Section
5 Aft end
5.1 Symbols
5.1.1 The symbols used in this Chapter are defined as follows:
L
|
= |
Rule length, in metres |
L2
|
= |
Rule length, L, but need not be taken greater than
300 m |
s
|
= |
stiffener spacing, in mm. |
5.2 General
5.2.1
Application.
- The requirements of this Section apply to structure located
between the aft peak bulkhead and the aft end of the ship unit.
- The requirements of this Section do not apply to the
following:
- rudder horns;
- structures which are not integral with the hull, such as
rudders, steering nozzles and propellers;
- other appendages permanently attached to the hull.
Where such items are fitted, the relevant requirements of the Rules
for Ships are to be complied with.
- The deck plating thickness and supporting structure are to be
suitably reinforced for the steering gear, mooring windlasses, and other
deck machinery.
5.2.3
Minimum thickness.
- In addition to the scantling requirements as given in Pt 10, Ch 3, 5.3 Bottom structure to Pt 10, Ch 3, 5.8 Miscellaneous structures, the plating and stiffeners are to
comply with the minimum thickness requirements for the cargo region, except
as given in Table 3.5.1 Minimum net
thickness of structure aft of the aft peak bulkhead.
Table 3.5.1 Minimum net
thickness of structure aft of the aft peak bulkhead
Scantling
location
|
Net
thickness (mm)
|
Pillar bulkhead plating
|
7,5
|
Bottom girders and aft peak floors
|
5,5
+ 0,02L2
|
Web plating of primary support
members
|
6,5
+ 0,015L2
|
5.3 Bottom structure
5.3.1
General.
- Floors are to be fitted at each frame space in the aft peak and
carried to a height at least above the sterntube, where fitted. Where floors
do not extend to flats or decks, they are to be stiffened by flanges at
their upper end.
- The centreline bottom girder is to extend as far aft as is
practicable and be suitably scarphed into the stern frame or transom.
- For self-propelled units with conventional propulsion and
steering arrangements, the relevant Sections of the Rules for Ships are to
be complied with.
5.4 Shell structure
5.4.1
Shell plating.
- The net thickness of the side shell and transom plating,
tnet
, is to comply with the requirements in Pt 10, Ch 3, 3.11 Scantling requirements 3.11.2.(a).
- The net plating thickness of shell, t
net, attached to the stern frame is to comply with the
requirements in Pt 10, Ch 3, 3.11 Scantling requirements 3.11.2.(a) and is not to be less
than:
tnet
= 0,094 (L2
– 43) + 0,009s mm.
- In way of the boss and heel plate, the shell net plating
thickness, tnet
, is not to be less than:
tnet
= 0,105 (L2
– 47) + 0,011s mm.
- Within the extents specified in Pt 10, Ch 3, 2.3 Hull envelope plating 2.3.4.(c), the thickness of the side
shell plating is to comply with the requirements in Pt 10, Ch 3, 2.3 Hull envelope plating 2.3.4.(b).
5.4.3
Shell primary support members.
- The requirements of Pt 10, Ch 3, 5.4 Shell structure 5.4.3 apply to single side skin construction
supported by a system of vertical webs and/or horizontal stringers or
flats.
- Where a longitudinal framing system is adopted, longitudinals
are to be supported by vertical primary support members extending from the
floors to the upper deck. Deck transverses are to be fitted in line with the
web frames.
- Where a transverse framing system is adopted, frames are to be
supported by horizontal primary support members spanning between the
vertical primary support members.
- The scantlings of web frames supporting longitudinal framing,
stringers and transverse framing are to be determined from Pt 10, Ch 3, 3.11 Scantling requirements 3.11.3.
- The web depth of primary support members is not to be less than
14 per cent of the bending span and is to be at least 2,5 times as deep as
the slots for stiffeners if the slots are not closed.
5.5 Deck structure
5.5.3
Deck primary support members.
- The section modulus and shear area of primary support members
are to comply with the requirements in Pt 10, Ch 3, 3.11 Scantling requirements 3.11.3.
- The web depth of primary support members is not to be less than
10 per cent and 7 per cent of the unsupported span in bending in tanks and
in dry spaces, respectively, and is not to be less than 2,5 times the depth
of the slots if the slots are not closed. In the case of a grillage
structure, the unsupported span is the distance between connections to other
primary support members.
- In way of concentrated loads from heavy equipment, the
scantlings of the deck structure are to be determined based on the actual
loading.
5.6 Tank bulkheads
5.7 Watertight boundaries
5.8 Miscellaneous structures
5.8.1
Pillar bulkheads.
- Bulkheads that support girders, or pillars and longitudinal
bulkheads which are fitted in lieu of girders, are to be stiffened to
provide supports no less effective than those required for stanchions or
pillars. The acting load and the required net cross-sectional area of the
pillar section are to be determined using the requirements of Pt 10, Ch 3, 5.5 Deck structure 5.5.4. The net moment of inertia of the
stiffener is to be calculated with a width of 40tnet
of the plating, where tnet
is net plating thickness, in mm.
- Pillar bulkheads are to meet the following requirements:
- the distance between bulkhead stiffeners is not to
exceed 1500 mm;
- where corrugated, the depth of the corrugation is not to
be less than 100 mm.
5.8.2
Rudder trunk.
- Where a rudder trunk is fitted, the scantlings are to be in
accordance with the shell plating and framing in Pt 10, Ch 3, 5.4 Shell structure 5.4.1 and Pt 10, Ch 3, 5.4 Shell structure 5.4.2. Where the rudder trunk is open to the
sea, a seal or stuffing box is to be fitted above the deepest load waterline
to prevent water from entering the steering gear compartment.
5.8.3
Stern thruster tunnels.
- The net thickness of the tunnel plating, ttun-net
, is not to be less than required for shell plating in the vicinity of
the thruster. In addition ttun-net
is not to be taken less than:
ttun-net
= 0,008dtun
+ 1,8 m
where
dtun
|
= |
inside diameter of tunnel, in mm, but not to be
taken less than 970 mm. |
- Where the outboard ends of the tunnel are provided with bars or
grids, the bars or grids are to be effectively secured.
|