Collapse Mechanism Of Transmission Tower-line System Under Multi-support And Multi-dimensional Ground Motions

China's electric power demand is expanding constantly with the development of modernization.As the carrier of energy,transmission tower-line system plays an important role in the development of national economy.Its normal work is the most basic condition to ensure the normal proceeding of people's production and life.As one of the countries with frequent earthquakes,the collapse and destruction of transmission tower-line system are of common occurrence in China,which prevent the the post disaster relief from developing smoothly.In addition,the dynamic responses of transmission tower-line system under seismic excitations are very complex.Many studies showed that researches on the seismic behavior of large span structure should take the influence of the spatially varying effects of the ground motions into consideration.Therefore,the study of the collapse mechanism of transmission tower-line system under multi-dimensional and multi-support ground motions is of great scientific significance.Taking the 500kV transmission tower-line system as the research object,the collapse processes of transmission tower-line system under seismic excitations are investigated based on explicit analysis method.The work of this thesis is divided into the following aspects:(1)Based on the power spectrum and the coherence function on base rock,the simulation method of multi-support and multi-dimensional ground motions in the complicated terrain area is carried out.The time history curves aof different points in the complicated terrain area with multiple soil layers are generated.Through the comparison of the coincidence degree of the power spectra and the coherence function,the accuracy of results is verified(2)The mechanical properties and critical instability parameter of angle are studied by a method of combining experiment and finite element analysis.Based on the constitutive model-Tian-Ma-Qu model,the test results of angle steel under cyclic loading are simulated,and the test and analysis results are introduced into the ABAQUS user subroutine,the program can be used to study the subsequent collapse analysis of the transmission tower-line system.(3)The dynamic responses of large span transmission tower-line system under non-uniform seismic excitations are investigated through the shaking table test.Based on the multi-support and multi-dimensional ground motions generated,the model uniform and non-uniform excitations of transmission tower-line system are conducted.The influence of traveling wave effect,coherence effect and local site effect on the structural response are studied.(4)Based on the finite element software,the ultimate bearing capacity and collapse processes the transmission tower under different seismic excitaitions is studied.Considering the mechanical properties of angle member,the collapse processes of transmission tower-line system subjected to multi-dimensional and multi-support excitation,as well as to multi-dimensional and simple-support excitation are studied.The member buckling,inter-story displacement angle and the weak position of the structure under different excitations are analyzed.