Experimental and numerical investigation of fatigue damage due to wave-induced vibrations in a containership in head seas

• Published in: Journal of marine science and technology Vol. 13; no. 4; pp. 428 - 445
• Main Authors: Drummen, Ingo, Storhaug, Gaute, Moan, Torgeir
• Format: Journal Article
• Language: English
• Published: Japan Springer Japan 01.11.2008; Springer Nature B.V
• Subjects: Automotive Engineering; Engineering; Engineering Design; Engineering Fluid Dynamics; Marine; Materials fatigue; Mechanical Engineering; Offshore Engineering; Original Article; Ships; AN, North Atlantic; Strip theory; Hydroelastic; Experiments; Fatigue damage; Containership
• ISSN: 0948-4280; 1437-8213
• DOI: 10.1007/s00773-008-0006-5

Fatigue cracks have been known to occur in welded ships for several decades. For large ocean-going ships wave-induced vibrations can, depending on trade and design, cause up to 50% of the fatigue damage. The vibrations may be due to springing and whipping effects. In this paper, we address the fatigue damage caused by wave-induced vibrations in a containership of newer design trading in the North Atlantic. The fatigue damage was obtained both experimentally and numerically. The experimental results were found from tests performed with a flexible model of the ship, while the numerical predictions were done using nonlinear hydroelastic strip theory. The measurements showed that the wave-induced vibrations contributed approximately 40% of the total fatigue damage. The numerical method predicted the wave frequency damage well, but was found to overestimate the total fatigue damage by 50%. This was mainly due to an overprediction of the wave-induced vibrations. The discrepancy is partly related to three-dimensional (3D) effects which are not included in the two-dimensional (2D) slamming calculation, and partly to an overprediction of the springing contribution. Moreover, the numerical method does not account for the steady wave due to forward speed. By using a simplified approach we show that high-frequency damage can be significantly reduced by including the steady wave for the relevant vessel, implying better agreement with the experimental results.