Structural integrity

Technical Bulletin 2015

The three papers in this section deal with different areas of structural integrity, shaft alignment, collision ship structural response and structural downgrading due to progressive fatigue damage accumulation.

Shaft alignment has been for years and remains today very delicate and important as overheating of the circumferential groove journal bearing is to be avoided. Among all potential sources of shaft bearing failure for high power engines the oil film pressure is particularly important over the whole operating period and especially during the period between stand still start up and stabilized operating regime.

Collision has not up to now been considered a design case from a structural point of view. Nevertheless prescriptive IMO or Flag regulations exist and, sometimes it is difficult to comply with these regulations as it may limit the carrying capacity of a cargo ship. Following   the Goal Based Standards approach, IMO prescriptive regulation may be worked around by demonstrating that an alternative design provides at least the same safety level as the design based on prescriptive regulation. This process requires evidence that may be provided by collision simulation tools which consider a representative sample of possible cases and compare the consequence applying both prescriptive regulation and alternative design.

Fatigue is always an issue in ship design as it affects the total cost of ship and the lifetime cost effectiveness. Bureau Veritas has developed fatigue guidance notes and since rules for ship fatigue design. This paper analyses feedback of fatigue design on different ships or ship shaped marine structures. It points out that if fatigue calculation methods are relevant fatigue design is to a large extent based on a good knowledge of the local structural arrangement.  The major experience accumulated by Bureau Veritas allows anticipation of most fatigue sources on new concepts.

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