Investigation of vessel slamming and fatigue using a full-scale test sequence

Abstract

Full-scale measurements were recorded during open-water test sequences on a polar class research vessel. Rainflow cycle counting and Miner’s law are used to quantify fatigue response from recorded strain-time series. Both low-frequency wave bending and high-frequency flexural bending are considered. Acceleration measurements further investigate the latter component using a state-of-the-art slamming-detection algorithm and operational modal analysis. Severe slamming is observed for waves approaching the stern of the stationary vessel as they impact the flat exposed transom. In comparison to the head sea test, a 14 fold increase in slamming count with following waves accrues 46.3 times more damage, with this damage dominated by flexural excitation due to whipping. Furthermore, increased slamming frequency and intensity correspond to increased excitation of the dominating vertical bending modes. This highlights the importance of flexural fatigue and slamming considerations at a design and operational level.