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. Ongoing harmonization studies, IMO documents SLF 42/5 and SLF 43/3/2, EU project HARDER, Lützen and Rusas (2. Int. Conf. Collision and Grounding of Ships, Copenhagen, DTU, 2001), aim at one single damage stability rule applicable to all kinds of ships. Such a harmonization requires due consideration of both the calculation of the attained index describing the probability of survival, and specification of a suitable minimum level, taking into account the consequences of loss of the vessel. The authors address here the calculation of the Attained Index A. The robustness of the calculation procedure for the Attained Index A is evaluated by considering three ro-ro ferries (PRR1: length over all 194.30 m, subdivision length 178.25 m, PRR2: length over all 194.30 m, subdivision length 192.25 m, PRR3: length over all 68.83 m, subdivision length 68.73 m). The subdivision of each vessel was modeled first in one or two simplified forms (with a reduced number of bulkheads) and later as the actual vessel. This has a dual purpose: 1) To test the software of the different partners in order to verify the robustness against other software and different users, 2) To investigate how the complexity in the modeling of the subdivision affects the Attained Index. The probabilistic damage stability is calculated according to SOLAS, Part B.1 for cargo ships, but with a maximum heel angle of 30 deg. In the calculation of the survivability index s, heel angles of 10, 20 and 30 deg are used; no down-flooding points are defined except for one case. The permeability in the damaged compartments is always set to 95 %, the density of seawater to 1025 kg/m3. The different software programs give fairly similar results in all cases. Differences for each damage zone tend to be larger than the differences in the final Attained Index A. These differences may be due to possible modeling errors. Comparison between Attained Index A for simplified models and the actual built design shows that even large simplifications do not change the Attained Index A significantly.
Robustness of the probabilistic damage stability concept to the degree of details in the subdivision
Sensitivität probabilistischer Berechnungsverfahren zur Havariesicherheit von Schiffen hinsichtlich der Detailgenauigkeit der zugrundegelegten Schiffsmodelle
Ship Technology Research / Schiffstechnik ; 49 , 4 ; 151-159
2002
9 Seiten, 8 Bilder, 7 Tabellen, 2 Quellen
Aufsatz (Zeitschrift)
Englisch
Robustness of the Probabilistic Damage Stability Concept to the Degree of Details in the Subdivision
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