Section 4 Design load systems for longitudinally effective components

4.1.1 The design load values calculated here are to be used to determine the scantlings of bottom shell plating and stiffeners between the keel and the turn of bilge, see Figure 2.4.1 Loads to be applied to bottom shell structure

4.1.2 The design normal pressure, P _BS, for the bottom shell plating and stiffeners is to be taken as:

where

4.1.3 The design impulse pressure, P _BS, for the bottom shell plating and stiffeners is to be taken as

where

4.1.4 The design global vertical bending moment for bottom shell plating and longitudinals is to be taken as M _D, as defined in Vol 1, Pt 7, Ch 2, 3.3 Design global loads – Intact conditions or Vol 1, Pt 7, Ch 2, 3.4 Design global loads – Damaged conditions or Residual Strength Assessment (RSA) conditions

4.1.5 The design transverse load, LT _BS, due to hydrostatic and hydrodynamic compressive loading is to be taken as follows:

where

P _SS is to be taken at a height H _d/2 above the keel. P _SS is defined in Vol 1, Pt 7, Ch 2, 3.6 External shell pressures 3.6.1

4.1.6 The design global shear force, Q _D, may be ignored for the bottom plating.

4.1.7 The design loads for bottom structure primary members are given in Vol 1, Pt 7, Ch 2, 4.6 Bottom longitudinal girders (BG), bottom longitudinal girders, and Vol 1, Pt 7, Ch 2, 5.4 Transverse floors (FL), transverse floors.

4.2.1 The design pressures calculated here are to be used to determine the scantlings of side shell plating and stiffeners from the turn of bilge up to the weather deck, see Figure 2.4.3 Loads to be applied to side shell structure

4.2.2 For the side shell structure the design normal pressure, P _SS, is to be taken as defined in Vol 1, Pt 7, Ch 2, 3.6 External shell pressures 3.6.1

4.2.3 The design impulse pressure, P _SS, for the side shell plating and stiffeners is to be taken as follows:

1. up to the design waterline

   P _SS = P _bi kN/m² (bottom impact)

2. above the design waterline

   P _SS = P _bf kN/m² (bow flare impact)

where

P _bi and P _bf are defined in Vol 1, Pt 7, Ch 2, 2.1 Nomenclature 2.1.2

4.2.4 The design global vertical bending moment is to be taken as M _D, as defined in Vol 1, Pt 7, Ch 2, 3.3 Design global loads – Intact conditions or Vol 1, Pt 7, Ch 2, 3.4 Design global loads – Damaged conditions or Residual Strength Assessment (RSA) conditions

4.2.5 The design vertical load, LV _SS, supported by the side shell plating and stiffeners is to be taken as:

where

4.2.6 The design global shear force is to be taken as Q _D, as defined in Vol 1, Pt 7, Ch 2, 3.3 Design global loads – Intact conditions or Vol 1, Pt 7, Ch 2, 3.4 Design global loads – Damaged conditions or Residual Strength Assessment (RSA) conditions

4.2.7 The design loads for side shell primary members are given in Vol 1, Pt 7, Ch 2, 4.8 Longitudinal stringers (ST) for longitudinal stringers and in Vol 1, Pt 7, Ch 2, 5.5 Side frames and web frames (SF) for side frames and web frames.

4.3.1 The design normal pressure, P _DK, for the deck plating and stiffeners is to be taken as the greater of the following, provided that the load component is applicable:

1. P _WD (weather deck pressure), see Vol 1, Pt 7, Ch 2, 3.6 External shell pressures 3.6.2

2. (interior deck pressure), see Vol 1, Pt 7, Ch 2, 5.1 Deck structures (DK) 5.1.3

3. P _CD (cargo deck pressure), see Vol 1, Pt 7, Ch 2, 5.1 Deck structures (DK) 5.1.2

4. P _tk (deep tank boundary, where appropriate).

4.3.2 For loading conditions which represent damaged situations and for decks that form part of the watertight subdivision, the design normal pressure, P _DK, is to be taken as follows if this is greater than Vol 1, Pt 7, Ch 2, 4.3 Strength deck and internal deck structures (DK) 4.3.1:

1. P _da (damage head).

4.3.3 The design load matrix, [F _DK], in kN for the deck plating and stiffeners is to be taken as the combination of the following, as appropriate:

These loads are to be applied in addition to the design pressures above.

4.3.4 Normally, the design impulse pressure, P _DK, for the deck plating and stiffeners may be ignored. However, the design impulse pressure will need to be considered for decks designed to withstand helicopter or aircraft landing operations, cargo handling at sea or similar.

4.3.5 The design global vertical bending moment is to be taken as M _D, as defined in Vol 1, Pt 7, Ch 2, 3.3 Design global loads – Intact conditions or Vol 1, Pt 7, Ch 2, 3.4 Design global loads – Damaged conditions or Residual Strength Assessment (RSA) conditions.

4.3.6 The design transverse load, LT _DK, due to hydrostatic and hydrodynamic compressive loading is to be taken as follows, see also Vol 1, Pt 7, Ch 2, 4.3 Strength deck and internal deck structures (DK) 4.3.8:

where

P _SS is to be taken at the mid height of the H _d depth, P _SS is defined in Vol 1, Pt 7, Ch 2, 3.6 External shell pressures 3.6.1

H _d is illustrated in Figure 2.4.2 Design parameter Hd for transverse load

4.3.7 Normally, the design global shear force may be ignored for the deck plating. However if the structural arrangement is such that significant shear load is carried by the deck, then it should be considered. In this case the design global shear force is to be taken as Q _D, as defined in Vol 1, Pt 7, Ch 2, 3.3 Design global loads – Intact conditions or Vol 1, Pt 7, Ch 2, 3.4 Design global loads – Damaged conditions or Residual Strength Assessment (RSA) conditions

4.3.8 If the deck is not continuous across the full breadth, due to the presence of large openings, then LT _DK may be taken as zero over the opening breadth. In this case it may be necessary to consider the local shear force in the deck plating due to hydrostatic and hydrodynamic loading on the longitudinal span of the deck. This shear force acts in the transverse direction and is to be taken as:

where

P _SS and H _d are defined in Vol 1, Pt 7, Ch 2, 4.3 Strength deck and internal deck structures (DK) 4.3.6

The shear area of the deck plate supporting this shear load is to be based on the breadth of the deck edge strip, B _do.

4.3.9 The transverse load, LT _DK, in way of the full breadth decks at the ends of the deck opening is to be increased by the ratio:

The efficiency of the deck, ε_DK see Vol 1, Pt 7, Ch 2, 4.3 Strength deck and internal deck structures (DK) 4.3.6, may be reduced provided that the transverse bulkheads are capable of carrying more of the transverse loading.

4.3.10 The design loads for deck primary members are given in Vol 1, Pt 7, Ch 2, 4.7 Deck girders (DG) for deck girders and in Vol 1, Pt 7, Ch 2, 5.6 Deck beams (BM) for deck beams.

4.4.1 For all loading conditions, the design normal pressure, , for the inner bottom plating and stiffeners is to be taken as the greater of:

1. (interior deck pressure), see Vol 1, Pt 7, Ch 2, 5.1 Deck structures (DK) 5.1.3

2. P _CD (cargo deck pressure), see Vol 1, Pt 7, Ch 2, 5.1 Deck structures (DK) 5.1.2

3. P _tk (deep tank pressure, where appropriate).

4.4.2 For loading conditions which represent damaged situations, the design normal pressure, , for the inner bottom plating and stiffeners is to be taken as the greater of the following. If this is greater than Vol 1, Pt 7, Ch 2, 4.4 Inner bottom structures (IB) 4.4.1:

1. P _da (damage head).

2. P _SS (pressure on shell plating, where appropriate).

4.4.3 The design load matrix, [], in kN for the inner bottom plating and stiffeners is to be taken as:

[F _CD] (equipment or other deck loads), see Vol 1, Pt 7, Ch 2, 5.1 Deck structures (DK) 5.1.5

4.4.4 The design impulse pressure for the inner bottom plating and stiffeners may be ignored.

4.4.5 The design global vertical bending moment for the inner bottom plating and stiffeners is to be taken as M _D, as defined in Vol 1, Pt 7, Ch 2, 3.3 Design global loads – Intact conditions or Vol 1, Pt 7, Ch 2, 3.4 Design global loads – Damaged conditions or Residual Strength Assessment (RSA) conditions.

4.4.6 The design transverse load, , due to hydrostatic and hydrodynamic compressive loading is to be taken as follows:

where

P _SS is to be taken at a height of H _d/₂ above the keel, P _SS is defined in Vol 1, Pt 7, Ch 2, 3.6 External shell pressures

H _d is illustrated in Figure 2.4.2 Design parameter Hd for transverse load

4.4.7 The design global shear force, Q _D, may be ignored for the inner bottom plating.

4.4.8 The design loads for inner bottom structure primary members are given in Vol 1, Pt 7, Ch 2, 4.6 Bottom longitudinal girders (BG) for bottom longitudinal girders and in Vol 1, Pt 7, Ch 2, 5.4 Transverse floors (FL) for transverse floors.

4.5.1 The design normal pressure for longitudinal bulkhead plating with longitudinal stiffeners is to be taken as the same for both the plating and stiffeners. The design normal pressure, P _LB, is to be taken as P_{B HP} as given in Vol 1, Pt 7, Ch 2, 5.2 Transverse watertight and deep tank bulkheads (BH) 5.2.1

4.5.2 The design normal pressure for longitudinal bulkhead plating with vertical stiffeners is to be considered separately for the plating and the vertical stiffeners. The design normal pressure for the plating, P _LB, is to be taken as P _BHP as given in Vol 1, Pt 7, Ch 2, 5.2 Transverse watertight and deep tank bulkheads (BH) 5.2.1. The design normal pressure for the stiffener, P _LBS, is to be taken as P _BHS as given in Vol 1, Pt 7, Ch 2, 5.2 Transverse watertight and deep tank bulkheads (BH) 5.2.1

4.5.3 The design impulse pressure, P _LB, for the longitudinal bulkhead plating and stiffeners may be ignored, unless these members are likely to be subjected to significant sloshing loads or similar.

4.5.4 The design global vertical bending moment for longitudinal bulkhead plating and stiffeners is to be taken as M _D as defined in Vol 1, Pt 7, Ch 2, 3.3 Design global loads – Intact conditions or Vol 1, Pt 7, Ch 2, 3.4 Design global loads – Damaged conditions or Residual Strength Assessment (RSA) conditions

4.5.5 The design vertical load, LV _LB, at each intersecting deck level is to derived as follows:

where

is the effective deck area supported by the longitudinal bulkhead and can be taken as follows, see Figure 2.4.6 Loads to be applied to longitudinal bulkhead plating

4.5.6 The design global shear force for longitudinal bulkhead plating is to be taken as Q _D, as defined in Vol 1, Pt 7, Ch 2, 3.3 Design global loads – Intact conditions or Vol 1, Pt 7, Ch 2, 3.4 Design global loads – Damaged conditions or Residual Strength Assessment (RSA) conditions.

4.5.7 If the longitudinal bulkhead is not continuous over the full depth of the ship then it will be necessary to consider the local shear force in the longitudinal bulkhead plating as the vertical load must be transferred into the supporting structure, such as transverse bulkheads. This shear force acts in the vertical direction and is to be taken as:

The shear area of the longitudinal bulkhead plate supporting this shear load is to be based on the depth of the longitudinal bulkhead between decks.

4.5.8 The design loads for longitudinal bulkhead primary members are given in Vol 1, Pt 7, Ch 2, 4.8 Longitudinal stringers (ST) for longitudinal stringers and in Vol 1, Pt 7, Ch 2, 5.5 Side frames and web frames (SF) for side frames and web frames.

4.6.1 This sub-Section covers double bottom and single bottom girders. Figure 2.4.7 Loads to be applied to bottom girders illustrates the design loads.

4.6.2 The design normal pressure, P _BG, for girder web plating is to be taken as the greater of:

1. P _tk kN/m² (Deep Tank, if applicable), see Vol 1, Pt 7, Ch 2, 5.1 Deck structures (DK) 5.1.4

2. P _da kN/m² (WT subdivision, only if applicable and for loading conditions which represent damaged situations), see Vol 1, Pt 7, Ch 2, 5.1 Deck structures (DK) 5.1.4

3. 5,0 (minimum value for no direct loading).

4.6.3 The design impulse pressure, P _BG, for the bottom girder web plating may be ignored, unless these members are subjected to sloshing loads or similar.

4.6.4 The design global vertical bending moment for bottom girder plating and stiffeners is to be taken as M _D, as defined in Vol 1, Pt 7, Ch 2, 3.3 Design global loads – Intact conditions or Vol 1, Pt 7, Ch 2, 3.4 Design global loads – Damaged conditions or Residual Strength Assessment (RSA) conditions

4.6.5 The design vertical load, LV _BG, acting on the web plating of bottom girders is to be based on the supported loads. Typically these include downwards local inertial pressures, P _CD, inertial forces, [F _CD], and pillar bulkhead loads above, L _A, all acting on the plating of the inner bottom or the bottom girder flange and the upwards buoyancy loads on the bottom shell plating, P _BS. The design vertical load is to be taken as:

where

P _BS is defined in Vol 1, Pt 7, Ch 2, 4.1 Bottom shell structures (BS) 4.1.2

P _CD is defined in Vol 1, Pt 7, Ch 2, 5.1 Deck structures (DK) 5.1.2

4.6.6 The design shear force for the bottom girder web plating is to include local and global components.

1. The design global shear force is to be taken as Q _D, as defined in Vol 1, Pt 7, Ch 2, 3.3 Design global loads – Intact conditions or Vol 1, Pt 7, Ch 2, 3.4 Design global loads – Damaged conditions or Residual Strength Assessment (RSA) conditions. If the girder depth is reasonably small then Q _D may be ignored.

2. The local shear force component, QV_BG, is due to the difference between the buoyancy and the inertial forces. It acts in the vertical direction and is to be taken as:

   QVBG

   =

   εBG (B bg S bg (P CD – P BS) + [F CD] + L A)/2

where

4.6.7 The design bending load for bottom girder primary member is to be taken as:

ε_BG (B _bg S _bg (P _CD – P _BS ) + [F _CD] + L _A) kN

4.6.8 The membrane loads acting on the bottom shell plating are defined in Vol 1, Pt 7, Ch 2, 4.1 Bottom shell structures (BS) The membrane loads acting on the inner bottom plating are defined in Vol 1, Pt 7, Ch 2, 4.4 Inner bottom structures (IB). These loads are required to assess the bottom girder beam in addition to the local bending loads.

4.7.1 The design normal pressure, P _DG, for deck girder web plating may be ignored.

4.7.2 The design impulse pressure, P _DG, for deck girder web plating may be ignored, unless these members are subjected to sloshing loads or similar.

4.7.3 The design global vertical bending moment for deck girders is to be taken as M _D, as defined in Vol 1, Pt 7, Ch 2, 3.3 Design global loads – Intact conditions or Vol 1, Pt 7, Ch 2, 3.4 Design global loads – Damaged conditions or Residual Strength Assessment (RSA) conditions.

4.7.4 The design vertical load for deck girder webs may be ignored.

4.7.5 The design shear force for the deck girder web plating is to include local and global components.

1. The design global shear force is to be taken as Q _D, as defined in Vol 1, Pt 7, Ch 2, 3.3 Design global loads – Intact conditions or Vol 1, Pt 7, Ch 2, 3.4 Design global loads – Damaged conditions or Residual Strength Assessment (RSA) conditions. If the girder depth is reasonably small then Q _D may be ignored.

2. The local shear force component, QV_DG, is due to the difference between the buoyancy and the inertial forces. It acts in the vertical direction and is to be taken as:

where

4.7.6 The membrane loads acting on the deck plating are defined in Vol 1, Pt 7, Ch 2, 4.3 Strength deck and internal deck structures (DK)

4.7.7 The design bending load for the deck girder primary member is to be taken as:

ε_BG (B _dg S _dg P _CD + [F _CD] + L _A) kN.

4.8.1 This sub-Section covers stringers supporting side shell plating, horizontal girders on longitudinal bulkheads and also covers horizontal diaphragms fitted between a double skin. The design loads are illustrated in Figure 2.4.9 Design loads for longitudinal stringers

4.8.2 The design normal pressure, P _ST, for the web plating of stringer may be ignored unless the stringer forms part of a tank boundary or watertight subdivision, i.e. a watertight horizontal diaphragm. In this case the design pressure is to be taken as the greater of

1. P _tk kN/m² (Deep Tank, if applicable), see Vol 1, Pt 7, Ch 2, 5.1 Deck structures (DK) 5.1.4

2. P _da kN/m² (WT subdivision, only if applicable and for loading conditions which represent damaged situations), see Vol 1, Pt 7, Ch 2, 5.1 Deck structures (DK) 5.1.4.

3. 5,0 (minimum value for no direct loading).

4.8.3 The design impulse pressure, P _ST, for the web plating of stringer may be ignored, unless these members are subjected to sloshing loads or similar.

4.8.4 The design global vertical bending moment for longitudinal stringers is to be taken as M _D, as defined in Vol 1, Pt 7, Ch 2, 3.3 Design global loads – Intact conditions or Vol 1, Pt 7, Ch 2, 3.4 Design global loads – Damaged conditions or Residual Strength Assessment (RSA) conditions

4.8.5 The design transverse load, LT _ST, acting on the web plating of horizontal diaphragms is to be based on the pressure loads acting on the plating of the inner skin or longitudinal bulkhead P _LB (outwards) and the side shell P _SS (inwards). The design transverse load, LT _ST, is to be taken as the lesser of:

1. –ε_ST B _st S _st P _SS kN

2. –ε_ST B _st S _st P _LB kN

where

P _SS is to be taken as the side shell pressure at the height of the stringer, see Vol 1, Pt 7, Ch 2, 3.6 External shell pressures 3.6.1. P _SS is to be ignored for horizontal girders attached to longitudinal bulkheads.

P _LB is to be taken as the longitudinal bulkhead normal pressure at the height of the horizontal girder, see Vol 1, Pt 7, Ch 2, 4.5 Longitudinal bulkhead structures (LB) 4.5.1 This is only required for longitudinal bulkheads that form part of a deep tank or watertight boundary.

4.8.6 The design transverse load, LT _ST, for stringers and horizontal girders may be ignored.

4.8.7 The design shear force, QT _ST, in the stringer web due to hydrostatic, hydrodynamic or tank loading acts in the transverse direction is to be taken as the greater of:

1. ε_ST H _st S _st P _SS/2

2. ε_ST H _st S _st P _LB/2

where

4.8.8 The design bending load for the deck girder primary member is to be taken as:

1. ε_ST H _st S _st (P _SS – P _LB)

where

4.8.9 The membrane loads acting on the side shell and longitudinal bulkhead plating are defined in Vol 1, Pt 7, Ch 2, 4.2 Side shell structures (SS) and Vol 1, Pt 7, Ch 2, 4.5 Longitudinal bulkhead structures (LB), these loads are required to assess the longitudinal stringer beam in addition to the local bending loads.