Branko Blagojević

On the Assessment of Redundancy of Ship Structural Components

This paper firstly sums up some of the views on structural redundancy with particular emphasis on ship and marine structures. Next, it places the engineering decision process in the event space and, consequently, applies the representation of operational modes by systems of events. Furthermore, the paper takes some of the relations from the entropy concept in information theory. The entropy concept in probability theory is employed in the paper to redefine the structural redundancy in terms of conditional entropy of operational modes. The redundancy modeling is presented by systems of operational modes in which some of the transitive events may lead to new operational states. Finally, a ship substructure example of a stiffened panel with a girder is elaborated. The conclusion supports the thesis that the efficient structural redundancy can be comprehended as the most uniform distribution of the operational modes probabilities. Moreover, the efficient structural redundancy can be maximized.Copyright

Fatigue Yield of Ship Structures

The paper on the first place summarizes the fatigue yield approach as a cause-effect interaction between fatigue damage progression and fatigue endurance. Secondly it investigates the fatigue strength worsening on experimental S-N data and the load variability effects in shipbuilding. Next it applies the Classification Society’s rule-based procedure for fatigue analysis of ship’s structure that uses a simplified fatigue strength assessment method. The example elaborates fatigue yield effect on the seagoing operation of a double hull 47400 tdw tanker. At the end the paper recommends the procedure for assessment of ship lifetime shortening due to the fatigue yielding under constant and variable amplitude block loadings.Copyright