Nonlinear Analysis of a Dynamical System Being Pulled by Cables

Offshore pipeline must, in certain situation, be pulled by means of cables placed in a barge. An important nonlinear aspect of the wave-induced dynamic motion is the fact that the cable can become loose. This paper analyzes a simplified dynamical model whose steady state is obtained analytically. A feature of this model is that the output steady state frequency changes from ω to ω/2 as the input (wave) frequency ω increases. An order of magnitude analysis shows that this nonlinear effect is of importance for the usual offshore pipeline.