Abstract: HYDROELASTIC RESPONSE OF MARINE STRUCTURES TO IMPACT-INDUCED VIBRATIONS by Nabanita Datta Chair : Armin W. Troesch This research deals with the numerical analysis of the hydroelastic behavior of marine vessels under hydrodynamic impact loads, which causes potentially detrimental local flexural vibrations in the vessel. The objective is to provide the dynamic response spectra for transient water-structure dynamics subject to typical impact loads and time scales, using one-way coupling between the fluid and the structure. The hydrodynamic pressure is assumed to be applied on the rigid plate, and then the plate is modelled to respond elastically. The structural vibrations are assumed not to influence the hydrodynamic pressure field. The changing wetted surface is the prime complexity of the problem. The sweeping load sets the plate into small amplitude vibrations, exciting all its natural frequencies (fundamental and overtones). The time-scales of the problem are : (a) the duration of the forcing when sweeping across the plate, and (b) the natural period of the structure. Assuming small deflections of the structure, normal mode summation is used to calculate the vibratory response. The total deflection is assumed to be a series summation of the modal deflections. When the amplitude of the vibrations is small, the dynamic stresses are directly proportional to the flexural displacement. xx Two configurations of the moving load, i.e. (i) uniform stretching load and (ii) impact load, are applied. The coupled system of modal governing differential equation is non-dimensionalized in space and time, and the Dynamic Loading Factor (DLF) of the loading is numerically evaluated by the fourth-order Runge-Kutta method. The corresponding static deflections are calculated by Galerkin’s method. The ratio of the maximum dynamic deflection to the maximum static deflection is the DLF. This analysis provides recommendations to the structural designer, who typically relies on static analysis. The modal participation spectra relative to the dominant fundamental mode for various impact speeds is used to establish modal truncation guidelines. The variation of the response with respect to space and time, and with respect to various parameters like the aspect ratio, damping ratio, boundary conditions, and deadrise angles has been studied. The change in natural frequencies of the structure due to these parameters, and immersion, has also been evaluated.