الفهرس 
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Abstract
Sandwich Panel System (SPS) consists of two metal plates separated by a core. It can be used as an alternative to conventional stiffened plate construction. Two case studies are presented in this thesis. Part 1: the ultimate longitudinal strength of a conventional hull of a self-propelled barge is evaluated by nonlinear finite element analysis (NLFEA). The moment-curvature relationship is developed and the ultimate bending moment capacity of the hull is obtained. Based on the Lloyd’s provisional rules for the application of sandwich panel, an equivalent SPS hull was developed. The ultimate strength characteristics of the equivalent hull were also assessed. The weight of the conventional and the SPS hulls were estimated and compared. Significant reduction in the hull weight based on SPS was observed. Also, core material dissipates the strain energy over a large area, which reduces the stress concentration and the possibility of permanent deformations. SPS eliminates the need for secondary stiffeners which make the structure less complex.Part 2: use of laser-welded web-core sandwich plates as an alternative to conventional stiffened plate construction is investigated. The ultimate strength of conventional bottom of a self-propelled barge subjected to longitudinal in-plane compression is evaluated by NonLinear Finite Element Analysis (NLFEA) using ANSYS software. In this work, the possibilities for structural optimization of laser-welded sandwich panels with uni-directional vertical webs are investigated. Four design parameters are selected and different web-core panels are organized. By using NLFEA, ultimate strength of laser-welded sandwich panels is discussed and numerically evaluated to show the effect of parameter variations on ultimate strength and weight. Due to the number of design variables and constraints, a structural optimization based on the response surface methodology (RSM) is performed. Ultimate strength of steel sandwich panel is compared with conventional stiffened panel. The weights of the conventional and the optimum web-core panels are estimated and compared.Significant reduction in the hull weight based on web-core panel was observed. The main objective of this study is to find a steel sandwich structure that has an ultimate strength equivalent to the conventional stiffened panel with minimum weight.