Section 3 Buckling strength of plates and stiffeners
Clasification Society 2024 - Version 9.40
Clasifications Register Rules and Regulations - Rules and Regulations for the Classification of Offshore Units, July 2022 - Part 4 Steel Unit Structures - Chapter 5 Primary Hull Strength - Section 3 Buckling strength of plates and stiffeners

Section 3 Buckling strength of plates and stiffeners

3.1 Application

3.1.1 The requirements of this Section apply to plate panels, and attached stiffeners subject to overall hull structure compression and shear stresses. The maximum design values computed are to be determined in accordance with Pt 4, Ch 5, 1.2 Structural analysis.

3.1.2 For states of stress which cannot be defined by one single reference stress, the buckling characteristics are to be based on recognised interaction formulae.

3.1.3 LR’s ShipRight buckling modules may be used for the buckling assessment of flat rectangular plate panels by direct calculation.

3.2 Symbols

3.2.1 The symbols used in this Section are defined as follows:
E = modulus of elasticity, in N/mm2 (kgf/mm2)
= 206 000 N/mm2 (21 000 kgf/mm2) for steel
= specified minimum yield stress, in N/mm2 (kgf/mm2)
= critical buckling stress in compression, in N/mm2 (kgf/mm2), corrected for yielding effects
= elastic critical buckling stress in compression, in N/mm2 (kgf/mm2)
= critical buckling stress in shear, in N/mm2 (kgf/mm2), corrected for yielding effects
= elastic critical buckling stress in shear, in N/mm2 (kgf/mm2)
=

3.3 Elastic critical buckling stress

3.3.1 The elastic critical buckling stress of plating and stiffeners is to be determined in accordance with an agreed Code or Standard or according to Pt 3, Ch 4, 7.4 Design stress 7.4.1 and Pt 3, Ch 4, 7.5 Scantling criteria 7.5.3 in Pt 3, Ch 4, 7 Hull buckling strength, of the Rules and Regulations for the Classification of Ships (hereinafter referred to as the Rules for Ships).

3.4 Scantling criteria

3.4.1 The critical buckling stress in compression, corrected for yielding effects, , of plate panels and stiffeners, as derived from Pt 3, Ch 4, 7.4 Design stress 7.4.1 and Pt 3, Ch 4, 7.5 Scantling criteria 7.5.3 in Pt 3, Ch 4, 7 Hull buckling strength of the Rules for Ships, is to satisfy the following:

where

= factor of safety for compression in accordance with Pt 4, Ch 5, 2.1 General 2.1.1 for the appropriate load case.

3.4.2 The critical buckling stress in shear, corrected for yielding effects, , of plate panels as derived from Pt 3, Ch 4, 7.4 Design stress 7.4.1 (c) in Pt 3, Ch 4, 7 Hull buckling strength of the Rules for Ships, is to satisfy the following:

where

= factor of safety for shear buckling in accordance with Pt 4, Ch 5, 2.1 General 2.1.1 for the appropriate load case.
3.4.3 Buckling criteria are to be determined for plating and plate and stiffener combinations, including (but not limited to):
  • Flat bar stiffeners.
  • Bulb plate stiffeners.
  • Rolled angles.
  • Built-up profiles.
  • Floors or deep girders.
3.4.4 All appropriate buckling modes are to be investigated, including:
  • Column buckling.
  • Torsional buckling.
  • Web and flange buckling.

3.4.5 The stresses are to be determined with corrosion allowance deducted from the gross scantlings in accordance with Table 3.7.1 Corrosion rate for one side of structural member in Pt 4, Ch 3 Structural Design


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