Effect of Whipping on Fatigue and Extreme Loading of a 13000TEU Container Vessel in Bow Quartering Seas Based on Model Tests

Abstract

Many large and ultra large container vessels have entered operation lately and more vessels will enter operation in the coming years. The operational experience is limited and one of the concerns is the additional effect of hull girder vibrations especially from whipping (bow impacts), but also from springing (resonance). Whipping contributes both to increased fatigue and extreme loading, while springing does mainly contribute to increased fatigue loading. MAIB recommended the industry to join forces to investigate the effect of whipping after MSC Napoli, a Post-Panamax container vessel, broke in two in January 2007. This has been followed up by a JIP initiated in 2008 with the following participants: HHI, DNV, BV, CeSOS and Marintek. In 2009 a new design 13000TEU vessel was tested in head seas and reported in [1]. The current paper deals with fatigue and extreme loading of the same vessel, but from realistic quartering sea conditions tested in 2010. Different headings and the effect of wave energy spreading have been investigated and compared to results from head seas. Further, the effect of the vibrations have been investigated on torsion and horizontal bending, as the model is also allowed to vibrate with realistic frequencies in other modes in addition to vertical bending. The findings suggest that changing the course is not effective to reduce the fatigue loading of critical fatigue sensitive details amidships. The effect of wave energy spreading did also not reduce the fatigue loading significantly. For the highest observed vertical bending moments in each sea state and for the three cross sections the wave energy spreading in average reduced the maxima, but for the highest sea state the effect of wave spreading did not consistently give reduced maxima. This is an important aspect when considering the available safety margin that may be reduced by whipping. The whipping gave also a considerable contribution to horizontal bending and torsion. This suggests that validation of numerical tools is urgent with respect to off head sea conditions and that these tools must incorporate the real structural behavior to confirm the importance of the response from torsional and horizontal as well as for vertical vibrations.

Prediction of the vibratory properties of ship models with realistic structural configurations produced using additive manufacturing

“…Examples of such structures with particularly complex cross-sections include ships, which often feature, among others, several decks, a double bottom, double sides and a range of stiffeners. Understanding the dynamic behaviour of these structures has proven to be crucial, as loads due to structural vibrations can be of significant magnitude and have been suggested as the dominant cause of fatigue damage [1].…”

Modern Trends in Research on Steel, Aluminium and Composite Structures

“…In recent years, the problem was analysed in the experimental and numerical domain. In the experiments, both model tests (Storhaug et al 2010) and full-scale measurements (Gaidai et al 2016, Mao et al 2015 were carried out. In model testing, the tests are usually quite expensive, and only a limited number of cases could be investigated.…”

Fatigue Assessment of Very Large Container Ships Considering Springing Effect Based on Stochastic Approach

“…In addition to numerical attempts to solve the hydroelasticity problems as described above, studies using the model test and real ship measurement are continuously being conducted. Storhaug et al (2011) calculated the ultimate load and fatigue damage due to the hydroelastic response of large container ships through model tests. Kim et al (2018a) and Kim et al (2018b) analyzed the strain data based on actual ship data measured in a very large container ship, analyzed the vibration mode generated in the ship, and predicted the long-term fatigue damage.…”