Study On Seismic Performance Of UHV Transmission Line Tower Structure

UHV(Ultra High Voltage)transmission line tower structure is an important part of power transmission equipment,which has the characteristics of large height,long span,large flexibility and complex tower line coupling effect.In the past,transmission tower structure was destroyed in many earthquakes,which caused huge economic loss and social impact.The influence of wind,ice and other loads is mainly considered in the design of transmission line,and the seismic performance of UHV transmission tower structure is not clear yet.In this paper,the seismic performance of UHV transmission tower structure is taken as the research object.By means of seismic shaking table test,finite element numerical simulation and performance-based seismic engineering theoretical analysis,the dynamic characteristics of UHV transmission tower structure,tower line coupling effect,bidirectional ground motions,traveling wave effect and site effect on the seismic performance are studied.The damage index and damage grade of UHV transmission tower structure are studied by he prototype test and numerical simulation research,and the seismic vulnerability of UHV transmission tower structure is studied by cloud analysis method.The main work and achievements of this paper are as follows:(1)Shaking table test of UHV wine cup type transmission towerThe shaking table test models of UHV transmission tower,ground wire,insulator and equivalent tower are designed.The dynamic characteristics of single tower model,single tower hanging lumped mass model,three tower two line model and five tower four line model,the seismic response under small,medium and large earthquakes,tower line coupling effect,bi-directional ground motions and traveling wave effect are studied by shaking table test.(2)Numerical simulation of UHV transmission tower structureThe finite element software power tower,which uses Open Sees as the solver,is developed to simulate the shaking table test of UHV transmission tower.The finite element model of UHV transmission tower and the finite element model of five tower four line are established to analyze the dynamic characteristics and seismic time history response.The correlation between the analysis results and the test results is good,which shows that the finite element model can simulate the seismic response of the system well.(3)Study on seismic fortification classification of UHV transmission tower structureCombined with the seismic fortification objectives of power facilities,the seismic fortification objectives of UHV transmission tower structure are proposed.The seismic fortification classification method of UHV transmission tower structure is proposed,response spectrum analysis and time history analysis are carried out for UHV transmission tower of wine cup type.By using the beam-bar hybrid model,the seismic response of UHV transmission tower under different site types and different seismic fortification intensity is obtained,which he combination of seismic effect and wind load effect is considered.By comparing the seismic load effect stress ratio with the conventional load effect stress ratio,the seismic fortification demand coefficient is introduced to determine the seismic fortification classification of UHV transmission tower of wine cup type.(4)Prototype test simulation and damage classification of UHV transmission towerThe results of finite element simulation are in good agreement with the results of internal force and displacement of prototype test tower ZM2,which verifies the feasibility of obtaining structural damage index of UHV transmission tower by finite element simulation method.The damage level of UHV transmission tower and the corresponding macro damage phenomenon are proposed.The modified interlayer displacement angle ISDR is introduced as the damage index of UHV transmission tower.The damage grade of UHV transmission tower is divided by statistical analysis.(5)Seismic vulnerability analysis of UHV transmission tower structureBased on the theory of performance-based earthquake engineering proposed by the Pacific earthquake engineering center of the United States,a probabilistic earthquake demand framework for UHV transmission towers is proposed.The seismic parameters IM are Sa(T1,2%)and PGA.The seismic demand parameter EDP is ISDR.40 ground motions are selected without considering the near-field vibration.The seismic time history analysis of the UHV transmission tower ZM2 is carried out,and the seismic demand model of the UHV transmission tower is established by using the cloud chart method.The vulnerability analysis is carried out,and the vulnerability curves of each damage level are obtained under different damage indexes.The hazard functions of different sites are obtained by the hazard analysis of the site,and the hazard analysis of the probability seismic demand is carried out.The probability seismic demand hazard curves of different sites with the modified interlayer displacement angle ISDR as the EDP parameter are obtained.