Finite Element and Analytical Modelling of Ship Unloader

Abstract

The paper deals with the mathematical modelling of the dynamic behavior of the structure of the ship unloader. It is given the procedure for formulation of the reduced dynamic model which retains the main aspects of the behavior of the structure and yet is simple enough to be performed with standard engineering tools. The approach is applied on the real bridge-type grab ship unloader but can also be used on similar complex structures. Initially, the complete structure is modelled with finite element software where the natural frequencies were obtained. This 3D model is reduced to an equivalent plane model of the sea-side part of the boom. The postulation of the analytical approach is based on the model of a simple beam with an overhang where dynamic analysis is concerned with the Rayleigh Ritz method for estimating the adopted admissible functions. The results of the modal analysis of the reduced mathematical model showed a small difference from the results of finite element analysis which stands for the verification of the presented approach.