Section 1 Materials of construction
Clasification Society 2024 - Version 9.40
Clasifications Register Rules and Regulations - Rules and Regulations for the Classification of Linkspans, July 2022 - Part 3 Construction, Design and Test Requirements - Chapter 2 Materials - Section 1 Materials of construction

Section 1 Materials of construction

Parent topic: Chapter 2 Materials

1.1 General

1.1.1 In general the Rules relate to the construction of linkspans in steel or aluminium alloys, although consideration will be given to the use of other materials.

1.1.2 The materials used in the construction of classed linkspans are to be manufactured and tested in accordance with the requirements of Rules for the Manufacture, Testing and Certification of Materials, July 2022. 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.

1.2 Steel

1.2.1 Steel having a specified minimum yield stress of 235 N/mm2 (24 kgf/mm2) is regarded as mild steel.

1.2.2 For the determination of pontoon scantlings where higher tensile steel is used, a higher tensile steel factor, k, given in Table 2.1.1 Higher tensile steel factor, k, is to be applied as indicated in the various prescriptive scantling formulae given in Pt 3, Ch 4 Pontoons.

Table 2.1.1 Higher tensile steel factor, k

Specified minimum yield stress in N/mm2 k
315 0,78
340 0,74
355 0,72
390 0,68

Note 1. Intermediate values by linear interpolation.

Note 2. For mild steel k = 1,0.

1.3 Aluminium

1.3.1 Except where otherwise stated, equivalent scantlings are to be derived as follows where aluminium alloys are used:

Plating thickness;

Section modulus of stiffeners;

where
c = 0,95 for high corrosion resistant alloy
= 1,00 for other alloys
k a =
t a = equivalent thickness of aluminium plating
t s = thickness of mild steel plating
Z a = equivalent 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 (N/mm2).

1.3.2 In general, for welded structures, the maximum value of σa to be used in the derivation of scantlings is that of aluminium in the welded condition. However, consideration will be given to using unwelded values depending upon the weld line location, or other heat affected zones, in relation to the maximum applied stress on the member.

1.3.3 A comparison of the mechanical properties for selected welded and unwelded alloys is given in Table 2.1.2 Minimum mechanical properties for selected aluminium alloys.

Table 2.1.2 Minimum mechanical properties for selected aluminium alloys

Alloy Condition 0,2% proof stress N/mm2 Ultimate tensile strength N/mm2
  Unwelded Welded (see Note 4) Unwelded Welded (see Note 4)
5754 O/H111 80 80 190 190
5083 O/H111 125 125 275 275
5083 H112 125 125 275 275
5083 H116/H321 215 125 305 275
5086 O/H111 100 95 240 240
5086 H112 125 (see Note 2) 95 250 (see Note 2) 240
5086 H116/H321 195 95 275 240
6005A T5/T6 Extruded: Open Profile 215 100 260 160
(see Note 1) Extruded: Closed Profile 215 100 250 160
6061 T5/T6 Rolled 240 125 290 160
(see Note 1)   Extruded: Open Profile 240 125 260 160
    Extruded: Closed Profile 205 125 245 160
6082 T5/T6 Rolled 240 125 280 190
    Extruded: Open Profile 260 125 310 190
    Extruded: Closed Profile 240 125 290 190

Note 1. These alloys are not normally acceptable for application in direct contact with sea-water.

Note 2. See also Table 8.1.4 Minimum mechanical properties for acceptance purposes of selected extruded aluminium alloy products in Chapter 8 of the Rules for Materials.

Note 3. The mechanical properties to be used to determine scantlings in other types and grades aluminium alloy manufactured to national or propriety standards and specifications are to be individually agreed with LR, see also Ch 8, 1.1 Scope 1.1.5 of the Rules for Materials.

Note 4. Where detail structural analysis is carried out `Unwelded' stress values may be used away from heat affected zones and weld lines, see also Pt 3, Ch 2, 1.3 Aluminium 1.3.2.

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

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