Section 2 General

2.1 Loading conditions for determination of design bending moments

2.1.1 The following conditions are to be covered by the calculations of design bending moments:

Light condition (ship completely equipped, fresh water tanks, fuel tanks and lubricating oil tanks full, crew and stores on board and tanks partly filled or full with water ballast if intended to be carried in this condition).
Fully loaded condition, ship as in light condition and loaded with cargo, as evenly distributed as is practicable in the cargo compartment space, to the maximum allowable draught on even keel.
Any other loading condition of the ship giving higher values of bending moments or shear forces, caused by loading and discharging sequences and/or unusual or non-uniform cargo distribution, see also Pt 1, Ch 2, 2.1 Definitions 2.1.8, Pt 1, Ch 2, 2.1 Definitions 2.1.9 and ship type Chapters.

2.1.2 For ships designed, modified and/or arranged for navigation in Zones 3, 2 or 1 or for service extension, the additional wave bending moment and wave shear force for the particular zone or service extension area are to be added to the still water bending moment and shear force calculated for the conditions (a), (b) and (c) of Pt 3, Ch 4, 2.1 Loading conditions for determination of design bending moments 2.1.1 to obtain the actual maximum bending moment and shear force for calculation of the required hull section modulus.

2.1.3 The maximum still water bending moment corresponding to the ship’s longitudinal strength category, see Pt 3, Ch 4, 2.3 Longitudinal strength categories, may not be exceeded when the ship is partly loaded due to navigational or operational requirements.

2.1.4 The longitudinal strength will be specially considered for ships designed, modified and/or arranged for any unusual loading condition, uneven cargo distribution, etc.

2.2 Definition of loading sequences ‘T’, ‘O’ and ‘D’

2.2.1 Loading/discharging sequence ‘T’, for normal loading sequence.

	Self-propelled ships with machinery aft:
	Loading of the ship in two runs of practically equal mass, by distributing the cargo evenly over the full length of the cargo compartment space. The loading is to commence from the after end and to progress to the forward end and then be completed by loading from forward to aft. Discharging in two runs of practically equal mass, taking the cargo evenly from the full length of the cargo compartment space, progressing from the after end to forward and completing the discharging from forward to aft.
	Non-propelled ships:
	Loading and discharging in two runs of practically equal mass, by distributing the cargo evenly over the full length of the cargo compartment and discharging by taking the cargo evenly from the cargo compartment space. The loading may be carried out from forward to aft and be completed from aft to forward or in the opposite direction. Discharging may be carried out in the same manner as loading.

2.2.2 Loading/discharging sequence ‘O’ for accelerated loading sequence.

	Self-propelled ships with machinery aft:
	Loading in one run. Loading to commence from the after end of the cargo compartment space and to progress to the forward end with the total mass of cargo evenly distributed.
	Discharging in one run. Discharging to commence from the forward end of the cargo compartment space and to progress to the aft end.
	Non-propelled ships:
	Loading in one run, which may be commenced either from the forward end or the after end and evenly distributing the total mass of cargo to complete the loading at the other end of the cargo compartment space.
	Discharging in one run, which may be commenced either from the forward or the after end of the cargo compartment space.

2.2.3 Loading/discharging sequence ‘D’ for defined loading sequence.

2.3 Longitudinal strength categories

2.3.1 For the purpose of longitudinal strength (L.S.), the Rules distinguish between three ship categories, defined as follows:

Category ‘T’

Ships for which the required section modulus is based on the maximum bending moments and shear forces occurring when the ships are being loaded and/or discharged according to the loading sequence ‘T’, see Pt 3, Ch 4, 2.2 Definition of loading sequences ‘T’, ‘O’ and ‘D’ and/or ship type Chapter.

Category ‘O’

Ships for which the required section modulus is based on the maximum bending moments and shear forces occurring when the ships are being loaded and/or discharged according to the loading sequence ‘O’, see Pt 3, Ch 4, 2.2 Definition of loading sequences ‘T’, ‘O’ and ‘D’ and/or ship type Chapter.

Category ‘D’

At special request, acceptance of the required section modulus on the basis of lower design bending moment and shear forces than those associated with the loading sequence ‘T’, will be considered. However, these bending moments are generally not to be less than as given for MH _li and MS _lo in Table 4.5.2 Design bending moments in relation to longitudinal strength category. Where the notation L.S.‘D’ is assigned, a manual containing approved loading conditions as well as approved loading and discharge sequences is to be carried on board.

At special request, acceptance of the required section modulus on the basis of lower design bending moment and shear forces than those associated with the loading sequence ‘T’, will be considered. However, these bending moments are generally not to be less than as given for MH _li and MS _lo in Table 4.5.2 Design bending moments in relation to longitudinal strength category. Where the notation L.S. ‘D’ is assigned, a manual containing approved loading conditions as well as approved loading and discharge sequences is to be carried on board.

2.4 Specified non-uniform loading conditions

2.4.1 At special request the longitudinal strength, i.e. the required section modulus, may be based on bending moments and shear forces occurring in unusual and/or non-uniform loading conditions, in addition to those occurring when the ship is being loaded and/or discharged according to the loading sequence ‘T’ or ‘O’ as applicable. These bending moments and shear forces are to be verified by direct calculations and a manual containing the approved loading conditions as well as the approved loading and discharge sequences for the non-uniform conditions is to be carried on board.

2.5 Erections contributing to hull strength

2.5.1 Where a long superstructure or deck-house of a length greater than 0,2L is fitted, extending within the 0,5L amidships, the longitudinal strength of the hull including the long superstructure or deck-house will be considered in each case, see also Pt 3, Ch 3, 4 Design loading.

2.6 Approved calculation systems

2.6.1 Where the assumptions, method and procedures of a longitudinal strength calculation system have received general approval from LR, calculations using the system for a particular ship may be submitted.