Section
8 Non-oiltight bulkheads
8.1 General
8.1.2 Wash
bulkheads are generally to be of plane construction, horizontally
or vertically stiffened, having an area of perforations not less than
10 per cent of the total area of the bulkhead. The perforations are
to be so arranged that the efficiency of the bulkhead as a support
is not impaired.
8.1.3 Where
tanks are intended to be partially filled, the scantlings and structural
arrangements of the wash bulkheads are to be capable of withstanding
the loads imposed by the movement of liquid in the tanks. The magnitude
of the predicted loads, together with the scantling calculations,
may require to be submitted.
8.2 Symbols
8.2.1 The
symbols used in this Section are defined as follows:
|
a
|
= |
the
horizontal length of the plate panel, in mm |
|
a
T
|
= |
the cross-sectional area of the vertical web on longitudinal
bulkhead and associated bulkhead plating over one transverse space,
in cm2
|
|
b
L
|
= |
half the distance, in metres, between members supporting horizontal
girder, adjacent to the bulkhead under consideration, as shown in Figure 9.8.1 Horizontal girder
|
|
b
T
|
= |
overall breadth of tank, in metres |
|
D
1
|
= |
D, in metres, but is to be taken not less than
10 and need not be taken greater than 16
|
|
D
L
|
= |
the depth of the longitudinal bulkhead, including double bottom
girder, in metres |
|
d
L
|
= |
the distance, in metres, from the top of the longitudinal bulkhead
to the centre of the plate panel under consideration and need not
be taken greater than the distance to the bracket toe of the double
bottom transverse primary member |
|
h
|
= |
the
distance, in metres, from the centre of the load on the horizontal
girder to  m above the highest point of the tank, excluding the hatchway
|
|
d
H
|
= |
the mean depth of horizontal girders at the longitudinal bulkhead,
in metres, including the depth of the end brackets as shown in Figure 9.8.1 Horizontal girder
|
|
l
G
|
= |
the distance, in metres, from the horizontal girders to the
adjacent horizontal primary member below |
|
t
3
|
= |
 mm
|
|
τ |
= |
|
|
Q
SL
|
= |
the maximum still water shear force on the longitudinal bulkhead, in
kN, of the loading condition in question. |
| = |
Where two longitudinal bulkheads are fitted, Q
SL may be taken as:
|
| = |
|
| = |
Where one longitudinal bulkhead
is fitted, Q
SLmay be taken as:
|
| = |
|
| = |
Q
SL may
also be derived by direct calculation to determine the distribution
of shear force between the shell, inner hull and longitudinal bulkheads.
|
|
Q
SW
|
= |
design wave shear force on the longitudinal bulkhead, in kN. |
| = |
Where two longitudinal bulkheads are fitted,
QSW may be taken as:
|
| = |
|
| = |
Where one longitudinal bulkhead
is fitted, QSWmay be taken as:
|
| = |
|
T
|
= |
overall length
of tank, in metres |
|
F
d
|
= |
|
b
|
= |
the distance
between the transverse bulkheads (oiltight or non-oiltight) adjacent
to the bulkhead under consideration, in metres |
|
S
|
= |
spacing
of the double bottom transverse primary members, in metres |
|
T
p
|
= |
the maximum operating draught of ship, in metres, where the
tank with non-oiltight bulkhead is empty. |
|
W
h
|
= |
T
p + 0,023L e–0,0044L
|
|
α |
= |
 , but not to be taken greater than 1,0
|
Other symbols are defined in Pt 4, Ch 9, 1.5 General definitions and symbols.
8.3 Scantlings
8.3.2 Where
non-oiltight longitudinal wash bulkheads support a bottom
primary member, the following additional requirements are to be met:
-
The area of perforation
is to be not greater than 25 per cent of the total area of the bulkhead,
and consideration is to be given to the disposition and geometry of
the perforations so that the shear rigidity of the bulkhead is a maximum.
-
The net section
area of the bulkhead is to be not less than 0,135 l
T
b
T
D cm2.
-
The plating thickness
is to comply with Table 9.6.1 Inner hull and longitudinal
oiltight bulkhead scantlings (1)(d).
-
The thickness
of longitudinal bulkhead plating and web plating of the vertical web
on longitudinal bulkhead is generally to be not less than:
-
The thickness
of the longitudinal bulkheads supporting a transverse bulkhead horizontal
girder is in general to be not less than:
-
-
whichever is the greater.
The thickness is also to satisfy the buckling requirements
of Pt 3, Ch 4, 7 Hull buckling strength.
The increased thickness is to extend over the end bracket and
buttress of the horizontal girder down to a distance of 0,5l
G.
8.3.4 Where
non-oiltight transverse wash bulkheads support a primary
fore and aft bottom centreline girder, the following additional requirements
are to be met:
-
The area of perforation
is to be not greater than 25 per cent of the total area of the bulkhead,
and consideration is to be given to the disposition and geometry of
the perforations so that the shear rigidity of the bulkhead is a maximum.
-
The net section
area of the bulkhead is to be not less than 0,135l
b
b
T
D cm2.
-
The plating thickness
is to comply with Table 9.7.1 Transverse oiltight bulkhead
scantlings(1)(b).
In no case is either panel dimension to exceed 180 times the thickness
required by this sub-paragraph or by Pt 4, Ch 9, 8.3 Scantlings 8.3.1, whichever is the greater.
8.3.5 The
section modulus of transverse wash bulkhead stiffeners is to be not
less than:
8.4 Connections
|