Common Structural Rules - Common Structural Rules for Bulk Carriers and Oil Tankers, January 2019 - Part 1 General Hull Requirements - Chapter 9 Fatigue - Section 4 Simplified Stress Analysis - 3 Hull Girder Stress
3 Hull Girder Stress
3.1 Stress due to hull girder wave bending moments
3.1.1 The hull girder hot spot stress, in N/mm2, for load cases i1 and i2 of loading condition (j) is obtained from the following formula:
where:
Mwv-LC, ik : Vertical wave bending moment, in kNm, of the considered dynamic load case, as defined in Ch 4, Sec 4, at the hull girder load calculation point of the considered longitudinal position for the loading condition (j) for ik being equal to i1 and i2.
Mwh-LC, ik : Horizontal wave bending moment, in kNm, of the considered dynamic load case, as defined in Ch 4, Sec 4, at the hull girder load calculation point of the considered longitudinal position for the loading condition (j) for ik being equal to i1 and i2.
3.2 Stress due to still water hull girder bending moment
3.2.1
The hull girder hot spot stress due to still water bending moment, in N/mm2, in loading condition (j) is obtained from the following formula:
where:
Msw : Permissible still water vertical bending moment, in kNm, as defined in Ch 4, Sec 4 at the hull girder load calculation point of the considered longitudinal position.
β(j) : Fraction of permissible still water vertical bending moment, as defined in Table 1.
Table 1 : Fraction of permissible still water vertical bending moments, β(j)
|
Ship type |
Loading conditions |
Longitudinal position on the considered section |
β(j) |
|---|---|---|---|
|
Oil tankers |
Homogeneous |
N/A |
0.60 in sagging condition |
| Normal ballast | 0.80 in hogging condition | ||
|
Bulk carriers |
Homogeneous | 0.40 in sagging condition | |
| Alternate | 0.75 in hogging condition | ||
| Normal ballast | 0.80 in hogging condition | ||
|
Heavy ballast (See Figure 1) |
Ballast hold | 0.75 in sagging condition | |
|
Cargo holds adjacent to ballast hold |
Linear interpolation between 0.75 in sagging condition and 0.45 in hogging condition |
||
| Other cargo holds | 0.45 in hogging condition |
Figure 1 : Distribution of still water bending moment for fatigue assessment in way of ballast hold
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