| The transmission tower-line system is a highly elevated and largly spanned lifeline engineering project that inevitably faces various natural disasters during its service life,such as earthquakes and high winds.Currently,research on natural disasters of transmission towers mainly focuses on the analysis of the effects of individual natural disasters,and lacks in-depth research on the dynamic characteristics of transmission towers under the coupled effects of multiple natural disasters.In order to study the dynamic response change of the transmission tower structure under the coupled earthquake-wind load,this thesis uses ABAQUS software to establish an analysis model of a ±1000 k V ultra-high voltage transmission tower,and conducts numerical simulations on the seismic-wind coupling working conditions of the tower in the elastic and elastoplastic stages,exploring the influence of uncertain variables of wind loads on the dynamic characteristics of the structure.The main contents are as follows:1.Based on the ±1000 kV ultra-high voltage transmission towers of the Quan Dong-Wan Nan transmission line project,a refined "three towers and four lines" finite element model is established.According to the seismic response spectrum reflected by the transmission tower standard,earthquake response spectra and wind load dynamic time histories that comply with the "Technical Specifications for Structural Design of Overhead Transmission Line Towers" are selected.Numerical simulations are conducted on the elastic stage of the transmission tower under unidirectional seismic action and unidirectional seismic-wind coupling action,in order to study the influence of wind load on the unidirectional seismic response of the ultra-high voltage transmission tower in the elastic stage.The research results indicate that wind loads have a significant impact on the seismic response of transmission towers,and the influence of wind loads should be fully considered in their seismic design.2.Combination with the changes in the dynamic response of ultra-high voltage transmission towers under the coupled effects of unidirectional seismic and wind loads,numerical simulation analyses are conducted on the working conditions of multi-directional seismic-wind load coupling in the elastic stage of the transmission tower.Further research is carried out on the influence of uncertain variables such as wind speed,wind direction,and the time of seismic-wind load interaction on the multi-hazard dynamic response time history of the ultra-high voltage transmission tower.3.A method for determining the collapse state of ultra-high voltage transmission towers is proposed based on the basic principles of member failure criteria.This method comprehensively considers the influence of the aspect ratio of the main members of the tower structure and the plate effect of the nodes.The method is validated by comparing the results of full-scale tests and numerical simulations of the ZC30302 ultra-high voltage transmission tower under design failure conditions.The test results and simulation results of the ultra-high voltage transmission tower’s failure condition show that the main members above the tower’s foot first reach the compressive capacity limit,causing local compression and bending instability.The entire structure then collapses along the direction of this member,verifying the effectiveness of the collapse analysis method.4.Based on the proposed analysis method for transmission tower collapse,a method is developed to identify the failed members of the tower during the seismic-wind coupling analysis in the elastic-plastic stage of the tower.This is achieved by adding the attributes of life and death elements and stress-related ABAQUS subroutine software in the dynamic response analysis of the tower under seismic-wind coupling conditions.The effect of wind speed and direction changes on the structural stress state and collapse mode is also analyzed. |
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