A PSO-Based Method for Tracing the Motion of Neutral Axis Plane of Asymmetric Hull Cross-Sections and its Application

Abstract

The Smith’s method is stipulated by the International Association of Classification Societies in the Common Structure Rules as a standard method for estimating ultimate/residual strength of hull girder in both intact and damaged conditions. However, for the latter case where the effective hull cross-section is asymmetric and the neutral axis of damaged cross-section not only translates but also rotates, the additional force vector equilibrium also needs to be applied so as to determine the neutral axis plane. The commonly adopted iterative methods for the two-force-equilibrium problem do not always converge for the desired accuracy. This paper proposes a Particle Swarm Optimization based iteration method to trace the motion of the neutral axis plane of asymmetric cross sections. The translation and rotation of the neutral axis are taken as the two dimensions of particles in the model, and the force equilibrium error and the force vector equilibrium error are the objective functions. The neutral axis is determined by performing a random search within the entire range of possible position of neutral axis. The proposed method has been implemented and validated for the case of the DOW’s 1/3 frigate model, the analysis of efficiency and accuracy shows that the method performs in general better than traditional ones.

Ultimate Limit State Function and Its Fitting Method of Damaged Ship under Combined Loads

“…Since both the transition and rotation need to be accounted for, an appropriate algorithm is required to obtain the solution with fair accuracy. This, actually, is a problem to search for the optimum solution in a given space [20].…”

“…This algorithm is widely applied in many engineering areas for its simple implementation, fast convergence, and excellent accuracy. Li et al [20] applied the PSO algorithm to trace the instantaneous position of the neutral axis, and both the translation and rotation are dealt at the same time. Comparison of results showed that the accuracy is satisfactory.…”