PIAS Manual  2023
Program for the Integral Approach of Shipdesign
Tonnage: calculation of gross and net tonnage
This module calculates the gross and net tonnage from seagoing vessels, according to “The 1969 International Convention on Tonnage Measurement of Ships”.
When using this module it is of paramount importance that compartments for cargo are selected. See description of Calculate and print tonnage calculation (GT and NT) for more information.

Definition of superstructures not included in the hullform

At this stage superstructures are defined (primarily deckhouse layers) which are not included in the hull form. For example, a poop already included in the hullform (with a hull shape definition module Hulldef of Fairway) does not have to be defined in this module, while a bridge which is not already included in the hull form, should be defined in this module. For each superstructure, which is assumed to be rectangular, the location of the limiting bulkheads has to be specified by the user. Is the superstructure not of a rectangular shape, the mean values have to be specified. For each superstructure is specified :

  • Location of aft and forward bulkhead.
  • Location of low and high deck.
  • Half the breadth.

Definition general data for net tonnage

For the calculation of the Net Tonnage several specific particulars, as defined in the Tonnage Convention, have to be specified here.

Print sideview hull plus superstructures

For checking purposes with this option the hull and the superstructure are drawn schematically in plan view.

Calculate and print tonnage calculation (GT and NT)

This option calculates and prints the tonnage calculation. For the calculation of Net Tonnage, the volume of the cargo spaces has to be determined (reg. 4 from Annex I from the Tonnage Convention). To determine those volumes, the compartments as defined in Layout are used here, so there is no double definition of cargo spaces. To enable this module to recognize the appropriate compartments as cargo spaces, those compartments have to be selected in the compartment list (as discussed in Compartment list, calculation and printing of tank tables) of Layout before tonnage calculations are performed. All compartments not being part of the cargo space are not allowed to be selected. According to the regulations, the volumes of the cargo spaces are being calculated without deduction for construction (permeability = 1).

See underneath for an example of the output of tonnage calculations.

Example of the output, first page
Example of the output second page