Damage Stability - Static Equivalent Method

Discussion in 'Stability' started by Maritimer, Jun 10, 2010.

  1. Maritimer
    Joined: Jul 2007
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    Maritimer Junior Member

    I am working with stability on some old ro-ro passenger vessels (30-40 years old). These vessels do not meet two compartment damage stability so as an alternative a Static Equivalent Method (SEM) can be used for damaged stability. This method uses weather data and significant wave height to determine when a vessel can operate based on elevated water on the ro-ro deck. This is fairly new say the last 10 years or less.

    I have read a few papers on how to do this none being very clear so I am asking if anyone has a good resource that deals with how to actually calculate the elevation of the water surface inside the ship above mean sea level (h). Not exactly sure what to do with trim may need to fix trim to get parallel sinkage?Trying to figure out how to do this with GHS if at all possible.

    Some authors that appear to have done a lot of work on this is topic are Vassalos and Pawlowski.

    Appreciate any Help.
  2. daiquiri
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    daiquiri Engineering and Design

  3. RAraujo
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    RAraujo Senior Member - Naval Architect

    Are those vessels under SOLAS?
    What do you mean by SEM? Is it something like the criteria in Stockolm Agreement?
    If the vessels are SOLAS then the criteria specified in Ch. II-1, Part B, Reg. 8, as applicable according Reg. 8-1 and 8-2, must be satisfied.
    Criteria from Stockolm Agreement must be applied on top of these for vessels on regular international voyages arriving, or departing, from European ports.
    Please check with your vessel's flag administration.
  4. Maritimer
    Joined: Jul 2007
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    Maritimer Junior Member

    These ro-ro ferries are not SOLAS vessels. They are flagged Canadian and operate in Canadian waters. This SEM method is a Transport Canada regulation, but I believe it may be something that could eventually be incorporated in SOLAS for ro-ro's.
  5. jehardiman
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    jehardiman Senior Member

    The value of h is explicitly specificed in Annex B, Appendix A of TP 10943 E as 0.085 Hs^1.3.

    From a professional stand point it is reasonable and prudent to account for the static trim though it is not explictly stated in the Annex. If the vessel car deck is longitudinaly divided into a number of WT compartments above the margin line, then the sinkage and trim must be calculated at the critical heel angle (i.e. when Gz is max) with the flooding water as it is stated that "The total amount of water on the vehicle deck is modelled by treating it as a tank". See TP 10943 E Appendix 1 at http://www.tc.gc.ca/eng/marinesafety/tp-tp10943-appendix-1-1474.htm

    So, calculate the sinkage and trim due to the 1 compartment damage and the resulting critical heel. Calculate the flooding water and add the effect (sinkage and trim) of the flooding water, recalculate GZmax, recalculate flooding water...etc until convergence. Now do that for all 1 compartment cases. It might be nice if somebody automated it in GHS or SHCP.

    FWIW, partial flood up during damage is getting more looks after some recent casualities. The MV Rocknes was a wake-up call that the old damage stability methods might miss something.
    Last edited: Aug 20, 2010

  6. sudhir0201
    Joined: Aug 2010
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    sudhir0201 Junior Member

    help in Damage and probalistic stablity

    Dear friend, i m new in this field of stability, i m working on damage and Probabilistic stability. i m using tribon software for all these calculation. but i m facing a problem while doing probabilistic stability for an aircraft carrier. please help me in this issue. how i approach for probablistic stability for aircraft carrier
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