A method for identifying vulnerable components of a steel tube member of a power transmission tower subjected to vortex-induced vibration

Abstract

The application discloses a kind of power transmission tower steel pipe component vortex-induced vibration vulnerable component identification method.The method is first based on double Logistic model to construct the generalized characteristic function of smooth transition describing vortex-induced vibration lock area;Considering the actual structure of power transmission tower node, the inherent frequency calculation model of steel pipe component reflecting semi-rigid constraint characteristics is established by identifying rotational stiffness.On this basis, the independence principle is used to decompose the flow velocity, and the power law function of atmospheric boundary layer wind profile is combined to establish the joint probability density function including wind speed, wind direction and height variation.Finally, the integral of the nonlinear function of vortex vibration occurrence under specific inflow condition and the joint probability density of wind field is calculated, and the vortex-induced vibration occurrence probability of steel pipe component is quantified.The application can comprehensively consider the influence of structure attribute, geometric size, actual boundary condition and actual inflow wind field, realize the rapid screening and accurate identification of vortex-induced vibration risk of steel pipe component of whole tower of power transmission tower.

Description

Technical Field

[0001] This invention relates to the field of disaster prevention and mitigation technology, specifically to a method for identifying vulnerable components of transmission tower steel pipe structures that are susceptible to vortex-induced vibration, taking into account the characteristics of actual wind fields. Background Technology

[0002] Steel pipe transmission towers have been widely used in ultra-high voltage (UHV) power transmission projects due to their excellent economic and technical advantages. However, under low wind speeds, if the wind speed approaches the natural frequency of the steel pipe components, the risk of vortex-induced vibration increases significantly, potentially leading to structural fatigue failure. Therefore, effectively identifying vulnerable components in steel pipe transmission towers prone to vortex-induced vibration to prompt the implementation of necessary control measures is crucial.

[0003] Currently, industry standards and existing research still have the following shortcomings in identifying steel pipe components prone to vortex-induced vibration: (1) Insufficient consideration of the actual wind field environment of different steel pipe components: Existing identification methods are mostly based on deterministic wind speed analysis (e.g., only checking whether the design wind speed is in the locked zone). However, the wind field of the atmospheric boundary layer has obvious randomness, and the wind speed and wind direction change continuously over time. In addition, as a tall structure, the incoming wind field experienced by the steel pipe components at different heights of the transmission tower also varies greatly.

[0004] (2) Errors caused by simplification of boundary conditions: The current technical specification for the structural design of overhead transmission line towers (DL / T5486-2020) usually simplifies the two ends of steel pipe members to ideal "hinged" or "fixed" models to calculate the natural frequency. However, the constraint stiffness of actual transmission tower nodes is between the two, belonging to semi-rigid connections. Ignoring this will lead to deviations in the calculation of natural frequencies, which in turn will cause the prediction of the vortex-induced vibration locking wind speed range to fail.

[0005] (3) Lack of evaluation index for the probability of vortex-induced vibration: Traditional vortex vibration determination usually adopts a "0 / 1" binary step function (i.e., 1 in the locked area and 0 outside the area), which ignores the transition effect in the vortex vibration initiation and dissipation process, resulting in unstable probability prediction results of vortex-induced vibration. Summary of the Invention

[0006] To address the above technical problems, this invention provides a method for identifying vulnerable components of transmission tower steel pipe structures that are susceptible to vortex-induced vibration, taking into account both actual wind field characteristics and semi-rigid node constraints. The main technical solutions adopted are as follows: A method for identifying vulnerable components of transmission tower steel pipe structures subjected to vortex-induced vibration, the key of which includes the following steps: Step 1: Obtain the historical wind speed at the location of the transmission tower. with wind angle Data, establish a specified height from the base of the tower Initial distribution function of wind speed and wind direction at location Based on the height of the steel pipe component from the bottom of the tower And landform type, correct the initial distribution function of wind speed-wind direction The wind speed-wind direction joint distribution function model is obtained. ; Step 2: Establish a dynamic model of the steel pipe member considering semi-rigid end constraints; since the end constraints of the steel pipe member are usually between hinged and fixed, rotational stiffness is introduced. Constructing a structure including the length of steel pipe components 、 Bending stiffness rotational stiffness Frequency parameters and mass per unit length The characteristic equations were derived; finally, the true natural frequencies of the steel pipe members were obtained through numerical solutions. ; Step 3: Construct a system based on the calculated flow rate Generalized vortex-induced vibration excitation function To accurately describe the smooth transition of vortex-induced vibration from initiation to dissipation within the locked region, a double logistic model is used instead of the traditional step function; this model includes parameters describing the upper and lower boundaries of the vortex-induced vibration locked region. and and model parameters characterizing smoothness Therefore, it can continuously characterize the probability of vortex-induced vibration occurring; Step 4: Map the generalized excitation function to the actual wind field; introduce the "independence principle" to decompose the incoming wind velocity into a normal component perpendicular to the component axis. The influence of the tangential component is ignored; at the same time, the power-law formula of the atmospheric boundary layer wind profile is combined to correct the average wind speed at different heights, and the excitation function of vortex-induced vibration under different wind speed and direction conditions is constructed. ; Step 5: Based on the wind speed-wind direction joint distribution function model With vortex-induced vibration excitation function The probability of vortex-induced vibration occurring in steel pipe components is calculated using two-dimensional integrals. And then according to the rate The size of the steel pipe components is used to sort them, thereby identifying vulnerable steel pipe components that are prone to vortex-induced vibration, and the steel pipe components with a higher probability are designated as vulnerable components for key monitoring or reinforcement. Attached Figure Description

[0007] Figure 1 This is a schematic diagram of the structure of an ultra-high voltage transmission tower in Example 2; Figure 2 The wind speed-wind direction joint distribution function model obtained in Example 2 A schematic diagram; Figure 3 The excitation function for the double Logistic vortex-induced vibration in Example 2 A schematic diagram of the fitting process; Figure 4 This is a thermogram showing the probability distribution of vortex-induced vibration in each steel pipe component of an ultra-high voltage transmission tower in Example 2. Detailed Implementation

[0008] The present invention will be further described below with reference to the embodiments and accompanying drawings.

[0009] like Figure 1 and Figure 2 As shown Example 1: A method for identifying vulnerable components of transmission tower steel pipe structures subjected to vortex-induced vibration includes the following steps: Step 1: Obtain the historical wind speed at the location of the transmission tower. with wind angle Data, establishing different heights from the base of the tower Wind speed-direction joint distribution function model of steel pipe components at the location ; Specifically: First, obtain the specified height from the base of the tower. Historical wind speed Wind angle Statistical data to establish a wind direction distribution model And the wind speed distribution model under each wind direction. ;Specify height The value is typically taken as 10m; Then, establish the initial distribution function of wind speed and wind direction according to formula (1). : , formula (1); Finally, based on the height of the steel pipe component from the bottom of the tower... And landform type, correct the initial distribution function of wind speed-wind direction The wind speed-wind direction joint distribution function model is obtained. .

[0010] Initial distribution function of wind speed-wind direction The correction can be made according to the following formula (2): , formula (2); in: The height of the steel pipe component from the bottom of the tower. The wind profile index represents the wind profile index under different landform categories.

[0011] Wind speed distribution model A Weibull distribution can be used for fitting; wind direction distribution model A normal distribution can be used for fitting.

[0012] Step 2: Based on the geometric dimensions, cross-sectional properties, and semi-rigid constraint stiffness of the connection nodes of the steel pipe member, construct the characteristic equation and numerically solve it to obtain the true natural frequency of the steel pipe member. ; True natural frequencies of steel tubular members under actual semi-rigid constraints Calculate according to the following formula (3): , formula (3); in: For the bending stiffness of steel pipe components, Mass per unit length; Frequency parameter; intermediate variable Calculate according to the following formula (4): , formula (4); in: For the length of the component, The rotational stiffness of different connection nodes.

[0013] Step 3: Based on the double Logistic model, reduce the speed Using the independent variable, a generalized excitation function characterizing the vortex-induced vibration from initiation to extinction is established according to the following formula (5). : , formula (5); in: , The outer diameter of the steel pipe component. To describe the lower boundary of the vortex-induced vibration locking interval, To describe the upper boundary of the vortex-induced vibration locking interval, These are the model parameters that characterize smoothness; , , All of these are parameters to be fitted.

[0014] Step 4: Based on the principle of independence, establish the vortex-induced vibration excitation function under different wind speeds and directions according to the following formula (6). ; ;Formula (6); in: It is the azimuth angle of the normal to the steel pipe component in the horizontal plane.

[0015] Step 5: Based on the wind speed-wind direction joint distribution function model With vortex-induced vibration excitation function The probability of vortex-induced vibration occurring in steel pipe components is calculated using two-dimensional integrals. This allows for the identification of vulnerable steel pipe components prone to vortex-induced vibration.

[0016] The probability of vortex-induced vibration occurring in steel pipe components Calculate according to formula (7): , formula (7).

[0017] Different steel pipe components can be obtained sequentially by following the steps described above. The values ​​are used to sort the steel pipe components of the entire transmission tower, thereby identifying high-probability vulnerable steel pipe components.

[0018] It is recommended to take effective vibration reduction measures such as flow lines or dampers for high-probability vulnerable steel pipe components.

[0019] Example 2: Taking a steel pipe transmission tower (target tower) of the Baihetan-Zhejiang UHV transmission line (Anhui section) across the Yangtze River as the engineering background, the structure of the transmission tower is as follows: Figure 1 As shown, based on local meteorological data, steel pipe components prone to vortex-induced vibration are identified, including the following steps: (1) Modeling of the joint distribution function of wind speed and wind direction: Collect meteorological data for the target transmission tower area over the past 10 years, specifically the average wind speed data at a height of 10m above the tower base under 16 wind directions. and wind direction angle For each wind direction, a Weibull distribution is fitted to the statistical data of wind speed. For the probability of occurrence of each wind direction, a normal distribution is fitted. Finally, the initial distribution function of wind speed and wind direction is obtained using the multiplication theorem. :

[0020] in, =6.52, =2.5, and These are the scale parameter and the position parameter, respectively, which can be fitted using harmonic functions:

[0021]

[0022] in: and These are the average values ​​of the dimensional and positional parameters, respectively. and These are the dimensional parameters and positional parameters, respectively. The amplitude of the first harmonic. and These are the dimensional parameters and positional parameters, respectively. The initial phase of the first harmonic, with parameter values ​​shown in Table 1: Table 1 , , , Value table ; Furthermore, based on the height of the steel pipe component from the bottom of the tower... And landform type, correct the initial distribution function of wind speed-wind direction The wind speed-wind direction joint distribution function model is obtained. : ; in These are wind profile indices for different landform categories. The target tower is located in a Class B landform. The value is taken as 0.15; for the main and diagonal members of the transmission tower, the height of the midpoint from the tower bottom is taken as the height of the entire steel pipe member from the tower bottom. The fitted wind speed-wind direction joint distribution function model like Figure 2 As shown.

[0023] (2) Determination of the natural frequency of steel pipe components: Based on the geometric dimensions and structural properties of each steel pipe component of the transmission tower, and taking into account the end constraints, the constraint rotational stiffness between the main members is set. (Fixed constraint), the diagonal and horizontal members use a typical C-type connection node with a rotational stiffness of . ( The dimensionless stiffness ratio of this connection node was determined experimentally as follows: Therefore, the characteristic equations corresponding to each steel pipe component can be established: ; The unique unknown, the frequency parameter, is obtained by numerically solving the equation using Newton's iterative method. The natural frequencies of different steel pipe components were then calculated. : ; in: The mass per unit length of the steel pipe component. For the density of the steel pipe, and These are the outer diameter and inner diameter of the steel pipe component, respectively.

[0024] (3) Construction of the excitation function for generalized vortex-induced vibration: Based on the vortex-induced vibration test data of steel pipe components, the parameters of the double Logistic model can be obtained by fitting. , , Value: , , Thus, the following generalized excitation function is established. : ; Figure 3 The excitation function of vortex-induced vibration in the dual Logistic model is given. The fitted image shows that the function can effectively describe the characteristics of vortex-induced vibration. Its value approaches 1 when vortex-induced vibration occurs and drops to 0 when there is no vortex-induced vibration, which is consistent with the experimentally measured vortex-induced vibration data.

[0025] (4) Map the excitation function to the actual wind field: Based on the spatial position of different steel pipe components on the transmission tower, determine their normal angle on the horizontal projection plane. Combining the principle of independence, the generalized excitation function... Transformed into an excitation function for vortex-induced vibration with respect to actual meteorological wind speed and direction. : ; (5) Calculation of the probability of vortex-induced vibration: By correcting the combined wind speed and direction distribution and the excitation function of vortex-induced vibration under actual wind field conditions, the probability of vortex-induced vibration occurring in different steel pipe components can be obtained: ; The probability of vortex-induced vibration occurring for each steel pipe component of the target tower was calculated, and the results are as follows: Figure 4 As shown. From Figure 4 It can be seen that the probability of vortex-induced vibration of each steel pipe component of the target tower (each with a corresponding numerical value) is clear and quantifiable.

[0026] It is easy to see that the method of the present invention can effectively combine structural parameters and environmental parameters, and quantitatively give the probability of vortex-induced vibration.

[0027] The solution of the present invention has the following beneficial effects: ① Improved calculation accuracy: The method of this invention accurately simulates the semi-rigid characteristics of nodes by solving the characteristic equations that include rotational stiffness, thus avoiding missed detections or false alarms of vortex-induced vibrations caused by frequency misjudgment.

[0028] ② The impact of wind speed and direction statistics is quantified: The present invention abandons the traditional approach of checking wind speed alone. By integrating the probability of wind speed and direction together, it gives the probability value of vortex-induced vibration of steel pipe components, which is more in line with the random characteristics of actual engineering.

[0029] ③ The model is more in line with physical laws: The method of this invention uses a double Logistic model to describe the vortex-induced vibration locking region, which smooths the start-up and decay process and solves the problem of discontinuity of the traditional step function at the boundary.

[0030] ④ Highly efficient screening: The method of this invention can quickly process tens of thousands of components through analytical formulas, which makes it easy to quickly identify high-risk areas in the early stage of transmission tower design or operation and maintenance.

[0031] Finally, it should be noted that the above description is merely a preferred embodiment of the present invention. Those skilled in the art, under the guidance of the present invention, can make various similar representations without departing from the spirit and claims of the present invention, and such modifications all fall within the protection scope of the present invention.

Claims

1. A method for identifying vulnerable components of transmission tower steel pipe structures subjected to vortex-induced vibration, characterized in that... Includes the following steps: Step 1: Obtain the historical wind speed at the location of the transmission tower. with wind angle Data, establishing different heights from the base of the tower Wind speed-direction joint distribution function model of steel pipe components at the location ; Step 2: Based on the geometric dimensions, cross-sectional properties, and semi-rigid constraint stiffness of the connection nodes of the steel pipe member, construct the characteristic equation and numerically solve it to obtain the true natural frequency of the steel pipe member. ; Step 3: Establish a generalized excitation function to characterize the vortex-induced vibration from initiation to extinction. ; Step 4: Based on the principle of independence, establish the excitation function for vortex-induced vibration under different wind speeds and directions. ; Step 5: Based on the wind speed-wind direction joint distribution function model With vortex-induced vibration excitation function The probability of vortex-induced vibration occurring in steel pipe components is calculated using two-dimensional integrals. This allows for the identification of vulnerable steel pipe components prone to vortex-induced vibration.

2. The method for identifying vulnerable components of transmission tower steel pipe structures according to claim 1, characterized in that: In step one, the specified height from the bottom of the tower is first obtained. Historical wind speed Wind angle Statistical data to establish a wind direction distribution model And the wind speed distribution model under each wind direction. ; Then, establish the initial distribution function of wind speed and wind direction according to formula (1). : Formula (1); Finally, based on the height of the steel pipe component from the bottom of the tower... And landform type, correct the initial distribution function of wind speed-wind direction The wind speed-wind direction joint distribution function model is obtained. .

3. The method for identifying vulnerable components of transmission tower steel pipe structures according to claim 2, characterized in that: In step one, a Weibull distribution is fitted to the statistical data of wind speed in each direction to obtain a wind speed distribution model. ; A normal distribution model is used to fit the wind direction distribution. .

4. The method for identifying vulnerable components of transmission tower steel pipe structures according to claim 2, characterized in that: In step one, the initial distribution function of wind speed and wind direction is calculated according to the following formula (2). Make corrections: Formula (2); in: The height of the steel pipe component from the bottom of the tower. The wind profile index represents the wind profile index under different landform categories.

5. A method for identifying vulnerable components of transmission tower steel pipe structures according to any one of claims 1-4, characterized in that: In step two, the natural frequencies of different steel pipe components under actual semi-rigid constraints are determined according to the following formula (3). : Formula (3); in: For the bending stiffness of steel pipe components, This refers to the mass per unit length of the steel pipe component; This is a frequency parameter.

6. The method for identifying vulnerable components of transmission tower steel pipe structures according to any one of claims 5, characterized in that: Frequency parameters Calculate according to the following formula (4): , formula (4); in: For the length of the component, The rotational stiffness of different connection nodes.

7. A method for identifying vulnerable components of transmission tower steel pipe structures according to any one of claims 1-5, characterized in that: In step three, the reduction speed is... Using the independent variable, the generalized excitation function is established according to the following formula (5). : , formula (5); in: , The outer diameter of the steel pipe component. To describe the lower boundary of the vortex-induced vibration locking interval, To describe the upper boundary of the vortex-induced vibration locking interval, These are the model parameters that characterize smoothness; , , All of these are parameters to be fitted.

8. A method for identifying vulnerable components of transmission tower steel pipe structures according to any one of claims 1-5, characterized in that: In step four, the vortex-induced vibration excitation function is established according to the following formula (6). : Official (6); in: It is the azimuth angle of the normal to the steel pipe component in the horizontal plane.

9. A method for identifying vulnerable components of transmission tower steel pipe structures according to any one of claims 1-5, characterized in that: In step five, the probability of vortex-induced vibration occurring in the steel pipe component is... Calculate according to formula (7): , Official (7).

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