Section 1 General
Clasification Society 2024 - Version 9.40
Clasifications Register Rules and Regulations - Rules and Regulations for the Classification of Ships, July 2022 - Part 3 Ship Structures (General) - Chapter 8 Superstructures, Deckhouses and Bulwarks - Section 1 General

Section 1 General

Parent topic: Chapter 8 Superstructures, Deckhouses and Bulwarks

1.1 Application

1.1.1 This Chapter applies to all types of ships detailed in Pt 4 Ship Structures (Ship Types), except for deckhouses situated on forecastles of offshore supply ships, which are dealt with separately in Pt 4, Ch 4 Offshore Support Vessels.

1.1.2 The scantlings of exposed bulkheads and decks of superstructures and deckhouses are generally to comply with the following requirements, but increased scantlings may be required where the structure is subjected to loading additional to Rule. Where there is no access from inside the house to below the freeboard deck, or where a bulkhead is in a particularly sheltered location, the scantlings may be specially considered.

1.1.3 The term `erection' is used in this Section to include both superstructures and deckhouses.

1.1.4 For requirements relating to companionways, doors, accesses and skylights, see Pt 3, Ch 11 Closing Arrangements for Shell, Deck and Bulkheads.

1.1.5 The requirements in this Chapter are not applicable to Double Hull Oil Tankers or Bulk Carriers with a CSR notation. See Pt 1, Ch 2, 2.3 Class notations (hull).

1.2 Symbols

1.2.1 The following symbols and definitions are applicable to this Chapter, unless otherwise stated:

L, B, T and Cb = as defined in Pt 3, Ch 1, 6.1 Principal particulars
b = breadth of deckhouse, at the positions under consideration, in metres
k = higher tensile steel factor, see Pt 3, Ch 2, 1.2 Steel
e = effective length, in metres, of the stiffening member, deck beam or longitudinal measured between span points, see Pt 3, Ch 3, 3.3 Determination of span point
s = span, in metres, of stiffeners, and is to be taken as the 'tween deck or house height but in no case as less than 2,0 m
s = spacing of stiffeners, beams or longitudinals, in mm
s b = standard spacing, in mm, of stiffeners, beams or longitudinals, and is to be taken as:
= (a) for 0,05L from the ends:
= s b = 610 mm or that required by (b), whichever is the lesser
= (b) elsewhere:
= s b = 470 + 1,67L 2 mm
= but forward of 0,2L from the forward perpendicular s b is not to exceed 700 mm
B 1 = actual breadth of ship, at the section under consideration, measured at the weather deck, in metres
D = moulded depth of ship, in metres, to the uppermost continuous deck or the deck next above a height of 1,6T from the base line amidships, whichever is the lesser
L 2 = length of ship, in metres, but is not to be taken greater than 250 m or less than 50 m
L 3 = length of ship, in metres, but is not to be taken greater than 300 m
X = distance, in metres, between the after perpendicular and the bulkhead under consideration. When determining the scantlings of deckhouse sides, the deckhouse is to be subdivided into parts of approximately equal length not exceeding 0,15L each, and X is to be measured to the mid-length of each part
α = a coefficient given in Table 8.1.1 Values of α
β = 1,0 +
= 1,0 + 1,5
= C b is to be taken as not less than 0,6 nor greater than 0,8. Where the aft end of an erection is forward of amidships, the value of C b used in determining β for the aft end bulkhead need be taken as not less than 0,8
γ = vertical distance, in metres, from the summer load waterline to the mid-point of span of the bulkhead stiffener, or the mid-point of the plate panel, as appropriate
δ = 1,0 for exposed machinery casings and houses protecting openings to pump-rooms
= elsewhere, but in no case to be taken less than 0,475
λ = a coefficient given in Table 8.1.2 Values of λ.

1.3 Definition of tiers

1.3.1 The lowest, or first tier, is normally that which is directly situated on the deck to which D is measured. The second tier is the next tier above the lowest tier and so on.

Table 8.1.1 Values of α

Position α
Lowest tier - unprotected front 2,0 + 0,0083L 3
Second tier - unprotected front 1,0 + 0,0083L 3
Third tier and above - unprotected front 0,5 + 0,0067L 3
All tiers - protected fronts
All tiers - sides
All tiers - aft end where aft of amidships 0,7 + 0,001L 3 - 0,8
All tiers - aft end where forward of amidships 0,5 + 0,001L 3 - 0,4

Table 8.1.2 Values of λ

Length L λ Expression for λ
metres    
20 0,89 L ≤ 150 m
λ =
30 1,76
40 2,57
50 3,34
60 4,07
70 4,76
80 5,41
90 6,03
110 7,16
130 8,18
150 9,10
150 9,10 150 m ≤ L ≤ 300 mλ =
170 9,65
190 10,08
210 10,43
230 10,69
250 10,86
270 10,98
290 11,03
300 11,03
300 and above 11,03 L ≥ 300 m
λ = 11,03

1.3.2 Where the freeboard corresponding to the required summer moulded draught for the ship can be obtained by considering the ship to have a virtual moulded depth at least one standard superstructure height less than the Rule depth, D, measured to the uppermost continuous deck, proposals to treat the first tier erection as a second tier, and so on, will be specially considered. The standard height of superstructure is the height defined in the International Convention on Load Lines, 1966.

1.4 Design pressure head

1.4.1 The design pressure head, h, to be used in the determination of erection scantlings is to be taken as:

h = αδ(βλ − γ ) m

1.4.2 In no case is the design pressure head to be taken as less than the following:

  1. Lowest tier of unprotected fronts:

    minimum h = 2,5 + 0,01L 2 m

  2. All other locations:

    minimum h = 1,25 + 0,005L 2 m.

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