Page 189 - Ship Construction.DJ Eyres 6Ed

Ch17-H8070.fm Page 178 Wednesday, October 18, 2006 6:57 AM
178 Ship Construction
within the tank space. Frames supporting hatch end beams and those in
way of deck transverses where the deck is framed longitudinally, also have
increased scantlings.
Web frames, that is built up frames consisting of plate web and face flat,
where the web is considerably deeper than the conventional transverse
frame, are often introduced along the side shell (see Figure 17.3(a)).
A number are fitted in midship machinery spaces, generally not more than
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5 frame spaces apart but may be omitted if the size of normal framing is
increased. Forward of the collision bulkhead and in any deep tank adjacent
to the collision bulkhead, and in tween decks above such tanks, web frames
งานห้องสมุด ศูนย์ฝกพาณิชย์นาวี
are required at not more than 5 frame spaces apart. In the tween decks
above the after peak tank, web frames are required at every fourth frame
space abaft the aft peak bulkhead. In all cases the provision of web frames
is intended to increase the rigidity of the transverse ship section at that
point.

LONGITUDINAL FRAMING The longitudinal framing of the bottom
shell is dealt with in Chapter 16. If the side shell is longitudinally framed
offset bulb sections will often be employed with the greater section scant-
lings at the lower side shell. Direct continuity of strength is to be main-
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tained, and many of the details are similar to those illustrated for the tanker
longitudinals (see Chapter 22). Transverse webs are fitted to support the
side longitudinals, these being spaced not more than 3.8 m apart, in ships of
100m length or less, with increasing spacing being permitted for longer ships.
In the peaks the spacing is 2.5 m where the length of ship is less than 100 m
increasing linearly to a spacing of 3.5 m where the length exceeds 300 m.
Larger ships required to have a double hull are longitudinally framed at
the sides with transverse webs arranged in line with the floors in the double
bottom to ensure continuity of transverse strength. Horizontal perforated
flats are fitted between the inner and outer side plating to support the
transverse webs (see Figures 17.8 and 17.9).

Tank Side Brackets

The lower end of the frame may be connected to the tank top or hopper
side tank by means of a flanged or edge stiffened tank side bracket as
illustrated in Figure 17.3(b).

Local Strengthening of Shell Plating

The major region in which the shell plating is subjected to local forces at sea is
at the forward end. Strengthening of the forward bottom shell for pounding