Reliability analysis of a ship hull structure under combined loads including slamming loading

During the last decades, much attention has been paid to long-term structural reliability analyses applied to design and maintenance planning of ships. However, many extreme loads occur in short time periods in particular severe sea conditions. In this paper, a random process model of the ship hull girder subjected to still-water, wave- and slamming-induced loads is formulated based on the random process theory covering a short time period during extreme seas in the short time duration of slamming. The correlation of the peak value of slamming- and wave-induced loads is considered according to the fact that the wave and the velocity of the ship are the dominating causes of the slamming. Through the analysis of the stochastic process of limit state function, the reliability is evaluated by means of up-crossing analysis and parallel system reliability method. In a numerical example, the influences of the damping ratio, slamming rate and correlation coefficient on the failure probability are analysed, considering different failure modes. The results show that the buckling failure of the deck under compression is the most dangerous case and the damping ratio influences the impact of the slamming load on the reliability.