Section 2 Decks loaded by wheeled vehicles

2.1.1 Where it is proposed either to stow wheeled vehicles on the deck or to use wheeled vehicles for cargo handling, the deck and supporting structure are to be designed on the basis of the maximum loading to which they may be subjected in service. Where applicable, hatch covers are to be similarly designed. In no case, however, are the scantlings to be less than would be required for a deck in this location.

2.2.1 Details of the deck loading resulting from the proposed stowage or operation of vehicles are to be supplied by the Shipbuilder. These details are to include the wheel load, axle and wheel spacing, tyre print dimensions and type of tyre for the vehicles.

2.2.2 For design purposes where wheeled vehicles are to be used for cargo handling, the deck is to be taken as loaded with a normal head of cargo, except in way of the vehicle.

2.3.1 The deck plating thickness is to comply with Table 9.2.1 Loading by wheeled vehicles.

Table 9.2.1 Loading by wheeled vehicles

Item	Parameter	Requirements
(1) Deck plating	Plating thickness	t = + 1,5 mm, see Note
(2) Deck beams, longitudinals and stiffeners when fork lift trucks are to be used	Section modulus	Z = (0,375K 1 Ple + 1,25K 2 hsle 2 )k cm3
(3) Deck beams, longitudinals and stiffeners for decks permanently used for vehicles, in association with a value of h which need not exceed 2,5 m	Section modulus	Z = (0,536K 1 Ple + 1,25K 2 hsle 2)k cm3
(4) Deck girders and transverses	Section modulus	Z = 4,75bhle 2k cm3
Symbols
b = mean width of plating supported by a deck girder or transverse, in metres h = normal load height on the deck, in metres, see Pt 3, Ch 3, 4 Design loading le = effective length, in metres, of the beam between span points, see also Pt 3, Ch 3, 3.3 Determination of span point s = spacing of stiffeners, in metres t = thickness of plating, in mm K 1 and K 2 are factors given in Table 9.2.4 Values of K 1 and K 2 P = total weight of the vehicle divided by the number of axles. Where the distribution of weight is not uniform, P is to be taken as the maximum axle load. For fork lift trucks the total weight is to be applied to one axle, in tonnes P1 = corrected patch load obtained from Table 9.2.2 Corrected patch load calculation in tonnes Z = section modulus of the member, in cm3, see Pt 3, Ch 3, 3.2 Geometric properties of section α = thickness coefficient obtained from Figure 9.2.1 Tyre print load stress factor β = tyre print coefficient used in Figure 9.2.1 Tyre print load stress factor = log k = higher tensile steel factor, see Pt 3, Ch 2, 1.3 Steel 1.3.3
Note Where the necessary data of fork lift trucks are not initially available, the deck plate thickness may be estimated from the maximum beam spacing to plate thickness ratios s/t given in Table 9.2.3 Approximate deck thickness for fork lift trucks.

Table 9.2.2 Corrected patch load calculation

Symbols	Expression
a, s, u and v are as defined inFigure 9.2.1 Tyre print load stress factor P 1 = corrected patch load, in tonnes Φ1 = patch aspect ratio correction factor Φ2 = panel aspect ratio correction factor Φ3 = wide patch load factor P w = load, in tonnes, on the tyre print. For closely spaced wheels the shaded area shown in Figure 9.2.1 Tyre print load stress factor may be taken as the combined print	P 1 = 1,25Φ1Φ2Φ3 P w
	Φ1 =	v 1 = v, but ≤ s u 1 = u, but ≤ a
	Φ2 = 1,0	for u ≤ (a - s)
	=	for a ≥ u > (a – s)
	= 0,77	for u > a
	Φ3 = 1,0	for v < s
	= 0,6 + 0,4	for 1,5 > > 1,0
	= 1,2	for ≥ 1,5

2.3.3 Where it is proposed to use vehicles having steel wheels, deck thicknesses will be specially considered.

2.3.4 Where transversely framed decks contribute to the hull girder strength or where secondary stiffening is fitted perpendicular to the direction of vehicle lanes, the thickness, t, derived from Table 9.2.1 Loading by wheeled vehicles is to be increased by 1,0 mm.

2.3.5 Where decks are designed for the exclusive carriage of unladen wheeled vehicles, the deck plate thickness, t, derived from Table 9.2.1 Loading by wheeled vehicles may be reduced by 0,75 mm.

2.3.6 Where it is proposed to carry tracked vehicles, the patch dimensions may be taken as the track print dimensions and P _w is to be taken as half the total weight of the vehicle. The deckplate thickness, t, derived from Table 9.2.1 Loading by wheeled vehicles is to be increased by 0,5 mm. Deck fittings in way of vehicle lanes are to be recessed.

2.3.7 If wheeled vehicles are to be used on insulated decks or tanktops, consideration will be given to the permissible loading in association with the insulation arrangements and the plating thickness.

2.4.1 The section modulus, Z, of deck beams or longitudinals is to be not less than that required for a deck in this location, nor less than the following:

1. For general purpose cargo decks where fork lift trucks are to be used, the value of Z is to be as in Table 9.2.1 Loading by wheeled vehicles.

2. For permanent vehicle decks in association with a value of h which need not exceed 2,5 m, Z is to be as in Table 9.2.1 Loading by wheeled vehicles.

3. For decks designed for the carriage of wheeled vehicles only:

   that required to satisfy the most severe arrangement of print wheel loads on the stiffener in association with a bending stress of 100 N/mm² (10,2 kgf/mm²) assuming 100 per cent end fixity.

2.5.1 Where the load on deck girders and transverses is uniformly distributed the section modulus is to comply with Table 9.2.1 Loading by wheeled vehicles.

2.5.2 Where the member supports point loads, with or without the addition of uniformly distributed load, the section modulus is to be based on a stress of 123,6 N/mm² (12,6 kgf/mm²) assuming 100 per cent end fixity.

2.5.3 Where it is proposed to carry tracked vehicles, the total weight of the vehicle is to be taken when determining the section modulus of the transverse at the top of a ramp or at other changes of gradient.

2.6.1 Where heavy or special loads, such as machinery transporters or large tracked vehicles are proposed to be carried, the scantlings and arrangements of the deck structure will be individually considered.