New insights from full-scale measurements into structural response of high-speed catamarans to wave impacts

Increasing demand for efficient high-speed transportation has led to the evolution of high-speed catamarans for both commercial and military applications. In large wave conditions, all ships, including catamarans are prone to encounter waves imparting an impulsive slam load on the structure. Severe slam loads have been known to cause structural damage, while moderate impacts will cause whipping, which may have a negative effect on the fatigue life of catamarans. Extensive full-scale hull stress, motion, and wave measurements have been made during trials in the North Sea and North Atlantic region conducted by the US Navy on a 98 m Incat high-speed catamaran ferry designed by Revolution Design Pty Ltd and built by Incat Tasmania. The Empirical Mode Decomposition technique was used to remove both noise and the rigid body response from the acceleration signals to identify slam events. This was based on prior work by the authors and found to provide more reliable slam identification than traditional methods, but also provided a mechanism to isolate the structural response immediately following a slam, which was investigated in detail in the present study. A key outcome was the finding that slam events initiate from local impacts but produce a global structural response which can be traced over time between sensors, providing information about the impact location. These slam events were categorised based on port and starboard responses, and it was found that individual slams in head seas are rarely symmetric. This is a finding that will not be evident from model tests and simulations, and potentially calls into question the general validity of conducting model tests or simulations in pure head seas to study slams on multi-hull vessels. • Past research examines the magnitude of slam impact forces but not the location. • Tracing delays between sensors shows the propagation of global structural waves. • Tracing structural waves back to their epicentre locates the wave impact point. • Combining data from various sensors aids in locating wave impact. • Validity of ignoring asymmetry in head seas design load case is questioned.