Page 187 - Ship Construction.DJ Eyres 6Ed

Ch17-H8070.fm Page 176 Wednesday, October 18, 2006 6:57 AM
176 Ship Construction
TABLE 17.1

Requirement Structural member
1. Grade D where thickness less than Sheerstrake or rounded gunwale over
15 mm otherwise Grade E. 40 per cent of length amidships in ships
exceeding 250 m in length.
2. Grade A where thickness less than Sheerstrake and rounded gunwale
--- ใช้เพื่อการศึกษาเท่านั้น---
15 mm. Grade B where thickness 15 to over 40 per cent of length amidships
20 mm. Grade D where thickness 20 to in ships of 250 m or less in length.
งานห้องสมุด ศูนย์ฝกพาณิชย์นาวี
25 mm. Grade E where thickness greater Bilge strake (other than for vessels
than 25 mm. of less than 150 m with double bottom
over full breadth).
3. Grade A where thickness less than Bottom plating including keel. Bilge
20 mm. Grade B where thickness 20 to strake (ships of less than 150 m and
25 mm. Grade D where thickness 25 to with double bottom over full breadth).
40 mm. Grade E where thickness over
40 mm.
4. Grade A where thickness less than Side plating.
30 mm. Grade B where thickness 30 to
40 mm. Grade D where thickness
ึ
greater than 40 mm.

GRADES OF STEEL FOR SHELL PLATES In large ships it is necessary
to arrange strakes of steel with greater notch ductility at the more highly
stressed regions. Details of Lloyd’s requirements for mild steel and over
40 per cent of the length amidships are given in Table 17.1 as a guide. The
Rules also require thicker plating for the members referred to in Table 17.1
outside the amidships region to have greater notch ductility.

Framing
The bottom shell may be transversely or longitudinally framed, longitudinal
framing being preferred for larger ships, and generally required when the
ships length exceeds 120 metres. The side shell framing may also be trans-
versely or longitudinally framed, transverse framing being adopted in many
conventional cargo ships, particularly where the maximum bale capacity is
required. Bale capacities are often considerably reduced where deep
transverses are fitted to support longitudinal framing. Longitudinal fram-
ing is adopted within double hull spaces and is common within the hopper
and topside tanks of bulk carriers. Smaller single skin bulk carriers then
have transverse frames at the side shell fitted between the hopper and
topside tank (see Figure 17.7).