Studies On Wind-Induced Dynamic Response And Vibration Control Of Long Span Transmission Line System

Long span transmission line system is the lifeline project as the electric powe's carrier. Comparing with the normal overhead transmission line system, the long span transmission line system has higher transmission tower and longer span. Wind force is the dominant load due to its characteristics. The wind-induced dynamic response of this kind of structures is very complicated because of the interaction between the tower and the lines.A tallest transmission tower in the world, which is a part of the ZhouShan long span transmission line system is studied and a spatial finite element modal of the tower-line coupled system is established in this dissertation. The tower, isolator and the transmission line are simulated with the beam element, truss element and catenary cable element individually. A aeroelastic model is designed with discrete stiffness method and the wind tunnel test of the single tower model and tower-line system model have been conducted with different wind directions and velocities in the turbulent flow.Based on the time-domain analysis and experimental study, the response of the tower can be divided into two parts: background response and resonant response, and the influence of the transmission line is considered in the analysis. The simplified method to calculate the dynamic response is proposed according to the different features of the two parts: the background response can be calculated with the covariance analysis based on the quasi-static presumption;the resonant response can be calculated easier after predigested the transmission line system as a suspended mass pendulum system. The wind-induced dynamic response in frquency-domain is calculated with the simplified method and some important conclusions which will direct the design of long span transmission line system are obtained.The viscoelastic dampers taken as a passive energy absorbing devices are used to control the wind-induced dynamic response of the long span transmission line system for its dynamic characteristics and the emphasis of the discussion is focused on the dampers' optimal placement methods. A hybrid genetic method which is composed of the genetic algorithm and worst-out-best-in search algorithm based on the multi-objects optimization and a ameliorative adaptive weight method: generation compared weight method are presented. The H₂ norm and H_∞ norm of the transmission tower's displacements, the totalnumber of the dampers and the average energy absorption in a damper are selected as the objective functions. Applying the proposed optimal method, the feasible damper distribution within the tower can be obtained. The theoretical analysis and wind tunnel experimental results show the efficiency of the controlling system and provide the theory basis for the erection of the system in the future.