Dynamic Response Of Transmission Tower-line System Under Rockfall Impact

Transmission tower-line system is a key part of electrical power supply.The analysis and design of the transmission tower-line system lags significantly behind the actual needs compared with the rapid development of China's power system.Under this circumstance,frequent natural disasters entail manifold events of transmission tower-line system break down.This thesis,therefore,systematically studies the dynamic response of transmission tower-line systems under the impact of falling rocks.Dynamic tests and numerical simulations technique were employed to explore the effect of local damage of components,tower response modes,and tower-line coupling on the impact resistance capacity of transmission tower-line system.Since there are limitations in the general-purpose finite element software's built-in coupling method,a multi-scale interface coupling optimization method is then established.The relationship between the stress and displacement of the edge nodes of the interface are obtained by using the principle of virtual work,while the shape function is introduced to determine the equivalent displacement of the edge nodes of the interface.A better selection of coupling region result in improvement of the calculation efficiency while maintaining accuracy.Then,a scaled-model test of transmission tower line system was conducted.Here,Buckingham-? theorem is used to determine the similarity,and corresponding scale test model is made based on that;Single-point vibration pick-up method is used to perform a modal test on the scale model to determine the basic dynamic characteristics of tower model;Multi-mode simulated falling rock impact test was conducted to analyze the response mode of transmission tower under impact of falling rock,as well as the effect of impact angle and impact direction on the structure response,and the coupling effect of transmission tower and conductor vibration during vibration.Meanwhile,the results provide experimental basis for later simulation.Numerical simulation of multi-scale transmission tower model,which is established based on the interface coupling constraint optimization method,was conducted.By comparing the macro model with the multi-scale model,the model was verified;the simulation research was performed under more complex and extensive shock conditions.The four stages of the impact of falling rocks on the structure of the transmission tower were summarized: the initial contact stage,the elastoplastic press-in stage,and the unloading and rebound stage;The damage analysis of the members in the impact area shows that the transmission tower members perform local plasticity under the low impact energy.When the impact effect increases to a certain value,the response growth of various major structures will tend to be flat.