Safety Analysis Of Transmission Tower-line System Under Wind Loadings

As a carrier of power,the transmission tower-line system is an extremely important engineering structure in the power system.In recent years,with increasing height and span of transmission tower-line system,the risk of transmission tower-line system in use has been obviously improved,and the collapse of tansmission tower caused by strong winds occurs frequently.Therefore,the safety analysis of the transmission tower-line system under wind loadings is required,and the reliability of the wind loadings from the specification needs to be checked.In this paper,the 33.3m high upper-type transmission tower is used as the analysis object.The fluid calculation software Fluent and the finite element analysis software Midas Gen are used to numerically simulate the response of the transmission tower-line system under wind loadings.The main work of the thesis is as follows:1.Summarize the basic theory of computational wind engineering and fluid-structure couplingBased on the adverse effects of wind loadings on the structure,the limitations of the current specification on the design of transmission tower-line systems are discussed.The research status of current design methods,dynamic models and wind-induced response of transmission towers are reviewed.The theory of computational wind engineering and the theory of fluid-structure coupling are introduced,which provides a theoretical basis for wind field simulation.2.Established a finite element model of transmission tower-line systemAccording to the principle of shape finding of transmission lines,the shape of the transmission line was completed in Midas Gen,and a beam unit model of transmission tower-line system consisting of one tower and two lines is established in Midas Gen.The dynamic characteristics of the single-line,single-tower and transmission tower-line systems are analyzed respectively.The accuracy of the model is verified.By analyzing the interaction between the transmission line and the tower,it proves to be necessary to consider the coupling of tower-line in the calculation of wind-induced response.3.Numerical simulation of wind-induced structural response of transmission towers under wind loadingsBy establishing the solid element model of the transmission tower and the transmission line,based on the wind load characteristics and considering the unidirectional fluid-solid coupling(FSI)effect,the wind field simulation of the mean wind and the pulsating wind is completed in Fluent,and the pressure on the structural surface is obtained.The reliability of the wind pressure test results is verified by comparing with the similar wind tunnel test results.The results of pressure are applied to the transmission tower-line system model in Midas Gen to obtain the wind-induced structural response using the FSI method.4.Analysis of the safety of transmission tower-line system under wind loadingsConsidering the three conditions of 0° wind direction angle,90° wind direction angle and 45° wind direction angle,the displacement and internal force distribution of the structure are summarized.Time-history analysis is used to find the most unfavorable situation,and the strength and stability of the main components are analyzed and compared with the calculation results of the canonical method.5.Analysis of the safety of transmission tower-line architecture under ice loadingsFor the condition of 90° wind direction,the conditionof 5mm uniform icing is considered and the time-history analysis of the transmission tower-line system is carried out.The most unfavorable situation is by time-history analysis,and the strength and stability stress are compared with the calculated values of the canonical method.The above results show that the strength and stability stress of the canonical method are larger than those of the FSI method,regardless of the ice coating,indicating that the specification is conservative.However,under the 90° wind direction condition,the strength and stability results obtained by FSI method are very similar to those of the norm method,and the minimum error is only 1.2%,indicating that the tower-line structure system based on the norm design under the wind direction angle has a certain potential risk.When considering the uniform ice coating of 5mm,the strength and stability stress of the FSI method are larger than the calculated values of the canonical method,which indicates that the wind loadings value according to the specification is risky under this working condition,and the wind loadings under the working condition is required to be adjusted appropriately.