Section 5 Movable decks, lifts, internal and external ramps

5.1.1 Where required by the LA or Notation, see Vol 1, Pt 1, Ch 2, 1.1 Framework of Classification 1.1.12, or specified by the Owner, movable decks will be included as a classification item. In such cases, all movable decks on board the ship are to comply with the requirements of this Section.

5.1.2 Plans showing the proposed scantlings and arrangements of the system are to be submitted.

5.1.3 The operating and securing equipment or machinery is to be in accordance with all specified standards.

5.2.1 Positive means of control are to be provided to secure decks, ramps and lifts in the raised and lowered position.

5.2.2 For steel to steel bearings in securing and supporting devices, the nominal bearing pressure calculated by dividing the design force by the projected bearing area is not to exceed 80 per cent of the yield stress of the bearing material. For other bearing materials, the permissible bearing pressure is to be determined according to the manufacturer’s specifications.

5.2.3 The arrangement of securing and supporting devices is to be such that threaded bolts do not carry support forces. The maximum tension in way of threads of steel bolts not carrying support forces is not to exceed 125/k N/mm².

5.3.1 Details of the deck, ramp or lift loading resulting from the proposed stowage arrangements of vehicles are to be supplied by the Shipbuilder. These details are to include the axle and wheel spacing, the wheel load, type of tyre and tyre print dimensions for the vehicles. For design purposes the wheel loading is to be taken as not less than 3,0 kN. see Vol 1, Pt 4, Ch 3, 2 Vehicle decks and fixed ramps.

5.3.2 Where it is proposed also to use the decks, ramps or lifts for general cargo, the design loadings are to be submitted for consideration.

5.3.3 The forces imposed on the decks, ramps or lifts are to take due account of the ship motion for all the conditions In which they will be operated, see Vol 1, Pt 5, Ch 3, 6.2 Loads for ramps and lifts, Pra

5.3.4 The scantlings and arrangements are to be not less than those required by the Rules for the supporting or surrounding structure in which the decks ramps or lifts 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.

5.3.5 The buckling strength of primary members is to be verified as being adequate, see Vol 1, Pt 6, Ch 2, 3 Buckling

5.3.6  Decks, ramps or lifts and their supporting structure are to be designed for the maximum load that is to be carried; this may include loadings from emergency situations where they are specified by the Owner.

5.4.1 Movable decks are generally to be constructed as pontoons comprising a web structure with top decking. Other forms of construction will be individually considered.

5.4.2 The decks are to be efficiently supported, and hinges, pillars, chains or other means (or a combination of these) are to be designed on the basis of the imposed loads. Where supporting chains and fittings are required, they are to have a factor of safety of at least two on the proof load.

5.4.3 Where it is proposed to stow the pontoons on deck, when not in use, details of the proposals for racks, fittings, etc. are to be submitted for consideration.

5.4.4 Where wheeled vehicles are to be used, the supporting arrangements are to be such that the movement at the edge of one pontoon relative to the next does not exceed 50 mm during vehicle operations.

5.5.1 In addition to the loading specified in Vol 1, Pt 4, Ch 3, 5.3 Loading, ramps and lifts are to be assessed using weather deck loading in the closed position, see Vol 1, Pt 5, Ch 3, 5 Local design loads for decks and bulkheads.

5.6.1 In addition to the loading specified in Vol 1, Pt 4, Ch 3, 5.3 Loading, unprotected ramps are to be assessed using side shell loading in the closed position, see Vol 1, Pt 5, Ch 3, 3 Loads on shell envelope.

5.6.2 Scantlings of the primary members, securing and supporting devices of bow doors and inner doors are to be able to withstand the design loads defined in Vol 1, Pt 4, Ch 3, 3.6 Design loads. The shear, bending and equivalent stresses are not to exceed 80/k N/mm², 120/k N/mm² and 150/k N/mm² respectively.

5.7.1 The aircraft lift platform deck alignment is to be provided by keeps at the flight deck and stops at the hangar deck.

5.7.2 If the ship has an underwater shock notation, latches are also to be provided at the flight and hangar deck levels to restrain the aircraft lift platform when stationary.

5.7.3 When transferring the aircraft or equipment to, or from, the lift platform with the keeps engaged the deflection of the platform edge is not to be greater than 25 mm.