On the quasiperiodic galloping of a wind-excited tower

We report on quasiperiodic (QP) galloping of a tower under steady and unsteady wind flow. The cases where the unsteady wind induces either external excitation, parametric one, or both are considered and perturbation analysis is performed to obtain analytical expressions of QP solution and its modulation envelope. The wind velocity conditions under which QP galloping occurs are discussed for the three cases of excitation. The effect of the frequency of unsteady wind components on the frequency of the QP modulation response is analyzed. Numerical validations of the analytical finding are also presented.