Abstract
The paper complements an earlier publication by the authors addressing the probability of survival in the IMO framework for damage stability assessment, the s-factor. The focus here is on the probability of occurrence of a certain damage scenario (breach), conditional on its dimensions and location (centre and port or starboard side), the p-factor. Pertinent assumptions and limitations are explained, following its evolution for specific application to passenger ships. Attempts to provide analytical descriptions of the damage breach distributions as tetrahedra shapes positioned along the ship length whilst accounting for changes in ship geometry, structural arrangements, and subdivision for consumption by the wider profession has led to misconceptions and misunderstandings of what exactly the p-factor is in the context of probabilistic damage stability calculations. This is evidenced by the fact that the same original damage breach distributions, derived in Project HARDER, based on largely cargo ships with the age spread over the last three decades of the previous century, are still being used today for all ship types, including modern passenger ships. Filling this gap, a new database for passenger ships developed in the EC-funded Project FLARE, is briefly presented, leading to new damage breach distributions specifically for passenger ships. It is believed that this paper will throw considerable light in enhancing understanding on the p-factor, which has been cluttered with unnecessary complexity from the outset.
Highlights
The probabilistic assessment of ship survivability after an accident should be a comprehensive process estimating the conditional probability of losing ship stability in the wake of a casualty
The identification of d ferent accidents into collision and grounding is in line with the definition of accident typ Keeping in mind the 1995 SOLAS Conference and scope of the FLooding Accident REsponse (FLARE) project, worldwide accidents during the last 20 years have been investigated
Focussing on the requisite data for such calculation/simulation, no input is more important than the damage breaches for each related hazard and associated probabilistic content, the so-called p-factors
Summary
The probabilistic assessment of ship survivability after an accident should be a comprehensive process estimating the conditional probability of losing ship stability in the wake of a casualty. SOLAS provides a classification of the safety level of a ship based on the evaluation of indices instead of promoting a direct approach for the estimation of flooding risk In such a case, the resulting probabilistic assessment neglects relevant aspects for ship survivability, such as the operational area and operating environment, the structural arrangements, the breaches definition and distributions and the vessel type. Whilst the s-factor relates to the probability of a ship surviving a given damage (breach) in each loading condition and environment [4], the p-factor is used to define the probability of occurrence of a certain breach in each one of the pertinent hazards (collision, side and bottom grounding) conditional on its dimensions and location (centre and port or starboard side) This entails the need for probabilistic information pertaining to each of these elements, which is provided by the marginal distributions of the breach dimensions and location. Iannoptahretriceulleamr,etnhtewfahcetrtehcaotnthfuespiornobparbeivliatiylst,eirnmteirmmpsliocfitwinhattheexactly p-facttohrisdoise,shnoowt cithcaanngeb,eounsleydthtoe icmonpdroitvioendpameratagienisntagbtiolittyh,ehdoawmiat gisecsaizlceuilnataedgiavnedn hloo-w it is cationaipnptlhieedshoippt.imAsalalyr.eIsnulpt,aervtiecnultahro, uthgehftahcet cthoantcethpet hparos bbaebeniliatyrotuenrmd fiomrpdleicciatdinestihtehpas-factor not foduonedsannoyt crhealnagpe,polinclaytitohne icnonshdiiptiodnespigerntaiinnsinogfator athseddaammaaggeesstaizbeilintyaisgicvoenncleorcnaetdio.n in the Esahcihp.oAf tshaesreesausplte, cetvsewnitllhboeugfuhrtthheercaodndcerepstshedasinbetehne faorloluowndinfgorsedcetcioandse.s it has not found any real application in ship design in so far as damage stability is concerned
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