Section
9 Bulkheads
9.1 General
9.1.1 The
requirements of this Section cover watertight and deep tank transverse
and longitudinal bulkheads. Requirements are also given for shaft
tunnel boundaries and non-watertight bulkheads. For transverse bulkheads
in way of ballast holds, stools may be required, see
Pt 4, Ch 7, 10.2 Bulkheads supported by stools.
9.1.2 The
requirements of this Section apply to a vertical system of stiffening
on bulkheads. They may also be applied to a horizontal system of stiffening
provided that equivalent end support and alignment are provided.
9.2 Watertight and deep tank bulkheads
9.2.1 The scantlings of watertight and deep tank bulkheads are to comply with the
requirements of Table 1.9.1 Watertight and deep tank bulkhead
scantlings to Table 1.9.3 Bulkhead end constraint
factors. Where bulkhead stiffeners support deck girders,
transverses or pillars over, the requirements of Pt 4, Ch 1, 4.4 Deck supporting structure 4.4.11 are also to be satified.
Table 1.9.1 Watertight and deep tank bulkhead
scantlings
| Item and
requirement
|
Watertight bulkheads
|
Deep tank
bulkheads
|
| (1)
Plating thickness for plane, symmetrically corrugated and double plate
bulkheads
|
but not less than 5,5 mm
|
|
| but not less than 6,5
mm, where L < 90 m
|
|
|
not less than 7,5 mm, where L ≥ 90 m
|
| In the case of symmetrical corrugations, s is to be
taken as b or c in Figure 3.3.1 Corrugation dimensions in Pt 3, Ch 3, whichever is the
greater
|
| (2) Modulus of rolled
and built stiffeners, swedges, double plate bulkheads and symmetrical
corrugations
|
|
|
| In the case of symmetrical corrugations, s is to be taken
as p, see also Note 2
|
| (3) Inertia of rolled and built
stiffeners and swedges
|
—
|
|
| (4) Symmetrical corrugations and
double plate bulkheads
|
Additional requirements to be complied with as detailed in
Table 1.9.2 Symmetrical corrugations and
double plate bulkheads (additional requirements)
|
| (5) Stringers or webs
supporting vertical or horizontal stiffening
|
|
|
| (a) Modulus
|
Z = 5,5kh
4
Sl
e
2 cm3
|
Z = 11,7ρkh
4
Sl
e
2 cm3
|
| (b) Inertia
|
—
|
|
| Symbols
|
s, S,
I, k, ρ as defined in Pt 4, Ch 1, 1.5 Symbols and definitions 1.5.1
|
dw
|
= |
web depth of stiffening member, in mm |
|
f
|
= |
 but not to be taken greater than 1,0 |
|
h4
|
= |
load head, in metres, measured as follows: |
- For watertight bulkhead plating, the
distance vertically from a point one-third of the height of the plate
above its lower edge to a point 0,91 m above the bulkhead deck at side
or to the flooded load point, zFD, whichever is the
greater, see also
Figure 3.5.2 Heads for watertight and deep tank bulkheads in Pt 3 Ship Structures (General) and Pt 3, Ch 3, 5.5 Flooded loads.
- For deep tank bulkhead plating, the
distance from a point one-third of the height of the plate above its
lower edge to the top of the tank, or half the distance to the top of
the overflow, whichever is the greater, see also
Figure 3.5.2 Heads for watertight and deep tank bulkheads in Pt 3 Ship Structures (General).
- For watertight bulkhead stiffeners
or girders, the distance vertically from the middle of the effective
length to a point 0,91 m above the bulkhead deck at sideside, or to
the flooded load point , zFD, whichever is the
greater, see also
Figure 3.5.2 Heads for watertight and deep tank bulkheads in Pt 3 Ship Structures (General).
- For deep tank bulkhead stiffeners or
girders, the distance from the middle of the effective length to the
top of the tank, or half the distance to the top of the overflow,
whichever is the greater, see also
Figure 3.5.2 Heads for watertight and deep tank bulkheads in Pt 3 Ship Structures (General).
|
l
e
|
= |
effective length of stiffening member, in metres, and
for bulkhead stiffeners, to be taken as  , see also
Figure 1.9.1 End connections
|
|
p
|
= |
spacing of corrugations as shown in Figure 3.3.1 Corrugation dimensions
|
|
γ |
= |
1,4 for rolled or built sections and double plate
bulkheads |
| = |
1,6 for flat bars |
| = |
1,1 for symmetrical corrugations of deep tank
bulkheads |
| = |
1,0 for symmetrical corrugations of watertight
bulkheads |
|
ω, e
|
= |
as defined in Table 1.9.3 Bulkhead end constraint
factors, see also
Figure 1.9.1 End connections
|
|
Note
1. In no case are the scantlings of deep
tank bulkheads to be less than the requirements for watertight
bulkheads where watertight bulkheads are required by Pt 3, Ch 3, 5 Design loading.
|
Note
3. For rolled or built stiffeners with
flanges or face plates, the web thickness is to be not less than  whilst for flat bar stiffeners the web thickness is
to be not less than 
|
9.2.2 In way
of partially filled holds or tanks, the scantlings and structural
arrangements of the boundary bulkheads are to be capable of withstanding
the loads imposed by the movement of the liquid in those spaces. The
magnitude of the predicted loadings, together with the scantling calculations
may require to be submitted, see
Pt 3, Ch 3, 5.4 Design pressure for partially filled tanks.
9.2.3 In deep
tanks, fuel oil or oil carried as cargo is to have a flash point of
60°C or above (closed-cup test). Where tanks are intended for
other liquid cargoes of a special nature the scantlings and arrangements
will be considered in relation to the nature of the cargo.
9.2.4 Where
watertight bulkhead stiffeners are cut in way of watertight doors
in the lower part of a bulkhead, the opening is to be suitably framed
and reinforced. Where stiffeners are not cut but the spacing between
the stiffeners is increased on account of watertight doors, the stiffeners
at the sides of the doorways are to be increased in depth and strength
so that the efficiency is at least equal to that of the unpierced
bulkhead, without taking the stiffness of the door frame into consideration.
Watertight recesses in bulkheads are generally to be so framed and
stiffened as to provide strength and stiffness equivalent to the requirements
for watertight bulkheads.
9.2.5 A centreline bulkhead is, generally, to be fitted in deep tanks which
extend from side to side of the ship and are intended for the carriage of fuel oil for
the ship's use. The bulkhead may be intact or perforated as desired. If intact, the
scantlings are to be as required for boundary bulkheads. If perforated, the modulus of
the stiffeners may be 50 per cent of that required for boundary bulkheads, using
h4 measured to the crown of the tank. The stiffeners are to be
bracketed at top and bottom. The area of perforation is to be not less than five per
cent nor more than 10 per cent of the total area of the bulkhead. Where brackets from
horizontal girders on the boundary bulkheads terminate at the centreline bulkhead,
adequate support and continuity are to be maintained.
9.3 Shaft tunnels
9.3.1 Where shaft tunnels are required as specified in Pt 3, Ch 3, 4 Bulkhead requirements the thickness of the tunnel plating is to comply with
Table 1.9.1 Watertight and deep tank bulkhead
scantlings for holds or deep tanks as
appropriate. If the top plating is well curved, the thickness may be reduced by 10 per
cent in dry cargo holds. If the top plating is flat, it is to be not less than 1,1 times
the thickness required for watertight bulkheads in dry cargo holds. Under hatchways the
top plating is to be increased by 2 mm, unless covered with wood not less than the
thickness specified in Pt 4, Ch 1, 2.2 Protection of steelwork 2.2.2, which is to be secured by fastenings which do not
penetrate the plating. Where it is intended to use plywood or other forms of ceiling of
an approved type instead of planking, the thickness will be considered in each case. The
tunnel stiffeners are to comply with Table 1.9.1 Watertight and deep tank bulkhead
scantlings for holds or deep tanks, as
appropriate. When the section modulus of curved stiffeners is determined, the values of
ω1 and ω2 are to be taken as 1,0. The span of the stiffener,
l
e, is to be taken as the overall height of the tunnel, measured vertically at
the centreline of the tunnel. If the tunnel top is flat, scantlings of the stiffeners
are also to comply with Pt 4, Ch 1, 4.3 Deck stiffening. The lower end connection to the tank top is to be
welded. Additional strengthening is to be fitted under the heels of pillars or masts
stepped on the tunnel.
9.4 Non-watertight bulkheads
9.4.1 The scantlings are to be in accordance with Table 1.4.8 Non-watertight pillar
bulkheads.
Figure 1.9.1 End connections
Table 1.9.2 Symmetrical corrugations and
double plate bulkheads (additional requirements)
| Symbols
|
Type of bulkhead
|
Parameter
|
Watertight bulkheads
|
Deep tank bulkheads
|
| s, k as defined
in Pt 4, Ch 1, 1.5 Symbols and definitions 1.5.1
l
e as defined in Table 1.9.1 Watertight and deep tank bulkhead
scantlings
|
A
w
|
= |
shear area, in cm2, of webs of double
plate bulkhead |
|
θ |
= |
angle of web corrugation to plane of bulkhead |
|
Symmetrically
corrugated,
see also
Notes 1 and 2
|
|
Not to exceed: 85 at top, and
70 at bottom
|
Not to exceed:
70 at top, and
at bottom
|
| d
|
—
|
To be not less than: 39l
e mm
|
| θ
|
To be not
less than 40°
|
Note
1. The plating thickness at the middle of
span l
e of corrugated or double plate bulkheads is to extend not
less than 0,2l
e m above mid span.
Note
2. Where the span of corrugations exceeds
15 m, a diaphragm plate is to be arranged at about mid-span.
|
Double
plate,
see also
Notes 1 and 3
|
|
Not to exceed:
|
75 at top, and
65 at bottom
|
|
Not to exceed:
|
85 at top, and
75 at bottom
|
| d
|
—
|
To be not less than: 39l
e mm
|
| Aw
|
To be not less than:
 at top and
 at bottom
|
To be not less than:
 at top and
 at bottom
|
Table 1.9.3 Bulkhead end constraint
factors
| Type
|
End connection (see
Figure 1.9.1 End connections)
|
ω
|
e
|
μ
|
| Rolled or built stiffeners and swedges
|
| 1
|
End of stiffeners
unattached or attached to plating only
|
0
|
0
|
—
|
| 2
|
Members with webs and flanges (or bulbs) in line and attached at deck or
horizontal girder, see also Note 1
|
Adjacent member of B of smaller modulus
|
The
lesser of
or 1,0
|
0
|
—
|
| 3
|
Adjacent member of B of same or larger modulus
|
1,0
|
0
|
—
|
| 4
|
Bracketless connection to longitudinal member
|
Member A within length l
|
1,0
|
|
—
|
| 5
|
Member A outside length l
|
1,0
|
0
|
—
|
| 6
|
Bracketed connection
|
To
transverse member
|
Bracket extends to
floor
|
1,0
|
The
lesser of βa or 0,1l
|
—
|
| 7
|
Otherwise
|
1,0
|
0
|
—
|
| 8
|
To longitudinal member
|
1,0
|
The
lesser of βa or 0,1l
|
—
|
| Symmetrical corrugations or double plate bulkheads
|
| 9
|
Welded directly to deck -
no bulkhead in line
|
No longitudinal brackets
|
0
|
0
|
—
|
| 10
|
With longitudinal brackets and transverse stiffeners supporting
corrugated bulkhead
|
The
lesser of
or 1,0
|
0
|
—
|
| 11
|
Welded directly to
deck or girder
|
Bulkhead B, having same section, in line
|
The
least of
or 1,0
|
0
|
—
|
| 12
|
Welded directly to tank top and effectively supported by floors in line
with each bulkhead flange, see also Note 2
|
Thickness at bottom same as that at mid-span
|
The
least of
or 1,0
|
0
|
—
|
| 13
|
Thickness at bottom greater than that at mid-span
|
The
least of
or 1,0
|
The
lesser of αl or a
|
The
lesser of
|
| 14
|
Welded to stool efficiently supported by ship's structure
|
For
deep tank bulkheads 1,0
For watertight bulkheads the least of
or 1,0
|
The
lesser of αl or a
|
|
| Symbols
|
|
s,
 , ρ, k, as defined in Pt 4, Ch 1, 1.5 Symbols and definitions 1.5.1
|
a
|
= |
height, in metres, of bracket or end stool or lowest
strake of plating of symmetrically corrugated or double plate
bulkheads, see
Figure 1.9.1 End connections
|
|
d
A
|
= |
web depth, in mm, of adjacent member A |
|
e
|
= |
effective length, in metres, of bracket or end stool,
see
Figure 1.9.1 End connections
|
|
h
o
|
= |
h
4 but measured from the middle of the overall length
l |
le, p, h as defined in Table 1.9.1 Watertight and deep tank bulkhead
scantlings
|
t
B
|
= |
thickness, in mm, of flange plating of member B |
|
t
f
|
= |
thickness, in mm, of supporting floor |
|
t
m, t
e, |
= |
thickness, in mm, of flange plating of corrugation or
double plate bulkhead at mid-span or end, respectively Subscripts 1
and 2 when applied to ω, e, and a refer to the top
and bottom ends of stiffener |
|
M
1
|
= |
 for watertight bulkheads |
| = |
 for deep tank bulkheads |
|
M
2
|
= |
 for watertight bulkheads |
| = |
 for deep tank bulkheads |
In the case of symmetrical corrugations s = p
|
Z
B
|
= |
section modulus, in cm3, of adjacent
member B |
|
Z
s
|
= |
section modulus, in cm3, of horizontal
section of stool adjacent to deck or tank top over breadth s
or p (as applicable) |
All material which is continuous from top to bottom of stool may be
included in the calculation
|
|
α |
= |
a factor depending on μ and determined as
follows: |
- where μ ≤ 1,0 α = 0
where μ >1,0 α = 
|
β |
= |
a factor depending on the end bracket stiffening and
to be taken as:
1,0 for brackets with face bars
directly connected to stiffener face bars
0,7 for
flanged brackets
0,5 for unflanged brackets |
|
μ |
= |
a factor representing end constraint for symmetrical
corrugation and double plate bulkheads |
|
ω |
= |
an end constraint factor relating to the different
types of end connection, see
Figure 1.9.1 End connections
|
|
t
s
|
= |
thickness, in mm, of stool adjacent to bulkhead |
|
δ |
= |
1,0 generally |
|
δ |
= |
 for corrugated watertight bulkheads |
|
ξ |
= |
1,0 where full continuity of corrugation webs is
provided at the ends |
|
ξ |
= |
greater of 1,0 and (η + 0,333) where full continuity
is not provided |
|
η |
= |
lesser of 1,0 and  for welded sections |
|
η |
= |
lesser of 1,0 and  for cold formed sections |
|
Note
1. Where the end connection is similar to
type 2 or 3, but member flanges (or bulbs) are not aligned and brakets
are not fitted, ω=0.
Note
2. Where the end connection is similar to
type 12 or 13, but a transverse girder is arranged in place of one of
the supporting floors, special consideration will be required.
|
|