Tower strain simulation method and system based on thermal-mechanical coupling

Abstract

The invention provides a tower strain simulation method and system based on thermal-mechanical coupling, and the method comprises the steps: building a finite element model of a power transmission tower, dividing the power transmission tower into units, setting a plurality of working conditions, obtaining a force load corresponding to each unit of the power transmission tower under each working condition, and obtaining a thermal strain corresponding to each unit of the power transmission tower, the force load and the thermal strain corresponding to each unit of the transmission tower are taken as known quantities, the component stress and the component strain of each unit in each direction under each working condition are solved, and for the component stress of each unit in each direction under each working condition, the component stress ratio is obtained based on the ratio of the component stress to the maximum value capable of being borne by the unit; and selecting a plurality of transmission tower weak units of which the partial stress ratio exceeds the limit to install strain sensors, and judging the selection reliability of the transmission tower weak units based on the partial strain of each unit in each direction under each working condition. According to the method, the force load and the thermal strain received by the transmission tower are comprehensively considered, and the simulation effect is better.

Description

Technical Field

[0001] The present invention relates to the technical field of transmission tower simulation, and specifically relates to a tower strain simulation method and system based on thermal-mechanical coupling. Background Art

[0002] As a key infrastructure of the power grid, transmission towers undertake core functions such as electric energy transmission, regulation, and distribution. With the continuous expansion of the power grid coverage and the continuous increase in voltage levels, the complexity of system operation has increased significantly, which has put more stringent requirements on the intelligent monitoring technology of transmission lines. In the field of engineering mechanics research, the mechanical simulation analysis of transmission towers based on the finite element method provides an important theoretical basis for the intelligent monitoring system. In areas with extreme temperature differences, the change in temperature will directly cause the thermal expansion and contraction of steel structures, seriously affecting the deformation of the steel structures of transmission towers. The simulation calculation accuracy considering only mechanical properties is poor. How to improve the accuracy of mechanical simulation calculation of transmission towers has always been one of the key issues in theoretical research. Summary of the Invention

[0003] According to the deficiencies of the prior art, the purpose of the present invention is to provide a tower strain simulation method and system based on thermal-mechanical coupling, comprehensively considering the force load and thermal strain received by the transmission tower, and having a better simulation effect.

[0004] To solve the above technical problems, the technical solution adopted by the present invention is as follows:

[0005] A tower strain simulation method based on thermal-mechanical coupling, comprising:

[0006] Establish a finite element model of the transmission tower and discretize the transmission tower into elements;

[0007] Set several working conditions. Under each working condition, apply a gravity load, a wind load, and / or an ice coating load to the transmission tower, and obtain the force load corresponding to each element of the transmission tower based on the gravity load, the wind load, and / or the ice coating load. At the same time, apply a temperature load to the transmission tower and obtain the thermal strain corresponding to each element of the transmission tower based on the temperature load;

[0008] Taking the force load and thermal strain corresponding to each element of the transmission tower as known quantities, solve the normal stress and normal strain in each direction of each element under each working condition based on the elastodynamics control equation;

[0009] For the normal stress in each direction of each element under each working condition, obtain the normal stress ratio based on the ratio of the normal stress to the maximum value that the element can withstand, and select several weak elements of the transmission tower with the normal stress ratio exceeding the limit to install strain sensors;

[0010] Judge the reliability of the selection of weak elements of the transmission tower based on the normal strain in each direction of each element under each working condition.

[0011] Furthermore, the wind load includes the horizontal wind load perpendicular to the axial direction of the conductor or ground wire and / or the unit horizontal wind load of the transmission tower:

[0012] The horizontal wind load W perpendicular to the axial direction of the conductor and ground wire x is calculated by the formula:

[0013] W x = 0.625αμ sc β c (d + 2δ)l H (K h v) 2 × sin 2 θ × 10 -3

[0014] Wherein, α is the uneven coefficient of wind pressure of the conductor or ground wire; μ sc is the shape coefficient of the conductor or ground wire; β c is the wind load adjustment coefficient of the 500kV line wire acting on the transmission tower; K h is the wind speed height change coefficient at the average height of the conductor or ground wire; d is the outer diameter of the conductor or ground wire; δ is the ice coating thickness of the conductor or ground wire; l H is the horizontal span of the transmission tower; θ is the included angle between the wind direction and the axial direction of the conductor or ground wire;

[0015] The unit horizontal wind load F of the transmission tower t is calculated by the formula:

[0016]

[0017] Wherein, k is the wind shape coefficient; k z is the wind pressure height change coefficient; k T is the wind load adjustment coefficient; A c is the windward area of the steel structure of the transmission tower;

[0018] The calculation formula for the ice coating load is:

[0019]

[0020] Wherein, n is the number of members connected at the member connection point; ρ is the density of the ice coating; g is the acceleration of gravity; h z is the ice coating diameter height change coefficient; D is the diameter of the ice coating; l j is the length of a single member.

[0021] Furthermore, the calculation formula for obtaining the thermal strain corresponding to each unit of the transmission tower based on the temperature load is:

[0022] ε t = α·ΔT

[0023] In the formula, ε t is the thermal strain caused by temperature change; α is the coefficient of thermal expansion of the material, ΔT = T - T0, where T is the current temperature and T0 is the reference temperature.

[0024] Furthermore, with the force loads and thermal strains corresponding to each unit of the transmission tower as known quantities, the method for solving the component stresses and component strains in each direction of each unit under each working condition based on the control equations of elasticity is as follows:

[0025] Based on the equilibrium differential equations, the relationship between the stress matrix corresponding to the unit and the force load matrix is established as:

[0026]

[0027] In the formula: σ x , σ y , σ z are the stresses in the x, y, and z axis directions of the unit respectively, with tensile stress being positive and compressive stress being negative; τ xy , τ xz , τ yz , τ yx , τ zx , τ zy are shear stresses, and the subscript represents the direction of the normal of the acting surface and the stress direction, where τ xy = τ yx , τ xz = τ zx , τ yz = τ zy , and X, Y, Z are the force load components of the unit in the x, y, and z axis directions;

[0028] Based on the material constitutive equations, the relationship between the stress matrix corresponding to the node and the strain matrix is established as:

[0029]

[0030] In the formula: ε x , ε y , ε z , γ yz , γ xz , γ xy are strain components, and E and v represent Young's modulus of elasticity and Poisson's ratio respectively.

[0031] Furthermore, the method for obtaining the tensile stress or compressive stress in each direction of each unit is as follows:

[0032] Based on the finite element model of the transmission tower, the total strain of the unit is obtained, and the calculation formula is:

[0033] ε total = ε + εt

[0034] In the formula, ε total is the total strain; ε is the elastic strain; ε t is the thermal strain;

[0035] The mechanical stress is obtained according to the total stress, and the calculation formula is:

[0036] σ = E(ε total - α·ΔT)

[0037] In the formula, σ is the mechanical stress, and E is the Young's modulus of elasticity;

[0038] Decomposing the mechanical stress can obtain the tensile stress or compressive stress in each direction of the element.

[0039] Furthermore, various working conditions of the transmission tower include various working conditions under uniform settlement of the transmission tower and various working conditions under non-uniform settlement of the transmission tower. Multiple working conditions under uniform settlement of the transmission tower are obtained by settling one or more tower legs of the transmission tower with a first settlement value sequence of uniform increment, and multiple working conditions under non-uniform settlement of the transmission tower are obtained by settling one or more tower legs of the transmission tower with a second settlement value sequence of non-uniform increment.

[0040] Furthermore, the method for selecting several weak units of the transmission tower with excessive partial stress ratio and installing strain sensors is as follows:

[0041] A first sorting table is established by arranging in descending order of the partial stress ratio. In the first sorting table, units corresponding to the partial stress ratio exceeding the first threshold are extracted to establish a second sorting table, and units with the repetition times exceeding the second threshold in all the second sorting tables are obtained as the weak units of the transmission tower.

[0042] A tower strain simulation system based on thermo-mechanical coupling includes:

[0043] A finite element model establishment module, which is used to establish a finite element model of the transmission tower and discretize the transmission tower into elements;

[0044] A load application module, which is used to set several working conditions. Under each working condition, gravity load, wind load and / or ice coating load are applied to the transmission tower, the force load corresponding to each element of the transmission tower is obtained based on the gravity load, wind load and / or ice coating load, and at the same time, temperature load is applied to the transmission tower, and the thermal strain corresponding to each element of the transmission tower is obtained based on the temperature load;

[0045] An acquisition module, which is used to take the force load and thermal strain corresponding to each element of the transmission tower as known quantities, and solve the partial stress and partial strain in each direction of each element under each working condition based on the control equation of elasticity;

[0046] A strain sensor installation module is used to obtain the partial stress ratio for each unit in each direction under each working condition based on the ratio of the partial stress to the maximum value that the unit can withstand, and select several weak units of the transmission tower with the partial stress ratio exceeding the limit to install strain sensors.

[0047] A verification module is used to judge the reliability of the selection of weak units of the transmission tower based on the partial strain in each direction of each unit under each working condition.

[0048] An electronic device includes a memory, a processor, and a computer program stored on the memory and executable on the processor. When the processor executes the program, it implements the above-mentioned tower strain simulation method based on thermo-mechanical coupling.

[0049] A non-transitory computer-readable storage medium stores a computer program, and when the computer program is executed by a processor, it implements the above-mentioned tower strain simulation method based on thermo-mechanical coupling.

[0050] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0051] By simultaneously considering the effects of gravity load, wind load and / or ice coating load and temperature load, the present invention obtains the force load and thermal strain corresponding to each unit of the transmission tower, and can more accurately simulate the real behavior of the transmission tower in a complex environment. Based on the control equations of elasticity, the partial stress and partial strain in each direction of each unit under each working condition are solved. For the partial stress in each direction of each unit under each working condition, the partial stress ratio is obtained based on the ratio of the partial stress to the maximum value that the unit can withstand, and the units with the partial stress ratio exceeding the limit a certain number of times are selected as the weak units of the transmission tower. Several installation positions are selected from the weak units of the transmission tower to install strain sensors, which can identify potential risks, take measures in advance, and improve the safety of the transmission tower. The present invention can simulate the strain conditions under different environmental conditions and provide a reference for the performance of the transmission tower under various climate and geographical conditions. BRIEF DESCRIPTION OF THE DRAWINGS

[0052] The drawings described herein are used to provide a further understanding of the present invention and form a part of this application. The schematic embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation of the present invention. In the drawings:

[0053] Figure 1 is a flowchart of a tower strain simulation method based on thermo-mechanical coupling of the present invention;

[0054] Figure 2 is a schematic diagram of a finite element model of a transmission tower of the present invention;

[0055] Figure 3This is the stress distribution nephogram of the tower-line unit of the present invention;

[0056] Figure 4 This is the comparison result diagram of the strain distribution of the transmission tower unit obtained by the mechanical simulation and thermo-mechanical coupling simulation methods of the present invention;

[0057] Figure 5 This is the axial stress nephogram of the steel structure of the transmission tower of the present invention;

[0058] Figure 6 This is the curve of the stress of the key steel structure of the tower leg changing with the settlement amount of the present invention;

[0059] Figure 7 This is the schematic diagram of the strain sensor layout points of the transmission tower of the present invention;

[0060] Figure 8 This is the comparison diagram of the strain data between the simulation value and the measured value of the present invention;

[0061] Figure 9 This is the schematic diagram of a tower strain simulation system based on thermo-mechanical coupling of the present invention. Detailed implementation manners

[0062] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention.

[0063] In the description of the present invention, it should be understood that the orientation or positional relationship indicated by the terms "center", "longitudinal", "transverse", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc. is based on the orientation or positional relationship shown in the accompanying drawings, and is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the system or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the present invention. In addition, the terms "first", "second", etc. are only used for descriptive purposes, and cannot be understood as indicating or implying relative importance or implicitly specifying the quantity of the indicated technical features. Thus, the features defined with "first", "second", etc. may explicitly or implicitly include one or more of such features. In the description of the present invention, unless otherwise stated, the meaning of "a plurality" is two or more.

[0064] Embodiment 1

[0065] Embodiment 1 provides a tower strain simulation method based on thermo-mechanical coupling, including the following steps:

[0066] Step S1: Establish a finite element model of the transmission tower and discretize the transmission tower into units;

[0067] Step S2: Set several working conditions. Under each working condition, apply gravity load, wind load, and / or ice coating load to the transmission tower. Based on the gravity load, wind load, and / or ice coating load, obtain the force loads corresponding to each unit of the transmission tower. At the same time, apply temperature load to the transmission tower and obtain the thermal strain corresponding to each unit of the transmission tower based on the temperature load.

[0068] Step S3: Taking the force loads and thermal strains corresponding to each unit of the transmission tower as known quantities, solve the normal stresses and normal strains in each direction of each unit under each working condition based on the control equations of elasticity.

[0069] Step S4: For the normal stresses in each direction of each unit under each working condition, obtain the normal stress ratio based on the ratio of the normal stress to the maximum value that the unit can withstand. Select the units whose normal stress ratios exceed the limit a certain number of times as the weak units of the transmission tower, and select several installation positions among the weak units of the transmission tower to install strain sensors.

[0070] Step S5: Judge the reliability of the selection of the weak units of the transmission tower based on the normal strains in each direction of each unit under each working condition.

[0071] During the actual monitoring of the transmission tower, the change in temperature in extremely temperature-difference areas will directly cause the thermal expansion and contraction of the steel structure. In the case of the thermal expansion and contraction of the transmission tower, the thermal strain may be superimposed on the mechanical load, resulting in local stress exceeding the material strength. The existing technology ignores the thermal stress, which may lead to incorrect judgments on the safety of the transmission tower. A tower strain simulation method based on thermal-mechanical coupling provided in this embodiment not only considers applying gravity load, wind load, and / or ice coating load to the transmission tower, but also considers applying temperature load to the transmission tower. Through thermal-mechanical coupling simulation, the stress state of the transmission tower under actual working conditions can be more comprehensively simulated, and then the maximum value of the normal stress of each unit of the transmission tower under each working condition can be obtained. Select the units with the maximum normal stress exceeding the limit as the weak units of the transmission tower, and select several installation positions among the weak units of the transmission tower to install strain sensors, which can more accurately monitor the transmission tower and prevent the transmission tower from being damaged.

[0072] In an example, in step S1 when establishing the finite element model of the transmission tower, it is necessary to define the steel structure material properties of the transmission tower. The definition of material properties refers to setting a set of properties of a material in the simulation to simulate the actual material. For example, for steel, there are various specifications of steel such as Q235, Q345, and Q420. It is necessary to set their material properties respectively, including their density, elastic modulus, Poisson's ratio, yield strength, stress-strain curve, etc.

[0073] In step S2 of this embodiment, mechanical loads are applied to the units of the transmission tower by gravity load, wind load and / or ice coating load. Conductors and ground wires are also connected to the transmission tower body. The transmission tower body is fixedly connected by several steel structures. In addition to the action of the inherent load (i.e., its own gravity load), these components also bear the action of additional loads (ice coating load, wind load). When conducting simulation research, the loads must be accurately applied to ensure the accuracy and effectiveness of the calculation results.

[0074] The wind load includes the horizontal wind load perpendicular to the axial direction of the conductor or ground wire and / or the unit horizontal wind load of the transmission tower body:

[0075] The horizontal wind load W x perpendicular to the axial direction of the conductor or ground wire is calculated by the formula:

[0076] W x = 0.625αμ sc β c (d + 2δ)l H (K h v) 2 × sin 2 θ × 10 -3

[0077] In the formula, α is the uneven coefficient of wind pressure of the conductor or ground wire; μ sc is the shape coefficient of the conductor or ground wire; β c is the wind load adjustment coefficient of the 500kV line wire acting on the transmission tower body; K h is the wind speed height change coefficient at the average height of the conductor or ground wire; d is the outer diameter of the conductor or ground wire; δ is the ice coating thickness of the conductor or ground wire; l H is the horizontal span of the transmission tower body; θ is the angle between the wind direction and the axial direction of the conductor or ground wire;

[0078] The unit horizontal wind load F t of the transmission tower body is calculated by the formula:

[0079]

[0080] In the formula, k is the wind shape coefficient; k z is the wind pressure height change coefficient; k T is the wind load adjustment coefficient; A c is the windward area of the steel structure in the transmission tower body;

[0081] The calculation formula of the ice coating load is:

[0082]

[0083] Wherein, n is the number of components connected at the component connection point; ρ is the density of the ice coating; g is the acceleration due to gravity; h z is the coefficient of variation of the ice coating diameter with height; D is the diameter of the ice coating; l j is the length of a single component.

[0084] In one example, temperatures are set for all units of the transmission tower. Therefore, based on the above mechanical theory of the transmission tower, the influence of temperature on the deformation of the transmission tower is considered by adding temperature loads. The deformation caused by temperature is mainly achieved through the thermal expansion effect. The coefficient of thermal expansion of steel determines how physical quantities such as the length and volume of the material change when the temperature changes. First, define the coefficient of thermal expansion of the material to ensure that thermal stress and thermal deformation are generated under temperature changes; set the reference temperature as the initial temperature of zero thermal stress; select the units of the transmission tower and set their temperatures to simulate the actual temperature distribution; perform static or thermal stress analysis to solve the thermal stress and thermal deformation caused by temperature changes.

[0085] According to the theory of thermal expansion, the coefficient of thermal expansion of steel is known, and temperature changes will cause deformation of the material. Simply put, the coefficient of thermal expansion reflects the degree of expansion or contraction of the material when the temperature changes. When the temperature changes, the deformation of the material can be described by the following formula:

[0086] ε t = α·ΔT

[0087] Wherein, ε t is the thermal strain caused by temperature change; α is the coefficient of thermal expansion of the material, ΔT = T - T0, T is the current temperature, and T0 is the reference temperature.

[0088] Based on the finite element model, the total strain of each unit is obtained, and the calculation formula is:

[0089] ε total = ε + ε t

[0090] Wherein, ε total is the total strain; ε is the elastic strain; ε t is the thermal strain.

[0091] σ = E(ε total - α·ΔT)

[0092] Wherein, σ is the mechanical stress and E is the Young's modulus of elasticity.

[0093] Decomposing the mechanical stress can obtain the tensile stress or compressive stress in each direction of the unit. Furthermore, with the force loads and thermal strains corresponding to each unit of the transmission tower as known quantities, the component stresses and component strains in each direction of each unit under each working condition are solved based on the control equations of elasticity.

[0094] In one example, in the finite element-based mechanical simulation calculation, it is assumed that the four points at the bottom of the transmission tower body are firmly connected to the foundation, and the displacements of the connection points between the legs of the transmission tower body and the foundation do not change during line operation. It is necessary to fix all translational and rotational degrees of freedom in three coordinate directions.

[0095] In one example, for a specific transmission tower, the finite element method is used to establish a finite element model of the transmission tower, and the material properties are defined. With the force loads and thermal strains corresponding to each unit of the transmission tower as known quantities, the unknown variables such as the displacements, strains, and stresses of each unit are obtained, and the reliability of the transmission tower is judged in turn.

[0096] Specifically, with the force loads and thermal strains corresponding to each unit of the transmission tower as known quantities, the method for solving the component stresses and component strains of each unit in each direction under each working condition based on the elastic mechanics control equations is as follows:

[0097] Based on the equilibrium differential equations, the relationship between the stress matrix corresponding to the unit and the force load matrix is established as:

[0098]

[0099] In the formula: σ x , σ y , σ z are the stresses in the x, y, and z axis directions of the node respectively. Tensile stress is positive and compressive stress is negative; τ xy , τ xz , τ yz , τ yx , τ zx , τ zy are shear stresses, and the subscript indicates the direction of the normal of the acting surface and the stress direction. For example, τ xy is the shear stress acting on the surface perpendicular to the x axis and along the y direction, where τ xy = τ yx , τ xz = τ zx , τ yz = τ zy ; X, Y, and Z are the force load components of the unit in the x, y, and z axis directions.

[0100] Based on the material constitutive equations, the relationship between the stress matrix corresponding to the node and the strain matrix is established as:

[0101]

[0102] In the formula: ε x , ε y , ε z , γ yz , γ xz , γxy are strain components, representing the relationship between the displacement and strain of any point inside an object after it is deformed by force. E and v represent Young's modulus of elasticity and Poisson's ratio respectively, and satisfy Hooke's law.

[0103] Input the force loads, thermal strains corresponding to each node, and the displacements of each node into the relationships between the stress matrix and the gravity matrix, the strain matrix and the displacement matrix, and the stress matrix and the strain matrix, to obtain the component stresses in each direction of each node.

[0104] Various working conditions of the transmission tower include various conditions under uniform settlement of the transmission tower body and various conditions under non-uniform settlement of the transmission tower body. For the uniform settlement of the transmission tower, various conditions are obtained by settling 1 or more tower legs of the transmission tower body with a first settlement value sequence of uniform increments. For the non-uniform settlement of the transmission tower, various conditions are obtained by settling 1 or more tower legs of the transmission tower body with a second settlement value sequence of non-uniform increments.

[0105] In one example, the method for selecting the unit with the maximum component stress exceeding the limit as the weak point of the transmission tower is as follows:

[0106] Establish a first sorting table in descending order of the component stress ratio. Extract the units corresponding to the component stress ratio exceeding the first threshold in the first sorting table to establish a second sorting table. Obtain the units with the repetition times exceeding the second threshold in all the second sorting tables as the weak units of the transmission tower.

[0107] In one example, the strain sensor is a fiber Bragg grating sensor, and this embodiment does not limit this.

[0108] Next, a specific embodiment is used to describe in detail a tower strain simulation method based on thermal-mechanical coupling provided by this embodiment.

[0109] The object of this modeling is a certain 500 kV transmission tower, with a height of 41 m for the transmission tower and a total height of 43.4 m. The monitoring system installed on this transmission tower mainly includes: a solar and battery power supply module; a strain measurement and acquisition module; a remote host monitoring and data transmission module; a rainproof box and fixture fixing, etc. The modeling results Figure 2 are shown. Apply tower leg constraints, left-end conductor constraints, and right-end conductor constraints to the transmission tower.

[0110] Execute the above steps S1 to S5. Set the wind speed to 5 m / s, the ice coating thickness to 10 mm, and the steel structure temperature to -2 °C in the thermal-mechanical coupling simulation model, and obtain as Figure 3 shown in the stress distribution nephogram of the tower-line unit, Figure 4The comparison results of the strain distribution of the transmission tower unit obtained by the mechanical simulation and the thermo-mechanical coupling simulation are shown. The simulation data indicate that: the strain fields obtained by the two methods have significant spatial consistency, and the strain amplitude of the thermo-mechanical coupling model is smaller than that of the mechanical simulation. The reason is that the reference temperature is 20°C and the temperature of the steel structure is -2°C. At this time, the steel structure generates shrinkage thermal strain, and this negative thermal strain forms a superposition effect with the mechanical strain, reducing the total strain value, which further proves the feasibility of a tower strain simulation method based on thermo-mechanical coupling provided by this embodiment.

[0111] When simulating the uneven settlement of the tower foundation through simulation, it is assumed that tower foundation A among the 4 tower foundations does not settle, and the settlement amounts of tower foundations B, C, and D are in the ratio of 2:5:10. The settlement amount of tower foundation D starts from 10 mm and gradually increases, with an increment of 10 mm. For the convenience of description, the settlement amounts in this specific embodiment are all the settlement displacements of the tower foundation with the largest settlement, that is, tower foundation D. Under the condition of uneven settlement, when the settlement amount reaches 100 mm, the axial stress nephogram of the steel structure of the transmission tower is as Figure 5 shown.

[0112] Key steel structure No. 1636 unit of leg A, No. 789 unit of leg B, No. 724 unit of leg C, and No. 1571 unit of leg D on the tower legs connected to the first cross-section are respectively taken, and the variation curves of the unit axial stress with the settlement amount are as Figure 6 shown.

[0113] Under the condition of uneven settlement of the tower foundation, legs A and C bear relatively large axial compressive stresses, and legs B and D bear relatively large axial tensile stresses, indicating that legs A and C are squeezed inward, and legs B and D are stretched outward, and the diagonal root opening of the tower foundation will move and deform. In this case, the bottom cross-section of the tower body and the upper cross-section of the tower body will be damaged first, and the bottom diagonal members and main members of the tower body connected to them will also be damaged accordingly. When the settlement amount reaches 54 mm, the main member of the tower leg that has not settled will first reach the yield stress value.

[0114] Weak point positioning and measuring point arrangement of the transmission tower: Through the above finite element calculations, it can be found that although the ratio of the partial stresses at different positions of the transmission tower under different working conditions is not the same, in some working conditions, the positions where the units with relatively large partial stress ratios appear are repetitive. For example, under the condition of uniform ice coating, the unit number of the peak stress ratio is always unit No. 1266, and under the condition of non-uniform ice coating, unit No. 1266 and unit No. 1208 also exceed the stress ratio limit many times. It shows that under different working conditions, compared with the steel structures at other positions, the steel structures that exceed the stress ratio limit many times are more likely to yield, and these steel structures belong to the weak points of the transmission tower.

[0115] According to the calculation results under various working conditions, arrange them in descending order of the stress ratio of the steel structure, extract the 100 units with the largest partial stress ratio, count the units with the most repeated partial stress ratios and prone to exceeding the limit, calculate their occurrence frequencies, and select the units with a frequency exceeding 50%. Table 1 below shows the corresponding transmission tower structure units ranked in the top 35 in terms of frequency.

[0116] Table 1 Occurrence frequencies of weak units

[0117]

[0118] Under the foundation settlement working condition, the main members of the tower legs will bear large tensile and compressive stresses. Therefore, a strain sensor is arranged on the tower legs to monitor the deformation of the main members of the tower legs. Considering that the transmission tower of the transmission line is a space hyperstatic structure, the damage of a certain steel structure does not cause the failure of the overall structure, and the influence of the failure degree of the auxiliary materials or diagonal auxiliary materials on the stability of the transmission tower is less than the influence of the instability of the main materials on the stability of the transmission tower. Therefore, the stress and strain of the main material steel structure should be monitored keyly. There are 4 channels in total for the data demodulator in the monitoring system, and each channel contains 4 strain sensors. 16 monitoring points can be selected for strain data monitoring, and the structural units ranked in the top 16 in terms of frequency are selected as the monitoring points correspondingly. The layout plan is shown in Table 2 below:

[0119] Table 2 Sensor layout plan

[0120]

[0121] The real-time monitoring data of the steel structure strain of the transmission tower is measured by the strain on-line monitoring system. This monitoring system can perceive the mechanical state of the transmission tower structure in real time through distributed optical fiber sensors. There are 16 key stress monitoring points in the transmission tower structure, and their position distributions are as follows Figure 7 shown. Strain sensors are installed at the monitoring points to measure the steel structure strain values, and they are transmitted to the on-line monitoring system through the data acquisition system.

[0122] When comparing and analyzing the simulated strain data and the measured strain data, it is very important to consider the zero adjustment process of the measurement system. In the actual measurement process, the strain measurement system will perform zero adjustment and calibration to eliminate the initial errors caused by factors such as the deviation of the equipment itself and environmental impacts. The measured strain data after zero adjustment represents the strain value relative to the initial zero point, that is, the strain value after zero adjustment and correction. Therefore, the corresponding relative working condition processing is also required for the simulation working conditions.

[0123] Table 3 Meteorological conditions during the monitoring period

[0124]

[0125] Add the wind load and temperature during the zeroing time to the model simulation to obtain the simulated steel structure strain values at each measuring point. Use this strain simulation data as the zeroing reference for the simulation values. To obtain the relative values of the strain values for other working conditions, subtract the simulated results from the reference value. Finally, compare and analyze the simulated strain relative values with the measured data to verify the accuracy of the simulation results. Compare and analyze the simulation results without considering temperature, the simulation results considering temperature, and the simulation results with separately set upper and lower temperatures of the steel structure to obtain the following data. Under the weather conditions on February 13, 2024, the measurement system included 2 temperature sensors, located in the upper and lower parts of the transmission tower structure respectively. The temperatures measured by the temperature sensors under specific working conditions were 5.03 °C and 4.67 °C, and the upper and lower parts of the overall steel structure of the transmission tower were set respectively.

[0126] Table 4 Comparison of 2 simulation results

[0127]

[0128] From the analysis of the above results, it can be seen that the strain values corresponding to the simulation results without considering temperature are generally larger. The reason is that when not considering temperature, the temperature corresponding to the set steel structure material property parameters is the standard 20 °C, while the temperature of the steel structure under this working condition is about 5 °C. The material parameters of the steel structure differ greatly from the actual properties, and the error between its simulation value and the measured value reaches up to 38.64 με, and the average relative error is 51.91%; under the condition of considering temperature, the error between the simulation value and the measured value when setting the overall temperature of the steel structure is within the range of 16.55 με, and its average relative error is 15.03%; the error between the simulation value and the measured value when setting the upper and lower temperatures of the steel structure is within the range of 16.62 με, and its average relative error is 15.24%; the overall error situation between the two is almost the same. The reason is that when setting the upper and lower temperatures of the steel structure, they are 5.03 °C and 4.67 °C, and the temperature difference is only 0.36 °C. Therefore, the change in the simulation results is very small. After considering the influence of temperature, the mechanical simulation accuracy of the transmission tower is improved by 36%. Figure 8 It can be seen that the method proposed in the present invention can more accurately perform mechanical simulation on the transmission tower structure, further proving the accuracy of the thermal-mechanical coupling method.

[0129] Embodiment 2

[0130] Embodiment 2 provides a tower strain simulation system based on thermal-mechanical coupling, as Figure 9 shown, including:

[0131] A finite element model establishment module for establishing a finite element model of the transmission tower and discretizing the transmission tower into elements;

[0132] A load application module is used to set a number of working conditions. Under each working condition, a gravity load, a wind load, and / or an ice coating load is applied to the transmission tower. Based on the gravity load, the wind load, and / or the ice coating load, the force loads corresponding to each unit of the transmission tower are obtained. At the same time, a temperature load is applied to the transmission tower, and based on the temperature load, the thermal strains corresponding to each unit of the transmission tower are obtained.

[0133] An acquisition module is used to take the force loads and thermal strains corresponding to each unit of the transmission tower as known quantities, and solve the normal stresses and normal strains in each direction of each unit under each working condition based on the control equations of elasticity.

[0134] A strain sensor installation module is used to, for the normal stresses in each direction of each unit under each working condition, obtain the normal stress ratios based on the ratios of the normal stresses to the maximum values that the units can withstand, and select several weak units of the transmission tower with excessive normal stress ratios to install strain sensors.

[0135] A verification module is used to judge the reliability of the selection of the weak units of the transmission tower based on the normal strains in each direction of each unit under each working condition.

[0136] Embodiment 3

[0137] Embodiment 3 provides an electronic device, including a memory, a processor, and a computer program stored on the memory and executable on the processor. When the processor executes the program, the above-mentioned tower strain simulation method based on thermo-mechanical coupling is implemented.

[0138] Embodiment 4

[0139] Embodiment 4 provides a non-transitory computer-readable storage medium, on which a computer program is stored. When the computer program is executed by a processor, the above-mentioned tower strain simulation method based on thermo-mechanical coupling is implemented.

[0140] The memory in the embodiments of the present invention is used to store various types of data to support the operation of the electronic device. Examples of these data include: any computer program for operating on the electronic device.

[0141] The method for simulating the strain of a pole tower based on thermo-mechanical coupling disclosed in the embodiments of the present invention can be applied to a processor or implemented by a processor. The processor may be an integrated circuit chip with the ability to process signals. In the implementation process, the steps of the method for simulating the strain of a pole tower based on thermo-mechanical coupling can be completed by the integrated logic circuit of the hardware in the processor or the instructions in the form of software. The above-mentioned processor may be a general-purpose processor, a digital signal processor (DSP, Digital Signal Processor), or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components, etc. The processor can implement or execute the various methods, steps, and logic block diagrams disclosed in the embodiments of the present invention. The general-purpose processor may be a microprocessor or any conventional processor, etc. Combining the steps of the method disclosed in the embodiments of the present invention, it can be directly embodied as being executed and completed by a hardware decoding processor, or executed and completed by a combination of the hardware and software modules in the decoding processor. The software module may be located in a storage medium, and this storage medium is located in the memory. The processor reads the information in the memory and combines its hardware to complete the steps of the method for simulating the strain of a pole tower based on thermo-mechanical coupling provided in the embodiments of the present invention.

[0142] In an exemplary embodiment, the electronic device can be implemented by one or more application-specific integrated circuits (ASICs, Application Specific Integrated Circuits), DSPs, programmable logic devices (PLDs, Programmable Logic Devices), complex programmable logic devices (CPLDs, Complex Programmable Logic Devices), FPGAs, general-purpose processors, controllers, microcontroller units (MCUs, Micro Controller Units), microprocessors (Microprocessors), or other electronic components for performing the foregoing method.

[0143] It can be understood that the memory can be a volatile memory or a non-volatile memory, or can include both volatile and non-volatile memories. Among them, the non-volatile memory can be a read-only memory (ROM, Read Only Memory), a programmable read-only memory (PROM, Programmable Read-Only Memory), an erasable programmable read-only memory (EPROM, Erasable Programmable Read-Only Memory), an electrically erasable programmable read-only memory (EEPROM, Electrically Erasable Programmable Read-Only Memory), a ferromagnetic random access memory (FRAM, ferromagnetic random access memory), a flash memory (Flash Memory), a magnetic surface memory, an optical disc, or a compact disc read-only memory (CD-ROM, Compact Disc Read-Only Memory); the magnetic surface memory can be a disk memory or a tape memory. The volatile memory can be a random access memory (RAM, RandomAccessMemory), which is used as an external cache. By way of example but not limitation, many forms of RAM are available, such as a static random access memory (SRAM, Static Random Access Memory), a synchronous static random access memory (SSRAM, Synchronous Static Random Access Memory), a dynamic random access memory (DRAM, Dynamic Random Access Memory), a synchronous dynamic random access memory (SDRAM, SynchronousDynamic Random Access Memory), a double data rate synchronous dynamic random access memory (DDRSDRAM, Double Data Rate Synchronous Dynamic Random Access Memory), an enhanced synchronous dynamic random access memory (ESDRAM, Enhanced Synchronous Dynamic Random AccessMemory), a sync link dynamic random access memory (SLDRAM, SyncLink Dynamic Random AccessMemory), a direct rambus random access memory (DRRAM, Direct Rambus Random Access Memory). The memory described in the embodiments of the present invention is intended to include but not be limited to these and any other suitable types of memory.

[0144] The above embodiments are merely illustrative examples of the technical solution of the present invention. The method involved in the present invention is not limited to the content described in the above embodiments, but is subject to the scope defined by the claims. Any modification, supplement, or equivalent replacement made by those skilled in the art to which the present invention pertains on the basis of this embodiment is within the scope protected by the claims of the present invention.

Claims

1. A tower strain simulation method based on thermo-mechanical coupling, characterized in that, Including: Establish a finite element model of the transmission tower and discretize the transmission tower into elements; Set several working conditions. Under each working condition, apply gravity load, wind load and / or ice coating load to the transmission tower, obtain the force load corresponding to each element of the transmission tower based on the gravity load, wind load and / or ice coating load, and at the same time apply temperature load to the transmission tower, and obtain the thermal strain corresponding to each element of the transmission tower based on the temperature load; Taking the force load and thermal strain corresponding to each element of the transmission tower as known quantities, solve the normal stress and normal strain in each direction of each element under each working condition based on the control equations of elasticity; For the normal stress in each direction of each element under each working condition, obtain the normal stress ratio based on the ratio of the normal stress to the maximum value that the element can withstand, and select several weak elements of the transmission tower with the normal stress ratio exceeding the limit to install strain sensors; Judge the reliability of the selection of weak elements of the transmission tower based on the normal strain in each direction of each element under each working condition.

2. The method for simulating the strain of a pole tower based on thermo-mechanical coupling according to claim 1, wherein The wind load includes the horizontal wind load perpendicular to the axial direction of the conductor or ground wire and / or the unit horizontal wind load of the transmission tower: The horizontal wind load W perpendicular to the axial direction of the conductor and ground wire x The calculation formula is as follows: W x = 0.625αμ sc β c (d + 2δ)l H (K h v) 2 × sin 2 θ × 10 -3 where α is the uneven coefficient of wind pressure of conductors or ground wires; μ sc is the shape coefficient of conductors or ground wires; β c is the wind load adjustment coefficient of 500 kV line wires acting on transmission towers; K h is the wind speed height change coefficient at the average height of conductors or ground wires; d is the outer diameter of conductors or ground wires; δ is the ice coating thickness of conductors or ground wires; l H is the horizontal span of transmission towers; θ is the angle between the wind direction and the axis of conductors or ground wires; Unit horizontal wind load F of transmission tower t The calculation formula is as follows: In the formula, k is the wind load shape coefficient; k z is the wind pressure height change coefficient; k T is the wind load adjustment coefficient; A c is the windward area of the steel structure of the transmission tower; The calculation formula for the ice coating load is: Wherein, n is the number of components connected at the component connection point; ρ is the density of the ice coating; g is the acceleration due to gravity; h z is the coefficient of variation of the ice coating diameter with height; D is the diameter of the ice coating; l j is the length of a single component.

3. The method for simulating the strain of a pole tower based on thermo-mechanical coupling according to claim 1, wherein The calculation formula for obtaining the thermal strain corresponding to each element of the transmission tower based on the temperature load is: ε t = α·ΔT where ε t is the thermal strain caused by temperature change; α is the thermal expansion coefficient of the material, ΔT = T - T0, T is the current temperature, and T0 is the reference temperature.

4. The method for simulating the strain of a pole tower based on thermo-mechanical coupling according to claim 1, wherein Taking the force load and thermal strain corresponding to each element of the transmission tower as known quantities, the method for solving the normal stress and normal strain in each direction of each element under each working condition based on the control equations of elasticity is: Based on the equilibrium differential equations, establish the relationship between the stress matrix corresponding to the element and the force load matrix: where: σ x , σ y , σ z are the stresses in the x, y, and z-axis directions of the element, respectively. Tensile stress is positive and compressive stress is negative; τ xy , τ xz , τ yz , τ yx , τ zx , τ zy are shear stresses. The subscript represents the direction of the normal to the acting surface and the stress direction, where τ xy = τ yx , τ xz = τ zx , τ yz = τ zy , and X, Y, and Z are the force load components of the element in the x, y, and z-axis directions; Based on the material constitutive equations, establish the relationship between the stress matrix corresponding to the node and the strain matrix: where: ε x , ε y , ε z , γ yz , γ xz , γ xy are strain components, and E and v represent Young's modulus of elasticity and Poisson's ratio respectively.

5. The method for simulating the strain of a pole tower based on thermo-mechanical coupling according to claim 1, wherein The method for obtaining the tensile stress or compressive stress in each direction of each element is: Based on the finite element model of the transmission tower, obtain the total strain of the element, and the calculation formula is: ε total = ε + ε t where ε total is the total strain; ε is the elastic strain; ε t is the thermal strain; Obtain the mechanical stress according to the total stress, and the calculation formula is: σ = E(ε total - α·ΔT) In the formula, σ is the mechanical stress and E is the Young's modulus of elasticity; Decompose the mechanical stress to obtain the tensile stress or compressive stress in each direction of the element.

6. The tower strain simulation method based on thermo-mechanical coupling according to claim 1, characterized in that: Various working conditions of the transmission tower include various working conditions under uniform settlement of the transmission tower and various working conditions under non-uniform settlement of the transmission tower. Obtain various working conditions under uniform settlement of the transmission tower by settling 1 or more tower legs of the transmission tower with a first settlement value sequence of uniform increment, and obtain various working conditions under non-uniform settlement of the transmission tower by settling 1 or more tower legs of the transmission tower with a second settlement value sequence of non-uniform increment.

7. The method for simulating the strain of a pole tower based on thermal-mechanical coupling according to claim 1, characterized in that The method for selecting several weak elements of the transmission tower with the normal stress ratio exceeding the limit to install strain sensors is: Establish a first sorting table in descending order of the normal stress ratio, extract the elements corresponding to the normal stress ratio exceeding the first threshold in the first sorting table to establish a second sorting table, and obtain the elements with the repetition times exceeding the second threshold in all the second sorting tables as the weak elements of the transmission tower.

8. A tower strain simulation system based on thermo-mechanical coupling, characterized in that, Including: A finite element model establishment module for establishing a finite element model of the transmission tower and discretizing the transmission tower into elements; A load application module is used to set a number of working conditions. Under each working condition, a gravity load, a wind load, and / or an ice coating load is applied to the transmission tower. Based on the gravity load, the wind load, and / or the ice coating load, the force loads corresponding to each unit of the transmission tower are obtained. At the same time, a temperature load is applied to the transmission tower, and based on the temperature load, the thermal strains corresponding to each unit of the transmission tower are obtained. An acquisition module is used to take the force loads and thermal strains corresponding to each unit of the transmission tower as known quantities, and solve the normal stresses and normal strains in each direction of each unit under each working condition based on the control equations of elasticity. A strain sensor installation module is used to, for the normal stresses in each direction of each unit under each working condition, obtain the normal stress ratios based on the ratios of the normal stresses to the maximum values that the units can withstand, and select several weak units of the transmission tower with excessive normal stress ratios to install strain sensors. A verification module is used to judge the reliability of the selection of the weak units of the transmission tower based on the normal strains in each direction of each unit under each working condition.

9. An electronic device, comprising a memory, a processor, and a computer program stored on the memory and executable on the processor, characterized in that, When the processor executes the program, it implements the tower strain simulation method based on thermo-mechanical coupling according to any one of claims 1 to 7.

10. A non-transitory computer-readable storage medium having a computer program stored thereon, characterized in that, When the computer program is executed by the processor, it implements the tower strain simulation method based on thermo-mechanical coupling according to any one of claims 1 to 7.

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