Section 2 Longitudinal Strength Aspects

2.1 The program is to be capable of calculating still water shear forces and bending moments in any load, ballast or flooded (where applicable) condition at specified read-out points (up to about 25 may be required) and to indicate the respective permissible values. Where bulkhead shear force correction factors are included these will be checked. The calculated values are to be displayed and an indication given when the permissible limits are exceeded. The maximum values (and the minimum values where relevant), by percentage and numerical value, and their locations are also to be indicated. It is required that actual calculated values be shown and also expressed as a percentage of the maximum permissible value at the read-out point. More than one set of permissible values may be required, such as harbour and seagoing conditions or different hogging or sagging bending moments. The forward and aft draughts of the ship are also to be indicated.

2.2 Calculated results will be compared for computational accuracy with the results obtained from LR’s parallel calculation using the same input data and good agreement is required. A comparison of results would be expected to be within ±2% (±two percent) of the assigned permissible SF/BM at each read-out point but in no case should this exceed ±5% (±five percent).

2.3 Where the program can additionally carry out still water torsional moments calculations, output at the specified readout points and permissible values are to be indicated.

2.4 For Bulkcarriers where the program is required to assess local strength, output of the comparison of actual cargo mass against the permitted limits is to be shown.

2.5 For Bulkcarriers where the program is also required to predict SF/BM results in flooded hold conditions comparisons as outlined in paragraph Ch 1, Ch 3, 2 Longitudinal Strength Aspects 2.2 are also applicable.

2.6 In addition to the tabular output the program should include a graphical presentation of results, which is to be included with the test conditions submitted for appraisal. When the program produces results at numerous points along the vessel, a summary sheet of results at the specified readout points will be required.

2.7 A statement relating to the minimum draught forward (Table 1.7.3 Statement For Minimum Draught Forward) should be displayed on the screen when the user gains access to the longitudinal strength program. The statement should be acknowledged by the user prior to being able to continue. A warning message should be shown when any loading condition does not satisfy the specified criteria.

2.8 All longitudinal strength results should be derived from direct calculations within the software, using the basic data applicable to the vessel, i.e. Bonjean data/hull form, lightweight and dead-weight distributions. Where hydrostatics taken from the approved loading manual are used to trim the ship, it is the responsibility of the instrument manufacturer to ensure that this data is consistent with the hull form/Bonjean data used for the strength calculations. The use of coefficients derived by the pre-processing or any other means, is not a satisfactory method for any strength calculations.

2.9 Additional information is available in the “Guidance Technical Notes For Loading Instruments Performing Longitudinal Strength Calculations” a copy of which can be obtained from the local plan approval office.