Imo Weather Criteria For Pontoons

Discussion in 'Stability' started by nithink55, Sep 3, 2014.

  1. nithink55
    Joined: Jun 2013
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    nithink55 New Member

    Good day everyone,

    could please guide me to complete the runfile of Imo Weather Criteria For Pontoons.
    "The static angle of heel due to a uniformly distributed wind load of 0.54 kPa
    should not exceed an angle corresponding to half the freeboard for the relevant loading condition, where the lever of wind heeling moment is measured from the centroid of the windage area to half the draught."

    tan theta = (FB/2)/(B/2).

    how to add this condition in run file

    "
    clear
    clear report

    read 1.GF

    LBP 0 to 24 f
    LWL 24

    limit off


    Limit title IMO pontoon creiteria
    Limit (1) area from 0 to max > .08
    Limit (2) Angle from 0 to ra0 > 20
    Limit (3) GM at Equil > .15

    note Lightship condition


    Delete all weights
    WEIGHT 35,12f,0p,.756u

    TANKS (*) INTACT
    LOAD (01ballast.p) 0%
    Load (04ballast.s) 0%
    Load (02dirtyoil.p) 0%
    Load (03dirtyoil.s) 0%
    Load (05ballast.p) 0%
    Load (08ballast.s) 0%
    Load (06dirtyoil.p) 0%
    Load (07dirtyoil.s) 0%

    SOLVE
    so
    STATUS CART
    STATUS FLOAT DW WE DI CRT /FSM
    ra /lim /notes
    limit off

    roll imo
    roll ?
    wind (pressure)
    0.055
    hmmt wind/const
    SOLVE
    hmmt report
    limt title IMO pontoon creiteria

    ra /lim /notes

    "
     
  2. sameedck
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    sameedck Senior Member

    :) Will try to get back
     
  3. athvas
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    athvas Senior Member

    This can be checked in autocad itself. Steady angle of heel < 0.5 * Freeboard
     
  4. nithink55
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    nithink55 New Member

    Thanks for your reply :)
    can you paste the exact text(code) to be used
     
  5. TANSL
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    TANSL Senior Member

    Interesting formula.
    What units should be used ?.
    How this approach corresponds to the IMO stability criteria?
     
  6. NavalSArtichoke
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    NavalSArtichoke Senior Member

    You should double check this wind load. I believe the number in the IMO Code is 0.504 kPa.
     
  7. athvas
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    athvas Senior Member

    Yes we need to input the wind load 540 Pa in the run file itself.
     
  8. athvas
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    athvas Senior Member

    IMO Criteria for Pontoons
    ( IS code 2008 Part B – Recommendation for Certain Types of Ships and Additional Guidelines - Chapter 2 – Recommended design criteria for certain types of ships - 2.2 Pontoons )

    2.2.4.2. The static angle of heel due to a uniformly distributed wind load of 540 Pa (wind speed 30 m/s) should not exceed an angle corresponding to half the freeboard for the relevant loading condition, where the lever of wind heeling moment is measured from the centroid of the windage area to half the draught.
     
  9. TANSL
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    TANSL Senior Member

    That's what we all knew, but I think is not the same as saying your formula.
    Cheers
     
  10. athvas
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    athvas Senior Member

    Can you express the above statement in mathematical expression so that i can correct it.
     
  11. TANSL
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    TANSL Senior Member

    Sure, with pleasure.
    IMO said the following: "should not Exceed an angle corresponding to half the freeboard". (IMO says corresponding to, does not say "equal or less" than)
    You say the following: "Steady angle of heel <0.5 * Freeboard"
    Both statements are not the same. Looking at your formula dimensionally, the resulting angle be obtained in the same units as the freeboard, in meters, for example. Do you think that I should explain more?
     
  12. athvas
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    athvas Senior Member

    do you agree this ?

    Steady angle of heel < Angle corresponding to (0.5 * freeboard)
     
  13. TANSL
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    TANSL Senior Member

    It's more like what I agree. The term "steady" is misleading me.
    Why change what it says IMO?
     
  14. athvas
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    athvas Senior Member

    Static angle of heel .... is it ok ?
     

  15. TANSL
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    TANSL Senior Member

    Athvas, give it room, please.
     
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