Time-domain fatigue assessment of ship side-shell structures

Loads acting on ship side-shell structures are complex and vary randomly over time. The current study proposes a direct calculation procedure for the fatigue assessment of ship side-shell structures. The calculation procedure is characterised by nonlinear time-domain hydrodynamic simulations followed by finite element (FE) analyses. Sensitivity and feasibility analyses of the proposed time-domain procedure were carried out, and the calculated fatigue damages were compared with full-scale measurements made on a container vessel. Fatigue life analyses were carried out by both the spectral method and the time-domain approach. In addition, two approaches for local stress analysis are presented and discussed: an engineering-based definition of the stress concentration factor (SCF) and a proposed local stress factor (LSF) that utilises stress ranges extracted from the stress history. The results from the fatigue analysis using the LSF indicated a shorter fatigue life than the results obtained using the SCF. This difference is observed because the LSF accounts for the effects of wave-induced loads under ship operation conditions in a more realistic manner.