engleski

Influence of environmental and operational uncertainties on design wave loads of containerships

The purpose of the presentation is to investigate wave loads on containership on different shipping routes. The motivation is that assumptions built-in the IACS Recommendation No.34 “Standard Wave Data” need revision to account for speed reduction, course changes and wave energy spreading. The study concentrates on vertical wave bending moments and the bottom slamming pressure as the most important wave load component for longitudinal strength of containerships. Following parameters are investigated in the analysis: • choice of the wave scatter diagram, where following wave environments are considered: o IACS standard North Atlantic scatter diagram from Recommendation No.34 “Standard Wave Data” o shipping route in North Pacific o shipping route from North Europe to the Far East through the Suez Canal. • effect of the avoidance of heavy weather: o without operational restrictions, i.e. probability of occurrence of different significant wave heights are given directly in GWS o with operational restriction, i.e. probability density function of significant wave heights is truncated. • effect of maneuvering in heavy weather: o the effect of maneuvering in heavy weather is accounted by speed reduction. Constant speeds are considered on shipping routes as well as variable speed profile. • wave energy spreading o comparison of short and long crested seas are performed. Hydrodynamic analysis of three containerships is performed using linear strip theory. Long term distributions of vertical wave bending moments and bottom slamming pressures are computed using different combinations of the aforementioned assumptions. In addition, the uncertainty of the method for prediction of the long-term extreme slamming pressure is also studied. Results are compared between themselves as well as with loads from IACS rules.

Containership; wave loads; uncertainties

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