Section 8 Deck structures

8.1.1 Unless otherwise specified in this Section, the scantlings and arrangements for deck structures are to be determined in accordance with the procedures described in, or as required by, Pt 6, Ch 3, 8 Deck structures for mono-hull craft using the pressures from Pt 5 Design and Load Criteria appropriate to multi-hulls.

8.2.1 Design loads to be applied for cross-deck scantling calculations are transverse vertical bending moment and shear force, twin hull torsional connecting moment, external pressure load and appropriate internal loads as defined in Pt 3 General Requirements and Constructional Arrangements.

8.2.2 For craft up to 50 m in Rule length, L _R, where the cross-deck is formed by transverse primary stiffeners or bulkheads, and subjected to global transverse loads in accordance with Pt 6, Ch 4, 8.2 Arrangements 8.2.1 the scantling requirements to satisfy the global loading condition are given in Pt 6, Ch 6, 3.5 Strength of cross-deck structures.

8.2.3 Superstructures fitted on the cross-deck structures, on craft up to 50 m in Rule length, L _R, will, in general, be considered as non load carrying and are not to be included in the strength of the cross-deck. For designs where the superstructure is designed to absorb global loads, the requirements are given in Pt 6, Ch 6, 3.2 Hull longitudinal bending strength.

8.2.4 For craft more than 50 m in Rule length, L _R, global analysis is required to determine the response of the deck and superstructure as a system. Deck scantlings may then be derived for compliance with the requirements of Pt 6, Ch 6, 3 Additional hull girder strength requirements for multi-hull craft.

8.3.1 The thickness of the cross-deck plating is to be determined from the general plating equation given in Pt 6, Ch 3, 1.16 Plating 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 craft as appropriate.

8.3.2 The thickness of the cross-deck plating is in no case to be less than the appropriate minimum requirement given in Pt 6, Ch 4, 2 Minimum thickness requirements.

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

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

8.3.5 Where decks are sheathed with wood or other materials, details of the method of attachment are to be submitted, see also Pt 6, Ch 3, 2.4 Sheathing.

8.4.1 The Rule requirements for section modulus, inertia and web area for the cross-deck primary stiffeners are to be determined from the general equations given in Pt 6, Ch 3, 1.17 Stiffening general, using the design pressures from Pt 5, Ch 3, 3.1 Hull structures or Pt 5, Ch 4, 3.1 Hull structures for non-displacement or displacement craft as appropriate, and the coefficients Φ_Z, Φ_I, and Φ_A as detailed in Table 3.1.1 Section modulus, inertia and web area coefficients for the load model (a).

8.4.2 The Rule requirements for section modulus, inertia and web area of the strength/weather deck secondary stiffening are to be determined from the general equations given in Pt 6, Ch 3, 1.17 Stiffening general, using the design pressures from Pt 5, Ch 3, 3.1 Hull structures or Pt 5, Ch 4, 3.1 Hull structures for non-displacement or displacement craft as appropriate, and the coefficients Φ_Z, Φ_I, and Φ_A as detailed in Table 3.1.1 Section modulus, inertia and web area 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.

8.4.3 The geometric properties of stiffener sections are to be in accordance with Pt 6, Ch 3, 1.18 Geometric properties and proportions of stiffener sections.

8.4.4 For cases where there may be excessive rotations or deflections at supports or where the lateral pressure distribution is non-uniform, the above scantlings may require increasing appropriately.

8.4.5 Where stiffeners are subject to concentrated loads such as pillars, the concentrated loads are to be superimposed on the lateral pressure and strength calculations carried out to demonstrate compliance with the deflection and stress criteria given in Pt 6, Ch 7, 2 Deflection control and Pt 6, Ch 7, 3 Stress control.

8.4.6 Where stiffening members support plating of the extruded plank type, or the floating frame system is used, the plating is not to be included in the scantling derivation of the supporting structure.

8.4.7 Openings in the cross-deck for hatches etc. are to comply with the requirements of Pt 6, Ch 3, 8.11 Deck openings.

8.5.1 Where the cross-deck structure is of unusual design, form or proportions, the scantlings are to be determined by direct calculation and a copy submitted for consideration.