ABSTRACT

The importance of hydroelastic analysis of large and flexible container ships of today has been pointed out for structure design. As the size of container ships increases, whipping phenomena has been one of the important design considerations due to its significant effect on wave loads and fatigue analysis. In this paper, a 3D nonlinear hydroelasticity theory was introduced which is fit for time history simulation in irregular wave conditions. The numerical analysis method utilizes a 3D Green function method and a 2-D momentum model, which are coupled in the time domain. In the present study, theoretical calculation combined with model experiment is treated as the most effective approach. Therefore reliable model test data is needed to verify and validate the accuracy and applicability of the computational programs, thus it's possible to make use of the programs at the preliminary stage of ship design in order to decrease the cost. A model system for measurement of nonlinear wave loads which is composed of a backbone and segmented container ship model in which natural frequency of vertical bending is matched using a beam with rectangular-shaped variable cross-section, has been already built up and applied to a series of large ship models especially. A series of model tests have been carried out for selected cases of whipping in regular and irregular waves. The computational results were compared with those of a model test of a 10000-TEU containership. Verifications and validations between model tests results and theoretical calculation have been conducted. Discussions are focused on the asymmetry of wave elevation, vertical ship motion and vertical sectional loads responses, which are observed and calculated in irregular wave conditions, and they show good agreement between experimental and simulated results, basing on this the design vertical bending moment at midship can be obtained by using the nonlinear short-term and long-term analysis and the comparison between direct calculation and classification society rules is carried out, which shows good agreement with each other.

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