| Fatigue damage has become a significant damage form of ships. Especially forlarge-scale ships, constructed with high-strength steel, the question of ship hull structure’sfatigue damage is more outstanding. It has attracted widespread attention in ship industry.How to reasonably assess the fatigue strength of ships is becoming more imminent.River-sea direct link ships are different from inland boats and sea-going vessels, whichdirectly cross the river and sea, two different meteorological and hydro-logical conditions,and must be able to withstand the structural safety test of two different navigation areas.Wide and flat features of River-sea-through ships have a great effect on strength andstiffness of the hull structure. When river-sea-through ships sail in the river and sea, whichsuffer different wave loads, whose periods and wave heights are different. Therefore, it isnecessary to calculate and study the fatigue strength of river-sea-through ships.This paper describes the basic theory and methods of fatigue analysis of shipstructures, focusing on the spectral-based analysis method. Take for example of ariver-sea bulk carrier, hydrodynamic analysis method and finite element analysis methodare adopted. The long term prediction and short term prediction of wave induced motionand loads in the typical loading conditions are performed by SESAM software systemof DET NORSKE VERITAS (DNV), basing on which design wave parameters are determined.Then bending-torsional strength of whole ship structure are calculated. The stress anddeformation distribution of hull structure under equivalent design wave are obtained,according to which, fatigue check points are determined. The spectral-based fatigueanalysis are applied to access their fatigue strength, and their fatigue accumulating damageand fatigue life are gained. Influencing factors of fatigue damage are analysed.The results of this paper has some reference value for structure design ofriver-sea-through ships. The analysis methods are valuable for other types of shipstructure’s fatigue strength analysis. |
