COMPUTATIONAL ANALYSIS OF AEOLIAN CONDUCTOR VIBRATION WITH A STOCKBRIDGE-TYPE DAMPER

An iterative finite-difference scheme is derived to predict the vertical, steady-state, monofrequent, aeolian vibration of a single conductor span with a Stockbridge-type damper attached. This numerical scheme is based on empirical models developed to represent the vortex-induced lift force from the wind as well as the forces of dissipation associated with the conductor self-damping and the damper. The scheme has the capability to account for more than one spatial mode of conductor vibration, travelling-wave effects, conductor flexural rigidity, and damper mass. A two-part numerical analysis is performed in which the finite-difference scheme is applied to simulate aeolian vibrations of a typical conductor with and without a Stockbridge-type damper. The computed results are employed to investigate (a) the steady-state form of conductor vibration, (b) the conductor bending amplitudes near each span end as a function of the vibration frequency and damper location, and (c) the influence of conductor flexural rigidity and damper mass. In addition, results from the finite-difference scheme are compared with solutions from the widely used energy balance method as well as field data on aeolian conductor vibrations. The numerical scheme predicts that, with a Stockbridge-type damper attached near a conductor span end, a travelling wave continually propagates towards that span end during steady-state aeolian conductor vibration. It also predicts that, with no dampers attached to a conductor, steady-state aeolian conductor vibration is essentially in the form of a standing wave.