Use of a equivalent single layer plate theory in ship structural design
The paper presents review of the development of an effective direct strength analysis approach utilizing homogenization, the finite element method, and optimization. Homogenization is used to transform the originally periodic, stiffened plate or web-frame structure to an equivalent single layer (ESL) plate or beam structure, respectively. This makes the finite element analysis (FEA) very fast and allows modeling of the stiffness and mass of the complex structure accurately in an average sense. In most of the cases, classical first-order shear deformation theory (FSDT) is adequate, but new structural solutions require enhancement of the theory to account the influence of strain gradients. The averaged response produced by FEA is transformed to periodic response to allow prediction of spatially fluctuating stresses and first fiber estimate of the strength. The paper summarizes recent developments on the approach with respect to quasi-static and vibratory response, but also non-linear response such as post-buckling and tensile failure under multi-axial loading. The use of the method as part of optimization process of a full ship is presented. Finally, an outlook for future development is given.