Galloping of a Wind-Excited Tower Under Internal Parametric Damping

The effect of harmonic internal parametric damping (IPD) on the amplitude and the onset of the periodic galloping of a tower is investigated in the presence of steady and unsteady wind. The structure is modeled by a lumped single degree of freedom (sdof) equation and attention is focused on the cases where the unsteady (turbulent) wind activates the external excitation, the parametric one, or both. A perturbation analysis is performed to approximate periodic solutions and the effect of the IPD on the amplitude and the onset of periodic galloping is examined in different cases of loading. It is shown that the IPD substantially improves the reduction in the galloping amplitude for all cases of loading and it has no influence on the galloping onset.