A method for analyzing the vulnerability of transmission line towers considering wind directionality

Abstract

The present invention discloses a method for analyzing the vulnerability of transmission towers considering wind directionality, specifically: considering the uncertainty of transmission tower structure and wind load, numerically simulating the wind vibration response and anti-collapse capacity of transmission towers under wind load, analyzing two wind-induced vulnerability factors of transmission towers, the first wind-induced vulnerability factor of transmission towers is described as the probability that the structure reaches or exceeds a certain damage limit state under a certain wind speed, and the second wind-induced vulnerability factor of transmission towers is described as the conditional probability obtained by integrating the PDF of structural force and the CDF of structural resistance; considering wind directionality, calculating the failure probability of transmission towers, and further conducting optimal layout research of transmission towers under given wind fields and transmission towers. The present invention comprehensively considers factors of wind-induced vulnerability of transmission towers, has strong systematicity, and can be used for calculating the failure probability of transmission towers considering wind speed and wind direction and studying the optimal layout of transmission towers under given wind fields.

Description

Technical Field

[0001] The invention belongs to the technical field of wind resistance of transmission line towers, and in particular relates to a method for analyzing the vulnerability of transmission line towers taking wind directionality into consideration. Background Art

[0002] The transmission line tower system is a lightweight, highly flexible, low-damping, wind-sensitive structure. Wind load has become one of the main control factors in structural design. In recent years, the destruction or collapse of transmission line towers under strong winds has occurred frequently. As an important lifeline structural system, the collapse of transmission line towers not only causes economic losses itself, but also causes large-scale power outages, which will bring serious losses to society and people's property.

[0003] Wind-induced vulnerability assessment of transmission towers is of great significance in practical applications. It can not only provide a reference for engineers to design and build transmission towers, but also provide important data for the insurance industry to manage and transfer risks, and can also provide support for government departments to prevent and reduce disasters.

[0004] At present, considerable progress has been made in the research on wind-induced vulnerability of transmission line towers, but there are few systematic analyses and no transmission line tower vulnerability assessment considering wind directionality. Summary of the invention

[0005] In view of the above problems, the present invention provides a transmission line tower vulnerability analysis method taking wind directionality into consideration.

[0006] The invention discloses a method for analyzing the vulnerability of transmission towers taking into account wind directionality. Based on the uncertainty of the transmission tower structure and wind load, the wind-induced vibration response and anti-collapse capacity of the transmission tower under wind load are numerically simulated, and the wind-induced vulnerability factors of two transmission towers are analyzed.

[0007] The first wind-induced vulnerability factor of the transmission tower is described as the probability that the structure reaches or exceeds a certain damage limit state under a certain wind speed. The formula is:

[0008] F R (v)=P[Td>L s |V=v]

[0009] In the formula, F R is the fragility; P[] is the failure probability; Td is the tower top displacement, L s is the tower top displacement corresponding to a certain performance level or damage limit state of the structure; V is the average wind speed at a height of 10 meters of the transmission tower; v is the actual wind speed intensity under certain conditions.

[0010] The second wind-induced vulnerability factor of the transmission tower is described as the conditional probability obtained by integrating the PDF of the structural force and the CDF of the structural resistance. The formula is:

[0011]

[0012] In the formula, F Ls (L s |Td) represents the tower top displacement L that reaches a certain performance level under a given tower top displacement Td s The cumulative conditional probability distribution, f Td (Td|V) represents the conditional probability distribution of the tower top displacement Td given the basic wind speed V.

[0013] The failure probability of transmission towers is calculated by considering wind directionality, and the optimal layout of transmission towers is studied under given wind fields and transmission towers. Specifically:

[0014] (a) Use the equal division method to divide 360° into 12 intervals.

[0015] (b) Calculate the location parameters and scale parameters of the annual maximum wind speed in each wind direction interval that obeys the extreme value type I distribution.

[0016] (c) The position parameters and scale parameters of each wind direction interval are fitted using a harmonic function to obtain the position parameters and scale parameters of other directions.

[0017] (d) Combine wind field characteristics with vulnerability curves to calculate the probability of damage and collapse of transmission towers in different directions within one year.

[0018] (e) By changing the layout direction of the transmission towers, the failure probability of the transmission towers in different layout directions is calculated, and the optimal layout of the transmission towers is achieved based on the minimum failure probability.

[0019] Furthermore, the analysis steps of the first type of wind-induced vulnerability factors of transmission towers are as follows:

[0020] (1) Considering the uncertainty of wind load, the harmonic synthesis method is used to simulate the pulsating wind speed time history at various locations of the transmission tower and line under any basic wind speed V, and the time history curve is converted into a wind load curve according to the relevant specifications.

[0021] (2) Considering the uncertainty of the material properties and geometric dimensions of the transmission tower, the Latin hypercube sampling method is used to simulate 20 random structure samples, which are denoted as the uncertain structure samples S i , i=1,2,···,20.

[0022] (3) For each uncertain structure sample S i Conduct nonlinear buckling analysis to determine the failure displacement limit of each structural sample i=1,2,···,20 and collapse displacement limit value i=1, 2,..., 20.

[0023] (4) By changing the basic wind speed, that is, V = 30-75m / s, with an increment of 0.1m / s, for each uncertainty structure sample S i Dynamic incremental analysis was performed to calculate the top displacement of the transmission tower at different basic wind speeds. A total of 20 maximum displacement and basic wind speed curves were obtained, and the maximum displacement of each sample exceeded and Basic wind speed and i=1, 2,..., 20.

[0024] (5) Based on and Draw the wind-induced vulnerability curves of transmission tower damage and collapse under different wind directions.

[0025] Furthermore, the analysis steps of the second type of wind-induced vulnerability factors of transmission towers are as follows:

[0026] (1) Considering the uncertainty of wind load, the harmonic synthesis method is used to simulate the pulsating wind speed time history at various locations of the transmission tower and line under any basic wind speed V, and then converted into a wind load time history curve according to the relevant specifications.

[0027] (2) Considering the uncertainty of the material properties and geometric dimensions of the transmission tower, the Latin hypercube sampling method is used to simulate 20 random structure samples, which are denoted as the uncertain structure samples S i , i = 1, 2, ···, 20; obtain the critical failure displacement of each structure sample i=1,2,···,20 and critical collapse displacement i=1,2,···,20; by and The cumulative probability density function CDF of the transmission tower resistance is obtained through analysis and processing.

[0028] (3) For each uncertain structure sample S i , calculate the wind-induced response under the same basic wind speed V to obtain the tower top displacement i=1,2,···,20, through The probability density function PDF of the transmission tower force is obtained by analysis and processing, and the PDF under different basic wind speeds is obtained by adjusting the basic wind speed.

[0029] (4) The probability of damage and collapse of the transmission tower under a certain basic wind speed is obtained by convolving the probability distribution of the cumulative probability density function CDF of the transmission tower resistance and the probability density function PDF of the force, thereby obtaining the wind-induced fragility curve of the transmission tower.

[0030] The beneficial technical effects of the present invention are:

[0031] The present invention takes into account the wind-induced vulnerability of transmission line towers comprehensively and systematically, and can be used to calculate the failure probability of transmission line towers considering wind speed and direction and to study the optimal arrangement of transmission towers under a given wind field. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 This is the first step of analyzing wind-induced vulnerability factors of transmission towers according to the present invention.

[0033] Figure 2 This is the second step of analyzing wind-induced vulnerability factors of transmission towers according to the present invention.

[0034] Figure 3 The load-displacement curve of the top displacement of a transmission tower is obtained for the embodiment of the present invention. DETAILED DESCRIPTION

[0035] The present invention is further described in detail below with reference to the accompanying drawings and specific embodiments.

[0036] The present invention provides a method for analyzing the vulnerability of transmission towers considering wind directionality. Based on the uncertainty of transmission tower structure and wind load, the wind vibration response and anti-collapse capacity of transmission towers under wind load are numerically simulated, and two wind-induced vulnerability factors of transmission towers are analyzed. A method for calculating the failure probability of transmission towers considering wind directionality is proposed, and further research is conducted on the optimal layout of transmission towers under given wind fields and transmission towers.

[0037] The first wind-induced vulnerability factor of the transmission tower is described as the probability that the structure reaches or exceeds a certain damage limit state under a certain wind speed. The formula is:

[0038] F R (v)=P[Td>L s |V=v]

[0039] In the formula, F R is the fragility; P[] is the failure probability; Td is the tower top displacement, L s is the tower top displacement corresponding to a certain performance level or damage limit state of the structure; V is the average wind speed at a height of 10 meters at the transmission tower; v is the actual wind speed intensity (average wind speed) under certain conditions.

[0040] The first analysis process of wind-induced vulnerability factors of transmission towers is as follows: Figure 1 As shown, the specific steps are as follows:

[0041] (1) Considering the uncertainty of wind load, the harmonic synthesis method is used to simulate the pulsating wind speed time history at various locations of the transmission tower and line under any basic wind speed V, and then converted into a wind load time history curve according to the relevant specifications.

[0042] (2) Considering the uncertainty of the material properties and geometric dimensions of the transmission tower, the Latin hypercube sampling method is used to simulate 20 random structure samples, which are denoted as the uncertain structure samples S i , i=1,2,···,20.

[0043] (3) For each uncertain structure sample S i Conduct nonlinear buckling analysis (considering the role of transmission lines) to determine the limit displacement of each structural sample i=1,2,···,20 and collapse displacement limit value i=1, 2,..., 20.

[0044] (4) By changing the basic wind speed (V = 30-75m / s, with an increment of 0.1m / s), for each uncertainty structure sample S i Dynamic incremental analysis was performed to calculate the top displacement of the transmission tower at different basic wind speeds. A total of 20 maximum displacement and basic wind speed curves were obtained, and the maximum displacement of each sample exceeded and Basic wind speed and i=1, 2,..., 20.

[0045] (5) Based on and Draw the wind-induced vulnerability curves of transmission tower damage and collapse under different wind directions.

[0046] The second wind-induced vulnerability factor of the transmission tower is described as the conditional probability obtained by integrating the PDF of the structural force and the CDF of the structural resistance. The formula is:

[0047]

[0048] In the formula, F Ls (L s |Td) represents the tower top displacement L that reaches a certain performance level (damage or collapse) under a given tower top displacement Td. s The cumulative conditional probability distribution, f Td (Td|V) represents the conditional probability distribution of the tower top displacement Td given the basic wind speed V.

[0049] The second analysis process of wind-induced vulnerability factors of transmission towers is as follows: Figure 2 As shown, the specific steps are as follows:

[0050] (1) Considering the uncertainty of wind load, the harmonic synthesis method is used to simulate the pulsating wind speed time history at various locations of the transmission tower and line under any basic wind speed V, and the time history curve is converted into a wind load curve according to the relevant specifications.

[0051] (2) Considering the uncertainty of the material properties and geometric dimensions of the transmission tower, the Latin hypercube sampling method is used to simulate 20 random structure samples, which are denoted as the uncertain structure samples S i , i = 1, 2, ···, 20; obtain the critical failure displacement of each structure sample i=1,2,···,20 and critical collapse displacement i=1,2,···,20; by and The cumulative probability density function CDF of the transmission tower resistance is obtained through analysis and processing.

[0052] (3) For each uncertain structure sample S i , the wind-induced response calculation under the same basic wind speed V (considering the randomness of the fluctuating wind) is performed to obtain the tower top displacement i=1,2,···,20, through The probability density function PDF of the transmission tower force is obtained by analysis and processing, and the PDF under different basic wind speeds is obtained by adjusting the basic wind speed (30-75m / s).

[0053] (4) The probability of damage and collapse of the transmission tower under a certain basic wind speed is obtained by convolving the probability distribution of the cumulative probability density function CDF of the transmission tower resistance and the probability density function PDF of the force, thereby obtaining the wind-induced fragility curve of the transmission tower.

[0054] The failure probability of transmission towers is calculated by considering wind directionality, and the optimal layout of transmission towers is studied under given wind fields and transmission towers. Specifically:

[0055] (a) Use the equal division method to divide 360° into 12 intervals.

[0056] (b) Calculate the location parameters and scale parameters of the annual maximum wind speed in each wind direction interval that obeys the extreme value type I distribution.

[0057] (c) The position parameters and scale parameters of each wind direction interval are fitted using a harmonic function to obtain the position parameters and scale parameters of other directions.

[0058] (d) Combine wind field characteristics with vulnerability curves to calculate the probability of damage and collapse of transmission towers in different directions within one year.

[0059] (e) By changing the layout direction of the transmission towers, the failure probability of the transmission towers in different layout directions is calculated, and the optimal layout of the transmission towers is achieved based on the minimum failure probability.

[0060] In summary, this application provides a method for analyzing the vulnerability of transmission towers taking into account wind directionality, considers the uncertainty of wind loads and transmission towers, discusses two wind-induced vulnerability analysis methods, obtains the destruction probability and collapse probability of transmission towers at different wind directions, and calculates the failure probability of transmission towers taking into account wind directionality, thereby achieving the optimal layout of transmission towers.

[0061] Example:

[0062] To establish a finite element model of a transmission tower, this paper adopts a decoupling analysis method. First, the ANSYS software is used to separately model the conductor (ground) wire and insulator, and a nonlinear dynamic time history analysis is performed under wind load. The support reaction force of the insulator end (the node connected to the transmission tower) is extracted and loaded onto the single tower as a concentrated load, and analyzed and calculated together with the wind load on the tower body. The transmission tower is simulated using the BEAM188 spatial beam unit, and the conductor and insulator are simulated using the LINK10 unit.

[0063] The uncertainty model of the transmission tower is established, taking into account the uncertainty of the material properties and cross-sectional dimensions of the transmission tower. The material properties include elastic modulus, Poisson's ratio, density and yield strength. The geometric dimensions consider the limb thickness and limb width of the angle steel, and the outer diameter and wall thickness of the round steel pipe. The above variables are selected to determine their corresponding probability distribution. The Latin hypercube sampling method is used to perform Monte Carlo simulation on random variables. The generated random samples are used to establish a structural uncertainty model, and 20 structural samples can be obtained for vulnerability analysis.

[0064] Simulation of wind load on transmission tower system. This application uses harmonic synthesis method to simulate the fluctuating wind speed time history at each height of the transmission tower. The transmission tower is divided into 8 wind speed zones along the height direction. The wind speed of all points in each zone is the wind speed of the simulation point at the middle height of the zone. MATLAB is used to realize the fluctuating wind speed simulation of each simulation point of the transmission tower. The site category of the transmission line is Class B landform, the wind profile index is 0.16, the fluctuating wind speed power spectrum is Kaimal power spectrum, and the coherence function model is as follows:

[0065]

[0066] Where: f is frequency (HZ); C Z Respectively represent the attenuation coefficients of any two points in space, usually C Z =10; and Respectively represent along the height z i and z j The average wind speed; ΔZ = |z i -z j|. This embodiment lists the pulsating wind speed time history and the comparison between the simulated spectrum and the target spectrum when the average wind speed at the simulated point in the first wind speed zone of the transmission tower is 30m / s. Based on the quasi-steady assumption and the overhead transmission line tower structure design technology (DL / T 5154-2012), the wind speed can be converted into wind load.

[0067] The nonlinear buckling analysis of the transmission tower is carried out by using ANSYS finite element software. First, the eigenvalue buckling analysis of the transmission tower structure is carried out. According to the results of the eigenvalue buckling analysis, the initial defect is applied with the deformation of the eigenvalue buckling mode, and the nonlinear buckling analysis of the transmission tower line is carried out to obtain the displacement load displacement curve of the top of the transmission tower. Figure 3 As shown. The wind load on the transmission tower and the wind load on the transmission line acting on the transmission tower are obtained by the equivalent static wind load. The elastic stage, buckling point and limit displacement point of the structure can be intuitively observed from the load displacement curve. The present invention uses the horizontal displacement of the tower top as the control index, and defines the position where the structure begins to enter the plastic state as the critical failure point. The displacement at this time is defined as the limit value of the failure state of the transmission tower Δ d The position where the structure reaches the buckling state is defined as the critical collapse point, and the displacement angle at this time is defined as the displacement angle of the transmission tower collapse state Δ c The specific damage state of the transmission tower can be divided as follows: When the displacement angle of the transmission tower Δ d ≤Δ<Δ c When Δ≥Δ c The structure is in a collapsed state.

[0068] Incremental dynamic analysis of transmission towers is performed. Several sets of wind speed time histories can be obtained by adjusting the basic wind speed (30-75m / s). The basic wind speed increment is 0.1m / s. Wind-induced response analysis of uncertain transmission tower structure samples under different basic wind speeds is performed. The maximum horizontal displacement of the tower top and the basic wind speed curve can be obtained for each sample.

[0069] Draw the wind-induced vulnerability curve. According to method 1 and method 2, the wind-induced vulnerability curve of the transmission tower when it is damaged or collapsed can be drawn.

[0070] This paper adopts the method of equally dividing the intervals, dividing 360° into 12 intervals. The wind direction angles corresponding to the 12 directions are 0°, 30°, 60°, 90°, 120°, 150°, 180°, 210°, 240°, 270°, 300°, and 330°.

[0071] Statistical analysis of wind speed and direction data at a certain site, analyzing and processing all one-minute wind speed and direction measurement data of the KABI site of the US weather station from 2000 to 2013, and obtaining the average wind speed and wind direction for all 14 years, the probability distribution of the maximum monthly wind speed can be obtained first, and then the annual maximum wind speed can be derived. The location parameters and scale parameters of the annual maximum wind speed that obeys the extreme value type I distribution are obtained, so that the conditional probability distribution of the annual maximum average wind speed in a given wind direction can be obtained.

[0072] The characteristic parameters of the annual maximum wind speed probability distribution are fitted, and the location parameters and scale parameters are fitted by the harmonic function. The formula is as follows:

[0073]

[0074]

[0075] In the formula, a, b l , c l is the coefficient that needs to be determined. The subscripts m and δ represent the location parameter and scale parameter respectively. m With n δ is the order of the harmonic function, and θ is the direction angle. Through the above formula, the position parameters and scale parameters in other directions can be obtained.

[0076] The probability of damage and collapse of transmission towers within one year is calculated based on the measured wind field data and vulnerability curves. The probability of damage and collapse of transmission towers in different directions within one year is calculated as follows:

[0077] P f =∫∫F D (DU)f U (U|θ)f θ (θ)dUdθ

[0078] Where P f represents the probability of damage and collapse; D represents the critical wind speed for wind-induced damage and collapse of the transmission tower; U is the annual maximum average wind speed in a certain direction; θ represents the wind direction; F D (D|U) Cumulative conditional probability distribution of critical damage and collapse wind speed under given wind speed; f U (U|θ) is the conditional probability distribution of the annual maximum average wind speed for a given wind direction; f θ (θ) is the wind frequency.

[0079] The optimal layout of transmission towers is studied. By changing the layout direction of the transmission towers, the transmission towers are rotated 0°-180° counterclockwise along the X-axis with an interval of 15°, and the failure probability of the transmission towers in different layout directions is calculated. The probability of damage and collapse of the transmission towers in 12 directions can be obtained, thereby realizing the optimal layout study of the transmission towers.

Claims

1. A method for analyzing the vulnerability of transmission line towers considering wind directionality, characterized in that: Considering the uncertainty of transmission tower structure and wind load, numerical simulation is conducted on wind-induced vibration response and anti-collapse capacity of transmission tower under wind load, and wind-induced vulnerability factors of two types of transmission towers are analyzed. The first wind-induced vulnerability factor of the transmission tower is described as the probability that the structure reaches or exceeds a certain damage limit state under a certain wind speed. The formula is: F R (v)=P[Td>L s V=v] In the formula, F R is the fragility; P[] is the failure probability; Td is the tower top displacement, L s is the tower top displacement corresponding to a certain performance level or damage limit state of the structure; V is the average wind speed at a height of 10 meters of the transmission tower; v is the actual wind speed intensity under certain conditions; The second wind-induced vulnerability factor of the transmission tower is described as the conditional probability obtained by integrating the PDF of the structural force and the CDF of the structural resistance. The formula is: In the formula, F Ls (L s Td) represents the tower top displacement L that reaches a certain performance level under a given tower top displacement Td s The cumulative conditional probability distribution, f Td (TdV) represents the conditional probability distribution of the tower top displacement Td given the basic wind speed V; The failure probability of transmission towers is calculated by considering wind directionality, and the optimal layout of transmission towers is studied under given wind fields and transmission towers. Specifically: (a) Use the equal division interval method to divide 360° into 12 intervals; (b) Calculate the location parameters and scale parameters of the annual maximum wind speed in each wind direction interval that follows the extreme value type I distribution; (c) The position parameters and scale parameters of each wind direction interval are fitted using a harmonic function to obtain the position parameters and scale parameters of other directions; (d) Combine wind field characteristics with vulnerability curves to calculate the probability of damage and collapse of transmission towers in different directions within one year; (e) By changing the layout direction of the transmission towers, the failure probability of the transmission towers in different layout directions is calculated, and the optimal layout of the transmission towers is achieved based on the minimum failure probability.

2. A method for analyzing the vulnerability of transmission line towers considering wind directionality according to claim 1, characterized in that: The analysis steps of the wind-induced vulnerability factors of the first type of transmission tower are as follows: (1) Considering the uncertainty of wind load, the harmonic synthesis method is used to simulate the pulsating wind speed time history at various locations of the transmission tower and line under any basic wind speed V, and converted into a wind load time history curve according to the relevant specifications; (2) Considering the uncertainty of the material properties and geometric dimensions of the transmission tower, the Latin hypercube sampling method is used to simulate 20 random structure samples, which are denoted as the uncertain structure samples S i , i=1,2,···,20; (3) For each uncertain structure sample S i Conduct nonlinear buckling analysis to determine the failure displacement limit of each structural sample and collapse displacement limit (4) By changing the basic wind speed, that is, V = 30-75m / s, with an increment of 0.1m / s, for each uncertainty structure sample S i Dynamic incremental analysis was performed to calculate the top displacement of the transmission tower at different basic wind speeds. A total of 20 maximum displacement and basic wind speed curves were obtained, and the maximum displacement of each sample exceeded and Basic wind speed and (5) Based on and Draw the wind-induced vulnerability curves of transmission tower damage and collapse under different wind directions.

3. A method for analyzing the vulnerability of transmission line towers considering wind directionality according to claim 1, characterized in that: The analysis steps of the wind-induced vulnerability factors of the second type of transmission tower are as follows: (1) Considering the uncertainty of wind load, the harmonic synthesis method is used to simulate the pulsating wind speed time history at various locations of the transmission tower and line under any basic wind speed V, and converted into a wind load time history curve according to the relevant specifications; (2) Considering the uncertainty of the material properties and geometric dimensions of the transmission tower, the Latin hypercube sampling method is used to simulate 20 random structure samples, which are denoted as the uncertain structure samples S i , i = 1, 2, ···, 20; obtain the critical failure displacement of each structure sample i=1,2,···,20 and critical collapse displacement Through and The cumulative probability density function CDF of the transmission tower resistance is obtained by analysis and processing; (3) For each uncertain structure sample S i , calculate the wind-induced response under the same basic wind speed V to obtain the tower top displacement Through The probability density function PDF of the force acting on the transmission tower is obtained by analysis and processing, and the PDF under different basic wind speeds is obtained by adjusting the basic wind speed; (4) The probability of damage and collapse of the transmission tower under a certain basic wind speed is obtained by convolving the probability distribution of the cumulative probability density function CDF of the transmission tower resistance and the probability density function PDF of the force, thereby obtaining the wind-induced fragility curve of the transmission tower.

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