Scantling optimization of ship structures considering fatigue at the early design stage
Amrane, A.; Rigo, P. (2011). Scantling optimization of ship structures considering fatigue at the early design stage, in: Soares, C.G. et al. (Ed.) Advances in Marine Structures. pp. 569-579
In: Soares, C.G.; Fricke, W. (Ed.) (2011). Advances in Marine Structures. CRC Press: London. ISBN 9780203808115. 732 pp., more
Fatigue aspects are leading criterion for the scantling optimization of ships structures. LBR-5 software is an integrated package which performs, at the early design stage, cost and/or weight optimization of ships structures (scantling). This software takes into account structural constraints (yielding, buckling, displacement, ultimate strength). Until now, the fatigue failure issue was not implicitly included in the optimization loop. At the early design stage, limited information and details are available. Therefore simplified methods have to be applied. LBR-5 software provides the nominal stress, so chosen procedure uses the nominal stress and the Miner's rule. This approach requires a library of stress concentration factors for predefined typical structural details. The goal of the present work is to develop a tool for fatigue assessment that can be integrated on LBR5 optimization process, to realize global optimization taking into account the fatigue issues. Until now, the integration of the fatigue tool is not finished. Only fatigue verification on the optimized structure is possible. On the present paper, the procedure adopted is presented and a longitudinal scantling of the mid-ship section of a LNG is optimized with LBR-5. Production cost is considered as objective functions. The optimized scantling is checked by the fatigue tool. The fatigue criterion is not respected on some panels. Corrections are performed on these panels to have an optimized scantling without fatigue problems.
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