Hydroelasticity-based structural optimisation of a stepped barge backbone beam

Abstract

Structural optimisation that utilises ship hydroelasticity has significant gaps in marine structural design due to limitations in its practical applications. To address this issue, the present study initiates hydroelasticity-based structural optimisation using a scaled model of a barge by reducing the structural stiffness with a stepped beam approach. A multi-objective optimisation framework is proposed to minimise structural stiffness, considering the minimisation of heave motion and the maintenance of structural safety performance. The optimisation procedure integrates feasibility-based design, Pareto front, and TOPSIS (Technique for Order Preference by Similarity to an Ideal Solution). Numerical approaches strongly coupled between finite element analysis (FEA) and computational fluid dynamics (CFD) are utilised. Results from a total of 32 different designs of experiments show that reducing structural stiffness reduces both the vertical bending moment (VBM) in quadratic and difference heave displacement in linear trends. However, reducing the stiffness tends to increase the magnitude of bending stress due to varying stiffness levels along the barge. Based on the allowable stress criteria, only five configurations are considered feasible for optimisation. Through the Pareto front and TOPSIS approaches, configuration A4 is the optimum solution, which reduced the average vertical stiffness of a backbone by 17.2% without reducing strength capacity.