Clasification Society Rulefinder 2020 - Version 9.33 - Fix
Common Structural Rules - Common Structural Rules for Bulk Carriers and Oil Tankers, January 2019 - Part 1 General Hull Requirements - Chapter 8 Buckling - Appendix 1 Stress Based Reference Stresses - 2 Reference Stresses

2 Reference Stresses

2.1 Regular Panel

2.1.1 Longitudinal stress

The longitudinal stress σ x applied on the shorter edge of the buckling panel is to be calculated as follows:
  • For plate buckling assessment, the distribution of σ x(x) is assumed as 2nd order polynomial curve as:
    • σx(x) = C⋅x2 + D ⋅ x + E
    • The best fitting curve σx(x) is to be obtained by minimising the square error Π considering the area of each element as a weighting factor.
    • The unknown coefficients C, D and E must yield zero first derivatives, ∂Π with respect to C,D and E respectively.
    • The unknown coefficients C, D and E can be obtained by solving the 3 above equations.

If -D/2C < b/2 or -D/2C > a-b/2, σx3 is to be ignored. Otherwise, σx3 is taken as:

where:

The longitudinal stress is to be taken as:

The edge stress ratio is to be taken as:

  • For stiffener buckling assessment, σx(x) applied on the shorter edge of the attached plate is to be taken as:

The edge stress ratio ψx for the stress σx is equal to 1.0.

2.1.2 Transverse stress

The transverse stress σy applied along the longer edges of the buckling panel is to be calculated by extrapolation of the transverse stresses of all elements up to the shorter edges of the considered buckling panel.

Figure 1 : Buckling panel

The distribution of σy(x) is assumed as straight line. Therefore:

σy(x) = A + Bx

The best fitting curve σy(x) is to be obtained by the least square method minimising the square error Π considering area of each element as a weighting factor.

The unknown coefficients C and D must yield zero first partial derivatives, ∂Π with respect to C and D, respectively.

The unknown coefficients A and B are obtained by solving the 2 above equations and are given as follow:

σy = max (A, A + Ba)

2.1.3 Shear stress

The shear stress τ is to be calculated using a weighted average approach, and is to be taken as:

2.2 Irregular panel and curved panel

2.2.1 Reference stresses

The longitudinal, transverse and shear stresses are to be calculated using a weighted average approach. They are to be taken as:

The edge stress ratios are to be taken as:

ψx = 1

ψy = 1

Parent topic: Appendix 1 Stress Based Reference Stresses
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