الفهرس | Only 14 pages are availabe for public view |
Abstract During the life of the ship, the structure deteriorates to a lesser or greater degree. Such deterioration is due to a variety of causes. The main phenomenon, generally, is corrosion. Corrosion has a harmful consequence from the point of view of safety and can lead to thickness penetration, fatigue cracks, brittle fracture and unstable failure. This failure will imply a risk of loss of human lives and a risk of polluting the environment dependent on ship type. After the grounding of the Exxon Valdez in Alaska a new design practice is used in the design of tankers. It is demanded that new tankers be built with double bottom and double sides in order to avoid/minimize oil outflow in grounding and collision. The regulation, the geometric configuration and the structural arrangements of the double hull tanker of different sizes are discussed and outlined. Classification of the structure, stresses and the structural failure modes are carried out. A comparison between the procedures conducted in the strength based design and the reliability-based design are suggested. The assessment procedures of the existing structure are outlined. A survey of the structure reliability theory and concepts are reviewed. The uncertainties involved in the structural reliability analysis and in the modeling process are described. Definitions for the performance function and the probability of failure are stated. The reliability analysis methods required during the numerical example (Second moment methods ”FORM”) are reviewed. The difference between the conditional and the total reliability is described which will be used later in the case study. Modeling procedures of the structural resistance are mentioned in accordance with time dependency of the strength. Modeling of the loads applied on the structural element involving the still water and wave induced bending moment are discussed. The plate boundary conditions and plate modeling are outlined. The most common corrosion types attacking the marine structure are discussed in accordance with the different factors affecting the corrosion rate. The different deterministic and probabilistic corrosion rate modeling techniques are considered focusing on the deterministic and probabilistic linear model for the general corrosion used in the numerical example. Corrosion prevention techniques including coating and cathodic protection (sacrificial anodes) in accordance with the factors affecting these strategies are discussed. The allowable thickness reductions for the different locations through the ship’s hull are stated. |