Section 5 Shell envelope plating

5.1.1 Requirements are given in this Section for longitudinal or transversely framed shell plating, and attention is drawn to the requirements of Pt 4, Ch 1, 6.1 General 6.1.1. In ships with a transversely framed bottom construction, the bottom shell plating is, in general, to be reinforced with additional continuous, or intercostal, longitudinal stiffeners, see also Pt 4, Ch 1, 7.1 General 7.1.2. Alternative arrangements will be considered.

5.1.2 For ships intended to load or unload while aground, see Pt 3, Ch 9, 7 Bottom strengthening for loading and unloading aground.

5.2.1 The cross-sectional area and thickness of bar keels, and the width and thickness of plate keels, are to comply with the requirements of Table 1.5.1 Bar and plate keels. Forged or rolled bar keels are also to comply with the material requirements of Ch 3 Rolled Steel Plates, Strip, Sections and Bars of the Rules for the Manufacture, Testing and Certification of Materials (hereinafter referred to as the Rules for Materials).

5.3.1 In the midship region the thickness of bottom shell plating to the upper turn of bilge is to be that necessary to give the hull section modulus required by Pt 3, Ch 4, 5 Hull bending strength, and is to be not less than the minimum values given by Table 1.5.2 Bottom shell and bilge plating.

5.4.1 In the midship region, the thickness of side shell and sheerstrake plating including the sides of bridge superstructures is to be not less than the values given by Table 1.5.3 Side shell plating, but may be required to be increased locally on account of high shear forces in accordance with Pt 3, Ch 4, 6 Hull shear strength.

5.4.2 Sea inlets, or other openings, are to have well rounded corners and so far as possible, are to be kept clear of the bilge radius. Openings on, or near to, the bilge radius are to be elliptical. The thickness of sea inlet box plating is to be the same as the adjacent shell, but not less than 12,5 mm and need not exceed 25 mm.

5.4.3 Where a rounded sheerstrake is adopted the radius should, in general, be not less than 15 times the thickness.

5.4.4 The sheerstrake thickness is to be increased by 20 per cent at the ends of a bridge superstructure extending out to the ship's side. In the case of a bridge superstructure exceeding 0,15L, the side plating at the ends of the superstructure is also to be increased by 25 per cent and tapered gradually into the upper deck sheerstrake.

5.4.5 In general, compensation will not be required for holes in the steerstrake which are clear of the gunwale or any deck openings situated outside the line of the main hatchways and whose depth does not exceed 20 per cent of the depth of the sheerstrake or 380 mm, whichever is the lesser. Openings are not to be cut in a rounded gunwale. Cargo door openings are to have well rounded corners, and the proposed compensation for the door openings will be individually considered.

Table 1.5.2 Bottom shell and bilge plating

Location	Minimum thickness, in mm
	Longitudinal framing		Transverse framing
(1) Bottom plating, see Notes 1 and 2	The greater of the following:		The greater of the following:
	(a) (see Note 4)		(a) (see Note 4)
	(b)		(b)
(2) Bilge plating - where framed, see Notes 1 and 2	t as for (1)		t as for (1)
(3) Bilge plating - where unframed, see Note 3	Provided that transverses or adequate bilge brackets are spaced not more than
Symbols
L, D, T, s, S, k L, k as defined in Pt 4, Ch 1, 1.5 Symbols and definitions 1.5.1
C w is as defined in Pt 4, Ch 1, 1.5 Symbols and definitions 1.5.1.
Where L > 227 m, C w is not to be taken less than 6,446 m f 1 = h T2 = (T + 0,5 C w), in metres but need not be taken greater than 1,2T m
s 1 = s, but is not to be taken less than the smaller of
F B = as defined in Pt 3, Ch 4, 5.7 Local reduction factors
L 1 = L but need not be taken greater than 190 m
R B = bilge radius, in mm, see Note 3
Note 1. The thickness derived in accordance with (1) is also to satisfy the buckling requirements of Pt 3, Ch 4, 7 Hull buckling strength. Note 2. The thickness of bottom shell or bilge plating is to be not less than the basic shell end thickness for taper as given in Pt 3, Ch 3 Structural Design, Table 3.2.1 Taper requirements for hull envelope. Note 3. Where longitudinally framed and the lowest side longitudinal lies a distance a mm above the uppermost turn of bilge and/or the outermost bottom longitudinal lies a distance b inboard of the lower turn of bilge, the bilge radius is to be taken as mm. In no case is a or b to be greater than s. Note 4. Where separate maximum sagging and hogging still water bending moments are assigned, F B may be based on the hogging moment.

Table 1.5.3 Side shell plating

Location	Minimum thickness, in mm
	Longitudinal framing		Transverse framing
(1) Side shell clear of sheerstrake, see Notes 1, 2, 4 and 5	(a) Above from base: The greater of the following: (i) (ii)		(a) Within from the gunwale: The greater of the following: (i) (ii)
	(b) At upper turn of bilge, see Note 3: The greater of the following: (i) (ii)		(b) Within from mid-depth: The greater of the following: (i) (ii)
	(c) Between upper turn of bilge and from base: The greater of the following: (i) t from (b)(i) (ii) t from interpolation between (a)(ii) and (b)(ii)		(c) Within from base (excluding bilge plating) see Note 3: The greater of the following: (i) (ii)
(2) Sheerstrake, see Notes 1, 2 and 4	The greater of the following: (i) (ii) but t is to be not less than the thickness of the adjacent side plating		The greater of the following: (i) (ii) but t is to be not less than the thickness of the adjacent side plating
Symbols
L, D, T, S, s, k L, k, as defined in Pt 4, Ch 1, 1.5 Symbols and definitions 1.5.1
C w is as defined in Pt 4, Ch 1, 1.5 Symbols and definitions 1.5.1.
Where L > 227 m, C w is not to be taken less than 6,446 m
f 1 =
h T1 = T + C w m but need not be taken greater than 1,36T
h T2 = T + 0,5C w m but need not be taken greater than 1,2T
s 1 = s, but is not to be taken less than the smaller of
F D, F B = as defined in Pt 3, Ch 4, 5.7 Local reduction factors
F M = the greater of FD or F B
L 1 = L, but need not be taken greater than 190 m
Note 1. The thickness is also to satisfy the buckling requirements of Pt 3, Ch 4, 7 Hull buckling strength. Note 2. The thickness of side shell or sheerstrake plating is to be not less than the basic shell end thickness for taper, as given in Pt 3, Ch 3 Structural Design, Table 3.2.1 Taper requirements for hull envelope. The width of the sheerstrake (where of different thickness from the side shell) is to be not less than that required by Table 2.2.1 Material classes and grades in Pt 3, Ch 2 Materials. Note 3. The thickness of side shell need not exceed that determined from Table 1.5.2 Bottom shell and bilge plating for bottom shell, but using the spacing of side frames or longitudinals. Note 4. For the expressions contained in (i), where separate maximum sagging and hogging still water bending moments are assigned, F D may be based on the sagging moment and F B on the hogging moment. Note 5. Outside the Rule minimum of higher tensile steel as defined in Pt 3, Ch 3, 2.6 Vertical extent of higher tensile steel the value of kL can be taken as 1.