On-board monitoring and estimation of lateral accelerations through extreme value theory

Lateral accelerations experienced on-board of ships with high initial stability, especially in beam waves and at low speed, can be a source of risk for people and cargo. In the present paper, an on-board system that informs the crew on the actual situation of the vessel is described. The system monitors the lateral acceleration and estimates the extreme values that could occur in the short-term. A mid-sized stern trawler typical of the Galician fleet (Spain) has been selected to test the system. Fishing vessels are susceptible to dangerous dynamic phenomena in waves due to their hull form, loading conditions, size and operational profile. The vulnerability of the vessel has been confirmed by the application of the excessive acceleration failure mode, one of the Second Generation Intact Stability Criteria. Results have shown that the operability criterion for lateral acceleration is exceeded in many sea states. The on-board system has been tested against weakly non-linear time domain simulations and time series from experimental tests conducted at the University of A Coruna (Spain) towing tank. The estimated extreme values are close to the ones experienced, confirming the ability of the system to identify potentially dangerous situations.