This is a basic example for computing hydrostatics and ballasting of a barge. The data set has complete compartmentation and load groups defined so that it could be used for a jacket loadout; i.e. load groups are defined which correspond to the forces that the jacket will exert on the barge at when it is at a specified location.

Most of our examples contain a common set of "beginning" commands as well as a common "ending" command. Click here to get documentation for these commands. They will not be discussed directly. The files which are discussed here are:

• load_bal data
• load_bal commands
• load_bal log
• load_bal output

The entire analysis is done within the Hydrostatics menu which is entered via the command:

$
$*********************************************      ENTER HYDROSTATIC MENU
$
HSTATICS

$
$*********************************************      initial ballast
$
   &SUBTITLE NORTH TOW UNDER POWER LINES
   &INSTATE -CONDITION 27.5 0 -1.62
   &APPLY LIFT-OFF
   &COMPARTMENT -PERCENT  8/W 100 7PW 31.82 7SW 32.38 9// 100 9PW 87.75 \
                    10PW 32.51 10SW 33.06

The barge condition is set with the command &INSTATE -CONDITION where the three numbers specify the draft, roll, and trim respectively. The loads associated with the name "LIFT-OFF" are applied with the command &APPLY. Having loaded the barge and placed it in the desired condition, we set the initial ballast of the compartments with the &COMPARTMENT command. Ballasting is specified by pairs of data, a compartment selector and a percentage full, e.g. 7PW is a compartment name and 31.82 is the percentage full. We have used some wild characters, /, to select compartments. A / "matches" any character, thus here, 8/W selects tanks 8SW and 8PW to be filled 100 percent.

One of the primary things one wishes to accomplish here is to create a ballast plan which minimizes the deflection in the barge. Thus, we next investigate the longitudinal strength of the barge in this condition with:

$
$*********************************************      long. strength
$
   EQUI
   MOMENT -ALLOW 24.00 1.
      REPORT
      VLIST
      PLOT 1 4 -RAX 5
      1
      STRESS RATIO
      2
      DEFLECTION
      -1
      3
      LONGITUDINAL LOCATION (FT)
      4
      STRESS RATIO
      5
      DEFLECTION (INCHES)
      -1
   END

The command VLIST, short for view list, writes a numbered list of the variables available for selection to the screen, e.g.

                 The Variables Available for Selection are:
                 ==========================================
  1 Long Location           3 Moment                    5 Deflection Ratio
  2 Shear                   4 Stress Ratio

Before the program produces the plot it queries the user about the legend and titles it is going to use. The following is an example of the program queries:

                                 The Legend Is:
                                 ==============
 
        1  Stress Ratio
        2  Deflection Ratio
 
                        Enter No. Of Line To Be Changed
                        ===============================
 
?2
                                 Enter New Line
                                 ==============
 
?Deflection
                                 The Legend Is:
                                 ==============
 
        1  Stress Ratio
        2  Deflection

Intact stability is computed via:

$
$*********************************************      intact stability
$
   &SUBTITLE INTACT STABILITY NORTH TOW
   RARM 2.5 25 -ECHO N -WIND 100
      REPORT
      PLOT 2 5 7 -RAX 9
      2
      WIND HEEL ARM
      -1
      3
      ROLL (DEGREES)
      4
      RIGHTING ARM (ft)
      -1
   END

The command REPORT creates the standard righting arm report. This report will show table condition (draft, roll, and trim), minimum height of down flooding points, righting and heeling arms, areas under the righting and heeling arm, the ratio between the two arms, and the net arm. In the table, all the columns will have values which are not consistently zero, except the minimum height of down flooding points column. The down flooding points column will be zero because we did not define down flooding points. The PLOT command produces a plot of the stability results.

Damaged stability is done via the following commands:

$
$*********************************************      damaged stability
$
   &SUBTITLE DAMAGED STABILITY NORTH TOW ..TANK 3PW FLOODED
   &COMPARTMENT -FLOOD 3PW
   EQUI
   &STATUS B_W -HARD

Our next task is to compute a new ballast condition to get back to our original condition with 3PW flooded. This is accomplished with:

   &SUBTITLE COMPUTE BALLAST TO REGAIN TOW CONFIGURATION IN DAMAGED CONDITION
   &INSTATE -CONDITION 27.5 0 -1.62
   &STATUS B_W -HARD
   &STATUS COMPART -HARD
   &EVENT_STORE 1
   &SELECT :COMP -SELECT 7/W 10/W 8// 12//
   &CMP_BAL H109 :COMP
   &STATUS B_W -HARD

We create a selection criteria called :comp to be used in the ballasting. It selects 7 and 8 wing tanks, and all of the 8 and 12 tanks. The &CMP_BAL command automatically computes the amount of ballast in the selected tanks so that the barge will be in equilibrium at its current location. Here, H109 specifies the body to be ballasted, and :comp defines the compartments to ballast.

Again, we look at longitudinal strength calculations with:

   MOMENT -ALLOW 24.00 1.
      VIEW -RECORD 1 15  -SEL @
      REPORT
   END

In the final set of commands we return the barge to the intact condition via the following:

$
$*********************************************      restore condition
$
   &SUBTITLE RETURN TO INITIAL CONFIGURATION   NORTH TOW
   &INSTATE -EVENT 1
   &COMPARTMENT -NO_FLOOD 3PW
   EQUI
   &STATUS B_W

Contents