Page 51: of Maritime Reporter Magazine (June 2005)
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SOLAS, Chapter II-1.
As to environmental conditions, a
North Atlantic functional requirement was thought appropriate especially since bulk carriers and oil tankers in unre- stricted service were being considered.
Concerning fatigue life, which previ- ously was agreed to be longer than design life in order to protect against the uncertainties in calculating fatigue life and to provide a factor of safety, the working group agreed that it did not need to be longer than design life. Using the North Atlantic as a design environ- ment was considered conservative since ships do not generally trade exclusively in those waters and the factor of safety issue was already included in structural strength functional requirements.
The working group clarified that func- tional requirements for "structure" did not include requirements for superstruc- tures or accommodations; they were limited to hull structures. Structural strength functional requirements are to include safety margins for design parameters whose calculation involves uncertainty, including "loads, structural modeling, fatigue, corrosion, material imperfections, construction workman- ship errors, buckling and residual strength." In addition, ships must be able to withstand not only the environ- mental conditions anticipated for the design life but also a complete range of appropriate loading conditions: fully, partially and alternate-hold loaded, multi-port and ballast and occasional overloading during cargo operations.
The loading condition requirement is aimed those shipyards or designers who restrict the required loading manuals to a few or even unrealistic loading condi- tions. Structural strength is also to be assessed against specific modes of fail- ure: buckling, yielding and fatigue.
Ultimate strength calculations are to be made for the hull girder and plates and stiffeners. Residual structural strength is to be sufficient to withstand the damage conditions specified in SOLAS. And "ships should be of redundant design and construction so that localized dam- age of any one member will not lead to immediate, consequential failure of other structural members leading to loss of structural and watertight integrity of the ship."
A new functional requirement was added to the earlier draft for adequate watertight and weathertight integrity for the intended service and for adequate strength and redundancy of associated hull opening securing devices.
Measures to protect against corrosion are required to ensure that structural strength scantling requirements are maintained throughout the ship design life. Sub-functional requirements are specified for coatings and the corrosion allowance, or addition. These had been controversial in earlier meetings. In its submission for the December 2004
MSC meeting, Greece severely criti- cized a position advanced by European shipyards to the effect that a return to "robust ship types with a safety concept based on increased scantlings" was undesirable considering the commercial success of modern new-building, fully optimized ship structures-that is, ships that minimize lightship weight while maximizing payload. Greece argued that it was exactly the concept of an opti- mized ship design-light construction and inade- quate coating protection-that must be avoided since it had resulted
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