Mathematical models for hydroelastic analysis become increasingly important as ever larger container ships with specific design and exploitation characteristics are constructed. Compared with other merchant ships, these ships are characterized by relatively lower stiffness, which, in combination with encounter sea states related to their higher speed of approx. 27 knots, can cause resonance effects. In this thesis, a hydroelastic model for the analysis of large container ships, which is based on the modal superposition method, has been improved and its applicability for the determination of the linear springing effect on the ship structure fatigue has been investigated. The basic model has been developed through the cooperation between the Faculty of Mechanical Engineering and Naval Architecture, Zagreb, and the Bureau Veritas, Paris. Special attention is paid to the influence of shear on torsion and the contribution of transverse bulkheads and closed engine room structure to the hull stiffness. In the first chapter, the problem is presented in detail, a research hypothesis is formulated, and an overview of the basic literature and current knowledge is given, together with the research methodology and the structure of the thesis. A numerical procedure for the hydroelastic analysis of ship structures and a description of the existing hydroelastic model parts are given in the second chapter. In the third chapter, the effect of shear stress on the torsion of the ship hull is introduced into the basic structural model, following the analogy with the influence of shear on bending. Differential equations for coupled horizontal and torsional vibrations of a prismatic girder have been developed, and a finite element formulation for the application to the ship hull is derived using the energy approach. The fourth and the fifth chapter deal with the contribution of bulkheads and the engine room structure, as structural discontinuities, to the ship hull stiffness. Effective stiffness parameters are derived and the section distortion as a side-effect is dealt with. The sixth chapter gives a numerical example illustrating the application of the improved structural model for determining the global hydroelastic response of a 11 400 TEU container ship. The seventh chapter deals with the influence of springing on the fatigue life of the ship. The analysis was carried out by a combination of the improved hydroelastic model and a 3D FEM substructure model. Finally, conclusions are drawn and a scientific contribution of this doctoral thesis and suggestions for further research are pointed out. In the appendices, the influence of a consistent formulation of finite elements and of the neglect of mass rotation on the results is considered together with the influence of the bulkhead modelling on the structural response of a prismatic pontoon. The effective stiffness of thin-walled girders is also determined.