Optimization of web-core steel sandwich decks at concept design stage using envelope surface for stress assessment

• Envelope curve approach have been developed for periodic structures.
• Influence of periodic stresses have been discussed with respect to boundary conditions.
• The benefits of the method have been demonstrated through optimization example.

This paper presents an optimization method for laser-welded web-core steel sandwich panels supported by girder system. The method utilizes homogenized plate theory and offset beams. The static and eigenfrequency analyses are carried out using the Finite Element Method (FEM). In order to assess the influence of periodic stresses within the sandwich panel, an envelope surface approach is developed. The approach is aimed to capture the maximum stresses on elemental basis even though the actual positioning of the web plates is unknown. This makes the method attractive for concept design stage where nesting process is not yet done. The envelope surface approach is validated with 3D FEM and periodic solution based on localization. The agreement between methods is found to be excellent. The method is demonstrated through a case study on weight optimization of passenger ship deck. The optimization problem is solved using Particle Swarm Optimization method. The paper shows that the proposed approach can be efficiently used to assess the stresses of the sandwich panel and thus to design steel sandwich structures at concept design stage.