A method and system for safety evaluation of a tower foot of a power transmission tower

Abstract

This invention belongs to the field of power transmission line engineering and structural safety technology, and discloses a method and system for safety assessment of power transmission tower feet. The method includes: calculating the frost pull-out force of frozen soil; establishing a theoretical calculation model for calculating the pressure exerted by the ice-water mixture on the tower feet during the water-ice phase transition process; using the frost pull-out force of frozen soil as the load boundary condition, and constructing a finite element simulation model based on the theoretical calculation model; using the finite element simulation model to simulate and calculate the stress distribution at the tower feet under different liquid phase fractions, and determining the critical liquid phase fraction; performing a secondary loss assessment on the tower feet based on the ice expansion force after ice stabilization, and generating a judgment conclusion; using the critical liquid phase fraction and the judgment conclusion as safety criteria; predicting actual operating parameters and comparing them with the safety criteria, and integrating them to generate a power transmission tower foot safety assessment report. This invention provides a reliable theoretical basis for the safe operation and targeted design of power transmission towers in high-altitude and cold regions.

Description

Technical Field

[0001] This invention relates to the field of power transmission line engineering and structural safety technology, and in particular to a method and system for safety assessment of power transmission tower feet. Background Technology

[0002] Transmission towers in the cold regions of Northeast and Northwest my country have long faced severe challenges such as icing and frost heave. In winter, water around the tower foundation freezes into ice, and the expansion of the ice generates enormous "static ice pressure." This pressure acts on the tower base, altering the force transmission path of the structure, causing stress concentration in the main tower leg material, resulting in bending deformation. In severe cases, it can directly lead to tower yielding, joint failure, or even tower collapse, posing a serious threat to power grid safety.

[0003] Currently, research on ice loads largely focuses on theoretical analysis and local simulations, lacking a quantitative safety assessment and design system that closely integrates theoretical models with engineering practice. Existing design codes often rely on empirical formulas, failing to fully consider the precise impact of the dynamic changes in the freezing rate (i.e., liquid phase fraction) during the water-ice phase transition on the degree of damage, leading to conservative assessment results or inadequate design.

[0004] Therefore, how to provide a method and system for safety assessment of transmission tower feet is an urgent problem to be solved. Summary of the Invention

[0005] This invention provides a method and system for safety assessment of transmission tower feet to address problems in the prior art.

[0006] To provide a basic understanding of some aspects of the disclosed embodiments, a brief summary is given below. This summary is not intended as a general commentary, nor is it intended to identify key / important components or to describe the scope of protection of these embodiments. Its sole purpose is to present some concepts in a simple form as a prelude to the detailed description that follows.

[0007] According to a first aspect of the present invention, a method and system for safety assessment of the base of a power transmission tower are provided.

[0008] In one embodiment, a method for assessing the safety of transmission tower legs includes:

[0009] Based on the tangential frost heave force, the standard freezing depth of seasonally frozen soil, the freezing depth coefficient, and the perimeter of the pile under the influence of freezing depth, the frost pull-out force of frozen soil is calculated.

[0010] A theoretical calculation model is established to calculate the pressure exerted by the ice-water mixture on the tower foot during the water-ice phase transition process. The input parameters of the theoretical calculation model include ambient temperature, physical properties of water, physical properties of the tower foot material, and liquid phase fraction characterizing the freezing rate.

[0011] Using the frost pull-out force of frozen soil as the load boundary condition, and based on the theoretical calculation model, a finite element simulation model including the tower foot, pile foundation and surrounding water-ice medium is constructed.

[0012] Using the finite element simulation model, the stress distribution of the tower foot under different liquid phase fractions is simulated and calculated. Based on the coupling effect of the stress distribution and the freeze-pull force, the critical liquid phase fraction corresponding to when the maximum equivalent stress of the tower foot reaches its material yield strength is determined.

[0013] A secondary loss assessment is performed on the tower feet of the transmission tower based on the expansion force of the ice layer after it stabilizes, and a judgment conclusion is generated.

[0014] The critical liquid phase fraction and the judgment conclusion are used as safety criteria; the actual operating parameters are predicted based on the environmental data of the target area; the predicted actual operating parameters are compared with the safety criteria, and an integrated report on the safety assessment of the tower foot is generated.

[0015] In one embodiment, calculating the pressure exerted by the ice-water mixture on the tower foot during the water-ice phase transition includes:

[0016] The equivalent intrinsic strain of the mixture is calculated based on the liquid phase fraction and the volume expansion coefficient when it is completely frozen.

[0017] The equivalent elastic modulus of the mixture is calculated based on the liquid phase fraction, the elastic modulus of ice, and the preset exponential constant.

[0018] The equivalent stiffness of the mixture is calculated using the equivalent elastic modulus of the mixture and the Poisson's ratio of ice.

[0019] The equivalent stiffness of the tower feet is calculated based on the elastic modulus and Poisson's ratio of the tower foot material.

[0020] The pressure exerted by the ice-water mixture on the tower feet is calculated using the equivalent intrinsic strain of the mixture, the equivalent stiffness of the mixture, and the equivalent stiffness of the tower feet, through the equivalent relationship of the series springs.

[0021] In one embodiment, the formula for calculating the pressure of the ice-water mixture on the tower foot is as follows:

[0022] ;

[0023] In the formula, ε represents the liquid phase fraction; iw The equivalent intrinsic strain of the mixture; K represents the equivalent stiffness of the mixture. c This is the equivalent stiffness of the tower feet.

[0024] In one embodiment, the finite element simulation model includes a tower foot domain, a water-ice domain, and an air domain.

[0025] In one embodiment, the finite element simulation model is used to simulate and calculate the stress distribution of the tower foot under different liquid phase fractions. Based on the coupling effect of the stress distribution and the freeze-pull force, the critical liquid phase fraction corresponding to when the maximum equivalent stress of the tower foot reaches its material yield strength is determined, including:

[0026] Material properties are assigned to the tower foot region of the finite element geometric model. Combined with the theoretical calculation model and the frost pull-out force of the frozen soil, a thermo-mechanical coupling simulation is performed on the finite element geometric model to simulate the stress distribution at the tower foot under different liquid phase fractions.

[0027] Based on the simulation results of the thermo-mechanical coupling simulation of the finite element geometric model, the curve of the maximum equivalent stress at the tower foot as a function of the liquid phase fraction is plotted. The liquid phase fraction corresponding to the stress value reaching the yield strength of the tower foot material is taken as the critical liquid phase fraction.

[0028] In one embodiment, a finite element geometric model is established, comprising a tower foot region, a water-ice region, and an air region, and material properties are assigned to the tower foot region. Combining the theoretical calculation model with the frost pull-out force of frozen soil, a thermo-mechanical coupling simulation is performed on the finite element geometric model to simulate the stress distribution at the tower foot under different liquid phase fractions, including:

[0029] An ambient temperature function is applied to the air domain, phase change material properties are defined and thermal boundary conditions are set for the water-ice domain, and the temperature field and liquid fraction field of the entire computational domain are obtained through heat transfer simulation calculation.

[0030] Using the obtained liquid phase fraction field as input, the pressure distribution of the ice-water mixture on the tower foot is determined based on the theoretical calculation model, and static solutions are performed in conjunction with the comprehensive mechanical load to obtain the stress distribution at the tower foot.

[0031] In one embodiment, the combined mechanical load includes a surface load applied to the top of the tower foot for equivalent force transmission to the superstructure; and a frost pull-out load applied to the pile foundation for equivalent frost pull-out force.

[0032] In one embodiment, the secondary loss assessment of the transmission tower foot based on the ice expansion force after the ice layer stabilizes includes:

[0033] Based on the total thickness of the ice layer and the parameters of the heating process, calculate the ice expansion force of the upper and lower halves of the ice layer respectively;

[0034] Based on the expansion forces of the upper and lower halves of the ice layer, the average expansion pressure after the ice layer stabilizes is calculated.

[0035] Based on the average expansion pressure and the preset stress concentration factor, the local stress is calculated;

[0036] Based on the temperature of the target area, determine the fatigue limit of the tower foot material at the corresponding temperature;

[0037] The local stress is compared with the fatigue limit to achieve secondary loss determination.

[0038] In one embodiment, the critical liquid phase fraction and the judgment conclusion are used as safety criteria; actual operating parameters are predicted based on environmental data of the target area; the predicted actual operating parameters are compared with the safety criteria, and a transmission tower foot safety assessment report is generated by integrating the results, including:

[0039] The critical liquid phase fraction and the determination conclusion are used as safety criteria;

[0040] Based on environmental data of the target area, the actual liquid phase fraction and corresponding actual stress are predicted and integrated as parameters for predicting actual working conditions.

[0041] The actual liquid phase fraction in the predicted actual operating condition parameters is compared with the critical liquid phase fraction to generate a first comparison result;

[0042] The actual stress in the predicted actual working condition parameters is compared with the corresponding strength standard in the judgment conclusion to generate a second comparison result;

[0043] Integrate the first and second comparison results to generate a safety assessment report for the base of the transmission tower.

[0044] According to a second aspect of the present invention, a method and system for safety assessment of transmission tower feet are provided.

[0045] In one embodiment, a transmission tower foot safety assessment system includes:

[0046] The frost pull-out force calculation module is used to calculate the frost pull-out force of frozen soil based on tangential frost heave force, standard freezing depth of seasonally frozen soil, freezing depth coefficient, and the perimeter of the pile under the influence of freezing depth.

[0047] The theoretical calculation model module is used to establish a theoretical calculation model for calculating the pressure exerted by the ice-water mixture on the tower foot during the water-ice phase transition process. The input parameters of the theoretical calculation model include ambient temperature, physical properties of water, physical properties of the tower foot material, and liquid phase fraction characterizing the freezing rate.

[0048] The finite element simulation model building module is used to construct a finite element simulation model containing the tower foot, pile foundation and surrounding water-ice medium, based on the theoretical calculation model, with the frost pull-out force of frozen soil as the load boundary condition.

[0049] The finite element simulation model analysis module is used to simulate and calculate the stress distribution of the tower foot under different liquid phase fractions using the finite element simulation model. Based on the coupling effect of the stress distribution and the freeze-pull force, the critical liquid phase fraction corresponding to when the maximum equivalent stress of the tower foot reaches its material yield strength is determined.

[0050] The secondary damage calculation module is used to determine the secondary damage to the tower feet of the transmission tower based on the expansion force of the ice layer after the ice layer stabilizes, and generate a determination conclusion.

[0051] The safety assessment and decision output module is used to use the critical liquid phase fraction and the judgment conclusion as safety criteria; predict actual operating parameters based on environmental data of the target area; compare the predicted actual operating parameters with the safety criteria, and integrate them to generate a safety assessment report for the tower foot of the transmission tower.

[0052] According to a third aspect of the present invention, a computer device is provided.

[0053] In some embodiments, the computer device includes a memory and a processor, the memory storing a computer program, and the processor executing the computer program to implement the steps of the method described above.

[0054] According to a fourth aspect of the present invention, a computer-readable storage medium is provided.

[0055] In one embodiment, a computer program is stored on the computer-readable storage medium, which, when executed by a processor, implements the steps of the above method.

[0056] The technical solutions provided by the embodiments of the present invention may include the following beneficial effects:

[0057] This invention is used to assess the risk of ice damage to existing transmission towers under specific environments, or to set up protective measures to ensure that the maximum stress under actual ice load is lower than the material yield strength. This invention combines theoretical analysis with engineering practice, providing accurate and reliable theoretical basis and tools for the safe operation and targeted design of transmission towers in high-altitude and cold regions.

[0058] It should be understood that the above general description and the following detailed description are exemplary and explanatory only, and are not intended to limit the invention. Attached Figure Description

[0059] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments consistent with the invention and, together with the description, serve to explain the principles of the invention.

[0060] Figure 1 This is a flowchart illustrating a method for assessing the safety of transmission tower feet according to an exemplary embodiment;

[0061] Figure 2 This is a schematic block diagram illustrating a transmission tower foot safety assessment system according to an exemplary embodiment;

[0062] Figure 3 This is a general flowchart illustrating a method for assessing the safety of transmission tower feet according to an exemplary embodiment;

[0063] Figure 4 This is a schematic diagram of a finite element model of a transmission tower foot in a method for assessing the safety of transmission tower feet according to an exemplary embodiment;

[0064] Figure 5 This is one of the example diagrams of stress cloud diagrams of the tower foot under different liquid phase fractions in a method for safety assessment of the tower foot according to an exemplary embodiment;

[0065] Figure 6 This is the second example diagram of stress cloud diagrams of tower feet under different liquid phase fractions in a method for safety assessment of tower feet according to an exemplary embodiment;

[0066] Figure 7 This is the third example diagram of stress cloud diagrams of the tower foot under different liquid phase fractions in a method for safety assessment of the tower foot according to an exemplary embodiment;

[0067] Figure 8 This is a schematic diagram of the structure of a computer device according to an exemplary embodiment. Detailed Implementation

[0068] The following description and accompanying drawings fully illustrate specific embodiments described herein to enable those skilled in the art to practice them. Some portions and features of certain embodiments may be included in or replace portions and features of other embodiments. The scope of the embodiments herein includes the entire scope of the claims and all available equivalents thereof. The various embodiments described herein are presented in a progressive manner, with each embodiment focusing on its differences from other embodiments; similar or identical parts between embodiments can be referred to interchangeably.

[0069] The modules in the apparatus or system of this application can be implemented entirely or partially through software, hardware, or a combination thereof. These modules can be embedded in or independent of the processor in a computer device in hardware form, or stored in the memory of a computer device in software form, so that the processor can call and execute the operations corresponding to each module.

[0070] Where there is no conflict, the embodiments and features in the embodiments of the present invention can be combined with each other.

[0071] Figure 1An embodiment of the transmission tower foot safety assessment method and system of the present invention is shown.

[0072] In this optional embodiment, the method for assessing the safety of the transmission tower feet includes:

[0073] S101. Based on the tangential frost heave force, the standard freezing depth of seasonally frozen soil, the freezing depth coefficient, and the perimeter of the pile under the influence of freezing depth, the frost pull-out force of frozen soil is calculated.

[0074] It should be explained that, according to the "Technical Specification for Building Pile Foundations", the formula η is used. f ·q f The frost pull-out force of frozen soil is calculated using u·Z0. Where q f It is the tangential frost heave force, Z0 is the standard frost depth of seasonally frozen soil, and η is the tangential frost heave force. f is the frost depth coefficient, and u is the perimeter of the pile under the influence of frost depth.

[0075] S102. Establish a theoretical calculation model for calculating the pressure exerted by the ice-water mixture on the tower foot during the water-ice phase transition process. The input parameters of the theoretical calculation model include ambient temperature, physical properties of water, physical properties of the tower foot material, and liquid fraction characterizing the freezing rate.

[0076] In this optional embodiment, calculating the pressure exerted by the ice-water mixture on the tower feet during the water-ice phase transition includes:

[0077] The equivalent intrinsic strain of the mixture is calculated based on the liquid phase fraction and the volume expansion coefficient when it is completely frozen.

[0078] The equivalent elastic modulus of the mixture is calculated based on the liquid phase fraction, the elastic modulus of ice, and the preset exponential constant.

[0079] The equivalent stiffness of the mixture is calculated using the equivalent elastic modulus of the mixture and the Poisson's ratio of ice.

[0080] The equivalent stiffness of the tower feet is calculated based on the elastic modulus and Poisson's ratio of the tower foot material.

[0081] The pressure exerted by the ice-water mixture on the tower feet is calculated using the equivalent intrinsic strain of the mixture, the equivalent stiffness of the mixture, and the equivalent stiffness of the tower feet, through the equivalent relationship of the series springs.

[0082] It should be noted that the theoretical calculation model is a non-fully constrained model based on the equivalent stiffness method of series springs. The formula for calculating the pressure of the ice-water mixture on the tower foot is as follows:

[0083] ;

[0084] In the formula, ε represents the liquid phase fraction; iwThe equivalent intrinsic strain of the mixture; K represents the equivalent stiffness of the mixture. c This is the equivalent stiffness of the tower feet.

[0085] The formula for calculating the equivalent intrinsic strain of a mixture is as follows:

[0086] ;

[0087] In the formula, β is the volume expansion coefficient when the ice is completely frozen.

[0088] The formula for calculating the equivalent elastic modulus of a mixture is as follows:

[0089] ;

[0090] In the formula, v i E represents the Poisson's ratio for ice. iw It represents the equivalent elastic modulus.

[0091] E iw The calculation formula is as follows:

[0092] ;

[0093] In the formula, E i Let be the elastic modulus of ice; n is a constant greater than 1.

[0094] The formula for calculating the equivalent stiffness of the tower base is as follows:

[0095] ;

[0096] In the formula, E c v is the elastic modulus of the tower base material. c is the Poisson's ratio of the tower base material.

[0097] S103. Using the frost pull-out force of frozen soil as the load boundary condition, and based on the theoretical calculation model, construct a finite element simulation model that includes the tower foot, pile foundation and surrounding water-ice medium.

[0098] In this optional embodiment, the finite element simulation model includes the tower foot domain, the water-ice domain, and the air domain.

[0099] It needs to be explained that, for example Figure 4 The figure shown is a schematic diagram of the finite element model of the tower foot of the transmission tower.

[0100] S104. Using the finite element simulation model, simulate and calculate the stress distribution of the tower foot under different liquid phase fractions. Based on the coupling effect of the stress distribution and the freeze-pull force, determine the critical liquid phase fraction corresponding to when the maximum equivalent stress of the tower foot reaches its material yield strength.

[0101] It needs to be explained that, for example Figure 5-7 The image shown is an example of stress contour plots at the column foot for different liquid phase fractions. Figure 5-7 In this context, von Mises (MPa) represents the von Mises stress, and Principal Stress Directions represent the directions of the principal stresses within the material.

[0102] In this optional embodiment, the stress distribution of the tower foot under different liquid phase fractions is simulated and calculated using the finite element simulation model. Based on the coupling effect of the stress distribution and the freeze-pull force, the critical liquid phase fraction corresponding to when the maximum equivalent stress of the tower foot reaches its material yield strength is determined, including:

[0103] Material properties are assigned to the tower foot region of the finite element geometric model. Combined with the theoretical calculation model and the frost pull-out force of the frozen soil, a thermo-mechanical coupling simulation is performed on the finite element geometric model to simulate the stress distribution at the tower foot under different liquid phase fractions.

[0104] Based on the simulation results of the thermo-mechanical coupling simulation of the finite element geometric model, the curve of the maximum equivalent stress at the tower foot as a function of the liquid phase fraction is plotted. The liquid phase fraction corresponding to the stress value reaching the yield strength of the tower foot material is taken as the critical liquid phase fraction.

[0105] In this optional embodiment, a finite element geometric model is established, comprising a tower foot region, a water-ice region, and an air region, and material properties are assigned to the tower foot region. Combining the theoretical calculation model and the frost pull-out force of the frozen soil, a thermo-mechanical coupling simulation is performed on the finite element geometric model to simulate the stress distribution at the tower foot under different liquid phase fractions, including:

[0106] An ambient temperature function is applied to the air domain, phase change material properties are defined and thermal boundary conditions are set for the water-ice domain, and the temperature field and liquid fraction field of the entire computational domain are obtained through heat transfer simulation calculation.

[0107] Using the obtained liquid phase fraction field as input, the pressure distribution of the ice-water mixture on the tower foot is determined based on the theoretical calculation model, and static solutions are performed in conjunction with the comprehensive mechanical load to obtain the stress distribution at the tower foot.

[0108] In this optional embodiment, the combined mechanical load includes a surface load applied to the top of the tower foot for equivalent force transmission to the superstructure; and a frost pull-out load applied to the pile foundation for equivalent frost pull-out force.

[0109] It should be explained that when constructing the finite element simulation model, a sequential coupling method is used. Temperature field analysis is performed first, and analytical functions are globally defined in COMSOL, for example... ℃ is used as a temperature function of the weather. This function is added to the air domain. The boundary condition of the lower water layer is, for example, 4℃. Heat transfer is added between the water and air domains, and thermal insulation is added around the perimeter. Simulation calculations are performed to determine the liquid phase fractional field. Then, the liquid phase fractional field is applied as a load to the structural stress field analysis to achieve thermo-mechanical coupling simulation.

[0110] S105. Based on the expansion force of the ice layer after it stabilizes, a secondary loss assessment is performed on the tower feet of the transmission tower, and a assessment conclusion is generated.

[0111] In this optional embodiment, the secondary loss determination of the transmission tower feet based on the ice expansion force after the ice layer stabilizes includes:

[0112] Based on the total thickness of the ice layer and the parameters of the heating process, calculate the ice expansion force of the upper and lower halves of the ice layer respectively;

[0113] Based on the expansion forces of the upper and lower halves of the ice layer, the average expansion pressure after the ice layer stabilizes is calculated.

[0114] Based on the average expansion pressure and the preset stress concentration factor, the local stress is calculated;

[0115] Based on the temperature of the target area, determine the fatigue limit of the tower foot material at the corresponding temperature;

[0116] The local stress is compared with the fatigue limit to achieve secondary loss determination.

[0117] It should be explained that the expansion force after the ice layer stabilizes is the average expansion force after the ice layer is divided equally. The formula for the average expansion force is as follows:

[0118] ;

[0119] In the formula, P represents the final average expansion pressure of the ice layer; P1 represents the average ice pressure of the upper half of the ice layer; P2 represents the average ice pressure of the lower half of the ice layer; and h represents the total thickness of the ice layer, which is calculated using the following formula: H represents the depth of the water.

[0120] The formula for calculating the expansion force of each ice layer is as follows:

[0121] ;

[0122] In the formula, i represents the index; K represents the comprehensive impact coefficient; K s c represents the snow cover influence coefficient. h The transformation coefficients related to ice thickness; t a Δt represents the initial air temperature, T represents the duration of the temperature rise; a This represents the increase in air temperature due to continuous warming; m represents a constant in the formula. Under strong constraints, the stress increases locally, and its formula is... K r This represents the stress concentration factor, which is generally taken as 2 to 5. In this invention, we take 5 to study the maximum possibility.

[0123] S106. Use the critical liquid phase fraction and the judgment conclusion as safety criteria; predict actual operating parameters based on environmental data of the target area; compare the predicted actual operating parameters with the safety criteria, and integrate them to generate a safety assessment report for the tower foot of the transmission tower.

[0124] It needs to be explained that the process involves acquiring environmental data for the target area, predicting the potential liquid phase fraction and related data on secondary losses. If the predicted liquid phase fraction is lower than the critical liquid phase fraction and the conditions for secondary damage are met, the transmission tower is deemed to be at risk of ice damage. Using the critical liquid phase fraction as the design target, the maximum equivalent stress of the tower foot calculated by the finite element simulation model at the critical liquid phase fraction is lower than the allowable stress of the material by adjusting the material grade, structural dimensions, or setting stress relief structures around the tower foot. Setting stress relief structures refers to filling or setting low-stiffness buffer materials around the tower foot to change its equivalent stiffness K. c This reduces the pressure of ice load transmitted to the tower feet.

[0125] In this optional embodiment, the critical liquid phase fraction and the judgment conclusion are used as safety criteria; actual operating parameters are predicted based on environmental data of the target area; the predicted actual operating parameters are compared with the safety criteria, and an integrated safety assessment report for the transmission tower foot is generated, including:

[0126] The critical liquid phase fraction and the determination conclusion are used as safety criteria;

[0127] Based on environmental data of the target area, the actual liquid phase fraction and corresponding actual stress are predicted and integrated as parameters for predicting actual working conditions.

[0128] The actual liquid phase fraction in the predicted actual operating condition parameters is compared with the critical liquid phase fraction to generate a first comparison result;

[0129] The actual stress in the predicted actual working condition parameters is compared with the corresponding strength standard in the judgment conclusion to generate a second comparison result;

[0130] Integrate the first and second comparison results to generate a safety assessment report for the base of the transmission tower.

[0131] It needs to be explained that, for example Figure 3 As shown, the method for safety assessment of transmission tower feet is explained with reference to specific embodiments.

[0132] 1. System initialization and parameter input.

[0133] First, establish a material library and model template containing the following core parameters. The tower leg material library pre-sets the elastic modulus E of commonly used steels. c Poisson's ratio U c Density p c Yield strength a S Coefficient of thermal expansion a c Constant pressure heat capacity C c Thermal conductivity νc. Elastic modulus E of ice in ice-water material parameters. i =8.7GPa, Poisson's ratio ν i =0.3, density p i =917kg / m 3 The density of water, p w =1000kg / m 3 The latent heat of the water-ice phase transition, L, is 334 kJ / kg. The equivalent linear expansion coefficient, β, is 0.032. The calculation exponent for the equivalent elastic modulus of the mixture is n = 2.1. The geometric model template provides a parametric tower foot-water geometry model. Users can input the equivalent radius of the tower foot, a, the radius of the water accumulation area, b, and the water accumulation depth, H.

[0134] 2. Theoretical model calculation.

[0135] A built-in theoretical calculation model serves as a fast estimation tool. When the user inputs the target liquid fraction... ,For example When the value is 0.8, the theoretical calculation model automatically executes the following calculation sequence:

[0136] 1) Calculate the equivalent eigenstrain ;

[0137] 2) Calculate the equivalent elastic modulus of the mixture. ;

[0138] 3) Calculate the equivalent stiffness of the mixture ;

[0139] 4) Calculate the equivalent stiffness of the tower feet. ;

[0140] 5) Calculate the pressure of the ice-water mixture on the tower feet. .

[0141] This theoretical calculation model can be used to quickly scan the theoretical pressure under different liquid phase fractions, providing a reference for subsequent detailed simulations.

[0142] 3. Finite element simulation and analysis.

[0143] This is the core of the invention. Taking COMSOL Multiphysics software as an example, the specific operation process is as follows: Based on the input geometric parameters, establish... Figure 4The model shown is a 1 / 4 symmetric 3D model. The base region, water-ice region, and air region are defined respectively.

[0144] For the tower foot region, material properties are assigned. Equivalent surface forces from the superstructure and frost pull-out forces transmitted from the pile foundation are applied to the top of the tower foot. Symmetrical constraints are applied on the symmetry plane, and contact or bonding conditions are applied to the contact surface between the tower foot and the ice. For all regions, the initial conditions are set to an initial water temperature of 4°C, and the initial temperatures of the tower foot and air are set to the target low temperature. Boundary conditions are set as follows: the upper surface of the model is "thermal convection" with a convection coefficient f = 25 W / (m²·K), and the external temperature is -20°C; the bottom of the model is set to a constant temperature of 4°C; and the perimeter of the model is set to "thermal insulation".

[0145] In the material properties of the water-ice domain, enable the phase transition function, set the phase transition temperature to 0°C, and input the latent heat of phase transition L. Add a "thermal expansion" multiphysics coupling node and apply it to the water-ice domain. The key step is to define the inelastic strain: add a phase transition strain to the strain contribution and set its expression to [value missing] in all three dimensions. Then, the mesh of the tower foot surface and the tower foot-ice-water contact area is refined, with the element size controlled below 0.02m to ensure the calculation accuracy of stress concentration areas. A coarser mesh can be used in the water area far from the tower foot to save computational resources. After the calculation is completed, the maximum equivalent stress in the tower foot domain is extracted from all domains.

[0146] 4. Calculation of secondary damage.

[0147] A secondary loss assessment of the transmission tower feet is performed based on the expansion force of the ice layer after it stabilizes. This is done when the user inputs a water accumulation H of 1.5m and a predicted initial temperature t. a =-25℃, forecast high temperature T max =-10℃ and target liquid fraction (For example When the value is 0.8, the following calculation sequence will be executed automatically.

[0148] 1) Ice surface thickness h = H=30cm, Δt a =15℃;

[0149] 2) Divide the ice layer into two layers: the upper 15cm layer and the lower 15cm layer.

[0150] For the upper layer, refer to the formula Δt for the continuous temperature rise over several days. i1 =0.62·Δt a =9.3℃, where Δt i1 It reflects the range of change in upper ice temperature as air temperature rises;

[0151] For the lower layer, the temperature rise rate relationship is S2 = 0.4·S1, where S1 represents the average temperature rise rate of the upper ice layer, and S2 represents the average temperature rise rate of the lower ice layer. Upper layer temperature rise rate =1.55℃ / h, Δt i2 =6·S2=6·0.4·S1=3.72℃;

[0152] 3) According to the formula Substituting the corresponding calculation parameters, we get: P1 = 3.58 kg / cm² 2 P2 = 1.43 kg / cm³ 2 ;

[0153] 4) The final pressure is calculated as follows: =2.51kg / cm 2 =24.6 MPa. Calculate the local stress under strong constraints. =123MPa;

[0154] 5) Under strong constraint conditions, the fatigue limit of steel decreases by 8% for every 10°C decrease. Calculate the fatigue limit of steel Q345 at the corresponding temperature.

[0155] For example, at -20℃, the fatigue limit is σ. -1 =260·40%=104MPa.

[0156] 5. Safety assessment and decision output.

[0157] The system will determine the critical liquid fraction n d The core criterion is the expansion force of the ice layer after it stabilizes. The user inputs the predicted minimum temperature T for the target area. min Forecast of the highest temperature T max And the water depth H. Predict the minimum achievable liquid fraction n under these conditions using thermal simulation or empirical formulas. min And the corresponding local stress σ and the corresponding fatigue limit σ -1 .

[0158] If n min <n d The system generates a high-risk alert and recommends immediate de-icing or reinforcement measures. If n min ≤n d <n min +0.05, the system generates a medium-risk warning, suggesting enhanced monitoring and improved emergency preparedness. If n min ≥n d +0.05, σ>σ -1 The system generates a low-risk warning and suggests periodic checks. If n min ≥n d +0.05, σ < σ-1 The system generates a security assessment.

[0159] Figure 2 An embodiment of the transmission tower foot safety assessment method and system of the present invention is shown.

[0160] In this optional embodiment, the transmission tower foot safety assessment system includes:

[0161] The frost pull-out force calculation module 201 is used to calculate the frost pull-out force of frozen soil based on tangential frost heave force, standard freezing depth of seasonally frozen soil, freezing depth coefficient, and the perimeter of the pile under the influence of freezing depth.

[0162] The theoretical calculation model calculation module 202 is used to establish a theoretical calculation model for calculating the pressure exerted by the ice-water mixture on the tower foot during the water-ice phase transition process. The input parameters of the theoretical calculation model include ambient temperature, physical properties of water, physical properties of the tower foot material, and liquid phase fraction characterizing the freezing rate.

[0163] The finite element simulation model construction module 203 is used to construct a finite element simulation model containing the tower foot, pile foundation and surrounding water-ice medium based on the theoretical calculation model, using the frost pull-out force of frozen soil as the load boundary condition.

[0164] The finite element simulation model analysis module 204 is used to simulate and calculate the stress distribution of the tower foot under different liquid phase fractions using the finite element simulation model, and determine the critical liquid phase fraction corresponding to when the maximum equivalent stress of the tower foot reaches its material yield strength based on the coupling effect of the stress distribution and the freeze-pull force.

[0165] The secondary damage calculation module 205 is used to determine the secondary loss of the tower foot of the transmission tower based on the expansion force of the ice layer after the ice layer stabilizes, and generate a determination conclusion.

[0166] The safety assessment and decision output module 206 is used to use the critical liquid phase fraction and the judgment conclusion as safety criteria; predict actual operating parameters based on environmental data of the target area; compare the predicted actual operating parameters with the safety criteria, and integrate them to generate a safety assessment report for the tower foot of the transmission tower.

[0167] In one embodiment, a computer device is provided, which may be a server, and its internal structure diagram may be as follows: Figure 8As shown, the computer device includes a processor, memory, and a network interface connected via a system bus. The processor provides computing and control capabilities. The memory includes a non-volatile storage medium and internal memory. The non-volatile storage medium stores an operating system, computer programs, and a database. The internal memory provides an environment for the operation of the operating system and computer programs in the non-volatile storage medium. The database stores static and dynamic information data. The network interface communicates with external terminals via a network connection. When the computer program is executed by the processor, it implements the steps in the above method embodiments.

[0168] Those skilled in the art will understand that Figure 8 The structure shown is merely a block diagram of a portion of the structure related to the present invention and does not constitute a limitation on the computer device to which the present invention is applied. A specific computer device may include more or fewer components than those shown in the figure, or combine certain components, or have different component arrangements.

[0169] In addition, the present invention also provides a computer device, including a memory and a processor, wherein the memory stores a computer program, and the processor executes the computer program to implement the steps in the above method embodiments.

[0170] In addition, the present invention also provides a computer-readable storage medium having a computer program stored thereon, which, when executed by a processor, implements the steps in the above method embodiments.

[0171] Those skilled in the art will understand that all or part of the processes in the methods of the above embodiments can be implemented by a computer program instructing related hardware. The computer program can be stored in a non-volatile computer-readable storage medium, and when executed, it can include the processes of the embodiments of the methods described above. Any references to memory, storage, databases, or other media used in the embodiments provided by this invention can include at least one of non-volatile and volatile memory. Non-volatile memory can include read-only memory (ROM), magnetic tape, floppy disk, flash memory, or optical storage, etc. Volatile memory can include random access memory (RAM) or external cache memory. By way of illustration and not limitation, RAM can be in various forms, such as static random access memory (SRAM) or dynamic random access memory (DRAM), etc.

[0172] This invention is not limited to the structures described above and shown in the accompanying drawings, and various modifications and changes can be made without departing from its scope. The scope of this invention is limited only by the appended claims.

Claims

1. A method for safety assessment of transmission tower legs, characterized in that, The method includes: Based on the tangential frost heave force, the standard freezing depth of seasonally frozen soil, the freezing depth coefficient, and the perimeter of the pile under the influence of freezing depth, the frost pull-out force of frozen soil is calculated. A theoretical calculation model is established to calculate the pressure exerted by the ice-water mixture on the tower foot during the water-ice phase transition process. The input parameters of the theoretical calculation model include ambient temperature, physical properties of water, physical properties of the tower foot material, and liquid phase fraction characterizing the freezing rate. Using the frost pull-out force of frozen soil as the load boundary condition, and based on the theoretical calculation model, a finite element simulation model including the tower foot, pile foundation and surrounding water-ice medium is constructed. Using the finite element simulation model, the stress distribution of the tower foot under different liquid phase fractions is simulated and calculated. Based on the coupling effect of the stress distribution and the freeze-pull force, the critical liquid phase fraction corresponding to when the maximum equivalent stress of the tower foot reaches its material yield strength is determined. A secondary loss assessment is performed on the tower feet of the transmission tower based on the expansion force of the ice layer after it stabilizes, and a judgment conclusion is generated. The critical liquid phase fraction and the judgment conclusion are used as safety criteria; the actual operating parameters are predicted based on the environmental data of the target area; the predicted actual operating parameters are compared with the safety criteria, and an integrated report on the safety assessment of the tower foot is generated.

2. The method for safety assessment of transmission tower feet according to claim 1, characterized in that, The calculation of the pressure exerted by the ice-water mixture on the tower foot during the water-ice phase transition process includes: The equivalent intrinsic strain of the mixture is calculated based on the liquid phase fraction and the volume expansion coefficient when it is completely frozen. The equivalent elastic modulus of the mixture is calculated based on the liquid phase fraction, the elastic modulus of ice, and the preset exponential constant. The equivalent stiffness of the mixture is calculated using the equivalent elastic modulus of the mixture and the Poisson's ratio of ice. The equivalent stiffness of the tower feet is calculated based on the elastic modulus and Poisson's ratio of the tower foot material. The pressure exerted by the ice-water mixture on the tower feet is calculated using the equivalent intrinsic strain of the mixture, the equivalent stiffness of the mixture, and the equivalent stiffness of the tower feet, through the equivalent relationship of the series springs.

3. The method for safety assessment of transmission tower feet according to claim 2, characterized in that, The formula for calculating the pressure exerted by the ice-water mixture on the tower foot is as follows: ； In the formula, ε represents the liquid phase fraction; iw The equivalent intrinsic strain of the mixture; K represents the equivalent stiffness of the mixture. c This is the equivalent stiffness of the tower feet.

4. The method for safety assessment of transmission tower feet according to claim 1, characterized in that, The finite element simulation model includes the tower foot domain, the water-ice domain, and the air domain.

5. The method for safety assessment of transmission tower feet according to claim 4, characterized in that, The finite element simulation model is used to simulate and calculate the stress distribution of the tower foot under different liquid phase fractions. Based on the coupling effect of the stress distribution and the freeze-pull force, the critical liquid phase fraction corresponding to when the maximum equivalent stress of the tower foot reaches its material yield strength is determined, including: Material properties are assigned to the tower foot region of the finite element geometric model. Combined with the theoretical calculation model and the frost pull-out force of the frozen soil, a thermo-mechanical coupling simulation is performed on the finite element geometric model to simulate the stress distribution at the tower foot under different liquid phase fractions. Based on the simulation results of the thermo-mechanical coupling simulation of the finite element geometric model, the curve of the maximum equivalent stress at the tower foot as a function of the liquid phase fraction is plotted. The liquid phase fraction corresponding to the stress value reaching the yield strength of the tower foot material is taken as the critical liquid phase fraction.

6. The method for safety assessment of transmission tower feet according to claim 5, characterized in that, The process involves establishing a finite element geometric model encompassing the tower foot region, water-ice region, and air region, assigning material properties to the tower foot region, and combining the theoretical calculation model with the frost pull-out force of frozen soil. A thermo-mechanical coupling simulation is then performed on the finite element geometric model to simulate the stress distribution at the tower foot under different liquid phase fractions, including: An ambient temperature function is applied to the air domain, phase change material properties are defined and thermal boundary conditions are set for the water-ice domain, and the temperature field and liquid fraction field of the entire computational domain are obtained through heat transfer simulation calculation. Using the obtained liquid phase fraction field as input, the pressure distribution of the ice-water mixture on the tower foot is determined based on the theoretical calculation model, and static solutions are performed in conjunction with the comprehensive mechanical load to obtain the stress distribution at the tower foot.

7. The method for safety assessment of transmission tower feet according to claim 6, characterized in that, The comprehensive mechanical load includes a surface load applied to the top of the tower foot for equivalent force transmission to the superstructure; and a frost pull-out load applied to the pile foundation for equivalent frost pull-out force.

8. The method for safety assessment of transmission tower feet according to claim 1, characterized in that, The secondary loss assessment of the transmission tower feet based on the expansion force of the ice layer after it stabilizes includes: Based on the total thickness of the ice layer and the parameters of the heating process, calculate the ice expansion force of the upper and lower halves of the ice layer respectively; Based on the expansion forces of the upper and lower halves of the ice layer, the average expansion pressure after the ice layer stabilizes is calculated. Based on the average expansion pressure and the preset stress concentration factor, the local stress is calculated; Based on the temperature of the target area, determine the fatigue limit of the tower foot material at the corresponding temperature; The local stress is compared with the fatigue limit to achieve secondary loss determination.

9. The method for safety assessment of transmission tower feet according to claim 1, characterized in that, The critical liquid phase fraction and the determination conclusion are used as safety criteria; Predict actual operating parameters based on environmental data of the target area; By comparing the predicted actual operating parameters with the aforementioned safety criteria, a safety assessment report for the tower foot of the transmission tower is generated, including: The critical liquid phase fraction and the determination conclusion are used as safety criteria; Based on environmental data of the target area, the actual liquid phase fraction and corresponding actual stress are predicted and integrated as parameters for predicting actual working conditions. The actual liquid phase fraction in the predicted actual operating condition parameters is compared with the critical liquid phase fraction to generate a first comparison result; The actual stress in the predicted actual working condition parameters is compared with the corresponding strength standard in the judgment conclusion to generate a second comparison result; Integrate the first and second comparison results to generate a safety assessment report for the base of the transmission tower.

10. A safety assessment system for transmission tower feet, characterized in that, The system includes: The frost pull-out force calculation module is used to calculate the frost pull-out force of frozen soil based on tangential frost heave force, standard freezing depth of seasonally frozen soil, freezing depth coefficient, and the perimeter of the pile under the influence of freezing depth. The theoretical calculation model module is used to establish a theoretical calculation model for calculating the pressure exerted by the ice-water mixture on the tower foot during the water-ice phase transition process. The input parameters of the theoretical calculation model include ambient temperature, physical properties of water, physical properties of the tower foot material, and liquid phase fraction characterizing the freezing rate. The finite element simulation model building module is used to construct a finite element simulation model containing the tower foot, pile foundation and surrounding water-ice medium, based on the theoretical calculation model, with the frost pull-out force of frozen soil as the load boundary condition. The finite element simulation model analysis module is used to simulate and calculate the stress distribution of the tower foot under different liquid phase fractions using the finite element simulation model. Based on the coupling effect of the stress distribution and the freeze-pull force, the critical liquid phase fraction corresponding to when the maximum equivalent stress of the tower foot reaches its material yield strength is determined. The secondary damage calculation module is used to determine the secondary damage to the tower feet of the transmission tower based on the expansion force of the ice layer after the ice layer stabilizes, and generate a determination conclusion. The safety assessment and decision output module is used to use the critical liquid phase fraction and the judgment conclusion as safety criteria; predict actual operating parameters based on environmental data of the target area; compare the predicted actual operating parameters with the safety criteria, and integrate them to generate a safety assessment report for the tower foot of the transmission tower.

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