Procedure for Carrying Out a Probabilistic Assessment

This section summarizes the procedure when using Calc to do a Probabilistic Stability Assessment.

1. Edit the Ship Data node.

   On the Main Dimensions page, enter appropriate values for the subdivision length, subdivision and light service drafts.

2. Edit the Tankplan node

   On the Compartments page, enter appropriate damage permeability's. Especially for the HARDER tests, if the assigned permeability is negative (see UTWN above), then any damage case that includes the compartment, will automatically fail, that means, 's' = 0. Save and calculate the Tankplan.

3. Edit Other Data

   Edit Other Data, and enter protected and unprotected openings. Do not leave any blank lines in the table, as this will cause openings to be located at (0,0,0). This results in all damage cases failing with a zero 's' value!

   If the vessel carries passengers, then it is necessary to define the profile, for wind heeling calculations.

4. Set-up of Probabilistic Options and Zones

   Edit Probabilistic Setup, and on the Probabilistic Page, select the rules to be applied -

   • Cargo Ship - SOLAS 1992 Part B-1, Reg.25-1, or

   • Passenger Ship - IMO Res. A.265

   • New Harmonized Rules - IMO SLF 47/17 with amendments.

     Note:
     Other options may be in the list. These are alternative proposals for the new combined regulations. They are not finalised, and should not be used

     The passenger and lifeboat data, is only required to determine heeling moments, if there are passengers.This page allows you to select the Probabilistic Stability regulations. The compartment standard and other data associated with the Probabilistic regulations are also be entered on this page.

     On the Surfaces page select the bulkheads and decks that are relevant to the probabilistic stability calculations. Normally decks below the subdivision loadline are not considered. Also if the ship is symmetrical, it is not necessary to include longitudinal bulkheads on the port side (-ve y value).

     The Compartment Extents page gives the maximum and minimum extents for each compartment. This information is used by the procedure that sets up damage conditions for Probabilistic Stability calculations. Normally you should not need to change these figures, unless the automatic damage case generation, is incorrectly selecting compartments for inclusion in particular damage cases. This sort of problem can occur, for example, in wing tanks defined in GDS files, where the positive/negative portion combinations mean that Calc cannot reliably determine the actual extents.

     Save and calculate to generate the zoning information.

5. Generate Damage Cases

   Edit the Probabilistic Scenarios node and click the Create Damage Cases button.

   Select the damage side (normally Starboard).

   It is normal to damage to the bottom of the ship. If this is not ticked, then damage may start at any height, which generally produces more damage cases.

   Make sure that all relevant compartments are selected on the Compartments page.

   When OK is pressed the damage cases will be generated and assigned to the appropriate damage zones.

6. Run the Damage Cases and Assess Compliance

   Edit the Probabilistic Stability Assessment node.

   On the General Page set up the loading conditions to be analyzed. Currently the Cargo ship rules require two loading conditions and the Passenger ship rules, three. Clicking the Reset Conditions button, will set up default conditions according to the specified rules. However, the VCG's need to be entered.

   On the Damage and Waves page, select the damage conditions to be included in the analysis. It is possible, to just select a few conditions, to make sure that all is well, before running the complete analysis.

   Run the analysis and inspect the results.