need help in Damage and Probailistic stability

Discussion in 'Stability' started by sudhir0201, Aug 22, 2010.

  1. wimal
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    wimal Junior Member

    Hi Nettersheim

    What you said is correct, I did not point out the development and history. However for cargo ships regulation was imposed recently compare to passenger vessel.I developed this software in 1987-1991 period when I was in the University of Newcastle upon tyne, UK. It is not a window based software using FORTRAN language at the time. The software is able to calculate damage stability based on deterministic as well as probabilistic base that applied to cargo ship where probability of longitudinal extent, vertical extent and probability of survivability also calculated. Further any transverse extent also taken into consideration depending on the position longitudinal bulkhead. The same regulation given in SOLAS was used to find the attained index of subdivision and then compare with the required index. My project was to optimized subdivision arrangement of ro-ro cargo ship paying attention to damage survivability while investigating proposed probabilistic regulation at the time. Software can be used for hydrostatics, cross curves, Intact stability, stability of any single or multiple compartment damage. Further free trim inclination of the vessel is taken into consideration when estimating damaged righting lever and angles at opening immersion.
    I have used this for estimation damage stability of passenger and Cargo vessels registered in our country and submitted GL and IRS .
     
    Last edited: Sep 24, 2010
  2. sudhir0201
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    sudhir0201 Junior Member

    hi wimal,
    can u help me , doing probabilistic stability for warships(aircraft carrier)?,
     
  3. wimal
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    wimal Junior Member

    Yes I can, Only thing you have to get verify whether cargo ship regulation applies to war ships or not.

    Ths

    Wimal
     
  4. nettersheim
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    nettersheim Consultant

    Wimal, thank you for your reply dated 24/09/2010.
    Take care,
    Francois-Xavier Nettersheim
     
  5. sudhir0201
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    sudhir0201 Junior Member

    dear,wimal
    warships criteria is different from cargo ship. i want to know that what all inputs i required. and how i will proceed ? currently i m using tribon software. but it only having criteria related to cargo ship.now can u help me?,
    or if u don't know then plz tell me procedure of probabilistic stability for cargo ship. as i have no idea about probabilistic stability. i m new in this field. with your help at least i will be able to understand about probabilistic stability. how should i start etc.
     
  6. wimal
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    wimal Junior Member

    Probability means likelihood of something happening. Based on the previous damage statics of vessel, there had been probability distribution function derived for longitudinal extent of damage, vertical extent of damage and damage penetration into the vessel. When considering each damage case as mutually exclusive event, probability of flooding multiplied by probability of surviving which is to be calculated based on the righting lever of the damaged ship for that case of flooding and the summation of same multiplication for all possible cases of flooding should be less than 1 or equal to 1. That means if we define Pi as probability of longitudinal extent flooding, vi as vertical extent of flooding, ri as transverse extent of flooding and si as probability of surviving

    for a particular case of flooding Pi x vi x ri x si is the index. Such index has to be calculated for all possible cases of flooding and added together to get the attained index for the vessel considering all cases are mutually exclusive. Cases of flooding can be each single compartment taken separately, all adjacent two compartment cases, all adjacent 3 compartment cases etc. As the number of adjacent compartment become more, probability of surviving become zero and such cases not need to be considered but has to be verified by damage stability calculation. Ultimately, we compare the attained index with required index which is again based on the historical surviving cases . The requirement is that attained index should be greater than the required index. This is the simplest way of explanation to the probability without going into the deep theory. However for any case of damage stability calculation you should have software to calculate righting lever of the damage vessel for the case of flooding you considered. if you need further help please let me know and bye for the moment.

    If you have to war ship criteria, please send it to me and then I can see what it implies.
     
    Last edited: Sep 26, 2010
  7. sudhir0201
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    sudhir0201 Junior Member

    Dear wimal,
    Thanks for your help , this gives me a rough idea to understand the probabilistic stability. as you said you have to define the index for all possible cases. my question is that how you come to know about possible cases. and how u decide all the probability (Pi x vi x ri x si). suppose for example. ship's length is 200 meter having a max width of 50 m. ships depth is 20m and it has 5 decks of 5 m height, it is having two longitudinal watertight bulkhead,up to deck 4. so how i proceed .you can assume the data to explain me.

    I also don't know which type of data is required for warship calculation. the only thing i know is that its depends upon the seed of torpedo or missile fired, ship's speed etc. thats why i required help from somebody who already done probabilistic stability for warship
     
  8. wimal
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    wimal Junior Member

    I explain every thing according to cargo ship regulation. I do not know whether its is valid for war ship. Assuming so, this is how you select the possible cases. You have to calculate attained index for full load and partial load condition defined in the regulation. Regulation state how to calculate all the probability terms. Depending on the waterline of the loaded condition (let assume that two deck are already under water). Then first you consider damage to each wing compartment separately up to the first deck as set of cases and then damage to wing and inboard spaces up to first deck as another set of cases, similarly two adjacent and three adjacent etc. and then another set similar to above, but between deck one and deck two, another set including both decks together, like wise you have to consider possible cases. If the final waterline under damage goes above third deck, then you have get the 3rd level also involve for another set of cases. All these are hypothetical cases, assuming if it happens but should be in a realistic way ( means port side wing space and starboard side wing space cannot be flooded unless there is cross flooding between tanks.)

    Ok

    Wimal
     
  9. sudhir0201
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    sudhir0201 Junior Member

    Dear wimal
    thanks yr for your valuable support. but i m still not getting properly, can u provide me step by step details of any of the ship so that i will go through that, and it is easy for me to understand. means some document , or u can take any reference. thanks once again........
     
  10. wimal
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    wimal Junior Member

    Please send ur email- i will send u copy copy of a report
     
  11. sudhir0201
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    sudhir0201 Junior Member

    Dear wimal,
    thanks yr, here is my email id- "sudhir.pals@gmail.com"
     
  12. sudhir0201
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    sudhir0201 Junior Member

    Thanks wimal ,
    I got ur file. iI will go through ur calculation so it will take some time, if there is any doubt i will as u, wel which software u used in that particular calculation.
     
  13. sudhir0201
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    sudhir0201 Junior Member

    intact and damage stability

    dear friend,
    i have a question regarding intact and damage stability.,i'll explain with an example.
    suppose we have 6 decks and up to 3rd deck we have watertight bulkheads, above third deck we have an hanger space,and above that we have non watertight bulkheads. i have following doubts.

    1. for intact and damage stability calculation is it necessary to make compartments/blocks up to the weather deck or flight deck.
    2. if there is a opening in hangar expose to the sea. can we take hanger as a free flooded area.
    3. above hanger deck can we take rest of things as free flooded area as there is no watertight bulkhead in that deck.
     
  14. tahtoh25
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    tahtoh25 Junior Member

    please is it possible to use this criteria in autohydro
     

  15. sudhir0201
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    sudhir0201 Junior Member

    no . as i has to do these calculation in Tribon software only, but u can tell me the logic behind the calculation, software may be different but the theories and principle will remain same.
     
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