Section
8 Side and stern doors and other shell openings
8.1 Symbols
8.1.1 The
symbols used in this Section are defined as follows:
|
d
|
= |
distance
between closing devices, in metres |
|
k
|
= |
material
factor, see
Pt 3, Ch 2, 1.2 Steel,
but is not to be taken less than 0,72 unless demonstrated otherwise
by a direct strength analysis with regard to relevant modes of failure
|
|
σ |
= |
bending stress, in N/mm2
|
|
σe
|
= |
equivalent stress, in N/mm2 |
| = |
|
|
σo
|
= |
minimum yield stress of the bearing material, in N/mm2
|
|
τ |
= |
shear stress, in N/mm2. |
8.2 General
8.2.1 These
requirements cover cargo and service doors in the ship side (abaft
the collision bulkhead) and stern area, below the freeboard deck and
in enclosed superstructures.
8.2.4 In
general, and for passenger ships in particular, the lower edge of
door openings is not to be below a line drawn parallel to the freeboard
deck at side, which has at its lowest point at least 230 mm above
the upper edge of the uppermost Load Line.
8.2.5 When
the lower edge is below the line specified in Pt 3, Ch 11, 8.2 General 8.2.4, the arrangement will be
specially considered. Special consideration is to be given to preventing
the spread of leakage water over the deck. The reference to the uppermost
Load Line is to be taken as the tropical fresh waterline or, if timber
freeboards are assigned, the timber tropical fresh waterline.
8.2.6 Watertight
doors below the freeboard deck, with the exception of pilot doors
which are to open inwards, are to open outwards. Weathertight doors
are generally to be arranged to open outwards, however inward opening
doors will be considered provided these satisfy the requirements of Pt 3, Ch 11, 8.2 General 8.2.7.
8.2.7 Inward
opening doors situated in the first two 'tween decks above the summer
load waterline are to be fitted with a second independent securing
device, such as a strongback or equivalent arrangement, capable of
providing weathertight integrity. Where the consequences of water
ingress due to failure of the door are minimal, such as a small pilot
door giving access to a watertight trunk leading to the bulkhead deck,
the required enhancements will be specially considered.
8.2.8 For
passenger ships the following are also applicable:
-
Gangway, cargo
and service ports fitted below the margin line, see
Pt 3, Ch 3, 4.3 After peak bulkhead, are to satisfy the strength
requirements given for side doors in this Section. They are to be
effectively closed and secured watertight before the ship leaves port,
and are to be kept closed during navigation. Such ports are not to
have their lowest point below the deepest subdivision Load Line.
-
Where the inboard
end of a rubbish chute is below the margin line in a passenger ship,
the inboard end cover is to be watertight and, in addition to the
discharge flap interlock, a screwdown automatic non-return valve is
to be fitted in an easily accessible position above the deepest subdivision.
The valve is to be controlled from a position above the bulkhead deck
and provided with an open/shut indicator, and kept closed when not
in use. A suitable notice is to be displayed at the valve position.
8.2.9 For
ships complying with the requirements of this Section, the securing,
supporting and locking devices are defined as follows:
-
A securing device
is used to keep the door closed by preventing it from rotating about
its hinges or other pivoted attachments to the ship.
-
A supporting
device is used to transmit external and internal loads from the door
to a securing device and from the securing device to the ship's structure,
or a device other than a securing device, such as a hinge, stopper
or other fixed device, that transmits loads from the door to the ship's
structure.
-
A locking device
locks a securing device in the closed position.
8.2.10 Ro-ro
cargo spaces are spaces not normally subdivided in any way and extending
to either a substantial length or the entire length of the ship, in
which motor vehicles with fuel in their tanks for their own propulsion
and/or goods (packaged or in bulk, in or on rail or road cars, vehicles
(including road or rail tankers), trailers, containers, pallets, demountable
tanks in or on similar stowage units or other receptacles) can be
loaded and unloaded normally in a horizontal direction.
8.2.11 Special
category spaces are those enclosed spaces above and below the bulkhead
deck, into and from which vehicles can be driven and to which passengers
have access, and which may be accommodated on more than one deck where
total overall clear height for vehicles does not exceed 10 m.
8.3 Scantlings
8.3.1 In
general the strength of side and stern doors is to be equivalent to
the strength of the surrounding structure.
8.3.2 Door
openings in the side shell are to have well rounded corners and adequate
compensation is to be arranged with web frames at sides and stringers
or equivalent above and below, see
Pt 4, Ch 1, 5 Shell envelope plating.
8.3.3 Doors
are to be adequately stiffened, and means are to be provided to prevent
movement of the doors when closed. Adequate strength is to be provided
in the connections of the lifting/manoeuvring arms and hinges to the
door structure and to the ship structure.
8.3.4 The
thickness of the door plating is to be not less than the shell plating
calculated with the door stiffener spacing, and in no case to be less
than the minimum adjacent shell thickness.
8.3.5 Where
stern doors are protected against direct wave impact by a permanent
external ramp, the thickness of the stern door plating may be reduced
by 20 per cent relative to the requirements of Pt 3, Ch 11, 8.3 Scantlings 8.3.4. Those parts of the stern
door which are not protected by the ramp are to have the thickness
of plating in full compliance with Pt 3, Ch 11, 8.3 Scantlings 8.3.4.
8.3.7 The
section modulus of horizontal or vertical stiffeners is to be not
less than required for the adjacent shell framing using the actual
stiffener spacing. Consideration is to be given, where necessary,
to differences in fixity between ship's frames and door stiffeners.
8.3.8 Where
necessary, door secondary stiffeners are to be supported by primary
members constituting the main stiffening elements of the door.
8.3.9 The scantlings of such primary members are to be based on direct strength
calculations. Normally, formulae for simple beam theory may be applied to determine the
bending stress. Members are to be considered to have simply supported end connections.
The design load is the uniformly distributed external sea pressure, p
e, as defined in Pt 3, Ch 11, 8.2 General 8.2.6. For minimum scantlings, p
e is to be taken as 25 kN/m2 and the permissible stresses are as
follows:
8.3.10 The
webs of primary members are to be adequately stiffened, preferably
in a direction perpendicular to the shell plating.
8.3.11 The
stiffness of the edges of the doors and the hull structure in way
are to be sufficient to ensure weathertight integrity. Edge stiffeners/girders
are to be adequately stiffened against rotation and are to have a
moment of inertia not less than:
|
= |
d
4 cm4
|
where
|
= |
packing line pressure along edges, not to be taken less than 50
N/cm. |
For edge girders supporting main door girders between securing
devices, the moment of inertia is to be increased in relation to the
additional force.
8.3.12 The
buckling strength of primary members is to be specially considered.
8.3.13 All
load transmitting elements in the design load path from door through
securing and supporting devices into the ship structure, including
welded connections, are to be to the same strength standard as required
for the securing and supporting devices. These elements include pins,
supporting brackets and back-up brackets. Where cut-outs are made
in the supporting structure, the strength and stiffness will be specially
considered.
8.4 Doors serving as ramps
8.5 Arrangements for the closing, securing and supporting of doors
8.5.1 Doors
are to be fitted with adequate means of closing, securing and support
so as to be commensurate with the strength and stiffness of the surrounding
structure. The hull supporting structure in way of the doors is to
be suitable for the same design loads and design stresses as the securing
and supporting devices. Where packing is required, the packing material
is to be of comparatively soft type, and the supporting forces are
to be carried by the steel structure only. Other types of packing
may be considered. Maximum design clearance between securing and
supporting devices is generally not to exceed 3 mm.
8.5.2 Devices
are to be simple to operate and easily accessible. They are to be
of a design approved by Clasifications Register for the intended purpose.
8.5.3 Securing
devices are to be equipped with positive locking arrangements. Arrangements
are to be such that the securing devices are retained in the closed
position within design limits of inclination, vibration and other
motion-induced loads and in the event of loss of any actuating power
supply.
8.5.4 Systems
for door opening/closing and securing/ locking are to be interlocked
in such a way that they can only operate in a proper sequence. Hydraulic
systems are to comply with Pt 5, Ch 14, 9 Hydraulic systems.
8.5.5 Means are to be provided to enable the doors to be mechanically fixed in the
open position taking into account the self weight of the door and a minimum wind
pressure of 1,5 kN/m2 acting on the maximum projected area in the open
position.
8.5.6 The
spacing for cleats or closing devices should not exceed 2,5 m and
there should be cleats or closing devices positioned as close to the
corners as practicable. Alternative arrangements for ensuring weathertight
sealing will be specially considered.
8.6 Design loads
8.6.1 The
design force considered for the scantlings of primary members, securing
and supporting devices of side shell doors and stern doors are to
be taken not less than:
-
Design forces
for securing or supporting devices of doors opening inwards:
External force:
Internal force:
-
Design forces
for securing or supporting devices of doors opening outwards:
External force:
Internal force:
-
Design forces
for primary members:
External force:
Internal force:
whichever is the greater.
The symbols used are defined as follows:
|
p
e
|
= |
external sea pressure, in kN/m2, determined at the
centre of gravity of the door opening and is not to be taken less than: |
| = |
For ZG < T 10(T -
ZG) + 25 kN/m2 |
| = |
For ZG < T 25 kN/m2 |
| = |
For stern doors of ships fitted with bow doors,
Pe is not to be taken less than: |
|
pemin
|
= |
0,6λCH (0,8 +
0,6L0,5)2 kN/m2
|
|
T
|
= |
summer
draught, in metres |
|
Z
G
|
= |
height of the centre of area of the door, in m, above the base
line |
|
L
|
= |
length
of ship, but need not be taken greater than 200 m |
|
λ |
= |
coefficient
depending on the area where the ship is intended to be operated: |
| = |
1 for sea-going ships |
| = |
0,8 for ships operated in coastal waters |
| = |
0,5 for ships operated in sheltered waters |
|
CH
|
= |
0,0125L for L < 80 m
|
| = |
1 for L ≥ 80 m
|
|
A
|
= |
area,
in m2, of the door opening
|
|
W
|
= |
weight
of the door, in tonnes |
|
Pp
|
= |
total packing force, kN. When packing is fitted, the packing
line force per unit length is to be specified, normally not to be taken less
than: 5 kN/m |
|
Po
|
= |
the greater of P
c and 5A kN |
|
Pc
|
= |
accidental force, in kN, due to loose cargo, etc. to be
uniformly distributed over the area A and not to be taken less than
300 kN. For small doors such as bunker doors and pilot doors, the value of
P
c may be taken as zero, provided an additional structure such as
an inner ramp is fitted, which is capable of protecting the door from
accidental force due to loose cargoes. |
8.7 Design of securing and supporting devices
8.7.1 Securing
devices and supporting devices are to be designed to withstand the
forces given above using the following permissible stresses:
The terms `securing device' and `supporting device'
are defined in Pt 4, Ch 2, 8.2 General 8.2.8.
8.7.2 The
arrangement of securing and supporting devices is to be such that
threaded bolts are not to carry support forces. The maximum tensile
stress in way of threads of bolts, not carrying support forces, is
not to exceed:
8.7.3 For
steel to steel bearings in securing and supporting devices, the normal
bearing pressure is not to exceed 0,8σo, see
Pt 3, Ch 11, 8.1 Symbols 8.1.1. For other bearing materials,
the permissible bearing pressure is to be determined according to
the manufacturer's specification. The normal bearing pressure is
to be calculated by dividing the design force by the projected bearing
area.
8.7.4 The
distribution of the reaction forces acting on the securing and supporting
devices may require to be supported by direct calculations taking
into account the flexibility of the hull structure and the actual
position and stiffness of the supports. Small and/or flexible devices,
such as cleats, intended to provide load compression of the packing
material are not generally to be included in these calculations.
8.7.5 Only
the active supporting and securing devices having an effective stiffness
in the relevant direction are to be considered in the calculation
of the reaction forces acting on the devices.
8.7.7 The
arrangement of securing devices and supporting devices in way of these
securing devices is to be designed with redundancy so that in the
event of failure of any single securing or supporting device the remaining
devices are capable of withstanding the reaction forces, without exceeding,
by more than 20 per cent, the permissible stresses as defined in Pt 3, Ch 11, 8.7 Design of securing and supporting devices 8.7.1.
8.8 Operating and Maintenance Manual
8.8.1 An
Operating and Maintenance Manual for the doors is to be provided on
board and is to contain necessary information on:
-
main particulars
and design drawings,
-
service conditions,
e.g. service area restrictions, acceptable clearances for supports,
-
maintenance and
function testing,
-
register of inspections,
repairs and renewals.
8.8.2 For
passenger/vehicle ferries and roll on-roll off cargo ships, see
Pt 4, Ch 2, 1.1 Application 1.1.1, an Operating and
Maintenance Manual for the doors, as defined in Pt 4, Ch 2, 8.7 Operating and Maintenance Manual 8.7.1, is to be provided
on board instead of that required by Pt 3, Ch 11, 8.8 Operating and Maintenance Manual 8.8.1.
8.8.3 The
Manual is to be submitted for approval, and is to contain a note recommending
that recorded inspections of the door supporting and securing devices
be carried out by the ship's staff at monthly intervals or following
incidents that could result in damage, including heavy weather or
contact in the region of the doors. Any damages recorded during such
inspections are to be reported to LR.
8.8.4 Documented
operating procedures for closing and securing the doors are to be
kept on board and posted at an appropriate place.
|