Section
4 Deck structure
4.1 General
4.1.2 The
strength deck is to be longitudinally framed throughout the region
of container holds for ships where L ≥ 100 m.
4.1.3 Lower
decks/side stringers are to be efficiently scarfed into the machinery
space, and the fore end and aft end structure.
4.1.4 The
ShipRight FDA Procedure, Structural Detail Design Guide (SDDG),
indicates recommended examples of structural design configurations
in critical areas of deck structures.
4.2 Primary supporting structure
4.3 Deck plating and stiffeners
4.4 Cross decks
4.4.1 The
width and scantlings of cross-deck strips are to satisfy the requirements
of Pt 4, Ch 8, 4.2 Primary supporting structure. The thickness, t,
of cross-deck strips is to comply with the requirements of Table 8.4.1 Cross deck plating .
Table 8.4.1 Cross deck plating
| Location
|
Minimum
thickness, in mm
|
| At strength
deck
|
The greater
of the following:
(a) t = 0,012s1
(b) t = 10 + 0,01L
1
|
| At second
deck
|
The greater
of the following:
(a) t = 0,012s1 but need
not exceed 12
(b) t = 8,0
|
| Symbols
|
|
s
1 and L
1 as defined in Pt 4, Ch 8, 1.5 Symbols and definitions 1.5.1.
|
4.4.2 The
thickness may require to be increased locally in way of access openings.
4.4.3 Where
the difference between the thickness of plating inside and outside
the line of main hatchway openings exceeds 25 mm, a single transition
plate is to be fitted at the end of the cross deck strip. The thickness
of the transition plate is to be equal to the mean of the adjacent
plate thicknesses.
4.4.5 For
initial design purposes the width of the cross deck strips, w,
forming a transverse bulkhead top box (or equivalent) can be estimated
according to the following formula:
|
w
|
= |
32,5B + 400, or 1000 mm, whichever is the greater
|
where B is given in Pt 4, Ch 8, 1.5 Symbols and definitions 1.5.1.
4.5 Deck openings
4.5.1 The
corners of main hatchway openings are generally to be rounded. However,
corners with negative radii, or parabolic or elliptic profiles will
be specially considered.
4.5.4 Alternatively,
where the design of hatch corners has not been verified by direct
calculations:
-
The outboard radius
of main hatchway openings at strength deck level is, in general, to
be not less than 35 per cent of the width of the cross-deck strip
indicated in Pt 4, Ch 8, 4.4 Cross decks 4.4.5 with a
minimum of 300 mm.
-
The radius of
the hatch corners of the main hatchway openings adjacent to the engine
room is to be made as large as practicable, with a radius of approximately
40B mm.
-
Insert plates
at main hatch corners are to have an increased thickness above the
adjacent plating outside the line of hatchways of 15 per cent in way
of the container holds, and 25 per cent in container holds at engine
room bulkheads. The minimum increase is to be not less than 4,0 mm,
nor need exceed 7,0 mm, and the minimum fore and aft extent is to
be 1,0 m from the edge of the openings.
4.6 Local reinforcement
4.6.1 Attention
is to be paid to structural continuity, and abrupt changes of shape,
section or plate thickness are to be avoided, particularly in highly
stressed areas. Arrangements in way of openings are to be such as
to minimise the creation of stress concentrations.
4.6.2 In general,
large access openings are not to be arranged in the strength deck
outside the line of main hatchways in the region of container holds.
4.6.3 Small
openings, such as those for ventilation pipes or scuppers, are to
be kept clear of hold corners, ends of longitudinal hatch coamings,
ends of cross-deck strips and other critical locations.
4.7 Support for container corner seats
4.7.1 In general,
local stiffening is to be fitted under seats for container supports.
4.7.4 Doubler
plates are not to be utilised in connections subject to tensile loads.
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