Section 1 Materials of construction

1.1.1 The Rules relate in general to the construction of steel ships, although consideration will be given to the use of other materials.

1.1.2 The materials used in the construction of the ship are to be manufactured and tested in accordance with the requirements of the Rules for the Manufacture, Testing and Certification of Materials, July 2022 (hereinafter referred to as Rules for Materials). Materials for which provision is not made therein may be accepted, provided that they comply with an approved specification and such tests as may be considered necessary.

1.1.3 The requirements in this Chapter are not applicable to Double Hull Oil Tankers or Bulk Carriers with a CSR notation (see Pt 1, Ch 2, 2.3 Class notations (hull)) with the exception of Pt 3, Ch 2, 1.2 Steel 1.2.6 and Pt 3, Ch 2, 3.2 Prefabrication primers which are to be complied with.

1.2.1 Steel having a specified minimum yield stress of 235 N/mm² is regarded as mild steel. Steel having a higher specified minimum yield stress is regarded as higher tensile steel.

1.2.2 For the determination of the hull girder section modulus, where higher tensile steel is used, a higher tensile steel factor, k _L, is given in Table 2.1.1 Values of k L .

1.2.3 The local scantling requirements of higher tensile steel plating, longitudinals, stiffeners and girders may be based on a k factor determined as follows:

or 0,66, whichever is the greater,

1.2.4 For the application of the requirements of Pt 3, Ch 2, 1.2 Steel 1.2.2 and Pt 3, Ch 2, 1.2 Steel 1.2.3, special consideration will be given to steel where σ_o >355 N/mm². Where such steel grades are used in areas which are subject to fatigue loading, the structural details are to be verified using fatigue design assessment methods.

1.2.5 For container ships only a k_L factor of 0,62 may be applied to steel with a specified minimum yield stress of 460 N/mm² for structural members that contribute to the ship’s longitudinal strength, provided that:

1. the member’s plate or web thickness is greater than 50 mm, see also Pt 4, Ch 8, 2.3 Requirements for use of thick steel plates;

2. the requirements of Pt 3, Ch 2, 1.2 Steel 1.2.4 are satisfied; and

3. a spectral fatigue assessment is carried out in accordance with ShipRight Fatigue Design Assessment (FDA level 3) procedure, to demonstrate that key structural details sensitive to the hull girder loads have satisfactory fatigue performance. The assessment should normally include the following:

   • Hatch corners in way of cross-deck strips;
   • Hatch corners at the forward region;
   • Hatch corners forward and aft of the engine room and the accommodation blocks;
   • Connection of hatch coaming to supporting structure; and
   • Other critical locations subject to dynamic hull girder bending and torsional effects.

In addition, the ShipRight Construction Monitoring (CM) procedure is to be applied to the fatigue critical locations described above.

1.2.6 Where C, C-Mn and alloy steel castings or forgings are intended for hull structure applications for ships and offshore units for worldwide service such as sternframes, rudder frames, rudder stocks, propeller shaft brackets and other major structural items, they are to comply with Ch 4, 2 Castings for ship and other structural applications or Ch 5, 2 Forgings for ship and other structural applications of the Rules for the Manufacture, Testing and Certification of Materials, July 2022, as appropriate.

1.3.1 The use of aluminium alloy is permitted for superstructures, deckhouses, hatch covers, helicopter platforms, or other local components on board ships.

1.3.2 Aluminium is not to be used for the crowns or casings of Category A machinery spaces, see Pt 5, Ch 1, 4.9 Category A machinery spaces 4.9.1.

1.3.3 Except where otherwise stated, equivalent scantlings are to be derived as follows:

1. Plating thickness;

   

2. Section modulus of stiffeners;

   Z a

   =

   Z s k a c

   where

   c	=	0,95 for high corrosion resistant alloy
   	=	1,00 for other alloys
   k a	=
   t a	=	thickness of aluminium plating
   t s	=	thickness of mild steel plating
   Z a	=	section modulus of aluminium stiffener
   Z s	=	section modulus of mild steel stiffener
   σa	=	0,2 per cent proof stress or 70 per cent of the ultimate strength of the material, whichever is the lesser.

1.3.4 In general, for welded structure, the maximum value of σ_a to be used in the scantlings derivation is that of the aluminium in the welded condition. However, consideration will be given to using unwelded values depending upon the weld line location, other heat affected zones, in relation to the maximum applied stress on the member (e.g. extruded sections).

1.3.5 A comparison of the mechanical properties for selected welded and unwelded alloys is given in Ch 13, 8.3 Fabrication and welding 8.3.2 of the Rules for Materials.

1.3.6 Where strain hardened grades (designated Hxxx) are used, adequate protection by coating is to be provided to avoid the risk of stress corrosion cracking.