Indentification of slam events experienced by a high-speed craft

Ship structures are prone to fatigue cracking due to fluctuating loads caused by the seaway. This is especially the case for high-speed craft, as the slamming loads and associated response have been known to have a significant impact on the stress magnitudes experienced by the structure. Therefore, slamming may have a considerable influence on the fatigue life of high-speed craft when compared to accounting for the global wave induced stresses alone. The identification of the number and intensity of slam impacts of a vessel is used to build probabilistic theories of slamming occurrences. With respect to fatigue life, identification of slam events enables the evaluation of the influence of slamming and the associated whipping response on different areas of the vessel in a range of speeds, headings and sea states. Such knowledge supports informed decision-making in regards to the sustainability and maintainability of the vessel. This paper presents an investigation into various methods for identifying slams for structural response analysis. Full-scale measurements of hull girder stresses of an aluminium high-speed patrol boat are utilised to explore the characteristics of slam events that are significant in structural integrity assessment. The approach to analyse full-scale time records, decomposition of the wave-induced and impact components of stress, and definition and detection of slam events are discussed