Page 180 - Ship Construction.DJ Eyres 6Ed

Ch16-H8070.fm Page 169 Wednesday, October 18, 2006 6:57 AM
Bottom Structure 169
of the depth of the centre girder at the bracket floors. To reduce the span
of the frames, which should not exceed 2.5 meters, at the bracket floor,
vertical angle or channel bar struts may be fitted. Vertical stiffeners usually
in the form of welded flats will be attached to the solid plate floors, which
are further strengthened if they form a watertight or oiltight tank boundary.
One intercostal side girder is provided port and starboard where the
ship’s breadth exceeds 10 m but does not exceed 20 m and two are fitted
--- ใช้เพื่อการศึกษาเท่านั้น---
port and starboard where the ship’s breadth is greater. In way of the bracket
floors a vertical welded flat stiffener is attached to the side girder. Additional
side girders are provided in the engine room, and also in the pounding
งานห้องสมุด ศูนย์ฝกพาณิชย์นาวี
region.

LONGITUDINALLY FRAMED DOUBLE BOTTOM In a longitudinally
framed double bottom, solid plate floors are fitted at every frame space
under the main engines, and at alternate frames outboard of the engine
seating. They are also fitted under boiler seats, transverse bulkheads, and the
toes of stiffener brackets on deep tank bulkheads. Elsewhere the spacing of
solid plate floors does not exceed 3.8m, except in the pounding region where
they are on alternate frame spaces. At intermediate frame spaces brackets
are fitted at the tank side, and at the centre girder where they may be up
ึ
to 1.25m apart. Each bracket is flanged and will extend to the first longitudi-
nal (Figure 16.5).
One intercostal side girder is fitted port and starboard if the ship’s
breadth exceeds 14 m, and where the breadth exceeds 21 m two are fitted
port and starboard. These side girders always extend as far forward and aft
as possible. Additional side girders are provided in the engine room, and
under the main machinery, and they should run the full length of the engine
room, extending three frame spaces beyond this space. Forward the exten-
sion tapers into the longitudinal framing system. In the pounding region
there will also be additional intercostal side girders.
As the unsupported span of the bottom longitudinals should not exceed
2.5m, vertical angle or channel bar struts may be provided to support the
longitudinals between widely spaced solid floors.

ADDITIONAL STIFFENING IN THE POUNDING REGION If the min-
imum designed draft forward in any ballast or part loaded condition is
less than 4.5 per cent of the ship’s length then the bottom structure for
30 per cent of the ship’s length forward in sea-going ships exceeding 65 m in
length is to be additionally strengthened for pounding.
Where the double bottom is transversely framed, solid plate floors are
fitted at every frame space in the pounding region. Intercostal side girders
are fitted at a maximum spacing of 3 times the transverse floor spacing, and
half height intercostal side girders are provided midway between the full
height side girders.