| Due to unbalanced energy distribution in China,ultra high voltage(UHV)transmission lines,supporting high power,long distance and high density transmission,will play an important role in China's economic development.A super high-rise and longspan transmission tower-line system(SHLTTS)is a critical span in an UHV transmission line to cross the river.The height of a SHLTTS will exceed gradient wind height in load codes and the span of a SHLTTS is long.Thus,the SHLTTS is more affected by wind load than conventional transmission tower-line systems.Moreover,using composite structures with concrete-filled steel tube and steel tube,the mass of a super high-rise tower(SHT)is abrupt.Besides,SHTs and strain towers are part of SHLTTSs and the height difference between the two structures is significant.Thus,the transfer process of wind load on conductors will be affected by this significant difference.These characteristics not only have great influence on the wind-induced vibration characteristics of SHLTTSs,but also lead to the lack of the study of wind tunnel tests for the aeroelastic model of towerline systems considering gradient wind height and concrete-filled steel tube.For SHLTTSs,it is necessary to carry out systematic study on wind-induced vibration characteristics,computation models of design wind load and so on.The main contents of this paper are summarized as follows:(1)Wind tunnel tests for the aeroelastic model of a single tower with tower height exceeding gradient wind height were carried out,and the law of wind-induced vibration responses and the distribution of wind-induced vibration coefficients of this tower were analyzed.Through the aeroelastic model of a SHT,wind tunnel tests of atmospheric boundary layer were carried out.Based on wind tunnel tests data,3 different windinduced vibration coefficients were calculated under different wind yaw angle.Using numerical simulations,the influence of gradient wind height on wind-induced vibration responses and wind-induced vibration coefficients were analyzed.Results show that the greatest displacement occurs at 30 degrees along the line,and this wind yaw angle should be considered in tower design codes;considering the influence of gradient wind height,wind-induced vibration responses and wind-induced vibration coefficients of the SHT becomes smaller;distributions of wind-induced vibration coefficients of the SHT are different from those of conventional towers.(2)Based on an inertial force method,the calculation method of design wind load of single towers,with crossarms,diaphragms,gradient wind height and concrete-filled steel tube,was proposed,and the design formulas of the wind-induced vibration coefficient of single towers were derived.Establishing the calculation model of design wind load of single towers,formulas of different correction coefficients of a wind-induced vibration coefficient,with shape,mass,windshield area,gradient wind height and so on,were derived.For towers with cantilevered crossarms,the design formulas of wind load,suitable for conventional towers and SHTs,were derived.The correctness of derivation formulas was verified by examples.The result of example analyses showes that crossarms and concrete-filled steel tube have great influence on wind-induced vibration coefficients and wind-induced vibration responses of single towers.(3)Based on an effective load method,the calculation method of design wind load of single towers,with crossarms,diaphragms,gradient wind height and concrete-filled steel tube,was proposed,and the design formulas of the wind-induced vibration coefficient of single towers were derived.Using the computation model of design wind load based on inertial force method,equivalent resonant wind load was determined.Using a quasi-static method,the computation model of equivalent background design wind load was established,and formulas of correction coefficients,with shape,gradient wind height and concrete-filled steel tube,were derived.For towers with cantilevered crossarms,the design formulas of wind load,suitable for conventional towers and SHTs,were derived.The correctness of derivation formulas was verified by examples.The result of example analyses showes that crossarms and concrete-filled steel tube have influence on the resonance component of wind-induced vibration responses of single towers.(4)A method for wind tunnel tests of the aeroelastic model of SHLTTSs,with Froude number similarity criterion,variable ratio transmission line model,gradient wind height and concrete failure due to tension,was proposed,and wind tunnel tests of this model were carried out.Increasing the elastic stiffness of transmission lines and adopting an accurate variable ratio transmission line model,an aeroelastic model suitable for the SHLTTS was designed.Through this model,wind tunnel tests of atmospheric boundary layer were carried out,and wind-induced response characteristics of the SHLTTS were discussed.Using finite element models,the influence of concrete failure due to tension and gradient wind height on wind-induced vibration responses were analyzed.The results show that wind-induced vibration responses of a prototype tower can be accurately reflected by the design model;wind-induced vibration responses of the super high-rise tower and the conductor contain the response components of each other;considering gradient wind height,wind-induced responses of the super high-rise tower decrease;considering concrete failure due to tension,wind-induced responses of the super highrise tower increase.(5)A calculation model of maximum wind-induced vibration mechanical energy of transmission towers was established,and the transfer law of wind-induced vibration mechanical energy of the SHLTTS was analyzed.Based on stochastic vibration theory,calculation formulas of the maximum wind-induced vibration mechanical energy of transmission towers were derived.Calculating various operating conditions,the influence of transmission lines,wind velocity and gradient wind height on wind-induced vibration mechanical energy and transfer relation of energy between substructures(transmission tower and transmission line)were analyzed.A result show that long-span conductors play an important role in wind-induced vibration characteristics of the SHT.(6)Calculation models of the maximum windage yaw angle of a suspension insulator string and its wind-induced vibration coefficient,suitable for transmission tower-line systems with significant height difference,were proposed.Based on force balance and triangle rule,formulas for calculating windage yaw angle with line shape and line length were derived.Taking a condition under average wind loads as initial calculation values,based on stochastic vibration theory and linear superposition principle,the equivalent static wind load of windage yaw angle was derived,and the calculation method of the wind-induced vibration coefficient of windage yaw angle was proposed.Then,the influence of change in engineering design parameters on windage yaw angle and its wind-induced vibration coefficient were analyzed.A result show that wind velocity,span and ground roughness category have obvious influence on the wind-induced vibration coefficient of the windage yaw angle of insulator strings.(7)Using an equivalent damping ratio and a fluctuating reduction coefficient of tower wind load,the computation method of equivalent static wind load and responses of transmission towers,considering tower-line coupling effect,was proposed.A simplified calculation model of tower-line systems with one tower and two spans was established.Assuming conductor mode shape,the formula of wind-induced resonance response of transmission towers,considering tower-line coupling effect,was derived.The equivalent damping ratio and the fluctuating reduction coefficient of tower wind load used in tower designs were derived.The correctness of derivation formulas was verified by examples,and the parameter study of equivalent damping ratio and fluctuating reduction coefficient of tower wind load were carried out.A result show that when a tower-line separation method is used in tower designs,through the proposed design method,the influence of tower-line coupling can be accurately considered.For SHLTTSs,research achievements provided the method of wind tunnel tests,analyzed wind-induced vibration characteristics,and provided the computation method of design wind load of towers with tower-line coupling.These achievements provided references for the wind resistance design of SHLTTSs. |
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