Abstract
In this paper, the hydroelastic motion and load responses of a large flexible ship sailing in irregular seaways are predicted and the hull girder ultimate strength is subsequently evaluated. A three-dimensional time-domain nonlinear hydroelasticity theory is developed where the included nonlinearities are those arising from incident wave force, hydrostatic restoring force and slamming loads. The hull girder structure is simplified as a slender Timoshenko beam and fully coupled with the hydrodynamic model in a time domain. Segmented model towing-tank tests are then conducted to validate the proposed hydroelasticity theory. In addition, short-term and long-term predictions of ship responses in irregular seaways are conducted with the help of the developed hydroelastic code in order to determine the extreme design loads. Finally, a simplified strength-check equation is proposed, which will provide significant reference and convenience for ship design and evaluation. The hull girder ultimate strength is assessed by both the improved Rule approach and direct calculation.
Highlights
Predictions of ship hydrodynamics and wave-induced loads are the fundamental work for hull structural strength assessment
In the authors’ previous work [26], a 3D time-domain nonlinear hydroelasticity theory was developed to predict ship motion and load responses in regular waves; and the proposed hydroelasticity theory is extended to irregular wave case in this paper
The hull structure is discrete by 20 Timoshenko beam elements and and the the vertical vibration mode of the hull girder in vacuum is solved by the transfer matrix method (TMM)
Summary
Predictions of ship hydrodynamics and wave-induced loads are the fundamental work for hull structural strength assessment. The time-domain hydroelasticity theory sufficiently considers the effects of structural responses on the hydrodynamic forces and provides opportunities for the investigation of whipping and springing loads. In the authors’ previous work [26], a 3D time-domain nonlinear hydroelasticity theory was developed to predict ship motion and load responses in regular waves; and the proposed hydroelasticity theory is extended to irregular wave case in this paper. Long-term prediction of wave-induced hull girder loads considering the effect of various operational circumstances is of great importance for the determination of the extreme design loads and the subsequent ultimate strength assessment. The China Classification Society (CCS) issued calculation guidance notes that evaluate the effects of whipping and springing loads on hull structural fatigue strength [32].
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