Static and dynamic analyses of a transmission tower-line system using a simplified model.

摘要

The optimum design of a transmission line system requires a good understanding of both the static and dynamic behaviors of the system. The computational model should be capable of accurately representing the structure. In common practice, an isolated tower with loading from conductors is analyzed to represent an entire system of towers. It has been found that the behavior of the tower-cable system differs from the behavior of an isolated tower, especially for long span transmission systems. A misrepresentation of the model can lead to serious economical and social losses.;Free vibration analyses of an isolated tower and a transmission line system were conducted using the developed simplified model. The inclusion of cable spans in the model increases the number of mode shapes of vibration. The increase in the number of cable spans also increases the number of mode shapes.;Dynamic analyses of the system with different numbers of cable spans and different boundary conditions were also performed. The wind loading was modeled using a random, stationary and ergodic process. It was found that only two cable spans are required for the dynamic analysis of the system for the applied load case of wind perpendicular to the line. It was also concluded that the spring element can be used to represent the end towers.;In this study, a latticed tower shaft is modeled using a tapered and a prismatic 3D beam-column element to reduce the number of degree of freedom of the structure. These simplified elements were specially formulated and verified to represent detailed tower segments. The elements are incorporated into an in-house Finite Element program called Static and Dynamic Analysis Program. The program also includes all the necessary elements required in the analysis of the transmission line system such as a cable element, truss element, spring element, insulator string element and conventional beam-column element. The 3D cable element used to model guy wires and conductors are assumed to be parabolic in shape with a modified Dischinger's modulus of elasticity. The results obtained from the model using the simplified elements and those obtained from the detailed tower model, for both static and free vibration analyses, are within 7%.