Page 265 - Ship Construction.DJ Eyres 6Ed

Ch22-H8070.fm Page 254 Wednesday, October 18, 2006 6:59 AM
254 Ship Construction
Transverse
web
‘EH’
3 m ‘DH’ ‘DH’
‘EH’
Inner hull
Deck-transverse
web Longitudinal
bulkhead
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CENTRE
TANK
WING TANK
งานห้องสมุด ศูนย์ฝกพาณิชย์นาวี
Length B.P 315 m
Beam mld. 58 m Intermediate
Depth mld. 30.4 m
Stringer stringer
Plate
bracket
Inner bottom
3.5 m Floor
Floor
‘EH’
‘EH’ ‘DH’ ‘EH’ ‘DH’
FIGURE 22.2 Double hull oil tanker
ึ

Construction in Tank Spaces
Today’s ocean-going crude oil tankers are generally large and in way of the
tank spaces have a longitudinally framed double bottom supported by
transverse floors and a longitudinally framed deck supported by deck trans-
verses. The longitudinally framed side shell, inner hull and longitudinal
bulkheads are all supported by transverse webs aligned with the transverse
floors and deck transverses (see Figure 22.3).
LONGITUDINAL FRAMING Deck and bottom longitudinals have the
greatest scantlings since they are stiffening the more highly stressed flanges
of the hull girder. At the side shell the upper longitudinals have the least
scantlings, and a uniform increase in size occurs down the side shell until
the bilge is reached. The bilge longitudinal size then approaches that of the
bottom shell. For products carriers the deck longitudinals may be fitted
above the deck to provide a flush internal tank surface for cleaning (see
Figure 22.4). An important feature of the longitudinal framing is that conti-
nuity of strength is maintained, particularly at the bulkheads forming the
ends of the tanks. This feature is increasingly important as the ship length is
extended, the bottom and deck longitudinals being continuous through the
bulkhead where the ship length is excessive, unless an alternative arrangement