Section 2 Design heads
Clasification Society 2024 - Version 9.40
Clasifications Register Rules and Regulations - Rules and Regulations for the Classification of Offshore Units, July 2022 - Part 4 Steel Unit Structures - Chapter 6 Local Strength - Section 2 Design heads

Section 2 Design heads

Parent topic: Chapter 6 Local Strength

2.1 General

2.1.1 This Section contains the local design heads and pressures to be used in the derivation of scantlings for decks, and bulkheads. Where scantlings in excess of Rule requirements are fitted the procedure to be adopted to determine the permissible head/pressure is also given.

2.2 Symbols

2.2.1 The symbols used in this Section are defined as follows:

L and D as defined in Pt 4, Ch 1, 5 Definitions

= appropriate design head, in metres
p = design loading, in kN/m2 (tonne-f/m2)
= applied loading, in kN/m2 (tonne-f/m3)
C = stowage rate, in m3/tonne, see Pt 4, Ch 6, 2.3 Stowage rate and design heads
=
E = correction factor for height of platform
= – 0,15, but not less than zero

nor more than 0,147

T = or as defined in Pt 4, Ch 1, 5 Definitions as appropriate.

2.3 Stowage rate and design heads

2.3.1 The following standard stowage rates are to be used:
  1. 1,39 m3/tonne for weather or general loading on decks.
  2. 0,975 m3/tonne for tanks with liquid of density 1,025 tonne/m3 or less on tank bulkheads and for watertight bulkheads. For liquid of density greater than 1,025 tonne/m3, the corresponding stowage rates are to be adopted.

2.3.2 The design heads and permissible deck loading are shown in Table 6.2.1 Design heads and permissible deck loadings (SI units). For helicopter landing areas, see Pt 4, Ch 6, 5 Helicopter landing areas.

Table 6.2.1 Design heads and permissible deck loadings (SI units)

Structural item and position Component Standard stowage rate C, in m3/tonne Design loading p ,in kN/m2 Equivalent design head in metres Permissible deck loading in kN-/m2 Equivalent permissible head, in metres
1. Weather decks — — — — —
(a) Loading for minimum scantlings
(i) Exposed deck All structure 1,39 9,0 + 14,41E 1,28 + 2,04E 9,0 1,28
(b) Specified deck loading
(i) Exposed deck All structure 1,39 + 14,41E but not less than (a) above 0,14+ 2,04E 0,14
2. Other decks
(a) Loading for minimum scantlings
(i) Work areas All structure 1,39 9,0 — —
1,28
(ii) Storage areas All structure 1,39 14,13 — —
2,0
(iii) Decks forming crown of deep tanks All structure C (see Note 2) (see Note 2) — —
h
(iv) Accommodation decks All structure 1,39 8,5 — —
1,2
(b) Specified deck loading
(i) All areas All structure 1,39 + 14,41E but not less than (a) above — —
0,14
(c) Superstructure decks (see Note 3          
(i) 1st tier All structure — — 0,9 (see Note 4) — —
(ii) 2nd tier 0,6
(iii) 3rd tier and above 0,45
(d) Walkways and access areas All structure 1,39 4,5 — —
0,64
3. Watertight bulkheads All structure 0,975 10,07 see Table 6.7.1 Watertight and deep tank bulkhead scantlings — —
4. Deep tank bulkheads All structure C but ≤ 0,975 see Table 6.7.1 Watertight and deep tank bulkhead scantlings — —
NOTES
1. The equivalent design head is to be used in conjunction with the appropriate formulae in the Rules.
2. Where h equals half the distance to the top of the overflow above crown of tank.
3. For forecastle decks forward of 0,12L from F.P., see weather decks.
4. Where the deck is exposed to the weather add 2,04E to the design head.

Table 6.2.2 Design heads and permissible deck loadings (metric units)

Structural item and position Component Standard stowage rate C, in m3/tonne Design loading p ,in tonne —f/m2 Equivalent design head in metres Permissible deck loading in tonne-f/m2 Equivalent permissible head, in metres
1. Weather decks — — — — —
(a) Loading for minimum scantlings
(i) Exposed deck All structure 1,39 0,92 + 1,467E 1,28 + 2,04E 0,92 1,28
(b) Specified deck loading
(i) Exposed deck All structure 1,39 + 1,467E but not less than (a) above 1,4+ 2,04E 1,4
2. Other decks
(a) Loading for minimum scantlings
(i) Work areas All structure 1,39 0,92 — —
1,28
(ii) Storage areas All structure 1,39 1,44 — —
2,0
(iii) Decks forming crown of deep tanks All structure C (see Note 2) (see Note 2) — —
h
(iv) Accommodation decks All structure 1,39 0,865 — —
1,2
(b) Specified deck loading
(i) All areas All structure 1,39 + 1,467E but not less than (a) above — —
0,14
(c) Superstructure decks (see Note 3          
(i) 1st tier All structure — — 0,9 (see Note 4) — —
(ii) 2nd tier 0,6
(iii) 3rd tier and above 0,45
(d) Walkways and access areas All structure 1,39 0,46 — —
0,64
3. Watertight bulkheads All structure 0,975 see Table 6.7.1 Watertight and deep tank bulkhead scantlings — —
0,975
4. Deep tank bulkheads All structure C but ≤ 0,975 see Table 6.7.1 Watertight and deep tank bulkhead scantlings — —
NOTES
1. The equivalent design head is to be used in conjunction with the appropriate formulae in the Rules.
2. Where h equals half the distance to the top of the overflow above crown of tank.
3. For forecastle decks forward of 0,12L from F.P., see weather decks.
4. Where the deck is exposed to the weather add 2,04E to the design head.
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