Section
10 Deck structures
10.1 General
10.1.1 The requirements of this Section, unless specified otherwise, are
applicable to all ship types, NS1, NS2 and NS3.
10.1.2 The basic structural scantlings of NS1 ships are to be determined in
accordance with Vol 1, Pt 6, Ch 3, 3 NS1 scantling determination. The basic structural scantlings of NS2 and NS3
ships are to be determined in accordance with Vol 1, Pt 6, Ch 3, 4 NS2 and NS3 scantling determination The thickness of the deck plating is in no case to be less
than the appropriate minimum requirement given in Vol 1, Pt 6, Ch 3, 2 Minimum structural requirements. Arrangements of structures are to be in accordance with
Vol 1, Pt 3, Ch 2, 3.7 Deck structure
10.1.6 Decks forming the boundary of a tank are to comply with the requirements
for the appropriate deck and are to be additionally examined for compliance with the
requirements for deep tank plating.
10.1.7 Decks forming subdivision or watertight internal boundaries are to comply
with the requirements for the appropriate deck and are to be additionally examined for
compliance with the requirements for watertight plating and stiffening.
10.2 Deck plating
10.2.1 The
thickness of the strength deck stringer plate is to be increased by
20 per cent at the ends of superstructures extending out to the ship
side, deckhouses, poop and forecastle. The thickness of the strength
deck is to be increased by 20 per cent in way of the corners of effective
superstructures that are not full width.
10.3 Deck stiffening
10.3.1 Higher
tensile steel deck longitudinals where used are to be continuous irrespective
of the ship length.
10.3.4 Where the depth of web of a longitudinal girder at the strength deck within
0,3LR to 0,7LR exceeds:
-
55tw for mild steel members
-
65tw
 for higher tensile steel members
kL is defined in Vol 1, Pt 6, Ch 5, 3 Scantling determination for NS2 and NS3 ships.
Additional longitudinal web stiffeners are to be fitted at a spacing not
exceeding the value in (a) or (b) as appropriate. In cases where this spacing is
exceeded, the web thickness is, in general, to be suitably increased. Alternative
proposals will be considered.
10.3.5 Web stiffeners may be flat bars of thickness tw and depth
0,1dw, or 50 mm, whichever is greater. Alternative sections of
equivalent inertia may be adopted.
10.4 Deck openings
10.4.2 The
steel grade for corner inserts in way of openings for lifts, or cut
outs in the deck plating for side doors, etc. is to be Grade E or
EH.
10.4.3 Welded
attachments close to or on the free edge of the large opening corner
plating are to be avoided. The butt welds of corner insert plates
to the adjacent deck plating are to be located well clear of butts
in the opening coaming or bulkheads.
10.4.4 Where
minor deck openings, within 0,3L
R to 0,7L
R, have a total breadth or shadow area breadth in one transverse
section that exceeds the limitation given in Vol 1, Pt 6, Ch 4, 1.4 Calculation of hull section modulus 1.4.13 and Vol 1, Pt 6, Ch 4, 1.4 Calculation of hull section modulus 1.4.14, compensation will be required
to restore the excess. This is generally to be arranged by increasing
the deck plate thickness, but other proposals will be considered.
10.4.5 Plate
panels in which openings are cut are to be adequately stiffened, where
necessary, against compression and shear buckling. The corners of
all openings are to be well rounded and the edges smooth.
10.4.6 Minor
openings in the strength deck outside the line of major deck openings
having a stress concentration factor in excess of 2,4 will require
edge reinforcement in the form of a spigot of adequate dimensions,
but alternative arrangements will be considered. The area of any edge
reinforcement which may be required is not to be taken into account
in determining the required sectional area of compensation for the
opening. For example, elliptical openings having their major axis
fore and aft and a ratio of length to breadth not less than 2 to 1
will not normally require edge reinforcement.
10.4.7 Where
long, wide openings are arranged on lower decks, it may be necessary
to increase the deck plating thickness to ensure effective support
for side framing.
10.4.8 Lower
deck openings should be kept clear of the corners of major openings
and other areas of high stress, so far as possible. Compensation will
not, in general, be required unless the total width of openings in
any frame space, or between any two transverses, exceeds 15k
s per cent of the original effective plating width. The requirements
of Vol 1, Pt 6, Ch 3, 10.4 Deck openings 10.4.1 also apply to lower
deck openings except that:
-
the thickness
of inserts, if required, for the lower deck large opening corners
is to be 2,5 mm greater than the deck thickness;
-
inserts will
not generally be required for large opening corners on non-effective
decks or platform decks; and
-
reinforcement
will not generally be required for circular openings, provided that
the plate panels in which they are situated are otherwise adequately
stiffened against compression and shear buckling.
10.5 Sheathing
10.6 Decks used as ramps
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