Aftbody slamming and whipping loads
Author Kapsenberg G.K., Veer A.P. van 't, Hackett J.P. and Levadou M.M.D.
Title Aftbody slamming and whipping loads
Conference/Journal SNAME Annual Meeting, San Francisco
Month October
Year 2003

Abstract
This paper describes a method of measuring aftbody slamming loads on a ship model in the seakeeping basin. The method uses a large number of small pressure transducers mounted on the flat counter of the stern. The impact force is obtained by integrating the pressures. Experiments have been carried out on a scaled model of a modern cruise ship. The model was split into two segments at midships to simulate a simplified 2-node vibration mode. A structural mathematical model was made of the model as used for the tests. The analysis shows that the measured pressures can be used to predict the whipping loads on the segmented model. A fatigue analysis was made for the Vertical Bending Moment midships. It appears that for a following sea case the fatigue damage is dominated by the whipping contribution. The results also show that the fatigue damage of being 1 hr in a 4 m following Sea State is as high as sailing in a 9 m head Sea State. The extreme vertical hull bending moment is determined by sailing in high head waves. The results of the experiments show that the whipping component only contributes 5% to the extreme Vertical Bending Moment. It is concluded that the measured loads can also be used with a finite element model of the ship’s structure to predict whipping stresses in the actual ship structure.

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