Section 2 Deck structure

2.1.1 Where the upper deck is longitudinally framed outside the line of openings in the midship region, this system of framing is to be carried as far aft as possible. See also Pt 4, Ch 9, 1.3 Class notation and applicable Rules for CSR Double Hull Oil Tankers.

2.2.1 The thickness of strength/weather deck plating is to comply with the requirements of Table 6.2.1 Strength/weather deck plating aft (excluding poop deck).

2.2.2 The thickness of lower deck plating is to comply with the requirements of Table 6.2.2 Lower deck plating aft.

2.2.3 The taper thickness of the strength deck stringer plate is to be increased by 20 per cent at the ends of a poop or bridge where the end bulkhead is situated forward of 0,25L from the A.P. No increase is required where the end bulkhead lies aft of 0,2L from the A.P. The increase at intermediate positions is to be determined by interpolation.

2.2.4 The deck plating thickness and supporting structure are to be suitably reinforced in way of deck machinery, and in way of cranes, masts or derrick posts.

2.2.5 Where long, wide hatchways are arranged at lower decks it may be necessary to increase the deck plating thickness to ensure effective support for side framing.

2.3.1 The scantlings of strength/weather deck longitudinals are to comply with the requirements of Table 6.2.3 Strength/weather deck longitudinals aft.

2.3.2 The scantlings of cargo and accommodation deck longitudinals are to comply with the requirements given in Table 1.4.4 Cargo and accommodation deck longitudinals.

2.3.3 End connections of longitudinals to bulkheads are to provide adequate fixity, lateral support and so far as practicable, direct continuity of longitudinal strength.

2.3.4 The scantlings of weather deck beams are to comply with the midship requirements for the particular ship type.

2.3.5 The scantlings of lower deck beams are to comply with the requirements of Table 1.4.5 Strength/weather, cargo and accommodation deck beams in Pt 4, Ch 1 General Cargo Ships.

2.3.6 End connections of beams are to be in accordance with the requirements of Pt 3, Ch 10, 3 Secondary member end connections.

Table 6.2.1 Strength/weather deck plating aft (excluding poop deck)

Symbols	Location	Thickness, in mm
L, s, S, k, ρ as defined in Pt 3, Ch 6, 1.4 Symbols and definitions 1.4.1 f = 1,1 – but is to be taken not greater than 1,0	(1) Aft of 0,075L from the A.P.
h 4 = tank head, in metres, as defined in Pt 3, Ch 3, 5 Design loading s b = standard frame spacing as follows:	(2) Between 0,075L and 0,15L from the A.P.	The greater of the following: the taper thickness, see Notes 1, 2 and 3 for oil tankers, the thickness is also to be in accordance with Pt 4, Ch 9, 4.3 Deck plating 4.3.3
Aft of 0,15L from the A.P.: mm or 850 mm,	(3) Forward of 0,15L from the A.P.	The taper thickness, see Notes 1, 2 and 3, or as (2)(c) whichever is the greater
whichever is the lesser s 1 = s, but is to be taken not less than s b	(4) Inside poop extending forward of 0,15L	As for a lower deck, see Note 4
	(5) In way of the crown of a tank	or (1) to (4) as applicable, whichever is the greater but not less than 7,5 mm where L ≥ 90 m, or 6,5 mm where L < 90 m
Note 1. The taper thickness is to be determined from Table 3.2.1 Taper requirements for hull envelope in Chapter 3.
Note 2. For taper area requirements, see Table 3.2.1 Taper requirements for hull envelope in Chapter 3.
Note 3. For thickness of upper deck plating in way of the cargo tanks of oil tankers or ore carriers, see also Pt 4, Ch 9 Double Hull Oil Tankers, Pt 4, Ch 10 Single Hull Oil Tankers or Pt 4, Ch 11 Ore Carriers.
Note 4. The exposed weather deck taper thickness is to extend into a poop or bridge for at least one-third of the breadth of the ship from the superstructure end bulkhead.
Note 5. The taper requirements from Table 3.2.1 Taper requirements for hull envelope in Pt 3, Ch 3 Structural Designdo not apply to container ships or open ship types, see Pt 3, Ch 4, 2.3 Open type ships, where the requirements of Pt 4, Ch 8, 3.2 Longitudinal strength are applicable, nor to fast cargo ships where the requirements of Pt 4, Ch 1, 3 Longitudinal strength are applicable. See also Pt 3, Ch 4, 5 Hull bending strength for hull section modulus requirement away from the midship area.

Table 6.2.2 Lower deck plating aft

Symbols	Location	Thickness, in mm
L, s, S, k, ρ as defined in Pt 3, Ch 6, 1.4 Symbols and definitions 1.4.1 b = breadth of increased plating, in mm f = 1,1 – but is to be taken not greater than 1,0 h 4 = tank head, in metres, as defined in Pt 3, Ch 3, 5 Design loading K 2 = 2,5 mm at bottom of tank or 3,5 mm at crown of tank s 1 = s, but is to be taken not less than mm	(1) Aft of 0,075L from the A.P.	but not less than 6,5 mm
	(2) Forward of 0,075L from the A.P., inside line of openings	but not less than 6,5 mm
	(3) Forward of 0,075L from the A.P., outside line of openings	As determined by a taper line from the midship thickness to the end thickness given by (1)
	(4) In way of the crown or bottom of a tank
		or (1), (2) or (3) as applicable, whichever is the greater but not less than 7,5 mm where L ≥ 90 m, or 6,5 mm where L < 90 m
A f = girder face area, in cm2 L 1 = L, but need not be taken greater than 190 mm	(5) Plating forming upper flange of underdeck girders	Clear of cargo hatches
		In way of hatch side girders
Note Where the deck loading exceeds 43,2 kN/m2, the thickness of plating will be specially considered. This is equivalent to a 'tween deck height of 6,1 m in association with the standard stowage rate of 1,39 m3/tonne.		Minimum breadth	b = 760 mm

Table 6.2.3 Strength/weather deck longitudinals aft

Location	Modulus, in cm3	Inertia, in cm4
(1) Aft of 0,075L from the A.P.	The greater of the following:	—
(2) Forward of 0,075L from the A.P., inside line of openings	As (1)	—
(3) Forward of 0,075L from the A.P., outside line of openings	As determined from Table 3.2.1 Taper requirements for hull envelope in Chapter 3, see Note 1 For oil tankers (see Pt 3, Ch 6, 1.1 Application 1.1.4) and dry cargo ships the end modulus for taper at 0,075L from the A.P. is to be derived from Table 5.2.3 Strength/weather deck longitudinals forward item (2)	—
(4) In way of the crown of a tank	or as (1) to (3) as applicable, whichever is the greater
Symbols
L, s, k L, k, ρ as defined in Pt 3, Ch 6, 1.4 Symbols and definitions 1.4.1
b = 1,4 for rolled or built sections = 1,6 for flat bars
d w = web depth of longitudinal, in mm h 1 = weather head, in metres, as defined in Pt 3, Ch 3, 5 Design loading h 4 = tank head, in metres, as defined in Pt 3, Ch 3, 5 Design loading e = as defined in Pt 3, Ch 6, 1.4 Symbols and definitions 1.4.1, but is to be taken not less than 1,5 m L 1 = L but need not be taken greater than 190 m
Note 1. For taper area requirements, see Table 3.2.1 in Chapter 3. Note 2. Where weather decks are intended to carry deck cargo and the loading is in excess of 8,5 kN/m2 the scantlings of longitudinals are also to comply with the requirements for location (1) in Table 1.4.4 Cargo and accommodation deck longitudinals using the equivalent design head, for specified cargo loadings, for weather decks given in Table 3.5.1 Design heads and permissible cargo loadings. Note 3. For the scantlings of deck longitudinals aft in way of the cargo tanks of oil tankers (see Pt 3, Ch 6, 1.1 Application 1.1.4) or ore carriers, see also Pt 4, Ch 9 Double Hull Oil Tankers, Pt 4, Ch 10 Single Hull Oil Tankers or Pt 4, Ch 11 Ore Carriers as applicable. Note 4. The thickness of flat bar longitudinals, situated outside the line of openings is to be not less than the following: Note (a) mm where longitudinal continuous through bulkhead Note (b) mm where longitudinal cut at bulkhead Note 5. The web depth of longitudinal, d w, to be not less than 60 mm. Note 6. The taper requirements from Table 3.2.1 Taper requirements for hull envelope in Pt 3, Ch 3 Structural Designdo not apply to container ships or open ship types, see Pt 3, Ch 4, 2.3 Open type ships, where the requirements of Pt 4, Ch 8, 3.2 Longitudinal strength are applicable, nor to fast cargo ships where the requirements of Pt 4, Ch 1, 3 Longitudinal strength are applicable. See also Pt 3, Ch 4, 5 Hull bending strength for hull section modulus requirement away from the midship area.

2.4.1 The arrangements and scantlings of supporting structure are generally to be in accordance with the requirements given in Pt 4, Ch 1, 4 Deck structure except as required by Pt 3, Ch 6, 2.4 Deck supporting structure 2.4.2 to Pt 3, Ch 6, 2.4 Deck supporting structure 2.4.4.

2.4.2 At upper and lower decks above the after peak, deep beams are generally to be fitted in way of web frames. Deck girders are generally to be spaced not more than 3,0 m apart.

2.4.3 Primary structure in the topside tanks of bulk carriers is to comply with the requirements of Pt 4, Ch 7, 7 Topside tank structure.

2.4.4 Primary structure in the cargo tanks of oil tankers, or ore carriers, is to be determined from Pt 4, Ch 9 Double Hull Oil Tankers, Pt 4, Ch 10 Single Hull Oil Tankers or Pt 4, Ch 11 Ore Carriers, as applicable.

2.5.1 In dry cargo ships, the requirements for deck openings given in Pt 4, Ch 1, 4 Deck structure are generally applicable throughout the aft region except that aft of 0,25L from the A.P.:

1. The radii or dimensions of the corners of main cargo hatchway openings of the strength deck are to be in accordance with the requirements of Pt 4, Ch 1, 4.5 Deck openings. The thickness of the insert plates, where required, is not to be less than 20 per cent greater than the adjacent deck thickness outside the line of openings, with a minimum increase of 3 mm.

2. Insert plates will be required at lower decks in way of any rapid change in hull form to compensate for loss of deck cross-sectional area. Otherwise, insert plates will not normally be required.

3. Compensation and edge reinforcement for openings outside the line of main hatchways will be considered, bearing in mind their position, the deck arrangements and the type of ship concerned.

2.5.2 For deck openings in way of cargo tanks in oil tankers and ore carriers, see also Pt 4, Ch 9 Double Hull Oil Tankers, Pt 4, Ch 10 Single Hull Oil Tankers or Pt 4, Ch 11 Ore Carriers, as applicable. For main cargo hatchway openings on bulk carriers and container ships, see also Pt 4, Ch 7 Bulk Carriers and Pt 4, Ch 8 Container Ships, as applicable.