Trans RINA, Vol 153, Part A1, Intl J Maritime Eng, Jan-Mar 2011
to ships having large undivided continuous spaces, such as Ro-Ro vessels
and dynamic wave effects. particular aspect remains a topic for research and debate.
This general formulation is recognisable in the traditional sense by defined righting lever (GZ) parameters, such as maximum heel angle, minimum range and minimum height for intermediate and final stages of flooding:
GZ (metres) Min height
Max heel an
gle Min range
Heel (degrees)
Figure 4: Representation for probability of survival after flooding.
Since s represents cumulative probability distributions, it is difficult to define what this figure means in real terms. For example, if s equals 1 we can say that the vessel has a very high probability of surviving a damage case in wave heights of up to 4 metres. On the other hand, if s has a value of 0.8 we do not easily know which probability is deficient
or regulation.
For passenger ships, a deterministic calculation has been added to ensure that all passenger ships retain the capability to sustain minor damage cases along their full length and still meet the currently accepted minimum levels of heel and residual stability.
2.2 PASSENGER SHIP DESIGN ISSUES
For a modern passenger ship, the damage cases required for evaluation of the Attained Index, A, can run into many thousands. The index alone includes results from 200 to 300 selected cases. As a result, the time taken to complete the whole calculation process is substantially increased. Intermediate stages and cross flooding add to the complexity of the calculations. For example, small cruise ship designers can experience up to 15,000 damage cases taking up to 12 hours of computing time.
The margin line is no longer used as the flood limit restriction. The new regulations use horizontal escape routes, emergency control spaces and openings such as vents, doors and air pipes to determine the maximum intermediate and final equilibrium water planes after damage. This makes these areas much more important in the initial design stages of a passenger ship.
what the associated
distributions are. Herein lies a fundamental and core aspect
of dealing with future developments in the This
Services are no longer protected by one fifth of the breadth relative to the maximum inboard damage extent applied under SOLAS 90. For passenger ships with complex piping systems, these must now be designed to prevent progressive flooding from damaged spaces associated with positive contributions. A probabilistic approach, compliant restricted
however, allows for more diversity in bulkhead arrangements. This by
is somewhat deterministic elements in the new
regulations for side and bottom protection, along with the current application of the regional Stockholm Agreement covering water on deck for Ro-Ro passenger ships, which is based on the traditional deterministic SOLAS 90 and associated B/5 (breadth) longitudinal bulkhead protective locations.
2.3 CARGO SHIP DESIGN ISSUES
In the case of these ship types, the transition to SOLAS 2009 has had an impact, particularly on vessels such as Ro-Ro ships and car carries. This is due to the revised statistics and alterations in application, the most notable being the increased height
in the maximum damage
height and more onerous permeability values. Increased requirements for double bottom heights have also had a particular impact.
2.4 SPECIAL PURPOSE SHIPS
Under the 2008 SPS Code – Code of Safety for Special Purpose Ships, 2008 Resolution MSC.266(84), stability requirements for these ship types have been updated to reflect the new SOLAS 2009 probabilistic damage stability regulations. This Code includes research/survey ships, certain vessels processing living resources from the ocean and those which normally have many persons on board.
The previous regulations adopted a passenger ship
approach where ‘special personnel’ numbers on board were above 200. This has changed to requirements solely based on the passenger ship calculations. The reason behind this is that the basic formulations between cargo and passenger ship types under the new harmonized system are not meaningful these ships
for a variety of Appropriate safety standards have to be in
purposes. place
considering operational practicalities such as able personnel, how many persons are onboard and what training is received The new regulations not only implement a more complex method of calculating damage stability but
in certain cases PLAN APPROVAL require more
onerous ‘passenger’ ship related requirements. 3.
3.1 EXPLANATORY NOTES
The IMO published Explanatory Notes to SOLAS 2009 Chapter II-1 under Resolution MSC 281(85). These notes
the same and therefore do not allow a interpolation between the two. In reality are used
©2011: The Royal Institution of Naval Architects
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