Section
1 Materials of construction
1.1 General
1.1.1 The Rules relate in general to the construction of steel units, although
consideration will be given to the use of other materials. For the use of aluminium
alloys, see
Pt 4, Ch 2, 1.3 Aluminium.
1.1.2 The materials used in the construction of the unit are to be
manufactured and tested in accordance with the requirements of the Rules for the
Manufacture, Testing and Certification of Materials (hereinafter referred to
as the 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, see also
Pt 3, Ch 1, 4 Materials.
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. Steel having a higher specified
minimum yield stress is regarded as higher tensile steel.
1.2.2 When higher tensile steel is used in the construction of the unit the
local scantlings determined from the Rules for steel plating, longitudinals,
stiffeners and girders, etc., may be based on a k factor determined as
follows:
![](svgobject/43EB-41DA-9F8D-83F409642BB2.xml_d6646014e169.png)
or 0,66, whichever is the greater
where
![](svgobject/43EB-41DA-9F8D-83F409642BB2.xml_d6646014e288.png) |
= |
specified minimum yield stress, of the higher tensile steel in
N/mm2 (kgf/mm2). |
1.2.3 When higher tensile steel is used in the primary structure of ship
units, the determination of the hull girder section modulus is to be based on a
higher tensile steel factor ![](svgobject/43EB-41DA-9F8D-83F409642BB2.xml_d6646014e339.png) kL determined in accordance with Table 2.1.1 Values of
kL.
Table 2.1.1 Values of
kL
Specified minimum yield stress
In N/mm2 (kgf/mm2)
|
|
235
(24)
|
1,0
|
265
(27)
|
0,92
|
315
(32)
|
0,78
|
355
(36)
|
0,72
|
390
(40)
|
0,66
|
460
(47)
|
0,62
|
NOTES
|
1. Intermediate values by linear
interpolation.
|
2. For the purpose of calculating hull moment of
inertia as specified in Pt 3, Ch 4, 5.8 Hull moment of inertia 5.8.1 of the Rules for
Ships, =1,0.
|
1.2.4 For the application of the requirements of Pt 4, Ch 2, 1.2 Steel 1.2.2 and Pt 4, Ch 2, 1.2 Steel 1.2.3, special consideration will be given to steel
where > 355 N/mm2 (36 kgf/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.
1.3 Aluminium
1.3.2 Except where
otherwise stated, equivalent scantlings are to be derived as follows:
Plating thickness:
![](svgobject/43EB-41DA-9F8D-83F409642BB2.xml_d6646014e660.png)
Section modulus of stiffeners:
![](svgobject/43EB-41DA-9F8D-83F409642BB2.xml_d6646014e743.png)
where
c |
= |
0,95 for high corrosion resistant alloy |
= |
1,0 for other alloys |
![](svgobject/43EB-41DA-9F8D-83F409642BB2.xml_d6646014e831.png)
![](svgobject/43EB-41DA-9F8D-83F409642BB2.xml_d6646014e906.png) |
= |
thickness of aluminium plating |
![](svgobject/43EB-41DA-9F8D-83F409642BB2.xml_d6646014e946.png) |
= |
thickness of mild steel plating |
![](svgobject/43EB-41DA-9F8D-83F409642BB2.xml_d6646014e986.png) |
= |
section modulus of aluminium stiffener |
![](svgobject/43EB-41DA-9F8D-83F409642BB2.xml_d6646014e1027.png) |
= |
section modulus of mild steel stiffener |
![](svgobject/43EB-41DA-9F8D-83F409642BB2.xml_d6646014e1067.png) |
= |
0,2 per cent proof stress or 70 per cent of the ultimate
strength of the material, whichever is the lesser. |
1.3.3 In general, for welded structure, the maximum value of 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, or other heat affected zones, in
relation to the maximum applied stress on the member (e.g., extruded sections).
1.3.5 Where strain hardened grades (designated Hxxx) are used, adequate
protection by coating is to be provided to avoid the risk of stress corrosion
cracking.
1.3.6 The use of aluminium alloy for primary structure will be specially
considered.
Table 2.1.2 Minimum mechanical properties
for 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)
|
5083
|
O/H111
|
125
|
125
|
275
|
275
|
5083
|
H112
|
125
|
125
|
275
|
275
|
5083
|
H116/H321
|
215
|
125
|
305
|
275
|
5383
|
O/H111
|
145
|
145
|
290
|
290
|
5383
|
H116/H321
|
220
|
145
|
305
|
290
|
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
|
5059
|
O/H111
|
160
|
160
|
330
|
330
|
5059
|
H116/H321
|
260
|
160
|
360
|
300
|
5456
|
O
|
125
|
125
|
285
|
285
|
5456
|
H116
|
200
(see Note 5)
|
125
|
290
(see Note 5)
|
285
|
5456
|
H321
|
215
(see Note 5)
|
125
|
305
(see Note 5)
|
285
|
5754
|
O/H111
|
80
|
80
|
190
|
190
|
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
|
NOTES
|
1.
These alloys are not normally acceptable for application in direct
contact with sea-water.
|
2. See also
Table 8.1.2 Chemical composition,
percentage or Table 8.1.4 Minimum mechanical properties for
acceptance purposes of selected extruded aluminium alloy products of the Rules for
Materials.
|
3. The mechanical properties to be used to determine scantlings in
other types and grades of aluminium alloy manufactured to National
or proprietary 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.
|
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 4, Ch 2, 1.3 Aluminium 1.3.3.
|
5. For thickness less than 12,5 mm the minimum unwelded 0,2% proof
stress is to be taken as 230 N/mm2 and the minimum
tensile strength is to be taken as 315 N/mm2.
|
|