Response Of Free Standing Flexible Cylinders To Waves

Abstract

The effects of the surrounding water on the dynamic response of flexible, free standing, cylinders fixed at their base, is studied using linear diffraction theory and two different solution approaches. The first one uses a consistent transmitting boundary to reproduce the water, while the second expresses analytically the solution in terms of the natural modes of vibration of the water and of the structure. This approach, used first by Liaw and Chopra (Report EERC 73-25, University of California, 1973) proves to be very efficient and accurate. Results are presented in terms of change in the effective natural period of the cylinder due to the presence of the water, and the effective damping, considering both an incompressible and a compressible fluid. The same formulation is used next to determine the dynamic response of these cylinders to wave action. The results (base shear and overturning moment) for the flexible cylinders are compared to those that would be obtained assuming a rigid cylinder (only diffraction forces).