| The imbalance of resource distribution and economic development determines the basic energy flow of China's “West-to-East Power Transmission and North Coal-South Transportation”,which has promoted the vigorous development of the power grid industry.As an important lifeline project,the investment in power systems is huge and the consequences of accidents are serious.Especially for UHV lines,in order to effectively carry out the analysis and design of the transmission tower,this paper will use the multi-scale method to simulate the transmission tower line system.At the same time,as a special high-rise structure,the wind load is the main load that causes the transmission tower to be destroyed.First,the wind load itself has a strong uncertainty.Therefore,it is necessary to analyze the reliability of the transmission tower line system under wind load.Therefore,in this paper,while studying the multi-scale simulation of the transmission tower line system,a secondary reliability method with both efficiency and accuracy is proposed.This paper mainly makes the following research:Most of the second-order reliability methods are derived in an independent standard normal space.In practical engineering,random variables are often correlated and do not obey the standard normal distribution,and even the probability information of some random variables is incomplete(For example,only the first few statistical moment information is known.Therefore,the generalized Nataf transform is first introduced to transform the original variable space into an independent standard normal space,so that the method is applicable to the reliability analysis of the incomplete system of probability information.Secondly,In the standard normal space,the function function is quadratic polynomial fitting.In order to reduce the error generated during the fitting process,the gradient matrix is used to construct the rotation matrix,and the original variable space is transformed into the rotation variable space.Introducing a univariate dimensionreduction approximation model at the rotational variable space checkpoint,and further approximating each classification function into a quadratic polynomial;finally,converting the random variable to a standard normal distribution quadratic polynomial to a random variable obeying the chi-square distribution or A polynomial of non-central chisquare distribution and using integrals to solve for failure probabilities.At present,some scholars have introduced multi-scale methods into transmission tower research,but all of them have carried out single-tower multi-scale research,which does not take into account the characteristics of the transmission tower line system.For this purpose,the transmission tower line is carried out.In the multi-scale simulation study of the system,firstly,a reasonable macro-unit tower model is established,and the overall beam element model is generally used,and the overall analysis is carried out.Then,for the tower to be inspected,the weak nodes are found according to the calculation results,and the solid element is used for the node.Modeling,considering the bolt connection at the joint,and using the constraint equation to connect the solid element of the node with the beam element of the overall model,to establish a multi-scale tower model containing macroscopic and mesoscale units;finally,consider the large transmission line The system features a multi-tower multi-line system coupling model consisting of a macro-unit tower model and a multi-scale tower model and wires.The static and dynamic analysis of the multi-scale model under wind load is carried out.The calculation results are compared with the beam element model to verify the calculation accuracy of the multi-scale model.At the same time,the stress at the local model of the multi-scale model is given.Deformation response.Due to the uncertainty of wind load and structural resistance,the calculation results of deterministic research and analysis must be deviated from the actual.In this paper,we first introduce random variables for the load characteristics and structural characteristics of the transmission tower line system.Then,in addition to the maximum displacement of the tower top and the maximum stress overrun of the tower leg as the failure mode,the maximum stress overrun of the main material of the local node fine model is also As a failure mode,the SORM is used to calculate the failure probability of the transmission tower line system in each failure mode.Finally,the theory of equivalent extreme event is introduced to calculate the transmission tower line system under the joint action of multiple failure modes.Failure probability. |
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