Abstract
Traditionally, the evaluation of global loads experienced by passenger ships has been based on closed-form Classification Society Rule formulae or quasi direct analysis procedures. These approaches do not account for the combined influence of hull flexibility, slenderness, and environmental actions on global dynamic response. This paper presents a procedure for the prediction of the global wave-induced loads of a medium-size passenger ship using a potential flow Flexible Fluid Structure Interaction (FFSI) model. The study compares results from direct long-term hydro-structural computations against Classification Society Rules. It is demonstrated that for the specific vessel under consideration: (a) the elastic contributions of the responses on loads are negligible as springing effects occur outside of the wave energy spectrum, (b) deviations of the order of 28% arise by way of amidships when comparing direct hydrodynamic analysis predictions encompassing IACS UR S11A hog/sag nonlinear correction factors and the longitudinal strength standard, and (c) the interpretation of the wave scatter diagram influences predictions by approximately 20%. Based on these indications, it is recommended that further parametric studies over a range of passenger ship designs could help draw unified conclusions on the total influence of global and local hydrodynamic actions on passenger ship loads and dynamic response.
Highlights
Over the last ten years, the average size of passenger ships increased by approximately 30%
Modern passenger vessels comprise of large effective superstructures and slender hulls. These unique design features imply that hull flexibility could be important in terms of predicting wave-induced loads [2]
Fluid structure interaction (FSI) is implemented by assuming that the ship is a rigid body that balances on a trochoidal waveform
Summary
Over the last ten years, the average size of passenger ships increased by approximately 30%. Since the early 2000s, significant research efforts have focused on the validation of theoretical predictions by segmented model tests and the development of design procedures or methods that account for linear and weakly nonlinear effects on the dynamic response of slender, beam-like floating structures in waves. Their work shows that: (a) the combination of rigid and flexible ship dynamics may influence the long-term vertical sagging and hogging moments amidships and (b) Classification Society Rules for ultimate strength assessment may be dependent on sea state variations and the associated cycle times of alternate loads. There are no publications where three-dimensional hydroelasticity theories have been applied for the prediction of global long-term wave-induced loads on passenger ships. The main objective has been to compare itemized steady state, i.e., springing induced loads with Classification Rules and examine their influence on global long-term ship dynamic response in waves [27,28,29]
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