Probabilistic Analysis of Characteristic Pressure for LNG Tanks

The paper addresses the problem of determining characteristic extreme values of sloshing pressures for structural design. This involves estimating ship motion in a long-term period, fluid motion in the tank, excited pressures and relevant structural responses. Ship motion analysis is based on linear strip theory. In order to investigate the dependence of the sloshing response on sea conditions, a multimodal approach for an initial prediction of pressures in the tank is utilized. However, an appropriate theoretical / numerical approach which can be used for realistic prediction of the most extreme pressure has not yet been developed. Thus, experiments are utilized for the most severe sea states for a chosen tank filling level. In the analysis of experimental short term pressure distribution the choice and fit of probability distribution models is addressed, with due account of different physical mechanisms causing impacts. The most critical tank areas for sloshing loads are briefly discussed. Appropriate dynamic response of the tank structure needs to be investigated by accounting for temporal and spatial distribution of sloshing loads. These two factors are also addressed in the paper.