Comparative fatigue stregth analysis for a container ship with initial and optimized structure, under irregular wave loads

Abstract

This study is focused on the long term fatigue strength analysis of ship structures under irregular wave loads, taking into account the oscillations and the vibrations ship hydroelastic response influence. The fatigue assessment is based on the cumulative damage factor Palmgren-Miner method, considering the irregular sea long term description by World Wide Trade wave significant height histogram. The study is carried out on an 1100 TEU container ship, with total length of 173.42 m, speed 18 knots, for initial and optimized structure, on full cargo and intermediate cargo, without containers on deck, loading cases. The short term significant stresses for fatigue assessment are obtained by linear and non-linear hydroelastic ship response analysis, combined with stress hot-spots by 3D/1D-FEM global-local strength analysis. The 1D-FEM strength, the short term dynamic and long term fatigue numerical analyses are carried out with own program codes, and the 3DFEM strength analysis by SolidWorks program and own user subroutines. The short term strength analysis points out that the deck panels are the higher container ship structural risk domains and the optimized case is more sensitive to the fatigue.