PIAS Manual  2021
Program for the Integral Approach of Shipdesign
Tools for data overview, intact stability and damage stability
instead of being related to a specific PIAS module, this chapter describes a number of tools which can be applied at multiple tasks, and which are consequently included in a number of modules, which are:

Weight groups

A weight group is a category of cargo or other loading, for example `ballast water' or `heavy fuel oil', and is introduced to provide some order is lists of compartments and weight items. If weight groups are being used then, where relevant, Loading will also generate subtotals (of weights and sometimes also COGs) per weight group. Please realize that the concept `weight group' is an auxiliary tool, its use is not obligatory.

Weight groups can, up to a maximum of forty, be defined from Loading and Layout, an example of the input window is shown below, For each weight group can be given:

  • Its number, which is an identification number between 0 and 40. Each compartment or weight item can be assigned to a particular weight group by entering this number, however, it might be more convenient to press <Enter> there, which pops up a selection window with all full weight group names.
  • The hatching type which is used when hatching or filling in the compartments in tank sketch plots, as discussed in Sketches of tanks, compartments and damage cases.
  • The group color, which is the color representing this weight group, and which is used in plots, and also as background color in text windows if the last column of this weight group is set to ‘yes’.
  • The text color, which, if the last column is set to ‘yes’, specifies the foreground color in textual overview windows of the texts which belong to this weight group.
  • In table, which indicates whether the weight group color should also be used in overview tables of compartments and weight items.
  • Print summ., which indicates whether in the output only the subtotal should be printed. The calculation is based on all weight items though.
stabtools_gewichtsgroepen.png
Specify weight group properties

Sketches of tanks, compartments and damage cases

If this option has been purchased, it enables you to define views and section which will be used when printing compartment definition data, with damage stability calculations and with loading condition to generate large-scale (= small-size) drawings of compartments and hullform etc. The color and hatching type of these graphics can be specified per weight group, for which we refer to Weight groups. If multiple sketches are defined they will be ‘pasted on paper’ beneath each other, an example of the output is present at the end of this chapter.

This menu, where the sketch parameters can be given, can be called from many loactions, such as from Loading or Layout, but also from the general configurations with Config or equivalent. In each of these cases an input window appears where on each line the properties of one sketch can be given, with per column:

  • The first three columns, compart, intact en damage, determine whether this sketch is added to the output of compartment definition output from Layout, intact stability calculations and damage stability calculations respectively. In the output of intact stability calculations each compartment which is filled to some extent will be fully hatched, so no distinction will be made between partially and fully filled tanks.
  • The fourth column defined the type of sketch, where the choices are:
    • Vertical section.
    • Horizontal section.
    • Cross section.
    • Side view.
    • Top view.
    • List of compartments. This is an alphanumerical list of compartments which are relevant in this sketch.
    • Wind contour, which is only used in the output of intact stability.
    • Probability triangle, which is only used in the output of probabilistisc damage stability.
  • Location of the section. With function [Center] it can be specified that in case of damage stability calculations the section will go through the center of the damage case. And in case of compartment sketches from Layout or intact stability calculations the center of all applied compartments.
  • A reduction factor on the plot size. A factor of X will reduce the size of the sketch by X.
  • Axis & scale, which is used to specify whether a horizontal axis and a scale must be co-plotted.
  • With reference, which specifies whether a reference name and a reference number must be drawn into the compartment tank shapes. If this parameter is set to ‘yes’, then the following reference will be used:
    • If the setting of ‘compartment sketches with automatic tank numbers’ is set to `yes', then for each compartment a sequence number is generated, which is drawn into the sketch, and which also appearsd in the compartment list. With this seting to ‘no’ the first four characters of the second compartment name, as given in the menu which is discussed at Second name and abbreviation, are drawn into the compartment. The intention is to replace this ‘second name’ by the ‘abbreviation’, which is also given in Layout.
  • Waterline, a setting that indicated whether the waterline should be drawn as well into the sketches of the intact stability and the deterministic damage stability.
stabtools_tanksketch.png
A page with tank sketches containing 4 sections and a compartiment list

Input and edit damage cases

This tools, designed to define and edit damage cases, can be called upon from all modules which perform a damage stability task, both deterministic and probabilistic. Basically, this tool is rather simple, after all compartments have already been defined (with Layout), and here they can be clicked to toggle them between ‘flooded’ and ‘not flooded’. This tool contains a text window at the left and three graphical windows with three sections, see the example below.
stabtools_damage_cases800.png
Damage cases

In the graphical windows the damaged compartments are indicated with a blueish color, non-damaged compartments in geen-yellow. With the mouse the cursor can be placed or moved in such a window, which will make that the other sections will be adapted to the mouse position. The columns in the text window have the following meaning:

  • Slct, selected, yes or no.
  • Name, the name of the damage case.
  • Morecomp. Here ‘yes’ is given in case of a multi-compartment damage, and ‘no’ for a single-compartment damage. These data are only relevant for the damage stability criterion ‘Maximum statical angle according to IMO A.265’, so if this crietrionis notin your criteria set, this parameters need not to be given.
  • Aft> and fore, being the aft and forward boundary of the damage. These parameters are only relevant for the damage stabilitycriterion ‘deckline not submerged outside flooded area’, so also these parameters can be left out if this criterion is not applicable.

Additionally, a number of specific functions apply:

  • With [Flooding stages] non-standard intermediate stages of flooding can be defined, this is futher discussed at Complex stages of flooding (before 2021).
  • With [damage Box], interactively a rectangle can be dragged, which makes the contained compartments flooded. This is a quick and consistent tool for declaring a large number of compartments flooded simultaneously. When this function is activated, in the three graphical windows three white rectangles pop up, which are the projections of a three-dimensional rectangular damage. The vertices of the rectangles can be dragged, which adjusts the damage size and location. If the mouse butoon is released the flooded compartments are colored blueish, see the example below, and by clicking [damage Box] again this new damage case is stored.
  • [iMport] imports the selected damage cases as defined in other modules, such as the deterministic cases from Loading or the probabilistic from Probdam. The actual source of the imported cases can differ per module, this function might also be absent if importint is not relevant for the particular module from which this damage case definition window is called.
  • With [Unit longitudinl axis] the unit of the longitudinal axis can be chosen, where the choice is between meters and frames.
stabtools_damage_box.png
Interactive damage box

Finally, with the <Enter> key a subwindow opens up, as depicted in the figure below, where form each compartment is stated whether it is flooded. The last two columns, containing the intact weight and the intact density, only appear when defining damages for maximum allowable VCG in damaged condition, as discussed in Damage cases menu, for at those computation these intact content plays a role because it will flow out in case of damage (at the deterministic damage stability of a particular loading condition, as can be computed with Loading, the intact content obviously also flows out, but need not to be defined separately, becaause it is already known from the loading condition).

stabtools_compartments_320.png
Flooded compartments per damage case, with their intact content

Generate damage cases on basis of the extent of damage

In general, damage cases are not chosen at will, they are derived from the extent of damage as laid down in rules and regulations instead. For example it can be stipulated that a ship has to survive a damage with a length of 10% of the ship's length, 1/5 of the vessel's breadth and unlimited height. Subsequently it is up to the designer to identify and define all resulting damage cases. this task can also be preformed with this PIAS function.

For this purpose, the currently discussed functionality is developped, where damage dimensions can be entered. Even multiple sets of damage dimensions, because for different regions different extents of damage can be applicable (e.g. for the forward 30% of vessel a bottom damage with a breadth of 5 meter, while for the other 70% a breadth of 3 meter will suffice). For each damage dimension can be entered:

  • Description. This name is to recognize this set, and is also assigned to the damage cases generated under this set.
  • Damage type. Three kinds of damage types exist: side damage SB, side damage PS and bottom damage.
  • Length. The damage length, the longitudinal extent of damage.
  • Penetration. With side damage this is the transverse extent of damage (measured from CWL), with bottom damage this is the vertical extent of damage (measured from the bottom).
  • Dimension. With side damage this is the vertical extent of damage (which, by the way, is unlimited in most rules). With bottom damage this is the transverse extent of damage, the damage breadth.
  • Aft boundary and forward boundary. These are the boundaries of applicability of this dimension set. With the mentioned example where for the forward 30% another regime applies that for the other 70%, two dimension sets have to be defined, one with boundaries aft and 70%Lpp, and the other one with boundaries 70%Lpp and forward.

Furthermore, two additional functions are available:

  • [Standard]. A utility function, which can be used to calculate a standard dimension quickly. For example, a rule exists where the damage length is prescribed to be 1/3L2/3. With this function, [Standard], this equation be called and the number calculated. Because for each dimension (L, B and H) other rules apply this function works by menu cell.
  • [Generate]. With this function the damage cases will be generated. Prior to that, a window pops up where the generation preferences can be specified :
    • The choice of between ‘In addition to existing damage cases’ and ‘As replacement of existing damage cases’ existing damage will be obvious.
    • With ‘Prevent minor damages’ the so-called minor damages — damages from which the compartments are a subset of aother, more extensive, damage — will not be generated. If such minor damages are indeed to be generated, then systematically damages are created with less than the maximum penetration from the side, however, the vertical and longitudinal directions are not systematically searched for that purpose. For the reason that in that fashion relatively large amounts of minor damages would be found. which, as a rule, might be expected to be less severe than the main damage. And although hundreds of minor damages can very well be managed by PIAS, it leaves humans with very little overview.
    • Whether ‘ mutually identical damages’ should be avoided. As a rule, this will be desirable, what is after all the usefulness of multiple, identical damage cases which are inflicted from multiple directions (eg. side and bottom) ?
    By the way, regulations may allow that damage to the ER, or involving ER bulkheads, are not taken into account. Nevertheless these will be generated with this [Generate] function. Such superfluous damage cases will have to be removed by the user afterwards, under the slogan “throwing away is easier then adding”. A possibly easier alternative is to use different regions of damage dimensions, using the aft and forward boundaries thereof. One has to use region boundaries slightly aft or before the ER bulkhead, otherwise that bulkhead will unintendently still become damaged.