Wind-Induced Response Analysis And Equivalent Wind Loads Of UHV Transmission Tower

The study on the disaster tolerance of transmission tower-line system is still in the initial stage, hence a lot of defects in many aspects, such as mechanism of disaster load, structure analysis method, design theory and vibration control; consequently, the collapse and damage of transmission tower happen occasionally, resulting in huge economic losses and thus serious impacts on national economic construction and life orders. Wind load is the primary dynamic load of transmission tower-line system, so the correctness and accuracy of analysis on dynamic wind effect will directly affect the safety and rationality of structure. Therefore, it is necessary to further research transmission tower-line system in aspects of wind load action model, wind-induced response, equivalent wind load as well as wind tunnel experiment. Focusing on wind-induced response and equivalent wind load of transmission tower, this article mainly reaches achievements as following:(1) This article initially solves the problem about aeroelastic model design of lattice transmission tower. Owing to the light structure and big stiffness of lattice transmission tower, it is impossible to realize aeroelastic mode design for lattice transmission tower in traditional aeroelastic model design method, but the method of rigid section plus V-shape spring strip can simulate the dynamic characteristics of transmission power structure.(2) Aerodynamic damping is an important parameter for wind-induced response analysis on transmission tower structure. Through the combination of HHT method and RDT method, this article realizes aerodynamic damping identification of transmission tower-line system under ambient excitation, providing a basis for the wind-induced response analysis of transmission tower-line system.(3) According to the technical principles of high frequency balance and based on the quasi-steady assumption condition, this article derives a computing formula of space distribution of wind load on transmission tower, providing an important channel for the study on wind-induced vibration of transmission tower as well as a kind of convenient and reliable development of force measurement range of high frequency balance.(4) Through analysis on natural vibration characteristics, this article determines the simplified model of shear-bending storey model as used for dynamical computation; according to quasi-steady assumption, it is considered that the redistribution of incoming flow in structure surface can be ignored, the along-wind fluctuating wind load on one point of the structure is merely related to the wind speed at this very point, and thus the along-wind load action model of transmission tower is defined. Across-wind load and torsional wind load acting on the structure mainly result from the interaction of turbulent wind and separated shear flow with structure aspect and the combined action of wake excitation and random vortex shedding, and furthermore are significantly affected by the structural shape itself; therefore, across-wind load and torsional wind load are no longer applicable to the across-wind load distribution that is transformed directly from across-wind speed spectrum and derived through section estimation method according to the base bending moment from HFFB experiment. This article also develops finite-element CQC method, SRSS method and pseudo excitation method that can be used for transmission tower coupled buffeting analysis.(5) Harmonic synthesis is a simulation method of stochastic process, which is of high precision and unconditional stability. Based on the synthetic method of single-dimensional multivariable stochastic wind field, this article introduces the impact of cross spectrum of vertical and longitudinal turbulent wind velocity; after examination of spectrum density function and other related functions of simulation samples, it is verified that with this method, multi-dimensional multivariate stochastic samples meeting relevant requirements can be simulated accurately and effectively; on above basis, time domain buffering analysis of transmission tower-line system is realized.(6) This article develops the study on along-wind equivalent wind load of transmission tower based on LRC method. Considering the affect of cross-section contraction of transmission tower structure, this article derives a correction coefficient of mode shape for the generalized force spectrum of the first mode of simple transmission tower in along-wind, across-wind and torsional directions. In the three dimensional wind load cross-spectrum derived based on section estimation method, this article studies the equivalent wind load in three orthogonal directions of transmission tower structure.