Page 286 - Practical Design Ships and Floating Structures

Practical Design of Ships and Other Floating Structures 26 I
You-Sheng Wu, Wei-Cheng Cui and Guo-Jun Zhou (Eds)
0 2001 Elsevier Science Ltd. All rights reserved

SHIP DESIGN USING PROBABILISTIC DAMAGE STABILITY
RULES - A SENSITIVITY STUDY

Preben H. Lauridsen, Jmgen Juncher Jensen and Jan Baatrup
Department of Mechanical Engineering
Section for Maritime Engineering, Building 10 1E
Technical University of Denmark
DK 2800 Lyngby, Denmark

ABSTRACT

The current IMO resolutions contain two different probabilistic damage stability regulations: A.265 for
passenger vessels and SOLAS Part B-1 for dry cargo vessels. However, ongoing harmonization studies
as those presented in the IMO documents SLF 42/5 and SLF 431312 aim at one single damage stability
rule applicable to all kinds of ships. Such a harmonization requires due consideration of both the calcu-
lation of the attained index describing the probability of survival, and specification of a suitable mini-
mum level, taking into account the consequences of loss of the vessel.

The present paper addresses the calculation of the Attained Index A. The first part considers the varia-
tion of A with the degree of details in the modelling of the compartmentation. The exemplified vessel
is a recently built Danish ferry and both the SOLAS Part B-1 and the SLF 43/3/2 proposals are applied.
The contributions from single and multiple compartment damages are identified. The reason for the
different predictions from the two calculation procedures is discussed. The conclusions contain guide-
lines for the level of details needed in the geometrical definition of the vessel to predict the Attained
Index A with acceptable accuracy.

The second part of the paper considers the variation of the Attained Index A with change in main pa-
rameters in the preliminary design phase. The main conclusions are that the height of the main deck
may influence the attained index by up to 60 per cent for the present vessel, whereas the length of the
machinery room can change A by up to 20 per cent. This illustrates the importance of the horizontal
subdivision in the current probabilistic damage stability rules.

KEYWORDS
Ship design, Probabilistic damage stability, Attained Index A, Watertight subdivision