A Study On The Probabilistic Damage Stability Assessment Of Surface Combatants

One of the main influence factors to survivability of a surface combatant is her vulnerability to weapon effects and as such the damage stability determines the vulnerability of a vessel. Currently, a surface combatant’s damage stability is mainly assessed upon the deterministic method which assumes several damage cases under several loading conditions, then verifies whether the floating state and stability after damage are satisfied with a series of criteria. The criteria for deterministic method were developed from real life damage incidences of the Second World War, and there have been no significant changes during the course of use. With the development of science and technology, the attack ability of high-end anti-ship weapons are improved greatly, and the high building value of a surface combatant puts forward higher requirements for its survivability, so the applicability and limitation of the deterministic method have gradually led to the concerns of the ship designers and the Navy Department. In addition, the occurrence of marine accidents has the characteristics of randomness and the assessment of a surface combatant’s damage stability should take into account the damage effect of different weapons.Therefore, the deterministic method can’t have a comprehensive assessment of a surface combatant’s damage stability compared with the probabilistic method.However, in assessing the damage stability of merchant ships, the international maritime organization has renewed the rules for many times. SLOAS2009 has coordinated the SOLAS90 standards based on deterministic method for passenger ships with SOLAS92 standards based on probabilistic method for dry cargo ships, forming unified probabilistic damage stability requirements. As a complement to the deterministic method, the probabilistic method needs to be enforced in order to improve the security level of the ship in a damaged condition. Thus, there is a good trend to evaluate the damage stability of a surface combatant by using probabilistic method.Based on the above analysis, in order to evaluate the damage stability of a surface combatant much better, this paper discusses the probabilistic method for evaluating the damage stability of a surface combatant, puts forward a new method named variable interval linear interpolation for the calculation of survival probability and develops numerical procedures. Taken a certain combatant as an example, the 3D modeling and the damage stability calculation were carried out firstly in NAPA software.Then, through calculating the damage probability Pi and the survival probability Si, the subdivision index A is obtained by the sum of the product of Pi and Si for each compartment and compartment group. Finally, selects a subdivision optimization scheme based on anti-wind capacity, and the subdivision index A before and after optimization is compared. Research shows that, by taking the subdivision index A as an evaluation index and considering the damage effect of different weapons and collision, the probabilistic method can realize a quantitative and overall assessment of a surface combatant’s damage stability, thus provides a way to increase the survivability of a combatant by optimization of hull subdivision in primary stage of ship design, and provides some reference for the calculation of the subdivision index A in the formulation of the probability damage stability criterion for the surface combatants in China.