium that contains or stores a program, such as a USB flash drive, external hard drive, read-only memory (ROM), random access memory (RAM), magnetic disk, or optical disk. The program can be run after being read by a computer or processor, thereby enabling the simulation of cable continuity failure and bridge safety assessment.

[0123] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from its spirit or essential characteristics. Therefore, the embodiments should be considered in all respects as exemplary and non-limiting, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, all variations falling within the meaning and scope of equivalents of the claims are intended to be included within the present invention. No reference numerals in the claims should be construed as limiting the scope of the claims.

[0124] Furthermore, it should be understood that although this specification describes embodiments, not every embodiment contains only one independent technical solution. This narrative style is merely for clarity. Those skilled in the art should consider the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

Claims

1. A method for assessing the safety of a suspension bridge after the continuity of its suspension cables breaks, comprising the following specific steps: S1. Establish a suspension bridge model in finite element analysis software, and define state variables and field variables for the cable material. The state variables are used to store the stress state, damage level, and failure indicator information of the sling; S2. Set the user-defined field variable subroutine as the calculation subroutine for the suspension bridge model, monitor the equivalent stress of each cable in real time, construct a continuous damage variable D based on the stress ratio, and then quantify it into a graded damage variable. , are assigned to field variables to control the graded degradation of the elastic modulus; S3. When the equivalent stress of the sling reaches the stress threshold, the subroutine drives the field variable through graded damage variables. The field variable couples with the material constitutive model to realize a graded progressive elastic modulus degradation method, gradually reducing the elastic modulus of the sling to residual strength in N levels, simulating the sling losing its load-bearing capacity and breaking. Its tensile force is redistributed to adjacent slings. The elastic modulus degradation follows the following formula: ； in, It is the initial elastic modulus; It is the residual modulus, the residual modulus Initial elastic modulus 1%; S4. The subroutine continues to monitor the equivalent stress of adjacent slings after redistribution. If the stress of the slings on both sides exceeds the stress threshold after stress redistribution, the sling will automatically repeat the above damage judgment and failure process in subsequent load increment steps without presetting the fracture location, thereby simulating the continuous fracture process of the sling. S5. Before and after the cable breakage process, the bridge deck displacement data is collected in real time through displacement monitoring points set in key locations on the bridge deck. S6. Based on the displacement of the bridge deck caused by the breakage of the suspension cable, issue multi-level early warnings according to the ratio of the displacement to the allowable value in the specification, and make a bridge damage assessment. The characteristic is that, in step S2, the stress ratio is calculated according to the following formula: ； in, It is the stress ratio; It is the equivalent stress of the suspension cable; It is the stress threshold; Construct a continuous damage variable D based on the stress ratio: ； in, The initial damage stress ratio; For the complete failure stress ratio, 0 < < ; The continuous damage variable D is quantified into a graded damage variable. : ； Among them, round( ) represents the rounding function, where N is the number of levels, and the value of N is 5; The graded damage variables The value is assigned to the field variable to control the graded degradation of the elastic modulus.

2. The method for assessing bridge safety after cable continuity failure in a suspension bridge according to claim 1, characterized in that, The stress threshold value mentioned in step S2 is 1.0 times the ultimate tensile strength of the sling material.

3. The method for assessing bridge safety after cable continuity failure in a suspension bridge according to claim 1, characterized in that, The state variables include a first state variable, a second state variable, and a third state variable, wherein the first state variable is used to store the stress ratio, the second state variable is used to store the damage level, and the third state variable is used to store the failure indicator.

4. The method for assessing bridge safety after cable continuity failure in a suspension bridge according to claim 1, characterized in that, Step S1 specifically includes: S11. After establishing the main cable, suspension cables, bridge deck, and bridge tower components of the suspension bridge in the finite element analysis software, assemble them into a full suspension bridge model. S12. For the material corresponding to the sling, check Depvar and user-defined field variable attributes.

5. The method for assessing bridge safety after cable continuity failure in a suspension bridge according to claim 1, characterized in that, Step S5 specifically includes the following sub-steps: S51. Displacement monitoring points shall be set on the bridge deck directly above the suspension cables, at the mid-span of the bridge deck, on both sides of the bridge tower, and on the bridge deck at the ends of the entire bridge. S52. Real-time collection of vertical displacement value, lateral displacement value, displacement development rate and displacement difference of bridge deck with the number of cable failures through monitoring point equipment; S53. Data preprocessing: Based on the assumption that the displacement change rate is less than 1% for three consecutive time steps, noise reduction is performed to remove numerical oscillation interference during the simulation process. The valid displacement data is then retained and transmitted to the backend.

6. The method for assessing bridge safety after cable continuity failure in a suspension bridge according to claim 1, characterized in that, In step S6, the multi-level early warning is a three-level early warning, and the specific criteria are as follows: A Level 1 warning is issued when the vertical displacement of each monitoring point does not exceed 50% of the allowable value specified in the standard. A Level II warning is issued when the vertical displacement of each monitoring point is between 50% and 80% of the allowable value specified in the standard. A Level III warning will be issued when the vertical displacement of each monitoring point exceeds 80% of the allowable value specified in the standard or when the lateral displacement of the bridge deck exceeds the limit specified in the standard.

7. A system for assessing bridge safety after the continuity failure of suspension bridge cables, characterized in that, include: One or more processors; Memory, used to store one or more programs; When the one or more programs are executed by the one or more processors, the one or more processors cause the one or more processors to implement the method as described in any one of claims 1-6.

8. A computer-readable storage medium having a computer program stored thereon, characterized in that, When the program is executed by the processor, it implements the method as described in any one of claims 1-6.

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