Nonlinear Dynamics in the Motion of Floating Cranes

The nonlinear dynamics of a floating crane is investigated. The motion of the system – consisting of the hull with the crane, the load and a nonlinear mooring system – was found to exhibit various nonlinear phenomena. Operating conditions, in which the motion of the vessel or the load is highly dependent on the initial conditions or disturbances are of special interest. Bifurcations in which a small change of a parameter value causes a large qualitative change of the dynamics often limit the range of save operation.For a floating crane which is periodically forced by waves, different mathematical tools are used to investigate resonances and subharmonic motions. The multiple-scales method allows for the analysis in frequency domain and path following algorithms are applied for a numerical bifurcation analysis. The results of both methods agree very well with each other and both offer tools that could help for the evaluation of operating conditions of crane vessels.