Section
5 Movable decks, lifts, internal and external ramps
5.1 Classification
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 Arrangements and design
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 Loading
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.
5.3.4 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.
5.3.6 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 Movable decks
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 External deck ramps and lifts
5.6 External shell ramps
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 Aircraft lifts
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.
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