Study On Vulnerability Of Transmission Tower Line System Under Dynamic Load

As an important project for people’s livelihood,transmission lines ensure the regional power supply and people’s normal production and life.As an important component of transmission line,transmission tower has the mechanical characteristics of small mass and big flexibility.When it is subjected to the dynamic load represented by earthquake load and violent typhoon load,it is easy to be damaged or even collapsed.Once the transmission tower is damaged,it not only affects the normal transmission of power,but also may cause secondary disasters such as fire.The cost of transmission tower reconstruction is also expensive.Therefore,it is very important for transmission It is of great significance to study the damage mechanism and vulnerability of transmission lines.Based on this,this thesis takes a 220 k V transmission line in south China as the research object,uses the finite element software to build the transmission tower line coupling system model,and integrates the measured data of the transmission tower to check the dynamic characteristics of the drum transmission tower line system,the result show that the model can meet the requirements.By making the scale model,the average wind load is simulated as static load applied to many parts of the tower body,and the whole process of transmission tower from intact to partially damaged to completely damaged is simulated.Combined with the experimental results of transmission tower scale model,the maximum stress ratio of the main material at the key parts of the transmission tower body is used to divide multiple performance limit states of the transmission tower.In this thesis,the theory of non-uniform response is introduced.Multiple seismic wave data are selected from the Pacific Earthquake Engineering Research Center(PEER)to input the ground motion in the in-plane direction of the transmission line.The dynamic time history of the transmission line system is analyzed under two conditions of considering the traveling wave effect and not considering the traveling wave effect.The response of the tower top and the tower body is selected for comparison.The analysis results show that considering the traveling wave effect of seismic wave,the displacement response of transmission tower will be amplified and the velocity and acceleration of tower top and cross arm are greatly affected by traveling wave effect.In this thesis,considering the randomness of load input,the peak acceleration of ground motion is modulated,the incremental dynamic analysis of transmission line in-plane and out of plane direction is carried out,and the influence of traveling wave effect on transmission line is considered when acting along in-plane direction.Combined with the results of the reduced scale model experiment,the results of stress ratio of main material is used to determine several performance limit states of transmission tower.The incremental dynamic analysis shows that the displacement response of the top of the transmission tower under seismic load obeys log-normal distribution law.According to the IDA curve in plane and out of the plane,the vulnerability curve inside and outside the plane of the transmission line is drawn.The vulnerability analysis results show that the drum transmission tower studied in this thesis has good anti-seismic performance inside and outside the plane.This thesis introduces the theory of random wind field,establishes the non-stationary typhoon wind field,investigates the influence of wind direction angle on the transmission line,and determines direction out of plane as the control direction of the transmission line wind load.Considering the uncertainty of material parameters in the service process of transmission tower,Latin hypercube sampling is used to generate multiple sets of random model samples.By intercepting the multi-stage typhoon wind load with gradually increasing extreme wind speed and acting along the directionout of plane of the transmission line,the incremental dynamic analysis of the transmission tower line system is carried out,and the IDA curves of the transmission tower top displacement and typhoon wind speed extreme value under multiple sample conditions are obtained,and the performance of the transmission line is evaluated according to the vulnerability analysis theory.The results of vulnerability analysis show that the transmission tower has good wind resistance at the same time.Finally,this thesis summarizes the work done and gives suggestions and ideas for the later work that can be further studied.