Response of transmission lines to multiple support excitation

The effect of multiple support excitation on the response of overhead power transmission lines is analysed. The transmission towers are modelled by space truss elements, while the cable is modelled by straight two node elements that account for the nonlinear geometry of the cable. The structure is subjected to spatially incoherent seismic ground motions. The effects of wave propagation velocity, wave travel and the coherency of the seismic input waves are evaluated. The results indicate that the assumption of uniform ground motions at all supports of a transmission line does not provide the most critical case for the response calculations. It was found that the wave propagation velocity has a substantial effect on the system response. In order to obtain a representative analysis of transmission lines, an accurate estimation of wave velocity is required.