Structure Integrity
Technical Bulletin 2013

This section of the Bulletin gathers six papers dealing with various aspects of structural integrity, drawing a link between hydrodynamics and hydro-structure interaction on the one hand, and the final crucial question of the asset’s reliability and safety on the other hand.

The first paper describes some advanced nonlinear simulations of the structural response and structural strength, further to in situ reinforcement work on an oil production floating unit. Opposite to the usual verification procedures where the structure is initially un-deformed and unloaded, the distortion of the structure at the time of the construction work is here taken into account in the determination of the repaired structure’s behavior. The influence of the reinforced area on the ultimate strength of the adjacent structures is verified to make sure that the repair has no drawbacks regarding the safety of the unit.

The next two papers are dealing with the fatigue failure mode. The first paper shows some validation and application cases of Bureau Veritas numerical model for hydro elasticity, focusing on the linear model and its main outcome: fatigue damage computation of Ultra Large Container Ships structural details. The paper demonstrates that the spectral approach is still satisfactory in this context, sweeping away the objection of the response spectrum bandwidth effect. The second paper synthetizes a large amount of published data regarding fatigue S-N curves for steel, and derives a set of curves adapted for the fatigue life assessment of all the different practical cases in the ship industry, both for welded and non-welded details. Many parameters influencing the fatigue capacity are considered, such as material yield strength, mean stress, surface roughness.

The fifth paper introduces the Risk Based Inspection (RBI) approach for the rational development of the Inspection, Maintenance and Repair plans of offshore structures, with both theoretical and practical aspects. Although emphasis is put on the fatigue based quantitative type of RBI the paper gives some strong insights on the ingredients for the development of all types of sound RBI practices.

Last but not least, two papers are focused on ship structural response full scale measurements analysis methods. Indeed, feedback from the real world is crucial in research activities. But the interpretation and treatment of the measured signals, and their conversion into information of interest for the industry, are not straightforward. These two papers are describing some Bureau Veritas recent work on improving the measurement analysis techniques, in two different contexts: wave induced hull girder sectional loads on Ultra Large Container Ships, and ice loads on the local structure of arctic vessels.

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