Abstract
This Thesis describes a technique for collecting, moulding and testing naturally occurring ice accretions. Faithful reproductions of the ice shapes were cast in silicone rubber from which wind tunnel models were made. They were tested using a specifically designed wind tunnel rig which measured the aerodynamic lift, drag and pitching moment of the models. From the aerodynamic data the gradients of lift, drag and pitching moment of each ice shape were calculated. The aerodynamic data were consequently used in a two-dimensional two degree of freedom theoretical aerodynamic model which included aerodynamic lift, drag, moment, ice eccentricity, conductor wake effects and the mechanical properties of the conductor. Wind tunnel tests were carried out on a specifically designed wind tunnel dynamic rig. Instabilities of the coupled vertical/torsional galloping were established. Regions of instability were also predicted using a two-dimensional theoretical conductor model. The initial theoretical analysis formed the basis upon which a more sophisticated three-dimensional finite element aeroelastic model was developed. The effects of ice and wind on the natural frequencies and the stability of the conductor were investigated. The use of galloping control devices, the pendulum detuners was also examined. Results showed that the pendulums had a stabilising effect in controlling the vertical/torsional frequency ratio of twin bundles. The vibration characteristics and the stability of quad bundles were investigated using finite elements. In this case, the pendulums shifted the torsional frequencies of the bundle to higher values close to the corresponding vertical frequencies, thus enhancing coupling and having an adverse effect on stability. Finally, limitations in the performance of the pendulum detuners were predicted.