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 - 4 Load Model
4 Load Model
4.1 Lateral pressures and forces
4.1.1 General
The lateral pressures and forces to be considered as acting on hatch covers are given in [4.1.2] to [4.1.6]. When two or more panels are connected by hinges, each individual panel is to be considered separately.
In any case, the sea pressures defined in [4.1.2] are to be considered for hatch covers located on exposed decks.
Additionally, when the hatch cover is intended to carry uniform cargoes, special cargoes or containers, the pressures and forces defined in [4.1.3] to [4.1.6] are to be considered independently from the sea pressures.
4.1.2 Sea pressures
The still water and wave lateral pressures are to be considered and are to be taken equal to:
- Still water pressure: PS = 0.
- Wave pressure PW = PHC, as defined in Pt 1, Ch 4, Sec 5, [5.2].
4.1.3 Internal pressures due to ballast water
If applicable, the internal static and dynamic lateral pressures due to ballast water are to be considered and are defined in Pt 1, Ch 4, Sec 6, [1].
4.1.4 Pressures due to uniform cargoes
If applicable, the static and dynamic pressures due to uniform cargoes are to be considered and are defined in Pt 1, Ch 4, Sec 5, [5.3.1].
4.1.5 Pressures or forces due to special cargoes
In the case of carriage of special cargoes (e.g. pipes, etc) on the hatch covers which may temporarily retain water during navigation, the lateral pressures or forces to be applied are considered by the Society on a case-by-case basis.
4.1.6 Forces due to containers
In the case of carriage of containers on the hatch covers, the concentrated forces under the containers corners are to be determined in accordance with the applicable requirements of the Society.
4.1.7 Self weight
The effect of the hatch cover structure weight is to be included in the static loads but not in the dynamic loads.
4.2 Load point
4.2.1 Wave lateral pressure for hatch covers on exposed decks
The wave lateral pressure to be considered as acting on each hatch cover is to be calculated at a point located:
- Longitudinally, at the hatch cover mid-length.
- Transversely, on the longitudinal plane of symmetry of the ship.
- Vertically, at the top of the hatch cover.
4.2.2 Lateral pressures other than the wave pressure
The lateral pressure is to be calculated at the level of the tight boundary of the cover:
- In way of the geometrical centre of gravity of the plate panel, for plating.
- At mid-span, for stiffeners and primary supporting members.
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