Research On Seismic Behavior Analysis Of Long Span Transmission Tower-line System Under Multiple Support Excitations

Long span transmission tower-line system is a vital lifeline engineering, compared with the usual transmission line, it is of high structure and large span of tower body,as well as obvious of tower-line coupling. Therefore, it has a very important theoretical meaning and practical engineering value in considering the long span transmission tower-line system of seismic input problems. With practical engineering background, the paper researches differences dynamic responses of the system between multiple support excitations and simple support excitation and its effect factor by earthquake. The security issues of long span transmission tower-line system are discussed in multiple support excitations.Firstly, in this paper, using beam elements, rod elements and cable elements, large cross-transmission towers, insulators and transmission lines were simulated accurately. Finite element model of large transmission towers across the line coupling system was established. Then, with the result of deadweight and non-linear static of transmission lines at initial stress state as initial state, the dynamic traits and interactions of large single-span transmission tower, transmission lines and tower-line system were analyzed.Secondly, the horizontal and vertical seismic coherency functions were treated using Harichandran of coherency function and LIU Xian-ming's model. Harmonic synthesis of FFT technology proposed Professor Ye Ji-hong of Southeast University simulates ground motion input time process, which meets the above-mentioned coherent model. Parameters were set in a specific applications referring to specifications and documentation. While, adopting measures,the impact of discrete data was eliminated. Five grades whose apparent velocity is 50m/s, 100m/s, 200m/s, 300m/s, 500m/s respectively are chosen to simulate the ground motion.Thirdly, considering the influence of the non-linear wire, applying time history analysis method, structure dynamic responses of large single-span transmission tower and tower-line system were analyzed under simple support excitation and multiple support excitations of different wave velocity and horizontal seismic action. Base on aspects of the displacement, torsion, axial force of rod pieces, base shear, spool force and displacement of lead, seismic performance was evaluated.At last, comparing with the covered ice, and different span tower-line system, and different direction of earthquake wave, as well as different tower type, structure dynamic responses and variation of the long span transmission tower-line system were analyzed under simple support excitation and multiple support excitations, providing theoretical basis for the long span transmission tower-line system design.The results show that dynamic characteristics of glass-type tower are more complex than single tower. Because of appearing coupled space modes of vibration, long transmission tower-line system has a longer period, vibration modes of denseness, and lower fundamental frequency. The horizontal and vertical seismic under multiple support excitations have larger torsion, axial force of bar piece nearby support area, and influences of base reactions. The main actions of displacement of lead line are lateral under the above earthquakes. Meanwhile, under different effect factor, the maximum displacement, torsion effect and member internal force of long span transmission tower-line system by multiple support excitations are obvious differences by simple support excitation. It is necessary to consider these effect factors deeply, to ensure the long span transmission tower-line system safety under the seismic action.