The dynamics of a flexible articulated column in waves

A theoretical analysis is developed for the dynamic response of a flexible articulated column, excited harmonically by regular waves. Viscous effects in the fluid are neglected, but the hydrodynamic loading is evaluated by means of a complete wave diffraction and radiation analysis. The column is idealized by Euler-Bernoulli beam theory. Theoretical results for a doubly articulated column are successfully compared with experimental data from a model tested in random waves, and confidence in the analysis is thereby acquired. This is then emplyed in a parameter study of a range of column configurations. Important conclusions are that hydrodynamic damping plays a major role in limiting flexural resonances, and that strip theory can grossly overpredict or underpredict responses. The existence of cancellation effects is investigated, by recourse to the theoretical relationship between generalized wave force and radiation damping in any mode of vibration: this can result in zero responses at certain frequencies.