Clasification Society Rulefinder 2016 - Version 9.25
Clasification Society Rules and Regulations - Rules and Regulations for the Classification of Offshore Units, January 2016 - Part 4 STEEL UNIT STRUCTURES - Chapter 5 Primary Hull Strength - Section 2 Permissible stresses

Section 2 Permissible stresses

Parent topic: Chapter 5 Primary Hull Strength

2.1 General

2.1.1 For the combined load cases, as defined in Pt 4, Ch 3, 4.3 Load combinations, the maximum permissible stresses of steel structural members are to be based on the following factors of safety unless otherwise specified:
  1. Load case (a):
    • 2,50 for shear (based on the tensile yield stress)
    • 1,67 for shear buckling (based on the shear buckling stress)
    • 1,67 for tension and bending (based on the tensile yield stress)
    • 1,67 for compression (based on the lesser of the least buckling stress or the yield stress)
    • 1,43 for combined ‘comparative’ stress (based on the tensile yield stress).
  2. Load case (b) and (c):
    • 1,89 for shear (based on the tensile yield stress)
    • 1,25 for shear buckling (based on the shear buckling stress)
    • 1,25 for tension and bending (based on the tensile yield stress)
    • 1,25 for compression (based on the lesser of the least buckling stress or the yield stress)
    • 1,11 for combined ‘comparative’ stress (based on the tensile yield stress).
  3. Load case (d):
    • 1,72 for shear (based on the yield stress)
    • 1,0 for shear buckling (based on the shear buckling stress)
    • 1,0 for tension and bending (based on the tensile yield stress)
    • 1,0 for compression (based on the lesser of the least buckling stress or the yield stress)
    • 1,0 for combined ‘comparative’ stress (based on the tensile yield stress).

2.1.2 For plated structures, the combined ‘comparative’ stress is to be determined where necessary from the formula:

where and are the combined axial and bending stresses in the X and Y directions respectively, is the combined shear stress due to torsion and/or bending in the X-Y plane.

2.1.3 When finite element methods are used to verify scantlings, special consideration will be given to areas of the structure where localised peak stresses occur.

2.1.4 Non linear and plastic design methods may be used for verifying the local structure in load cases (c) and (d), as defined in Pt 4, Ch 3, 4.3 Load combinations. Local yielding and permanent deformation can be accepted; however, the structural arrangements must prevent progressive collapse.

2.1.5 The buckling strengths of plates and stiffeners are to comply with Pt 4, Ch 5, 3 Buckling strength of plates and stiffeners.

2.1.6 The buckling strength for individual primary members subjected to axial compression and combined axial compression and bending is to be in accordance with Pt 4, Ch 5, 4 Buckling strength of primary members.

2.1.7 Permissible stress levels for lattice type structures are to be determined as required by Pt 4, Ch 5, 1.3 Primary structure 1.3.8.

2.1.8 Permissible stresses in materials other than steel are to be specially considered.

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