Analysis On Controlling Internal Force Of Tower In Extra-voltage Transmission Line

Tower structure is very important in transmission line. Its security is very important for structure design. The current code which guide tower designing in transmission line,'Code for design of seismic of electrical installations'(GB 50260-96) and'Technical Regulation of design for tower and pole structures of overhead transmission line'(DL/T 5154-2002) indicate that: it is not necessary that seismic checking calculation is done for self-supporting transmission tower if the seismic fortification intensity is 8 degree or under 8 degree. There is not enough scientific basis about this define. Otherwise, along with the improvement of voltage grading, the height of transmission tower becomes higher and higher, and the span of two towers becomes larger and larger. The earthquake function's influence to structure design turns worse, Whether carrying on anti-seismic checking or not, controlling force play an important role. Now, one subject is the study of controlling force in the course of structural design and code amendment.In this dissertation, on the basis of reviewing the study and design data available, the structural theory of transmission tower is discussed, type tower-large span transmission tower as engineering background and Space truss finite element method as theoretical foundation. Various load cases taken account such as: earthquake effect ,wind load, etc, transmission tower model established by SAP2000 software, the dynamic characters and seismic response are analyzed. the controlling force of the elements on tower are compared whether considering the earthquake effect or not. Then, compare the regularity of the elements'force with the change of wind speed and tower height. So we can get some conclusion as following:1) More modes should be considered according to the modal mass participation ratio when the seismic response of the structure was investinated. We suggest that numbers of the modes whether the modal mass participation ratio achieve 90% or not .2) Force controlled by wind with wind speed variation and height below 185m, and it don't need seismic checking if the seismic fortification intensity is 8 degree or under 8 degree. Because the span of two towers in tower-large span transmission tower is too large, constitution measures should be stiffened on the web materials of the cross arm.3) Generally, whether considering seismic effect or not, the internal force of the diaphragms is not the main facts for its small value during materials selected, we usually select the materials according to slenderness ratio, but the constitution measures should be stiffened because of its confinement to tower.