Galloping of iced quad-conductors bundles based on curved beam theory

• We build a finite curved-beam model and a hybrid model based on curved-beam theory for galloping of quad-conductor bundles.
• We compare the results of several models in predicting equilibrium conductor position, natural frequencies, and galloping amplitudes.
• The torsional frequencies strongly depend on the sub-conductor spacing.
• The use of hinge, rather than rigid connection between sub-conductors and spacer, reduces the structural response amplitudes of galloping.

Galloping refers to wind-induced, low-frequency, large-amplitude oscillations that have been more frequently observed for a bundle conductor than for a single conductor. In the present work two different models are built to investigate the galloping of a bundle conductor: (1) a finite curved beam element method and (2) a hybrid model based on curved beam element theory. The finite curved beam element model is effective in dealing with the spacers between the bundled conductors and the joint between the conductors and spacers that can be simulated as a rigid joint or a hinge. Furthermore, the finite curved beam element model can be used to deal with large deformation. The hybrid model invokes the small deformation hypothesis and has a high computational efficiency. A hybrid model based on conventional cable element theory is also programmed to be compared with the aforementioned models based on curved beam element theory. Numerical examples are presented to assess the accuracy of the different models in predicting the equilibrium conductor position, natural frequencies and galloping amplitude. The results show that the curved beam element models, involving more degrees of freedom and coupling of translational and torsional motion, are more accurate at simulating the static and dynamic characters of an iced quad-conductor bundle. The use of hinges, rather than rigid connections, reduces the structural response amplitudes of a galloping conductor bundle.