Aerodynamic Characteristics and Wind-induced Responses of Bundled Conductors
|Course||Bridge and Tunnel Engineering|
|Keywords||Coupled conductor isolation-string system Aerodynamic characteristics Wind-induced response Time-history analysis method Load-response correlationmethod Aeroelastic model|
Due to their light weight and extreme flexibility, conductors used in transmissionline systems are prone to a variety of wind-induced vibrations. In current Chinesewind-resistant design practice of conductors, the wind loading due to mean wind isregarded as a static one, and the incomplete span-wise correlation of wind velocity isaccounted for by introducing an additional reduction factor. Consequently, specifictheory with transmission line wind-induced response has not yet been established.Additionally, wind-induced vibration response of bundled conductors is particularlycomplex. In this thesis, with wind tunnel tests and theoretical analysis, theaerodynamic forces and wind-induced vibration of conductor with8sub-conductors isinvestigated, and so is the dynamic response of coupled conductor isolation-stringsystem. The main work is as follows:(1) A review of various wind-induced vibrations and damage of conductors isgiven. And the development of methods for predicting wind-induced vibration aredescribed.(2) Sectional model of the conductor with1m long and with a aspect ratio about1:30is manufactured. The steady aerodynamic forces single conductor in differentvelocities is measured, and aerodynamic characteristics influence factors such asReynolds number、roughness and wake effect are analyzed. Then2,4,6and8conductors bundled wind tunnel sectional model tests with different wind directionsand velocities in the uniform flow are conducted. Hence, shielding effects coefficientof bundled conductor are discussed.(3)Firstly, finite element model of450m long coupled conductor isolation stringsystem is established. Secondly,based on2dimensional wind speed time series, staticwind effect and wind-induced vibration response are analyzed，and gust loading factorunder different conditions are obtained. The effect wind profile, aerodynamicdamping, spanwise correlation and roughness of ground on gust loading factor arediscussed. According to frequency domain analysis, wind vibration response can bedivided into two parts: background response and resonant response. Gust loadingfactors in different categories of terrains are obtained through simplifying two typesof responses，and the result of frequency-domain analysis is agreement with theprevious time-domain analysis. Finally, the result of theoretical analysis and Chinese design codes are compared, some reasonable suggestions are proposed accordingly.(4) The wind-induced response of conductors is further studied with aeroelasticmodel wind tunnel test. Based on Davenport’s method, the distorted aeroelastic modelis designed and constructed, the modal parameters of the aeroelastic model isexperimental obtained to confirm the model accuracy. The model is tested in smoothand turbulent wind to measure the mean response and fluctuating response. Theresults are compared to the numerical predictions. Some influencing effects causingthe difference between test and prediction are discussed.