| In this thesis, we propose a method to estimate the mean number of level upcrossings for the degrees of freedom (and/or their first and second derivatives) of a structure submitted to random excitation such as wave forces. Although this method could be applied to several types of systems, we are especially interested here in the study of the behaviour of an high speed ship for the comfort of passengers. The non linear modelization of the system and the representation of sea waves as a Gaussian stationnary process allows to have a different approach of problems like seakeeping than purely hydrodynamic and deterministic methods. Criteria of comfort may be given by statistics of the number of level upcrossings and a statistical analysis allows, by describing... |
