Section
9 Superstructures, deckhouses and bulwarks
9.1 General
9.1.1 Where practicable,
superstructures and deckhouses are to be designed with well cambered
decks and well radiused corners to build rigidity into the structure.
9.1.2 The plating
and supporting structure are to be suitably reinforced in way of localised
areas of high stress such as corners of openings, cranes, masts, derrick
posts, machinery, fittings and other heavy or vibrating loads.
9.1.3 Primary
stiffening members are to be continuous and substantially bracketed
at their end connections to maintain continuity of structural strength.
9.1.4 Secondary
stiffening members are to be effectively continuous and bracketed
at their end connections as appropriate.
9.1.5 Structures
subject to concentrated loads are to be suitably reinforced. Where
concentrations of loading on one side of a stiffener may occur, such
as pillars out of line, the stiffener is to be adequately stiffened
against torsion.
9.2 Symbols and definitions
9.2.1 The term
`house' is used in this Section to include both superstructures and
deckhouses.
9.3 House side plating
9.4 House front plating
9.5 House end plating
9.6 House top plating
9.7 Coachroof plating
9.8 Machinery casing plating
9.9 Forecastle requirements
9.9.1 The forecastle
side plating may be a continuation of the hull side shell plating
or fitted as a separate assembly. In both cases the plating thickness
is to be the same as the side shell plating at deck edge. Where fitted
as a separate assembly, suitable arrangements are to be made to ensure
continuity of the effect of the sheerstrake at the break and at the
upper edge of the forecastle side. Full penetration welding is to
be used.
9.9.2 The side
plating is to be stiffened by side frames effectively connected to
the deck structure. Deep webs are to be fitted to ensure overall rigidity.
9.9.3 The deck
plating thickness is to be increased by 20 per cent in way of the
end of the forecastle if this occurs at a position aft of 0,25L
R from the F.P. No increase is required if the forecastle end
bulkhead lies forward of 0,2L
R from the F.P.
The increase at intermediate positions of end bulkhead is to be obtained
by interpolation.
9.10 House side stiffeners
9.10.1 The Rule
requirements for section modulus, inertia and web area for the house
side primary stiffening are to be determined from the general
equations given in Pt 7, Ch 3, 1.17 Stiffening general, using
the design pressures from Pt 5, Ch 3, 3.1 Hull structures or Pt 5, Ch 4, 3.1 Hull structures for non-displacement or
displacement craft as appropriate, and the coefficients Φ
Z, Φ
I, and Φ
A as
detailed in Table 3.1.1 Section modulus, inertia and web
area coefficients for the
load model (a).
9.10.2 The Rule
requirements for section modulus, inertia and web area for house
side secondary stiffening are to be determined from the general
equations given in Pt 7, Ch 3, 1.17 Stiffening general, using
the design pressures from Pt 5, Ch 3, 3.1 Hull structures or Pt 5, Ch 4, 3.1 Hull structures for non-displacement or
displacement craft as appropriate, and the coefficients Φ
Z, Φ
I, and Φ
A as
detailed in Table 3.1.1 Section modulus, inertia and web
area coefficients for the
load model (b). Special consideration will be given to the application
of other load models subject to the structural arrangement and degree
of end fixity provided.
9.11 House front stiffeners
9.11.1 The Rule
requirements for section modulus, inertia and web area for house
front primary stiffening are to be determined from the general
equations given in Pt 7, Ch 3, 1.17 Stiffening general, using
the design pressures from Pt 5, Ch 3, 3.1 Hull structures or Pt 5, Ch 4, 3.1 Hull structures for non-displacement or
displacement craft as appropriate, and the coefficients Φ
Z, Φ
I, and Φ
A as
detailed in Table 3.1.1 Section modulus, inertia and web
area coefficients for the
load model (a).
9.11.2 The Rule
requirements for section modulus, inertia and web area for house
front secondary stiffening are to be determined from the general
equations given in Pt 7, Ch 3, 1.17 Stiffening general, using
the design pressures from Pt 5, Ch 3, 3.1 Hull structures or Pt 5, Ch 4, 3.1 Hull structures for non-displacement or
displacement craft as appropriate, and the coefficients Φ
Z, Φ
I, and Φ
A as
detailed in Table 3.1.1 Section modulus, inertia and web
area coefficients for the
load model (b). Special consideration will be given to the application
of other load models subject to the structural arrangement and degree
of end fixity provided.
9.12 House aft end stiffeners
9.12.1 The Rule
requirements for section modulus, inertia and web area for house
aft end primary stiffening are to be determined from the general
equations given in Pt 7, Ch 3, 1.17 Stiffening general, using
the design pressures from Pt 5, Ch 3, 3.1 Hull structures or Pt 5, Ch 4, 3.1 Hull structures for non-displacement or
displacement craft as appropriate, and the coefficients Φ
Z, Φ
I, and Φ
A as
detailed in Table 3.1.1 Section modulus, inertia and web
area coefficients for the
load model (a).
9.12.2 The Rule
requirements for section modulus, inertia and web area for house
aft end secondary stiffening are to be determined from the
general equations given in Pt 7, Ch 3, 1.17 Stiffening general,
using the design pressures from Pt 5, Ch 3, 3.1 Hull structures or Pt 5, Ch 4, 3.1 Hull structures for
non-displacement or displacement craft as appropriate, and the coefficients Φ
Z, Φ
I, and Φ
A as detailed in Table 3.1.1 Section modulus, inertia and web
area coefficients for the load model (b). Special consideration will be
given to the application of other load models subject to the structural
arrangement and degree of end fixity provided.
9.13 House top stiffeners
9.13.1 The house
top is to be effectively supported by a system of transverse or longitudinal
beams and girders. The span of the beams is in general not to exceed
2,4 m and the beams are to be effectively connected to the house upper
coamings and girders.
9.13.2 The Rule
requirements for section modulus, inertia and web area for house
top primary stiffening are to be determined from the general
equations given in Pt 7, Ch 3, 1.17 Stiffening general, using
the design pressures from Pt 5, Ch 3, 3.1 Hull structures or Pt 5, Ch 4, 3.1 Hull structures for non-displacement or
displacement craft as appropriate, and the coefficients Φ
Z, Φ
I, and Φ
A as
detailed in Table 3.1.1 Section modulus, inertia and web
area coefficients for the
load model (a).
9.13.3 The Rule
requirements for section modulus, inertia and web area for house
top secondary stiffening are to be determined from the general
equations given in Pt 7, Ch 3, 1.17 Stiffening general, using
the design pressures from Pt 5, Ch 3, 3.1 Hull structures or Pt 5, Ch 4, 3.1 Hull structures for non-displacement or
displacement craft as appropriate, and the coefficients Φ
Z, Φ
I, and Φ
A as
detailed in Table 3.1.1 Section modulus, inertia and web
area coefficients for the
load model (b). Special consideration will be given to the application
of other load models subject to the structural arrangement and degree
of end fixity provided.
9.14 Coachroof stiffeners
9.14.1 The Rule
requirements for section modulus, inertia and web area for coachroof
primary stiffening are to be determined from the general equations
given in Pt 7, Ch 3, 1.17 Stiffening general, using the design
pressures from Pt 5, Ch 3, 3.1 Hull structures or Pt 5, Ch 4, 3.1 Hull structures for non-displacement or
displacement craft as appropriate, and the coefficients Φ
Z, Φ
I, and Φ
A as
detailed in Table 3.1.1 Section modulus, inertia and web
area coefficients for the
load model (a).
9.14.2 The Rule
requirements for section modulus, inertia and web area for coachroof
secondary stiffening are to be determined from the general
equations given in Pt 7, Ch 3, 1.17 Stiffening general, using
the design pressures from Pt 5, Ch 3, 3.1 Hull structures or Pt 5, Ch 4, 3.1 Hull structures for non-displacement or
displacement craft as appropriate, and the coefficients Φ
Z, Φ
I, and Φ
A as
detailed in Table 3.1.1 Section modulus, inertia and web
area coefficients for the
load model (b). Special consideration will be given to the application
of other load models subject to the structural arrangement and degree
of end fixity provided.
9.15 Machinery casing stiffeners
9.15.1 The Rule
requirements for section modulus, inertia and web area for machinery
casing primary stiffening are to be determined from the general
equations given in Pt 7, Ch 3, 1.17 Stiffening general, using
the design pressures from Pt 5, Ch 3, 3.1 Hull structures or Pt 5, Ch 4, 3.1 Hull structures for non-displacement or
displacement craft as appropriate, and the coefficients Φ
Z, Φ
I, and Φ
A as
detailed in Table 3.1.1 Section modulus, inertia and web
area coefficients for the
load model (a).
9.15.2 The Rule
requirements for section modulus, inertia and web area for machinery
casing secondary stiffening are to be determined from the general
equations given in Pt 7, Ch 3, 1.17 Stiffening general, using
the design pressures from Pt 5, Ch 3, 3.1 Hull structures or Pt 5, Ch 4, 3.1 Hull structures for non-displacement or
displacement craft as appropriate, and the coefficients Φ
Z, Φ
I, and Φ
A as
detailed in Table 3.1.1 Section modulus, inertia and web
area coefficients for the
load model (b). Special consideration will be given to the application
of other load models subject to the structural arrangement and degree
of end fixity provided.
9.15.3 Where
casing stiffeners carry loads from deck transverses, girders, etc.
or where they are in line with pillars below, they are to be suitably
reinforced.
9.15.4 Where
casing sides act as girders supporting decks over, care is to be taken
that access openings do not seriously weaken the structure. Openings
are to be effectively framed and reinforced if found necessary. Particular
attention is to be paid to stiffening where the casing supports the
funnel or exhaust uptakes.
9.16 Forecastle stiffeners
9.16.1 The scantlings
of forecastle primary and secondary stiffening members are to be equivalent
to those for the side shell envelope framing at the deck edge as required
by Pt 7, Ch 3, 4 Shell envelope framing.
9.17 Superstructures formed by extending side structures
9.17.1 Superstructure
first tier sides formed by extending the hull side structure are to
be in accordance with the requirements for house fronts given in Pt 7, Ch 3, 9.4 House front plating and Pt 7, Ch 3, 9.11 House front stiffeners for
plating and stiffeners respectively, but need not be taken as greater
than the side structure requirements at the deck edge at the same
longitudinal position.
9.18 Fire aspects
9.19 Openings
9.19.1 All openings
are to be substantially framed and have well rounded corners. Arrangements
are to be made to minimise the effect of discontinuities in erections.
Continuous coamings or girders are to be fitted below and above doors
and similar openings.
9.19.2 Particular
attention is to be paid to the effectiveness of end bulkheads, and
the upper deck stiffening in way, when large openings for doors and
windows are fitted.
9.19.3 Special
care is to be taken to minimise the size and number of openings in
the side bulkheads in the region of the ends of erections within 0,5L
R amidships. Account is to be taken of the high
vertical shear loading which can occur in these areas.
9.20 Mullions
9.20.1 Window
openings are to be suitably framed and mullions will in general be
required.
9.20.2 The scantlings
of mullions are to be not less than as required for a stiffener in
the same position.
9.20.3 When
determining the stiffener requirements, the width of effective plating
is in no case to be taken as greater than the distance between adjacent
window openings.
9.20.4 Where
significant shear forces are to be vertically transmitted by the window
frames, adequate shear rigidity is to be verified by direct calculation.
9.21 Global strength
9.21.1 Transverse
rigidity is to be maintained throughout the length of the erection
by means of web frames, bulkheads or partial bulkheads. Particular
attention is to be paid when an upper tier is wider than its supporting
tier and when significant loads are carried on the house top.
9.21.2 Where
practicable, web frames are to be arranged in line with bulkheads
below.
9.21.3 Internal
bulkheads are to be fitted in line with bulkheads or deep primary
stiffeners below.
9.22 House/deck connection
9.22.1 Adequate
support under the ends of erections is to be provided in the form
of webs, pillars, diaphragms or bulkheads in conjunction with reinforced
deck beams.
9.22.2 Special
attention is to be given to the connection of the erection to the
deck in order to provide an adequate load distribution and avoid stress
concentrations.
9.22.4 Typical
design details of house/deck connections are given in LR's Guidance
Notes for Structural Details.
9.23 Sheathing
9.24 Erections contributing to longitudinal strength
9.24.1 For craft
above 40 m in length, L
R, or for designs where
the superstructure is designed to absorb global loads the effectiveness
of superstructures to carry these loads is to be determined. The effectiveness
may be assessed in accordance with Pt 7, Ch 6, 2.5 Superstructures global strength.
9.24.3 When
large openings or a large number of smaller openings are cut in the
superstructure sides, reducing the capability to transmit shear force
between decks, an assessment of structural efficiency may be required.
9.25 Novel features
9.25.1 Direct
calculations may be required to determine the plating and stiffener
requirements where the house is of unusual design, form or proportions.
9.26 Bulwarks
9.26.3 The requirements
for section modulus, inertia and web area are to be determined from
the general equations given in Pt 7, Ch 3, 1.17 Stiffening general,
using the design pressures from Pt 5, Ch 3, 3.1 Hull structures or Pt 5, Ch 4, 3.1 Hull structures for
non-displacement or displacement craft as appropriate, and the coefficients Φ
Z, Φ
I, and Φ
A as detailed in Table 3.1.1 Section modulus, inertia and web
area coefficients for the load model (d).
9.26.4 Bulwarks
are not to be cut for gangway or other openings near the breaks of
superstructures.
9.26.5 Attention
is to be paid to avoid discontinuity of strength of the bulwark, particularly
in way of local increases in stress and changes in height.
9.26.6 Welding
of bulwark to the top edge of sheerstrake within 0,5L
R amidship,
is generally to be avoided. However, if this arrangement is not practicable
welding to the sheerstrake may be accepted if care is taken to minimise
any notch effects.
9.26.7
Fishing
craft are to have bulwarks fitted. The bulwark may be formed
from a continuation of the side shell plating or connected as a separate
assembly. Where the bulwark is considered to be stressed and contributing
to the global strength of the craft, the plate thickness of the bulwark
is not to be less than the sheerstrake plating thickness. In no case
is the thickness of the bulwark plating to be taken as less than 80
per cent of the side shell thickness. The bulwark is to be supported
by suitable stiffening members which may be formed from a continuation
of the side frames, or from flanged plate stays of the same thickness
as the bulwark. In general these frames are to be spaced not more
than two side frame spacings apart.
9.26.8 In way
of gantries, trawl gallows, mooring pipes etc. the plate thickness
in way is to be increased by not less than 50 per cent.
9.26.9
Pilot
craft are to be fitted with sufficient hand rails adjacent
to the exposed areas of the working decks and platforms. In addition
these areas are to have non-skid surfaces.
9.27 Freeing arrangements
9.28 Free flow area
9.29 Guard rails
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