Section 3 Vehicle decks

3.1.1 These requirements are applicable to longitudinally or transversely framed craft intended for the carriage of wheeled vehicles, or where wheeled vehicles are to be used for cargo handling.

3.1.2 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, the hatch covers are to be similarly designed. In no case, however, are the scantlings to be less than would be required for a weather or cargo deck, or hatch cover, as applicable.

3.1.3 Details of the deck loading resulting from the proposed stowage or operation of vehicles are to be supplied by the Builder. These details are to include axle and wheel spacing, the wheel load, type of tyre and tyre print dimensions for the vehicles. The vehicle types and wheel loads for which the vehicle decks, including hatch covers where applicable, have been approved are to be included in the craft's documentation and contained in a notice displayed on each deck. For design purposes, the wheel loading is to be taken as not less than 3,0 kN.

3.1.4 The scantling requirements are based on structural strength and limitations on stress and deflection, with no allowance made for wear and tear. Local reinforcement is to be fitted as necessary, particularly in way of vehicle lanes and passenger routes.

3.1.5 The webs of vehicle deck stiffening members are in no cases to be scalloped.

3.2.1  Load area. The load area is defined as the footprint area of an individual wheel or the area enclosing a group of wheels when the distance between footprints is less than the smaller dimension of the individual prints.

3.3.1 The thickness, t _p, of vehicle deck plating is to be taken as not less than:

s and k _a are as defined in Pt 7, Ch 5, 1.2 Symbols and definitions.

3.4.1 The scantlings of vehicle deck stiffeners are to be as required to satisfy the most severe arrangement of print wheel loads in conjunction with the cargo/weather deck design head.

3.4.2 The minimum requirements for section modulus, inertia and web area of vehicle deck secondary stiffeners subject to wheel loading are to be calculated in accordance with Table 5.3.3 Secondary stiffener requirements, see also Figure 5.3.1 Tyre print chart and Table 5.3.2 Tyre correction factor, n.

3.4.3 When two or more load areas are located simultaneously on the same stiffener span, the scantling requirements are to be specially considered on the basis of direct calculation.

3.4.4 Where continuous secondary stiffeners pass through the webs of primary members, they are to be fully collared or lugged in way. The shear stresses at the connections are to be in compliance with Table 7.3.1 Limiting stress coefficients for local loading in Chapter 7.

3.5.1 The scantlings of vehicle deck primary girders and transverse web frames are to be determined on the basis of direct calculation in association with the limiting permissible stress and deflection criteria contained in Pt 7, Ch 7 Failure Modes Control.

3.6.1 Details of the connections to the hull of vehicle securing arrangements are to be submitted for approval.

3.6.2 Deck fittings in way of vehicle lanes are to be recessed.

3.6.3 The vehicle deck structure is to be of adequate strength for the upward forces imposed at fixed securing points. Local reinforcement is to be fitted as necessary.

3.7.1 Bow doors are to comply with the requirements of Pt 7, Ch 5, 4 Bow doors.

3.7.2 Where access to the vehicle deck is provided by side and stern doors the doors are to have scantlings equivalent to the structure in which they are fitted, see also Pt 3, Ch 4, 4 Side and stern doors and other shell openings.

3.7.3 Doors providing pedestrian access between vehicle decks and accommodation spaces are to be gastight, have scantlings equivalent to the surrounding structure and where applicable are to comply with the requirements of Pt 17 Fire Protection, Detection and Extinction.

3.8.1 The scantlings and arrangements of hatches and hatch covers located within vehicle decks are to be not less than that required by the Rules for the supporting structure in which such hatches are fitted. In general the end fixity of primary stiffening members is to be taken as simply supported. Local and secondary stiffening members may be either partially or fully fixed at their end connections dependent upon the proposed arrangement.

3.8.2 In no case, however, are the scantlings of plating and stiffeners to be less than would be required for a weather or cargo deck, or hatch cover, as applicable.

3.8.3 Where unusual arrangements of hatch cover stiffening are proposed, the scantlings of plating and stiffeners may be determined by direct calculations using a two-dimensional grillage model. A copy of the calculations is to be submitted.

3.9.1 Where heavy or special loads are proposed to be carried, the scantlings and arrangements of the deck structure will be individually considered on the basis of submitted calculations.

3.9.2 Due account is to be taken of the acceleration levels due to craft motion as applicable to particular items of heavy mass such as vehicles, containers, pallets, etc.

3.10.1 LR will consider direct calculations for the derivation of scantlings as an alternative to and equivalent to those derived by Rule requirements. The assumptions made and the calculation procedures used are to be submitted for appraisal in accordance with Pt 3, Ch 1, 2 Direct calculations.