This paper presents the numerical and experimental analysis of the seakeeping performances of a survey vessel operating in the Caspian Sea. For the numerical analysis we have developed our own code, based on a linear hydro-dynamic strip theory formulation. The irregular waves are modelled by short-term power density spectra JONSWAP, for the spectral parameters significant wave height and peak period corresponding to the Caspian Sea scattering diagram. The experimental study is developed at the towing tank from Naval Architecture Faculty of Galati, using a semi-captive scaled model 1:16 of the survey vessel, made of fibre glass and wood, being recorded the heave, pitch, roll motions and wave elongation. The experimental tests are carried out for two speeds and several significant heading cases: head, follow and beam regular waves. This study delivers the prediction of the survey vessel seakeeping capabilities and the validation of the numerical response amplitude operators by experiment.

During the past decade, welding remained the main technological procedure for joining steel components in shipbuilding industry. Though it has great benefits, welding is an aggressive process that introduces high stress and strains in the joined materials, causing distortion. Finite element method is an important instrument for predicting how structures are behaving under thermal loads. This paper is focused on studying the behaviour of small thickness ship panels, under straightening treatment, by performing thermal-structural-elastic-plastic analysis in Femap/NX Nastran. The proposed panel is tested under three different thermal loadings in order to study stresses and residual distortion.

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The design concepts of floating docks used for shipyards launching activities have to be assessed from the preliminary design phases by global strength criteria. At initial design, few technical data of floating docks are available, so that the global strength analysis can be developed only on simplified numerical models by the hull equivalent beam method. As loading conditions several docking cases and equivalent design waves, head and oblique conditions, are considered, according to the floating dock design rules. The computations are done with own codes, involving non-linear iterative procedures, which require as input data the 3D-CAD floating docks offset lines and on-board mass distributions. For studying floating dock models, the authors have considered three constructive versions: small dock with continuous and non-continuous side ballast tanks, large dock resulting from a conversion of an offshore barge. The global strength criteria are the admissible sectional efforts by design rules of statistical values and the ultimate strength vertical bending moment by Smith method. The free board operation criterion is also considered for safety evaluation. The preliminary operation limits of the analyzed floating docks are obtained, in terms of equivalent design wave height, pointing out the main differences between the three constructive versions included in this study.

In this study we have enhanced the structural assessment analysis of a river-shipyard small size floating dock, with length overall of 60 m, for equivalent quasi-static oblique design wave conditions. The small size floating dock hull has two constructive layouts for the water ballast side tanks. The oblique design wave heading angle is in the range of 0 to 360 deg. The floating dock equilibrium in oblique equivalent design waves is achieved by own non-linear three parameters iterative program. The numerical analyses are done on full extended 3D-FEM structural models, from side to side and from stern to bow, of the small size floating dock, with specific boundary conditions for global and local strength computations. The modelling of the external oblique equivalent design wave pressure has requested to develop specialized user functions into FEM code. There are considered several loading scenarios of the small size floating dock, according to the shipbuilding classification societies. The structural assessment is based on three criteria: yielding stress, buckling and freeboard limit values. The numerical results of the structural assessment for the small size floating dock in oblique equivalent design waves made possible to establish the wave design height limits, according to the safety criteria restrictions.