Section 3 Deck structure

3.1.1 In general, loadings for decks should comply with the requirements of Pt 4, Ch 1 General Cargo Ships except where specified in this Section.

3.1.2 Vehicle decks for the carriage of cars, trucks, etc. are to have a loading for wheeled vehicles as specified in Pt 3, Ch 9, 3 Decks loaded by wheeled vehicles. Where vehicle decks are also used for the carriage of cargo, the loadings derived from Pt 3, Ch 9, 3 Decks loaded by wheeled vehicles are to be not less than would be required by Pt 4, Ch 1 General Cargo Ships.

3.1.3 For ferries and passenger ships classed 100A1, the minimum design loadings for decks are not to be taken as less than those in Table 2.3.1 Design deck loadings (ferries and passenger ships only).

3.1.4 For ferries and passenger ships classed 100A1 with a specified operating area service notation, the loadings for decks in way of baggage and accommodation spaces are to be in accordance with Table 2.3.1 Design deck loadings (ferries and passenger ships only).

3.1.5 Mooring decks, afterward and forward, other than when part of the strength deck, are to comply with the requirements for forecastles, see Pt 3, Ch 8 Superstructures, Deckhouses and Bulwarks. Canopy decks or aprons protecting mooring decks are to be designed using the weather head for forecastle decks reduced by 0,3 m.

3.1.6 For movable decks, see Pt 3, Ch 9, 4 Movable decks.

3.1.7 For train decks, the minimum design loading will be specially considered.

Table 2.3.2 Thickness of deck plating for ferries and passenger ships where a relevant SDA is applied

Deck location	Plating thickness (mm)
Accommodation and public spaces	t = 0,008s
Baggage handling and storage	t = 0,009s
Storerooms	t = 0,01s
Workshops and machinery spaces	t = 0,01s
Weather exposed lifeboat deck	t = 0,00083s 1 + 2,5
Symbols
L, k, s as defined in Pt 4, Ch 1, 1.5 Symbols and definitions 1.5.1 s1 = s but is not to be taken less than the smaller of mm or 700 mm
Note The thickness of deck plating is in no case to be less than 5,0 mm

3.2.1 For ferries, roll on-roll off cargo ships and passenger ships (other than for vehicle decks), the minimum thicknesses of decks are to be in accordance with Pt 4, Ch 1 General Cargo Ships or Pt 3, Ch 8 Superstructures, Deckhouses and Bulwarks as appropriate.

3.2.2 For ferries and passenger ships where direct calculations have been carried out in accordance with the SDA procedure relevant to the ship type (including multi-decked ships), the minimum thicknesses of decks are to be in accordance with Table 2.3.2 Thickness of deck plating for ferries and passenger ships where a relevant SDA is applied.

3.2.3 For roll on-roll off cargo ships, the thickness of deck plating (other than for vehicle decks) will generally be in accordance with Pt 4, Ch 1 General Cargo Ships.

3.2.4 Where decks are required to resist hull girder bending, the thickness is to satisfy the requirements of Pt 3, Ch 4, 7 Hull buckling strength.

3.2.5 Where deck plating is required to form the effective flange of deck primary members, the thickness may need to be increased locally taking account of the compressive forces acting, see also Pt 3, Ch 10 Welding and Structural Details, Table 10.4.1 Minimum thickness of primary members.

3.2.6 Vehicle deck plating is to satisfy the requirements for plating loaded by wheeled vehicles as specified in Pt 3, Ch 9, 3 Decks loaded by wheeled vehicles. Where vehicle decks are also to be used for the carriage of cargo, the thickness of plating derived from Pt 3, Ch 9, 3 Decks loaded by wheeled vehicles is to be not less than would be required by Pt 4, Ch 1, 4.2 Deck plating.

3.2.7 The thickness of all other decks will generally be in accordance with Pt 4, Ch 1 General Cargo Ships.

3.3.1 For ferries, roll on-roll off cargo ships and passenger ships, the deck stiffening (other than for vehicle decks) is generally to be in accordance with Pt 4, Ch 1 General Cargo Ships or Pt 3, Ch 8 Superstructures, Deckhouses and Bulwarks as appropriate.

3.3.2 For ferries and passenger ships where direct calculations have been carried out in accordance with the SDA procedure relevant to the ship type (including multi-decked ships), the deck stiffening is to be in accordance with Table 2.3.3 Modulus of deck beams and longitudinals for ferries and passenger ships where a relevant SDA is applied.

3.3.3 Vehicle deck beams and longitudinals are to have scantlings in accordance with the requirements for wheeled vehicles as specified in Pt 3, Ch 9, 3 Decks loaded by wheeled vehicles. Where vehicle decks are also to be used for the carriage of cargo, the scantlings derived from Pt 3, Ch 9, 3 Decks loaded by wheeled vehicles are to be not less than would be required by Pt 4, Ch 1, 4.3 Deck stiffening.

Table 2.3.3 Modulus of deck beams and longitudinals for ferries and passenger ships where a relevant SDA is applied

Position of beam/longitudinal	Modulus, in cm3
Decks, excluding those for the stowage of cargo or vehicles	Z = 0,00083 R P s e 2 s k but not less than: Z = 0,025s
Symbols
e, s, Z, and k as defined in Pt 4, Ch 1, 1.5 Symbols and definitions P s = deck loading, in kN/m2, see Table 2.3.1 Design deck loadings (ferries and passenger ships only). f R = 1, for ships with unrestricted service f R = 0,81 for ships with a specified operating area service notation

3.4.1  For ferries, roll on-roll off cargo ships, and passenger ships the primary structure supporting four or more point loads or a uniformly distributed load is to be in accordance with Table 1.4.6 Deck girders, transverses and hatch beams.

3.4.2 For ferries and passenger ships where direct calculations have been carried out in accordance with the SDA procedure relevant to the ship type (including multi-decked ships), the section modulus of primary members supporting four or more point loads or a uniformly distributed load is not to be taken as less than:

• where

• , S, Z and k are as defined in Pt 4, Ch 1, 1.5 Symbols and definitions

• P s

  =

  deck design loading, in kN/m2, see Table 2.3.1 Design deck loadings (ferries and passenger ships only).

3.4.3 For ferries and passenger ships where direct calculations have been carried out in accordance with the SDA procedure relevant to the ship type (including multi-decked ships), the moment of inertia of primary members supporting more than four point loads is not to be taken as less than:

• where

• Z, and k are defined in Pt 4, Ch 1, 1.5 Symbols and definitions.

3.4.4 Scantlings of primary structure are to be verified for the following cases using direct calculation methods.

1. The structural support arrangement is complex either due to arrangement or loading pattern.

2. Large openings are incorporated in the webs of primary members.

3. The structure is of novel or unusual design.

4. Primary members supporting up to three point loads.

The stress criteria in Table 1.4.6 Deck girders, transverses and hatch beams in Chapter 1 are to be complied with.

3.4.5 Direct calculations should be carried out in accordance with the SDA procedure relevant to the ship type.

3.4.6 Vehicle deck structure is to be of adequate strength for the upward forces imposed at fixed securing points. Local reinforcement is to be fitted as necessary.