Section
7 Single bottom structures
7.1 General
7.1.1 The
requirements of this Section, unless specified otherwise, are applicable
to all ship types, NS1, NS2 and NS3.
7.2 Centreline girder
7.2.4 The
face flat thickness is to be not less than the thickness of the web.
7.2.5 The
ratio of the width to thickness of the face flat is to be not less
than 8 but is not to exceed 16.
7.3 Side girders
7.4 Floors - general
7.4.1 The
web thickness, t
w, of plate floors, is to
be accordance with Vol 1, Pt 6, Ch 2, 2.9 Proportions of stiffener sections and
is to be taken as not less than:
for NS1 ships
for NS2 and NS3 ships
where
d
f is to
be determined from Table 3.2.1 Minimum structural
requirements
k
s and S are as defined in Vol 1, Pt 6, Ch 3, 3.2 Symbols 3.2.1
Where the floor spacing, S is greater than 2,0 m it is recommended that the floor
thickness is calculated by direct calculations.
7.4.3 If
the side frames of the ship are attached to the floors by brackets,
the depth of floor may be reduced by 15 per cent and the floor thickness
determined using the reduced depth. The brackets are to be flanged
and have the same thickness as the floors, and their arm lengths clear
of the frame are to be the same as the reduced floor depth given above.
7.4.4 The face flat thickness is to be not less than the thickness of the web
plate. The ratio of the breadth of the face flat to the thickness of the face flat is to
be not less than 8 but is not to exceed 16.
7.4.5 Additionally
floors are to comply with the requirements for bottom transverse web
frames.
7.5 Single bottom structure in machinery spaces
7.5.3 The
depth and section modulus of floors anywhere between engine or gearbox
girders is to be not less than that required to maintain continuity
of structural integrity or 50 per cent of the depth given in Vol 1, Pt 6, Ch 3, 7.4 Floors - general The face flat area and web thickness
for such reduced floor heights are to be increased appropriately in
order to maintain continuity of structural strength.
7.5.4 In
way of machinery spaces situated amidships the minimum depth of floors
is to be at least 10 per cent greater than that required in Vol 1, Pt 6, Ch 3, 7.4 Floors - general. If the top of the floors is recessed
in way of the engines, the depth of the floors in way of the recess
should generally be not less than that required by Vol 1, Pt 6, Ch 3, 7.4 Floors - general, but this will be specially considered
in each case in relation to the arrangements proposed.
7.6 Rudder horns
7.6.1 The
shell plating thickness in way of the rudder horn is to be increased
locally, by generally not less than 50 per cent but need not to be
taken as greater than the keel thickness required by Vol 1, Pt 6, Ch 3, 2 Minimum structural requirements. The scantlings of rudder
horns will be specially considered.
7.7 Forefoot and stem
7.7.2 The
forefoot and stem is to be additionally reinforced with floors.
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