An Area-Specific Survivability Assessment for Passenger Ships

The survivability of a passenger ship after an accident is assessed by a probabilistic framework covering hazards like collisions and groundings. Such assessments are a key determinant  for the internal ship arrangement and layout, affecting ship design and operation, The framework pertains to static assessment, but it is common to use the same damage definitions for dynamic calculations. In the latter case, besides the breach characteristics, the environmental condition selection is of paramount importance. In the specific, irregular waves modelling, it is necessary to simulate the damage scenarios. In the common dynamic approaches to survivability, attention is paid to the significant wave height of the calculation, considering the wave period constant. The wave height is not always reflecting real scenarios but is derived from statistics of collisions (GOALS project). However, wave height and period influence ship dynamic in waves (in intact or damaged conditions), impacting survivability after damage. Aiming to a direct assessment of ship survivability and the probability of loss of lives determination in realistic operational scenarios, it is essential to properly study the influence of combined variations of wave height and periods and their occurrence. In the present study, dynamic simulations are carried out in site-specific conditions derived from the Global Wave Statistics. Critical cases are derived from conventional survivability analyses on a sample passenger ship. The same cases are then analysed using wave height and period combinations typical of the main sea areas of interest for passenger ships. This enhanced analysis allows to clearly identify the limiting environmental conditions for the critical damage cases, evaluating the effective survivability of the ship to a specific damage in an operational area.