Linear and nonlinear FE analyses of a container vessel in harsh sea state
Paper in proceedings, 2013

Container vessels have a challenging structural design with respect to fatigue; they are long and slender and have large openings in the deck. Their structural design in combination with high wave loads, makes these ships sensitive to fatigue damage. Classification societies mainly base their assumptions in the fatigue rules on elastic material response and the fatigue analysis is carried out using the stress-based approach. However, for harsh sea states the assumption of elastic material response is not fulfilled in local details where the stress concentration is high; cyclic plasticity may occur, which requires a strain-based fatigue assessment. The objective of this study is to present a methodology which combines the softwares SESAM and ABAQUS to enable realistic hydrodynamic, structure and fatigue analyses of a container vessel in a harsh sea state. Both of the softwares are needed in order to be able to choose a solver in the structure analysis to be either linear, or nonlinear, depending on the cyclic elastic or plastic material response. Analyses of a case study of a 4,400 TEU container vessel on the North Atlantic route are presented. A long-term fatigue analysis is performed in order to search for the fatigue-critical locations in the ship. A part of the side-shell structure was chosen for detailed study comparing results from a linear and nonlinear finite element analysis for two significant wave heights: 6.0 and 7.5 m. The results show that for both of these wave heights cyclic plasticity occurs locally, but at a very low accumulation rate and continued cyclic loading will most likely result in elastic shakedown of the material response. Hence, the overall conclusion is that, in the studied location, a strain-based approach to fatigue is not necessary.

FEA

direct calculation

fatigue

frequency domain

container vessel

Author

Jonas Ringsberg

Chalmers, Shipping and Marine Technology, Division of Marine Design

Zhiyuan Li

Chalmers, Shipping and Marine Technology, Division of Marine Design

Andrea Tesanovic

Chalmers, Shipping and Marine Technology, Division of Marine Design

Camilla Knifsund

Chalmers, Shipping and Marine Technology, Division of Marine Design

Analysis and Design of Marine Structures - Proceedings of the 4th International Conference on Marine Structures (MARSTRUCT 2013)

485-496

Analysis and Design of Marine Structures - Proceedings of the 4th International Conference on Marine Structures (MARSTRUCT 2013)
Helsingfors, Finland,

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10/9/2018