Longitudinal Strength Calculation of Tankers

Discussion in 'Stability' started by athvas, Sep 2, 2014.

  1. athvas
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    athvas Senior Member

    Hi

    Could anyone have the extract of the Rules and regulation BV for Longitudinal Strength Calculation . Plz share
     
  2. NavalSArtichoke
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    NavalSArtichoke Senior Member

    BV provides web access to their rules at this link:

    http://www.veristar.com/portal/veri...eneralinfo/giRulesRegulations/bvRules/bvRules

    Scroll down to 'Rules for the Classification of Steel Ships' (NR 467) and click on the link there. The pdf version of the BV Rules come in several parts.
     
  3. athvas
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    athvas Senior Member

  4. athvas
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    athvas Senior Member

    Hi

    In the Longitudinal strength calculation, I am getting a Max bending moment of 2372 MT-m (Hogging) in Lightship condition .
    How to check this with the rule requirements. Any Formula is there in class rules to check the limit.
     
  5. TANSL
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    TANSL Senior Member

    YES, any regulations having formulas to calculate the maximum permissible bending moments in both conditions, hogging and sagging; not the lightship but in the worst possible loading conditions.
     
  6. athvas
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    athvas Senior Member

    Could you please send me the extract or pdf preferably BV regulation i searched but couldn't find where it is.
     
  7. daiquiri
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    daiquiri Engineering and Design

    That's quite odd, because I have found it in less than 3 minutes through the link given by NavalsArtichoke.
    And it is not even my job to go through the rules, read them and understand them. That would actually be your job. ;)
     
  8. TANSL
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    TANSL Senior Member

    daiquiri, thanks for answering exactly as I would have done.
    Athvas, I'm afraid you have no choice but to work a little.
     
  9. athvas
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    athvas Senior Member

    TANSL, Daiquiri,
    I have got that i just want to know whether i've got the correct one or not.
    Anyway thanks

    2.2.2 If the design still water bending moments are not
    defined, at a preliminary design stage, at any hull transverse
    section, the longitudinal distributions shown in Fig 2 may
    be considered.
    In Fig 2, MSW is the design still water bending moment
    amidships, in hogging or sagging conditions, whose absolute
    values are to be taken not less than those obtained, in
    kN.m, from the following formulae:
    • hogging conditions:
    MSWM,H 175n1CL2B(CB + 0,7)10 –3 = – MWV,H
    • sagging conditions:
    MSWM,S 175n1CL2B(CB + 0,7)10 –3 = + MWV,S
    where MWV,H, MWV,S are the vertical wave bending moments,
    in kN.m, defined in [3.1]
     
  10. daiquiri
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    daiquiri Engineering and Design

    When you have these doubts, considering the importance of the project it is always a good practice to get in contact with your local BV office and have all the necessary clarifications from them.
    It would be a good idea to do it right at the beginning of the design stage, to make sure that you are proceeding with the correct data.
    Cheers
     
  11. NavalSArtichoke
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    NavalSArtichoke Senior Member

    In general, the bending moments obtained from one of the formulas is the Class Rulebook are basically for the design of the midship section of the vessel.

    If you have a vessel which is already built, what you must do is calculate the properties of the midship section, primarily the section modulus to the main deck and the bottom shell, and use the bending moments from a longitudinal strength calculation to determine the maximum bending stresses in your vessel. The Rule bending moments, and hence the required section modulus of the hull girder, are usually developed so that the max. bending stresses in a particular vessel are kept below a certain figure, which varies depending on the material used in the hull construction.

    The bending moment and bending stress calculations are just the basic ones considered nowadays. For vessels like tankers and bulk carriers, other types of calculations, like analyzing the hull girder for shear force and buckling, may also be required by the Class society depending on the vessel's size and service.
     
  12. athvas
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    athvas Senior Member

    Thanks NavalSArtichoke
     
  13. NavalSArtichoke
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    NavalSArtichoke Senior Member

    You don't want to spoil your day by having this happen:

    [​IMG]
     
  14. athvas
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    athvas Senior Member

    why does it happen?
     

  15. NavalSArtichoke
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    NavalSArtichoke Senior Member

    In this particular case, the Class society is still investigating, which is difficult since the vessel eventually broke in two, and both halves sank in the Indian Ocean in 2013. It is imperative that the investigation be completed, regardless of the difficulties, because there are several other vessels built to the same design which are still operating.

    http://en.wikipedia.org/wiki/MOL_Comfort

    In the case of large container ships, you are dealing with vessels which have very little structure at the main deck, due to providing hatches for stowing containers below deck. Also, it appears this particular vessel suffered a failure just forward of the machinery space, which suggests that there is some sort of structural discontinuity in the hull girder which possibly started the failure. Perhaps the final report of the investigation team will shed light on the cause of failure.
     
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