Section 4 NS2 and NS3 scantling determination
Clasification Society 2024 - Version 9.40
Clasifications Register Rules and Regulations - Rules and Regulations for the Classification of Naval Ships, January 2023 - Volume 1 Ship Structures - Part 6 Hull Construction in Steel - Chapter 3 Scantling Determination - Section 4 NS2 and NS3 scantling determination

Section 4 NS2 and NS3 scantling determination

Parent topic: Chapter 3 Scantling Determination

4.1 General

4.1.1 The scantlings for NS2 and NS3 ships may be determined from the global and local requirements defined in this Section. In addition, the general requirements of Vol 1, Pt 6, Ch 3, 5 Shell envelope plating to Vol 1, Pt 6, Ch 3, 15 Strengthening for wave impact loads above waterline are to be complied with.

4.1.2 This section contains various Tables indicating the design pressures, beam models and stiffener type coefficients which may be used in conjunction with the appropriate scantling formulae indicated in Vol 1, Pt 6, Ch 2 Design Tools and the structural design factors in Vol 1, Pt 6, Ch 5 Structural Design Factors to determine the required scantlings for both plating and stiffening members of NS2 and NS3 type ships.

4.1.3 In the determination of scantlings for stiffening members assumptions have been made about the degree of end fixity in way of their end connections. Where it can be demonstrated that the degree of end fixity is greater than that assumed then consideration will be given to lesser scantling requirements. In such cases the builders/designers are to submit sufficient information to enable an assessment of the degree of end fixity to be made and are to obtain acceptance of their proposals prior to submission of the scantling plans.

4.1.4 The geometric properties of stiffener sections are to be in accordance with Vol 1, Pt 6, Ch 2, 2.9 Proportions of stiffener sections

4.1.5 The scantlings in this Section are based on the assumption that the correct coatings are used and a proper maintenance regime is employed such that there is negligible loss in strength due to corrosion. For corrosion margins, see Vol 1, Pt 6, Ch 6, 3.8 Corrosion margin.

4.2 Hull girder strength

4.2.1 For all ships, the hull girder strength requirements of Vol 1, Pt 6, Ch 4, 2 Hull girder strength are to be complied with.

4.2.2 As required by Vol 1, Pt 6, Ch 4, 2 Hull girder strength, the hull girder bending and shear stresses for all longitudinally effective material is to be checked against the permissible stresses and the buckling requirements of Vol 1, Pt 6, Ch 2, 3 Buckling The lateral and torsional stability of all effective longitudinals, together with the web and flange buckling criteria, is to be verified in accordance with Vol 1, Pt 6, Ch 2, 3 Buckling.

4.3 Shell envelope plating

4.3.1 The requirements of this Section are applicable to longitudinally and transversely framed shell envelope plating.

4.3.2 The thickness of the shell envelope plating is in no case to be less than the appropriate minimum requirement given in Vol 1, Pt 6, Ch 3, 2 Minimum structural requirements

4.3.3 Additional requirements for shell envelope plating are indicated in Vol 1, Pt 6, Ch 3, 5 Shell envelope plating

4.3.4 The thickness requirement for shell envelope plating may be determined from the general equations given in Vol 1, Pt 6, Ch 2, 2.7 Plating general, the pressures given in Table 3.4.1 Shell envelope plating and the structural design factors in Vol 1, Pt 6, Ch 5 Structural Design Factors.

Table 3.4.1 Shell envelope plating

Structural element Design pressure
Bottom plating   Below waterline, the greater of
Bilge plating   (a) Ph + 1,26P W
Side shell plate   (b) 1,26P dl
Sheerstrake    
    Above the waterline
    1,26P s
Symbols
P h = the hydrostatic pressure on the shell plating, as defined in Vol 1, Pt 5, Ch 3, 3.3 Hydrostatic pressure on the shell plating, Ph
P w = the hydrodynamic wave pressure on the shell plating, as defined in Vol 1, Pt 5, Ch 3, 3.4 Hydrodynamic wave pressure, Pw
P s = the design pressure on the shell envelope, as defined in Vol 1, Pt 5, Ch 3, 3.2 Combined hydrostatic and hydrodynamic pressure on the shell plating, Ps
P = the bottom impact pressure for planing hull forms as defined in Vol 1, Pt 5, Ch 3, 4.5 Bottom impact pressure for ships operating in the planing regime This is not applicable for displacement hull forms.

4.3.5 For NS3 ships the minimum thickness requirement for bottom shell plating, see Figure 3.4.1 Extent of bottom shell, as detailed in Vol 1, Pt 6, Ch 3, 2 Minimum structural requirements, is to extend to the chine line or 150 mm above the design waterline, whichever is the greater.

Figure 3.4.1 Extent of bottom shell

4.3.6 Where a chine or knuckle is fitted between the bottom shell and side shell plating, the chine plate thickness is to be equivalent to the bottom shell thickness required to satisfy the Rule pressure loading, increased by 20 per cent, or 6 mm, whichever is the greater.

4.3.7 Where tube is used in chine construction, the minimum wall thickness is to be not less than the thickness of the bottom shell plating increased by 20 per cent.

4.3.8 Full penetration welding of shell plating in way of chine is to be maintained.

4.3.9 Chine details are to be such that the continuity of structural strength across the panel is maintained. Details of chines are to be submitted for consideration, see Figure 3.4.2 Chine detail

Figure 3.4.2 Chine detail

4.4 Shell envelope framing

4.4.1 The requirements of this Section are applicable to longitudinally and transversely framed shell envelopes.

4.4.2 Additional requirements for shell envelope framing are indicated in Vol 1, Pt 6, Ch 3, 6 Shell envelope framing

4.4.3 The section modulus, inertia and web area requirements for shell envelope stiffening may be determined from the general equations given in Vol 1, Pt 6, Ch 2, 2.8 Stiffening general, the pressures given in Table 3.4.2 Shell envelope framing and the structural design factors in Vol 1, Pt 6, Ch 5 Structural Design Factors

Table 3.4.2 Shell envelope framing

Structural element Design pressure Load model Stiffening type factor, δf Remarks
Longitudinal framing  
Bottom and bilge longitudinals

Side longitudinals
  • Below waterline
  • (a) δf (P h + 1,26P w)
  • (b) δf 1,26
Above waterline
δf 1,26P s 		B 0,8 See Note 1
Transverse framing  
Bottom transverse frames

Side frames
  • Below waterline
  • (a) δf (P h + 1,26P w)
  • (b) δf (P h + 1,26)
    Above waterline
    δf 1,26P s
B 0,8 See Note 1
Primary structure
  • Bottom girders
  • Side stringer

Floors

  • Bottom transverse web frames
  • Side transverse web frames
  • Below waterline
  • (a) δf (P h + 1,26P w)
  • (b) δf 1,26
    Above waterline
    δf 1,26P s
A 0,5 See Note 2
Symbols
P h = the hydrostatic pressure on the shell envelope, as defined in Vol 1, Pt 5, Ch 3, 3.3 Hydrostatic pressure on the shell plating, Ph
P w = the hydrodynamic wave pressure on the shell envelope, as defined in Vol 1, Pt 5, Ch 3, 3.4 Hydrodynamic wave pressure, Pw
P s = the design pressure on the shell envelope, as defined in Vol 1, Pt 5, Ch 3, 3.2 Combined hydrostatic and hydrodynamic pressure on the shell plating, Ps
= the bottom impact pressure for planing hull forms, as defined in Vol 1, Pt 5, Ch 3, 4.5 Bottom impact pressure for ships operating in the planing regime This is not applicable for displacement hull forms.

Note 1. Longitudinal and transverse frame stiffeners are secondary stiffening members, see Vol 1, Pt 3, Ch 2, 2.3 Definitions and structural terms 2.3.1 In general, secondary stiffening members, are to be designed using beam model ‘B’, see Table 2.2.1 Section modulus, inertia and web area coefficients for different load models. Such members are in general to be continuous or made effectively continuous by means of suitable bracketing.

Note 2. Guidelines for the design of primary stiffening members are given in Vol 1, Pt 3, Ch 2, 3.2 Primary members 3.2.1. In general, primary stiffening members are to be designed using load model ‘A’, see Table 2.2.1 Section modulus, inertia and web area coefficients for different load models. Primary members are to be substantially bracketed at their end connections.

4.5 Inner bottom structures

4.5.1 The requirements of this Section are applicable to longitudinally and transversely framed inner bottom structure.

4.5.2 The thickness of the inner bottom plating is in no case to be less than the appropriate minimum requirement given in Vol 1, Pt 6, Ch 3, 2 Minimum structural requirements.

4.5.3 Additional requirements for inner bottom structures are indicated in Vol 1, Pt 6, Ch 3, 8 Double bottom structures.

4.5.4 The thickness requirement for inner bottom plating may be determined from the general equations given in Vol 1, Pt 6, Ch 2, 2.7 Plating general, the pressures given in Table 3.4.3 Inner bottom structures and the structural design factors in Vol 1, Pt 6, Ch 5 Structural Design Factors

Table 3.4.3 Inner bottom structures

Structural element Design pressure Beam model Stiffening type factor, δf Remarks
Inner bottom plating Phd + 1,26Pw,da — —  
Longitudinal framing  
Inner bottom longitudinals δf (Phd + 1,26Pw,da) B 0,8 See Note 1
Transverse framing  
Inner bottom transverse frames δf (Phd + 1,26Pw,da) B 0,8 See Note 1
Symbols
Phd = is the Ph value for the local damaged stability draught envelope, where Ph is the hydrostatic pressure on the shell envelope, as defined in Vol 1, Pt 5, Ch 3, 3.3 Hydrostatic pressure on the shell plating, Ph
P w,da = the hydrodynamic wave pressure on the shell envelope, P w, as defined in Vol 1, Pt 5, Ch 3, 3.4 Hydrodynamic wave pressure, Pw, but based on a reduction in the local wave height for the damaged situation. The local wave height factor, f Hs, used to derive P w may be taken as specified in Vol 1, Pt 5, Ch 3, 1.2 Environmental conditions 1.2.2 but may be reduced by a factor of 1,85.
Hence P w,da = P w/1,85

Note 1. Longitudinal and transverse frame stiffeners are secondary stiffening members, see Vol 1, Pt 3, Ch 2, 2.3 Definitions and structural terms 2.3.1. In general, secondary stiffening members are to be designed using load model ‘B’, see Table 2.2.1 Section modulus, inertia and web area coefficients for different load models. Such members are in general to be continuous or made effectively continuous by means of suitable bracketing.

Note 2. Where the inner bottom forms the boundary of a deep tank, the deck is to be examined for compliance with the requirements for deep tanks, see Table 3.4.4 Watertight and deep tank bulkhead scantlings

Note 3. Where the inner bottom forms the boundary of a watertight subdivision, the inner bottom is to be examined for compliance with the requirements for watertight bulkheads, see Table 3.4.4 Watertight and deep tank bulkhead scantlings

Note 4. Where the inner bottom is subject to cargo deck or internal deck loadings, the inner bottom is to be examined for compliance with the requirements for lower decks and internal decks, see Table 3.4.5 Deck structures

Note 5. Where the inner bottom is subject to wheel loadings arising from vehicles or helicopters/aircraft, the inner bottom is to be examined for compliance with the requirements for vehicle decks, see Vol 1, Pt 4, Ch 3, 2 Vehicle decks and fixed ramps, or aircraft operation, see Vol 1, Pt 4, Ch 2, 10 Aircraft operations, as appropriate.

4.5.5 The section modulus, inertia and web area requirements for inner bottom stiffening may be determined from the general equations given in Vol 1, Pt 6, Ch 2, 2.8 Stiffening general, the pressures given in Table 3.4.3 Inner bottom structures and the structural design factors in Vol 1, Pt 6, Ch 5 Structural Design Factors

4.6 Watertight bulkheads and deep tanks

4.6.1 The requirements of this Section are applicable to longitudinally and transversely framed watertight bulkhead and deep tank structure.

4.6.2 The thickness of the bulkhead plating is in no case to be less than the appropriate minimum requirement given in Vol 1, Pt 6, Ch 3, 2 Minimum structural requirements

4.6.3 Additional requirements for watertight bulkhead and deep tank structure are indicated in Vol 1, Pt 6, Ch 3, 9 Bulkheads and deep tanks

4.6.4 The thickness requirement for bulkhead plating may be determined from the general equations given in Vol 1, Pt 6, Ch 2, 2.7 Plating general, the pressures given in Table 3.4.4 Watertight and deep tank bulkhead scantlings and the structural design factors in Vol 1, Pt 6, Ch 5 Structural Design Factors

4.6.5 The section modulus, inertia and web area requirements for bulkhead stiffening may be determined from the general equations given in Vol 1, Pt 6, Ch 2, 2.8 Stiffening general, the pressures given in Table 3.4.4 Watertight and deep tank bulkhead scantlings and the structural design factors in Vol 1, Pt 6, Ch 5 Structural Design Factors

Table 3.4.4 Watertight and deep tank bulkhead scantlings

Structural element Design pressure Beam model Stiffening type factor, δf Remarks
(1) Watertight bulkheads and decks        
  Plating P bhp — —  
  Secondary stiffeners P bhs B — See Note 1
  Primary stiffeners P bhs A — See Note 2
(2) Deep tank bulkheads and decks        
  Plating P bhp — —  
  Secondary stiffeners P bhs B — See Note 1
  Primary stiffeners P bhs A — See Note 2
(3) Collision bulkhead        
  Plating P bhp — —  
  Secondary stiffeners P bhs B — See Note 1
  Primary stiffeners P bhs A — See Note 2
Symbols
P bhp and P bhs = are the watertight bulkhead and deep tank pressure values of the plate panel and stiffener respectively, as defined in Vol 1, Pt 5, Ch 3, 5.8 Design pressures for watertight and deep tank bulkheads and boundaries.
P bhp and P bhs = pressure are the pressure values for the plate panel and stiffeners of the collision bulkhead as defined in Vol 1, Pt 5, Ch 3, 5.9 Design pressures for collision bulkheads.

Note 1. Secondary stiffening members are, in general, defined in Vol 1, Pt 3, Ch 2, 2.3 Definitions and structural terms 2.3.1. In general, secondary stiffening members are to be designed using load model ‘B’, see Table 2.2.1 Section modulus, inertia and web area coefficients for different load models. Such members are in general to be continuous or made effectively continuous by means of suitable bracketing.

Note 2. Guidelines for the design of primary stiffening members are given in Vol 1, Pt 3, Ch 2, 2.3 Definitions and structural terms 2.3.1 In general, primary stiffening members are to be designed using load model ‘A’, see Table 2.2.1 Section modulus, inertia and web area coefficients for different load models. Primary members are to be substantially bracketed at their end connections.

4.7 Deck structures

4.7.1 The requirements of this Section are applicable to longitudinally and transversely framed deck structure.

4.7.2 The thickness of the deck plating is in no case to be less than the appropriate minimum requirement given in Vol 1, Pt 6, Ch 3, 2 Minimum structural requirements

4.7.3 Additional requirements for deck structures are indicated in Vol 1, Pt 6, Ch 3, 10 Deck structures

4.7.4 The thickness requirement for deck plating may be determined from the general equations given in Vol 1, Pt 6, Ch 2, 2.7 Plating general, the pressures given in Table 3.4.5 Deck structures and the structural design factors in Vol 1, Pt 6, Ch 5 Structural Design Factors

4.7.5 The section modulus, inertia and web area requirements for deck stiffening may be determined from the general equations given in Vol 1, Pt 6, Ch 2, 2.8 Stiffening general, the pressures given in Table 3.4.5 Deck structuresand the structural design factors in Vol 1, Pt 6, Ch 5 Structural Design Factors

Table 3.4.5 Deck structures

Structural element Design pressure Beam model Stiffening type factor, δf Remarks
(1) Weather decks and exposed decks
Plating

The greater of

(a) 1,26P wd

(b) P cd

— — —
Secondary stiffening

Deck longitudinals or deck beams

The greater of

(a) δf 1,26P wd

(b) P cd

B 0,8 See Note 1
Primary stiffening
Deck girders or deck transverses or deep beams

The greater of

(a) δf 1,26P wd

(b) P cd

A 0,5 See Note 2
(2) Lower decks and internal decks
Plating

The greater of

(a) P in

(b) P cd

— — —
Secondary stiffening
Deck longitudinals or deck beams

The greater of

(a) P in
(b) P cd

B — See Note 1
Primary stiffening
Deck girders or deck transverses or deep beams

The greater of

(a) P in
(b) P cd

A — See Note 2
(3) Ramps and lifts
Plating P ra — — —
Secondary stiffening
Deck longitudinals or deck beams 		P ra B — See Note 1
Primary stiffening
Deck girders or deck transverses or deep beams 		P ra E — See Note 3
Symbols
P wd = the pressure acting on exposed and weather decks, as defined in Vol 1, Pt 5, Ch 3, 3.5 Pressure on exposed and weather decks, Pwd, see also Vol 1, Pt 5, Ch 3, 5.2 Pressure on external decks
P in = the pressure acting on internal decks, as defined in Vol 1, Pt 5, Ch 3, 5.3 Pressure on internal decks, Pin
P cd = the pressure acting on decks designed to carry cargo or heavy equipment loads, as defined in Vol 1, Pt 5, Ch 3, 5.4 Loads for decks designed for cargo or heavy equipment loads, Pcd and Wcd, where appropriate
P ra = the pressure on ramps and lifts, as defined in Vol 1, Pt 5, Ch 3, 6.2 Loads for ramps and lifts, Pra

Note 1. In general, secondary stiffening members are to be designed using load model ‘B’, see Table 2.2.1 Section modulus, inertia and web area coefficients for different load models. Such members are in general to be continuous or made effectively continuous by means of suitable bracketing.

Note 2. Guidelines for the design of primary stiffening members are given in Table 3.2. In general, primary stiffening members are to be designed using load model ‘A’, see Table 2.2.1 Section modulus, inertia and web area coefficients for different load models. Primary members are to be substantially bracketed at their end connections.

Note 3. In general, primary lift and ram stiffening members are to be designed using load model ‘E’, see Table 2.2.1 Section modulus, inertia and web area coefficients for different load models

Note 4. Where a deck forms the boundary of a deep tank, the deck is to be examined for compliance with the requirements for deep tanks, see Table 3.4.4 Watertight and deep tank bulkhead scantlings

Note 5. Where a deck forms the boundary of a watertight subdivision or part of the shell envelope, the deck is to be examined for compliance with the requirements for watertight bulkheads, see Table 3.4.4 Watertight and deep tank bulkhead scantlings, or the shell envelope respectively, see Table 3.4.2 Shell envelope framing

Note 6. Where a deck is subject to wheel loadings arising from vehicles or helicopters/aircraft, such decks are to be examined for compliance with the requirements for vehicle decks, see Vol 1, Pt 4, Ch 3, 2 Vehicle decks and fixed ramps, or aircraft operation, see Vol 1, Pt 4, Ch 2, 10 Aircraft operations, as appropriate.

4.8 Superstructures, deckhouses and bulwarks

4.8.1 The requirements of this Section are applicable to longitudinally and transversely framed superstructure, deckhouse and bulwark structures.

4.8.2 The thickness of the superstructure and deckhouse plating is in no case to be less than the appropriate minimum requirement given in Vol 1, Pt 6, Ch 3, 2 Minimum structural requirements

4.8.3 Additional requirements for superstructure, deckhouse and bulwark structures are indicated in Vol 1, Pt 6, Ch 3, 11 Superstructures, deckhouses and bulwarks

4.8.4 The thickness requirement for superstructure, deckhouse and bulwark may be determined from the general equations given in Vol 1, Pt 6, Ch 2, 2.7 Plating general, the pressures given in Table 3.4.6 Superstructure, deckhouse and bulwark structures and the structural design factors in Vol 1, Pt 6, Ch 5 Structural Design Factors

4.8.5 The section modulus, inertia and web area requirements for superstructure, deckhouse and bulwark stiffening may be determined from the general equations given in Vol 1, Pt 6, Ch 2, 2.8 Stiffening general, the pressures given in Table 3.4.6 Superstructure, deckhouse and bulwark structures and the structural design factors in Vol 1, Pt 6, Ch 5 Structural Design Factors

Table 3.4.6 Superstructure, deckhouse and bulwark structures

Structural element Design pressure Beam model Stiffening type factor, δf Remarks
(1) Superstructure sides, fronts and backs

Deckhouse sides, fronts and backs
Plating 1,26P dh — —  
Secondary stiffening

Side longitudinals

Side frames


δf 1,26P dh B 0,8 See Note 1
Primary stiffening

Side stringers


Side web frames

 δf 1,26P dh A 0,5 See Note 2
(2) Superstructure exposed decks

Deckhouse exposed decks
Plating 1,26P wd — —  
Secondary stiffening

Deck longitudinals

Deck beams

δf 1,26P wd B 0,8 See Note 1
Primary stiffening

Deck girders

Deck transverses or deep beams

 δf 1,26P wd A 0,5 See Note 2
(3) Superstructure internal decks

Deckhouse internal decks
Plating P in — —  
Secondary stiffening

Deck longitudinals

Deck beams

 P in B — See Note 1
Primary stiffening

Deck girders

Deck transverses or deep beams

 P in A — See Note 2
(4) Bulwarks
Plating 1,26P dh — —  
Secondary stiffening

Bulwark stays



 δf1,26P dh B
D 		0,8
1,0 		See Note 1
See Note 3
Symbols
P wd = the pressure acting on exposed and weather decks, as defined in Vol 1, Pt 5, Ch 3, 3.5 Pressure on exposed and weather decks, Pwd, see also Vol 1, Pt 5, Ch 3, 5.2 Pressure on external decks
P in = the pressure acting on internal decks, as defined in Vol 1, Pt 5, Ch 3, 5.3 Pressure on internal decks, Pin
P dh = the pressure acting on deckhouses, bulwarks and superstructures, as defined in Vol 1, Pt 5, Ch 3, 5.5 Loads for deckhouses, bulwarks and superstructures, Pdh

Note 1. In general, secondary stiffening members are to be designed using load model ‘B’, see Table 2.2.1 Section modulus, inertia and web area coefficients for different load models. Such members are in general to be continuous or made effectively continuous by means of suitable bracketing.

Note 2. Guidelines for the design of primary stiffening members are given in Vol 1, Pt 3, Ch 2, 3.2 Primary members 3.2.1. In general, primary stiffening members are to be designed using load model ‘A’, see Table 2.2.1 Section modulus, inertia and web area coefficients for different load models. Primary members are to be substantially bracketed at their end connections.

Note 3. Bulwark stays are to be designed using load model ‘D’ see Table 2.2.1 Section modulus, inertia and web area coefficients for different load models. The webs of the stays are to be carefully aligned with underdeck stiffeners and hard spots are to be avoided in way of end connections.

Note 4. Where a deck is subject to wheel loadings arising from vehicles or helicopters/aircraft, such decks are to be examined for compliance with the requirements for vehicle decks, see Vol 1, Pt 4, Ch 3, 2 Vehicle decks and fixed ramps, or aircraft operation, see Vol 1, Pt 4, Ch 2, 10 Aircraft operations as appropriate.

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