Common Structural Rules - Common Structural Rules for Bulk Carriers and Oil Tankers, January 2019 - Part 2 Ship Types - Chapter 1 Bulk Carriers - Section 5 Cargo Hatch Covers - 1 General
1 General
1.1 Application
1.1.1 The requirements in [1] to [8] apply to steel hatch covers in positions 1 and 2 on weather decks, as defined in Pt 1, Ch 1, Sec 4, [3.2].
1.2 Materials
1.2.1 Steel
The formulae for scantlings given in [5] are applicable to steel hatch covers.
Materials used for the construction of steel hatch covers are to comply with the applicable requirements of the Society.
1.2.2 Other materials
The use of materials other than steel is to be considered by the Society on a case-by-case basis, by checking that criteria adopted for scantlings are such as to ensure strength and stiffness equivalent to those of steel hatch covers.
1.3 Net scantlings
1.3.1 All scantlings referred to in this section are net, i.e. they do not include any margin for corrosion.
When calculating the stresses σ and τ in [5.3] and [5.4], the net scantlings are to be used.
The gross scantlings are obtained as specified in Pt 1, Ch 3, Sec 2.
The corrosion additions are given in [1.4].
1.4 Corrosion additions
1.4.1 The total corrosion addition for both sides to be considered for the plating and internal members of hatch covers is equal to the value specified in Table 1.
The corrosion addition for hatch coamings and coaming stays is defined according to Pt 1, Ch 3, Sec 3.
Table 1 : Corrosion addition tc for hatch covers
| Corrosion addition tc, in mm, for both sides | |
|---|---|
| Plating and stiffeners of single skin hatch cover | 2.0 |
| Top and bottom plating of double skin hatch cover | 2.0 |
| Internal structures of double skin hatch cover | 1.5 |
1.5 Allowable stresses
1.5.1 The allowable stresses σa and τa, in N/mm2, are to be obtained from Table 2.
Table 2 : Allowable stresses, in N/mm2
| Members of | Subjected to | σa, in N/mm2 | τ a, in N/mm2 |
|---|---|---|---|
| Weathertight hatch cover | External pressure, as defined in [4.1.2] | 0.80 ReH | 0.46 ReH |
| Weathertight hatch cover | Other loads, as defined in [4.1.3] to [4.1.6] | 0.90 ReH | 0.51 ReH |
The allowable buckling utilisation factors are given in Table 3:
Table 3 : Allowable buckling utilisation factors
| Structural component | Subject to | ηall, Allowable buckling utilisation factor |
|---|---|---|
| Plates and stiffeners Web of PSM | External pressure, as defined in [4.1.2] | 0.80 for load combination: S+D |
| Other loads, as defined in [4.1.3] to [4.1.6] |
0.80 for load combination: S+D 0.64 for load combination: S |
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