Section
3 Decks loaded by wheeled vehicles
3.1 General
3.1.1 Where it is proposed either to stow wheeled or tracked vehicles on the deck
or to use wheeled vehicles for cargo handling, the deck and supporting structure are to
be designed on the basis of the maximum loading to which they may be subjected in
service. Where applicable, the hatch covers are to be similarly designed. In no case,
however, are the scantlings to be less than would be required as a weather or cargo deck
or hatch cover, as applicable.
3.1.2 The
vehicles, types and axle loads, for which the vehicle carrying decks
including, where applicable, hatch covers have been approved, are
to be stated in the Loading Manual and be contained in a notice displayed
on each deck.
3.2 Symbols
3.3 Loading
3.3.1 Details
of the deck loading resulting from the proposed stowage or operation
of vehicles are to be supplied by the Shipbuilder. These details are
to include the wheel load, axle and wheel spacing, tyre print dimensions
and type of tyre for the vehicles.
3.3.2 For
design purposes, where wheeled vehicles are to be used for cargo handling,
the deck is to be taken as loaded with a normal head cargo, except
in way of the vehicle.
3.4 Deck plating
3.4.1 The
deck plate thickness, t, is to be not less than:
Table 9.3.1 Deck plate thickness
calculation
| Symbols
|
Expression
|
|
a, s, u, and v as defined in Figure 9.3.1 Tyre print chart
|
P
1 = φ1φ2φ3λPw
|
|
|
|
v
1 = v, but ≤s
u
1 = u, but ≤ a
|
|
P
w
|
= |
load, in tonnes, on the tyre print. For closely
spaced wheels the shaded area shown in Figure 9.3.1 Tyre print chart may be taken as the
combined print |
|
P
1
|
= |
corrected patch load, in tonnes |
|
|
for
u
≤ (a - s)
for a ≥ u > (a - s)
for u > a
|
|
λ |
= |
dynamic magnification factor |
|
φ1
|
= |
patch aspect ratio correction factor |
|
|
for
v
<s
for 1,5 >  ≥ 1,0
for  ≥ 1,5
|
|
φ2
|
= |
panel aspect ratio correction factor |
|
φ3
|
= |
wide patch load factor |
|
|
Figure 9.3.1 Tyre print chart
3.4.2 Where
transversely framed decks contribute to the hull girder strength,
or where secondary stiffening is fitted perpendicular to the direction
of vehicle lanes, the thickness, t, derived from Pt 3, Ch 9, 3.4 Deck plating 3.4.1 is to be increased by 1,0
mm.
3.4.3 Where
decks are designed for the exclusive carriage of unladen wheeled vehicles,
the deck plate thickness, t, may be reduced as follows:
|
t
|
= |
(t
1 − 0,75) + t
c mm.
|
3.4.4 Where
it is proposed to carry tracked vehicles, the patch dimensions may
be taken as the track print dimensions and P
w is
to be taken as half the total weight of the vehicle. The wear and
wastage allowance from Table 9.3.2 Wear and wastage allowance is
to be increased by 0,5 mm. Deck fittings in way of vehicle lanes are
to be recessed.
Table 9.3.2 Wear and wastage allowance
| Location
|
t
c, in mm
|
| Strength deck,
weather decks, decks forming crown of tank, inner bottom
|
1,5
|
| Internal decks
elsewhere
|
0,75
|
3.4.5 If wheeled
vehicles are to be used on insulated decks or tank tops, consideration
will be given to the permissible loading in association with the insulation
arrangements and the plating thickness.
Table 9.3.3 Tyre correction factor, n
| Number
of wheels in idealised patch
|
Pneumatic tyres
|
Solid
rubber tyres
|
Steel
or solid tyres
|
1
|
0,6
|
0,8
|
1,0
|
| 2 or more
|
0,75
|
0,9
|
1,0
|
|
Note For tracked vehicles, n
is taken as 1,0.
|
3.5 Deck longitudinals and beams
3.5.1 The scantlings of vehicle deck stiffeners are to satisfy the most severe arrangement of
print wheel loads.
3.5.3 When two or more load areas are located simultaneously on the same stiffener
span, or where decks are designed for the carriage of wheeled vehicles only, the
scantling requirements are to be specially considered on the basis of direct
calculation, assuming 100 per cent end fixity in association with the loads given in
Table 9.3.7 Design load cases and the structural
design factors given in Table 9.3.6 Structural design factors. The load area is defined as the footprint of an individual wheel or
the area enclosing a group of wheels when the distance between footprints is less than
the smaller dimension of the individual prints.
3.5.4 The vehicles are to be positioned so as to produce the most severe loading condition
for each structural member under consideration.
Table 9.3.4 Secondary stiffener requirements
| Scantling requirement
|
Load case
|
| d ≤
l
|
d >
l
|
| Section modulus
Z, in cm3
|
|
|
| Inertia, I, in
cm4
|
|
|
| Web area,
Aw, in cm2
|
|
|
|
|
where m =
d/l
|
|
| Symbols
|
|
l |
= |
overall secondary stiffener length, in metres |
|
|
s |
= |
stiffener spacing, in metres |
|
|
d |
= |
dimension of load area parallel to stiffener axis, in metres |
|
|
E |
= |
Young's Modulus of steel, to be taken as 206000
N/mm2 |
|
|
w |
= |
dimension of load area perpendicular to stiffener axis, in
metres |
|
|
kw |
= |
lateral loading factor |
| = |
1 for w ≤ s
|
| = |
s/w for w > s
|
|
|
|
|
|
|
|
|
|
|
σo |
= |
specified minimum yield strength of the material, in N/mm2
|
|
|
τo |
= |
shear strength of the material, in N/mm2 |
| = |
 |
|
Table 9.3.5 Bending moment factor
| Scantling requirement
|
Deck
stiffening
|
Hatch cover
stiffening
|
| Section modulus
|
24
|
20
|
| Inertia
|
384
|
288
|
| Web area
|
2
|
2
|
Table 9.3.6 Structural design factors
| Scenario
|
fσ
|
fτ
|
fδ
|
| 1.
Loading by fork lift trucks on general purpose cargo decks
|
1,5
|
1,5
|
0,001
|
| 2.
Loading by wheeled vehicles and other deck cargo
|
0,75
|
0,75
|
| 3.
Loading by wheeled vehicles only
|
0,75
|
0,75
|
| 4. Loading
by wheeled vehicles only on longitudinally effective structure
|
0,525
|
0,525
|
| 5. Loading by wheeled vehicles and other deck
cargo on longitudinally effective structure
|
0,525
|
0,525
|
|
Note Structural design
factors for equivalent stress are to be derived as appropriate.
|
Table 9.3.7 Design load cases
| Scenario
|
Loading
|
| UDL,
Ptyw, in kN/m2
|
Point load,
Ftys, in kN
|
| 1. Loading by fork lift trucks on general purpose cargo
decks
|
9,81h/C
|
Pw
|
| 2. Loading by wheeled vehicles and other deck cargo
|
9,81h/C, see Note 2
|
(1 +
naz) Pw
|
| 3. Loading by wheeled vehicles only, see Note
1
|
Internal
decks
|
-
|
(1 +
naz) Pw
|
| Exposed decks
|
2,16
|
(1 +
naz) Pw
|
| 4. Loading by wheeled vehicles only on longitudinally
effective structure, see Note 1
|
Internal
decks
|
-
|
(1 +
naz) Pw
|
| Exposed decks
|
2,16
|
(1 +
naz) Pw
|
| 5. Loading by wheeled vehicles and other deck
cargo on longitudinally effective structure
|
9,81h/C, see Note 2
|
(1 +
naz) Pw
|
| Symbols
|
|
Pw |
= |
is the load, in kN, on the tyre print. For closely
spaced wheels, the shaded area shown in Figure 9.3.1 Tyre print chart
can be taken as the combined print. |
|
h |
= |
is the deck cargo design head, in m, see
Pt 3, Ch 3, 5 Design loading
|
|
C |
= |
is the stowage factor, see
Pt 3, Ch 3, 5 Design loading |
|
n |
= |
is the tyre correction factor given in Table 9.3.3 Tyre correction factor, n |
|
az |
= |
is the vertical acceleration at the location under
consideration, see
Pt 3, Ch 9, 9.2 Loading 9.2.3 |
|
|
Note 2. The deck cargo design head, h, need not be taken greater
than 2,5 metres unless specified otherwise by designer/shipyard.
|
3.6 Deck girders and transverses
3.6.1 Where
the load on deck girders and transverses is uniformly distributed,
the section modulus is to be not less than:
|
Z
|
= |
4,75bh
e
2
k cm3
|
3.6.2 Where the member supports point loads, see
Table 9.3.7 Design load cases with or
without the addition of uniformly distributed load, the section modulus is to be based
on a stress of  , assuming 100 per cent end fixity. For exposed decks an allowance for
weather loading of 2,16 kN/m2 is to be assumed.
3.6.3 Where
it is proposed to carry tracked vehicles, the total weight of the
vehicle is to be taken when determining the section modulus of the
transverse at the top of a ramp or at other changes of gradient.
3.7 Hatch covers
3.7.1 Where wheeled vehicles are to be used, the hatch cover plating is to be not
less in thickness than that required by Pt 3, Ch 9, 3.4 Deck plating, and
the modulus of the stiffeners is to be not less than that required by Pt 3, Ch 9, 3.5 Deck longitudinals and beams.
In no case, however, are the scantlings of plating
and stiffeners to be less than would be required as a weather or cargo
deck hatch cover, as applicable.
3.8 Train decks
3.8.1 Decks
for the transport of railway rolling stock on fixed rails will be
specially considered.
3.9 Heavy and special loads
3.9.1 Where
heavy or special loads, such as machinery transporters, are proposed
to be carried, the scantlings and arrangements of the deck structure
will be individually considered.
3.10 Securing arrangements
3.10.1 Details
of the connections to the hull of vehicle securing arrangements are
to be submitted for approval.
|