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 forward as possible. In the case of oil tankers (see Pt 3, Ch 5, 1.1 Application 1.1.4) longitudinal framing is to extend to at least the forward end of the cargo tank section.

2.2.1 The thickness of strength/weather deck plating is to comply with the requirements of Table 5.2.1 Strength/weather deck plating forward (excluding forecastle deck).

2.2.2 The thickness of lower deck plating is to comply with the requirements of Table 5.2.2 Lower deck plating forward.

2.2.3 The taper thickness of the strength deck stringer plate is to be increased by 20 per cent at the end of a forecastle or bridge where the end bulkhead is situated aft of 0,25L from the F.P. No increase is required where the end bulkhead lies forward of 0,2L from the F.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 the anchor windlass and other 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 5.2.3 Strength/weather deck longitudinals forward.

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 in Pt 4, Ch 1 General Cargo Ships.

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 requirements of Table 5.2.4 Weather deck beams forward.

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.

Table 5.2.1 Strength/weather deck plating forward (excluding forecastle deck)

Symbols	Location		Thickness, in mm
L, D, T, s, S, k, ρ as defined in Pt 3, Ch 5, 1.4 Symbols and definitions 1.4.1 C = but is to be taken not greater than 1,0 nor less than 0,9	(1)	Forward of 0,075L from the F.P.
s 1 = s, but to be taken not less than s b s b = standard frame spacing as follows: (a) forward of 0,05L from the F.P.: s b = mm or 600 mm,	(2)	Between 0,075L and 0,2L from the F.P.	The greater of the following: (a) t = (5,5 + 0,02L) (b) the taper thickness (see Notes 1, 2 and 3) (c) For oil tankers, the thickness is also to be in accordance with Pt 4, Ch 9, 4.3 Deck plating 4.3.3
whichever is the lesser	(3)	Aft of 0,2L from the F.P.	The taper thickness (see Notes 1, 2 and 3) or as (2) (c) whichever is the greater
(b) between 0,05L and 0,2L from the F.P.:	(4)	Inside forecastle extending aft of 0,15L from the F.P.	As for a lower deck (see Note 4)
s b = mm or 700 mm, whichever is the lesser f = but to taken not greater than 1,0 h 4 = tank head, in metres, as defined in Ch 3,5	(5)	In way of crown of a tank	or as in (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.
Note 2. For taper area requirements, see Table 3.2.1 Taper requirements for hull envelope.
Note 3. For thickness of upper deck plating in way of the cargo and fore peak 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, as applicable.
Note 4. The exposed deck taper thickness is to extend into a forecastle 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 Design do 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 5.2.2 Lower deck plating forward

Symbols	Location		Thickness, in mm
L, s, S, k, ρ as defined in Pt 3, Ch 5, 1.4 Symbols and definitions 1.4.1 b = breadth of increased plating, in mm	(1)	Forward of 0,075L from the F.P.	but not less than 6,5 mm
f = but is to be taken not greater than 1,0	(2)	Aft of 0,075L from the F.P., inside line of openings	but not less than 6,5 mm
h 4 = tank head, in metres, as defined in Pt 3, Ch 3, 5 Design loading	(3)	Aft of 0,075L from the F.P., outside line of openings	As determined by a taper line from the midship thickness to the end thickness given by (1)
K 2 = 2,5 mm at bottom tank, or = 3,5 mm at crown of tank s 1 = s, but is to be taken not less than	(4)	In way of crown or bottom of tank	or as in (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 m	(5)	Plating forming the upper flange of underdeck girders	Clear of cargo hatches
Note 1. 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 1,39 m3/tonne.			In way of hatch side girders
Note 2. For minimum thickness of deck plating in oil tankers, see Pt 4, Ch 9, 10.2 Compartment minimum thickness.			Minimum breadth	b = 760 mm

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.

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 using the heads given in Pt 3, Ch 3, 5 Design loading for the particular region concerned, except as required by Pt 3, Ch 5, 2.4 Deck supporting structure 2.4.2 to Pt 3, Ch 5, 2.4 Deck supporting structure 2.4.4.

2.4.2 The spacings of girders and transverses are generally not to exceed the values given in Table 5.2.5 Spacing of girders and transverses under strength/weather decks forward.

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 and 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 forward region, except that forward of 0,25L from the F.P.:

1. The radii or dimensions of the corners of main cargo hatchway openings on 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 the 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.

Table 5.2.3 Strength/weather deck longitudinals forward

Location	Modulus, cm3	Inertia, cm4
(1) Forward of 0,075L from the F.P.	The greater of the following: (a) (b)	—
(2) At 0,075L from the F.P., for end modulus for taper	The greater of the following: (a) (b)	—
(3) Aft of 0,075L from the F.P., outside line of openings	As given by (4) or as determined from Table 3.2.1 Taper requirements for hull envelope whichever is the greater, see Note 1	—
(4) At 0,075L and between 0,075L and 0,12L from the F.P.	The greater of the following: (a) (b)	—
(5) Aft of 0,12L from the F.P., inside line of main cargo hatchways openings	The greater of the following: (a) (b)	—
(6) In way of the crown of a tank	As (1) to (5), as applicable, or whichever is the greater
Symbols
L, s, k L, k ρ as defined in Pt 3, Ch 5, 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 o = 1,2 m for dry cargo ships = m for oil tankers (see Pt 3, Ch 5, 1.1 Application 1.1.4)
h 1 = weather head, in metres, as defined in Pt 3, Ch 3, 5 Design loading for dry cargo ships = m for oil tankers (see Pt 3, Ch 5, 1.1 Application 1.1.4)
h 4 = tank head, in metres, as defined in Pt 3, Ch 3, 5 Design loading
e as defined in Pt 3, Ch 5, 1.4 Symbols and definitions 1.4.1, but is to be taken not less than 1,5 m
e1 is to be taken as the maximum span in metres in the midship cargo tank region for oil tankers (see Pt 3, Ch 5, 1.1 Application 1.1.4) and equal to e for dry cargo ships
L 1 = L but need not be taken greater than 190 m
Note 1. For area taper requirements, see also Table 3.2.1 Taper requirements for hull envelope.
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 may be required to be increased 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 forward in way of the cargo tanks of oil tankers (see Pt 3, Ch 5, 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.
4. The thickness of flat bar longitudinals situated outside the line of openings is to be not less than the following: where longitudinal continuous through bulkhead where longitudinal cut at bulkhead
Note 5. The web depth of longitudinal, d w, is 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 Design do 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 5.2.4 Weather deck beams forward

Location	Modulus, cm3	Inertia, cm4
(1) Forward of 0,075L from the F.P.	The lesser of the following: (a) (b)	__
(2) Between 0,075L and 0,12L from the F.P.	The lesser of the following: (a) (b)	__
(3) Aft of 0,12L from the F.P.	As required for location (1) of Table 1.4.5 Strength/weather, cargo and accommodation deck beams	__
(4) In way of the crown of a tank	As (1), (2) or (3), as applicable, or whichever is the greater
Symbols
B, D, T, s, ρ, k as defined in Pt 3, Ch 5, 1.4 Symbols and definitions 1.4.1 b = 1,4 for rolled or built sections = 1,6 for flat bars 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 5, 1.4 Symbols and definitions 1.4.1, but is to be taken not less than 1,83 m	K 1 = a factor dependent on the number of decks (including a bridge superstructure) at the position of the beam under consideration as follows: 1 deck – 20,0 2 decks – 13,3 3 decks – 10,5 4 decks or more – 9,3 For a forecastle deck, K 1 is to be taken as 13,3 K 3 = a factor dependent on the location of the beam as follows: Span adjacent to ship's side – 3,6 Elsewhere – 3,3 B 1 = B, but need not be taken greater than 21,5 m
Note 1. Beams at the upper deck inside superstructures are to have scantlings determined as for a lower deck, see Table 1.4.5 Strength/weather, cargo and accommodation deck beams.
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 beams are also to comply with the requirements for location (2) in Table 1.4.5 Strength/weather, cargo and accommodation deck beams 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. The web depth of beams, d w, is to be not less than 60 mm.
Note 4. The scantlings of deck beams forward in way of the cargo tanks of oil tankers or ore carriers will be specially considered, see Pt 4, Ch 9, 1.4 Class notation and applicable Rules for non-CSR Double Hull Oil Tankers 1.4.12.