Section 9 Primary structure in wing tanks

9.1.1 The scantlings of the bottom transverses are to be determined by means of direct calculations or, alternatively, in accordance with the requirements of Pt 4, Ch 10, 2.5 Bottom transverses.

9.2.1 The scantlings of the side transverses are to be determined by means of direct calculations or, alternatively, in accordance with the requirements of Pt 4, Ch 10, 2.7 Side transverses.

9.3.1 Cross ties in wing tanks are to comply with requirements in Pt 4, Ch 9, 9 Primary members supporting longitudinal framing.

9.3.2 Cross ties in wing tanks of vessels eligible for the notation Strengthened to carry cargoes which may liquefy (IMSBC Group A) are to comply with the requirements in:

• Pt 4, Ch 9, 9.3 Girders and floors in double bottom 9.3.3;
• Pt 4, Ch 9, 9.3 Girders and floors in double bottom 9.3.4; and
• Pt 4, Ch 9, 9.3 Girders and floors in double bottom 9.3.5.
• LR’s ShipRight Additional Design Procedure (ADP), Procedure for Assessment of Ore Carriers filled with Liquefied Cargoes.

9.3.3 Actual wing tank cross tie area, A_cl, in cm², is to satisfy:

A_cl≥ f_liqA_c

Where:

Ac	=	Area of cross tie, in cm2, see Pt 4, Ch 11, 9.5 Cross-ties 9.5.1
fliq	=	and is not to be taken less than 1,0. Where: C = stowage rate, in m3/t The stowage rate is defined in Table 11.7.1 Longitudinal and transverse bulkhead scantlings for ore loading but need not take into account the cargo overshoot defined in Pt 4, Ch 11, 13.4 Cargo loading conditions for design assessment 13.4.1.(e). flc = 1,0 If the cargo density of the intended loading condition is higher than the virtual cargo density , see Pt 4, Ch 11, 1.3 Class notation 1.3.4, then flc is the be taken as (see also Pt 4, Ch 11, 1.3 Class notation 1.3.4): flc = but is not to be taken less than 0,0 and need not be taken greater than 1,0. Where: ρlc = the loading condition cargo density (see Pt 4, Ch 11, 1.3 Class notation 1.3.4), in t/m3 hlc = the vertical distance from the centre of the cross tie to the level cargo surface, in m, with the loading condition density in an upright condition. The determination of cargo surface height need not take into account the cargo overshoot defined in Pt 4, Ch 11, 13.4 Cargo loading conditions for design assessment 13.4.1.(e). hc = the vertical distance from the centre of the cross-ties to deck at side amidships, in metres.

9.3.4 Cross tie flange thickness t_f, in mm, is not to be less than:

Where:

fa	=
Acl	=	actual wing tank cross tie area, in cm2
Ac	=	wing tank cross tie area in cm2, see Pt 4, Ch 11, 9.5 Cross-ties 9.5.1
fliq	=	scantling factor for cargo with moisture level exceeding TML, see Pt 4, Ch 9, 9.3 Girders and floors in double bottom 9.3.3
bf	=	flange breadth of cross tie, in mm.

9.3.5 Length of cross tie, S_c, as defined in Pt 4, Ch 9, 9.2 Symbols 9.2.1, is to be less than or equal to l_perm:

S_c ≤ l_perm

Where:

lperm	=	permissible length of cross tie, in metres, from the torsional buckling aspect:
	=
fa	=
Acl	=	actual wing tank cross tie area, in cm2
Ac	=	wing tank cross tie area in cm2, see Pt 4, Ch 11, 9.5 Cross-ties 9.5.1
fliq	=	scantling factor for cargo with moisture level exceeding TML, see Pt 4, Ch 9, 9.3 Girders and floors in double bottom 9.3.3
dw	=	web depth of cross tie, in mm
tw	=	web thickness of cross tie, in mm
bf	=	flange breadth of cross tie, in mm
tf	=	flange thickness of cross tie, in mm

9.4.1 The scantlings of the deck transverses are to be determined by means of direct calculations or, alternatively, in accordance with the requirements of Pt 4, Ch 10, 2.8 Deck transverses.

9.5.1 The scantlings and arrangement of the cross-ties are to be determined by means of direct calculations or, alternatively, in accordance with the requirements of Pt 4, Ch 9, 9.6 Cross-ties.

9.6.1 The scantlings of primary members supporting bulkheads are, in general, to be determined by means of direct calculation, see also Pt 4, Ch 11, 9.6 Primary members supporting bulkheads 9.6.3, Pt 4, Ch 11, 9.6 Primary members supporting bulkheads 9.6.4 and Pt 4, Ch 11, 9.6 Primary members supporting bulkheads 9.6.5.

9.6.2 Vertical webs are to be arranged in line with deck transverses and the double bottom floors. Particular attention is to be paid to the alignment of the bulkhead web end brackets with the double bottom floors.

9.6.3 The section modulus of vertical webs on longitudinal bulkheads is to be as required by Pt 4, Ch 9, 9.7 Primary members supporting oiltight bulkheads 9.7.4.

9.6.4 The net sectional area of the web at any section is to be as required by Pt 4, Ch 9, 9.7 Primary members supporting oiltight bulkheads 9.7.5.

9.6.5 The moment of inertia of vertical webs on longitudinal bulkheads is to be as required by Pt 4, Ch 9, 9.7 Primary members supporting oiltight bulkheads 9.7.6.

9.7.1 The inner bottom plating is to be extended into the wing tank in the form of a horizontal diaphragm, arranged to ensure a smooth structural transition in way of transverse primary members and to maintain longitudinal continuity. The diaphragms are to be of sufficient width to provide effective scarfing of the inner bottom into the wing tank structure.

9.7.2 Floors intermediate between transverses are to be backed in the wing tanks by substantial vertical brackets extending transversely over at least three bottom longitudinal spaces and vertically to a sufficient height above the horizontal diaphragms to provide effective support for the double bottom structure.

9.8.1 The construction details are to comply with the requirements of Pt 7, Ch 10, 7 Water cooler refrigeration units with the exception of lateral stability of primary members which is to be as required by Pt 4, Ch 9, 10.11 Lateral stability of primary members.

9.8.2 The minimum thickness is to be as required by Pt 4, Ch 9, 10.2 Compartment minimum thickness.