Section 8 Deck Structures

8.1.1 The deck structure may be of either single skin or sandwich construction and is to be supported by transverse beams with fore and aft girders or by longitudinals with deep transverse beams.

8.1.2 Beams are to be fitted at each frame position and be bracketed to the side frames. Strong beams and deep transverse beams are to align with and be effectively connected to the side web frames. They are also to be fitted at the ends of large openings in the deck.

8.1.3 The ends of beams, longitudinals, girders and transverses are to be effectively built into the adjacent structure, or equivalent arrangements provided.

8.1.4 Primary stiffening members are to be continuous and substantially bracketed at their end connections to maintain continuity of structural strength.

8.1.5 Secondary stiffening members are to be effectively continuous and bracketed at their end connections as appropriate.

8.1.6 Deck structures subject to concentrated loads, such as pillars out of line, are to be suitably reinforced. Where concentrations of loading on one side of a stiffener may occur, the stiffener is to be adequately stiffened against torsion. Additional reinforcements may be required in way of localised areas of high stress.

8.1.7 Deck structures are to comply with the minimum thickness requirements of Pt 8, Ch 3, 2 Minimum thickness requirements.

8.1.8 Tripping brackets are to be fitted on deep webs.

8.2.1 The symbols defined in Pt 8, Ch 3, 1.5 Symbols and definitions 1.5.1 apply, unless otherwise specified.

8.3.1 The bending moment assumed to be carried by the strength/weather deck plating is to be not less than that determined from Pt 8, Ch 3, 1.9 Plate and sandwich laminates 1.9.1, using the design pressure from Pt 5, Ch 3, 3.1 Hull structures or Pt 5, Ch 4, 3.1 Hull structures for non-displacement or displacement type craft as appropriate. This bending moment is to be applied to laminates of both single skin and sandwich construction in the determination of the panel scantling required by Pt 8, Ch 3, 8.3 Strength/weather deck laminate 8.3.2 and Pt 8, Ch 3, 8.3 Strength/weather deck laminate 8.3.4 respectively.

8.3.2 An estimate of the thickness of strength/weather deck single skin plating is to be determined from Pt 8, Ch 3, 1.13 Determination of properties and stresses for single skin plate laminates 1.13.1. The tensile and compressive stresses are to be determined for each ply of reinforcement in the proposed laminate using Pt 8, Ch 3, 1.13 Determination of properties and stresses for single skin plate laminates 1.13.3 and Pt 8, Ch 3, 1.13 Determination of properties and stresses for single skin plate laminates 1.13.4, see also LR's Guidance Notes for Calculation Procedures for Composite Construction. The allowable tensile and compressive stress limits indicated in Table 7.3.1 Limiting stress criteria for local loading are to be complied with.

8.3.3 In no case is the minimum thickness of single skin plating to be taken as less than 4 mm.

8.3.4 An estimate of the stiffness E , thickness of single skin plating for outer and inner skins of the strength/weather deck sandwich panels and the thickness of core material is to be determined from Pt 8, Ch 3, 1.14 Mechanical properties sandwich laminates 1.14.2 and Pt 8, Ch 3, 1.14 Mechanical properties sandwich laminates 1.14.9 respectively. The tensile and compressive stresses are to be determined for each ply of reinforcement in the proposed laminate using Pt 8, Ch 3, 1.14 Mechanical properties sandwich laminates 1.14.7 and Pt 8, Ch 3, 1.14 Mechanical properties sandwich laminates 1.14.8. The allowable tensile and compressive stress limits indicated in Table 7.3.1 Limiting stress criteria for local loading are to be complied with.

8.3.5 The amount of reinforcement in laminates that form the skins of a sandwich laminate is to comply with the requirements of Pt 8, Ch 3, 2.5 Minimum skin reinforcement in sandwich laminates 2.5.1.

8.3.6 Special consideration may be given to laminate thicknesses lesser than that required by Pt 8, Ch 3, 8.3 Strength/weather deck laminate 8.3.3 and Pt 8, Ch 3, 8.3 Strength/weather deck laminate 8.3.5, provided that all of the structural strength requirements of the Rules are complied with, a satisfactory water barrier is provided, see Pt 8, Ch 3, 2.3 Sandwich skin laminate 2.3.1, and the equivalent impact resistance is demonstrated as required by Pt 8, Ch 3, 2.8 Impact considerations 2.8.2.

8.3.7 The scantlings of watertight cockpits are to be of equivalent strength to those for the strength/weather deck, see also Pt 4 Additional Requirements for Yachts.

8.3.8 It is recommended that working areas of the weather deck have an anti-slip surface.

8.3.9 Where decks are sheathed with wood or other materials, details of the method of attachment are to be submitted, see also Pt 8, Ch 3, 2.9 Sheathing.

8.4.1 The bending moment assumed to be carried by the lower deck/inside deckhouse deck plating is to be not less than that determined from Pt 8, Ch 3, 1.9 Plate and sandwich laminates 1.9.1, using the design pressure from Pt 5, Ch 3, 3.1 Hull structures or Pt 5, Ch 4, 3.1 Hull structures for non-displacement or displacement type craft as appropriate. This bending moment is to be applied to laminates of both single skin and sandwich construction in the determination of the panel scantling required by Pt 8, Ch 3, 8.4 Lower deck/inside deckhouse deck laminate 8.4.2 and Pt 8, Ch 3, 8.4 Lower deck/inside deckhouse deck laminate 8.4.4 respectively.

8.4.2 An estimate of the thickness of the lower deck/inside deckhouse deck single skin plating is to be determined from Pt 8, Ch 3, 1.13 Determination of properties and stresses for single skin plate laminates 1.13.1. The tensile and compressive stresses are to be determined for each ply of reinforcement in the proposed laminate using Pt 8, Ch 3, 1.13 Determination of properties and stresses for single skin plate laminates 1.13.3 and Pt 8, Ch 3, 1.13 Determination of properties and stresses for single skin plate laminates 1.13.4, see also LR's Guidance Notes for Calculation Procedures for Composite Construction. The allowable tensile and compressive stress limits indicated in Table 7.3.1 Limiting stress criteria for local loading are to be complied with.

8.4.3 In no case is the minimum thickness of single skin plating to be taken as less than 3 mm.

8.4.4 An estimate of the stiffness E , thickness of single skin plating for outer and inner skins of the lower deck/inside deckhouse deck sandwich panels and the thickness of core material is to be determined from Pt 8, Ch 3, 1.14 Mechanical properties sandwich laminates 1.14.2 and Pt 8, Ch 3, 1.14 Mechanical properties sandwich laminates 1.14.9 respectively. The tensile and compressive stresses are to be determined for each ply of reinforcement in the proposed laminate using Pt 8, Ch 3, 1.14 Mechanical properties sandwich laminates 1.14.7 and Pt 8, Ch 3, 1.14 Mechanical properties sandwich laminates 1.14.8. The allowable tensile and compressive stress limits indicated in Table 7.3.1 Limiting stress criteria for local loading are to be complied with.

8.4.5 The amount of reinforcement in laminates that form the skins of a sandwich laminate is to comply with the requirements of Pt 8, Ch 3, 2.5 Minimum skin reinforcement in sandwich laminates 2.5.1.

8.4.6 Special consideration may be given to laminate thicknesses lesser than that required by Pt 8, Ch 3, 8.4 Lower deck/inside deckhouse deck laminate 8.4.3 and Pt 8, Ch 3, 8.4 Lower deck/inside deckhouse deck laminate 8.4.5, provided that all of the structural strength requirements of the Rules are complied with.

8.5.1 Accommodation decks are, in general, to be treated as lower deck/inside deckhouse decks, with their scantling requirements determined in accordance with Pt 8, Ch 3, 8.4 Lower deck/inside deckhouse deck laminate.

8.5.2 Sandwich timber, plywood or other forms of deck construction will be considered on the basis of equivalent strength and stiffness.

8.6.1 The bending moment assumed to be carried by the cargo deck plating is to be not less than that determined from Pt 8, Ch 3, 1.9 Plate and sandwich laminates 1.9.1, using the design pressure from Pt 5, Ch 3, 3.1 Hull structures or Pt 5, Ch 4, 3.1 Hull structures for non-displacement or displacement type craft as appropriate. This bending moment is to be applied to laminates of both single skin and sandwich construction in the determination of the panel scantling required by Pt 8, Ch 3, 8.6 Cargo deck laminate 8.6.2 and Pt 8, Ch 3, 8.6 Cargo deck laminate 8.6.4 respectively.

8.6.2 An estimate of the thickness of the cargo deck single skin plating is to be determined from Pt 8, Ch 3, 1.13 Determination of properties and stresses for single skin plate laminates 1.13.1. The tensile and compressive stresses are to be determined for each ply of reinforcement in the proposed laminate using Pt 8, Ch 3, 1.13 Determination of properties and stresses for single skin plate laminates 1.13.3 and Pt 8, Ch 3, 1.13 Determination of properties and stresses for single skin plate laminates 1.13.4, see also LR's Guidance Notes for Calculation Procedures for Composite Construction. The allowable tensile and compressive stress limits indicated in Table 7.3.1 Limiting stress criteria for local loading are to be complied with.

8.6.3 In no case is the minimum thickness of single skin plating to be taken as less than 4 mm.

8.6.4 An estimate of the stiffness E , thickness of single skin plating for outer and inner skins of the cargo deck sandwich panels and the thickness of core material is to be determined from Pt 8, Ch 3, 1.14 Mechanical properties sandwich laminates 1.14.2 and Pt 8, Ch 3, 1.14 Mechanical properties sandwich laminates 1.14.9 respectively. The tensile and compressive stresses are to be determined for each ply of reinforcement in the proposed laminate using Pt 8, Ch 3, 1.14 Mechanical properties sandwich laminates 1.14.7 and Pt 8, Ch 3, 1.14 Mechanical properties sandwich laminates 1.14.8. The allowable tensile and compressive stress limits indicated in Table 7.3.1 Limiting stress criteria for local loading are to be complied with.

8.6.5 The amount of reinforcement in laminates that form the skins of a sandwich laminate is to comply with the requirements of Pt 8, Ch 3, 2.5 Minimum skin reinforcement in sandwich laminates 2.5.1.

8.6.6 Special consideration may be given to laminate thicknesses lesser than that required by Pt 8, Ch 3, 8.6 Cargo deck laminate 8.6.3 and Pt 8, Ch 3, 8.6 Cargo deck laminate 8.6.5, provided that all of the structural strength requirements of the Rules are complied with, a satisfactory water barrier is provided, see Pt 8, Ch 3, 2.3 Sandwich skin laminate 2.3.1, and the equivalent impact resistance is demonstrated as required by Pt 8, Ch 3, 2.8 Impact considerations 2.8.2.

8.7.1 Decks forming the crowns of tanks are to comply with the requirements for the appropriate deck, and are to be additionally examined for compliance with the requirements for deep tanks given in Pt 8, Ch 3, 7.4 Deep tanks.

8.8.1 The Rule requirements for bending moment, shear force, shear stress and deflection for the strength/weather deck primary stiffeners are to be determined from the general equations given in Pt 8, Ch 3, 1.15 Stiffeners general, using the design pressure from Pt 5, Ch 3, 3.1 Hull structures or Pt 5, Ch 4, 3.1 Hull structures for non-displacement or displacement type craft as appropriate, and the coefficients Φ_M, Φ_S and Φ_δ as indicated in Table 3.1.10 Shear force, bending moment and deflection coefficients for the load model (a).

8.8.2 The Rule requirements for bending moment, shear force, shear stress and deflection for the strength/weather deck secondary stiffeners are to be determined from the general equations given in Pt 8, Ch 3, 1.15 Stiffeners general, using the design pressure from Pt 5, Ch 3, 3.1 Hull structures or Pt 5, Ch 4, 3.1 Hull structures for non-displacement or displacement type craft as appropriate, and the coefficients Φ_M, Φ_S and Φ_δ as indicated in Table 3.1.10 Shear force, bending moment and deflection coefficients for the load model (b). Special consideration will be given to the application of other load models subject to the structural arrangement and degree of end fixity provided.

8.8.3 The allowable tensile, compressive and shear stress limits indicated in Table 7.3.1 Limiting stress criteria for local loading , and the span/deflection ratios indicated in Table 7.2.1 Limiting span/deflection ratio are to be complied with.

8.8.4 The geometric properties of stiffener sections are to be calculated in accordance with Pt 8, Ch 3, 1.16 Geometric properties stiffener sections using an effective width of attached plating as given in Pt 8, Ch 3, 1.7 Effective width of attached plating.

8.9.1 The Rule requirements for bending moment, shear force, shear stress and deflection for the lower deck/inside deckhouse stiffeners are to be determined from the general equations given in Pt 8, Ch 3, 1.15 Stiffeners general, using the design pressure from Pt 5, Ch 3, 3.1 Hull structures or Pt 5, Ch 4, 3.1 Hull structures for non-displacement or displacement type craft as appropriate, and the coefficients Φ_M, Φ_S and Φ_δ as indicated in Table 3.1.10 Shear force, bending moment and deflection coefficients for the appropriate load model. Primary members are assumed to be load model (a), secondary members are, in general, assumed to load model (b), however special consideration will be given to the application of other load models subject to the structural arrangement and degree of end fixity provided.

8.9.2 The allowable tensile, compressive and shear stress limits indicated in Table 7.3.1 Limiting stress criteria for local loading , and the span/deflection ratios indicated in Table 7.2.1 Limiting span/deflection ratio are to be complied with.

8.9.3 The geometric properties of stiffener sections are to be calculated in accordance with Pt 8, Ch 3, 1.16 Geometric properties stiffener sections using an effective width of attached plating as given in Pt 8, Ch 3, 1.7 Effective width of attached plating.

8.10.1 Accommodation decks are, in general, to be treated as lower deck/inside deckhouse decks, with their scantling requirements determined in accordance with Pt 8, Ch 3, 8.9 Lower deck/inside deckhouse stiffening.

8.11.1 The Rule requirements for bending moment, shear force, shear stress and deflection for cargo deck stiffeners are to be determined from the general equations given in Pt 8, Ch 3, 1.15 Stiffeners general, using the design pressure from Pt 5, Ch 3, 3.1 Hull structures or Pt 5, Ch 4, 3.1 Hull structures for non-displacement or displacement type craft as appropriate, and the coefficients Φ_M, Φ_S and Φ_δ as indicated in Table 3.1.10 Shear force, bending moment and deflection coefficients for the appropriate load model. Primary members are assumed to be load model (a), secondary members are, in general, assumed to be load model (b), however special consideration will be given to the application of other load models subject to the structural arrangement and degree of end fixity provided. Additionally where the cargo comprises wheeled vehicles the requirements of Pt 8, Ch 5, 3 Vehicle decks are to be complied with.

8.11.2 The allowable tensile, compressive and shear stress limits indicated in Table 7.3.1 Limiting stress criteria for local loading , and the span/deflection ratios indicated in Table 7.2.1 Limiting span/deflection ratio are to be complied with.

8.11.3 The geometric properties of stiffeners sections are to be calculated in accordance with Pt 8, Ch 3, 1.16 Geometric properties stiffener sections using an effective width of attached plating as given in Pt 8, Ch 3, 1.7 Effective width of attached plating.

8.12.1 All openings are to be supported by an adequate framing system, pillars or cantilevers. When cantilevers are used, stiffening requirements may be derived from direct calculations.

8.12.2 Where stiffening members are stopped in way of an opening, they are to be attached to carlings, girders, transverses or coamings.

8.12.3 The corners of large hatchways in the strength/weather deck within 0,5L amidships are to be elliptical, parabolic or rounded, with a radius generally not less than 1/24 of the breadth of the opening.

8.12.4 Where elliptical corners are arranged, the major axis is to be fore and aft, the ratio of the major to minor axis is to be not less than two to one, nor greater than 2,5 to 1, and the minimum half-length of the major axis is to be defined by l ₁ in Figure 3.8.1 Hatch opening geometry. Where parabolic corners are arranged, the dimensions are also to be as shown in Figure 3.8.1 Hatch opening geometry.

8.12.5 Where the corners are parabolic or elliptical, increased thickness of laminate will, in general, not be required.

8.12.6 For other shapes of corner, reinforcement of the size and extent shown in Figure 3.8.2 Reinforcement in way of hatch opening will, in general, be required. The required weight of reinforcement is to be not less than 25 per cent greater than the adjacent deck laminate.

8.12.7 For lower decks the corners of large openings are to be rounded, with a radius generally not less than 1/24 of the breadth of the opening.

Figure 3.8.1 Hatch opening geometry

Figure 3.8.2 Reinforcement in way of hatch opening

8.12.8 Reinforcement as given in Pt 8, Ch 3, 8.12 Deck openings 8.12.6 will be required at lower decks in way of rapid change in hull form to compensate for loss of deck cross-sectional area. Otherwise, reinforcement will not normally be required.

8.12.9 Adequate transverse strength is to be provided in the deck area between large hatch openings and subjected to transverse and buckling loads.

8.12.10 The requirements for closing arrangements and outfit are given in Pt 3, Ch 4 Closing Arrangements and Outfit.

8.13.1 The requirements for deck sheathing are given in Pt 8, Ch 3, 2.9 Sheathing.

8.14.1 Novel features will be specially considered in accordance with Pt 8, Ch 3, 2.7 Novel features.

8.14.2 Where large or novel hatch openings are proposed, detailed calculations are to be submitted to demonstrate that the scantlings and arrangements in way of the openings are adequate to maintain continuity of structural strength.