Research On The Collapse Of Transmission Tower-line System Under Strong Earthquake

As the carrier of electricity, high voltage and ultra high voltage transmission tower-line systems are important lifeline engineering. In order to solve the problems of energy and environment in the eastern region of China, the long distance transmission line construction is very rapid. In addition, China is one of the countries in the world whose earthquake disasters are very serious. The damage to the transmission tower-line system always occurs during the past earthquake. The conditions of large span transmission tower-line system would affect the supply of regional electricity and disaster relief directly. Therefore, it is of vital importance and realistic meaning to make sure the safety of large span transmission tower-line system. Based on explicit analysis method, the collapse of large span transmission tower-line system under strong earthquake is simulated and the duration effect of ground motions on structural damage is investigated. The four aspects of research work done in this thesis are listed as follows:(1) Considering material nonlinearity and geometric nonlinearity, the three dimensional models of steel pipe tower and large span transmission tower-line system is established based on practical engineering. The dynamic characteristic analysis of steel pipe tower and large span transmission tower-line system is conducted to realize the dynamic characteristic of structures. The effect of joint mass and side tower on characteristic of structures are studied respectively.(2) Considering material damage effect and member buckling effect, the user material subroutine is complied to simulate the compressive and tensile response of steel pipe. The effectiveness of the program is verified by tests of single steel pipe under cyclic axial loading. The critical compressive stress of steel pipe which is calculated by buckling analysis is introduced into the program as the judgement standard of member buckling. Based on this subroutine, the ultimate bearing capacity of steel pipe tower under longitudinal and transverse earthqauek excitation is investigated.(3) Based on two element failure modes and the collpase criterias of transmission tower, the collapse simulation of large span transmission tower-line system under single-component ground motion and multi-component ground motion is conducted respectively using dynamic time history method. The type and position of initial fracture element, damage distribution, fracture reasons and weak region of large span transmission tower-line system are studied. The result can provide the meaningful references for the seismic design and reinforce of transmission tower.(4) Seismic duration effect on the structural nonlinear seismic response and damage accumulation is important. The Arias intensity is selected as judgment of duration of ground motions. The effect of duration effect on the number of failure element, the damage degree of failure element and the collapse of large-span transmission tower line system is studied.